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fix false positives for unused_parens around unary and binary operations #110257

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merged 2 commits into from
Apr 17, 2023
+109 −41
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fix false positives for unused_parens around unary and binary operations #110257

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8df1f41
fix false positives for `unused_parens` around unary and binary opera…
Apr 12, 2023
0d0949d
emit `unused_parens` for `break` if it is not immediately followed by…
Apr 12, 2023
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50 changes: 32 additions & 18 deletions compiler/rustc_lint/src/unused.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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(
Expand Down
19 changes: 17 additions & 2 deletions tests/ui/lint/unused/issue-54538-unused-parens-lint.fixed
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Original file line number Diff line number Diff line change
Expand Up @@ -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) {
Expand Down
19 changes: 17 additions & 2 deletions tests/ui/lint/unused/issue-54538-unused-parens-lint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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) {
Expand Down
62 changes: 43 additions & 19 deletions tests/ui/lint/unused/issue-54538-unused-parens-lint.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -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 {}
| ^ ^
Expand All @@ -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,) {}
| ^ ^
Expand All @@ -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] {}
| ^ ^
Expand All @@ -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 {}
| ^ ^
Expand All @@ -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) {}
| ^ ^
Expand All @@ -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 }) {}
| ^ ^
Expand All @@ -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 | (_) => {}
| ^ ^
Expand All @@ -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) => {}
| ^ ^
Expand All @@ -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) => {}
| ^ ^
Expand All @@ -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) => {}
| ^ ^
Expand All @@ -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)) => {}
| ^ ^
Expand All @@ -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 | &(_) => {}
| ^ ^
Expand All @@ -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 | (_) => {}
| ^ ^
Expand All @@ -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) => {}
| ^ ^
Expand All @@ -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) => {}
| ^ ^
Expand All @@ -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) => {}
| ^ ^
Expand All @@ -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)) => {}
| ^ ^
Expand All @@ -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 | &(_) => {}
| ^ ^
Expand All @@ -291,5 +315,5 @@ LL - &(_) => {}
LL + &_ => {}
|

error: aborting due to 24 previous errors
error: aborting due to 26 previous errors