From 15082972b9678df3408fc607551cab2978f1a661 Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Mon, 7 Mar 2016 21:00:08 +0100
Subject: [PATCH] [mcs] Null conditional operator is never suppose to work with
 await according to current C# standard. Fixes #39266

---
 mcs/mcs/async.cs             |  6 ++-
 mcs/tests/test-async-83.cs   | 34 +++++++++++++++++
 mcs/tests/ver-il-net_4_x.xml | 74 ++++++++++++++++++------------------
 3 files changed, 76 insertions(+), 38 deletions(-)
 create mode 100644 mcs/tests/test-async-83.cs

diff --git a/mcs/mcs/async.cs b/mcs/mcs/async.cs
index 22e4c1b4b8c..b3efae32410 100644
--- a/mcs/mcs/async.cs
+++ b/mcs/mcs/async.cs
@@ -349,7 +349,11 @@ namespace Mono.CSharp
 
 			var errors_printer = new SessionReportPrinter ();
 			var old = bc.Report.SetPrinter (errors_printer);
-			ama = new Invocation (ama, args).Resolve (bc);
+
+			//
+			// The expression await t is classified the same way as the expression (t).GetAwaiter().GetResult(). 
+			//
+			ama = new Invocation (new ParenthesizedExpression (ama, Location.Null), args).Resolve (bc);
 			bc.Report.SetPrinter (old);
 
 			if (errors_printer.ErrorsCount > 0 || !MemberAccess.IsValidDotExpression (ama.Type)) {
diff --git a/mcs/tests/test-async-83.cs b/mcs/tests/test-async-83.cs
new file mode 100644
index 00000000000..b12dd20fa74
--- /dev/null
+++ b/mcs/tests/test-async-83.cs
@@ -0,0 +1,34 @@
+using System;
+using System.Threading.Tasks;
+
+class MainClass
+{
+	public static int Main ()
+	{
+		var t = GetSomeStrings (null);
+		try {
+			var s = t.Result;
+			return 1;
+		} catch (AggregateException e) {
+			if (e.InnerException is NullReferenceException)
+				return 0;
+
+			return 2;
+		}
+	}
+
+	public static async Task<string> GetSomeStrings (AsyncStringFactory myFactory)
+	{
+		var res = await myFactory?.GetSomeStringAsync ();
+		return res;
+	}
+}
+
+public class AsyncStringFactory
+{
+	public async Task<string> GetSomeStringAsync ()
+	{
+		await Task.Yield();
+		return "foo";
+	}
+}
\ 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 702908fa939..b3846fd0d97 100644
--- a/mcs/tests/ver-il-net_4_x.xml
+++ b/mcs/tests/ver-il-net_4_x.xml
@@ -62865,43 +62865,6 @@
       </method>
     </type>
   </test>
-  <test name="test-async-19.cs">
-    <type name="C">
-      <method name="Void Test(System.Threading.ManualResetEvent)" attrs="145">
-        <size>35</size>
-      </method>
-      <method name="Int32 Main()" attrs="150">
-        <size>96</size>
-      </method>
-      <method name="Void CurrentDomain_UnhandledException(System.Object, System.UnhandledExceptionEventArgs)" attrs="145">
-        <size>29</size>
-      </method>
-      <method name="Void .ctor()" attrs="6278">
-        <size>7</size>
-      </method>
-      <method name="Void .cctor()" attrs="6289">
-        <size>12</size>
-      </method>
-    </type>
-    <type name="C+&lt;Test&gt;c__async0">
-      <method name="Void MoveNext()" attrs="486">
-        <size>227</size>
-      </method>
-    </type>
-    <type name="C+&lt;Test&gt;c__async0+&lt;Test&gt;c__AnonStorey1">
-      <method name="Void &lt;&gt;m__0()" attrs="131">
-        <size>29</size>
-      </method>
-      <method name="Void .ctor()" attrs="6278">
-        <size>7</size>
-      </method>
-    </type>
-    <type name="C+&lt;Test&gt;c__async0">
-      <method name="Void SetStateMachine(System.Runtime.CompilerServices.IAsyncStateMachine)" attrs="486">
-        <size>13</size>
-      </method>
-    </type>
-  </test>
   <test name="test-async-20.cs">
     <type name="Base">
       <method name="Void .ctor()" attrs="6278">
@@ -65651,6 +65614,43 @@
       </method>
     </type>
   </test>
+  <test name="test-async-83.cs">
+    <type name="MainClass">
+      <method name="Int32 Main()" attrs="150">
+        <size>57</size>
+      </method>
+      <method name="System.Threading.Tasks.Task`1[System.String] GetSomeStrings(AsyncStringFactory)" attrs="150">
+        <size>41</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+    <type name="AsyncStringFactory">
+      <method name="System.Threading.Tasks.Task`1[System.String] GetSomeStringAsync()" attrs="134">
+        <size>33</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+    <type name="MainClass+&lt;GetSomeStrings&gt;c__async0">
+      <method name="Void MoveNext()" attrs="486">
+        <size>191</size>
+      </method>
+      <method name="Void SetStateMachine(System.Runtime.CompilerServices.IAsyncStateMachine)" attrs="486">
+        <size>13</size>
+      </method>
+    </type>
+    <type name="AsyncStringFactory+&lt;GetSomeStringAsync&gt;c__async0">
+      <method name="Void MoveNext()" attrs="486">
+        <size>171</size>
+      </method>
+      <method name="Void SetStateMachine(System.Runtime.CompilerServices.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