<===> input.scss
foo.bar.baz asd.qwe xyz, second {
  length: length(&);
  length: length(nth(&, 1));
  length: length(nth(nth(&, 1), 1));
}
<===> output.css
foo.bar.baz asd.qwe xyz, second {
  length: 2;
  length: 3;
  length: 1;
}