I have some LESS for making margins based on the side being passed (top, right, bottom, left or all):

      .margin(@px,@side) when (@side = top) {
          (){ margin-top: ~"@{px}px"; }
       }
       .margin(@px,@side) when (@side = right) {
          (){ margin-right: ~"@{px}px"; }
       }
       .margin(@px,@side) when (@side = bottom) {
          (){ margin-bottom: ~"@{px}px"; }
       }
       .margin(@px,@side) when (@side = left) {
          (){ margin-left: ~"@{px}px"; }
        }
       .margin(@px,@side) when (@side = all) {
          (){ margin-top: ~"@{px}px";
          margin-right: ~"@{px}px";
          margin-bottom: ~"@{px}px";
          margin-left: ~"@{px}px"; }
        }

My question is that if I have an ID like this:

    #testfeature {
    .margin(10px,l);
    .margin(10px,r);
    }

Then LESS compiles it like this:

    #testfeature {
    margin-left:10px;
    }

    #testfeature {
    margin-right:10px;
    }

How do I get it to compile like this:

    #testfeature {
    margin-left:10px;
    margin-right:10px;
    }