Code for a blog entry about inner objects and inner traits. This won't compile, but I think maybe it should.

InnerObjectVisibiltiy.Scala

trait TopTrait {
  def topDef:String
}

trait BeyondTrait {

  def innerThing:InnerTrait

  trait InnerTrait extends TopTrait{
    def innerDef = "innerDef"
    def topDef = "topDef"
  }
}

class Beyond extends BeyondTrait {
  override def innerThing = new InnerTrait{
    def beyondDef = "innerThing from beyond"
  }
}

class OuterClass(beyond: Beyond){
//making beyond a val lets it work (because InnerTrait isn't private anymore.)
//class OuterClass(val beyond: Beyond){

  object InnerObject {

    // this won't compile
    // "private value beyond escapes its defining scope as part of type OuterClass.this.beyond.InnerTrait"
    // the compiler won't walk up the tree to find TopTrait
    // and it won't decide that it has access to the private beyond member
    val innerThing = beyond.innerThing

    // and innerThing won't be defined
    val topDefResult = innerThing.topDef
    val innerDefResult = innerThing.innerDef

    // this will compile, cast up to TopTrait. innerDef is not available, but everything else works
//    val innerThing:TopTrait = beyond.innerThing

    //but this works as expected
//    val innerDefResult = beyond.innerThing.innerDef

    //as does this
//    val topDefResult = beyond.innerThing.topDef

    val comboResult = s"$innerDefResult and $topDefResult"
  }
}

object ShowIt{
  println(new OuterClass(new Beyond()).InnerObject.comboResult)
}