Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.1.0-beta)
// ----

@mixin addLeft($one, $two){
  left : $one + $two; 
}

@mixin addTop($one, $two){
  top : $one + $two; 
}

$nums : (1px, 2px);

.myClass {
  @include addLeft($nums...);
  
  //note that only the 1px shows up in the css because $nums is now null
  bottom : $nums 1px;
  
  //comment in the following line and the compilation failes because $nums is now null
  // @include addTop($nums...);
}
  

SassMeister-output.css

.myClass {
  left: 3px;
  bottom: 1px; }