static <A> Cl<A> lambdaMapLike filterCollectionInPlace(IPred<A> pred, Cl<A> l) {
  if (l == null) ret l;
  var it = l.iterator();
  while (it.hasNext())
    if (!pred.get(it.next()))
      it.remove();
  ret l;
}

static <A> Cl<A> lambdaMapLike filterCollectionInPlace(Cl<A> l, IPred<A> pred) {
  ret filterCollectionInPlace(pred, l);
}

Began life as a copy of #1019151