Genalgo Collections Fiddle

object Example {
  import scala.collection.IndexedSeqLike

  trait BaseLike

  class DNABase extends BaseLike

  trait BioSequence[B <: BaseLike] extends IndexedSeq[B]

  class DNA extends BioSequence[DNABase] with IndexedSeqLike[DNABase, DNA] {
    override def newBuilder = ???
    def length = 1
    def apply(idx: Int) = {
      new DNABase
    }
  }

  val myDNA = new DNA
  val droppedDNA: DNA = myDNA.drop(1) // Compiles because DNA extends IndexedSeqLike
  def processSequence[B <: BaseLike, C <: BioSequence[B]](seq: C): C = {
    seq.drop(1) // Doesn't compile because BioSequence doesn't extend IndexedSeqLike
  }
}

object ScalaJSExample extends js.JSApp {
  def main() = {
    
  }
}