Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.3)
// ----

@mixin outer {
  @content;
}

@mixin inner {
  color: red;
}

.foo {
  @include outer {
    @include inner;
  }
}

@include outer {
  .foo-2 {
    @include inner;
  }
}

SassMeister-output.css

.foo {
  color: red;
}

.foo-2 {
  color: red;
}