static Set<S> collectNotNullsAsCISet(Iterable c, S field) {
  new Set<S> set;
  fOr (O a : c)
    addIfNotNull(set, (S) getOpt(a, field));
  ret set;
}

static Set<S> mapMethodLike collectNotNullsAsCISet(S field, Iterable c) {
  ret collectNotNullsAsCISet(c, field);
}