[DI] Document PHP-DSL service_closure() function

Author: HypeMC

service_container/service_closures.rst

@@ -77,12 +77,33 @@ argument of type ``service_closure``:
         namespace Symfony\Component\DependencyInjection\Loader\Configurator;
 
         use App\Service\MyService;
-        use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
-        use Symfony\Component\DependencyInjection\Reference;
+        use function Symfony\Component\DependencyInjection\Loader\Configurator\service_closure;
 
         return function (ContainerConfigurator $configurator) {
             $services = $configurator->services();
 
             $services->set(MyService::class)
-                ->args([new ServiceClosureArgument(new Reference('mailer'))]);
+                ->args([service_closure('mailer')]);
+
+            // In case the dependency is optional
+            // $services->set(MyService::class)
+            //     ->args([service_closure('mailer')->nullOnInvalid()]);
         };
+
+Using Service Closures in Compiler Passes
+-----------------------------------------
+
+In :doc:`compiler passes </service_container/compiler_passes>` you can create
+a service closure by wrapping the service reference into an instance of
+:class:`Symfony\\Component\\DependencyInjection\\Argument\\ServiceClosureArgument`::
+
+    use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
+    use Symfony\Component\DependencyInjection\ContainerBuilder;
+    use Symfony\Component\DependencyInjection\Reference;
+
+    public function process(ContainerBuilder $container): void
+    {
+        // ...
+
+        $myService->addArgument(new ServiceClosureArgument(new Reference('mailer')));
+    }