Issue symfony#58821: [DependencyInjection] Support interfaces in ContainerBuilder::getReflectionClass().

Author: donquixote

src/Symfony/Component/DependencyInjection/ContainerBuilder.php

@@ -369,7 +369,7 @@ public function getReflectionClass(?string $class, bool $throw = true): ?\Reflec
                 $resource = new ClassExistenceResource($class, false);
                 $classReflector = $resource->isFresh(0) ? false : new \ReflectionClass($class);
             } else {
-                $classReflector = class_exists($class) ? new \ReflectionClass($class) : false;
+                $classReflector = class_exists($class) || interface_exists($class, false) ? new \ReflectionClass($class) : false;
             }
         } catch (\ReflectionException $e) {
             if ($throw) {