[DI] dont mandate a class on inline services with a factory

src/Symfony/Component/DependencyInjection/Compiler/CheckDefinitionValidityPass.php

@@ -14,6 +14,7 @@
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Exception\EnvParameterException;
 use Symfony\Component\DependencyInjection\Exception\RuntimeException;
+use Symfony\Component\DependencyInjection\Loader\FileLoader;
 
 /**
  * This pass validates each definition individually only taking the information
@@ -43,7 +44,7 @@ public function process(ContainerBuilder $container)
             }
 
             // non-synthetic, non-abstract service has class
-            if (!$definition->isAbstract() && !$definition->isSynthetic() && !$definition->getClass()) {
+            if (!$definition->isAbstract() && !$definition->isSynthetic() && !$definition->getClass() && (!$definition->getFactory() || !preg_match(FileLoader::ANONYMOUS_ID_REGEXP, $id))) {
                 if ($definition->getFactory()) {
                     throw new RuntimeException(sprintf('Please add the class to service "%s" even if it is constructed by a factory since we might need to add method calls based on compile-time checks.', $id));
                 }

src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php

@@ -33,6 +33,7 @@
 use Symfony\Component\DependencyInjection\ExpressionLanguage;
 use Symfony\Component\DependencyInjection\LazyProxy\PhpDumper\DumperInterface as ProxyDumper;
 use Symfony\Component\DependencyInjection\LazyProxy\PhpDumper\NullDumper;
+use Symfony\Component\DependencyInjection\Loader\FileLoader;
 use Symfony\Component\DependencyInjection\Parameter;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\ServiceLocator as BaseServiceLocator;
@@ -1206,7 +1207,7 @@ private function addRemovedIds(): string
             $ids = array_keys($ids);
             sort($ids);
             foreach ($ids as $id) {
-                if (preg_match('/^\.\d+_[^~]++~[._a-zA-Z\d]{7}$/', $id)) {
+                if (preg_match(FileLoader::ANONYMOUS_ID_REGEXP, $id)) {
                     continue;
                 }
                 $code .= '            '.$this->doExport($id)." => true,\n";

src/Symfony/Component/DependencyInjection/Loader/FileLoader.php

@@ -26,6 +26,8 @@
  */
 abstract class FileLoader extends BaseFileLoader
 {
+    public const ANONYMOUS_ID_REGEXP = '/^\.\d+_[^~]++~[._a-zA-Z\d]{7}$/';
+
     protected $container;
     protected $isLoadingInstanceof = false;
     protected $instanceof = [];

src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckDefinitionValidityPassTest.php

@@ -14,6 +14,7 @@
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\DependencyInjection\Compiler\CheckDefinitionValidityPass;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
 
 class CheckDefinitionValidityPassTest extends TestCase
 {
@@ -35,6 +36,19 @@ public function testProcessDetectsNonSyntheticNonAbstractDefinitionWithoutClass(
         $this->process($container);
     }
 
+    public function testProcessDetectsFactoryWithoutClass()
+    {
+        $container = new ContainerBuilder();
+
+        $container->register('.123_anonymous_service_id_should_not_throw_~1234567')->setFactory('factory');
+        $this->process($container);
+
+        $this->expectException(RuntimeException::class);
+        $container->register('.any_non_anonymous_id_throws')->setFactory('factory');
+
+        $this->process($container);
+    }
+
     public function testProcess()
     {
         $container = new ContainerBuilder();