[bcl] Allow conversion from enums and their basetypes in both directions with Delegate.CreateDelegate (). Fixes mono#6255. (case 977917)

Author: vargaz

mcs/class/corlib/System/Delegate.cs

@@ -134,6 +134,8 @@ private static bool arg_type_match (Type delArgType, Type argType) {
 			if (!match) {
 				if (delArgType.IsEnum && Enum.GetUnderlyingType (delArgType) == argType)
 					match = true;
+				else if (argType.IsEnum && Enum.GetUnderlyingType (argType) == delArgType)
+					match = true;
 			}
 
 			return match;

mcs/class/corlib/Test/System/DelegateTest.cs

@@ -1395,6 +1395,23 @@ public void EnumBaseTypeConversion () {
 			Assert.IsTrue (d (0, 0));
 		}
 
+		[Test]
+		public void EnumBaseTypeConversion2 () {
+			Func<Enum22, int> dm = EnumArg;
+			var d = (Func<int, int>)Delegate.CreateDelegate (typeof (Func<int, int>), dm.Method);
+			Assert.AreEqual (1, d (1));
+		}
+
+		public enum Enum22 {
+			none,
+			one,
+			two
+		}
+
+		public static int EnumArg (Enum22 e) {
+			return (int)e;
+		}
+
 #if !MONOTOUCH && !FULL_AOT_RUNTIME
 		public static void DynInvokeWithClosedFirstArg (object a, object b)
 		{