[mono/mono] f33bd8ad: Adds async type inference of void return type. Fixes #15238

   Branch: refs/heads/master
     Home: https://github.com/mono/mono
  Compare: https://github.com/mono/mono/compare/cf2ac2171b7d...f33bd8ad7fe9

   Commit: f33bd8ad7fe9470b1fae626b4e425a632a0963ca
   Author: Marek Safar <[email protected]> (marek-safar)
     Date: 2013-10-08 17:30:32 GMT
      URL: https://github.com/mono/mono/commit/f33bd8ad7fe9470b1fae626b4e425a632a0963ca

Adds async type inference of void return type. Fixes #15238

Changed paths:
  M mcs/mcs/anonymous.cs
  M mcs/mcs/generic.cs
  M mcs/mcs/statement.cs
  M mcs/tests/ver-il-net_4_5.xml
Added paths:
  A mcs/tests/test-async-52.cs

Modified: mcs/mcs/anonymous.cs
===================================================================
@@ -1535,10 +1535,14 @@ public AnonymousExpression Compatible (ResolveContext ec, AnonymousExpression ae
 
 				//
 				// If e is synchronous the inferred return type is T
-				// If e is asynchronous the inferred return type is Task<T>
+				// If e is asynchronous and the body of F is either an expression classified as nothing
+				// or a statement block where no return statements have expressions, the inferred return type is Task
+				// If e is async and has an inferred result type T, the inferred return type is Task<T>
 				//
 				if (block.IsAsync && ReturnType != null) {
-					ReturnType = ec.Module.PredefinedTypes.TaskGeneric.TypeSpec.MakeGenericType (ec, new [] { ReturnType });
+					ReturnType = ReturnType.Kind == MemberKind.Void ?
+						ec.Module.PredefinedTypes.Task.TypeSpec :
+						ec.Module.PredefinedTypes.TaskGeneric.TypeSpec.MakeGenericType (ec, new [] { ReturnType });
 				}
 			}
 

Modified: mcs/mcs/generic.cs
===================================================================
@@ -2948,15 +2948,20 @@ public TypeInferenceContext ()
 
 		public void AddCommonTypeBound (TypeSpec type)
 		{
-			AddToBounds (new BoundInfo (type, BoundKind.Lower), 0);
+			AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, false);
 		}
 
-		void AddToBounds (BoundInfo bound, int index)
+		public void AddCommonTypeBoundAsync (TypeSpec type)
+		{
+			AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, true);
+		}
+
+		void AddToBounds (BoundInfo bound, int index, bool voidAllowed)
 		{
 			//
 			// Some types cannot be used as type arguments
 			//
-			if (bound.Type.Kind == MemberKind.Void || bound.Type.IsPointer || bound.Type.IsSpecialRuntimeType ||
+			if ((bound.Type.Kind == MemberKind.Void && !voidAllowed) || bound.Type.IsPointer || bound.Type.IsSpecialRuntimeType ||
 				bound.Type == InternalType.MethodGroup || bound.Type == InternalType.AnonymousMethod)
 				return;
 
@@ -3030,7 +3035,7 @@ public int ExactInference (TypeSpec u, TypeSpec v)
 			if (pos == -1)
 				return 0;
 
-			AddToBounds (new BoundInfo (u, BoundKind.Exact), pos);
+			AddToBounds (new BoundInfo (u, BoundKind.Exact), pos, false);
 			return 1;
 		}
 
@@ -3361,7 +3366,7 @@ int LowerBoundInference (TypeSpec u, TypeSpec v, bool inversed)
 			// If V is one of the unfixed type arguments
 			int pos = IsUnfixed (v);
 			if (pos != -1) {
-				AddToBounds (new BoundInfo (u, inversed ? BoundKind.Upper : BoundKind.Lower), pos);
+				AddToBounds (new BoundInfo (u, inversed ? BoundKind.Upper : BoundKind.Lower), pos, false);
 				return 1;
 			}			
 

Modified: mcs/mcs/statement.cs
===================================================================
@@ -902,7 +902,7 @@ protected override bool DoResolve (BlockContext ec)
 						var async_type = storey.ReturnType;
 
 						if (async_type == null && async_block.ReturnTypeInference != null) {
-							async_block.ReturnTypeInference.AddCommonTypeBound (expr.Type);
+							async_block.ReturnTypeInference.AddCommonTypeBoundAsync (expr.Type);
 							return true;
 						}
 

Added: mcs/tests/test-async-52.cs
===================================================================
@@ -0,0 +1,23 @@
+using System;
+using System.Threading.Tasks;
+
+public delegate T ActualValueDelegate<T> ();
+
+class X
+{
+	public static void Main ()
+	{
+		Matches (async () => await Throw());
+	}
+
+	static bool Matches<T>(ActualValueDelegate<T> del) where T : Task
+	{
+		del ().Wait ();
+		return true;
+	}
+
+	static async Task Throw()
+	{
+		await Task.Delay (1);
+	}
+}
\ No newline at end of file

Modified: mcs/tests/ver-il-net_4_5.xml
===================================================================
@@ -59671,6 +59671,55 @@
       </method>
     </type>
   </test>
+  <test name="test-async-52.cs">
+    <type name="ActualValueDelegate`1[T]">
+      <method name="T Invoke()" attrs="454">
+        <size>0</size>
+      </method>
+      <method name="IAsyncResult BeginInvoke(System.AsyncCallback, System.Object)" attrs="454">
+        <size>0</size>
+      </method>
+      <method name="T EndInvoke(IAsyncResult)" attrs="454">
+        <size>0</size>
+      </method>
+      <method name="Void .ctor(Object, IntPtr)" attrs="6278">
+        <size>0</size>
+      </method>
+    </type>
+    <type name="X">
+      <method name="Void Main()" attrs="150">
+        <size>37</size>
+      </method>
+      <method name="Boolean Matches[T](ActualValueDelegate`1[T])" attrs="145">
+        <size>30</size>
+      </method>
+      <method name="System.Threading.Tasks.Task Throw()" attrs="145">
+        <size>33</size>
+      </method>
+      <method name="System.Threading.Tasks.Task &lt;Main&gt;m__0()" attrs="145">
+        <size>33</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+    <type name="X+&lt;Throw&gt;c__async0">
+      <method name="Void MoveNext()" attrs="486">
+        <size>157</size>
+      </method>
+      <method name="Void SetStateMachine(IAsyncStateMachine)" attrs="486">
+        <size>13</size>
+      </method>
+    </type>
+    <type name="X+&lt;Main&gt;c__async3">
+      <method name="Void MoveNext()" attrs="486">
+        <size>160</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">



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