aggregate TMap into Dictionary instead of deriving from it

src/serializer.cpp

@@ -2165,7 +2165,7 @@ template<> FSerializer &Serialize(FSerializer &arc, const char *key, FFont *&fon
 FString DictionaryToString(const Dictionary &dict)
 {
 	Dictionary::ConstPair *pair;
-	Dictionary::ConstIterator i { dict };
+	Dictionary::ConstIterator i { dict.Map };
 
 	rapidjson::StringBuffer buffer;
 	rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
@@ -2214,7 +2214,7 @@ Dictionary *DictionaryFromString(const FString &string)
 			return dict;
 		}
 
-		dict->Insert(i->name.GetString(), i->value.GetString());
+		dict->Map.Insert(i->name.GetString(), i->value.GetString());
 	}
 
 	return dict;

src/utility/dictionary.cpp

@@ -42,7 +42,7 @@ void Dictionary::Serialize(FSerializer &arc)
 		// Receive new Dictionary, copy contents, clean up.
 		Dictionary *pointerToDeserializedDictionary;
 		arc(key, pointerToDeserializedDictionary);
-		TransferFrom(*pointerToDeserializedDictionary);
+		Map.TransferFrom(pointerToDeserializedDictionary->Map);
 		delete pointerToDeserializedDictionary;
 	}
 }
@@ -56,12 +56,12 @@ static Dictionary *DictCreate()
 
 static void DictInsert(Dictionary *dict, const FString &key, const FString &value)
 {
-	dict->Insert(key, value);
+	dict->Map.Insert(key, value);
 }
 
 static void DictAt(const Dictionary *dict, const FString &key, FString *result)
 {
-	const FString *value = dict->CheckKey(key);
+	const FString *value = dict->Map.CheckKey(key);
 	*result = value ? *value : "";
 }
 
@@ -72,7 +72,7 @@ static void DictToString(const Dictionary *dict, FString *result)
 
 static void DictRemove(Dictionary *dict, const FString &key)
 {
-	dict->Remove(key);
+	dict->Map.Remove(key);
 }
 
 //=====================================================================================
@@ -150,7 +150,7 @@ void DictionaryIterator::Serialize(FSerializer &arc)
 
 void DictionaryIterator::init(Dictionary *dict)
 {
-	Iterator = std::make_unique<Dictionary::ConstIterator>(*dict);
+	Iterator = std::make_unique<Dictionary::ConstIterator>(dict->Map);
 	Dict = dict;
 
 	GC::WriteBarrier(this, Dict);

src/utility/dictionary.h

@@ -13,13 +13,19 @@
  *
  * It is derived from DObject to be a part of normal GC process.
  */
-class Dictionary final : public DObject, public TMap<FString, FString>
+class Dictionary final : public DObject
 {
 	DECLARE_CLASS(Dictionary, DObject)
 
 public:
 
+	using StringMap = TMap<FString, FString>;
+	using ConstIterator = StringMap::ConstIterator;
+	using ConstPair = StringMap::ConstPair;
+
 	void Serialize(FSerializer &arc) override;
+
+	StringMap Map;
 };
 
 /**