Rollup merge of #110257 - lukas-code:why-would-anyone-write-code-like-that-anyway, r=oli-obk

matthiaskrgr · web-flow · commit 06d12f668ebb · 2023-04-17T18:13:33.000+02:00
fix false positives for `unused_parens` around unary and binary operations fix #110251
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
 

Original file line number	Diff line number	Diff line change
`@@ -75,8 +75,32 @@ LL - let _ = \|(a): u8\| 0;`
`75`	`75`	`LL + let _ = \|a: u8\| 0;`
`76`	`76`	`\|`
`77`	`77`
	`78`	+error: unnecessary parentheses around `if` condition
	`79`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:45:15`
	`80`	`+ \|`
	`81`	`+LL \| loop { if (break) {} }`
	`82`	`+ \| ^ ^`
	`83`	`+ \|`
	`84`	`+help: remove these parentheses`
	`85`	`+ \|`
	`86`	`+LL - loop { if (break) {} }`
	`87`	`+LL + loop { if break {} }`
	`88`	`+ \|`
	`89`	`+`
	`90`	+error: unnecessary parentheses around `if` condition
	`91`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:46:15`
	`92`	`+ \|`
	`93`	`+LL \| loop { if (break ({ println!("hello") })) {} }`
	`94`	`+ \| ^ ^`
	`95`	`+ \|`
	`96`	`+help: remove these parentheses`
	`97`	`+ \|`
	`98`	`+LL - loop { if (break ({ println!("hello") })) {} }`
	`99`	`+LL + loop { if break ({ println!("hello") }) {} }`
	`100`	`+ \|`
	`101`	`+`
`78`	`102`	`error: unnecessary parentheses around pattern`
`79`		`- --> $DIR/issue-54538-unused-parens-lint.rs:56:12`
	`103`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:71:12`
`80`	`104`	`\|`
`81`	`105`	`LL \| if let (0 \| 1) = 0 {}`
`82`	`106`	`\| ^ ^`
`@@ -88,7 +112,7 @@ LL + if let 0 \| 1 = 0 {}`
`88`	`112`	`\|`
`89`	`113`
`90`	`114`	`error: unnecessary parentheses around pattern`
`91`		`- --> $DIR/issue-54538-unused-parens-lint.rs:57:13`
	`115`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:72:13`
`92`	`116`	`\|`
`93`	`117`	`LL \| if let ((0 \| 1),) = (0,) {}`
`94`	`118`	`\| ^ ^`
`@@ -100,7 +124,7 @@ LL + if let (0 \| 1,) = (0,) {}`
`100`	`124`	`\|`
`101`	`125`
`102`	`126`	`error: unnecessary parentheses around pattern`
`103`		`- --> $DIR/issue-54538-unused-parens-lint.rs:58:13`
	`127`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:73:13`
`104`	`128`	`\|`
`105`	`129`	`LL \| if let [(0 \| 1)] = [0] {}`
`106`	`130`	`\| ^ ^`
`@@ -112,7 +136,7 @@ LL + if let [0 \| 1] = [0] {}`
`112`	`136`	`\|`
`113`	`137`
`114`	`138`	`error: unnecessary parentheses around pattern`
`115`		`- --> $DIR/issue-54538-unused-parens-lint.rs:59:16`
	`139`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:74:16`
`116`	`140`	`\|`
`117`	`141`	`LL \| if let 0 \| (1 \| 2) = 0 {}`
`118`	`142`	`\| ^ ^`
`@@ -124,7 +148,7 @@ LL + if let 0 \| 1 \| 2 = 0 {}`
`124`	`148`	`\|`
`125`	`149`
`126`	`150`	`error: unnecessary parentheses around pattern`
`127`		`- --> $DIR/issue-54538-unused-parens-lint.rs:61:15`
	`151`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:76:15`
`128`	`152`	`\|`
`129`	`153`	`LL \| if let TS((0 \| 1)) = TS(0) {}`
`130`	`154`	`\| ^ ^`
`@@ -136,7 +160,7 @@ LL + if let TS(0 \| 1) = TS(0) {}`
`136`	`160`	`\|`
`137`	`161`
`138`	`162`	`error: unnecessary parentheses around pattern`
`139`		`- --> $DIR/issue-54538-unused-parens-lint.rs:63:20`
	`163`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:78:20`
`140`	`164`	`\|`
`141`	`165`	`LL \| if let NS { f: (0 \| 1) } = (NS { f: 0 }) {}`
`142`	`166`	`\| ^ ^`
`@@ -148,7 +172,7 @@ LL + if let NS { f: 0 \| 1 } = (NS { f: 0 }) {}`
`148`	`172`	`\|`
`149`	`173`
`150`	`174`	`error: unnecessary parentheses around pattern`
`151`		`- --> $DIR/issue-54538-unused-parens-lint.rs:73:9`
	`175`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:88:9`
`152`	`176`	`\|`
`153`	`177`	`LL \| (_) => {}`
`154`	`178`	`\| ^ ^`
`@@ -160,7 +184,7 @@ LL + _ => {}`
`160`	`184`	`\|`
`161`	`185`
`162`	`186`	`error: unnecessary parentheses around pattern`
`163`		`- --> $DIR/issue-54538-unused-parens-lint.rs:74:9`
	`187`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:89:9`
`164`	`188`	`\|`
`165`	`189`	`LL \| (y) => {}`
`166`	`190`	`\| ^ ^`
`@@ -172,7 +196,7 @@ LL + y => {}`
`172`	`196`	`\|`
`173`	`197`
`174`	`198`	`error: unnecessary parentheses around pattern`
`175`		`- --> $DIR/issue-54538-unused-parens-lint.rs:75:9`
	`199`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:90:9`
`176`	`200`	`\|`
`177`	`201`	`LL \| (ref r) => {}`
`178`	`202`	`\| ^ ^`
`@@ -184,7 +208,7 @@ LL + ref r => {}`
`184`	`208`	`\|`
`185`	`209`
`186`	`210`	`error: unnecessary parentheses around pattern`
`187`		`- --> $DIR/issue-54538-unused-parens-lint.rs:76:9`
	`211`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:91:9`
`188`	`212`	`\|`
`189`	`213`	`LL \| (e @ 1...2) => {}`
`190`	`214`	`\| ^ ^`
`@@ -196,7 +220,7 @@ LL + e @ 1...2 => {}`
`196`	`220`	`\|`
`197`	`221`
`198`	`222`	`error: unnecessary parentheses around pattern`
`199`		`- --> $DIR/issue-54538-unused-parens-lint.rs:82:9`
	`223`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:97:9`
`200`	`224`	`\|`
`201`	`225`	`LL \| (e @ &(1...2)) => {}`
`202`	`226`	`\| ^ ^`
`@@ -208,7 +232,7 @@ LL + e @ &(1...2) => {}`
`208`	`232`	`\|`
`209`	`233`
`210`	`234`	`error: unnecessary parentheses around pattern`
`211`		`- --> $DIR/issue-54538-unused-parens-lint.rs:83:10`
	`235`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:98:10`
`212`	`236`	`\|`
`213`	`237`	`LL \| &(_) => {}`
`214`	`238`	`\| ^ ^`
`@@ -220,7 +244,7 @@ LL + &_ => {}`
`220`	`244`	`\|`
`221`	`245`
`222`	`246`	`error: unnecessary parentheses around pattern`
`223`		`- --> $DIR/issue-54538-unused-parens-lint.rs:94:9`
	`247`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:109:9`
`224`	`248`	`\|`
`225`	`249`	`LL \| (_) => {}`
`226`	`250`	`\| ^ ^`
`@@ -232,7 +256,7 @@ LL + _ => {}`
`232`	`256`	`\|`
`233`	`257`
`234`	`258`	`error: unnecessary parentheses around pattern`
`235`		`- --> $DIR/issue-54538-unused-parens-lint.rs:95:9`
	`259`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:110:9`
`236`	`260`	`\|`
`237`	`261`	`LL \| (y) => {}`
`238`	`262`	`\| ^ ^`
`@@ -244,7 +268,7 @@ LL + y => {}`
`244`	`268`	`\|`
`245`	`269`
`246`	`270`	`error: unnecessary parentheses around pattern`
`247`		`- --> $DIR/issue-54538-unused-parens-lint.rs:96:9`
	`271`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:111:9`
`248`	`272`	`\|`
`249`	`273`	`LL \| (ref r) => {}`
`250`	`274`	`\| ^ ^`
`@@ -256,7 +280,7 @@ LL + ref r => {}`
`256`	`280`	`\|`
`257`	`281`
`258`	`282`	`error: unnecessary parentheses around pattern`
`259`		`- --> $DIR/issue-54538-unused-parens-lint.rs:97:9`
	`283`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:112:9`
`260`	`284`	`\|`
`261`	`285`	`LL \| (e @ 1..=2) => {}`
`262`	`286`	`\| ^ ^`
`@@ -268,7 +292,7 @@ LL + e @ 1..=2 => {}`
`268`	`292`	`\|`
`269`	`293`
`270`	`294`	`error: unnecessary parentheses around pattern`
`271`		`- --> $DIR/issue-54538-unused-parens-lint.rs:103:9`
	`295`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:118:9`
`272`	`296`	`\|`
`273`	`297`	`LL \| (e @ &(1..=2)) => {}`
`274`	`298`	`\| ^ ^`
`@@ -280,7 +304,7 @@ LL + e @ &(1..=2) => {}`
`280`	`304`	`\|`
`281`	`305`
`282`	`306`	`error: unnecessary parentheses around pattern`
`283`		`- --> $DIR/issue-54538-unused-parens-lint.rs:104:10`
	`307`	`+ --> $DIR/issue-54538-unused-parens-lint.rs:119:10`
`284`	`308`	`\|`
`285`	`309`	`LL \| &(_) => {}`
`286`	`310`	`\| ^ ^`
`@@ -291,5 +315,5 @@ LL - &(_) => {}`
`291`	`315`	`LL + &_ => {}`
`292`	`316`	`\|`
`293`	`317`
`294`		`-error: aborting due to 24 previous errors`
	`318`	`+error: aborting due to 26 previous errors`
`295`	`319`