@Override
  protected boolean parsePrimaryExpr(PsiBuilder builder) {
    if (builder.getTokenType() == XPathTokenTypes.DOT) {
      PsiBuilder.Marker mark = builder.mark();
      builder.advanceLexer();
      mark.done(XPath2ElementTypes.CONTEXT_ITEM);
      return true;
    } else {
      return super.parsePrimaryExpr(builder);
    }
  }
@Override
  protected boolean parsePrimaryExpr(PsiBuilder builder)