  BasicWriter &operator<<(IntFormatSpec<T, Spec, FillChar> spec) {
    internal::CharTraits<Char>::convert(FillChar());
    write_int(spec.value(), spec);
    return *this;
  }
  BasicWriter &operator<<(IntFormatSpec<T, Spec, FillChar> spec) {
    internal::CharTraits<Char>::convert(FillChar());
    write_int(spec.value(), spec);
    return *this;
  }