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allow(unused_variables) doesn't work on struct field bindings in patterns #138428

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camsteffen opened this issue Mar 12, 2025 · 0 comments · Fixed by #138434
Closed

allow(unused_variables) doesn't work on struct field bindings in patterns #138428

camsteffen opened this issue Mar 12, 2025 · 0 comments · Fixed by #138434
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A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. A-patterns Relating to patterns and pattern matching C-bug Category: This is a bug. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@camsteffen
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I tried this code:

pub struct Foo {
    bar: u32,
    baz: u32,
}

pub fn test(foo: Foo) {
    let Foo {
        #[allow(unused_variables)]
        bar,
        #[allow(unused_variables)]
        baz,
    } = foo;
}

I expected to see this happen:

no lint

Instead, this happened:

unused_variables lint occurs even though it is allowed

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rustc version 1.85.0

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@camsteffen camsteffen added the C-bug Category: This is a bug. label Mar 12, 2025
@rustbot rustbot added the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Mar 12, 2025
@fmease fmease changed the title allow(unused_variables) doesn't work on struct field in this case allow(unused_variables) doesn't work on struct field bindings in patterns Mar 12, 2025
@compiler-errors compiler-errors self-assigned this Mar 13, 2025
@compiler-errors compiler-errors mentioned this issue Mar 13, 2025
Merged
@jieyouxu jieyouxu added A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. and removed needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. labels Mar 13, 2025
@fmease fmease added L-unused_variables Lint: unused_variables A-patterns Relating to patterns and pattern matching and removed L-unused_variables Lint: unused_variables labels Mar 13, 2025
@bors bors closed this as completed in fb2a7fa Mar 14, 2025
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Mar 14, 2025
@rust-timer
Unrolled build for rust-lang#138434
47ff4af 
Rollup merge of rust-lang#138434 - compiler-errors:lint-level-pat-field, r=jieyouxu

Visit `PatField` when collecting lint levels

Fixes rust-lang#138428

Side-note, I vaguely skimmed over the other nodes we could be visiting here and it doesn't *seem* to me that we're missing anything, though I may be mistaken given recent(?) support for attrs in where clauses(??). Can be fixed in a follow-up PR.
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A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. A-patterns Relating to patterns and pattern matching C-bug Category: This is a bug. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Visit PatField when collecting lint levels compiler-errors/rust
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@compiler-errors @camsteffen @fmease @jieyouxu @rustbot