From 62c968fec22e1de53979952e17497477f3d04713 Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Fri, 16 Nov 2012 13:57:23 +0100
Subject: [PATCH] Fix unambiguous check between async Task and Task<T>. Fixes
 #8414

---
 mcs/mcs/ecore.cs             |  6 +----
 mcs/tests/test-async-41.cs   | 30 ++++++++++++++++++++++++
 mcs/tests/ver-il-net_4_5.xml | 44 ++++++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+), 5 deletions(-)
 create mode 100644 mcs/tests/test-async-41.cs

diff --git a/mcs/mcs/ecore.cs b/mcs/mcs/ecore.cs
index 5f523e4bc7f..745e4224946 100644
--- a/mcs/mcs/ecore.cs
+++ b/mcs/mcs/ecore.cs
@@ -3822,11 +3822,7 @@ namespace Mono.CSharp {
 				// better conversion is performed between underlying types Y1 and Y2
 				//
 				if (p.IsGenericTask || q.IsGenericTask) {
-					if (am.Block.IsAsync) {
-						if (p.IsGenericTask != q.IsGenericTask) {
-							return 0;
-						}
-
+					if (am.Block.IsAsync && p.IsGenericTask && q.IsGenericTask) {
 						q = q.TypeArguments[0];
 						p = p.TypeArguments[0];
 					}
diff --git a/mcs/tests/test-async-41.cs b/mcs/tests/test-async-41.cs
new file mode 100644
index 00000000000..0e8c0fa1e95
--- /dev/null
+++ b/mcs/tests/test-async-41.cs
@@ -0,0 +1,30 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+public class AmbiguousGeneric
+{
+	public async void NestedVoidTestSuccess ()
+	{
+		await Run2 (async () => await ReturnOne ());
+	}
+
+	static Task<int> ReturnOne ()
+	{
+		return Task.Run (() => 1);
+	}
+
+	Task Run2 (Func<Task> arg)
+	{
+		return null;
+	}
+
+	Task Run2<T> (Func<T> arg)
+	{
+		return null;
+	}
+
+	public static void Main ()
+	{
+	}
+}
\ No newline at end of file
diff --git a/mcs/tests/ver-il-net_4_5.xml b/mcs/tests/ver-il-net_4_5.xml
index 812a1ac6cb0..cc0f40db316 100644
--- a/mcs/tests/ver-il-net_4_5.xml
+++ b/mcs/tests/ver-il-net_4_5.xml
@@ -57070,6 +57070,50 @@
       </method>
     </type>
   </test>
+  <test name="test-async-41.cs">
+    <type name="AmbiguousGeneric">
+      <method name="Void NestedVoidTestSuccess()" attrs="134">
+        <size>35</size>
+      </method>
+      <method name="System.Threading.Tasks.Task`1[System.Int32] ReturnOne()" attrs="145">
+        <size>43</size>
+      </method>
+      <method name="System.Threading.Tasks.Task Run2(System.Func`1[System.Threading.Tasks.Task])" attrs="129">
+        <size>10</size>
+      </method>
+      <method name="System.Threading.Tasks.Task Run2[T](System.Func`1[T])" attrs="129">
+        <size>10</size>
+      </method>
+      <method name="Void Main()" attrs="150">
+        <size>2</size>
+      </method>
+      <method name="Int32 &lt;ReturnOne&gt;m__0()" attrs="145">
+        <size>9</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+    <type name="AmbiguousGeneric+&lt;NestedVoidTestSuccess&gt;c__async0">
+      <method name="Void MoveNext()" attrs="486">
+        <size>191</size>
+      </method>
+      <method name="Void SetStateMachine(IAsyncStateMachine)" attrs="486">
+        <size>13</size>
+      </method>
+      <method name="System.Threading.Tasks.Task`1[System.Int32] &lt;&gt;m__1()" attrs="145">
+        <size>33</size>
+      </method>
+    </type>
+    <type name="AmbiguousGeneric+&lt;NestedVoidTestSuccess&gt;c__async0+&lt;NestedVoidTestSuccess&gt;c__async4">
+      <method name="Void MoveNext()" attrs="486">
+        <size>162</size>
+      </method>
+      <method name="Void SetStateMachine(IAsyncStateMachine)" attrs="486">
+        <size>13</size>
+      </method>
+    </type>
+  </test>
   <test name="test-cls-00.cs">
     <type name="CLSCLass_6">
       <method name="Void add_Disposed(Delegate)" attrs="2182">
-- 
2.25.1