t5954.scala:36: error: implementation restriction: package object A cannot contain case class D. Instead, class D should be placed directly in package A.
  case class D()
             ^
t5954.scala:35: error: implementation restriction: package object A cannot contain companion object C. Instead, object C should be placed directly in package A.
  object C
         ^
t5954.scala:34: error: implementation restriction: package object A cannot contain companion trait C. Instead, trait C should be placed directly in package A.
  trait C
        ^
t5954.scala:33: error: implementation restriction: package object A cannot contain companion object B. Instead, object B should be placed directly in package A.
  object B
         ^
t5954.scala:32: error: implementation restriction: package object A cannot contain companion class B. Instead, class B should be placed directly in package A.
  class B
        ^
5 errors found