The following compiles on trunk:

    struct NonMovable {
      NonMovable() = default;
      NonMovable(NonMovable&&) = delete;
    };

    static_assert( __reference_converts_from_temporary(int&&, int));
    static_assert(!__reference_converts_from_temporary(NonMovable&&, NonMovable));
    static_assert( __reference_constructs_from_temporary(int&&, int));
    static_assert(!__reference_constructs_from_temporary(NonMovable&&, NonMovable));

When the NonMovable assertions should fail because there *is* a temporary being bound to a reference (in exactly the same way as the int case).

We can observe it instantiating constructors that shouldn't be too:

    template<typename T>
    struct S {
      template<typename U = T>
      S(const S&&) noexcept(U()) {}
    };

    static_assert(__reference_converts_from_temporary(const S<bool>&&, const S<bool>));
    static_assert(__reference_converts_from_temporary(const S<void*>&&, const S<void*>));

Which complains about a conversion from void* to bool even though constructors shouldn't be looked at.