[DependencyInjection] Fix setting the class of auto-discovery services

Author: nicolas-grekas

Loader/FileLoader.php

@@ -138,6 +138,7 @@ public function registerClasses(Definition $prototype, string $namespace, string
 
                     continue;
                 }
+                $definition->setClass($class);
                 foreach (class_implements($class, false) as $interface) {
                     $this->singlyImplemented[$interface] = ($this->singlyImplemented[$interface] ?? $class) !== $class ? false : $class;
                 }
@@ -253,7 +254,7 @@ private function findClasses(string $namespace, string $pattern, array $excludeP
             foreach ($excludePaths as $path => $_) {
                 $class = $namespace.ltrim(str_replace('/', '\\', substr($path, $prefixLen, str_ends_with($path, '.php') ? -4 : null)), '\\');
                 if (!$this->container->has($class)) {
-                    $this->container->register($class)
+                    $this->container->register($class, $class)
                         ->setAbstract(true)
                         ->addTag('container.excluded', $attributes);
                 }