Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.0)
// Compass (v1.0.0.alpha.18)
// ----

/* nest */
.block {
	background-color: black;
	.block__elem1 { background-color: tomato;}
	&__elem2      { background-color: chocolate; }
	& &__elem3    {background-color: orange; }
	& &__elem3    {
  	&__elem3_1    { background: orange; }
	}
	@at-root { // = @at-root(without:rule)
	  &__elem4    {background-color: gold;}
	}
}

/* @media */
@media print {
  .block2 {
    background: tomato;
  	@at-root(without:media) {
  	  background: transparent;
  	  &__elem    { background-color: gold;}
  	}
  }
}

/* placeholder with & */
%p-block3 {
  background: red;
  &__elem {
    background: green;
  }
}
.block3 {
  @extend %p-block3;
  &__elem {
    @extend %p-block3__elem;
  }
}

/* placeholder */
%p-block4 {
  background: orange;
  %p-block4__elem {
    background: lime;
  }
}
.block4 {
  @extend %p-block4;
  &__elem {
    @extend %p-block4__elem;
  }
}


// ----
// from sass 3.3.0.rc.1 to sass3.3.0.rc.2
// ----

//.block3 {
//  $selector: &;
//  #{&}__element {
//    background: red;
//  }
//}

SassMeister-output.css

/* nest */
.block {
  background-color: black;
}
.block .block__elem1 {
  background-color: tomato;
}
.block__elem2 {
  background-color: chocolate;
}
.block .block__elem3 {
  background-color: orange;
}
.block .block__elem3__elem3_1 {
  background: orange;
}
.block__elem4 {
  background-color: gold;
}

/* @media */
@media print {
  .block2 {
    background: tomato;
  }
}
.block2 {
  background: transparent;
}
.block2__elem {
  background-color: gold;
}

/* placeholder with & */
.block3 {
  background: red;
}
.block3__elem {
  background: green;
}

/* placeholder */
.block4 {
  background: orange;
}
.block4 .block4__elem {
  background: lime;
}