import static com.google.common.util.concurrent.Futures.immediateCancelledFuture;
import static com.google.common.util.concurrent.Futures.immediateFailedFuture;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import static com.google.common.util.concurrent.SneakyThrows.sneakyThrow;
import static java.util.concurrent.Executors.callable;

      ListenableFuture<? extends O> output = function.apply(input);
      checkNotNull(
          output,
          "AsyncFunction.apply returned null instead of a Future. "
              + "Did you mean to return immediateFuture(null)? %s",
          function);
      return output;
    }

    @Override
    void setResult(ListenableFuture<? extends O> result) {
      setFuture(result);
    }
  }

  /**

import static com.google.common.util.concurrent.Futures.immediateCancelledFuture;
import static com.google.common.util.concurrent.Futures.immediateFailedFuture;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import static com.google.common.util.concurrent.SneakyThrows.sneakyThrow;
import static java.util.concurrent.Executors.callable;

import static com.google.common.util.concurrent.ExecutionSequencer.RunningState.STARTED;
import static com.google.common.util.concurrent.Futures.immediateCancelledFuture;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.Futures.immediateVoidFuture;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import static java.util.Objects.requireNonNull;

            return newValue;
          }
          try {
            return getAndRecordStats(key, hash, computingValueReference, immediateFuture(newValue));
          } catch (ExecutionException exception) {
            throw new AssertionError("impossible; Futures.immediateFuture can't throw");
          }
        } else if (createNewEntry || valueReference.isLoading()) {

    // While this seems like it might be too branch-y, simple benchmarking proves it to be
    // unmeasurable (comparing done AbstractFutures with immediateFuture)
    if (obj instanceof Cancellation) {
      Cancellation cancellation = (Cancellation) obj;
      Throwable cause = cancellation.cause;
      throw cancellationExceptionWithCause("Task was cancelled.", cause);

        if (previousValue == null) {
          V newValue = loader.load(key);
          return set(newValue) ? futureValue : immediateFuture(newValue);
        }
        ListenableFuture<V> newValue = loader.reload(key, previousValue);
        if (newValue == null) {
          return immediateFuture(null);
        }
        // To avoid a race, make sure the refreshed value is set into loadingValueReference

import static com.google.common.util.concurrent.ClosingFuture.Status.WILL_CREATE_VALUE_AND_CLOSER;
import static com.google.common.util.concurrent.Futures.getDone;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.Futures.nonCancellationPropagating;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;