@function linear-gradient($pos, $gradients...) {
  $type: linear;
  $pos-type: type-of(nth($pos, 1));

  // if $pos doesn't exist, fix $gradient
  @if ($pos-type == color) or (nth($pos, 1) == "transparent")  {
    $gradients: zip($pos $gradients);
    $pos: false;
  }

  $type-gradient: $type, $pos, $gradients;
  @return $type-gradient;
}