Aquí hay una pequeña convergencia de SASS a MENOS ... ¿Alguien sabe cuál es la sintaxis correcta para estos? El siguiente código es el puro SASS mixins que solía usar. Gracias por ayudar

@mixin linear-gradient($left, $right, $optional:false) {
  @if $optional and type_of($optional) == number {
    background: -webkit-linear-gradient($optional + deg, $left, $right);
    background: -o-linear-gradient($optional + deg, $left, $right);
    background: -moz-linear-gradient($optional + deg, $left, $right);
    background: linear-gradient($optional + deg, $left, $right);
  } @else {
    @if $optional == "right" {
      background: -webkit-linear-gradient(left, $left, $right);
      background: -o-linear-gradient(left, $left, $right);
      background: -moz-linear-gradient(left, $left, $right);
      background: linear-gradient(to right, $left, $right);
    } @if $optional == "left" {
      background: -webkit-linear-gradient(right, $left, $right);
      background: -o-linear-gradient(right, $left, $right);
      background: -moz-linear-gradient(right, $left, $right);
      background: linear-gradient(to left, $left, $right);
    } @else { // top to bottom
      background: -webkit-linear-gradient($right, $left);
      background: -o-linear-gradient($right, $left);
      background: -moz-linear-gradient($right, $left);
      background: linear-gradient($right, $left);
    }
  }
}