Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.4)
// Compass (v1.0.0.alpha.18)
// ----

// Making placeholders extendable within media queries

$prototypes: () !global;

@function exists($map, $value){
	@if type-of($map) == map {
		@if map-has-key($map, $value) {
			@return true;
		}
		@each $key, $i in $map {
			@if exists($i, $value) {
				@return true;
			}
		}
	} @return false;
}

@mixin prototype__build($prototype) {
  @each $property, $value in $prototype {
    @if type-of($value) == map {
      
      &:#{$property} {
        @each $mod_property, $mod_value in $value {
          #{$mod_property}: #{$mod_value};
        }
      }
      
    } @else {
      #{$property}: $value;
    }
  }
}

@mixin prototype($n) {
  
  @if exists($prototypes, $n) {
    
    %#{$n}--media {
      $init: map-get($prototypes, $n);
      
      @include prototype__build($init);
    }
    
  } @else {
    
    %#{$n} {
      @content;
    }
    
    // Here is where interpolating a stringified `@content`, and slicing up the output
    // into a map would come in handy...
    
    $prototype: ( #{$n}: ( styles: here, hover: ( pseudo-stuff: here, ), ), );
    $prototypes: map-merge($prototypes, $prototype) !global;
  }
}

@include prototype(clearfix) {
  zoom: 1;

  &:before, &:after {
      content: "\0020"; 
      display: block; 
      height: 0; 
      overflow: hidden; 
  }

  &:after {
      clear: both;
  }
}

.extendee {
  @extend %clearfix;
}
.extendee_2 {
  @extend %clearfix;
}

@media screen {
  @include prototype(clearfix);
  
  .media_extendee {
    @extend %clearfix--media;
  }
  .media_extendee_2 {
    @extend %clearfix--media;
  }
}

SassMeister-output.css

.extendee, .extendee_2 {
  zoom: 1;
}
.extendee:before, .extendee_2:before, .extendee:after, .extendee_2:after {
  content: "\0020";
  display: block;
  height: 0;
  overflow: hidden;
}
.extendee:after, .extendee_2:after {
  clear: both;
}

@media screen {
  .media_extendee, .media_extendee_2 {
    styles: here;
  }
  .media_extendee:hover, .media_extendee_2:hover {
    pseudo-stuff: here;
  }
}