t2213.scala:9: error: class C needs to be abstract, since:
it has 4 unimplemented members.
/** As seen from class C, the missing signatures are as follows.
 *  For convenience, these are usable as stub implementations.
 */
  def f: Int = ???
  def g: Int = ???
  val x: Int = ???
  val y: Int = ???

class C extends A {}
      ^
t2213.scala:11: error: object creation impossible, since:
it has 4 unimplemented members.
/** As seen from object Q, the missing signatures are as follows.
 *  For convenience, these are usable as stub implementations.
 */
  def f: Int = ???
  def g: Int = ???
  val x: Int = ???
  val y: Int = ???

object Q extends A { }
       ^
two errors found