Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.7)
// Compass (v1.0.0.alpha.18)
// ----

%a {
  color: red;
  &-suffix {
    display: none; // does not get extended
  }
}

%b {
  color: blue;
  &:before {
    display: none; // gets extended
  }
}

.a-extend {
  @extend %a;
}

.b-extend {
  @extend %b;
}

SassMeister-output.css

.a-extend {
  color: red;
}
.b-extend {
  color: blue;
}
.b-extend:before {
  display: none;
}