Fix unused_braces lint suggestion when encountering attributes

Author: Urgau

compiler/rustc_lint/src/unused.rs

@@ -1,8 +1,7 @@
 use std::iter;
 
-use rustc_ast as ast;
 use rustc_ast::util::{classify, parser};
-use rustc_ast::{ExprKind,StmtKind};
+use rustc_ast::{selfas ast,ExprKind,HasAttrsas _,StmtKind};
 use rustc_errors::{MultiSpan, pluralize};
 use rustc_hir::def::{DefKind,Res};
 use rustc_hir::def_id::DefId;
@@ -780,26 +779,30 @@ trait UnusedDelimLint {
 right_pos:Option<BytePos>,
 is_kw:bool,
 ){
-let spans = match value.kind{
- ast::ExprKind::Block(ref block,None)iflet[stmt] = block.stmts.as_slice() => stmt
-.span
-.find_ancestor_inside(value.span)
-.map(|span| (value.span.with_hi(span.lo()), value.span.with_lo(span.hi()))),
+let span_with_attrs = match value.kind{
+ ast::ExprKind::Block(ref block,None)iflet[stmt] = block.stmts.as_slice() => {
+// For the statements with attributes, like `{ #[allow()] println!("Hello!") }`,
+// the span should contains the attributes, or the suggestion will remove them.
+ifletSome(attr_lo) = stmt.attrs().iter().map(|attr| attr.span.lo()).min(){
+ stmt.span.with_lo(attr_lo)
+}else{
+ stmt.span
+}
+}
  ast::ExprKind::Paren(ref expr) => {
 // For the expr with attributes, like `let _ = (#[inline] || println!("Hello!"));`,
 // the span should contains the attributes, or the suggestion will remove them.
-let expr_span_with_attrs =
-ifletSome(attr_lo) = expr.attrs.iter().map(|attr| attr.span.lo()).min(){
- expr.span.with_lo(attr_lo)
-}else{
- expr.span
-};
- expr_span_with_attrs.find_ancestor_inside(value.span).map(|expr_span| {
-(value.span.with_hi(expr_span.lo()), value.span.with_lo(expr_span.hi()))
-})
+ifletSome(attr_lo) = expr.attrs.iter().map(|attr| attr.span.lo()).min(){
+ expr.span.with_lo(attr_lo)
+}else{
+ expr.span
+}
 }
  _ => return,
 };
+let spans = span_with_attrs
+.find_ancestor_inside(value.span)
+.map(|span| (value.span.with_hi(span.lo()), value.span.with_lo(span.hi())));
 let keep_space = (
  left_pos.is_some_and(|s| s >= value.span.lo()),
  right_pos.is_some_and(|s| s <= value.span.hi()),

tests/ui/lint/unused/unused-braces-attrs-issue-141549.fixed

@@ -0,0 +1,15 @@
+//@ check-pass
+//@ run-rustfix
+
+#![allow(dead_code)]
+#![warn(unused_braces)]
+
+use std::cmp::Ordering;
+
+#[rustfmt::skip]
+fn ptr_cmp<T: ?Sized>(p1: *const T, p2: *const T) -> Ordering {
+ #[expect(ambiguous_wide_pointer_comparisons)] p1.cmp(&p2)
+ //~^ WARN unnecessary braces around block return value
+}
+
+fn main() {}

tests/ui/lint/unused/unused-braces-attrs-issue-141549.rs

@@ -0,0 +1,15 @@
+//@ check-pass
+//@ run-rustfix
+
+#![allow(dead_code)]
+#![warn(unused_braces)]
+
+use std::cmp::Ordering;
+
+#[rustfmt::skip]
+fnptr_cmp<T: ?Sized>(p1:*constT,p2:*constT) -> Ordering{
+{#[expect(ambiguous_wide_pointer_comparisons)] p1.cmp(&p2)}
+//~^ WARN unnecessary braces around block return value
+}
+
+fnmain(){}

tests/ui/lint/unused/unused-braces-attrs-issue-141549.stderr

@@ -0,0 +1,19 @@
+warning: unnecessary braces around block return value
+ --> $DIR/unused-braces-attrs-issue-141549.rs:11:5
+ |
+LL | { #[expect(ambiguous_wide_pointer_comparisons)] p1.cmp(&p2) }
+ | ^^ ^^
+ |
+note: the lint level is defined here
+ --> $DIR/unused-braces-attrs-issue-141549.rs:5:9
+ |
+LL | #![warn(unused_braces)]
+ | ^^^^^^^^^^^^^
+help: remove these braces
+ |
+LL - { #[expect(ambiguous_wide_pointer_comparisons)] p1.cmp(&p2) }
+LL + #[expect(ambiguous_wide_pointer_comparisons)] p1.cmp(&p2)
+ |
+
+warning: 1 warning emitted
+