diff -r 000000000000 -r 7f95f8617b0b vendor/symfony/src/Symfony/Component/DependencyInjection/Compiler/CheckCircularReferencesPass.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vendor/symfony/src/Symfony/Component/DependencyInjection/Compiler/CheckCircularReferencesPass.php	Sat Sep 24 15:40:41 2011 +0200
@@ -0,0 +1,69 @@
+<?php
+
+/*
+ * This file is part of the Symfony framework.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+namespace Symfony\Component\DependencyInjection\Compiler;
+
+use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * Checks your services for circular references
+ *
+ * References from method calls are ignored since we might be able to resolve
+ * these references depending on the order in which services are called.
+ *
+ * Circular reference from method calls will only be detected at run-time.
+ *
+ * @author Johannes M. Schmitt <schmittjoh@gmail.com>
+ */
+class CheckCircularReferencesPass implements CompilerPassInterface
+{
+    private $currentId;
+    private $currentPath;
+
+    /**
+     * Checks the ContainerBuilder object for circular references.
+     *
+     * @param ContainerBuilder $container The ContainerBuilder instances
+     */
+    public function process(ContainerBuilder $container)
+    {
+        $graph = $container->getCompiler()->getServiceReferenceGraph();
+
+        foreach ($graph->getNodes() as $id => $node) {
+            $this->currentId = $id;
+            $this->currentPath = array($id);
+
+            $this->checkOutEdges($node->getOutEdges());
+        }
+    }
+
+    /**
+     * Checks for circular references.
+     *
+     * @param array $edges An array of Nodes
+     * @throws \RuntimeException When a circular reference is found.
+     */
+    private function checkOutEdges(array $edges)
+    {
+        foreach ($edges as $edge) {
+            $node = $edge->getDestNode();
+            $this->currentPath[] = $id = $node->getId();
+
+            if ($this->currentId === $id) {
+                throw new ServiceCircularReferenceException($this->currentId, $this->currentPath);
+            }
+
+            $this->checkOutEdges($node->getOutEdges());
+            array_pop($this->currentPath);
+        }
+    }
+}