Casting enum to int in a template parameter

Question

I have defined a custom enum for convenience over a particular class, and it is now getting in the way for getting it processed by more general processes.

How should I perform this typecast?

// A templated value holder:
template <typename T>
struct Holder {
    T _value;
};

// A more general process..
template <typename T>
struct General {
    Holder<T> *holder;
};
// ..over integral types:
struct IntGeneral : General<int> {};
// Here is something interesting: I can tell that this process will work on
// any enum type. But I've found no way to make this explicit.

// Convenience for a particular case
typedef enum {One, Two, Three} Enum;
typedef Holder<Enum> Particular;


int main() { 

    Particular* a( new Particular { One } );
    IntGeneral ig { static_cast<Holder<int>*>(a) }; // compiler grumbles

    return EXIT_SUCCESS;
}

This is what I get:

error: invalid static_cast from type ‘Particular* {aka Holder<Enum>*}’ to type ‘Holder<int>*’

Is there a way I can keep the convenient Enum and get this code compiled?

---

EDIT: This turned out to be an XY problem. An answer to Y has been accepted here, and several discussed. X has been moved to another question.

Answer 1

Is it sufficient to replace:

IntGeneral ig { static_cast<Holder<int>*>(a) }; // compiler grumbles

With:

IntGeneral ig { new Holder<int>{a->_value} };

Since it is a struct, you can access the value. Personally I would use getters and setter, but as presented, that should do what you want.

Alternately

You could replace:

typedef Holder<Enum> Particular;

With:

typedef Holder<int> Particular;

Since the int can hold the Enum