std::variant 'attempting to reference a deleted function' - c++

Question

When trying to compile I get the error: Error C2280 'std::variant<Tree::Position<int>,Tree::Position<std::string>,Tree::Position<double>,Tree::Position<bool>>::variant(const std::variant<Tree::Position<int>,Tree::Position<std::string>,Tree::Position<double>,Tree::Position<bool>> &)': attempting to reference a deleted function
I have a Tree class with a template sub-class Position. When using the load function of the Tree class, an instance of the Position class is added to the Tree's treePositionList. Also in the constructor function of the Position class an instance of the Position class is added to its childenList. I think the problem is related to the adding of an instance to those lists, though I do not understand what goes wrong exactly.
template <typename E>
class Node {
private:
string column;
E element;
public:
Node(E el, string col) { element = el; column = col;}
};
class Tree {
public:
template <typename E>
class Position {
private:
typedef variant<Position<int>, Position<string>, Position<double>, Position<bool>> Position_ManyTypes;
typedef list<Position_ManyTypes> PositionList;
Node<E>* node;
PositionList childrenList;
public:
Position(Tree* tree, const E element, const string column, const Json::Value &children);
Position(Position<E>& position);
~Position();
Position<E>& operator=(const Position<E> &position);
friend class Tree;
};
typedef variant<Position<int>, Position<string>, Position<double>, Position<bool>> Position_ManyTypes;
typedef list<Position_ManyTypes> PositionList;
Tree() {}
bool load(string filename);
private:
PositionList treePositionList;
};
bool Tree::load(string filename) {
ifstream rules_file(filename, ifstream::in);
Json::Value rules;
rules_file >> rules;
rules_file.close();
Position<string> root_position = Position<string>(this, "string123", "string456", rules["children"]);
treePositionList.push_back(root_position);
return true;
}
template <typename E>
Tree::Position<E>::Position(Tree::Position<E>& position) {
node = position.node;
childrenList = position.childrenList;
}
template <typename E>
Tree::Position<E>& Tree::Position<E>::operator=(const Tree::Position<E>& position) {
if (this != &position) {
delete node;
node = position.node;
childrenList = position.childrenList;
}
return *this;
}
template <typename E>
Tree::Position<E>::~Position() {
delete node;
}
template <typename E>
Tree::Position<E>::Position(Tree* tree, const E el, const string col, const Json::Value &children) {
node = new Node<E>(el, col);
Position<string> pos = Position<string>(tree, "string123", "string456", children[0]["children"]);
childrenList.push_back(pos);
}