Illformed test case for clang crash

Illformed.cpp

template <bool v>
struct __bool_constant {
  static constexpr bool value = v;
};

__bool_constant<true>;

template <int>
struct conditional {};

template <typename B> struct __and_ : conditional<B::value> {
  static constexpr bool value = true;
};

template <typename A>
using _Requires = __and_<A>::value;

template <typename _Tp, typename... _Args>
struct __is_constructible_impl : __bool_constant<__is_constructible(_Tp, _Args...)> {};

template <typename> struct Meta;

template <typename _Tp> struct optional {
  template <typename _Up, _Requires<__is_constructible_impl<_Tp, _Up>> = true> optional(_Up);
  namespace d {
    struct MoveOnly {};
    struct S : MoveOnly {};
    struct TryBase {
      TryBase(optional<S>);
    };
    class Try : TryBase, MoveOnly {
      using TryBase::TryBase;
    };
  }
};

template <typename T, bool = false>
struct MPMCQueue : MPMCQueueBase<MPMCQueue<T>> {
  namespace c {
    template <template <typename, bool>
              class Derived,
              typename T>
    struct MPMCQueueBase<Derived<T, false>> {
      static_assert(__is_constructible_impl<T, T>::value);
    };
    MPMCQueue<d::Try> queue_;
  }
};