static PTElement ai_parseBottomUpToTree(S input) {
  final new AI_BottomUpParser1 parser;
  parser.parse(input);
  AI_BottomUpParser1.Word w = parser.fullGroup();
  if (w == null) null;
  ret ai_completeParseTree(parser, ChooseCategory(w, withoutQuoted(w.classes)));
}