missing use statements :s

src/Composer/Installer/PackageEvent.php

@@ -15,6 +15,11 @@ namespace Composer\Installer;
 use Composer\Composer;
 use Composer\IO\IOInterface;
 use Composer\DependencyResolver\Operation\OperationInterface;
+use Composer\DependencyResolver\PolicyInterface;
+use Composer\DependencyResolver\Pool;
+use Composer\DependencyResolver\Request;
+use Composer\EventDispatcher\Event;
+use Composer\Repository\CompositeRepository;
 
 /**
  * The Package Event.