def f[R](a: AA[R]): Option[a.R] = Some(1).map(_ => a.r)

object Main {
  trait AA[RR] { type R = RR; def r: R }

  def test1(a: AA[B] forSome { type B }) = {
    val f = () => a.r
    // The tree a.r is given the type `a.R` which normalizes
    // to B', where B' is a distinct symbol ("captured existential skolem")
    // to substitute for the reference to an existential skolem of B.
    //
    // inference of the result type of the function computes the
    // packed type of tree `a.r` to make sure that terms and types
    // local to the body of the function don't leak into its result
    // type. The captured existential skolem is considered to be local
    // so it is abstracted to its upper bound, Any.
    f: (() => a.R)

    // The workaround is to annotate the function type, rather than
    // relying in inference.
    val g: (() => a.R) () => a.r

    ()
  }
  // typer debug trace: http://rawgit.com/retronym/d5aeaf8e0a4a2e6eef4b/raw/out.html
}

object Test {
  def foo1[A1] = new { private type A2 = A1 ; def bar: A2 = ??? }
  // def foo2[A1] = new {         type A2 = A1 ; def bar: A2 = ??? }
 
  def f1: Int = foo1[Int].bar
  // def f2: Int = foo2[Int].bar
}