Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.3.2)
// ----

/* Old */
@mixin link($link, $hover: $link, $active: $link, $focus: $link, $visited: $link) {
  $sameProps: ();
  & {
    @if $hover != $link {
      &:hover {
        color: $hover;
      }
    } @else {
      $sameProps: append($sameProps, '&:hover', comma)
    }
    
    @if $active != $link {
      &:active {
        color: $active;
      }
    } @else {
      $sameProps: append($sameProps, '&:active', comma)
    }
    
    @if $focus != $link {
      &:focus {
        color: $focus;
      }
    } @else {
      $sameProps: append($sameProps, '&:focus', comma)
    }
    
    @if $visited != $link {
      &:visited {
        color: $visited;
      }
    } @else {
      $sameProps: append($sameProps, '&:visited', comma)
    }
    
    &, #{$sameProps} {
      color: $link;
    }
  }
}

a {
  @include link(red, green, blue)
}

/* New */


@mixin _link($initial-state, $states) {
  $same-props: ();
  $states: map-merge((
    'hover': $initial-state,
    'active': $initial-state,
    'focus': $initial-state,
    'visited': $initial-state,
  ), $states);

  @each $state, $color in $states {
    @if ($initial-state != $color) {
      &:#{$state} {
        color: $color;
      }
    } @else {
      $same-props: append($same-props, '&:#{$state}', 'comma');
    }
  }
  
  &, #{$same-props} {
    color: $initial-state;
  }
}

a {
  @include _link(red, ('hover': green, 'active': green));
}

SassMeister-output.css

a:hover {
  color: green;
}

a:active {
  color: blue;
}

a, a:focus, a:visited {
  color: red;
}

/* New */
a:hover {
  color: green;
}

a:active {
  color: blue;
}

a, a:focus, a:visited {
  color: red;
}