non-circular dep fks

demo.scala

package demo

package ids {
  import record.Id
  object FooId extends Id[Int]
  object BarId extends Id[Int]
  object BazId extends Id[String]
}

package foomodel {
  import barmodel.fk.HasBarFK
  import bazmodel.fk.HasBazFK
  import ids.FooId
  class Foo(id: FooId.Type) extends HasBarFK with HasBazFK
}

package barmodel {
  import ids.BarId
  import bazmodel.fk.HasBazFK
  package fk { trait HasBarFK { object barId extends record.IntFKField(BarId.tag) }}
  trait HasBar { def bar: Bar }
  class Bar(id: BarId.Type) extends HasBazFK { def nameBar = "Bar" + id}
}

package bazmodel {
  import barmodel.fk.HasBarFK
  import ids.BazId
  package fk { trait HasBazFK { object bazId extends record.StringFKField(BazId.tag) }}
  trait HasBaz { def baz: Baz }
  class Baz(id: BazId.Type) extends HasBarFK { def nameBaz = "Baz" + id }
}

object FKDemo {
  import foomodel.Foo
  import barmodel.Bar
  import bazmodel.Baz
  val f1 = new Foo(ids.FooId(1))
  val bar = new Bar(f1.barId.fk)
  val baz = new Baz(f1.bazId.fk)
}

package record {
  trait IdTagger[T, U] { def apply(in: T) = in.asInstanceOf[U]}
  trait Id[T] {
    type Type = T with Object { type Tag = Object }
    def apply(in: T): Type = tag.apply(in)
    object tag extends IdTagger[T, Type]
  }

  trait Field[T] { def value: T }
  trait IntField extends Field[Int] {override def value = 5 }
  trait StringField extends Field[String] { override def value = "6"}
  trait FK[IdT] { def fk: IdT }
  class IntFKField[IdT](tagger: IdTagger[Int, IdT]) extends FK[IdT] with IntField { def fk = tagger(value) }
  class StringFKField[IdT](tagger: IdTagger[String, IdT]) extends FK[IdT] with StringField { def fk = tagger(value) }
}