public interface AsyncFunction<I extends @Nullable Object, O extends @Nullable Object> {
  /**
   * Returns an output {@code Future} to use in place of the given {@code input}. The output {@code
   * Future} need not be {@linkplain Future#isDone done}, making {@code AsyncFunction} suitable for
   * asynchronous derivations.
   *
   * <p>Throwing an exception from this method is equivalent to returning a failing {@code Future}.
   */

    // don't execute 'immediately'.  By checking isDone here we avoid that.
    // A corollary to all that is that we don't need to check isDone inside the loop because if we
    // get into the loop we know that we weren't done when we entered and therefore we aren't under
    // an obligation to execute 'immediately'.
    if (!isDone()) {
      Listener oldHead = listeners;

     */
    @CanIgnoreReturnValue
    @Override
    public V get() throws InterruptedException, ExecutionException {
      return sync.get();
    }

    @Override
    public boolean isDone() {
      return sync.isDone();
    }

    @Override
    public boolean isCancelled() {
      return sync.isCancelled();
    }

    @CanIgnoreReturnValue
    @Override

     */
    @CanIgnoreReturnValue
    @Override
    public V get() throws InterruptedException, ExecutionException {
      return sync.get();
    }

    @Override
    public boolean isDone() {
      return sync.isDone();
    }

    @Override
    public boolean isCancelled() {
      return sync.isCancelled();
    }

    @CanIgnoreReturnValue
    @Override

   * does not include "was cancelled." To be explicit: If this method returns a non-null value,
   * then:
   *
   * <ul>
   *   <li>{@code isDone()} must return {@code true}
   *   <li>{@code isCancelled()} must return {@code false}
   *   <li>{@code get()} must not block, and it must throw an {@code ExecutionException} with the

            isInterruptibleRegistered.countDown();
            new CountDownLatch(1).await(); // the interrupt will wake us up
            return null;
          }

          @Override
          boolean isDone() {
            return false;
          }

          @Override
          String toPendingString() {
            return "";
          }

          @Override

    }

    assertThat(future.isDone()).isFalse();
    assertThat(future.set(1)).isTrue();
    assertSuccessful(future, 1);
  }

  public void testSetFutureNull() throws Exception {
    try {
      future.setFuture(null);
      fail();
    } catch (NullPointerException expected) {
    }

    assertThat(future.isDone()).isFalse();
    assertThat(future.set(1)).isTrue();

        // joint-compilation doesn't work with the Error Prone annotation processor
        extension.enabled.convention(this.name == "main")

        project.dependencies.addProvider(
            annotationProcessorConfigurationName,
            extension.enabled.filter { it }.map { "com.google.errorprone:error_prone_core:2.24.1" }
        )

        project.tasks.named<JavaCompile>(this.compileJavaTaskName) {

    // stop it.
    blockingCallable.waitForStart();

    // Give the second task a chance to (incorrectly) start up while the first task is running.
    assertThat(future2.isDone()).isFalse();

    // Stop the first task. The second task should then run.
    blockingCallable.stop();
    executor.shutdown();
    assertThat(executor.awaitTermination(10, TimeUnit.SECONDS)).isTrue();

    // stop it.
    blockingCallable.waitForStart();

    // Give the second task a chance to (incorrectly) start up while the first task is running.
    assertThat(future2.isDone()).isFalse();

    // Stop the first task. The second task should then run.
    blockingCallable.stop();
    executor.shutdown();
    assertThat(executor.awaitTermination(10, TimeUnit.SECONDS)).isTrue();