1 //! Lint on unnecessary double comparisons. Some examples:
3 use rustc::declare_lint_pass;
5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
6 use rustc_errors::Applicability;
7 use rustc_session::declare_tool_lint;
8 use syntax::source_map::Span;
10 use crate::utils::{snippet_with_applicability, span_lint_and_sugg, SpanlessEq};
12 declare_clippy_lint! {
13 /// **What it does:** Checks for double comparisons that could be simplified to a single expression.
16 /// **Why is this bad?** Readability.
18 /// **Known problems:** None.
24 /// if x == y || x < y {}
27 /// Could be written as:
34 pub DOUBLE_COMPARISONS,
36 "unnecessary double comparisons that can be simplified"
39 declare_lint_pass!(DoubleComparisons => [DOUBLE_COMPARISONS]);
41 impl<'a, 'tcx> DoubleComparisons {
42 #[allow(clippy::similar_names)]
43 fn check_binop(cx: &LateContext<'a, 'tcx>, op: BinOpKind, lhs: &'tcx Expr, rhs: &'tcx Expr, span: Span) {
44 let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (&lhs.kind, &rhs.kind) {
45 (ExprKind::Binary(lb, llhs, lrhs), ExprKind::Binary(rb, rlhs, rrhs)) => {
46 (lb.node, llhs, lrhs, rb.node, rlhs, rrhs)
50 let mut spanless_eq = SpanlessEq::new(cx).ignore_fn();
51 if !(spanless_eq.eq_expr(&llhs, &rlhs) && spanless_eq.eq_expr(&lrhs, &rrhs)) {
54 macro_rules! lint_double_comparison {
56 let mut applicability = Applicability::MachineApplicable;
57 let lhs_str = snippet_with_applicability(cx, llhs.span, "", &mut applicability);
58 let rhs_str = snippet_with_applicability(cx, lrhs.span, "", &mut applicability);
59 let sugg = format!("{} {} {}", lhs_str, stringify!($op), rhs_str);
64 "This binary expression can be simplified",
72 match (op, lkind, rkind) {
73 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Lt) | (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Eq) => {
74 lint_double_comparison!(<=)
76 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Eq) => {
77 lint_double_comparison!(>=)
79 (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Lt) => {
80 lint_double_comparison!(!=)
82 (BinOpKind::And, BinOpKind::Le, BinOpKind::Ge) | (BinOpKind::And, BinOpKind::Ge, BinOpKind::Le) => {
83 lint_double_comparison!(==)
90 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DoubleComparisons {
91 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
92 if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = expr.kind {
93 Self::check_binop(cx, kind.node, lhs, rhs, expr.span);