// unmeasurable (comparing done AbstractFutures with immediateFuture)
    if (obj instanceof Cancellation) {
      Cancellation cancellation = (Cancellation) obj;
      Throwable cause = cancellation.cause;
      throw cancellationExceptionWithCause("Task was cancelled.", cause);
    } else if (obj instanceof Failure) {
      Failure failure = (Failure) obj;

 *
 * <p>This class has limited support for cancellation and other "early completions":
 *
 * <ul>
 *   <li>While calls to {@code submit} and {@code submitAsync} return a {@code Future} that can be
 *       cancelled, cancellation never propagates to a task that has started to run -- neither to
 *       the callable itself nor to any {@code Future} returned by an {@code AsyncCallable}.

import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/** Tests for {@link AbstractFuture} with the cancellation cause system property set */
@AndroidIncompatible // custom classloading

@NullUnmarked
@GwtIncompatible
@J2ktIncompatible
public class AbstractFutureCancellationCauseTest extends TestCase {

import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/** Tests for {@link AbstractFuture} with the cancellation cause system property set */
@AndroidIncompatible // custom classloading

@NullUnmarked
@GwtIncompatible
@J2ktIncompatible
public class AbstractFutureCancellationCauseTest extends TestCase {

  /**
   * Tests that a canceled future throws a cancellation exception.
   *
   * <p>This method checks the cancel, isCancelled, and isDone methods.
   */
  public void testCanceledFutureThrowsCancellation() throws Exception {

    assertFalse(future.isDone());
    assertFalse(future.isCancelled());

    CountDownLatch successLatch = new CountDownLatch(1);

    // Run cancellation in a separate thread as an extra thread-safety test.

  }
}
```

This is implemented using `suspendCancellableCoroutine`
but uses the standard Dispatcher in OkHttp. This means
that by default Kotlin's Dispatchers are not used.

Cancellation if implemented sensibly in both directions.
Cancelling a coroutine scope, will cancel the call.
Cancelling a call, will throw a CancellationException

     * All elements of `futures` are completed, or this future has already completed and read
     * `futures` into a local variable (in preparation for propagating cancellation to them). In
     * either case, no one needs to read `futures` for cancellation purposes later. (And
     * cancellation purposes are the main reason to access `futures`, as discussed in its docs.)
     */
    this.futures = null;
  }

  enum ReleaseResourcesReason {

 * earliest one wins. This applies to both executions scheduled with [TaskRunner.Queue.schedule] and
 * those implied by the returned execution delay.
 *
 * Cancellation
 * ------------
 *
 * Tasks may be canceled while they are waiting to be executed, or while they are executing.
 *
 * Canceling a task that is waiting to execute prevents that upcoming execution. Canceling a task

 * limitations under the License.
 */
package okhttp3

import okio.IOException

interface Callback {
  /**
   * Called when the request could not be executed due to cancellation, a connectivity problem or
   * timeout. Because networks can fail during an exchange, it is possible that the remote server
   * accepted the request before the failure.
   */
  fun onFailure(
    call: Call,

  /**
   * Tests that a canceled future throws a cancellation exception.
   *
   * <p>This method checks the cancel, isCancelled, and isDone methods.
   */
  public void testCanceledFutureThrowsCancellation() throws Exception {

    assertFalse(future.isDone());
    assertFalse(future.isCancelled());

    CountDownLatch successLatch = new CountDownLatch(1);

    // Run cancellation in a separate thread as an extra thread-safety test.