// f : Concept -> Concept
static Concept conceptGraphMap_aggressive(Concept c, O f) {
  ret conceptGraphMap_aggressive_impl(c, f, new IdentityHashMap);
}

static Concept conceptGraphMap_aggressive_impl(Concept c, O f, IdentityHashMap<Concept, Concept> seen) {
  if (seen.containsKey(c))
    ret seen.get(c);
  Concept d = cast callF(f, c);
  if (d != c) {
    Concept last = c;
    while (d != last && d != null) {
      last = d;
      d = (Concept) callF(f, d);
    }
  }
  
  if (d == null) {
    seen.put(c, null);
    null;
  }

  Concept e = cnew(d.getClass());
  seen.put(c, e);
  
  for (S field : conceptFields(d)) {
    O val = cget(d, field);
    if (!val instanceof Concept)
      cset(e, field, val);
    else
      cset(e, field, conceptGraphMap_aggressive_impl(val/Concept, f, seen));
  }
  ret e;
}

Began life as a copy of #1005477