Welcome to Scala version 2.11.1 (OpenJDK 64-Bit Server VM, Java 1.7.0_55).
Type in expressions to have them evaluated.
Type :help for more information.

scala> trait Cm[F[_], A]
defined trait Cm

scala> case class C[A]() extends Cm[C, A]
defined class C

scala> case class D[S,A]() extends Cm[({type l[a] = D[S,a]})#l, A]
<console>:8: error: illegal cyclic reference involving class D
       case class D[S,A]() extends Cm[({type l[a] = D[S,a]})#l, A]
                  ^
<console>:8: error: D does not take type parameters
       case class D[S,A]() extends Cm[({type l[a] = D[S,a]})#l, A]
                                                    ^