React\Promise\Deferred::resolve PHP Method

    public function resolve($value = null)
    {
        $this->promise();
        call_user_func($this->resolveCallback, $value);
    }

 /**
  * Make a directory as described in the task description
  * @param Deferred $deferred
  * @param TaskInterface $task
  * @return bool
  */
 protected function processDeferred(Deferred $deferred, TaskInterface $task)
 {
     yield;
     /** @var Description $description */
     $description = $task->getDescription();
     $deferred->notify(new Notification("Creating directory '{$description->getName()}'", Notification::PRIORITY_NORMAL));
     if ($this->getFileSystem()->isDirectory($description->getName())) {
         $deferred->resolve("Directory '{$description->getName()}' already exists");
         return;
     }
     if ($this->getFileSystem()->makeDirectory($description->getName())) {
         $deferred->resolve("Created directory '{$description->getName()}'");
         return;
     }
     $deferred->reject("Directory '{$description->getName()}' could not be created");
 }