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Extend precedence to lint for masking bits and shifts #8735

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Extend precedence to lint for masking bits and shifts #8735

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168 changes: 101 additions & 67 deletions clippy_lints/src/precedence.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ declare_clippy_lint! {
/// * a "negative" numeric literal (which is really a unary `-` followed by a
/// numeric literal)
/// followed by a method call
/// * bit masking (`&`) before a shifing operator without parentheses
///
/// ### Why is this bad?
/// Not everyone knows the precedence of those operators by
Expand All @@ -42,6 +43,7 @@ declare_clippy_lint! {
/// ### Example
/// * `1 << 2 + 3` equals 32, while `(1 << 2) + 3` equals 7
/// * `-1i32.abs()` equals -1, while `(-1i32).abs()` equals 1
/// * `0x2345 & 0xF000 >> 12` equals 5, while `(0x2345 & 0xF000) >> 12` equals 2
#[clippy::version = "pre 1.29.0"]
pub PRECEDENCE,
complexity,
Expand All @@ -56,86 +58,118 @@ impl EarlyLintPass for Precedence {
return;
}

if let ExprKind::Binary(Spanned { node: op, .. }, ref left, ref right) = expr.kind {
let span_sugg = |expr: &Expr, sugg, appl| {
check_expr_binary(cx, expr);
check_expr_unary(cx, expr);
}
}

fn check_expr_binary(cx: &EarlyContext<'_>, expr: &Expr) {
if let ExprKind::Binary(Spanned { node: op, .. }, ref left, ref right) = expr.kind {
let span_sugg = |expr: &Expr, sugg, appl| {
span_lint_and_sugg(
cx,
PRECEDENCE,
expr.span,
"operator precedence can trip the unwary",
"consider parenthesizing your expression",
sugg,
appl,
);
};

if !is_bit_op(op) {
return;
}
let mut applicability = Applicability::MachineApplicable;
match (is_arith_expr(left), is_arith_expr(right)) {
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This is the match expression that would need to change.

(true, true) => {
let sugg = format!(
"({}) {} ({})",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(true, false) => {
let sugg = format!(
"({}) {} {}",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(false, true) => {
let sugg = format!(
"{} {} ({})",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(false, false) => (),
}

if_chain! {
if matches!(op, BinOpKind::BitAnd);
if let ExprKind::Binary(Spanned { node: op_inner, .. }, left_inner, right_inner) = &right.kind;
if matches!(op_inner, BinOpKind::Shl | BinOpKind::Shr);
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
PRECEDENCE,
expr.span,
"operator precedence can trip the unwary",
"consider parenthesizing your expression",
sugg,
appl,
);
};

if !is_bit_op(op) {
return;
}
let mut applicability = Applicability::MachineApplicable;
match (is_arith_expr(left), is_arith_expr(right)) {
(true, true) => {
let sugg = format!(
"({}) {} ({})",
format!(
"({} {} {}) {} {}",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(true, false) => {
let sugg = format!(
"({}) {} {}",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(false, true) => {
let sugg = format!(
"{} {} ({})",
snippet_with_applicability(cx, left.span, "..", &mut applicability),
op.to_string(),
snippet_with_applicability(cx, right.span, "..", &mut applicability)
);
span_sugg(expr, sugg, applicability);
},
(false, false) => (),
snippet_with_applicability(cx, left_inner.span, "..", &mut applicability),
op_inner.to_string(),
snippet_with_applicability(cx, right_inner.span, "..", &mut applicability)
),
applicability,
);
}
}
}
}

if let ExprKind::Unary(UnOp::Neg, operand) = &expr.kind {
let mut arg = operand;
fn check_expr_unary(cx: &EarlyContext<'_>, expr: &Expr) {
if let ExprKind::Unary(UnOp::Neg, operand) = &expr.kind {
let mut arg = operand;

let mut all_odd = true;
while let ExprKind::MethodCall(path_segment, args, _) = &arg.kind {
let path_segment_str = path_segment.ident.name.as_str();
all_odd &= ALLOWED_ODD_FUNCTIONS
.iter()
.any(|odd_function| **odd_function == *path_segment_str);
arg = args.first().expect("A method always has a receiver.");
}
let mut all_odd = true;
while let ExprKind::MethodCall(path_segment, args, _) = &arg.kind {
let path_segment_str = path_segment.ident.name.as_str();
all_odd &= ALLOWED_ODD_FUNCTIONS
.iter()
.any(|odd_function| **odd_function == *path_segment_str);
arg = args.first().expect("A method always has a receiver.");
}

if_chain! {
if !all_odd;
if let ExprKind::Lit(lit) = &arg.kind;
if let LitKind::Int(..) | LitKind::Float(..) = &lit.kind;
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
PRECEDENCE,
expr.span,
"unary minus has lower precedence than method call",
"consider adding parentheses to clarify your intent",
format!(
"-({})",
snippet_with_applicability(cx, operand.span, "..", &mut applicability)
),
applicability,
);
}
if_chain! {
if !all_odd;
if let ExprKind::Lit(lit) = &arg.kind;
if let LitKind::Int(..) | LitKind::Float(..) = &lit.kind;
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
PRECEDENCE,
expr.span,
"unary minus has lower precedence than method call",
"consider adding parentheses to clarify your intent",
format!(
"-({})",
snippet_with_applicability(cx, operand.span, "..", &mut applicability)
),
applicability,
);
}
}
}
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/precedence.fixed
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,8 @@ fn main() {
1 ^ (1 - 1);
3 | (2 - 1);
3 & (5 - 2);
(12 & 0xF000) << 4;
(12 & 0xF000) >> 4;
-(1i32.abs());
-(1f32.abs());

Expand Down
2 changes: 2 additions & 0 deletions tests/ui/precedence.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,8 @@ fn main() {
1 ^ 1 - 1;
3 | 2 - 1;
3 & 5 - 2;
12 & 0xF000 << 4;
12 & 0xF000 >> 4;
-1i32.abs();
-1f32.abs();

Expand Down
24 changes: 18 additions & 6 deletions tests/ui/precedence.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -42,35 +42,47 @@ error: operator precedence can trip the unwary
LL | 3 & 5 - 2;
| ^^^^^^^^^ help: consider parenthesizing your expression: `3 & (5 - 2)`

error: unary minus has lower precedence than method call
error: operator precedence can trip the unwary
--> $DIR/precedence.rs:24:5
|
LL | 12 & 0xF000 << 4;
| ^^^^^^^^^^^^^^^^ help: consider parenthesizing your expression: `(12 & 0xF000) << 4`

error: operator precedence can trip the unwary
--> $DIR/precedence.rs:25:5
|
LL | 12 & 0xF000 >> 4;
| ^^^^^^^^^^^^^^^^ help: consider parenthesizing your expression: `(12 & 0xF000) >> 4`

error: unary minus has lower precedence than method call
--> $DIR/precedence.rs:26:5
|
LL | -1i32.abs();
| ^^^^^^^^^^^ help: consider adding parentheses to clarify your intent: `-(1i32.abs())`

error: unary minus has lower precedence than method call
--> $DIR/precedence.rs:25:5
--> $DIR/precedence.rs:27:5
|
LL | -1f32.abs();
| ^^^^^^^^^^^ help: consider adding parentheses to clarify your intent: `-(1f32.abs())`

error: unary minus has lower precedence than method call
--> $DIR/precedence.rs:52:13
--> $DIR/precedence.rs:54:13
|
LL | let _ = -1.0_f64.cos().cos();
| ^^^^^^^^^^^^^^^^^^^^ help: consider adding parentheses to clarify your intent: `-(1.0_f64.cos().cos())`

error: unary minus has lower precedence than method call
--> $DIR/precedence.rs:53:13
--> $DIR/precedence.rs:55:13
|
LL | let _ = -1.0_f64.cos().sin();
| ^^^^^^^^^^^^^^^^^^^^ help: consider adding parentheses to clarify your intent: `-(1.0_f64.cos().sin())`

error: unary minus has lower precedence than method call
--> $DIR/precedence.rs:54:13
--> $DIR/precedence.rs:56:13
|
LL | let _ = -1.0_f64.sin().cos();
| ^^^^^^^^^^^^^^^^^^^^ help: consider adding parentheses to clarify your intent: `-(1.0_f64.sin().cos())`

error: aborting due to 12 previous errors
error: aborting due to 14 previous errors