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// providing the type parameter in the recursive call to all4Impl
// avoids the problem
// covariant linked list
abstract class M
{ self =>
type T
final type selfType = M {type T <: self.T}
type actualSelfType >: self.type <: selfType
def next: selfType
// I don't understand why this doesn't compile, but that's a separate matter
// error: method all2 cannot be accessed in M.this.selfType
// because its instance type => Stream[M{type T <: M.this.selfType#T}]
// contains a malformed type: M.this.selfType#T
// def all2: Stream[M {type T <: self.T}] = Stream.cons(self: actualSelfType, next.all2)
// compiles successfully
// def all3: Stream[M {type T <: self.T}] = all3Impl(self: actualSelfType)
// private def all3Impl(first: M {type T <: self.T}): Stream[M {type T <: self.T}] = Stream.cons(first, all3Impl(first.next))
def all4: Stream[M {type T <: self.T}] = Unrelated.all4Impl[T](self: actualSelfType)
}
object Unrelated
{
def all4Impl[U](first: M {type T <: U}): Stream[M {type T <: U}] = Stream.cons(first, all4Impl(first.next))
// compiles successfully
// def all4Impl[U](first: M {type T <: U}): Stream[M {type T <: U}] = Stream.cons(first, all4Impl[U](first.next))
}
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