Trait for creating the line path builder instances for the PolygonLikeMapBuilder type class, for classes / traits you control, should go in the companion object of B. The first type parameter is called B, because to corresponds to the B in map(f: A => B): ArrB function.
BuffT can be inbuilt Jvm type like ArrayBuffer[Int] for B = Int and BB = Ints, or it can be a compile time wrapped Arraybuffer inheriting from BuffProdHomo.
BuffT can be inbuilt Jvm type like ArrayBuffer[Int] for B = Int and BB = Ints, or it can be a compile time wrapped Arraybuffer inheriting from BuffProdHomo.