fix false positives for unused_parens around unary and binary operations

Lukas Markeffsky · Lukas Markeffsky · commit 8df1f41b9c11 · 2023-04-13T18:08:52.000+02:00
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
@@ -569,36 +569,48 @@ 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::Break(..)
+                | ExprKind::Yield(..)
+                | ExprKind::Yeet(..) => return true,
+
+                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
@@ -32,6 +32,14 @@ fn _no_lint_yeet() -> Result<(), ()> {
     Ok(())
 }
 
+fn _no_lint_ops() {
+    #![allow(unreachable_code, irrefutable_let_patterns)]
+    if ((..{}) == ..{}) {}
+    if (!return) {}
+    loop { match (() = () = () = break {}) {} }
+    while let () = (*&mut false |= true && return) {}
+}
+
 // 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
@@ -32,6 +32,14 @@ fn _no_lint_yeet() -> Result<(), ()> {
     Ok(())
 }
 
+fn _no_lint_ops() {
+    #![allow(unreachable_code, irrefutable_let_patterns)]
+    if ((..{}) == ..{}) {}
+    if (!return) {}
+    loop { match (() = () = () = break {}) {} }
+    while let () = (*&mut false |= true && return) {}
+}
+
 // 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
@@ -76,7 +76,7 @@ LL +     let _ = |a: u8| 0;
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:56:12
+  --> $DIR/issue-54538-unused-parens-lint.rs:64:12
    |
 LL |     if let (0 | 1) = 0 {}
    |            ^     ^
@@ -88,7 +88,7 @@ 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:65:13
    |
 LL |     if let ((0 | 1),) = (0,) {}
    |             ^     ^
@@ -100,7 +100,7 @@ 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:66:13
    |
 LL |     if let [(0 | 1)] = [0] {}
    |             ^     ^
@@ -112,7 +112,7 @@ 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:67:16
    |
 LL |     if let 0 | (1 | 2) = 0 {}
    |                ^     ^
@@ -124,7 +124,7 @@ 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:69:15
    |
 LL |     if let TS((0 | 1)) = TS(0) {}
    |               ^     ^
@@ -136,7 +136,7 @@ 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:71:20
    |
 LL |     if let NS { f: (0 | 1) } = (NS { f: 0 }) {}
    |                    ^     ^
@@ -148,7 +148,7 @@ 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:81:9
    |
 LL |         (_) => {}
    |         ^ ^
@@ -160,7 +160,7 @@ LL +         _ => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:74:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:82:9
    |
 LL |         (y) => {}
    |         ^ ^
@@ -172,7 +172,7 @@ LL +         y => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:75:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:83:9
    |
 LL |         (ref r) => {}
    |         ^     ^
@@ -184,7 +184,7 @@ LL +         ref r => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:76:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:84:9
    |
 LL |         (e @ 1...2) => {}
    |         ^         ^
@@ -196,7 +196,7 @@ 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:90:9
    |
 LL |         (e @ &(1...2)) => {}
    |         ^            ^
@@ -208,7 +208,7 @@ 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:91:10
    |
 LL |         &(_) => {}
    |          ^ ^
@@ -220,7 +220,7 @@ LL +         &_ => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:94:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:102:9
    |
 LL |         (_) => {}
    |         ^ ^
@@ -232,7 +232,7 @@ LL +         _ => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:95:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:103:9
    |
 LL |         (y) => {}
    |         ^ ^
@@ -244,7 +244,7 @@ LL +         y => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:96:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:104:9
    |
 LL |         (ref r) => {}
    |         ^     ^
@@ -256,7 +256,7 @@ LL +         ref r => {}
    |
 
 error: unnecessary parentheses around pattern
-  --> $DIR/issue-54538-unused-parens-lint.rs:97:9
+  --> $DIR/issue-54538-unused-parens-lint.rs:105:9
    |
 LL |         (e @ 1..=2) => {}
    |         ^         ^
@@ -268,7 +268,7 @@ 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:111:9
    |
 LL |         (e @ &(1..=2)) => {}
    |         ^            ^
@@ -280,7 +280,7 @@ 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:112:10
    |
 LL |         &(_) => {}
    |          ^ ^

Original file line number	Diff line number	Diff line change
`@@ -76,7 +76,7 @@ LL + let _ = \|a: u8\| 0;`
`76`	`76`	`\|`
`77`	`77`
`78`	`78`	`error: unnecessary parentheses around pattern`
`79`		`- --> $DIR/issue-54538-unused-parens-lint.rs:56:12`
	`79`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:64:12`
`80`	`80`	`\|`
`81`	`81`	`LL \| if let (0 \| 1) = 0 {}`
`82`	`82`	`\| ^ ^`
`@@ -88,7 +88,7 @@ LL + if let 0 \| 1 = 0 {}`
`88`	`88`	`\|`
`89`	`89`
`90`	`90`	`error: unnecessary parentheses around pattern`
`91`		`- --> $DIR/issue-54538-unused-parens-lint.rs:57:13`
	`91`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:65:13`
`92`	`92`	`\|`
`93`	`93`	`LL \| if let ((0 \| 1),) = (0,) {}`
`94`	`94`	`\| ^ ^`
`@@ -100,7 +100,7 @@ LL + if let (0 \| 1,) = (0,) {}`
`100`	`100`	`\|`
`101`	`101`
`102`	`102`	`error: unnecessary parentheses around pattern`
`103`		`- --> $DIR/issue-54538-unused-parens-lint.rs:58:13`
	`103`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:66:13`
`104`	`104`	`\|`
`105`	`105`	`LL \| if let [(0 \| 1)] = [0] {}`
`106`	`106`	`\| ^ ^`
`@@ -112,7 +112,7 @@ LL + if let [0 \| 1] = [0] {}`
`112`	`112`	`\|`
`113`	`113`
`114`	`114`	`error: unnecessary parentheses around pattern`
`115`		`- --> $DIR/issue-54538-unused-parens-lint.rs:59:16`
	`115`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:67:16`
`116`	`116`	`\|`
`117`	`117`	`LL \| if let 0 \| (1 \| 2) = 0 {}`
`118`	`118`	`\| ^ ^`
`@@ -124,7 +124,7 @@ LL + if let 0 \| 1 \| 2 = 0 {}`
`124`	`124`	`\|`
`125`	`125`
`126`	`126`	`error: unnecessary parentheses around pattern`
`127`		`- --> $DIR/issue-54538-unused-parens-lint.rs:61:15`
	`127`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:69:15`
`128`	`128`	`\|`
`129`	`129`	`LL \| if let TS((0 \| 1)) = TS(0) {}`
`130`	`130`	`\| ^ ^`
`@@ -136,7 +136,7 @@ LL + if let TS(0 \| 1) = TS(0) {}`
`136`	`136`	`\|`
`137`	`137`
`138`	`138`	`error: unnecessary parentheses around pattern`
`139`		`- --> $DIR/issue-54538-unused-parens-lint.rs:63:20`
	`139`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:71:20`
`140`	`140`	`\|`
`141`	`141`	`LL \| if let NS { f: (0 \| 1) } = (NS { f: 0 }) {}`
`142`	`142`	`\| ^ ^`
`@@ -148,7 +148,7 @@ LL + if let NS { f: 0 \| 1 } = (NS { f: 0 }) {}`
`148`	`148`	`\|`
`149`	`149`
`150`	`150`	`error: unnecessary parentheses around pattern`
`151`		`- --> $DIR/issue-54538-unused-parens-lint.rs:73:9`
	`151`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:81:9`
`152`	`152`	`\|`
`153`	`153`	`LL \| (_) => {}`
`154`	`154`	`\| ^ ^`
`@@ -160,7 +160,7 @@ LL + _ => {}`
`160`	`160`	`\|`
`161`	`161`
`162`	`162`	`error: unnecessary parentheses around pattern`
`163`		`- --> $DIR/issue-54538-unused-parens-lint.rs:74:9`
	`163`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:82:9`
`164`	`164`	`\|`
`165`	`165`	`LL \| (y) => {}`
`166`	`166`	`\| ^ ^`
`@@ -172,7 +172,7 @@ LL + y => {}`
`172`	`172`	`\|`
`173`	`173`
`174`	`174`	`error: unnecessary parentheses around pattern`
`175`		`- --> $DIR/issue-54538-unused-parens-lint.rs:75:9`
	`175`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:83:9`
`176`	`176`	`\|`
`177`	`177`	`LL \| (ref r) => {}`
`178`	`178`	`\| ^ ^`
`@@ -184,7 +184,7 @@ LL + ref r => {}`
`184`	`184`	`\|`
`185`	`185`
`186`	`186`	`error: unnecessary parentheses around pattern`
`187`		`- --> $DIR/issue-54538-unused-parens-lint.rs:76:9`
	`187`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:84:9`
`188`	`188`	`\|`
`189`	`189`	`LL \| (e @ 1...2) => {}`
`190`	`190`	`\| ^ ^`
`@@ -196,7 +196,7 @@ LL + e @ 1...2 => {}`
`196`	`196`	`\|`
`197`	`197`
`198`	`198`	`error: unnecessary parentheses around pattern`
`199`		`- --> $DIR/issue-54538-unused-parens-lint.rs:82:9`
	`199`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:90:9`
`200`	`200`	`\|`
`201`	`201`	`LL \| (e @ &(1...2)) => {}`
`202`	`202`	`\| ^ ^`
`@@ -208,7 +208,7 @@ LL + e @ &(1...2) => {}`
`208`	`208`	`\|`
`209`	`209`
`210`	`210`	`error: unnecessary parentheses around pattern`
`211`		`- --> $DIR/issue-54538-unused-parens-lint.rs:83:10`
	`211`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:91:10`
`212`	`212`	`\|`
`213`	`213`	`LL \| &(_) => {}`
`214`	`214`	`\| ^ ^`
`@@ -220,7 +220,7 @@ LL + &_ => {}`
`220`	`220`	`\|`
`221`	`221`
`222`	`222`	`error: unnecessary parentheses around pattern`
`223`		`- --> $DIR/issue-54538-unused-parens-lint.rs:94:9`
	`223`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:102:9`
`224`	`224`	`\|`
`225`	`225`	`LL \| (_) => {}`
`226`	`226`	`\| ^ ^`
`@@ -232,7 +232,7 @@ LL + _ => {}`
`232`	`232`	`\|`
`233`	`233`
`234`	`234`	`error: unnecessary parentheses around pattern`
`235`		`- --> $DIR/issue-54538-unused-parens-lint.rs:95:9`
	`235`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:103:9`
`236`	`236`	`\|`
`237`	`237`	`LL \| (y) => {}`
`238`	`238`	`\| ^ ^`
`@@ -244,7 +244,7 @@ LL + y => {}`
`244`	`244`	`\|`
`245`	`245`
`246`	`246`	`error: unnecessary parentheses around pattern`
`247`		`- --> $DIR/issue-54538-unused-parens-lint.rs:96:9`
	`247`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:104:9`
`248`	`248`	`\|`
`249`	`249`	`LL \| (ref r) => {}`
`250`	`250`	`\| ^ ^`
`@@ -256,7 +256,7 @@ LL + ref r => {}`
`256`	`256`	`\|`
`257`	`257`
`258`	`258`	`error: unnecessary parentheses around pattern`
`259`		`- --> $DIR/issue-54538-unused-parens-lint.rs:97:9`
	`259`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:105:9`
`260`	`260`	`\|`
`261`	`261`	`LL \| (e @ 1..=2) => {}`
`262`	`262`	`\| ^ ^`
`@@ -268,7 +268,7 @@ LL + e @ 1..=2 => {}`
`268`	`268`	`\|`
`269`	`269`
`270`	`270`	`error: unnecessary parentheses around pattern`
`271`		`- --> $DIR/issue-54538-unused-parens-lint.rs:103:9`
	`271`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:111:9`
`272`	`272`	`\|`
`273`	`273`	`LL \| (e @ &(1..=2)) => {}`
`274`	`274`	`\| ^ ^`
`@@ -280,7 +280,7 @@ LL + e @ &(1..=2) => {}`
`280`	`280`	`\|`
`281`	`281`
`282`	`282`	`error: unnecessary parentheses around pattern`
`283`		`- --> $DIR/issue-54538-unused-parens-lint.rs:104:10`
	`283`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:112:10`
`284`	`284`	`\|`
`285`	`285`	`LL \| &(_) => {}`
`286`	`286`	`\| ^ ^`