[indirect.obs]

constexpr const T& operator*() const & noexcept;
constexpr T& operator*() & noexcept;

Returns: *p.

constexpr const T&& operator*() const && noexcept;
constexpr T&& operator*() && noexcept;

Returns: std::move(*p).

constexpr const_pointer operator->() const noexcept;
constexpr pointer operator->() noexcept;

Returns: p.

constexpr bool valueless_after_move() const noexcept;

Returns: true if *this is valueless, otherwise false.

constexpr allocator_type get_allocator() const noexcept;

Returns: alloc.

20 Memory management library [mem]