Acquaintance.scala

sealed abstract class Kind {
  def isCustomer = this.isInstanceOf[CustomerKind]
  def isProspect = this.isInstanceOf[ProspectKind]
  def isSupplier = this.isInstanceOf[SupplierKind]
}

sealed trait CustomerKind { this: AcquaintanceKind => }
sealed trait ProspectKind { this: AcquaintanceKind => }
sealed trait SupplierKind { this: AcquaintanceKind => }

type Customer = Kind with CustomerKind
type Prospect = Kind with ProspectKind
type Supplier = Kind with SupplierKind
type CustomerSupplier = Customer with Supplier
type ProspectSupplier = Prospect with Supplier

val Customer = new Customer
val Prospect = new Prospect
val Supplier = new Supplier
val CustomerSupplier = new CustomerSupplier
val ProspectSupplier = new ProspectSupplier

case class Acquaintance[+K <: Kind](id: UUID, name: String, kind: K)

Main.scala

object Main extends App {
  val a = new Acquaintance[CustomerSupplier](UUID.v4, "x", CustomerSupplier)
}