static final boolean GENERATE_CANCELLATION_CAUSES = false;

  /**
   * Tag interface marking trusted subclasses. This enables some optimizations. The implementation
   * of this interface must also be an AbstractFuture and must not override or expose for overriding
   * any of the public methods of ListenableFuture.
   */
  interface Trusted<V extends @Nullable Object> extends ListenableFuture<V> {}

              // does nothing but delegate to this method.
              AbstractFuture<?> trusted = (AbstractFuture<?>) futureToPropagateTo;
              localValue = trusted.value;
              if (localValue == null | localValue instanceof SetFuture) {
                abstractFuture = trusted;
                continue; // loop back up and try to complete the new future
              }
            } else {