Rollup merge of #77931 - aticu:fix_60336, r=petrochenkov

Fix false positive for `unused_parens` lint Fixes #60336
rust-lang · Oct 20, 2020 · 378ca5e · 378ca5e
2 parents 6df79bf + 39867f3
commit 378ca5e
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Showing 4 changed files with 17 additions and 6 deletions.
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
@@ -751,13 +751,20 @@ impl UnusedDelimLint for UnusedParens {
                 if !Self::is_expr_delims_necessary(inner, followed_by_block)
                     && value.attrs.is_empty()
                     && !value.span.from_expansion()
+                    && (ctx != UnusedDelimsCtx::LetScrutineeExpr
+                        || match inner.kind {
+                            ast::ExprKind::Binary(
+                                rustc_span::source_map::Spanned { node, .. },
+                                _,
+                                _,
+                            ) if node.lazy() => false,
+                            _ => true,
+                        })
                 {
                     self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos)
                 }
             }
             ast::ExprKind::Let(_, ref expr) => {
-                // FIXME(#60336): Properly handle `let true = (false && true)`
-                // actually needing the parenthesis.
                 self.check_unused_delims_expr(
                     cx,
                     expr,

diff --git a/src/test/ui/lint/lint-unnecessary-parens.fixed b/src/test/ui/lint/lint-unnecessary-parens.fixed
@@ -60,6 +60,8 @@ fn main() {
     if (v == X { y: true }) {}
     if (X { y: true } == v) {}
     if (X { y: false }.y) {}
+    // this shouldn't warn, because the parens are necessary to disambiguate let chains
+    if let true = (true && false) {}
 
     while (X { y: false }.foo(true)) {}
     while (true | X { y: false }.y) {}

diff --git a/src/test/ui/lint/lint-unnecessary-parens.rs b/src/test/ui/lint/lint-unnecessary-parens.rs
@@ -60,6 +60,8 @@ fn main() {
     if (v == X { y: true }) {}
     if (X { y: true } == v) {}
     if (X { y: false }.y) {}
+    // this shouldn't warn, because the parens are necessary to disambiguate let chains
+    if let true = (true && false) {}
 
     while (X { y: false }.foo(true)) {}
     while (true | X { y: false }.y) {}

diff --git a/src/test/ui/lint/lint-unnecessary-parens.stderr b/src/test/ui/lint/lint-unnecessary-parens.stderr
@@ -83,25 +83,25 @@ LL |     while let 1 = (2) {}
    |                   ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around method argument
-  --> $DIR/lint-unnecessary-parens.rs:71:24
+  --> $DIR/lint-unnecessary-parens.rs:73:24
    |
 LL |     X { y: false }.foo((true));
    |                        ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:73:18
+  --> $DIR/lint-unnecessary-parens.rs:75:18
    |
 LL |     let mut _a = (0);
    |                  ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:74:10
+  --> $DIR/lint-unnecessary-parens.rs:76:10
    |
 LL |     _a = (0);
    |          ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:75:11
+  --> $DIR/lint-unnecessary-parens.rs:77:11
    |
 LL |     _a += (1);
    |           ^^^ help: remove these parentheses