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Don't suggest replacing closure parameter with type name

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When a closure has an inferred parameter type like `|ch|` and the
expected type differs in borrowing (e.g., `char` vs `&char`), the
suggestion code would incorrectly suggest `|char|` instead of the
valid `|ch: char|`.

This happened because the code couldn't walk explicit `&` references
in the HIR when the type is inferred, and fell back to replacing the
entire parameter span with the expected type name.

Fix by only emitting the suggestion when we can properly identify the
`&` syntax to remove.
This commit is contained in:
Heath Dutton🕴️ 2026-01-12 18:04:32 -05:00
parent aefa10405d
commit afe76df79c
2 changed files with 3 additions and 11 deletions
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9
compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
View file

@ -5323,12 +5323,9 @@ fn hint_missing_borrow<'tcx>(
ty = mut_ty.ty;
left -= 1;
}
let sugg = if left == 0 {
(span, String::new())
} else {
(arg.span, expected_arg.to_string())
};
remove_borrow.push(sugg);
if left == 0 {
remove_borrow.push((span, String::new()));
}
}
}
}

5
tests/ui/closures/multiple-fn-bounds.stderr
View file

@ -19,11 +19,6 @@ note: required by a bound in `foo`
|
LL | fn foo<F: Fn(&char) -> bool + Fn(char) -> bool>(f: F) {
| ^^^^^^^^^^^^^^^^ required by this bound in `foo`
help: consider adjusting the signature so it does not borrow its argument
|
LL - foo(move |x| v);
LL + foo(move |char| v);
|
error: aborting due to 1 previous error