Generated compound selectors in Sass 3.3

SassMeister-input.scss

// ----
// Sass (v3.3.8)
// Compass (v1.0.0.alpha.19)
// ----

@mixin element-compound($selector) {
  $elements: a, p, div;
  @each $el in $elements {
    @at-root #{$el + $selector} {
      @extend #{$selector};
    }
  }
}

.foo {
  @include element-compound(".foo");
  content: 'hiya';
}

SassMeister-output.css

.foo, a.foo, p.foo, div.foo {
  content: 'hiya';
}