default:
          throw new AssertionError("unexpected state: " + state);
      }
    }
  }

  abstract static class OldAbstractFuture<V> implements ListenableFuture<V> {

    /** Synchronization control for AbstractFutures. */
    private final Sync<V> sync = new Sync<V>();

    // The execution list to hold our executors.
    private final ExecutionList executionList = new ExecutionList();

        default:
          throw new AssertionError("unexpected state: " + state);
      }
    }
  }

  abstract static class OldAbstractFuture<V> implements ListenableFuture<V> {

    /** Synchronization control for AbstractFutures. */
    private final Sync<V> sync = new Sync<V>();

    // The execution list to hold our executors.
    private final ExecutionList executionList = new ExecutionList();