Fix incompatibility with old PHP versions

CHANGELOG

@@ -1,7 +1,7 @@
 # 3.9.0 (2024-XX-XX)
 
  * Deprecate AbstractNodeVisitor
- * Deprecate passing Template to Environment::resolveTemplate() and Template::loadTemplate()
+ * Deprecate passing Template to Environment::resolveTemplate(), Environment::load(), and Template::loadTemplate()
  * Add a new "yield" mode for output generation;
    Node implementations that use "echo" or "print" should use "yield" instead;
    all Node implementations should be flagged with `#[YieldReady]` once they've been made ready for "yield";

doc/deprecated.rst

@@ -23,3 +23,11 @@ Node Visitors
 
 * The ``Twig\NodeVisitor\AbstractNodeVisitor`` class is deprecated, implement the
   ``Twig\NodeVisitor\NodeVisitorInterface`` interface instead.
+
+Templates
+---------
+
+* Passing ``Twig\\Template`` instances to Twig public API is deprecated (like
+  in ``Environment::resolveTemplate()``, ``Environment::load()``, and
+  ``Template::loadTemplate()``); pass instances of ``Twig\\TemplateWrapper``
+  instead.

src/Environment.php

@@ -327,6 +327,11 @@ class Environment
         if ($name instanceof TemplateWrapper) {
             return $name;
         }
+        if ($name instanceof Template) {
+            trigger_deprecation('twig/twig', '3.9', 'Passing a "%s" instance to "%s" is deprecated.', self::class, __METHOD__);
+
+            return $name;
+        }
 
         return new TemplateWrapper($this, $this->loadTemplate($this->getTemplateClass($name), $name));
     }
@@ -448,7 +453,7 @@ class Environment
      * @throws LoaderError When none of the templates can be found
      * @throws SyntaxError When an error occurred during compilation
      */
-    public function resolveTemplate(string|TemplateWrapper|Template|array $names): TemplateWrapper
+    public function resolveTemplate($names): TemplateWrapper
     {
         if (!\is_array($names)) {
             return $this->load($names);

src/Template.php

@@ -253,7 +253,7 @@ abstract class Template
      *
      * @return self|TemplateWrapper
      */
-    protected function loadTemplate(string|TemplateWrapper|self|array $template, $templateName = null, $line = null, $index = null)
+    protected function loadTemplate($template, $templateName = null, $line = null, $index = null)
     {
         try {
             if (\is_array($template)) {