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extract the constant codepath

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switch around `*_amount` and `*_expr` -- otherwise the order gets
confusing now because of both of them being `Expr`s
This commit is contained in:
Ada Alakbarova 2025-08-03 18:16:02 +02:00
parent 8e3315f292
commit c9ee445abd
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1 changed files with 28 additions and 27 deletions
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55
clippy_lints/src/manual_rotate.rs
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@ -56,20 +56,14 @@ impl Display for ShiftDirection {
}
}
fn parse_shift<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'tcx>,
) -> Option<(ShiftDirection, u128, &'tcx Expr<'tcx>)> {
fn parse_shift<'tcx>(expr: &'tcx Expr<'tcx>) -> Option<(ShiftDirection, &'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
if let ExprKind::Binary(op, l, r) = expr.kind {
let dir = match op.node {
BinOpKind::Shl => ShiftDirection::Left,
BinOpKind::Shr => ShiftDirection::Right,
_ => return None,
};
let const_expr = ConstEvalCtxt::new(cx).eval_local(r, expr.span.ctxt())?;
if let Constant::Int(shift) = const_expr {
return Some((dir, shift, l));
}
return Some((dir, l, r));
}
None
}
@ -78,8 +72,8 @@ impl LateLintPass<'_> for ManualRotate {
fn check_expr<'tcx>(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
if let ExprKind::Binary(op, l, r) = expr.kind
&& let BinOpKind::Add | BinOpKind::BitOr = op.node
&& let Some((l_shift_dir, l_amount, l_expr)) = parse_shift(cx, l)
&& let Some((r_shift_dir, r_amount, r_expr)) = parse_shift(cx, r)
&& let Some((l_shift_dir, l_expr, l_amount)) = parse_shift(l)
&& let Some((r_shift_dir, r_expr, r_amount)) = parse_shift(r)
&& l_shift_dir != r_shift_dir
&& clippy_utils::eq_expr_value(cx, l_expr, r_expr)
&& let Some(bit_width) = match cx.typeck_results().expr_ty(expr).kind() {
@ -87,24 +81,31 @@ impl LateLintPass<'_> for ManualRotate {
ty::Uint(itype) => itype.bit_width(),
_ => return,
}
&& l_amount + r_amount == u128::from(bit_width)
{
let (shift_function, amount) = if l_amount < r_amount {
(l_shift_dir, l_amount)
} else {
(r_shift_dir, r_amount)
};
let mut applicability = Applicability::MachineApplicable;
let expr_sugg = sugg::Sugg::hir_with_applicability(cx, l_expr, "_", &mut applicability).maybe_paren();
span_lint_and_sugg(
cx,
MANUAL_ROTATE,
expr.span,
"there is no need to manually implement bit rotation",
"this expression can be rewritten as",
format!("{expr_sugg}.{shift_function}({amount})"),
Applicability::MachineApplicable,
);
let const_eval = ConstEvalCtxt::new(cx);
let ctxt = expr.span.ctxt();
if let Some(Constant::Int(l_amount)) = const_eval.eval_local(l_amount, ctxt)
&& let Some(Constant::Int(r_amount)) = const_eval.eval_local(r_amount, ctxt)
&& l_amount + r_amount == u128::from(bit_width)
{
let (shift_function, amount) = if l_amount < r_amount {
(l_shift_dir, l_amount)
} else {
(r_shift_dir, r_amount)
};
let mut applicability = Applicability::MachineApplicable;
let expr_sugg = sugg::Sugg::hir_with_applicability(cx, l_expr, "_", &mut applicability).maybe_paren();
span_lint_and_sugg(
cx,
MANUAL_ROTATE,
expr.span,
"there is no need to manually implement bit rotation",
"this expression can be rewritten as",
format!("{expr_sugg}.{shift_function}({amount})"),
Applicability::MachineApplicable,
);
}
}
}
}