static constexpr auto apply(Xs xs, X x) { return lazy_cons(x, hana::make_lazy(xs)); }
static constexpr auto apply(Xs xs, X x) { return lazy_cons(x, lazy(xs)); }
static constexpr auto apply(Xs xs, X x) { return lazy_cons(x, hana::make_lazy(xs)); }
static constexpr auto apply(Xs xs, X x) { return lazy_cons(x, lazy(xs)); }