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Document the situation with unused_parens lint and braced macro calls

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David Tolnay 2023-12-27 20:11:00 -08:00
parent 0ca322c774
commit c6c18a0151
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1 changed files with 28 additions and 4 deletions
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32
compiler/rustc_lint/src/unused.rs
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@ -677,6 +677,33 @@ trait UnusedDelimLint {
}
// Check if LHS needs parens to prevent false-positives in cases like `fn x() -> u8 { ({ 0 } + 1) }`.
//
// FIXME: https://github.com/rust-lang/rust/issues/119426
// The syntax tree in this code is from after macro expansion, so the
// current implementation has both false negatives and false positives
// related to expressions containing macros.
//
// macro_rules! m1 {
// () => {
// 1
// };
// }
//
// fn f1() -> u8 {
// // Lint says parens are not needed, but they are.
// (m1! {} + 1)
// }
//
// macro_rules! m2 {
// () => {
// loop { break 1; }
// };
// }
//
// fn f2() -> u8 {
// // Lint says parens are needed, but they are not.
// (m2!() + 1)
// }
{
let mut innermost = inner;
loop {
@ -688,10 +715,7 @@ trait UnusedDelimLint {
ExprKind::Index(base, _subscript, _) => base,
_ => break,
};
if match innermost.kind {
ExprKind::MacCall(_) => false,
_ => !classify::expr_requires_semi_to_be_stmt(innermost),
} {
if !classify::expr_requires_semi_to_be_stmt(innermost) {
return true;
}
}