static ItIt<LS> parseExtendedCSV_iterator(ExtendedCSVParser parser default new, S csv) {
  parser.csv = csv;
  ret iff_endOnNull(new IF0<LS>() {
    new LS currentRecord;
    bool recordComplete;
    
    {
      parser.onValueFound = v -> currentRecord.add(v);
      parser.onEndOfRecord = () -> set recordComplete;
    }
    
    public LS get() {
      while (!recordComplete)
        if (!parser.step())
          null;
      recordComplete = false;
      LS record = currentRecord;
      currentRecord = new L;
      ret record;
    }
  });
}

Began life as a copy of #1030417