Add `do yeet` expressions to allow experimentation in nightly #96376

scottmcm · 2022-04-25T01:28:55Z

Two main goals for this:

Ensure that trait restructuring in Tracking Issue for try_trait_v2, A new design for the ? desugaring (RFC#3058) #84277 (comment) doesn't accidentally close us off from the possibility of doing this in future, as sketched in https://rust-lang.github.io/rfcs/3058-try-trait-v2.html#possibilities-for-yeet
Experiment with the existence of syntax for this, to be able to weight the syntax-vs-library tradeoffs better than we can right now. Notably the syntax (with do) and name in this PR are not intended as candidates for stabilization, but they make a good v0 PR for adding this with minimal impact to compiler maintenance or priming one possible name choice over another.

r? @oli-obk
The lang second for doing this: rust-lang/lang-team#160 (comment)

Tracking issues

calebcartwright · 2022-04-25T03:35:57Z

src/tools/rustfmt/src/expr.rs

+        ast::ExprKind::Yeet(None) => Some("do yeet".to_owned()),
+        ast::ExprKind::Yeet(Some(ref expr)) => {
+            rewrite_unary_prefix(context, "do yeet ", &**expr, shape)
+        }


Typically with a new variant we'd start with rustfmt just spitting back out whatever the user wrote, but in this particular case I can't imagine a universe where we'd do anything different. As such I've no concerns with these rustfmt changes 👍

Will use this to mention an aside, and realize the style team hasn't fully come to fruition yet @joshtriplett, but I think one future question/consideration for that team should be when/how new syntax gets incorporated into the guide, including for cases like this that are obvious and noncontroversial.

Oh, thanks @calebcartwright; I wasn't thinking about the stability details here at all. But yes, I agree that I'd be very surprised if we wanted this to format differently from return/break. Also, the syntax for this will change later, so we'll have another opportunity to rethink the formatting once that happens.

As another aside: Is there a way this match could have a catch-all arm that just does the "spit back what the user wrote", so that additions to the AST like this would do the right thing without needing a code change? I only updated the file because the PR build broke when I did nothing.

Is there a way this match could have a catch-all arm that just does the "spit back what the user wrote", so that additions to the AST like this would do the right thing without needing a code change?

Potentially. IIRC many of the big match expressions used to have a catch-all pattern arm in the earlier days when rustfmt used the AP crates, but that was intentionally changed some time back as part of an effort to ensure the rustfmt team would become aware of new syntax associated with new variants.

If/when we can implement some of the process changes previously discussed elsewhere then I'd certainly be open to adding such arms back. In the interim, for future reference, the behavior can be triggered with None or something like Some(context.snippet(<<span>>).to_owned())

compiler/rustc_ast_passes/src/feature_gate.rs

rustbot · 2022-04-25T19:08:14Z

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oli-obk · 2022-04-27T10:18:22Z

compiler/rustc_ast_lowering/src/expr.rs

+        );
+
+        if let Some(catch_node) = self.catch_scope {
+            let target_id = Ok(self.lower_node_id(catch_node));


preexisting, but I wish we didn't have to lower the node id twice.

oli-obk · 2022-04-27T10:27:06Z

src/test/ui/inference/question-mark-type-infer.stderr

-   |                     ^^^^^^^ cannot infer type
-   |
-   = note: cannot satisfy `<_ as Try>::Residual == _`
-help: consider specifying the type argument in the method call
-   |
-LL |     l.iter().map(f).collect::<B>()?
-   |                            +++++
+   |                              ^ cannot infer type


Unfortunate that the second FromResidual impl breaks this

oli-obk · 2022-04-27T10:28:13Z

src/test/ui/impl-trait/cross-return-site-inference.stderr

+   = help: the following other types implement trait `FromResidual<R>`:
+             <Result<T, F> as FromResidual<Result<Infallible, E>>>
+             <Result<T, F> as FromResidual<Yeet<E>>>


Technically adding a second impl when there was only one before is a breaking change I think. There are some cases where inference figures something out. Considering that users can't mention FromResidual themselves, we're good here, but probably good to keep in mind.

Crater says we're clean, but I think the other thing that helps is the direction in which we're using it -- AsRef<T> has this problem all the time when used as a method, because with self known then if there's only one impl it's easy to know the T. But here we're going the other direction, and I know know that the inference engine allows taking advantage of "FromResidual<Concrete> is only implemented for one type", since that's fundamentally less stable, as anyone who wants could implement that themselves later if they want.

(And if there is a way that adding another impl here can be a breaking change, all the better to get a second one in early to keep anyone from finding a way to write stable code that depends on it 🙃)

oli-obk · 2022-04-27T10:29:42Z

Should we crater this? I think there are no actual problems here, but may have missed something

scottmcm · 2022-04-27T21:49:52Z

Looks like the crater queue is currently empty, so might as well -- especially since check-only is fine.

@bors try

bors · 2022-04-27T21:50:08Z

⌛ Trying commit 778944ca1ffaf781928cc846a5d41389c95da009 with merge ea2bf32540662c61547071aad6cf0851a0b02f58...

bors · 2022-04-27T23:13:24Z

☀️ Try build successful - checks-actions
Build commit: ea2bf32540662c61547071aad6cf0851a0b02f58 (ea2bf32540662c61547071aad6cf0851a0b02f58)

scottmcm · 2022-04-27T23:13:59Z

@craterbot check

craterbot · 2022-04-27T23:14:06Z

👌 Experiment pr-96376 created and queued.
🤖 Automatically detected try build ea2bf32540662c61547071aad6cf0851a0b02f58
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2022-04-27T23:14:09Z

🚧 Experiment pr-96376 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2022-04-30T17:16:28Z

🎉 Experiment pr-96376 is completed!
📊 6 regressed and 4 fixed (229604 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

scottmcm · 2022-04-30T17:42:41Z

No real regressions here.

Errors:

[INFO] [stdout] error[E0583]: file not found for module `bitrust_pb`
[INFO] [stdout]  --> /opt/rustwide/target/debug/build/bitrust-a3e48e3b381fb594/out/proto_mod.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | pub mod bitrust_pb;
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = help: to create the module `bitrust_pb`, create file "/opt/rustwide/target/debug/build/bitrust-a3e48e3b381fb594/out/proto_mod/bitrust_pb.rs" or "/opt/rustwide/target/debug/build/bitrust-a3e48e3b381fb594/out/proto_mod/bitrust_pb/mod.rs"

[INFO] [stdout] error[E0583]: file not found for module `proto_mod`
[INFO] [stdout]  --> /opt/rustwide/target/debug/build/ledger-transport-zemu-9fbd9f2b9055f698/out/proto_mod.rs:2:1
[INFO] [stdout]   |
[INFO] [stdout] 2 | pub mod proto_mod;
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = help: to create the module `proto_mod`, create file "/opt/rustwide/target/debug/build/ledger-transport-zemu-9fbd9f2b9055f698/out/proto_mod/proto_mod.rs" or "/opt/rustwide/target/debug/build/ledger-transport-zemu-9fbd9f2b9055f698/out/proto_mod/proto_mod/mod.rs"

[INFO] [stderr]   thread 'main' panicked at 'failed to create required symlink: Os { code: 17, kind: AlreadyExists, message: "File exists" }', /opt/rustwide/cargo-home/git/checkouts/binaryninja-api-3c86176688a74ccb/661d7c9/rust/binaryninjacore-sys/build.rs:70:14

[INFO] [stderr]   thread 'main' panicked at 'failed to create required symlink: Os { code: 17, kind: AlreadyExists, message: "File exists" }', /opt/rustwide/cargo-home/git/checkouts/binaryninja-api-3c86176688a74ccb/998d8ba/rust/binaryninjacore-sys/build.rs:70:14

[INFO] [stdout] error: expected expression, found `<eof>`
[INFO] [stdout]  --> /opt/rustwide/target/debug/build/sailfish-compiler-d2f5ef8f8c6f2180/out/templates/style-1065dfe86ae1c352:0:1
[INFO] [stdout]   |
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: non-statement macro in statement position: include
[INFO] [stdout]  --> src/style.rs:5:10
[INFO] [stdout]   |
[INFO] [stdout] 5 | #[derive(TemplateOnce)]
[INFO] [stdout]   |          ^^^^^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: this error originates in the derive macro `TemplateOnce` (in Nightly builds, run with -Z macro-backtrace for more info)

[INFO] [stderr]   thread 'main' panicked at '失败：不能删除原来的 /opt/rustwide/target/assets 符号链接文件: Os { code: 20, kind: NotADirectory, message: "Not a directory" }', build.rs:72:14

But it looks like I have some conflicts to fix, so
@rustbot author

Using an obviously-placeholder syntax. An RFC would still be needed before this could have any chance at stabilization, and it might be removed at any point. But I'd really like to have it in nightly at least to ensure it works well with try_trait_v2, especially as we refactor the traits.

scottmcm · 2022-05-01T02:15:50Z

Conflicts were nothing interesting, just in the UI tests, so I think this is good to go, @oli-obk .

@rustbot ready

oli-obk · 2022-05-01T13:04:52Z

@bors r+

bors · 2022-05-01T13:04:53Z

📌 Commit b317ec1 has been approved by oli-obk

bors · 2022-05-01T13:10:24Z

⌛ Testing commit b317ec1 with merge 508e058...

bors · 2022-05-01T15:25:10Z

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing 508e058 to master...

rust-timer · 2022-05-01T17:12:30Z

Finished benchmarking commit (508e058): comparison url.

Summary: This benchmark run did not return any relevant results.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

isc30

The new syntax doesn't bring anything over return Err(...)

Cypher1 · 2023-01-28T06:58:28Z

@isc30 From #96373

@reza-ebrahimi yeet has an implicit .into() conversion that return Err(…) lacks.

So... kinda

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Document PR 96376 jakevossen5/areweyeetyet.rs#3

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This was referenced Apr 27, 2022

Tracking Issue for experimental yeet expressions (feature(yeet_expr)) #96373

Open

Tracking Issue for ops::Yeet (feature(try_trait_v2_yeet)) #96374

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scottmcm added 5 commits April 30, 2022 17:40

Fix the clippy build

a15c3a3

Fix the rustfmt build

944ba8c

Bless the UI tests

9b5766c

Feature-gate do yeet inside cfgs too

b317ec1

scottmcm force-pushed the do-yeet branch from 778944c to b317ec1 Compare May 1, 2022 01:10

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Daily Hacker News 06-05-2022 xueyuanl/daily-hackernews#608

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Add `do yeet` expressions to allow experimentation in nightly #96376

Add `do yeet` expressions to allow experimentation in nightly #96376

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Add do yeet expressions to allow experimentation in nightly #96376

Add do yeet expressions to allow experimentation in nightly #96376

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Cypher1 commented Jan 28, 2023

Add `do yeet` expressions to allow experimentation in nightly #96376

Add `do yeet` expressions to allow experimentation in nightly #96376

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