Method visit_unhandled_arg

ext/src/cppformat/format.cc:247–250

  explicit WidthHandler(fmt::FormatSpec &spec) : spec_(spec) {}

  unsigned visit_unhandled_arg() {
    FMT_THROW(fmt::FormatError("width is not integer"));
    return 0;
  }

  template <typename T>
  unsigned visit_any_int(T value) {