InternalEntry<K, V, ?> e,
        WeakValueReference<K, V, ? extends InternalEntry<K, V, ?>> valueReference) {
      StrongKeyWeakValueEntry<K, V> entry = castForTesting(e);
      @SuppressWarnings("unchecked")
      WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> newValueReference =
          (WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>>) valueReference;

        InternalEntry<K, V, ?> e,
        WeakValueReference<K, V, ? extends InternalEntry<K, V, ?>> valueReference) {
      StrongKeyWeakValueEntry<K, V> entry = castForTesting(e);
      @SuppressWarnings("unchecked")
      WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>> newValueReference =
          (WeakValueReference<K, V, StrongKeyWeakValueEntry<K, V>>) valueReference;

      this.previousWrite = previous;
    }
  }

  /** References a weak value. */
  static class WeakValueReference<K, V> extends WeakReference<V> implements ValueReference<K, V> {
    final ReferenceEntry<K, V> entry;

    WeakValueReference(ReferenceQueue<V> queue, V referent, ReferenceEntry<K, V> entry) {
      super(referent, queue);
      this.entry = entry;
    }

      this.previousWrite = previous;
    }
  }

  /** References a weak value. */
  static class WeakValueReference<K, V> extends WeakReference<V> implements ValueReference<K, V> {
    final ReferenceEntry<K, V> entry;

    WeakValueReference(ReferenceQueue<V> queue, V referent, ReferenceEntry<K, V> entry) {
      super(referent, queue);
      this.entry = entry;
    }