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Fix case where rem was considered commutative

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This commit is contained in:
Evan Typanski 2022-06-22 13:26:13 -04:00
parent 75ed0c9f26
commit 93e41d3305
3 changed files with 21 additions and 8 deletions
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21
clippy_lints/src/manual_rem_euclid.rs
View file

@ -55,13 +55,13 @@ impl<'tcx> LateLintPass<'tcx> for ManualRemEuclid {
if_chain! {
if let ExprKind::Binary(op1, ..) = expr.kind;
if op1.node == BinOpKind::Rem;
if let Some((const1, expr1)) = check_for_positive_int_constant(cx, expr);
if let Some((const1, expr1)) = check_for_positive_int_constant(cx, expr, false);
if let ExprKind::Binary(op2, ..) = expr1.kind;
if op2.node == BinOpKind::Add;
if let Some((const2, expr2)) = check_for_positive_int_constant(cx, expr1);
if let Some((const2, expr2)) = check_for_positive_int_constant(cx, expr1, true);
if let ExprKind::Binary(op3, ..) = expr2.kind;
if op3.node == BinOpKind::Rem;
if let Some((const3, expr3)) = check_for_positive_int_constant(cx, expr2);
if let Some((const3, expr3)) = check_for_positive_int_constant(cx, expr2, false);
if const1 == const2 && const2 == const3;
// Only apply if we see an explicit type annotation on the local.
if let Some(hir_id) = path_to_local(expr3);
@ -91,13 +91,18 @@ impl<'tcx> LateLintPass<'tcx> for ManualRemEuclid {
}
// Takes a binary expression and separates the operands into the int constant and the other
// operand. Ensures the int constant is positive.
fn check_for_positive_int_constant<'a>(cx: &'a LateContext<'_>, expr: &'a Expr<'_>) -> Option<(u128, &'a Expr<'a>)> {
// operand. Ensures the int constant is positive. Operators that are not commutative must have the
// constant appear on the right hand side to return a value.
fn check_for_positive_int_constant<'a>(
cx: &'a LateContext<'_>,
expr: &'a Expr<'_>,
is_commutative: bool,
) -> Option<(u128, &'a Expr<'a>)> {
let (int_const, other_op) = if let ExprKind::Binary(_, left, right) = expr.kind {
if let Some(int_const) = constant_full_int(cx, cx.typeck_results(), left) {
(int_const, right)
} else if let Some(int_const) = constant_full_int(cx, cx.typeck_results(), right) {
if let Some(int_const) = constant_full_int(cx, cx.typeck_results(), right) {
(int_const, left)
} else if is_commutative && let Some(int_const) = constant_full_int(cx, cx.typeck_results(), left) {
(int_const, right)
} else {
return None;
}

4
tests/ui/manual_rem_euclid.fixed
View file

@ -21,4 +21,8 @@ fn main() {
let _ = ((not_annotated % 4) + 4) % 4;
let inferred: _ = 24;
let _ = ((inferred % 4) + 4) % 4;
// For lint to apply the constant must always be on the RHS of the previous value for %
let _: i32 = 4 % ((value % 4) + 4);
let _: i32 = ((4 % value) + 4) % 4;
}

4
tests/ui/manual_rem_euclid.rs
View file

@ -21,4 +21,8 @@ fn main() {
let _ = ((not_annotated % 4) + 4) % 4;
let inferred: _ = 24;
let _ = ((inferred % 4) + 4) % 4;
// For lint to apply the constant must always be on the RHS of the previous value for %
let _: i32 = 4 % ((value % 4) + 4);
let _: i32 = ((4 % value) + 4) % 4;
}