Method format_custom

include/fmt/base.h:2265–2274

  // Formats an argument of a custom type, such as a user-defined class.
  template <typename T>
  static void format_custom(void* arg, parse_context<char_type>& parse_ctx,
                            Context& ctx) {
    auto f = formatter<T, char_type>();
    parse_ctx.advance_to(f.parse(parse_ctx));
    using qualified_type =
        conditional_t<has_formatter<const T, char_type>(), const T, T>;
    // format must be const for compatibility with std::format and compilation.
    const auto& cf = f;
    ctx.advance_to(cf.format(*static_cast<qualified_type*>(arg), ctx));
  }
};

enum { packed_arg_bits = 4 };