Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.3)
// Compass (v1.0.0.alpha.18)
// ----

/*----ex1----*/

%block1 {
  color: red;
  &--modifier {
    color: blue;
  }
}

.block1 {
  @extend %block1;

  &--modifier {
    @extend %block1;
    @extend %block1--modifier;
  }
}

/*----ex2----*/

%block2 {
  color: red;
  &--modifier {
    @extend %block2;
    color: blue;
  }
}

.block2 {
  @extend %block2;

  &--modifier {
    @extend %block2--modifier;
  }
}

SassMeister-output.css

/*----ex1----*/
.block1, .block1--modifier {
  color: red;
}
.block1--modifier {
  color: blue;
}

/*----ex2----*/
.block2--modifier, .block2 {
  color: red;
}
.block2--modifier {
  color: blue;
}