Solved the specialized method definition case with a new version of

MemberDefiniton that works without user upcasts.

ICSharpCode.NRefactory/TypeSystem/Implementation/SpecializedMethod.cs

@@ -200,9 +200,10 @@ namespace ICSharpCode.NRefactory.TypeSystem.Implementation
 			}
 		}
 
-		public IMethod GetDefinition ()
+		public new IMethod MemberDefinition {
-		{
+			get {
-			return methodDefinition;
+				return (IMethod)base.MemberDefinition; 
+			}
 		}
 
 		public override string ToString()