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.
10 use crate::consts::{constant_simple, Constant};
11 use crate::rustc::hir::*;
12 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
13 use crate::rustc::{declare_tool_lint, lint_array};
14 use crate::syntax::source_map::Span;
15 use crate::utils::{in_macro, span_lint};
17 /// **What it does:** Checks for erasing operations, e.g. `x * 0`.
19 /// **Why is this bad?** The whole expression can be replaced by zero.
20 /// This is most likely not the intended outcome and should probably be
23 /// **Known problems:** None.
31 declare_clippy_lint! {
34 "using erasing operations, e.g. `x * 0` or `y & 0`"
37 #[derive(Copy, Clone)]
40 impl LintPass for ErasingOp {
41 fn get_lints(&self) -> LintArray {
42 lint_array!(ERASING_OP)
46 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ErasingOp {
47 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
51 if let ExprKind::Binary(ref cmp, ref left, ref right) = e.node {
53 BinOpKind::Mul | BinOpKind::BitAnd => {
54 check(cx, left, e.span);
55 check(cx, right, e.span);
57 BinOpKind::Div => check(cx, left, e.span),
64 fn check(cx: &LateContext<'_, '_>, e: &Expr, span: Span) {
65 if let Some(Constant::Int(v)) = constant_simple(cx, cx.tables, e) {
71 "this operation will always return zero. This is likely not the intended outcome",