为何下程序运行不了

#include<iostream>
#include<unordered_map>
#include<windows.h>
using std::string;
using std::cout;
class Object {
	private:
		void *arg;
	public:
		Object& operator=(Object a) {
			arg=a.arg;
			return *this;
		}
		template<typename t>
		Object& operator=(t a) {
			free(arg);
			arg=new t(a);
			return *this;
		}
		template<typename t>
		operator t() {
			return *static_cast<t*>(arg);
		}
		Object() : arg(NULL) {}
};
int main() {
	Object a;
	a = "4";
	cout << (string)a;
	return 0;
}

将其中赋值语句改为整数,类型转换改为int就能运行..