My own implementation of decay, just to be sure it does what I think

decay.cpp

#include <type_traits>
 
template<typename T, typename U>
constexpr bool is_decay_equ = std::is_same_v<std::decay_t<T>, U>;

template<typename T>
struct MyDecay
{
    static auto Helper(T x)
    {
        return x;
    }
    typedef decltype(Helper(std::declval<T>())) type;
    };

template<typename T, typename U>
constexpr bool my_decay_equ = std::is_same_v<typename MyDecay<T>::type, U>;

int main()
{
    static_assert
    (
        is_decay_equ<int, int> &&
        ! is_decay_equ<int, float> &&
        is_decay_equ<int&, int> &&
        is_decay_equ<int&&, int> &&
        is_decay_equ<const int&, int> &&
        is_decay_equ<int[2], int*> &&
        ! is_decay_equ<int[4][2], int*> &&
        ! is_decay_equ<int[4][2], int**> &&
        is_decay_equ<int[4][2], int(*)[2]> &&
        is_decay_equ<int(int), int(*)(int)>
    );
    static_assert
    (
        my_decay_equ<int, int> &&
        ! my_decay_equ<int, float> &&
        my_decay_equ<int&, int> &&
        my_decay_equ<int&&, int> &&
        my_decay_equ<const int&, int> &&
        my_decay_equ<int[2], int*> &&
        ! my_decay_equ<int[4][2], int*> &&
        ! my_decay_equ<int[4][2], int**> &&
        my_decay_equ<int[4][2], int(*)[2]> &&
        my_decay_equ<int(int), int(*)(int)>
    );
}