static LS collectNemptyStrings(Iterable c, S field) {
  ret collectNemptyStrings(field, c);
}

static LS mapMethodLike collectNemptyStrings(S field, Iterable c) {
  new LS l;
  if (c != null) for (O a : c) {
    S x = cast getOpt(a, field);
    if (nempty(x)) l.add(x);
  }
  ret l;
}

Began life as a copy of #1021464