Function or_else

include/experimental/expected.hpp:1673–1675

  }

  template <class F> constexpr auto or_else(F &&f) & {
    return detail::expected_or_else_impl(*this, std::forward<F>(f));
  }
  template <class F> constexpr auto or_else(F &&f) && {
    return detail::expected_or_else_impl(std::move(*this), std::forward<F>(f));
  }