Thanks for implementing this LWG issue resolution! 😺

I pushed a small change for consistency, although it wasn't a correctness issue. We have machinery (used by allocator_traits via _Normal_allocator_traits) that inspects user-defined allocators to detect whether they provide pointer etc. typedefs and member functions. Because it's possible for user-defined allocators to derive from std::allocator, it would be undesirable if this detection machinery warned about using the old std::allocator members, when they weren't being directly mentioned by the user. Therefore, we suppress the deprecation warnings around the detection machinery. I added such suppression around _Get_is_always_equal for consistency. This wasn't actually leading to any warnings, because we also have suppression around _Normal_allocator_traits:

I manually tested this with:

#include <memory>
#include <type_traits>
using namespace std;

template <typename T>
struct UserAlloc : allocator<T> {
    UserAlloc()                 = default;
    UserAlloc(const UserAlloc&) = default;
    template <typename U>
    UserAlloc(const UserAlloc<U>&) {}

    template <typename U>
    struct rebind {
        using other = UserAlloc<U>;
    };
};

int main() {
#ifdef ACCESS_DIRECTLY
    static_assert(is_same_v<UserAlloc<int>::is_always_equal, true_type>);
#endif

    static_assert(is_same_v<allocator_traits<UserAlloc<int>>::is_always_equal, true_type>);
}

Finally, as an exception to our using convention, we used typedef when deprecating, due to an EDG bug that was fixed long ago. I think that's no longer a problem (and the tests are passing), so applying the attribute to using here is reasonable. If this causes problems for our ancient CUDA 9.2 coverage in our internal test harness, I'll push a change, but let's see if it works.

Thanks for implementing another LWG issue resolution and encouraging users to modernize their code! 🎉