beman::optional::optional::operator=

constexpr
optional&
operator=(optional const& other)
requires std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T> &&
                     std::is_trivially_copy_constructible_v<T> && std::is_trivially_copy_assignable_v<T> = default;

constexpr
optional<T>&
operator=(optional const& rhs)
requires std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T> &&
             (!std::is_trivially_copy_assignable_v<T>);

template<class U>
constexpr
optional<T>&
operator=(optional<U> const& rhs)
requires (detail::enable_assign_from_other<T, U, const U&>);

constexpr
optional&
operator=(optional&& other)
requires std::is_move_constructible_v<T> && std::is_move_assignable_v<T> &&
                     std::is_trivially_move_constructible_v<T> && std::is_trivially_move_assignable_v<T> = default;

constexpr
optional<T>&
operator=(optional&& rhs) noexcept(std::is_nothrow_move_constructible_v<T>)
requires std::is_move_constructible_v<T> && std::is_move_assignable_v<T> &&
             (!std::is_trivially_move_assignable_v<T>);

template<class U>
constexpr
optional<T>&
operator=(optional<U>&& rhs)
requires (detail::enable_assign_from_other<T, U, U>);

constexpr
optional<T>&
operator=(nullopt_t value) noexcept;

template<class U = T>
constexpr
optional<T>&
operator=(U&& u)
requires detail::enable_assign_forward<T, U>;