From a59453d4b73376693cdaf8e5d0f081bc216de1c0 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 22 Apr 2020 11:52:26 +0200
Subject: [PATCH] AK: Tweak exchange() implementation

Make it constexpr and do perfect forwarding.
---
 AK/StdLibExtras.h | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/AK/StdLibExtras.h b/AK/StdLibExtras.h
index 5a714fee2f..0d95585aa0 100644
--- a/AK/StdLibExtras.h
+++ b/AK/StdLibExtras.h
@@ -81,14 +81,6 @@ inline T&& move(T& arg)
 #    pragma clang diagnostic pop
 #endif
 
-template<typename T, typename U>
-inline T exchange(T& a, U&& b)
-{
-    T tmp = move(a);
-    a = move(b);
-    return tmp;
-}
-
 template<typename T, typename U>
 inline void swap(T& a, U& b)
 {
@@ -370,6 +362,14 @@ struct MakeUnsigned<unsigned long long> {
     typedef unsigned long long type;
 };
 
+template<typename T, typename U = T>
+inline constexpr T exchange(T& slot, U&& value)
+{
+    T old_value = move(slot);
+    slot = forward<U>(value);
+    return old_value;
+}
+
 }
 
 using AK::ceil_div;