meta_hell.cpp

#include<iostream>
#include<type_traits>

template<typename T1, typename T2>
struct First {};

template<typename T1, typename T2>
struct Second {};

template <typename T1, typename T2>
struct IsHell : std::false_type {};

template <typename T1, typename T2, typename T3>
struct IsHell<First<T1, T2>, Second<T2, T3>> : std::true_type {};

int main() {
    std::cout << std::boolalpha;
    std::cout << IsHell<First<int, double>, Second<double, int>>::value << std::endl;
    std::cout << IsHell<First<int, double>, Second<long, int>>::value << std::endl;
    std::cout << IsHell<Second<long, int>, First<int, double>>::value << std::endl;
    std::cout << IsHell<int, int>::value << std::endl;
}

true
false
false
false