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

vendor/symfony/dependency-injection/Compiler/ServiceReferenceGraphEdge.php

@@ -0,0 +1,70 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\DependencyInjection\Compiler;
+
+/**
+ * Represents an edge in your service graph.
+ *
+ * Value is typically a reference.
+ *
+ * @author Johannes M. Schmitt <schmittjoh@gmail.com>
+ */
+class ServiceReferenceGraphEdge
+{
+    private $sourceNode;
+    private $destNode;
+    private $value;
+
+    /**
+     * Constructor.
+     *
+     * @param ServiceReferenceGraphNode $sourceNode
+     * @param ServiceReferenceGraphNode $destNode
+     * @param string                    $value
+     */
+    public function __construct(ServiceReferenceGraphNode $sourceNode, ServiceReferenceGraphNode $destNode, $value = null)
+    {
+        $this->sourceNode = $sourceNode;
+        $this->destNode = $destNode;
+        $this->value = $value;
+    }
+
+    /**
+     * Returns the value of the edge.
+     *
+     * @return ServiceReferenceGraphNode
+     */
+    public function getValue()
+    {
+        return $this->value;
+    }
+
+    /**
+     * Returns the source node.
+     *
+     * @return ServiceReferenceGraphNode
+     */
+    public function getSourceNode()
+    {
+        return $this->sourceNode;
+    }
+
+    /**
+     * Returns the destination node.
+     *
+     * @return ServiceReferenceGraphNode
+     */
+    public function getDestNode()
+    {
+        return $this->destNode;
+    }
+}