namespace std {
    enum hash_traits_result {
        always_true,
        always_false,
        runtime
    };
    template<typename T> struct hash_traits {
        template<typename A, typename B> struct heterogenous {
            static constexpr hash_traits_result result = always_false;
        };
    };
    template<> struct hash_traits<std::hash<>> {
        template<typename A, typename B> struct heterogenous;
    };
    template<typename T> struct hash_traits<std::hash<>>::heterogenous<std::unique_ptr<T>, T*> {
        static constexpr hash_traits_result result = always_true;
    };
}
struct mah_hasher {
    bool do_the_right_thing;
};
template<> struct hash_traits<mah_hasher>::heterogenous<X, Y> {
    static constexpr hash_traits_result result = runtime;
    bool operator()(const mah_hasher& ref) {
        return ref.do_the_right_thing;
    }
};