[DI] Add missing deprecation on Extension::getClassesToCompile

UPGRADE-3.3.md

@@ -266,7 +266,7 @@ HttpKernel
  * Deprecated the `Kernel::getRootDir()` method. Use the new `Kernel::getProjectDir()`
    method instead.
 
- * The `Extension::addClassesToCompile()` method has been deprecated and will be removed in 4.0.
+ * The `Extension::addClassesToCompile()` and `Extension::getClassesToCompile()` methods have been deprecated and will be removed in 4.0.
 
  * The `Psr6CacheClearer::addPool()` method has been deprecated. Pass an array
    of pools indexed by name to the constructor instead.

UPGRADE-4.0.md

@@ -376,7 +376,7 @@ HttpKernel
  * Removed the `Kernel::getRootDir()` method. Use the `Kernel::getProjectDir()`
    method instead.
 
- * The `Extension::addClassesToCompile()` method has been removed.
+ * The `Extension::addClassesToCompile()` and `Extension::getClassesToCompile()` methods have been removed.
 
  * Possibility to pass non-scalar values as URI attributes to the ESI and SSI
    renderers has been removed. The inline fragment renderer should be used with

src/Symfony/Component/HttpKernel/CHANGELOG.md

@@ -10,7 +10,7 @@ CHANGELOG
  * deprecated the special `SYMFONY__` environment variables
  * added the possibility to change the query string parameter used by `UriSigner`
  * deprecated `LazyLoadingFragmentHandler::addRendererService()`
- * deprecated `Extension::addClassesToCompile()`
+ * deprecated `Extension::addClassesToCompile()` and `Extension::getClassesToCompile()`
  * deprecated `Psr6CacheClearer::addPool()`
 
 3.2.0

src/Symfony/Component/HttpKernel/DependencyInjection/Extension.php

@@ -27,9 +27,15 @@ abstract class Extension extends BaseExtension
      * Gets the classes to cache.
      *
      * @return array An array of classes
+     *
+     * @deprecated since version 3.3, to be removed in 4.0.
      */
     public function getClassesToCompile()
     {
+        if (PHP_VERSION_ID >= 70000) {
+            @trigger_error(__METHOD__.'() is deprecated since version 3.3, to be removed in 4.0.', E_USER_DEPRECATED);
+        }
+
         return $this->classes;
     }