1 //! Lint on unnecessary double comparisons. Some examples:
5 use rustc::{declare_lint, lint_array};
6 use syntax::source_map::Span;
8 use crate::utils::{snippet, span_lint_and_sugg, SpanlessEq};
10 /// **What it does:** Checks for double comparions that could be simpified to a single expression.
13 /// **Why is this bad?** Readability.
15 /// **Known problems:** None.
22 /// Could be written as:
27 declare_clippy_lint! {
28 pub DOUBLE_COMPARISONS,
30 "unnecessary double comparisons that can be simplified"
33 pub struct DoubleComparisonPass;
35 impl LintPass for DoubleComparisonPass {
36 fn get_lints(&self) -> LintArray {
37 lint_array!(DOUBLE_COMPARISONS)
41 impl<'a, 'tcx> DoubleComparisonPass {
44 cx: &LateContext<'a, 'tcx>,
50 let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (lhs.node.clone(), rhs.node.clone()) {
51 (ExprKind::Binary(lb, llhs, lrhs), ExprKind::Binary(rb, rlhs, rrhs)) => {
52 (lb.node, llhs, lrhs, rb.node, rlhs, rrhs)
56 let mut spanless_eq = SpanlessEq::new(cx).ignore_fn();
57 if !(spanless_eq.eq_expr(&llhs, &rlhs) && spanless_eq.eq_expr(&lrhs, &rrhs)) {
60 macro_rules! lint_double_comparison {
62 let lhs_str = snippet(cx, llhs.span, "");
63 let rhs_str = snippet(cx, lrhs.span, "");
64 let sugg = format!("{} {} {}", lhs_str, stringify!($op), rhs_str);
65 span_lint_and_sugg(cx, DOUBLE_COMPARISONS, span,
66 "This binary expression can be simplified",
70 match (op, lkind, rkind) {
71 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Lt) | (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Eq) => lint_double_comparison!(<=),
72 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Eq) => lint_double_comparison!(>=),
73 (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Lt) => lint_double_comparison!(!=),
74 (BinOpKind::And, BinOpKind::Le, BinOpKind::Ge) | (BinOpKind::And, BinOpKind::Ge, BinOpKind::Le) => lint_double_comparison!(==),
80 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DoubleComparisonPass {
81 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
82 if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = expr.node {
83 self.check_binop(cx, kind.node, lhs, rhs, expr.span);