Cyclic Reference Error when unpickling Scala2 sources

[felixmulder]

// User.scala
package foo

trait User {
  type Entry <: ChildContainer#Entry // error
}

// Containers.scala
package foo

trait ParentContainer {
  sealed trait Entry
}

class ChildContainer extends ParentContainer {
  trait LazyEntry extends Entry
}

Steps to Reproduce

1. Compile both sources using scalac
2. Compile "User.scala" using dotty

Notes

I tried a bunch of different variations to see what is the permutation that would trigger the unpickling exception. If I leave out sealed in ParentContainer#Entry, it compiles fine. I can use any combination of class/trait - but it seems to me that it is the sealed portion that kills the unpickler.

Ping @odersky, @smarter