Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.21)
// Compass (v1.0.3)
// ----

@mixin tag($elt) {
  @at-root #{$elt}#{&} {
    @content;
  }
}

.foo {
  @include tag(fum) {
    bar: baz;
  }
}

.media {
  background-color: lightgray;
  
  @include tag(form) {
    border: 1px solid;
  }
}

SassMeister-output.css

fum.foo {
  bar: baz;
}

.media {
  background-color: lightgray;
}
form.media {
  border: 1px solid;
}