From 6631480a7b7cb7b3e7d53c9c4cd7915f7ebc3110 Mon Sep 17 00:00:00 2001
From: blyxyas <blyxyas@gmail.com>
Date: Mon, 13 Mar 2023 19:13:56 +0100
Subject: [PATCH] Fix false positive with `a = a`

---
 clippy_lints/src/swap.rs | 1 +
 tests/ui/swap.fixed      | 8 ++++++++
 tests/ui/swap.rs         | 8 ++++++++
 3 files changed, 17 insertions(+)

diff --git a/clippy_lints/src/swap.rs b/clippy_lints/src/swap.rs
index 1aeac724ab1..5087c19e5f3 100644
--- a/clippy_lints/src/swap.rs
+++ b/clippy_lints/src/swap.rs
@@ -190,6 +190,7 @@ fn check_suspicious_swap(cx: &LateContext<'_>, block: &Block<'_>) {
             && first.span.eq_ctxt(second.span)
             && is_same(cx, lhs0, rhs1)
             && is_same(cx, lhs1, rhs0)
+			&& !is_same(cx, lhs1, rhs1) // Ignore a = b; a = a (#10421)
             && let Some(lhs_sugg) = match &lhs0 {
                 ExprOrIdent::Expr(expr) => Sugg::hir_opt(cx, expr),
                 ExprOrIdent::Ident(ident) => Some(Sugg::NonParen(ident.as_str().into())),
diff --git a/tests/ui/swap.fixed b/tests/ui/swap.fixed
index 04008c0d9b3..775b0dbde88 100644
--- a/tests/ui/swap.fixed
+++ b/tests/ui/swap.fixed
@@ -186,3 +186,11 @@ const fn issue_9864(mut u: u32) -> u32 {
     v = temp;
     u + v
 }
+
+#[allow(clippy::let_and_return)]
+const fn issue_10421(x: u32) -> u32 {
+    let a = x;
+    let a = a;
+    let a = a;
+    a
+}
diff --git a/tests/ui/swap.rs b/tests/ui/swap.rs
index ef8a81c8341..bc9a78b49c7 100644
--- a/tests/ui/swap.rs
+++ b/tests/ui/swap.rs
@@ -215,3 +215,11 @@ const fn issue_9864(mut u: u32) -> u32 {
     v = temp;
     u + v
 }
+
+#[allow(clippy::let_and_return)]
+const fn issue_10421(x: u32) -> u32 {
+    let a = x;
+    let a = a;
+    let a = a;
+    a
+}