diff --git a/tests/ui/impl-trait/in-ctfe/array-len-size-of.rs b/tests/ui/impl-trait/in-ctfe/array-len-size-of.rs
new file mode 100644
index 0000000000000..01ba902ef0c0d
--- /dev/null
+++ b/tests/ui/impl-trait/in-ctfe/array-len-size-of.rs
@@ -0,0 +1,16 @@
+//! Check that const eval can use the size of opaque types.
+// check-pass
+use std::mem;
+fn returns_opaque() -> impl Sized {
+    0u8
+}
+
+struct NamedOpaqueType {
+    data: [mem::MaybeUninit<u8>; size_of_fut(returns_opaque)],
+}
+
+const fn size_of_fut<FUT>(x: fn() -> FUT) -> usize {
+    mem::size_of::<FUT>()
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/in-ctfe/array-len.rs b/tests/ui/impl-trait/in-ctfe/array-len.rs
new file mode 100644
index 0000000000000..73ae20495d577
--- /dev/null
+++ b/tests/ui/impl-trait/in-ctfe/array-len.rs
@@ -0,0 +1,22 @@
+//! Check that array lengths can observe associated types of opaque types
+// check-pass
+trait MyTrait: Copy {
+    const ASSOC: usize;
+}
+
+impl MyTrait for u8 {
+    const ASSOC: usize = 32;
+}
+
+const fn yeet() -> impl MyTrait {
+    0u8
+}
+
+const fn output<T: MyTrait>(_: T) -> usize {
+    <T as MyTrait>::ASSOC
+}
+
+fn main() {
+    let x = [0u8; output(yeet())];
+    println!("{:?}", x);
+}
diff --git a/tests/ui/impl-trait/in-ctfe/enum-discr.rs b/tests/ui/impl-trait/in-ctfe/enum-discr.rs
new file mode 100644
index 0000000000000..8e4384adaa4cb
--- /dev/null
+++ b/tests/ui/impl-trait/in-ctfe/enum-discr.rs
@@ -0,0 +1,26 @@
+//! check that const eval can observe associated types of opaque types.
+// check-pass
+trait MyTrait: Copy {
+    const ASSOC: usize;
+}
+
+impl MyTrait for u8 {
+    const ASSOC: usize = 32;
+}
+
+const fn yeet() -> impl MyTrait {
+    0u8
+}
+
+const fn output<T: MyTrait>(_: T) -> usize {
+    <T as MyTrait>::ASSOC
+}
+
+#[repr(usize)]
+enum Foo {
+    Bar = output(yeet()),
+}
+
+fn main() {
+    println!("{}", Foo::Bar as usize);
+}
diff --git a/tests/ui/impl-trait/in-ctfe/match-arm-exhaustive.rs b/tests/ui/impl-trait/in-ctfe/match-arm-exhaustive.rs
new file mode 100644
index 0000000000000..8e3269726fc4a
--- /dev/null
+++ b/tests/ui/impl-trait/in-ctfe/match-arm-exhaustive.rs
@@ -0,0 +1,24 @@
+//! Check that pattern matching can observe the hidden type of opaque types.
+// check-pass
+trait MyTrait: Copy {
+    const ASSOC: u8;
+}
+
+impl MyTrait for () {
+    const ASSOC: u8 = 0;
+}
+
+const fn yeet() -> impl MyTrait {}
+
+const fn output<T: MyTrait>(_: T) -> u8 {
+    <T as MyTrait>::ASSOC
+}
+
+const CT: u8 = output(yeet());
+
+fn main() {
+    match 0 {
+        CT => (),
+        1.. => (),
+    }
+}
diff --git a/tests/ui/impl-trait/transmute/in-defining-scope.rs b/tests/ui/impl-trait/transmute/in-defining-scope.rs
new file mode 100644
index 0000000000000..b0b77d60b245e
--- /dev/null
+++ b/tests/ui/impl-trait/transmute/in-defining-scope.rs
@@ -0,0 +1,14 @@
+// This causes a query cycle due to using `Reveal::All`,
+// in #119821 const eval was changed to always use `Reveal::All`
+//
+// See that PR for more details.
+use std::mem::transmute;
+fn foo() -> impl Sized {
+    //~^ ERROR cycle detected when computing type of
+    unsafe {
+        transmute::<_, u8>(foo());
+    }
+    0u8
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/transmute/in-defining-scope.stderr b/tests/ui/impl-trait/transmute/in-defining-scope.stderr
new file mode 100644
index 0000000000000..69812f43072b0
--- /dev/null
+++ b/tests/ui/impl-trait/transmute/in-defining-scope.stderr
@@ -0,0 +1,29 @@
+error[E0391]: cycle detected when computing type of `foo::{opaque#0}`
+  --> $DIR/in-defining-scope.rs:6:13
+   |
+LL | fn foo() -> impl Sized {
+   |             ^^^^^^^^^^
+   |
+note: ...which requires computing type of opaque `foo::{opaque#0}`...
+  --> $DIR/in-defining-scope.rs:6:13
+   |
+LL | fn foo() -> impl Sized {
+   |             ^^^^^^^^^^
+note: ...which requires type-checking `foo`...
+  --> $DIR/in-defining-scope.rs:6:1
+   |
+LL | fn foo() -> impl Sized {
+   | ^^^^^^^^^^^^^^^^^^^^^^
+   = note: ...which requires computing layout of `foo::{opaque#0}`...
+   = note: ...which requires normalizing `foo::{opaque#0}`...
+   = note: ...which again requires computing type of `foo::{opaque#0}`, completing the cycle
+note: cycle used when checking that `foo::{opaque#0}` is well-formed
+  --> $DIR/in-defining-scope.rs:6:13
+   |
+LL | fn foo() -> impl Sized {
+   |             ^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0391`.
diff --git a/tests/ui/impl-trait/transmute/outside-of-defining-scope.rs b/tests/ui/impl-trait/transmute/outside-of-defining-scope.rs
new file mode 100644
index 0000000000000..7bc22ea416f06
--- /dev/null
+++ b/tests/ui/impl-trait/transmute/outside-of-defining-scope.rs
@@ -0,0 +1,12 @@
+//! Check that typeck can observe the size of an opaque type.
+// check-pass
+use std::mem::transmute;
+fn foo() -> impl Sized {
+    0u8
+}
+
+fn main() {
+    unsafe {
+        transmute::<_, u8>(foo());
+    }
+}
diff --git a/tests/ui/specialization/ctfe/default-assoc-const.rs b/tests/ui/specialization/ctfe/default-assoc-const.rs
new file mode 100644
index 0000000000000..bb3b735caa312
--- /dev/null
+++ b/tests/ui/specialization/ctfe/default-assoc-const.rs
@@ -0,0 +1,18 @@
+//! Regression test for revealing associated types through specialization during const eval.
+// check-pass
+#![feature(specialization)]
+//~^ WARNING the feature `specialization` is incomplete and may not be safe to use
+
+trait Foo {
+    const ASSOC: usize;
+}
+
+impl Foo for u32 {
+    default const ASSOC: usize = 0;
+}
+
+fn foo() -> [u8; 0] {
+    [0; <u32 as Foo>::ASSOC]
+}
+
+fn main() {}
diff --git a/tests/ui/specialization/ctfe/default-assoc-const.stderr b/tests/ui/specialization/ctfe/default-assoc-const.stderr
new file mode 100644
index 0000000000000..5caa79211ffb9
--- /dev/null
+++ b/tests/ui/specialization/ctfe/default-assoc-const.stderr
@@ -0,0 +1,12 @@
+warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/default-assoc-const.rs:6:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+   = help: consider using `min_specialization` instead, which is more stable and complete
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/specialization/ctfe/default-assoc-type.rs b/tests/ui/specialization/ctfe/default-assoc-type.rs
new file mode 100644
index 0000000000000..5dc46907ab545
--- /dev/null
+++ b/tests/ui/specialization/ctfe/default-assoc-type.rs
@@ -0,0 +1,27 @@
+//! Regression test showing that we can access assoicated types during const eval,
+//! even if they rely on specialization.
+// check-pass
+#![feature(specialization)]
+//~^ WARNING the feature `specialization` is incomplete and may not be safe to use
+
+trait Foo {
+    type Assoc: Trait;
+}
+
+impl<T> Foo for Vec<T> {
+    default type Assoc = u32;
+}
+
+trait Trait {
+    const ASSOC: usize;
+}
+
+impl Trait for u32 {
+    const ASSOC: usize = 0;
+}
+
+fn foo() -> [u8; 0] {
+    [0; <<Vec<u32> as Foo>::Assoc as Trait>::ASSOC]
+}
+
+fn main() {}
diff --git a/tests/ui/specialization/ctfe/default-assoc-type.stderr b/tests/ui/specialization/ctfe/default-assoc-type.stderr
new file mode 100644
index 0000000000000..2e0a815179f4f
--- /dev/null
+++ b/tests/ui/specialization/ctfe/default-assoc-type.stderr
@@ -0,0 +1,12 @@
+warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/default-assoc-type.rs:6:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+   = help: consider using `min_specialization` instead, which is more stable and complete
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/type-alias-impl-trait/in-where-clause.rs b/tests/ui/type-alias-impl-trait/in-where-clause.rs
new file mode 100644
index 0000000000000..0ad6e7a6f6014
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/in-where-clause.rs
@@ -0,0 +1,16 @@
+//! We evaluate `1 + 2` with `Reveal::All` during typeck, causing
+//! us to to get the concrete type of `Bar` while computing it.
+//! This again requires type checking `foo`.
+#![feature(type_alias_impl_trait)]
+type Bar = impl Sized;
+//~^ ERROR: cycle
+//~| ERROR: cycle
+
+fn foo() -> Bar
+where
+    Bar: Send,
+{
+    [0; 1 + 2]
+}
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/in-where-clause.stderr b/tests/ui/type-alias-impl-trait/in-where-clause.stderr
new file mode 100644
index 0000000000000..9c08b8f127d27
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/in-where-clause.stderr
@@ -0,0 +1,50 @@
+error[E0391]: cycle detected when computing type of `Bar::{opaque#0}`
+  --> $DIR/in-where-clause.rs:5:12
+   |
+LL | type Bar = impl Sized;
+   |            ^^^^^^^^^^
+   |
+note: ...which requires computing type of opaque `Bar::{opaque#0}`...
+  --> $DIR/in-where-clause.rs:5:12
+   |
+LL | type Bar = impl Sized;
+   |            ^^^^^^^^^^
+note: ...which requires type-checking `foo`...
+  --> $DIR/in-where-clause.rs:9:1
+   |
+LL | / fn foo() -> Bar
+LL | | where
+LL | |     Bar: Send,
+   | |______________^
+   = note: ...which requires revealing opaque types in `[Binder { value: TraitPredicate(<Bar as core::marker::Send>, polarity:Positive), bound_vars: [] }]`...
+   = note: ...which again requires computing type of `Bar::{opaque#0}`, completing the cycle
+note: cycle used when checking that `Bar::{opaque#0}` is well-formed
+  --> $DIR/in-where-clause.rs:5:12
+   |
+LL | type Bar = impl Sized;
+   |            ^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error[E0391]: cycle detected when computing type of opaque `Bar::{opaque#0}`
+  --> $DIR/in-where-clause.rs:5:12
+   |
+LL | type Bar = impl Sized;
+   |            ^^^^^^^^^^
+   |
+note: ...which requires type-checking `foo`...
+  --> $DIR/in-where-clause.rs:13:9
+   |
+LL |     [0; 1 + 2]
+   |         ^^^^^
+   = note: ...which requires evaluating trait selection obligation `Bar: core::marker::Send`...
+   = note: ...which again requires computing type of opaque `Bar::{opaque#0}`, completing the cycle
+note: cycle used when computing type of `Bar::{opaque#0}`
+  --> $DIR/in-where-clause.rs:5:12
+   |
+LL | type Bar = impl Sized;
+   |            ^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0391`.