[`unused_braces`] Lint multiline blocks as long as not in arms #102432

kraktus · 2022-09-28T19:41:41Z

The commit message include removing braces in arm matches but I could not find a way to make a suggestion for it, since it some cases you would need to replace the block by a comma
Example:

match expr {
    pat => {()}
    _ => println!("foo")
}

We still do not lint multiline match arms used for formatting reasons

match expr {
   pat => {
       somewhat_long_expression
   }
 // ...
}

?r @lcnr since we discussed briefly about it on zulip. Happy to have your feedback on this

rust-highfive · 2022-09-28T19:41:45Z

r? @Mark-Simulacrum

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rustbot · 2022-09-28T19:41:46Z

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

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kraktus · 2022-09-28T19:42:13Z

r? @lcnr

library/std/src/collections/hash/map.rs

lcnr

instead of modifying the ui tests, can you add #![allow(unused_braces)] to the tests instead

apart from that these changes look good to me, not sure if changing a style lint like this warrants a more formal decision, so I am just going to get another compiler member to also sign this off 🤷

compiler/rustc_lint/src/unused.rs

lcnr · 2022-09-29T08:32:26Z

r? compiler

compiler/rustc_span/src/hygiene.rs

compiler/rustc_middle/src/ty/layout.rs

rustbot · 2022-09-30T14:44:57Z

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

compiler/rustc_codegen_cranelift/src/base.rs

src/test/ui/binding/expr-match-generic-unique1.rs

kraktus · 2022-09-30T15:06:32Z

Saving the comments before rebasing

with_no_trimmed_paths!({
I think this should stay the same. The content of the block is a statement, not an expression. Same for the other changed use of with_no_trimmed_paths in cg_cl

I think you should skip changing tests. It may unintentionally change the meaning of the tests. We don't run rustfmt on tests at all.

calebcartwright · 2023-01-11T23:06:06Z

I just want to emphasize that the concern raised was not exclusive to match_ast! nor any other singular macro. Applying a precise workaround to the current macro at hand would indeed be a helpful step forward, but I also wonder if it would be worthwhile (or practical) to run a broader test. Not sure if crater runs can be used to flag potential issues with new lints?

kraktus · 2023-01-13T18:31:38Z

I just want to emphasize that the concern raised was not exclusive to match_ast! nor any other singular macro. Applying a precise workaround to the current macro at hand would indeed be a helpful step forward, but I also wonder if it would be worthwhile (or practical) to run a broader test. Not sure if crater runs can be used to flag potential issues with new lints?

Afaik craters only look at compilation failures, so this lint could be sent as deny before running it and see how many crates now fail to compile.

To be accurate the number of failure should not take into account crates that would have triggered this lint before its scope expansion.

kraktus · 2023-01-14T09:07:03Z

Solution 2. (silencing the warning on match_ast!) has been applied and tests are passing. Waiting for more input on the possible crater run.

bors · 2023-01-16T01:23:57Z

☔ The latest upstream changes (presumably #106914) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2023-01-26T06:48:02Z

☔ The latest upstream changes (presumably #105582) made this pull request unmergeable. Please resolve the merge conflicts.

Currently the lint faces a severe limitation: since it only catches single-line block, running rustfmt beforehand will remove all occurences of it, because it breaks them into multiline blocks. We do not check match `Arm` for two reasons: - In case it does not use commas to separate arms, removing the block would result in a compilation error Example: ``` match expr { pat => {()} _ => println!("foo") } ``` - Do not lint multiline match arms used for formatting reasons ``` match expr { pat => { somewhat_long_expression } // ... } ``` Delete `unused-braces-lint` test The modified lint correctly provide a span in its suggestion. ```shell error: unnecessary braces around block return value --> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:9:5 | LL | / { LL | | { | |________^ LL | use std; LL | } | __________^ LL | | } | |_____^ | note: the lint level is defined here --> /rust/src/test/rustdoc-ui/unused-braces-lint.rs:6:9 | LL | #![deny(unused_braces)] | ^^^^^^^^^^^^^ help: remove these braces | LL ~ { LL | use std; LL ~ } | ``` It is unclear to which extend rust-lang#70814 is still an issue, as the inital MCVE does not trigger the lint on stable either,[rust playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=b6ff31a449c0b73a08daac8ee43b1fa6) Fix code with expanded `unused_braces` lint Also allow `unused_braces` on tests Mute `unused_braces` on `match_ast!`

kraktus · 2023-02-01T15:15:34Z

Solution 2. (silencing the warning on match_ast!) has been applied and tests are passing. Waiting for more input on the possible crater run.

@calebcartwright gentle ping about this

bors · 2023-02-16T14:16:30Z

☔ The latest upstream changes (presumably #101841) made this pull request unmergeable. Please resolve the merge conflicts.

compiler-errors · 2023-02-23T19:38:43Z

T-style discussed this yesterday in our meeting.

Our recommendation is that this change should not be enforced within macro args. Is it possible to modify your implementation to continue silently accepting those cases? It should be possible with the visitor structure of the lint.

Also, I would be keen on reverting the usages of with_no_trimmed_paths!({ .. }), etc. from a compiler reviewer perspective.

compiler-errors · 2023-03-01T05:02:41Z

@rustbot author

Waiting on changes to be made + a rebase, use @rustbot author to mark it ready for review :)

lnicola · 2023-03-03T11:16:56Z

Our recommendation is that this change should not be enforced within macro args.

Given this, do we still need the RA change?

kraktus · 2023-03-03T11:28:02Z

It shouldn't be necessary anymore

JohnCSimon · 2023-05-28T13:33:41Z

@kraktus
ping from triage - can you post your status on this PR? There hasn't been an update in a few months. Thanks!

FYI: when a PR is ready for review, send a message containing
@rustbot ready to switch to S-waiting-on-review so the PR is in the reviewer's backlog.

lnicola · 2023-05-28T18:03:15Z

It shouldn't be necessary anymore

FWIW it's still there 🙂.

kraktus · 2023-05-28T18:21:41Z

Hey, thanks for the ping, I don’t plan to work on this PR in the foreseeable future.

compiler-errors · 2023-06-15T19:03:40Z

In that case, closing this PR. Thanks for the contribution.

rust-highfive assigned Mark-Simulacrum Sep 28, 2022

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kraktus force-pushed the useless_braces branch from f81fc72 to 0d0a96b Compare September 29, 2022 13:42

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kraktus marked this pull request as draft September 30, 2022 15:03

kraktus force-pushed the useless_braces branch 3 times, most recently from 76cc9cc to 4653e5c Compare September 30, 2022 15:56

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kraktus force-pushed the useless_braces branch 5 times, most recently from f79f70c to 0e5a741 Compare January 13, 2023 23:59

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kraktus force-pushed the useless_braces branch from 9f203f2 to e641393 Compare January 27, 2023 19:39

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add failing test about macro arg

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[`unused_braces`] Lint multiline blocks as long as not in arms #102432

[`unused_braces`] Lint multiline blocks as long as not in arms #102432

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[unused_braces] Lint multiline blocks as long as not in arms #102432

[unused_braces] Lint multiline blocks as long as not in arms #102432

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[`unused_braces`] Lint multiline blocks as long as not in arms #102432

[`unused_braces`] Lint multiline blocks as long as not in arms #102432

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