Bad Example Of C++ Cons List

template<class T> class List
{
private:

    enum class CtorType { Empty, Cons };

    union U
    {
        struct Cons { T item; List<T> * next; } cons;
        struct Empty {} empty;
    };

    CtorType type;

    U constructor;

    List(void)
        : type(CtorType::Empty), item(), next(nullptr)
    {}

    List(const T & item, const List<T> & next)
        : type(CtorType::Cons), item(item), next(&next)
    {}

public:

    bool IsEmpty()
    {
        return this->type == CtorType::Empty;
    }

    T Head()
    {
        switch(this->type)
        {
            case CtorType::Ctor: return this->constructor.cons.item;
            default: assert(false, "Attempt to get Head on empty list");
        }
    }

    static List<T> CreateEmpty()
    {
        return List<T>();
    }

    static List<T> CreateCons(const T & item, const List<T> & next)
    {
        return List<T>(item, next);
    }
};