From fb14ae86f5637ea51c349fe2f7fcf9b8c6fa1a5a Mon Sep 17 00:00:00 2001
From: Ben Adams <thundercat@illyriad.co.uk>
Date: Mon, 3 Feb 2020 04:18:06 +0000
Subject: [PATCH] Skip EqualityComparer<TKey>.Default creation in Dictionary
 .ctor (#31629)

* Skip EqualityComparer<TKey>.Default creation in Ditctionary .ctor

* Update src/libraries/System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs

Co-Authored-By: Stephen Toub <stoub@microsoft.com>
---
 .../System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs b/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs
index 8ed75d5..05afb1b 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs
@@ -79,7 +79,7 @@ namespace System.Collections.Generic
         {
             if (capacity < 0) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity);
             if (capacity > 0) Initialize(capacity);
-            if (comparer != EqualityComparer<TKey>.Default)
+            if (comparer != null && comparer != EqualityComparer<TKey>.Default) // first check for null to avoid forcing default comparer instantiation unnecessarily
             {
                 _comparer = comparer;
             }
-- 
2.7.4