Rollup merge of rust-lang#110257 - lukas-code:why-would-anyone-write-…

…code-like-that-anyway, r=oli-obk fix false positives for `unused_parens` around unary and binary operations fix rust-lang#110251
matthiaskrgr · Apr 17, 2023 · 06d12f6 · 06d12f6
2 parents 91fe117 + 0d0949d
commit 06d12f6
Show file tree

Hide file tree

Showing 4 changed files with 109 additions and 41 deletions.
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
@@ -569,36 +569,50 @@ trait UnusedDelimLint {
             }
         }
 
-        // Prevent false-positives in cases like `fn x() -> u8 { ({ 0 } + 1) }`
-        let lhs_needs_parens = {
+        // Check if LHS needs parens to prevent false-positives in cases like `fn x() -> u8 { ({ 0 } + 1) }`.
+        {
             let mut innermost = inner;
             loop {
                 innermost = match &innermost.kind {
-                    ExprKind::Binary(_, lhs, _rhs) => lhs,
+                    ExprKind::Binary(_op, lhs, _rhs) => lhs,
                     ExprKind::Call(fn_, _params) => fn_,
                     ExprKind::Cast(expr, _ty) => expr,
                     ExprKind::Type(expr, _ty) => expr,
                     ExprKind::Index(base, _subscript) => base,
-                    _ => break false,
+                    _ => break,
                 };
                 if !classify::expr_requires_semi_to_be_stmt(innermost) {
-                    break true;
+                    return true;
                 }
             }
-        };
+        }
 
-        lhs_needs_parens
-            || (followed_by_block
-                && match &inner.kind {
-                    ExprKind::Ret(_)
-                    | ExprKind::Break(..)
-                    | ExprKind::Yield(..)
-                    | ExprKind::Yeet(..) => true,
-                    ExprKind::Range(_lhs, Some(rhs), _limits) => {
-                        matches!(rhs.kind, ExprKind::Block(..))
-                    }
-                    _ => parser::contains_exterior_struct_lit(&inner),
-                })
+        // Check if RHS needs parens to prevent false-positives in cases like `if (() == return) {}`.
+        if !followed_by_block {
+            return false;
+        }
+        let mut innermost = inner;
+        loop {
+            innermost = match &innermost.kind {
+                ExprKind::Unary(_op, expr) => expr,
+                ExprKind::Binary(_op, _lhs, rhs) => rhs,
+                ExprKind::AssignOp(_op, _lhs, rhs) => rhs,
+                ExprKind::Assign(_lhs, rhs, _span) => rhs,
+
+                ExprKind::Ret(_) | ExprKind::Yield(..) | ExprKind::Yeet(..) => return true,
+
+                ExprKind::Break(_label, None) => return false,
+                ExprKind::Break(_label, Some(break_expr)) => {
+                    return matches!(break_expr.kind, ExprKind::Block(..));
+                }
+
+                ExprKind::Range(_lhs, Some(rhs), _limits) => {
+                    return matches!(rhs.kind, ExprKind::Block(..));
+                }
+
+                _ => return parser::contains_exterior_struct_lit(&inner),
+            }
+        }
     }
 
     fn emit_unused_delims_expr(

diff --git a/tests/ui/lint/unused/issue-54538-unused-parens-lint.fixed b/tests/ui/lint/unused/issue-54538-unused-parens-lint.fixed
@@ -21,17 +21,32 @@ fn lint_on_top_level() {
     let _ = |a: u8| 0; //~ ERROR unnecessary parentheses around pattern
 }
 
-fn _no_lint_attr() {
+fn no_lint_attr() {
     let _x = #[allow(dead_code)] (1 + 2);
 }
 
-fn _no_lint_yeet() -> Result<(), ()> {
+fn no_lint_yeet() -> Result<(), ()> {
     #[allow(unreachable_code)]
     if (do yeet) {}
 
     Ok(())
 }
 
+fn no_lint_ops() {
+    #![allow(unreachable_code, irrefutable_let_patterns)]
+    if ((..{}) == ..{}) {}
+    if (!return) {}
+    loop { match (() = () = () = break {}) {} }
+    while let () = (*&mut false |= true && return) {}
+}
+
+fn lint_break_if_not_followed_by_block() {
+    #![allow(unreachable_code)]
+    loop { if break {} } //~ ERROR unnecessary parentheses
+    loop { if break ({ println!("hello") }) {} } //~ ERROR unnecessary parentheses
+    loop { if (break { println!("hello") }) {} }
+}
+
 // Don't lint in these cases (#64106).
 fn or_patterns_no_lint() {
     match Box::new(0) {

diff --git a/tests/ui/lint/unused/issue-54538-unused-parens-lint.rs b/tests/ui/lint/unused/issue-54538-unused-parens-lint.rs
@@ -21,17 +21,32 @@ fn lint_on_top_level() {
     let _ = |(a): u8| 0; //~ ERROR unnecessary parentheses around pattern
 }
 
-fn _no_lint_attr() {
+fn no_lint_attr() {
     let _x = #[allow(dead_code)] (1 + 2);
 }
 
-fn _no_lint_yeet() -> Result<(), ()> {
+fn no_lint_yeet() -> Result<(), ()> {
     #[allow(unreachable_code)]
     if (do yeet) {}
 
     Ok(())
 }
 
+fn no_lint_ops() {
+    #![allow(unreachable_code, irrefutable_let_patterns)]
+    if ((..{}) == ..{}) {}
+    if (!return) {}
+    loop { match (() = () = () = break {}) {} }
+    while let () = (*&mut false |= true && return) {}
+}
+
+fn lint_break_if_not_followed_by_block() {
+    #![allow(unreachable_code)]
+    loop { if (break) {} } //~ ERROR unnecessary parentheses
+    loop { if (break ({ println!("hello") })) {} } //~ ERROR unnecessary parentheses
+    loop { if (break { println!("hello") }) {} }
+}
+
 // Don't lint in these cases (#64106).
 fn or_patterns_no_lint() {
     match Box::new(0) {

diff --git a/tests/ui/lint/unused/issue-54538-unused-parens-lint.stderr b/tests/ui/lint/unused/issue-54538-unused-parens-lint.stderr
@@ -75,8 +75,32 @@ LL -     let _ = |(a): u8| 0;
 LL +     let _ = |a: u8| 0;
    |
 
+error: unnecessary parentheses around `if` condition
+  --> $DIR/issue-54538-unused-parens-lint.rs:45:15
+   |
+LL |     loop { if (break) {} }
+   |               ^     ^
+   |
+help: remove these parentheses
+   |
+LL -     loop { if (break) {} }
+LL +     loop { if break {} }
+   |
+
+error: unnecessary parentheses around `if` condition
+  --> $DIR/issue-54538-unused-parens-lint.rs:46:15
+   |
+LL |     loop { if (break ({ println!("hello") })) {} }
+   |               ^                             ^
+   |
+help: remove these parentheses
+   |
+LL -     loop { if (break ({ println!("hello") })) {} }
+LL +     loop { if break ({ println!("hello") }) {} }
+   |
+
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:56:12
+  --> $DIR/issue-54538-unused-parens-lint.rs:71:12
    |
 LL |     if let (0 | 1) = 0 {}
    |            ^     ^
@@ -88,7 +112,7 @@ LL +     if let 0 | 1 = 0 {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:57:13
+  --> $DIR/issue-54538-unused-parens-lint.rs:72:13
    |
 LL |     if let ((0 | 1),) = (0,) {}
    |             ^     ^
@@ -100,7 +124,7 @@ LL +     if let (0 | 1,) = (0,) {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:58:13
+  --> $DIR/issue-54538-unused-parens-lint.rs:73:13
    |
 LL |     if let [(0 | 1)] = [0] {}
    |             ^     ^
@@ -112,7 +136,7 @@ LL +     if let [0 | 1] = [0] {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:59:16
+  --> $DIR/issue-54538-unused-parens-lint.rs:74:16
    |
 LL |     if let 0 | (1 | 2) = 0 {}
    |                ^     ^
@@ -124,7 +148,7 @@ LL +     if let 0 | 1 | 2 = 0 {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:61:15
+  --> $DIR/issue-54538-unused-parens-lint.rs:76:15
    |
 LL |     if let TS((0 | 1)) = TS(0) {}
    |               ^     ^
@@ -136,7 +160,7 @@ LL +     if let TS(0 | 1) = TS(0) {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:63:20
+  --> $DIR/issue-54538-unused-parens-lint.rs:78:20
    |
 LL |     if let NS { f: (0 | 1) } = (NS { f: 0 }) {}
    |                    ^     ^
@@ -148,7 +172,7 @@ LL +     if let NS { f: 0 | 1 } = (NS { f: 0 }) {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:73:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:88:9
    |
 LL |         (_) => {}
    |         ^ ^
@@ -160,7 +184,7 @@ LL +         _ => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:74:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:89:9
    |
 LL |         (y) => {}
    |         ^ ^
@@ -172,7 +196,7 @@ LL +         y => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:75:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:90:9
    |
 LL |         (ref r) => {}
    |         ^     ^
@@ -184,7 +208,7 @@ LL +         ref r => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:76:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:91:9
    |
 LL |         (e @ 1...2) => {}
    |         ^         ^
@@ -196,7 +220,7 @@ LL +         e @ 1...2 => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:82:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:97:9
    |
 LL |         (e @ &(1...2)) => {}
    |         ^            ^
@@ -208,7 +232,7 @@ LL +         e @ &(1...2) => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:83:10
+  --> $DIR/issue-54538-unused-parens-lint.rs:98:10
    |
 LL |         &(_) => {}
    |          ^ ^
@@ -220,7 +244,7 @@ LL +         &_ => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:94:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:109:9
    |
 LL |         (_) => {}
    |         ^ ^
@@ -232,7 +256,7 @@ LL +         _ => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:95:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:110:9
    |
 LL |         (y) => {}
    |         ^ ^
@@ -244,7 +268,7 @@ LL +         y => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:96:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:111:9
    |
 LL |         (ref r) => {}
    |         ^     ^
@@ -256,7 +280,7 @@ LL +         ref r => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:97:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:112:9
    |
 LL |         (e @ 1..=2) => {}
    |         ^         ^
@@ -268,7 +292,7 @@ LL +         e @ 1..=2 => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:103:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:118:9
    |
 LL |         (e @ &(1..=2)) => {}
    |         ^            ^
@@ -280,7 +304,7 @@ LL +         e @ &(1..=2) => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:104:10
+  --> $DIR/issue-54538-unused-parens-lint.rs:119:10
    |
 LL |         &(_) => {}
    |          ^ ^
@@ -291,5 +315,5 @@ LL -         &(_) => {}
 LL +         &_ => {}
    |
 
-error: aborting due to 24 previous errors
+error: aborting due to 26 previous errors