1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 use crate::consts::{constant_simple, Constant};
12 use crate::rustc::hir::*;
13 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
14 use crate::rustc::{declare_tool_lint, lint_array};
15 use crate::syntax::source_map::Span;
16 use crate::utils::{in_macro, span_lint};
18 /// **What it does:** Checks for erasing operations, e.g. `x * 0`.
20 /// **Why is this bad?** The whole expression can be replaced by zero.
21 /// This is most likely not the intended outcome and should probably be
24 /// **Known problems:** None.
28 /// 0 / x; 0 * x; x & 0
30 declare_clippy_lint! {
33 "using erasing operations, e.g. `x * 0` or `y & 0`"
36 #[derive(Copy, Clone)]
39 impl LintPass for ErasingOp {
40 fn get_lints(&self) -> LintArray {
41 lint_array!(ERASING_OP)
45 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ErasingOp {
46 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
50 if let ExprKind::Binary(ref cmp, ref left, ref right) = e.node {
52 BinOpKind::Mul | BinOpKind::BitAnd => {
53 check(cx, left, e.span);
54 check(cx, right, e.span);
56 BinOpKind::Div => check(cx, left, e.span),
63 fn check(cx: &LateContext<'_, '_>, e: &Expr, span: Span) {
64 if let Some(Constant::Int(v)) = constant_simple(cx, cx.tables, e) {
70 "this operation will always return zero. This is likely not the intended outcome",