t4879.scala:6: error: pattern type is incompatible with expected type;
 found   : object C
 required: C
Note: if you intended to match against the class, try `case _: C` or `case C(_)`
    case C  => true
         ^
t4879.scala:10: error: pattern type is incompatible with expected type;
 found   : object D
 required: D[T,U,V]
Note: if you intended to match against the class, try `case _: D[_,_,_]` or `case D(_,_,_)`
    case D  => true
         ^
two errors found