[lapla-cogito]

Fixes #165169

[rustbot]

r? @mu001999

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[mu001999]

But removing the parentheses would not lead to success (play):

#![feature(guard_patterns)]
#![expect(incomplete_features)]

fn main() {
    let x: !;
    match 1 {
        (y if x) => {}
    }
}

would give

error: unexpected parentheses surrounding `match` arm pattern
 --> src/main.rs:7:9
  |
7 |         (y if x) => {}
  |         ^      ^
  |
help: remove parentheses surrounding the pattern
  |
7 -         (y if x) => {}
7 +         y if x => {}
  |

warning: unreachable expression
 --> src/main.rs:7:21
  |
7 |         (y if x) => {}
  |               -     ^^ unreachable expression
  |               |
  |               any code following this expression is unreachable
  |
  = note: `#[warn(unreachable_code)]` (part of `#[warn(unused)]`) on by default

error[E0004]: non-exhaustive patterns: `i32::MIN..=i32::MAX` not covered
 --> src/main.rs:6:11
  |
6 |     match 1 {
  |           ^ pattern `i32::MIN..=i32::MAX` not covered
  |
  = note: the matched value is of type `i32`
  = note: match arms with guards don't count towards exhaustivity
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
  |
7 ~         (y if x) => {},
8 +         i32::MIN..=i32::MAX => todo!()
  |

I think the behaviors should be consistent.

[lapla-cogito]

But removing the parentheses would not lead to success (play):

#![feature(guard_patterns)]
#![expect(incomplete_features)]

fn main() {
    let x: !;
    match 1 {
        (y if x) => {}
    }
}

would give

error: unexpected parentheses surrounding `match` arm pattern
 --> src/main.rs:7:9
  |
7 |         (y if x) => {}
  |         ^      ^
  |
help: remove parentheses surrounding the pattern
  |
7 -         (y if x) => {}
7 +         y if x => {}
  |

warning: unreachable expression
 --> src/main.rs:7:21
  |
7 |         (y if x) => {}
  |               -     ^^ unreachable expression
  |               |
  |               any code following this expression is unreachable
  |
  = note: `#[warn(unreachable_code)]` (part of `#[warn(unused)]`) on by default

error[E0004]: non-exhaustive patterns: `i32::MIN..=i32::MAX` not covered
 --> src/main.rs:6:11
  |
6 |     match 1 {
  |           ^ pattern `i32::MIN..=i32::MAX` not covered
  |
  = note: the matched value is of type `i32`
  = note: match arms with guards don't count towards exhaustivity
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
  |
7 ~         (y if x) => {},
8 +         i32::MIN..=i32::MAX => todo!()
  |

I think the behaviors should be consistent.

But is this really an issue that should be fixed with this patch? It seems like something that should be handled on the parser side. (Of course I can work on a follow-up PR later for this.)

@rustbot reviewer

[mu001999]

But is this really an issue that should be fixed with this patch? It seems like something that should be handled on the parser side. (Of course I can work on a follow-up PR later for this.)

I think it is reasonable. And I find #164465 would support this.

Thanks!

@bors r+ rollup

[rust-bors]

📌 Commit fc3192b has been approved by mu001999

It is now in the queue for this repository.

[WaffleLapkin]

@bors r-

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[WaffleLapkin]

I don't get this. This should definitely not compile. What is even going on here?

[rust-bors]

This pull request was unapproved.

View changes since this unapproval