sS checkForRedeclaredFields(O o) {
  new Map<S, Field> map;
  fOr (Field f : nonStaticFieldObjects(o)) {
    Field f2 = map.put(f.getName(), f);
    if (f2 != null)
      ret "Field redeclared (not good): " + f + " / " + f2;
  }
  null;
}