gistfile1.scala

scala> class Foo extends scala.collection.mutable.Queue[Int] {
     | 
     |   def foo = last0
     | }
defined class Foo

scala> new Foo
res0: Foo = ()

scala> res0.enqueue(1)

scala> res0.dequeue
res2: Int = 1

scala> res0.length
res3: Int = 0

scala> res0.foo
res4: scala.collection.mutable.LinkedList[Int] = LinkedList(1)