diff -r 6d109e3804ac -r 9a001a04b634 Twig-1.3.0/lib/Twig/NodeVisitor/SafeAnalysis.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Twig-1.3.0/lib/Twig/NodeVisitor/SafeAnalysis.php	Tue Oct 25 23:56:28 2011 +0200
@@ -0,0 +1,107 @@
+<?php
+
+class Twig_NodeVisitor_SafeAnalysis implements Twig_NodeVisitorInterface
+{
+    protected $data = array();
+
+    public function getSafe(Twig_NodeInterface $node)
+    {
+        $hash = spl_object_hash($node);
+        if (isset($this->data[$hash])) {
+            foreach($this->data[$hash] as $bucket) {
+                if ($bucket['key'] === $node) {
+                    return $bucket['value'];
+                }
+            }
+        }
+        return null;
+    }
+
+    protected function setSafe(Twig_NodeInterface $node, array $safe)
+    {
+        $hash = spl_object_hash($node);
+        if (isset($this->data[$hash])) {
+            foreach($this->data[$hash] as &$bucket) {
+                if ($bucket['key'] === $node) {
+                    $bucket['value'] = $safe;
+                    return;
+                }
+            }
+        }
+        $this->data[$hash][] = array(
+            'key' => $node,
+            'value' => $safe,
+        );
+    }
+
+    public function enterNode(Twig_NodeInterface $node, Twig_Environment $env)
+    {
+        return $node;
+    }
+
+    public function leaveNode(Twig_NodeInterface $node, Twig_Environment $env)
+    {
+        if ($node instanceof Twig_Node_Expression_Constant) {
+            // constants are marked safe for all
+            $this->setSafe($node, array('all'));
+        } elseif ($node instanceof Twig_Node_Expression_BlockReference) {
+            // blocks are safe by definition
+            $this->setSafe($node, array('all'));
+        } elseif ($node instanceof Twig_Node_Expression_Parent) {
+            // parent block is safe by definition
+            $this->setSafe($node, array('all'));
+        } elseif ($node instanceof Twig_Node_Expression_Conditional) {
+            // intersect safeness of both operands
+            $safe = $this->intersectSafe($this->getSafe($node->getNode('expr2')), $this->getSafe($node->getNode('expr3')));
+            $this->setSafe($node, $safe);
+        } elseif ($node instanceof Twig_Node_Expression_Filter) {
+            // filter expression is safe when the filter is safe
+            $name = $node->getNode('filter')->getAttribute('value');
+            $args = $node->getNode('arguments');
+            if (false !== $filter = $env->getFilter($name)) {
+                $this->setSafe($node, $filter->getSafe($args));
+            } else {
+                $this->setSafe($node, array());
+            }
+        } elseif ($node instanceof Twig_Node_Expression_Function) {
+            // function expression is safe when the function is safe
+            $name = $node->getAttribute('name');
+            $args = $node->getNode('arguments');
+            $function = $env->getFunction($name);
+            if (false !== $function) {
+                $this->setSafe($node, $function->getSafe($args));
+            } else {
+                $this->setSafe($node, array());
+            }
+        } else {
+            $this->setSafe($node, array());
+        }
+
+        return $node;
+    }
+
+    protected function intersectSafe(array $a = null, array $b = null)
+    {
+        if (null === $a || null === $b) {
+            return array();
+        }
+
+        if (in_array('all', $a)) {
+            return $b;
+        }
+
+        if (in_array('all', $b)) {
+            return $a;
+        }
+
+        return array_intersect($a, $b);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getPriority()
+    {
+        return 0;
+    }
+}