LESS to SASS conversion - issue

sample.less

// LESS
.form-field {
  border: 1px solid #ccc;
  padding: .5em 1em;
  input& {
    height: 2em;
  }
  textarea& {
    height: auto;
  }
}

sample.scss

// SASS
.form-field {
  border: 1px solid #ccc;
  padding: .5em 1em;
  @at-root input#{&} {
    height: 2em;
  }
  @at-root textarea#{&} {
    height: auto;
  }
}

While converting some code I ran into this issue.

"&" may only be used at the beginning of a compound selector

The @at-root selector helped me out, but this doesn't feel like the way to do it.