1 use crate::consts::{constant_simple, Constant};
2 use crate::utils::{in_macro, span_lint};
4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
5 use rustc::{declare_tool_lint, lint_array};
6 use syntax::source_map::Span;
9 /// **What it does:** Checks for erasing operations, e.g. `x * 0`.
11 /// **Why is this bad?** The whole expression can be replaced by zero.
12 /// This is most likely not the intended outcome and should probably be
15 /// **Known problems:** None.
25 "using erasing operations, e.g. `x * 0` or `y & 0`"
28 #[derive(Copy, Clone)]
31 impl LintPass for ErasingOp {
32 fn get_lints(&self) -> LintArray {
33 lint_array!(ERASING_OP)
36 fn name(&self) -> &'static str {
41 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ErasingOp {
42 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
46 if let ExprKind::Binary(ref cmp, ref left, ref right) = e.node {
48 BinOpKind::Mul | BinOpKind::BitAnd => {
49 check(cx, left, e.span);
50 check(cx, right, e.span);
52 BinOpKind::Div => check(cx, left, e.span),
59 fn check(cx: &LateContext<'_, '_>, e: &Expr, span: Span) {
60 if let Some(Constant::Int(v)) = constant_simple(cx, cx.tables, e) {
66 "this operation will always return zero. This is likely not the intended outcome",