Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/doctrine/collections/tests/Doctrine/Tests/LazyArrayCollection.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Doctrine\Tests;
+
+use Doctrine\Common\Collections\AbstractLazyCollection;
+use Doctrine\Common\Collections\ArrayCollection;
+
+/**
+ * Simple lazy collection that used an ArrayCollection as backed collection
+ */
+class LazyArrayCollection extends AbstractLazyCollection
+{
+    /**
+     * Do the initialization logic
+     *
+     * @return void
+     */
+    protected function doInitialize()
+    {
+        $this->collection = new ArrayCollection(array('a', 'b', 'c'));
+    }
+}