Make sure Hana avoids undesirable instantiations because of ADL.

no_adl.cpp

template <typename ...T>
struct _tuple_t {
    struct _;
};

template <typename ...T>
struct _tuple_t<T...>::_
    : _tuple_t<T...>
{ };

template <typename ...T>
using tuple_t = typename _tuple_t<T...>::_;

template <bool b = false>
struct invalid { static_assert(b, "invalid must not be instantiated"); };

template <typename T> void adl(T) { }
template <typename ...T> void adl_pattern(_tuple_t<T...>) { }

int main() {
    adl(tuple_t<invalid<>>{});
    adl_pattern(tuple_t<invalid<>>{});
}