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compiler/middle/lint: Suggest #[expect(dead_code)] instead of #[allow(dead_code)] #147717

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compiler/middle/lint: Suggest #[expect(dead_code)] instead of #[allow(dead_code)] #147717

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c7385fe
Add `dead-code/unused-fn-with-check-pass` UI test
Turbo87 Oct 15, 2025
47d1a5a
compiler/middle/lint: Suggest `#[expect(dead_code)]` instead of `#[al…
Turbo87 Oct 15, 2025
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3 changes: 2 additions & 1 deletion compiler/rustc_middle/src/lint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -264,8 +264,9 @@ fn explain_lint_level_source(
"`{flag} {hyphen_case_lint_name}` implied by `{flag} {hyphen_case_flag_val}`"
));
if matches!(orig_level, Level::Warn | Level::Deny) {
let suggestion = if name == "dead_code" { "expect" } else { "allow" };
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I scoped this to only the dead_code suggestion for now. It might make sense to extend it to others in the future too though.
err.help_once(format!(
"to override `{flag} {hyphen_case_flag_val}` add `#[allow({name})]`"
"to override `{flag} {hyphen_case_flag_val}` add `#[{suggestion}({name})]`"
));
}
}
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2 changes: 1 addition & 1 deletion tests/ui/derives/derive-debug-uninhabited-enum.stderr
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Expand Up @@ -9,7 +9,7 @@ LL | Void(Void),
|
= note: `Foo` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
= note: `-W dead-code` implied by `-W unused`
= help: to override `-W unused` add `#[allow(dead_code)]`
= help: to override `-W unused` add `#[expect(dead_code)]`

warning: 1 warning emitted

8 changes: 8 additions & 0 deletions tests/ui/lint/dead-code/unused-fn-with-check-pass.rs
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@@ -0,0 +1,8 @@
//@ check-pass
//@ compile-flags: -Wunused

fn foo() -> &'static str { //~ WARN function `foo` is never used
"hello"
}

fn main() {}
11 changes: 11 additions & 0 deletions tests/ui/lint/dead-code/unused-fn-with-check-pass.stderr
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@@ -0,0 +1,11 @@
warning: function `foo` is never used
--> $DIR/unused-fn-with-check-pass.rs:4:4
|
LL | fn foo() -> &'static str {
| ^^^
|
= note: `-W dead-code` implied by `-W unused`
= help: to override `-W unused` add `#[expect(dead_code)]`

warning: 1 warning emitted

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