tagged-type.scala

import shapeless.tag.@@
import org.scalacheck.Prop.forAll
import org.scalacheck.Shapeless._

trait Baz

case class Foo(s: String @@ Baz)

case class Bar(f: Foo)

implicit def arbTagged[A : Arbitrary, B]: Arbitrary[A @@ B] = Arbitrary(arbitrary[A].map(a => tag[B](a)))

property("myprop") = forAll { b: Bar =>
  true
}