C++의 템플릿으로 일반화된 Stack 자료구조를 구현하는데 컴파일 오류가 있습니다..

#pragma once
 
template <class E>
class Node
{
private:
    E elem; // E& elem
    Node* next;
 
    template <class E>
    friend class Stack;
 
public:
    // Node 생성자 정의 추가
    Node(const E& elem) : elem(elem), next(nullptr) {
 
    }
};
 
 
 
template <class E>
class Stack
{
public:
    Stack();
    ~Stack();
    void push(const E& e);
    void pop();
    const E& top() const;
    const bool empty() const;
    const int size() const;
private:
    Node<E>* head; // Node* head;
    Node<E>* tail; // Node* tail;
    Node<E>* current; // Node* current;
    int capacity;
};
 
template <class E>
Stack<E>::Stack() { // Stack::Stack() {
    head = nullptr;
    tail = nullptr;
    current = nullptr;
    capacity = 0;
}
 
template <class E>
Stack<E>::~Stack() // Stack::~Stack()
{
    if (head != nullptr) {
        current = head->next;
        delete head;
        head = current;
    }
}
 
template <class E>
void Stack<E>::push(const E & e) // void Stack::push(const E & e)
{
    current = new Node<E>(e); // current = new Node;
    current->elem = e;
    current->next = head;
    head = current;
    capacity++;
}
 
template <class E>
void Stack<E>::pop() // void Stack::pop()
{
    if (head != nullptr) {
        current = head->next;
        delete head;
        head = current;
        capacity--;
    }
}
 
template <class E>
const E & Stack<E>::top() const // const E & Stack::top() const
{
    return head->elem;
}
 
template <class E>
const bool Stack<E>::empty() const // const bool Stack::empty() const
{
    if (capacity != 0) return false;
    else return true;
}
 
template <class E>
const int Stack<E>::size() const // const int Stack::size() const
{
    return capacity;
}

#include <iostream>
#include "Stack2.h"
using namespace std;
 
int main2() {
    Stack<int> a; // Stack a;
    a.pop();
    a.push(7);
    cout << "사이즈: " << a.size() << endl;
    a.push(13);
    cout << a.top() << endl;
    a.pop();
    a.push(9);
    cout << a.top() << endl;
    cout << a.top() << endl; a.pop();
    Stack<const char *> B; // Stack B;
    B.push("bob");
    B.push("Alice");
    cout << B.top() << endl; B.pop();
    B.push("Eve");
    return 0;
}