The code compiles and runs, but I’m trying to understand how the expression (obj.*funcPtr)(12) can be evaluated at compile-time when obj is not declared as constexpr. I would expect that this might not meet the standard requirements for compile-time evaluation.

#include <iostream>
#include <stdexcept>

template <typename T, size_t N>
class Array
{
public:

    T& operator[](size_t i)
    {
        if (i>=N)
        {
            throw std::out_of_range("Bd index!");
        }
        return data_[i];
    }
    constexpr size_t Size() const
    {
        return N;
    }

private:
    T data_[N]{};
};



class MyClass
{
public:
   constexpr int myFunction(int value)
    {
        return value*2;
    }
};

int main()
{

   constexpr int (MyClass::*funcPtr)(int) = &MyClass::myFunction;
   MyClass obj;
   Array<int ,  (obj.*funcPtr)(12) > arr;
   std::cout << arr.Size() << 'n';

}