class A<T> {
              T foo(T t) {1}
           }

          class B extends A<Long>{
              Long foo(Long l){2}
          }
          def b = new B();
          try {
            b.foo(new Object())
            assert false
          } catch (ClassCastException cce) {
            assert true
          }
          assert b.foo((Long) 1) == 2