Rollup merge of #64472 - Mark-Simulacrum:unused-parens-attr, r=varkor

Don't mark expression with attributes as not needing parentheses

This is not perfectly correct as `#[attr] (5)` will still not lint, but it does seem good enough, in particular as the parentheses in that case are not unambiguously incorrect; I might personally prefer to see them for clarity.

Fixes #43279.

Author: Centril

src/librustc_lint/unused.rs

@@ -370,7 +370,8 @@ impl UnusedParens {
                                      right_pos: Option<BytePos>) {
         match value.node {
             ast::ExprKind::Paren(ref inner) => {
-                if !Self::is_expr_parens_necessary(inner, followed_by_block) {
+                if !Self::is_expr_parens_necessary(inner, followed_by_block) &&
+                    value.attrs.is_empty() {
                     let expr_text = if let Ok(snippet) = cx.sess().source_map()
                         .span_to_snippet(value.span) {
                             snippet

src/test/ui/lint/issue-54538-unused-parens-lint.rs

@@ -1,4 +1,4 @@
-#![feature(box_patterns)]
+#![feature(box_patterns, stmt_expr_attributes)]
 
 #![feature(or_patterns)]
 //~^ WARN the feature `or_patterns` is incomplete
@@ -17,6 +17,10 @@ fn lint_on_top_level() {
     let _ = |(a): u8| 0; //~ ERROR unnecessary parentheses around pattern
 }
 
+fn _no_lint_attr() {
+    let _x = #[allow(dead_code)] (1 + 2);
+}
+
 // Don't lint in these cases (#64106).
 fn or_patterns_no_lint() {
     match Box::new(0) {

src/test/ui/lint/issue-54538-unused-parens-lint.stderr

@@ -49,109 +49,109 @@ LL |     let _ = |(a): u8| 0;
    |              ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:41:12
+  --> $DIR/issue-54538-unused-parens-lint.rs:45:12
    |
 LL |     if let (0 | 1) = 0 {}
    |            ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:42:13
+  --> $DIR/issue-54538-unused-parens-lint.rs:46:13
    |
 LL |     if let ((0 | 1),) = (0,) {}
    |             ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:43:13
+  --> $DIR/issue-54538-unused-parens-lint.rs:47:13
    |
 LL |     if let [(0 | 1)] = [0] {}
    |             ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:44:16
+  --> $DIR/issue-54538-unused-parens-lint.rs:48:16
    |
 LL |     if let 0 | (1 | 2) = 0 {}
    |                ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:46:15
+  --> $DIR/issue-54538-unused-parens-lint.rs:50:15
    |
 LL |     if let TS((0 | 1)) = TS(0) {}
    |               ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:48:20
+  --> $DIR/issue-54538-unused-parens-lint.rs:52:20
    |
 LL |     if let NS { f: (0 | 1) } = (NS { f: 0 }) {}
    |                    ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:58:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:62:9
    |
 LL |         (_) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:59:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:63:9
    |
 LL |         (y) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:60:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:64:9
    |
 LL |         (ref r) => {}
    |         ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:61:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:65:9
    |
 LL |         (e @ 1...2) => {}
    |         ^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:67:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:71:9
    |
 LL |         (e @ &(1...2)) => {}
    |         ^^^^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:68:10
+  --> $DIR/issue-54538-unused-parens-lint.rs:72:10
    |
 LL |         &(_) => {}
    |          ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:79:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:83:9
    |
 LL |         (_) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:80:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:84:9
    |
 LL |         (y) => {}
    |         ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:81:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:85:9
    |
 LL |         (ref r) => {}
    |         ^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:82:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:86:9
    |
 LL |         (e @ 1..=2) => {}
    |         ^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:88:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:92:9
    |
 LL |         (e @ &(1..=2)) => {}
    |         ^^^^^^^^^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:89:10
+  --> $DIR/issue-54538-unused-parens-lint.rs:93:10
    |
 LL |         &(_) => {}
    |          ^^^ help: remove these parentheses