mbo

  trait Hash[A]:
    extension (a: A) def hash: Int

  trait PrettyPrint[A]:
    extension (a: A) def pretty: String

  // If you have Hash for A, you automatically get PrettyPrint for A
  given autoDerive[A](using h: Hash[A]): PrettyPrint[A] with
    extension (a: A) def pretty: String = s"<#${a.hash.toHexString}>"

  trait Trait[A]:
    type Assoc

  object A:
    given instance: Trait[Unit] with
      type Assoc = Long

    def makeAssoc: instance.Assoc = 0L

  object B:
    given instance: Trait[Unit] with
      type Assoc = String

    def dropAssoc(a: instance.Assoc): Unit =
      val s: String = a
      println(s.length)

  @main def entry(): Unit =
    B.dropAssoc(A.makeAssoc) // Found: Playground.A.instance.Assoc Required: Playground.B.instance².Assoc²