1 use clippy_utils::consts::{constant_simple, Constant};
2 use clippy_utils::diagnostics::span_lint;
3 use rustc_hir::{BinOpKind, Expr, ExprKind};
4 use rustc_lint::{LateContext, LateLintPass};
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
6 use rustc_span::source_map::Span;
10 /// Checks for erasing operations, e.g., `x * 0`.
12 /// ### Why is this bad?
13 /// The whole expression can be replaced by zero.
14 /// This is most likely not the intended outcome and should probably be
24 #[clippy::version = "pre 1.29.0"]
27 "using erasing operations, e.g., `x * 0` or `y & 0`"
30 declare_lint_pass!(ErasingOp => [ERASING_OP]);
32 impl<'tcx> LateLintPass<'tcx> for ErasingOp {
33 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
34 if e.span.from_expansion() {
37 if let ExprKind::Binary(ref cmp, left, right) = e.kind {
39 BinOpKind::Mul | BinOpKind::BitAnd => {
40 check(cx, left, e.span);
41 check(cx, right, e.span);
43 BinOpKind::Div => check(cx, left, e.span),
50 fn check(cx: &LateContext<'_>, e: &Expr<'_>, span: Span) {
51 if constant_simple(cx, cx.typeck_results(), e) == Some(Constant::Int(0)) {
56 "this operation will always return zero. This is likely not the intended outcome",