t5189b.scala:38: error: type mismatch;
 found   : TestNeg.Wrapped[?T7] where type ?T7 <: T (this is a GADT skolem)
 required: TestNeg.Wrapped[T]
Note: ?T7 <: T, but class Wrapped is invariant in type W.
You may wish to define W as +W instead. (SLS 4.5)
    case Wrapper/*[_ <: T ]*/(wrapped) => wrapped // : Wrapped[_ <: T], which is a subtype of Wrapped[T] if and only if Wrapped is covariant in its type parameter
                                          ^
t5189b.scala:51: error: value foo is not a member of type parameter T
    case Some(xs) => xs.foo // the error message should not refer to a skolem (testing extrapolation)
                        ^
two errors found