Function noexcept

include/experimental/expected.hpp:173–176

  template <class Err = E, enable_if_t<is_assignable_v<E, Err &&>> * = nullptr,
            bool NoExcept = is_nothrow_assignable_v<E, Err &&>>
  constexpr unexpected &operator=(unexpected<Err> &&e) noexcept(NoExcept) {
    m_val = std::move(e.m_val);
    return *this;
  }
  constexpr const E &value() const &noexcept { return m_val; }
  constexpr E &value() &noexcept { return m_val; }
  constexpr E &&value() &&noexcept { return std::move(m_val); }