Prevented a key already exists exception (but it's not a real fix for

the problem).

ICSharpCode.NRefactory.CSharp/TypeSystem/CSharpAssembly.cs

@@ -187,6 +187,9 @@ namespace ICSharpCode.NRefactory.CSharp.TypeSystem
 					}
 					typeDef = new DefaultResolvedTypeDefinition(new SimpleTypeResolveContext(parentType), parts.ToArray());
 					foreach (var part in parts) {
+						// TODO: Fix that hack !
+						if (nestedTypeDict.ContainsKey (part))
+							continue;
 						nestedTypeDict.Add(part, typeDef);
 					}
 					return typeDef;