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