FilterImpl

template <template <typename Arg> class P, TypeList TL>
    struct FilterImpl{
        using Ret = Nil;
    };

    template <template <typename> class P, TypeSequence TS>
    struct FilterImpl<P, TS> {
    private:
        template <typename T>
        using NotP = ApplyLogicNotToValue<P<T>>;

        using Skipped = typename Impl::SkipWhileImpl<NotP, TS>::Ret;  // Skip all args for which P is false.

        template <TypeList TL_>
        struct AfterSkip;

        template <TypeSequence TS_>
        struct AfterSkip<TS_> {
            using Head = typename TS_::Head;
            using Tail = typename FilterImpl<P, typename TS_::Tail>::Ret;
        };

        template <Empty TE>
        struct AfterSkip<TE> : Nil {};
    public:
        using Ret = AfterSkip<Skipped>;
    };