wrong 'parent' (&) when using @at-root with nested selectors

[rnonhebel]

Example:

div {
    span {
        @at-root {
            & {
                color: red;
            }
        }
    }
}

should produce (tested using https://www.sassmeister.com/, https://beautifytools.com/scss-compiler.php and https://sass.js.org/):

div span {
  color: red;
}

but using scssphp the result is:

span {
  color: red;
}

[stof]

I'm adding that to the 2.0 milestone, as I fear it will be hard to fix it in the 1.x codebase.