hash.scala:3: method clone in trait SynchronizedMap of type ()scala.collection.mutable.Map[A,B]
 cannot override method clone in class HashMap of type ()scala.collection.mutable.HashMap[A,B]
class Foo[A,B] extends HashMap[A, B] with SynchronizedMap[A,B];
                                          ^
hash.scala:3: class Foo needs to be abstract, since method get in trait SynchronizedMap is marked `abstract' and\
 `override' and overrides an incomplete superclass member in scala.collection.mutable.HashMap[A,B]
class Foo[A,B] extends HashMap[A, B] with SynchronizedMap[A,B];
      ^
two errors found