Merge commit '4911ab124c481430672a3833b37075e6435ec34d' into clippyup

[rust.git] / clippy_lints / src / comparison_chain.rs

diff --git a/clippy_lints/src/comparison_chain.rs b/clippy_lints/src/comparison_chain.rs
index d3a3b85b331a2a2b1c7a65d5c9c0b66c64a067a3..ae1143b2c50ce8fbbe5647c56f6d52e386b70155 100644 (file)
--- a/clippy_lints/src/comparison_chain.rs
+++ b/clippy_lints/src/comparison_chain.rs
@@ -1,7 +1,7 @@
 use crate::utils::{
-    get_trait_def_id, if_sequence, implements_trait, parent_node_is_if_expr, paths, span_help_and_lint, SpanlessEq,
+    get_trait_def_id, if_sequence, implements_trait, parent_node_is_if_expr, paths, span_lint_and_help, SpanlessEq,
 };
-use rustc_hir::*;
+use rustc_hir::{BinOpKind, Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
@@ -12,7 +12,8 @@
     /// **Why is this bad?** `if` is not guaranteed to be exhaustive and conditionals can get
     /// repetitive
     ///
-    /// **Known problems:** None.
+    /// **Known problems:** The match statement may be slower due to the compiler
+    /// not inlining the call to cmp. See issue #5354
     ///
     /// **Example:**
     /// ```rust,ignore
@@ -52,8 +53,8 @@
 
 declare_lint_pass!(ComparisonChain => [COMPARISON_CHAIN]);
 
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ComparisonChain {
-    fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
+impl<'tcx> LateLintPass<'tcx> for ComparisonChain {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         if expr.span.from_expansion() {
             return;
         }
@@ -81,14 +82,25 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
 
                 // Check that both sets of operands are equal
                 let mut spanless_eq = SpanlessEq::new(cx);
-                if (!spanless_eq.eq_expr(lhs1, lhs2) || !spanless_eq.eq_expr(rhs1, rhs2))
-                    && (!spanless_eq.eq_expr(lhs1, rhs2) || !spanless_eq.eq_expr(rhs1, lhs2))
-                {
+                let same_fixed_operands = spanless_eq.eq_expr(lhs1, lhs2) && spanless_eq.eq_expr(rhs1, rhs2);
+                let same_transposed_operands = spanless_eq.eq_expr(lhs1, rhs2) && spanless_eq.eq_expr(rhs1, lhs2);
+
+                if !same_fixed_operands && !same_transposed_operands {
                     return;
                 }
 
+                // Check that if the operation is the same, either it's not `==` or the operands are transposed
+                if kind1.node == kind2.node {
+                    if kind1.node == BinOpKind::Eq {
+                        return;
+                    }
+                    if !same_transposed_operands {
+                        return;
+                    }
+                }
+
                 // Check that the type being compared implements `core::cmp::Ord`
-                let ty = cx.tables.expr_ty(lhs1);
+                let ty = cx.typeck_results().expr_ty(lhs1);
                 let is_ord = get_trait_def_id(cx, &paths::ORD).map_or(false, |id| implements_trait(cx, ty, id, &[]));
 
                 if !is_ord {
@@ -99,19 +111,17 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
                 return;
             }
         }
-        span_help_and_lint(
+        span_lint_and_help(
             cx,
             COMPARISON_CHAIN,
             expr.span,
             "`if` chain can be rewritten with `match`",
+            None,
             "Consider rewriting the `if` chain to use `cmp` and `match`.",
         )
     }
 }
 
 fn kind_is_cmp(kind: BinOpKind) -> bool {
-    match kind {
-        BinOpKind::Lt | BinOpKind::Gt | BinOpKind::Eq => true,
-        _ => false,
-    }
+    matches!(kind, BinOpKind::Lt | BinOpKind::Gt | BinOpKind::Eq)
 }