// tok = CNC
// returns [(index, tree leaf)]
static LPair<Int, O> matchStartUsingWordTree_all(L<S> tok, Map<S, O> tree) {
  O best = null; // best leaf
  int bestIndex = 0; // best index
  
  int j = 1;
  LPair<Int, O> out = new L;
  while (j < l(tok)) {
    O def = tree.get("<default>");
    if (def != null) { best = def; bestIndex = j; }
   
    O t = tree.get(tok.get(j));
    j += 2;
    if (t == null) break;
    if (!t instanceof Map) break with addPair(out, j, t); // leaf!
    tree = (Map) t;
  }
  
  if (best != null) addPair(out, bestIndex, best);
  ret out;
}

Began life as a copy of #1017908