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