1 //! Lint on unnecessary double comparisons. Some examples:
4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
5 use rustc::{declare_lint_pass, declare_tool_lint};
6 use rustc_errors::Applicability;
7 use syntax::source_map::Span;
9 use crate::utils::{snippet_with_applicability, span_lint_and_sugg, SpanlessEq};
11 declare_clippy_lint! {
12 /// **What it does:** Checks for double comparions that could be simplified to a single expression.
15 /// **Why is this bad?** Readability.
17 /// **Known problems:** None.
24 /// Could be written as:
29 pub DOUBLE_COMPARISONS,
31 "unnecessary double comparisons that can be simplified"
34 declare_lint_pass!(DoubleComparisons => [DOUBLE_COMPARISONS]);
36 impl<'a, 'tcx> DoubleComparisons {
37 #[allow(clippy::similar_names)]
38 fn check_binop(self, cx: &LateContext<'a, 'tcx>, op: BinOpKind, lhs: &'tcx Expr, rhs: &'tcx Expr, span: Span) {
39 let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (lhs.node.clone(), rhs.node.clone()) {
40 (ExprKind::Binary(lb, llhs, lrhs), ExprKind::Binary(rb, rlhs, rrhs)) => {
41 (lb.node, llhs, lrhs, rb.node, rlhs, rrhs)
45 let mut spanless_eq = SpanlessEq::new(cx).ignore_fn();
46 if !(spanless_eq.eq_expr(&llhs, &rlhs) && spanless_eq.eq_expr(&lrhs, &rrhs)) {
49 macro_rules! lint_double_comparison {
51 let mut applicability = Applicability::MachineApplicable;
52 let lhs_str = snippet_with_applicability(cx, llhs.span, "", &mut applicability);
53 let rhs_str = snippet_with_applicability(cx, lrhs.span, "", &mut applicability);
54 let sugg = format!("{} {} {}", lhs_str, stringify!($op), rhs_str);
59 "This binary expression can be simplified",
66 match (op, lkind, rkind) {
67 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Lt) | (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Eq) => {
68 lint_double_comparison!(<=)
70 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Eq) => {
71 lint_double_comparison!(>=)
73 (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Lt) => {
74 lint_double_comparison!(!=)
76 (BinOpKind::And, BinOpKind::Le, BinOpKind::Ge) | (BinOpKind::And, BinOpKind::Ge, BinOpKind::Le) => {
77 lint_double_comparison!(==)
84 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DoubleComparisons {
85 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
86 if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = expr.node {
87 self.check_binop(cx, kind.node, lhs, rhs, expr.span);