From 2d189dc93c8af9c941b316a829b68b8ab3fbce10 Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Tue, 22 Nov 2016 17:01:15 +0100
Subject: [PATCH] [mcs] Null coalescing over typed null constants.

---
 mcs/mcs/nullable.cs          | 2 +-
 mcs/tests/gtest-621.cs       | 6 ++++++
 mcs/tests/ver-il-net_4_x.xml | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/mcs/mcs/nullable.cs b/mcs/mcs/nullable.cs
index cce1f8419ce..93314df322a 100644
--- a/mcs/mcs/nullable.cs
+++ b/mcs/mcs/nullable.cs
@@ -1210,7 +1210,7 @@ namespace Mono.CSharp.Nullable
 						//
 						// Special case null ?? null
 						//
-						if (right.IsNull && ltype == right.Type)
+						if (right is NullLiteral && ltype == right.Type)
 							return null;
 
 						return ReducedExpression.Create (lc != null ? right : left, this, false);
diff --git a/mcs/tests/gtest-621.cs b/mcs/tests/gtest-621.cs
index cfff301328e..6444cb7918e 100644
--- a/mcs/tests/gtest-621.cs
+++ b/mcs/tests/gtest-621.cs
@@ -26,4 +26,10 @@ class X
 			
 		return 0;
 	}
+
+	const Action cf = null;
+	void Foo (Action f)
+	{
+		var x = f ?? cf;
+	}
 }
\ No newline at end of file
diff --git a/mcs/tests/ver-il-net_4_x.xml b/mcs/tests/ver-il-net_4_x.xml
index ddb13732d04..4502b9b63be 100644
--- a/mcs/tests/ver-il-net_4_x.xml
+++ b/mcs/tests/ver-il-net_4_x.xml
@@ -19564,6 +19564,9 @@
       <method name="Void .ctor()" attrs="6278">
         <size>7</size>
       </method>
+      <method name="Void Foo(System.Action)" attrs="129">
+        <size>4</size>
+      </method>
     </type>
   </test>
   <test name="gtest-622.cs">
-- 
2.25.1