Move code from ExtendsTokenParser to Parser

CHANGELOG

@@ -1,5 +1,6 @@
 # 3.12.0 (2024-XX-XX)
 
+ * Deprecate passing `null` to `Twig\Parser::setParent()`
  * Update `Node::__toString()` to include the node tag if set
  * Add support for integers in methods of `Twig\Node\Node` that take a Node name
  * Deprecate not passing a `BodyNode` instance as the body of a `ModuleNode` or `MacroNode` constructor

doc/deprecated.rst

@@ -166,6 +166,9 @@ Parser
 * The ``Twig\ExpressionParser::parseArrayExpression()`` method is deprecated, use
   ``Twig\ExpressionParser::parseSequenceExpression()`` instead.
 
+* Passing ``null`` to ``Twig\Parser::setParent()`` is deprecated as of Twig
+  3.12.
+
 Templates
 ---------
 

src/Parser.php

@@ -292,6 +292,14 @@ class Parser
 
     public function setParent(?Node $parent): void
     {
+        if (null === $parent) {
+            trigger_deprecation('twig/twig', '3.12', 'Passing "null" to "%s()" is deprecated.', __METHOD__);
+        }
+
+        if (null !== $this->parent) {
+            throw new SyntaxError('Multiple extends tags are forbidden.', $parent->getTemplateLine(), $parent->getSourceContext());
+        }
+
         $this->parent = $parent;
     }
 

src/TokenParser/ExtendsTokenParser.php

@@ -35,9 +35,6 @@ final class ExtendsTokenParser extends AbstractTokenParser
             throw new SyntaxError('Cannot use "extend" in a macro.', $token->getLine(), $stream->getSourceContext());
         }
 
-        if (null !== $this->parser->getParent()) {
-            throw new SyntaxError('Multiple extends tags are forbidden.', $token->getLine(), $stream->getSourceContext());
-        }
         $this->parser->setParent($this->parser->getExpressionParser()->parseExpression());
 
         $stream->expect(Token::BLOCK_END_TYPE);