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Check for both signed and unsigned constant expressions

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This commit is contained in:
teor 2024-01-16 18:03:35 +10:00
parent c5e8487d63
commit e74fe4362a
2 changed files with 30 additions and 7 deletions
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35
clippy_lints/src/casts/cast_sign_loss.rs
View File

@ -66,8 +66,7 @@ fn should_lint<'cx>(cx: &LateContext<'cx>, cast_op: &Expr<'_>, cast_from: Ty<'cx
// a % b => [a]
let exprs = exprs_with_selected_binop_peeled(cast_op);
for expr in exprs {
let ty = cx.typeck_results().expr_ty(expr);
match expr_sign(cx, expr, ty) {
match expr_sign(cx, expr, None) {
Sign::Negative => negative_count += 1,
Sign::Uncertain => uncertain_count += 1,
Sign::ZeroOrPositive => (),
@ -85,7 +84,11 @@ fn should_lint<'cx>(cx: &LateContext<'cx>, cast_op: &Expr<'_>, cast_from: Ty<'cx
}
}
fn get_const_int_eval<'cx>(cx: &LateContext<'cx>, expr: &Expr<'_>, ty: impl Into<Option<Ty<'cx>>>) -> Option<i128> {
fn get_const_signed_int_eval<'cx>(
cx: &LateContext<'cx>,
expr: &Expr<'_>,
ty: impl Into<Option<Ty<'cx>>>,
) -> Option<i128> {
let ty = ty.into().unwrap_or_else(|| cx.typeck_results().expr_ty(expr));
if let Constant::Int(n) = constant(cx, cx.typeck_results(), expr)?
@ -96,6 +99,22 @@ fn get_const_int_eval<'cx>(cx: &LateContext<'cx>, expr: &Expr<'_>, ty: impl Into
None
}
fn get_const_unsigned_int_eval<'cx>(
cx: &LateContext<'cx>,
expr: &Expr<'_>,
ty: impl Into<Option<Ty<'cx>>>,
) -> Option<u128> {
let ty = ty.into().unwrap_or_else(|| cx.typeck_results().expr_ty(expr));
if let Constant::Int(n) = constant(cx, cx.typeck_results(), expr)?
&& let ty::Uint(_ity) = *ty.kind()
{
return Some(n);
}
None
}
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
enum Sign {
ZeroOrPositive,
Negative,
@ -104,9 +123,12 @@ enum Sign {
fn expr_sign<'cx>(cx: &LateContext<'cx>, expr: &Expr<'_>, ty: impl Into<Option<Ty<'cx>>>) -> Sign {
// Try evaluate this expr first to see if it's positive
if let Some(val) = get_const_int_eval(cx, expr, ty) {
if let Some(val) = get_const_signed_int_eval(cx, expr, ty) {
return if val >= 0 { Sign::ZeroOrPositive } else { Sign::Negative };
}
if let Some(_val) = get_const_unsigned_int_eval(cx, expr, None) {
return Sign::ZeroOrPositive;
}
// Calling on methods that always return non-negative values.
if let ExprKind::MethodCall(path, caller, args, ..) = expr.kind {
@ -144,12 +166,13 @@ fn expr_sign<'cx>(cx: &LateContext<'cx>, expr: &Expr<'_>, ty: impl Into<Option<T
/// Otherwise, returns [`Sign::Uncertain`].
fn pow_call_result_sign(cx: &LateContext<'_>, base: &Expr<'_>, exponent: &Expr<'_>) -> Sign {
let base_sign = expr_sign(cx, base, None);
let exponent_val = get_const_int_eval(cx, exponent, None);
// Rust's integer pow() functions take an unsigned exponent.
let exponent_val = get_const_unsigned_int_eval(cx, exponent, None);
let exponent_is_even = exponent_val.map(|val| val % 2 == 0);
match (base_sign, exponent_is_even) {
// Non-negative bases always return non-negative results, ignoring overflow.
// This is because Rust's integer pow() functions take an unsigned exponent.
(Sign::ZeroOrPositive, _) => Sign::ZeroOrPositive,
// Any base raised to an even exponent is non-negative.

2
tests/ui/cast.stderr
View File

@ -600,5 +600,5 @@ error: casting `i32` to `u32` may lose the sign of the value
LL | (a.abs() * b.pow(2) / c.abs()) as u32
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 77 previous errors
error: aborting due to 76 previous errors