Generated by SassMeister.com.

SassMeister-input.scss

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

@mixin headings($from: 1, $to: 6) {
  %headings-#{$from}-#{$to} {
    @content
  }

  @if $from >= 1 and $to <= 6 {
    @for $i from $from through $to {
      h#{$i} {
        @extend %headings-#{$from}-#{$to};
      }
    }
  }
}

@include headings(1, 6) {
  color: red;
  font-weight: 300;
}

.something-else {
  @include headings(1, 6) {
    color: blue;
  }
}

.another-else {
  @include headings(1, 6) {
    color: green;
  }
}

.lol {
  @include headings(1, 6) {
    color: pink;
    font-weight: 600;
  }
}

SassMeister-output.css

h1, h2, h3, h4, h5, h6, .something-else h1, .something-else h2, .something-else h3, .something-else h4, .something-else h5, .something-else h6, .another-else h1, .another-else h2, .another-else h3, .another-else h4, .another-else h5, .another-else h6, .lol h1, .lol h2, .lol h3, .lol h4, .lol h5, .lol h6 {
  color: red;
  font-weight: 300;
}

.something-else h1, .something-else h2, .something-else h3, .something-else h4, .something-else h5, .something-else h6 {
  color: blue;
}

.another-else h1, .another-else h2, .another-else h3, .another-else h4, .another-else h5, .another-else h6 {
  color: green;
}

.lol h1, .lol h2, .lol h3, .lol h4, .lol h5, .lol h6 {
  color: pink;
  font-weight: 600;
}