// i must point at the opening bracket ("<")
// index returned is index of closing bracket or comma 
static int tok_findEndOfTypeArg(L<S> cnc, int i) {
  int j = i+2, level = 1;
  while (j < cnc.size()) {
    S t = cnc.get(j);
    if (t.equals("<")) ++level;
    else if (t.equals(">")) --level;
    if (level == 0 || level == 1 && eq(t, ","))
      return j;
    ++j;
  }
  ret cnc.size();
}