Stackoverflow 65178794 (AUX Pattern, path dependency)

file.scala

sealed trait Kind

case object B extends Kind
case object C extends Kind

sealed trait Test {
  type K <: Kind
  val kind: K
}

object Test {
  type Aux[KK <: Kind] = Test { type K = KK }
  def test[KK <: Kind](kk: KK): Aux[KK] = new Test{ type K = KK; val kind = kk }
}

sealed trait Suite{
  type K <: Kind
  val kind: K
  val tests: List[Test.Aux[K]]
}

object SuiteB extends Suite {
  type K = B.type
  val kind:K = B
  val tests = List(Test.test(B), Test.test(B))
}

object SuiteC extends Suite {
  type K = C.type
  val kind:K = C
  val tests = List(Test.test(C), Test.test(C))
}

def runSuite(suite: Suite): Unit = {
  val x: suite.K = suite.kind
  suite match {
    case s@SuiteB =>
      val tests: List[Test.Aux[B.type]] = s.tests
      //
    case s@SuiteC =>
      val tests: List[Test.Aux[C.type]] = s.tests
      //
  }
}