ValueRefEq.scala

class ZipModelR[M, S, SS](root: ModelR[M, M], get1: M => S, get2: M => SS)(implicit cts: ClassTag[S], ctss: ClassTag[SS]) extends ModelR[M, (S, SS)] {
  private var zipped = Tuple2[S, SS](null.asInstanceOf[S], null.asInstanceOf[SS])

  // ZipModel uses optimized `get` functions to compare if the contents of the tuple has changed or not
  // Different comparison functions are used for boxed values and real references
  private def getXX(compS: (S, S) => Boolean, compSS: (SS, SS) => Boolean)(model: M) = {
    // check if inner references have changed
    val v1 = get1(root.value)
    val v2 = get2(root.value)
    if (compS(zipped._1, v1) || compSS(zipped._2, v2)) {
      // create a new tuple
      zipped = (v1, v2)
    }
    zipped
  }

  def valueEq[A](v1: A, v2: A) = v1 != v2

  def refEq[A](v1: A, v2: A) = v1.asInstanceOf[AnyRef] ne v2.asInstanceOf[AnyRef]

  def chooseEq(ct: ClassTag[_]) = {
    ct match {
      case ClassTag.Char => valueEq _
      case ClassTag.Int => valueEq _
      case ClassTag.Boolean => valueEq _
      case ClassTag.Long => valueEq _
      case ClassTag.Byte => valueEq _
      case ClassTag.Short => valueEq _
      case ClassTag.Float => valueEq _
      case ClassTag.Double => valueEq _
      case _ => refEq _
    }
  }

  // choose correct getXX function base on types of S and SS
  private val get = getXX(chooseEq(cts), chooseEq(ctss)) _
}

This test scala.runtime.ScalaRunTime.isValueClass(classTag[Int].runtimeClass) is runtimeClass.isPrimitive. Or case Char | Int | Boolean => valueEq _ is less verbose.