From 39b3c0ef7ef599b95ac74de594deb06097a115c9 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 19 Jan 2020 10:29:21 +0100
Subject: [PATCH] AK: Make it possible to swap() a NonnullRefPtr with itself

The generic swap() is not able to swap a NonnullRefPtr with itself,
due to its use of a temporary and NonnullRefPtr asserting when trying
to move() from an already move()'d instance.
---
 AK/NonnullRefPtr.h             | 6 ++++++
 AK/Tests/TestNonnullRefPtr.cpp | 7 +++++++
 2 files changed, 13 insertions(+)

diff --git a/AK/NonnullRefPtr.h b/AK/NonnullRefPtr.h
index 46686927e9..a30a3c96bc 100644
--- a/AK/NonnullRefPtr.h
+++ b/AK/NonnullRefPtr.h
@@ -267,6 +267,12 @@ inline const LogStream& operator<<(const LogStream& stream, const NonnullRefPtr<
     return stream << value.ptr();
 }
 
+template<typename T, typename U>
+inline void swap(NonnullRefPtr<T>& a, NonnullRefPtr<U>& b)
+{
+    a.swap(b);
+}
+
 }
 
 using AK::adopt;
diff --git a/AK/Tests/TestNonnullRefPtr.cpp b/AK/Tests/TestNonnullRefPtr.cpp
index a8c77ae1ea..1cd183c0e3 100644
--- a/AK/Tests/TestNonnullRefPtr.cpp
+++ b/AK/Tests/TestNonnullRefPtr.cpp
@@ -73,4 +73,11 @@ TEST_CASE(assign_owner_of_self)
     EXPECT_EQ(child->ref_count(), 1);
 }
 
+TEST_CASE(swap_with_self)
+{
+    auto object = adopt(*new Object);
+    swap(object, object);
+    EXPECT_EQ(object->ref_count(), 1);
+}
+
 TEST_MAIN(String)