Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

@mixin v-spacing($margin: 30px, $padding: 0) {
  
  $selector-chain: &;
  $top-level-selector: false;

  @each $selector in $selector-chain {
    $top-level-selector: nth($selector, length($selector))
  }

  + #{$top-level-selector} {
    color: red;
  }
}

.toggle-list {
  @include v-spacing(30px);

  .toggle {
    @include v-spacing(30px);
  }
  
  .test .foo .bar {
    @include v-spacing(30px);
  }
}

SassMeister-output.css

.toggle-list + .toggle-list {
  color: red;
}

.toggle-list .toggle + .toggle {
  color: red;
}

.toggle-list .test .foo .bar + .bar {
  color: red;
}