Redesigned JsonVariant to leverage converting constructors instead of assignment operators

include/ArduinoJson/Internals/List.hpp

@@ -39,7 +39,7 @@ class List {
 
   // Returns the numbers of elements in the list.
   // For a JsonObject, it would return the number of key-value pairs
-  int size() const;
+  size_t size() const;
 
   iterator begin() { return iterator(_firstNode); }
   iterator end() { return iterator(NULL); }
@@ -48,19 +48,20 @@ class List {
   const_iterator end() const { return const_iterator(NULL); }
 
  protected:
-  node_type *createNode() {
+  node_type *addNewNode() {
     if (!_buffer) return NULL;
-    return new (_buffer) node_type();
-  }
 
-  void addNode(node_type *nodeToAdd) {
+    node_type *newNode = new (_buffer) node_type();
+
     if (_firstNode) {
       node_type *lastNode = _firstNode;
       while (lastNode->next) lastNode = lastNode->next;
-      lastNode->next = nodeToAdd;
+      lastNode->next = newNode;
     } else {
-      _firstNode = nodeToAdd;
+      _firstNode = newNode;
     }
+
+    return newNode;
   }
 
   void removeNode(node_type *nodeToRemove);