Function parse_dynamic_spec

include/fmt/base.h:1383–1413

// Parses integer | "{" [arg_id] "}".
template <typename Char>
FMT_CONSTEXPR auto parse_dynamic_spec(const Char* begin, const Char* end,
                                      int& value, arg_ref<Char>& ref,
                                      parse_context<Char>& ctx)
    -> parse_dynamic_spec_result<Char> {
  FMT_ASSERT(begin != end, "");
  auto kind = arg_id_kind::none;
  if ('0' <= *begin && *begin <= '9') {
    int val = parse_nonnegative_int(begin, end, -1);
    if (val == -1) report_error("number is too big");
    value = val;
  } else {
    if (*begin == '{') {
      ++begin;
      if (begin != end) {
        Char c = *begin;
        if (c == '}' || c == ':') {
          int id = ctx.next_arg_id();
          ref = id;
          kind = arg_id_kind::index;
          ctx.check_dynamic_spec(id);
        } else {
          begin = parse_arg_id(begin, end,
                               dynamic_spec_handler<Char>{ctx, ref, kind});
        }
      }
      if (begin != end && *begin == '}') return {++begin, kind};
    }
    report_error("invalid format string");
  }
  return {begin, kind};
}

template <typename Char>
FMT_CONSTEXPR auto parse_width(const Char* begin, const Char* end,