1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 //! Lint on unnecessary double comparisons. Some examples:
13 use crate::rustc::hir::*;
14 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
15 use crate::rustc::{declare_tool_lint, lint_array};
16 use crate::syntax::source_map::Span;
18 use crate::utils::{snippet, span_lint_and_sugg, SpanlessEq};
20 /// **What it does:** Checks for double comparions that could be simpified to a single expression.
23 /// **Why is this bad?** Readability.
25 /// **Known problems:** None.
32 /// Could be written as:
37 declare_clippy_lint! {
38 pub DOUBLE_COMPARISONS,
40 "unnecessary double comparisons that can be simplified"
43 #[allow(clippy::stutter)]
44 pub struct DoubleComparisonPass;
46 impl LintPass for DoubleComparisonPass {
47 fn get_lints(&self) -> LintArray {
48 lint_array!(DOUBLE_COMPARISONS)
52 impl<'a, 'tcx> DoubleComparisonPass {
53 #[allow(clippy::similar_names)]
56 cx: &LateContext<'a, 'tcx>,
62 let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (lhs.node.clone(), rhs.node.clone()) {
63 (ExprKind::Binary(lb, llhs, lrhs), ExprKind::Binary(rb, rlhs, rrhs)) => {
64 (lb.node, llhs, lrhs, rb.node, rlhs, rrhs)
68 let mut spanless_eq = SpanlessEq::new(cx).ignore_fn();
69 if !(spanless_eq.eq_expr(&llhs, &rlhs) && spanless_eq.eq_expr(&lrhs, &rrhs)) {
72 macro_rules! lint_double_comparison {
74 let lhs_str = snippet(cx, llhs.span, "");
75 let rhs_str = snippet(cx, lrhs.span, "");
76 let sugg = format!("{} {} {}", lhs_str, stringify!($op), rhs_str);
77 span_lint_and_sugg(cx, DOUBLE_COMPARISONS, span,
78 "This binary expression can be simplified",
82 match (op, lkind, rkind) {
83 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Lt) | (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Eq) => lint_double_comparison!(<=),
84 (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Eq) => lint_double_comparison!(>=),
85 (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Lt) => lint_double_comparison!(!=),
86 (BinOpKind::And, BinOpKind::Le, BinOpKind::Ge) | (BinOpKind::And, BinOpKind::Ge, BinOpKind::Le) => lint_double_comparison!(==),
92 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DoubleComparisonPass {
93 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
94 if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = expr.node {
95 self.check_binop(cx, kind.node, lhs, rhs, expr.span);