* delegating calls until it returns valid data.
   *
   * <p>If {@code delegate} is an instance created by an earlier call to {@code memoize}, it is
   * returned directly.
   */
  public static <T extends @Nullable Object> Supplier<T> memoize(Supplier<T> delegate) {
    if (delegate instanceof NonSerializableMemoizingSupplier
        || delegate instanceof MemoizingSupplier) {
      return delegate;
    }

    // Once more, with feeling.
    holder.value = 4;
    assertEquals(6, getDone(transformedFuture).intValue());
    assertEquals(8, adder.apply(4).intValue());

    // Memoized get also retains the value.
    assertEquals(6, getDoneFromTimeoutOverload(transformedFuture).intValue());

    // Unsurprisingly, recomposing the future will return an updated value.

    // Once more, with feeling.
    holder.value = 4;
    assertEquals(6, getDone(transformedFuture).intValue());
    assertEquals(8, adder.apply(4).intValue());

    // Memoized get also retains the value.
    assertEquals(6, getDoneFromTimeoutOverload(transformedFuture).intValue());

    // Unsurprisingly, recomposing the future will return an updated value.

   * delegating calls until it returns valid data.
   *
   * <p>If {@code delegate} is an instance created by an earlier call to {@code memoize}, it is
   * returned directly.
   */
  public static <T extends @Nullable Object> Supplier<T> memoize(Supplier<T> delegate) {
    if (delegate instanceof NonSerializableMemoizingSupplier
        || delegate instanceof MemoizingSupplier) {
      return delegate;
    }