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while let suggestion missing when E0308 happens in closure body #113354

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e2-71828 opened this issue Jul 5, 2023 · 0 comments · Fixed by #113567
Closed

while let suggestion missing when E0308 happens in closure body #113354

e2-71828 opened this issue Jul 5, 2023 · 0 comments · Fixed by #113567
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@chenyukang
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A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@e2-71828
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e2-71828 commented Jul 5, 2023

Code

fn main() {
    let _ = || { while Some(_) = None { } };
}

Current output

error[E0308]: mismatched types
 --> src/main.rs:2:24
  |
2 |     let _ = || { while Some(_) = None { } };
  |                        ^^^^^^^^^^^^^^ expected `bool`, found `()`

For more information about this error, try `rustc --explain E0308`.

Desired output

error[E0308]: mismatched types
 --> src/main.rs:2:24
  |
2 |     let _ = || { while Some(_) = None { } };
  |                        ^^^^^^^^^^^^^^ expected `bool`, found `()`
help: consider adding `let`
  |
2 |     let _ = || { while let Some(_) = None { } };
  |                           

For more information about this error, try `rustc --explain E0308`.

Rationale and extra context

When an assignment is used as the test in a while statement, the compiler will add a help message suggesting while let instead. This message fails to appear when the erroneous while statement is inside a closure body.

Other cases

No response

Anything else?

This problem was discovered while investigating #113352 .
@e2-71828 e2-71828 added A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 5, 2023
@chenyukang chenyukang self-assigned this Jul 6, 2023
@chenyukang chenyukang mentioned this issue Jul 11, 2023
Merged
workingjubilee added a commit to workingjubilee/rustc that referenced this issue Jul 12, 2023
@workingjubilee
Rollup merge of rust-lang#113567 - chenyukang:yukang-fix-113354-while…
11f3bcf 
…-let, r=cjgillot

While let suggestion will work for closure body

Fixes rust-lang#113354
@bors bors closed this as completed in f7a34f9 Jul 12, 2023
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While let suggestion will work for closure body chenyukang/rust
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