TypeLevelBitFields.scala

object Test extends App {

  trait BitPrinter[B <: BitDescription] {
    def printBits(value: Long): (List[String], Long)

  }


  trait BitDescription
  trait BitField extends BitDescription
  trait BitFieldWidth1 extends BitField
  trait BitFieldWidth2 extends BitField
  trait BitFieldWidth3 extends BitField
  trait BitFieldWidth4 extends BitField
  trait BitFieldWidth8 extends BitField

  def fixedWidthBitFieldPrinter[B <: BitField](width: Int): BitPrinter[B] = new BitPrinter[B] {
    final def printLastHex(value: Long, n: Int): String = s"$n bits: ${(value & ((1 << n) - 1)).toHexString}"
    final def printLastBinary(value: Long, n: Int): String = s"$n bits: ${(value & ((1 << n) - 1)).toBinaryString}"

    override def printBits(value: Long): (List[String], Long) = (List(printLastBinary(value, width)), value >> width)
  }
  implicit def bfw1printer: BitPrinter[BitFieldWidth1] = fixedWidthBitFieldPrinter(1)
  implicit def bfw2printer: BitPrinter[BitFieldWidth2] = fixedWidthBitFieldPrinter(2)
  implicit def bfw3printer: BitPrinter[BitFieldWidth3] = fixedWidthBitFieldPrinter(3)
  implicit def bfw4printer: BitPrinter[BitFieldWidth4] = fixedWidthBitFieldPrinter(4)

  final case class BitCons[H <: BitDescription, T <: BitDescription](head: H, tail: T) extends BitDescription
  // sealed class BitNil extends BitDescription
  type ::[H <: BitDescription, T <: BitDescription]  = BitCons[H, T]


  implicit def NextBitConsPrinter[H <: BitDescription : BitPrinter, T <: BitDescription : BitPrinter] = new BitPrinter[BitCons[H, T]] {
    override def printBits(value: Long): (List[String], Long) = {
      val (head, remainder) = implicitly[BitPrinter[H]].printBits(value)
      val tail = implicitly[BitPrinter[T]].printBits(remainder)
      (head ++ tail._1, tail._2)
    }
  }


  trait BitFieldContainer[Repr <: Long] extends Any {
    def value: Repr
    type BitFields <: BitDescription
    protected def isNthBitSet(bit: Int) = (value & (1 >> bit)) != 0

    def showBits(implicit bitPrinter: BitPrinter[BitFields]) = bitPrinter.printBits(value).toString

  }

  class EsmClass(val value: Long) extends AnyVal with BitFieldContainer[Long] {

    type BitFields = BitFieldWidth1 :: BitFieldWidth1 :: BitFieldWidth4

    override def toString = showBits

  }


  println(
    new EsmClass(0x25)
  )

}