40 columns                              |
>>>
mixin    M1    on   UnaryNum     {  }
<<<
mixin M1 on UnaryNum {}
>>>
mixin   M2  on   UnaryNum   ,UnaryInt{   }
<<<
mixin M2 on UnaryNum, UnaryInt {}
>>>
mixin    M1    on   UnaryNum     {


  member() {}


  }
<<<
mixin M1 on UnaryNum {
  member() {}
}
>>> generic
mixin M<   A  ,B  >on   C  implements    D{ }
<<<
mixin M<A, B> on C implements D {}