<===> input.scss
%button-styles {
  color: red;

  &:focus {
    color: blue;
  }
}

[type="button"] {
  @extend %button-styles;
}


<===> output.css
[type="button"] {
  color: red;
}
[type="button"]:focus {
  color: blue;
}

<===> output-dart-sass.css
[type=button] {
  color: red;
}
[type=button]:focus {
  color: blue;
}