private static void parsePcreConditionalGroup(PsiBuilder builder) {
    final PsiBuilder.Marker marker = builder.mark();
    builder.advanceLexer();
    builder.advanceLexer();
    checkMatches(builder, RegExpTT.GROUP_END, RegExpBundle.message("parse.error.unclosed.group.reference"));
    marker.done(RegExpElementTypes.GROUP);
  }
private static void parsePcreConditionalGroup(PsiBuilder builder)