static Set allEmbeddingObjects(O o) {
  Set set = identityHashSet();
  allEmbeddingObjects_get(o, set);
  ret set;
}

svoid allEmbeddingObjects_get(O o, Set set) {
  if (!set.add(o)) ret;
  new Matches m;
  for (S field : allFields(o))
    if (startsWith(field, "this$", m) && isInteger(m.rest()))
      allEmbeddingObjects_get(get(o, field), set);
}

Began life as a copy of #1015800