sclass CodeSafetyChecker {
  // general data
  SS identifierSafetyMap;
  bool identifiersStartingWithDollarAreSafe;
  
  // data for code currently tested
  S code;
  Set<S> identifiers;
  Set<S> tags;
  
  void init {
    if (identifierSafetyMap == null)
      identifierSafetyMap = codeAnalysis_identifierSafetyMap();
  }
  
  run {
    init();
    identifiers = tok_allIdentifiers(code);
    tags = treeSet();
    for (S id : identifiers) {
      S tag;
      if (identifiersStartingWithDollarAreSafe && startsWith(id, "$"))
        tag = "safe";
      else
        tag = or2(mapGet(identifierSafetyMap, id), "?");
      tags.addAll(tokSplitAtComma(tag));
    }
    tags = simplifySafetyTags(tags);
    if (empty(tags)) tags.add("safe");
  }
  
  S checkCode(S code) {
    this.code = code;
    run();
    ret tags;
  }
}