1 //! Lint on unnecessary double comparisons. Some examples:
4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
5 use rustc::{declare_tool_lint, lint_array};
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"
36 impl LintPass for Pass {
37 fn get_lints(&self) -> LintArray {
38 lint_array!(DOUBLE_COMPARISONS)
41 fn name(&self) -> &'static str {
47 #[allow(clippy::similar_names)]
48 fn check_binop(&self, cx: &LateContext<'a, 'tcx>, op: BinOpKind, lhs: &'tcx Expr, rhs: &'tcx Expr, span: Span) {
49 let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (lhs.node.clone(), rhs.node.clone()) {
50 (ExprKind::Binary(lb, llhs, lrhs), ExprKind::Binary(rb, rlhs, rrhs)) => {
51 (lb.node, llhs, lrhs, rb.node, rlhs, rrhs)
55 let mut spanless_eq = SpanlessEq::new(cx).ignore_fn();
56 if !(spanless_eq.eq_expr(&llhs, &rlhs) && spanless_eq.eq_expr(&lrhs, &rrhs)) {
59 macro_rules! lint_double_comparison {
61 let mut applicability = Applicability::MachineApplicable;
62 let lhs_str = snippet_with_applicability(cx, llhs.span, "", &mut applicability);
63 let rhs_str = snippet_with_applicability(cx, lrhs.span, "", &mut applicability);
64 let sugg = format!("{} {} {}", lhs_str, stringify!($op), rhs_str);
69 "This binary expression can be simplified",
76 match (op, lkind, rkind) {
77 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Lt) | (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Eq) => {
78 lint_double_comparison!(<=)
80 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Eq) => {
81 lint_double_comparison!(>=)
83 (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Lt) => {
84 lint_double_comparison!(!=)
86 (BinOpKind::And, BinOpKind::Le, BinOpKind::Ge) | (BinOpKind::And, BinOpKind::Ge, BinOpKind::Le) => {
87 lint_double_comparison!(==)
94 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
95 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
96 if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = expr.node {
97 self.check_binop(cx, kind.node, lhs, rhs, expr.span);