t8146-non-finitary.scala:4: error: class graph is not finitary because type parameter A is expansively recursive
trait C[A] extends N[N[C[C[A]]]]
        ^
t8146-non-finitary.scala:6: error: type mismatch;
 found   : C[Int]
 required: N[C[Int]]
  def foo(c: C[Int]): N[C[Int]] = c
                                  ^
two errors found