I have a template class that takes std::variant as a template parameter:

template<class T>
class X
{
};

X<std::variant<int, float>> x;

I want to add a constraint for T to be derived from std::variant.
Then I want to extract template parameters of this variant to use them inside the class.
Like this:

template<class T, std::enable_if_t<
    std::is_base_of_v<std::variant<T::_Types>, T>, // _Types = int, float
bool> = true>
class X
{
    std::tuple<T::_Types> t; // std::tuple<int, float>
};

X<std::variant<int, float>> x;

The problem is that I cannot get these int, float parameters from the variant type.
Is there a way to do this in C++17?

This variant comes from return type of a function.
Because of this I cannot change it for something like variant parameters instead (to take int, float directly).