diff --git a/.gitattributes b/.gitattributes
index 51a670b5fbefd..82599b1450386 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -16,3 +16,11 @@ config.toml.example linguist-language=TOML
 *.ico binary
 *.woff binary
 *.woff2 binary
+
+# Needed as part of converting rustfmt to a subtree, can hopefully be removed later.
+src/tools/rustfmt/tests/source/issue-3494/crlf.rs -text
+src/tools/rustfmt/tests/source/comment_crlf_newline.rs -text
+src/tools/rustfmt/tests/source/configs/enum_discrim_align_threshold/40.rs -text
+src/tools/rustfmt/tests/target/issue-3494/crlf.rs -text
+src/tools/rustfmt/tests/target/comment_crlf_newline.rs -text
+src/tools/rustfmt/tests/target/configs/enum_discrim_align_threshold/40.rs -text
diff --git a/.gitmodules b/.gitmodules
index d4a80efc277e3..aee038aa4c8e5 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -16,9 +16,6 @@
 [submodule "src/tools/rls"]
 	path = src/tools/rls
 	url = https://github.com/rust-lang/rls.git
-[submodule "src/tools/rustfmt"]
-	path = src/tools/rustfmt
-	url = https://github.com/rust-lang/rustfmt.git
 [submodule "src/tools/miri"]
 	path = src/tools/miri
 	url = https://github.com/rust-lang/miri.git
diff --git a/Cargo.lock b/Cargo.lock
index e92b7287f3eb6..da65b376d191f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1985,11 +1985,11 @@ dependencies = [
 
 [[package]]
 name = "log"
-version = "0.4.11"
+version = "0.4.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4fabed175da42fed1fa0746b0ea71f412aa9d35e76e95e59b192c64b9dc2bf8b"
+checksum = "51b9bbe6c47d51fc3e1a9b945965946b4c44142ab8792c50835a980d362c2710"
 dependencies = [
- "cfg-if 0.1.10",
+ "cfg-if 1.0.0",
 ]
 
 [[package]]
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 789267aa880fa..f39e89a9d01f7 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -379,6 +379,7 @@ impl<'a> Builder<'a> {
                 check::Clippy,
                 check::Miri,
                 check::Rls,
+                check::Rustfmt,
                 check::Bootstrap
             ),
             Kind::Test => describe!(
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index 3e9d921d0f526..5003d6693f72c 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -342,10 +342,6 @@ macro_rules! tool_check_step {
                     true,
                 );
 
-                let libdir = builder.sysroot_libdir(compiler, target);
-                let hostdir = builder.sysroot_libdir(compiler, compiler.host);
-                add_to_sysroot(&builder, &libdir, &hostdir, &stamp(builder, compiler, target));
-
                 /// Cargo's output path in a given stage, compiled by a particular
                 /// compiler for the specified target.
                 fn stamp(
@@ -363,13 +359,14 @@ macro_rules! tool_check_step {
 }
 
 tool_check_step!(Rustdoc, "src/tools/rustdoc", "src/librustdoc", SourceType::InTree);
-// Clippy is a hybrid. It is an external tool, but uses a git subtree instead
+// Clippy and Rustfmt are hybrids. They are external tools, but use a git subtree instead
 // of a submodule. Since the SourceType only drives the deny-warnings
 // behavior, treat it as in-tree so that any new warnings in clippy will be
 // rejected.
 tool_check_step!(Clippy, "src/tools/clippy", SourceType::InTree);
 tool_check_step!(Miri, "src/tools/miri", SourceType::Submodule);
 tool_check_step!(Rls, "src/tools/rls", SourceType::Submodule);
+tool_check_step!(Rustfmt, "src/tools/rustfmt", SourceType::InTree);
 
 tool_check_step!(Bootstrap, "src/bootstrap", SourceType::InTree, false);
 
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 0e9c561c68994..98f753b25f05f 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -319,15 +319,9 @@ impl Step for Rustfmt {
         let host = self.host;
         let compiler = builder.compiler(stage, host);
 
-        let build_result = builder.ensure(tool::Rustfmt {
-            compiler,
-            target: self.host,
-            extra_features: Vec::new(),
-        });
-        if build_result.is_none() {
-            eprintln!("failed to test rustfmt: could not build");
-            return;
-        }
+        builder
+            .ensure(tool::Rustfmt { compiler, target: self.host, extra_features: Vec::new() })
+            .expect("in-tree tool");
 
         let mut cargo = tool::prepare_tool_cargo(
             builder,
@@ -346,9 +340,7 @@ impl Step for Rustfmt {
 
         cargo.add_rustc_lib_path(builder, compiler);
 
-        if try_run(builder, &mut cargo.into()) {
-            builder.save_toolstate("rustfmt", ToolState::TestPass);
-        }
+        builder.run(&mut cargo.into());
     }
 }
 
diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index 4f2426648fd8a..12571c1b97db6 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -726,7 +726,7 @@ macro_rules! tool_extended {
 // Note: tools need to be also added to `Builder::get_step_descriptions` in `builder.rs`
 // to make `./x.py build <tool>` work.
 tool_extended!((self, builder),
-    Cargofmt, rustfmt, "src/tools/rustfmt", "cargo-fmt", stable=true, {};
+    Cargofmt, rustfmt, "src/tools/rustfmt", "cargo-fmt", stable=true, in_tree=true, {};
     CargoClippy, clippy, "src/tools/clippy", "cargo-clippy", stable=true, in_tree=true, {};
     Clippy, clippy, "src/tools/clippy", "clippy-driver", stable=true, in_tree=true, {};
     Miri, miri, "src/tools/miri", "miri", stable=false, {};
@@ -740,7 +740,7 @@ tool_extended!((self, builder),
         self.extra_features.push("clippy".to_owned());
     };
     RustDemangler, rust_demangler, "src/tools/rust-demangler", "rust-demangler", stable=false, in_tree=true, {};
-    Rustfmt, rustfmt, "src/tools/rustfmt", "rustfmt", stable=true, {};
+    Rustfmt, rustfmt, "src/tools/rustfmt", "rustfmt", stable=true, in_tree=true, {};
     RustAnalyzer, rust_analyzer, "src/tools/rust-analyzer/crates/rust-analyzer", "rust-analyzer", stable=false, {};
 );
 
diff --git a/src/bootstrap/toolstate.rs b/src/bootstrap/toolstate.rs
index 205524ad84fb7..2394c5e020d2b 100644
--- a/src/bootstrap/toolstate.rs
+++ b/src/bootstrap/toolstate.rs
@@ -77,7 +77,6 @@ static STABLE_TOOLS: &[(&str, &str)] = &[
     ("rust-by-example", "src/doc/rust-by-example"),
     ("edition-guide", "src/doc/edition-guide"),
     ("rls", "src/tools/rls"),
-    ("rustfmt", "src/tools/rustfmt"),
 ];
 
 // These tools are permitted to not build on the beta/stable channels.
@@ -278,10 +277,9 @@ impl Builder<'_> {
         if self.config.dry_run {
             return;
         }
-        // Toolstate isn't tracked for clippy, but since most tools do, we avoid
-        // checking in all the places we could save toolstate and just do so
-        // here.
-        if tool == "clippy-driver" {
+        // Toolstate isn't tracked for clippy or rustfmt, but since most tools do, we avoid checking
+        // in all the places we could save toolstate and just do so here.
+        if tool == "clippy-driver" || tool == "rustfmt" {
             return;
         }
         if let Some(ref path) = self.config.save_toolstates {
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh b/src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh
index 49a8e5e88a039..412efe5c4480d 100755
--- a/src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh
@@ -15,7 +15,6 @@ python3 "$X_PY" test --stage 2 --no-fail-fast \
     src/doc/embedded-book \
     src/doc/edition-guide \
     src/tools/rls \
-    src/tools/rustfmt \
     src/tools/miri \
 
 set -e
@@ -24,3 +23,4 @@ set -e
 cat /tmp/toolstate/toolstates.json
 python3 "$X_PY" test --stage 2 check-tools
 python3 "$X_PY" test --stage 2 src/tools/clippy
+python3 "$X_PY" test --stage 2 src/tools/rustfmt
diff --git a/src/ci/scripts/should-skip-this.sh b/src/ci/scripts/should-skip-this.sh
index 36bf4368990c9..631a7b247d5e8 100755
--- a/src/ci/scripts/should-skip-this.sh
+++ b/src/ci/scripts/should-skip-this.sh
@@ -10,15 +10,23 @@ source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
 
 if [[ -z "${CI_ONLY_WHEN_SUBMODULES_CHANGED+x}" ]]; then
     echo "Executing the job since there is no skip rule in effect"
-elif git diff HEAD^ | grep --quiet "^index .* 160000"; then
+    exit 0
+fi
+
+git fetch "https://github.com/$GITHUB_REPOSITORY" "$GITHUB_BASE_REF"
+BASE_COMMIT="$(git merge-base FETCH_HEAD HEAD)"
+
+echo "Searching for toolstate changes between $BASE_COMMIT and $(git rev-parse HEAD)"
+
+if git diff "$BASE_COMMIT" | grep --quiet "^index .* 160000"; then
     # Submodules pseudo-files inside git have the 160000 permissions, so when
     # those files are present in the diff a submodule was updated.
     echo "Executing the job since submodules are updated"
-elif git diff --name-only HEAD^ | grep --quiet src/tools/clippy; then
+elif ! git diff --quiet "$BASE_COMMIT" -- src/tools/clippy src/tools/rustfmt; then
     # There is not an easy blanket search for subtrees. For now, manually list
-    # clippy.
-    echo "Executing the job since clippy subtree was updated"
+    # the subtrees.
+    echo "Executing the job since clippy or rustfmt subtree was updated"
 else
-    echo "Not executing this job since no submodules were updated"
+    echo "Not executing this job since no submodules nor subtrees were updated"
     ciCommandSetEnv SKIP_JOB 1
 fi
diff --git a/src/tools/rustfmt b/src/tools/rustfmt
deleted file mode 160000
index 2a3635d5d1218..0000000000000
--- a/src/tools/rustfmt
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 2a3635d5d1218c726ff58af4bc35418836143f69
diff --git a/src/tools/rustfmt/.editorconfig b/src/tools/rustfmt/.editorconfig
new file mode 100644
index 0000000000000..5bb92df3e0432
--- /dev/null
+++ b/src/tools/rustfmt/.editorconfig
@@ -0,0 +1,26 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 2
+indent_style = space
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.rs]
+indent_size = 4
+
+[tests/**/*.rs]
+charset = utf-8
+end_of_line = unset
+indent_size = unset
+indent_style = unset
+trim_trailing_whitespace = unset
+insert_final_newline = unset
+
+[appveyor.yml]
+end_of_line = unset
diff --git a/src/tools/rustfmt/.gitattributes b/src/tools/rustfmt/.gitattributes
new file mode 100644
index 0000000000000..91df4f0eb18dc
--- /dev/null
+++ b/src/tools/rustfmt/.gitattributes
@@ -0,0 +1,7 @@
+* text=auto eol=lf
+tests/source/issue-3494/crlf.rs -text
+tests/source/comment_crlf_newline.rs -text
+tests/source/configs/enum_discrim_align_threshold/40.rs -text
+tests/target/issue-3494/crlf.rs -text
+tests/target/comment_crlf_newline.rs -text
+tests/target/configs/enum_discrim_align_threshold/40.rs -text
diff --git a/src/tools/rustfmt/.github/workflows/integration.yml b/src/tools/rustfmt/.github/workflows/integration.yml
new file mode 100644
index 0000000000000..b79221d054369
--- /dev/null
+++ b/src/tools/rustfmt/.github/workflows/integration.yml
@@ -0,0 +1,85 @@
+name: integration
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  integration-tests:
+    runs-on: ubuntu-latest
+    name: ${{ matrix.integration }}
+    strategy:
+      # https://help.github.com/en/actions/getting-started-with-github-actions/about-github-actions#usage-limits
+      # There's a limit of 60 concurrent jobs across all repos in the rust-lang organization.
+      # In order to prevent overusing too much of that 60 limit, we throttle the
+      # number of rustfmt jobs that will run concurrently.
+      max-parallel: 4
+      fail-fast: false
+      matrix:
+        integration: [
+          bitflags,
+          error-chain,
+          log,
+          mdbook,
+          packed_simd,
+          rust-semverver,
+          tempdir,
+          futures-rs,
+          rust-clippy,
+          failure,
+        ]
+        include:
+          # Allowed Failures
+          # Actions doesn't yet support explicitly marking matrix legs as allowed failures
+          # https://github.community/t5/GitHub-Actions/continue-on-error-allow-failure-UI-indication/td-p/37033
+          # https://github.community/t5/GitHub-Actions/Why-a-matrix-step-will-be-canceled-if-another-one-failed/td-p/30920
+          # Instead, leverage `continue-on-error`
+          # https://help.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions#jobsjob_idstepscontinue-on-error
+          #
+          # Failing due to breaking changes in rustfmt 2.0 where empty
+          # match blocks have trailing commas removed
+          # https://github.com/rust-lang/rustfmt/pull/4226
+          - integration: chalk
+            allow-failure: true
+          - integration: crater
+            allow-failure: true
+          - integration: glob
+            allow-failure: true
+          - integration: stdsimd
+            allow-failure: true
+          # Using old rustfmt configuration option
+          - integration: rand
+            allow-failure: true
+          # Keep this as an allowed failure as it's fragile to breaking changes of rustc.
+          - integration: rust-clippy
+            allow-failure: true
+          # Using old rustfmt configuration option
+          - integration: packed_simd
+            allow-failure: true
+          # calebcartwright (2019-12-24)
+          # Keeping this as an allowed failure since it was flagged as such in the TravisCI config, even though
+          # it appears to have been passing for quite some time.
+          # Original comment was: temporal build failure due to breaking changes in the nightly compiler
+          - integration: rust-semverver
+            allow-failure: true
+          # Can be moved back to include section after https://github.com/rust-lang-nursery/failure/pull/298 is merged
+          - integration: failure
+            allow-failure: true
+
+    steps:
+    - name: checkout
+      uses: actions/checkout@v2
+
+      # Run build
+    - name: install rustup
+      run: |
+        curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs > rustup-init.sh
+        sh rustup-init.sh -y --default-toolchain none
+
+    - name: run integration tests
+      env:
+        INTEGRATION: ${{ matrix.integration }}
+        TARGET: x86_64-unknown-linux-gnu
+      run: ./ci/integration.sh
+      continue-on-error: ${{ matrix.allow-failure == true }}
diff --git a/src/tools/rustfmt/.github/workflows/linux.yml b/src/tools/rustfmt/.github/workflows/linux.yml
new file mode 100644
index 0000000000000..6eaae69c70805
--- /dev/null
+++ b/src/tools/rustfmt/.github/workflows/linux.yml
@@ -0,0 +1,42 @@
+name: linux
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    name: (${{ matrix.target }}, nightly)
+    strategy:
+      # https://help.github.com/en/actions/getting-started-with-github-actions/about-github-actions#usage-limits
+      # There's a limit of 60 concurrent jobs across all repos in the rust-lang organization.
+      # In order to prevent overusing too much of that 60 limit, we throttle the
+      # number of rustfmt jobs that will run concurrently.
+      max-parallel: 1
+      fail-fast: false
+      matrix:
+        target: [
+          x86_64-unknown-linux-gnu,
+        ]
+
+    steps:
+    - name: checkout
+      uses: actions/checkout@v2
+
+      # Run build
+    - name: install rustup
+      run: |
+        curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs > rustup-init.sh
+        sh rustup-init.sh -y --default-toolchain none
+        rustup target add ${{ matrix.target }}
+
+    - name: build
+      run: |
+        rustc -Vv
+        cargo -V
+        cargo build
+
+    - name: test
+      run: cargo test
diff --git a/src/tools/rustfmt/.github/workflows/mac.yml b/src/tools/rustfmt/.github/workflows/mac.yml
new file mode 100644
index 0000000000000..79e4f69163e03
--- /dev/null
+++ b/src/tools/rustfmt/.github/workflows/mac.yml
@@ -0,0 +1,39 @@
+name: mac
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  test:
+    # https://help.github.com/en/actions/automating-your-workflow-with-github-actions/virtual-environments-for-github-hosted-runners#supported-runners-and-hardware-resources
+    # macOS Catalina 10.15
+    runs-on: macos-latest
+    name: (${{ matrix.target }}, nightly)
+    strategy:
+      fail-fast: false
+      matrix:
+        target: [
+          x86_64-apple-darwin,
+        ]
+
+    steps:
+    - name: checkout
+      uses: actions/checkout@v2
+
+      # Run build
+    - name: install rustup
+      run: |
+        curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs > rustup-init.sh
+        sh rustup-init.sh -y --default-toolchain none
+        rustup target add ${{ matrix.target }}
+
+    - name: build
+      run: |
+        rustc -Vv
+        cargo -V
+        cargo build
+
+    - name: test
+      run: cargo test
diff --git a/src/tools/rustfmt/.github/workflows/upload-assets.yml b/src/tools/rustfmt/.github/workflows/upload-assets.yml
new file mode 100644
index 0000000000000..9a5fd0dd1d31b
--- /dev/null
+++ b/src/tools/rustfmt/.github/workflows/upload-assets.yml
@@ -0,0 +1,80 @@
+name: upload
+
+on:
+  release:
+    types: [created]
+
+jobs:
+  build-release:
+    name: build-release
+    strategy:
+      matrix:
+        build: [linux-x86_64, macos-x86_64, windows-x86_64-gnu, windows-x86_64-msvc]
+        include:
+          - build: linux-x86_64
+            os: ubuntu-latest
+            rust: nightly
+          - build: macos-x86_64
+            os: macos-latest
+            rust: nightly
+          - build: windows-x86_64-gnu
+            os: windows-latest
+            rust: nightly-x86_64-gnu
+          - build: windows-x86_64-msvc
+            os: windows-latest
+            rust: nightly-x86_64-msvc
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: ${{ matrix.rust }}
+          override: true
+
+      - name: Add mingw64 to path for x86_64-gnu
+        run: echo "C:\msys64\mingw64\bin" >> $GITHUB_PATH
+        if: matrix.rust == 'nightly-x86_64-gnu'
+        shell: bash
+
+      - name: Install cargo-make
+        uses: actions-rs/cargo@v1
+        with:
+          command: install
+          args: --force cargo-make
+
+      - name: Build release binaries
+        uses: actions-rs/cargo@v1
+        with:
+          command: make
+          args: release
+
+      - name: Build archive
+        shell: bash
+        run: |
+          staging="rustfmt_${{ matrix.build }}_${{ github.event.release.tag_name }}"
+          mkdir -p "$staging"
+
+          cp {README.md,Configurations.md,CHANGELOG.md,LICENSE-MIT,LICENSE-APACHE} "$staging/"
+
+          if [ "${{ matrix.os }}" = "windows-latest" ]; then
+            cp target/release/{rustfmt.exe,cargo-fmt.exe,rustfmt-format-diff.exe,git-rustfmt.exe} "$staging/"
+            7z a "$staging.zip" "$staging"
+            echo "ASSET=$staging.zip" >> $GITHUB_ENV
+          else
+            cp target/release/{rustfmt,cargo-fmt,rustfmt-format-diff,git-rustfmt} "$staging/"
+            tar czf "$staging.tar.gz" "$staging"
+            echo "ASSET=$staging.tar.gz" >> $GITHUB_ENV
+          fi
+
+      - name: Upload Release Asset
+        uses: actions/upload-release-asset@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: ${{ github.event.release.upload_url }}
+          asset_path: ${{ env.ASSET }}
+          asset_name: ${{ env.ASSET }}
+          asset_content_type: application/octet-stream
diff --git a/src/tools/rustfmt/.github/workflows/windows.yml b/src/tools/rustfmt/.github/workflows/windows.yml
new file mode 100644
index 0000000000000..08cb52eedaea7
--- /dev/null
+++ b/src/tools/rustfmt/.github/workflows/windows.yml
@@ -0,0 +1,69 @@
+name: windows
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  test:
+    runs-on: windows-latest
+    name: (${{ matrix.target }}, nightly)
+    strategy:
+      # https://help.github.com/en/actions/getting-started-with-github-actions/about-github-actions#usage-limits
+      # There's a limit of 60 concurrent jobs across all repos in the rust-lang organization.
+      # In order to prevent overusing too much of that 60 limit, we throttle the
+      # number of rustfmt jobs that will run concurrently.
+      max-parallel: 2
+      fail-fast: false
+      matrix:
+        target: [
+          i686-pc-windows-gnu,
+          i686-pc-windows-msvc,
+          x86_64-pc-windows-gnu,
+          x86_64-pc-windows-msvc,
+        ]
+
+    steps:
+    # The Windows runners have autocrlf enabled by default
+    # which causes failures for some of rustfmt's line-ending sensitive tests
+    - name: disable git eol translation
+      run: git config --global core.autocrlf false
+    - name: checkout
+      uses: actions/checkout@v2
+
+      # Run build
+    - name: Install Rustup using win.rustup.rs
+      run: |
+        # Disable the download progress bar which can cause perf issues
+        $ProgressPreference = "SilentlyContinue"
+        Invoke-WebRequest https://win.rustup.rs/ -OutFile rustup-init.exe
+        .\rustup-init.exe -y --default-host=x86_64-pc-windows-msvc --default-toolchain=none
+        del rustup-init.exe
+        rustup target add ${{ matrix.target }}
+      shell: powershell
+
+    - name: Add mingw32 to path for i686-gnu
+      run: |
+        echo "C:\msys64\mingw32\bin" >> $GITHUB_PATH
+      if: matrix.target == 'i686-pc-windows-gnu' && matrix.channel == 'nightly'
+      shell: bash
+
+    - name: Add mingw64 to path for x86_64-gnu
+      run: echo "C:\msys64\mingw64\bin" >> $GITHUB_PATH
+      if: matrix.target == 'x86_64-pc-windows-gnu' && matrix.channel == 'nightly'
+      shell: bash
+
+    - name: cargo-make
+      run: cargo install --force cargo-make
+
+    - name: build
+      run: |
+        rustc -Vv
+        cargo -V
+        cargo build
+      shell: cmd
+
+    - name: test
+      run: cargo test
+      shell: cmd
diff --git a/src/tools/rustfmt/.gitignore b/src/tools/rustfmt/.gitignore
new file mode 100644
index 0000000000000..37adf8751ca8f
--- /dev/null
+++ b/src/tools/rustfmt/.gitignore
@@ -0,0 +1,24 @@
+
+# Created by https://www.gitignore.io/api/rust
+
+### Rust ###
+# Generated by Cargo
+# will have compiled files and executables
+/target
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+# Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# End of https://www.gitignore.io/api/rust
+
+# Used by macOS' file system to track custom attributes of containing folder
+.DS_Store
+
+# Editors' specific files
+.idea/
+.vscode/
+*~
diff --git a/src/tools/rustfmt/.travis.yml b/src/tools/rustfmt/.travis.yml
new file mode 100644
index 0000000000000..d699bd842eecc
--- /dev/null
+++ b/src/tools/rustfmt/.travis.yml
@@ -0,0 +1,77 @@
+sudo: false
+language: rust
+rust: nightly
+os: linux
+cache:
+ directories:
+  - $HOME/.cargo
+
+addons:
+  apt:
+    packages:
+    - libcurl4-openssl-dev
+    - libelf-dev
+    - libdw-dev
+
+matrix:
+  include:
+    - env: DEPLOY=LINUX
+    - env: CFG_RELEASE_CHANNEL=beta
+    - os: osx
+    - env: INTEGRATION=bitflags
+    - env: INTEGRATION=chalk
+    - env: INTEGRATION=crater
+    - env: INTEGRATION=error-chain
+    - env: INTEGRATION=glob
+    - env: INTEGRATION=log
+    - env: INTEGRATION=mdbook
+    - env: INTEGRATION=packed_simd
+    - env: INTEGRATION=rust-semverver
+    - env: INTEGRATION=stdsimd TARGET=x86_64-unknown-linux-gnu
+    - env: INTEGRATION=tempdir
+    - env: INTEGRATION=futures-rs
+  allow_failures:
+    # Using old configuration option
+    - env: INTEGRATION=rand
+    # Doesn't build - keep this in allow_failures as it's fragile to breaking changes of rustc.
+    - env: INTEGRATION=rust-clippy
+    # Doesn't build - seems to be because of an option
+    - env: INTEGRATION=packed_simd
+    # Doesn't build - a temporal build failure due to breaking changes in the nightly compilre
+    - env: INTEGRATION=rust-semverver
+    # can be moved back to include section after https://github.com/rust-lang-nursery/failure/pull/298 is merged
+    - env: INTEGRATION=failure
+    # `cargo test` doesn't finish - disabling for now.
+    # - env: INTEGRATION=cargo
+
+script:
+  - |
+    if [ -z ${INTEGRATION} ]; then
+      export CFG_RELEASE_CHANNEL=nightly
+      export CFG_RELEASE=nightly
+      cargo build
+      cargo test
+      cargo test -- --ignored
+    else
+      ./ci/integration.sh
+    fi
+
+after_success:
+- if [ -z ${INTEGRATION} ]; then travis-cargo coveralls --no-sudo; fi
+
+before_deploy:
+  # TODO: cross build
+ - cargo build --release --target=x86_64-unknown-linux-gnu
+ - tar czf rustfmt-x86_64-unknown-linux-gnu.tar.gz Contributing.md Design.md README.md -C target/x86_64-unknown-linux-gnu/release/rustfmt rustfmt
+
+deploy:
+  provider: releases
+  api_key:
+    secure: "your own encrypted key"
+  file:
+  - rustfmt-x86_64-unknown-linux-gnu.tar.gz
+  on:
+    repo: nrc/rustfmt
+    tags: true
+    condition: "$DEPLOY = LINUX"
+  skip_cleanup: true
diff --git a/src/tools/rustfmt/CHANGELOG.md b/src/tools/rustfmt/CHANGELOG.md
new file mode 100644
index 0000000000000..0f23663d6c2f9
--- /dev/null
+++ b/src/tools/rustfmt/CHANGELOG.md
@@ -0,0 +1,1168 @@
+# Changelog
+
+## [Unreleased]
+
+## [1.4.37] 2021-04-03
+
+### Changed
+
+- `rustc-ap-*` crates updated to v712.0.0
+
+### Fixed
+- Resolve idempotence issue related to indentation of macro defs that contain or-patterns with inner comments ([#4603](https://github.com/rust-lang/rustfmt/issues/4603))
+- Addressed various clippy and rustc warnings
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - *pending*
+- **GitHub Release Binaries** - [Release v1.4.37](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.37)
+- **Build from source** - [Tag v1.4.37](https://github.com/rust-lang/rustfmt/tree/v1.4.37), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.36] 2021-02-07
+
+### Changed
+
+- `rustc-ap-*` crates updated to v705.0.0
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - *pending*
+- **GitHub Release Binaries** - [Release v1.4.36](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.36)
+- **Build from source** - [Tag v1.4.36](https://github.com/rust-lang/rustfmt/tree/v1.4.36), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.35] 2021-02-03
+
+### Changed
+
+- `rustc-ap-*` crates updated to v702.0.0
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - *n/a (superseded by [v1.4.36](#1436-2021-02-07))
+- **GitHub Release Binaries** - [Release v1.4.35](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.35)
+- **Build from source** - [Tag v1.4.35](https://github.com/rust-lang/rustfmt/tree/v1.4.35), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.34] 2021-01-28
+
+### Fixed
+- Don't insert trailing comma on (base-less) rest in struct literals within macros ([#4675](https://github.com/rust-lang/rustfmt/issues/4675))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2021-01-31`
+- **GitHub Release Binaries** - [Release v1.4.34](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.34)
+- **Build from source** - [Tag v1.4.34](https://github.com/rust-lang/rustfmt/tree/v1.4.34), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.33] 2021-01-27
+
+### Changed
+- `merge_imports` configuration has been deprecated in favor of the new `imports_granularity` option. Any existing usage of `merge_imports` will be automatically mapped to the corresponding value on `imports_granularity` with a warning message printed to encourage users to update their config files.
+
+### Added
+- New `imports_granularity` option has been added which succeeds `merge_imports`. This new option supports several additional variants which allow users to merge imports at different levels (crate or module), and even flatten imports to have a single use statement per item. ([PR #4634](https://github.com/rust-lang/rustfmt/pull/4634), [PR #4639](https://github.com/rust-lang/rustfmt/pull/4639))
+
+See the section on the configuration site for more information
+https://rust-lang.github.io/rustfmt/?version=v1.4.33&search=#imports_granularity
+
+### Fixed
+- Fix erroneous removal of `const` keyword on const trait impl ([#4084](https://github.com/rust-lang/rustfmt/issues/4084))
+- Fix incorrect span usage wit const generics in supertraits ([#4204](https://github.com/rust-lang/rustfmt/issues/4204))
+- Use correct span for const generic params ([#4263](https://github.com/rust-lang/rustfmt/issues/4263))
+- Correct span on const generics to include type bounds ([#4310](https://github.com/rust-lang/rustfmt/issues/4310))
+- Idempotence issue on blocks containing only empty statements ([#4627](https://github.com/rust-lang/rustfmt/issues/4627) and [#3868](https://github.com/rust-lang/rustfmt/issues/3868))
+- Fix issue with semicolon placement on required functions that have a trailing comment that ends in a line-style comment before the semicolon ([#4646](https://github.com/rust-lang/rustfmt/issues/4646))
+- Avoid shared interned cfg_if symbol since rustfmt can re-initialize the rustc_ast globals on multiple inputs ([#4656](https://github.com/rust-lang/rustfmt/issues/4656))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - n/a (superseded by [v1.4.34](#1434-2021-01-28))
+- **GitHub Release Binaries** - [Release v1.4.33](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.33)
+- **Build from source** - [Tag v1.4.33](https://github.com/rust-lang/rustfmt/tree/v1.4.33), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.32] 2021-01-16
+
+### Fixed
+- Indentation now correct on first bound in cases where the generic bounds are multiline formatted and the first bound itself is multiline formatted ([#4636](https://github.com/rust-lang/rustfmt/issues/4636))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2021-01-18`
+- **GitHub Release Binaries** - [Release v1.4.32](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.32)
+- **Build from source** - [Tag v1.4.32](https://github.com/rust-lang/rustfmt/tree/v1.4.32), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.31] 2021-01-09
+
+### Changed
+
+- `rustc-ap-*` crates updated to v697.0.0
+
+### Added
+- Support for 2021 Edition [#4618](https://github.com/rust-lang/rustfmt/pull/4618))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2021-01-16`
+- **GitHub Release Binaries** - [Release v1.4.31](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.31)
+- **Build from source** - [Tag v1.4.31](https://github.com/rust-lang/rustfmt/tree/v1.4.31), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.30] 2020-12-20
+
+### Fixed
+- Last character in derive no longer erroneously stripped when `indent_style` is overridden to `Visual`. ([#4584](https://github.com/rust-lang/rustfmt/issues/4584))
+- Brace wrapping of closure bodies maintained in cases where the closure has an explicit return type and the body consists of a single expression statement. ([#4577](https://github.com/rust-lang/rustfmt/issues/4577))
+- No more panics on invalid code with `err` and `typeof` types ([#4357](https://github.com/rust-lang/rustfmt/issues/4357), [#4586](https://github.com/rust-lang/rustfmt/issues/4586))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2020-12-25`
+- **GitHub Release Binaries** - [Release v1.4.30](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.30)
+- **Build from source** - [Tag v1.4.30](https://github.com/rust-lang/rustfmt/tree/v1.4.30), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.29] 2020-12-04
+
+### Fixed
+- Negative polarity on non-trait impl now preserved. ([#4566](https://github.com/rust-lang/rustfmt/issues/4566))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2020-12-07`
+- **GitHub Release Binaries** - [Release v1.4.29](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.29)
+- **Build from source** - [Tag v1.4.29](https://github.com/rust-lang/rustfmt/tree/v1.4.29), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.28] 2020-11-29
+
+### Changed
+
+- `rustc-ap-*` crates updated to v691.0.0
+- In the event of an invalid inner attribute on a `cfg_if` condition, rustfmt will now attempt to continue and format the imported modules. Previously rustfmt would emit the parser error about an inner attribute being invalid in this position, but for rustfmt's purposes the invalid attribute doesn't prevent nor impact module formatting.
+
+### Added
+
+- [`group_imports`][group-imports-config-docs] - a new configuration option that allows users to control the strategy used for grouping imports ([#4107](https://github.com/rust-lang/rustfmt/issues/4107))
+
+[group-imports-config-docs]: https://github.com/rust-lang/rustfmt/blob/v1.4.28/Configurations.md#group_imports
+
+### Fixed
+- Formatting of malformed derived attributes is no longer butchered. ([#3898](https://github.com/rust-lang/rustfmt/issues/3898), [#4029](https://github.com/rust-lang/rustfmt/issues/4029), [#4115](https://github.com/rust-lang/rustfmt/issues/4115), [#4545](https://github.com/rust-lang/rustfmt/issues/4545))
+- Correct indentation used in macro branches when `hard_tabs` is enabled. ([#4152](https://github.com/rust-lang/rustfmt/issues/4152))
+- Comments between the visibility modifier and item name are no longer dropped. ([#2781](https://github.com/rust-lang/rustfmt/issues/2781))
+- Comments preceding the assignment operator in type aliases are no longer dropped. ([#4244](https://github.com/rust-lang/rustfmt/issues/4244))
+- Comments between {`&` operator, lifetime, `mut` kw, type} are no longer dropped. ([#4245](https://github.com/rust-lang/rustfmt/issues/4245))
+- Comments between type bounds are no longer dropped. ([#4243](https://github.com/rust-lang/rustfmt/issues/4243))
+- Function headers are no longer dropped on foreign function items. ([#4288](https://github.com/rust-lang/rustfmt/issues/4288))
+- Foreign function blocks are no longer dropped. ([#4313](https://github.com/rust-lang/rustfmt/issues/4313))
+- `where_single_line` is no longer incorrectly applied to multiline function signatures that have no `where` clause. ([#4547](https://github.com/rust-lang/rustfmt/issues/4547))
+- `matches!` expressions with multiple patterns and a destructure pattern are now able to be formatted. ([#4512](https://github.com/rust-lang/rustfmt/issues/4512))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - n/a (superseded by [v1.4.29](#1429-2020-12-04))
+- **GitHub Release Binaries** - [Release v1.4.28](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.28)
+- **Build from source** - [Tag v1.4.28](https://github.com/rust-lang/rustfmt/tree/v1.4.28), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.27] 2020-11-16
+
+### Fixed
+
+- Leading comments in an extern block are no longer dropped (a bug that exists in v1.4.26). ([#4528](https://github.com/rust-lang/rustfmt/issues/4528))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2020-11-18`
+- **GitHub Release Binaries** - [Release v1.4.27](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.27)
+- **Build from source** - [Tag v1.4.27](https://github.com/rust-lang/rustfmt/tree/v1.4.27), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.26] 2020-11-14
+
+### Changed
+
+- Original comment indentation for trailing comments within an `if` is now taken into account when determining the indentation level to use for the trailing comment in formatted code. This does not modify any existing code formatted with rustfmt; it simply gives the programmer discretion to specify whether the comment is associated to the `else` block, or if the trailing comment is just a member of the `if` block. ([#1575](https://github.com/rust-lang/rustfmt/issues/1575), [#4120](https://github.com/rust-lang/rustfmt/issues/4120), [#4506](https://github.com/rust-lang/rustfmt/issues/4506)) 
+
+In this example the `// else comment` refers to the `else`:
+```rust
+// if comment
+if cond {
+    "if"
+// else comment
+} else {
+    "else"
+}
+```
+
+Whereas in this case the `// continue` comments are members of their respective blocks and do not refer to the `else` below.
+```rust
+if toks.eat_token(Token::Word("modify"))? && toks.eat_token(Token::Word("labels"))? {
+    if toks.eat_token(Token::Colon)? {
+        // ate the token
+    } else if toks.eat_token(Token::Word("to"))? {
+        // optionally eat the colon after to, e.g.:
+        // @rustbot modify labels to: -S-waiting-on-author, +S-waiting-on-review
+        toks.eat_token(Token::Colon)?;
+    } else {
+        // It's okay if there's no to or colon, we can just eat labels
+        // afterwards.
+    }
+    1 + 2;
+    // continue
+} else if toks.eat_token(Token::Word("label"))? {
+    // continue
+} else {
+    return Ok(None);
+}
+```
+
+### Fixed
+- Formatting of empty blocks with attributes which only contained comments is no longer butchered.([#4475](https://github.com/rust-lang/rustfmt/issues/4475), [#4467](https://github.com/rust-lang/rustfmt/issues/4467), [#4452](https://github.com/rust-lang/rustfmt/issues/4452#issuecomment-705886282), [#4522](https://github.com/rust-lang/rustfmt/issues/4522))
+- Indentation of trailing comments in non-empty extern blocks is now correct. ([#4120](https://github.com/rust-lang/rustfmt/issues/4120#issuecomment-696491872)) 
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2020-11-16`
+- **GitHub Release Binaries** - [Release v1.4.26](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.26)
+- **Build from source** - [Tag v1.4.26](https://github.com/rust-lang/rustfmt/tree/v1.4.26), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.25] 2020-11-10
+
+### Changed
+
+- Semicolons are no longer automatically inserted on trailing expressions in macro definition arms ([#4507](https://github.com/rust-lang/rustfmt/pull/4507)). This gives the programmer control and discretion over whether there should be semicolons in these scenarios so that potential expansion issues can be avoided.
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2020-11-14`
+- **GitHub Release Binaries** - [Release v1.4.25](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.25)
+- **Build from source** - [Tag v1.4.25](https://github.com/rust-lang/rustfmt/tree/v1.4.25), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.24] 2020-11-05
+
+### Changed
+
+- Block wrapped match arm bodies containing a single macro call expression are no longer flattened ([#4496](https://github.com/rust-lang/rustfmt/pull/4496)). This allows programmer discretion so that the block wrapping can be preserved in cases where needed to prevent issues in expansion, such as with trailing semicolons, and aligns with updated [Style Guide guidance](https://github.com/rust-dev-tools/fmt-rfcs/blob/master/guide/expressions.md#macro-call-expressions) for such scenarios.
+
+### Fixed
+- Remove useless `deprecated` attribute on a trait impl block in the rustfmt lib, as these now trigger errors ([rust-lang/rust/#78626](https://github.com/rust-lang/rust/pull/78626))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - Starting in `2020-11-09`
+- **GitHub Release Binaries** - [Release v1.4.24](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.24)
+- **Build from source** - [Tag v1.4.24](https://github.com/rust-lang/rustfmt/tree/v1.4.24), see instructions for how to [install rustfmt from source][install-from-source]
+
+## [1.4.23] 2020-10-30
+
+### Changed
+
+- Update `rustc-ap-*` crates to v686.0.0
+
+### Added
+- Initial support for formatting new ConstBlock syntax ([#4478](https://github.com/rust-lang/rustfmt/pull/4478))
+
+### Fixed
+- Handling of unclosed delimiter-only parsing errors in input files ([#4466](https://github.com/rust-lang/rustfmt/issues/4466))
+- Misc. minor parser bugs ([#4418](https://github.com/rust-lang/rustfmt/issues/4418) and [#4431](https://github.com/rust-lang/rustfmt/issues/4431))
+- Panic on nested tuple access ([#4355](https://github.com/rust-lang/rustfmt/issues/4355))
+- Unable to disable license template path via cli override ([#4487](https://github.com/rust-lang/rustfmt/issues/4487))
+- Preserve comments in empty statements [#4018](https://github.com/rust-lang/rustfmt/issues/4018))
+- Indentation on skipped code [#4398](https://github.com/rust-lang/rustfmt/issues/4398))
+
+### Install/Download Options
+- **crates.io package** - *pending*
+- **rustup (nightly)** - n/a (superseded by [v1.4.24](#1424-2020-11-05))
+- **GitHub Release Binaries** - [Release v1.4.23](https://github.com/rust-lang/rustfmt/releases/tag/v1.4.23)
+- **Build from source** - [Tag v1.4.23](https://github.com/rust-lang/rustfmt/tree/v1.4.23), see instructions for how to [install rustfmt from source][install-from-source]
+
+
+
+## [1.4.22] 2020-10-04
+
+### Changed
+
+- Update `rustc-ap-*` crates to v679.0.0
+- Add config option to allow control of leading match arm pipes
+- Support `RUSTFMT` environment variable in `cargo fmt` to run specified `rustfmt` instance
+
+### Fixed
+
+- Fix preservation of type aliases within extern blocks
+
+
+## [1.4.9] 2019-10-07
+
+### Changed
+
+- Update `rustc-ap-*` crates to 606.0.0.
+
+### Fixed
+
+- Fix aligning comments of different group
+- Fix flattening imports with a single `self`.
+- Fix removing attributes on function parameters.
+- Fix removing `impl` keyword from opaque type. 
+
+## [1.4.8] 2019-09-08
+
+### Changed
+
+- Update `rustc-ap-*` crates to 583.0.0.
+
+## [1.4.7] 2019-09-06
+
+### Added
+
+- Add `--config` command line option.
+
+### Changed
+
+- Update `rustc-ap-*` crates to 581.0.0.
+- rustfmt now do not warn against trailing whitespaces inside macro calls.
+
+### Fixed
+
+- Fix `merge_imports` generating invalid code.
+- Fix removing discriminant values on enum variants.
+- Fix modules defined inside `cfg_if!` not being formatted.
+- Fix minor formatting issues.
+
+## [1.4.6] 2019-08-28
+
+### Added
+
+- Add `--message-format` command line option to `cargo-fmt`.
+- Add `-l,--files-with-diff` command line option to `rustfmt`.
+- Add `json` emit mode. 
+
+### Fixed
+
+- Fix removing attributes on struct pattern's fields.
+- Fix non-idempotent formatting of match arm.
+- Fix `merge_imports` generating invalid code.
+- Fix imports with `#![macro_use]` getting reordered with `reorder_imports`.
+- Fix calculation of line numbers in checkstyle output.
+- Fix poor formatting of complex fn type.
+
+## [1.4.5] 2019-08-13
+
+### Fixed
+
+- Fix generating invalid code when formatting an impl block with const generics inside a where clause.
+- Fix adding a trailing space after a `dyn` keyword which is used as a macro argument by itself.
+
+## [1.4.4] 2019-08-06
+
+### Fixed
+
+- Fix `cargo fmt` incorrectly formatting crates that is not part of the workspace or the path dependencies.
+- Fix removing a trailing comma from a tuple pattern.
+
+## [1.4.3] 2019-08-02
+
+### Changed
+
+- Update `rustc-ap-*` crates to 546.0.0.
+
+### Fixed
+
+- Fix an underscore pattern getting removed.
+
+## [1.4.2] 2019-07-31
+
+### Changed
+
+- Explicitly require the version of `rustfmt-config_proc_macro` to be 0.1.2 or later.
+
+## [1.4.1] 2019-07-30
+
+### Changed
+
+- Update `rustc-ap-*` crates to 542.0.0.
+
+## [1.4.0] 2019-07-29
+
+### Added
+
+- Add new attribute `rustfmt::skip::attributes` to prevent rustfmt 
+from formatting an attribute #3665
+
+### Changed
+
+- Update `rustc-ap-*` crates to 541.0.0.
+- Remove multiple semicolons.
+
+## [1.3.3] 2019-07-15
+
+### Added
+
+- Add `--manifest-path` support to `cargo fmt` (#3683).
+
+### Fixed
+
+- Fix `cargo fmt -- --help` printing nothing (#3620).
+- Fix inserting an extra comma (#3677).
+- Fix incorrect handling of CRLF with `file-lines` (#3684).
+- Fix `print-config=minimal` option (#3687).
+
+## [1.3.2] 2019-07-06
+
+### Fixed
+
+- Fix rustfmt crashing when `await!` macro call is used in a method chain.
+- Fix rustfmt not recognizing a package whose name differs from its directory's name.
+
+## [1.3.1] 2019-06-30
+
+### Added
+
+- Implement the `Display` trait on the types of `Config`.
+
+### Changed
+
+- `ignore` configuration option now only supports paths separated by `/`. Windows-style paths are not supported.
+- Running `cargo fmt` in a sub-directory of a project is now supported.
+
+### Fixed
+
+- Fix bugs that may cause rustfmt to crash.
+
+## [1.3.0] 2019-06-09
+
+### Added
+
+- Format modules defined inside `cfg_if` macro calls #3600
+
+### Changed
+
+- Change option `format_doc_comment` to `format_code_in_doc_comment`.
+- `use_small_heuristics` changed to be an enum and stabilised. Configuration
+  options are now ready for 1.0.
+- Stabilise `fn_args_density` configuration option and rename it to `fn_args_layout` #3581
+- Update `rustc-ap-*` crates to 486.0.0
+- Ignore sub-modules when skip-children is used #3607
+- Removed bitrig support #3608
+
+### Fixed
+
+- `wrap_comments` should not imply `format_doc_comments` #3535
+- Incorrect handling of const generics #3555
+- Add the handling for `vec!` with paren inside macro #3576
+- Format trait aliases with where clauses #3586
+- Catch panics from the parser while rewriting macro calls #3589
+- Fix erasing inner attributes in struct #3593
+- Inline the attribute with its item even with the `macro_use` attribute or when `reorder_imports` is disabled #3598
+- Fix the bug add unwanted code to impl #3602
+
+## [1.2.2] 2019-04-24
+
+### Fixed
+
+- Fix processing of `ignore` paths #3522
+- Attempt to format attributes if only they exist #3523
+
+## [1.2.1] 2019-04-18
+
+### Added
+
+- Add `--print-config current` CLI option b473e65
+- Create GitHub [page](https://rust-lang.github.io/rustfmt/) for Configuration.md #3485
+
+### Fixed
+
+- Keep comment appearing between parameter's name and its type #3491
+- Do not delete semicolon after macro call with square brackets #3500
+- Fix `--version` CLI option #3506
+- Fix duplication of attributes on a match arm's body #3510
+- Avoid overflowing item with attributes #3511
+
+## [1.2.0] 2019-03-27
+
+### Added
+
+- Add new attribute `rustfmt::skip::macros` to prevent rustfmt from formatting a macro #3454
+
+### Changed
+
+- Discard error report in silent_emitter #3466
+
+### Fixed
+
+- Fix bad performance on deeply nested binary expressions #3467
+- Use BTreeMap to guarantee consistent ordering b4d4b57
+
+## [1.1.1] 2019-03-21
+
+### Fixed
+
+- Avoid panic on macro inside deeply nested block c9479de
+- Fix line numbering in missed spans and handle file_lines in edge cases cdd08da
+- Fix formatting of async blocks 1fa06ec
+- Avoid duplication on the presence of spaces between macro name and `!` #3464
+
+## [1.1.0] 2019-03-17
+
+### Added
+
+- Add `inline_attribute_width` configuration option to write an item and its attribute on the same line if their combined width is below a threshold #3409
+- Support `const` generics f0c861b
+- Support path clarity module #3448
+
+### Changed
+
+- Align loop and while formatting 7d9a2ef
+- Support `EmitMode::ModifiedLines` with stdin input #3424
+- Update `rustc-ap-*` crates to 407.0.0
+- Remove trailing whitespaces in missing spans 2d5bc69
+
+### Fixed
+
+- Do not remove comment in the case of no arg 8e3ef3e
+- Fix `Ident of macro+ident gets duplicated` error 40ff078
+- Format the if expression at the end of the block in a single line 5f3dfe6
+
+## [1.0.3] 2019-02-14
+
+### Added
+
+- Point unstable options to tracking issues 412dcc7
+
+### Changed
+
+- Update `rustc-ap-*` crates to 373.0.0
+
+## [1.0.2] 2019-02-12
+
+### Added
+
+- Add a [section](https://github.com/rust-lang/rustfmt/blob/ae331be/Contributing.md#version-gate-formatting-changes) to the Contributing.md file about version-gating formatting changes 36e2cb0
+- Allow specifying package with `-p` CLI option a8d2591
+- Support `rustfmt::skip` on imports #3289
+- Support global `rustfmt.toml` to be written in user config directory #3280
+- Format visibility on trait alias 96a3df3
+
+### Changed
+
+- Do not modify original source code inside macro call #3260
+- Recognize strings inside comments in order to avoid indenting them baa62c6
+- Use Unicode-standard char width to wrap comments or strings a01990c
+- Change new line point in the case of no args #3294
+- Use the same formatting rule between functions and macros #3298
+- Update rustc-ap-rustc_target to 366.0.0, rustc-ap-syntax to 366.0.0, and rustc-ap-syntax_pos to 366.0.0
+
+### Fixed
+
+- rewrite_comment: fix block fallback when failing to rewrite an itemized block ab7f4e1
+- Catch possible tokenizer panics #3240
+- Fix macro indentation on Windows #3266
+- Fix shape when formatting return or break expr on statement position #3259
+- rewrite_comment: fix block fallback when failing to rewrite an itemized block
+- Keep leading double-colon to respect the 2018 edition of rust's paths a2bfc02
+- Fix glob and nested global imports 2125ad2
+- Do not force trailing comma when using mixed layout #3306
+- Prioritize `single_line_fn` and `empty_item_single_line` over `brace_style` #3308
+- Fix `internal error: left behind trailing whitespace` with long lines c2534f5
+- Fix attribute duplication #3325
+- Fix formatting of strings within a macro 813aa79
+- Handle a macro argument with a single keyword 9a7ea6a
+
+## [1.0.1] 2018-12-09
+
+### Added
+
+- Add a `version` option 378994b
+
+### Changed
+
+- End expressions like return/continue/break with a semicolon #3223
+- Update rustc-ap-rustc_target to 306.0.0, rustc-ap-syntax to 306.0.0, and rustc-ap-syntax_pos to 306.0.0
+
+### Fixed
+
+- Allow to run a rustfmt command from cargo-fmt even when there is no target a2da636
+- Fix `un-closed delimiter` errors when formatting break labels 40174e9
+
+## [1.0.0] 2018-11-19
+
+### Changed
+
+- Preserve possibly one whitespace for brace macros 1a3bc79
+- Prefer to break arguments over putting output type on the next line 1dd54e6
+
+## [0.99.9] 2018-11-15
+
+### Changed
+
+- Update rustc-ap-rustc_target to 297.0.0, rustc-ap-syntax to 297.0.0, to rustc-ap-syntax_pos to 297.0.0
+- Don't align comments on `extern crate`s dd7add7
+
+## [0.99.8] 2018-11-14
+
+### Added
+
+- Add `overflow_delimited_expr` config option to more aggressively allow overflow #3175
+
+### Fixed
+
+- Fix the logic for retaining a comment before the arrow in a match #3181
+- Do not wrap comments in doctest to avoid failing doctest runs #3183
+- Fix comment rewriting that was wrapping code into a line comment #3188
+- Fix formatting of unit-struct with `where`-clause #3200
+
+## [0.99.7] 2018-11-07
+
+### Changed
+
+- Force a newline after the `if` condition if there is a different indentation level #3109
+- Use correct width when formatting type on local statement #3126
+- Treat crates non-alphabetically when ordering 799005f
+- Fix formatting of code that is annotated with rustfmt::skip #3113
+- Stabilize `edition` configuration option 9c3ae2d
+- cargo-fmt: detect Rust edition in use #3129
+- Trim the indentation on macros which heuristically appear to use block-style indentation #3178
+
+### Fixed
+
+- Do not remove path disambiugator inside macro #3142
+- Improve handling of Windows newlines #3141
+- Fix alignment of a struct's fields (`struct_field_align_threshold` option) with the Visual `indent_style` #3165
+- Fix a bug in formatting markdown lists within comments #3172
+
+## [0.99.6] 2018-10-18
+
+### Added
+
+- Add `enum_discrim_align_threshold` option to vertically align enum discriminants cc22869
+- Add `println!`-like heuristic to the `fail` attribute #3067
+- Handle itemized items inside comments #3083
+- Add `format_doc_comments` configuration option to control the formatting of code snippets inside comments #3089
+
+### Changed
+
+- Makes brace behavior consistent with empty bodies for traits and impls 2727d41
+- Consider a multi-lined array as a block-like expression #3969
+- Improve formatting of strings #3073
+- Get rid of extra commas in Visual struct literal formatting #3077
+- Update rustc-ap-rustc_target to 274.0.0, rustc-ap-syntax to 274.0.0, and rustc-ap-syntax_pos to 274.0.0
+- Format macro calls with item-like arguments #3080
+- Avoid control flow expressions conditions to go multi line ef59b34
+- Simplify multi-lining binop expressions #3101
+
+### Fixed
+
+- Do not format a code block in documentation if it is annotated with ignore or text 2bcc3a9
+- Fix inconsistent overflow behavior in Visual style #3078
+- Fix corner cases of the string formatting implementation #3083
+- Do not add parens around lifetimes 0ac68c9
+- Catch parser panic in format_snippet 8c4e92a
+
+## [0.99.5] 2018-09-25
+
+### Added
+
+- Handle leading module separator for 2018 Edition #2952
+- Add configuration option `normalize_doc_attributes`: convert doc attributes to comments #3002
+
+### Changed
+
+- Accept 2015 and 2018 instead of Edition2015 and Edition2018 for edition option eec7436
+- Support platforms without a timer 46e2a2e
+- Update rustc-ap-rustc_target to 263.0.0, rustc-ap-syntax to 263.0.0, and rustc-ap-syntax_pos to 263.0.0
+
+### Fixed
+
+- Format of attributes with commas #2971
+- Fix optional arg condensing #2972
+- Improve formatting of long function parameters #2981
+- Fix formatting of raw string literals #2983
+- Handle chain with try operators with spaces #2986
+- Use correct shape in Visual tuple rewriting #2987
+- Impove formatting of arguments with `visual_style = "Visual"` option #2988
+- Change `print_diff` to output the correct line number 992b179
+- Propagate errors about failing to rewrite a macro 6f318e3
+- Handle formatting of long function signature #3010
+- Fix indent computation of a macro with braces c3edf6d
+- Format generics on associated types #3035
+- Incorrect indentation of multiline block match expression #3042
+- Fix bug in import where two consecutive module separators were possible 98a0ef2
+- Prevent right-shifting of block comments with bare lines 5fdb6db
+
+## [0.99.4] 2018-08-27
+
+### Added
+
+- Handle formatting of underscore imports #2951
+- Handle formatting of try blocks #2965
+
+### Changed
+
+- Update rustc-ap-rustc_target to 237.0.0, rustc-ap-syntax to 237.0.0, and rustc-ap-syntax_pos to 237.0.0 ca19c9a
+- Consider `dev` channel as nightly for unstable features #2948
+
+### Fixed
+
+- Fix formatting of patterns with ellipsis # 2942
+
+## [0.99.3] 2018-08-23
+
+### Added
+
+- Use path attribute when searching for modules #2901
+- Expose FileLines JSON representation to allow external libraries to use the file_lines option #2915
+
+### Changed
+
+- Replace '--conifig-help' with '--config=help' cb10e06
+- Improve formatting of slice patterns #2912
+
+### Fixed
+
+- Format chains with comment #2899
+- Fix indentation of formatted macro body #2920
+- Fix indentation of block comments f23e6aa
+
+## [0.99.2] 2018-08-07
+
+### Changed
+
+- Update rustc-ap-rustc_target to 218.0.0, rustc-ap-syntax to 218.0.0, and rustc-ap-syntax_pos to 218.0.0 5c9a2b6
+- Combine function-like attributes #2900
+
+### Fixed
+
+- Explicitly handle semicolon after the item in statement position d96e3ca
+- Fix parsing '#'-hiding of rustdoc 2eca09e
+
+## [0.99.1] 2018-08-04
+
+### Fixed
+
+- fix use statements ordering when a number is present 1928ae7
+
+## [0.99.0] 2018-08-03
+
+- 1.0 RC release
+
+### Changed
+
+- Clarification in README.md 30fe66b
+
+## [0.9.0] 2018-08-01
+
+### Added
+
+- Handle raw identifiers 3027c21
+- Format async closure 60ce411
+- Add max_width option for all heuristics c2ae39e
+- Add config option `format_macro_matchers` to format the metavariable matching patterns in macros 79c5ee8
+- Add config option `format_macro_bodies` to format the bodies of macros 79c5ee8
+- Format exitential type fc307ff
+- Support raw identifiers in struct expressions f121b1a
+- Format Async block and async function 0b25f60
+
+### Changed
+
+- Update rustc-ap-rustc_target to 211.0.0, rustc-ap-syntax to 211.0.0, and rustc-ap-syntax_pos to 211.0.0
+- Put each nested import on its own line while putting non-nested imports on the same line as much as possible 42ab258
+- Respect `empty_item_single_line` config option when formatting empty impls. Put the `where` on its own line to improve readability #2771
+- Strip leading `|` in match arm patterns 1d4b988
+- Apply short function call heuristic to attributes 3abebf9
+- Indent a match guard if the pattern is multiline be4d37d
+- Change default newline style to `Native` 9d8f381
+- Improve formatting of series of binop expressions a4cdb68
+- Trigger an internal error if we skip formatting due to a lost comment b085113
+- Refactor chain formatting #2838
+
+### Fixed
+
+- Do not insert spaces around braces with empty body or multiple lines 2f65852
+- Allow using mixed layout with comments #2766
+- Handle break labels #2726
+- fix rewrite_string when a line feed is present 472a2ed
+- Fix an anomaly with comments and array literals b28a0cd
+- Check for comments after the `=>` in a match arm 6899471
+
+## [0.8.0,0.8.1,0.8.2] 2018-05-28
+
+### Added
+
+- Use scoped attributes for skip attribute https://github.com/rust-lang/rustfmt/pull/2703
+
+### Changed
+
+- Comment options `wrap_comments` and `normalize_comments` are reverted back to unstable 416bc4c
+- Stabilise `reorder_imports` and `reorder_modules` options 7b6d2b4
+- Remove `spaces_within_parens_and_brackets` option d726492
+- Stabilise shorthand options: `use_try_shorthand`, `use_field_init_shorthand`, and `force_explicit_abi` 8afe367
+- Stabilise `remove_nested_parens` and set default to true a70f716
+- Unstabilise `unstable_features` dd9c15a
+- Remove `remove_blank_lines_at_start_or_end_of_block` option 2ee8b0e
+- Update rustc-ap-syntax to 146.0.0 and rustc-ap-rustc_target to 146.0.0 2c275a2
+- Audit the public API #2639
+
+### Fixed
+
+- Handle code block in doc comment without rust prefix f1974e2
+
+## [0.7.0] 2018-05-14
+
+### Added
+
+- Add integration tests against crates in the rust-lang-nursery c79f39a
+
+### Changed
+
+- Update rustc-ap-syntax to 128.0.0 and ustc-ap-rustc_target to 128.0.0 195395f
+- Put operands on its own line when each fits in a single line f8439ce
+- Improve CLI options 55ac062 1869888 798bffb 4d9de48 eca7796 8396da1 5d9f5aa
+
+### Fixed
+
+- Use correct line width for list attribute 61a401a
+- Avoid flip-flopping impl items when reordering them 37c216c
+- Formatting breaks short lines when max_width is less than 100 9b36156
+- Fix variant "Mixed" of imports_layout option 8c8676c
+- Improve handling of long lines f885039
+- Fix up lines exceeding max width 51c07f4
+- Fix handling of modules in non_modrs_mods style cf573e8
+- Do not duplicate attributes on use items e59ceaf
+- Do not insert an extra brace in macros with native newlines 4c9ef93
+
+## [0.6.1] 2018-05-01
+
+### Changed
+
+- Change the default value of imports_indent to IndentStyle::Block https://github.com/rust-lang/rustfmt/pull/2662
+
+### Fixed
+
+- Handle formatting of auto traits 5b5a72c
+- Use consistent formatting for empty enum and struct https://github.com/rust-lang/rustfmt/pull/2656
+
+## [0.6.0] 2018-04-20
+
+### Changed
+
+- Improve public API 8669004
+
+## [0.5.0] 2018-04-20
+
+### Added
+
+- Add `verbose-diff` CLI option 5194984
+
+### Changed
+
+- Update rustc-ap-syntax to 103.0.0 dd807e2
+- Refactor to make a sensible public API ca610d3
+
+### Fixed
+
+- Add spaces between consecutive `..` `..=` 61d29eb
+
+## [0.4.2] 2018-04-12
+
+### Added
+
+- Handle binary operators and lifetimes 0fd174d
+- Add reorder_impl_items config option 94f5a05
+- Add `--unstable-features` CLI option to list unstable options from the `--help` output 8208f8a
+- Add merge_imports config option 5dd203e
+
+### Changed
+
+- Format macro arguments with vertical layout ec71459
+- Reorder imports by default 164cf7d
+- Do not collapse block around expr with condition on match arm 5b9b7d5
+- Use vertical layout for complex attributes c77708f
+- Format array using heuristics for function calls 98c6f7b
+- Implement stable ordering for impl items with the the following item priority: type, const, macro, then method fa80ddf
+- Reorder imports by default 164cf7d
+- Group `extern crate` by default 3a138a2
+- Make `error_on_line_overflow` false by default f146711
+- Merge imports with the same prefix into a single nested import 1954513
+- Squash the various 'reorder imports' option into one 911395a
+
+### Fixed
+
+- Print version is missing the channel ca6fc67
+- Do not add the beginning vert to the match arm 1e1d9d4
+- Follow indent style config when formatting attributes efd295a
+- Do not insert newline when item is empty a8022f3
+- Do not indent or unindent inside string literal ec1907b
+
+## [0.4.1] 2018-03-16
+
+### Added
+
+- Add `ignore` configuration option.
+- Add `license_template_path` configuration option.
+- Format `lazy_static!`.
+
+### Fixed
+
+- Fix formatting bugs.
+- Fix setting `reorder_modules` removing inline modules.
+- Format attributes on block expressions.
+- Support `dyn trait` syntax.
+- Support multiple patterns in `if let` and `while let`.
+- Support a pattern with parentheses.
+
+## [0.4.0] 2018-03-02
+
+### Changed
+
+- Do not print verbose outputs when formatting with stdin.
+- Preserve trailing whitespaces in doc comments.
+- Scale the values of width heuristics by `max_width`.
+
+### Fixed
+
+- Do not reorder items with `#[macro_use]`.
+- Fix formatting bugs.
+- Support the beginning `|` on a match arm.
+
+## [0.3.8] 2018-02-04
+
+### Added
+
+- Format (or at least try to format) `macro_rules!`.
+
+## [0.3.7] 2018-02-01
+
+### Added
+
+- Add `use_field_init_shorthand` config option.
+- Add `reorder_modules` configuration option.
+
+## [0.3.6] 2018-01-18
+
+### Fixed
+
+- Fix panicking on formatting certain macros (#2371).
+
+## [0.3.5] 2018-01-15
+
+### Changed
+
+- Format code block in comments when `wrap_comments` is set to `true`.
+- Remove `same_line_attributes` configuration option.
+- Rename `git-fmt` to `git-rustfmt`.
+
+### Fixed
+
+- Rustup to `rustc 1.25.0-nightly (e6072a7b3 2018-01-13)`.
+- Fix formatting bugs.
+
+## [0.3.4] 2017-12-23
+
+### Added
+
+- Add `--version` flag to `cargo-fmt`, allow `cargo fmt --version`.
+
+### Fixed
+
+- Rustup to `rustc 1.24.0-nightly (5165ee9e2 2017-12-22)`.
+
+## [0.3.3] 2017-12-22
+
+### Added
+
+- Format trait aliases.
+
+### Changed
+
+- `cargo fmt` will format every workspace member.
+
+### Fixed
+
+- Rustup to `rustc 1.24.0-nightly (250b49205 2017-12-21)`
+- Fix formatting bugs.
+
+## [0.3.2] 2017-12-15
+
+### Changed
+
+- Warn when unknown configuration option is used.
+
+### Fixed
+
+- Rustup to `rustc 1.24.0-nightly (0077d128d 2017-12-14)`.
+
+## [0.3.1] 2017-12-11
+
+### Added
+
+- Add `error_on_unformatted` configuration option.
+- Add `--error-on-unformatted` command line option.
+
+### Changed
+
+- Do not report formatting errors on comments or strings by default.
+- Rename `error_on_line_overflow_comments` to `error_on_unformatted`.
+
+### Fixed
+
+- Fix formatting bugs.
+- Fix adding a trailing whitespace inside code block when `wrap_comments = true`.
+
+## [0.3.0] 2017-12-11
+
+### Added
+
+- Support nested imports.
+
+### Changed
+
+- Do not report errors on skipped items.
+- Do not format code block inside comments when `wrap_comments = true`.
+- Keep vertical spaces between items within range.
+- Format `format!` and its variants using compressed style.
+- Format `write!` and its variants using compressed style.
+- Format **simple** array using compressed style.
+
+### Fixed
+
+- Fix `rustfmt --package package_name` not working properly.
+- Fix formatting bugs.
+
+## [0.2.17] 2017-12-03
+
+### Added
+
+- Add `blank_lines_lower_bound` and `blank_lines_upper_bound` configuration options.
+
+### Changed
+
+- Combine configuration options related to width heuristic into `width_heuristic`.
+- If the match arm's body is `if` expression, force to use block.
+
+### Fixed
+
+- Fix `cargo fmt --all` being trapped in an infinite loop.
+- Fix many formatting bugs.
+
+### Removed
+
+- Remove legacy configuration options.
+
+## [0.2.16] 2017-11-21
+
+### Added
+
+- Remove empty lines at the beginning of the file.
+- Soft wrapping on doc comments.
+
+### Changed
+
+- Break before `|` when using multiple lines for match arm patterns.
+- Combine `control_style`, `where_style` and `*_indent` config options into `indent_style`.
+- Combine `item_brace_style` and `fn_brace_style` config options into `brace_style`.
+- Combine config options related spacing around colons into `space_before_colon` and `space_after_colon`.
+
+### Fixed
+
+- Fix many bugs.
+
+## [0.2.15] 2017-11-08
+
+### Added
+
+- Add git-fmt tool
+- `where_single_line` configuration option.
+
+### Changed
+
+- Rename `chain_one_line_max` to `chain_width`.
+- Change the suffix of indent-related configuration options to `_indent`.
+
+## [0.2.14] 2017-11-06
+
+### Fixed
+
+- Rustup to the latest nightly.
+
+## [0.2.13] 2017-10-30
+
+### Fixed
+
+- Rustup to the latest nightly.
+
+## [0.2.12] 2017-10-29
+
+### Fixed
+
+- Fix a bug that `cargo fmt` hangs forever.
+
+## [0.2.11] 2017-10-29
+
+### Fixed
+
+- Fix a bug that `cargo fmt` crashes.
+
+## [0.2.10] 2017-10-28
+
+## [0.2.9] 2017-10-16
+
+## [0.2.8] 2017-09-28
+
+## [0.2.7] 2017-09-21
+
+### Added
+
+- `binop_separator` configuration option (#1964).
+
+### Changed
+
+- Use horizontal layout for function call with a single argument.
+
+### Fixed
+
+- Fix panicking when calling `cargo fmt --all` (#1963).
+- Refactorings & faster rustfmt.
+
+## [0.2.6] 2017-09-14
+
+### Fixed
+
+- Fix a performance issue with nested block (#1940).
+- Refactorings & faster rustfmt.
+
+## [0.2.5] 2017-08-31
+
+### Added
+
+- Format and preserve attributes on statements (#1933).
+
+### Fixed
+
+- Use getters to access `Span` fields (#1899).
+
+## [0.2.4] 2017-08-30
+
+### Added
+
+- Add support for `Yield` (#1928).
+
+## [0.2.3] 2017-08-30
+
+### Added
+
+- `multiline_closure_forces_block` configuration option (#1898).
+- `multiline_match_arm_forces_block` configuration option (#1898).
+- `merge_derives` configuration option (#1910).
+- `struct_remove_empty_braces` configuration option (#1930).
+- Various refactorings.
+
+### Changed
+
+- Put single-lined block comments on the same line with list-like structure's item (#1923).
+- Preserve blank line between doc comment and attribute (#1925).
+- Put the opening and the closing braces of enum and struct on the same line, even when `item_brace_style = "AlwaysNextLine"` (#1930).
+
+### Fixed
+
+- Format attributes on `ast::ForeignItem` and take max width into account (#1916).
+- Ignore empty lines when calculating the shortest indent width inside macro with braces (#1918).
+- Handle tabs properly inside macro with braces (#1918).
+- Fix a typo in `compute_budgets_for_args()` (#1924).
+- Recover comment between keyword (`impl` and `trait`) and `{` which used to get removed (#1925).
+
+
+[install-from-source]: https://github.com/rust-lang/rustfmt#installing-from-source
diff --git a/src/tools/rustfmt/CODE_OF_CONDUCT.md b/src/tools/rustfmt/CODE_OF_CONDUCT.md
new file mode 100644
index 0000000000000..d70b2b52aca1b
--- /dev/null
+++ b/src/tools/rustfmt/CODE_OF_CONDUCT.md
@@ -0,0 +1,40 @@
+# The Rust Code of Conduct
+
+A version of this document [can be found online](https://www.rust-lang.org/conduct.html).
+
+## Conduct
+
+**Contact**: [rust-mods@rust-lang.org](mailto:rust-mods@rust-lang.org)
+
+* We are committed to providing a friendly, safe and welcoming environment for all, regardless of level of experience, gender identity and expression, sexual orientation, disability, personal appearance, body size, race, ethnicity, age, religion, nationality, or other similar characteristic.
+* On IRC, please avoid using overtly sexual nicknames or other nicknames that might detract from a friendly, safe and welcoming environment for all.
+* Please be kind and courteous. There's no need to be mean or rude.
+* Respect that people have differences of opinion and that every design or implementation choice carries a trade-off and numerous costs. There is seldom a right answer.
+* Please keep unstructured critique to a minimum. If you have solid ideas you want to experiment with, make a fork and see how it works.
+* We will exclude you from interaction if you insult, demean or harass anyone. That is not welcome behavior. We interpret the term "harassment" as including the definition in the <a href="http://citizencodeofconduct.org/">Citizen Code of Conduct</a>; if you have any lack of clarity about what might be included in that concept, please read their definition. In particular, we don't tolerate behavior that excludes people in socially marginalized groups.
+* Private harassment is also unacceptable. No matter who you are, if you feel you have been or are being harassed or made uncomfortable by a community member, please contact one of the channel ops or any of the [Rust moderation team][mod_team] immediately. Whether you're a regular contributor or a newcomer, we care about making this community a safe place for you and we've got your back.
+* Likewise any spamming, trolling, flaming, baiting or other attention-stealing behavior is not welcome.
+
+## Moderation
+
+
+These are the policies for upholding our community's standards of conduct. If you feel that a thread needs moderation, please contact the [Rust moderation team][mod_team].
+
+1. Remarks that violate the Rust standards of conduct, including hateful, hurtful, oppressive, or exclusionary remarks, are not allowed. (Cursing is allowed, but never targeting another user, and never in a hateful manner.)
+2. Remarks that moderators find inappropriate, whether listed in the code of conduct or not, are also not allowed.
+3. Moderators will first respond to such remarks with a warning.
+4. If the warning is unheeded, the user will be "kicked," i.e., kicked out of the communication channel to cool off.
+5. If the user comes back and continues to make trouble, they will be banned, i.e., indefinitely excluded.
+6. Moderators may choose at their discretion to un-ban the user if it was a first offense and they offer the offended party a genuine apology.
+7. If a moderator bans someone and you think it was unjustified, please take it up with that moderator, or with a different moderator, **in private**. Complaints about bans in-channel are not allowed.
+8. Moderators are held to a higher standard than other community members. If a moderator creates an inappropriate situation, they should expect less leeway than others.
+
+In the Rust community we strive to go the extra step to look out for each other. Don't just aim to be technically unimpeachable, try to be your best self. In particular, avoid flirting with offensive or sensitive issues, particularly if they're off-topic; this all too often leads to unnecessary fights, hurt feelings, and damaged trust; worse, it can drive people away from the community entirely.
+
+And if someone takes issue with something you said or did, resist the urge to be defensive. Just stop doing what it was they complained about and apologize. Even if you feel you were misinterpreted or unfairly accused, chances are good there was something you could've communicated better — remember that it's your responsibility to make your fellow Rustaceans comfortable. Everyone wants to get along and we are all here first and foremost because we want to talk about cool technology. You will find that people will be eager to assume good intent and forgive as long as you earn their trust.
+
+The enforcement policies listed above apply to all official Rust venues; including official IRC channels (#rust, #rust-internals, #rust-tools, #rust-libs, #rustc, #rust-beginners, #rust-docs, #rust-community, #rust-lang, and #cargo); GitHub repositories under rust-lang, rust-lang-nursery, and rust-lang-deprecated; and all forums under rust-lang.org (users.rust-lang.org, internals.rust-lang.org). For other projects adopting the Rust Code of Conduct, please contact the maintainers of those projects for enforcement. If you wish to use this code of conduct for your own project, consider explicitly mentioning your moderation policy or making a copy with your own moderation policy so as to avoid confusion.
+
+*Adapted from the [Node.js Policy on Trolling](http://blog.izs.me/post/30036893703/policy-on-trolling) as well as the [Contributor Covenant v1.3.0](https://www.contributor-covenant.org/version/1/3/0/).*
+
+[mod_team]: https://www.rust-lang.org/team.html#Moderation-team
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diff --git a/src/tools/rustfmt/Cargo.toml b/src/tools/rustfmt/Cargo.toml
new file mode 100644
index 0000000000000..3a04fb28f7cbf
--- /dev/null
+++ b/src/tools/rustfmt/Cargo.toml
@@ -0,0 +1,67 @@
+[package]
+
+name = "rustfmt-nightly"
+version = "1.4.37"
+authors = ["Nicholas Cameron <ncameron@mozilla.com>", "The Rustfmt developers"]
+description = "Tool to find and fix Rust formatting issues"
+repository = "https://github.com/rust-lang/rustfmt"
+readme = "README.md"
+license = "Apache-2.0/MIT"
+build = "build.rs"
+categories = ["development-tools"]
+edition = "2018"
+
+[[bin]]
+name = "rustfmt"
+path = "src/bin/main.rs"
+
+[[bin]]
+name = "cargo-fmt"
+path = "src/cargo-fmt/main.rs"
+
+[[bin]]
+name = "rustfmt-format-diff"
+path = "src/format-diff/main.rs"
+
+[[bin]]
+name = "git-rustfmt"
+path = "src/git-rustfmt/main.rs"
+
+[features]
+default = ["cargo-fmt", "rustfmt-format-diff"]
+cargo-fmt = []
+rustfmt-format-diff = []
+generic-simd = ["bytecount/generic-simd"]
+
+[dependencies]
+itertools = "0.8"
+toml = "0.5"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+unicode-segmentation = "1.0.0"
+regex = "1.0"
+term = "0.6"
+diff = "0.1"
+log = "0.4.14"
+env_logger = "0.6"
+getopts = "0.2"
+derive-new = "0.5"
+cargo_metadata = "0.8"
+bytecount = "0.6"
+unicode-width = "0.1.5"
+unicode_categories = "0.1.1"
+dirs = "2.0.1"
+ignore = "0.4.11"
+annotate-snippets = { version = "0.8", features = ["color"] }
+structopt = "0.3"
+rustfmt-config_proc_macro = { version = "0.2", path = "config_proc_macro" }
+lazy_static = "1.0.0"
+anyhow = "1.0"
+thiserror = "1.0"
+
+# A noop dependency that changes in the Rust repository, it's a bit of a hack.
+# See the `src/tools/rustc-workspace-hack/README.md` file in `rust-lang/rust`
+# for more information.
+rustc-workspace-hack = "1.0.0"
+
+# Rustc dependencies are loaded from the sysroot, Cargo doesn't know about them.
diff --git a/src/tools/rustfmt/Configurations.md b/src/tools/rustfmt/Configurations.md
new file mode 100644
index 0000000000000..37cb7474130c8
--- /dev/null
+++ b/src/tools/rustfmt/Configurations.md
@@ -0,0 +1,2773 @@
+# Configuring Rustfmt
+
+Rustfmt is designed to be very configurable. You can create a TOML file called `rustfmt.toml` or `.rustfmt.toml`, place it in the project or any other parent directory and it will apply the options in that file. If none of these directories contain such a file, both your home directory and a directory called `rustfmt` in your [global config directory](https://docs.rs/dirs/1.0.4/dirs/fn.config_dir.html) (e.g. `.config/rustfmt/`) are checked as well.
+
+A possible content of `rustfmt.toml` or `.rustfmt.toml` might look like this:
+
+```toml
+indent_style = "Block"
+reorder_imports = false
+```
+
+Each configuration option is either stable or unstable.
+Stable options can be used directly, while unstable options are opt-in.
+To enable unstable options, set `unstable_features = true` in `rustfmt.toml` or pass `--unstable-features` to rustfmt.
+
+# Configuration Options
+
+Below you find a detailed visual guide on all the supported configuration options of rustfmt:
+
+## `array_width` 
+
+Maximum width of an array literal before falling back to vertical formatting.
+
+- **Default value**: `60`
+- **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
+- **Stable**: Yes
+
+By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `array_width` will take precedence. 
+
+See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
+
+## `attr_fn_like_width` 
+
+Maximum width of the args of a function-like attributes before falling back to vertical formatting.
+
+- **Default value**: `70`
+- **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
+- **Stable**: Yes
+
+By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `attr_fn_like_width` will take precedence. 
+
+See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
+
+## `binop_separator`
+
+Where to put a binary operator when a binary expression goes multiline.
+
+- **Default value**: `"Front"`
+- **Possible values**: `"Front"`, `"Back"`
+- **Stable**: No (tracking issue: #3368)
+
+#### `"Front"` (default):
+
+```rust
+fn main() {
+    let or = foofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoo
+        || barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar;
+
+    let sum = 123456789012345678901234567890
+        + 123456789012345678901234567890
+        + 123456789012345678901234567890;
+
+    let range = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        ..bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+}
+```
+
+#### `"Back"`:
+
+```rust
+fn main() {
+    let or = foofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoo ||
+        barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar;
+
+    let sum = 123456789012345678901234567890 +
+        123456789012345678901234567890 +
+        123456789012345678901234567890;
+
+    let range = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+}
+```
+
+## `blank_lines_lower_bound`
+
+Minimum number of blank lines which must be put between items. If two items have fewer blank lines between
+them, additional blank lines are inserted.
+
+- **Default value**: `0`
+- **Possible values**: *unsigned integer*
+- **Stable**: No (tracking issue: #3382)
+
+### Example
+Original Code (rustfmt will not change it with the default value of `0`):
+
+```rust
+#![rustfmt::skip]
+
+fn foo() {
+    println!("a");
+}
+fn bar() {
+    println!("b");
+    println!("c");
+}
+```
+
+#### `1`
+```rust
+fn foo() {
+
+    println!("a");
+}
+
+fn bar() {
+
+    println!("b");
+
+    println!("c");
+}
+```
+
+
+## `blank_lines_upper_bound`
+
+Maximum number of blank lines which can be put between items. If more than this number of consecutive empty
+lines are found, they are trimmed down to match this integer.
+
+- **Default value**: `1`
+- **Possible values**: any non-negative integer
+- **Stable**: No (tracking issue: #3381)
+
+### Example
+Original Code:
+
+```rust
+#![rustfmt::skip]
+
+fn foo() {
+    println!("a");
+}
+
+
+
+fn bar() {
+    println!("b");
+
+
+    println!("c");
+}
+```
+
+#### `1` (default):
+```rust
+fn foo() {
+    println!("a");
+}
+
+fn bar() {
+    println!("b");
+
+    println!("c");
+}
+```
+
+#### `2`:
+```rust
+fn foo() {
+    println!("a");
+}
+
+
+fn bar() {
+    println!("b");
+
+
+    println!("c");
+}
+```
+
+See also: [`blank_lines_lower_bound`](#blank_lines_lower_bound)
+
+## `brace_style`
+
+Brace style for items
+
+- **Default value**: `"SameLineWhere"`
+- **Possible values**: `"AlwaysNextLine"`, `"PreferSameLine"`, `"SameLineWhere"`
+- **Stable**: No (tracking issue: #3376)
+
+### Functions
+
+#### `"SameLineWhere"` (default):
+
+```rust
+fn lorem() {
+    // body
+}
+
+fn lorem(ipsum: usize) {
+    // body
+}
+
+fn lorem<T>(ipsum: T)
+where
+    T: Add + Sub + Mul + Div,
+{
+    // body
+}
+```
+
+#### `"AlwaysNextLine"`:
+
+```rust
+fn lorem()
+{
+    // body
+}
+
+fn lorem(ipsum: usize)
+{
+    // body
+}
+
+fn lorem<T>(ipsum: T)
+where
+    T: Add + Sub + Mul + Div,
+{
+    // body
+}
+```
+
+#### `"PreferSameLine"`:
+
+```rust
+fn lorem() {
+    // body
+}
+
+fn lorem(ipsum: usize) {
+    // body
+}
+
+fn lorem<T>(ipsum: T)
+where
+    T: Add + Sub + Mul + Div, {
+    // body
+}
+```
+
+### Structs and enums
+
+#### `"SameLineWhere"` (default):
+
+```rust
+struct Lorem {
+    ipsum: bool,
+}
+
+struct Dolor<T>
+where
+    T: Eq,
+{
+    sit: T,
+}
+```
+
+#### `"AlwaysNextLine"`:
+
+```rust
+struct Lorem
+{
+    ipsum: bool,
+}
+
+struct Dolor<T>
+where
+    T: Eq,
+{
+    sit: T,
+}
+```
+
+#### `"PreferSameLine"`:
+
+```rust
+struct Lorem {
+    ipsum: bool,
+}
+
+struct Dolor<T>
+where
+    T: Eq, {
+    sit: T,
+}
+```
+
+## `chain_width` 
+
+Maximum width of a chain to fit on one line.
+
+- **Default value**: `60`
+- **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
+- **Stable**: Yes
+
+By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `chain_width` will take precedence. 
+
+See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
+
+## `color`
+
+Whether to use colored output or not.
+
+- **Default value**: `"Auto"`
+- **Possible values**: "Auto", "Always", "Never"
+- **Stable**: No (tracking issue: #3385)
+
+## `combine_control_expr`
+
+Combine control expressions with function calls.
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3369)
+
+#### `true` (default):
+
+```rust
+fn example() {
+    // If
+    foo!(if x {
+        foo();
+    } else {
+        bar();
+    });
+
+    // IfLet
+    foo!(if let Some(..) = x {
+        foo();
+    } else {
+        bar();
+    });
+
+    // While
+    foo!(while x {
+        foo();
+        bar();
+    });
+
+    // WhileLet
+    foo!(while let Some(..) = x {
+        foo();
+        bar();
+    });
+
+    // ForLoop
+    foo!(for x in y {
+        foo();
+        bar();
+    });
+
+    // Loop
+    foo!(loop {
+        foo();
+        bar();
+    });
+}
+```
+
+#### `false`:
+
+```rust
+fn example() {
+    // If
+    foo!(
+        if x {
+            foo();
+        } else {
+            bar();
+        }
+    );
+
+    // IfLet
+    foo!(
+        if let Some(..) = x {
+            foo();
+        } else {
+            bar();
+        }
+    );
+
+    // While
+    foo!(
+        while x {
+            foo();
+            bar();
+        }
+    );
+
+    // WhileLet
+    foo!(
+        while let Some(..) = x {
+            foo();
+            bar();
+        }
+    );
+
+    // ForLoop
+    foo!(
+        for x in y {
+            foo();
+            bar();
+        }
+    );
+
+    // Loop
+    foo!(
+        loop {
+            foo();
+            bar();
+        }
+    );
+}
+```
+
+## `comment_width`
+
+Maximum length of comments. No effect unless`wrap_comments = true`.
+
+- **Default value**: `80`
+- **Possible values**: any positive integer
+- **Stable**: No (tracking issue: #3349)
+
+**Note:** A value of `0` results in [`wrap_comments`](#wrap_comments) being applied regardless of a line's width.
+
+#### `80` (default; comments shorter than `comment_width`):
+```rust
+// Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+```
+
+#### `60` (comments longer than `comment_width`):
+```rust
+// Lorem ipsum dolor sit amet,
+// consectetur adipiscing elit.
+```
+
+See also [`wrap_comments`](#wrap_comments).
+
+## `condense_wildcard_suffixes`
+
+Replace strings of _ wildcards by a single .. in tuple patterns
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3384)
+
+#### `false` (default):
+
+```rust
+fn main() {
+    let (lorem, ipsum, _, _) = (1, 2, 3, 4);
+    let (lorem, ipsum, ..) = (1, 2, 3, 4);
+}
+```
+
+#### `true`:
+
+```rust
+fn main() {
+    let (lorem, ipsum, ..) = (1, 2, 3, 4);
+}
+```
+
+## `control_brace_style`
+
+Brace style for control flow constructs
+
+- **Default value**: `"AlwaysSameLine"`
+- **Possible values**: `"AlwaysNextLine"`, `"AlwaysSameLine"`, `"ClosingNextLine"`
+- **Stable**: No (tracking issue: #3377)
+
+#### `"AlwaysSameLine"` (default):
+
+```rust
+fn main() {
+    if lorem {
+        println!("ipsum!");
+    } else {
+        println!("dolor!");
+    }
+}
+```
+
+#### `"AlwaysNextLine"`:
+
+```rust
+fn main() {
+    if lorem
+    {
+        println!("ipsum!");
+    }
+    else
+    {
+        println!("dolor!");
+    }
+}
+```
+
+#### `"ClosingNextLine"`:
+
+```rust
+fn main() {
+    if lorem {
+        println!("ipsum!");
+    }
+    else {
+        println!("dolor!");
+    }
+}
+```
+
+## `disable_all_formatting`
+
+Don't reformat anything
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3388)
+
+## `edition`
+
+Specifies which edition is used by the parser.
+
+- **Default value**: `"2015"`
+- **Possible values**: `"2015"`, `"2018"`, `"2021"`
+- **Stable**: Yes
+
+Rustfmt is able to pick up the edition used by reading the `Cargo.toml` file if executed
+through the Cargo's formatting tool `cargo fmt`. Otherwise, the edition needs to be specified
+in your config file:
+
+```toml
+edition = "2018"
+```
+
+## `empty_item_single_line`
+
+Put empty-body functions and impls on a single line
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3356)
+
+#### `true` (default):
+
+```rust
+fn lorem() {}
+
+impl Lorem {}
+```
+
+#### `false`:
+
+```rust
+fn lorem() {
+}
+
+impl Lorem {
+}
+```
+
+See also [`brace_style`](#brace_style), [`control_brace_style`](#control_brace_style).
+
+
+## `enum_discrim_align_threshold`
+
+The maximum length of enum variant having discriminant, that gets vertically aligned with others.
+Variants without discriminants would be ignored for the purpose of alignment.
+
+Note that this is not how much whitespace is inserted, but instead the longest variant name that
+doesn't get ignored when aligning.
+
+- **Default value** : 0
+- **Possible values**: any positive integer
+- **Stable**: No (tracking issue: #3372)
+
+#### `0` (default):
+
+```rust
+enum Bar {
+    A = 0,
+    Bb = 1,
+    RandomLongVariantGoesHere = 10,
+    Ccc = 71,
+}
+
+enum Bar {
+    VeryLongVariantNameHereA = 0,
+    VeryLongVariantNameHereBb = 1,
+    VeryLongVariantNameHereCcc = 2,
+}
+```
+
+#### `20`:
+
+```rust
+enum Foo {
+    A   = 0,
+    Bb  = 1,
+    RandomLongVariantGoesHere = 10,
+    Ccc = 2,
+}
+
+enum Bar {
+    VeryLongVariantNameHereA = 0,
+    VeryLongVariantNameHereBb = 1,
+    VeryLongVariantNameHereCcc = 2,
+}
+```
+
+
+## `error_on_line_overflow`
+
+Error if Rustfmt is unable to get all lines within `max_width`, except for comments and string
+literals. If this happens, then it is a bug in Rustfmt. You might be able to work around the bug by
+refactoring your code to avoid long/complex expressions, usually by extracting a local variable or
+using a shorter name.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3391)
+
+See also [`max_width`](#max_width).
+
+## `error_on_unformatted`
+
+Error if unable to get comments or string literals within `max_width`, or they are left with
+trailing whitespaces.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3392)
+
+## `fn_args_layout`
+
+Control the layout of arguments in a function
+
+- **Default value**: `"Tall"`
+- **Possible values**: `"Compressed"`, `"Tall"`, `"Vertical"`
+- **Stable**: Yes
+
+#### `"Tall"` (default):
+
+```rust
+trait Lorem {
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
+        // body
+    }
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: Consectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    );
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: Consectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    ) {
+        // body
+    }
+}
+```
+
+#### `"Compressed"`:
+
+```rust
+trait Lorem {
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
+        // body
+    }
+
+    fn lorem(
+        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
+        adipiscing: Adipiscing, elit: Elit,
+    );
+
+    fn lorem(
+        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
+        adipiscing: Adipiscing, elit: Elit,
+    ) {
+        // body
+    }
+}
+```
+
+#### `"Vertical"`:
+
+```rust
+trait Lorem {
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+    );
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+    ) {
+        // body
+    }
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: Consectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    );
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: Consectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    ) {
+        // body
+    }
+}
+```
+
+## `fn_call_width` 
+
+Maximum width of the args of a function call before falling back to vertical formatting.
+
+- **Default value**: `60`
+- **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
+- **Stable**: Yes
+
+By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `fn_call_width` will take precedence. 
+
+See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
+
+## `fn_single_line`
+
+Put single-expression functions on a single line
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3358)
+
+#### `false` (default):
+
+```rust
+fn lorem() -> usize {
+    42
+}
+
+fn lorem() -> usize {
+    let ipsum = 42;
+    ipsum
+}
+```
+
+#### `true`:
+
+```rust
+fn lorem() -> usize { 42 }
+
+fn lorem() -> usize {
+    let ipsum = 42;
+    ipsum
+}
+```
+
+See also [`control_brace_style`](#control_brace_style).
+
+
+## `force_explicit_abi`
+
+Always print the abi for extern items
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+**Note:** Non-"C" ABIs are always printed. If `false` then "C" is removed.
+
+#### `true` (default):
+
+```rust
+extern "C" {
+    pub static lorem: c_int;
+}
+```
+
+#### `false`:
+
+```rust
+extern {
+    pub static lorem: c_int;
+}
+```
+
+## `force_multiline_blocks`
+
+Force multiline closure and match arm bodies to be wrapped in a block
+
+- **Default value**: `false`
+- **Possible values**: `false`, `true`
+- **Stable**: No (tracking issue: #3374)
+
+#### `false` (default):
+
+```rust
+fn main() {
+    result.and_then(|maybe_value| match maybe_value {
+        None => foo(),
+        Some(value) => bar(),
+    });
+
+    match lorem {
+        None => |ipsum| {
+            println!("Hello World");
+        },
+        Some(dolor) => foo(),
+    }
+}
+```
+
+#### `true`:
+
+```rust
+fn main() {
+    result.and_then(|maybe_value| {
+        match maybe_value {
+            None => foo(),
+            Some(value) => bar(),
+        }
+    });
+
+    match lorem {
+        None => {
+            |ipsum| {
+                println!("Hello World");
+            }
+        }
+        Some(dolor) => foo(),
+    }
+}
+```
+
+
+## `format_code_in_doc_comments`
+
+Format code snippet included in doc comments.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3348)
+
+#### `false` (default):
+
+```rust
+/// Adds one to the number given.
+///
+/// # Examples
+///
+/// ```rust
+/// let five=5;
+///
+/// assert_eq!(
+///     6,
+///     add_one(5)
+/// );
+/// # fn add_one(x: i32) -> i32 {
+/// #     x + 1
+/// # }
+/// ```
+fn add_one(x: i32) -> i32 {
+    x + 1
+}
+```
+
+#### `true`
+
+```rust
+/// Adds one to the number given.
+///
+/// # Examples
+///
+/// ```rust
+/// let five = 5;
+///
+/// assert_eq!(6, add_one(5));
+/// # fn add_one(x: i32) -> i32 {
+/// #     x + 1
+/// # }
+/// ```
+fn add_one(x: i32) -> i32 {
+    x + 1
+}
+```
+
+## `format_macro_matchers`
+
+Format the metavariable matching patterns in macros.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3354)
+
+#### `false` (default):
+
+```rust
+macro_rules! foo {
+    ($a: ident : $b: ty) => {
+        $a(42): $b;
+    };
+    ($a: ident $b: ident $c: ident) => {
+        $a = $b + $c;
+    };
+}
+```
+
+#### `true`:
+
+```rust
+macro_rules! foo {
+    ($a:ident : $b:ty) => {
+        $a(42): $b;
+    };
+    ($a:ident $b:ident $c:ident) => {
+        $a = $b + $c;
+    };
+}
+```
+
+See also [`format_macro_bodies`](#format_macro_bodies).
+
+
+## `format_macro_bodies`
+
+Format the bodies of macros.
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3355)
+
+#### `true` (default):
+
+```rust
+macro_rules! foo {
+    ($a: ident : $b: ty) => {
+        $a(42): $b;
+    };
+    ($a: ident $b: ident $c: ident) => {
+        $a = $b + $c;
+    };
+}
+```
+
+#### `false`:
+
+```rust
+macro_rules! foo {
+    ($a: ident : $b: ty) => { $a(42): $b; };
+    ($a: ident $b: ident $c: ident) => { $a=$b+$c; };
+}
+```
+
+See also [`format_macro_matchers`](#format_macro_matchers).
+
+
+## `format_strings`
+
+Format string literals where necessary
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3353)
+
+#### `false` (default):
+
+```rust
+fn main() {
+    let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit amet consectetur adipiscing";
+}
+```
+
+#### `true`:
+
+```rust
+fn main() {
+    let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit amet \
+                 consectetur adipiscing";
+}
+```
+
+See also [`max_width`](#max_width).
+
+## `hard_tabs`
+
+Use tab characters for indentation, spaces for alignment
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+#### `false` (default):
+
+```rust
+fn lorem() -> usize {
+    42 // spaces before 42
+}
+```
+
+#### `true`:
+
+```rust
+fn lorem() -> usize {
+	42 // tabs before 42
+}
+```
+
+See also: [`tab_spaces`](#tab_spaces).
+
+
+## `hide_parse_errors`
+
+Do not show parse errors if the parser failed to parse files.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3390)
+
+## `ignore`
+
+Skip formatting files and directories that match the specified pattern.
+The pattern format is the same as [.gitignore](https://git-scm.com/docs/gitignore#_pattern_format). Be sure to use Unix/forwardslash `/` style  paths. This path style will work on all platforms. Windows style paths with backslashes `\` are not supported.
+
+- **Default value**: format every file
+- **Possible values**: See an example below
+- **Stable**: No (tracking issue: #3395)
+
+### Example
+
+If you want to ignore specific files, put the following to your config file:
+
+```toml
+ignore = [
+    "src/types.rs",
+    "src/foo/bar.rs",
+]
+```
+
+If you want to ignore every file under `examples/`, put the following to your config file:
+
+```toml
+ignore = [
+    "examples",
+]
+```
+
+If you want to ignore every file under the directory where you put your rustfmt.toml:
+
+```toml
+ignore = ["/"]
+```
+
+## `imports_indent`
+
+Indent style of imports
+
+- **Default Value**: `"Block"`
+- **Possible values**: `"Block"`, `"Visual"`
+- **Stable**: No (tracking issue: #3360)
+
+#### `"Block"` (default):
+
+```rust
+use foo::{
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+    zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
+};
+```
+
+#### `"Visual"`:
+
+```rust
+use foo::{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+          zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz};
+```
+
+See also: [`imports_layout`](#imports_layout).
+
+## `imports_layout`
+
+Item layout inside a imports block
+
+- **Default value**: "Mixed"
+- **Possible values**: "Horizontal", "HorizontalVertical", "Mixed", "Vertical"
+- **Stable**: No (tracking issue: #3361)
+
+#### `"Mixed"` (default):
+
+```rust
+use foo::{xxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz};
+
+use foo::{
+    aaaaaaaaaaaaaaaaaa, bbbbbbbbbbbbbbbbbb, cccccccccccccccccc, dddddddddddddddddd,
+    eeeeeeeeeeeeeeeeee, ffffffffffffffffff,
+};
+```
+
+#### `"Horizontal"`:
+
+**Note**: This option forces all imports onto one line and may exceed `max_width`.
+
+```rust
+use foo::{xxx, yyy, zzz};
+
+use foo::{aaa, bbb, ccc, ddd, eee, fff};
+```
+
+#### `"HorizontalVertical"`:
+
+```rust
+use foo::{xxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz};
+
+use foo::{
+    aaaaaaaaaaaaaaaaaa,
+    bbbbbbbbbbbbbbbbbb,
+    cccccccccccccccccc,
+    dddddddddddddddddd,
+    eeeeeeeeeeeeeeeeee,
+    ffffffffffffffffff,
+};
+```
+
+#### `"Vertical"`:
+
+```rust
+use foo::{
+    xxx,
+    yyy,
+    zzz,
+};
+
+use foo::{
+    aaa,
+    bbb,
+    ccc,
+    ddd,
+    eee,
+    fff,
+};
+```
+
+## `indent_style`
+
+Indent on expressions or items.
+
+- **Default value**: `"Block"`
+- **Possible values**: `"Block"`, `"Visual"`
+- **Stable**: No (tracking issue: #3346)
+
+### Array
+
+#### `"Block"` (default):
+
+```rust
+fn main() {
+    let lorem = vec![
+        "ipsum",
+        "dolor",
+        "sit",
+        "amet",
+        "consectetur",
+        "adipiscing",
+        "elit",
+    ];
+}
+```
+
+#### `"Visual"`:
+
+```rust
+fn main() {
+    let lorem = vec!["ipsum",
+                     "dolor",
+                     "sit",
+                     "amet",
+                     "consectetur",
+                     "adipiscing",
+                     "elit"];
+}
+```
+
+### Control flow
+
+#### `"Block"` (default):
+
+```rust
+fn main() {
+    if lorem_ipsum
+        && dolor_sit
+        && amet_consectetur
+        && lorem_sit
+        && dolor_consectetur
+        && amet_ipsum
+        && lorem_consectetur
+    {
+        // ...
+    }
+}
+```
+
+#### `"Visual"`:
+
+```rust
+fn main() {
+    if lorem_ipsum
+       && dolor_sit
+       && amet_consectetur
+       && lorem_sit
+       && dolor_consectetur
+       && amet_ipsum
+       && lorem_consectetur
+    {
+        // ...
+    }
+}
+```
+
+See also: [`control_brace_style`](#control_brace_style).
+
+### Function arguments
+
+#### `"Block"` (default):
+
+```rust
+fn lorem() {}
+
+fn lorem(ipsum: usize) {}
+
+fn lorem(
+    ipsum: usize,
+    dolor: usize,
+    sit: usize,
+    amet: usize,
+    consectetur: usize,
+    adipiscing: usize,
+    elit: usize,
+) {
+    // body
+}
+```
+
+#### `"Visual"`:
+
+```rust
+fn lorem() {}
+
+fn lorem(ipsum: usize) {}
+
+fn lorem(ipsum: usize,
+         dolor: usize,
+         sit: usize,
+         amet: usize,
+         consectetur: usize,
+         adipiscing: usize,
+         elit: usize) {
+    // body
+}
+```
+
+### Function calls
+
+#### `"Block"` (default):
+
+```rust
+fn main() {
+    lorem(
+        "lorem",
+        "ipsum",
+        "dolor",
+        "sit",
+        "amet",
+        "consectetur",
+        "adipiscing",
+        "elit",
+    );
+}
+```
+
+#### `"Visual"`:
+
+```rust
+fn main() {
+    lorem("lorem",
+          "ipsum",
+          "dolor",
+          "sit",
+          "amet",
+          "consectetur",
+          "adipiscing",
+          "elit");
+}
+```
+
+### Generics
+
+#### `"Block"` (default):
+
+```rust
+fn lorem<
+    Ipsum: Eq = usize,
+    Dolor: Eq = usize,
+    Sit: Eq = usize,
+    Amet: Eq = usize,
+    Adipiscing: Eq = usize,
+    Consectetur: Eq = usize,
+    Elit: Eq = usize,
+>(
+    ipsum: Ipsum,
+    dolor: Dolor,
+    sit: Sit,
+    amet: Amet,
+    adipiscing: Adipiscing,
+    consectetur: Consectetur,
+    elit: Elit,
+) -> T {
+    // body
+}
+```
+
+#### `"Visual"`:
+
+```rust
+fn lorem<Ipsum: Eq = usize,
+         Dolor: Eq = usize,
+         Sit: Eq = usize,
+         Amet: Eq = usize,
+         Adipiscing: Eq = usize,
+         Consectetur: Eq = usize,
+         Elit: Eq = usize>(
+    ipsum: Ipsum,
+    dolor: Dolor,
+    sit: Sit,
+    amet: Amet,
+    adipiscing: Adipiscing,
+    consectetur: Consectetur,
+    elit: Elit)
+    -> T {
+    // body
+}
+```
+
+#### Struct
+
+#### `"Block"` (default):
+
+```rust
+fn main() {
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+}
+```
+
+#### `"Visual"`:
+
+```rust
+fn main() {
+    let lorem = Lorem { ipsum: dolor,
+                        sit: amet };
+}
+```
+
+See also: [`struct_lit_single_line`](#struct_lit_single_line), [`indent_style`](#indent_style).
+
+### Where predicates
+
+#### `"Block"` (default):
+
+```rust
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
+where
+    Ipsum: Eq,
+    Dolor: Eq,
+    Sit: Eq,
+    Amet: Eq,
+{
+    // body
+}
+```
+
+#### `"Visual"`:
+
+```rust
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
+    where Ipsum: Eq,
+          Dolor: Eq,
+          Sit: Eq,
+          Amet: Eq
+{
+    // body
+}
+```
+
+## `inline_attribute_width`
+
+Write an item and its attribute on the same line if their combined width is below a threshold
+
+- **Default value**: 0
+- **Possible values**: any positive integer
+- **Stable**: No (tracking issue: #3343)
+
+### Example
+
+#### `0` (default):
+```rust
+#[cfg(feature = "alloc")]
+use core::slice;
+```
+
+#### `50`:
+```rust
+#[cfg(feature = "alloc")] use core::slice;
+```
+
+## `license_template_path`
+
+Check whether beginnings of files match a license template.
+
+- **Default value**: `""`
+- **Possible values**: path to a license template file
+- **Stable**: No (tracking issue: #3352)
+
+A license template is a plain text file which is matched literally against the
+beginning of each source file, except for `{}`-delimited blocks, which are
+matched as regular expressions. The following license template therefore
+matches strings like `// Copyright 2017 The Rust Project Developers.`, `//
+Copyright 2018 The Rust Project Developers.`, etc.:
+
+```
+// Copyright {\d+} The Rust Project Developers.
+```
+
+`\{`, `\}` and `\\` match literal braces / backslashes.
+
+## `match_arm_blocks`
+
+Wrap the body of arms in blocks when it does not fit on the same line with the pattern of arms
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3373)
+
+#### `true` (default):
+
+```rust
+fn main() {
+    match lorem {
+        true => {
+            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x)
+        }
+        false => println!("{}", sit),
+    }
+}
+```
+
+#### `false`:
+
+```rust
+fn main() {
+    match lorem {
+        true =>
+            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
+        false => println!("{}", sit),
+    }
+}
+```
+
+See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
+
+## `match_arm_leading_pipes`
+
+Controls whether to include a leading pipe on match arms
+
+- **Default value**: `Never`
+- **Possible values**: `Always`, `Never`, `Preserve`
+- **Stable**: Yes
+
+#### `Never` (default):
+```rust
+// Leading pipes are removed from this:
+// fn foo() {
+//     match foo {
+//         | "foo" | "bar" => {}
+//         | "baz"
+//         | "something relatively long"
+//         | "something really really really realllllllllllllly long" => println!("x"),
+//         | "qux" => println!("y"),
+//         _ => {}
+//     }
+// }
+
+// Becomes
+fn foo() {
+    match foo {
+        "foo" | "bar" => {}
+        "baz"
+        | "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        "qux" => println!("y"),
+        _ => {}
+    }
+}
+```
+
+#### `Always`:
+```rust
+// Leading pipes are emitted on all arms of this:
+// fn foo() {
+//     match foo {
+//         "foo" | "bar" => {}
+//         "baz"
+//         | "something relatively long"
+//         | "something really really really realllllllllllllly long" => println!("x"),
+//         "qux" => println!("y"),
+//         _ => {}
+//     }
+// }
+
+// Becomes:
+fn foo() {
+    match foo {
+        | "foo" | "bar" => {}
+        | "baz"
+        | "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        | "qux" => println!("y"),
+        | _ => {}
+    }
+}
+```
+
+#### `Preserve`:
+```rust
+fn foo() {
+    match foo {
+        | "foo" | "bar" => {}
+        | "baz"
+        | "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        | "qux" => println!("y"),
+        _ => {}
+    }
+
+    match baz {
+        "qux" => {}
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
+```
+
+## `match_block_trailing_comma`
+
+Put a trailing comma after a block based match arm (non-block arms are not affected)
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3380)
+
+#### `false` (default):
+
+```rust
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            println!("ipsum");
+        }
+        Lorem::Dolor => println!("dolor"),
+    }
+}
+```
+
+#### `true`:
+
+```rust
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            println!("ipsum");
+        },
+        Lorem::Dolor => println!("dolor"),
+    }
+}
+```
+
+See also: [`trailing_comma`](#trailing_comma), [`match_arm_blocks`](#match_arm_blocks).
+
+## `max_width`
+
+Maximum width of each line
+
+- **Default value**: `100`
+- **Possible values**: any positive integer
+- **Stable**: Yes
+
+See also [`error_on_line_overflow`](#error_on_line_overflow).
+
+## `merge_derives`
+
+Merge multiple derives into a single one.
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+#### `true` (default):
+
+```rust
+#[derive(Eq, PartialEq, Debug, Copy, Clone)]
+pub enum Foo {}
+```
+
+#### `false`:
+
+```rust
+#[derive(Eq, PartialEq)]
+#[derive(Debug)]
+#[derive(Copy, Clone)]
+pub enum Foo {}
+```
+
+## `imports_granularity`
+
+How imports should be grouped into `use` statements. Imports will be merged or split to the configured level of granularity.
+
+- **Default value**: `Preserve`
+- **Possible values**: `Preserve`, `Crate`, `Module`, `Item`
+- **Stable**: No
+
+#### `Preserve` (default):
+
+Do not change the granularity of any imports and preserve the original structure written by the developer.
+
+```rust
+use foo::b;
+use foo::b::{f, g};
+use foo::{a, c, d::e};
+use qux::{h, i};
+```
+
+#### `Crate`:
+
+Merge imports from the same crate into a single `use` statement. Conversely, imports from different crates are split into separate statements.
+
+```rust
+use foo::{
+    a, b,
+    b::{f, g},
+    c,
+    d::e,
+};
+use qux::{h, i};
+```
+
+#### `Module`:
+
+Merge imports from the same module into a single `use` statement. Conversely, imports from different modules are split into separate statements.
+
+```rust
+use foo::b::{f, g};
+use foo::d::e;
+use foo::{a, b, c};
+use qux::{h, i};
+```
+
+#### `Item`:
+
+Flatten imports so that each has its own `use` statement.
+
+```rust
+use foo::a;
+use foo::b;
+use foo::b::f;
+use foo::b::g;
+use foo::c;
+use foo::d::e;
+use qux::h;
+use qux::i;
+```
+
+## `merge_imports`
+
+This option is deprecated. Use `imports_granularity = "Crate"` instead.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+
+#### `false` (default):
+
+```rust
+use foo::{a, c, d};
+use foo::{b, g};
+use foo::{e, f};
+```
+
+#### `true`:
+
+```rust
+use foo::{a, b, c, d, e, f, g};
+```
+
+
+## `newline_style`
+
+Unix or Windows line endings
+
+- **Default value**: `"Auto"`
+- **Possible values**: `"Auto"`, `"Native"`, `"Unix"`, `"Windows"`
+- **Stable**: Yes
+
+#### `Auto` (default):
+
+The newline style is detected automatically on a per-file basis. Files
+with mixed line endings will be converted to the first detected line
+ending style.
+
+#### `Native`
+
+Line endings will be converted to `\r\n` on Windows and `\n` on all
+other platforms.
+
+#### `Unix`
+
+Line endings will be converted to `\n`.
+
+#### `Windows`
+
+Line endings will be converted to `\r\n`.
+
+## `normalize_comments`
+
+Convert /* */ comments to // comments where possible
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3350)
+
+#### `false` (default):
+
+```rust
+// Lorem ipsum:
+fn dolor() -> usize {}
+
+/* sit amet: */
+fn adipiscing() -> usize {}
+```
+
+#### `true`:
+
+```rust
+// Lorem ipsum:
+fn dolor() -> usize {}
+
+// sit amet:
+fn adipiscing() -> usize {}
+```
+
+## `normalize_doc_attributes`
+
+Convert `#![doc]` and `#[doc]` attributes to `//!` and `///` doc comments.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3351)
+
+#### `false` (default):
+
+```rust
+#![doc = "Example documentation"]
+
+#[doc = "Example item documentation"]
+pub enum Foo {}
+```
+
+#### `true`:
+
+```rust
+//! Example documentation
+
+/// Example item documentation
+pub enum Foo {}
+```
+
+## `overflow_delimited_expr`
+
+When structs, slices, arrays, and block/array-like macros are used as the last
+argument in an expression list, allow them to overflow (like blocks/closures)
+instead of being indented on a new line.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3370)
+
+#### `false` (default):
+
+```rust
+fn example() {
+    foo(ctx, |param| {
+        action();
+        foo(param)
+    });
+
+    foo(
+        ctx,
+        Bar {
+            x: value,
+            y: value2,
+        },
+    );
+
+    foo(
+        ctx,
+        &[
+            MAROON_TOMATOES,
+            PURPLE_POTATOES,
+            ORGANE_ORANGES,
+            GREEN_PEARS,
+            RED_APPLES,
+        ],
+    );
+
+    foo(
+        ctx,
+        vec![
+            MAROON_TOMATOES,
+            PURPLE_POTATOES,
+            ORGANE_ORANGES,
+            GREEN_PEARS,
+            RED_APPLES,
+        ],
+    );
+}
+```
+
+#### `true`:
+
+```rust
+fn example() {
+    foo(ctx, |param| {
+        action();
+        foo(param)
+    });
+
+    foo(ctx, Bar {
+        x: value,
+        y: value2,
+    });
+
+    foo(ctx, &[
+        MAROON_TOMATOES,
+        PURPLE_POTATOES,
+        ORGANE_ORANGES,
+        GREEN_PEARS,
+        RED_APPLES,
+    ]);
+
+    foo(ctx, vec![
+        MAROON_TOMATOES,
+        PURPLE_POTATOES,
+        ORGANE_ORANGES,
+        GREEN_PEARS,
+        RED_APPLES,
+    ]);
+}
+```
+
+## `remove_nested_parens`
+
+Remove nested parens.
+
+- **Default value**: `true`,
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+
+#### `true` (default):
+```rust
+fn main() {
+    (foo());
+}
+```
+
+#### `false`:
+```rust
+fn main() {
+    ((((foo()))));
+}
+```
+
+
+## `reorder_impl_items`
+
+Reorder impl items. `type` and `const` are put first, then macros and methods.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3363)
+
+#### `false` (default)
+
+```rust
+struct Dummy;
+
+impl Iterator for Dummy {
+    fn next(&mut self) -> Option<Self::Item> {
+        None
+    }
+
+    type Item = i32;
+}
+```
+
+#### `true`
+
+```rust
+struct Dummy;
+
+impl Iterator for Dummy {
+    type Item = i32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        None
+    }
+}
+```
+
+## `reorder_imports`
+
+Reorder import and extern crate statements alphabetically in groups (a group is
+separated by a newline).
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+#### `true` (default):
+
+```rust
+use dolor;
+use ipsum;
+use lorem;
+use sit;
+```
+
+#### `false`:
+
+```rust
+use lorem;
+use ipsum;
+use dolor;
+use sit;
+```
+
+## `group_imports`
+
+Controls the strategy for how imports are grouped together.
+
+- **Default value**: `Preserve`
+- **Possible values**: `Preserve`, `StdExternalCrate`
+- **Stable**: No
+
+#### `Preserve` (default):
+
+Preserve the source file's import groups.
+
+```rust
+use super::update::convert_publish_payload;
+use chrono::Utc;
+
+use alloc::alloc::Layout;
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+
+use std::sync::Arc;
+
+use broker::database::PooledConnection;
+
+use super::schema::{Context, Payload};
+use crate::models::Event;
+use core::f32;
+```
+
+#### `StdExternalCrate`:
+
+Discard existing import groups, and create three groups for:
+1. `std`, `core` and `alloc`,
+2. external crates,
+3. `self`, `super` and `crate` imports.
+
+```rust
+use alloc::alloc::Layout;
+use core::f32;
+use std::sync::Arc;
+
+use broker::database::PooledConnection;
+use chrono::Utc;
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+
+use super::schema::{Context, Payload};
+use super::update::convert_publish_payload;
+use crate::models::Event;
+```
+
+## `reorder_modules`
+
+Reorder `mod` declarations alphabetically in group.
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+#### `true` (default)
+
+```rust
+mod a;
+mod b;
+
+mod dolor;
+mod ipsum;
+mod lorem;
+mod sit;
+```
+
+#### `false`
+
+```rust
+mod b;
+mod a;
+
+mod lorem;
+mod ipsum;
+mod dolor;
+mod sit;
+```
+
+**Note** `mod` with `#[macro_export]` will not be reordered since that could change the semantics
+of the original source code.
+
+## `report_fixme`
+
+Report `FIXME` items in comments.
+
+- **Default value**: `"Never"`
+- **Possible values**: `"Always"`, `"Unnumbered"`, `"Never"`
+- **Stable**: No (tracking issue: #3394)
+
+Warns about any comments containing `FIXME` in them when set to `"Always"`. If
+it contains a `#X` (with `X` being a number) in parentheses following the
+`FIXME`, `"Unnumbered"` will ignore it.
+
+See also [`report_todo`](#report_todo).
+
+
+## `report_todo`
+
+Report `TODO` items in comments.
+
+- **Default value**: `"Never"`
+- **Possible values**: `"Always"`, `"Unnumbered"`, `"Never"`
+- **Stable**: No (tracking issue: #3393)
+
+Warns about any comments containing `TODO` in them when set to `"Always"`. If
+it contains a `#X` (with `X` being a number) in parentheses following the
+`TODO`, `"Unnumbered"` will ignore it.
+
+See also [`report_fixme`](#report_fixme).
+
+## `required_version`
+
+Require a specific version of rustfmt. If you want to make sure that the
+specific version of rustfmt is used in your CI, use this option.
+
+- **Default value**: `CARGO_PKG_VERSION`
+- **Possible values**: any published version (e.g. `"0.3.8"`)
+- **Stable**: No (tracking issue: #3386)
+
+## `skip_children`
+
+Don't reformat out of line modules
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3389)
+
+## `single_line_if_else_max_width` 
+
+Maximum line length for single line if-else expressions. A value of `0` (zero) results in if-else expressions always being broken into multiple lines. Note this occurs when `use_small_heuristics` is set to `Off`.
+
+- **Default value**: `50`
+- **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
+- **Stable**: Yes
+
+By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `single_line_if_else_max_width` will take precedence. 
+
+See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
+
+## `space_after_colon`
+
+Leave a space after the colon.
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3366)
+
+#### `true` (default):
+
+```rust
+fn lorem<T: Eq>(t: T) {
+    let lorem: Dolor = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+}
+```
+
+#### `false`:
+
+```rust
+fn lorem<T:Eq>(t:T) {
+    let lorem:Dolor = Lorem {
+        ipsum:dolor,
+        sit:amet,
+    };
+}
+```
+
+See also: [`space_before_colon`](#space_before_colon).
+
+## `space_before_colon`
+
+Leave a space before the colon.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3365)
+
+#### `false` (default):
+
+```rust
+fn lorem<T: Eq>(t: T) {
+    let lorem: Dolor = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+}
+```
+
+#### `true`:
+
+```rust
+fn lorem<T : Eq>(t : T) {
+    let lorem : Dolor = Lorem {
+        ipsum : dolor,
+        sit : amet,
+    };
+}
+```
+
+See also: [`space_after_colon`](#space_after_colon).
+
+## `spaces_around_ranges`
+
+Put spaces around the .., ..=, and ... range operators
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3367)
+
+#### `false` (default):
+
+```rust
+fn main() {
+    let lorem = 0..10;
+    let ipsum = 0..=10;
+
+    match lorem {
+        1..5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1..=5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1...5 => foo(),
+        _ => bar,
+    }
+}
+```
+
+#### `true`:
+
+```rust
+fn main() {
+    let lorem = 0 .. 10;
+    let ipsum = 0 ..= 10;
+
+    match lorem {
+        1 .. 5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1 ..= 5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1 ... 5 => foo(),
+        _ => bar,
+    }
+}
+```
+
+## `struct_field_align_threshold`
+
+The maximum diff of width between struct fields to be aligned with each other.
+
+- **Default value** : 0
+- **Possible values**: any non-negative integer
+- **Stable**: No (tracking issue: #3371)
+
+#### `0` (default):
+
+```rust
+struct Foo {
+    x: u32,
+    yy: u32,
+    zzz: u32,
+}
+```
+
+#### `20`:
+
+```rust
+struct Foo {
+    x:   u32,
+    yy:  u32,
+    zzz: u32,
+}
+```
+
+## `struct_lit_single_line`
+
+Put small struct literals on a single line
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3357)
+
+#### `true` (default):
+
+```rust
+fn main() {
+    let lorem = Lorem { foo: bar, baz: ofo };
+}
+```
+
+#### `false`:
+
+```rust
+fn main() {
+    let lorem = Lorem {
+        foo: bar,
+        baz: ofo,
+    };
+}
+```
+
+See also: [`indent_style`](#indent_style).
+
+## `struct_lit_width` 
+
+Maximum width in the body of a struct literal before falling back to vertical formatting. A value of `0` (zero) results in struct literals always being broken into multiple lines. Note this occurs when `use_small_heuristics` is set to `Off`.
+
+- **Default value**: `18`
+- **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
+- **Stable**: Yes
+
+By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `struct_lit_width` will take precedence. 
+
+See also [`max_width`](#max_width), [`use_small_heuristics`](#use_small_heuristics), and [`struct_lit_single_line`](#struct_lit_single_line)
+
+## `struct_variant_width` 
+
+Maximum width in the body of a struct variant before falling back to vertical formatting. A value of `0` (zero) results in struct literals always being broken into multiple lines. Note this occurs when `use_small_heuristics` is set to `Off`.
+
+- **Default value**: `35`
+- **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
+- **Stable**: Yes
+
+By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `struct_variant_width` will take precedence. 
+
+See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
+
+## `tab_spaces`
+
+Number of spaces per tab
+
+- **Default value**: `4`
+- **Possible values**: any positive integer
+- **Stable**: Yes
+
+#### `4` (default):
+
+```rust
+fn lorem() {
+    let ipsum = dolor();
+    let sit = vec![
+        "amet consectetur adipiscing elit amet",
+        "consectetur adipiscing elit amet consectetur.",
+    ];
+}
+```
+
+#### `2`:
+
+```rust
+fn lorem() {
+  let ipsum = dolor();
+  let sit = vec![
+    "amet consectetur adipiscing elit amet",
+    "consectetur adipiscing elit amet consectetur.",
+  ];
+}
+```
+
+See also: [`hard_tabs`](#hard_tabs).
+
+
+## `trailing_comma`
+
+How to handle trailing commas for lists
+
+- **Default value**: `"Vertical"`
+- **Possible values**: `"Always"`, `"Never"`, `"Vertical"`
+- **Stable**: No (tracking issue: #3379)
+
+#### `"Vertical"` (default):
+
+```rust
+fn main() {
+    let Lorem { ipsum, dolor, sit } = amet;
+    let Lorem {
+        ipsum,
+        dolor,
+        sit,
+        amet,
+        consectetur,
+        adipiscing,
+    } = elit;
+}
+```
+
+#### `"Always"`:
+
+```rust
+fn main() {
+    let Lorem { ipsum, dolor, sit, } = amet;
+    let Lorem {
+        ipsum,
+        dolor,
+        sit,
+        amet,
+        consectetur,
+        adipiscing,
+    } = elit;
+}
+```
+
+#### `"Never"`:
+
+```rust
+fn main() {
+    let Lorem { ipsum, dolor, sit } = amet;
+    let Lorem {
+        ipsum,
+        dolor,
+        sit,
+        amet,
+        consectetur,
+        adipiscing
+    } = elit;
+}
+```
+
+See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
+
+## `trailing_semicolon`
+
+Add trailing semicolon after break, continue and return
+
+- **Default value**: `true`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3378)
+
+#### `true` (default):
+```rust
+fn foo() -> usize {
+    return 0;
+}
+```
+
+#### `false`:
+```rust
+fn foo() -> usize {
+    return 0
+}
+```
+
+## `type_punctuation_density`
+
+Determines if `+` or `=` are wrapped in spaces in the punctuation of types
+
+- **Default value**: `"Wide"`
+- **Possible values**: `"Compressed"`, `"Wide"`
+- **Stable**: No (tracking issue: #3364)
+
+#### `"Wide"` (default):
+
+```rust
+fn lorem<Ipsum: Dolor + Sit = Amet>() {
+    // body
+}
+```
+
+#### `"Compressed"`:
+
+```rust
+fn lorem<Ipsum: Dolor+Sit=Amet>() {
+    // body
+}
+```
+
+## `unstable_features`
+
+Enable unstable features on the unstable channel.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3387)
+
+## `use_field_init_shorthand`
+
+Use field initialize shorthand if possible.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+#### `false` (default):
+
+```rust
+struct Foo {
+    x: u32,
+    y: u32,
+    z: u32,
+}
+
+fn main() {
+    let x = 1;
+    let y = 2;
+    let z = 3;
+    let a = Foo { x: x, y: y, z: z };
+}
+```
+
+#### `true`:
+
+```rust
+struct Foo {
+    x: u32,
+    y: u32,
+    z: u32,
+}
+
+fn main() {
+    let x = 1;
+    let y = 2;
+    let z = 3;
+    let a = Foo { x, y, z };
+}
+```
+
+## `use_small_heuristics`
+
+This option can be used to simplify the management and bulk updates of the granular width configuration settings ([`fn_call_width`](#fn_call_width), [`attr_fn_like_width`](#attr_fn_like_width), [`struct_lit_width`](#struct_lit_width), [`struct_variant_width`](#struct_variant_width), [`array_width`](#array_width), [`chain_width`](#chain_width), [`single_line_if_else_max_width`](#single_line_if_else_max_width)), that respectively control when formatted constructs are multi-lined/vertical based on width.
+
+Note that explicitly provided values for the width configuration settings take precedence and override the calculated values determined by `use_small_heuristics`. 
+
+- **Default value**: `"Default"`
+- **Possible values**: `"Default"`, `"Off"`, `"Max"`
+- **Stable**: Yes
+
+#### `Default` (default):
+When `use_small_heuristics` is set to `Default`, the values for the granular width settings are calculated as a ratio of the value for `max_width`.
+
+The ratios are:
+* [`fn_call_width`](#fn_call_width) - `60%`
+* [`attr_fn_like_width`](#attr_fn_like_width) - `70%`
+* [`struct_lit_width`](#struct_lit_width) - `18%`
+* [`struct_variant_width`](#struct_variant_width) - `35%`
+* [`array_width`](#array_width) - `60%`
+* [`chain_width`](#chain_width) - `60%`
+* [`single_line_if_else_max_width`](#single_line_if_else_max_width) - `50%`
+
+For example when `max_width` is set to `100`, the width settings are:
+* `fn_call_width=60`
+* `attr_fn_like_width=70`
+* `struct_lit_width=18`
+* `struct_variant_width=35`
+* `array_width=60`
+* `chain_width=60`
+* `single_line_if_else_max_width=50`
+
+and when `max_width` is set to `200`:
+* `fn_call_width=120`
+* `attr_fn_like_width=140`
+* `struct_lit_width=36`
+* `struct_variant_width=70`
+* `array_width=120`
+* `chain_width=120`
+* `single_line_if_else_max_width=100`
+
+```rust
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit { amet: Consectetur, adipiscing: Elit },
+}
+
+fn main() {
+    lorem(
+        "lorem",
+        "ipsum",
+        "dolor",
+        "sit",
+        "amet",
+        "consectetur",
+        "adipiscing",
+    );
+
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+    let lorem = Lorem { ipsum: dolor };
+
+    let lorem = if ipsum { dolor } else { sit };
+}
+```
+
+#### `Off`:
+When `use_small_heuristics` is set to `Off`, the granular width settings are functionally disabled and ignored. See the documentation for the respective width config options for specifics. 
+
+```rust
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit {
+        amet: Consectetur,
+        adipiscing: Elit,
+    },
+}
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
+
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+
+    let lorem = if ipsum {
+        dolor
+    } else {
+        sit
+    };
+}
+```
+
+#### `Max`:
+When `use_small_heuristics` is set to `Max`, then each granular width setting is set to the same value as `max_width`.
+
+So if `max_width` is set to `200`, then all the width settings are also set to `200`.
+* `fn_call_width=200`
+* `attr_fn_like_width=200`
+* `struct_lit_width=200`
+* `struct_variant_width=200`
+* `array_width=200`
+* `chain_width=200`
+* `single_line_if_else_max_width=200`
+
+```rust
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit { amet: Consectetur, adipiscing: Elit },
+}
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
+
+    let lorem = Lorem { ipsum: dolor, sit: amet };
+
+    let lorem = if ipsum { dolor } else { sit };
+}
+```
+
+
+See also:
+* [`max_width`](#max_width)
+* [`fn_call_width`](#fn_call_width)
+* [`attr_fn_like_width`](#attr_fn_like_width)
+* [`struct_lit_width`](#struct_lit_width)
+* [`struct_variant_width`](#struct_variant_width)
+* [`array_width`](#array_width)
+* [`chain_width`](#chain_width)
+* [`single_line_if_else_max_width`](#single_line_if_else_max_width)
+
+## `use_try_shorthand`
+
+Replace uses of the try! macro by the ? shorthand
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: Yes
+
+#### `false` (default):
+
+```rust
+fn main() {
+    let lorem = try!(ipsum.map(|dolor| dolor.sit()));
+}
+```
+
+#### `true`:
+
+```rust
+fn main() {
+    let lorem = ipsum.map(|dolor| dolor.sit())?;
+}
+```
+
+## `version`
+
+Which version of the formatting rules to use. `Version::One` is backwards-compatible
+with Rustfmt 1.0. Other versions are only backwards compatible within a major
+version number.
+
+- **Default value**: `One`
+- **Possible values**: `One`, `Two`
+- **Stable**: No (tracking issue: #3383)
+
+### Example
+
+```toml
+version = "Two"
+```
+
+## `where_single_line`
+
+Forces the `where` clause to be laid out on a single line.
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3359)
+
+#### `false` (default):
+
+```rust
+impl<T> Lorem for T
+where
+    Option<T>: Ipsum,
+{
+    // body
+}
+```
+
+#### `true`:
+
+```rust
+impl<T> Lorem for T
+where Option<T>: Ipsum
+{
+    // body
+}
+```
+
+See also [`brace_style`](#brace_style), [`control_brace_style`](#control_brace_style).
+
+
+## `wrap_comments`
+
+Break comments to fit on the line
+
+- **Default value**: `false`
+- **Possible values**: `true`, `false`
+- **Stable**: No (tracking issue: #3347)
+
+#### `false` (default):
+
+```rust
+// Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+```
+
+#### `true`:
+
+```rust
+// Lorem ipsum dolor sit amet, consectetur adipiscing elit,
+// sed do eiusmod tempor incididunt ut labore et dolore
+// magna aliqua. Ut enim ad minim veniam, quis nostrud
+// exercitation ullamco laboris nisi ut aliquip ex ea
+// commodo consequat.
+```
+
+# Internal Options
+
+## `emit_mode`
+
+Internal option
+
+## `make_backup`
+
+Internal option, use `--backup`
+
+## `print_misformatted_file_names`
+
+Internal option, use `-l` or `--files-with-diff`
diff --git a/src/tools/rustfmt/Contributing.md b/src/tools/rustfmt/Contributing.md
new file mode 100644
index 0000000000000..131f38dd06a2b
--- /dev/null
+++ b/src/tools/rustfmt/Contributing.md
@@ -0,0 +1,251 @@
+# Contributing
+
+There are many ways to contribute to Rustfmt. This document lays out what they
+are and has information on how to get started. If you have any questions about
+contributing or need help with anything, please ask in the WG-Rustfmt channel
+on [Discord](https://discordapp.com/invite/rust-lang). Feel free to also ask questions
+on issues, or file new issues specifically to get help.
+
+All contributors are expected to follow our [Code of
+Conduct](CODE_OF_CONDUCT.md).
+
+## Test and file issues
+
+It would be really useful to have people use rustfmt on their projects and file
+issues where it does something you don't expect.
+
+
+## Create test cases
+
+Having a strong test suite for a tool like this is essential. It is very easy
+to create regressions. Any tests you can add are very much appreciated.
+
+The tests can be run with `cargo test`. This does a number of things:
+* runs the unit tests for a number of internal functions;
+* makes sure that rustfmt run on every file in `./tests/source/` is equal to its
+  associated file in `./tests/target/`;
+* runs idempotence tests on the files in `./tests/target/`. These files should
+  not be changed by rustfmt;
+* checks that rustfmt's code is not changed by running on itself. This ensures
+  that the project bootstraps.
+
+Creating a test is as easy as creating a new file in `./tests/source/` and an
+equally named one in `./tests/target/`. If it is only required that rustfmt
+leaves a piece of code unformatted, it may suffice to only create a target file.
+
+Whenever there's a discrepancy between the expected output when running tests, a
+colourised diff will be printed so that the offending line(s) can quickly be
+identified.
+
+Without explicit settings, the tests will be run using rustfmt's default
+configuration. It is possible to run a test using non-default settings in several 
+ways. Firstly, you can include configuration parameters in comments at the top
+of the file. For example: to use 3 spaces per tab, start your test with
+`// rustfmt-tab_spaces: 3`. Just remember that the comment is part of the input,
+so include in both the source and target files! It is also possible to
+explicitly specify the name of the expected output file in the target directory.
+Use `// rustfmt-target: filename.rs` for this. You can also specify a custom
+configuration by using the `rustfmt-config` directive. Rustfmt will then use
+that toml file located in `./tests/config/` for its configuration. Including
+`// rustfmt-config: small_tabs.toml` will run your test with the configuration
+file found at `./tests/config/small_tabs.toml`. The final option is used when the
+test source file contains no configuration parameter comments. In this case, the
+test harness looks for a configuration file with the same filename as the test
+file in the `./tests/config/` directory, so a test source file named `test-indent.rs`
+would need a configuration file named `test-indent.toml` in that directory. As an
+example, the `issue-1111.rs` test file is configured by the file
+`./tests/config/issue-1111.toml`.
+
+## Debugging
+
+Some `rewrite_*` methods use the `debug!` macro for printing useful information.
+These messages can be printed by using the environment variable `RUST_LOG=rustfmt=DEBUG`.
+These traces can be helpful in understanding which part of the code was used
+and get a better grasp on the execution flow.
+
+## Hack!
+
+Here are some [good starting issues](https://github.com/rust-lang/rustfmt/issues?q=is%3Aopen+is%3Aissue+label%3Agood-first-issue).
+
+If you've found areas which need polish and don't have issues, please submit a
+PR, don't feel there needs to be an issue.
+
+
+### Guidelines
+
+Rustfmt bootstraps, that is part of its test suite is running itself on its
+source code. So, basically, the only style guideline is that you must pass the
+tests. That ensures that the Rustfmt source code adheres to our own conventions.
+
+Talking of tests, if you add a new feature or fix a bug, please also add a test.
+It's really easy, see above for details. Please run `cargo test` before
+submitting a PR to ensure your patch passes all tests, it's pretty quick.
+
+Rustfmt is post-1.0 and within major version releases we strive for backwards
+compatibility (at least when using the default options). That means any code
+which changes Rustfmt's output must be guarded by either an option or a version
+check. The latter is implemented as an option called `option`. See the section on
+[configuration](#Configuration) below.
+
+Please try to avoid leaving `TODO`s in the code. There are a few around, but I
+wish there weren't. You can leave `FIXME`s, preferably with an issue number.
+
+
+### Version-gate formatting changes
+
+A change that introduces a different code-formatting should be gated on the
+`version` configuration. This is to ensure the formatting of the current major
+release is preserved, while allowing fixes to be implemented for the next
+release.
+
+This is done by conditionally guarding the change like so:
+
+```rust
+if config.version() == Version::One { // if the current major release is 1.x
+    // current formatting
+} else {
+    // new formatting
+}
+```
+
+This allows the user to apply the next formatting explicitly via the
+configuration, while being stable by default.
+
+When the next major release is done, the code block of the previous formatting
+can be deleted, e.g., the first block in the example above when going from `1.x`
+to `2.x`.
+
+| Note: Only formatting changes with default options need to be gated. |
+| --- |
+
+### A quick tour of Rustfmt
+
+Rustfmt is basically a pretty printer - that is, its mode of operation is to
+take an AST (abstract syntax tree) and print it in a nice way (including staying
+under the maximum permitted width for a line). In order to get that AST, we
+first have to parse the source text, we use the Rust compiler's parser to do
+that (see [src/lib.rs](src/lib.rs)). We shy away from doing anything too fancy, such as
+algebraic approaches to pretty printing, instead relying on an heuristic
+approach, 'manually' crafting a string for each AST node. This results in quite
+a lot of code, but it is relatively simple.
+
+The AST is a tree view of source code. It carries all the semantic information
+about the code, but not all of the syntax. In particular, we lose white space
+and comments (although doc comments are preserved). Rustfmt uses a view of the
+AST before macros are expanded, so there are still macro uses in the code. The
+arguments to macros are not an AST, but raw tokens - this makes them harder to
+format.
+
+There are different nodes for every kind of item and expression in Rust. For
+more details see the source code in the compiler -
+[ast.rs](https://dxr.mozilla.org/rust/source/src/libsyntax/ast.rs) - and/or the
+[docs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/ast/index.html).
+
+Many nodes in the AST (but not all, annoyingly) have a `Span`. A `Span` is a
+range in the source code, it can easily be converted to a snippet of source
+text. When the AST does not contain enough information for us, we rely heavily
+on `Span`s. For example, we can look between spans to try and find comments, or
+parse a snippet to see how the user wrote their source code.
+
+The downside of using the AST is that we miss some information - primarily white
+space and comments. White space is sometimes significant, although mostly we
+want to ignore it and make our own. We strive to reproduce all comments, but
+this is sometimes difficult. The crufty corners of Rustfmt are where we hack
+around the absence of comments in the AST and try to recreate them as best we
+can.
+
+Our primary tool here is to look between spans for text we've missed. For
+example, in a function call `foo(a, b)`, we have spans for `a` and `b`, in this
+case, there is only a comma and a single space between the end of `a` and the
+start of `b`, so there is nothing much to do. But if we look at
+`foo(a /* a comment */, b)`, then between `a` and `b` we find the comment.
+
+At a higher level, Rustfmt has machinery so that we account for text between
+'top level' items. Then we can reproduce that text pretty much verbatim. We only
+count spans we actually reformat, so if we can't format a span it is not missed
+completely but is reproduced in the output without being formatted. This is
+mostly handled in [src/missed_spans.rs](src/missed_spans.rs). See also `FmtVisitor::last_pos` in
+[src/visitor.rs](src/visitor.rs).
+
+
+#### Some important elements
+
+At the highest level, Rustfmt uses a `Visitor` implementation called `FmtVisitor`
+to walk the AST. This is in [src/visitor.rs](src/visitor.rs). This is really just used to walk
+items, rather than the bodies of functions. We also cover macros and attributes
+here. Most methods of the visitor call out to `Rewrite` implementations that
+then walk their own children.
+
+The `Rewrite` trait is defined in [src/rewrite.rs](src/rewrite.rs). It is implemented for many
+things that can be rewritten, mostly AST nodes. It has a single function,
+`rewrite`, which is called to rewrite `self` into an `Option<String>`. The
+arguments are `width` which is the horizontal space we write into and `offset`
+which is how much we are currently indented from the lhs of the page. We also
+take a context which contains information used for parsing, the current block
+indent, and a configuration (see below).
+
+##### Rewrite and Indent
+
+To understand the indents, consider
+
+```
+impl Foo {
+    fn foo(...) {
+        bar(argument_one,
+            baz());
+    }
+}
+```
+
+When formatting the `bar` call we will format the arguments in order, after the
+first one we know we are working on multiple lines (imagine it is longer than
+written). So, when we come to the second argument, the indent we pass to
+`rewrite` is 12, which puts us under the first argument. The current block
+indent (stored in the context) is 8. The former is used for visual indenting
+(when objects are vertically aligned with some marker), the latter is used for
+block indenting (when objects are tabbed in from the lhs). The width available
+for `baz()` will be the maximum width, minus the space used for indenting, minus
+the space used for the `);`. (Note that actual argument formatting does not
+quite work like this, but it's close enough).
+
+The `rewrite` function returns an `Option` - either we successfully rewrite and
+return the rewritten string for the caller to use, or we fail to rewrite and
+return `None`. This could be because Rustfmt encounters something it doesn't
+know how to reformat, but more often it is because Rustfmt can't fit the item
+into the required width. How to handle this is up to the caller. Often the
+caller just gives up, ultimately relying on the missed spans system to paste in
+the un-formatted source. A better solution (although not performed in many
+places) is for the caller to shuffle around some of its other items to make
+more width, then call the function again with more space.
+
+Since it is common for callers to bail out when a callee fails, we often use a
+`?` operator to make this pattern more succinct.
+
+One way we might find out that we don't have enough space is when computing how much
+space we have. Something like `available_space = budget - overhead`. Since
+widths are unsized integers, this would cause underflow. Therefore we use
+checked subtraction: `available_space = budget.checked_sub(overhead)?`.
+`checked_sub` returns an `Option`, and if we would underflow `?` returns
+`None`, otherwise, we proceed with the computed space.
+
+##### Rewrite of list-like expressions
+
+Much of the syntax in Rust is lists: lists of arguments, lists of fields, lists of
+array elements, etc. We have some generic code to handle lists, including how to
+space them in horizontal and vertical space, indentation, comments between
+items, trailing separators, etc. However, since there are so many options, the
+code is a bit complex. Look in [src/lists.rs](src/lists.rs). `write_list` is the key function,
+and `ListFormatting` the key structure for configuration. You'll need to make a
+`ListItems` for input, this is usually done using `itemize_list`.
+
+##### Configuration
+
+Rustfmt strives to be highly configurable. Often the first part of a patch is
+creating a configuration option for the feature you are implementing. All
+handling of configuration options is done in [src/config/mod.rs](src/config/mod.rs). Look for the
+`create_config!` macro at the end of the file for all the options. The rest of
+the file defines a bunch of enums used for options, and the machinery to produce
+the config struct and parse a config file, etc. Checking an option is done by
+accessing the correct field on the config struct, e.g., `config.max_width()`. Most
+functions have a `Config`, or one can be accessed via a visitor or context of
+some kind.
diff --git a/src/tools/rustfmt/Design.md b/src/tools/rustfmt/Design.md
new file mode 100644
index 0000000000000..00a7652aee0dc
--- /dev/null
+++ b/src/tools/rustfmt/Design.md
@@ -0,0 +1,184 @@
+# Some thoughts on the design of rustfmt
+
+## Use cases
+
+A formatting tool can be used in different ways and the different use cases can
+affect the design of the tool. The use cases I'm particularly concerned with are:
+
+* running on a whole repo before check-in
+  - in particular, to replace the `make tidy` pass on the Rust distro
+* running on code from another project that you are adding to your own
+* using for mass changes in code style over a project
+
+Some valid use cases for a formatting tool which I am explicitly not trying to
+address (although it would be nice, if possible):
+
+* running 'as you type' in an IDE
+* running on arbitrary snippets of code
+* running on Rust-like code, specifically code which doesn't parse
+* use as a pretty printer inside the compiler
+* refactoring
+* formatting totally unformatted source code
+
+
+## Scope and vision
+
+I do not subscribe to the notion that a formatting tool should only change
+whitespace. I believe that we should semantics preserving, but not necessarily
+syntax preserving, i.e., we can change the AST of a program.
+
+I.e., we might change glob imports to list or single imports, re-order imports,
+move bounds to where clauses, combine multiple impls into a single impl, etc.
+
+However, we will not change the names of variables or make any changes which
+*could* change the semantics. To be ever so slightly formal, we might imagine
+a compilers high level intermediate representation, we should strive to only
+make changes which do not change the HIR, even if they do change the AST.
+
+I would like to be able to output refactoring scripts for making deeper changes
+though. (E.g., renaming variables to satisfy our style guidelines).
+
+My long term goal is that all style lints can be moved from the compiler to
+rustfmt and, as well as warning, can either fix problems or emit refactoring
+scripts to do so.
+
+### Configurability
+
+I believe reformatting should be configurable to some extent. We should read in
+options from a configuration file and reformat accordingly. We should supply at
+least a config file which matches the Rust style guidelines.
+
+There should be multiple modes for running the tool. As well as simply replacing
+each file, we should be able to show the user a list of the changes we would
+make, or show a list of violations without corrections (the difference being
+that there are multiple ways to satisfy a given set of style guidelines, and we
+should distinguish violations from deviations from our own model).
+
+
+## Implementation philosophy
+
+Some details of the philosophy behind the implementation.
+
+
+### Operate on the AST
+
+A reformatting tool can be based on either the AST or a token stream (in Rust
+this is actually a stream of token trees, but it's not a fundamental difference).
+There are pros and cons to the two approaches. I have chosen to use the AST
+approach. The primary reasons are that it allows us to do more sophisticated
+manipulations, rather than just change whitespace, and it gives us more context
+when making those changes.
+
+The advantage of the tokens approach is that you can operate on non-parsable
+code. I don't care too much about that, it would be nice, but I think being able
+to perform sophisticated transformations is more important. In the future, I hope to
+(optionally) be able to use type information for informing reformatting too. One
+specific case of unparsable code is macros. Using tokens is certainly easier
+here, but I believe it is perfectly solvable with the AST approach. At the limit,
+we can operate on just tokens in the macro case.
+
+I believe that there is not in fact that much difference between the two
+approaches. Due to imperfect span information, under the AST approach, we
+sometimes are reduced to examining tokens or do some re-lexing of our own. Under
+the tokens approach, you need to implement your own (much simpler) parser. I
+believe that as the tool gets more sophisticated, you end up doing more at the
+token-level, or having an increasingly sophisticated parser, until at the limit
+you have the same tool.
+
+However, I believe starting from the AST gets you more quickly to a usable and
+useful tool.
+
+
+### Heuristic rather than algorithmic
+
+Many formatting tools use a very general algorithmic or even algebraic tool for
+pretty printing. This results in very elegant code, but I believe does not give
+the best results. I prefer a more ad hoc approach where each expression/item is
+formatted using custom rules. We hopefully don't end up with too much code due
+to good old fashioned abstraction and code sharing. This will give a bigger code
+base, but hopefully a better result.
+
+It also means that there will be some cases we can't format and we have to give
+up. I think that is OK. Hopefully, they are rare enough that manually fixing them
+is not painful. Better to have a tool that gives great code in 99% of cases and
+fails in 1% than a tool which gives 50% great code and 50% ugly code, but never
+fails.
+
+
+### Incremental development
+
+I want rustfmt to be useful as soon as possible and to always be useful. I
+specifically don't want to have to wait for a feature (or worse, the whole tool)
+to be perfect before it is useful. The main ways this is achieved is to output
+the source code where we can't yet reformat, be able to turn off new features
+until they are ready, and the 'do no harm' principle (see next section).
+
+
+### First, do no harm
+
+Until rustfmt is perfect, there will always be a trade-off between doing more and
+doing existing things well. I want to err on the side of the latter.
+Specifically, rustfmt should never take OK code and make it look worse. If we
+can't make it better, we should leave it as is. That might mean being less
+aggressive than we like or using configurability.
+
+
+### Use the source code as guidance
+
+There are often multiple ways to format code and satisfy standards. Where this
+is the case, we should use the source code as a hint for reformatting.
+Furthermore, where the code has been formatted in a particular way that satisfies
+the coding standard, it should not be changed (this is sometimes not possible or
+not worthwhile due to uniformity being desirable, but it is a useful goal).
+
+
+### Architecture details
+
+We use the AST from [syntex_syntax], an export of rustc's libsyntax. We use
+syntex_syntax's visit module to walk the AST to find starting points for
+reformatting. Eventually, we should reformat everything and we shouldn't need
+the visit module. We keep track of the last formatted position in the code, and
+when we reformat the next piece of code we make sure to output the span for all
+the code in between (handled by missed_spans.rs).
+
+[syntex_syntax]: https://crates.io/crates/syntex_syntax
+
+We read in formatting configuration from a `rustfmt.toml` file if there is one.
+The options and their defaults are defined in `config.rs`. A `Config` object is
+passed throughout the formatting code, and each formatting routine looks there
+for its configuration.
+
+Our visitor keeps track of the desired current indent due to blocks (
+`block_indent`). Each `visit_*` method reformats code according to this indent,
+`config.comment_width()` and `config.max_width()`. Most reformatting that is done 
+in the `visit_*` methods is a bit hacky and is meant to be temporary until it can 
+be done properly.
+
+There are a bunch of methods called `rewrite_*`. They do the bulk of the
+reformatting. These take the AST node to be reformatted (this may not literally
+be an AST node from syntex_syntax: there might be multiple parameters
+describing a logical node), the current indent, and the current width budget.
+They return a `String` (or sometimes an `Option<String>`) which formats the
+code in the box given by the indent and width budget. If the method fails, it
+returns `None` and the calling method then has to fallback in some way to give
+the callee more space.
+
+So, in summary, to format a node, we calculate the width budget and then walk down
+the tree from the node. At a leaf, we generate an actual string and then unwind,
+combining these strings as we go back up the tree.
+
+For example, consider a method definition:
+
+```
+    fn foo(a: A, b: B) {
+        ...
+    }
+```
+
+We start at indent 4, the rewrite function for the whole function knows it must
+write `fn foo(` before the arguments and `) {` after them, assuming the max width
+is 100, it thus asks the rewrite argument list function to rewrite with an indent
+of 11 and in a width of 86. Assuming that is possible (obviously in this case),
+it returns a string for the arguments and it can make a string for the function
+header. If the arguments couldn't be fitted in that space, we might try to
+fallback to a hanging indent, so we try again with indent 8 and width 89.
diff --git a/src/tools/rustfmt/LICENSE-APACHE b/src/tools/rustfmt/LICENSE-APACHE
new file mode 100644
index 0000000000000..212ba1f318481
--- /dev/null
+++ b/src/tools/rustfmt/LICENSE-APACHE
@@ -0,0 +1,201 @@
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new file mode 100644
index 0000000000000..1baa137f605b7
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+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/src/tools/rustfmt/Makefile.toml b/src/tools/rustfmt/Makefile.toml
new file mode 100644
index 0000000000000..597dd1205643d
--- /dev/null
+++ b/src/tools/rustfmt/Makefile.toml
@@ -0,0 +1,71 @@
+[env]
+CFG_RELEASE = { value = "${CARGO_MAKE_RUST_VERSION}", condition = { env_not_set = ["CFG_RELEASE"] } }
+CFG_RELEASE_CHANNEL = { value = "${CARGO_MAKE_RUST_CHANNEL}", condition = { env_not_set = ["CFG_RELEASE_CHANNEL"] } }
+
+[tasks.build-bin]
+command = "cargo"
+args = [
+  "build",
+  "--bin",
+  "rustfmt",
+  "--bin",
+  "cargo-fmt",
+]
+
+[tasks.build-bins]
+command = "cargo"
+args = [
+  "build",
+  "--bins",
+]
+
+[tasks.install]
+command = "cargo"
+args = [
+  "install",
+  "--path",
+  ".",
+  "--force",
+  "--locked", # Respect Cargo.lock
+]
+
+[tasks.release]
+command = "cargo"
+args = [
+  "build",
+	"--release",
+]
+
+[tasks.test]
+command = "cargo"
+args = [
+  "test",
+]
+
+[tasks.test-all]
+dependencies = ["build-bin"]
+run_task = { name = ["test", "test-ignored"] }
+
+[tasks.test-ignored]
+command = "cargo"
+args = [
+  "test",
+	"--",
+	"--ignored",
+]
+
+[tasks.b]
+alias = "build"
+
+[tasks.bb]
+alias = "build-bin"
+
+[tasks.bins]
+alias = "build-bins"
+
+[tasks.c]
+alias = "check"
+
+[tasks.t]
+alias = "test"
+
diff --git a/src/tools/rustfmt/Processes.md b/src/tools/rustfmt/Processes.md
new file mode 100644
index 0000000000000..9d86d52b122d8
--- /dev/null
+++ b/src/tools/rustfmt/Processes.md
@@ -0,0 +1,57 @@
+This document outlines processes regarding management of rustfmt.
+
+# Stabilising an Option
+
+In this Section, we describe how to stabilise an option of the rustfmt's configration.
+
+## Conditions
+
+- Is the default value correct ?
+- The design and implementation of the option are sound and clean.
+- The option is well tested, both in unit tests and, optimally, in real usage.
+- There is no open bug about the option that prevents its use.
+
+## Steps
+
+Open a pull request that closes the tracking issue. The tracking issue is listed beside the option in `Configurations.md`.
+
+- Update the `Config` enum marking the option as stable.
+- Update the the `Configuration.md` file marking the option as stable.
+- Update `CHANGELOG.md` marking the option as stable.
+
+## After the stabilisation
+
+The option should remain backward-compatible with previous parameters of the option. For instance, if the option is an enum `enum Foo { Alice, Bob }` and the variant `Foo::Bob` is removed/renamed, existing use of the `Foo::Bob` variant should map to the new logic. Breaking changes can be applied under the condition they are version-gated.
+
+# Make a Release
+
+## 0. Update CHANGELOG.md
+
+## 1. Update Cargo.toml and Cargo.lock
+
+For example, 1.0.0 -> 1.0.1:
+
+```diff
+-version = "1.0.0"
++version = "1.0.1"
+```
+
+## 2. Push the commit to the master branch
+
+E.g., https://github.com/rust-lang/rustfmt/commit/5274b49caa1a7db6ac10c76bf1a3d5710ccef569
+
+## 3. Create a release tag
+
+```sh
+git tag -s v1.2.3 -m "Release 1.2.3"
+```
+
+## 4. Publish to crates.io
+
+`cargo publish`
+
+## 5. Create a PR to rust-lang/rust to update the rustfmt submodule
+
+Note that if you are updating `rustc-ap-*` crates, then you need to update **every** submodules in the rust-lang/rust repository that depend on the crates to use the same version of those.
+
+As of 2019/05, there are two such crates: `rls` and `racer` (`racer` depends on `rustc-ap-syntax` and `rls` depends on `racer`, and `rls` is one of submodules of the rust-lang/rust repository).
diff --git a/src/tools/rustfmt/README.md b/src/tools/rustfmt/README.md
new file mode 100644
index 0000000000000..7a97d31bab9c7
--- /dev/null
+++ b/src/tools/rustfmt/README.md
@@ -0,0 +1,234 @@
+# rustfmt [![Build Status](https://travis-ci.com/rust-lang/rustfmt.svg?branch=master)](https://travis-ci.com/rust-lang/rustfmt) [![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-lang/rustfmt?svg=true)](https://ci.appveyor.com/project/rust-lang-libs/rustfmt) [![crates.io](https://img.shields.io/crates/v/rustfmt-nightly.svg)](https://crates.io/crates/rustfmt-nightly) [![Travis Configuration Status](https://img.shields.io/travis/davidalber/rustfmt-travis.svg?label=travis%20example)](https://travis-ci.org/davidalber/rustfmt-travis)
+
+A tool for formatting Rust code according to style guidelines.
+
+If you'd like to help out (and you should, it's a fun project!), see
+[Contributing.md](Contributing.md) and our [Code of
+Conduct](CODE_OF_CONDUCT.md).
+
+You can use rustfmt in Travis CI builds. We provide a minimal Travis CI
+configuration (see [here](#checking-style-on-a-ci-server)) and verify its status
+using another repository. The status of that repository's build is reported by
+the "travis example" badge above.
+
+## Quick start
+
+You can run `rustfmt` with Rust 1.24 and above.
+
+### On the Stable toolchain
+
+To install:
+
+```sh
+rustup component add rustfmt
+```
+
+To run on a cargo project in the current working directory:
+
+```sh
+cargo fmt
+```
+
+### On the Nightly toolchain
+
+For the latest and greatest `rustfmt`, nightly is required.
+
+To install:
+
+```sh
+rustup component add rustfmt --toolchain nightly
+```
+
+To run on a cargo project in the current working directory:
+
+```sh
+cargo +nightly fmt
+```
+
+## Limitations
+
+Rustfmt tries to work on as much Rust code as possible, sometimes, the code
+doesn't even need to compile! As we approach a 1.0 release we are also looking
+to limit areas of instability; in particular, post-1.0, the formatting of most
+code should not change as Rustfmt improves. However, there are some things that
+Rustfmt can't do or can't do well (and thus where formatting might change
+significantly, even post-1.0). We would like to reduce the list of limitations
+over time.
+
+The following list enumerates areas where Rustfmt does not work or where the
+stability guarantees do not apply (we don't make a distinction between the two
+because in the future Rustfmt might work on code where it currently does not):
+
+* a program where any part of the program does not parse (parsing is an early
+  stage of compilation and in Rust includes macro expansion).
+* Macro declarations and uses (current status: some macro declarations and uses
+  are formatted).
+* Comments, including any AST node with a comment 'inside' (Rustfmt does not
+  currently attempt to format comments, it does format code with comments inside, but that formatting may change in the future).
+* Rust code in code blocks in comments.
+* Any fragment of a program (i.e., stability guarantees only apply to whole
+  programs, even where fragments of a program can be formatted today).
+* Code containing non-ascii unicode characters (we believe Rustfmt mostly works
+  here, but do not have the test coverage or experience to be 100% sure).
+* Bugs in Rustfmt (like any software, Rustfmt has bugs, we do not consider bug
+  fixes to break our stability guarantees).
+
+
+## Installation
+
+```sh
+rustup component add rustfmt
+```
+
+## Installing from source
+
+To install from source (nightly required), first checkout to the tag or branch you want to install, then issue
+
+```sh
+cargo install --path .
+```
+
+This will install `rustfmt` in your `~/.cargo/bin`. Make sure to add `~/.cargo/bin` directory to
+your PATH variable.
+
+
+## Running
+
+You can run Rustfmt by just typing `rustfmt filename` if you used `cargo
+install`. This runs rustfmt on the given file, if the file includes out of line
+modules, then we reformat those too. So to run on a whole module or crate, you
+just need to run on the root file (usually mod.rs or lib.rs). Rustfmt can also
+read data from stdin. Alternatively, you can use `cargo fmt` to format all
+binary and library targets of your crate.
+
+You can run `rustfmt --help` for information about available arguments.
+
+When running with `--check`, Rustfmt will exit with `0` if Rustfmt would not
+make any formatting changes to the input, and `1` if Rustfmt would make changes.
+In other modes, Rustfmt will exit with `1` if there was some error during
+formatting (for example a parsing or internal error) and `0` if formatting
+completed without error (whether or not changes were made).
+
+
+
+## Running Rustfmt from your editor
+
+* [Vim](https://github.com/rust-lang/rust.vim#formatting-with-rustfmt)
+* [Emacs](https://github.com/rust-lang/rust-mode)
+* [Sublime Text 3](https://packagecontrol.io/packages/RustFmt)
+* [Atom](atom.md)
+* Visual Studio Code using [vscode-rust](https://github.com/editor-rs/vscode-rust), [vsc-rustfmt](https://github.com/Connorcpu/vsc-rustfmt) or [rls_vscode](https://github.com/jonathandturner/rls_vscode) through RLS.
+* [IntelliJ or CLion](intellij.md)
+
+
+## Checking style on a CI server
+
+To keep your code base consistently formatted, it can be helpful to fail the CI build
+when a pull request contains unformatted code. Using `--check` instructs
+rustfmt to exit with an error code if the input is not formatted correctly.
+It will also print any found differences. (Older versions of Rustfmt don't
+support `--check`, use `--write-mode diff`).
+
+A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
+
+```yaml
+language: rust
+before_script:
+- rustup component add rustfmt
+script:
+- cargo build
+- cargo test
+- cargo fmt --all -- --check
+```
+
+See [this blog post](https://medium.com/@ag_dubs/enforcing-style-in-ci-for-rust-projects-18f6b09ec69d)
+for more info.
+
+## How to build and test
+
+`cargo build` to build.
+
+`cargo test` to run all tests.
+
+To run rustfmt after this, use `cargo run --bin rustfmt -- filename`. See the
+notes above on running rustfmt.
+
+
+## Configuring Rustfmt
+
+Rustfmt is designed to be very configurable. You can create a TOML file called
+`rustfmt.toml` or `.rustfmt.toml`, place it in the project or any other parent
+directory and it will apply the options in that file. See `rustfmt
+--help=config` for the options which are available, or if you prefer to see
+visual style previews, [GitHub page](https://rust-lang.github.io/rustfmt/).
+
+By default, Rustfmt uses a style which conforms to the [Rust style guide][style
+guide] that has been formalized through the [style RFC
+process][fmt rfcs].
+
+Configuration options are either stable or unstable. Stable options can always
+be used, while unstable ones are only available on a nightly toolchain, and opt-in.
+See [GitHub page](https://rust-lang.github.io/rustfmt/) for details.
+
+### Rust's Editions
+
+Rustfmt is able to pick up the edition used by reading the `Cargo.toml` file if
+executed through the Cargo's formatting tool `cargo fmt`. Otherwise, the edition
+needs to be specified in `rustfmt.toml`, e.g., with `edition = "2018"`.
+
+## Tips
+
+* For things you do not want rustfmt to mangle, use `#[rustfmt::skip]`
+* To prevent rustfmt from formatting a macro or an attribute,
+  use `#[rustfmt::skip::macros(target_macro_name)]` or 
+  `#[rustfmt::skip::attributes(target_attribute_name)]`
+
+  Example:
+
+    ```rust
+    #![rustfmt::skip::attributes(custom_attribute)]   
+
+    #[custom_attribute(formatting , here , should , be , Skipped)]
+    #[rustfmt::skip::macros(html)]
+    fn main() {
+        let macro_result1 = html! { <div>
+    Hello</div>
+        }.to_string();
+    ```
+* When you run rustfmt, place a file named `rustfmt.toml` or `.rustfmt.toml` in
+  target file directory or its parents to override the default settings of
+  rustfmt. You can generate a file containing the default configuration with
+  `rustfmt --print-config default rustfmt.toml` and customize as needed.
+* After successful compilation, a `rustfmt` executable can be found in the
+  target directory.
+* If you're having issues compiling Rustfmt (or compile errors when trying to
+  install), make sure you have the most recent version of Rust installed.
+
+* You can change the way rustfmt emits the changes with the --emit flag:
+
+  Example:
+
+  ```sh
+  cargo fmt -- --emit files
+  ```
+
+  Options:
+
+  | Flag |Description| Nightly Only |
+  |:---:|:---:|:---:|
+  | files | overwrites output to files | No |
+  | stdout | writes output to stdout | No |
+  | coverage | displays how much of the input file was processed | Yes |
+  | checkstyle | emits in a checkstyle format | Yes |
+  | json | emits diffs in a json format | Yes |
+
+## License
+
+Rustfmt is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT) for details.
+
+[rust]: https://github.com/rust-lang/rust
+[fmt rfcs]: https://github.com/rust-lang-nursery/fmt-rfcs
+[style guide]: https://github.com/rust-lang-nursery/fmt-rfcs/blob/master/guide/guide.md
diff --git a/src/tools/rustfmt/appveyor.yml b/src/tools/rustfmt/appveyor.yml
new file mode 100644
index 0000000000000..7bfe696009fac
--- /dev/null
+++ b/src/tools/rustfmt/appveyor.yml
@@ -0,0 +1,55 @@
+# This is based on https://github.com/japaric/rust-everywhere/blob/master/appveyor.yml
+# and modified (mainly removal of deployment) to suit rustfmt.
+
+environment:
+  global:
+    PROJECT_NAME: rustfmt
+  matrix:
+    # Stable channel
+    # - TARGET: i686-pc-windows-gnu
+    #   CHANNEL: stable
+    # - TARGET: i686-pc-windows-msvc
+    #   CHANNEL: stable
+    # - TARGET: x86_64-pc-windows-gnu
+    #   CHANNEL: stable
+    # - TARGET: x86_64-pc-windows-msvc
+    #   CHANNEL: stable
+    # Beta channel
+    # - TARGET: i686-pc-windows-gnu
+    #   CHANNEL: beta
+    # - TARGET: i686-pc-windows-msvc
+    #   CHANNEL: beta
+    # - TARGET: x86_64-pc-windows-gnu
+    #   CHANNEL: beta
+    # - TARGET: x86_64-pc-windows-msvc
+    #   CHANNEL: beta
+    # Nightly channel
+    - TARGET: i686-pc-windows-gnu
+      CHANNEL: nightly
+    - TARGET: i686-pc-windows-msvc
+      CHANNEL: nightly
+    - TARGET: x86_64-pc-windows-gnu
+      CHANNEL: nightly
+    - TARGET: x86_64-pc-windows-msvc
+      CHANNEL: nightly
+
+# Install Rust and Cargo
+# (Based on from https://github.com/rust-lang/libc/blob/master/appveyor.yml)
+install:
+  - appveyor-retry appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
+  - if "%TARGET%" == "i686-pc-windows-gnu" set PATH=%PATH%;C:\msys64\mingw32\bin
+  - if "%TARGET%" == "x86_64-pc-windows-gnu" set PATH=%PATH%;C:\msys64\mingw64\bin
+  - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
+  - rustup-init.exe --default-host %TARGET% --default-toolchain %CHANNEL% -y
+  - rustc -Vv
+  - cargo -V
+
+# ???
+build: false
+
+test_script:
+  - set CFG_RELEASE_CHANNEL=nightly
+  - set CFG_RELEASE=nightly
+  - cargo build --verbose
+  - cargo test
+  - cargo test -- --ignored
diff --git a/src/tools/rustfmt/atom.md b/src/tools/rustfmt/atom.md
new file mode 100644
index 0000000000000..f77ac1490721d
--- /dev/null
+++ b/src/tools/rustfmt/atom.md
@@ -0,0 +1,31 @@
+# Running Rustfmt from Atom
+
+## RLS
+
+Rustfmt is included with the Rust Language Server, itself provided by [ide-rust](https://atom.io/packages/ide-rust).
+
+`apm install ide-rust`
+
+Once installed a file is formatted with `ctrl-shift-c` or `cmd-shift-c`, also available in context menu.
+
+## atom-beautify
+
+Another way is to install [Beautify](https://atom.io/packages/atom-beautify), you
+can do this by running `apm install atom-beautify`.
+
+There are 2 settings that need to be configured in the atom beautifier configuration.
+
+-  Install rustfmt as per the [readme](README.md).
+-  Open the atom beautifier settings
+
+   Go to Edit->Preferences. Click the packages on the left side and click on setting for atom-beautifier
+
+-  Set rustfmt as the beautifier
+
+   Find the setting labeled *Language Config - Rust - Default Beautifier* and make sure it is set to rustfmt as shown below. You can also set the beautifier to auto format on save here.
+![image](https://cloud.githubusercontent.com/assets/6623285/11147685/c8ade16c-8a3d-11e5-9da5-bd3d998d97f9.png)
+
+-  Set the path to your rustfmt location
+
+   Find the setting labeled *Rust - Rustfmt Path*. This setting is towards the bottom and you will need to scroll a bit. Set it to the path for your rustfmt executable.
+![image](https://cloud.githubusercontent.com/assets/6623285/11147718/f4d10224-8a3d-11e5-9f69-9e900cbe0278.png)
diff --git a/src/tools/rustfmt/bootstrap.sh b/src/tools/rustfmt/bootstrap.sh
new file mode 100755
index 0000000000000..05ac0ce2f306f
--- /dev/null
+++ b/src/tools/rustfmt/bootstrap.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# Make sure you double check the diffs after running this script - with great
+# power comes great responsibility.
+# We deliberately avoid reformatting files with rustfmt comment directives.
+
+cargo build --release
+
+target/release/rustfmt src/lib.rs
+target/release/rustfmt src/bin/main.rs
+target/release/rustfmt src/cargo-fmt/main.rs
+
+for filename in tests/target/*.rs; do
+    if ! grep -q "rustfmt-" "$filename"; then
+        target/release/rustfmt $filename
+    fi
+done
diff --git a/src/tools/rustfmt/build.rs b/src/tools/rustfmt/build.rs
new file mode 100644
index 0000000000000..e7b1e1b854c07
--- /dev/null
+++ b/src/tools/rustfmt/build.rs
@@ -0,0 +1,55 @@
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+fn main() {
+    // Only check .git/HEAD dirty status if it exists - doing so when
+    // building dependent crates may lead to false positives and rebuilds
+    if Path::new(".git/HEAD").exists() {
+        println!("cargo:rerun-if-changed=.git/HEAD");
+    }
+
+    println!("cargo:rerun-if-env-changed=CFG_RELEASE_CHANNEL");
+
+    let out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+
+    File::create(out_dir.join("commit-info.txt"))
+        .unwrap()
+        .write_all(commit_info().as_bytes())
+        .unwrap();
+}
+
+// Try to get hash and date of the last commit on a best effort basis. If anything goes wrong
+// (git not installed or if this is not a git repository) just return an empty string.
+fn commit_info() -> String {
+    match (channel(), commit_hash(), commit_date()) {
+        (channel, Some(hash), Some(date)) => format!("{} ({} {})", channel, hash.trim_end(), date),
+        _ => String::new(),
+    }
+}
+
+fn channel() -> String {
+    if let Ok(channel) = env::var("CFG_RELEASE_CHANNEL") {
+        channel
+    } else {
+        "nightly".to_owned()
+    }
+}
+
+fn commit_hash() -> Option<String> {
+    Command::new("git")
+        .args(&["rev-parse", "--short", "HEAD"])
+        .output()
+        .ok()
+        .and_then(|r| String::from_utf8(r.stdout).ok())
+}
+
+fn commit_date() -> Option<String> {
+    Command::new("git")
+        .args(&["log", "-1", "--date=short", "--pretty=format:%cd"])
+        .output()
+        .ok()
+        .and_then(|r| String::from_utf8(r.stdout).ok())
+}
diff --git a/src/tools/rustfmt/ci/integration.sh b/src/tools/rustfmt/ci/integration.sh
new file mode 100755
index 0000000000000..13a3ecaa1961c
--- /dev/null
+++ b/src/tools/rustfmt/ci/integration.sh
@@ -0,0 +1,107 @@
+#!/usr/bin/env bash
+
+set -ex
+
+: ${INTEGRATION?"The INTEGRATION environment variable must be set."}
+
+# FIXME: this means we can get a stale cargo-fmt from a previous run.
+#
+# `which rustfmt` fails if rustfmt is not found. Since we don't install
+# `rustfmt` via `rustup`, this is the case unless we manually install it. Once
+# that happens, `cargo install --force` will be called, which installs
+# `rustfmt`, `cargo-fmt`, etc to `~/.cargo/bin`. This directory is cached by
+# travis (see `.travis.yml`'s "cache" key), such that build-bots that arrive
+# here after the first installation will find `rustfmt` and won't need to build
+# it again.
+#
+#which cargo-fmt || cargo install --force
+CFG_RELEASE=nightly CFG_RELEASE_CHANNEL=nightly cargo install --path . --force 
+
+echo "Integration tests for: ${INTEGRATION}"
+cargo fmt -- --version
+
+# Checks that:
+#
+# * `cargo fmt --all` succeeds without any warnings or errors
+# * `cargo fmt --all -- --check` after formatting returns success
+# * `cargo test --all` still passes (formatting did not break the build)
+function check_fmt_with_all_tests {
+    check_fmt_base "--all"
+    return $?
+}
+
+# Checks that:
+#
+# * `cargo fmt --all` succeeds without any warnings or errors
+# * `cargo fmt --all -- --check` after formatting returns success
+# * `cargo test --lib` still passes (formatting did not break the build)
+function check_fmt_with_lib_tests {
+    check_fmt_base "--lib"
+    return $?
+}
+
+function check_fmt_base {
+    local test_args="$1"
+    local build=$(cargo test $test_args 2>&1)
+    if [[ "$build" =~ "build failed" ]] || [[ "$build" =~ "test result: FAILED." ]]; then
+          return 0
+    fi
+    touch rustfmt.toml
+    cargo fmt --all -v |& tee rustfmt_output
+    if [[ ${PIPESTATUS[0]} != 0 ]]; then
+        cat rustfmt_output
+        return 1
+    fi
+    cat rustfmt_output
+    ! cat rustfmt_output | grep -q "internal error"
+    if [[ $? != 0 ]]; then
+        return 1
+    fi
+    ! cat rustfmt_output | grep -q "warning"
+    if [[ $? != 0 ]]; then
+        return 1
+    fi
+    ! cat rustfmt_output | grep -q "Warning"
+    if [[ $? != 0 ]]; then
+        return 1
+    fi
+    cargo fmt --all -- --check |& tee rustfmt_check_output
+    if [[ ${PIPESTATUS[0]} != 0 ]]; then
+        cat rustfmt_check_output
+        return 1
+    fi
+    cargo test $test_args
+    if [[ $? != 0 ]]; then
+        return $?
+    fi
+}
+
+function show_head {
+    local head=$(git rev-parse HEAD)
+    echo "Head commit of ${INTEGRATION}: $head"
+}
+
+case ${INTEGRATION} in
+    cargo)
+        git clone --depth=1 https://github.com/rust-lang/${INTEGRATION}.git
+        cd ${INTEGRATION}
+        show_head
+        export CFG_DISABLE_CROSS_TESTS=1
+        check_fmt_with_all_tests
+        cd -
+        ;;
+    crater)
+        git clone --depth=1 https://github.com/rust-lang-nursery/${INTEGRATION}.git
+        cd ${INTEGRATION}
+        show_head
+        check_fmt_with_lib_tests
+        cd -
+        ;;
+    *)
+        git clone --depth=1 https://github.com/rust-lang-nursery/${INTEGRATION}.git
+        cd ${INTEGRATION}
+        show_head
+        check_fmt_with_all_tests
+        cd -
+        ;;
+esac
diff --git a/src/tools/rustfmt/config_proc_macro/.gitignore b/src/tools/rustfmt/config_proc_macro/.gitignore
new file mode 100644
index 0000000000000..9f970225adb6a
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/.gitignore
@@ -0,0 +1 @@
+target/
\ No newline at end of file
diff --git a/src/tools/rustfmt/config_proc_macro/Cargo.lock b/src/tools/rustfmt/config_proc_macro/Cargo.lock
new file mode 100644
index 0000000000000..abcf9654e5d77
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/Cargo.lock
@@ -0,0 +1,68 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "proc-macro2"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rustfmt-config_proc_macro"
+version = "0.1.2"
+dependencies = [
+ "proc-macro2 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.99 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "serde"
+version = "1.0.99"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "serde_derive 1.0.99 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.99"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "syn"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[metadata]
+"checksum proc-macro2 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "e98a83a9f9b331f54b924e68a66acb1bb35cb01fb0a23645139967abefb697e8"
+"checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe"
+"checksum serde 1.0.99 (registry+https://github.com/rust-lang/crates.io-index)" = "fec2851eb56d010dc9a21b89ca53ee75e6528bab60c11e89d38390904982da9f"
+"checksum serde_derive 1.0.99 (registry+https://github.com/rust-lang/crates.io-index)" = "cb4dc18c61206b08dc98216c98faa0232f4337e1e1b8574551d5bad29ea1b425"
+"checksum syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "66850e97125af79138385e9b88339cbcd037e3f28ceab8c5ad98e64f0f1f80bf"
+"checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
diff --git a/src/tools/rustfmt/config_proc_macro/Cargo.toml b/src/tools/rustfmt/config_proc_macro/Cargo.toml
new file mode 100644
index 0000000000000..cc995571602b9
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "rustfmt-config_proc_macro"
+version = "0.2.0"
+authors = ["topecongiro <seuchida@gmail.com>"]
+edition = "2018"
+description = "A collection of procedural macros for rustfmt"
+license = "Apache-2.0/MIT"
+categories = ["development-tools::procedural-macro-helpers"]
+repository = "https://github.com/rust-lang/rustfmt"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "1.0", features = ["full", "visit"] }
+
+[dev-dependencies]
+serde = { version = "1.0", features = ["derive"] }
+
+[features]
+default = []
+debug-with-rustfmt = []
diff --git a/src/tools/rustfmt/config_proc_macro/src/attrs.rs b/src/tools/rustfmt/config_proc_macro/src/attrs.rs
new file mode 100644
index 0000000000000..0baba046f9e91
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/src/attrs.rs
@@ -0,0 +1,57 @@
+//! This module provides utilities for handling attributes on variants
+//! of `config_type` enum. Currently there are two types of attributes
+//! that could appear on the variants of `config_type` enum: `doc_hint`
+//! and `value`. Both comes in the form of name-value pair whose value
+//! is string literal.
+
+/// Returns the value of the first `doc_hint` attribute in the given slice or
+/// `None` if `doc_hint` attribute is not available.
+pub fn find_doc_hint(attrs: &[syn::Attribute]) -> Option<String> {
+    attrs.iter().filter_map(doc_hint).next()
+}
+
+/// Returns `true` if the given attribute is a `doc_hint` attribute.
+pub fn is_doc_hint(attr: &syn::Attribute) -> bool {
+    is_attr_name_value(attr, "doc_hint")
+}
+
+/// Returns a string literal value if the given attribute is `doc_hint`
+/// attribute or `None` otherwise.
+pub fn doc_hint(attr: &syn::Attribute) -> Option<String> {
+    get_name_value_str_lit(attr, "doc_hint")
+}
+
+/// Returns the value of the first `value` attribute in the given slice or
+/// `None` if `value` attribute is not available.
+pub fn find_config_value(attrs: &[syn::Attribute]) -> Option<String> {
+    attrs.iter().filter_map(config_value).next()
+}
+
+/// Returns a string literal value if the given attribute is `value`
+/// attribute or `None` otherwise.
+pub fn config_value(attr: &syn::Attribute) -> Option<String> {
+    get_name_value_str_lit(attr, "value")
+}
+
+/// Returns `true` if the given attribute is a `value` attribute.
+pub fn is_config_value(attr: &syn::Attribute) -> bool {
+    is_attr_name_value(attr, "value")
+}
+
+fn is_attr_name_value(attr: &syn::Attribute, name: &str) -> bool {
+    attr.parse_meta().ok().map_or(false, |meta| match meta {
+        syn::Meta::NameValue(syn::MetaNameValue { ref path, .. }) if path.is_ident(name) => true,
+        _ => false,
+    })
+}
+
+fn get_name_value_str_lit(attr: &syn::Attribute, name: &str) -> Option<String> {
+    attr.parse_meta().ok().and_then(|meta| match meta {
+        syn::Meta::NameValue(syn::MetaNameValue {
+            ref path,
+            lit: syn::Lit::Str(ref lit_str),
+            ..
+        }) if path.is_ident(name) => Some(lit_str.value()),
+        _ => None,
+    })
+}
diff --git a/src/tools/rustfmt/config_proc_macro/src/config_type.rs b/src/tools/rustfmt/config_proc_macro/src/config_type.rs
new file mode 100644
index 0000000000000..93a78b8463ec5
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/src/config_type.rs
@@ -0,0 +1,15 @@
+use proc_macro2::TokenStream;
+
+use crate::item_enum::define_config_type_on_enum;
+use crate::item_struct::define_config_type_on_struct;
+
+/// Defines `config_type` on enum or struct.
+// FIXME: Implement this on struct.
+pub fn define_config_type(input: &syn::Item) -> TokenStream {
+    match input {
+        syn::Item::Struct(st) => define_config_type_on_struct(st),
+        syn::Item::Enum(en) => define_config_type_on_enum(en),
+        _ => panic!("Expected enum or struct"),
+    }
+    .unwrap()
+}
diff --git a/src/tools/rustfmt/config_proc_macro/src/item_enum.rs b/src/tools/rustfmt/config_proc_macro/src/item_enum.rs
new file mode 100644
index 0000000000000..dcee77a8549c5
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/src/item_enum.rs
@@ -0,0 +1,208 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+
+use crate::attrs::*;
+use crate::utils::*;
+
+type Variants = syn::punctuated::Punctuated<syn::Variant, syn::Token![,]>;
+
+/// Defines and implements `config_type` enum.
+pub fn define_config_type_on_enum(em: &syn::ItemEnum) -> syn::Result<TokenStream> {
+    let syn::ItemEnum {
+        vis,
+        enum_token,
+        ident,
+        generics,
+        variants,
+        ..
+    } = em;
+
+    let mod_name_str = format!("__define_config_type_on_enum_{}", ident);
+    let mod_name = syn::Ident::new(&mod_name_str, ident.span());
+    let variants = fold_quote(variants.iter().map(process_variant), |meta| quote!(#meta,));
+
+    let impl_doc_hint = impl_doc_hint(&em.ident, &em.variants);
+    let impl_from_str = impl_from_str(&em.ident, &em.variants);
+    let impl_display = impl_display(&em.ident, &em.variants);
+    let impl_serde = impl_serde(&em.ident, &em.variants);
+    let impl_deserialize = impl_deserialize(&em.ident, &em.variants);
+
+    Ok(quote! {
+        #[allow(non_snake_case)]
+        mod #mod_name {
+            #[derive(Debug, Copy, Clone, Eq, PartialEq)]
+            pub #enum_token #ident #generics { #variants }
+            #impl_display
+            #impl_doc_hint
+            #impl_from_str
+            #impl_serde
+            #impl_deserialize
+        }
+        #vis use #mod_name::#ident;
+    })
+}
+
+/// Remove attributes specific to `config_proc_macro` from enum variant fields.
+fn process_variant(variant: &syn::Variant) -> TokenStream {
+    let metas = variant
+        .attrs
+        .iter()
+        .filter(|attr| !is_doc_hint(attr) && !is_config_value(attr));
+    let attrs = fold_quote(metas, |meta| quote!(#meta));
+    let syn::Variant { ident, fields, .. } = variant;
+    quote!(#attrs #ident #fields)
+}
+
+fn impl_doc_hint(ident: &syn::Ident, variants: &Variants) -> TokenStream {
+    let doc_hint = variants
+        .iter()
+        .map(doc_hint_of_variant)
+        .collect::<Vec<_>>()
+        .join("|");
+    let doc_hint = format!("[{}]", doc_hint);
+    quote! {
+        use crate::config::ConfigType;
+        impl ConfigType for #ident {
+            fn doc_hint() -> String {
+                #doc_hint.to_owned()
+            }
+        }
+    }
+}
+
+fn impl_display(ident: &syn::Ident, variants: &Variants) -> TokenStream {
+    let vs = variants
+        .iter()
+        .filter(|v| is_unit(v))
+        .map(|v| (config_value_of_variant(v), &v.ident));
+    let match_patterns = fold_quote(vs, |(s, v)| {
+        quote! {
+            #ident::#v => write!(f, "{}", #s),
+        }
+    });
+    quote! {
+        use std::fmt;
+        impl fmt::Display for #ident {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                match self {
+                    #match_patterns
+                    _ => unimplemented!(),
+                }
+            }
+        }
+    }
+}
+
+fn impl_from_str(ident: &syn::Ident, variants: &Variants) -> TokenStream {
+    let vs = variants
+        .iter()
+        .filter(|v| is_unit(v))
+        .map(|v| (config_value_of_variant(v), &v.ident));
+    let if_patterns = fold_quote(vs, |(s, v)| {
+        quote! {
+            if #s.eq_ignore_ascii_case(s) {
+                return Ok(#ident::#v);
+            }
+        }
+    });
+    let mut err_msg = String::from("Bad variant, expected one of:");
+    for v in variants.iter().filter(|v| is_unit(v)) {
+        err_msg.push_str(&format!(" `{}`", v.ident));
+    }
+
+    quote! {
+        impl ::std::str::FromStr for #ident {
+            type Err = &'static str;
+
+            fn from_str(s: &str) -> Result<Self, Self::Err> {
+                #if_patterns
+                return Err(#err_msg);
+            }
+        }
+    }
+}
+
+fn doc_hint_of_variant(variant: &syn::Variant) -> String {
+    find_doc_hint(&variant.attrs).unwrap_or(variant.ident.to_string())
+}
+
+fn config_value_of_variant(variant: &syn::Variant) -> String {
+    find_config_value(&variant.attrs).unwrap_or(variant.ident.to_string())
+}
+
+fn impl_serde(ident: &syn::Ident, variants: &Variants) -> TokenStream {
+    let arms = fold_quote(variants.iter(), |v| {
+        let v_ident = &v.ident;
+        let pattern = match v.fields {
+            syn::Fields::Named(..) => quote!(#ident::v_ident{..}),
+            syn::Fields::Unnamed(..) => quote!(#ident::#v_ident(..)),
+            syn::Fields::Unit => quote!(#ident::#v_ident),
+        };
+        let option_value = config_value_of_variant(v);
+        quote! {
+            #pattern => serializer.serialize_str(&#option_value),
+        }
+    });
+
+    quote! {
+        impl ::serde::ser::Serialize for #ident {
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+            where
+                S: ::serde::ser::Serializer,
+            {
+                use serde::ser::Error;
+                match self {
+                    #arms
+                    _ => Err(S::Error::custom(format!("Cannot serialize {:?}", self))),
+                }
+            }
+        }
+    }
+}
+
+// Currently only unit variants are supported.
+fn impl_deserialize(ident: &syn::Ident, variants: &Variants) -> TokenStream {
+    let supported_vs = variants.iter().filter(|v| is_unit(v));
+    let if_patterns = fold_quote(supported_vs, |v| {
+        let config_value = config_value_of_variant(v);
+        let variant_ident = &v.ident;
+        quote! {
+            if #config_value.eq_ignore_ascii_case(s) {
+                return Ok(#ident::#variant_ident);
+            }
+        }
+    });
+
+    let supported_vs = variants.iter().filter(|v| is_unit(v));
+    let allowed = fold_quote(supported_vs.map(config_value_of_variant), |s| quote!(#s,));
+
+    quote! {
+        impl<'de> serde::de::Deserialize<'de> for #ident {
+            fn deserialize<D>(d: D) -> Result<Self, D::Error>
+            where
+                D: serde::Deserializer<'de>,
+            {
+                use serde::de::{Error, Visitor};
+                use std::marker::PhantomData;
+                use std::fmt;
+                struct StringOnly<T>(PhantomData<T>);
+                impl<'de, T> Visitor<'de> for StringOnly<T>
+                where T: serde::Deserializer<'de> {
+                    type Value = String;
+                    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+                        formatter.write_str("string")
+                    }
+                    fn visit_str<E>(self, value: &str) -> Result<String, E> {
+                        Ok(String::from(value))
+                    }
+                }
+                let s = &d.deserialize_string(StringOnly::<D>(PhantomData))?;
+
+                #if_patterns
+
+                static ALLOWED: &'static[&str] = &[#allowed];
+                Err(D::Error::unknown_variant(&s, ALLOWED))
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/config_proc_macro/src/item_struct.rs b/src/tools/rustfmt/config_proc_macro/src/item_struct.rs
new file mode 100644
index 0000000000000..f03ff7e30d82e
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/src/item_struct.rs
@@ -0,0 +1,5 @@
+use proc_macro2::TokenStream;
+
+pub fn define_config_type_on_struct(_st: &syn::ItemStruct) -> syn::Result<TokenStream> {
+    unimplemented!()
+}
diff --git a/src/tools/rustfmt/config_proc_macro/src/lib.rs b/src/tools/rustfmt/config_proc_macro/src/lib.rs
new file mode 100644
index 0000000000000..78e7e098ed9e1
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/src/lib.rs
@@ -0,0 +1,25 @@
+//! This crate provides a derive macro for `ConfigType`.
+
+#![recursion_limit = "256"]
+
+mod attrs;
+mod config_type;
+mod item_enum;
+mod item_struct;
+mod utils;
+
+use proc_macro::TokenStream;
+use syn::parse_macro_input;
+
+#[proc_macro_attribute]
+pub fn config_type(_args: TokenStream, input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as syn::Item);
+    let output = config_type::define_config_type(&input);
+
+    #[cfg(feature = "debug-with-rustfmt")]
+    {
+        utils::debug_with_rustfmt(&output);
+    }
+
+    TokenStream::from(output)
+}
diff --git a/src/tools/rustfmt/config_proc_macro/src/utils.rs b/src/tools/rustfmt/config_proc_macro/src/utils.rs
new file mode 100644
index 0000000000000..5b68d2748490f
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/src/utils.rs
@@ -0,0 +1,52 @@
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+
+pub fn fold_quote<F, I, T>(input: impl Iterator<Item = I>, f: F) -> TokenStream
+where
+    F: Fn(I) -> T,
+    T: ToTokens,
+{
+    input.fold(quote! {}, |acc, x| {
+        let y = f(x);
+        quote! { #acc #y }
+    })
+}
+
+pub fn is_unit(v: &syn::Variant) -> bool {
+    match v.fields {
+        syn::Fields::Unit => true,
+        _ => false,
+    }
+}
+
+#[cfg(feature = "debug-with-rustfmt")]
+/// Pretty-print the output of proc macro using rustfmt.
+pub fn debug_with_rustfmt(input: &TokenStream) {
+    use std::io::Write;
+    use std::process::{Command, Stdio};
+    use std::env;
+    use std::ffi::OsStr;
+
+    let rustfmt_var = env::var_os("RUSTFMT");
+    let rustfmt = match &rustfmt_var {
+        Some(rustfmt) => rustfmt,
+        None => OsStr::new("rustfmt"),
+    };
+    let mut child = Command::new(rustfmt)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .spawn()
+        .expect("Failed to spawn rustfmt in stdio mode");
+    {
+        let stdin = child.stdin.as_mut().expect("Failed to get stdin");
+        stdin
+            .write_all(format!("{}", input).as_bytes())
+            .expect("Failed to write to stdin");
+    }
+    let rustfmt_output = child.wait_with_output().expect("rustfmt has failed");
+
+    eprintln!(
+        "{}",
+        String::from_utf8(rustfmt_output.stdout).expect("rustfmt returned non-UTF8 string")
+    );
+}
diff --git a/src/tools/rustfmt/config_proc_macro/tests/smoke.rs b/src/tools/rustfmt/config_proc_macro/tests/smoke.rs
new file mode 100644
index 0000000000000..940a8a0c251e4
--- /dev/null
+++ b/src/tools/rustfmt/config_proc_macro/tests/smoke.rs
@@ -0,0 +1,20 @@
+pub mod config {
+    pub trait ConfigType: Sized {
+        fn doc_hint() -> String;
+    }
+}
+
+#[allow(dead_code)]
+#[allow(unused_imports)]
+mod tests {
+    use rustfmt_config_proc_macro::config_type;
+
+    #[config_type]
+    enum Bar {
+        Foo,
+        Bar,
+        #[doc_hint = "foo_bar"]
+        FooBar,
+        FooFoo(i32),
+    }
+}
diff --git a/src/tools/rustfmt/docs/index.html b/src/tools/rustfmt/docs/index.html
new file mode 100644
index 0000000000000..2a12da3881f05
--- /dev/null
+++ b/src/tools/rustfmt/docs/index.html
@@ -0,0 +1,191 @@
+<!doctype html>
+<html>
+    <head>
+      <meta name="viewport" content="width=device-width">
+      <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/github-markdown-css/3.0.1/github-markdown.css" />
+      <script src="https://cdn.jsdelivr.net/npm/marked/marked.min.js"></script>
+      <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
+      <script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.18.0/axios.min.js"></script>
+      <style>
+        @media (max-width: 767px) {
+          .markdown-body {
+            padding: 15px;
+          }
+
+          #search {
+            max-width: 85%;
+          }
+        }
+        body {
+          overflow: scroll;
+        }
+        .markdown-body {
+          box-sizing: border-box;
+          min-width: 200px;
+          max-width: 980px;
+          margin: 0 auto;
+          padding: 45px;
+        }
+        #search {
+          border: 1px solid #d1d5da;
+          padding-left: 30px;
+          overflow: hidden;
+        }
+        .searchCondition {
+          display: flex;
+          flex-wrap: wrap;
+        }
+        .searchCondition > div {
+          margin-right: 30px;
+        }
+      </style>
+    </head>
+    <body>
+        <div id="app">
+          <article class="markdown-body">
+            <div class="searchCondition">
+              <div>
+                <form style="display:flex;">
+                  <label for="search" style="margin-right: 3px;" >search:</label>
+                  <div style="position: relative;">
+                    <input id="search" placeholder="Search all options" v-model="searchCondition">
+                    <svg style="position: absolute; left: 8px; top: 7px;" class="octicon octicon-search subnav-search-icon" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true">
+                      <path fill-rule="evenodd" d="M15.7 13.3l-3.81-3.83A5.93 5.93 0 0 0 13 6c0-3.31-2.69-6-6-6S1 2.69 1 6s2.69 6 6 6c1.3 0 2.48-.41 3.47-1.11l3.83 3.81c.19.2.45.3.7.3.25 0 .52-.09.7-.3a.996.996 0 0 0 0-1.41v.01zM7 10.7c-2.59 0-4.7-2.11-4.7-4.7 0-2.59 2.11-4.7 4.7-4.7 2.59 0 4.7 2.11 4.7 4.7 0 2.59-2.11 4.7-4.7 4.7z"></path>
+                    </svg>
+                  </div>
+                </form>
+              </div>
+              <div>
+                  <label for="stable">stable: </label>
+                  <input type="checkbox" id="stable" v-model="shouldStable">
+              </div>
+            </div>
+            <div v-html="aboutHtml"></div>
+            <div v-html="configurationAboutHtml"></div>
+            <div v-html="outputHtml"></div>
+          </article>
+        </div>
+        <script>
+            const ConfigurationMdUrl = 'https://raw.githubusercontent.com/rust-lang/rustfmt/master/Configurations.md';
+            const UrlHash = window.location.hash.replace(/^#/, '');
+            new Vue({
+              el: '#app',
+              data() {
+                const configurationDescriptions = [];
+                configurationDescriptions.links = {};
+                return {
+                  aboutHtml: '',
+                  configurationAboutHtml: '',
+                  searchCondition: UrlHash,
+                  configurationDescriptions,
+                  shouldStable: false
+                }
+              },
+              computed: {
+                outputHtml() {
+                  const ast = this.configurationDescriptions
+                                  .filter(({ head, text, stable }) => {
+                                    
+                                    if (
+                                      text.includes(this.searchCondition) === false &&
+                                      head.includes(this.searchCondition) === false
+                                    ) {
+                                      return false;
+                                    }
+                                    return (this.shouldStable)
+                                      ? stable === true
+                                      : true;
+                                  })
+                                  .reduce((stack, { value }) => {
+                                    return stack.concat(value);
+                                  }, []);
+                  ast.links = {};
+                  return marked.parser(ast);
+                }
+              },
+              created: async function() {
+                const res = await axios.get(ConfigurationMdUrl);
+                const { 
+                  about,
+                  configurationAbout,
+                  configurationDescriptions
+                } = parseMarkdownAst(res.data);
+                this.aboutHtml = marked.parser(about);
+                this.configurationAboutHtml = marked.parser(configurationAbout);
+                this.configurationDescriptions = configurationDescriptions;
+              },
+              mounted() {
+                if (UrlHash === '') return;
+                const interval = setInterval(() => {
+                  const target = document.querySelector(`#${UrlHash}`);
+                  if (target != null) {
+                    target.scrollIntoView(true);
+                    clearInterval(interval);
+                  }
+                }, 100);
+              }
+            });
+            const extractDepthOnes = (ast) => {
+              return ast.reduce((stack, next) => {
+                if (next.depth === 1) {
+                  stack.push([]);
+                }
+                const lastIndex = stack.length - 1;
+                stack[lastIndex].push(next);
+                return stack;
+              }, []);
+            }
+            const extractDepthTwos = (ast) => {
+              return ast.map((elem) => {
+                return elem.reduce((stack, next) => {
+                  if (next.depth === 2) {
+                    stack.push([]);
+                  }
+                  const lastIndex = stack.length - 1;
+                  stack[lastIndex].push(next);
+                  return stack;
+                }, 
+                [[]]);
+              });
+            }
+            const createHeadAndValue = (ast) => {
+              return ast.map((elem) => {
+                return elem.map((val) => {
+                  return {
+                    head: val[0].text,
+                    value: val,
+                    stable: val.some((elem) => {
+                      return !!elem.text && elem.text.includes("**Stable**: Yes")
+                    }),
+                    text: val.reduce((result, next) => {
+                      return next.text != null
+                        ? `${result} ${next.text}`
+                        : result;
+                    }, '')
+                  }
+                });
+              })
+            }
+            const parseMarkdownAst = (rawMarkdown) => {
+              const ast = marked.lexer(rawMarkdown);
+              const depthOnes = extractDepthOnes(ast);
+              const depthTwos = extractDepthTwos(depthOnes);
+              const [
+                abouts, configurations
+              ] = createHeadAndValue(depthTwos);
+              const about = abouts[0].value;
+              about.links = {};
+              const [
+                configurationAbout, ...configurationDescriptions
+              ] = configurations;
+              configurationAbout.value.links = {};
+              
+              return {
+                about,
+                configurationAbout: configurationAbout.value,
+                configurationDescriptions
+              };
+            }
+        </script>
+    </body>
+</html>
\ No newline at end of file
diff --git a/src/tools/rustfmt/intellij.md b/src/tools/rustfmt/intellij.md
new file mode 100644
index 0000000000000..7aea6222b8bc5
--- /dev/null
+++ b/src/tools/rustfmt/intellij.md
@@ -0,0 +1,26 @@
+# Running Rustfmt from IntelliJ or CLion
+
+## Installation
+
+- Install [CLion](https://www.jetbrains.com/clion/), [IntelliJ Ultimate or CE](https://www.jetbrains.com/idea/) through the direct download link or using the [JetBrains Toolbox](https://www.jetbrains.com/toolbox/).
+  CLion provides a built-in debugger interface but its not free like IntelliJ CE - which does not provide the debugger interface. (IntelliJ seems to lack the toolchain for that, see this discussion [intellij-rust/issues/535](https://github.com/intellij-rust/intellij-rust/issues/535))
+  
+- Install the [Rust Plugin](https://intellij-rust.github.io/) by navigating to File -> Settings -> Plugins and press "Install JetBrains Plugin"
+  ![plugins](https://user-images.githubusercontent.com/1133787/47240861-f40af680-d3e9-11e8-9b82-cdd5c8d5f5b8.png)
+
+- Press "Install" on the rust plugin
+  ![install rust](https://user-images.githubusercontent.com/1133787/47240803-c0c86780-d3e9-11e8-9265-22f735e4d7ed.png)
+  
+- Restart CLion/IntelliJ
+
+## Configuration
+
+- Open the settings window (File -> Settings) and search for "reformat"
+  ![keymap](https://user-images.githubusercontent.com/1133787/47240922-2ae10c80-d3ea-11e8-9d8f-c798d9749240.png)
+- Right-click on "Reformat File with Rustfmt" and assign a keyboard shortcut
+
+  ![shortcut_window](https://user-images.githubusercontent.com/1133787/47240981-5b28ab00-d3ea-11e8-882e-8b864164db74.png)
+- Press "OK"
+  ![shortcut_after](https://user-images.githubusercontent.com/1133787/47241000-6976c700-d3ea-11e8-9342-50ebc2f9f97b.png)
+  
+- Done. You can now use rustfmt in an opened *.rs file with your previously specified shortcut
diff --git a/src/tools/rustfmt/legacy-rustfmt.toml b/src/tools/rustfmt/legacy-rustfmt.toml
new file mode 100644
index 0000000000000..f976fa68e4c7d
--- /dev/null
+++ b/src/tools/rustfmt/legacy-rustfmt.toml
@@ -0,0 +1,2 @@
+indent_style = "Visual"
+combine_control_expr = false
diff --git a/src/tools/rustfmt/rust-toolchain b/src/tools/rustfmt/rust-toolchain
new file mode 100644
index 0000000000000..7c9d02d933d08
--- /dev/null
+++ b/src/tools/rustfmt/rust-toolchain
@@ -0,0 +1,3 @@
+[toolchain]
+channel = "nightly-2021-05-13"
+components = ["rustc-dev"]
diff --git a/src/tools/rustfmt/rustfmt.toml b/src/tools/rustfmt/rustfmt.toml
new file mode 100644
index 0000000000000..eccd5f9bd19ee
--- /dev/null
+++ b/src/tools/rustfmt/rustfmt.toml
@@ -0,0 +1,3 @@
+error_on_line_overflow = true
+error_on_unformatted = true
+version = "Two"
diff --git a/src/tools/rustfmt/src/attr.rs b/src/tools/rustfmt/src/attr.rs
new file mode 100644
index 0000000000000..c5ffb074ba554
--- /dev/null
+++ b/src/tools/rustfmt/src/attr.rs
@@ -0,0 +1,534 @@
+//! Format attributes and meta items.
+
+use rustc_ast::ast;
+use rustc_ast::AstLike;
+use rustc_span::{symbol::sym, Span, Symbol};
+
+use self::doc_comment::DocCommentFormatter;
+use crate::comment::{contains_comment, rewrite_doc_comment, CommentStyle};
+use crate::config::lists::*;
+use crate::config::IndentStyle;
+use crate::expr::rewrite_literal;
+use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
+use crate::overflow;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::types::{rewrite_path, PathContext};
+use crate::utils::{count_newlines, mk_sp};
+
+mod doc_comment;
+
+pub(crate) fn contains_name(attrs: &[ast::Attribute], name: Symbol) -> bool {
+    attrs.iter().any(|attr| attr.has_name(name))
+}
+
+pub(crate) fn first_attr_value_str_by_name(
+    attrs: &[ast::Attribute],
+    name: Symbol,
+) -> Option<Symbol> {
+    attrs
+        .iter()
+        .find(|attr| attr.has_name(name))
+        .and_then(|attr| attr.value_str())
+}
+
+/// Returns attributes on the given statement.
+pub(crate) fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
+    stmt.attrs()
+}
+
+pub(crate) fn get_span_without_attrs(stmt: &ast::Stmt) -> Span {
+    match stmt.kind {
+        ast::StmtKind::Local(ref local) => local.span,
+        ast::StmtKind::Item(ref item) => item.span,
+        ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => expr.span,
+        ast::StmtKind::MacCall(ref mac_stmt) => mac_stmt.mac.span(),
+        ast::StmtKind::Empty => stmt.span,
+    }
+}
+
+/// Returns attributes that are within `outer_span`.
+pub(crate) fn filter_inline_attrs(
+    attrs: &[ast::Attribute],
+    outer_span: Span,
+) -> Vec<ast::Attribute> {
+    attrs
+        .iter()
+        .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
+        .cloned()
+        .collect()
+}
+
+fn is_derive(attr: &ast::Attribute) -> bool {
+    attr.has_name(sym::derive)
+}
+
+// The shape of the arguments to a function-like attribute.
+fn argument_shape(
+    left: usize,
+    right: usize,
+    combine: bool,
+    shape: Shape,
+    context: &RewriteContext<'_>,
+) -> Option<Shape> {
+    match context.config.indent_style() {
+        IndentStyle::Block => {
+            if combine {
+                shape.offset_left(left)
+            } else {
+                Some(
+                    shape
+                        .block_indent(context.config.tab_spaces())
+                        .with_max_width(context.config),
+                )
+            }
+        }
+        IndentStyle::Visual => shape
+            .visual_indent(0)
+            .shrink_left(left)
+            .and_then(|s| s.sub_width(right)),
+    }
+}
+
+fn format_derive(
+    derives: &[ast::Attribute],
+    shape: Shape,
+    context: &RewriteContext<'_>,
+) -> Option<String> {
+    // Collect all items from all attributes
+    let all_items = derives
+        .iter()
+        .map(|attr| {
+            // Parse the derive items and extract the span for each item; if any
+            // attribute is not parseable, none of the attributes will be
+            // reformatted.
+            let item_spans = attr.meta_item_list().map(|meta_item_list| {
+                meta_item_list
+                    .into_iter()
+                    .map(|nested_meta_item| nested_meta_item.span())
+            })?;
+
+            let items = itemize_list(
+                context.snippet_provider,
+                item_spans,
+                ")",
+                ",",
+                |span| span.lo(),
+                |span| span.hi(),
+                |span| Some(context.snippet(*span).to_owned()),
+                attr.span.lo(),
+                attr.span.hi(),
+                false,
+            );
+
+            Some(items)
+        })
+        // Fail if any attribute failed.
+        .collect::<Option<Vec<_>>>()?
+        // Collect the results into a single, flat, Vec.
+        .into_iter()
+        .flatten()
+        .collect::<Vec<_>>();
+
+    // Collect formatting parameters.
+    let prefix = attr_prefix(&derives[0]);
+    let argument_shape = argument_shape(
+        "[derive()]".len() + prefix.len(),
+        ")]".len(),
+        false,
+        shape,
+        context,
+    )?;
+    let one_line_shape = shape
+        .offset_left("[derive()]".len() + prefix.len())?
+        .sub_width("()]".len())?;
+    let one_line_budget = one_line_shape.width;
+
+    let tactic = definitive_tactic(
+        &all_items,
+        ListTactic::HorizontalVertical,
+        Separator::Comma,
+        argument_shape.width,
+    );
+    let trailing_separator = match context.config.indent_style() {
+        // We always add the trailing comma and remove it if it is not needed.
+        IndentStyle::Block => SeparatorTactic::Always,
+        IndentStyle::Visual => SeparatorTactic::Never,
+    };
+
+    // Format the collection of items.
+    let fmt = ListFormatting::new(argument_shape, context.config)
+        .tactic(tactic)
+        .trailing_separator(trailing_separator)
+        .ends_with_newline(false);
+    let item_str = write_list(&all_items, &fmt)?;
+
+    debug!("item_str: '{}'", item_str);
+
+    // Determine if the result will be nested, i.e. if we're using the block
+    // indent style and either the items are on multiple lines or we've exceeded
+    // our budget to fit on a single line.
+    let nested = context.config.indent_style() == IndentStyle::Block
+        && (item_str.contains('\n') || item_str.len() > one_line_budget);
+
+    // Format the final result.
+    let mut result = String::with_capacity(128);
+    result.push_str(prefix);
+    result.push_str("[derive(");
+    if nested {
+        let nested_indent = argument_shape.indent.to_string_with_newline(context.config);
+        result.push_str(&nested_indent);
+        result.push_str(&item_str);
+        result.push_str(&shape.indent.to_string_with_newline(context.config));
+    } else if let SeparatorTactic::Always = context.config.trailing_comma() {
+        // Retain the trailing comma.
+        result.push_str(&item_str);
+    } else if item_str.ends_with(",") {
+        // Remove the trailing comma.
+        result.push_str(&item_str[..item_str.len() - 1]);
+    } else {
+        result.push_str(&item_str);
+    }
+    result.push_str(")]");
+
+    Some(result)
+}
+
+/// Returns the first group of attributes that fills the given predicate.
+/// We consider two doc comments are in different group if they are separated by normal comments.
+fn take_while_with_pred<'a, P>(
+    context: &RewriteContext<'_>,
+    attrs: &'a [ast::Attribute],
+    pred: P,
+) -> &'a [ast::Attribute]
+where
+    P: Fn(&ast::Attribute) -> bool,
+{
+    let mut len = 0;
+    let mut iter = attrs.iter().peekable();
+
+    while let Some(attr) = iter.next() {
+        if pred(attr) {
+            len += 1;
+        } else {
+            break;
+        }
+        if let Some(next_attr) = iter.peek() {
+            // Extract comments between two attributes.
+            let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
+            let snippet = context.snippet(span_between_attr);
+            if count_newlines(snippet) >= 2 || snippet.contains('/') {
+                break;
+            }
+        }
+    }
+
+    &attrs[..len]
+}
+
+/// Rewrite the any doc comments which come before any other attributes.
+fn rewrite_initial_doc_comments(
+    context: &RewriteContext<'_>,
+    attrs: &[ast::Attribute],
+    shape: Shape,
+) -> Option<(usize, Option<String>)> {
+    if attrs.is_empty() {
+        return Some((0, None));
+    }
+    // Rewrite doc comments
+    let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_doc_comment());
+    if !sugared_docs.is_empty() {
+        let snippet = sugared_docs
+            .iter()
+            .map(|a| context.snippet(a.span))
+            .collect::<Vec<_>>()
+            .join("\n");
+        return Some((
+            sugared_docs.len(),
+            Some(rewrite_doc_comment(
+                &snippet,
+                shape.comment(context.config),
+                context.config,
+            )?),
+        ));
+    }
+
+    Some((0, None))
+}
+
+impl Rewrite for ast::NestedMetaItem {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match self {
+            ast::NestedMetaItem::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
+            ast::NestedMetaItem::Literal(ref l) => rewrite_literal(context, l, shape),
+        }
+    }
+}
+
+fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
+    // Look at before and after comment and see if there are any empty lines.
+    let comment_begin = comment.find('/');
+    let len = comment_begin.unwrap_or_else(|| comment.len());
+    let mlb = count_newlines(&comment[..len]) > 1;
+    let mla = if comment_begin.is_none() {
+        mlb
+    } else {
+        comment
+            .chars()
+            .rev()
+            .take_while(|c| c.is_whitespace())
+            .filter(|&c| c == '\n')
+            .count()
+            > 1
+    };
+    (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
+}
+
+impl Rewrite for ast::MetaItem {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        Some(match self.kind {
+            ast::MetaItemKind::Word => {
+                rewrite_path(context, PathContext::Type, None, &self.path, shape)?
+            }
+            ast::MetaItemKind::List(ref list) => {
+                let path = rewrite_path(context, PathContext::Type, None, &self.path, shape)?;
+                let has_trailing_comma = crate::expr::span_ends_with_comma(context, self.span);
+                overflow::rewrite_with_parens(
+                    context,
+                    &path,
+                    list.iter(),
+                    // 1 = "]"
+                    shape.sub_width(1)?,
+                    self.span,
+                    context.config.attr_fn_like_width(),
+                    Some(if has_trailing_comma {
+                        SeparatorTactic::Always
+                    } else {
+                        SeparatorTactic::Never
+                    }),
+                )?
+            }
+            ast::MetaItemKind::NameValue(ref literal) => {
+                let path = rewrite_path(context, PathContext::Type, None, &self.path, shape)?;
+                // 3 = ` = `
+                let lit_shape = shape.shrink_left(path.len() + 3)?;
+                // `rewrite_literal` returns `None` when `literal` exceeds max
+                // width. Since a literal is basically unformattable unless it
+                // is a string literal (and only if `format_strings` is set),
+                // we might be better off ignoring the fact that the attribute
+                // is longer than the max width and continue on formatting.
+                // See #2479 for example.
+                let value = rewrite_literal(context, literal, lit_shape)
+                    .unwrap_or_else(|| context.snippet(literal.span).to_owned());
+                format!("{} = {}", path, value)
+            }
+        })
+    }
+}
+
+impl Rewrite for ast::Attribute {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let snippet = context.snippet(self.span);
+        if self.is_doc_comment() {
+            rewrite_doc_comment(snippet, shape.comment(context.config), context.config)
+        } else {
+            let should_skip = self
+                .ident()
+                .map(|s| context.skip_context.skip_attribute(&s.name.as_str()))
+                .unwrap_or(false);
+            let prefix = attr_prefix(self);
+
+            if should_skip || contains_comment(snippet) {
+                return Some(snippet.to_owned());
+            }
+
+            if let Some(ref meta) = self.meta() {
+                // This attribute is possibly a doc attribute needing normalization to a doc comment
+                if context.config.normalize_doc_attributes() && meta.has_name(sym::doc) {
+                    if let Some(ref literal) = meta.value_str() {
+                        let comment_style = match self.style {
+                            ast::AttrStyle::Inner => CommentStyle::Doc,
+                            ast::AttrStyle::Outer => CommentStyle::TripleSlash,
+                        };
+
+                        let literal_str = literal.as_str();
+                        let doc_comment_formatter =
+                            DocCommentFormatter::new(&*literal_str, comment_style);
+                        let doc_comment = format!("{}", doc_comment_formatter);
+                        return rewrite_doc_comment(
+                            &doc_comment,
+                            shape.comment(context.config),
+                            context.config,
+                        );
+                    }
+                }
+
+                // 1 = `[`
+                let shape = shape.offset_left(prefix.len() + 1)?;
+                Some(
+                    meta.rewrite(context, shape)
+                        .map_or_else(|| snippet.to_owned(), |rw| format!("{}[{}]", prefix, rw)),
+                )
+            } else {
+                Some(snippet.to_owned())
+            }
+        }
+    }
+}
+
+impl Rewrite for [ast::Attribute] {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        if self.is_empty() {
+            return Some(String::new());
+        }
+
+        // The current remaining attributes.
+        let mut attrs = self;
+        let mut result = String::new();
+
+        // This is not just a simple map because we need to handle doc comments
+        // (where we take as many doc comment attributes as possible) and possibly
+        // merging derives into a single attribute.
+        loop {
+            if attrs.is_empty() {
+                return Some(result);
+            }
+
+            // Handle doc comments.
+            let (doc_comment_len, doc_comment_str) =
+                rewrite_initial_doc_comments(context, attrs, shape)?;
+            if doc_comment_len > 0 {
+                let doc_comment_str = doc_comment_str.expect("doc comments, but no result");
+                result.push_str(&doc_comment_str);
+
+                let missing_span = attrs
+                    .get(doc_comment_len)
+                    .map(|next| mk_sp(attrs[doc_comment_len - 1].span.hi(), next.span.lo()));
+                if let Some(missing_span) = missing_span {
+                    let snippet = context.snippet(missing_span);
+                    let (mla, mlb) = has_newlines_before_after_comment(snippet);
+                    let comment = crate::comment::recover_missing_comment_in_span(
+                        missing_span,
+                        shape.with_max_width(context.config),
+                        context,
+                        0,
+                    )?;
+                    let comment = if comment.is_empty() {
+                        format!("\n{}", mlb)
+                    } else {
+                        format!("{}{}\n{}", mla, comment, mlb)
+                    };
+                    result.push_str(&comment);
+                    result.push_str(&shape.indent.to_string(context.config));
+                }
+
+                attrs = &attrs[doc_comment_len..];
+
+                continue;
+            }
+
+            // Handle derives if we will merge them.
+            if context.config.merge_derives() && is_derive(&attrs[0]) {
+                let derives = take_while_with_pred(context, attrs, is_derive);
+                let derive_str = format_derive(derives, shape, context)?;
+                result.push_str(&derive_str);
+
+                let missing_span = attrs
+                    .get(derives.len())
+                    .map(|next| mk_sp(attrs[derives.len() - 1].span.hi(), next.span.lo()));
+                if let Some(missing_span) = missing_span {
+                    let comment = crate::comment::recover_missing_comment_in_span(
+                        missing_span,
+                        shape.with_max_width(context.config),
+                        context,
+                        0,
+                    )?;
+                    result.push_str(&comment);
+                    if let Some(next) = attrs.get(derives.len()) {
+                        if next.is_doc_comment() {
+                            let snippet = context.snippet(missing_span);
+                            let (_, mlb) = has_newlines_before_after_comment(snippet);
+                            result.push_str(&mlb);
+                        }
+                    }
+                    result.push('\n');
+                    result.push_str(&shape.indent.to_string(context.config));
+                }
+
+                attrs = &attrs[derives.len()..];
+
+                continue;
+            }
+
+            // If we get here, then we have a regular attribute, just handle one
+            // at a time.
+
+            let formatted_attr = attrs[0].rewrite(context, shape)?;
+            result.push_str(&formatted_attr);
+
+            let missing_span = attrs
+                .get(1)
+                .map(|next| mk_sp(attrs[0].span.hi(), next.span.lo()));
+            if let Some(missing_span) = missing_span {
+                let comment = crate::comment::recover_missing_comment_in_span(
+                    missing_span,
+                    shape.with_max_width(context.config),
+                    context,
+                    0,
+                )?;
+                result.push_str(&comment);
+                if let Some(next) = attrs.get(1) {
+                    if next.is_doc_comment() {
+                        let snippet = context.snippet(missing_span);
+                        let (_, mlb) = has_newlines_before_after_comment(snippet);
+                        result.push_str(&mlb);
+                    }
+                }
+                result.push('\n');
+                result.push_str(&shape.indent.to_string(context.config));
+            }
+
+            attrs = &attrs[1..];
+        }
+    }
+}
+
+fn attr_prefix(attr: &ast::Attribute) -> &'static str {
+    match attr.style {
+        ast::AttrStyle::Inner => "#!",
+        ast::AttrStyle::Outer => "#",
+    }
+}
+
+pub(crate) trait MetaVisitor<'ast> {
+    fn visit_meta_item(&mut self, meta_item: &'ast ast::MetaItem) {
+        match meta_item.kind {
+            ast::MetaItemKind::Word => self.visit_meta_word(meta_item),
+            ast::MetaItemKind::List(ref list) => self.visit_meta_list(meta_item, list),
+            ast::MetaItemKind::NameValue(ref lit) => self.visit_meta_name_value(meta_item, lit),
+        }
+    }
+
+    fn visit_meta_list(
+        &mut self,
+        _meta_item: &'ast ast::MetaItem,
+        list: &'ast [ast::NestedMetaItem],
+    ) {
+        for nm in list {
+            self.visit_nested_meta_item(nm);
+        }
+    }
+
+    fn visit_meta_word(&mut self, _meta_item: &'ast ast::MetaItem) {}
+
+    fn visit_meta_name_value(&mut self, _meta_item: &'ast ast::MetaItem, _lit: &'ast ast::Lit) {}
+
+    fn visit_nested_meta_item(&mut self, nm: &'ast ast::NestedMetaItem) {
+        match nm {
+            ast::NestedMetaItem::MetaItem(ref meta_item) => self.visit_meta_item(meta_item),
+            ast::NestedMetaItem::Literal(ref lit) => self.visit_literal(lit),
+        }
+    }
+
+    fn visit_literal(&mut self, _lit: &'ast ast::Lit) {}
+}
diff --git a/src/tools/rustfmt/src/attr/doc_comment.rs b/src/tools/rustfmt/src/attr/doc_comment.rs
new file mode 100644
index 0000000000000..c3dcb84c9488d
--- /dev/null
+++ b/src/tools/rustfmt/src/attr/doc_comment.rs
@@ -0,0 +1,83 @@
+use crate::comment::CommentStyle;
+use std::fmt::{self, Display};
+
+/// Formats a string as a doc comment using the given [`CommentStyle`].
+#[derive(new)]
+pub(super) struct DocCommentFormatter<'a> {
+    literal: &'a str,
+    style: CommentStyle<'a>,
+}
+
+impl Display for DocCommentFormatter<'_> {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let opener = self.style.opener().trim_end();
+        let mut lines = self.literal.lines().peekable();
+
+        // Handle `#[doc = ""]`.
+        if lines.peek().is_none() {
+            return write!(formatter, "{}", opener);
+        }
+
+        while let Some(line) = lines.next() {
+            let is_last_line = lines.peek().is_none();
+            if is_last_line {
+                write!(formatter, "{}{}", opener, line)?;
+            } else {
+                writeln!(formatter, "{}{}", opener, line)?;
+            }
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn literal_controls_leading_spaces() {
+        test_doc_comment_is_formatted_correctly(
+            "    Lorem ipsum",
+            "///    Lorem ipsum",
+            CommentStyle::TripleSlash,
+        );
+    }
+
+    #[test]
+    fn single_line_doc_comment_is_formatted_correctly() {
+        test_doc_comment_is_formatted_correctly(
+            "Lorem ipsum",
+            "///Lorem ipsum",
+            CommentStyle::TripleSlash,
+        );
+    }
+
+    #[test]
+    fn multi_line_doc_comment_is_formatted_correctly() {
+        test_doc_comment_is_formatted_correctly(
+            "Lorem ipsum\nDolor sit amet",
+            "///Lorem ipsum\n///Dolor sit amet",
+            CommentStyle::TripleSlash,
+        );
+    }
+
+    #[test]
+    fn whitespace_within_lines_is_preserved() {
+        test_doc_comment_is_formatted_correctly(
+            " Lorem ipsum \n Dolor sit amet ",
+            "/// Lorem ipsum \n/// Dolor sit amet ",
+            CommentStyle::TripleSlash,
+        );
+    }
+
+    fn test_doc_comment_is_formatted_correctly(
+        literal: &str,
+        expected_comment: &str,
+        style: CommentStyle<'_>,
+    ) {
+        assert_eq!(
+            expected_comment,
+            format!("{}", DocCommentFormatter::new(&literal, style))
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/bin/main.rs b/src/tools/rustfmt/src/bin/main.rs
new file mode 100644
index 0000000000000..56b07222212f8
--- /dev/null
+++ b/src/tools/rustfmt/src/bin/main.rs
@@ -0,0 +1,705 @@
+use anyhow::{format_err, Result};
+
+use io::Error as IoError;
+use thiserror::Error;
+
+use rustfmt_nightly as rustfmt;
+
+use std::collections::HashMap;
+use std::env;
+use std::fs::File;
+use std::io::{self, stdout, Read, Write};
+use std::path::{Path, PathBuf};
+use std::str::FromStr;
+
+use getopts::{Matches, Options};
+
+use crate::rustfmt::{
+    load_config, CliOptions, Color, Config, Edition, EmitMode, FileLines, FileName,
+    FormatReportFormatterBuilder, Input, Session, Verbosity,
+};
+
+fn main() {
+    env_logger::init();
+    let opts = make_opts();
+
+    let exit_code = match execute(&opts) {
+        Ok(code) => code,
+        Err(e) => {
+            eprintln!("{}", e.to_string());
+            1
+        }
+    };
+    // Make sure standard output is flushed before we exit.
+    std::io::stdout().flush().unwrap();
+
+    // Exit with given exit code.
+    //
+    // NOTE: this immediately terminates the process without doing any cleanup,
+    // so make sure to finish all necessary cleanup before this is called.
+    std::process::exit(exit_code);
+}
+
+/// Rustfmt operations.
+enum Operation {
+    /// Format files and their child modules.
+    Format {
+        files: Vec<PathBuf>,
+        minimal_config_path: Option<String>,
+    },
+    /// Print the help message.
+    Help(HelpOp),
+    /// Print version information
+    Version,
+    /// Output default config to a file, or stdout if None
+    ConfigOutputDefault { path: Option<String> },
+    /// Output current config (as if formatting to a file) to stdout
+    ConfigOutputCurrent { path: Option<String> },
+    /// No file specified, read from stdin
+    Stdin { input: String },
+}
+
+/// Rustfmt operations errors.
+#[derive(Error, Debug)]
+pub enum OperationError {
+    /// An unknown help topic was requested.
+    #[error("Unknown help topic: `{0}`.")]
+    UnknownHelpTopic(String),
+    /// An unknown print-config option was requested.
+    #[error("Unknown print-config option: `{0}`.")]
+    UnknownPrintConfigTopic(String),
+    /// Attempt to generate a minimal config from standard input.
+    #[error("The `--print-config=minimal` option doesn't work with standard input.")]
+    MinimalPathWithStdin,
+    /// An io error during reading or writing.
+    #[error("{0}")]
+    IoError(IoError),
+    /// Attempt to use --check with stdin, which isn't currently
+    /// supported.
+    #[error("The `--check` option is not supported with standard input.")]
+    CheckWithStdin,
+    /// Attempt to use --emit=json with stdin, which isn't currently
+    /// supported.
+    #[error("Using `--emit` other than stdout is not supported with standard input.")]
+    EmitWithStdin,
+}
+
+impl From<IoError> for OperationError {
+    fn from(e: IoError) -> OperationError {
+        OperationError::IoError(e)
+    }
+}
+
+/// Arguments to `--help`
+enum HelpOp {
+    None,
+    Config,
+    FileLines,
+}
+
+fn make_opts() -> Options {
+    let mut opts = Options::new();
+
+    opts.optflag(
+        "",
+        "check",
+        "Run in 'check' mode. Exits with 0 if input is formatted correctly. Exits \
+         with 1 and prints a diff if formatting is required.",
+    );
+    let is_nightly = is_nightly();
+    let emit_opts = if is_nightly {
+        "[files|stdout|coverage|checkstyle|json]"
+    } else {
+        "[files|stdout]"
+    };
+    opts.optopt("", "emit", "What data to emit and how", emit_opts);
+    opts.optflag("", "backup", "Backup any modified files.");
+    opts.optopt(
+        "",
+        "config-path",
+        "Recursively searches the given path for the rustfmt.toml config file. If not \
+         found reverts to the input file path",
+        "[Path for the configuration file]",
+    );
+    opts.optopt("", "edition", "Rust edition to use", "[2015|2018]");
+    opts.optopt(
+        "",
+        "color",
+        "Use colored output (if supported)",
+        "[always|never|auto]",
+    );
+    opts.optopt(
+        "",
+        "print-config",
+        "Dumps a default or minimal config to PATH. A minimal config is the \
+         subset of the current config file used for formatting the current program. \
+         `current` writes to stdout current config as if formatting the file at PATH.",
+        "[default|minimal|current] PATH",
+    );
+    opts.optflag(
+        "l",
+        "files-with-diff",
+        "Prints the names of mismatched files that were formatted. Prints the names of \
+         files that would be formated when used with `--check` mode. ",
+    );
+    opts.optmulti(
+        "",
+        "config",
+        "Set options from command line. These settings take priority over .rustfmt.toml",
+        "[key1=val1,key2=val2...]",
+    );
+
+    if is_nightly {
+        opts.optflag(
+            "",
+            "unstable-features",
+            "Enables unstable features. Only available on nightly channel.",
+        );
+        opts.optopt(
+            "",
+            "file-lines",
+            "Format specified line ranges. Run with `--help=file-lines` for \
+             more detail (unstable).",
+            "JSON",
+        );
+        opts.optflag(
+            "",
+            "error-on-unformatted",
+            "Error if unable to get comments or string literals within max_width, \
+             or they are left with trailing whitespaces (unstable).",
+        );
+        opts.optflag(
+            "",
+            "skip-children",
+            "Don't reformat child modules (unstable).",
+        );
+    }
+
+    opts.optflag("v", "verbose", "Print verbose output");
+    opts.optflag("q", "quiet", "Print less output");
+    opts.optflag("V", "version", "Show version information");
+    opts.optflagopt(
+        "h",
+        "help",
+        "Show this message or help about a specific topic: `config` or `file-lines`",
+        "=TOPIC",
+    );
+
+    opts
+}
+
+fn is_nightly() -> bool {
+    option_env!("CFG_RELEASE_CHANNEL").map_or(true, |c| c == "nightly" || c == "dev")
+}
+
+// Returned i32 is an exit code
+fn execute(opts: &Options) -> Result<i32> {
+    let matches = opts.parse(env::args().skip(1))?;
+    let options = GetOptsOptions::from_matches(&matches)?;
+
+    match determine_operation(&matches)? {
+        Operation::Help(HelpOp::None) => {
+            print_usage_to_stdout(opts, "");
+            Ok(0)
+        }
+        Operation::Help(HelpOp::Config) => {
+            Config::print_docs(&mut stdout(), options.unstable_features);
+            Ok(0)
+        }
+        Operation::Help(HelpOp::FileLines) => {
+            print_help_file_lines();
+            Ok(0)
+        }
+        Operation::Version => {
+            print_version();
+            Ok(0)
+        }
+        Operation::ConfigOutputDefault { path } => {
+            let toml = Config::default().all_options().to_toml()?;
+            if let Some(path) = path {
+                let mut file = File::create(path)?;
+                file.write_all(toml.as_bytes())?;
+            } else {
+                io::stdout().write_all(toml.as_bytes())?;
+            }
+            Ok(0)
+        }
+        Operation::ConfigOutputCurrent { path } => {
+            let path = match path {
+                Some(path) => path,
+                None => return Err(format_err!("PATH required for `--print-config current`")),
+            };
+
+            let file = PathBuf::from(path);
+            let file = file.canonicalize().unwrap_or(file);
+
+            let (config, _) = load_config(Some(file.parent().unwrap()), Some(options))?;
+            let toml = config.all_options().to_toml()?;
+            io::stdout().write_all(toml.as_bytes())?;
+
+            Ok(0)
+        }
+        Operation::Stdin { input } => format_string(input, options),
+        Operation::Format {
+            files,
+            minimal_config_path,
+        } => format(files, minimal_config_path, &options),
+    }
+}
+
+fn format_string(input: String, options: GetOptsOptions) -> Result<i32> {
+    // try to read config from local directory
+    let (mut config, _) = load_config(Some(Path::new(".")), Some(options.clone()))?;
+
+    if options.check {
+        return Err(OperationError::CheckWithStdin.into());
+    }
+    if let Some(emit_mode) = options.emit_mode {
+        if emit_mode != EmitMode::Stdout {
+            return Err(OperationError::EmitWithStdin.into());
+        }
+    }
+    // emit mode is always Stdout for Stdin.
+    config.set().emit_mode(EmitMode::Stdout);
+    config.set().verbose(Verbosity::Quiet);
+
+    // parse file_lines
+    config.set().file_lines(options.file_lines);
+    for f in config.file_lines().files() {
+        match *f {
+            FileName::Stdin => {}
+            _ => eprintln!("Warning: Extra file listed in file_lines option '{}'", f),
+        }
+    }
+
+    let out = &mut stdout();
+    let mut session = Session::new(config, Some(out));
+    format_and_emit_report(&mut session, Input::Text(input));
+
+    let exit_code = if session.has_operational_errors() || session.has_parsing_errors() {
+        1
+    } else {
+        0
+    };
+    Ok(exit_code)
+}
+
+fn format(
+    files: Vec<PathBuf>,
+    minimal_config_path: Option<String>,
+    options: &GetOptsOptions,
+) -> Result<i32> {
+    options.verify_file_lines(&files);
+    let (config, config_path) = load_config(None, Some(options.clone()))?;
+
+    if config.verbose() == Verbosity::Verbose {
+        if let Some(path) = config_path.as_ref() {
+            println!("Using rustfmt config file {}", path.display());
+        }
+    }
+
+    let out = &mut stdout();
+    let mut session = Session::new(config, Some(out));
+
+    for file in files {
+        if !file.exists() {
+            eprintln!("Error: file `{}` does not exist", file.to_str().unwrap());
+            session.add_operational_error();
+        } else if file.is_dir() {
+            eprintln!("Error: `{}` is a directory", file.to_str().unwrap());
+            session.add_operational_error();
+        } else {
+            // Check the file directory if the config-path could not be read or not provided
+            if config_path.is_none() {
+                let (local_config, config_path) =
+                    load_config(Some(file.parent().unwrap()), Some(options.clone()))?;
+                if local_config.verbose() == Verbosity::Verbose {
+                    if let Some(path) = config_path {
+                        println!(
+                            "Using rustfmt config file {} for {}",
+                            path.display(),
+                            file.display()
+                        );
+                    }
+                }
+
+                session.override_config(local_config, |sess| {
+                    format_and_emit_report(sess, Input::File(file))
+                });
+            } else {
+                format_and_emit_report(&mut session, Input::File(file));
+            }
+        }
+    }
+
+    // If we were given a path via dump-minimal-config, output any options
+    // that were used during formatting as TOML.
+    if let Some(path) = minimal_config_path {
+        let mut file = File::create(path)?;
+        let toml = session.config.used_options().to_toml()?;
+        file.write_all(toml.as_bytes())?;
+    }
+
+    let exit_code = if session.has_operational_errors()
+        || session.has_parsing_errors()
+        || ((session.has_diff() || session.has_check_errors()) && options.check)
+    {
+        1
+    } else {
+        0
+    };
+    Ok(exit_code)
+}
+
+fn format_and_emit_report<T: Write>(session: &mut Session<'_, T>, input: Input) {
+    match session.format(input) {
+        Ok(report) => {
+            if report.has_warnings() {
+                eprintln!(
+                    "{}",
+                    FormatReportFormatterBuilder::new(&report)
+                        .enable_colors(should_print_with_colors(session))
+                        .build()
+                );
+            }
+        }
+        Err(msg) => {
+            eprintln!("Error writing files: {}", msg);
+            session.add_operational_error();
+        }
+    }
+}
+
+fn should_print_with_colors<T: Write>(session: &mut Session<'_, T>) -> bool {
+    match term::stderr() {
+        Some(ref t)
+            if session.config.color().use_colored_tty()
+                && t.supports_color()
+                && t.supports_attr(term::Attr::Bold) =>
+        {
+            true
+        }
+        _ => false,
+    }
+}
+
+fn print_usage_to_stdout(opts: &Options, reason: &str) {
+    let sep = if reason.is_empty() {
+        String::new()
+    } else {
+        format!("{}\n\n", reason)
+    };
+    let msg = format!(
+        "{}Format Rust code\n\nusage: {} [options] <file>...",
+        sep,
+        env::args_os().next().unwrap().to_string_lossy()
+    );
+    println!("{}", opts.usage(&msg));
+}
+
+fn print_help_file_lines() {
+    println!(
+        "If you want to restrict reformatting to specific sets of lines, you can
+use the `--file-lines` option. Its argument is a JSON array of objects
+with `file` and `range` properties, where `file` is a file name, and
+`range` is an array representing a range of lines like `[7,13]`. Ranges
+are 1-based and inclusive of both end points. Specifying an empty array
+will result in no files being formatted. For example,
+
+```
+rustfmt --file-lines '[
+    {{\"file\":\"src/lib.rs\",\"range\":[7,13]}},
+    {{\"file\":\"src/lib.rs\",\"range\":[21,29]}},
+    {{\"file\":\"src/foo.rs\",\"range\":[10,11]}},
+    {{\"file\":\"src/foo.rs\",\"range\":[15,15]}}]'
+```
+
+would format lines `7-13` and `21-29` of `src/lib.rs`, and lines `10-11`,
+and `15` of `src/foo.rs`. No other files would be formatted, even if they
+are included as out of line modules from `src/lib.rs`."
+    );
+}
+
+fn print_version() {
+    let version_info = format!(
+        "{}-{}",
+        option_env!("CARGO_PKG_VERSION").unwrap_or("unknown"),
+        include_str!(concat!(env!("OUT_DIR"), "/commit-info.txt"))
+    );
+
+    println!("rustfmt {}", version_info);
+}
+
+fn determine_operation(matches: &Matches) -> Result<Operation, OperationError> {
+    if matches.opt_present("h") {
+        let topic = matches.opt_str("h");
+        if topic == None {
+            return Ok(Operation::Help(HelpOp::None));
+        } else if topic == Some("config".to_owned()) {
+            return Ok(Operation::Help(HelpOp::Config));
+        } else if topic == Some("file-lines".to_owned()) {
+            return Ok(Operation::Help(HelpOp::FileLines));
+        } else {
+            return Err(OperationError::UnknownHelpTopic(topic.unwrap()));
+        }
+    }
+    let mut free_matches = matches.free.iter();
+
+    let mut minimal_config_path = None;
+    if let Some(kind) = matches.opt_str("print-config") {
+        let path = free_matches.next().cloned();
+        match kind.as_str() {
+            "default" => return Ok(Operation::ConfigOutputDefault { path }),
+            "current" => return Ok(Operation::ConfigOutputCurrent { path }),
+            "minimal" => {
+                minimal_config_path = path;
+                if minimal_config_path.is_none() {
+                    eprintln!("WARNING: PATH required for `--print-config minimal`.");
+                }
+            }
+            _ => {
+                return Err(OperationError::UnknownPrintConfigTopic(kind));
+            }
+        }
+    }
+
+    if matches.opt_present("version") {
+        return Ok(Operation::Version);
+    }
+
+    let files: Vec<_> = free_matches
+        .map(|s| {
+            let p = PathBuf::from(s);
+            // we will do comparison later, so here tries to canonicalize first
+            // to get the expected behavior.
+            p.canonicalize().unwrap_or(p)
+        })
+        .collect();
+
+    // if no file argument is supplied, read from stdin
+    if files.is_empty() {
+        if minimal_config_path.is_some() {
+            return Err(OperationError::MinimalPathWithStdin);
+        }
+        let mut buffer = String::new();
+        io::stdin().read_to_string(&mut buffer)?;
+
+        return Ok(Operation::Stdin { input: buffer });
+    }
+
+    Ok(Operation::Format {
+        files,
+        minimal_config_path,
+    })
+}
+
+const STABLE_EMIT_MODES: [EmitMode; 3] = [EmitMode::Files, EmitMode::Stdout, EmitMode::Diff];
+
+/// Parsed command line options.
+#[derive(Clone, Debug, Default)]
+struct GetOptsOptions {
+    skip_children: Option<bool>,
+    quiet: bool,
+    verbose: bool,
+    config_path: Option<PathBuf>,
+    inline_config: HashMap<String, String>,
+    emit_mode: Option<EmitMode>,
+    backup: bool,
+    check: bool,
+    edition: Option<Edition>,
+    color: Option<Color>,
+    file_lines: FileLines, // Default is all lines in all files.
+    unstable_features: bool,
+    error_on_unformatted: Option<bool>,
+    print_misformatted_file_names: bool,
+}
+
+impl GetOptsOptions {
+    pub fn from_matches(matches: &Matches) -> Result<GetOptsOptions> {
+        let mut options = GetOptsOptions::default();
+        options.verbose = matches.opt_present("verbose");
+        options.quiet = matches.opt_present("quiet");
+        if options.verbose && options.quiet {
+            return Err(format_err!("Can't use both `--verbose` and `--quiet`"));
+        }
+
+        let rust_nightly = is_nightly();
+
+        if rust_nightly {
+            options.unstable_features = matches.opt_present("unstable-features");
+
+            if options.unstable_features {
+                if matches.opt_present("skip-children") {
+                    options.skip_children = Some(true);
+                }
+                if matches.opt_present("error-on-unformatted") {
+                    options.error_on_unformatted = Some(true);
+                }
+                if let Some(ref file_lines) = matches.opt_str("file-lines") {
+                    options.file_lines = file_lines.parse()?;
+                }
+            } else {
+                let mut unstable_options = vec![];
+                if matches.opt_present("skip-children") {
+                    unstable_options.push("`--skip-children`");
+                }
+                if matches.opt_present("error-on-unformatted") {
+                    unstable_options.push("`--error-on-unformatted`");
+                }
+                if matches.opt_present("file-lines") {
+                    unstable_options.push("`--file-lines`");
+                }
+                if !unstable_options.is_empty() {
+                    let s = if unstable_options.len() == 1 { "" } else { "s" };
+                    return Err(format_err!(
+                        "Unstable option{} ({}) used without `--unstable-features`",
+                        s,
+                        unstable_options.join(", "),
+                    ));
+                }
+            }
+        }
+
+        options.config_path = matches.opt_str("config-path").map(PathBuf::from);
+
+        options.inline_config = matches
+            .opt_strs("config")
+            .iter()
+            .flat_map(|config| config.split(','))
+            .map(
+                |key_val| match key_val.char_indices().find(|(_, ch)| *ch == '=') {
+                    Some((middle, _)) => {
+                        let (key, val) = (&key_val[..middle], &key_val[middle + 1..]);
+                        if !Config::is_valid_key_val(key, val) {
+                            Err(format_err!("invalid key=val pair: `{}`", key_val))
+                        } else {
+                            Ok((key.to_string(), val.to_string()))
+                        }
+                    }
+
+                    None => Err(format_err!(
+                        "--config expects comma-separated list of key=val pairs, found `{}`",
+                        key_val
+                    )),
+                },
+            )
+            .collect::<Result<HashMap<_, _>, _>>()?;
+
+        options.check = matches.opt_present("check");
+        if let Some(ref emit_str) = matches.opt_str("emit") {
+            if options.check {
+                return Err(format_err!("Invalid to use `--emit` and `--check`"));
+            }
+
+            options.emit_mode = Some(emit_mode_from_emit_str(emit_str)?);
+        }
+
+        if let Some(ref edition_str) = matches.opt_str("edition") {
+            options.edition = Some(edition_from_edition_str(edition_str)?);
+        }
+
+        if matches.opt_present("backup") {
+            options.backup = true;
+        }
+
+        if matches.opt_present("files-with-diff") {
+            options.print_misformatted_file_names = true;
+        }
+
+        if !rust_nightly {
+            if let Some(ref emit_mode) = options.emit_mode {
+                if !STABLE_EMIT_MODES.contains(emit_mode) {
+                    return Err(format_err!(
+                        "Invalid value for `--emit` - using an unstable \
+                         value without `--unstable-features`",
+                    ));
+                }
+            }
+        }
+
+        if let Some(ref color) = matches.opt_str("color") {
+            match Color::from_str(color) {
+                Ok(color) => options.color = Some(color),
+                _ => return Err(format_err!("Invalid color: {}", color)),
+            }
+        }
+
+        Ok(options)
+    }
+
+    fn verify_file_lines(&self, files: &[PathBuf]) {
+        for f in self.file_lines.files() {
+            match *f {
+                FileName::Real(ref f) if files.contains(f) => {}
+                FileName::Real(_) => {
+                    eprintln!("Warning: Extra file listed in file_lines option '{}'", f)
+                }
+                FileName::Stdin => eprintln!("Warning: Not a file '{}'", f),
+            }
+        }
+    }
+}
+
+impl CliOptions for GetOptsOptions {
+    fn apply_to(self, config: &mut Config) {
+        if self.verbose {
+            config.set().verbose(Verbosity::Verbose);
+        } else if self.quiet {
+            config.set().verbose(Verbosity::Quiet);
+        } else {
+            config.set().verbose(Verbosity::Normal);
+        }
+        config.set().file_lines(self.file_lines);
+        config.set().unstable_features(self.unstable_features);
+        if let Some(skip_children) = self.skip_children {
+            config.set().skip_children(skip_children);
+        }
+        if let Some(error_on_unformatted) = self.error_on_unformatted {
+            config.set().error_on_unformatted(error_on_unformatted);
+        }
+        if let Some(edition) = self.edition {
+            config.set().edition(edition);
+        }
+        if self.check {
+            config.set().emit_mode(EmitMode::Diff);
+        } else if let Some(emit_mode) = self.emit_mode {
+            config.set().emit_mode(emit_mode);
+        }
+        if self.backup {
+            config.set().make_backup(true);
+        }
+        if let Some(color) = self.color {
+            config.set().color(color);
+        }
+        if self.print_misformatted_file_names {
+            config.set().print_misformatted_file_names(true);
+        }
+
+        for (key, val) in self.inline_config {
+            config.override_value(&key, &val);
+        }
+    }
+
+    fn config_path(&self) -> Option<&Path> {
+        self.config_path.as_deref()
+    }
+}
+
+fn edition_from_edition_str(edition_str: &str) -> Result<Edition> {
+    match edition_str {
+        "2015" => Ok(Edition::Edition2015),
+        "2018" => Ok(Edition::Edition2018),
+        _ => Err(format_err!("Invalid value for `--edition`")),
+    }
+}
+
+fn emit_mode_from_emit_str(emit_str: &str) -> Result<EmitMode> {
+    match emit_str {
+        "files" => Ok(EmitMode::Files),
+        "stdout" => Ok(EmitMode::Stdout),
+        "coverage" => Ok(EmitMode::Coverage),
+        "checkstyle" => Ok(EmitMode::Checkstyle),
+        "json" => Ok(EmitMode::Json),
+        _ => Err(format_err!("Invalid value for `--emit`")),
+    }
+}
diff --git a/src/tools/rustfmt/src/cargo-fmt/main.rs b/src/tools/rustfmt/src/cargo-fmt/main.rs
new file mode 100644
index 0000000000000..9062a2952ec1a
--- /dev/null
+++ b/src/tools/rustfmt/src/cargo-fmt/main.rs
@@ -0,0 +1,760 @@
+// Inspired by Paul Woolcock's cargo-fmt (https://github.com/pwoolcoc/cargo-fmt/).
+
+#![deny(warnings)]
+
+use std::cmp::Ordering;
+use std::collections::{BTreeMap, BTreeSet};
+use std::env;
+use std::ffi::OsStr;
+use std::fs;
+use std::hash::{Hash, Hasher};
+use std::io::{self, Write};
+use std::iter::FromIterator;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::str;
+
+use structopt::StructOpt;
+
+#[derive(StructOpt, Debug)]
+#[structopt(
+    bin_name = "cargo fmt",
+    about = "This utility formats all bin and lib files of \
+             the current crate using rustfmt."
+)]
+pub struct Opts {
+    /// No output printed to stdout
+    #[structopt(short = "q", long = "quiet")]
+    quiet: bool,
+
+    /// Use verbose output
+    #[structopt(short = "v", long = "verbose")]
+    verbose: bool,
+
+    /// Print rustfmt version and exit
+    #[structopt(long = "version")]
+    version: bool,
+
+    /// Specify package to format (only usable in workspaces)
+    #[structopt(short = "p", long = "package", value_name = "package")]
+    packages: Vec<String>,
+
+    /// Specify path to Cargo.toml
+    #[structopt(long = "manifest-path", value_name = "manifest-path")]
+    manifest_path: Option<String>,
+
+    /// Specify message-format: short|json|human
+    #[structopt(long = "message-format", value_name = "message-format")]
+    message_format: Option<String>,
+
+    /// Options passed to rustfmt
+    // 'raw = true' to make `--` explicit.
+    #[structopt(name = "rustfmt_options", raw(true))]
+    rustfmt_options: Vec<String>,
+
+    /// Format all packages (only usable in workspaces)
+    #[structopt(long = "all")]
+    format_all: bool,
+}
+
+fn main() {
+    let exit_status = execute();
+    std::io::stdout().flush().unwrap();
+    std::process::exit(exit_status);
+}
+
+const SUCCESS: i32 = 0;
+const FAILURE: i32 = 1;
+
+fn execute() -> i32 {
+    // Drop extra `fmt` argument provided by `cargo`.
+    let mut found_fmt = false;
+    let args = env::args().filter(|x| {
+        if found_fmt {
+            true
+        } else {
+            found_fmt = x == "fmt";
+            x != "fmt"
+        }
+    });
+
+    let opts = Opts::from_iter(args);
+
+    let verbosity = match (opts.verbose, opts.quiet) {
+        (false, false) => Verbosity::Normal,
+        (false, true) => Verbosity::Quiet,
+        (true, false) => Verbosity::Verbose,
+        (true, true) => {
+            print_usage_to_stderr("quiet mode and verbose mode are not compatible");
+            return FAILURE;
+        }
+    };
+
+    if opts.version {
+        return handle_command_status(get_rustfmt_info(&[String::from("--version")]));
+    }
+    if opts.rustfmt_options.iter().any(|s| {
+        ["--print-config", "-h", "--help", "-V", "--version"].contains(&s.as_str())
+            || s.starts_with("--help=")
+            || s.starts_with("--print-config=")
+    }) {
+        return handle_command_status(get_rustfmt_info(&opts.rustfmt_options));
+    }
+
+    let strategy = CargoFmtStrategy::from_opts(&opts);
+    let mut rustfmt_args = opts.rustfmt_options;
+    if let Some(message_format) = opts.message_format {
+        if let Err(msg) = convert_message_format_to_rustfmt_args(&message_format, &mut rustfmt_args)
+        {
+            print_usage_to_stderr(&msg);
+            return FAILURE;
+        }
+    }
+
+    if let Some(specified_manifest_path) = opts.manifest_path {
+        if !specified_manifest_path.ends_with("Cargo.toml") {
+            print_usage_to_stderr("the manifest-path must be a path to a Cargo.toml file");
+            return FAILURE;
+        }
+        let manifest_path = PathBuf::from(specified_manifest_path);
+        handle_command_status(format_crate(
+            verbosity,
+            &strategy,
+            rustfmt_args,
+            Some(&manifest_path),
+        ))
+    } else {
+        handle_command_status(format_crate(verbosity, &strategy, rustfmt_args, None))
+    }
+}
+
+fn rustfmt_command() -> Command {
+    let rustfmt_var = env::var_os("RUSTFMT");
+    let rustfmt = match &rustfmt_var {
+        Some(rustfmt) => rustfmt,
+        None => OsStr::new("rustfmt"),
+    };
+    Command::new(rustfmt)
+}
+
+fn convert_message_format_to_rustfmt_args(
+    message_format: &str,
+    rustfmt_args: &mut Vec<String>,
+) -> Result<(), String> {
+    let mut contains_emit_mode = false;
+    let mut contains_check = false;
+    let mut contains_list_files = false;
+    for arg in rustfmt_args.iter() {
+        if arg.starts_with("--emit") {
+            contains_emit_mode = true;
+        }
+        if arg == "--check" {
+            contains_check = true;
+        }
+        if arg == "-l" || arg == "--files-with-diff" {
+            contains_list_files = true;
+        }
+    }
+    match message_format {
+        "short" => {
+            if !contains_list_files {
+                rustfmt_args.push(String::from("-l"));
+            }
+            Ok(())
+        }
+        "json" => {
+            if contains_emit_mode {
+                return Err(String::from(
+                    "cannot include --emit arg when --message-format is set to json",
+                ));
+            }
+            if contains_check {
+                return Err(String::from(
+                    "cannot include --check arg when --message-format is set to json",
+                ));
+            }
+            rustfmt_args.push(String::from("--emit"));
+            rustfmt_args.push(String::from("json"));
+            Ok(())
+        }
+        "human" => Ok(()),
+        _ => {
+            return Err(format!(
+                "invalid --message-format value: {}. Allowed values are: short|json|human",
+                message_format
+            ));
+        }
+    }
+}
+
+fn print_usage_to_stderr(reason: &str) {
+    eprintln!("{}", reason);
+    let app = Opts::clap();
+    app.after_help("")
+        .write_help(&mut io::stderr())
+        .expect("failed to write to stderr");
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum Verbosity {
+    Verbose,
+    Normal,
+    Quiet,
+}
+
+fn handle_command_status(status: Result<i32, io::Error>) -> i32 {
+    match status {
+        Err(e) => {
+            print_usage_to_stderr(&e.to_string());
+            FAILURE
+        }
+        Ok(status) => status,
+    }
+}
+
+fn get_rustfmt_info(args: &[String]) -> Result<i32, io::Error> {
+    let mut command = rustfmt_command()
+        .stdout(std::process::Stdio::inherit())
+        .args(args)
+        .spawn()
+        .map_err(|e| match e.kind() {
+            io::ErrorKind::NotFound => io::Error::new(
+                io::ErrorKind::Other,
+                "Could not run rustfmt, please make sure it is in your PATH.",
+            ),
+            _ => e,
+        })?;
+    let result = command.wait()?;
+    if result.success() {
+        Ok(SUCCESS)
+    } else {
+        Ok(result.code().unwrap_or(SUCCESS))
+    }
+}
+
+fn format_crate(
+    verbosity: Verbosity,
+    strategy: &CargoFmtStrategy,
+    rustfmt_args: Vec<String>,
+    manifest_path: Option<&Path>,
+) -> Result<i32, io::Error> {
+    let targets = get_targets(strategy, manifest_path)?;
+
+    // Currently only bin and lib files get formatted.
+    run_rustfmt(&targets, &rustfmt_args, verbosity)
+}
+
+/// Target uses a `path` field for equality and hashing.
+#[derive(Debug)]
+pub struct Target {
+    /// A path to the main source file of the target.
+    path: PathBuf,
+    /// A kind of target (e.g., lib, bin, example, ...).
+    kind: String,
+    /// Rust edition for this target.
+    edition: String,
+}
+
+impl Target {
+    pub fn from_target(target: &cargo_metadata::Target) -> Self {
+        let path = PathBuf::from(&target.src_path);
+        let canonicalized = fs::canonicalize(&path).unwrap_or(path);
+
+        Target {
+            path: canonicalized,
+            kind: target.kind[0].clone(),
+            edition: target.edition.clone(),
+        }
+    }
+}
+
+impl PartialEq for Target {
+    fn eq(&self, other: &Target) -> bool {
+        self.path == other.path
+    }
+}
+
+impl PartialOrd for Target {
+    fn partial_cmp(&self, other: &Target) -> Option<Ordering> {
+        Some(self.path.cmp(&other.path))
+    }
+}
+
+impl Ord for Target {
+    fn cmp(&self, other: &Target) -> Ordering {
+        self.path.cmp(&other.path)
+    }
+}
+
+impl Eq for Target {}
+
+impl Hash for Target {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.path.hash(state);
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum CargoFmtStrategy {
+    /// Format every packages and dependencies.
+    All,
+    /// Format packages that are specified by the command line argument.
+    Some(Vec<String>),
+    /// Format the root packages only.
+    Root,
+}
+
+impl CargoFmtStrategy {
+    pub fn from_opts(opts: &Opts) -> CargoFmtStrategy {
+        match (opts.format_all, opts.packages.is_empty()) {
+            (false, true) => CargoFmtStrategy::Root,
+            (true, _) => CargoFmtStrategy::All,
+            (false, false) => CargoFmtStrategy::Some(opts.packages.clone()),
+        }
+    }
+}
+
+/// Based on the specified `CargoFmtStrategy`, returns a set of main source files.
+fn get_targets(
+    strategy: &CargoFmtStrategy,
+    manifest_path: Option<&Path>,
+) -> Result<BTreeSet<Target>, io::Error> {
+    let mut targets = BTreeSet::new();
+
+    match *strategy {
+        CargoFmtStrategy::Root => get_targets_root_only(manifest_path, &mut targets)?,
+        CargoFmtStrategy::All => {
+            get_targets_recursive(manifest_path, &mut targets, &mut BTreeSet::new())?
+        }
+        CargoFmtStrategy::Some(ref hitlist) => {
+            get_targets_with_hitlist(manifest_path, hitlist, &mut targets)?
+        }
+    }
+
+    if targets.is_empty() {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "Failed to find targets".to_owned(),
+        ))
+    } else {
+        Ok(targets)
+    }
+}
+
+fn get_targets_root_only(
+    manifest_path: Option<&Path>,
+    targets: &mut BTreeSet<Target>,
+) -> Result<(), io::Error> {
+    let metadata = get_cargo_metadata(manifest_path, false)?;
+    let workspace_root_path = PathBuf::from(&metadata.workspace_root).canonicalize()?;
+    let (in_workspace_root, current_dir_manifest) = if let Some(target_manifest) = manifest_path {
+        (
+            workspace_root_path == target_manifest,
+            target_manifest.canonicalize()?,
+        )
+    } else {
+        let current_dir = env::current_dir()?.canonicalize()?;
+        (
+            workspace_root_path == current_dir,
+            current_dir.join("Cargo.toml"),
+        )
+    };
+
+    let package_targets = match metadata.packages.len() {
+        1 => metadata.packages.into_iter().next().unwrap().targets,
+        _ => metadata
+            .packages
+            .into_iter()
+            .filter(|p| {
+                in_workspace_root
+                    || PathBuf::from(&p.manifest_path)
+                        .canonicalize()
+                        .unwrap_or_default()
+                        == current_dir_manifest
+            })
+            .map(|p| p.targets)
+            .flatten()
+            .collect(),
+    };
+
+    for target in package_targets {
+        targets.insert(Target::from_target(&target));
+    }
+
+    Ok(())
+}
+
+fn get_targets_recursive(
+    manifest_path: Option<&Path>,
+    mut targets: &mut BTreeSet<Target>,
+    visited: &mut BTreeSet<String>,
+) -> Result<(), io::Error> {
+    let metadata = get_cargo_metadata(manifest_path, false)?;
+    let metadata_with_deps = get_cargo_metadata(manifest_path, true)?;
+
+    for package in metadata.packages {
+        add_targets(&package.targets, &mut targets);
+
+        // Look for local dependencies.
+        for dependency in package.dependencies {
+            if dependency.source.is_some() || visited.contains(&dependency.name) {
+                continue;
+            }
+
+            let dependency_package = metadata_with_deps
+                .packages
+                .iter()
+                .find(|p| p.name == dependency.name && p.source.is_none());
+            let manifest_path = if dependency_package.is_some() {
+                PathBuf::from(&dependency_package.unwrap().manifest_path)
+            } else {
+                let mut package_manifest_path = PathBuf::from(&package.manifest_path);
+                package_manifest_path.pop();
+                package_manifest_path.push(&dependency.name);
+                package_manifest_path.push("Cargo.toml");
+                package_manifest_path
+            };
+
+            if manifest_path.exists() {
+                visited.insert(dependency.name);
+                get_targets_recursive(Some(&manifest_path), &mut targets, visited)?;
+            }
+        }
+    }
+
+    Ok(())
+}
+
+fn get_targets_with_hitlist(
+    manifest_path: Option<&Path>,
+    hitlist: &[String],
+    targets: &mut BTreeSet<Target>,
+) -> Result<(), io::Error> {
+    let metadata = get_cargo_metadata(manifest_path, false)?;
+
+    let mut workspace_hitlist: BTreeSet<&String> = BTreeSet::from_iter(hitlist);
+
+    for package in metadata.packages {
+        if workspace_hitlist.remove(&package.name) {
+            for target in package.targets {
+                targets.insert(Target::from_target(&target));
+            }
+        }
+    }
+
+    if workspace_hitlist.is_empty() {
+        Ok(())
+    } else {
+        let package = workspace_hitlist.iter().next().unwrap();
+        Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!("package `{}` is not a member of the workspace", package),
+        ))
+    }
+}
+
+fn add_targets(target_paths: &[cargo_metadata::Target], targets: &mut BTreeSet<Target>) {
+    for target in target_paths {
+        targets.insert(Target::from_target(target));
+    }
+}
+
+fn run_rustfmt(
+    targets: &BTreeSet<Target>,
+    fmt_args: &[String],
+    verbosity: Verbosity,
+) -> Result<i32, io::Error> {
+    let by_edition = targets
+        .iter()
+        .inspect(|t| {
+            if verbosity == Verbosity::Verbose {
+                println!("[{} ({})] {:?}", t.kind, t.edition, t.path)
+            }
+        })
+        .fold(BTreeMap::new(), |mut h, t| {
+            h.entry(&t.edition).or_insert_with(Vec::new).push(&t.path);
+            h
+        });
+
+    let mut status = vec![];
+    for (edition, files) in by_edition {
+        let stdout = if verbosity == Verbosity::Quiet {
+            std::process::Stdio::null()
+        } else {
+            std::process::Stdio::inherit()
+        };
+
+        if verbosity == Verbosity::Verbose {
+            print!("rustfmt");
+            print!(" --edition {}", edition);
+            fmt_args.iter().for_each(|f| print!(" {}", f));
+            files.iter().for_each(|f| print!(" {}", f.display()));
+            println!();
+        }
+
+        let mut command = rustfmt_command()
+            .stdout(stdout)
+            .args(files)
+            .args(&["--edition", edition])
+            .args(fmt_args)
+            .spawn()
+            .map_err(|e| match e.kind() {
+                io::ErrorKind::NotFound => io::Error::new(
+                    io::ErrorKind::Other,
+                    "Could not run rustfmt, please make sure it is in your PATH.",
+                ),
+                _ => e,
+            })?;
+
+        status.push(command.wait()?);
+    }
+
+    Ok(status
+        .iter()
+        .filter_map(|s| if s.success() { None } else { s.code() })
+        .next()
+        .unwrap_or(SUCCESS))
+}
+
+fn get_cargo_metadata(
+    manifest_path: Option<&Path>,
+    include_deps: bool,
+) -> Result<cargo_metadata::Metadata, io::Error> {
+    let mut cmd = cargo_metadata::MetadataCommand::new();
+    if !include_deps {
+        cmd.no_deps();
+    }
+    if let Some(manifest_path) = manifest_path {
+        cmd.manifest_path(manifest_path);
+    }
+    cmd.other_options(&[String::from("--offline")]);
+
+    match cmd.exec() {
+        Ok(metadata) => Ok(metadata),
+        Err(_) => {
+            cmd.other_options(vec![]);
+            match cmd.exec() {
+                Ok(metadata) => Ok(metadata),
+                Err(error) => Err(io::Error::new(io::ErrorKind::Other, error.to_string())),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod cargo_fmt_tests {
+    use super::*;
+
+    #[test]
+    fn default_options() {
+        let empty: Vec<String> = vec![];
+        let o = Opts::from_iter(&empty);
+        assert_eq!(false, o.quiet);
+        assert_eq!(false, o.verbose);
+        assert_eq!(false, o.version);
+        assert_eq!(empty, o.packages);
+        assert_eq!(empty, o.rustfmt_options);
+        assert_eq!(false, o.format_all);
+        assert_eq!(None, o.manifest_path);
+        assert_eq!(None, o.message_format);
+    }
+
+    #[test]
+    fn good_options() {
+        let o = Opts::from_iter(&[
+            "test",
+            "-q",
+            "-p",
+            "p1",
+            "-p",
+            "p2",
+            "--message-format",
+            "short",
+            "--",
+            "--edition",
+            "2018",
+        ]);
+        assert_eq!(true, o.quiet);
+        assert_eq!(false, o.verbose);
+        assert_eq!(false, o.version);
+        assert_eq!(vec!["p1", "p2"], o.packages);
+        assert_eq!(vec!["--edition", "2018"], o.rustfmt_options);
+        assert_eq!(false, o.format_all);
+        assert_eq!(Some(String::from("short")), o.message_format);
+    }
+
+    #[test]
+    fn unexpected_option() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "unexpected"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn unexpected_flag() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "--flag"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn mandatory_separator() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "--check"])
+                .is_err()
+        );
+        assert!(
+            !Opts::clap()
+                .get_matches_from_safe(&["test", "--", "--check"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn multiple_packages_one_by_one() {
+        let o = Opts::from_iter(&[
+            "test",
+            "-p",
+            "package1",
+            "--package",
+            "package2",
+            "-p",
+            "package3",
+        ]);
+        assert_eq!(3, o.packages.len());
+    }
+
+    #[test]
+    fn multiple_packages_grouped() {
+        let o = Opts::from_iter(&[
+            "test",
+            "--package",
+            "package1",
+            "package2",
+            "-p",
+            "package3",
+            "package4",
+        ]);
+        assert_eq!(4, o.packages.len());
+    }
+
+    #[test]
+    fn empty_packages_1() {
+        assert!(Opts::clap().get_matches_from_safe(&["test", "-p"]).is_err());
+    }
+
+    #[test]
+    fn empty_packages_2() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "-p", "--", "--check"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn empty_packages_3() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "-p", "--verbose"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn empty_packages_4() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "-p", "--check"])
+                .is_err()
+        );
+    }
+
+    mod convert_message_format_to_rustfmt_args_tests {
+        use super::*;
+
+        #[test]
+        fn invalid_message_format() {
+            assert_eq!(
+                convert_message_format_to_rustfmt_args("awesome", &mut vec![]),
+                Err(String::from(
+                    "invalid --message-format value: awesome. Allowed values are: short|json|human"
+                )),
+            );
+        }
+
+        #[test]
+        fn json_message_format_and_check_arg() {
+            let mut args = vec![String::from("--check")];
+            assert_eq!(
+                convert_message_format_to_rustfmt_args("json", &mut args),
+                Err(String::from(
+                    "cannot include --check arg when --message-format is set to json"
+                )),
+            );
+        }
+
+        #[test]
+        fn json_message_format_and_emit_arg() {
+            let mut args = vec![String::from("--emit"), String::from("checkstyle")];
+            assert_eq!(
+                convert_message_format_to_rustfmt_args("json", &mut args),
+                Err(String::from(
+                    "cannot include --emit arg when --message-format is set to json"
+                )),
+            );
+        }
+
+        #[test]
+        fn json_message_format() {
+            let mut args = vec![String::from("--edition"), String::from("2018")];
+            assert!(convert_message_format_to_rustfmt_args("json", &mut args).is_ok());
+            assert_eq!(
+                args,
+                vec![
+                    String::from("--edition"),
+                    String::from("2018"),
+                    String::from("--emit"),
+                    String::from("json")
+                ]
+            );
+        }
+
+        #[test]
+        fn human_message_format() {
+            let exp_args = vec![String::from("--emit"), String::from("json")];
+            let mut act_args = exp_args.clone();
+            assert!(convert_message_format_to_rustfmt_args("human", &mut act_args).is_ok());
+            assert_eq!(act_args, exp_args);
+        }
+
+        #[test]
+        fn short_message_format() {
+            let mut args = vec![String::from("--check")];
+            assert!(convert_message_format_to_rustfmt_args("short", &mut args).is_ok());
+            assert_eq!(args, vec![String::from("--check"), String::from("-l")]);
+        }
+
+        #[test]
+        fn short_message_format_included_short_list_files_flag() {
+            let mut args = vec![String::from("--check"), String::from("-l")];
+            assert!(convert_message_format_to_rustfmt_args("short", &mut args).is_ok());
+            assert_eq!(args, vec![String::from("--check"), String::from("-l")]);
+        }
+
+        #[test]
+        fn short_message_format_included_long_list_files_flag() {
+            let mut args = vec![String::from("--check"), String::from("--files-with-diff")];
+            assert!(convert_message_format_to_rustfmt_args("short", &mut args).is_ok());
+            assert_eq!(
+                args,
+                vec![String::from("--check"), String::from("--files-with-diff")]
+            );
+        }
+    }
+}
diff --git a/src/tools/rustfmt/src/chains.rs b/src/tools/rustfmt/src/chains.rs
new file mode 100644
index 0000000000000..8053f0e8fecc1
--- /dev/null
+++ b/src/tools/rustfmt/src/chains.rs
@@ -0,0 +1,891 @@
+//! Formatting of chained expressions, i.e., expressions that are chained by
+//! dots: struct and enum field access, method calls, and try shorthand (`?`).
+//!
+//! Instead of walking these subexpressions one-by-one, as is our usual strategy
+//! for expression formatting, we collect maximal sequences of these expressions
+//! and handle them simultaneously.
+//!
+//! Whenever possible, the entire chain is put on a single line. If that fails,
+//! we put each subexpression on a separate, much like the (default) function
+//! argument function argument strategy.
+//!
+//! Depends on config options: `chain_indent` is the indent to use for
+//! blocks in the parent/root/base of the chain (and the rest of the chain's
+//! alignment).
+//! E.g., `let foo = { aaaa; bbb; ccc }.bar.baz();`, we would layout for the
+//! following values of `chain_indent`:
+//! Block:
+//!
+//! ```text
+//! let foo = {
+//!     aaaa;
+//!     bbb;
+//!     ccc
+//! }.bar
+//!     .baz();
+//! ```
+//!
+//! Visual:
+//!
+//! ```text
+//! let foo = {
+//!               aaaa;
+//!               bbb;
+//!               ccc
+//!           }
+//!           .bar
+//!           .baz();
+//! ```
+//!
+//! If the first item in the chain is a block expression, we align the dots with
+//! the braces.
+//! Block:
+//!
+//! ```text
+//! let a = foo.bar
+//!     .baz()
+//!     .qux
+//! ```
+//!
+//! Visual:
+//!
+//! ```text
+//! let a = foo.bar
+//!            .baz()
+//!            .qux
+//! ```
+
+use std::borrow::Cow;
+use std::cmp::min;
+
+use rustc_ast::{ast, ptr};
+use rustc_span::{symbol, BytePos, Span};
+
+use crate::comment::{rewrite_comment, CharClasses, FullCodeCharKind, RichChar};
+use crate::config::{IndentStyle, Version};
+use crate::expr::rewrite_call;
+use crate::lists::extract_pre_comment;
+use crate::macros::convert_try_mac;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::utils::{
+    self, first_line_width, last_line_extendable, last_line_width, mk_sp, rewrite_ident,
+    trimmed_last_line_width, wrap_str,
+};
+
+pub(crate) fn rewrite_chain(
+    expr: &ast::Expr,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    let chain = Chain::from_ast(expr, context);
+    debug!("rewrite_chain {:?} {:?}", chain, shape);
+
+    // If this is just an expression with some `?`s, then format it trivially and
+    // return early.
+    if chain.children.is_empty() {
+        return chain.parent.rewrite(context, shape);
+    }
+
+    chain.rewrite(context, shape)
+}
+
+#[derive(Debug)]
+enum CommentPosition {
+    Back,
+    Top,
+}
+
+// An expression plus trailing `?`s to be formatted together.
+#[derive(Debug)]
+struct ChainItem {
+    kind: ChainItemKind,
+    tries: usize,
+    span: Span,
+}
+
+// FIXME: we can't use a reference here because to convert `try!` to `?` we
+// synthesise the AST node. However, I think we could use `Cow` and that
+// would remove a lot of cloning.
+#[derive(Debug)]
+enum ChainItemKind {
+    Parent(ast::Expr),
+    MethodCall(
+        ast::PathSegment,
+        Vec<ast::GenericArg>,
+        Vec<ptr::P<ast::Expr>>,
+    ),
+    StructField(symbol::Ident),
+    TupleField(symbol::Ident, bool),
+    Await,
+    Comment(String, CommentPosition),
+}
+
+impl ChainItemKind {
+    fn is_block_like(&self, context: &RewriteContext<'_>, reps: &str) -> bool {
+        match self {
+            ChainItemKind::Parent(ref expr) => utils::is_block_expr(context, expr, reps),
+            ChainItemKind::MethodCall(..)
+            | ChainItemKind::StructField(..)
+            | ChainItemKind::TupleField(..)
+            | ChainItemKind::Await
+            | ChainItemKind::Comment(..) => false,
+        }
+    }
+
+    fn is_tup_field_access(expr: &ast::Expr) -> bool {
+        match expr.kind {
+            ast::ExprKind::Field(_, ref field) => {
+                field.name.to_string().chars().all(|c| c.is_digit(10))
+            }
+            _ => false,
+        }
+    }
+
+    fn from_ast(context: &RewriteContext<'_>, expr: &ast::Expr) -> (ChainItemKind, Span) {
+        let (kind, span) = match expr.kind {
+            ast::ExprKind::MethodCall(ref segment, ref expressions, _) => {
+                let types = if let Some(ref generic_args) = segment.args {
+                    if let ast::GenericArgs::AngleBracketed(ref data) = **generic_args {
+                        data.args
+                            .iter()
+                            .filter_map(|x| match x {
+                                ast::AngleBracketedArg::Arg(ref generic_arg) => {
+                                    Some(generic_arg.clone())
+                                }
+                                _ => None,
+                            })
+                            .collect::<Vec<_>>()
+                    } else {
+                        vec![]
+                    }
+                } else {
+                    vec![]
+                };
+                let span = mk_sp(expressions[0].span.hi(), expr.span.hi());
+                let kind = ChainItemKind::MethodCall(segment.clone(), types, expressions.clone());
+                (kind, span)
+            }
+            ast::ExprKind::Field(ref nested, field) => {
+                let kind = if Self::is_tup_field_access(expr) {
+                    ChainItemKind::TupleField(field, Self::is_tup_field_access(nested))
+                } else {
+                    ChainItemKind::StructField(field)
+                };
+                let span = mk_sp(nested.span.hi(), field.span.hi());
+                (kind, span)
+            }
+            ast::ExprKind::Await(ref nested) => {
+                let span = mk_sp(nested.span.hi(), expr.span.hi());
+                (ChainItemKind::Await, span)
+            }
+            _ => return (ChainItemKind::Parent(expr.clone()), expr.span),
+        };
+
+        // Remove comments from the span.
+        let lo = context.snippet_provider.span_before(span, ".");
+        (kind, mk_sp(lo, span.hi()))
+    }
+}
+
+impl Rewrite for ChainItem {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let shape = shape.sub_width(self.tries)?;
+        let rewrite = match self.kind {
+            ChainItemKind::Parent(ref expr) => expr.rewrite(context, shape)?,
+            ChainItemKind::MethodCall(ref segment, ref types, ref exprs) => {
+                Self::rewrite_method_call(segment.ident, types, exprs, self.span, context, shape)?
+            }
+            ChainItemKind::StructField(ident) => format!(".{}", rewrite_ident(context, ident)),
+            ChainItemKind::TupleField(ident, nested) => format!(
+                "{}.{}",
+                if nested && context.config.version() == Version::One {
+                    " "
+                } else {
+                    ""
+                },
+                rewrite_ident(context, ident)
+            ),
+            ChainItemKind::Await => ".await".to_owned(),
+            ChainItemKind::Comment(ref comment, _) => {
+                rewrite_comment(comment, false, shape, context.config)?
+            }
+        };
+        Some(format!("{}{}", rewrite, "?".repeat(self.tries)))
+    }
+}
+
+impl ChainItem {
+    fn new(context: &RewriteContext<'_>, expr: &ast::Expr, tries: usize) -> ChainItem {
+        let (kind, span) = ChainItemKind::from_ast(context, expr);
+        ChainItem { kind, tries, span }
+    }
+
+    fn comment(span: Span, comment: String, pos: CommentPosition) -> ChainItem {
+        ChainItem {
+            kind: ChainItemKind::Comment(comment, pos),
+            tries: 0,
+            span,
+        }
+    }
+
+    fn is_comment(&self) -> bool {
+        match self.kind {
+            ChainItemKind::Comment(..) => true,
+            _ => false,
+        }
+    }
+
+    fn rewrite_method_call(
+        method_name: symbol::Ident,
+        types: &[ast::GenericArg],
+        args: &[ptr::P<ast::Expr>],
+        span: Span,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+    ) -> Option<String> {
+        let type_str = if types.is_empty() {
+            String::new()
+        } else {
+            let type_list = types
+                .iter()
+                .map(|ty| ty.rewrite(context, shape))
+                .collect::<Option<Vec<_>>>()?;
+
+            format!("::<{}>", type_list.join(", "))
+        };
+        let callee_str = format!(".{}{}", rewrite_ident(context, method_name), type_str);
+        rewrite_call(context, &callee_str, &args[1..], span, shape)
+    }
+}
+
+#[derive(Debug)]
+struct Chain {
+    parent: ChainItem,
+    children: Vec<ChainItem>,
+}
+
+impl Chain {
+    fn from_ast(expr: &ast::Expr, context: &RewriteContext<'_>) -> Chain {
+        let subexpr_list = Self::make_subexpr_list(expr, context);
+
+        // Un-parse the expression tree into ChainItems
+        let mut rev_children = vec![];
+        let mut sub_tries = 0;
+        for subexpr in &subexpr_list {
+            match subexpr.kind {
+                ast::ExprKind::Try(_) => sub_tries += 1,
+                _ => {
+                    rev_children.push(ChainItem::new(context, subexpr, sub_tries));
+                    sub_tries = 0;
+                }
+            }
+        }
+
+        fn is_tries(s: &str) -> bool {
+            s.chars().all(|c| c == '?')
+        }
+
+        fn is_post_comment(s: &str) -> bool {
+            let comment_start_index = s.chars().position(|c| c == '/');
+            if comment_start_index.is_none() {
+                return false;
+            }
+
+            let newline_index = s.chars().position(|c| c == '\n');
+            if newline_index.is_none() {
+                return true;
+            }
+
+            comment_start_index.unwrap() < newline_index.unwrap()
+        }
+
+        fn handle_post_comment(
+            post_comment_span: Span,
+            post_comment_snippet: &str,
+            prev_span_end: &mut BytePos,
+            children: &mut Vec<ChainItem>,
+        ) {
+            let white_spaces: &[_] = &[' ', '\t'];
+            if post_comment_snippet
+                .trim_matches(white_spaces)
+                .starts_with('\n')
+            {
+                // No post comment.
+                return;
+            }
+            let trimmed_snippet = trim_tries(post_comment_snippet);
+            if is_post_comment(&trimmed_snippet) {
+                children.push(ChainItem::comment(
+                    post_comment_span,
+                    trimmed_snippet.trim().to_owned(),
+                    CommentPosition::Back,
+                ));
+                *prev_span_end = post_comment_span.hi();
+            }
+        }
+
+        let parent = rev_children.pop().unwrap();
+        let mut children = vec![];
+        let mut prev_span_end = parent.span.hi();
+        let mut iter = rev_children.into_iter().rev().peekable();
+        if let Some(first_chain_item) = iter.peek() {
+            let comment_span = mk_sp(prev_span_end, first_chain_item.span.lo());
+            let comment_snippet = context.snippet(comment_span);
+            if !is_tries(comment_snippet.trim()) {
+                handle_post_comment(
+                    comment_span,
+                    comment_snippet,
+                    &mut prev_span_end,
+                    &mut children,
+                );
+            }
+        }
+        while let Some(chain_item) = iter.next() {
+            let comment_snippet = context.snippet(chain_item.span);
+            // FIXME: Figure out the way to get a correct span when converting `try!` to `?`.
+            let handle_comment =
+                !(context.config.use_try_shorthand() || is_tries(comment_snippet.trim()));
+
+            // Pre-comment
+            if handle_comment {
+                let pre_comment_span = mk_sp(prev_span_end, chain_item.span.lo());
+                let pre_comment_snippet = trim_tries(context.snippet(pre_comment_span));
+                let (pre_comment, _) = extract_pre_comment(&pre_comment_snippet);
+                match pre_comment {
+                    Some(ref comment) if !comment.is_empty() => {
+                        children.push(ChainItem::comment(
+                            pre_comment_span,
+                            comment.to_owned(),
+                            CommentPosition::Top,
+                        ));
+                    }
+                    _ => (),
+                }
+            }
+
+            prev_span_end = chain_item.span.hi();
+            children.push(chain_item);
+
+            // Post-comment
+            if !handle_comment || iter.peek().is_none() {
+                continue;
+            }
+
+            let next_lo = iter.peek().unwrap().span.lo();
+            let post_comment_span = mk_sp(prev_span_end, next_lo);
+            let post_comment_snippet = context.snippet(post_comment_span);
+            handle_post_comment(
+                post_comment_span,
+                post_comment_snippet,
+                &mut prev_span_end,
+                &mut children,
+            );
+        }
+
+        Chain { parent, children }
+    }
+
+    // Returns a Vec of the prefixes of the chain.
+    // E.g., for input `a.b.c` we return [`a.b.c`, `a.b`, 'a']
+    fn make_subexpr_list(expr: &ast::Expr, context: &RewriteContext<'_>) -> Vec<ast::Expr> {
+        let mut subexpr_list = vec![expr.clone()];
+
+        while let Some(subexpr) = Self::pop_expr_chain(subexpr_list.last().unwrap(), context) {
+            subexpr_list.push(subexpr.clone());
+        }
+
+        subexpr_list
+    }
+
+    // Returns the expression's subexpression, if it exists. When the subexpr
+    // is a try! macro, we'll convert it to shorthand when the option is set.
+    fn pop_expr_chain(expr: &ast::Expr, context: &RewriteContext<'_>) -> Option<ast::Expr> {
+        match expr.kind {
+            ast::ExprKind::MethodCall(_, ref expressions, _) => {
+                Some(Self::convert_try(&expressions[0], context))
+            }
+            ast::ExprKind::Field(ref subexpr, _)
+            | ast::ExprKind::Try(ref subexpr)
+            | ast::ExprKind::Await(ref subexpr) => Some(Self::convert_try(subexpr, context)),
+            _ => None,
+        }
+    }
+
+    fn convert_try(expr: &ast::Expr, context: &RewriteContext<'_>) -> ast::Expr {
+        match expr.kind {
+            ast::ExprKind::MacCall(ref mac) if context.config.use_try_shorthand() => {
+                if let Some(subexpr) = convert_try_mac(mac, context) {
+                    subexpr
+                } else {
+                    expr.clone()
+                }
+            }
+            _ => expr.clone(),
+        }
+    }
+}
+
+impl Rewrite for Chain {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        debug!("rewrite chain {:?} {:?}", self, shape);
+
+        let mut formatter = match context.config.indent_style() {
+            IndentStyle::Block => {
+                Box::new(ChainFormatterBlock::new(self)) as Box<dyn ChainFormatter>
+            }
+            IndentStyle::Visual => {
+                Box::new(ChainFormatterVisual::new(self)) as Box<dyn ChainFormatter>
+            }
+        };
+
+        formatter.format_root(&self.parent, context, shape)?;
+        if let Some(result) = formatter.pure_root() {
+            return wrap_str(result, context.config.max_width(), shape);
+        }
+
+        // Decide how to layout the rest of the chain.
+        let child_shape = formatter.child_shape(context, shape)?;
+
+        formatter.format_children(context, child_shape)?;
+        formatter.format_last_child(context, shape, child_shape)?;
+
+        let result = formatter.join_rewrites(context, child_shape)?;
+        wrap_str(result, context.config.max_width(), shape)
+    }
+}
+
+// There are a few types for formatting chains. This is because there is a lot
+// in common between formatting with block vs visual indent, but they are
+// different enough that branching on the indent all over the place gets ugly.
+// Anything that can format a chain is a ChainFormatter.
+trait ChainFormatter {
+    // Parent is the first item in the chain, e.g., `foo` in `foo.bar.baz()`.
+    // Root is the parent plus any other chain items placed on the first line to
+    // avoid an orphan. E.g.,
+    // ```text
+    // foo.bar
+    //     .baz()
+    // ```
+    // If `bar` were not part of the root, then foo would be orphaned and 'float'.
+    fn format_root(
+        &mut self,
+        parent: &ChainItem,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+    ) -> Option<()>;
+    fn child_shape(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<Shape>;
+    fn format_children(&mut self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<()>;
+    fn format_last_child(
+        &mut self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        child_shape: Shape,
+    ) -> Option<()>;
+    fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String>;
+    // Returns `Some` if the chain is only a root, None otherwise.
+    fn pure_root(&mut self) -> Option<String>;
+}
+
+// Data and behaviour that is shared by both chain formatters. The concrete
+// formatters can delegate much behaviour to `ChainFormatterShared`.
+struct ChainFormatterShared<'a> {
+    // The current working set of child items.
+    children: &'a [ChainItem],
+    // The current rewrites of items (includes trailing `?`s, but not any way to
+    // connect the rewrites together).
+    rewrites: Vec<String>,
+    // Whether the chain can fit on one line.
+    fits_single_line: bool,
+    // The number of children in the chain. This is not equal to `self.children.len()`
+    // because `self.children` will change size as we process the chain.
+    child_count: usize,
+}
+
+impl<'a> ChainFormatterShared<'a> {
+    fn new(chain: &'a Chain) -> ChainFormatterShared<'a> {
+        ChainFormatterShared {
+            children: &chain.children,
+            rewrites: Vec::with_capacity(chain.children.len() + 1),
+            fits_single_line: false,
+            child_count: chain.children.len(),
+        }
+    }
+
+    fn pure_root(&mut self) -> Option<String> {
+        if self.children.is_empty() {
+            assert_eq!(self.rewrites.len(), 1);
+            Some(self.rewrites.pop().unwrap())
+        } else {
+            None
+        }
+    }
+
+    // Rewrite the last child. The last child of a chain requires special treatment. We need to
+    // know whether 'overflowing' the last child make a better formatting:
+    //
+    // A chain with overflowing the last child:
+    // ```text
+    // parent.child1.child2.last_child(
+    //     a,
+    //     b,
+    //     c,
+    // )
+    // ```
+    //
+    // A chain without overflowing the last child (in vertical layout):
+    // ```text
+    // parent
+    //     .child1
+    //     .child2
+    //     .last_child(a, b, c)
+    // ```
+    //
+    // In particular, overflowing is effective when the last child is a method with a multi-lined
+    // block-like argument (e.g., closure):
+    // ```text
+    // parent.child1.child2.last_child(|a, b, c| {
+    //     let x = foo(a, b, c);
+    //     let y = bar(a, b, c);
+    //
+    //     // ...
+    //
+    //     result
+    // })
+    // ```
+    fn format_last_child(
+        &mut self,
+        may_extend: bool,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        child_shape: Shape,
+    ) -> Option<()> {
+        let last = self.children.last()?;
+        let extendable = may_extend && last_line_extendable(&self.rewrites[0]);
+        let prev_last_line_width = last_line_width(&self.rewrites[0]);
+
+        // Total of all items excluding the last.
+        let almost_total = if extendable {
+            prev_last_line_width
+        } else {
+            self.rewrites
+                .iter()
+                .map(|rw| utils::unicode_str_width(&rw))
+                .sum()
+        } + last.tries;
+        let one_line_budget = if self.child_count == 1 {
+            shape.width
+        } else {
+            min(shape.width, context.config.chain_width())
+        }
+        .saturating_sub(almost_total);
+
+        let all_in_one_line = !self.children.iter().any(ChainItem::is_comment)
+            && self.rewrites.iter().all(|s| !s.contains('\n'))
+            && one_line_budget > 0;
+        let last_shape = if all_in_one_line {
+            shape.sub_width(last.tries)?
+        } else if extendable {
+            child_shape.sub_width(last.tries)?
+        } else {
+            child_shape.sub_width(shape.rhs_overhead(context.config) + last.tries)?
+        };
+
+        let mut last_subexpr_str = None;
+        if all_in_one_line || extendable {
+            // First we try to 'overflow' the last child and see if it looks better than using
+            // vertical layout.
+            let one_line_shape = if context.use_block_indent() {
+                last_shape.offset_left(almost_total)
+            } else {
+                last_shape
+                    .visual_indent(almost_total)
+                    .sub_width(almost_total)
+            };
+
+            if let Some(one_line_shape) = one_line_shape {
+                if let Some(rw) = last.rewrite(context, one_line_shape) {
+                    // We allow overflowing here only if both of the following conditions match:
+                    // 1. The entire chain fits in a single line except the last child.
+                    // 2. `last_child_str.lines().count() >= 5`.
+                    let line_count = rw.lines().count();
+                    let could_fit_single_line = first_line_width(&rw) <= one_line_budget;
+                    if could_fit_single_line && line_count >= 5 {
+                        last_subexpr_str = Some(rw);
+                        self.fits_single_line = all_in_one_line;
+                    } else {
+                        // We could not know whether overflowing is better than using vertical
+                        // layout, just by looking at the overflowed rewrite. Now we rewrite the
+                        // last child on its own line, and compare two rewrites to choose which is
+                        // better.
+                        let last_shape = child_shape
+                            .sub_width(shape.rhs_overhead(context.config) + last.tries)?;
+                        match last.rewrite(context, last_shape) {
+                            Some(ref new_rw) if !could_fit_single_line => {
+                                last_subexpr_str = Some(new_rw.clone());
+                            }
+                            Some(ref new_rw) if new_rw.lines().count() >= line_count => {
+                                last_subexpr_str = Some(rw);
+                                self.fits_single_line = could_fit_single_line && all_in_one_line;
+                            }
+                            new_rw @ Some(..) => {
+                                last_subexpr_str = new_rw;
+                            }
+                            _ => {
+                                last_subexpr_str = Some(rw);
+                                self.fits_single_line = could_fit_single_line && all_in_one_line;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        let last_shape = if context.use_block_indent() {
+            last_shape
+        } else {
+            child_shape.sub_width(shape.rhs_overhead(context.config) + last.tries)?
+        };
+
+        last_subexpr_str = last_subexpr_str.or_else(|| last.rewrite(context, last_shape));
+        self.rewrites.push(last_subexpr_str?);
+        Some(())
+    }
+
+    fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String> {
+        let connector = if self.fits_single_line {
+            // Yay, we can put everything on one line.
+            Cow::from("")
+        } else {
+            // Use new lines.
+            if context.force_one_line_chain.get() {
+                return None;
+            }
+            child_shape.to_string_with_newline(context.config)
+        };
+
+        let mut rewrite_iter = self.rewrites.iter();
+        let mut result = rewrite_iter.next().unwrap().clone();
+        let children_iter = self.children.iter();
+        let iter = rewrite_iter.zip(children_iter);
+
+        for (rewrite, chain_item) in iter {
+            match chain_item.kind {
+                ChainItemKind::Comment(_, CommentPosition::Back) => result.push(' '),
+                ChainItemKind::Comment(_, CommentPosition::Top) => result.push_str(&connector),
+                _ => result.push_str(&connector),
+            }
+            result.push_str(&rewrite);
+        }
+
+        Some(result)
+    }
+}
+
+// Formats a chain using block indent.
+struct ChainFormatterBlock<'a> {
+    shared: ChainFormatterShared<'a>,
+    root_ends_with_block: bool,
+}
+
+impl<'a> ChainFormatterBlock<'a> {
+    fn new(chain: &'a Chain) -> ChainFormatterBlock<'a> {
+        ChainFormatterBlock {
+            shared: ChainFormatterShared::new(chain),
+            root_ends_with_block: false,
+        }
+    }
+}
+
+impl<'a> ChainFormatter for ChainFormatterBlock<'a> {
+    fn format_root(
+        &mut self,
+        parent: &ChainItem,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+    ) -> Option<()> {
+        let mut root_rewrite: String = parent.rewrite(context, shape)?;
+
+        let mut root_ends_with_block = parent.kind.is_block_like(context, &root_rewrite);
+        let tab_width = context.config.tab_spaces().saturating_sub(shape.offset);
+
+        while root_rewrite.len() <= tab_width && !root_rewrite.contains('\n') {
+            let item = &self.shared.children[0];
+            if let ChainItemKind::Comment(..) = item.kind {
+                break;
+            }
+            let shape = shape.offset_left(root_rewrite.len())?;
+            match &item.rewrite(context, shape) {
+                Some(rewrite) => root_rewrite.push_str(rewrite),
+                None => break,
+            }
+
+            root_ends_with_block = last_line_extendable(&root_rewrite);
+
+            self.shared.children = &self.shared.children[1..];
+            if self.shared.children.is_empty() {
+                break;
+            }
+        }
+        self.shared.rewrites.push(root_rewrite);
+        self.root_ends_with_block = root_ends_with_block;
+        Some(())
+    }
+
+    fn child_shape(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<Shape> {
+        Some(
+            if self.root_ends_with_block {
+                shape.block_indent(0)
+            } else {
+                shape.block_indent(context.config.tab_spaces())
+            }
+            .with_max_width(context.config),
+        )
+    }
+
+    fn format_children(&mut self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<()> {
+        for item in &self.shared.children[..self.shared.children.len() - 1] {
+            let rewrite = item.rewrite(context, child_shape)?;
+            self.shared.rewrites.push(rewrite);
+        }
+        Some(())
+    }
+
+    fn format_last_child(
+        &mut self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        child_shape: Shape,
+    ) -> Option<()> {
+        self.shared
+            .format_last_child(true, context, shape, child_shape)
+    }
+
+    fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String> {
+        self.shared.join_rewrites(context, child_shape)
+    }
+
+    fn pure_root(&mut self) -> Option<String> {
+        self.shared.pure_root()
+    }
+}
+
+// Format a chain using visual indent.
+struct ChainFormatterVisual<'a> {
+    shared: ChainFormatterShared<'a>,
+    // The extra offset from the chain's shape to the position of the `.`
+    offset: usize,
+}
+
+impl<'a> ChainFormatterVisual<'a> {
+    fn new(chain: &'a Chain) -> ChainFormatterVisual<'a> {
+        ChainFormatterVisual {
+            shared: ChainFormatterShared::new(chain),
+            offset: 0,
+        }
+    }
+}
+
+impl<'a> ChainFormatter for ChainFormatterVisual<'a> {
+    fn format_root(
+        &mut self,
+        parent: &ChainItem,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+    ) -> Option<()> {
+        let parent_shape = shape.visual_indent(0);
+        let mut root_rewrite = parent.rewrite(context, parent_shape)?;
+        let multiline = root_rewrite.contains('\n');
+        self.offset = if multiline {
+            last_line_width(&root_rewrite).saturating_sub(shape.used_width())
+        } else {
+            trimmed_last_line_width(&root_rewrite)
+        };
+
+        if !multiline || parent.kind.is_block_like(context, &root_rewrite) {
+            let item = &self.shared.children[0];
+            if let ChainItemKind::Comment(..) = item.kind {
+                self.shared.rewrites.push(root_rewrite);
+                return Some(());
+            }
+            let child_shape = parent_shape
+                .visual_indent(self.offset)
+                .sub_width(self.offset)?;
+            let rewrite = item.rewrite(context, child_shape)?;
+            match wrap_str(rewrite, context.config.max_width(), shape) {
+                Some(rewrite) => root_rewrite.push_str(&rewrite),
+                None => {
+                    // We couldn't fit in at the visual indent, try the last
+                    // indent.
+                    let rewrite = item.rewrite(context, parent_shape)?;
+                    root_rewrite.push_str(&rewrite);
+                    self.offset = 0;
+                }
+            }
+
+            self.shared.children = &self.shared.children[1..];
+        }
+
+        self.shared.rewrites.push(root_rewrite);
+        Some(())
+    }
+
+    fn child_shape(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<Shape> {
+        shape
+            .with_max_width(context.config)
+            .offset_left(self.offset)
+            .map(|s| s.visual_indent(0))
+    }
+
+    fn format_children(&mut self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<()> {
+        for item in &self.shared.children[..self.shared.children.len() - 1] {
+            let rewrite = item.rewrite(context, child_shape)?;
+            self.shared.rewrites.push(rewrite);
+        }
+        Some(())
+    }
+
+    fn format_last_child(
+        &mut self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        child_shape: Shape,
+    ) -> Option<()> {
+        self.shared
+            .format_last_child(false, context, shape, child_shape)
+    }
+
+    fn join_rewrites(&self, context: &RewriteContext<'_>, child_shape: Shape) -> Option<String> {
+        self.shared.join_rewrites(context, child_shape)
+    }
+
+    fn pure_root(&mut self) -> Option<String> {
+        self.shared.pure_root()
+    }
+}
+
+/// Removes try operators (`?`s) that appear in the given string. If removing
+/// them leaves an empty line, remove that line as well unless it is the first
+/// line (we need the first newline for detecting pre/post comment).
+fn trim_tries(s: &str) -> String {
+    let mut result = String::with_capacity(s.len());
+    let mut line_buffer = String::with_capacity(s.len());
+    for (kind, rich_char) in CharClasses::new(s.chars()) {
+        match rich_char.get_char() {
+            '\n' => {
+                if result.is_empty() || !line_buffer.trim().is_empty() {
+                    result.push_str(&line_buffer);
+                    result.push('\n')
+                }
+                line_buffer.clear();
+            }
+            '?' if kind == FullCodeCharKind::Normal => continue,
+            c => line_buffer.push(c),
+        }
+    }
+    if !line_buffer.trim().is_empty() {
+        result.push_str(&line_buffer);
+    }
+    result
+}
diff --git a/src/tools/rustfmt/src/closures.rs b/src/tools/rustfmt/src/closures.rs
new file mode 100644
index 0000000000000..3d65077ddc209
--- /dev/null
+++ b/src/tools/rustfmt/src/closures.rs
@@ -0,0 +1,429 @@
+use rustc_ast::{ast, ptr};
+use rustc_span::Span;
+
+use crate::attr::get_attrs_from_stmt;
+use crate::config::lists::*;
+use crate::config::Version;
+use crate::expr::{block_contains_comment, is_simple_block, is_unsafe_block, rewrite_cond};
+use crate::items::{span_hi_for_param, span_lo_for_param};
+use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
+use crate::overflow::OverflowableItem;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::utils::{last_line_width, left_most_sub_expr, stmt_expr, NodeIdExt};
+
+// This module is pretty messy because of the rules around closures and blocks:
+// FIXME - the below is probably no longer true in full.
+//   * if there is a return type, then there must be braces,
+//   * given a closure with braces, whether that is parsed to give an inner block
+//     or not depends on if there is a return type and if there are statements
+//     in that block,
+//   * if the first expression in the body ends with a block (i.e., is a
+//     statement without needing a semi-colon), then adding or removing braces
+//     can change whether it is treated as an expression or statement.
+
+pub(crate) fn rewrite_closure(
+    capture: ast::CaptureBy,
+    is_async: &ast::Async,
+    movability: ast::Movability,
+    fn_decl: &ast::FnDecl,
+    body: &ast::Expr,
+    span: Span,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    debug!("rewrite_closure {:?}", body);
+
+    let (prefix, extra_offset) = rewrite_closure_fn_decl(
+        capture, is_async, movability, fn_decl, body, span, context, shape,
+    )?;
+    // 1 = space between `|...|` and body.
+    let body_shape = shape.offset_left(extra_offset)?;
+
+    if let ast::ExprKind::Block(ref block, _) = body.kind {
+        // The body of the closure is an empty block.
+        if block.stmts.is_empty() && !block_contains_comment(context, block) {
+            return body
+                .rewrite(context, shape)
+                .map(|s| format!("{} {}", prefix, s));
+        }
+
+        let result = match fn_decl.output {
+            ast::FnRetTy::Default(_) if !context.inside_macro() => {
+                try_rewrite_without_block(body, &prefix, context, shape, body_shape)
+            }
+            _ => None,
+        };
+
+        result.or_else(|| {
+            // Either we require a block, or tried without and failed.
+            rewrite_closure_block(block, &prefix, context, body_shape)
+        })
+    } else {
+        rewrite_closure_expr(body, &prefix, context, body_shape).or_else(|| {
+            // The closure originally had a non-block expression, but we can't fit on
+            // one line, so we'll insert a block.
+            rewrite_closure_with_block(body, &prefix, context, body_shape)
+        })
+    }
+}
+
+fn try_rewrite_without_block(
+    expr: &ast::Expr,
+    prefix: &str,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    body_shape: Shape,
+) -> Option<String> {
+    let expr = get_inner_expr(expr, prefix, context);
+
+    if is_block_closure_forced(context, expr) {
+        rewrite_closure_with_block(expr, prefix, context, shape)
+    } else {
+        rewrite_closure_expr(expr, prefix, context, body_shape)
+    }
+}
+
+fn get_inner_expr<'a>(
+    expr: &'a ast::Expr,
+    prefix: &str,
+    context: &RewriteContext<'_>,
+) -> &'a ast::Expr {
+    if let ast::ExprKind::Block(ref block, _) = expr.kind {
+        if !needs_block(block, prefix, context) {
+            // block.stmts.len() == 1 except with `|| {{}}`;
+            // https://github.com/rust-lang/rustfmt/issues/3844
+            if let Some(expr) = block.stmts.first().and_then(stmt_expr) {
+                return get_inner_expr(expr, prefix, context);
+            }
+        }
+    }
+
+    expr
+}
+
+// Figure out if a block is necessary.
+fn needs_block(block: &ast::Block, prefix: &str, context: &RewriteContext<'_>) -> bool {
+    let has_attributes = block.stmts.first().map_or(false, |first_stmt| {
+        !get_attrs_from_stmt(first_stmt).is_empty()
+    });
+
+    is_unsafe_block(block)
+        || block.stmts.len() > 1
+        || has_attributes
+        || block_contains_comment(context, block)
+        || prefix.contains('\n')
+}
+
+fn veto_block(e: &ast::Expr) -> bool {
+    match e.kind {
+        ast::ExprKind::Call(..)
+        | ast::ExprKind::Binary(..)
+        | ast::ExprKind::Cast(..)
+        | ast::ExprKind::Type(..)
+        | ast::ExprKind::Assign(..)
+        | ast::ExprKind::AssignOp(..)
+        | ast::ExprKind::Field(..)
+        | ast::ExprKind::Index(..)
+        | ast::ExprKind::Range(..)
+        | ast::ExprKind::Try(..) => true,
+        _ => false,
+    }
+}
+
+// Rewrite closure with a single expression wrapping its body with block.
+// || { #[attr] foo() } -> Block { #[attr] foo() }
+fn rewrite_closure_with_block(
+    body: &ast::Expr,
+    prefix: &str,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    let left_most = left_most_sub_expr(body);
+    let veto_block = veto_block(body) && !expr_requires_semi_to_be_stmt(left_most);
+    if veto_block {
+        return None;
+    }
+
+    let block = ast::Block {
+        stmts: vec![ast::Stmt {
+            id: ast::NodeId::root(),
+            kind: ast::StmtKind::Expr(ptr::P(body.clone())),
+            span: body.span,
+        }],
+        id: ast::NodeId::root(),
+        rules: ast::BlockCheckMode::Default,
+        tokens: None,
+        span: body
+            .attrs
+            .first()
+            .map(|attr| attr.span.to(body.span))
+            .unwrap_or(body.span),
+    };
+    let block = crate::expr::rewrite_block_with_visitor(
+        context,
+        "",
+        &block,
+        Some(&body.attrs),
+        None,
+        shape,
+        false,
+    )?;
+    Some(format!("{} {}", prefix, block))
+}
+
+// Rewrite closure with a single expression without wrapping its body with block.
+fn rewrite_closure_expr(
+    expr: &ast::Expr,
+    prefix: &str,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    fn allow_multi_line(expr: &ast::Expr) -> bool {
+        match expr.kind {
+            ast::ExprKind::Match(..)
+            | ast::ExprKind::Async(..)
+            | ast::ExprKind::Block(..)
+            | ast::ExprKind::TryBlock(..)
+            | ast::ExprKind::Loop(..)
+            | ast::ExprKind::Struct(..) => true,
+
+            ast::ExprKind::AddrOf(_, _, ref expr)
+            | ast::ExprKind::Box(ref expr)
+            | ast::ExprKind::Try(ref expr)
+            | ast::ExprKind::Unary(_, ref expr)
+            | ast::ExprKind::Cast(ref expr, _) => allow_multi_line(expr),
+
+            _ => false,
+        }
+    }
+
+    // When rewriting closure's body without block, we require it to fit in a single line
+    // unless it is a block-like expression or we are inside macro call.
+    let veto_multiline = (!allow_multi_line(expr) && !context.inside_macro())
+        || context.config.force_multiline_blocks();
+    expr.rewrite(context, shape)
+        .and_then(|rw| {
+            if veto_multiline && rw.contains('\n') {
+                None
+            } else {
+                Some(rw)
+            }
+        })
+        .map(|rw| format!("{} {}", prefix, rw))
+}
+
+// Rewrite closure whose body is block.
+fn rewrite_closure_block(
+    block: &ast::Block,
+    prefix: &str,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    Some(format!("{} {}", prefix, block.rewrite(context, shape)?))
+}
+
+// Return type is (prefix, extra_offset)
+fn rewrite_closure_fn_decl(
+    capture: ast::CaptureBy,
+    asyncness: &ast::Async,
+    movability: ast::Movability,
+    fn_decl: &ast::FnDecl,
+    body: &ast::Expr,
+    span: Span,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<(String, usize)> {
+    let is_async = if asyncness.is_async() { "async " } else { "" };
+    let mover = if capture == ast::CaptureBy::Value {
+        "move "
+    } else {
+        ""
+    };
+    let immovable = if movability == ast::Movability::Static {
+        "static "
+    } else {
+        ""
+    };
+    // 4 = "|| {".len(), which is overconservative when the closure consists of
+    // a single expression.
+    let nested_shape = shape
+        .shrink_left(is_async.len() + mover.len() + immovable.len())?
+        .sub_width(4)?;
+
+    // 1 = |
+    let param_offset = nested_shape.indent + 1;
+    let param_shape = nested_shape.offset_left(1)?.visual_indent(0);
+    let ret_str = fn_decl.output.rewrite(context, param_shape)?;
+
+    let param_items = itemize_list(
+        context.snippet_provider,
+        fn_decl.inputs.iter(),
+        "|",
+        ",",
+        |param| span_lo_for_param(param),
+        |param| span_hi_for_param(context, param),
+        |param| param.rewrite(context, param_shape),
+        context.snippet_provider.span_after(span, "|"),
+        body.span.lo(),
+        false,
+    );
+    let item_vec = param_items.collect::<Vec<_>>();
+    // 1 = space between parameters and return type.
+    let horizontal_budget = nested_shape.width.saturating_sub(ret_str.len() + 1);
+    let tactic = definitive_tactic(
+        &item_vec,
+        ListTactic::HorizontalVertical,
+        Separator::Comma,
+        horizontal_budget,
+    );
+    let param_shape = match tactic {
+        DefinitiveListTactic::Horizontal => param_shape.sub_width(ret_str.len() + 1)?,
+        _ => param_shape,
+    };
+
+    let fmt = ListFormatting::new(param_shape, context.config)
+        .tactic(tactic)
+        .preserve_newline(true);
+    let list_str = write_list(&item_vec, &fmt)?;
+    let mut prefix = format!("{}{}{}|{}|", is_async, immovable, mover, list_str);
+
+    if !ret_str.is_empty() {
+        if prefix.contains('\n') {
+            prefix.push('\n');
+            prefix.push_str(&param_offset.to_string(context.config));
+        } else {
+            prefix.push(' ');
+        }
+        prefix.push_str(&ret_str);
+    }
+    // 1 = space between `|...|` and body.
+    let extra_offset = last_line_width(&prefix) + 1;
+
+    Some((prefix, extra_offset))
+}
+
+// Rewriting closure which is placed at the end of the function call's arg.
+// Returns `None` if the reformatted closure 'looks bad'.
+pub(crate) fn rewrite_last_closure(
+    context: &RewriteContext<'_>,
+    expr: &ast::Expr,
+    shape: Shape,
+) -> Option<String> {
+    if let ast::ExprKind::Closure(capture, ref is_async, movability, ref fn_decl, ref body, _) =
+        expr.kind
+    {
+        let body = match body.kind {
+            ast::ExprKind::Block(ref block, _)
+                if !is_unsafe_block(block)
+                    && !context.inside_macro()
+                    && is_simple_block(context, block, Some(&body.attrs)) =>
+            {
+                stmt_expr(&block.stmts[0]).unwrap_or(body)
+            }
+            _ => body,
+        };
+        let (prefix, extra_offset) = rewrite_closure_fn_decl(
+            capture, is_async, movability, fn_decl, body, expr.span, context, shape,
+        )?;
+        // If the closure goes multi line before its body, do not overflow the closure.
+        if prefix.contains('\n') {
+            return None;
+        }
+
+        let body_shape = shape.offset_left(extra_offset)?;
+
+        // We force to use block for the body of the closure for certain kinds of expressions.
+        if is_block_closure_forced(context, body) {
+            return rewrite_closure_with_block(body, &prefix, context, body_shape).and_then(
+                |body_str| {
+                    match fn_decl.output {
+                        ast::FnRetTy::Default(..) if body_str.lines().count() <= 7 => {
+                            // If the expression can fit in a single line, we need not force block
+                            // closure.  However, if the closure has a return type, then we must
+                            // keep the blocks.
+                            match rewrite_closure_expr(body, &prefix, context, shape) {
+                                Some(ref single_line_body_str)
+                                    if !single_line_body_str.contains('\n') =>
+                                {
+                                    Some(single_line_body_str.clone())
+                                }
+                                _ => Some(body_str),
+                            }
+                        }
+                        _ => Some(body_str),
+                    }
+                },
+            );
+        }
+
+        // When overflowing the closure which consists of a single control flow expression,
+        // force to use block if its condition uses multi line.
+        let is_multi_lined_cond = rewrite_cond(context, body, body_shape).map_or(false, |cond| {
+            cond.contains('\n') || cond.len() > body_shape.width
+        });
+        if is_multi_lined_cond {
+            return rewrite_closure_with_block(body, &prefix, context, body_shape);
+        }
+
+        // Seems fine, just format the closure in usual manner.
+        return expr.rewrite(context, shape);
+    }
+    None
+}
+
+/// Returns `true` if the given vector of arguments has more than one `ast::ExprKind::Closure`.
+pub(crate) fn args_have_many_closure(args: &[OverflowableItem<'_>]) -> bool {
+    args.iter()
+        .filter_map(OverflowableItem::to_expr)
+        .filter(|expr| match expr.kind {
+            ast::ExprKind::Closure(..) => true,
+            _ => false,
+        })
+        .count()
+        > 1
+}
+
+fn is_block_closure_forced(context: &RewriteContext<'_>, expr: &ast::Expr) -> bool {
+    // If we are inside macro, we do not want to add or remove block from closure body.
+    if context.inside_macro() {
+        false
+    } else {
+        is_block_closure_forced_inner(expr, context.config.version())
+    }
+}
+
+fn is_block_closure_forced_inner(expr: &ast::Expr, version: Version) -> bool {
+    match expr.kind {
+        ast::ExprKind::If(..) | ast::ExprKind::While(..) | ast::ExprKind::ForLoop(..) => true,
+        ast::ExprKind::Loop(..) if version == Version::Two => true,
+        ast::ExprKind::AddrOf(_, _, ref expr)
+        | ast::ExprKind::Box(ref expr)
+        | ast::ExprKind::Try(ref expr)
+        | ast::ExprKind::Unary(_, ref expr)
+        | ast::ExprKind::Cast(ref expr, _) => is_block_closure_forced_inner(expr, version),
+        _ => false,
+    }
+}
+
+/// Does this expression require a semicolon to be treated
+/// as a statement? The negation of this: 'can this expression
+/// be used as a statement without a semicolon' -- is used
+/// as an early-bail-out in the parser so that, for instance,
+///     if true {...} else {...}
+///      |x| 5
+/// isn't parsed as (if true {...} else {...} | x) | 5
+// From https://github.com/rust-lang/rust/blob/master/src/libsyntax/parse/classify.rs.
+fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
+    match e.kind {
+        ast::ExprKind::If(..)
+        | ast::ExprKind::Match(..)
+        | ast::ExprKind::Block(..)
+        | ast::ExprKind::While(..)
+        | ast::ExprKind::Loop(..)
+        | ast::ExprKind::ForLoop(..)
+        | ast::ExprKind::TryBlock(..) => false,
+        _ => true,
+    }
+}
diff --git a/src/tools/rustfmt/src/comment.rs b/src/tools/rustfmt/src/comment.rs
new file mode 100644
index 0000000000000..c71302fdd182b
--- /dev/null
+++ b/src/tools/rustfmt/src/comment.rs
@@ -0,0 +1,1920 @@
+// Formatting and tools for comments.
+
+use std::{self, borrow::Cow, iter};
+
+use itertools::{multipeek, MultiPeek};
+use rustc_span::Span;
+
+use crate::config::Config;
+use crate::rewrite::RewriteContext;
+use crate::shape::{Indent, Shape};
+use crate::string::{rewrite_string, StringFormat};
+use crate::utils::{
+    count_newlines, first_line_width, last_line_width, trim_left_preserve_layout, unicode_str_width,
+};
+use crate::{ErrorKind, FormattingError};
+
+fn is_custom_comment(comment: &str) -> bool {
+    if !comment.starts_with("//") {
+        false
+    } else if let Some(c) = comment.chars().nth(2) {
+        !c.is_alphanumeric() && !c.is_whitespace()
+    } else {
+        false
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub(crate) enum CommentStyle<'a> {
+    DoubleSlash,
+    TripleSlash,
+    Doc,
+    SingleBullet,
+    DoubleBullet,
+    Exclamation,
+    Custom(&'a str),
+}
+
+fn custom_opener(s: &str) -> &str {
+    s.lines().next().map_or("", |first_line| {
+        first_line
+            .find(' ')
+            .map_or(first_line, |space_index| &first_line[0..=space_index])
+    })
+}
+
+impl<'a> CommentStyle<'a> {
+    /// Returns `true` if the commenting style covers a line only.
+    pub(crate) fn is_line_comment(&self) -> bool {
+        match *self {
+            CommentStyle::DoubleSlash
+            | CommentStyle::TripleSlash
+            | CommentStyle::Doc
+            | CommentStyle::Custom(_) => true,
+            _ => false,
+        }
+    }
+
+    /// Returns `true` if the commenting style can span over multiple lines.
+    pub(crate) fn is_block_comment(&self) -> bool {
+        match *self {
+            CommentStyle::SingleBullet | CommentStyle::DoubleBullet | CommentStyle::Exclamation => {
+                true
+            }
+            _ => false,
+        }
+    }
+
+    /// Returns `true` if the commenting style is for documentation.
+    pub(crate) fn is_doc_comment(&self) -> bool {
+        match *self {
+            CommentStyle::TripleSlash | CommentStyle::Doc => true,
+            _ => false,
+        }
+    }
+
+    pub(crate) fn opener(&self) -> &'a str {
+        match *self {
+            CommentStyle::DoubleSlash => "// ",
+            CommentStyle::TripleSlash => "/// ",
+            CommentStyle::Doc => "//! ",
+            CommentStyle::SingleBullet => "/* ",
+            CommentStyle::DoubleBullet => "/** ",
+            CommentStyle::Exclamation => "/*! ",
+            CommentStyle::Custom(opener) => opener,
+        }
+    }
+
+    pub(crate) fn closer(&self) -> &'a str {
+        match *self {
+            CommentStyle::DoubleSlash
+            | CommentStyle::TripleSlash
+            | CommentStyle::Custom(..)
+            | CommentStyle::Doc => "",
+            CommentStyle::SingleBullet | CommentStyle::DoubleBullet | CommentStyle::Exclamation => {
+                " */"
+            }
+        }
+    }
+
+    pub(crate) fn line_start(&self) -> &'a str {
+        match *self {
+            CommentStyle::DoubleSlash => "// ",
+            CommentStyle::TripleSlash => "/// ",
+            CommentStyle::Doc => "//! ",
+            CommentStyle::SingleBullet | CommentStyle::DoubleBullet | CommentStyle::Exclamation => {
+                " * "
+            }
+            CommentStyle::Custom(opener) => opener,
+        }
+    }
+
+    pub(crate) fn to_str_tuplet(&self) -> (&'a str, &'a str, &'a str) {
+        (self.opener(), self.closer(), self.line_start())
+    }
+}
+
+pub(crate) fn comment_style(orig: &str, normalize_comments: bool) -> CommentStyle<'_> {
+    if !normalize_comments {
+        if orig.starts_with("/**") && !orig.starts_with("/**/") {
+            CommentStyle::DoubleBullet
+        } else if orig.starts_with("/*!") {
+            CommentStyle::Exclamation
+        } else if orig.starts_with("/*") {
+            CommentStyle::SingleBullet
+        } else if orig.starts_with("///") && orig.chars().nth(3).map_or(true, |c| c != '/') {
+            CommentStyle::TripleSlash
+        } else if orig.starts_with("//!") {
+            CommentStyle::Doc
+        } else if is_custom_comment(orig) {
+            CommentStyle::Custom(custom_opener(orig))
+        } else {
+            CommentStyle::DoubleSlash
+        }
+    } else if (orig.starts_with("///") && orig.chars().nth(3).map_or(true, |c| c != '/'))
+        || (orig.starts_with("/**") && !orig.starts_with("/**/"))
+    {
+        CommentStyle::TripleSlash
+    } else if orig.starts_with("//!") || orig.starts_with("/*!") {
+        CommentStyle::Doc
+    } else if is_custom_comment(orig) {
+        CommentStyle::Custom(custom_opener(orig))
+    } else {
+        CommentStyle::DoubleSlash
+    }
+}
+
+/// Returns true if the last line of the passed string finishes with a block-comment.
+pub(crate) fn is_last_comment_block(s: &str) -> bool {
+    s.trim_end().ends_with("*/")
+}
+
+/// Combine `prev_str` and `next_str` into a single `String`. `span` may contain
+/// comments between two strings. If there are such comments, then that will be
+/// recovered. If `allow_extend` is true and there is no comment between the two
+/// strings, then they will be put on a single line as long as doing so does not
+/// exceed max width.
+pub(crate) fn combine_strs_with_missing_comments(
+    context: &RewriteContext<'_>,
+    prev_str: &str,
+    next_str: &str,
+    span: Span,
+    shape: Shape,
+    allow_extend: bool,
+) -> Option<String> {
+    trace!(
+        "combine_strs_with_missing_comments `{}` `{}` {:?} {:?}",
+        prev_str,
+        next_str,
+        span,
+        shape
+    );
+
+    let mut result =
+        String::with_capacity(prev_str.len() + next_str.len() + shape.indent.width() + 128);
+    result.push_str(prev_str);
+    let mut allow_one_line = !prev_str.contains('\n') && !next_str.contains('\n');
+    let first_sep = if prev_str.is_empty() || next_str.is_empty() {
+        ""
+    } else {
+        " "
+    };
+    let mut one_line_width =
+        last_line_width(prev_str) + first_line_width(next_str) + first_sep.len();
+
+    let config = context.config;
+    let indent = shape.indent;
+    let missing_comment = rewrite_missing_comment(span, shape, context)?;
+
+    if missing_comment.is_empty() {
+        if allow_extend && prev_str.len() + first_sep.len() + next_str.len() <= shape.width {
+            result.push_str(first_sep);
+        } else if !prev_str.is_empty() {
+            result.push_str(&indent.to_string_with_newline(config))
+        }
+        result.push_str(next_str);
+        return Some(result);
+    }
+
+    // We have a missing comment between the first expression and the second expression.
+
+    // Peek the the original source code and find out whether there is a newline between the first
+    // expression and the second expression or the missing comment. We will preserve the original
+    // layout whenever possible.
+    let original_snippet = context.snippet(span);
+    let prefer_same_line = if let Some(pos) = original_snippet.find('/') {
+        !original_snippet[..pos].contains('\n')
+    } else {
+        !original_snippet.contains('\n')
+    };
+
+    one_line_width -= first_sep.len();
+    let first_sep = if prev_str.is_empty() || missing_comment.is_empty() {
+        Cow::from("")
+    } else {
+        let one_line_width = last_line_width(prev_str) + first_line_width(&missing_comment) + 1;
+        if prefer_same_line && one_line_width <= shape.width {
+            Cow::from(" ")
+        } else {
+            indent.to_string_with_newline(config)
+        }
+    };
+    result.push_str(&first_sep);
+    result.push_str(&missing_comment);
+
+    let second_sep = if missing_comment.is_empty() || next_str.is_empty() {
+        Cow::from("")
+    } else if missing_comment.starts_with("//") {
+        indent.to_string_with_newline(config)
+    } else {
+        one_line_width += missing_comment.len() + first_sep.len() + 1;
+        allow_one_line &= !missing_comment.starts_with("//") && !missing_comment.contains('\n');
+        if prefer_same_line && allow_one_line && one_line_width <= shape.width {
+            Cow::from(" ")
+        } else {
+            indent.to_string_with_newline(config)
+        }
+    };
+    result.push_str(&second_sep);
+    result.push_str(next_str);
+
+    Some(result)
+}
+
+pub(crate) fn rewrite_doc_comment(orig: &str, shape: Shape, config: &Config) -> Option<String> {
+    identify_comment(orig, false, shape, config, true)
+}
+
+pub(crate) fn rewrite_comment(
+    orig: &str,
+    block_style: bool,
+    shape: Shape,
+    config: &Config,
+) -> Option<String> {
+    identify_comment(orig, block_style, shape, config, false)
+}
+
+fn identify_comment(
+    orig: &str,
+    block_style: bool,
+    shape: Shape,
+    config: &Config,
+    is_doc_comment: bool,
+) -> Option<String> {
+    let style = comment_style(orig, false);
+
+    // Computes the byte length of line taking into account a newline if the line is part of a
+    // paragraph.
+    fn compute_len(orig: &str, line: &str) -> usize {
+        if orig.len() > line.len() {
+            if orig.as_bytes()[line.len()] == b'\r' {
+                line.len() + 2
+            } else {
+                line.len() + 1
+            }
+        } else {
+            line.len()
+        }
+    }
+
+    // Get the first group of line comments having the same commenting style.
+    //
+    // Returns a tuple with:
+    // - a boolean indicating if there is a blank line
+    // - a number indicating the size of the first group of comments
+    fn consume_same_line_comments(
+        style: CommentStyle<'_>,
+        orig: &str,
+        line_start: &str,
+    ) -> (bool, usize) {
+        let mut first_group_ending = 0;
+        let mut hbl = false;
+
+        for line in orig.lines() {
+            let trimmed_line = line.trim_start();
+            if trimmed_line.is_empty() {
+                hbl = true;
+                break;
+            } else if trimmed_line.starts_with(line_start)
+                || comment_style(trimmed_line, false) == style
+            {
+                first_group_ending += compute_len(&orig[first_group_ending..], line);
+            } else {
+                break;
+            }
+        }
+        (hbl, first_group_ending)
+    }
+
+    let (has_bare_lines, first_group_ending) = match style {
+        CommentStyle::DoubleSlash | CommentStyle::TripleSlash | CommentStyle::Doc => {
+            let line_start = style.line_start().trim_start();
+            consume_same_line_comments(style, orig, line_start)
+        }
+        CommentStyle::Custom(opener) => {
+            let trimmed_opener = opener.trim_end();
+            consume_same_line_comments(style, orig, trimmed_opener)
+        }
+        // for a block comment, search for the closing symbol
+        CommentStyle::DoubleBullet | CommentStyle::SingleBullet | CommentStyle::Exclamation => {
+            let closer = style.closer().trim_start();
+            let mut count = orig.matches(closer).count();
+            let mut closing_symbol_offset = 0;
+            let mut hbl = false;
+            let mut first = true;
+            for line in orig.lines() {
+                closing_symbol_offset += compute_len(&orig[closing_symbol_offset..], line);
+                let mut trimmed_line = line.trim_start();
+                if !trimmed_line.starts_with('*')
+                    && !trimmed_line.starts_with("//")
+                    && !trimmed_line.starts_with("/*")
+                {
+                    hbl = true;
+                }
+
+                // Remove opener from consideration when searching for closer
+                if first {
+                    let opener = style.opener().trim_end();
+                    trimmed_line = &trimmed_line[opener.len()..];
+                    first = false;
+                }
+                if trimmed_line.ends_with(closer) {
+                    count -= 1;
+                    if count == 0 {
+                        break;
+                    }
+                }
+            }
+            (hbl, closing_symbol_offset)
+        }
+    };
+
+    let (first_group, rest) = orig.split_at(first_group_ending);
+    let rewritten_first_group =
+        if !config.normalize_comments() && has_bare_lines && style.is_block_comment() {
+            trim_left_preserve_layout(first_group, shape.indent, config)?
+        } else if !config.normalize_comments()
+            && !config.wrap_comments()
+            && !config.format_code_in_doc_comments()
+        {
+            light_rewrite_comment(first_group, shape.indent, config, is_doc_comment)
+        } else {
+            rewrite_comment_inner(
+                first_group,
+                block_style,
+                style,
+                shape,
+                config,
+                is_doc_comment || style.is_doc_comment(),
+            )?
+        };
+    if rest.is_empty() {
+        Some(rewritten_first_group)
+    } else {
+        identify_comment(
+            rest.trim_start(),
+            block_style,
+            shape,
+            config,
+            is_doc_comment,
+        )
+        .map(|rest_str| {
+            format!(
+                "{}\n{}{}{}",
+                rewritten_first_group,
+                // insert back the blank line
+                if has_bare_lines && style.is_line_comment() {
+                    "\n"
+                } else {
+                    ""
+                },
+                shape.indent.to_string(config),
+                rest_str
+            )
+        })
+    }
+}
+
+/// Attributes for code blocks in rustdoc.
+/// See https://doc.rust-lang.org/rustdoc/print.html#attributes
+enum CodeBlockAttribute {
+    Rust,
+    Ignore,
+    Text,
+    ShouldPanic,
+    NoRun,
+    CompileFail,
+}
+
+impl CodeBlockAttribute {
+    fn new(attribute: &str) -> CodeBlockAttribute {
+        match attribute {
+            "rust" | "" => CodeBlockAttribute::Rust,
+            "ignore" => CodeBlockAttribute::Ignore,
+            "text" => CodeBlockAttribute::Text,
+            "should_panic" => CodeBlockAttribute::ShouldPanic,
+            "no_run" => CodeBlockAttribute::NoRun,
+            "compile_fail" => CodeBlockAttribute::CompileFail,
+            _ => CodeBlockAttribute::Text,
+        }
+    }
+}
+
+/// Block that is formatted as an item.
+///
+/// An item starts with either a star `*` or a dash `-`. Different level of indentation are
+/// handled by shrinking the shape accordingly.
+struct ItemizedBlock {
+    /// the lines that are identified as part of an itemized block
+    lines: Vec<String>,
+    /// the number of whitespaces up to the item sigil
+    indent: usize,
+    /// the string that marks the start of an item
+    opener: String,
+    /// sequence of whitespaces to prefix new lines that are part of the item
+    line_start: String,
+}
+
+impl ItemizedBlock {
+    /// Returns `true` if the line is formatted as an item
+    fn is_itemized_line(line: &str) -> bool {
+        let trimmed = line.trim_start();
+        trimmed.starts_with("* ") || trimmed.starts_with("- ")
+    }
+
+    /// Creates a new ItemizedBlock described with the given line.
+    /// The `is_itemized_line` needs to be called first.
+    fn new(line: &str) -> ItemizedBlock {
+        let space_to_sigil = line.chars().take_while(|c| c.is_whitespace()).count();
+        let indent = space_to_sigil + 2;
+        ItemizedBlock {
+            lines: vec![line[indent..].to_string()],
+            indent,
+            opener: line[..indent].to_string(),
+            line_start: " ".repeat(indent),
+        }
+    }
+
+    /// Returns a `StringFormat` used for formatting the content of an item.
+    fn create_string_format<'a>(&'a self, fmt: &'a StringFormat<'_>) -> StringFormat<'a> {
+        StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "",
+            line_end: "",
+            shape: Shape::legacy(fmt.shape.width.saturating_sub(self.indent), Indent::empty()),
+            trim_end: true,
+            config: fmt.config,
+        }
+    }
+
+    /// Returns `true` if the line is part of the current itemized block.
+    /// If it is, then it is added to the internal lines list.
+    fn add_line(&mut self, line: &str) -> bool {
+        if !ItemizedBlock::is_itemized_line(line)
+            && self.indent <= line.chars().take_while(|c| c.is_whitespace()).count()
+        {
+            self.lines.push(line.to_string());
+            return true;
+        }
+        false
+    }
+
+    /// Returns the block as a string, with each line trimmed at the start.
+    fn trimmed_block_as_string(&self) -> String {
+        self.lines
+            .iter()
+            .map(|line| format!("{} ", line.trim_start()))
+            .collect::<String>()
+    }
+
+    /// Returns the block as a string under its original form.
+    fn original_block_as_string(&self) -> String {
+        self.lines.join("\n")
+    }
+}
+
+struct CommentRewrite<'a> {
+    result: String,
+    code_block_buffer: String,
+    is_prev_line_multi_line: bool,
+    code_block_attr: Option<CodeBlockAttribute>,
+    item_block: Option<ItemizedBlock>,
+    comment_line_separator: String,
+    indent_str: String,
+    max_width: usize,
+    fmt_indent: Indent,
+    fmt: StringFormat<'a>,
+
+    opener: String,
+    closer: String,
+    line_start: String,
+}
+
+impl<'a> CommentRewrite<'a> {
+    fn new(
+        orig: &'a str,
+        block_style: bool,
+        shape: Shape,
+        config: &'a Config,
+    ) -> CommentRewrite<'a> {
+        let (opener, closer, line_start) = if block_style {
+            CommentStyle::SingleBullet.to_str_tuplet()
+        } else {
+            comment_style(orig, config.normalize_comments()).to_str_tuplet()
+        };
+
+        let max_width = shape
+            .width
+            .checked_sub(closer.len() + opener.len())
+            .unwrap_or(1);
+        let indent_str = shape.indent.to_string_with_newline(config).to_string();
+
+        let mut cr = CommentRewrite {
+            result: String::with_capacity(orig.len() * 2),
+            code_block_buffer: String::with_capacity(128),
+            is_prev_line_multi_line: false,
+            code_block_attr: None,
+            item_block: None,
+            comment_line_separator: format!("{}{}", indent_str, line_start),
+            max_width,
+            indent_str,
+            fmt_indent: shape.indent,
+
+            fmt: StringFormat {
+                opener: "",
+                closer: "",
+                line_start,
+                line_end: "",
+                shape: Shape::legacy(max_width, shape.indent),
+                trim_end: true,
+                config,
+            },
+
+            opener: opener.to_owned(),
+            closer: closer.to_owned(),
+            line_start: line_start.to_owned(),
+        };
+        cr.result.push_str(opener);
+        cr
+    }
+
+    fn join_block(s: &str, sep: &str) -> String {
+        let mut result = String::with_capacity(s.len() + 128);
+        let mut iter = s.lines().peekable();
+        while let Some(line) = iter.next() {
+            result.push_str(line);
+            result.push_str(match iter.peek() {
+                Some(next_line) if next_line.is_empty() => sep.trim_end(),
+                Some(..) => &sep,
+                None => "",
+            });
+        }
+        result
+    }
+
+    fn finish(mut self) -> String {
+        if !self.code_block_buffer.is_empty() {
+            // There is a code block that is not properly enclosed by backticks.
+            // We will leave them untouched.
+            self.result.push_str(&self.comment_line_separator);
+            self.result.push_str(&Self::join_block(
+                &trim_custom_comment_prefix(&self.code_block_buffer),
+                &self.comment_line_separator,
+            ));
+        }
+
+        if let Some(ref ib) = self.item_block {
+            // the last few lines are part of an itemized block
+            self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+            let item_fmt = ib.create_string_format(&self.fmt);
+            self.result.push_str(&self.comment_line_separator);
+            self.result.push_str(&ib.opener);
+            match rewrite_string(
+                &ib.trimmed_block_as_string(),
+                &item_fmt,
+                self.max_width.saturating_sub(ib.indent),
+            ) {
+                Some(s) => self.result.push_str(&Self::join_block(
+                    &s,
+                    &format!("{}{}", self.comment_line_separator, ib.line_start),
+                )),
+                None => self.result.push_str(&Self::join_block(
+                    &ib.original_block_as_string(),
+                    &self.comment_line_separator,
+                )),
+            };
+        }
+
+        self.result.push_str(&self.closer);
+        if self.result.ends_with(&self.opener) && self.opener.ends_with(' ') {
+            // Trailing space.
+            self.result.pop();
+        }
+
+        self.result
+    }
+
+    fn handle_line(
+        &mut self,
+        orig: &'a str,
+        i: usize,
+        line: &'a str,
+        has_leading_whitespace: bool,
+    ) -> bool {
+        let is_last = i == count_newlines(orig);
+
+        if let Some(ref mut ib) = self.item_block {
+            if ib.add_line(&line) {
+                return false;
+            }
+            self.is_prev_line_multi_line = false;
+            self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+            let item_fmt = ib.create_string_format(&self.fmt);
+            self.result.push_str(&self.comment_line_separator);
+            self.result.push_str(&ib.opener);
+            match rewrite_string(
+                &ib.trimmed_block_as_string(),
+                &item_fmt,
+                self.max_width.saturating_sub(ib.indent),
+            ) {
+                Some(s) => self.result.push_str(&Self::join_block(
+                    &s,
+                    &format!("{}{}", self.comment_line_separator, ib.line_start),
+                )),
+                None => self.result.push_str(&Self::join_block(
+                    &ib.original_block_as_string(),
+                    &self.comment_line_separator,
+                )),
+            };
+        } else if self.code_block_attr.is_some() {
+            if line.starts_with("```") {
+                let code_block = match self.code_block_attr.as_ref().unwrap() {
+                    CodeBlockAttribute::Ignore | CodeBlockAttribute::Text => {
+                        trim_custom_comment_prefix(&self.code_block_buffer)
+                    }
+                    _ if self.code_block_buffer.is_empty() => String::new(),
+                    _ => {
+                        let mut config = self.fmt.config.clone();
+                        config.set().wrap_comments(false);
+                        if config.format_code_in_doc_comments() {
+                            if let Some(s) =
+                                crate::format_code_block(&self.code_block_buffer, &config, false)
+                            {
+                                trim_custom_comment_prefix(&s.snippet)
+                            } else {
+                                trim_custom_comment_prefix(&self.code_block_buffer)
+                            }
+                        } else {
+                            trim_custom_comment_prefix(&self.code_block_buffer)
+                        }
+                    }
+                };
+                if !code_block.is_empty() {
+                    self.result.push_str(&self.comment_line_separator);
+                    self.result
+                        .push_str(&Self::join_block(&code_block, &self.comment_line_separator));
+                }
+                self.code_block_buffer.clear();
+                self.result.push_str(&self.comment_line_separator);
+                self.result.push_str(line);
+                self.code_block_attr = None;
+            } else {
+                self.code_block_buffer
+                    .push_str(&hide_sharp_behind_comment(line));
+                self.code_block_buffer.push('\n');
+            }
+            return false;
+        }
+
+        self.code_block_attr = None;
+        self.item_block = None;
+        if line.starts_with("```") {
+            self.code_block_attr = Some(CodeBlockAttribute::new(&line[3..]))
+        } else if self.fmt.config.wrap_comments() && ItemizedBlock::is_itemized_line(&line) {
+            let ib = ItemizedBlock::new(&line);
+            self.item_block = Some(ib);
+            return false;
+        }
+
+        if self.result == self.opener {
+            let force_leading_whitespace = &self.opener == "/* " && count_newlines(orig) == 0;
+            if !has_leading_whitespace && !force_leading_whitespace && self.result.ends_with(' ') {
+                self.result.pop();
+            }
+            if line.is_empty() {
+                return false;
+            }
+        } else if self.is_prev_line_multi_line && !line.is_empty() {
+            self.result.push(' ')
+        } else if is_last && line.is_empty() {
+            // trailing blank lines are unwanted
+            if !self.closer.is_empty() {
+                self.result.push_str(&self.indent_str);
+            }
+            return true;
+        } else {
+            self.result.push_str(&self.comment_line_separator);
+            if !has_leading_whitespace && self.result.ends_with(' ') {
+                self.result.pop();
+            }
+        }
+
+        if self.fmt.config.wrap_comments()
+            && unicode_str_width(line) > self.fmt.shape.width
+            && !has_url(line)
+        {
+            match rewrite_string(line, &self.fmt, self.max_width) {
+                Some(ref s) => {
+                    self.is_prev_line_multi_line = s.contains('\n');
+                    self.result.push_str(s);
+                }
+                None if self.is_prev_line_multi_line => {
+                    // We failed to put the current `line` next to the previous `line`.
+                    // Remove the trailing space, then start rewrite on the next line.
+                    self.result.pop();
+                    self.result.push_str(&self.comment_line_separator);
+                    self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+                    match rewrite_string(line, &self.fmt, self.max_width) {
+                        Some(ref s) => {
+                            self.is_prev_line_multi_line = s.contains('\n');
+                            self.result.push_str(s);
+                        }
+                        None => {
+                            self.is_prev_line_multi_line = false;
+                            self.result.push_str(line);
+                        }
+                    }
+                }
+                None => {
+                    self.is_prev_line_multi_line = false;
+                    self.result.push_str(line);
+                }
+            }
+
+            self.fmt.shape = if self.is_prev_line_multi_line {
+                // 1 = " "
+                let offset = 1 + last_line_width(&self.result) - self.line_start.len();
+                Shape {
+                    width: self.max_width.saturating_sub(offset),
+                    indent: self.fmt_indent,
+                    offset: self.fmt.shape.offset + offset,
+                }
+            } else {
+                Shape::legacy(self.max_width, self.fmt_indent)
+            };
+        } else {
+            if line.is_empty() && self.result.ends_with(' ') && !is_last {
+                // Remove space if this is an empty comment or a doc comment.
+                self.result.pop();
+            }
+            self.result.push_str(line);
+            self.fmt.shape = Shape::legacy(self.max_width, self.fmt_indent);
+            self.is_prev_line_multi_line = false;
+        }
+
+        false
+    }
+}
+
+fn rewrite_comment_inner(
+    orig: &str,
+    block_style: bool,
+    style: CommentStyle<'_>,
+    shape: Shape,
+    config: &Config,
+    is_doc_comment: bool,
+) -> Option<String> {
+    let mut rewriter = CommentRewrite::new(orig, block_style, shape, config);
+
+    let line_breaks = count_newlines(orig.trim_end());
+    let lines = orig
+        .lines()
+        .enumerate()
+        .map(|(i, mut line)| {
+            line = trim_end_unless_two_whitespaces(line.trim_start(), is_doc_comment);
+            // Drop old closer.
+            if i == line_breaks && line.ends_with("*/") && !line.starts_with("//") {
+                line = line[..(line.len() - 2)].trim_end();
+            }
+
+            line
+        })
+        .map(|s| left_trim_comment_line(s, &style))
+        .map(|(line, has_leading_whitespace)| {
+            if orig.starts_with("/*") && line_breaks == 0 {
+                (
+                    line.trim_start(),
+                    has_leading_whitespace || config.normalize_comments(),
+                )
+            } else {
+                (line, has_leading_whitespace || config.normalize_comments())
+            }
+        });
+
+    for (i, (line, has_leading_whitespace)) in lines.enumerate() {
+        if rewriter.handle_line(orig, i, line, has_leading_whitespace) {
+            break;
+        }
+    }
+
+    Some(rewriter.finish())
+}
+
+const RUSTFMT_CUSTOM_COMMENT_PREFIX: &str = "//#### ";
+
+fn hide_sharp_behind_comment(s: &str) -> Cow<'_, str> {
+    let s_trimmed = s.trim();
+    if s_trimmed.starts_with("# ") || s_trimmed == "#" {
+        Cow::from(format!("{}{}", RUSTFMT_CUSTOM_COMMENT_PREFIX, s))
+    } else {
+        Cow::from(s)
+    }
+}
+
+fn trim_custom_comment_prefix(s: &str) -> String {
+    s.lines()
+        .map(|line| {
+            let left_trimmed = line.trim_start();
+            if left_trimmed.starts_with(RUSTFMT_CUSTOM_COMMENT_PREFIX) {
+                left_trimmed.trim_start_matches(RUSTFMT_CUSTOM_COMMENT_PREFIX)
+            } else {
+                line
+            }
+        })
+        .collect::<Vec<_>>()
+        .join("\n")
+}
+
+/// Returns `true` if the given string MAY include URLs or alike.
+fn has_url(s: &str) -> bool {
+    // This function may return false positive, but should get its job done in most cases.
+    s.contains("https://") || s.contains("http://") || s.contains("ftp://") || s.contains("file://")
+}
+
+/// Given the span, rewrite the missing comment inside it if available.
+/// Note that the given span must only include comments (or leading/trailing whitespaces).
+pub(crate) fn rewrite_missing_comment(
+    span: Span,
+    shape: Shape,
+    context: &RewriteContext<'_>,
+) -> Option<String> {
+    let missing_snippet = context.snippet(span);
+    let trimmed_snippet = missing_snippet.trim();
+    // check the span starts with a comment
+    let pos = trimmed_snippet.find('/');
+    if !trimmed_snippet.is_empty() && pos.is_some() {
+        rewrite_comment(trimmed_snippet, false, shape, context.config)
+    } else {
+        Some(String::new())
+    }
+}
+
+/// Recover the missing comments in the specified span, if available.
+/// The layout of the comments will be preserved as long as it does not break the code
+/// and its total width does not exceed the max width.
+pub(crate) fn recover_missing_comment_in_span(
+    span: Span,
+    shape: Shape,
+    context: &RewriteContext<'_>,
+    used_width: usize,
+) -> Option<String> {
+    let missing_comment = rewrite_missing_comment(span, shape, context)?;
+    if missing_comment.is_empty() {
+        Some(String::new())
+    } else {
+        let missing_snippet = context.snippet(span);
+        let pos = missing_snippet.find('/')?;
+        // 1 = ` `
+        let total_width = missing_comment.len() + used_width + 1;
+        let force_new_line_before_comment =
+            missing_snippet[..pos].contains('\n') || total_width > context.config.max_width();
+        let sep = if force_new_line_before_comment {
+            shape.indent.to_string_with_newline(context.config)
+        } else {
+            Cow::from(" ")
+        };
+        Some(format!("{}{}", sep, missing_comment))
+    }
+}
+
+/// Trim trailing whitespaces unless they consist of two or more whitespaces.
+fn trim_end_unless_two_whitespaces(s: &str, is_doc_comment: bool) -> &str {
+    if is_doc_comment && s.ends_with("  ") {
+        s
+    } else {
+        s.trim_end()
+    }
+}
+
+/// Trims whitespace and aligns to indent, but otherwise does not change comments.
+fn light_rewrite_comment(
+    orig: &str,
+    offset: Indent,
+    config: &Config,
+    is_doc_comment: bool,
+) -> String {
+    let lines: Vec<&str> = orig
+        .lines()
+        .map(|l| {
+            // This is basically just l.trim(), but in the case that a line starts
+            // with `*` we want to leave one space before it, so it aligns with the
+            // `*` in `/*`.
+            let first_non_whitespace = l.find(|c| !char::is_whitespace(c));
+            let left_trimmed = if let Some(fnw) = first_non_whitespace {
+                if l.as_bytes()[fnw] == b'*' && fnw > 0 {
+                    &l[fnw - 1..]
+                } else {
+                    &l[fnw..]
+                }
+            } else {
+                ""
+            };
+            // Preserve markdown's double-space line break syntax in doc comment.
+            trim_end_unless_two_whitespaces(left_trimmed, is_doc_comment)
+        })
+        .collect();
+    lines.join(&format!("\n{}", offset.to_string(config)))
+}
+
+/// Trims comment characters and possibly a single space from the left of a string.
+/// Does not trim all whitespace. If a single space is trimmed from the left of the string,
+/// this function returns true.
+fn left_trim_comment_line<'a>(line: &'a str, style: &CommentStyle<'_>) -> (&'a str, bool) {
+    if line.starts_with("//! ")
+        || line.starts_with("/// ")
+        || line.starts_with("/*! ")
+        || line.starts_with("/** ")
+    {
+        (&line[4..], true)
+    } else if let CommentStyle::Custom(opener) = *style {
+        if line.starts_with(opener) {
+            (&line[opener.len()..], true)
+        } else {
+            (&line[opener.trim_end().len()..], false)
+        }
+    } else if line.starts_with("/* ")
+        || line.starts_with("// ")
+        || line.starts_with("//!")
+        || line.starts_with("///")
+        || line.starts_with("** ")
+        || line.starts_with("/*!")
+        || (line.starts_with("/**") && !line.starts_with("/**/"))
+    {
+        (&line[3..], line.chars().nth(2).unwrap() == ' ')
+    } else if line.starts_with("/*")
+        || line.starts_with("* ")
+        || line.starts_with("//")
+        || line.starts_with("**")
+    {
+        (&line[2..], line.chars().nth(1).unwrap() == ' ')
+    } else if line.starts_with('*') {
+        (&line[1..], false)
+    } else {
+        (line, line.starts_with(' '))
+    }
+}
+
+pub(crate) trait FindUncommented {
+    fn find_uncommented(&self, pat: &str) -> Option<usize>;
+    fn find_last_uncommented(&self, pat: &str) -> Option<usize>;
+}
+
+impl FindUncommented for str {
+    fn find_uncommented(&self, pat: &str) -> Option<usize> {
+        let mut needle_iter = pat.chars();
+        for (kind, (i, b)) in CharClasses::new(self.char_indices()) {
+            match needle_iter.next() {
+                None => {
+                    return Some(i - pat.len());
+                }
+                Some(c) => match kind {
+                    FullCodeCharKind::Normal | FullCodeCharKind::InString if b == c => {}
+                    _ => {
+                        needle_iter = pat.chars();
+                    }
+                },
+            }
+        }
+
+        // Handle case where the pattern is a suffix of the search string
+        match needle_iter.next() {
+            Some(_) => None,
+            None => Some(self.len() - pat.len()),
+        }
+    }
+
+    fn find_last_uncommented(&self, pat: &str) -> Option<usize> {
+        if let Some(left) = self.find_uncommented(pat) {
+            let mut result = left;
+            // add 1 to use find_last_uncommented for &str after pat
+            while let Some(next) = self[(result + 1)..].find_last_uncommented(pat) {
+                result += next + 1;
+            }
+            Some(result)
+        } else {
+            None
+        }
+    }
+}
+
+// Returns the first byte position after the first comment. The given string
+// is expected to be prefixed by a comment, including delimiters.
+// Good: `/* /* inner */ outer */ code();`
+// Bad:  `code(); // hello\n world!`
+pub(crate) fn find_comment_end(s: &str) -> Option<usize> {
+    let mut iter = CharClasses::new(s.char_indices());
+    for (kind, (i, _c)) in &mut iter {
+        if kind == FullCodeCharKind::Normal || kind == FullCodeCharKind::InString {
+            return Some(i);
+        }
+    }
+
+    // Handle case where the comment ends at the end of `s`.
+    if iter.status == CharClassesStatus::Normal {
+        Some(s.len())
+    } else {
+        None
+    }
+}
+
+/// Returns `true` if text contains any comment.
+pub(crate) fn contains_comment(text: &str) -> bool {
+    CharClasses::new(text.chars()).any(|(kind, _)| kind.is_comment())
+}
+
+pub(crate) struct CharClasses<T>
+where
+    T: Iterator,
+    T::Item: RichChar,
+{
+    base: MultiPeek<T>,
+    status: CharClassesStatus,
+}
+
+pub(crate) trait RichChar {
+    fn get_char(&self) -> char;
+}
+
+impl RichChar for char {
+    fn get_char(&self) -> char {
+        *self
+    }
+}
+
+impl RichChar for (usize, char) {
+    fn get_char(&self) -> char {
+        self.1
+    }
+}
+
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+enum CharClassesStatus {
+    Normal,
+    /// Character is within a string
+    LitString,
+    LitStringEscape,
+    /// Character is within a raw string
+    LitRawString(u32),
+    RawStringPrefix(u32),
+    RawStringSuffix(u32),
+    LitChar,
+    LitCharEscape,
+    /// Character inside a block comment, with the integer indicating the nesting deepness of the
+    /// comment
+    BlockComment(u32),
+    /// Character inside a block-commented string, with the integer indicating the nesting deepness
+    /// of the comment
+    StringInBlockComment(u32),
+    /// Status when the '/' has been consumed, but not yet the '*', deepness is
+    /// the new deepness (after the comment opening).
+    BlockCommentOpening(u32),
+    /// Status when the '*' has been consumed, but not yet the '/', deepness is
+    /// the new deepness (after the comment closing).
+    BlockCommentClosing(u32),
+    /// Character is within a line comment
+    LineComment,
+}
+
+/// Distinguish between functional part of code and comments
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+pub(crate) enum CodeCharKind {
+    Normal,
+    Comment,
+}
+
+/// Distinguish between functional part of code and comments,
+/// describing opening and closing of comments for ease when chunking
+/// code from tagged characters
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+pub(crate) enum FullCodeCharKind {
+    Normal,
+    /// The first character of a comment, there is only one for a comment (always '/')
+    StartComment,
+    /// Any character inside a comment including the second character of comment
+    /// marks ("//", "/*")
+    InComment,
+    /// Last character of a comment, '\n' for a line comment, '/' for a block comment.
+    EndComment,
+    /// Start of a mutlitine string inside a comment
+    StartStringCommented,
+    /// End of a mutlitine string inside a comment
+    EndStringCommented,
+    /// Inside a commented string
+    InStringCommented,
+    /// Start of a mutlitine string
+    StartString,
+    /// End of a mutlitine string
+    EndString,
+    /// Inside a string.
+    InString,
+}
+
+impl FullCodeCharKind {
+    pub(crate) fn is_comment(self) -> bool {
+        match self {
+            FullCodeCharKind::StartComment
+            | FullCodeCharKind::InComment
+            | FullCodeCharKind::EndComment
+            | FullCodeCharKind::StartStringCommented
+            | FullCodeCharKind::InStringCommented
+            | FullCodeCharKind::EndStringCommented => true,
+            _ => false,
+        }
+    }
+
+    /// Returns true if the character is inside a comment
+    pub(crate) fn inside_comment(self) -> bool {
+        match self {
+            FullCodeCharKind::InComment
+            | FullCodeCharKind::StartStringCommented
+            | FullCodeCharKind::InStringCommented
+            | FullCodeCharKind::EndStringCommented => true,
+            _ => false,
+        }
+    }
+
+    pub(crate) fn is_string(self) -> bool {
+        self == FullCodeCharKind::InString || self == FullCodeCharKind::StartString
+    }
+
+    /// Returns true if the character is within a commented string
+    pub(crate) fn is_commented_string(self) -> bool {
+        self == FullCodeCharKind::InStringCommented
+            || self == FullCodeCharKind::StartStringCommented
+    }
+
+    fn to_codecharkind(self) -> CodeCharKind {
+        if self.is_comment() {
+            CodeCharKind::Comment
+        } else {
+            CodeCharKind::Normal
+        }
+    }
+}
+
+impl<T> CharClasses<T>
+where
+    T: Iterator,
+    T::Item: RichChar,
+{
+    pub(crate) fn new(base: T) -> CharClasses<T> {
+        CharClasses {
+            base: multipeek(base),
+            status: CharClassesStatus::Normal,
+        }
+    }
+}
+
+fn is_raw_string_suffix<T>(iter: &mut MultiPeek<T>, count: u32) -> bool
+where
+    T: Iterator,
+    T::Item: RichChar,
+{
+    for _ in 0..count {
+        match iter.peek() {
+            Some(c) if c.get_char() == '#' => continue,
+            _ => return false,
+        }
+    }
+    true
+}
+
+impl<T> Iterator for CharClasses<T>
+where
+    T: Iterator,
+    T::Item: RichChar,
+{
+    type Item = (FullCodeCharKind, T::Item);
+
+    fn next(&mut self) -> Option<(FullCodeCharKind, T::Item)> {
+        let item = self.base.next()?;
+        let chr = item.get_char();
+        let mut char_kind = FullCodeCharKind::Normal;
+        self.status = match self.status {
+            CharClassesStatus::LitRawString(sharps) => {
+                char_kind = FullCodeCharKind::InString;
+                match chr {
+                    '"' => {
+                        if sharps == 0 {
+                            char_kind = FullCodeCharKind::Normal;
+                            CharClassesStatus::Normal
+                        } else if is_raw_string_suffix(&mut self.base, sharps) {
+                            CharClassesStatus::RawStringSuffix(sharps)
+                        } else {
+                            CharClassesStatus::LitRawString(sharps)
+                        }
+                    }
+                    _ => CharClassesStatus::LitRawString(sharps),
+                }
+            }
+            CharClassesStatus::RawStringPrefix(sharps) => {
+                char_kind = FullCodeCharKind::InString;
+                match chr {
+                    '#' => CharClassesStatus::RawStringPrefix(sharps + 1),
+                    '"' => CharClassesStatus::LitRawString(sharps),
+                    _ => CharClassesStatus::Normal, // Unreachable.
+                }
+            }
+            CharClassesStatus::RawStringSuffix(sharps) => {
+                match chr {
+                    '#' => {
+                        if sharps == 1 {
+                            CharClassesStatus::Normal
+                        } else {
+                            char_kind = FullCodeCharKind::InString;
+                            CharClassesStatus::RawStringSuffix(sharps - 1)
+                        }
+                    }
+                    _ => CharClassesStatus::Normal, // Unreachable
+                }
+            }
+            CharClassesStatus::LitString => {
+                char_kind = FullCodeCharKind::InString;
+                match chr {
+                    '"' => CharClassesStatus::Normal,
+                    '\\' => CharClassesStatus::LitStringEscape,
+                    _ => CharClassesStatus::LitString,
+                }
+            }
+            CharClassesStatus::LitStringEscape => {
+                char_kind = FullCodeCharKind::InString;
+                CharClassesStatus::LitString
+            }
+            CharClassesStatus::LitChar => match chr {
+                '\\' => CharClassesStatus::LitCharEscape,
+                '\'' => CharClassesStatus::Normal,
+                _ => CharClassesStatus::LitChar,
+            },
+            CharClassesStatus::LitCharEscape => CharClassesStatus::LitChar,
+            CharClassesStatus::Normal => match chr {
+                'r' => match self.base.peek().map(RichChar::get_char) {
+                    Some('#') | Some('"') => {
+                        char_kind = FullCodeCharKind::InString;
+                        CharClassesStatus::RawStringPrefix(0)
+                    }
+                    _ => CharClassesStatus::Normal,
+                },
+                '"' => {
+                    char_kind = FullCodeCharKind::InString;
+                    CharClassesStatus::LitString
+                }
+                '\'' => {
+                    // HACK: Work around mut borrow.
+                    match self.base.peek() {
+                        Some(next) if next.get_char() == '\\' => {
+                            self.status = CharClassesStatus::LitChar;
+                            return Some((char_kind, item));
+                        }
+                        _ => (),
+                    }
+
+                    match self.base.peek() {
+                        Some(next) if next.get_char() == '\'' => CharClassesStatus::LitChar,
+                        _ => CharClassesStatus::Normal,
+                    }
+                }
+                '/' => match self.base.peek() {
+                    Some(next) if next.get_char() == '*' => {
+                        self.status = CharClassesStatus::BlockCommentOpening(1);
+                        return Some((FullCodeCharKind::StartComment, item));
+                    }
+                    Some(next) if next.get_char() == '/' => {
+                        self.status = CharClassesStatus::LineComment;
+                        return Some((FullCodeCharKind::StartComment, item));
+                    }
+                    _ => CharClassesStatus::Normal,
+                },
+                _ => CharClassesStatus::Normal,
+            },
+            CharClassesStatus::StringInBlockComment(deepness) => {
+                char_kind = FullCodeCharKind::InStringCommented;
+                if chr == '"' {
+                    CharClassesStatus::BlockComment(deepness)
+                } else if chr == '*' && self.base.peek().map(RichChar::get_char) == Some('/') {
+                    char_kind = FullCodeCharKind::InComment;
+                    CharClassesStatus::BlockCommentClosing(deepness - 1)
+                } else {
+                    CharClassesStatus::StringInBlockComment(deepness)
+                }
+            }
+            CharClassesStatus::BlockComment(deepness) => {
+                assert_ne!(deepness, 0);
+                char_kind = FullCodeCharKind::InComment;
+                match self.base.peek() {
+                    Some(next) if next.get_char() == '/' && chr == '*' => {
+                        CharClassesStatus::BlockCommentClosing(deepness - 1)
+                    }
+                    Some(next) if next.get_char() == '*' && chr == '/' => {
+                        CharClassesStatus::BlockCommentOpening(deepness + 1)
+                    }
+                    _ if chr == '"' => CharClassesStatus::StringInBlockComment(deepness),
+                    _ => self.status,
+                }
+            }
+            CharClassesStatus::BlockCommentOpening(deepness) => {
+                assert_eq!(chr, '*');
+                self.status = CharClassesStatus::BlockComment(deepness);
+                return Some((FullCodeCharKind::InComment, item));
+            }
+            CharClassesStatus::BlockCommentClosing(deepness) => {
+                assert_eq!(chr, '/');
+                if deepness == 0 {
+                    self.status = CharClassesStatus::Normal;
+                    return Some((FullCodeCharKind::EndComment, item));
+                } else {
+                    self.status = CharClassesStatus::BlockComment(deepness);
+                    return Some((FullCodeCharKind::InComment, item));
+                }
+            }
+            CharClassesStatus::LineComment => match chr {
+                '\n' => {
+                    self.status = CharClassesStatus::Normal;
+                    return Some((FullCodeCharKind::EndComment, item));
+                }
+                _ => {
+                    self.status = CharClassesStatus::LineComment;
+                    return Some((FullCodeCharKind::InComment, item));
+                }
+            },
+        };
+        Some((char_kind, item))
+    }
+}
+
+/// An iterator over the lines of a string, paired with the char kind at the
+/// end of the line.
+pub(crate) struct LineClasses<'a> {
+    base: iter::Peekable<CharClasses<std::str::Chars<'a>>>,
+    kind: FullCodeCharKind,
+}
+
+impl<'a> LineClasses<'a> {
+    pub(crate) fn new(s: &'a str) -> Self {
+        LineClasses {
+            base: CharClasses::new(s.chars()).peekable(),
+            kind: FullCodeCharKind::Normal,
+        }
+    }
+}
+
+impl<'a> Iterator for LineClasses<'a> {
+    type Item = (FullCodeCharKind, String);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.base.peek()?;
+
+        let mut line = String::new();
+
+        let start_kind = match self.base.peek() {
+            Some((kind, _)) => *kind,
+            None => unreachable!(),
+        };
+
+        while let Some((kind, c)) = self.base.next() {
+            // needed to set the kind of the ending character on the last line
+            self.kind = kind;
+            if c == '\n' {
+                self.kind = match (start_kind, kind) {
+                    (FullCodeCharKind::Normal, FullCodeCharKind::InString) => {
+                        FullCodeCharKind::StartString
+                    }
+                    (FullCodeCharKind::InString, FullCodeCharKind::Normal) => {
+                        FullCodeCharKind::EndString
+                    }
+                    (FullCodeCharKind::InComment, FullCodeCharKind::InStringCommented) => {
+                        FullCodeCharKind::StartStringCommented
+                    }
+                    (FullCodeCharKind::InStringCommented, FullCodeCharKind::InComment) => {
+                        FullCodeCharKind::EndStringCommented
+                    }
+                    _ => kind,
+                };
+                break;
+            }
+            line.push(c);
+        }
+
+        // Workaround for CRLF newline.
+        if line.ends_with('\r') {
+            line.pop();
+        }
+
+        Some((self.kind, line))
+    }
+}
+
+/// Iterator over functional and commented parts of a string. Any part of a string is either
+/// functional code, either *one* block comment, either *one* line comment. Whitespace between
+/// comments is functional code. Line comments contain their ending newlines.
+struct UngroupedCommentCodeSlices<'a> {
+    slice: &'a str,
+    iter: iter::Peekable<CharClasses<std::str::CharIndices<'a>>>,
+}
+
+impl<'a> UngroupedCommentCodeSlices<'a> {
+    fn new(code: &'a str) -> UngroupedCommentCodeSlices<'a> {
+        UngroupedCommentCodeSlices {
+            slice: code,
+            iter: CharClasses::new(code.char_indices()).peekable(),
+        }
+    }
+}
+
+impl<'a> Iterator for UngroupedCommentCodeSlices<'a> {
+    type Item = (CodeCharKind, usize, &'a str);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let (kind, (start_idx, _)) = self.iter.next()?;
+        match kind {
+            FullCodeCharKind::Normal | FullCodeCharKind::InString => {
+                // Consume all the Normal code
+                while let Some(&(char_kind, _)) = self.iter.peek() {
+                    if char_kind.is_comment() {
+                        break;
+                    }
+                    let _ = self.iter.next();
+                }
+            }
+            FullCodeCharKind::StartComment => {
+                // Consume the whole comment
+                loop {
+                    match self.iter.next() {
+                        Some((kind, ..)) if kind.inside_comment() => continue,
+                        _ => break,
+                    }
+                }
+            }
+            _ => panic!(),
+        }
+        let slice = match self.iter.peek() {
+            Some(&(_, (end_idx, _))) => &self.slice[start_idx..end_idx],
+            None => &self.slice[start_idx..],
+        };
+        Some((
+            if kind.is_comment() {
+                CodeCharKind::Comment
+            } else {
+                CodeCharKind::Normal
+            },
+            start_idx,
+            slice,
+        ))
+    }
+}
+
+/// Iterator over an alternating sequence of functional and commented parts of
+/// a string. The first item is always a, possibly zero length, subslice of
+/// functional text. Line style comments contain their ending newlines.
+pub(crate) struct CommentCodeSlices<'a> {
+    slice: &'a str,
+    last_slice_kind: CodeCharKind,
+    last_slice_end: usize,
+}
+
+impl<'a> CommentCodeSlices<'a> {
+    pub(crate) fn new(slice: &'a str) -> CommentCodeSlices<'a> {
+        CommentCodeSlices {
+            slice,
+            last_slice_kind: CodeCharKind::Comment,
+            last_slice_end: 0,
+        }
+    }
+}
+
+impl<'a> Iterator for CommentCodeSlices<'a> {
+    type Item = (CodeCharKind, usize, &'a str);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.last_slice_end == self.slice.len() {
+            return None;
+        }
+
+        let mut sub_slice_end = self.last_slice_end;
+        let mut first_whitespace = None;
+        let subslice = &self.slice[self.last_slice_end..];
+        let mut iter = CharClasses::new(subslice.char_indices());
+
+        for (kind, (i, c)) in &mut iter {
+            let is_comment_connector = self.last_slice_kind == CodeCharKind::Normal
+                && &subslice[..2] == "//"
+                && [' ', '\t'].contains(&c);
+
+            if is_comment_connector && first_whitespace.is_none() {
+                first_whitespace = Some(i);
+            }
+
+            if kind.to_codecharkind() == self.last_slice_kind && !is_comment_connector {
+                let last_index = match first_whitespace {
+                    Some(j) => j,
+                    None => i,
+                };
+                sub_slice_end = self.last_slice_end + last_index;
+                break;
+            }
+
+            if !is_comment_connector {
+                first_whitespace = None;
+            }
+        }
+
+        if let (None, true) = (iter.next(), sub_slice_end == self.last_slice_end) {
+            // This was the last subslice.
+            sub_slice_end = match first_whitespace {
+                Some(i) => self.last_slice_end + i,
+                None => self.slice.len(),
+            };
+        }
+
+        let kind = match self.last_slice_kind {
+            CodeCharKind::Comment => CodeCharKind::Normal,
+            CodeCharKind::Normal => CodeCharKind::Comment,
+        };
+        let res = (
+            kind,
+            self.last_slice_end,
+            &self.slice[self.last_slice_end..sub_slice_end],
+        );
+        self.last_slice_end = sub_slice_end;
+        self.last_slice_kind = kind;
+
+        Some(res)
+    }
+}
+
+/// Checks is `new` didn't miss any comment from `span`, if it removed any, return previous text
+/// (if it fits in the width/offset, else return `None`), else return `new`
+pub(crate) fn recover_comment_removed(
+    new: String,
+    span: Span,
+    context: &RewriteContext<'_>,
+) -> Option<String> {
+    let snippet = context.snippet(span);
+    if snippet != new && changed_comment_content(snippet, &new) {
+        // We missed some comments. Warn and keep the original text.
+        if context.config.error_on_unformatted() {
+            context.report.append(
+                context.parse_sess.span_to_filename(span),
+                vec![FormattingError::from_span(
+                    span,
+                    &context.parse_sess,
+                    ErrorKind::LostComment,
+                )],
+            );
+        }
+        Some(snippet.to_owned())
+    } else {
+        Some(new)
+    }
+}
+
+pub(crate) fn filter_normal_code(code: &str) -> String {
+    let mut buffer = String::with_capacity(code.len());
+    LineClasses::new(code).for_each(|(kind, line)| match kind {
+        FullCodeCharKind::Normal
+        | FullCodeCharKind::StartString
+        | FullCodeCharKind::InString
+        | FullCodeCharKind::EndString => {
+            buffer.push_str(&line);
+            buffer.push('\n');
+        }
+        _ => (),
+    });
+    if !code.ends_with('\n') && buffer.ends_with('\n') {
+        buffer.pop();
+    }
+    buffer
+}
+
+/// Returns `true` if the two strings of code have the same payload of comments.
+/// The payload of comments is everything in the string except:
+/// - actual code (not comments),
+/// - comment start/end marks,
+/// - whitespace,
+/// - '*' at the beginning of lines in block comments.
+fn changed_comment_content(orig: &str, new: &str) -> bool {
+    // Cannot write this as a fn since we cannot return types containing closures.
+    let code_comment_content = |code| {
+        let slices = UngroupedCommentCodeSlices::new(code);
+        slices
+            .filter(|&(ref kind, _, _)| *kind == CodeCharKind::Comment)
+            .flat_map(|(_, _, s)| CommentReducer::new(s))
+    };
+    let res = code_comment_content(orig).ne(code_comment_content(new));
+    debug!(
+        "comment::changed_comment_content: {}\norig: '{}'\nnew: '{}'\nraw_old: {}\nraw_new: {}",
+        res,
+        orig,
+        new,
+        code_comment_content(orig).collect::<String>(),
+        code_comment_content(new).collect::<String>()
+    );
+    res
+}
+
+/// Iterator over the 'payload' characters of a comment.
+/// It skips whitespace, comment start/end marks, and '*' at the beginning of lines.
+/// The comment must be one comment, ie not more than one start mark (no multiple line comments,
+/// for example).
+struct CommentReducer<'a> {
+    is_block: bool,
+    at_start_line: bool,
+    iter: std::str::Chars<'a>,
+}
+
+impl<'a> CommentReducer<'a> {
+    fn new(comment: &'a str) -> CommentReducer<'a> {
+        let is_block = comment.starts_with("/*");
+        let comment = remove_comment_header(comment);
+        CommentReducer {
+            is_block,
+            // There are no supplementary '*' on the first line.
+            at_start_line: false,
+            iter: comment.chars(),
+        }
+    }
+}
+
+impl<'a> Iterator for CommentReducer<'a> {
+    type Item = char;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            let mut c = self.iter.next()?;
+            if self.is_block && self.at_start_line {
+                while c.is_whitespace() {
+                    c = self.iter.next()?;
+                }
+                // Ignore leading '*'.
+                if c == '*' {
+                    c = self.iter.next()?;
+                }
+            } else if c == '\n' {
+                self.at_start_line = true;
+            }
+            if !c.is_whitespace() {
+                return Some(c);
+            }
+        }
+    }
+}
+
+fn remove_comment_header(comment: &str) -> &str {
+    if comment.starts_with("///") || comment.starts_with("//!") {
+        &comment[3..]
+    } else if comment.starts_with("//") {
+        &comment[2..]
+    } else if (comment.starts_with("/**") && !comment.starts_with("/**/"))
+        || comment.starts_with("/*!")
+    {
+        &comment[3..comment.len() - 2]
+    } else {
+        assert!(
+            comment.starts_with("/*"),
+            "string '{}' is not a comment",
+            comment
+        );
+        &comment[2..comment.len() - 2]
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::shape::{Indent, Shape};
+
+    #[test]
+    fn char_classes() {
+        let mut iter = CharClasses::new("//\n\n".chars());
+
+        assert_eq!((FullCodeCharKind::StartComment, '/'), iter.next().unwrap());
+        assert_eq!((FullCodeCharKind::InComment, '/'), iter.next().unwrap());
+        assert_eq!((FullCodeCharKind::EndComment, '\n'), iter.next().unwrap());
+        assert_eq!((FullCodeCharKind::Normal, '\n'), iter.next().unwrap());
+        assert_eq!(None, iter.next());
+    }
+
+    #[test]
+    fn comment_code_slices() {
+        let input = "code(); /* test */ 1 + 1";
+        let mut iter = CommentCodeSlices::new(input);
+
+        assert_eq!((CodeCharKind::Normal, 0, "code(); "), iter.next().unwrap());
+        assert_eq!(
+            (CodeCharKind::Comment, 8, "/* test */"),
+            iter.next().unwrap()
+        );
+        assert_eq!((CodeCharKind::Normal, 18, " 1 + 1"), iter.next().unwrap());
+        assert_eq!(None, iter.next());
+    }
+
+    #[test]
+    fn comment_code_slices_two() {
+        let input = "// comment\n    test();";
+        let mut iter = CommentCodeSlices::new(input);
+
+        assert_eq!((CodeCharKind::Normal, 0, ""), iter.next().unwrap());
+        assert_eq!(
+            (CodeCharKind::Comment, 0, "// comment\n"),
+            iter.next().unwrap()
+        );
+        assert_eq!(
+            (CodeCharKind::Normal, 11, "    test();"),
+            iter.next().unwrap()
+        );
+        assert_eq!(None, iter.next());
+    }
+
+    #[test]
+    fn comment_code_slices_three() {
+        let input = "1 // comment\n    // comment2\n\n";
+        let mut iter = CommentCodeSlices::new(input);
+
+        assert_eq!((CodeCharKind::Normal, 0, "1 "), iter.next().unwrap());
+        assert_eq!(
+            (CodeCharKind::Comment, 2, "// comment\n    // comment2\n"),
+            iter.next().unwrap()
+        );
+        assert_eq!((CodeCharKind::Normal, 29, "\n"), iter.next().unwrap());
+        assert_eq!(None, iter.next());
+    }
+
+    #[test]
+    #[rustfmt::skip]
+    fn format_doc_comments() {
+        let mut wrap_normalize_config: crate::config::Config = Default::default();
+        wrap_normalize_config.set().wrap_comments(true);
+        wrap_normalize_config.set().normalize_comments(true);
+
+        let mut wrap_config: crate::config::Config = Default::default();
+        wrap_config.set().wrap_comments(true);
+
+        let comment = rewrite_comment(" //test",
+                                      true,
+                                      Shape::legacy(100, Indent::new(0, 100)),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!("/* test */", comment);
+
+        let comment = rewrite_comment("// comment on a",
+                                      false,
+                                      Shape::legacy(10, Indent::empty()),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!("// comment\n// on a", comment);
+
+        let comment = rewrite_comment("//  A multi line comment\n             // between args.",
+                                      false,
+                                      Shape::legacy(60, Indent::new(0, 12)),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!("//  A multi line comment\n            // between args.", comment);
+
+        let input = "// comment";
+        let expected =
+            "/* comment */";
+        let comment = rewrite_comment(input,
+                                      true,
+                                      Shape::legacy(9, Indent::new(0, 69)),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!(expected, comment);
+
+        let comment = rewrite_comment("/*   trimmed    */",
+                                      true,
+                                      Shape::legacy(100, Indent::new(0, 100)),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!("/* trimmed */", comment);
+
+        // Check that different comment style are properly recognised.
+        let comment = rewrite_comment(r#"/// test1
+                                         /// test2
+                                         /*
+                                          * test3
+                                          */"#,
+                                      false,
+                                      Shape::legacy(100, Indent::new(0, 0)),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!("/// test1\n/// test2\n// test3", comment);
+
+        // Check that the blank line marks the end of a commented paragraph.
+        let comment = rewrite_comment(r#"// test1
+
+                                         // test2"#,
+                                      false,
+                                      Shape::legacy(100, Indent::new(0, 0)),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!("// test1\n\n// test2", comment);
+
+        // Check that the blank line marks the end of a custom-commented paragraph.
+        let comment = rewrite_comment(r#"//@ test1
+
+                                         //@ test2"#,
+                                      false,
+                                      Shape::legacy(100, Indent::new(0, 0)),
+                                      &wrap_normalize_config).unwrap();
+        assert_eq!("//@ test1\n\n//@ test2", comment);
+
+        // Check that bare lines are just indented but otherwise left unchanged.
+        let comment = rewrite_comment(r#"// test1
+                                         /*
+                                           a bare line!
+
+                                                another bare line!
+                                          */"#,
+                                      false,
+                                      Shape::legacy(100, Indent::new(0, 0)),
+                                      &wrap_config).unwrap();
+        assert_eq!("// test1\n/*\n a bare line!\n\n      another bare line!\n*/", comment);
+    }
+
+    // This is probably intended to be a non-test fn, but it is not used.
+    // We should keep this around unless it helps us test stuff to remove it.
+    fn uncommented(text: &str) -> String {
+        CharClasses::new(text.chars())
+            .filter_map(|(s, c)| match s {
+                FullCodeCharKind::Normal | FullCodeCharKind::InString => Some(c),
+                _ => None,
+            })
+            .collect()
+    }
+
+    #[test]
+    fn test_uncommented() {
+        assert_eq!(&uncommented("abc/*...*/"), "abc");
+        assert_eq!(
+            &uncommented("// .... /* \n../* /* *** / */ */a/* // */c\n"),
+            "..ac\n"
+        );
+        assert_eq!(&uncommented("abc \" /* */\" qsdf"), "abc \" /* */\" qsdf");
+    }
+
+    #[test]
+    fn test_contains_comment() {
+        assert_eq!(contains_comment("abc"), false);
+        assert_eq!(contains_comment("abc // qsdf"), true);
+        assert_eq!(contains_comment("abc /* kqsdf"), true);
+        assert_eq!(contains_comment("abc \" /* */\" qsdf"), false);
+    }
+
+    #[test]
+    fn test_find_uncommented() {
+        fn check(haystack: &str, needle: &str, expected: Option<usize>) {
+            assert_eq!(expected, haystack.find_uncommented(needle));
+        }
+
+        check("/*/ */test", "test", Some(6));
+        check("//test\ntest", "test", Some(7));
+        check("/* comment only */", "whatever", None);
+        check(
+            "/* comment */ some text /* more commentary */ result",
+            "result",
+            Some(46),
+        );
+        check("sup // sup", "p", Some(2));
+        check("sup", "x", None);
+        check(r#"π? /**/ π is nice!"#, r#"π is nice"#, Some(9));
+        check("/*sup yo? \n sup*/ sup", "p", Some(20));
+        check("hel/*lohello*/lo", "hello", None);
+        check("acb", "ab", None);
+        check(",/*A*/ ", ",", Some(0));
+        check("abc", "abc", Some(0));
+        check("/* abc */", "abc", None);
+        check("/**/abc/* */", "abc", Some(4));
+        check("\"/* abc */\"", "abc", Some(4));
+        check("\"/* abc", "abc", Some(4));
+    }
+
+    #[test]
+    fn test_filter_normal_code() {
+        let s = r#"
+fn main() {
+    println!("hello, world");
+}
+"#;
+        assert_eq!(s, filter_normal_code(s));
+        let s_with_comment = r#"
+fn main() {
+    // hello, world
+    println!("hello, world");
+}
+"#;
+        assert_eq!(s, filter_normal_code(s_with_comment));
+    }
+}
diff --git a/src/tools/rustfmt/src/config/config_type.rs b/src/tools/rustfmt/src/config/config_type.rs
new file mode 100644
index 0000000000000..2f567b2552106
--- /dev/null
+++ b/src/tools/rustfmt/src/config/config_type.rs
@@ -0,0 +1,448 @@
+use crate::config::file_lines::FileLines;
+use crate::config::options::{IgnoreList, WidthHeuristics};
+
+/// Trait for types that can be used in `Config`.
+pub(crate) trait ConfigType: Sized {
+    /// Returns hint text for use in `Config::print_docs()`. For enum types, this is a
+    /// pipe-separated list of variants; for other types it returns "<type>".
+    fn doc_hint() -> String;
+}
+
+impl ConfigType for bool {
+    fn doc_hint() -> String {
+        String::from("<boolean>")
+    }
+}
+
+impl ConfigType for usize {
+    fn doc_hint() -> String {
+        String::from("<unsigned integer>")
+    }
+}
+
+impl ConfigType for isize {
+    fn doc_hint() -> String {
+        String::from("<signed integer>")
+    }
+}
+
+impl ConfigType for String {
+    fn doc_hint() -> String {
+        String::from("<string>")
+    }
+}
+
+impl ConfigType for FileLines {
+    fn doc_hint() -> String {
+        String::from("<json>")
+    }
+}
+
+impl ConfigType for WidthHeuristics {
+    fn doc_hint() -> String {
+        String::new()
+    }
+}
+
+impl ConfigType for IgnoreList {
+    fn doc_hint() -> String {
+        String::from("[<string>,..]")
+    }
+}
+
+macro_rules! create_config {
+    ($($i:ident: $ty:ty, $def:expr, $stb:expr, $( $dstring:expr ),+ );+ $(;)*) => (
+        #[cfg(test)]
+        use std::collections::HashSet;
+        use std::io::Write;
+
+        use serde::{Deserialize, Serialize};
+
+        #[derive(Clone)]
+        #[allow(unreachable_pub)]
+        pub struct Config {
+            // if a license_template_path has been specified, successfully read, parsed and compiled
+            // into a regex, it will be stored here
+            pub license_template: Option<Regex>,
+            // For each config item, we store a bool indicating whether it has
+            // been accessed and the value, and a bool whether the option was
+            // manually initialised, or taken from the default,
+            $($i: (Cell<bool>, bool, $ty, bool)),+
+        }
+
+        // Just like the Config struct but with each property wrapped
+        // as Option<T>. This is used to parse a rustfmt.toml that doesn't
+        // specify all properties of `Config`.
+        // We first parse into `PartialConfig`, then create a default `Config`
+        // and overwrite the properties with corresponding values from `PartialConfig`.
+        #[derive(Deserialize, Serialize, Clone)]
+        #[allow(unreachable_pub)]
+        pub struct PartialConfig {
+            $(pub $i: Option<$ty>),+
+        }
+
+        // Macro hygiene won't allow us to make `set_$i()` methods on Config
+        // for each item, so this struct is used to give the API to set values:
+        // `config.set().option(false)`. It's pretty ugly. Consider replacing
+        // with `config.set_option(false)` if we ever get a stable/usable
+        // `concat_idents!()`.
+        #[allow(unreachable_pub)]
+        pub struct ConfigSetter<'a>(&'a mut Config);
+
+        impl<'a> ConfigSetter<'a> {
+            $(
+            #[allow(unreachable_pub)]
+            pub fn $i(&mut self, value: $ty) {
+                (self.0).$i.2 = value;
+                match stringify!($i) {
+                    "max_width"
+                    | "use_small_heuristics"
+                    | "fn_call_width"
+                    | "single_line_if_else_max_width"
+                    | "attr_fn_like_width"
+                    | "struct_lit_width"
+                    | "struct_variant_width"
+                    | "array_width"
+                    | "chain_width" => self.0.set_heuristics(),
+                    "license_template_path" => self.0.set_license_template(),
+                    "merge_imports" => self.0.set_merge_imports(),
+                    &_ => (),
+                }
+            }
+            )+
+        }
+
+        // Query each option, returns true if the user set the option, false if
+        // a default was used.
+        #[allow(unreachable_pub)]
+        pub struct ConfigWasSet<'a>(&'a Config);
+
+        impl<'a> ConfigWasSet<'a> {
+            $(
+            #[allow(unreachable_pub)]
+            pub fn $i(&self) -> bool {
+                (self.0).$i.1
+            }
+            )+
+        }
+
+        impl Config {
+            $(
+            #[allow(unreachable_pub)]
+            pub fn $i(&self) -> $ty {
+                self.$i.0.set(true);
+                self.$i.2.clone()
+            }
+            )+
+
+            #[allow(unreachable_pub)]
+            pub fn set(&mut self) -> ConfigSetter<'_> {
+                ConfigSetter(self)
+            }
+
+            #[allow(unreachable_pub)]
+            pub fn was_set(&self) -> ConfigWasSet<'_> {
+                ConfigWasSet(self)
+            }
+
+            fn fill_from_parsed_config(mut self, parsed: PartialConfig, dir: &Path) -> Config {
+            $(
+                if let Some(val) = parsed.$i {
+                    if self.$i.3 {
+                        self.$i.1 = true;
+                        self.$i.2 = val;
+                    } else {
+                        if crate::is_nightly_channel!() {
+                            self.$i.1 = true;
+                            self.$i.2 = val;
+                        } else {
+                            eprintln!("Warning: can't set `{} = {:?}`, unstable features are only \
+                                       available in nightly channel.", stringify!($i), val);
+                        }
+                    }
+                }
+            )+
+                self.set_heuristics();
+                self.set_license_template();
+                self.set_ignore(dir);
+                self.set_merge_imports();
+                self
+            }
+
+            /// Returns a hash set initialized with every user-facing config option name.
+            #[cfg(test)]
+            pub(crate) fn hash_set() -> HashSet<String> {
+                let mut hash_set = HashSet::new();
+                $(
+                    hash_set.insert(stringify!($i).to_owned());
+                )+
+                hash_set
+            }
+
+            pub(crate) fn is_valid_name(name: &str) -> bool {
+                match name {
+                    $(
+                        stringify!($i) => true,
+                    )+
+                        _ => false,
+                }
+            }
+
+            #[allow(unreachable_pub)]
+            pub fn is_valid_key_val(key: &str, val: &str) -> bool {
+                match key {
+                    $(
+                        stringify!($i) => val.parse::<$ty>().is_ok(),
+                    )+
+                        _ => false,
+                }
+            }
+
+            #[allow(unreachable_pub)]
+            pub fn used_options(&self) -> PartialConfig {
+                PartialConfig {
+                    $(
+                        $i: if self.$i.0.get() {
+                                Some(self.$i.2.clone())
+                            } else {
+                                None
+                            },
+                    )+
+                }
+            }
+
+            #[allow(unreachable_pub)]
+            pub fn all_options(&self) -> PartialConfig {
+                PartialConfig {
+                    $(
+                        $i: Some(self.$i.2.clone()),
+                    )+
+                }
+            }
+
+            #[allow(unreachable_pub)]
+            pub fn override_value(&mut self, key: &str, val: &str)
+            {
+                match key {
+                    $(
+                        stringify!($i) => {
+                            self.$i.1 = true;
+                            self.$i.2 = val.parse::<$ty>()
+                                .expect(&format!("Failed to parse override for {} (\"{}\") as a {}",
+                                                 stringify!($i),
+                                                 val,
+                                                 stringify!($ty)));
+                        }
+                    )+
+                    _ => panic!("Unknown config key in override: {}", key)
+                }
+
+                match key {
+                    "max_width"
+                    | "use_small_heuristics"
+                    | "fn_call_width"
+                    | "single_line_if_else_max_width"
+                    | "attr_fn_like_width"
+                    | "struct_lit_width"
+                    | "struct_variant_width"
+                    | "array_width"
+                    | "chain_width" => self.set_heuristics(),
+                    "license_template_path" => self.set_license_template(),
+                    "merge_imports" => self.set_merge_imports(),
+                    &_ => (),
+                }
+            }
+
+            #[allow(unreachable_pub)]
+            pub fn is_hidden_option(name: &str) -> bool {
+                const HIDE_OPTIONS: [&str; 5] =
+                    ["verbose", "verbose_diff", "file_lines", "width_heuristics", "merge_imports"];
+                HIDE_OPTIONS.contains(&name)
+            }
+
+            #[allow(unreachable_pub)]
+            pub fn print_docs(out: &mut dyn Write, include_unstable: bool) {
+                use std::cmp;
+                let max = 0;
+                $( let max = cmp::max(max, stringify!($i).len()+1); )+
+                let space_str = " ".repeat(max);
+                writeln!(out, "Configuration Options:").unwrap();
+                $(
+                    if $stb || include_unstable {
+                        let name_raw = stringify!($i);
+
+                        if !Config::is_hidden_option(name_raw) {
+                            let mut name_out = String::with_capacity(max);
+                            for _ in name_raw.len()..max-1 {
+                                name_out.push(' ')
+                            }
+                            name_out.push_str(name_raw);
+                            name_out.push(' ');
+                            let mut default_str = format!("{}", $def);
+                            if default_str.is_empty() {
+                                default_str = String::from("\"\"");
+                            }
+                            writeln!(out,
+                                    "{}{} Default: {}{}",
+                                    name_out,
+                                    <$ty>::doc_hint(),
+                                    default_str,
+                                    if !$stb { " (unstable)" } else { "" }).unwrap();
+                            $(
+                                writeln!(out, "{}{}", space_str, $dstring).unwrap();
+                            )+
+                            writeln!(out).unwrap();
+                        }
+                    }
+                )+
+            }
+
+            fn set_width_heuristics(&mut self, heuristics: WidthHeuristics) {
+                let max_width = self.max_width.2;
+                let get_width_value = |
+                    was_set: bool,
+                    override_value: usize,
+                    heuristic_value: usize,
+                    config_key: &str,
+                | -> usize {
+                    if !was_set {
+                        return heuristic_value;
+                    }
+                    if override_value > max_width {
+                        eprintln!(
+                            "`{0}` cannot have a value that exceeds `max_width`. \
+                            `{0}` will be set to the same value as `max_width`",
+                            config_key,
+                        );
+                        return max_width;
+                    }
+                    override_value
+                };
+
+                let fn_call_width = get_width_value(
+                    self.was_set().fn_call_width(),
+                    self.fn_call_width.2,
+                    heuristics.fn_call_width,
+                    "fn_call_width",
+                );
+                self.fn_call_width.2 = fn_call_width;
+
+                let attr_fn_like_width = get_width_value(
+                    self.was_set().attr_fn_like_width(),
+                    self.attr_fn_like_width.2,
+                    heuristics.attr_fn_like_width,
+                    "attr_fn_like_width",
+                );
+                self.attr_fn_like_width.2 = attr_fn_like_width;
+
+                let struct_lit_width = get_width_value(
+                    self.was_set().struct_lit_width(),
+                    self.struct_lit_width.2,
+                    heuristics.struct_lit_width,
+                    "struct_lit_width",
+                );
+                self.struct_lit_width.2 = struct_lit_width;
+
+                let struct_variant_width = get_width_value(
+                    self.was_set().struct_variant_width(),
+                    self.struct_variant_width.2,
+                    heuristics.struct_variant_width,
+                    "struct_variant_width",
+                );
+                self.struct_variant_width.2 = struct_variant_width;
+
+                let array_width = get_width_value(
+                    self.was_set().array_width(),
+                    self.array_width.2,
+                    heuristics.array_width,
+                    "array_width",
+                );
+                self.array_width.2 = array_width;
+
+                let chain_width = get_width_value(
+                    self.was_set().chain_width(),
+                    self.chain_width.2,
+                    heuristics.chain_width,
+                    "chain_width",
+                );
+                self.chain_width.2 = chain_width;
+
+                let single_line_if_else_max_width = get_width_value(
+                    self.was_set().single_line_if_else_max_width(),
+                    self.single_line_if_else_max_width.2,
+                    heuristics.single_line_if_else_max_width,
+                    "single_line_if_else_max_width",
+                );
+                self.single_line_if_else_max_width.2 = single_line_if_else_max_width;
+            }
+
+            fn set_heuristics(&mut self) {
+                let max_width = self.max_width.2;
+                match self.use_small_heuristics.2 {
+                    Heuristics::Default =>
+                        self.set_width_heuristics(WidthHeuristics::scaled(max_width)),
+                    Heuristics::Max => self.set_width_heuristics(WidthHeuristics::set(max_width)),
+                    Heuristics::Off => self.set_width_heuristics(WidthHeuristics::null()),
+                };
+            }
+
+            fn set_license_template(&mut self) {
+                if self.was_set().license_template_path() {
+                    let lt_path = self.license_template_path();
+                    if lt_path.len() > 0 {
+                        match license::load_and_compile_template(&lt_path) {
+                            Ok(re) => self.license_template = Some(re),
+                            Err(msg) => eprintln!("Warning for license template file {:?}: {}",
+                                                lt_path, msg),
+                        }
+                    } else {
+                        self.license_template = None;
+                    }
+                }
+            }
+
+            fn set_ignore(&mut self, dir: &Path) {
+                self.ignore.2.add_prefix(dir);
+            }
+
+            fn set_merge_imports(&mut self) {
+                if self.was_set().merge_imports() {
+                    eprintln!(
+                        "Warning: the `merge_imports` option is deprecated. \
+                        Use `imports_granularity=Crate` instead"
+                    );
+                    if !self.was_set().imports_granularity() {
+                        self.imports_granularity.2 = if self.merge_imports() {
+                            ImportGranularity::Crate
+                        } else {
+                            ImportGranularity::Preserve
+                        };
+                    }
+                }
+            }
+
+            #[allow(unreachable_pub)]
+            /// Returns `true` if the config key was explicitly set and is the default value.
+            pub fn is_default(&self, key: &str) -> bool {
+                $(
+                    if let stringify!($i) = key {
+                        return self.$i.1 && self.$i.2 == $def;
+                    }
+                 )+
+                false
+            }
+        }
+
+        // Template for the default configuration
+        impl Default for Config {
+            fn default() -> Config {
+                Config {
+                    license_template: None,
+                    $(
+                        $i: (Cell::new(false), false, $def, $stb),
+                    )+
+                }
+            }
+        }
+    )
+}
diff --git a/src/tools/rustfmt/src/config/file_lines.rs b/src/tools/rustfmt/src/config/file_lines.rs
new file mode 100644
index 0000000000000..22dd091cb5101
--- /dev/null
+++ b/src/tools/rustfmt/src/config/file_lines.rs
@@ -0,0 +1,440 @@
+//! This module contains types and functions to support formatting specific line ranges.
+
+use itertools::Itertools;
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::{cmp, fmt, iter, str};
+
+use rustc_data_structures::sync::Lrc;
+use rustc_span::{self, SourceFile};
+use serde::{ser, Deserialize, Deserializer, Serialize, Serializer};
+use serde_json as json;
+use thiserror::Error;
+
+/// A range of lines in a file, inclusive of both ends.
+pub struct LineRange {
+    pub file: Lrc<SourceFile>,
+    pub lo: usize,
+    pub hi: usize,
+}
+
+/// Defines the name of an input - either a file or stdin.
+#[derive(Clone, Debug, Eq, PartialEq, Hash, Ord, PartialOrd)]
+pub enum FileName {
+    Real(PathBuf),
+    Stdin,
+}
+
+impl From<rustc_span::FileName> for FileName {
+    fn from(name: rustc_span::FileName) -> FileName {
+        match name {
+            rustc_span::FileName::Real(rustc_span::RealFileName::LocalPath(p)) => FileName::Real(p),
+            rustc_span::FileName::Custom(ref f) if f == "stdin" => FileName::Stdin,
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl fmt::Display for FileName {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            FileName::Real(p) => write!(f, "{}", p.to_str().unwrap()),
+            FileName::Stdin => write!(f, "stdin"),
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for FileName {
+    fn deserialize<D>(deserializer: D) -> Result<FileName, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let s = String::deserialize(deserializer)?;
+        if s == "stdin" {
+            Ok(FileName::Stdin)
+        } else {
+            Ok(FileName::Real(s.into()))
+        }
+    }
+}
+
+impl Serialize for FileName {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let s = match self {
+            FileName::Stdin => Ok("stdin"),
+            FileName::Real(path) => path
+                .to_str()
+                .ok_or_else(|| ser::Error::custom("path can't be serialized as UTF-8 string")),
+        };
+
+        s.and_then(|s| serializer.serialize_str(s))
+    }
+}
+
+impl LineRange {
+    pub fn file_name(&self) -> FileName {
+        self.file.name.clone().into()
+    }
+}
+
+/// A range that is inclusive of both ends.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd, Ord, Deserialize)]
+pub struct Range {
+    lo: usize,
+    hi: usize,
+}
+
+impl<'a> From<&'a LineRange> for Range {
+    fn from(range: &'a LineRange) -> Range {
+        Range::new(range.lo, range.hi)
+    }
+}
+
+impl fmt::Display for Range {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}..{}", self.lo, self.hi)
+    }
+}
+
+impl Range {
+    pub fn new(lo: usize, hi: usize) -> Range {
+        Range { lo, hi }
+    }
+
+    fn is_empty(self) -> bool {
+        self.lo > self.hi
+    }
+
+    #[allow(dead_code)]
+    fn contains(self, other: Range) -> bool {
+        if other.is_empty() {
+            true
+        } else {
+            !self.is_empty() && self.lo <= other.lo && self.hi >= other.hi
+        }
+    }
+
+    fn intersects(self, other: Range) -> bool {
+        if self.is_empty() || other.is_empty() {
+            false
+        } else {
+            (self.lo <= other.hi && other.hi <= self.hi)
+                || (other.lo <= self.hi && self.hi <= other.hi)
+        }
+    }
+
+    fn adjacent_to(self, other: Range) -> bool {
+        if self.is_empty() || other.is_empty() {
+            false
+        } else {
+            self.hi + 1 == other.lo || other.hi + 1 == self.lo
+        }
+    }
+
+    /// Returns a new `Range` with lines from `self` and `other` if they were adjacent or
+    /// intersect; returns `None` otherwise.
+    fn merge(self, other: Range) -> Option<Range> {
+        if self.adjacent_to(other) || self.intersects(other) {
+            Some(Range::new(
+                cmp::min(self.lo, other.lo),
+                cmp::max(self.hi, other.hi),
+            ))
+        } else {
+            None
+        }
+    }
+}
+
+/// A set of lines in files.
+///
+/// It is represented as a multimap keyed on file names, with values a collection of
+/// non-overlapping ranges sorted by their start point. An inner `None` is interpreted to mean all
+/// lines in all files.
+#[derive(Clone, Debug, Default, PartialEq)]
+pub struct FileLines(Option<HashMap<FileName, Vec<Range>>>);
+
+impl fmt::Display for FileLines {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match &self.0 {
+            None => write!(f, "None")?,
+            Some(map) => {
+                for (file_name, ranges) in map.iter() {
+                    write!(f, "{}: ", file_name)?;
+                    write!(f, "{}\n", ranges.iter().format(", "))?;
+                }
+            }
+        };
+        Ok(())
+    }
+}
+
+/// Normalizes the ranges so that the invariants for `FileLines` hold: ranges are non-overlapping,
+/// and ordered by their start point.
+fn normalize_ranges(ranges: &mut HashMap<FileName, Vec<Range>>) {
+    for ranges in ranges.values_mut() {
+        ranges.sort();
+        let mut result = vec![];
+        let mut iter = ranges.iter_mut().peekable();
+        while let Some(next) = iter.next() {
+            let mut next = *next;
+            while let Some(&&mut peek) = iter.peek() {
+                if let Some(merged) = next.merge(peek) {
+                    iter.next().unwrap();
+                    next = merged;
+                } else {
+                    break;
+                }
+            }
+            result.push(next)
+        }
+        *ranges = result;
+    }
+}
+
+impl FileLines {
+    /// Creates a `FileLines` that contains all lines in all files.
+    pub(crate) fn all() -> FileLines {
+        FileLines(None)
+    }
+
+    /// Returns `true` if this `FileLines` contains all lines in all files.
+    pub(crate) fn is_all(&self) -> bool {
+        self.0.is_none()
+    }
+
+    pub fn from_ranges(mut ranges: HashMap<FileName, Vec<Range>>) -> FileLines {
+        normalize_ranges(&mut ranges);
+        FileLines(Some(ranges))
+    }
+
+    /// Returns an iterator over the files contained in `self`.
+    pub fn files(&self) -> Files<'_> {
+        Files(self.0.as_ref().map(HashMap::keys))
+    }
+
+    /// Returns JSON representation as accepted by the `--file-lines JSON` arg.
+    pub fn to_json_spans(&self) -> Vec<JsonSpan> {
+        match &self.0 {
+            None => vec![],
+            Some(file_ranges) => file_ranges
+                .iter()
+                .flat_map(|(file, ranges)| ranges.iter().map(move |r| (file, r)))
+                .map(|(file, range)| JsonSpan {
+                    file: file.to_owned(),
+                    range: (range.lo, range.hi),
+                })
+                .collect(),
+        }
+    }
+
+    /// Returns `true` if `self` includes all lines in all files. Otherwise runs `f` on all ranges
+    /// in the designated file (if any) and returns true if `f` ever does.
+    fn file_range_matches<F>(&self, file_name: &FileName, f: F) -> bool
+    where
+        F: FnMut(&Range) -> bool,
+    {
+        let map = match self.0 {
+            // `None` means "all lines in all files".
+            None => return true,
+            Some(ref map) => map,
+        };
+
+        match canonicalize_path_string(file_name).and_then(|file| map.get(&file)) {
+            Some(ranges) => ranges.iter().any(f),
+            None => false,
+        }
+    }
+
+    /// Returns `true` if `range` is fully contained in `self`.
+    #[allow(dead_code)]
+    pub(crate) fn contains(&self, range: &LineRange) -> bool {
+        self.file_range_matches(&range.file_name(), |r| r.contains(Range::from(range)))
+    }
+
+    /// Returns `true` if any lines in `range` are in `self`.
+    pub(crate) fn intersects(&self, range: &LineRange) -> bool {
+        self.file_range_matches(&range.file_name(), |r| r.intersects(Range::from(range)))
+    }
+
+    /// Returns `true` if `line` from `file_name` is in `self`.
+    pub(crate) fn contains_line(&self, file_name: &FileName, line: usize) -> bool {
+        self.file_range_matches(file_name, |r| r.lo <= line && r.hi >= line)
+    }
+
+    /// Returns `true` if all the lines between `lo` and `hi` from `file_name` are in `self`.
+    pub(crate) fn contains_range(&self, file_name: &FileName, lo: usize, hi: usize) -> bool {
+        self.file_range_matches(file_name, |r| r.contains(Range::new(lo, hi)))
+    }
+}
+
+/// `FileLines` files iterator.
+pub struct Files<'a>(Option<::std::collections::hash_map::Keys<'a, FileName, Vec<Range>>>);
+
+impl<'a> iter::Iterator for Files<'a> {
+    type Item = &'a FileName;
+
+    fn next(&mut self) -> Option<&'a FileName> {
+        self.0.as_mut().and_then(Iterator::next)
+    }
+}
+
+fn canonicalize_path_string(file: &FileName) -> Option<FileName> {
+    match *file {
+        FileName::Real(ref path) => path.canonicalize().ok().map(FileName::Real),
+        _ => Some(file.clone()),
+    }
+}
+
+#[derive(Error, Debug)]
+pub enum FileLinesError {
+    #[error("{0}")]
+    Json(json::Error),
+    #[error("Can't canonicalize {0}")]
+    CannotCanonicalize(FileName),
+}
+
+// This impl is needed for `Config::override_value` to work for use in tests.
+impl str::FromStr for FileLines {
+    type Err = FileLinesError;
+
+    fn from_str(s: &str) -> Result<FileLines, Self::Err> {
+        let v: Vec<JsonSpan> = json::from_str(s).map_err(FileLinesError::Json)?;
+        let mut m = HashMap::new();
+        for js in v {
+            let (s, r) = JsonSpan::into_tuple(js)?;
+            m.entry(s).or_insert_with(|| vec![]).push(r);
+        }
+        Ok(FileLines::from_ranges(m))
+    }
+}
+
+// For JSON decoding.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Deserialize, Serialize)]
+pub struct JsonSpan {
+    file: FileName,
+    range: (usize, usize),
+}
+
+impl JsonSpan {
+    fn into_tuple(self) -> Result<(FileName, Range), FileLinesError> {
+        let (lo, hi) = self.range;
+        let canonical = canonicalize_path_string(&self.file)
+            .ok_or_else(|| FileLinesError::CannotCanonicalize(self.file))?;
+        Ok((canonical, Range::new(lo, hi)))
+    }
+}
+
+// This impl is needed for inclusion in the `Config` struct. We don't have a toml representation
+// for `FileLines`, so it will just panic instead.
+impl<'de> ::serde::de::Deserialize<'de> for FileLines {
+    fn deserialize<D>(_: D) -> Result<Self, D::Error>
+    where
+        D: ::serde::de::Deserializer<'de>,
+    {
+        panic!(
+            "FileLines cannot be deserialized from a project rustfmt.toml file: please \
+             specify it via the `--file-lines` option instead"
+        );
+    }
+}
+
+// We also want to avoid attempting to serialize a FileLines to toml. The
+// `Config` struct should ensure this impl is never reached.
+impl ::serde::ser::Serialize for FileLines {
+    fn serialize<S>(&self, _: S) -> Result<S::Ok, S::Error>
+    where
+        S: ::serde::ser::Serializer,
+    {
+        unreachable!("FileLines cannot be serialized. This is a rustfmt bug.");
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::Range;
+
+    #[test]
+    fn test_range_intersects() {
+        assert!(Range::new(1, 2).intersects(Range::new(1, 1)));
+        assert!(Range::new(1, 2).intersects(Range::new(2, 2)));
+        assert!(!Range::new(1, 2).intersects(Range::new(0, 0)));
+        assert!(!Range::new(1, 2).intersects(Range::new(3, 10)));
+        assert!(!Range::new(1, 3).intersects(Range::new(5, 5)));
+    }
+
+    #[test]
+    fn test_range_adjacent_to() {
+        assert!(!Range::new(1, 2).adjacent_to(Range::new(1, 1)));
+        assert!(!Range::new(1, 2).adjacent_to(Range::new(2, 2)));
+        assert!(Range::new(1, 2).adjacent_to(Range::new(0, 0)));
+        assert!(Range::new(1, 2).adjacent_to(Range::new(3, 10)));
+        assert!(!Range::new(1, 3).adjacent_to(Range::new(5, 5)));
+    }
+
+    #[test]
+    fn test_range_contains() {
+        assert!(Range::new(1, 2).contains(Range::new(1, 1)));
+        assert!(Range::new(1, 2).contains(Range::new(2, 2)));
+        assert!(!Range::new(1, 2).contains(Range::new(0, 0)));
+        assert!(!Range::new(1, 2).contains(Range::new(3, 10)));
+    }
+
+    #[test]
+    fn test_range_merge() {
+        assert_eq!(None, Range::new(1, 3).merge(Range::new(5, 5)));
+        assert_eq!(None, Range::new(4, 7).merge(Range::new(0, 1)));
+        assert_eq!(
+            Some(Range::new(3, 7)),
+            Range::new(3, 5).merge(Range::new(4, 7))
+        );
+        assert_eq!(
+            Some(Range::new(3, 7)),
+            Range::new(3, 5).merge(Range::new(5, 7))
+        );
+        assert_eq!(
+            Some(Range::new(3, 7)),
+            Range::new(3, 5).merge(Range::new(6, 7))
+        );
+        assert_eq!(
+            Some(Range::new(3, 7)),
+            Range::new(3, 7).merge(Range::new(4, 5))
+        );
+    }
+
+    use super::json::{self, json};
+    use super::{FileLines, FileName};
+    use std::{collections::HashMap, path::PathBuf};
+
+    #[test]
+    fn file_lines_to_json() {
+        let ranges: HashMap<FileName, Vec<Range>> = [
+            (
+                FileName::Real(PathBuf::from("src/main.rs")),
+                vec![Range::new(1, 3), Range::new(5, 7)],
+            ),
+            (
+                FileName::Real(PathBuf::from("src/lib.rs")),
+                vec![Range::new(1, 7)],
+            ),
+        ]
+        .iter()
+        .cloned()
+        .collect();
+
+        let file_lines = FileLines::from_ranges(ranges);
+        let mut spans = file_lines.to_json_spans();
+        spans.sort();
+        let json = json::to_value(&spans).unwrap();
+        assert_eq!(
+            json,
+            json! {[
+                {"file": "src/lib.rs",  "range": [1, 7]},
+                {"file": "src/main.rs", "range": [1, 3]},
+                {"file": "src/main.rs", "range": [5, 7]},
+            ]}
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/config/license.rs b/src/tools/rustfmt/src/config/license.rs
new file mode 100644
index 0000000000000..121a1b1c151f4
--- /dev/null
+++ b/src/tools/rustfmt/src/config/license.rs
@@ -0,0 +1,266 @@
+use std::fmt;
+use std::fs::File;
+use std::io;
+use std::io::Read;
+
+use regex;
+use regex::Regex;
+
+#[derive(Debug)]
+pub(crate) enum LicenseError {
+    IO(io::Error),
+    Regex(regex::Error),
+    Parse(String),
+}
+
+impl fmt::Display for LicenseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            LicenseError::IO(ref err) => err.fmt(f),
+            LicenseError::Regex(ref err) => err.fmt(f),
+            LicenseError::Parse(ref err) => write!(f, "parsing failed, {}", err),
+        }
+    }
+}
+
+impl From<io::Error> for LicenseError {
+    fn from(err: io::Error) -> LicenseError {
+        LicenseError::IO(err)
+    }
+}
+
+impl From<regex::Error> for LicenseError {
+    fn from(err: regex::Error) -> LicenseError {
+        LicenseError::Regex(err)
+    }
+}
+
+// the template is parsed using a state machine
+enum ParsingState {
+    Lit,
+    LitEsc,
+    // the u32 keeps track of brace nesting
+    Re(u32),
+    ReEsc(u32),
+    Abort(String),
+}
+
+use self::ParsingState::*;
+
+pub(crate) struct TemplateParser {
+    parsed: String,
+    buffer: String,
+    state: ParsingState,
+    linum: u32,
+    open_brace_line: u32,
+}
+
+impl TemplateParser {
+    fn new() -> Self {
+        Self {
+            parsed: "^".to_owned(),
+            buffer: String::new(),
+            state: Lit,
+            linum: 1,
+            // keeps track of last line on which a regex placeholder was started
+            open_brace_line: 0,
+        }
+    }
+
+    /// Converts a license template into a string which can be turned into a regex.
+    ///
+    /// The license template could use regex syntax directly, but that would require a lot of manual
+    /// escaping, which is inconvenient. It is therefore literal by default, with optional regex
+    /// subparts delimited by `{` and `}`. Additionally:
+    ///
+    /// - to insert literal `{`, `}` or `\`, escape it with `\`
+    /// - an empty regex placeholder (`{}`) is shorthand for `{.*?}`
+    ///
+    /// This function parses this input format and builds a properly escaped *string* representation
+    /// of the equivalent regular expression. It **does not** however guarantee that the returned
+    /// string is a syntactically valid regular expression.
+    ///
+    /// # Examples
+    ///
+    /// ```text
+    /// assert_eq!(
+    ///     TemplateParser::parse(
+    ///         r"
+    /// // Copyright {\d+} The \} Rust \\ Project \{ Developers. See the {([A-Z]+)}
+    /// // file at the top-level directory of this distribution and at
+    /// // {}.
+    /// //
+    /// // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+    /// // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+    /// // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+    /// // option. This file may not be copied, modified, or distributed
+    /// // except according to those terms.
+    /// "
+    ///     ).unwrap(),
+    ///     r"^
+    /// // Copyright \d+ The \} Rust \\ Project \{ Developers\. See the ([A-Z]+)
+    /// // file at the top\-level directory of this distribution and at
+    /// // .*?\.
+    /// //
+    /// // Licensed under the Apache License, Version 2\.0 <LICENSE\-APACHE or
+    /// // http://www\.apache\.org/licenses/LICENSE\-2\.0> or the MIT license
+    /// // <LICENSE\-MIT or http://opensource\.org/licenses/MIT>, at your
+    /// // option\. This file may not be copied, modified, or distributed
+    /// // except according to those terms\.
+    /// "
+    /// );
+    /// ```
+    pub(crate) fn parse(template: &str) -> Result<String, LicenseError> {
+        let mut parser = Self::new();
+        for chr in template.chars() {
+            if chr == '\n' {
+                parser.linum += 1;
+            }
+            parser.state = match parser.state {
+                Lit => parser.trans_from_lit(chr),
+                LitEsc => parser.trans_from_litesc(chr),
+                Re(brace_nesting) => parser.trans_from_re(chr, brace_nesting),
+                ReEsc(brace_nesting) => parser.trans_from_reesc(chr, brace_nesting),
+                Abort(msg) => return Err(LicenseError::Parse(msg)),
+            };
+        }
+        // check if we've ended parsing in a valid state
+        match parser.state {
+            Abort(msg) => return Err(LicenseError::Parse(msg)),
+            Re(_) | ReEsc(_) => {
+                return Err(LicenseError::Parse(format!(
+                    "escape or balance opening brace on l. {}",
+                    parser.open_brace_line
+                )));
+            }
+            LitEsc => {
+                return Err(LicenseError::Parse(format!(
+                    "incomplete escape sequence on l. {}",
+                    parser.linum
+                )));
+            }
+            _ => (),
+        }
+        parser.parsed.push_str(&regex::escape(&parser.buffer));
+
+        Ok(parser.parsed)
+    }
+
+    fn trans_from_lit(&mut self, chr: char) -> ParsingState {
+        match chr {
+            '{' => {
+                self.parsed.push_str(&regex::escape(&self.buffer));
+                self.buffer.clear();
+                self.open_brace_line = self.linum;
+                Re(1)
+            }
+            '}' => Abort(format!(
+                "escape or balance closing brace on l. {}",
+                self.linum
+            )),
+            '\\' => LitEsc,
+            _ => {
+                self.buffer.push(chr);
+                Lit
+            }
+        }
+    }
+
+    fn trans_from_litesc(&mut self, chr: char) -> ParsingState {
+        self.buffer.push(chr);
+        Lit
+    }
+
+    fn trans_from_re(&mut self, chr: char, brace_nesting: u32) -> ParsingState {
+        match chr {
+            '{' => {
+                self.buffer.push(chr);
+                Re(brace_nesting + 1)
+            }
+            '}' => {
+                match brace_nesting {
+                    1 => {
+                        // default regex for empty placeholder {}
+                        if self.buffer.is_empty() {
+                            self.parsed.push_str(".*?");
+                        } else {
+                            self.parsed.push_str(&self.buffer);
+                        }
+                        self.buffer.clear();
+                        Lit
+                    }
+                    _ => {
+                        self.buffer.push(chr);
+                        Re(brace_nesting - 1)
+                    }
+                }
+            }
+            '\\' => {
+                self.buffer.push(chr);
+                ReEsc(brace_nesting)
+            }
+            _ => {
+                self.buffer.push(chr);
+                Re(brace_nesting)
+            }
+        }
+    }
+
+    fn trans_from_reesc(&mut self, chr: char, brace_nesting: u32) -> ParsingState {
+        self.buffer.push(chr);
+        Re(brace_nesting)
+    }
+}
+
+pub(crate) fn load_and_compile_template(path: &str) -> Result<Regex, LicenseError> {
+    let mut lt_file = File::open(&path)?;
+    let mut lt_str = String::new();
+    lt_file.read_to_string(&mut lt_str)?;
+    let lt_parsed = TemplateParser::parse(&lt_str)?;
+    Ok(Regex::new(&lt_parsed)?)
+}
+
+#[cfg(test)]
+mod test {
+    use super::TemplateParser;
+
+    #[test]
+    fn test_parse_license_template() {
+        assert_eq!(
+            TemplateParser::parse("literal (.*)").unwrap(),
+            r"^literal \(\.\*\)"
+        );
+        assert_eq!(
+            TemplateParser::parse(r"escaping \}").unwrap(),
+            r"^escaping \}"
+        );
+        assert!(TemplateParser::parse("unbalanced } without escape").is_err());
+        assert_eq!(
+            TemplateParser::parse(r"{\d+} place{-?}holder{s?}").unwrap(),
+            r"^\d+ place-?holders?"
+        );
+        assert_eq!(TemplateParser::parse("default {}").unwrap(), "^default .*?");
+        assert_eq!(
+            TemplateParser::parse(r"unbalanced nested braces {\{{3}}").unwrap(),
+            r"^unbalanced nested braces \{{3}"
+        );
+        assert_eq!(
+            &TemplateParser::parse("parsing error }")
+                .unwrap_err()
+                .to_string(),
+            "parsing failed, escape or balance closing brace on l. 1"
+        );
+        assert_eq!(
+            &TemplateParser::parse("parsing error {\nsecond line")
+                .unwrap_err()
+                .to_string(),
+            "parsing failed, escape or balance opening brace on l. 1"
+        );
+        assert_eq!(
+            &TemplateParser::parse(r"parsing error \")
+                .unwrap_err()
+                .to_string(),
+            "parsing failed, incomplete escape sequence on l. 1"
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/config/lists.rs b/src/tools/rustfmt/src/config/lists.rs
new file mode 100644
index 0000000000000..11cb17068fb4a
--- /dev/null
+++ b/src/tools/rustfmt/src/config/lists.rs
@@ -0,0 +1,92 @@
+//! Configuration options related to rewriting a list.
+
+use rustfmt_config_proc_macro::config_type;
+
+use crate::config::IndentStyle;
+
+/// The definitive formatting tactic for lists.
+#[derive(Eq, PartialEq, Debug, Copy, Clone)]
+pub enum DefinitiveListTactic {
+    Vertical,
+    Horizontal,
+    Mixed,
+    /// Special case tactic for `format!()`, `write!()` style macros.
+    SpecialMacro(usize),
+}
+
+impl DefinitiveListTactic {
+    pub fn ends_with_newline(&self, indent_style: IndentStyle) -> bool {
+        match indent_style {
+            IndentStyle::Block => *self != DefinitiveListTactic::Horizontal,
+            IndentStyle::Visual => false,
+        }
+    }
+}
+
+/// Formatting tactic for lists. This will be cast down to a
+/// `DefinitiveListTactic` depending on the number and length of the items and
+/// their comments.
+#[config_type]
+pub enum ListTactic {
+    /// One item per row.
+    Vertical,
+    /// All items on one row.
+    Horizontal,
+    /// Try Horizontal layout, if that fails then vertical.
+    HorizontalVertical,
+    /// HorizontalVertical with a soft limit of n characters.
+    LimitedHorizontalVertical(usize),
+    /// Pack as many items as possible per row over (possibly) many rows.
+    Mixed,
+}
+
+#[config_type]
+pub enum SeparatorTactic {
+    Always,
+    Never,
+    Vertical,
+}
+
+impl SeparatorTactic {
+    pub fn from_bool(b: bool) -> SeparatorTactic {
+        if b {
+            SeparatorTactic::Always
+        } else {
+            SeparatorTactic::Never
+        }
+    }
+}
+
+/// Where to put separator.
+#[config_type]
+pub enum SeparatorPlace {
+    Front,
+    Back,
+}
+
+impl SeparatorPlace {
+    pub fn is_front(self) -> bool {
+        self == SeparatorPlace::Front
+    }
+
+    pub fn is_back(self) -> bool {
+        self == SeparatorPlace::Back
+    }
+
+    pub fn from_tactic(
+        default: SeparatorPlace,
+        tactic: DefinitiveListTactic,
+        sep: &str,
+    ) -> SeparatorPlace {
+        match tactic {
+            DefinitiveListTactic::Vertical => default,
+            _ => {
+                if sep == "," {
+                    SeparatorPlace::Back
+                } else {
+                    default
+                }
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/src/config/mod.rs b/src/tools/rustfmt/src/config/mod.rs
new file mode 100644
index 0000000000000..8c04363b1fd4b
--- /dev/null
+++ b/src/tools/rustfmt/src/config/mod.rs
@@ -0,0 +1,963 @@
+use std::cell::Cell;
+use std::default::Default;
+use std::fs::File;
+use std::io::{Error, ErrorKind, Read};
+use std::path::{Path, PathBuf};
+use std::{env, fs};
+
+use regex::Regex;
+use thiserror::Error;
+
+use crate::config::config_type::ConfigType;
+#[allow(unreachable_pub)]
+pub use crate::config::file_lines::{FileLines, FileName, Range};
+#[allow(unreachable_pub)]
+pub use crate::config::lists::*;
+#[allow(unreachable_pub)]
+pub use crate::config::options::*;
+
+#[macro_use]
+pub(crate) mod config_type;
+#[macro_use]
+pub(crate) mod options;
+
+pub(crate) mod file_lines;
+pub(crate) mod license;
+pub(crate) mod lists;
+
+// This macro defines configuration options used in rustfmt. Each option
+// is defined as follows:
+//
+// `name: value type, default value, is stable, description;`
+create_config! {
+    // Fundamental stuff
+    max_width: usize, 100, true, "Maximum width of each line";
+    hard_tabs: bool, false, true, "Use tab characters for indentation, spaces for alignment";
+    tab_spaces: usize, 4, true, "Number of spaces per tab";
+    newline_style: NewlineStyle, NewlineStyle::Auto, true, "Unix or Windows line endings";
+    indent_style: IndentStyle, IndentStyle::Block, false, "How do we indent expressions or items";
+
+    // Width Heuristics
+    use_small_heuristics: Heuristics, Heuristics::Default, true, "Whether to use different \
+        formatting for items and expressions if they satisfy a heuristic notion of 'small'";
+    width_heuristics: WidthHeuristics, WidthHeuristics::scaled(100), false,
+        "'small' heuristic values";
+    fn_call_width: usize, 60, true, "Maximum width of the args of a function call before \
+        falling back to vertical formatting.";
+    attr_fn_like_width: usize, 70, true, "Maximum width of the args of a function-like \
+        attributes before falling back to vertical formatting.";
+    struct_lit_width: usize, 18, true, "Maximum width in the body of a struct lit before \
+        falling back to vertical formatting.";
+    struct_variant_width: usize, 35, true, "Maximum width in the body of a struct variant before \
+        falling back to vertical formatting.";
+    array_width: usize, 60, true,  "Maximum width of an array literal before falling \
+        back to vertical formatting.";
+    chain_width: usize, 60, true, "Maximum length of a chain to fit on a single line.";
+    single_line_if_else_max_width: usize, 50, true, "Maximum line length for single line if-else \
+        expressions. A value of zero means always break if-else expressions.";
+
+    // Comments. macros, and strings
+    wrap_comments: bool, false, false, "Break comments to fit on the line";
+    format_code_in_doc_comments: bool, false, false, "Format the code snippet in doc comments.";
+    comment_width: usize, 80, false,
+        "Maximum length of comments. No effect unless wrap_comments = true";
+    normalize_comments: bool, false, false, "Convert /* */ comments to // comments where possible";
+    normalize_doc_attributes: bool, false, false, "Normalize doc attributes as doc comments";
+    license_template_path: String, String::default(), false,
+        "Beginning of file must match license template";
+    format_strings: bool, false, false, "Format string literals where necessary";
+    format_macro_matchers: bool, false, false,
+        "Format the metavariable matching patterns in macros";
+    format_macro_bodies: bool, true, false, "Format the bodies of macros";
+
+    // Single line expressions and items
+    empty_item_single_line: bool, true, false,
+        "Put empty-body functions and impls on a single line";
+    struct_lit_single_line: bool, true, false,
+        "Put small struct literals on a single line";
+    fn_single_line: bool, false, false, "Put single-expression functions on a single line";
+    where_single_line: bool, false, false, "Force where-clauses to be on a single line";
+
+    // Imports
+    imports_indent: IndentStyle, IndentStyle::Block, false, "Indent of imports";
+    imports_layout: ListTactic, ListTactic::Mixed, false, "Item layout inside a import block";
+    imports_granularity: ImportGranularity, ImportGranularity::Preserve, false,
+        "Merge or split imports to the provided granularity";
+    group_imports: GroupImportsTactic, GroupImportsTactic::Preserve, false,
+        "Controls the strategy for how imports are grouped together";
+    merge_imports: bool, false, false, "(deprecated: use imports_granularity instead)";
+
+    // Ordering
+    reorder_imports: bool, true, true, "Reorder import and extern crate statements alphabetically";
+    reorder_modules: bool, true, true, "Reorder module statements alphabetically in group";
+    reorder_impl_items: bool, false, false, "Reorder impl items";
+
+    // Spaces around punctuation
+    type_punctuation_density: TypeDensity, TypeDensity::Wide, false,
+        "Determines if '+' or '=' are wrapped in spaces in the punctuation of types";
+    space_before_colon: bool, false, false, "Leave a space before the colon";
+    space_after_colon: bool, true, false, "Leave a space after the colon";
+    spaces_around_ranges: bool, false, false, "Put spaces around the  .. and ..= range operators";
+    binop_separator: SeparatorPlace, SeparatorPlace::Front, false,
+        "Where to put a binary operator when a binary expression goes multiline";
+
+    // Misc.
+    remove_nested_parens: bool, true, true, "Remove nested parens";
+    combine_control_expr: bool, true, false, "Combine control expressions with function calls";
+    overflow_delimited_expr: bool, false, false,
+        "Allow trailing bracket/brace delimited expressions to overflow";
+    struct_field_align_threshold: usize, 0, false,
+        "Align struct fields if their diffs fits within threshold";
+    enum_discrim_align_threshold: usize, 0, false,
+        "Align enum variants discrims, if their diffs fit within threshold";
+    match_arm_blocks: bool, true, false, "Wrap the body of arms in blocks when it does not fit on \
+        the same line with the pattern of arms";
+    match_arm_leading_pipes: MatchArmLeadingPipe, MatchArmLeadingPipe::Never, true,
+        "Determines whether leading pipes are emitted on match arms";
+    force_multiline_blocks: bool, false, false,
+        "Force multiline closure bodies and match arms to be wrapped in a block";
+    fn_args_layout: Density, Density::Tall, true,
+        "Control the layout of arguments in a function";
+    brace_style: BraceStyle, BraceStyle::SameLineWhere, false, "Brace style for items";
+    control_brace_style: ControlBraceStyle, ControlBraceStyle::AlwaysSameLine, false,
+        "Brace style for control flow constructs";
+    trailing_semicolon: bool, true, false,
+        "Add trailing semicolon after break, continue and return";
+    trailing_comma: SeparatorTactic, SeparatorTactic::Vertical, false,
+        "How to handle trailing commas for lists";
+    match_block_trailing_comma: bool, false, false,
+        "Put a trailing comma after a block based match arm (non-block arms are not affected)";
+    blank_lines_upper_bound: usize, 1, false,
+        "Maximum number of blank lines which can be put between items";
+    blank_lines_lower_bound: usize, 0, false,
+        "Minimum number of blank lines which must be put between items";
+    edition: Edition, Edition::Edition2015, true, "The edition of the parser (RFC 2052)";
+    version: Version, Version::One, false, "Version of formatting rules";
+    inline_attribute_width: usize, 0, false,
+        "Write an item and its attribute on the same line \
+        if their combined width is below a threshold";
+
+    // Options that can change the source code beyond whitespace/blocks (somewhat linty things)
+    merge_derives: bool, true, true, "Merge multiple `#[derive(...)]` into a single one";
+    use_try_shorthand: bool, false, true, "Replace uses of the try! macro by the ? shorthand";
+    use_field_init_shorthand: bool, false, true, "Use field initialization shorthand if possible";
+    force_explicit_abi: bool, true, true, "Always print the abi for extern items";
+    condense_wildcard_suffixes: bool, false, false, "Replace strings of _ wildcards by a single .. \
+                                                     in tuple patterns";
+
+    // Control options (changes the operation of rustfmt, rather than the formatting)
+    color: Color, Color::Auto, false,
+        "What Color option to use when none is supplied: Always, Never, Auto";
+    required_version: String, env!("CARGO_PKG_VERSION").to_owned(), false,
+        "Require a specific version of rustfmt";
+    unstable_features: bool, false, false,
+            "Enables unstable features. Only available on nightly channel";
+    disable_all_formatting: bool, false, false, "Don't reformat anything";
+    skip_children: bool, false, false, "Don't reformat out of line modules";
+    hide_parse_errors: bool, false, false, "Hide errors from the parser";
+    error_on_line_overflow: bool, false, false, "Error if unable to get all lines within max_width";
+    error_on_unformatted: bool, false, false,
+        "Error if unable to get comments or string literals within max_width, \
+         or they are left with trailing whitespaces";
+    report_todo: ReportTactic, ReportTactic::Never, false,
+        "Report all, none or unnumbered occurrences of TODO in source file comments";
+    report_fixme: ReportTactic, ReportTactic::Never, false,
+        "Report all, none or unnumbered occurrences of FIXME in source file comments";
+    ignore: IgnoreList, IgnoreList::default(), false,
+        "Skip formatting the specified files and directories";
+
+    // Not user-facing
+    verbose: Verbosity, Verbosity::Normal, false, "How much to information to emit to the user";
+    file_lines: FileLines, FileLines::all(), false,
+        "Lines to format; this is not supported in rustfmt.toml, and can only be specified \
+         via the --file-lines option";
+    emit_mode: EmitMode, EmitMode::Files, false,
+        "What emit Mode to use when none is supplied";
+    make_backup: bool, false, false, "Backup changed files";
+    print_misformatted_file_names: bool, false, true,
+        "Prints the names of mismatched files that were formatted. Prints the names of \
+         files that would be formated when used with `--check` mode. ";
+}
+
+#[derive(Error, Debug)]
+#[error("Could not output config: {0}")]
+pub struct ToTomlError(toml::ser::Error);
+
+impl PartialConfig {
+    pub fn to_toml(&self) -> Result<String, ToTomlError> {
+        // Non-user-facing options can't be specified in TOML
+        let mut cloned = self.clone();
+        cloned.file_lines = None;
+        cloned.verbose = None;
+        cloned.width_heuristics = None;
+        cloned.print_misformatted_file_names = None;
+        cloned.merge_imports = None;
+
+        ::toml::to_string(&cloned).map_err(ToTomlError)
+    }
+}
+
+impl Config {
+    pub(crate) fn version_meets_requirement(&self) -> bool {
+        if self.was_set().required_version() {
+            let version = env!("CARGO_PKG_VERSION");
+            let required_version = self.required_version();
+            if version != required_version {
+                println!(
+                    "Error: rustfmt version ({}) doesn't match the required version ({})",
+                    version, required_version,
+                );
+                return false;
+            }
+        }
+
+        true
+    }
+
+    /// Constructs a `Config` from the toml file specified at `file_path`.
+    ///
+    /// This method only looks at the provided path, for a method that
+    /// searches parents for a `rustfmt.toml` see `from_resolved_toml_path`.
+    ///
+    /// Returns a `Config` if the config could be read and parsed from
+    /// the file, otherwise errors.
+    pub(super) fn from_toml_path(file_path: &Path) -> Result<Config, Error> {
+        let mut file = File::open(&file_path)?;
+        let mut toml = String::new();
+        file.read_to_string(&mut toml)?;
+        Config::from_toml(&toml, file_path.parent().unwrap())
+            .map_err(|err| Error::new(ErrorKind::InvalidData, err))
+    }
+
+    /// Resolves the config for input in `dir`.
+    ///
+    /// Searches for `rustfmt.toml` beginning with `dir`, and
+    /// recursively checking parents of `dir` if no config file is found.
+    /// If no config file exists in `dir` or in any parent, a
+    /// default `Config` will be returned (and the returned path will be empty).
+    ///
+    /// Returns the `Config` to use, and the path of the project file if there was
+    /// one.
+    pub(super) fn from_resolved_toml_path(dir: &Path) -> Result<(Config, Option<PathBuf>), Error> {
+        /// Try to find a project file in the given directory and its parents.
+        /// Returns the path of a the nearest project file if one exists,
+        /// or `None` if no project file was found.
+        fn resolve_project_file(dir: &Path) -> Result<Option<PathBuf>, Error> {
+            let mut current = if dir.is_relative() {
+                env::current_dir()?.join(dir)
+            } else {
+                dir.to_path_buf()
+            };
+
+            current = fs::canonicalize(current)?;
+
+            loop {
+                match get_toml_path(&current) {
+                    Ok(Some(path)) => return Ok(Some(path)),
+                    Err(e) => return Err(e),
+                    _ => (),
+                }
+
+                // If the current directory has no parent, we're done searching.
+                if !current.pop() {
+                    break;
+                }
+            }
+
+            // If nothing was found, check in the home directory.
+            if let Some(home_dir) = dirs::home_dir() {
+                if let Some(path) = get_toml_path(&home_dir)? {
+                    return Ok(Some(path));
+                }
+            }
+
+            // If none was found ther either, check in the user's configuration directory.
+            if let Some(mut config_dir) = dirs::config_dir() {
+                config_dir.push("rustfmt");
+                if let Some(path) = get_toml_path(&config_dir)? {
+                    return Ok(Some(path));
+                }
+            }
+
+            Ok(None)
+        }
+
+        match resolve_project_file(dir)? {
+            None => Ok((Config::default(), None)),
+            Some(path) => Config::from_toml_path(&path).map(|config| (config, Some(path))),
+        }
+    }
+
+    pub(crate) fn from_toml(toml: &str, dir: &Path) -> Result<Config, String> {
+        let parsed: ::toml::Value = toml
+            .parse()
+            .map_err(|e| format!("Could not parse TOML: {}", e))?;
+        let mut err = String::new();
+        let table = parsed
+            .as_table()
+            .ok_or_else(|| String::from("Parsed config was not table"))?;
+        for key in table.keys() {
+            if !Config::is_valid_name(key) {
+                let msg = &format!("Warning: Unknown configuration option `{}`\n", key);
+                err.push_str(msg)
+            }
+        }
+        match parsed.try_into() {
+            Ok(parsed_config) => {
+                if !err.is_empty() {
+                    eprint!("{}", err);
+                }
+                Ok(Config::default().fill_from_parsed_config(parsed_config, dir))
+            }
+            Err(e) => {
+                err.push_str("Error: Decoding config file failed:\n");
+                err.push_str(format!("{}\n", e).as_str());
+                err.push_str("Please check your config file.");
+                Err(err)
+            }
+        }
+    }
+}
+
+/// Loads a config by checking the client-supplied options and if appropriate, the
+/// file system (including searching the file system for overrides).
+pub fn load_config<O: CliOptions>(
+    file_path: Option<&Path>,
+    options: Option<O>,
+) -> Result<(Config, Option<PathBuf>), Error> {
+    let over_ride = match options {
+        Some(ref opts) => config_path(opts)?,
+        None => None,
+    };
+
+    let result = if let Some(over_ride) = over_ride {
+        Config::from_toml_path(over_ride.as_ref()).map(|p| (p, Some(over_ride.to_owned())))
+    } else if let Some(file_path) = file_path {
+        Config::from_resolved_toml_path(file_path)
+    } else {
+        Ok((Config::default(), None))
+    };
+
+    result.map(|(mut c, p)| {
+        if let Some(options) = options {
+            options.apply_to(&mut c);
+        }
+        (c, p)
+    })
+}
+
+// Check for the presence of known config file names (`rustfmt.toml, `.rustfmt.toml`) in `dir`
+//
+// Return the path if a config file exists, empty if no file exists, and Error for IO errors
+fn get_toml_path(dir: &Path) -> Result<Option<PathBuf>, Error> {
+    const CONFIG_FILE_NAMES: [&str; 2] = [".rustfmt.toml", "rustfmt.toml"];
+    for config_file_name in &CONFIG_FILE_NAMES {
+        let config_file = dir.join(config_file_name);
+        match fs::metadata(&config_file) {
+            // Only return if it's a file to handle the unlikely situation of a directory named
+            // `rustfmt.toml`.
+            Ok(ref md) if md.is_file() => return Ok(Some(config_file)),
+            // Return the error if it's something other than `NotFound`; otherwise we didn't
+            // find the project file yet, and continue searching.
+            Err(e) => {
+                if e.kind() != ErrorKind::NotFound {
+                    return Err(e);
+                }
+            }
+            _ => {}
+        }
+    }
+    Ok(None)
+}
+
+fn config_path(options: &dyn CliOptions) -> Result<Option<PathBuf>, Error> {
+    let config_path_not_found = |path: &str| -> Result<Option<PathBuf>, Error> {
+        Err(Error::new(
+            ErrorKind::NotFound,
+            format!(
+                "Error: unable to find a config file for the given path: `{}`",
+                path
+            ),
+        ))
+    };
+
+    // Read the config_path and convert to parent dir if a file is provided.
+    // If a config file cannot be found from the given path, return error.
+    match options.config_path() {
+        Some(path) if !path.exists() => config_path_not_found(path.to_str().unwrap()),
+        Some(path) if path.is_dir() => {
+            let config_file_path = get_toml_path(path)?;
+            if config_file_path.is_some() {
+                Ok(config_file_path)
+            } else {
+                config_path_not_found(path.to_str().unwrap())
+            }
+        }
+        path => Ok(path.map(ToOwned::to_owned)),
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use std::str;
+
+    #[allow(dead_code)]
+    mod mock {
+        use super::super::*;
+
+        create_config! {
+            // Options that are used by the generated functions
+            max_width: usize, 100, true, "Maximum width of each line";
+            license_template_path: String, String::default(), false,
+                "Beginning of file must match license template";
+            required_version: String, env!("CARGO_PKG_VERSION").to_owned(), false,
+                "Require a specific version of rustfmt.";
+            ignore: IgnoreList, IgnoreList::default(), false,
+                "Skip formatting the specified files and directories.";
+            verbose: Verbosity, Verbosity::Normal, false,
+                "How much to information to emit to the user";
+            file_lines: FileLines, FileLines::all(), false,
+                "Lines to format; this is not supported in rustfmt.toml, and can only be specified \
+                    via the --file-lines option";
+
+            // merge_imports deprecation
+            imports_granularity: ImportGranularity, ImportGranularity::Preserve, false,
+                "Merge imports";
+            merge_imports: bool, false, false, "(deprecated: use imports_granularity instead)";
+
+            // Width Heuristics
+            use_small_heuristics: Heuristics, Heuristics::Default, true,
+                "Whether to use different formatting for items and \
+                 expressions if they satisfy a heuristic notion of 'small'.";
+            width_heuristics: WidthHeuristics, WidthHeuristics::scaled(100), false,
+                "'small' heuristic values";
+
+            fn_call_width: usize, 60, true, "Maximum width of the args of a function call before \
+                falling back to vertical formatting.";
+            attr_fn_like_width: usize, 70, true, "Maximum width of the args of a function-like \
+                attributes before falling back to vertical formatting.";
+            struct_lit_width: usize, 18, true, "Maximum width in the body of a struct lit before \
+                falling back to vertical formatting.";
+            struct_variant_width: usize, 35, true, "Maximum width in the body of a struct \
+                variant before falling back to vertical formatting.";
+            array_width: usize, 60, true,  "Maximum width of an array literal before falling \
+                back to vertical formatting.";
+            chain_width: usize, 60, true, "Maximum length of a chain to fit on a single line.";
+            single_line_if_else_max_width: usize, 50, true, "Maximum line length for single \
+                line if-else expressions. A value of zero means always break if-else expressions.";
+
+            // Options that are used by the tests
+            stable_option: bool, false, true, "A stable option";
+            unstable_option: bool, false, false, "An unstable option";
+        }
+    }
+
+    #[test]
+    fn test_config_set() {
+        let mut config = Config::default();
+        config.set().verbose(Verbosity::Quiet);
+        assert_eq!(config.verbose(), Verbosity::Quiet);
+        config.set().verbose(Verbosity::Normal);
+        assert_eq!(config.verbose(), Verbosity::Normal);
+    }
+
+    #[test]
+    fn test_config_used_to_toml() {
+        let config = Config::default();
+
+        let merge_derives = config.merge_derives();
+        let skip_children = config.skip_children();
+
+        let used_options = config.used_options();
+        let toml = used_options.to_toml().unwrap();
+        assert_eq!(
+            toml,
+            format!(
+                "merge_derives = {}\nskip_children = {}\n",
+                merge_derives, skip_children,
+            )
+        );
+    }
+
+    #[test]
+    fn test_was_set() {
+        let config = Config::from_toml("hard_tabs = true", Path::new("")).unwrap();
+
+        assert_eq!(config.was_set().hard_tabs(), true);
+        assert_eq!(config.was_set().verbose(), false);
+    }
+
+    #[test]
+    fn test_print_docs_exclude_unstable() {
+        use self::mock::Config;
+
+        let mut output = Vec::new();
+        Config::print_docs(&mut output, false);
+
+        let s = str::from_utf8(&output).unwrap();
+
+        assert_eq!(s.contains("stable_option"), true);
+        assert_eq!(s.contains("unstable_option"), false);
+        assert_eq!(s.contains("(unstable)"), false);
+    }
+
+    #[test]
+    fn test_print_docs_include_unstable() {
+        use self::mock::Config;
+
+        let mut output = Vec::new();
+        Config::print_docs(&mut output, true);
+
+        let s = str::from_utf8(&output).unwrap();
+        assert_eq!(s.contains("stable_option"), true);
+        assert_eq!(s.contains("unstable_option"), true);
+        assert_eq!(s.contains("(unstable)"), true);
+    }
+
+    #[test]
+    fn test_empty_string_license_template_path() {
+        let toml = r#"license_template_path = """#;
+        let config = Config::from_toml(toml, Path::new("")).unwrap();
+        assert!(config.license_template.is_none());
+    }
+
+    #[test]
+    fn test_valid_license_template_path() {
+        if !crate::is_nightly_channel!() {
+            return;
+        }
+        let toml = r#"license_template_path = "tests/license-template/lt.txt""#;
+        let config = Config::from_toml(toml, Path::new("")).unwrap();
+        assert!(config.license_template.is_some());
+    }
+
+    #[test]
+    fn test_override_existing_license_with_no_license() {
+        if !crate::is_nightly_channel!() {
+            return;
+        }
+        let toml = r#"license_template_path = "tests/license-template/lt.txt""#;
+        let mut config = Config::from_toml(toml, Path::new("")).unwrap();
+        assert!(config.license_template.is_some());
+        config.override_value("license_template_path", "");
+        assert!(config.license_template.is_none());
+    }
+
+    #[test]
+    fn test_dump_default_config() {
+        let default_config = format!(
+            r#"max_width = 100
+hard_tabs = false
+tab_spaces = 4
+newline_style = "Auto"
+indent_style = "Block"
+use_small_heuristics = "Default"
+fn_call_width = 60
+attr_fn_like_width = 70
+struct_lit_width = 18
+struct_variant_width = 35
+array_width = 60
+chain_width = 60
+single_line_if_else_max_width = 50
+wrap_comments = false
+format_code_in_doc_comments = false
+comment_width = 80
+normalize_comments = false
+normalize_doc_attributes = false
+license_template_path = ""
+format_strings = false
+format_macro_matchers = false
+format_macro_bodies = true
+empty_item_single_line = true
+struct_lit_single_line = true
+fn_single_line = false
+where_single_line = false
+imports_indent = "Block"
+imports_layout = "Mixed"
+imports_granularity = "Preserve"
+group_imports = "Preserve"
+reorder_imports = true
+reorder_modules = true
+reorder_impl_items = false
+type_punctuation_density = "Wide"
+space_before_colon = false
+space_after_colon = true
+spaces_around_ranges = false
+binop_separator = "Front"
+remove_nested_parens = true
+combine_control_expr = true
+overflow_delimited_expr = false
+struct_field_align_threshold = 0
+enum_discrim_align_threshold = 0
+match_arm_blocks = true
+match_arm_leading_pipes = "Never"
+force_multiline_blocks = false
+fn_args_layout = "Tall"
+brace_style = "SameLineWhere"
+control_brace_style = "AlwaysSameLine"
+trailing_semicolon = true
+trailing_comma = "Vertical"
+match_block_trailing_comma = false
+blank_lines_upper_bound = 1
+blank_lines_lower_bound = 0
+edition = "2015"
+version = "One"
+inline_attribute_width = 0
+merge_derives = true
+use_try_shorthand = false
+use_field_init_shorthand = false
+force_explicit_abi = true
+condense_wildcard_suffixes = false
+color = "Auto"
+required_version = "{}"
+unstable_features = false
+disable_all_formatting = false
+skip_children = false
+hide_parse_errors = false
+error_on_line_overflow = false
+error_on_unformatted = false
+report_todo = "Never"
+report_fixme = "Never"
+ignore = []
+emit_mode = "Files"
+make_backup = false
+"#,
+            env!("CARGO_PKG_VERSION")
+        );
+        let toml = Config::default().all_options().to_toml().unwrap();
+        assert_eq!(&toml, &default_config);
+    }
+
+    // FIXME(#2183): these tests cannot be run in parallel because they use env vars.
+    // #[test]
+    // fn test_as_not_nightly_channel() {
+    //     let mut config = Config::default();
+    //     assert_eq!(config.was_set().unstable_features(), false);
+    //     config.set().unstable_features(true);
+    //     assert_eq!(config.was_set().unstable_features(), false);
+    // }
+
+    // #[test]
+    // fn test_as_nightly_channel() {
+    //     let v = ::std::env::var("CFG_RELEASE_CHANNEL").unwrap_or(String::from(""));
+    //     ::std::env::set_var("CFG_RELEASE_CHANNEL", "nightly");
+    //     let mut config = Config::default();
+    //     config.set().unstable_features(true);
+    //     assert_eq!(config.was_set().unstable_features(), false);
+    //     config.set().unstable_features(true);
+    //     assert_eq!(config.unstable_features(), true);
+    //     ::std::env::set_var("CFG_RELEASE_CHANNEL", v);
+    // }
+
+    // #[test]
+    // fn test_unstable_from_toml() {
+    //     let mut config = Config::from_toml("unstable_features = true").unwrap();
+    //     assert_eq!(config.was_set().unstable_features(), false);
+    //     let v = ::std::env::var("CFG_RELEASE_CHANNEL").unwrap_or(String::from(""));
+    //     ::std::env::set_var("CFG_RELEASE_CHANNEL", "nightly");
+    //     config = Config::from_toml("unstable_features = true").unwrap();
+    //     assert_eq!(config.was_set().unstable_features(), true);
+    //     assert_eq!(config.unstable_features(), true);
+    //     ::std::env::set_var("CFG_RELEASE_CHANNEL", v);
+    // }
+
+    #[cfg(test)]
+    mod deprecated_option_merge_imports {
+        use super::*;
+
+        #[test]
+        fn test_old_option_set() {
+            if !crate::is_nightly_channel!() {
+                return;
+            }
+            let toml = r#"
+                unstable_features = true
+                merge_imports = true
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.imports_granularity(), ImportGranularity::Crate);
+        }
+
+        #[test]
+        fn test_both_set() {
+            if !crate::is_nightly_channel!() {
+                return;
+            }
+            let toml = r#"
+                unstable_features = true
+                merge_imports = true
+                imports_granularity = "Preserve"
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.imports_granularity(), ImportGranularity::Preserve);
+        }
+
+        #[test]
+        fn test_new_overridden() {
+            if !crate::is_nightly_channel!() {
+                return;
+            }
+            let toml = r#"
+                unstable_features = true
+                merge_imports = true
+            "#;
+            let mut config = Config::from_toml(toml, Path::new("")).unwrap();
+            config.override_value("imports_granularity", "Preserve");
+            assert_eq!(config.imports_granularity(), ImportGranularity::Preserve);
+        }
+
+        #[test]
+        fn test_old_overridden() {
+            if !crate::is_nightly_channel!() {
+                return;
+            }
+            let toml = r#"
+                unstable_features = true
+                imports_granularity = "Module"
+            "#;
+            let mut config = Config::from_toml(toml, Path::new("")).unwrap();
+            config.override_value("merge_imports", "true");
+            // no effect: the new option always takes precedence
+            assert_eq!(config.imports_granularity(), ImportGranularity::Module);
+        }
+    }
+
+    #[cfg(test)]
+    mod use_small_heuristics {
+        use super::*;
+
+        #[test]
+        fn test_default_sets_correct_widths() {
+            let toml = r#"
+                use_small_heuristics = "Default"
+                max_width = 200
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.array_width(), 120);
+            assert_eq!(config.attr_fn_like_width(), 140);
+            assert_eq!(config.chain_width(), 120);
+            assert_eq!(config.fn_call_width(), 120);
+            assert_eq!(config.single_line_if_else_max_width(), 100);
+            assert_eq!(config.struct_lit_width(), 36);
+            assert_eq!(config.struct_variant_width(), 70);
+        }
+
+        #[test]
+        fn test_max_sets_correct_widths() {
+            let toml = r#"
+                use_small_heuristics = "Max"
+                max_width = 120
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.array_width(), 120);
+            assert_eq!(config.attr_fn_like_width(), 120);
+            assert_eq!(config.chain_width(), 120);
+            assert_eq!(config.fn_call_width(), 120);
+            assert_eq!(config.single_line_if_else_max_width(), 120);
+            assert_eq!(config.struct_lit_width(), 120);
+            assert_eq!(config.struct_variant_width(), 120);
+        }
+
+        #[test]
+        fn test_off_sets_correct_widths() {
+            let toml = r#"
+                use_small_heuristics = "Off"
+                max_width = 100
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.array_width(), usize::max_value());
+            assert_eq!(config.attr_fn_like_width(), usize::max_value());
+            assert_eq!(config.chain_width(), usize::max_value());
+            assert_eq!(config.fn_call_width(), usize::max_value());
+            assert_eq!(config.single_line_if_else_max_width(), 0);
+            assert_eq!(config.struct_lit_width(), 0);
+            assert_eq!(config.struct_variant_width(), 0);
+        }
+
+        #[test]
+        fn test_override_works_with_default() {
+            let toml = r#"
+                use_small_heuristics = "Default"
+                array_width = 20
+                attr_fn_like_width = 40
+                chain_width = 20
+                fn_call_width = 90
+                single_line_if_else_max_width = 40
+                struct_lit_width = 30
+                struct_variant_width = 34
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.array_width(), 20);
+            assert_eq!(config.attr_fn_like_width(), 40);
+            assert_eq!(config.chain_width(), 20);
+            assert_eq!(config.fn_call_width(), 90);
+            assert_eq!(config.single_line_if_else_max_width(), 40);
+            assert_eq!(config.struct_lit_width(), 30);
+            assert_eq!(config.struct_variant_width(), 34);
+        }
+
+        #[test]
+        fn test_override_with_max() {
+            let toml = r#"
+                use_small_heuristics = "Max"
+                array_width = 20
+                attr_fn_like_width = 40
+                chain_width = 20
+                fn_call_width = 90
+                single_line_if_else_max_width = 40
+                struct_lit_width = 30
+                struct_variant_width = 34
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.array_width(), 20);
+            assert_eq!(config.attr_fn_like_width(), 40);
+            assert_eq!(config.chain_width(), 20);
+            assert_eq!(config.fn_call_width(), 90);
+            assert_eq!(config.single_line_if_else_max_width(), 40);
+            assert_eq!(config.struct_lit_width(), 30);
+            assert_eq!(config.struct_variant_width(), 34);
+        }
+
+        #[test]
+        fn test_override_with_off() {
+            let toml = r#"
+                use_small_heuristics = "Off"
+                array_width = 20
+                attr_fn_like_width = 40
+                chain_width = 20
+                fn_call_width = 90
+                single_line_if_else_max_width = 40
+                struct_lit_width = 30
+                struct_variant_width = 34
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.array_width(), 20);
+            assert_eq!(config.attr_fn_like_width(), 40);
+            assert_eq!(config.chain_width(), 20);
+            assert_eq!(config.fn_call_width(), 90);
+            assert_eq!(config.single_line_if_else_max_width(), 40);
+            assert_eq!(config.struct_lit_width(), 30);
+            assert_eq!(config.struct_variant_width(), 34);
+        }
+
+        #[test]
+        fn test_fn_call_width_config_exceeds_max_width() {
+            let toml = r#"
+                max_width = 90
+                fn_call_width = 95
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.fn_call_width(), 90);
+        }
+
+        #[test]
+        fn test_attr_fn_like_width_config_exceeds_max_width() {
+            let toml = r#"
+                max_width = 80
+                attr_fn_like_width = 90
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.attr_fn_like_width(), 80);
+        }
+
+        #[test]
+        fn test_struct_lit_config_exceeds_max_width() {
+            let toml = r#"
+                max_width = 78
+                struct_lit_width = 90
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.struct_lit_width(), 78);
+        }
+
+        #[test]
+        fn test_struct_variant_width_config_exceeds_max_width() {
+            let toml = r#"
+                max_width = 80
+                struct_variant_width = 90
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.struct_variant_width(), 80);
+        }
+
+        #[test]
+        fn test_array_width_config_exceeds_max_width() {
+            let toml = r#"
+                max_width = 60
+                array_width = 80
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.array_width(), 60);
+        }
+
+        #[test]
+        fn test_chain_width_config_exceeds_max_width() {
+            let toml = r#"
+                max_width = 80
+                chain_width = 90
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.chain_width(), 80);
+        }
+
+        #[test]
+        fn test_single_line_if_else_max_width_config_exceeds_max_width() {
+            let toml = r#"
+                max_width = 70
+                single_line_if_else_max_width = 90
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.single_line_if_else_max_width(), 70);
+        }
+
+        #[test]
+        fn test_override_fn_call_width_exceeds_max_width() {
+            let mut config = Config::default();
+            config.override_value("fn_call_width", "101");
+            assert_eq!(config.fn_call_width(), 100);
+        }
+
+        #[test]
+        fn test_override_attr_fn_like_width_exceeds_max_width() {
+            let mut config = Config::default();
+            config.override_value("attr_fn_like_width", "101");
+            assert_eq!(config.attr_fn_like_width(), 100);
+        }
+
+        #[test]
+        fn test_override_struct_lit_exceeds_max_width() {
+            let mut config = Config::default();
+            config.override_value("struct_lit_width", "101");
+            assert_eq!(config.struct_lit_width(), 100);
+        }
+
+        #[test]
+        fn test_override_struct_variant_width_exceeds_max_width() {
+            let mut config = Config::default();
+            config.override_value("struct_variant_width", "101");
+            assert_eq!(config.struct_variant_width(), 100);
+        }
+
+        #[test]
+        fn test_override_array_width_exceeds_max_width() {
+            let mut config = Config::default();
+            config.override_value("array_width", "101");
+            assert_eq!(config.array_width(), 100);
+        }
+
+        #[test]
+        fn test_override_chain_width_exceeds_max_width() {
+            let mut config = Config::default();
+            config.override_value("chain_width", "101");
+            assert_eq!(config.chain_width(), 100);
+        }
+
+        #[test]
+        fn test_override_single_line_if_else_max_width_exceeds_max_width() {
+            let mut config = Config::default();
+            config.override_value("single_line_if_else_max_width", "101");
+            assert_eq!(config.single_line_if_else_max_width(), 100);
+        }
+    }
+}
diff --git a/src/tools/rustfmt/src/config/options.rs b/src/tools/rustfmt/src/config/options.rs
new file mode 100644
index 0000000000000..3b91021813c16
--- /dev/null
+++ b/src/tools/rustfmt/src/config/options.rs
@@ -0,0 +1,444 @@
+use std::collections::{hash_set, HashSet};
+use std::fmt;
+use std::path::{Path, PathBuf};
+use std::str::FromStr;
+
+use itertools::Itertools;
+use rustfmt_config_proc_macro::config_type;
+use serde::de::{SeqAccess, Visitor};
+use serde::ser::SerializeSeq;
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+use crate::config::lists::*;
+use crate::config::Config;
+
+#[config_type]
+pub enum NewlineStyle {
+    /// Auto-detect based on the raw source input.
+    Auto,
+    /// Force CRLF (`\r\n`).
+    Windows,
+    /// Force CR (`\n).
+    Unix,
+    /// `\r\n` in Windows, `\n`` on other platforms.
+    Native,
+}
+
+#[config_type]
+/// Where to put the opening brace of items (`fn`, `impl`, etc.).
+pub enum BraceStyle {
+    /// Put the opening brace on the next line.
+    AlwaysNextLine,
+    /// Put the opening brace on the same line, if possible.
+    PreferSameLine,
+    /// Prefer the same line except where there is a where-clause, in which
+    /// case force the brace to be put on the next line.
+    SameLineWhere,
+}
+
+#[config_type]
+/// Where to put the opening brace of conditional expressions (`if`, `match`, etc.).
+pub enum ControlBraceStyle {
+    /// K&R style, Rust community default
+    AlwaysSameLine,
+    /// Stroustrup style
+    ClosingNextLine,
+    /// Allman style
+    AlwaysNextLine,
+}
+
+#[config_type]
+/// How to indent.
+pub enum IndentStyle {
+    /// First line on the same line as the opening brace, all lines aligned with
+    /// the first line.
+    Visual,
+    /// First line is on a new line and all lines align with **block** indent.
+    Block,
+}
+
+#[config_type]
+/// How to place a list-like items.
+/// FIXME: Issue-3581: this should be renamed to ItemsLayout when publishing 2.0
+pub enum Density {
+    /// Fit as much on one line as possible.
+    Compressed,
+    /// Items are placed horizontally if sufficient space, vertically otherwise.
+    Tall,
+    /// Place every item on a separate line.
+    Vertical,
+}
+
+#[config_type]
+/// Spacing around type combinators.
+pub enum TypeDensity {
+    /// No spaces around "=" and "+"
+    Compressed,
+    /// Spaces around " = " and " + "
+    Wide,
+}
+
+#[config_type]
+/// Heuristic settings that can be used to simply
+/// the configuration of the granular width configurations
+/// like `struct_lit_width`, `array_width`, etc.
+pub enum Heuristics {
+    /// Turn off any heuristics
+    Off,
+    /// Turn on max heuristics
+    Max,
+    /// Use scaled values based on the value of `max_width`
+    Default,
+}
+
+impl Density {
+    pub fn to_list_tactic(self, len: usize) -> ListTactic {
+        match self {
+            Density::Compressed => ListTactic::Mixed,
+            Density::Tall => ListTactic::HorizontalVertical,
+            Density::Vertical if len == 1 => ListTactic::Horizontal,
+            Density::Vertical => ListTactic::Vertical,
+        }
+    }
+}
+
+#[config_type]
+/// Configuration for import groups, i.e. sets of imports separated by newlines.
+pub enum GroupImportsTactic {
+    /// Keep groups as they are.
+    Preserve,
+    /// Discard existing groups, and create new groups for
+    ///  1. `std` / `core` / `alloc` imports
+    ///  2. other imports
+    ///  3. `self` / `crate` / `super` imports
+    StdExternalCrate,
+}
+
+#[config_type]
+/// How to merge imports.
+pub enum ImportGranularity {
+    /// Do not merge imports.
+    Preserve,
+    /// Use one `use` statement per crate.
+    Crate,
+    /// Use one `use` statement per module.
+    Module,
+    /// Use one `use` statement per imported item.
+    Item,
+}
+
+#[config_type]
+pub enum ReportTactic {
+    Always,
+    Unnumbered,
+    Never,
+}
+
+/// What Rustfmt should emit. Mostly corresponds to the `--emit` command line
+/// option.
+#[config_type]
+pub enum EmitMode {
+    /// Emits to files.
+    Files,
+    /// Writes the output to stdout.
+    Stdout,
+    /// Displays how much of the input file was processed
+    Coverage,
+    /// Unfancy stdout
+    Checkstyle,
+    /// Writes the resulting diffs in a JSON format. Returns an empty array
+    /// `[]` if there were no diffs.
+    Json,
+    /// Output the changed lines (for internal value only)
+    ModifiedLines,
+    /// Checks if a diff can be generated. If so, rustfmt outputs a diff and
+    /// quits with exit code 1.
+    /// This option is designed to be run in CI where a non-zero exit signifies
+    /// non-standard code formatting. Used for `--check`.
+    Diff,
+}
+
+/// Client-preference for coloured output.
+#[config_type]
+pub enum Color {
+    /// Always use color, whether it is a piped or terminal output
+    Always,
+    /// Never use color
+    Never,
+    /// Automatically use color, if supported by terminal
+    Auto,
+}
+
+#[config_type]
+/// rustfmt format style version.
+pub enum Version {
+    /// 1.x.y. When specified, rustfmt will format in the same style as 1.0.0.
+    One,
+    /// 2.x.y. When specified, rustfmt will format in the the latest style.
+    Two,
+}
+
+impl Color {
+    /// Whether we should use a coloured terminal.
+    pub fn use_colored_tty(self) -> bool {
+        match self {
+            Color::Always | Color::Auto => true,
+            Color::Never => false,
+        }
+    }
+}
+
+/// How chatty should Rustfmt be?
+#[config_type]
+pub enum Verbosity {
+    /// Emit more.
+    Verbose,
+    /// Default.
+    Normal,
+    /// Emit as little as possible.
+    Quiet,
+}
+
+#[derive(Deserialize, Serialize, Clone, Debug, PartialEq)]
+pub struct WidthHeuristics {
+    // Maximum width of the args of a function call before falling back
+    // to vertical formatting.
+    pub fn_call_width: usize,
+    // Maximum width of the args of a function-like attributes before falling
+    // back to vertical formatting.
+    pub attr_fn_like_width: usize,
+    // Maximum width in the body of a struct lit before falling back to
+    // vertical formatting.
+    pub struct_lit_width: usize,
+    // Maximum width in the body of a struct variant before falling back
+    // to vertical formatting.
+    pub struct_variant_width: usize,
+    // Maximum width of an array literal before falling back to vertical
+    // formatting.
+    pub array_width: usize,
+    // Maximum length of a chain to fit on a single line.
+    pub chain_width: usize,
+    // Maximum line length for single line if-else expressions. A value
+    // of zero means always break if-else expressions.
+    pub single_line_if_else_max_width: usize,
+}
+
+impl fmt::Display for WidthHeuristics {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
+impl WidthHeuristics {
+    // Using this WidthHeuristics means we ignore heuristics.
+    pub fn null() -> WidthHeuristics {
+        WidthHeuristics {
+            fn_call_width: usize::max_value(),
+            attr_fn_like_width: usize::max_value(),
+            struct_lit_width: 0,
+            struct_variant_width: 0,
+            array_width: usize::max_value(),
+            chain_width: usize::max_value(),
+            single_line_if_else_max_width: 0,
+        }
+    }
+
+    pub fn set(max_width: usize) -> WidthHeuristics {
+        WidthHeuristics {
+            fn_call_width: max_width,
+            attr_fn_like_width: max_width,
+            struct_lit_width: max_width,
+            struct_variant_width: max_width,
+            array_width: max_width,
+            chain_width: max_width,
+            single_line_if_else_max_width: max_width,
+        }
+    }
+
+    // scale the default WidthHeuristics according to max_width
+    pub fn scaled(max_width: usize) -> WidthHeuristics {
+        const DEFAULT_MAX_WIDTH: usize = 100;
+        let max_width_ratio = if max_width > DEFAULT_MAX_WIDTH {
+            let ratio = max_width as f32 / DEFAULT_MAX_WIDTH as f32;
+            // round to the closest 0.1
+            (ratio * 10.0).round() / 10.0
+        } else {
+            1.0
+        };
+        WidthHeuristics {
+            fn_call_width: (60.0 * max_width_ratio).round() as usize,
+            attr_fn_like_width: (70.0 * max_width_ratio).round() as usize,
+            struct_lit_width: (18.0 * max_width_ratio).round() as usize,
+            struct_variant_width: (35.0 * max_width_ratio).round() as usize,
+            array_width: (60.0 * max_width_ratio).round() as usize,
+            chain_width: (60.0 * max_width_ratio).round() as usize,
+            single_line_if_else_max_width: (50.0 * max_width_ratio).round() as usize,
+        }
+    }
+}
+
+impl ::std::str::FromStr for WidthHeuristics {
+    type Err = &'static str;
+
+    fn from_str(_: &str) -> Result<Self, Self::Err> {
+        Err("WidthHeuristics is not parsable")
+    }
+}
+
+impl Default for EmitMode {
+    fn default() -> EmitMode {
+        EmitMode::Files
+    }
+}
+
+/// A set of directories, files and modules that rustfmt should ignore.
+#[derive(Default, Clone, Debug, PartialEq)]
+pub struct IgnoreList {
+    /// A set of path specified in rustfmt.toml.
+    path_set: HashSet<PathBuf>,
+    /// A path to rustfmt.toml.
+    rustfmt_toml_path: PathBuf,
+}
+
+impl fmt::Display for IgnoreList {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "[{}]",
+            self.path_set
+                .iter()
+                .format_with(", ", |path, f| f(&format_args!(
+                    "{}",
+                    path.to_string_lossy()
+                )))
+        )
+    }
+}
+
+impl Serialize for IgnoreList {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut seq = serializer.serialize_seq(Some(self.path_set.len()))?;
+        for e in &self.path_set {
+            seq.serialize_element(e)?;
+        }
+        seq.end()
+    }
+}
+
+impl<'de> Deserialize<'de> for IgnoreList {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        struct HashSetVisitor;
+        impl<'v> Visitor<'v> for HashSetVisitor {
+            type Value = HashSet<PathBuf>;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+                formatter.write_str("a sequence of path")
+            }
+
+            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+            where
+                A: SeqAccess<'v>,
+            {
+                let mut path_set = HashSet::new();
+                while let Some(elem) = seq.next_element()? {
+                    path_set.insert(elem);
+                }
+                Ok(path_set)
+            }
+        }
+        Ok(IgnoreList {
+            path_set: deserializer.deserialize_seq(HashSetVisitor)?,
+            rustfmt_toml_path: PathBuf::new(),
+        })
+    }
+}
+
+impl<'a> IntoIterator for &'a IgnoreList {
+    type Item = &'a PathBuf;
+    type IntoIter = hash_set::Iter<'a, PathBuf>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.path_set.iter()
+    }
+}
+
+impl IgnoreList {
+    pub fn add_prefix(&mut self, dir: &Path) {
+        self.rustfmt_toml_path = dir.to_path_buf();
+    }
+
+    pub fn rustfmt_toml_path(&self) -> &Path {
+        &self.rustfmt_toml_path
+    }
+}
+
+impl FromStr for IgnoreList {
+    type Err = &'static str;
+
+    fn from_str(_: &str) -> Result<Self, Self::Err> {
+        Err("IgnoreList is not parsable")
+    }
+}
+
+/// Maps client-supplied options to Rustfmt's internals, mostly overriding
+/// values in a config with values from the command line.
+pub trait CliOptions {
+    fn apply_to(self, config: &mut Config);
+    fn config_path(&self) -> Option<&Path>;
+}
+
+/// The edition of the syntax and semntics of code (RFC 2052).
+#[config_type]
+pub enum Edition {
+    #[value = "2015"]
+    #[doc_hint = "2015"]
+    /// Edition 2015.
+    Edition2015,
+    #[value = "2018"]
+    #[doc_hint = "2018"]
+    /// Edition 2018.
+    Edition2018,
+    #[value = "2021"]
+    #[doc_hint = "2021"]
+    /// Edition 2021.
+    Edition2021,
+}
+
+impl Default for Edition {
+    fn default() -> Edition {
+        Edition::Edition2015
+    }
+}
+
+impl From<Edition> for rustc_span::edition::Edition {
+    fn from(edition: Edition) -> Self {
+        match edition {
+            Edition::Edition2015 => Self::Edition2015,
+            Edition::Edition2018 => Self::Edition2018,
+            Edition::Edition2021 => Self::Edition2021,
+        }
+    }
+}
+
+impl PartialOrd for Edition {
+    fn partial_cmp(&self, other: &Edition) -> Option<std::cmp::Ordering> {
+        rustc_span::edition::Edition::partial_cmp(&(*self).into(), &(*other).into())
+    }
+}
+
+/// Controls how rustfmt should handle leading pipes on match arms.
+#[config_type]
+pub enum MatchArmLeadingPipe {
+    /// Place leading pipes on all match arms
+    Always,
+    /// Never emit leading pipes on match arms
+    Never,
+    /// Preserve any existing leading pipes
+    Preserve,
+}
diff --git a/src/tools/rustfmt/src/coverage.rs b/src/tools/rustfmt/src/coverage.rs
new file mode 100644
index 0000000000000..f5a0497425145
--- /dev/null
+++ b/src/tools/rustfmt/src/coverage.rs
@@ -0,0 +1,15 @@
+use crate::{Config, EmitMode};
+use std::borrow::Cow;
+
+pub(crate) fn transform_missing_snippet<'a>(config: &Config, string: &'a str) -> Cow<'a, str> {
+    match config.emit_mode() {
+        EmitMode::Coverage => Cow::from(replace_chars(string)),
+        _ => Cow::from(string),
+    }
+}
+
+fn replace_chars(s: &str) -> String {
+    s.chars()
+        .map(|ch| if ch.is_whitespace() { ch } else { 'X' })
+        .collect()
+}
diff --git a/src/tools/rustfmt/src/emitter.rs b/src/tools/rustfmt/src/emitter.rs
new file mode 100644
index 0000000000000..dc2c99a301e38
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter.rs
@@ -0,0 +1,52 @@
+pub(crate) use self::checkstyle::*;
+pub(crate) use self::diff::*;
+pub(crate) use self::files::*;
+pub(crate) use self::files_with_backup::*;
+pub(crate) use self::json::*;
+pub(crate) use self::modified_lines::*;
+pub(crate) use self::stdout::*;
+use crate::FileName;
+use std::io::{self, Write};
+use std::path::Path;
+
+mod checkstyle;
+mod diff;
+mod files;
+mod files_with_backup;
+mod json;
+mod modified_lines;
+mod stdout;
+
+pub(crate) struct FormattedFile<'a> {
+    pub(crate) filename: &'a FileName,
+    pub(crate) original_text: &'a str,
+    pub(crate) formatted_text: &'a str,
+}
+
+#[derive(Debug, Default, Clone)]
+pub(crate) struct EmitterResult {
+    pub(crate) has_diff: bool,
+}
+
+pub(crate) trait Emitter {
+    fn emit_formatted_file(
+        &mut self,
+        output: &mut dyn Write,
+        formatted_file: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error>;
+
+    fn emit_header(&self, _output: &mut dyn Write) -> Result<(), io::Error> {
+        Ok(())
+    }
+
+    fn emit_footer(&self, _output: &mut dyn Write) -> Result<(), io::Error> {
+        Ok(())
+    }
+}
+
+fn ensure_real_path(filename: &FileName) -> &Path {
+    match *filename {
+        FileName::Real(ref path) => path,
+        _ => panic!("cannot format `{}` and emit to files", filename),
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/checkstyle.rs b/src/tools/rustfmt/src/emitter/checkstyle.rs
new file mode 100644
index 0000000000000..4448214f3ff2c
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/checkstyle.rs
@@ -0,0 +1,148 @@
+use self::xml::XmlEscaped;
+use super::*;
+use crate::rustfmt_diff::{make_diff, DiffLine, Mismatch};
+use std::io::{self, Write};
+use std::path::Path;
+
+mod xml;
+
+#[derive(Debug, Default)]
+pub(crate) struct CheckstyleEmitter;
+
+impl Emitter for CheckstyleEmitter {
+    fn emit_header(&self, output: &mut dyn Write) -> Result<(), io::Error> {
+        writeln!(output, r#"<?xml version="1.0" encoding="utf-8"?>"#)?;
+        write!(output, r#"<checkstyle version="4.3">"#)?;
+        Ok(())
+    }
+
+    fn emit_footer(&self, output: &mut dyn Write) -> Result<(), io::Error> {
+        writeln!(output, "</checkstyle>")
+    }
+
+    fn emit_formatted_file(
+        &mut self,
+        output: &mut dyn Write,
+        FormattedFile {
+            filename,
+            original_text,
+            formatted_text,
+        }: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error> {
+        const CONTEXT_SIZE: usize = 0;
+        let filename = ensure_real_path(filename);
+        let diff = make_diff(original_text, formatted_text, CONTEXT_SIZE);
+        output_checkstyle_file(output, filename, diff)?;
+        Ok(EmitterResult::default())
+    }
+}
+
+pub(crate) fn output_checkstyle_file<T>(
+    mut writer: T,
+    filename: &Path,
+    diff: Vec<Mismatch>,
+) -> Result<(), io::Error>
+where
+    T: Write,
+{
+    write!(writer, r#"<file name="{}">"#, filename.display())?;
+    for mismatch in diff {
+        let begin_line = mismatch.line_number;
+        let mut current_line;
+        let mut line_counter = 0;
+        for line in mismatch.lines {
+            // Do nothing with `DiffLine::Context` and `DiffLine::Resulting`.
+            if let DiffLine::Expected(message) = line {
+                current_line = begin_line + line_counter;
+                line_counter += 1;
+                write!(
+                    writer,
+                    r#"<error line="{}" severity="warning" message="Should be `{}`" />"#,
+                    current_line,
+                    XmlEscaped(&message)
+                )?;
+            }
+        }
+    }
+    write!(writer, "</file>")?;
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::path::PathBuf;
+
+    #[test]
+    fn emits_empty_record_on_file_with_no_mismatches() {
+        let file_name = "src/well_formatted.rs";
+        let mut writer = Vec::new();
+        let _ = output_checkstyle_file(&mut writer, &PathBuf::from(file_name), vec![]);
+        assert_eq!(
+            &writer[..],
+            format!(r#"<file name="{}"></file>"#, file_name).as_bytes()
+        );
+    }
+
+    // https://github.com/rust-lang/rustfmt/issues/1636
+    #[test]
+    fn emits_single_xml_tree_containing_all_files() {
+        let bin_file = "src/bin.rs";
+        let bin_original = vec!["fn main() {", "println!(\"Hello, world!\");", "}"];
+        let bin_formatted = vec!["fn main() {", "    println!(\"Hello, world!\");", "}"];
+        let lib_file = "src/lib.rs";
+        let lib_original = vec!["fn greet() {", "println!(\"Greetings!\");", "}"];
+        let lib_formatted = vec!["fn greet() {", "    println!(\"Greetings!\");", "}"];
+        let mut writer = Vec::new();
+        let mut emitter = CheckstyleEmitter::default();
+        let _ = emitter.emit_header(&mut writer);
+        let _ = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from(bin_file)),
+                    original_text: &bin_original.join("\n"),
+                    formatted_text: &bin_formatted.join("\n"),
+                },
+            )
+            .unwrap();
+        let _ = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from(lib_file)),
+                    original_text: &lib_original.join("\n"),
+                    formatted_text: &lib_formatted.join("\n"),
+                },
+            )
+            .unwrap();
+        let _ = emitter.emit_footer(&mut writer);
+        let exp_bin_xml = vec![
+            format!(r#"<file name="{}">"#, bin_file),
+            format!(
+                r#"<error line="2" severity="warning" message="Should be `{}`" />"#,
+                XmlEscaped(&r#"    println!("Hello, world!");"#),
+            ),
+            String::from("</file>"),
+        ];
+        let exp_lib_xml = vec![
+            format!(r#"<file name="{}">"#, lib_file),
+            format!(
+                r#"<error line="2" severity="warning" message="Should be `{}`" />"#,
+                XmlEscaped(&r#"    println!("Greetings!");"#),
+            ),
+            String::from("</file>"),
+        ];
+        assert_eq!(
+            String::from_utf8(writer).unwrap(),
+            vec![
+                r#"<?xml version="1.0" encoding="utf-8"?>"#,
+                "\n",
+                r#"<checkstyle version="4.3">"#,
+                &format!("{}{}", exp_bin_xml.join(""), exp_lib_xml.join("")),
+                "</checkstyle>\n",
+            ]
+            .join(""),
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/checkstyle/xml.rs b/src/tools/rustfmt/src/emitter/checkstyle/xml.rs
new file mode 100644
index 0000000000000..f251aabe8785f
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/checkstyle/xml.rs
@@ -0,0 +1,52 @@
+use std::fmt::{self, Display};
+
+/// Convert special characters into XML entities.
+/// This is needed for checkstyle output.
+pub(super) struct XmlEscaped<'a>(pub(super) &'a str);
+
+impl<'a> Display for XmlEscaped<'a> {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        for char in self.0.chars() {
+            match char {
+                '<' => write!(formatter, "&lt;"),
+                '>' => write!(formatter, "&gt;"),
+                '"' => write!(formatter, "&quot;"),
+                '\'' => write!(formatter, "&apos;"),
+                '&' => write!(formatter, "&amp;"),
+                _ => write!(formatter, "{}", char),
+            }?;
+        }
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn special_characters_are_escaped() {
+        assert_eq!(
+            "&lt;&gt;&quot;&apos;&amp;",
+            format!("{}", XmlEscaped(r#"<>"'&"#)),
+        );
+    }
+
+    #[test]
+    fn special_characters_are_escaped_in_string_with_other_characters() {
+        assert_eq!(
+            "The quick brown &quot;🦊&quot; jumps &lt;over&gt; the lazy 🐶",
+            format!(
+                "{}",
+                XmlEscaped(r#"The quick brown "🦊" jumps <over> the lazy 🐶"#)
+            ),
+        );
+    }
+
+    #[test]
+    fn other_characters_are_not_escaped() {
+        let string = "The quick brown 🦊 jumps over the lazy 🐶";
+        assert_eq!(string, format!("{}", XmlEscaped(string)));
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/diff.rs b/src/tools/rustfmt/src/emitter/diff.rs
new file mode 100644
index 0000000000000..9be4fb28f993f
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/diff.rs
@@ -0,0 +1,138 @@
+use super::*;
+use crate::config::Config;
+use crate::rustfmt_diff::{make_diff, print_diff};
+
+pub(crate) struct DiffEmitter {
+    config: Config,
+}
+
+impl DiffEmitter {
+    pub(crate) fn new(config: Config) -> Self {
+        Self { config }
+    }
+}
+
+impl Emitter for DiffEmitter {
+    fn emit_formatted_file(
+        &mut self,
+        output: &mut dyn Write,
+        FormattedFile {
+            filename,
+            original_text,
+            formatted_text,
+        }: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error> {
+        const CONTEXT_SIZE: usize = 3;
+        let mismatch = make_diff(&original_text, formatted_text, CONTEXT_SIZE);
+        let has_diff = !mismatch.is_empty();
+
+        if has_diff {
+            if self.config.print_misformatted_file_names() {
+                writeln!(output, "{}", ensure_real_path(filename).display())?;
+            } else {
+                print_diff(
+                    mismatch,
+                    |line_num| format!("Diff in {} at line {}:", filename, line_num),
+                    &self.config,
+                );
+            }
+        } else if original_text != formatted_text {
+            // This occurs when the only difference between the original and formatted values
+            // is the newline style. This happens because The make_diff function compares the
+            // original and formatted values line by line, independent of line endings.
+            let file_path = ensure_real_path(filename);
+            writeln!(output, "Incorrect newline style in {}", file_path.display())?;
+            return Ok(EmitterResult { has_diff: true });
+        }
+
+        return Ok(EmitterResult { has_diff });
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::config::Config;
+    use crate::FileName;
+    use std::path::PathBuf;
+
+    #[test]
+    fn does_not_print_when_no_files_reformatted() {
+        let mut writer = Vec::new();
+        let config = Config::default();
+        let mut emitter = DiffEmitter::new(config);
+        let result = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from("src/lib.rs")),
+                    original_text: "fn empty() {}\n",
+                    formatted_text: "fn empty() {}\n",
+                },
+            )
+            .unwrap();
+        assert_eq!(result.has_diff, false);
+        assert_eq!(writer.len(), 0);
+    }
+
+    #[test]
+    fn prints_file_names_when_config_is_enabled() {
+        let bin_file = "src/bin.rs";
+        let bin_original = "fn main() {\nprintln!(\"Hello, world!\");\n}";
+        let bin_formatted = "fn main() {\n    println!(\"Hello, world!\");\n}";
+        let lib_file = "src/lib.rs";
+        let lib_original = "fn greet() {\nprintln!(\"Greetings!\");\n}";
+        let lib_formatted = "fn greet() {\n    println!(\"Greetings!\");\n}";
+
+        let mut writer = Vec::new();
+        let mut config = Config::default();
+        config.set().print_misformatted_file_names(true);
+        let mut emitter = DiffEmitter::new(config);
+        let _ = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from(bin_file)),
+                    original_text: bin_original,
+                    formatted_text: bin_formatted,
+                },
+            )
+            .unwrap();
+        let _ = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from(lib_file)),
+                    original_text: lib_original,
+                    formatted_text: lib_formatted,
+                },
+            )
+            .unwrap();
+
+        assert_eq!(
+            String::from_utf8(writer).unwrap(),
+            format!("{}\n{}\n", bin_file, lib_file),
+        )
+    }
+
+    #[test]
+    fn prints_newline_message_with_only_newline_style_diff() {
+        let mut writer = Vec::new();
+        let config = Config::default();
+        let mut emitter = DiffEmitter::new(config);
+        let _ = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from("src/lib.rs")),
+                    original_text: "fn empty() {}\n",
+                    formatted_text: "fn empty() {}\r\n",
+                },
+            )
+            .unwrap();
+        assert_eq!(
+            String::from_utf8(writer).unwrap(),
+            String::from("Incorrect newline style in src/lib.rs\n")
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/files.rs b/src/tools/rustfmt/src/emitter/files.rs
new file mode 100644
index 0000000000000..6360b73ee615e
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/files.rs
@@ -0,0 +1,37 @@
+use super::*;
+use std::fs;
+
+#[derive(Debug, Default)]
+pub(crate) struct FilesEmitter {
+    print_misformatted_file_names: bool,
+}
+
+impl FilesEmitter {
+    pub(crate) fn new(print_misformatted_file_names: bool) -> Self {
+        Self {
+            print_misformatted_file_names,
+        }
+    }
+}
+
+impl Emitter for FilesEmitter {
+    fn emit_formatted_file(
+        &mut self,
+        output: &mut dyn Write,
+        FormattedFile {
+            filename,
+            original_text,
+            formatted_text,
+        }: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error> {
+        // Write text directly over original file if there is a diff.
+        let filename = ensure_real_path(filename);
+        if original_text != formatted_text {
+            fs::write(filename, formatted_text)?;
+            if self.print_misformatted_file_names {
+                writeln!(output, "{}", filename.display())?;
+            }
+        }
+        Ok(EmitterResult::default())
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/files_with_backup.rs b/src/tools/rustfmt/src/emitter/files_with_backup.rs
new file mode 100644
index 0000000000000..4c15f6fa5ec7a
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/files_with_backup.rs
@@ -0,0 +1,31 @@
+use super::*;
+use std::fs;
+
+#[derive(Debug, Default)]
+pub(crate) struct FilesWithBackupEmitter;
+
+impl Emitter for FilesWithBackupEmitter {
+    fn emit_formatted_file(
+        &mut self,
+        _output: &mut dyn Write,
+        FormattedFile {
+            filename,
+            original_text,
+            formatted_text,
+        }: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error> {
+        let filename = ensure_real_path(filename);
+        if original_text != formatted_text {
+            // Do a little dance to make writing safer - write to a temp file
+            // rename the original to a .bk, then rename the temp file to the
+            // original.
+            let tmp_name = filename.with_extension("tmp");
+            let bk_name = filename.with_extension("bk");
+
+            fs::write(&tmp_name, formatted_text)?;
+            fs::rename(filename, bk_name)?;
+            fs::rename(tmp_name, filename)?;
+        }
+        Ok(EmitterResult::default())
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/json.rs b/src/tools/rustfmt/src/emitter/json.rs
new file mode 100644
index 0000000000000..269dd2d4daf57
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/json.rs
@@ -0,0 +1,349 @@
+use super::*;
+use crate::rustfmt_diff::{make_diff, DiffLine, Mismatch};
+use serde::Serialize;
+use serde_json::to_string as to_json_string;
+use std::io::{self, Write};
+use std::path::Path;
+
+#[derive(Debug, Default)]
+pub(crate) struct JsonEmitter {
+    num_files: u32,
+}
+
+#[derive(Debug, Default, Serialize)]
+struct MismatchedBlock {
+    original_begin_line: u32,
+    original_end_line: u32,
+    expected_begin_line: u32,
+    expected_end_line: u32,
+    original: String,
+    expected: String,
+}
+
+#[derive(Debug, Default, Serialize)]
+struct MismatchedFile {
+    name: String,
+    mismatches: Vec<MismatchedBlock>,
+}
+
+impl Emitter for JsonEmitter {
+    fn emit_header(&self, output: &mut dyn Write) -> Result<(), io::Error> {
+        write!(output, "[")?;
+        Ok(())
+    }
+
+    fn emit_footer(&self, output: &mut dyn Write) -> Result<(), io::Error> {
+        write!(output, "]")?;
+        Ok(())
+    }
+
+    fn emit_formatted_file(
+        &mut self,
+        output: &mut dyn Write,
+        FormattedFile {
+            filename,
+            original_text,
+            formatted_text,
+        }: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error> {
+        const CONTEXT_SIZE: usize = 0;
+        let filename = ensure_real_path(filename);
+        let diff = make_diff(original_text, formatted_text, CONTEXT_SIZE);
+        let has_diff = !diff.is_empty();
+
+        if has_diff {
+            output_json_file(output, filename, diff, self.num_files)?;
+            self.num_files += 1;
+        }
+
+        Ok(EmitterResult { has_diff })
+    }
+}
+
+fn output_json_file<T>(
+    mut writer: T,
+    filename: &Path,
+    diff: Vec<Mismatch>,
+    num_emitted_files: u32,
+) -> Result<(), io::Error>
+where
+    T: Write,
+{
+    let mut mismatches = vec![];
+    for mismatch in diff {
+        let original_begin_line = mismatch.line_number_orig;
+        let expected_begin_line = mismatch.line_number;
+        let mut original_end_line = original_begin_line;
+        let mut expected_end_line = expected_begin_line;
+        let mut original_line_counter = 0;
+        let mut expected_line_counter = 0;
+        let mut original_lines = vec![];
+        let mut expected_lines = vec![];
+
+        for line in mismatch.lines {
+            match line {
+                DiffLine::Expected(msg) => {
+                    expected_end_line = expected_begin_line + expected_line_counter;
+                    expected_line_counter += 1;
+                    expected_lines.push(msg)
+                }
+                DiffLine::Resulting(msg) => {
+                    original_end_line = original_begin_line + original_line_counter;
+                    original_line_counter += 1;
+                    original_lines.push(msg)
+                }
+                DiffLine::Context(_) => continue,
+            }
+        }
+
+        mismatches.push(MismatchedBlock {
+            original_begin_line,
+            original_end_line,
+            expected_begin_line,
+            expected_end_line,
+            original: original_lines.join("\n"),
+            expected: expected_lines.join("\n"),
+        });
+    }
+    let json = to_json_string(&MismatchedFile {
+        name: String::from(filename.to_str().unwrap()),
+        mismatches,
+    })?;
+    let prefix = if num_emitted_files > 0 { "," } else { "" };
+    write!(writer, "{}{}", prefix, &json)?;
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::FileName;
+    use std::path::PathBuf;
+
+    #[test]
+    fn expected_line_range_correct_when_single_line_split() {
+        let file = "foo/bar.rs";
+        let mismatched_file = MismatchedFile {
+            name: String::from(file),
+            mismatches: vec![MismatchedBlock {
+                original_begin_line: 79,
+                original_end_line: 79,
+                expected_begin_line: 79,
+                expected_end_line: 82,
+                original: String::from("fn Foo<T>() where T: Bar {"),
+                expected: String::from("fn Foo<T>()\nwhere\n    T: Bar,\n{"),
+            }],
+        };
+        let mismatch = Mismatch {
+            line_number: 79,
+            line_number_orig: 79,
+            lines: vec![
+                DiffLine::Resulting(String::from("fn Foo<T>() where T: Bar {")),
+                DiffLine::Expected(String::from("fn Foo<T>()")),
+                DiffLine::Expected(String::from("where")),
+                DiffLine::Expected(String::from("    T: Bar,")),
+                DiffLine::Expected(String::from("{")),
+            ],
+        };
+
+        let mut writer = Vec::new();
+        let exp_json = to_json_string(&mismatched_file).unwrap();
+        let _ = output_json_file(&mut writer, &PathBuf::from(file), vec![mismatch], 0);
+        assert_eq!(&writer[..], format!("{}", exp_json).as_bytes());
+    }
+
+    #[test]
+    fn context_lines_ignored() {
+        let file = "src/lib.rs";
+        let mismatched_file = MismatchedFile {
+            name: String::from(file),
+            mismatches: vec![MismatchedBlock {
+                original_begin_line: 5,
+                original_end_line: 5,
+                expected_begin_line: 5,
+                expected_end_line: 5,
+                original: String::from(
+                    "fn foo(_x: &u64) -> Option<&(dyn::std::error::Error + 'static)> {",
+                ),
+                expected: String::from(
+                    "fn foo(_x: &u64) -> Option<&(dyn ::std::error::Error + 'static)> {",
+                ),
+            }],
+        };
+        let mismatch = Mismatch {
+            line_number: 5,
+            line_number_orig: 5,
+            lines: vec![
+                DiffLine::Context(String::new()),
+                DiffLine::Resulting(String::from(
+                    "fn foo(_x: &u64) -> Option<&(dyn::std::error::Error + 'static)> {",
+                )),
+                DiffLine::Context(String::new()),
+                DiffLine::Expected(String::from(
+                    "fn foo(_x: &u64) -> Option<&(dyn ::std::error::Error + 'static)> {",
+                )),
+                DiffLine::Context(String::new()),
+            ],
+        };
+
+        let mut writer = Vec::new();
+        let exp_json = to_json_string(&mismatched_file).unwrap();
+        let _ = output_json_file(&mut writer, &PathBuf::from(file), vec![mismatch], 0);
+        assert_eq!(&writer[..], format!("{}", exp_json).as_bytes());
+    }
+
+    #[test]
+    fn emits_empty_array_on_no_diffs() {
+        let mut writer = Vec::new();
+        let mut emitter = JsonEmitter::default();
+        let _ = emitter.emit_header(&mut writer);
+        let result = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from("src/lib.rs")),
+                    original_text: "fn empty() {}\n",
+                    formatted_text: "fn empty() {}\n",
+                },
+            )
+            .unwrap();
+        let _ = emitter.emit_footer(&mut writer);
+        assert_eq!(result.has_diff, false);
+        assert_eq!(&writer[..], "[]".as_bytes());
+    }
+
+    #[test]
+    fn emits_array_with_files_with_diffs() {
+        let file_name = "src/bin.rs";
+        let original = vec![
+            "fn main() {",
+            "println!(\"Hello, world!\");",
+            "}",
+            "",
+            "#[cfg(test)]",
+            "mod tests {",
+            "#[test]",
+            "fn it_works() {",
+            "    assert_eq!(2 + 2, 4);",
+            "}",
+            "}",
+        ];
+        let formatted = vec![
+            "fn main() {",
+            "    println!(\"Hello, world!\");",
+            "}",
+            "",
+            "#[cfg(test)]",
+            "mod tests {",
+            "    #[test]",
+            "    fn it_works() {",
+            "        assert_eq!(2 + 2, 4);",
+            "    }",
+            "}",
+        ];
+        let mut writer = Vec::new();
+        let mut emitter = JsonEmitter::default();
+        let _ = emitter.emit_header(&mut writer);
+        let result = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from(file_name)),
+                    original_text: &original.join("\n"),
+                    formatted_text: &formatted.join("\n"),
+                },
+            )
+            .unwrap();
+        let _ = emitter.emit_footer(&mut writer);
+        let exp_json = to_json_string(&MismatchedFile {
+            name: String::from(file_name),
+            mismatches: vec![
+                MismatchedBlock {
+                    original_begin_line: 2,
+                    original_end_line: 2,
+                    expected_begin_line: 2,
+                    expected_end_line: 2,
+                    original: String::from("println!(\"Hello, world!\");"),
+                    expected: String::from("    println!(\"Hello, world!\");"),
+                },
+                MismatchedBlock {
+                    original_begin_line: 7,
+                    original_end_line: 10,
+                    expected_begin_line: 7,
+                    expected_end_line: 10,
+                    original: String::from(
+                        "#[test]\nfn it_works() {\n    assert_eq!(2 + 2, 4);\n}",
+                    ),
+                    expected: String::from(
+                        "    #[test]\n    fn it_works() {\n        assert_eq!(2 + 2, 4);\n    }",
+                    ),
+                },
+            ],
+        })
+        .unwrap();
+        assert_eq!(result.has_diff, true);
+        assert_eq!(&writer[..], format!("[{}]", exp_json).as_bytes());
+    }
+
+    #[test]
+    fn emits_valid_json_with_multiple_files() {
+        let bin_file = "src/bin.rs";
+        let bin_original = vec!["fn main() {", "println!(\"Hello, world!\");", "}"];
+        let bin_formatted = vec!["fn main() {", "    println!(\"Hello, world!\");", "}"];
+        let lib_file = "src/lib.rs";
+        let lib_original = vec!["fn greet() {", "println!(\"Greetings!\");", "}"];
+        let lib_formatted = vec!["fn greet() {", "    println!(\"Greetings!\");", "}"];
+        let mut writer = Vec::new();
+        let mut emitter = JsonEmitter::default();
+        let _ = emitter.emit_header(&mut writer);
+        let _ = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from(bin_file)),
+                    original_text: &bin_original.join("\n"),
+                    formatted_text: &bin_formatted.join("\n"),
+                },
+            )
+            .unwrap();
+        let _ = emitter
+            .emit_formatted_file(
+                &mut writer,
+                FormattedFile {
+                    filename: &FileName::Real(PathBuf::from(lib_file)),
+                    original_text: &lib_original.join("\n"),
+                    formatted_text: &lib_formatted.join("\n"),
+                },
+            )
+            .unwrap();
+        let _ = emitter.emit_footer(&mut writer);
+        let exp_bin_json = to_json_string(&MismatchedFile {
+            name: String::from(bin_file),
+            mismatches: vec![MismatchedBlock {
+                original_begin_line: 2,
+                original_end_line: 2,
+                expected_begin_line: 2,
+                expected_end_line: 2,
+                original: String::from("println!(\"Hello, world!\");"),
+                expected: String::from("    println!(\"Hello, world!\");"),
+            }],
+        })
+        .unwrap();
+        let exp_lib_json = to_json_string(&MismatchedFile {
+            name: String::from(lib_file),
+            mismatches: vec![MismatchedBlock {
+                original_begin_line: 2,
+                original_end_line: 2,
+                expected_begin_line: 2,
+                expected_end_line: 2,
+                original: String::from("println!(\"Greetings!\");"),
+                expected: String::from("    println!(\"Greetings!\");"),
+            }],
+        })
+        .unwrap();
+        assert_eq!(
+            &writer[..],
+            format!("[{},{}]", exp_bin_json, exp_lib_json).as_bytes()
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/modified_lines.rs b/src/tools/rustfmt/src/emitter/modified_lines.rs
new file mode 100644
index 0000000000000..94ff570a8a9cb
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/modified_lines.rs
@@ -0,0 +1,24 @@
+use super::*;
+use crate::rustfmt_diff::{make_diff, ModifiedLines};
+use std::io::Write;
+
+#[derive(Debug, Default)]
+pub(crate) struct ModifiedLinesEmitter;
+
+impl Emitter for ModifiedLinesEmitter {
+    fn emit_formatted_file(
+        &mut self,
+        output: &mut dyn Write,
+        FormattedFile {
+            original_text,
+            formatted_text,
+            ..
+        }: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error> {
+        const CONTEXT_SIZE: usize = 0;
+        let mismatch = make_diff(original_text, formatted_text, CONTEXT_SIZE);
+        let has_diff = !mismatch.is_empty();
+        write!(output, "{}", ModifiedLines::from(mismatch))?;
+        Ok(EmitterResult { has_diff })
+    }
+}
diff --git a/src/tools/rustfmt/src/emitter/stdout.rs b/src/tools/rustfmt/src/emitter/stdout.rs
new file mode 100644
index 0000000000000..9fddd515e4921
--- /dev/null
+++ b/src/tools/rustfmt/src/emitter/stdout.rs
@@ -0,0 +1,32 @@
+use super::*;
+use crate::config::Verbosity;
+use std::io::Write;
+
+#[derive(Debug)]
+pub(crate) struct StdoutEmitter {
+    verbosity: Verbosity,
+}
+
+impl StdoutEmitter {
+    pub(crate) fn new(verbosity: Verbosity) -> Self {
+        Self { verbosity }
+    }
+}
+
+impl Emitter for StdoutEmitter {
+    fn emit_formatted_file(
+        &mut self,
+        output: &mut dyn Write,
+        FormattedFile {
+            filename,
+            formatted_text,
+            ..
+        }: FormattedFile<'_>,
+    ) -> Result<EmitterResult, io::Error> {
+        if self.verbosity != Verbosity::Quiet {
+            writeln!(output, "{}:\n", filename)?;
+        }
+        write!(output, "{}", formatted_text)?;
+        Ok(EmitterResult::default())
+    }
+}
diff --git a/src/tools/rustfmt/src/expr.rs b/src/tools/rustfmt/src/expr.rs
new file mode 100644
index 0000000000000..ced382c4915a1
--- /dev/null
+++ b/src/tools/rustfmt/src/expr.rs
@@ -0,0 +1,2076 @@
+use std::borrow::Cow;
+use std::cmp::min;
+
+use itertools::Itertools;
+use rustc_ast::token::{DelimToken, LitKind};
+use rustc_ast::{ast, ptr};
+use rustc_span::{BytePos, Span};
+
+use crate::chains::rewrite_chain;
+use crate::closures;
+use crate::comment::{
+    combine_strs_with_missing_comments, contains_comment, recover_comment_removed, rewrite_comment,
+    rewrite_missing_comment, CharClasses, FindUncommented,
+};
+use crate::config::lists::*;
+use crate::config::{Config, ControlBraceStyle, IndentStyle, Version};
+use crate::lists::{
+    definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
+    struct_lit_tactic, write_list, ListFormatting, Separator,
+};
+use crate::macros::{rewrite_macro, MacroPosition};
+use crate::matches::rewrite_match;
+use crate::overflow::{self, IntoOverflowableItem, OverflowableItem};
+use crate::pairs::{rewrite_all_pairs, rewrite_pair, PairParts};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::{Indent, Shape};
+use crate::source_map::{LineRangeUtils, SpanUtils};
+use crate::spanned::Spanned;
+use crate::string::{rewrite_string, StringFormat};
+use crate::types::{rewrite_path, PathContext};
+use crate::utils::{
+    colon_spaces, contains_skip, count_newlines, first_line_ends_with, inner_attributes,
+    last_line_extendable, last_line_width, mk_sp, outer_attributes, semicolon_for_expr,
+    unicode_str_width, wrap_str,
+};
+use crate::vertical::rewrite_with_alignment;
+use crate::visitor::FmtVisitor;
+
+impl Rewrite for ast::Expr {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        format_expr(self, ExprType::SubExpression, context, shape)
+    }
+}
+
+#[derive(Copy, Clone, PartialEq)]
+pub(crate) enum ExprType {
+    Statement,
+    SubExpression,
+}
+
+pub(crate) fn format_expr(
+    expr: &ast::Expr,
+    expr_type: ExprType,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    skip_out_of_file_lines_range!(context, expr.span);
+
+    if contains_skip(&*expr.attrs) {
+        return Some(context.snippet(expr.span()).to_owned());
+    }
+    let shape = if expr_type == ExprType::Statement && semicolon_for_expr(context, expr) {
+        shape.sub_width(1)?
+    } else {
+        shape
+    };
+
+    let expr_rw = match expr.kind {
+        ast::ExprKind::Array(ref expr_vec) => rewrite_array(
+            "",
+            expr_vec.iter(),
+            expr.span,
+            context,
+            shape,
+            choose_separator_tactic(context, expr.span),
+            None,
+        ),
+        ast::ExprKind::Lit(ref l) => {
+            if let Some(expr_rw) = rewrite_literal(context, l, shape) {
+                Some(expr_rw)
+            } else {
+                if let LitKind::StrRaw(_) = l.token.kind {
+                    Some(context.snippet(l.span).trim().into())
+                } else {
+                    None
+                }
+            }
+        }
+        ast::ExprKind::Call(ref callee, ref args) => {
+            let inner_span = mk_sp(callee.span.hi(), expr.span.hi());
+            let callee_str = callee.rewrite(context, shape)?;
+            rewrite_call(context, &callee_str, args, inner_span, shape)
+        }
+        ast::ExprKind::Paren(ref subexpr) => rewrite_paren(context, subexpr, shape, expr.span),
+        ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
+            // FIXME: format comments between operands and operator
+            rewrite_all_pairs(expr, shape, context).or_else(|| {
+                rewrite_pair(
+                    &**lhs,
+                    &**rhs,
+                    PairParts::infix(&format!(" {} ", context.snippet(op.span))),
+                    context,
+                    shape,
+                    context.config.binop_separator(),
+                )
+            })
+        }
+        ast::ExprKind::Unary(op, ref subexpr) => rewrite_unary_op(context, op, subexpr, shape),
+        ast::ExprKind::Struct(ref struct_expr) => {
+            let ast::StructExpr { fields, path, rest } = &**struct_expr;
+            rewrite_struct_lit(context, path, fields, rest, &expr.attrs, expr.span, shape)
+        }
+        ast::ExprKind::Tup(ref items) => {
+            rewrite_tuple(context, items.iter(), expr.span, shape, items.len() == 1)
+        }
+        ast::ExprKind::Let(..) => None,
+        ast::ExprKind::If(..)
+        | ast::ExprKind::ForLoop(..)
+        | ast::ExprKind::Loop(..)
+        | ast::ExprKind::While(..) => to_control_flow(expr, expr_type)
+            .and_then(|control_flow| control_flow.rewrite(context, shape)),
+        ast::ExprKind::ConstBlock(ref anon_const) => {
+            Some(format!("const {}", anon_const.rewrite(context, shape)?))
+        }
+        ast::ExprKind::Block(ref block, opt_label) => {
+            match expr_type {
+                ExprType::Statement => {
+                    if is_unsafe_block(block) {
+                        rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
+                    } else if let rw @ Some(_) =
+                        rewrite_empty_block(context, block, Some(&expr.attrs), opt_label, "", shape)
+                    {
+                        // Rewrite block without trying to put it in a single line.
+                        rw
+                    } else {
+                        let prefix = block_prefix(context, block, shape)?;
+
+                        rewrite_block_with_visitor(
+                            context,
+                            &prefix,
+                            block,
+                            Some(&expr.attrs),
+                            opt_label,
+                            shape,
+                            true,
+                        )
+                    }
+                }
+                ExprType::SubExpression => {
+                    rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
+                }
+            }
+        }
+        ast::ExprKind::Match(ref cond, ref arms) => {
+            rewrite_match(context, cond, arms, shape, expr.span, &expr.attrs)
+        }
+        ast::ExprKind::Path(ref qself, ref path) => {
+            rewrite_path(context, PathContext::Expr, qself.as_ref(), path, shape)
+        }
+        ast::ExprKind::Assign(ref lhs, ref rhs, _) => {
+            rewrite_assignment(context, lhs, rhs, None, shape)
+        }
+        ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
+            rewrite_assignment(context, lhs, rhs, Some(op), shape)
+        }
+        ast::ExprKind::Continue(ref opt_label) => {
+            let id_str = match *opt_label {
+                Some(label) => format!(" {}", label.ident),
+                None => String::new(),
+            };
+            Some(format!("continue{}", id_str))
+        }
+        ast::ExprKind::Break(ref opt_label, ref opt_expr) => {
+            let id_str = match *opt_label {
+                Some(label) => format!(" {}", label.ident),
+                None => String::new(),
+            };
+
+            if let Some(ref expr) = *opt_expr {
+                rewrite_unary_prefix(context, &format!("break{} ", id_str), &**expr, shape)
+            } else {
+                Some(format!("break{}", id_str))
+            }
+        }
+        ast::ExprKind::Yield(ref opt_expr) => {
+            if let Some(ref expr) = *opt_expr {
+                rewrite_unary_prefix(context, "yield ", &**expr, shape)
+            } else {
+                Some("yield".to_string())
+            }
+        }
+        ast::ExprKind::Closure(capture, ref is_async, movability, ref fn_decl, ref body, _) => {
+            closures::rewrite_closure(
+                capture, is_async, movability, fn_decl, body, expr.span, context, shape,
+            )
+        }
+        ast::ExprKind::Try(..) | ast::ExprKind::Field(..) | ast::ExprKind::MethodCall(..) => {
+            rewrite_chain(expr, context, shape)
+        }
+        ast::ExprKind::MacCall(ref mac) => {
+            rewrite_macro(mac, None, context, shape, MacroPosition::Expression).or_else(|| {
+                wrap_str(
+                    context.snippet(expr.span).to_owned(),
+                    context.config.max_width(),
+                    shape,
+                )
+            })
+        }
+        ast::ExprKind::Ret(None) => Some("return".to_owned()),
+        ast::ExprKind::Ret(Some(ref expr)) => {
+            rewrite_unary_prefix(context, "return ", &**expr, shape)
+        }
+        ast::ExprKind::Box(ref expr) => rewrite_unary_prefix(context, "box ", &**expr, shape),
+        ast::ExprKind::AddrOf(borrow_kind, mutability, ref expr) => {
+            rewrite_expr_addrof(context, borrow_kind, mutability, expr, shape)
+        }
+        ast::ExprKind::Cast(ref expr, ref ty) => rewrite_pair(
+            &**expr,
+            &**ty,
+            PairParts::infix(" as "),
+            context,
+            shape,
+            SeparatorPlace::Front,
+        ),
+        ast::ExprKind::Type(ref expr, ref ty) => rewrite_pair(
+            &**expr,
+            &**ty,
+            PairParts::infix(": "),
+            context,
+            shape,
+            SeparatorPlace::Back,
+        ),
+        ast::ExprKind::Index(ref expr, ref index) => {
+            rewrite_index(&**expr, &**index, context, shape)
+        }
+        ast::ExprKind::Repeat(ref expr, ref repeats) => rewrite_pair(
+            &**expr,
+            &*repeats.value,
+            PairParts::new("[", "; ", "]"),
+            context,
+            shape,
+            SeparatorPlace::Back,
+        ),
+        ast::ExprKind::Range(ref lhs, ref rhs, limits) => {
+            let delim = match limits {
+                ast::RangeLimits::HalfOpen => "..",
+                ast::RangeLimits::Closed => "..=",
+            };
+
+            fn needs_space_before_range(context: &RewriteContext<'_>, lhs: &ast::Expr) -> bool {
+                match lhs.kind {
+                    ast::ExprKind::Lit(ref lit) => match lit.kind {
+                        ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
+                            context.snippet(lit.span).ends_with('.')
+                        }
+                        _ => false,
+                    },
+                    ast::ExprKind::Unary(_, ref expr) => needs_space_before_range(context, &expr),
+                    _ => false,
+                }
+            }
+
+            fn needs_space_after_range(rhs: &ast::Expr) -> bool {
+                match rhs.kind {
+                    // Don't format `.. ..` into `....`, which is invalid.
+                    //
+                    // This check is unnecessary for `lhs`, because a range
+                    // starting from another range needs parentheses as `(x ..) ..`
+                    // (`x .. ..` is a range from `x` to `..`).
+                    ast::ExprKind::Range(None, _, _) => true,
+                    _ => false,
+                }
+            }
+
+            let default_sp_delim = |lhs: Option<&ast::Expr>, rhs: Option<&ast::Expr>| {
+                let space_if = |b: bool| if b { " " } else { "" };
+
+                format!(
+                    "{}{}{}",
+                    lhs.map_or("", |lhs| space_if(needs_space_before_range(context, lhs))),
+                    delim,
+                    rhs.map_or("", |rhs| space_if(needs_space_after_range(rhs))),
+                )
+            };
+
+            match (lhs.as_ref().map(|x| &**x), rhs.as_ref().map(|x| &**x)) {
+                (Some(lhs), Some(rhs)) => {
+                    let sp_delim = if context.config.spaces_around_ranges() {
+                        format!(" {} ", delim)
+                    } else {
+                        default_sp_delim(Some(lhs), Some(rhs))
+                    };
+                    rewrite_pair(
+                        &*lhs,
+                        &*rhs,
+                        PairParts::infix(&sp_delim),
+                        context,
+                        shape,
+                        context.config.binop_separator(),
+                    )
+                }
+                (None, Some(rhs)) => {
+                    let sp_delim = if context.config.spaces_around_ranges() {
+                        format!("{} ", delim)
+                    } else {
+                        default_sp_delim(None, Some(rhs))
+                    };
+                    rewrite_unary_prefix(context, &sp_delim, &*rhs, shape)
+                }
+                (Some(lhs), None) => {
+                    let sp_delim = if context.config.spaces_around_ranges() {
+                        format!(" {}", delim)
+                    } else {
+                        default_sp_delim(Some(lhs), None)
+                    };
+                    rewrite_unary_suffix(context, &sp_delim, &*lhs, shape)
+                }
+                (None, None) => Some(delim.to_owned()),
+            }
+        }
+        // We do not format these expressions yet, but they should still
+        // satisfy our width restrictions.
+        // Style Guide RFC for InlineAsm variant pending
+        // https://github.com/rust-dev-tools/fmt-rfcs/issues/152
+        ast::ExprKind::LlvmInlineAsm(..) | ast::ExprKind::InlineAsm(..) => {
+            Some(context.snippet(expr.span).to_owned())
+        }
+        ast::ExprKind::TryBlock(ref block) => {
+            if let rw @ Some(_) =
+                rewrite_single_line_block(context, "try ", block, Some(&expr.attrs), None, shape)
+            {
+                rw
+            } else {
+                // 9 = `try `
+                let budget = shape.width.saturating_sub(9);
+                Some(format!(
+                    "{}{}",
+                    "try ",
+                    rewrite_block(
+                        block,
+                        Some(&expr.attrs),
+                        None,
+                        context,
+                        Shape::legacy(budget, shape.indent)
+                    )?
+                ))
+            }
+        }
+        ast::ExprKind::Async(capture_by, _node_id, ref block) => {
+            let mover = if capture_by == ast::CaptureBy::Value {
+                "move "
+            } else {
+                ""
+            };
+            if let rw @ Some(_) = rewrite_single_line_block(
+                context,
+                format!("{}{}", "async ", mover).as_str(),
+                block,
+                Some(&expr.attrs),
+                None,
+                shape,
+            ) {
+                rw
+            } else {
+                // 6 = `async `
+                let budget = shape.width.saturating_sub(6);
+                Some(format!(
+                    "{}{}{}",
+                    "async ",
+                    mover,
+                    rewrite_block(
+                        block,
+                        Some(&expr.attrs),
+                        None,
+                        context,
+                        Shape::legacy(budget, shape.indent)
+                    )?
+                ))
+            }
+        }
+        ast::ExprKind::Await(_) => rewrite_chain(expr, context, shape),
+        ast::ExprKind::Underscore => Some("_".to_owned()),
+        ast::ExprKind::Err => None,
+    };
+
+    expr_rw
+        .and_then(|expr_str| recover_comment_removed(expr_str, expr.span, context))
+        .and_then(|expr_str| {
+            let attrs = outer_attributes(&expr.attrs);
+            let attrs_str = attrs.rewrite(context, shape)?;
+            let span = mk_sp(
+                attrs.last().map_or(expr.span.lo(), |attr| attr.span.hi()),
+                expr.span.lo(),
+            );
+            combine_strs_with_missing_comments(context, &attrs_str, &expr_str, span, shape, false)
+        })
+}
+
+pub(crate) fn rewrite_array<'a, T: 'a + IntoOverflowableItem<'a>>(
+    name: &'a str,
+    exprs: impl Iterator<Item = &'a T>,
+    span: Span,
+    context: &'a RewriteContext<'_>,
+    shape: Shape,
+    force_separator_tactic: Option<SeparatorTactic>,
+    delim_token: Option<DelimToken>,
+) -> Option<String> {
+    overflow::rewrite_with_square_brackets(
+        context,
+        name,
+        exprs,
+        shape,
+        span,
+        force_separator_tactic,
+        delim_token,
+    )
+}
+
+fn rewrite_empty_block(
+    context: &RewriteContext<'_>,
+    block: &ast::Block,
+    attrs: Option<&[ast::Attribute]>,
+    label: Option<ast::Label>,
+    prefix: &str,
+    shape: Shape,
+) -> Option<String> {
+    if block_has_statements(&block) {
+        return None;
+    }
+
+    let label_str = rewrite_label(label);
+    if attrs.map_or(false, |a| !inner_attributes(a).is_empty()) {
+        return None;
+    }
+
+    if !block_contains_comment(context, block) && shape.width >= 2 {
+        return Some(format!("{}{}{{}}", prefix, label_str));
+    }
+
+    // If a block contains only a single-line comment, then leave it on one line.
+    let user_str = context.snippet(block.span);
+    let user_str = user_str.trim();
+    if user_str.starts_with('{') && user_str.ends_with('}') {
+        let comment_str = user_str[1..user_str.len() - 1].trim();
+        if block.stmts.is_empty()
+            && !comment_str.contains('\n')
+            && !comment_str.starts_with("//")
+            && comment_str.len() + 4 <= shape.width
+        {
+            return Some(format!("{}{}{{ {} }}", prefix, label_str, comment_str));
+        }
+    }
+
+    None
+}
+
+fn block_prefix(context: &RewriteContext<'_>, block: &ast::Block, shape: Shape) -> Option<String> {
+    Some(match block.rules {
+        ast::BlockCheckMode::Unsafe(..) => {
+            let snippet = context.snippet(block.span);
+            let open_pos = snippet.find_uncommented("{")?;
+            // Extract comment between unsafe and block start.
+            let trimmed = &snippet[6..open_pos].trim();
+
+            if !trimmed.is_empty() {
+                // 9 = "unsafe  {".len(), 7 = "unsafe ".len()
+                let budget = shape.width.checked_sub(9)?;
+                format!(
+                    "unsafe {} ",
+                    rewrite_comment(
+                        trimmed,
+                        true,
+                        Shape::legacy(budget, shape.indent + 7),
+                        context.config,
+                    )?
+                )
+            } else {
+                "unsafe ".to_owned()
+            }
+        }
+        ast::BlockCheckMode::Default => String::new(),
+    })
+}
+
+fn rewrite_single_line_block(
+    context: &RewriteContext<'_>,
+    prefix: &str,
+    block: &ast::Block,
+    attrs: Option<&[ast::Attribute]>,
+    label: Option<ast::Label>,
+    shape: Shape,
+) -> Option<String> {
+    if is_simple_block(context, block, attrs) {
+        let expr_shape = shape.offset_left(last_line_width(prefix))?;
+        let expr_str = block.stmts[0].rewrite(context, expr_shape)?;
+        let label_str = rewrite_label(label);
+        let result = format!("{}{}{{ {} }}", prefix, label_str, expr_str);
+        if result.len() <= shape.width && !result.contains('\n') {
+            return Some(result);
+        }
+    }
+    None
+}
+
+pub(crate) fn rewrite_block_with_visitor(
+    context: &RewriteContext<'_>,
+    prefix: &str,
+    block: &ast::Block,
+    attrs: Option<&[ast::Attribute]>,
+    label: Option<ast::Label>,
+    shape: Shape,
+    has_braces: bool,
+) -> Option<String> {
+    if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, prefix, shape) {
+        return rw;
+    }
+
+    let mut visitor = FmtVisitor::from_context(context);
+    visitor.block_indent = shape.indent;
+    visitor.is_if_else_block = context.is_if_else_block();
+    match (block.rules, label) {
+        (ast::BlockCheckMode::Unsafe(..), _) | (ast::BlockCheckMode::Default, Some(_)) => {
+            let snippet = context.snippet(block.span);
+            let open_pos = snippet.find_uncommented("{")?;
+            visitor.last_pos = block.span.lo() + BytePos(open_pos as u32)
+        }
+        (ast::BlockCheckMode::Default, None) => visitor.last_pos = block.span.lo(),
+    }
+
+    let inner_attrs = attrs.map(inner_attributes);
+    let label_str = rewrite_label(label);
+    visitor.visit_block(block, inner_attrs.as_ref().map(|a| &**a), has_braces);
+    let visitor_context = visitor.get_context();
+    context
+        .skipped_range
+        .borrow_mut()
+        .append(&mut visitor_context.skipped_range.borrow_mut());
+    Some(format!("{}{}{}", prefix, label_str, visitor.buffer))
+}
+
+impl Rewrite for ast::Block {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        rewrite_block(self, None, None, context, shape)
+    }
+}
+
+fn rewrite_block(
+    block: &ast::Block,
+    attrs: Option<&[ast::Attribute]>,
+    label: Option<ast::Label>,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    let prefix = block_prefix(context, block, shape)?;
+
+    // shape.width is used only for the single line case: either the empty block `{}`,
+    // or an unsafe expression `unsafe { e }`.
+    if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, &prefix, shape) {
+        return rw;
+    }
+
+    let result = rewrite_block_with_visitor(context, &prefix, block, attrs, label, shape, true);
+    if let Some(ref result_str) = result {
+        if result_str.lines().count() <= 3 {
+            if let rw @ Some(_) =
+                rewrite_single_line_block(context, &prefix, block, attrs, label, shape)
+            {
+                return rw;
+            }
+        }
+    }
+
+    result
+}
+
+// Rewrite condition if the given expression has one.
+pub(crate) fn rewrite_cond(
+    context: &RewriteContext<'_>,
+    expr: &ast::Expr,
+    shape: Shape,
+) -> Option<String> {
+    match expr.kind {
+        ast::ExprKind::Match(ref cond, _) => {
+            // `match `cond` {`
+            let cond_shape = match context.config.indent_style() {
+                IndentStyle::Visual => shape.shrink_left(6).and_then(|s| s.sub_width(2))?,
+                IndentStyle::Block => shape.offset_left(8)?,
+            };
+            cond.rewrite(context, cond_shape)
+        }
+        _ => to_control_flow(expr, ExprType::SubExpression).and_then(|control_flow| {
+            let alt_block_sep =
+                String::from("\n") + &shape.indent.block_only().to_string(context.config);
+            control_flow
+                .rewrite_cond(context, shape, &alt_block_sep)
+                .and_then(|rw| Some(rw.0))
+        }),
+    }
+}
+
+// Abstraction over control flow expressions
+#[derive(Debug)]
+struct ControlFlow<'a> {
+    cond: Option<&'a ast::Expr>,
+    block: &'a ast::Block,
+    else_block: Option<&'a ast::Expr>,
+    label: Option<ast::Label>,
+    pat: Option<&'a ast::Pat>,
+    keyword: &'a str,
+    matcher: &'a str,
+    connector: &'a str,
+    allow_single_line: bool,
+    // HACK: `true` if this is an `if` expression in an `else if`.
+    nested_if: bool,
+    span: Span,
+}
+
+fn extract_pats_and_cond(expr: &ast::Expr) -> (Option<&ast::Pat>, &ast::Expr) {
+    match expr.kind {
+        ast::ExprKind::Let(ref pat, ref cond) => (Some(pat), cond),
+        _ => (None, expr),
+    }
+}
+
+// FIXME: Refactor this.
+fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow<'_>> {
+    match expr.kind {
+        ast::ExprKind::If(ref cond, ref if_block, ref else_block) => {
+            let (pat, cond) = extract_pats_and_cond(cond);
+            Some(ControlFlow::new_if(
+                cond,
+                pat,
+                if_block,
+                else_block.as_ref().map(|e| &**e),
+                expr_type == ExprType::SubExpression,
+                false,
+                expr.span,
+            ))
+        }
+        ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
+            Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
+        }
+        ast::ExprKind::Loop(ref block, label) => {
+            Some(ControlFlow::new_loop(block, label, expr.span))
+        }
+        ast::ExprKind::While(ref cond, ref block, label) => {
+            let (pat, cond) = extract_pats_and_cond(cond);
+            Some(ControlFlow::new_while(pat, cond, block, label, expr.span))
+        }
+        _ => None,
+    }
+}
+
+fn choose_matcher(pat: Option<&ast::Pat>) -> &'static str {
+    pat.map_or("", |_| "let")
+}
+
+impl<'a> ControlFlow<'a> {
+    fn new_if(
+        cond: &'a ast::Expr,
+        pat: Option<&'a ast::Pat>,
+        block: &'a ast::Block,
+        else_block: Option<&'a ast::Expr>,
+        allow_single_line: bool,
+        nested_if: bool,
+        span: Span,
+    ) -> ControlFlow<'a> {
+        let matcher = choose_matcher(pat);
+        ControlFlow {
+            cond: Some(cond),
+            block,
+            else_block,
+            label: None,
+            pat,
+            keyword: "if",
+            matcher,
+            connector: " =",
+            allow_single_line,
+            nested_if,
+            span,
+        }
+    }
+
+    fn new_loop(block: &'a ast::Block, label: Option<ast::Label>, span: Span) -> ControlFlow<'a> {
+        ControlFlow {
+            cond: None,
+            block,
+            else_block: None,
+            label,
+            pat: None,
+            keyword: "loop",
+            matcher: "",
+            connector: "",
+            allow_single_line: false,
+            nested_if: false,
+            span,
+        }
+    }
+
+    fn new_while(
+        pat: Option<&'a ast::Pat>,
+        cond: &'a ast::Expr,
+        block: &'a ast::Block,
+        label: Option<ast::Label>,
+        span: Span,
+    ) -> ControlFlow<'a> {
+        let matcher = choose_matcher(pat);
+        ControlFlow {
+            cond: Some(cond),
+            block,
+            else_block: None,
+            label,
+            pat,
+            keyword: "while",
+            matcher,
+            connector: " =",
+            allow_single_line: false,
+            nested_if: false,
+            span,
+        }
+    }
+
+    fn new_for(
+        pat: &'a ast::Pat,
+        cond: &'a ast::Expr,
+        block: &'a ast::Block,
+        label: Option<ast::Label>,
+        span: Span,
+    ) -> ControlFlow<'a> {
+        ControlFlow {
+            cond: Some(cond),
+            block,
+            else_block: None,
+            label,
+            pat: Some(pat),
+            keyword: "for",
+            matcher: "",
+            connector: " in",
+            allow_single_line: false,
+            nested_if: false,
+            span,
+        }
+    }
+
+    fn rewrite_single_line(
+        &self,
+        pat_expr_str: &str,
+        context: &RewriteContext<'_>,
+        width: usize,
+    ) -> Option<String> {
+        assert!(self.allow_single_line);
+        let else_block = self.else_block?;
+        let fixed_cost = self.keyword.len() + "  {  } else {  }".len();
+
+        if let ast::ExprKind::Block(ref else_node, _) = else_block.kind {
+            if !is_simple_block(context, self.block, None)
+                || !is_simple_block(context, else_node, None)
+                || pat_expr_str.contains('\n')
+            {
+                return None;
+            }
+
+            let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
+            let expr = &self.block.stmts[0];
+            let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
+
+            let new_width = new_width.checked_sub(if_str.len())?;
+            let else_expr = &else_node.stmts[0];
+            let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
+
+            if if_str.contains('\n') || else_str.contains('\n') {
+                return None;
+            }
+
+            let result = format!(
+                "{} {} {{ {} }} else {{ {} }}",
+                self.keyword, pat_expr_str, if_str, else_str
+            );
+
+            if result.len() <= width {
+                return Some(result);
+            }
+        }
+
+        None
+    }
+}
+
+/// Returns `true` if the last line of pat_str has leading whitespace and it is wider than the
+/// shape's indent.
+fn last_line_offsetted(start_column: usize, pat_str: &str) -> bool {
+    let mut leading_whitespaces = 0;
+    for c in pat_str.chars().rev() {
+        match c {
+            '\n' => break,
+            _ if c.is_whitespace() => leading_whitespaces += 1,
+            _ => leading_whitespaces = 0,
+        }
+    }
+    leading_whitespaces > start_column
+}
+
+impl<'a> ControlFlow<'a> {
+    fn rewrite_pat_expr(
+        &self,
+        context: &RewriteContext<'_>,
+        expr: &ast::Expr,
+        shape: Shape,
+        offset: usize,
+    ) -> Option<String> {
+        debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pat, expr);
+
+        let cond_shape = shape.offset_left(offset)?;
+        if let Some(pat) = self.pat {
+            let matcher = if self.matcher.is_empty() {
+                self.matcher.to_owned()
+            } else {
+                format!("{} ", self.matcher)
+            };
+            let pat_shape = cond_shape
+                .offset_left(matcher.len())?
+                .sub_width(self.connector.len())?;
+            let pat_string = pat.rewrite(context, pat_shape)?;
+            let comments_lo = context
+                .snippet_provider
+                .span_after(self.span, self.connector.trim());
+            let comments_span = mk_sp(comments_lo, expr.span.lo());
+            return rewrite_assign_rhs_with_comments(
+                context,
+                &format!("{}{}{}", matcher, pat_string, self.connector),
+                expr,
+                cond_shape,
+                RhsTactics::Default,
+                comments_span,
+                true,
+            );
+        }
+
+        let expr_rw = expr.rewrite(context, cond_shape);
+        // The expression may (partially) fit on the current line.
+        // We do not allow splitting between `if` and condition.
+        if self.keyword == "if" || expr_rw.is_some() {
+            return expr_rw;
+        }
+
+        // The expression won't fit on the current line, jump to next.
+        let nested_shape = shape
+            .block_indent(context.config.tab_spaces())
+            .with_max_width(context.config);
+        let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
+        expr.rewrite(context, nested_shape)
+            .map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
+    }
+
+    fn rewrite_cond(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        alt_block_sep: &str,
+    ) -> Option<(String, usize)> {
+        // Do not take the rhs overhead from the upper expressions into account
+        // when rewriting pattern.
+        let new_width = context.budget(shape.used_width());
+        let fresh_shape = Shape {
+            width: new_width,
+            ..shape
+        };
+        let constr_shape = if self.nested_if {
+            // We are part of an if-elseif-else chain. Our constraints are tightened.
+            // 7 = "} else " .len()
+            fresh_shape.offset_left(7)?
+        } else {
+            fresh_shape
+        };
+
+        let label_string = rewrite_label(self.label);
+        // 1 = space after keyword.
+        let offset = self.keyword.len() + label_string.len() + 1;
+
+        let pat_expr_string = match self.cond {
+            Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
+            None => String::new(),
+        };
+
+        let brace_overhead =
+            if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
+                // 2 = ` {`
+                2
+            } else {
+                0
+            };
+        let one_line_budget = context
+            .config
+            .max_width()
+            .saturating_sub(constr_shape.used_width() + offset + brace_overhead);
+        let force_newline_brace = (pat_expr_string.contains('\n')
+            || pat_expr_string.len() > one_line_budget)
+            && (!last_line_extendable(&pat_expr_string)
+                || last_line_offsetted(shape.used_width(), &pat_expr_string));
+
+        // Try to format if-else on single line.
+        if self.allow_single_line && context.config.single_line_if_else_max_width() > 0 {
+            let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
+
+            if let Some(cond_str) = trial {
+                if cond_str.len() <= context.config.single_line_if_else_max_width() {
+                    return Some((cond_str, 0));
+                }
+            }
+        }
+
+        let cond_span = if let Some(cond) = self.cond {
+            cond.span
+        } else {
+            mk_sp(self.block.span.lo(), self.block.span.lo())
+        };
+
+        // `for event in event`
+        // Do not include label in the span.
+        let lo = self
+            .label
+            .map_or(self.span.lo(), |label| label.ident.span.hi());
+        let between_kwd_cond = mk_sp(
+            context
+                .snippet_provider
+                .span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
+            if self.pat.is_none() {
+                cond_span.lo()
+            } else if self.matcher.is_empty() {
+                self.pat.unwrap().span.lo()
+            } else {
+                context
+                    .snippet_provider
+                    .span_before(self.span, self.matcher.trim())
+            },
+        );
+
+        let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
+
+        let after_cond_comment =
+            extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
+
+        let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
+            ""
+        } else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
+            || force_newline_brace
+        {
+            alt_block_sep
+        } else {
+            " "
+        };
+
+        let used_width = if pat_expr_string.contains('\n') {
+            last_line_width(&pat_expr_string)
+        } else {
+            // 2 = spaces after keyword and condition.
+            label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
+        };
+
+        Some((
+            format!(
+                "{}{}{}{}{}",
+                label_string,
+                self.keyword,
+                between_kwd_cond_comment.as_ref().map_or(
+                    if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
+                        ""
+                    } else {
+                        " "
+                    },
+                    |s| &**s,
+                ),
+                pat_expr_string,
+                after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
+            ),
+            used_width,
+        ))
+    }
+}
+
+impl<'a> Rewrite for ControlFlow<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
+
+        let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
+        let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
+        // If `used_width` is 0, it indicates that whole control flow is written in a single line.
+        if used_width == 0 {
+            return Some(cond_str);
+        }
+
+        let block_width = shape.width.saturating_sub(used_width);
+        // This is used only for the empty block case: `{}`. So, we use 1 if we know
+        // we should avoid the single line case.
+        let block_width = if self.else_block.is_some() || self.nested_if {
+            min(1, block_width)
+        } else {
+            block_width
+        };
+        let block_shape = Shape {
+            width: block_width,
+            ..shape
+        };
+        let block_str = {
+            let old_val = context.is_if_else_block.replace(self.else_block.is_some());
+            let result =
+                rewrite_block_with_visitor(context, "", self.block, None, None, block_shape, true);
+            context.is_if_else_block.replace(old_val);
+            result?
+        };
+
+        let mut result = format!("{}{}", cond_str, block_str);
+
+        if let Some(else_block) = self.else_block {
+            let shape = Shape::indented(shape.indent, context.config);
+            let mut last_in_chain = false;
+            let rewrite = match else_block.kind {
+                // If the else expression is another if-else expression, prevent it
+                // from being formatted on a single line.
+                // Note how we're passing the original shape, as the
+                // cost of "else" should not cascade.
+                ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
+                    let (pats, cond) = extract_pats_and_cond(cond);
+                    ControlFlow::new_if(
+                        cond,
+                        pats,
+                        if_block,
+                        next_else_block.as_ref().map(|e| &**e),
+                        false,
+                        true,
+                        mk_sp(else_block.span.lo(), self.span.hi()),
+                    )
+                    .rewrite(context, shape)
+                }
+                _ => {
+                    last_in_chain = true;
+                    // When rewriting a block, the width is only used for single line
+                    // blocks, passing 1 lets us avoid that.
+                    let else_shape = Shape {
+                        width: min(1, shape.width),
+                        ..shape
+                    };
+                    format_expr(else_block, ExprType::Statement, context, else_shape)
+                }
+            };
+
+            let between_kwd_else_block = mk_sp(
+                self.block.span.hi(),
+                context
+                    .snippet_provider
+                    .span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
+            );
+            let between_kwd_else_block_comment =
+                extract_comment(between_kwd_else_block, context, shape);
+
+            let after_else = mk_sp(
+                context
+                    .snippet_provider
+                    .span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
+                else_block.span.lo(),
+            );
+            let after_else_comment = extract_comment(after_else, context, shape);
+
+            let between_sep = match context.config.control_brace_style() {
+                ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
+                    &*alt_block_sep
+                }
+                ControlBraceStyle::AlwaysSameLine => " ",
+            };
+            let after_sep = match context.config.control_brace_style() {
+                ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
+                _ => " ",
+            };
+
+            result.push_str(&format!(
+                "{}else{}",
+                between_kwd_else_block_comment
+                    .as_ref()
+                    .map_or(between_sep, |s| &**s),
+                after_else_comment.as_ref().map_or(after_sep, |s| &**s),
+            ));
+            result.push_str(&rewrite?);
+        }
+
+        Some(result)
+    }
+}
+
+fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
+    match opt_label {
+        Some(label) => Cow::from(format!("{}: ", label.ident)),
+        None => Cow::from(""),
+    }
+}
+
+fn extract_comment(span: Span, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+    match rewrite_missing_comment(span, shape, context) {
+        Some(ref comment) if !comment.is_empty() => Some(format!(
+            "{indent}{}{indent}",
+            comment,
+            indent = shape.indent.to_string_with_newline(context.config)
+        )),
+        _ => None,
+    }
+}
+
+pub(crate) fn block_contains_comment(context: &RewriteContext<'_>, block: &ast::Block) -> bool {
+    contains_comment(context.snippet(block.span))
+}
+
+// Checks that a block contains no statements, an expression and no comments or
+// attributes.
+// FIXME: incorrectly returns false when comment is contained completely within
+// the expression.
+pub(crate) fn is_simple_block(
+    context: &RewriteContext<'_>,
+    block: &ast::Block,
+    attrs: Option<&[ast::Attribute]>,
+) -> bool {
+    block.stmts.len() == 1
+        && stmt_is_expr(&block.stmts[0])
+        && !block_contains_comment(context, block)
+        && attrs.map_or(true, |a| a.is_empty())
+}
+
+/// Checks whether a block contains at most one statement or expression, and no
+/// comments or attributes.
+pub(crate) fn is_simple_block_stmt(
+    context: &RewriteContext<'_>,
+    block: &ast::Block,
+    attrs: Option<&[ast::Attribute]>,
+) -> bool {
+    block.stmts.len() <= 1
+        && !block_contains_comment(context, block)
+        && attrs.map_or(true, |a| a.is_empty())
+}
+
+fn block_has_statements(block: &ast::Block) -> bool {
+    block
+        .stmts
+        .iter()
+        .any(|stmt| !matches!(stmt.kind, ast::StmtKind::Empty))
+}
+
+/// Checks whether a block contains no statements, expressions, comments, or
+/// inner attributes.
+pub(crate) fn is_empty_block(
+    context: &RewriteContext<'_>,
+    block: &ast::Block,
+    attrs: Option<&[ast::Attribute]>,
+) -> bool {
+    !block_has_statements(&block)
+        && !block_contains_comment(context, block)
+        && attrs.map_or(true, |a| inner_attributes(a).is_empty())
+}
+
+pub(crate) fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
+    match stmt.kind {
+        ast::StmtKind::Expr(..) => true,
+        _ => false,
+    }
+}
+
+pub(crate) fn is_unsafe_block(block: &ast::Block) -> bool {
+    if let ast::BlockCheckMode::Unsafe(..) = block.rules {
+        true
+    } else {
+        false
+    }
+}
+
+pub(crate) fn rewrite_literal(
+    context: &RewriteContext<'_>,
+    l: &ast::Lit,
+    shape: Shape,
+) -> Option<String> {
+    match l.kind {
+        ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
+        _ => wrap_str(
+            context.snippet(l.span).to_owned(),
+            context.config.max_width(),
+            shape,
+        ),
+    }
+}
+
+fn rewrite_string_lit(context: &RewriteContext<'_>, span: Span, shape: Shape) -> Option<String> {
+    let string_lit = context.snippet(span);
+
+    if !context.config.format_strings() {
+        if string_lit
+            .lines()
+            .dropping_back(1)
+            .all(|line| line.ends_with('\\'))
+            && context.config.version() == Version::Two
+        {
+            return Some(string_lit.to_owned());
+        } else {
+            return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
+        }
+    }
+
+    // Remove the quote characters.
+    let str_lit = &string_lit[1..string_lit.len() - 1];
+
+    rewrite_string(
+        str_lit,
+        &StringFormat::new(shape.visual_indent(0), context.config),
+        shape.width.saturating_sub(2),
+    )
+}
+
+fn choose_separator_tactic(context: &RewriteContext<'_>, span: Span) -> Option<SeparatorTactic> {
+    if context.inside_macro() {
+        if span_ends_with_comma(context, span) {
+            Some(SeparatorTactic::Always)
+        } else {
+            Some(SeparatorTactic::Never)
+        }
+    } else {
+        None
+    }
+}
+
+pub(crate) fn rewrite_call(
+    context: &RewriteContext<'_>,
+    callee: &str,
+    args: &[ptr::P<ast::Expr>],
+    span: Span,
+    shape: Shape,
+) -> Option<String> {
+    overflow::rewrite_with_parens(
+        context,
+        callee,
+        args.iter(),
+        shape,
+        span,
+        context.config.fn_call_width(),
+        choose_separator_tactic(context, span),
+    )
+}
+
+pub(crate) fn is_simple_expr(expr: &ast::Expr) -> bool {
+    match expr.kind {
+        ast::ExprKind::Lit(..) => true,
+        ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
+        ast::ExprKind::AddrOf(_, _, ref expr)
+        | ast::ExprKind::Box(ref expr)
+        | ast::ExprKind::Cast(ref expr, _)
+        | ast::ExprKind::Field(ref expr, _)
+        | ast::ExprKind::Try(ref expr)
+        | ast::ExprKind::Unary(_, ref expr) => is_simple_expr(expr),
+        ast::ExprKind::Index(ref lhs, ref rhs) => is_simple_expr(lhs) && is_simple_expr(rhs),
+        ast::ExprKind::Repeat(ref lhs, ref rhs) => {
+            is_simple_expr(lhs) && is_simple_expr(&*rhs.value)
+        }
+        _ => false,
+    }
+}
+
+pub(crate) fn is_every_expr_simple(lists: &[OverflowableItem<'_>]) -> bool {
+    lists.iter().all(OverflowableItem::is_simple)
+}
+
+pub(crate) fn can_be_overflowed_expr(
+    context: &RewriteContext<'_>,
+    expr: &ast::Expr,
+    args_len: usize,
+) -> bool {
+    match expr.kind {
+        _ if !expr.attrs.is_empty() => false,
+        ast::ExprKind::Match(..) => {
+            (context.use_block_indent() && args_len == 1)
+                || (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
+                || context.config.overflow_delimited_expr()
+        }
+        ast::ExprKind::If(..)
+        | ast::ExprKind::ForLoop(..)
+        | ast::ExprKind::Loop(..)
+        | ast::ExprKind::While(..) => {
+            context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
+        }
+
+        // Handle always block-like expressions
+        ast::ExprKind::Async(..) | ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
+
+        // Handle `[]` and `{}`-like expressions
+        ast::ExprKind::Array(..) | ast::ExprKind::Struct(..) => {
+            context.config.overflow_delimited_expr()
+                || (context.use_block_indent() && args_len == 1)
+        }
+        ast::ExprKind::MacCall(ref mac) => {
+            match (
+                rustc_ast::ast::MacDelimiter::from_token(mac.args.delim()),
+                context.config.overflow_delimited_expr(),
+            ) {
+                (Some(ast::MacDelimiter::Bracket), true)
+                | (Some(ast::MacDelimiter::Brace), true) => true,
+                _ => context.use_block_indent() && args_len == 1,
+            }
+        }
+
+        // Handle parenthetical expressions
+        ast::ExprKind::Call(..) | ast::ExprKind::MethodCall(..) | ast::ExprKind::Tup(..) => {
+            context.use_block_indent() && args_len == 1
+        }
+
+        // Handle unary-like expressions
+        ast::ExprKind::AddrOf(_, _, ref expr)
+        | ast::ExprKind::Box(ref expr)
+        | ast::ExprKind::Try(ref expr)
+        | ast::ExprKind::Unary(_, ref expr)
+        | ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
+        _ => false,
+    }
+}
+
+pub(crate) fn is_nested_call(expr: &ast::Expr) -> bool {
+    match expr.kind {
+        ast::ExprKind::Call(..) | ast::ExprKind::MacCall(..) => true,
+        ast::ExprKind::AddrOf(_, _, ref expr)
+        | ast::ExprKind::Box(ref expr)
+        | ast::ExprKind::Try(ref expr)
+        | ast::ExprKind::Unary(_, ref expr)
+        | ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
+        _ => false,
+    }
+}
+
+/// Returns `true` if a function call or a method call represented by the given span ends with a
+/// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
+/// comma from macro can potentially break the code.
+pub(crate) fn span_ends_with_comma(context: &RewriteContext<'_>, span: Span) -> bool {
+    let mut result: bool = Default::default();
+    let mut prev_char: char = Default::default();
+    let closing_delimiters = &[')', '}', ']'];
+
+    for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
+        match c {
+            _ if kind.is_comment() || c.is_whitespace() => continue,
+            c if closing_delimiters.contains(&c) => {
+                result &= !closing_delimiters.contains(&prev_char);
+            }
+            ',' => result = true,
+            _ => result = false,
+        }
+        prev_char = c;
+    }
+
+    result
+}
+
+fn rewrite_paren(
+    context: &RewriteContext<'_>,
+    mut subexpr: &ast::Expr,
+    shape: Shape,
+    mut span: Span,
+) -> Option<String> {
+    debug!("rewrite_paren, shape: {:?}", shape);
+
+    // Extract comments within parens.
+    let mut pre_span;
+    let mut post_span;
+    let mut pre_comment;
+    let mut post_comment;
+    let remove_nested_parens = context.config.remove_nested_parens();
+    loop {
+        // 1 = "(" or ")"
+        pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
+        post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
+        pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
+        post_comment = rewrite_missing_comment(post_span, shape, context)?;
+
+        // Remove nested parens if there are no comments.
+        if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.kind {
+            if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
+                span = subexpr.span;
+                subexpr = subsubexpr;
+                continue;
+            }
+        }
+
+        break;
+    }
+
+    // 1 = `(` and `)`
+    let sub_shape = shape.offset_left(1)?.sub_width(1)?;
+    let subexpr_str = subexpr.rewrite(context, sub_shape)?;
+    let fits_single_line = !pre_comment.contains("//") && !post_comment.contains("//");
+    if fits_single_line {
+        Some(format!("({}{}{})", pre_comment, subexpr_str, post_comment))
+    } else {
+        rewrite_paren_in_multi_line(context, subexpr, shape, pre_span, post_span)
+    }
+}
+
+fn rewrite_paren_in_multi_line(
+    context: &RewriteContext<'_>,
+    subexpr: &ast::Expr,
+    shape: Shape,
+    pre_span: Span,
+    post_span: Span,
+) -> Option<String> {
+    let nested_indent = shape.indent.block_indent(context.config);
+    let nested_shape = Shape::indented(nested_indent, context.config);
+    let pre_comment = rewrite_missing_comment(pre_span, nested_shape, context)?;
+    let post_comment = rewrite_missing_comment(post_span, nested_shape, context)?;
+    let subexpr_str = subexpr.rewrite(context, nested_shape)?;
+
+    let mut result = String::with_capacity(subexpr_str.len() * 2);
+    result.push('(');
+    if !pre_comment.is_empty() {
+        result.push_str(&nested_indent.to_string_with_newline(context.config));
+        result.push_str(&pre_comment);
+    }
+    result.push_str(&nested_indent.to_string_with_newline(context.config));
+    result.push_str(&subexpr_str);
+    if !post_comment.is_empty() {
+        result.push_str(&nested_indent.to_string_with_newline(context.config));
+        result.push_str(&post_comment);
+    }
+    result.push_str(&shape.indent.to_string_with_newline(context.config));
+    result.push(')');
+
+    Some(result)
+}
+
+fn rewrite_index(
+    expr: &ast::Expr,
+    index: &ast::Expr,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    let expr_str = expr.rewrite(context, shape)?;
+
+    let offset = last_line_width(&expr_str) + 1;
+    let rhs_overhead = shape.rhs_overhead(context.config);
+    let index_shape = if expr_str.contains('\n') {
+        Shape::legacy(context.config.max_width(), shape.indent)
+            .offset_left(offset)
+            .and_then(|shape| shape.sub_width(1 + rhs_overhead))
+    } else {
+        match context.config.indent_style() {
+            IndentStyle::Block => shape
+                .offset_left(offset)
+                .and_then(|shape| shape.sub_width(1)),
+            IndentStyle::Visual => shape.visual_indent(offset).sub_width(offset + 1),
+        }
+    };
+    let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
+
+    // Return if index fits in a single line.
+    match orig_index_rw {
+        Some(ref index_str) if !index_str.contains('\n') => {
+            return Some(format!("{}[{}]", expr_str, index_str));
+        }
+        _ => (),
+    }
+
+    // Try putting index on the next line and see if it fits in a single line.
+    let indent = shape.indent.block_indent(context.config);
+    let index_shape = Shape::indented(indent, context.config).offset_left(1)?;
+    let index_shape = index_shape.sub_width(1 + rhs_overhead)?;
+    let new_index_rw = index.rewrite(context, index_shape);
+    match (orig_index_rw, new_index_rw) {
+        (_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
+            "{}{}[{}]",
+            expr_str,
+            indent.to_string_with_newline(context.config),
+            new_index_str,
+        )),
+        (None, Some(ref new_index_str)) => Some(format!(
+            "{}{}[{}]",
+            expr_str,
+            indent.to_string_with_newline(context.config),
+            new_index_str,
+        )),
+        (Some(ref index_str), _) => Some(format!("{}[{}]", expr_str, index_str)),
+        _ => None,
+    }
+}
+
+fn struct_lit_can_be_aligned(fields: &[ast::ExprField], has_base: bool) -> bool {
+    !has_base && fields.iter().all(|field| !field.is_shorthand)
+}
+
+fn rewrite_struct_lit<'a>(
+    context: &RewriteContext<'_>,
+    path: &ast::Path,
+    fields: &'a [ast::ExprField],
+    struct_rest: &ast::StructRest,
+    attrs: &[ast::Attribute],
+    span: Span,
+    shape: Shape,
+) -> Option<String> {
+    debug!("rewrite_struct_lit: shape {:?}", shape);
+
+    enum StructLitField<'a> {
+        Regular(&'a ast::ExprField),
+        Base(&'a ast::Expr),
+        Rest(&'a Span),
+    }
+
+    // 2 = " {".len()
+    let path_shape = shape.sub_width(2)?;
+    let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
+
+    let has_base = match struct_rest {
+        ast::StructRest::None if fields.is_empty() => return Some(format!("{} {{}}", path_str)),
+        ast::StructRest::Rest(_) if fields.is_empty() => {
+            return Some(format!("{} {{ .. }}", path_str));
+        }
+        ast::StructRest::Base(_) => true,
+        _ => false,
+    };
+
+    // Foo { a: Foo } - indent is +3, width is -5.
+    let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
+
+    let one_line_width = h_shape.map_or(0, |shape| shape.width);
+    let body_lo = context.snippet_provider.span_after(span, "{");
+    let fields_str = if struct_lit_can_be_aligned(fields, has_base)
+        && context.config.struct_field_align_threshold() > 0
+    {
+        rewrite_with_alignment(
+            fields,
+            context,
+            v_shape,
+            mk_sp(body_lo, span.hi()),
+            one_line_width,
+        )?
+    } else {
+        let field_iter = fields.iter().map(StructLitField::Regular).chain(
+            match struct_rest {
+                ast::StructRest::Base(expr) => Some(StructLitField::Base(&**expr)),
+                ast::StructRest::Rest(span) => Some(StructLitField::Rest(span)),
+                ast::StructRest::None => None,
+            }
+            .into_iter(),
+        );
+
+        let span_lo = |item: &StructLitField<'_>| match *item {
+            StructLitField::Regular(field) => field.span().lo(),
+            StructLitField::Base(expr) => {
+                let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
+                let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
+                let pos = snippet.find_uncommented("..").unwrap();
+                last_field_hi + BytePos(pos as u32)
+            }
+            StructLitField::Rest(span) => span.lo(),
+        };
+        let span_hi = |item: &StructLitField<'_>| match *item {
+            StructLitField::Regular(field) => field.span().hi(),
+            StructLitField::Base(expr) => expr.span.hi(),
+            StructLitField::Rest(span) => span.hi(),
+        };
+        let rewrite = |item: &StructLitField<'_>| match *item {
+            StructLitField::Regular(field) => {
+                // The 1 taken from the v_budget is for the comma.
+                rewrite_field(context, field, v_shape.sub_width(1)?, 0)
+            }
+            StructLitField::Base(expr) => {
+                // 2 = ..
+                expr.rewrite(context, v_shape.offset_left(2)?)
+                    .map(|s| format!("..{}", s))
+            }
+            StructLitField::Rest(_) => Some("..".to_owned()),
+        };
+
+        let items = itemize_list(
+            context.snippet_provider,
+            field_iter,
+            "}",
+            ",",
+            span_lo,
+            span_hi,
+            rewrite,
+            body_lo,
+            span.hi(),
+            false,
+        );
+        let item_vec = items.collect::<Vec<_>>();
+
+        let tactic = struct_lit_tactic(h_shape, context, &item_vec);
+        let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
+
+        let ends_with_comma = span_ends_with_comma(context, span);
+        let force_no_trailing_comma = context.inside_macro() && !ends_with_comma;
+
+        let fmt = struct_lit_formatting(
+            nested_shape,
+            tactic,
+            context,
+            force_no_trailing_comma
+                || has_base
+                || !context.use_block_indent()
+                || matches!(struct_rest, ast::StructRest::Rest(_)),
+        );
+
+        write_list(&item_vec, &fmt)?
+    };
+
+    let fields_str =
+        wrap_struct_field(context, &attrs, &fields_str, shape, v_shape, one_line_width)?;
+    Some(format!("{} {{{}}}", path_str, fields_str))
+
+    // FIXME if context.config.indent_style() == Visual, but we run out
+    // of space, we should fall back to BlockIndent.
+}
+
+pub(crate) fn wrap_struct_field(
+    context: &RewriteContext<'_>,
+    attrs: &[ast::Attribute],
+    fields_str: &str,
+    shape: Shape,
+    nested_shape: Shape,
+    one_line_width: usize,
+) -> Option<String> {
+    let should_vertical = context.config.indent_style() == IndentStyle::Block
+        && (fields_str.contains('\n')
+            || !context.config.struct_lit_single_line()
+            || fields_str.len() > one_line_width);
+
+    let inner_attrs = &inner_attributes(attrs);
+    if inner_attrs.is_empty() {
+        if should_vertical {
+            Some(format!(
+                "{}{}{}",
+                nested_shape.indent.to_string_with_newline(context.config),
+                fields_str,
+                shape.indent.to_string_with_newline(context.config)
+            ))
+        } else {
+            // One liner or visual indent.
+            Some(format!(" {} ", fields_str))
+        }
+    } else {
+        Some(format!(
+            "{}{}{}{}{}",
+            nested_shape.indent.to_string_with_newline(context.config),
+            inner_attrs.rewrite(context, shape)?,
+            nested_shape.indent.to_string_with_newline(context.config),
+            fields_str,
+            shape.indent.to_string_with_newline(context.config)
+        ))
+    }
+}
+
+pub(crate) fn struct_lit_field_separator(config: &Config) -> &str {
+    colon_spaces(config)
+}
+
+pub(crate) fn rewrite_field(
+    context: &RewriteContext<'_>,
+    field: &ast::ExprField,
+    shape: Shape,
+    prefix_max_width: usize,
+) -> Option<String> {
+    if contains_skip(&field.attrs) {
+        return Some(context.snippet(field.span()).to_owned());
+    }
+    let mut attrs_str = field.attrs.rewrite(context, shape)?;
+    if !attrs_str.is_empty() {
+        attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
+    };
+    let name = context.snippet(field.ident.span);
+    if field.is_shorthand {
+        Some(attrs_str + name)
+    } else {
+        let mut separator = String::from(struct_lit_field_separator(context.config));
+        for _ in 0..prefix_max_width.saturating_sub(name.len()) {
+            separator.push(' ');
+        }
+        let overhead = name.len() + separator.len();
+        let expr_shape = shape.offset_left(overhead)?;
+        let expr = field.expr.rewrite(context, expr_shape);
+
+        match expr {
+            Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
+                Some(attrs_str + name)
+            }
+            Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
+            None => {
+                let expr_offset = shape.indent.block_indent(context.config);
+                let expr = field
+                    .expr
+                    .rewrite(context, Shape::indented(expr_offset, context.config));
+                expr.map(|s| {
+                    format!(
+                        "{}{}:\n{}{}",
+                        attrs_str,
+                        name,
+                        expr_offset.to_string(context.config),
+                        s
+                    )
+                })
+            }
+        }
+    }
+}
+
+fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
+    context: &RewriteContext<'_>,
+    mut items: impl Iterator<Item = &'a T>,
+    span: Span,
+    shape: Shape,
+    is_singleton_tuple: bool,
+) -> Option<String> {
+    // In case of length 1, need a trailing comma
+    debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
+    if is_singleton_tuple {
+        // 3 = "(" + ",)"
+        let nested_shape = shape.sub_width(3)?.visual_indent(1);
+        return items
+            .next()
+            .unwrap()
+            .rewrite(context, nested_shape)
+            .map(|s| format!("({},)", s));
+    }
+
+    let list_lo = context.snippet_provider.span_after(span, "(");
+    let nested_shape = shape.sub_width(2)?.visual_indent(1);
+    let items = itemize_list(
+        context.snippet_provider,
+        items,
+        ")",
+        ",",
+        |item| item.span().lo(),
+        |item| item.span().hi(),
+        |item| item.rewrite(context, nested_shape),
+        list_lo,
+        span.hi() - BytePos(1),
+        false,
+    );
+    let item_vec: Vec<_> = items.collect();
+    let tactic = definitive_tactic(
+        &item_vec,
+        ListTactic::HorizontalVertical,
+        Separator::Comma,
+        nested_shape.width,
+    );
+    let fmt = ListFormatting::new(nested_shape, context.config)
+        .tactic(tactic)
+        .ends_with_newline(false);
+    let list_str = write_list(&item_vec, &fmt)?;
+
+    Some(format!("({})", list_str))
+}
+
+pub(crate) fn rewrite_tuple<'a, T: 'a + IntoOverflowableItem<'a>>(
+    context: &'a RewriteContext<'_>,
+    items: impl Iterator<Item = &'a T>,
+    span: Span,
+    shape: Shape,
+    is_singleton_tuple: bool,
+) -> Option<String> {
+    debug!("rewrite_tuple {:?}", shape);
+    if context.use_block_indent() {
+        // We use the same rule as function calls for rewriting tuples.
+        let force_tactic = if context.inside_macro() {
+            if span_ends_with_comma(context, span) {
+                Some(SeparatorTactic::Always)
+            } else {
+                Some(SeparatorTactic::Never)
+            }
+        } else if is_singleton_tuple {
+            Some(SeparatorTactic::Always)
+        } else {
+            None
+        };
+        overflow::rewrite_with_parens(
+            context,
+            "",
+            items,
+            shape,
+            span,
+            context.config.fn_call_width(),
+            force_tactic,
+        )
+    } else {
+        rewrite_tuple_in_visual_indent_style(context, items, span, shape, is_singleton_tuple)
+    }
+}
+
+pub(crate) fn rewrite_unary_prefix<R: Rewrite>(
+    context: &RewriteContext<'_>,
+    prefix: &str,
+    rewrite: &R,
+    shape: Shape,
+) -> Option<String> {
+    rewrite
+        .rewrite(context, shape.offset_left(prefix.len())?)
+        .map(|r| format!("{}{}", prefix, r))
+}
+
+// FIXME: this is probably not correct for multi-line Rewrites. we should
+// subtract suffix.len() from the last line budget, not the first!
+pub(crate) fn rewrite_unary_suffix<R: Rewrite>(
+    context: &RewriteContext<'_>,
+    suffix: &str,
+    rewrite: &R,
+    shape: Shape,
+) -> Option<String> {
+    rewrite
+        .rewrite(context, shape.sub_width(suffix.len())?)
+        .map(|mut r| {
+            r.push_str(suffix);
+            r
+        })
+}
+
+fn rewrite_unary_op(
+    context: &RewriteContext<'_>,
+    op: ast::UnOp,
+    expr: &ast::Expr,
+    shape: Shape,
+) -> Option<String> {
+    // For some reason, an UnOp is not spanned like BinOp!
+    rewrite_unary_prefix(context, ast::UnOp::to_string(op), expr, shape)
+}
+
+fn rewrite_assignment(
+    context: &RewriteContext<'_>,
+    lhs: &ast::Expr,
+    rhs: &ast::Expr,
+    op: Option<&ast::BinOp>,
+    shape: Shape,
+) -> Option<String> {
+    let operator_str = match op {
+        Some(op) => context.snippet(op.span),
+        None => "=",
+    };
+
+    // 1 = space between lhs and operator.
+    let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
+    let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
+
+    rewrite_assign_rhs(context, lhs_str, rhs, shape)
+}
+
+/// Controls where to put the rhs.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) enum RhsTactics {
+    /// Use heuristics.
+    Default,
+    /// Put the rhs on the next line if it uses multiple line, without extra indentation.
+    ForceNextLineWithoutIndent,
+    /// Allow overflowing max width if neither `Default` nor `ForceNextLineWithoutIndent`
+    /// did not work.
+    AllowOverflow,
+}
+
+// The left hand side must contain everything up to, and including, the
+// assignment operator.
+pub(crate) fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
+    context: &RewriteContext<'_>,
+    lhs: S,
+    ex: &R,
+    shape: Shape,
+) -> Option<String> {
+    rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
+}
+
+pub(crate) fn rewrite_assign_rhs_expr<R: Rewrite>(
+    context: &RewriteContext<'_>,
+    lhs: &str,
+    ex: &R,
+    shape: Shape,
+    rhs_tactics: RhsTactics,
+) -> Option<String> {
+    let last_line_width = last_line_width(&lhs).saturating_sub(if lhs.contains('\n') {
+        shape.indent.width()
+    } else {
+        0
+    });
+    // 1 = space between operator and rhs.
+    let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
+        width: 0,
+        offset: shape.offset + last_line_width + 1,
+        ..shape
+    });
+    let has_rhs_comment = if let Some(offset) = lhs.find_last_uncommented("=") {
+        lhs.trim_end().len() > offset + 1
+    } else {
+        false
+    };
+
+    choose_rhs(
+        context,
+        ex,
+        orig_shape,
+        ex.rewrite(context, orig_shape),
+        rhs_tactics,
+        has_rhs_comment,
+    )
+}
+
+pub(crate) fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
+    context: &RewriteContext<'_>,
+    lhs: S,
+    ex: &R,
+    shape: Shape,
+    rhs_tactics: RhsTactics,
+) -> Option<String> {
+    let lhs = lhs.into();
+    let rhs = rewrite_assign_rhs_expr(context, &lhs, ex, shape, rhs_tactics)?;
+    Some(lhs + &rhs)
+}
+
+pub(crate) fn rewrite_assign_rhs_with_comments<S: Into<String>, R: Rewrite>(
+    context: &RewriteContext<'_>,
+    lhs: S,
+    ex: &R,
+    shape: Shape,
+    rhs_tactics: RhsTactics,
+    between_span: Span,
+    allow_extend: bool,
+) -> Option<String> {
+    let lhs = lhs.into();
+    let contains_comment = contains_comment(context.snippet(between_span));
+    let shape = if contains_comment {
+        shape.block_left(context.config.tab_spaces())?
+    } else {
+        shape
+    };
+    let rhs = rewrite_assign_rhs_expr(context, &lhs, ex, shape, rhs_tactics)?;
+
+    if contains_comment {
+        let rhs = rhs.trim_start();
+        combine_strs_with_missing_comments(context, &lhs, &rhs, between_span, shape, allow_extend)
+    } else {
+        Some(lhs + &rhs)
+    }
+}
+
+fn choose_rhs<R: Rewrite>(
+    context: &RewriteContext<'_>,
+    expr: &R,
+    shape: Shape,
+    orig_rhs: Option<String>,
+    rhs_tactics: RhsTactics,
+    has_rhs_comment: bool,
+) -> Option<String> {
+    match orig_rhs {
+        Some(ref new_str)
+            if !new_str.contains('\n') && unicode_str_width(new_str) <= shape.width =>
+        {
+            Some(format!(" {}", new_str))
+        }
+        _ => {
+            // Expression did not fit on the same line as the identifier.
+            // Try splitting the line and see if that works better.
+            let new_shape = shape_from_rhs_tactic(context, shape, rhs_tactics)?;
+            let new_rhs = expr.rewrite(context, new_shape);
+            let new_indent_str = &shape
+                .indent
+                .block_indent(context.config)
+                .to_string_with_newline(context.config);
+            let before_space_str = if has_rhs_comment { "" } else { " " };
+
+            match (orig_rhs, new_rhs) {
+                (Some(ref orig_rhs), Some(ref new_rhs))
+                    if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
+                        .is_none() =>
+                {
+                    Some(format!("{}{}", before_space_str, orig_rhs))
+                }
+                (Some(ref orig_rhs), Some(ref new_rhs))
+                    if prefer_next_line(orig_rhs, new_rhs, rhs_tactics) =>
+                {
+                    Some(format!("{}{}", new_indent_str, new_rhs))
+                }
+                (None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
+                (None, None) if rhs_tactics == RhsTactics::AllowOverflow => {
+                    let shape = shape.infinite_width();
+                    expr.rewrite(context, shape)
+                        .map(|s| format!("{}{}", before_space_str, s))
+                }
+                (None, None) => None,
+                (Some(orig_rhs), _) => Some(format!("{}{}", before_space_str, orig_rhs)),
+            }
+        }
+    }
+}
+
+fn shape_from_rhs_tactic(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    rhs_tactic: RhsTactics,
+) -> Option<Shape> {
+    match rhs_tactic {
+        RhsTactics::ForceNextLineWithoutIndent => shape
+            .with_max_width(context.config)
+            .sub_width(shape.indent.width()),
+        RhsTactics::Default | RhsTactics::AllowOverflow => {
+            Shape::indented(shape.indent.block_indent(context.config), context.config)
+                .sub_width(shape.rhs_overhead(context.config))
+        }
+    }
+}
+
+/// Returns true if formatting next_line_rhs is better on a new line when compared to the
+/// original's line formatting.
+///
+/// It is considered better if:
+/// 1. the tactic is ForceNextLineWithoutIndent
+/// 2. next_line_rhs doesn't have newlines
+/// 3. the original line has more newlines than next_line_rhs
+/// 4. the original formatting of the first line ends with `(`, `{`, or `[` and next_line_rhs
+///    doesn't
+pub(crate) fn prefer_next_line(
+    orig_rhs: &str,
+    next_line_rhs: &str,
+    rhs_tactics: RhsTactics,
+) -> bool {
+    rhs_tactics == RhsTactics::ForceNextLineWithoutIndent
+        || !next_line_rhs.contains('\n')
+        || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
+        || first_line_ends_with(orig_rhs, '(') && !first_line_ends_with(next_line_rhs, '(')
+        || first_line_ends_with(orig_rhs, '{') && !first_line_ends_with(next_line_rhs, '{')
+        || first_line_ends_with(orig_rhs, '[') && !first_line_ends_with(next_line_rhs, '[')
+}
+
+fn rewrite_expr_addrof(
+    context: &RewriteContext<'_>,
+    borrow_kind: ast::BorrowKind,
+    mutability: ast::Mutability,
+    expr: &ast::Expr,
+    shape: Shape,
+) -> Option<String> {
+    let operator_str = match (mutability, borrow_kind) {
+        (ast::Mutability::Not, ast::BorrowKind::Ref) => "&",
+        (ast::Mutability::Not, ast::BorrowKind::Raw) => "&raw const ",
+        (ast::Mutability::Mut, ast::BorrowKind::Ref) => "&mut ",
+        (ast::Mutability::Mut, ast::BorrowKind::Raw) => "&raw mut ",
+    };
+    rewrite_unary_prefix(context, operator_str, expr, shape)
+}
+
+pub(crate) fn is_method_call(expr: &ast::Expr) -> bool {
+    match expr.kind {
+        ast::ExprKind::MethodCall(..) => true,
+        ast::ExprKind::AddrOf(_, _, ref expr)
+        | ast::ExprKind::Box(ref expr)
+        | ast::ExprKind::Cast(ref expr, _)
+        | ast::ExprKind::Try(ref expr)
+        | ast::ExprKind::Unary(_, ref expr) => is_method_call(expr),
+        _ => false,
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::last_line_offsetted;
+
+    #[test]
+    fn test_last_line_offsetted() {
+        let lines = "one\n    two";
+        assert_eq!(last_line_offsetted(2, lines), true);
+        assert_eq!(last_line_offsetted(4, lines), false);
+        assert_eq!(last_line_offsetted(6, lines), false);
+
+        let lines = "one    two";
+        assert_eq!(last_line_offsetted(2, lines), false);
+        assert_eq!(last_line_offsetted(0, lines), false);
+
+        let lines = "\ntwo";
+        assert_eq!(last_line_offsetted(2, lines), false);
+        assert_eq!(last_line_offsetted(0, lines), false);
+
+        let lines = "one\n    two      three";
+        assert_eq!(last_line_offsetted(2, lines), true);
+        let lines = "one\n two      three";
+        assert_eq!(last_line_offsetted(2, lines), false);
+    }
+}
diff --git a/src/tools/rustfmt/src/format-diff/main.rs b/src/tools/rustfmt/src/format-diff/main.rs
new file mode 100644
index 0000000000000..c751932273b0a
--- /dev/null
+++ b/src/tools/rustfmt/src/format-diff/main.rs
@@ -0,0 +1,280 @@
+// Inspired by Clang's clang-format-diff:
+//
+// https://github.com/llvm-mirror/clang/blob/master/tools/clang-format/clang-format-diff.py
+
+#![deny(warnings)]
+
+#[macro_use]
+extern crate log;
+
+use serde::{Deserialize, Serialize};
+use serde_json as json;
+use thiserror::Error;
+
+use std::collections::HashSet;
+use std::env;
+use std::ffi::OsStr;
+use std::io::{self, BufRead};
+use std::process;
+
+use regex::Regex;
+
+use structopt::clap::AppSettings;
+use structopt::StructOpt;
+
+/// The default pattern of files to format.
+///
+/// We only want to format rust files by default.
+const DEFAULT_PATTERN: &str = r".*\.rs";
+
+#[derive(Error, Debug)]
+enum FormatDiffError {
+    #[error("{0}")]
+    IncorrectOptions(#[from] getopts::Fail),
+    #[error("{0}")]
+    IncorrectFilter(#[from] regex::Error),
+    #[error("{0}")]
+    IoError(#[from] io::Error),
+}
+
+#[derive(StructOpt, Debug)]
+#[structopt(
+    name = "rustfmt-format-diff",
+    setting = AppSettings::DisableVersion,
+    setting = AppSettings::NextLineHelp
+)]
+pub struct Opts {
+    /// Skip the smallest prefix containing NUMBER slashes
+    #[structopt(
+        short = "p",
+        long = "skip-prefix",
+        value_name = "NUMBER",
+        default_value = "0"
+    )]
+    skip_prefix: u32,
+
+    /// Custom pattern selecting file paths to reformat
+    #[structopt(
+        short = "f",
+        long = "filter",
+        value_name = "PATTERN",
+        default_value = DEFAULT_PATTERN
+    )]
+    filter: String,
+}
+
+fn main() {
+    env_logger::init();
+    let opts = Opts::from_args();
+    if let Err(e) = run(opts) {
+        println!("{}", e);
+        Opts::clap().print_help().expect("cannot write to stdout");
+        process::exit(1);
+    }
+}
+
+#[derive(Debug, Eq, PartialEq, Serialize, Deserialize)]
+struct Range {
+    file: String,
+    range: [u32; 2],
+}
+
+fn run(opts: Opts) -> Result<(), FormatDiffError> {
+    let (files, ranges) = scan_diff(io::stdin(), opts.skip_prefix, &opts.filter)?;
+    run_rustfmt(&files, &ranges)
+}
+
+fn run_rustfmt(files: &HashSet<String>, ranges: &[Range]) -> Result<(), FormatDiffError> {
+    if files.is_empty() || ranges.is_empty() {
+        debug!("No files to format found");
+        return Ok(());
+    }
+
+    let ranges_as_json = json::to_string(ranges).unwrap();
+
+    debug!("Files: {:?}", files);
+    debug!("Ranges: {:?}", ranges);
+
+    let rustfmt_var = env::var_os("RUSTFMT");
+    let rustfmt = match &rustfmt_var {
+        Some(rustfmt) => rustfmt,
+        None => OsStr::new("rustfmt"),
+    };
+    let exit_status = process::Command::new(rustfmt)
+        .args(files)
+        .arg("--file-lines")
+        .arg(ranges_as_json)
+        .status()?;
+
+    if !exit_status.success() {
+        return Err(FormatDiffError::IoError(io::Error::new(
+            io::ErrorKind::Other,
+            format!("rustfmt failed with {}", exit_status),
+        )));
+    }
+    Ok(())
+}
+
+/// Scans a diff from `from`, and returns the set of files found, and the ranges
+/// in those files.
+fn scan_diff<R>(
+    from: R,
+    skip_prefix: u32,
+    file_filter: &str,
+) -> Result<(HashSet<String>, Vec<Range>), FormatDiffError>
+where
+    R: io::Read,
+{
+    let diff_pattern = format!(r"^\+\+\+\s(?:.*?/){{{}}}(\S*)", skip_prefix);
+    let diff_pattern = Regex::new(&diff_pattern).unwrap();
+
+    let lines_pattern = Regex::new(r"^@@.*\+(\d+)(,(\d+))?").unwrap();
+
+    let file_filter = Regex::new(&format!("^{}$", file_filter))?;
+
+    let mut current_file = None;
+
+    let mut files = HashSet::new();
+    let mut ranges = vec![];
+    for line in io::BufReader::new(from).lines() {
+        let line = line.unwrap();
+
+        if let Some(captures) = diff_pattern.captures(&line) {
+            current_file = Some(captures.get(1).unwrap().as_str().to_owned());
+        }
+
+        let file = match current_file {
+            Some(ref f) => &**f,
+            None => continue,
+        };
+
+        // FIXME(emilio): We could avoid this most of the time if needed, but
+        // it's not clear it's worth it.
+        if !file_filter.is_match(file) {
+            continue;
+        }
+
+        let lines_captures = match lines_pattern.captures(&line) {
+            Some(captures) => captures,
+            None => continue,
+        };
+
+        let start_line = lines_captures
+            .get(1)
+            .unwrap()
+            .as_str()
+            .parse::<u32>()
+            .unwrap();
+        let line_count = match lines_captures.get(3) {
+            Some(line_count) => line_count.as_str().parse::<u32>().unwrap(),
+            None => 1,
+        };
+
+        if line_count == 0 {
+            continue;
+        }
+
+        let end_line = start_line + line_count - 1;
+        files.insert(file.to_owned());
+        ranges.push(Range {
+            file: file.to_owned(),
+            range: [start_line, end_line],
+        });
+    }
+
+    Ok((files, ranges))
+}
+
+#[test]
+fn scan_simple_git_diff() {
+    const DIFF: &str = include_str!("test/bindgen.diff");
+    let (files, ranges) = scan_diff(DIFF.as_bytes(), 1, r".*\.rs").expect("scan_diff failed?");
+
+    assert!(
+        files.contains("src/ir/traversal.rs"),
+        "Should've matched the filter"
+    );
+
+    assert!(
+        !files.contains("tests/headers/anon_enum.hpp"),
+        "Shouldn't have matched the filter"
+    );
+
+    assert_eq!(
+        &ranges,
+        &[
+            Range {
+                file: "src/ir/item.rs".to_owned(),
+                range: [148, 158],
+            },
+            Range {
+                file: "src/ir/item.rs".to_owned(),
+                range: [160, 170],
+            },
+            Range {
+                file: "src/ir/traversal.rs".to_owned(),
+                range: [9, 16],
+            },
+            Range {
+                file: "src/ir/traversal.rs".to_owned(),
+                range: [35, 43],
+            },
+        ]
+    );
+}
+
+#[cfg(test)]
+mod cmd_line_tests {
+    use super::*;
+
+    #[test]
+    fn default_options() {
+        let empty: Vec<String> = vec![];
+        let o = Opts::from_iter(&empty);
+        assert_eq!(DEFAULT_PATTERN, o.filter);
+        assert_eq!(0, o.skip_prefix);
+    }
+
+    #[test]
+    fn good_options() {
+        let o = Opts::from_iter(&["test", "-p", "10", "-f", r".*\.hs"]);
+        assert_eq!(r".*\.hs", o.filter);
+        assert_eq!(10, o.skip_prefix);
+    }
+
+    #[test]
+    fn unexpected_option() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "unexpected"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn unexpected_flag() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "--flag"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn overridden_option() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "-p", "10", "-p", "20"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn negative_filter() {
+        assert!(
+            Opts::clap()
+                .get_matches_from_safe(&["test", "-p", "-1"])
+                .is_err()
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/format-diff/test/bindgen.diff b/src/tools/rustfmt/src/format-diff/test/bindgen.diff
new file mode 100644
index 0000000000000..d2fd379f47165
--- /dev/null
+++ b/src/tools/rustfmt/src/format-diff/test/bindgen.diff
@@ -0,0 +1,67 @@
+diff --git a/src/ir/item.rs b/src/ir/item.rs
+index 7f3afefb..90d15e96 100644
+--- a/src/ir/item.rs
++++ b/src/ir/item.rs
+@@ -148,7 +148,11 @@ impl<'a, 'b> Iterator for ItemAncestorsIter<'a, 'b>
+ impl AsTemplateParam for ItemId {
+     type Extra = ();
+ 
+-    fn as_template_param(&self, ctx: &BindgenContext, _: &()) -> Option<ItemId> {
++    fn as_template_param(
++        &self,
++        ctx: &BindgenContext,
++        _: &(),
++    ) -> Option<ItemId> {
+         ctx.resolve_item(*self).as_template_param(ctx, &())
+     }
+ }
+@@ -156,7 +160,11 @@ impl AsTemplateParam for ItemId {
+ impl AsTemplateParam for Item {
+     type Extra = ();
+ 
+-    fn as_template_param(&self, ctx: &BindgenContext, _: &()) -> Option<ItemId> {
++    fn as_template_param(
++        &self,
++        ctx: &BindgenContext,
++        _: &(),
++    ) -> Option<ItemId> {
+         self.kind.as_template_param(ctx, self)
+     }
+ }
+diff --git a/src/ir/traversal.rs b/src/ir/traversal.rs
+index 762a3e2d..b9c9dd4e 100644
+--- a/src/ir/traversal.rs
++++ b/src/ir/traversal.rs
+@@ -9,6 +9,8 @@ use std::collections::{BTreeMap, VecDeque};
+ ///
+ ///   from --> to
+ ///
++/// Random content to generate a diff.
++///
+ /// The `from` is left implicit: it is the concrete `Trace` implementer which
+ /// yielded this outgoing edge.
+ #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+@@ -33,7 +35,9 @@ impl Into<ItemId> for Edge {
+     }
+ }
+ 
+-/// The kind of edge reference. This is useful when we wish to only consider
++/// The kind of edge reference.
++///
++/// This is useful when we wish to only consider
+ /// certain kinds of edges for a particular traversal or analysis.
+ #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+ pub enum EdgeKind {
+diff --git a/tests/headers/anon_enum.hpp b/tests/headers/anon_enum.hpp
+index 1961fe6c..34759df3 100644
+--- a/tests/headers/anon_enum.hpp
++++ b/tests/headers/anon_enum.hpp
+@@ -1,7 +1,7 @@
+ struct Test {
+   int foo;
+   float bar;
+-  enum { T_NONE };
++  enum { T_NONE, T_SOME };
+ };
+ 
+ typedef enum {
diff --git a/src/tools/rustfmt/src/format_report_formatter.rs b/src/tools/rustfmt/src/format_report_formatter.rs
new file mode 100644
index 0000000000000..c820259256c47
--- /dev/null
+++ b/src/tools/rustfmt/src/format_report_formatter.rs
@@ -0,0 +1,150 @@
+use crate::formatting::FormattingError;
+use crate::{ErrorKind, FormatReport};
+use annotate_snippets::display_list::{DisplayList, FormatOptions};
+use annotate_snippets::snippet::{Annotation, AnnotationType, Slice, Snippet, SourceAnnotation};
+use std::fmt::{self, Display};
+
+/// A builder for [`FormatReportFormatter`].
+pub struct FormatReportFormatterBuilder<'a> {
+    report: &'a FormatReport,
+    enable_colors: bool,
+}
+
+impl<'a> FormatReportFormatterBuilder<'a> {
+    /// Creates a new [`FormatReportFormatterBuilder`].
+    pub fn new(report: &'a FormatReport) -> Self {
+        Self {
+            report,
+            enable_colors: false,
+        }
+    }
+
+    /// Enables colors and formatting in the output.
+    pub fn enable_colors(self, enable_colors: bool) -> Self {
+        Self {
+            enable_colors,
+            ..self
+        }
+    }
+
+    /// Creates a new [`FormatReportFormatter`] from the settings in this builder.
+    pub fn build(self) -> FormatReportFormatter<'a> {
+        FormatReportFormatter {
+            report: self.report,
+            enable_colors: self.enable_colors,
+        }
+    }
+}
+
+/// Formats the warnings/errors in a [`FormatReport`].
+///
+/// Can be created using a [`FormatReportFormatterBuilder`].
+pub struct FormatReportFormatter<'a> {
+    report: &'a FormatReport,
+    enable_colors: bool,
+}
+
+impl<'a> Display for FormatReportFormatter<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let errors_by_file = &self.report.internal.borrow().0;
+
+        let opt = FormatOptions {
+            color: self.enable_colors,
+            ..Default::default()
+        };
+
+        for (file, errors) in errors_by_file {
+            for error in errors {
+                let error_kind = error.kind.to_string();
+                let title = Some(Annotation {
+                    id: if error.is_internal() {
+                        Some("internal")
+                    } else {
+                        None
+                    },
+                    label: Some(&error_kind),
+                    annotation_type: error_kind_to_snippet_annotation_type(&error.kind),
+                });
+
+                let message_suffix = error.msg_suffix();
+                let footer = if !message_suffix.is_empty() {
+                    Some(Annotation {
+                        id: None,
+                        label: Some(message_suffix),
+                        annotation_type: AnnotationType::Note,
+                    })
+                } else {
+                    None
+                };
+
+                let origin = format!("{}:{}", file, error.line);
+                let slice = Slice {
+                    source: &error.line_buffer.clone(),
+                    line_start: error.line,
+                    origin: Some(origin.as_str()),
+                    fold: false,
+                    annotations: slice_annotation(error).into_iter().collect(),
+                };
+
+                let snippet = Snippet {
+                    title,
+                    footer: footer.into_iter().collect(),
+                    slices: vec![slice],
+                    opt,
+                };
+                writeln!(f, "{}\n", DisplayList::from(snippet))?;
+            }
+        }
+
+        if !errors_by_file.is_empty() {
+            let label = format!(
+                "rustfmt has failed to format. See previous {} errors.",
+                self.report.warning_count()
+            );
+            let snippet = Snippet {
+                title: Some(Annotation {
+                    id: None,
+                    label: Some(&label),
+                    annotation_type: AnnotationType::Warning,
+                }),
+                footer: Vec::new(),
+                slices: Vec::new(),
+                opt,
+            };
+            writeln!(f, "{}", DisplayList::from(snippet))?;
+        }
+
+        Ok(())
+    }
+}
+
+fn slice_annotation(error: &FormattingError) -> Option<SourceAnnotation<'_>> {
+    let (range_start, range_length) = error.format_len();
+    let range_end = range_start + range_length;
+
+    if range_length > 0 {
+        Some(SourceAnnotation {
+            annotation_type: AnnotationType::Error,
+            range: (range_start, range_end),
+            label: "",
+        })
+    } else {
+        None
+    }
+}
+
+fn error_kind_to_snippet_annotation_type(error_kind: &ErrorKind) -> AnnotationType {
+    match error_kind {
+        ErrorKind::LineOverflow(..)
+        | ErrorKind::TrailingWhitespace
+        | ErrorKind::IoError(_)
+        | ErrorKind::ModuleResolutionError(_)
+        | ErrorKind::ParseError
+        | ErrorKind::LostComment
+        | ErrorKind::LicenseCheck
+        | ErrorKind::BadAttr
+        | ErrorKind::InvalidGlobPattern(_)
+        | ErrorKind::VersionMismatch => AnnotationType::Error,
+        ErrorKind::BadIssue(_) | ErrorKind::DeprecatedAttr => AnnotationType::Warning,
+    }
+}
diff --git a/src/tools/rustfmt/src/formatting.rs b/src/tools/rustfmt/src/formatting.rs
new file mode 100644
index 0000000000000..b69ecdc5cb8ae
--- /dev/null
+++ b/src/tools/rustfmt/src/formatting.rs
@@ -0,0 +1,610 @@
+// High level formatting functions.
+
+use std::collections::HashMap;
+use std::io::{self, Write};
+use std::time::{Duration, Instant};
+
+use rustc_ast::ast;
+use rustc_span::Span;
+
+use self::newline_style::apply_newline_style;
+use crate::comment::{CharClasses, FullCodeCharKind};
+use crate::config::{Config, FileName, Verbosity};
+use crate::issues::BadIssueSeeker;
+use crate::modules::Module;
+use crate::syntux::parser::{DirectoryOwnership, Parser, ParserError};
+use crate::syntux::session::ParseSess;
+use crate::utils::count_newlines;
+use crate::visitor::FmtVisitor;
+use crate::{modules, source_file, ErrorKind, FormatReport, Input, Session};
+
+mod newline_style;
+
+// A map of the files of a crate, with their new content
+pub(crate) type SourceFile = Vec<FileRecord>;
+pub(crate) type FileRecord = (FileName, String);
+
+impl<'b, T: Write + 'b> Session<'b, T> {
+    pub(crate) fn format_input_inner(
+        &mut self,
+        input: Input,
+        is_macro_def: bool,
+    ) -> Result<FormatReport, ErrorKind> {
+        if !self.config.version_meets_requirement() {
+            return Err(ErrorKind::VersionMismatch);
+        }
+
+        rustc_span::with_session_globals(self.config.edition().into(), || {
+            if self.config.disable_all_formatting() {
+                // When the input is from stdin, echo back the input.
+                if let Input::Text(ref buf) = input {
+                    if let Err(e) = io::stdout().write_all(buf.as_bytes()) {
+                        return Err(From::from(e));
+                    }
+                }
+                return Ok(FormatReport::new());
+            }
+
+            let config = &self.config.clone();
+            let format_result = format_project(input, config, self, is_macro_def);
+
+            format_result.map(|report| {
+                self.errors.add(&report.internal.borrow().1);
+                report
+            })
+        })
+    }
+}
+
+// Format an entire crate (or subset of the module tree).
+fn format_project<T: FormatHandler>(
+    input: Input,
+    config: &Config,
+    handler: &mut T,
+    is_macro_def: bool,
+) -> Result<FormatReport, ErrorKind> {
+    let mut timer = Timer::start();
+
+    let main_file = input.file_name();
+    let input_is_stdin = main_file == FileName::Stdin;
+
+    let parse_session = ParseSess::new(config)?;
+    if config.skip_children() && parse_session.ignore_file(&main_file) {
+        return Ok(FormatReport::new());
+    }
+
+    // Parse the crate.
+    let mut report = FormatReport::new();
+    let directory_ownership = input.to_directory_ownership();
+    let krate = match Parser::parse_crate(input, &parse_session) {
+        Ok(krate) => krate,
+        // Surface parse error via Session (errors are merged there from report)
+        Err(e) => {
+            let forbid_verbose = input_is_stdin || e != ParserError::ParsePanicError;
+            should_emit_verbose(forbid_verbose, config, || {
+                eprintln!("The Rust parser panicked");
+            });
+            report.add_parsing_error();
+            return Ok(report);
+        }
+    };
+
+    let mut context = FormatContext::new(&krate, report, parse_session, config, handler);
+    let files = modules::ModResolver::new(
+        &context.parse_session,
+        directory_ownership.unwrap_or(DirectoryOwnership::UnownedViaBlock),
+        !input_is_stdin && !config.skip_children(),
+    )
+    .visit_crate(&krate)?;
+
+    timer = timer.done_parsing();
+
+    // Suppress error output if we have to do any further parsing.
+    context.parse_session.set_silent_emitter();
+
+    for (path, module) in files {
+        let should_ignore = !input_is_stdin && context.ignore_file(&path);
+        if (config.skip_children() && path != main_file) || should_ignore {
+            continue;
+        }
+        should_emit_verbose(input_is_stdin, config, || println!("Formatting {}", path));
+        context.format_file(path, &module, is_macro_def)?;
+    }
+    timer = timer.done_formatting();
+
+    should_emit_verbose(input_is_stdin, config, || {
+        println!(
+            "Spent {0:.3} secs in the parsing phase, and {1:.3} secs in the formatting phase",
+            timer.get_parse_time(),
+            timer.get_format_time(),
+        )
+    });
+
+    Ok(context.report)
+}
+
+// Used for formatting files.
+#[derive(new)]
+struct FormatContext<'a, T: FormatHandler> {
+    krate: &'a ast::Crate,
+    report: FormatReport,
+    parse_session: ParseSess,
+    config: &'a Config,
+    handler: &'a mut T,
+}
+
+impl<'a, T: FormatHandler + 'a> FormatContext<'a, T> {
+    fn ignore_file(&self, path: &FileName) -> bool {
+        self.parse_session.ignore_file(path)
+    }
+
+    // Formats a single file/module.
+    fn format_file(
+        &mut self,
+        path: FileName,
+        module: &Module<'_>,
+        is_macro_def: bool,
+    ) -> Result<(), ErrorKind> {
+        let snippet_provider = self.parse_session.snippet_provider(module.span);
+        let mut visitor = FmtVisitor::from_parse_sess(
+            &self.parse_session,
+            &self.config,
+            &snippet_provider,
+            self.report.clone(),
+        );
+        visitor.skip_context.update_with_attrs(&self.krate.attrs);
+        visitor.is_macro_def = is_macro_def;
+        visitor.last_pos = snippet_provider.start_pos();
+        visitor.skip_empty_lines(snippet_provider.end_pos());
+        visitor.format_separate_mod(module, snippet_provider.end_pos());
+
+        debug_assert_eq!(
+            visitor.line_number,
+            count_newlines(&visitor.buffer),
+            "failed in format_file visitor.buffer:\n {:?}",
+            &visitor.buffer
+        );
+
+        // For some reason, the source_map does not include terminating
+        // newlines so we must add one on for each file. This is sad.
+        source_file::append_newline(&mut visitor.buffer);
+
+        format_lines(
+            &mut visitor.buffer,
+            &path,
+            &visitor.skipped_range.borrow(),
+            &self.config,
+            &self.report,
+        );
+
+        apply_newline_style(
+            self.config.newline_style(),
+            &mut visitor.buffer,
+            snippet_provider.entire_snippet(),
+        );
+
+        if visitor.macro_rewrite_failure {
+            self.report.add_macro_format_failure();
+        }
+        self.report
+            .add_non_formatted_ranges(visitor.skipped_range.borrow().clone());
+
+        self.handler.handle_formatted_file(
+            &self.parse_session,
+            path,
+            visitor.buffer.to_owned(),
+            &mut self.report,
+        )
+    }
+}
+
+// Handle the results of formatting.
+trait FormatHandler {
+    fn handle_formatted_file(
+        &mut self,
+        parse_session: &ParseSess,
+        path: FileName,
+        result: String,
+        report: &mut FormatReport,
+    ) -> Result<(), ErrorKind>;
+}
+
+impl<'b, T: Write + 'b> FormatHandler for Session<'b, T> {
+    // Called for each formatted file.
+    fn handle_formatted_file(
+        &mut self,
+        parse_session: &ParseSess,
+        path: FileName,
+        result: String,
+        report: &mut FormatReport,
+    ) -> Result<(), ErrorKind> {
+        if let Some(ref mut out) = self.out {
+            match source_file::write_file(
+                Some(parse_session),
+                &path,
+                &result,
+                out,
+                &mut *self.emitter,
+                self.config.newline_style(),
+            ) {
+                Ok(ref result) if result.has_diff => report.add_diff(),
+                Err(e) => {
+                    // Create a new error with path_str to help users see which files failed
+                    let err_msg = format!("{}: {}", path, e);
+                    return Err(io::Error::new(e.kind(), err_msg).into());
+                }
+                _ => {}
+            }
+        }
+
+        self.source_file.push((path, result));
+        Ok(())
+    }
+}
+
+pub(crate) struct FormattingError {
+    pub(crate) line: usize,
+    pub(crate) kind: ErrorKind,
+    is_comment: bool,
+    is_string: bool,
+    pub(crate) line_buffer: String,
+}
+
+impl FormattingError {
+    pub(crate) fn from_span(
+        span: Span,
+        parse_sess: &ParseSess,
+        kind: ErrorKind,
+    ) -> FormattingError {
+        FormattingError {
+            line: parse_sess.line_of_byte_pos(span.lo()),
+            is_comment: kind.is_comment(),
+            kind,
+            is_string: false,
+            line_buffer: parse_sess.span_to_first_line_string(span),
+        }
+    }
+
+    pub(crate) fn is_internal(&self) -> bool {
+        match self.kind {
+            ErrorKind::LineOverflow(..)
+            | ErrorKind::TrailingWhitespace
+            | ErrorKind::IoError(_)
+            | ErrorKind::ParseError
+            | ErrorKind::LostComment => true,
+            _ => false,
+        }
+    }
+
+    pub(crate) fn msg_suffix(&self) -> &str {
+        if self.is_comment || self.is_string {
+            "set `error_on_unformatted = false` to suppress \
+             the warning against comments or string literals\n"
+        } else {
+            ""
+        }
+    }
+
+    // (space, target)
+    pub(crate) fn format_len(&self) -> (usize, usize) {
+        match self.kind {
+            ErrorKind::LineOverflow(found, max) => (max, found - max),
+            ErrorKind::TrailingWhitespace
+            | ErrorKind::DeprecatedAttr
+            | ErrorKind::BadIssue(_)
+            | ErrorKind::BadAttr
+            | ErrorKind::LostComment
+            | ErrorKind::LicenseCheck => {
+                let trailing_ws_start = self
+                    .line_buffer
+                    .rfind(|c: char| !c.is_whitespace())
+                    .map(|pos| pos + 1)
+                    .unwrap_or(0);
+                (
+                    trailing_ws_start,
+                    self.line_buffer.len() - trailing_ws_start,
+                )
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
+pub(crate) type FormatErrorMap = HashMap<FileName, Vec<FormattingError>>;
+
+#[derive(Default, Debug, PartialEq)]
+pub(crate) struct ReportedErrors {
+    // Encountered e.g., an IO error.
+    pub(crate) has_operational_errors: bool,
+
+    // Failed to reformat code because of parsing errors.
+    pub(crate) has_parsing_errors: bool,
+
+    // Code is valid, but it is impossible to format it properly.
+    pub(crate) has_formatting_errors: bool,
+
+    // Code contains macro call that was unable to format.
+    pub(crate) has_macro_format_failure: bool,
+
+    // Failed a check, such as the license check or other opt-in checking.
+    pub(crate) has_check_errors: bool,
+
+    /// Formatted code differs from existing code (--check only).
+    pub(crate) has_diff: bool,
+
+    /// Formatted code missed something, like lost comments or extra trailing space
+    pub(crate) has_unformatted_code_errors: bool,
+}
+
+impl ReportedErrors {
+    /// Combine two summaries together.
+    pub(crate) fn add(&mut self, other: &ReportedErrors) {
+        self.has_operational_errors |= other.has_operational_errors;
+        self.has_parsing_errors |= other.has_parsing_errors;
+        self.has_formatting_errors |= other.has_formatting_errors;
+        self.has_macro_format_failure |= other.has_macro_format_failure;
+        self.has_check_errors |= other.has_check_errors;
+        self.has_diff |= other.has_diff;
+        self.has_unformatted_code_errors |= other.has_unformatted_code_errors;
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+enum Timer {
+    Disabled,
+    Initialized(Instant),
+    DoneParsing(Instant, Instant),
+    DoneFormatting(Instant, Instant, Instant),
+}
+
+impl Timer {
+    fn start() -> Timer {
+        if cfg!(target_arch = "wasm32") {
+            Timer::Disabled
+        } else {
+            Timer::Initialized(Instant::now())
+        }
+    }
+    fn done_parsing(self) -> Self {
+        match self {
+            Timer::Disabled => Timer::Disabled,
+            Timer::Initialized(init_time) => Timer::DoneParsing(init_time, Instant::now()),
+            _ => panic!("Timer can only transition to DoneParsing from Initialized state"),
+        }
+    }
+
+    fn done_formatting(self) -> Self {
+        match self {
+            Timer::Disabled => Timer::Disabled,
+            Timer::DoneParsing(init_time, parse_time) => {
+                Timer::DoneFormatting(init_time, parse_time, Instant::now())
+            }
+            _ => panic!("Timer can only transition to DoneFormatting from DoneParsing state"),
+        }
+    }
+
+    /// Returns the time it took to parse the source files in seconds.
+    fn get_parse_time(&self) -> f32 {
+        match *self {
+            Timer::Disabled => panic!("this platform cannot time execution"),
+            Timer::DoneParsing(init, parse_time) | Timer::DoneFormatting(init, parse_time, _) => {
+                // This should never underflow since `Instant::now()` guarantees monotonicity.
+                Self::duration_to_f32(parse_time.duration_since(init))
+            }
+            Timer::Initialized(..) => unreachable!(),
+        }
+    }
+
+    /// Returns the time it took to go from the parsed AST to the formatted output. Parsing time is
+    /// not included.
+    fn get_format_time(&self) -> f32 {
+        match *self {
+            Timer::Disabled => panic!("this platform cannot time execution"),
+            Timer::DoneFormatting(_init, parse_time, format_time) => {
+                Self::duration_to_f32(format_time.duration_since(parse_time))
+            }
+            Timer::DoneParsing(..) | Timer::Initialized(..) => unreachable!(),
+        }
+    }
+
+    fn duration_to_f32(d: Duration) -> f32 {
+        d.as_secs() as f32 + d.subsec_nanos() as f32 / 1_000_000_000f32
+    }
+}
+
+// Formatting done on a char by char or line by line basis.
+// FIXME(#20): other stuff for parity with make tidy.
+fn format_lines(
+    text: &mut String,
+    name: &FileName,
+    skipped_range: &[(usize, usize)],
+    config: &Config,
+    report: &FormatReport,
+) {
+    let mut formatter = FormatLines::new(name, skipped_range, config);
+    formatter.check_license(text);
+    formatter.iterate(text);
+
+    if formatter.newline_count > 1 {
+        debug!("track truncate: {} {}", text.len(), formatter.newline_count);
+        let line = text.len() - formatter.newline_count + 1;
+        text.truncate(line);
+    }
+
+    report.append(name.clone(), formatter.errors);
+}
+
+struct FormatLines<'a> {
+    name: &'a FileName,
+    skipped_range: &'a [(usize, usize)],
+    last_was_space: bool,
+    line_len: usize,
+    cur_line: usize,
+    newline_count: usize,
+    errors: Vec<FormattingError>,
+    issue_seeker: BadIssueSeeker,
+    line_buffer: String,
+    current_line_contains_string_literal: bool,
+    format_line: bool,
+    allow_issue_seek: bool,
+    config: &'a Config,
+}
+
+impl<'a> FormatLines<'a> {
+    fn new(
+        name: &'a FileName,
+        skipped_range: &'a [(usize, usize)],
+        config: &'a Config,
+    ) -> FormatLines<'a> {
+        let issue_seeker = BadIssueSeeker::new(config.report_todo(), config.report_fixme());
+        FormatLines {
+            name,
+            skipped_range,
+            last_was_space: false,
+            line_len: 0,
+            cur_line: 1,
+            newline_count: 0,
+            errors: vec![],
+            allow_issue_seek: !issue_seeker.is_disabled(),
+            issue_seeker,
+            line_buffer: String::with_capacity(config.max_width() * 2),
+            current_line_contains_string_literal: false,
+            format_line: config.file_lines().contains_line(name, 1),
+            config,
+        }
+    }
+
+    fn check_license(&mut self, text: &mut String) {
+        if let Some(ref license_template) = self.config.license_template {
+            if !license_template.is_match(text) {
+                self.errors.push(FormattingError {
+                    line: self.cur_line,
+                    kind: ErrorKind::LicenseCheck,
+                    is_comment: false,
+                    is_string: false,
+                    line_buffer: String::new(),
+                });
+            }
+        }
+    }
+
+    // Iterate over the chars in the file map.
+    fn iterate(&mut self, text: &mut String) {
+        for (kind, c) in CharClasses::new(text.chars()) {
+            if c == '\r' {
+                continue;
+            }
+
+            if self.allow_issue_seek && self.format_line {
+                // Add warnings for bad todos/ fixmes
+                if let Some(issue) = self.issue_seeker.inspect(c) {
+                    self.push_err(ErrorKind::BadIssue(issue), false, false);
+                }
+            }
+
+            if c == '\n' {
+                self.new_line(kind);
+            } else {
+                self.char(c, kind);
+            }
+        }
+    }
+
+    fn new_line(&mut self, kind: FullCodeCharKind) {
+        if self.format_line {
+            // Check for (and record) trailing whitespace.
+            if self.last_was_space {
+                if self.should_report_error(kind, &ErrorKind::TrailingWhitespace)
+                    && !self.is_skipped_line()
+                {
+                    self.push_err(
+                        ErrorKind::TrailingWhitespace,
+                        kind.is_comment(),
+                        kind.is_string(),
+                    );
+                }
+                self.line_len -= 1;
+            }
+
+            // Check for any line width errors we couldn't correct.
+            let error_kind = ErrorKind::LineOverflow(self.line_len, self.config.max_width());
+            if self.line_len > self.config.max_width()
+                && !self.is_skipped_line()
+                && self.should_report_error(kind, &error_kind)
+            {
+                let is_string = self.current_line_contains_string_literal;
+                self.push_err(error_kind, kind.is_comment(), is_string);
+            }
+        }
+
+        self.line_len = 0;
+        self.cur_line += 1;
+        self.format_line = self
+            .config
+            .file_lines()
+            .contains_line(self.name, self.cur_line);
+        self.newline_count += 1;
+        self.last_was_space = false;
+        self.line_buffer.clear();
+        self.current_line_contains_string_literal = false;
+    }
+
+    fn char(&mut self, c: char, kind: FullCodeCharKind) {
+        self.newline_count = 0;
+        self.line_len += if c == '\t' {
+            self.config.tab_spaces()
+        } else {
+            1
+        };
+        self.last_was_space = c.is_whitespace();
+        self.line_buffer.push(c);
+        if kind.is_string() {
+            self.current_line_contains_string_literal = true;
+        }
+    }
+
+    fn push_err(&mut self, kind: ErrorKind, is_comment: bool, is_string: bool) {
+        self.errors.push(FormattingError {
+            line: self.cur_line,
+            kind,
+            is_comment,
+            is_string,
+            line_buffer: self.line_buffer.clone(),
+        });
+    }
+
+    fn should_report_error(&self, char_kind: FullCodeCharKind, error_kind: &ErrorKind) -> bool {
+        let allow_error_report = if char_kind.is_comment()
+            || self.current_line_contains_string_literal
+            || error_kind.is_comment()
+        {
+            self.config.error_on_unformatted()
+        } else {
+            true
+        };
+
+        match error_kind {
+            ErrorKind::LineOverflow(..) => {
+                self.config.error_on_line_overflow() && allow_error_report
+            }
+            ErrorKind::TrailingWhitespace | ErrorKind::LostComment => allow_error_report,
+            _ => true,
+        }
+    }
+
+    /// Returns `true` if the line with the given line number was skipped by `#[rustfmt::skip]`.
+    fn is_skipped_line(&self) -> bool {
+        self.skipped_range
+            .iter()
+            .any(|&(lo, hi)| lo <= self.cur_line && self.cur_line <= hi)
+    }
+}
+
+fn should_emit_verbose<F>(forbid_verbose_output: bool, config: &Config, f: F)
+where
+    F: Fn(),
+{
+    if config.verbose() == Verbosity::Verbose && !forbid_verbose_output {
+        f();
+    }
+}
diff --git a/src/tools/rustfmt/src/formatting/newline_style.rs b/src/tools/rustfmt/src/formatting/newline_style.rs
new file mode 100644
index 0000000000000..ac62009490001
--- /dev/null
+++ b/src/tools/rustfmt/src/formatting/newline_style.rs
@@ -0,0 +1,250 @@
+use crate::NewlineStyle;
+
+/// Apply this newline style to the formatted text. When the style is set
+/// to `Auto`, the `raw_input_text` is used to detect the existing line
+/// endings.
+///
+/// If the style is set to `Auto` and `raw_input_text` contains no
+/// newlines, the `Native` style will be used.
+pub(crate) fn apply_newline_style(
+    newline_style: NewlineStyle,
+    formatted_text: &mut String,
+    raw_input_text: &str,
+) {
+    *formatted_text = match effective_newline_style(newline_style, raw_input_text) {
+        EffectiveNewlineStyle::Windows => convert_to_windows_newlines(formatted_text),
+        EffectiveNewlineStyle::Unix => convert_to_unix_newlines(formatted_text),
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+enum EffectiveNewlineStyle {
+    Windows,
+    Unix,
+}
+
+fn effective_newline_style(
+    newline_style: NewlineStyle,
+    raw_input_text: &str,
+) -> EffectiveNewlineStyle {
+    match newline_style {
+        NewlineStyle::Auto => auto_detect_newline_style(raw_input_text),
+        NewlineStyle::Native => native_newline_style(),
+        NewlineStyle::Windows => EffectiveNewlineStyle::Windows,
+        NewlineStyle::Unix => EffectiveNewlineStyle::Unix,
+    }
+}
+
+const LINE_FEED: char = '\n';
+const CARRIAGE_RETURN: char = '\r';
+const WINDOWS_NEWLINE: &str = "\r\n";
+const UNIX_NEWLINE: &str = "\n";
+
+fn auto_detect_newline_style(raw_input_text: &str) -> EffectiveNewlineStyle {
+    let first_line_feed_pos = raw_input_text.chars().position(|ch| ch == LINE_FEED);
+    match first_line_feed_pos {
+        Some(first_line_feed_pos) => {
+            let char_before_line_feed_pos = first_line_feed_pos.saturating_sub(1);
+            let char_before_line_feed = raw_input_text.chars().nth(char_before_line_feed_pos);
+            match char_before_line_feed {
+                Some(CARRIAGE_RETURN) => EffectiveNewlineStyle::Windows,
+                _ => EffectiveNewlineStyle::Unix,
+            }
+        }
+        None => native_newline_style(),
+    }
+}
+
+fn native_newline_style() -> EffectiveNewlineStyle {
+    if cfg!(windows) {
+        EffectiveNewlineStyle::Windows
+    } else {
+        EffectiveNewlineStyle::Unix
+    }
+}
+
+fn convert_to_windows_newlines(formatted_text: &String) -> String {
+    let mut transformed = String::with_capacity(2 * formatted_text.capacity());
+    let mut chars = formatted_text.chars().peekable();
+    while let Some(current_char) = chars.next() {
+        let next_char = chars.peek();
+        match current_char {
+            LINE_FEED => transformed.push_str(WINDOWS_NEWLINE),
+            CARRIAGE_RETURN if next_char == Some(&LINE_FEED) => {}
+            current_char => transformed.push(current_char),
+        }
+    }
+    transformed
+}
+
+fn convert_to_unix_newlines(formatted_text: &String) -> String {
+    formatted_text.replace(WINDOWS_NEWLINE, UNIX_NEWLINE)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn auto_detects_unix_newlines() {
+        assert_eq!(
+            EffectiveNewlineStyle::Unix,
+            auto_detect_newline_style("One\nTwo\nThree")
+        );
+    }
+
+    #[test]
+    fn auto_detects_windows_newlines() {
+        assert_eq!(
+            EffectiveNewlineStyle::Windows,
+            auto_detect_newline_style("One\r\nTwo\r\nThree")
+        );
+    }
+
+    #[test]
+    fn auto_detects_windows_newlines_with_multibyte_char_on_first_line() {
+        assert_eq!(
+            EffectiveNewlineStyle::Windows,
+            auto_detect_newline_style("A 🎢 of a first line\r\nTwo\r\nThree")
+        );
+    }
+
+    #[test]
+    fn falls_back_to_native_newlines_if_no_newlines_are_found() {
+        let expected_newline_style = if cfg!(windows) {
+            EffectiveNewlineStyle::Windows
+        } else {
+            EffectiveNewlineStyle::Unix
+        };
+        assert_eq!(
+            expected_newline_style,
+            auto_detect_newline_style("One Two Three")
+        );
+    }
+
+    #[test]
+    fn auto_detects_and_applies_unix_newlines() {
+        let formatted_text = "One\nTwo\nThree";
+        let raw_input_text = "One\nTwo\nThree";
+
+        let mut out = String::from(formatted_text);
+        apply_newline_style(NewlineStyle::Auto, &mut out, raw_input_text);
+        assert_eq!("One\nTwo\nThree", &out, "auto should detect 'lf'");
+    }
+
+    #[test]
+    fn auto_detects_and_applies_windows_newlines() {
+        let formatted_text = "One\nTwo\nThree";
+        let raw_input_text = "One\r\nTwo\r\nThree";
+
+        let mut out = String::from(formatted_text);
+        apply_newline_style(NewlineStyle::Auto, &mut out, raw_input_text);
+        assert_eq!("One\r\nTwo\r\nThree", &out, "auto should detect 'crlf'");
+    }
+
+    #[test]
+    fn auto_detects_and_applies_native_newlines() {
+        let formatted_text = "One\nTwo\nThree";
+        let raw_input_text = "One Two Three";
+
+        let mut out = String::from(formatted_text);
+        apply_newline_style(NewlineStyle::Auto, &mut out, raw_input_text);
+
+        if cfg!(windows) {
+            assert_eq!(
+                "One\r\nTwo\r\nThree", &out,
+                "auto-native-windows should detect 'crlf'"
+            );
+        } else {
+            assert_eq!(
+                "One\nTwo\nThree", &out,
+                "auto-native-unix should detect 'lf'"
+            );
+        }
+    }
+
+    #[test]
+    fn applies_unix_newlines() {
+        test_newlines_are_applied_correctly(
+            "One\r\nTwo\nThree",
+            "One\nTwo\nThree",
+            NewlineStyle::Unix,
+        );
+    }
+
+    #[test]
+    fn applying_unix_newlines_changes_nothing_for_unix_newlines() {
+        let formatted_text = "One\nTwo\nThree";
+        test_newlines_are_applied_correctly(formatted_text, formatted_text, NewlineStyle::Unix);
+    }
+
+    #[test]
+    fn applies_unix_newlines_to_string_with_unix_and_windows_newlines() {
+        test_newlines_are_applied_correctly(
+            "One\r\nTwo\r\nThree\nFour",
+            "One\nTwo\nThree\nFour",
+            NewlineStyle::Unix,
+        );
+    }
+
+    #[test]
+    fn applies_windows_newlines_to_string_with_unix_and_windows_newlines() {
+        test_newlines_are_applied_correctly(
+            "One\nTwo\nThree\r\nFour",
+            "One\r\nTwo\r\nThree\r\nFour",
+            NewlineStyle::Windows,
+        );
+    }
+
+    #[test]
+    fn applying_windows_newlines_changes_nothing_for_windows_newlines() {
+        let formatted_text = "One\r\nTwo\r\nThree";
+        test_newlines_are_applied_correctly(formatted_text, formatted_text, NewlineStyle::Windows);
+    }
+
+    #[test]
+    fn keeps_carriage_returns_when_applying_windows_newlines_to_str_with_unix_newlines() {
+        test_newlines_are_applied_correctly(
+            "One\nTwo\nThree\rDrei",
+            "One\r\nTwo\r\nThree\rDrei",
+            NewlineStyle::Windows,
+        );
+    }
+
+    #[test]
+    fn keeps_carriage_returns_when_applying_unix_newlines_to_str_with_unix_newlines() {
+        test_newlines_are_applied_correctly(
+            "One\nTwo\nThree\rDrei",
+            "One\nTwo\nThree\rDrei",
+            NewlineStyle::Unix,
+        );
+    }
+
+    #[test]
+    fn keeps_carriage_returns_when_applying_windows_newlines_to_str_with_windows_newlines() {
+        test_newlines_are_applied_correctly(
+            "One\r\nTwo\r\nThree\rDrei",
+            "One\r\nTwo\r\nThree\rDrei",
+            NewlineStyle::Windows,
+        );
+    }
+
+    #[test]
+    fn keeps_carriage_returns_when_applying_unix_newlines_to_str_with_windows_newlines() {
+        test_newlines_are_applied_correctly(
+            "One\r\nTwo\r\nThree\rDrei",
+            "One\nTwo\nThree\rDrei",
+            NewlineStyle::Unix,
+        );
+    }
+
+    fn test_newlines_are_applied_correctly(
+        input: &str,
+        expected: &str,
+        newline_style: NewlineStyle,
+    ) {
+        let mut out = String::from(input);
+        apply_newline_style(newline_style, &mut out, input);
+        assert_eq!(expected, &out);
+    }
+}
diff --git a/src/tools/rustfmt/src/git-rustfmt/main.rs b/src/tools/rustfmt/src/git-rustfmt/main.rs
new file mode 100644
index 0000000000000..16f5d1dd4f234
--- /dev/null
+++ b/src/tools/rustfmt/src/git-rustfmt/main.rs
@@ -0,0 +1,192 @@
+#[macro_use]
+extern crate log;
+
+use std::env;
+use std::io::stdout;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::str::FromStr;
+
+use getopts::{Matches, Options};
+use rustfmt_nightly as rustfmt;
+
+use crate::rustfmt::{load_config, CliOptions, FormatReportFormatterBuilder, Input, Session};
+
+fn prune_files(files: Vec<&str>) -> Vec<&str> {
+    let prefixes: Vec<_> = files
+        .iter()
+        .filter(|f| f.ends_with("mod.rs") || f.ends_with("lib.rs"))
+        .map(|f| &f[..f.len() - 6])
+        .collect();
+
+    let mut pruned_prefixes = vec![];
+    for p1 in prefixes {
+        if p1.starts_with("src/bin/") || pruned_prefixes.iter().all(|p2| !p1.starts_with(p2)) {
+            pruned_prefixes.push(p1);
+        }
+    }
+    debug!("prefixes: {:?}", pruned_prefixes);
+
+    files
+        .into_iter()
+        .filter(|f| {
+            if f.ends_with("mod.rs") || f.ends_with("lib.rs") || f.starts_with("src/bin/") {
+                return true;
+            }
+            pruned_prefixes.iter().all(|pp| !f.starts_with(pp))
+        })
+        .collect()
+}
+
+fn git_diff(commits: &str) -> String {
+    let mut cmd = Command::new("git");
+    cmd.arg("diff");
+    if commits != "0" {
+        cmd.arg(format!("HEAD~{}", commits));
+    }
+    let output = cmd.output().expect("Couldn't execute `git diff`");
+    String::from_utf8_lossy(&output.stdout).into_owned()
+}
+
+fn get_files(input: &str) -> Vec<&str> {
+    input
+        .lines()
+        .filter(|line| line.starts_with("+++ b/") && line.ends_with(".rs"))
+        .map(|line| &line[6..])
+        .collect()
+}
+
+fn fmt_files(files: &[&str]) -> i32 {
+    let (config, _) =
+        load_config::<NullOptions>(Some(Path::new(".")), None).expect("couldn't load config");
+
+    let mut exit_code = 0;
+    let mut out = stdout();
+    let mut session = Session::new(config, Some(&mut out));
+    for file in files {
+        let report = session.format(Input::File(PathBuf::from(file))).unwrap();
+        if report.has_warnings() {
+            eprintln!("{}", FormatReportFormatterBuilder::new(&report).build());
+        }
+        if !session.has_no_errors() {
+            exit_code = 1;
+        }
+    }
+    exit_code
+}
+
+struct NullOptions;
+
+impl CliOptions for NullOptions {
+    fn apply_to(self, _: &mut rustfmt::Config) {
+        unreachable!();
+    }
+    fn config_path(&self) -> Option<&Path> {
+        unreachable!();
+    }
+}
+
+fn uncommitted_files() -> Vec<String> {
+    let mut cmd = Command::new("git");
+    cmd.arg("ls-files");
+    cmd.arg("--others");
+    cmd.arg("--modified");
+    cmd.arg("--exclude-standard");
+    let output = cmd.output().expect("Couldn't execute Git");
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    stdout
+        .lines()
+        .filter(|s| s.ends_with(".rs"))
+        .map(std::borrow::ToOwned::to_owned)
+        .collect()
+}
+
+fn check_uncommitted() {
+    let uncommitted = uncommitted_files();
+    debug!("uncommitted files: {:?}", uncommitted);
+    if !uncommitted.is_empty() {
+        println!("Found untracked changes:");
+        for f in &uncommitted {
+            println!("  {}", f);
+        }
+        println!("Commit your work, or run with `-u`.");
+        println!("Exiting.");
+        std::process::exit(1);
+    }
+}
+
+fn make_opts() -> Options {
+    let mut opts = Options::new();
+    opts.optflag("h", "help", "show this message");
+    opts.optflag("c", "check", "check only, don't format (unimplemented)");
+    opts.optflag("u", "uncommitted", "format uncommitted files");
+    opts
+}
+
+struct Config {
+    commits: String,
+    uncommitted: bool,
+}
+
+impl Config {
+    fn from_args(matches: &Matches, opts: &Options) -> Config {
+        // `--help` display help message and quit
+        if matches.opt_present("h") {
+            let message = format!(
+                "\nusage: {} <commits> [options]\n\n\
+                 commits: number of commits to format, default: 1",
+                env::args_os().next().unwrap().to_string_lossy()
+            );
+            println!("{}", opts.usage(&message));
+            std::process::exit(0);
+        }
+
+        let mut config = Config {
+            commits: "1".to_owned(),
+            uncommitted: false,
+        };
+
+        if matches.opt_present("c") {
+            unimplemented!();
+        }
+
+        if matches.opt_present("u") {
+            config.uncommitted = true;
+        }
+
+        if matches.free.len() > 1 {
+            panic!("unknown arguments, use `-h` for usage");
+        }
+        if matches.free.len() == 1 {
+            let commits = matches.free[0].trim();
+            if u32::from_str(commits).is_err() {
+                panic!("Couldn't parse number of commits");
+            }
+            config.commits = commits.to_owned();
+        }
+
+        config
+    }
+}
+
+fn main() {
+    env_logger::init();
+
+    let opts = make_opts();
+    let matches = opts
+        .parse(env::args().skip(1))
+        .expect("Couldn't parse command line");
+    let config = Config::from_args(&matches, &opts);
+
+    if !config.uncommitted {
+        check_uncommitted();
+    }
+
+    let stdout = git_diff(&config.commits);
+    let files = get_files(&stdout);
+    debug!("files: {:?}", files);
+    let files = prune_files(files);
+    debug!("pruned files: {:?}", files);
+    let exit_code = fmt_files(&files);
+    std::process::exit(exit_code);
+}
diff --git a/src/tools/rustfmt/src/ignore_path.rs b/src/tools/rustfmt/src/ignore_path.rs
new file mode 100644
index 0000000000000..d8974e12b8f5f
--- /dev/null
+++ b/src/tools/rustfmt/src/ignore_path.rs
@@ -0,0 +1,57 @@
+use ignore::{self, gitignore};
+
+use crate::config::{FileName, IgnoreList};
+
+pub(crate) struct IgnorePathSet {
+    ignore_set: gitignore::Gitignore,
+}
+
+impl IgnorePathSet {
+    pub(crate) fn from_ignore_list(ignore_list: &IgnoreList) -> Result<Self, ignore::Error> {
+        let mut ignore_builder = gitignore::GitignoreBuilder::new(ignore_list.rustfmt_toml_path());
+
+        for ignore_path in ignore_list {
+            ignore_builder.add_line(None, ignore_path.to_str().unwrap())?;
+        }
+
+        Ok(IgnorePathSet {
+            ignore_set: ignore_builder.build()?,
+        })
+    }
+
+    pub(crate) fn is_match(&self, file_name: &FileName) -> bool {
+        match file_name {
+            FileName::Stdin => false,
+            FileName::Real(p) => self
+                .ignore_set
+                .matched_path_or_any_parents(p, false)
+                .is_ignore(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::path::{Path, PathBuf};
+
+    use crate::config::{Config, FileName};
+    use crate::ignore_path::IgnorePathSet;
+
+    #[test]
+    fn test_ignore_path_set() {
+        match option_env!("CFG_RELEASE_CHANNEL") {
+            // this test requires nightly
+            None | Some("nightly") => {
+                let config =
+                    Config::from_toml(r#"ignore = ["foo.rs", "bar_dir/*"]"#, Path::new(""))
+                        .unwrap();
+                let ignore_path_set = IgnorePathSet::from_ignore_list(&config.ignore()).unwrap();
+
+                assert!(ignore_path_set.is_match(&FileName::Real(PathBuf::from("src/foo.rs"))));
+                assert!(ignore_path_set.is_match(&FileName::Real(PathBuf::from("bar_dir/baz.rs"))));
+                assert!(!ignore_path_set.is_match(&FileName::Real(PathBuf::from("src/bar.rs"))));
+            }
+            _ => (),
+        };
+    }
+}
diff --git a/src/tools/rustfmt/src/imports.rs b/src/tools/rustfmt/src/imports.rs
new file mode 100644
index 0000000000000..0f635fe1ccb35
--- /dev/null
+++ b/src/tools/rustfmt/src/imports.rs
@@ -0,0 +1,1210 @@
+use std::borrow::Cow;
+use std::cmp::Ordering;
+use std::fmt;
+
+use rustc_ast::ast::{self, UseTreeKind};
+use rustc_span::{
+    symbol::{self, sym},
+    BytePos, Span, DUMMY_SP,
+};
+
+use crate::comment::combine_strs_with_missing_comments;
+use crate::config::lists::*;
+use crate::config::{Edition, IndentStyle};
+use crate::lists::{
+    definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
+};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::spanned::Spanned;
+use crate::utils::{is_same_visibility, mk_sp, rewrite_ident};
+use crate::visitor::FmtVisitor;
+
+/// Returns a name imported by a `use` declaration.
+/// E.g., returns `Ordering` for `std::cmp::Ordering` and `self` for `std::cmp::self`.
+pub(crate) fn path_to_imported_ident(path: &ast::Path) -> symbol::Ident {
+    path.segments.last().unwrap().ident
+}
+
+impl<'a> FmtVisitor<'a> {
+    pub(crate) fn format_import(&mut self, item: &ast::Item, tree: &ast::UseTree) {
+        let span = item.span();
+        let shape = self.shape();
+        let rw = UseTree::from_ast(
+            &self.get_context(),
+            tree,
+            None,
+            Some(item.vis.clone()),
+            Some(item.span.lo()),
+            Some(item.attrs.clone()),
+        )
+        .rewrite_top_level(&self.get_context(), shape);
+        match rw {
+            Some(ref s) if s.is_empty() => {
+                // Format up to last newline
+                let prev_span = mk_sp(self.last_pos, source!(self, span).lo());
+                let trimmed_snippet = self.snippet(prev_span).trim_end();
+                let span_end = self.last_pos + BytePos(trimmed_snippet.len() as u32);
+                self.format_missing(span_end);
+                // We have an excessive newline from the removed import.
+                if self.buffer.ends_with('\n') {
+                    self.buffer.pop();
+                    self.line_number -= 1;
+                }
+                self.last_pos = source!(self, span).hi();
+            }
+            Some(ref s) => {
+                self.format_missing_with_indent(source!(self, span).lo());
+                self.push_str(s);
+                self.last_pos = source!(self, span).hi();
+            }
+            None => {
+                self.format_missing_with_indent(source!(self, span).lo());
+                self.format_missing(source!(self, span).hi());
+            }
+        }
+    }
+}
+
+// Ordering of imports
+
+// We order imports by translating to our own representation and then sorting.
+// The Rust AST data structures are really bad for this. Rustfmt applies a bunch
+// of normalisations to imports and since we want to sort based on the result
+// of these (and to maintain idempotence) we must apply the same normalisations
+// to the data structures for sorting.
+//
+// We sort `self` and `super` before other imports, then identifier imports,
+// then glob imports, then lists of imports. We do not take aliases into account
+// when ordering unless the imports are identical except for the alias (rare in
+// practice).
+
+// FIXME(#2531): we should unify the comparison code here with the formatting
+// code elsewhere since we are essentially string-ifying twice. Furthermore, by
+// parsing to our own format on comparison, we repeat a lot of work when
+// sorting.
+
+// FIXME we do a lot of allocation to make our own representation.
+#[derive(Clone, Eq, PartialEq)]
+pub(crate) enum UseSegment {
+    Ident(String, Option<String>),
+    Slf(Option<String>),
+    Super(Option<String>),
+    Crate(Option<String>),
+    Glob,
+    List(Vec<UseTree>),
+}
+
+#[derive(Clone)]
+pub(crate) struct UseTree {
+    pub(crate) path: Vec<UseSegment>,
+    pub(crate) span: Span,
+    // Comment information within nested use tree.
+    pub(crate) list_item: Option<ListItem>,
+    // Additional fields for top level use items.
+    // Should we have another struct for top-level use items rather than reusing this?
+    visibility: Option<ast::Visibility>,
+    attrs: Option<Vec<ast::Attribute>>,
+}
+
+impl PartialEq for UseTree {
+    fn eq(&self, other: &UseTree) -> bool {
+        self.path == other.path
+    }
+}
+impl Eq for UseTree {}
+
+impl Spanned for UseTree {
+    fn span(&self) -> Span {
+        let lo = if let Some(ref attrs) = self.attrs {
+            attrs.iter().next().map_or(self.span.lo(), |a| a.span.lo())
+        } else {
+            self.span.lo()
+        };
+        mk_sp(lo, self.span.hi())
+    }
+}
+
+impl UseSegment {
+    // Clone a version of self with any top-level alias removed.
+    fn remove_alias(&self) -> UseSegment {
+        match *self {
+            UseSegment::Ident(ref s, _) => UseSegment::Ident(s.clone(), None),
+            UseSegment::Slf(_) => UseSegment::Slf(None),
+            UseSegment::Super(_) => UseSegment::Super(None),
+            UseSegment::Crate(_) => UseSegment::Crate(None),
+            _ => self.clone(),
+        }
+    }
+
+    fn from_path_segment(
+        context: &RewriteContext<'_>,
+        path_seg: &ast::PathSegment,
+        modsep: bool,
+    ) -> Option<UseSegment> {
+        let name = rewrite_ident(context, path_seg.ident);
+        if name.is_empty() || name == "{{root}}" {
+            return None;
+        }
+        Some(match name {
+            "self" => UseSegment::Slf(None),
+            "super" => UseSegment::Super(None),
+            "crate" => UseSegment::Crate(None),
+            _ => {
+                let mod_sep = if modsep { "::" } else { "" };
+                UseSegment::Ident(format!("{}{}", mod_sep, name), None)
+            }
+        })
+    }
+}
+
+pub(crate) fn merge_use_trees(use_trees: Vec<UseTree>, merge_by: SharedPrefix) -> Vec<UseTree> {
+    let mut result = Vec::with_capacity(use_trees.len());
+    for use_tree in use_trees {
+        if use_tree.has_comment() || use_tree.attrs.is_some() {
+            result.push(use_tree);
+            continue;
+        }
+
+        for flattened in use_tree.flatten() {
+            if let Some(tree) = result
+                .iter_mut()
+                .find(|tree| tree.share_prefix(&flattened, merge_by))
+            {
+                tree.merge(&flattened, merge_by);
+            } else {
+                result.push(flattened);
+            }
+        }
+    }
+    result
+}
+
+pub(crate) fn flatten_use_trees(use_trees: Vec<UseTree>) -> Vec<UseTree> {
+    use_trees
+        .into_iter()
+        .flat_map(UseTree::flatten)
+        .map(|mut tree| {
+            // If a path ends in `::self`, rewrite it to `::{self}`.
+            if let Some(UseSegment::Slf(..)) = tree.path.last() {
+                let self_segment = tree.path.pop().unwrap();
+                tree.path.push(UseSegment::List(vec![UseTree::from_path(
+                    vec![self_segment],
+                    DUMMY_SP,
+                )]));
+            }
+            tree
+        })
+        .collect()
+}
+
+impl fmt::Debug for UseTree {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Debug for UseSegment {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for UseSegment {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            UseSegment::Glob => write!(f, "*"),
+            UseSegment::Ident(ref s, _) => write!(f, "{}", s),
+            UseSegment::Slf(..) => write!(f, "self"),
+            UseSegment::Super(..) => write!(f, "super"),
+            UseSegment::Crate(..) => write!(f, "crate"),
+            UseSegment::List(ref list) => {
+                write!(f, "{{")?;
+                for (i, item) in list.iter().enumerate() {
+                    if i != 0 {
+                        write!(f, ", ")?;
+                    }
+                    write!(f, "{}", item)?;
+                }
+                write!(f, "}}")
+            }
+        }
+    }
+}
+impl fmt::Display for UseTree {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        for (i, segment) in self.path.iter().enumerate() {
+            if i != 0 {
+                write!(f, "::")?;
+            }
+            write!(f, "{}", segment)?;
+        }
+        Ok(())
+    }
+}
+
+impl UseTree {
+    // Rewrite use tree with `use ` and a trailing `;`.
+    pub(crate) fn rewrite_top_level(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+    ) -> Option<String> {
+        let vis = self.visibility.as_ref().map_or(Cow::from(""), |vis| {
+            crate::utils::format_visibility(context, &vis)
+        });
+        let use_str = self
+            .rewrite(context, shape.offset_left(vis.len())?)
+            .map(|s| {
+                if s.is_empty() {
+                    s
+                } else {
+                    format!("{}use {};", vis, s)
+                }
+            })?;
+        match self.attrs {
+            Some(ref attrs) if !attrs.is_empty() => {
+                let attr_str = attrs.rewrite(context, shape)?;
+                let lo = attrs.last().as_ref()?.span.hi();
+                let hi = self.span.lo();
+                let span = mk_sp(lo, hi);
+
+                let allow_extend = if attrs.len() == 1 {
+                    let line_len = attr_str.len() + 1 + use_str.len();
+                    !attrs.first().unwrap().is_doc_comment()
+                        && context.config.inline_attribute_width() >= line_len
+                } else {
+                    false
+                };
+
+                combine_strs_with_missing_comments(
+                    context,
+                    &attr_str,
+                    &use_str,
+                    span,
+                    shape,
+                    allow_extend,
+                )
+            }
+            _ => Some(use_str),
+        }
+    }
+
+    // FIXME: Use correct span?
+    // The given span is essentially incorrect, since we are reconstructing
+    // use-statements. This should not be a problem, though, since we have
+    // already tried to extract comment and observed that there are no comment
+    // around the given use item, and the span will not be used afterward.
+    fn from_path(path: Vec<UseSegment>, span: Span) -> UseTree {
+        UseTree {
+            path,
+            span,
+            list_item: None,
+            visibility: None,
+            attrs: None,
+        }
+    }
+
+    pub(crate) fn from_ast_with_normalization(
+        context: &RewriteContext<'_>,
+        item: &ast::Item,
+    ) -> Option<UseTree> {
+        match item.kind {
+            ast::ItemKind::Use(ref use_tree) => Some(
+                UseTree::from_ast(
+                    context,
+                    use_tree,
+                    None,
+                    Some(item.vis.clone()),
+                    Some(item.span.lo()),
+                    if item.attrs.is_empty() {
+                        None
+                    } else {
+                        Some(item.attrs.clone())
+                    },
+                )
+                .normalize(),
+            ),
+            _ => None,
+        }
+    }
+
+    fn from_ast(
+        context: &RewriteContext<'_>,
+        a: &ast::UseTree,
+        list_item: Option<ListItem>,
+        visibility: Option<ast::Visibility>,
+        opt_lo: Option<BytePos>,
+        attrs: Option<Vec<ast::Attribute>>,
+    ) -> UseTree {
+        let span = if let Some(lo) = opt_lo {
+            mk_sp(lo, a.span.hi())
+        } else {
+            a.span
+        };
+        let mut result = UseTree {
+            path: vec![],
+            span,
+            list_item,
+            visibility,
+            attrs,
+        };
+
+        let leading_modsep =
+            context.config.edition() >= Edition::Edition2018 && a.prefix.is_global();
+
+        let mut modsep = leading_modsep;
+
+        for p in &a.prefix.segments {
+            if let Some(use_segment) = UseSegment::from_path_segment(context, p, modsep) {
+                result.path.push(use_segment);
+                modsep = false;
+            }
+        }
+
+        match a.kind {
+            UseTreeKind::Glob => {
+                // in case of a global path and the glob starts at the root, e.g., "::*"
+                if a.prefix.segments.len() == 1 && leading_modsep {
+                    result.path.push(UseSegment::Ident("".to_owned(), None));
+                }
+                result.path.push(UseSegment::Glob);
+            }
+            UseTreeKind::Nested(ref list) => {
+                // Extract comments between nested use items.
+                // This needs to be done before sorting use items.
+                let items: Vec<_> = itemize_list(
+                    context.snippet_provider,
+                    list.iter().map(|(tree, _)| tree),
+                    "}",
+                    ",",
+                    |tree| tree.span.lo(),
+                    |tree| tree.span.hi(),
+                    |_| Some("".to_owned()), // We only need comments for now.
+                    context.snippet_provider.span_after(a.span, "{"),
+                    a.span.hi(),
+                    false,
+                )
+                .collect();
+                // in case of a global path and the nested list starts at the root,
+                // e.g., "::{foo, bar}"
+                if a.prefix.segments.len() == 1 && leading_modsep {
+                    result.path.push(UseSegment::Ident("".to_owned(), None));
+                }
+                result.path.push(UseSegment::List(
+                    list.iter()
+                        .zip(items.into_iter())
+                        .map(|(t, list_item)| {
+                            Self::from_ast(context, &t.0, Some(list_item), None, None, None)
+                        })
+                        .collect(),
+                ));
+            }
+            UseTreeKind::Simple(ref rename, ..) => {
+                // If the path has leading double colons and is composed of only 2 segments, then we
+                // bypass the call to path_to_imported_ident which would get only the ident and
+                // lose the path root, e.g., `that` in `::that`.
+                // The span of `a.prefix` contains the leading colons.
+                let name = if a.prefix.segments.len() == 2 && leading_modsep {
+                    context.snippet(a.prefix.span).to_owned()
+                } else {
+                    rewrite_ident(context, path_to_imported_ident(&a.prefix)).to_owned()
+                };
+                let alias = rename.and_then(|ident| {
+                    if ident.name == sym::underscore_imports {
+                        // for impl-only-use
+                        Some("_".to_owned())
+                    } else if ident == path_to_imported_ident(&a.prefix) {
+                        None
+                    } else {
+                        Some(rewrite_ident(context, ident).to_owned())
+                    }
+                });
+                let segment = match name.as_ref() {
+                    "self" => UseSegment::Slf(alias),
+                    "super" => UseSegment::Super(alias),
+                    "crate" => UseSegment::Crate(alias),
+                    _ => UseSegment::Ident(name, alias),
+                };
+
+                // `name` is already in result.
+                result.path.pop();
+                result.path.push(segment);
+            }
+        }
+        result
+    }
+
+    // Do the adjustments that rustfmt does elsewhere to use paths.
+    pub(crate) fn normalize(mut self) -> UseTree {
+        let mut last = self.path.pop().expect("Empty use tree?");
+        // Hack around borrow checker.
+        let mut normalize_sole_list = false;
+        let mut aliased_self = false;
+
+        // Remove foo::{} or self without attributes.
+        match last {
+            _ if self.attrs.is_some() => (),
+            UseSegment::List(ref list) if list.is_empty() => {
+                self.path = vec![];
+                return self;
+            }
+            UseSegment::Slf(None) if self.path.is_empty() && self.visibility.is_some() => {
+                self.path = vec![];
+                return self;
+            }
+            _ => (),
+        }
+
+        // Normalise foo::self -> foo.
+        if let UseSegment::Slf(None) = last {
+            if !self.path.is_empty() {
+                return self;
+            }
+        }
+
+        // Normalise foo::self as bar -> foo as bar.
+        if let UseSegment::Slf(_) = last {
+            match self.path.last() {
+                Some(UseSegment::Ident(_, None)) => {
+                    aliased_self = true;
+                }
+                _ => {}
+            }
+        }
+
+        let mut done = false;
+        if aliased_self {
+            match self.path.last_mut() {
+                Some(UseSegment::Ident(_, ref mut old_rename)) => {
+                    assert!(old_rename.is_none());
+                    if let UseSegment::Slf(Some(rename)) = last.clone() {
+                        *old_rename = Some(rename);
+                        done = true;
+                    }
+                }
+                _ => unreachable!(),
+            }
+        }
+
+        if done {
+            return self;
+        }
+
+        // Normalise foo::{bar} -> foo::bar
+        if let UseSegment::List(ref list) = last {
+            if list.len() == 1 && list[0].to_string() != "self" {
+                normalize_sole_list = true;
+            }
+        }
+
+        if normalize_sole_list {
+            match last {
+                UseSegment::List(list) => {
+                    for seg in &list[0].path {
+                        self.path.push(seg.clone());
+                    }
+                    return self.normalize();
+                }
+                _ => unreachable!(),
+            }
+        }
+
+        // Recursively normalize elements of a list use (including sorting the list).
+        if let UseSegment::List(list) = last {
+            let mut list = list.into_iter().map(UseTree::normalize).collect::<Vec<_>>();
+            list.sort();
+            last = UseSegment::List(list);
+        }
+
+        self.path.push(last);
+        self
+    }
+
+    fn has_comment(&self) -> bool {
+        self.list_item.as_ref().map_or(false, ListItem::has_comment)
+    }
+
+    fn same_visibility(&self, other: &UseTree) -> bool {
+        match (&self.visibility, &other.visibility) {
+            (
+                Some(ast::Visibility {
+                    kind: ast::VisibilityKind::Inherited,
+                    ..
+                }),
+                None,
+            )
+            | (
+                None,
+                Some(ast::Visibility {
+                    kind: ast::VisibilityKind::Inherited,
+                    ..
+                }),
+            )
+            | (None, None) => true,
+            (Some(ref a), Some(ref b)) => is_same_visibility(a, b),
+            _ => false,
+        }
+    }
+
+    fn share_prefix(&self, other: &UseTree, shared_prefix: SharedPrefix) -> bool {
+        if self.path.is_empty()
+            || other.path.is_empty()
+            || self.attrs.is_some()
+            || !self.same_visibility(other)
+        {
+            false
+        } else {
+            match shared_prefix {
+                SharedPrefix::Crate => self.path[0] == other.path[0],
+                SharedPrefix::Module => {
+                    self.path[..self.path.len() - 1] == other.path[..other.path.len() - 1]
+                }
+            }
+        }
+    }
+
+    fn flatten(self) -> Vec<UseTree> {
+        if self.path.is_empty() {
+            return vec![self];
+        }
+        match self.path.clone().last().unwrap() {
+            UseSegment::List(list) => {
+                if list.len() == 1 && list[0].path.len() == 1 {
+                    match list[0].path[0] {
+                        UseSegment::Slf(..) => return vec![self],
+                        _ => (),
+                    };
+                }
+                let prefix = &self.path[..self.path.len() - 1];
+                let mut result = vec![];
+                for nested_use_tree in list {
+                    for flattend in &mut nested_use_tree.clone().flatten() {
+                        let mut new_path = prefix.to_vec();
+                        new_path.append(&mut flattend.path);
+                        result.push(UseTree {
+                            path: new_path,
+                            span: self.span,
+                            list_item: None,
+                            visibility: self.visibility.clone(),
+                            attrs: None,
+                        });
+                    }
+                }
+
+                result
+            }
+            _ => vec![self],
+        }
+    }
+
+    fn merge(&mut self, other: &UseTree, merge_by: SharedPrefix) {
+        let mut prefix = 0;
+        for (a, b) in self.path.iter().zip(other.path.iter()) {
+            if *a == *b {
+                prefix += 1;
+            } else {
+                break;
+            }
+        }
+        if let Some(new_path) = merge_rest(&self.path, &other.path, prefix, merge_by) {
+            self.path = new_path;
+            self.span = self.span.to(other.span);
+        }
+    }
+}
+
+fn merge_rest(
+    a: &[UseSegment],
+    b: &[UseSegment],
+    mut len: usize,
+    merge_by: SharedPrefix,
+) -> Option<Vec<UseSegment>> {
+    if a.len() == len && b.len() == len {
+        return None;
+    }
+    if a.len() != len && b.len() != len {
+        if let UseSegment::List(ref list) = a[len] {
+            let mut list = list.clone();
+            merge_use_trees_inner(
+                &mut list,
+                UseTree::from_path(b[len..].to_vec(), DUMMY_SP),
+                merge_by,
+            );
+            let mut new_path = b[..len].to_vec();
+            new_path.push(UseSegment::List(list));
+            return Some(new_path);
+        }
+    } else if len == 1 {
+        let rest = if a.len() == len { &b[1..] } else { &a[1..] };
+        return Some(vec![
+            b[0].clone(),
+            UseSegment::List(vec![
+                UseTree::from_path(vec![UseSegment::Slf(None)], DUMMY_SP),
+                UseTree::from_path(rest.to_vec(), DUMMY_SP),
+            ]),
+        ]);
+    } else {
+        len -= 1;
+    }
+    let mut list = vec![
+        UseTree::from_path(a[len..].to_vec(), DUMMY_SP),
+        UseTree::from_path(b[len..].to_vec(), DUMMY_SP),
+    ];
+    list.sort();
+    let mut new_path = b[..len].to_vec();
+    new_path.push(UseSegment::List(list));
+    Some(new_path)
+}
+
+fn merge_use_trees_inner(trees: &mut Vec<UseTree>, use_tree: UseTree, merge_by: SharedPrefix) {
+    let similar_trees = trees
+        .iter_mut()
+        .filter(|tree| tree.share_prefix(&use_tree, merge_by));
+    if use_tree.path.len() == 1 && merge_by == SharedPrefix::Crate {
+        if let Some(tree) = similar_trees.min_by_key(|tree| tree.path.len()) {
+            if tree.path.len() == 1 {
+                return;
+            }
+        }
+    } else if let Some(tree) = similar_trees.max_by_key(|tree| tree.path.len()) {
+        if tree.path.len() > 1 {
+            tree.merge(&use_tree, merge_by);
+            return;
+        }
+    }
+    trees.push(use_tree);
+    trees.sort();
+}
+
+impl PartialOrd for UseSegment {
+    fn partial_cmp(&self, other: &UseSegment) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+impl PartialOrd for UseTree {
+    fn partial_cmp(&self, other: &UseTree) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+impl Ord for UseSegment {
+    fn cmp(&self, other: &UseSegment) -> Ordering {
+        use self::UseSegment::*;
+
+        fn is_upper_snake_case(s: &str) -> bool {
+            s.chars()
+                .all(|c| c.is_uppercase() || c == '_' || c.is_numeric())
+        }
+
+        match (self, other) {
+            (&Slf(ref a), &Slf(ref b))
+            | (&Super(ref a), &Super(ref b))
+            | (&Crate(ref a), &Crate(ref b)) => a.cmp(b),
+            (&Glob, &Glob) => Ordering::Equal,
+            (&Ident(ref ia, ref aa), &Ident(ref ib, ref ab)) => {
+                // snake_case < CamelCase < UPPER_SNAKE_CASE
+                if ia.starts_with(char::is_uppercase) && ib.starts_with(char::is_lowercase) {
+                    return Ordering::Greater;
+                }
+                if ia.starts_with(char::is_lowercase) && ib.starts_with(char::is_uppercase) {
+                    return Ordering::Less;
+                }
+                if is_upper_snake_case(ia) && !is_upper_snake_case(ib) {
+                    return Ordering::Greater;
+                }
+                if !is_upper_snake_case(ia) && is_upper_snake_case(ib) {
+                    return Ordering::Less;
+                }
+                let ident_ord = ia.cmp(ib);
+                if ident_ord != Ordering::Equal {
+                    return ident_ord;
+                }
+                if aa.is_none() && ab.is_some() {
+                    return Ordering::Less;
+                }
+                if aa.is_some() && ab.is_none() {
+                    return Ordering::Greater;
+                }
+                aa.cmp(ab)
+            }
+            (&List(ref a), &List(ref b)) => {
+                for (a, b) in a.iter().zip(b.iter()) {
+                    let ord = a.cmp(b);
+                    if ord != Ordering::Equal {
+                        return ord;
+                    }
+                }
+
+                a.len().cmp(&b.len())
+            }
+            (&Slf(_), _) => Ordering::Less,
+            (_, &Slf(_)) => Ordering::Greater,
+            (&Super(_), _) => Ordering::Less,
+            (_, &Super(_)) => Ordering::Greater,
+            (&Crate(_), _) => Ordering::Less,
+            (_, &Crate(_)) => Ordering::Greater,
+            (&Ident(..), _) => Ordering::Less,
+            (_, &Ident(..)) => Ordering::Greater,
+            (&Glob, _) => Ordering::Less,
+            (_, &Glob) => Ordering::Greater,
+        }
+    }
+}
+impl Ord for UseTree {
+    fn cmp(&self, other: &UseTree) -> Ordering {
+        for (a, b) in self.path.iter().zip(other.path.iter()) {
+            let ord = a.cmp(b);
+            // The comparison without aliases is a hack to avoid situations like
+            // comparing `a::b` to `a as c` - where the latter should be ordered
+            // first since it is shorter.
+            if ord != Ordering::Equal && a.remove_alias().cmp(&b.remove_alias()) != Ordering::Equal
+            {
+                return ord;
+            }
+        }
+
+        self.path.len().cmp(&other.path.len())
+    }
+}
+
+fn rewrite_nested_use_tree(
+    context: &RewriteContext<'_>,
+    use_tree_list: &[UseTree],
+    shape: Shape,
+) -> Option<String> {
+    let mut list_items = Vec::with_capacity(use_tree_list.len());
+    let nested_shape = match context.config.imports_indent() {
+        IndentStyle::Block => shape
+            .block_indent(context.config.tab_spaces())
+            .with_max_width(context.config)
+            .sub_width(1)?,
+        IndentStyle::Visual => shape.visual_indent(0),
+    };
+    for use_tree in use_tree_list {
+        if let Some(mut list_item) = use_tree.list_item.clone() {
+            list_item.item = use_tree.rewrite(context, nested_shape);
+            list_items.push(list_item);
+        } else {
+            list_items.push(ListItem::from_str(use_tree.rewrite(context, nested_shape)?));
+        }
+    }
+    let has_nested_list = use_tree_list.iter().any(|use_segment| {
+        use_segment
+            .path
+            .last()
+            .map_or(false, |last_segment| match last_segment {
+                UseSegment::List(..) => true,
+                _ => false,
+            })
+    });
+
+    let remaining_width = if has_nested_list {
+        0
+    } else {
+        shape.width.saturating_sub(2)
+    };
+
+    let tactic = definitive_tactic(
+        &list_items,
+        context.config.imports_layout(),
+        Separator::Comma,
+        remaining_width,
+    );
+
+    let ends_with_newline = context.config.imports_indent() == IndentStyle::Block
+        && tactic != DefinitiveListTactic::Horizontal;
+    let trailing_separator = if ends_with_newline {
+        context.config.trailing_comma()
+    } else {
+        SeparatorTactic::Never
+    };
+    let fmt = ListFormatting::new(nested_shape, context.config)
+        .tactic(tactic)
+        .trailing_separator(trailing_separator)
+        .ends_with_newline(ends_with_newline)
+        .preserve_newline(true)
+        .nested(has_nested_list);
+
+    let list_str = write_list(&list_items, &fmt)?;
+
+    let result = if (list_str.contains('\n') || list_str.len() > remaining_width)
+        && context.config.imports_indent() == IndentStyle::Block
+    {
+        format!(
+            "{{\n{}{}\n{}}}",
+            nested_shape.indent.to_string(context.config),
+            list_str,
+            shape.indent.to_string(context.config)
+        )
+    } else {
+        format!("{{{}}}", list_str)
+    };
+
+    Some(result)
+}
+
+impl Rewrite for UseSegment {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        Some(match self {
+            UseSegment::Ident(ref ident, Some(ref rename)) => format!("{} as {}", ident, rename),
+            UseSegment::Ident(ref ident, None) => ident.clone(),
+            UseSegment::Slf(Some(ref rename)) => format!("self as {}", rename),
+            UseSegment::Slf(None) => "self".to_owned(),
+            UseSegment::Super(Some(ref rename)) => format!("super as {}", rename),
+            UseSegment::Super(None) => "super".to_owned(),
+            UseSegment::Crate(Some(ref rename)) => format!("crate as {}", rename),
+            UseSegment::Crate(None) => "crate".to_owned(),
+            UseSegment::Glob => "*".to_owned(),
+            UseSegment::List(ref use_tree_list) => rewrite_nested_use_tree(
+                context,
+                use_tree_list,
+                // 1 = "{" and "}"
+                shape.offset_left(1)?.sub_width(1)?,
+            )?,
+        })
+    }
+}
+
+impl Rewrite for UseTree {
+    // This does NOT format attributes and visibility or add a trailing `;`.
+    fn rewrite(&self, context: &RewriteContext<'_>, mut shape: Shape) -> Option<String> {
+        let mut result = String::with_capacity(256);
+        let mut iter = self.path.iter().peekable();
+        while let Some(ref segment) = iter.next() {
+            let segment_str = segment.rewrite(context, shape)?;
+            result.push_str(&segment_str);
+            if iter.peek().is_some() {
+                result.push_str("::");
+                // 2 = "::"
+                shape = shape.offset_left(2 + segment_str.len())?;
+            }
+        }
+        Some(result)
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub(crate) enum SharedPrefix {
+    Crate,
+    Module,
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use rustc_span::DUMMY_SP;
+
+    // Parse the path part of an import. This parser is not robust and is only
+    // suitable for use in a test harness.
+    fn parse_use_tree(s: &str) -> UseTree {
+        use std::iter::Peekable;
+        use std::mem::swap;
+        use std::str::Chars;
+
+        struct Parser<'a> {
+            input: Peekable<Chars<'a>>,
+        }
+
+        impl<'a> Parser<'a> {
+            fn bump(&mut self) {
+                self.input.next().unwrap();
+            }
+
+            fn eat(&mut self, c: char) {
+                assert!(self.input.next().unwrap() == c);
+            }
+
+            fn push_segment(
+                result: &mut Vec<UseSegment>,
+                buf: &mut String,
+                alias_buf: &mut Option<String>,
+            ) {
+                if !buf.is_empty() {
+                    let mut alias = None;
+                    swap(alias_buf, &mut alias);
+
+                    match buf.as_ref() {
+                        "self" => {
+                            result.push(UseSegment::Slf(alias));
+                            *buf = String::new();
+                            *alias_buf = None;
+                        }
+                        "super" => {
+                            result.push(UseSegment::Super(alias));
+                            *buf = String::new();
+                            *alias_buf = None;
+                        }
+                        "crate" => {
+                            result.push(UseSegment::Crate(alias));
+                            *buf = String::new();
+                            *alias_buf = None;
+                        }
+                        _ => {
+                            let mut name = String::new();
+                            swap(buf, &mut name);
+                            result.push(UseSegment::Ident(name, alias));
+                        }
+                    }
+                }
+            }
+
+            fn parse_in_list(&mut self) -> UseTree {
+                let mut result = vec![];
+                let mut buf = String::new();
+                let mut alias_buf = None;
+                while let Some(&c) = self.input.peek() {
+                    match c {
+                        '{' => {
+                            assert!(buf.is_empty());
+                            self.bump();
+                            result.push(UseSegment::List(self.parse_list()));
+                            self.eat('}');
+                        }
+                        '*' => {
+                            assert!(buf.is_empty());
+                            self.bump();
+                            result.push(UseSegment::Glob);
+                        }
+                        ':' => {
+                            self.bump();
+                            self.eat(':');
+                            Self::push_segment(&mut result, &mut buf, &mut alias_buf);
+                        }
+                        '}' | ',' => {
+                            Self::push_segment(&mut result, &mut buf, &mut alias_buf);
+                            return UseTree {
+                                path: result,
+                                span: DUMMY_SP,
+                                list_item: None,
+                                visibility: None,
+                                attrs: None,
+                            };
+                        }
+                        ' ' => {
+                            self.bump();
+                            self.eat('a');
+                            self.eat('s');
+                            self.eat(' ');
+                            alias_buf = Some(String::new());
+                        }
+                        c => {
+                            self.bump();
+                            if let Some(ref mut buf) = alias_buf {
+                                buf.push(c);
+                            } else {
+                                buf.push(c);
+                            }
+                        }
+                    }
+                }
+                Self::push_segment(&mut result, &mut buf, &mut alias_buf);
+                UseTree {
+                    path: result,
+                    span: DUMMY_SP,
+                    list_item: None,
+                    visibility: None,
+                    attrs: None,
+                }
+            }
+
+            fn parse_list(&mut self) -> Vec<UseTree> {
+                let mut result = vec![];
+                loop {
+                    match self.input.peek().unwrap() {
+                        ',' | ' ' => self.bump(),
+                        '}' => {
+                            return result;
+                        }
+                        _ => result.push(self.parse_in_list()),
+                    }
+                }
+            }
+        }
+
+        let mut parser = Parser {
+            input: s.chars().peekable(),
+        };
+        parser.parse_in_list()
+    }
+
+    macro_rules! parse_use_trees {
+        ($($s:expr),* $(,)*) => {
+            vec![
+                $(parse_use_tree($s),)*
+            ]
+        }
+    }
+
+    macro_rules! test_merge {
+        ($by:ident, [$($input:expr),* $(,)*], [$($output:expr),* $(,)*]) => {
+            assert_eq!(
+                merge_use_trees(parse_use_trees!($($input,)*), SharedPrefix::$by),
+                parse_use_trees!($($output,)*),
+            );
+        }
+    }
+
+    #[test]
+    fn test_use_tree_merge_crate() {
+        test_merge!(
+            Crate,
+            ["a::b::{c, d}", "a::b::{e, f}"],
+            ["a::b::{c, d, e, f}"]
+        );
+        test_merge!(Crate, ["a::b::c", "a::b"], ["a::{b, b::c}"]);
+        test_merge!(Crate, ["a::b", "a::b"], ["a::b"]);
+        test_merge!(Crate, ["a", "a::b", "a::b::c"], ["a::{self, b, b::c}"]);
+        test_merge!(
+            Crate,
+            ["a", "a::b", "a::b::c", "a::b::c::d"],
+            ["a::{self, b, b::{c, c::d}}"]
+        );
+        test_merge!(
+            Crate,
+            ["a", "a::b", "a::b::c", "a::b"],
+            ["a::{self, b, b::c}"]
+        );
+        test_merge!(
+            Crate,
+            ["a::{b::{self, c}, d::e}", "a::d::f"],
+            ["a::{b::{self, c}, d::{e, f}}"]
+        );
+        test_merge!(
+            Crate,
+            ["a::d::f", "a::{b::{self, c}, d::e}"],
+            ["a::{b::{self, c}, d::{e, f}}"]
+        );
+        test_merge!(
+            Crate,
+            ["a::{c, d, b}", "a::{d, e, b, a, f}", "a::{f, g, c}"],
+            ["a::{a, b, c, d, e, f, g}"]
+        );
+        test_merge!(
+            Crate,
+            ["a::{self}", "b::{self as foo}"],
+            ["a::{self}", "b::{self as foo}"]
+        );
+    }
+
+    #[test]
+    fn test_use_tree_merge_module() {
+        test_merge!(
+            Module,
+            ["foo::b", "foo::{a, c, d::e}"],
+            ["foo::{a, b, c}", "foo::d::e"]
+        );
+
+        test_merge!(
+            Module,
+            ["foo::{a::b, a::c, d::e, d::f}"],
+            ["foo::a::{b, c}", "foo::d::{e, f}"]
+        );
+    }
+
+    #[test]
+    fn test_flatten_use_trees() {
+        assert_eq!(
+            flatten_use_trees(parse_use_trees!["foo::{a::{b, c}, d::e}"]),
+            parse_use_trees!["foo::a::b", "foo::a::c", "foo::d::e"]
+        );
+
+        assert_eq!(
+            flatten_use_trees(parse_use_trees!["foo::{self, a, b::{c, d}, e::*}"]),
+            parse_use_trees![
+                "foo::{self}",
+                "foo::a",
+                "foo::b::c",
+                "foo::b::d",
+                "foo::e::*"
+            ]
+        );
+    }
+
+    #[test]
+    fn test_use_tree_flatten() {
+        assert_eq!(
+            parse_use_tree("a::b::{c, d, e, f}").flatten(),
+            parse_use_trees!("a::b::c", "a::b::d", "a::b::e", "a::b::f",)
+        );
+
+        assert_eq!(
+            parse_use_tree("a::b::{c::{d, e, f}, g, h::{i, j, k}}").flatten(),
+            parse_use_trees![
+                "a::b::c::d",
+                "a::b::c::e",
+                "a::b::c::f",
+                "a::b::g",
+                "a::b::h::i",
+                "a::b::h::j",
+                "a::b::h::k",
+            ]
+        );
+    }
+
+    #[test]
+    fn test_use_tree_normalize() {
+        assert_eq!(parse_use_tree("a::self").normalize(), parse_use_tree("a"));
+        assert_eq!(
+            parse_use_tree("a::self as foo").normalize(),
+            parse_use_tree("a as foo")
+        );
+        assert_eq!(
+            parse_use_tree("a::{self}").normalize(),
+            parse_use_tree("a::{self}")
+        );
+        assert_eq!(parse_use_tree("a::{b}").normalize(), parse_use_tree("a::b"));
+        assert_eq!(
+            parse_use_tree("a::{b, c::self}").normalize(),
+            parse_use_tree("a::{b, c}")
+        );
+        assert_eq!(
+            parse_use_tree("a::{b as bar, c::self}").normalize(),
+            parse_use_tree("a::{b as bar, c}")
+        );
+    }
+
+    #[test]
+    fn test_use_tree_ord() {
+        assert!(parse_use_tree("a").normalize() < parse_use_tree("aa").normalize());
+        assert!(parse_use_tree("a").normalize() < parse_use_tree("a::a").normalize());
+        assert!(parse_use_tree("a").normalize() < parse_use_tree("*").normalize());
+        assert!(parse_use_tree("a").normalize() < parse_use_tree("{a, b}").normalize());
+        assert!(parse_use_tree("*").normalize() < parse_use_tree("{a, b}").normalize());
+
+        assert!(
+            parse_use_tree("aaaaaaaaaaaaaaa::{bb, cc, dddddddd}").normalize()
+                < parse_use_tree("aaaaaaaaaaaaaaa::{bb, cc, ddddddddd}").normalize()
+        );
+        assert!(
+            parse_use_tree("serde::de::{Deserialize}").normalize()
+                < parse_use_tree("serde_json").normalize()
+        );
+        assert!(parse_use_tree("a::b::c").normalize() < parse_use_tree("a::b::*").normalize());
+        assert!(
+            parse_use_tree("foo::{Bar, Baz}").normalize()
+                < parse_use_tree("{Bar, Baz}").normalize()
+        );
+
+        assert!(
+            parse_use_tree("foo::{qux as bar}").normalize()
+                < parse_use_tree("foo::{self as bar}").normalize()
+        );
+        assert!(
+            parse_use_tree("foo::{qux as bar}").normalize()
+                < parse_use_tree("foo::{baz, qux as bar}").normalize()
+        );
+        assert!(
+            parse_use_tree("foo::{self as bar, baz}").normalize()
+                < parse_use_tree("foo::{baz, qux as bar}").normalize()
+        );
+
+        assert!(parse_use_tree("foo").normalize() < parse_use_tree("Foo").normalize());
+        assert!(parse_use_tree("foo").normalize() < parse_use_tree("foo::Bar").normalize());
+
+        assert!(
+            parse_use_tree("std::cmp::{d, c, b, a}").normalize()
+                < parse_use_tree("std::cmp::{b, e, g, f}").normalize()
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/issues.rs b/src/tools/rustfmt/src/issues.rs
new file mode 100644
index 0000000000000..d369b75541ef9
--- /dev/null
+++ b/src/tools/rustfmt/src/issues.rs
@@ -0,0 +1,317 @@
+// Objects for seeking through a char stream for occurrences of TODO and FIXME.
+// Depending on the loaded configuration, may also check that these have an
+// associated issue number.
+
+use std::fmt;
+
+use crate::config::ReportTactic;
+
+const TO_DO_CHARS: &[char] = &['t', 'o', 'd', 'o'];
+const FIX_ME_CHARS: &[char] = &['f', 'i', 'x', 'm', 'e'];
+
+// Enabled implementation detail is here because it is
+// irrelevant outside the issues module
+fn is_enabled(report_tactic: ReportTactic) -> bool {
+    report_tactic != ReportTactic::Never
+}
+
+#[derive(Clone, Copy)]
+enum Seeking {
+    Issue { todo_idx: usize, fixme_idx: usize },
+    Number { issue: Issue, part: NumberPart },
+}
+
+#[derive(Clone, Copy)]
+enum NumberPart {
+    OpenParen,
+    Pound,
+    Number,
+    CloseParen,
+}
+
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+pub struct Issue {
+    issue_type: IssueType,
+    // Indicates whether we're looking for issues with missing numbers, or
+    // all issues of this type.
+    missing_number: bool,
+}
+
+impl fmt::Display for Issue {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        let msg = match self.issue_type {
+            IssueType::Todo => "TODO",
+            IssueType::Fixme => "FIXME",
+        };
+        let details = if self.missing_number {
+            " without issue number"
+        } else {
+            ""
+        };
+
+        write!(fmt, "{}{}", msg, details)
+    }
+}
+
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+enum IssueType {
+    Todo,
+    Fixme,
+}
+
+enum IssueClassification {
+    Good,
+    Bad(Issue),
+    None,
+}
+
+pub(crate) struct BadIssueSeeker {
+    state: Seeking,
+    report_todo: ReportTactic,
+    report_fixme: ReportTactic,
+}
+
+impl BadIssueSeeker {
+    pub(crate) fn new(report_todo: ReportTactic, report_fixme: ReportTactic) -> BadIssueSeeker {
+        BadIssueSeeker {
+            state: Seeking::Issue {
+                todo_idx: 0,
+                fixme_idx: 0,
+            },
+            report_todo,
+            report_fixme,
+        }
+    }
+
+    pub(crate) fn is_disabled(&self) -> bool {
+        !is_enabled(self.report_todo) && !is_enabled(self.report_fixme)
+    }
+
+    // Check whether or not the current char is conclusive evidence for an
+    // unnumbered TO-DO or FIX-ME.
+    pub(crate) fn inspect(&mut self, c: char) -> Option<Issue> {
+        match self.state {
+            Seeking::Issue {
+                todo_idx,
+                fixme_idx,
+            } => {
+                self.state = self.inspect_issue(c, todo_idx, fixme_idx);
+            }
+            Seeking::Number { issue, part } => {
+                let result = self.inspect_number(c, issue, part);
+
+                if let IssueClassification::None = result {
+                    return None;
+                }
+
+                self.state = Seeking::Issue {
+                    todo_idx: 0,
+                    fixme_idx: 0,
+                };
+
+                if let IssueClassification::Bad(issue) = result {
+                    return Some(issue);
+                }
+            }
+        }
+
+        None
+    }
+
+    fn inspect_issue(&mut self, c: char, mut todo_idx: usize, mut fixme_idx: usize) -> Seeking {
+        if let Some(lower_case_c) = c.to_lowercase().next() {
+            if is_enabled(self.report_todo) && lower_case_c == TO_DO_CHARS[todo_idx] {
+                todo_idx += 1;
+                if todo_idx == TO_DO_CHARS.len() {
+                    return Seeking::Number {
+                        issue: Issue {
+                            issue_type: IssueType::Todo,
+                            missing_number: if let ReportTactic::Unnumbered = self.report_todo {
+                                true
+                            } else {
+                                false
+                            },
+                        },
+                        part: NumberPart::OpenParen,
+                    };
+                }
+                fixme_idx = 0;
+            } else if is_enabled(self.report_fixme) && lower_case_c == FIX_ME_CHARS[fixme_idx] {
+                // Exploit the fact that the character sets of todo and fixme
+                // are disjoint by adding else.
+                fixme_idx += 1;
+                if fixme_idx == FIX_ME_CHARS.len() {
+                    return Seeking::Number {
+                        issue: Issue {
+                            issue_type: IssueType::Fixme,
+                            missing_number: if let ReportTactic::Unnumbered = self.report_fixme {
+                                true
+                            } else {
+                                false
+                            },
+                        },
+                        part: NumberPart::OpenParen,
+                    };
+                }
+                todo_idx = 0;
+            } else {
+                todo_idx = 0;
+                fixme_idx = 0;
+            }
+        }
+
+        Seeking::Issue {
+            todo_idx,
+            fixme_idx,
+        }
+    }
+
+    fn inspect_number(
+        &mut self,
+        c: char,
+        issue: Issue,
+        mut part: NumberPart,
+    ) -> IssueClassification {
+        if !issue.missing_number || c == '\n' {
+            return IssueClassification::Bad(issue);
+        } else if c == ')' {
+            return if let NumberPart::CloseParen = part {
+                IssueClassification::Good
+            } else {
+                IssueClassification::Bad(issue)
+            };
+        }
+
+        match part {
+            NumberPart::OpenParen => {
+                if c != '(' {
+                    return IssueClassification::Bad(issue);
+                } else {
+                    part = NumberPart::Pound;
+                }
+            }
+            NumberPart::Pound => {
+                if c == '#' {
+                    part = NumberPart::Number;
+                }
+            }
+            NumberPart::Number => {
+                if c >= '0' && c <= '9' {
+                    part = NumberPart::CloseParen;
+                } else {
+                    return IssueClassification::Bad(issue);
+                }
+            }
+            NumberPart::CloseParen => {}
+        }
+
+        self.state = Seeking::Number { part, issue };
+
+        IssueClassification::None
+    }
+}
+
+#[test]
+fn find_unnumbered_issue() {
+    fn check_fail(text: &str, failing_pos: usize) {
+        let mut seeker = BadIssueSeeker::new(ReportTactic::Unnumbered, ReportTactic::Unnumbered);
+        assert_eq!(
+            Some(failing_pos),
+            text.find(|c| seeker.inspect(c).is_some())
+        );
+    }
+
+    fn check_pass(text: &str) {
+        let mut seeker = BadIssueSeeker::new(ReportTactic::Unnumbered, ReportTactic::Unnumbered);
+        assert_eq!(None, text.find(|c| seeker.inspect(c).is_some()));
+    }
+
+    check_fail("TODO\n", 4);
+    check_pass(" TO FIX DOME\n");
+    check_fail(" \n FIXME\n", 8);
+    check_fail("FIXME(\n", 6);
+    check_fail("FIXME(#\n", 7);
+    check_fail("FIXME(#1\n", 8);
+    check_fail("FIXME(#)1\n", 7);
+    check_pass("FIXME(#1222)\n");
+    check_fail("FIXME(#12\n22)\n", 9);
+    check_pass("FIXME(@maintainer, #1222, hello)\n");
+    check_fail("TODO(#22) FIXME\n", 15);
+}
+
+#[test]
+fn find_issue() {
+    fn is_bad_issue(text: &str, report_todo: ReportTactic, report_fixme: ReportTactic) -> bool {
+        let mut seeker = BadIssueSeeker::new(report_todo, report_fixme);
+        text.chars().any(|c| seeker.inspect(c).is_some())
+    }
+
+    assert!(is_bad_issue(
+        "TODO(@maintainer, #1222, hello)\n",
+        ReportTactic::Always,
+        ReportTactic::Never,
+    ));
+
+    assert!(!is_bad_issue(
+        "TODO: no number\n",
+        ReportTactic::Never,
+        ReportTactic::Always,
+    ));
+
+    assert!(!is_bad_issue(
+        "Todo: mixed case\n",
+        ReportTactic::Never,
+        ReportTactic::Always,
+    ));
+
+    assert!(is_bad_issue(
+        "This is a FIXME(#1)\n",
+        ReportTactic::Never,
+        ReportTactic::Always,
+    ));
+
+    assert!(is_bad_issue(
+        "This is a FixMe(#1) mixed case\n",
+        ReportTactic::Never,
+        ReportTactic::Always,
+    ));
+
+    assert!(!is_bad_issue(
+        "bad FIXME\n",
+        ReportTactic::Always,
+        ReportTactic::Never,
+    ));
+}
+
+#[test]
+fn issue_type() {
+    let mut seeker = BadIssueSeeker::new(ReportTactic::Always, ReportTactic::Never);
+    let expected = Some(Issue {
+        issue_type: IssueType::Todo,
+        missing_number: false,
+    });
+
+    assert_eq!(
+        expected,
+        "TODO(#100): more awesomeness"
+            .chars()
+            .map(|c| seeker.inspect(c))
+            .find(Option::is_some)
+            .unwrap()
+    );
+
+    let mut seeker = BadIssueSeeker::new(ReportTactic::Never, ReportTactic::Unnumbered);
+    let expected = Some(Issue {
+        issue_type: IssueType::Fixme,
+        missing_number: true,
+    });
+
+    assert_eq!(
+        expected,
+        "Test. FIXME: bad, bad, not good"
+            .chars()
+            .map(|c| seeker.inspect(c))
+            .find(Option::is_some)
+            .unwrap()
+    );
+}
diff --git a/src/tools/rustfmt/src/items.rs b/src/tools/rustfmt/src/items.rs
new file mode 100644
index 0000000000000..ecbd0bd12ec6e
--- /dev/null
+++ b/src/tools/rustfmt/src/items.rs
@@ -0,0 +1,3291 @@
+// Formatting top-level items - functions, structs, enums, traits, impls.
+
+use std::borrow::Cow;
+use std::cmp::{max, min, Ordering};
+
+use regex::Regex;
+use rustc_ast::visit;
+use rustc_ast::{ast, ptr};
+use rustc_span::{symbol, BytePos, Span, DUMMY_SP};
+
+use crate::attr::filter_inline_attrs;
+use crate::comment::{
+    combine_strs_with_missing_comments, contains_comment, is_last_comment_block,
+    recover_comment_removed, recover_missing_comment_in_span, rewrite_missing_comment,
+    FindUncommented,
+};
+use crate::config::lists::*;
+use crate::config::{BraceStyle, Config, IndentStyle, Version};
+use crate::expr::{
+    is_empty_block, is_simple_block_stmt, rewrite_assign_rhs, rewrite_assign_rhs_with,
+    rewrite_assign_rhs_with_comments, RhsTactics,
+};
+use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
+use crate::macros::{rewrite_macro, MacroPosition};
+use crate::overflow;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::{Indent, Shape};
+use crate::source_map::{LineRangeUtils, SpanUtils};
+use crate::spanned::Spanned;
+use crate::stmt::Stmt;
+use crate::utils::*;
+use crate::vertical::rewrite_with_alignment;
+use crate::visitor::FmtVisitor;
+
+const DEFAULT_VISIBILITY: ast::Visibility = ast::Visibility {
+    kind: ast::VisibilityKind::Inherited,
+    span: DUMMY_SP,
+    tokens: None,
+};
+
+fn type_annotation_separator(config: &Config) -> &str {
+    colon_spaces(config)
+}
+
+// Statements of the form
+// let pat: ty = init;
+impl Rewrite for ast::Local {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        debug!(
+            "Local::rewrite {:?} {} {:?}",
+            self, shape.width, shape.indent
+        );
+
+        skip_out_of_file_lines_range!(context, self.span);
+
+        if contains_skip(&self.attrs) {
+            return None;
+        }
+
+        let attrs_str = self.attrs.rewrite(context, shape)?;
+        let mut result = if attrs_str.is_empty() {
+            "let ".to_owned()
+        } else {
+            combine_strs_with_missing_comments(
+                context,
+                &attrs_str,
+                "let ",
+                mk_sp(
+                    self.attrs.last().map(|a| a.span.hi()).unwrap(),
+                    self.span.lo(),
+                ),
+                shape,
+                false,
+            )?
+        };
+
+        // 4 = "let ".len()
+        let pat_shape = shape.offset_left(4)?;
+        // 1 = ;
+        let pat_shape = pat_shape.sub_width(1)?;
+        let pat_str = self.pat.rewrite(context, pat_shape)?;
+        result.push_str(&pat_str);
+
+        // String that is placed within the assignment pattern and expression.
+        let infix = {
+            let mut infix = String::with_capacity(32);
+
+            if let Some(ref ty) = self.ty {
+                let separator = type_annotation_separator(context.config);
+                let ty_shape = if pat_str.contains('\n') {
+                    shape.with_max_width(context.config)
+                } else {
+                    shape
+                }
+                .offset_left(last_line_width(&result) + separator.len())?
+                // 2 = ` =`
+                .sub_width(2)?;
+
+                let rewrite = ty.rewrite(context, ty_shape)?;
+
+                infix.push_str(separator);
+                infix.push_str(&rewrite);
+            }
+
+            if self.init.is_some() {
+                infix.push_str(" =");
+            }
+
+            infix
+        };
+
+        result.push_str(&infix);
+
+        if let Some(ref ex) = self.init {
+            // 1 = trailing semicolon;
+            let nested_shape = shape.sub_width(1)?;
+
+            result = rewrite_assign_rhs(context, result, &**ex, nested_shape)?;
+        }
+
+        result.push(';');
+        Some(result)
+    }
+}
+
+// FIXME convert to using rewrite style rather than visitor
+// FIXME format modules in this style
+#[allow(dead_code)]
+#[derive(Debug)]
+struct Item<'a> {
+    unsafety: ast::Unsafe,
+    abi: Cow<'static, str>,
+    vis: Option<&'a ast::Visibility>,
+    body: Vec<BodyElement<'a>>,
+    span: Span,
+}
+
+impl<'a> Item<'a> {
+    fn from_foreign_mod(fm: &'a ast::ForeignMod, span: Span, config: &Config) -> Item<'a> {
+        Item {
+            unsafety: fm.unsafety,
+            abi: format_extern(
+                ast::Extern::from_abi(fm.abi),
+                config.force_explicit_abi(),
+                true,
+            ),
+            vis: None,
+            body: fm
+                .items
+                .iter()
+                .map(|i| BodyElement::ForeignItem(i))
+                .collect(),
+            span,
+        }
+    }
+}
+
+#[derive(Debug)]
+enum BodyElement<'a> {
+    // Stmt(&'a ast::Stmt),
+    // Field(&'a ast::ExprField),
+    // Variant(&'a ast::Variant),
+    // Item(&'a ast::Item),
+    ForeignItem(&'a ast::ForeignItem),
+}
+
+/// Represents a fn's signature.
+pub(crate) struct FnSig<'a> {
+    decl: &'a ast::FnDecl,
+    generics: &'a ast::Generics,
+    ext: ast::Extern,
+    is_async: Cow<'a, ast::Async>,
+    constness: ast::Const,
+    defaultness: ast::Defaultness,
+    unsafety: ast::Unsafe,
+    visibility: ast::Visibility,
+}
+
+impl<'a> FnSig<'a> {
+    pub(crate) fn from_method_sig(
+        method_sig: &'a ast::FnSig,
+        generics: &'a ast::Generics,
+        visibility: ast::Visibility,
+    ) -> FnSig<'a> {
+        FnSig {
+            unsafety: method_sig.header.unsafety,
+            is_async: Cow::Borrowed(&method_sig.header.asyncness),
+            constness: method_sig.header.constness,
+            defaultness: ast::Defaultness::Final,
+            ext: method_sig.header.ext,
+            decl: &*method_sig.decl,
+            generics,
+            visibility,
+        }
+    }
+
+    pub(crate) fn from_fn_kind(
+        fn_kind: &'a visit::FnKind<'_>,
+        generics: &'a ast::Generics,
+        decl: &'a ast::FnDecl,
+        defaultness: ast::Defaultness,
+    ) -> FnSig<'a> {
+        match *fn_kind {
+            visit::FnKind::Fn(fn_ctxt, _, fn_sig, vis, _) => match fn_ctxt {
+                visit::FnCtxt::Assoc(..) => {
+                    let mut fn_sig = FnSig::from_method_sig(fn_sig, generics, vis.clone());
+                    fn_sig.defaultness = defaultness;
+                    fn_sig
+                }
+                _ => FnSig {
+                    decl,
+                    generics,
+                    ext: fn_sig.header.ext,
+                    constness: fn_sig.header.constness,
+                    is_async: Cow::Borrowed(&fn_sig.header.asyncness),
+                    defaultness,
+                    unsafety: fn_sig.header.unsafety,
+                    visibility: vis.clone(),
+                },
+            },
+            _ => unreachable!(),
+        }
+    }
+
+    fn to_str(&self, context: &RewriteContext<'_>) -> String {
+        let mut result = String::with_capacity(128);
+        // Vis defaultness constness unsafety abi.
+        result.push_str(&*format_visibility(context, &self.visibility));
+        result.push_str(format_defaultness(self.defaultness));
+        result.push_str(format_constness(self.constness));
+        result.push_str(format_async(&self.is_async));
+        result.push_str(format_unsafety(self.unsafety));
+        result.push_str(&format_extern(
+            self.ext,
+            context.config.force_explicit_abi(),
+            false,
+        ));
+        result
+    }
+}
+
+impl<'a> FmtVisitor<'a> {
+    fn format_item(&mut self, item: &Item<'_>) {
+        self.buffer.push_str(format_unsafety(item.unsafety));
+        self.buffer.push_str(&item.abi);
+
+        let snippet = self.snippet(item.span);
+        let brace_pos = snippet.find_uncommented("{").unwrap();
+
+        self.push_str("{");
+        if !item.body.is_empty() || contains_comment(&snippet[brace_pos..]) {
+            // FIXME: this skips comments between the extern keyword and the opening
+            // brace.
+            self.last_pos = item.span.lo() + BytePos(brace_pos as u32 + 1);
+            self.block_indent = self.block_indent.block_indent(self.config);
+
+            if !item.body.is_empty() {
+                for item in &item.body {
+                    self.format_body_element(item);
+                }
+            }
+
+            self.format_missing_no_indent(item.span.hi() - BytePos(1));
+            self.block_indent = self.block_indent.block_unindent(self.config);
+            let indent_str = self.block_indent.to_string(self.config);
+            self.push_str(&indent_str);
+        }
+
+        self.push_str("}");
+        self.last_pos = item.span.hi();
+    }
+
+    fn format_body_element(&mut self, element: &BodyElement<'_>) {
+        match *element {
+            BodyElement::ForeignItem(item) => self.format_foreign_item(item),
+        }
+    }
+
+    pub(crate) fn format_foreign_mod(&mut self, fm: &ast::ForeignMod, span: Span) {
+        let item = Item::from_foreign_mod(fm, span, self.config);
+        self.format_item(&item);
+    }
+
+    fn format_foreign_item(&mut self, item: &ast::ForeignItem) {
+        let rewrite = item.rewrite(&self.get_context(), self.shape());
+        let hi = item.span.hi();
+        let span = if item.attrs.is_empty() {
+            item.span
+        } else {
+            mk_sp(item.attrs[0].span.lo(), hi)
+        };
+        self.push_rewrite(span, rewrite);
+        self.last_pos = hi;
+    }
+
+    pub(crate) fn rewrite_fn_before_block(
+        &mut self,
+        indent: Indent,
+        ident: symbol::Ident,
+        fn_sig: &FnSig<'_>,
+        span: Span,
+    ) -> Option<(String, FnBraceStyle)> {
+        let context = self.get_context();
+
+        let mut fn_brace_style = newline_for_brace(self.config, &fn_sig.generics.where_clause);
+        let (result, _, force_newline_brace) =
+            rewrite_fn_base(&context, indent, ident, fn_sig, span, fn_brace_style)?;
+
+        // 2 = ` {`
+        if self.config.brace_style() == BraceStyle::AlwaysNextLine
+            || force_newline_brace
+            || last_line_width(&result) + 2 > self.shape().width
+        {
+            fn_brace_style = FnBraceStyle::NextLine
+        }
+
+        Some((result, fn_brace_style))
+    }
+
+    pub(crate) fn rewrite_required_fn(
+        &mut self,
+        indent: Indent,
+        ident: symbol::Ident,
+        sig: &ast::FnSig,
+        generics: &ast::Generics,
+        span: Span,
+    ) -> Option<String> {
+        // Drop semicolon or it will be interpreted as comment.
+        let span = mk_sp(span.lo(), span.hi() - BytePos(1));
+        let context = self.get_context();
+
+        let (mut result, ends_with_comment, _) = rewrite_fn_base(
+            &context,
+            indent,
+            ident,
+            &FnSig::from_method_sig(sig, generics, DEFAULT_VISIBILITY),
+            span,
+            FnBraceStyle::None,
+        )?;
+
+        // If `result` ends with a comment, then remember to add a newline
+        if ends_with_comment {
+            result.push_str(&indent.to_string_with_newline(context.config));
+        }
+
+        // Re-attach semicolon
+        result.push(';');
+
+        Some(result)
+    }
+
+    pub(crate) fn single_line_fn(
+        &self,
+        fn_str: &str,
+        block: &ast::Block,
+        inner_attrs: Option<&[ast::Attribute]>,
+    ) -> Option<String> {
+        if fn_str.contains('\n') || inner_attrs.map_or(false, |a| !a.is_empty()) {
+            return None;
+        }
+
+        let context = self.get_context();
+
+        if self.config.empty_item_single_line()
+            && is_empty_block(&context, block, None)
+            && self.block_indent.width() + fn_str.len() + 3 <= self.config.max_width()
+            && !last_line_contains_single_line_comment(fn_str)
+        {
+            return Some(format!("{} {{}}", fn_str));
+        }
+
+        if !self.config.fn_single_line() || !is_simple_block_stmt(&context, block, None) {
+            return None;
+        }
+
+        let res = Stmt::from_ast_node(block.stmts.first()?, true)
+            .rewrite(&self.get_context(), self.shape())?;
+
+        let width = self.block_indent.width() + fn_str.len() + res.len() + 5;
+        if !res.contains('\n') && width <= self.config.max_width() {
+            Some(format!("{} {{ {} }}", fn_str, res))
+        } else {
+            None
+        }
+    }
+
+    pub(crate) fn visit_static(&mut self, static_parts: &StaticParts<'_>) {
+        let rewrite = rewrite_static(&self.get_context(), static_parts, self.block_indent);
+        self.push_rewrite(static_parts.span, rewrite);
+    }
+
+    pub(crate) fn visit_struct(&mut self, struct_parts: &StructParts<'_>) {
+        let is_tuple = match struct_parts.def {
+            ast::VariantData::Tuple(..) => true,
+            _ => false,
+        };
+        let rewrite = format_struct(&self.get_context(), struct_parts, self.block_indent, None)
+            .map(|s| if is_tuple { s + ";" } else { s });
+        self.push_rewrite(struct_parts.span, rewrite);
+    }
+
+    pub(crate) fn visit_enum(
+        &mut self,
+        ident: symbol::Ident,
+        vis: &ast::Visibility,
+        enum_def: &ast::EnumDef,
+        generics: &ast::Generics,
+        span: Span,
+    ) {
+        let enum_header =
+            format_header(&self.get_context(), "enum ", ident, vis, self.block_indent);
+        self.push_str(&enum_header);
+
+        let enum_snippet = self.snippet(span);
+        let brace_pos = enum_snippet.find_uncommented("{").unwrap();
+        let body_start = span.lo() + BytePos(brace_pos as u32 + 1);
+        let generics_str = format_generics(
+            &self.get_context(),
+            generics,
+            self.config.brace_style(),
+            if enum_def.variants.is_empty() {
+                BracePos::ForceSameLine
+            } else {
+                BracePos::Auto
+            },
+            self.block_indent,
+            // make a span that starts right after `enum Foo`
+            mk_sp(ident.span.hi(), body_start),
+            last_line_width(&enum_header),
+        )
+        .unwrap();
+        self.push_str(&generics_str);
+
+        self.last_pos = body_start;
+
+        match self.format_variant_list(enum_def, body_start, span.hi()) {
+            Some(ref s) if enum_def.variants.is_empty() => self.push_str(s),
+            rw => {
+                self.push_rewrite(mk_sp(body_start, span.hi()), rw);
+                self.block_indent = self.block_indent.block_unindent(self.config);
+            }
+        }
+    }
+
+    // Format the body of an enum definition
+    fn format_variant_list(
+        &mut self,
+        enum_def: &ast::EnumDef,
+        body_lo: BytePos,
+        body_hi: BytePos,
+    ) -> Option<String> {
+        if enum_def.variants.is_empty() {
+            let mut buffer = String::with_capacity(128);
+            // 1 = "}"
+            let span = mk_sp(body_lo, body_hi - BytePos(1));
+            format_empty_struct_or_tuple(
+                &self.get_context(),
+                span,
+                self.block_indent,
+                &mut buffer,
+                "",
+                "}",
+            );
+            return Some(buffer);
+        }
+        let mut result = String::with_capacity(1024);
+        let original_offset = self.block_indent;
+        self.block_indent = self.block_indent.block_indent(self.config);
+
+        // If enum variants have discriminants, try to vertically align those,
+        // provided the discrims are not shifted too much  to the right
+        let align_threshold: usize = self.config.enum_discrim_align_threshold();
+        let discr_ident_lens: Vec<usize> = enum_def
+            .variants
+            .iter()
+            .filter(|var| var.disr_expr.is_some())
+            .map(|var| rewrite_ident(&self.get_context(), var.ident).len())
+            .collect();
+        // cut the list at the point of longest discrim shorter than the threshold
+        // All of the discrims under the threshold will get padded, and all above - left as is.
+        let pad_discrim_ident_to = *discr_ident_lens
+            .iter()
+            .filter(|&l| *l <= align_threshold)
+            .max()
+            .unwrap_or(&0);
+
+        let itemize_list_with = |one_line_width: usize| {
+            itemize_list(
+                self.snippet_provider,
+                enum_def.variants.iter(),
+                "}",
+                ",",
+                |f| {
+                    if !f.attrs.is_empty() {
+                        f.attrs[0].span.lo()
+                    } else {
+                        f.span.lo()
+                    }
+                },
+                |f| f.span.hi(),
+                |f| self.format_variant(f, one_line_width, pad_discrim_ident_to),
+                body_lo,
+                body_hi,
+                false,
+            )
+            .collect()
+        };
+        let mut items: Vec<_> = itemize_list_with(self.config.struct_variant_width());
+
+        // If one of the variants use multiple lines, use multi-lined formatting for all variants.
+        let has_multiline_variant = items.iter().any(|item| item.inner_as_ref().contains('\n'));
+        let has_single_line_variant = items.iter().any(|item| !item.inner_as_ref().contains('\n'));
+        if has_multiline_variant && has_single_line_variant {
+            items = itemize_list_with(0);
+        }
+
+        let shape = self.shape().sub_width(2)?;
+        let fmt = ListFormatting::new(shape, self.config)
+            .trailing_separator(self.config.trailing_comma())
+            .preserve_newline(true);
+
+        let list = write_list(&items, &fmt)?;
+        result.push_str(&list);
+        result.push_str(&original_offset.to_string_with_newline(self.config));
+        result.push('}');
+        Some(result)
+    }
+
+    // Variant of an enum.
+    fn format_variant(
+        &self,
+        field: &ast::Variant,
+        one_line_width: usize,
+        pad_discrim_ident_to: usize,
+    ) -> Option<String> {
+        if contains_skip(&field.attrs) {
+            let lo = field.attrs[0].span.lo();
+            let span = mk_sp(lo, field.span.hi());
+            return Some(self.snippet(span).to_owned());
+        }
+
+        let context = self.get_context();
+        // 1 = ','
+        let shape = self.shape().sub_width(1)?;
+        let attrs_str = field.attrs.rewrite(&context, shape)?;
+        let lo = field
+            .attrs
+            .last()
+            .map_or(field.span.lo(), |attr| attr.span.hi());
+        let span = mk_sp(lo, field.span.lo());
+
+        let variant_body = match field.data {
+            ast::VariantData::Tuple(..) | ast::VariantData::Struct(..) => format_struct(
+                &context,
+                &StructParts::from_variant(field),
+                self.block_indent,
+                Some(one_line_width),
+            )?,
+            ast::VariantData::Unit(..) => rewrite_ident(&context, field.ident).to_owned(),
+        };
+
+        let variant_body = if let Some(ref expr) = field.disr_expr {
+            let lhs = format!("{:1$} =", variant_body, pad_discrim_ident_to);
+            rewrite_assign_rhs_with(
+                &context,
+                lhs,
+                &*expr.value,
+                shape,
+                RhsTactics::AllowOverflow,
+            )?
+        } else {
+            variant_body
+        };
+
+        combine_strs_with_missing_comments(&context, &attrs_str, &variant_body, span, shape, false)
+    }
+
+    fn visit_impl_items(&mut self, items: &[ptr::P<ast::AssocItem>]) {
+        if self.get_context().config.reorder_impl_items() {
+            // Create visitor for each items, then reorder them.
+            let mut buffer = vec![];
+            for item in items {
+                self.visit_impl_item(item);
+                buffer.push((self.buffer.clone(), item.clone()));
+                self.buffer.clear();
+            }
+
+            fn is_type(ty: &Option<rustc_ast::ptr::P<ast::Ty>>) -> bool {
+                if let Some(lty) = ty {
+                    if let ast::TyKind::ImplTrait(..) = lty.kind {
+                        return false;
+                    }
+                }
+                true
+            }
+
+            fn is_opaque(ty: &Option<rustc_ast::ptr::P<ast::Ty>>) -> bool {
+                !is_type(ty)
+            }
+
+            fn both_type(
+                a: &Option<rustc_ast::ptr::P<ast::Ty>>,
+                b: &Option<rustc_ast::ptr::P<ast::Ty>>,
+            ) -> bool {
+                is_type(a) && is_type(b)
+            }
+
+            fn both_opaque(
+                a: &Option<rustc_ast::ptr::P<ast::Ty>>,
+                b: &Option<rustc_ast::ptr::P<ast::Ty>>,
+            ) -> bool {
+                is_opaque(a) && is_opaque(b)
+            }
+
+            // In rustc-ap-v638 the `OpaqueTy` AssocItemKind variant was removed but
+            // we still need to differentiate to maintain sorting order.
+
+            // type -> opaque -> const -> macro -> method
+            use crate::ast::AssocItemKind::*;
+            fn need_empty_line(a: &ast::AssocItemKind, b: &ast::AssocItemKind) -> bool {
+                match (a, b) {
+                    (TyAlias(lty), TyAlias(rty))
+                        if both_type(&lty.3, &rty.3) || both_opaque(&lty.3, &rty.3) =>
+                    {
+                        false
+                    }
+                    (Const(..), Const(..)) => false,
+                    _ => true,
+                }
+            }
+
+            buffer.sort_by(|(_, a), (_, b)| match (&a.kind, &b.kind) {
+                (TyAlias(lty), TyAlias(rty))
+                    if both_type(&lty.3, &rty.3) || both_opaque(&lty.3, &rty.3) =>
+                {
+                    a.ident.as_str().cmp(&b.ident.as_str())
+                }
+                (Const(..), Const(..)) | (MacCall(..), MacCall(..)) => {
+                    a.ident.as_str().cmp(&b.ident.as_str())
+                }
+                (Fn(..), Fn(..)) => a.span.lo().cmp(&b.span.lo()),
+                (TyAlias(ty), _) if is_type(&ty.3) => Ordering::Less,
+                (_, TyAlias(ty)) if is_type(&ty.3) => Ordering::Greater,
+                (TyAlias(..), _) => Ordering::Less,
+                (_, TyAlias(..)) => Ordering::Greater,
+                (Const(..), _) => Ordering::Less,
+                (_, Const(..)) => Ordering::Greater,
+                (MacCall(..), _) => Ordering::Less,
+                (_, MacCall(..)) => Ordering::Greater,
+            });
+            let mut prev_kind = None;
+            for (buf, item) in buffer {
+                // Make sure that there are at least a single empty line between
+                // different impl items.
+                if prev_kind
+                    .as_ref()
+                    .map_or(false, |prev_kind| need_empty_line(prev_kind, &item.kind))
+                {
+                    self.push_str("\n");
+                }
+                let indent_str = self.block_indent.to_string_with_newline(self.config);
+                self.push_str(&indent_str);
+                self.push_str(buf.trim());
+                prev_kind = Some(item.kind.clone());
+            }
+        } else {
+            for item in items {
+                self.visit_impl_item(item);
+            }
+        }
+    }
+}
+
+pub(crate) fn format_impl(
+    context: &RewriteContext<'_>,
+    item: &ast::Item,
+    offset: Indent,
+) -> Option<String> {
+    if let ast::ItemKind::Impl(impl_kind) = &item.kind {
+        let ast::ImplKind {
+            ref generics,
+            ref self_ty,
+            ref items,
+            ..
+        } = **impl_kind;
+        let mut result = String::with_capacity(128);
+        let ref_and_type = format_impl_ref_and_type(context, item, offset)?;
+        let sep = offset.to_string_with_newline(context.config);
+        result.push_str(&ref_and_type);
+
+        let where_budget = if result.contains('\n') {
+            context.config.max_width()
+        } else {
+            context.budget(last_line_width(&result))
+        };
+
+        let mut option = WhereClauseOption::snuggled(&ref_and_type);
+        let snippet = context.snippet(item.span);
+        let open_pos = snippet.find_uncommented("{")? + 1;
+        if !contains_comment(&snippet[open_pos..])
+            && items.is_empty()
+            && generics.where_clause.predicates.len() == 1
+            && !result.contains('\n')
+        {
+            option.suppress_comma();
+            option.snuggle();
+            option.allow_single_line();
+        }
+
+        let missing_span = mk_sp(self_ty.span.hi(), item.span.hi());
+        let where_span_end = context.snippet_provider.opt_span_before(missing_span, "{");
+        let where_clause_str = rewrite_where_clause(
+            context,
+            &generics.where_clause,
+            context.config.brace_style(),
+            Shape::legacy(where_budget, offset.block_only()),
+            false,
+            "{",
+            where_span_end,
+            self_ty.span.hi(),
+            option,
+        )?;
+
+        // If there is no where-clause, we may have missing comments between the trait name and
+        // the opening brace.
+        if generics.where_clause.predicates.is_empty() {
+            if let Some(hi) = where_span_end {
+                match recover_missing_comment_in_span(
+                    mk_sp(self_ty.span.hi(), hi),
+                    Shape::indented(offset, context.config),
+                    context,
+                    last_line_width(&result),
+                ) {
+                    Some(ref missing_comment) if !missing_comment.is_empty() => {
+                        result.push_str(missing_comment);
+                    }
+                    _ => (),
+                }
+            }
+        }
+
+        if is_impl_single_line(context, items.as_slice(), &result, &where_clause_str, item)? {
+            result.push_str(&where_clause_str);
+            if where_clause_str.contains('\n') || last_line_contains_single_line_comment(&result) {
+                // if the where_clause contains extra comments AND
+                // there is only one where-clause predicate
+                // recover the suppressed comma in single line where_clause formatting
+                if generics.where_clause.predicates.len() == 1 {
+                    result.push_str(",");
+                }
+                result.push_str(&format!("{}{{{}}}", sep, sep));
+            } else {
+                result.push_str(" {}");
+            }
+            return Some(result);
+        }
+
+        result.push_str(&where_clause_str);
+
+        let need_newline = last_line_contains_single_line_comment(&result) || result.contains('\n');
+        match context.config.brace_style() {
+            _ if need_newline => result.push_str(&sep),
+            BraceStyle::AlwaysNextLine => result.push_str(&sep),
+            BraceStyle::PreferSameLine => result.push(' '),
+            BraceStyle::SameLineWhere => {
+                if !where_clause_str.is_empty() {
+                    result.push_str(&sep);
+                } else {
+                    result.push(' ');
+                }
+            }
+        }
+
+        result.push('{');
+        // this is an impl body snippet(impl SampleImpl { /* here */ })
+        let lo = max(self_ty.span.hi(), generics.where_clause.span.hi());
+        let snippet = context.snippet(mk_sp(lo, item.span.hi()));
+        let open_pos = snippet.find_uncommented("{")? + 1;
+
+        if !items.is_empty() || contains_comment(&snippet[open_pos..]) {
+            let mut visitor = FmtVisitor::from_context(context);
+            let item_indent = offset.block_only().block_indent(context.config);
+            visitor.block_indent = item_indent;
+            visitor.last_pos = lo + BytePos(open_pos as u32);
+
+            visitor.visit_attrs(&item.attrs, ast::AttrStyle::Inner);
+            visitor.visit_impl_items(items);
+
+            visitor.format_missing(item.span.hi() - BytePos(1));
+
+            let inner_indent_str = visitor.block_indent.to_string_with_newline(context.config);
+            let outer_indent_str = offset.block_only().to_string_with_newline(context.config);
+
+            result.push_str(&inner_indent_str);
+            result.push_str(visitor.buffer.trim());
+            result.push_str(&outer_indent_str);
+        } else if need_newline || !context.config.empty_item_single_line() {
+            result.push_str(&sep);
+        }
+
+        result.push('}');
+
+        Some(result)
+    } else {
+        unreachable!();
+    }
+}
+
+fn is_impl_single_line(
+    context: &RewriteContext<'_>,
+    items: &[ptr::P<ast::AssocItem>],
+    result: &str,
+    where_clause_str: &str,
+    item: &ast::Item,
+) -> Option<bool> {
+    let snippet = context.snippet(item.span);
+    let open_pos = snippet.find_uncommented("{")? + 1;
+
+    Some(
+        context.config.empty_item_single_line()
+            && items.is_empty()
+            && !result.contains('\n')
+            && result.len() + where_clause_str.len() <= context.config.max_width()
+            && !contains_comment(&snippet[open_pos..]),
+    )
+}
+
+fn format_impl_ref_and_type(
+    context: &RewriteContext<'_>,
+    item: &ast::Item,
+    offset: Indent,
+) -> Option<String> {
+    if let ast::ItemKind::Impl(impl_kind) = &item.kind {
+        let ast::ImplKind {
+            unsafety,
+            polarity,
+            defaultness,
+            constness,
+            ref generics,
+            of_trait: ref trait_ref,
+            ref self_ty,
+            ..
+        } = **impl_kind;
+        let mut result = String::with_capacity(128);
+
+        result.push_str(&format_visibility(context, &item.vis));
+        result.push_str(format_defaultness(defaultness));
+        result.push_str(format_unsafety(unsafety));
+
+        let shape = if context.config.version() == Version::Two {
+            Shape::indented(offset + last_line_width(&result), context.config)
+        } else {
+            generics_shape_from_config(
+                context.config,
+                Shape::indented(offset + last_line_width(&result), context.config),
+                0,
+            )?
+        };
+        let generics_str = rewrite_generics(context, "impl", generics, shape)?;
+        result.push_str(&generics_str);
+        result.push_str(format_constness_right(constness));
+
+        let polarity_str = match polarity {
+            ast::ImplPolarity::Negative(_) => "!",
+            ast::ImplPolarity::Positive => "",
+        };
+
+        let polarity_overhead;
+        let trait_ref_overhead;
+        if let Some(ref trait_ref) = *trait_ref {
+            let result_len = last_line_width(&result);
+            result.push_str(&rewrite_trait_ref(
+                context,
+                trait_ref,
+                offset,
+                polarity_str,
+                result_len,
+            )?);
+            polarity_overhead = 0; // already written
+            trait_ref_overhead = " for".len();
+        } else {
+            polarity_overhead = polarity_str.len();
+            trait_ref_overhead = 0;
+        }
+
+        // Try to put the self type in a single line.
+        let curly_brace_overhead = if generics.where_clause.predicates.is_empty() {
+            // If there is no where-clause adapt budget for type formatting to take space and curly
+            // brace into account.
+            match context.config.brace_style() {
+                BraceStyle::AlwaysNextLine => 0,
+                _ => 2,
+            }
+        } else {
+            0
+        };
+        let used_space = last_line_width(&result)
+            + polarity_overhead
+            + trait_ref_overhead
+            + curly_brace_overhead;
+        // 1 = space before the type.
+        let budget = context.budget(used_space + 1);
+        if let Some(self_ty_str) = self_ty.rewrite(context, Shape::legacy(budget, offset)) {
+            if !self_ty_str.contains('\n') {
+                if trait_ref.is_some() {
+                    result.push_str(" for ");
+                } else {
+                    result.push(' ');
+                    result.push_str(polarity_str);
+                }
+                result.push_str(&self_ty_str);
+                return Some(result);
+            }
+        }
+
+        // Couldn't fit the self type on a single line, put it on a new line.
+        result.push('\n');
+        // Add indentation of one additional tab.
+        let new_line_offset = offset.block_indent(context.config);
+        result.push_str(&new_line_offset.to_string(context.config));
+        if trait_ref.is_some() {
+            result.push_str("for ");
+        } else {
+            result.push_str(polarity_str);
+        }
+        let budget = context.budget(last_line_width(&result) + polarity_overhead);
+        let type_offset = match context.config.indent_style() {
+            IndentStyle::Visual => new_line_offset + trait_ref_overhead,
+            IndentStyle::Block => new_line_offset,
+        };
+        result.push_str(&*self_ty.rewrite(context, Shape::legacy(budget, type_offset))?);
+        Some(result)
+    } else {
+        unreachable!();
+    }
+}
+
+fn rewrite_trait_ref(
+    context: &RewriteContext<'_>,
+    trait_ref: &ast::TraitRef,
+    offset: Indent,
+    polarity_str: &str,
+    result_len: usize,
+) -> Option<String> {
+    // 1 = space between generics and trait_ref
+    let used_space = 1 + polarity_str.len() + result_len;
+    let shape = Shape::indented(offset + used_space, context.config);
+    if let Some(trait_ref_str) = trait_ref.rewrite(context, shape) {
+        if !trait_ref_str.contains('\n') {
+            return Some(format!(" {}{}", polarity_str, trait_ref_str));
+        }
+    }
+    // We could not make enough space for trait_ref, so put it on new line.
+    let offset = offset.block_indent(context.config);
+    let shape = Shape::indented(offset, context.config);
+    let trait_ref_str = trait_ref.rewrite(context, shape)?;
+    Some(format!(
+        "{}{}{}",
+        offset.to_string_with_newline(context.config),
+        polarity_str,
+        trait_ref_str
+    ))
+}
+
+pub(crate) struct StructParts<'a> {
+    prefix: &'a str,
+    ident: symbol::Ident,
+    vis: &'a ast::Visibility,
+    def: &'a ast::VariantData,
+    generics: Option<&'a ast::Generics>,
+    span: Span,
+}
+
+impl<'a> StructParts<'a> {
+    fn format_header(&self, context: &RewriteContext<'_>, offset: Indent) -> String {
+        format_header(context, self.prefix, self.ident, self.vis, offset)
+    }
+
+    fn from_variant(variant: &'a ast::Variant) -> Self {
+        StructParts {
+            prefix: "",
+            ident: variant.ident,
+            vis: &DEFAULT_VISIBILITY,
+            def: &variant.data,
+            generics: None,
+            span: variant.span,
+        }
+    }
+
+    pub(crate) fn from_item(item: &'a ast::Item) -> Self {
+        let (prefix, def, generics) = match item.kind {
+            ast::ItemKind::Struct(ref def, ref generics) => ("struct ", def, generics),
+            ast::ItemKind::Union(ref def, ref generics) => ("union ", def, generics),
+            _ => unreachable!(),
+        };
+        StructParts {
+            prefix,
+            ident: item.ident,
+            vis: &item.vis,
+            def,
+            generics: Some(generics),
+            span: item.span,
+        }
+    }
+}
+
+fn format_struct(
+    context: &RewriteContext<'_>,
+    struct_parts: &StructParts<'_>,
+    offset: Indent,
+    one_line_width: Option<usize>,
+) -> Option<String> {
+    match *struct_parts.def {
+        ast::VariantData::Unit(..) => format_unit_struct(context, struct_parts, offset),
+        ast::VariantData::Tuple(ref fields, _) => {
+            format_tuple_struct(context, struct_parts, fields, offset)
+        }
+        ast::VariantData::Struct(ref fields, _) => {
+            format_struct_struct(context, struct_parts, fields, offset, one_line_width)
+        }
+    }
+}
+
+pub(crate) fn format_trait(
+    context: &RewriteContext<'_>,
+    item: &ast::Item,
+    offset: Indent,
+) -> Option<String> {
+    if let ast::ItemKind::Trait(trait_kind) = &item.kind {
+        let ast::TraitKind(is_auto, unsafety, ref generics, ref generic_bounds, ref trait_items) =
+            **trait_kind;
+        let mut result = String::with_capacity(128);
+        let header = format!(
+            "{}{}{}trait ",
+            format_visibility(context, &item.vis),
+            format_unsafety(unsafety),
+            format_auto(is_auto),
+        );
+        result.push_str(&header);
+
+        let body_lo = context.snippet_provider.span_after(item.span, "{");
+
+        let shape = Shape::indented(offset, context.config).offset_left(result.len())?;
+        let generics_str =
+            rewrite_generics(context, rewrite_ident(context, item.ident), generics, shape)?;
+        result.push_str(&generics_str);
+
+        // FIXME(#2055): rustfmt fails to format when there are comments between trait bounds.
+        if !generic_bounds.is_empty() {
+            let ident_hi = context
+                .snippet_provider
+                .span_after(item.span, &item.ident.as_str());
+            let bound_hi = generic_bounds.last().unwrap().span().hi();
+            let snippet = context.snippet(mk_sp(ident_hi, bound_hi));
+            if contains_comment(snippet) {
+                return None;
+            }
+
+            result = rewrite_assign_rhs_with(
+                context,
+                result + ":",
+                generic_bounds,
+                shape,
+                RhsTactics::ForceNextLineWithoutIndent,
+            )?;
+        }
+
+        // Rewrite where-clause.
+        if !generics.where_clause.predicates.is_empty() {
+            let where_on_new_line = context.config.indent_style() != IndentStyle::Block;
+
+            let where_budget = context.budget(last_line_width(&result));
+            let pos_before_where = if generic_bounds.is_empty() {
+                generics.where_clause.span.lo()
+            } else {
+                generic_bounds[generic_bounds.len() - 1].span().hi()
+            };
+            let option = WhereClauseOption::snuggled(&generics_str);
+            let where_clause_str = rewrite_where_clause(
+                context,
+                &generics.where_clause,
+                context.config.brace_style(),
+                Shape::legacy(where_budget, offset.block_only()),
+                where_on_new_line,
+                "{",
+                None,
+                pos_before_where,
+                option,
+            )?;
+            // If the where-clause cannot fit on the same line,
+            // put the where-clause on a new line
+            if !where_clause_str.contains('\n')
+                && last_line_width(&result) + where_clause_str.len() + offset.width()
+                    > context.config.comment_width()
+            {
+                let width = offset.block_indent + context.config.tab_spaces() - 1;
+                let where_indent = Indent::new(0, width);
+                result.push_str(&where_indent.to_string_with_newline(context.config));
+            }
+            result.push_str(&where_clause_str);
+        } else {
+            let item_snippet = context.snippet(item.span);
+            if let Some(lo) = item_snippet.find('/') {
+                // 1 = `{`
+                let comment_hi = body_lo - BytePos(1);
+                let comment_lo = item.span.lo() + BytePos(lo as u32);
+                if comment_lo < comment_hi {
+                    match recover_missing_comment_in_span(
+                        mk_sp(comment_lo, comment_hi),
+                        Shape::indented(offset, context.config),
+                        context,
+                        last_line_width(&result),
+                    ) {
+                        Some(ref missing_comment) if !missing_comment.is_empty() => {
+                            result.push_str(missing_comment);
+                        }
+                        _ => (),
+                    }
+                }
+            }
+        }
+
+        match context.config.brace_style() {
+            _ if last_line_contains_single_line_comment(&result)
+                || last_line_width(&result) + 2 > context.budget(offset.width()) =>
+            {
+                result.push_str(&offset.to_string_with_newline(context.config));
+            }
+            BraceStyle::AlwaysNextLine => {
+                result.push_str(&offset.to_string_with_newline(context.config));
+            }
+            BraceStyle::PreferSameLine => result.push(' '),
+            BraceStyle::SameLineWhere => {
+                if result.contains('\n')
+                    || (!generics.where_clause.predicates.is_empty() && !trait_items.is_empty())
+                {
+                    result.push_str(&offset.to_string_with_newline(context.config));
+                } else {
+                    result.push(' ');
+                }
+            }
+        }
+        result.push('{');
+
+        let block_span = mk_sp(generics.where_clause.span.hi(), item.span.hi());
+        let snippet = context.snippet(block_span);
+        let open_pos = snippet.find_uncommented("{")? + 1;
+        let outer_indent_str = offset.block_only().to_string_with_newline(context.config);
+
+        if !trait_items.is_empty() || contains_comment(&snippet[open_pos..]) {
+            let mut visitor = FmtVisitor::from_context(context);
+            visitor.block_indent = offset.block_only().block_indent(context.config);
+            visitor.last_pos = block_span.lo() + BytePos(open_pos as u32);
+
+            for item in trait_items {
+                visitor.visit_trait_item(item);
+            }
+
+            visitor.format_missing(item.span.hi() - BytePos(1));
+
+            let inner_indent_str = visitor.block_indent.to_string_with_newline(context.config);
+
+            result.push_str(&inner_indent_str);
+            result.push_str(visitor.buffer.trim());
+            result.push_str(&outer_indent_str);
+        } else if result.contains('\n') {
+            result.push_str(&outer_indent_str);
+        }
+
+        result.push('}');
+        Some(result)
+    } else {
+        unreachable!();
+    }
+}
+
+struct OpaqueTypeBounds<'a> {
+    generic_bounds: &'a ast::GenericBounds,
+}
+
+impl<'a> Rewrite for OpaqueTypeBounds<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        self.generic_bounds
+            .rewrite(context, shape)
+            .map(|s| format!("impl {}", s))
+    }
+}
+
+pub(crate) struct TraitAliasBounds<'a> {
+    generic_bounds: &'a ast::GenericBounds,
+    generics: &'a ast::Generics,
+}
+
+impl<'a> Rewrite for TraitAliasBounds<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let generic_bounds_str = self.generic_bounds.rewrite(context, shape)?;
+
+        let mut option = WhereClauseOption::new(true, WhereClauseSpace::None);
+        option.allow_single_line();
+
+        let where_str = rewrite_where_clause(
+            context,
+            &self.generics.where_clause,
+            context.config.brace_style(),
+            shape,
+            false,
+            ";",
+            None,
+            self.generics.where_clause.span.lo(),
+            option,
+        )?;
+
+        let fits_single_line = !generic_bounds_str.contains('\n')
+            && !where_str.contains('\n')
+            && generic_bounds_str.len() + where_str.len() + 1 <= shape.width;
+        let space = if generic_bounds_str.is_empty() || where_str.is_empty() {
+            Cow::from("")
+        } else if fits_single_line {
+            Cow::from(" ")
+        } else {
+            shape.indent.to_string_with_newline(&context.config)
+        };
+
+        Some(format!("{}{}{}", generic_bounds_str, space, where_str))
+    }
+}
+
+pub(crate) fn format_trait_alias(
+    context: &RewriteContext<'_>,
+    ident: symbol::Ident,
+    vis: &ast::Visibility,
+    generics: &ast::Generics,
+    generic_bounds: &ast::GenericBounds,
+    shape: Shape,
+) -> Option<String> {
+    let alias = rewrite_ident(context, ident);
+    // 6 = "trait ", 2 = " ="
+    let g_shape = shape.offset_left(6)?.sub_width(2)?;
+    let generics_str = rewrite_generics(context, &alias, generics, g_shape)?;
+    let vis_str = format_visibility(context, vis);
+    let lhs = format!("{}trait {} =", vis_str, generics_str);
+    // 1 = ";"
+    let trait_alias_bounds = TraitAliasBounds {
+        generics,
+        generic_bounds,
+    };
+    rewrite_assign_rhs(context, lhs, &trait_alias_bounds, shape.sub_width(1)?).map(|s| s + ";")
+}
+
+fn format_unit_struct(
+    context: &RewriteContext<'_>,
+    p: &StructParts<'_>,
+    offset: Indent,
+) -> Option<String> {
+    let header_str = format_header(context, p.prefix, p.ident, p.vis, offset);
+    let generics_str = if let Some(generics) = p.generics {
+        let hi = context.snippet_provider.span_before(p.span, ";");
+        format_generics(
+            context,
+            generics,
+            context.config.brace_style(),
+            BracePos::None,
+            offset,
+            // make a span that starts right after `struct Foo`
+            mk_sp(p.ident.span.hi(), hi),
+            last_line_width(&header_str),
+        )?
+    } else {
+        String::new()
+    };
+    Some(format!("{}{};", header_str, generics_str))
+}
+
+pub(crate) fn format_struct_struct(
+    context: &RewriteContext<'_>,
+    struct_parts: &StructParts<'_>,
+    fields: &[ast::FieldDef],
+    offset: Indent,
+    one_line_width: Option<usize>,
+) -> Option<String> {
+    let mut result = String::with_capacity(1024);
+    let span = struct_parts.span;
+
+    let header_str = struct_parts.format_header(context, offset);
+    result.push_str(&header_str);
+
+    let header_hi = struct_parts.ident.span.hi();
+    let body_lo = context.snippet_provider.span_after(span, "{");
+
+    let generics_str = match struct_parts.generics {
+        Some(g) => format_generics(
+            context,
+            g,
+            context.config.brace_style(),
+            if fields.is_empty() {
+                BracePos::ForceSameLine
+            } else {
+                BracePos::Auto
+            },
+            offset,
+            // make a span that starts right after `struct Foo`
+            mk_sp(header_hi, body_lo),
+            last_line_width(&result),
+        )?,
+        None => {
+            // 3 = ` {}`, 2 = ` {`.
+            let overhead = if fields.is_empty() { 3 } else { 2 };
+            if (context.config.brace_style() == BraceStyle::AlwaysNextLine && !fields.is_empty())
+                || context.config.max_width() < overhead + result.len()
+            {
+                format!("\n{}{{", offset.block_only().to_string(context.config))
+            } else {
+                " {".to_owned()
+            }
+        }
+    };
+    // 1 = `}`
+    let overhead = if fields.is_empty() { 1 } else { 0 };
+    let total_width = result.len() + generics_str.len() + overhead;
+    if !generics_str.is_empty()
+        && !generics_str.contains('\n')
+        && total_width > context.config.max_width()
+    {
+        result.push('\n');
+        result.push_str(&offset.to_string(context.config));
+        result.push_str(generics_str.trim_start());
+    } else {
+        result.push_str(&generics_str);
+    }
+
+    if fields.is_empty() {
+        let inner_span = mk_sp(body_lo, span.hi() - BytePos(1));
+        format_empty_struct_or_tuple(context, inner_span, offset, &mut result, "", "}");
+        return Some(result);
+    }
+
+    // 3 = ` ` and ` }`
+    let one_line_budget = context.budget(result.len() + 3 + offset.width());
+    let one_line_budget =
+        one_line_width.map_or(0, |one_line_width| min(one_line_width, one_line_budget));
+
+    let items_str = rewrite_with_alignment(
+        fields,
+        context,
+        Shape::indented(offset.block_indent(context.config), context.config).sub_width(1)?,
+        mk_sp(body_lo, span.hi()),
+        one_line_budget,
+    )?;
+
+    if !items_str.contains('\n')
+        && !result.contains('\n')
+        && items_str.len() <= one_line_budget
+        && !last_line_contains_single_line_comment(&items_str)
+    {
+        Some(format!("{} {} }}", result, items_str))
+    } else {
+        Some(format!(
+            "{}\n{}{}\n{}}}",
+            result,
+            offset
+                .block_indent(context.config)
+                .to_string(context.config),
+            items_str,
+            offset.to_string(context.config)
+        ))
+    }
+}
+
+fn get_bytepos_after_visibility(vis: &ast::Visibility, default_span: Span) -> BytePos {
+    match vis.kind {
+        ast::VisibilityKind::Crate(..) | ast::VisibilityKind::Restricted { .. } => vis.span.hi(),
+        _ => default_span.lo(),
+    }
+}
+
+// Format tuple or struct without any fields. We need to make sure that the comments
+// inside the delimiters are preserved.
+fn format_empty_struct_or_tuple(
+    context: &RewriteContext<'_>,
+    span: Span,
+    offset: Indent,
+    result: &mut String,
+    opener: &str,
+    closer: &str,
+) {
+    // 3 = " {}" or "();"
+    let used_width = last_line_used_width(&result, offset.width()) + 3;
+    if used_width > context.config.max_width() {
+        result.push_str(&offset.to_string_with_newline(context.config))
+    }
+    result.push_str(opener);
+    match rewrite_missing_comment(span, Shape::indented(offset, context.config), context) {
+        Some(ref s) if s.is_empty() => (),
+        Some(ref s) => {
+            if !is_single_line(s) || first_line_contains_single_line_comment(s) {
+                let nested_indent_str = offset
+                    .block_indent(context.config)
+                    .to_string_with_newline(context.config);
+                result.push_str(&nested_indent_str);
+            }
+            result.push_str(s);
+            if last_line_contains_single_line_comment(s) {
+                result.push_str(&offset.to_string_with_newline(context.config));
+            }
+        }
+        None => result.push_str(context.snippet(span)),
+    }
+    result.push_str(closer);
+}
+
+fn format_tuple_struct(
+    context: &RewriteContext<'_>,
+    struct_parts: &StructParts<'_>,
+    fields: &[ast::FieldDef],
+    offset: Indent,
+) -> Option<String> {
+    let mut result = String::with_capacity(1024);
+    let span = struct_parts.span;
+
+    let header_str = struct_parts.format_header(context, offset);
+    result.push_str(&header_str);
+
+    let body_lo = if fields.is_empty() {
+        let lo = get_bytepos_after_visibility(struct_parts.vis, span);
+        context
+            .snippet_provider
+            .span_after(mk_sp(lo, span.hi()), "(")
+    } else {
+        fields[0].span.lo()
+    };
+    let body_hi = if fields.is_empty() {
+        context
+            .snippet_provider
+            .span_after(mk_sp(body_lo, span.hi()), ")")
+    } else {
+        // This is a dirty hack to work around a missing `)` from the span of the last field.
+        let last_arg_span = fields[fields.len() - 1].span;
+        context
+            .snippet_provider
+            .opt_span_after(mk_sp(last_arg_span.hi(), span.hi()), ")")
+            .unwrap_or_else(|| last_arg_span.hi())
+    };
+
+    let where_clause_str = match struct_parts.generics {
+        Some(generics) => {
+            let budget = context.budget(last_line_width(&header_str));
+            let shape = Shape::legacy(budget, offset);
+            let generics_str = rewrite_generics(context, "", generics, shape)?;
+            result.push_str(&generics_str);
+
+            let where_budget = context.budget(last_line_width(&result));
+            let option = WhereClauseOption::new(true, WhereClauseSpace::Newline);
+            rewrite_where_clause(
+                context,
+                &generics.where_clause,
+                context.config.brace_style(),
+                Shape::legacy(where_budget, offset.block_only()),
+                false,
+                ";",
+                None,
+                body_hi,
+                option,
+            )?
+        }
+        None => "".to_owned(),
+    };
+
+    if fields.is_empty() {
+        let body_hi = context
+            .snippet_provider
+            .span_before(mk_sp(body_lo, span.hi()), ")");
+        let inner_span = mk_sp(body_lo, body_hi);
+        format_empty_struct_or_tuple(context, inner_span, offset, &mut result, "(", ")");
+    } else {
+        let shape = Shape::indented(offset, context.config).sub_width(1)?;
+        result = overflow::rewrite_with_parens(
+            context,
+            &result,
+            fields.iter(),
+            shape,
+            span,
+            context.config.fn_call_width(),
+            None,
+        )?;
+    }
+
+    if !where_clause_str.is_empty()
+        && !where_clause_str.contains('\n')
+        && (result.contains('\n')
+            || offset.block_indent + result.len() + where_clause_str.len() + 1
+                > context.config.max_width())
+    {
+        // We need to put the where-clause on a new line, but we didn't
+        // know that earlier, so the where-clause will not be indented properly.
+        result.push('\n');
+        result.push_str(
+            &(offset.block_only() + (context.config.tab_spaces() - 1)).to_string(context.config),
+        );
+    }
+    result.push_str(&where_clause_str);
+
+    Some(result)
+}
+
+fn rewrite_type<R: Rewrite>(
+    context: &RewriteContext<'_>,
+    indent: Indent,
+    ident: symbol::Ident,
+    vis: &ast::Visibility,
+    generics: &ast::Generics,
+    generic_bounds_opt: Option<&ast::GenericBounds>,
+    rhs: Option<&R>,
+    span: Span,
+) -> Option<String> {
+    let mut result = String::with_capacity(128);
+    result.push_str(&format!("{}type ", format_visibility(context, vis)));
+    let ident_str = rewrite_ident(context, ident);
+
+    if generics.params.is_empty() {
+        result.push_str(ident_str)
+    } else {
+        // 2 = `= `
+        let g_shape = Shape::indented(indent, context.config)
+            .offset_left(result.len())?
+            .sub_width(2)?;
+        let generics_str = rewrite_generics(context, ident_str, generics, g_shape)?;
+        result.push_str(&generics_str);
+    }
+
+    if let Some(bounds) = generic_bounds_opt {
+        if !bounds.is_empty() {
+            // 2 = `: `
+            let shape = Shape::indented(indent, context.config).offset_left(result.len() + 2)?;
+            let type_bounds = bounds.rewrite(context, shape).map(|s| format!(": {}", s))?;
+            result.push_str(&type_bounds);
+        }
+    }
+
+    let where_budget = context.budget(last_line_width(&result));
+    let mut option = WhereClauseOption::snuggled(&result);
+    if rhs.is_none() {
+        option.suppress_comma();
+    }
+    let where_clause_str = rewrite_where_clause(
+        context,
+        &generics.where_clause,
+        context.config.brace_style(),
+        Shape::legacy(where_budget, indent),
+        false,
+        "=",
+        None,
+        generics.span.hi(),
+        option,
+    )?;
+    result.push_str(&where_clause_str);
+
+    if let Some(ty) = rhs {
+        // If there's a where clause, add a newline before the assignment. Otherwise just add a
+        // space.
+        let has_where = !generics.where_clause.predicates.is_empty();
+        if has_where {
+            result.push_str(&indent.to_string_with_newline(context.config));
+        } else {
+            result.push(' ');
+        }
+
+        let comment_span = context
+            .snippet_provider
+            .opt_span_before(span, "=")
+            .map(|op_lo| mk_sp(generics.where_clause.span.hi(), op_lo));
+
+        let lhs = match comment_span {
+            Some(comment_span)
+                if contains_comment(context.snippet_provider.span_to_snippet(comment_span)?) =>
+            {
+                let comment_shape = if has_where {
+                    Shape::indented(indent, context.config)
+                } else {
+                    Shape::indented(indent, context.config)
+                        .block_left(context.config.tab_spaces())?
+                };
+
+                combine_strs_with_missing_comments(
+                    context,
+                    result.trim_end(),
+                    "=",
+                    comment_span,
+                    comment_shape,
+                    true,
+                )?
+            }
+            _ => format!("{}=", result),
+        };
+
+        // 1 = `;`
+        let shape = Shape::indented(indent, context.config).sub_width(1)?;
+        rewrite_assign_rhs(context, lhs, &*ty, shape).map(|s| s + ";")
+    } else {
+        Some(format!("{};", result))
+    }
+}
+
+pub(crate) fn rewrite_opaque_type(
+    context: &RewriteContext<'_>,
+    indent: Indent,
+    ident: symbol::Ident,
+    generic_bounds: &ast::GenericBounds,
+    generics: &ast::Generics,
+    vis: &ast::Visibility,
+    span: Span,
+) -> Option<String> {
+    let opaque_type_bounds = OpaqueTypeBounds { generic_bounds };
+    rewrite_type(
+        context,
+        indent,
+        ident,
+        vis,
+        generics,
+        Some(generic_bounds),
+        Some(&opaque_type_bounds),
+        span,
+    )
+}
+
+fn type_annotation_spacing(config: &Config) -> (&str, &str) {
+    (
+        if config.space_before_colon() { " " } else { "" },
+        if config.space_after_colon() { " " } else { "" },
+    )
+}
+
+pub(crate) fn rewrite_struct_field_prefix(
+    context: &RewriteContext<'_>,
+    field: &ast::FieldDef,
+) -> Option<String> {
+    let vis = format_visibility(context, &field.vis);
+    let type_annotation_spacing = type_annotation_spacing(context.config);
+    Some(match field.ident {
+        Some(name) => format!(
+            "{}{}{}:",
+            vis,
+            rewrite_ident(context, name),
+            type_annotation_spacing.0
+        ),
+        None => vis.to_string(),
+    })
+}
+
+impl Rewrite for ast::FieldDef {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        rewrite_struct_field(context, self, shape, 0)
+    }
+}
+
+pub(crate) fn rewrite_struct_field(
+    context: &RewriteContext<'_>,
+    field: &ast::FieldDef,
+    shape: Shape,
+    lhs_max_width: usize,
+) -> Option<String> {
+    if contains_skip(&field.attrs) {
+        return Some(context.snippet(field.span()).to_owned());
+    }
+
+    let type_annotation_spacing = type_annotation_spacing(context.config);
+    let prefix = rewrite_struct_field_prefix(context, field)?;
+
+    let attrs_str = field.attrs.rewrite(context, shape)?;
+    let attrs_extendable = field.ident.is_none() && is_attributes_extendable(&attrs_str);
+    let missing_span = if field.attrs.is_empty() {
+        mk_sp(field.span.lo(), field.span.lo())
+    } else {
+        mk_sp(field.attrs.last().unwrap().span.hi(), field.span.lo())
+    };
+    let mut spacing = String::from(if field.ident.is_some() {
+        type_annotation_spacing.1
+    } else {
+        ""
+    });
+    // Try to put everything on a single line.
+    let attr_prefix = combine_strs_with_missing_comments(
+        context,
+        &attrs_str,
+        &prefix,
+        missing_span,
+        shape,
+        attrs_extendable,
+    )?;
+    let overhead = trimmed_last_line_width(&attr_prefix);
+    let lhs_offset = lhs_max_width.saturating_sub(overhead);
+    for _ in 0..lhs_offset {
+        spacing.push(' ');
+    }
+    // In this extreme case we will be missing a space between an attribute and a field.
+    if prefix.is_empty() && !attrs_str.is_empty() && attrs_extendable && spacing.is_empty() {
+        spacing.push(' ');
+    }
+    let orig_ty = shape
+        .offset_left(overhead + spacing.len())
+        .and_then(|ty_shape| field.ty.rewrite(context, ty_shape));
+    if let Some(ref ty) = orig_ty {
+        if !ty.contains('\n') {
+            return Some(attr_prefix + &spacing + ty);
+        }
+    }
+
+    let is_prefix_empty = prefix.is_empty();
+    // We must use multiline. We are going to put attributes and a field on different lines.
+    let field_str = rewrite_assign_rhs(context, prefix, &*field.ty, shape)?;
+    // Remove a leading white-space from `rewrite_assign_rhs()` when rewriting a tuple struct.
+    let field_str = if is_prefix_empty {
+        field_str.trim_start()
+    } else {
+        &field_str
+    };
+    combine_strs_with_missing_comments(context, &attrs_str, field_str, missing_span, shape, false)
+}
+
+pub(crate) struct StaticParts<'a> {
+    prefix: &'a str,
+    vis: &'a ast::Visibility,
+    ident: symbol::Ident,
+    ty: &'a ast::Ty,
+    mutability: ast::Mutability,
+    expr_opt: Option<&'a ptr::P<ast::Expr>>,
+    defaultness: Option<ast::Defaultness>,
+    span: Span,
+}
+
+impl<'a> StaticParts<'a> {
+    pub(crate) fn from_item(item: &'a ast::Item) -> Self {
+        let (defaultness, prefix, ty, mutability, expr) = match item.kind {
+            ast::ItemKind::Static(ref ty, mutability, ref expr) => {
+                (None, "static", ty, mutability, expr)
+            }
+            ast::ItemKind::Const(defaultness, ref ty, ref expr) => {
+                (Some(defaultness), "const", ty, ast::Mutability::Not, expr)
+            }
+            _ => unreachable!(),
+        };
+        StaticParts {
+            prefix,
+            vis: &item.vis,
+            ident: item.ident,
+            ty,
+            mutability,
+            expr_opt: expr.as_ref(),
+            defaultness,
+            span: item.span,
+        }
+    }
+
+    pub(crate) fn from_trait_item(ti: &'a ast::AssocItem) -> Self {
+        let (defaultness, ty, expr_opt) = match ti.kind {
+            ast::AssocItemKind::Const(defaultness, ref ty, ref expr_opt) => {
+                (defaultness, ty, expr_opt)
+            }
+            _ => unreachable!(),
+        };
+        StaticParts {
+            prefix: "const",
+            vis: &DEFAULT_VISIBILITY,
+            ident: ti.ident,
+            ty,
+            mutability: ast::Mutability::Not,
+            expr_opt: expr_opt.as_ref(),
+            defaultness: Some(defaultness),
+            span: ti.span,
+        }
+    }
+
+    pub(crate) fn from_impl_item(ii: &'a ast::AssocItem) -> Self {
+        let (defaultness, ty, expr) = match ii.kind {
+            ast::AssocItemKind::Const(defaultness, ref ty, ref expr) => (defaultness, ty, expr),
+            _ => unreachable!(),
+        };
+        StaticParts {
+            prefix: "const",
+            vis: &ii.vis,
+            ident: ii.ident,
+            ty,
+            mutability: ast::Mutability::Not,
+            expr_opt: expr.as_ref(),
+            defaultness: Some(defaultness),
+            span: ii.span,
+        }
+    }
+}
+
+fn rewrite_static(
+    context: &RewriteContext<'_>,
+    static_parts: &StaticParts<'_>,
+    offset: Indent,
+) -> Option<String> {
+    let colon = colon_spaces(context.config);
+    let mut prefix = format!(
+        "{}{}{} {}{}{}",
+        format_visibility(context, static_parts.vis),
+        static_parts.defaultness.map_or("", format_defaultness),
+        static_parts.prefix,
+        format_mutability(static_parts.mutability),
+        rewrite_ident(context, static_parts.ident),
+        colon,
+    );
+    // 2 = " =".len()
+    let ty_shape =
+        Shape::indented(offset.block_only(), context.config).offset_left(prefix.len() + 2)?;
+    let ty_str = match static_parts.ty.rewrite(context, ty_shape) {
+        Some(ty_str) => ty_str,
+        None => {
+            if prefix.ends_with(' ') {
+                prefix.pop();
+            }
+            let nested_indent = offset.block_indent(context.config);
+            let nested_shape = Shape::indented(nested_indent, context.config);
+            let ty_str = static_parts.ty.rewrite(context, nested_shape)?;
+            format!(
+                "{}{}",
+                nested_indent.to_string_with_newline(context.config),
+                ty_str
+            )
+        }
+    };
+
+    if let Some(expr) = static_parts.expr_opt {
+        let comments_lo = context.snippet_provider.span_after(static_parts.span, "=");
+        let expr_lo = expr.span.lo();
+        let comments_span = mk_sp(comments_lo, expr_lo);
+
+        let lhs = format!("{}{} =", prefix, ty_str);
+
+        // 1 = ;
+        let remaining_width = context.budget(offset.block_indent + 1);
+        rewrite_assign_rhs_with_comments(
+            context,
+            &lhs,
+            &**expr,
+            Shape::legacy(remaining_width, offset.block_only()),
+            RhsTactics::Default,
+            comments_span,
+            true,
+        )
+        .and_then(|res| recover_comment_removed(res, static_parts.span, context))
+        .map(|s| if s.ends_with(';') { s } else { s + ";" })
+    } else {
+        Some(format!("{}{};", prefix, ty_str))
+    }
+}
+
+pub(crate) fn rewrite_type_alias(
+    ident: symbol::Ident,
+    ty_opt: Option<&ptr::P<ast::Ty>>,
+    generics: &ast::Generics,
+    generic_bounds_opt: Option<&ast::GenericBounds>,
+    context: &RewriteContext<'_>,
+    indent: Indent,
+    vis: &ast::Visibility,
+    span: Span,
+) -> Option<String> {
+    rewrite_type(
+        context,
+        indent,
+        ident,
+        vis,
+        generics,
+        generic_bounds_opt,
+        ty_opt,
+        span,
+    )
+}
+
+struct OpaqueType<'a> {
+    bounds: &'a ast::GenericBounds,
+}
+
+impl<'a> Rewrite for OpaqueType<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let shape = shape.offset_left(5)?; // `impl `
+        self.bounds
+            .rewrite(context, shape)
+            .map(|s| format!("impl {}", s))
+    }
+}
+
+pub(crate) fn rewrite_opaque_impl_type(
+    context: &RewriteContext<'_>,
+    ident: symbol::Ident,
+    generics: &ast::Generics,
+    generic_bounds: &ast::GenericBounds,
+    indent: Indent,
+) -> Option<String> {
+    let ident_str = rewrite_ident(context, ident);
+    // 5 = "type "
+    let generics_shape = Shape::indented(indent, context.config).offset_left(5)?;
+    let generics_str = rewrite_generics(context, ident_str, generics, generics_shape)?;
+    let prefix = format!("type {} =", generics_str);
+    let rhs = OpaqueType {
+        bounds: generic_bounds,
+    };
+
+    rewrite_assign_rhs(
+        context,
+        &prefix,
+        &rhs,
+        Shape::indented(indent, context.config).sub_width(1)?,
+    )
+    .map(|s| s + ";")
+}
+
+pub(crate) fn rewrite_associated_impl_type(
+    ident: symbol::Ident,
+    vis: &ast::Visibility,
+    defaultness: ast::Defaultness,
+    ty_opt: Option<&ptr::P<ast::Ty>>,
+    generics: &ast::Generics,
+    context: &RewriteContext<'_>,
+    indent: Indent,
+    span: Span,
+) -> Option<String> {
+    let result = rewrite_type_alias(ident, ty_opt, generics, None, context, indent, vis, span)?;
+
+    match defaultness {
+        ast::Defaultness::Default(..) => Some(format!("default {}", result)),
+        _ => Some(result),
+    }
+}
+
+impl Rewrite for ast::FnRetTy {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match *self {
+            ast::FnRetTy::Default(_) => Some(String::new()),
+            ast::FnRetTy::Ty(ref ty) => {
+                if context.config.version() == Version::One
+                    || context.config.indent_style() == IndentStyle::Visual
+                {
+                    let inner_width = shape.width.checked_sub(3)?;
+                    return ty
+                        .rewrite(context, Shape::legacy(inner_width, shape.indent + 3))
+                        .map(|r| format!("-> {}", r));
+                }
+
+                ty.rewrite(context, shape.offset_left(3)?)
+                    .map(|s| format!("-> {}", s))
+            }
+        }
+    }
+}
+
+fn is_empty_infer(ty: &ast::Ty, pat_span: Span) -> bool {
+    match ty.kind {
+        ast::TyKind::Infer => ty.span.hi() == pat_span.hi(),
+        _ => false,
+    }
+}
+
+/// Recover any missing comments between the param and the type.
+///
+/// # Returns
+///
+/// A 2-len tuple with the comment before the colon in first position, and the comment after the
+/// colon in second position.
+fn get_missing_param_comments(
+    context: &RewriteContext<'_>,
+    pat_span: Span,
+    ty_span: Span,
+    shape: Shape,
+) -> (String, String) {
+    let missing_comment_span = mk_sp(pat_span.hi(), ty_span.lo());
+
+    let span_before_colon = {
+        let missing_comment_span_hi = context
+            .snippet_provider
+            .span_before(missing_comment_span, ":");
+        mk_sp(pat_span.hi(), missing_comment_span_hi)
+    };
+    let span_after_colon = {
+        let missing_comment_span_lo = context
+            .snippet_provider
+            .span_after(missing_comment_span, ":");
+        mk_sp(missing_comment_span_lo, ty_span.lo())
+    };
+
+    let comment_before_colon = rewrite_missing_comment(span_before_colon, shape, context)
+        .filter(|comment| !comment.is_empty())
+        .map_or(String::new(), |comment| format!(" {}", comment));
+    let comment_after_colon = rewrite_missing_comment(span_after_colon, shape, context)
+        .filter(|comment| !comment.is_empty())
+        .map_or(String::new(), |comment| format!("{} ", comment));
+    (comment_before_colon, comment_after_colon)
+}
+
+impl Rewrite for ast::Param {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let param_attrs_result = self
+            .attrs
+            .rewrite(context, Shape::legacy(shape.width, shape.indent))?;
+        let (span, has_multiple_attr_lines) = if !self.attrs.is_empty() {
+            let num_attrs = self.attrs.len();
+            (
+                mk_sp(self.attrs[num_attrs - 1].span.hi(), self.pat.span.lo()),
+                param_attrs_result.contains("\n"),
+            )
+        } else {
+            (mk_sp(self.span.lo(), self.span.lo()), false)
+        };
+
+        if let Some(ref explicit_self) = self.to_self() {
+            rewrite_explicit_self(
+                context,
+                explicit_self,
+                &param_attrs_result,
+                span,
+                shape,
+                has_multiple_attr_lines,
+            )
+        } else if is_named_param(self) {
+            let mut result = combine_strs_with_missing_comments(
+                context,
+                &param_attrs_result,
+                &self
+                    .pat
+                    .rewrite(context, Shape::legacy(shape.width, shape.indent))?,
+                span,
+                shape,
+                !has_multiple_attr_lines,
+            )?;
+
+            if !is_empty_infer(&*self.ty, self.pat.span) {
+                let (before_comment, after_comment) =
+                    get_missing_param_comments(context, self.pat.span, self.ty.span, shape);
+                result.push_str(&before_comment);
+                result.push_str(colon_spaces(context.config));
+                result.push_str(&after_comment);
+                let overhead = last_line_width(&result);
+                let max_width = shape.width.checked_sub(overhead)?;
+                let ty_str = self
+                    .ty
+                    .rewrite(context, Shape::legacy(max_width, shape.indent))?;
+                result.push_str(&ty_str);
+            }
+
+            Some(result)
+        } else {
+            self.ty.rewrite(context, shape)
+        }
+    }
+}
+
+fn rewrite_explicit_self(
+    context: &RewriteContext<'_>,
+    explicit_self: &ast::ExplicitSelf,
+    param_attrs: &str,
+    span: Span,
+    shape: Shape,
+    has_multiple_attr_lines: bool,
+) -> Option<String> {
+    match explicit_self.node {
+        ast::SelfKind::Region(lt, m) => {
+            let mut_str = format_mutability(m);
+            match lt {
+                Some(ref l) => {
+                    let lifetime_str = l.rewrite(
+                        context,
+                        Shape::legacy(context.config.max_width(), Indent::empty()),
+                    )?;
+                    Some(combine_strs_with_missing_comments(
+                        context,
+                        &param_attrs,
+                        &format!("&{} {}self", lifetime_str, mut_str),
+                        span,
+                        shape,
+                        !has_multiple_attr_lines,
+                    )?)
+                }
+                None => Some(combine_strs_with_missing_comments(
+                    context,
+                    &param_attrs,
+                    &format!("&{}self", mut_str),
+                    span,
+                    shape,
+                    !has_multiple_attr_lines,
+                )?),
+            }
+        }
+        ast::SelfKind::Explicit(ref ty, mutability) => {
+            let type_str = ty.rewrite(
+                context,
+                Shape::legacy(context.config.max_width(), Indent::empty()),
+            )?;
+
+            Some(combine_strs_with_missing_comments(
+                context,
+                &param_attrs,
+                &format!("{}self: {}", format_mutability(mutability), type_str),
+                span,
+                shape,
+                !has_multiple_attr_lines,
+            )?)
+        }
+        ast::SelfKind::Value(mutability) => Some(combine_strs_with_missing_comments(
+            context,
+            &param_attrs,
+            &format!("{}self", format_mutability(mutability)),
+            span,
+            shape,
+            !has_multiple_attr_lines,
+        )?),
+    }
+}
+
+pub(crate) fn span_lo_for_param(param: &ast::Param) -> BytePos {
+    if param.attrs.is_empty() {
+        if is_named_param(param) {
+            param.pat.span.lo()
+        } else {
+            param.ty.span.lo()
+        }
+    } else {
+        param.attrs[0].span.lo()
+    }
+}
+
+pub(crate) fn span_hi_for_param(context: &RewriteContext<'_>, param: &ast::Param) -> BytePos {
+    match param.ty.kind {
+        ast::TyKind::Infer if context.snippet(param.ty.span) == "_" => param.ty.span.hi(),
+        ast::TyKind::Infer if is_named_param(param) => param.pat.span.hi(),
+        _ => param.ty.span.hi(),
+    }
+}
+
+pub(crate) fn is_named_param(param: &ast::Param) -> bool {
+    if let ast::PatKind::Ident(_, ident, _) = param.pat.kind {
+        ident.name != symbol::kw::Empty
+    } else {
+        true
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub(crate) enum FnBraceStyle {
+    SameLine,
+    NextLine,
+    None,
+}
+
+// Return type is (result, force_new_line_for_brace)
+fn rewrite_fn_base(
+    context: &RewriteContext<'_>,
+    indent: Indent,
+    ident: symbol::Ident,
+    fn_sig: &FnSig<'_>,
+    span: Span,
+    fn_brace_style: FnBraceStyle,
+) -> Option<(String, bool, bool)> {
+    let mut force_new_line_for_brace = false;
+
+    let where_clause = &fn_sig.generics.where_clause;
+
+    let mut result = String::with_capacity(1024);
+    result.push_str(&fn_sig.to_str(context));
+
+    // fn foo
+    result.push_str("fn ");
+
+    // Generics.
+    let overhead = if let FnBraceStyle::SameLine = fn_brace_style {
+        // 4 = `() {`
+        4
+    } else {
+        // 2 = `()`
+        2
+    };
+    let used_width = last_line_used_width(&result, indent.width());
+    let one_line_budget = context.budget(used_width + overhead);
+    let shape = Shape {
+        width: one_line_budget,
+        indent,
+        offset: used_width,
+    };
+    let fd = fn_sig.decl;
+    let generics_str = rewrite_generics(
+        context,
+        rewrite_ident(context, ident),
+        fn_sig.generics,
+        shape,
+    )?;
+    result.push_str(&generics_str);
+
+    let snuggle_angle_bracket = generics_str
+        .lines()
+        .last()
+        .map_or(false, |l| l.trim_start().len() == 1);
+
+    // Note that the width and indent don't really matter, we'll re-layout the
+    // return type later anyway.
+    let ret_str = fd
+        .output
+        .rewrite(context, Shape::indented(indent, context.config))?;
+
+    let multi_line_ret_str = ret_str.contains('\n');
+    let ret_str_len = if multi_line_ret_str { 0 } else { ret_str.len() };
+
+    // Params.
+    let (one_line_budget, multi_line_budget, mut param_indent) = compute_budgets_for_params(
+        context,
+        &result,
+        indent,
+        ret_str_len,
+        fn_brace_style,
+        multi_line_ret_str,
+    )?;
+
+    debug!(
+        "rewrite_fn_base: one_line_budget: {}, multi_line_budget: {}, param_indent: {:?}",
+        one_line_budget, multi_line_budget, param_indent
+    );
+
+    result.push('(');
+    // Check if vertical layout was forced.
+    if one_line_budget == 0
+        && !snuggle_angle_bracket
+        && context.config.indent_style() == IndentStyle::Visual
+    {
+        result.push_str(&param_indent.to_string_with_newline(context.config));
+    }
+
+    // Skip `pub(crate)`.
+    let lo_after_visibility = get_bytepos_after_visibility(&fn_sig.visibility, span);
+    // A conservative estimation, the goal is to be over all parens in generics
+    let params_start = fn_sig
+        .generics
+        .params
+        .last()
+        .map_or(lo_after_visibility, |param| param.span().hi());
+    let params_end = if fd.inputs.is_empty() {
+        context
+            .snippet_provider
+            .span_after(mk_sp(params_start, span.hi()), ")")
+    } else {
+        let last_span = mk_sp(fd.inputs[fd.inputs.len() - 1].span().hi(), span.hi());
+        context.snippet_provider.span_after(last_span, ")")
+    };
+    let params_span = mk_sp(
+        context
+            .snippet_provider
+            .span_after(mk_sp(params_start, span.hi()), "("),
+        params_end,
+    );
+    let param_str = rewrite_params(
+        context,
+        &fd.inputs,
+        one_line_budget,
+        multi_line_budget,
+        indent,
+        param_indent,
+        params_span,
+        fd.c_variadic(),
+    )?;
+
+    let put_params_in_block = match context.config.indent_style() {
+        IndentStyle::Block => param_str.contains('\n') || param_str.len() > one_line_budget,
+        _ => false,
+    } && !fd.inputs.is_empty();
+
+    let mut params_last_line_contains_comment = false;
+    let mut no_params_and_over_max_width = false;
+
+    if put_params_in_block {
+        param_indent = indent.block_indent(context.config);
+        result.push_str(&param_indent.to_string_with_newline(context.config));
+        result.push_str(&param_str);
+        result.push_str(&indent.to_string_with_newline(context.config));
+        result.push(')');
+    } else {
+        result.push_str(&param_str);
+        let used_width = last_line_used_width(&result, indent.width()) + first_line_width(&ret_str);
+        // Put the closing brace on the next line if it overflows the max width.
+        // 1 = `)`
+        let closing_paren_overflow_max_width =
+            fd.inputs.is_empty() && used_width + 1 > context.config.max_width();
+        // If the last line of params contains comment, we cannot put the closing paren
+        // on the same line.
+        params_last_line_contains_comment = param_str
+            .lines()
+            .last()
+            .map_or(false, |last_line| last_line.contains("//"));
+
+        if context.config.version() == Version::Two {
+            if closing_paren_overflow_max_width {
+                result.push(')');
+                result.push_str(&indent.to_string_with_newline(context.config));
+                no_params_and_over_max_width = true;
+            } else if params_last_line_contains_comment {
+                result.push_str(&indent.to_string_with_newline(context.config));
+                result.push(')');
+                no_params_and_over_max_width = true;
+            } else {
+                result.push(')');
+            }
+        } else {
+            if closing_paren_overflow_max_width || params_last_line_contains_comment {
+                result.push_str(&indent.to_string_with_newline(context.config));
+            }
+            result.push(')');
+        }
+    }
+
+    // Return type.
+    if let ast::FnRetTy::Ty(..) = fd.output {
+        let ret_should_indent = match context.config.indent_style() {
+            // If our params are block layout then we surely must have space.
+            IndentStyle::Block if put_params_in_block || fd.inputs.is_empty() => false,
+            _ if params_last_line_contains_comment => false,
+            _ if result.contains('\n') || multi_line_ret_str => true,
+            _ => {
+                // If the return type would push over the max width, then put the return type on
+                // a new line. With the +1 for the signature length an additional space between
+                // the closing parenthesis of the param and the arrow '->' is considered.
+                let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
+
+                // If there is no where-clause, take into account the space after the return type
+                // and the brace.
+                if where_clause.predicates.is_empty() {
+                    sig_length += 2;
+                }
+
+                sig_length > context.config.max_width()
+            }
+        };
+        let ret_shape = if ret_should_indent {
+            if context.config.version() == Version::One
+                || context.config.indent_style() == IndentStyle::Visual
+            {
+                let indent = if param_str.is_empty() {
+                    // Aligning with non-existent params looks silly.
+                    force_new_line_for_brace = true;
+                    indent + 4
+                } else {
+                    // FIXME: we might want to check that using the param indent
+                    // doesn't blow our budget, and if it does, then fallback to
+                    // the where-clause indent.
+                    param_indent
+                };
+
+                result.push_str(&indent.to_string_with_newline(context.config));
+                Shape::indented(indent, context.config)
+            } else {
+                let mut ret_shape = Shape::indented(indent, context.config);
+                if param_str.is_empty() {
+                    // Aligning with non-existent params looks silly.
+                    force_new_line_for_brace = true;
+                    ret_shape = if context.use_block_indent() {
+                        ret_shape.offset_left(4).unwrap_or(ret_shape)
+                    } else {
+                        ret_shape.indent = ret_shape.indent + 4;
+                        ret_shape
+                    };
+                }
+
+                result.push_str(&ret_shape.indent.to_string_with_newline(context.config));
+                ret_shape
+            }
+        } else {
+            if context.config.version() == Version::Two {
+                if !param_str.is_empty() || !no_params_and_over_max_width {
+                    result.push(' ');
+                }
+            } else {
+                result.push(' ');
+            }
+
+            let ret_shape = Shape::indented(indent, context.config);
+            ret_shape
+                .offset_left(last_line_width(&result))
+                .unwrap_or(ret_shape)
+        };
+
+        if multi_line_ret_str || ret_should_indent {
+            // Now that we know the proper indent and width, we need to
+            // re-layout the return type.
+            let ret_str = fd.output.rewrite(context, ret_shape)?;
+            result.push_str(&ret_str);
+        } else {
+            result.push_str(&ret_str);
+        }
+
+        // Comment between return type and the end of the decl.
+        let snippet_lo = fd.output.span().hi();
+        if where_clause.predicates.is_empty() {
+            let snippet_hi = span.hi();
+            let snippet = context.snippet(mk_sp(snippet_lo, snippet_hi));
+            // Try to preserve the layout of the original snippet.
+            let original_starts_with_newline = snippet
+                .find(|c| c != ' ')
+                .map_or(false, |i| starts_with_newline(&snippet[i..]));
+            let original_ends_with_newline = snippet
+                .rfind(|c| c != ' ')
+                .map_or(false, |i| snippet[i..].ends_with('\n'));
+            let snippet = snippet.trim();
+            if !snippet.is_empty() {
+                result.push(if original_starts_with_newline {
+                    '\n'
+                } else {
+                    ' '
+                });
+                result.push_str(snippet);
+                if original_ends_with_newline {
+                    force_new_line_for_brace = true;
+                }
+            }
+        }
+    }
+
+    let pos_before_where = match fd.output {
+        ast::FnRetTy::Default(..) => params_span.hi(),
+        ast::FnRetTy::Ty(ref ty) => ty.span.hi(),
+    };
+
+    let is_params_multi_lined = param_str.contains('\n');
+
+    let space = if put_params_in_block && ret_str.is_empty() {
+        WhereClauseSpace::Space
+    } else {
+        WhereClauseSpace::Newline
+    };
+    let mut option = WhereClauseOption::new(fn_brace_style == FnBraceStyle::None, space);
+    if is_params_multi_lined {
+        option.veto_single_line();
+    }
+    let where_clause_str = rewrite_where_clause(
+        context,
+        where_clause,
+        context.config.brace_style(),
+        Shape::indented(indent, context.config),
+        true,
+        "{",
+        Some(span.hi()),
+        pos_before_where,
+        option,
+    )?;
+    // If there are neither where-clause nor return type, we may be missing comments between
+    // params and `{`.
+    if where_clause_str.is_empty() {
+        if let ast::FnRetTy::Default(ret_span) = fd.output {
+            match recover_missing_comment_in_span(
+                mk_sp(params_span.hi(), ret_span.hi()),
+                shape,
+                context,
+                last_line_width(&result),
+            ) {
+                Some(ref missing_comment) if !missing_comment.is_empty() => {
+                    result.push_str(missing_comment);
+                    force_new_line_for_brace = true;
+                }
+                _ => (),
+            }
+        }
+    }
+
+    result.push_str(&where_clause_str);
+
+    let ends_with_comment = last_line_contains_single_line_comment(&result);
+    force_new_line_for_brace |= ends_with_comment;
+    force_new_line_for_brace |=
+        is_params_multi_lined && context.config.where_single_line() && !where_clause_str.is_empty();
+    Some((result, ends_with_comment, force_new_line_for_brace))
+}
+
+/// Kind of spaces to put before `where`.
+#[derive(Copy, Clone)]
+enum WhereClauseSpace {
+    /// A single space.
+    Space,
+    /// A new line.
+    Newline,
+    /// Nothing.
+    None,
+}
+
+#[derive(Copy, Clone)]
+struct WhereClauseOption {
+    suppress_comma: bool, // Force no trailing comma
+    snuggle: WhereClauseSpace,
+    allow_single_line: bool, // Try single line where-clause instead of vertical layout
+    veto_single_line: bool,  // Disallow a single-line where-clause.
+}
+
+impl WhereClauseOption {
+    fn new(suppress_comma: bool, snuggle: WhereClauseSpace) -> WhereClauseOption {
+        WhereClauseOption {
+            suppress_comma,
+            snuggle,
+            allow_single_line: false,
+            veto_single_line: false,
+        }
+    }
+
+    fn snuggled(current: &str) -> WhereClauseOption {
+        WhereClauseOption {
+            suppress_comma: false,
+            snuggle: if last_line_width(current) == 1 {
+                WhereClauseSpace::Space
+            } else {
+                WhereClauseSpace::Newline
+            },
+            allow_single_line: false,
+            veto_single_line: false,
+        }
+    }
+
+    fn suppress_comma(&mut self) {
+        self.suppress_comma = true
+    }
+
+    fn allow_single_line(&mut self) {
+        self.allow_single_line = true
+    }
+
+    fn snuggle(&mut self) {
+        self.snuggle = WhereClauseSpace::Space
+    }
+
+    fn veto_single_line(&mut self) {
+        self.veto_single_line = true;
+    }
+}
+
+fn rewrite_params(
+    context: &RewriteContext<'_>,
+    params: &[ast::Param],
+    one_line_budget: usize,
+    multi_line_budget: usize,
+    indent: Indent,
+    param_indent: Indent,
+    span: Span,
+    variadic: bool,
+) -> Option<String> {
+    if params.is_empty() {
+        let comment = context
+            .snippet(mk_sp(
+                span.lo(),
+                // to remove ')'
+                span.hi() - BytePos(1),
+            ))
+            .trim();
+        return Some(comment.to_owned());
+    }
+    let param_items: Vec<_> = itemize_list(
+        context.snippet_provider,
+        params.iter(),
+        ")",
+        ",",
+        |param| span_lo_for_param(param),
+        |param| param.ty.span.hi(),
+        |param| {
+            param
+                .rewrite(context, Shape::legacy(multi_line_budget, param_indent))
+                .or_else(|| Some(context.snippet(param.span()).to_owned()))
+        },
+        span.lo(),
+        span.hi(),
+        false,
+    )
+    .collect();
+
+    let tactic = definitive_tactic(
+        &param_items,
+        context
+            .config
+            .fn_args_layout()
+            .to_list_tactic(param_items.len()),
+        Separator::Comma,
+        one_line_budget,
+    );
+    let budget = match tactic {
+        DefinitiveListTactic::Horizontal => one_line_budget,
+        _ => multi_line_budget,
+    };
+    let indent = match context.config.indent_style() {
+        IndentStyle::Block => indent.block_indent(context.config),
+        IndentStyle::Visual => param_indent,
+    };
+    let trailing_separator = if variadic {
+        SeparatorTactic::Never
+    } else {
+        match context.config.indent_style() {
+            IndentStyle::Block => context.config.trailing_comma(),
+            IndentStyle::Visual => SeparatorTactic::Never,
+        }
+    };
+    let fmt = ListFormatting::new(Shape::legacy(budget, indent), context.config)
+        .tactic(tactic)
+        .trailing_separator(trailing_separator)
+        .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
+        .preserve_newline(true);
+    write_list(&param_items, &fmt)
+}
+
+fn compute_budgets_for_params(
+    context: &RewriteContext<'_>,
+    result: &str,
+    indent: Indent,
+    ret_str_len: usize,
+    fn_brace_style: FnBraceStyle,
+    force_vertical_layout: bool,
+) -> Option<(usize, usize, Indent)> {
+    debug!(
+        "compute_budgets_for_params {} {:?}, {}, {:?}",
+        result.len(),
+        indent,
+        ret_str_len,
+        fn_brace_style,
+    );
+    // Try keeping everything on the same line.
+    if !result.contains('\n') && !force_vertical_layout {
+        // 2 = `()`, 3 = `() `, space is before ret_string.
+        let overhead = if ret_str_len == 0 { 2 } else { 3 };
+        let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
+        match fn_brace_style {
+            FnBraceStyle::None => used_space += 1,     // 1 = `;`
+            FnBraceStyle::SameLine => used_space += 2, // 2 = `{}`
+            FnBraceStyle::NextLine => (),
+        }
+        let one_line_budget = context.budget(used_space);
+
+        if one_line_budget > 0 {
+            // 4 = "() {".len()
+            let (indent, multi_line_budget) = match context.config.indent_style() {
+                IndentStyle::Block => {
+                    let indent = indent.block_indent(context.config);
+                    (indent, context.budget(indent.width() + 1))
+                }
+                IndentStyle::Visual => {
+                    let indent = indent + result.len() + 1;
+                    let multi_line_overhead = match fn_brace_style {
+                        FnBraceStyle::SameLine => 4,
+                        _ => 2,
+                    } + indent.width();
+                    (indent, context.budget(multi_line_overhead))
+                }
+            };
+
+            return Some((one_line_budget, multi_line_budget, indent));
+        }
+    }
+
+    // Didn't work. we must force vertical layout and put params on a newline.
+    let new_indent = indent.block_indent(context.config);
+    let used_space = match context.config.indent_style() {
+        // 1 = `,`
+        IndentStyle::Block => new_indent.width() + 1,
+        // Account for `)` and possibly ` {`.
+        IndentStyle::Visual => new_indent.width() + if ret_str_len == 0 { 1 } else { 3 },
+    };
+    Some((0, context.budget(used_space), new_indent))
+}
+
+fn newline_for_brace(config: &Config, where_clause: &ast::WhereClause) -> FnBraceStyle {
+    let predicate_count = where_clause.predicates.len();
+
+    if config.where_single_line() && predicate_count == 1 {
+        return FnBraceStyle::SameLine;
+    }
+    let brace_style = config.brace_style();
+
+    let use_next_line = brace_style == BraceStyle::AlwaysNextLine
+        || (brace_style == BraceStyle::SameLineWhere && predicate_count > 0);
+    if use_next_line {
+        FnBraceStyle::NextLine
+    } else {
+        FnBraceStyle::SameLine
+    }
+}
+
+fn rewrite_generics(
+    context: &RewriteContext<'_>,
+    ident: &str,
+    generics: &ast::Generics,
+    shape: Shape,
+) -> Option<String> {
+    // FIXME: convert bounds to where-clauses where they get too big or if
+    // there is a where-clause at all.
+
+    if generics.params.is_empty() {
+        return Some(ident.to_owned());
+    }
+
+    let params = generics.params.iter();
+    overflow::rewrite_with_angle_brackets(context, ident, params, shape, generics.span)
+}
+
+fn generics_shape_from_config(config: &Config, shape: Shape, offset: usize) -> Option<Shape> {
+    match config.indent_style() {
+        IndentStyle::Visual => shape.visual_indent(1 + offset).sub_width(offset + 2),
+        IndentStyle::Block => {
+            // 1 = ","
+            shape
+                .block()
+                .block_indent(config.tab_spaces())
+                .with_max_width(config)
+                .sub_width(1)
+        }
+    }
+}
+
+fn rewrite_where_clause_rfc_style(
+    context: &RewriteContext<'_>,
+    where_clause: &ast::WhereClause,
+    shape: Shape,
+    terminator: &str,
+    span_end: Option<BytePos>,
+    span_end_before_where: BytePos,
+    where_clause_option: WhereClauseOption,
+) -> Option<String> {
+    let (where_keyword, allow_single_line) = rewrite_where_keyword(
+        context,
+        where_clause,
+        shape,
+        span_end_before_where,
+        where_clause_option,
+    )?;
+
+    // 1 = `,`
+    let clause_shape = shape
+        .block()
+        .with_max_width(context.config)
+        .block_left(context.config.tab_spaces())?
+        .sub_width(1)?;
+    let force_single_line = context.config.where_single_line()
+        && where_clause.predicates.len() == 1
+        && !where_clause_option.veto_single_line;
+
+    let preds_str = rewrite_bounds_on_where_clause(
+        context,
+        where_clause,
+        clause_shape,
+        terminator,
+        span_end,
+        where_clause_option,
+        force_single_line,
+    )?;
+
+    // 6 = `where `
+    let clause_sep =
+        if allow_single_line && !preds_str.contains('\n') && 6 + preds_str.len() <= shape.width
+            || force_single_line
+        {
+            Cow::from(" ")
+        } else {
+            clause_shape.indent.to_string_with_newline(context.config)
+        };
+
+    Some(format!("{}{}{}", where_keyword, clause_sep, preds_str))
+}
+
+/// Rewrite `where` and comment around it.
+fn rewrite_where_keyword(
+    context: &RewriteContext<'_>,
+    where_clause: &ast::WhereClause,
+    shape: Shape,
+    span_end_before_where: BytePos,
+    where_clause_option: WhereClauseOption,
+) -> Option<(String, bool)> {
+    let block_shape = shape.block().with_max_width(context.config);
+    // 1 = `,`
+    let clause_shape = block_shape
+        .block_left(context.config.tab_spaces())?
+        .sub_width(1)?;
+
+    let comment_separator = |comment: &str, shape: Shape| {
+        if comment.is_empty() {
+            Cow::from("")
+        } else {
+            shape.indent.to_string_with_newline(context.config)
+        }
+    };
+
+    let (span_before, span_after) =
+        missing_span_before_after_where(span_end_before_where, where_clause);
+    let (comment_before, comment_after) =
+        rewrite_comments_before_after_where(context, span_before, span_after, shape)?;
+
+    let starting_newline = match where_clause_option.snuggle {
+        WhereClauseSpace::Space if comment_before.is_empty() => Cow::from(" "),
+        WhereClauseSpace::None => Cow::from(""),
+        _ => block_shape.indent.to_string_with_newline(context.config),
+    };
+
+    let newline_before_where = comment_separator(&comment_before, shape);
+    let newline_after_where = comment_separator(&comment_after, clause_shape);
+    let result = format!(
+        "{}{}{}where{}{}",
+        starting_newline, comment_before, newline_before_where, newline_after_where, comment_after
+    );
+    let allow_single_line = where_clause_option.allow_single_line
+        && comment_before.is_empty()
+        && comment_after.is_empty();
+
+    Some((result, allow_single_line))
+}
+
+/// Rewrite bounds on a where clause.
+fn rewrite_bounds_on_where_clause(
+    context: &RewriteContext<'_>,
+    where_clause: &ast::WhereClause,
+    shape: Shape,
+    terminator: &str,
+    span_end: Option<BytePos>,
+    where_clause_option: WhereClauseOption,
+    force_single_line: bool,
+) -> Option<String> {
+    let span_start = where_clause.predicates[0].span().lo();
+    // If we don't have the start of the next span, then use the end of the
+    // predicates, but that means we miss comments.
+    let len = where_clause.predicates.len();
+    let end_of_preds = where_clause.predicates[len - 1].span().hi();
+    let span_end = span_end.unwrap_or(end_of_preds);
+    let items = itemize_list(
+        context.snippet_provider,
+        where_clause.predicates.iter(),
+        terminator,
+        ",",
+        |pred| pred.span().lo(),
+        |pred| pred.span().hi(),
+        |pred| pred.rewrite(context, shape),
+        span_start,
+        span_end,
+        false,
+    );
+    let comma_tactic = if where_clause_option.suppress_comma || force_single_line {
+        SeparatorTactic::Never
+    } else {
+        context.config.trailing_comma()
+    };
+
+    // shape should be vertical only and only if we have `force_single_line` option enabled
+    // and the number of items of the where-clause is equal to 1
+    let shape_tactic = if force_single_line {
+        DefinitiveListTactic::Horizontal
+    } else {
+        DefinitiveListTactic::Vertical
+    };
+
+    let fmt = ListFormatting::new(shape, context.config)
+        .tactic(shape_tactic)
+        .trailing_separator(comma_tactic)
+        .preserve_newline(true);
+    write_list(&items.collect::<Vec<_>>(), &fmt)
+}
+
+fn rewrite_where_clause(
+    context: &RewriteContext<'_>,
+    where_clause: &ast::WhereClause,
+    brace_style: BraceStyle,
+    shape: Shape,
+    on_new_line: bool,
+    terminator: &str,
+    span_end: Option<BytePos>,
+    span_end_before_where: BytePos,
+    where_clause_option: WhereClauseOption,
+) -> Option<String> {
+    if where_clause.predicates.is_empty() {
+        return Some(String::new());
+    }
+
+    if context.config.indent_style() == IndentStyle::Block {
+        return rewrite_where_clause_rfc_style(
+            context,
+            where_clause,
+            shape,
+            terminator,
+            span_end,
+            span_end_before_where,
+            where_clause_option,
+        );
+    }
+
+    let extra_indent = Indent::new(context.config.tab_spaces(), 0);
+
+    let offset = match context.config.indent_style() {
+        IndentStyle::Block => shape.indent + extra_indent.block_indent(context.config),
+        // 6 = "where ".len()
+        IndentStyle::Visual => shape.indent + extra_indent + 6,
+    };
+    // FIXME: if indent_style != Visual, then the budgets below might
+    // be out by a char or two.
+
+    let budget = context.config.max_width() - offset.width();
+    let span_start = where_clause.predicates[0].span().lo();
+    // If we don't have the start of the next span, then use the end of the
+    // predicates, but that means we miss comments.
+    let len = where_clause.predicates.len();
+    let end_of_preds = where_clause.predicates[len - 1].span().hi();
+    let span_end = span_end.unwrap_or(end_of_preds);
+    let items = itemize_list(
+        context.snippet_provider,
+        where_clause.predicates.iter(),
+        terminator,
+        ",",
+        |pred| pred.span().lo(),
+        |pred| pred.span().hi(),
+        |pred| pred.rewrite(context, Shape::legacy(budget, offset)),
+        span_start,
+        span_end,
+        false,
+    );
+    let item_vec = items.collect::<Vec<_>>();
+    // FIXME: we don't need to collect here
+    let tactic = definitive_tactic(&item_vec, ListTactic::Vertical, Separator::Comma, budget);
+
+    let mut comma_tactic = context.config.trailing_comma();
+    // Kind of a hack because we don't usually have trailing commas in where-clauses.
+    if comma_tactic == SeparatorTactic::Vertical || where_clause_option.suppress_comma {
+        comma_tactic = SeparatorTactic::Never;
+    }
+
+    let fmt = ListFormatting::new(Shape::legacy(budget, offset), context.config)
+        .tactic(tactic)
+        .trailing_separator(comma_tactic)
+        .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
+        .preserve_newline(true);
+    let preds_str = write_list(&item_vec, &fmt)?;
+
+    let end_length = if terminator == "{" {
+        // If the brace is on the next line we don't need to count it otherwise it needs two
+        // characters " {"
+        match brace_style {
+            BraceStyle::AlwaysNextLine | BraceStyle::SameLineWhere => 0,
+            BraceStyle::PreferSameLine => 2,
+        }
+    } else if terminator == "=" {
+        2
+    } else {
+        terminator.len()
+    };
+    if on_new_line
+        || preds_str.contains('\n')
+        || shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width
+    {
+        Some(format!(
+            "\n{}where {}",
+            (shape.indent + extra_indent).to_string(context.config),
+            preds_str
+        ))
+    } else {
+        Some(format!(" where {}", preds_str))
+    }
+}
+
+fn missing_span_before_after_where(
+    before_item_span_end: BytePos,
+    where_clause: &ast::WhereClause,
+) -> (Span, Span) {
+    let missing_span_before = mk_sp(before_item_span_end, where_clause.span.lo());
+    // 5 = `where`
+    let pos_after_where = where_clause.span.lo() + BytePos(5);
+    let missing_span_after = mk_sp(pos_after_where, where_clause.predicates[0].span().lo());
+    (missing_span_before, missing_span_after)
+}
+
+fn rewrite_comments_before_after_where(
+    context: &RewriteContext<'_>,
+    span_before_where: Span,
+    span_after_where: Span,
+    shape: Shape,
+) -> Option<(String, String)> {
+    let before_comment = rewrite_missing_comment(span_before_where, shape, context)?;
+    let after_comment = rewrite_missing_comment(
+        span_after_where,
+        shape.block_indent(context.config.tab_spaces()),
+        context,
+    )?;
+    Some((before_comment, after_comment))
+}
+
+fn format_header(
+    context: &RewriteContext<'_>,
+    item_name: &str,
+    ident: symbol::Ident,
+    vis: &ast::Visibility,
+    offset: Indent,
+) -> String {
+    let mut result = String::with_capacity(128);
+    let shape = Shape::indented(offset, context.config);
+
+    result.push_str(&format_visibility(context, vis).trim());
+
+    // Check for a missing comment between the visibility and the item name.
+    let after_vis = vis.span.hi();
+    if let Some(before_item_name) = context
+        .snippet_provider
+        .opt_span_before(mk_sp(vis.span.lo(), ident.span.hi()), item_name.trim())
+    {
+        let missing_span = mk_sp(after_vis, before_item_name);
+        if let Some(result_with_comment) = combine_strs_with_missing_comments(
+            context,
+            &result,
+            item_name,
+            missing_span,
+            shape,
+            /* allow_extend */ true,
+        ) {
+            result = result_with_comment;
+        }
+    }
+
+    result.push_str(&rewrite_ident(context, ident));
+
+    result
+}
+
+#[derive(PartialEq, Eq, Clone, Copy)]
+enum BracePos {
+    None,
+    Auto,
+    ForceSameLine,
+}
+
+fn format_generics(
+    context: &RewriteContext<'_>,
+    generics: &ast::Generics,
+    brace_style: BraceStyle,
+    brace_pos: BracePos,
+    offset: Indent,
+    span: Span,
+    used_width: usize,
+) -> Option<String> {
+    let shape = Shape::legacy(context.budget(used_width + offset.width()), offset);
+    let mut result = rewrite_generics(context, "", generics, shape)?;
+
+    // If the generics are not parameterized then generics.span.hi() == 0,
+    // so we use span.lo(), which is the position after `struct Foo`.
+    let span_end_before_where = if !generics.params.is_empty() {
+        generics.span.hi()
+    } else {
+        span.lo()
+    };
+    let (same_line_brace, missed_comments) = if !generics.where_clause.predicates.is_empty() {
+        let budget = context.budget(last_line_used_width(&result, offset.width()));
+        let mut option = WhereClauseOption::snuggled(&result);
+        if brace_pos == BracePos::None {
+            option.suppress_comma = true;
+        }
+        let where_clause_str = rewrite_where_clause(
+            context,
+            &generics.where_clause,
+            brace_style,
+            Shape::legacy(budget, offset.block_only()),
+            true,
+            "{",
+            Some(span.hi()),
+            span_end_before_where,
+            option,
+        )?;
+        result.push_str(&where_clause_str);
+        (
+            brace_pos == BracePos::ForceSameLine || brace_style == BraceStyle::PreferSameLine,
+            // missed comments are taken care of in #rewrite_where_clause
+            None,
+        )
+    } else {
+        (
+            brace_pos == BracePos::ForceSameLine
+                || (result.contains('\n') && brace_style == BraceStyle::PreferSameLine
+                    || brace_style != BraceStyle::AlwaysNextLine)
+                || trimmed_last_line_width(&result) == 1,
+            rewrite_missing_comment(
+                mk_sp(
+                    span_end_before_where,
+                    if brace_pos == BracePos::None {
+                        span.hi()
+                    } else {
+                        context.snippet_provider.span_before(span, "{")
+                    },
+                ),
+                shape,
+                context,
+            ),
+        )
+    };
+    // add missing comments
+    let missed_line_comments = missed_comments
+        .filter(|missed_comments| !missed_comments.is_empty())
+        .map_or(false, |missed_comments| {
+            let is_block = is_last_comment_block(&missed_comments);
+            let sep = if is_block { " " } else { "\n" };
+            result.push_str(sep);
+            result.push_str(&missed_comments);
+            !is_block
+        });
+    if brace_pos == BracePos::None {
+        return Some(result);
+    }
+    let total_used_width = last_line_used_width(&result, used_width);
+    let remaining_budget = context.budget(total_used_width);
+    // If the same line brace if forced, it indicates that we are rewriting an item with empty body,
+    // and hence we take the closer into account as well for one line budget.
+    // We assume that the closer has the same length as the opener.
+    let overhead = if brace_pos == BracePos::ForceSameLine {
+        // 3 = ` {}`
+        3
+    } else {
+        // 2 = ` {`
+        2
+    };
+    let forbid_same_line_brace = missed_line_comments || overhead > remaining_budget;
+    if !forbid_same_line_brace && same_line_brace {
+        result.push(' ');
+    } else {
+        result.push('\n');
+        result.push_str(&offset.block_only().to_string(context.config));
+    }
+    result.push('{');
+
+    Some(result)
+}
+
+impl Rewrite for ast::ForeignItem {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let attrs_str = self.attrs.rewrite(context, shape)?;
+        // Drop semicolon or it will be interpreted as comment.
+        // FIXME: this may be a faulty span from libsyntax.
+        let span = mk_sp(self.span.lo(), self.span.hi() - BytePos(1));
+
+        let item_str = match self.kind {
+            ast::ForeignItemKind::Fn(ref fn_kind) => {
+                let ast::FnKind(defaultness, ref fn_sig, ref generics, ref block) = **fn_kind;
+                if let Some(ref body) = block {
+                    let mut visitor = FmtVisitor::from_context(context);
+                    visitor.block_indent = shape.indent;
+                    visitor.last_pos = self.span.lo();
+                    let inner_attrs = inner_attributes(&self.attrs);
+                    let fn_ctxt = visit::FnCtxt::Foreign;
+                    visitor.visit_fn(
+                        visit::FnKind::Fn(fn_ctxt, self.ident, &fn_sig, &self.vis, Some(body)),
+                        generics,
+                        &fn_sig.decl,
+                        self.span,
+                        defaultness,
+                        Some(&inner_attrs),
+                    );
+                    Some(visitor.buffer.to_owned())
+                } else {
+                    rewrite_fn_base(
+                        context,
+                        shape.indent,
+                        self.ident,
+                        &FnSig::from_method_sig(&fn_sig, generics, self.vis.clone()),
+                        span,
+                        FnBraceStyle::None,
+                    )
+                    .map(|(s, _, _)| format!("{};", s))
+                }
+            }
+            ast::ForeignItemKind::Static(ref ty, mutability, _) => {
+                // FIXME(#21): we're dropping potential comments in between the
+                // function kw here.
+                let vis = format_visibility(context, &self.vis);
+                let mut_str = format_mutability(mutability);
+                let prefix = format!(
+                    "{}static {}{}:",
+                    vis,
+                    mut_str,
+                    rewrite_ident(context, self.ident)
+                );
+                // 1 = ;
+                rewrite_assign_rhs(context, prefix, &**ty, shape.sub_width(1)?).map(|s| s + ";")
+            }
+            ast::ForeignItemKind::TyAlias(ref ty_alias_kind) => {
+                let ast::TyAliasKind(_, ref generics, ref generic_bounds, ref type_default) =
+                    **ty_alias_kind;
+                rewrite_type_alias(
+                    self.ident,
+                    type_default.as_ref(),
+                    generics,
+                    Some(generic_bounds),
+                    &context,
+                    shape.indent,
+                    &self.vis,
+                    self.span,
+                )
+            }
+            ast::ForeignItemKind::MacCall(ref mac) => {
+                rewrite_macro(mac, None, context, shape, MacroPosition::Item)
+            }
+        }?;
+
+        let missing_span = if self.attrs.is_empty() {
+            mk_sp(self.span.lo(), self.span.lo())
+        } else {
+            mk_sp(self.attrs[self.attrs.len() - 1].span.hi(), self.span.lo())
+        };
+        combine_strs_with_missing_comments(
+            context,
+            &attrs_str,
+            &item_str,
+            missing_span,
+            shape,
+            false,
+        )
+    }
+}
+
+/// Rewrite the attributes of an item.
+fn rewrite_attrs(
+    context: &RewriteContext<'_>,
+    item: &ast::Item,
+    item_str: &str,
+    shape: Shape,
+) -> Option<String> {
+    let attrs = filter_inline_attrs(&item.attrs, item.span());
+    let attrs_str = attrs.rewrite(context, shape)?;
+
+    let missed_span = if attrs.is_empty() {
+        mk_sp(item.span.lo(), item.span.lo())
+    } else {
+        mk_sp(attrs[attrs.len() - 1].span.hi(), item.span.lo())
+    };
+
+    let allow_extend = if attrs.len() == 1 {
+        let line_len = attrs_str.len() + 1 + item_str.len();
+        !attrs.first().unwrap().is_doc_comment()
+            && context.config.inline_attribute_width() >= line_len
+    } else {
+        false
+    };
+
+    combine_strs_with_missing_comments(
+        context,
+        &attrs_str,
+        &item_str,
+        missed_span,
+        shape,
+        allow_extend,
+    )
+}
+
+/// Rewrite an inline mod.
+/// The given shape is used to format the mod's attributes.
+pub(crate) fn rewrite_mod(
+    context: &RewriteContext<'_>,
+    item: &ast::Item,
+    attrs_shape: Shape,
+) -> Option<String> {
+    let mut result = String::with_capacity(32);
+    result.push_str(&*format_visibility(context, &item.vis));
+    result.push_str("mod ");
+    result.push_str(rewrite_ident(context, item.ident));
+    result.push(';');
+    rewrite_attrs(context, item, &result, attrs_shape)
+}
+
+/// Rewrite `extern crate foo;`.
+/// The given shape is used to format the extern crate's attributes.
+pub(crate) fn rewrite_extern_crate(
+    context: &RewriteContext<'_>,
+    item: &ast::Item,
+    attrs_shape: Shape,
+) -> Option<String> {
+    assert!(is_extern_crate(item));
+    let new_str = context.snippet(item.span);
+    let item_str = if contains_comment(new_str) {
+        new_str.to_owned()
+    } else {
+        let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
+        String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
+    };
+    rewrite_attrs(context, item, &item_str, attrs_shape)
+}
+
+/// Returns `true` for `mod foo;`, false for `mod foo { .. }`.
+pub(crate) fn is_mod_decl(item: &ast::Item) -> bool {
+    match item.kind {
+        ast::ItemKind::Mod(_, ast::ModKind::Loaded(_, ast::Inline::Yes, _)) => false,
+        _ => true,
+    }
+}
+
+pub(crate) fn is_use_item(item: &ast::Item) -> bool {
+    match item.kind {
+        ast::ItemKind::Use(_) => true,
+        _ => false,
+    }
+}
+
+pub(crate) fn is_extern_crate(item: &ast::Item) -> bool {
+    match item.kind {
+        ast::ItemKind::ExternCrate(..) => true,
+        _ => false,
+    }
+}
diff --git a/src/tools/rustfmt/src/lib.rs b/src/tools/rustfmt/src/lib.rs
new file mode 100644
index 0000000000000..8a798777e0e80
--- /dev/null
+++ b/src/tools/rustfmt/src/lib.rs
@@ -0,0 +1,670 @@
+#![feature(rustc_private)]
+#![deny(rust_2018_idioms)]
+#![warn(unreachable_pub)]
+
+#[macro_use]
+extern crate derive_new;
+#[cfg(test)]
+#[macro_use]
+extern crate lazy_static;
+#[macro_use]
+extern crate log;
+
+// N.B. these crates are loaded from the sysroot, so they need extern crate.
+extern crate rustc_ast;
+extern crate rustc_ast_pretty;
+extern crate rustc_data_structures;
+extern crate rustc_errors;
+extern crate rustc_expand;
+extern crate rustc_parse;
+extern crate rustc_session;
+extern crate rustc_span;
+
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::fmt;
+use std::io::{self, Write};
+use std::mem;
+use std::panic;
+use std::path::PathBuf;
+use std::rc::Rc;
+
+use ignore;
+use rustc_ast::ast;
+use rustc_span::symbol;
+use thiserror::Error;
+
+use crate::comment::LineClasses;
+use crate::emitter::Emitter;
+use crate::formatting::{FormatErrorMap, FormattingError, ReportedErrors, SourceFile};
+use crate::issues::Issue;
+use crate::modules::ModuleResolutionError;
+use crate::shape::Indent;
+use crate::syntux::parser::DirectoryOwnership;
+use crate::utils::indent_next_line;
+
+pub use crate::config::{
+    load_config, CliOptions, Color, Config, Edition, EmitMode, FileLines, FileName, NewlineStyle,
+    Range, Verbosity,
+};
+
+pub use crate::format_report_formatter::{FormatReportFormatter, FormatReportFormatterBuilder};
+
+pub use crate::rustfmt_diff::{ModifiedChunk, ModifiedLines};
+
+#[macro_use]
+mod utils;
+
+mod attr;
+mod chains;
+mod closures;
+mod comment;
+pub(crate) mod config;
+mod coverage;
+mod emitter;
+mod expr;
+mod format_report_formatter;
+pub(crate) mod formatting;
+mod ignore_path;
+mod imports;
+mod issues;
+mod items;
+mod lists;
+mod macros;
+mod matches;
+mod missed_spans;
+pub(crate) mod modules;
+mod overflow;
+mod pairs;
+mod patterns;
+mod release_channel;
+mod reorder;
+mod rewrite;
+pub(crate) mod rustfmt_diff;
+mod shape;
+mod skip;
+pub(crate) mod source_file;
+pub(crate) mod source_map;
+mod spanned;
+mod stmt;
+mod string;
+mod syntux;
+#[cfg(test)]
+mod test;
+mod types;
+mod vertical;
+pub(crate) mod visitor;
+
+/// The various errors that can occur during formatting. Note that not all of
+/// these can currently be propagated to clients.
+#[derive(Error, Debug)]
+pub enum ErrorKind {
+    /// Line has exceeded character limit (found, maximum).
+    #[error(
+        "line formatted, but exceeded maximum width \
+         (maximum: {1} (see `max_width` option), found: {0})"
+    )]
+    LineOverflow(usize, usize),
+    /// Line ends in whitespace.
+    #[error("left behind trailing whitespace")]
+    TrailingWhitespace,
+    /// TODO or FIXME item without an issue number.
+    #[error("found {0}")]
+    BadIssue(Issue),
+    /// License check has failed.
+    #[error("license check failed")]
+    LicenseCheck,
+    /// Used deprecated skip attribute.
+    #[error("`rustfmt_skip` is deprecated; use `rustfmt::skip`")]
+    DeprecatedAttr,
+    /// Used a rustfmt:: attribute other than skip or skip::macros.
+    #[error("invalid attribute")]
+    BadAttr,
+    /// An io error during reading or writing.
+    #[error("io error: {0}")]
+    IoError(io::Error),
+    /// Error during module resolution.
+    #[error("{0}")]
+    ModuleResolutionError(#[from] ModuleResolutionError),
+    /// Parse error occurred when parsing the input.
+    #[error("parse error")]
+    ParseError,
+    /// The user mandated a version and the current version of Rustfmt does not
+    /// satisfy that requirement.
+    #[error("version mismatch")]
+    VersionMismatch,
+    /// If we had formatted the given node, then we would have lost a comment.
+    #[error("not formatted because a comment would be lost")]
+    LostComment,
+    /// Invalid glob pattern in `ignore` configuration option.
+    #[error("Invalid glob pattern found in ignore list: {0}")]
+    InvalidGlobPattern(ignore::Error),
+}
+
+impl ErrorKind {
+    fn is_comment(&self) -> bool {
+        match self {
+            ErrorKind::LostComment => true,
+            _ => false,
+        }
+    }
+}
+
+impl From<io::Error> for ErrorKind {
+    fn from(e: io::Error) -> ErrorKind {
+        ErrorKind::IoError(e)
+    }
+}
+
+/// Result of formatting a snippet of code along with ranges of lines that didn't get formatted,
+/// i.e., that got returned as they were originally.
+#[derive(Debug)]
+struct FormattedSnippet {
+    snippet: String,
+    non_formatted_ranges: Vec<(usize, usize)>,
+}
+
+impl FormattedSnippet {
+    /// In case the snippet needed to be wrapped in a function, this shifts down the ranges of
+    /// non-formatted code.
+    fn unwrap_code_block(&mut self) {
+        self.non_formatted_ranges
+            .iter_mut()
+            .for_each(|(low, high)| {
+                *low -= 1;
+                *high -= 1;
+            });
+    }
+
+    /// Returns `true` if the line n did not get formatted.
+    fn is_line_non_formatted(&self, n: usize) -> bool {
+        self.non_formatted_ranges
+            .iter()
+            .any(|(low, high)| *low <= n && n <= *high)
+    }
+}
+
+/// Reports on any issues that occurred during a run of Rustfmt.
+///
+/// Can be reported to the user using the `Display` impl on [`FormatReportFormatter`].
+#[derive(Clone)]
+pub struct FormatReport {
+    // Maps stringified file paths to their associated formatting errors.
+    internal: Rc<RefCell<(FormatErrorMap, ReportedErrors)>>,
+    non_formatted_ranges: Vec<(usize, usize)>,
+}
+
+impl FormatReport {
+    fn new() -> FormatReport {
+        FormatReport {
+            internal: Rc::new(RefCell::new((HashMap::new(), ReportedErrors::default()))),
+            non_formatted_ranges: Vec::new(),
+        }
+    }
+
+    fn add_non_formatted_ranges(&mut self, mut ranges: Vec<(usize, usize)>) {
+        self.non_formatted_ranges.append(&mut ranges);
+    }
+
+    fn append(&self, f: FileName, mut v: Vec<FormattingError>) {
+        self.track_errors(&v);
+        self.internal
+            .borrow_mut()
+            .0
+            .entry(f)
+            .and_modify(|fe| fe.append(&mut v))
+            .or_insert(v);
+    }
+
+    fn track_errors(&self, new_errors: &[FormattingError]) {
+        let errs = &mut self.internal.borrow_mut().1;
+        if !new_errors.is_empty() {
+            errs.has_formatting_errors = true;
+        }
+        if errs.has_operational_errors && errs.has_check_errors && errs.has_unformatted_code_errors
+        {
+            return;
+        }
+        for err in new_errors {
+            match err.kind {
+                ErrorKind::LineOverflow(..) => {
+                    errs.has_operational_errors = true;
+                }
+                ErrorKind::TrailingWhitespace => {
+                    errs.has_operational_errors = true;
+                    errs.has_unformatted_code_errors = true;
+                }
+                ErrorKind::LostComment => {
+                    errs.has_unformatted_code_errors = true;
+                }
+                ErrorKind::BadIssue(_)
+                | ErrorKind::LicenseCheck
+                | ErrorKind::DeprecatedAttr
+                | ErrorKind::BadAttr
+                | ErrorKind::VersionMismatch => {
+                    errs.has_check_errors = true;
+                }
+                _ => {}
+            }
+        }
+    }
+
+    fn add_diff(&mut self) {
+        self.internal.borrow_mut().1.has_diff = true;
+    }
+
+    fn add_macro_format_failure(&mut self) {
+        self.internal.borrow_mut().1.has_macro_format_failure = true;
+    }
+
+    fn add_parsing_error(&mut self) {
+        self.internal.borrow_mut().1.has_parsing_errors = true;
+    }
+
+    fn warning_count(&self) -> usize {
+        self.internal
+            .borrow()
+            .0
+            .iter()
+            .map(|(_, errors)| errors.len())
+            .sum()
+    }
+
+    /// Whether any warnings or errors are present in the report.
+    pub fn has_warnings(&self) -> bool {
+        self.internal.borrow().1.has_formatting_errors
+    }
+
+    /// Print the report to a terminal using colours and potentially other
+    /// fancy output.
+    #[deprecated(note = "Use FormatReportFormatter with colors enabled instead")]
+    pub fn fancy_print(
+        &self,
+        mut t: Box<dyn term::Terminal<Output = io::Stderr>>,
+    ) -> Result<(), term::Error> {
+        writeln!(
+            t,
+            "{}",
+            FormatReportFormatterBuilder::new(&self)
+                .enable_colors(true)
+                .build()
+        )?;
+        Ok(())
+    }
+}
+
+/// Deprecated - Use FormatReportFormatter instead
+// https://github.com/rust-lang/rust/issues/78625
+// https://github.com/rust-lang/rust/issues/39935
+impl fmt::Display for FormatReport {
+    // Prints all the formatting errors.
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        write!(fmt, "{}", FormatReportFormatterBuilder::new(&self).build())?;
+        Ok(())
+    }
+}
+
+/// Format the given snippet. The snippet is expected to be *complete* code.
+/// When we cannot parse the given snippet, this function returns `None`.
+fn format_snippet(snippet: &str, config: &Config, is_macro_def: bool) -> Option<FormattedSnippet> {
+    let mut config = config.clone();
+    panic::catch_unwind(|| {
+        let mut out: Vec<u8> = Vec::with_capacity(snippet.len() * 2);
+        config.set().emit_mode(config::EmitMode::Stdout);
+        config.set().verbose(Verbosity::Quiet);
+        config.set().hide_parse_errors(true);
+        if is_macro_def {
+            config.set().error_on_unformatted(true);
+        }
+
+        let (formatting_error, result) = {
+            let input = Input::Text(snippet.into());
+            let mut session = Session::new(config, Some(&mut out));
+            let result = session.format_input_inner(input, is_macro_def);
+            (
+                session.errors.has_macro_format_failure
+                    || session.out.as_ref().unwrap().is_empty() && !snippet.is_empty()
+                    || result.is_err()
+                    || (is_macro_def && session.has_unformatted_code_errors()),
+                result,
+            )
+        };
+        if formatting_error {
+            None
+        } else {
+            String::from_utf8(out).ok().map(|snippet| FormattedSnippet {
+                snippet,
+                non_formatted_ranges: result.unwrap().non_formatted_ranges,
+            })
+        }
+    })
+    // Discard panics encountered while formatting the snippet
+    // The ? operator is needed to remove the extra Option
+    .ok()?
+}
+
+/// Format the given code block. Mainly targeted for code block in comment.
+/// The code block may be incomplete (i.e., parser may be unable to parse it).
+/// To avoid panic in parser, we wrap the code block with a dummy function.
+/// The returned code block does **not** end with newline.
+fn format_code_block(
+    code_snippet: &str,
+    config: &Config,
+    is_macro_def: bool,
+) -> Option<FormattedSnippet> {
+    const FN_MAIN_PREFIX: &str = "fn main() {\n";
+
+    fn enclose_in_main_block(s: &str, config: &Config) -> String {
+        let indent = Indent::from_width(config, config.tab_spaces());
+        let mut result = String::with_capacity(s.len() * 2);
+        result.push_str(FN_MAIN_PREFIX);
+        let mut need_indent = true;
+        for (kind, line) in LineClasses::new(s) {
+            if need_indent {
+                result.push_str(&indent.to_string(config));
+            }
+            result.push_str(&line);
+            result.push('\n');
+            need_indent = indent_next_line(kind, &line, config);
+        }
+        result.push('}');
+        result
+    }
+
+    // Wrap the given code block with `fn main()` if it does not have one.
+    let snippet = enclose_in_main_block(code_snippet, config);
+    let mut result = String::with_capacity(snippet.len());
+    let mut is_first = true;
+
+    // While formatting the code, ignore the config's newline style setting and always use "\n"
+    // instead of "\r\n" for the newline characters. This is ok because the output here is
+    // not directly outputted by rustfmt command, but used by the comment formatter's input.
+    // We have output-file-wide "\n" ==> "\r\n" conversion process after here if it's necessary.
+    let mut config_with_unix_newline = config.clone();
+    config_with_unix_newline
+        .set()
+        .newline_style(NewlineStyle::Unix);
+    let mut formatted = format_snippet(&snippet, &config_with_unix_newline, is_macro_def)?;
+    // Remove wrapping main block
+    formatted.unwrap_code_block();
+
+    // Trim "fn main() {" on the first line and "}" on the last line,
+    // then unindent the whole code block.
+    let block_len = formatted
+        .snippet
+        .rfind('}')
+        .unwrap_or_else(|| formatted.snippet.len());
+    let mut is_indented = true;
+    let indent_str = Indent::from_width(config, config.tab_spaces()).to_string(config);
+    for (kind, ref line) in LineClasses::new(&formatted.snippet[FN_MAIN_PREFIX.len()..block_len]) {
+        if !is_first {
+            result.push('\n');
+        } else {
+            is_first = false;
+        }
+        let trimmed_line = if !is_indented {
+            line
+        } else if line.len() > config.max_width() {
+            // If there are lines that are larger than max width, we cannot tell
+            // whether we have succeeded but have some comments or strings that
+            // are too long, or we have failed to format code block. We will be
+            // conservative and just return `None` in this case.
+            return None;
+        } else if line.len() > indent_str.len() {
+            // Make sure that the line has leading whitespaces.
+            if line.starts_with(indent_str.as_ref()) {
+                let offset = if config.hard_tabs() {
+                    1
+                } else {
+                    config.tab_spaces()
+                };
+                &line[offset..]
+            } else {
+                line
+            }
+        } else {
+            line
+        };
+        result.push_str(trimmed_line);
+        is_indented = indent_next_line(kind, line, config);
+    }
+    Some(FormattedSnippet {
+        snippet: result,
+        non_formatted_ranges: formatted.non_formatted_ranges,
+    })
+}
+
+/// A session is a run of rustfmt across a single or multiple inputs.
+pub struct Session<'b, T: Write> {
+    pub config: Config,
+    pub out: Option<&'b mut T>,
+    pub(crate) errors: ReportedErrors,
+    source_file: SourceFile,
+    emitter: Box<dyn Emitter + 'b>,
+}
+
+impl<'b, T: Write + 'b> Session<'b, T> {
+    pub fn new(config: Config, mut out: Option<&'b mut T>) -> Session<'b, T> {
+        let emitter = create_emitter(&config);
+
+        if let Some(ref mut out) = out {
+            let _ = emitter.emit_header(out);
+        }
+
+        Session {
+            config,
+            out,
+            emitter,
+            errors: ReportedErrors::default(),
+            source_file: SourceFile::new(),
+        }
+    }
+
+    /// The main entry point for Rustfmt. Formats the given input according to the
+    /// given config. `out` is only necessary if required by the configuration.
+    pub fn format(&mut self, input: Input) -> Result<FormatReport, ErrorKind> {
+        self.format_input_inner(input, false)
+    }
+
+    pub fn override_config<F, U>(&mut self, mut config: Config, f: F) -> U
+    where
+        F: FnOnce(&mut Session<'b, T>) -> U,
+    {
+        mem::swap(&mut config, &mut self.config);
+        let result = f(self);
+        mem::swap(&mut config, &mut self.config);
+        result
+    }
+
+    pub fn add_operational_error(&mut self) {
+        self.errors.has_operational_errors = true;
+    }
+
+    pub fn has_operational_errors(&self) -> bool {
+        self.errors.has_operational_errors
+    }
+
+    pub fn has_parsing_errors(&self) -> bool {
+        self.errors.has_parsing_errors
+    }
+
+    pub fn has_formatting_errors(&self) -> bool {
+        self.errors.has_formatting_errors
+    }
+
+    pub fn has_check_errors(&self) -> bool {
+        self.errors.has_check_errors
+    }
+
+    pub fn has_diff(&self) -> bool {
+        self.errors.has_diff
+    }
+
+    pub fn has_unformatted_code_errors(&self) -> bool {
+        self.errors.has_unformatted_code_errors
+    }
+
+    pub fn has_no_errors(&self) -> bool {
+        !(self.has_operational_errors()
+            || self.has_parsing_errors()
+            || self.has_formatting_errors()
+            || self.has_check_errors()
+            || self.has_diff()
+            || self.has_unformatted_code_errors()
+            || self.errors.has_macro_format_failure)
+    }
+}
+
+pub(crate) fn create_emitter<'a>(config: &Config) -> Box<dyn Emitter + 'a> {
+    match config.emit_mode() {
+        EmitMode::Files if config.make_backup() => {
+            Box::new(emitter::FilesWithBackupEmitter::default())
+        }
+        EmitMode::Files => Box::new(emitter::FilesEmitter::new(
+            config.print_misformatted_file_names(),
+        )),
+        EmitMode::Stdout | EmitMode::Coverage => {
+            Box::new(emitter::StdoutEmitter::new(config.verbose()))
+        }
+        EmitMode::Json => Box::new(emitter::JsonEmitter::default()),
+        EmitMode::ModifiedLines => Box::new(emitter::ModifiedLinesEmitter::default()),
+        EmitMode::Checkstyle => Box::new(emitter::CheckstyleEmitter::default()),
+        EmitMode::Diff => Box::new(emitter::DiffEmitter::new(config.clone())),
+    }
+}
+
+impl<'b, T: Write + 'b> Drop for Session<'b, T> {
+    fn drop(&mut self) {
+        if let Some(ref mut out) = self.out {
+            let _ = self.emitter.emit_footer(out);
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum Input {
+    File(PathBuf),
+    Text(String),
+}
+
+impl Input {
+    fn file_name(&self) -> FileName {
+        match *self {
+            Input::File(ref file) => FileName::Real(file.clone()),
+            Input::Text(..) => FileName::Stdin,
+        }
+    }
+
+    fn to_directory_ownership(&self) -> Option<DirectoryOwnership> {
+        match self {
+            Input::File(ref file) => {
+                // If there exists a directory with the same name as an input,
+                // then the input should be parsed as a sub module.
+                let file_stem = file.file_stem()?;
+                if file.parent()?.to_path_buf().join(file_stem).is_dir() {
+                    Some(DirectoryOwnership::Owned {
+                        relative: file_stem.to_str().map(symbol::Ident::from_str),
+                    })
+                } else {
+                    None
+                }
+            }
+            _ => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod unit_tests {
+    use super::*;
+
+    #[test]
+    fn test_no_panic_on_format_snippet_and_format_code_block() {
+        // `format_snippet()` and `format_code_block()` should not panic
+        // even when we cannot parse the given snippet.
+        let snippet = "let";
+        assert!(format_snippet(snippet, &Config::default(), false).is_none());
+        assert!(format_code_block(snippet, &Config::default(), false).is_none());
+    }
+
+    fn test_format_inner<F>(formatter: F, input: &str, expected: &str) -> bool
+    where
+        F: Fn(&str, &Config, bool) -> Option<FormattedSnippet>,
+    {
+        let output = formatter(input, &Config::default(), false);
+        output.is_some() && output.unwrap().snippet == expected
+    }
+
+    #[test]
+    fn test_format_snippet() {
+        let snippet = "fn main() { println!(\"hello, world\"); }";
+        #[cfg(not(windows))]
+        let expected = "fn main() {\n    \
+                        println!(\"hello, world\");\n\
+                        }\n";
+        #[cfg(windows)]
+        let expected = "fn main() {\r\n    \
+                        println!(\"hello, world\");\r\n\
+                        }\r\n";
+        assert!(test_format_inner(format_snippet, snippet, expected));
+    }
+
+    #[test]
+    fn test_format_code_block_fail() {
+        #[rustfmt::skip]
+        let code_block = "this_line_is_100_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(x, y, z);";
+        assert!(format_code_block(code_block, &Config::default(), false).is_none());
+    }
+
+    #[test]
+    fn test_format_code_block() {
+        // simple code block
+        let code_block = "let x=3;";
+        let expected = "let x = 3;";
+        assert!(test_format_inner(format_code_block, code_block, expected));
+
+        // more complex code block, taken from chains.rs.
+        let code_block =
+"let (nested_shape, extend) = if !parent_rewrite_contains_newline && is_continuable(&parent) {
+(
+chain_indent(context, shape.add_offset(parent_rewrite.len())),
+context.config.indent_style() == IndentStyle::Visual || is_small_parent,
+)
+} else if is_block_expr(context, &parent, &parent_rewrite) {
+match context.config.indent_style() {
+// Try to put the first child on the same line with parent's last line
+IndentStyle::Block => (parent_shape.block_indent(context.config.tab_spaces()), true),
+// The parent is a block, so align the rest of the chain with the closing
+// brace.
+IndentStyle::Visual => (parent_shape, false),
+}
+} else {
+(
+chain_indent(context, shape.add_offset(parent_rewrite.len())),
+false,
+)
+};
+";
+        let expected =
+"let (nested_shape, extend) = if !parent_rewrite_contains_newline && is_continuable(&parent) {
+    (
+        chain_indent(context, shape.add_offset(parent_rewrite.len())),
+        context.config.indent_style() == IndentStyle::Visual || is_small_parent,
+    )
+} else if is_block_expr(context, &parent, &parent_rewrite) {
+    match context.config.indent_style() {
+        // Try to put the first child on the same line with parent's last line
+        IndentStyle::Block => (parent_shape.block_indent(context.config.tab_spaces()), true),
+        // The parent is a block, so align the rest of the chain with the closing
+        // brace.
+        IndentStyle::Visual => (parent_shape, false),
+    }
+} else {
+    (
+        chain_indent(context, shape.add_offset(parent_rewrite.len())),
+        false,
+    )
+};";
+        assert!(test_format_inner(format_code_block, code_block, expected));
+    }
+}
diff --git a/src/tools/rustfmt/src/lists.rs b/src/tools/rustfmt/src/lists.rs
new file mode 100644
index 0000000000000..ccf8f784c0454
--- /dev/null
+++ b/src/tools/rustfmt/src/lists.rs
@@ -0,0 +1,930 @@
+//! Format list-like expressions and items.
+
+use std::cmp;
+use std::iter::Peekable;
+
+use rustc_span::BytePos;
+
+use crate::comment::{find_comment_end, rewrite_comment, FindUncommented};
+use crate::config::lists::*;
+use crate::config::{Config, IndentStyle};
+use crate::rewrite::RewriteContext;
+use crate::shape::{Indent, Shape};
+use crate::utils::{
+    count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline,
+    unicode_str_width,
+};
+use crate::visitor::SnippetProvider;
+
+pub(crate) struct ListFormatting<'a> {
+    tactic: DefinitiveListTactic,
+    separator: &'a str,
+    trailing_separator: SeparatorTactic,
+    separator_place: SeparatorPlace,
+    shape: Shape,
+    // Non-expressions, e.g., items, will have a new line at the end of the list.
+    // Important for comment styles.
+    ends_with_newline: bool,
+    // Remove newlines between list elements for expressions.
+    preserve_newline: bool,
+    // Nested import lists get some special handling for the "Mixed" list type
+    nested: bool,
+    // Whether comments should be visually aligned.
+    align_comments: bool,
+    config: &'a Config,
+}
+
+impl<'a> ListFormatting<'a> {
+    pub(crate) fn new(shape: Shape, config: &'a Config) -> Self {
+        ListFormatting {
+            tactic: DefinitiveListTactic::Vertical,
+            separator: ",",
+            trailing_separator: SeparatorTactic::Never,
+            separator_place: SeparatorPlace::Back,
+            shape,
+            ends_with_newline: true,
+            preserve_newline: false,
+            nested: false,
+            align_comments: true,
+            config,
+        }
+    }
+
+    pub(crate) fn tactic(mut self, tactic: DefinitiveListTactic) -> Self {
+        self.tactic = tactic;
+        self
+    }
+
+    pub(crate) fn separator(mut self, separator: &'a str) -> Self {
+        self.separator = separator;
+        self
+    }
+
+    pub(crate) fn trailing_separator(mut self, trailing_separator: SeparatorTactic) -> Self {
+        self.trailing_separator = trailing_separator;
+        self
+    }
+
+    pub(crate) fn separator_place(mut self, separator_place: SeparatorPlace) -> Self {
+        self.separator_place = separator_place;
+        self
+    }
+
+    pub(crate) fn ends_with_newline(mut self, ends_with_newline: bool) -> Self {
+        self.ends_with_newline = ends_with_newline;
+        self
+    }
+
+    pub(crate) fn preserve_newline(mut self, preserve_newline: bool) -> Self {
+        self.preserve_newline = preserve_newline;
+        self
+    }
+
+    pub(crate) fn nested(mut self, nested: bool) -> Self {
+        self.nested = nested;
+        self
+    }
+
+    pub(crate) fn align_comments(mut self, align_comments: bool) -> Self {
+        self.align_comments = align_comments;
+        self
+    }
+
+    pub(crate) fn needs_trailing_separator(&self) -> bool {
+        match self.trailing_separator {
+            // We always put separator in front.
+            SeparatorTactic::Always => true,
+            SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
+            SeparatorTactic::Never => {
+                self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
+            }
+        }
+    }
+}
+
+impl AsRef<ListItem> for ListItem {
+    fn as_ref(&self) -> &ListItem {
+        self
+    }
+}
+
+#[derive(PartialEq, Eq, Debug, Copy, Clone)]
+pub(crate) enum ListItemCommentStyle {
+    // Try to keep the comment on the same line with the item.
+    SameLine,
+    // Put the comment on the previous or the next line of the item.
+    DifferentLine,
+    // No comment available.
+    None,
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct ListItem {
+    // None for comments mean that they are not present.
+    pub(crate) pre_comment: Option<String>,
+    pub(crate) pre_comment_style: ListItemCommentStyle,
+    // Item should include attributes and doc comments. None indicates a failed
+    // rewrite.
+    pub(crate) item: Option<String>,
+    pub(crate) post_comment: Option<String>,
+    // Whether there is extra whitespace before this item.
+    pub(crate) new_lines: bool,
+}
+
+impl ListItem {
+    pub(crate) fn empty() -> ListItem {
+        ListItem {
+            pre_comment: None,
+            pre_comment_style: ListItemCommentStyle::None,
+            item: None,
+            post_comment: None,
+            new_lines: false,
+        }
+    }
+
+    pub(crate) fn inner_as_ref(&self) -> &str {
+        self.item.as_ref().map_or("", |s| s)
+    }
+
+    pub(crate) fn is_different_group(&self) -> bool {
+        self.inner_as_ref().contains('\n')
+            || self.pre_comment.is_some()
+            || self
+                .post_comment
+                .as_ref()
+                .map_or(false, |s| s.contains('\n'))
+    }
+
+    pub(crate) fn is_multiline(&self) -> bool {
+        self.inner_as_ref().contains('\n')
+            || self
+                .pre_comment
+                .as_ref()
+                .map_or(false, |s| s.contains('\n'))
+            || self
+                .post_comment
+                .as_ref()
+                .map_or(false, |s| s.contains('\n'))
+    }
+
+    pub(crate) fn has_single_line_comment(&self) -> bool {
+        self.pre_comment
+            .as_ref()
+            .map_or(false, |comment| comment.trim_start().starts_with("//"))
+            || self
+                .post_comment
+                .as_ref()
+                .map_or(false, |comment| comment.trim_start().starts_with("//"))
+    }
+
+    pub(crate) fn has_comment(&self) -> bool {
+        self.pre_comment.is_some() || self.post_comment.is_some()
+    }
+
+    pub(crate) fn from_str<S: Into<String>>(s: S) -> ListItem {
+        ListItem {
+            pre_comment: None,
+            pre_comment_style: ListItemCommentStyle::None,
+            item: Some(s.into()),
+            post_comment: None,
+            new_lines: false,
+        }
+    }
+
+    // Returns `true` if the item causes something to be written.
+    fn is_substantial(&self) -> bool {
+        fn empty(s: &Option<String>) -> bool {
+            match *s {
+                Some(ref s) if !s.is_empty() => false,
+                _ => true,
+            }
+        }
+
+        !(empty(&self.pre_comment) && empty(&self.item) && empty(&self.post_comment))
+    }
+}
+
+/// The type of separator for lists.
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub(crate) enum Separator {
+    Comma,
+    VerticalBar,
+}
+
+impl Separator {
+    pub(crate) fn len(self) -> usize {
+        match self {
+            // 2 = `, `
+            Separator::Comma => 2,
+            // 3 = ` | `
+            Separator::VerticalBar => 3,
+        }
+    }
+}
+
+pub(crate) fn definitive_tactic<I, T>(
+    items: I,
+    tactic: ListTactic,
+    sep: Separator,
+    width: usize,
+) -> DefinitiveListTactic
+where
+    I: IntoIterator<Item = T> + Clone,
+    T: AsRef<ListItem>,
+{
+    let pre_line_comments = items
+        .clone()
+        .into_iter()
+        .any(|item| item.as_ref().has_single_line_comment());
+
+    let limit = match tactic {
+        _ if pre_line_comments => return DefinitiveListTactic::Vertical,
+        ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
+        ListTactic::Vertical => return DefinitiveListTactic::Vertical,
+        ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
+        ListTactic::Mixed | ListTactic::HorizontalVertical => width,
+    };
+
+    let (sep_count, total_width) = calculate_width(items.clone());
+    let total_sep_len = sep.len() * sep_count.saturating_sub(1);
+    let real_total = total_width + total_sep_len;
+
+    if real_total <= limit && !items.into_iter().any(|item| item.as_ref().is_multiline()) {
+        DefinitiveListTactic::Horizontal
+    } else {
+        match tactic {
+            ListTactic::Mixed => DefinitiveListTactic::Mixed,
+            _ => DefinitiveListTactic::Vertical,
+        }
+    }
+}
+
+// Format a list of commented items into a string.
+pub(crate) fn write_list<I, T>(items: I, formatting: &ListFormatting<'_>) -> Option<String>
+where
+    I: IntoIterator<Item = T> + Clone,
+    T: AsRef<ListItem>,
+{
+    let tactic = formatting.tactic;
+    let sep_len = formatting.separator.len();
+
+    // Now that we know how we will layout, we can decide for sure if there
+    // will be a trailing separator.
+    let mut trailing_separator = formatting.needs_trailing_separator();
+    let mut result = String::with_capacity(128);
+    let cloned_items = items.clone();
+    let mut iter = items.into_iter().enumerate().peekable();
+    let mut item_max_width: Option<usize> = None;
+    let sep_place =
+        SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
+    let mut prev_item_had_post_comment = false;
+    let mut prev_item_is_nested_import = false;
+
+    let mut line_len = 0;
+    let indent_str = &formatting.shape.indent.to_string(formatting.config);
+    while let Some((i, item)) = iter.next() {
+        let item = item.as_ref();
+        let inner_item = item.item.as_ref()?;
+        let first = i == 0;
+        let last = iter.peek().is_none();
+        let mut separate = match sep_place {
+            SeparatorPlace::Front => !first,
+            SeparatorPlace::Back => !last || trailing_separator,
+        };
+        let item_sep_len = if separate { sep_len } else { 0 };
+
+        // Item string may be multi-line. Its length (used for block comment alignment)
+        // should be only the length of the last line.
+        let item_last_line = if item.is_multiline() {
+            inner_item.lines().last().unwrap_or("")
+        } else {
+            inner_item.as_ref()
+        };
+        let mut item_last_line_width = item_last_line.len() + item_sep_len;
+        if item_last_line.starts_with(&**indent_str) {
+            item_last_line_width -= indent_str.len();
+        }
+
+        if !item.is_substantial() {
+            continue;
+        }
+
+        match tactic {
+            DefinitiveListTactic::Horizontal if !first => {
+                result.push(' ');
+            }
+            DefinitiveListTactic::SpecialMacro(num_args_before) => {
+                if i == 0 {
+                    // Nothing
+                } else if i < num_args_before {
+                    result.push(' ');
+                } else if i <= num_args_before + 1 {
+                    result.push('\n');
+                    result.push_str(indent_str);
+                } else {
+                    result.push(' ');
+                }
+            }
+            DefinitiveListTactic::Vertical
+                if !first && !inner_item.is_empty() && !result.is_empty() =>
+            {
+                result.push('\n');
+                result.push_str(indent_str);
+            }
+            DefinitiveListTactic::Mixed => {
+                let total_width = total_item_width(item) + item_sep_len;
+
+                // 1 is space between separator and item.
+                if (line_len > 0 && line_len + 1 + total_width > formatting.shape.width)
+                    || prev_item_had_post_comment
+                    || (formatting.nested
+                        && (prev_item_is_nested_import || (!first && inner_item.contains("::"))))
+                {
+                    result.push('\n');
+                    result.push_str(indent_str);
+                    line_len = 0;
+                    if formatting.ends_with_newline {
+                        trailing_separator = true;
+                    }
+                } else if line_len > 0 {
+                    result.push(' ');
+                    line_len += 1;
+                }
+
+                if last && formatting.ends_with_newline {
+                    separate = formatting.trailing_separator != SeparatorTactic::Never;
+                }
+
+                line_len += total_width;
+            }
+            _ => {}
+        }
+
+        // Pre-comments
+        if let Some(ref comment) = item.pre_comment {
+            // Block style in non-vertical mode.
+            let block_mode = tactic == DefinitiveListTactic::Horizontal;
+            // Width restriction is only relevant in vertical mode.
+            let comment =
+                rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
+            result.push_str(&comment);
+
+            if !inner_item.is_empty() {
+                if tactic == DefinitiveListTactic::Vertical || tactic == DefinitiveListTactic::Mixed
+                {
+                    // We cannot keep pre-comments on the same line if the comment if normalized.
+                    let keep_comment = if formatting.config.normalize_comments()
+                        || item.pre_comment_style == ListItemCommentStyle::DifferentLine
+                    {
+                        false
+                    } else {
+                        // We will try to keep the comment on the same line with the item here.
+                        // 1 = ` `
+                        let total_width = total_item_width(item) + item_sep_len + 1;
+                        total_width <= formatting.shape.width
+                    };
+                    if keep_comment {
+                        result.push(' ');
+                    } else {
+                        result.push('\n');
+                        result.push_str(indent_str);
+                        // This is the width of the item (without comments).
+                        line_len = item.item.as_ref().map_or(0, |s| unicode_str_width(&s));
+                    }
+                } else {
+                    result.push(' ');
+                }
+            }
+            item_max_width = None;
+        }
+
+        if separate && sep_place.is_front() && !first {
+            result.push_str(formatting.separator.trim());
+            result.push(' ');
+        }
+        result.push_str(inner_item);
+
+        // Post-comments
+        if tactic == DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
+            let comment = item.post_comment.as_ref().unwrap();
+            let formatted_comment = rewrite_comment(
+                comment,
+                true,
+                Shape::legacy(formatting.shape.width, Indent::empty()),
+                formatting.config,
+            )?;
+
+            result.push(' ');
+            result.push_str(&formatted_comment);
+        }
+
+        if separate && sep_place.is_back() {
+            result.push_str(formatting.separator);
+        }
+
+        if tactic != DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
+            let comment = item.post_comment.as_ref().unwrap();
+            let overhead = last_line_width(&result) + first_line_width(comment.trim());
+
+            let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
+                if item_max_width.is_none() && !last && !inner_item.contains('\n') {
+                    *item_max_width = Some(max_width_of_item_with_post_comment(
+                        &cloned_items,
+                        i,
+                        overhead,
+                        formatting.config.max_width(),
+                    ));
+                }
+                let overhead = if starts_with_newline(comment) {
+                    0
+                } else if let Some(max_width) = *item_max_width {
+                    max_width + 2
+                } else {
+                    // 1 = space between item and comment.
+                    item_last_line_width + 1
+                };
+                let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
+                let offset = formatting.shape.indent + overhead;
+                let comment_shape = Shape::legacy(width, offset);
+
+                // Use block-style only for the last item or multiline comments.
+                let block_style = !formatting.ends_with_newline && last
+                    || comment.trim().contains('\n')
+                    || comment.trim().len() > width;
+
+                rewrite_comment(
+                    comment.trim_start(),
+                    block_style,
+                    comment_shape,
+                    formatting.config,
+                )
+            };
+
+            let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
+
+            if !starts_with_newline(comment) {
+                if formatting.align_comments {
+                    let mut comment_alignment =
+                        post_comment_alignment(item_max_width, inner_item.len());
+                    if first_line_width(&formatted_comment)
+                        + last_line_width(&result)
+                        + comment_alignment
+                        + 1
+                        > formatting.config.max_width()
+                    {
+                        item_max_width = None;
+                        formatted_comment = rewrite_post_comment(&mut item_max_width)?;
+                        comment_alignment =
+                            post_comment_alignment(item_max_width, inner_item.len());
+                    }
+                    for _ in 0..=comment_alignment {
+                        result.push(' ');
+                    }
+                }
+                // An additional space for the missing trailing separator (or
+                // if we skipped alignment above).
+                if !formatting.align_comments
+                    || (last
+                        && item_max_width.is_some()
+                        && !separate
+                        && !formatting.separator.is_empty())
+                {
+                    result.push(' ');
+                }
+            } else {
+                result.push('\n');
+                result.push_str(indent_str);
+            }
+            if formatted_comment.contains('\n') {
+                item_max_width = None;
+            }
+            result.push_str(&formatted_comment);
+        } else {
+            item_max_width = None;
+        }
+
+        if formatting.preserve_newline
+            && !last
+            && tactic == DefinitiveListTactic::Vertical
+            && item.new_lines
+        {
+            item_max_width = None;
+            result.push('\n');
+        }
+
+        prev_item_had_post_comment = item.post_comment.is_some();
+        prev_item_is_nested_import = inner_item.contains("::");
+    }
+
+    Some(result)
+}
+
+fn max_width_of_item_with_post_comment<I, T>(
+    items: &I,
+    i: usize,
+    overhead: usize,
+    max_budget: usize,
+) -> usize
+where
+    I: IntoIterator<Item = T> + Clone,
+    T: AsRef<ListItem>,
+{
+    let mut max_width = 0;
+    let mut first = true;
+    for item in items.clone().into_iter().skip(i) {
+        let item = item.as_ref();
+        let inner_item_width = item.inner_as_ref().len();
+        if !first
+            && (item.is_different_group()
+                || item.post_comment.is_none()
+                || inner_item_width + overhead > max_budget)
+        {
+            return max_width;
+        }
+        if max_width < inner_item_width {
+            max_width = inner_item_width;
+        }
+        if item.new_lines {
+            return max_width;
+        }
+        first = false;
+    }
+    max_width
+}
+
+fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
+    item_max_width.unwrap_or(0).saturating_sub(inner_item_len)
+}
+
+pub(crate) struct ListItems<'a, I, F1, F2, F3>
+where
+    I: Iterator,
+{
+    snippet_provider: &'a SnippetProvider,
+    inner: Peekable<I>,
+    get_lo: F1,
+    get_hi: F2,
+    get_item_string: F3,
+    prev_span_end: BytePos,
+    next_span_start: BytePos,
+    terminator: &'a str,
+    separator: &'a str,
+    leave_last: bool,
+}
+
+pub(crate) fn extract_pre_comment(pre_snippet: &str) -> (Option<String>, ListItemCommentStyle) {
+    let trimmed_pre_snippet = pre_snippet.trim();
+    // Both start and end are checked to support keeping a block comment inline with
+    // the item, even if there are preceeding line comments, while still supporting
+    // a snippet that starts with a block comment but also contains one or more
+    // trailing single line comments.
+    // https://github.com/rust-lang/rustfmt/issues/3025
+    // https://github.com/rust-lang/rustfmt/pull/3048
+    // https://github.com/rust-lang/rustfmt/issues/3839
+    let starts_with_block_comment = trimmed_pre_snippet.starts_with("/*");
+    let ends_with_block_comment = trimmed_pre_snippet.ends_with("*/");
+    let starts_with_single_line_comment = trimmed_pre_snippet.starts_with("//");
+    if ends_with_block_comment {
+        let comment_end = pre_snippet.rfind(|c| c == '/').unwrap();
+        if pre_snippet[comment_end..].contains('\n') {
+            (
+                Some(trimmed_pre_snippet.to_owned()),
+                ListItemCommentStyle::DifferentLine,
+            )
+        } else {
+            (
+                Some(trimmed_pre_snippet.to_owned()),
+                ListItemCommentStyle::SameLine,
+            )
+        }
+    } else if starts_with_single_line_comment || starts_with_block_comment {
+        (
+            Some(trimmed_pre_snippet.to_owned()),
+            ListItemCommentStyle::DifferentLine,
+        )
+    } else {
+        (None, ListItemCommentStyle::None)
+    }
+}
+
+pub(crate) fn extract_post_comment(
+    post_snippet: &str,
+    comment_end: usize,
+    separator: &str,
+) -> Option<String> {
+    let white_space: &[_] = &[' ', '\t'];
+
+    // Cleanup post-comment: strip separators and whitespace.
+    let post_snippet = post_snippet[..comment_end].trim();
+    let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
+        post_snippet[1..].trim_matches(white_space)
+    } else if post_snippet.starts_with(separator) {
+        post_snippet[separator.len()..].trim_matches(white_space)
+    }
+    // not comment or over two lines
+    else if post_snippet.ends_with(',')
+        && (!post_snippet.trim().starts_with("//") || post_snippet.trim().contains('\n'))
+    {
+        post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
+    } else {
+        post_snippet
+    };
+    // FIXME(#3441): post_snippet includes 'const' now
+    // it should not include here
+    let removed_newline_snippet = post_snippet_trimmed.trim();
+    if !post_snippet_trimmed.is_empty()
+        && (removed_newline_snippet.starts_with("//") || removed_newline_snippet.starts_with("/*"))
+    {
+        Some(post_snippet_trimmed.to_owned())
+    } else {
+        None
+    }
+}
+
+pub(crate) fn get_comment_end(
+    post_snippet: &str,
+    separator: &str,
+    terminator: &str,
+    is_last: bool,
+) -> usize {
+    if is_last {
+        return post_snippet
+            .find_uncommented(terminator)
+            .unwrap_or_else(|| post_snippet.len());
+    }
+
+    let mut block_open_index = post_snippet.find("/*");
+    // check if it really is a block comment (and not `//*` or a nested comment)
+    if let Some(i) = block_open_index {
+        match post_snippet.find('/') {
+            Some(j) if j < i => block_open_index = None,
+            _ if post_snippet[..i].ends_with('/') => block_open_index = None,
+            _ => (),
+        }
+    }
+    let newline_index = post_snippet.find('\n');
+    if let Some(separator_index) = post_snippet.find_uncommented(separator) {
+        match (block_open_index, newline_index) {
+            // Separator before comment, with the next item on same line.
+            // Comment belongs to next item.
+            (Some(i), None) if i > separator_index => separator_index + 1,
+            // Block-style post-comment before the separator.
+            (Some(i), None) => cmp::max(
+                find_comment_end(&post_snippet[i..]).unwrap() + i,
+                separator_index + 1,
+            ),
+            // Block-style post-comment. Either before or after the separator.
+            (Some(i), Some(j)) if i < j => cmp::max(
+                find_comment_end(&post_snippet[i..]).unwrap() + i,
+                separator_index + 1,
+            ),
+            // Potential *single* line comment.
+            (_, Some(j)) if j > separator_index => j + 1,
+            _ => post_snippet.len(),
+        }
+    } else if let Some(newline_index) = newline_index {
+        // Match arms may not have trailing comma. In any case, for match arms,
+        // we will assume that the post comment belongs to the next arm if they
+        // do not end with trailing comma.
+        newline_index + 1
+    } else {
+        0
+    }
+}
+
+// Account for extra whitespace between items. This is fiddly
+// because of the way we divide pre- and post- comments.
+pub(crate) fn has_extra_newline(post_snippet: &str, comment_end: usize) -> bool {
+    if post_snippet.is_empty() || comment_end == 0 {
+        return false;
+    }
+
+    let len_last = post_snippet[..comment_end]
+        .chars()
+        .last()
+        .unwrap()
+        .len_utf8();
+    // Everything from the separator to the next item.
+    let test_snippet = &post_snippet[comment_end - len_last..];
+    let first_newline = test_snippet
+        .find('\n')
+        .unwrap_or_else(|| test_snippet.len());
+    // From the end of the first line of comments.
+    let test_snippet = &test_snippet[first_newline..];
+    let first = test_snippet
+        .find(|c: char| !c.is_whitespace())
+        .unwrap_or_else(|| test_snippet.len());
+    // From the end of the first line of comments to the next non-whitespace char.
+    let test_snippet = &test_snippet[..first];
+
+    // There were multiple line breaks which got trimmed to nothing.
+    count_newlines(test_snippet) > 1
+}
+
+impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
+where
+    I: Iterator<Item = T>,
+    F1: Fn(&T) -> BytePos,
+    F2: Fn(&T) -> BytePos,
+    F3: Fn(&T) -> Option<String>,
+{
+    type Item = ListItem;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next().map(|item| {
+            // Pre-comment
+            let pre_snippet = self
+                .snippet_provider
+                .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
+                .unwrap_or("");
+            let (pre_comment, pre_comment_style) = extract_pre_comment(pre_snippet);
+
+            // Post-comment
+            let next_start = match self.inner.peek() {
+                Some(next_item) => (self.get_lo)(next_item),
+                None => self.next_span_start,
+            };
+            let post_snippet = self
+                .snippet_provider
+                .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
+                .unwrap_or("");
+            let comment_end = get_comment_end(
+                post_snippet,
+                self.separator,
+                self.terminator,
+                self.inner.peek().is_none(),
+            );
+            let new_lines = has_extra_newline(post_snippet, comment_end);
+            let post_comment = extract_post_comment(post_snippet, comment_end, self.separator);
+
+            self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
+
+            ListItem {
+                pre_comment,
+                pre_comment_style,
+                item: if self.inner.peek().is_none() && self.leave_last {
+                    None
+                } else {
+                    (self.get_item_string)(&item)
+                },
+                post_comment,
+                new_lines,
+            }
+        })
+    }
+}
+
+#[allow(clippy::too_many_arguments)]
+// Creates an iterator over a list's items with associated comments.
+pub(crate) fn itemize_list<'a, T, I, F1, F2, F3>(
+    snippet_provider: &'a SnippetProvider,
+    inner: I,
+    terminator: &'a str,
+    separator: &'a str,
+    get_lo: F1,
+    get_hi: F2,
+    get_item_string: F3,
+    prev_span_end: BytePos,
+    next_span_start: BytePos,
+    leave_last: bool,
+) -> ListItems<'a, I, F1, F2, F3>
+where
+    I: Iterator<Item = T>,
+    F1: Fn(&T) -> BytePos,
+    F2: Fn(&T) -> BytePos,
+    F3: Fn(&T) -> Option<String>,
+{
+    ListItems {
+        snippet_provider,
+        inner: inner.peekable(),
+        get_lo,
+        get_hi,
+        get_item_string,
+        prev_span_end,
+        next_span_start,
+        terminator,
+        separator,
+        leave_last,
+    }
+}
+
+/// Returns the count and total width of the list items.
+fn calculate_width<I, T>(items: I) -> (usize, usize)
+where
+    I: IntoIterator<Item = T>,
+    T: AsRef<ListItem>,
+{
+    items
+        .into_iter()
+        .map(|item| total_item_width(item.as_ref()))
+        .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
+}
+
+pub(crate) fn total_item_width(item: &ListItem) -> usize {
+    comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
+        + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
+        + &item.item.as_ref().map_or(0, |s| unicode_str_width(&s))
+}
+
+fn comment_len(comment: Option<&str>) -> usize {
+    match comment {
+        Some(s) => {
+            let text_len = s.trim().len();
+            if text_len > 0 {
+                // We'll put " /*" before and " */" after inline comments.
+                text_len + 6
+            } else {
+                text_len
+            }
+        }
+        None => 0,
+    }
+}
+
+// Compute horizontal and vertical shapes for a struct-lit-like thing.
+pub(crate) fn struct_lit_shape(
+    shape: Shape,
+    context: &RewriteContext<'_>,
+    prefix_width: usize,
+    suffix_width: usize,
+) -> Option<(Option<Shape>, Shape)> {
+    let v_shape = match context.config.indent_style() {
+        IndentStyle::Visual => shape
+            .visual_indent(0)
+            .shrink_left(prefix_width)?
+            .sub_width(suffix_width)?,
+        IndentStyle::Block => {
+            let shape = shape.block_indent(context.config.tab_spaces());
+            Shape {
+                width: context.budget(shape.indent.width()),
+                ..shape
+            }
+        }
+    };
+    let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
+    if let Some(w) = shape_width {
+        let shape_width = cmp::min(w, context.config.struct_lit_width());
+        Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
+    } else {
+        Some((None, v_shape))
+    }
+}
+
+// Compute the tactic for the internals of a struct-lit-like thing.
+pub(crate) fn struct_lit_tactic(
+    h_shape: Option<Shape>,
+    context: &RewriteContext<'_>,
+    items: &[ListItem],
+) -> DefinitiveListTactic {
+    if let Some(h_shape) = h_shape {
+        let prelim_tactic = match (context.config.indent_style(), items.len()) {
+            (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
+            _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
+            _ => ListTactic::Vertical,
+        };
+        definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
+    } else {
+        DefinitiveListTactic::Vertical
+    }
+}
+
+// Given a tactic and possible shapes for horizontal and vertical layout,
+// come up with the actual shape to use.
+pub(crate) fn shape_for_tactic(
+    tactic: DefinitiveListTactic,
+    h_shape: Option<Shape>,
+    v_shape: Shape,
+) -> Shape {
+    match tactic {
+        DefinitiveListTactic::Horizontal => h_shape.unwrap(),
+        _ => v_shape,
+    }
+}
+
+// Create a ListFormatting object for formatting the internals of a
+// struct-lit-like thing, that is a series of fields.
+pub(crate) fn struct_lit_formatting<'a>(
+    shape: Shape,
+    tactic: DefinitiveListTactic,
+    context: &'a RewriteContext<'_>,
+    force_no_trailing_comma: bool,
+) -> ListFormatting<'a> {
+    let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
+        && tactic == DefinitiveListTactic::Vertical;
+    ListFormatting {
+        tactic,
+        separator: ",",
+        trailing_separator: if force_no_trailing_comma {
+            SeparatorTactic::Never
+        } else {
+            context.config.trailing_comma()
+        },
+        separator_place: SeparatorPlace::Back,
+        shape,
+        ends_with_newline,
+        preserve_newline: true,
+        nested: false,
+        align_comments: true,
+        config: context.config,
+    }
+}
diff --git a/src/tools/rustfmt/src/macros.rs b/src/tools/rustfmt/src/macros.rs
new file mode 100644
index 0000000000000..bf4769b34aa84
--- /dev/null
+++ b/src/tools/rustfmt/src/macros.rs
@@ -0,0 +1,1612 @@
+// Format list-like macro invocations. These are invocations whose token trees
+// can be interpreted as expressions and separated by commas.
+// Note that these token trees do not actually have to be interpreted as
+// expressions by the compiler. An example of an invocation we would reformat is
+// foo!( x, y, z ). The token x may represent an identifier in the code, but we
+// interpreted as an expression.
+// Macro uses which are not-list like, such as bar!(key => val), will not be
+// reformatted.
+// List-like invocations with parentheses will be formatted as function calls,
+// and those with brackets will be formatted as array literals.
+
+use std::collections::HashMap;
+use std::panic::{catch_unwind, AssertUnwindSafe};
+
+use rustc_ast::token::{BinOpToken, DelimToken, Token, TokenKind};
+use rustc_ast::tokenstream::{Cursor, Spacing, TokenStream, TokenTree};
+use rustc_ast::{ast, ptr};
+use rustc_ast_pretty::pprust;
+use rustc_parse::parser::{ForceCollect, Parser};
+use rustc_parse::{stream_to_parser, MACRO_ARGUMENTS};
+use rustc_span::{
+    symbol::{self, kw},
+    BytePos, Span, Symbol, DUMMY_SP,
+};
+
+use crate::comment::{
+    contains_comment, CharClasses, FindUncommented, FullCodeCharKind, LineClasses,
+};
+use crate::config::lists::*;
+use crate::expr::rewrite_array;
+use crate::lists::{itemize_list, write_list, ListFormatting};
+use crate::overflow;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::{Indent, Shape};
+use crate::source_map::SpanUtils;
+use crate::spanned::Spanned;
+use crate::utils::{
+    format_visibility, indent_next_line, is_empty_line, mk_sp, remove_trailing_white_spaces,
+    rewrite_ident, trim_left_preserve_layout, wrap_str, NodeIdExt,
+};
+use crate::visitor::FmtVisitor;
+
+const FORCED_BRACKET_MACROS: &[&str] = &["vec!"];
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum MacroPosition {
+    Item,
+    Statement,
+    Expression,
+    Pat,
+}
+
+#[derive(Debug)]
+pub(crate) enum MacroArg {
+    Expr(ptr::P<ast::Expr>),
+    Ty(ptr::P<ast::Ty>),
+    Pat(ptr::P<ast::Pat>),
+    Item(ptr::P<ast::Item>),
+    Keyword(symbol::Ident, Span),
+}
+
+impl MacroArg {
+    fn is_item(&self) -> bool {
+        match self {
+            MacroArg::Item(..) => true,
+            _ => false,
+        }
+    }
+}
+
+impl Rewrite for ast::Item {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let mut visitor = crate::visitor::FmtVisitor::from_context(context);
+        visitor.block_indent = shape.indent;
+        visitor.last_pos = self.span().lo();
+        visitor.visit_item(self);
+        Some(visitor.buffer.to_owned())
+    }
+}
+
+impl Rewrite for MacroArg {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match *self {
+            MacroArg::Expr(ref expr) => expr.rewrite(context, shape),
+            MacroArg::Ty(ref ty) => ty.rewrite(context, shape),
+            MacroArg::Pat(ref pat) => pat.rewrite(context, shape),
+            MacroArg::Item(ref item) => item.rewrite(context, shape),
+            MacroArg::Keyword(ident, _) => Some(ident.name.to_string()),
+        }
+    }
+}
+
+fn build_parser<'a>(context: &RewriteContext<'a>, cursor: Cursor) -> Parser<'a> {
+    stream_to_parser(
+        context.parse_sess.inner(),
+        cursor.collect(),
+        MACRO_ARGUMENTS,
+    )
+}
+
+fn parse_macro_arg<'a, 'b: 'a>(parser: &'a mut Parser<'b>) -> Option<MacroArg> {
+    macro_rules! parse_macro_arg {
+        ($macro_arg:ident, $parser:expr, $f:expr) => {
+            let mut cloned_parser = (*parser).clone();
+            match $parser(&mut cloned_parser) {
+                Ok(x) => {
+                    if parser.sess.span_diagnostic.has_errors() {
+                        parser.sess.span_diagnostic.reset_err_count();
+                    } else {
+                        // Parsing succeeded.
+                        *parser = cloned_parser;
+                        return Some(MacroArg::$macro_arg($f(x)?));
+                    }
+                }
+                Err(mut e) => {
+                    e.cancel();
+                    parser.sess.span_diagnostic.reset_err_count();
+                }
+            }
+        };
+    }
+
+    parse_macro_arg!(
+        Expr,
+        |parser: &mut rustc_parse::parser::Parser<'b>| parser.parse_expr(),
+        |x: ptr::P<ast::Expr>| Some(x)
+    );
+    parse_macro_arg!(
+        Ty,
+        |parser: &mut rustc_parse::parser::Parser<'b>| parser.parse_ty(),
+        |x: ptr::P<ast::Ty>| Some(x)
+    );
+    parse_macro_arg!(
+        Pat,
+        |parser: &mut rustc_parse::parser::Parser<'b>| parser.parse_pat_no_top_alt(None),
+        |x: ptr::P<ast::Pat>| Some(x)
+    );
+    // `parse_item` returns `Option<ptr::P<ast::Item>>`.
+    parse_macro_arg!(
+        Item,
+        |parser: &mut rustc_parse::parser::Parser<'b>| parser.parse_item(ForceCollect::No),
+        |x: Option<ptr::P<ast::Item>>| x
+    );
+
+    None
+}
+
+/// Rewrite macro name without using pretty-printer if possible.
+fn rewrite_macro_name(
+    context: &RewriteContext<'_>,
+    path: &ast::Path,
+    extra_ident: Option<symbol::Ident>,
+) -> String {
+    let name = if path.segments.len() == 1 {
+        // Avoid using pretty-printer in the common case.
+        format!("{}!", rewrite_ident(context, path.segments[0].ident))
+    } else {
+        format!("{}!", pprust::path_to_string(path))
+    };
+    match extra_ident {
+        Some(ident) if ident.name != kw::Empty => format!("{} {}", name, ident),
+        _ => name,
+    }
+}
+
+// Use this on failing to format the macro call.
+fn return_macro_parse_failure_fallback(
+    context: &RewriteContext<'_>,
+    indent: Indent,
+    span: Span,
+) -> Option<String> {
+    // Mark this as a failure however we format it
+    context.macro_rewrite_failure.replace(true);
+
+    // Heuristically determine whether the last line of the macro uses "Block" style
+    // rather than using "Visual" style, or another indentation style.
+    let is_like_block_indent_style = context
+        .snippet(span)
+        .lines()
+        .last()
+        .map(|closing_line| {
+            closing_line.trim().chars().all(|ch| match ch {
+                '}' | ')' | ']' => true,
+                _ => false,
+            })
+        })
+        .unwrap_or(false);
+    if is_like_block_indent_style {
+        return trim_left_preserve_layout(context.snippet(span), indent, &context.config);
+    }
+
+    context.skipped_range.borrow_mut().push((
+        context.parse_sess.line_of_byte_pos(span.lo()),
+        context.parse_sess.line_of_byte_pos(span.hi()),
+    ));
+
+    // Return the snippet unmodified if the macro is not block-like
+    Some(context.snippet(span).to_owned())
+}
+
+pub(crate) fn rewrite_macro(
+    mac: &ast::MacCall,
+    extra_ident: Option<symbol::Ident>,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    position: MacroPosition,
+) -> Option<String> {
+    let should_skip = context
+        .skip_context
+        .skip_macro(&context.snippet(mac.path.span).to_owned());
+    if should_skip {
+        None
+    } else {
+        let guard = context.enter_macro();
+        let result = catch_unwind(AssertUnwindSafe(|| {
+            rewrite_macro_inner(
+                mac,
+                extra_ident,
+                context,
+                shape,
+                position,
+                guard.is_nested(),
+            )
+        }));
+        match result {
+            Err(..) | Ok(None) => {
+                context.macro_rewrite_failure.replace(true);
+                None
+            }
+            Ok(rw) => rw,
+        }
+    }
+}
+
+fn check_keyword<'a, 'b: 'a>(parser: &'a mut Parser<'b>) -> Option<MacroArg> {
+    for &keyword in RUST_KW.iter() {
+        if parser.token.is_keyword(keyword)
+            && parser.look_ahead(1, |t| {
+                t.kind == TokenKind::Eof
+                    || t.kind == TokenKind::Comma
+                    || t.kind == TokenKind::CloseDelim(DelimToken::NoDelim)
+            })
+        {
+            parser.bump();
+            return Some(MacroArg::Keyword(
+                symbol::Ident::with_dummy_span(keyword),
+                parser.prev_token.span,
+            ));
+        }
+    }
+    None
+}
+
+fn rewrite_macro_inner(
+    mac: &ast::MacCall,
+    extra_ident: Option<symbol::Ident>,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    position: MacroPosition,
+    is_nested_macro: bool,
+) -> Option<String> {
+    if context.config.use_try_shorthand() {
+        if let Some(expr) = convert_try_mac(mac, context) {
+            context.leave_macro();
+            return expr.rewrite(context, shape);
+        }
+    }
+
+    let original_style = macro_style(mac, context);
+
+    let macro_name = rewrite_macro_name(context, &mac.path, extra_ident);
+
+    let style = if FORCED_BRACKET_MACROS.contains(&&macro_name[..]) && !is_nested_macro {
+        DelimToken::Bracket
+    } else {
+        original_style
+    };
+
+    let ts = mac.args.inner_tokens();
+    let has_comment = contains_comment(context.snippet(mac.span()));
+    if ts.is_empty() && !has_comment {
+        return match style {
+            DelimToken::Paren if position == MacroPosition::Item => {
+                Some(format!("{}();", macro_name))
+            }
+            DelimToken::Bracket if position == MacroPosition::Item => {
+                Some(format!("{}[];", macro_name))
+            }
+            DelimToken::Paren => Some(format!("{}()", macro_name)),
+            DelimToken::Bracket => Some(format!("{}[]", macro_name)),
+            DelimToken::Brace => Some(format!("{} {{}}", macro_name)),
+            _ => unreachable!(),
+        };
+    }
+    // Format well-known macros which cannot be parsed as a valid AST.
+    if macro_name == "lazy_static!" && !has_comment {
+        if let success @ Some(..) = format_lazy_static(context, shape, &ts) {
+            return success;
+        }
+    }
+
+    let mut parser = build_parser(context, ts.trees());
+    let mut arg_vec = Vec::new();
+    let mut vec_with_semi = false;
+    let mut trailing_comma = false;
+
+    if DelimToken::Brace != style {
+        loop {
+            if let Some(arg) = check_keyword(&mut parser) {
+                arg_vec.push(arg);
+            } else if let Some(arg) = parse_macro_arg(&mut parser) {
+                arg_vec.push(arg);
+            } else {
+                return return_macro_parse_failure_fallback(context, shape.indent, mac.span());
+            }
+
+            match parser.token.kind {
+                TokenKind::Eof => break,
+                TokenKind::Comma => (),
+                TokenKind::Semi => {
+                    // Try to parse `vec![expr; expr]`
+                    if FORCED_BRACKET_MACROS.contains(&&macro_name[..]) {
+                        parser.bump();
+                        if parser.token.kind != TokenKind::Eof {
+                            match parse_macro_arg(&mut parser) {
+                                Some(arg) => {
+                                    arg_vec.push(arg);
+                                    parser.bump();
+                                    if parser.token.kind == TokenKind::Eof && arg_vec.len() == 2 {
+                                        vec_with_semi = true;
+                                        break;
+                                    }
+                                }
+                                None => {
+                                    return return_macro_parse_failure_fallback(
+                                        context,
+                                        shape.indent,
+                                        mac.span(),
+                                    );
+                                }
+                            }
+                        }
+                    }
+                    return return_macro_parse_failure_fallback(context, shape.indent, mac.span());
+                }
+                _ if arg_vec.last().map_or(false, MacroArg::is_item) => continue,
+                _ => return return_macro_parse_failure_fallback(context, shape.indent, mac.span()),
+            }
+
+            parser.bump();
+
+            if parser.token.kind == TokenKind::Eof {
+                trailing_comma = true;
+                break;
+            }
+        }
+    }
+
+    if !arg_vec.is_empty() && arg_vec.iter().all(MacroArg::is_item) {
+        return rewrite_macro_with_items(
+            context,
+            &arg_vec,
+            &macro_name,
+            shape,
+            style,
+            position,
+            mac.span(),
+        );
+    }
+
+    match style {
+        DelimToken::Paren => {
+            // Handle special case: `vec!(expr; expr)`
+            if vec_with_semi {
+                handle_vec_semi(context, shape, arg_vec, macro_name, style)
+            } else {
+                // Format macro invocation as function call, preserve the trailing
+                // comma because not all macros support them.
+                overflow::rewrite_with_parens(
+                    context,
+                    &macro_name,
+                    arg_vec.iter(),
+                    shape,
+                    mac.span(),
+                    context.config.fn_call_width(),
+                    if trailing_comma {
+                        Some(SeparatorTactic::Always)
+                    } else {
+                        Some(SeparatorTactic::Never)
+                    },
+                )
+                .map(|rw| match position {
+                    MacroPosition::Item => format!("{};", rw),
+                    _ => rw,
+                })
+            }
+        }
+        DelimToken::Bracket => {
+            // Handle special case: `vec![expr; expr]`
+            if vec_with_semi {
+                handle_vec_semi(context, shape, arg_vec, macro_name, style)
+            } else {
+                // If we are rewriting `vec!` macro or other special macros,
+                // then we can rewrite this as an usual array literal.
+                // Otherwise, we must preserve the original existence of trailing comma.
+                let macro_name = &macro_name.as_str();
+                let mut force_trailing_comma = if trailing_comma {
+                    Some(SeparatorTactic::Always)
+                } else {
+                    Some(SeparatorTactic::Never)
+                };
+                if FORCED_BRACKET_MACROS.contains(macro_name) && !is_nested_macro {
+                    context.leave_macro();
+                    if context.use_block_indent() {
+                        force_trailing_comma = Some(SeparatorTactic::Vertical);
+                    };
+                }
+                let rewrite = rewrite_array(
+                    macro_name,
+                    arg_vec.iter(),
+                    mac.span(),
+                    context,
+                    shape,
+                    force_trailing_comma,
+                    Some(original_style),
+                )?;
+                let comma = match position {
+                    MacroPosition::Item => ";",
+                    _ => "",
+                };
+
+                Some(format!("{}{}", rewrite, comma))
+            }
+        }
+        DelimToken::Brace => {
+            // For macro invocations with braces, always put a space between
+            // the `macro_name!` and `{ /* macro_body */ }` but skip modifying
+            // anything in between the braces (for now).
+            let snippet = context.snippet(mac.span()).trim_start_matches(|c| c != '{');
+            match trim_left_preserve_layout(snippet, shape.indent, &context.config) {
+                Some(macro_body) => Some(format!("{} {}", macro_name, macro_body)),
+                None => Some(format!("{} {}", macro_name, snippet)),
+            }
+        }
+        _ => unreachable!(),
+    }
+}
+
+fn handle_vec_semi(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    arg_vec: Vec<MacroArg>,
+    macro_name: String,
+    delim_token: DelimToken,
+) -> Option<String> {
+    let (left, right) = match delim_token {
+        DelimToken::Paren => ("(", ")"),
+        DelimToken::Bracket => ("[", "]"),
+        _ => unreachable!(),
+    };
+
+    let mac_shape = shape.offset_left(macro_name.len())?;
+    // 8 = `vec![]` + `; ` or `vec!()` + `; `
+    let total_overhead = 8;
+    let nested_shape = mac_shape.block_indent(context.config.tab_spaces());
+    let lhs = arg_vec[0].rewrite(context, nested_shape)?;
+    let rhs = arg_vec[1].rewrite(context, nested_shape)?;
+    if !lhs.contains('\n')
+        && !rhs.contains('\n')
+        && lhs.len() + rhs.len() + total_overhead <= shape.width
+    {
+        // macro_name(lhs; rhs) or macro_name[lhs; rhs]
+        Some(format!("{}{}{}; {}{}", macro_name, left, lhs, rhs, right))
+    } else {
+        // macro_name(\nlhs;\nrhs\n) or macro_name[\nlhs;\nrhs\n]
+        Some(format!(
+            "{}{}{}{};{}{}{}{}",
+            macro_name,
+            left,
+            nested_shape.indent.to_string_with_newline(context.config),
+            lhs,
+            nested_shape.indent.to_string_with_newline(context.config),
+            rhs,
+            shape.indent.to_string_with_newline(context.config),
+            right
+        ))
+    }
+}
+
+pub(crate) fn rewrite_macro_def(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    indent: Indent,
+    def: &ast::MacroDef,
+    ident: symbol::Ident,
+    vis: &ast::Visibility,
+    span: Span,
+) -> Option<String> {
+    let snippet = Some(remove_trailing_white_spaces(context.snippet(span)));
+    if snippet.as_ref().map_or(true, |s| s.ends_with(';')) {
+        return snippet;
+    }
+
+    let ts = def.body.inner_tokens();
+    let mut parser = MacroParser::new(ts.into_trees());
+    let parsed_def = match parser.parse() {
+        Some(def) => def,
+        None => return snippet,
+    };
+
+    let mut result = if def.macro_rules {
+        String::from("macro_rules!")
+    } else {
+        format!("{}macro", format_visibility(context, vis))
+    };
+
+    result += " ";
+    result += rewrite_ident(context, ident);
+
+    let multi_branch_style = def.macro_rules || parsed_def.branches.len() != 1;
+
+    let arm_shape = if multi_branch_style {
+        shape
+            .block_indent(context.config.tab_spaces())
+            .with_max_width(context.config)
+    } else {
+        shape
+    };
+
+    let branch_items = itemize_list(
+        context.snippet_provider,
+        parsed_def.branches.iter(),
+        "}",
+        ";",
+        |branch| branch.span.lo(),
+        |branch| branch.span.hi(),
+        |branch| match branch.rewrite(context, arm_shape, multi_branch_style) {
+            Some(v) => Some(v),
+            // if the rewrite returned None because a macro could not be rewritten, then return the
+            // original body
+            None if context.macro_rewrite_failure.get() => {
+                Some(context.snippet(branch.body).trim().to_string())
+            }
+            None => None,
+        },
+        context.snippet_provider.span_after(span, "{"),
+        span.hi(),
+        false,
+    )
+    .collect::<Vec<_>>();
+
+    let fmt = ListFormatting::new(arm_shape, context.config)
+        .separator(if def.macro_rules { ";" } else { "" })
+        .trailing_separator(SeparatorTactic::Always)
+        .preserve_newline(true);
+
+    if multi_branch_style {
+        result += " {";
+        result += &arm_shape.indent.to_string_with_newline(context.config);
+    }
+
+    match write_list(&branch_items, &fmt) {
+        Some(ref s) => result += s,
+        None => return snippet,
+    }
+
+    if multi_branch_style {
+        result += &indent.to_string_with_newline(context.config);
+        result += "}";
+    }
+
+    Some(result)
+}
+
+fn register_metavariable(
+    map: &mut HashMap<String, String>,
+    result: &mut String,
+    name: &str,
+    dollar_count: usize,
+) {
+    let mut new_name = "$".repeat(dollar_count - 1);
+    let mut old_name = "$".repeat(dollar_count);
+
+    new_name.push('z');
+    new_name.push_str(name);
+    old_name.push_str(name);
+
+    result.push_str(&new_name);
+    map.insert(old_name, new_name);
+}
+
+// Replaces `$foo` with `zfoo`. We must check for name overlap to ensure we
+// aren't causing problems.
+// This should also work for escaped `$` variables, where we leave earlier `$`s.
+fn replace_names(input: &str) -> Option<(String, HashMap<String, String>)> {
+    // Each substitution will require five or six extra bytes.
+    let mut result = String::with_capacity(input.len() + 64);
+    let mut substs = HashMap::new();
+    let mut dollar_count = 0;
+    let mut cur_name = String::new();
+
+    for (kind, c) in CharClasses::new(input.chars()) {
+        if kind != FullCodeCharKind::Normal {
+            result.push(c);
+        } else if c == '$' {
+            dollar_count += 1;
+        } else if dollar_count == 0 {
+            result.push(c);
+        } else if !c.is_alphanumeric() && !cur_name.is_empty() {
+            // Terminates a name following one or more dollars.
+            register_metavariable(&mut substs, &mut result, &cur_name, dollar_count);
+
+            result.push(c);
+            dollar_count = 0;
+            cur_name.clear();
+        } else if c == '(' && cur_name.is_empty() {
+            // FIXME: Support macro def with repeat.
+            return None;
+        } else if c.is_alphanumeric() || c == '_' {
+            cur_name.push(c);
+        }
+    }
+
+    if !cur_name.is_empty() {
+        register_metavariable(&mut substs, &mut result, &cur_name, dollar_count);
+    }
+
+    debug!("replace_names `{}` {:?}", result, substs);
+
+    Some((result, substs))
+}
+
+#[derive(Debug, Clone)]
+enum MacroArgKind {
+    /// e.g., `$x: expr`.
+    MetaVariable(Symbol, String),
+    /// e.g., `$($foo: expr),*`
+    Repeat(
+        /// `()`, `[]` or `{}`.
+        DelimToken,
+        /// Inner arguments inside delimiters.
+        Vec<ParsedMacroArg>,
+        /// Something after the closing delimiter and the repeat token, if available.
+        Option<Box<ParsedMacroArg>>,
+        /// The repeat token. This could be one of `*`, `+` or `?`.
+        Token,
+    ),
+    /// e.g., `[derive(Debug)]`
+    Delimited(DelimToken, Vec<ParsedMacroArg>),
+    /// A possible separator. e.g., `,` or `;`.
+    Separator(String, String),
+    /// Other random stuff that does not fit to other kinds.
+    /// e.g., `== foo` in `($x: expr == foo)`.
+    Other(String, String),
+}
+
+fn delim_token_to_str(
+    context: &RewriteContext<'_>,
+    delim_token: DelimToken,
+    shape: Shape,
+    use_multiple_lines: bool,
+    inner_is_empty: bool,
+) -> (String, String) {
+    let (lhs, rhs) = match delim_token {
+        DelimToken::Paren => ("(", ")"),
+        DelimToken::Bracket => ("[", "]"),
+        DelimToken::Brace => {
+            if inner_is_empty || use_multiple_lines {
+                ("{", "}")
+            } else {
+                ("{ ", " }")
+            }
+        }
+        DelimToken::NoDelim => ("", ""),
+    };
+    if use_multiple_lines {
+        let indent_str = shape.indent.to_string_with_newline(context.config);
+        let nested_indent_str = shape
+            .indent
+            .block_indent(context.config)
+            .to_string_with_newline(context.config);
+        (
+            format!("{}{}", lhs, nested_indent_str),
+            format!("{}{}", indent_str, rhs),
+        )
+    } else {
+        (lhs.to_owned(), rhs.to_owned())
+    }
+}
+
+impl MacroArgKind {
+    fn starts_with_brace(&self) -> bool {
+        match *self {
+            MacroArgKind::Repeat(DelimToken::Brace, _, _, _)
+            | MacroArgKind::Delimited(DelimToken::Brace, _) => true,
+            _ => false,
+        }
+    }
+
+    fn starts_with_dollar(&self) -> bool {
+        match *self {
+            MacroArgKind::Repeat(..) | MacroArgKind::MetaVariable(..) => true,
+            _ => false,
+        }
+    }
+
+    fn ends_with_space(&self) -> bool {
+        match *self {
+            MacroArgKind::Separator(..) => true,
+            _ => false,
+        }
+    }
+
+    fn has_meta_var(&self) -> bool {
+        match *self {
+            MacroArgKind::MetaVariable(..) => true,
+            MacroArgKind::Repeat(_, ref args, _, _) => args.iter().any(|a| a.kind.has_meta_var()),
+            _ => false,
+        }
+    }
+
+    fn rewrite(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        use_multiple_lines: bool,
+    ) -> Option<String> {
+        let rewrite_delimited_inner = |delim_tok, args| -> Option<(String, String, String)> {
+            let inner = wrap_macro_args(context, args, shape)?;
+            let (lhs, rhs) = delim_token_to_str(context, delim_tok, shape, false, inner.is_empty());
+            if lhs.len() + inner.len() + rhs.len() <= shape.width {
+                return Some((lhs, inner, rhs));
+            }
+
+            let (lhs, rhs) = delim_token_to_str(context, delim_tok, shape, true, false);
+            let nested_shape = shape
+                .block_indent(context.config.tab_spaces())
+                .with_max_width(context.config);
+            let inner = wrap_macro_args(context, args, nested_shape)?;
+            Some((lhs, inner, rhs))
+        };
+
+        match *self {
+            MacroArgKind::MetaVariable(ty, ref name) => Some(format!("${}:{}", name, ty)),
+            MacroArgKind::Repeat(delim_tok, ref args, ref another, ref tok) => {
+                let (lhs, inner, rhs) = rewrite_delimited_inner(delim_tok, args)?;
+                let another = another
+                    .as_ref()
+                    .and_then(|a| a.rewrite(context, shape, use_multiple_lines))
+                    .unwrap_or_else(|| "".to_owned());
+                let repeat_tok = pprust::token_to_string(tok);
+
+                Some(format!("${}{}{}{}{}", lhs, inner, rhs, another, repeat_tok))
+            }
+            MacroArgKind::Delimited(delim_tok, ref args) => {
+                rewrite_delimited_inner(delim_tok, args)
+                    .map(|(lhs, inner, rhs)| format!("{}{}{}", lhs, inner, rhs))
+            }
+            MacroArgKind::Separator(ref sep, ref prefix) => Some(format!("{}{} ", prefix, sep)),
+            MacroArgKind::Other(ref inner, ref prefix) => Some(format!("{}{}", prefix, inner)),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+struct ParsedMacroArg {
+    kind: MacroArgKind,
+    span: Span,
+}
+
+impl ParsedMacroArg {
+    fn rewrite(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        use_multiple_lines: bool,
+    ) -> Option<String> {
+        self.kind.rewrite(context, shape, use_multiple_lines)
+    }
+}
+
+/// Parses macro arguments on macro def.
+struct MacroArgParser {
+    /// Either a name of the next metavariable, a separator, or junk.
+    buf: String,
+    /// The start position on the current buffer.
+    lo: BytePos,
+    /// The first token of the current buffer.
+    start_tok: Token,
+    /// `true` if we are parsing a metavariable or a repeat.
+    is_meta_var: bool,
+    /// The position of the last token.
+    hi: BytePos,
+    /// The last token parsed.
+    last_tok: Token,
+    /// Holds the parsed arguments.
+    result: Vec<ParsedMacroArg>,
+}
+
+fn last_tok(tt: &TokenTree) -> Token {
+    match *tt {
+        TokenTree::Token(ref t) => t.clone(),
+        TokenTree::Delimited(delim_span, delim, _) => Token {
+            kind: TokenKind::CloseDelim(delim),
+            span: delim_span.close,
+        },
+    }
+}
+
+impl MacroArgParser {
+    fn new() -> MacroArgParser {
+        MacroArgParser {
+            lo: BytePos(0),
+            hi: BytePos(0),
+            buf: String::new(),
+            is_meta_var: false,
+            last_tok: Token {
+                kind: TokenKind::Eof,
+                span: DUMMY_SP,
+            },
+            start_tok: Token {
+                kind: TokenKind::Eof,
+                span: DUMMY_SP,
+            },
+            result: vec![],
+        }
+    }
+
+    fn set_last_tok(&mut self, tok: &TokenTree) {
+        self.hi = tok.span().hi();
+        self.last_tok = last_tok(tok);
+    }
+
+    fn add_separator(&mut self) {
+        let prefix = if self.need_space_prefix() {
+            " ".to_owned()
+        } else {
+            "".to_owned()
+        };
+        self.result.push(ParsedMacroArg {
+            kind: MacroArgKind::Separator(self.buf.clone(), prefix),
+            span: mk_sp(self.lo, self.hi),
+        });
+        self.buf.clear();
+    }
+
+    fn add_other(&mut self) {
+        let prefix = if self.need_space_prefix() {
+            " ".to_owned()
+        } else {
+            "".to_owned()
+        };
+        self.result.push(ParsedMacroArg {
+            kind: MacroArgKind::Other(self.buf.clone(), prefix),
+            span: mk_sp(self.lo, self.hi),
+        });
+        self.buf.clear();
+    }
+
+    fn add_meta_variable(&mut self, iter: &mut Cursor) -> Option<()> {
+        match iter.next() {
+            Some(TokenTree::Token(Token {
+                kind: TokenKind::Ident(name, _),
+                span,
+            })) => {
+                self.result.push(ParsedMacroArg {
+                    kind: MacroArgKind::MetaVariable(name, self.buf.clone()),
+                    span: mk_sp(self.lo, span.hi()),
+                });
+
+                self.buf.clear();
+                self.is_meta_var = false;
+                Some(())
+            }
+            _ => None,
+        }
+    }
+
+    fn add_delimited(&mut self, inner: Vec<ParsedMacroArg>, delim: DelimToken, span: Span) {
+        self.result.push(ParsedMacroArg {
+            kind: MacroArgKind::Delimited(delim, inner),
+            span,
+        });
+    }
+
+    // $($foo: expr),?
+    fn add_repeat(
+        &mut self,
+        inner: Vec<ParsedMacroArg>,
+        delim: DelimToken,
+        iter: &mut Cursor,
+        span: Span,
+    ) -> Option<()> {
+        let mut buffer = String::new();
+        let mut first = true;
+        let mut lo = span.lo();
+        let mut hi = span.hi();
+
+        // Parse '*', '+' or '?.
+        for tok in iter {
+            self.set_last_tok(&tok);
+            if first {
+                first = false;
+                lo = tok.span().lo();
+            }
+
+            match tok {
+                TokenTree::Token(Token {
+                    kind: TokenKind::BinOp(BinOpToken::Plus),
+                    ..
+                })
+                | TokenTree::Token(Token {
+                    kind: TokenKind::Question,
+                    ..
+                })
+                | TokenTree::Token(Token {
+                    kind: TokenKind::BinOp(BinOpToken::Star),
+                    ..
+                }) => {
+                    break;
+                }
+                TokenTree::Token(ref t) => {
+                    buffer.push_str(&pprust::token_to_string(&t));
+                    hi = t.span.hi();
+                }
+                _ => return None,
+            }
+        }
+
+        // There could be some random stuff between ')' and '*', '+' or '?'.
+        let another = if buffer.trim().is_empty() {
+            None
+        } else {
+            Some(Box::new(ParsedMacroArg {
+                kind: MacroArgKind::Other(buffer, "".to_owned()),
+                span: mk_sp(lo, hi),
+            }))
+        };
+
+        self.result.push(ParsedMacroArg {
+            kind: MacroArgKind::Repeat(delim, inner, another, self.last_tok.clone()),
+            span: mk_sp(self.lo, self.hi),
+        });
+        Some(())
+    }
+
+    fn update_buffer(&mut self, t: &Token) {
+        if self.buf.is_empty() {
+            self.lo = t.span.lo();
+            self.start_tok = t.clone();
+        } else {
+            let needs_space = match next_space(&self.last_tok.kind) {
+                SpaceState::Ident => ident_like(t),
+                SpaceState::Punctuation => !ident_like(t),
+                SpaceState::Always => true,
+                SpaceState::Never => false,
+            };
+            if force_space_before(&t.kind) || needs_space {
+                self.buf.push(' ');
+            }
+        }
+
+        self.buf.push_str(&pprust::token_to_string(t));
+    }
+
+    fn need_space_prefix(&self) -> bool {
+        if self.result.is_empty() {
+            return false;
+        }
+
+        let last_arg = self.result.last().unwrap();
+        if let MacroArgKind::MetaVariable(..) = last_arg.kind {
+            if ident_like(&self.start_tok) {
+                return true;
+            }
+            if self.start_tok.kind == TokenKind::Colon {
+                return true;
+            }
+        }
+
+        if force_space_before(&self.start_tok.kind) {
+            return true;
+        }
+
+        false
+    }
+
+    /// Returns a collection of parsed macro def's arguments.
+    fn parse(mut self, tokens: TokenStream) -> Option<Vec<ParsedMacroArg>> {
+        let mut iter = tokens.trees();
+
+        while let Some(tok) = iter.next() {
+            match tok {
+                TokenTree::Token(Token {
+                    kind: TokenKind::Dollar,
+                    span,
+                }) => {
+                    // We always want to add a separator before meta variables.
+                    if !self.buf.is_empty() {
+                        self.add_separator();
+                    }
+
+                    // Start keeping the name of this metavariable in the buffer.
+                    self.is_meta_var = true;
+                    self.lo = span.lo();
+                    self.start_tok = Token {
+                        kind: TokenKind::Dollar,
+                        span,
+                    };
+                }
+                TokenTree::Token(Token {
+                    kind: TokenKind::Colon,
+                    ..
+                }) if self.is_meta_var => {
+                    self.add_meta_variable(&mut iter)?;
+                }
+                TokenTree::Token(ref t) => self.update_buffer(t),
+                TokenTree::Delimited(delimited_span, delimited, ref tts) => {
+                    if !self.buf.is_empty() {
+                        if next_space(&self.last_tok.kind) == SpaceState::Always {
+                            self.add_separator();
+                        } else {
+                            self.add_other();
+                        }
+                    }
+
+                    // Parse the stuff inside delimiters.
+                    let mut parser = MacroArgParser::new();
+                    parser.lo = delimited_span.open.lo();
+                    let delimited_arg = parser.parse(tts.clone())?;
+
+                    let span = delimited_span.entire();
+                    if self.is_meta_var {
+                        self.add_repeat(delimited_arg, delimited, &mut iter, span)?;
+                        self.is_meta_var = false;
+                    } else {
+                        self.add_delimited(delimited_arg, delimited, span);
+                    }
+                }
+            }
+
+            self.set_last_tok(&tok);
+        }
+
+        // We are left with some stuff in the buffer. Since there is nothing
+        // left to separate, add this as `Other`.
+        if !self.buf.is_empty() {
+            self.add_other();
+        }
+
+        Some(self.result)
+    }
+}
+
+fn wrap_macro_args(
+    context: &RewriteContext<'_>,
+    args: &[ParsedMacroArg],
+    shape: Shape,
+) -> Option<String> {
+    wrap_macro_args_inner(context, args, shape, false)
+        .or_else(|| wrap_macro_args_inner(context, args, shape, true))
+}
+
+fn wrap_macro_args_inner(
+    context: &RewriteContext<'_>,
+    args: &[ParsedMacroArg],
+    shape: Shape,
+    use_multiple_lines: bool,
+) -> Option<String> {
+    let mut result = String::with_capacity(128);
+    let mut iter = args.iter().peekable();
+    let indent_str = shape.indent.to_string_with_newline(context.config);
+
+    while let Some(ref arg) = iter.next() {
+        result.push_str(&arg.rewrite(context, shape, use_multiple_lines)?);
+
+        if use_multiple_lines
+            && (arg.kind.ends_with_space() || iter.peek().map_or(false, |a| a.kind.has_meta_var()))
+        {
+            if arg.kind.ends_with_space() {
+                result.pop();
+            }
+            result.push_str(&indent_str);
+        } else if let Some(ref next_arg) = iter.peek() {
+            let space_before_dollar =
+                !arg.kind.ends_with_space() && next_arg.kind.starts_with_dollar();
+            let space_before_brace = next_arg.kind.starts_with_brace();
+            if space_before_dollar || space_before_brace {
+                result.push(' ');
+            }
+        }
+    }
+
+    if !use_multiple_lines && result.len() >= shape.width {
+        None
+    } else {
+        Some(result)
+    }
+}
+
+// This is a bit sketchy. The token rules probably need tweaking, but it works
+// for some common cases. I hope the basic logic is sufficient. Note that the
+// meaning of some tokens is a bit different here from usual Rust, e.g., `*`
+// and `(`/`)` have special meaning.
+//
+// We always try and format on one line.
+// FIXME: Use multi-line when every thing does not fit on one line.
+fn format_macro_args(
+    context: &RewriteContext<'_>,
+    token_stream: TokenStream,
+    shape: Shape,
+) -> Option<String> {
+    if !context.config.format_macro_matchers() {
+        let span = span_for_token_stream(&token_stream);
+        return Some(match span {
+            Some(span) => context.snippet(span).to_owned(),
+            None => String::new(),
+        });
+    }
+    let parsed_args = MacroArgParser::new().parse(token_stream)?;
+    wrap_macro_args(context, &parsed_args, shape)
+}
+
+fn span_for_token_stream(token_stream: &TokenStream) -> Option<Span> {
+    token_stream.trees().next().map(|tt| tt.span())
+}
+
+// We should insert a space if the next token is a:
+#[derive(Copy, Clone, PartialEq)]
+enum SpaceState {
+    Never,
+    Punctuation,
+    Ident, // Or ident/literal-like thing.
+    Always,
+}
+
+fn force_space_before(tok: &TokenKind) -> bool {
+    debug!("tok: force_space_before {:?}", tok);
+
+    match tok {
+        TokenKind::Eq
+        | TokenKind::Lt
+        | TokenKind::Le
+        | TokenKind::EqEq
+        | TokenKind::Ne
+        | TokenKind::Ge
+        | TokenKind::Gt
+        | TokenKind::AndAnd
+        | TokenKind::OrOr
+        | TokenKind::Not
+        | TokenKind::Tilde
+        | TokenKind::BinOpEq(_)
+        | TokenKind::At
+        | TokenKind::RArrow
+        | TokenKind::LArrow
+        | TokenKind::FatArrow
+        | TokenKind::BinOp(_)
+        | TokenKind::Pound
+        | TokenKind::Dollar => true,
+        _ => false,
+    }
+}
+
+fn ident_like(tok: &Token) -> bool {
+    match tok.kind {
+        TokenKind::Ident(..) | TokenKind::Literal(..) | TokenKind::Lifetime(_) => true,
+        _ => false,
+    }
+}
+
+fn next_space(tok: &TokenKind) -> SpaceState {
+    debug!("next_space: {:?}", tok);
+
+    match tok {
+        TokenKind::Not
+        | TokenKind::BinOp(BinOpToken::And)
+        | TokenKind::Tilde
+        | TokenKind::At
+        | TokenKind::Comma
+        | TokenKind::Dot
+        | TokenKind::DotDot
+        | TokenKind::DotDotDot
+        | TokenKind::DotDotEq
+        | TokenKind::Question => SpaceState::Punctuation,
+
+        TokenKind::ModSep
+        | TokenKind::Pound
+        | TokenKind::Dollar
+        | TokenKind::OpenDelim(_)
+        | TokenKind::CloseDelim(_) => SpaceState::Never,
+
+        TokenKind::Literal(..) | TokenKind::Ident(..) | TokenKind::Lifetime(_) => SpaceState::Ident,
+
+        _ => SpaceState::Always,
+    }
+}
+
+/// Tries to convert a macro use into a short hand try expression. Returns `None`
+/// when the macro is not an instance of `try!` (or parsing the inner expression
+/// failed).
+pub(crate) fn convert_try_mac(
+    mac: &ast::MacCall,
+    context: &RewriteContext<'_>,
+) -> Option<ast::Expr> {
+    let path = &pprust::path_to_string(&mac.path);
+    if path == "try" || path == "r#try" {
+        let ts = mac.args.inner_tokens();
+        let mut parser = build_parser(context, ts.trees());
+
+        Some(ast::Expr {
+            id: ast::NodeId::root(), // dummy value
+            kind: ast::ExprKind::Try(parser.parse_expr().ok()?),
+            span: mac.span(), // incorrect span, but shouldn't matter too much
+            attrs: ast::AttrVec::new(),
+            tokens: None,
+        })
+    } else {
+        None
+    }
+}
+
+pub(crate) fn macro_style(mac: &ast::MacCall, context: &RewriteContext<'_>) -> DelimToken {
+    let snippet = context.snippet(mac.span());
+    let paren_pos = snippet.find_uncommented("(").unwrap_or(usize::max_value());
+    let bracket_pos = snippet.find_uncommented("[").unwrap_or(usize::max_value());
+    let brace_pos = snippet.find_uncommented("{").unwrap_or(usize::max_value());
+
+    if paren_pos < bracket_pos && paren_pos < brace_pos {
+        DelimToken::Paren
+    } else if bracket_pos < brace_pos {
+        DelimToken::Bracket
+    } else {
+        DelimToken::Brace
+    }
+}
+
+// A very simple parser that just parses a macros 2.0 definition into its branches.
+// Currently we do not attempt to parse any further than that.
+#[derive(new)]
+struct MacroParser {
+    toks: Cursor,
+}
+
+impl MacroParser {
+    // (`(` ... `)` `=>` `{` ... `}`)*
+    fn parse(&mut self) -> Option<Macro> {
+        let mut branches = vec![];
+        while self.toks.look_ahead(1).is_some() {
+            branches.push(self.parse_branch()?);
+        }
+
+        Some(Macro { branches })
+    }
+
+    // `(` ... `)` `=>` `{` ... `}`
+    fn parse_branch(&mut self) -> Option<MacroBranch> {
+        let tok = self.toks.next()?;
+        let (lo, args_paren_kind) = match tok {
+            TokenTree::Token(..) => return None,
+            TokenTree::Delimited(delimited_span, d, _) => (delimited_span.open.lo(), d),
+        };
+        let args = TokenStream::new(vec![(tok, Spacing::Joint)]);
+        match self.toks.next()? {
+            TokenTree::Token(Token {
+                kind: TokenKind::FatArrow,
+                ..
+            }) => {}
+            _ => return None,
+        }
+        let (mut hi, body, whole_body) = match self.toks.next()? {
+            TokenTree::Token(..) => return None,
+            TokenTree::Delimited(delimited_span, ..) => {
+                let data = delimited_span.entire().data();
+                (
+                    data.hi,
+                    Span::new(data.lo + BytePos(1), data.hi - BytePos(1), data.ctxt),
+                    delimited_span.entire(),
+                )
+            }
+        };
+        if let Some(TokenTree::Token(Token {
+            kind: TokenKind::Semi,
+            span,
+        })) = self.toks.look_ahead(0)
+        {
+            hi = span.hi();
+            self.toks.next();
+        }
+        Some(MacroBranch {
+            span: mk_sp(lo, hi),
+            args_paren_kind,
+            args,
+            body,
+            whole_body,
+        })
+    }
+}
+
+// A parsed macros 2.0 macro definition.
+struct Macro {
+    branches: Vec<MacroBranch>,
+}
+
+// FIXME: it would be more efficient to use references to the token streams
+// rather than clone them, if we can make the borrowing work out.
+struct MacroBranch {
+    span: Span,
+    args_paren_kind: DelimToken,
+    args: TokenStream,
+    body: Span,
+    whole_body: Span,
+}
+
+impl MacroBranch {
+    fn rewrite(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        multi_branch_style: bool,
+    ) -> Option<String> {
+        // Only attempt to format function-like macros.
+        if self.args_paren_kind != DelimToken::Paren {
+            // FIXME(#1539): implement for non-sugared macros.
+            return None;
+        }
+
+        // 5 = " => {"
+        let mut result = format_macro_args(context, self.args.clone(), shape.sub_width(5)?)?;
+
+        if multi_branch_style {
+            result += " =>";
+        }
+
+        if !context.config.format_macro_bodies() {
+            result += " ";
+            result += context.snippet(self.whole_body);
+            return Some(result);
+        }
+
+        // The macro body is the most interesting part. It might end up as various
+        // AST nodes, but also has special variables (e.g, `$foo`) which can't be
+        // parsed as regular Rust code (and note that these can be escaped using
+        // `$$`). We'll try and format like an AST node, but we'll substitute
+        // variables for new names with the same length first.
+
+        let old_body = context.snippet(self.body).trim();
+        let (body_str, substs) = replace_names(old_body)?;
+        let has_block_body = old_body.starts_with('{');
+
+        let mut config = context.config.clone();
+        config.set().hide_parse_errors(true);
+
+        result += " {";
+
+        let body_indent = if has_block_body {
+            shape.indent
+        } else {
+            shape.indent.block_indent(&config)
+        };
+        let new_width = config.max_width() - body_indent.width();
+        config.set().max_width(new_width);
+
+        // First try to format as items, then as statements.
+        let new_body_snippet = match crate::format_snippet(&body_str, &config, true) {
+            Some(new_body) => new_body,
+            None => {
+                let new_width = new_width + config.tab_spaces();
+                config.set().max_width(new_width);
+                match crate::format_code_block(&body_str, &config, true) {
+                    Some(new_body) => new_body,
+                    None => return None,
+                }
+            }
+        };
+        let new_body = wrap_str(
+            new_body_snippet.snippet.to_string(),
+            config.max_width(),
+            shape,
+        )?;
+
+        // Indent the body since it is in a block.
+        let indent_str = body_indent.to_string(&config);
+        let mut new_body = LineClasses::new(new_body.trim_end())
+            .enumerate()
+            .fold(
+                (String::new(), true),
+                |(mut s, need_indent), (i, (kind, ref l))| {
+                    if !is_empty_line(l)
+                        && need_indent
+                        && !new_body_snippet.is_line_non_formatted(i + 1)
+                    {
+                        s += &indent_str;
+                    }
+                    (s + l + "\n", indent_next_line(kind, &l, &config))
+                },
+            )
+            .0;
+
+        // Undo our replacement of macro variables.
+        // FIXME: this could be *much* more efficient.
+        for (old, new) in &substs {
+            if old_body.find(new).is_some() {
+                debug!("rewrite_macro_def: bailing matching variable: `{}`", new);
+                return None;
+            }
+            new_body = new_body.replace(new, old);
+        }
+
+        if has_block_body {
+            result += new_body.trim();
+        } else if !new_body.is_empty() {
+            result += "\n";
+            result += &new_body;
+            result += &shape.indent.to_string(&config);
+        }
+
+        result += "}";
+
+        Some(result)
+    }
+}
+
+/// Format `lazy_static!` from https://crates.io/crates/lazy_static.
+///
+/// # Expected syntax
+///
+/// ```text
+/// lazy_static! {
+///     [pub] static ref NAME_1: TYPE_1 = EXPR_1;
+///     [pub] static ref NAME_2: TYPE_2 = EXPR_2;
+///     ...
+///     [pub] static ref NAME_N: TYPE_N = EXPR_N;
+/// }
+/// ```
+fn format_lazy_static(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    ts: &TokenStream,
+) -> Option<String> {
+    let mut result = String::with_capacity(1024);
+    let mut parser = build_parser(context, ts.trees());
+    let nested_shape = shape
+        .block_indent(context.config.tab_spaces())
+        .with_max_width(context.config);
+
+    result.push_str("lazy_static! {");
+    result.push_str(&nested_shape.indent.to_string_with_newline(context.config));
+
+    macro_rules! parse_or {
+        ($method:ident $(,)* $($arg:expr),* $(,)*) => {
+            match parser.$method($($arg,)*) {
+                Ok(val) => {
+                    if parser.sess.span_diagnostic.has_errors() {
+                        parser.sess.span_diagnostic.reset_err_count();
+                        return None;
+                    } else {
+                        val
+                    }
+                }
+                Err(mut err) => {
+                    err.cancel();
+                    parser.sess.span_diagnostic.reset_err_count();
+                    return None;
+                }
+            }
+        }
+    }
+
+    while parser.token.kind != TokenKind::Eof {
+        // Parse a `lazy_static!` item.
+        let vis = crate::utils::format_visibility(
+            context,
+            &parse_or!(parse_visibility, rustc_parse::parser::FollowedByType::No),
+        );
+        parser.eat_keyword(kw::Static);
+        parser.eat_keyword(kw::Ref);
+        let id = parse_or!(parse_ident);
+        parser.eat(&TokenKind::Colon);
+        let ty = parse_or!(parse_ty);
+        parser.eat(&TokenKind::Eq);
+        let expr = parse_or!(parse_expr);
+        parser.eat(&TokenKind::Semi);
+
+        // Rewrite as a static item.
+        let mut stmt = String::with_capacity(128);
+        stmt.push_str(&format!(
+            "{}static ref {}: {} =",
+            vis,
+            id,
+            ty.rewrite(context, nested_shape)?
+        ));
+        result.push_str(&crate::expr::rewrite_assign_rhs(
+            context,
+            stmt,
+            &*expr,
+            nested_shape.sub_width(1)?,
+        )?);
+        result.push(';');
+        if parser.token.kind != TokenKind::Eof {
+            result.push_str(&nested_shape.indent.to_string_with_newline(context.config));
+        }
+    }
+
+    result.push_str(&shape.indent.to_string_with_newline(context.config));
+    result.push('}');
+
+    Some(result)
+}
+
+fn rewrite_macro_with_items(
+    context: &RewriteContext<'_>,
+    items: &[MacroArg],
+    macro_name: &str,
+    shape: Shape,
+    style: DelimToken,
+    position: MacroPosition,
+    span: Span,
+) -> Option<String> {
+    let (opener, closer) = match style {
+        DelimToken::Paren => ("(", ")"),
+        DelimToken::Bracket => ("[", "]"),
+        DelimToken::Brace => (" {", "}"),
+        _ => return None,
+    };
+    let trailing_semicolon = match style {
+        DelimToken::Paren | DelimToken::Bracket if position == MacroPosition::Item => ";",
+        _ => "",
+    };
+
+    let mut visitor = FmtVisitor::from_context(context);
+    visitor.block_indent = shape.indent.block_indent(context.config);
+    visitor.last_pos = context.snippet_provider.span_after(span, opener.trim());
+    for item in items {
+        let item = match item {
+            MacroArg::Item(item) => item,
+            _ => return None,
+        };
+        visitor.visit_item(&item);
+    }
+
+    let mut result = String::with_capacity(256);
+    result.push_str(&macro_name);
+    result.push_str(opener);
+    result.push_str(&visitor.block_indent.to_string_with_newline(context.config));
+    result.push_str(visitor.buffer.trim());
+    result.push_str(&shape.indent.to_string_with_newline(context.config));
+    result.push_str(closer);
+    result.push_str(trailing_semicolon);
+    Some(result)
+}
+
+const RUST_KW: [Symbol; 59] = [
+    kw::PathRoot,
+    kw::DollarCrate,
+    kw::Underscore,
+    kw::As,
+    kw::Box,
+    kw::Break,
+    kw::Const,
+    kw::Continue,
+    kw::Crate,
+    kw::Else,
+    kw::Enum,
+    kw::Extern,
+    kw::False,
+    kw::Fn,
+    kw::For,
+    kw::If,
+    kw::Impl,
+    kw::In,
+    kw::Let,
+    kw::Loop,
+    kw::Match,
+    kw::Mod,
+    kw::Move,
+    kw::Mut,
+    kw::Pub,
+    kw::Ref,
+    kw::Return,
+    kw::SelfLower,
+    kw::SelfUpper,
+    kw::Static,
+    kw::Struct,
+    kw::Super,
+    kw::Trait,
+    kw::True,
+    kw::Type,
+    kw::Unsafe,
+    kw::Use,
+    kw::Where,
+    kw::While,
+    kw::Abstract,
+    kw::Become,
+    kw::Do,
+    kw::Final,
+    kw::Macro,
+    kw::Override,
+    kw::Priv,
+    kw::Typeof,
+    kw::Unsized,
+    kw::Virtual,
+    kw::Yield,
+    kw::Dyn,
+    kw::Async,
+    kw::Try,
+    kw::UnderscoreLifetime,
+    kw::StaticLifetime,
+    kw::Auto,
+    kw::Catch,
+    kw::Default,
+    kw::Union,
+];
diff --git a/src/tools/rustfmt/src/matches.rs b/src/tools/rustfmt/src/matches.rs
new file mode 100644
index 0000000000000..f33fedce92da5
--- /dev/null
+++ b/src/tools/rustfmt/src/matches.rs
@@ -0,0 +1,596 @@
+//! Format match expression.
+
+use std::iter::repeat;
+
+use rustc_ast::{ast, ptr};
+use rustc_span::{BytePos, Span};
+
+use crate::comment::{combine_strs_with_missing_comments, rewrite_comment};
+use crate::config::lists::*;
+use crate::config::{Config, ControlBraceStyle, IndentStyle, MatchArmLeadingPipe, Version};
+use crate::expr::{
+    format_expr, is_empty_block, is_simple_block, is_unsafe_block, prefer_next_line, rewrite_cond,
+    ExprType, RhsTactics,
+};
+use crate::lists::{itemize_list, write_list, ListFormatting};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::spanned::Spanned;
+use crate::utils::{
+    contains_skip, extra_offset, first_line_width, inner_attributes, last_line_extendable, mk_sp,
+    mk_sp_lo_plus_one, semicolon_for_expr, trimmed_last_line_width, unicode_str_width,
+};
+
+/// A simple wrapper type against `ast::Arm`. Used inside `write_list()`.
+struct ArmWrapper<'a> {
+    arm: &'a ast::Arm,
+    /// `true` if the arm is the last one in match expression. Used to decide on whether we should
+    /// add trailing comma to the match arm when `config.trailing_comma() == Never`.
+    is_last: bool,
+    /// Holds a byte position of `|` at the beginning of the arm pattern, if available.
+    beginning_vert: Option<BytePos>,
+}
+
+impl<'a> ArmWrapper<'a> {
+    fn new(arm: &'a ast::Arm, is_last: bool, beginning_vert: Option<BytePos>) -> ArmWrapper<'a> {
+        ArmWrapper {
+            arm,
+            is_last,
+            beginning_vert,
+        }
+    }
+}
+
+impl<'a> Spanned for ArmWrapper<'a> {
+    fn span(&self) -> Span {
+        if let Some(lo) = self.beginning_vert {
+            let lo = std::cmp::min(lo, self.arm.span().lo());
+            mk_sp(lo, self.arm.span().hi())
+        } else {
+            self.arm.span()
+        }
+    }
+}
+
+impl<'a> Rewrite for ArmWrapper<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        rewrite_match_arm(
+            context,
+            self.arm,
+            shape,
+            self.is_last,
+            self.beginning_vert.is_some(),
+        )
+    }
+}
+
+pub(crate) fn rewrite_match(
+    context: &RewriteContext<'_>,
+    cond: &ast::Expr,
+    arms: &[ast::Arm],
+    shape: Shape,
+    span: Span,
+    attrs: &[ast::Attribute],
+) -> Option<String> {
+    // Do not take the rhs overhead from the upper expressions into account
+    // when rewriting match condition.
+    let cond_shape = Shape {
+        width: context.budget(shape.used_width()),
+        ..shape
+    };
+    // 6 = `match `
+    let cond_shape = match context.config.indent_style() {
+        IndentStyle::Visual => cond_shape.shrink_left(6)?,
+        IndentStyle::Block => cond_shape.offset_left(6)?,
+    };
+    let cond_str = cond.rewrite(context, cond_shape)?;
+    let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
+    let block_sep = match context.config.control_brace_style() {
+        ControlBraceStyle::AlwaysNextLine => alt_block_sep,
+        _ if last_line_extendable(&cond_str) => " ",
+        // 2 = ` {`
+        _ if cond_str.contains('\n') || cond_str.len() + 2 > cond_shape.width => alt_block_sep,
+        _ => " ",
+    };
+
+    let nested_indent_str = shape
+        .indent
+        .block_indent(context.config)
+        .to_string(context.config);
+    // Inner attributes.
+    let inner_attrs = &inner_attributes(attrs);
+    let inner_attrs_str = if inner_attrs.is_empty() {
+        String::new()
+    } else {
+        inner_attrs
+            .rewrite(context, shape)
+            .map(|s| format!("{}{}\n", nested_indent_str, s))?
+    };
+
+    let open_brace_pos = if inner_attrs.is_empty() {
+        let hi = if arms.is_empty() {
+            span.hi()
+        } else {
+            arms[0].span().lo()
+        };
+        context
+            .snippet_provider
+            .span_after(mk_sp(cond.span.hi(), hi), "{")
+    } else {
+        inner_attrs[inner_attrs.len() - 1].span.hi()
+    };
+
+    if arms.is_empty() {
+        let snippet = context.snippet(mk_sp(open_brace_pos, span.hi() - BytePos(1)));
+        if snippet.trim().is_empty() {
+            Some(format!("match {} {{}}", cond_str))
+        } else {
+            // Empty match with comments or inner attributes? We are not going to bother, sorry ;)
+            Some(context.snippet(span).to_owned())
+        }
+    } else {
+        let span_after_cond = mk_sp(cond.span.hi(), span.hi());
+        Some(format!(
+            "match {}{}{{\n{}{}{}\n{}}}",
+            cond_str,
+            block_sep,
+            inner_attrs_str,
+            nested_indent_str,
+            rewrite_match_arms(context, arms, shape, span_after_cond, open_brace_pos)?,
+            shape.indent.to_string(context.config),
+        ))
+    }
+}
+
+fn arm_comma(config: &Config, body: &ast::Expr, is_last: bool) -> &'static str {
+    if is_last && config.trailing_comma() == SeparatorTactic::Never {
+        ""
+    } else if config.match_block_trailing_comma() {
+        ","
+    } else if let ast::ExprKind::Block(ref block, _) = body.kind {
+        if let ast::BlockCheckMode::Default = block.rules {
+            ""
+        } else {
+            ","
+        }
+    } else {
+        ","
+    }
+}
+
+/// Collect a byte position of the beginning `|` for each arm, if available.
+fn collect_beginning_verts(
+    context: &RewriteContext<'_>,
+    arms: &[ast::Arm],
+) -> Vec<Option<BytePos>> {
+    arms.iter()
+        .map(|a| {
+            context
+                .snippet_provider
+                .opt_span_before(mk_sp_lo_plus_one(a.pat.span.lo()), "|")
+        })
+        .collect()
+}
+
+fn rewrite_match_arms(
+    context: &RewriteContext<'_>,
+    arms: &[ast::Arm],
+    shape: Shape,
+    span: Span,
+    open_brace_pos: BytePos,
+) -> Option<String> {
+    let arm_shape = shape
+        .block_indent(context.config.tab_spaces())
+        .with_max_width(context.config);
+
+    let arm_len = arms.len();
+    let is_last_iter = repeat(false)
+        .take(arm_len.saturating_sub(1))
+        .chain(repeat(true));
+    let beginning_verts = collect_beginning_verts(context, arms);
+    let items = itemize_list(
+        context.snippet_provider,
+        arms.iter()
+            .zip(is_last_iter)
+            .zip(beginning_verts.into_iter())
+            .map(|((arm, is_last), beginning_vert)| ArmWrapper::new(arm, is_last, beginning_vert)),
+        "}",
+        "|",
+        |arm| arm.span().lo(),
+        |arm| arm.span().hi(),
+        |arm| arm.rewrite(context, arm_shape),
+        open_brace_pos,
+        span.hi(),
+        false,
+    );
+    let arms_vec: Vec<_> = items.collect();
+    // We will add/remove commas inside `arm.rewrite()`, and hence no separator here.
+    let fmt = ListFormatting::new(arm_shape, context.config)
+        .separator("")
+        .preserve_newline(true);
+
+    write_list(&arms_vec, &fmt)
+}
+
+fn rewrite_match_arm(
+    context: &RewriteContext<'_>,
+    arm: &ast::Arm,
+    shape: Shape,
+    is_last: bool,
+    has_leading_pipe: bool,
+) -> Option<String> {
+    let (missing_span, attrs_str) = if !arm.attrs.is_empty() {
+        if contains_skip(&arm.attrs) {
+            let (_, body) = flatten_arm_body(context, &arm.body, None);
+            // `arm.span()` does not include trailing comma, add it manually.
+            return Some(format!(
+                "{}{}",
+                context.snippet(arm.span()),
+                arm_comma(context.config, body, is_last),
+            ));
+        }
+        let missing_span = mk_sp(arm.attrs[arm.attrs.len() - 1].span.hi(), arm.pat.span.lo());
+        (missing_span, arm.attrs.rewrite(context, shape)?)
+    } else {
+        (mk_sp(arm.span().lo(), arm.span().lo()), String::new())
+    };
+
+    // Leading pipe offset
+    // 2 = `| `
+    let (pipe_offset, pipe_str) = match context.config.match_arm_leading_pipes() {
+        MatchArmLeadingPipe::Never => (0, ""),
+        MatchArmLeadingPipe::Preserve if !has_leading_pipe => (0, ""),
+        MatchArmLeadingPipe::Preserve | MatchArmLeadingPipe::Always => (2, "| "),
+    };
+
+    // Patterns
+    // 5 = ` => {`
+    let pat_shape = shape.sub_width(5)?.offset_left(pipe_offset)?;
+    let pats_str = arm.pat.rewrite(context, pat_shape)?;
+
+    // Guard
+    let block_like_pat = trimmed_last_line_width(&pats_str) <= context.config.tab_spaces();
+    let new_line_guard = pats_str.contains('\n') && !block_like_pat;
+    let guard_str = rewrite_guard(
+        context,
+        &arm.guard,
+        shape,
+        trimmed_last_line_width(&pats_str),
+        new_line_guard,
+    )?;
+
+    let lhs_str = combine_strs_with_missing_comments(
+        context,
+        &attrs_str,
+        &format!("{}{}{}", pipe_str, pats_str, guard_str),
+        missing_span,
+        shape,
+        false,
+    )?;
+
+    let arrow_span = mk_sp(arm.pat.span.hi(), arm.body.span().lo());
+    rewrite_match_body(
+        context,
+        &arm.body,
+        &lhs_str,
+        shape,
+        guard_str.contains('\n'),
+        arrow_span,
+        is_last,
+    )
+}
+
+fn stmt_is_expr_mac(stmt: &ast::Stmt) -> bool {
+    if let ast::StmtKind::Expr(expr) = &stmt.kind {
+        if let ast::ExprKind::MacCall(_) = &expr.kind {
+            return true;
+        }
+    }
+    false
+}
+
+fn block_can_be_flattened<'a>(
+    context: &RewriteContext<'_>,
+    expr: &'a ast::Expr,
+) -> Option<&'a ast::Block> {
+    match expr.kind {
+        ast::ExprKind::Block(ref block, _)
+            if !is_unsafe_block(block)
+                && !context.inside_macro()
+                && is_simple_block(context, block, Some(&expr.attrs))
+                && !stmt_is_expr_mac(&block.stmts[0]) =>
+        {
+            Some(&*block)
+        }
+        _ => None,
+    }
+}
+
+// (extend, body)
+// @extend: true if the arm body can be put next to `=>`
+// @body: flattened body, if the body is block with a single expression
+fn flatten_arm_body<'a>(
+    context: &'a RewriteContext<'_>,
+    body: &'a ast::Expr,
+    opt_shape: Option<Shape>,
+) -> (bool, &'a ast::Expr) {
+    let can_extend =
+        |expr| !context.config.force_multiline_blocks() && can_flatten_block_around_this(expr);
+
+    if let Some(ref block) = block_can_be_flattened(context, body) {
+        if let ast::StmtKind::Expr(ref expr) = block.stmts[0].kind {
+            if let ast::ExprKind::Block(..) = expr.kind {
+                flatten_arm_body(context, expr, None)
+            } else {
+                let cond_becomes_muti_line = opt_shape
+                    .and_then(|shape| rewrite_cond(context, expr, shape))
+                    .map_or(false, |cond| cond.contains('\n'));
+                if cond_becomes_muti_line {
+                    (false, &*body)
+                } else {
+                    (can_extend(expr), &*expr)
+                }
+            }
+        } else {
+            (false, &*body)
+        }
+    } else {
+        (can_extend(body), &*body)
+    }
+}
+
+fn rewrite_match_body(
+    context: &RewriteContext<'_>,
+    body: &ptr::P<ast::Expr>,
+    pats_str: &str,
+    shape: Shape,
+    has_guard: bool,
+    arrow_span: Span,
+    is_last: bool,
+) -> Option<String> {
+    let (extend, body) = flatten_arm_body(
+        context,
+        body,
+        shape.offset_left(extra_offset(pats_str, shape) + 4),
+    );
+    let (is_block, is_empty_block) = if let ast::ExprKind::Block(ref block, _) = body.kind {
+        (true, is_empty_block(context, block, Some(&body.attrs)))
+    } else {
+        (false, false)
+    };
+
+    let comma = arm_comma(context.config, body, is_last);
+    let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
+
+    let combine_orig_body = |body_str: &str| {
+        let block_sep = match context.config.control_brace_style() {
+            ControlBraceStyle::AlwaysNextLine if is_block => alt_block_sep,
+            _ => " ",
+        };
+
+        Some(format!("{} =>{}{}{}", pats_str, block_sep, body_str, comma))
+    };
+
+    let next_line_indent = if !is_block || is_empty_block {
+        shape.indent.block_indent(context.config)
+    } else {
+        shape.indent
+    };
+
+    let forbid_same_line =
+        (has_guard && pats_str.contains('\n') && !is_empty_block) || !body.attrs.is_empty();
+
+    // Look for comments between `=>` and the start of the body.
+    let arrow_comment = {
+        let arrow_snippet = context.snippet(arrow_span).trim();
+        // search for the arrow starting from the end of the snippet since there may be a match
+        // expression within the guard
+        let arrow_index = arrow_snippet.rfind("=>").unwrap();
+        // 2 = `=>`
+        let comment_str = arrow_snippet[arrow_index + 2..].trim();
+        if comment_str.is_empty() {
+            String::new()
+        } else {
+            rewrite_comment(comment_str, false, shape, &context.config)?
+        }
+    };
+
+    let combine_next_line_body = |body_str: &str| {
+        let nested_indent_str = next_line_indent.to_string_with_newline(context.config);
+
+        if is_block {
+            let mut result = pats_str.to_owned();
+            result.push_str(" =>");
+            if !arrow_comment.is_empty() {
+                result.push_str(&nested_indent_str);
+                result.push_str(&arrow_comment);
+            }
+            result.push_str(&nested_indent_str);
+            result.push_str(&body_str);
+            return Some(result);
+        }
+
+        let indent_str = shape.indent.to_string_with_newline(context.config);
+        let (body_prefix, body_suffix) =
+            if context.config.match_arm_blocks() && !context.inside_macro() {
+                let comma = if context.config.match_block_trailing_comma() {
+                    ","
+                } else {
+                    ""
+                };
+                let semicolon = if context.config.version() == Version::One {
+                    ""
+                } else {
+                    if semicolon_for_expr(context, body) {
+                        ";"
+                    } else {
+                        ""
+                    }
+                };
+                ("{", format!("{}{}}}{}", semicolon, indent_str, comma))
+            } else {
+                ("", String::from(","))
+            };
+
+        let block_sep = match context.config.control_brace_style() {
+            ControlBraceStyle::AlwaysNextLine => format!("{}{}", alt_block_sep, body_prefix),
+            _ if body_prefix.is_empty() => "".to_owned(),
+            _ if forbid_same_line || !arrow_comment.is_empty() => {
+                format!("{}{}", alt_block_sep, body_prefix)
+            }
+            _ => format!(" {}", body_prefix),
+        } + &nested_indent_str;
+
+        let mut result = pats_str.to_owned();
+        result.push_str(" =>");
+        if !arrow_comment.is_empty() {
+            result.push_str(&indent_str);
+            result.push_str(&arrow_comment);
+        }
+        result.push_str(&block_sep);
+        result.push_str(&body_str);
+        result.push_str(&body_suffix);
+        Some(result)
+    };
+
+    // Let's try and get the arm body on the same line as the condition.
+    // 4 = ` => `.len()
+    let orig_body_shape = shape
+        .offset_left(extra_offset(pats_str, shape) + 4)
+        .and_then(|shape| shape.sub_width(comma.len()));
+    let orig_body = if forbid_same_line || !arrow_comment.is_empty() {
+        None
+    } else if let Some(body_shape) = orig_body_shape {
+        let rewrite = nop_block_collapse(
+            format_expr(body, ExprType::Statement, context, body_shape),
+            body_shape.width,
+        );
+
+        match rewrite {
+            Some(ref body_str)
+                if is_block
+                    || (!body_str.contains('\n')
+                        && unicode_str_width(body_str) <= body_shape.width) =>
+            {
+                return combine_orig_body(body_str);
+            }
+            _ => rewrite,
+        }
+    } else {
+        None
+    };
+    let orig_budget = orig_body_shape.map_or(0, |shape| shape.width);
+
+    // Try putting body on the next line and see if it looks better.
+    let next_line_body_shape = Shape::indented(next_line_indent, context.config);
+    let next_line_body = nop_block_collapse(
+        format_expr(body, ExprType::Statement, context, next_line_body_shape),
+        next_line_body_shape.width,
+    );
+    match (orig_body, next_line_body) {
+        (Some(ref orig_str), Some(ref next_line_str))
+            if prefer_next_line(orig_str, next_line_str, RhsTactics::Default) =>
+        {
+            combine_next_line_body(next_line_str)
+        }
+        (Some(ref orig_str), _) if extend && first_line_width(orig_str) <= orig_budget => {
+            combine_orig_body(orig_str)
+        }
+        (Some(ref orig_str), Some(ref next_line_str)) if orig_str.contains('\n') => {
+            combine_next_line_body(next_line_str)
+        }
+        (None, Some(ref next_line_str)) => combine_next_line_body(next_line_str),
+        (None, None) => None,
+        (Some(ref orig_str), _) => combine_orig_body(orig_str),
+    }
+}
+
+// The `if ...` guard on a match arm.
+fn rewrite_guard(
+    context: &RewriteContext<'_>,
+    guard: &Option<ptr::P<ast::Expr>>,
+    shape: Shape,
+    // The amount of space used up on this line for the pattern in
+    // the arm (excludes offset).
+    pattern_width: usize,
+    multiline_pattern: bool,
+) -> Option<String> {
+    if let Some(ref guard) = *guard {
+        // First try to fit the guard string on the same line as the pattern.
+        // 4 = ` if `, 5 = ` => {`
+        let cond_shape = shape
+            .offset_left(pattern_width + 4)
+            .and_then(|s| s.sub_width(5));
+        if !multiline_pattern {
+            if let Some(cond_shape) = cond_shape {
+                if let Some(cond_str) = guard.rewrite(context, cond_shape) {
+                    if !cond_str.contains('\n') || pattern_width <= context.config.tab_spaces() {
+                        return Some(format!(" if {}", cond_str));
+                    }
+                }
+            }
+        }
+
+        // Not enough space to put the guard after the pattern, try a newline.
+        // 3 = `if `, 5 = ` => {`
+        let cond_shape = Shape::indented(shape.indent.block_indent(context.config), context.config)
+            .offset_left(3)
+            .and_then(|s| s.sub_width(5));
+        if let Some(cond_shape) = cond_shape {
+            if let Some(cond_str) = guard.rewrite(context, cond_shape) {
+                return Some(format!(
+                    "{}if {}",
+                    cond_shape.indent.to_string_with_newline(context.config),
+                    cond_str
+                ));
+            }
+        }
+
+        None
+    } else {
+        Some(String::new())
+    }
+}
+
+fn nop_block_collapse(block_str: Option<String>, budget: usize) -> Option<String> {
+    debug!("nop_block_collapse {:?} {}", block_str, budget);
+    block_str.map(|block_str| {
+        if block_str.starts_with('{')
+            && budget >= 2
+            && (block_str[1..].find(|c: char| !c.is_whitespace()).unwrap() == block_str.len() - 2)
+        {
+            String::from("{}")
+        } else {
+            block_str
+        }
+    })
+}
+
+fn can_flatten_block_around_this(body: &ast::Expr) -> bool {
+    match body.kind {
+        // We do not allow `if` to stay on the same line, since we could easily mistake
+        // `pat => if cond { ... }` and `pat if cond => { ... }`.
+        ast::ExprKind::If(..) => false,
+        // We do not allow collapsing a block around expression with condition
+        // to avoid it being cluttered with match arm.
+        ast::ExprKind::ForLoop(..) | ast::ExprKind::While(..) => false,
+        ast::ExprKind::Loop(..)
+        | ast::ExprKind::Match(..)
+        | ast::ExprKind::Block(..)
+        | ast::ExprKind::Closure(..)
+        | ast::ExprKind::Array(..)
+        | ast::ExprKind::Call(..)
+        | ast::ExprKind::MethodCall(..)
+        | ast::ExprKind::MacCall(..)
+        | ast::ExprKind::Struct(..)
+        | ast::ExprKind::Tup(..) => true,
+        ast::ExprKind::AddrOf(_, _, ref expr)
+        | ast::ExprKind::Box(ref expr)
+        | ast::ExprKind::Try(ref expr)
+        | ast::ExprKind::Unary(_, ref expr)
+        | ast::ExprKind::Index(ref expr, _)
+        | ast::ExprKind::Cast(ref expr, _) => can_flatten_block_around_this(expr),
+        _ => false,
+    }
+}
diff --git a/src/tools/rustfmt/src/missed_spans.rs b/src/tools/rustfmt/src/missed_spans.rs
new file mode 100644
index 0000000000000..17b11ed6cf49c
--- /dev/null
+++ b/src/tools/rustfmt/src/missed_spans.rs
@@ -0,0 +1,361 @@
+use rustc_span::{BytePos, Pos, Span};
+
+use crate::comment::{is_last_comment_block, rewrite_comment, CodeCharKind, CommentCodeSlices};
+use crate::config::file_lines::FileLines;
+use crate::config::FileName;
+use crate::config::Version;
+use crate::coverage::transform_missing_snippet;
+use crate::shape::{Indent, Shape};
+use crate::source_map::LineRangeUtils;
+use crate::utils::{count_lf_crlf, count_newlines, last_line_width, mk_sp};
+use crate::visitor::FmtVisitor;
+
+struct SnippetStatus {
+    /// An offset to the current line from the beginning of the original snippet.
+    line_start: usize,
+    /// A length of trailing whitespaces on the current line.
+    last_wspace: Option<usize>,
+    /// The current line number.
+    cur_line: usize,
+}
+
+impl SnippetStatus {
+    fn new(cur_line: usize) -> Self {
+        SnippetStatus {
+            line_start: 0,
+            last_wspace: None,
+            cur_line,
+        }
+    }
+}
+
+impl<'a> FmtVisitor<'a> {
+    fn output_at_start(&self) -> bool {
+        self.buffer.is_empty()
+    }
+
+    pub(crate) fn format_missing(&mut self, end: BytePos) {
+        // HACK(topecongiro): we use `format_missing()` to extract a missing comment between
+        // a macro (or similar) and a trailing semicolon. Here we just try to avoid calling
+        // `format_missing_inner` in the common case where there is no such comment.
+        // This is a hack, ideally we should fix a possible bug in `format_missing_inner`
+        // or refactor `visit_mac` and `rewrite_macro`, but this should suffice to fix the
+        // issue (#2727).
+        let missing_snippet = self.snippet(mk_sp(self.last_pos, end));
+        if missing_snippet.trim() == ";" {
+            self.push_str(";");
+            self.last_pos = end;
+            return;
+        }
+        self.format_missing_inner(end, |this, last_snippet, _| this.push_str(last_snippet))
+    }
+
+    pub(crate) fn format_missing_with_indent(&mut self, end: BytePos) {
+        let config = self.config;
+        self.format_missing_inner(end, |this, last_snippet, snippet| {
+            this.push_str(last_snippet.trim_end());
+            if last_snippet == snippet && !this.output_at_start() {
+                // No new lines in the snippet.
+                this.push_str("\n");
+            }
+            let indent = this.block_indent.to_string(config);
+            this.push_str(&indent);
+        })
+    }
+
+    pub(crate) fn format_missing_no_indent(&mut self, end: BytePos) {
+        self.format_missing_inner(end, |this, last_snippet, _| {
+            this.push_str(last_snippet.trim_end());
+        })
+    }
+
+    fn format_missing_inner<F: Fn(&mut FmtVisitor<'_>, &str, &str)>(
+        &mut self,
+        end: BytePos,
+        process_last_snippet: F,
+    ) {
+        let start = self.last_pos;
+
+        if start == end {
+            // Do nothing if this is the beginning of the file.
+            if !self.output_at_start() {
+                process_last_snippet(self, "", "");
+            }
+            return;
+        }
+
+        assert!(
+            start < end,
+            "Request to format inverted span: {}",
+            self.parse_sess.span_to_debug_info(mk_sp(start, end)),
+        );
+
+        self.last_pos = end;
+        let span = mk_sp(start, end);
+        let snippet = self.snippet(span);
+
+        // Do nothing for spaces in the beginning of the file
+        if start == BytePos(0) && end.0 as usize == snippet.len() && snippet.trim().is_empty() {
+            return;
+        }
+
+        if snippet.trim().is_empty() && !out_of_file_lines_range!(self, span) {
+            // Keep vertical spaces within range.
+            self.push_vertical_spaces(count_newlines(snippet));
+            process_last_snippet(self, "", snippet);
+        } else {
+            self.write_snippet(span, &process_last_snippet);
+        }
+    }
+
+    fn push_vertical_spaces(&mut self, mut newline_count: usize) {
+        let offset = self.buffer.chars().rev().take_while(|c| *c == '\n').count();
+        let newline_upper_bound = self.config.blank_lines_upper_bound() + 1;
+        let newline_lower_bound = self.config.blank_lines_lower_bound() + 1;
+
+        if newline_count + offset > newline_upper_bound {
+            if offset >= newline_upper_bound {
+                newline_count = 0;
+            } else {
+                newline_count = newline_upper_bound - offset;
+            }
+        } else if newline_count + offset < newline_lower_bound {
+            if offset >= newline_lower_bound {
+                newline_count = 0;
+            } else {
+                newline_count = newline_lower_bound - offset;
+            }
+        }
+
+        let blank_lines = "\n".repeat(newline_count);
+        self.push_str(&blank_lines);
+    }
+
+    fn write_snippet<F>(&mut self, span: Span, process_last_snippet: F)
+    where
+        F: Fn(&mut FmtVisitor<'_>, &str, &str),
+    {
+        // Get a snippet from the file start to the span's hi without allocating.
+        // We need it to determine what precedes the current comment. If the comment
+        // follows code on the same line, we won't touch it.
+        let big_span_lo = self.snippet_provider.start_pos();
+        let big_snippet = self.snippet_provider.entire_snippet();
+        let big_diff = (span.lo() - big_span_lo).to_usize();
+
+        let snippet = self.snippet(span);
+
+        debug!("write_snippet `{}`", snippet);
+
+        self.write_snippet_inner(big_snippet, snippet, big_diff, span, process_last_snippet);
+    }
+
+    fn write_snippet_inner<F>(
+        &mut self,
+        big_snippet: &str,
+        old_snippet: &str,
+        big_diff: usize,
+        span: Span,
+        process_last_snippet: F,
+    ) where
+        F: Fn(&mut FmtVisitor<'_>, &str, &str),
+    {
+        // Trim whitespace from the right hand side of each line.
+        // Annoyingly, the library functions for splitting by lines etc. are not
+        // quite right, so we must do it ourselves.
+        let line = self.parse_sess.line_of_byte_pos(span.lo());
+        let file_name = &self.parse_sess.span_to_filename(span);
+        let mut status = SnippetStatus::new(line);
+
+        let snippet = &*transform_missing_snippet(self.config, old_snippet);
+
+        let slice_within_file_lines_range =
+            |file_lines: FileLines, cur_line, s| -> (usize, usize, bool) {
+                let (lf_count, crlf_count) = count_lf_crlf(s);
+                let newline_count = lf_count + crlf_count;
+                let within_file_lines_range = file_lines.contains_range(
+                    file_name,
+                    cur_line,
+                    // if a newline character is at the end of the slice, then the number of
+                    // newlines needs to be decreased by 1 so that the range checked against
+                    // the file_lines is the visual range one would expect.
+                    cur_line + newline_count - if s.ends_with('\n') { 1 } else { 0 },
+                );
+                (lf_count, crlf_count, within_file_lines_range)
+            };
+        for (kind, offset, subslice) in CommentCodeSlices::new(snippet) {
+            debug!("{:?}: {:?}", kind, subslice);
+
+            let (lf_count, crlf_count, within_file_lines_range) =
+                slice_within_file_lines_range(self.config.file_lines(), status.cur_line, subslice);
+            let newline_count = lf_count + crlf_count;
+            if CodeCharKind::Comment == kind && within_file_lines_range {
+                // 1: comment.
+                self.process_comment(
+                    &mut status,
+                    snippet,
+                    &big_snippet[..(offset + big_diff)],
+                    offset,
+                    subslice,
+                );
+            } else if subslice.trim().is_empty() && newline_count > 0 && within_file_lines_range {
+                // 2: blank lines.
+                self.push_vertical_spaces(newline_count);
+                status.cur_line += newline_count;
+                status.line_start = offset + lf_count + crlf_count * 2;
+            } else {
+                // 3: code which we failed to format or which is not within file-lines range.
+                self.process_missing_code(&mut status, snippet, subslice, offset, file_name);
+            }
+        }
+
+        let last_snippet = &snippet[status.line_start..];
+        let (_, _, within_file_lines_range) =
+            slice_within_file_lines_range(self.config.file_lines(), status.cur_line, last_snippet);
+        if within_file_lines_range {
+            process_last_snippet(self, last_snippet, snippet);
+        } else {
+            // just append what's left
+            self.push_str(last_snippet);
+        }
+    }
+
+    fn process_comment(
+        &mut self,
+        status: &mut SnippetStatus,
+        snippet: &str,
+        big_snippet: &str,
+        offset: usize,
+        subslice: &str,
+    ) {
+        let last_char = big_snippet
+            .chars()
+            .rev()
+            .skip_while(|rev_c| [' ', '\t'].contains(rev_c))
+            .next();
+
+        let fix_indent = last_char.map_or(true, |rev_c| ['{', '\n'].contains(&rev_c));
+        let mut on_same_line = false;
+
+        let comment_indent = if fix_indent {
+            if let Some('{') = last_char {
+                self.push_str("\n");
+            }
+            let indent_str = self.block_indent.to_string(self.config);
+            self.push_str(&indent_str);
+            self.block_indent
+        } else if self.config.version() == Version::Two && !snippet.starts_with('\n') {
+            // The comment appears on the same line as the previous formatted code.
+            // Assuming that comment is logically associated with that code, we want to keep it on
+            // the same level and avoid mixing it with possible other comment.
+            on_same_line = true;
+            self.push_str(" ");
+            self.block_indent
+        } else {
+            self.push_str(" ");
+            Indent::from_width(self.config, last_line_width(&self.buffer))
+        };
+
+        let comment_width = ::std::cmp::min(
+            self.config.comment_width(),
+            self.config.max_width() - self.block_indent.width(),
+        );
+        let comment_shape = Shape::legacy(comment_width, comment_indent);
+
+        if on_same_line {
+            match subslice.find("\n") {
+                None => {
+                    self.push_str(subslice);
+                }
+                Some(offset) if offset + 1 == subslice.len() => {
+                    self.push_str(&subslice[..offset]);
+                }
+                Some(offset) => {
+                    // keep first line as is: if it were too long and wrapped, it may get mixed
+                    // with the other lines.
+                    let first_line = &subslice[..offset];
+                    self.push_str(first_line);
+                    self.push_str(&comment_indent.to_string_with_newline(self.config));
+
+                    let other_lines = &subslice[offset + 1..];
+                    let comment_str =
+                        rewrite_comment(other_lines, false, comment_shape, self.config)
+                            .unwrap_or_else(|| String::from(other_lines));
+                    self.push_str(&comment_str);
+                }
+            }
+        } else {
+            let comment_str = rewrite_comment(subslice, false, comment_shape, self.config)
+                .unwrap_or_else(|| String::from(subslice));
+            self.push_str(&comment_str);
+        }
+
+        status.last_wspace = None;
+        status.line_start = offset + subslice.len();
+
+        // Add a newline:
+        // - if there isn't one already
+        // - otherwise, only if the last line is a line comment
+        if status.line_start <= snippet.len() {
+            match snippet[status.line_start..]
+                .chars()
+                // skip trailing whitespaces
+                .skip_while(|c| *c == ' ' || *c == '\t')
+                .next()
+            {
+                Some('\n') | Some('\r') => {
+                    if !is_last_comment_block(subslice) {
+                        self.push_str("\n");
+                    }
+                }
+                _ => self.push_str("\n"),
+            }
+        }
+
+        status.cur_line += count_newlines(subslice);
+    }
+
+    fn process_missing_code(
+        &mut self,
+        status: &mut SnippetStatus,
+        snippet: &str,
+        subslice: &str,
+        offset: usize,
+        file_name: &FileName,
+    ) {
+        for (mut i, c) in subslice.char_indices() {
+            i += offset;
+
+            if c == '\n' {
+                let skip_this_line = !self
+                    .config
+                    .file_lines()
+                    .contains_line(file_name, status.cur_line);
+                if skip_this_line {
+                    status.last_wspace = None;
+                }
+
+                if let Some(lw) = status.last_wspace {
+                    self.push_str(&snippet[status.line_start..lw]);
+                    self.push_str("\n");
+                    status.last_wspace = None;
+                } else {
+                    self.push_str(&snippet[status.line_start..=i]);
+                }
+
+                status.cur_line += 1;
+                status.line_start = i + 1;
+            } else if c.is_whitespace() && status.last_wspace.is_none() {
+                status.last_wspace = Some(i);
+            } else {
+                status.last_wspace = None;
+            }
+        }
+
+        let remaining = snippet[status.line_start..subslice.len() + offset].trim();
+        if !remaining.is_empty() {
+            self.push_str(&self.block_indent.to_string(self.config));
+            self.push_str(remaining);
+            status.line_start = subslice.len() + offset;
+        }
+    }
+}
diff --git a/src/tools/rustfmt/src/modules.rs b/src/tools/rustfmt/src/modules.rs
new file mode 100644
index 0000000000000..c3f4406860135
--- /dev/null
+++ b/src/tools/rustfmt/src/modules.rs
@@ -0,0 +1,552 @@
+use std::borrow::Cow;
+use std::collections::BTreeMap;
+use std::path::{Path, PathBuf};
+
+use rustc_ast::ast;
+use rustc_ast::visit::Visitor;
+use rustc_ast::AstLike;
+use rustc_span::symbol::{self, sym, Symbol};
+use rustc_span::Span;
+use thiserror::Error;
+
+use crate::attr::MetaVisitor;
+use crate::config::FileName;
+use crate::items::is_mod_decl;
+use crate::syntux::parser::{
+    Directory, DirectoryOwnership, ModError, ModulePathSuccess, Parser, ParserError,
+};
+use crate::syntux::session::ParseSess;
+use crate::utils::contains_skip;
+
+mod visitor;
+
+type FileModMap<'ast> = BTreeMap<FileName, Module<'ast>>;
+
+/// Represents module with its inner attributes.
+#[derive(Debug, Clone)]
+pub(crate) struct Module<'a> {
+    ast_mod_kind: Option<Cow<'a, ast::ModKind>>,
+    pub(crate) items: Cow<'a, Vec<rustc_ast::ptr::P<ast::Item>>>,
+    attrs: Cow<'a, Vec<ast::Attribute>>,
+    inner_attr: Vec<ast::Attribute>,
+    pub(crate) span: Span,
+}
+
+impl<'a> Module<'a> {
+    pub(crate) fn new(
+        mod_span: Span,
+        ast_mod_kind: Option<Cow<'a, ast::ModKind>>,
+        mod_items: Cow<'a, Vec<rustc_ast::ptr::P<ast::Item>>>,
+        mod_attrs: Cow<'a, Vec<ast::Attribute>>,
+    ) -> Self {
+        let inner_attr = mod_attrs
+            .iter()
+            .filter(|attr| attr.style == ast::AttrStyle::Inner)
+            .cloned()
+            .collect();
+        Module {
+            items: mod_items,
+            attrs: mod_attrs,
+            inner_attr,
+            span: mod_span,
+            ast_mod_kind,
+        }
+    }
+}
+
+impl<'a> AstLike for Module<'a> {
+    const SUPPORTS_CUSTOM_INNER_ATTRS: bool = true;
+    fn attrs(&self) -> &[ast::Attribute] {
+        &self.inner_attr
+    }
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<ast::Attribute>)) {
+        f(&mut self.inner_attr)
+    }
+    fn tokens_mut(&mut self) -> Option<&mut Option<rustc_ast::tokenstream::LazyTokenStream>> {
+        unimplemented!()
+    }
+}
+
+/// Maps each module to the corresponding file.
+pub(crate) struct ModResolver<'ast, 'sess> {
+    parse_sess: &'sess ParseSess,
+    directory: Directory,
+    file_map: FileModMap<'ast>,
+    recursive: bool,
+}
+
+/// Represents errors while trying to resolve modules.
+#[derive(Debug, Error)]
+#[error("failed to resolve mod `{module}`: {kind}")]
+pub struct ModuleResolutionError {
+    pub(crate) module: String,
+    pub(crate) kind: ModuleResolutionErrorKind,
+}
+
+#[derive(Debug, Error)]
+pub(crate) enum ModuleResolutionErrorKind {
+    /// Find a file that cannot be parsed.
+    #[error("cannot parse {file}")]
+    ParseError { file: PathBuf },
+    /// File cannot be found.
+    #[error("{file} does not exist")]
+    NotFound { file: PathBuf },
+}
+
+#[derive(Clone)]
+enum SubModKind<'a, 'ast> {
+    /// `mod foo;`
+    External(PathBuf, DirectoryOwnership, Module<'ast>),
+    /// `mod foo;` with multiple sources.
+    MultiExternal(Vec<(PathBuf, DirectoryOwnership, Module<'ast>)>),
+    /// `mod foo {}`
+    Internal(&'a ast::Item),
+}
+
+impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
+    /// Creates a new `ModResolver`.
+    pub(crate) fn new(
+        parse_sess: &'sess ParseSess,
+        directory_ownership: DirectoryOwnership,
+        recursive: bool,
+    ) -> Self {
+        ModResolver {
+            directory: Directory {
+                path: PathBuf::new(),
+                ownership: directory_ownership,
+            },
+            file_map: BTreeMap::new(),
+            parse_sess,
+            recursive,
+        }
+    }
+
+    /// Creates a map that maps a file name to the module in AST.
+    pub(crate) fn visit_crate(
+        mut self,
+        krate: &'ast ast::Crate,
+    ) -> Result<FileModMap<'ast>, ModuleResolutionError> {
+        let root_filename = self.parse_sess.span_to_filename(krate.span);
+        self.directory.path = match root_filename {
+            FileName::Real(ref p) => p.parent().unwrap_or(Path::new("")).to_path_buf(),
+            _ => PathBuf::new(),
+        };
+
+        // Skip visiting sub modules when the input is from stdin.
+        if self.recursive {
+            self.visit_mod_from_ast(&krate.items)?;
+        }
+
+        self.file_map.insert(
+            root_filename,
+            Module::new(
+                krate.span,
+                None,
+                Cow::Borrowed(&krate.items),
+                Cow::Borrowed(&krate.attrs),
+            ),
+        );
+        Ok(self.file_map)
+    }
+
+    /// Visit `cfg_if` macro and look for module declarations.
+    fn visit_cfg_if(&mut self, item: Cow<'ast, ast::Item>) -> Result<(), ModuleResolutionError> {
+        let mut visitor = visitor::CfgIfVisitor::new(self.parse_sess);
+        visitor.visit_item(&item);
+        for module_item in visitor.mods() {
+            if let ast::ItemKind::Mod(_, ref sub_mod_kind) = module_item.item.kind {
+                self.visit_sub_mod(
+                    &module_item.item,
+                    Module::new(
+                        module_item.item.span,
+                        Some(Cow::Owned(sub_mod_kind.clone())),
+                        Cow::Owned(vec![]),
+                        Cow::Owned(vec![]),
+                    ),
+                )?;
+            }
+        }
+        Ok(())
+    }
+
+    /// Visit modules defined inside macro calls.
+    fn visit_mod_outside_ast(
+        &mut self,
+        items: Vec<rustc_ast::ptr::P<ast::Item>>,
+    ) -> Result<(), ModuleResolutionError> {
+        for item in items {
+            if is_cfg_if(&item) {
+                self.visit_cfg_if(Cow::Owned(item.into_inner()))?;
+                continue;
+            }
+
+            if let ast::ItemKind::Mod(_, ref sub_mod_kind) = item.kind {
+                let span = item.span;
+                self.visit_sub_mod(
+                    &item,
+                    Module::new(
+                        span,
+                        Some(Cow::Owned(sub_mod_kind.clone())),
+                        Cow::Owned(vec![]),
+                        Cow::Owned(vec![]),
+                    ),
+                )?;
+            }
+        }
+        Ok(())
+    }
+
+    /// Visit modules from AST.
+    fn visit_mod_from_ast(
+        &mut self,
+        items: &'ast Vec<rustc_ast::ptr::P<ast::Item>>,
+    ) -> Result<(), ModuleResolutionError> {
+        for item in items {
+            if is_cfg_if(item) {
+                self.visit_cfg_if(Cow::Borrowed(item))?;
+            }
+
+            if let ast::ItemKind::Mod(_, ref sub_mod_kind) = item.kind {
+                let span = item.span;
+                self.visit_sub_mod(
+                    item,
+                    Module::new(
+                        span,
+                        Some(Cow::Borrowed(sub_mod_kind)),
+                        Cow::Owned(vec![]),
+                        Cow::Borrowed(&item.attrs),
+                    ),
+                )?;
+            }
+        }
+        Ok(())
+    }
+
+    fn visit_sub_mod(
+        &mut self,
+        item: &'c ast::Item,
+        sub_mod: Module<'ast>,
+    ) -> Result<(), ModuleResolutionError> {
+        let old_directory = self.directory.clone();
+        let sub_mod_kind = self.peek_sub_mod(item, &sub_mod)?;
+        if let Some(sub_mod_kind) = sub_mod_kind {
+            self.insert_sub_mod(sub_mod_kind.clone())?;
+            self.visit_sub_mod_inner(sub_mod, sub_mod_kind)?;
+        }
+        self.directory = old_directory;
+        Ok(())
+    }
+
+    /// Inspect the given sub-module which we are about to visit and returns its kind.
+    fn peek_sub_mod(
+        &self,
+        item: &'c ast::Item,
+        sub_mod: &Module<'ast>,
+    ) -> Result<Option<SubModKind<'c, 'ast>>, ModuleResolutionError> {
+        if contains_skip(&item.attrs) {
+            return Ok(None);
+        }
+
+        if is_mod_decl(item) {
+            // mod foo;
+            // Look for an extern file.
+            self.find_external_module(item.ident, &item.attrs, sub_mod)
+        } else {
+            // An internal module (`mod foo { /* ... */ }`);
+            Ok(Some(SubModKind::Internal(item)))
+        }
+    }
+
+    fn insert_sub_mod(
+        &mut self,
+        sub_mod_kind: SubModKind<'c, 'ast>,
+    ) -> Result<(), ModuleResolutionError> {
+        match sub_mod_kind {
+            SubModKind::External(mod_path, _, sub_mod) => {
+                self.file_map
+                    .entry(FileName::Real(mod_path))
+                    .or_insert(sub_mod);
+            }
+            SubModKind::MultiExternal(mods) => {
+                for (mod_path, _, sub_mod) in mods {
+                    self.file_map
+                        .entry(FileName::Real(mod_path))
+                        .or_insert(sub_mod);
+                }
+            }
+            _ => (),
+        }
+        Ok(())
+    }
+
+    fn visit_sub_mod_inner(
+        &mut self,
+        sub_mod: Module<'ast>,
+        sub_mod_kind: SubModKind<'c, 'ast>,
+    ) -> Result<(), ModuleResolutionError> {
+        match sub_mod_kind {
+            SubModKind::External(mod_path, directory_ownership, sub_mod) => {
+                let directory = Directory {
+                    path: mod_path.parent().unwrap().to_path_buf(),
+                    ownership: directory_ownership,
+                };
+                self.visit_sub_mod_after_directory_update(sub_mod, Some(directory))
+            }
+            SubModKind::Internal(ref item) => {
+                self.push_inline_mod_directory(item.ident, &item.attrs);
+                self.visit_sub_mod_after_directory_update(sub_mod, None)
+            }
+            SubModKind::MultiExternal(mods) => {
+                for (mod_path, directory_ownership, sub_mod) in mods {
+                    let directory = Directory {
+                        path: mod_path.parent().unwrap().to_path_buf(),
+                        ownership: directory_ownership,
+                    };
+                    self.visit_sub_mod_after_directory_update(sub_mod, Some(directory))?;
+                }
+                Ok(())
+            }
+        }
+    }
+
+    fn visit_sub_mod_after_directory_update(
+        &mut self,
+        sub_mod: Module<'ast>,
+        directory: Option<Directory>,
+    ) -> Result<(), ModuleResolutionError> {
+        if let Some(directory) = directory {
+            self.directory = directory;
+        }
+        match (sub_mod.ast_mod_kind, sub_mod.items) {
+            (Some(Cow::Borrowed(ast::ModKind::Loaded(items, ast::Inline::No, _))), _) => {
+                self.visit_mod_from_ast(&items)
+            }
+            (Some(Cow::Owned(..)), Cow::Owned(items)) => self.visit_mod_outside_ast(items),
+            (_, _) => Ok(()),
+        }
+    }
+
+    /// Find a file path in the filesystem which corresponds to the given module.
+    fn find_external_module(
+        &self,
+        mod_name: symbol::Ident,
+        attrs: &[ast::Attribute],
+        sub_mod: &Module<'ast>,
+    ) -> Result<Option<SubModKind<'c, 'ast>>, ModuleResolutionError> {
+        let relative = match self.directory.ownership {
+            DirectoryOwnership::Owned { relative } => relative,
+            DirectoryOwnership::UnownedViaBlock => None,
+        };
+        if let Some(path) = Parser::submod_path_from_attr(attrs, &self.directory.path) {
+            if self.parse_sess.is_file_parsed(&path) {
+                return Ok(None);
+            }
+            return match Parser::parse_file_as_module(self.parse_sess, &path, sub_mod.span) {
+                Ok((ref attrs, _, _)) if contains_skip(attrs) => Ok(None),
+                Ok((attrs, items, span)) => Ok(Some(SubModKind::External(
+                    path,
+                    DirectoryOwnership::Owned { relative: None },
+                    Module::new(
+                        span,
+                        Some(Cow::Owned(ast::ModKind::Unloaded)),
+                        Cow::Owned(items),
+                        Cow::Owned(attrs),
+                    ),
+                ))),
+                Err(ParserError::ParseError) => Err(ModuleResolutionError {
+                    module: mod_name.to_string(),
+                    kind: ModuleResolutionErrorKind::ParseError { file: path },
+                }),
+                Err(..) => Err(ModuleResolutionError {
+                    module: mod_name.to_string(),
+                    kind: ModuleResolutionErrorKind::NotFound { file: path },
+                }),
+            };
+        }
+
+        // Look for nested path, like `#[cfg_attr(feature = "foo", path = "bar.rs")]`.
+        let mut mods_outside_ast = self.find_mods_outside_of_ast(attrs, sub_mod);
+
+        match self
+            .parse_sess
+            .default_submod_path(mod_name, relative, &self.directory.path)
+        {
+            Ok(ModulePathSuccess {
+                file_path,
+                dir_ownership,
+                ..
+            }) => {
+                let outside_mods_empty = mods_outside_ast.is_empty();
+                let should_insert = !mods_outside_ast
+                    .iter()
+                    .any(|(outside_path, _, _)| outside_path == &file_path);
+                if self.parse_sess.is_file_parsed(&file_path) {
+                    if outside_mods_empty {
+                        return Ok(None);
+                    } else {
+                        if should_insert {
+                            mods_outside_ast.push((file_path, dir_ownership, sub_mod.clone()));
+                        }
+                        return Ok(Some(SubModKind::MultiExternal(mods_outside_ast)));
+                    }
+                }
+                match Parser::parse_file_as_module(self.parse_sess, &file_path, sub_mod.span) {
+                    Ok((ref attrs, _, _)) if contains_skip(attrs) => Ok(None),
+                    Ok((attrs, items, span)) if outside_mods_empty => {
+                        Ok(Some(SubModKind::External(
+                            file_path,
+                            dir_ownership,
+                            Module::new(
+                                span,
+                                Some(Cow::Owned(ast::ModKind::Unloaded)),
+                                Cow::Owned(items),
+                                Cow::Owned(attrs),
+                            ),
+                        )))
+                    }
+                    Ok((attrs, items, span)) => {
+                        mods_outside_ast.push((
+                            file_path.clone(),
+                            dir_ownership,
+                            Module::new(
+                                span,
+                                Some(Cow::Owned(ast::ModKind::Unloaded)),
+                                Cow::Owned(items),
+                                Cow::Owned(attrs),
+                            ),
+                        ));
+                        if should_insert {
+                            mods_outside_ast.push((file_path, dir_ownership, sub_mod.clone()));
+                        }
+                        Ok(Some(SubModKind::MultiExternal(mods_outside_ast)))
+                    }
+                    Err(ParserError::ParseError) => Err(ModuleResolutionError {
+                        module: mod_name.to_string(),
+                        kind: ModuleResolutionErrorKind::ParseError { file: file_path },
+                    }),
+                    Err(..) if outside_mods_empty => Err(ModuleResolutionError {
+                        module: mod_name.to_string(),
+                        kind: ModuleResolutionErrorKind::NotFound { file: file_path },
+                    }),
+                    Err(..) => {
+                        if should_insert {
+                            mods_outside_ast.push((file_path, dir_ownership, sub_mod.clone()));
+                        }
+                        Ok(Some(SubModKind::MultiExternal(mods_outside_ast)))
+                    }
+                }
+            }
+            Err(mod_err) if !mods_outside_ast.is_empty() => {
+                if let ModError::ParserError(mut e) = mod_err {
+                    e.cancel();
+                }
+                Ok(Some(SubModKind::MultiExternal(mods_outside_ast)))
+            }
+            Err(_) => Err(ModuleResolutionError {
+                module: mod_name.to_string(),
+                kind: ModuleResolutionErrorKind::NotFound {
+                    file: self.directory.path.clone(),
+                },
+            }),
+        }
+    }
+
+    fn push_inline_mod_directory(&mut self, id: symbol::Ident, attrs: &[ast::Attribute]) {
+        if let Some(path) = find_path_value(attrs) {
+            self.directory.path.push(&*path.as_str());
+            self.directory.ownership = DirectoryOwnership::Owned { relative: None };
+        } else {
+            // We have to push on the current module name in the case of relative
+            // paths in order to ensure that any additional module paths from inline
+            // `mod x { ... }` come after the relative extension.
+            //
+            // For example, a `mod z { ... }` inside `x/y.rs` should set the current
+            // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
+            if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
+                if let Some(ident) = relative.take() {
+                    // remove the relative offset
+                    self.directory.path.push(&*ident.as_str());
+                }
+            }
+            self.directory.path.push(&*id.as_str());
+        }
+    }
+
+    fn find_mods_outside_of_ast(
+        &self,
+        attrs: &[ast::Attribute],
+        sub_mod: &Module<'ast>,
+    ) -> Vec<(PathBuf, DirectoryOwnership, Module<'ast>)> {
+        // Filter nested path, like `#[cfg_attr(feature = "foo", path = "bar.rs")]`.
+        let mut path_visitor = visitor::PathVisitor::default();
+        for attr in attrs.iter() {
+            if let Some(meta) = attr.meta() {
+                path_visitor.visit_meta_item(&meta)
+            }
+        }
+        let mut result = vec![];
+        for path in path_visitor.paths() {
+            let mut actual_path = self.directory.path.clone();
+            actual_path.push(&path);
+            if !actual_path.exists() {
+                continue;
+            }
+            if self.parse_sess.is_file_parsed(&actual_path) {
+                // If the specified file is already parsed, then we just use that.
+                result.push((
+                    actual_path,
+                    DirectoryOwnership::Owned { relative: None },
+                    sub_mod.clone(),
+                ));
+                continue;
+            }
+            let (attrs, items, span) =
+                match Parser::parse_file_as_module(self.parse_sess, &actual_path, sub_mod.span) {
+                    Ok((ref attrs, _, _)) if contains_skip(attrs) => continue,
+                    Ok(m) => m,
+                    Err(..) => continue,
+                };
+
+            result.push((
+                actual_path,
+                DirectoryOwnership::Owned { relative: None },
+                Module::new(
+                    span,
+                    Some(Cow::Owned(ast::ModKind::Unloaded)),
+                    Cow::Owned(items),
+                    Cow::Owned(attrs),
+                ),
+            ))
+        }
+        result
+    }
+}
+
+fn path_value(attr: &ast::Attribute) -> Option<Symbol> {
+    if attr.has_name(sym::path) {
+        attr.value_str()
+    } else {
+        None
+    }
+}
+
+// N.B., even when there are multiple `#[path = ...]` attributes, we just need to
+// examine the first one, since rustc ignores the second and the subsequent ones
+// as unused attributes.
+fn find_path_value(attrs: &[ast::Attribute]) -> Option<Symbol> {
+    attrs.iter().flat_map(path_value).next()
+}
+
+fn is_cfg_if(item: &ast::Item) -> bool {
+    match item.kind {
+        ast::ItemKind::MacCall(ref mac) => {
+            if let Some(first_segment) = mac.path.segments.first() {
+                if first_segment.ident.name == Symbol::intern("cfg_if") {
+                    return true;
+                }
+            }
+            false
+        }
+        _ => false,
+    }
+}
diff --git a/src/tools/rustfmt/src/modules/visitor.rs b/src/tools/rustfmt/src/modules/visitor.rs
new file mode 100644
index 0000000000000..d5acf3f1cbcb4
--- /dev/null
+++ b/src/tools/rustfmt/src/modules/visitor.rs
@@ -0,0 +1,108 @@
+use rustc_ast::ast;
+use rustc_ast::visit::Visitor;
+use rustc_span::Symbol;
+
+use crate::attr::MetaVisitor;
+use crate::syntux::parser::Parser;
+use crate::syntux::session::ParseSess;
+
+pub(crate) struct ModItem {
+    pub(crate) item: ast::Item,
+}
+
+/// Traverse `cfg_if!` macro and fetch modules.
+pub(crate) struct CfgIfVisitor<'a> {
+    parse_sess: &'a ParseSess,
+    mods: Vec<ModItem>,
+}
+
+impl<'a> CfgIfVisitor<'a> {
+    pub(crate) fn new(parse_sess: &'a ParseSess) -> CfgIfVisitor<'a> {
+        CfgIfVisitor {
+            mods: vec![],
+            parse_sess,
+        }
+    }
+
+    pub(crate) fn mods(self) -> Vec<ModItem> {
+        self.mods
+    }
+}
+
+impl<'a, 'ast: 'a> Visitor<'ast> for CfgIfVisitor<'a> {
+    fn visit_mac_call(&mut self, mac: &'ast ast::MacCall) {
+        match self.visit_mac_inner(mac) {
+            Ok(()) => (),
+            Err(e) => debug!("{}", e),
+        }
+    }
+}
+
+impl<'a, 'ast: 'a> CfgIfVisitor<'a> {
+    fn visit_mac_inner(&mut self, mac: &'ast ast::MacCall) -> Result<(), &'static str> {
+        // Support both:
+        // ```
+        // extern crate cfg_if;
+        // cfg_if::cfg_if! {..}
+        // ```
+        // And:
+        // ```
+        // #[macro_use]
+        // extern crate cfg_if;
+        // cfg_if! {..}
+        // ```
+        match mac.path.segments.first() {
+            Some(first_segment) => {
+                if first_segment.ident.name != Symbol::intern("cfg_if") {
+                    return Err("Expected cfg_if");
+                }
+            }
+            None => {
+                return Err("Expected cfg_if");
+            }
+        };
+
+        let items = Parser::parse_cfg_if(self.parse_sess, mac)?;
+        self.mods
+            .append(&mut items.into_iter().map(|item| ModItem { item }).collect());
+
+        Ok(())
+    }
+}
+
+/// Extracts `path = "foo.rs"` from attributes.
+#[derive(Default)]
+pub(crate) struct PathVisitor {
+    /// A list of path defined in attributes.
+    paths: Vec<String>,
+}
+
+impl PathVisitor {
+    pub(crate) fn paths(self) -> Vec<String> {
+        self.paths
+    }
+}
+
+impl<'ast> MetaVisitor<'ast> for PathVisitor {
+    fn visit_meta_name_value(&mut self, meta_item: &'ast ast::MetaItem, lit: &'ast ast::Lit) {
+        if meta_item.has_name(Symbol::intern("path")) && lit.kind.is_str() {
+            self.paths.push(lit_to_str(lit));
+        }
+    }
+}
+
+#[cfg(not(windows))]
+fn lit_to_str(lit: &ast::Lit) -> String {
+    match lit.kind {
+        ast::LitKind::Str(symbol, ..) => symbol.to_string(),
+        _ => unreachable!(),
+    }
+}
+
+#[cfg(windows)]
+fn lit_to_str(lit: &ast::Lit) -> String {
+    match lit.kind {
+        ast::LitKind::Str(symbol, ..) => symbol.as_str().replace("/", "\\"),
+        _ => unreachable!(),
+    }
+}
diff --git a/src/tools/rustfmt/src/overflow.rs b/src/tools/rustfmt/src/overflow.rs
new file mode 100644
index 0000000000000..d670b0a41e818
--- /dev/null
+++ b/src/tools/rustfmt/src/overflow.rs
@@ -0,0 +1,786 @@
+//! Rewrite a list some items with overflow.
+
+use std::cmp::min;
+
+use itertools::Itertools;
+use rustc_ast::token::DelimToken;
+use rustc_ast::{ast, ptr};
+use rustc_span::Span;
+
+use crate::closures;
+use crate::config::lists::*;
+use crate::config::Version;
+use crate::expr::{
+    can_be_overflowed_expr, is_every_expr_simple, is_method_call, is_nested_call, is_simple_expr,
+    rewrite_cond,
+};
+use crate::lists::{
+    definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
+};
+use crate::macros::MacroArg;
+use crate::patterns::{can_be_overflowed_pat, TuplePatField};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::spanned::Spanned;
+use crate::types::{can_be_overflowed_type, SegmentParam};
+use crate::utils::{count_newlines, extra_offset, first_line_width, last_line_width, mk_sp};
+
+const SHORT_ITEM_THRESHOLD: usize = 10;
+
+/// A list of `format!`-like macros, that take a long format string and a list of arguments to
+/// format.
+///
+/// Organized as a list of `(&str, usize)` tuples, giving the name of the macro and the number of
+/// arguments before the format string (none for `format!("format", ...)`, one for `assert!(result,
+/// "format", ...)`, two for `assert_eq!(left, right, "format", ...)`).
+const SPECIAL_MACRO_WHITELIST: &[(&str, usize)] = &[
+    // format! like macros
+    // From the Rust Standard Library.
+    ("eprint!", 0),
+    ("eprintln!", 0),
+    ("format!", 0),
+    ("format_args!", 0),
+    ("print!", 0),
+    ("println!", 0),
+    ("panic!", 0),
+    ("unreachable!", 0),
+    // From the `log` crate.
+    ("debug!", 0),
+    ("error!", 0),
+    ("info!", 0),
+    ("warn!", 0),
+    // write! like macros
+    ("assert!", 1),
+    ("debug_assert!", 1),
+    ("write!", 1),
+    ("writeln!", 1),
+    // assert_eq! like macros
+    ("assert_eq!", 2),
+    ("assert_ne!", 2),
+    ("debug_assert_eq!", 2),
+    ("debug_assert_ne!", 2),
+];
+
+const SPECIAL_ATTR_WHITELIST: &[(&str, usize)] = &[
+    // From the `failure` crate.
+    ("fail", 0),
+];
+
+#[derive(Debug)]
+pub(crate) enum OverflowableItem<'a> {
+    Expr(&'a ast::Expr),
+    GenericParam(&'a ast::GenericParam),
+    MacroArg(&'a MacroArg),
+    NestedMetaItem(&'a ast::NestedMetaItem),
+    SegmentParam(&'a SegmentParam<'a>),
+    FieldDef(&'a ast::FieldDef),
+    TuplePatField(&'a TuplePatField<'a>),
+    Ty(&'a ast::Ty),
+}
+
+impl<'a> Rewrite for OverflowableItem<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        self.map(|item| item.rewrite(context, shape))
+    }
+}
+
+impl<'a> Spanned for OverflowableItem<'a> {
+    fn span(&self) -> Span {
+        self.map(|item| item.span())
+    }
+}
+
+impl<'a> OverflowableItem<'a> {
+    fn has_attrs(&self) -> bool {
+        match self {
+            OverflowableItem::Expr(ast::Expr { attrs, .. })
+            | OverflowableItem::GenericParam(ast::GenericParam { attrs, .. }) => !attrs.is_empty(),
+            OverflowableItem::FieldDef(ast::FieldDef { attrs, .. }) => !attrs.is_empty(),
+            OverflowableItem::MacroArg(MacroArg::Expr(expr)) => !expr.attrs.is_empty(),
+            OverflowableItem::MacroArg(MacroArg::Item(item)) => !item.attrs.is_empty(),
+            _ => false,
+        }
+    }
+
+    pub(crate) fn map<F, T>(&self, f: F) -> T
+    where
+        F: Fn(&dyn IntoOverflowableItem<'a>) -> T,
+    {
+        match self {
+            OverflowableItem::Expr(expr) => f(*expr),
+            OverflowableItem::GenericParam(gp) => f(*gp),
+            OverflowableItem::MacroArg(macro_arg) => f(*macro_arg),
+            OverflowableItem::NestedMetaItem(nmi) => f(*nmi),
+            OverflowableItem::SegmentParam(sp) => f(*sp),
+            OverflowableItem::FieldDef(sf) => f(*sf),
+            OverflowableItem::TuplePatField(pat) => f(*pat),
+            OverflowableItem::Ty(ty) => f(*ty),
+        }
+    }
+
+    pub(crate) fn is_simple(&self) -> bool {
+        match self {
+            OverflowableItem::Expr(expr) => is_simple_expr(expr),
+            OverflowableItem::MacroArg(MacroArg::Keyword(..)) => true,
+            OverflowableItem::MacroArg(MacroArg::Expr(expr)) => is_simple_expr(expr),
+            OverflowableItem::NestedMetaItem(nested_meta_item) => match nested_meta_item {
+                ast::NestedMetaItem::Literal(..) => true,
+                ast::NestedMetaItem::MetaItem(ref meta_item) => match meta_item.kind {
+                    ast::MetaItemKind::Word => true,
+                    _ => false,
+                },
+            },
+            _ => false,
+        }
+    }
+
+    pub(crate) fn is_expr(&self) -> bool {
+        match self {
+            OverflowableItem::Expr(..) => true,
+            OverflowableItem::MacroArg(MacroArg::Expr(..)) => true,
+            _ => false,
+        }
+    }
+
+    pub(crate) fn is_nested_call(&self) -> bool {
+        match self {
+            OverflowableItem::Expr(expr) => is_nested_call(expr),
+            OverflowableItem::MacroArg(MacroArg::Expr(expr)) => is_nested_call(expr),
+            _ => false,
+        }
+    }
+
+    pub(crate) fn to_expr(&self) -> Option<&'a ast::Expr> {
+        match self {
+            OverflowableItem::Expr(expr) => Some(expr),
+            OverflowableItem::MacroArg(macro_arg) => match macro_arg {
+                MacroArg::Expr(ref expr) => Some(expr),
+                _ => None,
+            },
+            _ => None,
+        }
+    }
+
+    pub(crate) fn can_be_overflowed(&self, context: &RewriteContext<'_>, len: usize) -> bool {
+        match self {
+            OverflowableItem::Expr(expr) => can_be_overflowed_expr(context, expr, len),
+            OverflowableItem::MacroArg(macro_arg) => match macro_arg {
+                MacroArg::Expr(ref expr) => can_be_overflowed_expr(context, expr, len),
+                MacroArg::Ty(ref ty) => can_be_overflowed_type(context, ty, len),
+                MacroArg::Pat(..) => false,
+                MacroArg::Item(..) => len == 1,
+                MacroArg::Keyword(..) => false,
+            },
+            OverflowableItem::NestedMetaItem(nested_meta_item) if len == 1 => {
+                match nested_meta_item {
+                    ast::NestedMetaItem::Literal(..) => false,
+                    ast::NestedMetaItem::MetaItem(..) => true,
+                }
+            }
+            OverflowableItem::SegmentParam(seg) => match seg {
+                SegmentParam::Type(ty) => can_be_overflowed_type(context, ty, len),
+                _ => false,
+            },
+            OverflowableItem::TuplePatField(pat) => can_be_overflowed_pat(context, pat, len),
+            OverflowableItem::Ty(ty) => can_be_overflowed_type(context, ty, len),
+            _ => false,
+        }
+    }
+
+    fn whitelist(&self) -> &'static [(&'static str, usize)] {
+        match self {
+            OverflowableItem::MacroArg(..) => SPECIAL_MACRO_WHITELIST,
+            OverflowableItem::NestedMetaItem(..) => SPECIAL_ATTR_WHITELIST,
+            _ => &[],
+        }
+    }
+}
+
+pub(crate) trait IntoOverflowableItem<'a>: Rewrite + Spanned {
+    fn into_overflowable_item(&'a self) -> OverflowableItem<'a>;
+}
+
+impl<'a, T: 'a + IntoOverflowableItem<'a>> IntoOverflowableItem<'a> for ptr::P<T> {
+    fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
+        (**self).into_overflowable_item()
+    }
+}
+
+macro_rules! impl_into_overflowable_item_for_ast_node {
+    ($($ast_node:ident),*) => {
+        $(
+            impl<'a> IntoOverflowableItem<'a> for ast::$ast_node {
+                fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
+                    OverflowableItem::$ast_node(self)
+                }
+            }
+        )*
+    }
+}
+
+macro_rules! impl_into_overflowable_item_for_rustfmt_types {
+    ([$($ty:ident),*], [$($ty_with_lifetime:ident),*]) => {
+        $(
+            impl<'a> IntoOverflowableItem<'a> for $ty {
+                fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
+                    OverflowableItem::$ty(self)
+                }
+            }
+        )*
+        $(
+            impl<'a> IntoOverflowableItem<'a> for $ty_with_lifetime<'a> {
+                fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
+                    OverflowableItem::$ty_with_lifetime(self)
+                }
+            }
+        )*
+    }
+}
+
+impl_into_overflowable_item_for_ast_node!(Expr, GenericParam, NestedMetaItem, FieldDef, Ty);
+impl_into_overflowable_item_for_rustfmt_types!([MacroArg], [SegmentParam, TuplePatField]);
+
+pub(crate) fn into_overflowable_list<'a, T>(
+    iter: impl Iterator<Item = &'a T>,
+) -> impl Iterator<Item = OverflowableItem<'a>>
+where
+    T: 'a + IntoOverflowableItem<'a>,
+{
+    iter.map(|x| IntoOverflowableItem::into_overflowable_item(x))
+}
+
+pub(crate) fn rewrite_with_parens<'a, T: 'a + IntoOverflowableItem<'a>>(
+    context: &'a RewriteContext<'_>,
+    ident: &'a str,
+    items: impl Iterator<Item = &'a T>,
+    shape: Shape,
+    span: Span,
+    item_max_width: usize,
+    force_separator_tactic: Option<SeparatorTactic>,
+) -> Option<String> {
+    Context::new(
+        context,
+        items,
+        ident,
+        shape,
+        span,
+        "(",
+        ")",
+        item_max_width,
+        force_separator_tactic,
+        None,
+    )
+    .rewrite(shape)
+}
+
+pub(crate) fn rewrite_with_angle_brackets<'a, T: 'a + IntoOverflowableItem<'a>>(
+    context: &'a RewriteContext<'_>,
+    ident: &'a str,
+    items: impl Iterator<Item = &'a T>,
+    shape: Shape,
+    span: Span,
+) -> Option<String> {
+    Context::new(
+        context,
+        items,
+        ident,
+        shape,
+        span,
+        "<",
+        ">",
+        context.config.max_width(),
+        None,
+        None,
+    )
+    .rewrite(shape)
+}
+
+pub(crate) fn rewrite_with_square_brackets<'a, T: 'a + IntoOverflowableItem<'a>>(
+    context: &'a RewriteContext<'_>,
+    name: &'a str,
+    items: impl Iterator<Item = &'a T>,
+    shape: Shape,
+    span: Span,
+    force_separator_tactic: Option<SeparatorTactic>,
+    delim_token: Option<DelimToken>,
+) -> Option<String> {
+    let (lhs, rhs) = match delim_token {
+        Some(DelimToken::Paren) => ("(", ")"),
+        Some(DelimToken::Brace) => ("{", "}"),
+        _ => ("[", "]"),
+    };
+    Context::new(
+        context,
+        items,
+        name,
+        shape,
+        span,
+        lhs,
+        rhs,
+        context.config.array_width(),
+        force_separator_tactic,
+        Some(("[", "]")),
+    )
+    .rewrite(shape)
+}
+
+struct Context<'a> {
+    context: &'a RewriteContext<'a>,
+    items: Vec<OverflowableItem<'a>>,
+    ident: &'a str,
+    prefix: &'static str,
+    suffix: &'static str,
+    one_line_shape: Shape,
+    nested_shape: Shape,
+    span: Span,
+    item_max_width: usize,
+    one_line_width: usize,
+    force_separator_tactic: Option<SeparatorTactic>,
+    custom_delims: Option<(&'a str, &'a str)>,
+}
+
+impl<'a> Context<'a> {
+    fn new<T: 'a + IntoOverflowableItem<'a>>(
+        context: &'a RewriteContext<'_>,
+        items: impl Iterator<Item = &'a T>,
+        ident: &'a str,
+        shape: Shape,
+        span: Span,
+        prefix: &'static str,
+        suffix: &'static str,
+        item_max_width: usize,
+        force_separator_tactic: Option<SeparatorTactic>,
+        custom_delims: Option<(&'a str, &'a str)>,
+    ) -> Context<'a> {
+        let used_width = extra_offset(ident, shape);
+        // 1 = `()`
+        let one_line_width = shape.width.saturating_sub(used_width + 2);
+
+        // 1 = "(" or ")"
+        let one_line_shape = shape
+            .offset_left(last_line_width(ident) + 1)
+            .and_then(|shape| shape.sub_width(1))
+            .unwrap_or(Shape { width: 0, ..shape });
+        let nested_shape = shape_from_indent_style(context, shape, used_width + 2, used_width + 1);
+        Context {
+            context,
+            items: into_overflowable_list(items).collect(),
+            ident,
+            one_line_shape,
+            nested_shape,
+            span,
+            prefix,
+            suffix,
+            item_max_width,
+            one_line_width,
+            force_separator_tactic,
+            custom_delims,
+        }
+    }
+
+    fn last_item(&self) -> Option<&OverflowableItem<'_>> {
+        self.items.last()
+    }
+
+    fn items_span(&self) -> Span {
+        let span_lo = self
+            .context
+            .snippet_provider
+            .span_after(self.span, self.prefix);
+        mk_sp(span_lo, self.span.hi())
+    }
+
+    fn rewrite_last_item_with_overflow(
+        &self,
+        last_list_item: &mut ListItem,
+        shape: Shape,
+    ) -> Option<String> {
+        let last_item = self.last_item()?;
+        let rewrite = match last_item {
+            OverflowableItem::Expr(ref expr) => {
+                match expr.kind {
+                    // When overflowing the closure which consists of a single control flow
+                    // expression, force to use block if its condition uses multi line.
+                    ast::ExprKind::Closure(..) => {
+                        // If the argument consists of multiple closures, we do not overflow
+                        // the last closure.
+                        if closures::args_have_many_closure(&self.items) {
+                            None
+                        } else {
+                            closures::rewrite_last_closure(self.context, expr, shape)
+                        }
+                    }
+
+                    // When overflowing the expressions which consists of a control flow
+                    // expression, avoid condition to use multi line.
+                    ast::ExprKind::If(..)
+                    | ast::ExprKind::ForLoop(..)
+                    | ast::ExprKind::Loop(..)
+                    | ast::ExprKind::While(..)
+                    | ast::ExprKind::Match(..) => {
+                        let multi_line = rewrite_cond(self.context, expr, shape)
+                            .map_or(false, |cond| cond.contains('\n'));
+
+                        if multi_line {
+                            None
+                        } else {
+                            expr.rewrite(self.context, shape)
+                        }
+                    }
+
+                    _ => expr.rewrite(self.context, shape),
+                }
+            }
+            item => item.rewrite(self.context, shape),
+        };
+
+        if let Some(rewrite) = rewrite {
+            // splitn(2, *).next().unwrap() is always safe.
+            let rewrite_first_line = Some(rewrite.splitn(2, '\n').next().unwrap().to_owned());
+            last_list_item.item = rewrite_first_line;
+            Some(rewrite)
+        } else {
+            None
+        }
+    }
+
+    fn default_tactic(&self, list_items: &[ListItem]) -> DefinitiveListTactic {
+        definitive_tactic(
+            list_items,
+            ListTactic::LimitedHorizontalVertical(self.item_max_width),
+            Separator::Comma,
+            self.one_line_width,
+        )
+    }
+
+    fn try_overflow_last_item(&self, list_items: &mut Vec<ListItem>) -> DefinitiveListTactic {
+        // 1 = "("
+        let combine_arg_with_callee = self.items.len() == 1
+            && self.items[0].is_expr()
+            && !self.items[0].has_attrs()
+            && self.ident.len() < self.context.config.tab_spaces();
+        let overflow_last = combine_arg_with_callee || can_be_overflowed(self.context, &self.items);
+
+        // Replace the last item with its first line to see if it fits with
+        // first arguments.
+        let placeholder = if overflow_last {
+            let old_value = self.context.force_one_line_chain.get();
+            match self.last_item() {
+                Some(OverflowableItem::Expr(expr))
+                    if !combine_arg_with_callee && is_method_call(expr) =>
+                {
+                    self.context.force_one_line_chain.replace(true);
+                }
+                Some(OverflowableItem::MacroArg(MacroArg::Expr(expr)))
+                    if !combine_arg_with_callee
+                        && is_method_call(expr)
+                        && self.context.config.version() == Version::Two =>
+                {
+                    self.context.force_one_line_chain.replace(true);
+                }
+                _ => (),
+            }
+            let result = last_item_shape(
+                &self.items,
+                list_items,
+                self.one_line_shape,
+                self.item_max_width,
+            )
+            .and_then(|arg_shape| {
+                self.rewrite_last_item_with_overflow(
+                    &mut list_items[self.items.len() - 1],
+                    arg_shape,
+                )
+            });
+            self.context.force_one_line_chain.replace(old_value);
+            result
+        } else {
+            None
+        };
+
+        let mut tactic = definitive_tactic(
+            &*list_items,
+            ListTactic::LimitedHorizontalVertical(self.item_max_width),
+            Separator::Comma,
+            self.one_line_width,
+        );
+
+        // Replace the stub with the full overflowing last argument if the rewrite
+        // succeeded and its first line fits with the other arguments.
+        match (overflow_last, tactic, placeholder) {
+            (true, DefinitiveListTactic::Horizontal, Some(ref overflowed))
+                if self.items.len() == 1 =>
+            {
+                // When we are rewriting a nested function call, we restrict the
+                // budget for the inner function to avoid them being deeply nested.
+                // However, when the inner function has a prefix or a suffix
+                // (e.g., `foo() as u32`), this budget reduction may produce poorly
+                // formatted code, where a prefix or a suffix being left on its own
+                // line. Here we explicitlly check those cases.
+                if count_newlines(overflowed) == 1 {
+                    let rw = self
+                        .items
+                        .last()
+                        .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
+                    let no_newline = rw.as_ref().map_or(false, |s| !s.contains('\n'));
+                    if no_newline {
+                        list_items[self.items.len() - 1].item = rw;
+                    } else {
+                        list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
+                    }
+                } else {
+                    list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
+                }
+            }
+            (true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => {
+                list_items[self.items.len() - 1].item = placeholder;
+            }
+            _ if !self.items.is_empty() => {
+                list_items[self.items.len() - 1].item = self
+                    .items
+                    .last()
+                    .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
+
+                // Use horizontal layout for a function with a single argument as long as
+                // everything fits in a single line.
+                // `self.one_line_width == 0` means vertical layout is forced.
+                if self.items.len() == 1
+                    && self.one_line_width != 0
+                    && !list_items[0].has_comment()
+                    && !list_items[0].inner_as_ref().contains('\n')
+                    && crate::lists::total_item_width(&list_items[0]) <= self.one_line_width
+                {
+                    tactic = DefinitiveListTactic::Horizontal;
+                } else {
+                    tactic = self.default_tactic(list_items);
+
+                    if tactic == DefinitiveListTactic::Vertical {
+                        if let Some((all_simple, num_args_before)) =
+                            maybe_get_args_offset(self.ident, &self.items)
+                        {
+                            let one_line = all_simple
+                                && definitive_tactic(
+                                    &list_items[..num_args_before],
+                                    ListTactic::HorizontalVertical,
+                                    Separator::Comma,
+                                    self.nested_shape.width,
+                                ) == DefinitiveListTactic::Horizontal
+                                && definitive_tactic(
+                                    &list_items[num_args_before + 1..],
+                                    ListTactic::HorizontalVertical,
+                                    Separator::Comma,
+                                    self.nested_shape.width,
+                                ) == DefinitiveListTactic::Horizontal;
+
+                            if one_line {
+                                tactic = DefinitiveListTactic::SpecialMacro(num_args_before);
+                            };
+                        } else if is_every_expr_simple(&self.items) && no_long_items(list_items) {
+                            tactic = DefinitiveListTactic::Mixed;
+                        }
+                    }
+                }
+            }
+            _ => (),
+        }
+
+        tactic
+    }
+
+    fn rewrite_items(&self) -> Option<(bool, String)> {
+        let span = self.items_span();
+        let items = itemize_list(
+            self.context.snippet_provider,
+            self.items.iter(),
+            self.suffix,
+            ",",
+            |item| item.span().lo(),
+            |item| item.span().hi(),
+            |item| item.rewrite(self.context, self.nested_shape),
+            span.lo(),
+            span.hi(),
+            true,
+        );
+        let mut list_items: Vec<_> = items.collect();
+
+        // Try letting the last argument overflow to the next line with block
+        // indentation. If its first line fits on one line with the other arguments,
+        // we format the function arguments horizontally.
+        let tactic = self.try_overflow_last_item(&mut list_items);
+        let trailing_separator = if let Some(tactic) = self.force_separator_tactic {
+            tactic
+        } else if !self.context.use_block_indent() {
+            SeparatorTactic::Never
+        } else {
+            self.context.config.trailing_comma()
+        };
+        let ends_with_newline = match tactic {
+            DefinitiveListTactic::Vertical | DefinitiveListTactic::Mixed => {
+                self.context.use_block_indent()
+            }
+            _ => false,
+        };
+
+        let fmt = ListFormatting::new(self.nested_shape, self.context.config)
+            .tactic(tactic)
+            .trailing_separator(trailing_separator)
+            .ends_with_newline(ends_with_newline);
+
+        write_list(&list_items, &fmt)
+            .map(|items_str| (tactic == DefinitiveListTactic::Horizontal, items_str))
+    }
+
+    fn wrap_items(&self, items_str: &str, shape: Shape, is_extendable: bool) -> String {
+        let shape = Shape {
+            width: shape.width.saturating_sub(last_line_width(self.ident)),
+            ..shape
+        };
+
+        let (prefix, suffix) = match self.custom_delims {
+            Some((lhs, rhs)) => (lhs, rhs),
+            _ => (self.prefix, self.suffix),
+        };
+
+        let extend_width = if items_str.is_empty() {
+            2
+        } else {
+            first_line_width(items_str) + 1
+        };
+        let nested_indent_str = self
+            .nested_shape
+            .indent
+            .to_string_with_newline(self.context.config);
+        let indent_str = shape
+            .block()
+            .indent
+            .to_string_with_newline(self.context.config);
+        let mut result = String::with_capacity(
+            self.ident.len() + items_str.len() + 2 + indent_str.len() + nested_indent_str.len(),
+        );
+        result.push_str(self.ident);
+        result.push_str(prefix);
+        let force_single_line = if self.context.config.version() == Version::Two {
+            !self.context.use_block_indent() || (is_extendable && extend_width <= shape.width)
+        } else {
+            // 2 = `()`
+            let fits_one_line = items_str.len() + 2 <= shape.width;
+            !self.context.use_block_indent()
+                || (self.context.inside_macro() && !items_str.contains('\n') && fits_one_line)
+                || (is_extendable && extend_width <= shape.width)
+        };
+        if force_single_line {
+            result.push_str(items_str);
+        } else {
+            if !items_str.is_empty() {
+                result.push_str(&nested_indent_str);
+                result.push_str(items_str);
+            }
+            result.push_str(&indent_str);
+        }
+        result.push_str(suffix);
+        result
+    }
+
+    fn rewrite(&self, shape: Shape) -> Option<String> {
+        let (extendable, items_str) = self.rewrite_items()?;
+
+        // If we are using visual indent style and failed to format, retry with block indent.
+        if !self.context.use_block_indent()
+            && need_block_indent(&items_str, self.nested_shape)
+            && !extendable
+        {
+            self.context.use_block.replace(true);
+            let result = self.rewrite(shape);
+            self.context.use_block.replace(false);
+            return result;
+        }
+
+        Some(self.wrap_items(&items_str, shape, extendable))
+    }
+}
+
+fn need_block_indent(s: &str, shape: Shape) -> bool {
+    s.lines().skip(1).any(|s| {
+        s.find(|c| !char::is_whitespace(c))
+            .map_or(false, |w| w + 1 < shape.indent.width())
+    })
+}
+
+fn can_be_overflowed(context: &RewriteContext<'_>, items: &[OverflowableItem<'_>]) -> bool {
+    items
+        .last()
+        .map_or(false, |x| x.can_be_overflowed(context, items.len()))
+}
+
+/// Returns a shape for the last argument which is going to be overflowed.
+fn last_item_shape(
+    lists: &[OverflowableItem<'_>],
+    items: &[ListItem],
+    shape: Shape,
+    args_max_width: usize,
+) -> Option<Shape> {
+    if items.len() == 1 && !lists.get(0)?.is_nested_call() {
+        return Some(shape);
+    }
+    let offset = items
+        .iter()
+        .dropping_back(1)
+        .map(|i| {
+            // 2 = ", "
+            2 + i.inner_as_ref().len()
+        })
+        .sum();
+    Shape {
+        width: min(args_max_width, shape.width),
+        ..shape
+    }
+    .offset_left(offset)
+}
+
+fn shape_from_indent_style(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    overhead: usize,
+    offset: usize,
+) -> Shape {
+    let (shape, overhead) = if context.use_block_indent() {
+        let shape = shape
+            .block()
+            .block_indent(context.config.tab_spaces())
+            .with_max_width(context.config);
+        (shape, 1) // 1 = ","
+    } else {
+        (shape.visual_indent(offset), overhead)
+    };
+    Shape {
+        width: shape.width.saturating_sub(overhead),
+        ..shape
+    }
+}
+
+fn no_long_items(list: &[ListItem]) -> bool {
+    list.iter()
+        .all(|item| item.inner_as_ref().len() <= SHORT_ITEM_THRESHOLD)
+}
+
+/// In case special-case style is required, returns an offset from which we start horizontal layout.
+pub(crate) fn maybe_get_args_offset(
+    callee_str: &str,
+    args: &[OverflowableItem<'_>],
+) -> Option<(bool, usize)> {
+    if let Some(&(_, num_args_before)) = args
+        .get(0)?
+        .whitelist()
+        .iter()
+        .find(|&&(s, _)| s == callee_str)
+    {
+        let all_simple = args.len() > num_args_before
+            && is_every_expr_simple(&args[0..num_args_before])
+            && is_every_expr_simple(&args[num_args_before + 1..]);
+
+        Some((all_simple, num_args_before))
+    } else {
+        None
+    }
+}
diff --git a/src/tools/rustfmt/src/pairs.rs b/src/tools/rustfmt/src/pairs.rs
new file mode 100644
index 0000000000000..0f3d5e8f878ba
--- /dev/null
+++ b/src/tools/rustfmt/src/pairs.rs
@@ -0,0 +1,318 @@
+use rustc_ast::ast;
+
+use crate::config::lists::*;
+use crate::config::IndentStyle;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::utils::{
+    first_line_width, is_single_line, last_line_width, trimmed_last_line_width, wrap_str,
+};
+
+/// Sigils that decorate a binop pair.
+#[derive(new, Clone, Copy)]
+pub(crate) struct PairParts<'a> {
+    prefix: &'a str,
+    infix: &'a str,
+    suffix: &'a str,
+}
+
+impl<'a> PairParts<'a> {
+    pub(crate) fn infix(infix: &'a str) -> PairParts<'a> {
+        PairParts {
+            prefix: "",
+            infix,
+            suffix: "",
+        }
+    }
+}
+
+// Flattens a tree of pairs into a list and tries to rewrite them all at once.
+// FIXME would be nice to reuse the lists API for this, but because each separator
+// can be different, we can't.
+pub(crate) fn rewrite_all_pairs(
+    expr: &ast::Expr,
+    shape: Shape,
+    context: &RewriteContext<'_>,
+) -> Option<String> {
+    expr.flatten(context, shape).and_then(|list| {
+        // First we try formatting on one line.
+        rewrite_pairs_one_line(&list, shape, context)
+            .or_else(|| rewrite_pairs_multiline(&list, shape, context))
+    })
+}
+
+// This may return a multi-line result since we allow the last expression to go
+// multiline in a 'single line' formatting.
+fn rewrite_pairs_one_line<T: Rewrite>(
+    list: &PairList<'_, '_, T>,
+    shape: Shape,
+    context: &RewriteContext<'_>,
+) -> Option<String> {
+    assert!(list.list.len() >= 2, "Not a pair?");
+
+    let mut result = String::new();
+    let base_shape = shape.block();
+
+    for ((_, rewrite), s) in list.list.iter().zip(list.separators.iter()) {
+        if let Some(rewrite) = rewrite {
+            if !is_single_line(&rewrite) || result.len() > shape.width {
+                return None;
+            }
+
+            result.push_str(&rewrite);
+            result.push(' ');
+            result.push_str(s);
+            result.push(' ');
+        } else {
+            return None;
+        }
+    }
+
+    let prefix_len = result.len();
+    let last = list.list.last()?.0;
+    let cur_shape = base_shape.offset_left(last_line_width(&result))?;
+    let last_rewrite = last.rewrite(context, cur_shape)?;
+    result.push_str(&last_rewrite);
+
+    if first_line_width(&result) > shape.width {
+        return None;
+    }
+
+    // Check the last expression in the list. We sometimes let this expression
+    // go over multiple lines, but we check for some ugly conditions.
+    if !(is_single_line(&result) || last_rewrite.starts_with('{'))
+        && (last_rewrite.starts_with('(') || prefix_len > context.config.tab_spaces())
+    {
+        return None;
+    }
+
+    wrap_str(result, context.config.max_width(), shape)
+}
+
+fn rewrite_pairs_multiline<T: Rewrite>(
+    list: &PairList<'_, '_, T>,
+    shape: Shape,
+    context: &RewriteContext<'_>,
+) -> Option<String> {
+    let rhs_offset = shape.rhs_overhead(&context.config);
+    let nested_shape = (match context.config.indent_style() {
+        IndentStyle::Visual => shape.visual_indent(0),
+        IndentStyle::Block => shape.block_indent(context.config.tab_spaces()),
+    })
+    .with_max_width(&context.config)
+    .sub_width(rhs_offset)?;
+
+    let indent_str = nested_shape.indent.to_string_with_newline(context.config);
+    let mut result = String::new();
+
+    result.push_str(&list.list[0].1.as_ref()?);
+
+    for ((e, default_rw), s) in list.list[1..].iter().zip(list.separators.iter()) {
+        // The following test checks if we should keep two subexprs on the same
+        // line. We do this if not doing so would create an orphan and there is
+        // enough space to do so.
+        let offset = if result.contains('\n') {
+            0
+        } else {
+            shape.used_width()
+        };
+        if last_line_width(&result) + offset <= nested_shape.used_width() {
+            // We must snuggle the next line onto the previous line to avoid an orphan.
+            if let Some(line_shape) =
+                shape.offset_left(s.len() + 2 + trimmed_last_line_width(&result))
+            {
+                if let Some(rewrite) = e.rewrite(context, line_shape) {
+                    result.push(' ');
+                    result.push_str(s);
+                    result.push(' ');
+                    result.push_str(&rewrite);
+                    continue;
+                }
+            }
+        }
+
+        match context.config.binop_separator() {
+            SeparatorPlace::Back => {
+                result.push(' ');
+                result.push_str(s);
+                result.push_str(&indent_str);
+            }
+            SeparatorPlace::Front => {
+                result.push_str(&indent_str);
+                result.push_str(s);
+                result.push(' ');
+            }
+        }
+
+        result.push_str(&default_rw.as_ref()?);
+    }
+    Some(result)
+}
+
+// Rewrites a single pair.
+pub(crate) fn rewrite_pair<LHS, RHS>(
+    lhs: &LHS,
+    rhs: &RHS,
+    pp: PairParts<'_>,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    separator_place: SeparatorPlace,
+) -> Option<String>
+where
+    LHS: Rewrite,
+    RHS: Rewrite,
+{
+    let tab_spaces = context.config.tab_spaces();
+    let lhs_overhead = match separator_place {
+        SeparatorPlace::Back => shape.used_width() + pp.prefix.len() + pp.infix.trim_end().len(),
+        SeparatorPlace::Front => shape.used_width(),
+    };
+    let lhs_shape = Shape {
+        width: context.budget(lhs_overhead),
+        ..shape
+    };
+    let lhs_result = lhs
+        .rewrite(context, lhs_shape)
+        .map(|lhs_str| format!("{}{}", pp.prefix, lhs_str))?;
+
+    // Try to put both lhs and rhs on the same line.
+    let rhs_orig_result = shape
+        .offset_left(last_line_width(&lhs_result) + pp.infix.len())
+        .and_then(|s| s.sub_width(pp.suffix.len()))
+        .and_then(|rhs_shape| rhs.rewrite(context, rhs_shape));
+    if let Some(ref rhs_result) = rhs_orig_result {
+        // If the length of the lhs is equal to or shorter than the tab width or
+        // the rhs looks like block expression, we put the rhs on the same
+        // line with the lhs even if the rhs is multi-lined.
+        let allow_same_line = lhs_result.len() <= tab_spaces
+            || rhs_result
+                .lines()
+                .next()
+                .map(|first_line| first_line.ends_with('{'))
+                .unwrap_or(false);
+        if !rhs_result.contains('\n') || allow_same_line {
+            let one_line_width = last_line_width(&lhs_result)
+                + pp.infix.len()
+                + first_line_width(rhs_result)
+                + pp.suffix.len();
+            if one_line_width <= shape.width {
+                return Some(format!(
+                    "{}{}{}{}",
+                    lhs_result, pp.infix, rhs_result, pp.suffix
+                ));
+            }
+        }
+    }
+
+    // We have to use multiple lines.
+    // Re-evaluate the rhs because we have more space now:
+    let mut rhs_shape = match context.config.indent_style() {
+        IndentStyle::Visual => shape
+            .sub_width(pp.suffix.len() + pp.prefix.len())?
+            .visual_indent(pp.prefix.len()),
+        IndentStyle::Block => {
+            // Try to calculate the initial constraint on the right hand side.
+            let rhs_overhead = shape.rhs_overhead(context.config);
+            Shape::indented(shape.indent.block_indent(context.config), context.config)
+                .sub_width(rhs_overhead)?
+        }
+    };
+    let infix = match separator_place {
+        SeparatorPlace::Back => pp.infix.trim_end(),
+        SeparatorPlace::Front => pp.infix.trim_start(),
+    };
+    if separator_place == SeparatorPlace::Front {
+        rhs_shape = rhs_shape.offset_left(infix.len())?;
+    }
+    let rhs_result = rhs.rewrite(context, rhs_shape)?;
+    let indent_str = rhs_shape.indent.to_string_with_newline(context.config);
+    let infix_with_sep = match separator_place {
+        SeparatorPlace::Back => format!("{}{}", infix, indent_str),
+        SeparatorPlace::Front => format!("{}{}", indent_str, infix),
+    };
+    Some(format!(
+        "{}{}{}{}",
+        lhs_result, infix_with_sep, rhs_result, pp.suffix
+    ))
+}
+
+// A pair which forms a tree and can be flattened (e.g., binops).
+trait FlattenPair: Rewrite + Sized {
+    fn flatten(&self, _: &RewriteContext<'_>, _: Shape) -> Option<PairList<'_, '_, Self>> {
+        None
+    }
+}
+
+struct PairList<'a, 'b, T: Rewrite> {
+    list: Vec<(&'b T, Option<String>)>,
+    separators: Vec<&'a str>,
+}
+
+impl FlattenPair for ast::Expr {
+    fn flatten(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+    ) -> Option<PairList<'_, '_, ast::Expr>> {
+        let top_op = match self.kind {
+            ast::ExprKind::Binary(op, _, _) => op.node,
+            _ => return None,
+        };
+
+        let default_rewrite = |node: &ast::Expr, sep: usize, is_first: bool| {
+            if is_first {
+                return node.rewrite(context, shape);
+            }
+            let nested_overhead = sep + 1;
+            let rhs_offset = shape.rhs_overhead(&context.config);
+            let nested_shape = (match context.config.indent_style() {
+                IndentStyle::Visual => shape.visual_indent(0),
+                IndentStyle::Block => shape.block_indent(context.config.tab_spaces()),
+            })
+            .with_max_width(&context.config)
+            .sub_width(rhs_offset)?;
+            let default_shape = match context.config.binop_separator() {
+                SeparatorPlace::Back => nested_shape.sub_width(nested_overhead)?,
+                SeparatorPlace::Front => nested_shape.offset_left(nested_overhead)?,
+            };
+            node.rewrite(context, default_shape)
+        };
+
+        // Turn a tree of binop expressions into a list using a depth-first,
+        // in-order traversal.
+        let mut stack = vec![];
+        let mut list = vec![];
+        let mut separators = vec![];
+        let mut node = self;
+        loop {
+            match node.kind {
+                ast::ExprKind::Binary(op, ref lhs, _) if op.node == top_op => {
+                    stack.push(node);
+                    node = lhs;
+                }
+                _ => {
+                    let op_len = separators.last().map_or(0, |s: &&str| s.len());
+                    let rw = default_rewrite(node, op_len, list.is_empty());
+                    list.push((node, rw));
+                    if let Some(pop) = stack.pop() {
+                        match pop.kind {
+                            ast::ExprKind::Binary(op, _, ref rhs) => {
+                                separators.push(op.node.to_string());
+                                node = rhs;
+                            }
+                            _ => unreachable!(),
+                        }
+                    } else {
+                        break;
+                    }
+                }
+            }
+        }
+
+        assert_eq!(list.len() - 1, separators.len());
+        Some(PairList { list, separators })
+    }
+}
+
+impl FlattenPair for ast::Ty {}
+impl FlattenPair for ast::Pat {}
diff --git a/src/tools/rustfmt/src/patterns.rs b/src/tools/rustfmt/src/patterns.rs
new file mode 100644
index 0000000000000..6824fc661ba72
--- /dev/null
+++ b/src/tools/rustfmt/src/patterns.rs
@@ -0,0 +1,525 @@
+use rustc_ast::ast::{self, BindingMode, Pat, PatField, PatKind, RangeEnd, RangeSyntax};
+use rustc_ast::ptr;
+use rustc_span::{BytePos, Span};
+
+use crate::comment::{combine_strs_with_missing_comments, FindUncommented};
+use crate::config::lists::*;
+use crate::expr::{can_be_overflowed_expr, rewrite_unary_prefix, wrap_struct_field};
+use crate::lists::{
+    definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
+    struct_lit_tactic, write_list, ListFormatting, ListItem, Separator,
+};
+use crate::macros::{rewrite_macro, MacroPosition};
+use crate::overflow;
+use crate::pairs::{rewrite_pair, PairParts};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::spanned::Spanned;
+use crate::types::{rewrite_path, PathContext};
+use crate::utils::{format_mutability, mk_sp, mk_sp_lo_plus_one, rewrite_ident};
+
+/// Returns `true` if the given pattern is "short".
+/// A short pattern is defined by the following grammar:
+///
+/// [small, ntp]:
+///     - single token
+///     - `&[single-line, ntp]`
+///
+/// [small]:
+///     - `[small, ntp]`
+///     - unary tuple constructor `([small, ntp])`
+///     - `&[small]`
+pub(crate) fn is_short_pattern(pat: &ast::Pat, pat_str: &str) -> bool {
+    // We also require that the pattern is reasonably 'small' with its literal width.
+    pat_str.len() <= 20 && !pat_str.contains('\n') && is_short_pattern_inner(pat)
+}
+
+fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
+    match pat.kind {
+        ast::PatKind::Rest | ast::PatKind::Wild | ast::PatKind::Lit(_) => true,
+        ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
+        ast::PatKind::Struct(..)
+        | ast::PatKind::MacCall(..)
+        | ast::PatKind::Slice(..)
+        | ast::PatKind::Path(..)
+        | ast::PatKind::Range(..) => false,
+        ast::PatKind::Tuple(ref subpats) => subpats.len() <= 1,
+        ast::PatKind::TupleStruct(ref path, ref subpats) => {
+            path.segments.len() <= 1 && subpats.len() <= 1
+        }
+        ast::PatKind::Box(ref p) | ast::PatKind::Ref(ref p, _) | ast::PatKind::Paren(ref p) => {
+            is_short_pattern_inner(&*p)
+        }
+        PatKind::Or(ref pats) => pats.iter().all(|p| is_short_pattern_inner(p)),
+    }
+}
+
+struct RangeOperand<'a>(&'a Option<ptr::P<ast::Expr>>);
+
+impl<'a> Rewrite for RangeOperand<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match &self.0 {
+            None => Some("".to_owned()),
+            Some(ref exp) => exp.rewrite(context, shape),
+        }
+    }
+}
+
+impl Rewrite for Pat {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match self.kind {
+            PatKind::Or(ref pats) => {
+                let pat_strs = pats
+                    .iter()
+                    .map(|p| p.rewrite(context, shape))
+                    .collect::<Option<Vec<_>>>()?;
+
+                let use_mixed_layout = pats
+                    .iter()
+                    .zip(pat_strs.iter())
+                    .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
+                let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
+                let tactic = if use_mixed_layout {
+                    DefinitiveListTactic::Mixed
+                } else {
+                    definitive_tactic(
+                        &items,
+                        ListTactic::HorizontalVertical,
+                        Separator::VerticalBar,
+                        shape.width,
+                    )
+                };
+                let fmt = ListFormatting::new(shape, context.config)
+                    .tactic(tactic)
+                    .separator(" |")
+                    .separator_place(context.config.binop_separator())
+                    .ends_with_newline(false);
+                write_list(&items, &fmt)
+            }
+            PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
+            PatKind::Ident(binding_mode, ident, ref sub_pat) => {
+                let (prefix, mutability) = match binding_mode {
+                    BindingMode::ByRef(mutability) => ("ref", mutability),
+                    BindingMode::ByValue(mutability) => ("", mutability),
+                };
+                let mut_infix = format_mutability(mutability).trim();
+                let id_str = rewrite_ident(context, ident);
+                let sub_pat = match *sub_pat {
+                    Some(ref p) => {
+                        // 2 - `@ `.
+                        let width = shape
+                            .width
+                            .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 2)?;
+                        let lo = context.snippet_provider.span_after(self.span, "@");
+                        combine_strs_with_missing_comments(
+                            context,
+                            "@",
+                            &p.rewrite(context, Shape::legacy(width, shape.indent))?,
+                            mk_sp(lo, p.span.lo()),
+                            shape,
+                            true,
+                        )?
+                    }
+                    None => "".to_owned(),
+                };
+
+                // combine prefix and mut
+                let (first_lo, first) = if !prefix.is_empty() && !mut_infix.is_empty() {
+                    let hi = context.snippet_provider.span_before(self.span, "mut");
+                    let lo = context.snippet_provider.span_after(self.span, "ref");
+                    (
+                        context.snippet_provider.span_after(self.span, "mut"),
+                        combine_strs_with_missing_comments(
+                            context,
+                            prefix,
+                            mut_infix,
+                            mk_sp(lo, hi),
+                            shape,
+                            true,
+                        )?,
+                    )
+                } else if !prefix.is_empty() {
+                    (
+                        context.snippet_provider.span_after(self.span, "ref"),
+                        prefix.to_owned(),
+                    )
+                } else if !mut_infix.is_empty() {
+                    (
+                        context.snippet_provider.span_after(self.span, "mut"),
+                        mut_infix.to_owned(),
+                    )
+                } else {
+                    (self.span.lo(), "".to_owned())
+                };
+
+                let next = if !sub_pat.is_empty() {
+                    let hi = context.snippet_provider.span_before(self.span, "@");
+                    combine_strs_with_missing_comments(
+                        context,
+                        id_str,
+                        &sub_pat,
+                        mk_sp(ident.span.hi(), hi),
+                        shape,
+                        true,
+                    )?
+                } else {
+                    id_str.to_owned()
+                };
+
+                combine_strs_with_missing_comments(
+                    context,
+                    &first,
+                    &next,
+                    mk_sp(first_lo, ident.span.lo()),
+                    shape,
+                    true,
+                )
+            }
+            PatKind::Wild => {
+                if 1 <= shape.width {
+                    Some("_".to_owned())
+                } else {
+                    None
+                }
+            }
+            PatKind::Rest => {
+                if 1 <= shape.width {
+                    Some("..".to_owned())
+                } else {
+                    None
+                }
+            }
+            PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
+                let infix = match end_kind.node {
+                    RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
+                    RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
+                    RangeEnd::Excluded => "..",
+                };
+                let infix = if context.config.spaces_around_ranges() {
+                    let lhs_spacing = match lhs {
+                        None => "",
+                        Some(_) => " ",
+                    };
+                    let rhs_spacing = match rhs {
+                        None => "",
+                        Some(_) => " ",
+                    };
+                    format!("{}{}{}", lhs_spacing, infix, rhs_spacing)
+                } else {
+                    infix.to_owned()
+                };
+                rewrite_pair(
+                    &RangeOperand(lhs),
+                    &RangeOperand(rhs),
+                    PairParts::infix(&infix),
+                    context,
+                    shape,
+                    SeparatorPlace::Front,
+                )
+            }
+            PatKind::Ref(ref pat, mutability) => {
+                let prefix = format!("&{}", format_mutability(mutability));
+                rewrite_unary_prefix(context, &prefix, &**pat, shape)
+            }
+            PatKind::Tuple(ref items) => rewrite_tuple_pat(items, None, self.span, context, shape),
+            PatKind::Path(ref q_self, ref path) => {
+                rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
+            }
+            PatKind::TupleStruct(ref path, ref pat_vec) => {
+                let path_str = rewrite_path(context, PathContext::Expr, None, path, shape)?;
+                rewrite_tuple_pat(pat_vec, Some(path_str), self.span, context, shape)
+            }
+            PatKind::Lit(ref expr) => expr.rewrite(context, shape),
+            PatKind::Slice(ref slice_pat) => {
+                let rw: Vec<String> = slice_pat
+                    .iter()
+                    .map(|p| {
+                        if let Some(rw) = p.rewrite(context, shape) {
+                            rw
+                        } else {
+                            format!("{}", context.snippet(p.span))
+                        }
+                    })
+                    .collect();
+                Some(format!("[{}]", rw.join(", ")))
+            }
+            PatKind::Struct(ref path, ref fields, ellipsis) => {
+                rewrite_struct_pat(path, fields, ellipsis, self.span, context, shape)
+            }
+            PatKind::MacCall(ref mac) => {
+                rewrite_macro(mac, None, context, shape, MacroPosition::Pat)
+            }
+            PatKind::Paren(ref pat) => pat
+                .rewrite(context, shape.offset_left(1)?.sub_width(1)?)
+                .map(|inner_pat| format!("({})", inner_pat)),
+        }
+    }
+}
+
+fn rewrite_struct_pat(
+    path: &ast::Path,
+    fields: &[ast::PatField],
+    ellipsis: bool,
+    span: Span,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    // 2 =  ` {`
+    let path_shape = shape.sub_width(2)?;
+    let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
+
+    if fields.is_empty() && !ellipsis {
+        return Some(format!("{} {{}}", path_str));
+    }
+
+    let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
+
+    // 3 = ` { `, 2 = ` }`.
+    let (h_shape, v_shape) =
+        struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
+
+    let items = itemize_list(
+        context.snippet_provider,
+        fields.iter(),
+        terminator,
+        ",",
+        |f| {
+            if f.attrs.is_empty() {
+                f.span.lo()
+            } else {
+                f.attrs.first().unwrap().span.lo()
+            }
+        },
+        |f| f.span.hi(),
+        |f| f.rewrite(context, v_shape),
+        context.snippet_provider.span_after(span, "{"),
+        span.hi(),
+        false,
+    );
+    let item_vec = items.collect::<Vec<_>>();
+
+    let tactic = struct_lit_tactic(h_shape, context, &item_vec);
+    let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
+    let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
+
+    let mut fields_str = write_list(&item_vec, &fmt)?;
+    let one_line_width = h_shape.map_or(0, |shape| shape.width);
+
+    if ellipsis {
+        if fields_str.contains('\n') || fields_str.len() > one_line_width {
+            // Add a missing trailing comma.
+            if context.config.trailing_comma() == SeparatorTactic::Never {
+                fields_str.push_str(",");
+            }
+            fields_str.push_str("\n");
+            fields_str.push_str(&nested_shape.indent.to_string(context.config));
+            fields_str.push_str("..");
+        } else {
+            if !fields_str.is_empty() {
+                // there are preceding struct fields being matched on
+                if tactic == DefinitiveListTactic::Vertical {
+                    // if the tactic is Vertical, write_list already added a trailing ,
+                    fields_str.push_str(" ");
+                } else {
+                    fields_str.push_str(", ");
+                }
+            }
+            fields_str.push_str("..");
+        }
+    }
+
+    // ast::Pat doesn't have attrs so use &[]
+    let fields_str = wrap_struct_field(context, &[], &fields_str, shape, v_shape, one_line_width)?;
+    Some(format!("{} {{{}}}", path_str, fields_str))
+}
+
+impl Rewrite for PatField {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let hi_pos = if let Some(last) = self.attrs.last() {
+            last.span.hi()
+        } else {
+            self.pat.span.lo()
+        };
+
+        let attrs_str = if self.attrs.is_empty() {
+            String::from("")
+        } else {
+            self.attrs.rewrite(context, shape)?
+        };
+
+        let pat_str = self.pat.rewrite(context, shape)?;
+        if self.is_shorthand {
+            combine_strs_with_missing_comments(
+                context,
+                &attrs_str,
+                &pat_str,
+                mk_sp(hi_pos, self.pat.span.lo()),
+                shape,
+                false,
+            )
+        } else {
+            let nested_shape = shape.block_indent(context.config.tab_spaces());
+            let id_str = rewrite_ident(context, self.ident);
+            let one_line_width = id_str.len() + 2 + pat_str.len();
+            let pat_and_id_str = if one_line_width <= shape.width {
+                format!("{}: {}", id_str, pat_str)
+            } else {
+                format!(
+                    "{}:\n{}{}",
+                    id_str,
+                    nested_shape.indent.to_string(context.config),
+                    self.pat.rewrite(context, nested_shape)?
+                )
+            };
+            combine_strs_with_missing_comments(
+                context,
+                &attrs_str,
+                &pat_and_id_str,
+                mk_sp(hi_pos, self.pat.span.lo()),
+                nested_shape,
+                false,
+            )
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) enum TuplePatField<'a> {
+    Pat(&'a ptr::P<ast::Pat>),
+    Dotdot(Span),
+}
+
+impl<'a> Rewrite for TuplePatField<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match *self {
+            TuplePatField::Pat(p) => p.rewrite(context, shape),
+            TuplePatField::Dotdot(_) => Some("..".to_string()),
+        }
+    }
+}
+
+impl<'a> Spanned for TuplePatField<'a> {
+    fn span(&self) -> Span {
+        match *self {
+            TuplePatField::Pat(p) => p.span(),
+            TuplePatField::Dotdot(span) => span,
+        }
+    }
+}
+
+impl<'a> TuplePatField<'a> {
+    fn is_dotdot(&self) -> bool {
+        match self {
+            TuplePatField::Pat(pat) => match pat.kind {
+                ast::PatKind::Rest => true,
+                _ => false,
+            },
+            TuplePatField::Dotdot(_) => true,
+        }
+    }
+}
+
+pub(crate) fn can_be_overflowed_pat(
+    context: &RewriteContext<'_>,
+    pat: &TuplePatField<'_>,
+    len: usize,
+) -> bool {
+    match *pat {
+        TuplePatField::Pat(pat) => match pat.kind {
+            ast::PatKind::Path(..)
+            | ast::PatKind::Tuple(..)
+            | ast::PatKind::Struct(..)
+            | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
+            ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
+                can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
+            }
+            ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
+            _ => false,
+        },
+        TuplePatField::Dotdot(..) => false,
+    }
+}
+
+fn rewrite_tuple_pat(
+    pats: &[ptr::P<ast::Pat>],
+    path_str: Option<String>,
+    span: Span,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    let mut pat_vec: Vec<_> = pats.iter().map(|x| TuplePatField::Pat(x)).collect();
+
+    if pat_vec.is_empty() {
+        return Some(format!("{}()", path_str.unwrap_or_default()));
+    }
+    let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
+    let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
+    {
+        let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
+        let sp = pat_vec[new_item_count - 1].span();
+        let snippet = context.snippet(sp);
+        let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
+        pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp_lo_plus_one(lo));
+        (
+            &pat_vec[..new_item_count],
+            mk_sp(span.lo(), lo + BytePos(1)),
+        )
+    } else {
+        (&pat_vec[..], span)
+    };
+
+    let is_last_pat_dotdot = pat_vec.last().map_or(false, |p| p.is_dotdot());
+    let add_comma = path_str.is_none() && pat_vec.len() == 1 && !is_last_pat_dotdot;
+    let path_str = path_str.unwrap_or_default();
+
+    overflow::rewrite_with_parens(
+        &context,
+        &path_str,
+        pat_vec.iter(),
+        shape,
+        span,
+        context.config.max_width(),
+        if add_comma {
+            Some(SeparatorTactic::Always)
+        } else {
+            None
+        },
+    )
+}
+
+fn count_wildcard_suffix_len(
+    context: &RewriteContext<'_>,
+    patterns: &[TuplePatField<'_>],
+    span: Span,
+    shape: Shape,
+) -> usize {
+    let mut suffix_len = 0;
+
+    let items: Vec<_> = itemize_list(
+        context.snippet_provider,
+        patterns.iter(),
+        ")",
+        ",",
+        |item| item.span().lo(),
+        |item| item.span().hi(),
+        |item| item.rewrite(context, shape),
+        context.snippet_provider.span_after(span, "("),
+        span.hi() - BytePos(1),
+        false,
+    )
+    .collect();
+
+    for item in items.iter().rev().take_while(|i| match i.item {
+        Some(ref internal_string) if internal_string == "_" => true,
+        _ => false,
+    }) {
+        suffix_len += 1;
+
+        if item.has_comment() {
+            break;
+        }
+    }
+
+    suffix_len
+}
diff --git a/src/tools/rustfmt/src/release_channel.rs b/src/tools/rustfmt/src/release_channel.rs
new file mode 100644
index 0000000000000..948247b3c9700
--- /dev/null
+++ b/src/tools/rustfmt/src/release_channel.rs
@@ -0,0 +1,16 @@
+/// Checks if we're in a nightly build.
+///
+/// The environment variable `CFG_RELEASE_CHANNEL` is set during the rustc bootstrap
+/// to "stable", "beta", or "nightly" depending on what toolchain is being built.
+/// If we are being built as part of the stable or beta toolchains, we want
+/// to disable unstable configuration options.
+///
+/// If we're being built by cargo (e.g., `cargo +nightly install rustfmt-nightly`),
+/// `CFG_RELEASE_CHANNEL` is not set. As we only support being built against the
+/// nightly compiler when installed from crates.io, default to nightly mode.
+#[macro_export]
+macro_rules! is_nightly_channel {
+    () => {
+        option_env!("CFG_RELEASE_CHANNEL").map_or(true, |c| c == "nightly" || c == "dev")
+    };
+}
diff --git a/src/tools/rustfmt/src/reorder.rs b/src/tools/rustfmt/src/reorder.rs
new file mode 100644
index 0000000000000..ac65ff2c1086e
--- /dev/null
+++ b/src/tools/rustfmt/src/reorder.rs
@@ -0,0 +1,332 @@
+//! Reorder items.
+//!
+//! `mod`, `extern crate` and `use` declarations are reordered in alphabetical
+//! order. Trait items are reordered in pre-determined order (associated types
+//! and constants comes before methods).
+
+// FIXME(#2455): Reorder trait items.
+
+use std::cmp::{Ord, Ordering};
+
+use rustc_ast::ast;
+use rustc_span::{symbol::sym, Span};
+
+use crate::config::{Config, GroupImportsTactic, ImportGranularity};
+use crate::imports::{flatten_use_trees, merge_use_trees, SharedPrefix, UseSegment, UseTree};
+use crate::items::{is_mod_decl, rewrite_extern_crate, rewrite_mod};
+use crate::lists::{itemize_list, write_list, ListFormatting, ListItem};
+use crate::rewrite::RewriteContext;
+use crate::shape::Shape;
+use crate::source_map::LineRangeUtils;
+use crate::spanned::Spanned;
+use crate::utils::{contains_skip, mk_sp};
+use crate::visitor::FmtVisitor;
+
+/// Choose the ordering between the given two items.
+fn compare_items(a: &ast::Item, b: &ast::Item) -> Ordering {
+    match (&a.kind, &b.kind) {
+        (&ast::ItemKind::Mod(..), &ast::ItemKind::Mod(..)) => {
+            a.ident.as_str().cmp(&b.ident.as_str())
+        }
+        (&ast::ItemKind::ExternCrate(ref a_name), &ast::ItemKind::ExternCrate(ref b_name)) => {
+            // `extern crate foo as bar;`
+            //               ^^^ Comparing this.
+            let a_orig_name = a_name.map_or_else(|| a.ident.as_str(), rustc_span::Symbol::as_str);
+            let b_orig_name = b_name.map_or_else(|| b.ident.as_str(), rustc_span::Symbol::as_str);
+            let result = a_orig_name.cmp(&b_orig_name);
+            if result != Ordering::Equal {
+                return result;
+            }
+
+            // `extern crate foo as bar;`
+            //                      ^^^ Comparing this.
+            match (a_name, b_name) {
+                (Some(..), None) => Ordering::Greater,
+                (None, Some(..)) => Ordering::Less,
+                (None, None) => Ordering::Equal,
+                (Some(..), Some(..)) => a.ident.as_str().cmp(&b.ident.as_str()),
+            }
+        }
+        _ => unreachable!(),
+    }
+}
+
+fn wrap_reorderable_items(
+    context: &RewriteContext<'_>,
+    list_items: &[ListItem],
+    shape: Shape,
+) -> Option<String> {
+    let fmt = ListFormatting::new(shape, context.config)
+        .separator("")
+        .align_comments(false);
+    write_list(list_items, &fmt)
+}
+
+fn rewrite_reorderable_item(
+    context: &RewriteContext<'_>,
+    item: &ast::Item,
+    shape: Shape,
+) -> Option<String> {
+    match item.kind {
+        ast::ItemKind::ExternCrate(..) => rewrite_extern_crate(context, item, shape),
+        ast::ItemKind::Mod(..) => rewrite_mod(context, item, shape),
+        _ => None,
+    }
+}
+
+/// Rewrite a list of items with reordering and/or regrouping. Every item
+/// in `items` must have the same `ast::ItemKind`. Whether reordering, regrouping,
+/// or both are done is determined from the `context`.
+fn rewrite_reorderable_or_regroupable_items(
+    context: &RewriteContext<'_>,
+    reorderable_items: &[&ast::Item],
+    shape: Shape,
+    span: Span,
+) -> Option<String> {
+    match reorderable_items[0].kind {
+        // FIXME: Remove duplicated code.
+        ast::ItemKind::Use(..) => {
+            let mut normalized_items: Vec<_> = reorderable_items
+                .iter()
+                .filter_map(|item| UseTree::from_ast_with_normalization(context, item))
+                .collect();
+            let cloned = normalized_items.clone();
+            // Add comments before merging.
+            let list_items = itemize_list(
+                context.snippet_provider,
+                cloned.iter(),
+                "",
+                ";",
+                |item| item.span().lo(),
+                |item| item.span().hi(),
+                |_item| Some("".to_owned()),
+                span.lo(),
+                span.hi(),
+                false,
+            );
+            for (item, list_item) in normalized_items.iter_mut().zip(list_items) {
+                item.list_item = Some(list_item.clone());
+            }
+            normalized_items = match context.config.imports_granularity() {
+                ImportGranularity::Crate => merge_use_trees(normalized_items, SharedPrefix::Crate),
+                ImportGranularity::Module => {
+                    merge_use_trees(normalized_items, SharedPrefix::Module)
+                }
+                ImportGranularity::Item => flatten_use_trees(normalized_items),
+                ImportGranularity::Preserve => normalized_items,
+            };
+
+            let mut regrouped_items = match context.config.group_imports() {
+                GroupImportsTactic::Preserve => vec![normalized_items],
+                GroupImportsTactic::StdExternalCrate => group_imports(normalized_items),
+            };
+
+            if context.config.reorder_imports() {
+                regrouped_items.iter_mut().for_each(|items| items.sort())
+            }
+
+            // 4 = "use ", 1 = ";"
+            let nested_shape = shape.offset_left(4)?.sub_width(1)?;
+            let item_vec: Vec<_> = regrouped_items
+                .into_iter()
+                .filter(|use_group| !use_group.is_empty())
+                .map(|use_group| {
+                    let item_vec: Vec<_> = use_group
+                        .into_iter()
+                        .map(|use_tree| ListItem {
+                            item: use_tree.rewrite_top_level(context, nested_shape),
+                            ..use_tree.list_item.unwrap_or_else(ListItem::empty)
+                        })
+                        .collect();
+                    wrap_reorderable_items(context, &item_vec, nested_shape)
+                })
+                .collect::<Option<Vec<_>>>()?;
+
+            let join_string = format!("\n\n{}", shape.indent.to_string(context.config));
+            Some(item_vec.join(&join_string))
+        }
+        _ => {
+            let list_items = itemize_list(
+                context.snippet_provider,
+                reorderable_items.iter(),
+                "",
+                ";",
+                |item| item.span().lo(),
+                |item| item.span().hi(),
+                |item| rewrite_reorderable_item(context, item, shape),
+                span.lo(),
+                span.hi(),
+                false,
+            );
+
+            let mut item_pair_vec: Vec<_> = list_items.zip(reorderable_items.iter()).collect();
+            item_pair_vec.sort_by(|a, b| compare_items(a.1, b.1));
+            let item_vec: Vec<_> = item_pair_vec.into_iter().map(|pair| pair.0).collect();
+
+            wrap_reorderable_items(context, &item_vec, shape)
+        }
+    }
+}
+
+fn contains_macro_use_attr(item: &ast::Item) -> bool {
+    crate::attr::contains_name(&item.attrs, sym::macro_use)
+}
+
+/// Divides imports into three groups, corresponding to standard, external
+/// and local imports. Sorts each subgroup.
+fn group_imports(uts: Vec<UseTree>) -> Vec<Vec<UseTree>> {
+    let mut std_imports = Vec::new();
+    let mut external_imports = Vec::new();
+    let mut local_imports = Vec::new();
+
+    for ut in uts.into_iter() {
+        if ut.path.is_empty() {
+            external_imports.push(ut);
+            continue;
+        }
+        match &ut.path[0] {
+            UseSegment::Ident(id, _) => match id.as_ref() {
+                "std" | "alloc" | "core" => std_imports.push(ut),
+                _ => external_imports.push(ut),
+            },
+            UseSegment::Slf(_) | UseSegment::Super(_) | UseSegment::Crate(_) => {
+                local_imports.push(ut)
+            }
+            // These are probably illegal here
+            UseSegment::Glob | UseSegment::List(_) => external_imports.push(ut),
+        }
+    }
+
+    vec![std_imports, external_imports, local_imports]
+}
+
+/// A simplified version of `ast::ItemKind`.
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+enum ReorderableItemKind {
+    ExternCrate,
+    Mod,
+    Use,
+    /// An item that cannot be reordered. Either has an unreorderable item kind
+    /// or an `macro_use` attribute.
+    Other,
+}
+
+impl ReorderableItemKind {
+    fn from(item: &ast::Item) -> Self {
+        match item.kind {
+            _ if contains_macro_use_attr(item) | contains_skip(&item.attrs) => {
+                ReorderableItemKind::Other
+            }
+            ast::ItemKind::ExternCrate(..) => ReorderableItemKind::ExternCrate,
+            ast::ItemKind::Mod(..) if is_mod_decl(item) => ReorderableItemKind::Mod,
+            ast::ItemKind::Use(..) => ReorderableItemKind::Use,
+            _ => ReorderableItemKind::Other,
+        }
+    }
+
+    fn is_same_item_kind(self, item: &ast::Item) -> bool {
+        ReorderableItemKind::from(item) == self
+    }
+
+    fn is_reorderable(self, config: &Config) -> bool {
+        match self {
+            ReorderableItemKind::ExternCrate => config.reorder_imports(),
+            ReorderableItemKind::Mod => config.reorder_modules(),
+            ReorderableItemKind::Use => config.reorder_imports(),
+            ReorderableItemKind::Other => false,
+        }
+    }
+
+    fn is_regroupable(self, config: &Config) -> bool {
+        match self {
+            ReorderableItemKind::ExternCrate
+            | ReorderableItemKind::Mod
+            | ReorderableItemKind::Other => false,
+            ReorderableItemKind::Use => config.group_imports() != GroupImportsTactic::Preserve,
+        }
+    }
+
+    fn in_group(self, config: &Config) -> bool {
+        match self {
+            ReorderableItemKind::ExternCrate | ReorderableItemKind::Mod => true,
+            ReorderableItemKind::Use => config.group_imports() == GroupImportsTactic::Preserve,
+            ReorderableItemKind::Other => false,
+        }
+    }
+}
+
+impl<'b, 'a: 'b> FmtVisitor<'a> {
+    /// Format items with the same item kind and reorder them, regroup them, or
+    /// both. If `in_group` is `true`, then the items separated by an empty line
+    /// will not be reordered together.
+    fn walk_reorderable_or_regroupable_items(
+        &mut self,
+        items: &[&ast::Item],
+        item_kind: ReorderableItemKind,
+        in_group: bool,
+    ) -> usize {
+        let mut last = self.parse_sess.lookup_line_range(items[0].span());
+        let item_length = items
+            .iter()
+            .take_while(|ppi| {
+                item_kind.is_same_item_kind(&***ppi)
+                    && (!in_group || {
+                        let current = self.parse_sess.lookup_line_range(ppi.span());
+                        let in_same_group = current.lo < last.hi + 2;
+                        last = current;
+                        in_same_group
+                    })
+            })
+            .count();
+        let items = &items[..item_length];
+
+        let at_least_one_in_file_lines = items
+            .iter()
+            .any(|item| !out_of_file_lines_range!(self, item.span));
+
+        if at_least_one_in_file_lines && !items.is_empty() {
+            let lo = items.first().unwrap().span().lo();
+            let hi = items.last().unwrap().span().hi();
+            let span = mk_sp(lo, hi);
+            let rw = rewrite_reorderable_or_regroupable_items(
+                &self.get_context(),
+                items,
+                self.shape(),
+                span,
+            );
+            self.push_rewrite(span, rw);
+        } else {
+            for item in items {
+                self.push_rewrite(item.span, None);
+            }
+        }
+
+        item_length
+    }
+
+    /// Visits and format the given items. Items are reordered If they are
+    /// consecutive and reorderable.
+    pub(crate) fn visit_items_with_reordering(&mut self, mut items: &[&ast::Item]) {
+        while !items.is_empty() {
+            // If the next item is a `use`, `extern crate` or `mod`, then extract it and any
+            // subsequent items that have the same item kind to be reordered within
+            // `walk_reorderable_items`. Otherwise, just format the next item for output.
+            let item_kind = ReorderableItemKind::from(items[0]);
+            if item_kind.is_reorderable(self.config) || item_kind.is_regroupable(self.config) {
+                let visited_items_num = self.walk_reorderable_or_regroupable_items(
+                    items,
+                    item_kind,
+                    item_kind.in_group(self.config),
+                );
+                let (_, rest) = items.split_at(visited_items_num);
+                items = rest;
+            } else {
+                // Reaching here means items were not reordered. There must be at least
+                // one item left in `items`, so calling `unwrap()` here is safe.
+                let (item, rest) = items.split_first().unwrap();
+                self.visit_item(item);
+                items = rest;
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/src/rewrite.rs b/src/tools/rustfmt/src/rewrite.rs
new file mode 100644
index 0000000000000..c8abe70141b5c
--- /dev/null
+++ b/src/tools/rustfmt/src/rewrite.rs
@@ -0,0 +1,98 @@
+// A generic trait to abstract the rewriting of an element (of the AST).
+
+use std::cell::{Cell, RefCell};
+use std::rc::Rc;
+
+use rustc_ast::ptr;
+use rustc_span::Span;
+
+use crate::config::{Config, IndentStyle};
+use crate::shape::Shape;
+use crate::skip::SkipContext;
+use crate::syntux::session::ParseSess;
+use crate::visitor::SnippetProvider;
+use crate::FormatReport;
+
+pub(crate) trait Rewrite {
+    /// Rewrite self into shape.
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String>;
+}
+
+impl<T: Rewrite> Rewrite for ptr::P<T> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        (**self).rewrite(context, shape)
+    }
+}
+
+#[derive(Clone)]
+pub(crate) struct RewriteContext<'a> {
+    pub(crate) parse_sess: &'a ParseSess,
+    pub(crate) config: &'a Config,
+    pub(crate) inside_macro: Rc<Cell<bool>>,
+    // Force block indent style even if we are using visual indent style.
+    pub(crate) use_block: Cell<bool>,
+    // When `is_if_else_block` is true, unindent the comment on top
+    // of the `else` or `else if`.
+    pub(crate) is_if_else_block: Cell<bool>,
+    // When rewriting chain, veto going multi line except the last element
+    pub(crate) force_one_line_chain: Cell<bool>,
+    pub(crate) snippet_provider: &'a SnippetProvider,
+    // Used for `format_snippet`
+    pub(crate) macro_rewrite_failure: Cell<bool>,
+    pub(crate) is_macro_def: bool,
+    pub(crate) report: FormatReport,
+    pub(crate) skip_context: SkipContext,
+    pub(crate) skipped_range: Rc<RefCell<Vec<(usize, usize)>>>,
+}
+
+pub(crate) struct InsideMacroGuard {
+    is_nested_macro_context: bool,
+    inside_macro_ref: Rc<Cell<bool>>,
+}
+
+impl InsideMacroGuard {
+    pub(crate) fn is_nested(&self) -> bool {
+        self.is_nested_macro_context
+    }
+}
+
+impl Drop for InsideMacroGuard {
+    fn drop(&mut self) {
+        self.inside_macro_ref.replace(self.is_nested_macro_context);
+    }
+}
+
+impl<'a> RewriteContext<'a> {
+    pub(crate) fn snippet(&self, span: Span) -> &str {
+        self.snippet_provider.span_to_snippet(span).unwrap()
+    }
+
+    /// Returns `true` if we should use block indent style for rewriting function call.
+    pub(crate) fn use_block_indent(&self) -> bool {
+        self.config.indent_style() == IndentStyle::Block || self.use_block.get()
+    }
+
+    pub(crate) fn budget(&self, used_width: usize) -> usize {
+        self.config.max_width().saturating_sub(used_width)
+    }
+
+    pub(crate) fn inside_macro(&self) -> bool {
+        self.inside_macro.get()
+    }
+
+    pub(crate) fn enter_macro(&self) -> InsideMacroGuard {
+        let is_nested_macro_context = self.inside_macro.replace(true);
+        InsideMacroGuard {
+            is_nested_macro_context,
+            inside_macro_ref: self.inside_macro.clone(),
+        }
+    }
+
+    pub(crate) fn leave_macro(&self) {
+        self.inside_macro.replace(false);
+    }
+
+    pub(crate) fn is_if_else_block(&self) -> bool {
+        self.is_if_else_block.get()
+    }
+}
diff --git a/src/tools/rustfmt/src/rustfmt_diff.rs b/src/tools/rustfmt/src/rustfmt_diff.rs
new file mode 100644
index 0000000000000..fc2c7d06e264e
--- /dev/null
+++ b/src/tools/rustfmt/src/rustfmt_diff.rs
@@ -0,0 +1,403 @@
+use std::collections::VecDeque;
+use std::fmt;
+use std::io;
+use std::io::Write;
+
+use crate::config::{Color, Config, Verbosity};
+
+#[derive(Debug, PartialEq)]
+pub enum DiffLine {
+    Context(String),
+    Expected(String),
+    Resulting(String),
+}
+
+#[derive(Debug, PartialEq)]
+pub struct Mismatch {
+    /// The line number in the formatted version.
+    pub line_number: u32,
+    /// The line number in the original version.
+    pub line_number_orig: u32,
+    /// The set of lines (context and old/new) in the mismatch.
+    pub lines: Vec<DiffLine>,
+}
+
+impl Mismatch {
+    fn new(line_number: u32, line_number_orig: u32) -> Mismatch {
+        Mismatch {
+            line_number,
+            line_number_orig,
+            lines: Vec::new(),
+        }
+    }
+}
+
+/// A single span of changed lines, with 0 or more removed lines
+/// and a vector of 0 or more inserted lines.
+#[derive(Debug, PartialEq, Eq)]
+pub struct ModifiedChunk {
+    /// The first to be removed from the original text
+    pub line_number_orig: u32,
+    /// The number of lines which have been replaced
+    pub lines_removed: u32,
+    /// The new lines
+    pub lines: Vec<String>,
+}
+
+/// Set of changed sections of a file.
+#[derive(Debug, PartialEq, Eq)]
+pub struct ModifiedLines {
+    /// The set of changed chunks.
+    pub chunks: Vec<ModifiedChunk>,
+}
+
+impl From<Vec<Mismatch>> for ModifiedLines {
+    fn from(mismatches: Vec<Mismatch>) -> ModifiedLines {
+        let chunks = mismatches.into_iter().map(|mismatch| {
+            let lines = mismatch.lines.iter();
+            let num_removed = lines
+                .filter(|line| match line {
+                    DiffLine::Resulting(_) => true,
+                    _ => false,
+                })
+                .count();
+
+            let new_lines = mismatch.lines.into_iter().filter_map(|line| match line {
+                DiffLine::Context(_) | DiffLine::Resulting(_) => None,
+                DiffLine::Expected(str) => Some(str),
+            });
+
+            ModifiedChunk {
+                line_number_orig: mismatch.line_number_orig,
+                lines_removed: num_removed as u32,
+                lines: new_lines.collect(),
+            }
+        });
+
+        ModifiedLines {
+            chunks: chunks.collect(),
+        }
+    }
+}
+
+// Converts a `Mismatch` into a serialized form, which just includes
+// enough information to modify the original file.
+// Each section starts with a line with three integers, space separated:
+//     lineno num_removed num_added
+// followed by (`num_added`) lines of added text. The line numbers are
+// relative to the original file.
+impl fmt::Display for ModifiedLines {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        for chunk in &self.chunks {
+            writeln!(
+                f,
+                "{} {} {}",
+                chunk.line_number_orig,
+                chunk.lines_removed,
+                chunk.lines.iter().count()
+            )?;
+
+            for line in &chunk.lines {
+                writeln!(f, "{}", line)?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+// Allows to convert `Display`ed `ModifiedLines` back to the structural data.
+impl std::str::FromStr for ModifiedLines {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<ModifiedLines, ()> {
+        let mut chunks = vec![];
+
+        let mut lines = s.lines();
+        while let Some(header) = lines.next() {
+            let mut header = header.split_whitespace();
+            let (orig, rem, new_lines) = match (header.next(), header.next(), header.next()) {
+                (Some(orig), Some(removed), Some(added)) => (orig, removed, added),
+                _ => return Err(()),
+            };
+            let (orig, rem, new_lines): (u32, u32, usize) =
+                match (orig.parse(), rem.parse(), new_lines.parse()) {
+                    (Ok(a), Ok(b), Ok(c)) => (a, b, c),
+                    _ => return Err(()),
+                };
+            let lines = lines.by_ref().take(new_lines);
+            let lines: Vec<_> = lines.map(ToOwned::to_owned).collect();
+            if lines.len() != new_lines {
+                return Err(());
+            }
+
+            chunks.push(ModifiedChunk {
+                line_number_orig: orig,
+                lines_removed: rem,
+                lines,
+            });
+        }
+
+        Ok(ModifiedLines { chunks })
+    }
+}
+
+// This struct handles writing output to stdout and abstracts away the logic
+// of printing in color, if it's possible in the executing environment.
+pub(crate) struct OutputWriter {
+    terminal: Option<Box<dyn term::Terminal<Output = io::Stdout>>>,
+}
+
+impl OutputWriter {
+    // Create a new OutputWriter instance based on the caller's preference
+    // for colorized output and the capabilities of the terminal.
+    pub(crate) fn new(color: Color) -> Self {
+        if let Some(t) = term::stdout() {
+            if color.use_colored_tty() && t.supports_color() {
+                return OutputWriter { terminal: Some(t) };
+            }
+        }
+        OutputWriter { terminal: None }
+    }
+
+    // Write output in the optionally specified color. The output is written
+    // in the specified color if this OutputWriter instance contains a
+    // Terminal in its `terminal` field.
+    pub(crate) fn writeln(&mut self, msg: &str, color: Option<term::color::Color>) {
+        match &mut self.terminal {
+            Some(ref mut t) => {
+                if let Some(color) = color {
+                    t.fg(color).unwrap();
+                }
+                writeln!(t, "{}", msg).unwrap();
+                if color.is_some() {
+                    t.reset().unwrap();
+                }
+            }
+            None => println!("{}", msg),
+        }
+    }
+}
+
+// Produces a diff between the expected output and actual output of rustfmt.
+pub(crate) fn make_diff(expected: &str, actual: &str, context_size: usize) -> Vec<Mismatch> {
+    let mut line_number = 1;
+    let mut line_number_orig = 1;
+    let mut context_queue: VecDeque<&str> = VecDeque::with_capacity(context_size);
+    let mut lines_since_mismatch = context_size + 1;
+    let mut results = Vec::new();
+    let mut mismatch = Mismatch::new(0, 0);
+
+    for result in diff::lines(expected, actual) {
+        match result {
+            diff::Result::Left(str) => {
+                if lines_since_mismatch >= context_size && lines_since_mismatch > 0 {
+                    results.push(mismatch);
+                    mismatch = Mismatch::new(
+                        line_number - context_queue.len() as u32,
+                        line_number_orig - context_queue.len() as u32,
+                    );
+                }
+
+                while let Some(line) = context_queue.pop_front() {
+                    mismatch.lines.push(DiffLine::Context(line.to_owned()));
+                }
+
+                mismatch.lines.push(DiffLine::Resulting(str.to_owned()));
+                line_number_orig += 1;
+                lines_since_mismatch = 0;
+            }
+            diff::Result::Right(str) => {
+                if lines_since_mismatch >= context_size && lines_since_mismatch > 0 {
+                    results.push(mismatch);
+                    mismatch = Mismatch::new(
+                        line_number - context_queue.len() as u32,
+                        line_number_orig - context_queue.len() as u32,
+                    );
+                }
+
+                while let Some(line) = context_queue.pop_front() {
+                    mismatch.lines.push(DiffLine::Context(line.to_owned()));
+                }
+
+                mismatch.lines.push(DiffLine::Expected(str.to_owned()));
+                line_number += 1;
+                lines_since_mismatch = 0;
+            }
+            diff::Result::Both(str, _) => {
+                if context_queue.len() >= context_size {
+                    let _ = context_queue.pop_front();
+                }
+
+                if lines_since_mismatch < context_size {
+                    mismatch.lines.push(DiffLine::Context(str.to_owned()));
+                } else if context_size > 0 {
+                    context_queue.push_back(str);
+                }
+
+                line_number += 1;
+                line_number_orig += 1;
+                lines_since_mismatch += 1;
+            }
+        }
+    }
+
+    results.push(mismatch);
+    results.remove(0);
+
+    results
+}
+
+pub(crate) fn print_diff<F>(diff: Vec<Mismatch>, get_section_title: F, config: &Config)
+where
+    F: Fn(u32) -> String,
+{
+    let color = config.color();
+    let line_terminator = if config.verbose() == Verbosity::Verbose {
+        "⏎"
+    } else {
+        ""
+    };
+
+    let mut writer = OutputWriter::new(color);
+
+    for mismatch in diff {
+        let title = get_section_title(mismatch.line_number_orig);
+        writer.writeln(&title, None);
+
+        for line in mismatch.lines {
+            match line {
+                DiffLine::Context(ref str) => {
+                    writer.writeln(&format!(" {}{}", str, line_terminator), None)
+                }
+                DiffLine::Expected(ref str) => writer.writeln(
+                    &format!("+{}{}", str, line_terminator),
+                    Some(term::color::GREEN),
+                ),
+                DiffLine::Resulting(ref str) => writer.writeln(
+                    &format!("-{}{}", str, line_terminator),
+                    Some(term::color::RED),
+                ),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::DiffLine::*;
+    use super::{make_diff, Mismatch};
+    use super::{ModifiedChunk, ModifiedLines};
+
+    #[test]
+    fn diff_simple() {
+        let src = "one\ntwo\nthree\nfour\nfive\n";
+        let dest = "one\ntwo\ntrois\nfour\nfive\n";
+        let diff = make_diff(src, dest, 1);
+        assert_eq!(
+            diff,
+            vec![Mismatch {
+                line_number: 2,
+                line_number_orig: 2,
+                lines: vec![
+                    Context("two".to_owned()),
+                    Resulting("three".to_owned()),
+                    Expected("trois".to_owned()),
+                    Context("four".to_owned()),
+                ],
+            }]
+        );
+    }
+
+    #[test]
+    fn diff_simple2() {
+        let src = "one\ntwo\nthree\nfour\nfive\nsix\nseven\n";
+        let dest = "one\ntwo\ntrois\nfour\ncinq\nsix\nseven\n";
+        let diff = make_diff(src, dest, 1);
+        assert_eq!(
+            diff,
+            vec![
+                Mismatch {
+                    line_number: 2,
+                    line_number_orig: 2,
+                    lines: vec![
+                        Context("two".to_owned()),
+                        Resulting("three".to_owned()),
+                        Expected("trois".to_owned()),
+                        Context("four".to_owned()),
+                    ],
+                },
+                Mismatch {
+                    line_number: 5,
+                    line_number_orig: 5,
+                    lines: vec![
+                        Resulting("five".to_owned()),
+                        Expected("cinq".to_owned()),
+                        Context("six".to_owned()),
+                    ],
+                },
+            ]
+        );
+    }
+
+    #[test]
+    fn diff_zerocontext() {
+        let src = "one\ntwo\nthree\nfour\nfive\n";
+        let dest = "one\ntwo\ntrois\nfour\nfive\n";
+        let diff = make_diff(src, dest, 0);
+        assert_eq!(
+            diff,
+            vec![Mismatch {
+                line_number: 3,
+                line_number_orig: 3,
+                lines: vec![Resulting("three".to_owned()), Expected("trois".to_owned())],
+            }]
+        );
+    }
+
+    #[test]
+    fn diff_trailing_newline() {
+        let src = "one\ntwo\nthree\nfour\nfive";
+        let dest = "one\ntwo\nthree\nfour\nfive\n";
+        let diff = make_diff(src, dest, 1);
+        assert_eq!(
+            diff,
+            vec![Mismatch {
+                line_number: 5,
+                line_number_orig: 5,
+                lines: vec![Context("five".to_owned()), Expected("".to_owned())],
+            }]
+        );
+    }
+
+    #[test]
+    fn modified_lines_from_str() {
+        use std::str::FromStr;
+
+        let src = "1 6 2\nfn some() {}\nfn main() {}\n25 3 1\n  struct Test {}";
+        let lines = ModifiedLines::from_str(src).unwrap();
+        assert_eq!(
+            lines,
+            ModifiedLines {
+                chunks: vec![
+                    ModifiedChunk {
+                        line_number_orig: 1,
+                        lines_removed: 6,
+                        lines: vec!["fn some() {}".to_owned(), "fn main() {}".to_owned(),]
+                    },
+                    ModifiedChunk {
+                        line_number_orig: 25,
+                        lines_removed: 3,
+                        lines: vec!["  struct Test {}".to_owned()]
+                    }
+                ]
+            }
+        );
+
+        let src = "1 5 3";
+        assert_eq!(ModifiedLines::from_str(src), Err(()));
+
+        let src = "1 5 3\na\nb";
+        assert_eq!(ModifiedLines::from_str(src), Err(()));
+    }
+}
diff --git a/src/tools/rustfmt/src/shape.rs b/src/tools/rustfmt/src/shape.rs
new file mode 100644
index 0000000000000..4376fd12b5260
--- /dev/null
+++ b/src/tools/rustfmt/src/shape.rs
@@ -0,0 +1,373 @@
+use std::borrow::Cow;
+use std::cmp::min;
+use std::ops::{Add, Sub};
+
+use crate::Config;
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct Indent {
+    // Width of the block indent, in characters. Must be a multiple of
+    // Config::tab_spaces.
+    pub(crate) block_indent: usize,
+    // Alignment in characters.
+    pub(crate) alignment: usize,
+}
+
+// INDENT_BUFFER.len() = 81
+const INDENT_BUFFER_LEN: usize = 80;
+const INDENT_BUFFER: &str =
+    "\n                                                                                ";
+
+impl Indent {
+    pub(crate) fn new(block_indent: usize, alignment: usize) -> Indent {
+        Indent {
+            block_indent,
+            alignment,
+        }
+    }
+
+    pub(crate) fn from_width(config: &Config, width: usize) -> Indent {
+        if config.hard_tabs() {
+            let tab_num = width / config.tab_spaces();
+            let alignment = width % config.tab_spaces();
+            Indent::new(config.tab_spaces() * tab_num, alignment)
+        } else {
+            Indent::new(width, 0)
+        }
+    }
+
+    pub(crate) fn empty() -> Indent {
+        Indent::new(0, 0)
+    }
+
+    pub(crate) fn block_only(&self) -> Indent {
+        Indent {
+            block_indent: self.block_indent,
+            alignment: 0,
+        }
+    }
+
+    pub(crate) fn block_indent(mut self, config: &Config) -> Indent {
+        self.block_indent += config.tab_spaces();
+        self
+    }
+
+    pub(crate) fn block_unindent(mut self, config: &Config) -> Indent {
+        if self.block_indent < config.tab_spaces() {
+            Indent::new(self.block_indent, 0)
+        } else {
+            self.block_indent -= config.tab_spaces();
+            self
+        }
+    }
+
+    pub(crate) fn width(&self) -> usize {
+        self.block_indent + self.alignment
+    }
+
+    pub(crate) fn to_string(&self, config: &Config) -> Cow<'static, str> {
+        self.to_string_inner(config, 1)
+    }
+
+    pub(crate) fn to_string_with_newline(&self, config: &Config) -> Cow<'static, str> {
+        self.to_string_inner(config, 0)
+    }
+
+    fn to_string_inner(&self, config: &Config, offset: usize) -> Cow<'static, str> {
+        let (num_tabs, num_spaces) = if config.hard_tabs() {
+            (self.block_indent / config.tab_spaces(), self.alignment)
+        } else {
+            (0, self.width())
+        };
+        let num_chars = num_tabs + num_spaces;
+        if num_tabs == 0 && num_chars + offset <= INDENT_BUFFER_LEN {
+            Cow::from(&INDENT_BUFFER[offset..=num_chars])
+        } else {
+            let mut indent = String::with_capacity(num_chars + if offset == 0 { 1 } else { 0 });
+            if offset == 0 {
+                indent.push('\n');
+            }
+            for _ in 0..num_tabs {
+                indent.push('\t')
+            }
+            for _ in 0..num_spaces {
+                indent.push(' ')
+            }
+            Cow::from(indent)
+        }
+    }
+}
+
+impl Add for Indent {
+    type Output = Indent;
+
+    fn add(self, rhs: Indent) -> Indent {
+        Indent {
+            block_indent: self.block_indent + rhs.block_indent,
+            alignment: self.alignment + rhs.alignment,
+        }
+    }
+}
+
+impl Sub for Indent {
+    type Output = Indent;
+
+    fn sub(self, rhs: Indent) -> Indent {
+        Indent::new(
+            self.block_indent - rhs.block_indent,
+            self.alignment - rhs.alignment,
+        )
+    }
+}
+
+impl Add<usize> for Indent {
+    type Output = Indent;
+
+    fn add(self, rhs: usize) -> Indent {
+        Indent::new(self.block_indent, self.alignment + rhs)
+    }
+}
+
+impl Sub<usize> for Indent {
+    type Output = Indent;
+
+    fn sub(self, rhs: usize) -> Indent {
+        Indent::new(self.block_indent, self.alignment - rhs)
+    }
+}
+
+// 8096 is close enough to infinite for rustfmt.
+const INFINITE_SHAPE_WIDTH: usize = 8096;
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct Shape {
+    pub(crate) width: usize,
+    // The current indentation of code.
+    pub(crate) indent: Indent,
+    // Indentation + any already emitted text on the first line of the current
+    // statement.
+    pub(crate) offset: usize,
+}
+
+impl Shape {
+    /// `indent` is the indentation of the first line. The next lines
+    /// should begin with at least `indent` spaces (except backwards
+    /// indentation). The first line should not begin with indentation.
+    /// `width` is the maximum number of characters on the last line
+    /// (excluding `indent`). The width of other lines is not limited by
+    /// `width`.
+    /// Note that in reality, we sometimes use width for lines other than the
+    /// last (i.e., we are conservative).
+    // .......*-------*
+    //        |       |
+    //        |     *-*
+    //        *-----|
+    // |<------------>|  max width
+    // |<---->|          indent
+    //        |<--->|    width
+    pub(crate) fn legacy(width: usize, indent: Indent) -> Shape {
+        Shape {
+            width,
+            indent,
+            offset: indent.alignment,
+        }
+    }
+
+    pub(crate) fn indented(indent: Indent, config: &Config) -> Shape {
+        Shape {
+            width: config.max_width().saturating_sub(indent.width()),
+            indent,
+            offset: indent.alignment,
+        }
+    }
+
+    pub(crate) fn with_max_width(&self, config: &Config) -> Shape {
+        Shape {
+            width: config.max_width().saturating_sub(self.indent.width()),
+            ..*self
+        }
+    }
+
+    pub(crate) fn visual_indent(&self, extra_width: usize) -> Shape {
+        let alignment = self.offset + extra_width;
+        Shape {
+            width: self.width,
+            indent: Indent::new(self.indent.block_indent, alignment),
+            offset: alignment,
+        }
+    }
+
+    pub(crate) fn block_indent(&self, extra_width: usize) -> Shape {
+        if self.indent.alignment == 0 {
+            Shape {
+                width: self.width,
+                indent: Indent::new(self.indent.block_indent + extra_width, 0),
+                offset: 0,
+            }
+        } else {
+            Shape {
+                width: self.width,
+                indent: self.indent + extra_width,
+                offset: self.indent.alignment + extra_width,
+            }
+        }
+    }
+
+    pub(crate) fn block_left(&self, width: usize) -> Option<Shape> {
+        self.block_indent(width).sub_width(width)
+    }
+
+    pub(crate) fn add_offset(&self, extra_width: usize) -> Shape {
+        Shape {
+            offset: self.offset + extra_width,
+            ..*self
+        }
+    }
+
+    pub(crate) fn block(&self) -> Shape {
+        Shape {
+            indent: self.indent.block_only(),
+            ..*self
+        }
+    }
+
+    pub(crate) fn saturating_sub_width(&self, width: usize) -> Shape {
+        self.sub_width(width).unwrap_or(Shape { width: 0, ..*self })
+    }
+
+    pub(crate) fn sub_width(&self, width: usize) -> Option<Shape> {
+        Some(Shape {
+            width: self.width.checked_sub(width)?,
+            ..*self
+        })
+    }
+
+    pub(crate) fn shrink_left(&self, width: usize) -> Option<Shape> {
+        Some(Shape {
+            width: self.width.checked_sub(width)?,
+            indent: self.indent + width,
+            offset: self.offset + width,
+        })
+    }
+
+    pub(crate) fn offset_left(&self, width: usize) -> Option<Shape> {
+        self.add_offset(width).sub_width(width)
+    }
+
+    pub(crate) fn used_width(&self) -> usize {
+        self.indent.block_indent + self.offset
+    }
+
+    pub(crate) fn rhs_overhead(&self, config: &Config) -> usize {
+        config
+            .max_width()
+            .saturating_sub(self.used_width() + self.width)
+    }
+
+    pub(crate) fn comment(&self, config: &Config) -> Shape {
+        let width = min(
+            self.width,
+            config.comment_width().saturating_sub(self.indent.width()),
+        );
+        Shape { width, ..*self }
+    }
+
+    pub(crate) fn to_string_with_newline(&self, config: &Config) -> Cow<'static, str> {
+        let mut offset_indent = self.indent;
+        offset_indent.alignment = self.offset;
+        offset_indent.to_string_inner(config, 0)
+    }
+
+    /// Creates a `Shape` with a virtually infinite width.
+    pub(crate) fn infinite_width(&self) -> Shape {
+        Shape {
+            width: INFINITE_SHAPE_WIDTH,
+            ..*self
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn indent_add_sub() {
+        let indent = Indent::new(4, 8) + Indent::new(8, 12);
+        assert_eq!(12, indent.block_indent);
+        assert_eq!(20, indent.alignment);
+
+        let indent = indent - Indent::new(4, 4);
+        assert_eq!(8, indent.block_indent);
+        assert_eq!(16, indent.alignment);
+    }
+
+    #[test]
+    fn indent_add_sub_alignment() {
+        let indent = Indent::new(4, 8) + 4;
+        assert_eq!(4, indent.block_indent);
+        assert_eq!(12, indent.alignment);
+
+        let indent = indent - 4;
+        assert_eq!(4, indent.block_indent);
+        assert_eq!(8, indent.alignment);
+    }
+
+    #[test]
+    fn indent_to_string_spaces() {
+        let config = Config::default();
+        let indent = Indent::new(4, 8);
+
+        // 12 spaces
+        assert_eq!("            ", indent.to_string(&config));
+    }
+
+    #[test]
+    fn indent_to_string_hard_tabs() {
+        let mut config = Config::default();
+        config.set().hard_tabs(true);
+        let indent = Indent::new(8, 4);
+
+        // 2 tabs + 4 spaces
+        assert_eq!("\t\t    ", indent.to_string(&config));
+    }
+
+    #[test]
+    fn shape_visual_indent() {
+        let config = Config::default();
+        let indent = Indent::new(4, 8);
+        let shape = Shape::legacy(config.max_width(), indent);
+        let shape = shape.visual_indent(20);
+
+        assert_eq!(config.max_width(), shape.width);
+        assert_eq!(4, shape.indent.block_indent);
+        assert_eq!(28, shape.indent.alignment);
+        assert_eq!(28, shape.offset);
+    }
+
+    #[test]
+    fn shape_block_indent_without_alignment() {
+        let config = Config::default();
+        let indent = Indent::new(4, 0);
+        let shape = Shape::legacy(config.max_width(), indent);
+        let shape = shape.block_indent(20);
+
+        assert_eq!(config.max_width(), shape.width);
+        assert_eq!(24, shape.indent.block_indent);
+        assert_eq!(0, shape.indent.alignment);
+        assert_eq!(0, shape.offset);
+    }
+
+    #[test]
+    fn shape_block_indent_with_alignment() {
+        let config = Config::default();
+        let indent = Indent::new(4, 8);
+        let shape = Shape::legacy(config.max_width(), indent);
+        let shape = shape.block_indent(20);
+
+        assert_eq!(config.max_width(), shape.width);
+        assert_eq!(4, shape.indent.block_indent);
+        assert_eq!(28, shape.indent.alignment);
+        assert_eq!(28, shape.offset);
+    }
+}
diff --git a/src/tools/rustfmt/src/skip.rs b/src/tools/rustfmt/src/skip.rs
new file mode 100644
index 0000000000000..6c500635a9551
--- /dev/null
+++ b/src/tools/rustfmt/src/skip.rs
@@ -0,0 +1,76 @@
+//! Module that contains skip related stuffs.
+
+use rustc_ast::ast;
+use rustc_ast_pretty::pprust;
+
+/// Take care of skip name stack. You can update it by attributes slice or
+/// by other context. Query this context to know if you need skip a block.
+#[derive(Default, Clone)]
+pub(crate) struct SkipContext {
+    macros: Vec<String>,
+    attributes: Vec<String>,
+}
+
+impl SkipContext {
+    pub(crate) fn update_with_attrs(&mut self, attrs: &[ast::Attribute]) {
+        self.macros.append(&mut get_skip_names("macros", attrs));
+        self.attributes
+            .append(&mut get_skip_names("attributes", attrs));
+    }
+
+    pub(crate) fn update(&mut self, mut other: SkipContext) {
+        self.macros.append(&mut other.macros);
+        self.attributes.append(&mut other.attributes);
+    }
+
+    pub(crate) fn skip_macro(&self, name: &str) -> bool {
+        self.macros.iter().any(|n| n == name)
+    }
+
+    pub(crate) fn skip_attribute(&self, name: &str) -> bool {
+        self.attributes.iter().any(|n| n == name)
+    }
+}
+
+static RUSTFMT: &'static str = "rustfmt";
+static SKIP: &'static str = "skip";
+
+/// Say if you're playing with `rustfmt`'s skip attribute
+pub(crate) fn is_skip_attr(segments: &[ast::PathSegment]) -> bool {
+    if segments.len() < 2 || segments[0].ident.to_string() != RUSTFMT {
+        return false;
+    }
+    match segments.len() {
+        2 => segments[1].ident.to_string() == SKIP,
+        3 => {
+            segments[1].ident.to_string() == SKIP
+                && ["macros", "attributes"]
+                    .iter()
+                    .any(|&n| n == &pprust::path_segment_to_string(&segments[2]))
+        }
+        _ => false,
+    }
+}
+
+fn get_skip_names(kind: &str, attrs: &[ast::Attribute]) -> Vec<String> {
+    let mut skip_names = vec![];
+    let path = format!("{}::{}::{}", RUSTFMT, SKIP, kind);
+    for attr in attrs {
+        // rustc_ast::ast::Path is implemented partialEq
+        // but it is designed for segments.len() == 1
+        if let ast::AttrKind::Normal(attr_item, _) = &attr.kind {
+            if pprust::path_to_string(&attr_item.path) != path {
+                continue;
+            }
+        }
+
+        if let Some(list) = attr.meta_item_list() {
+            for nested_meta_item in list {
+                if let Some(name) = nested_meta_item.ident() {
+                    skip_names.push(name.to_string());
+                }
+            }
+        }
+    }
+    skip_names
+}
diff --git a/src/tools/rustfmt/src/source_file.rs b/src/tools/rustfmt/src/source_file.rs
new file mode 100644
index 0000000000000..5a9a2cbd80c7e
--- /dev/null
+++ b/src/tools/rustfmt/src/source_file.rs
@@ -0,0 +1,105 @@
+use std::fs;
+use std::io::{self, Write};
+use std::path::Path;
+
+use crate::config::FileName;
+use crate::emitter::{self, Emitter};
+use crate::syntux::session::ParseSess;
+use crate::NewlineStyle;
+
+#[cfg(test)]
+use crate::config::Config;
+#[cfg(test)]
+use crate::create_emitter;
+#[cfg(test)]
+use crate::formatting::FileRecord;
+
+use rustc_data_structures::sync::Lrc;
+
+// Append a newline to the end of each file.
+pub(crate) fn append_newline(s: &mut String) {
+    s.push_str("\n");
+}
+
+#[cfg(test)]
+pub(crate) fn write_all_files<T>(
+    source_file: &[FileRecord],
+    out: &mut T,
+    config: &Config,
+) -> Result<(), io::Error>
+where
+    T: Write,
+{
+    let mut emitter = create_emitter(config);
+
+    emitter.emit_header(out)?;
+    for &(ref filename, ref text) in source_file {
+        write_file(
+            None,
+            filename,
+            text,
+            out,
+            &mut *emitter,
+            config.newline_style(),
+        )?;
+    }
+    emitter.emit_footer(out)?;
+
+    Ok(())
+}
+
+pub(crate) fn write_file<T>(
+    parse_sess: Option<&ParseSess>,
+    filename: &FileName,
+    formatted_text: &str,
+    out: &mut T,
+    emitter: &mut dyn Emitter,
+    newline_style: NewlineStyle,
+) -> Result<emitter::EmitterResult, io::Error>
+where
+    T: Write,
+{
+    fn ensure_real_path(filename: &FileName) -> &Path {
+        match *filename {
+            FileName::Real(ref path) => path,
+            _ => panic!("cannot format `{}` and emit to files", filename),
+        }
+    }
+
+    impl From<&FileName> for rustc_span::FileName {
+        fn from(filename: &FileName) -> rustc_span::FileName {
+            match filename {
+                FileName::Real(path) => {
+                    rustc_span::FileName::Real(rustc_span::RealFileName::LocalPath(path.to_owned()))
+                }
+                FileName::Stdin => rustc_span::FileName::Custom("stdin".to_owned()),
+            }
+        }
+    }
+
+    // SourceFile's in the SourceMap will always have Unix-style line endings
+    // See: https://github.com/rust-lang/rustfmt/issues/3850
+    // So if the user has explicitly overridden the rustfmt `newline_style`
+    // config and `filename` is FileName::Real, then we must check the file system
+    // to get the original file value in order to detect newline_style conflicts.
+    // Otherwise, parse session is around (cfg(not(test))) and newline_style has been
+    // left as the default value, then try getting source from the parse session
+    // source map instead of hitting the file system. This also supports getting
+    // original text for `FileName::Stdin`.
+    let original_text = if newline_style != NewlineStyle::Auto && *filename != FileName::Stdin {
+        Lrc::new(fs::read_to_string(ensure_real_path(filename))?)
+    } else {
+        match parse_sess.and_then(|sess| sess.get_original_snippet(filename)) {
+            Some(ori) => ori,
+            None => Lrc::new(fs::read_to_string(ensure_real_path(filename))?),
+        }
+    };
+
+    let formatted_file = emitter::FormattedFile {
+        filename,
+        original_text: original_text.as_str(),
+        formatted_text,
+    };
+
+    emitter.emit_formatted_file(out, formatted_file)
+}
diff --git a/src/tools/rustfmt/src/source_map.rs b/src/tools/rustfmt/src/source_map.rs
new file mode 100644
index 0000000000000..76e0d24cf1eb6
--- /dev/null
+++ b/src/tools/rustfmt/src/source_map.rs
@@ -0,0 +1,82 @@
+//! This module contains utilities that work with the `SourceMap` from `libsyntax`/`syntex_syntax`.
+//! This includes extension traits and methods for looking up spans and line ranges for AST nodes.
+
+use rustc_span::{BytePos, Span};
+
+use crate::comment::FindUncommented;
+use crate::config::file_lines::LineRange;
+use crate::visitor::SnippetProvider;
+
+pub(crate) trait SpanUtils {
+    fn span_after(&self, original: Span, needle: &str) -> BytePos;
+    fn span_after_last(&self, original: Span, needle: &str) -> BytePos;
+    fn span_before(&self, original: Span, needle: &str) -> BytePos;
+    fn span_before_last(&self, original: Span, needle: &str) -> BytePos;
+    fn opt_span_after(&self, original: Span, needle: &str) -> Option<BytePos>;
+    fn opt_span_before(&self, original: Span, needle: &str) -> Option<BytePos>;
+}
+
+pub(crate) trait LineRangeUtils {
+    /// Returns the `LineRange` that corresponds to `span` in `self`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `span` crosses a file boundary, which shouldn't happen.
+    fn lookup_line_range(&self, span: Span) -> LineRange;
+}
+
+impl SpanUtils for SnippetProvider {
+    fn span_after(&self, original: Span, needle: &str) -> BytePos {
+        self.opt_span_after(original, needle).unwrap_or_else(|| {
+            panic!(
+                "bad span: `{}`: `{}`",
+                needle,
+                self.span_to_snippet(original).unwrap()
+            )
+        })
+    }
+
+    fn span_after_last(&self, original: Span, needle: &str) -> BytePos {
+        let snippet = self.span_to_snippet(original).unwrap();
+        let mut offset = 0;
+
+        while let Some(additional_offset) = snippet[offset..].find_uncommented(needle) {
+            offset += additional_offset + needle.len();
+        }
+
+        original.lo() + BytePos(offset as u32)
+    }
+
+    fn span_before(&self, original: Span, needle: &str) -> BytePos {
+        self.opt_span_before(original, needle).unwrap_or_else(|| {
+            panic!(
+                "bad span: `{}`: `{}`",
+                needle,
+                self.span_to_snippet(original).unwrap()
+            )
+        })
+    }
+
+    fn span_before_last(&self, original: Span, needle: &str) -> BytePos {
+        let snippet = self.span_to_snippet(original).unwrap();
+        let mut offset = 0;
+
+        while let Some(additional_offset) = snippet[offset..].find_uncommented(needle) {
+            offset += additional_offset + needle.len();
+        }
+
+        original.lo() + BytePos(offset as u32 - 1)
+    }
+
+    fn opt_span_after(&self, original: Span, needle: &str) -> Option<BytePos> {
+        self.opt_span_before(original, needle)
+            .map(|bytepos| bytepos + BytePos(needle.len() as u32))
+    }
+
+    fn opt_span_before(&self, original: Span, needle: &str) -> Option<BytePos> {
+        let snippet = self.span_to_snippet(original)?;
+        let offset = snippet.find_uncommented(needle)?;
+
+        Some(original.lo() + BytePos(offset as u32))
+    }
+}
diff --git a/src/tools/rustfmt/src/spanned.rs b/src/tools/rustfmt/src/spanned.rs
new file mode 100644
index 0000000000000..7e3786b7cd94c
--- /dev/null
+++ b/src/tools/rustfmt/src/spanned.rs
@@ -0,0 +1,206 @@
+use std::cmp::max;
+
+use rustc_ast::{ast, ptr};
+use rustc_span::{source_map, Span};
+
+use crate::macros::MacroArg;
+use crate::utils::{mk_sp, outer_attributes};
+
+/// Spanned returns a span including attributes, if available.
+pub(crate) trait Spanned {
+    fn span(&self) -> Span;
+}
+
+impl<T: Spanned> Spanned for ptr::P<T> {
+    fn span(&self) -> Span {
+        (**self).span()
+    }
+}
+
+impl<T> Spanned for source_map::Spanned<T> {
+    fn span(&self) -> Span {
+        self.span
+    }
+}
+
+macro_rules! span_with_attrs_lo_hi {
+    ($this:ident, $lo:expr, $hi:expr) => {{
+        let attrs = outer_attributes(&$this.attrs);
+        if attrs.is_empty() {
+            mk_sp($lo, $hi)
+        } else {
+            mk_sp(attrs[0].span.lo(), $hi)
+        }
+    }};
+}
+
+macro_rules! span_with_attrs {
+    ($this:ident) => {
+        span_with_attrs_lo_hi!($this, $this.span.lo(), $this.span.hi())
+    };
+}
+
+macro_rules! implement_spanned {
+    ($this:ty) => {
+        impl Spanned for $this {
+            fn span(&self) -> Span {
+                span_with_attrs!(self)
+            }
+        }
+    };
+}
+
+// Implement `Spanned` for structs with `attrs` field.
+implement_spanned!(ast::AssocItem);
+implement_spanned!(ast::Expr);
+implement_spanned!(ast::ExprField);
+implement_spanned!(ast::ForeignItem);
+implement_spanned!(ast::Item);
+implement_spanned!(ast::Local);
+
+impl Spanned for ast::Stmt {
+    fn span(&self) -> Span {
+        match self.kind {
+            ast::StmtKind::Local(ref local) => mk_sp(local.span().lo(), self.span.hi()),
+            ast::StmtKind::Item(ref item) => mk_sp(item.span().lo(), self.span.hi()),
+            ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => {
+                mk_sp(expr.span().lo(), self.span.hi())
+            }
+            ast::StmtKind::MacCall(ref mac_stmt) => {
+                if mac_stmt.attrs.is_empty() {
+                    self.span
+                } else {
+                    mk_sp(mac_stmt.attrs[0].span.lo(), self.span.hi())
+                }
+            }
+            ast::StmtKind::Empty => self.span,
+        }
+    }
+}
+
+impl Spanned for ast::Pat {
+    fn span(&self) -> Span {
+        self.span
+    }
+}
+
+impl Spanned for ast::Ty {
+    fn span(&self) -> Span {
+        self.span
+    }
+}
+
+impl Spanned for ast::Arm {
+    fn span(&self) -> Span {
+        let lo = if self.attrs.is_empty() {
+            self.pat.span.lo()
+        } else {
+            self.attrs[0].span.lo()
+        };
+        span_with_attrs_lo_hi!(self, lo, self.body.span.hi())
+    }
+}
+
+impl Spanned for ast::Param {
+    fn span(&self) -> Span {
+        if crate::items::is_named_param(self) {
+            mk_sp(self.pat.span.lo(), self.ty.span.hi())
+        } else {
+            self.ty.span
+        }
+    }
+}
+
+impl Spanned for ast::GenericParam {
+    fn span(&self) -> Span {
+        let lo = if let ast::GenericParamKind::Const {
+            ty: _,
+            kw_span,
+            default: _,
+        } = self.kind
+        {
+            kw_span.lo()
+        } else if self.attrs.is_empty() {
+            self.ident.span.lo()
+        } else {
+            self.attrs[0].span.lo()
+        };
+        let hi = if self.bounds.is_empty() {
+            self.ident.span.hi()
+        } else {
+            self.bounds.last().unwrap().span().hi()
+        };
+        let ty_hi = if let ast::GenericParamKind::Type {
+            default: Some(ref ty),
+        }
+        | ast::GenericParamKind::Const { ref ty, .. } = self.kind
+        {
+            ty.span().hi()
+        } else {
+            hi
+        };
+        mk_sp(lo, max(hi, ty_hi))
+    }
+}
+
+impl Spanned for ast::FieldDef {
+    fn span(&self) -> Span {
+        span_with_attrs_lo_hi!(self, self.span.lo(), self.ty.span.hi())
+    }
+}
+
+impl Spanned for ast::WherePredicate {
+    fn span(&self) -> Span {
+        match *self {
+            ast::WherePredicate::BoundPredicate(ref p) => p.span,
+            ast::WherePredicate::RegionPredicate(ref p) => p.span,
+            ast::WherePredicate::EqPredicate(ref p) => p.span,
+        }
+    }
+}
+
+impl Spanned for ast::FnRetTy {
+    fn span(&self) -> Span {
+        match *self {
+            ast::FnRetTy::Default(span) => span,
+            ast::FnRetTy::Ty(ref ty) => ty.span,
+        }
+    }
+}
+
+impl Spanned for ast::GenericArg {
+    fn span(&self) -> Span {
+        match *self {
+            ast::GenericArg::Lifetime(ref lt) => lt.ident.span,
+            ast::GenericArg::Type(ref ty) => ty.span(),
+            ast::GenericArg::Const(ref _const) => _const.value.span(),
+        }
+    }
+}
+
+impl Spanned for ast::GenericBound {
+    fn span(&self) -> Span {
+        match *self {
+            ast::GenericBound::Trait(ref ptr, _) => ptr.span,
+            ast::GenericBound::Outlives(ref l) => l.ident.span,
+        }
+    }
+}
+
+impl Spanned for MacroArg {
+    fn span(&self) -> Span {
+        match *self {
+            MacroArg::Expr(ref expr) => expr.span(),
+            MacroArg::Ty(ref ty) => ty.span(),
+            MacroArg::Pat(ref pat) => pat.span(),
+            MacroArg::Item(ref item) => item.span(),
+            MacroArg::Keyword(_, span) => span,
+        }
+    }
+}
+
+impl Spanned for ast::NestedMetaItem {
+    fn span(&self) -> Span {
+        self.span()
+    }
+}
diff --git a/src/tools/rustfmt/src/stmt.rs b/src/tools/rustfmt/src/stmt.rs
new file mode 100644
index 0000000000000..0b3854425ea5f
--- /dev/null
+++ b/src/tools/rustfmt/src/stmt.rs
@@ -0,0 +1,116 @@
+use rustc_ast::ast;
+use rustc_span::Span;
+
+use crate::comment::recover_comment_removed;
+use crate::config::Version;
+use crate::expr::{format_expr, ExprType};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::LineRangeUtils;
+use crate::spanned::Spanned;
+use crate::utils::semicolon_for_stmt;
+
+pub(crate) struct Stmt<'a> {
+    inner: &'a ast::Stmt,
+    is_last: bool,
+}
+
+impl<'a> Spanned for Stmt<'a> {
+    fn span(&self) -> Span {
+        self.inner.span()
+    }
+}
+
+impl<'a> Stmt<'a> {
+    pub(crate) fn as_ast_node(&self) -> &ast::Stmt {
+        self.inner
+    }
+
+    pub(crate) fn to_item(&self) -> Option<&ast::Item> {
+        match self.inner.kind {
+            ast::StmtKind::Item(ref item) => Some(&**item),
+            _ => None,
+        }
+    }
+
+    pub(crate) fn from_ast_node(inner: &'a ast::Stmt, is_last: bool) -> Self {
+        Stmt { inner, is_last }
+    }
+
+    pub(crate) fn from_ast_nodes<I>(iter: I) -> Vec<Self>
+    where
+        I: Iterator<Item = &'a ast::Stmt>,
+    {
+        let mut result = vec![];
+        let mut iter = iter.peekable();
+        while iter.peek().is_some() {
+            result.push(Stmt {
+                inner: iter.next().unwrap(),
+                is_last: iter.peek().is_none(),
+            })
+        }
+        result
+    }
+
+    pub(crate) fn is_empty(&self) -> bool {
+        matches!(self.inner.kind, ast::StmtKind::Empty)
+    }
+
+    fn is_last_expr(&self) -> bool {
+        if !self.is_last {
+            return false;
+        }
+
+        match self.as_ast_node().kind {
+            ast::StmtKind::Expr(ref expr) => match expr.kind {
+                ast::ExprKind::Ret(..) | ast::ExprKind::Continue(..) | ast::ExprKind::Break(..) => {
+                    false
+                }
+                _ => true,
+            },
+            _ => false,
+        }
+    }
+}
+
+impl<'a> Rewrite for Stmt<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let expr_type = if context.config.version() == Version::Two && self.is_last_expr() {
+            ExprType::SubExpression
+        } else {
+            ExprType::Statement
+        };
+        format_stmt(context, shape, self.as_ast_node(), expr_type)
+    }
+}
+
+impl Rewrite for ast::Stmt {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        format_stmt(context, shape, self, ExprType::Statement)
+    }
+}
+
+fn format_stmt(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    stmt: &ast::Stmt,
+    expr_type: ExprType,
+) -> Option<String> {
+    skip_out_of_file_lines_range!(context, stmt.span());
+
+    let result = match stmt.kind {
+        ast::StmtKind::Local(ref local) => local.rewrite(context, shape),
+        ast::StmtKind::Expr(ref ex) | ast::StmtKind::Semi(ref ex) => {
+            let suffix = if semicolon_for_stmt(context, stmt) {
+                ";"
+            } else {
+                ""
+            };
+
+            let shape = shape.sub_width(suffix.len())?;
+            format_expr(ex, expr_type, context, shape).map(|s| s + suffix)
+        }
+        ast::StmtKind::MacCall(..) | ast::StmtKind::Item(..) | ast::StmtKind::Empty => None,
+    };
+    result.and_then(|res| recover_comment_removed(res, stmt.span(), context))
+}
diff --git a/src/tools/rustfmt/src/string.rs b/src/tools/rustfmt/src/string.rs
new file mode 100644
index 0000000000000..080c4f1778823
--- /dev/null
+++ b/src/tools/rustfmt/src/string.rs
@@ -0,0 +1,691 @@
+// Format string literals.
+
+use regex::Regex;
+use unicode_categories::UnicodeCategories;
+use unicode_segmentation::UnicodeSegmentation;
+
+use crate::config::Config;
+use crate::shape::Shape;
+use crate::utils::{unicode_str_width, wrap_str};
+
+const MIN_STRING: usize = 10;
+
+/// Describes the layout of a piece of text.
+pub(crate) struct StringFormat<'a> {
+    /// The opening sequence of characters for the piece of text
+    pub(crate) opener: &'a str,
+    /// The closing sequence of characters for the piece of text
+    pub(crate) closer: &'a str,
+    /// The opening sequence of characters for a line
+    pub(crate) line_start: &'a str,
+    /// The closing sequence of characters for a line
+    pub(crate) line_end: &'a str,
+    /// The allocated box to fit the text into
+    pub(crate) shape: Shape,
+    /// Trim trailing whitespaces
+    pub(crate) trim_end: bool,
+    pub(crate) config: &'a Config,
+}
+
+impl<'a> StringFormat<'a> {
+    pub(crate) fn new(shape: Shape, config: &'a Config) -> StringFormat<'a> {
+        StringFormat {
+            opener: "\"",
+            closer: "\"",
+            line_start: " ",
+            line_end: "\\",
+            shape,
+            trim_end: false,
+            config,
+        }
+    }
+
+    /// Returns the maximum number of graphemes that is possible on a line while taking the
+    /// indentation into account.
+    ///
+    /// If we cannot put at least a single character per line, the rewrite won't succeed.
+    fn max_width_with_indent(&self) -> Option<usize> {
+        Some(
+            self.shape
+                .width
+                .checked_sub(self.opener.len() + self.line_end.len() + 1)?
+                + 1,
+        )
+    }
+
+    /// Like max_width_with_indent but the indentation is not subtracted.
+    /// This allows to fit more graphemes from the string on a line when
+    /// SnippetState::EndWithLineFeed.
+    fn max_width_without_indent(&self) -> Option<usize> {
+        Some(self.config.max_width().checked_sub(self.line_end.len())?)
+    }
+}
+
+pub(crate) fn rewrite_string<'a>(
+    orig: &str,
+    fmt: &StringFormat<'a>,
+    newline_max_chars: usize,
+) -> Option<String> {
+    let max_width_with_indent = fmt.max_width_with_indent()?;
+    let max_width_without_indent = fmt.max_width_without_indent()?;
+    let indent_with_newline = fmt.shape.indent.to_string_with_newline(fmt.config);
+    let indent_without_newline = fmt.shape.indent.to_string(fmt.config);
+
+    // Strip line breaks.
+    // With this regex applied, all remaining whitespaces are significant
+    let strip_line_breaks_re = Regex::new(r"([^\\](\\\\)*)\\[\n\r][[:space:]]*").unwrap();
+    let stripped_str = strip_line_breaks_re.replace_all(orig, "$1");
+
+    let graphemes = UnicodeSegmentation::graphemes(&*stripped_str, false).collect::<Vec<&str>>();
+
+    // `cur_start` is the position in `orig` of the start of the current line.
+    let mut cur_start = 0;
+    let mut result = String::with_capacity(
+        stripped_str
+            .len()
+            .checked_next_power_of_two()
+            .unwrap_or(usize::max_value()),
+    );
+    result.push_str(fmt.opener);
+
+    // Snip a line at a time from `stripped_str` until it is used up. Push the snippet
+    // onto result.
+    let mut cur_max_width = max_width_with_indent;
+    let is_bareline_ok = fmt.line_start.is_empty() || is_whitespace(fmt.line_start);
+    loop {
+        // All the input starting at cur_start fits on the current line
+        if graphemes_width(&graphemes[cur_start..]) <= cur_max_width {
+            for (i, grapheme) in graphemes[cur_start..].iter().enumerate() {
+                if is_new_line(grapheme) {
+                    // take care of blank lines
+                    result = trim_end_but_line_feed(fmt.trim_end, result);
+                    result.push_str("\n");
+                    if !is_bareline_ok && cur_start + i + 1 < graphemes.len() {
+                        result.push_str(&indent_without_newline);
+                        result.push_str(fmt.line_start);
+                    }
+                } else {
+                    result.push_str(grapheme);
+                }
+            }
+            result = trim_end_but_line_feed(fmt.trim_end, result);
+            break;
+        }
+
+        // The input starting at cur_start needs to be broken
+        match break_string(
+            cur_max_width,
+            fmt.trim_end,
+            fmt.line_end,
+            &graphemes[cur_start..],
+        ) {
+            SnippetState::LineEnd(line, len) => {
+                result.push_str(&line);
+                result.push_str(fmt.line_end);
+                result.push_str(&indent_with_newline);
+                result.push_str(fmt.line_start);
+                cur_max_width = newline_max_chars;
+                cur_start += len;
+            }
+            SnippetState::EndWithLineFeed(line, len) => {
+                if line == "\n" && fmt.trim_end {
+                    result = result.trim_end().to_string();
+                }
+                result.push_str(&line);
+                if is_bareline_ok {
+                    // the next line can benefit from the full width
+                    cur_max_width = max_width_without_indent;
+                } else {
+                    result.push_str(&indent_without_newline);
+                    result.push_str(fmt.line_start);
+                    cur_max_width = max_width_with_indent;
+                }
+                cur_start += len;
+            }
+            SnippetState::EndOfInput(line) => {
+                result.push_str(&line);
+                break;
+            }
+        }
+    }
+
+    result.push_str(fmt.closer);
+    wrap_str(result, fmt.config.max_width(), fmt.shape)
+}
+
+/// Returns the index to the end of the URL if the split at index of the given string includes an
+/// URL or alike. Otherwise, returns `None`.
+fn detect_url(s: &[&str], index: usize) -> Option<usize> {
+    let start = match s[..=index].iter().rposition(|g| is_whitespace(g)) {
+        Some(pos) => pos + 1,
+        None => 0,
+    };
+    // 8 = minimum length for a string to contain a URL
+    if s.len() < start + 8 {
+        return None;
+    }
+    let split = s[start..].concat();
+    if split.contains("https://")
+        || split.contains("http://")
+        || split.contains("ftp://")
+        || split.contains("file://")
+    {
+        match s[index..].iter().position(|g| is_whitespace(g)) {
+            Some(pos) => Some(index + pos - 1),
+            None => Some(s.len() - 1),
+        }
+    } else {
+        None
+    }
+}
+
+/// Trims whitespaces to the right except for the line feed character.
+fn trim_end_but_line_feed(trim_end: bool, result: String) -> String {
+    let whitespace_except_line_feed = |c: char| c.is_whitespace() && c != '\n';
+    if trim_end && result.ends_with(whitespace_except_line_feed) {
+        result
+            .trim_end_matches(whitespace_except_line_feed)
+            .to_string()
+    } else {
+        result
+    }
+}
+
+/// Result of breaking a string so it fits in a line and the state it ended in.
+/// The state informs about what to do with the snippet and how to continue the breaking process.
+#[derive(Debug, PartialEq)]
+enum SnippetState {
+    /// The input could not be broken and so rewriting the string is finished.
+    EndOfInput(String),
+    /// The input could be broken and the returned snippet should be ended with a
+    /// `[StringFormat::line_end]`. The next snippet needs to be indented.
+    ///
+    /// The returned string is the line to print out and the number is the length that got read in
+    /// the text being rewritten. That length may be greater than the returned string if trailing
+    /// whitespaces got trimmed.
+    LineEnd(String, usize),
+    /// The input could be broken but a newline is present that cannot be trimmed. The next snippet
+    /// to be rewritten *could* use more width than what is specified by the given shape. For
+    /// example with a multiline string, the next snippet does not need to be indented, allowing
+    /// more characters to be fit within a line.
+    ///
+    /// The returned string is the line to print out and the number is the length that got read in
+    /// the text being rewritten.
+    EndWithLineFeed(String, usize),
+}
+
+fn not_whitespace_except_line_feed(g: &str) -> bool {
+    is_new_line(g) || !is_whitespace(g)
+}
+
+/// Break the input string at a boundary character around the offset `max_width`. A boundary
+/// character is either a punctuation or a whitespace.
+/// FIXME(issue#3281): We must follow UAX#14 algorithm instead of this.
+fn break_string(max_width: usize, trim_end: bool, line_end: &str, input: &[&str]) -> SnippetState {
+    let break_at = |index /* grapheme at index is included */| {
+        // Take in any whitespaces to the left/right of `input[index]` while
+        // preserving line feeds
+        let index_minus_ws = input[0..=index]
+            .iter()
+            .rposition(|grapheme| not_whitespace_except_line_feed(grapheme))
+            .unwrap_or(index);
+        // Take into account newlines occurring in input[0..=index], i.e., the possible next new
+        // line. If there is one, then text after it could be rewritten in a way that the available
+        // space is fully used.
+        for (i, grapheme) in input[0..=index].iter().enumerate() {
+            if is_new_line(grapheme) {
+                if i <= index_minus_ws {
+                    let mut line = &input[0..i].concat()[..];
+                    if trim_end {
+                        line = line.trim_end();
+                    }
+                    return SnippetState::EndWithLineFeed(format!("{}\n", line), i + 1);
+                }
+                break;
+            }
+        }
+
+        let mut index_plus_ws = index;
+        for (i, grapheme) in input[index + 1..].iter().enumerate() {
+            if !trim_end && is_new_line(grapheme) {
+                return SnippetState::EndWithLineFeed(
+                    input[0..=index + 1 + i].concat(),
+                    index + 2 + i,
+                );
+            } else if not_whitespace_except_line_feed(grapheme) {
+                index_plus_ws = index + i;
+                break;
+            }
+        }
+
+        if trim_end {
+            SnippetState::LineEnd(input[0..=index_minus_ws].concat(), index_plus_ws + 1)
+        } else {
+            SnippetState::LineEnd(input[0..=index_plus_ws].concat(), index_plus_ws + 1)
+        }
+    };
+
+    // find a first index where the unicode width of input[0..x] become > max_width
+    let max_width_index_in_input = {
+        let mut cur_width = 0;
+        let mut cur_index = 0;
+        for (i, grapheme) in input.iter().enumerate() {
+            cur_width += unicode_str_width(grapheme);
+            cur_index = i;
+            if cur_width > max_width {
+                break;
+            }
+        }
+        cur_index
+    };
+
+    // Find the position in input for breaking the string
+    if line_end.is_empty()
+        && trim_end
+        && !is_whitespace(input[max_width_index_in_input - 1])
+        && is_whitespace(input[max_width_index_in_input])
+    {
+        // At a breaking point already
+        // The line won't invalidate the rewriting because:
+        // - no extra space needed for the line_end character
+        // - extra whitespaces to the right can be trimmed
+        return break_at(max_width_index_in_input - 1);
+    }
+    if let Some(url_index_end) = detect_url(input, max_width_index_in_input) {
+        let index_plus_ws = url_index_end
+            + input[url_index_end..]
+                .iter()
+                .skip(1)
+                .position(|grapheme| not_whitespace_except_line_feed(grapheme))
+                .unwrap_or(0);
+        return if trim_end {
+            SnippetState::LineEnd(input[..=url_index_end].concat(), index_plus_ws + 1)
+        } else {
+            return SnippetState::LineEnd(input[..=index_plus_ws].concat(), index_plus_ws + 1);
+        };
+    }
+
+    match input[0..max_width_index_in_input]
+        .iter()
+        .rposition(|grapheme| is_whitespace(grapheme))
+    {
+        // Found a whitespace and what is on its left side is big enough.
+        Some(index) if index >= MIN_STRING => break_at(index),
+        // No whitespace found, try looking for a punctuation instead
+        _ => match input[0..max_width_index_in_input]
+            .iter()
+            .rposition(|grapheme| is_punctuation(grapheme))
+        {
+            // Found a punctuation and what is on its left side is big enough.
+            Some(index) if index >= MIN_STRING => break_at(index),
+            // Either no boundary character was found to the left of `input[max_chars]`, or the line
+            // got too small. We try searching for a boundary character to the right.
+            _ => match input[max_width_index_in_input..]
+                .iter()
+                .position(|grapheme| is_whitespace(grapheme) || is_punctuation(grapheme))
+            {
+                // A boundary was found after the line limit
+                Some(index) => break_at(max_width_index_in_input + index),
+                // No boundary to the right, the input cannot be broken
+                None => SnippetState::EndOfInput(input.concat()),
+            },
+        },
+    }
+}
+
+fn is_new_line(grapheme: &str) -> bool {
+    let bytes = grapheme.as_bytes();
+    bytes.starts_with(b"\n") || bytes.starts_with(b"\r\n")
+}
+
+fn is_whitespace(grapheme: &str) -> bool {
+    grapheme.chars().all(char::is_whitespace)
+}
+
+fn is_punctuation(grapheme: &str) -> bool {
+    grapheme
+        .chars()
+        .all(UnicodeCategories::is_punctuation_other)
+}
+
+fn graphemes_width(graphemes: &[&str]) -> usize {
+    graphemes.iter().map(|s| unicode_str_width(s)).sum()
+}
+
+#[cfg(test)]
+mod test {
+    use super::{break_string, detect_url, rewrite_string, SnippetState, StringFormat};
+    use crate::config::Config;
+    use crate::shape::{Indent, Shape};
+    use unicode_segmentation::UnicodeSegmentation;
+
+    #[test]
+    fn issue343() {
+        let config = Default::default();
+        let fmt = StringFormat::new(Shape::legacy(2, Indent::empty()), &config);
+        rewrite_string("eq_", &fmt, 2);
+    }
+
+    #[test]
+    fn should_break_on_whitespace() {
+        let string = "Placerat felis. Mauris porta ante sagittis purus.";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(20, false, "", &graphemes[..]),
+            SnippetState::LineEnd("Placerat felis. ".to_string(), 16)
+        );
+        assert_eq!(
+            break_string(20, true, "", &graphemes[..]),
+            SnippetState::LineEnd("Placerat felis.".to_string(), 16)
+        );
+    }
+
+    #[test]
+    fn should_break_on_punctuation() {
+        let string = "Placerat_felis._Mauris_porta_ante_sagittis_purus.";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(20, false, "", &graphemes[..]),
+            SnippetState::LineEnd("Placerat_felis.".to_string(), 15)
+        );
+    }
+
+    #[test]
+    fn should_break_forward() {
+        let string = "Venenatis_tellus_vel_tellus. Aliquam aliquam dolor at justo.";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(20, false, "", &graphemes[..]),
+            SnippetState::LineEnd("Venenatis_tellus_vel_tellus. ".to_string(), 29)
+        );
+        assert_eq!(
+            break_string(20, true, "", &graphemes[..]),
+            SnippetState::LineEnd("Venenatis_tellus_vel_tellus.".to_string(), 29)
+        );
+    }
+
+    #[test]
+    fn nothing_to_break() {
+        let string = "Venenatis_tellus_vel_tellus";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(20, false, "", &graphemes[..]),
+            SnippetState::EndOfInput("Venenatis_tellus_vel_tellus".to_string())
+        );
+    }
+
+    #[test]
+    fn significant_whitespaces() {
+        let string = "Neque in sem.      \n      Pellentesque tellus augue.";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(15, false, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Neque in sem.      \n".to_string(), 20)
+        );
+        assert_eq!(
+            break_string(25, false, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Neque in sem.      \n".to_string(), 20)
+        );
+
+        assert_eq!(
+            break_string(15, true, "", &graphemes[..]),
+            SnippetState::LineEnd("Neque in sem.".to_string(), 19)
+        );
+        assert_eq!(
+            break_string(25, true, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Neque in sem.\n".to_string(), 20)
+        );
+    }
+
+    #[test]
+    fn big_whitespace() {
+        let string = "Neque in sem.            Pellentesque tellus augue.";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(20, false, "", &graphemes[..]),
+            SnippetState::LineEnd("Neque in sem.            ".to_string(), 25)
+        );
+        assert_eq!(
+            break_string(20, true, "", &graphemes[..]),
+            SnippetState::LineEnd("Neque in sem.".to_string(), 25)
+        );
+    }
+
+    #[test]
+    fn newline_in_candidate_line() {
+        let string = "Nulla\nconsequat erat at massa. Vivamus id mi.";
+
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(
+            break_string(25, false, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Nulla\n".to_string(), 6)
+        );
+        assert_eq!(
+            break_string(25, true, "", &graphemes[..]),
+            SnippetState::EndWithLineFeed("Nulla\n".to_string(), 6)
+        );
+
+        let mut config: Config = Default::default();
+        config.set().max_width(27);
+        let fmt = StringFormat::new(Shape::legacy(25, Indent::empty()), &config);
+        let rewritten_string = rewrite_string(string, &fmt, 27);
+        assert_eq!(
+            rewritten_string,
+            Some("\"Nulla\nconsequat erat at massa. \\\n Vivamus id mi.\"".to_string())
+        );
+    }
+
+    #[test]
+    fn last_line_fit_with_trailing_whitespaces() {
+        let string = "Vivamus id mi.  ";
+        let config: Config = Default::default();
+        let mut fmt = StringFormat::new(Shape::legacy(25, Indent::empty()), &config);
+
+        fmt.trim_end = true;
+        let rewritten_string = rewrite_string(string, &fmt, 25);
+        assert_eq!(rewritten_string, Some("\"Vivamus id mi.\"".to_string()));
+
+        fmt.trim_end = false; // default value of trim_end
+        let rewritten_string = rewrite_string(string, &fmt, 25);
+        assert_eq!(rewritten_string, Some("\"Vivamus id mi.  \"".to_string()));
+    }
+
+    #[test]
+    fn last_line_fit_with_newline() {
+        let string = "Vivamus id mi.\nVivamus id mi.";
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(100, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let rewritten_string = rewrite_string(string, &fmt, 100);
+        assert_eq!(
+            rewritten_string,
+            Some("Vivamus id mi.\n    // Vivamus id mi.".to_string())
+        );
+    }
+
+    #[test]
+    fn overflow_in_non_string_content() {
+        let comment = "Aenean metus.\nVestibulum ac lacus. Vivamus porttitor";
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(30, Indent::from_width(&config, 8)),
+            trim_end: true,
+            config: &config,
+        };
+
+        assert_eq!(
+            rewrite_string(comment, &fmt, 30),
+            Some(
+                "Aenean metus.\n        // Vestibulum ac lacus. Vivamus\n        // porttitor"
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn overflow_in_non_string_content_with_line_end() {
+        let comment = "Aenean metus.\nVestibulum ac lacus. Vivamus porttitor";
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "@",
+            shape: Shape::legacy(30, Indent::from_width(&config, 8)),
+            trim_end: true,
+            config: &config,
+        };
+
+        assert_eq!(
+            rewrite_string(comment, &fmt, 30),
+            Some(
+                "Aenean metus.\n        // Vestibulum ac lacus. Vivamus@\n        // porttitor"
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn blank_line_with_non_empty_line_start() {
+        let config: Config = Default::default();
+        let mut fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(30, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let comment = "Aenean metus. Vestibulum\n\nac lacus. Vivamus porttitor";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 30),
+            Some(
+                "Aenean metus. Vestibulum\n    //\n    // ac lacus. Vivamus porttitor".to_string()
+            )
+        );
+
+        fmt.shape = Shape::legacy(15, Indent::from_width(&config, 4));
+        let comment = "Aenean\n\nmetus. Vestibulum ac lacus. Vivamus porttitor";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 15),
+            Some(
+                r#"Aenean
+    //
+    // metus. Vestibulum
+    // ac lacus. Vivamus
+    // porttitor"#
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn retain_blank_lines() {
+        let config: Config = Default::default();
+        let fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(20, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let comment = "Aenean\n\nmetus. Vestibulum ac lacus.\n\n";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 20),
+            Some(
+                "Aenean\n    //\n    // metus. Vestibulum ac\n    // lacus.\n    //\n".to_string()
+            )
+        );
+
+        let comment = "Aenean\n\nmetus. Vestibulum ac lacus.\n";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 20),
+            Some("Aenean\n    //\n    // metus. Vestibulum ac\n    // lacus.\n".to_string())
+        );
+
+        let comment = "Aenean\n        \nmetus. Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 20),
+            Some("Aenean\n    //\n    // metus. Vestibulum ac\n    // lacus.".to_string())
+        );
+    }
+
+    #[test]
+    fn boundary_on_edge() {
+        let config: Config = Default::default();
+        let mut fmt = StringFormat {
+            opener: "",
+            closer: "",
+            line_start: "// ",
+            line_end: "",
+            shape: Shape::legacy(13, Indent::from_width(&config, 4)),
+            trim_end: true,
+            config: &config,
+        };
+
+        let comment = "Aenean metus. Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 13),
+            Some("Aenean metus.\n    // Vestibulum ac\n    // lacus.".to_string())
+        );
+
+        fmt.trim_end = false;
+        let comment = "Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 13),
+            Some("Vestibulum \n    // ac lacus.".to_string())
+        );
+
+        fmt.trim_end = true;
+        fmt.line_end = "\\";
+        let comment = "Vestibulum ac lacus.";
+        assert_eq!(
+            rewrite_string(comment, &fmt, 13),
+            Some("Vestibulum\\\n    // ac lacus.".to_string())
+        );
+    }
+
+    #[test]
+    fn detect_urls() {
+        let string = "aaa http://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(21));
+
+        let string = "https://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 0), Some(18));
+
+        let string = "aaa ftp://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(20));
+
+        let string = "aaa file://example.org something";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(21));
+
+        let string = "aaa http not an url";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 6), None);
+
+        let string = "aaa file://example.org";
+        let graphemes = UnicodeSegmentation::graphemes(&*string, false).collect::<Vec<&str>>();
+        assert_eq!(detect_url(&graphemes, 8), Some(21));
+    }
+}
diff --git a/src/tools/rustfmt/src/syntux.rs b/src/tools/rustfmt/src/syntux.rs
new file mode 100644
index 0000000000000..845576bd8d8bb
--- /dev/null
+++ b/src/tools/rustfmt/src/syntux.rs
@@ -0,0 +1,4 @@
+//! This module defines a thin abstract layer on top of the rustc's parser and syntax libraries.
+
+pub(crate) mod parser;
+pub(crate) mod session;
diff --git a/src/tools/rustfmt/src/syntux/parser.rs b/src/tools/rustfmt/src/syntux/parser.rs
new file mode 100644
index 0000000000000..0b94749f3c6f4
--- /dev/null
+++ b/src/tools/rustfmt/src/syntux/parser.rs
@@ -0,0 +1,263 @@
+use std::panic::{catch_unwind, AssertUnwindSafe};
+use std::path::{Path, PathBuf};
+
+use rustc_ast::token::{DelimToken, TokenKind};
+use rustc_ast::{ast, ptr};
+use rustc_errors::Diagnostic;
+use rustc_parse::{
+    new_parser_from_file,
+    parser::{ForceCollect, Parser as RawParser},
+};
+use rustc_span::{sym, symbol::kw, Span};
+
+use crate::attr::first_attr_value_str_by_name;
+use crate::syntux::session::ParseSess;
+use crate::Input;
+
+pub(crate) type DirectoryOwnership = rustc_expand::module::DirOwnership;
+pub(crate) type ModulePathSuccess = rustc_expand::module::ModulePathSuccess;
+pub(crate) type ModError<'a> = rustc_expand::module::ModError<'a>;
+
+#[derive(Clone)]
+pub(crate) struct Directory {
+    pub(crate) path: PathBuf,
+    pub(crate) ownership: DirectoryOwnership,
+}
+
+/// A parser for Rust source code.
+pub(crate) struct Parser<'a> {
+    parser: RawParser<'a>,
+}
+
+/// A builder for the `Parser`.
+#[derive(Default)]
+pub(crate) struct ParserBuilder<'a> {
+    sess: Option<&'a ParseSess>,
+    input: Option<Input>,
+}
+
+impl<'a> ParserBuilder<'a> {
+    pub(crate) fn input(mut self, input: Input) -> ParserBuilder<'a> {
+        self.input = Some(input);
+        self
+    }
+
+    pub(crate) fn sess(mut self, sess: &'a ParseSess) -> ParserBuilder<'a> {
+        self.sess = Some(sess);
+        self
+    }
+
+    pub(crate) fn build(self) -> Result<Parser<'a>, ParserError> {
+        let sess = self.sess.ok_or(ParserError::NoParseSess)?;
+        let input = self.input.ok_or(ParserError::NoInput)?;
+
+        let parser = match Self::parser(sess.inner(), input) {
+            Ok(p) => p,
+            Err(db) => {
+                if let Some(diagnostics) = db {
+                    sess.emit_diagnostics(diagnostics);
+                    return Err(ParserError::ParserCreationError);
+                }
+                return Err(ParserError::ParsePanicError);
+            }
+        };
+
+        Ok(Parser { parser })
+    }
+
+    fn parser(
+        sess: &'a rustc_session::parse::ParseSess,
+        input: Input,
+    ) -> Result<rustc_parse::parser::Parser<'a>, Option<Vec<Diagnostic>>> {
+        match input {
+            Input::File(ref file) => catch_unwind(AssertUnwindSafe(move || {
+                new_parser_from_file(sess, file, None)
+            }))
+            .map_err(|_| None),
+            Input::Text(text) => rustc_parse::maybe_new_parser_from_source_str(
+                sess,
+                rustc_span::FileName::Custom("stdin".to_owned()),
+                text,
+            )
+            .map_err(|db| Some(db)),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub(crate) enum ParserError {
+    NoParseSess,
+    NoInput,
+    ParserCreationError,
+    ParseError,
+    ParsePanicError,
+}
+
+impl<'a> Parser<'a> {
+    pub(crate) fn submod_path_from_attr(attrs: &[ast::Attribute], path: &Path) -> Option<PathBuf> {
+        let path_string = first_attr_value_str_by_name(attrs, sym::path)?.as_str();
+        // On windows, the base path might have the form
+        // `\\?\foo\bar` in which case it does not tolerate
+        // mixed `/` and `\` separators, so canonicalize
+        // `/` to `\`.
+        #[cfg(windows)]
+        let path_string = path_string.replace("/", "\\");
+
+        Some(path.join(&*path_string))
+    }
+
+    pub(crate) fn parse_file_as_module(
+        sess: &'a ParseSess,
+        path: &Path,
+        span: Span,
+    ) -> Result<(Vec<ast::Attribute>, Vec<ptr::P<ast::Item>>, Span), ParserError> {
+        let result = catch_unwind(AssertUnwindSafe(|| {
+            let mut parser = new_parser_from_file(sess.inner(), &path, Some(span));
+            match parser.parse_mod(&TokenKind::Eof) {
+                Ok(result) => Some(result),
+                Err(mut e) => {
+                    sess.emit_or_cancel_diagnostic(&mut e);
+                    if sess.can_reset_errors() {
+                        sess.reset_errors();
+                    }
+                    None
+                }
+            }
+        }));
+        match result {
+            Ok(Some(m)) => {
+                if !sess.has_errors() {
+                    return Ok(m);
+                }
+
+                if sess.can_reset_errors() {
+                    sess.reset_errors();
+                    return Ok(m);
+                }
+                Err(ParserError::ParseError)
+            }
+            Ok(None) => Err(ParserError::ParseError),
+            Err(..) if path.exists() => Err(ParserError::ParseError),
+            Err(_) => Err(ParserError::ParsePanicError),
+        }
+    }
+
+    pub(crate) fn parse_crate(
+        input: Input,
+        sess: &'a ParseSess,
+    ) -> Result<ast::Crate, ParserError> {
+        let krate = Parser::parse_crate_inner(input, sess)?;
+        if !sess.has_errors() {
+            return Ok(krate);
+        }
+
+        if sess.can_reset_errors() {
+            sess.reset_errors();
+            return Ok(krate);
+        }
+
+        Err(ParserError::ParseError)
+    }
+
+    fn parse_crate_inner(input: Input, sess: &'a ParseSess) -> Result<ast::Crate, ParserError> {
+        ParserBuilder::default()
+            .input(input)
+            .sess(sess)
+            .build()?
+            .parse_crate_mod()
+    }
+
+    fn parse_crate_mod(&mut self) -> Result<ast::Crate, ParserError> {
+        let mut parser = AssertUnwindSafe(&mut self.parser);
+
+        match catch_unwind(move || parser.parse_crate_mod()) {
+            Ok(Ok(k)) => Ok(k),
+            Ok(Err(mut db)) => {
+                db.emit();
+                Err(ParserError::ParseError)
+            }
+            Err(_) => Err(ParserError::ParsePanicError),
+        }
+    }
+
+    pub(crate) fn parse_cfg_if(
+        sess: &'a ParseSess,
+        mac: &'a ast::MacCall,
+    ) -> Result<Vec<ast::Item>, &'static str> {
+        match catch_unwind(AssertUnwindSafe(|| Parser::parse_cfg_if_inner(sess, mac))) {
+            Ok(Ok(items)) => Ok(items),
+            Ok(err @ Err(_)) => err,
+            Err(..) => Err("failed to parse cfg_if!"),
+        }
+    }
+
+    fn parse_cfg_if_inner(
+        sess: &'a ParseSess,
+        mac: &'a ast::MacCall,
+    ) -> Result<Vec<ast::Item>, &'static str> {
+        let token_stream = mac.args.inner_tokens();
+        let mut parser =
+            rustc_parse::stream_to_parser(sess.inner(), token_stream.clone(), Some(""));
+
+        let mut items = vec![];
+        let mut process_if_cfg = true;
+
+        while parser.token.kind != TokenKind::Eof {
+            if process_if_cfg {
+                if !parser.eat_keyword(kw::If) {
+                    return Err("Expected `if`");
+                }
+                // Inner attributes are not actually syntactically permitted here, but we don't
+                // care about inner vs outer attributes in this position. Our purpose with this
+                // special case parsing of cfg_if macros is to ensure we can correctly resolve
+                // imported modules that may have a custom `path` defined.
+                //
+                // As such, we just need to advance the parser past the attribute and up to
+                // to the opening brace.
+                // See also https://github.com/rust-lang/rust/pull/79433
+                parser
+                    .parse_attribute(rustc_parse::parser::attr::InnerAttrPolicy::Permitted)
+                    .map_err(|_| "Failed to parse attributes")?;
+            }
+
+            if !parser.eat(&TokenKind::OpenDelim(DelimToken::Brace)) {
+                return Err("Expected an opening brace");
+            }
+
+            while parser.token != TokenKind::CloseDelim(DelimToken::Brace)
+                && parser.token.kind != TokenKind::Eof
+            {
+                let item = match parser.parse_item(ForceCollect::No) {
+                    Ok(Some(item_ptr)) => item_ptr.into_inner(),
+                    Ok(None) => continue,
+                    Err(mut err) => {
+                        err.cancel();
+                        parser.sess.span_diagnostic.reset_err_count();
+                        return Err(
+                            "Expected item inside cfg_if block, but failed to parse it as an item",
+                        );
+                    }
+                };
+                if let ast::ItemKind::Mod(..) = item.kind {
+                    items.push(item);
+                }
+            }
+
+            if !parser.eat(&TokenKind::CloseDelim(DelimToken::Brace)) {
+                return Err("Expected a closing brace");
+            }
+
+            if parser.eat(&TokenKind::Eof) {
+                break;
+            }
+
+            if !parser.eat_keyword(kw::Else) {
+                return Err("Expected `else`");
+            }
+
+            process_if_cfg = parser.token.is_keyword(kw::If);
+        }
+
+        Ok(items)
+    }
+}
diff --git a/src/tools/rustfmt/src/syntux/session.rs b/src/tools/rustfmt/src/syntux/session.rs
new file mode 100644
index 0000000000000..870f0acfe395c
--- /dev/null
+++ b/src/tools/rustfmt/src/syntux/session.rs
@@ -0,0 +1,463 @@
+use std::path::Path;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+use rustc_data_structures::sync::{Lrc, Send};
+use rustc_errors::emitter::{Emitter, EmitterWriter};
+use rustc_errors::{ColorConfig, Diagnostic, Handler, Level as DiagnosticLevel};
+use rustc_session::parse::ParseSess as RawParseSess;
+use rustc_span::{
+    source_map::{FilePathMapping, SourceMap},
+    symbol, BytePos, Span,
+};
+
+use crate::config::file_lines::LineRange;
+use crate::ignore_path::IgnorePathSet;
+use crate::source_map::LineRangeUtils;
+use crate::utils::starts_with_newline;
+use crate::visitor::SnippetProvider;
+use crate::{Config, ErrorKind, FileName};
+
+/// ParseSess holds structs necessary for constructing a parser.
+pub(crate) struct ParseSess {
+    parse_sess: RawParseSess,
+    ignore_path_set: Lrc<IgnorePathSet>,
+    can_reset_errors: Lrc<AtomicBool>,
+}
+
+/// Emitter which discards every error.
+struct SilentEmitter;
+
+impl Emitter for SilentEmitter {
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+        None
+    }
+    fn emit_diagnostic(&mut self, _db: &Diagnostic) {}
+}
+
+fn silent_emitter() -> Box<dyn Emitter + Send> {
+    Box::new(SilentEmitter {})
+}
+
+/// Emit errors against every files expect ones specified in the `ignore_path_set`.
+struct SilentOnIgnoredFilesEmitter {
+    ignore_path_set: Lrc<IgnorePathSet>,
+    source_map: Lrc<SourceMap>,
+    emitter: Box<dyn Emitter + Send>,
+    has_non_ignorable_parser_errors: bool,
+    can_reset: Lrc<AtomicBool>,
+}
+
+impl SilentOnIgnoredFilesEmitter {
+    fn handle_non_ignoreable_error(&mut self, db: &Diagnostic) {
+        self.has_non_ignorable_parser_errors = true;
+        self.can_reset.store(false, Ordering::Release);
+        self.emitter.emit_diagnostic(db);
+    }
+}
+
+impl Emitter for SilentOnIgnoredFilesEmitter {
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+        None
+    }
+    fn emit_diagnostic(&mut self, db: &Diagnostic) {
+        if db.level == DiagnosticLevel::Fatal {
+            return self.handle_non_ignoreable_error(db);
+        }
+        if let Some(primary_span) = &db.span.primary_span() {
+            let file_name = self.source_map.span_to_filename(*primary_span);
+            if let rustc_span::FileName::Real(rustc_span::RealFileName::LocalPath(ref path)) =
+                file_name
+            {
+                if self
+                    .ignore_path_set
+                    .is_match(&FileName::Real(path.to_path_buf()))
+                {
+                    if !self.has_non_ignorable_parser_errors {
+                        self.can_reset.store(true, Ordering::Release);
+                    }
+                    return;
+                }
+            };
+        }
+        self.handle_non_ignoreable_error(db);
+    }
+}
+
+fn default_handler(
+    source_map: Lrc<SourceMap>,
+    ignore_path_set: Lrc<IgnorePathSet>,
+    can_reset: Lrc<AtomicBool>,
+    hide_parse_errors: bool,
+) -> Handler {
+    let supports_color = term::stderr().map_or(false, |term| term.supports_color());
+    let color_cfg = if supports_color {
+        ColorConfig::Auto
+    } else {
+        ColorConfig::Never
+    };
+
+    let emitter = if hide_parse_errors {
+        silent_emitter()
+    } else {
+        Box::new(EmitterWriter::stderr(
+            color_cfg,
+            Some(source_map.clone()),
+            false,
+            false,
+            None,
+            false,
+        ))
+    };
+    Handler::with_emitter(
+        true,
+        None,
+        Box::new(SilentOnIgnoredFilesEmitter {
+            has_non_ignorable_parser_errors: false,
+            source_map,
+            emitter,
+            ignore_path_set,
+            can_reset,
+        }),
+    )
+}
+
+impl ParseSess {
+    pub(crate) fn new(config: &Config) -> Result<ParseSess, ErrorKind> {
+        let ignore_path_set = match IgnorePathSet::from_ignore_list(&config.ignore()) {
+            Ok(ignore_path_set) => Lrc::new(ignore_path_set),
+            Err(e) => return Err(ErrorKind::InvalidGlobPattern(e)),
+        };
+        let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let can_reset_errors = Lrc::new(AtomicBool::new(false));
+
+        let handler = default_handler(
+            Lrc::clone(&source_map),
+            Lrc::clone(&ignore_path_set),
+            Lrc::clone(&can_reset_errors),
+            config.hide_parse_errors(),
+        );
+        let parse_sess = RawParseSess::with_span_handler(handler, source_map);
+
+        Ok(ParseSess {
+            parse_sess,
+            ignore_path_set,
+            can_reset_errors,
+        })
+    }
+
+    pub(crate) fn default_submod_path(
+        &self,
+        id: symbol::Ident,
+        relative: Option<symbol::Ident>,
+        dir_path: &Path,
+    ) -> Result<rustc_expand::module::ModulePathSuccess, rustc_expand::module::ModError<'_>> {
+        rustc_expand::module::default_submod_path(&self.parse_sess, id, relative, dir_path)
+    }
+
+    pub(crate) fn is_file_parsed(&self, path: &Path) -> bool {
+        self.parse_sess
+            .source_map()
+            .get_source_file(&rustc_span::FileName::Real(
+                rustc_span::RealFileName::LocalPath(path.to_path_buf()),
+            ))
+            .is_some()
+    }
+
+    pub(crate) fn ignore_file(&self, path: &FileName) -> bool {
+        self.ignore_path_set.as_ref().is_match(&path)
+    }
+
+    pub(crate) fn set_silent_emitter(&mut self) {
+        self.parse_sess.span_diagnostic = Handler::with_emitter(true, None, silent_emitter());
+    }
+
+    pub(crate) fn span_to_filename(&self, span: Span) -> FileName {
+        self.parse_sess.source_map().span_to_filename(span).into()
+    }
+
+    pub(crate) fn span_to_first_line_string(&self, span: Span) -> String {
+        let file_lines = self.parse_sess.source_map().span_to_lines(span).ok();
+
+        match file_lines {
+            Some(fl) => fl
+                .file
+                .get_line(fl.lines[0].line_index)
+                .map_or_else(String::new, |s| s.to_string()),
+            None => String::new(),
+        }
+    }
+
+    pub(crate) fn line_of_byte_pos(&self, pos: BytePos) -> usize {
+        self.parse_sess.source_map().lookup_char_pos(pos).line
+    }
+
+    pub(crate) fn span_to_debug_info(&self, span: Span) -> String {
+        self.parse_sess.source_map().span_to_diagnostic_string(span)
+    }
+
+    pub(crate) fn inner(&self) -> &RawParseSess {
+        &self.parse_sess
+    }
+
+    pub(crate) fn snippet_provider(&self, span: Span) -> SnippetProvider {
+        let source_file = self.parse_sess.source_map().lookup_char_pos(span.lo()).file;
+        SnippetProvider::new(
+            source_file.start_pos,
+            source_file.end_pos,
+            Lrc::clone(source_file.src.as_ref().unwrap()),
+        )
+    }
+
+    pub(crate) fn get_original_snippet(&self, file_name: &FileName) -> Option<Lrc<String>> {
+        self.parse_sess
+            .source_map()
+            .get_source_file(&file_name.into())
+            .and_then(|source_file| source_file.src.clone())
+    }
+}
+
+// Methods that should be restricted within the syntux module.
+impl ParseSess {
+    pub(super) fn emit_diagnostics(&self, diagnostics: Vec<Diagnostic>) {
+        for diagnostic in diagnostics {
+            self.parse_sess.span_diagnostic.emit_diagnostic(&diagnostic);
+        }
+    }
+
+    pub(crate) fn emit_or_cancel_diagnostic(&self, diagnostic: &mut Diagnostic) {
+        self.parse_sess.span_diagnostic.emit_diagnostic(diagnostic);
+        // The Handler will check whether the diagnostic should be emitted
+        // based on the user's rustfmt configuration and the originating file
+        // that caused the parser error. If the Handler determined it should skip
+        // emission then we need to ensure the diagnostic is cancelled.
+        if !diagnostic.cancelled() {
+            diagnostic.cancel();
+        }
+    }
+
+    pub(super) fn can_reset_errors(&self) -> bool {
+        self.can_reset_errors.load(Ordering::Acquire)
+    }
+
+    pub(super) fn has_errors(&self) -> bool {
+        self.parse_sess.span_diagnostic.has_errors()
+    }
+
+    pub(super) fn reset_errors(&self) {
+        self.parse_sess.span_diagnostic.reset_err_count();
+    }
+}
+
+impl LineRangeUtils for ParseSess {
+    fn lookup_line_range(&self, span: Span) -> LineRange {
+        let snippet = self
+            .parse_sess
+            .source_map()
+            .span_to_snippet(span)
+            .unwrap_or_default();
+        let lo = self.parse_sess.source_map().lookup_line(span.lo()).unwrap();
+        let hi = self.parse_sess.source_map().lookup_line(span.hi()).unwrap();
+
+        debug_assert_eq!(
+            lo.sf.name, hi.sf.name,
+            "span crossed file boundary: lo: {:?}, hi: {:?}",
+            lo, hi
+        );
+
+        // in case the span starts with a newline, the line range is off by 1 without the
+        // adjustment below
+        let offset = 1 + if starts_with_newline(&snippet) { 1 } else { 0 };
+        // Line numbers start at 1
+        LineRange {
+            file: lo.sf.clone(),
+            lo: lo.line + offset,
+            hi: hi.line + offset,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    mod emitter {
+        use super::*;
+        use crate::config::IgnoreList;
+        use crate::is_nightly_channel;
+        use crate::utils::mk_sp;
+        use rustc_span::{FileName as SourceMapFileName, MultiSpan, RealFileName, DUMMY_SP};
+        use std::path::PathBuf;
+        use std::sync::atomic::AtomicU32;
+
+        struct TestEmitter {
+            num_emitted_errors: Lrc<AtomicU32>,
+        }
+
+        impl Emitter for TestEmitter {
+            fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+                None
+            }
+            fn emit_diagnostic(&mut self, _db: &Diagnostic) {
+                self.num_emitted_errors.fetch_add(1, Ordering::Release);
+            }
+        }
+
+        fn build_diagnostic(level: DiagnosticLevel, span: Option<MultiSpan>) -> Diagnostic {
+            Diagnostic {
+                level,
+                code: None,
+                message: vec![],
+                children: vec![],
+                suggestions: vec![],
+                span: span.unwrap_or_else(MultiSpan::new),
+                sort_span: DUMMY_SP,
+            }
+        }
+
+        fn build_emitter(
+            num_emitted_errors: Lrc<AtomicU32>,
+            can_reset: Lrc<AtomicBool>,
+            source_map: Option<Lrc<SourceMap>>,
+            ignore_list: Option<IgnoreList>,
+        ) -> SilentOnIgnoredFilesEmitter {
+            let emitter_writer = TestEmitter { num_emitted_errors };
+            let source_map =
+                source_map.unwrap_or_else(|| Lrc::new(SourceMap::new(FilePathMapping::empty())));
+            let ignore_path_set = Lrc::new(
+                IgnorePathSet::from_ignore_list(&ignore_list.unwrap_or_default()).unwrap(),
+            );
+            SilentOnIgnoredFilesEmitter {
+                has_non_ignorable_parser_errors: false,
+                source_map,
+                emitter: Box::new(emitter_writer),
+                ignore_path_set,
+                can_reset,
+            }
+        }
+
+        fn get_ignore_list(config: &str) -> IgnoreList {
+            Config::from_toml(config, Path::new("")).unwrap().ignore()
+        }
+
+        #[test]
+        fn handles_fatal_parse_error_in_ignored_file() {
+            let num_emitted_errors = Lrc::new(AtomicU32::new(0));
+            let can_reset_errors = Lrc::new(AtomicBool::new(false));
+            let ignore_list = get_ignore_list(r#"ignore = ["foo.rs"]"#);
+            let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+            let source =
+                String::from(r#"extern "system" fn jni_symbol!( funcName ) ( ... ) -> {} "#);
+            source_map.new_source_file(
+                SourceMapFileName::Real(RealFileName::LocalPath(PathBuf::from("foo.rs"))),
+                source,
+            );
+            let mut emitter = build_emitter(
+                Lrc::clone(&num_emitted_errors),
+                Lrc::clone(&can_reset_errors),
+                Some(Lrc::clone(&source_map)),
+                Some(ignore_list),
+            );
+            let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
+            let fatal_diagnostic = build_diagnostic(DiagnosticLevel::Fatal, Some(span));
+            emitter.emit_diagnostic(&fatal_diagnostic);
+            assert_eq!(num_emitted_errors.load(Ordering::Acquire), 1);
+            assert_eq!(can_reset_errors.load(Ordering::Acquire), false);
+        }
+
+        #[test]
+        fn handles_recoverable_parse_error_in_ignored_file() {
+            if !is_nightly_channel!() {
+                return;
+            }
+            let num_emitted_errors = Lrc::new(AtomicU32::new(0));
+            let can_reset_errors = Lrc::new(AtomicBool::new(false));
+            let ignore_list = get_ignore_list(r#"ignore = ["foo.rs"]"#);
+            let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+            let source = String::from(r#"pub fn bar() { 1x; }"#);
+            source_map.new_source_file(
+                SourceMapFileName::Real(RealFileName::LocalPath(PathBuf::from("foo.rs"))),
+                source,
+            );
+            let mut emitter = build_emitter(
+                Lrc::clone(&num_emitted_errors),
+                Lrc::clone(&can_reset_errors),
+                Some(Lrc::clone(&source_map)),
+                Some(ignore_list),
+            );
+            let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
+            let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(span));
+            emitter.emit_diagnostic(&non_fatal_diagnostic);
+            assert_eq!(num_emitted_errors.load(Ordering::Acquire), 0);
+            assert_eq!(can_reset_errors.load(Ordering::Acquire), true);
+        }
+
+        #[test]
+        fn handles_recoverable_parse_error_in_non_ignored_file() {
+            if !is_nightly_channel!() {
+                return;
+            }
+            let num_emitted_errors = Lrc::new(AtomicU32::new(0));
+            let can_reset_errors = Lrc::new(AtomicBool::new(false));
+            let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+            let source = String::from(r#"pub fn bar() { 1x; }"#);
+            source_map.new_source_file(
+                SourceMapFileName::Real(RealFileName::LocalPath(PathBuf::from("foo.rs"))),
+                source,
+            );
+            let mut emitter = build_emitter(
+                Lrc::clone(&num_emitted_errors),
+                Lrc::clone(&can_reset_errors),
+                Some(Lrc::clone(&source_map)),
+                None,
+            );
+            let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
+            let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(span));
+            emitter.emit_diagnostic(&non_fatal_diagnostic);
+            assert_eq!(num_emitted_errors.load(Ordering::Acquire), 1);
+            assert_eq!(can_reset_errors.load(Ordering::Acquire), false);
+        }
+
+        #[test]
+        fn handles_mix_of_recoverable_parse_error() {
+            if !is_nightly_channel!() {
+                return;
+            }
+            let num_emitted_errors = Lrc::new(AtomicU32::new(0));
+            let can_reset_errors = Lrc::new(AtomicBool::new(false));
+            let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+            let ignore_list = get_ignore_list(r#"ignore = ["foo.rs"]"#);
+            let bar_source = String::from(r#"pub fn bar() { 1x; }"#);
+            let foo_source = String::from(r#"pub fn foo() { 1x; }"#);
+            let fatal_source =
+                String::from(r#"extern "system" fn jni_symbol!( funcName ) ( ... ) -> {} "#);
+            source_map.new_source_file(
+                SourceMapFileName::Real(RealFileName::LocalPath(PathBuf::from("bar.rs"))),
+                bar_source,
+            );
+            source_map.new_source_file(
+                SourceMapFileName::Real(RealFileName::LocalPath(PathBuf::from("foo.rs"))),
+                foo_source,
+            );
+            source_map.new_source_file(
+                SourceMapFileName::Real(RealFileName::LocalPath(PathBuf::from("fatal.rs"))),
+                fatal_source,
+            );
+            let mut emitter = build_emitter(
+                Lrc::clone(&num_emitted_errors),
+                Lrc::clone(&can_reset_errors),
+                Some(Lrc::clone(&source_map)),
+                Some(ignore_list),
+            );
+            let bar_span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
+            let foo_span = MultiSpan::from_span(mk_sp(BytePos(21), BytePos(22)));
+            let bar_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(bar_span));
+            let foo_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(foo_span));
+            let fatal_diagnostic = build_diagnostic(DiagnosticLevel::Fatal, None);
+            emitter.emit_diagnostic(&bar_diagnostic);
+            emitter.emit_diagnostic(&foo_diagnostic);
+            emitter.emit_diagnostic(&fatal_diagnostic);
+            assert_eq!(num_emitted_errors.load(Ordering::Acquire), 2);
+            assert_eq!(can_reset_errors.load(Ordering::Acquire), false);
+        }
+    }
+}
diff --git a/src/tools/rustfmt/src/test/configuration_snippet.rs b/src/tools/rustfmt/src/test/configuration_snippet.rs
new file mode 100644
index 0000000000000..ef7dd0ddcd123
--- /dev/null
+++ b/src/tools/rustfmt/src/test/configuration_snippet.rs
@@ -0,0 +1,287 @@
+use std::collections::{HashMap, HashSet};
+use std::fs;
+use std::io::{BufRead, BufReader, Write};
+use std::iter::Enumerate;
+use std::path::{Path, PathBuf};
+
+use super::{print_mismatches, write_message, DIFF_CONTEXT_SIZE};
+use crate::config::{Config, EmitMode, Verbosity};
+use crate::rustfmt_diff::{make_diff, Mismatch};
+use crate::{Input, Session};
+
+const CONFIGURATIONS_FILE_NAME: &str = "Configurations.md";
+
+// This enum is used to represent one of three text features in Configurations.md: a block of code
+// with its starting line number, the name of a rustfmt configuration option, or the value of a
+// rustfmt configuration option.
+enum ConfigurationSection {
+    CodeBlock((String, u32)), // (String: block of code, u32: line number of code block start)
+    ConfigName(String),
+    ConfigValue(String),
+}
+
+impl ConfigurationSection {
+    fn get_section<I: Iterator<Item = String>>(
+        file: &mut Enumerate<I>,
+    ) -> Option<ConfigurationSection> {
+        lazy_static! {
+            static ref CONFIG_NAME_REGEX: regex::Regex =
+                regex::Regex::new(r"^## `([^`]+)`").expect("failed creating configuration pattern");
+            static ref CONFIG_VALUE_REGEX: regex::Regex =
+                regex::Regex::new(r#"^#### `"?([^`"]+)"?`"#)
+                    .expect("failed creating configuration value pattern");
+        }
+
+        loop {
+            match file.next() {
+                Some((i, line)) => {
+                    if line.starts_with("```rust") {
+                        // Get the lines of the code block.
+                        let lines: Vec<String> = file
+                            .map(|(_i, l)| l)
+                            .take_while(|l| !l.starts_with("```"))
+                            .collect();
+                        let block = format!("{}\n", lines.join("\n"));
+
+                        // +1 to translate to one-based indexing
+                        // +1 to get to first line of code (line after "```")
+                        let start_line = (i + 2) as u32;
+
+                        return Some(ConfigurationSection::CodeBlock((block, start_line)));
+                    } else if let Some(c) = CONFIG_NAME_REGEX.captures(&line) {
+                        return Some(ConfigurationSection::ConfigName(String::from(&c[1])));
+                    } else if let Some(c) = CONFIG_VALUE_REGEX.captures(&line) {
+                        return Some(ConfigurationSection::ConfigValue(String::from(&c[1])));
+                    }
+                }
+                None => return None, // reached the end of the file
+            }
+        }
+    }
+}
+
+// This struct stores the information about code blocks in the configurations
+// file, formats the code blocks, and prints formatting errors.
+struct ConfigCodeBlock {
+    config_name: Option<String>,
+    config_value: Option<String>,
+    code_block: Option<String>,
+    code_block_start: Option<u32>,
+}
+
+impl ConfigCodeBlock {
+    fn new() -> ConfigCodeBlock {
+        ConfigCodeBlock {
+            config_name: None,
+            config_value: None,
+            code_block: None,
+            code_block_start: None,
+        }
+    }
+
+    fn set_config_name(&mut self, name: Option<String>) {
+        self.config_name = name;
+        self.config_value = None;
+    }
+
+    fn set_config_value(&mut self, value: Option<String>) {
+        self.config_value = value;
+    }
+
+    fn set_code_block(&mut self, code_block: String, code_block_start: u32) {
+        self.code_block = Some(code_block);
+        self.code_block_start = Some(code_block_start);
+    }
+
+    fn get_block_config(&self) -> Config {
+        let mut config = Config::default();
+        config.set().verbose(Verbosity::Quiet);
+        if self.config_name.is_some() && self.config_value.is_some() {
+            config.override_value(
+                self.config_name.as_ref().unwrap(),
+                self.config_value.as_ref().unwrap(),
+            );
+        }
+        config
+    }
+
+    fn code_block_valid(&self) -> bool {
+        // We never expect to not have a code block.
+        assert!(self.code_block.is_some() && self.code_block_start.is_some());
+
+        // See if code block begins with #![rustfmt::skip].
+        let fmt_skip = self
+            .code_block
+            .as_ref()
+            .unwrap()
+            .lines()
+            .nth(0)
+            .unwrap_or("")
+            == "#![rustfmt::skip]";
+
+        if self.config_name.is_none() && !fmt_skip {
+            write_message(&format!(
+                "No configuration name for {}:{}",
+                CONFIGURATIONS_FILE_NAME,
+                self.code_block_start.unwrap()
+            ));
+            return false;
+        }
+        if self.config_value.is_none() && !fmt_skip {
+            write_message(&format!(
+                "No configuration value for {}:{}",
+                CONFIGURATIONS_FILE_NAME,
+                self.code_block_start.unwrap()
+            ));
+            return false;
+        }
+        true
+    }
+
+    fn has_parsing_errors<T: Write>(&self, session: &Session<'_, T>) -> bool {
+        if session.has_parsing_errors() {
+            write_message(&format!(
+                "\u{261d}\u{1f3fd} Cannot format {}:{}",
+                CONFIGURATIONS_FILE_NAME,
+                self.code_block_start.unwrap()
+            ));
+            return true;
+        }
+
+        false
+    }
+
+    fn print_diff(&self, compare: Vec<Mismatch>) {
+        let mut mismatches = HashMap::new();
+        mismatches.insert(PathBuf::from(CONFIGURATIONS_FILE_NAME), compare);
+        print_mismatches(mismatches, |line_num| {
+            format!(
+                "\nMismatch at {}:{}:",
+                CONFIGURATIONS_FILE_NAME,
+                line_num + self.code_block_start.unwrap() - 1
+            )
+        });
+    }
+
+    fn formatted_has_diff(&self, text: &str) -> bool {
+        let compare = make_diff(self.code_block.as_ref().unwrap(), text, DIFF_CONTEXT_SIZE);
+        if !compare.is_empty() {
+            self.print_diff(compare);
+            return true;
+        }
+
+        false
+    }
+
+    // Return a bool indicating if formatting this code block is an idempotent
+    // operation. This function also triggers printing any formatting failure
+    // messages.
+    fn formatted_is_idempotent(&self) -> bool {
+        // Verify that we have all of the expected information.
+        if !self.code_block_valid() {
+            return false;
+        }
+
+        let input = Input::Text(self.code_block.as_ref().unwrap().to_owned());
+        let mut config = self.get_block_config();
+        config.set().emit_mode(EmitMode::Stdout);
+        let mut buf: Vec<u8> = vec![];
+
+        {
+            let mut session = Session::new(config, Some(&mut buf));
+            session.format(input).unwrap();
+            if self.has_parsing_errors(&session) {
+                return false;
+            }
+        }
+
+        !self.formatted_has_diff(&String::from_utf8(buf).unwrap())
+    }
+
+    // Extract a code block from the iterator. Behavior:
+    // - Rust code blocks are identifed by lines beginning with "```rust".
+    // - One explicit configuration setting is supported per code block.
+    // - Rust code blocks with no configuration setting are illegal and cause an
+    //   assertion failure, unless the snippet begins with #![rustfmt::skip].
+    // - Configuration names in Configurations.md must be in the form of
+    //   "## `NAME`".
+    // - Configuration values in Configurations.md must be in the form of
+    //   "#### `VALUE`".
+    fn extract<I: Iterator<Item = String>>(
+        file: &mut Enumerate<I>,
+        prev: Option<&ConfigCodeBlock>,
+        hash_set: &mut HashSet<String>,
+    ) -> Option<ConfigCodeBlock> {
+        let mut code_block = ConfigCodeBlock::new();
+        code_block.config_name = prev.and_then(|cb| cb.config_name.clone());
+
+        loop {
+            match ConfigurationSection::get_section(file) {
+                Some(ConfigurationSection::CodeBlock((block, start_line))) => {
+                    code_block.set_code_block(block, start_line);
+                    break;
+                }
+                Some(ConfigurationSection::ConfigName(name)) => {
+                    assert!(
+                        Config::is_valid_name(&name),
+                        "an unknown configuration option was found: {}",
+                        name
+                    );
+                    assert!(
+                        hash_set.remove(&name),
+                        "multiple configuration guides found for option {}",
+                        name
+                    );
+                    code_block.set_config_name(Some(name));
+                }
+                Some(ConfigurationSection::ConfigValue(value)) => {
+                    code_block.set_config_value(Some(value));
+                }
+                None => return None, // end of file was reached
+            }
+        }
+
+        Some(code_block)
+    }
+}
+
+#[test]
+fn configuration_snippet_tests() {
+    super::init_log();
+    let blocks = get_code_blocks();
+    let failures = blocks
+        .iter()
+        .map(ConfigCodeBlock::formatted_is_idempotent)
+        .fold(0, |acc, r| acc + (!r as u32));
+
+    // Display results.
+    println!("Ran {} configurations tests.", blocks.len());
+    assert_eq!(failures, 0, "{} configurations tests failed", failures);
+}
+
+// Read Configurations.md and build a `Vec` of `ConfigCodeBlock` structs with one
+// entry for each Rust code block found.
+fn get_code_blocks() -> Vec<ConfigCodeBlock> {
+    let mut file_iter = BufReader::new(
+        fs::File::open(Path::new(CONFIGURATIONS_FILE_NAME))
+            .unwrap_or_else(|_| panic!("couldn't read file {}", CONFIGURATIONS_FILE_NAME)),
+    )
+    .lines()
+    .map(Result::unwrap)
+    .enumerate();
+    let mut code_blocks: Vec<ConfigCodeBlock> = Vec::new();
+    let mut hash_set = Config::hash_set();
+
+    while let Some(cb) = ConfigCodeBlock::extract(&mut file_iter, code_blocks.last(), &mut hash_set)
+    {
+        code_blocks.push(cb);
+    }
+
+    for name in hash_set {
+        if !Config::is_hidden_option(&name) {
+            panic!("{} does not have a configuration guide", name);
+        }
+    }
+
+    code_blocks
+}
diff --git a/src/tools/rustfmt/src/test/mod.rs b/src/tools/rustfmt/src/test/mod.rs
new file mode 100644
index 0000000000000..ce56a223f2b04
--- /dev/null
+++ b/src/tools/rustfmt/src/test/mod.rs
@@ -0,0 +1,905 @@
+use std::collections::HashMap;
+use std::env;
+use std::fs;
+use std::io::{self, BufRead, BufReader, Read, Write};
+use std::iter::Peekable;
+use std::mem;
+use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio};
+use std::str::Chars;
+use std::thread;
+
+use crate::config::{Color, Config, EmitMode, FileName, NewlineStyle, ReportTactic};
+use crate::formatting::{ReportedErrors, SourceFile};
+use crate::rustfmt_diff::{make_diff, print_diff, DiffLine, Mismatch, ModifiedChunk, OutputWriter};
+use crate::source_file;
+use crate::{is_nightly_channel, FormatReport, FormatReportFormatterBuilder, Input, Session};
+
+mod configuration_snippet;
+mod parser;
+
+const DIFF_CONTEXT_SIZE: usize = 3;
+
+// A list of files on which we want to skip testing.
+const SKIP_FILE_WHITE_LIST: &[&str] = &[
+    // We want to make sure that the `skip_children` is correctly working,
+    // so we do not want to test this file directly.
+    "configs/skip_children/foo/mod.rs",
+    "issue-3434/no_entry.rs",
+    "issue-3665/sub_mod.rs",
+    // Testing for issue-3779
+    "issue-3779/ice.rs",
+    // These files and directory are a part of modules defined inside `cfg_if!`.
+    "cfg_if/mod.rs",
+    "cfg_if/detect",
+    "issue-3253/foo.rs",
+    "issue-3253/bar.rs",
+    "issue-3253/paths",
+    // These files and directory are a part of modules defined inside `cfg_attr(..)`.
+    "cfg_mod/dir",
+    "cfg_mod/bar.rs",
+    "cfg_mod/foo.rs",
+    "cfg_mod/wasm32.rs",
+    "skip/foo.rs",
+];
+
+fn init_log() {
+    let _ = env_logger::builder().is_test(true).try_init();
+}
+
+struct TestSetting {
+    /// The size of the stack of the thread that run tests.
+    stack_size: usize,
+}
+
+impl Default for TestSetting {
+    fn default() -> Self {
+        TestSetting {
+            stack_size: 8_388_608, // 8MB
+        }
+    }
+}
+
+fn run_test_with<F>(test_setting: &TestSetting, f: F)
+where
+    F: FnOnce(),
+    F: Send + 'static,
+{
+    thread::Builder::new()
+        .stack_size(test_setting.stack_size)
+        .spawn(f)
+        .expect("Failed to create a test thread")
+        .join()
+        .expect("Failed to join a test thread")
+}
+
+fn is_subpath<P>(path: &Path, subpath: &P) -> bool
+where
+    P: AsRef<Path>,
+{
+    (0..path.components().count())
+        .map(|i| {
+            path.components()
+                .skip(i)
+                .take(subpath.as_ref().components().count())
+        })
+        .any(|c| c.zip(subpath.as_ref().components()).all(|(a, b)| a == b))
+}
+
+fn is_file_skip(path: &Path) -> bool {
+    SKIP_FILE_WHITE_LIST
+        .iter()
+        .any(|file_path| is_subpath(path, file_path))
+}
+
+// Returns a `Vec` containing `PathBuf`s of files with an  `rs` extension in the
+// given path. The `recursive` argument controls if files from subdirectories
+// are also returned.
+fn get_test_files(path: &Path, recursive: bool) -> Vec<PathBuf> {
+    let mut files = vec![];
+    if path.is_dir() {
+        for entry in fs::read_dir(path).expect(&format!(
+            "couldn't read directory {}",
+            path.to_str().unwrap()
+        )) {
+            let entry = entry.expect("couldn't get `DirEntry`");
+            let path = entry.path();
+            if path.is_dir() && recursive {
+                files.append(&mut get_test_files(&path, recursive));
+            } else if path.extension().map_or(false, |f| f == "rs") && !is_file_skip(&path) {
+                files.push(path);
+            }
+        }
+    }
+    files
+}
+
+fn verify_config_used(path: &Path, config_name: &str) {
+    for entry in fs::read_dir(path).expect(&format!(
+        "couldn't read {} directory",
+        path.to_str().unwrap()
+    )) {
+        let entry = entry.expect("couldn't get directory entry");
+        let path = entry.path();
+        if path.extension().map_or(false, |f| f == "rs") {
+            // check if "// rustfmt-<config_name>:" appears in the file.
+            let filebuf = BufReader::new(
+                fs::File::open(&path)
+                    .unwrap_or_else(|_| panic!("couldn't read file {}", path.display())),
+            );
+            assert!(
+                filebuf
+                    .lines()
+                    .map(Result::unwrap)
+                    .take_while(|l| l.starts_with("//"))
+                    .any(|l| l.starts_with(&format!("// rustfmt-{}", config_name))),
+                "config option file {} does not contain expected config name",
+                path.display()
+            );
+        }
+    }
+}
+
+#[test]
+fn verify_config_test_names() {
+    init_log();
+    for path in &[
+        Path::new("tests/source/configs"),
+        Path::new("tests/target/configs"),
+    ] {
+        for entry in fs::read_dir(path).expect("couldn't read configs directory") {
+            let entry = entry.expect("couldn't get directory entry");
+            let path = entry.path();
+            if path.is_dir() {
+                let config_name = path.file_name().unwrap().to_str().unwrap();
+
+                // Make sure that config name is used in the files in the directory.
+                verify_config_used(&path, config_name);
+            }
+        }
+    }
+}
+
+// This writes to the terminal using the same approach (via `term::stdout` or
+// `println!`) that is used by `rustfmt::rustfmt_diff::print_diff`. Writing
+// using only one or the other will cause the output order to differ when
+// `print_diff` selects the approach not used.
+fn write_message(msg: &str) {
+    let mut writer = OutputWriter::new(Color::Auto);
+    writer.writeln(msg, None);
+}
+
+// Integration tests. The files in `tests/source` are formatted and compared
+// to their equivalent in `tests/target`. The target file and config can be
+// overridden by annotations in the source file. The input and output must match
+// exactly.
+#[test]
+fn system_tests() {
+    init_log();
+    run_test_with(&TestSetting::default(), || {
+        // Get all files in the tests/source directory.
+        let files = get_test_files(Path::new("tests/source"), true);
+        let (_reports, count, fails) = check_files(files, &None);
+
+        // Display results.
+        println!("Ran {} system tests.", count);
+        assert_eq!(fails, 0, "{} system tests failed", fails);
+        assert!(
+            count >= 300,
+            "Expected a minimum of {} system tests to be executed",
+            300
+        )
+    });
+}
+
+// Do the same for tests/coverage-source directory.
+// The only difference is the coverage mode.
+#[test]
+fn coverage_tests() {
+    init_log();
+    let files = get_test_files(Path::new("tests/coverage/source"), true);
+    let (_reports, count, fails) = check_files(files, &None);
+
+    println!("Ran {} tests in coverage mode.", count);
+    assert_eq!(fails, 0, "{} tests failed", fails);
+}
+
+#[test]
+fn checkstyle_test() {
+    init_log();
+    let filename = "tests/writemode/source/fn-single-line.rs";
+    let expected_filename = "tests/writemode/target/checkstyle.xml";
+    assert_output(Path::new(filename), Path::new(expected_filename));
+}
+
+#[test]
+fn json_test() {
+    init_log();
+    let filename = "tests/writemode/source/json.rs";
+    let expected_filename = "tests/writemode/target/output.json";
+    assert_output(Path::new(filename), Path::new(expected_filename));
+}
+
+#[test]
+fn modified_test() {
+    init_log();
+    use std::io::BufRead;
+
+    // Test "modified" output
+    let filename = "tests/writemode/source/modified.rs";
+    let mut data = Vec::new();
+    let mut config = Config::default();
+    config
+        .set()
+        .emit_mode(crate::config::EmitMode::ModifiedLines);
+
+    {
+        let mut session = Session::new(config, Some(&mut data));
+        session.format(Input::File(filename.into())).unwrap();
+    }
+
+    let mut lines = data.lines();
+    let mut chunks = Vec::new();
+    while let Some(Ok(header)) = lines.next() {
+        // Parse the header line
+        let values: Vec<_> = header
+            .split(' ')
+            .map(|s| s.parse::<u32>().unwrap())
+            .collect();
+        assert_eq!(values.len(), 3);
+        let line_number_orig = values[0];
+        let lines_removed = values[1];
+        let num_added = values[2];
+        let mut added_lines = Vec::new();
+        for _ in 0..num_added {
+            added_lines.push(lines.next().unwrap().unwrap());
+        }
+        chunks.push(ModifiedChunk {
+            line_number_orig,
+            lines_removed,
+            lines: added_lines,
+        });
+    }
+
+    assert_eq!(
+        chunks,
+        vec![
+            ModifiedChunk {
+                line_number_orig: 4,
+                lines_removed: 4,
+                lines: vec!["fn blah() {}".into()],
+            },
+            ModifiedChunk {
+                line_number_orig: 9,
+                lines_removed: 6,
+                lines: vec!["#[cfg(a, b)]".into(), "fn main() {}".into()],
+            },
+        ],
+    );
+}
+
+// Helper function for comparing the results of rustfmt
+// to a known output file generated by one of the write modes.
+fn assert_output(source: &Path, expected_filename: &Path) {
+    let config = read_config(source);
+    let (_, source_file, _) = format_file(source, config.clone());
+
+    // Populate output by writing to a vec.
+    let mut out = vec![];
+    let _ = source_file::write_all_files(&source_file, &mut out, &config);
+    let output = String::from_utf8(out).unwrap();
+
+    let mut expected_file = fs::File::open(&expected_filename).expect("couldn't open target");
+    let mut expected_text = String::new();
+    expected_file
+        .read_to_string(&mut expected_text)
+        .expect("Failed reading target");
+
+    let compare = make_diff(&expected_text, &output, DIFF_CONTEXT_SIZE);
+    if !compare.is_empty() {
+        let mut failures = HashMap::new();
+        failures.insert(source.to_owned(), compare);
+        print_mismatches_default_message(failures);
+        panic!("Text does not match expected output");
+    }
+}
+
+// Idempotence tests. Files in tests/target are checked to be unaltered by
+// rustfmt.
+#[test]
+fn idempotence_tests() {
+    init_log();
+    run_test_with(&TestSetting::default(), || {
+        // these tests require nightly
+        if !is_nightly_channel!() {
+            return;
+        }
+        // Get all files in the tests/target directory.
+        let files = get_test_files(Path::new("tests/target"), true);
+        let (_reports, count, fails) = check_files(files, &None);
+
+        // Display results.
+        println!("Ran {} idempotent tests.", count);
+        assert_eq!(fails, 0, "{} idempotent tests failed", fails);
+        assert!(
+            count >= 400,
+            "Expected a minimum of {} idempotent tests to be executed",
+            400
+        )
+    });
+}
+
+// Run rustfmt on itself. This operation must be idempotent. We also check that
+// no warnings are emitted.
+#[test]
+fn self_tests() {
+    init_log();
+    // Issue-3443: these tests require nightly
+    if !is_nightly_channel!() {
+        return;
+    }
+    let mut files = get_test_files(Path::new("tests"), false);
+    let bin_directories = vec!["cargo-fmt", "git-rustfmt", "bin", "format-diff"];
+    for dir in bin_directories {
+        let mut path = PathBuf::from("src");
+        path.push(dir);
+        path.push("main.rs");
+        files.push(path);
+    }
+    files.push(PathBuf::from("src/lib.rs"));
+
+    let (reports, count, fails) = check_files(files, &Some(PathBuf::from("rustfmt.toml")));
+    let mut warnings = 0;
+
+    // Display results.
+    println!("Ran {} self tests.", count);
+    assert_eq!(fails, 0, "{} self tests failed", fails);
+
+    for format_report in reports {
+        println!(
+            "{}",
+            FormatReportFormatterBuilder::new(&format_report).build()
+        );
+        warnings += format_report.warning_count();
+    }
+
+    assert_eq!(
+        warnings, 0,
+        "Rustfmt's code generated {} warnings",
+        warnings
+    );
+}
+
+#[test]
+fn format_files_find_new_files_via_cfg_if() {
+    init_log();
+    run_test_with(&TestSetting::default(), || {
+        // To repro issue-4656, it is necessary that these files are parsed
+        // as a part of the same session (hence this separate test runner).
+        let files = vec![
+            Path::new("tests/source/issue-4656/lib2.rs"),
+            Path::new("tests/source/issue-4656/lib.rs"),
+        ];
+
+        let config = Config::default();
+        let mut session = Session::<io::Stdout>::new(config, None);
+
+        let mut write_result = HashMap::new();
+        for file in files {
+            assert!(file.exists());
+            let result = session.format(Input::File(file.into())).unwrap();
+            assert!(!session.has_formatting_errors());
+            assert!(!result.has_warnings());
+            let mut source_file = SourceFile::new();
+            mem::swap(&mut session.source_file, &mut source_file);
+
+            for (filename, text) in source_file {
+                if let FileName::Real(ref filename) = filename {
+                    write_result.insert(filename.to_owned(), text);
+                }
+            }
+        }
+        assert_eq!(
+            3,
+            write_result.len(),
+            "Should have uncovered an extra file (format_me_please.rs) via lib.rs"
+        );
+        assert!(handle_result(write_result, None).is_ok());
+    });
+}
+
+#[test]
+fn stdin_formatting_smoke_test() {
+    init_log();
+    let input = Input::Text("fn main () {}".to_owned());
+    let mut config = Config::default();
+    config.set().emit_mode(EmitMode::Stdout);
+    let mut buf: Vec<u8> = vec![];
+    {
+        let mut session = Session::new(config, Some(&mut buf));
+        session.format(input).unwrap();
+        assert!(session.has_no_errors());
+    }
+
+    #[cfg(not(windows))]
+    assert_eq!(buf, "stdin:\n\nfn main() {}\n".as_bytes());
+    #[cfg(windows)]
+    assert_eq!(buf, "stdin:\n\nfn main() {}\r\n".as_bytes());
+}
+
+#[test]
+fn stdin_parser_panic_caught() {
+    init_log();
+    // See issue #3239.
+    for text in ["{", "}"].iter().cloned().map(String::from) {
+        let mut buf = vec![];
+        let mut session = Session::new(Default::default(), Some(&mut buf));
+        let _ = session.format(Input::Text(text));
+
+        assert!(session.has_parsing_errors());
+    }
+}
+
+/// Ensures that `EmitMode::ModifiedLines` works with input from `stdin`. Useful
+/// when embedding Rustfmt (e.g. inside RLS).
+#[test]
+fn stdin_works_with_modified_lines() {
+    init_log();
+    let input = "\nfn\n some( )\n{\n}\nfn main () {}\n";
+    let output = "1 6 2\nfn some() {}\nfn main() {}\n";
+
+    let input = Input::Text(input.to_owned());
+    let mut config = Config::default();
+    config.set().newline_style(NewlineStyle::Unix);
+    config.set().emit_mode(EmitMode::ModifiedLines);
+    let mut buf: Vec<u8> = vec![];
+    {
+        let mut session = Session::new(config, Some(&mut buf));
+        session.format(input).unwrap();
+        let errors = ReportedErrors {
+            has_diff: true,
+            ..Default::default()
+        };
+        assert_eq!(session.errors, errors);
+    }
+    assert_eq!(buf, output.as_bytes());
+}
+
+#[test]
+fn stdin_disable_all_formatting_test() {
+    init_log();
+    match option_env!("CFG_RELEASE_CHANNEL") {
+        None | Some("nightly") => {}
+        // These tests require nightly.
+        _ => return,
+    }
+    let input = String::from("fn main() { println!(\"This should not be formatted.\"); }");
+    let mut child = Command::new(rustfmt().to_str().unwrap())
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .arg("--config-path=./tests/config/disable_all_formatting.toml")
+        .spawn()
+        .expect("failed to execute child");
+
+    {
+        let stdin = child.stdin.as_mut().expect("failed to get stdin");
+        stdin
+            .write_all(input.as_bytes())
+            .expect("failed to write stdin");
+    }
+
+    let output = child.wait_with_output().expect("failed to wait on child");
+    assert!(output.status.success());
+    assert!(output.stderr.is_empty());
+    assert_eq!(input, String::from_utf8(output.stdout).unwrap());
+}
+
+#[test]
+fn format_lines_errors_are_reported() {
+    init_log();
+    let long_identifier = String::from_utf8(vec![b'a'; 239]).unwrap();
+    let input = Input::Text(format!("fn {}() {{}}", long_identifier));
+    let mut config = Config::default();
+    config.set().error_on_line_overflow(true);
+    let mut session = Session::<io::Stdout>::new(config, None);
+    session.format(input).unwrap();
+    assert!(session.has_formatting_errors());
+}
+
+#[test]
+fn format_lines_errors_are_reported_with_tabs() {
+    init_log();
+    let long_identifier = String::from_utf8(vec![b'a'; 97]).unwrap();
+    let input = Input::Text(format!("fn a() {{\n\t{}\n}}", long_identifier));
+    let mut config = Config::default();
+    config.set().error_on_line_overflow(true);
+    config.set().hard_tabs(true);
+    let mut session = Session::<io::Stdout>::new(config, None);
+    session.format(input).unwrap();
+    assert!(session.has_formatting_errors());
+}
+
+// For each file, run rustfmt and collect the output.
+// Returns the number of files checked and the number of failures.
+fn check_files(files: Vec<PathBuf>, opt_config: &Option<PathBuf>) -> (Vec<FormatReport>, u32, u32) {
+    let mut count = 0;
+    let mut fails = 0;
+    let mut reports = vec![];
+
+    for file_name in files {
+        let sig_comments = read_significant_comments(&file_name);
+        if sig_comments.contains_key("unstable") && !is_nightly_channel!() {
+            debug!(
+                "Skipping '{}' because it requires unstable \
+                 features which are only available on nightly...",
+                file_name.display()
+            );
+            continue;
+        }
+
+        debug!("Testing '{}'...", file_name.display());
+
+        match idempotent_check(&file_name, &opt_config) {
+            Ok(ref report) if report.has_warnings() => {
+                print!("{}", FormatReportFormatterBuilder::new(&report).build());
+                fails += 1;
+            }
+            Ok(report) => reports.push(report),
+            Err(err) => {
+                if let IdempotentCheckError::Mismatch(msg) = err {
+                    print_mismatches_default_message(msg);
+                }
+                fails += 1;
+            }
+        }
+
+        count += 1;
+    }
+
+    (reports, count, fails)
+}
+
+fn print_mismatches_default_message(result: HashMap<PathBuf, Vec<Mismatch>>) {
+    for (file_name, diff) in result {
+        let mismatch_msg_formatter =
+            |line_num| format!("\nMismatch at {}:{}:", file_name.display(), line_num);
+        print_diff(diff, &mismatch_msg_formatter, &Default::default());
+    }
+
+    if let Some(mut t) = term::stdout() {
+        t.reset().unwrap_or(());
+    }
+}
+
+fn print_mismatches<T: Fn(u32) -> String>(
+    result: HashMap<PathBuf, Vec<Mismatch>>,
+    mismatch_msg_formatter: T,
+) {
+    for (_file_name, diff) in result {
+        print_diff(diff, &mismatch_msg_formatter, &Default::default());
+    }
+
+    if let Some(mut t) = term::stdout() {
+        t.reset().unwrap_or(());
+    }
+}
+
+fn read_config(filename: &Path) -> Config {
+    let sig_comments = read_significant_comments(filename);
+    // Look for a config file. If there is a 'config' property in the significant comments, use
+    // that. Otherwise, if there are no significant comments at all, look for a config file with
+    // the same name as the test file.
+    let mut config = if !sig_comments.is_empty() {
+        get_config(sig_comments.get("config").map(Path::new))
+    } else {
+        get_config(filename.with_extension("toml").file_name().map(Path::new))
+    };
+
+    for (key, val) in &sig_comments {
+        if key != "target" && key != "config" && key != "unstable" {
+            config.override_value(key, val);
+            if config.is_default(key) {
+                warn!("Default value {} used explicitly for {}", val, key);
+            }
+        }
+    }
+
+    // Don't generate warnings for to-do items.
+    config.set().report_todo(ReportTactic::Never);
+
+    config
+}
+
+fn format_file<P: Into<PathBuf>>(filepath: P, config: Config) -> (bool, SourceFile, FormatReport) {
+    let filepath = filepath.into();
+    let input = Input::File(filepath);
+    let mut session = Session::<io::Stdout>::new(config, None);
+    let result = session.format(input).unwrap();
+    let parsing_errors = session.has_parsing_errors();
+    let mut source_file = SourceFile::new();
+    mem::swap(&mut session.source_file, &mut source_file);
+    (parsing_errors, source_file, result)
+}
+
+enum IdempotentCheckError {
+    Mismatch(HashMap<PathBuf, Vec<Mismatch>>),
+    Parse,
+}
+
+fn idempotent_check(
+    filename: &PathBuf,
+    opt_config: &Option<PathBuf>,
+) -> Result<FormatReport, IdempotentCheckError> {
+    let sig_comments = read_significant_comments(filename);
+    let config = if let Some(ref config_file_path) = opt_config {
+        Config::from_toml_path(config_file_path).expect("`rustfmt.toml` not found")
+    } else {
+        read_config(filename)
+    };
+    let (parsing_errors, source_file, format_report) = format_file(filename, config);
+    if parsing_errors {
+        return Err(IdempotentCheckError::Parse);
+    }
+
+    let mut write_result = HashMap::new();
+    for (filename, text) in source_file {
+        if let FileName::Real(ref filename) = filename {
+            write_result.insert(filename.to_owned(), text);
+        }
+    }
+
+    let target = sig_comments.get("target").map(|x| &(*x)[..]);
+
+    handle_result(write_result, target).map(|_| format_report)
+}
+
+// Reads test config file using the supplied (optional) file name. If there's no file name or the
+// file doesn't exist, just return the default config. Otherwise, the file must be read
+// successfully.
+fn get_config(config_file: Option<&Path>) -> Config {
+    let config_file_name = match config_file {
+        None => return Default::default(),
+        Some(file_name) => {
+            let mut full_path = PathBuf::from("tests/config/");
+            full_path.push(file_name);
+            if !full_path.exists() {
+                return Default::default();
+            };
+            full_path
+        }
+    };
+
+    let mut def_config_file = fs::File::open(config_file_name).expect("couldn't open config");
+    let mut def_config = String::new();
+    def_config_file
+        .read_to_string(&mut def_config)
+        .expect("Couldn't read config");
+
+    Config::from_toml(&def_config, Path::new("tests/config/")).expect("invalid TOML")
+}
+
+// Reads significant comments of the form: `// rustfmt-key: value` into a hash map.
+fn read_significant_comments(file_name: &Path) -> HashMap<String, String> {
+    let file = fs::File::open(file_name)
+        .unwrap_or_else(|_| panic!("couldn't read file {}", file_name.display()));
+    let reader = BufReader::new(file);
+    let pattern = r"^\s*//\s*rustfmt-([^:]+):\s*(\S+)";
+    let regex = regex::Regex::new(pattern).expect("failed creating pattern 1");
+
+    // Matches lines containing significant comments or whitespace.
+    let line_regex = regex::Regex::new(r"(^\s*$)|(^\s*//\s*rustfmt-[^:]+:\s*\S+)")
+        .expect("failed creating pattern 2");
+
+    reader
+        .lines()
+        .map(|line| line.expect("failed getting line"))
+        .take_while(|line| line_regex.is_match(line))
+        .filter_map(|line| {
+            regex.captures_iter(&line).next().map(|capture| {
+                (
+                    capture
+                        .get(1)
+                        .expect("couldn't unwrap capture")
+                        .as_str()
+                        .to_owned(),
+                    capture
+                        .get(2)
+                        .expect("couldn't unwrap capture")
+                        .as_str()
+                        .to_owned(),
+                )
+            })
+        })
+        .collect()
+}
+
+// Compares output to input.
+// TODO: needs a better name, more explanation.
+fn handle_result(
+    result: HashMap<PathBuf, String>,
+    target: Option<&str>,
+) -> Result<(), IdempotentCheckError> {
+    let mut failures = HashMap::new();
+
+    for (file_name, fmt_text) in result {
+        // If file is in tests/source, compare to file with same name in tests/target.
+        let target = get_target(&file_name, target);
+        let open_error = format!("couldn't open target {:?}", target);
+        let mut f = fs::File::open(&target).expect(&open_error);
+
+        let mut text = String::new();
+        let read_error = format!("failed reading target {:?}", target);
+        f.read_to_string(&mut text).expect(&read_error);
+
+        // Ignore LF and CRLF difference for Windows.
+        if !string_eq_ignore_newline_repr(&fmt_text, &text) {
+            let diff = make_diff(&text, &fmt_text, DIFF_CONTEXT_SIZE);
+            assert!(
+                !diff.is_empty(),
+                "Empty diff? Maybe due to a missing a newline at the end of a file?"
+            );
+            failures.insert(file_name, diff);
+        }
+    }
+
+    if failures.is_empty() {
+        Ok(())
+    } else {
+        Err(IdempotentCheckError::Mismatch(failures))
+    }
+}
+
+// Maps source file paths to their target paths.
+fn get_target(file_name: &Path, target: Option<&str>) -> PathBuf {
+    if let Some(n) = file_name
+        .components()
+        .position(|c| c.as_os_str() == "source")
+    {
+        let mut target_file_name = PathBuf::new();
+        for (i, c) in file_name.components().enumerate() {
+            if i == n {
+                target_file_name.push("target");
+            } else {
+                target_file_name.push(c.as_os_str());
+            }
+        }
+        if let Some(replace_name) = target {
+            target_file_name.with_file_name(replace_name)
+        } else {
+            target_file_name
+        }
+    } else {
+        // This is either and idempotence check or a self check.
+        file_name.to_owned()
+    }
+}
+
+#[test]
+fn rustfmt_diff_make_diff_tests() {
+    init_log();
+    let diff = make_diff("a\nb\nc\nd", "a\ne\nc\nd", 3);
+    assert_eq!(
+        diff,
+        vec![Mismatch {
+            line_number: 1,
+            line_number_orig: 1,
+            lines: vec![
+                DiffLine::Context("a".into()),
+                DiffLine::Resulting("b".into()),
+                DiffLine::Expected("e".into()),
+                DiffLine::Context("c".into()),
+                DiffLine::Context("d".into()),
+            ],
+        }]
+    );
+}
+
+#[test]
+fn rustfmt_diff_no_diff_test() {
+    init_log();
+    let diff = make_diff("a\nb\nc\nd", "a\nb\nc\nd", 3);
+    assert_eq!(diff, vec![]);
+}
+
+// Compare strings without distinguishing between CRLF and LF
+fn string_eq_ignore_newline_repr(left: &str, right: &str) -> bool {
+    let left = CharsIgnoreNewlineRepr(left.chars().peekable());
+    let right = CharsIgnoreNewlineRepr(right.chars().peekable());
+    left.eq(right)
+}
+
+struct CharsIgnoreNewlineRepr<'a>(Peekable<Chars<'a>>);
+
+impl<'a> Iterator for CharsIgnoreNewlineRepr<'a> {
+    type Item = char;
+
+    fn next(&mut self) -> Option<char> {
+        self.0.next().map(|c| {
+            if c == '\r' {
+                if *self.0.peek().unwrap_or(&'\0') == '\n' {
+                    self.0.next();
+                    '\n'
+                } else {
+                    '\r'
+                }
+            } else {
+                c
+            }
+        })
+    }
+}
+
+#[test]
+fn string_eq_ignore_newline_repr_test() {
+    init_log();
+    assert!(string_eq_ignore_newline_repr("", ""));
+    assert!(!string_eq_ignore_newline_repr("", "abc"));
+    assert!(!string_eq_ignore_newline_repr("abc", ""));
+    assert!(string_eq_ignore_newline_repr("a\nb\nc\rd", "a\nb\r\nc\rd"));
+    assert!(string_eq_ignore_newline_repr("a\r\n\r\n\r\nb", "a\n\n\nb"));
+    assert!(!string_eq_ignore_newline_repr("a\r\nbcd", "a\nbcdefghijk"));
+}
+
+struct TempFile {
+    path: PathBuf,
+}
+
+fn make_temp_file(file_name: &'static str) -> TempFile {
+    use std::env::var;
+    use std::fs::File;
+
+    // Used in the Rust build system.
+    let target_dir = var("RUSTFMT_TEST_DIR").unwrap_or_else(|_| ".".to_owned());
+    let path = Path::new(&target_dir).join(file_name);
+
+    let mut file = File::create(&path).expect("couldn't create temp file");
+    let content = "fn main() {}\n";
+    file.write_all(content.as_bytes())
+        .expect("couldn't write temp file");
+    TempFile { path }
+}
+
+impl Drop for TempFile {
+    fn drop(&mut self) {
+        use std::fs::remove_file;
+        remove_file(&self.path).expect("couldn't delete temp file");
+    }
+}
+
+fn rustfmt() -> PathBuf {
+    let mut me = env::current_exe().expect("failed to get current executable");
+    // Chop of the test name.
+    me.pop();
+    // Chop off `deps`.
+    me.pop();
+
+    // If we run `cargo test --release`, we might only have a release build.
+    if cfg!(release) {
+        // `../release/`
+        me.pop();
+        me.push("release");
+    }
+    me.push("rustfmt");
+    assert!(
+        me.is_file() || me.with_extension("exe").is_file(),
+        "{}",
+        if cfg!(release) {
+            "no rustfmt bin, try running `cargo build --release` before testing"
+        } else {
+            "no rustfmt bin, try running `cargo build` before testing"
+        }
+    );
+    me
+}
+
+#[test]
+fn verify_check_works() {
+    init_log();
+    let temp_file = make_temp_file("temp_check.rs");
+
+    Command::new(rustfmt().to_str().unwrap())
+        .arg("--check")
+        .arg(temp_file.path.to_str().unwrap())
+        .status()
+        .expect("run with check option failed");
+}
diff --git a/src/tools/rustfmt/src/test/parser.rs b/src/tools/rustfmt/src/test/parser.rs
new file mode 100644
index 0000000000000..ae4a4f94d9280
--- /dev/null
+++ b/src/tools/rustfmt/src/test/parser.rs
@@ -0,0 +1,57 @@
+use std::io;
+use std::path::PathBuf;
+
+use super::read_config;
+
+use crate::modules::{ModuleResolutionError, ModuleResolutionErrorKind};
+use crate::{ErrorKind, Input, Session};
+
+#[test]
+fn parser_errors_in_submods_are_surfaced() {
+    // See also https://github.com/rust-lang/rustfmt/issues/4126
+    let filename = "tests/parser/issue-4126/lib.rs";
+    let input_file = PathBuf::from(filename);
+    let exp_mod_name = "invalid";
+    let config = read_config(&input_file);
+    let mut session = Session::<io::Stdout>::new(config, None);
+    if let Err(ErrorKind::ModuleResolutionError(ModuleResolutionError { module, kind })) =
+        session.format(Input::File(filename.into()))
+    {
+        assert_eq!(&module, exp_mod_name);
+        if let ModuleResolutionErrorKind::ParseError {
+            file: unparseable_file,
+        } = kind
+        {
+            assert_eq!(
+                unparseable_file,
+                PathBuf::from("tests/parser/issue-4126/invalid.rs"),
+            );
+        } else {
+            panic!("Expected parser error");
+        }
+    } else {
+        panic!("Expected ModuleResolution operation error");
+    }
+}
+
+fn assert_parser_error(filename: &str) {
+    let file = PathBuf::from(filename);
+    let config = read_config(&file);
+    let mut session = Session::<io::Stdout>::new(config, None);
+    let _ = session.format(Input::File(filename.into())).unwrap();
+    assert!(session.has_parsing_errors());
+}
+
+#[test]
+fn parser_creation_errors_on_entry_new_parser_from_file_panic() {
+    // See also https://github.com/rust-lang/rustfmt/issues/4418
+    let filename = "tests/parser/issue_4418.rs";
+    assert_parser_error(filename);
+}
+
+#[test]
+fn crate_parsing_errors_on_unclosed_delims() {
+    // See also https://github.com/rust-lang/rustfmt/issues/4466
+    let filename = "tests/parser/unclosed-delims/issue_4466.rs";
+    assert_parser_error(filename);
+}
diff --git a/src/tools/rustfmt/src/types.rs b/src/tools/rustfmt/src/types.rs
new file mode 100644
index 0000000000000..cda17e13eebb0
--- /dev/null
+++ b/src/tools/rustfmt/src/types.rs
@@ -0,0 +1,1051 @@
+use std::iter::ExactSizeIterator;
+use std::ops::Deref;
+
+use rustc_ast::ast::{self, FnRetTy, Mutability};
+use rustc_span::{symbol::kw, BytePos, Pos, Span};
+
+use crate::comment::{combine_strs_with_missing_comments, contains_comment};
+use crate::config::lists::*;
+use crate::config::{IndentStyle, TypeDensity, Version};
+use crate::expr::{
+    format_expr, rewrite_assign_rhs, rewrite_call, rewrite_tuple, rewrite_unary_prefix, ExprType,
+};
+use crate::lists::{
+    definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
+};
+use crate::macros::{rewrite_macro, MacroPosition};
+use crate::overflow;
+use crate::pairs::{rewrite_pair, PairParts};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::spanned::Spanned;
+use crate::utils::{
+    colon_spaces, extra_offset, first_line_width, format_extern, format_mutability,
+    last_line_extendable, last_line_width, mk_sp, rewrite_ident,
+};
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub(crate) enum PathContext {
+    Expr,
+    Type,
+    Import,
+}
+
+// Does not wrap on simple segments.
+pub(crate) fn rewrite_path(
+    context: &RewriteContext<'_>,
+    path_context: PathContext,
+    qself: Option<&ast::QSelf>,
+    path: &ast::Path,
+    shape: Shape,
+) -> Option<String> {
+    let skip_count = qself.map_or(0, |x| x.position);
+
+    let mut result = if path.is_global() && qself.is_none() && path_context != PathContext::Import {
+        "::".to_owned()
+    } else {
+        String::new()
+    };
+
+    let mut span_lo = path.span.lo();
+
+    if let Some(qself) = qself {
+        result.push('<');
+
+        let fmt_ty = qself.ty.rewrite(context, shape)?;
+        result.push_str(&fmt_ty);
+
+        if skip_count > 0 {
+            result.push_str(" as ");
+            if path.is_global() && path_context != PathContext::Import {
+                result.push_str("::");
+            }
+
+            // 3 = ">::".len()
+            let shape = shape.sub_width(3)?;
+
+            result = rewrite_path_segments(
+                PathContext::Type,
+                result,
+                path.segments.iter().take(skip_count),
+                span_lo,
+                path.span.hi(),
+                context,
+                shape,
+            )?;
+        }
+
+        result.push_str(">::");
+        span_lo = qself.ty.span.hi() + BytePos(1);
+    }
+
+    rewrite_path_segments(
+        path_context,
+        result,
+        path.segments.iter().skip(skip_count),
+        span_lo,
+        path.span.hi(),
+        context,
+        shape,
+    )
+}
+
+fn rewrite_path_segments<'a, I>(
+    path_context: PathContext,
+    mut buffer: String,
+    iter: I,
+    mut span_lo: BytePos,
+    span_hi: BytePos,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String>
+where
+    I: Iterator<Item = &'a ast::PathSegment>,
+{
+    let mut first = true;
+    let shape = shape.visual_indent(0);
+
+    for segment in iter {
+        // Indicates a global path, shouldn't be rendered.
+        if segment.ident.name == kw::PathRoot {
+            continue;
+        }
+        if first {
+            first = false;
+        } else {
+            buffer.push_str("::");
+        }
+
+        let extra_offset = extra_offset(&buffer, shape);
+        let new_shape = shape.shrink_left(extra_offset)?;
+        let segment_string = rewrite_segment(
+            path_context,
+            segment,
+            &mut span_lo,
+            span_hi,
+            context,
+            new_shape,
+        )?;
+
+        buffer.push_str(&segment_string);
+    }
+
+    Some(buffer)
+}
+
+#[derive(Debug)]
+pub(crate) enum SegmentParam<'a> {
+    Const(&'a ast::AnonConst),
+    LifeTime(&'a ast::Lifetime),
+    Type(&'a ast::Ty),
+    Binding(&'a ast::AssocTyConstraint),
+}
+
+impl<'a> SegmentParam<'a> {
+    fn from_generic_arg(arg: &ast::GenericArg) -> SegmentParam<'_> {
+        match arg {
+            ast::GenericArg::Lifetime(ref lt) => SegmentParam::LifeTime(lt),
+            ast::GenericArg::Type(ref ty) => SegmentParam::Type(ty),
+            ast::GenericArg::Const(const_) => SegmentParam::Const(const_),
+        }
+    }
+}
+
+impl<'a> Spanned for SegmentParam<'a> {
+    fn span(&self) -> Span {
+        match *self {
+            SegmentParam::Const(const_) => const_.value.span,
+            SegmentParam::LifeTime(lt) => lt.ident.span,
+            SegmentParam::Type(ty) => ty.span,
+            SegmentParam::Binding(binding) => binding.span,
+        }
+    }
+}
+
+impl<'a> Rewrite for SegmentParam<'a> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match *self {
+            SegmentParam::Const(const_) => const_.rewrite(context, shape),
+            SegmentParam::LifeTime(lt) => lt.rewrite(context, shape),
+            SegmentParam::Type(ty) => ty.rewrite(context, shape),
+            SegmentParam::Binding(assoc_ty_constraint) => {
+                let mut result = match assoc_ty_constraint.kind {
+                    ast::AssocTyConstraintKind::Bound { .. } => {
+                        format!("{}: ", rewrite_ident(context, assoc_ty_constraint.ident))
+                    }
+                    ast::AssocTyConstraintKind::Equality { .. } => {
+                        match context.config.type_punctuation_density() {
+                            TypeDensity::Wide => {
+                                format!("{} = ", rewrite_ident(context, assoc_ty_constraint.ident))
+                            }
+                            TypeDensity::Compressed => {
+                                format!("{}=", rewrite_ident(context, assoc_ty_constraint.ident))
+                            }
+                        }
+                    }
+                };
+
+                let budget = shape.width.checked_sub(result.len())?;
+                let rewrite = assoc_ty_constraint
+                    .kind
+                    .rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
+                result.push_str(&rewrite);
+                Some(result)
+            }
+        }
+    }
+}
+
+impl Rewrite for ast::AssocTyConstraintKind {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match self {
+            ast::AssocTyConstraintKind::Equality { ty } => ty.rewrite(context, shape),
+            ast::AssocTyConstraintKind::Bound { bounds } => bounds.rewrite(context, shape),
+        }
+    }
+}
+
+// Formats a path segment. There are some hacks involved to correctly determine
+// the segment's associated span since it's not part of the AST.
+//
+// The span_lo is assumed to be greater than the end of any previous segment's
+// parameters and lesser or equal than the start of current segment.
+//
+// span_hi is assumed equal to the end of the entire path.
+//
+// When the segment contains a positive number of parameters, we update span_lo
+// so that invariants described above will hold for the next segment.
+fn rewrite_segment(
+    path_context: PathContext,
+    segment: &ast::PathSegment,
+    span_lo: &mut BytePos,
+    span_hi: BytePos,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    let mut result = String::with_capacity(128);
+    result.push_str(rewrite_ident(context, segment.ident));
+
+    let ident_len = result.len();
+    let shape = if context.use_block_indent() {
+        shape.offset_left(ident_len)?
+    } else {
+        shape.shrink_left(ident_len)?
+    };
+
+    if let Some(ref args) = segment.args {
+        match **args {
+            ast::GenericArgs::AngleBracketed(ref data) if !data.args.is_empty() => {
+                let param_list = data
+                    .args
+                    .iter()
+                    .map(|x| match x {
+                        ast::AngleBracketedArg::Arg(generic_arg) => {
+                            SegmentParam::from_generic_arg(generic_arg)
+                        }
+                        ast::AngleBracketedArg::Constraint(constraint) => {
+                            SegmentParam::Binding(constraint)
+                        }
+                    })
+                    .collect::<Vec<_>>();
+
+                // HACK: squeeze out the span between the identifier and the parameters.
+                // The hack is requried so that we don't remove the separator inside macro calls.
+                // This does not work in the presence of comment, hoping that people are
+                // sane about where to put their comment.
+                let separator_snippet = context
+                    .snippet(mk_sp(segment.ident.span.hi(), data.span.lo()))
+                    .trim();
+                let force_separator = context.inside_macro() && separator_snippet.starts_with("::");
+                let separator = if path_context == PathContext::Expr || force_separator {
+                    "::"
+                } else {
+                    ""
+                };
+                result.push_str(separator);
+
+                let generics_str = overflow::rewrite_with_angle_brackets(
+                    context,
+                    "",
+                    param_list.iter(),
+                    shape,
+                    mk_sp(*span_lo, span_hi),
+                )?;
+
+                // Update position of last bracket.
+                *span_lo = context
+                    .snippet_provider
+                    .span_after(mk_sp(*span_lo, span_hi), "<");
+
+                result.push_str(&generics_str)
+            }
+            ast::GenericArgs::Parenthesized(ref data) => {
+                result.push_str(&format_function_type(
+                    data.inputs.iter().map(|x| &**x),
+                    &data.output,
+                    false,
+                    data.span,
+                    context,
+                    shape,
+                )?);
+            }
+            _ => (),
+        }
+    }
+
+    Some(result)
+}
+
+fn format_function_type<'a, I>(
+    inputs: I,
+    output: &FnRetTy,
+    variadic: bool,
+    span: Span,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String>
+where
+    I: ExactSizeIterator,
+    <I as Iterator>::Item: Deref,
+    <I::Item as Deref>::Target: Rewrite + Spanned + 'a,
+{
+    debug!("format_function_type {:#?}", shape);
+
+    let ty_shape = match context.config.indent_style() {
+        // 4 = " -> "
+        IndentStyle::Block => shape.offset_left(4)?,
+        IndentStyle::Visual => shape.block_left(4)?,
+    };
+    let output = match *output {
+        FnRetTy::Ty(ref ty) => {
+            let type_str = ty.rewrite(context, ty_shape)?;
+            format!(" -> {}", type_str)
+        }
+        FnRetTy::Default(..) => String::new(),
+    };
+
+    let list_shape = if context.use_block_indent() {
+        Shape::indented(
+            shape.block().indent.block_indent(context.config),
+            context.config,
+        )
+    } else {
+        // 2 for ()
+        let budget = shape.width.checked_sub(2)?;
+        // 1 for (
+        let offset = shape.indent + 1;
+        Shape::legacy(budget, offset)
+    };
+
+    let is_inputs_empty = inputs.len() == 0;
+    let list_lo = context.snippet_provider.span_after(span, "(");
+    let (list_str, tactic) = if is_inputs_empty {
+        let tactic = get_tactics(&[], &output, shape);
+        let list_hi = context.snippet_provider.span_before(span, ")");
+        let comment = context
+            .snippet_provider
+            .span_to_snippet(mk_sp(list_lo, list_hi))?
+            .trim();
+        let comment = if comment.starts_with("//") {
+            format!(
+                "{}{}{}",
+                &list_shape.indent.to_string_with_newline(context.config),
+                comment,
+                &shape.block().indent.to_string_with_newline(context.config)
+            )
+        } else {
+            comment.to_string()
+        };
+        (comment, tactic)
+    } else {
+        let items = itemize_list(
+            context.snippet_provider,
+            inputs,
+            ")",
+            ",",
+            |arg| arg.span().lo(),
+            |arg| arg.span().hi(),
+            |arg| arg.rewrite(context, list_shape),
+            list_lo,
+            span.hi(),
+            false,
+        );
+
+        let item_vec: Vec<_> = items.collect();
+        let tactic = get_tactics(&item_vec, &output, shape);
+        let trailing_separator = if !context.use_block_indent() || variadic {
+            SeparatorTactic::Never
+        } else {
+            context.config.trailing_comma()
+        };
+
+        let fmt = ListFormatting::new(list_shape, context.config)
+            .tactic(tactic)
+            .trailing_separator(trailing_separator)
+            .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
+            .preserve_newline(true);
+        (write_list(&item_vec, &fmt)?, tactic)
+    };
+
+    let args = if tactic == DefinitiveListTactic::Horizontal
+        || !context.use_block_indent()
+        || is_inputs_empty
+    {
+        format!("({})", list_str)
+    } else {
+        format!(
+            "({}{}{})",
+            list_shape.indent.to_string_with_newline(context.config),
+            list_str,
+            shape.block().indent.to_string_with_newline(context.config),
+        )
+    };
+    if output.is_empty() || last_line_width(&args) + first_line_width(&output) <= shape.width {
+        Some(format!("{}{}", args, output))
+    } else {
+        Some(format!(
+            "{}\n{}{}",
+            args,
+            list_shape.indent.to_string(context.config),
+            output.trim_start()
+        ))
+    }
+}
+
+fn type_bound_colon(context: &RewriteContext<'_>) -> &'static str {
+    colon_spaces(context.config)
+}
+
+// If the return type is multi-lined, then force to use multiple lines for
+// arguments as well.
+fn get_tactics(item_vec: &[ListItem], output: &str, shape: Shape) -> DefinitiveListTactic {
+    if output.contains('\n') {
+        DefinitiveListTactic::Vertical
+    } else {
+        definitive_tactic(
+            item_vec,
+            ListTactic::HorizontalVertical,
+            Separator::Comma,
+            // 2 is for the case of ',\n'
+            shape.width.saturating_sub(2 + output.len()),
+        )
+    }
+}
+
+impl Rewrite for ast::WherePredicate {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        // FIXME: dead spans?
+        let result = match *self {
+            ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
+                ref bound_generic_params,
+                ref bounded_ty,
+                ref bounds,
+                ..
+            }) => {
+                let type_str = bounded_ty.rewrite(context, shape)?;
+                let colon = type_bound_colon(context).trim_end();
+                let lhs = if let Some(lifetime_str) =
+                    rewrite_lifetime_param(context, shape, bound_generic_params)
+                {
+                    format!("for<{}> {}{}", lifetime_str, type_str, colon)
+                } else {
+                    format!("{}{}", type_str, colon)
+                };
+
+                rewrite_assign_rhs(context, lhs, bounds, shape)?
+            }
+            ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
+                ref lifetime,
+                ref bounds,
+                ..
+            }) => rewrite_bounded_lifetime(lifetime, bounds, context, shape)?,
+            ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
+                ref lhs_ty,
+                ref rhs_ty,
+                ..
+            }) => {
+                let lhs_ty_str = lhs_ty.rewrite(context, shape).map(|lhs| lhs + " =")?;
+                rewrite_assign_rhs(context, lhs_ty_str, &**rhs_ty, shape)?
+            }
+        };
+
+        Some(result)
+    }
+}
+
+impl Rewrite for ast::GenericArg {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match *self {
+            ast::GenericArg::Lifetime(ref lt) => lt.rewrite(context, shape),
+            ast::GenericArg::Type(ref ty) => ty.rewrite(context, shape),
+            ast::GenericArg::Const(ref const_) => const_.rewrite(context, shape),
+        }
+    }
+}
+
+fn rewrite_bounded_lifetime(
+    lt: &ast::Lifetime,
+    bounds: &[ast::GenericBound],
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    let result = lt.rewrite(context, shape)?;
+
+    if bounds.is_empty() {
+        Some(result)
+    } else {
+        let colon = type_bound_colon(context);
+        let overhead = last_line_width(&result) + colon.len();
+        let result = format!(
+            "{}{}{}",
+            result,
+            colon,
+            join_bounds(context, shape.sub_width(overhead)?, bounds, true)?
+        );
+        Some(result)
+    }
+}
+
+impl Rewrite for ast::AnonConst {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        format_expr(&self.value, ExprType::SubExpression, context, shape)
+    }
+}
+
+impl Rewrite for ast::Lifetime {
+    fn rewrite(&self, context: &RewriteContext<'_>, _: Shape) -> Option<String> {
+        Some(rewrite_ident(context, self.ident).to_owned())
+    }
+}
+
+impl Rewrite for ast::GenericBound {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match *self {
+            ast::GenericBound::Trait(ref poly_trait_ref, trait_bound_modifier) => {
+                let snippet = context.snippet(self.span());
+                let has_paren = snippet.starts_with('(') && snippet.ends_with(')');
+                let rewrite = match trait_bound_modifier {
+                    ast::TraitBoundModifier::None => poly_trait_ref.rewrite(context, shape),
+                    ast::TraitBoundModifier::Maybe => poly_trait_ref
+                        .rewrite(context, shape.offset_left(1)?)
+                        .map(|s| format!("?{}", s)),
+                    ast::TraitBoundModifier::MaybeConst => poly_trait_ref
+                        .rewrite(context, shape.offset_left(7)?)
+                        .map(|s| format!("?const {}", s)),
+                    ast::TraitBoundModifier::MaybeConstMaybe => poly_trait_ref
+                        .rewrite(context, shape.offset_left(8)?)
+                        .map(|s| format!("?const ?{}", s)),
+                };
+                rewrite.map(|s| if has_paren { format!("({})", s) } else { s })
+            }
+            ast::GenericBound::Outlives(ref lifetime) => lifetime.rewrite(context, shape),
+        }
+    }
+}
+
+impl Rewrite for ast::GenericBounds {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        if self.is_empty() {
+            return Some(String::new());
+        }
+
+        join_bounds(context, shape, self, true)
+    }
+}
+
+impl Rewrite for ast::GenericParam {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let mut result = String::with_capacity(128);
+        // FIXME: If there are more than one attributes, this will force multiline.
+        match self.attrs.rewrite(context, shape) {
+            Some(ref rw) if !rw.is_empty() => result.push_str(&format!("{} ", rw)),
+            _ => (),
+        }
+
+        if let ast::GenericParamKind::Const {
+            ref ty,
+            kw_span: _,
+            default: _,
+        } = &self.kind
+        {
+            result.push_str("const ");
+            result.push_str(rewrite_ident(context, self.ident));
+            result.push_str(": ");
+            result.push_str(&ty.rewrite(context, shape)?);
+        } else {
+            result.push_str(rewrite_ident(context, self.ident));
+        }
+
+        if !self.bounds.is_empty() {
+            result.push_str(type_bound_colon(context));
+            result.push_str(&self.bounds.rewrite(context, shape)?)
+        }
+        if let ast::GenericParamKind::Type {
+            default: Some(ref def),
+        } = self.kind
+        {
+            let eq_str = match context.config.type_punctuation_density() {
+                TypeDensity::Compressed => "=",
+                TypeDensity::Wide => " = ",
+            };
+            result.push_str(eq_str);
+            let budget = shape.width.checked_sub(result.len())?;
+            let rewrite =
+                def.rewrite(context, Shape::legacy(budget, shape.indent + result.len()))?;
+            result.push_str(&rewrite);
+        }
+
+        Some(result)
+    }
+}
+
+impl Rewrite for ast::PolyTraitRef {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        if let Some(lifetime_str) =
+            rewrite_lifetime_param(context, shape, &self.bound_generic_params)
+        {
+            // 6 is "for<> ".len()
+            let extra_offset = lifetime_str.len() + 6;
+            let path_str = self
+                .trait_ref
+                .rewrite(context, shape.offset_left(extra_offset)?)?;
+
+            Some(format!("for<{}> {}", lifetime_str, path_str))
+        } else {
+            self.trait_ref.rewrite(context, shape)
+        }
+    }
+}
+
+impl Rewrite for ast::TraitRef {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        rewrite_path(context, PathContext::Type, None, &self.path, shape)
+    }
+}
+
+impl Rewrite for ast::Ty {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match self.kind {
+            ast::TyKind::TraitObject(ref bounds, tobj_syntax) => {
+                // we have to consider 'dyn' keyword is used or not!!!
+                let is_dyn = tobj_syntax == ast::TraitObjectSyntax::Dyn;
+                // 4 is length of 'dyn '
+                let shape = if is_dyn { shape.offset_left(4)? } else { shape };
+                let mut res = bounds.rewrite(context, shape)?;
+                // We may have falsely removed a trailing `+` inside macro call.
+                if context.inside_macro() && bounds.len() == 1 {
+                    if context.snippet(self.span).ends_with('+') && !res.ends_with('+') {
+                        res.push('+');
+                    }
+                }
+                if is_dyn {
+                    Some(format!("dyn {}", res))
+                } else {
+                    Some(res)
+                }
+            }
+            ast::TyKind::Ptr(ref mt) => {
+                let prefix = match mt.mutbl {
+                    Mutability::Mut => "*mut ",
+                    Mutability::Not => "*const ",
+                };
+
+                rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
+            }
+            ast::TyKind::Rptr(ref lifetime, ref mt) => {
+                let mut_str = format_mutability(mt.mutbl);
+                let mut_len = mut_str.len();
+                let mut result = String::with_capacity(128);
+                result.push_str("&");
+                let ref_hi = context.snippet_provider.span_after(self.span(), "&");
+                let mut cmnt_lo = ref_hi;
+
+                if let Some(ref lifetime) = *lifetime {
+                    let lt_budget = shape.width.checked_sub(2 + mut_len)?;
+                    let lt_str = lifetime.rewrite(
+                        context,
+                        Shape::legacy(lt_budget, shape.indent + 2 + mut_len),
+                    )?;
+                    let before_lt_span = mk_sp(cmnt_lo, lifetime.ident.span.lo());
+                    if contains_comment(context.snippet(before_lt_span)) {
+                        result = combine_strs_with_missing_comments(
+                            context,
+                            &result,
+                            &lt_str,
+                            before_lt_span,
+                            shape,
+                            true,
+                        )?;
+                    } else {
+                        result.push_str(&lt_str);
+                    }
+                    result.push_str(" ");
+                    cmnt_lo = lifetime.ident.span.hi();
+                }
+
+                if ast::Mutability::Mut == mt.mutbl {
+                    let mut_hi = context.snippet_provider.span_after(self.span(), "mut");
+                    let before_mut_span = mk_sp(cmnt_lo, mut_hi - BytePos::from_usize(3));
+                    if contains_comment(context.snippet(before_mut_span)) {
+                        result = combine_strs_with_missing_comments(
+                            context,
+                            result.trim_end(),
+                            mut_str,
+                            before_mut_span,
+                            shape,
+                            true,
+                        )?;
+                    } else {
+                        result.push_str(mut_str);
+                    }
+                    cmnt_lo = mut_hi;
+                }
+
+                let before_ty_span = mk_sp(cmnt_lo, mt.ty.span.lo());
+                if contains_comment(context.snippet(before_ty_span)) {
+                    result = combine_strs_with_missing_comments(
+                        context,
+                        result.trim_end(),
+                        &mt.ty.rewrite(&context, shape)?,
+                        before_ty_span,
+                        shape,
+                        true,
+                    )?;
+                } else {
+                    let used_width = last_line_width(&result);
+                    let budget = shape.width.checked_sub(used_width)?;
+                    let ty_str = mt
+                        .ty
+                        .rewrite(&context, Shape::legacy(budget, shape.indent + used_width))?;
+                    result.push_str(&ty_str);
+                }
+
+                Some(result)
+            }
+            // FIXME: we drop any comments here, even though it's a silly place to put
+            // comments.
+            ast::TyKind::Paren(ref ty) => {
+                if context.config.version() == Version::One
+                    || context.config.indent_style() == IndentStyle::Visual
+                {
+                    let budget = shape.width.checked_sub(2)?;
+                    return ty
+                        .rewrite(context, Shape::legacy(budget, shape.indent + 1))
+                        .map(|ty_str| format!("({})", ty_str));
+                }
+
+                // 2 = ()
+                if let Some(sh) = shape.sub_width(2) {
+                    if let Some(ref s) = ty.rewrite(context, sh) {
+                        if !s.contains('\n') {
+                            return Some(format!("({})", s));
+                        }
+                    }
+                }
+
+                let indent_str = shape.indent.to_string_with_newline(context.config);
+                let shape = shape
+                    .block_indent(context.config.tab_spaces())
+                    .with_max_width(context.config);
+                let rw = ty.rewrite(context, shape)?;
+                Some(format!(
+                    "({}{}{})",
+                    shape.to_string_with_newline(context.config),
+                    rw,
+                    indent_str
+                ))
+            }
+            ast::TyKind::Slice(ref ty) => {
+                let budget = shape.width.checked_sub(4)?;
+                ty.rewrite(context, Shape::legacy(budget, shape.indent + 1))
+                    .map(|ty_str| format!("[{}]", ty_str))
+            }
+            ast::TyKind::Tup(ref items) => {
+                rewrite_tuple(context, items.iter(), self.span, shape, items.len() == 1)
+            }
+            ast::TyKind::Path(ref q_self, ref path) => {
+                rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
+            }
+            ast::TyKind::Array(ref ty, ref repeats) => rewrite_pair(
+                &**ty,
+                &*repeats.value,
+                PairParts::new("[", "; ", "]"),
+                context,
+                shape,
+                SeparatorPlace::Back,
+            ),
+            ast::TyKind::Infer => {
+                if shape.width >= 1 {
+                    Some("_".to_owned())
+                } else {
+                    None
+                }
+            }
+            ast::TyKind::BareFn(ref bare_fn) => rewrite_bare_fn(bare_fn, self.span, context, shape),
+            ast::TyKind::Never => Some(String::from("!")),
+            ast::TyKind::MacCall(ref mac) => {
+                rewrite_macro(mac, None, context, shape, MacroPosition::Expression)
+            }
+            ast::TyKind::ImplicitSelf => Some(String::from("")),
+            ast::TyKind::ImplTrait(_, ref it) => {
+                // Empty trait is not a parser error.
+                if it.is_empty() {
+                    return Some("impl".to_owned());
+                }
+                let rw = if context.config.version() == Version::One {
+                    it.rewrite(context, shape)
+                } else {
+                    join_bounds(context, shape, it, false)
+                };
+                rw.map(|it_str| {
+                    let space = if it_str.is_empty() { "" } else { " " };
+                    format!("impl{}{}", space, it_str)
+                })
+            }
+            ast::TyKind::CVarArgs => Some("...".to_owned()),
+            ast::TyKind::Err => Some(context.snippet(self.span).to_owned()),
+            ast::TyKind::Typeof(ref anon_const) => rewrite_call(
+                context,
+                "typeof",
+                &[anon_const.value.clone()],
+                self.span,
+                shape,
+            ),
+        }
+    }
+}
+
+fn rewrite_bare_fn(
+    bare_fn: &ast::BareFnTy,
+    span: Span,
+    context: &RewriteContext<'_>,
+    shape: Shape,
+) -> Option<String> {
+    debug!("rewrite_bare_fn {:#?}", shape);
+
+    let mut result = String::with_capacity(128);
+
+    if let Some(ref lifetime_str) = rewrite_lifetime_param(context, shape, &bare_fn.generic_params)
+    {
+        result.push_str("for<");
+        // 6 = "for<> ".len(), 4 = "for<".
+        // This doesn't work out so nicely for multiline situation with lots of
+        // rightward drift. If that is a problem, we could use the list stuff.
+        result.push_str(lifetime_str);
+        result.push_str("> ");
+    }
+
+    result.push_str(crate::utils::format_unsafety(bare_fn.unsafety));
+
+    result.push_str(&format_extern(
+        bare_fn.ext,
+        context.config.force_explicit_abi(),
+        false,
+    ));
+
+    result.push_str("fn");
+
+    let func_ty_shape = if context.use_block_indent() {
+        shape.offset_left(result.len())?
+    } else {
+        shape.visual_indent(result.len()).sub_width(result.len())?
+    };
+
+    let rewrite = format_function_type(
+        bare_fn.decl.inputs.iter(),
+        &bare_fn.decl.output,
+        bare_fn.decl.c_variadic(),
+        span,
+        context,
+        func_ty_shape,
+    )?;
+
+    result.push_str(&rewrite);
+
+    Some(result)
+}
+
+fn is_generic_bounds_in_order(generic_bounds: &[ast::GenericBound]) -> bool {
+    let is_trait = |b: &ast::GenericBound| match b {
+        ast::GenericBound::Outlives(..) => false,
+        ast::GenericBound::Trait(..) => true,
+    };
+    let is_lifetime = |b: &ast::GenericBound| !is_trait(b);
+    let last_trait_index = generic_bounds.iter().rposition(is_trait);
+    let first_lifetime_index = generic_bounds.iter().position(is_lifetime);
+    match (last_trait_index, first_lifetime_index) {
+        (Some(last_trait_index), Some(first_lifetime_index)) => {
+            last_trait_index < first_lifetime_index
+        }
+        _ => true,
+    }
+}
+
+fn join_bounds(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    items: &[ast::GenericBound],
+    need_indent: bool,
+) -> Option<String> {
+    join_bounds_inner(context, shape, items, need_indent, false)
+}
+
+fn join_bounds_inner(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    items: &[ast::GenericBound],
+    need_indent: bool,
+    force_newline: bool,
+) -> Option<String> {
+    debug_assert!(!items.is_empty());
+
+    let generic_bounds_in_order = is_generic_bounds_in_order(items);
+    let is_bound_extendable = |s: &str, b: &ast::GenericBound| match b {
+        ast::GenericBound::Outlives(..) => true,
+        ast::GenericBound::Trait(..) => last_line_extendable(s),
+    };
+
+    let result = items.iter().enumerate().try_fold(
+        (String::new(), None, false),
+        |(strs, prev_trailing_span, prev_extendable), (i, item)| {
+            let trailing_span = if i < items.len() - 1 {
+                let hi = context
+                    .snippet_provider
+                    .span_before(mk_sp(items[i + 1].span().lo(), item.span().hi()), "+");
+
+                Some(mk_sp(item.span().hi(), hi))
+            } else {
+                None
+            };
+            let (leading_span, has_leading_comment) = if i > 0 {
+                let lo = context
+                    .snippet_provider
+                    .span_after(mk_sp(items[i - 1].span().hi(), item.span().lo()), "+");
+
+                let span = mk_sp(lo, item.span().lo());
+
+                let has_comments = contains_comment(context.snippet(span));
+
+                (Some(mk_sp(lo, item.span().lo())), has_comments)
+            } else {
+                (None, false)
+            };
+            let prev_has_trailing_comment = match prev_trailing_span {
+                Some(ts) => contains_comment(context.snippet(ts)),
+                _ => false,
+            };
+
+            let shape = if need_indent && force_newline {
+                shape
+                    .block_indent(context.config.tab_spaces())
+                    .with_max_width(context.config)
+            } else {
+                shape
+            };
+            let whitespace = if force_newline && (!prev_extendable || !generic_bounds_in_order) {
+                shape
+                    .indent
+                    .to_string_with_newline(context.config)
+                    .to_string()
+            } else {
+                String::from(" ")
+            };
+
+            let joiner = match context.config.type_punctuation_density() {
+                TypeDensity::Compressed => String::from("+"),
+                TypeDensity::Wide => whitespace + "+ ",
+            };
+            let joiner = if has_leading_comment {
+                joiner.trim_end()
+            } else {
+                &joiner
+            };
+            let joiner = if prev_has_trailing_comment {
+                joiner.trim_start()
+            } else {
+                joiner
+            };
+
+            let (extendable, trailing_str) = if i == 0 {
+                let bound_str = item.rewrite(context, shape)?;
+                (is_bound_extendable(&bound_str, item), bound_str)
+            } else {
+                let bound_str = &item.rewrite(context, shape)?;
+                match leading_span {
+                    Some(ls) if has_leading_comment => (
+                        is_bound_extendable(bound_str, item),
+                        combine_strs_with_missing_comments(
+                            context, joiner, bound_str, ls, shape, true,
+                        )?,
+                    ),
+                    _ => (
+                        is_bound_extendable(bound_str, item),
+                        String::from(joiner) + bound_str,
+                    ),
+                }
+            };
+            match prev_trailing_span {
+                Some(ts) if prev_has_trailing_comment => combine_strs_with_missing_comments(
+                    context,
+                    &strs,
+                    &trailing_str,
+                    ts,
+                    shape,
+                    true,
+                )
+                .map(|v| (v, trailing_span, extendable)),
+                _ => Some((
+                    String::from(strs) + &trailing_str,
+                    trailing_span,
+                    extendable,
+                )),
+            }
+        },
+    )?;
+
+    if !force_newline
+        && items.len() > 1
+        && (result.0.contains('\n') || result.0.len() > shape.width)
+    {
+        join_bounds_inner(context, shape, items, need_indent, true)
+    } else {
+        Some(result.0)
+    }
+}
+
+pub(crate) fn can_be_overflowed_type(
+    context: &RewriteContext<'_>,
+    ty: &ast::Ty,
+    len: usize,
+) -> bool {
+    match ty.kind {
+        ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
+        ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
+            can_be_overflowed_type(context, &*mutty.ty, len)
+        }
+        _ => false,
+    }
+}
+
+/// Returns `None` if there is no `LifetimeDef` in the given generic parameters.
+fn rewrite_lifetime_param(
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    generic_params: &[ast::GenericParam],
+) -> Option<String> {
+    let result = generic_params
+        .iter()
+        .filter(|p| match p.kind {
+            ast::GenericParamKind::Lifetime => true,
+            _ => false,
+        })
+        .map(|lt| lt.rewrite(context, shape))
+        .collect::<Option<Vec<_>>>()?
+        .join(", ");
+    if result.is_empty() {
+        None
+    } else {
+        Some(result)
+    }
+}
diff --git a/src/tools/rustfmt/src/utils.rs b/src/tools/rustfmt/src/utils.rs
new file mode 100644
index 0000000000000..d3c349fb701e1
--- /dev/null
+++ b/src/tools/rustfmt/src/utils.rs
@@ -0,0 +1,706 @@
+use std::borrow::Cow;
+
+use rustc_ast::ast::{
+    self, Attribute, CrateSugar, MetaItem, MetaItemKind, NestedMetaItem, NodeId, Path, Visibility,
+    VisibilityKind,
+};
+use rustc_ast::ptr;
+use rustc_ast_pretty::pprust;
+use rustc_span::{sym, symbol, BytePos, ExpnId, Span, Symbol, SyntaxContext};
+use unicode_width::UnicodeWidthStr;
+
+use crate::comment::{filter_normal_code, CharClasses, FullCodeCharKind, LineClasses};
+use crate::config::{Config, Version};
+use crate::rewrite::RewriteContext;
+use crate::shape::{Indent, Shape};
+
+#[inline]
+pub(crate) fn depr_skip_annotation() -> Symbol {
+    Symbol::intern("rustfmt_skip")
+}
+
+#[inline]
+pub(crate) fn skip_annotation() -> Symbol {
+    Symbol::intern("rustfmt::skip")
+}
+
+pub(crate) fn rewrite_ident<'a>(context: &'a RewriteContext<'_>, ident: symbol::Ident) -> &'a str {
+    context.snippet(ident.span)
+}
+
+// Computes the length of a string's last line, minus offset.
+pub(crate) fn extra_offset(text: &str, shape: Shape) -> usize {
+    match text.rfind('\n') {
+        // 1 for newline character
+        Some(idx) => text.len().saturating_sub(idx + 1 + shape.used_width()),
+        None => text.len(),
+    }
+}
+
+pub(crate) fn is_same_visibility(a: &Visibility, b: &Visibility) -> bool {
+    match (&a.kind, &b.kind) {
+        (
+            VisibilityKind::Restricted { path: p, .. },
+            VisibilityKind::Restricted { path: q, .. },
+        ) => pprust::path_to_string(&p) == pprust::path_to_string(&q),
+        (VisibilityKind::Public, VisibilityKind::Public)
+        | (VisibilityKind::Inherited, VisibilityKind::Inherited)
+        | (
+            VisibilityKind::Crate(CrateSugar::PubCrate),
+            VisibilityKind::Crate(CrateSugar::PubCrate),
+        )
+        | (
+            VisibilityKind::Crate(CrateSugar::JustCrate),
+            VisibilityKind::Crate(CrateSugar::JustCrate),
+        ) => true,
+        _ => false,
+    }
+}
+
+// Uses Cow to avoid allocating in the common cases.
+pub(crate) fn format_visibility(
+    context: &RewriteContext<'_>,
+    vis: &Visibility,
+) -> Cow<'static, str> {
+    match vis.kind {
+        VisibilityKind::Public => Cow::from("pub "),
+        VisibilityKind::Inherited => Cow::from(""),
+        VisibilityKind::Crate(CrateSugar::PubCrate) => Cow::from("pub(crate) "),
+        VisibilityKind::Crate(CrateSugar::JustCrate) => Cow::from("crate "),
+        VisibilityKind::Restricted { ref path, .. } => {
+            let Path { ref segments, .. } = **path;
+            let mut segments_iter = segments.iter().map(|seg| rewrite_ident(context, seg.ident));
+            if path.is_global() {
+                segments_iter
+                    .next()
+                    .expect("Non-global path in pub(restricted)?");
+            }
+            let is_keyword = |s: &str| s == "self" || s == "super";
+            let path = segments_iter.collect::<Vec<_>>().join("::");
+            let in_str = if is_keyword(&path) { "" } else { "in " };
+
+            Cow::from(format!("pub({}{}) ", in_str, path))
+        }
+    }
+}
+
+#[inline]
+pub(crate) fn format_async(is_async: &ast::Async) -> &'static str {
+    match is_async {
+        ast::Async::Yes { .. } => "async ",
+        ast::Async::No => "",
+    }
+}
+
+#[inline]
+pub(crate) fn format_constness(constness: ast::Const) -> &'static str {
+    match constness {
+        ast::Const::Yes(..) => "const ",
+        ast::Const::No => "",
+    }
+}
+
+#[inline]
+pub(crate) fn format_constness_right(constness: ast::Const) -> &'static str {
+    match constness {
+        ast::Const::Yes(..) => " const",
+        ast::Const::No => "",
+    }
+}
+
+#[inline]
+pub(crate) fn format_defaultness(defaultness: ast::Defaultness) -> &'static str {
+    match defaultness {
+        ast::Defaultness::Default(..) => "default ",
+        ast::Defaultness::Final => "",
+    }
+}
+
+#[inline]
+pub(crate) fn format_unsafety(unsafety: ast::Unsafe) -> &'static str {
+    match unsafety {
+        ast::Unsafe::Yes(..) => "unsafe ",
+        ast::Unsafe::No => "",
+    }
+}
+
+#[inline]
+pub(crate) fn format_auto(is_auto: ast::IsAuto) -> &'static str {
+    match is_auto {
+        ast::IsAuto::Yes => "auto ",
+        ast::IsAuto::No => "",
+    }
+}
+
+#[inline]
+pub(crate) fn format_mutability(mutability: ast::Mutability) -> &'static str {
+    match mutability {
+        ast::Mutability::Mut => "mut ",
+        ast::Mutability::Not => "",
+    }
+}
+
+#[inline]
+pub(crate) fn format_extern(
+    ext: ast::Extern,
+    explicit_abi: bool,
+    is_mod: bool,
+) -> Cow<'static, str> {
+    let abi = match ext {
+        ast::Extern::None => "Rust".to_owned(),
+        ast::Extern::Implicit => "C".to_owned(),
+        ast::Extern::Explicit(abi) => abi.symbol_unescaped.to_string(),
+    };
+
+    if abi == "Rust" && !is_mod {
+        Cow::from("")
+    } else if abi == "C" && !explicit_abi {
+        Cow::from("extern ")
+    } else {
+        Cow::from(format!(r#"extern "{}" "#, abi))
+    }
+}
+
+#[inline]
+// Transform `Vec<rustc_ast::ptr::P<T>>` into `Vec<&T>`
+pub(crate) fn ptr_vec_to_ref_vec<T>(vec: &[ptr::P<T>]) -> Vec<&T> {
+    vec.iter().map(|x| &**x).collect::<Vec<_>>()
+}
+
+#[inline]
+pub(crate) fn filter_attributes(
+    attrs: &[ast::Attribute],
+    style: ast::AttrStyle,
+) -> Vec<ast::Attribute> {
+    attrs
+        .iter()
+        .filter(|a| a.style == style)
+        .cloned()
+        .collect::<Vec<_>>()
+}
+
+#[inline]
+pub(crate) fn inner_attributes(attrs: &[ast::Attribute]) -> Vec<ast::Attribute> {
+    filter_attributes(attrs, ast::AttrStyle::Inner)
+}
+
+#[inline]
+pub(crate) fn outer_attributes(attrs: &[ast::Attribute]) -> Vec<ast::Attribute> {
+    filter_attributes(attrs, ast::AttrStyle::Outer)
+}
+
+#[inline]
+pub(crate) fn is_single_line(s: &str) -> bool {
+    s.chars().find(|&c| c == '\n').is_none()
+}
+
+#[inline]
+pub(crate) fn first_line_contains_single_line_comment(s: &str) -> bool {
+    s.lines().next().map_or(false, |l| l.contains("//"))
+}
+
+#[inline]
+pub(crate) fn last_line_contains_single_line_comment(s: &str) -> bool {
+    s.lines().last().map_or(false, |l| l.contains("//"))
+}
+
+#[inline]
+pub(crate) fn is_attributes_extendable(attrs_str: &str) -> bool {
+    !attrs_str.contains('\n') && !last_line_contains_single_line_comment(attrs_str)
+}
+
+/// The width of the first line in s.
+#[inline]
+pub(crate) fn first_line_width(s: &str) -> usize {
+    unicode_str_width(s.splitn(2, '\n').next().unwrap_or(""))
+}
+
+/// The width of the last line in s.
+#[inline]
+pub(crate) fn last_line_width(s: &str) -> usize {
+    unicode_str_width(s.rsplitn(2, '\n').next().unwrap_or(""))
+}
+
+/// The total used width of the last line.
+#[inline]
+pub(crate) fn last_line_used_width(s: &str, offset: usize) -> usize {
+    if s.contains('\n') {
+        last_line_width(s)
+    } else {
+        offset + unicode_str_width(s)
+    }
+}
+
+#[inline]
+pub(crate) fn trimmed_last_line_width(s: &str) -> usize {
+    unicode_str_width(match s.rfind('\n') {
+        Some(n) => s[(n + 1)..].trim(),
+        None => s.trim(),
+    })
+}
+
+#[inline]
+pub(crate) fn last_line_extendable(s: &str) -> bool {
+    if s.ends_with("\"#") {
+        return true;
+    }
+    for c in s.chars().rev() {
+        match c {
+            '(' | ')' | ']' | '}' | '?' | '>' => continue,
+            '\n' => break,
+            _ if c.is_whitespace() => continue,
+            _ => return false,
+        }
+    }
+    true
+}
+
+#[inline]
+fn is_skip(meta_item: &MetaItem) -> bool {
+    match meta_item.kind {
+        MetaItemKind::Word => {
+            let path_str = pprust::path_to_string(&meta_item.path);
+            path_str == &*skip_annotation().as_str()
+                || path_str == &*depr_skip_annotation().as_str()
+        }
+        MetaItemKind::List(ref l) => {
+            meta_item.has_name(sym::cfg_attr) && l.len() == 2 && is_skip_nested(&l[1])
+        }
+        _ => false,
+    }
+}
+
+#[inline]
+fn is_skip_nested(meta_item: &NestedMetaItem) -> bool {
+    match meta_item {
+        NestedMetaItem::MetaItem(ref mi) => is_skip(mi),
+        NestedMetaItem::Literal(_) => false,
+    }
+}
+
+#[inline]
+pub(crate) fn contains_skip(attrs: &[Attribute]) -> bool {
+    attrs
+        .iter()
+        .any(|a| a.meta().map_or(false, |a| is_skip(&a)))
+}
+
+#[inline]
+pub(crate) fn semicolon_for_expr(context: &RewriteContext<'_>, expr: &ast::Expr) -> bool {
+    // Never try to insert semicolons on expressions when we're inside
+    // a macro definition - this can prevent the macro from compiling
+    // when used in expression position
+    if context.is_macro_def {
+        return false;
+    }
+
+    match expr.kind {
+        ast::ExprKind::Ret(..) | ast::ExprKind::Continue(..) | ast::ExprKind::Break(..) => {
+            context.config.trailing_semicolon()
+        }
+        _ => false,
+    }
+}
+
+#[inline]
+pub(crate) fn semicolon_for_stmt(context: &RewriteContext<'_>, stmt: &ast::Stmt) -> bool {
+    match stmt.kind {
+        ast::StmtKind::Semi(ref expr) => match expr.kind {
+            ast::ExprKind::While(..) | ast::ExprKind::Loop(..) | ast::ExprKind::ForLoop(..) => {
+                false
+            }
+            ast::ExprKind::Break(..) | ast::ExprKind::Continue(..) | ast::ExprKind::Ret(..) => {
+                context.config.trailing_semicolon()
+            }
+            _ => true,
+        },
+        ast::StmtKind::Expr(..) => false,
+        _ => true,
+    }
+}
+
+#[inline]
+pub(crate) fn stmt_expr(stmt: &ast::Stmt) -> Option<&ast::Expr> {
+    match stmt.kind {
+        ast::StmtKind::Expr(ref expr) => Some(expr),
+        _ => None,
+    }
+}
+
+/// Returns the number of LF and CRLF respectively.
+pub(crate) fn count_lf_crlf(input: &str) -> (usize, usize) {
+    let mut lf = 0;
+    let mut crlf = 0;
+    let mut is_crlf = false;
+    for c in input.as_bytes() {
+        match c {
+            b'\r' => is_crlf = true,
+            b'\n' if is_crlf => crlf += 1,
+            b'\n' => lf += 1,
+            _ => is_crlf = false,
+        }
+    }
+    (lf, crlf)
+}
+
+pub(crate) fn count_newlines(input: &str) -> usize {
+    // Using bytes to omit UTF-8 decoding
+    bytecount::count(input.as_bytes(), b'\n')
+}
+
+// For format_missing and last_pos, need to use the source callsite (if applicable).
+// Required as generated code spans aren't guaranteed to follow on from the last span.
+macro_rules! source {
+    ($this:ident, $sp:expr) => {
+        $sp.source_callsite()
+    };
+}
+
+pub(crate) fn mk_sp(lo: BytePos, hi: BytePos) -> Span {
+    Span::new(lo, hi, SyntaxContext::root())
+}
+
+pub(crate) fn mk_sp_lo_plus_one(lo: BytePos) -> Span {
+    Span::new(lo, lo + BytePos(1), SyntaxContext::root())
+}
+
+// Returns `true` if the given span does not intersect with file lines.
+macro_rules! out_of_file_lines_range {
+    ($self:ident, $span:expr) => {
+        !$self.config.file_lines().is_all()
+            && !$self
+                .config
+                .file_lines()
+                .intersects(&$self.parse_sess.lookup_line_range($span))
+    };
+}
+
+macro_rules! skip_out_of_file_lines_range {
+    ($self:ident, $span:expr) => {
+        if out_of_file_lines_range!($self, $span) {
+            return None;
+        }
+    };
+}
+
+macro_rules! skip_out_of_file_lines_range_visitor {
+    ($self:ident, $span:expr) => {
+        if out_of_file_lines_range!($self, $span) {
+            $self.push_rewrite($span, None);
+            return;
+        }
+    };
+}
+
+// Wraps String in an Option. Returns Some when the string adheres to the
+// Rewrite constraints defined for the Rewrite trait and None otherwise.
+pub(crate) fn wrap_str(s: String, max_width: usize, shape: Shape) -> Option<String> {
+    if is_valid_str(&filter_normal_code(&s), max_width, shape) {
+        Some(s)
+    } else {
+        None
+    }
+}
+
+fn is_valid_str(snippet: &str, max_width: usize, shape: Shape) -> bool {
+    if !snippet.is_empty() {
+        // First line must fits with `shape.width`.
+        if first_line_width(snippet) > shape.width {
+            return false;
+        }
+        // If the snippet does not include newline, we are done.
+        if is_single_line(snippet) {
+            return true;
+        }
+        // The other lines must fit within the maximum width.
+        if snippet
+            .lines()
+            .skip(1)
+            .any(|line| unicode_str_width(line) > max_width)
+        {
+            return false;
+        }
+        // A special check for the last line, since the caller may
+        // place trailing characters on this line.
+        if last_line_width(snippet) > shape.used_width() + shape.width {
+            return false;
+        }
+    }
+    true
+}
+
+#[inline]
+pub(crate) fn colon_spaces(config: &Config) -> &'static str {
+    let before = config.space_before_colon();
+    let after = config.space_after_colon();
+    match (before, after) {
+        (true, true) => " : ",
+        (true, false) => " :",
+        (false, true) => ": ",
+        (false, false) => ":",
+    }
+}
+
+#[inline]
+pub(crate) fn left_most_sub_expr(e: &ast::Expr) -> &ast::Expr {
+    match e.kind {
+        ast::ExprKind::Call(ref e, _)
+        | ast::ExprKind::Binary(_, ref e, _)
+        | ast::ExprKind::Cast(ref e, _)
+        | ast::ExprKind::Type(ref e, _)
+        | ast::ExprKind::Assign(ref e, _, _)
+        | ast::ExprKind::AssignOp(_, ref e, _)
+        | ast::ExprKind::Field(ref e, _)
+        | ast::ExprKind::Index(ref e, _)
+        | ast::ExprKind::Range(Some(ref e), _, _)
+        | ast::ExprKind::Try(ref e) => left_most_sub_expr(e),
+        _ => e,
+    }
+}
+
+#[inline]
+pub(crate) fn starts_with_newline(s: &str) -> bool {
+    s.starts_with('\n') || s.starts_with("\r\n")
+}
+
+#[inline]
+pub(crate) fn first_line_ends_with(s: &str, c: char) -> bool {
+    s.lines().next().map_or(false, |l| l.ends_with(c))
+}
+
+// States whether an expression's last line exclusively consists of closing
+// parens, braces, and brackets in its idiomatic formatting.
+pub(crate) fn is_block_expr(context: &RewriteContext<'_>, expr: &ast::Expr, repr: &str) -> bool {
+    match expr.kind {
+        ast::ExprKind::MacCall(..)
+        | ast::ExprKind::Call(..)
+        | ast::ExprKind::MethodCall(..)
+        | ast::ExprKind::Array(..)
+        | ast::ExprKind::Struct(..)
+        | ast::ExprKind::While(..)
+        | ast::ExprKind::If(..)
+        | ast::ExprKind::Block(..)
+        | ast::ExprKind::ConstBlock(..)
+        | ast::ExprKind::Async(..)
+        | ast::ExprKind::Loop(..)
+        | ast::ExprKind::ForLoop(..)
+        | ast::ExprKind::TryBlock(..)
+        | ast::ExprKind::Match(..) => repr.contains('\n'),
+        ast::ExprKind::Paren(ref expr)
+        | ast::ExprKind::Binary(_, _, ref expr)
+        | ast::ExprKind::Index(_, ref expr)
+        | ast::ExprKind::Unary(_, ref expr)
+        | ast::ExprKind::Closure(_, _, _, _, ref expr, _)
+        | ast::ExprKind::Try(ref expr)
+        | ast::ExprKind::Yield(Some(ref expr)) => is_block_expr(context, expr, repr),
+        // This can only be a string lit
+        ast::ExprKind::Lit(_) => {
+            repr.contains('\n') && trimmed_last_line_width(repr) <= context.config.tab_spaces()
+        }
+        ast::ExprKind::AddrOf(..)
+        | ast::ExprKind::Assign(..)
+        | ast::ExprKind::AssignOp(..)
+        | ast::ExprKind::Await(..)
+        | ast::ExprKind::Box(..)
+        | ast::ExprKind::Break(..)
+        | ast::ExprKind::Cast(..)
+        | ast::ExprKind::Continue(..)
+        | ast::ExprKind::Err
+        | ast::ExprKind::Field(..)
+        | ast::ExprKind::InlineAsm(..)
+        | ast::ExprKind::LlvmInlineAsm(..)
+        | ast::ExprKind::Let(..)
+        | ast::ExprKind::Path(..)
+        | ast::ExprKind::Range(..)
+        | ast::ExprKind::Repeat(..)
+        | ast::ExprKind::Ret(..)
+        | ast::ExprKind::Tup(..)
+        | ast::ExprKind::Type(..)
+        | ast::ExprKind::Yield(None)
+        | ast::ExprKind::Underscore => false,
+    }
+}
+
+/// Removes trailing spaces from the specified snippet. We do not remove spaces
+/// inside strings or comments.
+pub(crate) fn remove_trailing_white_spaces(text: &str) -> String {
+    let mut buffer = String::with_capacity(text.len());
+    let mut space_buffer = String::with_capacity(128);
+    for (char_kind, c) in CharClasses::new(text.chars()) {
+        match c {
+            '\n' => {
+                if char_kind == FullCodeCharKind::InString {
+                    buffer.push_str(&space_buffer);
+                }
+                space_buffer.clear();
+                buffer.push('\n');
+            }
+            _ if c.is_whitespace() => {
+                space_buffer.push(c);
+            }
+            _ => {
+                if !space_buffer.is_empty() {
+                    buffer.push_str(&space_buffer);
+                    space_buffer.clear();
+                }
+                buffer.push(c);
+            }
+        }
+    }
+    buffer
+}
+
+/// Indent each line according to the specified `indent`.
+/// e.g.
+///
+/// ```rust,compile_fail
+/// foo!{
+/// x,
+/// y,
+/// foo(
+///     a,
+///     b,
+///     c,
+/// ),
+/// }
+/// ```
+///
+/// will become
+///
+/// ```rust,compile_fail
+/// foo!{
+///     x,
+///     y,
+///     foo(
+///         a,
+///         b,
+///         c,
+///     ),
+/// }
+/// ```
+pub(crate) fn trim_left_preserve_layout(
+    orig: &str,
+    indent: Indent,
+    config: &Config,
+) -> Option<String> {
+    let mut lines = LineClasses::new(orig);
+    let first_line = lines.next().map(|(_, s)| s.trim_end().to_owned())?;
+    let mut trimmed_lines = Vec::with_capacity(16);
+
+    let mut veto_trim = false;
+    let min_prefix_space_width = lines
+        .filter_map(|(kind, line)| {
+            let mut trimmed = true;
+            let prefix_space_width = if is_empty_line(&line) {
+                None
+            } else {
+                Some(get_prefix_space_width(config, &line))
+            };
+
+            // just InString{Commented} in order to allow the start of a string to be indented
+            let new_veto_trim_value = (kind == FullCodeCharKind::InString
+                || (config.version() == Version::Two
+                    && kind == FullCodeCharKind::InStringCommented))
+                && !line.ends_with('\\');
+            let line = if veto_trim || new_veto_trim_value {
+                veto_trim = new_veto_trim_value;
+                trimmed = false;
+                line
+            } else {
+                line.trim().to_owned()
+            };
+            trimmed_lines.push((trimmed, line, prefix_space_width));
+
+            // Because there is a veto against trimming and indenting lines within a string,
+            // such lines should not be taken into account when computing the minimum.
+            match kind {
+                FullCodeCharKind::InStringCommented | FullCodeCharKind::EndStringCommented
+                    if config.version() == Version::Two =>
+                {
+                    None
+                }
+                FullCodeCharKind::InString | FullCodeCharKind::EndString => None,
+                _ => prefix_space_width,
+            }
+        })
+        .min()?;
+
+    Some(
+        first_line
+            + "\n"
+            + &trimmed_lines
+                .iter()
+                .map(
+                    |&(trimmed, ref line, prefix_space_width)| match prefix_space_width {
+                        _ if !trimmed => line.to_owned(),
+                        Some(original_indent_width) => {
+                            let new_indent_width = indent.width()
+                                + original_indent_width.saturating_sub(min_prefix_space_width);
+                            let new_indent = Indent::from_width(config, new_indent_width);
+                            format!("{}{}", new_indent.to_string(config), line)
+                        }
+                        None => String::new(),
+                    },
+                )
+                .collect::<Vec<_>>()
+                .join("\n"),
+    )
+}
+
+/// Based on the given line, determine if the next line can be indented or not.
+/// This allows to preserve the indentation of multi-line literals.
+pub(crate) fn indent_next_line(kind: FullCodeCharKind, _line: &str, config: &Config) -> bool {
+    !(kind.is_string() || (config.version() == Version::Two && kind.is_commented_string()))
+}
+
+pub(crate) fn is_empty_line(s: &str) -> bool {
+    s.is_empty() || s.chars().all(char::is_whitespace)
+}
+
+fn get_prefix_space_width(config: &Config, s: &str) -> usize {
+    let mut width = 0;
+    for c in s.chars() {
+        match c {
+            ' ' => width += 1,
+            '\t' => width += config.tab_spaces(),
+            _ => return width,
+        }
+    }
+    width
+}
+
+pub(crate) trait NodeIdExt {
+    fn root() -> Self;
+}
+
+impl NodeIdExt for NodeId {
+    fn root() -> NodeId {
+        NodeId::placeholder_from_expn_id(ExpnId::root())
+    }
+}
+
+pub(crate) fn unicode_str_width(s: &str) -> usize {
+    s.width()
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_remove_trailing_white_spaces() {
+        let s = "    r#\"\n        test\n    \"#";
+        assert_eq!(remove_trailing_white_spaces(&s), s);
+    }
+
+    #[test]
+    fn test_trim_left_preserve_layout() {
+        let s = "aaa\n\tbbb\n    ccc";
+        let config = Config::default();
+        let indent = Indent::new(4, 0);
+        assert_eq!(
+            trim_left_preserve_layout(&s, indent, &config),
+            Some("aaa\n    bbb\n    ccc".to_string())
+        );
+    }
+}
diff --git a/src/tools/rustfmt/src/vertical.rs b/src/tools/rustfmt/src/vertical.rs
new file mode 100644
index 0000000000000..c4208848c6c2a
--- /dev/null
+++ b/src/tools/rustfmt/src/vertical.rs
@@ -0,0 +1,285 @@
+// Format with vertical alignment.
+
+use std::cmp;
+
+use itertools::Itertools;
+use rustc_ast::ast;
+use rustc_span::{BytePos, Span};
+
+use crate::comment::combine_strs_with_missing_comments;
+use crate::config::lists::*;
+use crate::expr::rewrite_field;
+use crate::items::{rewrite_struct_field, rewrite_struct_field_prefix};
+use crate::lists::{
+    definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
+};
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::{Indent, Shape};
+use crate::source_map::SpanUtils;
+use crate::spanned::Spanned;
+use crate::utils::{
+    contains_skip, is_attributes_extendable, mk_sp, rewrite_ident, trimmed_last_line_width,
+};
+
+pub(crate) trait AlignedItem {
+    fn skip(&self) -> bool;
+    fn get_span(&self) -> Span;
+    fn rewrite_prefix(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String>;
+    fn rewrite_aligned_item(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        prefix_max_width: usize,
+    ) -> Option<String>;
+}
+
+impl AlignedItem for ast::FieldDef {
+    fn skip(&self) -> bool {
+        contains_skip(&self.attrs)
+    }
+
+    fn get_span(&self) -> Span {
+        self.span()
+    }
+
+    fn rewrite_prefix(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let attrs_str = self.attrs.rewrite(context, shape)?;
+        let missing_span = if self.attrs.is_empty() {
+            mk_sp(self.span.lo(), self.span.lo())
+        } else {
+            mk_sp(self.attrs.last().unwrap().span.hi(), self.span.lo())
+        };
+        let attrs_extendable = self.ident.is_none() && is_attributes_extendable(&attrs_str);
+        rewrite_struct_field_prefix(context, self).and_then(|field_str| {
+            combine_strs_with_missing_comments(
+                context,
+                &attrs_str,
+                &field_str,
+                missing_span,
+                shape,
+                attrs_extendable,
+            )
+        })
+    }
+
+    fn rewrite_aligned_item(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        prefix_max_width: usize,
+    ) -> Option<String> {
+        rewrite_struct_field(context, self, shape, prefix_max_width)
+    }
+}
+
+impl AlignedItem for ast::ExprField {
+    fn skip(&self) -> bool {
+        contains_skip(&self.attrs)
+    }
+
+    fn get_span(&self) -> Span {
+        self.span()
+    }
+
+    fn rewrite_prefix(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        let attrs_str = self.attrs.rewrite(context, shape)?;
+        let name = rewrite_ident(context, self.ident);
+        let missing_span = if self.attrs.is_empty() {
+            mk_sp(self.span.lo(), self.span.lo())
+        } else {
+            mk_sp(self.attrs.last().unwrap().span.hi(), self.span.lo())
+        };
+        combine_strs_with_missing_comments(
+            context,
+            &attrs_str,
+            name,
+            missing_span,
+            shape,
+            is_attributes_extendable(&attrs_str),
+        )
+    }
+
+    fn rewrite_aligned_item(
+        &self,
+        context: &RewriteContext<'_>,
+        shape: Shape,
+        prefix_max_width: usize,
+    ) -> Option<String> {
+        rewrite_field(context, self, shape, prefix_max_width)
+    }
+}
+
+pub(crate) fn rewrite_with_alignment<T: AlignedItem>(
+    fields: &[T],
+    context: &RewriteContext<'_>,
+    shape: Shape,
+    span: Span,
+    one_line_width: usize,
+) -> Option<String> {
+    let (spaces, group_index) = if context.config.struct_field_align_threshold() > 0 {
+        group_aligned_items(context, fields)
+    } else {
+        ("", fields.len() - 1)
+    };
+    let init = &fields[0..=group_index];
+    let rest = &fields[group_index + 1..];
+    let init_last_pos = if rest.is_empty() {
+        span.hi()
+    } else {
+        // Decide whether the missing comments should stick to init or rest.
+        let init_hi = init[init.len() - 1].get_span().hi();
+        let rest_lo = rest[0].get_span().lo();
+        let missing_span = mk_sp(init_hi, rest_lo);
+        let missing_span = mk_sp(
+            context.snippet_provider.span_after(missing_span, ","),
+            missing_span.hi(),
+        );
+
+        let snippet = context.snippet(missing_span);
+        if snippet.trim_start().starts_with("//") {
+            let offset = snippet.lines().next().map_or(0, str::len);
+            // 2 = "," + "\n"
+            init_hi + BytePos(offset as u32 + 2)
+        } else if snippet.trim_start().starts_with("/*") {
+            let comment_lines = snippet
+                .lines()
+                .position(|line| line.trim_end().ends_with("*/"))
+                .unwrap_or(0);
+
+            let offset = snippet
+                .lines()
+                .take(comment_lines + 1)
+                .collect::<Vec<_>>()
+                .join("\n")
+                .len();
+
+            init_hi + BytePos(offset as u32 + 2)
+        } else {
+            missing_span.lo()
+        }
+    };
+    let init_span = mk_sp(span.lo(), init_last_pos);
+    let one_line_width = if rest.is_empty() { one_line_width } else { 0 };
+    let result =
+        rewrite_aligned_items_inner(context, init, init_span, shape.indent, one_line_width)?;
+    if rest.is_empty() {
+        Some(result + spaces)
+    } else {
+        let rest_span = mk_sp(init_last_pos, span.hi());
+        let rest_str = rewrite_with_alignment(rest, context, shape, rest_span, one_line_width)?;
+        Some(format!(
+            "{}{}\n{}{}",
+            result,
+            spaces,
+            &shape.indent.to_string(context.config),
+            &rest_str
+        ))
+    }
+}
+
+fn struct_field_prefix_max_min_width<T: AlignedItem>(
+    context: &RewriteContext<'_>,
+    fields: &[T],
+    shape: Shape,
+) -> (usize, usize) {
+    fields
+        .iter()
+        .map(|field| {
+            field
+                .rewrite_prefix(context, shape)
+                .map(|field_str| trimmed_last_line_width(&field_str))
+        })
+        .fold_options((0, ::std::usize::MAX), |(max_len, min_len), len| {
+            (cmp::max(max_len, len), cmp::min(min_len, len))
+        })
+        .unwrap_or((0, 0))
+}
+
+fn rewrite_aligned_items_inner<T: AlignedItem>(
+    context: &RewriteContext<'_>,
+    fields: &[T],
+    span: Span,
+    offset: Indent,
+    one_line_width: usize,
+) -> Option<String> {
+    // 1 = ","
+    let item_shape = Shape::indented(offset, context.config).sub_width(1)?;
+    let (mut field_prefix_max_width, field_prefix_min_width) =
+        struct_field_prefix_max_min_width(context, fields, item_shape);
+    let max_diff = field_prefix_max_width.saturating_sub(field_prefix_min_width);
+    if max_diff > context.config.struct_field_align_threshold() {
+        field_prefix_max_width = 0;
+    }
+
+    let mut items = itemize_list(
+        context.snippet_provider,
+        fields.iter(),
+        "}",
+        ",",
+        |field| field.get_span().lo(),
+        |field| field.get_span().hi(),
+        |field| field.rewrite_aligned_item(context, item_shape, field_prefix_max_width),
+        span.lo(),
+        span.hi(),
+        false,
+    )
+    .collect::<Vec<_>>();
+
+    let tactic = definitive_tactic(
+        &items,
+        ListTactic::HorizontalVertical,
+        Separator::Comma,
+        one_line_width,
+    );
+
+    if tactic == DefinitiveListTactic::Horizontal {
+        // since the items fits on a line, there is no need to align them
+        let do_rewrite =
+            |field: &T| -> Option<String> { field.rewrite_aligned_item(context, item_shape, 0) };
+        fields
+            .iter()
+            .zip(items.iter_mut())
+            .for_each(|(field, list_item): (&T, &mut ListItem)| {
+                if list_item.item.is_some() {
+                    list_item.item = do_rewrite(field);
+                }
+            });
+    }
+
+    let fmt = ListFormatting::new(item_shape, context.config)
+        .tactic(tactic)
+        .trailing_separator(context.config.trailing_comma())
+        .preserve_newline(true);
+    write_list(&items, &fmt)
+}
+
+/// Returns the index in `fields` up to which a field belongs to the current group.
+/// The returned string is the group separator to use when rewriting the fields.
+/// Groups are defined by blank lines.
+fn group_aligned_items<T: AlignedItem>(
+    context: &RewriteContext<'_>,
+    fields: &[T],
+) -> (&'static str, usize) {
+    let mut index = 0;
+    for i in 0..fields.len() - 1 {
+        if fields[i].skip() {
+            return ("", index);
+        }
+        let span = mk_sp(fields[i].get_span().hi(), fields[i + 1].get_span().lo());
+        let snippet = context
+            .snippet(span)
+            .lines()
+            .skip(1)
+            .collect::<Vec<_>>()
+            .join("\n");
+        let has_blank_line = snippet
+            .lines()
+            .dropping_back(1)
+            .any(|l| l.trim().is_empty());
+        if has_blank_line {
+            return ("\n", index);
+        }
+        index += 1;
+    }
+    ("", index)
+}
diff --git a/src/tools/rustfmt/src/visitor.rs b/src/tools/rustfmt/src/visitor.rs
new file mode 100644
index 0000000000000..079568630cf52
--- /dev/null
+++ b/src/tools/rustfmt/src/visitor.rs
@@ -0,0 +1,1075 @@
+use std::cell::{Cell, RefCell};
+use std::rc::Rc;
+
+use rustc_ast::{ast, token::DelimToken, visit, AstLike};
+use rustc_data_structures::sync::Lrc;
+use rustc_span::{symbol, BytePos, Pos, Span, DUMMY_SP};
+
+use crate::attr::*;
+use crate::comment::{contains_comment, rewrite_comment, CodeCharKind, CommentCodeSlices};
+use crate::config::Version;
+use crate::config::{BraceStyle, Config};
+use crate::coverage::transform_missing_snippet;
+use crate::items::{
+    format_impl, format_trait, format_trait_alias, is_mod_decl, is_use_item,
+    rewrite_associated_impl_type, rewrite_extern_crate, rewrite_opaque_impl_type,
+    rewrite_opaque_type, rewrite_type_alias, FnBraceStyle, FnSig, StaticParts, StructParts,
+};
+use crate::macros::{macro_style, rewrite_macro, rewrite_macro_def, MacroPosition};
+use crate::modules::Module;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::{Indent, Shape};
+use crate::skip::{is_skip_attr, SkipContext};
+use crate::source_map::{LineRangeUtils, SpanUtils};
+use crate::spanned::Spanned;
+use crate::stmt::Stmt;
+use crate::syntux::session::ParseSess;
+use crate::utils::{
+    self, contains_skip, count_newlines, depr_skip_annotation, format_unsafety, inner_attributes,
+    last_line_width, mk_sp, ptr_vec_to_ref_vec, rewrite_ident, starts_with_newline, stmt_expr,
+};
+use crate::{ErrorKind, FormatReport, FormattingError};
+
+/// Creates a string slice corresponding to the specified span.
+pub(crate) struct SnippetProvider {
+    /// A pointer to the content of the file we are formatting.
+    big_snippet: Lrc<String>,
+    /// A position of the start of `big_snippet`, used as an offset.
+    start_pos: usize,
+    /// A end position of the file that this snippet lives.
+    end_pos: usize,
+}
+
+impl SnippetProvider {
+    pub(crate) fn span_to_snippet(&self, span: Span) -> Option<&str> {
+        let start_index = span.lo().to_usize().checked_sub(self.start_pos)?;
+        let end_index = span.hi().to_usize().checked_sub(self.start_pos)?;
+        Some(&self.big_snippet[start_index..end_index])
+    }
+
+    pub(crate) fn new(start_pos: BytePos, end_pos: BytePos, big_snippet: Lrc<String>) -> Self {
+        let start_pos = start_pos.to_usize();
+        let end_pos = end_pos.to_usize();
+        SnippetProvider {
+            big_snippet,
+            start_pos,
+            end_pos,
+        }
+    }
+
+    pub(crate) fn entire_snippet(&self) -> &str {
+        self.big_snippet.as_str()
+    }
+
+    pub(crate) fn start_pos(&self) -> BytePos {
+        BytePos::from_usize(self.start_pos)
+    }
+
+    pub(crate) fn end_pos(&self) -> BytePos {
+        BytePos::from_usize(self.end_pos)
+    }
+}
+
+pub(crate) struct FmtVisitor<'a> {
+    parent_context: Option<&'a RewriteContext<'a>>,
+    pub(crate) parse_sess: &'a ParseSess,
+    pub(crate) buffer: String,
+    pub(crate) last_pos: BytePos,
+    // FIXME: use an RAII util or closure for indenting
+    pub(crate) block_indent: Indent,
+    pub(crate) config: &'a Config,
+    pub(crate) is_if_else_block: bool,
+    pub(crate) snippet_provider: &'a SnippetProvider,
+    pub(crate) line_number: usize,
+    /// List of 1-based line ranges which were annotated with skip
+    /// Both bounds are inclusifs.
+    pub(crate) skipped_range: Rc<RefCell<Vec<(usize, usize)>>>,
+    pub(crate) macro_rewrite_failure: bool,
+    pub(crate) report: FormatReport,
+    pub(crate) skip_context: SkipContext,
+    pub(crate) is_macro_def: bool,
+}
+
+impl<'a> Drop for FmtVisitor<'a> {
+    fn drop(&mut self) {
+        if let Some(ctx) = self.parent_context {
+            if self.macro_rewrite_failure {
+                ctx.macro_rewrite_failure.replace(true);
+            }
+        }
+    }
+}
+
+impl<'b, 'a: 'b> FmtVisitor<'a> {
+    fn set_parent_context(&mut self, context: &'a RewriteContext<'_>) {
+        self.parent_context = Some(context);
+    }
+
+    pub(crate) fn shape(&self) -> Shape {
+        Shape::indented(self.block_indent, self.config)
+    }
+
+    fn next_span(&self, hi: BytePos) -> Span {
+        mk_sp(self.last_pos, hi)
+    }
+
+    fn visit_stmt(&mut self, stmt: &Stmt<'_>, include_empty_semi: bool) {
+        debug!(
+            "visit_stmt: {}",
+            self.parse_sess.span_to_debug_info(stmt.span())
+        );
+
+        if stmt.is_empty() {
+            // If the statement is empty, just skip over it. Before that, make sure any comment
+            // snippet preceding the semicolon is picked up.
+            let snippet = self.snippet(mk_sp(self.last_pos, stmt.span().lo()));
+            let original_starts_with_newline = snippet
+                .find(|c| c != ' ')
+                .map_or(false, |i| starts_with_newline(&snippet[i..]));
+            let snippet = snippet.trim();
+            if !snippet.is_empty() {
+                // FIXME(calebcartwright 2021-01-03) - This exists strictly to maintain legacy
+                // formatting where rustfmt would preserve redundant semicolons on Items in a
+                // statement position.
+                // See comment within `walk_stmts` for more info
+                if include_empty_semi {
+                    self.format_missing(stmt.span().hi());
+                } else {
+                    if original_starts_with_newline {
+                        self.push_str("\n");
+                    }
+
+                    self.push_str(&self.block_indent.to_string(self.config));
+                    self.push_str(snippet);
+                }
+            } else if include_empty_semi {
+                self.push_str(";");
+            }
+            self.last_pos = stmt.span().hi();
+            return;
+        }
+
+        match stmt.as_ast_node().kind {
+            ast::StmtKind::Item(ref item) => {
+                self.visit_item(item);
+                self.last_pos = stmt.span().hi();
+            }
+            ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
+                let attrs = get_attrs_from_stmt(stmt.as_ast_node());
+                if contains_skip(attrs) {
+                    self.push_skipped_with_span(
+                        attrs,
+                        stmt.span(),
+                        get_span_without_attrs(stmt.as_ast_node()),
+                    );
+                } else {
+                    let shape = self.shape();
+                    let rewrite = self.with_context(|ctx| stmt.rewrite(&ctx, shape));
+                    self.push_rewrite(stmt.span(), rewrite)
+                }
+            }
+            ast::StmtKind::MacCall(ref mac_stmt) => {
+                if self.visit_attrs(&mac_stmt.attrs, ast::AttrStyle::Outer) {
+                    self.push_skipped_with_span(
+                        &mac_stmt.attrs,
+                        stmt.span(),
+                        get_span_without_attrs(stmt.as_ast_node()),
+                    );
+                } else {
+                    self.visit_mac(&mac_stmt.mac, None, MacroPosition::Statement);
+                }
+                self.format_missing(stmt.span().hi());
+            }
+            ast::StmtKind::Empty => (),
+        }
+    }
+
+    /// Remove spaces between the opening brace and the first statement or the inner attribute
+    /// of the block.
+    fn trim_spaces_after_opening_brace(
+        &mut self,
+        b: &ast::Block,
+        inner_attrs: Option<&[ast::Attribute]>,
+    ) {
+        if let Some(first_stmt) = b.stmts.first() {
+            let hi = inner_attrs
+                .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
+                .unwrap_or_else(|| first_stmt.span().lo());
+            let missing_span = self.next_span(hi);
+            let snippet = self.snippet(missing_span);
+            let len = CommentCodeSlices::new(snippet)
+                .nth(0)
+                .and_then(|(kind, _, s)| {
+                    if kind == CodeCharKind::Normal {
+                        s.rfind('\n')
+                    } else {
+                        None
+                    }
+                });
+            if let Some(len) = len {
+                self.last_pos = self.last_pos + BytePos::from_usize(len);
+            }
+        }
+    }
+
+    pub(crate) fn visit_block(
+        &mut self,
+        b: &ast::Block,
+        inner_attrs: Option<&[ast::Attribute]>,
+        has_braces: bool,
+    ) {
+        debug!(
+            "visit_block: {}",
+            self.parse_sess.span_to_debug_info(b.span),
+        );
+
+        // Check if this block has braces.
+        let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
+
+        self.last_pos = self.last_pos + brace_compensation;
+        self.block_indent = self.block_indent.block_indent(self.config);
+        self.push_str("{");
+        self.trim_spaces_after_opening_brace(b, inner_attrs);
+
+        // Format inner attributes if available.
+        if let Some(attrs) = inner_attrs {
+            self.visit_attrs(attrs, ast::AttrStyle::Inner);
+        }
+
+        self.walk_block_stmts(b);
+
+        if !b.stmts.is_empty() {
+            if let Some(expr) = stmt_expr(&b.stmts[b.stmts.len() - 1]) {
+                if utils::semicolon_for_expr(&self.get_context(), expr) {
+                    self.push_str(";");
+                }
+            }
+        }
+
+        let rest_span = self.next_span(b.span.hi());
+        if out_of_file_lines_range!(self, rest_span) {
+            self.push_str(self.snippet(rest_span));
+            self.block_indent = self.block_indent.block_unindent(self.config);
+        } else {
+            // Ignore the closing brace.
+            let missing_span = self.next_span(b.span.hi() - brace_compensation);
+            self.close_block(missing_span, self.unindent_comment_on_closing_brace(b));
+        }
+        self.last_pos = source!(self, b.span).hi();
+    }
+
+    fn close_block(&mut self, span: Span, unindent_comment: bool) {
+        let config = self.config;
+
+        let mut last_hi = span.lo();
+        let mut unindented = false;
+        let mut prev_ends_with_newline = false;
+        let mut extra_newline = false;
+
+        let skip_normal = |s: &str| {
+            let trimmed = s.trim();
+            trimmed.is_empty() || trimmed.chars().all(|c| c == ';')
+        };
+
+        let comment_snippet = self.snippet(span);
+
+        let align_to_right = if unindent_comment && contains_comment(&comment_snippet) {
+            let first_lines = comment_snippet.splitn(2, '/').next().unwrap_or("");
+            last_line_width(first_lines) > last_line_width(&comment_snippet)
+        } else {
+            false
+        };
+
+        for (kind, offset, sub_slice) in CommentCodeSlices::new(comment_snippet) {
+            let sub_slice = transform_missing_snippet(config, sub_slice);
+
+            debug!("close_block: {:?} {:?} {:?}", kind, offset, sub_slice);
+
+            match kind {
+                CodeCharKind::Comment => {
+                    if !unindented && unindent_comment && !align_to_right {
+                        unindented = true;
+                        self.block_indent = self.block_indent.block_unindent(config);
+                    }
+                    let span_in_between = mk_sp(last_hi, span.lo() + BytePos::from_usize(offset));
+                    let snippet_in_between = self.snippet(span_in_between);
+                    let mut comment_on_same_line = !snippet_in_between.contains("\n");
+
+                    let mut comment_shape =
+                        Shape::indented(self.block_indent, config).comment(config);
+                    if self.config.version() == Version::Two && comment_on_same_line {
+                        self.push_str(" ");
+                        // put the first line of the comment on the same line as the
+                        // block's last line
+                        match sub_slice.find("\n") {
+                            None => {
+                                self.push_str(&sub_slice);
+                            }
+                            Some(offset) if offset + 1 == sub_slice.len() => {
+                                self.push_str(&sub_slice[..offset]);
+                            }
+                            Some(offset) => {
+                                let first_line = &sub_slice[..offset];
+                                self.push_str(first_line);
+                                self.push_str(&self.block_indent.to_string_with_newline(config));
+
+                                // put the other lines below it, shaping it as needed
+                                let other_lines = &sub_slice[offset + 1..];
+                                let comment_str =
+                                    rewrite_comment(other_lines, false, comment_shape, config);
+                                match comment_str {
+                                    Some(ref s) => self.push_str(s),
+                                    None => self.push_str(other_lines),
+                                }
+                            }
+                        }
+                    } else {
+                        if comment_on_same_line {
+                            // 1 = a space before `//`
+                            let offset_len = 1 + last_line_width(&self.buffer)
+                                .saturating_sub(self.block_indent.width());
+                            match comment_shape
+                                .visual_indent(offset_len)
+                                .sub_width(offset_len)
+                            {
+                                Some(shp) => comment_shape = shp,
+                                None => comment_on_same_line = false,
+                            }
+                        };
+
+                        if comment_on_same_line {
+                            self.push_str(" ");
+                        } else {
+                            if count_newlines(snippet_in_between) >= 2 || extra_newline {
+                                self.push_str("\n");
+                            }
+                            self.push_str(&self.block_indent.to_string_with_newline(config));
+                        }
+
+                        let comment_str = rewrite_comment(&sub_slice, false, comment_shape, config);
+                        match comment_str {
+                            Some(ref s) => self.push_str(s),
+                            None => self.push_str(&sub_slice),
+                        }
+                    }
+                }
+                CodeCharKind::Normal if skip_normal(&sub_slice) => {
+                    extra_newline = prev_ends_with_newline && sub_slice.contains('\n');
+                    continue;
+                }
+                CodeCharKind::Normal => {
+                    self.push_str(&self.block_indent.to_string_with_newline(config));
+                    self.push_str(sub_slice.trim());
+                }
+            }
+            prev_ends_with_newline = sub_slice.ends_with('\n');
+            extra_newline = false;
+            last_hi = span.lo() + BytePos::from_usize(offset + sub_slice.len());
+        }
+        if unindented {
+            self.block_indent = self.block_indent.block_indent(self.config);
+        }
+        self.block_indent = self.block_indent.block_unindent(self.config);
+        self.push_str(&self.block_indent.to_string_with_newline(config));
+        self.push_str("}");
+    }
+
+    fn unindent_comment_on_closing_brace(&self, b: &ast::Block) -> bool {
+        self.is_if_else_block && !b.stmts.is_empty()
+    }
+
+    // Note that this only gets called for function definitions. Required methods
+    // on traits do not get handled here.
+    pub(crate) fn visit_fn(
+        &mut self,
+        fk: visit::FnKind<'_>,
+        generics: &ast::Generics,
+        fd: &ast::FnDecl,
+        s: Span,
+        defaultness: ast::Defaultness,
+        inner_attrs: Option<&[ast::Attribute]>,
+    ) {
+        let indent = self.block_indent;
+        let block;
+        let rewrite = match fk {
+            visit::FnKind::Fn(_, ident, _, _, Some(ref b)) => {
+                block = b;
+                self.rewrite_fn_before_block(
+                    indent,
+                    ident,
+                    &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
+                    mk_sp(s.lo(), b.span.lo()),
+                )
+            }
+            _ => unreachable!(),
+        };
+
+        if let Some((fn_str, fn_brace_style)) = rewrite {
+            self.format_missing_with_indent(source!(self, s).lo());
+
+            if let Some(rw) = self.single_line_fn(&fn_str, block, inner_attrs) {
+                self.push_str(&rw);
+                self.last_pos = s.hi();
+                return;
+            }
+
+            self.push_str(&fn_str);
+            match fn_brace_style {
+                FnBraceStyle::SameLine => self.push_str(" "),
+                FnBraceStyle::NextLine => {
+                    self.push_str(&self.block_indent.to_string_with_newline(self.config))
+                }
+                _ => unreachable!(),
+            }
+            self.last_pos = source!(self, block.span).lo();
+        } else {
+            self.format_missing(source!(self, block.span).lo());
+        }
+
+        self.visit_block(block, inner_attrs, true)
+    }
+
+    pub(crate) fn visit_item(&mut self, item: &ast::Item) {
+        skip_out_of_file_lines_range_visitor!(self, item.span);
+
+        // This is where we bail out if there is a skip attribute. This is only
+        // complex in the module case. It is complex because the module could be
+        // in a separate file and there might be attributes in both files, but
+        // the AST lumps them all together.
+        let filtered_attrs;
+        let mut attrs = &item.attrs;
+        let skip_context_saved = self.skip_context.clone();
+        self.skip_context.update_with_attrs(&attrs);
+
+        let should_visit_node_again = match item.kind {
+            // For use/extern crate items, skip rewriting attributes but check for a skip attribute.
+            ast::ItemKind::Use(..) | ast::ItemKind::ExternCrate(_) => {
+                if contains_skip(attrs) {
+                    self.push_skipped_with_span(attrs.as_slice(), item.span(), item.span());
+                    false
+                } else {
+                    true
+                }
+            }
+            // Module is inline, in this case we treat it like any other item.
+            _ if !is_mod_decl(item) => {
+                if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
+                    self.push_skipped_with_span(item.attrs.as_slice(), item.span(), item.span());
+                    false
+                } else {
+                    true
+                }
+            }
+            // Module is not inline, but should be skipped.
+            ast::ItemKind::Mod(..) if contains_skip(&item.attrs) => false,
+            // Module is not inline and should not be skipped. We want
+            // to process only the attributes in the current file.
+            ast::ItemKind::Mod(..) => {
+                filtered_attrs = filter_inline_attrs(&item.attrs, item.span());
+                // Assert because if we should skip it should be caught by
+                // the above case.
+                assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
+                attrs = &filtered_attrs;
+                true
+            }
+            _ => {
+                if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
+                    self.push_skipped_with_span(item.attrs.as_slice(), item.span(), item.span());
+                    false
+                } else {
+                    true
+                }
+            }
+        };
+
+        // TODO(calebcartwright): consider enabling box_patterns feature gate
+        if should_visit_node_again {
+            match item.kind {
+                ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
+                ast::ItemKind::Impl { .. } => {
+                    let block_indent = self.block_indent;
+                    let rw = self.with_context(|ctx| format_impl(&ctx, item, block_indent));
+                    self.push_rewrite(item.span, rw);
+                }
+                ast::ItemKind::Trait(..) => {
+                    let block_indent = self.block_indent;
+                    let rw = self.with_context(|ctx| format_trait(&ctx, item, block_indent));
+                    self.push_rewrite(item.span, rw);
+                }
+                ast::ItemKind::TraitAlias(ref generics, ref generic_bounds) => {
+                    let shape = Shape::indented(self.block_indent, self.config);
+                    let rw = format_trait_alias(
+                        &self.get_context(),
+                        item.ident,
+                        &item.vis,
+                        generics,
+                        generic_bounds,
+                        shape,
+                    );
+                    self.push_rewrite(item.span, rw);
+                }
+                ast::ItemKind::ExternCrate(_) => {
+                    let rw = rewrite_extern_crate(&self.get_context(), item, self.shape());
+                    let span = if attrs.is_empty() {
+                        item.span
+                    } else {
+                        mk_sp(attrs[0].span.lo(), item.span.hi())
+                    };
+                    self.push_rewrite(span, rw);
+                }
+                ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
+                    self.visit_struct(&StructParts::from_item(item));
+                }
+                ast::ItemKind::Enum(ref def, ref generics) => {
+                    self.format_missing_with_indent(source!(self, item.span).lo());
+                    self.visit_enum(item.ident, &item.vis, def, generics, item.span);
+                    self.last_pos = source!(self, item.span).hi();
+                }
+                ast::ItemKind::Mod(unsafety, ref mod_kind) => {
+                    self.format_missing_with_indent(source!(self, item.span).lo());
+                    self.format_mod(mod_kind, unsafety, &item.vis, item.span, item.ident, attrs);
+                }
+                ast::ItemKind::MacCall(ref mac) => {
+                    self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
+                }
+                ast::ItemKind::ForeignMod(ref foreign_mod) => {
+                    self.format_missing_with_indent(source!(self, item.span).lo());
+                    self.format_foreign_mod(foreign_mod, item.span);
+                }
+                ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
+                    self.visit_static(&StaticParts::from_item(item));
+                }
+                ast::ItemKind::Fn(ref fn_kind) => {
+                    let ast::FnKind(defaultness, ref fn_signature, ref generics, ref block) =
+                        **fn_kind;
+                    if let Some(ref body) = block {
+                        let inner_attrs = inner_attributes(&item.attrs);
+                        let fn_ctxt = match fn_signature.header.ext {
+                            ast::Extern::None => visit::FnCtxt::Free,
+                            _ => visit::FnCtxt::Foreign,
+                        };
+                        self.visit_fn(
+                            visit::FnKind::Fn(
+                                fn_ctxt,
+                                item.ident,
+                                &fn_signature,
+                                &item.vis,
+                                Some(body),
+                            ),
+                            generics,
+                            &fn_signature.decl,
+                            item.span,
+                            defaultness,
+                            Some(&inner_attrs),
+                        )
+                    } else {
+                        let indent = self.block_indent;
+                        let rewrite = self.rewrite_required_fn(
+                            indent,
+                            item.ident,
+                            &fn_signature,
+                            generics,
+                            item.span,
+                        );
+                        self.push_rewrite(item.span, rewrite);
+                    }
+                }
+                ast::ItemKind::TyAlias(ref alias_kind) => {
+                    let ast::TyAliasKind(_, ref generics, ref generic_bounds, ref ty) =
+                        **alias_kind;
+                    match ty {
+                        Some(ty) => {
+                            let rewrite = rewrite_type_alias(
+                                item.ident,
+                                Some(&*ty),
+                                generics,
+                                Some(generic_bounds),
+                                &self.get_context(),
+                                self.block_indent,
+                                &item.vis,
+                                item.span,
+                            );
+                            self.push_rewrite(item.span, rewrite);
+                        }
+                        None => {
+                            let rewrite = rewrite_opaque_type(
+                                &self.get_context(),
+                                self.block_indent,
+                                item.ident,
+                                generic_bounds,
+                                generics,
+                                &item.vis,
+                                item.span,
+                            );
+                            self.push_rewrite(item.span, rewrite);
+                        }
+                    }
+                }
+                ast::ItemKind::GlobalAsm(..) => {
+                    let snippet = Some(self.snippet(item.span).to_owned());
+                    self.push_rewrite(item.span, snippet);
+                }
+                ast::ItemKind::MacroDef(ref def) => {
+                    let rewrite = rewrite_macro_def(
+                        &self.get_context(),
+                        self.shape(),
+                        self.block_indent,
+                        def,
+                        item.ident,
+                        &item.vis,
+                        item.span,
+                    );
+                    self.push_rewrite(item.span, rewrite);
+                }
+            };
+        }
+        self.skip_context = skip_context_saved;
+    }
+
+    pub(crate) fn visit_trait_item(&mut self, ti: &ast::AssocItem) {
+        skip_out_of_file_lines_range_visitor!(self, ti.span);
+
+        if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
+            self.push_skipped_with_span(ti.attrs.as_slice(), ti.span(), ti.span());
+            return;
+        }
+
+        // TODO(calebcartwright): consider enabling box_patterns feature gate
+        match ti.kind {
+            ast::AssocItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
+            ast::AssocItemKind::Fn(ref fn_kind) => {
+                let ast::FnKind(defaultness, ref sig, ref generics, ref block) = **fn_kind;
+                if let Some(ref body) = block {
+                    let inner_attrs = inner_attributes(&ti.attrs);
+                    let vis = ast::Visibility {
+                        kind: ast::VisibilityKind::Inherited,
+                        span: DUMMY_SP,
+                        tokens: None,
+                    };
+                    let fn_ctxt = visit::FnCtxt::Assoc(visit::AssocCtxt::Trait);
+                    self.visit_fn(
+                        visit::FnKind::Fn(fn_ctxt, ti.ident, sig, &vis, Some(body)),
+                        generics,
+                        &sig.decl,
+                        ti.span,
+                        defaultness,
+                        Some(&inner_attrs),
+                    );
+                } else {
+                    let indent = self.block_indent;
+                    let rewrite =
+                        self.rewrite_required_fn(indent, ti.ident, sig, generics, ti.span);
+                    self.push_rewrite(ti.span, rewrite);
+                }
+            }
+            ast::AssocItemKind::TyAlias(ref ty_alias_kind) => {
+                let ast::TyAliasKind(_, ref generics, ref generic_bounds, ref type_default) =
+                    **ty_alias_kind;
+                let rewrite = rewrite_type_alias(
+                    ti.ident,
+                    type_default.as_ref(),
+                    generics,
+                    Some(generic_bounds),
+                    &self.get_context(),
+                    self.block_indent,
+                    &ti.vis,
+                    ti.span,
+                );
+                self.push_rewrite(ti.span, rewrite);
+            }
+            ast::AssocItemKind::MacCall(ref mac) => {
+                self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
+            }
+        }
+    }
+
+    pub(crate) fn visit_impl_item(&mut self, ii: &ast::AssocItem) {
+        skip_out_of_file_lines_range_visitor!(self, ii.span);
+
+        if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
+            self.push_skipped_with_span(ii.attrs.as_slice(), ii.span, ii.span);
+            return;
+        }
+
+        match ii.kind {
+            ast::AssocItemKind::Fn(ref fn_kind) => {
+                let ast::FnKind(defaultness, ref sig, ref generics, ref block) = **fn_kind;
+                if let Some(ref body) = block {
+                    let inner_attrs = inner_attributes(&ii.attrs);
+                    let fn_ctxt = visit::FnCtxt::Assoc(visit::AssocCtxt::Impl);
+                    self.visit_fn(
+                        visit::FnKind::Fn(fn_ctxt, ii.ident, sig, &ii.vis, Some(body)),
+                        generics,
+                        &sig.decl,
+                        ii.span,
+                        defaultness,
+                        Some(&inner_attrs),
+                    );
+                } else {
+                    let indent = self.block_indent;
+                    let rewrite =
+                        self.rewrite_required_fn(indent, ii.ident, sig, generics, ii.span);
+                    self.push_rewrite(ii.span, rewrite);
+                }
+            }
+            ast::AssocItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
+            ast::AssocItemKind::TyAlias(ref ty_alias_kind) => {
+                let ast::TyAliasKind(defaultness, ref generics, _, ref ty) = **ty_alias_kind;
+                let rewrite_associated = || {
+                    rewrite_associated_impl_type(
+                        ii.ident,
+                        &ii.vis,
+                        defaultness,
+                        ty.as_ref(),
+                        &generics,
+                        &self.get_context(),
+                        self.block_indent,
+                        ii.span,
+                    )
+                };
+                let rewrite = match ty {
+                    None => rewrite_associated(),
+                    Some(ty) => match ty.kind {
+                        ast::TyKind::ImplTrait(_, ref bounds) => rewrite_opaque_impl_type(
+                            &self.get_context(),
+                            ii.ident,
+                            generics,
+                            bounds,
+                            self.block_indent,
+                        ),
+                        _ => rewrite_associated(),
+                    },
+                };
+                self.push_rewrite(ii.span, rewrite);
+            }
+            ast::AssocItemKind::MacCall(ref mac) => {
+                self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
+            }
+        }
+    }
+
+    fn visit_mac(&mut self, mac: &ast::MacCall, ident: Option<symbol::Ident>, pos: MacroPosition) {
+        skip_out_of_file_lines_range_visitor!(self, mac.span());
+
+        // 1 = ;
+        let shape = self.shape().saturating_sub_width(1);
+        let rewrite = self.with_context(|ctx| rewrite_macro(mac, ident, ctx, shape, pos));
+        // As of v638 of the rustc-ap-* crates, the associated span no longer includes
+        // the trailing semicolon. This determines the correct span to ensure scenarios
+        // with whitespace between the delimiters and trailing semi (i.e. `foo!(abc)     ;`)
+        // are formatted correctly.
+        let (span, rewrite) = match macro_style(mac, &self.get_context()) {
+            DelimToken::Bracket | DelimToken::Paren if MacroPosition::Item == pos => {
+                let search_span = mk_sp(mac.span().hi(), self.snippet_provider.end_pos());
+                let hi = self.snippet_provider.span_before(search_span, ";");
+                let target_span = mk_sp(mac.span().lo(), hi + BytePos(1));
+                let rewrite = rewrite.map(|rw| {
+                    if !rw.ends_with(";") {
+                        format!("{};", rw)
+                    } else {
+                        rw
+                    }
+                });
+                (target_span, rewrite)
+            }
+            _ => (mac.span(), rewrite),
+        };
+
+        self.push_rewrite(span, rewrite);
+    }
+
+    pub(crate) fn push_str(&mut self, s: &str) {
+        self.line_number += count_newlines(s);
+        self.buffer.push_str(s);
+    }
+
+    #[allow(clippy::needless_pass_by_value)]
+    fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
+        if let Some(ref s) = rewrite {
+            self.push_str(s);
+        } else {
+            let snippet = self.snippet(span);
+            self.push_str(snippet.trim());
+        }
+        self.last_pos = source!(self, span).hi();
+    }
+
+    pub(crate) fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
+        self.format_missing_with_indent(source!(self, span).lo());
+        self.push_rewrite_inner(span, rewrite);
+    }
+
+    pub(crate) fn push_skipped_with_span(
+        &mut self,
+        attrs: &[ast::Attribute],
+        item_span: Span,
+        main_span: Span,
+    ) {
+        self.format_missing_with_indent(source!(self, item_span).lo());
+        // do not take into account the lines with attributes as part of the skipped range
+        let attrs_end = attrs
+            .iter()
+            .map(|attr| self.parse_sess.line_of_byte_pos(attr.span.hi()))
+            .max()
+            .unwrap_or(1);
+        let first_line = self.parse_sess.line_of_byte_pos(main_span.lo());
+        // Statement can start after some newlines and/or spaces
+        // or it can be on the same line as the last attribute.
+        // So here we need to take a minimum between the two.
+        let lo = std::cmp::min(attrs_end + 1, first_line);
+        self.push_rewrite_inner(item_span, None);
+        let hi = self.line_number + 1;
+        self.skipped_range.borrow_mut().push((lo, hi));
+    }
+
+    pub(crate) fn from_context(ctx: &'a RewriteContext<'_>) -> FmtVisitor<'a> {
+        let mut visitor = FmtVisitor::from_parse_sess(
+            ctx.parse_sess,
+            ctx.config,
+            ctx.snippet_provider,
+            ctx.report.clone(),
+        );
+        visitor.skip_context.update(ctx.skip_context.clone());
+        visitor.set_parent_context(ctx);
+        visitor
+    }
+
+    pub(crate) fn from_parse_sess(
+        parse_session: &'a ParseSess,
+        config: &'a Config,
+        snippet_provider: &'a SnippetProvider,
+        report: FormatReport,
+    ) -> FmtVisitor<'a> {
+        FmtVisitor {
+            parent_context: None,
+            parse_sess: parse_session,
+            buffer: String::with_capacity(snippet_provider.big_snippet.len() * 2),
+            last_pos: BytePos(0),
+            block_indent: Indent::empty(),
+            config,
+            is_if_else_block: false,
+            snippet_provider,
+            line_number: 0,
+            skipped_range: Rc::new(RefCell::new(vec![])),
+            is_macro_def: false,
+            macro_rewrite_failure: false,
+            report,
+            skip_context: Default::default(),
+        }
+    }
+
+    pub(crate) fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
+        self.snippet_provider.span_to_snippet(span)
+    }
+
+    pub(crate) fn snippet(&'b self, span: Span) -> &'a str {
+        self.opt_snippet(span).unwrap()
+    }
+
+    // Returns true if we should skip the following item.
+    pub(crate) fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
+        for attr in attrs {
+            if attr.has_name(depr_skip_annotation()) {
+                let file_name = self.parse_sess.span_to_filename(attr.span);
+                self.report.append(
+                    file_name,
+                    vec![FormattingError::from_span(
+                        attr.span,
+                        self.parse_sess,
+                        ErrorKind::DeprecatedAttr,
+                    )],
+                );
+            } else {
+                match &attr.kind {
+                    ast::AttrKind::Normal(ref attribute_item, _)
+                        if self.is_unknown_rustfmt_attr(&attribute_item.path.segments) =>
+                    {
+                        let file_name = self.parse_sess.span_to_filename(attr.span);
+                        self.report.append(
+                            file_name,
+                            vec![FormattingError::from_span(
+                                attr.span,
+                                self.parse_sess,
+                                ErrorKind::BadAttr,
+                            )],
+                        );
+                    }
+                    _ => (),
+                }
+            }
+        }
+        if contains_skip(attrs) {
+            return true;
+        }
+
+        let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
+        if attrs.is_empty() {
+            return false;
+        }
+
+        let rewrite = attrs.rewrite(&self.get_context(), self.shape());
+        let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
+        self.push_rewrite(span, rewrite);
+
+        false
+    }
+
+    fn is_unknown_rustfmt_attr(&self, segments: &[ast::PathSegment]) -> bool {
+        if segments[0].ident.to_string() != "rustfmt" {
+            return false;
+        }
+        !is_skip_attr(segments)
+    }
+
+    fn walk_mod_items(&mut self, items: &Vec<rustc_ast::ptr::P<ast::Item>>) {
+        self.visit_items_with_reordering(&ptr_vec_to_ref_vec(&items));
+    }
+
+    fn walk_stmts(&mut self, stmts: &[Stmt<'_>], include_current_empty_semi: bool) {
+        if stmts.is_empty() {
+            return;
+        }
+
+        // Extract leading `use ...;`.
+        let items: Vec<_> = stmts
+            .iter()
+            .take_while(|stmt| stmt.to_item().map_or(false, is_use_item))
+            .filter_map(|stmt| stmt.to_item())
+            .collect();
+
+        if items.is_empty() {
+            self.visit_stmt(&stmts[0], include_current_empty_semi);
+
+            // FIXME(calebcartwright 2021-01-03) - This exists strictly to maintain legacy
+            // formatting where rustfmt would preserve redundant semicolons on Items in a
+            // statement position.
+            //
+            // Starting in rustc-ap-* v692 (~2020-12-01) the rustc parser now parses this as
+            // two separate statements (Item and Empty kinds), whereas before it was parsed as
+            // a single statement with the statement's span including the redundant semicolon.
+            //
+            // rustfmt typically tosses unnecessary/redundant semicolons, and eventually we
+            // should toss these as well, but doing so at this time would
+            // break the Stability Guarantee
+            // N.B. This could be updated to utilize the version gates.
+            let include_next_empty = if stmts.len() > 1 {
+                match (&stmts[0].as_ast_node().kind, &stmts[1].as_ast_node().kind) {
+                    (ast::StmtKind::Item(_), ast::StmtKind::Empty) => true,
+                    _ => false,
+                }
+            } else {
+                false
+            };
+
+            self.walk_stmts(&stmts[1..], include_next_empty);
+        } else {
+            self.visit_items_with_reordering(&items);
+            self.walk_stmts(&stmts[items.len()..], false);
+        }
+    }
+
+    fn walk_block_stmts(&mut self, b: &ast::Block) {
+        self.walk_stmts(&Stmt::from_ast_nodes(b.stmts.iter()), false)
+    }
+
+    fn format_mod(
+        &mut self,
+        mod_kind: &ast::ModKind,
+        unsafety: ast::Unsafe,
+        vis: &ast::Visibility,
+        s: Span,
+        ident: symbol::Ident,
+        attrs: &[ast::Attribute],
+    ) {
+        let vis_str = utils::format_visibility(&self.get_context(), vis);
+        self.push_str(&*vis_str);
+        self.push_str(format_unsafety(unsafety));
+        self.push_str("mod ");
+        // Calling `to_owned()` to work around borrow checker.
+        let ident_str = rewrite_ident(&self.get_context(), ident).to_owned();
+        self.push_str(&ident_str);
+
+        if let ast::ModKind::Loaded(ref items, ast::Inline::Yes, inner_span) = mod_kind {
+            match self.config.brace_style() {
+                BraceStyle::AlwaysNextLine => {
+                    let indent_str = self.block_indent.to_string_with_newline(self.config);
+                    self.push_str(&indent_str);
+                    self.push_str("{");
+                }
+                _ => self.push_str(" {"),
+            }
+            // Hackery to account for the closing }.
+            let mod_lo = self.snippet_provider.span_after(source!(self, s), "{");
+            let body_snippet =
+                self.snippet(mk_sp(mod_lo, source!(self, inner_span).hi() - BytePos(1)));
+            let body_snippet = body_snippet.trim();
+            if body_snippet.is_empty() {
+                self.push_str("}");
+            } else {
+                self.last_pos = mod_lo;
+                self.block_indent = self.block_indent.block_indent(self.config);
+                self.visit_attrs(attrs, ast::AttrStyle::Inner);
+                self.walk_mod_items(items);
+                let missing_span = self.next_span(inner_span.hi() - BytePos(1));
+                self.close_block(missing_span, false);
+            }
+            self.last_pos = source!(self, inner_span).hi();
+        } else {
+            self.push_str(";");
+            self.last_pos = source!(self, s).hi();
+        }
+    }
+
+    pub(crate) fn format_separate_mod(&mut self, m: &Module<'_>, end_pos: BytePos) {
+        self.block_indent = Indent::empty();
+        if self.visit_attrs(m.attrs(), ast::AttrStyle::Inner) {
+            self.push_skipped_with_span(m.attrs(), m.span, m.span);
+        } else {
+            self.walk_mod_items(&m.items);
+            self.format_missing_with_indent(end_pos);
+        }
+    }
+
+    pub(crate) fn skip_empty_lines(&mut self, end_pos: BytePos) {
+        while let Some(pos) = self
+            .snippet_provider
+            .opt_span_after(self.next_span(end_pos), "\n")
+        {
+            if let Some(snippet) = self.opt_snippet(self.next_span(pos)) {
+                if snippet.trim().is_empty() {
+                    self.last_pos = pos;
+                } else {
+                    return;
+                }
+            }
+        }
+    }
+
+    pub(crate) fn with_context<F>(&mut self, f: F) -> Option<String>
+    where
+        F: Fn(&RewriteContext<'_>) -> Option<String>,
+    {
+        let context = self.get_context();
+        let result = f(&context);
+
+        self.macro_rewrite_failure |= context.macro_rewrite_failure.get();
+        result
+    }
+
+    pub(crate) fn get_context(&self) -> RewriteContext<'_> {
+        RewriteContext {
+            parse_sess: self.parse_sess,
+            config: self.config,
+            inside_macro: Rc::new(Cell::new(false)),
+            use_block: Cell::new(false),
+            is_if_else_block: Cell::new(false),
+            force_one_line_chain: Cell::new(false),
+            snippet_provider: self.snippet_provider,
+            macro_rewrite_failure: Cell::new(false),
+            is_macro_def: self.is_macro_def,
+            report: self.report.clone(),
+            skip_context: self.skip_context.clone(),
+            skipped_range: self.skipped_range.clone(),
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/cargo-fmt/main.rs b/src/tools/rustfmt/tests/cargo-fmt/main.rs
new file mode 100644
index 0000000000000..5493b09e4aa63
--- /dev/null
+++ b/src/tools/rustfmt/tests/cargo-fmt/main.rs
@@ -0,0 +1,73 @@
+// Integration tests for cargo-fmt.
+
+use std::env;
+use std::process::Command;
+
+/// Run the cargo-fmt executable and return its output.
+fn cargo_fmt(args: &[&str]) -> (String, String) {
+    let mut bin_dir = env::current_exe().unwrap();
+    bin_dir.pop(); // chop off test exe name
+    if bin_dir.ends_with("deps") {
+        bin_dir.pop();
+    }
+    let cmd = bin_dir.join(format!("cargo-fmt{}", env::consts::EXE_SUFFIX));
+
+    // Ensure cargo-fmt runs the rustfmt binary from the local target dir.
+    let path = env::var_os("PATH").unwrap_or_default();
+    let mut paths = env::split_paths(&path).collect::<Vec<_>>();
+    paths.insert(0, bin_dir);
+    let new_path = env::join_paths(paths).unwrap();
+
+    match Command::new(&cmd).args(args).env("PATH", new_path).output() {
+        Ok(output) => (
+            String::from_utf8(output.stdout).expect("utf-8"),
+            String::from_utf8(output.stderr).expect("utf-8"),
+        ),
+        Err(e) => panic!("failed to run `{:?} {:?}`: {}", cmd, args, e),
+    }
+}
+
+macro_rules! assert_that {
+    ($args:expr, $check:ident $check_args:tt) => {
+        let (stdout, stderr) = cargo_fmt($args);
+        if !stdout.$check$check_args {
+            panic!(
+                "Output not expected for cargo-fmt {:?}\n\
+                 expected: {}{}\n\
+                 actual stdout:\n{}\n\
+                 actual stderr:\n{}",
+                $args,
+                stringify!($check),
+                stringify!($check_args),
+                stdout,
+                stderr
+            );
+        }
+    };
+}
+
+#[ignore]
+#[test]
+fn version() {
+    assert_that!(&["--version"], starts_with("rustfmt "));
+    assert_that!(&["--version"], starts_with("rustfmt "));
+    assert_that!(&["--", "-V"], starts_with("rustfmt "));
+    assert_that!(&["--", "--version"], starts_with("rustfmt "));
+}
+
+#[ignore]
+#[test]
+fn print_config() {
+    assert_that!(
+        &["--", "--print-config", "current", "."],
+        contains("max_width = ")
+    );
+}
+
+#[ignore]
+#[test]
+fn rustfmt_help() {
+    assert_that!(&["--", "--help"], contains("Format Rust code"));
+    assert_that!(&["--", "-h"], contains("Format Rust code"));
+    assert_that!(&["--", "--help=config"], contains("Configuration Options:"));
+}
diff --git a/src/tools/rustfmt/tests/config/disable_all_formatting.toml b/src/tools/rustfmt/tests/config/disable_all_formatting.toml
new file mode 100644
index 0000000000000..c7ad93bafe36c
--- /dev/null
+++ b/src/tools/rustfmt/tests/config/disable_all_formatting.toml
@@ -0,0 +1 @@
+disable_all_formatting = true
diff --git a/src/tools/rustfmt/tests/config/issue-1111.toml b/src/tools/rustfmt/tests/config/issue-1111.toml
new file mode 100644
index 0000000000000..44148a2d3c3ed
--- /dev/null
+++ b/src/tools/rustfmt/tests/config/issue-1111.toml
@@ -0,0 +1 @@
+reorder_imports = true
diff --git a/src/tools/rustfmt/tests/config/issue-2641.toml b/src/tools/rustfmt/tests/config/issue-2641.toml
new file mode 100644
index 0000000000000..11c9dca8a06c9
--- /dev/null
+++ b/src/tools/rustfmt/tests/config/issue-2641.toml
@@ -0,0 +1 @@
+newline_style = "Windows"
diff --git a/src/tools/rustfmt/tests/config/issue-3779.toml b/src/tools/rustfmt/tests/config/issue-3779.toml
new file mode 100644
index 0000000000000..6ca52aee32265
--- /dev/null
+++ b/src/tools/rustfmt/tests/config/issue-3779.toml
@@ -0,0 +1,3 @@
+ignore = [
+  "tests/**/issue-3779/ice.rs"
+]
diff --git a/src/tools/rustfmt/tests/config/issue-3802.toml b/src/tools/rustfmt/tests/config/issue-3802.toml
new file mode 100644
index 0000000000000..74ee8b010dd05
--- /dev/null
+++ b/src/tools/rustfmt/tests/config/issue-3802.toml
@@ -0,0 +1,2 @@
+unstable_features = true
+license_template_path = ""
diff --git a/src/tools/rustfmt/tests/config/skip_children.toml b/src/tools/rustfmt/tests/config/skip_children.toml
new file mode 100644
index 0000000000000..f52930d50b61e
--- /dev/null
+++ b/src/tools/rustfmt/tests/config/skip_children.toml
@@ -0,0 +1 @@
+skip_children = true
diff --git a/src/tools/rustfmt/tests/config/small_tabs.toml b/src/tools/rustfmt/tests/config/small_tabs.toml
new file mode 100644
index 0000000000000..35c8fd8646765
--- /dev/null
+++ b/src/tools/rustfmt/tests/config/small_tabs.toml
@@ -0,0 +1,12 @@
+max_width = 100
+comment_width = 80
+tab_spaces = 2
+newline_style = "Unix"
+brace_style = "SameLineWhere"
+fn_args_layout = "Tall"
+trailing_comma = "Vertical"
+indent_style = "Block"
+report_todo = "Always"
+report_fixme = "Never"
+reorder_imports = false
+format_strings = true
diff --git a/src/tools/rustfmt/tests/coverage/source/comments.rs b/src/tools/rustfmt/tests/coverage/source/comments.rs
new file mode 100644
index 0000000000000..10940039e8eab
--- /dev/null
+++ b/src/tools/rustfmt/tests/coverage/source/comments.rs
@@ -0,0 +1,7 @@
+// rustfmt-emit_mode: coverage
+/// Here's a doc comment!
+fn main() {
+    // foo is bar
+    let foo = "bar";
+    // loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong comment!!!!!
+}
diff --git a/src/tools/rustfmt/tests/coverage/target/comments.rs b/src/tools/rustfmt/tests/coverage/target/comments.rs
new file mode 100644
index 0000000000000..95e7b4705e3a0
--- /dev/null
+++ b/src/tools/rustfmt/tests/coverage/target/comments.rs
@@ -0,0 +1,7 @@
+XX XXXXXXXXXXXXXXXXXX XXXXXXXX
+/// Here's a doc comment!
+fn main() {
+    XX XXX XX XXX
+    let foo = "bar";
+    XX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXX
+}
diff --git a/src/tools/rustfmt/tests/license-template/lt.txt b/src/tools/rustfmt/tests/license-template/lt.txt
new file mode 100644
index 0000000000000..ea4390371a09a
--- /dev/null
+++ b/src/tools/rustfmt/tests/license-template/lt.txt
@@ -0,0 +1,2 @@
+// rustfmt-license_template_path: tests/license-template/lt.txt
+// Copyright {\d+} The rustfmt developers.
diff --git a/src/tools/rustfmt/tests/parser/issue-4126/invalid.rs b/src/tools/rustfmt/tests/parser/issue-4126/invalid.rs
new file mode 100644
index 0000000000000..7709c8484642d
--- /dev/null
+++ b/src/tools/rustfmt/tests/parser/issue-4126/invalid.rs
@@ -0,0 +1,6 @@
+fn foo() {
+    if bar && if !baz {
+        next_is_none = Some(true);
+    }
+    println!("foo");
+}
diff --git a/src/tools/rustfmt/tests/parser/issue-4126/lib.rs b/src/tools/rustfmt/tests/parser/issue-4126/lib.rs
new file mode 100644
index 0000000000000..aac63e3557fea
--- /dev/null
+++ b/src/tools/rustfmt/tests/parser/issue-4126/lib.rs
@@ -0,0 +1 @@
+mod invalid;
diff --git a/src/tools/rustfmt/tests/parser/issue_4418.rs b/src/tools/rustfmt/tests/parser/issue_4418.rs
new file mode 100644
index 0000000000000..ff30235f076b3
--- /dev/null
+++ b/src/tools/rustfmt/tests/parser/issue_4418.rs
@@ -0,0 +1 @@
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/parser/unclosed-delims/issue_4466.rs b/src/tools/rustfmt/tests/parser/unclosed-delims/issue_4466.rs
new file mode 100644
index 0000000000000..2c2c81c91d196
--- /dev/null
+++ b/src/tools/rustfmt/tests/parser/unclosed-delims/issue_4466.rs
@@ -0,0 +1,11 @@
+fn main() {
+    if true {
+        println!("answer: {}", a_func();
+    } else {
+        println!("don't think so.");
+    }
+}
+
+fn a_func() -> i32 {
+    42
+} 
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/rustfmt/main.rs b/src/tools/rustfmt/tests/rustfmt/main.rs
new file mode 100644
index 0000000000000..8effb1c6fcab6
--- /dev/null
+++ b/src/tools/rustfmt/tests/rustfmt/main.rs
@@ -0,0 +1,108 @@
+//! Integration tests for rustfmt.
+
+use std::env;
+use std::fs::remove_file;
+use std::path::Path;
+use std::process::Command;
+
+/// Run the rustfmt executable and return its output.
+fn rustfmt(args: &[&str]) -> (String, String) {
+    let mut bin_dir = env::current_exe().unwrap();
+    bin_dir.pop(); // chop off test exe name
+    if bin_dir.ends_with("deps") {
+        bin_dir.pop();
+    }
+    let cmd = bin_dir.join(format!("rustfmt{}", env::consts::EXE_SUFFIX));
+
+    // Ensure the rustfmt binary runs from the local target dir.
+    let path = env::var_os("PATH").unwrap_or_default();
+    let mut paths = env::split_paths(&path).collect::<Vec<_>>();
+    paths.insert(0, bin_dir);
+    let new_path = env::join_paths(paths).unwrap();
+
+    match Command::new(&cmd).args(args).env("PATH", new_path).output() {
+        Ok(output) => (
+            String::from_utf8(output.stdout).expect("utf-8"),
+            String::from_utf8(output.stderr).expect("utf-8"),
+        ),
+        Err(e) => panic!("failed to run `{:?} {:?}`: {}", cmd, args, e),
+    }
+}
+
+macro_rules! assert_that {
+    ($args:expr, $($check:ident $check_args:tt)&&+) => {
+        let (stdout, stderr) = rustfmt($args);
+        if $(!stdout.$check$check_args && !stderr.$check$check_args)||* {
+            panic!(
+                "Output not expected for rustfmt {:?}\n\
+                 expected: {}\n\
+                 actual stdout:\n{}\n\
+                 actual stderr:\n{}",
+                $args,
+                stringify!($( $check$check_args )&&*),
+                stdout,
+                stderr
+            );
+        }
+    };
+}
+
+#[ignore]
+#[test]
+fn print_config() {
+    assert_that!(
+        &["--print-config", "unknown"],
+        starts_with("Unknown print-config option")
+    );
+    assert_that!(&["--print-config", "default"], contains("max_width = 100"));
+    assert_that!(&["--print-config", "minimal"], contains("PATH required"));
+    assert_that!(
+        &["--print-config", "minimal", "minimal-config"],
+        contains("doesn't work with standard input.")
+    );
+
+    let (stdout, stderr) = rustfmt(&[
+        "--print-config",
+        "minimal",
+        "minimal-config",
+        "src/shape.rs",
+    ]);
+    assert!(
+        Path::new("minimal-config").exists(),
+        "stdout:\n{}\nstderr:\n{}",
+        stdout,
+        stderr
+    );
+    remove_file("minimal-config").unwrap();
+}
+
+#[ignore]
+#[test]
+fn inline_config() {
+    // single invocation
+    assert_that!(
+        &[
+            "--print-config",
+            "current",
+            ".",
+            "--config=color=Never,edition=2018"
+        ],
+        contains("color = \"Never\"") && contains("edition = \"2018\"")
+    );
+
+    // multiple overriding invocations
+    assert_that!(
+        &[
+            "--print-config",
+            "current",
+            ".",
+            "--config",
+            "color=never,edition=2018",
+            "--config",
+            "color=always,format_strings=true"
+        ],
+        contains("color = \"Always\"")
+            && contains("edition = \"2018\"")
+            && contains("format_strings = true")
+    );
+}
diff --git a/src/tools/rustfmt/tests/source/alignment_2633/block_style.rs b/src/tools/rustfmt/tests/source/alignment_2633/block_style.rs
new file mode 100644
index 0000000000000..77fb2919edbd1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/alignment_2633/block_style.rs
@@ -0,0 +1,8 @@
+// rustfmt-struct_field_align_threshold: 50
+
+fn func() {
+    Ok(ServerInformation { name:         unwrap_message_string(items.get(0)),
+           vendor: unwrap_message_string(items.get(1)),
+           version: unwrap_message_string(items.get(2)),
+           spec_version: unwrap_message_string(items.get(3)), });
+}
diff --git a/src/tools/rustfmt/tests/source/alignment_2633/visual_style.rs b/src/tools/rustfmt/tests/source/alignment_2633/visual_style.rs
new file mode 100644
index 0000000000000..f34cc621e64c0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/alignment_2633/visual_style.rs
@@ -0,0 +1,9 @@
+// rustfmt-struct_field_align_threshold: 50
+// rustfmt-indent_style: Visual
+
+fn func() {
+    Ok(ServerInformation { name:         unwrap_message_string(items.get(0)),
+           vendor: unwrap_message_string(items.get(1)),
+           version: unwrap_message_string(items.get(2)),
+           spec_version: unwrap_message_string(items.get(3)), });
+}
diff --git a/src/tools/rustfmt/tests/source/array_comment.rs b/src/tools/rustfmt/tests/source/array_comment.rs
new file mode 100644
index 0000000000000..87372b2793fc1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/array_comment.rs
@@ -0,0 +1,19 @@
+// Issue 2842
+// The comment should not make the last line shorter
+
+static XXX: [i8; 64] = [
+    1, // Comment
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+];
+
+static XXX: [i8; 64] = [
+    1,
+    // Comment
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+];
+
+static XXX: [i8; 64] = [
+    1,
+    // Comment
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+];
diff --git a/src/tools/rustfmt/tests/source/assignment.rs b/src/tools/rustfmt/tests/source/assignment.rs
new file mode 100644
index 0000000000000..71de325566dd5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/assignment.rs
@@ -0,0 +1,34 @@
+// Test assignment
+
+fn main() {
+    let  some_var  : Type   ;
+
+    let  mut mutable;
+
+    let variable = AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA::BBBBBBBBBBBBBBBBBBBBBB::CCCCCCCCCCCCCCCCCCCCCC::EEEEEE;
+
+    variable =   LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOONG;
+
+    let single_line_fit =
+        DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD;
+
+    single_line_fit =   5;single_lit_fit    >>=  10;
+
+
+    // #2791
+    let x = 2;;;;
+}
+
+fn break_meee() {
+    {
+        (block_start, block_size, margin_block_start, margin_block_end) = match (block_start,
+                                                                                 block_end,
+                                                                                 block_size) {
+                x => 1,
+                _ => 2,
+            };
+    }
+}
+
+// #2018
+pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str = "Unsized tuple coercion is not stable enough for use and is subject to change";
diff --git a/src/tools/rustfmt/tests/source/associated-types-bounds-wrapping.rs b/src/tools/rustfmt/tests/source/associated-types-bounds-wrapping.rs
new file mode 100644
index 0000000000000..464f428c7f9a1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/associated-types-bounds-wrapping.rs
@@ -0,0 +1,5 @@
+// Test proper wrapping of long associated type bounds
+
+pub trait HttpService {
+    type WsService: 'static + Service<Request = WsCommand, Response = WsResponse, Error = ServerError>;
+}
diff --git a/src/tools/rustfmt/tests/source/associated_type_bounds.rs b/src/tools/rustfmt/tests/source/associated_type_bounds.rs
new file mode 100644
index 0000000000000..8572778a5a534
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/associated_type_bounds.rs
@@ -0,0 +1,13 @@
+// See #3657 - https://github.com/rust-lang/rustfmt/issues/3657
+
+#![feature(associated_type_bounds)]
+
+fn f<I: Iterator<Item: Clone>>() {}
+
+fn g<I: Iterator<Item : Clone>>() {}
+
+fn h<I: Iterator<Item :      Clone>>() {}
+
+fn i<I: Iterator<Item:Clone>>() {}
+
+fn j<I: Iterator<Item :  Clone+'a>>() {}
diff --git a/src/tools/rustfmt/tests/source/async_block.rs b/src/tools/rustfmt/tests/source/async_block.rs
new file mode 100644
index 0000000000000..3de51a084d260
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/async_block.rs
@@ -0,0 +1,35 @@
+// rustfmt-edition: 2018
+
+fn main() {
+    let x = async {
+        Ok(())
+    };
+}
+
+fn baz() {
+    // test
+    let x = async {
+        // async blocks are great
+        Ok(())
+    };
+
+    let y = async {
+        Ok(())
+    }; // comment
+
+    spawn(
+        a,
+        async move {
+            action();
+            Ok(())
+        },
+    );
+
+    spawn(
+        a,
+        async move || {
+            action();
+            Ok(())
+        },
+    );
+}
diff --git a/src/tools/rustfmt/tests/source/async_fn.rs b/src/tools/rustfmt/tests/source/async_fn.rs
new file mode 100644
index 0000000000000..c63cf5b0f51e1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/async_fn.rs
@@ -0,0 +1,28 @@
+// rustfmt-edition: 2018
+
+async fn bar() -> Result<(), ()> {
+    Ok(())
+}
+
+pub async fn baz() -> Result<(), ()> {
+    Ok(())
+}
+
+async unsafe fn foo() {
+    async move {
+        Ok(())
+    }
+}
+
+async unsafe fn rust() {
+    async move { // comment
+        Ok(())
+    }
+}
+
+async fn await_try() {
+    something
+     .await
+      ?
+     ;
+}
diff --git a/src/tools/rustfmt/tests/source/attrib.rs b/src/tools/rustfmt/tests/source/attrib.rs
new file mode 100644
index 0000000000000..d45fba5522436
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/attrib.rs
@@ -0,0 +1,234 @@
+// rustfmt-wrap_comments: true
+// Test attributes and doc comments are preserved.
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
+       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
+       html_root_url = "https://doc.rust-lang.org/nightly/",
+       html_playground_url = "https://play.rust-lang.org/", test(attr(deny(warnings))))]
+
+//! Doc comment
+
+#![attribute]
+
+//! Crate doc comment
+
+// Comment
+
+// Comment on attribute
+#![the(attribute)]
+
+// Another comment
+
+/// Blah blah blah.
+/// Blah blah blah.
+/// Blah blah blah.
+/// Blah blah blah.
+
+/// Blah blah blah.
+impl Bar {
+    /// Blah blah blooo.
+    /// Blah blah blooo.
+    /// Blah blah blooo.
+    /// Blah blah blooo.
+    #[an_attribute]
+    #[doc = "an attribute that shouldn't be normalized to a doc comment"]
+    fn foo(&mut self) -> isize {
+    }
+
+    /// Blah blah bing.
+    /// Blah blah bing.
+    /// Blah blah bing.
+
+
+    /// Blah blah bing.
+    /// Blah blah bing.
+    /// Blah blah bing.
+    pub fn f2(self) {
+        (foo, bar)
+    }
+
+    #[another_attribute]
+    fn f3(self) -> Dog {
+    }
+
+    /// Blah blah bing.
+
+    #[attrib1]
+    /// Blah blah bing.
+    #[attrib2]
+    // Another comment that needs rewrite because it's tooooooooooooooooooooooooooooooo loooooooooooong.
+    /// Blah blah bing.
+    fn f4(self) -> Cat {
+    }
+
+    // We want spaces around `=`
+    #[cfg(feature="nightly")]
+    fn f5(self) -> Monkey {}
+}
+
+// #984
+struct Foo {
+    # [ derive ( Clone , PartialEq , Debug , Deserialize , Serialize ) ]
+    foo: usize,
+}
+
+// #1668
+
+/// Default path (*nix)
+#[cfg(all(unix, not(target_os = "macos"), not(target_os = "ios"), not(target_os = "android")))]
+fn foo() {
+    #[cfg(target_os = "freertos")]
+    match port_id {
+        'a' | 'A' => GpioPort { port_address: GPIO_A },
+        'b' | 'B' => GpioPort { port_address: GPIO_B },
+        _ => panic!(),
+    }
+
+    #[cfg_attr(not(target_os = "freertos"), allow(unused_variables))]
+    let x = 3;
+}
+
+// #1777
+#[test]
+#[should_panic(expected = "(")]
+#[should_panic(expected = /* ( */ "(")]
+#[should_panic(/* ((((( */expected /* ((((( */= /* ((((( */ "("/* ((((( */)]
+#[should_panic(
+    /* (((((((( *//*
+    (((((((((()(((((((( */
+    expected = "("
+    // ((((((((
+)]
+fn foo() {}
+
+// #1799
+fn issue_1799() {
+    #[allow(unreachable_code)] // https://github.com/rust-lang/rust/issues/43336
+    Some( Err(error) ) ;
+
+    #[allow(unreachable_code)]
+    // https://github.com/rust-lang/rust/issues/43336
+    Some( Err(error) ) ;
+}
+
+// Formatting inner attributes
+fn inner_attributes() {
+    #![ this_is_an_inner_attribute ( foo ) ]
+
+    foo();
+}
+
+impl InnerAttributes() {
+    #![ this_is_an_inner_attribute ( foo ) ]
+
+    fn foo() {}
+}
+
+mod InnerAttributes {
+    #![ this_is_an_inner_attribute ( foo ) ]
+}
+
+fn attributes_on_statements() {
+    // Local
+    # [ attr ( on ( local ) ) ]
+    let x = 3;
+
+    // Item
+    # [ attr ( on ( item ) ) ]
+    use foo;
+
+    // Expr
+    # [ attr ( on ( expr ) ) ]
+    {}
+
+    // Semi
+    # [ attr ( on ( semi ) ) ]
+    foo();
+
+    // Mac
+    # [ attr ( on ( mac ) ) ]
+    foo!();
+}
+
+// Large derives
+#[derive(Add, Sub, Mul, Div, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Debug, Hash, Serialize, Mul)]
+
+
+/// Foo bar baz
+
+
+#[derive(Add, Sub, Mul, Div, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Debug, Hash, Serialize, Deserialize)]
+pub struct HP(pub u8);
+
+// Long `#[doc = "..."]`
+struct A { #[doc = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"] b: i32 }
+
+// #2647
+#[cfg(feature = "this_line_is_101_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx")]
+pub fn foo() {}
+
+// path attrs
+#[clippy::bar]
+#[clippy::bar(a, b, c)]
+pub fn foo() {}
+
+mod issue_2620 {
+    #[derive(Debug, StructOpt)]
+#[structopt(about = "Display information about the character on FF Logs")]
+pub struct Params {
+  #[structopt(help = "The server the character is on")]
+  server: String,
+  #[structopt(help = "The character's first name")]
+  first_name: String,
+  #[structopt(help = "The character's last name")]
+  last_name: String,
+  #[structopt(
+    short = "j",
+    long = "job",
+    help = "The job to look at",
+    parse(try_from_str)
+  )]
+  job: Option<Job>
+}
+}
+
+// #2969
+#[cfg(not(all(feature="std",
+              any(target_os = "linux", target_os = "android",
+                  target_os = "netbsd",
+                  target_os = "dragonfly",
+                  target_os = "haiku",
+                  target_os = "emscripten",
+                  target_os = "solaris",
+                  target_os = "cloudabi",
+                  target_os = "macos", target_os = "ios",
+                  target_os = "freebsd",
+                  target_os = "openbsd",
+                  target_os = "redox",
+                  target_os = "fuchsia",
+                  windows,
+                  all(target_arch = "wasm32", feature = "stdweb"),
+                  all(target_arch = "wasm32", feature = "wasm-bindgen"),
+              ))))]
+type Os = NoSource;
+
+// #3313
+fn stmt_expr_attributes() {
+    let foo ;
+    #[must_use]
+   foo = false ;
+}
+
+// #3509
+fn issue3509() {
+    match MyEnum {
+        MyEnum::Option1 if cfg!(target_os = "windows") =>
+            #[cfg(target_os = "windows")]{
+                1
+            }
+    }
+    match MyEnum {
+        MyEnum::Option1 if cfg!(target_os = "windows") =>
+            #[cfg(target_os = "windows")]
+                1,
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/big-impl-block.rs b/src/tools/rustfmt/tests/source/big-impl-block.rs
new file mode 100644
index 0000000000000..f71e6515c429e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/big-impl-block.rs
@@ -0,0 +1,123 @@
+// #1357
+impl<
+    'a,
+    Select,
+    From,
+    Distinct,
+    Where,
+    Order,
+    Limit,
+    Offset,
+    Groupby,
+    DB,
+> InternalBoxedDsl<'a, DB>
+    for SelectStatement<
+        Select,
+        From,
+        Distinct,
+        Where,
+        Order,
+        Limit,
+        Offset,
+        GroupBy,
+    > where
+        DB: Backend,
+        Select: QueryFragment<DB> + SelectableExpression<From> + 'a,
+        Distinct: QueryFragment<DB> + 'a,
+        Where: Into<Option<Box<QueryFragment<DB> + 'a>>>,
+        Order: QueryFragment<DB> + 'a,
+        Limit: QueryFragment<DB> + 'a,
+        Offset: QueryFragment<DB> + 'a,
+{
+    type Output = BoxedSelectStatement<'a, Select::SqlTypeForSelect, From, DB>;
+
+    fn internal_into_boxed(self) -> Self::Output {
+        BoxedSelectStatement::new(
+            Box::new(self.select),
+            self.from,
+            Box::new(self.distinct),
+            self.where_clause.into(),
+            Box::new(self.order),
+            Box::new(self.limit),
+            Box::new(self.offset),
+        )
+    }
+}
+
+// #1369
+impl<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> Foo for Bar {
+    fn foo() {}
+}
+impl Foo<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> for Bar {
+    fn foo() {}
+}
+impl<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> Foo<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> for Bar {
+    fn foo() {}
+}
+impl<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> Foo for Bar<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> {
+    fn foo() {}
+}
+impl Foo<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> for Bar<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> {
+    fn foo() {}
+}
+impl<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> Foo<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> for Bar<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> {
+    fn foo() {}
+}
+
+// #1689
+impl<M, S, F, X> SubSelectDirect<M, S, F, X>
+    where
+    M: select::Selector,
+    S: event::Stream,
+    F: for<'t> FnMut(transform::Api<
+            't,
+        Stream<ContentStream<S>>,
+        >)
+                     -> transform::Api<'t, X>,
+    X: event::Stream,
+{
+}
diff --git a/src/tools/rustfmt/tests/source/big-impl-visual.rs b/src/tools/rustfmt/tests/source/big-impl-visual.rs
new file mode 100644
index 0000000000000..7d906ac37f998
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/big-impl-visual.rs
@@ -0,0 +1,106 @@
+// rustfmt-indent_style: Visual
+
+// #1357
+impl<
+    'a,
+    Select,
+    From,
+    Distinct,
+    Where,
+    Order,
+    Limit,
+    Offset,
+    Groupby,
+    DB,
+> InternalBoxedDsl<'a, DB>
+    for SelectStatement<
+        Select,
+        From,
+        Distinct,
+        Where,
+        Order,
+        Limit,
+        Offset,
+        GroupBy,
+    > where
+        DB: Backend,
+        Select: QueryFragment<DB> + SelectableExpression<From> + 'a,
+        Distinct: QueryFragment<DB> + 'a,
+        Where: Into<Option<Box<QueryFragment<DB> + 'a>>>,
+        Order: QueryFragment<DB> + 'a,
+        Limit: QueryFragment<DB> + 'a,
+        Offset: QueryFragment<DB> + 'a,
+{
+    type Output = BoxedSelectStatement<'a, Select::SqlTypeForSelect, From, DB>;
+
+    fn internal_into_boxed(self) -> Self::Output {
+        BoxedSelectStatement::new(
+            Box::new(self.select),
+            self.from,
+            Box::new(self.distinct),
+            self.where_clause.into(),
+            Box::new(self.order),
+            Box::new(self.limit),
+            Box::new(self.offset),
+        )
+    }
+}
+
+// #1369
+impl<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> Foo for Bar {
+    fn foo() {}
+}
+impl Foo<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> for Bar {
+    fn foo() {}
+}
+impl<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> Foo<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> for Bar {
+    fn foo() {}
+}
+impl<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> Foo for Bar<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> {
+    fn foo() {}
+}
+impl Foo<
+    ExcessivelyLongGenericName,
+      ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> for Bar<
+    ExcessivelyLongGenericName,
+    ExcessivelyLongGenericName,
+    AnotherExcessivelyLongGenericName,
+> {
+    fn foo() {}
+}
+impl<ExcessivelyLongGenericName,
+     ExcessivelyLongGenericName,
+     AnotherExcessivelyLongGenericName> Foo<ExcessivelyLongGenericName,
+                                            ExcessivelyLongGenericName,
+                                            AnotherExcessivelyLongGenericName>
+    for Bar<ExcessivelyLongGenericName,
+            ExcessivelyLongGenericName,
+            AnotherExcessivelyLongGenericName> {
+    fn foo() {}
+}
diff --git a/src/tools/rustfmt/tests/source/binary-expr.rs b/src/tools/rustfmt/tests/source/binary-expr.rs
new file mode 100644
index 0000000000000..f7502931d9693
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/binary-expr.rs
@@ -0,0 +1,10 @@
+// Binary expressions
+
+fn foo() {
+    // 100
+    let x = aaaaaaaaaa || bbbbbbbbbb || cccccccccc || dddddddddd && eeeeeeeeee || ffffffffff || ggg;
+    // 101
+    let x = aaaaaaaaaa || bbbbbbbbbb || cccccccccc || dddddddddd && eeeeeeeeee || ffffffffff || gggg;
+    // 104
+    let x = aaaaaaaaaa || bbbbbbbbbb || cccccccccc || dddddddddd && eeeeeeeeee || ffffffffff || gggggggg;
+}
diff --git a/src/tools/rustfmt/tests/source/break-and-continue.rs b/src/tools/rustfmt/tests/source/break-and-continue.rs
new file mode 100644
index 0000000000000..c01d8a0784556
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/break-and-continue.rs
@@ -0,0 +1,23 @@
+// break and continue formatting
+
+#![feature(loop_break_value)]
+
+fn main() {
+    'a: loop {
+        break 'a;
+    }
+
+    let mut done = false;
+    'b: while !done {
+        done = true;
+        continue 'b;
+    }
+
+    let x = loop {
+        break 5;
+    };
+
+    let x = 'c: loop {
+        break 'c 5;
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/catch.rs b/src/tools/rustfmt/tests/source/catch.rs
new file mode 100644
index 0000000000000..541db1dc90c22
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/catch.rs
@@ -0,0 +1,28 @@
+// rustfmt-edition: 2018
+#![feature(try_blocks)]
+
+fn main() {
+    let x = try {
+        foo()?
+    };
+
+    let x = try /* Invisible comment */ { foo()? };
+
+    let x = try {
+        unsafe { foo()? }
+    };
+
+    let y = match (try {
+        foo()?
+    }) {
+        _ => (),
+    };
+
+    try {
+        foo()?;
+    };
+
+    try {
+        // Regular try block
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/arch/aarch64.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/aarch64.rs
new file mode 100644
index 0000000000000..ebae2bd285408
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/aarch64.rs
@@ -0,0 +1,106 @@
+//! Aarch64 run-time features.
+
+/// Checks if `aarch64` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal,stdsimd)]
+macro_rules! is_aarch64_feature_detected {
+    ("neon") => {
+        // FIXME: this should be removed once we rename Aarch64 neon to asimd
+        cfg!(target_feature = "neon") ||
+            $crate::detect::check_for($crate::detect::Feature::asimd)
+    };
+    ("asimd") => {
+        cfg!(target_feature = "neon") ||
+            $crate::detect::check_for($crate::detect::Feature::asimd)
+    };
+    ("pmull") => {
+        cfg!(target_feature = "pmull") ||
+            $crate::detect::check_for($crate::detect::Feature::pmull)
+    };
+    ("fp") => {
+        cfg!(target_feature = "fp") ||
+            $crate::detect::check_for($crate::detect::Feature::fp)
+    };
+    ("fp16") => {
+        cfg!(target_feature = "fp16") ||
+            $crate::detect::check_for($crate::detect::Feature::fp16)
+    };
+    ("sve") => {
+        cfg!(target_feature = "sve") ||
+            $crate::detect::check_for($crate::detect::Feature::sve)
+    };
+    ("crc") => {
+        cfg!(target_feature = "crc") ||
+            $crate::detect::check_for($crate::detect::Feature::crc)
+    };
+    ("crypto") => {
+        cfg!(target_feature = "crypto") ||
+            $crate::detect::check_for($crate::detect::Feature::crypto)
+    };
+    ("lse") => {
+        cfg!(target_feature = "lse") ||
+            $crate::detect::check_for($crate::detect::Feature::lse)
+    };
+    ("rdm") => {
+        cfg!(target_feature = "rdm") ||
+            $crate::detect::check_for($crate::detect::Feature::rdm)
+    };
+    ("rcpc") => {
+        cfg!(target_feature = "rcpc") ||
+            $crate::detect::check_for($crate::detect::Feature::rcpc)
+    };
+    ("dotprod") => {
+        cfg!(target_feature = "dotprod") ||
+            $crate::detect::check_for($crate::detect::Feature::dotprod)
+    };
+    ("ras") => {
+        compile_error!("\"ras\" feature cannot be detected at run-time")
+    };
+    ("v8.1a") => {
+        compile_error!("\"v8.1a\" feature cannot be detected at run-time")
+    };
+    ("v8.2a") => {
+        compile_error!("\"v8.2a\" feature cannot be detected at run-time")
+    };
+    ("v8.3a") => {
+        compile_error!("\"v8.3a\" feature cannot be detected at run-time")
+    };
+    ($t:tt,) => {
+        is_aarch64_feature_detected!($t);
+    };
+    ($t:tt) => { compile_error!(concat!("unknown aarch64 target feature: ", $t)) };
+}
+
+/// ARM Aarch64 CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// ARM Advanced SIMD (ASIMD)
+    asimd,
+    /// Polynomial Multiply
+    pmull,
+    /// Floating point support
+    fp,
+    /// Half-float support.
+    fp16,
+    /// Scalable Vector Extension (SVE)
+    sve,
+    /// CRC32 (Cyclic Redundancy Check)
+    crc,
+    /// Crypto: AES + PMULL + SHA1 + SHA2
+    crypto,
+    /// Atomics (Large System Extension)
+    lse,
+    /// Rounding Double Multiply (ASIMDRDM)
+    rdm,
+    /// Release consistent Processor consistent (RcPc)
+    rcpc,
+    /// Vector Dot-Product (ASIMDDP)
+    dotprod,
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/arch/arm.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/arm.rs
new file mode 100644
index 0000000000000..b2626bf2923b6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/arm.rs
@@ -0,0 +1,39 @@
+//! Run-time feature detection on ARM Aarch32.
+
+/// Checks if `arm` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal,stdsimd)]
+macro_rules! is_arm_feature_detected {
+    ("neon") => {
+        cfg!(target_feature = "neon") ||
+            $crate::detect::check_for($crate::detect::Feature::neon)
+    };
+    ("pmull") => {
+        cfg!(target_feature = "pmull") ||
+            $crate::detect::check_for($crate::detect::Feature::pmull)
+    };
+    ("v7") => { compile_error!("\"v7\" feature cannot be detected at run-time") };
+    ("vfp2") => { compile_error!("\"vfp2\" feature cannot be detected at run-time") };
+    ("vfp3") => { compile_error!("\"vfp3\" feature cannot be detected at run-time") };
+    ("vfp4") => { compile_error!("\"vfp4\" feature cannot be detected at run-time") };
+    ($t:tt,) => {
+        is_arm_feature_detected!($t);
+    };
+    ($t:tt) => { compile_error!(concat!("unknown arm target feature: ", $t)) };
+}
+
+/// ARM CPU Feature enum. Each variant denotes a position in a bitset for a
+/// particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// ARM Advanced SIMD (NEON) - Aarch32
+    neon,
+    /// Polynomial Multiply
+    pmull,
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/arch/mips.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/mips.rs
new file mode 100644
index 0000000000000..f4381b811cdf2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/mips.rs
@@ -0,0 +1,29 @@
+//! Run-time feature detection on MIPS.
+
+/// Checks if `mips` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal,stdsimd)]
+macro_rules! is_mips_feature_detected {
+    ("msa") => {
+        cfg!(target_feature = "msa") ||
+            $crate::detect::check_for($crate::detect::Feature::msa)
+    };
+    ($t:tt,) => {
+        is_mips_feature_detected!($t);
+    };
+    ($t:tt) => { compile_error!(concat!("unknown mips target feature: ", $t)) };
+}
+
+/// MIPS CPU Feature enum. Each variant denotes a position in a bitset for a
+/// particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// MIPS SIMD Architecture (MSA)
+    msa,
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/arch/mips64.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/mips64.rs
new file mode 100644
index 0000000000000..2663bc68ba980
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/mips64.rs
@@ -0,0 +1,29 @@
+//! Run-time feature detection on MIPS64.
+
+/// Checks if `mips64` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal,stdsimd)]
+macro_rules! is_mips64_feature_detected {
+    ("msa") => {
+        cfg!(target_feature = "msa") ||
+            $crate::detect::check_for($crate::detect::Feature::msa)
+    };
+    ($t:tt,) => {
+        is_mips64_feature_detected!($t);
+    };
+    ($t:tt) => { compile_error!(concat!("unknown mips64 target feature: ", $t)) };
+}
+
+/// MIPS64 CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// MIPS SIMD Architecture (MSA)
+    msa,
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/arch/powerpc.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/powerpc.rs
new file mode 100644
index 0000000000000..a342dc1aacc0c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/powerpc.rs
@@ -0,0 +1,42 @@
+//! Run-time feature detection on PowerPC.
+
+/// Checks if `powerpc` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal,stdsimd)]
+macro_rules! is_powerpc_feature_detected {
+    ("altivec") => {
+        cfg!(target_feature = "altivec") ||
+            $crate::detect::check_for($crate::detect::Feature::altivec)
+    };
+    ("vsx") => {
+        cfg!(target_feature = "vsx") ||
+            $crate::detect::check_for($crate::detect::Feature::vsx)
+    };
+    ("power8") => {
+        cfg!(target_feature = "power8") ||
+            $crate::detect::check_for($crate::detect::Feature::power8)
+    };
+    ($t:tt,) => {
+        is_powerpc_feature_detected!($t);
+    };
+    ($t:tt) => { compile_error!(concat!("unknown powerpc target feature: ", $t)) };
+}
+
+
+/// PowerPC CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// Altivec
+    altivec,
+    /// VSX
+    vsx,
+    /// Power8
+    power8,
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/arch/powerpc64.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/powerpc64.rs
new file mode 100644
index 0000000000000..2e82c569252ac
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/powerpc64.rs
@@ -0,0 +1,42 @@
+//! Run-time feature detection on PowerPC64.
+
+/// Checks if `powerpc64` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal,stdsimd)]
+macro_rules! is_powerpc64_feature_detected {
+    ("altivec") => {
+        cfg!(target_feature = "altivec") ||
+            $crate::detect::check_for($crate::detect::Feature::altivec)
+    };
+    ("vsx") => {
+        cfg!(target_feature = "vsx") ||
+            $crate::detect::check_for($crate::detect::Feature::vsx)
+    };
+    ("power8") => {
+        cfg!(target_feature = "power8") ||
+            $crate::detect::check_for($crate::detect::Feature::power8)
+    };
+    ($t:tt,) => {
+        is_powerpc64_feature_detected!($t);
+    };
+    ($t:tt) => { compile_error!(concat!("unknown powerpc64 target feature: ", $t)) };
+}
+
+
+/// PowerPC64 CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// Altivec
+    altivec,
+    /// VSX
+    vsx,
+    /// Power8
+    power8,
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/arch/x86.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/x86.rs
new file mode 100644
index 0000000000000..50d5cfa87c4c8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/arch/x86.rs
@@ -0,0 +1,348 @@
+//! This module implements minimal run-time feature detection for x86.
+//!
+//! The features are detected using the `detect_features` function below.
+//! This function uses the CPUID instruction to read the feature flags from the
+//! CPU and encodes them in an `usize` where each bit position represents
+//! whether a feature is available (bit is set) or unavaiable (bit is cleared).
+//!
+//! The enum `Feature` is used to map bit positions to feature names, and the
+//! the `__crate::detect::check_for!` macro is used to map string literals (e.g.,
+//! "avx") to these bit positions (e.g., `Feature::avx`).
+//!
+//! The run-time feature detection is performed by the
+//! `__crate::detect::check_for(Feature) -> bool` function. On its first call,
+//! this functions queries the CPU for the available features and stores them
+//! in a global `AtomicUsize` variable. The query is performed by just checking
+//! whether the feature bit in this global variable is set or cleared.
+
+/// A macro to test at *runtime* whether a CPU feature is available on
+/// x86/x86-64 platforms.
+///
+/// This macro is provided in the standard library and will detect at runtime
+/// whether the specified CPU feature is detected. This does **not** resolve at
+/// compile time unless the specified feature is already enabled for the entire
+/// crate. Runtime detection currently relies mostly on the `cpuid` instruction.
+///
+/// This macro only takes one argument which is a string literal of the feature
+/// being tested for. The feature names supported are the lowercase versions of
+/// the ones defined by Intel in [their documentation][docs].
+///
+/// ## Supported arguments
+///
+/// This macro supports the same names that `#[target_feature]` supports. Unlike
+/// `#[target_feature]`, however, this macro does not support names separated
+/// with a comma. Instead testing for multiple features must be done through
+/// separate macro invocations for now.
+///
+/// Supported arguments are:
+///
+/// * `"aes"`
+/// * `"pclmulqdq"`
+/// * `"rdrand"`
+/// * `"rdseed"`
+/// * `"tsc"`
+/// * `"mmx"`
+/// * `"sse"`
+/// * `"sse2"`
+/// * `"sse3"`
+/// * `"ssse3"`
+/// * `"sse4.1"`
+/// * `"sse4.2"`
+/// * `"sse4a"`
+/// * `"sha"`
+/// * `"avx"`
+/// * `"avx2"`
+/// * `"avx512f"`
+/// * `"avx512cd"`
+/// * `"avx512er"`
+/// * `"avx512pf"`
+/// * `"avx512bw"`
+/// * `"avx512dq"`
+/// * `"avx512vl"`
+/// * `"avx512ifma"`
+/// * `"avx512vbmi"`
+/// * `"avx512vpopcntdq"`
+/// * `"f16c"`
+/// * `"fma"`
+/// * `"bmi1"`
+/// * `"bmi2"`
+/// * `"abm"`
+/// * `"lzcnt"`
+/// * `"tbm"`
+/// * `"popcnt"`
+/// * `"fxsr"`
+/// * `"xsave"`
+/// * `"xsaveopt"`
+/// * `"xsaves"`
+/// * `"xsavec"`
+/// * `"adx"`
+/// * `"rtm"`
+///
+/// [docs]: https://software.intel.com/sites/landingpage/IntrinsicsGuide
+#[macro_export]
+#[stable(feature = "simd_x86", since = "1.27.0")]
+#[allow_internal_unstable(stdsimd_internal,stdsimd)]
+macro_rules! is_x86_feature_detected {
+    ("aes") => {
+        cfg!(target_feature = "aes") || $crate::detect::check_for(
+            $crate::detect::Feature::aes)  };
+    ("pclmulqdq") => {
+        cfg!(target_feature = "pclmulqdq") || $crate::detect::check_for(
+            $crate::detect::Feature::pclmulqdq)  };
+    ("rdrand") => {
+        cfg!(target_feature = "rdrand") || $crate::detect::check_for(
+            $crate::detect::Feature::rdrand)  };
+    ("rdseed") => {
+        cfg!(target_feature = "rdseed") || $crate::detect::check_for(
+            $crate::detect::Feature::rdseed)  };
+    ("tsc") => {
+        cfg!(target_feature = "tsc") || $crate::detect::check_for(
+            $crate::detect::Feature::tsc)  };
+    ("mmx") => {
+        cfg!(target_feature = "mmx") || $crate::detect::check_for(
+            $crate::detect::Feature::mmx)  };
+    ("sse") => {
+        cfg!(target_feature = "sse") || $crate::detect::check_for(
+            $crate::detect::Feature::sse)  };
+    ("sse2") => {
+        cfg!(target_feature = "sse2") || $crate::detect::check_for(
+            $crate::detect::Feature::sse2)
+    };
+    ("sse3") => {
+        cfg!(target_feature = "sse3") || $crate::detect::check_for(
+            $crate::detect::Feature::sse3)
+    };
+    ("ssse3") => {
+        cfg!(target_feature = "ssse3") || $crate::detect::check_for(
+            $crate::detect::Feature::ssse3)
+    };
+    ("sse4.1") => {
+        cfg!(target_feature = "sse4.1") || $crate::detect::check_for(
+            $crate::detect::Feature::sse4_1)
+    };
+    ("sse4.2") => {
+        cfg!(target_feature = "sse4.2") || $crate::detect::check_for(
+            $crate::detect::Feature::sse4_2)
+    };
+    ("sse4a") => {
+        cfg!(target_feature = "sse4a") || $crate::detect::check_for(
+            $crate::detect::Feature::sse4a)
+    };
+    ("sha") => {
+        cfg!(target_feature = "sha") || $crate::detect::check_for(
+            $crate::detect::Feature::sha)
+    };
+    ("avx") => {
+        cfg!(target_feature = "avx") || $crate::detect::check_for(
+            $crate::detect::Feature::avx)
+    };
+    ("avx2") => {
+        cfg!(target_feature = "avx2") || $crate::detect::check_for(
+            $crate::detect::Feature::avx2)
+    };
+    ("avx512f") => {
+        cfg!(target_feature = "avx512f") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512f)
+    };
+    ("avx512cd") => {
+        cfg!(target_feature = "avx512cd") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512cd)
+    };
+    ("avx512er") => {
+        cfg!(target_feature = "avx512er") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512er)
+    };
+    ("avx512pf") => {
+        cfg!(target_feature = "avx512pf") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512pf)
+    };
+    ("avx512bw") => {
+        cfg!(target_feature = "avx512bw") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512bw)
+    };
+    ("avx512dq") => {
+        cfg!(target_feature = "avx512dq") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512dq)
+    };
+    ("avx512vl") => {
+        cfg!(target_Feature = "avx512vl") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512vl)
+    };
+    ("avx512ifma") => {
+        cfg!(target_feature = "avx512ifma") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512_ifma)
+    };
+    ("avx512vbmi") => {
+        cfg!(target_feature = "avx512vbmi") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512_vbmi)
+    };
+    ("avx512vpopcntdq") => {
+        cfg!(target_feature = "avx512vpopcntdq") || $crate::detect::check_for(
+            $crate::detect::Feature::avx512_vpopcntdq)
+    };
+    ("f16c") => {
+        cfg!(target_feature = "f16c") || $crate::detect::check_for(
+            $crate::detect::Feature::f16c)
+    };
+    ("fma") => {
+        cfg!(target_feature = "fma") || $crate::detect::check_for(
+            $crate::detect::Feature::fma)
+    };
+    ("bmi1") => {
+        cfg!(target_feature = "bmi1") || $crate::detect::check_for(
+            $crate::detect::Feature::bmi)
+    };
+    ("bmi2") => {
+        cfg!(target_feature = "bmi2") || $crate::detect::check_for(
+            $crate::detect::Feature::bmi2)
+    };
+    ("abm") => {
+        cfg!(target_feature = "abm") || $crate::detect::check_for(
+            $crate::detect::Feature::abm)
+    };
+    ("lzcnt") => {
+        cfg!(target_feature = "lzcnt") || $crate::detect::check_for(
+            $crate::detect::Feature::abm)
+    };
+    ("tbm") => {
+        cfg!(target_feature = "tbm") || $crate::detect::check_for(
+            $crate::detect::Feature::tbm)
+    };
+    ("popcnt") => {
+        cfg!(target_feature = "popcnt") || $crate::detect::check_for(
+            $crate::detect::Feature::popcnt)
+    };
+    ("fxsr") => {
+        cfg!(target_feature = "fxsr") || $crate::detect::check_for(
+            $crate::detect::Feature::fxsr)
+    };
+    ("xsave") => {
+        cfg!(target_feature = "xsave") || $crate::detect::check_for(
+            $crate::detect::Feature::xsave)
+    };
+    ("xsaveopt") => {
+        cfg!(target_feature = "xsaveopt") || $crate::detect::check_for(
+            $crate::detect::Feature::xsaveopt)
+    };
+    ("xsaves") => {
+        cfg!(target_feature = "xsaves") || $crate::detect::check_for(
+            $crate::detect::Feature::xsaves)
+    };
+    ("xsavec") => {
+        cfg!(target_feature = "xsavec") || $crate::detect::check_for(
+            $crate::detect::Feature::xsavec)
+    };
+    ("cmpxchg16b") => {
+        cfg!(target_feature = "cmpxchg16b") || $crate::detect::check_for(
+            $crate::detect::Feature::cmpxchg16b)
+    };
+    ("adx") => {
+        cfg!(target_feature = "adx") || $crate::detect::check_for(
+            $crate::detect::Feature::adx)
+    };
+    ("rtm") => {
+        cfg!(target_feature = "rtm") || $crate::detect::check_for(
+            $crate::detect::Feature::rtm)
+    };
+    ($t:tt,) => {
+        is_x86_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown target feature: ", $t))
+    };
+}
+
+/// X86 CPU Feature enum. Each variant denotes a position in a bitset for a
+/// particular feature.
+///
+/// This is an unstable implementation detail subject to change.
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[doc(hidden)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// AES (Advanced Encryption Standard New Instructions AES-NI)
+    aes,
+    /// CLMUL (Carry-less Multiplication)
+    pclmulqdq,
+    /// RDRAND
+    rdrand,
+    /// RDSEED
+    rdseed,
+    /// TSC (Time Stamp Counter)
+    tsc,
+    /// MMX
+    mmx,
+    /// SSE (Streaming SIMD Extensions)
+    sse,
+    /// SSE2 (Streaming SIMD Extensions 2)
+    sse2,
+    /// SSE3 (Streaming SIMD Extensions 3)
+    sse3,
+    /// SSSE3 (Supplemental Streaming SIMD Extensions 3)
+    ssse3,
+    /// SSE4.1 (Streaming SIMD Extensions 4.1)
+    sse4_1,
+    /// SSE4.2 (Streaming SIMD Extensions 4.2)
+    sse4_2,
+    /// SSE4a (Streaming SIMD Extensions 4a)
+    sse4a,
+    /// SHA
+    sha,
+    /// AVX (Advanced Vector Extensions)
+    avx,
+    /// AVX2 (Advanced Vector Extensions 2)
+    avx2,
+    /// AVX-512 F (Foundation)
+    avx512f,
+    /// AVX-512 CD (Conflict Detection Instructions)
+    avx512cd,
+    /// AVX-512 ER (Exponential and Reciprocal Instructions)
+    avx512er,
+    /// AVX-512 PF (Prefetch Instructions)
+    avx512pf,
+    /// AVX-512 BW (Byte and Word Instructions)
+    avx512bw,
+    /// AVX-512 DQ (Doubleword and Quadword)
+    avx512dq,
+    /// AVX-512 VL (Vector Length Extensions)
+    avx512vl,
+    /// AVX-512 IFMA (Integer Fused Multiply Add)
+    avx512_ifma,
+    /// AVX-512 VBMI (Vector Byte Manipulation Instructions)
+    avx512_vbmi,
+    /// AVX-512 VPOPCNTDQ (Vector Population Count Doubleword and
+    /// Quadword)
+    avx512_vpopcntdq,
+    /// F16C (Conversions between IEEE-754 `binary16` and `binary32` formats)
+    f16c,
+    /// FMA (Fused Multiply Add)
+    fma,
+    /// BMI1 (Bit Manipulation Instructions 1)
+    bmi,
+    /// BMI1 (Bit Manipulation Instructions 2)
+    bmi2,
+    /// ABM (Advanced Bit Manipulation) on AMD / LZCNT (Leading Zero
+    /// Count) on Intel
+    abm,
+    /// TBM (Trailing Bit Manipulation)
+    tbm,
+    /// POPCNT (Population Count)
+    popcnt,
+    /// FXSR (Floating-point context fast save and restor)
+    fxsr,
+    /// XSAVE (Save Processor Extended States)
+    xsave,
+    /// XSAVEOPT (Save Processor Extended States Optimized)
+    xsaveopt,
+    /// XSAVES (Save Processor Extended States Supervisor)
+    xsaves,
+    /// XSAVEC (Save Processor Extended States Compacted)
+    xsavec,
+    /// CMPXCH16B, a 16-byte compare-and-swap instruction
+    cmpxchg16b,
+    /// ADX, Intel ADX (Multi-Precision Add-Carry Instruction Extensions)
+    adx,
+    /// RTM, Intel (Restricted Transactional Memory)
+    rtm,
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/bit.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/bit.rs
new file mode 100644
index 0000000000000..578f0b16b742a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/bit.rs
@@ -0,0 +1,9 @@
+//! Bit manipulation utilities.
+
+/// Tests the `bit` of `x`.
+#[allow(dead_code)]
+#[inline]
+pub(crate) fn test(x: usize, bit: u32) -> bool {
+    debug_assert!(bit < 32, "bit index out-of-bounds");
+    x & (1 << bit) != 0
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/cache.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/cache.rs
new file mode 100644
index 0000000000000..92bc4b58d1677
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/cache.rs
@@ -0,0 +1,164 @@
+//! Caches run-time feature detection so that it only needs to be computed
+//! once.
+
+#![allow(dead_code)] // not used on all platforms
+
+use crate::sync::atomic::Ordering;
+
+#[cfg(target_pointer_width = "64")]
+use crate::sync::atomic::AtomicU64;
+
+#[cfg(target_pointer_width = "32")]
+use crate::sync::atomic::AtomicU32;
+
+/// Sets the `bit` of `x`.
+#[inline]
+const fn set_bit(x: u64, bit: u32) -> u64 {
+    x | 1 << bit
+}
+
+/// Tests the `bit` of `x`.
+#[inline]
+const fn test_bit(x: u64, bit: u32) -> bool {
+    x & (1 << bit) != 0
+}
+
+/// Maximum number of features that can be cached.
+const CACHE_CAPACITY: u32 = 63;
+
+/// This type is used to initialize the cache
+#[derive(Copy, Clone)]
+pub(crate) struct Initializer(u64);
+
+#[allow(clippy::use_self)]
+impl Default for Initializer {
+    fn default() -> Self {
+        Initializer(0)
+    }
+}
+
+impl Initializer {
+    /// Tests the `bit` of the cache.
+    #[allow(dead_code)]
+    #[inline]
+    pub(crate) fn test(self, bit: u32) -> bool {
+        // FIXME: this way of making sure that the cache is large enough is
+        // brittle.
+        debug_assert!(
+            bit < CACHE_CAPACITY,
+            "too many features, time to increase the cache size!"
+        );
+        test_bit(self.0, bit)
+    }
+
+    /// Sets the `bit` of the cache.
+    #[inline]
+    pub(crate) fn set(&mut self, bit: u32) {
+        // FIXME: this way of making sure that the cache is large enough is
+        // brittle.
+        debug_assert!(
+            bit < CACHE_CAPACITY,
+            "too many features, time to increase the cache size!"
+        );
+        let v = self.0;
+        self.0 = set_bit(v, bit);
+    }
+}
+
+/// This global variable is a cache of the features supported by the CPU.
+static CACHE: Cache = Cache::uninitialized();
+
+/// Feature cache with capacity for `CACHE_CAPACITY` features.
+///
+/// Note: the last feature bit is used to represent an
+/// uninitialized cache.
+#[cfg(target_pointer_width = "64")]
+struct Cache(AtomicU64);
+
+#[cfg(target_pointer_width = "64")]
+#[allow(clippy::use_self)]
+impl Cache {
+    /// Creates an uninitialized cache.
+    #[allow(clippy::declare_interior_mutable_const)]
+    const fn uninitialized() -> Self {
+        Cache(AtomicU64::new(u64::max_value()))
+    }
+    /// Is the cache uninitialized?
+    #[inline]
+    pub(crate) fn is_uninitialized(&self) -> bool {
+        self.0.load(Ordering::Relaxed) == u64::max_value()
+    }
+
+    /// Is the `bit` in the cache set?
+    #[inline]
+    pub(crate) fn test(&self, bit: u32) -> bool {
+        test_bit(CACHE.0.load(Ordering::Relaxed), bit)
+    }
+
+    /// Initializes the cache.
+    #[inline]
+    pub(crate) fn initialize(&self, value: Initializer) {
+        self.0.store(value.0, Ordering::Relaxed);
+    }
+}
+
+/// Feature cache with capacity for `CACHE_CAPACITY` features.
+///
+/// Note: the last feature bit is used to represent an
+/// uninitialized cache.
+#[cfg(target_pointer_width = "32")]
+struct Cache(AtomicU32, AtomicU32);
+
+#[cfg(target_pointer_width = "32")]
+impl Cache {
+    /// Creates an uninitialized cache.
+    const fn uninitialized() -> Self {
+        Cache(
+            AtomicU32::new(u32::max_value()),
+            AtomicU32::new(u32::max_value()),
+        )
+    }
+    /// Is the cache uninitialized?
+    #[inline]
+    pub(crate) fn is_uninitialized(&self) -> bool {
+        self.1.load(Ordering::Relaxed) == u32::max_value()
+    }
+
+    /// Is the `bit` in the cache set?
+    #[inline]
+    pub(crate) fn test(&self, bit: u32) -> bool {
+        if bit < 32 {
+            test_bit(CACHE.0.load(Ordering::Relaxed) as u64, bit)
+        } else {
+            test_bit(CACHE.1.load(Ordering::Relaxed) as u64, bit - 32)
+        }
+    }
+
+    /// Initializes the cache.
+    #[inline]
+    pub(crate) fn initialize(&self, value: Initializer) {
+        let lo: u32 = value.0 as u32;
+        let hi: u32 = (value.0 >> 32) as u32;
+        self.0.store(lo, Ordering::Relaxed);
+        self.1.store(hi, Ordering::Relaxed);
+    }
+}
+
+/// Tests the `bit` of the storage. If the storage has not been initialized,
+/// initializes it with the result of `f()`.
+///
+/// On its first invocation, it detects the CPU features and caches them in the
+/// `CACHE` global variable as an `AtomicU64`.
+///
+/// It uses the `Feature` variant to index into this variable as a bitset. If
+/// the bit is set, the feature is enabled, and otherwise it is disabled.
+#[inline]
+pub(crate) fn test<F>(bit: u32, f: F) -> bool
+where
+    F: FnOnce() -> Initializer,
+{
+    if CACHE.is_uninitialized() {
+        CACHE.initialize(f());
+    }
+    CACHE.test(bit)
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/error_macros.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/error_macros.rs
new file mode 100644
index 0000000000000..6769757ed9331
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/error_macros.rs
@@ -0,0 +1,150 @@
+//! The `is_{target_arch}_feature_detected!` macro are only available on their
+//! architecture. These macros provide a better error messages when the user
+//! attempts to call them in a different architecture.
+
+/// Prevents compilation if `is_x86_feature_detected` is used somewhere
+/// else than `x86` and `x86_64` targets.
+#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_x86_feature_detected {
+    ($t: tt) => {
+        compile_error!(
+            r#"
+        is_x86_feature_detected can only be used on x86 and x86_64 targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
+                if is_x86_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_arm_feature_detected` is used somewhere else
+/// than `ARM` targets.
+#[cfg(not(target_arch = "arm"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_arm_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+        is_arm_feature_detected can only be used on ARM targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "arm")] {
+                if is_arm_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_aarch64_feature_detected` is used somewhere else
+/// than `aarch64` targets.
+#[cfg(not(target_arch = "aarch64"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_aarch64_feature_detected {
+    ($t: tt) => {
+        compile_error!(
+            r#"
+        is_aarch64_feature_detected can only be used on AArch64 targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "aarch64")] {
+                if is_aarch64_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_powerpc_feature_detected` is used somewhere else
+/// than `PowerPC` targets.
+#[cfg(not(target_arch = "powerpc"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_powerpc_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+is_powerpc_feature_detected can only be used on PowerPC targets.
+You can prevent it from being used in other architectures by
+guarding it behind a cfg(target_arch) as follows:
+
+    #[cfg(target_arch = "powerpc")] {
+        if is_powerpc_feature_detected(...) { ... }
+    }
+"#
+        )
+    };
+}
+
+/// Prevents compilation if `is_powerpc64_feature_detected` is used somewhere
+/// else than `PowerPC64` targets.
+#[cfg(not(target_arch = "powerpc64"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_powerpc64_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+is_powerpc64_feature_detected can only be used on PowerPC64 targets.
+You can prevent it from being used in other architectures by
+guarding it behind a cfg(target_arch) as follows:
+
+    #[cfg(target_arch = "powerpc64")] {
+        if is_powerpc64_feature_detected(...) { ... }
+    }
+"#
+        )
+    };
+}
+
+/// Prevents compilation if `is_mips_feature_detected` is used somewhere else
+/// than `MIPS` targets.
+#[cfg(not(target_arch = "mips"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_mips_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+        is_mips_feature_detected can only be used on MIPS targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "mips")] {
+                if is_mips_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_mips64_feature_detected` is used somewhere else
+/// than `MIPS64` targets.
+#[cfg(not(target_arch = "mips64"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_mips64_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+        is_mips64_feature_detected can only be used on MIPS64 targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "mips64")] {
+                if is_mips64_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/mod.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/mod.rs
new file mode 100644
index 0000000000000..f446e88eedc8c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/mod.rs
@@ -0,0 +1,85 @@
+//! This module implements run-time feature detection.
+//!
+//! The `is_{arch}_feature_detected!("feature-name")` macros take the name of a
+//! feature as a string-literal, and return a boolean indicating whether the
+//! feature is enabled at run-time or not.
+//!
+//! These macros do two things:
+//! * map the string-literal into an integer stored as a `Feature` enum,
+//! * call a `os::check_for(x: Feature)` function that returns `true` if the
+//! feature is enabled.
+//!
+//! The `Feature` enums are also implemented in the `arch/{target_arch}.rs`
+//! modules.
+//!
+//! The `check_for` functions are, in general, Operating System dependent. Most
+//! architectures do not allow user-space programs to query the feature bits
+//! due to security concerns (x86 is the big exception). These functions are
+//! implemented in the `os/{target_os}.rs` modules.
+
+#[macro_use]
+mod error_macros;
+
+cfg_if! {
+    if #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
+        #[path = "arch/x86.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "arm")] {
+        #[path = "arch/arm.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "aarch64")] {
+        #[path = "arch/aarch64.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "powerpc")] {
+        #[path = "arch/powerpc.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "powerpc64")] {
+        #[path = "arch/powerpc64.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "mips")] {
+        #[path = "arch/mips.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "mips64")] {
+        #[path = "arch/mips64.rs"]
+        #[macro_use]
+        mod arch;
+    } else {
+        // Unimplemented architecture:
+        mod arch {
+            pub enum Feature {
+                Null
+            }
+        }
+    }
+}
+pub use self::arch::Feature;
+
+mod bit;
+mod cache;
+
+cfg_if! {
+    if #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
+        // On x86/x86_64 no OS specific functionality is required.
+        #[path = "os/x86.rs"]
+        mod os;
+    } else if #[cfg(all(target_os = "linux", feature = "use_std"))] {
+        #[path = "os/linux/mod.rs"]
+        mod os;
+    } else if #[cfg(target_os = "freebsd")] {
+        #[cfg(target_arch = "aarch64")]
+        #[path = "os/aarch64.rs"]
+        mod aarch64;
+        #[path = "os/freebsd/mod.rs"]
+        mod os;
+    } else {
+        #[path = "os/other.rs"]
+        mod os;
+    }
+}
+pub use self::os::check_for;
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/aarch64.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/aarch64.rs
new file mode 100644
index 0000000000000..dfb8c87707f08
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/aarch64.rs
@@ -0,0 +1,79 @@
+//! Run-time feature detection for Aarch64 on any OS that emulates the mrs instruction.
+//!
+//! On FreeBSD >= 12.0, Linux >= 4.11 and other operating systems, it is possible to use
+//! privileged system registers from userspace to check CPU feature support.
+//!
+//! AArch64 system registers ID_AA64ISAR0_EL1, ID_AA64PFR0_EL1, ID_AA64ISAR1_EL1
+//! have bits dedicated to features like AdvSIMD, CRC32, AES, atomics (LSE), etc.
+//! Each part of the register indicates the level of support for a certain feature, e.g.
+//! when ID_AA64ISAR0_EL1\[7:4\] is >= 1, AES is supported; when it's >= 2, PMULL is supported.
+//!
+//! For proper support of [SoCs where different cores have different capabilities](https://medium.com/@jadr2ddude/a-big-little-problem-a-tale-of-big-little-gone-wrong-e7778ce744bb),
+//! the OS has to always report only the features supported by all cores, like [FreeBSD does](https://reviews.freebsd.org/D17137#393947).
+//!
+//! References:
+//!
+//! - [Zircon implementation](https://fuchsia.googlesource.com/zircon/+/master/kernel/arch/arm64/feature.cpp)
+//! - [Linux documentation](https://www.kernel.org/doc/Documentation/arm64/cpu-feature-registers.txt)
+
+use crate::detect::{Feature, cache};
+
+/// Try to read the features from the system registers.
+///
+/// This will cause SIGILL if the current OS is not trapping the mrs instruction.
+pub(crate) fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+
+    {
+        let mut enable_feature = |f, enable| {
+            if enable {
+                value.set(f as u32);
+            }
+        };
+
+        // ID_AA64ISAR0_EL1 - Instruction Set Attribute Register 0
+        let aa64isar0: u64;
+        unsafe { asm!("mrs $0, ID_AA64ISAR0_EL1" : "=r"(aa64isar0)); }
+
+        let aes = bits_shift(aa64isar0, 7, 4) >= 1;
+        let pmull = bits_shift(aa64isar0, 7, 4) >= 2;
+        let sha1 = bits_shift(aa64isar0, 11, 8) >= 1;
+        let sha2 = bits_shift(aa64isar0, 15, 12) >= 1;
+        enable_feature(Feature::pmull, pmull);
+        // Crypto is specified as AES + PMULL + SHA1 + SHA2 per LLVM/hosts.cpp
+        enable_feature(Feature::crypto, aes && pmull && sha1 && sha2);
+        enable_feature(Feature::lse, bits_shift(aa64isar0, 23, 20) >= 1);
+        enable_feature(Feature::crc, bits_shift(aa64isar0, 19, 16) >= 1);
+
+        // ID_AA64PFR0_EL1 - Processor Feature Register 0
+        let aa64pfr0: u64;
+        unsafe { asm!("mrs $0, ID_AA64PFR0_EL1" : "=r"(aa64pfr0)); }
+
+        let fp = bits_shift(aa64pfr0, 19, 16) < 0xF;
+        let fphp = bits_shift(aa64pfr0, 19, 16) >= 1;
+        let asimd = bits_shift(aa64pfr0, 23, 20) < 0xF;
+        let asimdhp = bits_shift(aa64pfr0, 23, 20) >= 1;
+        enable_feature(Feature::fp, fp);
+        enable_feature(Feature::fp16, fphp);
+        // SIMD support requires float support - if half-floats are
+        // supported, it also requires half-float support:
+        enable_feature(Feature::asimd, fp && asimd && (!fphp | asimdhp));
+        // SIMD extensions require SIMD support:
+        enable_feature(Feature::rdm, asimd && bits_shift(aa64isar0, 31, 28) >= 1);
+        enable_feature(Feature::dotprod, asimd && bits_shift(aa64isar0, 47, 44) >= 1);
+        enable_feature(Feature::sve, asimd && bits_shift(aa64pfr0, 35, 32) >= 1);
+
+        // ID_AA64ISAR1_EL1 - Instruction Set Attribute Register 1
+        let aa64isar1: u64;
+        unsafe { asm!("mrs $0, ID_AA64ISAR1_EL1" : "=r"(aa64isar1)); }
+
+        enable_feature(Feature::rcpc, bits_shift(aa64isar1, 23, 20) >= 1);
+    }
+
+    value
+}
+
+#[inline]
+fn bits_shift(x: u64, high: usize, low: usize) -> u64 {
+    (x >> low) & ((1 << (high - low + 1)) - 1)
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/aarch64.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/aarch64.rs
new file mode 100644
index 0000000000000..910d2f33b3904
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/aarch64.rs
@@ -0,0 +1,28 @@
+//! Run-time feature detection for Aarch64 on FreeBSD.
+
+use crate::detect::{Feature, cache};
+use super::super::aarch64::detect_features;
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn dump() {
+        println!("asimd: {:?}", is_aarch64_feature_detected!("asimd"));
+        println!("pmull: {:?}", is_aarch64_feature_detected!("pmull"));
+        println!("fp: {:?}", is_aarch64_feature_detected!("fp"));
+        println!("fp16: {:?}", is_aarch64_feature_detected!("fp16"));
+        println!("sve: {:?}", is_aarch64_feature_detected!("sve"));
+        println!("crc: {:?}", is_aarch64_feature_detected!("crc"));
+        println!("crypto: {:?}", is_aarch64_feature_detected!("crypto"));
+        println!("lse: {:?}", is_aarch64_feature_detected!("lse"));
+        println!("rdm: {:?}", is_aarch64_feature_detected!("rdm"));
+        println!("rcpc: {:?}", is_aarch64_feature_detected!("rcpc"));
+        println!("dotprod: {:?}", is_aarch64_feature_detected!("dotprod"));
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/arm.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/arm.rs
new file mode 100644
index 0000000000000..e13847dcbd895
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/arm.rs
@@ -0,0 +1,27 @@
+//! Run-time feature detection for ARM on FreeBSD
+
+use crate::detect::{Feature, cache};
+use super::{auxvec};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::neon, auxv.hwcap & 0x00001000 != 0);
+        enable_feature(&mut value, Feature::pmull, auxv.hwcap2 & 0x00000002 != 0);
+        return value;
+    }
+    value
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/auxvec.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/auxvec.rs
new file mode 100644
index 0000000000000..a2bac7676014d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/auxvec.rs
@@ -0,0 +1,86 @@
+//! Parses ELF auxiliary vectors.
+#![cfg_attr(any(target_arch = "arm", target_arch = "powerpc64"), allow(dead_code))]
+
+/// Key to access the CPU Hardware capabilities bitfield.
+pub(crate) const AT_HWCAP: usize = 25;
+/// Key to access the CPU Hardware capabilities 2 bitfield.
+pub(crate) const AT_HWCAP2: usize = 26;
+
+/// Cache HWCAP bitfields of the ELF Auxiliary Vector.
+///
+/// If an entry cannot be read all the bits in the bitfield are set to zero.
+/// This should be interpreted as all the features being disabled.
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct AuxVec {
+    pub hwcap: usize,
+    pub hwcap2: usize,
+}
+
+/// ELF Auxiliary Vector
+///
+/// The auxiliary vector is a memory region in a running ELF program's stack
+/// composed of (key: usize, value: usize) pairs.
+///
+/// The keys used in the aux vector are platform dependent. For FreeBSD, they are
+/// defined in [sys/elf_common.h][elf_common_h]. The hardware capabilities of a given
+/// CPU can be queried with the  `AT_HWCAP` and `AT_HWCAP2` keys.
+///
+/// Note that run-time feature detection is not invoked for features that can
+/// be detected at compile-time.
+///
+/// [elf_common.h]: https://svnweb.freebsd.org/base/release/12.0.0/sys/sys/elf_common.h?revision=341707
+pub(crate) fn auxv() -> Result<AuxVec, ()> {
+    if let Ok(hwcap) = archauxv(AT_HWCAP) {
+        if let Ok(hwcap2) = archauxv(AT_HWCAP2) {
+            if hwcap != 0 && hwcap2 != 0 {
+                return Ok(AuxVec { hwcap, hwcap2 });
+            }
+        }
+    }
+    Err(())
+}
+
+/// Tries to read the `key` from the auxiliary vector.
+fn archauxv(key: usize) -> Result<usize, ()> {
+    use crate::mem;
+
+    #[derive (Copy, Clone)]
+    #[repr(C)]
+    pub struct Elf_Auxinfo {
+        pub a_type: usize,
+        pub a_un: unnamed,
+    }
+    #[derive (Copy, Clone)]
+    #[repr(C)]
+    pub union unnamed {
+        pub a_val: libc::c_long,
+        pub a_ptr: *mut libc::c_void,
+        pub a_fcn: Option<unsafe extern "C" fn() -> ()>,
+    }
+
+    let mut auxv: [Elf_Auxinfo; 27] =
+        [Elf_Auxinfo{a_type: 0, a_un: unnamed{a_val: 0,},}; 27];
+
+    let mut len: libc::c_uint = mem::size_of_val(&auxv) as libc::c_uint;
+
+    unsafe {
+        let mut mib = [libc::CTL_KERN, libc::KERN_PROC, libc::KERN_PROC_AUXV, libc::getpid()];
+    
+        let ret = libc::sysctl(mib.as_mut_ptr(),
+                       mib.len() as u32,
+                       &mut auxv as *mut _ as *mut _,
+                       &mut len as *mut _ as *mut _,
+                       0 as *mut libc::c_void,
+                       0,
+                );
+    
+        if ret != -1 {
+            for i in 0..auxv.len() {
+                if auxv[i].a_type == key {
+                    return Ok(auxv[i].a_un.a_val as usize);
+                }
+            }
+        }
+    }
+    return Ok(0);
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/mod.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/mod.rs
new file mode 100644
index 0000000000000..1a5338a355595
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/mod.rs
@@ -0,0 +1,22 @@
+//! Run-time feature detection on FreeBSD
+
+mod auxvec;
+
+cfg_if! {
+    if #[cfg(target_arch = "aarch64")] {
+        mod aarch64;
+        pub use self::aarch64::check_for;
+    } else if #[cfg(target_arch = "arm")] {
+        mod arm;
+        pub use self::arm::check_for;
+    } else if #[cfg(target_arch = "powerpc64")] {
+        mod powerpc;
+        pub use self::powerpc::check_for;
+    } else {
+        use crate::arch::detect::Feature;
+        /// Performs run-time feature detection.
+        pub fn check_for(_x: Feature) -> bool {
+            false
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/powerpc.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/powerpc.rs
new file mode 100644
index 0000000000000..c7f761d4d6058
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/freebsd/powerpc.rs
@@ -0,0 +1,27 @@
+//! Run-time feature detection for PowerPC on FreeBSD.
+
+use crate::detect::{Feature, cache};
+use super::{auxvec};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::altivec, auxv.hwcap & 0x10000000 != 0);
+        enable_feature(&mut value, Feature::vsx, auxv.hwcap & 0x00000080 != 0);
+        enable_feature(&mut value, Feature::power8, auxv.hwcap2 & 0x80000000 != 0);
+        return value;
+    }
+    value
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/aarch64.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/aarch64.rs
new file mode 100644
index 0000000000000..f7dc0f0222e59
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/aarch64.rs
@@ -0,0 +1,157 @@
+//! Run-time feature detection for Aarch64 on Linux.
+
+use crate::detect::{Feature, cache, bit};
+use super::{auxvec, cpuinfo};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from /proc/cpuinfo.
+fn detect_features() -> cache::Initializer {
+    if let Ok(auxv) = auxvec::auxv() {
+        let hwcap: AtHwcap = auxv.into();
+        return hwcap.cache();
+    }
+    if let Ok(c) = cpuinfo::CpuInfo::new() {
+        let hwcap: AtHwcap = c.into();
+        return hwcap.cache();
+    }
+    cache::Initializer::default()
+}
+
+/// These values are part of the platform-specific [asm/hwcap.h][hwcap] .
+///
+/// [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h
+struct AtHwcap {
+    fp: bool, // 0
+    asimd: bool, // 1
+    // evtstrm: bool, // 2
+    aes: bool, // 3
+    pmull: bool, // 4
+    sha1: bool, // 5
+    sha2: bool, // 6
+    crc32: bool, // 7
+    atomics: bool, // 8
+    fphp: bool, // 9
+    asimdhp: bool, // 10
+    // cpuid: bool, // 11
+    asimdrdm: bool, // 12
+    // jscvt: bool, // 13
+    // fcma: bool, // 14
+    lrcpc: bool, // 15
+    // dcpop: bool, // 16
+    // sha3: bool, // 17
+    // sm3: bool, // 18
+    // sm4: bool, // 19
+    asimddp: bool, // 20
+    // sha512: bool, // 21
+    sve: bool, // 22
+}
+
+impl From<auxvec::AuxVec> for AtHwcap {
+    /// Reads AtHwcap from the auxiliary vector.
+    fn from(auxv: auxvec::AuxVec) -> Self {
+        AtHwcap {
+            fp: bit::test(auxv.hwcap, 0),
+            asimd: bit::test(auxv.hwcap, 1),
+            // evtstrm: bit::test(auxv.hwcap, 2),
+            aes: bit::test(auxv.hwcap, 3),
+            pmull: bit::test(auxv.hwcap, 4),
+            sha1: bit::test(auxv.hwcap, 5),
+            sha2: bit::test(auxv.hwcap, 6),
+            crc32: bit::test(auxv.hwcap, 7),
+            atomics: bit::test(auxv.hwcap, 8),
+            fphp: bit::test(auxv.hwcap, 9),
+            asimdhp: bit::test(auxv.hwcap, 10),
+            // cpuid: bit::test(auxv.hwcap, 11),
+            asimdrdm: bit::test(auxv.hwcap, 12),
+            // jscvt: bit::test(auxv.hwcap, 13),
+            // fcma: bit::test(auxv.hwcap, 14),
+            lrcpc: bit::test(auxv.hwcap, 15),
+            // dcpop: bit::test(auxv.hwcap, 16),
+            // sha3: bit::test(auxv.hwcap, 17),
+            // sm3: bit::test(auxv.hwcap, 18),
+            // sm4: bit::test(auxv.hwcap, 19),
+            asimddp: bit::test(auxv.hwcap, 20),
+            // sha512: bit::test(auxv.hwcap, 21),
+            sve: bit::test(auxv.hwcap, 22),
+        }
+    }
+}
+
+impl From<cpuinfo::CpuInfo> for AtHwcap {
+    /// Reads AtHwcap from /proc/cpuinfo .
+    fn from(c: cpuinfo::CpuInfo) -> Self {
+        let f = &c.field("Features");
+        AtHwcap {
+            // 64-bit names. FIXME: In 32-bit compatibility mode /proc/cpuinfo will
+            // map some of the 64-bit names to some 32-bit feature names. This does not
+            // cover that yet.
+            fp: f.has("fp"),
+            asimd: f.has("asimd"),
+            // evtstrm: f.has("evtstrm"),
+            aes: f.has("aes"),
+            pmull: f.has("pmull"),
+            sha1: f.has("sha1"),
+            sha2: f.has("sha2"),
+            crc32: f.has("crc32"),
+            atomics: f.has("atomics"),
+            fphp: f.has("fphp"),
+            asimdhp: f.has("asimdhp"),
+            // cpuid: f.has("cpuid"),
+            asimdrdm: f.has("asimdrdm"),
+            // jscvt: f.has("jscvt"),
+            // fcma: f.has("fcma"),
+            lrcpc: f.has("lrcpc"),
+            // dcpop: f.has("dcpop"),
+            // sha3: f.has("sha3"),
+            // sm3: f.has("sm3"),
+            // sm4: f.has("sm4"),
+            asimddp: f.has("asimddp"),
+            // sha512: f.has("sha512"),
+            sve: f.has("sve"),
+        }
+    }
+}
+
+impl AtHwcap {
+    /// Initializes the cache from the feature -bits.
+    ///
+    /// The features are enabled approximately like in LLVM host feature detection:
+    /// https://github.com/llvm-mirror/llvm/blob/master/lib/Support/Host.cpp#L1273
+    fn cache(self) -> cache::Initializer {
+        let mut value = cache::Initializer::default();
+        {
+            let mut enable_feature = |f, enable| {
+                if enable {
+                    value.set(f as u32);
+                }
+            };
+
+            enable_feature(Feature::fp, self.fp);
+            // Half-float support requires float support
+            enable_feature(Feature::fp16, self.fp && self.fphp);
+            enable_feature(Feature::pmull, self.pmull);
+            enable_feature(Feature::crc, self.crc32);
+            enable_feature(Feature::lse, self.atomics);
+            enable_feature(Feature::rcpc, self.lrcpc);
+
+            // SIMD support requires float support - if half-floats are
+            // supported, it also requires half-float support:
+            let asimd = self.fp && self.asimd && (!self.fphp | self.asimdhp);
+            enable_feature(Feature::asimd, asimd);
+            // SIMD extensions require SIMD support:
+            enable_feature(Feature::rdm, self.asimdrdm && asimd);
+            enable_feature(Feature::dotprod, self.asimddp && asimd);
+            enable_feature(Feature::sve, self.sve && asimd);
+
+            // Crypto is specified as AES + PMULL + SHA1 + SHA2 per LLVM/hosts.cpp
+            enable_feature(Feature::crypto, self.aes && self.pmull && self.sha1 && self.sha2);
+        }
+        value
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/arm.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/arm.rs
new file mode 100644
index 0000000000000..0d58a847cd626
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/arm.rs
@@ -0,0 +1,49 @@
+//! Run-time feature detection for ARM on Linux.
+
+use crate::detect::{Feature, cache, bit};
+use super::{auxvec, cpuinfo};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from /proc/cpuinfo.
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    // The values are part of the platform-specific [asm/hwcap.h][hwcap]
+    //
+    // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::neon, bit::test(auxv.hwcap, 12));
+        enable_feature(&mut value, Feature::pmull, bit::test(auxv.hwcap2, 1));
+        return value;
+    }
+
+    if let Ok(c) = cpuinfo::CpuInfo::new() {
+        enable_feature(&mut value, Feature::neon, c.field("Features").has("neon") &&
+            !has_broken_neon(&c));
+        enable_feature(&mut value, Feature::pmull, c.field("Features").has("pmull"));
+        return value;
+    }
+    value
+}
+
+/// Is the CPU known to have a broken NEON unit?
+///
+/// See https://crbug.com/341598.
+fn has_broken_neon(cpuinfo: &cpuinfo::CpuInfo) -> bool {
+    cpuinfo.field("CPU implementer") == "0x51"
+        && cpuinfo.field("CPU architecture") == "7"
+        && cpuinfo.field("CPU variant") == "0x1"
+        && cpuinfo.field("CPU part") == "0x04d"
+        && cpuinfo.field("CPU revision") == "0"
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/auxvec.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/auxvec.rs
new file mode 100644
index 0000000000000..07b6432eafd98
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/auxvec.rs
@@ -0,0 +1,307 @@
+//! Parses ELF auxiliary vectors.
+#![cfg_attr(not(target_arch = "aarch64"), allow(dead_code))]
+
+#[cfg(feature = "std_detect_file_io")]
+use crate::{fs::File, io::Read};
+
+/// Key to access the CPU Hardware capabilities bitfield.
+pub(crate) const AT_HWCAP: usize = 16;
+/// Key to access the CPU Hardware capabilities 2 bitfield.
+#[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+pub(crate) const AT_HWCAP2: usize = 26;
+
+/// Cache HWCAP bitfields of the ELF Auxiliary Vector.
+///
+/// If an entry cannot be read all the bits in the bitfield are set to zero.
+/// This should be interpreted as all the features being disabled.
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct AuxVec {
+    pub hwcap: usize,
+    #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+    pub hwcap2: usize,
+}
+
+/// ELF Auxiliary Vector
+///
+/// The auxiliary vector is a memory region in a running ELF program's stack
+/// composed of (key: usize, value: usize) pairs.
+///
+/// The keys used in the aux vector are platform dependent. For Linux, they are
+/// defined in [linux/auxvec.h][auxvec_h]. The hardware capabilities of a given
+/// CPU can be queried with the  `AT_HWCAP` and `AT_HWCAP2` keys.
+///
+/// There is no perfect way of reading the auxiliary vector.
+///
+/// - If the `std_detect_dlsym_getauxval` cargo feature is enabled, this will use
+/// `getauxval` if its linked to the binary, and otherwise proceed to a fallback implementation.
+/// When `std_detect_dlsym_getauxval` is disabled, this will assume that `getauxval` is
+/// linked to the binary - if that is not the case the behavior is undefined.
+/// - Otherwise, if the `std_detect_file_io` cargo feature is enabled, it will
+///   try to read `/proc/self/auxv`.
+/// - If that fails, this function returns an error.
+///
+/// Note that run-time feature detection is not invoked for features that can
+/// be detected at compile-time. Also note that if this function returns an
+/// error, cpuinfo still can (and will) be used to try to perform run-time
+/// feature detecton on some platforms.
+///
+/// For more information about when `getauxval` is available check the great
+/// [`auxv` crate documentation][auxv_docs].
+///
+/// [auxvec_h]: https://github.com/torvalds/linux/blob/master/include/uapi/linux/auxvec.h
+/// [auxv_docs]: https://docs.rs/auxv/0.3.3/auxv/
+pub(crate) fn auxv() -> Result<AuxVec, ()> {
+    #[cfg(feature = "std_detect_dlsym_getauxval")] {
+        // Try to call a dynamically-linked getauxval function.
+        if let Ok(hwcap) = getauxval(AT_HWCAP) {
+            // Targets with only AT_HWCAP:
+            #[cfg(any(target_arch = "aarch64", target_arch = "mips",
+                      target_arch = "mips64"))]
+            {
+                if hwcap != 0 {
+                    return Ok(AuxVec { hwcap });
+                }
+            }
+
+            // Targets with AT_HWCAP and AT_HWCAP2:
+            #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+            {
+                if let Ok(hwcap2) = getauxval(AT_HWCAP2) {
+                    if hwcap != 0 && hwcap2 != 0 {
+                        return Ok(AuxVec { hwcap, hwcap2 });
+                    }
+                }
+            }
+            drop(hwcap);
+        }
+        #[cfg(feature = "std_detect_file_io")] {
+            // If calling getauxval fails, try to read the auxiliary vector from
+            // its file:
+            auxv_from_file("/proc/self/auxv")
+        }
+        #[cfg(not(feature = "std_detect_file_io"))] {
+            Err(())
+        }
+    }
+
+    #[cfg(not(feature = "std_detect_dlsym_getauxval"))] {
+        let hwcap = unsafe { ffi_getauxval(AT_HWCAP) };
+
+        // Targets with only AT_HWCAP:
+        #[cfg(any(target_arch = "aarch64", target_arch = "mips",
+                  target_arch = "mips64"))]
+        {
+            if hwcap != 0 {
+                return Ok(AuxVec { hwcap });
+            }
+        }
+
+        // Targets with AT_HWCAP and AT_HWCAP2:
+        #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+        {
+            let hwcap2 = unsafe { ffi_getauxval(AT_HWCAP2) };
+            if hwcap != 0 && hwcap2 != 0 {
+                return Ok(AuxVec { hwcap, hwcap2 });
+            }
+        }
+    }
+}
+
+/// Tries to read the `key` from the auxiliary vector by calling the
+/// dynamically-linked `getauxval` function. If the function is not linked,
+/// this function return `Err`.
+#[cfg(feature = "std_detect_dlsym_getauxval")]
+fn getauxval(key: usize) -> Result<usize, ()> {
+    use libc;
+    pub type F = unsafe extern "C" fn(usize) -> usize;
+    unsafe {
+        let ptr = libc::dlsym(
+            libc::RTLD_DEFAULT,
+            "getauxval\0".as_ptr() as *const _,
+        );
+        if ptr.is_null() {
+            return Err(());
+        }
+
+        let ffi_getauxval: F = mem::transmute(ptr);
+        Ok(ffi_getauxval(key))
+    }
+}
+
+/// Tries to read the auxiliary vector from the `file`. If this fails, this
+/// function returns `Err`.
+#[cfg(feature = "std_detect_file_io")]
+fn auxv_from_file(file: &str) -> Result<AuxVec, ()> {
+    let mut file = File::open(file).map_err(|_| ())?;
+
+    // See <https://github.com/torvalds/linux/blob/v3.19/include/uapi/linux/auxvec.h>.
+    //
+    // The auxiliary vector contains at most 32 (key,value) fields: from
+    // `AT_EXECFN = 31` to `AT_NULL = 0`. That is, a buffer of
+    // 2*32 `usize` elements is enough to read the whole vector.
+    let mut buf = [0_usize; 64];
+    {
+        let raw: &mut [u8; 64 * mem::size_of::<usize>()] =
+            unsafe { mem::transmute(&mut buf) };
+        file.read(raw).map_err(|_| ())?;
+    }
+    auxv_from_buf(&buf)
+}
+
+/// Tries to interpret the `buffer` as an auxiliary vector. If that fails, this
+/// function returns `Err`.
+#[cfg(feature = "std_detect_file_io")]
+fn auxv_from_buf(buf: &[usize; 64]) -> Result<AuxVec, ()> {
+    // Targets with only AT_HWCAP:
+    #[cfg(any(target_arch = "aarch64", target_arch = "mips",
+              target_arch = "mips64"))]
+    {
+        for el in buf.chunks(2) {
+            match el[0] {
+                AT_HWCAP => return Ok(AuxVec { hwcap: el[1] }),
+                _ => (),
+            }
+        }
+    }
+    // Targets with AT_HWCAP and AT_HWCAP2:
+    #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+    {
+        let mut hwcap = None;
+        let mut hwcap2 = None;
+        for el in buf.chunks(2) {
+            match el[0] {
+                AT_HWCAP => hwcap = Some(el[1]),
+                AT_HWCAP2 => hwcap2 = Some(el[1]),
+                _ => (),
+            }
+        }
+
+        if let (Some(hwcap), Some(hwcap2)) = (hwcap, hwcap2) {
+            return Ok(AuxVec { hwcap, hwcap2 });
+        }
+    }
+    drop(buf);
+    Err(())
+}
+
+#[cfg(test)]
+mod tests {
+    extern crate auxv as auxv_crate;
+    use super::*;
+
+    // Reads the Auxiliary Vector key from /proc/self/auxv
+    // using the auxv crate.
+    #[cfg(feature = "std_detect_file_io")]
+    fn auxv_crate_getprocfs(key: usize) -> Option<usize> {
+        use self::auxv_crate::AuxvType;
+        use self::auxv_crate::procfs::search_procfs_auxv;
+        let k = key as AuxvType;
+        match search_procfs_auxv(&[k]) {
+            Ok(v) => Some(v[&k] as usize),
+            Err(_) => None,
+        }
+    }
+
+    // Reads the Auxiliary Vector key from getauxval()
+    // using the auxv crate.
+    #[cfg(not(any(target_arch = "mips", target_arch = "mips64")))]
+    fn auxv_crate_getauxval(key: usize) -> Option<usize> {
+        use self::auxv_crate::AuxvType;
+        use self::auxv_crate::getauxval::Getauxval;
+        let q = auxv_crate::getauxval::NativeGetauxval {};
+        match q.getauxval(key as AuxvType) {
+            Ok(v) => Some(v as usize),
+            Err(_) => None,
+        }
+    }
+
+    // FIXME: on mips/mips64 getauxval returns 0, and /proc/self/auxv
+    // does not always contain the AT_HWCAP key under qemu.
+    #[cfg(not(any(target_arch = "mips", target_arch = "mips64", target_arch = "powerpc")))]
+    #[test]
+    fn auxv_crate() {
+        let v = auxv();
+        if let Some(hwcap) = auxv_crate_getauxval(AT_HWCAP) {
+            let rt_hwcap = v.expect("failed to find hwcap key").hwcap;
+            assert_eq!(rt_hwcap, hwcap);
+        }
+
+        // Targets with AT_HWCAP and AT_HWCAP2:
+        #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+        {
+            if let Some(hwcap2) = auxv_crate_getauxval(AT_HWCAP2) {
+                let rt_hwcap2 = v.expect("failed to find hwcap2 key").hwcap2;
+                assert_eq!(rt_hwcap2, hwcap2);
+            }
+        }
+    }
+
+    #[test]
+    fn auxv_dump() {
+        if let Ok(auxvec) = auxv() {
+            println!("{:?}", auxvec);
+        } else {
+            println!("both getauxval() and reading /proc/self/auxv failed!");
+        }
+    }
+
+    #[cfg(feature = "std_detect_file_io")]
+    cfg_if! {
+        if #[cfg(target_arch = "arm")] {
+            #[test]
+            fn linux_rpi3() {
+                let file = concat!(env!("CARGO_MANIFEST_DIR"), "/src/detect/test_data/linux-rpi3.auxv");
+                println!("file: {}", file);
+                let v = auxv_from_file(file).unwrap();
+                assert_eq!(v.hwcap, 4174038);
+                assert_eq!(v.hwcap2, 16);
+            }
+
+            #[test]
+            #[should_panic]
+            fn linux_macos_vb() {
+                let file = concat!(env!("CARGO_MANIFEST_DIR"), "/src/detect/test_data/macos-virtualbox-linux-x86-4850HQ.auxv");
+                println!("file: {}", file);
+                let v = auxv_from_file(file).unwrap();
+                // this file is incomplete (contains hwcap but not hwcap2), we
+                // want to fall back to /proc/cpuinfo in this case, so
+                // reading should fail. assert_eq!(v.hwcap, 126614527);
+                // assert_eq!(v.hwcap2, 0);
+            }
+        } else if #[cfg(target_arch = "aarch64")] {
+            #[test]
+            fn linux_x64() {
+                let file = concat!(env!("CARGO_MANIFEST_DIR"), "/src/detect/test_data/linux-x64-i7-6850k.auxv");
+                println!("file: {}", file);
+                let v = auxv_from_file(file).unwrap();
+                assert_eq!(v.hwcap, 3219913727);
+            }
+        }
+    }
+
+    #[test]
+    #[cfg(feature = "std_detect_file_io")]
+    fn auxv_dump_procfs() {
+        if let Ok(auxvec) = auxv_from_file("/proc/self/auxv") {
+            println!("{:?}", auxvec);
+        } else {
+            println!("reading /proc/self/auxv failed!");
+        }
+    }
+
+    #[test]
+    fn auxv_crate_procfs() {
+        let v = auxv();
+        if let Some(hwcap) = auxv_crate_getprocfs(AT_HWCAP) {
+            assert_eq!(v.unwrap().hwcap, hwcap);
+        }
+
+        // Targets with AT_HWCAP and AT_HWCAP2:
+        #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+        {
+            if let Some(hwcap2) = auxv_crate_getprocfs(AT_HWCAP2) {
+                assert_eq!(v.unwrap().hwcap2, hwcap2);
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/cpuinfo.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/cpuinfo.rs
new file mode 100644
index 0000000000000..b3168578537fc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/cpuinfo.rs
@@ -0,0 +1,301 @@
+//! Parses /proc/cpuinfo
+#![cfg_attr(not(target_arch = "arm"), allow(dead_code))]
+
+extern crate std;
+use self::std::{prelude::v1::*, fs::File, io, io::Read};
+
+/// cpuinfo
+pub(crate) struct CpuInfo {
+    raw: String,
+}
+
+impl CpuInfo {
+    /// Reads /proc/cpuinfo into CpuInfo.
+    pub(crate) fn new() -> Result<Self, io::Error> {
+        let mut file = File::open("/proc/cpuinfo")?;
+        let mut cpui = Self { raw: String::new() };
+        file.read_to_string(&mut cpui.raw)?;
+        Ok(cpui)
+    }
+    /// Returns the value of the cpuinfo `field`.
+    pub(crate) fn field(&self, field: &str) -> CpuInfoField {
+        for l in self.raw.lines() {
+            if l.trim().starts_with(field) {
+                return CpuInfoField::new(l.split(": ").nth(1));
+            }
+        }
+        CpuInfoField(None)
+    }
+
+    /// Returns the `raw` contents of `/proc/cpuinfo`
+    #[cfg(test)]
+    fn raw(&self) -> &String {
+        &self.raw
+    }
+
+    #[cfg(test)]
+    fn from_str(other: &str) -> Result<Self, ::std::io::Error> {
+        Ok(Self {
+            raw: String::from(other),
+        })
+    }
+}
+
+/// Field of cpuinfo
+#[derive(Debug)]
+pub(crate) struct CpuInfoField<'a>(Option<&'a str>);
+
+impl<'a> PartialEq<&'a str> for CpuInfoField<'a> {
+    fn eq(&self, other: &&'a str) -> bool {
+        match self.0 {
+            None => other.is_empty(),
+            Some(f) => f == other.trim(),
+        }
+    }
+}
+
+impl<'a> CpuInfoField<'a> {
+    pub(crate) fn new<'b>(v: Option<&'b str>) -> CpuInfoField<'b> {
+        match v {
+            None => CpuInfoField::<'b>(None),
+            Some(f) => CpuInfoField::<'b>(Some(f.trim())),
+        }
+    }
+    /// Does the field exist?
+    #[cfg(test)]
+    pub(crate) fn exists(&self) -> bool {
+        self.0.is_some()
+    }
+    /// Does the field contain `other`?
+    pub(crate) fn has(&self, other: &str) -> bool {
+        match self.0 {
+            None => other.is_empty(),
+            Some(f) => {
+                let other = other.trim();
+                for v in f.split(' ') {
+                    if v == other {
+                        return true;
+                    }
+                }
+                false
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn raw_dump() {
+        let cpuinfo = CpuInfo::new().unwrap();
+        if cpuinfo.field("vendor_id") == "GenuineIntel" {
+            assert!(cpuinfo.field("flags").exists());
+            assert!(!cpuinfo.field("vendor33_id").exists());
+            assert!(cpuinfo.field("flags").has("sse"));
+            assert!(!cpuinfo.field("flags").has("avx314"));
+        }
+        println!("{}", cpuinfo.raw());
+    }
+
+    const CORE_DUO_T6500: &str = r"processor       : 0
+vendor_id       : GenuineIntel
+cpu family      : 6
+model           : 23
+model name      : Intel(R) Core(TM)2 Duo CPU     T6500  @ 2.10GHz
+stepping        : 10
+microcode       : 0xa0b
+cpu MHz         : 1600.000
+cache size      : 2048 KB
+physical id     : 0
+siblings        : 2
+core id         : 0
+cpu cores       : 2
+apicid          : 0
+initial apicid  : 0
+fdiv_bug        : no
+hlt_bug         : no
+f00f_bug        : no
+coma_bug        : no
+fpu             : yes
+fpu_exception   : yes
+cpuid level     : 13
+wp              : yes
+flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm
+bogomips        : 4190.43
+clflush size    : 64
+cache_alignment : 64
+address sizes   : 36 bits physical, 48 bits virtual
+power management:
+";
+
+    #[test]
+    fn core_duo_t6500() {
+        let cpuinfo = CpuInfo::from_str(CORE_DUO_T6500).unwrap();
+        assert_eq!(cpuinfo.field("vendor_id"), "GenuineIntel");
+        assert_eq!(cpuinfo.field("cpu family"), "6");
+        assert_eq!(cpuinfo.field("model"), "23");
+        assert_eq!(
+            cpuinfo.field("model name"),
+            "Intel(R) Core(TM)2 Duo CPU     T6500  @ 2.10GHz"
+        );
+        assert_eq!(
+            cpuinfo.field("flags"),
+            "fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm"
+        );
+        assert!(cpuinfo.field("flags").has("fpu"));
+        assert!(cpuinfo.field("flags").has("dtherm"));
+        assert!(cpuinfo.field("flags").has("sse2"));
+        assert!(!cpuinfo.field("flags").has("avx"));
+    }
+
+    const ARM_CORTEX_A53: &str =
+        r"Processor   : AArch64 Processor rev 3 (aarch64)
+        processor   : 0
+        processor   : 1
+        processor   : 2
+        processor   : 3
+        processor   : 4
+        processor   : 5
+        processor   : 6
+        processor   : 7
+        Features    : fp asimd evtstrm aes pmull sha1 sha2 crc32
+        CPU implementer : 0x41
+        CPU architecture: AArch64
+        CPU variant : 0x0
+        CPU part    : 0xd03
+        CPU revision    : 3
+
+        Hardware    : HiKey Development Board
+        ";
+
+    #[test]
+    fn arm_cortex_a53() {
+        let cpuinfo = CpuInfo::from_str(ARM_CORTEX_A53).unwrap();
+        assert_eq!(
+            cpuinfo.field("Processor"),
+            "AArch64 Processor rev 3 (aarch64)"
+        );
+        assert_eq!(
+            cpuinfo.field("Features"),
+            "fp asimd evtstrm aes pmull sha1 sha2 crc32"
+        );
+        assert!(cpuinfo.field("Features").has("pmull"));
+        assert!(!cpuinfo.field("Features").has("neon"));
+        assert!(cpuinfo.field("Features").has("asimd"));
+    }
+
+    const ARM_CORTEX_A57: &str = r"Processor	: Cortex A57 Processor rev 1 (aarch64)
+processor	: 0
+processor	: 1
+processor	: 2
+processor	: 3
+Features	: fp asimd aes pmull sha1 sha2 crc32 wp half thumb fastmult vfp edsp neon vfpv3 tlsi vfpv4 idiva idivt
+CPU implementer	: 0x41
+CPU architecture: 8
+CPU variant	: 0x1
+CPU part	: 0xd07
+CPU revision	: 1";
+
+    #[test]
+    fn arm_cortex_a57() {
+        let cpuinfo = CpuInfo::from_str(ARM_CORTEX_A57).unwrap();
+        assert_eq!(
+            cpuinfo.field("Processor"),
+            "Cortex A57 Processor rev 1 (aarch64)"
+        );
+        assert_eq!(
+            cpuinfo.field("Features"),
+            "fp asimd aes pmull sha1 sha2 crc32 wp half thumb fastmult vfp edsp neon vfpv3 tlsi vfpv4 idiva idivt"
+        );
+        assert!(cpuinfo.field("Features").has("pmull"));
+        assert!(cpuinfo.field("Features").has("neon"));
+        assert!(cpuinfo.field("Features").has("asimd"));
+    }
+
+    const POWER8E_POWERKVM: &str = r"processor       : 0
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+processor       : 1
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+processor       : 2
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+processor       : 3
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+timebase        : 512000000
+platform        : pSeries
+model           : IBM pSeries (emulated by qemu)
+machine         : CHRP IBM pSeries (emulated by qemu)";
+
+    #[test]
+    fn power8_powerkvm() {
+        let cpuinfo = CpuInfo::from_str(POWER8E_POWERKVM).unwrap();
+        assert_eq!(cpuinfo.field("cpu"), "POWER8E (raw), altivec supported");
+
+        assert!(cpuinfo.field("cpu").has("altivec"));
+    }
+
+    const POWER5P: &str = r"processor       : 0
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 1
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 2
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 3
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 4
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 5
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 6
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 7
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+timebase        : 237331000
+platform        : pSeries
+machine         : CHRP IBM,9133-55A";
+
+    #[test]
+    fn power5p() {
+        let cpuinfo = CpuInfo::from_str(POWER5P).unwrap();
+        assert_eq!(cpuinfo.field("cpu"), "POWER5+ (gs)");
+
+        assert!(!cpuinfo.field("cpu").has("altivec"));
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/mips.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/mips.rs
new file mode 100644
index 0000000000000..c0a5fb2e5d887
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/mips.rs
@@ -0,0 +1,31 @@
+//! Run-time feature detection for MIPS on Linux.
+
+use crate::detect::{Feature, cache, bit};
+use super::auxvec;
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from `/proc/cpuinfo`.
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    // The values are part of the platform-specific [asm/hwcap.h][hwcap]
+    //
+    // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::msa, bit::test(auxv.hwcap, 1));
+        return value;
+    }
+    // TODO: fall back via `cpuinfo`.
+    value
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/mod.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/mod.rs
new file mode 100644
index 0000000000000..e02d5e6dcda7a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/mod.rs
@@ -0,0 +1,28 @@
+//! Run-time feature detection on Linux
+
+mod auxvec;
+
+#[cfg(feature = "std_detect_file_io")]
+mod cpuinfo;
+
+cfg_if! {
+    if #[cfg(target_arch = "aarch64")] {
+        mod aarch64;
+        pub use self::aarch64::check_for;
+    } else if #[cfg(target_arch = "arm")] {
+        mod arm;
+        pub use self::arm::check_for;
+    } else  if #[cfg(any(target_arch = "mips", target_arch = "mips64"))] {
+        mod mips;
+        pub use self::mips::check_for;
+    } else if #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))] {
+        mod powerpc;
+        pub use self::powerpc::check_for;
+    } else {
+        use crate::detect::Feature;
+        /// Performs run-time feature detection.
+        pub fn check_for(_x: Feature) -> bool {
+            false
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/powerpc.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/powerpc.rs
new file mode 100644
index 0000000000000..1c08a58443db8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/linux/powerpc.rs
@@ -0,0 +1,41 @@
+//! Run-time feature detection for PowerPC on Linux.
+
+use crate::detect::{Feature, cache};
+use super::{auxvec, cpuinfo};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from /proc/cpuinfo.
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    // The values are part of the platform-specific [asm/cputable.h][cputable]
+    //
+    // [cputable]: https://github.com/torvalds/linux/blob/master/arch/powerpc/include/uapi/asm/cputable.h
+    if let Ok(auxv) = auxvec::auxv() {
+        // note: the PowerPC values are the mask to do the test (instead of the
+        // index of the bit to test like in ARM and Aarch64)
+        enable_feature(&mut value, Feature::altivec, auxv.hwcap & 0x10000000 != 0);
+        enable_feature(&mut value, Feature::vsx, auxv.hwcap & 0x00000080 != 0);
+        enable_feature(&mut value, Feature::power8, auxv.hwcap2 & 0x80000000 != 0);
+        return value;
+    }
+
+    // PowerPC's /proc/cpuinfo lacks a proper Feature field,
+    // but `altivec` support is indicated in the `cpu` field.
+    if let Ok(c) = cpuinfo::CpuInfo::new() {
+        enable_feature(&mut value, Feature::altivec, c.field("cpu").has("altivec"));
+        return value;
+    }
+    value
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/other.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/other.rs
new file mode 100644
index 0000000000000..23e399ea79074
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/other.rs
@@ -0,0 +1,9 @@
+//! Other operating systems
+
+use crate::detect::Feature;
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(_x: Feature) -> bool {
+    false
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/detect/os/x86.rs b/src/tools/rustfmt/tests/source/cfg_if/detect/os/x86.rs
new file mode 100644
index 0000000000000..9257b8a4be636
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/detect/os/x86.rs
@@ -0,0 +1,375 @@
+//! x86 run-time feature detection is OS independent.
+
+#[cfg(target_arch = "x86")]
+use crate::arch::x86::*;
+#[cfg(target_arch = "x86_64")]
+use crate::arch::x86_64::*;
+
+use crate::mem;
+
+use crate::detect::{Feature, cache, bit};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Run-time feature detection on x86 works by using the CPUID instruction.
+///
+/// The [CPUID Wikipedia page][wiki_cpuid] contains
+/// all the information about which flags to set to query which values, and in
+/// which registers these are reported.
+///
+/// The definitive references are:
+/// - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2:
+///   Instruction Set Reference, A-Z][intel64_ref].
+/// - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and
+///   System Instructions][amd64_ref].
+///
+/// [wiki_cpuid]: https://en.wikipedia.org/wiki/CPUID
+/// [intel64_ref]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
+/// [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf
+#[allow(clippy::similar_names)]
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+
+    // If the x86 CPU does not support the CPUID instruction then it is too
+    // old to support any of the currently-detectable features.
+    if !has_cpuid() {
+        return value;
+    }
+
+    // Calling `__cpuid`/`__cpuid_count` from here on is safe because the CPU
+    // has `cpuid` support.
+
+    // 0. EAX = 0: Basic Information:
+    // - EAX returns the "Highest Function Parameter", that is, the maximum
+    // leaf value for subsequent calls of `cpuinfo` in range [0,
+    // 0x8000_0000]. - The vendor ID is stored in 12 u8 ascii chars,
+    // returned in EBX, EDX, and   ECX (in that order):
+    let (max_basic_leaf, vendor_id) = unsafe {
+        let CpuidResult {
+            eax: max_basic_leaf,
+            ebx,
+            ecx,
+            edx,
+        } = __cpuid(0);
+        let vendor_id: [[u8; 4]; 3] = [
+            mem::transmute(ebx),
+            mem::transmute(edx),
+            mem::transmute(ecx),
+        ];
+        let vendor_id: [u8; 12] = mem::transmute(vendor_id);
+        (max_basic_leaf, vendor_id)
+    };
+
+    if max_basic_leaf < 1 {
+        // Earlier Intel 486, CPUID not implemented
+        return value;
+    }
+
+    // EAX = 1, ECX = 0: Queries "Processor Info and Feature Bits";
+    // Contains information about most x86 features.
+    let CpuidResult {
+        ecx: proc_info_ecx,
+        edx: proc_info_edx,
+        ..
+    } = unsafe { __cpuid(0x0000_0001_u32) };
+
+    // EAX = 7, ECX = 0: Queries "Extended Features";
+    // Contains information about bmi,bmi2, and avx2 support.
+    let (extended_features_ebx, extended_features_ecx) = if max_basic_leaf >= 7
+    {
+        let CpuidResult { ebx, ecx, .. } = unsafe { __cpuid(0x0000_0007_u32) };
+        (ebx, ecx)
+    } else {
+        (0, 0) // CPUID does not support "Extended Features"
+    };
+
+    // EAX = 0x8000_0000, ECX = 0: Get Highest Extended Function Supported
+    // - EAX returns the max leaf value for extended information, that is,
+    // `cpuid` calls in range [0x8000_0000; u32::MAX]:
+    let CpuidResult {
+        eax: extended_max_basic_leaf,
+        ..
+    } = unsafe { __cpuid(0x8000_0000_u32) };
+
+    // EAX = 0x8000_0001, ECX=0: Queries "Extended Processor Info and Feature
+    // Bits"
+    let extended_proc_info_ecx = if extended_max_basic_leaf >= 1 {
+        let CpuidResult { ecx, .. } = unsafe { __cpuid(0x8000_0001_u32) };
+        ecx
+    } else {
+        0
+    };
+
+    {
+        // borrows value till the end of this scope:
+        let mut enable = |r, rb, f| {
+            if bit::test(r as usize, rb) {
+                value.set(f as u32);
+            }
+        };
+
+        enable(proc_info_ecx, 0, Feature::sse3);
+        enable(proc_info_ecx, 1, Feature::pclmulqdq);
+        enable(proc_info_ecx, 9, Feature::ssse3);
+        enable(proc_info_ecx, 13, Feature::cmpxchg16b);
+        enable(proc_info_ecx, 19, Feature::sse4_1);
+        enable(proc_info_ecx, 20, Feature::sse4_2);
+        enable(proc_info_ecx, 23, Feature::popcnt);
+        enable(proc_info_ecx, 25, Feature::aes);
+        enable(proc_info_ecx, 29, Feature::f16c);
+        enable(proc_info_ecx, 30, Feature::rdrand);
+        enable(extended_features_ebx, 18, Feature::rdseed);
+        enable(extended_features_ebx, 19, Feature::adx);
+        enable(extended_features_ebx, 11, Feature::rtm);
+        enable(proc_info_edx, 4, Feature::tsc);
+        enable(proc_info_edx, 23, Feature::mmx);
+        enable(proc_info_edx, 24, Feature::fxsr);
+        enable(proc_info_edx, 25, Feature::sse);
+        enable(proc_info_edx, 26, Feature::sse2);
+        enable(extended_features_ebx, 29, Feature::sha);
+
+        enable(extended_features_ebx, 3, Feature::bmi);
+        enable(extended_features_ebx, 8, Feature::bmi2);
+
+        // `XSAVE` and `AVX` support:
+        let cpu_xsave = bit::test(proc_info_ecx as usize, 26);
+        if cpu_xsave {
+            // 0. Here the CPU supports `XSAVE`.
+
+            // 1. Detect `OSXSAVE`, that is, whether the OS is AVX enabled and
+            // supports saving the state of the AVX/AVX2 vector registers on
+            // context-switches, see:
+            //
+            // - [intel: is avx enabled?][is_avx_enabled],
+            // - [mozilla: sse.cpp][mozilla_sse_cpp].
+            //
+            // [is_avx_enabled]: https://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled
+            // [mozilla_sse_cpp]: https://hg.mozilla.org/mozilla-central/file/64bab5cbb9b6/mozglue/build/SSE.cpp#l190
+            let cpu_osxsave = bit::test(proc_info_ecx as usize, 27);
+
+            if cpu_osxsave {
+                // 2. The OS must have signaled the CPU that it supports saving and
+                // restoring the:
+                //
+                // * SSE -> `XCR0.SSE[1]`
+                // * AVX -> `XCR0.AVX[2]`
+                // * AVX-512 -> `XCR0.AVX-512[7:5]`.
+                //
+                // by setting the corresponding bits of `XCR0` to `1`.
+                //
+                // This is safe because the CPU supports `xsave`
+                // and the OS has set `osxsave`.
+                let xcr0 = unsafe { _xgetbv(0) };
+                // Test `XCR0.SSE[1]` and `XCR0.AVX[2]` with the mask `0b110 == 6`:
+                let os_avx_support = xcr0 & 6 == 6;
+                // Test `XCR0.AVX-512[7:5]` with the mask `0b1110_0000 == 224`:
+                let os_avx512_support = xcr0 & 224 == 224;
+
+                // Only if the OS and the CPU support saving/restoring the AVX
+                // registers we enable `xsave` support:
+                if os_avx_support {
+                    // See "13.3 ENABLING THE XSAVE FEATURE SET AND XSAVE-ENABLED
+                    // FEATURES" in the "Intel® 64 and IA-32 Architectures Software
+                    // Developer’s Manual, Volume 1: Basic Architecture":
+                    //
+                    // "Software enables the XSAVE feature set by setting
+                    // CR4.OSXSAVE[bit 18] to 1 (e.g., with the MOV to CR4
+                    // instruction). If this bit is 0, execution of any of XGETBV,
+                    // XRSTOR, XRSTORS, XSAVE, XSAVEC, XSAVEOPT, XSAVES, and XSETBV
+                    // causes an invalid-opcode exception (#UD)"
+                    //
+                    enable(proc_info_ecx, 26, Feature::xsave);
+
+                    // For `xsaveopt`, `xsavec`, and `xsaves` we need to query:
+                    // Processor Extended State Enumeration Sub-leaf (EAX = 0DH,
+                    // ECX = 1):
+                    if max_basic_leaf >= 0xd {
+                        let CpuidResult {
+                            eax: proc_extended_state1_eax,
+                            ..
+                        } = unsafe { __cpuid_count(0xd_u32, 1) };
+                        enable(proc_extended_state1_eax, 0, Feature::xsaveopt);
+                        enable(proc_extended_state1_eax, 1, Feature::xsavec);
+                        enable(proc_extended_state1_eax, 3, Feature::xsaves);
+                    }
+
+                    // FMA (uses 256-bit wide registers):
+                    enable(proc_info_ecx, 12, Feature::fma);
+
+                    // And AVX/AVX2:
+                    enable(proc_info_ecx, 28, Feature::avx);
+                    enable(extended_features_ebx, 5, Feature::avx2);
+
+                    // For AVX-512 the OS also needs to support saving/restoring
+                    // the extended state, only then we enable AVX-512 support:
+                    if os_avx512_support {
+                        enable(extended_features_ebx, 16, Feature::avx512f);
+                        enable(extended_features_ebx, 17, Feature::avx512dq);
+                        enable(extended_features_ebx, 21, Feature::avx512_ifma);
+                        enable(extended_features_ebx, 26, Feature::avx512pf);
+                        enable(extended_features_ebx, 27, Feature::avx512er);
+                        enable(extended_features_ebx, 28, Feature::avx512cd);
+                        enable(extended_features_ebx, 30, Feature::avx512bw);
+                        enable(extended_features_ebx, 31, Feature::avx512vl);
+                        enable(extended_features_ecx, 1, Feature::avx512_vbmi);
+                        enable(
+                            extended_features_ecx,
+                            14,
+                            Feature::avx512_vpopcntdq,
+                        );
+                    }
+                }
+            }
+        }
+
+        // This detects ABM on AMD CPUs and LZCNT on Intel CPUs.
+        // On intel CPUs with popcnt, lzcnt implements the
+        // "missing part" of ABM, so we map both to the same
+        // internal feature.
+        //
+        // The `is_x86_feature_detected!("lzcnt")` macro then
+        // internally maps to Feature::abm.
+        enable(extended_proc_info_ecx, 5, Feature::abm);
+        // As Hygon Dhyana originates from AMD technology and shares most of the architecture with
+        // AMD's family 17h, but with different CPU Vendor ID("HygonGenuine")/Family series
+        // number(Family 18h).
+        //
+        // For CPUID feature bits, Hygon Dhyana(family 18h) share the same definition with AMD
+        // family 17h.
+        //
+        // Related AMD CPUID specification is https://www.amd.com/system/files/TechDocs/25481.pdf.
+        // Related Hygon kernel patch can be found on
+        // http://lkml.kernel.org/r/5ce86123a7b9dad925ac583d88d2f921040e859b.1538583282.git.puwen@hygon.cn
+        if vendor_id == *b"AuthenticAMD" || vendor_id == *b"HygonGenuine" {
+            // These features are available on AMD arch CPUs:
+            enable(extended_proc_info_ecx, 6, Feature::sse4a);
+            enable(extended_proc_info_ecx, 21, Feature::tbm);
+        }
+    }
+
+    value
+}
+
+#[cfg(test)]
+mod tests {
+    extern crate cupid;
+
+    #[test]
+    fn dump() {
+        println!("aes: {:?}", is_x86_feature_detected!("aes"));
+        println!("pclmulqdq: {:?}", is_x86_feature_detected!("pclmulqdq"));
+        println!("rdrand: {:?}", is_x86_feature_detected!("rdrand"));
+        println!("rdseed: {:?}", is_x86_feature_detected!("rdseed"));
+        println!("tsc: {:?}", is_x86_feature_detected!("tsc"));
+        println!("sse: {:?}", is_x86_feature_detected!("sse"));
+        println!("sse2: {:?}", is_x86_feature_detected!("sse2"));
+        println!("sse3: {:?}", is_x86_feature_detected!("sse3"));
+        println!("ssse3: {:?}", is_x86_feature_detected!("ssse3"));
+        println!("sse4.1: {:?}", is_x86_feature_detected!("sse4.1"));
+        println!("sse4.2: {:?}", is_x86_feature_detected!("sse4.2"));
+        println!("sse4a: {:?}", is_x86_feature_detected!("sse4a"));
+        println!("sha: {:?}", is_x86_feature_detected!("sha"));
+        println!("avx: {:?}", is_x86_feature_detected!("avx"));
+        println!("avx2: {:?}", is_x86_feature_detected!("avx2"));
+        println!("avx512f {:?}", is_x86_feature_detected!("avx512f"));
+        println!("avx512cd {:?}", is_x86_feature_detected!("avx512cd"));
+        println!("avx512er {:?}", is_x86_feature_detected!("avx512er"));
+        println!("avx512pf {:?}", is_x86_feature_detected!("avx512pf"));
+        println!("avx512bw {:?}", is_x86_feature_detected!("avx512bw"));
+        println!("avx512dq {:?}", is_x86_feature_detected!("avx512dq"));
+        println!("avx512vl {:?}", is_x86_feature_detected!("avx512vl"));
+        println!("avx512_ifma {:?}", is_x86_feature_detected!("avx512ifma"));
+        println!("avx512_vbmi {:?}", is_x86_feature_detected!("avx512vbmi"));
+        println!(
+            "avx512_vpopcntdq {:?}",
+            is_x86_feature_detected!("avx512vpopcntdq")
+        );
+        println!("fma: {:?}", is_x86_feature_detected!("fma"));
+        println!("abm: {:?}", is_x86_feature_detected!("abm"));
+        println!("bmi: {:?}", is_x86_feature_detected!("bmi1"));
+        println!("bmi2: {:?}", is_x86_feature_detected!("bmi2"));
+        println!("tbm: {:?}", is_x86_feature_detected!("tbm"));
+        println!("popcnt: {:?}", is_x86_feature_detected!("popcnt"));
+        println!("lzcnt: {:?}", is_x86_feature_detected!("lzcnt"));
+        println!("fxsr: {:?}", is_x86_feature_detected!("fxsr"));
+        println!("xsave: {:?}", is_x86_feature_detected!("xsave"));
+        println!("xsaveopt: {:?}", is_x86_feature_detected!("xsaveopt"));
+        println!("xsaves: {:?}", is_x86_feature_detected!("xsaves"));
+        println!("xsavec: {:?}", is_x86_feature_detected!("xsavec"));
+        println!("cmpxchg16b: {:?}", is_x86_feature_detected!("cmpxchg16b"));
+        println!("adx: {:?}", is_x86_feature_detected!("adx"));
+        println!("rtm: {:?}", is_x86_feature_detected!("rtm"));
+    }
+
+    #[test]
+    fn compare_with_cupid() {
+        let information = cupid::master().unwrap();
+        assert_eq!(is_x86_feature_detected!("aes"), information.aesni());
+        assert_eq!(is_x86_feature_detected!("pclmulqdq"), information.pclmulqdq());
+        assert_eq!(is_x86_feature_detected!("rdrand"), information.rdrand());
+        assert_eq!(is_x86_feature_detected!("rdseed"), information.rdseed());
+        assert_eq!(is_x86_feature_detected!("tsc"), information.tsc());
+        assert_eq!(is_x86_feature_detected!("sse"), information.sse());
+        assert_eq!(is_x86_feature_detected!("sse2"), information.sse2());
+        assert_eq!(is_x86_feature_detected!("sse3"), information.sse3());
+        assert_eq!(is_x86_feature_detected!("ssse3"), information.ssse3());
+        assert_eq!(is_x86_feature_detected!("sse4.1"), information.sse4_1());
+        assert_eq!(is_x86_feature_detected!("sse4.2"), information.sse4_2());
+        assert_eq!(is_x86_feature_detected!("sse4a"), information.sse4a());
+        assert_eq!(is_x86_feature_detected!("sha"), information.sha());
+        assert_eq!(is_x86_feature_detected!("avx"), information.avx());
+        assert_eq!(is_x86_feature_detected!("avx2"), information.avx2());
+        assert_eq!(is_x86_feature_detected!("avx512f"), information.avx512f());
+        assert_eq!(is_x86_feature_detected!("avx512cd"), information.avx512cd());
+        assert_eq!(is_x86_feature_detected!("avx512er"), information.avx512er());
+        assert_eq!(is_x86_feature_detected!("avx512pf"), information.avx512pf());
+        assert_eq!(is_x86_feature_detected!("avx512bw"), information.avx512bw());
+        assert_eq!(is_x86_feature_detected!("avx512dq"), information.avx512dq());
+        assert_eq!(is_x86_feature_detected!("avx512vl"), information.avx512vl());
+        assert_eq!(
+            is_x86_feature_detected!("avx512ifma"),
+            information.avx512_ifma()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("avx512vbmi"),
+            information.avx512_vbmi()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("avx512vpopcntdq"),
+            information.avx512_vpopcntdq()
+        );
+        assert_eq!(is_x86_feature_detected!("fma"), information.fma());
+        assert_eq!(is_x86_feature_detected!("bmi1"), information.bmi1());
+        assert_eq!(is_x86_feature_detected!("bmi2"), information.bmi2());
+        assert_eq!(is_x86_feature_detected!("popcnt"), information.popcnt());
+        assert_eq!(is_x86_feature_detected!("abm"), information.lzcnt());
+        assert_eq!(is_x86_feature_detected!("tbm"), information.tbm());
+        assert_eq!(is_x86_feature_detected!("lzcnt"), information.lzcnt());
+        assert_eq!(is_x86_feature_detected!("xsave"), information.xsave());
+        assert_eq!(is_x86_feature_detected!("xsaveopt"), information.xsaveopt());
+        assert_eq!(
+            is_x86_feature_detected!("xsavec"),
+            information.xsavec_and_xrstor()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("xsaves"),
+            information.xsaves_xrstors_and_ia32_xss()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("cmpxchg16b"),
+            information.cmpxchg16b(),
+        );
+        assert_eq!(
+            is_x86_feature_detected!("adx"),
+            information.adx(),
+        );
+        assert_eq!(
+            is_x86_feature_detected!("rtm"),
+            information.rtm(),
+        );
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_if/lib.rs b/src/tools/rustfmt/tests/source/cfg_if/lib.rs
new file mode 100644
index 0000000000000..8b3bb304f1c83
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/lib.rs
@@ -0,0 +1,49 @@
+//! Run-time feature detection for the Rust standard library.
+//!
+//! To detect whether a feature is enabled in the system running the binary
+//! use one of the appropriate macro for the target:
+//!
+//! * `x86` and `x86_64`: [`is_x86_feature_detected`]
+//! * `arm`: [`is_arm_feature_detected`]
+//! * `aarch64`: [`is_aarch64_feature_detected`]
+//! * `mips`: [`is_mips_feature_detected`]
+//! * `mips64`: [`is_mips64_feature_detected`]
+//! * `powerpc`: [`is_powerpc_feature_detected`]
+//! * `powerpc64`: [`is_powerpc64_feature_detected`]
+
+#![unstable(feature = "stdsimd", issue = "27731")]
+#![feature(const_fn, staged_api, stdsimd, doc_cfg, allow_internal_unstable)]
+#![allow(clippy::shadow_reuse)]
+#![deny(clippy::missing_inline_in_public_items)]
+#![cfg_attr(target_os = "linux", feature(linkage))]
+#![cfg_attr(all(target_os = "freebsd", target_arch = "aarch64"), feature(asm))]
+#![cfg_attr(stdsimd_strict, deny(warnings))]
+#![cfg_attr(test, allow(unused_imports))]
+#![no_std]
+
+#[macro_use]
+extern crate cfg_if;
+
+cfg_if! {
+    if #[cfg(feature = "std_detect_file_io")] {
+        #[cfg_attr(test, macro_use(println))]
+        extern crate std;
+
+        #[allow(unused_imports)]
+        use std::{arch, fs, io, mem, sync};
+    } else {
+        #[cfg(test)]
+        #[macro_use(println)]
+        extern crate std;
+
+        #[allow(unused_imports)]
+        use core::{arch, mem, sync};
+    }
+}
+
+#[cfg(feature = "std_detect_dlsym_getauxval")]
+extern crate libc;
+
+#[doc(hidden)]
+#[unstable(feature = "stdsimd", issue = "27731")]
+pub mod detect;
diff --git a/src/tools/rustfmt/tests/source/cfg_if/mod.rs b/src/tools/rustfmt/tests/source/cfg_if/mod.rs
new file mode 100644
index 0000000000000..b630e7ff383aa
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_if/mod.rs
@@ -0,0 +1,5 @@
+//! `std_detect`
+
+#[doc(hidden)] // unstable implementation detail
+#[unstable(feature = "stdsimd", issue = "27731")]
+pub mod detect;
diff --git a/src/tools/rustfmt/tests/source/cfg_mod/bar.rs b/src/tools/rustfmt/tests/source/cfg_mod/bar.rs
new file mode 100644
index 0000000000000..5b6b5f438370a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_mod/bar.rs
@@ -0,0 +1,3 @@
+fn bar( ) -> &str {
+"bar"
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_mod/dir/dir1/dir2/wasm32.rs b/src/tools/rustfmt/tests/source/cfg_mod/dir/dir1/dir2/wasm32.rs
new file mode 100644
index 0000000000000..0f8c0a3a7ac0f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_mod/dir/dir1/dir2/wasm32.rs
@@ -0,0 +1,6 @@
+fn
+    wasm32
+    () -> &str
+{
+    "wasm32"
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_mod/dir/dir1/dir3/wasm32.rs b/src/tools/rustfmt/tests/source/cfg_mod/dir/dir1/dir3/wasm32.rs
new file mode 100644
index 0000000000000..0f8c0a3a7ac0f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_mod/dir/dir1/dir3/wasm32.rs
@@ -0,0 +1,6 @@
+fn
+    wasm32
+    () -> &str
+{
+    "wasm32"
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_mod/foo.rs b/src/tools/rustfmt/tests/source/cfg_mod/foo.rs
new file mode 100644
index 0000000000000..de4ce55ef6ff1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_mod/foo.rs
@@ -0,0 +1,4 @@
+fn foo( )
+         -> &str {
+    "foo"
+}
diff --git a/src/tools/rustfmt/tests/source/cfg_mod/mod.rs b/src/tools/rustfmt/tests/source/cfg_mod/mod.rs
new file mode 100644
index 0000000000000..45ba86f11b3f5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_mod/mod.rs
@@ -0,0 +1,10 @@
+#[cfg_attr(feature = "foo", path = "foo.rs")]
+#[cfg_attr(not(feture = "foo"), path = "bar.rs")]
+mod sub_mod;
+
+#[cfg_attr(target_arch = "wasm32", path = "dir/dir1/dir2/wasm32.rs")]
+#[cfg_attr(not(target_arch = "wasm32"), path = "dir/dir1/dir3/wasm32.rs")]
+mod wasm32;
+
+#[some_attr(path = "somewhere.rs")]
+mod other;
diff --git a/src/tools/rustfmt/tests/source/cfg_mod/other.rs b/src/tools/rustfmt/tests/source/cfg_mod/other.rs
new file mode 100644
index 0000000000000..0b5c04d219202
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_mod/other.rs
@@ -0,0 +1 @@
+fn other() -> &str { "other"}
diff --git a/src/tools/rustfmt/tests/source/cfg_mod/wasm32.rs b/src/tools/rustfmt/tests/source/cfg_mod/wasm32.rs
new file mode 100644
index 0000000000000..3741e53fd4e8e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/cfg_mod/wasm32.rs
@@ -0,0 +1,4 @@
+fn
+    wasm32() -> &str {
+        "wasm32"
+    }
diff --git a/src/tools/rustfmt/tests/source/chains-visual.rs b/src/tools/rustfmt/tests/source/chains-visual.rs
new file mode 100644
index 0000000000000..20a96311e3414
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/chains-visual.rs
@@ -0,0 +1,158 @@
+// rustfmt-indent_style: Visual
+// Test chain formatting.
+
+fn main() {
+    // Don't put chains on a single line if it wasn't so in source.
+    let a = b .c
+    .d.1
+                .foo(|x| x + 1);
+
+    bbbbbbbbbbbbbbbbbbb.ccccccccccccccccccccccccccccccccccccc
+                       .ddddddddddddddddddddddddddd();
+
+    bbbbbbbbbbbbbbbbbbb.ccccccccccccccccccccccccccccccccccccc.ddddddddddddddddddddddddddd.eeeeeeee();
+
+    // Test case where first chain element isn't a path, but is shorter than
+    // the size of a tab.
+    x()
+        .y(|| match cond() { true => (), false => () });
+
+    loong_func()
+        .quux(move || if true {
+            1
+        } else {
+            2
+        });
+
+    some_fuuuuuuuuunction()
+        .method_call_a(aaaaa, bbbbb, |c| {
+            let x = c;
+            x
+        });
+
+    some_fuuuuuuuuunction().method_call_a(aaaaa, bbbbb, |c| {
+        let x = c;
+        x
+    }).method_call_b(aaaaa, bbbbb, |c| {
+        let x = c;
+        x
+    });
+
+    fffffffffffffffffffffffffffffffffff(a,
+                                        {
+                                            SCRIPT_TASK_ROOT
+                                            .with(|root| {
+                                                *root.borrow_mut()  =   Some(&script_task);
+                                            });
+                                        });                                        
+
+    let suuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuum = xxxxxxx
+        .map(|x| x + 5)
+        .map(|x| x / 2)
+        .fold(0, |acc, x| acc + x);
+
+    aaaaaaaaaaaaaaaa.map(|x| {
+                         x += 1;
+                         x
+                     }).filter(some_mod::some_filter)
+}
+
+fn floaters() {
+    let z = Foo {
+        field1: val1,
+        field2: val2,
+    };
+
+    let x = Foo {
+        field1: val1,
+        field2: val2,
+    }.method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                    Some(d) => d as usize - 1,
+                    None => return Err("bad param number".to_owned()),
+                }]
+                               .clone());
+            }
+        }
+    }
+
+    if cond { some(); } else { none(); }
+        .bar()
+        .baz();
+
+    Foo { x: val } .baz(|| { force(); multiline();    }) .quux(); 
+
+    Foo { y: i_am_multi_line, z: ok }
+        .baz(|| {
+            force(); multiline();
+        })
+        .quux(); 
+
+    a + match x { true => "yay!", false => "boo!" }.bar()
+}
+
+fn is_replaced_content() -> bool {
+    constellat.send(ConstellationMsg::ViewportConstrained(
+            self.id, constraints)).unwrap();
+}
+
+fn issue587() {
+    a.b::<()>(c);
+
+    std::mem::transmute(dl.symbol::<()>("init").unwrap())
+}
+
+fn issue_1389() {
+    let names = String::from_utf8(names)?.split('|').map(str::to_owned).collect();
+}
+
+fn issue1217() -> Result<Mnemonic, Error> {
+let random_chars: String = OsRng::new()?
+    .gen_ascii_chars()
+    .take(self.bit_length)
+    .collect();
+
+    Ok(Mnemonic::new(&random_chars))
+}
+
+fn issue1236(options: Vec<String>) -> Result<Option<String>> {
+let process = Command::new("dmenu").stdin(Stdio::piped())
+    .stdout(Stdio::piped())
+    .spawn()
+    .chain_err(|| "failed to spawn dmenu")?;
+}
+
+fn issue1434() {
+    for _ in 0..100 {
+        let prototype_id = PrototypeIdData::from_reader::<_, B>(&mut self.file_cursor).chain_err(|| {
+            format!("could not read prototype ID at offset {:#010x}",
+                    current_offset)
+        })?;
+    }
+}
+
+fn issue2264() {
+    {
+        something.function()
+            .map(|| {
+                if let a_very_very_very_very_very_very_very_very_long_variable =
+                    compute_this_variable()
+                {
+                    println!("Hello");
+                }
+            })
+            .collect();
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/chains.rs b/src/tools/rustfmt/tests/source/chains.rs
new file mode 100644
index 0000000000000..c77f5bac4cb21
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/chains.rs
@@ -0,0 +1,266 @@
+// rustfmt-use_small_heuristics: Off
+// Test chain formatting.
+
+fn main() {
+    let a = b .c
+    .d.1
+                .foo(|x| x + 1);
+
+    bbbbbbbbbbbbbbbbbbb.ccccccccccccccccccccccccccccccccccccc
+                       .ddddddddddddddddddddddddddd();
+
+    bbbbbbbbbbbbbbbbbbb.ccccccccccccccccccccccccccccccccccccc.ddddddddddddddddddddddddddd.eeeeeeee();
+
+    let f = fooooooooooooooooooooooooooooooooooooooooooooooooooo.baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaar;
+
+    // Test case where first chain element isn't a path, but is shorter than
+    // the size of a tab.
+    x()
+        .y(|| match cond() { true => (), false => () });
+
+    loong_func()
+        .quux(move || if true {
+            1
+        } else {
+            2
+        });
+
+    some_fuuuuuuuuunction()
+        .method_call_a(aaaaa, bbbbb, |c| {
+            let x = c;
+            x
+        });
+
+    some_fuuuuuuuuunction().method_call_a(aaaaa, bbbbb, |c| {
+        let x = c;
+        x
+    }).method_call_b(aaaaa, bbbbb, |c| {
+        let x = c;
+        x
+    });
+
+    fffffffffffffffffffffffffffffffffff(a,
+                                        {
+                                            SCRIPT_TASK_ROOT
+                                            .with(|root| {
+                                                *root.borrow_mut()  =   Some(&script_task);
+                                            });
+                                        });                                        
+
+    let suuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuum = xxxxxxx
+        .map(|x| x + 5)
+        .map(|x| x / 2)
+        .fold(0, |acc, x| acc + x);
+
+    body.fold(Body::new(), |mut body, chunk| {
+        body.extend(chunk);
+        Ok(body)
+    }).and_then(move |body| {
+            let req = Request::from_parts(parts, body);
+            f(req).map_err(|_| io::Error::new(io::ErrorKind::Other, ""))
+        });
+
+    aaaaaaaaaaaaaaaa.map(|x| {
+                         x += 1;
+                         x
+                     }).filter(some_mod::some_filter)
+}
+
+fn floaters() {
+    let z = Foo {
+        field1: val1,
+        field2: val2,
+    };
+
+    let x = Foo {
+        field1: val1,
+        field2: val2,
+    }.method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                    Some(d) => d as usize - 1,
+                    None => return Err("bad param number".to_owned()),
+                }]
+                               .clone());
+            }
+        }
+    }
+
+    if cond { some(); } else { none(); }
+        .bar()
+        .baz();
+
+    Foo { x: val } .baz(|| { force(); multiline();    }) .quux(); 
+
+    Foo { y: i_am_multi_line, z: ok }
+        .baz(|| {
+            force(); multiline();
+        })
+        .quux(); 
+
+    a + match x { true => "yay!", false => "boo!" }.bar()
+}
+
+fn is_replaced_content() -> bool {
+    constellat.send(ConstellationMsg::ViewportConstrained(
+            self.id, constraints)).unwrap();
+}
+
+fn issue587() {
+    a.b::<()>(c);
+
+    std::mem::transmute(dl.symbol::<()>("init").unwrap())
+}
+
+fn try_shorthand() {
+    let x = expr?;
+    let y = expr.kaas()?.test();
+    let loooooooooooooooooooooooooooooooooooooooooong = does_this?.look?.good?.should_we_break?.after_the_first_question_mark?;
+    let yyyy = expr?.another?.another?.another?.another?.another?.another?.another?.another?.test();
+    let zzzz = expr?.another?.another?.another?.another?;
+    let aaa =  x ????????????  ?????????????? ???? ?????  ?????????????? ?????????  ?????????????? ??;
+
+    let y = a.very .loooooooooooooooooooooooooooooooooooooong()  .chain()
+             .inside()          .weeeeeeeeeeeeeee()? .test()  .0
+        .x;
+
+                parameterized(f,
+                              substs,
+                              def_id,
+                              Ns::Value,
+                              &[],
+                              |tcx| tcx.lookup_item_type(def_id).generics)?;
+    fooooooooooooooooooooooooooo()?.bar()?.baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaz()?;
+}
+
+fn issue_1004() {
+         match *self {
+                ty::ImplOrTraitItem::MethodTraitItem(ref i) => write!(f, "{:?}", i),
+                ty::ImplOrTraitItem::ConstTraitItem(ref i) => write!(f, "{:?}", i),
+                ty::ImplOrTraitItem::TypeTraitItem(ref i) => write!(f, "{:?}", i),
+            }
+            ?;
+
+            ty::tls::with(|tcx| {
+                let tap = ty::Binder(TraitAndProjections(principal, projections));
+                in_binder(f, tcx, &ty::Binder(""), Some(tap))
+            })
+            ?;
+}
+
+fn issue1392() {
+    test_method(r#"
+        if foo {
+            a();
+        }
+        else {
+            b();
+        }
+        "#.trim());
+}
+
+// #2067
+impl Settings {
+    fn save(&self) -> Result<()> {
+        let mut file = File::create(&settings_path).chain_err(|| ErrorKind::WriteError(settings_path.clone()))?;
+    }
+}
+
+fn issue2126() {
+    {
+        {
+            {
+                {
+                    {
+                        let x = self.span_from(sub_span.expect("No span found for struct arant variant"));
+                        self.sspanpan_from_span(sub_span.expect("No span found for struct variant"));
+                        let x = self.spanpan_from_span(sub_span.expect("No span found for struct variant"))?;
+                    }
+                }
+            }
+        }
+    }
+}
+
+// #2200
+impl Foo {
+    pub fn from_ast(diagnostic: &::errors::Handler,
+                    attrs: &[ast::Attribute]) -> Attributes {
+        let other_attrs = attrs.iter().filter_map(|attr| {
+            attr.with_desugared_doc(|attr| {
+                if attr.check_name("doc") {
+                    if let Some(mi) = attr.meta() {
+                        if let Some(value) = mi.value_str() {
+                            doc_strings.push(DocFragment::Include(line,
+                                                                  attr.span,
+                                                                  filename,
+                                                                  contents));
+                        }
+                    }
+                }
+            })
+        }).collect();
+    }
+}
+
+// #2415
+// Avoid orphan in chain
+fn issue2415() {
+    let base_url = (|| {
+        // stuff
+
+        Ok((|| {
+            // stuff
+            Some(value.to_string())
+        })()
+           .ok_or("")?)
+    })()
+        .unwrap_or_else(|_: Box<::std::error::Error>| String::from(""));
+}
+
+impl issue_2786 {
+    fn thing(&self) {
+        foo(|a| {
+            println!("a");
+            println!("b");
+        }).bar(|c| {
+            println!("a");
+            println!("b");
+        })
+            .baz(|c| {
+                println!("a");
+                println!("b");
+            })
+    }
+}
+
+fn issue_2773() {
+    let bar = Some(0);
+    bar.or_else(|| {
+        // do stuff
+        None
+    }).or_else(|| {
+            // do other stuff
+            None
+        })
+        .and_then(|val| {
+            // do this stuff
+            None
+        });
+}
+
+fn issue_3034() {
+    disallowed_headers.iter().any(|header| *header == name) ||
+        disallowed_header_prefixes.iter().any(|prefix| name.starts_with(prefix))
+}
diff --git a/src/tools/rustfmt/tests/source/chains_with_comment.rs b/src/tools/rustfmt/tests/source/chains_with_comment.rs
new file mode 100644
index 0000000000000..91160711b8909
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/chains_with_comment.rs
@@ -0,0 +1,121 @@
+// Chains with comment.
+
+fn main() {
+    let x = y // comment
+        .z;
+
+    foo // foo
+        // comment after parent
+        .x
+        .y
+        // comment 1
+        .bar() // comment after bar()
+  // comment 2
+        .foobar
+  // comment after
+        // comment 3
+        .baz(x, y, z);
+
+    self.rev_dep_graph
+        .iter()
+       // Remove nodes that are not dirty
+        .filter(|&(unit, _)| dirties.contains(&unit))
+     // Retain only dirty dependencies of the ones that are dirty
+       .map(|(k, deps)| {
+            (
+                k.clone(),
+                deps.iter()
+                .cloned()
+               .filter(|d| dirties.contains(&d))
+              .collect(),
+            )
+        });
+
+    let y = expr /* comment */.kaas()?
+// comment
+       .test();
+    let loooooooooooooooooooooooooooooooooooooooooong = does_this?.look?.good?.should_we_break?.after_the_first_question_mark?;
+    let zzzz = expr?   // comment after parent
+// comment 0
+.another??? // comment 1
+.another????  // comment 2
+.another? // comment 3
+.another?;
+
+    let y = a.very .loooooooooooooooooooooooooooooooooooooong() /* comment */ .chain()
+        .inside()  /* comment */        .weeeeeeeeeeeeeee()? .test()  .0
+        .x;
+
+    parameterized(f,
+                  substs,
+                  def_id,
+                  Ns::Value,
+                  &[],
+                  |tcx| tcx.lookup_item_type(def_id).generics)?;
+    fooooooooooooooooooooooooooo()?.bar()?.baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaz()?;
+
+    // #2559
+    App::new("cargo-cache")
+.version(crate_version!())
+.bin_name("cargo")
+.about("Manage cargo cache")
+.author("matthiaskrgr")
+.subcommand(
+SubCommand::with_name("cache")
+.version(crate_version!())
+.bin_name("cargo-cache")
+.about("Manage cargo cache")
+.author("matthiaskrgr")
+.arg(&list_dirs)
+.arg(&remove_dir)
+.arg(&gc_repos)
+.arg(&info)
+.arg(&keep_duplicate_crates)    .arg(&dry_run)
+.arg(&auto_clean)
+.arg(&auto_clean_expensive),
+        ) // subcommand
+        .arg(&list_dirs);
+}
+
+// #2177
+impl Foo {
+    fn dirty_rev_dep_graph(
+        &self,
+        dirties: &HashSet<UnitKey>,
+    ) -> HashMap<UnitKey, HashSet<UnitKey>> {
+        let dirties = self.transitive_dirty_units(dirties);
+        trace!("transitive_dirty_units: {:?}", dirties);
+
+        self.rev_dep_graph.iter()
+        // Remove nodes that are not dirty
+            .filter(|&(unit, _)| dirties.contains(&unit))
+        // Retain only dirty dependencies of the ones that are dirty
+            .map(|(k, deps)| (k.clone(), deps.iter().cloned().filter(|d| dirties.contains(&d)).collect()))
+    }
+}
+
+// #2907
+fn foo() {
+    let x = foo
+        .bar??  ? // comment
+        .baz;
+    let x = foo
+        .bar?  ??
+    // comment
+        .baz;
+    let x = foo
+        .bar? ? ? // comment
+    // comment
+        .baz;
+    let x = foo
+        .bar? ?? // comment
+    // comment
+        ? ??
+    // comment
+        ?  ??
+    // comment
+        ???  
+    // comment
+        ? ? ?
+        .baz;
+}
diff --git a/src/tools/rustfmt/tests/source/closure-block-inside-macro.rs b/src/tools/rustfmt/tests/source/closure-block-inside-macro.rs
new file mode 100644
index 0000000000000..b3ddfb51263b4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/closure-block-inside-macro.rs
@@ -0,0 +1,9 @@
+// #1547
+fuzz_target!(|data: &[u8]| if let Some(first) = data.first() {
+    let index = *first as usize;
+    if index >= ENCODINGS.len() {
+        return;
+    }
+    let encoding = ENCODINGS[index];
+    dispatch_test(encoding, &data[1..]);
+});
diff --git a/src/tools/rustfmt/tests/source/closure.rs b/src/tools/rustfmt/tests/source/closure.rs
new file mode 100644
index 0000000000000..e93cc3fb40f59
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/closure.rs
@@ -0,0 +1,213 @@
+// rustfmt-normalize_comments: true
+// Closures
+
+fn main() {
+    let square = ( |i:  i32 | i  *  i );
+
+    let commented = |/* first */ a /*argument*/, /* second*/ b: WithType /* argument*/, /* ignored */ _ |
+        (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb);
+
+    let block_body = move   |xxxxxxxxxxxxxxxxxxxxxxxxxxxxx,  ref  yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy| {
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxx + yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
+        };
+
+    let loooooooooooooong_name = |field| {
+             // format comments.
+             if field.node.attrs.len() > 0 { field.node.attrs[0].span.lo()
+             } else {
+                 field.span.lo()
+             }};
+
+    let unblock_me = |trivial| {
+                         closure()
+                     };
+
+    let empty = |arg|    {};
+
+    let simple = |arg| { /*  comment formatting */ foo(arg) };
+
+    let test = |  | { do_something(); do_something_else(); };
+
+    let arg_test = |big_argument_name, test123| looooooooooooooooooong_function_naaaaaaaaaaaaaaaaame();
+
+    let arg_test = |big_argument_name, test123| {looooooooooooooooooong_function_naaaaaaaaaaaaaaaaame()};
+
+    let simple_closure = move ||   ->  () {};
+
+    let closure = |input: Ty| -> Option<String> {
+        foo()
+    };
+
+    let closure_with_return_type = |aaaaaaaaaaaaaaaaaaaaaaarg1, aaaaaaaaaaaaaaaaaaaaaaarg2| -> Strong { "sup".to_owned() };
+
+    |arg1, arg2, _, _, arg3, arg4| { let temp = arg4 + arg3;
+                                     arg2 * arg1 - temp };
+
+    let block_body_with_comment = args.iter()
+        .map(|a| {
+            // Emitting only dep-info is possible only for final crate type, as
+            // as others may emit required metadata for dependent crate types
+            if a.starts_with("--emit") && is_final_crate_type && !self.workspace_mode {
+                "--emit=dep-info"
+            } else { a }
+        });
+}
+
+fn issue311() {
+    let func = |x| println!("{}", x);
+
+    (func)(0.0);
+}
+
+fn issue863() {
+    let closure = |x| match x {
+        0 => true,
+        _ => false,
+    } == true;
+}
+
+fn issue934() {
+    let hash: &Fn(&&Block) -> u64 = &|block| -> u64 {
+        let mut h = SpanlessHash::new(cx);
+        h.hash_block(block);
+        h.finish()
+    };
+
+    let hash: &Fn(&&Block) -> u64 = &|block| -> u64 {
+        let mut h = SpanlessHash::new(cx);
+        h.hash_block(block);
+        h.finish();
+    };
+}
+
+impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
+    pub fn eq_expr(&self, left: &Expr, right: &Expr) -> bool {
+        match (&left.node, &right.node) {
+            (&ExprBinary(l_op, ref ll, ref lr), &ExprBinary(r_op, ref rl, ref rr)) => {
+                l_op.node == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr) ||
+                swap_binop(l_op.node, ll, lr).map_or(false, |(l_op, ll, lr)| l_op == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr))
+            }
+        }
+    }
+}
+
+fn foo() {
+    lifetimes_iter___map(|lasdfasfd| {
+        let hi = if l.bounds.is_empty() {
+            l.lifetime.span.hi()
+        };
+    });
+}
+
+fn issue1405() {
+    open_raw_fd(fd, b'r')
+        .and_then(|file| Capture::new_raw(None, |_, err| unsafe {
+            raw::pcap_fopen_offline(file, err)
+        }));
+}
+
+fn issue1466() {
+    let vertex_buffer = frame.scope(|ctx| {
+        let buffer =
+            ctx.create_host_visible_buffer::<VertexBuffer<Vertex>>(&vertices);
+        ctx.create_device_local_buffer(buffer)
+    });
+}
+
+fn issue470() {
+    {{{
+        let explicit_arg_decls =
+            explicit_arguments.into_iter()
+            .enumerate()
+            .map(|(index, (ty, pattern))| {
+                let lvalue = Lvalue::Arg(index as u32);
+                block = this.pattern(block,
+                                     argument_extent,
+                                     hair::PatternRef::Hair(pattern),
+                                     &lvalue);
+                ArgDecl { ty: ty }
+            });
+    }}}
+}
+
+// #1509
+impl Foo {
+    pub fn bar(&self) {
+        Some(SomeType {
+            push_closure_out_to_100_chars: iter(otherwise_it_works_ok.into_iter().map(|f| {
+                Ok(f)
+            })),
+        })
+    }
+}
+
+fn issue1329() {
+    aaaaaaaaaaaaaaaa.map(|x| {
+        x += 1;
+        x
+    })
+        .filter
+}
+
+fn issue325() {
+    let f = || unsafe { xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx };
+}
+
+fn issue1697() {
+    Test.func_a(A_VERY_LONG_CONST_VARIABLE_NAME, move |arg1, arg2, arg3, arg4| arg1 + arg2 + arg3 + arg4)
+}
+
+fn issue1694() {
+    foooooo(|_referencefffffffff: _, _target_reference: _, _oid: _, _target_oid: _| format!("refs/pull/{}/merge", pr_id))
+}
+
+fn issue1713() {
+    rayon::join(
+        || recurse(left, is_less, pred, limit),
+        || recurse(right, is_less, Some(pivot), limit),
+    );
+
+    rayon::join(
+        1,
+        || recurse(left, is_less, pred, limit),
+        2,
+        || recurse(right, is_less, Some(pivot), limit),
+    );
+}
+
+fn issue2063() {
+    |ctx: Ctx<(String, String)>| -> io::Result<Response> {
+        Ok(Response::new().with_body(ctx.params.0))
+    }
+}
+
+fn issue1524() {
+    let f = |x| {{{{x}}}};
+    let f = |x| {{{x}}};
+    let f = |x| {{x}};
+    let f = |x| {x};
+    let f = |x| x;
+}
+
+fn issue2171() {
+    foo(|| unsafe {
+        if PERIPHERALS {
+            loop {}
+        } else {
+            PERIPHERALS = true;
+        }
+    })
+}
+
+fn issue2207() {
+    a.map(|_| unsafe {
+        a_very_very_very_very_very_very_very_long_function_name_or_anything_else()
+    }.to_string())
+}
+
+fn issue2262() {
+    result.init(&mut result.slave.borrow_mut(), &mut (result.strategy)()).map_err(|factory| Error {
+        factory,
+        slave: None,
+    })?;
+}
diff --git a/src/tools/rustfmt/tests/source/comment.rs b/src/tools/rustfmt/tests/source/comment.rs
new file mode 100644
index 0000000000000..b6ce5267fcb1d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/comment.rs
@@ -0,0 +1,90 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+//! Doc comment
+fn test() {
+            /*!
+             * Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam */
+
+// comment
+        // comment2
+
+    code(); /* leave this comment alone!
+             * ok? */
+
+        /* Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a
+         * diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+         * viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+         * Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam
+         * tincidunt congue enim, ut porta lorem lacinia consectetur. Donec ut
+         * libero sed arcu vehicula ultricies a non tortor. Lorem ipsum dolor sit
+         * amet, consectetur adipiscing elit. Aenean ut gravida lorem. Ut turpis
+         * felis, pulvinar a semper sed, adipiscing id dolor. */
+
+    // Very looooooooooooooooooooooooooooooooooooooooooooooooooooooooong comment that should be split
+
+                    // println!("{:?}", rewrite_comment(subslice,
+                    //                                       false,
+                    //                                       comment_width,
+                    //                                       self.block_indent,
+                    //                                       self.config)
+                    //                           .unwrap());
+
+    funk(); //dontchangeme
+            // or me
+
+    // #1388
+    const EXCEPTION_PATHS: &'static [&'static str] =
+        &[// std crates
+          "src/libstd/sys/", // Platform-specific code for std lives here.
+          "src/bootstrap"];
+}
+
+  /// test123
+fn doc_comment() {
+}
+
+fn chains() {
+                foo.bar(|| { 
+                let x = 10;
+                /* comment */ x })
+}
+
+fn issue_1086() {
+    /**/
+}
+
+/*
+ * random comment */
+
+fn main() {/* Test */}
+
+// #1643
+fn some_fn() /* some comment */
+{
+}
+
+fn some_fn1()
+// some comment
+{
+}
+
+fn some_fn2() // some comment
+{
+}
+
+fn some_fn3() /* some comment some comment some comment some comment some comment some comment so */
+{
+}
+
+fn some_fn4()
+/* some comment some comment some comment some comment some comment some comment some comment */
+{
+}
+
+// #1603
+pub enum Foo {
+    A, // `/** **/`
+    B, // `/*!`
+    C,
+}
diff --git a/src/tools/rustfmt/tests/source/comment2.rs b/src/tools/rustfmt/tests/source/comment2.rs
new file mode 100644
index 0000000000000..d68bb5483dc83
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/comment2.rs
@@ -0,0 +1,4 @@
+// rustfmt-wrap_comments: true
+
+/// This is a long line that angers rustfmt. Rustfmt shall deal with it swiftly and justly.
+pub mod foo {}
diff --git a/src/tools/rustfmt/tests/source/comment3.rs b/src/tools/rustfmt/tests/source/comment3.rs
new file mode 100644
index 0000000000000..f19a858633447
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/comment3.rs
@@ -0,0 +1,5 @@
+// rustfmt-wrap_comments: true
+
+//! This is a long line that angers rustfmt. Rustfmt shall deal with it swiftly and justly.
+
+pub mod foo {}
diff --git a/src/tools/rustfmt/tests/source/comment4.rs b/src/tools/rustfmt/tests/source/comment4.rs
new file mode 100644
index 0000000000000..f53a8a4a1fe02
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/comment4.rs
@@ -0,0 +1,52 @@
+#![allow(dead_code)] // bar
+
+//! Doc comment
+fn test() {
+// comment
+        // comment2
+
+    code(); /* leave this comment alone!
+             * ok? */
+
+        /* Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a
+         * diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+         * viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+         * Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam
+         * tincidunt congue enim, ut porta lorem lacinia consectetur. Donec ut
+         * libero sed arcu vehicula ultricies a non tortor. Lorem ipsum dolor sit
+         * amet, consectetur adipiscing elit. Aenean ut gravida lorem. Ut turpis
+         * felis, pulvinar a semper sed, adipiscing id dolor. */
+
+    // Very loooooooooooooooooooooooooooooooooooooooooooooooooooooooong comment that should be split
+
+                    // println!("{:?}", rewrite_comment(subslice,
+                    //                                       false,
+                    //                                       comment_width,
+                    //                                       self.block_indent,
+                    //                                       self.config)
+                    //                           .unwrap());
+
+    funk(); //dontchangeme
+            // or me
+}
+
+  /// test123
+fn doc_comment() {
+}
+
+/*
+Regression test for issue #956
+
+(some very important text)
+*/
+
+/*
+fn debug_function() {
+    println!("hello");
+}
+// */
+
+#[link_section=".vectors"]
+#[no_mangle] // Test this attribute is preserved.
+#[cfg_attr(rustfmt, rustfmt::skip)]
+pub static ISSUE_1284: [i32; 16] = [];
diff --git a/src/tools/rustfmt/tests/source/comment5.rs b/src/tools/rustfmt/tests/source/comment5.rs
new file mode 100644
index 0000000000000..2835d8b257856
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/comment5.rs
@@ -0,0 +1,14 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+//@ special comment
+//@ Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec adiam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+//@
+//@foo
+fn test() {}
+
+//@@@ another special comment
+//@@@ Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec adiam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+//@@@
+//@@@foo
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/source/comment6.rs b/src/tools/rustfmt/tests/source/comment6.rs
new file mode 100644
index 0000000000000..e5d72113ce61f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/comment6.rs
@@ -0,0 +1,10 @@
+// rustfmt-wrap_comments: true
+
+// Pendant la nuit du 9 mars 1860, les nuages, se confondant avec la mer, limitaient à quelques brasses la portée de la vue.
+// Sur cette mer démontée, dont les lames déferlaient en projetant des lueurs livides, un léger bâtiment fuyait presque à sec de toile.
+
+pub mod foo {}
+
+// ゆく河の流れは絶えずして、しかももとの水にあらず。淀みに浮かぶうたかたは、かつ消えかつ結びて、久しくとどまりたるためしなし。世の中にある人とすみかと、またかくのごとし。
+
+pub mod bar {}
diff --git a/src/tools/rustfmt/tests/source/comment_crlf_newline.rs b/src/tools/rustfmt/tests/source/comment_crlf_newline.rs
new file mode 100644
index 0000000000000..7a65f762f6c92
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/comment_crlf_newline.rs
@@ -0,0 +1,4 @@
+// rustfmt-normalize_comments: true
+/* Block comments followed by CRLF newlines should not an extra newline at the end */
+
+/* Something else */
diff --git a/src/tools/rustfmt/tests/source/configs/blank_lines_lower_bound/1.rs b/src/tools/rustfmt/tests/source/configs/blank_lines_lower_bound/1.rs
new file mode 100644
index 0000000000000..c6058a55b0aee
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/blank_lines_lower_bound/1.rs
@@ -0,0 +1,13 @@
+// rustfmt-blank_lines_lower_bound: 1
+
+fn foo() {}
+fn bar() {}
+// comment
+fn foobar() {}
+
+fn foo1() {}
+fn bar1() {}
+
+// comment
+
+fn foobar1() {}
diff --git a/src/tools/rustfmt/tests/source/configs/brace_style/fn_always_next_line.rs b/src/tools/rustfmt/tests/source/configs/brace_style/fn_always_next_line.rs
new file mode 100644
index 0000000000000..d3bd9ac09aa6d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/brace_style/fn_always_next_line.rs
@@ -0,0 +1,14 @@
+// rustfmt-brace_style: AlwaysNextLine
+// Function brace style
+
+fn lorem() {
+    // body
+}
+
+fn lorem(ipsum: usize) {
+    // body
+}
+
+fn lorem<T>(ipsum: T) where T: Add + Sub + Mul + Div {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/brace_style/fn_prefer_same_line.rs b/src/tools/rustfmt/tests/source/configs/brace_style/fn_prefer_same_line.rs
new file mode 100644
index 0000000000000..78a4495243d88
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/brace_style/fn_prefer_same_line.rs
@@ -0,0 +1,14 @@
+// rustfmt-brace_style: PreferSameLine
+// Function brace style
+
+fn lorem() {
+    // body
+}
+
+fn lorem(ipsum: usize) {
+    // body
+}
+
+fn lorem<T>(ipsum: T) where T: Add + Sub + Mul + Div {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/brace_style/fn_same_line_where.rs b/src/tools/rustfmt/tests/source/configs/brace_style/fn_same_line_where.rs
new file mode 100644
index 0000000000000..3b78932e1776a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/brace_style/fn_same_line_where.rs
@@ -0,0 +1,14 @@
+// rustfmt-brace_style: SameLineWhere
+// Function brace style
+
+fn lorem() {
+    // body
+}
+
+fn lorem(ipsum: usize) {
+    // body
+}
+
+fn lorem<T>(ipsum: T) where T: Add + Sub + Mul + Div {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/brace_style/item_always_next_line.rs b/src/tools/rustfmt/tests/source/configs/brace_style/item_always_next_line.rs
new file mode 100644
index 0000000000000..0cc19b34da7ef
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/brace_style/item_always_next_line.rs
@@ -0,0 +1,20 @@
+// rustfmt-brace_style: AlwaysNextLine
+// Item brace style
+
+enum Foo {}
+
+struct Bar {}
+
+struct Lorem {
+    ipsum: bool,
+}
+
+struct Dolor<T> where T: Eq {
+    sit: T,
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/brace_style/item_prefer_same_line.rs b/src/tools/rustfmt/tests/source/configs/brace_style/item_prefer_same_line.rs
new file mode 100644
index 0000000000000..4412bc869a268
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/brace_style/item_prefer_same_line.rs
@@ -0,0 +1,16 @@
+// rustfmt-brace_style: PreferSameLine
+// Item brace style
+
+struct Lorem {
+    ipsum: bool,
+}
+
+struct Dolor<T> where T: Eq {
+    sit: T,
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/brace_style/item_same_line_where.rs b/src/tools/rustfmt/tests/source/configs/brace_style/item_same_line_where.rs
new file mode 100644
index 0000000000000..b8e69147dc5a8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/brace_style/item_same_line_where.rs
@@ -0,0 +1,16 @@
+// rustfmt-brace_style: SameLineWhere
+// Item brace style
+
+struct Lorem {
+    ipsum: bool,
+}
+
+struct Dolor<T> where T: Eq {
+    sit: T,
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/chain_width/always.rs b/src/tools/rustfmt/tests/source/configs/chain_width/always.rs
new file mode 100644
index 0000000000000..2d16d66aec12d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/chain_width/always.rs
@@ -0,0 +1,23 @@
+// rustfmt-chain_width: 1
+// setting an unachievable chain_width to always get chains
+// on separate lines
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should be left alone
+    test.blorp();
+
+    // should be wrapped
+    test.blorp().blorp();
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+}
diff --git a/src/tools/rustfmt/tests/source/configs/chain_width/small.rs b/src/tools/rustfmt/tests/source/configs/chain_width/small.rs
new file mode 100644
index 0000000000000..26f9354537a35
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/chain_width/small.rs
@@ -0,0 +1,23 @@
+// rustfmt-chain_width: 40
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+
+    // should be wrapped
+    test.blorp().blorp().blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp().blorp().blorp();
+}
diff --git a/src/tools/rustfmt/tests/source/configs/chain_width/tiny.rs b/src/tools/rustfmt/tests/source/configs/chain_width/tiny.rs
new file mode 100644
index 0000000000000..fffc81dd5d6da
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/chain_width/tiny.rs
@@ -0,0 +1,21 @@
+// rustfmt-chain_width: 20
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+
+    // should be wrapped
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+}
diff --git a/src/tools/rustfmt/tests/source/configs/comment_width/above.rs b/src/tools/rustfmt/tests/source/configs/comment_width/above.rs
new file mode 100644
index 0000000000000..36187ce0af4cb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/comment_width/above.rs
@@ -0,0 +1,7 @@
+// rustfmt-comment_width: 40
+// rustfmt-wrap_comments: true
+// Comment width
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+}
diff --git a/src/tools/rustfmt/tests/source/configs/comment_width/below.rs b/src/tools/rustfmt/tests/source/configs/comment_width/below.rs
new file mode 100644
index 0000000000000..abbc5930c4ce1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/comment_width/below.rs
@@ -0,0 +1,7 @@
+// rustfmt-comment_width: 80
+// rustfmt-wrap_comments: true
+// Comment width
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+}
diff --git a/src/tools/rustfmt/tests/source/configs/comment_width/ignore.rs b/src/tools/rustfmt/tests/source/configs/comment_width/ignore.rs
new file mode 100644
index 0000000000000..c86e71c28981b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/comment_width/ignore.rs
@@ -0,0 +1,7 @@
+// rustfmt-comment_width: 40
+// rustfmt-wrap_comments: false
+// Comment width
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+}
diff --git a/src/tools/rustfmt/tests/source/configs/condense_wildcard_suffixes/false.rs b/src/tools/rustfmt/tests/source/configs/condense_wildcard_suffixes/false.rs
new file mode 100644
index 0000000000000..3b967f35a8e8f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/condense_wildcard_suffixes/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-condense_wildcard_suffixes: false
+// Condense wildcard suffixes
+
+fn main() {
+    let (lorem, ipsum, _, _) = (1, 2, 3, 4);
+}
diff --git a/src/tools/rustfmt/tests/source/configs/condense_wildcard_suffixes/true.rs b/src/tools/rustfmt/tests/source/configs/condense_wildcard_suffixes/true.rs
new file mode 100644
index 0000000000000..3798a6b990204
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/condense_wildcard_suffixes/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-condense_wildcard_suffixes: true
+// Condense wildcard suffixes
+
+fn main() {
+    let (lorem, ipsum, _, _) = (1, 2, 3, 4);
+}
diff --git a/src/tools/rustfmt/tests/source/configs/control_brace_style/always_next_line.rs b/src/tools/rustfmt/tests/source/configs/control_brace_style/always_next_line.rs
new file mode 100644
index 0000000000000..c4ddad9ce2734
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/control_brace_style/always_next_line.rs
@@ -0,0 +1,10 @@
+// rustfmt-control_brace_style: AlwaysNextLine
+// Control brace style
+
+fn main() {
+    if lorem { println!("ipsum!"); } else { println!("dolor!"); }
+    match magi {
+        Homura => "Akemi",
+        Madoka => "Kaname",
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/control_brace_style/always_same_line.rs b/src/tools/rustfmt/tests/source/configs/control_brace_style/always_same_line.rs
new file mode 100644
index 0000000000000..a9c699d27e3e2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/control_brace_style/always_same_line.rs
@@ -0,0 +1,10 @@
+// rustfmt-control_brace_style: AlwaysSameLine
+// Control brace style
+
+fn main() {
+    if lorem { println!("ipsum!"); } else { println!("dolor!"); }
+    match magi {
+        Homura => "Akemi",
+        Madoka => "Kaname",
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/control_brace_style/closing_next_line.rs b/src/tools/rustfmt/tests/source/configs/control_brace_style/closing_next_line.rs
new file mode 100644
index 0000000000000..1a74a28f26a9f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/control_brace_style/closing_next_line.rs
@@ -0,0 +1,10 @@
+// rustfmt-control_brace_style: ClosingNextLine
+// Control brace style
+
+fn main() {
+    if lorem { println!("ipsum!"); } else { println!("dolor!"); }
+    match magi {
+        Homura => "Akemi",
+        Madoka => "Kaname",
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/disable_all_formatting/false.rs b/src/tools/rustfmt/tests/source/configs/disable_all_formatting/false.rs
new file mode 100644
index 0000000000000..834ca7a3c89e5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/disable_all_formatting/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-disable_all_formatting: false
+// Disable all formatting
+
+fn main() {
+    if lorem{println!("ipsum!");}else{println!("dolor!");}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/disable_all_formatting/true.rs b/src/tools/rustfmt/tests/source/configs/disable_all_formatting/true.rs
new file mode 100644
index 0000000000000..56955bf384d6b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/disable_all_formatting/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-disable_all_formatting: true
+// Disable all formatting
+
+fn main() {
+    iflorem{println!("ipsum!");}else{println!("dolor!");}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/empty_item_single_line/false.rs b/src/tools/rustfmt/tests/source/configs/empty_item_single_line/false.rs
new file mode 100644
index 0000000000000..9bfb2b964eaa3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/empty_item_single_line/false.rs
@@ -0,0 +1,16 @@
+// rustfmt-empty_item_single_line: false
+// Empty impl on single line
+
+impl Lorem {
+
+}
+
+impl Ipsum {
+
+}
+
+fn lorem() {
+}
+
+fn lorem() {
+}
diff --git a/src/tools/rustfmt/tests/source/configs/empty_item_single_line/true.rs b/src/tools/rustfmt/tests/source/configs/empty_item_single_line/true.rs
new file mode 100644
index 0000000000000..8af8b88ffff83
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/empty_item_single_line/true.rs
@@ -0,0 +1,16 @@
+// rustfmt-empty_item_single_line: true
+// Empty impl on single line
+
+impl Lorem {
+
+}
+
+impl Ipsum {
+
+}
+
+fn lorem() {
+}
+
+fn lorem() {
+}
diff --git a/src/tools/rustfmt/tests/source/configs/enum_discrim_align_threshold/40.rs b/src/tools/rustfmt/tests/source/configs/enum_discrim_align_threshold/40.rs
new file mode 100644
index 0000000000000..796e47c384ba5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/enum_discrim_align_threshold/40.rs
@@ -0,0 +1,34 @@
+// rustfmt-enum_discrim_align_threshold: 40
+
+enum Standard {
+    A = 1,
+    Bcdef = 2,
+}
+
+enum NoDiscrims {
+    ThisIsAFairlyLongEnumVariantWithoutDiscrimLongerThan40,
+    A = 1,
+    ThisIsAnotherFairlyLongEnumVariantWithoutDiscrimLongerThan40,
+    Bcdef = 2,
+}
+
+enum TooLong {
+    ThisOneHasDiscrimAaaaaaaaaaaaaaaaaaaaaaChar40 = 10,
+    A = 1,
+    Bcdef = 2,
+}
+
+enum Borderline {
+    ThisOneHasDiscrimAaaaaaaaaaaaaaaaaaaaaa = 10,
+    A = 1,
+    Bcdef = 2,
+}
+
+// Live specimen from #1686
+enum LongWithSmallDiff {
+    SceneColorimetryEstimates = 0x73636F65,
+    SceneAppearanceEstimates = 0x73617065,
+    FocalPlaneColorimetryEstimates = 0x66706365,
+    ReflectionHardcopyOriginalColorimetry = 0x72686F63,
+    ReflectionPrintOutputColorimetry = 0x72706F63,
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/configs/error_on_line_overflow/false.rs b/src/tools/rustfmt/tests/source/configs/error_on_line_overflow/false.rs
new file mode 100644
index 0000000000000..fa70ae78352f9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/error_on_line_overflow/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-error_on_line_overflow: false
+// Error on line overflow
+
+fn main() {
+    let lorem_ipsum_dolor_sit_amet_consectetur_adipiscing_elit_lorem_ipsum_dolor_sit_amet_consectetur_adipiscing_elit;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/fn_args_layout/compressed.rs b/src/tools/rustfmt/tests/source/configs/fn_args_layout/compressed.rs
new file mode 100644
index 0000000000000..66a371c259f0c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/fn_args_layout/compressed.rs
@@ -0,0 +1,16 @@
+// rustfmt-fn_args_layout: Compressed
+// Function arguments density
+
+trait Lorem {
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
+        // body
+    }
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur, adipiscing: Adipiscing, elit: Elit);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur, adipiscing: Adipiscing, elit: Elit) {
+        // body
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/fn_args_layout/tall.rs b/src/tools/rustfmt/tests/source/configs/fn_args_layout/tall.rs
new file mode 100644
index 0000000000000..f11e86fd3139c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/fn_args_layout/tall.rs
@@ -0,0 +1,16 @@
+// rustfmt-fn_args_layout: Tall
+// Function arguments density
+
+trait Lorem {
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
+        // body
+    }
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur, adipiscing: Adipiscing, elit: Elit);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur, adipiscing: Adipiscing, elit: Elit) {
+        // body
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/fn_args_layout/vertical.rs b/src/tools/rustfmt/tests/source/configs/fn_args_layout/vertical.rs
new file mode 100644
index 0000000000000..a23cc025225fb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/fn_args_layout/vertical.rs
@@ -0,0 +1,16 @@
+// rustfmt-fn_args_layout: Vertical
+// Function arguments density
+
+trait Lorem {
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
+        // body
+    }
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur, adipiscing: Adipiscing, elit: Elit);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur, adipiscing: Adipiscing, elit: Elit) {
+        // body
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/fn_single_line/false.rs b/src/tools/rustfmt/tests/source/configs/fn_single_line/false.rs
new file mode 100644
index 0000000000000..3d092f0c0bf5a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/fn_single_line/false.rs
@@ -0,0 +1,11 @@
+// rustfmt-fn_single_line: false
+// Single-expression function on single line
+
+fn lorem() -> usize {
+    42
+}
+
+fn lorem() -> usize {
+    let ipsum = 42;
+    ipsum
+}
diff --git a/src/tools/rustfmt/tests/source/configs/fn_single_line/true.rs b/src/tools/rustfmt/tests/source/configs/fn_single_line/true.rs
new file mode 100644
index 0000000000000..3cb0fdedf0b61
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/fn_single_line/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-fn_single_line: true
+// Single-expression function on single line
+
+fn lorem() -> usize {
+    42
+}
+
+fn lorem() -> usize {
+    let ipsum = 42;
+    ipsum
+}
diff --git a/src/tools/rustfmt/tests/source/configs/force_explicit_abi/false.rs b/src/tools/rustfmt/tests/source/configs/force_explicit_abi/false.rs
new file mode 100644
index 0000000000000..3c48f8e0c78db
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/force_explicit_abi/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-force_explicit_abi: false
+// Force explicit abi
+
+extern {
+    pub static lorem: c_int;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/force_explicit_abi/true.rs b/src/tools/rustfmt/tests/source/configs/force_explicit_abi/true.rs
new file mode 100644
index 0000000000000..e5ff6cf7dd7e1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/force_explicit_abi/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-force_explicit_abi: true
+// Force explicit abi
+
+extern {
+    pub static lorem: c_int;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/force_multiline_block/false.rs b/src/tools/rustfmt/tests/source/configs/force_multiline_block/false.rs
new file mode 100644
index 0000000000000..b97e348e5da12
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/force_multiline_block/false.rs
@@ -0,0 +1,22 @@
+// rustfmt-force_multiline_blocks: false
+// Option forces multiline match arm and closure bodies to be wrapped in a block
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            if ipsum {
+                println!("dolor");
+            }
+        }
+        Lorem::Dolor => println!("amet"),
+    }
+}
+
+fn main() {
+    result.and_then(|maybe_value| {
+        match maybe_value {
+            None => Err("oops"),
+            Some(value) => Ok(1),
+        }
+    });
+}
diff --git a/src/tools/rustfmt/tests/source/configs/force_multiline_block/true.rs b/src/tools/rustfmt/tests/source/configs/force_multiline_block/true.rs
new file mode 100644
index 0000000000000..db9d3de46141e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/force_multiline_block/true.rs
@@ -0,0 +1,18 @@
+// rustfmt-force_multiline_blocks: true
+// Option forces multiline match arm and closure bodies to be wrapped in a block
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => if ipsum {
+            println!("dolor");
+        },
+        Lorem::Dolor => println!("amet"),
+    }
+}
+
+fn main() {
+    result.and_then(|maybe_value| match maybe_value {
+        None => Err("oops"),
+        Some(value) => Ok(1),
+    });
+}
diff --git a/src/tools/rustfmt/tests/source/configs/format_macro_bodies/false.rs b/src/tools/rustfmt/tests/source/configs/format_macro_bodies/false.rs
new file mode 100644
index 0000000000000..d618a1ac3f9b2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/format_macro_bodies/false.rs
@@ -0,0 +1,7 @@
+// rustfmt-format_macro_bodies: false
+
+macro_rules! foo {
+    ($a: ident : $b: ty) => { $a(42): $b; };
+    ($a: ident $b: ident $c: ident) => { $a=$b+$c; };
+}
+
diff --git a/src/tools/rustfmt/tests/source/configs/format_macro_bodies/true.rs b/src/tools/rustfmt/tests/source/configs/format_macro_bodies/true.rs
new file mode 100644
index 0000000000000..b254b82d71931
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/format_macro_bodies/true.rs
@@ -0,0 +1,7 @@
+// rustfmt-format_macro_bodies: true
+
+macro_rules! foo {
+    ($a: ident : $b: ty) => { $a(42): $b; };
+    ($a: ident $b: ident $c: ident) => { $a=$b+$c; };
+}
+
diff --git a/src/tools/rustfmt/tests/source/configs/format_macro_matchers/false.rs b/src/tools/rustfmt/tests/source/configs/format_macro_matchers/false.rs
new file mode 100644
index 0000000000000..a721bb55c23a2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/format_macro_matchers/false.rs
@@ -0,0 +1,7 @@
+// rustfmt-format_macro_matchers: false
+
+macro_rules! foo {
+    ($a: ident : $b: ty) => { $a(42): $b; };
+    ($a: ident $b: ident $c: ident) => { $a=$b+$c; };
+}
+
diff --git a/src/tools/rustfmt/tests/source/configs/format_macro_matchers/true.rs b/src/tools/rustfmt/tests/source/configs/format_macro_matchers/true.rs
new file mode 100644
index 0000000000000..fa0442e228ac8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/format_macro_matchers/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-format_macro_matchers: true
+
+macro_rules! foo {
+    ($a: ident : $b: ty) => { $a(42): $b; };
+    ($a: ident $b: ident $c: ident) => { $a=$b+$c; };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/format_strings/false.rs b/src/tools/rustfmt/tests/source/configs/format_strings/false.rs
new file mode 100644
index 0000000000000..ecca0d7d1fca5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/format_strings/false.rs
@@ -0,0 +1,8 @@
+// rustfmt-format_strings: false
+// rustfmt-max_width: 50
+// rustfmt-error_on_line_overflow: false
+// Force format strings
+
+fn main() {
+    let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit";
+}
diff --git a/src/tools/rustfmt/tests/source/configs/format_strings/true.rs b/src/tools/rustfmt/tests/source/configs/format_strings/true.rs
new file mode 100644
index 0000000000000..337314478212e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/format_strings/true.rs
@@ -0,0 +1,7 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+// Force format strings
+
+fn main() {
+    let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit";
+}
diff --git a/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-merge_imports.rs b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-merge_imports.rs
new file mode 100644
index 0000000000000..ea7f6280a64af
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-merge_imports.rs
@@ -0,0 +1,17 @@
+// rustfmt-group_imports: StdExternalCrate
+// rustfmt-imports_granularity: Crate
+use chrono::Utc;
+use super::update::convert_publish_payload;
+
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+use alloc::alloc::Layout;
+
+use std::sync::Arc;
+use alloc::vec::Vec;
+
+use broker::database::PooledConnection;
+
+use super::schema::{Context, Payload};
+use core::f32;
+use crate::models::Event;
diff --git a/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-nested.rs b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-nested.rs
new file mode 100644
index 0000000000000..08f4e07b704e6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-nested.rs
@@ -0,0 +1,6 @@
+// rustfmt-group_imports: StdExternalCrate
+mod test {
+    use crate::foo::bar;
+    use std::path;
+    use crate::foo::bar2;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-no_reorder.rs b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-no_reorder.rs
new file mode 100644
index 0000000000000..08c9a72ae61e0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate-no_reorder.rs
@@ -0,0 +1,17 @@
+// rustfmt-group_imports: StdExternalCrate
+// rustfmt-reorder_imports: false
+
+use chrono::Utc;
+use super::update::convert_publish_payload;
+
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+use alloc::alloc::Layout;
+
+use std::sync::Arc;
+
+use broker::database::PooledConnection;
+
+use super::schema::{Context, Payload};
+use core::f32;
+use crate::models::Event;
diff --git a/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate.rs b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate.rs
new file mode 100644
index 0000000000000..d49c8941e6d56
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/group_imports/StdExternalCrate.rs
@@ -0,0 +1,15 @@
+// rustfmt-group_imports: StdExternalCrate
+use chrono::Utc;
+use super::update::convert_publish_payload;
+
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+use alloc::alloc::Layout;
+
+use std::sync::Arc;
+
+use broker::database::PooledConnection;
+
+use super::schema::{Context, Payload};
+use core::f32;
+use crate::models::Event;
diff --git a/src/tools/rustfmt/tests/source/configs/hard_tabs/false.rs b/src/tools/rustfmt/tests/source/configs/hard_tabs/false.rs
new file mode 100644
index 0000000000000..bf92162b4240a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/hard_tabs/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-hard_tabs: false
+// Hard tabs
+
+fn lorem() -> usize {
+42 // spaces before 42
+}
diff --git a/src/tools/rustfmt/tests/source/configs/hard_tabs/true.rs b/src/tools/rustfmt/tests/source/configs/hard_tabs/true.rs
new file mode 100644
index 0000000000000..738922a4dfb04
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/hard_tabs/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-hard_tabs: true
+// Hard tabs
+
+fn lorem() -> usize {
+42 // spaces before 42
+}
diff --git a/src/tools/rustfmt/tests/source/configs/imports_layout/merge_mixed.rs b/src/tools/rustfmt/tests/source/configs/imports_layout/merge_mixed.rs
new file mode 100644
index 0000000000000..477c4aa1684b7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/imports_layout/merge_mixed.rs
@@ -0,0 +1,6 @@
+// rustfmt-imports_indent: Block
+// rustfmt-imports_granularity: Crate
+// rustfmt-imports_layout: Mixed
+
+use std::{fmt, io, str};
+use std::str::FromStr;
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_args.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_args.rs
new file mode 100644
index 0000000000000..4d2d280a16bc5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_args.rs
@@ -0,0 +1,26 @@
+// rustfmt-indent_style: Block
+// Function arguments layout
+
+fn lorem() {}
+
+fn lorem(ipsum: usize) {}
+
+fn lorem(ipsum: usize, dolor: usize, sit: usize, amet: usize, consectetur: usize, adipiscing: usize, elit: usize) {
+    // body
+}
+
+// #1441
+extern "system" {
+    pub fn GetConsoleHistoryInfo(console_history_info: *mut ConsoleHistoryInfo) -> Boooooooooooooool;
+}
+
+// rustfmt should not add trailing comma for variadic function. See #1623.
+extern "C" {
+    pub fn variadic_fn(first_parameter: FirstParameterType,
+                       second_parameter: SecondParameterType,
+                       ...);
+}
+
+// #1652
+fn deconstruct(foo: Bar) -> (SocketAddr, Header, Method, RequestUri, HttpVersion, AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) {
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_array.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_array.rs
new file mode 100644
index 0000000000000..8404f65f471c3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_array.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Block
+// Array layout
+
+fn main() {
+    let lorem = vec!["ipsum","dolor","sit","amet","consectetur","adipiscing","elit"];
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_call.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_call.rs
new file mode 100644
index 0000000000000..c82b6b8e38f83
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_call.rs
@@ -0,0 +1,133 @@
+// rustfmt-indent_style: Block
+// Function call style
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing", "elit");
+    // #1501
+    let hyper = Arc::new(Client::with_connector(HttpsConnector::new(TlsClient::new())));
+
+    // chain
+    let x = yooooooooooooo.fooooooooooooooo.baaaaaaaaaaaaar(hello, world);
+
+    // #1380
+    {
+        {
+            let creds = self.client
+                .client_credentials(&self.config.auth.oauth2.id, &self.config.auth.oauth2.secret)?;
+        }
+    }
+
+    // nesting macro and function call
+    try!(foo(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx));
+    try!(foo(try!(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx)));
+}
+
+// #1521
+impl Foo {
+    fn map_pixel_to_coords(&self, point: &Vector2i, view: &View) -> Vector2f {
+        unsafe {
+            Vector2f::from_raw(ffi::sfRenderTexture_mapPixelToCoords(self.render_texture, point.raw(), view.raw()))
+        }
+    }
+}
+
+fn issue1420() {
+    given(
+        r#"
+        # Getting started
+        ...
+    "#,
+    )
+        .running(waltz)
+}
+
+// #1563
+fn query(conn: &Connection) -> Result<()> {
+    conn.query_row(
+        r#"
+            SELECT title, date
+            FROM posts,
+            WHERE DATE(date) = $1
+        "#,
+        &[],
+        |row| {
+            Post {
+                title: row.get(0),
+                date: row.get(1),
+            }
+        },
+    )?;
+
+    Ok(())
+}
+
+// #1449
+fn future_rayon_wait_1_thread() {
+    // run with only 1 worker thread; this would deadlock if we couldn't make progress
+    let mut result = None;
+    ThreadPool::new(Configuration::new().num_threads(1))
+        .unwrap()
+        .install(
+            || {
+                scope(
+                    |s| {
+                        use std::sync::mpsc::channel;
+                        let (tx, rx) = channel();
+                        let a = s.spawn_future(lazy(move || Ok::<usize, ()>(rx.recv().unwrap())));
+                        //                          ^^^^ FIXME: why is this needed?
+                        let b = s.spawn_future(a.map(|v| v + 1));
+                        let c = s.spawn_future(b.map(|v| v + 1));
+                        s.spawn(move |_| tx.send(20).unwrap());
+                        result = Some(c.rayon_wait().unwrap());
+                    },
+                );
+            },
+        );
+    assert_eq!(result, Some(22));
+}
+
+// #1494
+impl Cursor {
+    fn foo() {
+        self.cur_type()
+            .num_template_args()
+            .or_else(|| {
+                let n: c_int = unsafe { clang_Cursor_getNumTemplateArguments(self.x) };
+
+                if n >= 0 {
+                    Some(n as u32)
+                } else {
+                    debug_assert_eq!(n, -1);
+                    None
+                }
+            })
+            .or_else(|| {
+                let canonical = self.canonical();
+                if canonical != *self {
+                    canonical.num_template_args()
+                } else {
+                    None
+                }
+            });
+    }
+}
+
+fn issue1581() {
+    bootstrap.checks.register(
+        "PERSISTED_LOCATIONS",
+        move || if locations2.0.inner_mut.lock().poisoned {
+            Check::new(
+                State::Error,
+                "Persisted location storage is poisoned due to a write failure",
+            )
+        } else {
+            Check::new(State::Healthy, "Persisted location storage is healthy")
+        },
+    );
+}
+
+fn issue1651() {
+    {
+        let type_list: Vec<_> = try_opt!(types.iter().map(|ty| ty.rewrite(context, shape)).collect());
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_chain.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_chain.rs
new file mode 100644
index 0000000000000..41d91469114c9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_chain.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Block
+// Chain indent
+
+fn main() {
+    let lorem = ipsum.dolor().sit().amet().consectetur().adipiscing().elite();
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_generic.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_generic.rs
new file mode 100644
index 0000000000000..2cf17be56eff2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_generic.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Block
+// Generics indent
+
+fn lorem<Ipsum: Eq = usize, Dolor: Eq = usize, Sit: Eq = usize, Amet: Eq = usize, Adipiscing: Eq = usize, Consectetur: Eq = usize, Elit: Eq = usize>(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, adipiscing: Adipiscing, consectetur: Consectetur, elit: Elit) -> T {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_struct_lit.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_struct_lit.rs
new file mode 100644
index 0000000000000..47a6994f40ca2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_struct_lit.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Block
+// Struct literal-style
+
+fn main() {
+    let lorem = Lorem { ipsum: dolor, sit: amet };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_trailing_comma_call/one.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_trailing_comma_call/one.rs
new file mode 100644
index 0000000000000..6d48ea742fc78
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_trailing_comma_call/one.rs
@@ -0,0 +1,9 @@
+// rustfmt-version: One
+// rustfmt-error_on_line_overflow: false
+// rustfmt-indent_style: Block
+
+// rustfmt should not add trailing comma when rewriting macro. See #1528.
+fn a() {
+    panic!("this is a long string that goes past the maximum line length causing rustfmt to insert a comma here:");
+    foo(a, oooptoptoptoptptooptoptoptoptptooptoptoptoptptoptoptoptoptpt());
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_trailing_comma_call/two.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_trailing_comma_call/two.rs
new file mode 100644
index 0000000000000..7a62d722c6e00
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_trailing_comma_call/two.rs
@@ -0,0 +1,9 @@
+// rustfmt-version: Two
+// rustfmt-error_on_line_overflow: false
+// rustfmt-indent_style: Block
+
+// rustfmt should not add trailing comma when rewriting macro. See #1528.
+fn a() {
+    panic!("this is a long string that goes past the maximum line length causing rustfmt to insert a comma here:");
+    foo(a, oooptoptoptoptptooptoptoptoptptooptoptoptoptptoptoptoptoptpt());
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/block_where_pred.rs b/src/tools/rustfmt/tests/source/configs/indent_style/block_where_pred.rs
new file mode 100644
index 0000000000000..450491f02705e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/block_where_pred.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Block
+// Where predicate indent
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T where Ipsum: Eq, Dolor: Eq, Sit: Eq, Amet: Eq {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/default.rs b/src/tools/rustfmt/tests/source/configs/indent_style/default.rs
new file mode 100644
index 0000000000000..f08f5c64460a7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/default.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Visual
+// Where style
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T where Ipsum: Eq, Dolor: Eq, Sit: Eq, Amet: Eq {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/rfc_where.rs b/src/tools/rustfmt/tests/source/configs/indent_style/rfc_where.rs
new file mode 100644
index 0000000000000..012840be28dcc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/rfc_where.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Block
+// Where style
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T where Ipsum: Eq, Dolor: Eq, Sit: Eq, Amet: Eq {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_args.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_args.rs
new file mode 100644
index 0000000000000..5aa28a62b9cef
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_args.rs
@@ -0,0 +1,32 @@
+// rustfmt-indent_style: Visual
+// Function arguments layout
+
+fn lorem() {}
+
+fn lorem(ipsum: usize) {}
+
+fn lorem(ipsum: usize, dolor: usize, sit: usize, amet: usize, consectetur: usize, adipiscing: usize, elit: usize) {
+    // body
+}
+
+// #1922
+extern "C" {
+    pub fn LAPACKE_csytrs_rook_work(matrix_layout: c_int,
+            uplo: c_char,
+                n: lapack_int,
+        nrhs: lapack_int,
+        a: *const lapack_complex_float,
+                    lda: lapack_int, ipiv: *const lapack_int,
+        b: *mut lapack_complex_float,
+            ldb: lapack_int
+    )-> lapack_int;
+
+    pub fn LAPACKE_csytrs_rook_work(matrix_layout: c_int,
+            uplo: c_char,
+                n: lapack_int,
+        nrhs: lapack_int,
+                    lda: lapack_int, ipiv: *const lapack_int,
+        b: *mut lapack_complex_float,
+            ldb: lapack_int
+    ) -> lapack_int;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_array.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_array.rs
new file mode 100644
index 0000000000000..05bbf00b1d27d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_array.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Visual
+// Array layout
+
+fn main() {
+    let lorem = vec!["ipsum","dolor","sit","amet","consectetur","adipiscing","elit"];
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_call.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_call.rs
new file mode 100644
index 0000000000000..9a679d6bb4c98
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_call.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Visual
+// Function call style
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing", "elit");
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_chain.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_chain.rs
new file mode 100644
index 0000000000000..b749487539803
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_chain.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Visual
+// Chain indent
+
+fn main() {
+    let lorem = ipsum.dolor().sit().amet().consectetur().adipiscing().elite();
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_generics.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_generics.rs
new file mode 100644
index 0000000000000..1f910d32d87a0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_generics.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Visual
+// Generics indent
+
+fn lorem<Ipsum: Eq = usize, Dolor: Eq = usize, Sit: Eq = usize, Amet: Eq = usize, Adipiscing: Eq = usize, Consectetur: Eq = usize, Elit: Eq = usize>(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, adipiscing: Adipiscing, consectetur: Consectetur, elit: Elit) -> T {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_struct_lit.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_struct_lit.rs
new file mode 100644
index 0000000000000..45538e70482d2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_struct_lit.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Visual
+// Struct literal-style
+
+fn main() {
+    let lorem = Lorem { ipsum: dolor, sit: amet };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_trailing_comma.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_trailing_comma.rs
new file mode 100644
index 0000000000000..9738d397dbf63
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_trailing_comma.rs
@@ -0,0 +1,7 @@
+// rustfmt-error_on_line_overflow: false
+// rustfmt-indent_style: Visual
+
+// rustfmt should not add trailing comma when rewriting macro. See #1528.
+fn a() {
+    panic!("this is a long string that goes past the maximum line length causing rustfmt to insert a comma here:");
+}
diff --git a/src/tools/rustfmt/tests/source/configs/indent_style/visual_where_pred.rs b/src/tools/rustfmt/tests/source/configs/indent_style/visual_where_pred.rs
new file mode 100644
index 0000000000000..055806b68629e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/indent_style/visual_where_pred.rs
@@ -0,0 +1,6 @@
+// rustfmt-indent_style: Visual
+// Where predicate indent
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T where Ipsum: Eq, Dolor: Eq, Sit: Eq, Amet: Eq {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/source/configs/match_arm_blocks/false.rs b/src/tools/rustfmt/tests/source/configs/match_arm_blocks/false.rs
new file mode 100644
index 0000000000000..53e37e13c4f2b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/match_arm_blocks/false.rs
@@ -0,0 +1,11 @@
+// rustfmt-match_arm_blocks: false
+// Wrap match-arms
+
+fn main() {
+    match lorem {
+        true => foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
+        false => {
+            println!("{}", sit)
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/match_arm_blocks/true.rs b/src/tools/rustfmt/tests/source/configs/match_arm_blocks/true.rs
new file mode 100644
index 0000000000000..a452b13cd27db
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/match_arm_blocks/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-match_arm_blocks: true
+// Wrap match-arms
+
+fn main() {
+    match lorem {
+        true => foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
+        false => {
+            println!("{}", sit)
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/always.rs b/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/always.rs
new file mode 100644
index 0000000000000..162d812d8cffc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/always.rs
@@ -0,0 +1,27 @@
+// rustfmt-match_arm_leading_pipes: Always
+
+fn foo() {
+    match foo {
+        "foo"  |    "bar" => {}
+        "baz"
+        |  "something relatively long"
+        |     "something really really really realllllllllllllly long" => println!("x"),
+        "qux" => println!("y"),
+        _ => {}
+    }
+}
+
+fn issue_3973() {
+    match foo {
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
+
+fn bar() {
+    match baz {
+        "qux" => {}
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/never.rs b/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/never.rs
new file mode 100644
index 0000000000000..8a68fe21407ee
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/never.rs
@@ -0,0 +1,28 @@
+// rustfmt-match_arm_leading_pipes: Never
+
+fn foo() {
+    match foo {
+        | "foo" | "bar" => {}
+        | "baz"
+        | "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        | "qux" => println!("y"),
+        _ => {}
+    }
+}
+
+fn issue_3973() {
+    match foo {
+        | "foo"
+        | "bar" => {}
+        _ => {}
+    }
+}
+
+fn bar() {
+    match baz {
+        "qux" => {}
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/preserve.rs b/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/preserve.rs
new file mode 100644
index 0000000000000..ea303e857def5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/match_arm_leading_pipes/preserve.rs
@@ -0,0 +1,28 @@
+// rustfmt-match_arm_leading_pipes: Preserve
+
+fn foo() {
+    match foo {
+        | "foo"      | "bar" => {}
+        | "baz"
+        |                   "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        | "qux" =>           println!("y"),
+        _ => {}
+    }
+}
+
+fn issue_3973() {
+    match foo {
+        | "foo"
+        | "bar" => {}
+        _ => {}
+    }
+}
+
+fn bar() {
+    match baz {
+        "qux"     => {    }
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/match_block_trailing_comma/false.rs b/src/tools/rustfmt/tests/source/configs/match_block_trailing_comma/false.rs
new file mode 100644
index 0000000000000..70e02955fb01d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/match_block_trailing_comma/false.rs
@@ -0,0 +1,11 @@
+// rustfmt-match_block_trailing_comma: false
+// Match block trailing comma
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            println!("ipsum");
+        }
+        Lorem::Dolor => println!("dolor"),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/match_block_trailing_comma/true.rs b/src/tools/rustfmt/tests/source/configs/match_block_trailing_comma/true.rs
new file mode 100644
index 0000000000000..b9af3d47202fc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/match_block_trailing_comma/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-match_block_trailing_comma: true
+// Match block trailing comma
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            println!("ipsum");
+        }
+        Lorem::Dolor => println!("dolor"),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/merge_derives/true.rs b/src/tools/rustfmt/tests/source/configs/merge_derives/true.rs
new file mode 100644
index 0000000000000..18b8443f0d7bb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/merge_derives/true.rs
@@ -0,0 +1,46 @@
+// rustfmt-merge_derives: true
+// Merge multiple derives to a single one.
+
+#[bar]
+#[derive(Eq, PartialEq)]
+#[foo]
+#[derive(Debug)]
+#[foobar]
+#[derive(Copy, Clone)]
+pub enum Foo {}
+
+#[derive(Eq, PartialEq)]
+#[derive(Debug)]
+#[foobar]
+#[derive(Copy, Clone)]
+pub enum Bar {}
+
+#[derive(Eq, PartialEq)]
+#[derive(Debug)]
+#[derive(Copy, Clone)]
+pub enum FooBar {}
+
+mod foo {
+#[bar]
+#[derive(Eq, PartialEq)]
+#[foo]
+#[derive(Debug)]
+#[foobar]
+#[derive(Copy, Clone)]
+pub enum Foo {}
+}
+
+mod bar {
+#[derive(Eq, PartialEq)]
+#[derive(Debug)]
+#[foobar]
+#[derive(Copy, Clone)]
+pub enum Bar {}
+}
+
+mod foobar {
+#[derive(Eq, PartialEq)]
+#[derive(Debug)]
+#[derive(Copy, Clone)]
+pub enum FooBar {}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/normalize_comments/false.rs b/src/tools/rustfmt/tests/source/configs/normalize_comments/false.rs
new file mode 100644
index 0000000000000..488962ed9362d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/normalize_comments/false.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_comments: false
+// Normalize comments
+
+// Lorem ipsum:
+fn dolor() -> usize {}
+
+/* sit amet: */
+fn adipiscing() -> usize {}
+
+// #652
+////////////////////////////////////////////////////////////////////////////////
+// Basic slice extension methods
+////////////////////////////////////////////////////////////////////////////////
diff --git a/src/tools/rustfmt/tests/source/configs/normalize_comments/true.rs b/src/tools/rustfmt/tests/source/configs/normalize_comments/true.rs
new file mode 100644
index 0000000000000..c74a9808e61db
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/normalize_comments/true.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_comments: true
+// Normalize comments
+
+// Lorem ipsum:
+fn dolor() -> usize {}
+
+/* sit amet: */
+fn adipiscing() -> usize {}
+
+// #652
+////////////////////////////////////////////////////////////////////////////////
+// Basic slice extension methods
+////////////////////////////////////////////////////////////////////////////////
diff --git a/src/tools/rustfmt/tests/source/configs/normalize_doc_attributes/false.rs b/src/tools/rustfmt/tests/source/configs/normalize_doc_attributes/false.rs
new file mode 100644
index 0000000000000..f8eb64273c3d6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/normalize_doc_attributes/false.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_doc_attributes: false
+// Normalize doc attributes
+
+#![doc = " Example documentation"]
+
+#[doc = " Example item documentation"]
+pub enum Foo {}
+
+#[doc = "        Lots of space"]
+pub enum Bar {}
+
+#[doc = "no leading space"]
+pub mod FooBar {}
diff --git a/src/tools/rustfmt/tests/source/configs/normalize_doc_attributes/true.rs b/src/tools/rustfmt/tests/source/configs/normalize_doc_attributes/true.rs
new file mode 100644
index 0000000000000..894c00a4dc058
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/normalize_doc_attributes/true.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_doc_attributes: true
+// Normalize doc attributes
+
+#![doc = " Example documentation"]
+
+#[doc = " Example item documentation"]
+pub enum Foo {}
+
+#[doc = "        Lots of space"]
+pub enum Bar {}
+
+#[doc = "no leading space"]
+pub mod FooBar {}
diff --git a/src/tools/rustfmt/tests/source/configs/remove_nested_parens/remove_nested_parens.rs b/src/tools/rustfmt/tests/source/configs/remove_nested_parens/remove_nested_parens.rs
new file mode 100644
index 0000000000000..87aed09c14a08
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/remove_nested_parens/remove_nested_parens.rs
@@ -0,0 +1,5 @@
+// rustfmt-remove_nested_parens: true
+
+fn main() {
+    ((((((foo()))))));
+}
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_impl_items/false.rs b/src/tools/rustfmt/tests/source/configs/reorder_impl_items/false.rs
new file mode 100644
index 0000000000000..beb99f0fb8e6a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_impl_items/false.rs
@@ -0,0 +1,11 @@
+// rustfmt-reorder_impl_items: false
+
+struct Dummy;
+
+impl Iterator for Dummy {
+    fn next(&mut self) -> Option<Self::Item> {
+        None
+    }
+
+    type Item = i32;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_impl_items/true.rs b/src/tools/rustfmt/tests/source/configs/reorder_impl_items/true.rs
new file mode 100644
index 0000000000000..612b1c84abdfb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_impl_items/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-reorder_impl_items: true
+
+struct Dummy;
+
+impl Iterator for Dummy {
+    fn next(&mut self) -> Option<Self::Item> {
+        None
+    }
+
+    type Item = i32;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_imports/false.rs b/src/tools/rustfmt/tests/source/configs/reorder_imports/false.rs
new file mode 100644
index 0000000000000..4b85684dc013d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_imports/false.rs
@@ -0,0 +1,7 @@
+// rustfmt-reorder_imports: false
+// Reorder imports
+
+use lorem;
+use ipsum;
+use dolor;
+use sit;
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_imports/true.rs b/src/tools/rustfmt/tests/source/configs/reorder_imports/true.rs
new file mode 100644
index 0000000000000..2a40f6d069f93
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_imports/true.rs
@@ -0,0 +1,19 @@
+// rustfmt-reorder_imports: true
+// Reorder imports
+
+use lorem;
+use ipsum;
+use dolor;
+use sit;
+
+fn foo() {
+    use C;
+    use B;
+    use A;
+
+    bar();
+
+    use F;
+    use E;
+    use D;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_modules/dolor/mod.rs b/src/tools/rustfmt/tests/source/configs/reorder_modules/dolor/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_modules/dolor/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_modules/false.rs b/src/tools/rustfmt/tests/source/configs/reorder_modules/false.rs
new file mode 100644
index 0000000000000..56b1aa03ed795
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_modules/false.rs
@@ -0,0 +1,7 @@
+// rustfmt-reorder_modules: false
+// Reorder modules
+
+mod lorem;
+mod ipsum;
+mod dolor;
+mod sit;
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_modules/ipsum/mod.rs b/src/tools/rustfmt/tests/source/configs/reorder_modules/ipsum/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_modules/ipsum/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_modules/lorem/mod.rs b/src/tools/rustfmt/tests/source/configs/reorder_modules/lorem/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_modules/lorem/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_modules/sit/mod.rs b/src/tools/rustfmt/tests/source/configs/reorder_modules/sit/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_modules/sit/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/source/configs/reorder_modules/true.rs b/src/tools/rustfmt/tests/source/configs/reorder_modules/true.rs
new file mode 100644
index 0000000000000..79b0ab1e35546
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/reorder_modules/true.rs
@@ -0,0 +1,7 @@
+// rustfmt-reorder_modules: true
+// Reorder modules
+
+mod lorem;
+mod ipsum;
+mod dolor;
+mod sit;
diff --git a/src/tools/rustfmt/tests/source/configs/skip_children/foo/mod.rs b/src/tools/rustfmt/tests/source/configs/skip_children/foo/mod.rs
new file mode 100644
index 0000000000000..d7ff6cdb8290e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/skip_children/foo/mod.rs
@@ -0,0 +1,3 @@
+fn skip_formatting_this() {
+    println ! ( "Skip this" ) ;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/skip_children/true.rs b/src/tools/rustfmt/tests/source/configs/skip_children/true.rs
new file mode 100644
index 0000000000000..e51889dd4c91f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/skip_children/true.rs
@@ -0,0 +1,4 @@
+// rustfmt-skip_children: true
+
+mod foo  ;
+mod void;
diff --git a/src/tools/rustfmt/tests/source/configs/space_before_colon/true.rs b/src/tools/rustfmt/tests/source/configs/space_before_colon/true.rs
new file mode 100644
index 0000000000000..0a597602528a4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/space_before_colon/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-space_before_colon: true
+// Space before colon
+
+fn lorem<T : Eq>(t : T) {
+    let ipsum: Dolor = sit;
+}
+
+const LOREM : Lorem = Lorem {
+    ipsum : dolor,
+    sit : amet,
+};
diff --git a/src/tools/rustfmt/tests/source/configs/spaces_around_ranges/false.rs b/src/tools/rustfmt/tests/source/configs/spaces_around_ranges/false.rs
new file mode 100644
index 0000000000000..1878c68a5a0c4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/spaces_around_ranges/false.rs
@@ -0,0 +1,34 @@
+// rustfmt-spaces_around_ranges: false
+// Spaces around ranges
+
+fn main() {
+    let lorem = 0 .. 10;
+    let ipsum = 0 ..= 10;
+
+    match lorem {
+        1 .. 5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1 ..= 5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1 ... 5 => foo(),
+        _ => bar,
+    }
+}
+
+fn half_open() {
+    match [5 .. 4, 99 .. 105, 43 .. 44] {
+        [_, 99 .., _] => {}
+        [_, .. 105, _] => {}
+        _ => {}
+    };
+
+    if let ..=   5 = 0 {}
+    if let .. 5 = 0 {}
+    if let 5 .. = 0 {}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/spaces_around_ranges/true.rs b/src/tools/rustfmt/tests/source/configs/spaces_around_ranges/true.rs
new file mode 100644
index 0000000000000..0eadfb2851579
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/spaces_around_ranges/true.rs
@@ -0,0 +1,34 @@
+// rustfmt-spaces_around_ranges: true
+// Spaces around ranges
+
+fn main() {
+    let lorem = 0..10;
+    let ipsum = 0..=10;
+
+    match lorem {
+        1..5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1..=5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1...5 => foo(),
+        _ => bar,
+    }
+}
+
+fn half_open() {
+    match [5..4, 99..105, 43..44] {
+        [_, 99.., _] => {}
+        [_, ..105, _] => {}
+        _ => {}
+    };
+
+    if let ..=5 = 0 {}
+    if let ..5 = 0 {}
+    if let 5.. = 0 {}
+}
diff --git a/src/tools/rustfmt/tests/source/configs/struct_field_align_threshold/20.rs b/src/tools/rustfmt/tests/source/configs/struct_field_align_threshold/20.rs
new file mode 100644
index 0000000000000..81253c460376c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/struct_field_align_threshold/20.rs
@@ -0,0 +1,383 @@
+// rustfmt-struct_field_align_threshold: 20
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-error_on_line_overflow: false
+
+struct Foo {
+    x: u32,
+    yy: u32, // comment
+    zzz: u32,
+}
+
+pub struct Bar {
+    x: u32,
+    yy: u32,
+    zzz: u32,
+
+    xxxxxxx: u32,
+}
+
+fn main() {
+    let foo = Foo {
+        x: 0,
+        yy: 1,
+        zzz: 2,
+    };
+
+    let bar = Bar {
+        x: 0,
+        yy: 1,
+        zzz: 2,
+
+        xxxxxxx: 3,
+    };
+}
+
+                                                                       /// A Doc comment
+#[AnAttribute]
+pub struct Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f: SomeType, // Comment beside a field
+    // Comment on a field
+    #[AnAttribute]
+    g: SomeOtherType,
+      /// A doc comment on a field
+    h: AThirdType,
+    pub i: TypeForPublicField
+}
+
+// #1029
+pub struct Foo {
+    #[doc(hidden)]
+    // This will NOT get deleted!
+    bar: String, // hi
+}
+
+// #1029
+struct X {
+    // `x` is an important number.
+    #[allow(unused)] // TODO: use
+    x: u32,
+}
+
+// #410
+#[allow(missing_docs)]
+pub struct Writebatch<K: Key> {
+    #[allow(dead_code)] //only used for holding the internal pointer
+    writebatch: RawWritebatch,
+    marker: PhantomData<K>,
+}
+
+struct Bar;
+
+struct NewType(Type,       OtherType);
+
+struct
+NewInt     <T: Copy>(pub i32, SomeType /* inline comment */, T /* sup */
+
+
+    );
+
+struct Qux<'a,
+           N: Clone + 'a,
+           E: Clone + 'a,
+           G: Labeller<'a, N, E> + GraphWalk<'a, N, E>,
+           W: Write + Copy>
+(
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, // Comment
+    BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+    #[AnAttr]
+    // Comment
+    /// Testdoc
+    G,
+    pub W,
+);
+
+struct Tuple(/*Comment 1*/ AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+             /* Comment 2   */ BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,);
+
+// With a where-clause and generics.
+pub struct Foo<'a, Y: Baz>
+    where X: Whatever
+{
+    f: SomeType, // Comment beside a field
+}
+
+struct Baz {
+
+    a: A,  // Comment A
+    b: B, // Comment B
+    c: C,   // Comment C
+
+}
+
+struct Baz {
+    a: A,  // Comment A
+
+    b: B, // Comment B
+
+
+
+
+    c: C,   // Comment C
+}
+
+struct Baz {
+
+    a: A,
+
+    b: B,
+    c: C,
+
+
+
+    
+    d: D
+
+}
+
+struct Baz
+{
+    // Comment A
+    a: A,
+    
+    // Comment B
+b: B,
+    // Comment C
+      c: C,}
+
+// Will this be a one-liner?
+struct Tuple(
+    A, //Comment
+    B
+);
+
+pub struct State<F: FnMut() -> time::Timespec> { now: F }
+
+pub struct State<F: FnMut() -> ()> { now: F }
+
+pub struct State<F: FnMut()> { now: F }
+
+struct Palette { /// A map of indices in the palette to a count of pixels in approximately that color
+                    foo: i32}
+
+// Splitting a single line comment into a block previously had a misalignment
+// when the field had attributes
+struct FieldsWithAttributes {
+    // Pre Comment
+    #[rustfmt::skip] pub host:String, // Post comment BBBBBBBBBBBBBB BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBBB BBBBBBBBBBB
+    //Another pre comment
+    #[attr1]
+    #[attr2] pub id: usize // CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCC CCCCCCCCCCCC
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep: node::Handle<IdRef<'id, Node<K, V>>,
+                                                     Type,
+                                                     NodeType>,
+}
+
+struct Foo<T>(T);
+struct Foo<T>(T) where T: Copy, T: Eq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUU);
+struct Foo<T>(TTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTT) where T: PartialEq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTTTT) where T: PartialEq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUU) where T: PartialEq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, // Foo
+              UUUUUUUUUUUUUUUUUUUUUUUU /* Bar */,
+              // Baz
+              TTTTTTTTTTTTTTTTTTT,
+              // Qux (FIXME #572 - doc comment)
+              UUUUUUUUUUUUUUUUUUU);
+
+mod m {
+    struct X<T> where T: Sized {
+        a: T,
+    }
+}
+
+struct Foo<T>(TTTTTTTTTTTTTTTTTTT,
+              /// Qux
+    UUUUUUUUUUUUUUUUUUU);
+
+struct Issue677 {
+    pub ptr: *const libc::c_void,
+    pub trace: fn(  obj: 
+          *const libc::c_void, tracer   : *mut   JSTracer   ),
+}
+
+struct Foo {}
+struct Foo {
+    }
+struct Foo {
+    // comment
+    }
+struct Foo {
+    // trailing space ->    
+
+
+    }
+struct Foo { /* comment */ }
+struct Foo( /* comment */ );
+
+struct LongStruct {
+    a: A,
+    the_quick_brown_fox_jumps_over_the_lazy_dog:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep: node::Handle<IdRef<'id, Node<Key, Value>>,
+                                                                         Type,
+                                                                         NodeType>,
+}
+
+struct Foo<C=()>(String);
+
+// #1364
+fn foo() {
+    convex_shape.set_point(0, &Vector2f { x: 400.0, y: 100.0 });
+    convex_shape.set_point(1, &Vector2f { x: 500.0, y: 70.0 });
+    convex_shape.set_point(2, &Vector2f { x: 450.0, y: 100.0 });
+    convex_shape.set_point(3, &Vector2f { x: 580.0, y: 150.0 });
+}
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo {a: x };
+
+    Foo { a: foo() /* comment*/, /* comment*/ b: bar(), ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a:Bar,
+          b:f() };
+
+    Quux { x: if cond { bar(); }, y: baz() };
+
+    A { 
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+    first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item
+    };
+
+    Some(Data::MethodCallData(MethodCallData {
+        span: sub_span.unwrap(),
+        scope: self.enclosing_scope(id),
+        ref_id: def_id,
+        decl_id: Some(decl_id),
+    }));
+
+    Diagram { /*                 o        This graph demonstrates how                  
+               *                / \       significant whitespace is           
+               *               o   o      preserved.  
+               *              /|\   \
+               *             o o o   o */
+              graph: G, }
+}
+
+fn matcher() {
+    TagTerminatedByteMatcher {
+        matcher: ByteMatcher {
+        pattern: b"<HTML",
+        mask: b"\xFF\xDF\xDF\xDF\xDF\xFF",
+    },
+    };
+}
+
+fn issue177() {
+    struct Foo<T> { memb: T }
+    let foo = Foo::<i64> { memb: 10 };
+}
+
+fn issue201() {
+    let s = S{a:0, ..  b};
+}
+
+fn issue201_2() {
+    let s = S{a: S2{    .. c}, ..  b};
+}
+
+fn issue278() {
+    let s = S {
+        a: 0,
+        //       
+        b: 0,
+    };
+    let s1 = S {
+        a: 0,
+        // foo
+        //      
+        // bar
+        b: 0,
+    };
+}
+
+fn struct_exprs() {
+    Foo
+    { a :  1, b:f( 2)};
+    Foo{a:1,b:f(2),..g(3)};
+    LoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongStruct { ..base };
+    IntrinsicISizesContribution { content_intrinsic_sizes: IntrinsicISizes { minimum_inline_size: 0, }, };
+}
+
+fn issue123() {
+    Foo { a: b, c: d, e: f };
+
+    Foo { a: bb, c: dd, e: ff };
+
+    Foo { a: ddddddddddddddddddddd, b: cccccccccccccccccccccccccccccccccccccc };
+}
+
+fn issue491() {
+    Foo {
+        guard: None,
+        arm: 0, // Comment
+    };
+
+    Foo {
+        arm: 0, // Comment
+    };
+
+    Foo { a: aaaaaaaaaa, b: bbbbbbbb, c: cccccccccc, d: dddddddddd, /* a comment */
+      e: eeeeeeeee };
+}
+
+fn issue698() {
+    Record {
+        ffffffffffffffffffffffffffields: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    };
+    Record {
+        ffffffffffffffffffffffffffields: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    }
+}
+
+fn issue835() {
+    MyStruct {};
+    MyStruct { /* a comment */ };
+    MyStruct {
+        // Another comment
+    };
+    MyStruct {}
+}
+
+fn field_init_shorthand() {
+    MyStruct { x, y, z };
+    MyStruct { x, y, z, .. base };
+    Foo { aaaaaaaaaa, bbbbbbbb, cccccccccc, dddddddddd, /* a comment */
+        eeeeeeeee };
+    Record { ffffffffffffffffffffffffffieldsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/struct_lit_single_line/false.rs b/src/tools/rustfmt/tests/source/configs/struct_lit_single_line/false.rs
new file mode 100644
index 0000000000000..17cad8dde290d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/struct_lit_single_line/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-struct_lit_single_line: false
+// Struct literal multiline-style
+
+fn main() {
+    let lorem = Lorem { ipsum: dolor, sit: amet };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/tab_spaces/2.rs b/src/tools/rustfmt/tests/source/configs/tab_spaces/2.rs
new file mode 100644
index 0000000000000..5c2667bc2c792
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/tab_spaces/2.rs
@@ -0,0 +1,11 @@
+// rustfmt-tab_spaces: 2
+// rustfmt-max_width: 30
+// rustfmt-indent_style: Block
+// Tab spaces
+
+fn lorem() {
+let ipsum = dolor();
+let sit = vec![
+"amet", "consectetur", "adipiscing", "elit."
+];
+}
diff --git a/src/tools/rustfmt/tests/source/configs/tab_spaces/4.rs b/src/tools/rustfmt/tests/source/configs/tab_spaces/4.rs
new file mode 100644
index 0000000000000..da61bbd42a7c7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/tab_spaces/4.rs
@@ -0,0 +1,11 @@
+// rustfmt-tab_spaces: 4
+// rustfmt-max_width: 30
+// rustfmt-indent_style: Block
+// Tab spaces
+
+fn lorem() {
+let ipsum = dolor();
+let sit = vec![
+"amet", "consectetur", "adipiscing", "elit."
+];
+}
diff --git a/src/tools/rustfmt/tests/source/configs/trailing_comma/always.rs b/src/tools/rustfmt/tests/source/configs/trailing_comma/always.rs
new file mode 100644
index 0000000000000..57e874cd822c6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/trailing_comma/always.rs
@@ -0,0 +1,7 @@
+// rustfmt-trailing_comma: Always
+// Trailing comma
+
+fn main() {
+    let Lorem { ipsum, dolor, sit, } = amet;
+    let Lorem { ipsum, dolor, sit, amet, consectetur, adipiscing } = elit;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/trailing_comma/never.rs b/src/tools/rustfmt/tests/source/configs/trailing_comma/never.rs
new file mode 100644
index 0000000000000..4da3b996f2994
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/trailing_comma/never.rs
@@ -0,0 +1,23 @@
+// rustfmt-trailing_comma: Never
+// Trailing comma
+
+fn main() {
+    let Lorem { ipsum, dolor, sit, } = amet;
+    let Lorem { ipsum, dolor, sit, amet, consectetur, adipiscing } = elit;
+
+    // #1544
+    if let VrMsg::ClientReply {request_num: reply_req_num, value, ..} = msg {
+        let _ = safe_assert_eq!(reply_req_num, request_num, op);
+        return Ok((request_num, op, value));
+    }
+
+    // #1710
+    pub struct FileInput {
+        input: StringInput,
+        file_name: OsString,
+    }
+    match len {
+        Some(len) => Ok(new(self.input, self.pos + len)),
+        None => Err(self),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/configs/trailing_comma/vertical.rs b/src/tools/rustfmt/tests/source/configs/trailing_comma/vertical.rs
new file mode 100644
index 0000000000000..c903e82215891
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/trailing_comma/vertical.rs
@@ -0,0 +1,7 @@
+// rustfmt-trailing_comma: Vertical
+// Trailing comma
+
+fn main() {
+    let Lorem { ipsum, dolor, sit, } = amet;
+    let Lorem { ipsum, dolor, sit, amet, consectetur, adipiscing } = elit;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/type_punctuation_density/compressed.rs b/src/tools/rustfmt/tests/source/configs/type_punctuation_density/compressed.rs
new file mode 100644
index 0000000000000..223b9a2f0f022
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/type_punctuation_density/compressed.rs
@@ -0,0 +1,37 @@
+// rustfmt-type_punctuation_density: Compressed
+// Type punctuation density
+
+fn lorem<Ipsum:Dolor+Sit=Amet>() {
+    // body
+}
+
+struct Foo<T: Eq + Clone, U>
+where U: Eq + Clone {
+    // body
+}
+
+trait Foo<'a, T = usize>
+where T: 'a + Eq + Clone
+{
+    type Bar: Eq + Clone;
+}
+
+trait Foo: Eq + Clone {
+    // body
+}
+
+impl<T> Foo<'a> for Bar
+where for<'a> T: 'a + Eq + Clone
+{
+    // body
+}
+
+fn foo<'a, 'b, 'c>()
+where 'a: 'b + 'c
+{
+    // body
+}
+
+fn Foo<T = Foo, Output = Expr<'tcx> + Foo>() {
+    let i = 6;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/type_punctuation_density/wide.rs b/src/tools/rustfmt/tests/source/configs/type_punctuation_density/wide.rs
new file mode 100644
index 0000000000000..fe0c0816701b5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/type_punctuation_density/wide.rs
@@ -0,0 +1,37 @@
+// rustfmt-type_punctuation_density: Wide
+// Type punctuation density
+
+fn lorem<Ipsum:Dolor+Sit=Amet>() {
+    // body
+}
+
+struct Foo<T: Eq + Clone, U>
+where U: Eq + Clone {
+    // body
+}
+
+trait Foo<'a, T = usize>
+where T: 'a + Eq + Clone
+{
+    type Bar: Eq + Clone;
+}
+
+trait Foo: Eq + Clone {
+    // body
+}
+
+impl<T> Foo<'a> for Bar
+where for<'a> T: 'a + Eq + Clone
+{
+    // body
+}
+
+fn foo<'a, 'b, 'c>()
+where 'a: 'b + 'c
+{
+    // body
+}
+
+fn Foo<T = Foo, Output = Expr<'tcx> + Foo>() {
+    let i = 6;
+}
diff --git a/src/tools/rustfmt/tests/source/configs/use_field_init_shorthand/false.rs b/src/tools/rustfmt/tests/source/configs/use_field_init_shorthand/false.rs
new file mode 100644
index 0000000000000..4c2eb1de179c8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/use_field_init_shorthand/false.rs
@@ -0,0 +1,19 @@
+// rustfmt-use_field_init_shorthand: false
+// Use field initialization shorthand if possible.
+
+fn main() {
+    let a = Foo {
+        x: x,
+        y: y,
+        z: z,
+    };
+
+    let b = Bar {
+        x: x,
+        y: y,
+        #[attr]
+        z: z,
+        #[rustfmt::skip]
+        skipped: skipped,
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/use_field_init_shorthand/true.rs b/src/tools/rustfmt/tests/source/configs/use_field_init_shorthand/true.rs
new file mode 100644
index 0000000000000..dcde28d74e0f1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/use_field_init_shorthand/true.rs
@@ -0,0 +1,19 @@
+// rustfmt-use_field_init_shorthand: true
+// Use field initialization shorthand if possible.
+
+fn main() {
+    let a = Foo {
+        x: x,
+        y: y,
+        z: z,
+    };
+
+    let b = Bar {
+        x: x,
+        y: y,
+        #[attr]
+        z: z,
+        #[rustfmt::skip]
+        skipped: skipped,
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/use_small_heuristics/default.rs b/src/tools/rustfmt/tests/source/configs/use_small_heuristics/default.rs
new file mode 100644
index 0000000000000..68bc40271a1d4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/use_small_heuristics/default.rs
@@ -0,0 +1,25 @@
+// rustfmt-use_small_heuristics: Default
+
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit {
+        amet: Consectetur,
+        adipiscing: Elit,
+    },
+}
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
+
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+
+    let lorem = if ipsum {
+        dolor
+    } else {
+        sit
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/use_small_heuristics/max.rs b/src/tools/rustfmt/tests/source/configs/use_small_heuristics/max.rs
new file mode 100644
index 0000000000000..8d30932e2c24d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/use_small_heuristics/max.rs
@@ -0,0 +1,25 @@
+// rustfmt-use_small_heuristics: Max
+
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit {
+        amet: Consectetur,
+        adipiscing: Elit,
+    },
+}
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
+
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+
+    let lorem = if ipsum {
+        dolor
+    } else {
+        sit
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/use_small_heuristics/off.rs b/src/tools/rustfmt/tests/source/configs/use_small_heuristics/off.rs
new file mode 100644
index 0000000000000..f76392d2404be
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/use_small_heuristics/off.rs
@@ -0,0 +1,25 @@
+// rustfmt-use_small_heuristics: Off
+
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit {
+        amet: Consectetur,
+        adipiscing: Elit,
+    },
+}
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
+
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+
+    let lorem = if ipsum {
+        dolor
+    } else {
+        sit
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/configs/use_try_shorthand/false.rs b/src/tools/rustfmt/tests/source/configs/use_try_shorthand/false.rs
new file mode 100644
index 0000000000000..de7f8b4a5e248
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/use_try_shorthand/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-use_try_shorthand: false
+// Use try! shorthand
+
+fn main() {
+    let lorem = try!(ipsum.map(|dolor| dolor.sit()));
+}
diff --git a/src/tools/rustfmt/tests/source/configs/use_try_shorthand/true.rs b/src/tools/rustfmt/tests/source/configs/use_try_shorthand/true.rs
new file mode 100644
index 0000000000000..9015ec41e5e49
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/use_try_shorthand/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-use_try_shorthand: true
+// Use try! shorthand
+
+fn main() {
+    let lorem = try!(ipsum.map(|dolor| dolor.sit()));
+}
diff --git a/src/tools/rustfmt/tests/source/configs/where_single_line/true.rs b/src/tools/rustfmt/tests/source/configs/where_single_line/true.rs
new file mode 100644
index 0000000000000..9de98283b5e5d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/where_single_line/true.rs
@@ -0,0 +1,26 @@
+// rustfmt-where_single_line: true
+// Where style
+
+
+fn lorem_two_items<Ipsum, Dolor, Sit, Amet>() -> T where Ipsum: Eq, Lorem: Eq {
+    // body
+}
+
+fn lorem_multi_line<Ipsum, Dolor, Sit, Amet>(
+    a: Aaaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbbbb,
+    c: Ccccccccccccccccc,
+    d: Ddddddddddddddddddddddddd,
+    e: Eeeeeeeeeeeeeeeeeee,
+) -> T
+where
+    Ipsum: Eq,
+{
+    // body
+}
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T where Ipsum: Eq {
+    // body
+}
+
+unsafe impl Sync for Foo where (): Send {}
diff --git a/src/tools/rustfmt/tests/source/configs/wrap_comments/false.rs b/src/tools/rustfmt/tests/source/configs/wrap_comments/false.rs
new file mode 100644
index 0000000000000..48ecd88accbf9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/wrap_comments/false.rs
@@ -0,0 +1,8 @@
+// rustfmt-wrap_comments: false
+// rustfmt-max_width: 50
+// rustfmt-error_on_line_overflow: false
+// Wrap comments
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+}
diff --git a/src/tools/rustfmt/tests/source/configs/wrap_comments/true.rs b/src/tools/rustfmt/tests/source/configs/wrap_comments/true.rs
new file mode 100644
index 0000000000000..39a79a4cacc46
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/configs/wrap_comments/true.rs
@@ -0,0 +1,15 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 50
+// Wrap comments
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+}
+
+fn code_block() {
+    // ```rust
+    // let x = 3;
+    //
+    // println!("x = {}", x);
+    // ```
+}
diff --git a/src/tools/rustfmt/tests/source/const_generics.rs b/src/tools/rustfmt/tests/source/const_generics.rs
new file mode 100644
index 0000000000000..01b764dbe45df
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/const_generics.rs
@@ -0,0 +1,44 @@
+struct Message {
+    field2: Vec<
+      "MessageEntity"
+    >,
+    field3: Vec<
+      1
+    >,
+    field4: Vec<
+      2 ,    3
+    >,
+
+}
+
+struct RectangularArray<T, const WIDTH: usize, const HEIGHT: usize> {
+    array: [[T; WIDTH]; HEIGHT],
+}
+
+fn main() {
+  const X: usize = 7;
+  let x: RectangularArray<i32, 2, 4>;
+  let y: RectangularArray<i32,  X,  {2 
+  * 2} >;
+}
+
+fn foo<const X: usize>() {
+    const Y: usize = X * 2;
+    static Z: (usize, usize) = (X, X);
+
+    struct Foo([i32; X]);
+}
+
+type Foo<const N: usize> = [i32; N + 1];
+
+pub trait Foo: Bar<{Baz::COUNT}> {
+	const ASD: usize;
+}
+
+// #4263
+fn const_generics_on_params<
+    // AAAA
+        const BBBB: usize,
+    /* CCCC */
+    const DDDD: usize,
+    >() {}
diff --git a/src/tools/rustfmt/tests/source/control-brace-style-always-next-line.rs b/src/tools/rustfmt/tests/source/control-brace-style-always-next-line.rs
new file mode 100644
index 0000000000000..9079fb46c0cd7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/control-brace-style-always-next-line.rs
@@ -0,0 +1,44 @@
+// rustfmt-control_brace_style: AlwaysNextLine
+
+fn main() {
+    loop {
+        ();
+        ();
+        }
+
+
+    'label: loop // loop comment  
+    {
+        ();
+    }
+
+
+    cond = true;
+    while cond {
+        ();
+    }
+
+
+    'while_label: while cond { // while comment
+        ();
+    }
+
+
+    for obj in iter {
+        for sub_obj in obj
+        {
+            'nested_while_label: while cond {
+                ();
+            }
+        }
+    }
+
+    match some_var { // match comment
+        pattern0 => val0,
+        pattern1 => val1,
+        pattern2 | pattern3 => {
+            do_stuff();
+            val2
+        },
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/control-brace-style-always-same-line.rs b/src/tools/rustfmt/tests/source/control-brace-style-always-same-line.rs
new file mode 100644
index 0000000000000..45111aaab08cd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/control-brace-style-always-same-line.rs
@@ -0,0 +1,42 @@
+fn main() {
+    loop {
+        ();
+        ();
+        }
+
+
+    'label: loop // loop comment  
+    {
+        ();
+    }
+
+
+    cond = true;
+    while cond {
+        ();
+    }
+
+
+    'while_label: while cond { // while comment
+        ();
+    }
+
+
+    for obj in iter {
+        for sub_obj in obj
+        {
+            'nested_while_label: while cond {
+                ();
+            }
+        }
+    }
+
+    match some_var { // match comment
+        pattern0 => val0,
+        pattern1 => val1,
+        pattern2 | pattern3 => {
+            do_stuff();
+            val2
+        },
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/doc-attrib.rs b/src/tools/rustfmt/tests/source/doc-attrib.rs
new file mode 100644
index 0000000000000..dde88c6e95520
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/doc-attrib.rs
@@ -0,0 +1,118 @@
+// rustfmt-wrap_comments: true
+// rustfmt-normalize_doc_attributes: true
+
+// Only doc = "" attributes should be normalized
+#![doc = " Example doc attribute comment"]
+#![doc = "          Example doc attribute comment with 10 leading spaces"]
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
+       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
+       html_root_url = "https://doc.rust-lang.org/nightly/",
+       html_playground_url = "https://play.rust-lang.org/", test(attr(deny(warnings))))]
+
+
+// Long `#[doc = "..."]`
+struct A { #[doc = " xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"] b: i32 }
+
+
+#[doc = " The `nodes` and `edges` method each return instantiations of `Cow<[T]>` to leave implementers the freedom to create entirely new vectors or to pass back slices into internally owned vectors."]
+struct B { b: i32 }
+
+
+#[doc = " Level 1 comment"]
+mod tests {
+    #[doc = " Level 2 comment"]
+    impl A {
+        #[doc = " Level 3 comment"]
+        fn f() {
+            #[doc = " Level 4 comment"]
+            fn g() {
+            }
+        }
+    }
+}
+
+struct C {
+    #[doc = " item doc attrib comment"]
+    // regular item comment
+    b: i32,
+
+    // regular item comment
+    #[doc = " item doc attrib comment"]
+    c: i32,
+}
+
+// non-regression test for regular attributes, from #2647
+#[cfg(feature = "this_line_is_101_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx")]
+pub fn foo() {}
+
+// path attrs
+#[clippy::bar]
+#[clippy::bar(a, b, c)]
+pub fn foo() {}
+
+mod issue_2620 {
+    #[derive(Debug, StructOpt)]
+#[structopt(about = "Display information about the character on FF Logs")]
+pub struct Params {
+  #[structopt(help = "The server the character is on")]
+  server: String,
+  #[structopt(help = "The character's first name")]
+  first_name: String,
+  #[structopt(help = "The character's last name")]
+  last_name: String,
+  #[structopt(
+    short = "j",
+    long = "job",
+    help = "The job to look at",
+    parse(try_from_str)
+  )]
+  job: Option<Job>
+}
+}
+
+// non-regression test for regular attributes, from #2969
+#[cfg(not(all(feature="std",
+              any(target_os = "linux", target_os = "android",
+                  target_os = "netbsd",
+                  target_os = "dragonfly",
+                  target_os = "haiku",
+                  target_os = "emscripten",
+                  target_os = "solaris",
+                  target_os = "cloudabi",
+                  target_os = "macos", target_os = "ios",
+                  target_os = "freebsd",
+                  target_os = "openbsd",
+                  target_os = "redox",
+                  target_os = "fuchsia",
+                  windows,
+                  all(target_arch = "wasm32", feature = "stdweb"),
+                  all(target_arch = "wasm32", feature = "wasm-bindgen"),
+              ))))]
+type Os = NoSource;
+
+// use cases from bindgen needing precise control over leading spaces
+#[doc = " <div rustbindgen accessor></div>"]
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct ContradictAccessors {
+    #[doc = "<foo>no leading spaces here</foo>"]
+    pub mBothAccessors: ::std::os::raw::c_int,
+    #[doc = " <div rustbindgen accessor=\"false\"></div>"]
+    pub mNoAccessors: ::std::os::raw::c_int,
+    #[doc = " <div rustbindgen accessor=\"unsafe\"></div>"]
+    pub mUnsafeAccessors: ::std::os::raw::c_int,
+    #[doc = " <div rustbindgen accessor=\"immutable\"></div>"]
+    pub mImmutableAccessor: ::std::os::raw::c_int,
+}
+
+#[doc = " \\brief          MPI structure"]
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct mbedtls_mpi {
+    #[doc = "<  integer sign"]
+    pub s: ::std::os::raw::c_int,
+    #[doc = "<  total # of limbs"]
+    pub n: ::std::os::raw::c_ulong,
+    #[doc = "<  pointer to limbs"]
+    pub p: *mut mbedtls_mpi_uint,
+}
diff --git a/src/tools/rustfmt/tests/source/doc-comment-with-example.rs b/src/tools/rustfmt/tests/source/doc-comment-with-example.rs
new file mode 100644
index 0000000000000..e74ceefd19588
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/doc-comment-with-example.rs
@@ -0,0 +1,12 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// Foo
+///
+/// # Example
+/// ```
+/// # #![cfg_attr(not(dox), feature(cfg_target_feature, target_feature, stdsimd))]
+/// # #![cfg_attr(not(dox), no_std)]
+/// fn foo() {  }
+/// ```
+///
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/source/doc.rs b/src/tools/rustfmt/tests/source/doc.rs
new file mode 100644
index 0000000000000..3b25918b12ec4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/doc.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+// Part of multiple.rs
+
+// sadfsdfa
+//sdffsdfasdf
diff --git a/src/tools/rustfmt/tests/source/dyn_trait.rs b/src/tools/rustfmt/tests/source/dyn_trait.rs
new file mode 100644
index 0000000000000..012643be92c29
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/dyn_trait.rs
@@ -0,0 +1,20 @@
+#![feature(dyn_trait)]
+
+fn main() {
+    // #2506
+    // checks rustfmt doesn't remove dyn
+    trait MyTrait {
+        fn method(&self) -> u64;
+    }
+    fn f1(a: Box<dyn MyTrait>) {}
+
+    // checks if line wrap works correctly
+    trait Very_______________________Long__________________Name_______________________________Trait {
+        fn method(&self) -> u64;
+    }
+
+    fn f2(a: Box<dyn Very_______________________Long__________________Name____________________Trait+ 'static,>) {}
+
+    // #2582
+    let _: &dyn (::std::any::Any) = &msg;
+}
diff --git a/src/tools/rustfmt/tests/source/else-if-brace-style-always-next-line.rs b/src/tools/rustfmt/tests/source/else-if-brace-style-always-next-line.rs
new file mode 100644
index 0000000000000..7b4870fc65aa0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/else-if-brace-style-always-next-line.rs
@@ -0,0 +1,54 @@
+// rustfmt-control_brace_style: AlwaysNextLine
+
+fn main() {
+    if false
+    {
+        ();
+        ();
+    }
+
+    if false // lone if comment
+    {
+        ();
+        ();
+    }
+
+
+    let a =
+        if 0 > 1 {
+            unreachable!()
+        }
+        else
+        {
+            0x0
+        };
+
+
+    if true
+    {
+        ();
+    } else if false {
+        ();
+        ();
+    }
+    else {
+        ();
+        ();
+        ();
+    }
+
+    if true // else-if-chain if comment
+    {
+        ();
+    }
+    else if false // else-if-chain else-if comment
+    {
+        ();
+        ();
+    } else // else-if-chain else comment
+    {
+        ();
+        ();
+        ();
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/else-if-brace-style-always-same-line.rs b/src/tools/rustfmt/tests/source/else-if-brace-style-always-same-line.rs
new file mode 100644
index 0000000000000..37c9417ea160b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/else-if-brace-style-always-same-line.rs
@@ -0,0 +1,52 @@
+fn main() {
+    if false
+    {
+        ();
+        ();
+    }
+
+    if false // lone if comment
+    {
+        ();
+        ();
+    }
+
+
+    let a =
+        if 0 > 1 {
+            unreachable!()
+        }
+        else
+        {
+            0x0
+        };
+
+
+    if true
+    {
+        ();
+    } else if false {
+        ();
+        ();
+    }
+    else {
+        ();
+        ();
+        ();
+    }
+
+    if true // else-if-chain if comment
+    {
+        ();
+    }
+    else if false // else-if-chain else-if comment
+    {
+        ();
+        ();
+    } else // else-if-chain else comment
+    {
+        ();
+        ();
+        ();
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/else-if-brace-style-closing-next-line.rs b/src/tools/rustfmt/tests/source/else-if-brace-style-closing-next-line.rs
new file mode 100644
index 0000000000000..3b885b3faaa5d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/else-if-brace-style-closing-next-line.rs
@@ -0,0 +1,54 @@
+// rustfmt-control_brace_style: ClosingNextLine
+
+fn main() {
+    if false
+    {
+        ();
+        ();
+    }
+
+    if false // lone if comment
+    {
+        ();
+        ();
+    }
+
+
+    let a =
+        if 0 > 1 {
+            unreachable!()
+        }
+        else
+        {
+            0x0
+        };
+
+
+    if true
+    {
+        ();
+    } else if false {
+        ();
+        ();
+    }
+    else {
+        ();
+        ();
+        ();
+    }
+
+    if true // else-if-chain if comment
+    {
+        ();
+    }
+    else if false // else-if-chain else-if comment
+    {
+        ();
+        ();
+    } else // else-if-chain else comment
+    {
+        ();
+        ();
+        ();
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/empty_file.rs b/src/tools/rustfmt/tests/source/empty_file.rs
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/src/tools/rustfmt/tests/source/enum.rs b/src/tools/rustfmt/tests/source/enum.rs
new file mode 100644
index 0000000000000..0ed9651abe722
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/enum.rs
@@ -0,0 +1,212 @@
+// rustfmt-wrap_comments: true
+// Enums test
+
+#[atrr]
+pub enum Test {
+    A, B(u32, 
+         A /* comment */, 
+         SomeType),
+    /// Doc comment
+    C,
+}
+
+pub enum Foo<'a, Y: Baz> where X: Whatever
+{ A, }
+
+enum EmtpyWithComment {
+    // Some comment
+}
+
+// C-style enum
+enum Bar {
+    A = 1,
+    #[someAttr(test)]
+    B = 2, // comment
+    C,
+}
+
+enum LongVariants {
+First(LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOONG, // comment
+VARIANT),
+    // This is the second variant
+    Second
+}
+
+enum StructLikeVariants {
+    Normal(u32, String, ),
+    StructLike { x: i32, // Test comment
+        // Pre-comment
+        #[Attr50] y: SomeType, // Aanother Comment
+    }, SL { a: A }
+}
+
+enum X {
+    CreateWebGLPaintTask(Size2D<i32>, GLContextAttributes, IpcSender<Result<(IpcSender<CanvasMsg>, usize), String>>), // This is a post comment
+}
+
+pub enum EnumWithAttributes {
+    //This is a pre comment AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    TupleVar(usize, usize, usize), // AAAA AAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    // Pre Comment
+    #[rustfmt::skip]
+    SkippedItem(String,String,), // Post-comment
+    #[another_attr]
+    #[attr2]
+    ItemStruct {x: usize, y: usize}, // Comment AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    // And another
+    ForcedPreflight // AAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+}
+
+pub enum SingleTuple {
+    // Pre Comment AAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    Match(usize, usize, String) // Post-comment AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+}
+
+pub enum SingleStruct {
+    Match {name: String, loc: usize} // Post-comment
+}
+
+pub enum GenericEnum<I, T>
+where I: Iterator<Item = T> {
+    // Pre Comment
+    Left {list: I, root: T}, // Post-comment
+    Right {list: I, root: T} // Post Comment
+}
+
+
+enum EmtpyWithComment {
+    // Some comment
+}
+
+enum TestFormatFails {
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+}
+
+fn nested_enum_test() {
+    if true {
+        enum TestEnum {
+            One(usize, usize, usize, usize, usize, usize, usize, usize, usize, usize, usize, usize, usize, usize, usize, usize,), // AAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAA
+            Two // AAAAAAAAAAAAAAAAAA  AAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAA
+        }
+        enum TestNestedFormatFail {
+            AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        }
+    }
+}
+
+   pub  struct  EmtpyWithComment {
+    // FIXME: Implement this struct
+}
+
+// #1115
+pub enum Bencoding<'i> {
+    Str(&'i [u8]),
+    Int(i64),
+    List(Vec<Bencoding<'i>>),
+    /// A bencoded dict value. The first element the slice of bytes in the source that the dict is
+    /// composed of. The second is the dict, decoded into an ordered map.
+    // TODO make Dict "structlike" AKA name the two values.
+    Dict(&'i [u8], BTreeMap<&'i [u8], Bencoding<'i>>),
+}
+
+// #1261
+pub enum CoreResourceMsg {
+    SetCookieForUrl(
+        ServoUrl,
+        #[serde(deserialize_with = "::hyper_serde::deserialize",
+                serialize_with = "::hyper_serde::serialize")]
+        Cookie,
+        CookieSource
+    ),
+}
+
+enum Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong {}
+enum Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong {}
+enum Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong {}
+enum Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong { Foo }
+
+// #1046
+pub enum Entry<'a, K: 'a, V: 'a> {
+    Vacant(
+        #[ stable( feature = "rust1", since = "1.0.0" ) ]   VacantEntry<'a, K, V>,
+    ),
+    Occupied(
+        #[ stable( feature = "rust1", since = "1.0.0" ) ]
+         OccupiedEntry<'a, K, V>,
+    ),
+}
+
+// #2081
+pub enum ForegroundColor {
+    CYAN = (winapi::FOREGROUND_INTENSITY | winapi::FOREGROUND_GREEN | winapi::FOREGROUND_BLUE) as u16,
+}
+
+// #2098
+pub enum E<'a> {
+    V ( < std::slice::Iter<'a, Xxxxxxxxxxxxxx> as Iterator> :: Item ) ,
+}
+
+// #1809
+enum State {
+    TryRecv {
+        pos: usize,
+        lap: u8,
+        closed_count: usize,
+    },
+    Subscribe { pos: usize },
+    IsReady { pos: usize, ready: bool },
+    Unsubscribe {
+        pos: usize,
+        lap: u8,
+        id_woken: usize,
+    },
+    FinalTryRecv { pos: usize, id_woken: usize },
+    TimedOut,
+    Disconnected,
+}
+
+// #2190
+#[derive(Debug, Fail)]
+enum AnError {
+    #[fail(display = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")]
+    UnexpectedSingleToken { token: syn::Token },
+}
+
+// #2193
+enum WidthOf101 {
+    #[fail(display = ".....................................................")] Io(::std::io::Error),
+    #[fail(display = ".....................................................")] Ioo(::std::io::Error),
+    Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(::std::io::Error),
+    Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(::std::io::Error),
+}
+
+// #2389
+pub enum QlError {
+    #[fail(display = "Parsing error: {}", 0)] LexError(parser::lexer::LexError),
+    #[fail(display = "Parsing error: {:?}", 0)] ParseError(parser::ParseError),
+    #[fail(display = "Validation error: {:?}", 0)] ValidationError(Vec<validation::Error>),
+    #[fail(display = "Execution error: {}", 0)] ExecutionError(String),
+    // (from, to)
+    #[fail(display = "Translation error: from {} to {}", 0, 1)] TranslationError(String, String),
+    // (kind, input, expected)
+    #[fail(display = "aaaaaaaaaaaaCould not find {}: Found: {}, expected: {:?}", 0, 1, 2)] ResolveError(&'static str, String, Option<String>),
+}
+
+// #2594
+enum Foo {}
+enum Bar { }
+
+// #3562
+enum PublishedFileVisibility {
+    Public = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPublic,
+    FriendsOnly = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityFriendsOnly,
+    Private = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPrivate,
+}
+
+// #3771
+//#![feature(arbitrary_enum_discriminant)]
+#[repr(u32)]
+pub enum E {
+    A { a: u32 } = 0x100,
+    B { field1: u32, field2: u8, field3: m::M } = 0x300 // comment
+}
diff --git a/src/tools/rustfmt/tests/source/existential_type.rs b/src/tools/rustfmt/tests/source/existential_type.rs
new file mode 100644
index 0000000000000..33bb9a9515966
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/existential_type.rs
@@ -0,0 +1,23 @@
+// Opaque type.
+
+    #![feature(type_alias_impl_trait)]
+
+pub type Adder<F, T>
+where
+    T: Clone,
+    F: Copy
+    = impl Fn(T) -> T;
+
+pub type Adderrr<T> = impl Fn(  T  ) -> T;
+
+impl Foo for Bar {
+type E  = impl Trait;
+}
+
+pub type Adder_without_impl<F, T>
+where
+    T: Clone,
+    F: Copy
+    = Fn(T) -> T;
+
+pub type Adderrr_without_impl<T> = Fn(  T  ) -> T;
diff --git a/src/tools/rustfmt/tests/source/expr-block.rs b/src/tools/rustfmt/tests/source/expr-block.rs
new file mode 100644
index 0000000000000..a3e6100b7f222
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/expr-block.rs
@@ -0,0 +1,300 @@
+// Test expressions with block formatting.
+
+fn arrays() {
+    [      ];
+    let empty = [];
+
+    let foo = [a_long_name, a_very_lng_name, a_long_name];
+
+    let foo = [a_long_name, a_very_lng_name, a_long_name, a_very_lng_name, a_long_name, a_very_lng_name, a_long_name, a_very_lng_name];
+
+    vec![a_long_name, a_very_lng_name, a_long_name, a_very_lng_name, a_long_name, a_very_lng_name, a_very_lng_name];
+
+    [a_long_name, a_very_lng_name, a_long_name, a_very_lng_name, a_long_name, a_very_lng_name, a_very_lng_name]
+}
+
+fn arrays() {
+    let x = [0,
+         1,
+         2,
+         3,
+         4,
+         5,
+         6,
+         7,
+         8,
+         9,
+         0,
+         1,
+         2,
+         3,
+         4,
+         5,
+         6,
+         7,
+         8,
+         9,
+         0,
+         7,
+         8,
+         9,
+         0,
+         1,
+         2,
+         3,
+         4,
+         5,
+         6,
+         7,
+         8,
+         9,
+         0];
+
+    let y = [/* comment */ 1, 2 /* post comment */, 3];
+
+    let xy =    [ strukt  { test123: value_one_two_three_four, turbo: coolio(), } , /* comment  */   1 ];
+
+        let a =WeightedChoice::new(&mut [Weighted {
+            weight: x,
+            item: 0,
+        },
+                                  Weighted {
+            weight: 1,
+            item: 1,
+        },
+                                  Weighted {
+            weight: x,
+            item: 2,
+        },
+                                  Weighted {
+            weight: 1,
+            item: 3,
+        }]);
+
+    let z = [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzz, q];
+
+    [ 1 +   3, 4 ,  5, 6, 7, 7, fncall::<Vec<_>>(3-1)]
+}
+
+fn function_calls() {
+    let items = itemize_list(context.source_map,
+                             args.iter(),
+                             ")",
+                             |item| item.span.lo(),
+                             |item| item.span.hi(),
+                             |item| {
+                                 item.rewrite(context,
+                                              Shape {
+                                                  width: remaining_width,
+                                                  ..nested_shape
+                                              })
+                             },
+                             span.lo(),
+                             span.hi());
+
+    itemize_list(context.source_map,
+                             args.iter(),
+                             ")",
+                             |item| item.span.lo(),
+                             |item| item.span.hi(),
+                             |item| {
+                                 item.rewrite(context,
+                                              Shape {
+                                                  width: remaining_width,
+                                                  ..nested_shape
+                                              })
+                             },
+                             span.lo(),
+                             span.hi())
+}
+
+fn macros() {
+    baz!(do_not, add, trailing, commas, inside, of, function, like, macros, even, if_they, are, long);
+
+    baz!(one_item_macro_which_is_also_loooooooooooooooooooooooooooooooooooooooooooooooong);
+
+    let _ = match option {
+        None => baz!(function, like, macro_as, expression, which, is, loooooooooooooooong),
+        Some(p) => baz!(one_item_macro_as_expression_which_is_also_loooooooooooooooong),
+    };
+}
+
+fn issue_1450() {
+    if selfstate
+        .compare_exchandsfasdsdfgsdgsdfgsdfgsdfgsdfgsdfgfsfdsage_weak(
+            STATE_PARKED,
+            STATE_UNPARKED,
+            Release,
+            Relaxed,
+            Release,
+            Relaxed,
+        )
+        .is_ok() {
+        return;
+    }
+}
+
+fn foo() {
+    if real_total <= limit && !pre_line_comments &&
+            !items.into_iter().any(|item| item.as_ref().is_multiline()) {
+         DefinitiveListTactic::Horizontal
+    }
+}
+
+fn combine_block() {
+    foo(
+        Bar {
+            x: value,
+            y: value2,
+        },
+    );
+
+    foo((Bar {
+        x: value,
+        y: value2,
+    },));
+
+    foo((1, 2, 3, Bar {
+        x: value,
+        y: value2,
+    }));
+
+    foo((1, 2, 3, |x| {
+        let y = x + 1;
+        let z = y + 1;
+        z
+    }));
+
+    let opt = Some(
+        Struct(
+            long_argument_one,
+            long_argument_two,
+            long_argggggggg,
+        ),
+    );
+
+    do_thing(
+        |param| {
+            action();
+            foo(param)
+        },
+    );
+
+    do_thing(
+        x,
+        |param| {
+            action();
+            foo(param)
+        },
+    );
+
+    do_thing(
+        x,
+        (
+            1,
+            2,
+            3,
+            |param| {
+                action();
+                foo(param)
+            },
+        ),
+    );
+
+    Ok(
+        some_function(
+            lllllllllong_argument_one,
+            lllllllllong_argument_two,
+            lllllllllllllllllllllllllllllong_argument_three,
+        ),
+    );
+
+    foo(
+        thing,
+        bar(
+            param2,
+            pparam1param1param1param1param1param1param1param1param1param1aram1,
+            param3,
+        ),
+    );
+
+    foo.map_or(
+        || {
+            Ok(
+                SomeStruct {
+                    f1: 0,
+                    f2: 0,
+                    f3: 0,
+                },
+            )
+        },
+    );
+
+    match opt {
+        Some(x) => somefunc(anotherfunc(
+            long_argument_one,
+            long_argument_two,
+            long_argument_three,
+        )),
+        Some(x) => |x| {
+            let y = x + 1;
+            let z = y + 1;
+            z
+        },
+        Some(x) => (1, 2, |x| {
+            let y = x + 1;
+            let z = y + 1;
+            z
+        }),
+        Some(x) => SomeStruct {
+            f1: long_argument_one,
+            f2: long_argument_two,
+            f3: long_argument_three,
+        },
+        None => Ok(SomeStruct {
+            f1: long_argument_one,
+            f2: long_argument_two,
+            f3: long_argument_three,
+        }),
+    };
+
+    match x {
+        y => func(
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        ),
+        _ => func(
+            x,
+            yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+            zzz,
+        ),
+    }
+}
+
+fn issue_1862() {
+    foo(
+        /* bar = */ None ,
+        something_something,
+        /* baz = */ None ,
+        /* This comment waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay too long to be kept on the same line */ None ,
+        /* com */ this_last_arg_is_tooooooooooooooooooooooooooooooooo_long_to_be_kept_with_the_pre_comment ,
+    )
+}
+
+fn issue_3025() {
+    foo(
+        // This describes the argument below.
+        /* bar = */ None ,
+        // This describes the argument below.
+        something_something,
+        // This describes the argument below. */
+        None ,
+        // This describes the argument below.
+        /* This comment waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay too long to be kept on the same line */ None ,
+        // This describes the argument below.
+        /* com */ this_last_arg_is_tooooooooooooooooooooooooooooooooo_long_to_be_kept_with_the_pre_comment ,
+    )
+}
+
+fn issue_1878() {
+    let channel: &str = seq.next_element()?.ok_or_else(|| de::Error::invalid_length(2, &self))?;
+}
diff --git a/src/tools/rustfmt/tests/source/expr-overflow-delimited.rs b/src/tools/rustfmt/tests/source/expr-overflow-delimited.rs
new file mode 100644
index 0000000000000..cd80ca6fcebcc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/expr-overflow-delimited.rs
@@ -0,0 +1,155 @@
+// rustfmt-overflow_delimited_expr: true
+
+fn combine_blocklike() {
+    do_thing(
+        |param| {
+            action();
+            foo(param)
+        },
+    );
+
+    do_thing(
+        x,
+        |param| {
+            action();
+            foo(param)
+        },
+    );
+
+    do_thing(
+        x,
+
+        // I'll be discussing the `action` with your para(m)legal counsel
+        |param| {
+            action();
+            foo(param)
+        },
+    );
+
+    do_thing(
+        Bar {
+            x: value,
+            y: value2,
+        },
+    );
+
+    do_thing(
+        x,
+        Bar {
+            x: value,
+            y: value2,
+        },
+    );
+
+    do_thing(
+        x,
+
+        // Let me tell you about that one time at the `Bar`
+        Bar {
+            x: value,
+            y: value2,
+        },
+    );
+
+    do_thing(
+        &[
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(
+        x,
+        &[
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(
+        x,
+
+        // Just admit it; my list is longer than can be folded on to one line
+        &[
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(
+        vec![
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(
+        x,
+        vec![
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(
+        x,
+
+        // Just admit it; my list is longer than can be folded on to one line
+        vec![
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(
+        x,
+        (
+            1,
+            2,
+            3,
+            |param| {
+                action();
+                foo(param)
+            },
+        ),
+    );
+}
+
+fn combine_struct_sample() {
+    let identity = verify(
+        &ctx,
+        VerifyLogin {
+            type_: LoginType::Username,
+            username: args.username.clone(),
+            password: Some(args.password.clone()),
+            domain: None,
+        },
+    )?;
+}
+
+fn combine_macro_sample() {
+    rocket::ignite()
+        .mount(
+            "/",
+            routes![
+                http::auth::login,
+                http::auth::logout,
+                http::cors::options,
+                http::action::dance,
+                http::action::sleep,
+            ],
+        )
+        .launch();
+}
diff --git a/src/tools/rustfmt/tests/source/expr.rs b/src/tools/rustfmt/tests/source/expr.rs
new file mode 100644
index 0000000000000..21f8a4a43668a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/expr.rs
@@ -0,0 +1,579 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// Test expressions
+
+fn foo() -> bool {
+    let boxed: Box<i32> = box   5;
+    let referenced = &5 ;
+
+    let very_long_variable_name = ( a +  first +   simple + test   );
+    let very_long_variable_name = (a + first + simple + test + AAAAAAAAAAAAA + BBBBBBBBBBBBBBBBB + b + c);
+
+    let is_internalxxxx = self.source_map.span_to_filename(s) == self.source_map.span_to_filename(m.inner);
+
+    let some_val = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa * bbbb / (bbbbbb -
+        function_call(x, *very_long_pointer, y))
+    + 1000  ;
+
+some_ridiculously_loooooooooooooooooooooong_function(10000 * 30000000000 + 40000 / 1002200000000
+                                                     - 50000 * sqrt(-1),
+                                                     trivial_value);
+    (((((((((aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + a +
+             aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + aaaaa)))))))))   ;
+
+    { for _ in 0..10 {} }
+
+    {{{{}}}}
+
+     if  1  + 2 > 0  { let result = 5; result } else { 4};
+
+    if  let   Some(x)  =  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {
+        // Nothing
+    }
+
+    if  let   Some(x)  =  (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) {}
+
+    if let (some_very_large,
+            tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple) = 1
+        + 2 + 3 {
+    }
+
+    if let (some_very_large,
+            tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple) = 1111 + 2222 {}
+
+    if let (some_very_large, tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple) = 1
+ + 2 + 3 {
+    }
+
+    if let ast::ItemKind::Trait(_, unsafety, ref generics, ref type_param_bounds, ref trait_items) = item.node
+    {
+        // nothing
+    }
+
+    let test = if true { 5 } else { 3 };
+
+    if cond() {
+        something();
+    } else  if different_cond() {
+        something_else();
+    } else {
+        // Check subformatting
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    }
+
+    // #2884
+    let _ = [0; {struct Foo; impl Foo {const fn get(&self) -> usize {5}}; Foo.get()}];
+}
+
+fn bar() {
+    let range = (   111111111 + 333333333333333333 + 1111 +   400000000000000000) .. (2222 +  2333333333333333);
+
+    let another_range = 5..some_func( a , b /* comment */);
+
+    for _  in  1 ..{ call_forever(); }
+
+    syntactically_correct(loop { sup( '?'); }, if cond { 0 } else { 1 });
+
+    let third = ..10;
+    let infi_range = ..   ;
+    let foo = 1..;
+    let bar = 5 ;
+    let nonsense = (10 .. 0)..(0..10);
+
+    loop{if true {break}}
+
+    let x = (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa &&
+             aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+             a);
+}
+
+fn baz() {
+    unsafe    /*    {}{}{}{{{{}}   */   {
+        let foo = 1u32;
+    }
+
+    unsafe /* very looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong comment */ {}
+
+    unsafe // So this is a very long comment.
+           // Multi-line, too.
+           // Will it still format correctly?
+    {
+    }
+
+    unsafe {
+        // Regular unsafe block
+    }
+
+    unsafe {
+        foo()
+    }
+
+    unsafe {
+        foo();
+    }
+
+    // #2289
+    let identifier_0 = unsafe { this_is_58_chars_long_and_line_is_93_chars_long_xxxxxxxxxx };
+    let identifier_1 = unsafe { this_is_59_chars_long_and_line_is_94_chars_long_xxxxxxxxxxx };
+    let identifier_2 = unsafe { this_is_65_chars_long_and_line_is_100_chars_long_xxxxxxxxxxxxxxxx };
+    let identifier_3 = unsafe { this_is_66_chars_long_and_line_is_101_chars_long_xxxxxxxxxxxxxxxxx };
+}
+
+// Test some empty blocks.
+fn qux() {
+    {}
+    // FIXME this one could be done better.
+    { /* a block with a comment */ }
+    {
+
+    }
+    {
+        // A block with a comment.
+    }
+}
+
+fn issue227() {
+    {
+        let handler = box DocumentProgressHandler::new(addr, DocumentProgressTask::DOMContentLoaded);
+    }
+}
+
+fn issue184(source: &str) {
+    for c in source.chars() {
+        if index < 'a' {
+            continue;
+        }
+    }
+}
+
+fn arrays() {
+    let x = [0,
+         1,
+         2,
+         3,
+         4,
+         5,
+         6,
+         7,
+         8,
+         9,
+         0,
+         1,
+         2,
+         3,
+         4,
+         5,
+         6,
+         7,
+         8,
+         9,
+         0,
+         7,
+         8,
+         9,
+         0,
+         1,
+         2,
+         3,
+         4,
+         5,
+         6,
+         7,
+         8,
+         9,
+         0];
+
+    let y = [/* comment */ 1, 2 /* post comment */, 3];
+
+    let xy =    [ strukt  { test123: value_one_two_three_four, turbo: coolio(), } , /* comment  */   1 ];
+
+        let a =WeightedChoice::new(&mut [Weighted {
+            weightweight: x,
+            item: 0,
+        },
+                                  Weighted {
+            weightweight: 1,
+            item: 1,
+        },
+                                  Weighted {
+            weightweight: x,
+            item: 2,
+        },
+                                  Weighted {
+            weightweight: 1,
+            item: 3,
+        }]);
+
+    let z = [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz, q];
+
+    [ 1 +   3, 4 ,  5, 6, 7, 7, fncall::<Vec<_>>(3-1)]
+}
+
+fn returns() {
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa && return;
+
+    return aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;
+}
+
+fn addrof() {
+    &    mut(aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa+bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb);
+    &    (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa+bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb);
+
+    // raw reference operator
+    & raw   const  a;
+    & raw   mut    b;
+}
+
+fn casts() {
+    fn unpack(packed: u32) -> [u16; 2] {
+        [
+            (packed >> 16) as u16,
+            (packed >>  0) as u16,
+        ]
+    }
+
+    let some_trait_xxx = xxxxxxxxxxx + xxxxxxxxxxxxx
+        as SomeTraitXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX;
+    let slightly_longer_trait = yyyyyyyyy + yyyyyyyyyyy as SomeTraitYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY;
+}
+
+fn indices() {
+    let x = (aaaaaaaaaaaaaaaaaaaaaaaaaaaa+bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb+cccccccccccccccc) [ x + y + z ];
+    let y = (aaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccc)[ xxxxx + yyyyy + zzzzz ];
+    let z = xxxxxxxxxx.x().y().zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz()[aaaaa];
+    let z = xxxxxxxxxx.x().y().zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz()[aaaaa];
+}
+
+fn repeats() {
+    let x = [aaaaaaaaaaaaaaaaaaaaaaaaaaaa+bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb+cccccccccccccccc; x + y + z ];
+    let y = [aaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccc; xxxxx + yyyyy + zzzzz ];
+}
+
+fn blocks() {
+    if 1 + 1 == 2 {
+        println!("yay arithmetix!");
+    };
+}
+
+fn issue767() {
+    if false {
+        if false {
+        } else {
+            // A let binding here seems necessary to trigger it.
+            let _ = ();
+        }
+    } else if let false = false {
+    }
+}
+
+fn ranges() {
+    let x = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa .. bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+    let y = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ..= bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+    let z = ..= x ;
+
+    // #1766
+    let x = [0. ..10.0];
+    let x = [0. ..=10.0];
+
+    a ..= b
+
+    // the expr below won't compile because inclusive ranges need a defined end
+    // let a = 0 ..= ;
+}
+
+fn if_else() {
+  let exact = diff /
+            (if size == 0 {
+    1
+} else {
+    size
+});
+
+            let cx = tp1.x +
+                 any * radius *
+                 if anticlockwise {
+            1.0
+      } else {
+           -1.0
+       };
+}
+
+fn complex_if_else() {
+    if let Some(x) = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx {
+    } else if let Some(x) = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx {
+        ha();
+    } else if xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx + xxxxxxxx {
+        yo();
+    } else if let Some(x) = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx {
+        ha();
+    } else if xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx + xxxxxxxxx {
+        yo();
+    }
+}
+
+fn issue1106() {
+    {
+    if let hir::ItemEnum(ref enum_def, ref generics) = self.ast_map.expect_item(enum_node_id).node {
+    }
+    }
+
+    for entry in
+    WalkDir::new(path)
+        .into_iter()
+        .filter_entry(|entry| exclusions.filter_entry(entry)) {
+    }
+}
+
+fn issue1570() {
+    a_very_long_function_name({some_func(1, {1})})
+}
+
+fn issue1714() {
+    v = &mut {v}[mid..];
+    let (left, right) = {v}.split_at_mut(mid);
+}
+
+// Multi-lined index should be put on the next line if it fits in one line.
+fn issue1749() {
+    {
+        {
+            {
+                if self.shape[(r as f32 + self.x_offset) as usize][(c as f32 + self.y_offset) as usize] != 0 {
+                    // hello
+                }
+            }
+        }
+    }
+}
+
+// #1172
+fn newlines_between_list_like_expr() {
+    foo(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+
+        zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
+    );
+
+    vec![
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+
+        zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
+    ];
+
+    match x {
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx |
+
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy |
+
+        zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz => foo(a, b, c),
+        _ => bar(),
+    };
+}
+
+fn issue2178() {
+    Ok(result.iter().map(|item| ls_util::rls_to_location(item)).collect())
+}
+
+// #2493
+impl Foo {
+fn bar(&self) {
+    {
+        let x = match () {
+            () => {
+                let i;
+                i == self.install_config.storage.experimental_compressed_block_size as usize
+            }
+        };
+    }
+}
+}
+
+fn dots() {
+    .. .. ..; // (.. (.. (..)))
+    ..= ..= ..;
+    (..) .. ..; // ((..) .. (..))
+}
+
+// #2676
+// A function call with a large single argument.
+fn foo() {
+    let my_var =
+        Mutex::new(RpcClientType::connect(server_iddd).chain_err(|| "Unable to create RPC client")?);
+}
+
+// #2704
+// Method call with prefix and suffix.
+fn issue2704() {
+    // We should not combine the callee with a multi-lined method call.
+    let requires = requires.set(&requires0
+                                .concat(&requires1)
+                                .concat(&requires2)
+                                .distinct_total());
+    let requires = requires.set(box requires0
+                                .concat(&requires1)
+                                .concat(&requires2)
+                                .distinct_total());
+    let requires = requires.set(requires0
+                                .concat(&requires1)
+                                .concat(&requires2)
+                                .distinct_total() as u32);
+    let requires = requires.set(requires0
+                                .concat(&requires1)
+                                .concat(&requires2)
+                                .distinct_total()?);
+    let requires = requires.set(!requires0
+                                .concat(&requires1)
+                                .concat(&requires2)
+                                .distinct_total());
+    // We should combine a small callee with an argument.
+    bar(vec![22]
+        .into_iter()
+        .map(|x| x * 2)
+        .filter(|_| true)
+        .collect());
+    // But we should not combine a long callee with an argument.
+    barrrr(vec![22]
+        .into_iter()
+        .map(|x| x * 2)
+        .filter(|_| true)
+        .collect());
+}
+
+// #2782
+fn issue2782() {
+    {let f={let f={{match f{F(f,_)=>{{loop{let f={match f{F(f,_)=>{{match f{F(f,_)=>{{loop{let f={let f={match f{'-'=>F(f,()),}};};}}}}}}}};}}}}}};};}
+}
+
+fn issue_2802() {
+    function_to_fill_this_line(some_arg, some_arg, some_arg)
+        * a_very_specific_length(specific_length_arg) * very_specific_length(Foo {
+        a: some_much_much_longer_value,
+    }) * some_value
+}
+
+fn issue_3003() {
+    let mut path: PathBuf = [
+        env!("CARGO_MANIFEST_DIR"),
+        "tests",
+        "support",
+        "dejavu-fonts-ttf-2.37",
+        "ttf",
+    ]
+        .iter()
+        .collect();
+}
+
+fn issue3226() {
+    {
+        {
+            {
+                return Err(ErrorKind::ManagementInterfaceError("Server exited unexpectedly").into())
+            }
+        }
+    }
+    {
+        {
+            {
+                break Err(ErrorKind::ManagementInterfaceError("Server exited unexpectedlyy").into())
+            }
+        }
+    }
+}
+
+// #3457
+fn issue3457() {
+    {
+        {
+            {
+                {
+                    {
+                        {
+                            {
+                                {
+                                    {
+                                        {
+                                            {
+                                                {
+                                                    {
+                                                        {
+                                                            {
+                                                                {
+                                                                    {
+                                                                        {
+                                                                            {
+                                                                                {
+                                                                                    {
+                                                                                        {
+                                                                                            {
+                                                                                                {
+                                                                                                    println!("Test");
+                                                                                                }
+                                                                                            }
+                                                                                        }
+                                                                                    }
+                                                                                }
+                                                                            }
+                                                                        }
+                                                                    }
+                                                                }
+                                                            }
+                                                        }
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+// #3498
+static REPRO: &[usize] = &[#[cfg(feature = "zero")]
+                           0];
+
+fn overflow_with_attr() {
+    foo(#[cfg(feature = "zero")]
+        0);
+    foobar(#[cfg(feature = "zero")]
+           0);
+    foobar(x, y, #[cfg(feature = "zero")]
+           {});
+}
+
+
+// https://github.com/rust-lang/rustfmt/issues/3765
+fn foo() {
+    async {
+        // Do
+        // some
+        // work
+    }
+    .await;
+
+    async {
+        // Do
+        // some
+        // work
+    }
+        .await;
+}
+
+fn underscore() {
+        _= 1;
+        _;
+        [  _,a,_  ] = [1, 2, 3];
+    (a,   _) = (8, 9);
+    TupleStruct(  _, a) = TupleStruct(2, 2);
+
+    let _  : usize = foo(_, _);
+}
diff --git a/src/tools/rustfmt/tests/source/extern.rs b/src/tools/rustfmt/tests/source/extern.rs
new file mode 100644
index 0000000000000..d0a033b12432a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/extern.rs
@@ -0,0 +1,79 @@
+// rustfmt-normalize_comments: true
+
+ extern crate       foo    ;   
+    extern crate       foo       as bar    ;   
+
+extern crate futures;
+extern crate dotenv;
+extern crate chrono;
+
+extern crate foo;
+extern crate bar;
+
+// #2315
+extern crate proc_macro2;
+extern crate proc_macro;
+
+// #3128
+extern crate serde; // 1.0.78
+extern crate serde_derive; // 1.0.78
+extern crate serde_json; // 1.0.27
+
+ extern  "C" {
+  fn c_func(x: *mut *mut libc::c_void);
+
+  fn c_func(x: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX, y: YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY);
+
+    #[test123]
+    fn foo() -> uint64_t;
+
+pub fn bar() ;
+   }
+
+extern {
+        fn DMR_GetDevice(pHDev: *mut HDEV, searchMode: DeviceSearchMode, pSearchString: *const c_char, devNr: c_uint, wildcard: c_char) -> TDMR_ERROR;
+        
+    fn quux() -> (); // Post comment
+
+  pub      type
+      Foo;
+
+          type   Bar;
+}
+
+extern "Rust" { static ext:  u32;
+    // Some comment.
+     pub static  mut var : SomeType ; }
+
+extern "C" {
+            fn syscall(number: libc::c_long /* comment 1 */, /* comm 2 */ ... /* sup? */) -> libc::c_long;
+
+    fn  foo  (x:  *const c_char ,    ...   ) ->
+libc::c_long;
+        }
+
+   extern    {  
+                       pub fn freopen(filename: *const c_char, mode: *const c_char
+                               , mode2: *const c_char
+                               , mode3: *const c_char,
+                               file: *mut FILE)
+                              -> *mut FILE;
+
+
+       const fn foo(
+
+       ) ->
+                            *mut Bar;
+       unsafe fn foo(
+
+       ) -> *
+       mut
+       Bar;
+
+       pub(super) const fn foo() -> *mut Bar;
+       pub(crate) unsafe fn foo() -> *mut Bar;
+   }
+
+extern {
+
+}
diff --git a/src/tools/rustfmt/tests/source/extern_not_explicit.rs b/src/tools/rustfmt/tests/source/extern_not_explicit.rs
new file mode 100644
index 0000000000000..9d6c4c2a1cd52
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/extern_not_explicit.rs
@@ -0,0 +1,14 @@
+// rustfmt-force_explicit_abi: false
+
+ extern  "C" {
+   fn some_fn() -> ();
+ }
+
+ extern "C" fn sup() {
+
+ }
+
+type funky_func = extern "C" fn (unsafe extern "rust-call" fn(*const JSJitInfo, *mut JSContext,
+                                              HandleObject, *mut libc::c_void, u32,
+                                              *mut JSVal)
+                                              -> u8);
diff --git a/src/tools/rustfmt/tests/source/file-lines-1.rs b/src/tools/rustfmt/tests/source/file-lines-1.rs
new file mode 100644
index 0000000000000..0164e30a854c5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-1.rs
@@ -0,0 +1,29 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-1.rs","range":[4,8]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/file-lines-2.rs b/src/tools/rustfmt/tests/source/file-lines-2.rs
new file mode 100644
index 0000000000000..6f44ec6e69d1b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-2.rs
@@ -0,0 +1,29 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-2.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+            .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/file-lines-3.rs b/src/tools/rustfmt/tests/source/file-lines-3.rs
new file mode 100644
index 0000000000000..4b825b9f58cee
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-3.rs
@@ -0,0 +1,29 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-3.rs","range":[4,8]},{"file":"tests/source/file-lines-3.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/file-lines-4.rs b/src/tools/rustfmt/tests/source/file-lines-4.rs
new file mode 100644
index 0000000000000..83928bf6fecfa
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-4.rs
@@ -0,0 +1,30 @@
+// rustfmt-file_lines: []
+// (Test that nothing is formatted if an empty array is specified.)
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2	
+            }
+                .method_call();
+                                                                                              // aaaaaaaaaaaaa
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }    
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/file-lines-5.rs b/src/tools/rustfmt/tests/source/file-lines-5.rs
new file mode 100644
index 0000000000000..8ec2c67bc4446
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-5.rs
@@ -0,0 +1,17 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-5.rs","range":[3,5]}]
+
+struct A {
+t: i64,     
+}
+
+mod foo {
+    fn bar() {
+                         // test
+                             let i = 12;
+                                 // test
+    }
+    // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    fn baz() {
+        let j = 15;     
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/file-lines-6.rs b/src/tools/rustfmt/tests/source/file-lines-6.rs
new file mode 100644
index 0000000000000..2eacc8a0e7522
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-6.rs
@@ -0,0 +1,18 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-6.rs","range":[9,10]}]
+
+struct A {
+    t: i64,
+}
+
+mod foo {
+    fn bar() {
+                         // test	
+                             let i = 12;
+                                 // test
+    }
+
+    fn baz() {
+///
+        let j = 15;     
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/file-lines-7.rs b/src/tools/rustfmt/tests/source/file-lines-7.rs
new file mode 100644
index 0000000000000..b227ac35dccda
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-7.rs
@@ -0,0 +1,24 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-7.rs","range":[8,15]}]
+
+struct A {
+    t: i64,
+}
+
+mod foo {
+    fn bar() {
+
+
+
+        // test 
+        let i = 12;
+        // test
+    }
+
+    fn baz() {
+
+
+
+        ///
+        let j = 15;     
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/file-lines-item.rs b/src/tools/rustfmt/tests/source/file-lines-item.rs
new file mode 100644
index 0000000000000..fe52a7fa17618
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/file-lines-item.rs
@@ -0,0 +1,21 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-item.rs","range":[6,8]}]
+
+use foo::{c, b, a};
+use bar;
+
+fn foo() {
+    bar ( ) ;
+}
+
+impl Drop for Context {
+     fn drop(&mut self) {
+    }
+}
+
+impl Bar for Baz {
+    fn foo() {
+        bar(
+            baz, // Who knows?
+        )
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/fn-custom-2.rs b/src/tools/rustfmt/tests/source/fn-custom-2.rs
new file mode 100644
index 0000000000000..a3697c36d0f6f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-custom-2.rs
@@ -0,0 +1,35 @@
+// Test different indents.
+
+fn foo(a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc, d: Ddddddddddddddddddddddddd, e: Eeeeeeeeeeeeeeeeeee) {
+    foo();
+}
+
+fn bar<'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb, TTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW>(a: Aaaaaaaaaaaaaaa) {
+    bar();
+}
+
+fn baz() where X: TTTTTTTT {
+    baz();
+}
+
+fn qux() where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}
+
+impl Foo {
+    fn foo(self, a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc, d: Ddddddddddddddddddddddddd, e: Eeeeeeeeeeeeeeeeeee) {
+        foo();
+    }    
+
+    fn bar<'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb, TTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW>(a: Aaaaaaaaaaaaaaa) {
+        bar();
+    }
+
+    fn baz() where X: TTTTTTTT {
+        baz();
+    }
+}
+
+struct Foo<TTTTTTTTTTTTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUU, VVVVVVVVVVVVVVVVVVVVVVVVVVV, WWWWWWWWWWWWWWWWWWWWWWWW> {
+    foo: Foo,
+}
diff --git a/src/tools/rustfmt/tests/source/fn-custom-3.rs b/src/tools/rustfmt/tests/source/fn-custom-3.rs
new file mode 100644
index 0000000000000..a5e0f9af26dd4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-custom-3.rs
@@ -0,0 +1,31 @@
+// Test different indents.
+
+fn foo(a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc, d: Ddddddddddddddddddddddddd, e: Eeeeeeeeeeeeeeeeeee) {
+    foo();
+}
+
+fn bar<'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb, TTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW>(a: Aaaaaaaaaaaaaaa) {
+    bar();
+}
+
+fn qux() where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}
+
+fn qux() where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}
+
+impl Foo {
+    fn foo(self, a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc, d: Ddddddddddddddddddddddddd, e: Eeeeeeeeeeeeeeeeeee) {
+        foo();
+    }    
+
+    fn bar<'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb, TTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW>(a: Aaaaaaaaaaaaaaa) {
+        bar();
+    }
+}
+
+struct Foo<TTTTTTTTTTTTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUU, VVVVVVVVVVVVVVVVVVVVVVVVVVV, WWWWWWWWWWWWWWWWWWWWWWWW> {
+    foo: Foo,
+}
diff --git a/src/tools/rustfmt/tests/source/fn-custom-4.rs b/src/tools/rustfmt/tests/source/fn-custom-4.rs
new file mode 100644
index 0000000000000..6e18b6f9fe2b7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-custom-4.rs
@@ -0,0 +1,13 @@
+// Test different indents.
+
+fn qux() where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}
+
+fn qux() where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}
+
+fn qux(a: Aaaaaaaaaaaaaaaaa) where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}
diff --git a/src/tools/rustfmt/tests/source/fn-custom-6.rs b/src/tools/rustfmt/tests/source/fn-custom-6.rs
new file mode 100644
index 0000000000000..807084575fa96
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-custom-6.rs
@@ -0,0 +1,40 @@
+// rustfmt-brace_style: PreferSameLine
+// Test different indents.
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) -> String {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) where T: UUUUUUUUUUU {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) where T: UUUUUUUUUUU {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String where T: UUUUUUUUUUU {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) -> String where T: UUUUUUUUUUU {
+    bar();
+}
+
+trait Test {
+    fn foo(a: u8) {}
+
+    fn bar(a: u8) -> String {}
+}
diff --git a/src/tools/rustfmt/tests/source/fn-custom-7.rs b/src/tools/rustfmt/tests/source/fn-custom-7.rs
new file mode 100644
index 0000000000000..d5330196bf795
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-custom-7.rs
@@ -0,0 +1,24 @@
+// rustfmt-normalize_comments: true
+// rustfmt-fn_args_layout: Vertical
+// rustfmt-brace_style: AlwaysNextLine
+
+// Case with only one variable.
+fn foo(a: u8) -> u8 {
+    bar()
+}
+
+// Case with 2 variables and some pre-comments.
+fn foo(a: u8 /* Comment 1 */, b: u8 /* Comment 2 */) -> u8 {
+    bar()
+}
+
+// Case with 2 variables and some post-comments.
+fn foo(/* Comment 1 */ a: u8, /* Comment 2 */ b: u8) -> u8 {
+    bar()
+}
+
+trait Test {
+    fn foo(a: u8) {}
+
+    fn bar(a: u8) -> String {}
+}
diff --git a/src/tools/rustfmt/tests/source/fn-custom-8.rs b/src/tools/rustfmt/tests/source/fn-custom-8.rs
new file mode 100644
index 0000000000000..0dd64868b2d54
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-custom-8.rs
@@ -0,0 +1,48 @@
+// rustfmt-brace_style: PreferSameLine
+// Test different indents.
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) -> String {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) where T: UUUUUUUUUUU {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) where T: UUUUUUUUUUU {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String where T: UUUUUUUUUUU {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) -> String where T: UUUUUUUUUUU {
+    bar();
+}
+
+trait Test {
+    fn foo(
+        a: u8) {
+
+    }
+
+    fn bar(a: u8)
+    -> String {
+
+    }
+
+    fn bar(a: u8) -> String where Foo: foooo, Bar: barrr {}
+}
diff --git a/src/tools/rustfmt/tests/source/fn-custom.rs b/src/tools/rustfmt/tests/source/fn-custom.rs
new file mode 100644
index 0000000000000..77ced4c5e0e10
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-custom.rs
@@ -0,0 +1,13 @@
+// rustfmt-fn_args_layout: Compressed
+// Test some of the ways function signatures can be customised.
+
+// Test compressed layout of args.
+fn foo(a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc, d: Ddddddddddddddddddddddddd, e: Eeeeeeeeeeeeeeeeeee) {
+    foo();
+}
+
+impl Foo {
+    fn foo(self, a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc, d: Ddddddddddddddddddddddddd, e: Eeeeeeeeeeeeeeeeeee) {
+        foo();
+    }    
+}
diff --git a/src/tools/rustfmt/tests/source/fn-param-attributes.rs b/src/tools/rustfmt/tests/source/fn-param-attributes.rs
new file mode 100644
index 0000000000000..3407a3b2ef2e5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-param-attributes.rs
@@ -0,0 +1,57 @@
+// https://github.com/rust-lang/rustfmt/issues/3623
+
+fn foo(#[cfg(something)] x: i32, y: i32) -> i32 {
+    x + y
+}
+
+fn foo_b(#[cfg(something)]x: i32, y: i32) -> i32 {
+    x + y
+}
+
+fn add(#[cfg(something)]#[deny(C)]  x: i32, y: i32) -> i32 {
+    x + y
+}
+
+struct NamedSelfRefStruct {}
+impl NamedSelfRefStruct {
+    fn foo(
+#[cfg(something)]  self: &Self,
+    ) {}
+}
+
+struct MutStruct {}
+impl MutStruct {
+    fn foo(
+        #[cfg(foo)]&mut self,#[deny(C)] b: i32,
+    ) {}
+}
+
+fn main() {
+    let c = |
+        #[allow(C)]a: u32,
+        #[cfg(something)] b: i32,
+        #[cfg_attr(something, cfg(nothing))]#[deny(C)] c: i32,
+    | {};
+    let _ = c(1, 2);
+}
+
+pub fn bar(
+    /// bar
+#[test] a: u32,
+    /// Bar
+            #[must_use]
+/// Baz
+    #[no_mangle] b: i32,
+) {}
+
+
+fn abc(
+    #[foo]
+    #[bar] param: u32,
+) {
+    // ...
+}
+
+fn really_really_really_loooooooooooooooooooong(#[cfg(some_even_longer_config_feature_that_keeps_going_and_going_and_going_forever_and_ever_and_ever_on_and_on)] b: i32) {
+    // ...
+}
diff --git a/src/tools/rustfmt/tests/source/fn-simple.rs b/src/tools/rustfmt/tests/source/fn-simple.rs
new file mode 100644
index 0000000000000..528b9a0292a9e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-simple.rs
@@ -0,0 +1,74 @@
+// rustfmt-normalize_comments: true
+
+fn simple(/*pre-comment on a function!?*/ i: i32/*yes, it's possible!  */   
+                                        ,response: NoWay /* hose */) {
+fn op(x: Typ, key : &[u8], upd : Box<Fn(Option<&memcache::Item>) -> (memcache::Status, Result<memcache::Item, Option<String>>)>) -> MapResult {}
+
+        "cool"}
+
+
+fn weird_comment(/* /*/ double level */ comment */ x: Hello /*/*/* triple, even */*/*/,
+// Does this work?
+y: World
+) {
+        simple(/* does this preserve comments now? */ 42, NoWay)
+}
+
+fn generic<T>(arg: T) -> &SomeType
+    where T: Fn(// First arg
+        A,
+        // Second argument
+        B, C, D, /* pre comment */ E /* last comment */) -> &SomeType {
+    arg(a, b, c, d, e)
+}
+
+fn foo()  ->  !  {}
+
+pub fn http_fetch_async(listener:Box< AsyncCORSResponseListener+Send >,  script_chan:  Box<ScriptChan+Send>) {
+}
+
+fn some_func<T:Box<Trait+Bound>>(val:T){}
+
+fn zzzzzzzzzzzzzzzzzzzz<Type, NodeType>
+                       (selff: Type, mut handle: node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>)
+                        -> SearchStack<'a, K, V, Type, NodeType>{
+}
+
+unsafe fn generic_call(cx: *mut JSContext, argc: libc::c_uint, vp: *mut JSVal,
+    is_lenient: bool,
+                       call: unsafe extern fn(*const JSJitInfo, *mut JSContext,
+                                              HandleObject, *mut libc::c_void, u32,
+                                              *mut JSVal)
+                                              -> u8) {
+    let f:  fn  ( _ , _  ) ->  _   =  panic!()  ;
+}
+
+pub fn start_export_thread<C: CryptoSchemee + 'static>(database: &Database, crypto_scheme: &C, block_size: usize, source_path: &Path) -> BonzoResult<mpsc::Consumer<'static, FileInstruction>> {}
+
+pub fn waltz(cwd: &Path) -> CliAssert {
+    {
+        {
+            formatted_comment = rewrite_comment(comment, block_style, width, offset, formatting_fig);
+        }
+    }
+}
+
+// #2003
+mod foo {
+    fn __bindgen_test_layout_i_open0_c_open1_char_a_open2_char_close2_close1_close0_instantiation() {
+        foo();
+    }
+}
+
+// #2082
+pub(crate) fn init() {}
+
+crate fn init() {}
+
+// #2630
+fn make_map<T, F: (Fn(&T) -> String)>(records: &Vec<T>, key_fn: F) -> HashMap<String, usize> {}
+
+// #2956
+fn bar(beans: Asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf, spam: bool, eggs: bool) -> bool{
+    unimplemented!();
+}
diff --git a/src/tools/rustfmt/tests/source/fn-single-line/version_one.rs b/src/tools/rustfmt/tests/source/fn-single-line/version_one.rs
new file mode 100644
index 0000000000000..469ab621567b5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-single-line/version_one.rs
@@ -0,0 +1,80 @@
+// rustfmt-fn_single_line: true
+// rustfmt-version: One
+// Test single-line functions.
+
+fn foo_expr() {
+    1
+}
+
+fn foo_stmt() {
+    foo();
+}
+
+fn foo_decl_local()  {
+    let z = 5;
+   }
+
+fn    foo_decl_item(x: &mut i32) {
+    x = 3;
+}
+
+   fn empty()     {
+
+}
+
+fn foo_return() -> String {
+    "yay"
+}
+
+fn foo_where() -> T where T: Sync {
+    let x = 2;
+}
+
+fn fooblock() {
+    {
+        "inner-block"
+    }
+}
+
+fn fooblock2(x: i32) {
+    let z = match x {
+        _ => 2,
+    };
+}
+
+fn comment() {
+    // this is a test comment
+    1
+}
+
+fn comment2() {
+    // multi-line comment
+    let z = 2;
+    1
+}
+
+fn only_comment() {
+    // Keep this here
+}
+
+fn aaaaaaaaaaaaaaaaa_looooooooooooooooooooooong_name() {
+    let z = "aaaaaaawwwwwwwwwwwwwwwwwwwwwwwwwwww";
+}
+
+fn lots_of_space                      ()                                                           {
+                           1                 
+}
+
+fn mac() -> Vec<i32> { vec![] }
+
+trait CoolTypes {
+    fn dummy(&self) {
+    }
+}
+
+trait CoolerTypes { fn dummy(&self) { 
+}
+}
+
+fn Foo<T>() where T: Bar {
+}
diff --git a/src/tools/rustfmt/tests/source/fn-single-line/version_two.rs b/src/tools/rustfmt/tests/source/fn-single-line/version_two.rs
new file mode 100644
index 0000000000000..bf381ff106514
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn-single-line/version_two.rs
@@ -0,0 +1,80 @@
+// rustfmt-fn_single_line: true
+// rustfmt-version: Two
+// Test single-line functions.
+
+fn foo_expr() {
+    1
+}
+
+fn foo_stmt() {
+    foo();
+}
+
+fn foo_decl_local()  {
+    let z = 5;
+   }
+
+fn    foo_decl_item(x: &mut i32) {
+    x = 3;
+}
+
+   fn empty()     {
+
+}
+
+fn foo_return() -> String {
+    "yay"
+}
+
+fn foo_where() -> T where T: Sync {
+    let x = 2;
+}
+
+fn fooblock() {
+    {
+        "inner-block"
+    }
+}
+
+fn fooblock2(x: i32) {
+    let z = match x {
+        _ => 2,
+    };
+}
+
+fn comment() {
+    // this is a test comment
+    1
+}
+
+fn comment2() {
+    // multi-line comment
+    let z = 2;
+    1
+}
+
+fn only_comment() {
+    // Keep this here
+}
+
+fn aaaaaaaaaaaaaaaaa_looooooooooooooooooooooong_name() {
+    let z = "aaaaaaawwwwwwwwwwwwwwwwwwwwwwwwwwww";
+}
+
+fn lots_of_space                      ()                                                           {
+                           1                 
+}
+
+fn mac() -> Vec<i32> { vec![] }
+
+trait CoolTypes {
+    fn dummy(&self) {
+    }
+}
+
+trait CoolerTypes { fn dummy(&self) { 
+}
+}
+
+fn Foo<T>() where T: Bar {
+}
diff --git a/src/tools/rustfmt/tests/source/fn_args_indent-block.rs b/src/tools/rustfmt/tests/source/fn_args_indent-block.rs
new file mode 100644
index 0000000000000..955f390cca2ca
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn_args_indent-block.rs
@@ -0,0 +1,77 @@
+// rustfmt-normalize_comments: true
+
+fn foo() {
+    foo();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String {
+    foo();
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) -> String {
+    bar();
+}
+
+fn foo(a: u8 /* Comment 1 */, b: u8 /* Comment 2 */) -> u8 {
+    bar()
+}
+
+fn foo(a: u8 /* Comment 1 */, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee /* Comment 2 */) -> u8 {
+    bar()
+}
+
+fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) -> String where X: Fooooo, Y: Baaar  {
+    bar();
+}
+
+fn foo() -> T {
+    foo();
+}
+
+fn foo() -> T where X: Foooo, Y: Baaar {
+    foo();
+}
+
+fn foo() where X: Foooo {
+}
+
+fn foo() where X: Foooo, Y: Baaar {
+}
+
+fn foo() -> (Loooooooooooooooooooooong, Reeeeeeeeeeeeeeeeeeeeeeeeturn, iiiiiiiiis, Looooooooooooooooong) {
+    foo();
+}
+
+fn foo<g: G>() {
+    foo();
+}
+
+fn foo<L: Loooooooooooooooooooooong, G: Geeeeeeeeeeeneric, I: iiiiiiiiis, L: Looooooooooooooooong>() {
+    foo();
+}
+
+fn foo<L: Loooooooooooooooooooong, G: Geeeeeeeeeeneric, I: iiiiiiiiis, L: Loooooooooooooooong>() {
+    foo();
+}
+
+trait Test {
+    fn foo(a: u8) {}
+
+    fn bar(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd, e: Eeeeeeeeeeeeeee) -> String {}
+}
+
+fn foo<L: Loooooooooooooooooooong, G: Geeeeeeeeeeneric, I: iiiiiiiiis, L: Loooooooooooooooong>(a: Aaaaaaaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbbb, c: Cccccccccccccccccc, d: Dddddddddddddddd) {
+    foo();
+}
+
+fn foo() -> (Looooooooooooooooooooooooooong, Reeeeeeeeeeeeeeeeeeeeeeeeeeeeeturn, iiiiiiiiiiiiiis, Loooooooooooooooooooooong) {
+    foo();
+}
diff --git a/src/tools/rustfmt/tests/source/fn_args_layout-vertical.rs b/src/tools/rustfmt/tests/source/fn_args_layout-vertical.rs
new file mode 100644
index 0000000000000..759bc83d01570
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/fn_args_layout-vertical.rs
@@ -0,0 +1,33 @@
+// rustfmt-fn_args_layout: Vertical
+
+// Empty list should stay on one line.
+fn do_bar(
+
+) -> u8 {
+    bar()
+}
+
+// A single argument should stay on the same line.
+fn do_bar(
+        a: u8) -> u8 {
+    bar()
+}
+
+// Multiple arguments should each get their own line.
+fn do_bar(a: u8, mut b: u8, c: &u8, d: &mut u8, closure: &Fn(i32) -> i32) -> i32 {
+    // This feature should not affect closures.
+    let bar = |x: i32, y: i32| -> i32 { x + y };
+    bar(a, b)
+}
+
+// If the first argument doesn't fit on the same line with the function name,
+// the whole list should probably be pushed to the next line with hanging
+// indent. That's not what happens though, so check current behaviour instead.
+// In any case, it should maintain single argument per line.
+fn do_this_that_and_the_other_thing(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: u8,
+        b: u8, c: u8, d: u8) {
+    this();
+    that();
+    the_other_thing();
+}
diff --git a/src/tools/rustfmt/tests/source/hard-tabs.rs b/src/tools/rustfmt/tests/source/hard-tabs.rs
new file mode 100644
index 0000000000000..e4a0f41700751
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/hard-tabs.rs
@@ -0,0 +1,84 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-hard_tabs: true
+
+fn main() {
+let x = Bar;
+
+let y = Foo {a: x };
+
+Foo { a: foo() /* comment*/, /* comment*/ b: bar(), ..something };
+
+fn foo(a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32) {}
+
+let str = "AAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAa";
+
+if let (some_very_large, tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple) = 1
++ 2 + 3 {
+}
+
+    if cond() {
+        something();
+    } else  if different_cond() {
+        something_else();
+    } else {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    }
+    
+unsafe /* very looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong comment */ {}
+
+unsafe // So this is a very long comment.
+   // Multi-line, too.
+   // Will it still format correctly?
+{
+}
+
+let chain = funktion_kall().go_to_next_line_with_tab().go_to_next_line_with_tab().go_to_next_line_with_tab();
+
+let z = [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz, q];
+
+fn generic<T>(arg: T) -> &SomeType
+    where T: Fn(// First arg
+        A,
+        // Second argument
+        B, C, D, /* pre comment */ E /* last comment */) -> &SomeType {
+    arg(a, b, c, d, e)    
+}
+
+    loong_func().quux(move || {
+        if true {
+            1
+        } else {
+            2
+        }
+    });
+
+    fffffffffffffffffffffffffffffffffff(a,
+                                        {
+                                            SCRIPT_TASK_ROOT
+                                            .with(|root| {
+                                                *root.borrow_mut()  =   Some(&script_task);
+                                            });
+                                        });
+    a.b
+     .c
+     .d();
+    
+    x().y(|| {
+        match cond() {
+            true => (),
+            false => (),
+        }
+    });
+}
+
+// #2296
+impl Foo {
+	// a comment
+	// on multiple lines
+	fn foo() {
+		// another comment
+		// on multiple lines
+		let x = true;
+	}
+}
diff --git a/src/tools/rustfmt/tests/source/hello.rs b/src/tools/rustfmt/tests/source/hello.rs
new file mode 100644
index 0000000000000..f892e6debb10d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/hello.rs
@@ -0,0 +1,6 @@
+// rustfmt-config: small_tabs.toml
+// rustfmt-target: hello.rs
+
+// Smoke test - hello world.
+
+fn main() { println!("Hello world!"); }
diff --git a/src/tools/rustfmt/tests/source/hello2.rs b/src/tools/rustfmt/tests/source/hello2.rs
new file mode 100644
index 0000000000000..48af7de388747
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/hello2.rs
@@ -0,0 +1,8 @@
+// rustfmt-config: small_tabs.toml
+// rustfmt-target: hello.rs
+
+// Smoke test - hello world.
+
+fn main( ) {
+println!("Hello world!");
+}
diff --git a/src/tools/rustfmt/tests/source/if_while_or_patterns.rs b/src/tools/rustfmt/tests/source/if_while_or_patterns.rs
new file mode 100644
index 0000000000000..f01df7e91586d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/if_while_or_patterns.rs
@@ -0,0 +1,27 @@
+#![feature(if_while_or_patterns)]
+
+fn main() {
+    if let 0 | 1 = 0 {
+        println!("hello, world");
+    };
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaa | bbbbbbbbbbbbbbbbbbbbbbbbbbb | cccccccccccccccc | d_100 = 0 {
+        println!("hello, world");
+    }
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaa | bbbbbbbbbbbbbbbbbbbbbbb | ccccccccccccccccccccc | d_101 = 0 {
+        println!("hello, world");
+    }
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaaaa | bbbbbbbbbbbbbbbbbbbbbbb | ccccccccccccccccccccc | d_103 = 0 {
+        println!("hello, world");
+    }
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | bbbbbbbbbbbbbbbbbbbbbbb | ccccccccccccccccccccc | d_105 = 0 {
+        println!("hello, world");
+    }
+
+    while let xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx = foo_bar(bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb, cccccccccccccccccccccccccccccccccccccccc) {
+        println!("hello, world");
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/immovable_generators.rs b/src/tools/rustfmt/tests/source/immovable_generators.rs
new file mode 100644
index 0000000000000..c57a1e1448349
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/immovable_generators.rs
@@ -0,0 +1,7 @@
+#![feature(generators)]
+
+unsafe fn foo() {
+    let mut ga = static || { 
+        yield 1;
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/impls.rs b/src/tools/rustfmt/tests/source/impls.rs
new file mode 100644
index 0000000000000..fb8701989fa19
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/impls.rs
@@ -0,0 +1,170 @@
+// rustfmt-normalize_comments: true
+impl Foo for Bar { fn foo() { "hi" } }
+
+pub impl Foo for Bar {
+    // Associated Constants
+    const   Baz:   i32 =   16;
+    // Associated Types
+    type   FooBar  =   usize;
+    // Comment 1
+    fn foo() { "hi" }
+    // Comment 2
+    fn foo() { "hi" }
+    // Comment 3
+}
+
+pub unsafe impl<'a, 'b, X, Y: Foo<Bar>> !Foo<'a, X> for Bar<'b, Y> where X: Foo<'a, Z> {
+    fn foo() { "hi" }    
+}
+
+impl<'a, 'b, X, Y: Foo<Bar>> Foo<'a, X> for Bar<'b, Y> where X: Fooooooooooooooooooooooooooooo<'a, Z>
+{
+    fn foo() { "hi" }    
+}
+
+impl<'a, 'b, X, Y: Foo<Bar>> Foo<'a, X> for Bar<'b, Y> where X: Foooooooooooooooooooooooooooo<'a, Z>
+{
+    fn foo() { "hi" }    
+}
+
+impl<T> Foo for Bar<T> where T: Baz 
+{
+}
+
+impl<T> Foo for Bar<T> where T: Baz { /* Comment */ }
+
+impl Foo {
+    fn foo() {}
+}
+
+impl Boo {
+
+    // BOO
+    fn boo() {}
+    // FOO
+
+    
+    
+}
+
+mod a {
+    impl Foo {
+        // Hello!
+        fn foo() {}
+    }
+}
+
+
+mod b {
+    mod a {
+        impl Foo {
+            fn foo() {}
+        }
+    }
+}
+
+impl Foo { add_fun!(); }
+
+impl Blah {
+    fn boop() {}
+    add_fun!();
+}
+
+impl X { fn do_parse(  mut  self : X ) {} }
+
+impl Y5000 {
+    fn bar(self: X< 'a ,  'b >, y: Y) {}
+
+    fn bad(&self, ( x, y): CoorT) {}
+
+    fn turbo_bad(self: X< 'a ,  'b >  , ( x, y): CoorT) {
+        
+    }
+}
+
+pub impl<T> Foo for Bar<T> where T: Foo
+{
+    fn foo() { "hi" }
+}
+
+pub impl<T, Z> Foo for Bar<T, Z> where T: Foo, Z: Baz {}
+
+mod m {
+    impl<T> PartialEq for S<T> where T: PartialEq {
+        fn eq(&self, other: &Self) {
+            true
+        }
+      }
+
+        impl<T> PartialEq for S<T> where T: PartialEq {      }
+ }
+
+impl<BorrowType, K, V, NodeType, HandleType> Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType> {
+}
+
+impl<BorrowType, K, V, NodeType, HandleType> PartialEq for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType> {
+}
+
+mod x {
+    impl<A, B, C, D> Foo
+        where A: 'static,
+              B: 'static,
+              C: 'static,
+              D: 'static { }
+}
+
+impl<ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNodeFoo> Issue1249<ConcreteThreadSafeLayoutNode> {
+    // Creates a new flow constructor.
+   fn foo() {}
+}
+
+// #1600
+impl<#[may_dangle] K, #[may_dangle] V> Drop for RawTable<K, V> {
+    fn drop() {}
+}
+
+// #1168
+pub trait Number: Copy + Eq +      Not<Output = Self> + Shl<u8, Output = Self> +
+    Shr<u8, Output = Self>       +
+    BitAnd<Self, Output=Self> +    BitOr<Self, Output=Self>  + BitAndAssign + BitOrAssign
+
+
+
+{
+    // test
+    fn zero() -> Self;
+}
+
+// #1642
+pub trait SomeTrait : Clone + Eq + PartialEq + Ord + PartialOrd + Default + Hash + Debug + Display + Write + Read + FromStr {
+    // comment
+}
+
+// #1995
+impl Foo {
+    fn f(
+		    S {
+			      aaaaaaaaaa: aaaaaaaaaa,
+			      bbbbbbbbbb: bbbbbbbbbb,
+			      cccccccccc: cccccccccc,
+		    }: S
+    ) -> u32{
+        1
+    }
+}
+
+// #2491
+impl<'a, 'b, 'c> SomeThing<Something> for (&'a mut SomethingLong, &'b mut SomethingLong, &'c mut SomethingLong) {
+    fn foo() {}
+}
+
+// #2746
+impl<'seq1, 'seq2, 'body, 'scope, Channel> Adc12< Dual, MasterRunningDma<'seq1, 'body, 'scope, Channel>, SlaveRunningDma<'seq2, 'body, 'scope>, > where Channel: DmaChannel, {}
+
+// #4084
+impl     const       std::default::Default for Struct {
+    #[inline]
+    fn default() -> Self {
+        Self { f: 12.5 }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/imports-impl-only-use.rs b/src/tools/rustfmt/tests/source/imports-impl-only-use.rs
new file mode 100644
index 0000000000000..d290d8d91858d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports-impl-only-use.rs
@@ -0,0 +1,4 @@
+#![feature(underscore_imports)]
+
+use attr;
+use std::iter::Iterator as _;
diff --git a/src/tools/rustfmt/tests/source/imports-reorder-lines-and-items.rs b/src/tools/rustfmt/tests/source/imports-reorder-lines-and-items.rs
new file mode 100644
index 0000000000000..b6380f31c6104
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports-reorder-lines-and-items.rs
@@ -0,0 +1,7 @@
+/// This comment should stay with `use std::str;`
+use std::str;
+use std::cmp::{d, c, b, a};
+use std::ddd::aaa;
+use std::ddd::{d as p, c as g, b, a};
+// This comment should stay with `use std::ddd:bbb;`
+use std::ddd::bbb;
diff --git a/src/tools/rustfmt/tests/source/imports-reorder-lines.rs b/src/tools/rustfmt/tests/source/imports-reorder-lines.rs
new file mode 100644
index 0000000000000..2b018544eaeb2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports-reorder-lines.rs
@@ -0,0 +1,32 @@
+use std::str;
+use std::cmp::{d, c, b, a};
+use std::cmp::{b, e, g, f};
+use std::ddd::aaa;
+// This comment should stay with `use std::ddd;`
+use std::ddd;
+use std::ddd::bbb;
+
+mod test {
+}
+
+use aaa::bbb;
+use aaa;
+use aaa::*;
+
+mod test {}
+// If item names are equal, order by rename
+
+use test::{a as bb, b};
+use test::{a as aa, c};
+
+mod test {}
+// If item names are equal, order by rename - no rename comes before a rename
+
+use test::{a as bb, b};
+use test::{a, c};
+
+mod test {}
+// `self` always comes first
+
+use test::{a as aa, c};
+use test::{self as bb, b};
diff --git a/src/tools/rustfmt/tests/source/imports-reorder.rs b/src/tools/rustfmt/tests/source/imports-reorder.rs
new file mode 100644
index 0000000000000..cbe9d6ca78ad7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports-reorder.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+
+use path::{C,/*A*/ A, B /* B */, self /* self */};
+
+use {ab, ac, aa, Z, b};
diff --git a/src/tools/rustfmt/tests/source/imports.rs b/src/tools/rustfmt/tests/source/imports.rs
new file mode 100644
index 0000000000000..4dfc6ed94e34f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports.rs
@@ -0,0 +1,107 @@
+// rustfmt-normalize_comments: true
+
+// Imports.
+
+// Long import.
+use rustc_ast::ast::{ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic, ItemDefaultImpl};
+use exceedingly::looooooooooooooooooooooooooooooooooooooooooooooooooooooooooong::import::path::{ItemA, ItemB};
+use exceedingly::loooooooooooooooooooooooooooooooooooooooooooooooooooooooong::import::path::{ItemA, ItemB};
+
+use list::{
+    // Some item
+    SomeItem /* Comment */, /* Another item */ AnotherItem /* Another Comment */, // Last Item
+    LastItem
+};
+
+use test::{  Other          /* C   */  , /*   A   */ self  /*    B     */    };
+
+use rustc_ast::{self};
+use {/* Pre-comment! */
+     Foo, Bar /* comment */};
+use Foo::{Bar, Baz};
+pub use rustc_ast::ast::{Expr_, Expr, ExprAssign, ExprCall, ExprMethodCall, ExprPath};
+
+use rustc_ast::some::{};
+
+use self;
+use std::io::{self};
+use std::io::self;
+
+mod Foo {
+    pub use rustc_ast::ast::{
+        ItemForeignMod,
+        ItemImpl,
+        ItemMac,
+        ItemMod,
+        ItemStatic,
+        ItemDefaultImpl
+    };
+
+    mod Foo2 {
+        pub use rustc_ast::ast::{ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic, self, ItemDefaultImpl};
+    }
+}
+
+fn test() {
+use Baz::*;
+        use Qux;
+}
+
+// Simple imports
+use  foo::bar::baz as baz ;
+use bar::quux  as    kaas;
+use  foo;
+
+// With aliases.
+use foo::{self as bar, baz};
+use foo::{self as bar};
+use foo::{qux as bar};
+use foo::{baz, qux as bar};
+
+// With absolute paths
+use ::foo;
+use ::foo::{Bar};
+use ::foo::{Bar, Baz};
+use ::{Foo};
+use ::{Bar, Baz};
+
+// Root globs
+use *;
+use ::*;
+
+// spaces used to cause glob imports to disappear (#1356)
+use super:: * ;
+use foo::issue_1356:: * ;
+
+// We shouldn't remove imports which have attributes attached (#1858)
+#[cfg(unix)]
+use self::unix::{};
+
+// nested imports
+use foo::{a, bar::{baz, qux, xxxxxxxxxxx, yyyyyyyyyyyyy, zzzzzzzzzzzzzzzz, foo::{a, b, cxxxxxxxxxxxxx, yyyyyyyyyyyyyy, zzzzzzzzzzzzzzzz}}, b, boo, c,};
+
+use fooo::{baar::{foobar::{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz}}, z, bar, bar::*, x, y};
+
+use exonum::{api::{Api, ApiError}, blockchain::{self, BlockProof, Blockchain, Transaction, TransactionSet}, crypto::{Hash, PublicKey}, helpers::Height, node::TransactionSend, storage::{ListProof, MapProof}};
+
+// nested imports with a single sub-tree.
+use a::{b::{c::*}};
+use a::{b::{c::{}}};
+use a::{b::{c::d}};
+use a::{b::{c::{xxx, yyy, zzz}}};
+
+// #2645
+/// This line is not affected.
+// This line is deleted.
+use c;
+
+// #2670
+#[macro_use]
+use imports_with_attr;
+
+// #2888
+use std::f64::consts::{SQRT_2, E, PI};
+
+// #3273
+#[rustfmt::skip]
+use std::fmt::{self, {Display, Formatter}};
diff --git a/src/tools/rustfmt/tests/source/imports_block_indent.rs b/src/tools/rustfmt/tests/source/imports_block_indent.rs
new file mode 100644
index 0000000000000..016deefe58c0f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports_block_indent.rs
@@ -0,0 +1,2 @@
+// #2569
+use apns2::request::notification::{Notificatio, NotificationBuilder, Priority, SilentNotificationBuilder};
diff --git a/src/tools/rustfmt/tests/source/imports_granularity_crate.rs b/src/tools/rustfmt/tests/source/imports_granularity_crate.rs
new file mode 100644
index 0000000000000..d16681b01b561
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports_granularity_crate.rs
@@ -0,0 +1,37 @@
+// rustfmt-imports_granularity: Crate
+
+use a::{c,d,b};
+use a::{d, e, b, a, f};
+use a::{f, g, c};
+
+#[doc(hidden)]
+use a::b;
+use a::c;
+use a::d;
+
+use a::{c, d, e};
+#[doc(hidden)]
+use a::b;
+use a::d;
+
+pub use foo::bar;
+use foo::{a, b, c};
+pub use foo::foobar;
+
+use a::{b::{c::*}};
+use a::{b::{c::{}}};
+use a::{b::{c::d}};
+use a::{b::{c::{xxx, yyy, zzz}}};
+
+// https://github.com/rust-lang/rustfmt/issues/3808
+use d::{self};
+use e::{self as foo};
+use f::{self, b};
+use g::a;
+use g::{self, b};
+use h::{a};
+use i::a::{self};
+use j::{a::{self}};
+
+use {k::{a, b}, l::{a, b}};
+use {k::{c, d}, l::{c, d}};
diff --git a/src/tools/rustfmt/tests/source/imports_granularity_item.rs b/src/tools/rustfmt/tests/source/imports_granularity_item.rs
new file mode 100644
index 0000000000000..d0e94df66ae2a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports_granularity_item.rs
@@ -0,0 +1,6 @@
+// rustfmt-imports_granularity: Item
+
+use a::{b, c, d};
+use a::{f::g, h::{i, j}};
+use a::{l::{self, m, n::o, p::*}};
+use a::q::{self};
diff --git a/src/tools/rustfmt/tests/source/imports_granularity_module.rs b/src/tools/rustfmt/tests/source/imports_granularity_module.rs
new file mode 100644
index 0000000000000..5a4fad5872bdd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/imports_granularity_module.rs
@@ -0,0 +1,18 @@
+// rustfmt-imports_granularity: Module
+
+use a::{b::c, d::e};
+use a::{f, g::{h, i}};
+use a::{j::{self, k::{self, l}, m}, n::{o::p, q}};
+pub use a::{r::s, t};
+
+#[cfg(test)]
+use foo::{a::b, c::d};
+use foo::e;
+
+use bar::{
+    // comment
+    a::b,
+    // more comment
+    c::d,
+    e::f,
+};
diff --git a/src/tools/rustfmt/tests/source/invalid-rust-code-in-doc-comment.rs b/src/tools/rustfmt/tests/source/invalid-rust-code-in-doc-comment.rs
new file mode 100644
index 0000000000000..835b0261b760b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/invalid-rust-code-in-doc-comment.rs
@@ -0,0 +1,20 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// ```rust
+/// if (true) { … }
+/// ```
+fn a() {
+}
+
+/// ```rust
+/// if foo() {
+///     …
+/// }
+/// ```
+fn a() {
+}
+
+/// ```rust
+/// k1 == k2 ⇒ hash(k1) == hash(k2)
+/// ```
+pub   struct   a   ;
diff --git a/src/tools/rustfmt/tests/source/issue-1021.rs b/src/tools/rustfmt/tests/source/issue-1021.rs
new file mode 100644
index 0000000000000..380e24cc0b023
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1021.rs
@@ -0,0 +1,22 @@
+// rustfmt-normalize_comments: true
+fn main() {
+    match x {
+        S(true , .., true ) => (),
+        S(true , .. ) => (),
+        S(.., true ) => (),
+        S( .. ) => (),
+        S(_) => (),
+        S(/* .. */ .. ) => (),
+        S(/* .. */ .., true ) => (),
+    }
+
+    match y {
+        (true , .., true ) => (),
+        (true , .. ) => (),
+        (.., true ) => (),
+        ( .. ) => (),
+        (_,) => (),
+        (/* .. */ .. ) => (),
+        (/* .. */ .., true ) => (),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1049.rs b/src/tools/rustfmt/tests/source/issue-1049.rs
new file mode 100644
index 0000000000000..bcfba41e7687d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1049.rs
@@ -0,0 +1,18 @@
+// Test overlong function signature
+pub unsafe fn reborrow_mut(&mut X: Abcde) -> Handle<NodeRef<marker::Mut, K, V, NodeType>, HandleType> {
+}
+
+pub fn merge(mut X: Abcdef) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+}
+
+impl Handle {
+    pub fn merge(a: Abcd) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+    }
+}
+
+// Long function without return type that should not be reformatted.
+fn veeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {}
+
+fn veeeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {}
+
+fn veeeeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {}
diff --git a/src/tools/rustfmt/tests/source/issue-1111.rs b/src/tools/rustfmt/tests/source/issue-1111.rs
new file mode 100644
index 0000000000000..2e1a89ad78eb9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1111.rs
@@ -0,0 +1 @@
+use bar;
diff --git a/src/tools/rustfmt/tests/source/issue-1120.rs b/src/tools/rustfmt/tests/source/issue-1120.rs
new file mode 100644
index 0000000000000..e85c9af99d457
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1120.rs
@@ -0,0 +1,9 @@
+// rustfmt-reorder_imports: true
+
+// Ensure that a use at the start of an inline module is correctly formatted.
+mod foo {use bar;}
+
+// Ensure that an indented `use` gets the correct indentation.
+mod foo {
+        use bar;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1124.rs b/src/tools/rustfmt/tests/source/issue-1124.rs
new file mode 100644
index 0000000000000..35c2197fa346f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1124.rs
@@ -0,0 +1,15 @@
+// rustfmt-reorder_imports: true
+
+use d; use c; use b; use a; 
+// The previous line has a space after the `use a;` 
+
+mod a { use d; use c; use b; use a; }
+
+use z;
+
+use y;
+
+
+
+use x;
+use a;
diff --git a/src/tools/rustfmt/tests/source/issue-1127.rs b/src/tools/rustfmt/tests/source/issue-1127.rs
new file mode 100644
index 0000000000000..b49db4e3f65d6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1127.rs
@@ -0,0 +1,23 @@
+// rustfmt-max_width: 120
+// rustfmt-match_arm_blocks: false
+// rustfmt-match_block_trailing_comma: true
+
+fn a_very_very_very_very_very_very_very_very_very_very_very_long_function_name() -> i32 {
+    42
+}
+
+enum TestEnum {
+    AVeryVeryLongEnumName,
+    AnotherVeryLongEnumName,
+    TheLastVeryLongEnumName,
+}
+
+fn main() {
+    let var = TestEnum::AVeryVeryLongEnumName;
+    let num = match var {
+        TestEnum::AVeryVeryLongEnumName => a_very_very_very_very_very_very_very_very_very_very_very_long_function_name(),
+        TestEnum::AnotherVeryLongEnumName => a_very_very_very_very_very_very_very_very_very_very_very_long_function_name(),
+        TestEnum::TheLastVeryLongEnumName => a_very_very_very_very_very_very_very_very_very_very_very_long_function_name(),
+    };
+}
+
diff --git a/src/tools/rustfmt/tests/source/issue-1158.rs b/src/tools/rustfmt/tests/source/issue-1158.rs
new file mode 100644
index 0000000000000..6742e17459efe
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1158.rs
@@ -0,0 +1,3 @@
+trait T {
+	itemmacro!(this, is.now() .formatted(yay));
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1177.rs b/src/tools/rustfmt/tests/source/issue-1177.rs
new file mode 100644
index 0000000000000..3ac423c5aef9b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1177.rs
@@ -0,0 +1,7 @@
+// rustfmt-normalize_comments: true
+fn main() {
+    // Line Comment
+    /* Block Comment */
+
+    let d = 5;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1192.rs b/src/tools/rustfmt/tests/source/issue-1192.rs
new file mode 100644
index 0000000000000..4e39fbf9a3668
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1192.rs
@@ -0,0 +1,3 @@
+fn main() {
+    assert!(true)   ;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1210/a.rs b/src/tools/rustfmt/tests/source/issue-1210/a.rs
new file mode 100644
index 0000000000000..6bb9964b4e353
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1210/a.rs
@@ -0,0 +1,12 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+impl Foo {
+    fn cxx(&self, target: &str) -> &Path {
+        match self.cxx.get(target) {
+            Some(p) => p.path(),
+            None => panic!("\n\ntarget `{}` is not configured as a host,
+                            only as a target\n\n", target),
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1210/b.rs b/src/tools/rustfmt/tests/source/issue-1210/b.rs
new file mode 100644
index 0000000000000..8c71ef98b7fcf
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1210/b.rs
@@ -0,0 +1,12 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+impl Foo {
+    fn cxx(&self, target: &str) -> &Path {
+        match self.cxx.get(target) {
+            Some(p) => p.path(),
+            None => panic!("\ntarget `{}`: is not, configured as a host,
+                            only as a target\n\n", target),
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1210/c.rs b/src/tools/rustfmt/tests/source/issue-1210/c.rs
new file mode 100644
index 0000000000000..c080cef950b3d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1210/c.rs
@@ -0,0 +1,5 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+const foo: String = "trailing_spaces!!            
+                keep them! Amet neque. Praesent rhoncus eros non velit.";
diff --git a/src/tools/rustfmt/tests/source/issue-1210/d.rs b/src/tools/rustfmt/tests/source/issue-1210/d.rs
new file mode 100644
index 0000000000000..783736bc3b2c5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1210/d.rs
@@ -0,0 +1,4 @@
+// rustfmt-wrap_comments: true
+
+// trailing_spaces_in_comment!!                   
+//                remove those from above
diff --git a/src/tools/rustfmt/tests/source/issue-1210/e.rs b/src/tools/rustfmt/tests/source/issue-1210/e.rs
new file mode 100644
index 0000000000000..9abada1d6d86f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1210/e.rs
@@ -0,0 +1,8 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+// explicit line breaks should be kept in order to preserve the layout
+
+const foo: String = "Suspendisse vel augue at felis tincidunt sollicitudin. Fusce arcu.
+               Duis et odio et leo
+        sollicitudin consequat. Aliquam lobortis.  Phasellus condimentum.";
diff --git a/src/tools/rustfmt/tests/source/issue-1211.rs b/src/tools/rustfmt/tests/source/issue-1211.rs
new file mode 100644
index 0000000000000..5818736bf6baf
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1211.rs
@@ -0,0 +1,15 @@
+fn main() {
+    for iface in &ifaces {
+        match iface.addr {
+            get_if_addrs::IfAddr::V4(ref addr) => {
+                match addr.broadcast {
+                    Some(ip) => {
+                        sock.send_to(&buf, (ip, 8765)).expect("foobar");
+                    }
+                    _ => ()
+                }
+            }
+            _ => ()
+        };
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1216.rs b/src/tools/rustfmt/tests/source/issue-1216.rs
new file mode 100644
index 0000000000000..d727c158ab8e5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1216.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+enum E {
+    A, //* I am not a block comment (caused panic)
+    B,
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1239.rs b/src/tools/rustfmt/tests/source/issue-1239.rs
new file mode 100644
index 0000000000000..913058257ed3d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1239.rs
@@ -0,0 +1,9 @@
+fn foo() {
+    let with_alignment = if condition__uses_alignment_for_first_if__0 ||
+                            condition__uses_alignment_for_first_if__1 ||
+                            condition__uses_alignment_for_first_if__2 {
+    } else if condition__no_alignment_for_later_else__0 ||
+                                   condition__no_alignment_for_later_else__1 ||
+                                   condition__no_alignment_for_later_else__2 {
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1278.rs b/src/tools/rustfmt/tests/source/issue-1278.rs
new file mode 100644
index 0000000000000..e25376561a949
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1278.rs
@@ -0,0 +1,9 @@
+// rustfmt-indent_style = "block"
+
+#![feature(pub_restricted)]
+
+mod inner_mode {
+    pub(super) fn func_name(abc: i32) -> i32 {
+        abc
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1350.rs b/src/tools/rustfmt/tests/source/issue-1350.rs
new file mode 100644
index 0000000000000..1baa1985a7ea0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1350.rs
@@ -0,0 +1,16 @@
+// rustfmt-max_width: 120
+// rustfmt-comment_width: 110
+
+impl Struct {
+    fn fun() {
+        let result = match <R::RequestResult as serde::Deserialize>::deserialize(&json) {
+            Ok(v) => v,
+            Err(e) => {
+                match <R::ErrorResult as serde::Deserialize>::deserialize(&json) {
+                    Ok(v) => return Err(Error::with_json(v)),
+                    Err(e2) => return Err(Error::with_json(e)),
+                }
+            }
+        };
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1366.rs b/src/tools/rustfmt/tests/source/issue-1366.rs
new file mode 100644
index 0000000000000..9d2964fc77cc7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1366.rs
@@ -0,0 +1,12 @@
+fn main() {
+    fn f() -> Option<i32> {
+        Some("fffffffsssssssssddddssssfffffddddff").map(|s| s).map(|s| s.to_string()).map(|res| {
+            match Some(res) {
+                Some(ref s) if s == "" => 41,
+                Some(_) => 42,
+                _ => 43,
+            }
+        })
+    }
+    println!("{:?}", f())
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1468.rs b/src/tools/rustfmt/tests/source/issue-1468.rs
new file mode 100644
index 0000000000000..4d0d4f0eb9855
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1468.rs
@@ -0,0 +1,27 @@
+fn issue1468() {
+euc_jp_decoder_functions!({
+let trail_minus_offset = byte.wrapping_sub(0xA1);
+// Fast-track Hiragana (60% according to Lunde)
+// and Katakana (10% according to Lunde).
+if jis0208_lead_minus_offset == 0x03 &&
+trail_minus_offset < 0x53 {
+// Hiragana
+handle.write_upper_bmp(0x3041 + trail_minus_offset as u16)
+} else if jis0208_lead_minus_offset == 0x04 &&
+trail_minus_offset < 0x56 {
+// Katakana
+handle.write_upper_bmp(0x30A1 + trail_minus_offset as u16)
+} else if trail_minus_offset > (0xFE - 0xA1) {
+if byte < 0x80 {
+return (DecoderResult::Malformed(1, 0),
+unread_handle_trail.unread(),
+handle.written());
+}
+return (DecoderResult::Malformed(2, 0),
+unread_handle_trail.consumed(),
+handle.written());
+} else {
+unreachable!();
+}
+});
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1693.rs b/src/tools/rustfmt/tests/source/issue-1693.rs
new file mode 100644
index 0000000000000..0622ce5023510
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1693.rs
@@ -0,0 +1,3 @@
+fn issue1693() {
+    let pixel_data = vec![(f16::from_f32(0.82), f16::from_f32(1.78), f16::from_f32(0.21)); 256 * 256];
+}
diff --git a/src/tools/rustfmt/tests/source/issue-1800.rs b/src/tools/rustfmt/tests/source/issue-1800.rs
new file mode 100644
index 0000000000000..eae226532589d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1800.rs
@@ -0,0 +1,3 @@
+#![doc(html_root_url    =    "http://example.com")]
+#[cfg(feature    =    "foo")]
+fn a() {}
diff --git a/src/tools/rustfmt/tests/source/issue-1914.rs b/src/tools/rustfmt/tests/source/issue-1914.rs
new file mode 100644
index 0000000000000..447296c4b874e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-1914.rs
@@ -0,0 +1,6 @@
+// rustfmt-max_width: 80
+
+extern "C" {
+#[link_name = "_ZN7MyClass26example_check_no_collisionE"]
+    pub static mut  MyClass_example_check_no_collision  :  * const :: std :: os :: raw :: c_int ;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2025.rs b/src/tools/rustfmt/tests/source/issue-2025.rs
new file mode 100644
index 0000000000000..c6f61b4e3e19b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2025.rs
@@ -0,0 +1,8 @@
+
+
+
+
+// See if rustfmt removes empty lines on top of the file.
+pub fn foo() {
+    println!("hello, world");
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2111.rs b/src/tools/rustfmt/tests/source/issue-2111.rs
new file mode 100644
index 0000000000000..ccd113696e101
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2111.rs
@@ -0,0 +1,26 @@
+// An import with single line comments.
+use super::{
+    SCHEMA_VERSIONS,
+    LodaModel,
+    ModelProperties,
+    StringMap,
+    ModelSelector,
+    RequestDescription,
+    MethodDescription,
+    ModelBehaviour,
+    ModelRequestGraph,
+    DelayChoice,
+    Holding,
+    Destinations,
+    ModelEdges,
+    Switch,
+    //    ModelMetaData,
+    //    Generated,
+    //    SecondsString,
+    //    DateString,
+    //    ModelConfiguration,
+    //    ModelRequests,
+    //    RestResponse,
+    //    RestResponseCode,
+    //    UniformHolding
+};
diff --git a/src/tools/rustfmt/tests/source/issue-2164.rs b/src/tools/rustfmt/tests/source/issue-2164.rs
new file mode 100644
index 0000000000000..6c288e1bd62aa
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2164.rs
@@ -0,0 +1,4 @@
+// A stress test against code generated by bindgen.
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct emacs_env_25 { pub size : isize , pub private_members : * mut emacs_env_private , pub make_global_ref : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , any_reference : emacs_value ) -> emacs_value > , pub free_global_ref : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , global_reference : emacs_value ) > , pub non_local_exit_check : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env ) -> emacs_funcall_exit > , pub non_local_exit_clear : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env ) > , pub non_local_exit_get : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , non_local_exit_symbol_out : * mut emacs_value , non_local_exit_data_out : * mut emacs_value ) -> emacs_funcall_exit > , pub non_local_exit_signal : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , non_local_exit_symbol : emacs_value , non_local_exit_data : emacs_value ) > , pub non_local_exit_throw : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , tag : emacs_value , value : emacs_value ) > , pub make_function : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , min_arity : isize , max_arity : isize , function : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , nargs : isize , args : * mut emacs_value , arg1 : * mut ::libc :: c_void ) -> emacs_value > , documentation : * const ::libc :: c_char , data : * mut ::libc :: c_void ) -> emacs_value > , pub funcall : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , function : emacs_value , nargs : isize , args : * mut emacs_value ) -> emacs_value > , pub intern : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , symbol_name : * const ::libc :: c_char ) -> emacs_value > , pub type_of : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , value : emacs_value ) -> emacs_value > , pub is_not_nil : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , value : emacs_value ) -> bool > , pub eq : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , a : emacs_value , b : emacs_value ) -> bool > , pub extract_integer : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , value : emacs_value ) -> intmax_t > , pub make_integer : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , value : intmax_t ) -> emacs_value > , pub extract_float : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , value : emacs_value ) -> f64 > , pub make_float : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , value : f64 ) -> emacs_value > , pub copy_string_contents : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , value : emacs_value , buffer : * mut ::libc :: c_char , size_inout : * mut isize ) -> bool > , pub make_string : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , contents : * const ::libc :: c_char , length : isize ) -> emacs_value > , pub make_user_ptr : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , fin : :: std :: option :: Option < unsafe extern "C" fn ( arg1 : * mut ::libc :: c_void ) > , ptr : * mut ::libc :: c_void ) -> emacs_value > , pub get_user_ptr : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , uptr : emacs_value ) -> * mut ::libc :: c_void > , pub set_user_ptr : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , uptr : emacs_value , ptr : * mut ::libc :: c_void ) > , pub get_user_finalizer : :: std :: option :: Option < unsafe extern "C" fn ( arg1 : * mut ::libc :: c_void , env : * mut emacs_env , uptr : emacs_value ) -> :: std :: option :: Option < unsafe extern "C" fn ( arg1 : * mut ::libc :: c_void , env : * mut emacs_env , uptr : emacs_value ) > > , pub set_user_finalizer : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , uptr : emacs_value , fin : :: std :: option :: Option < unsafe extern "C" fn ( arg1 : * mut ::libc :: c_void ) > ) > , pub vec_get : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , vec : emacs_value , i : isize ) -> emacs_value > , pub vec_set : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , vec : emacs_value , i : isize , val : emacs_value ) > , pub vec_size : :: std :: option :: Option < unsafe extern "C" fn ( env : * mut emacs_env , vec : emacs_value ) -> isize > , }
diff --git a/src/tools/rustfmt/tests/source/issue-2179/one.rs b/src/tools/rustfmt/tests/source/issue-2179/one.rs
new file mode 100644
index 0000000000000..d23947931fffd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2179/one.rs
@@ -0,0 +1,36 @@
+// rustfmt-version: One
+// rustfmt-error_on_line_overflow: false
+
+fn issue_2179() {
+    let (opts, rustflags, clear_env_rust_log) =
+        {
+            // We mustn't lock configuration for the whole build process
+            let rls_config = rls_config.lock().unwrap();
+
+            let opts = CargoOptions::new(&rls_config);
+            trace!("Cargo compilation options:\n{:?}", opts);
+            let rustflags = prepare_cargo_rustflags(&rls_config);
+
+            // Warn about invalid specified bin target or package depending on current mode
+            // TODO: Return client notifications along with diagnostics to inform the user
+            if !rls_config.workspace_mode {
+                let cur_pkg_targets = ws.current().unwrap().targets();
+
+                if let &Some(ref build_bin) = rls_config.build_bin.as_ref() {
+                    let mut bins = cur_pkg_targets.iter().filter(|x| x.is_bin());
+                    if let None = bins.find(|x| x.name() == build_bin) {
+                        warn!("cargo - couldn't find binary `{}` specified in `build_bin` configuration", build_bin);
+                    }
+                }
+            } else {
+                for package in &opts.package {
+                    if let None = ws.members().find(|x| x.name() == package) {
+                        warn!("cargo - couldn't find member package `{}` specified in `analyze_package` configuration", package);
+                    }
+                }
+            }
+
+            (opts, rustflags, rls_config.clear_env_rust_log)
+        };
+
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2179/two.rs b/src/tools/rustfmt/tests/source/issue-2179/two.rs
new file mode 100644
index 0000000000000..f4cc9cc488bfc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2179/two.rs
@@ -0,0 +1,36 @@
+// rustfmt-version: Two
+// rustfmt-error_on_line_overflow: false
+
+fn issue_2179() {
+    let (opts, rustflags, clear_env_rust_log) =
+        {
+            // We mustn't lock configuration for the whole build process
+            let rls_config = rls_config.lock().unwrap();
+
+            let opts = CargoOptions::new(&rls_config);
+            trace!("Cargo compilation options:\n{:?}", opts);
+            let rustflags = prepare_cargo_rustflags(&rls_config);
+
+            // Warn about invalid specified bin target or package depending on current mode
+            // TODO: Return client notifications along with diagnostics to inform the user
+            if !rls_config.workspace_mode {
+                let cur_pkg_targets = ws.current().unwrap().targets();
+
+                if let &Some(ref build_bin) = rls_config.build_bin.as_ref() {
+                    let mut bins = cur_pkg_targets.iter().filter(|x| x.is_bin());
+                    if let None = bins.find(|x| x.name() == build_bin) {
+                        warn!("cargo - couldn't find binary `{}` specified in `build_bin` configuration", build_bin);
+                    }
+                }
+            } else {
+                for package in &opts.package {
+                    if let None = ws.members().find(|x| x.name() == package) {
+                        warn!("cargo - couldn't find member package `{}` specified in `analyze_package` configuration", package);
+                    }
+                }
+            }
+
+            (opts, rustflags, rls_config.clear_env_rust_log)
+        };
+
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2256.rs b/src/tools/rustfmt/tests/source/issue-2256.rs
new file mode 100644
index 0000000000000..a206e8db6cf4d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2256.rs
@@ -0,0 +1,12 @@
+// こんにちは
+use std::{};
+use std::borrow::Cow;
+
+/* comment 1 */ use std::{};
+/* comment 2 */ use std::{};
+
+
+
+
+
+/* comment 3 */ use std::{};
diff --git a/src/tools/rustfmt/tests/source/issue-2342.rs b/src/tools/rustfmt/tests/source/issue-2342.rs
new file mode 100644
index 0000000000000..f86d24a146b43
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2342.rs
@@ -0,0 +1,5 @@
+// rustfmt-max_width: 80
+
+struct Foo {
+    #[cfg(feature = "serde")] bytes: [[u8; 17]; 5], // Same size as signature::ED25519_PKCS8_V2_LEN
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2445.rs b/src/tools/rustfmt/tests/source/issue-2445.rs
new file mode 100644
index 0000000000000..84ce6e647b83c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2445.rs
@@ -0,0 +1,21 @@
+test!(RunPassPretty {
+            // comment
+    path: "src/test/run-pass/pretty",
+    mode: "pretty",
+    suite: "run-pass",
+    default: false,
+    host: true  // should, force, , no trailing comma here
+});
+
+test!(RunPassPretty {
+            // comment
+    path: "src/test/run-pass/pretty",
+    mode: "pretty",
+    suite: "run-pass",
+    default: false,
+    host: true,         // should, , preserve, the trailing comma
+});
+
+test!(Test{
+    field: i32, // comment
+});
diff --git a/src/tools/rustfmt/tests/source/issue-2446.rs b/src/tools/rustfmt/tests/source/issue-2446.rs
new file mode 100644
index 0000000000000..ad649d95c5494
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2446.rs
@@ -0,0 +1,11 @@
+enum Issue2446 {
+    V {
+        f: u8, // x
+    },
+}
+
+enum Issue2446TrailingCommentsOnly {
+    V {
+        f: u8, /* */
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2479.rs b/src/tools/rustfmt/tests/source/issue-2479.rs
new file mode 100644
index 0000000000000..df50236d05d34
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2479.rs
@@ -0,0 +1,2 @@
+// Long attributes.
+# [ derive ( Clone , Copy , Debug , PartialEq ) ] pub enum POLARITYR {    # [ doc = "Task mode: No effect on pin from OUT[n] task. Event mode: no IN[n] event generated on pin activity." ] NONE , # [ doc = "Task mode: Set pin from OUT[n] task. Event mode: Generate IN[n] event when rising edge on pin." ] LOTOHI , # [ doc = "Task mode: Clear pin from OUT[n] task. Event mode: Generate IN[n] event when falling edge on pin." ] HITOLO , # [ doc = "Task mode: Toggle pin from OUT[n]. Event mode: Generate IN[n] when any change on pin." ] TOGGLE }
diff --git a/src/tools/rustfmt/tests/source/issue-2482/a.rs b/src/tools/rustfmt/tests/source/issue-2482/a.rs
new file mode 100644
index 0000000000000..fbbcb52a878aa
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2482/a.rs
@@ -0,0 +1,9 @@
+// rustfmt-reorder_modules: true
+
+// Do not reorder inline modules.
+
+mod c;
+mod a {
+    fn a() {}
+}
+mod b;
diff --git a/src/tools/rustfmt/tests/source/issue-2482/b.rs b/src/tools/rustfmt/tests/source/issue-2482/b.rs
new file mode 100644
index 0000000000000..40a8d942126c9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2482/b.rs
@@ -0,0 +1 @@
+pub fn b() {}
diff --git a/src/tools/rustfmt/tests/source/issue-2482/c.rs b/src/tools/rustfmt/tests/source/issue-2482/c.rs
new file mode 100644
index 0000000000000..d937545511eff
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2482/c.rs
@@ -0,0 +1 @@
+pub fn c() {}
diff --git a/src/tools/rustfmt/tests/source/issue-2496.rs b/src/tools/rustfmt/tests/source/issue-2496.rs
new file mode 100644
index 0000000000000..0ebd4b510ece6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2496.rs
@@ -0,0 +1,16 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    match option {
+        None => some_function(first_reasonably_long_argument,
+                              second_reasonably_long_argument),
+    }
+}
+
+fn main() {
+    match option {
+        None => {
+            some_function(first_reasonably_long_argument,
+                          second_reasonably_long_argument)
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2520.rs b/src/tools/rustfmt/tests/source/issue-2520.rs
new file mode 100644
index 0000000000000..5a23f10430d1a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2520.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+//! ```rust
+//! println!( "hello, world" );
+//! ```
+
+#![deny( missing_docs )]
+
+//! ```rust
+//! println!("hello, world");
+
+#![deny( missing_docs )]
diff --git a/src/tools/rustfmt/tests/source/issue-2523.rs b/src/tools/rustfmt/tests/source/issue-2523.rs
new file mode 100644
index 0000000000000..491d5c38fc22a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2523.rs
@@ -0,0 +1,18 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+// Do not unindent macro calls in comment with unformattable syntax.
+//! ```rust
+//! let x = 3  ;
+//! some_macro!(pub fn fn foo() (
+//!     println!("Don't unindent me!");
+//! ));
+//! ```
+
+// Format items that appear as arguments of macro call.
+//! ```rust
+//! let x = 3  ;
+//! some_macro!(pub fn foo() {
+//! println!("Don't unindent me!");
+//! });
+//! ```
diff --git a/src/tools/rustfmt/tests/source/issue-2582.rs b/src/tools/rustfmt/tests/source/issue-2582.rs
new file mode 100644
index 0000000000000..bba8ce1504ce0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2582.rs
@@ -0,0 +1 @@
+    fn main() {}
diff --git a/src/tools/rustfmt/tests/source/issue-2641.rs b/src/tools/rustfmt/tests/source/issue-2641.rs
new file mode 100644
index 0000000000000..c7ad60674fd54
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2641.rs
@@ -0,0 +1,3 @@
+macro_rules! a {
+    () => {{}}
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2644.rs b/src/tools/rustfmt/tests/source/issue-2644.rs
new file mode 100644
index 0000000000000..fa9d16f444dd3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2644.rs
@@ -0,0 +1,11 @@
+// rustfmt-max_width: 80
+fn foo(e: Enum) {
+    match e {
+        Enum::Var {
+            element1,
+            element2,
+        } => {
+            return;
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2728.rs b/src/tools/rustfmt/tests/source/issue-2728.rs
new file mode 100644
index 0000000000000..6cb41b75b6d09
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2728.rs
@@ -0,0 +1,8 @@
+// rustfmt-wrap_comments: true
+// rustfmt-newline_style: Windows
+
+//! ```rust
+//! extern crate uom;
+//! ```
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/source/issue-2761.rs b/src/tools/rustfmt/tests/source/issue-2761.rs
new file mode 100644
index 0000000000000..bc312319034b0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2761.rs
@@ -0,0 +1,15 @@
+const DATA: &'static [u8] = &[
+    0x42, 0x50, 0x54, 0x44,  //type
+    0x23, 0x00, 0x00, 0x00,  //size
+    0x00, 0x00, 0x04, 0x00,  //flags
+    0xEC, 0x0C, 0x00, 0x00,  //id
+    0x00, 0x00, 0x00, 0x00,  //revision
+    0x2B, 0x00,  //version
+    0x00, 0x00,  //unknown
+    0x42, 0x50, 0x54, 0x4E,  //field type
+    0x1D, 0x00,  //field size
+    0x19, 0x00, 0x00, 0x00,  //decompressed field size
+    0x75, 0xc5, 0x21, 0x0d, 0x00, 0x00, 0x08, 0x05, 0xd1, 0x6c,  //field data (compressed)
+    0x6c, 0xdc, 0x57, 0x48, 0x3c, 0xfd, 0x5b, 0x5c, 0x02, 0xd4,  //field data (compressed)
+    0x6b, 0x32, 0xb5, 0xdc, 0xa3  //field data (compressed)
+];
diff --git a/src/tools/rustfmt/tests/source/issue-2781.rs b/src/tools/rustfmt/tests/source/issue-2781.rs
new file mode 100644
index 0000000000000..2c15b29b6dcd4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2781.rs
@@ -0,0 +1,11 @@
+pub      // Oh, no. A line comment.
+struct Foo {}
+
+pub     /* Oh, no. A block comment. */     struct Foo {}
+
+mod inner {
+pub      // Oh, no. A line comment.
+struct Foo {}
+
+pub     /* Oh, no. A block comment. */     struct Foo {}
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2794.rs b/src/tools/rustfmt/tests/source/issue-2794.rs
new file mode 100644
index 0000000000000..c3f9c0412a46d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2794.rs
@@ -0,0 +1,7 @@
+// rustfmt-indent_style: Block
+// rustfmt-imports_indent: Block
+// rustfmt-imports_layout: Vertical
+
+use std::{
+    env, fs, io::{Read, Write},
+};
diff --git a/src/tools/rustfmt/tests/source/issue-2835.rs b/src/tools/rustfmt/tests/source/issue-2835.rs
new file mode 100644
index 0000000000000..2219b0b38e40f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2835.rs
@@ -0,0 +1,7 @@
+// rustfmt-brace_style: AlwaysNextLine
+// rustfmt-fn_single_line: true
+
+fn lorem() -> i32
+{
+    42
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2863.rs b/src/tools/rustfmt/tests/source/issue-2863.rs
new file mode 100644
index 0000000000000..1bda857be766a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2863.rs
@@ -0,0 +1,25 @@
+// rustfmt-reorder_impl_items: true
+
+impl<T> IntoIterator for SafeVec<T> {
+    type F = impl Trait;
+    type IntoIter = self::IntoIter<T>;
+    type Item = T;
+    // comment on foo()
+    fn foo() {println!("hello, world");}
+    type Bar = u32;
+    fn foo1() {println!("hello, world");}
+    type FooBar = u32;
+    fn foo2() {println!("hello, world");}
+    fn foo3() {println!("hello, world");}
+    const SomeConst: i32 = 100;
+    fn foo4() {println!("hello, world");}
+    fn foo5() {println!("hello, world");}
+    // comment on FoooooBar
+    type FoooooBar = u32;
+    fn foo6() {println!("hello, world");}
+    fn foo7() {println!("hello, world");}
+    type BarFoo = u32;
+    type E = impl Trait;
+    const AnotherConst: i32 = 100;
+    fn foo8() {println!("hello, world");}
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2869.rs b/src/tools/rustfmt/tests/source/issue-2869.rs
new file mode 100644
index 0000000000000..d18adfb462e9c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2869.rs
@@ -0,0 +1,41 @@
+// rustfmt-struct_field_align_threshold: 50
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "PascalCase")]
+struct AuditLog1 {
+    creation_time: String,
+    id: String,
+    operation: String,
+    organization_id: String,
+    record_type: u32,
+    result_status: Option<String>,
+    #[serde(rename = "ClientIP")]
+    client_ip: Option<IpAddr>,
+    object_id: String,
+    actor: Option<Vec<IDType>>,
+    actor_context_id: Option<String>,
+    actor_ip_address: Option<IpAddr>,
+    azure_active_directory_event_type: Option<u8>,
+
+    #[serde(rename = "very")]
+    aaaaa: String,
+    #[serde(rename = "cool")]
+    bb: i32,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "PascalCase")]
+struct AuditLog2 {
+    creation_time: String,
+    id: String,
+    operation: String,
+    organization_id: String,
+    record_type: u32,
+    result_status: Option<String>,
+    client_ip: Option<IpAddr>,
+    object_id: String,
+    actor: Option<Vec<IDType>>,
+    actor_context_id: Option<String>,
+    actor_ip_address: Option<IpAddr>,
+    azure_active_directory_event_type: Option<u8>,
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2896.rs b/src/tools/rustfmt/tests/source/issue-2896.rs
new file mode 100644
index 0000000000000..f648e64b1e373
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2896.rs
@@ -0,0 +1,161 @@
+extern crate rand;
+extern crate timely;
+extern crate differential_dataflow;
+
+use rand::{Rng, SeedableRng, StdRng};
+
+use timely::dataflow::operators::*;
+
+use differential_dataflow::AsCollection;
+use differential_dataflow::operators::*;
+use differential_dataflow::input::InputSession;
+
+// mod loglikelihoodratio;
+
+fn main() {
+
+  // define a new timely dataflow computation. 
+  timely::execute_from_args(std::env::args().skip(6), move |worker| {
+
+    // capture parameters of the experiment.
+    let users: usize = std::env::args().nth(1).unwrap().parse().unwrap();
+    let items: usize = std::env::args().nth(2).unwrap().parse().unwrap();
+    let scale: usize = std::env::args().nth(3).unwrap().parse().unwrap();
+    let batch: usize = std::env::args().nth(4).unwrap().parse().unwrap();
+    let noisy: bool = std::env::args().nth(5).unwrap() == "noisy";
+
+    let index = worker.index();
+    let peers = worker.peers();
+
+    let (input, probe) = worker.dataflow(|scope| {
+
+      // input of (user, item) collection.
+      let (input, occurrences) = scope.new_input();
+      let occurrences = occurrences.as_collection();
+
+      //TODO adjust code to only work with upper triangular half of cooccurrence matrix
+
+      /* Compute the cooccurrence matrix C = A'A from the binary interaction matrix A. */
+      let cooccurrences = 
+      occurrences
+        .join_map(&occurrences, |_user, &item_a, &item_b| (item_a, item_b))
+        .filter(|&(item_a, item_b)| item_a != item_b)
+        .count();
+
+      /* compute the rowsums of C indicating how often we encounter individual items. */
+      let row_sums = 
+      occurrences
+        .map(|(_user, item)| item)
+        .count();
+
+      // row_sums.inspect(|record| println!("[row_sums] {:?}", record));
+
+      /* Join the cooccurrence pairs with the corresponding row sums. */
+      let mut cooccurrences_with_row_sums = cooccurrences
+        .map(|((item_a, item_b), num_cooccurrences)| (item_a, (item_b, num_cooccurrences)))
+        .join_map(&row_sums, |&item_a, &(item_b, num_cooccurrences), &row_sum_a| {
+          assert!(row_sum_a > 0);
+          (item_b, (item_a, num_cooccurrences, row_sum_a))
+        })
+        .join_map(&row_sums, |&item_b, &(item_a, num_cooccurrences, row_sum_a), &row_sum_b| {
+          assert!(row_sum_a > 0);
+          assert!(row_sum_b > 0);
+          (item_a, (item_b, num_cooccurrences, row_sum_a, row_sum_b))
+        });
+
+      // cooccurrences_with_row_sums
+      //     .inspect(|record| println!("[cooccurrences_with_row_sums] {:?}", record));
+
+      // //TODO compute top-k "similar items" per item
+      // /* Compute LLR scores for each item pair. */
+      // let llr_scores = cooccurrences_with_row_sums.map(
+      //   |(item_a, (item_b, num_cooccurrences, row_sum_a, row_sum_b))| {
+
+      //     println!(
+      //       "[llr_scores] item_a={} item_b={}, num_cooccurrences={} row_sum_a={} row_sum_b={}",
+      //       item_a, item_b, num_cooccurrences, row_sum_a, row_sum_b);
+
+      //     let k11: isize = num_cooccurrences;
+      //     let k12: isize = row_sum_a as isize - k11;
+      //     let k21: isize = row_sum_b as isize - k11;
+      //     let k22: isize = 10000 - k12 - k21 + k11;
+
+      //     let llr_score = loglikelihoodratio::log_likelihood_ratio(k11, k12, k21, k22);
+
+      //     ((item_a, item_b), llr_score)
+      //   });
+
+      if noisy {
+        cooccurrences_with_row_sums = 
+        cooccurrences_with_row_sums
+          .inspect(|x| println!("change: {:?}", x));
+      }
+
+      let probe = 
+      cooccurrences_with_row_sums
+          .probe();
+/*
+      // produce the (item, item) collection
+      let cooccurrences = occurrences
+        .join_map(&occurrences, |_user, &item_a, &item_b| (item_a, item_b));
+      // count the occurrences of each item.
+      let counts = cooccurrences
+        .map(|(item_a,_)| item_a)
+        .count();
+      // produce ((item1, item2), count1, count2, count12) tuples
+      let cooccurrences_with_counts = cooccurrences
+        .join_map(&counts, |&item_a, &item_b, &count_item_a| (item_b, (item_a, count_item_a)))
+        .join_map(&counts, |&item_b, &(item_a, count_item_a), &count_item_b| {
+          ((item_a, item_b), count_item_a, count_item_b)
+        });
+      let probe = cooccurrences_with_counts
+        .inspect(|x| println!("change: {:?}", x))
+        .probe();
+*/
+      (input, probe)
+    });
+
+    let seed: &[_] = &[1, 2, 3, index];
+    let mut rng1: StdRng = SeedableRng::from_seed(seed);  // rng for edge additions
+    let mut rng2: StdRng = SeedableRng::from_seed(seed);  // rng for edge deletions
+
+    let mut input = InputSession::from(input);
+
+    for count in 0 .. scale {
+      if count % peers == index {
+        let user = rng1.gen_range(0, users);
+        let item = rng1.gen_range(0, items);
+        // println!("[INITIAL INPUT] ({}, {})", user, item);
+        input.insert((user, item));
+      }
+    }
+
+    // load the initial data up!
+    while probe.less_than(input.time()) { worker.step(); }
+
+    for round in 1 .. {
+
+      for element in (round * batch) .. ((round + 1) * batch) {
+        if element % peers == index {
+          // advance the input timestamp.
+          input.advance_to(round * batch);
+          // insert a new item.
+          let user = rng1.gen_range(0, users);
+          let item = rng1.gen_range(0, items);
+          if noisy { println!("[INPUT: insert] ({}, {})", user, item); }
+          input.insert((user, item));
+          // remove an old item.
+          let user = rng2.gen_range(0, users);
+          let item = rng2.gen_range(0, items);
+          if noisy { println!("[INPUT: remove] ({}, {})", user, item); }
+          input.remove((user, item));
+        }
+      }
+
+      input.advance_to(round * batch);
+      input.flush();
+
+      while probe.less_than(input.time()) { worker.step(); }
+    }
+  }).unwrap();
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2916.rs b/src/tools/rustfmt/tests/source/issue-2916.rs
new file mode 100644
index 0000000000000..ccb1f8486c5ea
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2916.rs
@@ -0,0 +1,2 @@
+a_macro!(name<Param1, Param2>,
+)    ;
diff --git a/src/tools/rustfmt/tests/source/issue-2917/packed_simd.rs b/src/tools/rustfmt/tests/source/issue-2917/packed_simd.rs
new file mode 100644
index 0000000000000..afa9e67c8ab61
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2917/packed_simd.rs
@@ -0,0 +1,63 @@
+// rustfmt-wrap_comments: true
+//! Implements `From` and `Into` for vector types.
+
+macro_rules! impl_from_vector {
+    ([$elem_ty:ident; $elem_count:expr]: $id:ident | $test_tt:tt | $source:ident) => {
+        impl From<$source> for $id {
+            #[inline]
+            fn from(source: $source) -> Self {
+                fn static_assert_same_number_of_lanes<T, U>()
+                where
+                    T: crate::sealed::Simd,
+                    U: crate::sealed::Simd<LanesType = T::LanesType>,
+                {
+                }
+                use llvm::simd_cast;
+                static_assert_same_number_of_lanes::<$id, $source>();
+                Simd(unsafe { simd_cast(source.0) })
+            }
+        }
+
+        // FIXME: `Into::into` is not inline, but due to
+                // the blanket impl in `std`, which is not
+                // marked `default`, we cannot override it here with
+                // specialization.
+                /*
+                impl Into<$id> for $source {
+                    #[inline]
+                    fn into(self) -> $id {
+                        unsafe { simd_cast(self) }
+                    }
+                }
+                */
+
+        test_if!{
+            $test_tt:
+            interpolate_idents! {
+                mod [$id _from_ $source] {
+                    use super::*;
+                    #[test]
+                    fn from() {
+                        assert_eq!($id::lanes(), $source::lanes());
+                        let source: $source = Default::default();
+                        let vec: $id = Default::default();
+
+                        let e = $id::from(source);
+                        assert_eq!(e, vec);
+
+                        let e: $id = source.into();
+                        assert_eq!(e, vec);
+                    }
+                }
+            }
+        }
+    };
+}
+
+macro_rules! impl_from_vectors {
+    ([$elem_ty:ident; $elem_count:expr]: $id:ident | $test_tt:tt | $($source:ident),*) => {
+        $(
+            impl_from_vector!([$elem_ty; $elem_count]: $id | $test_tt | $source);
+        )*
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2922.rs b/src/tools/rustfmt/tests/source/issue-2922.rs
new file mode 100644
index 0000000000000..44fae0b645d0d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2922.rs
@@ -0,0 +1,9 @@
+// rustfmt-indent_style: Visual
+struct Functions {
+    RunListenServer: unsafe extern "C" fn(*mut c_void,
+     *mut c_char,
+     *mut c_char,
+     *mut c_char,
+     *mut c_void,
+     *mut c_void) -> c_int,
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2927-2.rs b/src/tools/rustfmt/tests/source/issue-2927-2.rs
new file mode 100644
index 0000000000000..d87761fdc9c37
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2927-2.rs
@@ -0,0 +1,7 @@
+// rustfmt-edition: 2015
+#![feature(rust_2018_preview, uniform_paths)]
+use futures::prelude::*;
+use http_03::cli::Cli;
+use hyper::{service::service_fn_ok, Body, Response, Server};
+use ::log::{error, info, log};
+use structopt::StructOpt;
diff --git a/src/tools/rustfmt/tests/source/issue-2927.rs b/src/tools/rustfmt/tests/source/issue-2927.rs
new file mode 100644
index 0000000000000..a7df32084f3b6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2927.rs
@@ -0,0 +1,7 @@
+// rustfmt-edition: 2018
+#![feature(rust_2018_preview, uniform_paths)]
+use futures::prelude::*;
+use http_03::cli::Cli;
+use hyper::{service::service_fn_ok, Body, Response, Server};
+use ::log::{error, info, log};
+use structopt::StructOpt;
diff --git a/src/tools/rustfmt/tests/source/issue-2930.rs b/src/tools/rustfmt/tests/source/issue-2930.rs
new file mode 100644
index 0000000000000..962c3e4fe04e2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2930.rs
@@ -0,0 +1,5 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    let (first_variable, second_variable) = (this_is_something_with_an_extraordinarily_long_name,
+    this_variable_name_is_also_pretty_long);
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2936.rs b/src/tools/rustfmt/tests/source/issue-2936.rs
new file mode 100644
index 0000000000000..55b5c56e69844
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2936.rs
@@ -0,0 +1,19 @@
+struct AStruct {
+    A: u32,
+    B: u32,
+    C: u32,
+}
+
+impl Something for AStruct {
+    fn a_func() {
+        match a_val {
+            ContextualParseError::InvalidMediaRule(ref err) => {
+                let err: &CStr = match err.kind {
+                    ParseErrorKind::Custom(StyleParseErrorKind::MediaQueryExpectedFeatureName(..)) => {
+                        cstr!("PEMQExpectedFeatureName")
+                    },
+                };
+            }
+        };
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2955.rs b/src/tools/rustfmt/tests/source/issue-2955.rs
new file mode 100644
index 0000000000000..525e070a57eee
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2955.rs
@@ -0,0 +1,6 @@
+// rustfmt-condense_wildcard_suffixes: true
+fn main() {
+    match (1, 2, 3) {
+        (_, _, _) => (),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2973.rs b/src/tools/rustfmt/tests/source/issue-2973.rs
new file mode 100644
index 0000000000000..5256dd7c9601e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2973.rs
@@ -0,0 +1,158 @@
+#[cfg(test)]
+mod test {
+  summary_test! {
+        tokenize_recipe_interpolation_eol,
+    "foo: # some comment
+ {{hello}}
+",
+    "foo: \
+ {{hello}} \
+{{ahah}}",
+        "N:#$>^{N}$<.",
+      }
+
+  summary_test! {
+    tokenize_strings,
+    r#"a = "'a'" + '"b"' + "'c'" + '"d"'#echo hello"#,
+    r#"N="+'+"+'#."#,
+  }
+
+  summary_test! {
+        tokenize_recipe_interpolation_eol,
+    "foo: # some comment
+ {{hello}}
+",
+        "N:#$>^{N}$<.",
+      }
+
+  summary_test! {
+        tokenize_recipe_interpolation_eof,
+    "foo: # more comments
+ {{hello}}
+# another comment
+",
+        "N:#$>^{N}$<#$.",
+      }
+
+  summary_test! {
+    tokenize_recipe_complex_interpolation_expression,
+    "foo: #lol\n {{a + b + \"z\" + blarg}}",
+    "N:#$>^{N+N+\"+N}<.",
+  }
+
+  summary_test! {
+    tokenize_recipe_multiple_interpolations,
+    "foo:,#ok\n {{a}}0{{b}}1{{c}}",
+    "N:,#$>^{N}_{N}_{N}<.",
+  }
+
+  summary_test! {
+        tokenize_junk,
+    "bob
+
+hello blah blah blah : a b c #whatever
+    ",
+        "N$$NNNN:NNN#$.",
+      }
+
+  summary_test! {
+        tokenize_empty_lines,
+    "
+# this does something
+hello:
+  asdf
+  bsdf
+
+  csdf
+
+  dsdf # whatever
+
+# yolo
+  ",
+        "$#$N:$>^_$^_$$^_$$^_$$<#$.",
+      }
+
+  summary_test! {
+        tokenize_comment_before_variable,
+    "
+#
+A='1'
+echo:
+  echo {{A}}
+  ",
+        "$#$N='$N:$>^_{N}$<.",
+      }
+
+  summary_test! {
+    tokenize_interpolation_backticks,
+    "hello:\n echo {{`echo hello` + `echo goodbye`}}",
+    "N:$>^_{`+`}<.",
+  }
+
+  summary_test! {
+    tokenize_assignment_backticks,
+    "a = `echo hello` + `echo goodbye`",
+    "N=`+`.",
+  }
+
+  summary_test! {
+        tokenize_multiple,
+    "
+hello:
+  a
+  b
+
+  c
+
+  d
+
+# hello
+bob:
+  frank
+  ",
+
+        "$N:$>^_$^_$$^_$$^_$$<#$N:$>^_$<.",
+      }
+
+  summary_test! {
+    tokenize_comment,
+    "a:=#",
+    "N:=#."
+  }
+
+  summary_test! {
+    tokenize_comment_with_bang,
+    "a:=#foo!",
+    "N:=#."
+  }
+
+  summary_test! {
+        tokenize_order,
+    r"
+b: a
+  @mv a b
+
+a:
+  @touch F
+  @touch a
+
+d: c
+  @rm c
+
+c: b
+  @mv b c",
+        "$N:N$>^_$$<N:$>^_$^_$$<N:N$>^_$$<N:N$>^_<.",
+      }
+
+  summary_test! {
+    tokenize_parens,
+    r"((())) )abc(+",
+    "((())))N(+.",
+  }
+
+  summary_test! {
+    crlf_newline,
+    "#\r\n#asdf\r\n",
+    "#$#$.",
+  }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2977/impl.rs b/src/tools/rustfmt/tests/source/issue-2977/impl.rs
new file mode 100644
index 0000000000000..8d7bb9414eb7b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2977/impl.rs
@@ -0,0 +1,44 @@
+macro_rules! atomic_bits {
+    // the println macro cannot be rewritten because of the asm macro
+    ($type:ty, $ldrex:expr, $strex:expr) => {
+        impl AtomicBits for $type {
+            unsafe fn load_excl(address: usize) -> Self {
+                let raw: $type;
+                asm!($ldrex
+                     : "=r"(raw)
+                     : "r"(address)
+                     :
+                     : "volatile");
+                raw
+            }
+
+            unsafe fn store_excl(self, address: usize) -> bool {
+                let status: $type;
+                println!("{}",
+                         status);
+                status == 0
+            }
+        }
+    };
+
+    // the println macro should be rewritten here
+    ($type:ty) => {
+        fn some_func(self) {
+            let status: $type;
+            println!("{}", status);
+        }
+    };
+
+    // unrewritale macro in func
+    ($type:ty, $ldrex:expr) => {
+        unsafe fn load_excl(address: usize) -> Self {
+            let raw: $type;
+            asm!($ldrex
+                 : "=r"(raw)
+                 : "r"(address)
+                 :
+                 : "volatile");
+            raw
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2977/trait.rs b/src/tools/rustfmt/tests/source/issue-2977/trait.rs
new file mode 100644
index 0000000000000..ae20668cd75f2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2977/trait.rs
@@ -0,0 +1,44 @@
+macro_rules! atomic_bits {
+    // the println macro cannot be rewritten because of the asm macro
+    ($type:ty, $ldrex:expr, $strex:expr) => {
+        trait $type {
+            unsafe fn load_excl(address: usize) -> Self {
+                let raw: $type;
+                asm!($ldrex
+                     : "=r"(raw)
+                     : "r"(address)
+                     :
+                     : "volatile");
+                raw
+            }
+
+            unsafe fn store_excl(self, address: usize) -> bool {
+                let status: $type;
+                println!("{}",
+                         status);
+                status == 0
+            }
+        }
+    };
+
+    // the println macro should be rewritten here
+    ($type:ty) => {
+        fn some_func(self) {
+            let status: $type;
+            println!("{}", status);
+        }
+    };
+
+    // unrewritale macro in func
+    ($type:ty, $ldrex:expr) => {
+        unsafe fn load_excl(address: usize) -> Self {
+            let raw: $type;
+            asm!($ldrex
+                 : "=r"(raw)
+                 : "r"(address)
+                 :
+                 : "volatile");
+            raw
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2985.rs b/src/tools/rustfmt/tests/source/issue-2985.rs
new file mode 100644
index 0000000000000..bde4da8314c13
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2985.rs
@@ -0,0 +1,35 @@
+// rustfmt-indent_style: Visual
+fn foo() {
+    {
+        {
+            let extra_encoder_settings = extra_encoder_settings.iter()
+                                                               .filter_map(|&(name, value)| {
+                                                         value.split()
+                                                              .next()
+                                                              .something()
+                                                              .something2()
+                                                              .something3()
+                                                              .something4()
+                                                     });
+            let extra_encoder_settings = extra_encoder_settings.iter()
+                                                               .filter_map(|&(name, value)| {
+                                                                               value.split()
+                                                                                    .next()
+                                                                                    .something()
+                                                                                    .something2()
+                                                                                    .something3()
+                                                                                    .something4()
+                                                                           })
+                                                               .something();
+            if let Some(subpod) = pod.subpods.iter().find(|s| {
+                                                              !s.plaintext
+                                                                .as_ref()
+                                                                .map(String::as_ref)
+                                                                .unwrap_or("")
+                                                                .is_empty()
+                                                          }) {
+                do_something();
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-2995.rs b/src/tools/rustfmt/tests/source/issue-2995.rs
new file mode 100644
index 0000000000000..accf7c3a1ad5d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-2995.rs
@@ -0,0 +1,7 @@
+fn issue_2995() {
+    // '\u{2028}' is inserted in the code below.
+
+    [0, 
1];
+    [0, 
/* */ 1];
+    
[
0
,
1
]
;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3029.rs b/src/tools/rustfmt/tests/source/issue-3029.rs
new file mode 100644
index 0000000000000..a7ac5c32b066f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3029.rs
@@ -0,0 +1,94 @@
+fn keep_if() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    if FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_if_let() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    if let Some(e) = FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_for() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    for conv in FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_loop() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(loop {
+                    FromJSValConvertible::from_jsval(cx, rval.handle(), ());
+                })
+            }
+        }
+    }
+}
+
+fn keep_while() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    while FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_while_let() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    while let Some(e) = FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_match() {
+    {
+        {
+            EvaluateJSReply::NumberValue(
+                match FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                    Ok(ConversionResult::Success(v)) => v,
+                    _ => unreachable!(),
+                },
+            )
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3038.rs b/src/tools/rustfmt/tests/source/issue-3038.rs
new file mode 100644
index 0000000000000..0fbb05ddc0e62
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3038.rs
@@ -0,0 +1,20 @@
+impl HTMLTableElement {
+    fn func() {
+        if number_of_row_elements == 0 {
+            if let Some(last_tbody) = node.rev_children()
+                    .filter_map(DomRoot::downcast::<Element>)
+                    .find(|n| n.is::<HTMLTableSectionElement>() && n.local_name() == &local_name!("tbody")) {
+                        last_tbody.upcast::<Node>().AppendChild(new_row.upcast::<Node>())
+                                                   .expect("InsertRow failed to append first row.");
+                    }
+        }
+
+        if number_of_row_elements == 0 {
+            if let Some(last_tbody) = node
+                    .find(|n| n.is::<HTMLTableSectionElement>() && n.local_name() == &local_name!("tbody")) {
+                        last_tbody.upcast::<Node>().AppendChild(new_row.upcast::<Node>())
+                                                   .expect("InsertRow failed to append first row.");
+                    }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3049.rs b/src/tools/rustfmt/tests/source/issue-3049.rs
new file mode 100644
index 0000000000000..43742683e4cd3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3049.rs
@@ -0,0 +1,45 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    something.aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .bench_function(|| {
+                                 let x = hello();
+                             });
+
+    something.aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .bench_function(arg, || {
+                 let x = hello();
+             });
+
+    something.aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .bench_function(arg,
+                             || {
+                                 let x = hello();
+                             },
+                             arg);
+
+    AAAAAAAAAAA.function(|| {
+                   let _ = ();
+               });
+
+    AAAAAAAAAAA.chain().function(|| {
+        let _ = ();
+    })
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3055/original.rs b/src/tools/rustfmt/tests/source/issue-3055/original.rs
new file mode 100644
index 0000000000000..45e58473a4a86
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3055/original.rs
@@ -0,0 +1,43 @@
+// rustfmt-wrap_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+/// Vestibulum elit nibh, rhoncus non, euismod sit amet, pretium eu, enim. Nunc commodo ultricies dui.
+///
+/// Should not format with text attribute
+/// ```text
+///           .--------------.
+///           |              v
+/// Park <- Idle -> Poll -> Probe -> Download -> Install -> Reboot
+///           ^      ^        '          '          '
+///           '      '        '          '          '
+///           '      `--------'          '          '
+///           `---------------'          '          '
+///           `--------------------------'          '
+///           `-------------------------------------'
+/// ```
+///
+/// Should not format with ignore attribute
+/// ```text
+///           .--------------.
+///           |              v
+/// Park <- Idle -> Poll -> Probe -> Download -> Install -> Reboot
+///           ^      ^        '          '          '
+///           '      '        '          '          '
+///           '      `--------'          '          '
+///           `---------------'          '          '
+///           `--------------------------'          '
+///           `-------------------------------------'
+/// ```
+///
+/// Should format with rust attribute
+/// ```rust
+/// let x =
+///    42;
+/// ```
+///
+/// Should format with no attribute as it defaults to rust
+/// ```
+/// let x =
+///    42;
+/// ```
+fn func() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3059.rs b/src/tools/rustfmt/tests/source/issue-3059.rs
new file mode 100644
index 0000000000000..49a75cd67abba
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3059.rs
@@ -0,0 +1,7 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 80
+
+/// Vestibulum elit nibh, rhoncus non, euismod sit amet, pretium eu, enim. Nunc commodo ultricies dui.
+/// Cras gravida rutrum massa. Donec accumsan mattis turpis. Quisque sem. Quisque elementum sapien
+/// iaculis augue. In dui sem, congue sit amet, feugiat quis, lobortis at, eros.
+fn func4() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3066.rs b/src/tools/rustfmt/tests/source/issue-3066.rs
new file mode 100644
index 0000000000000..4d1ece43defcd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3066.rs
@@ -0,0 +1,7 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    Struct { field: aaaaaaaaaaa };
+    Struct { field: aaaaaaaaaaaa, };
+    Struct { field: value,
+             field2: value2, };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3131.rs b/src/tools/rustfmt/tests/source/issue-3131.rs
new file mode 100644
index 0000000000000..c4cb2d8c03c03
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3131.rs
@@ -0,0 +1,8 @@
+fn main() {
+    match 3 {
+        t if match t {
+            _ => true,
+        } => {},
+        _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3153.rs b/src/tools/rustfmt/tests/source/issue-3153.rs
new file mode 100644
index 0000000000000..2836ce97cf8de
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3153.rs
@@ -0,0 +1,9 @@
+// rustfmt-wrap_comments: true
+
+/// This may panic if:
+/// - there are fewer than `max_header_bytes` bytes preceding the body
+/// - there are fewer than `max_footer_bytes` bytes following the body
+/// - the sum of the body bytes and post-body bytes is less than the sum
+///   of `min_body_and_padding_bytes` and `max_footer_bytes` (in other
+///   words, the minimum body and padding byte requirement is not met)
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3194.rs b/src/tools/rustfmt/tests/source/issue-3194.rs
new file mode 100644
index 0000000000000..b80ce346b6c36
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3194.rs
@@ -0,0 +1,13 @@
+mod m { struct S where A: B; }
+
+mod n { struct Foo where A: B { foo: usize } }
+
+mod o { enum Bar where A: B { Bar } }
+
+mod with_comments {
+  mod m { struct S /* before where */ where A: B; /* after where */ }
+  
+  mod n { struct Foo /* before where */ where A: B /* after where */ { foo: usize } }
+  
+  mod o { enum Bar /* before where */ where A: B /* after where */ { Bar } }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3198.rs b/src/tools/rustfmt/tests/source/issue-3198.rs
new file mode 100644
index 0000000000000..48cb24a00259e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3198.rs
@@ -0,0 +1,99 @@
+impl TestTrait {
+    fn foo_one_pre(/* Important comment1 */
+    self) {
+    }
+
+    fn foo_one_post(self
+    /* Important comment1 */) {
+    }
+
+    fn foo_pre(
+        /* Important comment1 */
+        self,
+        /* Important comment2 */
+        a: i32,
+    ) {
+    }
+
+    fn foo_post(
+        self
+        /* Important comment1 */,
+        a: i32
+        /* Important comment2 */,
+    ) {
+    }
+
+    fn bar_pre(
+            /* Important comment1 */
+    &mut self,
+        /* Important comment2 */
+            a: i32,
+    ) {
+    }
+
+    fn bar_post(
+    &mut self
+            /* Important comment1 */,
+            a: i32
+        /* Important comment2 */,
+    ) {
+    }
+
+    fn baz_pre(
+    /* Important comment1 */
+            self: X< 'a ,  'b >,
+            /* Important comment2 */
+    a: i32,
+    ) {
+    }
+
+    fn baz_post(
+            self: X< 'a ,  'b >
+    /* Important comment1 */,
+    a: i32
+            /* Important comment2 */,
+    ) {
+    }
+
+    fn baz_tree_pre(
+    /* Important comment1 */
+            self: X< 'a ,  'b >,
+        /* Important comment2 */
+        a: i32,
+        /* Important comment3 */
+        b: i32,
+    ) {
+    }
+
+    fn baz_tree_post(
+            self: X< 'a ,  'b >
+    /* Important comment1 */,
+        a: i32
+        /* Important comment2 */,
+        b: i32
+        /* Important comment3 */,){
+    }
+
+    fn multi_line(
+        self: X<'a, 'b>, /* Important comment1-1 */
+  /* Important comment1-2 */
+        a: i32, /* Important comment2 */
+        b: i32, /* Important comment3 */
+    ) {
+    }
+
+    fn two_line_comment(
+        self: X<'a, 'b>, /* Important comment1-1
+      Important comment1-2 */
+        a: i32, /* Important comment2 */
+        b: i32, /* Important comment3 */
+    ) {
+    }
+
+    fn no_first_line_comment(
+        self: X<'a, 'b>,
+        /* Important comment2 */a: i32,
+        /* Important comment3 */b: i32,
+    ) {
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3213/version_one.rs b/src/tools/rustfmt/tests/source/issue-3213/version_one.rs
new file mode 100644
index 0000000000000..f9f4cab55e325
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3213/version_one.rs
@@ -0,0 +1,9 @@
+// rustfmt-version: One
+
+fn foo() {
+    match 0 {
+        0 => return AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+        1 => AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+        _ => "",
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3213/version_two.rs b/src/tools/rustfmt/tests/source/issue-3213/version_two.rs
new file mode 100644
index 0000000000000..0f068c19d7446
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3213/version_two.rs
@@ -0,0 +1,9 @@
+// rustfmt-version: Two
+
+fn foo() {
+    match 0 {
+        0 => return AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+        1 => AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+        _ => "",
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3217.rs b/src/tools/rustfmt/tests/source/issue-3217.rs
new file mode 100644
index 0000000000000..176c702002a28
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3217.rs
@@ -0,0 +1,8 @@
+#![feature(label_break_value)]
+
+fn main() {
+    let mut res = 0;
+    's_39: { if res == 0i32 { println!("Hello, world!"); } }
+    's_40: loop { println!("res = {}", res); res += 1; if res == 3i32 { break 's_40; } }
+    let toto = || { if true { 42 } else { 24 } };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3227/two.rs b/src/tools/rustfmt/tests/source/issue-3227/two.rs
new file mode 100644
index 0000000000000..c1572c00d57a4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3227/two.rs
@@ -0,0 +1,13 @@
+// rustfmt-version: Two
+
+fn main() {
+    thread::spawn(|| {
+        while true {
+            println!("iteration");
+        }
+    });
+
+    thread::spawn(|| loop {
+        println!("iteration");
+    });
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3234.rs b/src/tools/rustfmt/tests/source/issue-3234.rs
new file mode 100644
index 0000000000000..120740a72339b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3234.rs
@@ -0,0 +1,14 @@
+macro_rules! fuzz_target {
+    (|$data:ident: &[u8]| $body:block) => {};
+}
+
+fuzz_target!(|data: &[u8]| {
+
+    if let Ok(app_img) = AppImage::parse(data) {
+        if let Ok(app_img) = app_img.sign_for_secureboot(include_str!("../../test-data/signing-key")) {
+            assert!(app_img.is_signed());
+            Gbl::from_app_image(app_img).to_bytes();
+        }
+    }
+
+});
diff --git a/src/tools/rustfmt/tests/source/issue-3241.rs b/src/tools/rustfmt/tests/source/issue-3241.rs
new file mode 100644
index 0000000000000..090284a21fdce
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3241.rs
@@ -0,0 +1,11 @@
+// rustfmt-edition: 2018
+
+use ::ignore;
+use ::ignore::some::more;
+use ::{foo, bar};
+use ::*;
+use ::baz::{foo, bar};
+
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3253/bar.rs b/src/tools/rustfmt/tests/source/issue-3253/bar.rs
new file mode 100644
index 0000000000000..eaeffd3ad00cf
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3253/bar.rs
@@ -0,0 +1,4 @@
+// Empty
+   fn empty()     {
+
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3253/foo.rs b/src/tools/rustfmt/tests/source/issue-3253/foo.rs
new file mode 100644
index 0000000000000..4ebe5326b3c8f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3253/foo.rs
@@ -0,0 +1,6 @@
+pub    fn hello(  )
+    {
+println!("Hello World!");
+
+            }
+
diff --git a/src/tools/rustfmt/tests/source/issue-3253/lib.rs b/src/tools/rustfmt/tests/source/issue-3253/lib.rs
new file mode 100644
index 0000000000000..3eef586bd6792
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3253/lib.rs
@@ -0,0 +1,14 @@
+#[macro_use]
+extern crate cfg_if;
+
+cfg_if! {
+    if #[cfg(target_family = "unix")] {
+        mod foo;
+        #[path = "paths/bar_foo.rs"]
+        mod bar_foo;
+    } else {
+        mod bar;
+        #[path = "paths/foo_bar.rs"]
+        mod foo_bar;
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3253/paths/bar_foo.rs b/src/tools/rustfmt/tests/source/issue-3253/paths/bar_foo.rs
new file mode 100644
index 0000000000000..da19f9dfaa162
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3253/paths/bar_foo.rs
@@ -0,0 +1,3 @@
+fn    foo_decl_item(x: &mut i32) {
+    x = 3;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3253/paths/excluded.rs b/src/tools/rustfmt/tests/source/issue-3253/paths/excluded.rs
new file mode 100644
index 0000000000000..5c63eb83203eb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3253/paths/excluded.rs
@@ -0,0 +1,6 @@
+// This module is not imported in the cfg_if macro in lib.rs so it is ignored
+// while the foo and bar mods are formatted.
+// Check the corresponding file in tests/target/issue-3253/paths/excluded.rs
+trait CoolerTypes { fn dummy(&self) {
+}
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3253/paths/foo_bar.rs b/src/tools/rustfmt/tests/source/issue-3253/paths/foo_bar.rs
new file mode 100644
index 0000000000000..fbb5d92c6e33b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3253/paths/foo_bar.rs
@@ -0,0 +1,4 @@
+
+
+fn Foo<T>() where T: Bar {
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3265.rs b/src/tools/rustfmt/tests/source/issue-3265.rs
new file mode 100644
index 0000000000000..e927cf2be466b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3265.rs
@@ -0,0 +1,14 @@
+// rustfmt-newline_style: Windows
+#[cfg(test)]
+mod test {
+    summary_test! {
+        tokenize_recipe_interpolation_eol,
+    "foo: # some comment
+ {{hello}}
+",
+    "foo: \
+ {{hello}} \
+{{ahah}}",
+        "N:#$>^{N}$<.",
+      }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3270/one.rs b/src/tools/rustfmt/tests/source/issue-3270/one.rs
new file mode 100644
index 0000000000000..3c2e27e2293df
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3270/one.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: One
+
+pub fn main() {
+    /*   let s = String::from(
+        "
+hello
+world
+",
+    ); */
+
+    assert_eq!(s, "\nhello\nworld\n");
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3270/two.rs b/src/tools/rustfmt/tests/source/issue-3270/two.rs
new file mode 100644
index 0000000000000..0eb756471e748
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3270/two.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: Two
+
+pub fn main() {
+ /*   let s = String::from(
+        "
+hello
+world
+",
+    ); */
+
+    assert_eq!(s, "\nhello\nworld\n");
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3272/v1.rs b/src/tools/rustfmt/tests/source/issue-3272/v1.rs
new file mode 100644
index 0000000000000..f4c1b7c992bf1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3272/v1.rs
@@ -0,0 +1,15 @@
+// rustfmt-version: One
+
+fn main() {
+    assert!(HAYSTACK
+            .par_iter()
+            .find_any(|&&x| x[0] % 1000 == 999)
+            .is_some());
+
+    assert(
+        HAYSTACK
+            .par_iter()
+            .find_any(|&&x| x[0] % 1000 == 999)
+            .is_some(),
+    );
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3272/v2.rs b/src/tools/rustfmt/tests/source/issue-3272/v2.rs
new file mode 100644
index 0000000000000..0148368edc8ed
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3272/v2.rs
@@ -0,0 +1,15 @@
+// rustfmt-version: Two
+
+fn main() {
+    assert!(HAYSTACK
+            .par_iter()
+            .find_any(|&&x| x[0] % 1000 == 999)
+            .is_some());
+
+    assert(
+        HAYSTACK
+            .par_iter()
+            .find_any(|&&x| x[0] % 1000 == 999)
+            .is_some(),
+    );
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3278/version_one.rs b/src/tools/rustfmt/tests/source/issue-3278/version_one.rs
new file mode 100644
index 0000000000000..580679fbae34b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3278/version_one.rs
@@ -0,0 +1,8 @@
+// rustfmt-version: One
+
+pub fn parse_conditional<'a, I: 'a>(
+) -> impl Parser<Input = I, Output = Expr, PartialState = ()> + 'a
+where
+    I: Stream<Item = char>,
+{
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3278/version_two.rs b/src/tools/rustfmt/tests/source/issue-3278/version_two.rs
new file mode 100644
index 0000000000000..c17b1742d396b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3278/version_two.rs
@@ -0,0 +1,8 @@
+// rustfmt-version: Two
+
+pub fn parse_conditional<'a, I: 'a>()
+-> impl Parser<Input = I, Output = Expr, PartialState = ()> + 'a
+where
+    I: Stream<Item = char>,
+{
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3295/two.rs b/src/tools/rustfmt/tests/source/issue-3295/two.rs
new file mode 100644
index 0000000000000..0eaf022249bec
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3295/two.rs
@@ -0,0 +1,13 @@
+// rustfmt-version: Two
+pub enum TestEnum {
+    a,
+    b,
+}
+
+fn the_test(input: TestEnum) {
+    match input {
+        TestEnum::a => String::from("aaa"),
+        TestEnum::b => String::from("this is a very very very very very very very very very very very very very very very ong string"),
+        
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3302.rs b/src/tools/rustfmt/tests/source/issue-3302.rs
new file mode 100644
index 0000000000000..c037584fd7107
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3302.rs
@@ -0,0 +1,43 @@
+// rustfmt-version: Two
+
+macro_rules! moo1 {
+    () => {
+        bar! {
+"
+"
+        }
+    };
+}
+
+macro_rules! moo2 {
+    () => {
+        bar! {
+        "
+"
+        }
+    };
+}
+
+macro_rules! moo3 {
+    () => {
+        42
+        /*
+        bar! {
+        "
+        toto
+tata"
+        }
+        */
+    };
+}
+
+macro_rules! moo4 {
+    () => {
+        bar! {
+"
+    foo
+        bar
+baz"
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3343.rs b/src/tools/rustfmt/tests/source/issue-3343.rs
new file mode 100644
index 0000000000000..5670b04f5d6cd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3343.rs
@@ -0,0 +1,47 @@
+// rustfmt-inline_attribute_width: 50
+
+#[cfg(feature = "alloc")]
+use core::slice;
+
+#[cfg(feature = "alloc")]
+use total_len_is::_50__;
+
+#[cfg(feature = "alloc")]
+use total_len_is::_51___;
+
+#[cfg(feature = "alloc")]
+extern crate len_is_50_;
+
+#[cfg(feature = "alloc")]
+extern crate len_is_51__;
+
+/// this is a comment to test is_sugared_doc property
+use core::convert;
+
+#[fooooo]
+#[barrrrr]
+use total_len_is_::_51______;
+
+#[cfg(not(all(
+    feature = "std",
+    any(
+        target_os = "linux",
+        target_os = "android",
+        target_os = "netbsd",
+        target_os = "dragonfly",
+        target_os = "haiku",
+        target_os = "emscripten",
+        target_os = "solaris",
+        target_os = "cloudabi",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "redox",
+        target_os = "fuchsia",
+        windows,
+        all(target_arch = "wasm32", feature = "stdweb"),
+        all(target_arch = "wasm32", feature = "wasm-bindgen"),
+    )
+)))]
+use core::slice;
diff --git a/src/tools/rustfmt/tests/source/issue-3423.rs b/src/tools/rustfmt/tests/source/issue-3423.rs
new file mode 100644
index 0000000000000..fbe8e5c372eb0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3423.rs
@@ -0,0 +1,5 @@
+/* a nice comment with a trailing whitespace */ 
+fn foo() {}
+
+/* a nice comment with a trailing tab */			
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3434/lib.rs b/src/tools/rustfmt/tests/source/issue-3434/lib.rs
new file mode 100644
index 0000000000000..7e396b3838880
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3434/lib.rs
@@ -0,0 +1,57 @@
+#![rustfmt::skip::macros(skip_macro_mod)]
+
+mod no_entry;
+
+#[rustfmt::skip::macros(html, skip_macro)]
+fn main() {
+    let macro_result1 = html! { <div>
+this should be skipped</div>
+    }
+    .to_string();
+
+    let macro_result2 = not_skip_macro! { <div>
+this should be mangled</div>
+        }
+    .to_string();
+
+    skip_macro! {
+this should be skipped
+};
+
+    foo();
+}
+
+fn foo() {
+    let macro_result1 = html! { <div>
+this should be mangled</div>
+            }
+    .to_string();
+}
+
+fn bar() {
+    let macro_result1 = skip_macro_mod! { <div>
+this should be skipped</div>
+        }
+    .to_string();
+}
+
+fn visitor_made_from_same_context() {
+    let pair = (
+        || {
+            foo!(<div>
+this should be mangled</div>
+            );
+            skip_macro_mod!(<div>
+this should be skipped</div>
+            );
+        },
+        || {
+            foo!(<div>
+this should be mangled</div>
+            );
+            skip_macro_mod!(<div>
+this should be skipped</div>
+            );
+        },
+    );
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3434/no_entry.rs b/src/tools/rustfmt/tests/source/issue-3434/no_entry.rs
new file mode 100644
index 0000000000000..0838829fed348
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3434/no_entry.rs
@@ -0,0 +1,18 @@
+#[rustfmt::skip::macros(another_macro)]
+fn foo() {
+    another_macro!(
+This should be skipped.
+        );
+}
+
+fn bar() {
+    skip_macro_mod!(
+This should be skipped.
+        );
+}
+
+fn baz() {
+    let macro_result1 = no_skip_macro! { <div>
+this should be mangled</div>
+    }.to_string();
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3434/not_skip_macro.rs b/src/tools/rustfmt/tests/source/issue-3434/not_skip_macro.rs
new file mode 100644
index 0000000000000..1d7d73c523d62
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3434/not_skip_macro.rs
@@ -0,0 +1,8 @@
+#[this::is::not::skip::macros(ouch)]
+
+fn main() {
+    let macro_result1 = ouch! { <div>
+this should be mangled</div>
+    }
+    .to_string();
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3465.rs b/src/tools/rustfmt/tests/source/issue-3465.rs
new file mode 100644
index 0000000000000..0bc95ad4616f4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3465.rs
@@ -0,0 +1,42 @@
+fn main() {
+    ((((((((((((((((((((((((((((((((((((((((((0) + 1) + 1)
+                                           + 1)
+                                          + 1)
+                                         + 1)
+                                        + 1)
+                                       + 1)
+                                      + 1)
+                                     + 1)
+                                    + 1)
+                                   + 1)
+                                  + 1)
+                                 + 1)
+                                + 1)
+                               + 1)
+                              + 1)
+                             + 1)
+                            + 1)
+                           + 1)
+                          + 1)
+                         + 1)
+                        + 1)
+                       + 1)
+                      + 1)
+                     + 1)
+                    + 1)
+                   + 1)
+                  + 1)
+                 + 1)
+                + 1)
+               + 1)
+              + 1)
+             + 1)
+            + 1)
+           + 1)
+          + 1)
+         + 1)
+        + 1)
+       + 1)
+      + 1)
+     + 1);
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3494/crlf.rs b/src/tools/rustfmt/tests/source/issue-3494/crlf.rs
new file mode 100644
index 0000000000000..9ce457c7b068e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3494/crlf.rs
@@ -0,0 +1,8 @@
+// rustfmt-file_lines: [{"file":"tests/source/issue-3494/crlf.rs","range":[4,5]}]
+
+pub fn main()
+{
+let world1 = "world"; println!("Hello, {}!", world1);
+let world2 = "world"; println!("Hello, {}!", world2);
+let world3 = "world"; println!("Hello, {}!", world3);
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3494/lf.rs b/src/tools/rustfmt/tests/source/issue-3494/lf.rs
new file mode 100644
index 0000000000000..bdbe69cef4a64
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3494/lf.rs
@@ -0,0 +1,8 @@
+// rustfmt-file_lines: [{"file":"tests/source/issue-3494/lf.rs","range":[4,5]}]
+
+pub fn main()
+{
+let world1 = "world"; println!("Hello, {}!", world1);
+let world2 = "world"; println!("Hello, {}!", world2);
+let world3 = "world"; println!("Hello, {}!", world3);
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3508.rs b/src/tools/rustfmt/tests/source/issue-3508.rs
new file mode 100644
index 0000000000000..821e947c707c7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3508.rs
@@ -0,0 +1,29 @@
+fn foo<F>(foo2: F)
+where
+    F: Fn(
+          // this comment is deleted
+),
+{
+}
+
+fn foo_block<F>(foo2: F)
+where
+    F: Fn(
+        /* this comment is deleted */
+  ),
+{
+}
+
+fn bar(
+    bar2: impl Fn(
+          // this comment is deleted
+    ),
+) {
+}
+
+fn bar_block(
+    bar2: impl Fn(
+        /* this comment is deleted */
+    ),
+) {
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3515.rs b/src/tools/rustfmt/tests/source/issue-3515.rs
new file mode 100644
index 0000000000000..9f760cb94e8f8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3515.rs
@@ -0,0 +1,6 @@
+// rustfmt-reorder_imports: false
+
+use std :: fmt :: { self , Display } ;
+use std :: collections :: HashMap ;
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3532.rs b/src/tools/rustfmt/tests/source/issue-3532.rs
new file mode 100644
index 0000000000000..ec0c01610cd4f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3532.rs
@@ -0,0 +1,7 @@
+fn foo(a: T) {
+    match a {
+1 => {}
+    0 => {}
+    // _ => panic!("doesn't format!"),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3585/extern_crate.rs b/src/tools/rustfmt/tests/source/issue-3585/extern_crate.rs
new file mode 100644
index 0000000000000..6716983ba0f39
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3585/extern_crate.rs
@@ -0,0 +1,12 @@
+// rustfmt-inline_attribute_width: 100
+
+#[macro_use]
+extern crate static_assertions;
+
+#[cfg(unix)]
+extern crate static_assertions;
+
+// a comment before the attribute
+#[macro_use]
+// some comment after
+extern crate static_assertions;
diff --git a/src/tools/rustfmt/tests/source/issue-3585/reorder_imports_disabled.rs b/src/tools/rustfmt/tests/source/issue-3585/reorder_imports_disabled.rs
new file mode 100644
index 0000000000000..45b1bb9fdd9d0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3585/reorder_imports_disabled.rs
@@ -0,0 +1,12 @@
+// rustfmt-inline_attribute_width: 100
+// rustfmt-reorder_imports: false
+
+#[cfg(unix)]
+extern crate crateb;
+#[cfg(unix)]
+extern crate cratea;
+
+#[cfg(unix)]
+use crateb;
+#[cfg(unix)]
+use cratea;
diff --git a/src/tools/rustfmt/tests/source/issue-3585/reorder_imports_enabled.rs b/src/tools/rustfmt/tests/source/issue-3585/reorder_imports_enabled.rs
new file mode 100644
index 0000000000000..9f433e5ca21b3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3585/reorder_imports_enabled.rs
@@ -0,0 +1,12 @@
+// rustfmt-inline_attribute_width: 100
+// rustfmt-reorder_imports: true
+
+#[cfg(unix)]
+extern crate crateb;
+#[cfg(unix)]
+extern crate cratea;
+
+#[cfg(unix)]
+use crateb;
+#[cfg(unix)]
+use cratea;
diff --git a/src/tools/rustfmt/tests/source/issue-3585/use.rs b/src/tools/rustfmt/tests/source/issue-3585/use.rs
new file mode 100644
index 0000000000000..e71ba9008ce44
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3585/use.rs
@@ -0,0 +1,7 @@
+// rustfmt-inline_attribute_width: 100
+
+#[macro_use]
+use static_assertions;
+
+#[cfg(unix)]
+use static_assertions;
diff --git a/src/tools/rustfmt/tests/source/issue-3636.rs b/src/tools/rustfmt/tests/source/issue-3636.rs
new file mode 100644
index 0000000000000..edfa03012f29c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3636.rs
@@ -0,0 +1,10 @@
+// rustfmt-file_lines: [{"file":"tests/source/issue-3636.rs","range":[4,7]},{"file":"tests/target/issue-3636.rs","range":[3,6]}]
+
+fn foo() {
+    let x =
+        42;
+    let y =
+        42;
+    let z = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+    let z = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";   
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3639.rs b/src/tools/rustfmt/tests/source/issue-3639.rs
new file mode 100644
index 0000000000000..7b16b2dfde065
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3639.rs
@@ -0,0 +1,5 @@
+trait Foo where {}
+struct Bar where {}
+struct Bax where;
+struct Baz(String) where;
+impl<> Foo<> for Bar<> where {}
diff --git a/src/tools/rustfmt/tests/source/issue-3651.rs b/src/tools/rustfmt/tests/source/issue-3651.rs
new file mode 100644
index 0000000000000..c153e99d0f011
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3651.rs
@@ -0,0 +1,4 @@
+fn f() -> Box<
+    dyn FnMut() -> Thing< WithType = LongItemName, Error = LONGLONGLONGLONGLONGONGEvenLongerErrorNameLongerLonger>,
+>{
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue-3665/lib.rs b/src/tools/rustfmt/tests/source/issue-3665/lib.rs
new file mode 100644
index 0000000000000..e049fbc5680e3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3665/lib.rs
@@ -0,0 +1,33 @@
+#![rustfmt::skip::attributes(skip_mod_attr)]
+
+mod sub_mod;
+
+#[rustfmt::skip::attributes(other, skip_attr)]
+fn main() {
+    #[other(should,
+skip,
+        this,                               format)]
+    struct S {}
+
+    #[skip_attr(should, skip,
+this,                               format,too)]
+    fn doesnt_mater() {}
+
+    #[skip_mod_attr(should, skip,
+this,                               format,
+         enerywhere)]
+    fn more() {}
+
+    #[not_skip(not,
+skip,    me)]
+    struct B {}
+}
+
+#[other(should, not, skip,
+this,                               format, here)]
+fn foo() {}
+
+#[skip_mod_attr(should, skip,
+this,                               format,in,                    master,
+                    and, sub, module)]
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3665/not_skip_attribute.rs b/src/tools/rustfmt/tests/source/issue-3665/not_skip_attribute.rs
new file mode 100644
index 0000000000000..14985259a50f3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3665/not_skip_attribute.rs
@@ -0,0 +1,4 @@
+#![this::is::not::skip::attribute(ouch)]
+
+#[ouch(not,      skip,  me)]
+fn main() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3665/sub_mod.rs b/src/tools/rustfmt/tests/source/issue-3665/sub_mod.rs
new file mode 100644
index 0000000000000..75fb24b4a65dd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3665/sub_mod.rs
@@ -0,0 +1,14 @@
+#[rustfmt::skip::attributes(more_skip)]
+#[more_skip(should,
+      skip,
+this,                               format)]
+fn foo() {}
+
+#[skip_mod_attr(should, skip,
+this,                               format,in,                    master,
+                    and, sub, module)]
+fn bar() {}
+
+#[skip_attr(should,  not,
+  skip,      this, attribute,    here)]
+fn baz() {}
diff --git a/src/tools/rustfmt/tests/source/issue-3672.rs b/src/tools/rustfmt/tests/source/issue-3672.rs
new file mode 100644
index 0000000000000..82616bd4253af
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3672.rs
@@ -0,0 +1,4 @@
+fn main() {
+    let x = 5;;
+    
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue-3675.rs b/src/tools/rustfmt/tests/source/issue-3675.rs
new file mode 100644
index 0000000000000..f16efb2dcac15
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3675.rs
@@ -0,0 +1,5 @@
+ fn main() {
+    println!("{}"
+        // comment
+        , 111);
+ }
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue-3701/one.rs b/src/tools/rustfmt/tests/source/issue-3701/one.rs
new file mode 100644
index 0000000000000..a7f0bd3aa17a4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3701/one.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: One
+
+fn build_sorted_static_get_entry_names(
+    mut entries: Vec<(u8, &'static str)>,
+) -> (impl Fn(
+    AlphabeticalTraversal,
+    Box<dyn dirents_sink::Sink<AlphabeticalTraversal>>,
+) -> BoxFuture<'static, Result<Box<dyn dirents_sink::Sealed>, Status>>
+      + Send
+      + Sync
+      + 'static) {
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3701/two.rs b/src/tools/rustfmt/tests/source/issue-3701/two.rs
new file mode 100644
index 0000000000000..8e15c58b8b259
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3701/two.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: Two
+
+fn build_sorted_static_get_entry_names(
+    mut entries: Vec<(u8, &'static str)>,
+) -> (impl Fn(
+    AlphabeticalTraversal,
+    Box<dyn dirents_sink::Sink<AlphabeticalTraversal>>,
+) -> BoxFuture<'static, Result<Box<dyn dirents_sink::Sealed>, Status>>
+      + Send
+      + Sync
+      + 'static) {
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3709.rs b/src/tools/rustfmt/tests/source/issue-3709.rs
new file mode 100644
index 0000000000000..73c2a624e5243
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3709.rs
@@ -0,0 +1,10 @@
+// rustfmt-edition: 2018
+
+macro_rules! token {
+    ($t:tt) => {};
+}
+
+fn main() {
+    token!(dyn);
+    token!(dyn );
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3740.rs b/src/tools/rustfmt/tests/source/issue-3740.rs
new file mode 100644
index 0000000000000..2769a8cc9b15f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3740.rs
@@ -0,0 +1,10 @@
+impl<T, const SIZE: usize> IntoNormalized for Vector<T, { SIZE }>
+    where
+        Vector<T, { SIZE }>: Div<Vector<T, { SIZE }>>,
+        for<'a> &'a Vector<T, { SIZE }>: IntoLength<Output = T>,
+{
+    type Output = Vector<T, { SIZE }>;
+    fn into_normalized(self) -> Self::Output {
+
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3750.rs b/src/tools/rustfmt/tests/source/issue-3750.rs
new file mode 100644
index 0000000000000..1189a99d2b6d6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3750.rs
@@ -0,0 +1,16 @@
+// rustfmt-imports_granularity: Crate
+
+pub mod foo {
+    pub mod bar {
+        pub struct Bar;
+    }
+
+    pub fn bar() {}
+}
+
+use foo::bar;
+use foo::bar::Bar;
+
+fn main() {
+    bar();
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3751.rs b/src/tools/rustfmt/tests/source/issue-3751.rs
new file mode 100644
index 0000000000000..1343f80e66e55
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3751.rs
@@ -0,0 +1,10 @@
+// rustfmt-format_code_in_doc_comments: true
+
+//! Empty pound line
+//!
+//! ```rust
+//! #
+//! # fn main() {
+//!  foo ( )  ;
+//! # }
+//! ```
diff --git a/src/tools/rustfmt/tests/source/issue-3779/ice.rs b/src/tools/rustfmt/tests/source/issue-3779/ice.rs
new file mode 100644
index 0000000000000..cde21412d9458
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3779/ice.rs
@@ -0,0 +1,3 @@
+pub fn bar() {
+    1x;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3779/lib.rs b/src/tools/rustfmt/tests/source/issue-3779/lib.rs
new file mode 100644
index 0000000000000..16e9d48337bde
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3779/lib.rs
@@ -0,0 +1,9 @@
+// rustfmt-unstable: true
+// rustfmt-config: issue-3779.toml
+
+#[path = "ice.rs"]
+mod ice;
+
+fn foo() {
+println!("abc") ;
+    }
diff --git a/src/tools/rustfmt/tests/source/issue-3786.rs b/src/tools/rustfmt/tests/source/issue-3786.rs
new file mode 100644
index 0000000000000..54f8211ed4f8b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3786.rs
@@ -0,0 +1,12 @@
+fn main() {
+    let _ = 
+r#"
+this is a very long string exceeded maximum width in this case maximum 100. (current this line width is about 115)
+"#;
+
+    let _with_newline = 
+    
+r#"
+this is a very long string exceeded maximum width in this case maximum 100. (current this line width is about 115)
+"#;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3787.rs b/src/tools/rustfmt/tests/source/issue-3787.rs
new file mode 100644
index 0000000000000..bcdc131a05e9e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3787.rs
@@ -0,0 +1,9 @@
+// rustfmt-wrap_comments: true
+
+//! URLs in items
+//! * [This is a link with a very loooooooooooooooooooooooooooooooooooooooooong URL.](https://example.com/This/is/a/link/with/a/very/loooooooooooooooooooooooooooooooooooooooooong/URL)
+//! * This is a [link](https://example.com/This/is/a/link/with/a/very/loooooooooooooooooooooooooooooooooooooooooong/URL) with a very loooooooooooooooooooooooooooooooooooooooooong URL.
+//! * there is no link here: In hac habitasse platea dictumst. Maecenas in ligula. Duis tincidunt odio sollicitudin quam. Nullam non mauris. Phasellus lacinia, velit sit amet bibendum euismod, leo diam interdum ligula, eu scelerisque sem purus in tellus.
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3840/version-one_hard-tabs.rs b/src/tools/rustfmt/tests/source/issue-3840/version-one_hard-tabs.rs
new file mode 100644
index 0000000000000..bf7ea7da0ebc3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3840/version-one_hard-tabs.rs
@@ -0,0 +1,15 @@
+// rustfmt-hard_tabs: true
+
+impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+{
+    type Ctx = C;
+    type Event = Vec<Target>;
+}
+
+mod foo {
+    impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+    {
+        type Ctx = C;
+        type Event = Vec<Target>;
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3840/version-one_soft-tabs.rs b/src/tools/rustfmt/tests/source/issue-3840/version-one_soft-tabs.rs
new file mode 100644
index 0000000000000..3fc26224d5035
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3840/version-one_soft-tabs.rs
@@ -0,0 +1,13 @@
+impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+{
+    type Ctx = C;
+    type Event = Vec<Target>;
+}
+
+mod foo {
+    impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+    {
+        type Ctx = C;
+        type Event = Vec<Target>;
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3840/version-two_hard-tabs.rs b/src/tools/rustfmt/tests/source/issue-3840/version-two_hard-tabs.rs
new file mode 100644
index 0000000000000..7b505fda87c2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3840/version-two_hard-tabs.rs
@@ -0,0 +1,16 @@
+// rustfmt-hard_tabs: true
+// rustfmt-version: Two
+
+impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+{
+    type Ctx = C;
+    type Event = Vec<Target>;
+}
+
+mod foo {
+    impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+    {
+        type Ctx = C;
+        type Event = Vec<Target>;
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-3840/version-two_soft-tabs.rs b/src/tools/rustfmt/tests/source/issue-3840/version-two_soft-tabs.rs
new file mode 100644
index 0000000000000..39c8ef31292ca
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-3840/version-two_soft-tabs.rs
@@ -0,0 +1,15 @@
+// rustfmt-version: Two
+
+impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+{
+    type Ctx = C;
+    type Event = Vec<Target>;
+}
+
+mod foo {
+    impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B>
+    {
+        type Ctx = C;
+        type Event = Vec<Target>;
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4018.rs b/src/tools/rustfmt/tests/source/issue-4018.rs
new file mode 100644
index 0000000000000..9a91dd9a30669
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4018.rs
@@ -0,0 +1,13 @@
+fn main() {
+    ;
+           /* extra comment */            ;
+}
+
+fn main() {
+    println!("");
+    // comment 1
+    // comment 2
+    // comment 3
+    // comment 4
+    ;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4079.rs b/src/tools/rustfmt/tests/source/issue-4079.rs
new file mode 100644
index 0000000000000..eb1ce5ed2a5b0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4079.rs
@@ -0,0 +1,8 @@
+// rustfmt-wrap_comments: true
+
+/*!
+ * Lorem ipsum dolor sit amet, consectetur adipiscing elit. In lacinia
+ * ullamcorper lorem, non hendrerit enim convallis ut. Curabitur id sem volutpat
+ */
+
+/*! Lorem ipsum dolor sit amet, consectetur adipiscing elit. In lacinia ullamcorper lorem, non hendrerit enim convallis ut. Curabitur id sem volutpat */
diff --git a/src/tools/rustfmt/tests/source/issue-4120.rs b/src/tools/rustfmt/tests/source/issue-4120.rs
new file mode 100644
index 0000000000000..c9ce838c51adb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4120.rs
@@ -0,0 +1,85 @@
+fn main() {
+    let x = if true {
+        1
+            // In if
+    } else {
+        0
+            // In else
+    };
+
+    let x = if true {
+        1
+             /* In if */
+    } else {
+        0
+             /* In else */
+    };
+
+    let z = if true {
+        if true {
+            1
+
+                 // In if level 2
+        } else {
+            2
+        }
+    } else {
+        3
+    };
+
+    let a = if true {
+        1
+  // In if
+    } else {
+        0
+  // In else
+    };
+
+    let a = if true {
+        1
+
+    // In if
+    } else {
+        0
+    // In else
+    };
+
+    let b = if true {
+        1
+
+    // In if
+    } else {
+        0
+        // In else
+    };
+
+    let c = if true {
+        1
+
+        // In if
+    } else {
+        0
+        // In else
+    };
+    for i in 0..2 {
+        println!("Something");
+        // In for
+    }
+
+    for i in 0..2 {
+        println!("Something");
+        /* In for */
+    }
+
+    extern "C" {
+        fn first();
+
+        // In foreign mod
+    }
+
+    extern "C" {
+        fn first();
+
+        /* In foreign mod */
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4243.rs b/src/tools/rustfmt/tests/source/issue-4243.rs
new file mode 100644
index 0000000000000..d8a27f7a4a408
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4243.rs
@@ -0,0 +1,21 @@
+fn main() {
+    type A: AA /*AA*/ + /*AB*/ AB 
++ AC = AA 
+/*AA*/ + 
+ /*AB*/ AB+AC;
+
+    type B: BA /*BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA*/+/*BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB*/ BB
+   + BC = BA /*BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA*/ + /*BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB*/ BB+ BC;
+
+    type C: CA // CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 
+// CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+  +
+        // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+   CB + CC = CA // CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    // CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    +
+    // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        CB+ CC;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4244.rs b/src/tools/rustfmt/tests/source/issue-4244.rs
new file mode 100644
index 0000000000000..34b51085e131d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4244.rs
@@ -0,0 +1,16 @@
+pub struct SS {}
+
+pub type  A  /* A Comment */      = SS;
+
+pub type  B // Comment
+// B
+= SS;
+
+pub type C 
+ /* Comment C */ = SS;
+
+pub trait D <T> {
+		type E /* Comment E */ = SS;
+}
+
+type F<'a: 'static, T: Ord + 'static>: Eq + PartialEq where T: 'static + Copy     /* x */   = Vec<u8>;
diff --git a/src/tools/rustfmt/tests/source/issue-4245.rs b/src/tools/rustfmt/tests/source/issue-4245.rs
new file mode 100644
index 0000000000000..57d7e192d0af6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4245.rs
@@ -0,0 +1,26 @@
+
+
+fn a(a: & // Comment  
+	// Another comment
+    'a File) {}
+
+fn b(b: & /* Another Comment */'a File) {}
+
+fn c(c: &'a /*Comment */ mut /*Comment */ File){}
+
+fn d(c: & // Comment
+'b // Multi Line
+// Comment
+mut // Multi Line
+// Comment
+File
+) {}
+
+fn e(c: &// Comment
+File) {}
+
+fn d(c: &// Comment
+mut // Multi Line
+// Comment
+File
+) {}
diff --git a/src/tools/rustfmt/tests/source/issue-4312.rs b/src/tools/rustfmt/tests/source/issue-4312.rs
new file mode 100644
index 0000000000000..b36b0efdb9e29
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4312.rs
@@ -0,0 +1,22 @@
+// issue 4312
+fn main() {
+    /* " */
+    println!("Hello, world!");
+    /* abc " */
+    println!("Hello, world!");
+    /* " abc */
+    println!("Hello, world!");
+    let y = 4;
+    let x = match 1 + y == 3 {
+        True => 3,
+        False => 4,
+        /* " unreachable */
+    };
+}
+
+// issue 4806
+enum X {
+    A,
+    B,
+    /*"*/
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4382.rs b/src/tools/rustfmt/tests/source/issue-4382.rs
new file mode 100644
index 0000000000000..cbf0c4ed6d464
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4382.rs
@@ -0,0 +1,4 @@
+pub const NAME_MAX: usize = {
+    #[cfg(target_os = "linux")]   { 1024 }
+    #[cfg(target_os = "freebsd")] {  255 }
+};
diff --git a/src/tools/rustfmt/tests/source/issue-4398.rs b/src/tools/rustfmt/tests/source/issue-4398.rs
new file mode 100644
index 0000000000000..b0095aaac7918
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4398.rs
@@ -0,0 +1,19 @@
+impl Struct {
+    /// Documentation for `foo`
+    #[rustfmt::skip] // comment on why use a skip here
+    pub fn foo(&self) {}
+}
+
+impl Struct {
+    /// Documentation for `foo`
+       #[rustfmt::skip] // comment on why use a skip here
+    pub fn foo(&self) {}
+}
+
+/// Documentation for `Struct`
+#[rustfmt::skip] // comment
+impl Struct {
+    /// Documentation for `foo`
+       #[rustfmt::skip] // comment on why use a skip here
+    pub fn foo(&self) {}
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4427.rs b/src/tools/rustfmt/tests/source/issue-4427.rs
new file mode 100644
index 0000000000000..e14e039b98f54
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4427.rs
@@ -0,0 +1,31 @@
+const A: usize = 
+  // Some constant
+    2;
+
+const B: usize =   
+/* constant */
+3;
+
+const C :   usize   
+      = /* foo */5;
+
+const D: usize =    // baz
+/*    Some constant */
+            /* ba */
+ {  3  
+ // foo   
+    };
+const E:   usize=             /* foo */5;
+const F: usize =
+{
+        7
+    };
+const G: usize = /* foooooooooooooooooooooooooooooooooooooooooooooooooooooooo0000000000000000xx00 */ 5;
+                  const H: usize = /* asdfasdf */ match G > 1 {
+                    true => 1,
+                    false => 3,
+                };
+            
+                pub static FOO_BAR: Vec<u8> =    //f
+                {
+                    vec![]};
diff --git a/src/tools/rustfmt/tests/source/issue-447.rs b/src/tools/rustfmt/tests/source/issue-447.rs
new file mode 100644
index 0000000000000..7c542cb58c2d4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-447.rs
@@ -0,0 +1,39 @@
+// rustfmt-normalize_comments: true
+
+fn main() {
+	if /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	cond /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	{
+	} /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	else /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	if /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	cond /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	{
+	} /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	else /* shouldn't be dropped
+	shouldn't be dropped */
+	
+	{
+	}
+	
+	if /* shouldn't be dropped
+	shouldn't be dropped */
+	let Some(x) = y/* shouldn't be dropped
+	shouldn't be dropped */
+	{
+	}
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4577.rs b/src/tools/rustfmt/tests/source/issue-4577.rs
new file mode 100644
index 0000000000000..79975dd73ffc4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4577.rs
@@ -0,0 +1,20 @@
+fn main() {
+    let s: String = "ABAABBAA".chars()
+        .filter(|c| {
+            if *c == 'A' {
+                true
+            }
+            else {
+                false
+            }
+        })
+        .map(|c| -> char {
+        if c == 'A' {
+            '0'
+        } else {
+            '1'
+        }
+    }).collect();
+    
+    println!("{}", s);
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4603.rs b/src/tools/rustfmt/tests/source/issue-4603.rs
new file mode 100644
index 0000000000000..ba0803e0ecaba
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4603.rs
@@ -0,0 +1,47 @@
+// Formatting when original macro snippet is used
+
+// Original issue #4603 code
+#![feature(or_patterns)]
+macro_rules! t_or_f {
+    () => {
+        (true // some comment
+        | false)
+    };
+}
+
+// Other test cases variations
+macro_rules! RULES {
+    () => {
+        (
+		xxxxxxx // COMMENT
+        | yyyyyyy
+        )
+    };
+}
+macro_rules! RULES {
+    () => {
+        (xxxxxxx // COMMENT
+            | yyyyyyy)
+    };
+}
+
+fn main() {
+	macro_rules! RULES {
+		() => {
+			(xxxxxxx // COMMENT
+			| yyyyyyy)
+		};
+	}
+}
+
+macro_rules! RULES {
+    () => {
+        (xxxxxxx /* COMMENT */ | yyyyyyy)
+    };
+}
+macro_rules! RULES {
+    () => {
+        (xxxxxxx /* COMMENT */
+        | yyyyyyy)
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4646.rs b/src/tools/rustfmt/tests/source/issue-4646.rs
new file mode 100644
index 0000000000000..ee0f23220c97b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4646.rs
@@ -0,0 +1,20 @@
+trait Foo {
+    fn bar(&self)
+    // where
+    //     Self: Bar
+    ;
+}
+
+trait Foo {
+    fn bar(&self)
+    // where
+    //     Self: Bar
+;
+}
+
+trait Foo {
+    fn bar(&self)
+    // where
+    //     Self: Bar
+        ;
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4656/format_me_please.rs b/src/tools/rustfmt/tests/source/issue-4656/format_me_please.rs
new file mode 100644
index 0000000000000..7de753016497a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4656/format_me_please.rs
@@ -0,0 +1,2 @@
+
+pub fn     hello(   )  {     }
diff --git a/src/tools/rustfmt/tests/source/issue-4656/lib.rs b/src/tools/rustfmt/tests/source/issue-4656/lib.rs
new file mode 100644
index 0000000000000..5dac91b8aab2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4656/lib.rs
@@ -0,0 +1,7 @@
+extern crate cfg_if;
+
+cfg_if::cfg_if! {
+    if #[cfg(target_family = "unix")] {
+        mod format_me_please;
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-4656/lib2.rs b/src/tools/rustfmt/tests/source/issue-4656/lib2.rs
new file mode 100644
index 0000000000000..b17fffc58e1dd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-4656/lib2.rs
@@ -0,0 +1,3 @@
+its_a_macro! {
+    // Contents
+}
diff --git a/src/tools/rustfmt/tests/source/issue-510.rs b/src/tools/rustfmt/tests/source/issue-510.rs
new file mode 100644
index 0000000000000..4c60859e6cf39
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-510.rs
@@ -0,0 +1,37 @@
+impl ISizeAndMarginsComputer for AbsoluteNonReplaced {
+fn solve_inline_size_constraints(&self,
+block: &mut BlockFlow,
+input: &ISizeConstraintInput)
+-> ISizeConstraintSolution {
+let (inline_start,inline_size,margin_inline_start,margin_inline_end) =
+match (inline_startssssssxxxxxxsssssxxxxxxxxxssssssxxx,inline_startssssssxxxxxxsssssxxxxxxxxxssssssxxx) {
+(MaybeAuto::Auto, MaybeAuto::Auto, MaybeAuto::Auto) => {
+let margin_start = inline_start_margin.specified_or_zero();
+let margin_end = inline_end_margin.specified_or_zero();
+// Now it is the same situation as inline-start Specified and inline-end
+// and inline-size Auto.
+//
+// Set inline-end to zero to calculate inline-size.
+let inline_size = block.get_shrink_to_fit_inline_size(available_inline_size -
+(margin_start + margin_end));
+(Au(0), inline_size, margin_start, margin_end)
+}
+};
+
+        let (inline_start, inline_size, margin_inline_start, margin_inline_end) =
+            match (inline_start, inline_end, computed_inline_size) {
+                (MaybeAuto::Auto, MaybeAuto::Auto, MaybeAuto::Auto) => {
+                    let margin_start = inline_start_margin.specified_or_zero();
+                    let margin_end = inline_end_margin.specified_or_zero();
+                    // Now it is the same situation as inline-start Specified and inline-end
+                    // and inline-size Auto.
+                    //
+                    // Set inline-end to zero to calculate inline-size.
+                    let inline_size =
+                        block.get_shrink_to_fit_inline_size(available_inline_size -
+                                                            (margin_start + margin_end));
+                    (Au(0), inline_size, margin_start, margin_end)
+                }
+            };
+}
+}
diff --git a/src/tools/rustfmt/tests/source/issue-539.rs b/src/tools/rustfmt/tests/source/issue-539.rs
new file mode 100644
index 0000000000000..d70682e3bee46
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-539.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+/*
+  FIXME (#3300): Should allow items to be anonymous. Right now
+  we just use dummy names for anon items.
+ */
diff --git a/src/tools/rustfmt/tests/source/issue-683.rs b/src/tools/rustfmt/tests/source/issue-683.rs
new file mode 100644
index 0000000000000..fd99015ea51ca
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-683.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+/*
+ * FIXME (#3300): Should allow items to be anonymous. Right now
+ * we just use dummy names for anon items.
+ */
diff --git a/src/tools/rustfmt/tests/source/issue-811.rs b/src/tools/rustfmt/tests/source/issue-811.rs
new file mode 100644
index 0000000000000..b7a89b5d0f9dc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-811.rs
@@ -0,0 +1,19 @@
+trait FooTrait<T>: Sized {
+    type Bar: BarTrait<T>;
+}
+
+trait BarTrait<T>: Sized {
+    type Baz;
+    fn foo();
+}
+
+type Foo<T: FooTrait> = <<T as FooTrait<U>>::Bar as BarTrait<U>>::Baz;
+type Bar<T: BarTrait> = <T as BarTrait<U>>::Baz;
+
+fn some_func<T: FooTrait<U>, U>() {
+    <<T as FooTrait<U>>::Bar as BarTrait<U>>::foo();
+}
+
+fn some_func<T: BarTrait<U>>() {
+    <T as BarTrait<U>>::foo();
+}
diff --git a/src/tools/rustfmt/tests/source/issue-850.rs b/src/tools/rustfmt/tests/source/issue-850.rs
new file mode 100644
index 0000000000000..c939716a6a881
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-850.rs
@@ -0,0 +1 @@
+const unsafe fn x() {}
diff --git a/src/tools/rustfmt/tests/source/issue-855.rs b/src/tools/rustfmt/tests/source/issue-855.rs
new file mode 100644
index 0000000000000..8f33fa685ae98
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-855.rs
@@ -0,0 +1,20 @@
+fn main() {
+    'running: loop {
+        for event in event_pump.poll_iter() {
+            match event {
+                Event::Quit {..} | Event::KeyDown { keycode: Some(Keycode::Escape), .. } => break 'running,
+            }
+        }
+    }
+}
+
+fn main2() {
+    'running: loop {
+        for event in event_pump.poll_iter() {
+            match event {
+                Event::Quit {..} |
+                Event::KeyDownXXXXXXXXXXXXX { keycode: Some(Keycode::Escape), .. } => break 'running,
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-913.rs b/src/tools/rustfmt/tests/source/issue-913.rs
new file mode 100644
index 0000000000000..25b9d42fd4140
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-913.rs
@@ -0,0 +1,20 @@
+mod client {
+    impl Client {
+        fn test(self) -> Result<()> {
+            let next_state = match self.state {
+                State::V5(v5::State::Command(v5::coand::State::WriteVersion(ref mut response))) => {
+                         let x   =   reformat . meeee()  ; 
+                }
+            };
+
+            let next_state = match self.state {
+                State::V5(v5::State::Command(v5::comand::State::WriteVersion(ref mut response))) => {
+                    // The pattern cannot be formatted in a way that the match stays
+                    // within the column limit. The rewrite should therefore be
+                    // skipped.
+                    let x =  dont . reformat . meeee();
+                }
+            };
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/issue-945.rs b/src/tools/rustfmt/tests/source/issue-945.rs
new file mode 100644
index 0000000000000..37d703c4679f8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-945.rs
@@ -0,0 +1,5 @@
+impl Bar { default const unsafe fn foo() { "hi" } }
+
+impl Baz { default unsafe extern "C" fn foo() { "hi" } }
+
+impl Foo for Bar { default fn foo() { "hi" } }
diff --git a/src/tools/rustfmt/tests/source/issue-977.rs b/src/tools/rustfmt/tests/source/issue-977.rs
new file mode 100644
index 0000000000000..fe16387b7b234
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue-977.rs
@@ -0,0 +1,7 @@
+// rustfmt-normalize_comments: true
+
+trait NameC { /* comment */ }
+struct FooC { /* comment */ }
+enum MooC { /* comment */ }
+mod BarC { /* comment */ }
+extern { /* comment */ }
diff --git a/src/tools/rustfmt/tests/source/issue_3839.rs b/src/tools/rustfmt/tests/source/issue_3839.rs
new file mode 100644
index 0000000000000..3933d31ee1a37
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_3839.rs
@@ -0,0 +1,8 @@
+struct Foo {
+        a: i32,
+/*
+asd
+*/
+        // foo
+b: i32,
+}
diff --git a/src/tools/rustfmt/tests/source/issue_3844.rs b/src/tools/rustfmt/tests/source/issue_3844.rs
new file mode 100644
index 0000000000000..15441b2b05c44
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_3844.rs
@@ -0,0 +1,3 @@
+fn main() {
+|| {{}};
+}
diff --git a/src/tools/rustfmt/tests/source/issue_3853.rs b/src/tools/rustfmt/tests/source/issue_3853.rs
new file mode 100644
index 0000000000000..c41309bc78828
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_3853.rs
@@ -0,0 +1,52 @@
+fn by_ref_with_block_before_ident() {
+if let Some(ref     /*def*/      state)=        foo{
+				println!(
+        "asdfasdfasdf");	}
+}
+
+fn mut_block_before_ident() {
+if   let Some(mut     /*def*/    state  ) =foo{
+				println!(
+        "123"   );	}
+}
+
+fn ref_and_mut_blocks_before_ident() {
+if   let Some(ref  /*abc*/
+    mut     /*def*/    state  )    =       foo {
+				println!(
+ "deefefefefefwea"   );	}
+}
+
+fn sub_pattern() {
+    let foo @             /*foo*/
+bar(f) = 42;
+}
+
+fn no_prefix_block_before_ident() {
+if   let Some(
+    /*def*/    state  )    =       foo {
+				println!(
+ "129387123123"   );	}
+}
+
+fn issue_3853() {
+if let Some(ref /*mut*/ state) = foo {
+					}
+}
+
+fn double_slash_comment_between_lhs_and_rhs() {
+    if let Some(e) =
+				 // self.foo.bar(e, tx)
+				 packet.transaction.state.committed
+                {
+            // body
+                            println!(
+                                "a2304712836123");
+                                }
+}
+
+fn block_comment_between_lhs_and_rhs() {
+if let Some(ref     /*def*/  mut     /*abc*/       state)=          /*abc*/foo{
+				println!(
+        "asdfasdfasdf");	}
+}
diff --git a/src/tools/rustfmt/tests/source/issue_3868.rs b/src/tools/rustfmt/tests/source/issue_3868.rs
new file mode 100644
index 0000000000000..6c46c3c9e180c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_3868.rs
@@ -0,0 +1,13 @@
+fn foo() {
+    ;
+}
+
+fn bar() {
+    for _ in 0..1 {
+        ;
+    }
+}
+
+fn baz() {
+    ();
+    }
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue_4057.rs b/src/tools/rustfmt/tests/source/issue_4057.rs
new file mode 100644
index 0000000000000..7cd80734bd995
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4057.rs
@@ -0,0 +1,15 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// ```
+/// # #[rustversion::since(1.36)]
+/// # fn dox() {
+/// # use std::pin::Pin;
+/// # type Projection<'a> = &'a ();
+/// # type ProjectionRef<'a> = &'a ();
+/// # trait Dox {
+/// fn   project_ex (self: Pin<&mut Self>) -> Projection<'_>;
+/// fn   project_ref(self: Pin<&Self>) -> ProjectionRef<'_>;
+/// # }
+/// # }
+/// ```
+struct Foo;
diff --git a/src/tools/rustfmt/tests/source/issue_4086.rs b/src/tools/rustfmt/tests/source/issue_4086.rs
new file mode 100644
index 0000000000000..ffa6442e930fa
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4086.rs
@@ -0,0 +1,2 @@
+#[cfg(any())]
+extern  "C++"     {}
diff --git a/src/tools/rustfmt/tests/source/issue_4374.rs b/src/tools/rustfmt/tests/source/issue_4374.rs
new file mode 100644
index 0000000000000..2a45a022e7e7d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4374.rs
@@ -0,0 +1,13 @@
+fn a<F>(_f: F) -> ()
+where
+  F: FnOnce() -> (),
+{
+}
+fn main() {
+  a(|| {
+    #[allow(irrefutable_let_patterns)]
+    while let _ = 0 {
+      break;
+    }
+  });
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue_4475.rs b/src/tools/rustfmt/tests/source/issue_4475.rs
new file mode 100644
index 0000000000000..241dc91d7ba66
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4475.rs
@@ -0,0 +1,27 @@
+fn main() {
+    #[cfg(debug_assertions)]
+    { println!("DEBUG"); }
+}
+
+fn main() {
+    #[cfg(feature = "foo")]
+    {
+        /*
+        let foo = 0
+        */
+    }
+}
+
+fn main() {
+    #[cfg(feature = "foo")]
+    { /* let foo = 0; */ }
+}
+
+fn main() {
+    #[foo]
+    #[bar]
+    #[baz]
+    {
+        // let foo = 0;
+    }
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue_4528.rs b/src/tools/rustfmt/tests/source/issue_4528.rs
new file mode 100644
index 0000000000000..85f6d8c0387c7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4528.rs
@@ -0,0 +1,8 @@
+#![allow(clippy::no_effect)]
+ 
+extern "C" {
+ // N.B., mutability can be easily incorrect in FFI calls -- as
+     // in C, the default is mutable pointers.
+    fn ffi(c: *mut u8);
+     fn int_ffi(c: *mut i32);
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue_4584.rs b/src/tools/rustfmt/tests/source/issue_4584.rs
new file mode 100644
index 0000000000000..695c5590559d0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4584.rs
@@ -0,0 +1,19 @@
+// rustfmt-indent_style: Visual
+
+#[derive(Debug,)]
+pub enum Case {
+    Upper,
+    Lower
+}
+
+#[derive(Debug, Clone, PartialEq, Eq,)]
+pub enum Case {
+    Upper,
+    Lower
+}
+
+// NB - This formatting looks potentially off the desired state, but is
+// consistent with current behavior. Included here to provide a line wrapped
+// derive case with the changes applied to resolve issue #4584
+#[derive(Add, Sub, Mul, Div, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Debug, Hash, Serialize, Mul,)]
+struct Foo {}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue_4636.rs b/src/tools/rustfmt/tests/source/issue_4636.rs
new file mode 100644
index 0000000000000..ea7079f6c7309
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4636.rs
@@ -0,0 +1,13 @@
+pub trait PrettyPrinter<'tcx>:
+    Printer<
+        'tcx,
+        Error = fmt::Error,
+        Path = Self,
+        Region = Self,
+        Type = Self,
+        DynExistential = Self,
+        Const = Self,
+    > + fmt::Write
+    {
+         //
+    }
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/issue_4675.rs b/src/tools/rustfmt/tests/source/issue_4675.rs
new file mode 100644
index 0000000000000..66613eed000c7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/issue_4675.rs
@@ -0,0 +1,8 @@
+macro_rules! foo {
+    ($s:ident ( $p:pat )) => {
+        Foo {
+            name: Name::$s($p),
+            ..
+    }
+    };
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/item-brace-style-always-next-line.rs b/src/tools/rustfmt/tests/source/item-brace-style-always-next-line.rs
new file mode 100644
index 0000000000000..38094d67a7737
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/item-brace-style-always-next-line.rs
@@ -0,0 +1,29 @@
+// rustfmt-brace_style: AlwaysNextLine
+
+mod M {
+    enum A {
+        A,
+    }
+
+    struct B {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C {}
+
+    struct D {}
+
+    enum A<T> where T: Copy {
+        A,
+    }
+
+    struct B<T> where T: Copy {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C<T> where T: Copy {}
+
+    struct D<T> where T: Copy {}
+}
diff --git a/src/tools/rustfmt/tests/source/item-brace-style-prefer-same-line.rs b/src/tools/rustfmt/tests/source/item-brace-style-prefer-same-line.rs
new file mode 100644
index 0000000000000..dff89b8b66b59
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/item-brace-style-prefer-same-line.rs
@@ -0,0 +1,29 @@
+// rustfmt-brace_style: PreferSameLine
+
+mod M {
+    enum A
+    {
+        A,
+    }
+
+    struct B
+    {
+        b: i32,
+    }
+
+    enum C {}
+
+    struct D {}
+
+    enum A<T> where T: Copy {
+        A,
+    }
+
+    struct B<T> where T: Copy {
+        b: i32,
+    }
+
+    enum C<T> where T: Copy {}
+
+    struct D<T> where T: Copy {}
+}
diff --git a/src/tools/rustfmt/tests/source/item-brace-style-same-line-where.rs b/src/tools/rustfmt/tests/source/item-brace-style-same-line-where.rs
new file mode 100644
index 0000000000000..1d034089f694d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/item-brace-style-same-line-where.rs
@@ -0,0 +1,29 @@
+mod M {
+    enum A
+    {
+        A,
+    }
+
+    struct B
+    {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C {}
+
+    struct D {}
+
+    enum A<T> where T: Copy {
+        A,
+    }
+
+    struct B<T> where T: Copy {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C<T> where T: Copy {}
+
+    struct D<T> where T: Copy {}
+}
diff --git a/src/tools/rustfmt/tests/source/itemized-blocks/no_wrap.rs b/src/tools/rustfmt/tests/source/itemized-blocks/no_wrap.rs
new file mode 100644
index 0000000000000..a7b6a10a01050
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/itemized-blocks/no_wrap.rs
@@ -0,0 +1,47 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+//! This is a list:
+//!  * Outer
+//!  * Outer
+//!   * Inner
+//!   * Inner with lots of text so that it could be reformatted something something something lots of text so that it could be reformatted something something something
+//!
+//! This example shows how to configure fern to output really nicely colored logs
+//! - when the log level is error, the whole line is red
+//! - when the log level is warn, the whole line is yellow
+//! - when the log level is info, the level name is green and the rest of the line is white
+//! - when the log level is debug, the whole line is white
+//! - when the log level is trace, the whole line is gray ("bright black")
+
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor
+fn func1() {}
+
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+/// ```
+/// let x =     42;
+/// ```
+fn func2() {}
+
+/// Look:
+///
+/// ```
+/// let x =     42;
+/// ```
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+fn func3() {}
diff --git a/src/tools/rustfmt/tests/source/itemized-blocks/rewrite_fail.rs b/src/tools/rustfmt/tests/source/itemized-blocks/rewrite_fail.rs
new file mode 100644
index 0000000000000..f99c2cc5ff9cf
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/itemized-blocks/rewrite_fail.rs
@@ -0,0 +1,11 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 50
+
+// This example shows how to configure fern to output really nicely colored logs
+// - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 
+//   - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 
+//     - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 
+//     - when the log level is info, the level name is green and the rest of the line is white
+//   - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 
+//   - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 
+fn func1() {}
diff --git a/src/tools/rustfmt/tests/source/itemized-blocks/urls.rs b/src/tools/rustfmt/tests/source/itemized-blocks/urls.rs
new file mode 100644
index 0000000000000..2eaaafbbc4aa6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/itemized-blocks/urls.rs
@@ -0,0 +1,22 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 79
+
+//! CMSIS: Cortex Microcontroller Software Interface Standard
+//!
+//! The version 5 of the standard can be found at:
+//!
+//! http://arm-software.github.io/CMSIS_5/Core/html/index.html
+//!
+//! The API reference of the standard can be found at:
+//!
+//! - example -- http://example.org -- something something something something something something
+//! - something something something something something something more -- http://example.org
+//! - http://example.org/something/something/something/something/something/something and the rest
+//! - Core function access -- http://arm-software.github.io/CMSIS_5/Core/html/group__Core__Register__gr.html
+//! - Intrinsic functions for CPU instructions -- http://arm-software.github.io/CMSIS_5/Core/html/group__intrinsic__CPU__gr.html
+//! - Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Vestibulum sem lacus, commodo vitae.
+//!
+//! The reference C implementation used as the base of this Rust port can be
+//! found at
+//!
+//! https://github.com/ARM-software/CMSIS_5/blob/5.3.0/CMSIS/Core/Include/cmsis_gcc.h
diff --git a/src/tools/rustfmt/tests/source/itemized-blocks/wrap.rs b/src/tools/rustfmt/tests/source/itemized-blocks/wrap.rs
new file mode 100644
index 0000000000000..955cc698b79f2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/itemized-blocks/wrap.rs
@@ -0,0 +1,55 @@
+// rustfmt-wrap_comments: true
+// rustfmt-format_code_in_doc_comments: true
+// rustfmt-max_width: 50
+
+//! This is a list:
+//!  * Outer
+//!  * Outer
+//!   * Inner
+//!   * Inner with lots of text so that it could be reformatted something something something lots of text so that it could be reformatted something something something
+//!
+//! This example shows how to configure fern to output really nicely colored logs
+//! - when the log level is error, the whole line is red
+//! - when the log level is warn, the whole line is yellow
+//! - when the log level is info, the level name is green and the rest of the line is white
+//! - when the log level is debug, the whole line is white
+//! - when the log level is trace, the whole line is gray ("bright black")
+
+// This example shows how to configure fern to output really nicely colored logs
+// - when the log level is error, the whole line is red
+//   - when the log level is warn, the whole line is yellow
+//     - when the log level is info, the level name is green and the rest of the line is white
+//   - when the log level is debug, the whole line is white
+//   - when the log level is trace, the whole line is gray ("bright black")
+
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor
+fn func1() {}
+
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+/// ```
+/// let x =     42;
+/// ```
+fn func2() {}
+
+/// Look:
+///
+/// ```
+/// let x =     42;
+/// ```
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+fn func3() {}
diff --git a/src/tools/rustfmt/tests/source/label_break.rs b/src/tools/rustfmt/tests/source/label_break.rs
new file mode 100644
index 0000000000000..2c79fd35e70ca
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/label_break.rs
@@ -0,0 +1,28 @@
+// format with label break value.
+fn main() {
+
+'empty_block: {}
+
+'block: {
+    do_thing();
+    if condition_not_met() {
+        break 'block;
+    }
+    do_next_thing();
+    if condition_not_met() {
+        break 'block;
+    }
+    do_last_thing();
+}
+
+let result = 'block: {
+    if foo() {
+        // comment
+        break 'block       1;
+    }
+    if bar() { /* comment */
+        break 'block      2;
+    }
+    3
+};
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/large-block.rs b/src/tools/rustfmt/tests/source/large-block.rs
new file mode 100644
index 0000000000000..09e9169f34085
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/large-block.rs
@@ -0,0 +1,5 @@
+fn issue1351() {
+    std_fmt_Arguments_new_v1_std_rt_begin_panic_fmt_sdfasfasdfasdf({
+        static __STATIC_FMTSTR: &'static [&'static str] = &[];
+    });
+}
diff --git a/src/tools/rustfmt/tests/source/large_vec.rs b/src/tools/rustfmt/tests/source/large_vec.rs
new file mode 100644
index 0000000000000..34d5bf399544d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/large_vec.rs
@@ -0,0 +1,29 @@
+// See #1470.
+
+impl Environment {
+    pub fn new_root() -> Rc<RefCell<Environment>> {
+        let mut env = Environment::new();
+        let builtin_functions = &[("println",
+                                   Function::NativeVoid(CallSign {
+                                                            num_params: 0,
+                                                            variadic: true,
+                                                            param_types: vec![],
+                                                        },
+                                                        native_println)),
+                                  ("run_http_server",
+                                   Function::NativeVoid(CallSign {
+                                                            num_params: 1,
+                                                            variadic: false,
+                                                            param_types:
+                                                                vec![Some(ConstraintType::Function)],
+                                                        },
+                                                        native_run_http_server)),
+                                  ("len",
+                                   Function::NativeReturning(CallSign {
+                                                                 num_params: 1,
+                                                                 variadic: false,
+                                                                 param_types: vec![None],
+                                                             },
+                                                             native_len))];
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/lazy_static.rs b/src/tools/rustfmt/tests/source/lazy_static.rs
new file mode 100644
index 0000000000000..38fefbcbef5ef
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/lazy_static.rs
@@ -0,0 +1,45 @@
+// Format `lazy_static!`.
+
+lazy_static! {
+static ref CONFIG_NAME_REGEX: regex::Regex =
+regex::Regex::new(r"^## `([^`]+)`").expect("Failed creating configuration pattern");
+static ref CONFIG_VALUE_REGEX: regex::Regex = regex::Regex::new(r#"^#### `"?([^`"]+)"?`"#)
+.expect("Failed creating configuration value pattern");
+}
+
+// We need to be able to format `lazy_static!` without known syntax.
+lazy_static!(
+    xxx,
+yyyy ,
+    zzzzz
+);
+
+lazy_static!{
+}
+
+// #2354
+lazy_static ! {
+pub static ref Sbase64_encode_string : :: lisp :: LispSubrRef = {
+let subr = :: remacs_sys :: Lisp_Subr {
+header : :: remacs_sys :: Lisp_Vectorlike_Header {
+size : (
+( :: remacs_sys :: PseudovecType :: PVEC_SUBR as :: libc :: ptrdiff_t ) << ::
+remacs_sys :: PSEUDOVECTOR_AREA_BITS ) , } , function : self ::
+Fbase64_encode_string as * const :: libc :: c_void , min_args : 1i16 ,
+max_args : 2i16 , symbol_name : ( b"base64-encode-string\x00" ) . as_ptr (  )
+as * const :: libc :: c_char , intspec : :: std :: ptr :: null (  ) , doc : ::
+std :: ptr :: null (  ) , lang : :: remacs_sys :: Lisp_Subr_Lang_Rust , } ;
+unsafe {
+let ptr = :: remacs_sys :: xmalloc (
+:: std :: mem :: size_of :: < :: remacs_sys :: Lisp_Subr > (  ) ) as * mut ::
+remacs_sys :: Lisp_Subr ; :: std :: ptr :: copy_nonoverlapping (
+& subr , ptr , 1 ) ; :: std :: mem :: forget ( subr ) ; :: lisp :: ExternalPtr
+:: new ( ptr ) } } ; }
+
+
+lazy_static! {
+static ref FOO: HashMap<String,
+(&'static str,
+fn(Foo) -> Result<Box<Bar>, Either<FooError, BarError>>
+),> = HashMap::new();
+}
diff --git a/src/tools/rustfmt/tests/source/license-templates/empty_license_path.rs b/src/tools/rustfmt/tests/source/license-templates/empty_license_path.rs
new file mode 100644
index 0000000000000..d3a91e4231d19
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/license-templates/empty_license_path.rs
@@ -0,0 +1,5 @@
+// rustfmt-config: issue-3802.toml
+
+fn main() {
+println!("Hello world!");
+}
diff --git a/src/tools/rustfmt/tests/source/license-templates/license.rs b/src/tools/rustfmt/tests/source/license-templates/license.rs
new file mode 100644
index 0000000000000..6816011c60dc5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/license-templates/license.rs
@@ -0,0 +1,6 @@
+// rustfmt-license_template_path: tests/license-template/lt.txt
+// Copyright 2019 The rustfmt developers.
+
+fn main() {
+println!("Hello world!");
+}
diff --git a/src/tools/rustfmt/tests/source/long-fn-1/version_one.rs b/src/tools/rustfmt/tests/source/long-fn-1/version_one.rs
new file mode 100644
index 0000000000000..d6832c2af0954
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/long-fn-1/version_one.rs
@@ -0,0 +1,21 @@
+// rustfmt-version: One
+// Tests that a function which is almost short enough, but not quite, gets
+// formatted correctly.
+
+impl Foo {
+    fn some_input(&mut self, input: Input, input_path: Option<PathBuf>, ) -> (Input, Option<PathBuf>) {}
+
+    fn some_inpu(&mut self, input: Input, input_path: Option<PathBuf>) -> (Input, Option<PathBuf>) {}
+}
+
+// #1843
+#[allow(non_snake_case)]
+pub extern "C" fn Java_com_exonum_binding_storage_indices_ValueSetIndexProxy_nativeContainsByHash() -> bool {
+    false
+}
+
+// #3009
+impl Something {
+    fn my_function_name_is_way_to_long_but_used_as_a_case_study_or_an_example_its_fine(
+) -> Result<  (), String  > {}
+}
diff --git a/src/tools/rustfmt/tests/source/long-fn-1/version_two.rs b/src/tools/rustfmt/tests/source/long-fn-1/version_two.rs
new file mode 100644
index 0000000000000..f402a26e8b6a8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/long-fn-1/version_two.rs
@@ -0,0 +1,21 @@
+// rustfmt-version: Two
+// Tests that a function which is almost short enough, but not quite, gets
+// formatted correctly.
+
+impl Foo {
+    fn some_input(&mut self, input: Input, input_path: Option<PathBuf>, ) -> (Input, Option<PathBuf>) {}
+
+    fn some_inpu(&mut self, input: Input, input_path: Option<PathBuf>) -> (Input, Option<PathBuf>) {}
+}
+
+// #1843
+#[allow(non_snake_case)]
+pub extern "C" fn Java_com_exonum_binding_storage_indices_ValueSetIndexProxy_nativeContainsByHash() -> bool {
+    false
+}
+
+// #3009
+impl Something {
+    fn my_function_name_is_way_to_long_but_used_as_a_case_study_or_an_example_its_fine(
+) -> Result<  (), String  > {}
+}
diff --git a/src/tools/rustfmt/tests/source/long-match-arms-brace-newline.rs b/src/tools/rustfmt/tests/source/long-match-arms-brace-newline.rs
new file mode 100644
index 0000000000000..927ada0ffb2e0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/long-match-arms-brace-newline.rs
@@ -0,0 +1,15 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 80
+// rustfmt-control_brace_style: AlwaysNextLine
+
+fn main() {
+    match x {
+        aaaaaaaa::Bbbbb::Ccccccccccccc(_, Some(ref x)) if x ==
+            "aaaaaaaaaaa \
+            aaaaaaa \
+            aaaaaa" => {
+            Ok(())
+        }
+            _ => Err(x),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/long-use-statement-issue-3154.rs b/src/tools/rustfmt/tests/source/long-use-statement-issue-3154.rs
new file mode 100644
index 0000000000000..339382b5bbf23
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/long-use-statement-issue-3154.rs
@@ -0,0 +1,3 @@
+// rustfmt-reorder_imports: false
+
+pub use self :: super :: super :: super :: root::mozilla::detail::StringClassFlags as nsTStringRepr_ClassFlags ;
diff --git a/src/tools/rustfmt/tests/source/long_field_access.rs b/src/tools/rustfmt/tests/source/long_field_access.rs
new file mode 100644
index 0000000000000..7aa626221aea5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/long_field_access.rs
@@ -0,0 +1,3 @@
+fn f() {
+    block_flow.base.stacking_relative_position_of_display_port = self.base.stacking_relative_position_of_display_port;
+}
diff --git a/src/tools/rustfmt/tests/source/loop.rs b/src/tools/rustfmt/tests/source/loop.rs
new file mode 100644
index 0000000000000..6e92cdc6c2c03
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/loop.rs
@@ -0,0 +1,29 @@
+
+fn main() {
+    loop    
+    {   return some_val;}
+
+let x = loop { do_forever(); };
+
+       'label :  loop {
+        // Just comments
+    }
+
+    'a: while loooooooooooooooooooooooooooooooooong_variable_name + another_value > some_other_value{}
+
+   while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa > bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb {
+   }
+
+    while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {}
+
+    'b: for xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx in some_iter(arg1, arg2) {
+        // do smth
+    }
+
+    while let  Some(i) =     x.find('s')
+    {
+        x.update();
+        continue;
+        continue 'foo;
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/macro_not_expr.rs b/src/tools/rustfmt/tests/source/macro_not_expr.rs
new file mode 100644
index 0000000000000..d8de4dce38f23
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/macro_not_expr.rs
@@ -0,0 +1,7 @@
+macro_rules! test {
+    ($($t:tt)*) => {}
+}
+
+fn main() {
+    test!( a : B => c d );
+}
diff --git a/src/tools/rustfmt/tests/source/macro_rules.rs b/src/tools/rustfmt/tests/source/macro_rules.rs
new file mode 100644
index 0000000000000..5aaca0c83fa31
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/macro_rules.rs
@@ -0,0 +1,301 @@
+// rustfmt-format_macro_matchers: true
+
+macro_rules! m {
+    () => ();
+    ( $ x : ident ) => ();
+    ( $ m1 : ident , $ m2 : ident , $ x : ident ) => ();
+    ( $($beginning:ident),*;$middle:ident;$($end:ident),* ) => ();
+    ( $($beginning: ident),*; $middle: ident; $($end: ident),*; $($beginning: ident),*; $middle: ident; $($end: ident),* ) => {};
+    ( $ name : ident ( $ ( $ dol : tt $ var : ident ) * ) $ ( $ body : tt ) * ) => ();
+    ( $( $ i : ident : $ ty : ty , $def : expr , $stb : expr , $ ( $ dstring : tt ) , + ) ; + $ ( ; ) *
+      $( $ i : ident : $ ty : ty , $def : expr , $stb : expr , $ ( $ dstring : tt ) , + ) ; + $ ( ; ) *
+    ) => {};
+    ( $foo: tt foo [$ attr : meta] $name: ident ) => {};
+    ( $foo: tt [$ attr: meta] $name: ident ) => {};
+    ( $foo: tt &'a [$attr : meta] $name: ident ) => {};
+    ( $foo: tt foo # [ $attr : meta] $name: ident ) => {};
+    ( $foo: tt # [ $attr : meta] $name: ident) => {};
+    ( $foo: tt &'a # [ $attr : meta] $name: ident ) => {};
+    ( $ x : tt foo bar foo bar foo bar $ y : tt => x*y*z $ z : tt , $ ( $a: tt ) , * ) => {};
+}
+
+
+macro_rules! impl_a_method {
+    ($n:ident ( $a:ident : $ta:ty ) -> $ret:ty { $body:expr }) => {
+        fn $n($a:$ta) -> $ret { $body }
+        macro_rules! $n { ($va:expr) => { $n($va) } }
+    };
+    ($n:ident ( $a:ident : $ta:ty, $b:ident : $tb:ty ) -> $ret:ty { $body:expr }) => {
+        fn $n($a:$ta, $b:$tb) -> $ret { $body }
+        macro_rules! $n { ($va:expr, $vb:expr) => { $n($va, $vb) } }
+    };
+    ($n:ident ( $a:ident : $ta:ty, $b:ident : $tb:ty, $c:ident : $tc:ty ) -> $ret:ty { $body:expr }) => {
+        fn $n($a:$ta, $b:$tb, $c:$tc) -> $ret { $body }
+        macro_rules! $n { ($va:expr, $vb:expr, $vc:expr) => { $n($va, $vb, $vc) } }
+    };
+    ($n:ident ( $a:ident : $ta:ty, $b:ident : $tb:ty, $c:ident : $tc:ty, $d:ident : $td:ty ) -> $ret:ty { $body:expr }) => {
+        fn $n($a:$ta, $b:$tb, $c:$tc, $d:$td) -> $ret { $body }
+        macro_rules! $n { ($va:expr, $vb:expr, $vc:expr, $vd:expr) => { $n($va, $vb, $vc, $vd) } }
+    };
+}
+
+macro_rules! m {
+	// a
+	($expr :expr,  $( $func : ident    ) *   ) => {
+		{
+		let    x =    $expr;
+									                $func (
+														x
+											)
+	}
+	};
+
+				/* b */
+
+   	()           => {/* c */};
+
+		 				(@tag)   =>
+						 {
+
+						 };
+
+// d
+( $item:ident  ) =>      {
+	mod macro_item    {  struct $item ; }
+};
+}
+
+macro m2 {
+	// a
+	($expr :expr,  $( $func : ident    ) *   ) => {
+		{
+		let    x =    $expr;
+									                $func (
+														x
+											)
+	}
+	}
+
+				/* b */
+
+   	()           => {/* c */}
+
+		 				(@tag)   =>
+						 {
+
+						 }
+
+// d
+( $item:ident  ) =>      {
+	mod macro_item    {  struct $item ; }
+}
+}
+
+// #2438, #2476
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_98_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+            );
+        }
+    }
+}
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_99_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+);
+        }
+    };
+}
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_100_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+);
+        }
+    };
+}
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_101_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+            );
+        }
+    };
+}
+
+// #2439
+macro_rules! m {
+    ($line0_xxxxxxxxxxxxxxxxx: expr, $line1_xxxxxxxxxxxxxxxxx: expr, $line2_xxxxxxxxxxxxxxxxx: expr, $line3_xxxxxxxxxxxxxxxxx: expr,) => {};
+}
+
+// #2466
+// Skip formatting `macro_rules!` that are not using `{}`.
+macro_rules! m (
+    () => ()
+);
+macro_rules! m [
+    () => ()
+];
+
+// #2470
+macro foo($type_name: ident, $docs: expr) {
+    #[allow(non_camel_case_types)]
+    #[doc=$docs]
+    #[derive(Debug, Clone, Copy)]
+    pub struct $type_name;
+}
+
+// #2534
+macro_rules! foo {
+    ($a:ident : $b:ty) => {};
+    ($a:ident $b:ident $c:ident) => {};
+}
+
+// #2538
+macro_rules! add_message_to_notes {
+    ($msg:expr) => {{
+        let mut lines = message.lines();
+        notes.push_str(&format!("\n{}: {}", level, lines.next().unwrap()));
+        for line in lines {
+            notes.push_str(&format!(
+                "\n{:indent$}{line}",
+                "",
+                indent = level.len() + 2,
+                line = line,
+            ));
+        }
+    }}
+}
+
+// #2560
+macro_rules! binary {
+    ($_self:ident,$expr:expr, $lhs:expr,$func:ident) => {
+        while $_self.matched($expr) {
+            let op = $_self.get_binary_op()?;
+
+            let rhs = Box::new($_self.$func()?);
+
+           $lhs = Spanned {
+                span: $lhs.get_span().to(rhs.get_span()),
+                value: Expression::Binary {
+                    lhs: Box::new($lhs),
+                    op,
+                    rhs,
+                },
+            }
+        }
+    };
+}
+
+// #2558
+macro_rules! m {
+    ($x:) => {};
+    ($($foo:expr)()?) => {};
+}
+
+// #2749
+macro_rules! foo {
+    ($(x)* {}) => {};
+    ($(x)* ()) => {};
+    ($(x)* []) => {};
+}
+macro_rules! __wundergraph_expand_sqlite_mutation {
+    ( $mutation_name:ident $((context = $($context:tt)*))*{ $( $entity_name:ident( $(insert = $insert:ident,)* $(update = $update:ident,)* $(delete = $($delete:tt)+)* ), )* } ) => {};
+}
+
+// #2607
+macro_rules! bench {
+    ($ty:ident) => {
+        criterion_group!(
+            name = benches;
+            config = ::common_bench::reduced_samples();
+            targets = call, map;
+        );
+    };
+}
+
+// #2770
+macro_rules! save_regs {
+    () => {
+        asm!("push rax
+              push rcx
+              push rdx
+              push rsi
+              push rdi
+              push r8
+              push r9
+              push r10
+              push r11"
+             :::: "intel", "volatile");
+    };
+}
+
+// #2721
+macro_rules! impl_as_byte_slice_arrays {
+    ($n:expr,) => {};
+    ($n:expr, $N:ident, $($NN:ident,)*) => {
+        impl_as_byte_slice_arrays!($n - 1, $($NN,)*);
+        
+        impl<T> AsByteSliceMut for [T; $n] where [T]: AsByteSliceMut {
+            fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+                self[..].as_byte_slice_mut()
+            }
+
+            fn to_le(&mut self) {
+                self[..].to_le()
+            }
+        }
+    };
+    (!div $n:expr,) => {};
+    (!div $n:expr, $N:ident, $($NN:ident,)*) => {
+        impl_as_byte_slice_arrays!(!div $n / 2, $($NN,)*);
+
+        impl<T> AsByteSliceMut for [T; $n] where [T]: AsByteSliceMut {
+            fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+                self[..].as_byte_slice_mut()
+            }
+            
+            fn to_le(&mut self) {
+                self[..].to_le()
+            }
+        }
+    };
+}
+
+// #2919
+fn foo() {
+    {
+        macro_rules! touch_value {
+            ($func:ident, $value:expr) => {{
+                let result = API::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppendMode::paTouch);
+                let result = API::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppend);
+                let result = API::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppendM);
+                let result = APIIIIIIIII::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppendM);
+                let result = API::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppendMMMMMMMMMM);
+                debug_assert!(result == 0);
+            }};
+        }
+    }
+}
+
+// #2642
+macro_rules! template {
+    ($name: expr) => {
+        format_args!(r##"
+"http://example.com"
+
+# test
+"##, $name)
+    }
+}
+
+macro_rules! template {
+    () => {
+        format_args!(r"
+//
+
+")
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/macros.rs b/src/tools/rustfmt/tests/source/macros.rs
new file mode 100644
index 0000000000000..3b286579ca8f1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/macros.rs
@@ -0,0 +1,486 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_macro_matchers: true
+itemmacro!(this, is.now() .formatted(yay));
+
+itemmacro!(really, long.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbb() .is.formatted());
+
+itemmacro!{this, is.brace().formatted()}
+
+fn main() {
+    foo! ( );
+
+    foo!(,);
+
+    bar!( a , b , c );
+
+    bar!( a , b , c , );
+
+    baz!(1+2+3, quux. kaas());
+
+    quux!(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB);
+
+    kaas!(/* comments */ a /* post macro */, b /* another */);
+
+    trailingcomma!( a , b , c , );
+    // Preserve trailing comma only when necessary.
+    ok!(file.seek(
+        SeekFrom::Start(
+            table.map(|table| fixture.offset(table)).unwrap_or(0),
+        )
+    ));
+
+    noexpr!( i am not an expression, OK? );
+
+    vec! [ a , b , c];
+
+    vec! [AAAAAA, AAAAAA, AAAAAA, AAAAAA, AAAAAA, AAAAAA, AAAAAA, AAAAAA, AAAAAA,
+          BBBBB, 5, 100-30, 1.33, b, b, b];
+
+    vec! [a /* comment */];
+
+    // Trailing spaces after a comma
+    vec![
+    a,   
+    ];
+    
+    vec![a; b];
+    vec!(a; b);
+    vec!{a; b};
+
+    vec![a, b; c];
+    vec![a; b, c];
+
+    vec![a; (|x| { let y = x + 1; let z = y + 1; z })(2)];
+    vec![a; xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx];
+    vec![a; unsafe {
+        x + 1
+    }];
+
+    unknown_bracket_macro__comma_should_not_be_stripped![
+    a,
+    ];
+    
+    foo(makro!(1,   3));
+
+    hamkaas!{ () };
+
+    macrowithbraces! {dont,    format, me}
+
+    x!(fn);
+
+    some_macro!(
+        
+    );
+
+    some_macro![
+    ];
+
+    some_macro!{
+        // comment
+    };
+
+    some_macro!{
+        // comment
+    };
+
+    some_macro!(
+        // comment
+        not function like
+    );
+
+    // #1712
+    let image = gray_image!(
+        00, 01, 02;
+        10, 11, 12;
+        20, 21, 22);
+
+    // #1092
+    chain!(input, a:take!(max_size), || []);
+
+    // #2727
+    foo!("bar")
+;
+}
+
+impl X {
+    empty_invoc!{}
+    empty_invoc! {}
+}
+
+fn issue_1279() {
+    println!("dsfs"); // a comment
+}
+
+fn issue_1555() {
+    let hello = &format!("HTTP/1.1 200 OK\r\nServer: {}\r\n\r\n{}",
+                         "65454654654654654654654655464",
+                         "4");
+}
+
+fn issue1178() {
+    macro_rules! foo {
+        (#[$attr:meta] $name:ident) => {}
+    }
+
+    foo!(#[doc = "bar"] baz);
+}
+
+fn issue1739() {
+    sql_function!(add_rss_item,
+                  add_rss_item_t,
+                  (a: types::Integer,
+                   b: types::Timestamptz,
+                   c: types::Text,
+                   d: types::Text,
+                   e: types::Text));
+
+    w.slice_mut(s![.., init_size[1] - extreeeeeeeeeeeeeeeeeeeeeeeem..init_size[1], ..])
+        .par_map_inplace(|el| *el = 0.);
+}
+
+fn issue_1885() {
+    let threads = people.into_iter().map(|name| {
+        chan_select! {
+            rx.recv() => {}
+        }
+    }).collect::<Vec<_>>();
+}
+
+fn issue_1917() {
+    mod x {
+        quickcheck! {
+            fn test(a: String, s: String, b: String) -> TestResult {
+                if a.find(&s).is_none() {
+
+                    TestResult::from_bool(true)
+                } else {
+                    TestResult::discard()
+                }
+            }
+        }
+    }
+}
+
+fn issue_1921() {
+    // Macro with tabs.
+    lazy_static! {
+	static ref ONE: u32 = 1;
+	static ref TWO: u32 = 2;
+	static ref THREE: u32 = 3;
+	static ref FOUR: u32 = {
+		let mut acc = 1;
+		acc += 1;
+		acc += 2;
+		acc
+	}
+}
+}
+
+// #1577
+fn issue1577() {
+    let json = json!({
+        "foo": "bar",
+    });
+}
+
+// #3174
+fn issue_3174() {
+    let data =
+        if let Some(debug) = error.debug_info() {
+            json!({
+                "errorKind": format!("{:?}", error.err_kind()),
+                "debugMessage": debug.message,
+            })
+        } else {
+            json!({"errorKind": format!("{:?}", error.err_kind())})
+        };
+}
+
+gfx_pipeline!(pipe {
+    vbuf: gfx::VertexBuffer<Vertex> = (),
+    out: gfx::RenderTarget<ColorFormat> = "Target0",
+});
+
+// #1919
+#[test]
+fn __bindgen_test_layout_HandleWithDtor_open0_int_close0_instantiation() {
+    assert_eq!(
+        ::std::mem::size_of::<HandleWithDtor<::std::os::raw::c_int>>(),
+        8usize,
+        concat!(
+            "Size of template specialization: ",
+            stringify ! ( HandleWithDtor < :: std :: os :: raw :: c_int > )
+        )
+    );
+    assert_eq ! ( :: std :: mem :: align_of :: < HandleWithDtor < :: std :: os :: raw :: c_int > > ( ) , 8usize , concat ! ( "Alignment of template specialization: " , stringify ! ( HandleWithDtor < :: std :: os :: raw :: c_int > ) ) );
+}
+
+// #878
+macro_rules! try_opt {
+    ($expr:expr) => (match $expr {  
+        Some(val) => val,
+          
+        None => { return None; }
+    })
+}
+
+// #2214
+// macro call whose argument is an array with trailing comma.
+fn issue2214() {
+make_test!(str_searcher_ascii_haystack, "bb", "abbcbbd", [
+    Reject(0, 1),
+    Match (1, 3),
+    Reject(3, 4),
+    Match (4, 6),
+    Reject(6, 7),
+]);
+}
+
+fn special_case_macros() {
+    let p = eprint!();
+    let q = eprint!("{}", 1);
+    let r = eprint!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    let s = eprint!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    let q = eprintln!("{}", 1);
+    let r = eprintln!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    let s = eprintln!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    let q = format!("{}", 1);
+    let r = format!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    let s = format!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    let q = format_args!("{}", 1);
+    let r = format_args!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    let s = format_args!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    let q = print!("{}", 1);
+    let r = print!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    let s = print!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    let q = println!("{}", 1);
+    let r = println!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    let s = println!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    let q = unreachable!("{}", 1);
+    let r = unreachable!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    let s = unreachable!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    debug!("{}", 1);
+    debug!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    debug!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    error!("{}", 1);
+    error!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    error!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    info!("{}", 1);
+    info!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    info!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    panic!("{}", 1);
+    panic!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    panic!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    warn!("{}", 1);
+    warn!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+    warn!("{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    assert!();
+    assert!(result == 42);
+    assert!(result == 42, "Ahoy there, {}!", target);
+    assert!(result == 42, "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')", result, input, expected);
+    assert!(result == 42, "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    assert_eq!();
+    assert_eq!(left);
+    assert_eq!(left, right);
+    assert_eq!(left, right, "Ahoy there, {}!", target);
+    assert_eq!(left, right, "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')", result, input, expected);
+    assert_eq!(first_realllllllllllly_long_variable_that_doesnt_fit_one_one_line, second_reallllllllllly_long_variable_that_doesnt_fit_one_one_line, "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')", result, input, expected);
+    assert_eq!(left + 42, right, "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')", result, input, expected);
+    assert_eq!(left, right, "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    write!(&mut s, "Ahoy there, {}!", target);
+    write!(&mut s, "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')", result, input, expected);
+    write!(&mut s, "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+
+    writeln!(&mut s, "Ahoy there, {}!", target);
+    writeln!(&mut s, "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')", result, input, expected);
+    writeln!(&mut s, "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26);
+}
+
+// #1209
+impl Foo {
+    /// foo
+    pub fn foo(&self) -> Bar<foo!(   )> {}
+}
+
+// #819
+fn macro_in_pattern_position () {
+    let x = match y {
+        foo!(  ) => (),
+        bar!(            a, b,
+                         c) => (),
+        bar!(a
+             , b
+             , c
+             ,) => (),
+        baz!( 1 + 2 + 3, quux.kaas(  )
+        ) => (),
+        quux!(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB) => (),
+    };
+}
+
+macro foo() {
+
+
+}
+
+pub macro bar($x:ident+$y:expr; ) {
+    fn foo($x: Foo) {
+    long_function(a_long_argument_to_a_long_function_is_what_this_is(AAAAAAAAAAAAAAAAAAAAAAAAAAAA),
+                  $x.bar($y));
+    }
+}
+
+macro foo() {
+  // a comment
+  fn foo() {
+  // another comment
+  bar();
+  }
+}
+
+// #2574
+macro_rules! test {
+    () => {{}}
+}
+
+macro lex_err($kind: ident $(, $body: expr)*) {
+    Err(QlError::LexError(LexError::$kind($($body,)*)))
+}
+
+// Preserve trailing comma on item-level macro with `()` or `[]`.
+methods![ get, post, delete, ];
+methods!( get, post, delete, );
+
+// #2588
+macro_rules! m {
+    () => {
+        r#"
+            test
+        "#
+    };
+}
+fn foo() {
+    f!{r#"
+            test
+       "#};
+}
+
+// #2591
+fn foo() {
+    match 0u32 {
+        0 => (),
+        _ => unreachable!(/* obviously */),
+    }
+}
+
+fn foo() {
+    let _ = column!(/* here */);
+}
+
+// #2616
+// Preserve trailing comma when using mixed layout for macro call.
+fn foo() {
+    foo!(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1);
+    foo!(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,);
+}
+
+// #2830
+// Preserve trailing comma-less/ness inside nested macro.
+named!(
+    do_parse_gsv<GsvData>,
+    map_res!(
+        do_parse!(
+            number_of_sentences: map_res!(digit, parse_num::<u16>)
+                >> char!(',')
+                >> sentence_index: map_res!(digit, parse_num::<u16>)
+                >> char!(',')
+                >> total_number_of_sats: map_res!(digit, parse_num::<u16>)
+                >> char!(',')
+                >> sat0: opt!(complete!(parse_gsv_sat_info))
+                >> sat1: opt!(complete!(parse_gsv_sat_info))
+                >> sat2: opt!(complete!(parse_gsv_sat_info))
+                >> sat3: opt!(complete!(parse_gsv_sat_info))
+                >> (
+                    number_of_sentences,
+                    sentence_index,
+                    total_number_of_sats,
+                    sat0,
+                    sat1,
+                    sat2,
+                    sat3
+                )
+        ),
+        construct_gsv_data
+    )
+);
+
+// #2857
+convert_args!(vec!(1, 2, 3));
+
+// #3031
+thread_local!(
+/// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new()) ;
+) ;
+
+thread_local![
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new()) ;
+
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new(0)) ;
+
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new(), xxx, yyy) ;
+
+    /// TLV Holds a set of JSTraceables that need to be rooted
+static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new(1234)) ;
+
+] ;
+
+fn issue3004() {
+    foo!(|_| { (  ) });
+    stringify!(( foo+ ));
+}
+
+// #3331
+pub fn fold_abi<V: Fold + ?Sized>(_visitor: &mut V, _i: Abi) -> Abi {
+    Abi {
+        extern_token: Token ! [ extern ](tokens_helper(_visitor, &_i.extern_token.span)),
+        name: (_i.name).map(|it| _visitor.fold_lit_str(it)),
+    }
+}
+
+// #3463
+x ! {()}
+
+// #3746
+f!(match a {
+    4 =>
+        &[
+            (3, false), // Missing
+            (4, true)   // I-frame
+        ]  [..],
+});
+
+// #3583
+foo!(|x = y|);
diff --git a/src/tools/rustfmt/tests/source/markdown-comment-with-options.rs b/src/tools/rustfmt/tests/source/markdown-comment-with-options.rs
new file mode 100644
index 0000000000000..2c4d6a5cc2be9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/markdown-comment-with-options.rs
@@ -0,0 +1,17 @@
+// rustfmt-wrap_comments: true
+
+// Preserve two trailing whitespaces in doc comment,
+// but trim any whitespaces in normal comment.
+
+//! hello world  
+//! hello world 
+
+/// hello world    
+/// hello world 
+/// hello world  
+fn foo() {
+    // hello world  
+    // hello world 
+    let x = 3;
+    println!("x = {}", x);
+}
diff --git a/src/tools/rustfmt/tests/source/markdown-comment.rs b/src/tools/rustfmt/tests/source/markdown-comment.rs
new file mode 100644
index 0000000000000..1ec26562fe282
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/markdown-comment.rs
@@ -0,0 +1,15 @@
+// Preserve two trailing whitespaces in doc comment,
+// but trim any whitespaces in normal comment.
+
+//! hello world  
+//! hello world 
+
+/// hello world    
+/// hello world 
+/// hello world  
+fn foo() {
+    // hello world  
+    // hello world 
+    let x = 3;
+    println!("x = {}", x);
+}
diff --git a/src/tools/rustfmt/tests/source/match-block-trailing-comma.rs b/src/tools/rustfmt/tests/source/match-block-trailing-comma.rs
new file mode 100644
index 0000000000000..e9daac13bf96f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/match-block-trailing-comma.rs
@@ -0,0 +1,14 @@
+// rustfmt-match_block_trailing_comma: true
+// Match expressions, no unwrapping of block arms or wrapping of multiline
+// expressions.
+
+fn foo() {
+    match x {
+        a => {
+            "line1";
+            "line2"
+        }
+        b => (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+              bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/match-flattening.rs b/src/tools/rustfmt/tests/source/match-flattening.rs
new file mode 100644
index 0000000000000..935ece53b83bc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/match-flattening.rs
@@ -0,0 +1,21 @@
+fn main() {
+    match option {
+        None => if condition {
+            true
+        } else {
+            false
+        },
+    }
+}
+
+fn main() {
+    match option {
+        None => {
+            if condition {
+                true
+            } else {
+                false
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/match-nowrap-trailing-comma.rs b/src/tools/rustfmt/tests/source/match-nowrap-trailing-comma.rs
new file mode 100644
index 0000000000000..134d2fdf9a4a5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/match-nowrap-trailing-comma.rs
@@ -0,0 +1,15 @@
+// rustfmt-match_arm_blocks: false
+// rustfmt-match_block_trailing_comma: true
+// Match expressions, no unwrapping of block arms or wrapping of multiline
+// expressions.
+
+fn foo() {
+    match x {
+        a => {
+            "line1";
+            "line2"
+        }
+        b => (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+              bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/match-nowrap.rs b/src/tools/rustfmt/tests/source/match-nowrap.rs
new file mode 100644
index 0000000000000..db22cd9f01066
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/match-nowrap.rs
@@ -0,0 +1,12 @@
+// rustfmt-match_arm_blocks: false
+// Match expressions, no unwrapping of block arms or wrapping of multiline
+// expressions.
+
+fn foo() {
+    match x {
+        a => { foo() }
+        b =>
+            (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+            bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb),
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/match.rs b/src/tools/rustfmt/tests/source/match.rs
new file mode 100644
index 0000000000000..da20517203a65
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/match.rs
@@ -0,0 +1,570 @@
+// rustfmt-normalize_comments: true
+// Match expressions.
+
+fn foo() {
+    // A match expression.
+    match x {
+        // Some comment.
+        a => foo(),
+        b if 0 < 42 => foo(),
+        c => { // Another comment.
+            // Comment.
+            an_expression;
+            foo()
+        }
+        Foo(ref bar) =>
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        Pattern1 | Pattern2 | Pattern3 => false,
+        Paternnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn |
+        Paternnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn => {
+            blah
+        }
+        Patternnnnnnnnnnnnnnnnnnn |
+        Patternnnnnnnnnnnnnnnnnnn |
+        Patternnnnnnnnnnnnnnnnnnn |
+        Patternnnnnnnnnnnnnnnnnnn => meh,
+
+        Patternnnnnnnnnnnnnnnnnnn |
+        Patternnnnnnnnnnnnnnnnnnn if looooooooooooooooooong_guard => meh,
+
+        Patternnnnnnnnnnnnnnnnnnnnnnnnn |
+        Patternnnnnnnnnnnnnnnnnnnnnnnnn if looooooooooooooooooooooooooooooooooooooooong_guard =>
+            meh,
+
+        // Test that earlier patterns can take the guard space
+        (aaaa, bbbbb, ccccccc, aaaaa, bbbbbbbb, cccccc, aaaa, bbbbbbbb, cccccc, dddddd) |
+        Patternnnnnnnnnnnnnnnnnnnnnnnnn if loooooooooooooooooooooooooooooooooooooooooong_guard => {}
+
+        _ => {}
+        ast::PathParameters::AngleBracketedParameters(ref data) if data.lifetimes.len() > 0 ||
+                                                                   data.types.len() > 0 ||
+                                                                   data.bindings.len() > 0 => {}
+    }
+
+    let whatever = match something {
+        /// DOC COMMENT!
+        Some(_) => 42,
+        // Comment on an attribute.
+        #[an_attribute]
+        // Comment after an attribute.
+        None => 0,
+        #[rustfmt::skip]
+        Blurb     =>     {                  }
+    };
+}
+
+// Test that a match on an overflow line is laid out properly.
+fn main() {
+    let sub_span =
+        match xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx {
+            Some(sub_span) => Some(sub_span),
+            None => sub_span,
+        };
+}
+
+// Test that one-line bodies align.
+fn main() {
+    match r {
+        Variableeeeeeeeeeeeeeeeee => (    "variable",
+                                      vec!("id", "name", "qualname",
+                                           "value", "type", "scopeid"),
+                                      true,
+                                      true),
+        Enummmmmmmmmmmmmmmmmmmmm => ("enum",
+                                     vec!("id","qualname","scopeid","value"),
+                                     true,
+                                     true),
+        Variantttttttttttttttttttttttt => ("variant",
+                                           vec!("id",
+                                                "name",
+                                                "qualname",
+                                                "type",
+                                                "value",
+                                                "scopeid"),
+                                           true,
+                                           true),
+    };
+
+    match  x{
+    y=>{/*Block with comment. Preserve me.*/  }
+    z=>{stmt();} }
+}
+
+fn matches() {
+    match 1 {
+        -1 => 10,
+        1 => 1, // foo
+        2 => 2,
+        // bar
+        3 => 3,
+        _ => 0 // baz
+    }
+}
+
+fn match_skip() {
+    let _ = match Some(1) {
+        #[rustfmt::skip]
+        Some( n ) => n,
+        None      => 1,
+    };
+}
+
+fn issue339() {
+    match a {
+        b => {}
+        c => { }
+        d => {
+        }
+        e => {
+
+
+
+        }
+        // collapsing here is safe
+        ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff => {
+        }
+        // collapsing here exceeds line length
+        ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffg => {
+        }
+        h => { // comment above block
+        }
+        i => {
+        } // comment below block
+        j => {
+            // comment inside block
+        }
+        j2 => {
+            // comments inside...
+        } // ... and after
+        // TODO uncomment when vertical whitespace is handled better
+        // k => {
+        //
+        //     // comment with WS above
+        // }
+        // l => {
+        //     // comment with ws below
+        //     
+        // }
+        m => {
+        } n => { } o =>
+        {
+
+        }
+        p => { // Don't collapse me
+        } q => { } r =>
+        {
+
+        }
+        s => 0, // s comment
+        // t comment
+        t => 1,
+        u => 2,
+        v => {
+        } /* funky block
+           * comment */
+        // final comment
+    }
+}
+
+fn issue355() {
+    match mac {
+        a => println!("a", b),
+        b => vec!(1, 2),
+        c => vec!(3; 4),
+        d => {
+            println!("a", b)
+        }
+        e => {
+            vec!(1, 2)
+        }
+        f => {
+            vec!(3; 4)
+        }
+        h => println!("a", b), // h comment
+        i => vec!(1, 2), // i comment
+        j => vec!(3; 4), // j comment
+        // k comment
+        k => println!("a", b),
+        // l comment
+        l => vec!(1, 2),
+        // m comment
+        m => vec!(3; 4),
+        // Rewrite splits macro
+        nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn => println!("a", b),
+        // Rewrite splits macro
+        oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo => vec!(1, 2),
+        // Macro support fails to recognise this macro as splittable
+        // We push the whole expr to a new line, TODO split this macro as well
+        pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp => vec!(3; 4),
+        // q, r and s: Rewrite splits match arm
+        qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq => println!("a", b),
+        rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr => vec!(1, 2),
+        ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss => vec!(3; 4),
+        // Funky bracketing styles
+        t =>      println!{"a", b},
+        u => vec!{1, 2},
+        v => vec!{3; 4},
+        w => println!["a", b],
+        x =>      vec![1, 2],
+        y =>vec![3; 4],
+        // Brackets with comments
+        tc => println!{"a", b}, // comment
+        uc => vec!{1, 2}, // comment
+        vc =>vec!{3; 4}, // comment
+        wc =>println!["a", b], // comment
+        xc => vec![1,2], // comment
+        yc =>        vec![3; 4], // comment
+        yd =>
+            looooooooooooooooooooooooooooooooooooooooooooooooooooooooong_func(aaaaaaaaaa,
+                                                                              bbbbbbbbbb,
+                                                                              cccccccccc,
+                                                                              dddddddddd),
+    }
+}
+
+fn issue280() {
+    {
+        match x {
+            CompressionMode::DiscardNewline | CompressionMode::CompressWhitespaceNewline => ch ==
+                                                                                            '\n',
+            ast::ItemConst(ref typ, ref expr) => self.process_static_or_const_item(item,
+                                                                                   &typ,
+                                                                                   &expr),
+        }
+    }
+}
+
+fn issue383() {
+    match resolution.last_private {LastImport{..} => false, _ => true};
+}
+
+fn issue507() {
+    match 1 {
+        1 => unsafe { std::intrinsics::abort() },
+        _ => (),
+    }
+}
+
+fn issue508() {
+    match s.type_id() {
+        Some(NodeTypeId::Element(ElementTypeId::HTMLElement(
+                    HTMLElementTypeId::HTMLCanvasElement))) => true,
+        Some(NodeTypeId::Element(ElementTypeId::HTMLElement(
+                        HTMLElementTypeId::HTMLObjectElement))) => s.has_object_data(),
+        Some(NodeTypeId::Element(_)) => false,
+    }
+}
+
+fn issue496() {{{{
+    match def {
+        def::DefConst(def_id) | def::DefAssociatedConst(def_id) =>
+            match const_eval::lookup_const_by_id(cx.tcx, def_id, Some(self.pat.id)) {
+                Some(const_expr) => { x }}}}}}}
+
+fn issue494() {
+    {
+        match stmt.node {
+             hir::StmtExpr(ref expr, id) | hir::StmtSemi(ref expr, id) =>
+                result.push(
+                    StmtRef::Mirror(
+                        Box::new(Stmt { span: stmt.span,
+                                        kind: StmtKind::Expr {
+                                            scope: cx.tcx.region_maps.node_extent(id),
+                                            expr: expr.to_ref() } }))),
+        }
+    }
+}
+
+fn issue386() {
+    match foo {
+        BiEq | BiLt | BiLe | BiNe | BiGt | BiGe =>
+                    true,
+        BiAnd | BiOr | BiAdd | BiSub | BiMul | BiDiv | BiRem |
+        BiBitXor | BiBitAnd | BiBitOr | BiShl | BiShr =>
+            false,
+    }
+}
+
+fn guards() {
+    match foo {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa if foooooooooooooo && barrrrrrrrrrrr => {}
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa if foooooooooooooo && barrrrrrrrrrrr => {}
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+            if fooooooooooooooooooooo &&
+               (bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb || cccccccccccccccccccccccccccccccccccccccc) => {}
+    }
+}
+
+fn issue1371() {
+    Some(match type_ {
+        sfEvtClosed => Closed,
+        sfEvtResized => {
+            let e = unsafe { *event.size.as_ref() };
+
+            Resized {
+                width: e.width,
+                height: e.height,
+            }
+        }
+        sfEvtLostFocus => LostFocus,
+        sfEvtGainedFocus => GainedFocus,
+        sfEvtTextEntered => {
+            TextEntered {
+                unicode: unsafe {
+                    ::std::char::from_u32((*event.text.as_ref()).unicode)
+                        .expect("Invalid unicode encountered on TextEntered event")
+                },
+            }
+        }
+        sfEvtKeyPressed => {
+            let e = unsafe { event.key.as_ref() };
+
+            KeyPressed {
+                code: unsafe { ::std::mem::transmute(e.code) },
+                alt: e.alt.to_bool(),
+                ctrl: e.control.to_bool(),
+                shift: e.shift.to_bool(),
+                system: e.system.to_bool(),
+            }
+        }
+        sfEvtKeyReleased => {
+            let e = unsafe { event.key.as_ref() };
+
+            KeyReleased {
+                code: unsafe { ::std::mem::transmute(e.code) },
+                alt: e.alt.to_bool(),
+                ctrl: e.control.to_bool(),
+                shift: e.shift.to_bool(),
+                system: e.system.to_bool(),
+            }
+        }
+    })
+}
+
+fn issue1395() {
+    let bar = Some(true);
+    let foo = Some(true);
+    let mut x = false;
+    bar.and_then(|_| {
+        match foo {
+            None => None,
+            Some(b) => {
+                x = true;
+                Some(b)
+            }
+        }
+    });
+}
+
+fn issue1456() {
+    Ok(Recording {
+        artists: match reader.evaluate(".//mb:recording/mb:artist-credit/mb:name-credit")? {
+            Nodeset(nodeset) => {
+                let res: Result<Vec<ArtistRef>, ReadError> = nodeset
+                    .iter()
+                    .map(|node| {
+                        XPathNodeReader::new(node, &context).and_then(|r| ArtistRef::from_xml(&r))
+                    })
+                    .collect();
+                res?
+            }
+            _ => Vec::new(),
+        },
+    })
+}
+
+fn issue1460() {
+    let _ = match foo {
+        REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT => "internal_spec_insert_internal_spec_insert_internal_spec_insert",
+        _ => "reorder_something",
+    };
+}
+
+fn issue525() {
+    foobar(f, "{}", match *self {
+        TaskState::Started => "started",
+        TaskState::Success => "success",
+        TaskState::Failed => "failed",
+    });
+}
+
+// #1838, #1839
+fn match_with_near_max_width() {
+    let (this_line_uses_99_characters_and_is_formatted_properly, x012345) = match some_expression   {
+        _ => unimplemented!(),
+    };
+
+    let (should_be_formatted_like_the_line_above_using_100_characters, x0) = match some_expression  {
+        _ => unimplemented!(),
+    };
+
+    let (should_put_the_brace_on_the_next_line_using_101_characters, x0000) = match some_expression
+    {
+        _ => unimplemented!(),
+    };
+    match m {
+        Variant::Tag | Variant::Tag2 | Variant::Tag3 | Variant::Tag4 | Variant::Tag5 | Variant::Tag6 =>
+        {}
+    }
+}
+
+fn match_with_trailing_spaces() {
+    match x {    
+        
+        Some(..) => 0,
+        None => 1,
+    }
+}
+
+fn issue_2099() {
+    let a = match x {
+};
+    let b = match x {
+        
+    };
+
+    match x {}
+}
+
+// #2021
+impl<'tcx> Const<'tcx> {
+    pub fn from_constval<'a>() -> Const<'tcx> {
+        let val = match *cv {
+            ConstVal::Variant(_) | ConstVal::Aggregate(..) | ConstVal::Unevaluated(..) => bug!("MIR must not use `{:?}` (aggregates are expanded to MIR rvalues)", cv),
+        };
+    }
+}
+
+// #2151
+fn issue_2151() {
+    match either {
+        x => {
+
+        }y => ()
+    }
+}
+
+// #2152
+fn issue_2152() {
+    match m {
+        "aaaaaaaaaaaaa" | "bbbbbbbbbbbbb" | "cccccccccccccccccccccccccccccccccccccccccccc" if true => {}
+        "bind" | "writev" | "readv" | "sendmsg" | "recvmsg" if android && (aarch64 || x86_64) => true,
+    }
+}
+
+// #2376
+// Preserve block around expressions with condition.
+fn issue_2376() {
+    let mut x = None;
+    match x {
+        Some(0) => {
+            for i in 1..11 {
+                x = Some(i);
+            }
+        }
+        Some(ref mut y) => {
+            while *y < 10 {
+                *y += 1;
+            }
+        }
+        None => {
+            while let None = x {
+                x = Some(10);
+            }
+        }
+    }
+}
+
+// #2621
+// Strip leading `|` in match arm patterns
+fn issue_2621() {
+    let x = Foo::A;
+    match x {
+        Foo::A => println!("No vert single condition"),
+        Foo::B | Foo::C => println!("Center vert two conditions"),
+        | Foo::D => println!("Preceding vert single condition"),
+        | Foo::E
+        | Foo::F => println!("Preceding vert over two lines"),
+        Foo::G |
+        Foo::H => println!("Trailing vert over two lines"),
+        // Comment on its own line
+        | Foo::I => println!("With comment"), // Comment after line
+    }
+}
+
+fn issue_2377() {
+    match tok {
+        Tok::Not
+        | Tok::BNot
+        | Tok::Plus
+        | Tok::Minus
+        | Tok::PlusPlus
+        | Tok::MinusMinus
+        | Tok::Void
+        | Tok::Delete if prec <= 16 => {
+            // code here...
+        }
+        Tok::TypeOf if prec <= 16 => {}
+    }
+}
+
+// #3040
+fn issue_3040() {
+    {
+        match foo {
+            DevtoolScriptControlMsg::WantsLiveNotifications(id, to_send) => {
+                match documents.find_window(id) {
+                    Some(window) => devtools::handle_wants_live_notifications(window.upcast(), to_send),
+                    None => return warn!("Message sent to closed pipeline {}.", id),
+                }
+            }
+        }
+    }
+}
+
+// #3030
+fn issue_3030() {
+    match input.trim().parse::<f64>() {
+        Ok(val)
+            if !(
+    // A valid number is the same as what rust considers to be valid,
+    // except for +1., NaN, and Infinity.
+                val.is_infinite() || val
+                    .is_nan() || input.ends_with(".") || input.starts_with("+")
+            )
+            => {
+            }
+    }
+}
+
+fn issue_3005() {
+            match *token {
+                 Token::Dimension {
+                     value, ref unit, ..
+                 } if num_context.is_ok(context.parsing_mode, value) =>
+                 {
+                     return NoCalcLength::parse_dimension(context, value, unit)
+                         .map(LengthOrPercentage::Length)
+                         .map_err(|()| location.new_unexpected_token_error(token.clone()));
+                 },
+             }
+}
+
+// #3774
+fn issue_3774() {
+    {
+        {
+            {
+                match foo {
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreachab(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreacha!(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreachabl(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreachae!(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreachable(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreachable!(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => rrunreachable!(),
+                }
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/match_overflow_expr.rs b/src/tools/rustfmt/tests/source/match_overflow_expr.rs
new file mode 100644
index 0000000000000..91275a8942947
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/match_overflow_expr.rs
@@ -0,0 +1,53 @@
+// rustfmt-overflow_delimited_expr: true
+
+fn main() {
+    println!(
+        "Foobar: {}",
+        match "input" {
+            "a" => "",
+            "b" => "",
+            "c" => "",
+            "d" => "",
+            "e" => "",
+            "f" => "",
+            "g" => "",
+            "h" => "",
+            "i" => "",
+            "j" => "",
+            "k" => "",
+            "l" => "",
+            "m" => "",
+            "n" => "",
+            "o" => "",
+            "p" => "",
+            "q" => "",
+            "r" => "Rust",
+        }
+    );
+}
+
+fn main() {
+    println!(
+        "Very Long Input String Which Makes It Impossible To Fit On The Same Line: {}",
+        match "input" {
+            "a" => "",
+            "b" => "",
+            "c" => "",
+            "d" => "",
+            "e" => "",
+            "f" => "",
+            "g" => "",
+            "h" => "",
+            "i" => "",
+            "j" => "",
+            "k" => "",
+            "l" => "",
+            "m" => "",
+            "n" => "",
+            "o" => "",
+            "p" => "",
+            "q" => "",
+            "r" => "Rust",
+        }
+    );
+}
diff --git a/src/tools/rustfmt/tests/source/max-line-length-in-chars.rs b/src/tools/rustfmt/tests/source/max-line-length-in-chars.rs
new file mode 100644
index 0000000000000..d49fbb7e30e5a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/max-line-length-in-chars.rs
@@ -0,0 +1,4 @@
+// rustfmt-max_width: 25
+
+// абвгдеёжзийклмнопрст
+fn main() {}
diff --git a/src/tools/rustfmt/tests/source/merge_imports_true_compat.rs b/src/tools/rustfmt/tests/source/merge_imports_true_compat.rs
new file mode 100644
index 0000000000000..bcea9435129f6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/merge_imports_true_compat.rs
@@ -0,0 +1,4 @@
+// rustfmt-merge_imports: true
+
+use a::b;
+use a::c;
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/mod-1.rs b/src/tools/rustfmt/tests/source/mod-1.rs
new file mode 100644
index 0000000000000..427a355b6bee0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/mod-1.rs
@@ -0,0 +1,29 @@
+// Deeply indented modules.
+
+  mod foo { mod bar { mod baz {} } }
+
+mod foo {
+    mod bar {
+    mod baz {
+    fn foo() { bar() }
+    }
+    }
+
+    mod qux {
+
+    }
+}
+
+mod boxed { pub use std::boxed::{Box, HEAP}; }
+
+pub  mod x {
+        pub fn freopen(filename: *const c_char,
+                   mode: *const c_char,
+                     mode2: *const c_char,
+                   mode3: *const c_char,
+                   file: *mut FILE)
+                   -> *mut FILE{}
+}
+
+  mod    y    { // sup boooooiiii
+   }
diff --git a/src/tools/rustfmt/tests/source/mod-2.rs b/src/tools/rustfmt/tests/source/mod-2.rs
new file mode 100644
index 0000000000000..7202e00203ec9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/mod-2.rs
@@ -0,0 +1,4 @@
+// Some nested mods
+
+#[cfg(test)]  mod   nestedmod  ;
+pub  mod no_new_line_beginning;
diff --git a/src/tools/rustfmt/tests/source/mod_skip_child.rs b/src/tools/rustfmt/tests/source/mod_skip_child.rs
new file mode 100644
index 0000000000000..d48c4a37e810a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/mod_skip_child.rs
@@ -0,0 +1,2 @@
+// rustfmt-skip_children: true
+mod nested_skipped;
diff --git a/src/tools/rustfmt/tests/source/multiple.rs b/src/tools/rustfmt/tests/source/multiple.rs
new file mode 100644
index 0000000000000..f89f4f68da9ba
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/multiple.rs
@@ -0,0 +1,134 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-format_strings: true
+// Test of lots of random stuff.
+// FIXME split this into multiple, self-contained tests.
+
+
+#[attr1] extern crate foo;
+#[attr2] #[attr3] extern crate foo;
+#[attr1]extern crate foo;
+#[attr2]#[attr3]extern crate foo;
+
+use std::cell::*;
+use std::{any, ascii, self, borrow, boxed, char, borrow, boxed, char, borrow, borrow, boxed, char, borrow, boxed, char, borrow, boxed, char, borrow, boxed, char, borrow, boxed, char, borrow, boxed, char, borrow, boxed, char, borrow, boxed, char};
+
+mod doc;
+mod other;
+
+
+// sfdgfffffffffffffffffffffffffffffffffffffffffffffffffffffff ffffffffffffffffffffffffffffffffffffffffff
+
+                                                         fn foo(a: isize,
+     b: u32, /* blah blah */
+         c: f64) {
+
+}
+
+fn foo()->Box<Write+'static> where 'a: 'b, for<'a> D<'b>: 'a {
+    hello!()
+}
+
+fn baz<'a: 'b /* comment on 'a */, T: SomsssssssssssssssssssssssssssssssssssssssssssssssssssssseType /* comment on T */>(a: A, b: B /* comment on b */, c: C) -> Bob {
+    #[attr1] extern crate foo;
+    #[attr2] #[attr3] extern crate foo;
+    #[attr1]extern crate foo;
+    #[attr2]#[attr3]extern crate foo;
+}
+
+#[rustfmt::skip]
+fn qux(a: dadsfa,   // Comment 1
+       b: sdfasdfa, // Comment 2
+       c: dsfdsafa) // Comment 3
+{
+
+}
+
+/// Blah blah blah.
+impl Bar {
+    fn foo(&mut self, a: sdfsdfcccccccccccccccccccccccccccccccccccccccccccccccccc, // comment on a
+           b: sdfasdfsdfasfs /*closing comment*/ ) -> isize {}
+
+    /// Blah blah blah.
+    pub fn f2(self) {
+        (foo, bar)
+    }
+
+    #[an_attribute]
+    fn f3(self) -> Dog {
+    }
+}
+
+/// The `nodes` and `edges` method each return instantiations of
+/// `Cow<[T]>` to leave implementers the freedom to create
+
+/// entirely new vectors or to pass back slices into internally owned
+/// vectors.
+pub trait GraphWalk<'a, N, E> {
+    /// Returns all the nodes in this graph.
+    fn nodes(&'a self) -> Nodes<'a, N>;
+    /// Returns all of the edges in this graph.
+    fn edges(&'a self) -> Edges<'a, E>;
+    /// The source node for `edge`.
+    fn source(&'a self, edge: &E) -> N;
+    /// The target node for `edge`.
+    fn target(&'a self, edge: &E) -> N;
+}
+
+/// A Doc comment
+#[AnAttribute]
+pub struct Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f :   SomeType, // Comment beside a field
+    // Comment on a field
+    g: SomeOtherType,
+    /// A doc comment on a field
+    h: AThirdType,}
+
+struct Bar;
+
+// With a where-clause and generics.
+pub struct Foo<'a, Y: Baz>
+    where X: Whatever
+{
+    f: SomeType, // Comment beside a field
+}
+
+fn foo(ann: &'a (PpAnn+'a)) {}
+
+fn main() {
+    for i in 0i32..4 {
+        println!("{}", i);
+    }
+
+
+    while true {
+        hello();
+    }
+
+        let rc = Cell::new(42usize,42usize, Cell::new(42usize, remaining_widthremaining_widthremaining_widthremaining_width), 42usize);
+    let rc = RefCell::new(42usize,remaining_width,           remaining_width);  // a comment
+      let x = "Hello!!!!!!!!! abcd  abcd abcd abcd abcd abcd\n abcd abcd abcd abcd abcd abcd abcd abcd abcd \
+                   abcd  abcd abcd abcd abcd abcd abcd abcd abcd abcd \
+                    abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd";
+           let s = expand(a
+    ,    
+    b); }
+
+fn deconstruct() -> (SocketAddr, Method, Headers,
+                     RequestUri, HttpVersion,
+                     AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) {
+}
+
+fn deconstruct(foo: Bar) -> (SocketAddr, Method, Headers,
+                     RequestUri, HttpVersion,
+                     AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) {
+}
+
+#[rustfmt::skip]
+mod a{
+fn foo(x:    T) {
+    let x:    T = dfasdf;
+}
+}
diff --git a/src/tools/rustfmt/tests/source/negative-impl.rs b/src/tools/rustfmt/tests/source/negative-impl.rs
new file mode 100644
index 0000000000000..da242d4f3dca4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/negative-impl.rs
@@ -0,0 +1,7 @@
+impl ! Display for JoinHandle { }
+
+impl ! Box < JoinHandle > { }
+
+impl ! std :: fmt :: Display for JoinHandle < T : std :: future :: Future + std :: marker :: Send + std :: marker :: Sync > { }
+
+impl ! JoinHandle < T : std :: future :: Future < Output > + std :: marker :: Send + std :: marker :: Sync + 'static > + 'static { }
diff --git a/src/tools/rustfmt/tests/source/nested-if-else.rs b/src/tools/rustfmt/tests/source/nested-if-else.rs
new file mode 100644
index 0000000000000..9a54789ddcd68
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nested-if-else.rs
@@ -0,0 +1,11 @@
+fn issue1518() {
+    Some(Object {
+        field: if a {
+            a_thing
+        } else if b {
+            b_thing
+        } else {
+            c_thing
+        },
+    })
+}
diff --git a/src/tools/rustfmt/tests/source/nested_skipped/mod.rs b/src/tools/rustfmt/tests/source/nested_skipped/mod.rs
new file mode 100644
index 0000000000000..44b25ca8797d5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nested_skipped/mod.rs
@@ -0,0 +1,3 @@
+fn ugly() {
+92;
+}
diff --git a/src/tools/rustfmt/tests/source/nestedmod/mod.rs b/src/tools/rustfmt/tests/source/nestedmod/mod.rs
new file mode 100644
index 0000000000000..d04e49570a4f6
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nestedmod/mod.rs
@@ -0,0 +1,13 @@
+
+mod mod2a;
+mod mod2b;
+
+mod mymod1 {
+          use mod2a::{Foo,Bar};
+mod mod3a;
+}
+
+#[path="mod2c.rs"]
+mod mymod2;
+
+mod submod2;
diff --git a/src/tools/rustfmt/tests/source/nestedmod/mod2a.rs b/src/tools/rustfmt/tests/source/nestedmod/mod2a.rs
new file mode 100644
index 0000000000000..5df457a831653
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nestedmod/mod2a.rs
@@ -0,0 +1,4 @@
+// This is an empty file containing only
+// comments
+
+// ...................
diff --git a/src/tools/rustfmt/tests/source/nestedmod/mod2b.rs b/src/tools/rustfmt/tests/source/nestedmod/mod2b.rs
new file mode 100644
index 0000000000000..f128e2da6dbfb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nestedmod/mod2b.rs
@@ -0,0 +1,3 @@
+
+#[path="mod2a.rs"]
+mod c;
diff --git a/src/tools/rustfmt/tests/source/nestedmod/mod2c.rs b/src/tools/rustfmt/tests/source/nestedmod/mod2c.rs
new file mode 100644
index 0000000000000..eda6b233e4bea
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nestedmod/mod2c.rs
@@ -0,0 +1,3 @@
+// A standard mod
+
+fn a(   )     {}
diff --git a/src/tools/rustfmt/tests/source/nestedmod/mymod1/mod3a.rs b/src/tools/rustfmt/tests/source/nestedmod/mymod1/mod3a.rs
new file mode 100644
index 0000000000000..f28bde5e56dbb
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nestedmod/mymod1/mod3a.rs
@@ -0,0 +1,2 @@
+// Another mod
+fn a(          ) {       }
diff --git a/src/tools/rustfmt/tests/source/nestedmod/submod2/a.rs b/src/tools/rustfmt/tests/source/nestedmod/submod2/a.rs
new file mode 100644
index 0000000000000..0eaf08f0d2ca7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nestedmod/submod2/a.rs
@@ -0,0 +1,6 @@
+// Yet Another mod
+// Nested
+
+use c::a;
+
+fn foo(    ) {    }
diff --git a/src/tools/rustfmt/tests/source/nestedmod/submod2/mod.rs b/src/tools/rustfmt/tests/source/nestedmod/submod2/mod.rs
new file mode 100644
index 0000000000000..52f8be910227f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/nestedmod/submod2/mod.rs
@@ -0,0 +1,5 @@
+// Another mod
+
+mod a;
+
+use a::a;
diff --git a/src/tools/rustfmt/tests/source/no_arg_with_commnet.rs b/src/tools/rustfmt/tests/source/no_arg_with_commnet.rs
new file mode 100644
index 0000000000000..ea4ee0f1eee0a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/no_arg_with_commnet.rs
@@ -0,0 +1,2 @@
+fn foo(  /* cooment */
+) {}
diff --git a/src/tools/rustfmt/tests/source/no_new_line_beginning.rs b/src/tools/rustfmt/tests/source/no_new_line_beginning.rs
new file mode 100644
index 0000000000000..f79c691f0853c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/no_new_line_beginning.rs
@@ -0,0 +1,2 @@
+fn main() {
+}
diff --git a/src/tools/rustfmt/tests/source/normalize_doc_attributes_should_not_imply_format_doc_comments.rs b/src/tools/rustfmt/tests/source/normalize_doc_attributes_should_not_imply_format_doc_comments.rs
new file mode 100644
index 0000000000000..a97705bfb3bf1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/normalize_doc_attributes_should_not_imply_format_doc_comments.rs
@@ -0,0 +1,15 @@
+// rustfmt-normalize_doc_attributes: true
+
+/// Foo
+///
+/// # Example
+/// ```
+/// # #![cfg_attr(not(dox), feature(cfg_target_feature, target_feature, stdsimd))]
+/// # #![cfg_attr(not(dox), no_std)]
+/// fn foo() {  }
+/// ```
+///
+fn foo() {}
+
+#[doc = "Bar documents"]
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/source/normalize_multiline_doc_attribute.rs b/src/tools/rustfmt/tests/source/normalize_multiline_doc_attribute.rs
new file mode 100644
index 0000000000000..3564e3e7ad056
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/normalize_multiline_doc_attribute.rs
@@ -0,0 +1,12 @@
+// rustfmt-unstable: true
+// rustfmt-normalize_doc_attributes: true
+
+#[doc = "This comment
+is split
+on multiple lines"]
+fn foo() {}
+
+#[doc = " B1"]
+#[doc = ""]
+#[doc = " A1"]
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/source/one_line_if_v1.rs b/src/tools/rustfmt/tests/source/one_line_if_v1.rs
new file mode 100644
index 0000000000000..d3dcbe6787a11
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/one_line_if_v1.rs
@@ -0,0 +1,42 @@
+// rustfmt-version: One
+
+fn plain_if(x: bool) -> u8 {
+    if x {
+        0
+    } else {
+        1
+    }
+}
+
+fn paren_if(x: bool) -> u8 {
+    (if x { 0 } else { 1 })
+}
+
+fn let_if(x: bool) -> u8 {
+    let x = if x {
+        foo()
+    } else {
+        bar()
+    };
+    x
+}
+
+fn return_if(x: bool) -> u8 {
+    return if x {
+        0
+    } else {
+        1
+    };
+}
+
+fn multi_if() {
+    use std::io;
+    if x { foo() } else { bar() }
+    if x { foo() } else { bar() }
+}
+
+fn middle_if() {
+    use std::io;
+    if x { foo() } else { bar() }
+    let x = 1;
+}
diff --git a/src/tools/rustfmt/tests/source/one_line_if_v2.rs b/src/tools/rustfmt/tests/source/one_line_if_v2.rs
new file mode 100644
index 0000000000000..40c834959f90e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/one_line_if_v2.rs
@@ -0,0 +1,42 @@
+// rustfmt-version: Two
+
+fn plain_if(x: bool) -> u8 {
+    if x {
+        0
+    } else {
+        1
+    }
+}
+
+fn paren_if(x: bool) -> u8 {
+    (if x { 0 } else { 1 })
+}
+
+fn let_if(x: bool) -> u8 {
+    let x = if x {
+        foo()
+    } else {
+        bar()
+    };
+    x
+}
+
+fn return_if(x: bool) -> u8 {
+    return if x {
+        0
+    } else {
+        1
+    };
+}
+
+fn multi_if() {
+    use std::io;
+    if x { foo() } else { bar() }
+    if x { foo() } else { bar() }
+}
+
+fn middle_if() {
+    use std::io;
+    if x { foo() } else { bar() }
+    let x = 1;
+}
diff --git a/src/tools/rustfmt/tests/source/other.rs b/src/tools/rustfmt/tests/source/other.rs
new file mode 100644
index 0000000000000..dfce84fcdc477
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/other.rs
@@ -0,0 +1,5 @@
+// Part of multiple.rs
+
+fn bob() {
+    println!("hello other!");
+}
diff --git a/src/tools/rustfmt/tests/source/paren.rs b/src/tools/rustfmt/tests/source/paren.rs
new file mode 100644
index 0000000000000..04e5ab7a55497
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/paren.rs
@@ -0,0 +1,6 @@
+fn main() {
+    let x = (((1)));
+    let y = (/* comment */((2)));
+    let z = (((3)/* comment */));
+    let a = (((4/* comment */)));
+}
diff --git a/src/tools/rustfmt/tests/source/path_clarity/foo.rs b/src/tools/rustfmt/tests/source/path_clarity/foo.rs
new file mode 100644
index 0000000000000..cd247fabfe340
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/path_clarity/foo.rs
@@ -0,0 +1,2 @@
+// rustfmt-edition: 2018
+mod bar;
diff --git a/src/tools/rustfmt/tests/source/path_clarity/foo/bar.rs b/src/tools/rustfmt/tests/source/path_clarity/foo/bar.rs
new file mode 100644
index 0000000000000..8c1be504c0908
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/path_clarity/foo/bar.rs
@@ -0,0 +1,3 @@
+pub fn fn_in_bar( ) {
+    println!( "foo/bar.rs" );
+}
diff --git a/src/tools/rustfmt/tests/source/paths.rs b/src/tools/rustfmt/tests/source/paths.rs
new file mode 100644
index 0000000000000..ebc26f146e4ab
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/paths.rs
@@ -0,0 +1,25 @@
+// rustfmt-normalize_comments: true
+
+fn main() {
+   let constellation_chan = Constellation::<layout::layout_task::LayoutTask,  script::script_task::ScriptTask> ::start(
+     compositor_proxy,
+     resource_task,
+     image_cache_task,font_cache_task,
+     time_profiler_chan,
+     mem_profiler_chan,
+     devtools_chan,
+     storage_task,
+     supports_clipboard
+    );
+
+     Quux::<ParamOne,   // Comment 1
+            ParamTwo,   // Comment 2
+                    >::some_func();
+
+    < *mut JSObject >:: relocate(entry);
+
+    let x: Foo<A   >;
+    let x: Foo/*::*/<A>;
+}
+
+fn op(foo: Bar, key : &[u8], upd : Fn(Option<&memcache::Item> , Baz  ) -> Result) -> MapResult {}
diff --git a/src/tools/rustfmt/tests/source/pattern-condense-wildcards.rs b/src/tools/rustfmt/tests/source/pattern-condense-wildcards.rs
new file mode 100644
index 0000000000000..69c3fa3cbad8d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/pattern-condense-wildcards.rs
@@ -0,0 +1,12 @@
+// rustfmt-normalize_comments: true
+// rustfmt-condense_wildcard_suffixes: true
+
+fn main() {
+    match x {
+        Butt (_,_) => "hah",
+        Tup (_) =>  "nah",
+        Quad (_,_, x,_) =>   " also no rewrite",
+        Quad (x, _, _, _) => "condense me pls",
+        Weird (x, _, _, /* don't condense before */ _, _, _) => "pls work",
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/pattern.rs b/src/tools/rustfmt/tests/source/pattern.rs
new file mode 100644
index 0000000000000..f06d03cadf2f7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/pattern.rs
@@ -0,0 +1,90 @@
+// rustfmt-normalize_comments: true
+#![feature(exclusive_range_pattern)]
+use core::u8::MAX;
+
+fn main() {
+    let z = match x {
+        "pat1" => 1,
+        ( ref  x, ref  mut  y /*comment*/) => 2,
+    };
+
+    if let <  T as  Trait   > :: CONST = ident {
+        do_smth();
+    }
+
+    let Some ( ref   xyz  /*   comment!   */) = opt;
+
+    if let  None  =   opt2 { panic!("oh noes"); }
+
+    let foo@bar (f) = 42;
+    let a::foo ( ..) = 42;
+    let [ ] = 42;
+    let [a,     b,c ] = 42;
+    let [ a,b,c ] = 42;
+    let [a,    b, c, d,e,f,     g] = 42;
+    let foo {   } = 42;
+    let foo {..} = 42;
+    let foo { x, y: ref foo,     .. } = 42;
+    let foo { x, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,     .. } = 42;
+    let foo { x,       yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,      } = 42;
+    let foo { x, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,     .. };
+    let foo { x,       yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,      };
+
+    match b"12" {
+        [0,
+        1..MAX
+        ] => {}
+        _ => {}
+    }
+}
+
+impl<'a,'b> ResolveGeneratedContentFragmentMutator<'a,'b> {
+    fn mutate_fragment(&mut self, fragment: &mut Fragment) {
+        match **info {
+            GeneratedContentInfo::ContentItem(
+                ContentItem::Counter(
+                    ref counter_name,
+                    counter_style
+                )
+            ) => {}}}
+}
+
+fn issue_1319() {
+    if let (Event { .. }, .. ) = ev_state {}
+}
+
+fn issue_1874() {
+    if let Some(()) = x {
+y
+    }
+}
+
+fn combine_patterns() {
+    let x = match y {
+        Some(
+            Some(
+                Foo {
+                    z: Bar(..),
+                    a: Bar(..),
+                    b: Bar(..),
+                },
+            ),
+        ) => z,
+        _ => return,
+    };
+}
+
+fn slice_patterns() {
+    match b"123" {
+        [0, ..] => {}
+        [0, foo] => {}
+        _ => {}
+    }
+}
+
+fn issue3728() {
+    let foo = |
+    (c,)
+        | c;
+    foo((1,));
+}
diff --git a/src/tools/rustfmt/tests/source/preserves_carriage_return_for_unix.rs b/src/tools/rustfmt/tests/source/preserves_carriage_return_for_unix.rs
new file mode 100644
index 0000000000000..e5e0b28659896
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/preserves_carriage_return_for_unix.rs
@@ -0,0 +1,2 @@
+// rustfmt-newline_style: Unix
+// Foo
Bar
diff --git a/src/tools/rustfmt/tests/source/preserves_carriage_return_for_windows.rs b/src/tools/rustfmt/tests/source/preserves_carriage_return_for_windows.rs
new file mode 100644
index 0000000000000..1085360ee59e8
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/preserves_carriage_return_for_windows.rs
@@ -0,0 +1,2 @@
+// rustfmt-newline_style: Windows
+// Foo
Bar
diff --git a/src/tools/rustfmt/tests/source/pub-restricted.rs b/src/tools/rustfmt/tests/source/pub-restricted.rs
new file mode 100644
index 0000000000000..30051fa72ee7d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/pub-restricted.rs
@@ -0,0 +1,64 @@
+pub(   super   ) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+pub(  crate  ) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+  crate   enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+pub(in  ::global::  path :: to::some_mod  ) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+pub(   in  local::  path :: to::some_mod  ) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
diff --git a/src/tools/rustfmt/tests/source/remove_blank_lines.rs b/src/tools/rustfmt/tests/source/remove_blank_lines.rs
new file mode 100644
index 0000000000000..43733ce7636f3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/remove_blank_lines.rs
@@ -0,0 +1,44 @@
+fn main() {
+
+
+
+
+    let x = 1;
+
+
+    let y = 2;
+
+
+    println!("x + y = {}", x + y);
+
+
+
+}
+
+
+fn foo() {
+
+    #![attribute]
+
+    let x = 1;
+
+    // comment
+
+
+}
+// comment after item
+
+
+// comment before item
+fn bar() {
+    let x = 1;
+    // comment after statement
+
+
+    // comment before statement
+    let y = 2;
+    let z = 3;
+
+
+    println!("x + y + z = {}", x + y + z);
+}
diff --git a/src/tools/rustfmt/tests/source/reorder-impl-items.rs b/src/tools/rustfmt/tests/source/reorder-impl-items.rs
new file mode 100644
index 0000000000000..16efff55b0660
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/reorder-impl-items.rs
@@ -0,0 +1,15 @@
+// rustfmt-reorder_impl_items: true
+
+// The ordering of the following impl items should be idempotent.
+impl<'a> Command<'a> {
+    pub fn send_to(&self, w: &mut io::Write) -> io::Result<()> {
+        match self {
+            &Command::Data(ref c) => c.send_to(w),
+            &Command::Vrfy(ref c) => c.send_to(w),
+        }
+    }
+
+    pub fn parse(arg: &[u8]) -> Result<Command, ParseError> {
+        nom_to_result(command(arg))
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/single-line-if-else.rs b/src/tools/rustfmt/tests/source/single-line-if-else.rs
new file mode 100644
index 0000000000000..bcde390d1164d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/single-line-if-else.rs
@@ -0,0 +1,49 @@
+
+// Format if-else expressions on a single line, when possible.
+
+fn main() {
+    let a = if 1 > 2 {
+        unreachable!()
+    } else {
+        10
+    };
+
+    let a = if x { 1 } else if y { 2 } else { 3 };
+
+    let b = if cond() {
+        5
+    } else {
+        // Brief comment.
+        10
+    };
+
+    let c = if cond() {
+        statement();
+
+        5
+    } else {
+        10
+    };
+
+    let d   = if  let  Some(val)  =  turbo 
+    { "cool" } else {
+     "beans" };
+
+    if cond() { statement(); } else { other_statement(); }
+
+    if true  {
+        do_something()
+    }
+
+    let x = if veeeeeeeeery_loooooong_condition() { aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa } else { bbbbbbbbbb };
+  
+    let x = if veeeeeeeeery_loooooong_condition()     {    aaaaaaaaaaaaaaaaaaaaaaaaa }   else  {
+        bbbbbbbbbb };
+
+    funk(if test() {
+             1
+         } else {
+             2
+         },
+         arg2);
+}
diff --git a/src/tools/rustfmt/tests/source/single-line-macro/v1.rs b/src/tools/rustfmt/tests/source/single-line-macro/v1.rs
new file mode 100644
index 0000000000000..a3aa631ed4af3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/single-line-macro/v1.rs
@@ -0,0 +1,10 @@
+// rustfmt-version: One
+
+// #2652
+// Preserve trailing comma inside macro, even if it looks an array.
+macro_rules! bar {
+    ($m:ident) => {
+        $m!([a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z,]);
+        $m!([a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z]);
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/single-line-macro/v2.rs b/src/tools/rustfmt/tests/source/single-line-macro/v2.rs
new file mode 100644
index 0000000000000..51a665f756056
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/single-line-macro/v2.rs
@@ -0,0 +1,10 @@
+// rustfmt-version: Two
+
+// #2652
+// Preserve trailing comma inside macro, even if it looks an array.
+macro_rules! bar {
+    ($m:ident) => {
+        $m!([a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z,]);
+        $m!([a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z]);
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/soft-wrapping.rs b/src/tools/rustfmt/tests/source/soft-wrapping.rs
new file mode 100644
index 0000000000000..b0682d4db3a34
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/soft-wrapping.rs
@@ -0,0 +1,15 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 80
+// Soft wrapping for comments.
+
+// #535, soft wrapping for comments
+// Compare the lowest `f32` of both inputs for greater than or equal. The
+// lowest 32 bits of the result will be `0xffffffff` if `a.extract(0)` is
+// ggreater than or equal `b.extract(0)`, or `0` otherwise. The upper 96 bits off
+// the result are the upper 96 bits of `a`.
+
+/// Compares the lowest `f32` of both inputs for greater than or equal. The
+/// lowest 32 bits of the result will be `0xffffffff` if `a.extract(0)` is
+/// greater than or equal `b.extract(0)`, or `0` otherwise. The upper 96 bits off
+/// the result are the upper 96 bits of `a`.
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/source/space-not-before-newline.rs b/src/tools/rustfmt/tests/source/space-not-before-newline.rs
new file mode 100644
index 0000000000000..2a1e185690880
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/space-not-before-newline.rs
@@ -0,0 +1,8 @@
+struct Foo {
+    a: (),       
+    // spaces ^^^ to be removed
+}
+enum Foo {
+    Bar,     
+    // spaces ^^^ to be removed
+}
diff --git a/src/tools/rustfmt/tests/source/spaces-around-ranges.rs b/src/tools/rustfmt/tests/source/spaces-around-ranges.rs
new file mode 100644
index 0000000000000..1936b5e161f82
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/spaces-around-ranges.rs
@@ -0,0 +1,15 @@
+// rustfmt-spaces_around_ranges: true
+
+fn bar(v: &[u8]) {}
+
+fn foo() {
+    let a = vec![0; 20];
+    for j in 0..=20 {
+        for i in 0..3 {
+            bar(a[i..j]);
+            bar(a[i..]);
+            bar(a[..j]);
+            bar(a[..=(j + 1)]);
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/statements.rs b/src/tools/rustfmt/tests/source/statements.rs
new file mode 100644
index 0000000000000..c840b8ce105dd
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/statements.rs
@@ -0,0 +1,43 @@
+// FIXME(calebcartwright) - Hopefully one day we can
+// elide these redundant semis like we do in other contexts.
+fn redundant_item_semis() {
+    impl Foo {
+            fn get(&self) -> usize {
+                5
+            }
+        };
+        
+            impl Bar {
+            fn get(&self) -> usize {
+                5
+            }
+        } /*asdfsf*/;
+        
+        
+    impl Baz {
+        fn get(&self) -> usize {
+            5
+        }
+    } /*asdfsf*/
+    
+    // why would someone do this
+    ;
+    
+    
+        impl Qux {
+        fn get(&self) -> usize {
+            5
+        }
+    } 
+    
+    // why
+    ;
+    
+            impl Lorem {
+        fn get(&self) -> usize {
+            5
+        }
+    } 
+    // oh why
+    ;
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/static.rs b/src/tools/rustfmt/tests/source/static.rs
new file mode 100644
index 0000000000000..970786381cc47
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/static.rs
@@ -0,0 +1,23 @@
+const FILE_GENERIC_READ: DWORD =
+                STANDARD_RIGHTS_READ | FILE_READ_DATA |
+                FILE_READ_ATTRIBUTES | FILE_READ_EA | SYNCHRONIZE;
+
+static boolnames: &'static[&'static str] = &["bw", "am", "xsb", "xhp", "xenl", "eo",
+    "gn", "hc", "km", "hs", "in", "db", "da", "mir", "msgr", "os", "eslok", "xt", "hz", "ul", "xon",
+    "nxon", "mc5i", "chts", "nrrmc", "npc", "ndscr", "ccc", "bce", "hls", "xhpa", "crxm", "daisy",
+    "xvpa", "sam", "cpix", "lpix", "OTbs", "OTns", "OTnc", "OTMT", "OTNL", "OTpt", "OTxr"];
+
+static mut name: SomeType = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;
+
+ pub   static   count  :  u8  = 10 ;
+
+pub const test: &Type = &val;
+
+impl Color {
+    pub const WHITE: u32 = 10;
+}
+
+// #1391
+pub const XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX: NTSTATUS = 0 as usize;
+
+pub const XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX: Yyyyyyyyyyyyyyyyyyyyyyyyyyyy = 1;
diff --git a/src/tools/rustfmt/tests/source/string-lit-2.rs b/src/tools/rustfmt/tests/source/string-lit-2.rs
new file mode 100644
index 0000000000000..6b95e25a052b2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/string-lit-2.rs
@@ -0,0 +1,25 @@
+fn main() -> &'static str {
+    let too_many_lines = "Hello";
+    let leave_me = "sssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss\
+                    s
+                    jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj";
+}
+
+fn issue_1237() {
+    let msg = "eedadn\n\
+               drvtee\n\
+               eandsr\n\
+               raavrd\n\
+               atevrs\n\
+               tsrnev\n\
+               sdttsa\n\
+               rasrtv\n\
+               nssdts\n\
+               ntnada\n\
+               svetve\n\
+               tesnvt\n\
+               vntsnd\n\
+               vrdear\n\
+               dvrsen\n\
+               enarar";
+}
diff --git a/src/tools/rustfmt/tests/source/string-lit.rs b/src/tools/rustfmt/tests/source/string-lit.rs
new file mode 100644
index 0000000000000..7719e76ffe75c
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/string-lit.rs
@@ -0,0 +1,61 @@
+// rustfmt-format_strings: true
+// Long string literals
+
+fn main() -> &'static str {
+    let str = "AAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAaAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAa";
+    let str = "AAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAa";
+    let str = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+
+    let too_many_lines = "H\
+                          e\
+                          l\
+                          l\
+                          o";
+
+    // Make sure we don't break after an escape character.
+    let odd_length_name = "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
+    let even_length_name = "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
+
+    let really_long_variable_name = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+
+    let raw_string = r#"Do
+not
+remove
+formatting"#;
+
+    filename.replace(" ", "\\" );
+
+    let xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx =
+        funktion("yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy");
+        
+    let unicode = "a̐éö̲\r\n";
+    let unicode2 = "Löwe 老虎 Léopard";
+    let unicode3 = "中华Việt Nam";
+    let unicode4 = "☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃";
+
+    "stuffin'"
+}
+
+fn issue682() {
+    let a = "hello \\ o/";
+    let b = a.replace("\\ ", "\\");
+}
+
+fn issue716() {
+    println!("forall x. mult(e(), x) = x /\\
+              forall x. mult(x, x) = e()");
+}
+
+fn issue_1282() {
+    {
+        match foo {
+            Permission::AndroidPermissionAccessLocationExtraCommands => {
+                "android.permission.ACCESS_LOCATION_EXTRA_COMMANDS"
+            }
+        }
+    }
+}
+
+// #1987
+#[link_args = "-s NO_FILESYSTEM=1 -s NO_EXIT_RUNTIME=1 -s EXPORTED_RUNTIME_METHODS=[\"_malloc\"] -s NO_DYNAMIC_EXECUTION=1 -s ELIMINATE_DUPLICATE_FUNCTIONS=1 -s EVAL_CTORS=1"]
+extern "C" {}
diff --git a/src/tools/rustfmt/tests/source/string_punctuation.rs b/src/tools/rustfmt/tests/source/string_punctuation.rs
new file mode 100644
index 0000000000000..552c461ed3481
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/string_punctuation.rs
@@ -0,0 +1,9 @@
+// rustfmt-format_strings: true
+
+fn main() {
+    println!("ThisIsAReallyLongStringWithNoSpaces.It_should_prefer_to_break_onpunctuation:Likethisssssssssssss");
+    format!("{}__{}__{}ItShouldOnlyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyNoticeSemicolonsPeriodsColonsAndCommasAndResortToMid-CharBreaksAfterPunctuation{}{}",x,y,z,a,b);
+    println!("aaaaaaaaaaaaaaaaaaaaaaaaaaaaalhijalfhiigjapdighjapdigjapdighdapighapdighpaidhg;adopgihadoguaadbadgad,qeoihapethae8t0aet8haetadbjtaeg;ooeouthaoeutgadlgajduabgoiuadogabudogubaodugbadgadgadga;adoughaoeugbaouea");
+    println!("sentuhaesnuthaesnutheasunteahusnaethuseantuihaesntdiastnidaetnuhaideuhsenathe。WeShouldSupportNonAsciiPunctuations§ensuhatheasunteahsuneathusneathuasnuhaesnuhaesnuaethusnaetuheasnuth");
+    println!("ThisIsASampleOfCJKString.祇園精舍の鐘の声、諸行無常の響きあり。娑羅双樹の花の色、盛者必衰の理をあらはす。奢れる人も久しからず、ただ春の夜の夢のごとし。猛き者もつひにはほろびぬ、ひとへに風の前の塵に同じ。");
+}
diff --git a/src/tools/rustfmt/tests/source/struct-field-attributes.rs b/src/tools/rustfmt/tests/source/struct-field-attributes.rs
new file mode 100644
index 0000000000000..76d6eda88538e
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/struct-field-attributes.rs
@@ -0,0 +1,52 @@
+// #1535
+#![feature(struct_field_attributes)]
+
+struct Foo {
+    bar: u64,
+
+    #[cfg(test)]
+    qux: u64,
+}
+
+fn do_something() -> Foo {
+    Foo {
+        bar: 0,
+
+        #[cfg(test)]
+        qux: 1,
+    }
+}
+
+fn main() {
+    do_something();
+}
+
+// #1462
+struct Foo {
+    foo: usize,
+    #[cfg(feature="include-bar")]
+    bar: usize,
+}
+
+fn new_foo() -> Foo {
+    Foo {
+        foo: 0,
+        #[cfg(feature="include-bar")]
+        bar: 0,
+    }
+}
+
+// #2044
+pub enum State {
+    Closure(#[cfg_attr(feature = "serde_derive", serde(state_with = "::serialization::closure"))] GcPtr<ClosureData>),
+}
+
+struct Fields(
+    #[cfg_attr(feature = "serde_derive", serde(state_with = "::base::serialization::shared"))] Arc<Vec<InternedStr>>,
+);
+
+// #2309
+pub struct A {
+#[doc="XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"]
+pub foos:Vec<bool>
+}
diff --git a/src/tools/rustfmt/tests/source/struct_lits.rs b/src/tools/rustfmt/tests/source/struct_lits.rs
new file mode 100644
index 0000000000000..c5aaf7ef88193
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/struct_lits.rs
@@ -0,0 +1,143 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo {a: x };
+
+    Foo { a: foo() /* comment*/, /* comment*/ b: bar(), ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a:Bar,
+          b:f() };
+
+    Quux { x: if cond { bar(); }, y: baz() };
+
+    A { 
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+    first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item
+    };
+
+    Some(Data::MethodCallData(MethodCallData {
+        span: sub_span.unwrap(),
+        scope: self.enclosing_scope(id),
+        ref_id: def_id,
+        decl_id: Some(decl_id),
+    }));
+
+    Diagram { /*                 o        This graph demonstrates how                  
+               *                / \       significant whitespace is           
+               *               o   o      preserved.  
+               *              /|\   \
+               *             o o o   o */
+              graph: G, }
+}
+
+fn matcher() {
+    TagTerminatedByteMatcher {
+        matcher: ByteMatcher {
+        pattern: b"<HTML",
+        mask: b"\xFF\xDF\xDF\xDF\xDF\xFF",
+    },
+    };
+}
+
+fn issue177() {
+    struct Foo<T> { memb: T }
+    let foo = Foo::<i64> { memb: 10 };
+}
+
+fn issue201() {
+    let s = S{a:0, ..  b};
+}
+
+fn issue201_2() {
+    let s = S{a: S2{    .. c}, ..  b};
+}
+
+fn issue278() {
+    let s = S {
+        a: 0,
+        //       
+        b: 0,
+    };
+    let s1 = S {
+        a: 0,
+        // foo
+        //      
+        // bar
+        b: 0,
+    };
+}
+
+fn struct_exprs() {
+    Foo
+    { a :  1, b:f( 2)};
+    Foo{a:1,b:f(2),..g(3)};
+    LoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongStruct { ..base };
+    IntrinsicISizesContribution { content_intrinsic_sizes: IntrinsicISizes { minimum_inline_size: 0, }, };
+}
+
+fn issue123() {
+    Foo { a: b, c: d, e: f };
+
+    Foo { a: bb, c: dd, e: ff };
+
+    Foo { a: ddddddddddddddddddddd, b: cccccccccccccccccccccccccccccccccccccc };
+}
+
+fn issue491() {
+    Foo {
+        guard: None,
+        arm: 0, // Comment
+    };
+
+    Foo {
+        arm: 0, // Comment
+    };
+
+    Foo { a: aaaaaaaaaa, b: bbbbbbbb, c: cccccccccc, d: dddddddddd, /* a comment */
+      e: eeeeeeeee };
+}
+
+fn issue698() {
+    Record {
+        ffffffffffffffffffffffffffields: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    };
+    Record {
+        ffffffffffffffffffffffffffields: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    }
+}
+
+fn issue835() {
+    MyStruct {};
+    MyStruct { /* a comment */ };
+    MyStruct {
+        // Another comment
+    };
+    MyStruct {}
+}
+
+fn field_init_shorthand() {
+    MyStruct { x, y, z };
+    MyStruct { x, y, z, .. base };
+    Foo { aaaaaaaaaa, bbbbbbbb, cccccccccc, dddddddddd, /* a comment */
+        eeeeeeeee };
+    Record { ffffffffffffffffffffffffffieldsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa };
+}
diff --git a/src/tools/rustfmt/tests/source/struct_lits_multiline.rs b/src/tools/rustfmt/tests/source/struct_lits_multiline.rs
new file mode 100644
index 0000000000000..256ba1bbda3b1
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/struct_lits_multiline.rs
@@ -0,0 +1,81 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-struct_lit_single_line: false
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo {a: x };
+
+    Foo { a: foo() /* comment*/, /* comment*/ b: bar(), ..something };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: foo(), b: bar(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: foo(), b: bar(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a:Bar,
+          b:foo() };
+
+    Quux { x: if cond { bar(); }, y: baz() };
+
+    A {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+    first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item
+    };
+
+    Some(Data::MethodCallData(MethodCallData {
+        span: sub_span.unwrap(),
+        scope: self.enclosing_scope(id),
+        ref_id: def_id,
+        decl_id: Some(decl_id),
+    }));
+
+    Diagram { /*                 o        This graph demonstrates how
+               *                / \       significant whitespace is
+               *               o   o      preserved.
+               *              /|\   \
+               *             o o o   o */
+              graph: G, }
+}
+
+fn matcher() {
+    TagTerminatedByteMatcher {
+        matcher: ByteMatcher {
+        pattern: b"<HTML",
+        mask: b"\xFF\xDF\xDF\xDF\xDF\xFF",
+    },
+    };
+}
+
+fn issue177() {
+    struct Foo<T> { memb: T }
+    let foo = Foo::<i64> { memb: 10 };
+}
+
+fn issue201() {
+    let s = S{a:0, ..  b};
+}
+
+fn issue201_2() {
+    let s = S{a: S2{    .. c}, ..  b};
+}
+
+fn issue491() {
+    Foo {
+        guard: None,
+        arm: 0, // Comment
+    };
+}
diff --git a/src/tools/rustfmt/tests/source/struct_lits_visual.rs b/src/tools/rustfmt/tests/source/struct_lits_visual.rs
new file mode 100644
index 0000000000000..e84652e9ea9a0
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/struct_lits_visual.rs
@@ -0,0 +1,46 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-indent_style: Visual
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo {a: x };
+
+    Foo { a: foo() /* comment*/, /* comment*/ b: bar(), ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a:Bar,
+          b:f() };
+
+    Quux { x: if cond { bar(); }, y: baz() };
+
+    Baz { x: yxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, z: zzzzz // test
+    };
+
+    A { 
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+    first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item
+    };
+
+    Diagram { /*                 o        This graph demonstrates how                  
+               *                / \       significant whitespace is           
+               *               o   o      preserved.  
+               *              /|\   \
+               *             o o o   o */
+              graph: G, }
+}
diff --git a/src/tools/rustfmt/tests/source/struct_lits_visual_multiline.rs b/src/tools/rustfmt/tests/source/struct_lits_visual_multiline.rs
new file mode 100644
index 0000000000000..d2990f8da3dc3
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/struct_lits_visual_multiline.rs
@@ -0,0 +1,44 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-indent_style: Visual
+// rustfmt-struct_lit_single_line: false
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo {a: x };
+
+    Foo { a: foo() /* comment*/, /* comment*/ b: bar(), ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: foo(), b: bar(), };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a:Bar,
+          b:foo() };
+
+    Quux { x: if cond { bar(); }, y: baz() };
+
+    A {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+    first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item
+    };
+
+    Diagram { /*                 o        This graph demonstrates how
+               *                / \       significant whitespace is
+               *               o   o      preserved.
+               *              /|\   \
+               *             o o o   o */
+              graph: G, }
+}
diff --git a/src/tools/rustfmt/tests/source/struct_tuple_visual.rs b/src/tools/rustfmt/tests/source/struct_tuple_visual.rs
new file mode 100644
index 0000000000000..f95f3fe4fd39a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/struct_tuple_visual.rs
@@ -0,0 +1,36 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-indent_style: Visual
+fn foo() {
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(f(), b());
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(// Comment
+                                                                                      foo(), /* Comment */
+                                                                                      // Comment
+                                                                                      bar() /* Comment */);
+
+    Foo(Bar, f());
+
+    Quux(if cond {
+             bar();
+         },
+         baz());
+
+    Baz(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        zzzzz /* test */);
+
+    A(// Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+      // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante
+      // hendrerit. Donec et mollis dolor.
+      item(),
+      // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+      // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+      Item);
+
+    Diagram(//                 o        This graph demonstrates how
+            //                / \       significant whitespace is
+            //               o   o      preserved.
+            //              /|\   \
+            //             o o o   o
+            G)
+}
diff --git a/src/tools/rustfmt/tests/source/structs.rs b/src/tools/rustfmt/tests/source/structs.rs
new file mode 100644
index 0000000000000..537151b276a72
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/structs.rs
@@ -0,0 +1,298 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+                                                                       /// A Doc comment
+#[AnAttribute]
+pub struct Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f: SomeType, // Comment beside a field
+    // Comment on a field
+    #[AnAttribute]
+    g: SomeOtherType,
+      /// A doc comment on a field
+    h: AThirdType,
+    pub i: TypeForPublicField
+}
+
+// Destructuring
+fn foo() {
+    S { x: 5,
+        ..};
+        Struct {..} = Struct { a: 1, b: 4 };
+        Struct {      a,     .. } = Struct { a: 1, b: 2, c: 3};
+        TupleStruct(a,..,   b) = TupleStruct(1, 2);
+        TupleStruct(  ..) = TupleStruct(3, 4);
+        TupleStruct(aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, .., bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb) = TupleStruct(1, 2);
+}
+
+// #1095
+struct S<T: /* comment */> {
+    t: T,
+}
+
+// #1029
+pub struct Foo {
+    #[doc(hidden)]
+    // This will NOT get deleted!
+    bar: String, // hi
+}
+
+// #1029
+struct X {
+    // `x` is an important number.
+    #[allow(unused)] // TODO: use
+    x: u32,
+}
+
+// #410
+#[allow(missing_docs)]
+pub struct Writebatch<K: Key> {
+    #[allow(dead_code)] //only used for holding the internal pointer
+    writebatch: RawWritebatch,
+    marker: PhantomData<K>,
+}
+
+struct Bar;
+
+struct NewType(Type,       OtherType);
+
+struct
+NewInt     <T: Copy>(pub i32, SomeType /* inline comment */, T /* sup */
+
+
+    );
+
+struct Qux<'a,
+           N: Clone + 'a,
+           E: Clone + 'a,
+           G: Labeller<'a, N, E> + GraphWalk<'a, N, E>,
+           W: Write + Copy>
+(
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, // Comment
+    BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+    #[AnAttr]
+    // Comment
+    /// Testdoc
+    G,
+    pub W,
+);
+
+struct Tuple(/*Comment 1*/ AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+             /* Comment 2   */ BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,);
+
+// With a where-clause and generics.
+pub struct Foo<'a, Y: Baz>
+    where X: Whatever
+{
+    f: SomeType, // Comment beside a field
+}
+
+struct Baz {
+
+    a: A,  // Comment A
+    b: B, // Comment B
+    c: C,   // Comment C
+
+}
+
+struct Baz {
+    a: A,  // Comment A
+
+    b: B, // Comment B
+
+
+
+
+    c: C,   // Comment C
+}
+
+struct Baz {
+
+    a: A,
+
+    b: B,
+    c: C,
+
+
+
+    
+    d: D
+
+}
+
+struct Baz
+{
+    // Comment A
+    a: A,
+    
+    // Comment B
+b: B,
+    // Comment C
+      c: C,}
+
+// Will this be a one-liner?
+struct Tuple(
+    A, //Comment
+    B
+);
+
+pub struct State<F: FnMut() -> time::Timespec> { now: F }
+
+pub struct State<F: FnMut() -> ()> { now: F }
+
+pub struct State<F: FnMut()> { now: F }
+
+struct Palette { /// A map of indices in the palette to a count of pixels in approximately that color
+                    foo: i32}
+
+// Splitting a single line comment into a block previously had a misalignment
+// when the field had attributes
+struct FieldsWithAttributes {
+    // Pre Comment
+    #[rustfmt::skip] pub host:String, // Post comment BBBBBBBBBBBBBB BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBBB BBBBBBBBBBB
+    //Another pre comment
+    #[attr1]
+    #[attr2] pub id: usize // CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCC CCCCCCCCCCCC
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep: node::Handle<IdRef<'id, Node<K, V>>,
+                                                     Type,
+                                                     NodeType>,
+}
+
+struct Foo<T>(T);
+struct Foo<T>(T) where T: Copy, T: Eq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUU);
+struct Foo<T>(TTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTT) where T: PartialEq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTTTT) where T: PartialEq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUUUUUUU, TTTTTTTTTTTTTTTTTTT, UUUUUUUUUUUUUUUUUUU) where T: PartialEq;
+struct Foo<T>(TTTTTTTTTTTTTTTTT, // Foo
+              UUUUUUUUUUUUUUUUUUUUUUUU /* Bar */,
+              // Baz
+              TTTTTTTTTTTTTTTTTTT,
+              // Qux (FIXME #572 - doc comment)
+              UUUUUUUUUUUUUUUUUUU);
+
+mod m {
+    struct X<T> where T: Sized {
+        a: T,
+    }
+}
+
+struct Foo<T>(TTTTTTTTTTTTTTTTTTT,
+              /// Qux
+    UUUUUUUUUUUUUUUUUUU);
+
+struct Issue677 {
+    pub ptr: *const libc::c_void,
+    pub trace: fn(  obj: 
+          *const libc::c_void, tracer   : *mut   JSTracer   ),
+}
+
+struct Foo {}
+struct Foo {
+    }
+struct Foo {
+    // comment
+    }
+struct Foo {
+    // trailing space ->    
+
+
+    }
+struct Foo { /* comment */ }
+struct Foo( /* comment */ );
+
+struct LongStruct {
+    a: A,
+    the_quick_brown_fox_jumps_over_the_lazy_dog:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep: node::Handle<IdRef<'id, Node<Key, Value>>,
+                                                                         Type,
+                                                                         NodeType>,
+}
+
+struct Foo<C=()>(String);
+
+// #1364
+fn foo() {
+    convex_shape.set_point(0, &Vector2f { x: 400.0, y: 100.0 });
+    convex_shape.set_point(1, &Vector2f { x: 500.0, y: 70.0 });
+    convex_shape.set_point(2, &Vector2f { x: 450.0, y: 100.0 });
+    convex_shape.set_point(3, &Vector2f { x: 580.0, y: 150.0 });
+}
+
+// Vertical alignment
+struct Foo {
+    aaaaa: u32, // a
+
+    b: u32, // b
+    cc: u32, // cc
+
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 1
+    yy: u32, // comment2
+    zzz: u32, // comment3
+
+    aaaaaa: u32, // comment4
+    bb: u32, // comment5
+    // separate
+    dd: u32, // comment7
+    c: u32, // comment6
+
+    aaaaaaa: u32, /* multi
+     * line
+     * comment
+     */
+    b: u32, // hi
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    // separate
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    // separate
+    please_do_not_push_this_comment3: u32, // comment3
+}
+
+// structs with long identifier
+struct Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong {}
+struct Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong {}
+struct Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong {}
+struct Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong { x: i32 }
+
+// structs with visibility, do not duplicate visibility (#2110).
+pub(in self) struct Foo{}
+pub(super) struct Foo{}
+pub(crate) struct Foo{}
+pub(in self) struct Foo();
+pub(super) struct Foo();
+pub(crate) struct Foo();
+
+// #2125
+pub struct ReadinessCheckRegistry(Mutex<HashMap<Arc<String>, Box<Fn() -> ReadinessCheck + Sync + Send>>>);
+
+// #2144 unit struct with generics
+struct MyBox<T:?Sized>;
+struct MyBoxx<T, S> where T: ?Sized, S: Clone;
+
+// #2208
+struct Test {
+    /// foo
+    #[serde(default)]
+    pub join: Vec<String>,
+    #[serde(default)] pub tls: bool,
+}
+
+// #2818
+struct Paren((i32)) where i32: Trait;
+struct Parens((i32, i32)) where i32: Trait;
diff --git a/src/tools/rustfmt/tests/source/trailing-comma-never.rs b/src/tools/rustfmt/tests/source/trailing-comma-never.rs
new file mode 100644
index 0000000000000..c74267cd17903
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/trailing-comma-never.rs
@@ -0,0 +1,45 @@
+// rustfmt-trailing_comma: Never
+
+enum X {
+    A,
+    B,
+}
+
+enum Y {
+    A,
+    B
+}
+
+enum TupX {
+    A(u32),
+    B(i32, u16),
+}
+
+enum TupY {
+    A(u32),
+    B(i32, u16)
+}
+
+enum StructX {
+    A {
+        s: u16,
+    },
+    B {
+        u: u32,
+        i: i32,
+    },
+}
+
+enum StructY {
+    A {
+        s: u16,
+    },
+    B {
+        u: u32,
+        i: i32,
+    }
+}
+
+static XXX: [i8; 64] = [
+1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,1, 1, 1,
+];
diff --git a/src/tools/rustfmt/tests/source/trailing_commas.rs b/src/tools/rustfmt/tests/source/trailing_commas.rs
new file mode 100644
index 0000000000000..3e5fcc8080ffc
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/trailing_commas.rs
@@ -0,0 +1,47 @@
+// rustfmt-match_block_trailing_comma: true
+// rustfmt-trailing_comma: Always
+
+fn main() {
+    match foo {
+        x => {}
+        y => {
+            foo();
+        }
+        _ => x
+    }
+}
+
+fn f<S, T>(x: T, y: S) -> T where T: P, S: Q
+{
+    x
+}
+
+impl Trait for T where T: P
+{
+    fn f(x: T) -> T where T: Q + R
+    {
+        x
+    }
+}
+
+struct Pair<S, T> where T: P, S: P + Q {
+    a: T,
+    b: S
+}
+
+struct TupPair<S, T> (S, T) where T: P, S: P + Q;
+
+enum E<S, T> where S: P, T: P {
+    A {a: T},
+}
+
+type Double<T> where T: P, T: Q = Pair<T, T>;
+
+extern "C" {
+    fn f<S, T>(x: T, y: S) -> T where T: P, S: Q;
+}
+
+trait Q<S, T> where T: P, S: R
+{
+    fn f<U, V>(self, x: T, y: S, z: U) -> Self where U: P, V: P;
+}
diff --git a/src/tools/rustfmt/tests/source/trailing_comments/hard_tabs.rs b/src/tools/rustfmt/tests/source/trailing_comments/hard_tabs.rs
new file mode 100644
index 0000000000000..88249aa5fb997
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/trailing_comments/hard_tabs.rs
@@ -0,0 +1,21 @@
+// rustfmt-version: Two
+// rustfmt-wrap_comments: true
+// rustfmt-hard_tabs: true
+
+impl Foo {
+    fn foo() {
+        bar(); // comment 1
+        // comment 2
+        // comment 3
+        baz();
+    }
+}
+
+fn lorem_ipsum() {
+    let f = bar(); // Donec consequat mi. Quisque vitae dolor. Integer lobortis. Maecenas id nulla. Lorem.
+    // Id turpis. Nam posuere lectus vitae nibh. Etiam tortor orci, sagittis malesuada, rhoncus quis, hendrerit eget, libero. Quisque commodo nulla at nunc. Mauris consequat, enim vitae venenatis sollicitudin, dolor orci bibendum enim, a sagittis nulla nunc quis elit. Phasellus augue. Nunc suscipit, magna tincidunt lacinia faucibus, lacus tellus ornare purus, a pulvinar lacus orci eget nibh.  Maecenas sed nibh non lacus tempor faucibus. In hac habitasse platea dictumst. Vivamus a orci at nulla tristique condimentum. Donec arcu quam, dictum accumsan, convallis accumsan, cursus sit amet, ipsum.  In pharetra sagittis nunc.
+    let b = baz();
+
+    let normalized = self.ctfont.all_traits().normalized_weight(); // [-1.0, 1.0]
+    // TODO(emilio): It may make sense to make this range [.01, 10.0], to align with css-fonts-4's range of [1, 1000].
+}
diff --git a/src/tools/rustfmt/tests/source/trailing_comments/soft_tabs.rs b/src/tools/rustfmt/tests/source/trailing_comments/soft_tabs.rs
new file mode 100644
index 0000000000000..7845f713b8a93
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/trailing_comments/soft_tabs.rs
@@ -0,0 +1,21 @@
+// rustfmt-version: Two
+// rustfmt-wrap_comments: true
+
+pub const IFF_MULTICAST: ::c_int = 0x0000000800; // Supports multicast
+// Multicast using broadcst. add.
+
+pub const SQ_CRETAB: u16 = 0x000e; // CREATE TABLE
+pub const SQ_DRPTAB: u16 = 0x000f; // DROP TABLE
+pub const SQ_CREIDX: u16 = 0x0010; // CREATE INDEX
+//const SQ_DRPIDX: u16 = 0x0011;	// DROP INDEX
+//const SQ_GRANT: u16 = 0x0012;	// GRANT
+//const SQ_REVOKE: u16 = 0x0013;	// REVOKE
+
+fn foo() {
+    let f = bar(); // Donec consequat mi. Quisque vitae dolor. Integer lobortis. Maecenas id nulla. Lorem.
+    // Id turpis. Nam posuere lectus vitae nibh. Etiam tortor orci, sagittis malesuada, rhoncus quis, hendrerit eget, libero. Quisque commodo nulla at nunc. Mauris consequat, enim vitae venenatis sollicitudin, dolor orci bibendum enim, a sagittis nulla nunc quis elit. Phasellus augue. Nunc suscipit, magna tincidunt lacinia faucibus, lacus tellus ornare purus, a pulvinar lacus orci eget nibh.  Maecenas sed nibh non lacus tempor faucibus. In hac habitasse platea dictumst. Vivamus a orci at nulla tristique condimentum. Donec arcu quam, dictum accumsan, convallis accumsan, cursus sit amet, ipsum.  In pharetra sagittis nunc.
+    let b = baz();
+
+    let normalized = self.ctfont.all_traits().normalized_weight(); // [-1.0, 1.0]
+    // TODO(emilio): It may make sense to make this range [.01, 10.0], to align with css-fonts-4's range of [1, 1000].
+}
diff --git a/src/tools/rustfmt/tests/source/trait.rs b/src/tools/rustfmt/tests/source/trait.rs
new file mode 100644
index 0000000000000..80ee0188a6baa
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/trait.rs
@@ -0,0 +1,176 @@
+// Test traits
+
+trait Foo {
+    fn bar(x: i32   ) -> Baz<   U> {       Baz::new()
+  }
+
+    fn baz(a: AAAAAAAAAAAAAAAAAAAAAA,
+b: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB)
+-> RetType;
+
+    fn foo(a: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, // Another comment
+b: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB)
+           -> RetType              ; // Some comment
+
+    fn baz(&mut self        ) -> i32          ;
+
+fn increment(&     mut self, x: i32         );
+
+    fn read(&mut self,          x: BufReader<R> /* Used to be MemReader */)
+    where R: Read;
+}
+
+pub trait WriteMessage {
+    fn write_message  (&mut self, &FrontendMessage) ->   io::Result<()>;
+}
+
+trait Runnable {
+    fn handler(self: & Runnable   );
+}
+
+trait TraitWithExpr {
+    fn fn_with_expr(x: [i32;       1]);
+}
+
+trait Test {
+    fn read_struct<T, F>(&mut self, s_name: &str, len: usize, f: F) -> Result<T, Self::Error> where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+}
+
+trait T<> {}
+
+trait Foo { type Bar: Baz; type Inner: Foo   = Box< Foo >; }
+
+trait ConstCheck<T>:Foo   where   T: Baz { 
+        const   J:   i32;
+}
+
+trait Tttttttttttttttttttttttttttttttttttttttttttttttttttttttttt<T> 
+    where T: Foo {}
+
+trait Ttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt<T> where T: Foo {}
+
+trait FooBar<T> : Tttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt where J: Bar { fn test(); }
+
+trait WhereList<T, J> where T: Foo, J: Bar {}
+
+trait X /* comment */ {}
+trait Y // comment
+{
+}
+
+// #2055
+pub trait Foo:
+// A and C
+A + C
+// and B
+    + B
+{}
+
+// #2158
+trait Foo {
+    type ItRev = <MergingUntypedTimeSeries<SliceSeries<SliceWindow>> as UntypedTimeSeries>::IterRev;
+    type IteRev = <MergingUntypedTimeSeries<SliceSeries<SliceWindow>> as UntypedTimeSeries>::IterRev;
+}
+
+// #2331
+trait MyTrait<AAAAAAAAAAAAAAAAAAAA, BBBBBBBBBBBBBBBBBBBB, CCCCCCCCCCCCCCCCCCCC, DDDDDDDDDDDDDDDDDDDD> {
+    fn foo() {}
+}
+
+// Trait aliases
+trait FooBar =
+    Foo 
+    + Bar;
+trait FooBar <A, B, C>=
+    Foo 
+    + Bar;
+pub trait FooBar =
+    Foo 
+    + Bar;
+pub trait FooBar <A, B, C>=
+    Foo 
+    + Bar;
+trait AAAAAAAAAAAAAAAAAA = BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDD;
+pub trait AAAAAAAAAAAAAAAAAA = BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDD;
+trait AAAAAAAAAAAAAAAAAAA = BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDD;
+trait AAAAAAAAAAAAAAAAAA = BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDDD;
+trait AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA<A, B, C, D, E> = FooBar;
+trait AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA<A, B, C, D, E> = FooBar;
+#[rustfmt::skip]
+trait FooBar = Foo
+    + Bar;
+
+// #2637
+auto trait Example {}
+pub auto trait PubExample {}
+pub unsafe auto trait PubUnsafeExample {}
+
+// #3006
+trait Foo<'a> {
+    type Bar<  'a  >;
+}
+
+impl<'a> Foo<'a> for i32 {
+    type Bar<  'a  > = i32;
+}
+
+// #3092
+pub mod test {
+    pub trait ATraitWithALooongName {}
+    pub trait ATrait
+        :ATraitWithALooongName + ATraitWithALooongName + ATraitWithALooongName + ATraitWithALooongName
+{
+}
+}
+
+// Trait aliases with where clauses.
+trait A = where for<'b> &'b Self: Send;
+
+trait B = where for<'b> &'b Self: Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCCC;
+trait B = where for<'b> &'b Self: Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCCCC;
+trait B = where
+    for<'b> &'b Self:
+Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCCCCCCCCCCCCCCCC;
+trait B = where
+    for<'b> &'b Self:
+Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC;
+
+trait B = where
+    for<'b> &'b Self:
+Send
+    + Clone
+    + Copy
+    + SomeTrait
+    + AAAAAAAA
+    + BBBBBBB
+    + CCCCCCCCC
+    + DDDDDDD
+    + DDDDDDDD
+    + DDDDDDDDD
+    + EEEEEEE;
+
+trait A<'a, 'b, 'c> = Debug<T> + Foo where for<'b> &'b Self: Send;
+
+trait B<'a, 'b, 'c> = Debug<T> +Foo
+where for<'b> &'b Self:
+Send
+    + Clone
+    + Copy
+    + SomeTrait
+    + AAAAAAAA
+    + BBBBBBB
+    + CCCCCCCCC
+    + DDDDDDD;
+
+trait B<'a, 'b, 'c,T> = Debug<'a, T> where for<'b> &'b Self:
+Send
+    + Clone
+    + Copy
+    + SomeTrait
+    + AAAAAAAA
+    + BBBBBBB
+    + CCCCCCCCC
+    + DDDDDDD
+    + DDDDDDDD
+    + DDDDDDDDD
+    + EEEEEEE;
diff --git a/src/tools/rustfmt/tests/source/try-conversion.rs b/src/tools/rustfmt/tests/source/try-conversion.rs
new file mode 100644
index 0000000000000..ed83ee9e101c9
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/try-conversion.rs
@@ -0,0 +1,18 @@
+// rustfmt-use_try_shorthand: true
+
+fn main() {
+    let x = try!(some_expr());
+
+    let y = try!(a.very.loooooooooooooooooooooooooooooooooooooong().chain().inside().weeeeeeeeeeeeeee()).test().0.x;
+}
+
+fn test() {
+    a?
+}
+
+fn issue1291() {
+    try!(fs::create_dir_all(&gitfiledir).chain_err(|| {
+        format!("failed to create the {} submodule directory for the workarea",
+                name)
+    }));
+}
diff --git a/src/tools/rustfmt/tests/source/try_block.rs b/src/tools/rustfmt/tests/source/try_block.rs
new file mode 100644
index 0000000000000..2e8d61f7e66a5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/try_block.rs
@@ -0,0 +1,30 @@
+// rustfmt-edition: 2018
+
+fn main() -> Result<(), !> {
+    let _x: Option<_> = try {
+        4
+    };
+
+    try {}
+}
+
+fn baz() -> Option<i32> {
+    if (1 == 1) {
+        return try {
+            5
+        };
+    }
+
+    // test
+    let x: Option<()> = try {
+        // try blocks are great
+    };
+
+    let y: Option<i32> = try {
+        6
+    }; // comment
+
+    let x: Option<i32> = try { baz()?; baz()?; baz()?; 7 };
+
+    return None;
+}
diff --git a/src/tools/rustfmt/tests/source/tuple.rs b/src/tools/rustfmt/tests/source/tuple.rs
new file mode 100644
index 0000000000000..9a0f979fbca38
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/tuple.rs
@@ -0,0 +1,63 @@
+// Test tuple litterals
+
+fn foo() {
+    let a = (a, a, a, a, a);
+    let aaaaaaaaaaaaaaaa = (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, aaaaaaaaaaaaaa, aaaaaaaaaaaaaa);
+    let aaaaaaaaaaaaaaaaaaaaaa = (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+                                  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+                                  aaaaaaaaaaaaaaaaaaaaaaaaa,
+                                  aaaa);
+    let a = (a,);
+
+    let b = (// This is a comment
+             b, // Comment
+             b /* Trailing comment */);
+
+    // #1063
+    foo(x.0 .0);
+}
+
+fn a() {
+    ((aaaaaaaa,
+      aaaaaaaaaaaaa,
+      aaaaaaaaaaaaaaaaa,
+      aaaaaaaaaaaaaa,
+      aaaaaaaaaaaaaaaa,
+      aaaaaaaaaaaaaa),)
+}
+
+fn b() {
+    ((bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb, bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb),
+     bbbbbbbbbbbbbbbbbb)
+}
+
+fn issue550() {
+    self.visitor.visit_volume(self.level.sector_id(sector), (floor_y,
+    if is_sky_flat(ceil_tex) {from_wad_height(self.height_range.1)} else {ceil_y}));
+}
+
+fn issue775() {
+    if indent {
+        let a = mk_object(&[("a".to_string(), Boolean(true)),
+                            ("b".to_string(),
+                             Array(vec![mk_object(&[("c".to_string(),
+                                                     String("\x0c\r".to_string()))]),
+                                        mk_object(&[("d".to_string(), String("".to_string()))])]))]);
+    }
+}
+
+fn issue1725() {
+    bench_antialiased_lines!(bench_draw_antialiased_line_segment_diagonal, (10, 10), (450, 450));
+    bench_antialiased_lines!(bench_draw_antialiased_line_segment_shallow, (10, 10), (450, 80));
+}
+
+fn issue_4355() {
+    let _ = ((1,),).0.0;
+}
+
+// https://github.com/rust-lang/rustfmt/issues/4410
+impl Drop for LockGuard {
+    fn drop(&mut self) {
+        LockMap::unlock(&self.0.0, &self.0.1);
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/tuple_v2.rs b/src/tools/rustfmt/tests/source/tuple_v2.rs
new file mode 100644
index 0000000000000..9223033832b24
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/tuple_v2.rs
@@ -0,0 +1,5 @@
+// rustfmt-version: Two
+
+fn issue_4355() {
+    let _ = ((1,),).0 .0;
+}
diff --git a/src/tools/rustfmt/tests/source/type-ascription.rs b/src/tools/rustfmt/tests/source/type-ascription.rs
new file mode 100644
index 0000000000000..4874094ccc4c4
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/type-ascription.rs
@@ -0,0 +1,10 @@
+
+fn main() {
+    let xxxxxxxxxxx = yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy  :  SomeTrait<AA, BB, CC>;
+
+    let xxxxxxxxxxxxxxx = yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA;
+
+    let z = funk(yyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzz, wwwwww): AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA;
+
+    x : u32 - 1u32 / 10f32 : u32
+}
diff --git a/src/tools/rustfmt/tests/source/type.rs b/src/tools/rustfmt/tests/source/type.rs
new file mode 100644
index 0000000000000..57f31dc901e77
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/type.rs
@@ -0,0 +1,174 @@
+// rustfmt-normalize_comments: true
+fn types() {
+    let x: [ Vec   < _ > ] = [];
+    let y:  * mut [ SomeType ; konst_funk() ] = expr();
+    let z: (/*#digits*/ usize, /*exp*/ i16) = funk();
+    let z: ( usize  /*#digits*/ , i16 /*exp*/ ) = funk();
+}
+
+struct F {
+    f: extern "C" fn(x: u8, ... /* comment */),
+    g: extern "C" fn(x: u8,/* comment */ ...),
+    h: extern "C" fn(x: u8, ... ),
+    i: extern "C" fn(x: u8, /* comment 4*/ y: String, // comment 3
+                     z: Foo, /* comment */ .../* comment 2*/ ),
+}
+
+fn issue_1006(def_id_to_string: for<'a, 'b> unsafe fn(TyCtxt<'b, 'tcx, 'tcx>, DefId) -> String) {}
+
+fn impl_trait_fn_1() -> impl Fn(i32) -> Option<u8> {}
+
+fn impl_trait_fn_2<E>() -> impl Future<Item=&'a i64,Error=E> {}
+
+fn issue_1234() {
+    do_parse!(name: take_while1!(is_token) >> (Header))
+}
+
+// #2510
+impl CombineTypes {
+    pub fn pop_callback(
+        &self,
+        query_id: Uuid,
+    ) -> Option<
+        (
+            ProjectId,
+            Box<FnMut(&ProjectState, serde_json::Value, bool) -> () + Sync + Send>,
+        ),
+    > {
+        self.query_callbacks()(&query_id)
+    }
+}
+
+// #2859
+pub fn do_something<'a, T: Trait1 + Trait2 + 'a>(&fooo: u32) -> impl Future<
+    Item = (
+        impl Future<Item = (
+        ), Error =   SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+impl Future<Item = (), Error = SomeError > + 'a,
+    ),
+    Error = SomeError,
+    >
+    +
+    'a {
+}
+
+pub fn do_something<'a, T: Trait1 + Trait2 + 'a>(    &fooo: u32,
+) -> impl Future<
+    Item = (
+impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+    ),
+    Error = SomeError,
+    >
+    + Future<
+    Item = (
+        impl Future<Item = (), Error = SomeError> + 'a,
+impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+    ),
+    Error = SomeError,
+        >
+    + Future<
+    Item = (
+        impl Future<Item = (), Error = SomeError> + 'a,
+   impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+    ),
+    Error = SomeError,
+        >
+    +
+    'a + 'b +
+    'c {
+}
+
+// #3051
+token![impl];
+token![ impl ];
+
+// #3060
+macro_rules! foo {
+    ($foo_api: ty) => {
+        type Target = ( $foo_api ) + 'static;
+    }
+}
+
+type Target = ( FooAPI ) + 'static;
+
+// #3137
+fn foo<T>(t: T)
+where
+    T: ( FnOnce() -> () ) + Clone,
+    U: ( FnOnce() -> () ) + 'static,
+{
+}
+
+// #3117
+fn issue3117() {
+    {
+        {
+            {
+                {
+                    {
+                        {
+                            {
+                                {
+                                    let opt: &mut Option<MyLongTypeHere> =
+                                        unsafe { &mut *self.future.get() };
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+// #3139
+fn issue3139() {
+    assert_eq!(
+        to_json_value(&None ::  <i32>).unwrap(),
+        json!(  { "test": None  ::  <i32> }  )
+    );
+}
+
+// #3180
+fn foo(a: SomeLongComplexType, b: SomeOtherLongComplexType) -> Box<Future<Item = AnotherLongType, Error = ALongErrorType>> {
+}
+
+type MyFn = fn(a: SomeLongComplexType, b: SomeOtherLongComplexType,) -> Box<Future<Item = AnotherLongType, Error = ALongErrorType>>;
+
+// Const opt-out
+
+trait T: ?   const  Super {}
+
+const fn maybe_const<S: ?   const    T>() -> i32 { <S as T>::CONST }
+
+struct S<T:?  const   ?  Sized>(std::marker::PhantomData<T>);
+
+impl ?    const T {}
+
+fn trait_object() -> &'static dyn ?  const T { &S }
+
+fn i(_: impl IntoIterator<Item = Box<dyn ?    const    T>>) {}
+
+fn apit(_: impl ?const T) {}
+
+fn rpit() -> impl ?  const T { S }
+
+pub struct Foo<T: Trait>(T);
+impl<T:   ?  const Trait> Foo<T> {
+    fn new(t: T) -> Self {
+        // not calling methods on `t`, so we opt out of requiring
+        // `<T as Trait>` to have const methods via `?const`
+        Self(t)
+    }
+}
+
+// #4357
+type T = typeof(
+1);
+impl T for  .. {
+}
\ No newline at end of file
diff --git a/src/tools/rustfmt/tests/source/type_alias.rs b/src/tools/rustfmt/tests/source/type_alias.rs
new file mode 100644
index 0000000000000..58c807f4029e2
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/type_alias.rs
@@ -0,0 +1,34 @@
+// rustfmt-normalize_comments: true
+
+type PrivateTest<'a, I> = (Box<Parser<Input=I, Output=char> + 'a>, Box<Parser<Input=I, Output=char> + 'a>);
+
+pub type PublicTest<'a, I, O> = Result<Vec<MyLongType>, Box<Parser<Input=I, Output=char> + 'a>, Box<Parser<Input=I, Output=char> + 'a>>;
+
+pub type LongGenericListTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, LONGPARAMETERNAME, A, B, C> = Option<Vec<MyType>>;
+
+pub type Exactly100CharsTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, A, B> = Vec<i32>;
+
+pub type Exactly101CharsTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, A, B> = Vec<Test>;
+
+pub type Exactly100CharsToEqualTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, A, B, C> = Vec<i32>;
+
+pub type GenericsFitButNotEqualTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, A1, B, C> = Vec<i32>;
+
+pub type CommentTest< /* Lifetime */ 'a
+            ,
+        // Type
+        T
+                    > = ();
+
+
+pub type WithWhereClause<LONGPARAMETERNAME, T> where T: Clone, LONGPARAMETERNAME: Clone + Eq + OtherTrait = Option<T>;
+
+pub type Exactly100CharstoEqualWhereTest<T, U, PARAMET> where T: Clone + Ord + Eq + SomeOtherTrait = Option<T>;
+
+pub type Exactly101CharstoEqualWhereTest<T, U, PARAMETE> where T: Clone + Ord + Eq + SomeOtherTrait = Option<T>;
+
+type RegisterPlugin = unsafe fn(pt: *const c_char, plugin: *mut c_void, data: *mut CallbackData);
+
+// #1683
+pub type Between<Lhs, Rhs> = super::operators::Between<Lhs, super::operators::And<AsExpr<Rhs, Lhs>, AsExpr<Rhs, Lhs>>>;
+pub type NotBetween<Lhs, Rhs> = super::operators::NotBetween<Lhs, super::operators::And<AsExpr<Rhs, Lhs>, AsExpr<Rhs, Lhs>>>;
diff --git a/src/tools/rustfmt/tests/source/unicode.rs b/src/tools/rustfmt/tests/source/unicode.rs
new file mode 100644
index 0000000000000..4c2119af5754b
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/unicode.rs
@@ -0,0 +1,33 @@
+// rustfmt-wrap_comments: true
+
+fn foo() {
+    let s = "this line goes to 100: ͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶ";
+    let s     =     42;
+
+    // a comment of length 80, with the starting sigil: ҘҘҘҘҘҘҘҘҘҘ ҘҘҘҘҘҘҘҘҘҘҘҘҘҘ
+    let s     =     42;
+}
+
+pub fn bar(config: &Config) {
+    let csv = RefCell::new(create_csv(config, "foo"));
+    {
+        let mut csv = csv.borrow_mut();
+        for (i1, i2, i3) in iproduct!(0..2, 0..3, 0..3) {
+            csv.write_field(format!("γ[{}.{}.{}]", i1, i2, i3))
+                .unwrap();
+            csv.write_field(format!("d[{}.{}.{}]", i1, i2, i3))
+                .unwrap();
+            csv.write_field(format!("i[{}.{}.{}]", i1, i2, i3))
+                .unwrap();
+        }
+        csv.write_record(None::<&[u8]>).unwrap();
+    }
+}
+
+// The NotUnicode line is below 100 wrt chars but over it wrt String::len
+fn baz() {
+    let our_error_b = result_b_from_func.or_else(|e| match e {
+        NotPresent => Err(e).chain_err(|| "env var wasn't provided"),
+        NotUnicode(_) => Err(e).chain_err(|| "env var was very very very bork文字化ã"),
+    });
+}
diff --git a/src/tools/rustfmt/tests/source/unions.rs b/src/tools/rustfmt/tests/source/unions.rs
new file mode 100644
index 0000000000000..53630788fe5c7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/unions.rs
@@ -0,0 +1,195 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+                                                                       /// A Doc comment
+#[AnAttribute]
+pub union Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f: SomeType, // Comment beside a field
+    // Comment on a field
+    #[AnAttribute]
+    g: SomeOtherType,
+      /// A doc comment on a field
+    h: AThirdType,
+    pub i: TypeForPublicField
+}
+
+// #1029
+pub union Foo {
+    #[doc(hidden)]
+    // This will NOT get deleted!
+    bar: String, // hi
+}
+
+// #1029
+union X {
+    // `x` is an important number.
+    #[allow(unused)] // TODO: use
+    x: u32,
+}
+
+// #410
+#[allow(missing_docs)]
+pub union Writebatch<K: Key> {
+    #[allow(dead_code)] //only used for holding the internal pointer
+    writebatch: RawWritebatch,
+    marker: PhantomData<K>,
+}
+
+// With a where-clause and generics.
+pub union Foo<'a, Y: Baz>
+    where X: Whatever
+{
+    f: SomeType, // Comment beside a field
+}
+
+union Baz {
+
+    a: A,  // Comment A
+    b: B, // Comment B
+    c: C,   // Comment C
+
+}
+
+union Baz {
+    a: A,  // Comment A
+
+    b: B, // Comment B
+
+
+
+
+    c: C,   // Comment C
+}
+
+union Baz {
+
+    a: A,
+
+    b: B,
+    c: C,
+
+
+
+    
+    d: D
+
+}
+
+union Baz
+{
+    // Comment A
+    a: A,
+    
+    // Comment B
+b: B,
+    // Comment C
+      c: C,}
+
+pub union State<F: FnMut() -> time::Timespec> { now: F }
+
+pub union State<F: FnMut() -> ()> { now: F }
+
+pub union State<F: FnMut()> { now: F }
+
+union Palette { /// A map of indices in the palette to a count of pixels in approximately that color
+                    foo: i32}
+
+// Splitting a single line comment into a block previously had a misalignment
+// when the field had attributes
+union FieldsWithAttributes {
+    // Pre Comment
+    #[rustfmt::skip] pub host:String, // Post comment BBBBBBBBBBBBBB BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBBB BBBBBBBBBBB
+    //Another pre comment
+    #[attr1]
+    #[attr2] pub id: usize // CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCC CCCCCCCCCCCC
+}
+
+union Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep: node::Handle<IdRef<'id, Node<K, V>>,
+                                                     Type,
+                                                     NodeType>,
+}
+
+mod m {
+    union X<T> where T: Sized {
+        a: T,
+    }
+}
+
+union Issue677 {
+    pub ptr: *const libc::c_void,
+    pub trace: fn(  obj: 
+          *const libc::c_void, tracer   : *mut   JSTracer   ),
+}
+
+union Foo {}
+union Foo {
+    }
+union Foo {
+    // comment
+    }
+union Foo {
+    // trailing space ->    
+
+
+    }
+union Foo { /* comment */ }
+
+union LongUnion {
+    a: A,
+    the_quick_brown_fox_jumps_over_the_lazy_dog:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+}
+
+union Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep: node::Handle<IdRef<'id, Node<Key, Value>>,
+                                                                         Type,
+                                                                         NodeType>,
+}
+
+// #1364
+fn foo() {
+    convex_shape.set_point(0, &Vector2f { x: 400.0, y: 100.0 });
+    convex_shape.set_point(1, &Vector2f { x: 500.0, y: 70.0 });
+    convex_shape.set_point(2, &Vector2f { x: 450.0, y: 100.0 });
+    convex_shape.set_point(3, &Vector2f { x: 580.0, y: 150.0 });
+}
+
+// Vertical alignment
+union Foo {
+    aaaaa: u32, // a
+
+    b: u32, // b
+    cc: u32, // cc
+
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 1
+    yy: u32, // comment2
+    zzz: u32, // comment3
+
+    aaaaaa: u32, // comment4
+    bb: u32, // comment5
+    // separate
+    dd: u32, // comment7
+    c: u32, // comment6
+
+    aaaaaaa: u32, /* multi
+     * line
+     * comment
+     */
+    b: u32, // hi
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    // separate
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    // separate
+    please_do_not_push_this_comment3: u32, // comment3
+}
diff --git a/src/tools/rustfmt/tests/source/unsafe-mod.rs b/src/tools/rustfmt/tests/source/unsafe-mod.rs
new file mode 100644
index 0000000000000..9996b06271a5a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/unsafe-mod.rs
@@ -0,0 +1,7 @@
+// These are supported by rustc syntactically but not semantically.
+
+#[cfg(any())]
+unsafe mod m { }
+
+#[cfg(any())]
+unsafe extern "C++" { }
diff --git a/src/tools/rustfmt/tests/source/visibility.rs b/src/tools/rustfmt/tests/source/visibility.rs
new file mode 100644
index 0000000000000..1c5919ccff97d
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/visibility.rs
@@ -0,0 +1,8 @@
+// #2398
+pub mod outer_mod {
+    pub mod inner_mod {
+       pub ( in outer_mod ) fn outer_mod_visible_fn() {}
+         pub ( super ) fn super_mod_visible_fn() {}
+      pub ( self ) fn inner_mod_visible_fn() {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/visual-fn-type.rs b/src/tools/rustfmt/tests/source/visual-fn-type.rs
new file mode 100644
index 0000000000000..67dad5fa4602f
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/visual-fn-type.rs
@@ -0,0 +1,10 @@
+// rustfmt-indent_style: Visual
+type CNodeSetAtts = unsafe extern "C" fn(node: *const RsvgNode,
+                                         node_impl: *const RsvgCNodeImpl,
+                                         handle: *const RsvgHandle,
+                                         pbag: *const PropertyBag)
+                                         ;
+type CNodeDraw = unsafe extern "C" fn(node: *const RsvgNode,
+                                      node_impl: *const RsvgCNodeImpl,
+                                      draw_ctx: *const RsvgDrawingCtx,
+                                      dominate: i32);
diff --git a/src/tools/rustfmt/tests/source/where-clause-rfc.rs b/src/tools/rustfmt/tests/source/where-clause-rfc.rs
new file mode 100644
index 0000000000000..219a9bddb11b5
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/where-clause-rfc.rs
@@ -0,0 +1,73 @@
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) where T: FOo, U: Bar {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) where T: FOo {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape, shape: &Shape) where T: FOo, U: Bar {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape, shape: &Shape) where T: FOo {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) -> Option<String> where T: FOo, U: Bar {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) -> Option<String> where T: FOo {
+    let mut effects = HashMap::new();
+}
+
+pub trait Test {
+    fn very_long_method_name<F>(self, f: F) -> MyVeryLongReturnType where F: FnMut(Self::Item) -> bool;
+
+    fn exactly_100_chars1<F>(self, f: F) -> MyVeryLongReturnType where F: FnMut(Self::Item) -> bool;
+}
+
+fn very_long_function_name<F>(very_long_argument: F) -> MyVeryLongReturnType where F: FnMut(Self::Item) -> bool { }
+
+struct VeryLongTupleStructName<A, B, C, D, E>(LongLongTypename, LongLongTypename, i32, i32) where A: LongTrait;
+
+struct Exactly100CharsToSemicolon<A, B, C, D, E>
+    (LongLongTypename, i32, i32)
+    where A: LongTrait1234;
+
+struct AlwaysOnNextLine<LongLongTypename, LongTypename, A, B, C, D, E, F> where A: LongTrait {
+    x: i32
+}
+
+pub trait SomeTrait<T>
+    where
+    T: Something + Sync + Send + Display     + Debug     + Copy + Hash + Debug + Display + Write + Read + FromStr
+{
+}
+
+// #2020
+impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
+    fn elaborate_bounds<F>(&mut self, bounds: &[ty::PolyTraitRef<'tcx>], mut mk_cand: F)
+    where F: for<'b> FnMut(&mut ProbeContext<'b, 'gcx, 'tcx>, ty::PolyTraitRef<'tcx>, ty::AssociatedItem),
+    {
+        // ...
+    }
+}
+
+// #2497
+fn handle_update<'a, Tab, Conn, R, C>(executor: &Executor<PooledConnection<ConnectionManager<Conn>>>, change_set: &'a C) -> ExecutionResult
+where &'a C: Identifiable + AsChangeset<Target = Tab> + HasTable<Table = Tab>,
+      <&'a C as AsChangeset>::Changeset: QueryFragment<Conn::Backend>,
+      Tab: Table + HasTable<Table = Tab>,
+      Tab::PrimaryKey: EqAll<<&'a C as Identifiable>::Id>,
+      Tab::FromClause: QueryFragment<Conn::Backend>,
+      Tab: FindDsl<<&'a C as Identifiable>::Id>,
+      Find<Tab, <&'a C as Identifiable>::Id>: IntoUpdateTarget<Table = Tab>,
+      <Find<Tab, <&'a C as Identifiable>::Id> as IntoUpdateTarget>::WhereClause: QueryFragment<Conn::Backend>,
+      Tab::Query: FilterDsl<<Tab::PrimaryKey as EqAll<<&'a C as Identifiable>::Id>>::Output>,
+      Filter<Tab::Query, <Tab::PrimaryKey as EqAll<<&'a C as Identifiable>::Id>>::Output>: LimitDsl,
+      Limit<Filter<Tab::Query, <Tab::PrimaryKey as EqAll<<&'a C as Identifiable>::Id>>::Output>>: QueryDsl + BoxedDsl< 'a, Conn::Backend, Output = BoxedSelectStatement<'a, R::SqlType, Tab, Conn::Backend>>,
+      R: LoadingHandler<Conn, Table = Tab, SqlType = Tab::SqlType> + GraphQLType<TypeInfo = (), Context = ()>, {
+    unimplemented!()
+}
diff --git a/src/tools/rustfmt/tests/source/where-clause.rs b/src/tools/rustfmt/tests/source/where-clause.rs
new file mode 100644
index 0000000000000..2a9160825487a
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/where-clause.rs
@@ -0,0 +1,58 @@
+// rustfmt-indent_style: Visual
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) where T: FOo, U: Bar {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) where T: FOo {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape, shape: &Shape) where T: FOo, U: Bar {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape, shape: &Shape) where T: FOo {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) -> Option<String> where T: FOo, U: Bar {
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape) -> Option<String> where T: FOo {
+    let mut effects = HashMap::new();
+}
+
+pub trait Test {
+    fn very_long_method_name<F>(self, f: F) -> MyVeryLongReturnType where F: FnMut(Self::Item) -> bool;
+
+    fn exactly_100_chars1<F>(self, f: F) -> MyVeryLongReturnType where F: FnMut(Self::Item) -> bool;
+}
+
+fn very_long_function_name<F>(very_long_argument: F) -> MyVeryLongReturnType where F: FnMut(Self::Item) -> bool { }
+
+struct VeryLongTupleStructName<A, B, C, D, E>(LongLongTypename, LongLongTypename, i32, i32) where A: LongTrait;
+
+struct Exactly100CharsToSemicolon<A, B, C, D, E>
+    (LongLongTypename, i32, i32)
+    where A: LongTrait1234;
+
+struct AlwaysOnNextLine<LongLongTypename, LongTypename, A, B, C, D, E, F> where A: LongTrait {
+    x: i32
+}
+
+pub trait SomeTrait<T>
+    where
+    T: Something + Sync + Send + Display     + Debug     + Copy + Hash + Debug + Display + Write + Read + FromStr
+{
+}
+
+// #2020
+impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
+    fn elaborate_bounds<F>(&mut self, bounds: &[ty::PolyTraitRef<'tcx>], mut mk_cand: F)
+    where F: for<'b> FnMut(&mut ProbeContext<'b, 'gcx, 'tcx>, ty::PolyTraitRef<'tcx>, ty::AssociatedItem),
+    {
+        // ...
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/width-heuristics.rs b/src/tools/rustfmt/tests/source/width-heuristics.rs
new file mode 100644
index 0000000000000..a591218b4ccc7
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/width-heuristics.rs
@@ -0,0 +1,28 @@
+// rustfmt-max_width: 120
+
+// elems on multiple lines for max_width 100, but same line for max_width 120
+fn foo(e: Enum) {
+    match e {
+        Enum::Var {
+            elem1,
+            elem2,
+            elem3,
+        } => {
+            return;
+        }
+    }
+}
+
+// elems not on same line for either max_width 100 or 120
+fn bar(e: Enum) {
+    match e {
+        Enum::Var {
+            elem1,
+            elem2,
+            elem3,
+            elem4,
+        } => {
+            return;
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/source/wrap_comments_should_not_imply_format_doc_comments.rs b/src/tools/rustfmt/tests/source/wrap_comments_should_not_imply_format_doc_comments.rs
new file mode 100644
index 0000000000000..78b3ce146f289
--- /dev/null
+++ b/src/tools/rustfmt/tests/source/wrap_comments_should_not_imply_format_doc_comments.rs
@@ -0,0 +1,16 @@
+// rustfmt-wrap_comments: true
+
+/// Foo
+///
+/// # Example
+/// ```
+/// # #![cfg_attr(not(dox), feature(cfg_target_feature, target_feature, stdsimd))]
+/// # #![cfg_attr(not(dox), no_std)]
+/// fn foo() {  }
+/// ```
+///
+fn foo() {}
+
+/// A long commment for wrapping
+/// This is a long long long long long long long long long long long long long long long long long long long long sentence.
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/target/alignment_2633/block_style.rs b/src/tools/rustfmt/tests/target/alignment_2633/block_style.rs
new file mode 100644
index 0000000000000..f13e8a8760e7d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/alignment_2633/block_style.rs
@@ -0,0 +1,10 @@
+// rustfmt-struct_field_align_threshold: 50
+
+fn func() {
+    Ok(ServerInformation {
+        name:         unwrap_message_string(items.get(0)),
+        vendor:       unwrap_message_string(items.get(1)),
+        version:      unwrap_message_string(items.get(2)),
+        spec_version: unwrap_message_string(items.get(3)),
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/alignment_2633/horizontal_tactic.rs b/src/tools/rustfmt/tests/target/alignment_2633/horizontal_tactic.rs
new file mode 100644
index 0000000000000..a381945fd8b8f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/alignment_2633/horizontal_tactic.rs
@@ -0,0 +1,13 @@
+// rustfmt-struct_field_align_threshold: 5
+
+#[derive(Fail, Debug, Clone)]
+pub enum BuildError {
+    LineTooLong { length: usize, limit: usize },
+    DisallowedByte { b: u8, pos: usize },
+    ContainsNewLine { pos: usize },
+}
+
+enum Foo {
+    A { a: usize, bbbbb: () },
+    B { a: (), bbbbb: () },
+}
diff --git a/src/tools/rustfmt/tests/target/alignment_2633/visual_style.rs b/src/tools/rustfmt/tests/target/alignment_2633/visual_style.rs
new file mode 100644
index 0000000000000..7d21b599af4d4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/alignment_2633/visual_style.rs
@@ -0,0 +1,9 @@
+// rustfmt-struct_field_align_threshold: 50
+// rustfmt-indent_style: Visual
+
+fn func() {
+    Ok(ServerInformation { name:         unwrap_message_string(items.get(0)),
+                           vendor:       unwrap_message_string(items.get(1)),
+                           version:      unwrap_message_string(items.get(2)),
+                           spec_version: unwrap_message_string(items.get(3)), });
+}
diff --git a/src/tools/rustfmt/tests/target/array_comment.rs b/src/tools/rustfmt/tests/target/array_comment.rs
new file mode 100644
index 0000000000000..93e1f5f403457
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/array_comment.rs
@@ -0,0 +1,18 @@
+// Issue 2842
+// The comment should not make the last line shorter
+
+static XXX: [i8; 64] = [
+    1, // Comment
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+];
+
+static XXX: [i8; 64] = [
+    1, // Comment
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+];
+
+static XXX: [i8; 64] = [
+    1, // Comment
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1,
+];
diff --git a/src/tools/rustfmt/tests/target/assignment.rs b/src/tools/rustfmt/tests/target/assignment.rs
new file mode 100644
index 0000000000000..1a70d84813d01
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/assignment.rs
@@ -0,0 +1,39 @@
+// Test assignment
+
+fn main() {
+    let some_var: Type;
+
+    let mut mutable;
+
+    let variable =
+        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA::BBBBBBBBBBBBBBBBBBBBBB::CCCCCCCCCCCCCCCCCCCCCC::EEEEEE;
+
+    variable =
+        LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOONG;
+
+    let single_line_fit = DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD;
+
+    single_line_fit = 5;
+    single_lit_fit >>= 10;
+
+    // #2791
+    let x = 2;
+}
+
+fn break_meee() {
+    {
+        (
+            block_start,
+            block_size,
+            margin_block_start,
+            margin_block_end,
+        ) = match (block_start, block_end, block_size) {
+            x => 1,
+            _ => 2,
+        };
+    }
+}
+
+// #2018
+pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
+    "Unsized tuple coercion is not stable enough for use and is subject to change";
diff --git a/src/tools/rustfmt/tests/target/associated-items.rs b/src/tools/rustfmt/tests/target/associated-items.rs
new file mode 100644
index 0000000000000..1b0a828d0291d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/associated-items.rs
@@ -0,0 +1,3 @@
+fn main() {
+    println!("{}", <bool as ::std::default::Default>::default());
+}
diff --git a/src/tools/rustfmt/tests/target/associated-types-bounds-wrapping.rs b/src/tools/rustfmt/tests/target/associated-types-bounds-wrapping.rs
new file mode 100644
index 0000000000000..8aaeee3b16c7d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/associated-types-bounds-wrapping.rs
@@ -0,0 +1,6 @@
+// Test proper wrapping of long associated type bounds
+
+pub trait HttpService {
+    type WsService: 'static
+        + Service<Request = WsCommand, Response = WsResponse, Error = ServerError>;
+}
diff --git a/src/tools/rustfmt/tests/target/associated_type_bounds.rs b/src/tools/rustfmt/tests/target/associated_type_bounds.rs
new file mode 100644
index 0000000000000..2dcbd65f86db7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/associated_type_bounds.rs
@@ -0,0 +1,13 @@
+// See #3657 - https://github.com/rust-lang/rustfmt/issues/3657
+
+#![feature(associated_type_bounds)]
+
+fn f<I: Iterator<Item: Clone>>() {}
+
+fn g<I: Iterator<Item: Clone>>() {}
+
+fn h<I: Iterator<Item: Clone>>() {}
+
+fn i<I: Iterator<Item: Clone>>() {}
+
+fn j<I: Iterator<Item: Clone + 'a>>() {}
diff --git a/src/tools/rustfmt/tests/target/associated_type_defaults.rs b/src/tools/rustfmt/tests/target/associated_type_defaults.rs
new file mode 100644
index 0000000000000..d0a08133725a5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/associated_type_defaults.rs
@@ -0,0 +1,4 @@
+#![feature(associated_type_defaults)]
+trait Foo {
+    type Bar = ();
+}
diff --git a/src/tools/rustfmt/tests/target/async_block.rs b/src/tools/rustfmt/tests/target/async_block.rs
new file mode 100644
index 0000000000000..258dd937a6f56
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/async_block.rs
@@ -0,0 +1,25 @@
+// rustfmt-edition: 2018
+
+fn main() {
+    let x = async { Ok(()) };
+}
+
+fn baz() {
+    // test
+    let x = async {
+        // async blocks are great
+        Ok(())
+    };
+
+    let y = async { Ok(()) }; // comment
+
+    spawn(a, async move {
+        action();
+        Ok(())
+    });
+
+    spawn(a, async move || {
+        action();
+        Ok(())
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/async_closure.rs b/src/tools/rustfmt/tests/target/async_closure.rs
new file mode 100644
index 0000000000000..9364e7dcc67da
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/async_closure.rs
@@ -0,0 +1,22 @@
+// rustfmt-edition: 2018
+
+fn main() {
+    let async_closure = async {
+        let x = 3;
+        x
+    };
+
+    let f = async /* comment */ {
+        let x = 3;
+        x
+    };
+
+    let g = async /* comment */ move {
+        let x = 3;
+        x
+    };
+
+    let f = |x| async {
+        println!("hello, world");
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/async_fn.rs b/src/tools/rustfmt/tests/target/async_fn.rs
new file mode 100644
index 0000000000000..ac151dddb25e6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/async_fn.rs
@@ -0,0 +1,24 @@
+// rustfmt-edition: 2018
+
+async fn bar() -> Result<(), ()> {
+    Ok(())
+}
+
+pub async fn baz() -> Result<(), ()> {
+    Ok(())
+}
+
+async unsafe fn foo() {
+    async move { Ok(()) }
+}
+
+async unsafe fn rust() {
+    async move {
+        // comment
+        Ok(())
+    }
+}
+
+async fn await_try() {
+    something.await?;
+}
diff --git a/src/tools/rustfmt/tests/target/attrib-block-expr.rs b/src/tools/rustfmt/tests/target/attrib-block-expr.rs
new file mode 100644
index 0000000000000..1e9557dc039ed
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/attrib-block-expr.rs
@@ -0,0 +1,58 @@
+fn issue_2073() {
+    let x = {
+        #![my_attr]
+        do_something()
+    };
+
+    let x = #[my_attr]
+    {
+        do_something()
+    };
+
+    let x = #[my_attr]
+    {};
+
+    {
+        #![just_an_attribute]
+    };
+
+    let z = #[attr1]
+    #[attr2]
+    {
+        body()
+    };
+
+    x = |y| {
+        #![inner]
+    };
+
+    x = |y| #[outer]
+    {};
+
+    x = |y| {
+        //! ynot
+    };
+
+    x = |y| #[outer]
+    unsafe {};
+
+    let x = unsafe {
+        #![my_attr]
+        do_something()
+    };
+
+    let x = #[my_attr]
+    unsafe {
+        do_something()
+    };
+
+    // This is a dumb but possible case
+    let x = #[my_attr]
+    unsafe {};
+
+    x = |y| #[outer]
+    #[outer2]
+    unsafe {
+        //! Comment
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/attrib-extern-crate.rs b/src/tools/rustfmt/tests/target/attrib-extern-crate.rs
new file mode 100644
index 0000000000000..ed64a0aeb0710
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/attrib-extern-crate.rs
@@ -0,0 +1,17 @@
+// Attributes on extern crate.
+
+#[Attr1]
+extern crate Bar;
+#[Attr2]
+#[Attr2]
+extern crate Baz;
+extern crate Foo;
+
+fn foo() {
+    #[Attr1]
+    extern crate Bar;
+    #[Attr2]
+    #[Attr2]
+    extern crate Baz;
+    extern crate Foo;
+}
diff --git a/src/tools/rustfmt/tests/target/attrib.rs b/src/tools/rustfmt/tests/target/attrib.rs
new file mode 100644
index 0000000000000..7e61f68d76a14
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/attrib.rs
@@ -0,0 +1,271 @@
+// rustfmt-wrap_comments: true
+// Test attributes and doc comments are preserved.
+#![doc(
+    html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
+    html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
+    html_root_url = "https://doc.rust-lang.org/nightly/",
+    html_playground_url = "https://play.rust-lang.org/",
+    test(attr(deny(warnings)))
+)]
+
+//! Doc comment
+
+#![attribute]
+
+//! Crate doc comment
+
+// Comment
+
+// Comment on attribute
+#![the(attribute)]
+
+// Another comment
+
+/// Blah blah blah.
+/// Blah blah blah.
+/// Blah blah blah.
+/// Blah blah blah.
+
+/// Blah blah blah.
+impl Bar {
+    /// Blah blah blooo.
+    /// Blah blah blooo.
+    /// Blah blah blooo.
+    /// Blah blah blooo.
+    #[an_attribute]
+    #[doc = "an attribute that shouldn't be normalized to a doc comment"]
+    fn foo(&mut self) -> isize {}
+
+    /// Blah blah bing.
+    /// Blah blah bing.
+    /// Blah blah bing.
+
+    /// Blah blah bing.
+    /// Blah blah bing.
+    /// Blah blah bing.
+    pub fn f2(self) {
+        (foo, bar)
+    }
+
+    #[another_attribute]
+    fn f3(self) -> Dog {}
+
+    /// Blah blah bing.
+
+    #[attrib1]
+    /// Blah blah bing.
+    #[attrib2]
+    // Another comment that needs rewrite because it's tooooooooooooooooooooooooooooooo
+    // loooooooooooong.
+    /// Blah blah bing.
+    fn f4(self) -> Cat {}
+
+    // We want spaces around `=`
+    #[cfg(feature = "nightly")]
+    fn f5(self) -> Monkey {}
+}
+
+// #984
+struct Foo {
+    #[derive(Clone, PartialEq, Debug, Deserialize, Serialize)]
+    foo: usize,
+}
+
+// #1668
+
+/// Default path (*nix)
+#[cfg(all(
+    unix,
+    not(target_os = "macos"),
+    not(target_os = "ios"),
+    not(target_os = "android")
+))]
+fn foo() {
+    #[cfg(target_os = "freertos")]
+    match port_id {
+        'a' | 'A' => GpioPort {
+            port_address: GPIO_A,
+        },
+        'b' | 'B' => GpioPort {
+            port_address: GPIO_B,
+        },
+        _ => panic!(),
+    }
+
+    #[cfg_attr(not(target_os = "freertos"), allow(unused_variables))]
+    let x = 3;
+}
+
+// #1777
+#[test]
+#[should_panic(expected = "(")]
+#[should_panic(expected = /* ( */ "(")]
+#[should_panic(/* ((((( */expected /* ((((( */= /* ((((( */ "("/* ((((( */)]
+#[should_panic(
+    /* (((((((( *//*
+    (((((((((()(((((((( */
+    expected = "("
+    // ((((((((
+)]
+fn foo() {}
+
+// #1799
+fn issue_1799() {
+    #[allow(unreachable_code)] // https://github.com/rust-lang/rust/issues/43336
+    Some(Err(error));
+
+    #[allow(unreachable_code)]
+    // https://github.com/rust-lang/rust/issues/43336
+    Some(Err(error));
+}
+
+// Formatting inner attributes
+fn inner_attributes() {
+    #![this_is_an_inner_attribute(foo)]
+
+    foo();
+}
+
+impl InnerAttributes() {
+    #![this_is_an_inner_attribute(foo)]
+
+    fn foo() {}
+}
+
+mod InnerAttributes {
+    #![this_is_an_inner_attribute(foo)]
+}
+
+fn attributes_on_statements() {
+    // Local
+    #[attr(on(local))]
+    let x = 3;
+
+    // Item
+    #[attr(on(item))]
+    use foo;
+
+    // Expr
+    #[attr(on(expr))]
+    {}
+
+    // Semi
+    #[attr(on(semi))]
+    foo();
+
+    // Mac
+    #[attr(on(mac))]
+    foo!();
+}
+
+// Large derives
+#[derive(
+    Add, Sub, Mul, Div, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Debug, Hash, Serialize, Mul,
+)]
+
+/// Foo bar baz
+
+#[derive(
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Clone,
+    Copy,
+    Eq,
+    PartialEq,
+    Ord,
+    PartialOrd,
+    Debug,
+    Hash,
+    Serialize,
+    Deserialize,
+)]
+pub struct HP(pub u8);
+
+// Long `#[doc = "..."]`
+struct A {
+    #[doc = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"]
+    b: i32,
+}
+
+// #2647
+#[cfg(
+    feature = "this_line_is_101_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+)]
+pub fn foo() {}
+
+// path attrs
+#[clippy::bar]
+#[clippy::bar(a, b, c)]
+pub fn foo() {}
+
+mod issue_2620 {
+    #[derive(Debug, StructOpt)]
+    #[structopt(about = "Display information about the character on FF Logs")]
+    pub struct Params {
+        #[structopt(help = "The server the character is on")]
+        server: String,
+        #[structopt(help = "The character's first name")]
+        first_name: String,
+        #[structopt(help = "The character's last name")]
+        last_name: String,
+        #[structopt(
+            short = "j",
+            long = "job",
+            help = "The job to look at",
+            parse(try_from_str)
+        )]
+        job: Option<Job>,
+    }
+}
+
+// #2969
+#[cfg(not(all(
+    feature = "std",
+    any(
+        target_os = "linux",
+        target_os = "android",
+        target_os = "netbsd",
+        target_os = "dragonfly",
+        target_os = "haiku",
+        target_os = "emscripten",
+        target_os = "solaris",
+        target_os = "cloudabi",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "redox",
+        target_os = "fuchsia",
+        windows,
+        all(target_arch = "wasm32", feature = "stdweb"),
+        all(target_arch = "wasm32", feature = "wasm-bindgen"),
+    )
+)))]
+type Os = NoSource;
+
+// #3313
+fn stmt_expr_attributes() {
+    let foo;
+    #[must_use]
+    foo = false;
+}
+
+// #3509
+fn issue3509() {
+    match MyEnum {
+        MyEnum::Option1 if cfg!(target_os = "windows") =>
+        #[cfg(target_os = "windows")]
+        {
+            1
+        }
+    }
+    match MyEnum {
+        MyEnum::Option1 if cfg!(target_os = "windows") =>
+        {
+            #[cfg(target_os = "windows")]
+            1
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/big-impl-block.rs b/src/tools/rustfmt/tests/target/big-impl-block.rs
new file mode 100644
index 0000000000000..e3728caba3ff2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/big-impl-block.rs
@@ -0,0 +1,82 @@
+// #1357
+impl<'a, Select, From, Distinct, Where, Order, Limit, Offset, Groupby, DB> InternalBoxedDsl<'a, DB>
+    for SelectStatement<Select, From, Distinct, Where, Order, Limit, Offset, GroupBy>
+where
+    DB: Backend,
+    Select: QueryFragment<DB> + SelectableExpression<From> + 'a,
+    Distinct: QueryFragment<DB> + 'a,
+    Where: Into<Option<Box<QueryFragment<DB> + 'a>>>,
+    Order: QueryFragment<DB> + 'a,
+    Limit: QueryFragment<DB> + 'a,
+    Offset: QueryFragment<DB> + 'a,
+{
+    type Output = BoxedSelectStatement<'a, Select::SqlTypeForSelect, From, DB>;
+
+    fn internal_into_boxed(self) -> Self::Output {
+        BoxedSelectStatement::new(
+            Box::new(self.select),
+            self.from,
+            Box::new(self.distinct),
+            self.where_clause.into(),
+            Box::new(self.order),
+            Box::new(self.limit),
+            Box::new(self.offset),
+        )
+    }
+}
+
+// #1369
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo
+    for Bar
+{
+    fn foo() {}
+}
+impl Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar
+{
+    fn foo() {}
+}
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar
+{
+    fn foo() {}
+}
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo
+    for Bar<
+        ExcessivelyLongGenericName,
+        ExcessivelyLongGenericName,
+        AnotherExcessivelyLongGenericName,
+    >
+{
+    fn foo() {}
+}
+impl Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar<
+        ExcessivelyLongGenericName,
+        ExcessivelyLongGenericName,
+        AnotherExcessivelyLongGenericName,
+    >
+{
+    fn foo() {}
+}
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar<
+        ExcessivelyLongGenericName,
+        ExcessivelyLongGenericName,
+        AnotherExcessivelyLongGenericName,
+    >
+{
+    fn foo() {}
+}
+
+// #1689
+impl<M, S, F, X> SubSelectDirect<M, S, F, X>
+where
+    M: select::Selector,
+    S: event::Stream,
+    F: for<'t> FnMut(transform::Api<'t, Stream<ContentStream<S>>>) -> transform::Api<'t, X>,
+    X: event::Stream,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/big-impl-visual.rs b/src/tools/rustfmt/tests/target/big-impl-visual.rs
new file mode 100644
index 0000000000000..04b0a83fd97ea
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/big-impl-visual.rs
@@ -0,0 +1,65 @@
+// rustfmt-indent_style: Visual
+
+// #1357
+impl<'a, Select, From, Distinct, Where, Order, Limit, Offset, Groupby, DB> InternalBoxedDsl<'a, DB>
+    for SelectStatement<Select, From, Distinct, Where, Order, Limit, Offset, GroupBy>
+    where DB: Backend,
+          Select: QueryFragment<DB> + SelectableExpression<From> + 'a,
+          Distinct: QueryFragment<DB> + 'a,
+          Where: Into<Option<Box<QueryFragment<DB> + 'a>>>,
+          Order: QueryFragment<DB> + 'a,
+          Limit: QueryFragment<DB> + 'a,
+          Offset: QueryFragment<DB> + 'a
+{
+    type Output = BoxedSelectStatement<'a, Select::SqlTypeForSelect, From, DB>;
+
+    fn internal_into_boxed(self) -> Self::Output {
+        BoxedSelectStatement::new(Box::new(self.select),
+                                  self.from,
+                                  Box::new(self.distinct),
+                                  self.where_clause.into(),
+                                  Box::new(self.order),
+                                  Box::new(self.limit),
+                                  Box::new(self.offset))
+    }
+}
+
+// #1369
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo
+    for Bar
+{
+    fn foo() {}
+}
+impl Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar
+{
+    fn foo() {}
+}
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar
+{
+    fn foo() {}
+}
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo
+    for Bar<ExcessivelyLongGenericName,
+            ExcessivelyLongGenericName,
+            AnotherExcessivelyLongGenericName>
+{
+    fn foo() {}
+}
+impl Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar<ExcessivelyLongGenericName,
+            ExcessivelyLongGenericName,
+            AnotherExcessivelyLongGenericName>
+{
+    fn foo() {}
+}
+impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
+    for Bar<ExcessivelyLongGenericName,
+            ExcessivelyLongGenericName,
+            AnotherExcessivelyLongGenericName>
+{
+    fn foo() {}
+}
diff --git a/src/tools/rustfmt/tests/target/binary-expr.rs b/src/tools/rustfmt/tests/target/binary-expr.rs
new file mode 100644
index 0000000000000..93115b282cafa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/binary-expr.rs
@@ -0,0 +1,16 @@
+// Binary expressions
+
+fn foo() {
+    // 100
+    let x = aaaaaaaaaa || bbbbbbbbbb || cccccccccc || dddddddddd && eeeeeeeeee || ffffffffff || ggg;
+    // 101
+    let x =
+        aaaaaaaaaa || bbbbbbbbbb || cccccccccc || dddddddddd && eeeeeeeeee || ffffffffff || gggg;
+    // 104
+    let x = aaaaaaaaaa
+        || bbbbbbbbbb
+        || cccccccccc
+        || dddddddddd && eeeeeeeeee
+        || ffffffffff
+        || gggggggg;
+}
diff --git a/src/tools/rustfmt/tests/target/break-and-continue.rs b/src/tools/rustfmt/tests/target/break-and-continue.rs
new file mode 100644
index 0000000000000..c01d8a0784556
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/break-and-continue.rs
@@ -0,0 +1,23 @@
+// break and continue formatting
+
+#![feature(loop_break_value)]
+
+fn main() {
+    'a: loop {
+        break 'a;
+    }
+
+    let mut done = false;
+    'b: while !done {
+        done = true;
+        continue 'b;
+    }
+
+    let x = loop {
+        break 5;
+    };
+
+    let x = 'c: loop {
+        break 'c 5;
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/catch.rs b/src/tools/rustfmt/tests/target/catch.rs
new file mode 100644
index 0000000000000..ffe694f8e7252
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/catch.rs
@@ -0,0 +1,22 @@
+// rustfmt-edition: 2018
+#![feature(try_blocks)]
+
+fn main() {
+    let x = try { foo()? };
+
+    let x = try /* Invisible comment */ { foo()? };
+
+    let x = try { unsafe { foo()? } };
+
+    let y = match (try { foo()? }) {
+        _ => (),
+    };
+
+    try {
+        foo()?;
+    };
+
+    try {
+        // Regular try block
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/arch/aarch64.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/aarch64.rs
new file mode 100644
index 0000000000000..91c51ed89e6ff
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/aarch64.rs
@@ -0,0 +1,98 @@
+//! Aarch64 run-time features.
+
+/// Checks if `aarch64` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal, stdsimd)]
+macro_rules! is_aarch64_feature_detected {
+    ("neon") => {
+        // FIXME: this should be removed once we rename Aarch64 neon to asimd
+        cfg!(target_feature = "neon") || $crate::detect::check_for($crate::detect::Feature::asimd)
+    };
+    ("asimd") => {
+        cfg!(target_feature = "neon") || $crate::detect::check_for($crate::detect::Feature::asimd)
+    };
+    ("pmull") => {
+        cfg!(target_feature = "pmull") || $crate::detect::check_for($crate::detect::Feature::pmull)
+    };
+    ("fp") => {
+        cfg!(target_feature = "fp") || $crate::detect::check_for($crate::detect::Feature::fp)
+    };
+    ("fp16") => {
+        cfg!(target_feature = "fp16") || $crate::detect::check_for($crate::detect::Feature::fp16)
+    };
+    ("sve") => {
+        cfg!(target_feature = "sve") || $crate::detect::check_for($crate::detect::Feature::sve)
+    };
+    ("crc") => {
+        cfg!(target_feature = "crc") || $crate::detect::check_for($crate::detect::Feature::crc)
+    };
+    ("crypto") => {
+        cfg!(target_feature = "crypto")
+            || $crate::detect::check_for($crate::detect::Feature::crypto)
+    };
+    ("lse") => {
+        cfg!(target_feature = "lse") || $crate::detect::check_for($crate::detect::Feature::lse)
+    };
+    ("rdm") => {
+        cfg!(target_feature = "rdm") || $crate::detect::check_for($crate::detect::Feature::rdm)
+    };
+    ("rcpc") => {
+        cfg!(target_feature = "rcpc") || $crate::detect::check_for($crate::detect::Feature::rcpc)
+    };
+    ("dotprod") => {
+        cfg!(target_feature = "dotprod")
+            || $crate::detect::check_for($crate::detect::Feature::dotprod)
+    };
+    ("ras") => {
+        compile_error!("\"ras\" feature cannot be detected at run-time")
+    };
+    ("v8.1a") => {
+        compile_error!("\"v8.1a\" feature cannot be detected at run-time")
+    };
+    ("v8.2a") => {
+        compile_error!("\"v8.2a\" feature cannot be detected at run-time")
+    };
+    ("v8.3a") => {
+        compile_error!("\"v8.3a\" feature cannot be detected at run-time")
+    };
+    ($t:tt,) => {
+        is_aarch64_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown aarch64 target feature: ", $t))
+    };
+}
+
+/// ARM Aarch64 CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// ARM Advanced SIMD (ASIMD)
+    asimd,
+    /// Polynomial Multiply
+    pmull,
+    /// Floating point support
+    fp,
+    /// Half-float support.
+    fp16,
+    /// Scalable Vector Extension (SVE)
+    sve,
+    /// CRC32 (Cyclic Redundancy Check)
+    crc,
+    /// Crypto: AES + PMULL + SHA1 + SHA2
+    crypto,
+    /// Atomics (Large System Extension)
+    lse,
+    /// Rounding Double Multiply (ASIMDRDM)
+    rdm,
+    /// Release consistent Processor consistent (RcPc)
+    rcpc,
+    /// Vector Dot-Product (ASIMDDP)
+    dotprod,
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/arch/arm.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/arm.rs
new file mode 100644
index 0000000000000..90c61fed8acc7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/arm.rs
@@ -0,0 +1,47 @@
+//! Run-time feature detection on ARM Aarch32.
+
+/// Checks if `arm` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal, stdsimd)]
+macro_rules! is_arm_feature_detected {
+    ("neon") => {
+        cfg!(target_feature = "neon") || $crate::detect::check_for($crate::detect::Feature::neon)
+    };
+    ("pmull") => {
+        cfg!(target_feature = "pmull") || $crate::detect::check_for($crate::detect::Feature::pmull)
+    };
+    ("v7") => {
+        compile_error!("\"v7\" feature cannot be detected at run-time")
+    };
+    ("vfp2") => {
+        compile_error!("\"vfp2\" feature cannot be detected at run-time")
+    };
+    ("vfp3") => {
+        compile_error!("\"vfp3\" feature cannot be detected at run-time")
+    };
+    ("vfp4") => {
+        compile_error!("\"vfp4\" feature cannot be detected at run-time")
+    };
+    ($t:tt,) => {
+        is_arm_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown arm target feature: ", $t))
+    };
+}
+
+/// ARM CPU Feature enum. Each variant denotes a position in a bitset for a
+/// particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// ARM Advanced SIMD (NEON) - Aarch32
+    neon,
+    /// Polynomial Multiply
+    pmull,
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/arch/mips.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/mips.rs
new file mode 100644
index 0000000000000..2397a090602c1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/mips.rs
@@ -0,0 +1,30 @@
+//! Run-time feature detection on MIPS.
+
+/// Checks if `mips` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal, stdsimd)]
+macro_rules! is_mips_feature_detected {
+    ("msa") => {
+        cfg!(target_feature = "msa") || $crate::detect::check_for($crate::detect::Feature::msa)
+    };
+    ($t:tt,) => {
+        is_mips_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown mips target feature: ", $t))
+    };
+}
+
+/// MIPS CPU Feature enum. Each variant denotes a position in a bitset for a
+/// particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// MIPS SIMD Architecture (MSA)
+    msa,
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/arch/mips64.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/mips64.rs
new file mode 100644
index 0000000000000..d378defc5dfd1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/mips64.rs
@@ -0,0 +1,30 @@
+//! Run-time feature detection on MIPS64.
+
+/// Checks if `mips64` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal, stdsimd)]
+macro_rules! is_mips64_feature_detected {
+    ("msa") => {
+        cfg!(target_feature = "msa") || $crate::detect::check_for($crate::detect::Feature::msa)
+    };
+    ($t:tt,) => {
+        is_mips64_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown mips64 target feature: ", $t))
+    };
+}
+
+/// MIPS64 CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// MIPS SIMD Architecture (MSA)
+    msa,
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/arch/powerpc.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/powerpc.rs
new file mode 100644
index 0000000000000..e7a9daac68873
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/powerpc.rs
@@ -0,0 +1,42 @@
+//! Run-time feature detection on PowerPC.
+
+/// Checks if `powerpc` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal, stdsimd)]
+macro_rules! is_powerpc_feature_detected {
+    ("altivec") => {
+        cfg!(target_feature = "altivec")
+            || $crate::detect::check_for($crate::detect::Feature::altivec)
+    };
+    ("vsx") => {
+        cfg!(target_feature = "vsx") || $crate::detect::check_for($crate::detect::Feature::vsx)
+    };
+    ("power8") => {
+        cfg!(target_feature = "power8")
+            || $crate::detect::check_for($crate::detect::Feature::power8)
+    };
+    ($t:tt,) => {
+        is_powerpc_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown powerpc target feature: ", $t))
+    };
+}
+
+/// PowerPC CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// Altivec
+    altivec,
+    /// VSX
+    vsx,
+    /// Power8
+    power8,
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/arch/powerpc64.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/powerpc64.rs
new file mode 100644
index 0000000000000..c102202695ec5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/powerpc64.rs
@@ -0,0 +1,42 @@
+//! Run-time feature detection on PowerPC64.
+
+/// Checks if `powerpc64` feature is enabled.
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+#[allow_internal_unstable(stdsimd_internal, stdsimd)]
+macro_rules! is_powerpc64_feature_detected {
+    ("altivec") => {
+        cfg!(target_feature = "altivec")
+            || $crate::detect::check_for($crate::detect::Feature::altivec)
+    };
+    ("vsx") => {
+        cfg!(target_feature = "vsx") || $crate::detect::check_for($crate::detect::Feature::vsx)
+    };
+    ("power8") => {
+        cfg!(target_feature = "power8")
+            || $crate::detect::check_for($crate::detect::Feature::power8)
+    };
+    ($t:tt,) => {
+        is_powerpc64_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown powerpc64 target feature: ", $t))
+    };
+}
+
+/// PowerPC64 CPU Feature enum. Each variant denotes a position in a bitset
+/// for a particular feature.
+///
+/// PLEASE: do not use this, it is an implementation detail subject to change.
+#[doc(hidden)]
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// Altivec
+    altivec,
+    /// VSX
+    vsx,
+    /// Power8
+    power8,
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/arch/x86.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/x86.rs
new file mode 100644
index 0000000000000..9219a4a577f9a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/arch/x86.rs
@@ -0,0 +1,333 @@
+//! This module implements minimal run-time feature detection for x86.
+//!
+//! The features are detected using the `detect_features` function below.
+//! This function uses the CPUID instruction to read the feature flags from the
+//! CPU and encodes them in an `usize` where each bit position represents
+//! whether a feature is available (bit is set) or unavaiable (bit is cleared).
+//!
+//! The enum `Feature` is used to map bit positions to feature names, and the
+//! the `__crate::detect::check_for!` macro is used to map string literals (e.g.,
+//! "avx") to these bit positions (e.g., `Feature::avx`).
+//!
+//! The run-time feature detection is performed by the
+//! `__crate::detect::check_for(Feature) -> bool` function. On its first call,
+//! this functions queries the CPU for the available features and stores them
+//! in a global `AtomicUsize` variable. The query is performed by just checking
+//! whether the feature bit in this global variable is set or cleared.
+
+/// A macro to test at *runtime* whether a CPU feature is available on
+/// x86/x86-64 platforms.
+///
+/// This macro is provided in the standard library and will detect at runtime
+/// whether the specified CPU feature is detected. This does **not** resolve at
+/// compile time unless the specified feature is already enabled for the entire
+/// crate. Runtime detection currently relies mostly on the `cpuid` instruction.
+///
+/// This macro only takes one argument which is a string literal of the feature
+/// being tested for. The feature names supported are the lowercase versions of
+/// the ones defined by Intel in [their documentation][docs].
+///
+/// ## Supported arguments
+///
+/// This macro supports the same names that `#[target_feature]` supports. Unlike
+/// `#[target_feature]`, however, this macro does not support names separated
+/// with a comma. Instead testing for multiple features must be done through
+/// separate macro invocations for now.
+///
+/// Supported arguments are:
+///
+/// * `"aes"`
+/// * `"pclmulqdq"`
+/// * `"rdrand"`
+/// * `"rdseed"`
+/// * `"tsc"`
+/// * `"mmx"`
+/// * `"sse"`
+/// * `"sse2"`
+/// * `"sse3"`
+/// * `"ssse3"`
+/// * `"sse4.1"`
+/// * `"sse4.2"`
+/// * `"sse4a"`
+/// * `"sha"`
+/// * `"avx"`
+/// * `"avx2"`
+/// * `"avx512f"`
+/// * `"avx512cd"`
+/// * `"avx512er"`
+/// * `"avx512pf"`
+/// * `"avx512bw"`
+/// * `"avx512dq"`
+/// * `"avx512vl"`
+/// * `"avx512ifma"`
+/// * `"avx512vbmi"`
+/// * `"avx512vpopcntdq"`
+/// * `"f16c"`
+/// * `"fma"`
+/// * `"bmi1"`
+/// * `"bmi2"`
+/// * `"abm"`
+/// * `"lzcnt"`
+/// * `"tbm"`
+/// * `"popcnt"`
+/// * `"fxsr"`
+/// * `"xsave"`
+/// * `"xsaveopt"`
+/// * `"xsaves"`
+/// * `"xsavec"`
+/// * `"adx"`
+/// * `"rtm"`
+///
+/// [docs]: https://software.intel.com/sites/landingpage/IntrinsicsGuide
+#[macro_export]
+#[stable(feature = "simd_x86", since = "1.27.0")]
+#[allow_internal_unstable(stdsimd_internal, stdsimd)]
+macro_rules! is_x86_feature_detected {
+    ("aes") => {
+        cfg!(target_feature = "aes") || $crate::detect::check_for($crate::detect::Feature::aes)
+    };
+    ("pclmulqdq") => {
+        cfg!(target_feature = "pclmulqdq")
+            || $crate::detect::check_for($crate::detect::Feature::pclmulqdq)
+    };
+    ("rdrand") => {
+        cfg!(target_feature = "rdrand")
+            || $crate::detect::check_for($crate::detect::Feature::rdrand)
+    };
+    ("rdseed") => {
+        cfg!(target_feature = "rdseed")
+            || $crate::detect::check_for($crate::detect::Feature::rdseed)
+    };
+    ("tsc") => {
+        cfg!(target_feature = "tsc") || $crate::detect::check_for($crate::detect::Feature::tsc)
+    };
+    ("mmx") => {
+        cfg!(target_feature = "mmx") || $crate::detect::check_for($crate::detect::Feature::mmx)
+    };
+    ("sse") => {
+        cfg!(target_feature = "sse") || $crate::detect::check_for($crate::detect::Feature::sse)
+    };
+    ("sse2") => {
+        cfg!(target_feature = "sse2") || $crate::detect::check_for($crate::detect::Feature::sse2)
+    };
+    ("sse3") => {
+        cfg!(target_feature = "sse3") || $crate::detect::check_for($crate::detect::Feature::sse3)
+    };
+    ("ssse3") => {
+        cfg!(target_feature = "ssse3") || $crate::detect::check_for($crate::detect::Feature::ssse3)
+    };
+    ("sse4.1") => {
+        cfg!(target_feature = "sse4.1")
+            || $crate::detect::check_for($crate::detect::Feature::sse4_1)
+    };
+    ("sse4.2") => {
+        cfg!(target_feature = "sse4.2")
+            || $crate::detect::check_for($crate::detect::Feature::sse4_2)
+    };
+    ("sse4a") => {
+        cfg!(target_feature = "sse4a") || $crate::detect::check_for($crate::detect::Feature::sse4a)
+    };
+    ("sha") => {
+        cfg!(target_feature = "sha") || $crate::detect::check_for($crate::detect::Feature::sha)
+    };
+    ("avx") => {
+        cfg!(target_feature = "avx") || $crate::detect::check_for($crate::detect::Feature::avx)
+    };
+    ("avx2") => {
+        cfg!(target_feature = "avx2") || $crate::detect::check_for($crate::detect::Feature::avx2)
+    };
+    ("avx512f") => {
+        cfg!(target_feature = "avx512f")
+            || $crate::detect::check_for($crate::detect::Feature::avx512f)
+    };
+    ("avx512cd") => {
+        cfg!(target_feature = "avx512cd")
+            || $crate::detect::check_for($crate::detect::Feature::avx512cd)
+    };
+    ("avx512er") => {
+        cfg!(target_feature = "avx512er")
+            || $crate::detect::check_for($crate::detect::Feature::avx512er)
+    };
+    ("avx512pf") => {
+        cfg!(target_feature = "avx512pf")
+            || $crate::detect::check_for($crate::detect::Feature::avx512pf)
+    };
+    ("avx512bw") => {
+        cfg!(target_feature = "avx512bw")
+            || $crate::detect::check_for($crate::detect::Feature::avx512bw)
+    };
+    ("avx512dq") => {
+        cfg!(target_feature = "avx512dq")
+            || $crate::detect::check_for($crate::detect::Feature::avx512dq)
+    };
+    ("avx512vl") => {
+        cfg!(target_Feature = "avx512vl")
+            || $crate::detect::check_for($crate::detect::Feature::avx512vl)
+    };
+    ("avx512ifma") => {
+        cfg!(target_feature = "avx512ifma")
+            || $crate::detect::check_for($crate::detect::Feature::avx512_ifma)
+    };
+    ("avx512vbmi") => {
+        cfg!(target_feature = "avx512vbmi")
+            || $crate::detect::check_for($crate::detect::Feature::avx512_vbmi)
+    };
+    ("avx512vpopcntdq") => {
+        cfg!(target_feature = "avx512vpopcntdq")
+            || $crate::detect::check_for($crate::detect::Feature::avx512_vpopcntdq)
+    };
+    ("f16c") => {
+        cfg!(target_feature = "f16c") || $crate::detect::check_for($crate::detect::Feature::f16c)
+    };
+    ("fma") => {
+        cfg!(target_feature = "fma") || $crate::detect::check_for($crate::detect::Feature::fma)
+    };
+    ("bmi1") => {
+        cfg!(target_feature = "bmi1") || $crate::detect::check_for($crate::detect::Feature::bmi)
+    };
+    ("bmi2") => {
+        cfg!(target_feature = "bmi2") || $crate::detect::check_for($crate::detect::Feature::bmi2)
+    };
+    ("abm") => {
+        cfg!(target_feature = "abm") || $crate::detect::check_for($crate::detect::Feature::abm)
+    };
+    ("lzcnt") => {
+        cfg!(target_feature = "lzcnt") || $crate::detect::check_for($crate::detect::Feature::abm)
+    };
+    ("tbm") => {
+        cfg!(target_feature = "tbm") || $crate::detect::check_for($crate::detect::Feature::tbm)
+    };
+    ("popcnt") => {
+        cfg!(target_feature = "popcnt")
+            || $crate::detect::check_for($crate::detect::Feature::popcnt)
+    };
+    ("fxsr") => {
+        cfg!(target_feature = "fxsr") || $crate::detect::check_for($crate::detect::Feature::fxsr)
+    };
+    ("xsave") => {
+        cfg!(target_feature = "xsave") || $crate::detect::check_for($crate::detect::Feature::xsave)
+    };
+    ("xsaveopt") => {
+        cfg!(target_feature = "xsaveopt")
+            || $crate::detect::check_for($crate::detect::Feature::xsaveopt)
+    };
+    ("xsaves") => {
+        cfg!(target_feature = "xsaves")
+            || $crate::detect::check_for($crate::detect::Feature::xsaves)
+    };
+    ("xsavec") => {
+        cfg!(target_feature = "xsavec")
+            || $crate::detect::check_for($crate::detect::Feature::xsavec)
+    };
+    ("cmpxchg16b") => {
+        cfg!(target_feature = "cmpxchg16b")
+            || $crate::detect::check_for($crate::detect::Feature::cmpxchg16b)
+    };
+    ("adx") => {
+        cfg!(target_feature = "adx") || $crate::detect::check_for($crate::detect::Feature::adx)
+    };
+    ("rtm") => {
+        cfg!(target_feature = "rtm") || $crate::detect::check_for($crate::detect::Feature::rtm)
+    };
+    ($t:tt,) => {
+        is_x86_feature_detected!($t);
+    };
+    ($t:tt) => {
+        compile_error!(concat!("unknown target feature: ", $t))
+    };
+}
+
+/// X86 CPU Feature enum. Each variant denotes a position in a bitset for a
+/// particular feature.
+///
+/// This is an unstable implementation detail subject to change.
+#[allow(non_camel_case_types)]
+#[repr(u8)]
+#[doc(hidden)]
+#[unstable(feature = "stdsimd_internal", issue = "0")]
+pub enum Feature {
+    /// AES (Advanced Encryption Standard New Instructions AES-NI)
+    aes,
+    /// CLMUL (Carry-less Multiplication)
+    pclmulqdq,
+    /// RDRAND
+    rdrand,
+    /// RDSEED
+    rdseed,
+    /// TSC (Time Stamp Counter)
+    tsc,
+    /// MMX
+    mmx,
+    /// SSE (Streaming SIMD Extensions)
+    sse,
+    /// SSE2 (Streaming SIMD Extensions 2)
+    sse2,
+    /// SSE3 (Streaming SIMD Extensions 3)
+    sse3,
+    /// SSSE3 (Supplemental Streaming SIMD Extensions 3)
+    ssse3,
+    /// SSE4.1 (Streaming SIMD Extensions 4.1)
+    sse4_1,
+    /// SSE4.2 (Streaming SIMD Extensions 4.2)
+    sse4_2,
+    /// SSE4a (Streaming SIMD Extensions 4a)
+    sse4a,
+    /// SHA
+    sha,
+    /// AVX (Advanced Vector Extensions)
+    avx,
+    /// AVX2 (Advanced Vector Extensions 2)
+    avx2,
+    /// AVX-512 F (Foundation)
+    avx512f,
+    /// AVX-512 CD (Conflict Detection Instructions)
+    avx512cd,
+    /// AVX-512 ER (Exponential and Reciprocal Instructions)
+    avx512er,
+    /// AVX-512 PF (Prefetch Instructions)
+    avx512pf,
+    /// AVX-512 BW (Byte and Word Instructions)
+    avx512bw,
+    /// AVX-512 DQ (Doubleword and Quadword)
+    avx512dq,
+    /// AVX-512 VL (Vector Length Extensions)
+    avx512vl,
+    /// AVX-512 IFMA (Integer Fused Multiply Add)
+    avx512_ifma,
+    /// AVX-512 VBMI (Vector Byte Manipulation Instructions)
+    avx512_vbmi,
+    /// AVX-512 VPOPCNTDQ (Vector Population Count Doubleword and
+    /// Quadword)
+    avx512_vpopcntdq,
+    /// F16C (Conversions between IEEE-754 `binary16` and `binary32` formats)
+    f16c,
+    /// FMA (Fused Multiply Add)
+    fma,
+    /// BMI1 (Bit Manipulation Instructions 1)
+    bmi,
+    /// BMI1 (Bit Manipulation Instructions 2)
+    bmi2,
+    /// ABM (Advanced Bit Manipulation) on AMD / LZCNT (Leading Zero
+    /// Count) on Intel
+    abm,
+    /// TBM (Trailing Bit Manipulation)
+    tbm,
+    /// POPCNT (Population Count)
+    popcnt,
+    /// FXSR (Floating-point context fast save and restor)
+    fxsr,
+    /// XSAVE (Save Processor Extended States)
+    xsave,
+    /// XSAVEOPT (Save Processor Extended States Optimized)
+    xsaveopt,
+    /// XSAVES (Save Processor Extended States Supervisor)
+    xsaves,
+    /// XSAVEC (Save Processor Extended States Compacted)
+    xsavec,
+    /// CMPXCH16B, a 16-byte compare-and-swap instruction
+    cmpxchg16b,
+    /// ADX, Intel ADX (Multi-Precision Add-Carry Instruction Extensions)
+    adx,
+    /// RTM, Intel (Restricted Transactional Memory)
+    rtm,
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/bit.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/bit.rs
new file mode 100644
index 0000000000000..578f0b16b742a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/bit.rs
@@ -0,0 +1,9 @@
+//! Bit manipulation utilities.
+
+/// Tests the `bit` of `x`.
+#[allow(dead_code)]
+#[inline]
+pub(crate) fn test(x: usize, bit: u32) -> bool {
+    debug_assert!(bit < 32, "bit index out-of-bounds");
+    x & (1 << bit) != 0
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/cache.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/cache.rs
new file mode 100644
index 0000000000000..92bc4b58d1677
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/cache.rs
@@ -0,0 +1,164 @@
+//! Caches run-time feature detection so that it only needs to be computed
+//! once.
+
+#![allow(dead_code)] // not used on all platforms
+
+use crate::sync::atomic::Ordering;
+
+#[cfg(target_pointer_width = "64")]
+use crate::sync::atomic::AtomicU64;
+
+#[cfg(target_pointer_width = "32")]
+use crate::sync::atomic::AtomicU32;
+
+/// Sets the `bit` of `x`.
+#[inline]
+const fn set_bit(x: u64, bit: u32) -> u64 {
+    x | 1 << bit
+}
+
+/// Tests the `bit` of `x`.
+#[inline]
+const fn test_bit(x: u64, bit: u32) -> bool {
+    x & (1 << bit) != 0
+}
+
+/// Maximum number of features that can be cached.
+const CACHE_CAPACITY: u32 = 63;
+
+/// This type is used to initialize the cache
+#[derive(Copy, Clone)]
+pub(crate) struct Initializer(u64);
+
+#[allow(clippy::use_self)]
+impl Default for Initializer {
+    fn default() -> Self {
+        Initializer(0)
+    }
+}
+
+impl Initializer {
+    /// Tests the `bit` of the cache.
+    #[allow(dead_code)]
+    #[inline]
+    pub(crate) fn test(self, bit: u32) -> bool {
+        // FIXME: this way of making sure that the cache is large enough is
+        // brittle.
+        debug_assert!(
+            bit < CACHE_CAPACITY,
+            "too many features, time to increase the cache size!"
+        );
+        test_bit(self.0, bit)
+    }
+
+    /// Sets the `bit` of the cache.
+    #[inline]
+    pub(crate) fn set(&mut self, bit: u32) {
+        // FIXME: this way of making sure that the cache is large enough is
+        // brittle.
+        debug_assert!(
+            bit < CACHE_CAPACITY,
+            "too many features, time to increase the cache size!"
+        );
+        let v = self.0;
+        self.0 = set_bit(v, bit);
+    }
+}
+
+/// This global variable is a cache of the features supported by the CPU.
+static CACHE: Cache = Cache::uninitialized();
+
+/// Feature cache with capacity for `CACHE_CAPACITY` features.
+///
+/// Note: the last feature bit is used to represent an
+/// uninitialized cache.
+#[cfg(target_pointer_width = "64")]
+struct Cache(AtomicU64);
+
+#[cfg(target_pointer_width = "64")]
+#[allow(clippy::use_self)]
+impl Cache {
+    /// Creates an uninitialized cache.
+    #[allow(clippy::declare_interior_mutable_const)]
+    const fn uninitialized() -> Self {
+        Cache(AtomicU64::new(u64::max_value()))
+    }
+    /// Is the cache uninitialized?
+    #[inline]
+    pub(crate) fn is_uninitialized(&self) -> bool {
+        self.0.load(Ordering::Relaxed) == u64::max_value()
+    }
+
+    /// Is the `bit` in the cache set?
+    #[inline]
+    pub(crate) fn test(&self, bit: u32) -> bool {
+        test_bit(CACHE.0.load(Ordering::Relaxed), bit)
+    }
+
+    /// Initializes the cache.
+    #[inline]
+    pub(crate) fn initialize(&self, value: Initializer) {
+        self.0.store(value.0, Ordering::Relaxed);
+    }
+}
+
+/// Feature cache with capacity for `CACHE_CAPACITY` features.
+///
+/// Note: the last feature bit is used to represent an
+/// uninitialized cache.
+#[cfg(target_pointer_width = "32")]
+struct Cache(AtomicU32, AtomicU32);
+
+#[cfg(target_pointer_width = "32")]
+impl Cache {
+    /// Creates an uninitialized cache.
+    const fn uninitialized() -> Self {
+        Cache(
+            AtomicU32::new(u32::max_value()),
+            AtomicU32::new(u32::max_value()),
+        )
+    }
+    /// Is the cache uninitialized?
+    #[inline]
+    pub(crate) fn is_uninitialized(&self) -> bool {
+        self.1.load(Ordering::Relaxed) == u32::max_value()
+    }
+
+    /// Is the `bit` in the cache set?
+    #[inline]
+    pub(crate) fn test(&self, bit: u32) -> bool {
+        if bit < 32 {
+            test_bit(CACHE.0.load(Ordering::Relaxed) as u64, bit)
+        } else {
+            test_bit(CACHE.1.load(Ordering::Relaxed) as u64, bit - 32)
+        }
+    }
+
+    /// Initializes the cache.
+    #[inline]
+    pub(crate) fn initialize(&self, value: Initializer) {
+        let lo: u32 = value.0 as u32;
+        let hi: u32 = (value.0 >> 32) as u32;
+        self.0.store(lo, Ordering::Relaxed);
+        self.1.store(hi, Ordering::Relaxed);
+    }
+}
+
+/// Tests the `bit` of the storage. If the storage has not been initialized,
+/// initializes it with the result of `f()`.
+///
+/// On its first invocation, it detects the CPU features and caches them in the
+/// `CACHE` global variable as an `AtomicU64`.
+///
+/// It uses the `Feature` variant to index into this variable as a bitset. If
+/// the bit is set, the feature is enabled, and otherwise it is disabled.
+#[inline]
+pub(crate) fn test<F>(bit: u32, f: F) -> bool
+where
+    F: FnOnce() -> Initializer,
+{
+    if CACHE.is_uninitialized() {
+        CACHE.initialize(f());
+    }
+    CACHE.test(bit)
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/error_macros.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/error_macros.rs
new file mode 100644
index 0000000000000..6769757ed9331
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/error_macros.rs
@@ -0,0 +1,150 @@
+//! The `is_{target_arch}_feature_detected!` macro are only available on their
+//! architecture. These macros provide a better error messages when the user
+//! attempts to call them in a different architecture.
+
+/// Prevents compilation if `is_x86_feature_detected` is used somewhere
+/// else than `x86` and `x86_64` targets.
+#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_x86_feature_detected {
+    ($t: tt) => {
+        compile_error!(
+            r#"
+        is_x86_feature_detected can only be used on x86 and x86_64 targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
+                if is_x86_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_arm_feature_detected` is used somewhere else
+/// than `ARM` targets.
+#[cfg(not(target_arch = "arm"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_arm_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+        is_arm_feature_detected can only be used on ARM targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "arm")] {
+                if is_arm_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_aarch64_feature_detected` is used somewhere else
+/// than `aarch64` targets.
+#[cfg(not(target_arch = "aarch64"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_aarch64_feature_detected {
+    ($t: tt) => {
+        compile_error!(
+            r#"
+        is_aarch64_feature_detected can only be used on AArch64 targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "aarch64")] {
+                if is_aarch64_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_powerpc_feature_detected` is used somewhere else
+/// than `PowerPC` targets.
+#[cfg(not(target_arch = "powerpc"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_powerpc_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+is_powerpc_feature_detected can only be used on PowerPC targets.
+You can prevent it from being used in other architectures by
+guarding it behind a cfg(target_arch) as follows:
+
+    #[cfg(target_arch = "powerpc")] {
+        if is_powerpc_feature_detected(...) { ... }
+    }
+"#
+        )
+    };
+}
+
+/// Prevents compilation if `is_powerpc64_feature_detected` is used somewhere
+/// else than `PowerPC64` targets.
+#[cfg(not(target_arch = "powerpc64"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_powerpc64_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+is_powerpc64_feature_detected can only be used on PowerPC64 targets.
+You can prevent it from being used in other architectures by
+guarding it behind a cfg(target_arch) as follows:
+
+    #[cfg(target_arch = "powerpc64")] {
+        if is_powerpc64_feature_detected(...) { ... }
+    }
+"#
+        )
+    };
+}
+
+/// Prevents compilation if `is_mips_feature_detected` is used somewhere else
+/// than `MIPS` targets.
+#[cfg(not(target_arch = "mips"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_mips_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+        is_mips_feature_detected can only be used on MIPS targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "mips")] {
+                if is_mips_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
+
+/// Prevents compilation if `is_mips64_feature_detected` is used somewhere else
+/// than `MIPS64` targets.
+#[cfg(not(target_arch = "mips64"))]
+#[macro_export]
+#[unstable(feature = "stdsimd", issue = "27731")]
+macro_rules! is_mips64_feature_detected {
+    ($t:tt) => {
+        compile_error!(
+            r#"
+        is_mips64_feature_detected can only be used on MIPS64 targets.
+        You can prevent it from being used in other architectures by
+        guarding it behind a cfg(target_arch) as follows:
+
+            #[cfg(target_arch = "mips64")] {
+                if is_mips64_feature_detected(...) { ... }
+            }
+        "#
+        )
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/mod.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/mod.rs
new file mode 100644
index 0000000000000..f446e88eedc8c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/mod.rs
@@ -0,0 +1,85 @@
+//! This module implements run-time feature detection.
+//!
+//! The `is_{arch}_feature_detected!("feature-name")` macros take the name of a
+//! feature as a string-literal, and return a boolean indicating whether the
+//! feature is enabled at run-time or not.
+//!
+//! These macros do two things:
+//! * map the string-literal into an integer stored as a `Feature` enum,
+//! * call a `os::check_for(x: Feature)` function that returns `true` if the
+//! feature is enabled.
+//!
+//! The `Feature` enums are also implemented in the `arch/{target_arch}.rs`
+//! modules.
+//!
+//! The `check_for` functions are, in general, Operating System dependent. Most
+//! architectures do not allow user-space programs to query the feature bits
+//! due to security concerns (x86 is the big exception). These functions are
+//! implemented in the `os/{target_os}.rs` modules.
+
+#[macro_use]
+mod error_macros;
+
+cfg_if! {
+    if #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
+        #[path = "arch/x86.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "arm")] {
+        #[path = "arch/arm.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "aarch64")] {
+        #[path = "arch/aarch64.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "powerpc")] {
+        #[path = "arch/powerpc.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "powerpc64")] {
+        #[path = "arch/powerpc64.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "mips")] {
+        #[path = "arch/mips.rs"]
+        #[macro_use]
+        mod arch;
+    } else if #[cfg(target_arch = "mips64")] {
+        #[path = "arch/mips64.rs"]
+        #[macro_use]
+        mod arch;
+    } else {
+        // Unimplemented architecture:
+        mod arch {
+            pub enum Feature {
+                Null
+            }
+        }
+    }
+}
+pub use self::arch::Feature;
+
+mod bit;
+mod cache;
+
+cfg_if! {
+    if #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
+        // On x86/x86_64 no OS specific functionality is required.
+        #[path = "os/x86.rs"]
+        mod os;
+    } else if #[cfg(all(target_os = "linux", feature = "use_std"))] {
+        #[path = "os/linux/mod.rs"]
+        mod os;
+    } else if #[cfg(target_os = "freebsd")] {
+        #[cfg(target_arch = "aarch64")]
+        #[path = "os/aarch64.rs"]
+        mod aarch64;
+        #[path = "os/freebsd/mod.rs"]
+        mod os;
+    } else {
+        #[path = "os/other.rs"]
+        mod os;
+    }
+}
+pub use self::os::check_for;
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/aarch64.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/aarch64.rs
new file mode 100644
index 0000000000000..9adc938a26434
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/aarch64.rs
@@ -0,0 +1,88 @@
+//! Run-time feature detection for Aarch64 on any OS that emulates the mrs instruction.
+//!
+//! On FreeBSD >= 12.0, Linux >= 4.11 and other operating systems, it is possible to use
+//! privileged system registers from userspace to check CPU feature support.
+//!
+//! AArch64 system registers ID_AA64ISAR0_EL1, ID_AA64PFR0_EL1, ID_AA64ISAR1_EL1
+//! have bits dedicated to features like AdvSIMD, CRC32, AES, atomics (LSE), etc.
+//! Each part of the register indicates the level of support for a certain feature, e.g.
+//! when ID_AA64ISAR0_EL1\[7:4\] is >= 1, AES is supported; when it's >= 2, PMULL is supported.
+//!
+//! For proper support of [SoCs where different cores have different capabilities](https://medium.com/@jadr2ddude/a-big-little-problem-a-tale-of-big-little-gone-wrong-e7778ce744bb),
+//! the OS has to always report only the features supported by all cores, like [FreeBSD does](https://reviews.freebsd.org/D17137#393947).
+//!
+//! References:
+//!
+//! - [Zircon implementation](https://fuchsia.googlesource.com/zircon/+/master/kernel/arch/arm64/feature.cpp)
+//! - [Linux documentation](https://www.kernel.org/doc/Documentation/arm64/cpu-feature-registers.txt)
+
+use crate::detect::{cache, Feature};
+
+/// Try to read the features from the system registers.
+///
+/// This will cause SIGILL if the current OS is not trapping the mrs instruction.
+pub(crate) fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+
+    {
+        let mut enable_feature = |f, enable| {
+            if enable {
+                value.set(f as u32);
+            }
+        };
+
+        // ID_AA64ISAR0_EL1 - Instruction Set Attribute Register 0
+        let aa64isar0: u64;
+        unsafe {
+            asm!("mrs $0, ID_AA64ISAR0_EL1" : "=r"(aa64isar0));
+        }
+
+        let aes = bits_shift(aa64isar0, 7, 4) >= 1;
+        let pmull = bits_shift(aa64isar0, 7, 4) >= 2;
+        let sha1 = bits_shift(aa64isar0, 11, 8) >= 1;
+        let sha2 = bits_shift(aa64isar0, 15, 12) >= 1;
+        enable_feature(Feature::pmull, pmull);
+        // Crypto is specified as AES + PMULL + SHA1 + SHA2 per LLVM/hosts.cpp
+        enable_feature(Feature::crypto, aes && pmull && sha1 && sha2);
+        enable_feature(Feature::lse, bits_shift(aa64isar0, 23, 20) >= 1);
+        enable_feature(Feature::crc, bits_shift(aa64isar0, 19, 16) >= 1);
+
+        // ID_AA64PFR0_EL1 - Processor Feature Register 0
+        let aa64pfr0: u64;
+        unsafe {
+            asm!("mrs $0, ID_AA64PFR0_EL1" : "=r"(aa64pfr0));
+        }
+
+        let fp = bits_shift(aa64pfr0, 19, 16) < 0xF;
+        let fphp = bits_shift(aa64pfr0, 19, 16) >= 1;
+        let asimd = bits_shift(aa64pfr0, 23, 20) < 0xF;
+        let asimdhp = bits_shift(aa64pfr0, 23, 20) >= 1;
+        enable_feature(Feature::fp, fp);
+        enable_feature(Feature::fp16, fphp);
+        // SIMD support requires float support - if half-floats are
+        // supported, it also requires half-float support:
+        enable_feature(Feature::asimd, fp && asimd && (!fphp | asimdhp));
+        // SIMD extensions require SIMD support:
+        enable_feature(Feature::rdm, asimd && bits_shift(aa64isar0, 31, 28) >= 1);
+        enable_feature(
+            Feature::dotprod,
+            asimd && bits_shift(aa64isar0, 47, 44) >= 1,
+        );
+        enable_feature(Feature::sve, asimd && bits_shift(aa64pfr0, 35, 32) >= 1);
+
+        // ID_AA64ISAR1_EL1 - Instruction Set Attribute Register 1
+        let aa64isar1: u64;
+        unsafe {
+            asm!("mrs $0, ID_AA64ISAR1_EL1" : "=r"(aa64isar1));
+        }
+
+        enable_feature(Feature::rcpc, bits_shift(aa64isar1, 23, 20) >= 1);
+    }
+
+    value
+}
+
+#[inline]
+fn bits_shift(x: u64, high: usize, low: usize) -> u64 {
+    (x >> low) & ((1 << (high - low + 1)) - 1)
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/aarch64.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/aarch64.rs
new file mode 100644
index 0000000000000..97fe40f80a46c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/aarch64.rs
@@ -0,0 +1,28 @@
+//! Run-time feature detection for Aarch64 on FreeBSD.
+
+use super::super::aarch64::detect_features;
+use crate::detect::{cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn dump() {
+        println!("asimd: {:?}", is_aarch64_feature_detected!("asimd"));
+        println!("pmull: {:?}", is_aarch64_feature_detected!("pmull"));
+        println!("fp: {:?}", is_aarch64_feature_detected!("fp"));
+        println!("fp16: {:?}", is_aarch64_feature_detected!("fp16"));
+        println!("sve: {:?}", is_aarch64_feature_detected!("sve"));
+        println!("crc: {:?}", is_aarch64_feature_detected!("crc"));
+        println!("crypto: {:?}", is_aarch64_feature_detected!("crypto"));
+        println!("lse: {:?}", is_aarch64_feature_detected!("lse"));
+        println!("rdm: {:?}", is_aarch64_feature_detected!("rdm"));
+        println!("rcpc: {:?}", is_aarch64_feature_detected!("rcpc"));
+        println!("dotprod: {:?}", is_aarch64_feature_detected!("dotprod"));
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/arm.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/arm.rs
new file mode 100644
index 0000000000000..7aa040075e04a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/arm.rs
@@ -0,0 +1,27 @@
+//! Run-time feature detection for ARM on FreeBSD
+
+use super::auxvec;
+use crate::detect::{cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::neon, auxv.hwcap & 0x00001000 != 0);
+        enable_feature(&mut value, Feature::pmull, auxv.hwcap2 & 0x00000002 != 0);
+        return value;
+    }
+    value
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/auxvec.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/auxvec.rs
new file mode 100644
index 0000000000000..c595ec459b5d2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/auxvec.rs
@@ -0,0 +1,94 @@
+//! Parses ELF auxiliary vectors.
+#![cfg_attr(any(target_arch = "arm", target_arch = "powerpc64"), allow(dead_code))]
+
+/// Key to access the CPU Hardware capabilities bitfield.
+pub(crate) const AT_HWCAP: usize = 25;
+/// Key to access the CPU Hardware capabilities 2 bitfield.
+pub(crate) const AT_HWCAP2: usize = 26;
+
+/// Cache HWCAP bitfields of the ELF Auxiliary Vector.
+///
+/// If an entry cannot be read all the bits in the bitfield are set to zero.
+/// This should be interpreted as all the features being disabled.
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct AuxVec {
+    pub hwcap: usize,
+    pub hwcap2: usize,
+}
+
+/// ELF Auxiliary Vector
+///
+/// The auxiliary vector is a memory region in a running ELF program's stack
+/// composed of (key: usize, value: usize) pairs.
+///
+/// The keys used in the aux vector are platform dependent. For FreeBSD, they are
+/// defined in [sys/elf_common.h][elf_common_h]. The hardware capabilities of a given
+/// CPU can be queried with the  `AT_HWCAP` and `AT_HWCAP2` keys.
+///
+/// Note that run-time feature detection is not invoked for features that can
+/// be detected at compile-time.
+///
+/// [elf_common.h]: https://svnweb.freebsd.org/base/release/12.0.0/sys/sys/elf_common.h?revision=341707
+pub(crate) fn auxv() -> Result<AuxVec, ()> {
+    if let Ok(hwcap) = archauxv(AT_HWCAP) {
+        if let Ok(hwcap2) = archauxv(AT_HWCAP2) {
+            if hwcap != 0 && hwcap2 != 0 {
+                return Ok(AuxVec { hwcap, hwcap2 });
+            }
+        }
+    }
+    Err(())
+}
+
+/// Tries to read the `key` from the auxiliary vector.
+fn archauxv(key: usize) -> Result<usize, ()> {
+    use crate::mem;
+
+    #[derive(Copy, Clone)]
+    #[repr(C)]
+    pub struct Elf_Auxinfo {
+        pub a_type: usize,
+        pub a_un: unnamed,
+    }
+    #[derive(Copy, Clone)]
+    #[repr(C)]
+    pub union unnamed {
+        pub a_val: libc::c_long,
+        pub a_ptr: *mut libc::c_void,
+        pub a_fcn: Option<unsafe extern "C" fn() -> ()>,
+    }
+
+    let mut auxv: [Elf_Auxinfo; 27] = [Elf_Auxinfo {
+        a_type: 0,
+        a_un: unnamed { a_val: 0 },
+    }; 27];
+
+    let mut len: libc::c_uint = mem::size_of_val(&auxv) as libc::c_uint;
+
+    unsafe {
+        let mut mib = [
+            libc::CTL_KERN,
+            libc::KERN_PROC,
+            libc::KERN_PROC_AUXV,
+            libc::getpid(),
+        ];
+
+        let ret = libc::sysctl(
+            mib.as_mut_ptr(),
+            mib.len() as u32,
+            &mut auxv as *mut _ as *mut _,
+            &mut len as *mut _ as *mut _,
+            0 as *mut libc::c_void,
+            0,
+        );
+
+        if ret != -1 {
+            for i in 0..auxv.len() {
+                if auxv[i].a_type == key {
+                    return Ok(auxv[i].a_un.a_val as usize);
+                }
+            }
+        }
+    }
+    return Ok(0);
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/mod.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/mod.rs
new file mode 100644
index 0000000000000..1a5338a355595
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/mod.rs
@@ -0,0 +1,22 @@
+//! Run-time feature detection on FreeBSD
+
+mod auxvec;
+
+cfg_if! {
+    if #[cfg(target_arch = "aarch64")] {
+        mod aarch64;
+        pub use self::aarch64::check_for;
+    } else if #[cfg(target_arch = "arm")] {
+        mod arm;
+        pub use self::arm::check_for;
+    } else if #[cfg(target_arch = "powerpc64")] {
+        mod powerpc;
+        pub use self::powerpc::check_for;
+    } else {
+        use crate::arch::detect::Feature;
+        /// Performs run-time feature detection.
+        pub fn check_for(_x: Feature) -> bool {
+            false
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/powerpc.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/powerpc.rs
new file mode 100644
index 0000000000000..203e5cd7f2506
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/freebsd/powerpc.rs
@@ -0,0 +1,27 @@
+//! Run-time feature detection for PowerPC on FreeBSD.
+
+use super::auxvec;
+use crate::detect::{cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::altivec, auxv.hwcap & 0x10000000 != 0);
+        enable_feature(&mut value, Feature::vsx, auxv.hwcap & 0x00000080 != 0);
+        enable_feature(&mut value, Feature::power8, auxv.hwcap2 & 0x80000000 != 0);
+        return value;
+    }
+    value
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/aarch64.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/aarch64.rs
new file mode 100644
index 0000000000000..8d874f2280fc1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/aarch64.rs
@@ -0,0 +1,160 @@
+//! Run-time feature detection for Aarch64 on Linux.
+
+use super::{auxvec, cpuinfo};
+use crate::detect::{bit, cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from /proc/cpuinfo.
+fn detect_features() -> cache::Initializer {
+    if let Ok(auxv) = auxvec::auxv() {
+        let hwcap: AtHwcap = auxv.into();
+        return hwcap.cache();
+    }
+    if let Ok(c) = cpuinfo::CpuInfo::new() {
+        let hwcap: AtHwcap = c.into();
+        return hwcap.cache();
+    }
+    cache::Initializer::default()
+}
+
+/// These values are part of the platform-specific [asm/hwcap.h][hwcap] .
+///
+/// [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h
+struct AtHwcap {
+    fp: bool,    // 0
+    asimd: bool, // 1
+    // evtstrm: bool, // 2
+    aes: bool,     // 3
+    pmull: bool,   // 4
+    sha1: bool,    // 5
+    sha2: bool,    // 6
+    crc32: bool,   // 7
+    atomics: bool, // 8
+    fphp: bool,    // 9
+    asimdhp: bool, // 10
+    // cpuid: bool, // 11
+    asimdrdm: bool, // 12
+    // jscvt: bool, // 13
+    // fcma: bool, // 14
+    lrcpc: bool, // 15
+    // dcpop: bool, // 16
+    // sha3: bool, // 17
+    // sm3: bool, // 18
+    // sm4: bool, // 19
+    asimddp: bool, // 20
+    // sha512: bool, // 21
+    sve: bool, // 22
+}
+
+impl From<auxvec::AuxVec> for AtHwcap {
+    /// Reads AtHwcap from the auxiliary vector.
+    fn from(auxv: auxvec::AuxVec) -> Self {
+        AtHwcap {
+            fp: bit::test(auxv.hwcap, 0),
+            asimd: bit::test(auxv.hwcap, 1),
+            // evtstrm: bit::test(auxv.hwcap, 2),
+            aes: bit::test(auxv.hwcap, 3),
+            pmull: bit::test(auxv.hwcap, 4),
+            sha1: bit::test(auxv.hwcap, 5),
+            sha2: bit::test(auxv.hwcap, 6),
+            crc32: bit::test(auxv.hwcap, 7),
+            atomics: bit::test(auxv.hwcap, 8),
+            fphp: bit::test(auxv.hwcap, 9),
+            asimdhp: bit::test(auxv.hwcap, 10),
+            // cpuid: bit::test(auxv.hwcap, 11),
+            asimdrdm: bit::test(auxv.hwcap, 12),
+            // jscvt: bit::test(auxv.hwcap, 13),
+            // fcma: bit::test(auxv.hwcap, 14),
+            lrcpc: bit::test(auxv.hwcap, 15),
+            // dcpop: bit::test(auxv.hwcap, 16),
+            // sha3: bit::test(auxv.hwcap, 17),
+            // sm3: bit::test(auxv.hwcap, 18),
+            // sm4: bit::test(auxv.hwcap, 19),
+            asimddp: bit::test(auxv.hwcap, 20),
+            // sha512: bit::test(auxv.hwcap, 21),
+            sve: bit::test(auxv.hwcap, 22),
+        }
+    }
+}
+
+impl From<cpuinfo::CpuInfo> for AtHwcap {
+    /// Reads AtHwcap from /proc/cpuinfo .
+    fn from(c: cpuinfo::CpuInfo) -> Self {
+        let f = &c.field("Features");
+        AtHwcap {
+            // 64-bit names. FIXME: In 32-bit compatibility mode /proc/cpuinfo will
+            // map some of the 64-bit names to some 32-bit feature names. This does not
+            // cover that yet.
+            fp: f.has("fp"),
+            asimd: f.has("asimd"),
+            // evtstrm: f.has("evtstrm"),
+            aes: f.has("aes"),
+            pmull: f.has("pmull"),
+            sha1: f.has("sha1"),
+            sha2: f.has("sha2"),
+            crc32: f.has("crc32"),
+            atomics: f.has("atomics"),
+            fphp: f.has("fphp"),
+            asimdhp: f.has("asimdhp"),
+            // cpuid: f.has("cpuid"),
+            asimdrdm: f.has("asimdrdm"),
+            // jscvt: f.has("jscvt"),
+            // fcma: f.has("fcma"),
+            lrcpc: f.has("lrcpc"),
+            // dcpop: f.has("dcpop"),
+            // sha3: f.has("sha3"),
+            // sm3: f.has("sm3"),
+            // sm4: f.has("sm4"),
+            asimddp: f.has("asimddp"),
+            // sha512: f.has("sha512"),
+            sve: f.has("sve"),
+        }
+    }
+}
+
+impl AtHwcap {
+    /// Initializes the cache from the feature -bits.
+    ///
+    /// The features are enabled approximately like in LLVM host feature detection:
+    /// https://github.com/llvm-mirror/llvm/blob/master/lib/Support/Host.cpp#L1273
+    fn cache(self) -> cache::Initializer {
+        let mut value = cache::Initializer::default();
+        {
+            let mut enable_feature = |f, enable| {
+                if enable {
+                    value.set(f as u32);
+                }
+            };
+
+            enable_feature(Feature::fp, self.fp);
+            // Half-float support requires float support
+            enable_feature(Feature::fp16, self.fp && self.fphp);
+            enable_feature(Feature::pmull, self.pmull);
+            enable_feature(Feature::crc, self.crc32);
+            enable_feature(Feature::lse, self.atomics);
+            enable_feature(Feature::rcpc, self.lrcpc);
+
+            // SIMD support requires float support - if half-floats are
+            // supported, it also requires half-float support:
+            let asimd = self.fp && self.asimd && (!self.fphp | self.asimdhp);
+            enable_feature(Feature::asimd, asimd);
+            // SIMD extensions require SIMD support:
+            enable_feature(Feature::rdm, self.asimdrdm && asimd);
+            enable_feature(Feature::dotprod, self.asimddp && asimd);
+            enable_feature(Feature::sve, self.sve && asimd);
+
+            // Crypto is specified as AES + PMULL + SHA1 + SHA2 per LLVM/hosts.cpp
+            enable_feature(
+                Feature::crypto,
+                self.aes && self.pmull && self.sha1 && self.sha2,
+            );
+        }
+        value
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/arm.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/arm.rs
new file mode 100644
index 0000000000000..9c89500cc1000
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/arm.rs
@@ -0,0 +1,52 @@
+//! Run-time feature detection for ARM on Linux.
+
+use super::{auxvec, cpuinfo};
+use crate::detect::{bit, cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from /proc/cpuinfo.
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    // The values are part of the platform-specific [asm/hwcap.h][hwcap]
+    //
+    // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::neon, bit::test(auxv.hwcap, 12));
+        enable_feature(&mut value, Feature::pmull, bit::test(auxv.hwcap2, 1));
+        return value;
+    }
+
+    if let Ok(c) = cpuinfo::CpuInfo::new() {
+        enable_feature(
+            &mut value,
+            Feature::neon,
+            c.field("Features").has("neon") && !has_broken_neon(&c),
+        );
+        enable_feature(&mut value, Feature::pmull, c.field("Features").has("pmull"));
+        return value;
+    }
+    value
+}
+
+/// Is the CPU known to have a broken NEON unit?
+///
+/// See https://crbug.com/341598.
+fn has_broken_neon(cpuinfo: &cpuinfo::CpuInfo) -> bool {
+    cpuinfo.field("CPU implementer") == "0x51"
+        && cpuinfo.field("CPU architecture") == "7"
+        && cpuinfo.field("CPU variant") == "0x1"
+        && cpuinfo.field("CPU part") == "0x04d"
+        && cpuinfo.field("CPU revision") == "0"
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/auxvec.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/auxvec.rs
new file mode 100644
index 0000000000000..6ebae67fbf873
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/auxvec.rs
@@ -0,0 +1,304 @@
+//! Parses ELF auxiliary vectors.
+#![cfg_attr(not(target_arch = "aarch64"), allow(dead_code))]
+
+#[cfg(feature = "std_detect_file_io")]
+use crate::{fs::File, io::Read};
+
+/// Key to access the CPU Hardware capabilities bitfield.
+pub(crate) const AT_HWCAP: usize = 16;
+/// Key to access the CPU Hardware capabilities 2 bitfield.
+#[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+pub(crate) const AT_HWCAP2: usize = 26;
+
+/// Cache HWCAP bitfields of the ELF Auxiliary Vector.
+///
+/// If an entry cannot be read all the bits in the bitfield are set to zero.
+/// This should be interpreted as all the features being disabled.
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct AuxVec {
+    pub hwcap: usize,
+    #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+    pub hwcap2: usize,
+}
+
+/// ELF Auxiliary Vector
+///
+/// The auxiliary vector is a memory region in a running ELF program's stack
+/// composed of (key: usize, value: usize) pairs.
+///
+/// The keys used in the aux vector are platform dependent. For Linux, they are
+/// defined in [linux/auxvec.h][auxvec_h]. The hardware capabilities of a given
+/// CPU can be queried with the  `AT_HWCAP` and `AT_HWCAP2` keys.
+///
+/// There is no perfect way of reading the auxiliary vector.
+///
+/// - If the `std_detect_dlsym_getauxval` cargo feature is enabled, this will use
+/// `getauxval` if its linked to the binary, and otherwise proceed to a fallback implementation.
+/// When `std_detect_dlsym_getauxval` is disabled, this will assume that `getauxval` is
+/// linked to the binary - if that is not the case the behavior is undefined.
+/// - Otherwise, if the `std_detect_file_io` cargo feature is enabled, it will
+///   try to read `/proc/self/auxv`.
+/// - If that fails, this function returns an error.
+///
+/// Note that run-time feature detection is not invoked for features that can
+/// be detected at compile-time. Also note that if this function returns an
+/// error, cpuinfo still can (and will) be used to try to perform run-time
+/// feature detecton on some platforms.
+///
+/// For more information about when `getauxval` is available check the great
+/// [`auxv` crate documentation][auxv_docs].
+///
+/// [auxvec_h]: https://github.com/torvalds/linux/blob/master/include/uapi/linux/auxvec.h
+/// [auxv_docs]: https://docs.rs/auxv/0.3.3/auxv/
+pub(crate) fn auxv() -> Result<AuxVec, ()> {
+    #[cfg(feature = "std_detect_dlsym_getauxval")]
+    {
+        // Try to call a dynamically-linked getauxval function.
+        if let Ok(hwcap) = getauxval(AT_HWCAP) {
+            // Targets with only AT_HWCAP:
+            #[cfg(any(target_arch = "aarch64", target_arch = "mips", target_arch = "mips64"))]
+            {
+                if hwcap != 0 {
+                    return Ok(AuxVec { hwcap });
+                }
+            }
+
+            // Targets with AT_HWCAP and AT_HWCAP2:
+            #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+            {
+                if let Ok(hwcap2) = getauxval(AT_HWCAP2) {
+                    if hwcap != 0 && hwcap2 != 0 {
+                        return Ok(AuxVec { hwcap, hwcap2 });
+                    }
+                }
+            }
+            drop(hwcap);
+        }
+        #[cfg(feature = "std_detect_file_io")]
+        {
+            // If calling getauxval fails, try to read the auxiliary vector from
+            // its file:
+            auxv_from_file("/proc/self/auxv")
+        }
+        #[cfg(not(feature = "std_detect_file_io"))]
+        {
+            Err(())
+        }
+    }
+
+    #[cfg(not(feature = "std_detect_dlsym_getauxval"))]
+    {
+        let hwcap = unsafe { ffi_getauxval(AT_HWCAP) };
+
+        // Targets with only AT_HWCAP:
+        #[cfg(any(target_arch = "aarch64", target_arch = "mips", target_arch = "mips64"))]
+        {
+            if hwcap != 0 {
+                return Ok(AuxVec { hwcap });
+            }
+        }
+
+        // Targets with AT_HWCAP and AT_HWCAP2:
+        #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+        {
+            let hwcap2 = unsafe { ffi_getauxval(AT_HWCAP2) };
+            if hwcap != 0 && hwcap2 != 0 {
+                return Ok(AuxVec { hwcap, hwcap2 });
+            }
+        }
+    }
+}
+
+/// Tries to read the `key` from the auxiliary vector by calling the
+/// dynamically-linked `getauxval` function. If the function is not linked,
+/// this function return `Err`.
+#[cfg(feature = "std_detect_dlsym_getauxval")]
+fn getauxval(key: usize) -> Result<usize, ()> {
+    use libc;
+    pub type F = unsafe extern "C" fn(usize) -> usize;
+    unsafe {
+        let ptr = libc::dlsym(libc::RTLD_DEFAULT, "getauxval\0".as_ptr() as *const _);
+        if ptr.is_null() {
+            return Err(());
+        }
+
+        let ffi_getauxval: F = mem::transmute(ptr);
+        Ok(ffi_getauxval(key))
+    }
+}
+
+/// Tries to read the auxiliary vector from the `file`. If this fails, this
+/// function returns `Err`.
+#[cfg(feature = "std_detect_file_io")]
+fn auxv_from_file(file: &str) -> Result<AuxVec, ()> {
+    let mut file = File::open(file).map_err(|_| ())?;
+
+    // See <https://github.com/torvalds/linux/blob/v3.19/include/uapi/linux/auxvec.h>.
+    //
+    // The auxiliary vector contains at most 32 (key,value) fields: from
+    // `AT_EXECFN = 31` to `AT_NULL = 0`. That is, a buffer of
+    // 2*32 `usize` elements is enough to read the whole vector.
+    let mut buf = [0_usize; 64];
+    {
+        let raw: &mut [u8; 64 * mem::size_of::<usize>()] = unsafe { mem::transmute(&mut buf) };
+        file.read(raw).map_err(|_| ())?;
+    }
+    auxv_from_buf(&buf)
+}
+
+/// Tries to interpret the `buffer` as an auxiliary vector. If that fails, this
+/// function returns `Err`.
+#[cfg(feature = "std_detect_file_io")]
+fn auxv_from_buf(buf: &[usize; 64]) -> Result<AuxVec, ()> {
+    // Targets with only AT_HWCAP:
+    #[cfg(any(target_arch = "aarch64", target_arch = "mips", target_arch = "mips64"))]
+    {
+        for el in buf.chunks(2) {
+            match el[0] {
+                AT_HWCAP => return Ok(AuxVec { hwcap: el[1] }),
+                _ => (),
+            }
+        }
+    }
+    // Targets with AT_HWCAP and AT_HWCAP2:
+    #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+    {
+        let mut hwcap = None;
+        let mut hwcap2 = None;
+        for el in buf.chunks(2) {
+            match el[0] {
+                AT_HWCAP => hwcap = Some(el[1]),
+                AT_HWCAP2 => hwcap2 = Some(el[1]),
+                _ => (),
+            }
+        }
+
+        if let (Some(hwcap), Some(hwcap2)) = (hwcap, hwcap2) {
+            return Ok(AuxVec { hwcap, hwcap2 });
+        }
+    }
+    drop(buf);
+    Err(())
+}
+
+#[cfg(test)]
+mod tests {
+    extern crate auxv as auxv_crate;
+    use super::*;
+
+    // Reads the Auxiliary Vector key from /proc/self/auxv
+    // using the auxv crate.
+    #[cfg(feature = "std_detect_file_io")]
+    fn auxv_crate_getprocfs(key: usize) -> Option<usize> {
+        use self::auxv_crate::procfs::search_procfs_auxv;
+        use self::auxv_crate::AuxvType;
+        let k = key as AuxvType;
+        match search_procfs_auxv(&[k]) {
+            Ok(v) => Some(v[&k] as usize),
+            Err(_) => None,
+        }
+    }
+
+    // Reads the Auxiliary Vector key from getauxval()
+    // using the auxv crate.
+    #[cfg(not(any(target_arch = "mips", target_arch = "mips64")))]
+    fn auxv_crate_getauxval(key: usize) -> Option<usize> {
+        use self::auxv_crate::getauxval::Getauxval;
+        use self::auxv_crate::AuxvType;
+        let q = auxv_crate::getauxval::NativeGetauxval {};
+        match q.getauxval(key as AuxvType) {
+            Ok(v) => Some(v as usize),
+            Err(_) => None,
+        }
+    }
+
+    // FIXME: on mips/mips64 getauxval returns 0, and /proc/self/auxv
+    // does not always contain the AT_HWCAP key under qemu.
+    #[cfg(not(any(target_arch = "mips", target_arch = "mips64", target_arch = "powerpc")))]
+    #[test]
+    fn auxv_crate() {
+        let v = auxv();
+        if let Some(hwcap) = auxv_crate_getauxval(AT_HWCAP) {
+            let rt_hwcap = v.expect("failed to find hwcap key").hwcap;
+            assert_eq!(rt_hwcap, hwcap);
+        }
+
+        // Targets with AT_HWCAP and AT_HWCAP2:
+        #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+        {
+            if let Some(hwcap2) = auxv_crate_getauxval(AT_HWCAP2) {
+                let rt_hwcap2 = v.expect("failed to find hwcap2 key").hwcap2;
+                assert_eq!(rt_hwcap2, hwcap2);
+            }
+        }
+    }
+
+    #[test]
+    fn auxv_dump() {
+        if let Ok(auxvec) = auxv() {
+            println!("{:?}", auxvec);
+        } else {
+            println!("both getauxval() and reading /proc/self/auxv failed!");
+        }
+    }
+
+    #[cfg(feature = "std_detect_file_io")]
+    cfg_if! {
+        if #[cfg(target_arch = "arm")] {
+            #[test]
+            fn linux_rpi3() {
+                let file = concat!(env!("CARGO_MANIFEST_DIR"), "/src/detect/test_data/linux-rpi3.auxv");
+                println!("file: {}", file);
+                let v = auxv_from_file(file).unwrap();
+                assert_eq!(v.hwcap, 4174038);
+                assert_eq!(v.hwcap2, 16);
+            }
+
+            #[test]
+            #[should_panic]
+            fn linux_macos_vb() {
+                let file = concat!(env!("CARGO_MANIFEST_DIR"), "/src/detect/test_data/macos-virtualbox-linux-x86-4850HQ.auxv");
+                println!("file: {}", file);
+                let v = auxv_from_file(file).unwrap();
+                // this file is incomplete (contains hwcap but not hwcap2), we
+                // want to fall back to /proc/cpuinfo in this case, so
+                // reading should fail. assert_eq!(v.hwcap, 126614527);
+                // assert_eq!(v.hwcap2, 0);
+            }
+        } else if #[cfg(target_arch = "aarch64")] {
+            #[test]
+            fn linux_x64() {
+                let file = concat!(env!("CARGO_MANIFEST_DIR"), "/src/detect/test_data/linux-x64-i7-6850k.auxv");
+                println!("file: {}", file);
+                let v = auxv_from_file(file).unwrap();
+                assert_eq!(v.hwcap, 3219913727);
+            }
+        }
+    }
+
+    #[test]
+    #[cfg(feature = "std_detect_file_io")]
+    fn auxv_dump_procfs() {
+        if let Ok(auxvec) = auxv_from_file("/proc/self/auxv") {
+            println!("{:?}", auxvec);
+        } else {
+            println!("reading /proc/self/auxv failed!");
+        }
+    }
+
+    #[test]
+    fn auxv_crate_procfs() {
+        let v = auxv();
+        if let Some(hwcap) = auxv_crate_getprocfs(AT_HWCAP) {
+            assert_eq!(v.unwrap().hwcap, hwcap);
+        }
+
+        // Targets with AT_HWCAP and AT_HWCAP2:
+        #[cfg(any(target_arch = "arm", target_arch = "powerpc64"))]
+        {
+            if let Some(hwcap2) = auxv_crate_getprocfs(AT_HWCAP2) {
+                assert_eq!(v.unwrap().hwcap2, hwcap2);
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/cpuinfo.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/cpuinfo.rs
new file mode 100644
index 0000000000000..f76c48a4b16b0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/cpuinfo.rs
@@ -0,0 +1,300 @@
+//! Parses /proc/cpuinfo
+#![cfg_attr(not(target_arch = "arm"), allow(dead_code))]
+
+extern crate std;
+use self::std::{fs::File, io, io::Read, prelude::v1::*};
+
+/// cpuinfo
+pub(crate) struct CpuInfo {
+    raw: String,
+}
+
+impl CpuInfo {
+    /// Reads /proc/cpuinfo into CpuInfo.
+    pub(crate) fn new() -> Result<Self, io::Error> {
+        let mut file = File::open("/proc/cpuinfo")?;
+        let mut cpui = Self { raw: String::new() };
+        file.read_to_string(&mut cpui.raw)?;
+        Ok(cpui)
+    }
+    /// Returns the value of the cpuinfo `field`.
+    pub(crate) fn field(&self, field: &str) -> CpuInfoField {
+        for l in self.raw.lines() {
+            if l.trim().starts_with(field) {
+                return CpuInfoField::new(l.split(": ").nth(1));
+            }
+        }
+        CpuInfoField(None)
+    }
+
+    /// Returns the `raw` contents of `/proc/cpuinfo`
+    #[cfg(test)]
+    fn raw(&self) -> &String {
+        &self.raw
+    }
+
+    #[cfg(test)]
+    fn from_str(other: &str) -> Result<Self, ::std::io::Error> {
+        Ok(Self {
+            raw: String::from(other),
+        })
+    }
+}
+
+/// Field of cpuinfo
+#[derive(Debug)]
+pub(crate) struct CpuInfoField<'a>(Option<&'a str>);
+
+impl<'a> PartialEq<&'a str> for CpuInfoField<'a> {
+    fn eq(&self, other: &&'a str) -> bool {
+        match self.0 {
+            None => other.is_empty(),
+            Some(f) => f == other.trim(),
+        }
+    }
+}
+
+impl<'a> CpuInfoField<'a> {
+    pub(crate) fn new<'b>(v: Option<&'b str>) -> CpuInfoField<'b> {
+        match v {
+            None => CpuInfoField::<'b>(None),
+            Some(f) => CpuInfoField::<'b>(Some(f.trim())),
+        }
+    }
+    /// Does the field exist?
+    #[cfg(test)]
+    pub(crate) fn exists(&self) -> bool {
+        self.0.is_some()
+    }
+    /// Does the field contain `other`?
+    pub(crate) fn has(&self, other: &str) -> bool {
+        match self.0 {
+            None => other.is_empty(),
+            Some(f) => {
+                let other = other.trim();
+                for v in f.split(' ') {
+                    if v == other {
+                        return true;
+                    }
+                }
+                false
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn raw_dump() {
+        let cpuinfo = CpuInfo::new().unwrap();
+        if cpuinfo.field("vendor_id") == "GenuineIntel" {
+            assert!(cpuinfo.field("flags").exists());
+            assert!(!cpuinfo.field("vendor33_id").exists());
+            assert!(cpuinfo.field("flags").has("sse"));
+            assert!(!cpuinfo.field("flags").has("avx314"));
+        }
+        println!("{}", cpuinfo.raw());
+    }
+
+    const CORE_DUO_T6500: &str = r"processor       : 0
+vendor_id       : GenuineIntel
+cpu family      : 6
+model           : 23
+model name      : Intel(R) Core(TM)2 Duo CPU     T6500  @ 2.10GHz
+stepping        : 10
+microcode       : 0xa0b
+cpu MHz         : 1600.000
+cache size      : 2048 KB
+physical id     : 0
+siblings        : 2
+core id         : 0
+cpu cores       : 2
+apicid          : 0
+initial apicid  : 0
+fdiv_bug        : no
+hlt_bug         : no
+f00f_bug        : no
+coma_bug        : no
+fpu             : yes
+fpu_exception   : yes
+cpuid level     : 13
+wp              : yes
+flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm
+bogomips        : 4190.43
+clflush size    : 64
+cache_alignment : 64
+address sizes   : 36 bits physical, 48 bits virtual
+power management:
+";
+
+    #[test]
+    fn core_duo_t6500() {
+        let cpuinfo = CpuInfo::from_str(CORE_DUO_T6500).unwrap();
+        assert_eq!(cpuinfo.field("vendor_id"), "GenuineIntel");
+        assert_eq!(cpuinfo.field("cpu family"), "6");
+        assert_eq!(cpuinfo.field("model"), "23");
+        assert_eq!(
+            cpuinfo.field("model name"),
+            "Intel(R) Core(TM)2 Duo CPU     T6500  @ 2.10GHz"
+        );
+        assert_eq!(
+            cpuinfo.field("flags"),
+            "fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm"
+        );
+        assert!(cpuinfo.field("flags").has("fpu"));
+        assert!(cpuinfo.field("flags").has("dtherm"));
+        assert!(cpuinfo.field("flags").has("sse2"));
+        assert!(!cpuinfo.field("flags").has("avx"));
+    }
+
+    const ARM_CORTEX_A53: &str = r"Processor   : AArch64 Processor rev 3 (aarch64)
+        processor   : 0
+        processor   : 1
+        processor   : 2
+        processor   : 3
+        processor   : 4
+        processor   : 5
+        processor   : 6
+        processor   : 7
+        Features    : fp asimd evtstrm aes pmull sha1 sha2 crc32
+        CPU implementer : 0x41
+        CPU architecture: AArch64
+        CPU variant : 0x0
+        CPU part    : 0xd03
+        CPU revision    : 3
+
+        Hardware    : HiKey Development Board
+        ";
+
+    #[test]
+    fn arm_cortex_a53() {
+        let cpuinfo = CpuInfo::from_str(ARM_CORTEX_A53).unwrap();
+        assert_eq!(
+            cpuinfo.field("Processor"),
+            "AArch64 Processor rev 3 (aarch64)"
+        );
+        assert_eq!(
+            cpuinfo.field("Features"),
+            "fp asimd evtstrm aes pmull sha1 sha2 crc32"
+        );
+        assert!(cpuinfo.field("Features").has("pmull"));
+        assert!(!cpuinfo.field("Features").has("neon"));
+        assert!(cpuinfo.field("Features").has("asimd"));
+    }
+
+    const ARM_CORTEX_A57: &str = r"Processor	: Cortex A57 Processor rev 1 (aarch64)
+processor	: 0
+processor	: 1
+processor	: 2
+processor	: 3
+Features	: fp asimd aes pmull sha1 sha2 crc32 wp half thumb fastmult vfp edsp neon vfpv3 tlsi vfpv4 idiva idivt
+CPU implementer	: 0x41
+CPU architecture: 8
+CPU variant	: 0x1
+CPU part	: 0xd07
+CPU revision	: 1";
+
+    #[test]
+    fn arm_cortex_a57() {
+        let cpuinfo = CpuInfo::from_str(ARM_CORTEX_A57).unwrap();
+        assert_eq!(
+            cpuinfo.field("Processor"),
+            "Cortex A57 Processor rev 1 (aarch64)"
+        );
+        assert_eq!(
+            cpuinfo.field("Features"),
+            "fp asimd aes pmull sha1 sha2 crc32 wp half thumb fastmult vfp edsp neon vfpv3 tlsi vfpv4 idiva idivt"
+        );
+        assert!(cpuinfo.field("Features").has("pmull"));
+        assert!(cpuinfo.field("Features").has("neon"));
+        assert!(cpuinfo.field("Features").has("asimd"));
+    }
+
+    const POWER8E_POWERKVM: &str = r"processor       : 0
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+processor       : 1
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+processor       : 2
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+processor       : 3
+cpu             : POWER8E (raw), altivec supported
+clock           : 3425.000000MHz
+revision        : 2.1 (pvr 004b 0201)
+
+timebase        : 512000000
+platform        : pSeries
+model           : IBM pSeries (emulated by qemu)
+machine         : CHRP IBM pSeries (emulated by qemu)";
+
+    #[test]
+    fn power8_powerkvm() {
+        let cpuinfo = CpuInfo::from_str(POWER8E_POWERKVM).unwrap();
+        assert_eq!(cpuinfo.field("cpu"), "POWER8E (raw), altivec supported");
+
+        assert!(cpuinfo.field("cpu").has("altivec"));
+    }
+
+    const POWER5P: &str = r"processor       : 0
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 1
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 2
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 3
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 4
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 5
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 6
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+processor       : 7
+cpu             : POWER5+ (gs)
+clock           : 1900.098000MHz
+revision        : 2.1 (pvr 003b 0201)
+
+timebase        : 237331000
+platform        : pSeries
+machine         : CHRP IBM,9133-55A";
+
+    #[test]
+    fn power5p() {
+        let cpuinfo = CpuInfo::from_str(POWER5P).unwrap();
+        assert_eq!(cpuinfo.field("cpu"), "POWER5+ (gs)");
+
+        assert!(!cpuinfo.field("cpu").has("altivec"));
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/mips.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/mips.rs
new file mode 100644
index 0000000000000..46a47fb7b78e9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/mips.rs
@@ -0,0 +1,31 @@
+//! Run-time feature detection for MIPS on Linux.
+
+use super::auxvec;
+use crate::detect::{bit, cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from `/proc/cpuinfo`.
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    // The values are part of the platform-specific [asm/hwcap.h][hwcap]
+    //
+    // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::msa, bit::test(auxv.hwcap, 1));
+        return value;
+    }
+    // TODO: fall back via `cpuinfo`.
+    value
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/mod.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/mod.rs
new file mode 100644
index 0000000000000..e02d5e6dcda7a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/mod.rs
@@ -0,0 +1,28 @@
+//! Run-time feature detection on Linux
+
+mod auxvec;
+
+#[cfg(feature = "std_detect_file_io")]
+mod cpuinfo;
+
+cfg_if! {
+    if #[cfg(target_arch = "aarch64")] {
+        mod aarch64;
+        pub use self::aarch64::check_for;
+    } else if #[cfg(target_arch = "arm")] {
+        mod arm;
+        pub use self::arm::check_for;
+    } else  if #[cfg(any(target_arch = "mips", target_arch = "mips64"))] {
+        mod mips;
+        pub use self::mips::check_for;
+    } else if #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))] {
+        mod powerpc;
+        pub use self::powerpc::check_for;
+    } else {
+        use crate::detect::Feature;
+        /// Performs run-time feature detection.
+        pub fn check_for(_x: Feature) -> bool {
+            false
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/powerpc.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/powerpc.rs
new file mode 100644
index 0000000000000..dc19bc8eda539
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/linux/powerpc.rs
@@ -0,0 +1,41 @@
+//! Run-time feature detection for PowerPC on Linux.
+
+use super::{auxvec, cpuinfo};
+use crate::detect::{cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from /proc/cpuinfo.
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    // The values are part of the platform-specific [asm/cputable.h][cputable]
+    //
+    // [cputable]: https://github.com/torvalds/linux/blob/master/arch/powerpc/include/uapi/asm/cputable.h
+    if let Ok(auxv) = auxvec::auxv() {
+        // note: the PowerPC values are the mask to do the test (instead of the
+        // index of the bit to test like in ARM and Aarch64)
+        enable_feature(&mut value, Feature::altivec, auxv.hwcap & 0x10000000 != 0);
+        enable_feature(&mut value, Feature::vsx, auxv.hwcap & 0x00000080 != 0);
+        enable_feature(&mut value, Feature::power8, auxv.hwcap2 & 0x80000000 != 0);
+        return value;
+    }
+
+    // PowerPC's /proc/cpuinfo lacks a proper Feature field,
+    // but `altivec` support is indicated in the `cpu` field.
+    if let Ok(c) = cpuinfo::CpuInfo::new() {
+        enable_feature(&mut value, Feature::altivec, c.field("cpu").has("altivec"));
+        return value;
+    }
+    value
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/other.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/other.rs
new file mode 100644
index 0000000000000..23e399ea79074
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/other.rs
@@ -0,0 +1,9 @@
+//! Other operating systems
+
+use crate::detect::Feature;
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(_x: Feature) -> bool {
+    false
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/detect/os/x86.rs b/src/tools/rustfmt/tests/target/cfg_if/detect/os/x86.rs
new file mode 100644
index 0000000000000..2e228aa374527
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/detect/os/x86.rs
@@ -0,0 +1,367 @@
+//! x86 run-time feature detection is OS independent.
+
+#[cfg(target_arch = "x86")]
+use crate::arch::x86::*;
+#[cfg(target_arch = "x86_64")]
+use crate::arch::x86_64::*;
+
+use crate::mem;
+
+use crate::detect::{bit, cache, Feature};
+
+/// Performs run-time feature detection.
+#[inline]
+pub fn check_for(x: Feature) -> bool {
+    cache::test(x as u32, detect_features)
+}
+
+/// Run-time feature detection on x86 works by using the CPUID instruction.
+///
+/// The [CPUID Wikipedia page][wiki_cpuid] contains
+/// all the information about which flags to set to query which values, and in
+/// which registers these are reported.
+///
+/// The definitive references are:
+/// - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2:
+///   Instruction Set Reference, A-Z][intel64_ref].
+/// - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and
+///   System Instructions][amd64_ref].
+///
+/// [wiki_cpuid]: https://en.wikipedia.org/wiki/CPUID
+/// [intel64_ref]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
+/// [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf
+#[allow(clippy::similar_names)]
+fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+
+    // If the x86 CPU does not support the CPUID instruction then it is too
+    // old to support any of the currently-detectable features.
+    if !has_cpuid() {
+        return value;
+    }
+
+    // Calling `__cpuid`/`__cpuid_count` from here on is safe because the CPU
+    // has `cpuid` support.
+
+    // 0. EAX = 0: Basic Information:
+    // - EAX returns the "Highest Function Parameter", that is, the maximum
+    // leaf value for subsequent calls of `cpuinfo` in range [0,
+    // 0x8000_0000]. - The vendor ID is stored in 12 u8 ascii chars,
+    // returned in EBX, EDX, and   ECX (in that order):
+    let (max_basic_leaf, vendor_id) = unsafe {
+        let CpuidResult {
+            eax: max_basic_leaf,
+            ebx,
+            ecx,
+            edx,
+        } = __cpuid(0);
+        let vendor_id: [[u8; 4]; 3] = [
+            mem::transmute(ebx),
+            mem::transmute(edx),
+            mem::transmute(ecx),
+        ];
+        let vendor_id: [u8; 12] = mem::transmute(vendor_id);
+        (max_basic_leaf, vendor_id)
+    };
+
+    if max_basic_leaf < 1 {
+        // Earlier Intel 486, CPUID not implemented
+        return value;
+    }
+
+    // EAX = 1, ECX = 0: Queries "Processor Info and Feature Bits";
+    // Contains information about most x86 features.
+    let CpuidResult {
+        ecx: proc_info_ecx,
+        edx: proc_info_edx,
+        ..
+    } = unsafe { __cpuid(0x0000_0001_u32) };
+
+    // EAX = 7, ECX = 0: Queries "Extended Features";
+    // Contains information about bmi,bmi2, and avx2 support.
+    let (extended_features_ebx, extended_features_ecx) = if max_basic_leaf >= 7 {
+        let CpuidResult { ebx, ecx, .. } = unsafe { __cpuid(0x0000_0007_u32) };
+        (ebx, ecx)
+    } else {
+        (0, 0) // CPUID does not support "Extended Features"
+    };
+
+    // EAX = 0x8000_0000, ECX = 0: Get Highest Extended Function Supported
+    // - EAX returns the max leaf value for extended information, that is,
+    // `cpuid` calls in range [0x8000_0000; u32::MAX]:
+    let CpuidResult {
+        eax: extended_max_basic_leaf,
+        ..
+    } = unsafe { __cpuid(0x8000_0000_u32) };
+
+    // EAX = 0x8000_0001, ECX=0: Queries "Extended Processor Info and Feature
+    // Bits"
+    let extended_proc_info_ecx = if extended_max_basic_leaf >= 1 {
+        let CpuidResult { ecx, .. } = unsafe { __cpuid(0x8000_0001_u32) };
+        ecx
+    } else {
+        0
+    };
+
+    {
+        // borrows value till the end of this scope:
+        let mut enable = |r, rb, f| {
+            if bit::test(r as usize, rb) {
+                value.set(f as u32);
+            }
+        };
+
+        enable(proc_info_ecx, 0, Feature::sse3);
+        enable(proc_info_ecx, 1, Feature::pclmulqdq);
+        enable(proc_info_ecx, 9, Feature::ssse3);
+        enable(proc_info_ecx, 13, Feature::cmpxchg16b);
+        enable(proc_info_ecx, 19, Feature::sse4_1);
+        enable(proc_info_ecx, 20, Feature::sse4_2);
+        enable(proc_info_ecx, 23, Feature::popcnt);
+        enable(proc_info_ecx, 25, Feature::aes);
+        enable(proc_info_ecx, 29, Feature::f16c);
+        enable(proc_info_ecx, 30, Feature::rdrand);
+        enable(extended_features_ebx, 18, Feature::rdseed);
+        enable(extended_features_ebx, 19, Feature::adx);
+        enable(extended_features_ebx, 11, Feature::rtm);
+        enable(proc_info_edx, 4, Feature::tsc);
+        enable(proc_info_edx, 23, Feature::mmx);
+        enable(proc_info_edx, 24, Feature::fxsr);
+        enable(proc_info_edx, 25, Feature::sse);
+        enable(proc_info_edx, 26, Feature::sse2);
+        enable(extended_features_ebx, 29, Feature::sha);
+
+        enable(extended_features_ebx, 3, Feature::bmi);
+        enable(extended_features_ebx, 8, Feature::bmi2);
+
+        // `XSAVE` and `AVX` support:
+        let cpu_xsave = bit::test(proc_info_ecx as usize, 26);
+        if cpu_xsave {
+            // 0. Here the CPU supports `XSAVE`.
+
+            // 1. Detect `OSXSAVE`, that is, whether the OS is AVX enabled and
+            // supports saving the state of the AVX/AVX2 vector registers on
+            // context-switches, see:
+            //
+            // - [intel: is avx enabled?][is_avx_enabled],
+            // - [mozilla: sse.cpp][mozilla_sse_cpp].
+            //
+            // [is_avx_enabled]: https://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled
+            // [mozilla_sse_cpp]: https://hg.mozilla.org/mozilla-central/file/64bab5cbb9b6/mozglue/build/SSE.cpp#l190
+            let cpu_osxsave = bit::test(proc_info_ecx as usize, 27);
+
+            if cpu_osxsave {
+                // 2. The OS must have signaled the CPU that it supports saving and
+                // restoring the:
+                //
+                // * SSE -> `XCR0.SSE[1]`
+                // * AVX -> `XCR0.AVX[2]`
+                // * AVX-512 -> `XCR0.AVX-512[7:5]`.
+                //
+                // by setting the corresponding bits of `XCR0` to `1`.
+                //
+                // This is safe because the CPU supports `xsave`
+                // and the OS has set `osxsave`.
+                let xcr0 = unsafe { _xgetbv(0) };
+                // Test `XCR0.SSE[1]` and `XCR0.AVX[2]` with the mask `0b110 == 6`:
+                let os_avx_support = xcr0 & 6 == 6;
+                // Test `XCR0.AVX-512[7:5]` with the mask `0b1110_0000 == 224`:
+                let os_avx512_support = xcr0 & 224 == 224;
+
+                // Only if the OS and the CPU support saving/restoring the AVX
+                // registers we enable `xsave` support:
+                if os_avx_support {
+                    // See "13.3 ENABLING THE XSAVE FEATURE SET AND XSAVE-ENABLED
+                    // FEATURES" in the "Intel® 64 and IA-32 Architectures Software
+                    // Developer’s Manual, Volume 1: Basic Architecture":
+                    //
+                    // "Software enables the XSAVE feature set by setting
+                    // CR4.OSXSAVE[bit 18] to 1 (e.g., with the MOV to CR4
+                    // instruction). If this bit is 0, execution of any of XGETBV,
+                    // XRSTOR, XRSTORS, XSAVE, XSAVEC, XSAVEOPT, XSAVES, and XSETBV
+                    // causes an invalid-opcode exception (#UD)"
+                    //
+                    enable(proc_info_ecx, 26, Feature::xsave);
+
+                    // For `xsaveopt`, `xsavec`, and `xsaves` we need to query:
+                    // Processor Extended State Enumeration Sub-leaf (EAX = 0DH,
+                    // ECX = 1):
+                    if max_basic_leaf >= 0xd {
+                        let CpuidResult {
+                            eax: proc_extended_state1_eax,
+                            ..
+                        } = unsafe { __cpuid_count(0xd_u32, 1) };
+                        enable(proc_extended_state1_eax, 0, Feature::xsaveopt);
+                        enable(proc_extended_state1_eax, 1, Feature::xsavec);
+                        enable(proc_extended_state1_eax, 3, Feature::xsaves);
+                    }
+
+                    // FMA (uses 256-bit wide registers):
+                    enable(proc_info_ecx, 12, Feature::fma);
+
+                    // And AVX/AVX2:
+                    enable(proc_info_ecx, 28, Feature::avx);
+                    enable(extended_features_ebx, 5, Feature::avx2);
+
+                    // For AVX-512 the OS also needs to support saving/restoring
+                    // the extended state, only then we enable AVX-512 support:
+                    if os_avx512_support {
+                        enable(extended_features_ebx, 16, Feature::avx512f);
+                        enable(extended_features_ebx, 17, Feature::avx512dq);
+                        enable(extended_features_ebx, 21, Feature::avx512_ifma);
+                        enable(extended_features_ebx, 26, Feature::avx512pf);
+                        enable(extended_features_ebx, 27, Feature::avx512er);
+                        enable(extended_features_ebx, 28, Feature::avx512cd);
+                        enable(extended_features_ebx, 30, Feature::avx512bw);
+                        enable(extended_features_ebx, 31, Feature::avx512vl);
+                        enable(extended_features_ecx, 1, Feature::avx512_vbmi);
+                        enable(extended_features_ecx, 14, Feature::avx512_vpopcntdq);
+                    }
+                }
+            }
+        }
+
+        // This detects ABM on AMD CPUs and LZCNT on Intel CPUs.
+        // On intel CPUs with popcnt, lzcnt implements the
+        // "missing part" of ABM, so we map both to the same
+        // internal feature.
+        //
+        // The `is_x86_feature_detected!("lzcnt")` macro then
+        // internally maps to Feature::abm.
+        enable(extended_proc_info_ecx, 5, Feature::abm);
+        // As Hygon Dhyana originates from AMD technology and shares most of the architecture with
+        // AMD's family 17h, but with different CPU Vendor ID("HygonGenuine")/Family series
+        // number(Family 18h).
+        //
+        // For CPUID feature bits, Hygon Dhyana(family 18h) share the same definition with AMD
+        // family 17h.
+        //
+        // Related AMD CPUID specification is https://www.amd.com/system/files/TechDocs/25481.pdf.
+        // Related Hygon kernel patch can be found on
+        // http://lkml.kernel.org/r/5ce86123a7b9dad925ac583d88d2f921040e859b.1538583282.git.puwen@hygon.cn
+        if vendor_id == *b"AuthenticAMD" || vendor_id == *b"HygonGenuine" {
+            // These features are available on AMD arch CPUs:
+            enable(extended_proc_info_ecx, 6, Feature::sse4a);
+            enable(extended_proc_info_ecx, 21, Feature::tbm);
+        }
+    }
+
+    value
+}
+
+#[cfg(test)]
+mod tests {
+    extern crate cupid;
+
+    #[test]
+    fn dump() {
+        println!("aes: {:?}", is_x86_feature_detected!("aes"));
+        println!("pclmulqdq: {:?}", is_x86_feature_detected!("pclmulqdq"));
+        println!("rdrand: {:?}", is_x86_feature_detected!("rdrand"));
+        println!("rdseed: {:?}", is_x86_feature_detected!("rdseed"));
+        println!("tsc: {:?}", is_x86_feature_detected!("tsc"));
+        println!("sse: {:?}", is_x86_feature_detected!("sse"));
+        println!("sse2: {:?}", is_x86_feature_detected!("sse2"));
+        println!("sse3: {:?}", is_x86_feature_detected!("sse3"));
+        println!("ssse3: {:?}", is_x86_feature_detected!("ssse3"));
+        println!("sse4.1: {:?}", is_x86_feature_detected!("sse4.1"));
+        println!("sse4.2: {:?}", is_x86_feature_detected!("sse4.2"));
+        println!("sse4a: {:?}", is_x86_feature_detected!("sse4a"));
+        println!("sha: {:?}", is_x86_feature_detected!("sha"));
+        println!("avx: {:?}", is_x86_feature_detected!("avx"));
+        println!("avx2: {:?}", is_x86_feature_detected!("avx2"));
+        println!("avx512f {:?}", is_x86_feature_detected!("avx512f"));
+        println!("avx512cd {:?}", is_x86_feature_detected!("avx512cd"));
+        println!("avx512er {:?}", is_x86_feature_detected!("avx512er"));
+        println!("avx512pf {:?}", is_x86_feature_detected!("avx512pf"));
+        println!("avx512bw {:?}", is_x86_feature_detected!("avx512bw"));
+        println!("avx512dq {:?}", is_x86_feature_detected!("avx512dq"));
+        println!("avx512vl {:?}", is_x86_feature_detected!("avx512vl"));
+        println!("avx512_ifma {:?}", is_x86_feature_detected!("avx512ifma"));
+        println!("avx512_vbmi {:?}", is_x86_feature_detected!("avx512vbmi"));
+        println!(
+            "avx512_vpopcntdq {:?}",
+            is_x86_feature_detected!("avx512vpopcntdq")
+        );
+        println!("fma: {:?}", is_x86_feature_detected!("fma"));
+        println!("abm: {:?}", is_x86_feature_detected!("abm"));
+        println!("bmi: {:?}", is_x86_feature_detected!("bmi1"));
+        println!("bmi2: {:?}", is_x86_feature_detected!("bmi2"));
+        println!("tbm: {:?}", is_x86_feature_detected!("tbm"));
+        println!("popcnt: {:?}", is_x86_feature_detected!("popcnt"));
+        println!("lzcnt: {:?}", is_x86_feature_detected!("lzcnt"));
+        println!("fxsr: {:?}", is_x86_feature_detected!("fxsr"));
+        println!("xsave: {:?}", is_x86_feature_detected!("xsave"));
+        println!("xsaveopt: {:?}", is_x86_feature_detected!("xsaveopt"));
+        println!("xsaves: {:?}", is_x86_feature_detected!("xsaves"));
+        println!("xsavec: {:?}", is_x86_feature_detected!("xsavec"));
+        println!("cmpxchg16b: {:?}", is_x86_feature_detected!("cmpxchg16b"));
+        println!("adx: {:?}", is_x86_feature_detected!("adx"));
+        println!("rtm: {:?}", is_x86_feature_detected!("rtm"));
+    }
+
+    #[test]
+    fn compare_with_cupid() {
+        let information = cupid::master().unwrap();
+        assert_eq!(is_x86_feature_detected!("aes"), information.aesni());
+        assert_eq!(
+            is_x86_feature_detected!("pclmulqdq"),
+            information.pclmulqdq()
+        );
+        assert_eq!(is_x86_feature_detected!("rdrand"), information.rdrand());
+        assert_eq!(is_x86_feature_detected!("rdseed"), information.rdseed());
+        assert_eq!(is_x86_feature_detected!("tsc"), information.tsc());
+        assert_eq!(is_x86_feature_detected!("sse"), information.sse());
+        assert_eq!(is_x86_feature_detected!("sse2"), information.sse2());
+        assert_eq!(is_x86_feature_detected!("sse3"), information.sse3());
+        assert_eq!(is_x86_feature_detected!("ssse3"), information.ssse3());
+        assert_eq!(is_x86_feature_detected!("sse4.1"), information.sse4_1());
+        assert_eq!(is_x86_feature_detected!("sse4.2"), information.sse4_2());
+        assert_eq!(is_x86_feature_detected!("sse4a"), information.sse4a());
+        assert_eq!(is_x86_feature_detected!("sha"), information.sha());
+        assert_eq!(is_x86_feature_detected!("avx"), information.avx());
+        assert_eq!(is_x86_feature_detected!("avx2"), information.avx2());
+        assert_eq!(is_x86_feature_detected!("avx512f"), information.avx512f());
+        assert_eq!(is_x86_feature_detected!("avx512cd"), information.avx512cd());
+        assert_eq!(is_x86_feature_detected!("avx512er"), information.avx512er());
+        assert_eq!(is_x86_feature_detected!("avx512pf"), information.avx512pf());
+        assert_eq!(is_x86_feature_detected!("avx512bw"), information.avx512bw());
+        assert_eq!(is_x86_feature_detected!("avx512dq"), information.avx512dq());
+        assert_eq!(is_x86_feature_detected!("avx512vl"), information.avx512vl());
+        assert_eq!(
+            is_x86_feature_detected!("avx512ifma"),
+            information.avx512_ifma()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("avx512vbmi"),
+            information.avx512_vbmi()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("avx512vpopcntdq"),
+            information.avx512_vpopcntdq()
+        );
+        assert_eq!(is_x86_feature_detected!("fma"), information.fma());
+        assert_eq!(is_x86_feature_detected!("bmi1"), information.bmi1());
+        assert_eq!(is_x86_feature_detected!("bmi2"), information.bmi2());
+        assert_eq!(is_x86_feature_detected!("popcnt"), information.popcnt());
+        assert_eq!(is_x86_feature_detected!("abm"), information.lzcnt());
+        assert_eq!(is_x86_feature_detected!("tbm"), information.tbm());
+        assert_eq!(is_x86_feature_detected!("lzcnt"), information.lzcnt());
+        assert_eq!(is_x86_feature_detected!("xsave"), information.xsave());
+        assert_eq!(is_x86_feature_detected!("xsaveopt"), information.xsaveopt());
+        assert_eq!(
+            is_x86_feature_detected!("xsavec"),
+            information.xsavec_and_xrstor()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("xsaves"),
+            information.xsaves_xrstors_and_ia32_xss()
+        );
+        assert_eq!(
+            is_x86_feature_detected!("cmpxchg16b"),
+            information.cmpxchg16b(),
+        );
+        assert_eq!(is_x86_feature_detected!("adx"), information.adx(),);
+        assert_eq!(is_x86_feature_detected!("rtm"), information.rtm(),);
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_if/lib.rs b/src/tools/rustfmt/tests/target/cfg_if/lib.rs
new file mode 100644
index 0000000000000..8b3bb304f1c83
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/lib.rs
@@ -0,0 +1,49 @@
+//! Run-time feature detection for the Rust standard library.
+//!
+//! To detect whether a feature is enabled in the system running the binary
+//! use one of the appropriate macro for the target:
+//!
+//! * `x86` and `x86_64`: [`is_x86_feature_detected`]
+//! * `arm`: [`is_arm_feature_detected`]
+//! * `aarch64`: [`is_aarch64_feature_detected`]
+//! * `mips`: [`is_mips_feature_detected`]
+//! * `mips64`: [`is_mips64_feature_detected`]
+//! * `powerpc`: [`is_powerpc_feature_detected`]
+//! * `powerpc64`: [`is_powerpc64_feature_detected`]
+
+#![unstable(feature = "stdsimd", issue = "27731")]
+#![feature(const_fn, staged_api, stdsimd, doc_cfg, allow_internal_unstable)]
+#![allow(clippy::shadow_reuse)]
+#![deny(clippy::missing_inline_in_public_items)]
+#![cfg_attr(target_os = "linux", feature(linkage))]
+#![cfg_attr(all(target_os = "freebsd", target_arch = "aarch64"), feature(asm))]
+#![cfg_attr(stdsimd_strict, deny(warnings))]
+#![cfg_attr(test, allow(unused_imports))]
+#![no_std]
+
+#[macro_use]
+extern crate cfg_if;
+
+cfg_if! {
+    if #[cfg(feature = "std_detect_file_io")] {
+        #[cfg_attr(test, macro_use(println))]
+        extern crate std;
+
+        #[allow(unused_imports)]
+        use std::{arch, fs, io, mem, sync};
+    } else {
+        #[cfg(test)]
+        #[macro_use(println)]
+        extern crate std;
+
+        #[allow(unused_imports)]
+        use core::{arch, mem, sync};
+    }
+}
+
+#[cfg(feature = "std_detect_dlsym_getauxval")]
+extern crate libc;
+
+#[doc(hidden)]
+#[unstable(feature = "stdsimd", issue = "27731")]
+pub mod detect;
diff --git a/src/tools/rustfmt/tests/target/cfg_if/mod.rs b/src/tools/rustfmt/tests/target/cfg_if/mod.rs
new file mode 100644
index 0000000000000..b630e7ff383aa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_if/mod.rs
@@ -0,0 +1,5 @@
+//! `std_detect`
+
+#[doc(hidden)] // unstable implementation detail
+#[unstable(feature = "stdsimd", issue = "27731")]
+pub mod detect;
diff --git a/src/tools/rustfmt/tests/target/cfg_mod/bar.rs b/src/tools/rustfmt/tests/target/cfg_mod/bar.rs
new file mode 100644
index 0000000000000..20dc5b4a080ca
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_mod/bar.rs
@@ -0,0 +1,3 @@
+fn bar() -> &str {
+    "bar"
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_mod/dir/dir1/dir2/wasm32.rs b/src/tools/rustfmt/tests/target/cfg_mod/dir/dir1/dir2/wasm32.rs
new file mode 100644
index 0000000000000..ac437e4225aba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_mod/dir/dir1/dir2/wasm32.rs
@@ -0,0 +1,3 @@
+fn wasm32() -> &str {
+    "wasm32"
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_mod/dir/dir1/dir3/wasm32.rs b/src/tools/rustfmt/tests/target/cfg_mod/dir/dir1/dir3/wasm32.rs
new file mode 100644
index 0000000000000..ac437e4225aba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_mod/dir/dir1/dir3/wasm32.rs
@@ -0,0 +1,3 @@
+fn wasm32() -> &str {
+    "wasm32"
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_mod/foo.rs b/src/tools/rustfmt/tests/target/cfg_mod/foo.rs
new file mode 100644
index 0000000000000..053c8e6f3ed0f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_mod/foo.rs
@@ -0,0 +1,3 @@
+fn foo() -> &str {
+    "foo"
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_mod/mod.rs b/src/tools/rustfmt/tests/target/cfg_mod/mod.rs
new file mode 100644
index 0000000000000..45ba86f11b3f5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_mod/mod.rs
@@ -0,0 +1,10 @@
+#[cfg_attr(feature = "foo", path = "foo.rs")]
+#[cfg_attr(not(feture = "foo"), path = "bar.rs")]
+mod sub_mod;
+
+#[cfg_attr(target_arch = "wasm32", path = "dir/dir1/dir2/wasm32.rs")]
+#[cfg_attr(not(target_arch = "wasm32"), path = "dir/dir1/dir3/wasm32.rs")]
+mod wasm32;
+
+#[some_attr(path = "somewhere.rs")]
+mod other;
diff --git a/src/tools/rustfmt/tests/target/cfg_mod/other.rs b/src/tools/rustfmt/tests/target/cfg_mod/other.rs
new file mode 100644
index 0000000000000..5929b8dcf531a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_mod/other.rs
@@ -0,0 +1,3 @@
+fn other() -> &str {
+    "other"
+}
diff --git a/src/tools/rustfmt/tests/target/cfg_mod/wasm32.rs b/src/tools/rustfmt/tests/target/cfg_mod/wasm32.rs
new file mode 100644
index 0000000000000..ac437e4225aba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/cfg_mod/wasm32.rs
@@ -0,0 +1,3 @@
+fn wasm32() -> &str {
+    "wasm32"
+}
diff --git a/src/tools/rustfmt/tests/target/chains-visual.rs b/src/tools/rustfmt/tests/target/chains-visual.rs
new file mode 100644
index 0000000000000..76ef99a4b59f1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/chains-visual.rs
@@ -0,0 +1,158 @@
+// rustfmt-indent_style: Visual
+// Test chain formatting.
+
+fn main() {
+    // Don't put chains on a single line if it wasn't so in source.
+    let a = b.c.d.1.foo(|x| x + 1);
+
+    bbbbbbbbbbbbbbbbbbb.ccccccccccccccccccccccccccccccccccccc
+                       .ddddddddddddddddddddddddddd();
+
+    bbbbbbbbbbbbbbbbbbb.ccccccccccccccccccccccccccccccccccccc
+                       .ddddddddddddddddddddddddddd
+                       .eeeeeeee();
+
+    // Test case where first chain element isn't a path, but is shorter than
+    // the size of a tab.
+    x().y(|| match cond() {
+           true => (),
+           false => (),
+       });
+
+    loong_func().quux(move || if true { 1 } else { 2 });
+
+    some_fuuuuuuuuunction().method_call_a(aaaaa, bbbbb, |c| {
+                               let x = c;
+                               x
+                           });
+
+    some_fuuuuuuuuunction().method_call_a(aaaaa, bbbbb, |c| {
+                               let x = c;
+                               x
+                           })
+                           .method_call_b(aaaaa, bbbbb, |c| {
+                               let x = c;
+                               x
+                           });
+
+    fffffffffffffffffffffffffffffffffff(a, {
+        SCRIPT_TASK_ROOT.with(|root| {
+                            *root.borrow_mut() = Some(&script_task);
+                        });
+    });
+
+    let suuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuum =
+        xxxxxxx.map(|x| x + 5)
+               .map(|x| x / 2)
+               .fold(0, |acc, x| acc + x);
+
+    aaaaaaaaaaaaaaaa.map(|x| {
+                        x += 1;
+                        x
+                    })
+                    .filter(some_mod::some_filter)
+}
+
+fn floaters() {
+    let z = Foo { field1: val1,
+                  field2: val2 };
+
+    let x = Foo { field1: val1,
+                  field2: val2 }.method_call()
+                                .method_call();
+
+    let y = if cond { val1 } else { val2 }.method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                       Some(d) => d as usize - 1,
+                                       None => return Err("bad param number".to_owned()),
+                                   }].clone());
+            }
+        }
+    }
+
+    if cond {
+        some();
+    } else {
+        none();
+    }.bar()
+     .baz();
+
+    Foo { x: val }.baz(|| {
+                      force();
+                      multiline();
+                  })
+                  .quux();
+
+    Foo { y: i_am_multi_line,
+          z: ok }.baz(|| {
+                     force();
+                     multiline();
+                 })
+                 .quux();
+
+    a + match x {
+            true => "yay!",
+            false => "boo!",
+        }.bar()
+}
+
+fn is_replaced_content() -> bool {
+    constellat.send(ConstellationMsg::ViewportConstrained(self.id, constraints))
+              .unwrap();
+}
+
+fn issue587() {
+    a.b::<()>(c);
+
+    std::mem::transmute(dl.symbol::<()>("init").unwrap())
+}
+
+fn issue_1389() {
+    let names = String::from_utf8(names)?.split('|')
+                                         .map(str::to_owned)
+                                         .collect();
+}
+
+fn issue1217() -> Result<Mnemonic, Error> {
+    let random_chars: String = OsRng::new()?.gen_ascii_chars()
+                                            .take(self.bit_length)
+                                            .collect();
+
+    Ok(Mnemonic::new(&random_chars))
+}
+
+fn issue1236(options: Vec<String>) -> Result<Option<String>> {
+    let process = Command::new("dmenu").stdin(Stdio::piped())
+                                       .stdout(Stdio::piped())
+                                       .spawn()
+                                       .chain_err(|| "failed to spawn dmenu")?;
+}
+
+fn issue1434() {
+    for _ in 0..100 {
+        let prototype_id =
+            PrototypeIdData::from_reader::<_, B>(&mut self.file_cursor).chain_err(|| {
+                format!("could not read prototype ID at offset {:#010x}",
+                        current_offset)
+            })?;
+    }
+}
+
+fn issue2264() {
+    {
+        something.function()
+                 .map(|| {
+                     if let a_very_very_very_very_very_very_very_very_long_variable =
+                         compute_this_variable()
+                     {
+                         println!("Hello");
+                     }
+                 })
+                 .collect();
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/chains.rs b/src/tools/rustfmt/tests/target/chains.rs
new file mode 100644
index 0000000000000..292da29819544
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/chains.rs
@@ -0,0 +1,306 @@
+// rustfmt-use_small_heuristics: Off
+// Test chain formatting.
+
+fn main() {
+    let a = b.c.d.1.foo(|x| x + 1);
+
+    bbbbbbbbbbbbbbbbbbb.ccccccccccccccccccccccccccccccccccccc.ddddddddddddddddddddddddddd();
+
+    bbbbbbbbbbbbbbbbbbb
+        .ccccccccccccccccccccccccccccccccccccc
+        .ddddddddddddddddddddddddddd
+        .eeeeeeee();
+
+    let f = fooooooooooooooooooooooooooooooooooooooooooooooooooo
+        .baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaar;
+
+    // Test case where first chain element isn't a path, but is shorter than
+    // the size of a tab.
+    x().y(|| match cond() {
+        true => (),
+        false => (),
+    });
+
+    loong_func().quux(move || {
+        if true {
+            1
+        } else {
+            2
+        }
+    });
+
+    some_fuuuuuuuuunction().method_call_a(aaaaa, bbbbb, |c| {
+        let x = c;
+        x
+    });
+
+    some_fuuuuuuuuunction()
+        .method_call_a(aaaaa, bbbbb, |c| {
+            let x = c;
+            x
+        })
+        .method_call_b(aaaaa, bbbbb, |c| {
+            let x = c;
+            x
+        });
+
+    fffffffffffffffffffffffffffffffffff(a, {
+        SCRIPT_TASK_ROOT.with(|root| {
+            *root.borrow_mut() = Some(&script_task);
+        });
+    });
+
+    let suuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuum =
+        xxxxxxx.map(|x| x + 5).map(|x| x / 2).fold(0, |acc, x| acc + x);
+
+    body.fold(Body::new(), |mut body, chunk| {
+        body.extend(chunk);
+        Ok(body)
+    })
+    .and_then(move |body| {
+        let req = Request::from_parts(parts, body);
+        f(req).map_err(|_| io::Error::new(io::ErrorKind::Other, ""))
+    });
+
+    aaaaaaaaaaaaaaaa
+        .map(|x| {
+            x += 1;
+            x
+        })
+        .filter(some_mod::some_filter)
+}
+
+fn floaters() {
+    let z = Foo {
+        field1: val1,
+        field2: val2,
+    };
+
+    let x = Foo {
+        field1: val1,
+        field2: val2,
+    }
+    .method_call()
+    .method_call();
+
+    let y = if cond {
+        val1
+    } else {
+        val2
+    }
+    .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(
+                    mparams[match cur.to_digit(10) {
+                        Some(d) => d as usize - 1,
+                        None => return Err("bad param number".to_owned()),
+                    }]
+                    .clone(),
+                );
+            }
+        }
+    }
+
+    if cond {
+        some();
+    } else {
+        none();
+    }
+    .bar()
+    .baz();
+
+    Foo {
+        x: val,
+    }
+    .baz(|| {
+        force();
+        multiline();
+    })
+    .quux();
+
+    Foo {
+        y: i_am_multi_line,
+        z: ok,
+    }
+    .baz(|| {
+        force();
+        multiline();
+    })
+    .quux();
+
+    a + match x {
+        true => "yay!",
+        false => "boo!",
+    }
+    .bar()
+}
+
+fn is_replaced_content() -> bool {
+    constellat.send(ConstellationMsg::ViewportConstrained(self.id, constraints)).unwrap();
+}
+
+fn issue587() {
+    a.b::<()>(c);
+
+    std::mem::transmute(dl.symbol::<()>("init").unwrap())
+}
+
+fn try_shorthand() {
+    let x = expr?;
+    let y = expr.kaas()?.test();
+    let loooooooooooooooooooooooooooooooooooooooooong =
+        does_this?.look?.good?.should_we_break?.after_the_first_question_mark?;
+    let yyyy = expr?.another?.another?.another?.another?.another?.another?.another?.another?.test();
+    let zzzz = expr?.another?.another?.another?.another?;
+    let aaa = x??????????????????????????????????????????????????????????????????????????;
+
+    let y = a
+        .very
+        .loooooooooooooooooooooooooooooooooooooong()
+        .chain()
+        .inside()
+        .weeeeeeeeeeeeeee()?
+        .test()
+        .0
+        .x;
+
+    parameterized(f, substs, def_id, Ns::Value, &[], |tcx| tcx.lookup_item_type(def_id).generics)?;
+    fooooooooooooooooooooooooooo()?
+        .bar()?
+        .baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaz()?;
+}
+
+fn issue_1004() {
+    match *self {
+        ty::ImplOrTraitItem::MethodTraitItem(ref i) => write!(f, "{:?}", i),
+        ty::ImplOrTraitItem::ConstTraitItem(ref i) => write!(f, "{:?}", i),
+        ty::ImplOrTraitItem::TypeTraitItem(ref i) => write!(f, "{:?}", i),
+    }?;
+
+    ty::tls::with(|tcx| {
+        let tap = ty::Binder(TraitAndProjections(principal, projections));
+        in_binder(f, tcx, &ty::Binder(""), Some(tap))
+    })?;
+}
+
+fn issue1392() {
+    test_method(
+        r#"
+        if foo {
+            a();
+        }
+        else {
+            b();
+        }
+        "#
+        .trim(),
+    );
+}
+
+// #2067
+impl Settings {
+    fn save(&self) -> Result<()> {
+        let mut file = File::create(&settings_path)
+            .chain_err(|| ErrorKind::WriteError(settings_path.clone()))?;
+    }
+}
+
+fn issue2126() {
+    {
+        {
+            {
+                {
+                    {
+                        let x = self
+                            .span_from(sub_span.expect("No span found for struct arant variant"));
+                        self.sspanpan_from_span(
+                            sub_span.expect("No span found for struct variant"),
+                        );
+                        let x = self.spanpan_from_span(
+                            sub_span.expect("No span found for struct variant"),
+                        )?;
+                    }
+                }
+            }
+        }
+    }
+}
+
+// #2200
+impl Foo {
+    pub fn from_ast(diagnostic: &::errors::Handler, attrs: &[ast::Attribute]) -> Attributes {
+        let other_attrs = attrs
+            .iter()
+            .filter_map(|attr| {
+                attr.with_desugared_doc(|attr| {
+                    if attr.check_name("doc") {
+                        if let Some(mi) = attr.meta() {
+                            if let Some(value) = mi.value_str() {
+                                doc_strings.push(DocFragment::Include(
+                                    line, attr.span, filename, contents,
+                                ));
+                            }
+                        }
+                    }
+                })
+            })
+            .collect();
+    }
+}
+
+// #2415
+// Avoid orphan in chain
+fn issue2415() {
+    let base_url = (|| {
+        // stuff
+
+        Ok((|| {
+            // stuff
+            Some(value.to_string())
+        })()
+        .ok_or("")?)
+    })()
+    .unwrap_or_else(|_: Box<::std::error::Error>| String::from(""));
+}
+
+impl issue_2786 {
+    fn thing(&self) {
+        foo(|a| {
+            println!("a");
+            println!("b");
+        })
+        .bar(|c| {
+            println!("a");
+            println!("b");
+        })
+        .baz(|c| {
+            println!("a");
+            println!("b");
+        })
+    }
+}
+
+fn issue_2773() {
+    let bar = Some(0);
+    bar.or_else(|| {
+        // do stuff
+        None
+    })
+    .or_else(|| {
+        // do other stuff
+        None
+    })
+    .and_then(|val| {
+        // do this stuff
+        None
+    });
+}
+
+fn issue_3034() {
+    disallowed_headers.iter().any(|header| *header == name)
+        || disallowed_header_prefixes.iter().any(|prefix| name.starts_with(prefix))
+}
diff --git a/src/tools/rustfmt/tests/target/chains_with_comment.rs b/src/tools/rustfmt/tests/target/chains_with_comment.rs
new file mode 100644
index 0000000000000..522d70713bcd3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/chains_with_comment.rs
@@ -0,0 +1,137 @@
+// Chains with comment.
+
+fn main() {
+    let x = y // comment
+        .z;
+
+    foo // foo
+        // comment after parent
+        .x
+        .y
+        // comment 1
+        .bar() // comment after bar()
+        // comment 2
+        .foobar
+        // comment after
+        // comment 3
+        .baz(x, y, z);
+
+    self.rev_dep_graph
+        .iter()
+        // Remove nodes that are not dirty
+        .filter(|&(unit, _)| dirties.contains(&unit))
+        // Retain only dirty dependencies of the ones that are dirty
+        .map(|(k, deps)| {
+            (
+                k.clone(),
+                deps.iter()
+                    .cloned()
+                    .filter(|d| dirties.contains(&d))
+                    .collect(),
+            )
+        });
+
+    let y = expr /* comment */
+        .kaas()?
+        // comment
+        .test();
+    let loooooooooooooooooooooooooooooooooooooooooong = does_this?
+        .look?
+        .good?
+        .should_we_break?
+        .after_the_first_question_mark?;
+    let zzzz = expr? // comment after parent
+        // comment 0
+        .another??? // comment 1
+        .another???? // comment 2
+        .another? // comment 3
+        .another?;
+
+    let y = a
+        .very
+        .loooooooooooooooooooooooooooooooooooooong() /* comment */
+        .chain()
+        .inside() /* comment */
+        .weeeeeeeeeeeeeee()?
+        .test()
+        .0
+        .x;
+
+    parameterized(f, substs, def_id, Ns::Value, &[], |tcx| {
+        tcx.lookup_item_type(def_id).generics
+    })?;
+    fooooooooooooooooooooooooooo()?
+        .bar()?
+        .baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaz()?;
+
+    // #2559
+    App::new("cargo-cache")
+        .version(crate_version!())
+        .bin_name("cargo")
+        .about("Manage cargo cache")
+        .author("matthiaskrgr")
+        .subcommand(
+            SubCommand::with_name("cache")
+                .version(crate_version!())
+                .bin_name("cargo-cache")
+                .about("Manage cargo cache")
+                .author("matthiaskrgr")
+                .arg(&list_dirs)
+                .arg(&remove_dir)
+                .arg(&gc_repos)
+                .arg(&info)
+                .arg(&keep_duplicate_crates)
+                .arg(&dry_run)
+                .arg(&auto_clean)
+                .arg(&auto_clean_expensive),
+        ) // subcommand
+        .arg(&list_dirs);
+}
+
+// #2177
+impl Foo {
+    fn dirty_rev_dep_graph(
+        &self,
+        dirties: &HashSet<UnitKey>,
+    ) -> HashMap<UnitKey, HashSet<UnitKey>> {
+        let dirties = self.transitive_dirty_units(dirties);
+        trace!("transitive_dirty_units: {:?}", dirties);
+
+        self.rev_dep_graph
+            .iter()
+            // Remove nodes that are not dirty
+            .filter(|&(unit, _)| dirties.contains(&unit))
+            // Retain only dirty dependencies of the ones that are dirty
+            .map(|(k, deps)| {
+                (
+                    k.clone(),
+                    deps.iter()
+                        .cloned()
+                        .filter(|d| dirties.contains(&d))
+                        .collect(),
+                )
+            })
+    }
+}
+
+// #2907
+fn foo() {
+    let x = foo
+        .bar??? // comment
+        .baz;
+    let x = foo
+        .bar???
+        // comment
+        .baz;
+    let x = foo
+        .bar??? // comment
+        // comment
+        .baz;
+    let x = foo
+        .bar??????????????? // comment
+        // comment
+        // comment
+        // comment
+        // comment
+        .baz;
+}
diff --git a/src/tools/rustfmt/tests/target/closure-block-inside-macro.rs b/src/tools/rustfmt/tests/target/closure-block-inside-macro.rs
new file mode 100644
index 0000000000000..b3ddfb51263b4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/closure-block-inside-macro.rs
@@ -0,0 +1,9 @@
+// #1547
+fuzz_target!(|data: &[u8]| if let Some(first) = data.first() {
+    let index = *first as usize;
+    if index >= ENCODINGS.len() {
+        return;
+    }
+    let encoding = ENCODINGS[index];
+    dispatch_test(encoding, &data[1..]);
+});
diff --git a/src/tools/rustfmt/tests/target/closure.rs b/src/tools/rustfmt/tests/target/closure.rs
new file mode 100644
index 0000000000000..f3107d19c2fbf
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/closure.rs
@@ -0,0 +1,250 @@
+// rustfmt-normalize_comments: true
+// Closures
+
+fn main() {
+    let square = (|i: i32| i * i);
+
+    let commented = |// first
+                     a, // argument
+                     // second
+                     b: WithType, // argument
+                     // ignored
+                     _| {
+        (
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+            bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        )
+    };
+
+    let block_body = move |xxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+                           ref yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy| {
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxx + yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
+    };
+
+    let loooooooooooooong_name = |field| {
+        // format comments.
+        if field.node.attrs.len() > 0 {
+            field.node.attrs[0].span.lo()
+        } else {
+            field.span.lo()
+        }
+    };
+
+    let unblock_me = |trivial| closure();
+
+    let empty = |arg| {};
+
+    let simple = |arg| {
+        // comment formatting
+        foo(arg)
+    };
+
+    let test = || {
+        do_something();
+        do_something_else();
+    };
+
+    let arg_test =
+        |big_argument_name, test123| looooooooooooooooooong_function_naaaaaaaaaaaaaaaaame();
+
+    let arg_test =
+        |big_argument_name, test123| looooooooooooooooooong_function_naaaaaaaaaaaaaaaaame();
+
+    let simple_closure = move || -> () {};
+
+    let closure = |input: Ty| -> Option<String> { foo() };
+
+    let closure_with_return_type =
+        |aaaaaaaaaaaaaaaaaaaaaaarg1, aaaaaaaaaaaaaaaaaaaaaaarg2| -> Strong { "sup".to_owned() };
+
+    |arg1, arg2, _, _, arg3, arg4| {
+        let temp = arg4 + arg3;
+        arg2 * arg1 - temp
+    };
+
+    let block_body_with_comment = args.iter().map(|a| {
+        // Emitting only dep-info is possible only for final crate type, as
+        // as others may emit required metadata for dependent crate types
+        if a.starts_with("--emit") && is_final_crate_type && !self.workspace_mode {
+            "--emit=dep-info"
+        } else {
+            a
+        }
+    });
+}
+
+fn issue311() {
+    let func = |x| println!("{}", x);
+
+    (func)(0.0);
+}
+
+fn issue863() {
+    let closure = |x| match x {
+        0 => true,
+        _ => false,
+    } == true;
+}
+
+fn issue934() {
+    let hash: &Fn(&&Block) -> u64 = &|block| -> u64 {
+        let mut h = SpanlessHash::new(cx);
+        h.hash_block(block);
+        h.finish()
+    };
+
+    let hash: &Fn(&&Block) -> u64 = &|block| -> u64 {
+        let mut h = SpanlessHash::new(cx);
+        h.hash_block(block);
+        h.finish();
+    };
+}
+
+impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
+    pub fn eq_expr(&self, left: &Expr, right: &Expr) -> bool {
+        match (&left.node, &right.node) {
+            (&ExprBinary(l_op, ref ll, ref lr), &ExprBinary(r_op, ref rl, ref rr)) => {
+                l_op.node == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
+                    || swap_binop(l_op.node, ll, lr).map_or(false, |(l_op, ll, lr)| {
+                        l_op == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
+                    })
+            }
+        }
+    }
+}
+
+fn foo() {
+    lifetimes_iter___map(|lasdfasfd| {
+        let hi = if l.bounds.is_empty() {
+            l.lifetime.span.hi()
+        };
+    });
+}
+
+fn issue1405() {
+    open_raw_fd(fd, b'r').and_then(|file| {
+        Capture::new_raw(None, |_, err| unsafe { raw::pcap_fopen_offline(file, err) })
+    });
+}
+
+fn issue1466() {
+    let vertex_buffer = frame.scope(|ctx| {
+        let buffer = ctx.create_host_visible_buffer::<VertexBuffer<Vertex>>(&vertices);
+        ctx.create_device_local_buffer(buffer)
+    });
+}
+
+fn issue470() {
+    {
+        {
+            {
+                let explicit_arg_decls =
+                    explicit_arguments
+                        .into_iter()
+                        .enumerate()
+                        .map(|(index, (ty, pattern))| {
+                            let lvalue = Lvalue::Arg(index as u32);
+                            block = this.pattern(
+                                block,
+                                argument_extent,
+                                hair::PatternRef::Hair(pattern),
+                                &lvalue,
+                            );
+                            ArgDecl { ty: ty }
+                        });
+            }
+        }
+    }
+}
+
+// #1509
+impl Foo {
+    pub fn bar(&self) {
+        Some(SomeType {
+            push_closure_out_to_100_chars: iter(otherwise_it_works_ok.into_iter().map(|f| Ok(f))),
+        })
+    }
+}
+
+fn issue1329() {
+    aaaaaaaaaaaaaaaa
+        .map(|x| {
+            x += 1;
+            x
+        })
+        .filter
+}
+
+fn issue325() {
+    let f =
+        || unsafe { xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx };
+}
+
+fn issue1697() {
+    Test.func_a(
+        A_VERY_LONG_CONST_VARIABLE_NAME,
+        move |arg1, arg2, arg3, arg4| arg1 + arg2 + arg3 + arg4,
+    )
+}
+
+fn issue1694() {
+    foooooo(
+        |_referencefffffffff: _, _target_reference: _, _oid: _, _target_oid: _| {
+            format!("refs/pull/{}/merge", pr_id)
+        },
+    )
+}
+
+fn issue1713() {
+    rayon::join(
+        || recurse(left, is_less, pred, limit),
+        || recurse(right, is_less, Some(pivot), limit),
+    );
+
+    rayon::join(
+        1,
+        || recurse(left, is_less, pred, limit),
+        2,
+        || recurse(right, is_less, Some(pivot), limit),
+    );
+}
+
+fn issue2063() {
+    |ctx: Ctx<(String, String)>| -> io::Result<Response> {
+        Ok(Response::new().with_body(ctx.params.0))
+    }
+}
+
+fn issue1524() {
+    let f = |x| x;
+    let f = |x| x;
+    let f = |x| x;
+    let f = |x| x;
+    let f = |x| x;
+}
+
+fn issue2171() {
+    foo(|| unsafe {
+        if PERIPHERALS {
+            loop {}
+        } else {
+            PERIPHERALS = true;
+        }
+    })
+}
+
+fn issue2207() {
+    a.map(|_| {
+        unsafe { a_very_very_very_very_very_very_very_long_function_name_or_anything_else() }
+            .to_string()
+    })
+}
+
+fn issue2262() {
+    result
+        .init(&mut result.slave.borrow_mut(), &mut (result.strategy)())
+        .map_err(|factory| Error {
+            factory,
+            slave: None,
+        })?;
+}
diff --git a/src/tools/rustfmt/tests/target/comment-inside-const.rs b/src/tools/rustfmt/tests/target/comment-inside-const.rs
new file mode 100644
index 0000000000000..f847f2c69def4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment-inside-const.rs
@@ -0,0 +1,9 @@
+fn issue982() {
+    const SOME_CONSTANT: u32 =
+        // Explanation why SOME_CONSTANT needs FLAG_A to be set.
+        FLAG_A |
+        // Explanation why SOME_CONSTANT needs FLAG_B to be set.
+        FLAG_B |
+        // Explanation why SOME_CONSTANT needs FLAG_C to be set.
+        FLAG_C;
+}
diff --git a/src/tools/rustfmt/tests/target/comment-not-disappear.rs b/src/tools/rustfmt/tests/target/comment-not-disappear.rs
new file mode 100644
index 0000000000000..b1fa0ff6fe119
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment-not-disappear.rs
@@ -0,0 +1,38 @@
+// All the comments here should not disappear.
+
+fn a() {
+    match x {
+        X |
+        // A comment
+        Y => {}
+    };
+}
+
+fn b() {
+    match x {
+        X =>
+        // A comment
+        {
+            y
+        }
+    }
+}
+
+fn c() {
+    a() /* ... */;
+}
+
+fn foo() -> Vec<i32> {
+    (0..11)
+        .map(|x|
+        // This comment disappears.
+        if x % 2 == 0 { x } else { x * 2 })
+        .collect()
+}
+
+fn calc_page_len(prefix_len: usize, sofar: usize) -> usize {
+    2 // page type and flags
+    + 1 // stored depth
+    + 2 // stored count
+    + prefix_len + sofar // sum of size of all the actual items
+}
diff --git a/src/tools/rustfmt/tests/target/comment.rs b/src/tools/rustfmt/tests/target/comment.rs
new file mode 100644
index 0000000000000..b987c8a44f3d4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment.rs
@@ -0,0 +1,93 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+//! Doc comment
+fn test() {
+    //! Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam
+    //! lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+
+    // comment
+    // comment2
+
+    code(); // leave this comment alone!
+            // ok?
+
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a
+    // diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+    // viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+    // Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam
+    // tincidunt congue enim, ut porta lorem lacinia consectetur. Donec ut
+    // libero sed arcu vehicula ultricies a non tortor. Lorem ipsum dolor sit
+    // amet, consectetur adipiscing elit. Aenean ut gravida lorem. Ut turpis
+    // felis, pulvinar a semper sed, adipiscing id dolor.
+
+    // Very looooooooooooooooooooooooooooooooooooooooooooooooooooooooong comment
+    // that should be split
+
+    // println!("{:?}", rewrite_comment(subslice,
+    //                                       false,
+    //                                       comment_width,
+    //                                       self.block_indent,
+    //                                       self.config)
+    //                           .unwrap());
+
+    funk(); // dontchangeme
+            // or me
+
+    // #1388
+    const EXCEPTION_PATHS: &'static [&'static str] = &[
+        // std crates
+        "src/libstd/sys/", // Platform-specific code for std lives here.
+        "src/bootstrap",
+    ];
+}
+
+/// test123
+fn doc_comment() {}
+
+fn chains() {
+    foo.bar(|| {
+        let x = 10;
+        // comment
+        x
+    })
+}
+
+fn issue_1086() {
+    //
+}
+
+// random comment
+
+fn main() { // Test
+}
+
+// #1643
+fn some_fn() // some comment
+{
+}
+
+fn some_fn1()
+// some comment
+{
+}
+
+fn some_fn2() // some comment
+{
+}
+
+fn some_fn3() // some comment some comment some comment some comment some comment some comment so
+{
+}
+
+fn some_fn4()
+// some comment some comment some comment some comment some comment some comment some comment
+{
+}
+
+// #1603
+pub enum Foo {
+    A, // `/** **/`
+    B, // `/*!`
+    C,
+}
diff --git a/src/tools/rustfmt/tests/target/comment2.rs b/src/tools/rustfmt/tests/target/comment2.rs
new file mode 100644
index 0000000000000..04f84a15c957b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment2.rs
@@ -0,0 +1,5 @@
+// rustfmt-wrap_comments: true
+
+/// This is a long line that angers rustfmt. Rustfmt shall deal with it swiftly
+/// and justly.
+pub mod foo {}
diff --git a/src/tools/rustfmt/tests/target/comment3.rs b/src/tools/rustfmt/tests/target/comment3.rs
new file mode 100644
index 0000000000000..3a810590d7b3c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment3.rs
@@ -0,0 +1,6 @@
+// rustfmt-wrap_comments: true
+
+//! This is a long line that angers rustfmt. Rustfmt shall deal with it swiftly
+//! and justly.
+
+pub mod foo {}
diff --git a/src/tools/rustfmt/tests/target/comment4.rs b/src/tools/rustfmt/tests/target/comment4.rs
new file mode 100644
index 0000000000000..e2ef7de978f93
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment4.rs
@@ -0,0 +1,51 @@
+#![allow(dead_code)] // bar
+
+//! Doc comment
+fn test() {
+    // comment
+    // comment2
+
+    code(); /* leave this comment alone!
+             * ok? */
+
+    /* Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a
+     * diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+     * viverra nec consectetur ante hendrerit. Donec et mollis dolor.
+     * Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam
+     * tincidunt congue enim, ut porta lorem lacinia consectetur. Donec ut
+     * libero sed arcu vehicula ultricies a non tortor. Lorem ipsum dolor sit
+     * amet, consectetur adipiscing elit. Aenean ut gravida lorem. Ut turpis
+     * felis, pulvinar a semper sed, adipiscing id dolor. */
+
+    // Very loooooooooooooooooooooooooooooooooooooooooooooooooooooooong comment that should be split
+
+    // println!("{:?}", rewrite_comment(subslice,
+    //                                       false,
+    //                                       comment_width,
+    //                                       self.block_indent,
+    //                                       self.config)
+    //                           .unwrap());
+
+    funk(); //dontchangeme
+            // or me
+}
+
+/// test123
+fn doc_comment() {}
+
+/*
+Regression test for issue #956
+
+(some very important text)
+*/
+
+/*
+fn debug_function() {
+    println!("hello");
+}
+// */
+
+#[link_section=".vectors"]
+#[no_mangle] // Test this attribute is preserved.
+#[cfg_attr(rustfmt, rustfmt::skip)]
+pub static ISSUE_1284: [i32; 16] = [];
diff --git a/src/tools/rustfmt/tests/target/comment5.rs b/src/tools/rustfmt/tests/target/comment5.rs
new file mode 100644
index 0000000000000..82d171e6f6a69
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment5.rs
@@ -0,0 +1,16 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+//@ special comment
+//@ Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec adiam lectus.
+//@ Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+//@
+//@ foo
+fn test() {}
+
+//@@@ another special comment
+//@@@ Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec adiam
+//@@@ lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
+//@@@
+//@@@ foo
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/target/comment6.rs b/src/tools/rustfmt/tests/target/comment6.rs
new file mode 100644
index 0000000000000..565fee632f57b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment6.rs
@@ -0,0 +1,14 @@
+// rustfmt-wrap_comments: true
+
+// Pendant la nuit du 9 mars 1860, les nuages, se confondant avec la mer,
+// limitaient à quelques brasses la portée de la vue. Sur cette mer démontée,
+// dont les lames déferlaient en projetant des lueurs livides, un léger bâtiment
+// fuyait presque à sec de toile.
+
+pub mod foo {}
+
+// ゆく河の流れは絶えずして、しかももとの水にあらず。淀みに浮かぶうたかたは、
+// かつ消えかつ結びて、久しくとどまりたるためしなし。世の中にある人とすみかと、
+// またかくのごとし。
+
+pub mod bar {}
diff --git a/src/tools/rustfmt/tests/target/comment_crlf_newline.rs b/src/tools/rustfmt/tests/target/comment_crlf_newline.rs
new file mode 100644
index 0000000000000..aab9e94d9e6fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comment_crlf_newline.rs
@@ -0,0 +1,4 @@
+// rustfmt-normalize_comments: true
+// Block comments followed by CRLF newlines should not an extra newline at the end
+
+// Something else
diff --git a/src/tools/rustfmt/tests/target/comments-fn.rs b/src/tools/rustfmt/tests/target/comments-fn.rs
new file mode 100644
index 0000000000000..1f43bd93bb0cb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/comments-fn.rs
@@ -0,0 +1,38 @@
+// Test comments on functions are preserved.
+
+// Comment on foo.
+fn foo<F, G>(
+    a: aaaaaaaaaaaaa, // A comment
+    b: bbbbbbbbbbbbb, // a second comment
+    c: ccccccccccccc,
+    // Newline comment
+    d: ddddddddddddd,
+    //  A multi line comment
+    // between args.
+    e: eeeeeeeeeeeee, /* comment before paren */
+) -> bar
+where
+    F: Foo, // COmment after where-clause
+    G: Goo, // final comment
+{
+}
+
+fn bar<F /* comment on F */, G /* comment on G */>() {}
+
+fn baz() -> Baz /* Comment after return type */ {}
+
+fn some_fn<T>()
+where
+    T: Eq, // some comment
+{
+}
+
+fn issue458<F>(a: &str, f: F)
+// comment1
+where
+    // comment2
+    F: FnOnce(&str) -> bool,
+{
+    f(a);
+    ()
+}
diff --git a/src/tools/rustfmt/tests/target/configs/blank_lines_lower_bound/1.rs b/src/tools/rustfmt/tests/target/configs/blank_lines_lower_bound/1.rs
new file mode 100644
index 0000000000000..9706699dc7a3c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/blank_lines_lower_bound/1.rs
@@ -0,0 +1,16 @@
+// rustfmt-blank_lines_lower_bound: 1
+
+fn foo() {}
+
+fn bar() {}
+
+// comment
+fn foobar() {}
+
+fn foo1() {}
+
+fn bar1() {}
+
+// comment
+
+fn foobar1() {}
diff --git a/src/tools/rustfmt/tests/target/configs/brace_style/fn_always_next_line.rs b/src/tools/rustfmt/tests/target/configs/brace_style/fn_always_next_line.rs
new file mode 100644
index 0000000000000..2755a264689fb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/brace_style/fn_always_next_line.rs
@@ -0,0 +1,19 @@
+// rustfmt-brace_style: AlwaysNextLine
+// Function brace style
+
+fn lorem()
+{
+    // body
+}
+
+fn lorem(ipsum: usize)
+{
+    // body
+}
+
+fn lorem<T>(ipsum: T)
+where
+    T: Add + Sub + Mul + Div,
+{
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/brace_style/fn_prefer_same_line.rs b/src/tools/rustfmt/tests/target/configs/brace_style/fn_prefer_same_line.rs
new file mode 100644
index 0000000000000..23f98b6dd7a62
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/brace_style/fn_prefer_same_line.rs
@@ -0,0 +1,16 @@
+// rustfmt-brace_style: PreferSameLine
+// Function brace style
+
+fn lorem() {
+    // body
+}
+
+fn lorem(ipsum: usize) {
+    // body
+}
+
+fn lorem<T>(ipsum: T)
+where
+    T: Add + Sub + Mul + Div, {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/brace_style/fn_same_line_where.rs b/src/tools/rustfmt/tests/target/configs/brace_style/fn_same_line_where.rs
new file mode 100644
index 0000000000000..2afe59943a30c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/brace_style/fn_same_line_where.rs
@@ -0,0 +1,17 @@
+// rustfmt-brace_style: SameLineWhere
+// Function brace style
+
+fn lorem() {
+    // body
+}
+
+fn lorem(ipsum: usize) {
+    // body
+}
+
+fn lorem<T>(ipsum: T)
+where
+    T: Add + Sub + Mul + Div,
+{
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/brace_style/item_always_next_line.rs b/src/tools/rustfmt/tests/target/configs/brace_style/item_always_next_line.rs
new file mode 100644
index 0000000000000..c13018630be02
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/brace_style/item_always_next_line.rs
@@ -0,0 +1,25 @@
+// rustfmt-brace_style: AlwaysNextLine
+// Item brace style
+
+enum Foo {}
+
+struct Bar {}
+
+struct Lorem
+{
+    ipsum: bool,
+}
+
+struct Dolor<T>
+where
+    T: Eq,
+{
+    sit: T,
+}
+
+#[cfg(test)]
+mod tests
+{
+    #[test]
+    fn it_works() {}
+}
diff --git a/src/tools/rustfmt/tests/target/configs/brace_style/item_prefer_same_line.rs b/src/tools/rustfmt/tests/target/configs/brace_style/item_prefer_same_line.rs
new file mode 100644
index 0000000000000..5143d7517c75e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/brace_style/item_prefer_same_line.rs
@@ -0,0 +1,18 @@
+// rustfmt-brace_style: PreferSameLine
+// Item brace style
+
+struct Lorem {
+    ipsum: bool,
+}
+
+struct Dolor<T>
+where
+    T: Eq, {
+    sit: T,
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {}
+}
diff --git a/src/tools/rustfmt/tests/target/configs/brace_style/item_same_line_where.rs b/src/tools/rustfmt/tests/target/configs/brace_style/item_same_line_where.rs
new file mode 100644
index 0000000000000..8a3b285265479
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/brace_style/item_same_line_where.rs
@@ -0,0 +1,19 @@
+// rustfmt-brace_style: SameLineWhere
+// Item brace style
+
+struct Lorem {
+    ipsum: bool,
+}
+
+struct Dolor<T>
+where
+    T: Eq,
+{
+    sit: T,
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {}
+}
diff --git a/src/tools/rustfmt/tests/target/configs/chain_width/always.rs b/src/tools/rustfmt/tests/target/configs/chain_width/always.rs
new file mode 100644
index 0000000000000..b16d25251f621
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/chain_width/always.rs
@@ -0,0 +1,29 @@
+// rustfmt-chain_width: 1
+// setting an unachievable chain_width to always get chains
+// on separate lines
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should be left alone
+    test.blorp();
+
+    // should be wrapped
+    test.blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+}
diff --git a/src/tools/rustfmt/tests/target/configs/chain_width/small.rs b/src/tools/rustfmt/tests/target/configs/chain_width/small.rs
new file mode 100644
index 0000000000000..2f2f72777f8ba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/chain_width/small.rs
@@ -0,0 +1,32 @@
+// rustfmt-chain_width: 40
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+    test.blorp().blorp().blorp();
+    test.blorp().blorp().blorp().blorp();
+
+    // should be wrapped
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+}
diff --git a/src/tools/rustfmt/tests/target/configs/chain_width/tiny.rs b/src/tools/rustfmt/tests/target/configs/chain_width/tiny.rs
new file mode 100644
index 0000000000000..960d245f8a12c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/chain_width/tiny.rs
@@ -0,0 +1,26 @@
+// rustfmt-chain_width: 20
+
+struct Fluent {}
+
+impl Fluent {
+    fn blorp(&self) -> &Self {
+        self
+    }
+}
+
+fn main() {
+    let test = Fluent {};
+
+    // should not be wrapped
+    test.blorp();
+    test.blorp().blorp();
+
+    // should be wrapped
+    test.blorp()
+        .blorp()
+        .blorp();
+    test.blorp()
+        .blorp()
+        .blorp()
+        .blorp();
+}
diff --git a/src/tools/rustfmt/tests/target/configs/combine_control_expr/false.rs b/src/tools/rustfmt/tests/target/configs/combine_control_expr/false.rs
new file mode 100644
index 0000000000000..5ada9b1dd1485
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/combine_control_expr/false.rs
@@ -0,0 +1,134 @@
+// rustfmt-indent_style: Block
+// rustfmt-combine_control_expr: false
+
+// Combining openings and closings. See rust-lang/fmt-rfcs#61.
+
+fn main() {
+    // Call
+    foo(bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Mac
+    foo(foo!(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // MethodCall
+    foo(x.foo::<Bar, Baz>(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Block
+    foo!({
+        foo();
+        bar();
+    });
+
+    // Closure
+    foo(|x| {
+        let y = x + 1;
+        y
+    });
+
+    // Match
+    foo(match opt {
+        Some(x) => x,
+        None => y,
+    });
+
+    // Struct
+    foo(Bar {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    });
+
+    // If
+    foo!(
+        if x {
+            foo();
+        } else {
+            bar();
+        }
+    );
+
+    // IfLet
+    foo!(
+        if let Some(..) = x {
+            foo();
+        } else {
+            bar();
+        }
+    );
+
+    // While
+    foo!(
+        while x {
+            foo();
+            bar();
+        }
+    );
+
+    // WhileLet
+    foo!(
+        while let Some(..) = x {
+            foo();
+            bar();
+        }
+    );
+
+    // ForLoop
+    foo!(
+        for x in y {
+            foo();
+            bar();
+        }
+    );
+
+    // Loop
+    foo!(
+        loop {
+            foo();
+            bar();
+        }
+    );
+
+    // Tuple
+    foo((
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // AddrOf
+    foo(&bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Box
+    foo(box Bar {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    });
+
+    // Unary
+    foo(!bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Try
+    foo(bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    )?);
+
+    // Cast
+    foo(Bar {
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+    } as i64);
+}
diff --git a/src/tools/rustfmt/tests/target/configs/combine_control_expr/true.rs b/src/tools/rustfmt/tests/target/configs/combine_control_expr/true.rs
new file mode 100644
index 0000000000000..52acd26492add
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/combine_control_expr/true.rs
@@ -0,0 +1,122 @@
+// rustfmt-indent_style: Block
+// rustfmt-combine_control_expr: true
+
+// Combining openings and closings. See rust-lang/fmt-rfcs#61.
+
+fn main() {
+    // Call
+    foo(bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Mac
+    foo(foo!(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // MethodCall
+    foo(x.foo::<Bar, Baz>(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Block
+    foo!({
+        foo();
+        bar();
+    });
+
+    // Closure
+    foo(|x| {
+        let y = x + 1;
+        y
+    });
+
+    // Match
+    foo(match opt {
+        Some(x) => x,
+        None => y,
+    });
+
+    // Struct
+    foo(Bar {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    });
+
+    // If
+    foo!(if x {
+        foo();
+    } else {
+        bar();
+    });
+
+    // IfLet
+    foo!(if let Some(..) = x {
+        foo();
+    } else {
+        bar();
+    });
+
+    // While
+    foo!(while x {
+        foo();
+        bar();
+    });
+
+    // WhileLet
+    foo!(while let Some(..) = x {
+        foo();
+        bar();
+    });
+
+    // ForLoop
+    foo!(for x in y {
+        foo();
+        bar();
+    });
+
+    // Loop
+    foo!(loop {
+        foo();
+        bar();
+    });
+
+    // Tuple
+    foo((
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // AddrOf
+    foo(&bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Box
+    foo(box Bar {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    });
+
+    // Unary
+    foo(!bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ));
+
+    // Try
+    foo(bar(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    )?);
+
+    // Cast
+    foo(Bar {
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+    } as i64);
+}
diff --git a/src/tools/rustfmt/tests/target/configs/comment_width/above.rs b/src/tools/rustfmt/tests/target/configs/comment_width/above.rs
new file mode 100644
index 0000000000000..ddfecda65c1ab
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/comment_width/above.rs
@@ -0,0 +1,8 @@
+// rustfmt-comment_width: 40
+// rustfmt-wrap_comments: true
+// Comment width
+
+fn main() {
+    // Lorem ipsum dolor sit amet,
+    // consectetur adipiscing elit.
+}
diff --git a/src/tools/rustfmt/tests/target/configs/comment_width/below.rs b/src/tools/rustfmt/tests/target/configs/comment_width/below.rs
new file mode 100644
index 0000000000000..abbc5930c4ce1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/comment_width/below.rs
@@ -0,0 +1,7 @@
+// rustfmt-comment_width: 80
+// rustfmt-wrap_comments: true
+// Comment width
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+}
diff --git a/src/tools/rustfmt/tests/target/configs/comment_width/ignore.rs b/src/tools/rustfmt/tests/target/configs/comment_width/ignore.rs
new file mode 100644
index 0000000000000..c86e71c28981b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/comment_width/ignore.rs
@@ -0,0 +1,7 @@
+// rustfmt-comment_width: 40
+// rustfmt-wrap_comments: false
+// Comment width
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+}
diff --git a/src/tools/rustfmt/tests/target/configs/condense_wildcard_suffixes/false.rs b/src/tools/rustfmt/tests/target/configs/condense_wildcard_suffixes/false.rs
new file mode 100644
index 0000000000000..3b967f35a8e8f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/condense_wildcard_suffixes/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-condense_wildcard_suffixes: false
+// Condense wildcard suffixes
+
+fn main() {
+    let (lorem, ipsum, _, _) = (1, 2, 3, 4);
+}
diff --git a/src/tools/rustfmt/tests/target/configs/condense_wildcard_suffixes/true.rs b/src/tools/rustfmt/tests/target/configs/condense_wildcard_suffixes/true.rs
new file mode 100644
index 0000000000000..4f880abe80e7b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/condense_wildcard_suffixes/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-condense_wildcard_suffixes: true
+// Condense wildcard suffixes
+
+fn main() {
+    let (lorem, ipsum, ..) = (1, 2, 3, 4);
+}
diff --git a/src/tools/rustfmt/tests/target/configs/control_brace_style/always_next_line.rs b/src/tools/rustfmt/tests/target/configs/control_brace_style/always_next_line.rs
new file mode 100644
index 0000000000000..7dc06f207fe36
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/control_brace_style/always_next_line.rs
@@ -0,0 +1,18 @@
+// rustfmt-control_brace_style: AlwaysNextLine
+// Control brace style
+
+fn main() {
+    if lorem
+    {
+        println!("ipsum!");
+    }
+    else
+    {
+        println!("dolor!");
+    }
+    match magi
+    {
+        Homura => "Akemi",
+        Madoka => "Kaname",
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/control_brace_style/always_same_line.rs b/src/tools/rustfmt/tests/target/configs/control_brace_style/always_same_line.rs
new file mode 100644
index 0000000000000..993b6b681fed2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/control_brace_style/always_same_line.rs
@@ -0,0 +1,14 @@
+// rustfmt-control_brace_style: AlwaysSameLine
+// Control brace style
+
+fn main() {
+    if lorem {
+        println!("ipsum!");
+    } else {
+        println!("dolor!");
+    }
+    match magi {
+        Homura => "Akemi",
+        Madoka => "Kaname",
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/control_brace_style/closing_next_line.rs b/src/tools/rustfmt/tests/target/configs/control_brace_style/closing_next_line.rs
new file mode 100644
index 0000000000000..013852ee79ad5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/control_brace_style/closing_next_line.rs
@@ -0,0 +1,15 @@
+// rustfmt-control_brace_style: ClosingNextLine
+// Control brace style
+
+fn main() {
+    if lorem {
+        println!("ipsum!");
+    }
+    else {
+        println!("dolor!");
+    }
+    match magi {
+        Homura => "Akemi",
+        Madoka => "Kaname",
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/disable_all_formatting/false.rs b/src/tools/rustfmt/tests/target/configs/disable_all_formatting/false.rs
new file mode 100644
index 0000000000000..1a0477ddb39ee
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/disable_all_formatting/false.rs
@@ -0,0 +1,10 @@
+// rustfmt-disable_all_formatting: false
+// Disable all formatting
+
+fn main() {
+    if lorem {
+        println!("ipsum!");
+    } else {
+        println!("dolor!");
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/disable_all_formatting/true.rs b/src/tools/rustfmt/tests/target/configs/disable_all_formatting/true.rs
new file mode 100644
index 0000000000000..736ccf5694238
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/disable_all_formatting/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-disable_all_formatting: true
+// Disable all formatting
+
+fn main() {
+    if lorem{println!("ipsum!");}else{println!("dolor!");}
+}
diff --git a/src/tools/rustfmt/tests/target/configs/empty_item_single_line/false.rs b/src/tools/rustfmt/tests/target/configs/empty_item_single_line/false.rs
new file mode 100644
index 0000000000000..174fe330a8da5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/empty_item_single_line/false.rs
@@ -0,0 +1,14 @@
+// rustfmt-empty_item_single_line: false
+// Empty impl on single line
+
+impl Lorem {
+}
+
+impl Ipsum {
+}
+
+fn lorem() {
+}
+
+fn lorem() {
+}
diff --git a/src/tools/rustfmt/tests/target/configs/empty_item_single_line/true.rs b/src/tools/rustfmt/tests/target/configs/empty_item_single_line/true.rs
new file mode 100644
index 0000000000000..0755485fea95f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/empty_item_single_line/true.rs
@@ -0,0 +1,10 @@
+// rustfmt-empty_item_single_line: true
+// Empty impl on single line
+
+impl Lorem {}
+
+impl Ipsum {}
+
+fn lorem() {}
+
+fn lorem() {}
diff --git a/src/tools/rustfmt/tests/target/configs/enum_discrim_align_threshold/40.rs b/src/tools/rustfmt/tests/target/configs/enum_discrim_align_threshold/40.rs
new file mode 100644
index 0000000000000..3ed66039c9dd3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/enum_discrim_align_threshold/40.rs
@@ -0,0 +1,34 @@
+// rustfmt-enum_discrim_align_threshold: 40
+
+enum Standard {
+    A     = 1,
+    Bcdef = 2,
+}
+
+enum NoDiscrims {
+    ThisIsAFairlyLongEnumVariantWithoutDiscrimLongerThan40,
+    A     = 1,
+    ThisIsAnotherFairlyLongEnumVariantWithoutDiscrimLongerThan40,
+    Bcdef = 2,
+}
+
+enum TooLong {
+    ThisOneHasDiscrimAaaaaaaaaaaaaaaaaaaaaaChar40 = 10,
+    A     = 1,
+    Bcdef = 2,
+}
+
+enum Borderline {
+    ThisOneHasDiscrimAaaaaaaaaaaaaaaaaaaaaa = 10,
+    A                                       = 1,
+    Bcdef                                   = 2,
+}
+
+// Live specimen from #1686
+enum LongWithSmallDiff {
+    SceneColorimetryEstimates             = 0x73636F65,
+    SceneAppearanceEstimates              = 0x73617065,
+    FocalPlaneColorimetryEstimates        = 0x66706365,
+    ReflectionHardcopyOriginalColorimetry = 0x72686F63,
+    ReflectionPrintOutputColorimetry      = 0x72706F63,
+}
diff --git a/src/tools/rustfmt/tests/target/configs/error_on_line_overflow/false.rs b/src/tools/rustfmt/tests/target/configs/error_on_line_overflow/false.rs
new file mode 100644
index 0000000000000..fa70ae78352f9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/error_on_line_overflow/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-error_on_line_overflow: false
+// Error on line overflow
+
+fn main() {
+    let lorem_ipsum_dolor_sit_amet_consectetur_adipiscing_elit_lorem_ipsum_dolor_sit_amet_consectetur_adipiscing_elit;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/error_on_unformatted/false.rs b/src/tools/rustfmt/tests/target/configs/error_on_unformatted/false.rs
new file mode 100644
index 0000000000000..6a78374e2a269
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/error_on_unformatted/false.rs
@@ -0,0 +1,12 @@
+// rustfmt-error_on_unformatted: false
+// Error on line overflow comment or string literals.
+
+// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+fn main() {
+    // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+
+    let x = "                                                                                                  ";
+    let a = "
+  
+";
+}
diff --git a/src/tools/rustfmt/tests/target/configs/fn_args_layout/compressed.rs b/src/tools/rustfmt/tests/target/configs/fn_args_layout/compressed.rs
new file mode 100644
index 0000000000000..f189446e25d44
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/fn_args_layout/compressed.rs
@@ -0,0 +1,22 @@
+// rustfmt-fn_args_layout: Compressed
+// Function arguments density
+
+trait Lorem {
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
+        // body
+    }
+
+    fn lorem(
+        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur,
+        adipiscing: Adipiscing, elit: Elit,
+    );
+
+    fn lorem(
+        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: onsectetur,
+        adipiscing: Adipiscing, elit: Elit,
+    ) {
+        // body
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/fn_args_layout/tall.rs b/src/tools/rustfmt/tests/target/configs/fn_args_layout/tall.rs
new file mode 100644
index 0000000000000..20f308973acbc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/fn_args_layout/tall.rs
@@ -0,0 +1,32 @@
+// rustfmt-fn_args_layout: Tall
+// Function arguments density
+
+trait Lorem {
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
+
+    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
+        // body
+    }
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: onsectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    );
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: onsectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    ) {
+        // body
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/fn_args_layout/vertical.rs b/src/tools/rustfmt/tests/target/configs/fn_args_layout/vertical.rs
new file mode 100644
index 0000000000000..6c695a75df9a2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/fn_args_layout/vertical.rs
@@ -0,0 +1,42 @@
+// rustfmt-fn_args_layout: Vertical
+// Function arguments density
+
+trait Lorem {
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+    );
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+    ) {
+        // body
+    }
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: onsectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    );
+
+    fn lorem(
+        ipsum: Ipsum,
+        dolor: Dolor,
+        sit: Sit,
+        amet: Amet,
+        consectetur: onsectetur,
+        adipiscing: Adipiscing,
+        elit: Elit,
+    ) {
+        // body
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/fn_single_line/false.rs b/src/tools/rustfmt/tests/target/configs/fn_single_line/false.rs
new file mode 100644
index 0000000000000..3d092f0c0bf5a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/fn_single_line/false.rs
@@ -0,0 +1,11 @@
+// rustfmt-fn_single_line: false
+// Single-expression function on single line
+
+fn lorem() -> usize {
+    42
+}
+
+fn lorem() -> usize {
+    let ipsum = 42;
+    ipsum
+}
diff --git a/src/tools/rustfmt/tests/target/configs/fn_single_line/true.rs b/src/tools/rustfmt/tests/target/configs/fn_single_line/true.rs
new file mode 100644
index 0000000000000..10d94e02f16df
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/fn_single_line/true.rs
@@ -0,0 +1,9 @@
+// rustfmt-fn_single_line: true
+// Single-expression function on single line
+
+fn lorem() -> usize { 42 }
+
+fn lorem() -> usize {
+    let ipsum = 42;
+    ipsum
+}
diff --git a/src/tools/rustfmt/tests/target/configs/force_explicit_abi/false.rs b/src/tools/rustfmt/tests/target/configs/force_explicit_abi/false.rs
new file mode 100644
index 0000000000000..3c48f8e0c78db
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/force_explicit_abi/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-force_explicit_abi: false
+// Force explicit abi
+
+extern {
+    pub static lorem: c_int;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/force_explicit_abi/true.rs b/src/tools/rustfmt/tests/target/configs/force_explicit_abi/true.rs
new file mode 100644
index 0000000000000..90f5a8c4ecb9a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/force_explicit_abi/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-force_explicit_abi: true
+// Force explicit abi
+
+extern "C" {
+    pub static lorem: c_int;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/force_multiline_block/false.rs b/src/tools/rustfmt/tests/target/configs/force_multiline_block/false.rs
new file mode 100644
index 0000000000000..7cb4cac1d691e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/force_multiline_block/false.rs
@@ -0,0 +1,20 @@
+// rustfmt-force_multiline_blocks: false
+// Option forces multiline match arm and closure bodies to be wrapped in a block
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            if ipsum {
+                println!("dolor");
+            }
+        }
+        Lorem::Dolor => println!("amet"),
+    }
+}
+
+fn main() {
+    result.and_then(|maybe_value| match maybe_value {
+        None => Err("oops"),
+        Some(value) => Ok(1),
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/configs/force_multiline_block/true.rs b/src/tools/rustfmt/tests/target/configs/force_multiline_block/true.rs
new file mode 100644
index 0000000000000..aec50afe5a840
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/force_multiline_block/true.rs
@@ -0,0 +1,22 @@
+// rustfmt-force_multiline_blocks: true
+// Option forces multiline match arm and closure bodies to be wrapped in a block
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            if ipsum {
+                println!("dolor");
+            }
+        }
+        Lorem::Dolor => println!("amet"),
+    }
+}
+
+fn main() {
+    result.and_then(|maybe_value| {
+        match maybe_value {
+            None => Err("oops"),
+            Some(value) => Ok(1),
+        }
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/configs/format_macro_bodies/false.rs b/src/tools/rustfmt/tests/target/configs/format_macro_bodies/false.rs
new file mode 100644
index 0000000000000..ec871b25bf7c9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/format_macro_bodies/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-format_macro_bodies: false
+
+macro_rules! foo {
+    ($a: ident : $b: ty) => { $a(42): $b; };
+    ($a: ident $b: ident $c: ident) => { $a=$b+$c; };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/format_macro_bodies/true.rs b/src/tools/rustfmt/tests/target/configs/format_macro_bodies/true.rs
new file mode 100644
index 0000000000000..9dc2524c38961
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/format_macro_bodies/true.rs
@@ -0,0 +1,10 @@
+// rustfmt-format_macro_bodies: true
+
+macro_rules! foo {
+    ($a: ident : $b: ty) => {
+        $a(42): $b;
+    };
+    ($a: ident $b: ident $c: ident) => {
+        $a = $b + $c;
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/format_macro_matchers/false.rs b/src/tools/rustfmt/tests/target/configs/format_macro_matchers/false.rs
new file mode 100644
index 0000000000000..3966d21be7563
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/format_macro_matchers/false.rs
@@ -0,0 +1,10 @@
+// rustfmt-format_macro_matchers: false
+
+macro_rules! foo {
+    ($a: ident : $b: ty) => {
+        $a(42): $b;
+    };
+    ($a: ident $b: ident $c: ident) => {
+        $a = $b + $c;
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/format_macro_matchers/true.rs b/src/tools/rustfmt/tests/target/configs/format_macro_matchers/true.rs
new file mode 100644
index 0000000000000..e113af96f26be
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/format_macro_matchers/true.rs
@@ -0,0 +1,10 @@
+// rustfmt-format_macro_matchers: true
+
+macro_rules! foo {
+    ($a:ident : $b:ty) => {
+        $a(42): $b;
+    };
+    ($a:ident $b:ident $c:ident) => {
+        $a = $b + $c;
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/format_strings/false.rs b/src/tools/rustfmt/tests/target/configs/format_strings/false.rs
new file mode 100644
index 0000000000000..ecca0d7d1fca5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/format_strings/false.rs
@@ -0,0 +1,8 @@
+// rustfmt-format_strings: false
+// rustfmt-max_width: 50
+// rustfmt-error_on_line_overflow: false
+// Force format strings
+
+fn main() {
+    let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit";
+}
diff --git a/src/tools/rustfmt/tests/target/configs/format_strings/true.rs b/src/tools/rustfmt/tests/target/configs/format_strings/true.rs
new file mode 100644
index 0000000000000..fdd5ab2c97d1c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/format_strings/true.rs
@@ -0,0 +1,9 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+// Force format strings
+
+fn main() {
+    let lorem = "ipsum dolor sit amet \
+                 consectetur adipiscing elit \
+                 lorem ipsum dolor sit";
+}
diff --git a/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-merge_imports.rs b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-merge_imports.rs
new file mode 100644
index 0000000000000..5e4064dd8119f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-merge_imports.rs
@@ -0,0 +1,16 @@
+// rustfmt-group_imports: StdExternalCrate
+// rustfmt-imports_granularity: Crate
+use alloc::{alloc::Layout, vec::Vec};
+use core::f32;
+use std::sync::Arc;
+
+use broker::database::PooledConnection;
+use chrono::Utc;
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+
+use super::{
+    schema::{Context, Payload},
+    update::convert_publish_payload,
+};
+use crate::models::Event;
diff --git a/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-nested.rs b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-nested.rs
new file mode 100644
index 0000000000000..daf23375c0e46
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-nested.rs
@@ -0,0 +1,7 @@
+// rustfmt-group_imports: StdExternalCrate
+mod test {
+    use std::path;
+
+    use crate::foo::bar;
+    use crate::foo::bar2;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-no_reorder.rs b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-no_reorder.rs
new file mode 100644
index 0000000000000..76d3d6ccb9541
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate-no_reorder.rs
@@ -0,0 +1,15 @@
+// rustfmt-group_imports: StdExternalCrate
+// rustfmt-reorder_imports: false
+
+use alloc::alloc::Layout;
+use std::sync::Arc;
+use core::f32;
+
+use chrono::Utc;
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+use broker::database::PooledConnection;
+
+use super::update::convert_publish_payload;
+use super::schema::{Context, Payload};
+use crate::models::Event;
diff --git a/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate.rs b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate.rs
new file mode 100644
index 0000000000000..080257968982f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/group_imports/StdExternalCrate.rs
@@ -0,0 +1,13 @@
+// rustfmt-group_imports: StdExternalCrate
+use alloc::alloc::Layout;
+use core::f32;
+use std::sync::Arc;
+
+use broker::database::PooledConnection;
+use chrono::Utc;
+use juniper::{FieldError, FieldResult};
+use uuid::Uuid;
+
+use super::schema::{Context, Payload};
+use super::update::convert_publish_payload;
+use crate::models::Event;
diff --git a/src/tools/rustfmt/tests/target/configs/hard_tabs/false.rs b/src/tools/rustfmt/tests/target/configs/hard_tabs/false.rs
new file mode 100644
index 0000000000000..ccfb53d8c8656
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/hard_tabs/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-hard_tabs: false
+// Hard tabs
+
+fn lorem() -> usize {
+    42 // spaces before 42
+}
diff --git a/src/tools/rustfmt/tests/target/configs/hard_tabs/true.rs b/src/tools/rustfmt/tests/target/configs/hard_tabs/true.rs
new file mode 100644
index 0000000000000..3ed4e4f20aa47
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/hard_tabs/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-hard_tabs: true
+// Hard tabs
+
+fn lorem() -> usize {
+	42 // spaces before 42
+}
diff --git a/src/tools/rustfmt/tests/target/configs/imports_indent/block.rs b/src/tools/rustfmt/tests/target/configs/imports_indent/block.rs
new file mode 100644
index 0000000000000..84c3b26bd6e1a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/imports_indent/block.rs
@@ -0,0 +1,7 @@
+// rustfmt-imports_indent: Block
+
+use lists::{
+    definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
+    struct_lit_tactic, write_list, DefinitiveListTactic, ListFormatting, ListItem, ListTactic,
+    SeparatorTactic,
+};
diff --git a/src/tools/rustfmt/tests/target/configs/imports_layout/horizontal_vertical.rs b/src/tools/rustfmt/tests/target/configs/imports_layout/horizontal_vertical.rs
new file mode 100644
index 0000000000000..4a63556d45bca
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/imports_layout/horizontal_vertical.rs
@@ -0,0 +1,18 @@
+// rustfmt-imports_indent: Block
+// rustfmt-imports_layout: HorizontalVertical
+
+use comment::{contains_comment, recover_comment_removed, rewrite_comment, FindUncommented};
+use lists::{
+    definitive_tactic,
+    itemize_list,
+    shape_for_tactic,
+    struct_lit_formatting,
+    struct_lit_shape,
+    struct_lit_tactic,
+    write_list,
+    DefinitiveListTactic,
+    ListFormatting,
+    ListItem,
+    ListTactic,
+    SeparatorTactic,
+};
diff --git a/src/tools/rustfmt/tests/target/configs/imports_layout/merge_mixed.rs b/src/tools/rustfmt/tests/target/configs/imports_layout/merge_mixed.rs
new file mode 100644
index 0000000000000..bc0da92fffba5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/imports_layout/merge_mixed.rs
@@ -0,0 +1,5 @@
+// rustfmt-imports_indent: Block
+// rustfmt-imports_granularity: Crate
+// rustfmt-imports_layout: Mixed
+
+use std::{fmt, io, str, str::FromStr};
diff --git a/src/tools/rustfmt/tests/target/configs/imports_layout/mixed.rs b/src/tools/rustfmt/tests/target/configs/imports_layout/mixed.rs
new file mode 100644
index 0000000000000..5d3349a01bba7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/imports_layout/mixed.rs
@@ -0,0 +1,9 @@
+// rustfmt-imports_indent: Block
+// rustfmt-imports_layout: Mixed
+
+use comment::{contains_comment, recover_comment_removed, rewrite_comment, FindUncommented};
+use lists::{
+    definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
+    struct_lit_tactic, write_list, DefinitiveListTactic, ListFormatting, ListItem, ListTactic,
+    SeparatorTactic,
+};
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_args.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_args.rs
new file mode 100644
index 0000000000000..80f4e133356c5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_args.rs
@@ -0,0 +1,47 @@
+// rustfmt-indent_style: Block
+// Function arguments layout
+
+fn lorem() {}
+
+fn lorem(ipsum: usize) {}
+
+fn lorem(
+    ipsum: usize,
+    dolor: usize,
+    sit: usize,
+    amet: usize,
+    consectetur: usize,
+    adipiscing: usize,
+    elit: usize,
+) {
+    // body
+}
+
+// #1441
+extern "system" {
+    pub fn GetConsoleHistoryInfo(
+        console_history_info: *mut ConsoleHistoryInfo,
+    ) -> Boooooooooooooool;
+}
+
+// rustfmt should not add trailing comma for variadic function. See #1623.
+extern "C" {
+    pub fn variadic_fn(
+        first_parameter: FirstParameterType,
+        second_parameter: SecondParameterType,
+        ...
+    );
+}
+
+// #1652
+fn deconstruct(
+    foo: Bar,
+) -> (
+    SocketAddr,
+    Header,
+    Method,
+    RequestUri,
+    HttpVersion,
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+) {
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_array.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_array.rs
new file mode 100644
index 0000000000000..5d458248c0b93
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_array.rs
@@ -0,0 +1,14 @@
+// rustfmt-indent_style: Block
+// Array layout
+
+fn main() {
+    let lorem = vec![
+        "ipsum",
+        "dolor",
+        "sit",
+        "amet",
+        "consectetur",
+        "adipiscing",
+        "elit",
+    ];
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_call.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_call.rs
new file mode 100644
index 0000000000000..19c44dc019a26
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_call.rs
@@ -0,0 +1,151 @@
+// rustfmt-indent_style: Block
+// Function call style
+
+fn main() {
+    lorem(
+        "lorem",
+        "ipsum",
+        "dolor",
+        "sit",
+        "amet",
+        "consectetur",
+        "adipiscing",
+        "elit",
+    );
+    // #1501
+    let hyper = Arc::new(Client::with_connector(
+        HttpsConnector::new(TlsClient::new()),
+    ));
+
+    // chain
+    let x = yooooooooooooo
+        .fooooooooooooooo
+        .baaaaaaaaaaaaar(hello, world);
+
+    // #1380
+    {
+        {
+            let creds = self
+                .client
+                .client_credentials(&self.config.auth.oauth2.id, &self.config.auth.oauth2.secret)?;
+        }
+    }
+
+    // nesting macro and function call
+    try!(foo(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ));
+    try!(foo(try!(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    )));
+}
+
+// #1521
+impl Foo {
+    fn map_pixel_to_coords(&self, point: &Vector2i, view: &View) -> Vector2f {
+        unsafe {
+            Vector2f::from_raw(ffi::sfRenderTexture_mapPixelToCoords(
+                self.render_texture,
+                point.raw(),
+                view.raw(),
+            ))
+        }
+    }
+}
+
+fn issue1420() {
+    given(
+        r#"
+        # Getting started
+        ...
+    "#,
+    )
+    .running(waltz)
+}
+
+// #1563
+fn query(conn: &Connection) -> Result<()> {
+    conn.query_row(
+        r#"
+            SELECT title, date
+            FROM posts,
+            WHERE DATE(date) = $1
+        "#,
+        &[],
+        |row| Post {
+            title: row.get(0),
+            date: row.get(1),
+        },
+    )?;
+
+    Ok(())
+}
+
+// #1449
+fn future_rayon_wait_1_thread() {
+    // run with only 1 worker thread; this would deadlock if we couldn't make progress
+    let mut result = None;
+    ThreadPool::new(Configuration::new().num_threads(1))
+        .unwrap()
+        .install(|| {
+            scope(|s| {
+                use std::sync::mpsc::channel;
+                let (tx, rx) = channel();
+                let a = s.spawn_future(lazy(move || Ok::<usize, ()>(rx.recv().unwrap())));
+                //                          ^^^^ FIXME: why is this needed?
+                let b = s.spawn_future(a.map(|v| v + 1));
+                let c = s.spawn_future(b.map(|v| v + 1));
+                s.spawn(move |_| tx.send(20).unwrap());
+                result = Some(c.rayon_wait().unwrap());
+            });
+        });
+    assert_eq!(result, Some(22));
+}
+
+// #1494
+impl Cursor {
+    fn foo() {
+        self.cur_type()
+            .num_template_args()
+            .or_else(|| {
+                let n: c_int = unsafe { clang_Cursor_getNumTemplateArguments(self.x) };
+
+                if n >= 0 {
+                    Some(n as u32)
+                } else {
+                    debug_assert_eq!(n, -1);
+                    None
+                }
+            })
+            .or_else(|| {
+                let canonical = self.canonical();
+                if canonical != *self {
+                    canonical.num_template_args()
+                } else {
+                    None
+                }
+            });
+    }
+}
+
+fn issue1581() {
+    bootstrap.checks.register("PERSISTED_LOCATIONS", move || {
+        if locations2.0.inner_mut.lock().poisoned {
+            Check::new(
+                State::Error,
+                "Persisted location storage is poisoned due to a write failure",
+            )
+        } else {
+            Check::new(State::Healthy, "Persisted location storage is healthy")
+        }
+    });
+}
+
+fn issue1651() {
+    {
+        let type_list: Vec<_> =
+            try_opt!(types.iter().map(|ty| ty.rewrite(context, shape)).collect());
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_chain.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_chain.rs
new file mode 100644
index 0000000000000..23340a4aba2fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_chain.rs
@@ -0,0 +1,12 @@
+// rustfmt-indent_style: Block
+// Chain indent
+
+fn main() {
+    let lorem = ipsum
+        .dolor()
+        .sit()
+        .amet()
+        .consectetur()
+        .adipiscing()
+        .elite();
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_generic.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_generic.rs
new file mode 100644
index 0000000000000..c4fcaaf65d1c6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_generic.rs
@@ -0,0 +1,22 @@
+// rustfmt-indent_style: Block
+// Generics indent
+
+fn lorem<
+    Ipsum: Eq = usize,
+    Dolor: Eq = usize,
+    Sit: Eq = usize,
+    Amet: Eq = usize,
+    Adipiscing: Eq = usize,
+    Consectetur: Eq = usize,
+    Elit: Eq = usize,
+>(
+    ipsum: Ipsum,
+    dolor: Dolor,
+    sit: Sit,
+    amet: Amet,
+    adipiscing: Adipiscing,
+    consectetur: Consectetur,
+    elit: Elit,
+) -> T {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_struct_lit.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_struct_lit.rs
new file mode 100644
index 0000000000000..656b562266fd1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_struct_lit.rs
@@ -0,0 +1,9 @@
+// rustfmt-indent_style: Block
+// Struct literal-style
+
+fn main() {
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_tab_spaces_call.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_tab_spaces_call.rs
new file mode 100644
index 0000000000000..5531e61ddc8c4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_tab_spaces_call.rs
@@ -0,0 +1,14 @@
+// rustfmt-indent_style: Block
+// rustfmt-max_width: 80
+// rustfmt-tab_spaces: 2
+
+// #1427
+fn main() {
+  exceptaions::config(move || {
+    (
+      NmiConfig {},
+      HardFaultConfig {},
+      SysTickConfig { gpio_sbsrr },
+    )
+  });
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_trailing_comma_call/one.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_trailing_comma_call/one.rs
new file mode 100644
index 0000000000000..6b9489bef550b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_trailing_comma_call/one.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: One
+// rustfmt-error_on_line_overflow: false
+// rustfmt-indent_style: Block
+
+// rustfmt should not add trailing comma when rewriting macro. See #1528.
+fn a() {
+    panic!("this is a long string that goes past the maximum line length causing rustfmt to insert a comma here:");
+    foo(
+        a,
+        oooptoptoptoptptooptoptoptoptptooptoptoptoptptoptoptoptoptpt(),
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_trailing_comma_call/two.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_trailing_comma_call/two.rs
new file mode 100644
index 0000000000000..4f4292e5f4857
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_trailing_comma_call/two.rs
@@ -0,0 +1,14 @@
+// rustfmt-version: Two
+// rustfmt-error_on_line_overflow: false
+// rustfmt-indent_style: Block
+
+// rustfmt should not add trailing comma when rewriting macro. See #1528.
+fn a() {
+    panic!(
+        "this is a long string that goes past the maximum line length causing rustfmt to insert a comma here:"
+    );
+    foo(
+        a,
+        oooptoptoptoptptooptoptoptoptptooptoptoptoptptoptoptoptoptpt(),
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/block_where_pred.rs b/src/tools/rustfmt/tests/target/configs/indent_style/block_where_pred.rs
new file mode 100644
index 0000000000000..ad7e0b8f3633f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/block_where_pred.rs
@@ -0,0 +1,12 @@
+// rustfmt-indent_style: Block
+// Where predicate indent
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
+where
+    Ipsum: Eq,
+    Dolor: Eq,
+    Sit: Eq,
+    Amet: Eq,
+{
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/default.rs b/src/tools/rustfmt/tests/target/configs/indent_style/default.rs
new file mode 100644
index 0000000000000..a8f0902b34ea9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/default.rs
@@ -0,0 +1,11 @@
+// rustfmt-indent_style: Visual
+// Where style
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
+    where Ipsum: Eq,
+          Dolor: Eq,
+          Sit: Eq,
+          Amet: Eq
+{
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/rfc_control.rs b/src/tools/rustfmt/tests/target/configs/indent_style/rfc_control.rs
new file mode 100644
index 0000000000000..6619d8b263036
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/rfc_control.rs
@@ -0,0 +1,39 @@
+// rustfmt-indent_style: Block
+
+// #1618
+fn main() {
+    loop {
+        if foo {
+            if ((right_paddle_speed < 0.) && (right_paddle.position().y - paddle_size.y / 2. > 5.))
+                || ((right_paddle_speed > 0.)
+                    && (right_paddle.position().y + paddle_size.y / 2. < game_height as f32 - 5.))
+            {
+                foo
+            }
+            if ai_timer.elapsed_time().as_microseconds() > ai_time.as_microseconds() {
+                if ball.position().y + ball_radius > right_paddle.position().y + paddle_size.y / 2.
+                {
+                    foo
+                }
+            }
+        }
+    }
+}
+
+fn issue1656() {
+    {
+        {
+            match rewrite {
+                Some(ref body_str)
+                    if (!body_str.contains('\n') && body_str.len() <= arm_shape.width)
+                        || !context.config.match_arm_blocks()
+                        || (extend && first_line_width(body_str) <= arm_shape.width)
+                        || is_block =>
+                {
+                    return None;
+                }
+                _ => {}
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/rfc_where.rs b/src/tools/rustfmt/tests/target/configs/indent_style/rfc_where.rs
new file mode 100644
index 0000000000000..a7b9a4f02b3dc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/rfc_where.rs
@@ -0,0 +1,12 @@
+// rustfmt-indent_style: Block
+// Where style
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
+where
+    Ipsum: Eq,
+    Dolor: Eq,
+    Sit: Eq,
+    Amet: Eq,
+{
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_args.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_args.rs
new file mode 100644
index 0000000000000..04c2eaee3cf2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_args.rs
@@ -0,0 +1,40 @@
+// rustfmt-indent_style: Visual
+// Function arguments layout
+
+fn lorem() {}
+
+fn lorem(ipsum: usize) {}
+
+fn lorem(ipsum: usize,
+         dolor: usize,
+         sit: usize,
+         amet: usize,
+         consectetur: usize,
+         adipiscing: usize,
+         elit: usize) {
+    // body
+}
+
+// #1922
+extern "C" {
+    pub fn LAPACKE_csytrs_rook_work(matrix_layout: c_int,
+                                    uplo: c_char,
+                                    n: lapack_int,
+                                    nrhs: lapack_int,
+                                    a: *const lapack_complex_float,
+                                    lda: lapack_int,
+                                    ipiv: *const lapack_int,
+                                    b: *mut lapack_complex_float,
+                                    ldb: lapack_int)
+                                    -> lapack_int;
+
+    pub fn LAPACKE_csytrs_rook_work(matrix_layout: c_int,
+                                    uplo: c_char,
+                                    n: lapack_int,
+                                    nrhs: lapack_int,
+                                    lda: lapack_int,
+                                    ipiv: *const lapack_int,
+                                    b: *mut lapack_complex_float,
+                                    ldb: lapack_int)
+                                    -> lapack_int;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_array.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_array.rs
new file mode 100644
index 0000000000000..1da6ff2373870
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_array.rs
@@ -0,0 +1,12 @@
+// rustfmt-indent_style: Visual
+// Array layout
+
+fn main() {
+    let lorem = vec!["ipsum",
+                     "dolor",
+                     "sit",
+                     "amet",
+                     "consectetur",
+                     "adipiscing",
+                     "elit"];
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_call.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_call.rs
new file mode 100644
index 0000000000000..5454c44ef965d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_call.rs
@@ -0,0 +1,13 @@
+// rustfmt-indent_style: Visual
+// Function call style
+
+fn main() {
+    lorem("lorem",
+          "ipsum",
+          "dolor",
+          "sit",
+          "amet",
+          "consectetur",
+          "adipiscing",
+          "elit");
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_chain.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_chain.rs
new file mode 100644
index 0000000000000..569f3d8b81d78
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_chain.rs
@@ -0,0 +1,11 @@
+// rustfmt-indent_style: Visual
+// Chain indent
+
+fn main() {
+    let lorem = ipsum.dolor()
+                     .sit()
+                     .amet()
+                     .consectetur()
+                     .adipiscing()
+                     .elite();
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_generics.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_generics.rs
new file mode 100644
index 0000000000000..491075a146d1b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_generics.rs
@@ -0,0 +1,20 @@
+// rustfmt-indent_style: Visual
+// Generics indent
+
+fn lorem<Ipsum: Eq = usize,
+         Dolor: Eq = usize,
+         Sit: Eq = usize,
+         Amet: Eq = usize,
+         Adipiscing: Eq = usize,
+         Consectetur: Eq = usize,
+         Elit: Eq = usize>(
+    ipsum: Ipsum,
+    dolor: Dolor,
+    sit: Sit,
+    amet: Amet,
+    adipiscing: Adipiscing,
+    consectetur: Consectetur,
+    elit: Elit)
+    -> T {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_struct_lit.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_struct_lit.rs
new file mode 100644
index 0000000000000..ec49021d330e8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_struct_lit.rs
@@ -0,0 +1,7 @@
+// rustfmt-indent_style: Visual
+// Struct literal-style
+
+fn main() {
+    let lorem = Lorem { ipsum: dolor,
+                        sit: amet };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_trailing_comma.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_trailing_comma.rs
new file mode 100644
index 0000000000000..9738d397dbf63
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_trailing_comma.rs
@@ -0,0 +1,7 @@
+// rustfmt-error_on_line_overflow: false
+// rustfmt-indent_style: Visual
+
+// rustfmt should not add trailing comma when rewriting macro. See #1528.
+fn a() {
+    panic!("this is a long string that goes past the maximum line length causing rustfmt to insert a comma here:");
+}
diff --git a/src/tools/rustfmt/tests/target/configs/indent_style/visual_where_pred.rs b/src/tools/rustfmt/tests/target/configs/indent_style/visual_where_pred.rs
new file mode 100644
index 0000000000000..45799dcd5fcdd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/indent_style/visual_where_pred.rs
@@ -0,0 +1,11 @@
+// rustfmt-indent_style: Visual
+// Where predicate indent
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
+    where Ipsum: Eq,
+          Dolor: Eq,
+          Sit: Eq,
+          Amet: Eq
+{
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/match_arm_blocks/false.rs b/src/tools/rustfmt/tests/target/configs/match_arm_blocks/false.rs
new file mode 100644
index 0000000000000..7a9834168c750
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/match_arm_blocks/false.rs
@@ -0,0 +1,12 @@
+// rustfmt-match_arm_blocks: false
+// Wrap match-arms
+
+fn main() {
+    match lorem {
+        true =>
+            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
+        false => {
+            println!("{}", sit)
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/match_arm_blocks/true.rs b/src/tools/rustfmt/tests/target/configs/match_arm_blocks/true.rs
new file mode 100644
index 0000000000000..eb9e34059c7e9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/match_arm_blocks/true.rs
@@ -0,0 +1,13 @@
+// rustfmt-match_arm_blocks: true
+// Wrap match-arms
+
+fn main() {
+    match lorem {
+        true => {
+            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x)
+        }
+        false => {
+            println!("{}", sit)
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/always.rs b/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/always.rs
new file mode 100644
index 0000000000000..f2af81eac3ca1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/always.rs
@@ -0,0 +1,27 @@
+// rustfmt-match_arm_leading_pipes: Always
+
+fn foo() {
+    match foo {
+        | "foo" | "bar" => {}
+        | "baz"
+        | "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        | "qux" => println!("y"),
+        | _ => {}
+    }
+}
+
+fn issue_3973() {
+    match foo {
+        | "foo" | "bar" => {}
+        | _ => {}
+    }
+}
+
+fn bar() {
+    match baz {
+        | "qux" => {}
+        | "foo" | "bar" => {}
+        | _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/never.rs b/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/never.rs
new file mode 100644
index 0000000000000..345014e4b4e80
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/never.rs
@@ -0,0 +1,27 @@
+// rustfmt-match_arm_leading_pipes: Never
+
+fn foo() {
+    match foo {
+        "foo" | "bar" => {}
+        "baz"
+        | "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        "qux" => println!("y"),
+        _ => {}
+    }
+}
+
+fn issue_3973() {
+    match foo {
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
+
+fn bar() {
+    match baz {
+        "qux" => {}
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/preserve.rs b/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/preserve.rs
new file mode 100644
index 0000000000000..2beb1f5d8133d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/match_arm_leading_pipes/preserve.rs
@@ -0,0 +1,27 @@
+// rustfmt-match_arm_leading_pipes: Preserve
+
+fn foo() {
+    match foo {
+        | "foo" | "bar" => {}
+        | "baz"
+        | "something relatively long"
+        | "something really really really realllllllllllllly long" => println!("x"),
+        | "qux" => println!("y"),
+        _ => {}
+    }
+}
+
+fn issue_3973() {
+    match foo {
+        | "foo" | "bar" => {}
+        _ => {}
+    }
+}
+
+fn bar() {
+    match baz {
+        "qux" => {}
+        "foo" | "bar" => {}
+        _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/match_block_trailing_comma/false.rs b/src/tools/rustfmt/tests/target/configs/match_block_trailing_comma/false.rs
new file mode 100644
index 0000000000000..70e02955fb01d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/match_block_trailing_comma/false.rs
@@ -0,0 +1,11 @@
+// rustfmt-match_block_trailing_comma: false
+// Match block trailing comma
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            println!("ipsum");
+        }
+        Lorem::Dolor => println!("dolor"),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/match_block_trailing_comma/true.rs b/src/tools/rustfmt/tests/target/configs/match_block_trailing_comma/true.rs
new file mode 100644
index 0000000000000..b78b046dc1c9a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/match_block_trailing_comma/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-match_block_trailing_comma: true
+// Match block trailing comma
+
+fn main() {
+    match lorem {
+        Lorem::Ipsum => {
+            println!("ipsum");
+        },
+        Lorem::Dolor => println!("dolor"),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/merge_derives/true.rs b/src/tools/rustfmt/tests/target/configs/merge_derives/true.rs
new file mode 100644
index 0000000000000..4d0148b1c6e2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/merge_derives/true.rs
@@ -0,0 +1,40 @@
+// rustfmt-merge_derives: true
+// Merge multiple derives to a single one.
+
+#[bar]
+#[derive(Eq, PartialEq)]
+#[foo]
+#[derive(Debug)]
+#[foobar]
+#[derive(Copy, Clone)]
+pub enum Foo {}
+
+#[derive(Eq, PartialEq, Debug)]
+#[foobar]
+#[derive(Copy, Clone)]
+pub enum Bar {}
+
+#[derive(Eq, PartialEq, Debug, Copy, Clone)]
+pub enum FooBar {}
+
+mod foo {
+    #[bar]
+    #[derive(Eq, PartialEq)]
+    #[foo]
+    #[derive(Debug)]
+    #[foobar]
+    #[derive(Copy, Clone)]
+    pub enum Foo {}
+}
+
+mod bar {
+    #[derive(Eq, PartialEq, Debug)]
+    #[foobar]
+    #[derive(Copy, Clone)]
+    pub enum Bar {}
+}
+
+mod foobar {
+    #[derive(Eq, PartialEq, Debug, Copy, Clone)]
+    pub enum FooBar {}
+}
diff --git a/src/tools/rustfmt/tests/target/configs/normalize_comments/false.rs b/src/tools/rustfmt/tests/target/configs/normalize_comments/false.rs
new file mode 100644
index 0000000000000..488962ed9362d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/normalize_comments/false.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_comments: false
+// Normalize comments
+
+// Lorem ipsum:
+fn dolor() -> usize {}
+
+/* sit amet: */
+fn adipiscing() -> usize {}
+
+// #652
+////////////////////////////////////////////////////////////////////////////////
+// Basic slice extension methods
+////////////////////////////////////////////////////////////////////////////////
diff --git a/src/tools/rustfmt/tests/target/configs/normalize_comments/true.rs b/src/tools/rustfmt/tests/target/configs/normalize_comments/true.rs
new file mode 100644
index 0000000000000..0bdbe08ab4fde
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/normalize_comments/true.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_comments: true
+// Normalize comments
+
+// Lorem ipsum:
+fn dolor() -> usize {}
+
+// sit amet:
+fn adipiscing() -> usize {}
+
+// #652
+////////////////////////////////////////////////////////////////////////////////
+// Basic slice extension methods
+////////////////////////////////////////////////////////////////////////////////
diff --git a/src/tools/rustfmt/tests/target/configs/normalize_doc_attributes/false.rs b/src/tools/rustfmt/tests/target/configs/normalize_doc_attributes/false.rs
new file mode 100644
index 0000000000000..f8eb64273c3d6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/normalize_doc_attributes/false.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_doc_attributes: false
+// Normalize doc attributes
+
+#![doc = " Example documentation"]
+
+#[doc = " Example item documentation"]
+pub enum Foo {}
+
+#[doc = "        Lots of space"]
+pub enum Bar {}
+
+#[doc = "no leading space"]
+pub mod FooBar {}
diff --git a/src/tools/rustfmt/tests/target/configs/normalize_doc_attributes/true.rs b/src/tools/rustfmt/tests/target/configs/normalize_doc_attributes/true.rs
new file mode 100644
index 0000000000000..fadab985bea02
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/normalize_doc_attributes/true.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_doc_attributes: true
+// Normalize doc attributes
+
+//! Example documentation
+
+/// Example item documentation
+pub enum Foo {}
+
+///        Lots of space
+pub enum Bar {}
+
+///no leading space
+pub mod FooBar {}
diff --git a/src/tools/rustfmt/tests/target/configs/remove_nested_parens/remove_nested_parens.rs b/src/tools/rustfmt/tests/target/configs/remove_nested_parens/remove_nested_parens.rs
new file mode 100644
index 0000000000000..d896042c33cec
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/remove_nested_parens/remove_nested_parens.rs
@@ -0,0 +1,5 @@
+// rustfmt-remove_nested_parens: true
+
+fn main() {
+    (foo());
+}
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_impl_items/false.rs b/src/tools/rustfmt/tests/target/configs/reorder_impl_items/false.rs
new file mode 100644
index 0000000000000..beb99f0fb8e6a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_impl_items/false.rs
@@ -0,0 +1,11 @@
+// rustfmt-reorder_impl_items: false
+
+struct Dummy;
+
+impl Iterator for Dummy {
+    fn next(&mut self) -> Option<Self::Item> {
+        None
+    }
+
+    type Item = i32;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_impl_items/true.rs b/src/tools/rustfmt/tests/target/configs/reorder_impl_items/true.rs
new file mode 100644
index 0000000000000..f2294412a991a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_impl_items/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-reorder_impl_items: true
+
+struct Dummy;
+
+impl Iterator for Dummy {
+    type Item = i32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        None
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_imports/false.rs b/src/tools/rustfmt/tests/target/configs/reorder_imports/false.rs
new file mode 100644
index 0000000000000..4b85684dc013d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_imports/false.rs
@@ -0,0 +1,7 @@
+// rustfmt-reorder_imports: false
+// Reorder imports
+
+use lorem;
+use ipsum;
+use dolor;
+use sit;
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_imports/true.rs b/src/tools/rustfmt/tests/target/configs/reorder_imports/true.rs
new file mode 100644
index 0000000000000..e4ff7295fd0be
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_imports/true.rs
@@ -0,0 +1,19 @@
+// rustfmt-reorder_imports: true
+// Reorder imports
+
+use dolor;
+use ipsum;
+use lorem;
+use sit;
+
+fn foo() {
+    use A;
+    use B;
+    use C;
+
+    bar();
+
+    use D;
+    use E;
+    use F;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_modules/dolor/mod.rs b/src/tools/rustfmt/tests/target/configs/reorder_modules/dolor/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_modules/dolor/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_modules/false.rs b/src/tools/rustfmt/tests/target/configs/reorder_modules/false.rs
new file mode 100644
index 0000000000000..56b1aa03ed795
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_modules/false.rs
@@ -0,0 +1,7 @@
+// rustfmt-reorder_modules: false
+// Reorder modules
+
+mod lorem;
+mod ipsum;
+mod dolor;
+mod sit;
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_modules/ipsum/mod.rs b/src/tools/rustfmt/tests/target/configs/reorder_modules/ipsum/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_modules/ipsum/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_modules/lorem/mod.rs b/src/tools/rustfmt/tests/target/configs/reorder_modules/lorem/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_modules/lorem/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_modules/sit/mod.rs b/src/tools/rustfmt/tests/target/configs/reorder_modules/sit/mod.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_modules/sit/mod.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/target/configs/reorder_modules/true.rs b/src/tools/rustfmt/tests/target/configs/reorder_modules/true.rs
new file mode 100644
index 0000000000000..18361e88b5fcf
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/reorder_modules/true.rs
@@ -0,0 +1,7 @@
+// rustfmt-reorder_modules: true
+// Reorder modules
+
+mod dolor;
+mod ipsum;
+mod lorem;
+mod sit;
diff --git a/src/tools/rustfmt/tests/target/configs/skip_children/foo/mod.rs b/src/tools/rustfmt/tests/target/configs/skip_children/foo/mod.rs
new file mode 100644
index 0000000000000..d7ff6cdb8290e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/skip_children/foo/mod.rs
@@ -0,0 +1,3 @@
+fn skip_formatting_this() {
+    println ! ( "Skip this" ) ;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/skip_children/true.rs b/src/tools/rustfmt/tests/target/configs/skip_children/true.rs
new file mode 100644
index 0000000000000..33fd782b4fa2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/skip_children/true.rs
@@ -0,0 +1,4 @@
+// rustfmt-skip_children: true
+
+mod foo;
+mod void;
diff --git a/src/tools/rustfmt/tests/target/configs/space_before_colon/true.rs b/src/tools/rustfmt/tests/target/configs/space_before_colon/true.rs
new file mode 100644
index 0000000000000..e2895b5d77b13
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/space_before_colon/true.rs
@@ -0,0 +1,11 @@
+// rustfmt-space_before_colon: true
+// Space before colon
+
+fn lorem<T : Eq>(t : T) {
+    let ipsum : Dolor = sit;
+}
+
+const LOREM : Lorem = Lorem {
+    ipsum : dolor,
+    sit : amet,
+};
diff --git a/src/tools/rustfmt/tests/target/configs/spaces_around_ranges/false.rs b/src/tools/rustfmt/tests/target/configs/spaces_around_ranges/false.rs
new file mode 100644
index 0000000000000..72b1be4804c64
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/spaces_around_ranges/false.rs
@@ -0,0 +1,34 @@
+// rustfmt-spaces_around_ranges: false
+// Spaces around ranges
+
+fn main() {
+    let lorem = 0..10;
+    let ipsum = 0..=10;
+
+    match lorem {
+        1..5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1..=5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1...5 => foo(),
+        _ => bar,
+    }
+}
+
+fn half_open() {
+    match [5..4, 99..105, 43..44] {
+        [_, 99.., _] => {}
+        [_, ..105, _] => {}
+        _ => {}
+    };
+
+    if let ..=5 = 0 {}
+    if let ..5 = 0 {}
+    if let 5.. = 0 {}
+}
diff --git a/src/tools/rustfmt/tests/target/configs/spaces_around_ranges/true.rs b/src/tools/rustfmt/tests/target/configs/spaces_around_ranges/true.rs
new file mode 100644
index 0000000000000..c56fdbb02b681
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/spaces_around_ranges/true.rs
@@ -0,0 +1,34 @@
+// rustfmt-spaces_around_ranges: true
+// Spaces around ranges
+
+fn main() {
+    let lorem = 0 .. 10;
+    let ipsum = 0 ..= 10;
+
+    match lorem {
+        1 .. 5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1 ..= 5 => foo(),
+        _ => bar,
+    }
+
+    match lorem {
+        1 ... 5 => foo(),
+        _ => bar,
+    }
+}
+
+fn half_open() {
+    match [5 .. 4, 99 .. 105, 43 .. 44] {
+        [_, 99 .., _] => {}
+        [_, .. 105, _] => {}
+        _ => {}
+    };
+
+    if let ..= 5 = 0 {}
+    if let .. 5 = 0 {}
+    if let 5 .. = 0 {}
+}
diff --git a/src/tools/rustfmt/tests/target/configs/struct_field_align_threshold/20.rs b/src/tools/rustfmt/tests/target/configs/struct_field_align_threshold/20.rs
new file mode 100644
index 0000000000000..12a523e9d83df
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/struct_field_align_threshold/20.rs
@@ -0,0 +1,471 @@
+// rustfmt-struct_field_align_threshold: 20
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-error_on_line_overflow: false
+
+struct Foo {
+    x:   u32,
+    yy:  u32, // comment
+    zzz: u32,
+}
+
+pub struct Bar {
+    x:   u32,
+    yy:  u32,
+    zzz: u32,
+
+    xxxxxxx: u32,
+}
+
+fn main() {
+    let foo = Foo {
+        x:   0,
+        yy:  1,
+        zzz: 2,
+    };
+
+    let bar = Bar {
+        x:   0,
+        yy:  1,
+        zzz: 2,
+
+        xxxxxxx: 3,
+    };
+}
+
+/// A Doc comment
+#[AnAttribute]
+pub struct Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f:     SomeType, // Comment beside a field
+    // Comment on a field
+    #[AnAttribute]
+    g:     SomeOtherType,
+    /// A doc comment on a field
+    h:     AThirdType,
+    pub i: TypeForPublicField,
+}
+
+// #1029
+pub struct Foo {
+    #[doc(hidden)]
+    // This will NOT get deleted!
+    bar: String, // hi
+}
+
+// #1029
+struct X {
+    // `x` is an important number.
+    #[allow(unused)] // TODO: use
+    x: u32,
+}
+
+// #410
+#[allow(missing_docs)]
+pub struct Writebatch<K: Key> {
+    #[allow(dead_code)] // only used for holding the internal pointer
+    writebatch: RawWritebatch,
+    marker:     PhantomData<K>,
+}
+
+struct Bar;
+
+struct NewType(Type, OtherType);
+
+struct NewInt<T: Copy>(
+    pub i32,
+    SomeType, // inline comment
+    T,        // sup
+);
+
+struct Qux<
+    'a,
+    N: Clone + 'a,
+    E: Clone + 'a,
+    G: Labeller<'a, N, E> + GraphWalk<'a, N, E>,
+    W: Write + Copy,
+>(
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, // Comment
+    BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+    #[AnAttr]
+    // Comment
+    /// Testdoc
+    G,
+    pub W,
+);
+
+struct Tuple(
+    // Comment 1
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+    // Comment 2
+    BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+);
+
+// With a where-clause and generics.
+pub struct Foo<'a, Y: Baz>
+where
+    X: Whatever,
+{
+    f: SomeType, // Comment beside a field
+}
+
+struct Baz {
+    a: A, // Comment A
+    b: B, // Comment B
+    c: C, // Comment C
+}
+
+struct Baz {
+    a: A, // Comment A
+
+    b: B, // Comment B
+
+    c: C, // Comment C
+}
+
+struct Baz {
+    a: A,
+
+    b: B,
+    c: C,
+
+    d: D,
+}
+
+struct Baz {
+    // Comment A
+    a: A,
+
+    // Comment B
+    b: B,
+    // Comment C
+    c: C,
+}
+
+// Will this be a one-liner?
+struct Tuple(
+    A, // Comment
+    B,
+);
+
+pub struct State<F: FnMut() -> time::Timespec> {
+    now: F,
+}
+
+pub struct State<F: FnMut() -> ()> {
+    now: F,
+}
+
+pub struct State<F: FnMut()> {
+    now: F,
+}
+
+struct Palette {
+    /// A map of indices in the palette to a count of pixels in approximately
+    /// that color
+    foo: i32,
+}
+
+// Splitting a single line comment into a block previously had a misalignment
+// when the field had attributes
+struct FieldsWithAttributes {
+    // Pre Comment
+    #[rustfmt::skip] pub host:String, /* Post comment BBBBBBBBBBBBBB BBBBBBBBBBBBBBBB
+                                       * BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBBB BBBBBBBBBBB */
+    // Another pre comment
+    #[attr1]
+    #[attr2]
+    pub id: usize, /* CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCC
+                    * CCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCC CCCCCCCCCCCC */
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep:
+        node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>,
+}
+
+struct Foo<T>(T);
+struct Foo<T>(T)
+where
+    T: Copy,
+    T: Eq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUU,
+);
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTT,
+)
+where
+    T: PartialEq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTTTT,
+)
+where
+    T: PartialEq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUU,
+)
+where
+    T: PartialEq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,        // Foo
+    UUUUUUUUUUUUUUUUUUUUUUUU, // Bar
+    // Baz
+    TTTTTTTTTTTTTTTTTTT,
+    // Qux (FIXME #572 - doc comment)
+    UUUUUUUUUUUUUUUUUUU,
+);
+
+mod m {
+    struct X<T>
+    where
+        T: Sized,
+    {
+        a: T,
+    }
+}
+
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTTTT,
+    /// Qux
+    UUUUUUUUUUUUUUUUUUU,
+);
+
+struct Issue677 {
+    pub ptr:   *const libc::c_void,
+    pub trace: fn(obj: *const libc::c_void, tracer: *mut JSTracer),
+}
+
+struct Foo {}
+struct Foo {}
+struct Foo {
+    // comment
+}
+struct Foo {
+    // trailing space ->
+}
+struct Foo {
+    // comment
+}
+struct Foo(
+    // comment
+);
+
+struct LongStruct {
+    a: A,
+    the_quick_brown_fox_jumps_over_the_lazy_dog:
+        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep:
+        node::Handle<IdRef<'id, Node<Key, Value>>, Type, NodeType>,
+}
+
+struct Foo<C = ()>(String);
+
+// #1364
+fn foo() {
+    convex_shape.set_point(0, &Vector2f { x: 400.0, y: 100.0 });
+    convex_shape.set_point(1, &Vector2f { x: 500.0, y: 70.0 });
+    convex_shape.set_point(2, &Vector2f { x: 450.0, y: 100.0 });
+    convex_shape.set_point(3, &Vector2f { x: 580.0, y: 150.0 });
+}
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo { a: x };
+
+    Foo {
+        a: foo(), // comment
+        // comment
+        b: bar(),
+        ..something
+    };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b() };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        a: f(),
+        b: b(),
+    };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a: Bar, b: f() };
+
+    Quux {
+        x: if cond {
+            bar();
+        },
+        y: baz(),
+    };
+
+    A {
+        // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+        // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante
+        // hendrerit. Donec et mollis dolor.
+        first:  item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item,
+    };
+
+    Some(Data::MethodCallData(MethodCallData {
+        span:    sub_span.unwrap(),
+        scope:   self.enclosing_scope(id),
+        ref_id:  def_id,
+        decl_id: Some(decl_id),
+    }));
+
+    Diagram {
+        //                 o        This graph demonstrates how
+        //                / \       significant whitespace is
+        //               o   o      preserved.
+        //              /|\   \
+        //             o o o   o
+        graph: G,
+    }
+}
+
+fn matcher() {
+    TagTerminatedByteMatcher {
+        matcher: ByteMatcher {
+            pattern: b"<HTML",
+            mask:    b"\xFF\xDF\xDF\xDF\xDF\xFF",
+        },
+    };
+}
+
+fn issue177() {
+    struct Foo<T> {
+        memb: T,
+    }
+    let foo = Foo::<i64> { memb: 10 };
+}
+
+fn issue201() {
+    let s = S { a: 0, ..b };
+}
+
+fn issue201_2() {
+    let s = S { a: S2 { ..c }, ..b };
+}
+
+fn issue278() {
+    let s = S {
+        a: 0,
+        //
+        b: 0,
+    };
+    let s1 = S {
+        a: 0,
+        // foo
+        //
+        // bar
+        b: 0,
+    };
+}
+
+fn struct_exprs() {
+    Foo { a: 1, b: f(2) };
+    Foo {
+        a: 1,
+        b: f(2),
+        ..g(3)
+    };
+    LoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongStruct {
+        ..base
+    };
+    IntrinsicISizesContribution {
+        content_intrinsic_sizes: IntrinsicISizes {
+            minimum_inline_size: 0,
+        },
+    };
+}
+
+fn issue123() {
+    Foo { a: b, c: d, e: f };
+
+    Foo {
+        a: bb,
+        c: dd,
+        e: ff,
+    };
+
+    Foo {
+        a: ddddddddddddddddddddd,
+        b: cccccccccccccccccccccccccccccccccccccc,
+    };
+}
+
+fn issue491() {
+    Foo {
+        guard: None,
+        arm:   0, // Comment
+    };
+
+    Foo {
+        arm: 0, // Comment
+    };
+
+    Foo {
+        a: aaaaaaaaaa,
+        b: bbbbbbbb,
+        c: cccccccccc,
+        d: dddddddddd, // a comment
+        e: eeeeeeeee,
+    };
+}
+
+fn issue698() {
+    Record {
+        ffffffffffffffffffffffffffields: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    };
+    Record {
+        ffffffffffffffffffffffffffields:
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    }
+}
+
+fn issue835() {
+    MyStruct {};
+    MyStruct { /* a comment */ };
+    MyStruct {
+        // Another comment
+    };
+    MyStruct {}
+}
+
+fn field_init_shorthand() {
+    MyStruct { x, y, z };
+    MyStruct { x, y, z, ..base };
+    Foo {
+        aaaaaaaaaa,
+        bbbbbbbb,
+        cccccccccc,
+        dddddddddd, // a comment
+        eeeeeeeee,
+    };
+    Record {
+        ffffffffffffffffffffffffffieldsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/struct_lit_single_line/false.rs b/src/tools/rustfmt/tests/target/configs/struct_lit_single_line/false.rs
new file mode 100644
index 0000000000000..e2732b5a7c9b4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/struct_lit_single_line/false.rs
@@ -0,0 +1,9 @@
+// rustfmt-struct_lit_single_line: false
+// Struct literal multiline-style
+
+fn main() {
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/tab_spaces/2.rs b/src/tools/rustfmt/tests/target/configs/tab_spaces/2.rs
new file mode 100644
index 0000000000000..85961706ea72f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/tab_spaces/2.rs
@@ -0,0 +1,14 @@
+// rustfmt-tab_spaces: 2
+// rustfmt-max_width: 30
+// rustfmt-indent_style: Block
+// Tab spaces
+
+fn lorem() {
+  let ipsum = dolor();
+  let sit = vec![
+    "amet",
+    "consectetur",
+    "adipiscing",
+    "elit.",
+  ];
+}
diff --git a/src/tools/rustfmt/tests/target/configs/tab_spaces/4.rs b/src/tools/rustfmt/tests/target/configs/tab_spaces/4.rs
new file mode 100644
index 0000000000000..524a55121e4a8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/tab_spaces/4.rs
@@ -0,0 +1,14 @@
+// rustfmt-tab_spaces: 4
+// rustfmt-max_width: 30
+// rustfmt-indent_style: Block
+// Tab spaces
+
+fn lorem() {
+    let ipsum = dolor();
+    let sit = vec![
+        "amet",
+        "consectetur",
+        "adipiscing",
+        "elit.",
+    ];
+}
diff --git a/src/tools/rustfmt/tests/target/configs/trailing_comma/always.rs b/src/tools/rustfmt/tests/target/configs/trailing_comma/always.rs
new file mode 100644
index 0000000000000..951dc680912ed
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/trailing_comma/always.rs
@@ -0,0 +1,14 @@
+// rustfmt-trailing_comma: Always
+// Trailing comma
+
+fn main() {
+    let Lorem { ipsum, dolor, sit, } = amet;
+    let Lorem {
+        ipsum,
+        dolor,
+        sit,
+        amet,
+        consectetur,
+        adipiscing,
+    } = elit;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/trailing_comma/never.rs b/src/tools/rustfmt/tests/target/configs/trailing_comma/never.rs
new file mode 100644
index 0000000000000..ae0e50f96d18c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/trailing_comma/never.rs
@@ -0,0 +1,35 @@
+// rustfmt-trailing_comma: Never
+// Trailing comma
+
+fn main() {
+    let Lorem { ipsum, dolor, sit } = amet;
+    let Lorem {
+        ipsum,
+        dolor,
+        sit,
+        amet,
+        consectetur,
+        adipiscing
+    } = elit;
+
+    // #1544
+    if let VrMsg::ClientReply {
+        request_num: reply_req_num,
+        value,
+        ..
+    } = msg
+    {
+        let _ = safe_assert_eq!(reply_req_num, request_num, op);
+        return Ok((request_num, op, value));
+    }
+
+    // #1710
+    pub struct FileInput {
+        input: StringInput,
+        file_name: OsString
+    }
+    match len {
+        Some(len) => Ok(new(self.input, self.pos + len)),
+        None => Err(self)
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/configs/trailing_comma/vertical.rs b/src/tools/rustfmt/tests/target/configs/trailing_comma/vertical.rs
new file mode 100644
index 0000000000000..7283cde8d0602
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/trailing_comma/vertical.rs
@@ -0,0 +1,14 @@
+// rustfmt-trailing_comma: Vertical
+// Trailing comma
+
+fn main() {
+    let Lorem { ipsum, dolor, sit } = amet;
+    let Lorem {
+        ipsum,
+        dolor,
+        sit,
+        amet,
+        consectetur,
+        adipiscing,
+    } = elit;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/trailing_semicolon/false.rs b/src/tools/rustfmt/tests/target/configs/trailing_semicolon/false.rs
new file mode 100644
index 0000000000000..9fa746e9c0ffb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/trailing_semicolon/false.rs
@@ -0,0 +1,27 @@
+// rustfmt-trailing_semicolon: false
+
+#![feature(loop_break_value)]
+
+fn main() {
+    'a: loop {
+        break 'a
+    }
+
+    let mut done = false;
+    'b: while !done {
+        done = true;
+        continue 'b
+    }
+
+    let x = loop {
+        break 5
+    };
+
+    let x = 'c: loop {
+        break 'c 5
+    };
+}
+
+fn foo() -> usize {
+    return 0
+}
diff --git a/src/tools/rustfmt/tests/target/configs/trailing_semicolon/true.rs b/src/tools/rustfmt/tests/target/configs/trailing_semicolon/true.rs
new file mode 100644
index 0000000000000..61b6843d677cb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/trailing_semicolon/true.rs
@@ -0,0 +1,27 @@
+// rustfmt-trailing_semicolon: true
+
+#![feature(loop_break_value)]
+
+fn main() {
+    'a: loop {
+        break 'a;
+    }
+
+    let mut done = false;
+    'b: while !done {
+        done = true;
+        continue 'b;
+    }
+
+    let x = loop {
+        break 5;
+    };
+
+    let x = 'c: loop {
+        break 'c 5;
+    };
+}
+
+fn foo() -> usize {
+    return 0;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/type_punctuation_density/compressed.rs b/src/tools/rustfmt/tests/target/configs/type_punctuation_density/compressed.rs
new file mode 100644
index 0000000000000..6571e448e446a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/type_punctuation_density/compressed.rs
@@ -0,0 +1,41 @@
+// rustfmt-type_punctuation_density: Compressed
+// Type punctuation density
+
+fn lorem<Ipsum: Dolor+Sit=Amet>() {
+    // body
+}
+
+struct Foo<T: Eq+Clone, U>
+where
+    U: Eq+Clone, {
+    // body
+}
+
+trait Foo<'a, T=usize>
+where
+    T: 'a+Eq+Clone,
+{
+    type Bar: Eq+Clone;
+}
+
+trait Foo: Eq+Clone {
+    // body
+}
+
+impl<T> Foo<'a> for Bar
+where
+    for<'a> T: 'a+Eq+Clone,
+{
+    // body
+}
+
+fn foo<'a, 'b, 'c>()
+where
+    'a: 'b+'c,
+{
+    // body
+}
+
+fn Foo<T=Foo, Output=Expr<'tcx>+Foo>() {
+    let i = 6;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/type_punctuation_density/wide.rs b/src/tools/rustfmt/tests/target/configs/type_punctuation_density/wide.rs
new file mode 100644
index 0000000000000..01546c7b0a517
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/type_punctuation_density/wide.rs
@@ -0,0 +1,41 @@
+// rustfmt-type_punctuation_density: Wide
+// Type punctuation density
+
+fn lorem<Ipsum: Dolor + Sit = Amet>() {
+    // body
+}
+
+struct Foo<T: Eq + Clone, U>
+where
+    U: Eq + Clone, {
+    // body
+}
+
+trait Foo<'a, T = usize>
+where
+    T: 'a + Eq + Clone,
+{
+    type Bar: Eq + Clone;
+}
+
+trait Foo: Eq + Clone {
+    // body
+}
+
+impl<T> Foo<'a> for Bar
+where
+    for<'a> T: 'a + Eq + Clone,
+{
+    // body
+}
+
+fn foo<'a, 'b, 'c>()
+where
+    'a: 'b + 'c,
+{
+    // body
+}
+
+fn Foo<T = Foo, Output = Expr<'tcx> + Foo>() {
+    let i = 6;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/use_field_init_shorthand/false.rs b/src/tools/rustfmt/tests/target/configs/use_field_init_shorthand/false.rs
new file mode 100644
index 0000000000000..7433044688670
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/use_field_init_shorthand/false.rs
@@ -0,0 +1,15 @@
+// rustfmt-use_field_init_shorthand: false
+// Use field initialization shorthand if possible.
+
+fn main() {
+    let a = Foo { x: x, y: y, z: z };
+
+    let b = Bar {
+        x: x,
+        y: y,
+        #[attr]
+        z: z,
+        #[rustfmt::skip]
+        skipped: skipped,
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/use_field_init_shorthand/true.rs b/src/tools/rustfmt/tests/target/configs/use_field_init_shorthand/true.rs
new file mode 100644
index 0000000000000..8b80e81534b74
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/use_field_init_shorthand/true.rs
@@ -0,0 +1,15 @@
+// rustfmt-use_field_init_shorthand: true
+// Use field initialization shorthand if possible.
+
+fn main() {
+    let a = Foo { x, y, z };
+
+    let b = Bar {
+        x,
+        y,
+        #[attr]
+        z,
+        #[rustfmt::skip]
+        skipped: skipped,
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/use_small_heuristics/default.rs b/src/tools/rustfmt/tests/target/configs/use_small_heuristics/default.rs
new file mode 100644
index 0000000000000..d67bd9aafaf02
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/use_small_heuristics/default.rs
@@ -0,0 +1,26 @@
+// rustfmt-use_small_heuristics: Default
+
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit { amet: Consectetur, adipiscing: Elit },
+}
+
+fn main() {
+    lorem(
+        "lorem",
+        "ipsum",
+        "dolor",
+        "sit",
+        "amet",
+        "consectetur",
+        "adipiscing",
+    );
+
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+
+    let lorem = if ipsum { dolor } else { sit };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/use_small_heuristics/max.rs b/src/tools/rustfmt/tests/target/configs/use_small_heuristics/max.rs
new file mode 100644
index 0000000000000..785dfbea01439
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/use_small_heuristics/max.rs
@@ -0,0 +1,15 @@
+// rustfmt-use_small_heuristics: Max
+
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit { amet: Consectetur, adipiscing: Elit },
+}
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
+
+    let lorem = Lorem { ipsum: dolor, sit: amet };
+
+    let lorem = if ipsum { dolor } else { sit };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/use_small_heuristics/off.rs b/src/tools/rustfmt/tests/target/configs/use_small_heuristics/off.rs
new file mode 100644
index 0000000000000..f76392d2404be
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/use_small_heuristics/off.rs
@@ -0,0 +1,25 @@
+// rustfmt-use_small_heuristics: Off
+
+enum Lorem {
+    Ipsum,
+    Dolor(bool),
+    Sit {
+        amet: Consectetur,
+        adipiscing: Elit,
+    },
+}
+
+fn main() {
+    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
+
+    let lorem = Lorem {
+        ipsum: dolor,
+        sit: amet,
+    };
+
+    let lorem = if ipsum {
+        dolor
+    } else {
+        sit
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/configs/use_try_shorthand/false.rs b/src/tools/rustfmt/tests/target/configs/use_try_shorthand/false.rs
new file mode 100644
index 0000000000000..de7f8b4a5e248
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/use_try_shorthand/false.rs
@@ -0,0 +1,6 @@
+// rustfmt-use_try_shorthand: false
+// Use try! shorthand
+
+fn main() {
+    let lorem = try!(ipsum.map(|dolor| dolor.sit()));
+}
diff --git a/src/tools/rustfmt/tests/target/configs/use_try_shorthand/true.rs b/src/tools/rustfmt/tests/target/configs/use_try_shorthand/true.rs
new file mode 100644
index 0000000000000..d3aa035792c27
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/use_try_shorthand/true.rs
@@ -0,0 +1,6 @@
+// rustfmt-use_try_shorthand: true
+// Use try! shorthand
+
+fn main() {
+    let lorem = ipsum.map(|dolor| dolor.sit())?;
+}
diff --git a/src/tools/rustfmt/tests/target/configs/where_single_line/true-with-brace-style.rs b/src/tools/rustfmt/tests/target/configs/where_single_line/true-with-brace-style.rs
new file mode 100644
index 0000000000000..ec7f79b689caa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/where_single_line/true-with-brace-style.rs
@@ -0,0 +1,22 @@
+// rustfmt-brace_style: SameLineWhere
+// rustfmt-where_single_line: true
+
+fn lorem_multi_line_clauseless<Ipsum, Dolor, Sit, Amet>(
+    a: Aaaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbbbb,
+    c: Ccccccccccccccccc,
+    d: Ddddddddddddddddddddddddd,
+    e: Eeeeeeeeeeeeeeeeeee,
+) -> T {
+    // body
+}
+
+fn lorem_multi_line_clauseless<Ipsum, Dolor, Sit, Amet>(
+    a: Aaaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbbbb,
+    c: Ccccccccccccccccc,
+    d: Ddddddddddddddddddddddddd,
+    e: Eeeeeeeeeeeeeeeeeee,
+) {
+    // body
+}
diff --git a/src/tools/rustfmt/tests/target/configs/where_single_line/true.rs b/src/tools/rustfmt/tests/target/configs/where_single_line/true.rs
new file mode 100644
index 0000000000000..7f816459e3c6e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/where_single_line/true.rs
@@ -0,0 +1,30 @@
+// rustfmt-where_single_line: true
+// Where style
+
+fn lorem_two_items<Ipsum, Dolor, Sit, Amet>() -> T
+where
+    Ipsum: Eq,
+    Lorem: Eq,
+{
+    // body
+}
+
+fn lorem_multi_line<Ipsum, Dolor, Sit, Amet>(
+    a: Aaaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbbbb,
+    c: Ccccccccccccccccc,
+    d: Ddddddddddddddddddddddddd,
+    e: Eeeeeeeeeeeeeeeeeee,
+) -> T
+where
+    Ipsum: Eq,
+{
+    // body
+}
+
+fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
+where Ipsum: Eq {
+    // body
+}
+
+unsafe impl Sync for Foo where (): Send {}
diff --git a/src/tools/rustfmt/tests/target/configs/wrap_comments/false.rs b/src/tools/rustfmt/tests/target/configs/wrap_comments/false.rs
new file mode 100644
index 0000000000000..48ecd88accbf9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/wrap_comments/false.rs
@@ -0,0 +1,8 @@
+// rustfmt-wrap_comments: false
+// rustfmt-max_width: 50
+// rustfmt-error_on_line_overflow: false
+// Wrap comments
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+}
diff --git a/src/tools/rustfmt/tests/target/configs/wrap_comments/true.rs b/src/tools/rustfmt/tests/target/configs/wrap_comments/true.rs
new file mode 100644
index 0000000000000..4096fd4d89d2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/configs/wrap_comments/true.rs
@@ -0,0 +1,20 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 50
+// Wrap comments
+
+fn main() {
+    // Lorem ipsum dolor sit amet, consectetur
+    // adipiscing elit, sed do eiusmod tempor
+    // incididunt ut labore et dolore magna
+    // aliqua. Ut enim ad minim veniam, quis
+    // nostrud exercitation ullamco laboris nisi
+    // ut aliquip ex ea commodo consequat.
+}
+
+fn code_block() {
+    // ```rust
+    // let x = 3;
+    //
+    // println!("x = {}", x);
+    // ```
+}
diff --git a/src/tools/rustfmt/tests/target/const_generics.rs b/src/tools/rustfmt/tests/target/const_generics.rs
new file mode 100644
index 0000000000000..b30b7b58c12b9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/const_generics.rs
@@ -0,0 +1,37 @@
+struct Message {
+    field2: Vec<"MessageEntity">,
+    field3: Vec<1>,
+    field4: Vec<2, 3>,
+}
+
+struct RectangularArray<T, const WIDTH: usize, const HEIGHT: usize> {
+    array: [[T; WIDTH]; HEIGHT],
+}
+
+fn main() {
+    const X: usize = 7;
+    let x: RectangularArray<i32, 2, 4>;
+    let y: RectangularArray<i32, X, { 2 * 2 }>;
+}
+
+fn foo<const X: usize>() {
+    const Y: usize = X * 2;
+    static Z: (usize, usize) = (X, X);
+
+    struct Foo([i32; X]);
+}
+
+type Foo<const N: usize> = [i32; N + 1];
+
+pub trait Foo: Bar<{ Baz::COUNT }> {
+    const ASD: usize;
+}
+
+// #4263
+fn const_generics_on_params<
+    // AAAA
+    const BBBB: usize,
+    /* CCCC */
+    const DDDD: usize,
+>() {
+}
diff --git a/src/tools/rustfmt/tests/target/control-brace-style-always-next-line.rs b/src/tools/rustfmt/tests/target/control-brace-style-always-next-line.rs
new file mode 100644
index 0000000000000..054a3075ca0c5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/control-brace-style-always-next-line.rs
@@ -0,0 +1,50 @@
+// rustfmt-control_brace_style: AlwaysNextLine
+
+fn main() {
+    loop
+    {
+        ();
+        ();
+    }
+
+    'label: loop
+    // loop comment
+    {
+        ();
+    }
+
+    cond = true;
+    while cond
+    {
+        ();
+    }
+
+    'while_label: while cond
+    {
+        // while comment
+        ();
+    }
+
+    for obj in iter
+    {
+        for sub_obj in obj
+        {
+            'nested_while_label: while cond
+            {
+                ();
+            }
+        }
+    }
+
+    match some_var
+    {
+        // match comment
+        pattern0 => val0,
+        pattern1 => val1,
+        pattern2 | pattern3 =>
+        {
+            do_stuff();
+            val2
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/control-brace-style-always-same-line.rs b/src/tools/rustfmt/tests/target/control-brace-style-always-same-line.rs
new file mode 100644
index 0000000000000..cf3f82dfcf104
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/control-brace-style-always-same-line.rs
@@ -0,0 +1,40 @@
+fn main() {
+    loop {
+        ();
+        ();
+    }
+
+    'label: loop
+    // loop comment
+    {
+        ();
+    }
+
+    cond = true;
+    while cond {
+        ();
+    }
+
+    'while_label: while cond {
+        // while comment
+        ();
+    }
+
+    for obj in iter {
+        for sub_obj in obj {
+            'nested_while_label: while cond {
+                ();
+            }
+        }
+    }
+
+    match some_var {
+        // match comment
+        pattern0 => val0,
+        pattern1 => val1,
+        pattern2 | pattern3 => {
+            do_stuff();
+            val2
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/doc-attrib.rs b/src/tools/rustfmt/tests/target/doc-attrib.rs
new file mode 100644
index 0000000000000..36527b7cd4254
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/doc-attrib.rs
@@ -0,0 +1,131 @@
+// rustfmt-wrap_comments: true
+// rustfmt-normalize_doc_attributes: true
+
+// Only doc = "" attributes should be normalized
+//! Example doc attribute comment
+//!          Example doc attribute comment with 10 leading spaces
+#![doc(
+    html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
+    html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
+    html_root_url = "https://doc.rust-lang.org/nightly/",
+    html_playground_url = "https://play.rust-lang.org/",
+    test(attr(deny(warnings)))
+)]
+
+// Long `#[doc = "..."]`
+struct A {
+    /// xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    b: i32,
+}
+
+/// The `nodes` and `edges` method each return instantiations of `Cow<[T]>` to
+/// leave implementers the freedom to create entirely new vectors or to pass
+/// back slices into internally owned vectors.
+struct B {
+    b: i32,
+}
+
+/// Level 1 comment
+mod tests {
+    /// Level 2 comment
+    impl A {
+        /// Level 3 comment
+        fn f() {
+            /// Level 4 comment
+            fn g() {}
+        }
+    }
+}
+
+struct C {
+    /// item doc attrib comment
+    // regular item comment
+    b: i32,
+
+    // regular item comment
+    /// item doc attrib comment
+    c: i32,
+}
+
+// non-regression test for regular attributes, from #2647
+#[cfg(
+    feature = "this_line_is_101_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+)]
+pub fn foo() {}
+
+// path attrs
+#[clippy::bar]
+#[clippy::bar(a, b, c)]
+pub fn foo() {}
+
+mod issue_2620 {
+    #[derive(Debug, StructOpt)]
+    #[structopt(about = "Display information about the character on FF Logs")]
+    pub struct Params {
+        #[structopt(help = "The server the character is on")]
+        server: String,
+        #[structopt(help = "The character's first name")]
+        first_name: String,
+        #[structopt(help = "The character's last name")]
+        last_name: String,
+        #[structopt(
+            short = "j",
+            long = "job",
+            help = "The job to look at",
+            parse(try_from_str)
+        )]
+        job: Option<Job>,
+    }
+}
+
+// non-regression test for regular attributes, from #2969
+#[cfg(not(all(
+    feature = "std",
+    any(
+        target_os = "linux",
+        target_os = "android",
+        target_os = "netbsd",
+        target_os = "dragonfly",
+        target_os = "haiku",
+        target_os = "emscripten",
+        target_os = "solaris",
+        target_os = "cloudabi",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "redox",
+        target_os = "fuchsia",
+        windows,
+        all(target_arch = "wasm32", feature = "stdweb"),
+        all(target_arch = "wasm32", feature = "wasm-bindgen"),
+    )
+)))]
+type Os = NoSource;
+
+// use cases from bindgen needing precise control over leading spaces
+/// <div rustbindgen accessor></div>
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct ContradictAccessors {
+    ///<foo>no leading spaces here</foo>
+    pub mBothAccessors: ::std::os::raw::c_int,
+    /// <div rustbindgen accessor="false"></div>
+    pub mNoAccessors: ::std::os::raw::c_int,
+    /// <div rustbindgen accessor="unsafe"></div>
+    pub mUnsafeAccessors: ::std::os::raw::c_int,
+    /// <div rustbindgen accessor="immutable"></div>
+    pub mImmutableAccessor: ::std::os::raw::c_int,
+}
+
+/// \brief          MPI structure
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct mbedtls_mpi {
+    ///<  integer sign
+    pub s: ::std::os::raw::c_int,
+    ///<  total # of limbs
+    pub n: ::std::os::raw::c_ulong,
+    ///<  pointer to limbs
+    pub p: *mut mbedtls_mpi_uint,
+}
diff --git a/src/tools/rustfmt/tests/target/doc-comment-with-example.rs b/src/tools/rustfmt/tests/target/doc-comment-with-example.rs
new file mode 100644
index 0000000000000..c5a4e779ea224
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/doc-comment-with-example.rs
@@ -0,0 +1,11 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// Foo
+///
+/// # Example
+/// ```
+/// # #![cfg_attr(not(dox), feature(cfg_target_feature, target_feature, stdsimd))]
+/// # #![cfg_attr(not(dox), no_std)]
+/// fn foo() {}
+/// ```
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/doc.rs b/src/tools/rustfmt/tests/target/doc.rs
new file mode 100644
index 0000000000000..0f9e2d21c1fc6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/doc.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+// Part of multiple.rs
+
+// sadfsdfa
+// sdffsdfasdf
diff --git a/src/tools/rustfmt/tests/target/dyn_trait.rs b/src/tools/rustfmt/tests/target/dyn_trait.rs
new file mode 100644
index 0000000000000..b6e2810a57cb5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/dyn_trait.rs
@@ -0,0 +1,27 @@
+#![feature(dyn_trait)]
+
+fn main() {
+    // #2506
+    // checks rustfmt doesn't remove dyn
+    trait MyTrait {
+        fn method(&self) -> u64;
+    }
+    fn f1(a: Box<dyn MyTrait>) {}
+
+    // checks if line wrap works correctly
+    trait Very_______________________Long__________________Name_______________________________Trait
+    {
+        fn method(&self) -> u64;
+    }
+
+    fn f2(
+        a: Box<
+            dyn Very_______________________Long__________________Name____________________Trait
+                + 'static,
+        >,
+    ) {
+    }
+
+    // #2582
+    let _: &dyn (::std::any::Any) = &msg;
+}
diff --git a/src/tools/rustfmt/tests/target/else-if-brace-style-always-next-line.rs b/src/tools/rustfmt/tests/target/else-if-brace-style-always-next-line.rs
new file mode 100644
index 0000000000000..31e12cfa0d02e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/else-if-brace-style-always-next-line.rs
@@ -0,0 +1,53 @@
+// rustfmt-control_brace_style: AlwaysNextLine
+
+fn main() {
+    if false
+    {
+        ();
+        ();
+    }
+
+    if false
+    // lone if comment
+    {
+        ();
+        ();
+    }
+
+    let a = if 0 > 1 { unreachable!() } else { 0x0 };
+
+    if true
+    {
+        ();
+    }
+    else if false
+    {
+        ();
+        ();
+    }
+    else
+    {
+        ();
+        ();
+        ();
+    }
+
+    if true
+    // else-if-chain if comment
+    {
+        ();
+    }
+    else if false
+    // else-if-chain else-if comment
+    {
+        ();
+        ();
+    }
+    else
+    // else-if-chain else comment
+    {
+        ();
+        ();
+        ();
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/else-if-brace-style-always-same-line.rs b/src/tools/rustfmt/tests/target/else-if-brace-style-always-same-line.rs
new file mode 100644
index 0000000000000..07b71fd790dc8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/else-if-brace-style-always-same-line.rs
@@ -0,0 +1,43 @@
+fn main() {
+    if false {
+        ();
+        ();
+    }
+
+    if false
+    // lone if comment
+    {
+        ();
+        ();
+    }
+
+    let a = if 0 > 1 { unreachable!() } else { 0x0 };
+
+    if true {
+        ();
+    } else if false {
+        ();
+        ();
+    } else {
+        ();
+        ();
+        ();
+    }
+
+    if true
+    // else-if-chain if comment
+    {
+        ();
+    } else if false
+    // else-if-chain else-if comment
+    {
+        ();
+        ();
+    } else
+    // else-if-chain else comment
+    {
+        ();
+        ();
+        ();
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/else-if-brace-style-closing-next-line.rs b/src/tools/rustfmt/tests/target/else-if-brace-style-closing-next-line.rs
new file mode 100644
index 0000000000000..c99807dc06db4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/else-if-brace-style-closing-next-line.rs
@@ -0,0 +1,49 @@
+// rustfmt-control_brace_style: ClosingNextLine
+
+fn main() {
+    if false {
+        ();
+        ();
+    }
+
+    if false
+    // lone if comment
+    {
+        ();
+        ();
+    }
+
+    let a = if 0 > 1 { unreachable!() } else { 0x0 };
+
+    if true {
+        ();
+    }
+    else if false {
+        ();
+        ();
+    }
+    else {
+        ();
+        ();
+        ();
+    }
+
+    if true
+    // else-if-chain if comment
+    {
+        ();
+    }
+    else if false
+    // else-if-chain else-if comment
+    {
+        ();
+        ();
+    }
+    else
+    // else-if-chain else comment
+    {
+        ();
+        ();
+        ();
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/empty-tuple-no-conversion-to-unit-struct.rs b/src/tools/rustfmt/tests/target/empty-tuple-no-conversion-to-unit-struct.rs
new file mode 100644
index 0000000000000..0b9a15e8a9261
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/empty-tuple-no-conversion-to-unit-struct.rs
@@ -0,0 +1,12 @@
+enum TestEnum {
+    Arm1(),
+    Arm2,
+}
+
+fn foo() {
+    let test = TestEnum::Arm1;
+    match test {
+        TestEnum::Arm1() => {}
+        TestEnum::Arm2 => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/empty_file.rs b/src/tools/rustfmt/tests/target/empty_file.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/empty_file.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/target/enum.rs b/src/tools/rustfmt/tests/target/enum.rs
new file mode 100644
index 0000000000000..9a25126b44ecb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/enum.rs
@@ -0,0 +1,289 @@
+// rustfmt-wrap_comments: true
+// Enums test
+
+#[atrr]
+pub enum Test {
+    A,
+    B(u32, A /* comment */, SomeType),
+    /// Doc comment
+    C,
+}
+
+pub enum Foo<'a, Y: Baz>
+where
+    X: Whatever,
+{
+    A,
+}
+
+enum EmtpyWithComment {
+    // Some comment
+}
+
+// C-style enum
+enum Bar {
+    A = 1,
+    #[someAttr(test)]
+    B = 2, // comment
+    C,
+}
+
+enum LongVariants {
+    First(
+        LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOONG, // comment
+        VARIANT,
+    ),
+    // This is the second variant
+    Second,
+}
+
+enum StructLikeVariants {
+    Normal(u32, String),
+    StructLike {
+        x: i32, // Test comment
+        // Pre-comment
+        #[Attr50]
+        y: SomeType, // Aanother Comment
+    },
+    SL {
+        a: A,
+    },
+}
+
+enum X {
+    CreateWebGLPaintTask(
+        Size2D<i32>,
+        GLContextAttributes,
+        IpcSender<Result<(IpcSender<CanvasMsg>, usize), String>>,
+    ), // This is a post comment
+}
+
+pub enum EnumWithAttributes {
+    //This is a pre comment
+    // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    TupleVar(usize, usize, usize), /* AAAA AAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAA
+                                    * AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA */
+    // Pre Comment
+    #[rustfmt::skip]
+    SkippedItem(String,String,), // Post-comment
+    #[another_attr]
+    #[attr2]
+    ItemStruct {
+        x: usize,
+        y: usize,
+    }, /* Comment AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA */
+    // And another
+    ForcedPreflight, /* AAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+                      * AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA */
+}
+
+pub enum SingleTuple {
+    // Pre Comment AAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+    Match(usize, usize, String), /* Post-comment AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA */
+}
+
+pub enum SingleStruct {
+    Match { name: String, loc: usize }, // Post-comment
+}
+
+pub enum GenericEnum<I, T>
+where
+    I: Iterator<Item = T>,
+{
+    // Pre Comment
+    Left { list: I, root: T },  // Post-comment
+    Right { list: I, root: T }, // Post Comment
+}
+
+enum EmtpyWithComment {
+    // Some comment
+}
+
+enum TestFormatFails {
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+}
+
+fn nested_enum_test() {
+    if true {
+        enum TestEnum {
+            One(
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+                usize,
+            ), /* AAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAA
+                * AAAAAAAAAAAAAAAAAAAAAA */
+            Two, /* AAAAAAAAAAAAAAAAAA  AAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+                  * AAAAAAAAAAAAAAAAAA */
+        }
+        enum TestNestedFormatFail {
+            AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+        }
+    }
+}
+
+pub struct EmtpyWithComment {
+    // FIXME: Implement this struct
+}
+
+// #1115
+pub enum Bencoding<'i> {
+    Str(&'i [u8]),
+    Int(i64),
+    List(Vec<Bencoding<'i>>),
+    /// A bencoded dict value. The first element the slice of bytes in the
+    /// source that the dict is composed of. The second is the dict, decoded
+    /// into an ordered map.
+    // TODO make Dict "structlike" AKA name the two values.
+    Dict(&'i [u8], BTreeMap<&'i [u8], Bencoding<'i>>),
+}
+
+// #1261
+pub enum CoreResourceMsg {
+    SetCookieForUrl(
+        ServoUrl,
+        #[serde(
+            deserialize_with = "::hyper_serde::deserialize",
+            serialize_with = "::hyper_serde::serialize"
+        )]
+        Cookie,
+        CookieSource,
+    ),
+}
+
+enum Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{}
+enum Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{}
+enum Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{}
+enum Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{
+    Foo,
+}
+
+// #1046
+pub enum Entry<'a, K: 'a, V: 'a> {
+    Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
+    Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
+}
+
+// #2081
+pub enum ForegroundColor {
+    CYAN =
+        (winapi::FOREGROUND_INTENSITY | winapi::FOREGROUND_GREEN | winapi::FOREGROUND_BLUE) as u16,
+}
+
+// #2098
+pub enum E<'a> {
+    V(<std::slice::Iter<'a, Xxxxxxxxxxxxxx> as Iterator>::Item),
+}
+
+// #1809
+enum State {
+    TryRecv {
+        pos: usize,
+        lap: u8,
+        closed_count: usize,
+    },
+    Subscribe {
+        pos: usize,
+    },
+    IsReady {
+        pos: usize,
+        ready: bool,
+    },
+    Unsubscribe {
+        pos: usize,
+        lap: u8,
+        id_woken: usize,
+    },
+    FinalTryRecv {
+        pos: usize,
+        id_woken: usize,
+    },
+    TimedOut,
+    Disconnected,
+}
+
+// #2190
+#[derive(Debug, Fail)]
+enum AnError {
+    #[fail(
+        display = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+    )]
+    UnexpectedSingleToken { token: syn::Token },
+}
+
+// #2193
+enum WidthOf101 {
+    #[fail(display = ".....................................................")]
+    Io(::std::io::Error),
+    #[fail(display = ".....................................................")]
+    Ioo(::std::io::Error),
+    Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(::std::io::Error),
+    Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+        ::std::io::Error,
+    ),
+}
+
+// #2389
+pub enum QlError {
+    #[fail(display = "Parsing error: {}", 0)]
+    LexError(parser::lexer::LexError),
+    #[fail(display = "Parsing error: {:?}", 0)]
+    ParseError(parser::ParseError),
+    #[fail(display = "Validation error: {:?}", 0)]
+    ValidationError(Vec<validation::Error>),
+    #[fail(display = "Execution error: {}", 0)]
+    ExecutionError(String),
+    // (from, to)
+    #[fail(display = "Translation error: from {} to {}", 0, 1)]
+    TranslationError(String, String),
+    // (kind, input, expected)
+    #[fail(
+        display = "aaaaaaaaaaaaCould not find {}: Found: {}, expected: {:?}",
+        0, 1, 2
+    )]
+    ResolveError(&'static str, String, Option<String>),
+}
+
+// #2594
+enum Foo {}
+enum Bar {}
+
+// #3562
+enum PublishedFileVisibility {
+    Public =
+        sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPublic,
+    FriendsOnly = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityFriendsOnly,
+    Private =
+        sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPrivate,
+}
+
+// #3771
+//#![feature(arbitrary_enum_discriminant)]
+#[repr(u32)]
+pub enum E {
+    A {
+        a: u32,
+    } = 0x100,
+    B {
+        field1: u32,
+        field2: u8,
+        field3: m::M,
+    } = 0x300, // comment
+}
diff --git a/src/tools/rustfmt/tests/target/existential_type.rs b/src/tools/rustfmt/tests/target/existential_type.rs
new file mode 100644
index 0000000000000..ffc206875b590
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/existential_type.rs
@@ -0,0 +1,23 @@
+// Opaque type.
+
+#![feature(type_alias_impl_trait)]
+
+pub type Adder<F, T>
+where
+    T: Clone,
+    F: Copy,
+= impl Fn(T) -> T;
+
+pub type Adderrr<T> = impl Fn(T) -> T;
+
+impl Foo for Bar {
+    type E = impl Trait;
+}
+
+pub type Adder_without_impl<F, T>
+where
+    T: Clone,
+    F: Copy,
+= Fn(T) -> T;
+
+pub type Adderrr_without_impl<T> = Fn(T) -> T;
diff --git a/src/tools/rustfmt/tests/target/expr-block.rs b/src/tools/rustfmt/tests/target/expr-block.rs
new file mode 100644
index 0000000000000..c577006508733
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/expr-block.rs
@@ -0,0 +1,305 @@
+// Test expressions with block formatting.
+
+fn arrays() {
+    [];
+    let empty = [];
+
+    let foo = [a_long_name, a_very_lng_name, a_long_name];
+
+    let foo = [
+        a_long_name,
+        a_very_lng_name,
+        a_long_name,
+        a_very_lng_name,
+        a_long_name,
+        a_very_lng_name,
+        a_long_name,
+        a_very_lng_name,
+    ];
+
+    vec![
+        a_long_name,
+        a_very_lng_name,
+        a_long_name,
+        a_very_lng_name,
+        a_long_name,
+        a_very_lng_name,
+        a_very_lng_name,
+    ];
+
+    [
+        a_long_name,
+        a_very_lng_name,
+        a_long_name,
+        a_very_lng_name,
+        a_long_name,
+        a_very_lng_name,
+        a_very_lng_name,
+    ]
+}
+
+fn arrays() {
+    let x = [
+        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 7, 8, 9, 0, 1, 2, 3, 4, 5,
+        6, 7, 8, 9, 0,
+    ];
+
+    let y = [/* comment */ 1, 2 /* post comment */, 3];
+
+    let xy = [
+        strukt {
+            test123: value_one_two_three_four,
+            turbo: coolio(),
+        },
+        /* comment  */ 1,
+    ];
+
+    let a = WeightedChoice::new(&mut [
+        Weighted { weight: x, item: 0 },
+        Weighted { weight: 1, item: 1 },
+        Weighted { weight: x, item: 2 },
+        Weighted { weight: 1, item: 3 },
+    ]);
+
+    let z = [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyy,
+        zzzzzzzzzzzzzzzzz,
+        q,
+    ];
+
+    [1 + 3, 4, 5, 6, 7, 7, fncall::<Vec<_>>(3 - 1)]
+}
+
+fn function_calls() {
+    let items = itemize_list(
+        context.source_map,
+        args.iter(),
+        ")",
+        |item| item.span.lo(),
+        |item| item.span.hi(),
+        |item| {
+            item.rewrite(
+                context,
+                Shape {
+                    width: remaining_width,
+                    ..nested_shape
+                },
+            )
+        },
+        span.lo(),
+        span.hi(),
+    );
+
+    itemize_list(
+        context.source_map,
+        args.iter(),
+        ")",
+        |item| item.span.lo(),
+        |item| item.span.hi(),
+        |item| {
+            item.rewrite(
+                context,
+                Shape {
+                    width: remaining_width,
+                    ..nested_shape
+                },
+            )
+        },
+        span.lo(),
+        span.hi(),
+    )
+}
+
+fn macros() {
+    baz!(
+        do_not, add, trailing, commas, inside, of, function, like, macros, even, if_they, are, long
+    );
+
+    baz!(one_item_macro_which_is_also_loooooooooooooooooooooooooooooooooooooooooooooooong);
+
+    let _ = match option {
+        None => baz!(
+            function,
+            like,
+            macro_as,
+            expression,
+            which,
+            is,
+            loooooooooooooooong
+        ),
+        Some(p) => baz!(one_item_macro_as_expression_which_is_also_loooooooooooooooong),
+    };
+}
+
+fn issue_1450() {
+    if selfstate
+        .compare_exchandsfasdsdfgsdgsdfgsdfgsdfgsdfgsdfgfsfdsage_weak(
+            STATE_PARKED,
+            STATE_UNPARKED,
+            Release,
+            Relaxed,
+            Release,
+            Relaxed,
+        )
+        .is_ok()
+    {
+        return;
+    }
+}
+
+fn foo() {
+    if real_total <= limit
+        && !pre_line_comments
+        && !items.into_iter().any(|item| item.as_ref().is_multiline())
+    {
+        DefinitiveListTactic::Horizontal
+    }
+}
+
+fn combine_block() {
+    foo(Bar {
+        x: value,
+        y: value2,
+    });
+
+    foo((Bar {
+        x: value,
+        y: value2,
+    },));
+
+    foo((
+        1,
+        2,
+        3,
+        Bar {
+            x: value,
+            y: value2,
+        },
+    ));
+
+    foo((1, 2, 3, |x| {
+        let y = x + 1;
+        let z = y + 1;
+        z
+    }));
+
+    let opt = Some(Struct(
+        long_argument_one,
+        long_argument_two,
+        long_argggggggg,
+    ));
+
+    do_thing(|param| {
+        action();
+        foo(param)
+    });
+
+    do_thing(x, |param| {
+        action();
+        foo(param)
+    });
+
+    do_thing(
+        x,
+        (1, 2, 3, |param| {
+            action();
+            foo(param)
+        }),
+    );
+
+    Ok(some_function(
+        lllllllllong_argument_one,
+        lllllllllong_argument_two,
+        lllllllllllllllllllllllllllllong_argument_three,
+    ));
+
+    foo(
+        thing,
+        bar(
+            param2,
+            pparam1param1param1param1param1param1param1param1param1param1aram1,
+            param3,
+        ),
+    );
+
+    foo.map_or(|| {
+        Ok(SomeStruct {
+            f1: 0,
+            f2: 0,
+            f3: 0,
+        })
+    });
+
+    match opt {
+        Some(x) => somefunc(anotherfunc(
+            long_argument_one,
+            long_argument_two,
+            long_argument_three,
+        )),
+        Some(x) => |x| {
+            let y = x + 1;
+            let z = y + 1;
+            z
+        },
+        Some(x) => (1, 2, |x| {
+            let y = x + 1;
+            let z = y + 1;
+            z
+        }),
+        Some(x) => SomeStruct {
+            f1: long_argument_one,
+            f2: long_argument_two,
+            f3: long_argument_three,
+        },
+        None => Ok(SomeStruct {
+            f1: long_argument_one,
+            f2: long_argument_two,
+            f3: long_argument_three,
+        }),
+    };
+
+    match x {
+        y => func(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx),
+        _ => func(
+            x,
+            yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+            zzz,
+        ),
+    }
+}
+
+fn issue_1862() {
+    foo(
+        /* bar = */ None,
+        something_something,
+        /* baz = */ None,
+        /* This comment waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay too long to be kept on the same line */
+        None,
+        /* com */
+        this_last_arg_is_tooooooooooooooooooooooooooooooooo_long_to_be_kept_with_the_pre_comment,
+    )
+}
+
+fn issue_3025() {
+    foo(
+        // This describes the argument below.
+        /* bar = */ None,
+        // This describes the argument below.
+        something_something,
+        // This describes the argument below. */
+        None,
+        // This describes the argument below.
+        /* This comment waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay too long to be kept on the same line */
+        None,
+        // This describes the argument below.
+        /* com */
+        this_last_arg_is_tooooooooooooooooooooooooooooooooo_long_to_be_kept_with_the_pre_comment,
+    )
+}
+
+fn issue_1878() {
+    let channel: &str = seq
+        .next_element()?
+        .ok_or_else(|| de::Error::invalid_length(2, &self))?;
+}
diff --git a/src/tools/rustfmt/tests/target/expr-overflow-delimited.rs b/src/tools/rustfmt/tests/target/expr-overflow-delimited.rs
new file mode 100644
index 0000000000000..b00e81fcd5a50
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/expr-overflow-delimited.rs
@@ -0,0 +1,120 @@
+// rustfmt-overflow_delimited_expr: true
+
+fn combine_blocklike() {
+    do_thing(|param| {
+        action();
+        foo(param)
+    });
+
+    do_thing(x, |param| {
+        action();
+        foo(param)
+    });
+
+    do_thing(
+        x,
+        // I'll be discussing the `action` with your para(m)legal counsel
+        |param| {
+            action();
+            foo(param)
+        },
+    );
+
+    do_thing(Bar {
+        x: value,
+        y: value2,
+    });
+
+    do_thing(x, Bar {
+        x: value,
+        y: value2,
+    });
+
+    do_thing(
+        x,
+        // Let me tell you about that one time at the `Bar`
+        Bar {
+            x: value,
+            y: value2,
+        },
+    );
+
+    do_thing(&[
+        value_with_longer_name,
+        value2_with_longer_name,
+        value3_with_longer_name,
+        value4_with_longer_name,
+    ]);
+
+    do_thing(x, &[
+        value_with_longer_name,
+        value2_with_longer_name,
+        value3_with_longer_name,
+        value4_with_longer_name,
+    ]);
+
+    do_thing(
+        x,
+        // Just admit it; my list is longer than can be folded on to one line
+        &[
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(vec![
+        value_with_longer_name,
+        value2_with_longer_name,
+        value3_with_longer_name,
+        value4_with_longer_name,
+    ]);
+
+    do_thing(x, vec![
+        value_with_longer_name,
+        value2_with_longer_name,
+        value3_with_longer_name,
+        value4_with_longer_name,
+    ]);
+
+    do_thing(
+        x,
+        // Just admit it; my list is longer than can be folded on to one line
+        vec![
+            value_with_longer_name,
+            value2_with_longer_name,
+            value3_with_longer_name,
+            value4_with_longer_name,
+        ],
+    );
+
+    do_thing(
+        x,
+        (1, 2, 3, |param| {
+            action();
+            foo(param)
+        }),
+    );
+}
+
+fn combine_struct_sample() {
+    let identity = verify(&ctx, VerifyLogin {
+        type_: LoginType::Username,
+        username: args.username.clone(),
+        password: Some(args.password.clone()),
+        domain: None,
+    })?;
+}
+
+fn combine_macro_sample() {
+    rocket::ignite()
+        .mount("/", routes![
+            http::auth::login,
+            http::auth::logout,
+            http::cors::options,
+            http::action::dance,
+            http::action::sleep,
+        ])
+        .launch();
+}
diff --git a/src/tools/rustfmt/tests/target/expr.rs b/src/tools/rustfmt/tests/target/expr.rs
new file mode 100644
index 0000000000000..84df802bc70f9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/expr.rs
@@ -0,0 +1,671 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// Test expressions
+
+fn foo() -> bool {
+    let boxed: Box<i32> = box 5;
+    let referenced = &5;
+
+    let very_long_variable_name = (a + first + simple + test);
+    let very_long_variable_name =
+        (a + first + simple + test + AAAAAAAAAAAAA + BBBBBBBBBBBBBBBBB + b + c);
+
+    let is_internalxxxx =
+        self.source_map.span_to_filename(s) == self.source_map.span_to_filename(m.inner);
+
+    let some_val = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa * bbbb
+        / (bbbbbb - function_call(x, *very_long_pointer, y))
+        + 1000;
+
+    some_ridiculously_loooooooooooooooooooooong_function(
+        10000 * 30000000000 + 40000 / 1002200000000 - 50000 * sqrt(-1),
+        trivial_value,
+    );
+    (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        + a
+        + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        + aaaaa);
+
+    {
+        for _ in 0..10 {}
+    }
+
+    {
+        {
+            {
+                {}
+            }
+        }
+    }
+
+    if 1 + 2 > 0 {
+        let result = 5;
+        result
+    } else {
+        4
+    };
+
+    if let Some(x) = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {
+        // Nothing
+    }
+
+    if let Some(x) =
+        (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
+    {}
+
+    if let (
+        some_very_large,
+        tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple,
+    ) = 1 + 2 + 3
+    {}
+
+    if let (
+        some_very_large,
+        tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple,
+    ) = 1111 + 2222
+    {}
+
+    if let (
+        some_very_large,
+        tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple,
+    ) = 1 + 2 + 3
+    {}
+
+    if let ast::ItemKind::Trait(_, unsafety, ref generics, ref type_param_bounds, ref trait_items) =
+        item.node
+    {
+        // nothing
+    }
+
+    let test = if true { 5 } else { 3 };
+
+    if cond() {
+        something();
+    } else if different_cond() {
+        something_else();
+    } else {
+        // Check subformatting
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+            + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    }
+
+    // #2884
+    let _ = [0; {
+        struct Foo;
+        impl Foo {
+            const fn get(&self) -> usize {
+                5
+            }
+        };
+        Foo.get()
+    }];
+}
+
+fn bar() {
+    let range =
+        (111111111 + 333333333333333333 + 1111 + 400000000000000000)..(2222 + 2333333333333333);
+
+    let another_range = 5..some_func(a, b /* comment */);
+
+    for _ in 1.. {
+        call_forever();
+    }
+
+    syntactically_correct(
+        loop {
+            sup('?');
+        },
+        if cond { 0 } else { 1 },
+    );
+
+    let third = ..10;
+    let infi_range = ..;
+    let foo = 1..;
+    let bar = 5;
+    let nonsense = (10..0)..(0..10);
+
+    loop {
+        if true {
+            break;
+        }
+    }
+
+    let x = (
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa && aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        a,
+    );
+}
+
+fn baz() {
+    unsafe /* {}{}{}{{{{}} */ {
+        let foo = 1u32;
+    }
+
+    unsafe /* very looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+            * comment */ {
+    }
+
+    unsafe /* So this is a very long comment.
+            * Multi-line, too.
+            * Will it still format correctly? */ {
+    }
+
+    unsafe {
+        // Regular unsafe block
+    }
+
+    unsafe { foo() }
+
+    unsafe {
+        foo();
+    }
+
+    // #2289
+    let identifier_0 = unsafe { this_is_58_chars_long_and_line_is_93_chars_long_xxxxxxxxxx };
+    let identifier_1 = unsafe { this_is_59_chars_long_and_line_is_94_chars_long_xxxxxxxxxxx };
+    let identifier_2 = unsafe { this_is_65_chars_long_and_line_is_100_chars_long_xxxxxxxxxxxxxxxx };
+    let identifier_3 =
+        unsafe { this_is_66_chars_long_and_line_is_101_chars_long_xxxxxxxxxxxxxxxxx };
+}
+
+// Test some empty blocks.
+fn qux() {
+    {}
+    // FIXME this one could be done better.
+    { /* a block with a comment */ }
+    {}
+    {
+        // A block with a comment.
+    }
+}
+
+fn issue227() {
+    {
+        let handler =
+            box DocumentProgressHandler::new(addr, DocumentProgressTask::DOMContentLoaded);
+    }
+}
+
+fn issue184(source: &str) {
+    for c in source.chars() {
+        if index < 'a' {
+            continue;
+        }
+    }
+}
+
+fn arrays() {
+    let x = [
+        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 7, 8, 9, 0, 1, 2, 3, 4, 5,
+        6, 7, 8, 9, 0,
+    ];
+
+    let y = [/* comment */ 1, 2 /* post comment */, 3];
+
+    let xy = [
+        strukt {
+            test123: value_one_two_three_four,
+            turbo: coolio(),
+        },
+        // comment
+        1,
+    ];
+
+    let a = WeightedChoice::new(&mut [
+        Weighted {
+            weightweight: x,
+            item: 0,
+        },
+        Weighted {
+            weightweight: 1,
+            item: 1,
+        },
+        Weighted {
+            weightweight: x,
+            item: 2,
+        },
+        Weighted {
+            weightweight: 1,
+            item: 3,
+        },
+    ]);
+
+    let z = [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyy,
+        zzzzzzzzzzzzzzzzzz,
+        q,
+    ];
+
+    [1 + 3, 4, 5, 6, 7, 7, fncall::<Vec<_>>(3 - 1)]
+}
+
+fn returns() {
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        && return;
+
+    return aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;
+}
+
+fn addrof() {
+    &mut (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb);
+    &(aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb);
+
+    // raw reference operator
+    &raw const a;
+    &raw mut b;
+}
+
+fn casts() {
+    fn unpack(packed: u32) -> [u16; 2] {
+        [(packed >> 16) as u16, (packed >> 0) as u16]
+    }
+
+    let some_trait_xxx = xxxxxxxxxxx + xxxxxxxxxxxxx as SomeTraitXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX;
+    let slightly_longer_trait =
+        yyyyyyyyy + yyyyyyyyyyy as SomeTraitYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY;
+}
+
+fn indices() {
+    let x = (aaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccc)
+        [x + y + z];
+    let y = (aaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccc)
+        [xxxxx + yyyyy + zzzzz];
+    let z = xxxxxxxxxx
+        .x()
+        .y()
+        .zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz()[aaaaa];
+    let z = xxxxxxxxxx
+        .x()
+        .y()
+        .zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz()
+        [aaaaa];
+}
+
+fn repeats() {
+    let x = [aaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccc;
+        x + y + z];
+    let y = [aaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccc;
+        xxxxx + yyyyy + zzzzz];
+}
+
+fn blocks() {
+    if 1 + 1 == 2 {
+        println!("yay arithmetix!");
+    };
+}
+
+fn issue767() {
+    if false {
+        if false {
+        } else {
+            // A let binding here seems necessary to trigger it.
+            let _ = ();
+        }
+    } else if let false = false {
+    }
+}
+
+fn ranges() {
+    let x = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+    let y =
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..=bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+    let z = ..=x;
+
+    // #1766
+    let x = [0. ..10.0];
+    let x = [0. ..=10.0];
+
+    a..=b
+
+    // the expr below won't compile because inclusive ranges need a defined end
+    // let a = 0 ..= ;
+}
+
+fn if_else() {
+    let exact = diff / (if size == 0 { 1 } else { size });
+
+    let cx = tp1.x + any * radius * if anticlockwise { 1.0 } else { -1.0 };
+}
+
+fn complex_if_else() {
+    if let Some(x) = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx {
+    } else if let Some(x) = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx {
+        ha();
+    } else if xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx + xxxxxxxx {
+        yo();
+    } else if let Some(x) = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    {
+        ha();
+    } else if xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx + xxxxxxxxx
+    {
+        yo();
+    }
+}
+
+fn issue1106() {
+    {
+        if let hir::ItemEnum(ref enum_def, ref generics) =
+            self.ast_map.expect_item(enum_node_id).node
+        {}
+    }
+
+    for entry in WalkDir::new(path)
+        .into_iter()
+        .filter_entry(|entry| exclusions.filter_entry(entry))
+    {}
+}
+
+fn issue1570() {
+    a_very_long_function_name({ some_func(1, { 1 }) })
+}
+
+fn issue1714() {
+    v = &mut { v }[mid..];
+    let (left, right) = { v }.split_at_mut(mid);
+}
+
+// Multi-lined index should be put on the next line if it fits in one line.
+fn issue1749() {
+    {
+        {
+            {
+                if self.shape[(r as f32 + self.x_offset) as usize]
+                    [(c as f32 + self.y_offset) as usize]
+                    != 0
+                {
+                    // hello
+                }
+            }
+        }
+    }
+}
+
+// #1172
+fn newlines_between_list_like_expr() {
+    foo(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+        zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
+    );
+
+    vec![
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+        zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
+    ];
+
+    match x {
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+        | yyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
+        | zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz => foo(a, b, c),
+        _ => bar(),
+    };
+}
+
+fn issue2178() {
+    Ok(result
+        .iter()
+        .map(|item| ls_util::rls_to_location(item))
+        .collect())
+}
+
+// #2493
+impl Foo {
+    fn bar(&self) {
+        {
+            let x = match () {
+                () => {
+                    let i;
+                    i == self
+                        .install_config
+                        .storage
+                        .experimental_compressed_block_size as usize
+                }
+            };
+        }
+    }
+}
+
+fn dots() {
+    .. .. ..; // (.. (.. (..)))
+    ..= ..= ..;
+    (..).. ..; // ((..) .. (..))
+}
+
+// #2676
+// A function call with a large single argument.
+fn foo() {
+    let my_var = Mutex::new(
+        RpcClientType::connect(server_iddd).chain_err(|| "Unable to create RPC client")?,
+    );
+}
+
+// #2704
+// Method call with prefix and suffix.
+fn issue2704() {
+    // We should not combine the callee with a multi-lined method call.
+    let requires = requires.set(
+        &requires0
+            .concat(&requires1)
+            .concat(&requires2)
+            .distinct_total(),
+    );
+    let requires = requires.set(
+        box requires0
+            .concat(&requires1)
+            .concat(&requires2)
+            .distinct_total(),
+    );
+    let requires = requires.set(
+        requires0
+            .concat(&requires1)
+            .concat(&requires2)
+            .distinct_total() as u32,
+    );
+    let requires = requires.set(
+        requires0
+            .concat(&requires1)
+            .concat(&requires2)
+            .distinct_total()?,
+    );
+    let requires = requires.set(
+        !requires0
+            .concat(&requires1)
+            .concat(&requires2)
+            .distinct_total(),
+    );
+    // We should combine a small callee with an argument.
+    bar(vec![22]
+        .into_iter()
+        .map(|x| x * 2)
+        .filter(|_| true)
+        .collect());
+    // But we should not combine a long callee with an argument.
+    barrrr(
+        vec![22]
+            .into_iter()
+            .map(|x| x * 2)
+            .filter(|_| true)
+            .collect(),
+    );
+}
+
+// #2782
+fn issue2782() {
+    {
+        let f = {
+            let f = {
+                {
+                    match f {
+                        F(f, _) => loop {
+                            let f = {
+                                match f {
+                                    F(f, _) => match f {
+                                        F(f, _) => loop {
+                                            let f = {
+                                                let f = {
+                                                    match f {
+                                                        '-' => F(f, ()),
+                                                    }
+                                                };
+                                            };
+                                        },
+                                    },
+                                }
+                            };
+                        },
+                    }
+                }
+            };
+        };
+    }
+}
+
+fn issue_2802() {
+    function_to_fill_this_line(some_arg, some_arg, some_arg)
+        * a_very_specific_length(specific_length_arg)
+        * very_specific_length(Foo {
+            a: some_much_much_longer_value,
+        })
+        * some_value
+}
+
+fn issue_3003() {
+    let mut path: PathBuf = [
+        env!("CARGO_MANIFEST_DIR"),
+        "tests",
+        "support",
+        "dejavu-fonts-ttf-2.37",
+        "ttf",
+    ]
+    .iter()
+    .collect();
+}
+
+fn issue3226() {
+    {
+        {
+            {
+                return Err(
+                    ErrorKind::ManagementInterfaceError("Server exited unexpectedly").into(),
+                );
+            }
+        }
+    }
+    {
+        {
+            {
+                break Err(
+                    ErrorKind::ManagementInterfaceError("Server exited unexpectedlyy").into(),
+                );
+            }
+        }
+    }
+}
+
+// #3457
+fn issue3457() {
+    {
+        {
+            {
+                {
+                    {
+                        {
+                            {
+                                {
+                                    {
+                                        {
+                                            {
+                                                {
+                                                    {
+                                                        {
+                                                            {
+                                                                {
+                                                                    {
+                                                                        {
+                                                                            {
+                                                                                {
+                                                                                    {
+                                                                                        {
+                                                                                            {
+                                                                                                {
+                                                                                                    println!("Test");
+                                                                                                }
+                                                                                            }
+                                                                                        }
+                                                                                    }
+                                                                                }
+                                                                            }
+                                                                        }
+                                                                    }
+                                                                }
+                                                            }
+                                                        }
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+// #3498
+static REPRO: &[usize] = &[
+    #[cfg(feature = "zero")]
+    0,
+];
+
+fn overflow_with_attr() {
+    foo(
+        #[cfg(feature = "zero")]
+        0,
+    );
+    foobar(
+        #[cfg(feature = "zero")]
+        0,
+    );
+    foobar(
+        x,
+        y,
+        #[cfg(feature = "zero")]
+        {},
+    );
+}
+
+// https://github.com/rust-lang/rustfmt/issues/3765
+fn foo() {
+    async {
+        // Do
+        // some
+        // work
+    }
+    .await;
+
+    async {
+        // Do
+        // some
+        // work
+    }
+    .await;
+}
+
+fn underscore() {
+    _ = 1;
+    _;
+    [_, a, _] = [1, 2, 3];
+    (a, _) = (8, 9);
+    TupleStruct(_, a) = TupleStruct(2, 2);
+
+    let _: usize = foo(_, _);
+}
diff --git a/src/tools/rustfmt/tests/target/extern.rs b/src/tools/rustfmt/tests/target/extern.rs
new file mode 100644
index 0000000000000..44ed6d4b4756d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/extern.rs
@@ -0,0 +1,84 @@
+// rustfmt-normalize_comments: true
+
+extern crate foo;
+extern crate foo as bar;
+
+extern crate chrono;
+extern crate dotenv;
+extern crate futures;
+
+extern crate bar;
+extern crate foo;
+
+// #2315
+extern crate proc_macro;
+extern crate proc_macro2;
+
+// #3128
+extern crate serde; // 1.0.78
+extern crate serde_derive; // 1.0.78
+extern crate serde_json; // 1.0.27
+
+extern "C" {
+    fn c_func(x: *mut *mut libc::c_void);
+
+    fn c_func(
+        x: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX,
+        y: YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY,
+    );
+
+    #[test123]
+    fn foo() -> uint64_t;
+
+    pub fn bar();
+}
+
+extern "C" {
+    fn DMR_GetDevice(
+        pHDev: *mut HDEV,
+        searchMode: DeviceSearchMode,
+        pSearchString: *const c_char,
+        devNr: c_uint,
+        wildcard: c_char,
+    ) -> TDMR_ERROR;
+
+    fn quux() -> (); // Post comment
+
+    pub type Foo;
+
+    type Bar;
+}
+
+extern "Rust" {
+    static ext: u32;
+    // Some comment.
+    pub static mut var: SomeType;
+}
+
+extern "C" {
+    fn syscall(
+        number: libc::c_long, // comment 1
+        // comm 2
+        ... // sup?
+    ) -> libc::c_long;
+
+    fn foo(x: *const c_char, ...) -> libc::c_long;
+}
+
+extern "C" {
+    pub fn freopen(
+        filename: *const c_char,
+        mode: *const c_char,
+        mode2: *const c_char,
+        mode3: *const c_char,
+        file: *mut FILE,
+    ) -> *mut FILE;
+
+    const fn foo() -> *mut Bar;
+    unsafe fn foo() -> *mut Bar;
+
+    pub(super) const fn foo() -> *mut Bar;
+    pub(crate) unsafe fn foo() -> *mut Bar;
+}
+
+extern "C" {}
diff --git a/src/tools/rustfmt/tests/target/extern_not_explicit.rs b/src/tools/rustfmt/tests/target/extern_not_explicit.rs
new file mode 100644
index 0000000000000..b55b64d05b34e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/extern_not_explicit.rs
@@ -0,0 +1,18 @@
+// rustfmt-force_explicit_abi: false
+
+extern {
+    fn some_fn() -> ();
+}
+
+extern fn sup() {}
+
+type funky_func = extern fn(
+    unsafe extern "rust-call" fn(
+        *const JSJitInfo,
+        *mut JSContext,
+        HandleObject,
+        *mut libc::c_void,
+        u32,
+        *mut JSVal,
+    ) -> u8,
+);
diff --git a/src/tools/rustfmt/tests/target/file-lines-1.rs b/src/tools/rustfmt/tests/target/file-lines-1.rs
new file mode 100644
index 0000000000000..13820ec293faf
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-1.rs
@@ -0,0 +1,30 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-1.rs","range":[4,8]}]
+
+fn floaters() {
+    let x = Foo {
+        field1: val1,
+        field2: val2,
+    }
+    .method_call()
+    .method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/file-lines-2.rs b/src/tools/rustfmt/tests/target/file-lines-2.rs
new file mode 100644
index 0000000000000..bc25698c2ed0d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-2.rs
@@ -0,0 +1,24 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-2.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond { val1 } else { val2 }.method_call();
+
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/file-lines-3.rs b/src/tools/rustfmt/tests/target/file-lines-3.rs
new file mode 100644
index 0000000000000..77d6fb2635581
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-3.rs
@@ -0,0 +1,25 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-3.rs","range":[4,8]},{"file":"tests/source/file-lines-3.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+        field1: val1,
+        field2: val2,
+    }
+    .method_call()
+    .method_call();
+
+    let y = if cond { val1 } else { val2 }.method_call();
+
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/file-lines-4.rs b/src/tools/rustfmt/tests/target/file-lines-4.rs
new file mode 100644
index 0000000000000..83928bf6fecfa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-4.rs
@@ -0,0 +1,30 @@
+// rustfmt-file_lines: []
+// (Test that nothing is formatted if an empty array is specified.)
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2	
+            }
+                .method_call();
+                                                                                              // aaaaaaaaaaaaa
+    {
+        match x {
+            PushParam => {
+                // comment
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }    
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/file-lines-5.rs b/src/tools/rustfmt/tests/target/file-lines-5.rs
new file mode 100644
index 0000000000000..3966dc06303cc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-5.rs
@@ -0,0 +1,17 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-5.rs","range":[3,5]}]
+
+struct A {
+    t: i64,
+}
+
+mod foo {
+    fn bar() {
+                         // test
+                             let i = 12;
+                                 // test
+    }
+    // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    fn baz() {
+        let j = 15;     
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/file-lines-6.rs b/src/tools/rustfmt/tests/target/file-lines-6.rs
new file mode 100644
index 0000000000000..8a092df869a6f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-6.rs
@@ -0,0 +1,18 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-6.rs","range":[9,10]}]
+
+struct A {
+    t: i64,
+}
+
+mod foo {
+    fn bar() {
+        // test
+        let i = 12;
+                                 // test
+    }
+
+    fn baz() {
+///
+        let j = 15;     
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/file-lines-7.rs b/src/tools/rustfmt/tests/target/file-lines-7.rs
new file mode 100644
index 0000000000000..62d913d8823ec
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-7.rs
@@ -0,0 +1,21 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-7.rs","range":[8,15]}]
+
+struct A {
+    t: i64,
+}
+
+mod foo {
+    fn bar() {
+        // test
+        let i = 12;
+        // test
+    }
+
+    fn baz() {
+
+
+
+        ///
+        let j = 15;     
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/file-lines-item.rs b/src/tools/rustfmt/tests/target/file-lines-item.rs
new file mode 100644
index 0000000000000..8d39eb6095891
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/file-lines-item.rs
@@ -0,0 +1,21 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-item.rs","range":[6,8]}]
+
+use foo::{c, b, a};
+use bar;
+
+fn foo() {
+    bar();
+}
+
+impl Drop for Context {
+     fn drop(&mut self) {
+    }
+}
+
+impl Bar for Baz {
+    fn foo() {
+        bar(
+            baz, // Who knows?
+        )
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/fn-args-with-last-line-comment.rs b/src/tools/rustfmt/tests/target/fn-args-with-last-line-comment.rs
new file mode 100644
index 0000000000000..27e0e09653eee
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-args-with-last-line-comment.rs
@@ -0,0 +1,24 @@
+// #1587
+pub trait X {
+    fn a(&self) -> &'static str;
+    fn bcd(
+        &self,
+        c: &str,         // comment on this arg
+        d: u16,          // comment on this arg
+        e: &Vec<String>, // comment on this arg
+    ) -> Box<Q>;
+}
+
+// #1595
+fn foo(
+    arg1: LongTypeName,
+    arg2: LongTypeName,
+    arg3: LongTypeName,
+    arg4: LongTypeName,
+    arg5: LongTypeName,
+    arg6: LongTypeName,
+    arg7: LongTypeName,
+    //arg8: LongTypeName,
+) {
+    // do stuff
+}
diff --git a/src/tools/rustfmt/tests/target/fn-custom-2.rs b/src/tools/rustfmt/tests/target/fn-custom-2.rs
new file mode 100644
index 0000000000000..0e723396c6864
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-custom-2.rs
@@ -0,0 +1,77 @@
+// Test different indents.
+
+fn foo(
+    a: Aaaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbbbb,
+    c: Ccccccccccccccccc,
+    d: Ddddddddddddddddddddddddd,
+    e: Eeeeeeeeeeeeeeeeeee,
+) {
+    foo();
+}
+
+fn bar<
+    'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    TTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW,
+>(
+    a: Aaaaaaaaaaaaaaa,
+) {
+    bar();
+}
+
+fn baz()
+where
+    X: TTTTTTTT,
+{
+    baz();
+}
+
+fn qux()
+where
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+{
+    baz();
+}
+
+impl Foo {
+    fn foo(
+        self,
+        a: Aaaaaaaaaaaaaaa,
+        b: Bbbbbbbbbbbbbbbb,
+        c: Ccccccccccccccccc,
+        d: Ddddddddddddddddddddddddd,
+        e: Eeeeeeeeeeeeeeeeeee,
+    ) {
+        foo();
+    }
+
+    fn bar<
+        'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        TTTTTTTTTTTTT,
+        UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW,
+    >(
+        a: Aaaaaaaaaaaaaaa,
+    ) {
+        bar();
+    }
+
+    fn baz()
+    where
+        X: TTTTTTTT,
+    {
+        baz();
+    }
+}
+
+struct Foo<
+    TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUU,
+    VVVVVVVVVVVVVVVVVVVVVVVVVVV,
+    WWWWWWWWWWWWWWWWWWWWWWWW,
+> {
+    foo: Foo,
+}
diff --git a/src/tools/rustfmt/tests/target/fn-custom-3.rs b/src/tools/rustfmt/tests/target/fn-custom-3.rs
new file mode 100644
index 0000000000000..bfafe45360771
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-custom-3.rs
@@ -0,0 +1,71 @@
+// Test different indents.
+
+fn foo(
+    a: Aaaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbbbb,
+    c: Ccccccccccccccccc,
+    d: Ddddddddddddddddddddddddd,
+    e: Eeeeeeeeeeeeeeeeeee,
+) {
+    foo();
+}
+
+fn bar<
+    'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    TTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW,
+>(
+    a: Aaaaaaaaaaaaaaa,
+) {
+    bar();
+}
+
+fn qux()
+where
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+{
+    baz();
+}
+
+fn qux()
+where
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+{
+    baz();
+}
+
+impl Foo {
+    fn foo(
+        self,
+        a: Aaaaaaaaaaaaaaa,
+        b: Bbbbbbbbbbbbbbbb,
+        c: Ccccccccccccccccc,
+        d: Ddddddddddddddddddddddddd,
+        e: Eeeeeeeeeeeeeeeeeee,
+    ) {
+        foo();
+    }
+
+    fn bar<
+        'a: 'bbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        TTTTTTTTTTTTT,
+        UUUUUUUUUUUUUUUUUUUU: WWWWWWWWWWWWWWWWWWWWWWWW,
+    >(
+        a: Aaaaaaaaaaaaaaa,
+    ) {
+        bar();
+    }
+}
+
+struct Foo<
+    TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUU,
+    VVVVVVVVVVVVVVVVVVVVVVVVVVV,
+    WWWWWWWWWWWWWWWWWWWWWWWW,
+> {
+    foo: Foo,
+}
diff --git a/src/tools/rustfmt/tests/target/fn-custom-4.rs b/src/tools/rustfmt/tests/target/fn-custom-4.rs
new file mode 100644
index 0000000000000..5de16e251595e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-custom-4.rs
@@ -0,0 +1,26 @@
+// Test different indents.
+
+fn qux()
+where
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+{
+    baz();
+}
+
+fn qux()
+where
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+{
+    baz();
+}
+
+fn qux(a: Aaaaaaaaaaaaaaaaa)
+where
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+{
+    baz();
+}
diff --git a/src/tools/rustfmt/tests/target/fn-custom-6.rs b/src/tools/rustfmt/tests/target/fn-custom-6.rs
new file mode 100644
index 0000000000000..e891f4d58828c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-custom-6.rs
@@ -0,0 +1,71 @@
+// rustfmt-brace_style: PreferSameLine
+// Test different indents.
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) -> String {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb)
+where
+    T: UUUUUUUUUUU, {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) where
+    T: UUUUUUUUUUU, {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String
+where
+    T: UUUUUUUUUUU, {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) -> String
+where
+    T: UUUUUUUUUUU, {
+    bar();
+}
+
+trait Test {
+    fn foo(a: u8) {}
+
+    fn bar(a: u8) -> String {}
+}
diff --git a/src/tools/rustfmt/tests/target/fn-custom-7.rs b/src/tools/rustfmt/tests/target/fn-custom-7.rs
new file mode 100644
index 0000000000000..2c20ac5a75249
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-custom-7.rs
@@ -0,0 +1,36 @@
+// rustfmt-normalize_comments: true
+// rustfmt-fn_args_layout: Vertical
+// rustfmt-brace_style: AlwaysNextLine
+
+// Case with only one variable.
+fn foo(a: u8) -> u8
+{
+    bar()
+}
+
+// Case with 2 variables and some pre-comments.
+fn foo(
+    a: u8, // Comment 1
+    b: u8, // Comment 2
+) -> u8
+{
+    bar()
+}
+
+// Case with 2 variables and some post-comments.
+fn foo(
+    // Comment 1
+    a: u8,
+    // Comment 2
+    b: u8,
+) -> u8
+{
+    bar()
+}
+
+trait Test
+{
+    fn foo(a: u8) {}
+
+    fn bar(a: u8) -> String {}
+}
diff --git a/src/tools/rustfmt/tests/target/fn-custom-8.rs b/src/tools/rustfmt/tests/target/fn-custom-8.rs
new file mode 100644
index 0000000000000..29af3fca79dbe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-custom-8.rs
@@ -0,0 +1,77 @@
+// rustfmt-brace_style: PreferSameLine
+// Test different indents.
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) -> String {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb)
+where
+    T: UUUUUUUUUUU, {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) where
+    T: UUUUUUUUUUU, {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String
+where
+    T: UUUUUUUUUUU, {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) -> String
+where
+    T: UUUUUUUUUUU, {
+    bar();
+}
+
+trait Test {
+    fn foo(a: u8) {}
+
+    fn bar(a: u8) -> String {}
+
+    fn bar(a: u8) -> String
+    where
+        Foo: foooo,
+        Bar: barrr, {
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/fn-custom.rs b/src/tools/rustfmt/tests/target/fn-custom.rs
new file mode 100644
index 0000000000000..2eb2a973d243d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-custom.rs
@@ -0,0 +1,19 @@
+// rustfmt-fn_args_layout: Compressed
+// Test some of the ways function signatures can be customised.
+
+// Test compressed layout of args.
+fn foo(
+    a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc, d: Ddddddddddddddddddddddddd,
+    e: Eeeeeeeeeeeeeeeeeee,
+) {
+    foo();
+}
+
+impl Foo {
+    fn foo(
+        self, a: Aaaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbbbb, c: Ccccccccccccccccc,
+        d: Ddddddddddddddddddddddddd, e: Eeeeeeeeeeeeeeeeeee,
+    ) {
+        foo();
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/fn-param-attributes.rs b/src/tools/rustfmt/tests/target/fn-param-attributes.rs
new file mode 100644
index 0000000000000..829575518debd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-param-attributes.rs
@@ -0,0 +1,64 @@
+// https://github.com/rust-lang/rustfmt/issues/3623
+
+fn foo(#[cfg(something)] x: i32, y: i32) -> i32 {
+    x + y
+}
+
+fn foo_b(#[cfg(something)] x: i32, y: i32) -> i32 {
+    x + y
+}
+
+fn add(
+    #[cfg(something)]
+    #[deny(C)]
+    x: i32,
+    y: i32,
+) -> i32 {
+    x + y
+}
+
+struct NamedSelfRefStruct {}
+impl NamedSelfRefStruct {
+    fn foo(#[cfg(something)] self: &Self) {}
+}
+
+struct MutStruct {}
+impl MutStruct {
+    fn foo(#[cfg(foo)] &mut self, #[deny(C)] b: i32) {}
+}
+
+fn main() {
+    let c = |#[allow(C)] a: u32,
+             #[cfg(something)] b: i32,
+             #[cfg_attr(something, cfg(nothing))]
+             #[deny(C)]
+             c: i32| {};
+    let _ = c(1, 2);
+}
+
+pub fn bar(
+    /// bar
+    #[test]
+    a: u32,
+    /// Bar
+    #[must_use]
+    /// Baz
+    #[no_mangle]
+    b: i32,
+) {
+}
+
+fn abc(
+    #[foo]
+    #[bar]
+    param: u32,
+) {
+    // ...
+}
+
+fn really_really_really_loooooooooooooooooooong(
+    #[cfg(some_even_longer_config_feature_that_keeps_going_and_going_and_going_forever_and_ever_and_ever_on_and_on)]
+    b: i32,
+) {
+    // ...
+}
diff --git a/src/tools/rustfmt/tests/target/fn-simple.rs b/src/tools/rustfmt/tests/target/fn-simple.rs
new file mode 100644
index 0000000000000..692739fa6a9f8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-simple.rs
@@ -0,0 +1,120 @@
+// rustfmt-normalize_comments: true
+
+fn simple(
+    // pre-comment on a function!?
+    i: i32,          // yes, it's possible!
+    response: NoWay, // hose
+) {
+    fn op(
+        x: Typ,
+        key: &[u8],
+        upd: Box<
+            Fn(
+                Option<&memcache::Item>,
+            ) -> (memcache::Status, Result<memcache::Item, Option<String>>),
+        >,
+    ) -> MapResult {
+    }
+
+    "cool"
+}
+
+fn weird_comment(
+    // /*/ double level */ comment
+    x: Hello, // /*/* triple, even */*/
+    // Does this work?
+    y: World,
+) {
+    simple(/* does this preserve comments now? */ 42, NoWay)
+}
+
+fn generic<T>(arg: T) -> &SomeType
+where
+    T: Fn(
+        // First arg
+        A,
+        // Second argument
+        B,
+        C,
+        D,
+        // pre comment
+        E, // last comment
+    ) -> &SomeType,
+{
+    arg(a, b, c, d, e)
+}
+
+fn foo() -> ! {}
+
+pub fn http_fetch_async(
+    listener: Box<AsyncCORSResponseListener + Send>,
+    script_chan: Box<ScriptChan + Send>,
+) {
+}
+
+fn some_func<T: Box<Trait + Bound>>(val: T) {}
+
+fn zzzzzzzzzzzzzzzzzzzz<Type, NodeType>(
+    selff: Type,
+    mut handle: node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>,
+) -> SearchStack<'a, K, V, Type, NodeType> {
+}
+
+unsafe fn generic_call(
+    cx: *mut JSContext,
+    argc: libc::c_uint,
+    vp: *mut JSVal,
+    is_lenient: bool,
+    call: unsafe extern "C" fn(
+        *const JSJitInfo,
+        *mut JSContext,
+        HandleObject,
+        *mut libc::c_void,
+        u32,
+        *mut JSVal,
+    ) -> u8,
+) {
+    let f: fn(_, _) -> _ = panic!();
+}
+
+pub fn start_export_thread<C: CryptoSchemee + 'static>(
+    database: &Database,
+    crypto_scheme: &C,
+    block_size: usize,
+    source_path: &Path,
+) -> BonzoResult<mpsc::Consumer<'static, FileInstruction>> {
+}
+
+pub fn waltz(cwd: &Path) -> CliAssert {
+    {
+        {
+            formatted_comment =
+                rewrite_comment(comment, block_style, width, offset, formatting_fig);
+        }
+    }
+}
+
+// #2003
+mod foo {
+    fn __bindgen_test_layout_i_open0_c_open1_char_a_open2_char_close2_close1_close0_instantiation()
+    {
+        foo();
+    }
+}
+
+// #2082
+pub(crate) fn init() {}
+
+crate fn init() {}
+
+// #2630
+fn make_map<T, F: (Fn(&T) -> String)>(records: &Vec<T>, key_fn: F) -> HashMap<String, usize> {}
+
+// #2956
+fn bar(
+    beans: Asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf,
+    spam: bool,
+    eggs: bool,
+) -> bool {
+    unimplemented!();
+}
diff --git a/src/tools/rustfmt/tests/target/fn-single-line/version_one.rs b/src/tools/rustfmt/tests/target/fn-single-line/version_one.rs
new file mode 100644
index 0000000000000..013b2cd721615
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-single-line/version_one.rs
@@ -0,0 +1,71 @@
+// rustfmt-fn_single_line: true
+// rustfmt-version: One
+// Test single-line functions.
+
+fn foo_expr() { 1 }
+
+fn foo_stmt() { foo(); }
+
+fn foo_decl_local() { let z = 5; }
+
+fn foo_decl_item(x: &mut i32) { x = 3; }
+
+fn empty() {}
+
+fn foo_return() -> String { "yay" }
+
+fn foo_where() -> T
+where
+    T: Sync,
+{
+    let x = 2;
+}
+
+fn fooblock() {
+    {
+        "inner-block"
+    }
+}
+
+fn fooblock2(x: i32) {
+    let z = match x {
+        _ => 2,
+    };
+}
+
+fn comment() {
+    // this is a test comment
+    1
+}
+
+fn comment2() {
+    // multi-line comment
+    let z = 2;
+    1
+}
+
+fn only_comment() {
+    // Keep this here
+}
+
+fn aaaaaaaaaaaaaaaaa_looooooooooooooooooooooong_name() {
+    let z = "aaaaaaawwwwwwwwwwwwwwwwwwwwwwwwwwww";
+}
+
+fn lots_of_space() { 1 }
+
+fn mac() -> Vec<i32> { vec![] }
+
+trait CoolTypes {
+    fn dummy(&self) {}
+}
+
+trait CoolerTypes {
+    fn dummy(&self) {}
+}
+
+fn Foo<T>()
+where
+    T: Bar,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/fn-single-line/version_two.rs b/src/tools/rustfmt/tests/target/fn-single-line/version_two.rs
new file mode 100644
index 0000000000000..b8053d4c2f500
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-single-line/version_two.rs
@@ -0,0 +1,67 @@
+// rustfmt-fn_single_line: true
+// rustfmt-version: Two
+// Test single-line functions.
+
+fn foo_expr() { 1 }
+
+fn foo_stmt() { foo(); }
+
+fn foo_decl_local() { let z = 5; }
+
+fn foo_decl_item(x: &mut i32) { x = 3; }
+
+fn empty() {}
+
+fn foo_return() -> String { "yay" }
+
+fn foo_where() -> T
+where
+    T: Sync,
+{
+    let x = 2;
+}
+
+fn fooblock() { { "inner-block" } }
+
+fn fooblock2(x: i32) {
+    let z = match x {
+        _ => 2,
+    };
+}
+
+fn comment() {
+    // this is a test comment
+    1
+}
+
+fn comment2() {
+    // multi-line comment
+    let z = 2;
+    1
+}
+
+fn only_comment() {
+    // Keep this here
+}
+
+fn aaaaaaaaaaaaaaaaa_looooooooooooooooooooooong_name() {
+    let z = "aaaaaaawwwwwwwwwwwwwwwwwwwwwwwwwwww";
+}
+
+fn lots_of_space() { 1 }
+
+fn mac() -> Vec<i32> { vec![] }
+
+trait CoolTypes {
+    fn dummy(&self) {}
+}
+
+trait CoolerTypes {
+    fn dummy(&self) {}
+}
+
+fn Foo<T>()
+where
+    T: Bar,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/fn-ty.rs b/src/tools/rustfmt/tests/target/fn-ty.rs
new file mode 100644
index 0000000000000..7d48f3b32dbc1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn-ty.rs
@@ -0,0 +1,14 @@
+fn f(
+    xxxxxxxxxxxxxxxxxx: fn(a, b, b) -> a,
+    xxxxxxxxxxxxxxxxxx: fn() -> a,
+    xxxxxxxxxxxxxxxxxx: fn(a, b, b),
+    xxxxxxxxxxxxxxxxxx: fn(),
+    xxxxxxxxxxxxxxxxxx: fn(a, b, b) -> !,
+    xxxxxxxxxxxxxxxxxx: fn() -> !,
+) where
+    F1: Fn(a, b, b) -> a,
+    F2: Fn(a, b, b),
+    F3: Fn(),
+    F4: Fn() -> u32,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/fn.rs b/src/tools/rustfmt/tests/target/fn.rs
new file mode 100644
index 0000000000000..0ad775ee1ddf7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn.rs
@@ -0,0 +1,120 @@
+// Tests different fns
+
+fn foo(a: AAAA, b: BBB, c: CCC) -> RetType {}
+
+fn foo(a: AAAA, b: BBB /* some, weird, inline comment */, c: CCC) -> RetType
+where
+    T: Blah,
+{
+}
+
+fn foo(a: AAA /* (comment) */)
+where
+    T: Blah,
+{
+}
+
+fn foo(
+    a: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+    b: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+) -> RetType
+where
+    T: Blah,
+{
+}
+
+fn foo<U, T>(
+    a: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+    b: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+) -> RetType
+where
+    T: Blah,
+    U: dsfasdfasdfasd,
+{
+}
+
+fn foo<U: Fn(A) -> B /* paren inside generics */>() {}
+
+impl Foo {
+    fn with_no_errors<T, F>(&mut self, f: F) -> T
+    where
+        F: FnOnce(&mut Resolver) -> T,
+    {
+    }
+
+    fn foo(mut self, mut bar: u32) {}
+
+    fn bar(self, mut bazz: u32) {}
+}
+
+pub fn render<
+    'a,
+    N: Clone + 'a,
+    E: Clone + 'a,
+    G: Labeller<'a, N, E> + GraphWalk<'a, N, E>,
+    W: Write,
+>(
+    g: &'a G,
+    w: &mut W,
+) -> io::Result<()> {
+    render_opts(g, w, &[])
+}
+
+const fn foo() {
+    x;
+}
+
+pub const fn foo() {
+    x;
+}
+
+impl Foo {
+    const fn foo() {
+        x;
+    }
+}
+
+fn homura<T: Deref<Target = i32>>(_: T) {}
+
+fn issue377() -> (Box<CompositorProxy + Send>, Box<CompositorReceiver>) {}
+
+fn main() {
+    let _ = function(move || 5);
+    let _ = move || 42;
+    let _ = || unsafe { abort() };
+}
+
+// With inner attributes.
+fn inner() {
+    #![inline]
+    x
+}
+
+#[cfg_attr(rustfmt, rustfmt::skip)]
+fn foo(a: i32) -> i32 {
+    // comment
+    if a > 0 { 1 } else { 2 }
+}
+
+fn ______________________baz(
+    a: i32,
+) -> *mut ::std::option::Option<
+    extern "C" fn(arg1: i32, _____________________a: i32, arg3: i32) -> (),
+> {
+}
+
+pub fn check_path<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    path: &hir::Path,
+    id: ast::NodeId,
+    cb: &mut FnMut(DefId, Span, &Option<&Stability>, &Option<Depecation>),
+) {
+}
+
+pub fn check_path<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    path: &hir::Path,
+    id: ast::NodeId,
+    cb: &mut FnMut(DefId, Span, &Option<&Stability>, &Option<Deprecation>),
+) {
+}
diff --git a/src/tools/rustfmt/tests/target/fn_args_indent-block.rs b/src/tools/rustfmt/tests/target/fn_args_indent-block.rs
new file mode 100644
index 0000000000000..f5232a4881714
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn_args_indent-block.rs
@@ -0,0 +1,143 @@
+// rustfmt-normalize_comments: true
+
+fn foo() {
+    foo();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) {
+    bar();
+}
+
+fn foo(a: Aaaaaaaaaaaaaa, b: Bbbbbbbbbbbbbb) -> String {
+    foo();
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) -> String {
+    bar();
+}
+
+fn foo(a: u8 /* Comment 1 */, b: u8 /* Comment 2 */) -> u8 {
+    bar()
+}
+
+fn foo(
+    a: u8, // Comment 1
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee, // Comment 2
+) -> u8 {
+    bar()
+}
+
+fn bar(
+    a: Aaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+    e: Eeeeeeeeeeeeeee,
+) -> String
+where
+    X: Fooooo,
+    Y: Baaar,
+{
+    bar();
+}
+
+fn foo() -> T {
+    foo();
+}
+
+fn foo() -> T
+where
+    X: Foooo,
+    Y: Baaar,
+{
+    foo();
+}
+
+fn foo()
+where
+    X: Foooo,
+{
+}
+
+fn foo()
+where
+    X: Foooo,
+    Y: Baaar,
+{
+}
+
+fn foo() -> (
+    Loooooooooooooooooooooong,
+    Reeeeeeeeeeeeeeeeeeeeeeeeturn,
+    iiiiiiiiis,
+    Looooooooooooooooong,
+) {
+    foo();
+}
+
+fn foo<g: G>() {
+    foo();
+}
+
+fn foo<
+    L: Loooooooooooooooooooooong,
+    G: Geeeeeeeeeeeneric,
+    I: iiiiiiiiis,
+    L: Looooooooooooooooong,
+>() {
+    foo();
+}
+
+fn foo<L: Loooooooooooooooooooong, G: Geeeeeeeeeeneric, I: iiiiiiiiis, L: Loooooooooooooooong>() {
+    foo();
+}
+
+trait Test {
+    fn foo(a: u8) {}
+
+    fn bar(
+        a: Aaaaaaaaaaaaaa,
+        b: Bbbbbbbbbbbbbb,
+        c: Cccccccccccccccccc,
+        d: Dddddddddddddddd,
+        e: Eeeeeeeeeeeeeee,
+    ) -> String {
+    }
+}
+
+fn foo<L: Loooooooooooooooooooong, G: Geeeeeeeeeeneric, I: iiiiiiiiis, L: Loooooooooooooooong>(
+    a: Aaaaaaaaaaaaaaaaaaaa,
+    b: Bbbbbbbbbbbbbbbbb,
+    c: Cccccccccccccccccc,
+    d: Dddddddddddddddd,
+) {
+    foo();
+}
+
+fn foo() -> (
+    Looooooooooooooooooooooooooong,
+    Reeeeeeeeeeeeeeeeeeeeeeeeeeeeeturn,
+    iiiiiiiiiiiiiis,
+    Loooooooooooooooooooooong,
+) {
+    foo();
+}
diff --git a/src/tools/rustfmt/tests/target/fn_args_layout-vertical.rs b/src/tools/rustfmt/tests/target/fn_args_layout-vertical.rs
new file mode 100644
index 0000000000000..da0ac981d872d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn_args_layout-vertical.rs
@@ -0,0 +1,39 @@
+// rustfmt-fn_args_layout: Vertical
+
+// Empty list should stay on one line.
+fn do_bar() -> u8 {
+    bar()
+}
+
+// A single argument should stay on the same line.
+fn do_bar(a: u8) -> u8 {
+    bar()
+}
+
+// Multiple arguments should each get their own line.
+fn do_bar(
+    a: u8,
+    mut b: u8,
+    c: &u8,
+    d: &mut u8,
+    closure: &Fn(i32) -> i32,
+) -> i32 {
+    // This feature should not affect closures.
+    let bar = |x: i32, y: i32| -> i32 { x + y };
+    bar(a, b)
+}
+
+// If the first argument doesn't fit on the same line with the function name,
+// the whole list should probably be pushed to the next line with hanging
+// indent. That's not what happens though, so check current behaviour instead.
+// In any case, it should maintain single argument per line.
+fn do_this_that_and_the_other_thing(
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: u8,
+    b: u8,
+    c: u8,
+    d: u8,
+) {
+    this();
+    that();
+    the_other_thing();
+}
diff --git a/src/tools/rustfmt/tests/target/fn_once.rs b/src/tools/rustfmt/tests/target/fn_once.rs
new file mode 100644
index 0000000000000..42b8f98e78abf
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/fn_once.rs
@@ -0,0 +1,8 @@
+struct Add(usize);
+
+impl FnOnce<(usize,)> for Add {
+    type Output = Add;
+    extern "rust-call" fn call_once(self, to: (usize,)) -> Add {
+        Add(self.0 + to.0)
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/format_strings/issue-202.rs b/src/tools/rustfmt/tests/target/format_strings/issue-202.rs
new file mode 100644
index 0000000000000..2a2c24140ddfc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/format_strings/issue-202.rs
@@ -0,0 +1,25 @@
+// rustfmt-format_strings: true
+
+#[test]
+fn compile_empty_program() {
+    let result = get_result();
+    let expected = "; ModuleID = \'foo\'
+
+; Function Attrs: nounwind
+declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) #0
+
+declare i32 @write(i32, i8*, i32)
+
+declare i32 @putchar(i32)
+
+declare i32 @getchar()
+
+define i32 @main() {
+entry:
+  ret i32 0
+}
+
+attributes #0 = { nounwind }
+";
+    assert_eq!(result, CString::new(expected).unwrap());
+}
diff --git a/src/tools/rustfmt/tests/target/format_strings/issue-2833.rs b/src/tools/rustfmt/tests/target/format_strings/issue-2833.rs
new file mode 100644
index 0000000000000..70483532528c4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/format_strings/issue-2833.rs
@@ -0,0 +1,15 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 80
+
+fn test1() {
+    let expected = "\
+but Doctor Watson has to have it taken out for him and dusted,
+";
+}
+
+fn test2() {
+    let expected = "\
+[Omitted long matching line]
+but Doctor Watson has to have it taken out for him and dusted,
+";
+}
diff --git a/src/tools/rustfmt/tests/target/format_strings/issue-3263.rs b/src/tools/rustfmt/tests/target/format_strings/issue-3263.rs
new file mode 100644
index 0000000000000..72f7e9cc6277e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/format_strings/issue-3263.rs
@@ -0,0 +1,26 @@
+// rustfmt-format_strings: true
+// rustfmt-newline_style: Windows
+
+#[test]
+fn compile_empty_program() {
+    let result = get_result();
+    let expected = "; ModuleID = \'foo\'
+
+; Function Attrs: nounwind
+declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) #0
+
+declare i32 @write(i32, i8*, i32)
+
+declare i32 @putchar(i32)
+
+declare i32 @getchar()
+
+define i32 @main() {
+entry:
+  ret i32 0
+}
+
+attributes #0 = { nounwind }
+";
+    assert_eq!(result, CString::new(expected).unwrap());
+}
diff --git a/src/tools/rustfmt/tests/target/format_strings/issue-687.rs b/src/tools/rustfmt/tests/target/format_strings/issue-687.rs
new file mode 100644
index 0000000000000..21d292f9eb98a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/format_strings/issue-687.rs
@@ -0,0 +1,10 @@
+// rustfmt-format_strings: true
+
+fn foo() -> &'static str {
+    let sql = "ATTACH DATABASE ':memory:' AS my_attached;
+               BEGIN;
+               CREATE TABLE my_attached.foo(x INTEGER);
+               INSERT INTO my_attached.foo VALUES(42);
+               END;";
+    sql
+}
diff --git a/src/tools/rustfmt/tests/target/format_strings/issue564.rs b/src/tools/rustfmt/tests/target/format_strings/issue564.rs
new file mode 100644
index 0000000000000..d9ef077c25623
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/format_strings/issue564.rs
@@ -0,0 +1,7 @@
+// rustfmt-format_strings: true
+
+const USAGE: &'static str = "
+Usage: codegen project <name> <digits> <len> <codes> <prizes> <step> <shift>
+       codegen regenerate <name>
+       codegen verify <name> <code>
+";
diff --git a/src/tools/rustfmt/tests/target/hard-tabs.rs b/src/tools/rustfmt/tests/target/hard-tabs.rs
new file mode 100644
index 0000000000000..aca7e09c0eacf
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/hard-tabs.rs
@@ -0,0 +1,98 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-hard_tabs: true
+
+fn main() {
+	let x = Bar;
+
+	let y = Foo { a: x };
+
+	Foo {
+		a: foo(), // comment
+		// comment
+		b: bar(),
+		..something
+	};
+
+	fn foo(a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32, a: i32) {
+	}
+
+	let str = "AAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAa";
+
+	if let (
+		some_very_large,
+		tuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuple,
+	) = 1 + 2 + 3
+	{}
+
+	if cond() {
+		something();
+	} else if different_cond() {
+		something_else();
+	} else {
+		aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+			+ aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+	}
+
+	unsafe /* very looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+	        * comment */ {
+	}
+
+	unsafe /* So this is a very long comment.
+	        * Multi-line, too.
+	        * Will it still format correctly? */ {
+	}
+
+	let chain = funktion_kall()
+		.go_to_next_line_with_tab()
+		.go_to_next_line_with_tab()
+		.go_to_next_line_with_tab();
+
+	let z = [
+		xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+		yyyyyyyyyyyyyyyyyyyyyyyyyyy,
+		zzzzzzzzzzzzzzzzzz,
+		q,
+	];
+
+	fn generic<T>(arg: T) -> &SomeType
+	where
+		T: Fn(
+			// First arg
+			A,
+			// Second argument
+			B,
+			C,
+			D,
+			// pre comment
+			E, // last comment
+		) -> &SomeType,
+	{
+		arg(a, b, c, d, e)
+	}
+
+	loong_func().quux(move || if true { 1 } else { 2 });
+
+	fffffffffffffffffffffffffffffffffff(a, {
+		SCRIPT_TASK_ROOT.with(|root| {
+			*root.borrow_mut() = Some(&script_task);
+		});
+	});
+	a.b.c.d();
+
+	x().y(|| match cond() {
+		true => (),
+		false => (),
+	});
+}
+
+// #2296
+impl Foo {
+	// a comment
+	// on multiple lines
+	fn foo() {
+		// another comment
+		// on multiple lines
+		let x = true;
+	}
+}
diff --git a/src/tools/rustfmt/tests/target/hello.rs b/src/tools/rustfmt/tests/target/hello.rs
new file mode 100644
index 0000000000000..d9f90b0b5e800
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/hello.rs
@@ -0,0 +1,8 @@
+// rustfmt-config: small_tabs.toml
+// rustfmt-target: hello.rs
+
+// Smoke test - hello world.
+
+fn main() {
+  println!("Hello world!");
+}
diff --git a/src/tools/rustfmt/tests/target/if_while_or_patterns.rs b/src/tools/rustfmt/tests/target/if_while_or_patterns.rs
new file mode 100644
index 0000000000000..61a357afcbaea
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/if_while_or_patterns.rs
@@ -0,0 +1,38 @@
+#![feature(if_while_or_patterns)]
+
+fn main() {
+    if let 0 | 1 = 0 {
+        println!("hello, world");
+    };
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaa | bbbbbbbbbbbbbbbbbbbbbbbbbbb | cccccccccccccccc | d_100 = 0 {
+        println!("hello, world");
+    }
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaa | bbbbbbbbbbbbbbbbbbbbbbb | ccccccccccccccccccccc | d_101 = 0
+    {
+        println!("hello, world");
+    }
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaaaa | bbbbbbbbbbbbbbbbbbbbbbb | ccccccccccccccccccccc | d_103 =
+        0
+    {
+        println!("hello, world");
+    }
+
+    if let aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    | bbbbbbbbbbbbbbbbbbbbbbb
+    | ccccccccccccccccccccc
+    | d_105 = 0
+    {
+        println!("hello, world");
+    }
+
+    while let xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx
+    | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx | xxx = foo_bar(
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        cccccccccccccccccccccccccccccccccccccccc,
+    ) {
+        println!("hello, world");
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/immovable_generators.rs b/src/tools/rustfmt/tests/target/immovable_generators.rs
new file mode 100644
index 0000000000000..0bf7a2d91ba15
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/immovable_generators.rs
@@ -0,0 +1,7 @@
+#![feature(generators)]
+
+unsafe fn foo() {
+    let mut ga = static || {
+        yield 1;
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/impl.rs b/src/tools/rustfmt/tests/target/impl.rs
new file mode 100644
index 0000000000000..f37fbcf1fcbcc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/impl.rs
@@ -0,0 +1,43 @@
+// Test impls
+
+impl<T> JSTraceable for SmallVec<[T; 1]> {}
+
+impl<K, V, NodeRef: Deref<Target = Node<K, V>>> Handle<NodeRef, handle::Edge, handle::Internal> {
+    // Keep this.
+}
+
+impl<V> Test<V>
+where
+    V: Clone, // This comment is NOT removed by formatting!
+{
+    pub fn new(value: V) -> Self {
+        Test {
+            cloned_value: value.clone(),
+            value,
+        }
+    }
+}
+
+impl X<T> /* comment */ {}
+impl Y<T> // comment
+{
+}
+
+impl<T> Foo for T
+// comment1
+where
+    // comment2
+    // blah
+    T: Clone,
+{
+}
+
+// #1823
+default impl Trait for X {}
+default unsafe impl Trait for Y {}
+pub default unsafe impl Trait for Z {}
+
+// #2212
+impl ConstWithDefault {
+    default const CAN_RECONSTRUCT_QUERY_KEY: bool = false;
+}
diff --git a/src/tools/rustfmt/tests/target/impls.rs b/src/tools/rustfmt/tests/target/impls.rs
new file mode 100644
index 0000000000000..bf63f924a33b0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/impls.rs
@@ -0,0 +1,244 @@
+// rustfmt-normalize_comments: true
+impl Foo for Bar {
+    fn foo() {
+        "hi"
+    }
+}
+
+pub impl Foo for Bar {
+    // Associated Constants
+    const Baz: i32 = 16;
+    // Associated Types
+    type FooBar = usize;
+    // Comment 1
+    fn foo() {
+        "hi"
+    }
+    // Comment 2
+    fn foo() {
+        "hi"
+    }
+    // Comment 3
+}
+
+pub unsafe impl<'a, 'b, X, Y: Foo<Bar>> !Foo<'a, X> for Bar<'b, Y>
+where
+    X: Foo<'a, Z>,
+{
+    fn foo() {
+        "hi"
+    }
+}
+
+impl<'a, 'b, X, Y: Foo<Bar>> Foo<'a, X> for Bar<'b, Y>
+where
+    X: Fooooooooooooooooooooooooooooo<'a, Z>,
+{
+    fn foo() {
+        "hi"
+    }
+}
+
+impl<'a, 'b, X, Y: Foo<Bar>> Foo<'a, X> for Bar<'b, Y>
+where
+    X: Foooooooooooooooooooooooooooo<'a, Z>,
+{
+    fn foo() {
+        "hi"
+    }
+}
+
+impl<T> Foo for Bar<T> where T: Baz {}
+
+impl<T> Foo for Bar<T>
+where
+    T: Baz,
+{
+    // Comment
+}
+
+impl Foo {
+    fn foo() {}
+}
+
+impl Boo {
+    // BOO
+    fn boo() {}
+    // FOO
+}
+
+mod a {
+    impl Foo {
+        // Hello!
+        fn foo() {}
+    }
+}
+
+mod b {
+    mod a {
+        impl Foo {
+            fn foo() {}
+        }
+    }
+}
+
+impl Foo {
+    add_fun!();
+}
+
+impl Blah {
+    fn boop() {}
+    add_fun!();
+}
+
+impl X {
+    fn do_parse(mut self: X) {}
+}
+
+impl Y5000 {
+    fn bar(self: X<'a, 'b>, y: Y) {}
+
+    fn bad(&self, (x, y): CoorT) {}
+
+    fn turbo_bad(self: X<'a, 'b>, (x, y): CoorT) {}
+}
+
+pub impl<T> Foo for Bar<T>
+where
+    T: Foo,
+{
+    fn foo() {
+        "hi"
+    }
+}
+
+pub impl<T, Z> Foo for Bar<T, Z>
+where
+    T: Foo,
+    Z: Baz,
+{
+}
+
+mod m {
+    impl<T> PartialEq for S<T>
+    where
+        T: PartialEq,
+    {
+        fn eq(&self, other: &Self) {
+            true
+        }
+    }
+
+    impl<T> PartialEq for S<T> where T: PartialEq {}
+}
+
+impl<BorrowType, K, V, NodeType, HandleType>
+    Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
+{
+}
+
+impl<BorrowType, K, V, NodeType, HandleType> PartialEq
+    for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
+{
+}
+
+mod x {
+    impl<A, B, C, D> Foo
+    where
+        A: 'static,
+        B: 'static,
+        C: 'static,
+        D: 'static,
+    {
+    }
+}
+
+impl<ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNodeFoo>
+    Issue1249<ConcreteThreadSafeLayoutNode>
+{
+    // Creates a new flow constructor.
+    fn foo() {}
+}
+
+// #1600
+impl<#[may_dangle] K, #[may_dangle] V> Drop for RawTable<K, V> {
+    fn drop() {}
+}
+
+// #1168
+pub trait Number:
+    Copy
+    + Eq
+    + Not<Output = Self>
+    + Shl<u8, Output = Self>
+    + Shr<u8, Output = Self>
+    + BitAnd<Self, Output = Self>
+    + BitOr<Self, Output = Self>
+    + BitAndAssign
+    + BitOrAssign
+{
+    // test
+    fn zero() -> Self;
+}
+
+// #1642
+pub trait SomeTrait:
+    Clone
+    + Eq
+    + PartialEq
+    + Ord
+    + PartialOrd
+    + Default
+    + Hash
+    + Debug
+    + Display
+    + Write
+    + Read
+    + FromStr
+{
+    // comment
+}
+
+// #1995
+impl Foo {
+    fn f(
+        S {
+            aaaaaaaaaa: aaaaaaaaaa,
+            bbbbbbbbbb: bbbbbbbbbb,
+            cccccccccc: cccccccccc,
+        }: S,
+    ) -> u32 {
+        1
+    }
+}
+
+// #2491
+impl<'a, 'b, 'c> SomeThing<Something>
+    for (
+        &'a mut SomethingLong,
+        &'b mut SomethingLong,
+        &'c mut SomethingLong,
+    )
+{
+    fn foo() {}
+}
+
+// #2746
+impl<'seq1, 'seq2, 'body, 'scope, Channel>
+    Adc12<
+        Dual,
+        MasterRunningDma<'seq1, 'body, 'scope, Channel>,
+        SlaveRunningDma<'seq2, 'body, 'scope>,
+    >
+where
+    Channel: DmaChannel,
+{
+}
+
+// #4084
+impl const std::default::Default for Struct {
+    #[inline]
+    fn default() -> Self {
+        Self { f: 12.5 }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/import-fencepost-length.rs b/src/tools/rustfmt/tests/target/import-fencepost-length.rs
new file mode 100644
index 0000000000000..fd09d50d72d9a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/import-fencepost-length.rs
@@ -0,0 +1,7 @@
+use aaaaaaaaaaaaaaa::bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
+use aaaaaaaaaaaaaaa::{
+    bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb, ccccccccccccccccccccccccccccccc, dddddddd,
+};
+use aaaaaaaaaaaaaaa::{
+    bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb, ccccccccccccccccccccccccccccccc, ddddddddd,
+};
diff --git a/src/tools/rustfmt/tests/target/imports-impl-only-use.rs b/src/tools/rustfmt/tests/target/imports-impl-only-use.rs
new file mode 100644
index 0000000000000..d290d8d91858d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports-impl-only-use.rs
@@ -0,0 +1,4 @@
+#![feature(underscore_imports)]
+
+use attr;
+use std::iter::Iterator as _;
diff --git a/src/tools/rustfmt/tests/target/imports-reorder-lines-and-items.rs b/src/tools/rustfmt/tests/target/imports-reorder-lines-and-items.rs
new file mode 100644
index 0000000000000..98a5afe43480a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports-reorder-lines-and-items.rs
@@ -0,0 +1,7 @@
+use std::cmp::{a, b, c, d};
+use std::ddd::aaa;
+use std::ddd::{a, b, c as g, d as p};
+/// This comment should stay with `use std::str;`
+use std::str;
+// This comment should stay with `use std::ddd:bbb;`
+use std::ddd::bbb;
diff --git a/src/tools/rustfmt/tests/target/imports-reorder-lines.rs b/src/tools/rustfmt/tests/target/imports-reorder-lines.rs
new file mode 100644
index 0000000000000..5b85503b55d0b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports-reorder-lines.rs
@@ -0,0 +1,31 @@
+use std::cmp::{a, b, c, d};
+use std::cmp::{b, e, f, g};
+use std::ddd::aaa;
+use std::str;
+// This comment should stay with `use std::ddd;`
+use std::ddd;
+use std::ddd::bbb;
+
+mod test {}
+
+use aaa;
+use aaa::bbb;
+use aaa::*;
+
+mod test {}
+// If item names are equal, order by rename
+
+use test::{a as bb, b};
+use test::{a as aa, c};
+
+mod test {}
+// If item names are equal, order by rename - no rename comes before a rename
+
+use test::{a as bb, b};
+use test::{a, c};
+
+mod test {}
+// `self` always comes first
+
+use test::{self as bb, b};
+use test::{a as aa, c};
diff --git a/src/tools/rustfmt/tests/target/imports-reorder.rs b/src/tools/rustfmt/tests/target/imports-reorder.rs
new file mode 100644
index 0000000000000..84e97c0224f83
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports-reorder.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+
+use path::{self /* self */, /* A */ A, B /* B */, C};
+
+use {aa, ab, ac, b, Z};
diff --git a/src/tools/rustfmt/tests/target/imports.rs b/src/tools/rustfmt/tests/target/imports.rs
new file mode 100644
index 0000000000000..87584d89f6637
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports.rs
@@ -0,0 +1,129 @@
+// rustfmt-normalize_comments: true
+
+// Imports.
+
+// Long import.
+use exceedingly::loooooooooooooooooooooooooooooooooooooooooooooooooooooooong::import::path::{
+    ItemA, ItemB,
+};
+use exceedingly::looooooooooooooooooooooooooooooooooooooooooooooooooooooooooong::import::path::{
+    ItemA, ItemB,
+};
+use rustc_ast::ast::{ItemDefaultImpl, ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic};
+
+use list::{
+    // Another item
+    AnotherItem, // Another Comment
+    // Last Item
+    LastItem,
+    // Some item
+    SomeItem, // Comment
+};
+
+use test::{/* A */ self /* B */, Other /* C */};
+
+pub use rustc_ast::ast::{Expr, ExprAssign, ExprCall, ExprMethodCall, ExprPath, Expr_};
+use rustc_ast::{self};
+use Foo::{Bar, Baz};
+use {Bar /* comment */, /* Pre-comment! */ Foo};
+
+use std::io;
+use std::io::{self};
+
+mod Foo {
+    pub use rustc_ast::ast::{
+        ItemDefaultImpl, ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic,
+    };
+
+    mod Foo2 {
+        pub use rustc_ast::ast::{
+            self, ItemDefaultImpl, ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic,
+        };
+    }
+}
+
+fn test() {
+    use Baz::*;
+    use Qux;
+}
+
+// Simple imports
+use bar::quux as kaas;
+use foo;
+use foo::bar::baz;
+
+// With aliases.
+use foo::qux as bar;
+use foo::{self as bar};
+use foo::{self as bar, baz};
+use foo::{baz, qux as bar};
+
+// With absolute paths
+use foo;
+use foo::Bar;
+use foo::{Bar, Baz};
+use Foo;
+use {Bar, Baz};
+
+// Root globs
+use *;
+use *;
+
+// spaces used to cause glob imports to disappear (#1356)
+use super::*;
+use foo::issue_1356::*;
+
+// We shouldn't remove imports which have attributes attached (#1858)
+#[cfg(unix)]
+use self::unix::{};
+
+// nested imports
+use foo::{
+    a, b,
+    bar::{
+        baz,
+        foo::{a, b, cxxxxxxxxxxxxx, yyyyyyyyyyyyyy, zzzzzzzzzzzzzzzz},
+        qux, xxxxxxxxxxx, yyyyyyyyyyyyy, zzzzzzzzzzzzzzzz,
+    },
+    boo, c,
+};
+
+use fooo::{
+    baar::foobar::{
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
+        zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
+    },
+    bar,
+    bar::*,
+    x, y, z,
+};
+
+use exonum::{
+    api::{Api, ApiError},
+    blockchain::{self, BlockProof, Blockchain, Transaction, TransactionSet},
+    crypto::{Hash, PublicKey},
+    helpers::Height,
+    node::TransactionSend,
+    storage::{ListProof, MapProof},
+};
+
+// nested imports with a single sub-tree.
+use a::b::c::d;
+use a::b::c::*;
+use a::b::c::{xxx, yyy, zzz};
+
+// #2645
+/// This line is not affected.
+// This line is deleted.
+use c;
+
+// #2670
+#[macro_use]
+use imports_with_attr;
+
+// #2888
+use std::f64::consts::{E, PI, SQRT_2};
+
+// #3273
+#[rustfmt::skip]
+use std::fmt::{self, {Display, Formatter}};
diff --git a/src/tools/rustfmt/tests/target/imports_2021_edition.rs b/src/tools/rustfmt/tests/target/imports_2021_edition.rs
new file mode 100644
index 0000000000000..34dcc866a0bda
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports_2021_edition.rs
@@ -0,0 +1,3 @@
+// rustfmt-edition: 2021
+
+use ::happy::new::year;
diff --git a/src/tools/rustfmt/tests/target/imports_block_indent.rs b/src/tools/rustfmt/tests/target/imports_block_indent.rs
new file mode 100644
index 0000000000000..8c90f7ce29c81
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports_block_indent.rs
@@ -0,0 +1,4 @@
+// #2569
+use apns2::request::notification::{
+    Notificatio, NotificationBuilder, Priority, SilentNotificationBuilder,
+};
diff --git a/src/tools/rustfmt/tests/target/imports_granularity_crate.rs b/src/tools/rustfmt/tests/target/imports_granularity_crate.rs
new file mode 100644
index 0000000000000..d75906d30f18b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports_granularity_crate.rs
@@ -0,0 +1,28 @@
+// rustfmt-imports_granularity: Crate
+
+use a::{a, b, c, d, e, f, g};
+
+#[doc(hidden)]
+use a::b;
+use a::{c, d};
+
+#[doc(hidden)]
+use a::b;
+use a::{c, d, e};
+
+use foo::{a, b, c};
+pub use foo::{bar, foobar};
+
+use a::b::c::{d, xxx, yyy, zzz, *};
+
+// https://github.com/rust-lang/rustfmt/issues/3808
+use d::{self};
+use e::{self as foo};
+use f::{self, b};
+use g::{self, a, b};
+use h::a;
+use i::a::{self};
+use j::a::{self};
+
+use k::{a, b, c, d};
+use l::{a, b, c, d};
diff --git a/src/tools/rustfmt/tests/target/imports_granularity_item.rs b/src/tools/rustfmt/tests/target/imports_granularity_item.rs
new file mode 100644
index 0000000000000..eace785e6705e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports_granularity_item.rs
@@ -0,0 +1,13 @@
+// rustfmt-imports_granularity: Item
+
+use a::b;
+use a::c;
+use a::d;
+use a::f::g;
+use a::h::i;
+use a::h::j;
+use a::l::m;
+use a::l::n::o;
+use a::l::p::*;
+use a::l::{self};
+use a::q::{self};
diff --git a/src/tools/rustfmt/tests/target/imports_granularity_module.rs b/src/tools/rustfmt/tests/target/imports_granularity_module.rs
new file mode 100644
index 0000000000000..9c1387c466afa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/imports_granularity_module.rs
@@ -0,0 +1,20 @@
+// rustfmt-imports_granularity: Module
+
+use a::b::c;
+use a::d::e;
+use a::f;
+use a::g::{h, i};
+use a::j::k::{self, l};
+use a::j::{self, m};
+use a::n::o::p;
+use a::n::q;
+pub use a::r::s;
+pub use a::t;
+
+use foo::e;
+#[cfg(test)]
+use foo::{a::b, c::d};
+
+use bar::a::b;
+use bar::c::d;
+use bar::e::f;
diff --git a/src/tools/rustfmt/tests/target/indented-impl.rs b/src/tools/rustfmt/tests/target/indented-impl.rs
new file mode 100644
index 0000000000000..eff579dddac71
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/indented-impl.rs
@@ -0,0 +1,13 @@
+// rustfmt-brace_style: AlwaysNextLine
+mod x
+{
+    struct X(i8);
+
+    impl Y for X
+    {
+        fn y(self) -> ()
+        {
+            println!("ok");
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/inner-module-path/b.rs b/src/tools/rustfmt/tests/target/inner-module-path/b.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/inner-module-path/b.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/target/inner-module-path/c/d.rs b/src/tools/rustfmt/tests/target/inner-module-path/c/d.rs
new file mode 100644
index 0000000000000..8b137891791fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/inner-module-path/c/d.rs
@@ -0,0 +1 @@
+
diff --git a/src/tools/rustfmt/tests/target/inner-module-path/lib.rs b/src/tools/rustfmt/tests/target/inner-module-path/lib.rs
new file mode 100644
index 0000000000000..60d246dd5fb45
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/inner-module-path/lib.rs
@@ -0,0 +1,8 @@
+#[path = "."]
+mod a {
+    mod b;
+}
+
+mod c {
+    mod d;
+}
diff --git a/src/tools/rustfmt/tests/target/invalid-rust-code-in-doc-comment.rs b/src/tools/rustfmt/tests/target/invalid-rust-code-in-doc-comment.rs
new file mode 100644
index 0000000000000..f8479d4e34514
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/invalid-rust-code-in-doc-comment.rs
@@ -0,0 +1,18 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// ```rust
+/// if (true) { … }
+/// ```
+fn a() {}
+
+/// ```rust
+/// if foo() {
+///     …
+/// }
+/// ```
+fn a() {}
+
+/// ```rust
+/// k1 == k2 ⇒ hash(k1) == hash(k2)
+/// ```
+pub struct a;
diff --git a/src/tools/rustfmt/tests/target/issue-1021.rs b/src/tools/rustfmt/tests/target/issue-1021.rs
new file mode 100644
index 0000000000000..ba1029d4e61e2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1021.rs
@@ -0,0 +1,22 @@
+// rustfmt-normalize_comments: true
+fn main() {
+    match x {
+        S(true, .., true) => (),
+        S(true, ..) => (),
+        S(.., true) => (),
+        S(..) => (),
+        S(_) => (),
+        S(/* .. */ ..) => (),
+        S(/* .. */ .., true) => (),
+    }
+
+    match y {
+        (true, .., true) => (),
+        (true, ..) => (),
+        (.., true) => (),
+        (..) => (),
+        (_,) => (),
+        (/* .. */ ..) => (),
+        (/* .. */ .., true) => (),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1049.rs b/src/tools/rustfmt/tests/target/issue-1049.rs
new file mode 100644
index 0000000000000..c788519ca9a1e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1049.rs
@@ -0,0 +1,29 @@
+// Test overlong function signature
+pub unsafe fn reborrow_mut(
+    &mut X: Abcde,
+) -> Handle<NodeRef<marker::Mut, K, V, NodeType>, HandleType> {
+}
+
+pub fn merge(
+    mut X: Abcdef,
+) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+}
+
+impl Handle {
+    pub fn merge(
+        a: Abcd,
+    ) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+    }
+}
+
+// Long function without return type that should not be reformatted.
+fn veeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {}
+
+fn veeeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {
+}
+
+fn veeeeeeeeeeeeeeeeeeeeeeery_long_name(
+    a: FirstTypeeeeeeeeee,
+    b: SecondTypeeeeeeeeeeeeeeeeeeeeeee,
+) {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1055.rs b/src/tools/rustfmt/tests/target/issue-1055.rs
new file mode 100644
index 0000000000000..ee143e792b02d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1055.rs
@@ -0,0 +1,3 @@
+fn issue_1055() {
+    let foo = (|| {})();
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1096.rs b/src/tools/rustfmt/tests/target/issue-1096.rs
new file mode 100644
index 0000000000000..de78e736483f5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1096.rs
@@ -0,0 +1,71 @@
+struct StructA<T> /* comment 1 */ {
+    t: T,
+}
+
+struct StructB<T> /* comment 2 */;
+
+struct StructC /* comment 3 */;
+
+struct StructD /* comment 4 */ {
+    t: usize,
+}
+
+struct StructE<T>
+/* comment 5 */
+where
+    T: Clone,
+{
+    t: usize,
+}
+
+struct StructF
+/* comment 6 */
+where
+    T: Clone,
+{
+    t: usize,
+}
+
+struct StructG<T>
+/* comment 7 */
+// why a line comment??
+{
+    t: T,
+}
+
+struct StructH<T>
+/* comment 8 */
+// why a line comment??
+where
+    T: Clone,
+{
+    t: T,
+}
+
+enum EnumA<T> /* comment 8 */ {
+    Field(T),
+}
+
+enum EnumB /* comment 9 */ {
+    Field,
+}
+
+// Issue 2781
+struct StructX1<T>
+// where
+//     T: Clone
+{
+    inner: String,
+}
+
+struct StructX2<
+    T,
+    U: Iterator<Item = String>,
+    V: Iterator<Item = String>,
+    W: Iterator<Item = String>,
+>
+// where
+//     T: Clone
+{
+    inner: String,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1111.rs b/src/tools/rustfmt/tests/target/issue-1111.rs
new file mode 100644
index 0000000000000..2e1a89ad78eb9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1111.rs
@@ -0,0 +1 @@
+use bar;
diff --git a/src/tools/rustfmt/tests/target/issue-1113.rs b/src/tools/rustfmt/tests/target/issue-1113.rs
new file mode 100644
index 0000000000000..1245bcd057ca5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1113.rs
@@ -0,0 +1,33 @@
+pub fn foo() -> fmt::Result
+//pub fn writeStringToken
+{
+    panic!()
+}
+
+pub fn foo() -> fmt::Result // pub fn writeStringToken
+{
+    panic!()
+}
+
+pub fn foo() -> fmt::Result /* pub fn writeStringToken */ {
+    panic!()
+}
+
+pub fn foo() -> fmt::Result
+/* pub fn writeStringToken */ {
+    panic!()
+}
+
+pub fn foo() -> fmt::Result
+/* pub fn writeStringToken */
+{
+    panic!()
+}
+
+pub fn foo() -> fmt::Result /*
+                             *
+                             *
+                             */
+{
+    panic!()
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1120.rs b/src/tools/rustfmt/tests/target/issue-1120.rs
new file mode 100644
index 0000000000000..f44597e7d1eef
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1120.rs
@@ -0,0 +1,11 @@
+// rustfmt-reorder_imports: true
+
+// Ensure that a use at the start of an inline module is correctly formatted.
+mod foo {
+    use bar;
+}
+
+// Ensure that an indented `use` gets the correct indentation.
+mod foo {
+    use bar;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1124.rs b/src/tools/rustfmt/tests/target/issue-1124.rs
new file mode 100644
index 0000000000000..f0fc485a3c218
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1124.rs
@@ -0,0 +1,21 @@
+// rustfmt-reorder_imports: true
+
+use a;
+use b;
+use c;
+use d;
+// The previous line has a space after the `use a;`
+
+mod a {
+    use a;
+    use b;
+    use c;
+    use d;
+}
+
+use z;
+
+use y;
+
+use a;
+use x;
diff --git a/src/tools/rustfmt/tests/target/issue-1127.rs b/src/tools/rustfmt/tests/target/issue-1127.rs
new file mode 100644
index 0000000000000..fb09036d1f889
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1127.rs
@@ -0,0 +1,25 @@
+// rustfmt-max_width: 120
+// rustfmt-match_arm_blocks: false
+// rustfmt-match_block_trailing_comma: true
+
+fn a_very_very_very_very_very_very_very_very_very_very_very_long_function_name() -> i32 {
+    42
+}
+
+enum TestEnum {
+    AVeryVeryLongEnumName,
+    AnotherVeryLongEnumName,
+    TheLastVeryLongEnumName,
+}
+
+fn main() {
+    let var = TestEnum::AVeryVeryLongEnumName;
+    let num = match var {
+        TestEnum::AVeryVeryLongEnumName =>
+            a_very_very_very_very_very_very_very_very_very_very_very_long_function_name(),
+        TestEnum::AnotherVeryLongEnumName =>
+            a_very_very_very_very_very_very_very_very_very_very_very_long_function_name(),
+        TestEnum::TheLastVeryLongEnumName =>
+            a_very_very_very_very_very_very_very_very_very_very_very_long_function_name(),
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1158.rs b/src/tools/rustfmt/tests/target/issue-1158.rs
new file mode 100644
index 0000000000000..2abfa5a29f2d6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1158.rs
@@ -0,0 +1,3 @@
+trait T {
+    itemmacro!(this, is.now().formatted(yay));
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1177.rs b/src/tools/rustfmt/tests/target/issue-1177.rs
new file mode 100644
index 0000000000000..dcda397281439
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1177.rs
@@ -0,0 +1,7 @@
+// rustfmt-normalize_comments: true
+fn main() {
+    // Line Comment
+    // Block Comment
+
+    let d = 5;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1192.rs b/src/tools/rustfmt/tests/target/issue-1192.rs
new file mode 100644
index 0000000000000..432fe8cce7c86
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1192.rs
@@ -0,0 +1,3 @@
+fn main() {
+    assert!(true);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1210/a.rs b/src/tools/rustfmt/tests/target/issue-1210/a.rs
new file mode 100644
index 0000000000000..94c1b44e5e56d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1210/a.rs
@@ -0,0 +1,16 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+impl Foo {
+    fn cxx(&self, target: &str) -> &Path {
+        match self.cxx.get(target) {
+            Some(p) => p.path(),
+            None => panic!(
+                "\n\ntarget `{}` is not \
+                 configured as a host,
+                            only as a target\n\n",
+                target
+            ),
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1210/b.rs b/src/tools/rustfmt/tests/target/issue-1210/b.rs
new file mode 100644
index 0000000000000..a7b1e3bcdc893
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1210/b.rs
@@ -0,0 +1,16 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+impl Foo {
+    fn cxx(&self, target: &str) -> &Path {
+        match self.cxx.get(target) {
+            Some(p) => p.path(),
+            None => panic!(
+                "\ntarget `{}`: is not, \
+                 configured as a host,
+                            only as a target\n\n",
+                target
+            ),
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1210/c.rs b/src/tools/rustfmt/tests/target/issue-1210/c.rs
new file mode 100644
index 0000000000000..183d79f925860
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1210/c.rs
@@ -0,0 +1,7 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+const foo: String =
+    "trailing_spaces!!            
+                keep them! Amet neque. Praesent \
+     rhoncus eros non velit.";
diff --git a/src/tools/rustfmt/tests/target/issue-1210/d.rs b/src/tools/rustfmt/tests/target/issue-1210/d.rs
new file mode 100644
index 0000000000000..9279e6fc9990b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1210/d.rs
@@ -0,0 +1,4 @@
+// rustfmt-wrap_comments: true
+
+// trailing_spaces_in_comment!!
+//                remove those from above
diff --git a/src/tools/rustfmt/tests/target/issue-1210/e.rs b/src/tools/rustfmt/tests/target/issue-1210/e.rs
new file mode 100644
index 0000000000000..55f80c6c3cc24
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1210/e.rs
@@ -0,0 +1,11 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 50
+
+// explicit line breaks should be kept in order to preserve the layout
+
+const foo: String =
+    "Suspendisse vel augue at felis tincidunt \
+     sollicitudin. Fusce arcu.
+               Duis et odio et leo
+        sollicitudin consequat. Aliquam \
+     lobortis.  Phasellus condimentum.";
diff --git a/src/tools/rustfmt/tests/target/issue-1211.rs b/src/tools/rustfmt/tests/target/issue-1211.rs
new file mode 100644
index 0000000000000..de4c5c87ee670
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1211.rs
@@ -0,0 +1,13 @@
+fn main() {
+    for iface in &ifaces {
+        match iface.addr {
+            get_if_addrs::IfAddr::V4(ref addr) => match addr.broadcast {
+                Some(ip) => {
+                    sock.send_to(&buf, (ip, 8765)).expect("foobar");
+                }
+                _ => (),
+            },
+            _ => (),
+        };
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1214.rs b/src/tools/rustfmt/tests/target/issue-1214.rs
new file mode 100644
index 0000000000000..c622abb3a85b4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1214.rs
@@ -0,0 +1,8 @@
+/*!
+# Example
+
+```
+        // Here goes some example
+```
+ */
+struct Item;
diff --git a/src/tools/rustfmt/tests/target/issue-1216.rs b/src/tools/rustfmt/tests/target/issue-1216.rs
new file mode 100644
index 0000000000000..d727c158ab8e5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1216.rs
@@ -0,0 +1,5 @@
+// rustfmt-normalize_comments: true
+enum E {
+    A, //* I am not a block comment (caused panic)
+    B,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1239.rs b/src/tools/rustfmt/tests/target/issue-1239.rs
new file mode 100644
index 0000000000000..e950200b15bd0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1239.rs
@@ -0,0 +1,11 @@
+fn foo() {
+    let with_alignment = if condition__uses_alignment_for_first_if__0
+        || condition__uses_alignment_for_first_if__1
+        || condition__uses_alignment_for_first_if__2
+    {
+    } else if condition__no_alignment_for_later_else__0
+        || condition__no_alignment_for_later_else__1
+        || condition__no_alignment_for_later_else__2
+    {
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1247.rs b/src/tools/rustfmt/tests/target/issue-1247.rs
new file mode 100644
index 0000000000000..16c63e0f53d3e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1247.rs
@@ -0,0 +1,8 @@
+// rustfmt-max_width: 80
+
+fn foo() {
+    polyfill::slice::fill(
+        &mut self.pending[padding_pos..(self.algorithm.block_len - 8)],
+        0,
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1255.rs b/src/tools/rustfmt/tests/target/issue-1255.rs
new file mode 100644
index 0000000000000..2d4633844a9fe
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1255.rs
@@ -0,0 +1,10 @@
+// Test for issue #1255
+// Default annotation incorrectly removed on associated types
+#![feature(specialization)]
+
+trait Trait {
+    type Type;
+}
+impl<T> Trait for T {
+    default type Type = u64; // 'default' should not be removed
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1278.rs b/src/tools/rustfmt/tests/target/issue-1278.rs
new file mode 100644
index 0000000000000..e25376561a949
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1278.rs
@@ -0,0 +1,9 @@
+// rustfmt-indent_style = "block"
+
+#![feature(pub_restricted)]
+
+mod inner_mode {
+    pub(super) fn func_name(abc: i32) -> i32 {
+        abc
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1350.rs b/src/tools/rustfmt/tests/target/issue-1350.rs
new file mode 100644
index 0000000000000..2cf65509c931d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1350.rs
@@ -0,0 +1,14 @@
+// rustfmt-max_width: 120
+// rustfmt-comment_width: 110
+
+impl Struct {
+    fn fun() {
+        let result = match <R::RequestResult as serde::Deserialize>::deserialize(&json) {
+            Ok(v) => v,
+            Err(e) => match <R::ErrorResult as serde::Deserialize>::deserialize(&json) {
+                Ok(v) => return Err(Error::with_json(v)),
+                Err(e2) => return Err(Error::with_json(e)),
+            },
+        };
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1366.rs b/src/tools/rustfmt/tests/target/issue-1366.rs
new file mode 100644
index 0000000000000..eee147baab95a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1366.rs
@@ -0,0 +1,13 @@
+fn main() {
+    fn f() -> Option<i32> {
+        Some("fffffffsssssssssddddssssfffffddddff")
+            .map(|s| s)
+            .map(|s| s.to_string())
+            .map(|res| match Some(res) {
+                Some(ref s) if s == "" => 41,
+                Some(_) => 42,
+                _ => 43,
+            })
+    }
+    println!("{:?}", f())
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1397.rs b/src/tools/rustfmt/tests/target/issue-1397.rs
new file mode 100644
index 0000000000000..86b7a78411f32
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1397.rs
@@ -0,0 +1,25 @@
+pub enum TransactionState {
+    Committed(i64),
+}
+
+pub enum Packet {
+    Transaction { state: TransactionState },
+}
+
+fn baz(p: Packet) {
+    loop {
+        loop {
+            loop {
+                loop {
+                    if let Packet::Transaction {
+                        state: TransactionState::Committed(ts, ..),
+                        ..
+                    } = p
+                    {
+                        unreachable!()
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1468.rs b/src/tools/rustfmt/tests/target/issue-1468.rs
new file mode 100644
index 0000000000000..4c14a0f746a0b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1468.rs
@@ -0,0 +1,29 @@
+fn issue1468() {
+    euc_jp_decoder_functions!({
+        let trail_minus_offset = byte.wrapping_sub(0xA1);
+        // Fast-track Hiragana (60% according to Lunde)
+        // and Katakana (10% according to Lunde).
+        if jis0208_lead_minus_offset == 0x03 && trail_minus_offset < 0x53 {
+            // Hiragana
+            handle.write_upper_bmp(0x3041 + trail_minus_offset as u16)
+        } else if jis0208_lead_minus_offset == 0x04 && trail_minus_offset < 0x56 {
+            // Katakana
+            handle.write_upper_bmp(0x30A1 + trail_minus_offset as u16)
+        } else if trail_minus_offset > (0xFE - 0xA1) {
+            if byte < 0x80 {
+                return (
+                    DecoderResult::Malformed(1, 0),
+                    unread_handle_trail.unread(),
+                    handle.written(),
+                );
+            }
+            return (
+                DecoderResult::Malformed(2, 0),
+                unread_handle_trail.consumed(),
+                handle.written(),
+            );
+        } else {
+            unreachable!();
+        }
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1598.rs b/src/tools/rustfmt/tests/target/issue-1598.rs
new file mode 100644
index 0000000000000..c7e02c961a65b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1598.rs
@@ -0,0 +1,6 @@
+fn main() {
+    //foo
+    /*
+     */
+    format!("hello");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1624.rs b/src/tools/rustfmt/tests/target/issue-1624.rs
new file mode 100644
index 0000000000000..477fc27353f30
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1624.rs
@@ -0,0 +1,6 @@
+// #1624
+pub unsafe fn some_long_function_name(
+    arg1: Type1,
+    arg2: Type2,
+) -> (SomeLongTypeName, AnotherLongTypeName, AnotherLongTypeName) {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1681.rs b/src/tools/rustfmt/tests/target/issue-1681.rs
new file mode 100644
index 0000000000000..902765302eacb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1681.rs
@@ -0,0 +1,21 @@
+// rustfmt-max_width: 80
+
+// We would like to surround closure body with block when overflowing the last
+// argument of function call if the last argument has condition and without
+// block it may go multi lines.
+fn foo() {
+    refmut_map_result(self.cache.borrow_mut(), |cache| {
+        match cache.entry(cache_key) {
+            Occupied(entry) => Ok(entry.into_mut()),
+            Vacant(entry) => {
+                let statement = {
+                    let sql = try!(entry.key().sql(source));
+                    prepare_fn(&sql)
+                };
+
+                Ok(entry.insert(try!(statement)))
+            }
+        }
+    })
+    .map(MaybeCached::Cached)
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1693.rs b/src/tools/rustfmt/tests/target/issue-1693.rs
new file mode 100644
index 0000000000000..85421a123bb5c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1693.rs
@@ -0,0 +1,10 @@
+fn issue1693() {
+    let pixel_data = vec![
+        (
+            f16::from_f32(0.82),
+            f16::from_f32(1.78),
+            f16::from_f32(0.21)
+        );
+        256 * 256
+    ];
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1703.rs b/src/tools/rustfmt/tests/target/issue-1703.rs
new file mode 100644
index 0000000000000..4079ef4cfca3d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1703.rs
@@ -0,0 +1,9 @@
+// rustfmt should not remove doc comments or comments inside attributes.
+
+/**
+This function has a block doc comment.
+ */
+fn test_function() {}
+
+#[foo /* do not remove this! */]
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/issue-1800.rs b/src/tools/rustfmt/tests/target/issue-1800.rs
new file mode 100644
index 0000000000000..06c5cfd056726
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1800.rs
@@ -0,0 +1,3 @@
+#![doc(html_root_url = "http://example.com")]
+#[cfg(feature = "foo")]
+fn a() {}
diff --git a/src/tools/rustfmt/tests/target/issue-1802.rs b/src/tools/rustfmt/tests/target/issue-1802.rs
new file mode 100644
index 0000000000000..ef7ee891059d5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1802.rs
@@ -0,0 +1,9 @@
+// rustfmt-tab_spaces: 2
+// rustfmt-max_width: 30
+
+enum F {
+  X {
+    a: dddddddddddddd,
+    b: eeeeeeeeeeeeeee,
+  },
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1824.rs b/src/tools/rustfmt/tests/target/issue-1824.rs
new file mode 100644
index 0000000000000..1c4c2db46dcba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1824.rs
@@ -0,0 +1,5 @@
+pub trait Ingredient
+where
+    Self: Send,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/issue-1914.rs b/src/tools/rustfmt/tests/target/issue-1914.rs
new file mode 100644
index 0000000000000..d2d532af1dc36
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-1914.rs
@@ -0,0 +1,7 @@
+// rustfmt-max_width: 80
+
+extern "C" {
+    #[link_name = "_ZN7MyClass26example_check_no_collisionE"]
+    pub static mut MyClass_example_check_no_collision:
+        *const ::std::os::raw::c_int;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2025.rs b/src/tools/rustfmt/tests/target/issue-2025.rs
new file mode 100644
index 0000000000000..38bf369bea322
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2025.rs
@@ -0,0 +1,4 @@
+// See if rustfmt removes empty lines on top of the file.
+pub fn foo() {
+    println!("hello, world");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2103.rs b/src/tools/rustfmt/tests/target/issue-2103.rs
new file mode 100644
index 0000000000000..5a043d54b75ba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2103.rs
@@ -0,0 +1,14 @@
+struct X
+where
+    i32: Sized,
+{
+    x: i32,
+}
+
+struct X
+// with comment
+where
+    i32: Sized,
+{
+    x: i32,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2111.rs b/src/tools/rustfmt/tests/target/issue-2111.rs
new file mode 100644
index 0000000000000..42c1862e88648
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2111.rs
@@ -0,0 +1,26 @@
+// An import with single line comments.
+use super::{
+    DelayChoice,
+    Destinations,
+    Holding,
+    LodaModel,
+    MethodDescription,
+    ModelBehaviour,
+    ModelEdges,
+    ModelProperties,
+    ModelRequestGraph,
+    ModelSelector,
+    RequestDescription,
+    StringMap,
+    Switch,
+    //    ModelMetaData,
+    //    Generated,
+    //    SecondsString,
+    //    DateString,
+    //    ModelConfiguration,
+    //    ModelRequests,
+    //    RestResponse,
+    //    RestResponseCode,
+    //    UniformHolding
+    SCHEMA_VERSIONS,
+};
diff --git a/src/tools/rustfmt/tests/target/issue-2123.rs b/src/tools/rustfmt/tests/target/issue-2123.rs
new file mode 100644
index 0000000000000..5e9917b40234c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2123.rs
@@ -0,0 +1,6 @@
+// rustfmt-wrap_comments: true
+
+//hello
+//world
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2164.rs b/src/tools/rustfmt/tests/target/issue-2164.rs
new file mode 100644
index 0000000000000..dbf92107ce23c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2164.rs
@@ -0,0 +1,135 @@
+// A stress test against code generated by bindgen.
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct emacs_env_25 {
+    pub size: isize,
+    pub private_members: *mut emacs_env_private,
+    pub make_global_ref: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, any_reference: emacs_value) -> emacs_value,
+    >,
+    pub free_global_ref: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, global_reference: emacs_value),
+    >,
+    pub non_local_exit_check:
+        ::std::option::Option<unsafe extern "C" fn(env: *mut emacs_env) -> emacs_funcall_exit>,
+    pub non_local_exit_clear: ::std::option::Option<unsafe extern "C" fn(env: *mut emacs_env)>,
+    pub non_local_exit_get: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            non_local_exit_symbol_out: *mut emacs_value,
+            non_local_exit_data_out: *mut emacs_value,
+        ) -> emacs_funcall_exit,
+    >,
+    pub non_local_exit_signal: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            non_local_exit_symbol: emacs_value,
+            non_local_exit_data: emacs_value,
+        ),
+    >,
+    pub non_local_exit_throw: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, tag: emacs_value, value: emacs_value),
+    >,
+    pub make_function: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            min_arity: isize,
+            max_arity: isize,
+            function: ::std::option::Option<
+                unsafe extern "C" fn(
+                    env: *mut emacs_env,
+                    nargs: isize,
+                    args: *mut emacs_value,
+                    arg1: *mut ::libc::c_void,
+                ) -> emacs_value,
+            >,
+            documentation: *const ::libc::c_char,
+            data: *mut ::libc::c_void,
+        ) -> emacs_value,
+    >,
+    pub funcall: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            function: emacs_value,
+            nargs: isize,
+            args: *mut emacs_value,
+        ) -> emacs_value,
+    >,
+    pub intern: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            symbol_name: *const ::libc::c_char,
+        ) -> emacs_value,
+    >,
+    pub type_of: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, value: emacs_value) -> emacs_value,
+    >,
+    pub is_not_nil: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, value: emacs_value) -> bool,
+    >,
+    pub eq: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, a: emacs_value, b: emacs_value) -> bool,
+    >,
+    pub extract_integer: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, value: emacs_value) -> intmax_t,
+    >,
+    pub make_integer: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, value: intmax_t) -> emacs_value,
+    >,
+    pub extract_float:
+        ::std::option::Option<unsafe extern "C" fn(env: *mut emacs_env, value: emacs_value) -> f64>,
+    pub make_float:
+        ::std::option::Option<unsafe extern "C" fn(env: *mut emacs_env, value: f64) -> emacs_value>,
+    pub copy_string_contents: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            value: emacs_value,
+            buffer: *mut ::libc::c_char,
+            size_inout: *mut isize,
+        ) -> bool,
+    >,
+    pub make_string: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            contents: *const ::libc::c_char,
+            length: isize,
+        ) -> emacs_value,
+    >,
+    pub make_user_ptr: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            fin: ::std::option::Option<unsafe extern "C" fn(arg1: *mut ::libc::c_void)>,
+            ptr: *mut ::libc::c_void,
+        ) -> emacs_value,
+    >,
+    pub get_user_ptr: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, uptr: emacs_value) -> *mut ::libc::c_void,
+    >,
+    pub set_user_ptr: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, uptr: emacs_value, ptr: *mut ::libc::c_void),
+    >,
+    pub get_user_finalizer: ::std::option::Option<
+        unsafe extern "C" fn(
+            arg1: *mut ::libc::c_void,
+            env: *mut emacs_env,
+            uptr: emacs_value,
+        ) -> ::std::option::Option<
+            unsafe extern "C" fn(arg1: *mut ::libc::c_void, env: *mut emacs_env, uptr: emacs_value),
+        >,
+    >,
+    pub set_user_finalizer: ::std::option::Option<
+        unsafe extern "C" fn(
+            env: *mut emacs_env,
+            uptr: emacs_value,
+            fin: ::std::option::Option<unsafe extern "C" fn(arg1: *mut ::libc::c_void)>,
+        ),
+    >,
+    pub vec_get: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, vec: emacs_value, i: isize) -> emacs_value,
+    >,
+    pub vec_set: ::std::option::Option<
+        unsafe extern "C" fn(env: *mut emacs_env, vec: emacs_value, i: isize, val: emacs_value),
+    >,
+    pub vec_size:
+        ::std::option::Option<unsafe extern "C" fn(env: *mut emacs_env, vec: emacs_value) -> isize>,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2179/one.rs b/src/tools/rustfmt/tests/target/issue-2179/one.rs
new file mode 100644
index 0000000000000..3f98acc8dcde6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2179/one.rs
@@ -0,0 +1,37 @@
+// rustfmt-version: One
+// rustfmt-error_on_line_overflow: false
+
+fn issue_2179() {
+    let (opts, rustflags, clear_env_rust_log) = {
+        // We mustn't lock configuration for the whole build process
+        let rls_config = rls_config.lock().unwrap();
+
+        let opts = CargoOptions::new(&rls_config);
+        trace!("Cargo compilation options:\n{:?}", opts);
+        let rustflags = prepare_cargo_rustflags(&rls_config);
+
+        // Warn about invalid specified bin target or package depending on current mode
+        // TODO: Return client notifications along with diagnostics to inform the user
+        if !rls_config.workspace_mode {
+            let cur_pkg_targets = ws.current().unwrap().targets();
+
+            if let &Some(ref build_bin) = rls_config.build_bin.as_ref() {
+                let mut bins = cur_pkg_targets.iter().filter(|x| x.is_bin());
+                if let None = bins.find(|x| x.name() == build_bin) {
+                    warn!(
+                        "cargo - couldn't find binary `{}` specified in `build_bin` configuration",
+                        build_bin
+                    );
+                }
+            }
+        } else {
+            for package in &opts.package {
+                if let None = ws.members().find(|x| x.name() == package) {
+                    warn!("cargo - couldn't find member package `{}` specified in `analyze_package` configuration", package);
+                }
+            }
+        }
+
+        (opts, rustflags, rls_config.clear_env_rust_log)
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2179/two.rs b/src/tools/rustfmt/tests/target/issue-2179/two.rs
new file mode 100644
index 0000000000000..96531509ea2dd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2179/two.rs
@@ -0,0 +1,40 @@
+// rustfmt-version: Two
+// rustfmt-error_on_line_overflow: false
+
+fn issue_2179() {
+    let (opts, rustflags, clear_env_rust_log) = {
+        // We mustn't lock configuration for the whole build process
+        let rls_config = rls_config.lock().unwrap();
+
+        let opts = CargoOptions::new(&rls_config);
+        trace!("Cargo compilation options:\n{:?}", opts);
+        let rustflags = prepare_cargo_rustflags(&rls_config);
+
+        // Warn about invalid specified bin target or package depending on current mode
+        // TODO: Return client notifications along with diagnostics to inform the user
+        if !rls_config.workspace_mode {
+            let cur_pkg_targets = ws.current().unwrap().targets();
+
+            if let &Some(ref build_bin) = rls_config.build_bin.as_ref() {
+                let mut bins = cur_pkg_targets.iter().filter(|x| x.is_bin());
+                if let None = bins.find(|x| x.name() == build_bin) {
+                    warn!(
+                        "cargo - couldn't find binary `{}` specified in `build_bin` configuration",
+                        build_bin
+                    );
+                }
+            }
+        } else {
+            for package in &opts.package {
+                if let None = ws.members().find(|x| x.name() == package) {
+                    warn!(
+                        "cargo - couldn't find member package `{}` specified in `analyze_package` configuration",
+                        package
+                    );
+                }
+            }
+        }
+
+        (opts, rustflags, rls_config.clear_env_rust_log)
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2197.rs b/src/tools/rustfmt/tests/target/issue-2197.rs
new file mode 100644
index 0000000000000..d42c08e19dbc8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2197.rs
@@ -0,0 +1,17 @@
+// rustfmt-max_width: 79
+// rustfmt-wrap_comments: true
+
+/// ```rust
+/// unsafe fn sum_sse2(x: i32x4) -> i32 {
+///     let x = vendor::_mm_add_epi32(
+///         x,
+///         vendor::_mm_srli_si128(x.into(), 8).into(),
+///     );
+///     let x = vendor::_mm_add_epi32(
+///         x,
+///         vendor::_mm_srli_si128(x.into(), 4).into(),
+///     );
+///     vendor::_mm_cvtsi128_si32(x)
+/// }
+/// ```
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2256.rs b/src/tools/rustfmt/tests/target/issue-2256.rs
new file mode 100644
index 0000000000000..0a59c308394e3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2256.rs
@@ -0,0 +1,7 @@
+// こんにちは
+use std::borrow::Cow;
+
+/* comment 1 */
+/* comment 2 */
+
+/* comment 3 */
diff --git a/src/tools/rustfmt/tests/target/issue-2324.rs b/src/tools/rustfmt/tests/target/issue-2324.rs
new file mode 100644
index 0000000000000..9211b24d81f47
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2324.rs
@@ -0,0 +1,7 @@
+// nested function calls with cast.
+fn main() {
+    self.ptr
+        .set(intrinsics::arith_offset(self.ptr.get() as *mut u8, 1) as *mut T);
+    self.ptr
+        .set(intrinsics::arith_offset(self.ptr.get(), mem::size_of::<T>() as isize) as *mut u8);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2329.rs b/src/tools/rustfmt/tests/target/issue-2329.rs
new file mode 100644
index 0000000000000..e36e9546b2451
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2329.rs
@@ -0,0 +1,30 @@
+// Comments with characters which must be represented by multibyte.
+
+// フー
+use foo;
+// バー
+use bar;
+
+impl MyStruct {
+    // コメント
+    fn f1() {} // こんにちは
+    fn f2() {} // ありがとう
+               // コメント
+}
+
+trait MyTrait {
+    // コメント
+    fn f1() {} // こんにちは
+    fn f2() {} // ありがとう
+               // コメント
+}
+
+fn main() {
+    // コメント
+    let x = 1; // Ｘ
+    println!(
+        "x = {}", // xの値
+        x,        // Ｘ
+    );
+    // コメント
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2342.rs b/src/tools/rustfmt/tests/target/issue-2342.rs
new file mode 100644
index 0000000000000..f9c26857e15c8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2342.rs
@@ -0,0 +1,6 @@
+// rustfmt-max_width: 80
+
+struct Foo {
+    #[cfg(feature = "serde")]
+    bytes: [[u8; 17]; 5], // Same size as signature::ED25519_PKCS8_V2_LEN
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2346.rs b/src/tools/rustfmt/tests/target/issue-2346.rs
new file mode 100644
index 0000000000000..07817221a5108
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2346.rs
@@ -0,0 +1,4 @@
+// rustfmt-normalize_comments: true
+// the following empty comment should not have any trailing space added.
+//
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2401.rs b/src/tools/rustfmt/tests/target/issue-2401.rs
new file mode 100644
index 0000000000000..ec8f27b732ffa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2401.rs
@@ -0,0 +1,7 @@
+// rustfmt-hard_tabs = true
+// rustfmt-normalize_comments = true
+
+/// ```
+/// println!("Hello, World!");
+/// ```
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2445.rs b/src/tools/rustfmt/tests/target/issue-2445.rs
new file mode 100644
index 0000000000000..1bc7752fd1619
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2445.rs
@@ -0,0 +1,21 @@
+test!(RunPassPretty {
+    // comment
+    path: "src/test/run-pass/pretty",
+    mode: "pretty",
+    suite: "run-pass",
+    default: false,
+    host: true // should, force, , no trailing comma here
+});
+
+test!(RunPassPretty {
+    // comment
+    path: "src/test/run-pass/pretty",
+    mode: "pretty",
+    suite: "run-pass",
+    default: false,
+    host: true, // should, , preserve, the trailing comma
+});
+
+test!(Test {
+    field: i32, // comment
+});
diff --git a/src/tools/rustfmt/tests/target/issue-2446.rs b/src/tools/rustfmt/tests/target/issue-2446.rs
new file mode 100644
index 0000000000000..be62e9c9c3111
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2446.rs
@@ -0,0 +1,9 @@
+enum Issue2446 {
+    V {
+        f: u8, // x
+    },
+}
+
+enum Issue2446TrailingCommentsOnly {
+    V { f: u8 /* */ },
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2479.rs b/src/tools/rustfmt/tests/target/issue-2479.rs
new file mode 100644
index 0000000000000..3683ab2208955
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2479.rs
@@ -0,0 +1,12 @@
+// Long attributes.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum POLARITYR {
+    #[doc = "Task mode: No effect on pin from OUT[n] task. Event mode: no IN[n] event generated on pin activity."]
+    NONE,
+    #[doc = "Task mode: Set pin from OUT[n] task. Event mode: Generate IN[n] event when rising edge on pin."]
+    LOTOHI,
+    #[doc = "Task mode: Clear pin from OUT[n] task. Event mode: Generate IN[n] event when falling edge on pin."]
+    HITOLO,
+    #[doc = "Task mode: Toggle pin from OUT[n]. Event mode: Generate IN[n] when any change on pin."]
+    TOGGLE,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2482/a.rs b/src/tools/rustfmt/tests/target/issue-2482/a.rs
new file mode 100644
index 0000000000000..fbbcb52a878aa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2482/a.rs
@@ -0,0 +1,9 @@
+// rustfmt-reorder_modules: true
+
+// Do not reorder inline modules.
+
+mod c;
+mod a {
+    fn a() {}
+}
+mod b;
diff --git a/src/tools/rustfmt/tests/target/issue-2482/b.rs b/src/tools/rustfmt/tests/target/issue-2482/b.rs
new file mode 100644
index 0000000000000..40a8d942126c9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2482/b.rs
@@ -0,0 +1 @@
+pub fn b() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2482/c.rs b/src/tools/rustfmt/tests/target/issue-2482/c.rs
new file mode 100644
index 0000000000000..d937545511eff
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2482/c.rs
@@ -0,0 +1 @@
+pub fn c() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2496.rs b/src/tools/rustfmt/tests/target/issue-2496.rs
new file mode 100644
index 0000000000000..60c4f55ddffd8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2496.rs
@@ -0,0 +1,14 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    match option {
+        None => some_function(first_reasonably_long_argument,
+                              second_reasonably_long_argument),
+    }
+}
+
+fn main() {
+    match option {
+        None => some_function(first_reasonably_long_argument,
+                              second_reasonably_long_argument),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2520.rs b/src/tools/rustfmt/tests/target/issue-2520.rs
new file mode 100644
index 0000000000000..7c134d3972ba7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2520.rs
@@ -0,0 +1,13 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+//! ```rust
+//! println!("hello, world");
+//! ```
+
+#![deny(missing_docs)]
+
+//! ```rust
+//! println!("hello, world");
+
+#![deny(missing_docs)]
diff --git a/src/tools/rustfmt/tests/target/issue-2523.rs b/src/tools/rustfmt/tests/target/issue-2523.rs
new file mode 100644
index 0000000000000..612f93249acf5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2523.rs
@@ -0,0 +1,20 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+// Do not unindent macro calls in comment with unformattable syntax.
+//! ```rust
+//! let x = 3  ;
+//! some_macro!(pub fn fn foo() (
+//!     println!("Don't unindent me!");
+//! ));
+//! ```
+
+// Format items that appear as arguments of macro call.
+//! ```rust
+//! let x = 3;
+//! some_macro!(
+//!     pub fn foo() {
+//!         println!("Don't unindent me!");
+//!     }
+//! );
+//! ```
diff --git a/src/tools/rustfmt/tests/target/issue-2526.rs b/src/tools/rustfmt/tests/target/issue-2526.rs
new file mode 100644
index 0000000000000..7dd58aba3187d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2526.rs
@@ -0,0 +1,8 @@
+// Test that rustfmt will not warn about comments exceeding max width around lifetime.
+// See #2526.
+
+// comment comment comment comment comment comment comment comment comment comment comment comment comment
+fn foo() -> F<'a> {
+    bar()
+}
+// comment comment comment comment comment comment comment comment comment comment comment comment comment
diff --git a/src/tools/rustfmt/tests/target/issue-2551.rs b/src/tools/rustfmt/tests/target/issue-2551.rs
new file mode 100644
index 0000000000000..d7b0d625b9e90
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2551.rs
@@ -0,0 +1,3 @@
+mcro!(func(A {
+    a: 12345667800111111111111,
+}));
diff --git a/src/tools/rustfmt/tests/target/issue-2554.rs b/src/tools/rustfmt/tests/target/issue-2554.rs
new file mode 100644
index 0000000000000..d5f0563a6f100
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2554.rs
@@ -0,0 +1,13 @@
+// #2554
+// Do not add the beginning vert to the first match arm's pattern.
+
+fn main() {
+    match foo(|_| {
+        bar(|_| {
+            //
+        })
+    }) {
+        Ok(()) => (),
+        Err(_) => (),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2582.rs b/src/tools/rustfmt/tests/target/issue-2582.rs
new file mode 100644
index 0000000000000..f328e4d9d04c3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2582.rs
@@ -0,0 +1 @@
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2641.rs b/src/tools/rustfmt/tests/target/issue-2641.rs
new file mode 100644
index 0000000000000..fbf5326c330db
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2641.rs
@@ -0,0 +1,3 @@
+macro_rules! a {
+    () => {{}};
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2644.rs b/src/tools/rustfmt/tests/target/issue-2644.rs
new file mode 100644
index 0000000000000..a87e4c0b4feef
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2644.rs
@@ -0,0 +1,8 @@
+// rustfmt-max_width: 80
+fn foo(e: Enum) {
+    match e {
+        Enum::Var { element1, element2 } => {
+            return;
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/foo.rs b/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/foo.rs
new file mode 100644
index 0000000000000..5340816d61e0c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/foo.rs
@@ -0,0 +1,4 @@
+// rustfmt-config: skip_children.toml
+mod bar;
+
+mod baz {}
diff --git a/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/foo/bar.rs b/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/foo/bar.rs
new file mode 100644
index 0000000000000..9ceacd59d86f7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/foo/bar.rs
@@ -0,0 +1 @@
+fn dummy() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/lib.rs b/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/lib.rs
new file mode 100644
index 0000000000000..82425de565a22
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2673-nonmodrs-mods/lib.rs
@@ -0,0 +1,6 @@
+#![feature(non_modrs_mods)]
+
+// Test that submodules in non-mod.rs files work. This is just an idempotence
+// test since we just want to verify that rustfmt doesn't fail.
+
+mod foo;
diff --git a/src/tools/rustfmt/tests/target/issue-2728.rs b/src/tools/rustfmt/tests/target/issue-2728.rs
new file mode 100644
index 0000000000000..6cb41b75b6d09
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2728.rs
@@ -0,0 +1,8 @@
+// rustfmt-wrap_comments: true
+// rustfmt-newline_style: Windows
+
+//! ```rust
+//! extern crate uom;
+//! ```
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2759.rs b/src/tools/rustfmt/tests/target/issue-2759.rs
new file mode 100644
index 0000000000000..b7176ec66f850
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2759.rs
@@ -0,0 +1,65 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 89
+
+// Code block in doc comments that will exceed max width.
+/// ```rust
+/// extern crate actix_web;
+/// use actix_web::{actix, server, App, HttpResponse};
+///
+/// fn main() {
+///     // Run actix system, this method actually starts all async processes
+///     actix::System::run(|| {
+///         server::new(|| App::new().resource("/", |r| r.h(|_| HttpResponse::Ok())))
+///             .bind("127.0.0.1:0")
+///             .expect("Can not bind to 127.0.0.1:0")
+///             .start();
+/// #           actix::Arbiter::system().do_send(actix::msgs::SystemExit(0));
+///     });
+/// }
+/// ```
+fn foo() {}
+
+// Code block in doc comments without the closing '```'.
+/// ```rust
+/// # extern crate actix_web;
+/// use actix_web::{App, HttpResponse, http};
+///
+/// fn main() {
+///     let app = App::new()
+///         .resource(
+///             "/", |r| r.method(http::Method::GET).f(|r| HttpResponse::Ok()))
+///         .finish();
+/// }
+fn bar() {}
+
+// `#` with indent.
+/// ```rust
+/// # use std::thread;
+/// # extern crate actix_web;
+/// use actix_web::{server, App, HttpResponse};
+///
+/// struct State1;
+///
+/// struct State2;
+///
+/// fn main() {
+///     # thread::spawn(|| {
+///     server::new(|| {
+///         vec![
+///             App::with_state(State1)
+///                 .prefix("/app1")
+///                 .resource("/", |r| r.f(|r| HttpResponse::Ok()))
+///                 .boxed(),
+///             App::with_state(State2)
+///                 .prefix("/app2")
+///                 .resource("/", |r| r.f(|r| HttpResponse::Ok()))
+///                 .boxed(),
+///         ]
+///     })
+///     .bind("127.0.0.1:8080")
+///     .unwrap()
+///     .run()
+///     # });
+/// }
+/// ```
+fn foobar() {}
diff --git a/src/tools/rustfmt/tests/target/issue-2761.rs b/src/tools/rustfmt/tests/target/issue-2761.rs
new file mode 100644
index 0000000000000..ae4086617f81a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2761.rs
@@ -0,0 +1,15 @@
+const DATA: &'static [u8] = &[
+    0x42, 0x50, 0x54, 0x44, //type
+    0x23, 0x00, 0x00, 0x00, //size
+    0x00, 0x00, 0x04, 0x00, //flags
+    0xEC, 0x0C, 0x00, 0x00, //id
+    0x00, 0x00, 0x00, 0x00, //revision
+    0x2B, 0x00, //version
+    0x00, 0x00, //unknown
+    0x42, 0x50, 0x54, 0x4E, //field type
+    0x1D, 0x00, //field size
+    0x19, 0x00, 0x00, 0x00, //decompressed field size
+    0x75, 0xc5, 0x21, 0x0d, 0x00, 0x00, 0x08, 0x05, 0xd1, 0x6c, //field data (compressed)
+    0x6c, 0xdc, 0x57, 0x48, 0x3c, 0xfd, 0x5b, 0x5c, 0x02, 0xd4, //field data (compressed)
+    0x6b, 0x32, 0xb5, 0xdc, 0xa3, //field data (compressed)
+];
diff --git a/src/tools/rustfmt/tests/target/issue-2781.rs b/src/tools/rustfmt/tests/target/issue-2781.rs
new file mode 100644
index 0000000000000..f144d716be964
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2781.rs
@@ -0,0 +1,11 @@
+pub // Oh, no. A line comment.
+struct Foo {}
+
+pub /* Oh, no. A block comment. */ struct Foo {}
+
+mod inner {
+    pub // Oh, no. A line comment.
+    struct Foo {}
+
+    pub /* Oh, no. A block comment. */ struct Foo {}
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2794.rs b/src/tools/rustfmt/tests/target/issue-2794.rs
new file mode 100644
index 0000000000000..951c0af206d8c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2794.rs
@@ -0,0 +1,12 @@
+// rustfmt-indent_style: Block
+// rustfmt-imports_indent: Block
+// rustfmt-imports_layout: Vertical
+
+use std::{
+    env,
+    fs,
+    io::{
+        Read,
+        Write,
+    },
+};
diff --git a/src/tools/rustfmt/tests/target/issue-2810.rs b/src/tools/rustfmt/tests/target/issue-2810.rs
new file mode 100644
index 0000000000000..34140c7a1fc65
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2810.rs
@@ -0,0 +1,14 @@
+// rustfmt-newline_style: Windows
+
+#[macro_export]
+macro_rules! hmmm___ffi_error {
+    ($result:ident) => {
+        pub struct $result {
+            success: bool,
+        }
+
+        impl $result {
+            pub fn foo(self) {}
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2835.rs b/src/tools/rustfmt/tests/target/issue-2835.rs
new file mode 100644
index 0000000000000..21e8ce4114546
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2835.rs
@@ -0,0 +1,4 @@
+// rustfmt-brace_style: AlwaysNextLine
+// rustfmt-fn_single_line: true
+
+fn lorem() -> i32 { 42 }
diff --git a/src/tools/rustfmt/tests/target/issue-2863.rs b/src/tools/rustfmt/tests/target/issue-2863.rs
new file mode 100644
index 0000000000000..35a80f7a621e8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2863.rs
@@ -0,0 +1,54 @@
+// rustfmt-reorder_impl_items: true
+
+impl<T> IntoIterator for SafeVec<T> {
+    type Bar = u32;
+    type BarFoo = u32;
+    type FooBar = u32;
+    // comment on FoooooBar
+    type FoooooBar = u32;
+    type IntoIter = self::IntoIter<T>;
+    type Item = T;
+
+    type E = impl Trait;
+    type F = impl Trait;
+
+    const AnotherConst: i32 = 100;
+    const SomeConst: i32 = 100;
+
+    // comment on foo()
+    fn foo() {
+        println!("hello, world");
+    }
+
+    fn foo1() {
+        println!("hello, world");
+    }
+
+    fn foo2() {
+        println!("hello, world");
+    }
+
+    fn foo3() {
+        println!("hello, world");
+    }
+
+    fn foo4() {
+        println!("hello, world");
+    }
+
+    fn foo5() {
+        println!("hello, world");
+    }
+
+    fn foo6() {
+        println!("hello, world");
+    }
+
+    fn foo7() {
+        println!("hello, world");
+    }
+
+    fn foo8() {
+        println!("hello, world");
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2869.rs b/src/tools/rustfmt/tests/target/issue-2869.rs
new file mode 100644
index 0000000000000..6a68c2d95faa1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2869.rs
@@ -0,0 +1,41 @@
+// rustfmt-struct_field_align_threshold: 50
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "PascalCase")]
+struct AuditLog1 {
+    creation_time:                     String,
+    id:                                String,
+    operation:                         String,
+    organization_id:                   String,
+    record_type:                       u32,
+    result_status:                     Option<String>,
+    #[serde(rename = "ClientIP")]
+    client_ip:                         Option<IpAddr>,
+    object_id:                         String,
+    actor:                             Option<Vec<IDType>>,
+    actor_context_id:                  Option<String>,
+    actor_ip_address:                  Option<IpAddr>,
+    azure_active_directory_event_type: Option<u8>,
+
+    #[serde(rename = "very")]
+    aaaaa: String,
+    #[serde(rename = "cool")]
+    bb:    i32,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "PascalCase")]
+struct AuditLog2 {
+    creation_time:                     String,
+    id:                                String,
+    operation:                         String,
+    organization_id:                   String,
+    record_type:                       u32,
+    result_status:                     Option<String>,
+    client_ip:                         Option<IpAddr>,
+    object_id:                         String,
+    actor:                             Option<Vec<IDType>>,
+    actor_context_id:                  Option<String>,
+    actor_ip_address:                  Option<IpAddr>,
+    azure_active_directory_event_type: Option<u8>,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2896.rs b/src/tools/rustfmt/tests/target/issue-2896.rs
new file mode 100644
index 0000000000000..6fb6b12ed31d9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2896.rs
@@ -0,0 +1,165 @@
+extern crate differential_dataflow;
+extern crate rand;
+extern crate timely;
+
+use rand::{Rng, SeedableRng, StdRng};
+
+use timely::dataflow::operators::*;
+
+use differential_dataflow::input::InputSession;
+use differential_dataflow::operators::*;
+use differential_dataflow::AsCollection;
+
+// mod loglikelihoodratio;
+
+fn main() {
+    // define a new timely dataflow computation.
+    timely::execute_from_args(std::env::args().skip(6), move |worker| {
+        // capture parameters of the experiment.
+        let users: usize = std::env::args().nth(1).unwrap().parse().unwrap();
+        let items: usize = std::env::args().nth(2).unwrap().parse().unwrap();
+        let scale: usize = std::env::args().nth(3).unwrap().parse().unwrap();
+        let batch: usize = std::env::args().nth(4).unwrap().parse().unwrap();
+        let noisy: bool = std::env::args().nth(5).unwrap() == "noisy";
+
+        let index = worker.index();
+        let peers = worker.peers();
+
+        let (input, probe) = worker.dataflow(|scope| {
+            // input of (user, item) collection.
+            let (input, occurrences) = scope.new_input();
+            let occurrences = occurrences.as_collection();
+
+            //TODO adjust code to only work with upper triangular half of cooccurrence matrix
+
+            /* Compute the cooccurrence matrix C = A'A from the binary interaction matrix A. */
+            let cooccurrences = occurrences
+                .join_map(&occurrences, |_user, &item_a, &item_b| (item_a, item_b))
+                .filter(|&(item_a, item_b)| item_a != item_b)
+                .count();
+
+            /* compute the rowsums of C indicating how often we encounter individual items. */
+            let row_sums = occurrences.map(|(_user, item)| item).count();
+
+            // row_sums.inspect(|record| println!("[row_sums] {:?}", record));
+
+            /* Join the cooccurrence pairs with the corresponding row sums. */
+            let mut cooccurrences_with_row_sums = cooccurrences
+                .map(|((item_a, item_b), num_cooccurrences)| (item_a, (item_b, num_cooccurrences)))
+                .join_map(
+                    &row_sums,
+                    |&item_a, &(item_b, num_cooccurrences), &row_sum_a| {
+                        assert!(row_sum_a > 0);
+                        (item_b, (item_a, num_cooccurrences, row_sum_a))
+                    },
+                )
+                .join_map(
+                    &row_sums,
+                    |&item_b, &(item_a, num_cooccurrences, row_sum_a), &row_sum_b| {
+                        assert!(row_sum_a > 0);
+                        assert!(row_sum_b > 0);
+                        (item_a, (item_b, num_cooccurrences, row_sum_a, row_sum_b))
+                    },
+                );
+
+            // cooccurrences_with_row_sums
+            //     .inspect(|record| println!("[cooccurrences_with_row_sums] {:?}", record));
+
+            // //TODO compute top-k "similar items" per item
+            // /* Compute LLR scores for each item pair. */
+            // let llr_scores = cooccurrences_with_row_sums.map(
+            //   |(item_a, (item_b, num_cooccurrences, row_sum_a, row_sum_b))| {
+
+            //     println!(
+            //       "[llr_scores] item_a={} item_b={}, num_cooccurrences={} row_sum_a={} row_sum_b={}",
+            //       item_a, item_b, num_cooccurrences, row_sum_a, row_sum_b);
+
+            //     let k11: isize = num_cooccurrences;
+            //     let k12: isize = row_sum_a as isize - k11;
+            //     let k21: isize = row_sum_b as isize - k11;
+            //     let k22: isize = 10000 - k12 - k21 + k11;
+
+            //     let llr_score = loglikelihoodratio::log_likelihood_ratio(k11, k12, k21, k22);
+
+            //     ((item_a, item_b), llr_score)
+            //   });
+
+            if noisy {
+                cooccurrences_with_row_sums =
+                    cooccurrences_with_row_sums.inspect(|x| println!("change: {:?}", x));
+            }
+
+            let probe = cooccurrences_with_row_sums.probe();
+            /*
+                  // produce the (item, item) collection
+                  let cooccurrences = occurrences
+                    .join_map(&occurrences, |_user, &item_a, &item_b| (item_a, item_b));
+                  // count the occurrences of each item.
+                  let counts = cooccurrences
+                    .map(|(item_a,_)| item_a)
+                    .count();
+                  // produce ((item1, item2), count1, count2, count12) tuples
+                  let cooccurrences_with_counts = cooccurrences
+                    .join_map(&counts, |&item_a, &item_b, &count_item_a| (item_b, (item_a, count_item_a)))
+                    .join_map(&counts, |&item_b, &(item_a, count_item_a), &count_item_b| {
+                      ((item_a, item_b), count_item_a, count_item_b)
+                    });
+                  let probe = cooccurrences_with_counts
+                    .inspect(|x| println!("change: {:?}", x))
+                    .probe();
+            */
+            (input, probe)
+        });
+
+        let seed: &[_] = &[1, 2, 3, index];
+        let mut rng1: StdRng = SeedableRng::from_seed(seed); // rng for edge additions
+        let mut rng2: StdRng = SeedableRng::from_seed(seed); // rng for edge deletions
+
+        let mut input = InputSession::from(input);
+
+        for count in 0..scale {
+            if count % peers == index {
+                let user = rng1.gen_range(0, users);
+                let item = rng1.gen_range(0, items);
+                // println!("[INITIAL INPUT] ({}, {})", user, item);
+                input.insert((user, item));
+            }
+        }
+
+        // load the initial data up!
+        while probe.less_than(input.time()) {
+            worker.step();
+        }
+
+        for round in 1.. {
+            for element in (round * batch)..((round + 1) * batch) {
+                if element % peers == index {
+                    // advance the input timestamp.
+                    input.advance_to(round * batch);
+                    // insert a new item.
+                    let user = rng1.gen_range(0, users);
+                    let item = rng1.gen_range(0, items);
+                    if noisy {
+                        println!("[INPUT: insert] ({}, {})", user, item);
+                    }
+                    input.insert((user, item));
+                    // remove an old item.
+                    let user = rng2.gen_range(0, users);
+                    let item = rng2.gen_range(0, items);
+                    if noisy {
+                        println!("[INPUT: remove] ({}, {})", user, item);
+                    }
+                    input.remove((user, item));
+                }
+            }
+
+            input.advance_to(round * batch);
+            input.flush();
+
+            while probe.less_than(input.time()) {
+                worker.step();
+            }
+        }
+    })
+    .unwrap();
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2916.rs b/src/tools/rustfmt/tests/target/issue-2916.rs
new file mode 100644
index 0000000000000..fb07cc8065ca2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2916.rs
@@ -0,0 +1,2 @@
+a_macro!(name<Param1, Param2>,
+);
diff --git a/src/tools/rustfmt/tests/target/issue-2917/minimal.rs b/src/tools/rustfmt/tests/target/issue-2917/minimal.rs
new file mode 100644
index 0000000000000..e81e1e6a5a800
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2917/minimal.rs
@@ -0,0 +1,8 @@
+macro_rules! foo {
+    () => {
+        // comment
+        /*
+
+        */
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2917/packed_simd.rs b/src/tools/rustfmt/tests/target/issue-2917/packed_simd.rs
new file mode 100644
index 0000000000000..274614f83e2af
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2917/packed_simd.rs
@@ -0,0 +1,63 @@
+// rustfmt-wrap_comments: true
+//! Implements `From` and `Into` for vector types.
+
+macro_rules! impl_from_vector {
+    ([$elem_ty:ident; $elem_count:expr]: $id:ident | $test_tt:tt | $source:ident) => {
+        impl From<$source> for $id {
+            #[inline]
+            fn from(source: $source) -> Self {
+                fn static_assert_same_number_of_lanes<T, U>()
+                where
+                    T: crate::sealed::Simd,
+                    U: crate::sealed::Simd<LanesType = T::LanesType>,
+                {
+                }
+                use llvm::simd_cast;
+                static_assert_same_number_of_lanes::<$id, $source>();
+                Simd(unsafe { simd_cast(source.0) })
+            }
+        }
+
+        // FIXME: `Into::into` is not inline, but due to
+        // the blanket impl in `std`, which is not
+        // marked `default`, we cannot override it here with
+        // specialization.
+        /*
+        impl Into<$id> for $source {
+            #[inline]
+            fn into(self) -> $id {
+                unsafe { simd_cast(self) }
+            }
+        }
+        */
+
+        test_if! {
+            $test_tt:
+            interpolate_idents! {
+                mod [$id _from_ $source] {
+                    use super::*;
+                    #[test]
+                    fn from() {
+                        assert_eq!($id::lanes(), $source::lanes());
+                        let source: $source = Default::default();
+                        let vec: $id = Default::default();
+
+                        let e = $id::from(source);
+                        assert_eq!(e, vec);
+
+                        let e: $id = source.into();
+                        assert_eq!(e, vec);
+                    }
+                }
+            }
+        }
+    };
+}
+
+macro_rules! impl_from_vectors {
+    ([$elem_ty:ident; $elem_count:expr]: $id:ident | $test_tt:tt | $($source:ident),*) => {
+        $(
+            impl_from_vector!([$elem_ty; $elem_count]: $id | $test_tt | $source);
+        )*
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2922.rs b/src/tools/rustfmt/tests/target/issue-2922.rs
new file mode 100644
index 0000000000000..501f78c78b869
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2922.rs
@@ -0,0 +1,10 @@
+// rustfmt-indent_style: Visual
+struct Functions {
+    RunListenServer: unsafe extern "C" fn(*mut c_void,
+                                          *mut c_char,
+                                          *mut c_char,
+                                          *mut c_char,
+                                          *mut c_void,
+                                          *mut c_void)
+                                          -> c_int,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2927-2.rs b/src/tools/rustfmt/tests/target/issue-2927-2.rs
new file mode 100644
index 0000000000000..e895783ba8bb4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2927-2.rs
@@ -0,0 +1,7 @@
+// rustfmt-edition: 2015
+#![feature(rust_2018_preview, uniform_paths)]
+use futures::prelude::*;
+use http_03::cli::Cli;
+use hyper::{service::service_fn_ok, Body, Response, Server};
+use log::{error, info, log};
+use structopt::StructOpt;
diff --git a/src/tools/rustfmt/tests/target/issue-2927.rs b/src/tools/rustfmt/tests/target/issue-2927.rs
new file mode 100644
index 0000000000000..3267be28d7b70
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2927.rs
@@ -0,0 +1,7 @@
+// rustfmt-edition: 2018
+#![feature(rust_2018_preview, uniform_paths)]
+use ::log::{error, info, log};
+use futures::prelude::*;
+use http_03::cli::Cli;
+use hyper::{service::service_fn_ok, Body, Response, Server};
+use structopt::StructOpt;
diff --git a/src/tools/rustfmt/tests/target/issue-2930.rs b/src/tools/rustfmt/tests/target/issue-2930.rs
new file mode 100644
index 0000000000000..41e763a7c08c9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2930.rs
@@ -0,0 +1,5 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    let (first_variable, second_variable) = (this_is_something_with_an_extraordinarily_long_name,
+                                             this_variable_name_is_also_pretty_long);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2936.rs b/src/tools/rustfmt/tests/target/issue-2936.rs
new file mode 100644
index 0000000000000..1d6eb6d605274
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2936.rs
@@ -0,0 +1,21 @@
+struct AStruct {
+    A: u32,
+    B: u32,
+    C: u32,
+}
+
+impl Something for AStruct {
+    fn a_func() {
+        match a_val {
+            ContextualParseError::InvalidMediaRule(ref err) => {
+                let err: &CStr = match err.kind {
+                    ParseErrorKind::Custom(StyleParseErrorKind::MediaQueryExpectedFeatureName(
+                        ..,
+                    )) => {
+                        cstr!("PEMQExpectedFeatureName")
+                    }
+                };
+            }
+        };
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2941.rs b/src/tools/rustfmt/tests/target/issue-2941.rs
new file mode 100644
index 0000000000000..3c6c702c2ae03
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2941.rs
@@ -0,0 +1,5 @@
+// rustfmt-wrap_comments: true
+
+//! ```
+//! \
+//! ```
diff --git a/src/tools/rustfmt/tests/target/issue-2955.rs b/src/tools/rustfmt/tests/target/issue-2955.rs
new file mode 100644
index 0000000000000..799cd36e29ac2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2955.rs
@@ -0,0 +1,6 @@
+// rustfmt-condense_wildcard_suffixes: true
+fn main() {
+    match (1, 2, 3) {
+        (..) => (),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2973.rs b/src/tools/rustfmt/tests/target/issue-2973.rs
new file mode 100644
index 0000000000000..86574bd866860
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2973.rs
@@ -0,0 +1,158 @@
+#[cfg(test)]
+mod test {
+    summary_test! {
+        tokenize_recipe_interpolation_eol,
+    "foo: # some comment
+ {{hello}}
+",
+    "foo: \
+    {{hello}} \
+    {{ahah}}",
+        "N:#$>^{N}$<.",
+      }
+
+    summary_test! {
+      tokenize_strings,
+      r#"a = "'a'" + '"b"' + "'c'" + '"d"'#echo hello"#,
+      r#"N="+'+"+'#."#,
+    }
+
+    summary_test! {
+        tokenize_recipe_interpolation_eol,
+    "foo: # some comment
+ {{hello}}
+",
+        "N:#$>^{N}$<.",
+      }
+
+    summary_test! {
+        tokenize_recipe_interpolation_eof,
+    "foo: # more comments
+ {{hello}}
+# another comment
+",
+        "N:#$>^{N}$<#$.",
+      }
+
+    summary_test! {
+      tokenize_recipe_complex_interpolation_expression,
+      "foo: #lol\n {{a + b + \"z\" + blarg}}",
+      "N:#$>^{N+N+\"+N}<.",
+    }
+
+    summary_test! {
+      tokenize_recipe_multiple_interpolations,
+      "foo:,#ok\n {{a}}0{{b}}1{{c}}",
+      "N:,#$>^{N}_{N}_{N}<.",
+    }
+
+    summary_test! {
+        tokenize_junk,
+    "bob
+
+hello blah blah blah : a b c #whatever
+    ",
+        "N$$NNNN:NNN#$.",
+      }
+
+    summary_test! {
+        tokenize_empty_lines,
+    "
+# this does something
+hello:
+  asdf
+  bsdf
+
+  csdf
+
+  dsdf # whatever
+
+# yolo
+  ",
+        "$#$N:$>^_$^_$$^_$$^_$$<#$.",
+      }
+
+    summary_test! {
+        tokenize_comment_before_variable,
+    "
+#
+A='1'
+echo:
+  echo {{A}}
+  ",
+        "$#$N='$N:$>^_{N}$<.",
+      }
+
+    summary_test! {
+      tokenize_interpolation_backticks,
+      "hello:\n echo {{`echo hello` + `echo goodbye`}}",
+      "N:$>^_{`+`}<.",
+    }
+
+    summary_test! {
+      tokenize_assignment_backticks,
+      "a = `echo hello` + `echo goodbye`",
+      "N=`+`.",
+    }
+
+    summary_test! {
+        tokenize_multiple,
+    "
+hello:
+  a
+  b
+
+  c
+
+  d
+
+# hello
+bob:
+  frank
+  ",
+
+        "$N:$>^_$^_$$^_$$^_$$<#$N:$>^_$<.",
+      }
+
+    summary_test! {
+      tokenize_comment,
+      "a:=#",
+      "N:=#."
+    }
+
+    summary_test! {
+      tokenize_comment_with_bang,
+      "a:=#foo!",
+      "N:=#."
+    }
+
+    summary_test! {
+        tokenize_order,
+    r"
+b: a
+  @mv a b
+
+a:
+  @touch F
+  @touch a
+
+d: c
+  @rm c
+
+c: b
+  @mv b c",
+        "$N:N$>^_$$<N:$>^_$^_$$<N:N$>^_$$<N:N$>^_<.",
+      }
+
+    summary_test! {
+      tokenize_parens,
+      r"((())) )abc(+",
+      "((())))N(+.",
+    }
+
+    summary_test! {
+      crlf_newline,
+      "#\r\n#asdf\r\n",
+      "#$#$.",
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2976.rs b/src/tools/rustfmt/tests/target/issue-2976.rs
new file mode 100644
index 0000000000000..51c94a84ba295
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2976.rs
@@ -0,0 +1,3 @@
+fn a(_ /*comment*/: u8 /* toto */) {}
+fn b(/*comment*/ _: u8 /* tata */) {}
+fn c(_: /*comment*/ u8) {}
diff --git a/src/tools/rustfmt/tests/target/issue-2977/block.rs b/src/tools/rustfmt/tests/target/issue-2977/block.rs
new file mode 100644
index 0000000000000..d376e370c72e9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2977/block.rs
@@ -0,0 +1,11 @@
+macro_rules! atomic_bits {
+    ($ldrex:expr) => {
+        execute(|| {
+            asm!($ldrex
+                 : "=r"(raw)
+                 : "r"(address)
+                 :
+                 : "volatile");
+        })
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2977/impl.rs b/src/tools/rustfmt/tests/target/issue-2977/impl.rs
new file mode 100644
index 0000000000000..8d7bb9414eb7b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2977/impl.rs
@@ -0,0 +1,44 @@
+macro_rules! atomic_bits {
+    // the println macro cannot be rewritten because of the asm macro
+    ($type:ty, $ldrex:expr, $strex:expr) => {
+        impl AtomicBits for $type {
+            unsafe fn load_excl(address: usize) -> Self {
+                let raw: $type;
+                asm!($ldrex
+                     : "=r"(raw)
+                     : "r"(address)
+                     :
+                     : "volatile");
+                raw
+            }
+
+            unsafe fn store_excl(self, address: usize) -> bool {
+                let status: $type;
+                println!("{}",
+                         status);
+                status == 0
+            }
+        }
+    };
+
+    // the println macro should be rewritten here
+    ($type:ty) => {
+        fn some_func(self) {
+            let status: $type;
+            println!("{}", status);
+        }
+    };
+
+    // unrewritale macro in func
+    ($type:ty, $ldrex:expr) => {
+        unsafe fn load_excl(address: usize) -> Self {
+            let raw: $type;
+            asm!($ldrex
+                 : "=r"(raw)
+                 : "r"(address)
+                 :
+                 : "volatile");
+            raw
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2977/item.rs b/src/tools/rustfmt/tests/target/issue-2977/item.rs
new file mode 100644
index 0000000000000..857065ca93f7a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2977/item.rs
@@ -0,0 +1,11 @@
+macro_rules! atomic_bits {
+    ($ldrex:expr) => {
+        some_macro!(pub fn foo() {
+            asm!($ldrex
+                 : "=r"(raw)
+                 : "r"(address)
+                 :
+                 : "volatile");
+        })
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2977/trait.rs b/src/tools/rustfmt/tests/target/issue-2977/trait.rs
new file mode 100644
index 0000000000000..ae20668cd75f2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2977/trait.rs
@@ -0,0 +1,44 @@
+macro_rules! atomic_bits {
+    // the println macro cannot be rewritten because of the asm macro
+    ($type:ty, $ldrex:expr, $strex:expr) => {
+        trait $type {
+            unsafe fn load_excl(address: usize) -> Self {
+                let raw: $type;
+                asm!($ldrex
+                     : "=r"(raw)
+                     : "r"(address)
+                     :
+                     : "volatile");
+                raw
+            }
+
+            unsafe fn store_excl(self, address: usize) -> bool {
+                let status: $type;
+                println!("{}",
+                         status);
+                status == 0
+            }
+        }
+    };
+
+    // the println macro should be rewritten here
+    ($type:ty) => {
+        fn some_func(self) {
+            let status: $type;
+            println!("{}", status);
+        }
+    };
+
+    // unrewritale macro in func
+    ($type:ty, $ldrex:expr) => {
+        unsafe fn load_excl(address: usize) -> Self {
+            let raw: $type;
+            asm!($ldrex
+                 : "=r"(raw)
+                 : "r"(address)
+                 :
+                 : "volatile");
+            raw
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2985.rs b/src/tools/rustfmt/tests/target/issue-2985.rs
new file mode 100644
index 0000000000000..faad859236dc9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2985.rs
@@ -0,0 +1,36 @@
+// rustfmt-indent_style: Visual
+fn foo() {
+    {
+        {
+            let extra_encoder_settings = extra_encoder_settings.iter()
+                                                               .filter_map(|&(name, value)| {
+                                                                   value.split()
+                                                                        .next()
+                                                                        .something()
+                                                                        .something2()
+                                                                        .something3()
+                                                                        .something4()
+                                                               });
+            let extra_encoder_settings = extra_encoder_settings.iter()
+                                                               .filter_map(|&(name, value)| {
+                                                                   value.split()
+                                                                        .next()
+                                                                        .something()
+                                                                        .something2()
+                                                                        .something3()
+                                                                        .something4()
+                                                               })
+                                                               .something();
+            if let Some(subpod) = pod.subpods.iter().find(|s| {
+                                                        !s.plaintext
+                                                          .as_ref()
+                                                          .map(String::as_ref)
+                                                          .unwrap_or("")
+                                                          .is_empty()
+                                                    })
+            {
+                do_something();
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-2995.rs b/src/tools/rustfmt/tests/target/issue-2995.rs
new file mode 100644
index 0000000000000..890da8def92f3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-2995.rs
@@ -0,0 +1,7 @@
+fn issue_2995() {
+    // '\u{2028}' is inserted in the code below.
+
+    [0, 1];
+    [0, /* */ 1];
+    [0, 1];
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3029.rs b/src/tools/rustfmt/tests/target/issue-3029.rs
new file mode 100644
index 0000000000000..a7ac5c32b066f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3029.rs
@@ -0,0 +1,94 @@
+fn keep_if() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    if FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_if_let() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    if let Some(e) = FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_for() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    for conv in FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_loop() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(loop {
+                    FromJSValConvertible::from_jsval(cx, rval.handle(), ());
+                })
+            }
+        }
+    }
+}
+
+fn keep_while() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    while FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_while_let() {
+    {
+        {
+            {
+                EvaluateJSReply::NumberValue(
+                    while let Some(e) = FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                        unimplemented!();
+                    },
+                )
+            }
+        }
+    }
+}
+
+fn keep_match() {
+    {
+        {
+            EvaluateJSReply::NumberValue(
+                match FromJSValConvertible::from_jsval(cx, rval.handle(), ()) {
+                    Ok(ConversionResult::Success(v)) => v,
+                    _ => unreachable!(),
+                },
+            )
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3032.rs b/src/tools/rustfmt/tests/target/issue-3032.rs
new file mode 100644
index 0000000000000..3533a81fbc4a4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3032.rs
@@ -0,0 +1,36 @@
+pub fn get_array_index_from_id(_cx: *mut JSContext, id: HandleId) -> Option<u32> {
+    let raw_id = id.into();
+    unsafe {
+        if RUST_JSID_IS_INT(raw_id) {
+            return Some(RUST_JSID_TO_INT(raw_id) as u32);
+        }
+        None
+    }
+    // If `id` is length atom, `-1`, otherwise:
+    /*return if JSID_IS_ATOM(id) {
+        let atom = JSID_TO_ATOM(id);
+        //let s = *GetAtomChars(id);
+        if s > 'a' && s < 'z' {
+            return -1;
+        }
+
+        let i = 0;
+        let str = AtomToLinearString(JSID_TO_ATOM(id));
+       return if StringIsArray(str, &mut i) != 0 { i } else { -1 }
+    } else {
+        IdToInt32(cx, id);
+    }*/
+}
+
+impl Foo {
+    fn bar() -> usize {
+        42
+        /* a block comment */
+    }
+
+    fn baz() -> usize {
+        42
+        // this is a line
+        /* a block comment */
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3038.rs b/src/tools/rustfmt/tests/target/issue-3038.rs
new file mode 100644
index 0000000000000..3c398b825d7e7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3038.rs
@@ -0,0 +1,29 @@
+impl HTMLTableElement {
+    fn func() {
+        if number_of_row_elements == 0 {
+            if let Some(last_tbody) = node
+                .rev_children()
+                .filter_map(DomRoot::downcast::<Element>)
+                .find(|n| {
+                    n.is::<HTMLTableSectionElement>() && n.local_name() == &local_name!("tbody")
+                })
+            {
+                last_tbody
+                    .upcast::<Node>()
+                    .AppendChild(new_row.upcast::<Node>())
+                    .expect("InsertRow failed to append first row.");
+            }
+        }
+
+        if number_of_row_elements == 0 {
+            if let Some(last_tbody) = node.find(|n| {
+                n.is::<HTMLTableSectionElement>() && n.local_name() == &local_name!("tbody")
+            }) {
+                last_tbody
+                    .upcast::<Node>()
+                    .AppendChild(new_row.upcast::<Node>())
+                    .expect("InsertRow failed to append first row.");
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3043.rs b/src/tools/rustfmt/tests/target/issue-3043.rs
new file mode 100644
index 0000000000000..b54e244a4012d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3043.rs
@@ -0,0 +1,5 @@
+// rustfmt-edition: 2018
+
+use ::std::vec::Vec;
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3049.rs b/src/tools/rustfmt/tests/target/issue-3049.rs
new file mode 100644
index 0000000000000..fad15435433d1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3049.rs
@@ -0,0 +1,45 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    something.aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .bench_function(|| {
+                 let x = hello();
+             });
+
+    something.aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .bench_function(arg, || {
+                 let x = hello();
+             });
+
+    something.aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .aaaaaaaaaaaa()
+             .bench_function(arg,
+                             || {
+                                 let x = hello();
+                             },
+                             arg);
+
+    AAAAAAAAAAA.function(|| {
+                   let _ = ();
+               });
+
+    AAAAAAAAAAA.chain().function(|| {
+                           let _ = ();
+                       })
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3055/backtick.rs b/src/tools/rustfmt/tests/target/issue-3055/backtick.rs
new file mode 100644
index 0000000000000..f5bae8d3db4b8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3055/backtick.rs
@@ -0,0 +1,10 @@
+// rustfmt-wrap_comments: true
+
+/// Simple block
+///
+/// ```text
+///  `
+/// ```
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3055/empty-code-block.rs b/src/tools/rustfmt/tests/target/issue-3055/empty-code-block.rs
new file mode 100644
index 0000000000000..566f7ef9b6eac
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3055/empty-code-block.rs
@@ -0,0 +1,18 @@
+// rustfmt-wrap_comments: true
+
+/// Simple block
+///
+/// ```
+/// ```
+///
+/// ```no_run
+/// ```
+///
+/// ```should_panic
+/// ```
+///
+/// ```compile_fail
+/// ```
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3055/original.rs b/src/tools/rustfmt/tests/target/issue-3055/original.rs
new file mode 100644
index 0000000000000..2df6adbb5e2e5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3055/original.rs
@@ -0,0 +1,42 @@
+// rustfmt-wrap_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+/// Vestibulum elit nibh, rhoncus non, euismod sit amet, pretium eu, enim. Nunc
+/// commodo ultricies dui.
+///
+/// Should not format with text attribute
+/// ```text
+///           .--------------.
+///           |              v
+/// Park <- Idle -> Poll -> Probe -> Download -> Install -> Reboot
+///           ^      ^        '          '          '
+///           '      '        '          '          '
+///           '      `--------'          '          '
+///           `---------------'          '          '
+///           `--------------------------'          '
+///           `-------------------------------------'
+/// ```
+///
+/// Should not format with ignore attribute
+/// ```text
+///           .--------------.
+///           |              v
+/// Park <- Idle -> Poll -> Probe -> Download -> Install -> Reboot
+///           ^      ^        '          '          '
+///           '      '        '          '          '
+///           '      `--------'          '          '
+///           `---------------'          '          '
+///           `--------------------------'          '
+///           `-------------------------------------'
+/// ```
+///
+/// Should format with rust attribute
+/// ```rust
+/// let x = 42;
+/// ```
+///
+/// Should format with no attribute as it defaults to rust
+/// ```
+/// let x = 42;
+/// ```
+fn func() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3059.rs b/src/tools/rustfmt/tests/target/issue-3059.rs
new file mode 100644
index 0000000000000..f750c12875952
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3059.rs
@@ -0,0 +1,8 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 80
+
+/// Vestibulum elit nibh, rhoncus non, euismod sit amet, pretium eu, enim. Nunc
+/// commodo ultricies dui. Cras gravida rutrum massa. Donec accumsan mattis
+/// turpis. Quisque sem. Quisque elementum sapien iaculis augue. In dui sem,
+/// congue sit amet, feugiat quis, lobortis at, eros.
+fn func4() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3066.rs b/src/tools/rustfmt/tests/target/issue-3066.rs
new file mode 100644
index 0000000000000..d4dccc97e4825
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3066.rs
@@ -0,0 +1,7 @@
+// rustfmt-indent_style: Visual
+fn main() {
+    Struct { field: aaaaaaaaaaa };
+    Struct { field: aaaaaaaaaaaa };
+    Struct { field: value,
+             field2: value2 };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3105.rs b/src/tools/rustfmt/tests/target/issue-3105.rs
new file mode 100644
index 0000000000000..4f1123805b827
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3105.rs
@@ -0,0 +1,48 @@
+// rustfmt-wrap_comments: true
+
+/// Although the indentation of the skipped method is off, it shouldn't be
+/// changed.
+///
+/// ```
+/// pub unsafe fn _mm256_shufflehi_epi16(a: __m256i, imm8: i32) -> __m256i {
+///     let imm8 = (imm8 & 0xFF) as u8;
+///     let a = a.as_i16x16();
+///     macro_rules! shuffle_done {
+///         ($x01:expr, $x23:expr, $x45:expr, $x67:expr) => {
+///             #[cfg_attr(rustfmt, rustfmt_skip)]
+///       simd_shuffle16(a, a, [
+///           0, 1, 2, 3, 4+$x01, 4+$x23, 4+$x45, 4+$x67,
+///           8, 9, 10, 11, 12+$x01, 12+$x23, 12+$x45, 12+$x67
+///       ]);
+///         };
+///     }
+/// }
+/// ```
+pub unsafe fn _mm256_shufflehi_epi16(a: __m256i, imm8: i32) -> __m256i {
+    let imm8 = (imm8 & 0xFF) as u8;
+    let a = a.as_i16x16();
+    macro_rules! shuffle_done {
+        ($x01:expr, $x23:expr, $x45:expr, $x67:expr) => {
+            #[cfg_attr(rustfmt, rustfmt_skip)]
+                         simd_shuffle16(a, a, [
+                             0, 1, 2, 3, 4+$x01, 4+$x23, 4+$x45, 4+$x67,
+                             8, 9, 10, 11, 12+$x01, 12+$x23, 12+$x45, 12+$x67
+                         ]);
+        };
+    }
+}
+
+/// The skipped method shouldn't right-shift
+pub unsafe fn _mm256_shufflehi_epi32(a: __m256i, imm8: i32) -> __m256i {
+    let imm8 = (imm8 & 0xFF) as u8;
+    let a = a.as_i16x16();
+    macro_rules! shuffle_done {
+        ($x01:expr, $x23:expr, $x45:expr, $x67:expr) => {
+            #[cfg_attr(rustfmt, rustfmt_skip)]
+            simd_shuffle32(a, a, [
+                0, 1, 2, 3, 4+$x01, 4+$x23, 4+$x45, 4+$x67,
+                8, 9, 10, 11, 12+$x01, 12+$x23, 12+$x45, 12+$x67
+            ]);
+        };
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3118.rs b/src/tools/rustfmt/tests/target/issue-3118.rs
new file mode 100644
index 0000000000000..ce73a5c789cf7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3118.rs
@@ -0,0 +1,11 @@
+use {
+    crate::foo::bar,
+    bytes::{Buf, BufMut},
+    std::io,
+};
+
+mod foo {
+    pub mod bar {}
+}
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3124.rs b/src/tools/rustfmt/tests/target/issue-3124.rs
new file mode 100644
index 0000000000000..1083050d8f4f9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3124.rs
@@ -0,0 +1,14 @@
+pub fn fail1() {
+    // Some comment.
+    /**///
+}
+
+pub fn fail2() {
+    // Some comment.
+    /**/
+}
+
+pub fn fail3() {
+    // Some comment.
+    //
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3131.rs b/src/tools/rustfmt/tests/target/issue-3131.rs
new file mode 100644
index 0000000000000..c7304dd558553
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3131.rs
@@ -0,0 +1,8 @@
+fn main() {
+    match 3 {
+        t if match t {
+            _ => true,
+        } => {}
+        _ => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3132.rs b/src/tools/rustfmt/tests/target/issue-3132.rs
new file mode 100644
index 0000000000000..4dffe0ab83600
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3132.rs
@@ -0,0 +1,15 @@
+// rustfmt-version: Two
+
+fn test() {
+    /*
+    a
+    */
+    let x = 42;
+    /*
+    aaa
+    "line 1
+  line 2
+        line 3"
+    */
+    let x = 42;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3153.rs b/src/tools/rustfmt/tests/target/issue-3153.rs
new file mode 100644
index 0000000000000..39e569c0d5430
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3153.rs
@@ -0,0 +1,9 @@
+// rustfmt-wrap_comments: true
+
+/// This may panic if:
+/// - there are fewer than `max_header_bytes` bytes preceding the body
+/// - there are fewer than `max_footer_bytes` bytes following the body
+/// - the sum of the body bytes and post-body bytes is less than the sum of
+///   `min_body_and_padding_bytes` and `max_footer_bytes` (in other words, the
+///   minimum body and padding byte requirement is not met)
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3182.rs b/src/tools/rustfmt/tests/target/issue-3182.rs
new file mode 100644
index 0000000000000..d8de8443812e4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3182.rs
@@ -0,0 +1,10 @@
+// rustfmt-max_width: 79
+// rustfmt-wrap_comments: true
+
+/// ```rust
+/// # #![cfg_attr(not(dox), feature(cfg_target_feature, target_feature, stdsimd)not(dox), feature(cfg_target_feature, target_feature, stdsimd))]
+///
+/// // Est lectus hendrerit lorem, eget dignissim orci nisl sit amet massa. Etiam volutpat lobortis eros.
+/// let x = 42;
+/// ```
+fn func() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3184.rs b/src/tools/rustfmt/tests/target/issue-3184.rs
new file mode 100644
index 0000000000000..f8d9b169f1d51
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3184.rs
@@ -0,0 +1,5 @@
+/*/
+struct Error{
+    message: String,
+}
+*/
diff --git a/src/tools/rustfmt/tests/target/issue-3194.rs b/src/tools/rustfmt/tests/target/issue-3194.rs
new file mode 100644
index 0000000000000..a9614913ed14f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3194.rs
@@ -0,0 +1,52 @@
+mod m {
+    struct S
+    where
+        A: B;
+}
+
+mod n {
+    struct Foo
+    where
+        A: B,
+    {
+        foo: usize,
+    }
+}
+
+mod o {
+    enum Bar
+    where
+        A: B,
+    {
+        Bar,
+    }
+}
+
+mod with_comments {
+    mod m {
+        struct S
+        /* before where */
+        where
+            A: B; /* after where */
+    }
+
+    mod n {
+        struct Foo
+        /* before where */
+        where
+            A: B, /* after where */
+        {
+            foo: usize,
+        }
+    }
+
+    mod o {
+        enum Bar
+        /* before where */
+        where
+            A: B, /* after where */
+        {
+            Bar,
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3198.rs b/src/tools/rustfmt/tests/target/issue-3198.rs
new file mode 100644
index 0000000000000..9291f181d03a2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3198.rs
@@ -0,0 +1,67 @@
+impl TestTrait {
+    fn foo_one_pre(/* Important comment1 */ self) {}
+
+    fn foo_one_post(self /* Important comment1 */) {}
+
+    fn foo_pre(/* Important comment1 */ self, /* Important comment2 */ a: i32) {}
+
+    fn foo_post(self /* Important comment1 */, a: i32 /* Important comment2 */) {}
+
+    fn bar_pre(/* Important comment1 */ &mut self, /* Important comment2 */ a: i32) {}
+
+    fn bar_post(&mut self /* Important comment1 */, a: i32 /* Important comment2 */) {}
+
+    fn baz_pre(
+        /* Important comment1 */
+        self: X<'a, 'b>,
+        /* Important comment2 */
+        a: i32,
+    ) {
+    }
+
+    fn baz_post(
+        self: X<'a, 'b>, /* Important comment1 */
+        a: i32,          /* Important comment2 */
+    ) {
+    }
+
+    fn baz_tree_pre(
+        /* Important comment1 */
+        self: X<'a, 'b>,
+        /* Important comment2 */
+        a: i32,
+        /* Important comment3 */
+        b: i32,
+    ) {
+    }
+
+    fn baz_tree_post(
+        self: X<'a, 'b>, /* Important comment1 */
+        a: i32,          /* Important comment2 */
+        b: i32,          /* Important comment3 */
+    ) {
+    }
+
+    fn multi_line(
+        self: X<'a, 'b>, /* Important comment1-1 */
+        /* Important comment1-2 */
+        a: i32, /* Important comment2 */
+        b: i32, /* Important comment3 */
+    ) {
+    }
+
+    fn two_line_comment(
+        self: X<'a, 'b>, /* Important comment1-1
+                         Important comment1-2 */
+        a: i32, /* Important comment2 */
+        b: i32, /* Important comment3 */
+    ) {
+    }
+
+    fn no_first_line_comment(
+        self: X<'a, 'b>,
+        /* Important comment2 */ a: i32,
+        /* Important comment3 */ b: i32,
+    ) {
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3213/version_one.rs b/src/tools/rustfmt/tests/target/issue-3213/version_one.rs
new file mode 100644
index 0000000000000..307903b128b84
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3213/version_one.rs
@@ -0,0 +1,13 @@
+// rustfmt-version: One
+
+fn foo() {
+    match 0 {
+        0 => {
+            return AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        }
+        1 => {
+            AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        }
+        _ => "",
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3213/version_two.rs b/src/tools/rustfmt/tests/target/issue-3213/version_two.rs
new file mode 100644
index 0000000000000..de93d04ba9508
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3213/version_two.rs
@@ -0,0 +1,13 @@
+// rustfmt-version: Two
+
+fn foo() {
+    match 0 {
+        0 => {
+            return AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA;
+        }
+        1 => {
+            AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        }
+        _ => "",
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3217.rs b/src/tools/rustfmt/tests/target/issue-3217.rs
new file mode 100644
index 0000000000000..5121320a0975b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3217.rs
@@ -0,0 +1,24 @@
+#![feature(label_break_value)]
+
+fn main() {
+    let mut res = 0;
+    's_39: {
+        if res == 0i32 {
+            println!("Hello, world!");
+        }
+    }
+    's_40: loop {
+        println!("res = {}", res);
+        res += 1;
+        if res == 3i32 {
+            break 's_40;
+        }
+    }
+    let toto = || {
+        if true {
+            42
+        } else {
+            24
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3224.rs b/src/tools/rustfmt/tests/target/issue-3224.rs
new file mode 100644
index 0000000000000..6476d2117c661
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3224.rs
@@ -0,0 +1,11 @@
+// rustfmt-wrap_comments: true
+
+//! Test:
+//! * aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+//! * [`examples/simple`] – Demonstrates use of the [`init`] API with plain
+//!   structs.
+//! * [`examples/simple_flatbuffer`] – Demonstrates use of the [`init`] API with
+//!   FlatBuffers.
+//! * [`examples/gravity`] – Demonstrates use of the [`RLBot::set_game_state`]
+//!   API
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3227/one.rs b/src/tools/rustfmt/tests/target/issue-3227/one.rs
new file mode 100644
index 0000000000000..fcc8331000d33
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3227/one.rs
@@ -0,0 +1,13 @@
+// rustfmt-version: One
+
+fn main() {
+    thread::spawn(|| {
+        while true {
+            println!("iteration");
+        }
+    });
+
+    thread::spawn(|| loop {
+        println!("iteration");
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3227/two.rs b/src/tools/rustfmt/tests/target/issue-3227/two.rs
new file mode 100644
index 0000000000000..374ab54305d99
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3227/two.rs
@@ -0,0 +1,15 @@
+// rustfmt-version: Two
+
+fn main() {
+    thread::spawn(|| {
+        while true {
+            println!("iteration");
+        }
+    });
+
+    thread::spawn(|| {
+        loop {
+            println!("iteration");
+        }
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3234.rs b/src/tools/rustfmt/tests/target/issue-3234.rs
new file mode 100644
index 0000000000000..c7d9d42bdbe23
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3234.rs
@@ -0,0 +1,14 @@
+macro_rules! fuzz_target {
+    (|$data:ident: &[u8]| $body:block) => {};
+}
+
+fuzz_target!(|data: &[u8]| {
+    if let Ok(app_img) = AppImage::parse(data) {
+        if let Ok(app_img) =
+            app_img.sign_for_secureboot(include_str!("../../test-data/signing-key"))
+        {
+            assert!(app_img.is_signed());
+            Gbl::from_app_image(app_img).to_bytes();
+        }
+    }
+});
diff --git a/src/tools/rustfmt/tests/target/issue-3241.rs b/src/tools/rustfmt/tests/target/issue-3241.rs
new file mode 100644
index 0000000000000..60b452abdde91
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3241.rs
@@ -0,0 +1,11 @@
+// rustfmt-edition: 2018
+
+use ::baz::{bar, foo};
+use ::ignore;
+use ::ignore::some::more;
+use ::*;
+use ::{bar, foo};
+
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3253/bar.rs b/src/tools/rustfmt/tests/target/issue-3253/bar.rs
new file mode 100644
index 0000000000000..6c6ab945b88f7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3253/bar.rs
@@ -0,0 +1,2 @@
+// Empty
+fn empty() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3253/foo.rs b/src/tools/rustfmt/tests/target/issue-3253/foo.rs
new file mode 100644
index 0000000000000..1a42a10159e66
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3253/foo.rs
@@ -0,0 +1,3 @@
+pub fn hello() {
+    println!("Hello World!");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3253/lib.rs b/src/tools/rustfmt/tests/target/issue-3253/lib.rs
new file mode 100644
index 0000000000000..3eef586bd6792
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3253/lib.rs
@@ -0,0 +1,14 @@
+#[macro_use]
+extern crate cfg_if;
+
+cfg_if! {
+    if #[cfg(target_family = "unix")] {
+        mod foo;
+        #[path = "paths/bar_foo.rs"]
+        mod bar_foo;
+    } else {
+        mod bar;
+        #[path = "paths/foo_bar.rs"]
+        mod foo_bar;
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3253/paths/bar_foo.rs b/src/tools/rustfmt/tests/target/issue-3253/paths/bar_foo.rs
new file mode 100644
index 0000000000000..f7e1de29a3068
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3253/paths/bar_foo.rs
@@ -0,0 +1,3 @@
+fn foo_decl_item(x: &mut i32) {
+    x = 3;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3253/paths/excluded.rs b/src/tools/rustfmt/tests/target/issue-3253/paths/excluded.rs
new file mode 100644
index 0000000000000..9ab88414d4655
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3253/paths/excluded.rs
@@ -0,0 +1,17 @@
+// This module is not imported in the cfg_if macro in lib.rs so it is ignored
+// while the foo and bar mods are formatted.
+// Check the corresponding file in tests/source/issue-3253/paths/excluded.rs
+
+
+
+
+    fn Foo<T>() where T: Bar {
+}
+
+
+
+trait CoolerTypes { fn dummy(&self) {
+}
+}
+
+
diff --git a/src/tools/rustfmt/tests/target/issue-3253/paths/foo_bar.rs b/src/tools/rustfmt/tests/target/issue-3253/paths/foo_bar.rs
new file mode 100644
index 0000000000000..f52ac11b7399d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3253/paths/foo_bar.rs
@@ -0,0 +1,5 @@
+fn Foo<T>()
+where
+    T: Bar,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3265.rs b/src/tools/rustfmt/tests/target/issue-3265.rs
new file mode 100644
index 0000000000000..7db1dbd8b7325
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3265.rs
@@ -0,0 +1,14 @@
+// rustfmt-newline_style: Windows
+#[cfg(test)]
+mod test {
+    summary_test! {
+        tokenize_recipe_interpolation_eol,
+    "foo: # some comment
+ {{hello}}
+",
+    "foo: \
+    {{hello}} \
+    {{ahah}}",
+        "N:#$>^{N}$<.",
+      }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3270/one.rs b/src/tools/rustfmt/tests/target/issue-3270/one.rs
new file mode 100644
index 0000000000000..78de94732432b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3270/one.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: One
+
+pub fn main() {
+    /*   let s = String::from(
+            "
+    hello
+    world
+    ",
+        ); */
+
+    assert_eq!(s, "\nhello\nworld\n");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3270/two.rs b/src/tools/rustfmt/tests/target/issue-3270/two.rs
new file mode 100644
index 0000000000000..e48b592132910
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3270/two.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: Two
+
+pub fn main() {
+    /*   let s = String::from(
+        "
+hello
+world
+",
+    ); */
+
+    assert_eq!(s, "\nhello\nworld\n");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3270/wrap.rs b/src/tools/rustfmt/tests/target/issue-3270/wrap.rs
new file mode 100644
index 0000000000000..7435c5f0866e0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3270/wrap.rs
@@ -0,0 +1,13 @@
+// rustfmt-wrap_comments: true
+// rustfmt-version: Two
+
+// check that a line below max_width does not get over the limit when wrapping
+// it in a block comment
+fn func() {
+    let x = 42;
+    /*
+    let something = "one line line  line  line  line  line  line  line  line  line  line  line line
+  two lines
+         three lines";
+     */
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3272/v1.rs b/src/tools/rustfmt/tests/target/issue-3272/v1.rs
new file mode 100644
index 0000000000000..aab201027d561
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3272/v1.rs
@@ -0,0 +1,15 @@
+// rustfmt-version: One
+
+fn main() {
+    assert!(HAYSTACK
+        .par_iter()
+        .find_any(|&&x| x[0] % 1000 == 999)
+        .is_some());
+
+    assert(
+        HAYSTACK
+            .par_iter()
+            .find_any(|&&x| x[0] % 1000 == 999)
+            .is_some(),
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3272/v2.rs b/src/tools/rustfmt/tests/target/issue-3272/v2.rs
new file mode 100644
index 0000000000000..a42a2fccd5b0f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3272/v2.rs
@@ -0,0 +1,17 @@
+// rustfmt-version: Two
+
+fn main() {
+    assert!(
+        HAYSTACK
+            .par_iter()
+            .find_any(|&&x| x[0] % 1000 == 999)
+            .is_some()
+    );
+
+    assert(
+        HAYSTACK
+            .par_iter()
+            .find_any(|&&x| x[0] % 1000 == 999)
+            .is_some(),
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3278/version_one.rs b/src/tools/rustfmt/tests/target/issue-3278/version_one.rs
new file mode 100644
index 0000000000000..580679fbae34b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3278/version_one.rs
@@ -0,0 +1,8 @@
+// rustfmt-version: One
+
+pub fn parse_conditional<'a, I: 'a>(
+) -> impl Parser<Input = I, Output = Expr, PartialState = ()> + 'a
+where
+    I: Stream<Item = char>,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3278/version_two.rs b/src/tools/rustfmt/tests/target/issue-3278/version_two.rs
new file mode 100644
index 0000000000000..c17b1742d396b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3278/version_two.rs
@@ -0,0 +1,8 @@
+// rustfmt-version: Two
+
+pub fn parse_conditional<'a, I: 'a>()
+-> impl Parser<Input = I, Output = Expr, PartialState = ()> + 'a
+where
+    I: Stream<Item = char>,
+{
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3295/two.rs b/src/tools/rustfmt/tests/target/issue-3295/two.rs
new file mode 100644
index 0000000000000..3e669a0bb7562
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3295/two.rs
@@ -0,0 +1,14 @@
+// rustfmt-version: Two
+pub enum TestEnum {
+    a,
+    b,
+}
+
+fn the_test(input: TestEnum) {
+    match input {
+        TestEnum::a => String::from("aaa"),
+        TestEnum::b => String::from(
+            "this is a very very very very very very very very very very very very very very very ong string",
+        ),
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3302.rs b/src/tools/rustfmt/tests/target/issue-3302.rs
new file mode 100644
index 0000000000000..146cb98381933
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3302.rs
@@ -0,0 +1,43 @@
+// rustfmt-version: Two
+
+macro_rules! moo1 {
+    () => {
+        bar! {
+        "
+"
+        }
+    };
+}
+
+macro_rules! moo2 {
+    () => {
+        bar! {
+        "
+"
+        }
+    };
+}
+
+macro_rules! moo3 {
+    () => {
+        42
+        /*
+        bar! {
+        "
+        toto
+tata"
+        }
+        */
+    };
+}
+
+macro_rules! moo4 {
+    () => {
+        bar! {
+        "
+    foo
+        bar
+baz"
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3304.rs b/src/tools/rustfmt/tests/target/issue-3304.rs
new file mode 100644
index 0000000000000..cc1910ce25713
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3304.rs
@@ -0,0 +1,42 @@
+// rustfmt-error_on_line_overflow: true
+
+#[rustfmt::skip] use one::two::three::four::five::six::seven::eight::night::ten::eleven::twelve::thirteen::fourteen::fiveteen;
+#[rustfmt::skip]
+
+use one::two::three::four::five::six::seven::eight::night::ten::eleven::twelve::thirteen::fourteen::fiveteen;
+
+macro_rules! test_macro {
+    ($($id:ident),*) => {};
+}
+
+macro_rules! test_macro2 {
+    ($($id:ident),*) => {
+        1
+    };
+}
+
+fn main() {
+    #[rustfmt::skip] test_macro! { one, two, three, four, five, six, seven, eight, night, ten, eleven, twelve, thirteen, fourteen, fiveteen };
+    #[rustfmt::skip]
+    
+    test_macro! { one, two, three, four, five, six, seven, eight, night, ten, eleven, twelve, thirteen, fourteen, fiveteen };
+}
+
+fn test_local() {
+    #[rustfmt::skip] let x = test_macro! { one, two, three, four, five, six, seven, eight, night, ten, eleven, twelve, thirteen, fourteen, fiveteen };
+    #[rustfmt::skip]
+    
+    let x = test_macro! { one, two, three, four, five, six, seven, eight, night, ten, eleven, twelve, thirteen, fourteen, fiveteen };
+}
+
+fn test_expr(_: [u32]) -> u32 {
+    #[rustfmt::skip] test_expr([9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999]);
+    #[rustfmt::skip]
+    
+    test_expr([9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999, 9999999999999])
+}
+
+#[rustfmt::skip] mod test { use one::two::three::four::five::six::seven::eight::night::ten::eleven::twelve::thirteen::fourteen::fiveteen; }
+#[rustfmt::skip]
+
+mod test { use one::two::three::four::five::six::seven::eight::night::ten::eleven::twelve::thirteen::fourteen::fiveteen; }
diff --git a/src/tools/rustfmt/tests/target/issue-3314.rs b/src/tools/rustfmt/tests/target/issue-3314.rs
new file mode 100644
index 0000000000000..1cd32afb02f9a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3314.rs
@@ -0,0 +1,5 @@
+/*code
+/*code*/
+if true {
+    println!("1");
+}*/
diff --git a/src/tools/rustfmt/tests/target/issue-3343.rs b/src/tools/rustfmt/tests/target/issue-3343.rs
new file mode 100644
index 0000000000000..d0497758e66c0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3343.rs
@@ -0,0 +1,44 @@
+// rustfmt-inline_attribute_width: 50
+
+#[cfg(feature = "alloc")] use core::slice;
+
+#[cfg(feature = "alloc")] use total_len_is::_50__;
+
+#[cfg(feature = "alloc")]
+use total_len_is::_51___;
+
+#[cfg(feature = "alloc")] extern crate len_is_50_;
+
+#[cfg(feature = "alloc")]
+extern crate len_is_51__;
+
+/// this is a comment to test is_sugared_doc property
+use core::convert;
+
+#[fooooo]
+#[barrrrr]
+use total_len_is_::_51______;
+
+#[cfg(not(all(
+    feature = "std",
+    any(
+        target_os = "linux",
+        target_os = "android",
+        target_os = "netbsd",
+        target_os = "dragonfly",
+        target_os = "haiku",
+        target_os = "emscripten",
+        target_os = "solaris",
+        target_os = "cloudabi",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "redox",
+        target_os = "fuchsia",
+        windows,
+        all(target_arch = "wasm32", feature = "stdweb"),
+        all(target_arch = "wasm32", feature = "wasm-bindgen"),
+    )
+)))]
+use core::slice;
diff --git a/src/tools/rustfmt/tests/target/issue-3423.rs b/src/tools/rustfmt/tests/target/issue-3423.rs
new file mode 100644
index 0000000000000..cd60251771df5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3423.rs
@@ -0,0 +1,5 @@
+/* a nice comment with a trailing whitespace */
+fn foo() {}
+
+/* a nice comment with a trailing tab */
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3434/lib.rs b/src/tools/rustfmt/tests/target/issue-3434/lib.rs
new file mode 100644
index 0000000000000..2fd7aea21c758
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3434/lib.rs
@@ -0,0 +1,57 @@
+#![rustfmt::skip::macros(skip_macro_mod)]
+
+mod no_entry;
+
+#[rustfmt::skip::macros(html, skip_macro)]
+fn main() {
+    let macro_result1 = html! { <div>
+this should be skipped</div>
+    }
+    .to_string();
+
+    let macro_result2 = not_skip_macro! { <div>
+    this should be mangled</div>
+            }
+    .to_string();
+
+    skip_macro! {
+this should be skipped
+};
+
+    foo();
+}
+
+fn foo() {
+    let macro_result1 = html! { <div>
+    this should be mangled</div>
+                }
+    .to_string();
+}
+
+fn bar() {
+    let macro_result1 = skip_macro_mod! { <div>
+this should be skipped</div>
+        }
+    .to_string();
+}
+
+fn visitor_made_from_same_context() {
+    let pair = (
+        || {
+            foo!(<div>
+            this should be mangled</div>
+                        );
+            skip_macro_mod!(<div>
+this should be skipped</div>
+            );
+        },
+        || {
+            foo!(<div>
+            this should be mangled</div>
+                        );
+            skip_macro_mod!(<div>
+this should be skipped</div>
+            );
+        },
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3434/no_entry.rs b/src/tools/rustfmt/tests/target/issue-3434/no_entry.rs
new file mode 100644
index 0000000000000..a2ecf2c2f99bd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3434/no_entry.rs
@@ -0,0 +1,19 @@
+#[rustfmt::skip::macros(another_macro)]
+fn foo() {
+    another_macro!(
+This should be skipped.
+        );
+}
+
+fn bar() {
+    skip_macro_mod!(
+This should be skipped.
+        );
+}
+
+fn baz() {
+    let macro_result1 = no_skip_macro! { <div>
+    this should be mangled</div>
+        }
+    .to_string();
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3434/not_skip_macro.rs b/src/tools/rustfmt/tests/target/issue-3434/not_skip_macro.rs
new file mode 100644
index 0000000000000..c90d09744b281
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3434/not_skip_macro.rs
@@ -0,0 +1,8 @@
+#[this::is::not::skip::macros(ouch)]
+
+fn main() {
+    let macro_result1 = ouch! { <div>
+    this should be mangled</div>
+        }
+    .to_string();
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3442.rs b/src/tools/rustfmt/tests/target/issue-3442.rs
new file mode 100644
index 0000000000000..3664c50ee7a8b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3442.rs
@@ -0,0 +1,10 @@
+// rustfmt-file_lines: [{"file":"tests/target/issue-3442.rs","range":[5,5]},{"file":"tests/target/issue-3442.rs","range":[8,8]}]
+
+extern crate alpha; // comment 1
+extern crate beta; // comment 2
+#[allow(aaa)] // comment 3
+#[macro_use]
+extern crate gamma;
+#[allow(bbb)] // comment 4
+#[macro_use]
+extern crate lazy_static;
diff --git a/src/tools/rustfmt/tests/target/issue-3465.rs b/src/tools/rustfmt/tests/target/issue-3465.rs
new file mode 100644
index 0000000000000..9e2680f0feece
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3465.rs
@@ -0,0 +1,42 @@
+fn main() {
+    ((((((((((((((((((((((((((((((((((((((((((0) + 1) + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1)
+        + 1);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3494/crlf.rs b/src/tools/rustfmt/tests/target/issue-3494/crlf.rs
new file mode 100644
index 0000000000000..cae615a06664c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3494/crlf.rs
@@ -0,0 +1,8 @@
+// rustfmt-file_lines: [{"file":"tests/source/issue-3494/crlf.rs","range":[4,5]}]
+
+pub fn main() {
+    let world1 = "world";
+    println!("Hello, {}!", world1);
+let world2 = "world"; println!("Hello, {}!", world2);
+let world3 = "world"; println!("Hello, {}!", world3);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3494/lf.rs b/src/tools/rustfmt/tests/target/issue-3494/lf.rs
new file mode 100644
index 0000000000000..60aafe19a0291
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3494/lf.rs
@@ -0,0 +1,8 @@
+// rustfmt-file_lines: [{"file":"tests/source/issue-3494/lf.rs","range":[4,5]}]
+
+pub fn main() {
+    let world1 = "world";
+    println!("Hello, {}!", world1);
+let world2 = "world"; println!("Hello, {}!", world2);
+let world3 = "world"; println!("Hello, {}!", world3);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3499.rs b/src/tools/rustfmt/tests/target/issue-3499.rs
new file mode 100644
index 0000000000000..88fd7f7e16532
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3499.rs
@@ -0,0 +1 @@
+test![];
diff --git a/src/tools/rustfmt/tests/target/issue-3508.rs b/src/tools/rustfmt/tests/target/issue-3508.rs
new file mode 100644
index 0000000000000..5f4e156582d4d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3508.rs
@@ -0,0 +1,22 @@
+fn foo<F>(foo2: F)
+where
+    F: Fn(
+        // this comment is deleted
+    ),
+{
+}
+
+fn foo_block<F>(foo2: F)
+where
+    F: Fn(/* this comment is deleted */),
+{
+}
+
+fn bar(
+    bar2: impl Fn(
+        // this comment is deleted
+    ),
+) {
+}
+
+fn bar_block(bar2: impl Fn(/* this comment is deleted */)) {}
diff --git a/src/tools/rustfmt/tests/target/issue-3515.rs b/src/tools/rustfmt/tests/target/issue-3515.rs
new file mode 100644
index 0000000000000..b59d03c6c82a7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3515.rs
@@ -0,0 +1,6 @@
+// rustfmt-reorder_imports: false
+
+use std::fmt::{self, Display};
+use std::collections::HashMap;
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3532.rs b/src/tools/rustfmt/tests/target/issue-3532.rs
new file mode 100644
index 0000000000000..f41902620cd19
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3532.rs
@@ -0,0 +1,6 @@
+fn foo(a: T) {
+    match a {
+        1 => {}
+        0 => {} // _ => panic!("doesn't format!"),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3539.rs b/src/tools/rustfmt/tests/target/issue-3539.rs
new file mode 100644
index 0000000000000..aa2fa72ece324
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3539.rs
@@ -0,0 +1,8 @@
+use std::io::Error;
+
+fn main() {
+    let _read_num: fn() -> Result<(i32), Error> = || -> Result<(i32), Error> {
+        let a = 1;
+        Ok(a)
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3554.rs b/src/tools/rustfmt/tests/target/issue-3554.rs
new file mode 100644
index 0000000000000..4ece90403e1f2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3554.rs
@@ -0,0 +1,4 @@
+#![feature(const_generics)]
+
+pub struct S<const N: usize>;
+impl S<{ 0 }> {}
diff --git a/src/tools/rustfmt/tests/target/issue-3567.rs b/src/tools/rustfmt/tests/target/issue-3567.rs
new file mode 100644
index 0000000000000..3cf08628db0ba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3567.rs
@@ -0,0 +1,3 @@
+fn check() {
+    vec![vec!(0; 10); 10];
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3568.rs b/src/tools/rustfmt/tests/target/issue-3568.rs
new file mode 100644
index 0000000000000..a146f3df24ddc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3568.rs
@@ -0,0 +1 @@
+use a::b::{self};
diff --git a/src/tools/rustfmt/tests/target/issue-3585/extern_crate.rs b/src/tools/rustfmt/tests/target/issue-3585/extern_crate.rs
new file mode 100644
index 0000000000000..dc7c9e0246b20
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3585/extern_crate.rs
@@ -0,0 +1,10 @@
+// rustfmt-inline_attribute_width: 100
+
+#[macro_use] extern crate static_assertions;
+
+#[cfg(unix)] extern crate static_assertions;
+
+// a comment before the attribute
+#[macro_use]
+// some comment after
+extern crate static_assertions;
diff --git a/src/tools/rustfmt/tests/target/issue-3585/reorder_imports_disabled.rs b/src/tools/rustfmt/tests/target/issue-3585/reorder_imports_disabled.rs
new file mode 100644
index 0000000000000..f9637729b7eb3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3585/reorder_imports_disabled.rs
@@ -0,0 +1,8 @@
+// rustfmt-inline_attribute_width: 100
+// rustfmt-reorder_imports: false
+
+#[cfg(unix)] extern crate crateb;
+#[cfg(unix)] extern crate cratea;
+
+#[cfg(unix)] use crateb;
+#[cfg(unix)] use cratea;
diff --git a/src/tools/rustfmt/tests/target/issue-3585/reorder_imports_enabled.rs b/src/tools/rustfmt/tests/target/issue-3585/reorder_imports_enabled.rs
new file mode 100644
index 0000000000000..d040d0ed34148
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3585/reorder_imports_enabled.rs
@@ -0,0 +1,8 @@
+// rustfmt-inline_attribute_width: 100
+// rustfmt-reorder_imports: true
+
+#[cfg(unix)] extern crate cratea;
+#[cfg(unix)] extern crate crateb;
+
+#[cfg(unix)] use cratea;
+#[cfg(unix)] use crateb;
diff --git a/src/tools/rustfmt/tests/target/issue-3585/use.rs b/src/tools/rustfmt/tests/target/issue-3585/use.rs
new file mode 100644
index 0000000000000..c76a9eaacc828
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3585/use.rs
@@ -0,0 +1,5 @@
+// rustfmt-inline_attribute_width: 100
+
+#[macro_use] use static_assertions;
+
+#[cfg(unix)] use static_assertions;
diff --git a/src/tools/rustfmt/tests/target/issue-3595.rs b/src/tools/rustfmt/tests/target/issue-3595.rs
new file mode 100644
index 0000000000000..3e06538a4d32c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3595.rs
@@ -0,0 +1,4 @@
+struct ReqMsg();
+struct RespMsg();
+
+pub type TestType = fn() -> (ReqMsg, fn(RespMsg) -> ());
diff --git a/src/tools/rustfmt/tests/target/issue-3601.rs b/src/tools/rustfmt/tests/target/issue-3601.rs
new file mode 100644
index 0000000000000..c86ca24e70755
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3601.rs
@@ -0,0 +1,11 @@
+#![feature(const_generics)]
+
+trait A {
+    fn foo(&self);
+}
+
+pub struct B<const N: usize>([usize; N]);
+
+impl<const N: usize> A for B<{ N }> {
+    fn foo(&self) {}
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3614/version_one.rs b/src/tools/rustfmt/tests/target/issue-3614/version_one.rs
new file mode 100644
index 0000000000000..8ab28304732c1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3614/version_one.rs
@@ -0,0 +1,15 @@
+// rustfmt-version: One
+
+fn main() {
+    let toto = || {
+        if true {
+            42
+        } else {
+            24
+        }
+    };
+
+    {
+        T
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3614/version_two.rs b/src/tools/rustfmt/tests/target/issue-3614/version_two.rs
new file mode 100644
index 0000000000000..5d6f8e7a313b7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3614/version_two.rs
@@ -0,0 +1,8 @@
+// rustfmt-version: Two
+
+fn main() {
+    let toto = || {
+        if true { 42 } else { 24 }
+    };
+    { T }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3636.rs b/src/tools/rustfmt/tests/target/issue-3636.rs
new file mode 100644
index 0000000000000..d467ed7389f68
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3636.rs
@@ -0,0 +1,8 @@
+// rustfmt-file_lines: [{"file":"tests/source/issue-3636.rs","range":[4,7]},{"file":"tests/target/issue-3636.rs","range":[3,6]}]
+
+fn foo() {
+    let x = 42;
+    let y = 42;
+    let z = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+    let z = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";   
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3639.rs b/src/tools/rustfmt/tests/target/issue-3639.rs
new file mode 100644
index 0000000000000..e8fddce2de62c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3639.rs
@@ -0,0 +1,5 @@
+trait Foo {}
+struct Bar {}
+struct Bax;
+struct Baz(String);
+impl Foo for Bar {}
diff --git a/src/tools/rustfmt/tests/target/issue-3645.rs b/src/tools/rustfmt/tests/target/issue-3645.rs
new file mode 100644
index 0000000000000..14bf96e6383de
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3645.rs
@@ -0,0 +1,3 @@
+mod x {
+    use super::self as x;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3651.rs b/src/tools/rustfmt/tests/target/issue-3651.rs
new file mode 100644
index 0000000000000..4a95a1712ee53
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3651.rs
@@ -0,0 +1,7 @@
+fn f() -> Box<
+    dyn FnMut() -> Thing<
+        WithType = LongItemName,
+        Error = LONGLONGLONGLONGLONGONGEvenLongerErrorNameLongerLonger,
+    >,
+> {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3665/lib.rs b/src/tools/rustfmt/tests/target/issue-3665/lib.rs
new file mode 100644
index 0000000000000..c313f320368a1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3665/lib.rs
@@ -0,0 +1,31 @@
+#![rustfmt::skip::attributes(skip_mod_attr)]
+
+mod sub_mod;
+
+#[rustfmt::skip::attributes(other, skip_attr)]
+fn main() {
+    #[other(should,
+skip,
+        this,                               format)]
+    struct S {}
+
+    #[skip_attr(should, skip,
+this,                               format,too)]
+    fn doesnt_mater() {}
+
+    #[skip_mod_attr(should, skip,
+this,                               format,
+         enerywhere)]
+    fn more() {}
+
+    #[not_skip(not, skip, me)]
+    struct B {}
+}
+
+#[other(should, not, skip, this, format, here)]
+fn foo() {}
+
+#[skip_mod_attr(should, skip,
+this,                               format,in,                    master,
+                    and, sub, module)]
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3665/not_skip_attribute.rs b/src/tools/rustfmt/tests/target/issue-3665/not_skip_attribute.rs
new file mode 100644
index 0000000000000..a4e8b94873663
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3665/not_skip_attribute.rs
@@ -0,0 +1,4 @@
+#![this::is::not::skip::attribute(ouch)]
+
+#[ouch(not, skip, me)]
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3665/sub_mod.rs b/src/tools/rustfmt/tests/target/issue-3665/sub_mod.rs
new file mode 100644
index 0000000000000..30a2b0fd9d960
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3665/sub_mod.rs
@@ -0,0 +1,13 @@
+#[rustfmt::skip::attributes(more_skip)]
+#[more_skip(should,
+      skip,
+this,                               format)]
+fn foo() {}
+
+#[skip_mod_attr(should, skip,
+this,                               format,in,                    master,
+                    and, sub, module)]
+fn bar() {}
+
+#[skip_attr(should, not, skip, this, attribute, here)]
+fn baz() {}
diff --git a/src/tools/rustfmt/tests/target/issue-3672.rs b/src/tools/rustfmt/tests/target/issue-3672.rs
new file mode 100644
index 0000000000000..8cc3d3fd2c55d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3672.rs
@@ -0,0 +1,3 @@
+fn main() {
+    let x = 5;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3675.rs b/src/tools/rustfmt/tests/target/issue-3675.rs
new file mode 100644
index 0000000000000..62d986e77341f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3675.rs
@@ -0,0 +1,6 @@
+fn main() {
+    println!(
+        "{}", // comment
+        111
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3701/one.rs b/src/tools/rustfmt/tests/target/issue-3701/one.rs
new file mode 100644
index 0000000000000..9d1ef9eed9aed
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3701/one.rs
@@ -0,0 +1,12 @@
+// rustfmt-version: One
+
+fn build_sorted_static_get_entry_names(
+    mut entries: Vec<(u8, &'static str)>,
+) -> (impl Fn(
+    AlphabeticalTraversal,
+    Box<dyn dirents_sink::Sink<AlphabeticalTraversal>>,
+) -> BoxFuture<'static, Result<Box<dyn dirents_sink::Sealed>, Status>>
+        + Send
+        + Sync
+        + 'static) {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3701/two.rs b/src/tools/rustfmt/tests/target/issue-3701/two.rs
new file mode 100644
index 0000000000000..62ffc9d823dd8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3701/two.rs
@@ -0,0 +1,14 @@
+// rustfmt-version: Two
+
+fn build_sorted_static_get_entry_names(
+    mut entries: Vec<(u8, &'static str)>,
+) -> (
+    impl Fn(
+        AlphabeticalTraversal,
+        Box<dyn dirents_sink::Sink<AlphabeticalTraversal>>,
+    ) -> BoxFuture<'static, Result<Box<dyn dirents_sink::Sealed>, Status>>
+    + Send
+    + Sync
+    + 'static
+) {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3709.rs b/src/tools/rustfmt/tests/target/issue-3709.rs
new file mode 100644
index 0000000000000..0f3eae048d400
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3709.rs
@@ -0,0 +1,10 @@
+// rustfmt-edition: 2018
+
+macro_rules! token {
+    ($t:tt) => {};
+}
+
+fn main() {
+    token!(dyn);
+    token!(dyn);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3711.rs b/src/tools/rustfmt/tests/target/issue-3711.rs
new file mode 100644
index 0000000000000..62d986e77341f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3711.rs
@@ -0,0 +1,6 @@
+fn main() {
+    println!(
+        "{}", // comment
+        111
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3717.rs b/src/tools/rustfmt/tests/target/issue-3717.rs
new file mode 100644
index 0000000000000..b769cd3ecce26
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3717.rs
@@ -0,0 +1,7 @@
+fn main() {
+    {
+        #[rustfmt::skip]
+        let _ = 
+        [1];
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3718.rs b/src/tools/rustfmt/tests/target/issue-3718.rs
new file mode 100644
index 0000000000000..8ad21ffc708c7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3718.rs
@@ -0,0 +1,7 @@
+fn main() {
+    let x: &[i32] = &[2, 2];
+    match x {
+        [_a, _] => println!("Wrong username or password"),
+        _ => println!("Logged in"),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3740.rs b/src/tools/rustfmt/tests/target/issue-3740.rs
new file mode 100644
index 0000000000000..995a6bee3527c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3740.rs
@@ -0,0 +1,8 @@
+impl<T, const SIZE: usize> IntoNormalized for Vector<T, { SIZE }>
+where
+    Vector<T, { SIZE }>: Div<Vector<T, { SIZE }>>,
+    for<'a> &'a Vector<T, { SIZE }>: IntoLength<Output = T>,
+{
+    type Output = Vector<T, { SIZE }>;
+    fn into_normalized(self) -> Self::Output {}
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3741.rs b/src/tools/rustfmt/tests/target/issue-3741.rs
new file mode 100644
index 0000000000000..34d22dc91eb2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3741.rs
@@ -0,0 +1,5 @@
+pub enum PublishedFileVisibility {
+    Public = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPublic as i32,
+    FriendsOnly = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityFriendsOnly as i32,
+    Private = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPrivate as i32,
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3750.rs b/src/tools/rustfmt/tests/target/issue-3750.rs
new file mode 100644
index 0000000000000..6875f8d3897bf
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3750.rs
@@ -0,0 +1,15 @@
+// rustfmt-imports_granularity: Crate
+
+pub mod foo {
+    pub mod bar {
+        pub struct Bar;
+    }
+
+    pub fn bar() {}
+}
+
+use foo::{bar, bar::Bar};
+
+fn main() {
+    bar();
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3751.rs b/src/tools/rustfmt/tests/target/issue-3751.rs
new file mode 100644
index 0000000000000..e5a03956e9d0a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3751.rs
@@ -0,0 +1,10 @@
+// rustfmt-format_code_in_doc_comments: true
+
+//! Empty pound line
+//!
+//! ```rust
+//! #
+//! # fn main() {
+//! foo();
+//! # }
+//! ```
diff --git a/src/tools/rustfmt/tests/target/issue-3759.rs b/src/tools/rustfmt/tests/target/issue-3759.rs
new file mode 100644
index 0000000000000..b53f5391a3445
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3759.rs
@@ -0,0 +1,27 @@
+fn main() {
+    let Test {
+        #[cfg(feature = "test")]
+        x,
+    } = Test {
+        #[cfg(feature = "test")]
+        x: 1,
+    };
+
+    let Test {
+        #[cfg(feature = "test")]
+        // comment
+        x,
+    } = Test {
+        #[cfg(feature = "test")]
+        x: 1,
+    };
+
+    let Test {
+        // comment
+        #[cfg(feature = "test")]
+        x,
+    } = Test {
+        #[cfg(feature = "test")]
+        x: 1,
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3779/ice.rs b/src/tools/rustfmt/tests/target/issue-3779/ice.rs
new file mode 100644
index 0000000000000..cde21412d9458
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3779/ice.rs
@@ -0,0 +1,3 @@
+pub fn bar() {
+    1x;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3779/lib.rs b/src/tools/rustfmt/tests/target/issue-3779/lib.rs
new file mode 100644
index 0000000000000..a5673a4db7eca
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3779/lib.rs
@@ -0,0 +1,9 @@
+// rustfmt-unstable: true
+// rustfmt-config: issue-3779.toml
+
+#[path = "ice.rs"]
+mod ice;
+
+fn foo() {
+    println!("abc");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3786.rs b/src/tools/rustfmt/tests/target/issue-3786.rs
new file mode 100644
index 0000000000000..d90cba15d2019
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3786.rs
@@ -0,0 +1,9 @@
+fn main() {
+    let _ = r#"
+this is a very long string exceeded maximum width in this case maximum 100. (current this line width is about 115)
+"#;
+
+    let _with_newline = r#"
+this is a very long string exceeded maximum width in this case maximum 100. (current this line width is about 115)
+"#;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3787.rs b/src/tools/rustfmt/tests/target/issue-3787.rs
new file mode 100644
index 0000000000000..32cf7e3d7559e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3787.rs
@@ -0,0 +1,13 @@
+// rustfmt-wrap_comments: true
+
+//! URLs in items
+//! * [This is a link with a very loooooooooooooooooooooooooooooooooooooooooong URL.](https://example.com/This/is/a/link/with/a/very/loooooooooooooooooooooooooooooooooooooooooong/URL)
+//! * This is a [link](https://example.com/This/is/a/link/with/a/very/loooooooooooooooooooooooooooooooooooooooooong/URL)
+//!   with a very loooooooooooooooooooooooooooooooooooooooooong URL.
+//! * there is no link here: In hac habitasse platea dictumst. Maecenas in
+//!   ligula. Duis tincidunt odio sollicitudin quam. Nullam non mauris.
+//!   Phasellus lacinia, velit sit amet bibendum euismod, leo diam interdum
+//!   ligula, eu scelerisque sem purus in tellus.
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3815.rs b/src/tools/rustfmt/tests/target/issue-3815.rs
new file mode 100644
index 0000000000000..eff27e2de3c16
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3815.rs
@@ -0,0 +1,4 @@
+pub type Type = impl Deref<Target = i8>;
+
+pub type Type =
+    impl VeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeryLongType<Target = i8>;
diff --git a/src/tools/rustfmt/tests/target/issue-3840/version-one_hard-tabs.rs b/src/tools/rustfmt/tests/target/issue-3840/version-one_hard-tabs.rs
new file mode 100644
index 0000000000000..4aa905ce9e5a6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3840/version-one_hard-tabs.rs
@@ -0,0 +1,25 @@
+// rustfmt-hard_tabs: true
+
+impl<
+		Target: FromEvent<A> + FromEvent<B>,
+		A: Widget2<Ctx = C>,
+		B: Widget2<Ctx = C>,
+		C: for<'a> CtxFamily<'a>,
+	> Widget2 for WidgetEventLifter<Target, A, B>
+{
+	type Ctx = C;
+	type Event = Vec<Target>;
+}
+
+mod foo {
+	impl<
+			Target: FromEvent<A> + FromEvent<B>,
+			A: Widget2<Ctx = C>,
+			B: Widget2<Ctx = C>,
+			C: for<'a> CtxFamily<'a>,
+		> Widget2 for WidgetEventLifter<Target, A, B>
+	{
+		type Ctx = C;
+		type Event = Vec<Target>;
+	}
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3840/version-one_soft-tabs.rs b/src/tools/rustfmt/tests/target/issue-3840/version-one_soft-tabs.rs
new file mode 100644
index 0000000000000..099e68018230c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3840/version-one_soft-tabs.rs
@@ -0,0 +1,23 @@
+impl<
+        Target: FromEvent<A> + FromEvent<B>,
+        A: Widget2<Ctx = C>,
+        B: Widget2<Ctx = C>,
+        C: for<'a> CtxFamily<'a>,
+    > Widget2 for WidgetEventLifter<Target, A, B>
+{
+    type Ctx = C;
+    type Event = Vec<Target>;
+}
+
+mod foo {
+    impl<
+            Target: FromEvent<A> + FromEvent<B>,
+            A: Widget2<Ctx = C>,
+            B: Widget2<Ctx = C>,
+            C: for<'a> CtxFamily<'a>,
+        > Widget2 for WidgetEventLifter<Target, A, B>
+    {
+        type Ctx = C;
+        type Event = Vec<Target>;
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3840/version-two_hard-tabs.rs b/src/tools/rustfmt/tests/target/issue-3840/version-two_hard-tabs.rs
new file mode 100644
index 0000000000000..084db3d146561
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3840/version-two_hard-tabs.rs
@@ -0,0 +1,26 @@
+// rustfmt-hard_tabs: true
+// rustfmt-version: Two
+
+impl<
+	Target: FromEvent<A> + FromEvent<B>,
+	A: Widget2<Ctx = C>,
+	B: Widget2<Ctx = C>,
+	C: for<'a> CtxFamily<'a>,
+> Widget2 for WidgetEventLifter<Target, A, B>
+{
+	type Ctx = C;
+	type Event = Vec<Target>;
+}
+
+mod foo {
+	impl<
+		Target: FromEvent<A> + FromEvent<B>,
+		A: Widget2<Ctx = C>,
+		B: Widget2<Ctx = C>,
+		C: for<'a> CtxFamily<'a>,
+	> Widget2 for WidgetEventLifter<Target, A, B>
+	{
+		type Ctx = C;
+		type Event = Vec<Target>;
+	}
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3840/version-two_soft-tabs.rs b/src/tools/rustfmt/tests/target/issue-3840/version-two_soft-tabs.rs
new file mode 100644
index 0000000000000..bc59b0baa56c4
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3840/version-two_soft-tabs.rs
@@ -0,0 +1,25 @@
+// rustfmt-version: Two
+
+impl<
+    Target: FromEvent<A> + FromEvent<B>,
+    A: Widget2<Ctx = C>,
+    B: Widget2<Ctx = C>,
+    C: for<'a> CtxFamily<'a>,
+> Widget2 for WidgetEventLifter<Target, A, B>
+{
+    type Ctx = C;
+    type Event = Vec<Target>;
+}
+
+mod foo {
+    impl<
+        Target: FromEvent<A> + FromEvent<B>,
+        A: Widget2<Ctx = C>,
+        B: Widget2<Ctx = C>,
+        C: for<'a> CtxFamily<'a>,
+    > Widget2 for WidgetEventLifter<Target, A, B>
+    {
+        type Ctx = C;
+        type Event = Vec<Target>;
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3845.rs b/src/tools/rustfmt/tests/target/issue-3845.rs
new file mode 100644
index 0000000000000..877c05b86a90b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3845.rs
@@ -0,0 +1,8 @@
+fn main() {
+    || {
+        #[allow(deprecated)]
+        {
+            u8::max_value()
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3882.rs b/src/tools/rustfmt/tests/target/issue-3882.rs
new file mode 100644
index 0000000000000..5eb442af97470
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3882.rs
@@ -0,0 +1,4 @@
+// rustfmt-version: Two
+fn bar(_t: T, // bar
+) {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-3974.rs b/src/tools/rustfmt/tests/target/issue-3974.rs
new file mode 100644
index 0000000000000..a9f992ebd5c6f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-3974.rs
@@ -0,0 +1,10 @@
+fn emulate_foreign_item() {
+    match link_name {
+        // A comment here will duplicate the attribute
+        #[rustfmt::skip]
+        | "pthread_mutexattr_init"
+        | "pthread_mutexattr_settype"
+        | "pthread_mutex_init"
+        => {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4018.rs b/src/tools/rustfmt/tests/target/issue-4018.rs
new file mode 100644
index 0000000000000..cef3be061486f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4018.rs
@@ -0,0 +1,11 @@
+fn main() {
+    /* extra comment */
+}
+
+fn main() {
+    println!("");
+    // comment 1
+    // comment 2
+    // comment 3
+    // comment 4
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4020.rs b/src/tools/rustfmt/tests/target/issue-4020.rs
new file mode 100644
index 0000000000000..f29ecec028b77
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4020.rs
@@ -0,0 +1,9 @@
+// rustfmt-wrap_comments: true
+
+/** foobar */
+const foo1: u32 = 0;
+
+/**
+ * foobar
+ */
+const foo2: u32 = 0;
diff --git a/src/tools/rustfmt/tests/target/issue-4029.rs b/src/tools/rustfmt/tests/target/issue-4029.rs
new file mode 100644
index 0000000000000..314d018058857
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4029.rs
@@ -0,0 +1,7 @@
+// issue #4029
+#[derive(Debug, Clone, Default Hash)]
+struct S;
+
+// issue #3898
+#[derive(Debug, Clone, Default,, Hash)]
+struct T;
diff --git a/src/tools/rustfmt/tests/target/issue-4068.rs b/src/tools/rustfmt/tests/target/issue-4068.rs
new file mode 100644
index 0000000000000..cd8a1f2765f18
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4068.rs
@@ -0,0 +1,3 @@
+fn main() {
+    extern "C" fn packet_records_options_impl_layout_length_encoding_option_len_multiplier();
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4079.rs b/src/tools/rustfmt/tests/target/issue-4079.rs
new file mode 100644
index 0000000000000..1871c5b8a1338
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4079.rs
@@ -0,0 +1,11 @@
+// rustfmt-wrap_comments: true
+
+/*!
+ * Lorem ipsum dolor sit amet, consectetur adipiscing elit. In lacinia
+ * ullamcorper lorem, non hendrerit enim convallis ut. Curabitur id sem
+ * volutpat
+ */
+
+/*! Lorem ipsum dolor sit amet, consectetur adipiscing elit. In lacinia
+ * ullamcorper lorem, non hendrerit enim convallis ut. Curabitur id sem
+ * volutpat */
diff --git a/src/tools/rustfmt/tests/target/issue-4115.rs b/src/tools/rustfmt/tests/target/issue-4115.rs
new file mode 100644
index 0000000000000..0dd7bdbd04f00
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4115.rs
@@ -0,0 +1,8 @@
+#[derive(
+    A,
+    B,
+    C,
+    D,
+    // E,
+)]
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/issue-4120.rs b/src/tools/rustfmt/tests/target/issue-4120.rs
new file mode 100644
index 0000000000000..a7d461dcfdb5b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4120.rs
@@ -0,0 +1,85 @@
+fn main() {
+    let x = if true {
+        1
+        // In if
+    } else {
+        0
+        // In else
+    };
+
+    let x = if true {
+        1
+        /* In if */
+    } else {
+        0
+        /* In else */
+    };
+
+    let z = if true {
+        if true {
+            1
+
+            // In if level 2
+        } else {
+            2
+        }
+    } else {
+        3
+    };
+
+    let a = if true {
+        1
+    // In if
+    } else {
+        0
+        // In else
+    };
+
+    let a = if true {
+        1
+
+    // In if
+    } else {
+        0
+        // In else
+    };
+
+    let b = if true {
+        1
+
+    // In if
+    } else {
+        0
+        // In else
+    };
+
+    let c = if true {
+        1
+
+        // In if
+    } else {
+        0
+        // In else
+    };
+    for i in 0..2 {
+        println!("Something");
+        // In for
+    }
+
+    for i in 0..2 {
+        println!("Something");
+        /* In for */
+    }
+
+    extern "C" {
+        fn first();
+
+        // In foreign mod
+    }
+
+    extern "C" {
+        fn first();
+
+        /* In foreign mod */
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4152.rs b/src/tools/rustfmt/tests/target/issue-4152.rs
new file mode 100644
index 0000000000000..80f9ff5e30437
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4152.rs
@@ -0,0 +1,18 @@
+// rustfmt-hard_tabs: true
+
+macro_rules! bit {
+	($bool:expr) => {
+		if $bool {
+			1;
+			1
+		} else {
+			0;
+			0
+		}
+	};
+}
+macro_rules! add_one {
+	($vec:expr) => {{
+		$vec.push(1);
+	}};
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4159.rs b/src/tools/rustfmt/tests/target/issue-4159.rs
new file mode 100644
index 0000000000000..2f8cf20da2c9e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4159.rs
@@ -0,0 +1,18 @@
+extern "C" {
+    type A: Ord;
+
+    type A<'a>
+    where
+        'a: 'static;
+
+    type A<T: Ord>
+    where
+        T: 'static;
+
+    type A = u8;
+
+    type A<'a: 'static, T: Ord + 'static>: Eq + PartialEq
+    where
+        T: 'static + Copy,
+    = Vec<u8>;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4243.rs b/src/tools/rustfmt/tests/target/issue-4243.rs
new file mode 100644
index 0000000000000..67fa1d2a312fb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4243.rs
@@ -0,0 +1,28 @@
+fn main() {
+    type A: AA /*AA*/ + /*AB*/ AB + AC = AA
+        /*AA*/
+        +
+        /*AB*/
+        AB
+        + AC;
+
+    type B: BA /*BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA*/
+        + /*BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB*/ BB
+        + BC = BA /*BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA*/
+        + /*BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB*/ BB
+        + BC;
+
+    type C: CA // CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        // CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        +
+        // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        CB
+        + CC = CA // CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        // CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
+        +
+        // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        // CBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        CB
+        + CC;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4244.rs b/src/tools/rustfmt/tests/target/issue-4244.rs
new file mode 100644
index 0000000000000..8958ba99e80a7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4244.rs
@@ -0,0 +1,20 @@
+pub struct SS {}
+
+pub type A /* A Comment */ = SS;
+
+pub type B // Comment
+    // B
+    = SS;
+
+pub type C
+    /* Comment C */
+    = SS;
+
+pub trait D<T> {
+    type E /* Comment E */ = SS;
+}
+
+type F<'a: 'static, T: Ord + 'static>: Eq + PartialEq
+where
+    T: 'static + Copy, /* x */
+= Vec<u8>;
diff --git a/src/tools/rustfmt/tests/target/issue-4245.rs b/src/tools/rustfmt/tests/target/issue-4245.rs
new file mode 100644
index 0000000000000..e3d40eb426748
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4245.rs
@@ -0,0 +1,34 @@
+fn a(
+    a: & // Comment
+    // Another comment
+    'a File,
+) {
+}
+
+fn b(b: & /* Another Comment */ 'a File) {}
+
+fn c(c: &'a /*Comment */ mut /*Comment */ File) {}
+
+fn d(
+    c: & // Comment
+    'b // Multi Line
+    // Comment
+    mut // Multi Line
+    // Comment
+    File,
+) {
+}
+
+fn e(
+    c: & // Comment
+    File,
+) {
+}
+
+fn d(
+    c: & // Comment
+    mut // Multi Line
+    // Comment
+    File,
+) {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4310.rs b/src/tools/rustfmt/tests/target/issue-4310.rs
new file mode 100644
index 0000000000000..6cf494fc5b83f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4310.rs
@@ -0,0 +1,9 @@
+#![feature(const_generics)]
+
+fn foo<
+    const N: [u8; {
+        struct Inner<'a>(&'a ());
+        3
+    }],
+>() {
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4312.rs b/src/tools/rustfmt/tests/target/issue-4312.rs
new file mode 100644
index 0000000000000..b36b0efdb9e29
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4312.rs
@@ -0,0 +1,22 @@
+// issue 4312
+fn main() {
+    /* " */
+    println!("Hello, world!");
+    /* abc " */
+    println!("Hello, world!");
+    /* " abc */
+    println!("Hello, world!");
+    let y = 4;
+    let x = match 1 + y == 3 {
+        True => 3,
+        False => 4,
+        /* " unreachable */
+    };
+}
+
+// issue 4806
+enum X {
+    A,
+    B,
+    /*"*/
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4313.rs b/src/tools/rustfmt/tests/target/issue-4313.rs
new file mode 100644
index 0000000000000..c390ee6ba30fa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4313.rs
@@ -0,0 +1,5 @@
+extern "C" {
+    fn f() {
+        fn g() {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4382.rs b/src/tools/rustfmt/tests/target/issue-4382.rs
new file mode 100644
index 0000000000000..740fa9bfe0a87
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4382.rs
@@ -0,0 +1,10 @@
+pub const NAME_MAX: usize = {
+    #[cfg(target_os = "linux")]
+    {
+        1024
+    }
+    #[cfg(target_os = "freebsd")]
+    {
+        255
+    }
+};
diff --git a/src/tools/rustfmt/tests/target/issue-4398.rs b/src/tools/rustfmt/tests/target/issue-4398.rs
new file mode 100644
index 0000000000000..2ca894528e99b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4398.rs
@@ -0,0 +1,19 @@
+impl Struct {
+    /// Documentation for `foo`
+    #[rustfmt::skip] // comment on why use a skip here
+    pub fn foo(&self) {}
+}
+
+impl Struct {
+    /// Documentation for `foo`
+    #[rustfmt::skip] // comment on why use a skip here
+    pub fn foo(&self) {}
+}
+
+/// Documentation for `Struct`
+#[rustfmt::skip] // comment
+impl Struct {
+    /// Documentation for `foo`
+       #[rustfmt::skip] // comment on why use a skip here
+    pub fn foo(&self) {}
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4427.rs b/src/tools/rustfmt/tests/target/issue-4427.rs
new file mode 100644
index 0000000000000..c8a37ead8cb29
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4427.rs
@@ -0,0 +1,30 @@
+const A: usize =
+    // Some constant
+    2;
+
+const B: usize =
+    /* constant */
+    3;
+
+const C: usize = /* foo */ 5;
+
+const D: usize = // baz
+    /*    Some constant */
+    /* ba */
+    {
+        3
+        // foo
+    };
+const E: usize = /* foo */ 5;
+const F: usize = { 7 };
+const G: usize =
+    /* foooooooooooooooooooooooooooooooooooooooooooooooooooooooo0000000000000000xx00 */
+    5;
+const H: usize = /* asdfasdf */
+    match G > 1 {
+        true => 1,
+        false => 3,
+    };
+
+pub static FOO_BAR: Vec<u8> = //f
+    { vec![] };
diff --git a/src/tools/rustfmt/tests/target/issue-447.rs b/src/tools/rustfmt/tests/target/issue-447.rs
new file mode 100644
index 0000000000000..d41cdb65cd0a9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-447.rs
@@ -0,0 +1,40 @@
+// rustfmt-normalize_comments: true
+
+fn main() {
+    if
+    // shouldn't be dropped
+    // shouldn't be dropped
+    cond
+    // shouldn't be dropped
+    // shouldn't be dropped
+    {
+    }
+    // shouldn't be dropped
+    // shouldn't be dropped
+    else
+    // shouldn't be dropped
+    // shouldn't be dropped
+    if
+    // shouldn't be dropped
+    // shouldn't be dropped
+    cond
+    // shouldn't be dropped
+    // shouldn't be dropped
+    {
+    }
+    // shouldn't be dropped
+    // shouldn't be dropped
+    else
+    // shouldn't be dropped
+    // shouldn't be dropped
+    {
+    }
+
+    if
+    // shouldn't be dropped
+    // shouldn't be dropped
+    let Some(x) = y
+    // shouldn't be dropped
+    // shouldn't be dropped
+    {}
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4577.rs b/src/tools/rustfmt/tests/target/issue-4577.rs
new file mode 100644
index 0000000000000..1bd9eb6b80608
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4577.rs
@@ -0,0 +1,15 @@
+fn main() {
+    let s: String = "ABAABBAA"
+        .chars()
+        .filter(|c| if *c == 'A' { true } else { false })
+        .map(|c| -> char {
+            if c == 'A' {
+                '0'
+            } else {
+                '1'
+            }
+        })
+        .collect();
+
+    println!("{}", s);
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4603.rs b/src/tools/rustfmt/tests/target/issue-4603.rs
new file mode 100644
index 0000000000000..e8c368a247fd8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4603.rs
@@ -0,0 +1,47 @@
+// Formatting when original macro snippet is used
+
+// Original issue #4603 code
+#![feature(or_patterns)]
+macro_rules! t_or_f {
+    () => {
+        (true // some comment
+        | false)
+    };
+}
+
+// Other test cases variations
+macro_rules! RULES {
+    () => {
+        (
+		xxxxxxx // COMMENT
+        | yyyyyyy
+        )
+    };
+}
+macro_rules! RULES {
+    () => {
+        (xxxxxxx // COMMENT
+            | yyyyyyy)
+    };
+}
+
+fn main() {
+    macro_rules! RULES {
+		() => {
+			(xxxxxxx // COMMENT
+			| yyyyyyy)
+		};
+	}
+}
+
+macro_rules! RULES {
+    () => {
+        (xxxxxxx /* COMMENT */ | yyyyyyy)
+    };
+}
+macro_rules! RULES {
+    () => {
+        (xxxxxxx /* COMMENT */
+        | yyyyyyy)
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4646.rs b/src/tools/rustfmt/tests/target/issue-4646.rs
new file mode 100644
index 0000000000000..4e149399f062d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4646.rs
@@ -0,0 +1,20 @@
+trait Foo {
+    fn bar(&self)
+    // where
+    //     Self: Bar
+    ;
+}
+
+trait Foo {
+    fn bar(&self)
+    // where
+    //     Self: Bar
+    ;
+}
+
+trait Foo {
+    fn bar(&self)
+    // where
+    //     Self: Bar
+    ;
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4656/format_me_please.rs b/src/tools/rustfmt/tests/target/issue-4656/format_me_please.rs
new file mode 100644
index 0000000000000..421e195a2fbd9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4656/format_me_please.rs
@@ -0,0 +1 @@
+pub fn hello() {}
diff --git a/src/tools/rustfmt/tests/target/issue-4656/lib.rs b/src/tools/rustfmt/tests/target/issue-4656/lib.rs
new file mode 100644
index 0000000000000..5dac91b8aab2c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4656/lib.rs
@@ -0,0 +1,7 @@
+extern crate cfg_if;
+
+cfg_if::cfg_if! {
+    if #[cfg(target_family = "unix")] {
+        mod format_me_please;
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-4656/lib2.rs b/src/tools/rustfmt/tests/target/issue-4656/lib2.rs
new file mode 100644
index 0000000000000..b17fffc58e1dd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-4656/lib2.rs
@@ -0,0 +1,3 @@
+its_a_macro! {
+    // Contents
+}
diff --git a/src/tools/rustfmt/tests/target/issue-510.rs b/src/tools/rustfmt/tests/target/issue-510.rs
new file mode 100644
index 0000000000000..a166b68498fa0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-510.rs
@@ -0,0 +1,41 @@
+impl ISizeAndMarginsComputer for AbsoluteNonReplaced {
+    fn solve_inline_size_constraints(
+        &self,
+        block: &mut BlockFlow,
+        input: &ISizeConstraintInput,
+    ) -> ISizeConstraintSolution {
+        let (inline_start, inline_size, margin_inline_start, margin_inline_end) = match (
+            inline_startssssssxxxxxxsssssxxxxxxxxxssssssxxx,
+            inline_startssssssxxxxxxsssssxxxxxxxxxssssssxxx,
+        ) {
+            (MaybeAuto::Auto, MaybeAuto::Auto, MaybeAuto::Auto) => {
+                let margin_start = inline_start_margin.specified_or_zero();
+                let margin_end = inline_end_margin.specified_or_zero();
+                // Now it is the same situation as inline-start Specified and inline-end
+                // and inline-size Auto.
+                //
+                // Set inline-end to zero to calculate inline-size.
+                let inline_size = block.get_shrink_to_fit_inline_size(
+                    available_inline_size - (margin_start + margin_end),
+                );
+                (Au(0), inline_size, margin_start, margin_end)
+            }
+        };
+
+        let (inline_start, inline_size, margin_inline_start, margin_inline_end) =
+            match (inline_start, inline_end, computed_inline_size) {
+                (MaybeAuto::Auto, MaybeAuto::Auto, MaybeAuto::Auto) => {
+                    let margin_start = inline_start_margin.specified_or_zero();
+                    let margin_end = inline_end_margin.specified_or_zero();
+                    // Now it is the same situation as inline-start Specified and inline-end
+                    // and inline-size Auto.
+                    //
+                    // Set inline-end to zero to calculate inline-size.
+                    let inline_size = block.get_shrink_to_fit_inline_size(
+                        available_inline_size - (margin_start + margin_end),
+                    );
+                    (Au(0), inline_size, margin_start, margin_end)
+                }
+            };
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-539.rs b/src/tools/rustfmt/tests/target/issue-539.rs
new file mode 100644
index 0000000000000..adeb33555fb5c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-539.rs
@@ -0,0 +1,3 @@
+// rustfmt-normalize_comments: true
+// FIXME (#3300): Should allow items to be anonymous. Right now
+// we just use dummy names for anon items.
diff --git a/src/tools/rustfmt/tests/target/issue-64.rs b/src/tools/rustfmt/tests/target/issue-64.rs
new file mode 100644
index 0000000000000..c0660630203af
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-64.rs
@@ -0,0 +1,7 @@
+// Regression test for issue 64
+
+pub fn header_name<T: Header>() -> &'static str {
+    let name = <T as Header>::header_name();
+    let func = <T as Header>::header_name;
+    name
+}
diff --git a/src/tools/rustfmt/tests/target/issue-683.rs b/src/tools/rustfmt/tests/target/issue-683.rs
new file mode 100644
index 0000000000000..adeb33555fb5c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-683.rs
@@ -0,0 +1,3 @@
+// rustfmt-normalize_comments: true
+// FIXME (#3300): Should allow items to be anonymous. Right now
+// we just use dummy names for anon items.
diff --git a/src/tools/rustfmt/tests/target/issue-691.rs b/src/tools/rustfmt/tests/target/issue-691.rs
new file mode 100644
index 0000000000000..7473d070eff21
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-691.rs
@@ -0,0 +1,9 @@
+// rustfmt-normalize_comments: true
+
+//! `std` or `core` and simply link to this library. In case the target
+//! platform has no hardware
+//! support for some operation, software implementations provided by this
+//! library will be used automagically.
+// TODO: provide instructions to override default libm link and how to link to
+// this library.
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/issue-770.rs b/src/tools/rustfmt/tests/target/issue-770.rs
new file mode 100644
index 0000000000000..5fbedd7b7345c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-770.rs
@@ -0,0 +1,10 @@
+fn main() {
+    if false {
+        if false {
+        } else {
+            // A let binding here seems necessary to trigger it.
+            let _ = ();
+        }
+    } else if let false = false {
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-811.rs b/src/tools/rustfmt/tests/target/issue-811.rs
new file mode 100644
index 0000000000000..b7a89b5d0f9dc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-811.rs
@@ -0,0 +1,19 @@
+trait FooTrait<T>: Sized {
+    type Bar: BarTrait<T>;
+}
+
+trait BarTrait<T>: Sized {
+    type Baz;
+    fn foo();
+}
+
+type Foo<T: FooTrait> = <<T as FooTrait<U>>::Bar as BarTrait<U>>::Baz;
+type Bar<T: BarTrait> = <T as BarTrait<U>>::Baz;
+
+fn some_func<T: FooTrait<U>, U>() {
+    <<T as FooTrait<U>>::Bar as BarTrait<U>>::foo();
+}
+
+fn some_func<T: BarTrait<U>>() {
+    <T as BarTrait<U>>::foo();
+}
diff --git a/src/tools/rustfmt/tests/target/issue-831.rs b/src/tools/rustfmt/tests/target/issue-831.rs
new file mode 100644
index 0000000000000..1d6327c215806
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-831.rs
@@ -0,0 +1,9 @@
+fn main() {
+    let y = a.iter().any(|x| {
+        println!("a");
+    }) || b.iter().any(|x| {
+        println!("b");
+    }) || c.iter().any(|x| {
+        println!("c");
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/issue-850.rs b/src/tools/rustfmt/tests/target/issue-850.rs
new file mode 100644
index 0000000000000..c939716a6a881
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-850.rs
@@ -0,0 +1 @@
+const unsafe fn x() {}
diff --git a/src/tools/rustfmt/tests/target/issue-855.rs b/src/tools/rustfmt/tests/target/issue-855.rs
new file mode 100644
index 0000000000000..0430cc6295485
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-855.rs
@@ -0,0 +1,27 @@
+fn main() {
+    'running: loop {
+        for event in event_pump.poll_iter() {
+            match event {
+                Event::Quit { .. }
+                | Event::KeyDown {
+                    keycode: Some(Keycode::Escape),
+                    ..
+                } => break 'running,
+            }
+        }
+    }
+}
+
+fn main2() {
+    'running: loop {
+        for event in event_pump.poll_iter() {
+            match event {
+                Event::Quit { .. }
+                | Event::KeyDownXXXXXXXXXXXXX {
+                    keycode: Some(Keycode::Escape),
+                    ..
+                } => break 'running,
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-913.rs b/src/tools/rustfmt/tests/target/issue-913.rs
new file mode 100644
index 0000000000000..a2b5800a74518
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-913.rs
@@ -0,0 +1,22 @@
+mod client {
+    impl Client {
+        fn test(self) -> Result<()> {
+            let next_state = match self.state {
+                State::V5(v5::State::Command(v5::coand::State::WriteVersion(ref mut response))) => {
+                    let x = reformat.meeee();
+                }
+            };
+
+            let next_state = match self.state {
+                State::V5(v5::State::Command(v5::comand::State::WriteVersion(
+                    ref mut response,
+                ))) => {
+                    // The pattern cannot be formatted in a way that the match stays
+                    // within the column limit. The rewrite should therefore be
+                    // skipped.
+                    let x = dont.reformat.meeee();
+                }
+            };
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-945.rs b/src/tools/rustfmt/tests/target/issue-945.rs
new file mode 100644
index 0000000000000..d46c69a4f0934
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-945.rs
@@ -0,0 +1,17 @@
+impl Bar {
+    default const unsafe fn foo() {
+        "hi"
+    }
+}
+
+impl Baz {
+    default unsafe extern "C" fn foo() {
+        "hi"
+    }
+}
+
+impl Foo for Bar {
+    default fn foo() {
+        "hi"
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue-977.rs b/src/tools/rustfmt/tests/target/issue-977.rs
new file mode 100644
index 0000000000000..3784a3874503b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue-977.rs
@@ -0,0 +1,16 @@
+// rustfmt-normalize_comments: true
+
+trait NameC {
+    // comment
+}
+struct FooC {
+    // comment
+}
+enum MooC {
+    // comment
+}
+mod BarC { // comment
+}
+extern "C" {
+    // comment
+}
diff --git a/src/tools/rustfmt/tests/target/issue_3839.rs b/src/tools/rustfmt/tests/target/issue_3839.rs
new file mode 100644
index 0000000000000..b7bdf4c7579f6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_3839.rs
@@ -0,0 +1,8 @@
+struct Foo {
+    a: i32,
+    /*
+    asd
+    */
+    // foo
+    b: i32,
+}
diff --git a/src/tools/rustfmt/tests/target/issue_3844.rs b/src/tools/rustfmt/tests/target/issue_3844.rs
new file mode 100644
index 0000000000000..81d2083463e0e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_3844.rs
@@ -0,0 +1,3 @@
+fn main() {
+    || {};
+}
diff --git a/src/tools/rustfmt/tests/target/issue_3853.rs b/src/tools/rustfmt/tests/target/issue_3853.rs
new file mode 100644
index 0000000000000..eae59eff94e56
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_3853.rs
@@ -0,0 +1,47 @@
+fn by_ref_with_block_before_ident() {
+    if let Some(ref /*def*/ state) = foo {
+        println!("asdfasdfasdf");
+    }
+}
+
+fn mut_block_before_ident() {
+    if let Some(mut /*def*/ state) = foo {
+        println!("123");
+    }
+}
+
+fn ref_and_mut_blocks_before_ident() {
+    if let Some(ref /*abc*/ mut /*def*/ state) = foo {
+        println!("deefefefefefwea");
+    }
+}
+
+fn sub_pattern() {
+    let foo @ /*foo*/ bar(f) = 42;
+}
+
+fn no_prefix_block_before_ident() {
+    if let Some(/*def*/ state) = foo {
+        println!("129387123123");
+    }
+}
+
+fn issue_3853() {
+    if let Some(ref /*mut*/ state) = foo {}
+}
+
+fn double_slash_comment_between_lhs_and_rhs() {
+    if let Some(e) =
+        // self.foo.bar(e, tx)
+        packet.transaction.state.committed
+    {
+        // body
+        println!("a2304712836123");
+    }
+}
+
+fn block_comment_between_lhs_and_rhs() {
+    if let Some(ref /*def*/ mut /*abc*/ state) = /*abc*/ foo {
+        println!("asdfasdfasdf");
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue_3854.rs b/src/tools/rustfmt/tests/target/issue_3854.rs
new file mode 100644
index 0000000000000..3051335c27dab
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_3854.rs
@@ -0,0 +1,3 @@
+fn main() {
+    println!("{:?}", -1. ..1.);
+}
diff --git a/src/tools/rustfmt/tests/target/issue_3868.rs b/src/tools/rustfmt/tests/target/issue_3868.rs
new file mode 100644
index 0000000000000..067241359287b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_3868.rs
@@ -0,0 +1,9 @@
+fn foo() {}
+
+fn bar() {
+    for _ in 0..1 {}
+}
+
+fn baz() {
+    ();
+}
diff --git a/src/tools/rustfmt/tests/target/issue_3934.rs b/src/tools/rustfmt/tests/target/issue_3934.rs
new file mode 100644
index 0000000000000..68f9fd0aeca0d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_3934.rs
@@ -0,0 +1,8 @@
+mod repro {
+    pub fn push() -> Result<(), ()> {
+        self.api.map_api_result(|api| {
+            #[allow(deprecated)]
+            match api.apply_extrinsic_before_version_4_with_context()? {}
+        })
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4049.rs b/src/tools/rustfmt/tests/target/issue_4049.rs
new file mode 100644
index 0000000000000..fe025a0f64946
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4049.rs
@@ -0,0 +1,26 @@
+// rustfmt-max_width: 110
+// rustfmt-use_small_heuristics: Max
+// rustfmt-hard_tabs: true
+// rustfmt-use_field_init_shorthand: true
+// rustfmt-overflow_delimited_expr: true
+
+// https://github.com/rust-lang/rustfmt/issues/4049
+fn foo() {
+	{
+		{
+			if let Some(MpcEv::PlayDrum(pitch, vel)) =
+				// self.mpc.handle_input(e, /*btn_ctrl_down,*/ tx_launch_to_daw, state_view)
+				self.mpc.handle_input(e, &mut MyBorrowedState { tx_launch_to_daw, state_view })
+			{
+				println!("bar");
+			}
+
+			if let Some(e) =
+				// self.note_input.handle_input(e, /*btn_ctrl_down,*/ tx_launch_to_daw, state_view)
+				self.note_input.handle_input(e, &mut MyBorrowedState { tx_launch_to_daw, state_view })
+			{
+				println!("baz");
+			}
+		}
+	}
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4057.rs b/src/tools/rustfmt/tests/target/issue_4057.rs
new file mode 100644
index 0000000000000..467e67bca7c3c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4057.rs
@@ -0,0 +1,15 @@
+// rustfmt-format_code_in_doc_comments: true
+
+/// ```
+/// # #[rustversion::since(1.36)]
+/// # fn dox() {
+/// # use std::pin::Pin;
+/// # type Projection<'a> = &'a ();
+/// # type ProjectionRef<'a> = &'a ();
+/// # trait Dox {
+/// fn project_ex(self: Pin<&mut Self>) -> Projection<'_>;
+/// fn project_ref(self: Pin<&Self>) -> ProjectionRef<'_>;
+/// # }
+/// # }
+/// ```
+struct Foo;
diff --git a/src/tools/rustfmt/tests/target/issue_4086.rs b/src/tools/rustfmt/tests/target/issue_4086.rs
new file mode 100644
index 0000000000000..959d3b3d4682a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4086.rs
@@ -0,0 +1,2 @@
+#[cfg(any())]
+extern "C++" {}
diff --git a/src/tools/rustfmt/tests/target/issue_4374.rs b/src/tools/rustfmt/tests/target/issue_4374.rs
new file mode 100644
index 0000000000000..f5bf657bbc000
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4374.rs
@@ -0,0 +1,13 @@
+fn a<F>(_f: F) -> ()
+where
+    F: FnOnce() -> (),
+{
+}
+fn main() {
+    a(|| {
+        #[allow(irrefutable_let_patterns)]
+        while let _ = 0 {
+            break;
+        }
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4467.rs b/src/tools/rustfmt/tests/target/issue_4467.rs
new file mode 100644
index 0000000000000..f5ee96c4c148c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4467.rs
@@ -0,0 +1,6 @@
+pub fn main() {
+    #[cfg(feature = "std")]
+    {
+        // Comment
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4475.rs b/src/tools/rustfmt/tests/target/issue_4475.rs
new file mode 100644
index 0000000000000..ea6726c5a01d8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4475.rs
@@ -0,0 +1,29 @@
+fn main() {
+    #[cfg(debug_assertions)]
+    {
+        println!("DEBUG");
+    }
+}
+
+fn main() {
+    #[cfg(feature = "foo")]
+    {
+        /*
+        let foo = 0
+        */
+    }
+}
+
+fn main() {
+    #[cfg(feature = "foo")]
+    { /* let foo = 0; */ }
+}
+
+fn main() {
+    #[foo]
+    #[bar]
+    #[baz]
+    {
+        // let foo = 0;
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4522.rs b/src/tools/rustfmt/tests/target/issue_4522.rs
new file mode 100644
index 0000000000000..5ca70e1c090c3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4522.rs
@@ -0,0 +1,6 @@
+fn main() {
+    #[cfg(feature = "foo")]
+    {
+        // let foo = 0;
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4528.rs b/src/tools/rustfmt/tests/target/issue_4528.rs
new file mode 100644
index 0000000000000..7828804b098ea
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4528.rs
@@ -0,0 +1,8 @@
+#![allow(clippy::no_effect)]
+
+extern "C" {
+    // N.B., mutability can be easily incorrect in FFI calls -- as
+    // in C, the default is mutable pointers.
+    fn ffi(c: *mut u8);
+    fn int_ffi(c: *mut i32);
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4545.rs b/src/tools/rustfmt/tests/target/issue_4545.rs
new file mode 100644
index 0000000000000..f87c810365779
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4545.rs
@@ -0,0 +1,5 @@
+#[derive(Debug, Foo<T>)]
+enum Bar {}
+
+#[derive(Debug, , Default)]
+struct Struct(i32);
diff --git a/src/tools/rustfmt/tests/target/issue_4584.rs b/src/tools/rustfmt/tests/target/issue_4584.rs
new file mode 100644
index 0000000000000..20255beadb2c3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4584.rs
@@ -0,0 +1,32 @@
+// rustfmt-indent_style: Visual
+
+#[derive(Debug)]
+pub enum Case {
+    Upper,
+    Lower,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum Case {
+    Upper,
+    Lower,
+}
+
+// NB - This formatting looks potentially off the desired state, but is
+// consistent with current behavior. Included here to provide a line wrapped
+// derive case with the changes applied to resolve issue #4584
+#[derive(Add,
+           Sub,
+           Mul,
+           Div,
+           Clone,
+           Copy,
+           Eq,
+           PartialEq,
+           Ord,
+           PartialOrd,
+           Debug,
+           Hash,
+           Serialize,
+           Mul)]
+struct Foo {}
diff --git a/src/tools/rustfmt/tests/target/issue_4636.rs b/src/tools/rustfmt/tests/target/issue_4636.rs
new file mode 100644
index 0000000000000..a6465e29a0201
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4636.rs
@@ -0,0 +1,13 @@
+pub trait PrettyPrinter<'tcx>:
+    Printer<
+        'tcx,
+        Error = fmt::Error,
+        Path = Self,
+        Region = Self,
+        Type = Self,
+        DynExistential = Self,
+        Const = Self,
+    > + fmt::Write
+{
+    //
+}
diff --git a/src/tools/rustfmt/tests/target/issue_4675.rs b/src/tools/rustfmt/tests/target/issue_4675.rs
new file mode 100644
index 0000000000000..a65f86832eefd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/issue_4675.rs
@@ -0,0 +1,8 @@
+macro_rules! foo {
+    ($s:ident ( $p:pat )) => {
+        Foo {
+            name: Name::$s($p),
+            ..
+        }
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/item-brace-style-always-next-line.rs b/src/tools/rustfmt/tests/target/item-brace-style-always-next-line.rs
new file mode 100644
index 0000000000000..531ac59868314
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/item-brace-style-always-next-line.rs
@@ -0,0 +1,42 @@
+// rustfmt-brace_style: AlwaysNextLine
+
+mod M
+{
+    enum A
+    {
+        A,
+    }
+
+    struct B
+    {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C {}
+
+    struct D {}
+
+    enum A<T>
+    where
+        T: Copy,
+    {
+        A,
+    }
+
+    struct B<T>
+    where
+        T: Copy,
+    {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C<T>
+    where
+        T: Copy, {}
+
+    struct D<T>
+    where
+        T: Copy, {}
+}
diff --git a/src/tools/rustfmt/tests/target/item-brace-style-prefer-same-line.rs b/src/tools/rustfmt/tests/target/item-brace-style-prefer-same-line.rs
new file mode 100644
index 0000000000000..ef8dc028c2d01
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/item-brace-style-prefer-same-line.rs
@@ -0,0 +1,35 @@
+// rustfmt-brace_style: PreferSameLine
+
+mod M {
+    enum A {
+        A,
+    }
+
+    struct B {
+        b: i32,
+    }
+
+    enum C {}
+
+    struct D {}
+
+    enum A<T>
+    where
+        T: Copy, {
+        A,
+    }
+
+    struct B<T>
+    where
+        T: Copy, {
+        b: i32,
+    }
+
+    enum C<T>
+    where
+        T: Copy, {}
+
+    struct D<T>
+    where
+        T: Copy, {}
+}
diff --git a/src/tools/rustfmt/tests/target/item-brace-style-same-line-where.rs b/src/tools/rustfmt/tests/target/item-brace-style-same-line-where.rs
new file mode 100644
index 0000000000000..fabe5822c89c8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/item-brace-style-same-line-where.rs
@@ -0,0 +1,37 @@
+mod M {
+    enum A {
+        A,
+    }
+
+    struct B {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C {}
+
+    struct D {}
+
+    enum A<T>
+    where
+        T: Copy,
+    {
+        A,
+    }
+
+    struct B<T>
+    where
+        T: Copy,
+    {
+        b: i32,
+    }
+
+    // For empty enums and structs, the brace remains on the same line.
+    enum C<T>
+    where
+        T: Copy, {}
+
+    struct D<T>
+    where
+        T: Copy, {}
+}
diff --git a/src/tools/rustfmt/tests/target/itemized-blocks/no_wrap.rs b/src/tools/rustfmt/tests/target/itemized-blocks/no_wrap.rs
new file mode 100644
index 0000000000000..de88563827263
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/itemized-blocks/no_wrap.rs
@@ -0,0 +1,47 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_code_in_doc_comments: true
+
+//! This is a list:
+//!  * Outer
+//!  * Outer
+//!   * Inner
+//!   * Inner with lots of text so that it could be reformatted something something something lots of text so that it could be reformatted something something something
+//!
+//! This example shows how to configure fern to output really nicely colored logs
+//! - when the log level is error, the whole line is red
+//! - when the log level is warn, the whole line is yellow
+//! - when the log level is info, the level name is green and the rest of the line is white
+//! - when the log level is debug, the whole line is white
+//! - when the log level is trace, the whole line is gray ("bright black")
+
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor
+fn func1() {}
+
+/// All the parameters ***except for `from_theater`*** should be inserted as sent by the remote
+/// theater, i.e., as passed to [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+/// ```
+/// let x = 42;
+/// ```
+fn func2() {}
+
+/// Look:
+///
+/// ```
+/// let x = 42;
+/// ```
+///  * `from` is the sending (remote) [`ActorId`], as reported by the remote theater by theater-specific means
+///  * `to` is the receiving (local) [`ActorId`], as requested by the remote theater
+///  * `tag` is a tag that identifies the message type
+///  * `msg` is the (serialized) message
+fn func3() {}
diff --git a/src/tools/rustfmt/tests/target/itemized-blocks/rewrite_fail.rs b/src/tools/rustfmt/tests/target/itemized-blocks/rewrite_fail.rs
new file mode 100644
index 0000000000000..a118ef6faa184
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/itemized-blocks/rewrite_fail.rs
@@ -0,0 +1,14 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 50
+
+// This example shows how to configure fern to
+// output really nicely colored logs
+// - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+//   - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+//     - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+//     - when the log level is info, the level
+//       name is green and the rest of the line is
+//       white
+//   - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+//   - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+fn func1() {}
diff --git a/src/tools/rustfmt/tests/target/itemized-blocks/urls.rs b/src/tools/rustfmt/tests/target/itemized-blocks/urls.rs
new file mode 100644
index 0000000000000..bc46ea47e164f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/itemized-blocks/urls.rs
@@ -0,0 +1,25 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 79
+
+//! CMSIS: Cortex Microcontroller Software Interface Standard
+//!
+//! The version 5 of the standard can be found at:
+//!
+//! http://arm-software.github.io/CMSIS_5/Core/html/index.html
+//!
+//! The API reference of the standard can be found at:
+//!
+//! - example -- http://example.org -- something something something something
+//!   something something
+//! - something something something something something something more -- http://example.org
+//! - http://example.org/something/something/something/something/something/something
+//!   and the rest
+//! - Core function access -- http://arm-software.github.io/CMSIS_5/Core/html/group__Core__Register__gr.html
+//! - Intrinsic functions for CPU instructions -- http://arm-software.github.io/CMSIS_5/Core/html/group__intrinsic__CPU__gr.html
+//! - Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Vestibulum sem
+//!   lacus, commodo vitae.
+//!
+//! The reference C implementation used as the base of this Rust port can be
+//! found at
+//!
+//! https://github.com/ARM-software/CMSIS_5/blob/5.3.0/CMSIS/Core/Include/cmsis_gcc.h
diff --git a/src/tools/rustfmt/tests/target/itemized-blocks/wrap.rs b/src/tools/rustfmt/tests/target/itemized-blocks/wrap.rs
new file mode 100644
index 0000000000000..a4907303c9e1b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/itemized-blocks/wrap.rs
@@ -0,0 +1,89 @@
+// rustfmt-wrap_comments: true
+// rustfmt-format_code_in_doc_comments: true
+// rustfmt-max_width: 50
+
+//! This is a list:
+//!  * Outer
+//!  * Outer
+//!   * Inner
+//!   * Inner with lots of text so that it could
+//!     be reformatted something something
+//!     something lots of text so that it could be
+//!     reformatted something something something
+//!
+//! This example shows how to configure fern to
+//! output really nicely colored logs
+//! - when the log level is error, the whole line
+//!   is red
+//! - when the log level is warn, the whole line
+//!   is yellow
+//! - when the log level is info, the level name
+//!   is green and the rest of the line is white
+//! - when the log level is debug, the whole line
+//!   is white
+//! - when the log level is trace, the whole line
+//!   is gray ("bright black")
+
+// This example shows how to configure fern to
+// output really nicely colored logs
+// - when the log level is error, the whole line
+//   is red
+//   - when the log level is warn, the whole line
+//     is yellow
+//     - when the log level is info, the level
+//       name is green and the rest of the line is
+//       white
+//   - when the log level is debug, the whole line
+//     is white
+//   - when the log level is trace, the whole line
+//     is gray ("bright black")
+
+/// All the parameters ***except for
+/// `from_theater`*** should be inserted as sent
+/// by the remote theater, i.e., as passed to
+/// [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`],
+///    as reported by the remote theater by
+///    theater-specific means
+///  * `to` is the receiving (local) [`ActorId`],
+///    as requested by the remote theater
+///  * `tag` is a tag that identifies the message
+///    type
+///  * `msg` is the (serialized) message
+/// All the parameters ***except for
+/// `from_theater`*** should be inserted as sent
+/// by the remote theater, i.e., as passed to
+/// [`Theater::send`] on the remote actor
+fn func1() {}
+
+/// All the parameters ***except for
+/// `from_theater`*** should be inserted as sent
+/// by the remote theater, i.e., as passed to
+/// [`Theater::send`] on the remote actor:
+///  * `from` is the sending (remote) [`ActorId`],
+///    as reported by the remote theater by
+///    theater-specific means
+///  * `to` is the receiving (local) [`ActorId`],
+///    as requested by the remote theater
+///  * `tag` is a tag that identifies the message
+///    type
+///  * `msg` is the (serialized) message
+/// ```
+/// let x = 42;
+/// ```
+fn func2() {}
+
+/// Look:
+///
+/// ```
+/// let x = 42;
+/// ```
+///  * `from` is the sending (remote) [`ActorId`],
+///    as reported by the remote theater by
+///    theater-specific means
+///  * `to` is the receiving (local) [`ActorId`],
+///    as requested by the remote theater
+///  * `tag` is a tag that identifies the message
+///    type
+///  * `msg` is the (serialized) message
+fn func3() {}
diff --git a/src/tools/rustfmt/tests/target/label_break.rs b/src/tools/rustfmt/tests/target/label_break.rs
new file mode 100644
index 0000000000000..728d78137c99e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/label_break.rs
@@ -0,0 +1,28 @@
+// format with label break value.
+fn main() {
+    'empty_block: {}
+
+    'block: {
+        do_thing();
+        if condition_not_met() {
+            break 'block;
+        }
+        do_next_thing();
+        if condition_not_met() {
+            break 'block;
+        }
+        do_last_thing();
+    }
+
+    let result = 'block: {
+        if foo() {
+            // comment
+            break 'block 1;
+        }
+        if bar() {
+            /* comment */
+            break 'block 2;
+        }
+        3
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/large-block.rs b/src/tools/rustfmt/tests/target/large-block.rs
new file mode 100644
index 0000000000000..09e9169f34085
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/large-block.rs
@@ -0,0 +1,5 @@
+fn issue1351() {
+    std_fmt_Arguments_new_v1_std_rt_begin_panic_fmt_sdfasfasdfasdf({
+        static __STATIC_FMTSTR: &'static [&'static str] = &[];
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/large_vec.rs b/src/tools/rustfmt/tests/target/large_vec.rs
new file mode 100644
index 0000000000000..95d1fc43c03e5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/large_vec.rs
@@ -0,0 +1,42 @@
+// See #1470.
+
+impl Environment {
+    pub fn new_root() -> Rc<RefCell<Environment>> {
+        let mut env = Environment::new();
+        let builtin_functions = &[
+            (
+                "println",
+                Function::NativeVoid(
+                    CallSign {
+                        num_params: 0,
+                        variadic: true,
+                        param_types: vec![],
+                    },
+                    native_println,
+                ),
+            ),
+            (
+                "run_http_server",
+                Function::NativeVoid(
+                    CallSign {
+                        num_params: 1,
+                        variadic: false,
+                        param_types: vec![Some(ConstraintType::Function)],
+                    },
+                    native_run_http_server,
+                ),
+            ),
+            (
+                "len",
+                Function::NativeReturning(
+                    CallSign {
+                        num_params: 1,
+                        variadic: false,
+                        param_types: vec![None],
+                    },
+                    native_len,
+                ),
+            ),
+        ];
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/lazy_static.rs b/src/tools/rustfmt/tests/target/lazy_static.rs
new file mode 100644
index 0000000000000..3625e0a5f5c1b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/lazy_static.rs
@@ -0,0 +1,49 @@
+// Format `lazy_static!`.
+
+lazy_static! {
+    static ref CONFIG_NAME_REGEX: regex::Regex =
+        regex::Regex::new(r"^## `([^`]+)`").expect("Failed creating configuration pattern");
+    static ref CONFIG_VALUE_REGEX: regex::Regex = regex::Regex::new(r#"^#### `"?([^`"]+)"?`"#)
+        .expect("Failed creating configuration value pattern");
+}
+
+// We need to be able to format `lazy_static!` without known syntax.
+lazy_static!(xxx, yyyy, zzzzz);
+
+lazy_static! {}
+
+// #2354
+lazy_static! {
+    pub static ref Sbase64_encode_string: ::lisp::LispSubrRef = {
+        let subr = ::remacs_sys::Lisp_Subr {
+            header: ::remacs_sys::Lisp_Vectorlike_Header {
+                size: ((::remacs_sys::PseudovecType::PVEC_SUBR as ::libc::ptrdiff_t)
+                    << ::remacs_sys::PSEUDOVECTOR_AREA_BITS),
+            },
+            function: self::Fbase64_encode_string as *const ::libc::c_void,
+            min_args: 1i16,
+            max_args: 2i16,
+            symbol_name: (b"base64-encode-string\x00").as_ptr() as *const ::libc::c_char,
+            intspec: ::std::ptr::null(),
+            doc: ::std::ptr::null(),
+            lang: ::remacs_sys::Lisp_Subr_Lang_Rust,
+        };
+        unsafe {
+            let ptr = ::remacs_sys::xmalloc(::std::mem::size_of::<::remacs_sys::Lisp_Subr>())
+                as *mut ::remacs_sys::Lisp_Subr;
+            ::std::ptr::copy_nonoverlapping(&subr, ptr, 1);
+            ::std::mem::forget(subr);
+            ::lisp::ExternalPtr::new(ptr)
+        }
+    };
+}
+
+lazy_static! {
+    static ref FOO: HashMap<
+        String,
+        (
+            &'static str,
+            fn(Foo) -> Result<Box<Bar>, Either<FooError, BarError>>
+        ),
+    > = HashMap::new();
+}
diff --git a/src/tools/rustfmt/tests/target/license-templates/empty_license_path.rs b/src/tools/rustfmt/tests/target/license-templates/empty_license_path.rs
new file mode 100644
index 0000000000000..950f103ed3922
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/license-templates/empty_license_path.rs
@@ -0,0 +1,5 @@
+// rustfmt-config: issue-3802.toml
+
+fn main() {
+    println!("Hello world!");
+}
diff --git a/src/tools/rustfmt/tests/target/license-templates/license.rs b/src/tools/rustfmt/tests/target/license-templates/license.rs
new file mode 100644
index 0000000000000..7169c7b257615
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/license-templates/license.rs
@@ -0,0 +1,6 @@
+// rustfmt-license_template_path: tests/license-template/lt.txt
+// Copyright 2019 The rustfmt developers.
+
+fn main() {
+    println!("Hello world!");
+}
diff --git a/src/tools/rustfmt/tests/target/long-fn-1/version_one.rs b/src/tools/rustfmt/tests/target/long-fn-1/version_one.rs
new file mode 100644
index 0000000000000..05f69953c26d7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/long-fn-1/version_one.rs
@@ -0,0 +1,29 @@
+// rustfmt-version: One
+// Tests that a function which is almost short enough, but not quite, gets
+// formatted correctly.
+
+impl Foo {
+    fn some_input(
+        &mut self,
+        input: Input,
+        input_path: Option<PathBuf>,
+    ) -> (Input, Option<PathBuf>) {
+    }
+
+    fn some_inpu(&mut self, input: Input, input_path: Option<PathBuf>) -> (Input, Option<PathBuf>) {
+    }
+}
+
+// #1843
+#[allow(non_snake_case)]
+pub extern "C" fn Java_com_exonum_binding_storage_indices_ValueSetIndexProxy_nativeContainsByHash(
+) -> bool {
+    false
+}
+
+// #3009
+impl Something {
+    fn my_function_name_is_way_to_long_but_used_as_a_case_study_or_an_example_its_fine(
+    ) -> Result<(), String> {
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/long-fn-1/version_two.rs b/src/tools/rustfmt/tests/target/long-fn-1/version_two.rs
new file mode 100644
index 0000000000000..32794bccde2e8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/long-fn-1/version_two.rs
@@ -0,0 +1,29 @@
+// rustfmt-version: Two
+// Tests that a function which is almost short enough, but not quite, gets
+// formatted correctly.
+
+impl Foo {
+    fn some_input(
+        &mut self,
+        input: Input,
+        input_path: Option<PathBuf>,
+    ) -> (Input, Option<PathBuf>) {
+    }
+
+    fn some_inpu(&mut self, input: Input, input_path: Option<PathBuf>) -> (Input, Option<PathBuf>) {
+    }
+}
+
+// #1843
+#[allow(non_snake_case)]
+pub extern "C" fn Java_com_exonum_binding_storage_indices_ValueSetIndexProxy_nativeContainsByHash()
+-> bool {
+    false
+}
+
+// #3009
+impl Something {
+    fn my_function_name_is_way_to_long_but_used_as_a_case_study_or_an_example_its_fine()
+    -> Result<(), String> {
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/long-match-arms-brace-newline.rs b/src/tools/rustfmt/tests/target/long-match-arms-brace-newline.rs
new file mode 100644
index 0000000000000..aeb384e7203ed
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/long-match-arms-brace-newline.rs
@@ -0,0 +1,15 @@
+// rustfmt-format_strings: true
+// rustfmt-max_width: 80
+// rustfmt-control_brace_style: AlwaysNextLine
+
+fn main() {
+    match x
+    {
+        aaaaaaaa::Bbbbb::Ccccccccccccc(_, Some(ref x))
+            if x == "aaaaaaaaaaa aaaaaaa aaaaaa" =>
+        {
+            Ok(())
+        }
+        _ => Err(x),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/long-use-statement-issue-3154.rs b/src/tools/rustfmt/tests/target/long-use-statement-issue-3154.rs
new file mode 100644
index 0000000000000..877241e3b6fdb
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/long-use-statement-issue-3154.rs
@@ -0,0 +1,3 @@
+// rustfmt-reorder_imports: false
+
+pub use self::super::super::super::root::mozilla::detail::StringClassFlags as nsTStringRepr_ClassFlags;
diff --git a/src/tools/rustfmt/tests/target/long_field_access.rs b/src/tools/rustfmt/tests/target/long_field_access.rs
new file mode 100644
index 0000000000000..349d2c2f639ba
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/long_field_access.rs
@@ -0,0 +1,4 @@
+fn f() {
+    block_flow.base.stacking_relative_position_of_display_port =
+        self.base.stacking_relative_position_of_display_port;
+}
diff --git a/src/tools/rustfmt/tests/target/loop.rs b/src/tools/rustfmt/tests/target/loop.rs
new file mode 100644
index 0000000000000..f669e7e2c584d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/loop.rs
@@ -0,0 +1,34 @@
+fn main() {
+    loop {
+        return some_val;
+    }
+
+    let x = loop {
+        do_forever();
+    };
+
+    'label: loop {
+        // Just comments
+    }
+
+    'a: while loooooooooooooooooooooooooooooooooong_variable_name + another_value > some_other_value
+    {
+    }
+
+    while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa > bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb {
+    }
+
+    while aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {
+    }
+
+    'b: for xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx in some_iter(arg1, arg2)
+    {
+        // do smth
+    }
+
+    while let Some(i) = x.find('s') {
+        x.update();
+        continue;
+        continue 'foo;
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/macro_not_expr.rs b/src/tools/rustfmt/tests/target/macro_not_expr.rs
new file mode 100644
index 0000000000000..45f85ff2c93e3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/macro_not_expr.rs
@@ -0,0 +1,7 @@
+macro_rules! test {
+    ($($t:tt)*) => {};
+}
+
+fn main() {
+    test!( a : B => c d );
+}
diff --git a/src/tools/rustfmt/tests/target/macro_rules.rs b/src/tools/rustfmt/tests/target/macro_rules.rs
new file mode 100644
index 0000000000000..97444aef40443
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/macro_rules.rs
@@ -0,0 +1,360 @@
+// rustfmt-format_macro_matchers: true
+
+macro_rules! m {
+    () => {};
+    ($x:ident) => {};
+    ($m1:ident, $m2:ident, $x:ident) => {};
+    ($($beginning:ident),*; $middle:ident; $($end:ident),*) => {};
+    (
+        $($beginning:ident),*;
+        $middle:ident;
+        $($end:ident),*;
+        $($beginning:ident),*;
+        $middle:ident;
+        $($end:ident),*
+    ) => {};
+    ($name:ident($($dol:tt $var:ident)*) $($body:tt)*) => {};
+    (
+        $($i:ident : $ty:ty, $def:expr, $stb:expr, $($dstring:tt),+);+ $(;)*
+        $($i:ident : $ty:ty, $def:expr, $stb:expr, $($dstring:tt),+);+ $(;)*
+    ) => {};
+    ($foo:tt foo[$attr:meta] $name:ident) => {};
+    ($foo:tt[$attr:meta] $name:ident) => {};
+    ($foo:tt &'a[$attr:meta] $name:ident) => {};
+    ($foo:tt foo #[$attr:meta] $name:ident) => {};
+    ($foo:tt #[$attr:meta] $name:ident) => {};
+    ($foo:tt &'a #[$attr:meta] $name:ident) => {};
+    ($x:tt foo bar foo bar foo bar $y:tt => x * y * z $z:tt, $($a:tt),*) => {};
+}
+
+macro_rules! impl_a_method {
+    ($n:ident($a:ident : $ta:ty) -> $ret:ty { $body:expr }) => {
+        fn $n($a: $ta) -> $ret {
+            $body
+        }
+        macro_rules! $n {
+            ($va: expr) => {
+                $n($va)
+            };
+        }
+    };
+    ($n:ident($a:ident : $ta:ty, $b:ident : $tb:ty) -> $ret:ty { $body:expr }) => {
+        fn $n($a: $ta, $b: $tb) -> $ret {
+            $body
+        }
+        macro_rules! $n {
+            ($va: expr,$vb: expr) => {
+                $n($va, $vb)
+            };
+        }
+    };
+    (
+        $n:ident($a:ident : $ta:ty, $b:ident : $tb:ty, $c:ident : $tc:ty) -> $ret:ty { $body:expr }
+    ) => {
+        fn $n($a: $ta, $b: $tb, $c: $tc) -> $ret {
+            $body
+        }
+        macro_rules! $n {
+            ($va: expr,$vb: expr,$vc: expr) => {
+                $n($va, $vb, $vc)
+            };
+        }
+    };
+    (
+        $n:ident($a:ident : $ta:ty, $b:ident : $tb:ty, $c:ident : $tc:ty, $d:ident : $td:ty) ->
+        $ret:ty { $body:expr }
+    ) => {
+        fn $n($a: $ta, $b: $tb, $c: $tc, $d: $td) -> $ret {
+            $body
+        }
+        macro_rules! $n {
+            ($va: expr,$vb: expr,$vc: expr,$vd: expr) => {
+                $n($va, $vb, $vc, $vd)
+            };
+        }
+    };
+}
+
+macro_rules! m {
+    // a
+    ($expr:expr, $($func:ident)*) => {{
+        let x = $expr;
+        $func(x)
+    }};
+
+    /* b */
+    () => {
+        /* c */
+    };
+
+    (@tag) => {};
+
+    // d
+    ($item:ident) => {
+        mod macro_item {
+            struct $item;
+        }
+    };
+}
+
+macro m2 {
+    // a
+    ($expr:expr, $($func:ident)*) => {{
+        let x = $expr;
+        $func(x)
+    }}
+
+    /* b */
+    () => {
+        /* c */
+    }
+
+    (@tag) => {}
+
+    // d
+    ($item:ident) => {
+        mod macro_item {
+            struct $item;
+        }
+    }
+}
+
+// #2438, #2476
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_98_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx();
+        }
+    };
+}
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_99_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+            );
+        }
+    };
+}
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_100_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+            );
+        }
+    };
+}
+macro_rules! m {
+    () => {
+        fn foo() {
+            this_line_is_101_characters_long_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(
+            );
+        }
+    };
+}
+
+// #2439
+macro_rules! m {
+    (
+        $line0_xxxxxxxxxxxxxxxxx:expr,
+        $line1_xxxxxxxxxxxxxxxxx:expr,
+        $line2_xxxxxxxxxxxxxxxxx:expr,
+        $line3_xxxxxxxxxxxxxxxxx:expr,
+    ) => {};
+}
+
+// #2466
+// Skip formatting `macro_rules!` that are not using `{}`.
+macro_rules! m (
+    () => ()
+);
+macro_rules! m [
+    () => ()
+];
+
+// #2470
+macro foo($type_name:ident, $docs:expr) {
+    #[allow(non_camel_case_types)]
+    #[doc=$docs]
+    #[derive(Debug, Clone, Copy)]
+    pub struct $type_name;
+}
+
+// #2534
+macro_rules! foo {
+    ($a:ident : $b:ty) => {};
+    ($a:ident $b:ident $c:ident) => {};
+}
+
+// #2538
+macro_rules! add_message_to_notes {
+    ($msg:expr) => {{
+        let mut lines = message.lines();
+        notes.push_str(&format!("\n{}: {}", level, lines.next().unwrap()));
+        for line in lines {
+            notes.push_str(&format!(
+                "\n{:indent$}{line}",
+                "",
+                indent = level.len() + 2,
+                line = line,
+            ));
+        }
+    }};
+}
+
+// #2560
+macro_rules! binary {
+    ($_self:ident, $expr:expr, $lhs:expr, $func:ident) => {
+        while $_self.matched($expr) {
+            let op = $_self.get_binary_op()?;
+
+            let rhs = Box::new($_self.$func()?);
+
+            $lhs = Spanned {
+                span: $lhs.get_span().to(rhs.get_span()),
+                value: Expression::Binary {
+                    lhs: Box::new($lhs),
+                    op,
+                    rhs,
+                },
+            }
+        }
+    };
+}
+
+// #2558
+macro_rules! m {
+    ($x:) => {};
+    ($($foo:expr)()?) => {};
+}
+
+// #2749
+macro_rules! foo {
+    ($(x)* {}) => {};
+    ($(x)*()) => {};
+    ($(x)*[]) => {};
+}
+macro_rules! __wundergraph_expand_sqlite_mutation {
+    (
+        $mutation_name:ident $((context = $($context:tt)*))* {
+            $(
+                $entity_name:ident(
+                    $(insert = $insert:ident,)*
+                    $(update = $update:ident,)*
+                    $(delete = $($delete:tt)+)*
+                ),
+            )*
+        }
+    ) => {};
+}
+
+// #2607
+macro_rules! bench {
+    ($ty:ident) => {
+        criterion_group!(
+            name = benches;
+            config = ::common_bench::reduced_samples();
+            targets = call, map;
+        );
+    };
+}
+
+// #2770
+macro_rules! save_regs {
+    () => {
+        asm!("push rax
+              push rcx
+              push rdx
+              push rsi
+              push rdi
+              push r8
+              push r9
+              push r10
+              push r11"
+             :::: "intel", "volatile");
+    };
+}
+
+// #2721
+macro_rules! impl_as_byte_slice_arrays {
+    ($n:expr,) => {};
+    ($n:expr, $N:ident, $($NN:ident,)*) => {
+        impl_as_byte_slice_arrays!($n - 1, $($NN,)*);
+
+        impl<T> AsByteSliceMut for [T; $n] where [T]: AsByteSliceMut {
+            fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+                self[..].as_byte_slice_mut()
+            }
+
+            fn to_le(&mut self) {
+                self[..].to_le()
+            }
+        }
+    };
+    (!div $n:expr,) => {};
+    (!div $n:expr, $N:ident, $($NN:ident,)*) => {
+        impl_as_byte_slice_arrays!(!div $n / 2, $($NN,)*);
+
+        impl<T> AsByteSliceMut for [T; $n] where [T]: AsByteSliceMut {
+            fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+                self[..].as_byte_slice_mut()
+            }
+
+            fn to_le(&mut self) {
+                self[..].to_le()
+            }
+        }
+    };
+}
+
+// #2919
+fn foo() {
+    {
+        macro_rules! touch_value {
+            ($func:ident, $value:expr) => {{
+                let result = API::get_cached().$func(
+                    self,
+                    key.as_ptr(),
+                    $value,
+                    ffi::VSPropAppendMode::paTouch,
+                );
+                let result = API::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppend);
+                let result =
+                    API::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppendM);
+                let result =
+                    APIIIIIIIII::get_cached().$func(self, key.as_ptr(), $value, ffi::VSPropAppendM);
+                let result = API::get_cached().$func(
+                    self,
+                    key.as_ptr(),
+                    $value,
+                    ffi::VSPropAppendMMMMMMMMMM,
+                );
+                debug_assert!(result == 0);
+            }};
+        }
+    }
+}
+
+// #2642
+macro_rules! template {
+    ($name:expr) => {
+        format_args!(
+            r##"
+"http://example.com"
+
+# test
+"##,
+            $name
+        )
+    };
+}
+
+macro_rules! template {
+    () => {
+        format_args!(
+            r"
+//
+
+"
+        )
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/macro_rules_semi.rs b/src/tools/rustfmt/tests/target/macro_rules_semi.rs
new file mode 100644
index 0000000000000..84e12d16e6e97
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/macro_rules_semi.rs
@@ -0,0 +1,22 @@
+macro_rules! expr {
+    (no_semi) => {
+        return true
+    };
+    (semi) => {
+        return true;
+    };
+}
+
+fn foo() -> bool {
+    match true {
+        true => expr!(no_semi),
+        false if false => {
+            expr!(semi)
+        }
+        false => {
+            expr!(semi);
+        }
+    }
+}
+
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/macros.rs b/src/tools/rustfmt/tests/target/macros.rs
new file mode 100644
index 0000000000000..e930b5037d930
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/macros.rs
@@ -0,0 +1,1062 @@
+// rustfmt-normalize_comments: true
+// rustfmt-format_macro_matchers: true
+itemmacro!(this, is.now().formatted(yay));
+
+itemmacro!(
+    really,
+    long.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbb()
+        .is
+        .formatted()
+);
+
+itemmacro! {this, is.brace().formatted()}
+
+fn main() {
+    foo!();
+
+    foo!(,);
+
+    bar!(a, b, c);
+
+    bar!(a, b, c,);
+
+    baz!(1 + 2 + 3, quux.kaas());
+
+    quux!(
+        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+        BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+    );
+
+    kaas!(
+        // comments
+        a, // post macro
+        b  // another
+    );
+
+    trailingcomma!(a, b, c,);
+    // Preserve trailing comma only when necessary.
+    ok!(file.seek(SeekFrom::Start(
+        table.map(|table| fixture.offset(table)).unwrap_or(0),
+    )));
+
+    noexpr!( i am not an expression, OK? );
+
+    vec![a, b, c];
+
+    vec![
+        AAAAAA,
+        AAAAAA,
+        AAAAAA,
+        AAAAAA,
+        AAAAAA,
+        AAAAAA,
+        AAAAAA,
+        AAAAAA,
+        AAAAAA,
+        BBBBB,
+        5,
+        100 - 30,
+        1.33,
+        b,
+        b,
+        b,
+    ];
+
+    vec![a /* comment */];
+
+    // Trailing spaces after a comma
+    vec![a];
+
+    vec![a; b];
+    vec![a; b];
+    vec![a; b];
+
+    vec![a, b; c];
+    vec![a; b, c];
+
+    vec![
+        a;
+        (|x| {
+            let y = x + 1;
+            let z = y + 1;
+            z
+        })(2)
+    ];
+    vec![
+        a;
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ];
+    vec![a; unsafe { x + 1 }];
+
+    unknown_bracket_macro__comma_should_not_be_stripped![a,];
+
+    foo(makro!(1, 3));
+
+    hamkaas! { () };
+
+    macrowithbraces! {dont,    format, me}
+
+    x!(fn);
+
+    some_macro!();
+
+    some_macro![];
+
+    some_macro! {
+        // comment
+    };
+
+    some_macro! {
+        // comment
+    };
+
+    some_macro!(
+        // comment
+        not function like
+    );
+
+    // #1712
+    let image = gray_image!(
+        00, 01, 02;
+        10, 11, 12;
+        20, 21, 22);
+
+    // #1092
+    chain!(input, a: take!(max_size), || []);
+
+    // #2727
+    foo!("bar");
+}
+
+impl X {
+    empty_invoc! {}
+    empty_invoc! {}
+}
+
+fn issue_1279() {
+    println!("dsfs"); // a comment
+}
+
+fn issue_1555() {
+    let hello = &format!(
+        "HTTP/1.1 200 OK\r\nServer: {}\r\n\r\n{}",
+        "65454654654654654654654655464", "4"
+    );
+}
+
+fn issue1178() {
+    macro_rules! foo {
+        (#[$attr:meta] $name:ident) => {};
+    }
+
+    foo!(
+        #[doc = "bar"]
+        baz
+    );
+}
+
+fn issue1739() {
+    sql_function!(
+        add_rss_item,
+        add_rss_item_t,
+        (
+            a: types::Integer,
+            b: types::Timestamptz,
+            c: types::Text,
+            d: types::Text,
+            e: types::Text
+        )
+    );
+
+    w.slice_mut(s![
+        ..,
+        init_size[1] - extreeeeeeeeeeeeeeeeeeeeeeeem..init_size[1],
+        ..
+    ])
+    .par_map_inplace(|el| *el = 0.);
+}
+
+fn issue_1885() {
+    let threads = people
+        .into_iter()
+        .map(|name| {
+            chan_select! {
+                rx.recv() => {}
+            }
+        })
+        .collect::<Vec<_>>();
+}
+
+fn issue_1917() {
+    mod x {
+        quickcheck! {
+            fn test(a: String, s: String, b: String) -> TestResult {
+                if a.find(&s).is_none() {
+
+                    TestResult::from_bool(true)
+                } else {
+                    TestResult::discard()
+                }
+            }
+        }
+    }
+}
+
+fn issue_1921() {
+    // Macro with tabs.
+    lazy_static! {
+        static ref ONE: u32 = 1;
+        static ref TWO: u32 = 2;
+        static ref THREE: u32 = 3;
+        static ref FOUR: u32 = {
+            let mut acc = 1;
+            acc += 1;
+            acc += 2;
+            acc
+        };
+    }
+}
+
+// #1577
+fn issue1577() {
+    let json = json!({
+        "foo": "bar",
+    });
+}
+
+// #3174
+fn issue_3174() {
+    let data = if let Some(debug) = error.debug_info() {
+        json!({
+            "errorKind": format!("{:?}", error.err_kind()),
+            "debugMessage": debug.message,
+        })
+    } else {
+        json!({ "errorKind": format!("{:?}", error.err_kind()) })
+    };
+}
+
+gfx_pipeline!(pipe {
+    vbuf: gfx::VertexBuffer<Vertex> = (),
+    out: gfx::RenderTarget<ColorFormat> = "Target0",
+});
+
+// #1919
+#[test]
+fn __bindgen_test_layout_HandleWithDtor_open0_int_close0_instantiation() {
+    assert_eq!(
+        ::std::mem::size_of::<HandleWithDtor<::std::os::raw::c_int>>(),
+        8usize,
+        concat!(
+            "Size of template specialization: ",
+            stringify!(HandleWithDtor<::std::os::raw::c_int>)
+        )
+    );
+    assert_eq!(
+        ::std::mem::align_of::<HandleWithDtor<::std::os::raw::c_int>>(),
+        8usize,
+        concat!(
+            "Alignment of template specialization: ",
+            stringify!(HandleWithDtor<::std::os::raw::c_int>)
+        )
+    );
+}
+
+// #878
+macro_rules! try_opt {
+    ($expr:expr) => {
+        match $expr {
+            Some(val) => val,
+
+            None => {
+                return None;
+            }
+        }
+    };
+}
+
+// #2214
+// macro call whose argument is an array with trailing comma.
+fn issue2214() {
+    make_test!(
+        str_searcher_ascii_haystack,
+        "bb",
+        "abbcbbd",
+        [
+            Reject(0, 1),
+            Match(1, 3),
+            Reject(3, 4),
+            Match(4, 6),
+            Reject(6, 7),
+        ]
+    );
+}
+
+fn special_case_macros() {
+    let p = eprint!();
+    let q = eprint!("{}", 1);
+    let r = eprint!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    let s = eprint!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    let q = eprintln!("{}", 1);
+    let r = eprintln!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    let s = eprintln!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    let q = format!("{}", 1);
+    let r = format!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    let s = format!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    let q = format_args!("{}", 1);
+    let r = format_args!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    let s = format_args!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    let q = print!("{}", 1);
+    let r = print!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    let s = print!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    let q = println!("{}", 1);
+    let r = println!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    let s = println!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    let q = unreachable!("{}", 1);
+    let r = unreachable!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    let s = unreachable!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    debug!("{}", 1);
+    debug!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    debug!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    error!("{}", 1);
+    error!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    error!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    info!("{}", 1);
+    info!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    info!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    panic!("{}", 1);
+    panic!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    panic!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    warn!("{}", 1);
+    warn!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+    );
+    warn!(
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    assert!();
+    assert!(result == 42);
+    assert!(result == 42, "Ahoy there, {}!", target);
+    assert!(
+        result == 42,
+        "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')",
+        result,
+        input,
+        expected
+    );
+    assert!(
+        result == 42,
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    assert_eq!();
+    assert_eq!(left);
+    assert_eq!(left, right);
+    assert_eq!(left, right, "Ahoy there, {}!", target);
+    assert_eq!(
+        left, right,
+        "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')",
+        result, input, expected
+    );
+    assert_eq!(
+        first_realllllllllllly_long_variable_that_doesnt_fit_one_one_line,
+        second_reallllllllllly_long_variable_that_doesnt_fit_one_one_line,
+        "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')",
+        result,
+        input,
+        expected
+    );
+    assert_eq!(
+        left + 42,
+        right,
+        "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')",
+        result,
+        input,
+        expected
+    );
+    assert_eq!(
+        left,
+        right,
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    write!(&mut s, "Ahoy there, {}!", target);
+    write!(
+        &mut s,
+        "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')",
+        result, input, expected
+    );
+    write!(
+        &mut s,
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+
+    writeln!(&mut s, "Ahoy there, {}!", target);
+    writeln!(
+        &mut s,
+        "Arr! While plunderin' the hold, we got '{}' when given '{}' (we expected '{}')",
+        result, input, expected
+    );
+    writeln!(
+        &mut s,
+        "{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}",
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26
+    );
+}
+
+// #1209
+impl Foo {
+    /// foo
+    pub fn foo(&self) -> Bar<foo!()> {}
+}
+
+// #819
+fn macro_in_pattern_position() {
+    let x = match y {
+        foo!() => (),
+        bar!(a, b, c) => (),
+        bar!(a, b, c,) => (),
+        baz!(1 + 2 + 3, quux.kaas()) => (),
+        quux!(
+            AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+            BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
+        ) => (),
+    };
+}
+
+macro foo() {}
+
+pub macro bar($x:ident + $y:expr;) {
+    fn foo($x: Foo) {
+        long_function(
+            a_long_argument_to_a_long_function_is_what_this_is(AAAAAAAAAAAAAAAAAAAAAAAAAAAA),
+            $x.bar($y),
+        );
+    }
+}
+
+macro foo() {
+    // a comment
+    fn foo() {
+        // another comment
+        bar();
+    }
+}
+
+// #2574
+macro_rules! test {
+    () => {{}};
+}
+
+macro lex_err($kind: ident $(, $body: expr)*) {
+    Err(QlError::LexError(LexError::$kind($($body,)*)))
+}
+
+// Preserve trailing comma on item-level macro with `()` or `[]`.
+methods![get, post, delete,];
+methods!(get, post, delete,);
+
+// #2588
+macro_rules! m {
+    () => {
+        r#"
+            test
+        "#
+    };
+}
+fn foo() {
+    f! {r#"
+            test
+       "#};
+}
+
+// #2591
+fn foo() {
+    match 0u32 {
+        0 => (),
+        _ => unreachable!(/* obviously */),
+    }
+}
+
+fn foo() {
+    let _ = column!(/* here */);
+}
+
+// #2616
+// Preserve trailing comma when using mixed layout for macro call.
+fn foo() {
+    foo!(
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
+    );
+    foo!(
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    );
+}
+
+// #2830
+// Preserve trailing comma-less/ness inside nested macro.
+named!(
+    do_parse_gsv<GsvData>,
+    map_res!(
+        do_parse!(
+            number_of_sentences: map_res!(digit, parse_num::<u16>)
+                >> char!(',')
+                >> sentence_index: map_res!(digit, parse_num::<u16>)
+                >> char!(',')
+                >> total_number_of_sats: map_res!(digit, parse_num::<u16>)
+                >> char!(',')
+                >> sat0: opt!(complete!(parse_gsv_sat_info))
+                >> sat1: opt!(complete!(parse_gsv_sat_info))
+                >> sat2: opt!(complete!(parse_gsv_sat_info))
+                >> sat3: opt!(complete!(parse_gsv_sat_info))
+                >> (
+                    number_of_sentences,
+                    sentence_index,
+                    total_number_of_sats,
+                    sat0,
+                    sat1,
+                    sat2,
+                    sat3
+                )
+        ),
+        construct_gsv_data
+    )
+);
+
+// #2857
+convert_args!(vec!(1, 2, 3));
+
+// #3031
+thread_local!(
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> = RefCell::new(RootedTraceableSet::new());
+);
+
+thread_local![
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> = RefCell::new(RootedTraceableSet::new());
+
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new(0));
+
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new(), xxx, yyy);
+
+    /// TLV Holds a set of JSTraceables that need to be rooted
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new(1234));
+];
+
+fn issue3004() {
+    foo!(|_| { () });
+    stringify!((foo+));
+}
+
+// #3331
+pub fn fold_abi<V: Fold + ?Sized>(_visitor: &mut V, _i: Abi) -> Abi {
+    Abi {
+        extern_token: Token![extern](tokens_helper(_visitor, &_i.extern_token.span)),
+        name: (_i.name).map(|it| _visitor.fold_lit_str(it)),
+    }
+}
+
+// #3463
+x! {()}
+
+// #3746
+f!(match a {
+    4 => &[
+        (3, false), // Missing
+        (4, true)   // I-frame
+    ][..],
+});
+
+// #3583
+foo!(|x = y|);
diff --git a/src/tools/rustfmt/tests/target/markdown-comment-with-options.rs b/src/tools/rustfmt/tests/target/markdown-comment-with-options.rs
new file mode 100644
index 0000000000000..ede2bc0d035f5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/markdown-comment-with-options.rs
@@ -0,0 +1,17 @@
+// rustfmt-wrap_comments: true
+
+// Preserve two trailing whitespaces in doc comment,
+// but trim any whitespaces in normal comment.
+
+//! hello world  
+//! hello world
+
+/// hello world    
+/// hello world
+/// hello world  
+fn foo() {
+    // hello world
+    // hello world
+    let x = 3;
+    println!("x = {}", x);
+}
diff --git a/src/tools/rustfmt/tests/target/markdown-comment.rs b/src/tools/rustfmt/tests/target/markdown-comment.rs
new file mode 100644
index 0000000000000..71a9921d28628
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/markdown-comment.rs
@@ -0,0 +1,15 @@
+// Preserve two trailing whitespaces in doc comment,
+// but trim any whitespaces in normal comment.
+
+//! hello world  
+//! hello world
+
+/// hello world    
+/// hello world
+/// hello world  
+fn foo() {
+    // hello world
+    // hello world
+    let x = 3;
+    println!("x = {}", x);
+}
diff --git a/src/tools/rustfmt/tests/target/match-block-trailing-comma.rs b/src/tools/rustfmt/tests/target/match-block-trailing-comma.rs
new file mode 100644
index 0000000000000..44d1f289f8e0f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/match-block-trailing-comma.rs
@@ -0,0 +1,16 @@
+// rustfmt-match_block_trailing_comma: true
+// Match expressions, no unwrapping of block arms or wrapping of multiline
+// expressions.
+
+fn foo() {
+    match x {
+        a => {
+            "line1";
+            "line2"
+        },
+        b => (
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+            bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        ),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/match-flattening.rs b/src/tools/rustfmt/tests/target/match-flattening.rs
new file mode 100644
index 0000000000000..f246952a08d4b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/match-flattening.rs
@@ -0,0 +1,23 @@
+fn main() {
+    match option {
+        None => {
+            if condition {
+                true
+            } else {
+                false
+            }
+        }
+    }
+}
+
+fn main() {
+    match option {
+        None => {
+            if condition {
+                true
+            } else {
+                false
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/match-nowrap-trailing-comma.rs b/src/tools/rustfmt/tests/target/match-nowrap-trailing-comma.rs
new file mode 100644
index 0000000000000..19ef2144822a6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/match-nowrap-trailing-comma.rs
@@ -0,0 +1,17 @@
+// rustfmt-match_arm_blocks: false
+// rustfmt-match_block_trailing_comma: true
+// Match expressions, no unwrapping of block arms or wrapping of multiline
+// expressions.
+
+fn foo() {
+    match x {
+        a => {
+            "line1";
+            "line2"
+        },
+        b => (
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+            bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        ),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/match-nowrap.rs b/src/tools/rustfmt/tests/target/match-nowrap.rs
new file mode 100644
index 0000000000000..9e674b1e2f540
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/match-nowrap.rs
@@ -0,0 +1,13 @@
+// rustfmt-match_arm_blocks: false
+// Match expressions, no unwrapping of block arms or wrapping of multiline
+// expressions.
+
+fn foo() {
+    match x {
+        a => foo(),
+        b => (
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+            bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        ),
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/match.rs b/src/tools/rustfmt/tests/target/match.rs
new file mode 100644
index 0000000000000..e2c522bea10b1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/match.rs
@@ -0,0 +1,610 @@
+// rustfmt-normalize_comments: true
+// Match expressions.
+
+fn foo() {
+    // A match expression.
+    match x {
+        // Some comment.
+        a => foo(),
+        b if 0 < 42 => foo(),
+        c => {
+            // Another comment.
+            // Comment.
+            an_expression;
+            foo()
+        }
+        Foo(ref bar) => {
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        }
+        Pattern1 | Pattern2 | Pattern3 => false,
+        Paternnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn
+        | Paternnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn => blah,
+        Patternnnnnnnnnnnnnnnnnnn
+        | Patternnnnnnnnnnnnnnnnnnn
+        | Patternnnnnnnnnnnnnnnnnnn
+        | Patternnnnnnnnnnnnnnnnnnn => meh,
+
+        Patternnnnnnnnnnnnnnnnnnn | Patternnnnnnnnnnnnnnnnnnn if looooooooooooooooooong_guard => {
+            meh
+        }
+
+        Patternnnnnnnnnnnnnnnnnnnnnnnnn | Patternnnnnnnnnnnnnnnnnnnnnnnnn
+            if looooooooooooooooooooooooooooooooooooooooong_guard =>
+        {
+            meh
+        }
+
+        // Test that earlier patterns can take the guard space
+        (aaaa, bbbbb, ccccccc, aaaaa, bbbbbbbb, cccccc, aaaa, bbbbbbbb, cccccc, dddddd)
+        | Patternnnnnnnnnnnnnnnnnnnnnnnnn
+            if loooooooooooooooooooooooooooooooooooooooooong_guard => {}
+
+        _ => {}
+        ast::PathParameters::AngleBracketedParameters(ref data)
+            if data.lifetimes.len() > 0 || data.types.len() > 0 || data.bindings.len() > 0 => {}
+    }
+
+    let whatever = match something {
+        /// DOC COMMENT!
+        Some(_) => 42,
+        // Comment on an attribute.
+        #[an_attribute]
+        // Comment after an attribute.
+        None => 0,
+        #[rustfmt::skip]
+        Blurb     =>     {                  }
+    };
+}
+
+// Test that a match on an overflow line is laid out properly.
+fn main() {
+    let sub_span =
+        match xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx {
+            Some(sub_span) => Some(sub_span),
+            None => sub_span,
+        };
+}
+
+// Test that one-line bodies align.
+fn main() {
+    match r {
+        Variableeeeeeeeeeeeeeeeee => (
+            "variable",
+            vec!["id", "name", "qualname", "value", "type", "scopeid"],
+            true,
+            true,
+        ),
+        Enummmmmmmmmmmmmmmmmmmmm => (
+            "enum",
+            vec!["id", "qualname", "scopeid", "value"],
+            true,
+            true,
+        ),
+        Variantttttttttttttttttttttttt => (
+            "variant",
+            vec!["id", "name", "qualname", "type", "value", "scopeid"],
+            true,
+            true,
+        ),
+    };
+
+    match x {
+        y => { /*Block with comment. Preserve me.*/ }
+        z => {
+            stmt();
+        }
+    }
+}
+
+fn matches() {
+    match 1 {
+        -1 => 10,
+        1 => 1, // foo
+        2 => 2,
+        // bar
+        3 => 3,
+        _ => 0, // baz
+    }
+}
+
+fn match_skip() {
+    let _ = match Some(1) {
+        #[rustfmt::skip]
+        Some( n ) => n,
+        None => 1,
+    };
+}
+
+fn issue339() {
+    match a {
+        b => {}
+        c => {}
+        d => {}
+        e => {}
+        // collapsing here is safe
+        ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff => {}
+        // collapsing here exceeds line length
+        ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffg => {
+        }
+        h => { // comment above block
+        }
+        i => {} // comment below block
+        j => {
+            // comment inside block
+        }
+        j2 => {
+            // comments inside...
+        } // ... and after
+        // TODO uncomment when vertical whitespace is handled better
+        // k => {
+        //
+        //     // comment with WS above
+        // }
+        // l => {
+        //     // comment with ws below
+        //
+        // }
+        m => {}
+        n => {}
+        o => {}
+        p => { // Don't collapse me
+        }
+        q => {}
+        r => {}
+        s => 0, // s comment
+        // t comment
+        t => 1,
+        u => 2,
+        v => {} /* funky block
+                 * comment */
+                /* final comment */
+    }
+}
+
+fn issue355() {
+    match mac {
+        a => println!("a", b),
+        b => vec![1, 2],
+        c => vec![3; 4],
+        d => {
+            println!("a", b)
+        }
+        e => {
+            vec![1, 2]
+        }
+        f => {
+            vec![3; 4]
+        }
+        h => println!("a", b), // h comment
+        i => vec![1, 2],       // i comment
+        j => vec![3; 4],       // j comment
+        // k comment
+        k => println!("a", b),
+        // l comment
+        l => vec![1, 2],
+        // m comment
+        m => vec![3; 4],
+        // Rewrite splits macro
+        nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn => {
+            println!("a", b)
+        }
+        // Rewrite splits macro
+        oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo => {
+            vec![1, 2]
+        }
+        // Macro support fails to recognise this macro as splittable
+        // We push the whole expr to a new line, TODO split this macro as well
+        pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp => {
+            vec![3; 4]
+        }
+        // q, r and s: Rewrite splits match arm
+        qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq => {
+            println!("a", b)
+        }
+        rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr => {
+            vec![1, 2]
+        }
+        ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss => {
+            vec![3; 4]
+        }
+        // Funky bracketing styles
+        t => println! {"a", b},
+        u => vec![1, 2],
+        v => vec![3; 4],
+        w => println!["a", b],
+        x => vec![1, 2],
+        y => vec![3; 4],
+        // Brackets with comments
+        tc => println! {"a", b}, // comment
+        uc => vec![1, 2],        // comment
+        vc => vec![3; 4],        // comment
+        wc => println!["a", b],  // comment
+        xc => vec![1, 2],        // comment
+        yc => vec![3; 4],        // comment
+        yd => looooooooooooooooooooooooooooooooooooooooooooooooooooooooong_func(
+            aaaaaaaaaa, bbbbbbbbbb, cccccccccc, dddddddddd,
+        ),
+    }
+}
+
+fn issue280() {
+    {
+        match x {
+            CompressionMode::DiscardNewline | CompressionMode::CompressWhitespaceNewline => {
+                ch == '\n'
+            }
+            ast::ItemConst(ref typ, ref expr) => {
+                self.process_static_or_const_item(item, &typ, &expr)
+            }
+        }
+    }
+}
+
+fn issue383() {
+    match resolution.last_private {
+        LastImport { .. } => false,
+        _ => true,
+    };
+}
+
+fn issue507() {
+    match 1 {
+        1 => unsafe { std::intrinsics::abort() },
+        _ => (),
+    }
+}
+
+fn issue508() {
+    match s.type_id() {
+        Some(NodeTypeId::Element(ElementTypeId::HTMLElement(
+            HTMLElementTypeId::HTMLCanvasElement,
+        ))) => true,
+        Some(NodeTypeId::Element(ElementTypeId::HTMLElement(
+            HTMLElementTypeId::HTMLObjectElement,
+        ))) => s.has_object_data(),
+        Some(NodeTypeId::Element(_)) => false,
+    }
+}
+
+fn issue496() {
+    {
+        {
+            {
+                match def {
+                    def::DefConst(def_id) | def::DefAssociatedConst(def_id) => {
+                        match const_eval::lookup_const_by_id(cx.tcx, def_id, Some(self.pat.id)) {
+                            Some(const_expr) => x,
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn issue494() {
+    {
+        match stmt.node {
+            hir::StmtExpr(ref expr, id) | hir::StmtSemi(ref expr, id) => {
+                result.push(StmtRef::Mirror(Box::new(Stmt {
+                    span: stmt.span,
+                    kind: StmtKind::Expr {
+                        scope: cx.tcx.region_maps.node_extent(id),
+                        expr: expr.to_ref(),
+                    },
+                })))
+            }
+        }
+    }
+}
+
+fn issue386() {
+    match foo {
+        BiEq | BiLt | BiLe | BiNe | BiGt | BiGe => true,
+        BiAnd | BiOr | BiAdd | BiSub | BiMul | BiDiv | BiRem | BiBitXor | BiBitAnd | BiBitOr
+        | BiShl | BiShr => false,
+    }
+}
+
+fn guards() {
+    match foo {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+            if foooooooooooooo && barrrrrrrrrrrr => {}
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+        | aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+            if foooooooooooooo && barrrrrrrrrrrr => {}
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+            if fooooooooooooooooooooo
+                && (bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+                    || cccccccccccccccccccccccccccccccccccccccc) => {}
+    }
+}
+
+fn issue1371() {
+    Some(match type_ {
+        sfEvtClosed => Closed,
+        sfEvtResized => {
+            let e = unsafe { *event.size.as_ref() };
+
+            Resized {
+                width: e.width,
+                height: e.height,
+            }
+        }
+        sfEvtLostFocus => LostFocus,
+        sfEvtGainedFocus => GainedFocus,
+        sfEvtTextEntered => TextEntered {
+            unicode: unsafe {
+                ::std::char::from_u32((*event.text.as_ref()).unicode)
+                    .expect("Invalid unicode encountered on TextEntered event")
+            },
+        },
+        sfEvtKeyPressed => {
+            let e = unsafe { event.key.as_ref() };
+
+            KeyPressed {
+                code: unsafe { ::std::mem::transmute(e.code) },
+                alt: e.alt.to_bool(),
+                ctrl: e.control.to_bool(),
+                shift: e.shift.to_bool(),
+                system: e.system.to_bool(),
+            }
+        }
+        sfEvtKeyReleased => {
+            let e = unsafe { event.key.as_ref() };
+
+            KeyReleased {
+                code: unsafe { ::std::mem::transmute(e.code) },
+                alt: e.alt.to_bool(),
+                ctrl: e.control.to_bool(),
+                shift: e.shift.to_bool(),
+                system: e.system.to_bool(),
+            }
+        }
+    })
+}
+
+fn issue1395() {
+    let bar = Some(true);
+    let foo = Some(true);
+    let mut x = false;
+    bar.and_then(|_| match foo {
+        None => None,
+        Some(b) => {
+            x = true;
+            Some(b)
+        }
+    });
+}
+
+fn issue1456() {
+    Ok(Recording {
+        artists: match reader.evaluate(".//mb:recording/mb:artist-credit/mb:name-credit")? {
+            Nodeset(nodeset) => {
+                let res: Result<Vec<ArtistRef>, ReadError> = nodeset
+                    .iter()
+                    .map(|node| {
+                        XPathNodeReader::new(node, &context).and_then(|r| ArtistRef::from_xml(&r))
+                    })
+                    .collect();
+                res?
+            }
+            _ => Vec::new(),
+        },
+    })
+}
+
+fn issue1460() {
+    let _ = match foo {
+        REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT => {
+            "internal_spec_insert_internal_spec_insert_internal_spec_insert"
+        }
+        _ => "reorder_something",
+    };
+}
+
+fn issue525() {
+    foobar(
+        f,
+        "{}",
+        match *self {
+            TaskState::Started => "started",
+            TaskState::Success => "success",
+            TaskState::Failed => "failed",
+        },
+    );
+}
+
+// #1838, #1839
+fn match_with_near_max_width() {
+    let (this_line_uses_99_characters_and_is_formatted_properly, x012345) = match some_expression {
+        _ => unimplemented!(),
+    };
+
+    let (should_be_formatted_like_the_line_above_using_100_characters, x0) = match some_expression {
+        _ => unimplemented!(),
+    };
+
+    let (should_put_the_brace_on_the_next_line_using_101_characters, x0000) = match some_expression
+    {
+        _ => unimplemented!(),
+    };
+    match m {
+        Variant::Tag
+        | Variant::Tag2
+        | Variant::Tag3
+        | Variant::Tag4
+        | Variant::Tag5
+        | Variant::Tag6 => {}
+    }
+}
+
+fn match_with_trailing_spaces() {
+    match x {
+        Some(..) => 0,
+        None => 1,
+    }
+}
+
+fn issue_2099() {
+    let a = match x {};
+    let b = match x {};
+
+    match x {}
+}
+
+// #2021
+impl<'tcx> Const<'tcx> {
+    pub fn from_constval<'a>() -> Const<'tcx> {
+        let val = match *cv {
+            ConstVal::Variant(_) | ConstVal::Aggregate(..) | ConstVal::Unevaluated(..) => bug!(
+                "MIR must not use `{:?}` (aggregates are expanded to MIR rvalues)",
+                cv
+            ),
+        };
+    }
+}
+
+// #2151
+fn issue_2151() {
+    match either {
+        x => {}
+        y => (),
+    }
+}
+
+// #2152
+fn issue_2152() {
+    match m {
+        "aaaaaaaaaaaaa" | "bbbbbbbbbbbbb" | "cccccccccccccccccccccccccccccccccccccccccccc"
+            if true => {}
+        "bind" | "writev" | "readv" | "sendmsg" | "recvmsg" if android && (aarch64 || x86_64) => {
+            true
+        }
+    }
+}
+
+// #2376
+// Preserve block around expressions with condition.
+fn issue_2376() {
+    let mut x = None;
+    match x {
+        Some(0) => {
+            for i in 1..11 {
+                x = Some(i);
+            }
+        }
+        Some(ref mut y) => {
+            while *y < 10 {
+                *y += 1;
+            }
+        }
+        None => {
+            while let None = x {
+                x = Some(10);
+            }
+        }
+    }
+}
+
+// #2621
+// Strip leading `|` in match arm patterns
+fn issue_2621() {
+    let x = Foo::A;
+    match x {
+        Foo::A => println!("No vert single condition"),
+        Foo::B | Foo::C => println!("Center vert two conditions"),
+        Foo::D => println!("Preceding vert single condition"),
+        Foo::E | Foo::F => println!("Preceding vert over two lines"),
+        Foo::G | Foo::H => println!("Trailing vert over two lines"),
+        // Comment on its own line
+        Foo::I => println!("With comment"), // Comment after line
+    }
+}
+
+fn issue_2377() {
+    match tok {
+        Tok::Not
+        | Tok::BNot
+        | Tok::Plus
+        | Tok::Minus
+        | Tok::PlusPlus
+        | Tok::MinusMinus
+        | Tok::Void
+        | Tok::Delete
+            if prec <= 16 =>
+        {
+            // code here...
+        }
+        Tok::TypeOf if prec <= 16 => {}
+    }
+}
+
+// #3040
+fn issue_3040() {
+    {
+        match foo {
+            DevtoolScriptControlMsg::WantsLiveNotifications(id, to_send) => {
+                match documents.find_window(id) {
+                    Some(window) => {
+                        devtools::handle_wants_live_notifications(window.upcast(), to_send)
+                    }
+                    None => return warn!("Message sent to closed pipeline {}.", id),
+                }
+            }
+        }
+    }
+}
+
+// #3030
+fn issue_3030() {
+    match input.trim().parse::<f64>() {
+        Ok(val)
+            if !(
+                // A valid number is the same as what rust considers to be valid,
+                // except for +1., NaN, and Infinity.
+                val.is_infinite() || val.is_nan() || input.ends_with(".") || input.starts_with("+")
+            ) => {}
+    }
+}
+
+fn issue_3005() {
+    match *token {
+        Token::Dimension {
+            value, ref unit, ..
+        } if num_context.is_ok(context.parsing_mode, value) => {
+            return NoCalcLength::parse_dimension(context, value, unit)
+                .map(LengthOrPercentage::Length)
+                .map_err(|()| location.new_unexpected_token_error(token.clone()));
+        }
+    }
+}
+
+// #3774
+fn issue_3774() {
+    {
+        {
+            {
+                match foo {
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreachab(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => unreacha!(),
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => {
+                        unreachabl()
+                    }
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => {
+                        unreachae!()
+                    }
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => {
+                        unreachable()
+                    }
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => {
+                        unreachable!()
+                    }
+                    Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => {
+                        rrunreachable!()
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/match_overflow_expr.rs b/src/tools/rustfmt/tests/target/match_overflow_expr.rs
new file mode 100644
index 0000000000000..b817879d1f482
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/match_overflow_expr.rs
@@ -0,0 +1,50 @@
+// rustfmt-overflow_delimited_expr: true
+
+fn main() {
+    println!("Foobar: {}", match "input" {
+        "a" => "",
+        "b" => "",
+        "c" => "",
+        "d" => "",
+        "e" => "",
+        "f" => "",
+        "g" => "",
+        "h" => "",
+        "i" => "",
+        "j" => "",
+        "k" => "",
+        "l" => "",
+        "m" => "",
+        "n" => "",
+        "o" => "",
+        "p" => "",
+        "q" => "",
+        "r" => "Rust",
+    });
+}
+
+fn main() {
+    println!(
+        "Very Long Input String Which Makes It Impossible To Fit On The Same Line: {}",
+        match "input" {
+            "a" => "",
+            "b" => "",
+            "c" => "",
+            "d" => "",
+            "e" => "",
+            "f" => "",
+            "g" => "",
+            "h" => "",
+            "i" => "",
+            "j" => "",
+            "k" => "",
+            "l" => "",
+            "m" => "",
+            "n" => "",
+            "o" => "",
+            "p" => "",
+            "q" => "",
+            "r" => "Rust",
+        }
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/max-line-length-in-chars.rs b/src/tools/rustfmt/tests/target/max-line-length-in-chars.rs
new file mode 100644
index 0000000000000..d49fbb7e30e5a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/max-line-length-in-chars.rs
@@ -0,0 +1,4 @@
+// rustfmt-max_width: 25
+
+// абвгдеёжзийклмнопрст
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/merge_imports_true_compat.rs b/src/tools/rustfmt/tests/target/merge_imports_true_compat.rs
new file mode 100644
index 0000000000000..46cd0a3b8a0a3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/merge_imports_true_compat.rs
@@ -0,0 +1,3 @@
+// rustfmt-merge_imports: true
+
+use a::{b, c};
diff --git a/src/tools/rustfmt/tests/target/mod-1.rs b/src/tools/rustfmt/tests/target/mod-1.rs
new file mode 100644
index 0000000000000..4118d123dd06f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/mod-1.rs
@@ -0,0 +1,37 @@
+// Deeply indented modules.
+
+mod foo {
+    mod bar {
+        mod baz {}
+    }
+}
+
+mod foo {
+    mod bar {
+        mod baz {
+            fn foo() {
+                bar()
+            }
+        }
+    }
+
+    mod qux {}
+}
+
+mod boxed {
+    pub use std::boxed::{Box, HEAP};
+}
+
+pub mod x {
+    pub fn freopen(
+        filename: *const c_char,
+        mode: *const c_char,
+        mode2: *const c_char,
+        mode3: *const c_char,
+        file: *mut FILE,
+    ) -> *mut FILE {
+    }
+}
+
+mod y { // sup boooooiiii
+}
diff --git a/src/tools/rustfmt/tests/target/mod-2.rs b/src/tools/rustfmt/tests/target/mod-2.rs
new file mode 100644
index 0000000000000..1a093bd520128
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/mod-2.rs
@@ -0,0 +1,5 @@
+// Some nested mods
+
+#[cfg(test)]
+mod nestedmod;
+pub mod no_new_line_beginning;
diff --git a/src/tools/rustfmt/tests/target/mod_skip_child.rs b/src/tools/rustfmt/tests/target/mod_skip_child.rs
new file mode 100644
index 0000000000000..d48c4a37e810a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/mod_skip_child.rs
@@ -0,0 +1,2 @@
+// rustfmt-skip_children: true
+mod nested_skipped;
diff --git a/src/tools/rustfmt/tests/target/mulit-file.rs b/src/tools/rustfmt/tests/target/mulit-file.rs
new file mode 100644
index 0000000000000..1f829b36f3f00
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/mulit-file.rs
@@ -0,0 +1,10 @@
+// Tests that where a single file is referred to in multiple places, we don't
+// crash.
+
+#[cfg(all(foo))]
+#[path = "closure.rs"]
+pub mod imp;
+
+#[cfg(all(bar))]
+#[path = "closure.rs"]
+pub mod imp;
diff --git a/src/tools/rustfmt/tests/target/multiline_string_in_macro_def.rs b/src/tools/rustfmt/tests/target/multiline_string_in_macro_def.rs
new file mode 100644
index 0000000000000..dafc738f8dbd5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/multiline_string_in_macro_def.rs
@@ -0,0 +1,14 @@
+macro_rules! assert_approx_eq {
+    ($a:expr, $b:expr, $eps:expr) => {{
+        let (a, b) = (&$a, &$b);
+        assert!(
+            (*a - *b).abs() < $eps,
+            "assertion failed: `(left !== right)` \
+             (left: `{:?}`, right: `{:?}`, expect diff: `{:?}`, real diff: `{:?}`)",
+            *a,
+            *b,
+            $eps,
+            (*a - *b).abs()
+        );
+    }};
+}
diff --git a/src/tools/rustfmt/tests/target/multiple.rs b/src/tools/rustfmt/tests/target/multiple.rs
new file mode 100644
index 0000000000000..ee6ef220c4bc2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/multiple.rs
@@ -0,0 +1,180 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-format_strings: true
+// Test of lots of random stuff.
+// FIXME split this into multiple, self-contained tests.
+
+#[attr1]
+extern crate foo;
+#[attr2]
+#[attr3]
+extern crate foo;
+#[attr1]
+extern crate foo;
+#[attr2]
+#[attr3]
+extern crate foo;
+
+use std::cell::*;
+use std::{
+    self, any, ascii, borrow, borrow, borrow, borrow, borrow, borrow, borrow, borrow, borrow,
+    borrow, borrow, boxed, boxed, boxed, boxed, boxed, boxed, boxed, boxed, boxed, boxed, char,
+    char, char, char, char, char, char, char, char, char,
+};
+
+mod doc;
+mod other;
+
+// sfdgfffffffffffffffffffffffffffffffffffffffffffffffffffffff
+// ffffffffffffffffffffffffffffffffffffffffff
+
+fn foo(a: isize, b: u32 /* blah blah */, c: f64) {}
+
+fn foo() -> Box<Write + 'static>
+where
+    'a: 'b,
+    for<'a> D<'b>: 'a,
+{
+    hello!()
+}
+
+fn baz<
+    'a: 'b,                                                            // comment on 'a
+    T: SomsssssssssssssssssssssssssssssssssssssssssssssssssssssseType, // comment on T
+>(
+    a: A,
+    b: B, // comment on b
+    c: C,
+) -> Bob {
+    #[attr1]
+    extern crate foo;
+    #[attr2]
+    #[attr3]
+    extern crate foo;
+    #[attr1]
+    extern crate foo;
+    #[attr2]
+    #[attr3]
+    extern crate foo;
+}
+
+#[rustfmt::skip]
+fn qux(a: dadsfa,   // Comment 1
+       b: sdfasdfa, // Comment 2
+       c: dsfdsafa) // Comment 3
+{
+
+}
+
+/// Blah blah blah.
+impl Bar {
+    fn foo(
+        &mut self,
+        a: sdfsdfcccccccccccccccccccccccccccccccccccccccccccccccccc, // comment on a
+        b: sdfasdfsdfasfs,                                           // closing comment
+    ) -> isize {
+    }
+
+    /// Blah blah blah.
+    pub fn f2(self) {
+        (foo, bar)
+    }
+
+    #[an_attribute]
+    fn f3(self) -> Dog {}
+}
+
+/// The `nodes` and `edges` method each return instantiations of
+/// `Cow<[T]>` to leave implementers the freedom to create
+
+/// entirely new vectors or to pass back slices into internally owned
+/// vectors.
+pub trait GraphWalk<'a, N, E> {
+    /// Returns all the nodes in this graph.
+    fn nodes(&'a self) -> Nodes<'a, N>;
+    /// Returns all of the edges in this graph.
+    fn edges(&'a self) -> Edges<'a, E>;
+    /// The source node for `edge`.
+    fn source(&'a self, edge: &E) -> N;
+    /// The target node for `edge`.
+    fn target(&'a self, edge: &E) -> N;
+}
+
+/// A Doc comment
+#[AnAttribute]
+pub struct Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f: SomeType, // Comment beside a field
+    // Comment on a field
+    g: SomeOtherType,
+    /// A doc comment on a field
+    h: AThirdType,
+}
+
+struct Bar;
+
+// With a where-clause and generics.
+pub struct Foo<'a, Y: Baz>
+where
+    X: Whatever,
+{
+    f: SomeType, // Comment beside a field
+}
+
+fn foo(ann: &'a (PpAnn + 'a)) {}
+
+fn main() {
+    for i in 0i32..4 {
+        println!("{}", i);
+    }
+
+    while true {
+        hello();
+    }
+
+    let rc = Cell::new(
+        42usize,
+        42usize,
+        Cell::new(
+            42usize,
+            remaining_widthremaining_widthremaining_widthremaining_width,
+        ),
+        42usize,
+    );
+    let rc = RefCell::new(42usize, remaining_width, remaining_width); // a comment
+    let x = "Hello!!!!!!!!! abcd  abcd abcd abcd abcd abcd\n abcd abcd abcd abcd abcd abcd abcd \
+             abcd abcd abcd  abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd \
+             abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd abcd \
+             abcd abcd";
+    let s = expand(a, b);
+}
+
+fn deconstruct() -> (
+    SocketAddr,
+    Method,
+    Headers,
+    RequestUri,
+    HttpVersion,
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+) {
+}
+
+fn deconstruct(
+    foo: Bar,
+) -> (
+    SocketAddr,
+    Method,
+    Headers,
+    RequestUri,
+    HttpVersion,
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+) {
+}
+
+#[rustfmt::skip]
+mod a{
+fn foo(x:    T) {
+    let x:    T = dfasdf;
+}
+}
diff --git a/src/tools/rustfmt/tests/target/negative-impl.rs b/src/tools/rustfmt/tests/target/negative-impl.rs
new file mode 100644
index 0000000000000..16ce7e26a99aa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/negative-impl.rs
@@ -0,0 +1,14 @@
+impl !Display for JoinHandle {}
+
+impl !Box<JoinHandle> {}
+
+impl !std::fmt::Display
+    for JoinHandle<T: std::future::Future + std::marker::Send + std::marker::Sync>
+{
+}
+
+impl
+    !JoinHandle<T: std::future::Future<Output> + std::marker::Send + std::marker::Sync + 'static>
+        + 'static
+{
+}
diff --git a/src/tools/rustfmt/tests/target/nested-if-else.rs b/src/tools/rustfmt/tests/target/nested-if-else.rs
new file mode 100644
index 0000000000000..9a54789ddcd68
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nested-if-else.rs
@@ -0,0 +1,11 @@
+fn issue1518() {
+    Some(Object {
+        field: if a {
+            a_thing
+        } else if b {
+            b_thing
+        } else {
+            c_thing
+        },
+    })
+}
diff --git a/src/tools/rustfmt/tests/target/nested-visual-block.rs b/src/tools/rustfmt/tests/target/nested-visual-block.rs
new file mode 100644
index 0000000000000..fe7190d0abaa3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nested-visual-block.rs
@@ -0,0 +1,60 @@
+fn main() {
+    // #1078
+    let items = itemize_list(
+        context.source_map,
+        field_iter,
+        "}",
+        |item| match *item {
+            StructLitField::Regular(ref field) => field.span.lo(),
+            StructLitField::Base(ref expr) => {
+                let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
+                let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
+                let pos = snippet.find_uncommented("..").unwrap();
+                last_field_hi + BytePos(pos as u32)
+            }
+        },
+        |item| match *item {
+            StructLitField::Regular(ref field) => field.span.hi(),
+            StructLitField::Base(ref expr) => expr.span.hi(),
+        },
+        |item| {
+            match *item {
+                StructLitField::Regular(ref field) => rewrite_field(
+                    inner_context,
+                    &field,
+                    &Constraints::new(v_budget.checked_sub(1).unwrap_or(0), indent),
+                ),
+                StructLitField::Base(ref expr) => {
+                    // 2 = ..
+                    expr.rewrite(
+                        inner_context,
+                        &Constraints::new(try_opt!(v_budget.checked_sub(2)), indent + 2),
+                    )
+                    .map(|s| format!("..{}", s))
+                }
+            }
+        },
+        context.source_map.span_after(span, "{"),
+        span.hi(),
+    );
+
+    // #1580
+    self.0.pool.execute(move || {
+        let _timer = segments.0.rotate_timer.time();
+        if let Err(e) = segments.rotate_async(wal) {
+            error!("error compacting segment storage WAL", unsafe { error: e.display() });
+        }
+    });
+
+    // #1581
+    bootstrap.checks.register("PERSISTED_LOCATIONS", move || {
+        if locations2.0.inner_mut.lock().poisoned {
+            Check::new(
+                State::Error,
+                "Persisted location storage is poisoned due to a write failure",
+            )
+        } else {
+            Check::new(State::Healthy, "Persisted location storage is healthy")
+        }
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/nested_skipped/mod.rs b/src/tools/rustfmt/tests/target/nested_skipped/mod.rs
new file mode 100644
index 0000000000000..0ab6f081e4498
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nested_skipped/mod.rs
@@ -0,0 +1,3 @@
+fn ugly() {
+    92;
+}
diff --git a/src/tools/rustfmt/tests/target/nestedmod/mod.rs b/src/tools/rustfmt/tests/target/nestedmod/mod.rs
new file mode 100644
index 0000000000000..1df4629318466
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nestedmod/mod.rs
@@ -0,0 +1,12 @@
+mod mod2a;
+mod mod2b;
+
+mod mymod1 {
+    use mod2a::{Bar, Foo};
+    mod mod3a;
+}
+
+#[path = "mod2c.rs"]
+mod mymod2;
+
+mod submod2;
diff --git a/src/tools/rustfmt/tests/target/nestedmod/mod2a.rs b/src/tools/rustfmt/tests/target/nestedmod/mod2a.rs
new file mode 100644
index 0000000000000..5df457a831653
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nestedmod/mod2a.rs
@@ -0,0 +1,4 @@
+// This is an empty file containing only
+// comments
+
+// ...................
diff --git a/src/tools/rustfmt/tests/target/nestedmod/mod2b.rs b/src/tools/rustfmt/tests/target/nestedmod/mod2b.rs
new file mode 100644
index 0000000000000..9b6ea844e65dc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nestedmod/mod2b.rs
@@ -0,0 +1,2 @@
+#[path = "mod2a.rs"]
+mod c;
diff --git a/src/tools/rustfmt/tests/target/nestedmod/mod2c.rs b/src/tools/rustfmt/tests/target/nestedmod/mod2c.rs
new file mode 100644
index 0000000000000..7db4572e777c0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nestedmod/mod2c.rs
@@ -0,0 +1,3 @@
+// A standard mod
+
+fn a() {}
diff --git a/src/tools/rustfmt/tests/target/nestedmod/mymod1/mod3a.rs b/src/tools/rustfmt/tests/target/nestedmod/mymod1/mod3a.rs
new file mode 100644
index 0000000000000..ae09d8ddac0d1
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nestedmod/mymod1/mod3a.rs
@@ -0,0 +1,2 @@
+// Another mod
+fn a() {}
diff --git a/src/tools/rustfmt/tests/target/nestedmod/submod2/a.rs b/src/tools/rustfmt/tests/target/nestedmod/submod2/a.rs
new file mode 100644
index 0000000000000..120b17145e3a0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nestedmod/submod2/a.rs
@@ -0,0 +1,6 @@
+// Yet Another mod
+// Nested
+
+use c::a;
+
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/nestedmod/submod2/mod.rs b/src/tools/rustfmt/tests/target/nestedmod/submod2/mod.rs
new file mode 100644
index 0000000000000..52f8be910227f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/nestedmod/submod2/mod.rs
@@ -0,0 +1,5 @@
+// Another mod
+
+mod a;
+
+use a::a;
diff --git a/src/tools/rustfmt/tests/target/no_arg_with_commnet.rs b/src/tools/rustfmt/tests/target/no_arg_with_commnet.rs
new file mode 100644
index 0000000000000..69f61b60f29fc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/no_arg_with_commnet.rs
@@ -0,0 +1 @@
+fn foo(/* cooment */) {}
diff --git a/src/tools/rustfmt/tests/target/no_new_line_beginning.rs b/src/tools/rustfmt/tests/target/no_new_line_beginning.rs
new file mode 100644
index 0000000000000..f328e4d9d04c3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/no_new_line_beginning.rs
@@ -0,0 +1 @@
+fn main() {}
diff --git a/src/tools/rustfmt/tests/target/normalize_doc_attributes_should_not_imply_format_doc_comments.rs b/src/tools/rustfmt/tests/target/normalize_doc_attributes_should_not_imply_format_doc_comments.rs
new file mode 100644
index 0000000000000..562d9565e9a96
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/normalize_doc_attributes_should_not_imply_format_doc_comments.rs
@@ -0,0 +1,15 @@
+// rustfmt-normalize_doc_attributes: true
+
+/// Foo
+///
+/// # Example
+/// ```
+/// # #![cfg_attr(not(dox), feature(cfg_target_feature, target_feature, stdsimd))]
+/// # #![cfg_attr(not(dox), no_std)]
+/// fn foo() {  }
+/// ```
+///
+fn foo() {}
+
+///Bar documents
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/target/normalize_multiline_doc_attribute.rs b/src/tools/rustfmt/tests/target/normalize_multiline_doc_attribute.rs
new file mode 100644
index 0000000000000..890c9bb20cd8d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/normalize_multiline_doc_attribute.rs
@@ -0,0 +1,12 @@
+// rustfmt-unstable: true
+// rustfmt-normalize_doc_attributes: true
+
+///This comment
+///is split
+///on multiple lines
+fn foo() {}
+
+/// B1
+///
+/// A1
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/target/obsolete_in_place.rs b/src/tools/rustfmt/tests/target/obsolete_in_place.rs
new file mode 100644
index 0000000000000..3f364c1aecdc7
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/obsolete_in_place.rs
@@ -0,0 +1,9 @@
+// #2953
+
+macro_rules! demo {
+    ($a:ident <- $b:expr) => {};
+}
+
+fn main() {
+    demo!(i <- 0);
+}
diff --git a/src/tools/rustfmt/tests/target/one_line_if_v1.rs b/src/tools/rustfmt/tests/target/one_line_if_v1.rs
new file mode 100644
index 0000000000000..b3c6c4cbeb203
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/one_line_if_v1.rs
@@ -0,0 +1,46 @@
+// rustfmt-version: One
+
+fn plain_if(x: bool) -> u8 {
+    if x {
+        0
+    } else {
+        1
+    }
+}
+
+fn paren_if(x: bool) -> u8 {
+    (if x { 0 } else { 1 })
+}
+
+fn let_if(x: bool) -> u8 {
+    let x = if x { foo() } else { bar() };
+    x
+}
+
+fn return_if(x: bool) -> u8 {
+    return if x { 0 } else { 1 };
+}
+
+fn multi_if() {
+    use std::io;
+    if x {
+        foo()
+    } else {
+        bar()
+    }
+    if x {
+        foo()
+    } else {
+        bar()
+    }
+}
+
+fn middle_if() {
+    use std::io;
+    if x {
+        foo()
+    } else {
+        bar()
+    }
+    let x = 1;
+}
diff --git a/src/tools/rustfmt/tests/target/one_line_if_v2.rs b/src/tools/rustfmt/tests/target/one_line_if_v2.rs
new file mode 100644
index 0000000000000..81ca4c8b8b473
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/one_line_if_v2.rs
@@ -0,0 +1,38 @@
+// rustfmt-version: Two
+
+fn plain_if(x: bool) -> u8 {
+    if x { 0 } else { 1 }
+}
+
+fn paren_if(x: bool) -> u8 {
+    (if x { 0 } else { 1 })
+}
+
+fn let_if(x: bool) -> u8 {
+    let x = if x { foo() } else { bar() };
+    x
+}
+
+fn return_if(x: bool) -> u8 {
+    return if x { 0 } else { 1 };
+}
+
+fn multi_if() {
+    use std::io;
+    if x {
+        foo()
+    } else {
+        bar()
+    }
+    if x { foo() } else { bar() }
+}
+
+fn middle_if() {
+    use std::io;
+    if x {
+        foo()
+    } else {
+        bar()
+    }
+    let x = 1;
+}
diff --git a/src/tools/rustfmt/tests/target/other.rs b/src/tools/rustfmt/tests/target/other.rs
new file mode 100644
index 0000000000000..dfce84fcdc477
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/other.rs
@@ -0,0 +1,5 @@
+// Part of multiple.rs
+
+fn bob() {
+    println!("hello other!");
+}
diff --git a/src/tools/rustfmt/tests/target/paren.rs b/src/tools/rustfmt/tests/target/paren.rs
new file mode 100644
index 0000000000000..f7714d85dd1f9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/paren.rs
@@ -0,0 +1,6 @@
+fn main() {
+    let x = (1);
+    let y = (/* comment */(2));
+    let z = ((3)/* comment */);
+    let a = (4/* comment */);
+}
diff --git a/src/tools/rustfmt/tests/target/path_clarity/foo.rs b/src/tools/rustfmt/tests/target/path_clarity/foo.rs
new file mode 100644
index 0000000000000..cd247fabfe340
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/path_clarity/foo.rs
@@ -0,0 +1,2 @@
+// rustfmt-edition: 2018
+mod bar;
diff --git a/src/tools/rustfmt/tests/target/path_clarity/foo/bar.rs b/src/tools/rustfmt/tests/target/path_clarity/foo/bar.rs
new file mode 100644
index 0000000000000..b18a7d3499c54
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/path_clarity/foo/bar.rs
@@ -0,0 +1,3 @@
+pub fn fn_in_bar() {
+    println!("foo/bar.rs");
+}
diff --git a/src/tools/rustfmt/tests/target/paths.rs b/src/tools/rustfmt/tests/target/paths.rs
new file mode 100644
index 0000000000000..0d2ba797eb793
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/paths.rs
@@ -0,0 +1,28 @@
+// rustfmt-normalize_comments: true
+
+fn main() {
+    let constellation_chan =
+        Constellation::<layout::layout_task::LayoutTask, script::script_task::ScriptTask>::start(
+            compositor_proxy,
+            resource_task,
+            image_cache_task,
+            font_cache_task,
+            time_profiler_chan,
+            mem_profiler_chan,
+            devtools_chan,
+            storage_task,
+            supports_clipboard,
+        );
+
+    Quux::<
+        ParamOne, // Comment 1
+        ParamTwo, // Comment 2
+    >::some_func();
+
+    <*mut JSObject>::relocate(entry);
+
+    let x: Foo<A>;
+    let x: Foo/*::*/<A>;
+}
+
+fn op(foo: Bar, key: &[u8], upd: Fn(Option<&memcache::Item>, Baz) -> Result) -> MapResult {}
diff --git a/src/tools/rustfmt/tests/target/pattern-condense-wildcards.rs b/src/tools/rustfmt/tests/target/pattern-condense-wildcards.rs
new file mode 100644
index 0000000000000..a85a16004ad23
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/pattern-condense-wildcards.rs
@@ -0,0 +1,12 @@
+// rustfmt-normalize_comments: true
+// rustfmt-condense_wildcard_suffixes: true
+
+fn main() {
+    match x {
+        Butt(..) => "hah",
+        Tup(_) => "nah",
+        Quad(_, _, x, _) => " also no rewrite",
+        Quad(x, ..) => "condense me pls",
+        Weird(x, _, _, /* don't condense before */ ..) => "pls work",
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/pattern.rs b/src/tools/rustfmt/tests/target/pattern.rs
new file mode 100644
index 0000000000000..576018ac623fd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/pattern.rs
@@ -0,0 +1,98 @@
+// rustfmt-normalize_comments: true
+#![feature(exclusive_range_pattern)]
+use core::u8::MAX;
+
+fn main() {
+    let z = match x {
+        "pat1" => 1,
+        (ref x, ref mut y /* comment */) => 2,
+    };
+
+    if let <T as Trait>::CONST = ident {
+        do_smth();
+    }
+
+    let Some(ref xyz /* comment! */) = opt;
+
+    if let None = opt2 {
+        panic!("oh noes");
+    }
+
+    let foo @ bar(f) = 42;
+    let a::foo(..) = 42;
+    let [] = 42;
+    let [a, b, c] = 42;
+    let [a, b, c] = 42;
+    let [a, b, c, d, e, f, g] = 42;
+    let foo {} = 42;
+    let foo { .. } = 42;
+    let foo { x, y: ref foo, .. } = 42;
+    let foo {
+        x,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,
+        ..
+    } = 42;
+    let foo {
+        x,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,
+    } = 42;
+    let foo {
+        x,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,
+        ..
+    };
+    let foo {
+        x,
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: ref foo,
+    };
+
+    match b"12" {
+        [0, 1..MAX] => {}
+        _ => {}
+    }
+}
+
+impl<'a, 'b> ResolveGeneratedContentFragmentMutator<'a, 'b> {
+    fn mutate_fragment(&mut self, fragment: &mut Fragment) {
+        match **info {
+            GeneratedContentInfo::ContentItem(ContentItem::Counter(
+                ref counter_name,
+                counter_style,
+            )) => {}
+        }
+    }
+}
+
+fn issue_1319() {
+    if let (Event { .. }, ..) = ev_state {}
+}
+
+fn issue_1874() {
+    if let Some(()) = x {
+        y
+    }
+}
+
+fn combine_patterns() {
+    let x = match y {
+        Some(Some(Foo {
+            z: Bar(..),
+            a: Bar(..),
+            b: Bar(..),
+        })) => z,
+        _ => return,
+    };
+}
+
+fn slice_patterns() {
+    match b"123" {
+        [0, ..] => {}
+        [0, foo] => {}
+        _ => {}
+    }
+}
+
+fn issue3728() {
+    let foo = |(c,)| c;
+    foo((1,));
+}
diff --git a/src/tools/rustfmt/tests/target/preserves_carriage_return_for_unix.rs b/src/tools/rustfmt/tests/target/preserves_carriage_return_for_unix.rs
new file mode 100644
index 0000000000000..e5e0b28659896
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/preserves_carriage_return_for_unix.rs
@@ -0,0 +1,2 @@
+// rustfmt-newline_style: Unix
+// Foo
Bar
diff --git a/src/tools/rustfmt/tests/target/preserves_carriage_return_for_windows.rs b/src/tools/rustfmt/tests/target/preserves_carriage_return_for_windows.rs
new file mode 100644
index 0000000000000..1085360ee59e8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/preserves_carriage_return_for_windows.rs
@@ -0,0 +1,2 @@
+// rustfmt-newline_style: Windows
+// Foo
Bar
diff --git a/src/tools/rustfmt/tests/target/pub-restricted.rs b/src/tools/rustfmt/tests/target/pub-restricted.rs
new file mode 100644
index 0000000000000..8cc2ade612afa
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/pub-restricted.rs
@@ -0,0 +1,64 @@
+pub(super) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+pub(crate) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+crate enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+pub(in global::path::to::some_mod) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
+
+pub(in local::path::to::some_mod) enum WriteState<D> {
+    WriteId {
+        id: U64Writer,
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteSize {
+        size: U64Writer,
+        payload: Option<Writer<D>>,
+    },
+    WriteData(Writer<D>),
+}
diff --git a/src/tools/rustfmt/tests/target/raw_identifiers.rs b/src/tools/rustfmt/tests/target/raw_identifiers.rs
new file mode 100644
index 0000000000000..6ab0fdf053bcc
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/raw_identifiers.rs
@@ -0,0 +1,66 @@
+#![feature(custom_attribute)]
+#![feature(raw_identifiers)]
+#![feature(extern_types)]
+#![allow(invalid_type_param_default)]
+#![allow(unused_attributes)]
+
+use r#foo as r#alias_foo;
+
+// https://github.com/rust-lang/rustfmt/issues/3837
+pub(crate) static r#break: &'static str = "foo";
+
+fn main() {
+    #[r#attr]
+    r#foo::r#bar();
+
+    let r#local = r#Struct { r#field: () };
+    r#local.r#field = 1;
+    r#foo.r#barr();
+    let r#async = r#foo(r#local);
+    r#macro!();
+
+    if let r#sub_pat @ r#Foo(_) = r#Foo(3) {}
+
+    match r#async {
+        r#Foo | r#Bar => r#foo(),
+    }
+}
+
+fn r#bar<'a, r#T>(r#x: &'a r#T) {}
+
+mod r#foo {
+    pub fn r#bar() {}
+}
+
+enum r#Foo {
+    r#Bar {},
+}
+
+struct r#Struct {
+    r#field: r#FieldType,
+}
+
+trait r#Trait {
+    type r#Type;
+}
+
+impl r#Trait for r#Impl {
+    type r#Type = r#u32;
+    fn r#xxx(r#fjio: r#u32) {}
+}
+
+extern "C" {
+    type r#ccc;
+    static r#static_val: u32;
+}
+
+macro_rules! r#macro {
+    () => {};
+}
+
+macro_rules! foo {
+    ($x:expr) => {
+        let r#catch = $x + 1;
+        println!("{}", r#catch);
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/remove_blank_lines.rs b/src/tools/rustfmt/tests/target/remove_blank_lines.rs
new file mode 100644
index 0000000000000..de74c81ef57f3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/remove_blank_lines.rs
@@ -0,0 +1,28 @@
+fn main() {
+    let x = 1;
+
+    let y = 2;
+
+    println!("x + y = {}", x + y);
+}
+
+fn foo() {
+    #![attribute]
+
+    let x = 1;
+
+    // comment
+}
+// comment after item
+
+// comment before item
+fn bar() {
+    let x = 1;
+    // comment after statement
+
+    // comment before statement
+    let y = 2;
+    let z = 3;
+
+    println!("x + y + z = {}", x + y + z);
+}
diff --git a/src/tools/rustfmt/tests/target/reorder-impl-items.rs b/src/tools/rustfmt/tests/target/reorder-impl-items.rs
new file mode 100644
index 0000000000000..16efff55b0660
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/reorder-impl-items.rs
@@ -0,0 +1,15 @@
+// rustfmt-reorder_impl_items: true
+
+// The ordering of the following impl items should be idempotent.
+impl<'a> Command<'a> {
+    pub fn send_to(&self, w: &mut io::Write) -> io::Result<()> {
+        match self {
+            &Command::Data(ref c) => c.send_to(w),
+            &Command::Vrfy(ref c) => c.send_to(w),
+        }
+    }
+
+    pub fn parse(arg: &[u8]) -> Result<Command, ParseError> {
+        nom_to_result(command(arg))
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/should_not_format_string_when_format_strings_is_not_set.rs b/src/tools/rustfmt/tests/target/should_not_format_string_when_format_strings_is_not_set.rs
new file mode 100644
index 0000000000000..efb755d4aea86
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/should_not_format_string_when_format_strings_is_not_set.rs
@@ -0,0 +1,16 @@
+// format_strings is false by default.
+
+println!(
+    "DirEntry {{ \
+        binary_name: {:<64}, \
+        context_id: {:>2}, \
+        file_size: {:>6}, \
+        offset: 0x {:>08X}, \
+        actual_crc: 0x{:>08X} \
+    }}",
+    dir_entry.binary_name,
+    dir_entry.context_id,
+    dir_entry.file_size,
+    dir_entry.offset,
+    dir_entry.actual_crc
+);
diff --git a/src/tools/rustfmt/tests/target/single-line-if-else.rs b/src/tools/rustfmt/tests/target/single-line-if-else.rs
new file mode 100644
index 0000000000000..98fd793cba2d8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/single-line-if-else.rs
@@ -0,0 +1,58 @@
+// Format if-else expressions on a single line, when possible.
+
+fn main() {
+    let a = if 1 > 2 { unreachable!() } else { 10 };
+
+    let a = if x {
+        1
+    } else if y {
+        2
+    } else {
+        3
+    };
+
+    let b = if cond() {
+        5
+    } else {
+        // Brief comment.
+        10
+    };
+
+    let c = if cond() {
+        statement();
+
+        5
+    } else {
+        10
+    };
+
+    let d = if let Some(val) = turbo {
+        "cool"
+    } else {
+        "beans"
+    };
+
+    if cond() {
+        statement();
+    } else {
+        other_statement();
+    }
+
+    if true {
+        do_something()
+    }
+
+    let x = if veeeeeeeeery_loooooong_condition() {
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    } else {
+        bbbbbbbbbb
+    };
+
+    let x = if veeeeeeeeery_loooooong_condition() {
+        aaaaaaaaaaaaaaaaaaaaaaaaa
+    } else {
+        bbbbbbbbbb
+    };
+
+    funk(if test() { 1 } else { 2 }, arg2);
+}
diff --git a/src/tools/rustfmt/tests/target/single-line-macro/v1.rs b/src/tools/rustfmt/tests/target/single-line-macro/v1.rs
new file mode 100644
index 0000000000000..a3aa631ed4af3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/single-line-macro/v1.rs
@@ -0,0 +1,10 @@
+// rustfmt-version: One
+
+// #2652
+// Preserve trailing comma inside macro, even if it looks an array.
+macro_rules! bar {
+    ($m:ident) => {
+        $m!([a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z,]);
+        $m!([a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z]);
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/single-line-macro/v2.rs b/src/tools/rustfmt/tests/target/single-line-macro/v2.rs
new file mode 100644
index 0000000000000..9c6bcf33ad534
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/single-line-macro/v2.rs
@@ -0,0 +1,14 @@
+// rustfmt-version: Two
+
+// #2652
+// Preserve trailing comma inside macro, even if it looks an array.
+macro_rules! bar {
+    ($m:ident) => {
+        $m!([
+            a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z,
+        ]);
+        $m!([
+            a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z
+        ]);
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/skip.rs b/src/tools/rustfmt/tests/target/skip.rs
new file mode 100644
index 0000000000000..6c9737a3377e9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/skip.rs
@@ -0,0 +1,87 @@
+// Test the skip attribute works
+
+#[rustfmt::skip]
+fn foo() { badly; formatted; stuff
+; }
+
+#[rustfmt::skip]
+trait Foo
+{
+fn foo(
+);
+}
+
+impl LateLintPass for UsedUnderscoreBinding {
+    #[cfg_attr(rustfmt, rustfmt::skip)]
+    fn check_expr() { // comment
+    }
+}
+
+fn issue1346() {
+    #[cfg_attr(rustfmt, rustfmt::skip)]
+    Box::new(self.inner.call(req).then(move |result| {
+        match result {
+            Ok(resp) => Box::new(future::done(Ok(resp))),
+            Err(e) => {
+                try_error!(clo_stderr, "{}", e);
+                Box::new(future::err(e))
+            }
+        }
+    }))
+}
+
+fn skip_on_statements() {
+    // Outside block
+    #[rustfmt::skip]
+    {
+        foo; bar;
+            // junk
+    }
+
+    {
+        // Inside block
+        #![rustfmt::skip]
+        foo; bar;
+            // junk
+    }
+
+    // Semi
+    #[cfg_attr(rustfmt, rustfmt::skip)]
+    foo(
+        1, 2, 3, 4,
+        1, 2,
+        1, 2, 3,
+    );
+
+    // Local
+    #[cfg_attr(rustfmt, rustfmt::skip)]
+    let x = foo(  a,   b  ,  c);
+
+    // Item
+    #[cfg_attr(rustfmt, rustfmt::skip)]
+    use foobar;
+
+    // Mac
+    #[cfg_attr(rustfmt, rustfmt::skip)]
+    vec![
+        1, 2, 3, 4,
+        1, 2, 3, 4,
+        1, 2, 3, 4,
+        1, 2, 3,
+        1,
+        1, 2,
+        1,
+    ];
+
+    // Expr
+    #[cfg_attr(rustfmt, rustfmt::skip)]
+    foo(  a,   b  ,  c)
+}
+
+// Check that the skip attribute applies to other attributes.
+#[rustfmt::skip]
+#[cfg
+(  a , b
+)]
+fn
+main() {}
diff --git a/src/tools/rustfmt/tests/target/skip/foo.rs b/src/tools/rustfmt/tests/target/skip/foo.rs
new file mode 100644
index 0000000000000..776658f8fe574
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/skip/foo.rs
@@ -0,0 +1,5 @@
+#![rustfmt::skip]
+
+fn
+foo()
+{}
diff --git a/src/tools/rustfmt/tests/target/skip/main.rs b/src/tools/rustfmt/tests/target/skip/main.rs
new file mode 100644
index 0000000000000..2d33bef92519e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/skip/main.rs
@@ -0,0 +1,5 @@
+mod foo;
+
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/tools/rustfmt/tests/target/skip_mod.rs b/src/tools/rustfmt/tests/target/skip_mod.rs
new file mode 100644
index 0000000000000..d770ab349f4ef
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/skip_mod.rs
@@ -0,0 +1,3 @@
+#![rustfmt::skip]
+use a ::  b
+;
diff --git a/src/tools/rustfmt/tests/target/soft-wrapping.rs b/src/tools/rustfmt/tests/target/soft-wrapping.rs
new file mode 100644
index 0000000000000..5b4c6d9e85a52
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/soft-wrapping.rs
@@ -0,0 +1,15 @@
+// rustfmt-wrap_comments: true
+// rustfmt-max_width: 80
+// Soft wrapping for comments.
+
+// #535, soft wrapping for comments
+// Compare the lowest `f32` of both inputs for greater than or equal. The
+// lowest 32 bits of the result will be `0xffffffff` if `a.extract(0)` is
+// ggreater than or equal `b.extract(0)`, or `0` otherwise. The upper 96 bits
+// off the result are the upper 96 bits of `a`.
+
+/// Compares the lowest `f32` of both inputs for greater than or equal. The
+/// lowest 32 bits of the result will be `0xffffffff` if `a.extract(0)` is
+/// greater than or equal `b.extract(0)`, or `0` otherwise. The upper 96 bits
+/// off the result are the upper 96 bits of `a`.
+fn foo() {}
diff --git a/src/tools/rustfmt/tests/target/space-not-before-newline.rs b/src/tools/rustfmt/tests/target/space-not-before-newline.rs
new file mode 100644
index 0000000000000..9d75b726aa0a0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/space-not-before-newline.rs
@@ -0,0 +1,8 @@
+struct Foo {
+    a: (),
+    // spaces ^^^ to be removed
+}
+enum Foo {
+    Bar,
+    // spaces ^^^ to be removed
+}
diff --git a/src/tools/rustfmt/tests/target/spaces-around-ranges.rs b/src/tools/rustfmt/tests/target/spaces-around-ranges.rs
new file mode 100644
index 0000000000000..b53e5b58b8cd6
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/spaces-around-ranges.rs
@@ -0,0 +1,15 @@
+// rustfmt-spaces_around_ranges: true
+
+fn bar(v: &[u8]) {}
+
+fn foo() {
+    let a = vec![0; 20];
+    for j in 0 ..= 20 {
+        for i in 0 .. 3 {
+            bar(a[i .. j]);
+            bar(a[i ..]);
+            bar(a[.. j]);
+            bar(a[..= (j + 1)]);
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/statements.rs b/src/tools/rustfmt/tests/target/statements.rs
new file mode 100644
index 0000000000000..c1e7dc464c2a0
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/statements.rs
@@ -0,0 +1,42 @@
+// FIXME(calebcartwright) - Hopefully one day we can
+// elide these redundant semis like we do in other contexts.
+fn redundant_item_semis() {
+    impl Foo {
+        fn get(&self) -> usize {
+            5
+        }
+    };
+
+    impl Bar {
+        fn get(&self) -> usize {
+            5
+        }
+    } /*asdfsf*/
+    ;
+
+    impl Baz {
+        fn get(&self) -> usize {
+            5
+        }
+    } /*asdfsf*/
+
+    // why would someone do this
+    ;
+
+    impl Qux {
+        fn get(&self) -> usize {
+            5
+        }
+    }
+
+    // why
+    ;
+
+    impl Lorem {
+        fn get(&self) -> usize {
+            5
+        }
+    }
+    // oh why
+    ;
+}
diff --git a/src/tools/rustfmt/tests/target/static.rs b/src/tools/rustfmt/tests/target/static.rs
new file mode 100644
index 0000000000000..5daccf3e7f742
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/static.rs
@@ -0,0 +1,27 @@
+const FILE_GENERIC_READ: DWORD =
+    STANDARD_RIGHTS_READ | FILE_READ_DATA | FILE_READ_ATTRIBUTES | FILE_READ_EA | SYNCHRONIZE;
+
+static boolnames: &'static [&'static str] = &[
+    "bw", "am", "xsb", "xhp", "xenl", "eo", "gn", "hc", "km", "hs", "in", "db", "da", "mir",
+    "msgr", "os", "eslok", "xt", "hz", "ul", "xon", "nxon", "mc5i", "chts", "nrrmc", "npc",
+    "ndscr", "ccc", "bce", "hls", "xhpa", "crxm", "daisy", "xvpa", "sam", "cpix", "lpix", "OTbs",
+    "OTns", "OTnc", "OTMT", "OTNL", "OTpt", "OTxr",
+];
+
+static mut name: SomeType =
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;
+
+pub static count: u8 = 10;
+
+pub const test: &Type = &val;
+
+impl Color {
+    pub const WHITE: u32 = 10;
+}
+
+// #1391
+pub const XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX: NTSTATUS =
+    0 as usize;
+
+pub const XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:
+    Yyyyyyyyyyyyyyyyyyyyyyyyyyyy = 1;
diff --git a/src/tools/rustfmt/tests/target/string-lit-2.rs b/src/tools/rustfmt/tests/target/string-lit-2.rs
new file mode 100644
index 0000000000000..6b95e25a052b2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/string-lit-2.rs
@@ -0,0 +1,25 @@
+fn main() -> &'static str {
+    let too_many_lines = "Hello";
+    let leave_me = "sssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss\
+                    s
+                    jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj";
+}
+
+fn issue_1237() {
+    let msg = "eedadn\n\
+               drvtee\n\
+               eandsr\n\
+               raavrd\n\
+               atevrs\n\
+               tsrnev\n\
+               sdttsa\n\
+               rasrtv\n\
+               nssdts\n\
+               ntnada\n\
+               svetve\n\
+               tesnvt\n\
+               vntsnd\n\
+               vrdear\n\
+               dvrsen\n\
+               enarar";
+}
diff --git a/src/tools/rustfmt/tests/target/string-lit-custom.rs b/src/tools/rustfmt/tests/target/string-lit-custom.rs
new file mode 100644
index 0000000000000..89639b8ebd3f2
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/string-lit-custom.rs
@@ -0,0 +1,20 @@
+fn main() {
+    let expected = "; ModuleID = \'foo\'
+
+; Function Attrs: nounwind
+declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) #0
+
+declare i32 @write(i32, i8*, i32)
+
+declare i32 @putchar(i32)
+
+declare i32 @getchar()
+
+define i32 @main() {
+entry:
+  ret i32 0
+}
+
+attributes #0 = { nounwind }
+";
+}
diff --git a/src/tools/rustfmt/tests/target/string-lit.rs b/src/tools/rustfmt/tests/target/string-lit.rs
new file mode 100644
index 0000000000000..2d33061074de5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/string-lit.rs
@@ -0,0 +1,63 @@
+// rustfmt-format_strings: true
+// Long string literals
+
+fn main() -> &'static str {
+    let str = "AAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAaAA \
+               AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAa";
+    let str = "AAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaAa";
+    let str = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+
+    let too_many_lines = "Hello";
+
+    // Make sure we don't break after an escape character.
+    let odd_length_name =
+        "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
+    let even_length_name =
+        "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
+
+    let really_long_variable_name = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+
+    let raw_string = r#"Do
+not
+remove
+formatting"#;
+
+    filename.replace(" ", "\\");
+
+    let xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx =
+        funktion("yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy");
+
+    let unicode = "a̐éö̲\r\n";
+    let unicode2 = "Löwe 老虎 Léopard";
+    let unicode3 = "中华Việt Nam";
+    let unicode4 = "☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃☃";
+
+    "stuffin'"
+}
+
+fn issue682() {
+    let a = "hello \\ o/";
+    let b = a.replace("\\ ", "\\");
+}
+
+fn issue716() {
+    println!(
+        "forall x. mult(e(), x) = x /\\
+              forall x. mult(x, x) = e()"
+    );
+}
+
+fn issue_1282() {
+    {
+        match foo {
+            Permission::AndroidPermissionAccessLocationExtraCommands => {
+                "android.permission.ACCESS_LOCATION_EXTRA_COMMANDS"
+            }
+        }
+    }
+}
+
+// #1987
+#[link_args = "-s NO_FILESYSTEM=1 -s NO_EXIT_RUNTIME=1 -s EXPORTED_RUNTIME_METHODS=[\"_malloc\"] \
+               -s NO_DYNAMIC_EXECUTION=1 -s ELIMINATE_DUPLICATE_FUNCTIONS=1 -s EVAL_CTORS=1"]
+extern "C" {}
diff --git a/src/tools/rustfmt/tests/target/string_punctuation.rs b/src/tools/rustfmt/tests/target/string_punctuation.rs
new file mode 100644
index 0000000000000..0b8ec1b7f3935
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/string_punctuation.rs
@@ -0,0 +1,24 @@
+// rustfmt-format_strings: true
+
+fn main() {
+    println!(
+        "ThisIsAReallyLongStringWithNoSpaces.It_should_prefer_to_break_onpunctuation:\
+         Likethisssssssssssss"
+    );
+    format!("{}__{}__{}ItShouldOnlyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyNoticeSemicolonsPeriodsColonsAndCommasAndResortToMid-CharBreaksAfterPunctuation{}{}",x,y,z,a,b);
+    println!(
+        "aaaaaaaaaaaaaaaaaaaaaaaaaaaaalhijalfhiigjapdighjapdigjapdighdapighapdighpaidhg;\
+         adopgihadoguaadbadgad,qeoihapethae8t0aet8haetadbjtaeg;\
+         ooeouthaoeutgadlgajduabgoiuadogabudogubaodugbadgadgadga;adoughaoeugbaouea"
+    );
+    println!(
+        "sentuhaesnuthaesnutheasunteahusnaethuseantuihaesntdiastnidaetnuhaideuhsenathe。\
+         WeShouldSupportNonAsciiPunctuations§\
+         ensuhatheasunteahsuneathusneathuasnuhaesnuhaesnuaethusnaetuheasnuth"
+    );
+    println!(
+        "ThisIsASampleOfCJKString.祇園精舍の鐘の声、諸行無常の響きあり。娑羅双樹の花の色、\
+         盛者必衰の理をあらはす。奢れる人も久しからず、ただ春の夜の夢のごとし。\
+         猛き者もつひにはほろびぬ、ひとへに風の前の塵に同じ。"
+    );
+}
diff --git a/src/tools/rustfmt/tests/target/struct-field-attributes.rs b/src/tools/rustfmt/tests/target/struct-field-attributes.rs
new file mode 100644
index 0000000000000..0f461b98bc737
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/struct-field-attributes.rs
@@ -0,0 +1,62 @@
+// #1535
+#![feature(struct_field_attributes)]
+
+struct Foo {
+    bar: u64,
+
+    #[cfg(test)]
+    qux: u64,
+}
+
+fn do_something() -> Foo {
+    Foo {
+        bar: 0,
+
+        #[cfg(test)]
+        qux: 1,
+    }
+}
+
+fn main() {
+    do_something();
+}
+
+// #1462
+struct Foo {
+    foo: usize,
+    #[cfg(feature = "include-bar")]
+    bar: usize,
+}
+
+fn new_foo() -> Foo {
+    Foo {
+        foo: 0,
+        #[cfg(feature = "include-bar")]
+        bar: 0,
+    }
+}
+
+// #2044
+pub enum State {
+    Closure(
+        #[cfg_attr(
+            feature = "serde_derive",
+            serde(state_with = "::serialization::closure")
+        )]
+        GcPtr<ClosureData>,
+    ),
+}
+
+struct Fields(
+    #[cfg_attr(
+        feature = "serde_derive",
+        serde(state_with = "::base::serialization::shared")
+    )]
+    Arc<Vec<InternedStr>>,
+);
+
+// #2309
+pub struct A {
+    #[doc = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"]
+    pub foos: Vec<bool>,
+}
diff --git a/src/tools/rustfmt/tests/target/struct_lits.rs b/src/tools/rustfmt/tests/target/struct_lits.rs
new file mode 100644
index 0000000000000..d3bc364c3504a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/struct_lits.rs
@@ -0,0 +1,190 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo { a: x };
+
+    Foo {
+        a: foo(), // comment
+        // comment
+        b: bar(),
+        ..something
+    };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b() };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        a: f(),
+        b: b(),
+    };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo { a: Bar, b: f() };
+
+    Quux {
+        x: if cond {
+            bar();
+        },
+        y: baz(),
+    };
+
+    A {
+        // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+        // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit.
+        // Donec et mollis dolor.
+        first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item,
+    };
+
+    Some(Data::MethodCallData(MethodCallData {
+        span: sub_span.unwrap(),
+        scope: self.enclosing_scope(id),
+        ref_id: def_id,
+        decl_id: Some(decl_id),
+    }));
+
+    Diagram {
+        //                 o        This graph demonstrates how
+        //                / \       significant whitespace is
+        //               o   o      preserved.
+        //              /|\   \
+        //             o o o   o
+        graph: G,
+    }
+}
+
+fn matcher() {
+    TagTerminatedByteMatcher {
+        matcher: ByteMatcher {
+            pattern: b"<HTML",
+            mask: b"\xFF\xDF\xDF\xDF\xDF\xFF",
+        },
+    };
+}
+
+fn issue177() {
+    struct Foo<T> {
+        memb: T,
+    }
+    let foo = Foo::<i64> { memb: 10 };
+}
+
+fn issue201() {
+    let s = S { a: 0, ..b };
+}
+
+fn issue201_2() {
+    let s = S { a: S2 { ..c }, ..b };
+}
+
+fn issue278() {
+    let s = S {
+        a: 0,
+        //
+        b: 0,
+    };
+    let s1 = S {
+        a: 0,
+        // foo
+        //
+        // bar
+        b: 0,
+    };
+}
+
+fn struct_exprs() {
+    Foo { a: 1, b: f(2) };
+    Foo {
+        a: 1,
+        b: f(2),
+        ..g(3)
+    };
+    LoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongStruct {
+        ..base
+    };
+    IntrinsicISizesContribution {
+        content_intrinsic_sizes: IntrinsicISizes {
+            minimum_inline_size: 0,
+        },
+    };
+}
+
+fn issue123() {
+    Foo { a: b, c: d, e: f };
+
+    Foo {
+        a: bb,
+        c: dd,
+        e: ff,
+    };
+
+    Foo {
+        a: ddddddddddddddddddddd,
+        b: cccccccccccccccccccccccccccccccccccccc,
+    };
+}
+
+fn issue491() {
+    Foo {
+        guard: None,
+        arm: 0, // Comment
+    };
+
+    Foo {
+        arm: 0, // Comment
+    };
+
+    Foo {
+        a: aaaaaaaaaa,
+        b: bbbbbbbb,
+        c: cccccccccc,
+        d: dddddddddd, // a comment
+        e: eeeeeeeee,
+    };
+}
+
+fn issue698() {
+    Record {
+        ffffffffffffffffffffffffffields: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    };
+    Record {
+        ffffffffffffffffffffffffffields:
+            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    }
+}
+
+fn issue835() {
+    MyStruct {};
+    MyStruct { /* a comment */ };
+    MyStruct {
+        // Another comment
+    };
+    MyStruct {}
+}
+
+fn field_init_shorthand() {
+    MyStruct { x, y, z };
+    MyStruct { x, y, z, ..base };
+    Foo {
+        aaaaaaaaaa,
+        bbbbbbbb,
+        cccccccccc,
+        dddddddddd, // a comment
+        eeeeeeeee,
+    };
+    Record {
+        ffffffffffffffffffffffffffieldsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/struct_lits_multiline.rs b/src/tools/rustfmt/tests/target/struct_lits_multiline.rs
new file mode 100644
index 0000000000000..b29aafd05484a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/struct_lits_multiline.rs
@@ -0,0 +1,117 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-struct_lit_single_line: false
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo {
+        a: x,
+    };
+
+    Foo {
+        a: foo(), // comment
+        // comment
+        b: bar(),
+        ..something
+    };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        a: foo(),
+        b: bar(),
+    };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        a: foo(),
+        b: bar(),
+    };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo {
+        // Comment
+        a: foo(), // Comment
+        // Comment
+        b: bar(), // Comment
+    };
+
+    Foo {
+        a: Bar,
+        b: foo(),
+    };
+
+    Quux {
+        x: if cond {
+            bar();
+        },
+        y: baz(),
+    };
+
+    A {
+        // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+        // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit.
+        // Donec et mollis dolor.
+        first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item,
+    };
+
+    Some(Data::MethodCallData(MethodCallData {
+        span: sub_span.unwrap(),
+        scope: self.enclosing_scope(id),
+        ref_id: def_id,
+        decl_id: Some(decl_id),
+    }));
+
+    Diagram {
+        //                 o        This graph demonstrates how
+        //                / \       significant whitespace is
+        //               o   o      preserved.
+        //              /|\   \
+        //             o o o   o
+        graph: G,
+    }
+}
+
+fn matcher() {
+    TagTerminatedByteMatcher {
+        matcher: ByteMatcher {
+            pattern: b"<HTML",
+            mask: b"\xFF\xDF\xDF\xDF\xDF\xFF",
+        },
+    };
+}
+
+fn issue177() {
+    struct Foo<T> {
+        memb: T,
+    }
+    let foo = Foo::<i64> {
+        memb: 10,
+    };
+}
+
+fn issue201() {
+    let s = S {
+        a: 0,
+        ..b
+    };
+}
+
+fn issue201_2() {
+    let s = S {
+        a: S2 {
+            ..c
+        },
+        ..b
+    };
+}
+
+fn issue491() {
+    Foo {
+        guard: None,
+        arm: 0, // Comment
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/struct_lits_visual.rs b/src/tools/rustfmt/tests/target/struct_lits_visual.rs
new file mode 100644
index 0000000000000..a9627fb90f51f
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/struct_lits_visual.rs
@@ -0,0 +1,49 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-indent_style: Visual
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo { a: x };
+
+    Foo { a: foo(), // comment
+          // comment
+          b: bar(),
+          ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: f(), b: b() };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { // Comment
+                                                                                        a: foo(), /* Comment */
+                                                                                        // Comment
+                                                                                        b: bar() /* Comment */ };
+
+    Foo { a: Bar, b: f() };
+
+    Quux { x: if cond {
+               bar();
+           },
+           y: baz() };
+
+    Baz { x: yxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+          z: zzzzz /* test */ };
+
+    A { // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+        // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante
+        // hendrerit. Donec et mollis dolor.
+        first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item };
+
+    Diagram { //                 o        This graph demonstrates how
+              //                / \       significant whitespace is
+              //               o   o      preserved.
+              //              /|\   \
+              //             o o o   o
+              graph: G }
+}
diff --git a/src/tools/rustfmt/tests/target/struct_lits_visual_multiline.rs b/src/tools/rustfmt/tests/target/struct_lits_visual_multiline.rs
new file mode 100644
index 0000000000000..3f43ef0c981d5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/struct_lits_visual_multiline.rs
@@ -0,0 +1,49 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-indent_style: Visual
+// rustfmt-struct_lit_single_line: false
+
+// Struct literal expressions.
+
+fn main() {
+    let x = Bar;
+
+    // Comment
+    let y = Foo { a: x };
+
+    Foo { a: foo(), // comment
+          // comment
+          b: bar(),
+          ..something };
+
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { a: foo(),
+                                                                               b: bar() };
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo { // Comment
+                                                                                        a: foo(), /* Comment */
+                                                                                        // Comment
+                                                                                        b: bar() /* Comment */ };
+
+    Foo { a: Bar,
+          b: foo() };
+
+    Quux { x: if cond {
+               bar();
+           },
+           y: baz() };
+
+    A { // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+        // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante
+        // hendrerit. Donec et mollis dolor.
+        first: item(),
+        // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+        // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+        second: Item };
+
+    Diagram { //                 o        This graph demonstrates how
+              //                / \       significant whitespace is
+              //               o   o      preserved.
+              //              /|\   \
+              //             o o o   o
+              graph: G }
+}
diff --git a/src/tools/rustfmt/tests/target/struct_tuple_visual.rs b/src/tools/rustfmt/tests/target/struct_tuple_visual.rs
new file mode 100644
index 0000000000000..f95f3fe4fd39a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/struct_tuple_visual.rs
@@ -0,0 +1,36 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+// rustfmt-indent_style: Visual
+fn foo() {
+    Fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(f(), b());
+
+    Foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(// Comment
+                                                                                      foo(), /* Comment */
+                                                                                      // Comment
+                                                                                      bar() /* Comment */);
+
+    Foo(Bar, f());
+
+    Quux(if cond {
+             bar();
+         },
+         baz());
+
+    Baz(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
+        zzzzz /* test */);
+
+    A(// Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit
+      // amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante
+      // hendrerit. Donec et mollis dolor.
+      item(),
+      // Praesent et diam eget libero egestas mattis sit amet vitae augue.
+      // Nam tincidunt congue enim, ut porta lorem lacinia consectetur.
+      Item);
+
+    Diagram(//                 o        This graph demonstrates how
+            //                / \       significant whitespace is
+            //               o   o      preserved.
+            //              /|\   \
+            //             o o o   o
+            G)
+}
diff --git a/src/tools/rustfmt/tests/target/structs.rs b/src/tools/rustfmt/tests/target/structs.rs
new file mode 100644
index 0000000000000..4948e37a5a3df
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/structs.rs
@@ -0,0 +1,358 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+/// A Doc comment
+#[AnAttribute]
+pub struct Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f: SomeType, // Comment beside a field
+    // Comment on a field
+    #[AnAttribute]
+    g: SomeOtherType,
+    /// A doc comment on a field
+    h: AThirdType,
+    pub i: TypeForPublicField,
+}
+
+// Destructuring
+fn foo() {
+    S { x: 5, .. };
+    Struct { .. } = Struct { a: 1, b: 4 };
+    Struct { a, .. } = Struct { a: 1, b: 2, c: 3 };
+    TupleStruct(a, .., b) = TupleStruct(1, 2);
+    TupleStruct(..) = TupleStruct(3, 4);
+    TupleStruct(
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        ..,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    ) = TupleStruct(1, 2);
+}
+
+// #1095
+struct S<T /* comment */> {
+    t: T,
+}
+
+// #1029
+pub struct Foo {
+    #[doc(hidden)]
+    // This will NOT get deleted!
+    bar: String, // hi
+}
+
+// #1029
+struct X {
+    // `x` is an important number.
+    #[allow(unused)] // TODO: use
+    x: u32,
+}
+
+// #410
+#[allow(missing_docs)]
+pub struct Writebatch<K: Key> {
+    #[allow(dead_code)] // only used for holding the internal pointer
+    writebatch: RawWritebatch,
+    marker: PhantomData<K>,
+}
+
+struct Bar;
+
+struct NewType(Type, OtherType);
+
+struct NewInt<T: Copy>(
+    pub i32,
+    SomeType, // inline comment
+    T,        // sup
+);
+
+struct Qux<
+    'a,
+    N: Clone + 'a,
+    E: Clone + 'a,
+    G: Labeller<'a, N, E> + GraphWalk<'a, N, E>,
+    W: Write + Copy,
+>(
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, // Comment
+    BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+    #[AnAttr]
+    // Comment
+    /// Testdoc
+    G,
+    pub W,
+);
+
+struct Tuple(
+    // Comment 1
+    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+    // Comment 2
+    BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+);
+
+// With a where-clause and generics.
+pub struct Foo<'a, Y: Baz>
+where
+    X: Whatever,
+{
+    f: SomeType, // Comment beside a field
+}
+
+struct Baz {
+    a: A, // Comment A
+    b: B, // Comment B
+    c: C, // Comment C
+}
+
+struct Baz {
+    a: A, // Comment A
+
+    b: B, // Comment B
+
+    c: C, // Comment C
+}
+
+struct Baz {
+    a: A,
+
+    b: B,
+    c: C,
+
+    d: D,
+}
+
+struct Baz {
+    // Comment A
+    a: A,
+
+    // Comment B
+    b: B,
+    // Comment C
+    c: C,
+}
+
+// Will this be a one-liner?
+struct Tuple(
+    A, // Comment
+    B,
+);
+
+pub struct State<F: FnMut() -> time::Timespec> {
+    now: F,
+}
+
+pub struct State<F: FnMut() -> ()> {
+    now: F,
+}
+
+pub struct State<F: FnMut()> {
+    now: F,
+}
+
+struct Palette {
+    /// A map of indices in the palette to a count of pixels in approximately
+    /// that color
+    foo: i32,
+}
+
+// Splitting a single line comment into a block previously had a misalignment
+// when the field had attributes
+struct FieldsWithAttributes {
+    // Pre Comment
+    #[rustfmt::skip] pub host:String, /* Post comment BBBBBBBBBBBBBB BBBBBBBBBBBBBBBB
+                                       * BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBBB BBBBBBBBBBB */
+    // Another pre comment
+    #[attr1]
+    #[attr2]
+    pub id: usize, /* CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCC
+                    * CCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCC CCCCCCCCCCCC */
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep:
+        node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>,
+}
+
+struct Foo<T>(T);
+struct Foo<T>(T)
+where
+    T: Copy,
+    T: Eq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUU,
+);
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTT,
+)
+where
+    T: PartialEq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTTTT,
+)
+where
+    T: PartialEq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUUUUUUU,
+    TTTTTTTTTTTTTTTTTTT,
+    UUUUUUUUUUUUUUUUUUU,
+)
+where
+    T: PartialEq;
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTT,        // Foo
+    UUUUUUUUUUUUUUUUUUUUUUUU, // Bar
+    // Baz
+    TTTTTTTTTTTTTTTTTTT,
+    // Qux (FIXME #572 - doc comment)
+    UUUUUUUUUUUUUUUUUUU,
+);
+
+mod m {
+    struct X<T>
+    where
+        T: Sized,
+    {
+        a: T,
+    }
+}
+
+struct Foo<T>(
+    TTTTTTTTTTTTTTTTTTT,
+    /// Qux
+    UUUUUUUUUUUUUUUUUUU,
+);
+
+struct Issue677 {
+    pub ptr: *const libc::c_void,
+    pub trace: fn(obj: *const libc::c_void, tracer: *mut JSTracer),
+}
+
+struct Foo {}
+struct Foo {}
+struct Foo {
+    // comment
+}
+struct Foo {
+    // trailing space ->
+}
+struct Foo {
+    // comment
+}
+struct Foo(
+    // comment
+);
+
+struct LongStruct {
+    a: A,
+    the_quick_brown_fox_jumps_over_the_lazy_dog:
+        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+}
+
+struct Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep:
+        node::Handle<IdRef<'id, Node<Key, Value>>, Type, NodeType>,
+}
+
+struct Foo<C = ()>(String);
+
+// #1364
+fn foo() {
+    convex_shape.set_point(0, &Vector2f { x: 400.0, y: 100.0 });
+    convex_shape.set_point(1, &Vector2f { x: 500.0, y: 70.0 });
+    convex_shape.set_point(2, &Vector2f { x: 450.0, y: 100.0 });
+    convex_shape.set_point(3, &Vector2f { x: 580.0, y: 150.0 });
+}
+
+// Vertical alignment
+struct Foo {
+    aaaaa: u32, // a
+
+    b: u32,  // b
+    cc: u32, // cc
+
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 1
+    yy: u32,  // comment2
+    zzz: u32, // comment3
+
+    aaaaaa: u32, // comment4
+    bb: u32,     // comment5
+    // separate
+    dd: u32, // comment7
+    c: u32,  // comment6
+
+    aaaaaaa: u32, /* multi
+                   * line
+                   * comment
+                   */
+    b: u32, // hi
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    // separate
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    // separate
+    please_do_not_push_this_comment3: u32, // comment3
+}
+
+// structs with long identifier
+struct Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{}
+struct Looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{}
+struct Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{}
+struct Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
+{
+    x: i32,
+}
+
+// structs with visibility, do not duplicate visibility (#2110).
+pub(self) struct Foo {}
+pub(super) struct Foo {}
+pub(crate) struct Foo {}
+pub(self) struct Foo();
+pub(super) struct Foo();
+pub(crate) struct Foo();
+
+// #2125
+pub struct ReadinessCheckRegistry(
+    Mutex<HashMap<Arc<String>, Box<Fn() -> ReadinessCheck + Sync + Send>>>,
+);
+
+// #2144 unit struct with generics
+struct MyBox<T: ?Sized>;
+struct MyBoxx<T, S>
+where
+    T: ?Sized,
+    S: Clone;
+
+// #2208
+struct Test {
+    /// foo
+    #[serde(default)]
+    pub join: Vec<String>,
+    #[serde(default)]
+    pub tls: bool,
+}
+
+// #2818
+struct Paren((i32))
+where
+    i32: Trait;
+struct Parens((i32, i32))
+where
+    i32: Trait;
diff --git a/src/tools/rustfmt/tests/target/trailing-comma-never.rs b/src/tools/rustfmt/tests/target/trailing-comma-never.rs
new file mode 100644
index 0000000000000..ea199f5ff2945
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/trailing-comma-never.rs
@@ -0,0 +1,35 @@
+// rustfmt-trailing_comma: Never
+
+enum X {
+    A,
+    B
+}
+
+enum Y {
+    A,
+    B
+}
+
+enum TupX {
+    A(u32),
+    B(i32, u16)
+}
+
+enum TupY {
+    A(u32),
+    B(i32, u16)
+}
+
+enum StructX {
+    A { s: u16 },
+    B { u: u32, i: i32 }
+}
+
+enum StructY {
+    A { s: u16 },
+    B { u: u32, i: i32 }
+}
+
+static XXX: [i8; 64] = [
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
+];
diff --git a/src/tools/rustfmt/tests/target/trailing_commas.rs b/src/tools/rustfmt/tests/target/trailing_commas.rs
new file mode 100644
index 0000000000000..06f0a13b10ce5
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/trailing_commas.rs
@@ -0,0 +1,78 @@
+// rustfmt-match_block_trailing_comma: true
+// rustfmt-trailing_comma: Always
+
+fn main() {
+    match foo {
+        x => {},
+        y => {
+            foo();
+        },
+        _ => x,
+    }
+}
+
+fn f<S, T,>(x: T, y: S,) -> T
+where
+    T: P,
+    S: Q,
+{
+    x
+}
+
+impl Trait for T
+where
+    T: P,
+{
+    fn f(x: T,) -> T
+    where
+        T: Q + R,
+    {
+        x
+    }
+}
+
+struct Pair<S, T,>
+where
+    T: P,
+    S: P + Q,
+{
+    a: T,
+    b: S,
+}
+
+struct TupPair<S, T,>(S, T,)
+where
+    T: P,
+    S: P + Q;
+
+enum E<S, T,>
+where
+    S: P,
+    T: P,
+{
+    A { a: T, },
+}
+
+type Double<T,>
+where
+    T: P,
+    T: Q,
+= Pair<T, T,>;
+
+extern "C" {
+    fn f<S, T,>(x: T, y: S,) -> T
+    where
+        T: P,
+        S: Q;
+}
+
+trait Q<S, T,>
+where
+    T: P,
+    S: R,
+{
+    fn f<U, V,>(self, x: T, y: S, z: U,) -> Self
+    where
+        U: P,
+        V: P;
+}
diff --git a/src/tools/rustfmt/tests/target/trailing_comments/hard_tabs.rs b/src/tools/rustfmt/tests/target/trailing_comments/hard_tabs.rs
new file mode 100644
index 0000000000000..35e72f1affdbd
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/trailing_comments/hard_tabs.rs
@@ -0,0 +1,30 @@
+// rustfmt-version: Two
+// rustfmt-wrap_comments: true
+// rustfmt-hard_tabs: true
+
+impl Foo {
+	fn foo() {
+		bar(); // comment 1
+		// comment 2
+		// comment 3
+		baz();
+	}
+}
+
+fn lorem_ipsum() {
+	let f = bar(); // Donec consequat mi. Quisque vitae dolor. Integer lobortis. Maecenas id nulla. Lorem.
+	// Id turpis. Nam posuere lectus vitae nibh. Etiam tortor orci, sagittis
+	// malesuada, rhoncus quis, hendrerit eget, libero. Quisque commodo nulla at
+	// nunc. Mauris consequat, enim vitae venenatis sollicitudin, dolor orci
+	// bibendum enim, a sagittis nulla nunc quis elit. Phasellus augue. Nunc
+	// suscipit, magna tincidunt lacinia faucibus, lacus tellus ornare purus, a
+	// pulvinar lacus orci eget nibh.  Maecenas sed nibh non lacus tempor faucibus.
+	// In hac habitasse platea dictumst. Vivamus a orci at nulla tristique
+	// condimentum. Donec arcu quam, dictum accumsan, convallis accumsan, cursus sit
+	// amet, ipsum.  In pharetra sagittis nunc.
+	let b = baz();
+
+	let normalized = self.ctfont.all_traits().normalized_weight(); // [-1.0, 1.0]
+	// TODO(emilio): It may make sense to make this range [.01, 10.0], to align
+	// with css-fonts-4's range of [1, 1000].
+}
diff --git a/src/tools/rustfmt/tests/target/trailing_comments/soft_tabs.rs b/src/tools/rustfmt/tests/target/trailing_comments/soft_tabs.rs
new file mode 100644
index 0000000000000..eba943042ad0a
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/trailing_comments/soft_tabs.rs
@@ -0,0 +1,30 @@
+// rustfmt-version: Two
+// rustfmt-wrap_comments: true
+
+pub const IFF_MULTICAST: ::c_int = 0x0000000800; // Supports multicast
+// Multicast using broadcst. add.
+
+pub const SQ_CRETAB: u16 = 0x000e; // CREATE TABLE
+pub const SQ_DRPTAB: u16 = 0x000f; // DROP TABLE
+pub const SQ_CREIDX: u16 = 0x0010; // CREATE INDEX
+//const SQ_DRPIDX: u16 = 0x0011;	// DROP INDEX
+//const SQ_GRANT: u16 = 0x0012;	// GRANT
+//const SQ_REVOKE: u16 = 0x0013;	// REVOKE
+
+fn foo() {
+    let f = bar(); // Donec consequat mi. Quisque vitae dolor. Integer lobortis. Maecenas id nulla. Lorem.
+    // Id turpis. Nam posuere lectus vitae nibh. Etiam tortor orci, sagittis
+    // malesuada, rhoncus quis, hendrerit eget, libero. Quisque commodo nulla at
+    // nunc. Mauris consequat, enim vitae venenatis sollicitudin, dolor orci
+    // bibendum enim, a sagittis nulla nunc quis elit. Phasellus augue. Nunc
+    // suscipit, magna tincidunt lacinia faucibus, lacus tellus ornare purus, a
+    // pulvinar lacus orci eget nibh.  Maecenas sed nibh non lacus tempor faucibus.
+    // In hac habitasse platea dictumst. Vivamus a orci at nulla tristique
+    // condimentum. Donec arcu quam, dictum accumsan, convallis accumsan, cursus sit
+    // amet, ipsum.  In pharetra sagittis nunc.
+    let b = baz();
+
+    let normalized = self.ctfont.all_traits().normalized_weight(); // [-1.0, 1.0]
+    // TODO(emilio): It may make sense to make this range [.01, 10.0], to align
+    // with css-fonts-4's range of [1, 1000].
+}
diff --git a/src/tools/rustfmt/tests/target/trait.rs b/src/tools/rustfmt/tests/target/trait.rs
new file mode 100644
index 0000000000000..620046a71b29b
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/trait.rs
@@ -0,0 +1,213 @@
+// Test traits
+
+trait Foo {
+    fn bar(x: i32) -> Baz<U> {
+        Baz::new()
+    }
+
+    fn baz(a: AAAAAAAAAAAAAAAAAAAAAA, b: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB) -> RetType;
+
+    fn foo(
+        a: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, // Another comment
+        b: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB,
+    ) -> RetType; // Some comment
+
+    fn baz(&mut self) -> i32;
+
+    fn increment(&mut self, x: i32);
+
+    fn read(&mut self, x: BufReader<R> /* Used to be MemReader */)
+    where
+        R: Read;
+}
+
+pub trait WriteMessage {
+    fn write_message(&mut self, &FrontendMessage) -> io::Result<()>;
+}
+
+trait Runnable {
+    fn handler(self: &Runnable);
+}
+
+trait TraitWithExpr {
+    fn fn_with_expr(x: [i32; 1]);
+}
+
+trait Test {
+    fn read_struct<T, F>(&mut self, s_name: &str, len: usize, f: F) -> Result<T, Self::Error>
+    where
+        F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+}
+
+trait T {}
+
+trait Foo {
+    type Bar: Baz;
+    type Inner: Foo = Box<Foo>;
+}
+
+trait ConstCheck<T>: Foo
+where
+    T: Baz,
+{
+    const J: i32;
+}
+
+trait Tttttttttttttttttttttttttttttttttttttttttttttttttttttttttt<T>
+where
+    T: Foo,
+{
+}
+
+trait Ttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt<T>
+where
+    T: Foo,
+{
+}
+
+trait FooBar<T>: Tttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt
+where
+    J: Bar,
+{
+    fn test();
+}
+
+trait WhereList<T, J>
+where
+    T: Foo,
+    J: Bar,
+{
+}
+
+trait X /* comment */ {}
+trait Y // comment
+{
+}
+
+// #2055
+pub trait Foo:
+// A and C
+A + C
+// and B
+    + B
+{}
+
+// #2158
+trait Foo {
+    type ItRev = <MergingUntypedTimeSeries<SliceSeries<SliceWindow>> as UntypedTimeSeries>::IterRev;
+    type IteRev =
+        <MergingUntypedTimeSeries<SliceSeries<SliceWindow>> as UntypedTimeSeries>::IterRev;
+}
+
+// #2331
+trait MyTrait<
+    AAAAAAAAAAAAAAAAAAAA,
+    BBBBBBBBBBBBBBBBBBBB,
+    CCCCCCCCCCCCCCCCCCCC,
+    DDDDDDDDDDDDDDDDDDDD,
+>
+{
+    fn foo() {}
+}
+
+// Trait aliases
+trait FooBar = Foo + Bar;
+trait FooBar<A, B, C> = Foo + Bar;
+pub trait FooBar = Foo + Bar;
+pub trait FooBar<A, B, C> = Foo + Bar;
+trait AAAAAAAAAAAAAAAAAA = BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDD;
+pub trait AAAAAAAAAAAAAAAAAA =
+    BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDD;
+trait AAAAAAAAAAAAAAAAAAA =
+    BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDD;
+trait AAAAAAAAAAAAAAAAAA =
+    BBBBBBBBBBBBBBBBBBB + CCCCCCCCCCCCCCCCCCCCCCCCCCCCC + DDDDDDDDDDDDDDDDDDD;
+trait AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA<A, B, C, D, E> =
+    FooBar;
+trait AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA<
+    A,
+    B,
+    C,
+    D,
+    E,
+> = FooBar;
+#[rustfmt::skip]
+trait FooBar = Foo
+    + Bar;
+
+// #2637
+auto trait Example {}
+pub auto trait PubExample {}
+pub unsafe auto trait PubUnsafeExample {}
+
+// #3006
+trait Foo<'a> {
+    type Bar<'a>;
+}
+
+impl<'a> Foo<'a> for i32 {
+    type Bar<'a> = i32;
+}
+
+// #3092
+pub mod test {
+    pub trait ATraitWithALooongName {}
+    pub trait ATrait:
+        ATraitWithALooongName
+        + ATraitWithALooongName
+        + ATraitWithALooongName
+        + ATraitWithALooongName
+    {
+    }
+}
+
+// Trait aliases with where clauses.
+trait A = where for<'b> &'b Self: Send;
+
+trait B = where for<'b> &'b Self: Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCCC;
+trait B =
+    where for<'b> &'b Self: Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCCCC;
+trait B = where
+    for<'b> &'b Self:
+        Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCCCCCCCCCCCCCCCC;
+trait B = where
+    for<'b> &'b Self: Send
+        + Clone
+        + Copy
+        + SomeTrait
+        + AAAAAAAA
+        + BBBBBBB
+        + CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC;
+
+trait B = where
+    for<'b> &'b Self: Send
+        + Clone
+        + Copy
+        + SomeTrait
+        + AAAAAAAA
+        + BBBBBBB
+        + CCCCCCCCC
+        + DDDDDDD
+        + DDDDDDDD
+        + DDDDDDDDD
+        + EEEEEEE;
+
+trait A<'a, 'b, 'c> = Debug<T> + Foo where for<'b> &'b Self: Send;
+
+trait B<'a, 'b, 'c> = Debug<T> + Foo
+where
+    for<'b> &'b Self: Send + Clone + Copy + SomeTrait + AAAAAAAA + BBBBBBB + CCCCCCCCC + DDDDDDD;
+
+trait B<'a, 'b, 'c, T> = Debug<'a, T>
+where
+    for<'b> &'b Self: Send
+        + Clone
+        + Copy
+        + SomeTrait
+        + AAAAAAAA
+        + BBBBBBB
+        + CCCCCCCCC
+        + DDDDDDD
+        + DDDDDDDD
+        + DDDDDDDDD
+        + EEEEEEE;
diff --git a/src/tools/rustfmt/tests/target/try-conversion.rs b/src/tools/rustfmt/tests/target/try-conversion.rs
new file mode 100644
index 0000000000000..04992a0a0f6c3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/try-conversion.rs
@@ -0,0 +1,28 @@
+// rustfmt-use_try_shorthand: true
+
+fn main() {
+    let x = some_expr()?;
+
+    let y = a
+        .very
+        .loooooooooooooooooooooooooooooooooooooong()
+        .chain()
+        .inside()
+        .weeeeeeeeeeeeeee()?
+        .test()
+        .0
+        .x;
+}
+
+fn test() {
+    a?
+}
+
+fn issue1291() {
+    fs::create_dir_all(&gitfiledir).chain_err(|| {
+        format!(
+            "failed to create the {} submodule directory for the workarea",
+            name
+        )
+    })?;
+}
diff --git a/src/tools/rustfmt/tests/target/try_block.rs b/src/tools/rustfmt/tests/target/try_block.rs
new file mode 100644
index 0000000000000..19a3f3e148769
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/try_block.rs
@@ -0,0 +1,29 @@
+// rustfmt-edition: 2018
+
+fn main() -> Result<(), !> {
+    let _x: Option<_> = try { 4 };
+
+    try {}
+}
+
+fn baz() -> Option<i32> {
+    if (1 == 1) {
+        return try { 5 };
+    }
+
+    // test
+    let x: Option<()> = try {
+        // try blocks are great
+    };
+
+    let y: Option<i32> = try { 6 }; // comment
+
+    let x: Option<i32> = try {
+        baz()?;
+        baz()?;
+        baz()?;
+        7
+    };
+
+    return None;
+}
diff --git a/src/tools/rustfmt/tests/target/tuple.rs b/src/tools/rustfmt/tests/target/tuple.rs
new file mode 100644
index 0000000000000..68bb2f3bc2850
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/tuple.rs
@@ -0,0 +1,100 @@
+// Test tuple litterals
+
+fn foo() {
+    let a = (a, a, a, a, a);
+    let aaaaaaaaaaaaaaaa = (
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        aaaaaaaaaaaaaa,
+        aaaaaaaaaaaaaa,
+    );
+    let aaaaaaaaaaaaaaaaaaaaaa = (
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        aaaaaaaaaaaaaaaaaaaaaaaaa,
+        aaaa,
+    );
+    let a = (a,);
+
+    let b = (
+        // This is a comment
+        b, // Comment
+        b, /* Trailing comment */
+    );
+
+    // #1063
+    foo(x.0 .0);
+}
+
+fn a() {
+    ((
+        aaaaaaaa,
+        aaaaaaaaaaaaa,
+        aaaaaaaaaaaaaaaaa,
+        aaaaaaaaaaaaaa,
+        aaaaaaaaaaaaaaaa,
+        aaaaaaaaaaaaaa,
+    ),)
+}
+
+fn b() {
+    (
+        (
+            bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+            bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+        ),
+        bbbbbbbbbbbbbbbbbb,
+    )
+}
+
+fn issue550() {
+    self.visitor.visit_volume(
+        self.level.sector_id(sector),
+        (
+            floor_y,
+            if is_sky_flat(ceil_tex) {
+                from_wad_height(self.height_range.1)
+            } else {
+                ceil_y
+            },
+        ),
+    );
+}
+
+fn issue775() {
+    if indent {
+        let a = mk_object(&[
+            ("a".to_string(), Boolean(true)),
+            (
+                "b".to_string(),
+                Array(vec![
+                    mk_object(&[("c".to_string(), String("\x0c\r".to_string()))]),
+                    mk_object(&[("d".to_string(), String("".to_string()))]),
+                ]),
+            ),
+        ]);
+    }
+}
+
+fn issue1725() {
+    bench_antialiased_lines!(
+        bench_draw_antialiased_line_segment_diagonal,
+        (10, 10),
+        (450, 450)
+    );
+    bench_antialiased_lines!(
+        bench_draw_antialiased_line_segment_shallow,
+        (10, 10),
+        (450, 80)
+    );
+}
+
+fn issue_4355() {
+    let _ = ((1,),).0 .0;
+}
+
+// https://github.com/rust-lang/rustfmt/issues/4410
+impl Drop for LockGuard {
+    fn drop(&mut self) {
+        LockMap::unlock(&self.0 .0, &self.0 .1);
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/tuple_v2.rs b/src/tools/rustfmt/tests/target/tuple_v2.rs
new file mode 100644
index 0000000000000..ba653291c2f5d
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/tuple_v2.rs
@@ -0,0 +1,5 @@
+// rustfmt-version: Two
+
+fn issue_4355() {
+    let _ = ((1,),).0.0;
+}
diff --git a/src/tools/rustfmt/tests/target/type-ascription.rs b/src/tools/rustfmt/tests/target/type-ascription.rs
new file mode 100644
index 0000000000000..a2f082ba4b497
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/type-ascription.rs
@@ -0,0 +1,12 @@
+fn main() {
+    let xxxxxxxxxxx =
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: SomeTrait<AA, BB, CC>;
+
+    let xxxxxxxxxxxxxxx =
+        yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA;
+
+    let z = funk(yyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzz, wwwwww):
+        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA;
+
+    x: u32 - 1u32 / 10f32: u32
+}
diff --git a/src/tools/rustfmt/tests/target/type.rs b/src/tools/rustfmt/tests/target/type.rs
new file mode 100644
index 0000000000000..e7761251688a9
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/type.rs
@@ -0,0 +1,183 @@
+// rustfmt-normalize_comments: true
+fn types() {
+    let x: [Vec<_>] = [];
+    let y: *mut [SomeType; konst_funk()] = expr();
+    let z: (/* #digits */ usize, /* exp */ i16) = funk();
+    let z: (usize /* #digits */, i16 /* exp */) = funk();
+}
+
+struct F {
+    f: extern "C" fn(x: u8, ... /* comment */),
+    g: extern "C" fn(x: u8, /* comment */ ...),
+    h: extern "C" fn(x: u8, ...),
+    i: extern "C" fn(
+        x: u8,
+        // comment 4
+        y: String, // comment 3
+        z: Foo,
+        // comment
+        ... // comment 2
+    ),
+}
+
+fn issue_1006(def_id_to_string: for<'a, 'b> unsafe fn(TyCtxt<'b, 'tcx, 'tcx>, DefId) -> String) {}
+
+fn impl_trait_fn_1() -> impl Fn(i32) -> Option<u8> {}
+
+fn impl_trait_fn_2<E>() -> impl Future<Item = &'a i64, Error = E> {}
+
+fn issue_1234() {
+    do_parse!(name: take_while1!(is_token) >> (Header))
+}
+
+// #2510
+impl CombineTypes {
+    pub fn pop_callback(
+        &self,
+        query_id: Uuid,
+    ) -> Option<(
+        ProjectId,
+        Box<FnMut(&ProjectState, serde_json::Value, bool) -> () + Sync + Send>,
+    )> {
+        self.query_callbacks()(&query_id)
+    }
+}
+
+// #2859
+pub fn do_something<'a, T: Trait1 + Trait2 + 'a>(
+    &fooo: u32,
+) -> impl Future<
+    Item = (
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+    ),
+    Error = SomeError,
+> + 'a {
+}
+
+pub fn do_something<'a, T: Trait1 + Trait2 + 'a>(
+    &fooo: u32,
+) -> impl Future<
+    Item = (
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+    ),
+    Error = SomeError,
+> + Future<
+    Item = (
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+    ),
+    Error = SomeError,
+> + Future<
+    Item = (
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+        impl Future<Item = (), Error = SomeError> + 'a,
+    ),
+    Error = SomeError,
+> + 'a + 'b + 'c {
+}
+
+// #3051
+token![impl];
+token![impl];
+
+// #3060
+macro_rules! foo {
+    ($foo_api: ty) => {
+        type Target = ($foo_api) + 'static;
+    };
+}
+
+type Target = (FooAPI) + 'static;
+
+// #3137
+fn foo<T>(t: T)
+where
+    T: (FnOnce() -> ()) + Clone,
+    U: (FnOnce() -> ()) + 'static,
+{
+}
+
+// #3117
+fn issue3117() {
+    {
+        {
+            {
+                {
+                    {
+                        {
+                            {
+                                {
+                                    let opt: &mut Option<MyLongTypeHere> =
+                                        unsafe { &mut *self.future.get() };
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+// #3139
+fn issue3139() {
+    assert_eq!(
+        to_json_value(&None::<i32>).unwrap(),
+        json!({ "test": None::<i32> })
+    );
+}
+
+// #3180
+fn foo(
+    a: SomeLongComplexType,
+    b: SomeOtherLongComplexType,
+) -> Box<Future<Item = AnotherLongType, Error = ALongErrorType>> {
+}
+
+type MyFn = fn(
+    a: SomeLongComplexType,
+    b: SomeOtherLongComplexType,
+) -> Box<Future<Item = AnotherLongType, Error = ALongErrorType>>;
+
+// Const opt-out
+
+trait T: ?const Super {}
+
+const fn maybe_const<S: ?const T>() -> i32 {
+    <S as T>::CONST
+}
+
+struct S<T: ?const ?Sized>(std::marker::PhantomData<T>);
+
+impl ?const T {}
+
+fn trait_object() -> &'static dyn ?const T {
+    &S
+}
+
+fn i(_: impl IntoIterator<Item = Box<dyn ?const T>>) {}
+
+fn apit(_: impl ?const T) {}
+
+fn rpit() -> impl ?const T {
+    S
+}
+
+pub struct Foo<T: Trait>(T);
+impl<T: ?const Trait> Foo<T> {
+    fn new(t: T) -> Self {
+        // not calling methods on `t`, so we opt out of requiring
+        // `<T as Trait>` to have const methods via `?const`
+        Self(t)
+    }
+}
+
+// #4357
+type T = typeof(1);
+impl T for .. {}
diff --git a/src/tools/rustfmt/tests/target/type_alias.rs b/src/tools/rustfmt/tests/target/type_alias.rs
new file mode 100644
index 0000000000000..862f9ecbeec61
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/type_alias.rs
@@ -0,0 +1,76 @@
+// rustfmt-normalize_comments: true
+
+type PrivateTest<'a, I> = (
+    Box<Parser<Input = I, Output = char> + 'a>,
+    Box<Parser<Input = I, Output = char> + 'a>,
+);
+
+pub type PublicTest<'a, I, O> = Result<
+    Vec<MyLongType>,
+    Box<Parser<Input = I, Output = char> + 'a>,
+    Box<Parser<Input = I, Output = char> + 'a>,
+>;
+
+pub type LongGenericListTest<
+    'a,
+    'b,
+    'c,
+    'd,
+    LONGPARAMETERNAME,
+    LONGPARAMETERNAME,
+    LONGPARAMETERNAME,
+    A,
+    B,
+    C,
+> = Option<Vec<MyType>>;
+
+pub type Exactly100CharsTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, A, B> = Vec<i32>;
+
+pub type Exactly101CharsTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, A, B> =
+    Vec<Test>;
+
+pub type Exactly100CharsToEqualTest<'a, 'b, 'c, 'd, LONGPARAMETERNAME, LONGPARAMETERNAME, A, B, C> =
+    Vec<i32>;
+
+pub type GenericsFitButNotEqualTest<
+    'a,
+    'b,
+    'c,
+    'd,
+    LONGPARAMETERNAME,
+    LONGPARAMETERNAME,
+    A1,
+    B,
+    C,
+> = Vec<i32>;
+
+pub type CommentTest<
+    // Lifetime
+    'a,
+    // Type
+    T,
+> = ();
+
+pub type WithWhereClause<LONGPARAMETERNAME, T>
+where
+    T: Clone,
+    LONGPARAMETERNAME: Clone + Eq + OtherTrait,
+= Option<T>;
+
+pub type Exactly100CharstoEqualWhereTest<T, U, PARAMET>
+where
+    T: Clone + Ord + Eq + SomeOtherTrait,
+= Option<T>;
+
+pub type Exactly101CharstoEqualWhereTest<T, U, PARAMETE>
+where
+    T: Clone + Ord + Eq + SomeOtherTrait,
+= Option<T>;
+
+type RegisterPlugin = unsafe fn(pt: *const c_char, plugin: *mut c_void, data: *mut CallbackData);
+
+// #1683
+pub type Between<Lhs, Rhs> =
+    super::operators::Between<Lhs, super::operators::And<AsExpr<Rhs, Lhs>, AsExpr<Rhs, Lhs>>>;
+pub type NotBetween<Lhs, Rhs> =
+    super::operators::NotBetween<Lhs, super::operators::And<AsExpr<Rhs, Lhs>, AsExpr<Rhs, Lhs>>>;
diff --git a/src/tools/rustfmt/tests/target/unicode.rs b/src/tools/rustfmt/tests/target/unicode.rs
new file mode 100644
index 0000000000000..34a4f46347969
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/unicode.rs
@@ -0,0 +1,30 @@
+// rustfmt-wrap_comments: true
+
+fn foo() {
+    let s = "this line goes to 100: ͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶͶ";
+    let s = 42;
+
+    // a comment of length 80, with the starting sigil: ҘҘҘҘҘҘҘҘҘҘ ҘҘҘҘҘҘҘҘҘҘҘҘҘҘ
+    let s = 42;
+}
+
+pub fn bar(config: &Config) {
+    let csv = RefCell::new(create_csv(config, "foo"));
+    {
+        let mut csv = csv.borrow_mut();
+        for (i1, i2, i3) in iproduct!(0..2, 0..3, 0..3) {
+            csv.write_field(format!("γ[{}.{}.{}]", i1, i2, i3)).unwrap();
+            csv.write_field(format!("d[{}.{}.{}]", i1, i2, i3)).unwrap();
+            csv.write_field(format!("i[{}.{}.{}]", i1, i2, i3)).unwrap();
+        }
+        csv.write_record(None::<&[u8]>).unwrap();
+    }
+}
+
+// The NotUnicode line is below 100 wrt chars but over it wrt String::len
+fn baz() {
+    let our_error_b = result_b_from_func.or_else(|e| match e {
+        NotPresent => Err(e).chain_err(|| "env var wasn't provided"),
+        NotUnicode(_) => Err(e).chain_err(|| "env var was very very very bork文字化ã"),
+    });
+}
diff --git a/src/tools/rustfmt/tests/target/unindent_if_else_cond_comment.rs b/src/tools/rustfmt/tests/target/unindent_if_else_cond_comment.rs
new file mode 100644
index 0000000000000..98621b1eed150
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/unindent_if_else_cond_comment.rs
@@ -0,0 +1,27 @@
+// Comments on else block. See #1575.
+
+fn example() {
+    // `if` comment
+    if x {
+        foo();
+    // `else if` comment
+    } else if y {
+        foo();
+    // Comment on `else if`.
+    // Comment on `else if`.
+    } else if z {
+        bar();
+    /*
+     *  Multi line comment on `else if`
+     */
+    } else if xx {
+        bar();
+    /* Single line comment on `else if` */
+    } else if yy {
+        foo();
+    // `else` comment
+    } else {
+        foo();
+        // Comment at the end of `else` block
+    };
+}
diff --git a/src/tools/rustfmt/tests/target/unions.rs b/src/tools/rustfmt/tests/target/unions.rs
new file mode 100644
index 0000000000000..8ed16b269c230
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/unions.rs
@@ -0,0 +1,198 @@
+// rustfmt-normalize_comments: true
+// rustfmt-wrap_comments: true
+
+/// A Doc comment
+#[AnAttribute]
+pub union Foo {
+    #[rustfmt::skip]
+    f :   SomeType, // Comment beside a field
+    f: SomeType, // Comment beside a field
+    // Comment on a field
+    #[AnAttribute]
+    g: SomeOtherType,
+    /// A doc comment on a field
+    h: AThirdType,
+    pub i: TypeForPublicField,
+}
+
+// #1029
+pub union Foo {
+    #[doc(hidden)]
+    // This will NOT get deleted!
+    bar: String, // hi
+}
+
+// #1029
+union X {
+    // `x` is an important number.
+    #[allow(unused)] // TODO: use
+    x: u32,
+}
+
+// #410
+#[allow(missing_docs)]
+pub union Writebatch<K: Key> {
+    #[allow(dead_code)] // only used for holding the internal pointer
+    writebatch: RawWritebatch,
+    marker: PhantomData<K>,
+}
+
+// With a where-clause and generics.
+pub union Foo<'a, Y: Baz>
+where
+    X: Whatever,
+{
+    f: SomeType, // Comment beside a field
+}
+
+union Baz {
+    a: A, // Comment A
+    b: B, // Comment B
+    c: C, // Comment C
+}
+
+union Baz {
+    a: A, // Comment A
+
+    b: B, // Comment B
+
+    c: C, // Comment C
+}
+
+union Baz {
+    a: A,
+
+    b: B,
+    c: C,
+
+    d: D,
+}
+
+union Baz {
+    // Comment A
+    a: A,
+
+    // Comment B
+    b: B,
+    // Comment C
+    c: C,
+}
+
+pub union State<F: FnMut() -> time::Timespec> {
+    now: F,
+}
+
+pub union State<F: FnMut() -> ()> {
+    now: F,
+}
+
+pub union State<F: FnMut()> {
+    now: F,
+}
+
+union Palette {
+    /// A map of indices in the palette to a count of pixels in approximately
+    /// that color
+    foo: i32,
+}
+
+// Splitting a single line comment into a block previously had a misalignment
+// when the field had attributes
+union FieldsWithAttributes {
+    // Pre Comment
+    #[rustfmt::skip] pub host:String, /* Post comment BBBBBBBBBBBBBB BBBBBBBBBBBBBBBB
+                                       * BBBBBBBBBBBBBBBB BBBBBBBBBBBBBBBBB BBBBBBBBBBB */
+    // Another pre comment
+    #[attr1]
+    #[attr2]
+    pub id: usize, /* CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCCCC
+                    * CCCCCCCCCCCCCCCCCC CCCCCCCCCCCCCC CCCCCCCCCCCC */
+}
+
+union Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep:
+        node::Handle<IdRef<'id, Node<K, V>>, Type, NodeType>,
+}
+
+mod m {
+    union X<T>
+    where
+        T: Sized,
+    {
+        a: T,
+    }
+}
+
+union Issue677 {
+    pub ptr: *const libc::c_void,
+    pub trace: fn(obj: *const libc::c_void, tracer: *mut JSTracer),
+}
+
+union Foo {}
+union Foo {}
+union Foo {
+    // comment
+}
+union Foo {
+    // trailing space ->
+}
+union Foo {
+    // comment
+}
+
+union LongUnion {
+    a: A,
+    the_quick_brown_fox_jumps_over_the_lazy_dog:
+        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA,
+}
+
+union Deep {
+    deeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeep:
+        node::Handle<IdRef<'id, Node<Key, Value>>, Type, NodeType>,
+}
+
+// #1364
+fn foo() {
+    convex_shape.set_point(0, &Vector2f { x: 400.0, y: 100.0 });
+    convex_shape.set_point(1, &Vector2f { x: 500.0, y: 70.0 });
+    convex_shape.set_point(2, &Vector2f { x: 450.0, y: 100.0 });
+    convex_shape.set_point(3, &Vector2f { x: 580.0, y: 150.0 });
+}
+
+// Vertical alignment
+union Foo {
+    aaaaa: u32, // a
+
+    b: u32,  // b
+    cc: u32, // cc
+
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 1
+    yy: u32,  // comment2
+    zzz: u32, // comment3
+
+    aaaaaa: u32, // comment4
+    bb: u32,     // comment5
+    // separate
+    dd: u32, // comment7
+    c: u32,  // comment6
+
+    aaaaaaa: u32, /* multi
+                   * line
+                   * comment
+                   */
+    b: u32, // hi
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    // separate
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    please_do_not_push_this_comment3: u32, // comment3
+
+    do_not_push_this_comment1: u32, // comment1
+    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32, // 2
+    // separate
+    please_do_not_push_this_comment3: u32, // comment3
+}
diff --git a/src/tools/rustfmt/tests/target/unsafe-mod.rs b/src/tools/rustfmt/tests/target/unsafe-mod.rs
new file mode 100644
index 0000000000000..05ba2f54faf80
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/unsafe-mod.rs
@@ -0,0 +1,7 @@
+// These are supported by rustc syntactically but not semantically.
+
+#[cfg(any())]
+unsafe mod m {}
+
+#[cfg(any())]
+unsafe extern "C++" {}
diff --git a/src/tools/rustfmt/tests/target/visibility.rs b/src/tools/rustfmt/tests/target/visibility.rs
new file mode 100644
index 0000000000000..ca078422c1358
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/visibility.rs
@@ -0,0 +1,8 @@
+// #2398
+pub mod outer_mod {
+    pub mod inner_mod {
+        pub(in outer_mod) fn outer_mod_visible_fn() {}
+        pub(super) fn super_mod_visible_fn() {}
+        pub(self) fn inner_mod_visible_fn() {}
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/visual-fn-type.rs b/src/tools/rustfmt/tests/target/visual-fn-type.rs
new file mode 100644
index 0000000000000..052acde0209b8
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/visual-fn-type.rs
@@ -0,0 +1,9 @@
+// rustfmt-indent_style: Visual
+type CNodeSetAtts = unsafe extern "C" fn(node: *const RsvgNode,
+                                         node_impl: *const RsvgCNodeImpl,
+                                         handle: *const RsvgHandle,
+                                         pbag: *const PropertyBag);
+type CNodeDraw = unsafe extern "C" fn(node: *const RsvgNode,
+                                      node_impl: *const RsvgCNodeImpl,
+                                      draw_ctx: *const RsvgDrawingCtx,
+                                      dominate: i32);
diff --git a/src/tools/rustfmt/tests/target/where-clause-rfc.rs b/src/tools/rustfmt/tests/target/where-clause-rfc.rs
new file mode 100644
index 0000000000000..9c43e91d37078
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/where-clause-rfc.rs
@@ -0,0 +1,156 @@
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape)
+where
+    T: FOo,
+    U: Bar,
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape)
+where
+    T: FOo,
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(
+    node: &CompoundNode,
+    rule: &Rule,
+    args: &[Arg],
+    shape: &Shape,
+    shape: &Shape,
+) where
+    T: FOo,
+    U: Bar,
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(
+    node: &CompoundNode,
+    rule: &Rule,
+    args: &[Arg],
+    shape: &Shape,
+    shape: &Shape,
+) where
+    T: FOo,
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(
+    node: &CompoundNode,
+    rule: &Rule,
+    args: &[Arg],
+    shape: &Shape,
+) -> Option<String>
+where
+    T: FOo,
+    U: Bar,
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(
+    node: &CompoundNode,
+    rule: &Rule,
+    args: &[Arg],
+    shape: &Shape,
+) -> Option<String>
+where
+    T: FOo,
+{
+    let mut effects = HashMap::new();
+}
+
+pub trait Test {
+    fn very_long_method_name<F>(self, f: F) -> MyVeryLongReturnType
+    where
+        F: FnMut(Self::Item) -> bool;
+
+    fn exactly_100_chars1<F>(self, f: F) -> MyVeryLongReturnType
+    where
+        F: FnMut(Self::Item) -> bool;
+}
+
+fn very_long_function_name<F>(very_long_argument: F) -> MyVeryLongReturnType
+where
+    F: FnMut(Self::Item) -> bool,
+{
+}
+
+struct VeryLongTupleStructName<A, B, C, D, E>(LongLongTypename, LongLongTypename, i32, i32)
+where
+    A: LongTrait;
+
+struct Exactly100CharsToSemicolon<A, B, C, D, E>(LongLongTypename, i32, i32)
+where
+    A: LongTrait1234;
+
+struct AlwaysOnNextLine<LongLongTypename, LongTypename, A, B, C, D, E, F>
+where
+    A: LongTrait,
+{
+    x: i32,
+}
+
+pub trait SomeTrait<T>
+where
+    T: Something
+        + Sync
+        + Send
+        + Display
+        + Debug
+        + Copy
+        + Hash
+        + Debug
+        + Display
+        + Write
+        + Read
+        + FromStr,
+{
+}
+
+// #2020
+impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
+    fn elaborate_bounds<F>(&mut self, bounds: &[ty::PolyTraitRef<'tcx>], mut mk_cand: F)
+    where
+        F: for<'b> FnMut(
+            &mut ProbeContext<'b, 'gcx, 'tcx>,
+            ty::PolyTraitRef<'tcx>,
+            ty::AssociatedItem,
+        ),
+    {
+        // ...
+    }
+}
+
+// #2497
+fn handle_update<'a, Tab, Conn, R, C>(
+    executor: &Executor<PooledConnection<ConnectionManager<Conn>>>,
+    change_set: &'a C,
+) -> ExecutionResult
+where
+    &'a C: Identifiable + AsChangeset<Target = Tab> + HasTable<Table = Tab>,
+    <&'a C as AsChangeset>::Changeset: QueryFragment<Conn::Backend>,
+    Tab: Table + HasTable<Table = Tab>,
+    Tab::PrimaryKey: EqAll<<&'a C as Identifiable>::Id>,
+    Tab::FromClause: QueryFragment<Conn::Backend>,
+    Tab: FindDsl<<&'a C as Identifiable>::Id>,
+    Find<Tab, <&'a C as Identifiable>::Id>: IntoUpdateTarget<Table = Tab>,
+    <Find<Tab, <&'a C as Identifiable>::Id> as IntoUpdateTarget>::WhereClause:
+        QueryFragment<Conn::Backend>,
+    Tab::Query: FilterDsl<<Tab::PrimaryKey as EqAll<<&'a C as Identifiable>::Id>>::Output>,
+    Filter<Tab::Query, <Tab::PrimaryKey as EqAll<<&'a C as Identifiable>::Id>>::Output>: LimitDsl,
+    Limit<Filter<Tab::Query, <Tab::PrimaryKey as EqAll<<&'a C as Identifiable>::Id>>::Output>>:
+        QueryDsl
+            + BoxedDsl<
+                'a,
+                Conn::Backend,
+                Output = BoxedSelectStatement<'a, R::SqlType, Tab, Conn::Backend>,
+            >,
+    R: LoadingHandler<Conn, Table = Tab, SqlType = Tab::SqlType>
+        + GraphQLType<TypeInfo = (), Context = ()>,
+{
+    unimplemented!()
+}
diff --git a/src/tools/rustfmt/tests/target/where-clause.rs b/src/tools/rustfmt/tests/target/where-clause.rs
new file mode 100644
index 0000000000000..eb2f8d5e6e81e
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/where-clause.rs
@@ -0,0 +1,107 @@
+// rustfmt-indent_style: Visual
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape)
+    where T: FOo,
+          U: Bar
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode, rule: &Rule, args: &[Arg], shape: &Shape)
+    where T: FOo
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode,
+                              rule: &Rule,
+                              args: &[Arg],
+                              shape: &Shape,
+                              shape: &Shape)
+    where T: FOo,
+          U: Bar
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode,
+                              rule: &Rule,
+                              args: &[Arg],
+                              shape: &Shape,
+                              shape: &Shape)
+    where T: FOo
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode,
+                              rule: &Rule,
+                              args: &[Arg],
+                              shape: &Shape)
+                              -> Option<String>
+    where T: FOo,
+          U: Bar
+{
+    let mut effects = HashMap::new();
+}
+
+fn reflow_list_node_with_rule(node: &CompoundNode,
+                              rule: &Rule,
+                              args: &[Arg],
+                              shape: &Shape)
+                              -> Option<String>
+    where T: FOo
+{
+    let mut effects = HashMap::new();
+}
+
+pub trait Test {
+    fn very_long_method_name<F>(self, f: F) -> MyVeryLongReturnType
+        where F: FnMut(Self::Item) -> bool;
+
+    fn exactly_100_chars1<F>(self, f: F) -> MyVeryLongReturnType
+        where F: FnMut(Self::Item) -> bool;
+}
+
+fn very_long_function_name<F>(very_long_argument: F) -> MyVeryLongReturnType
+    where F: FnMut(Self::Item) -> bool
+{
+}
+
+struct VeryLongTupleStructName<A, B, C, D, E>(LongLongTypename, LongLongTypename, i32, i32)
+    where A: LongTrait;
+
+struct Exactly100CharsToSemicolon<A, B, C, D, E>(LongLongTypename, i32, i32) where A: LongTrait1234;
+
+struct AlwaysOnNextLine<LongLongTypename, LongTypename, A, B, C, D, E, F>
+    where A: LongTrait
+{
+    x: i32,
+}
+
+pub trait SomeTrait<T>
+    where T: Something
+              + Sync
+              + Send
+              + Display
+              + Debug
+              + Copy
+              + Hash
+              + Debug
+              + Display
+              + Write
+              + Read
+              + FromStr
+{
+}
+
+// #2020
+impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
+    fn elaborate_bounds<F>(&mut self, bounds: &[ty::PolyTraitRef<'tcx>], mut mk_cand: F)
+        where F: for<'b> FnMut(&mut ProbeContext<'b, 'gcx, 'tcx>,
+                               ty::PolyTraitRef<'tcx>,
+                               ty::AssociatedItem)
+    {
+        // ...
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/width-heuristics.rs b/src/tools/rustfmt/tests/target/width-heuristics.rs
new file mode 100644
index 0000000000000..e177a2152e815
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/width-heuristics.rs
@@ -0,0 +1,24 @@
+// rustfmt-max_width: 120
+
+// elems on multiple lines for max_width 100, but same line for max_width 120
+fn foo(e: Enum) {
+    match e {
+        Enum::Var { elem1, elem2, elem3 } => {
+            return;
+        }
+    }
+}
+
+// elems not on same line for either max_width 100 or 120
+fn bar(e: Enum) {
+    match e {
+        Enum::Var {
+            elem1,
+            elem2,
+            elem3,
+            elem4,
+        } => {
+            return;
+        }
+    }
+}
diff --git a/src/tools/rustfmt/tests/target/wrap_comments_should_not_imply_format_doc_comments.rs b/src/tools/rustfmt/tests/target/wrap_comments_should_not_imply_format_doc_comments.rs
new file mode 100644
index 0000000000000..d61d4d7c216a3
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/wrap_comments_should_not_imply_format_doc_comments.rs
@@ -0,0 +1,16 @@
+// rustfmt-wrap_comments: true
+
+/// Foo
+///
+/// # Example
+/// ```
+/// # #![cfg_attr(not(dox), feature(cfg_target_feature, target_feature, stdsimd))]
+/// # #![cfg_attr(not(dox), no_std)]
+/// fn foo() {  }
+/// ```
+fn foo() {}
+
+/// A long commment for wrapping
+/// This is a long long long long long long long long long long long long long
+/// long long long long long long long sentence.
+fn bar() {}
diff --git a/src/tools/rustfmt/tests/writemode/source/fn-single-line.rs b/src/tools/rustfmt/tests/writemode/source/fn-single-line.rs
new file mode 100644
index 0000000000000..ab1e13e17a789
--- /dev/null
+++ b/src/tools/rustfmt/tests/writemode/source/fn-single-line.rs
@@ -0,0 +1,80 @@
+// rustfmt-fn_single_line: true
+// rustfmt-emit_mode: checkstyle
+// Test single-line functions.
+
+fn foo_expr() {
+    1
+}
+
+fn foo_stmt() {
+    foo();
+}
+
+fn foo_decl_local()  {
+    let z = 5;
+   }
+
+fn    foo_decl_item(x: &mut i32) {
+    x = 3;
+}
+
+   fn empty()     {
+
+}
+
+fn foo_return() -> String {
+    "yay"
+}
+
+fn foo_where() -> T where T: Sync {
+    let x = 2;
+}
+
+fn fooblock() {
+    {
+        "inner-block"
+    }
+}
+
+fn fooblock2(x: i32) {
+    let z = match x {
+        _ => 2,
+    };
+}
+
+fn comment() {
+    // this is a test comment
+    1
+}
+
+fn comment2() {
+    // multi-line comment
+    let z = 2;
+    1
+}
+
+fn only_comment() {
+    // Keep this here
+}
+
+fn aaaaaaaaaaaaaaaaa_looooooooooooooooooooooong_name() {
+    let z = "aaaaaaawwwwwwwwwwwwwwwwwwwwwwwwwwww";
+}
+
+fn lots_of_space                      ()                                                           {
+                           1                 
+}
+
+fn mac() -> Vec<i32> { vec![] }
+
+trait CoolTypes {
+    fn dummy(&self) {
+    }
+}
+
+trait CoolerTypes { fn dummy(&self) { 
+}
+}
+
+fn Foo<T>() where T: Bar {
+}
diff --git a/src/tools/rustfmt/tests/writemode/source/json.rs b/src/tools/rustfmt/tests/writemode/source/json.rs
new file mode 100644
index 0000000000000..89dcf694183b4
--- /dev/null
+++ b/src/tools/rustfmt/tests/writemode/source/json.rs
@@ -0,0 +1,80 @@
+// rustfmt-fn_single_line: true
+// rustfmt-emit_mode: json
+// Test single-line functions.
+
+fn foo_expr() {
+    1
+}
+
+fn foo_stmt() {
+    foo();
+}
+
+fn foo_decl_local()  {
+    let z = 5;
+   }
+
+fn    foo_decl_item(x: &mut i32) {
+    x = 3;
+}
+
+   fn empty()     {
+
+}
+
+fn foo_return() -> String {
+    "yay"
+}
+
+fn foo_where() -> T where T: Sync {
+    let x = 2;
+}
+
+fn fooblock() {
+    {
+        "inner-block"
+    }
+}
+
+fn fooblock2(x: i32) {
+    let z = match x {
+        _ => 2,
+    };
+}
+
+fn comment() {
+    // this is a test comment
+    1
+}
+
+fn comment2() {
+    // multi-line comment
+    let z = 2;
+    1
+}
+
+fn only_comment() {
+    // Keep this here
+}
+
+fn aaaaaaaaaaaaaaaaa_looooooooooooooooooooooong_name() {
+    let z = "aaaaaaawwwwwwwwwwwwwwwwwwwwwwwwwwww";
+}
+
+fn lots_of_space                      ()                                                           {
+                           1                 
+}
+
+fn mac() -> Vec<i32> { vec![] }
+
+trait CoolTypes {
+    fn dummy(&self) {
+    }
+}
+
+trait CoolerTypes { fn dummy(&self) { 
+}
+}
+
+fn Foo<T>() where T: Bar {
+}
diff --git a/src/tools/rustfmt/tests/writemode/source/modified.rs b/src/tools/rustfmt/tests/writemode/source/modified.rs
new file mode 100644
index 0000000000000..948beb348dbbf
--- /dev/null
+++ b/src/tools/rustfmt/tests/writemode/source/modified.rs
@@ -0,0 +1,14 @@
+// rustfmt-write_mode: modified
+// Test "modified" output
+
+fn
+blah
+()
+{ }
+
+
+#[cfg
+(  a , b
+)]
+fn
+main() {}
diff --git a/src/tools/rustfmt/tests/writemode/target/checkstyle.xml b/src/tools/rustfmt/tests/writemode/target/checkstyle.xml
new file mode 100644
index 0000000000000..05bc3a2525d54
--- /dev/null
+++ b/src/tools/rustfmt/tests/writemode/target/checkstyle.xml
@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="utf-8"?>
+<checkstyle version="4.3"><file name="tests/writemode/source/fn-single-line.rs"><error line="5" severity="warning" message="Should be `fn foo_expr() { 1 }`" /><error line="7" severity="warning" message="Should be `fn foo_stmt() { foo(); }`" /><error line="9" severity="warning" message="Should be `fn foo_decl_local() { let z = 5; }`" /><error line="11" severity="warning" message="Should be `fn foo_decl_item(x: &amp;mut i32) { x = 3; }`" /><error line="13" severity="warning" message="Should be `fn empty() {}`" /><error line="15" severity="warning" message="Should be `fn foo_return() -&gt; String { &quot;yay&quot; }`" /><error line="17" severity="warning" message="Should be `fn foo_where() -&gt; T`" /><error line="18" severity="warning" message="Should be `where`" /><error line="19" severity="warning" message="Should be `    T: Sync,`" /><error line="20" severity="warning" message="Should be `{`" /><error line="55" severity="warning" message="Should be `fn lots_of_space() { 1 }`" /><error line="60" severity="warning" message="Should be `    fn dummy(&amp;self) {}`" /><error line="63" severity="warning" message="Should be `trait CoolerTypes {`" /><error line="64" severity="warning" message="Should be `    fn dummy(&amp;self) {}`" /><error line="67" severity="warning" message="Should be `fn Foo&lt;T&gt;()`" /><error line="68" severity="warning" message="Should be `where`" /><error line="69" severity="warning" message="Should be `    T: Bar,`" /><error line="70" severity="warning" message="Should be `{`" /></file></checkstyle>
diff --git a/src/tools/rustfmt/tests/writemode/target/modified.txt b/src/tools/rustfmt/tests/writemode/target/modified.txt
new file mode 100644
index 0000000000000..5c0539a665e68
--- /dev/null
+++ b/src/tools/rustfmt/tests/writemode/target/modified.txt
@@ -0,0 +1,5 @@
+4 4 1
+fn blah() {}
+10 5 2
+#[cfg(a, b)]
+fn main() {}
diff --git a/src/tools/rustfmt/tests/writemode/target/output.json b/src/tools/rustfmt/tests/writemode/target/output.json
new file mode 100644
index 0000000000000..b5f327b0a1ca6
--- /dev/null
+++ b/src/tools/rustfmt/tests/writemode/target/output.json
@@ -0,0 +1 @@
+[{"name":"tests/writemode/source/json.rs","mismatches":[{"original_begin_line":5,"original_end_line":7,"expected_begin_line":5,"expected_end_line":5,"original":"fn foo_expr() {\n    1\n}","expected":"fn foo_expr() { 1 }"},{"original_begin_line":9,"original_end_line":11,"expected_begin_line":7,"expected_end_line":7,"original":"fn foo_stmt() {\n    foo();\n}","expected":"fn foo_stmt() { foo(); }"},{"original_begin_line":13,"original_end_line":15,"expected_begin_line":9,"expected_end_line":9,"original":"fn foo_decl_local()  {\n    let z = 5;\n   }","expected":"fn foo_decl_local() { let z = 5; }"},{"original_begin_line":17,"original_end_line":19,"expected_begin_line":11,"expected_end_line":11,"original":"fn    foo_decl_item(x: &mut i32) {\n    x = 3;\n}","expected":"fn foo_decl_item(x: &mut i32) { x = 3; }"},{"original_begin_line":21,"original_end_line":21,"expected_begin_line":13,"expected_end_line":13,"original":"   fn empty()     {","expected":"fn empty() {}"},{"original_begin_line":23,"original_end_line":23,"expected_begin_line":15,"expected_end_line":15,"original":"}","expected":"fn foo_return() -> String { \"yay\" }"},{"original_begin_line":25,"original_end_line":29,"expected_begin_line":17,"expected_end_line":20,"original":"fn foo_return() -> String {\n    \"yay\"\n}\n\nfn foo_where() -> T where T: Sync {","expected":"fn foo_where() -> T\nwhere\n    T: Sync,\n{"},{"original_begin_line":64,"original_end_line":66,"expected_begin_line":55,"expected_end_line":55,"original":"fn lots_of_space                      ()                                                           {\n                           1                 \n}","expected":"fn lots_of_space() { 1 }"},{"original_begin_line":71,"original_end_line":72,"expected_begin_line":60,"expected_end_line":60,"original":"    fn dummy(&self) {\n    }","expected":"    fn dummy(&self) {}"},{"original_begin_line":75,"original_end_line":75,"expected_begin_line":63,"expected_end_line":64,"original":"trait CoolerTypes { fn dummy(&self) { ","expected":"trait CoolerTypes {\n    fn dummy(&self) {}"},{"original_begin_line":77,"original_end_line":77,"expected_begin_line":66,"expected_end_line":66,"original":"}","expected":""},{"original_begin_line":79,"original_end_line":79,"expected_begin_line":67,"expected_end_line":70,"original":"fn Foo<T>() where T: Bar {","expected":"fn Foo<T>()\nwhere\n    T: Bar,\n{"}]}]
\ No newline at end of file