t987.scala:15: error: illegal inheritance;
 class E inherits different type instances of trait B:
B[D] and B[C]
class E extends D
      ^
t987.scala:20: error: illegal inheritance;
 class F inherits different type instances of trait B:
B[D] and B[C]
class F extends D
      ^
t987.scala:25: error: illegal inheritance;
 class D inherits different type instances of trait B:
B[D] and B[C]
abstract class D extends C with B[D] {}
               ^
t987.scala:25: error: type arguments [D] do not conform to trait B's type parameter bounds [T <: B[T]]
abstract class D extends C with B[D] {}
                                ^
four errors found