diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs index ddd252cb290e4..c24079a6e4be2 100644 --- a/src/librustc_lint/unused.rs +++ b/src/librustc_lint/unused.rs @@ -380,11 +380,27 @@ trait UnusedDelimLint { ); fn is_expr_delims_necessary(inner: &ast::Expr, followed_by_block: bool) -> bool { - followed_by_block - && match inner.kind { - ExprKind::Ret(_) | ExprKind::Break(..) => true, - _ => parser::contains_exterior_struct_lit(&inner), + // Prevent false-positives in cases like `fn x() -> u8 { ({ 0 } + 1) }` + let lhs_needs_parens = { + let mut innermost = inner; + loop { + if let ExprKind::Binary(_, lhs, _rhs) = &innermost.kind { + innermost = lhs; + if !rustc_ast::util::classify::expr_requires_semi_to_be_stmt(innermost) { + break true; + } + } else { + break false; + } } + }; + + lhs_needs_parens + || (followed_by_block + && match inner.kind { + ExprKind::Ret(_) | ExprKind::Break(..) => true, + _ => parser::contains_exterior_struct_lit(&inner), + }) } fn emit_unused_delims_expr( diff --git a/src/test/ui/lint/issue-71290-unused-paren-binop.rs b/src/test/ui/lint/issue-71290-unused-paren-binop.rs new file mode 100644 index 0000000000000..24d77e36d94f5 --- /dev/null +++ b/src/test/ui/lint/issue-71290-unused-paren-binop.rs @@ -0,0 +1,23 @@ +// check-pass +// Make sure unused parens lint doesn't emit a false positive. +// See https://github.com/rust-lang/rust/issues/71290 for details. +#![deny(unused_parens)] + +fn x() -> u8 { + ({ 0 }) + 1 +} + +fn y() -> u8 { + ({ 0 } + 1) +} + +pub fn foo(a: bool, b: bool) -> u8 { + (if a { 1 } else { 0 } + if b { 1 } else { 0 }) +} + +pub fn bar() -> u8 { + // Make sure nested expressions are handled correctly as well + ({ 0 } + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9) +} + +fn main() {}