ifclass ListAndIndex
static LineAndColumn tokenToLineAndColumn(ListAndIndex<S> ptr) {
  ret ptr == null ?: tokenToLineAndColumn(ptr.list(), ptr.idx());
}
endif

static LineAndColumn tokenToLineAndColumn(LS tok, int tokenIndex) {
  int line = 1, col = 1;
  tokenIndex = min(tokenIndex, l(tok));
  for i to tokenIndex: {
    S t = tok.get(i);
    int n = l(t);
    for j to n:
      if (t.charAt(j) == '\n') {
        ++line;
        col = 1;
      } else
        ++col;
  }
  ret LineAndColumn(line, col);
}