sO safeUnstructureAllowingCertainClasses_preferUtils(S s, S... allowedClasses) {
  new Set<S> allowedClassesSet;
  fOr (S name : allowedClasses) {
    allowedClassesSet.add("main$" + name);
    allowedClassesSet.add("loadableUtils.utils$" + name);
  }
  O classFinder = func(S name) {
    if (!allowedClassesSet.contains(name)) fail("Class not allowed to unstructure: " + name);
    if (name.startsWith("main$")) {
      S name2 = "loadableUtils.utils$" + substring(name, 5);
      Class c = classForNameOpt(name2);
      if (c != null) ret c;
    }
    ret classForName(name);
  };
  ret unstructure(s, false, classFinder);
}