Class is_like_std_string

extlibs/fmt/include/fmt/ranges.h:79–88

/// Return true value if T has std::string interface, like std::string_view.
template <typename T> class is_like_std_string {
  template <typename U>
  static auto check(U* p)
      -> decltype((void)p->find('a'), p->length(), (void)p->data(), int());
  template <typename> static void check(...);

 public:
  static FMT_CONSTEXPR_DECL const bool value =
      is_string<T>::value || !std::is_void<decltype(check<T>(nullptr))>::value;
};

template <typename Char>
struct is_like_std_string<fmt::basic_string_view<Char>> : std::true_type {};