.mixin (...) { // matches 0-N arguments
.mixin () { // matches exactly 0 arguments
.mixin (@a: 1) { // matches 0-1 arguments
.mixin (@a: 1, ...) { // matches 0-N arguments
.mixin (@a, ...) { // matches 1-N arguments
Furthermore:
.mixin (@a, @rest...) {
// @rest is bound to arguments after @a
// @arguments is bound to all arguments
}
Testing this more, it appears to not work for things like box-shadow. For example, given the following mixin and arguments:
Which compiles to:
Note the missing comma between the two values, rendering the entire box-shadow property inert.