| use rustc_hir::{BinOpKind, Expr, ExprKind}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use rustc_span::source_map::Span; |
| |
| use crate::consts::{constant_simple, Constant}; |
| use crate::utils::span_lint; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for erasing operations, e.g., `x * 0`. |
| /// |
| /// **Why is this bad?** The whole expression can be replaced by zero. |
| /// This is most likely not the intended outcome and should probably be |
| /// corrected |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x = 1; |
| /// 0 / x; |
| /// 0 * x; |
| /// x & 0; |
| /// ``` |
| pub ERASING_OP, |
| correctness, |
| "using erasing operations, e.g., `x * 0` or `y & 0`" |
| } |
| |
| declare_lint_pass!(ErasingOp => [ERASING_OP]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ErasingOp { |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) { |
| if e.span.from_expansion() { |
| return; |
| } |
| if let ExprKind::Binary(ref cmp, ref left, ref right) = e.kind { |
| match cmp.node { |
| BinOpKind::Mul | BinOpKind::BitAnd => { |
| check(cx, left, e.span); |
| check(cx, right, e.span); |
| }, |
| BinOpKind::Div => check(cx, left, e.span), |
| _ => (), |
| } |
| } |
| } |
| } |
| |
| fn check(cx: &LateContext<'_, '_>, e: &Expr<'_>, span: Span) { |
| if let Some(Constant::Int(0)) = constant_simple(cx, cx.tables, e) { |
| span_lint( |
| cx, |
| ERASING_OP, |
| span, |
| "this operation will always return zero. This is likely not the intended outcome", |
| ); |
| } |
| } |