Consider having a simple class, that writes integers to cout depending on its state:

#include <iostream>

class NotAWriter{
public:
    NotAWriter& operator<<(const int& arg) {
        if (on) std::cout << arg;
        return *this;
    }
    void toggle() {on=!on;}
private:
    bool on = false;
};

Consider now I have a COMPILE-TIME constant number of toggles (i.e. calls to NotAWriter.toggle()).

I want a program to choose whether to print or not depending on the variable on in compile-time, something like this:

NotAWriter& operator<<(const int& arg) {
    if constexpr (on) std::cout << arg;
    return *this;
}

or this

std::enable_if<on, NotAWriter&> operator<<(const int& arg) {
    std::cout << arg;
    return *this;
}
std::enable_if<!on, NotAWriter&> operator<<(const int& arg) {return *this;}

However the usage of this in constant expressions is prohibited:

error: use of ‘this’ in a constant expression
  |      if constexpr (on) std::cout << arg;
  |      ^~

Is there a way to do this (choose overload or if-branch) depending on a member-variable at compile-time? If I sure the number of variable changes is compile-time constant, of course.