added a way to trigger deprecation notices for filters and functions

lib/Twig/ExpressionParser.php

@@ -578,6 +578,16 @@ class Twig_ExpressionParser
             throw new Twig_Error_Syntax($message, $line, $this->parser->getFilename());
         }
 
+        if ($function instanceof Twig_SimpleFunction && $function->isDeprecated()) {
+            $message = sprintf('Twig Function "%s" is deprecated', $function->getName());
+            if ($test->getAlternative()) {
+                $message .= sprintf('. Use "%s" instead', $function->getAlternative());
+            }
+            $message .= sprintf(' in %s at line %d.', $this->parser->getFilename(), $line);
+
+            @trigger_error($message, E_USER_DEPRECATED);
+        }
+
         if ($function instanceof Twig_SimpleFunction) {
             return $function->getNodeClass();
         }
@@ -598,6 +608,16 @@ class Twig_ExpressionParser
             throw new Twig_Error_Syntax($message, $line, $this->parser->getFilename());
         }
 
+        if ($filter instanceof Twig_SimpleFilter && $filter->isDeprecated()) {
+            $message = sprintf('Twig Filter "%s" is deprecated', $filter->getName());
+            if ($test->getAlternative()) {
+                $message .= sprintf('. Use "%s" instead', $filter->getAlternative());
+            }
+            $message .= sprintf(' in %s at line %d.', $this->parser->getFilename(), $line);
+
+            @trigger_error($message, E_USER_DEPRECATED);
+        }
+
         if ($filter instanceof Twig_SimpleFilter) {
             return $filter->getNodeClass();
         }

lib/Twig/SimpleFilter.php

@@ -34,6 +34,8 @@ class Twig_SimpleFilter
             'pre_escape' => null,
             'preserves_safety' => null,
             'node_class' => 'Twig_Node_Expression_Filter',
+            'deprecated' => false,
+            'alternative' => null,
         ), $options);
     }
 
@@ -97,4 +99,14 @@ class Twig_SimpleFilter
     {
         return $this->options['is_variadic'];
     }
+
+    public function isDeprecated()
+    {
+        return $this->options['deprecated'];
+    }
+
+    public function getAlternative()
+    {
+        return $this->options['alternative'];
+    }
 }

lib/Twig/SimpleFunction.php

@@ -32,6 +32,8 @@ class Twig_SimpleFunction
             'is_safe' => null,
             'is_safe_callback' => null,
             'node_class' => 'Twig_Node_Expression_Function',
+            'deprecated' => false,
+            'alternative' => null,
         ), $options);
     }
 
@@ -87,4 +89,14 @@ class Twig_SimpleFunction
     {
         return $this->options['is_variadic'];
     }
+
+    public function isDeprecated()
+    {
+        return $this->options['deprecated'];
+    }
+
+    public function getAlternative()
+    {
+        return $this->options['alternative'];
+    }
 }