This one will introduce way too much overhead. We don't really support identifiers that are custom object types.
What is the exact version of the ORM? I couldn't spot anything at line 2407.
I use a dev branch and updated the version since creation of the report, hence the line number changed to 2466.
UnitOfWork.php
} else { $entity = $this->newInstance($class); $oid = spl_object_hash($entity); $this->entityIdentifiers[$oid] = $id; $this->entityStates[$oid] = self::STATE_MANAGED; $this->originalEntityData[$oid] = $data; $this->identityMap[$class->rootEntityName][$idHash] = $entity; // <- 2466 if ($entity instanceof NotifyPropertyChanged) { $entity->addPropertyChangedListener($this); } $overrideLocalValues = true; }
Ok, I understand the overhead problem. I only tried to create a custom enum type that is represented by a class.
But i solved this by converting the value within the getter/setter of entity class.
It would have been nice to do this in the DBAL type, but it works that way.
Therefore, you might close the report or move it on a far future version "wishlist". 
Anyway, thank for your time.
Nevertheless the information you requested:
Composer: doctrine/orm [2.3.x-dev fdd0af3]
git reference: fdd0af34e6fced967b8751bc3e4792c11ef86d57
Additionally, exception trace might help
() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php:2466
Symfony/Component/HttpKernel/Debug/ErrorHandler->handle() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php:2466
Doctrine/ORM/UnitOfWork->createEntity() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/SimpleObjectHydrator.php:135
Doctrine/ORM/Internal/Hydration/SimpleObjectHydrator->hydrateRowData() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/SimpleObjectHydrator.php:50
Doctrine/ORM/Internal/Hydration/SimpleObjectHydrator->hydrateAllData() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php:111
Doctrine/ORM/Internal/Hydration/AbstractHydrator->hydrateAll() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/Persisters/BasicEntityPersister.php:678
Doctrine/ORM/Persisters/BasicEntityPersister->load() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/EntityRepository.php:171
Doctrine/ORM/EntityRepository->findOneBy() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/EntityRepository.php:211
Doctrine/ORM/EntityRepository->__call() at D:/projects/{projectname}/vendor/{customvendor}/lib-doctrine/src/{VendorNs}/Lib/Doctrine/DataFixtures/AbstractBaseFixture.php:123
{VendorNs}/Lib/Doctrine/ORM/Repository/BaseLookupRepository->findOneById() at D:/projects/{projectname}/vendor/{customvendor}/lib-doctrine/src/{VendorNs}/Lib/Doctrine/DataFixtures/AbstractBaseFixture.php:123
{VendorNs}/Lib/Doctrine/DataFixtures/AbstractBaseFixture->findPersistedEntity() at D:/projects/{projectname}/src/ProjectVendor/Bundle/DataFixturesBundle/Classes/ORM/LookupFixture.php:38
{ProjectNs}/Bundle/DataFixturesBundle/Classes/ORM/LookupFixture->lookupentityDefaultBuilder() at D:/projects/{projectname}/src/ProjectVendor/Bundle/DataFixturesBundle/DataFixtures/ORM/Main/User/LookupData.php:59
{ProjectNs}/Bundle/DataFixturesBundle/DataFixtures/ORM/Main/User/LookupData->onlinestatusBuild() at n/a:n/a
call_user_func() at D:/projects/{projectname}/src/ProjectVendor/Bundle/DataFixturesBundle/Classes/ORM/LookupFixture.php:78
{ProjectNs}/Bundle/DataFixturesBundle/Classes/ORM/LookupFixture->lookupentityDefaultLoader() at D:/projects/{projectname}/src/ProjectVendor/Bundle/DataFixturesBundle/DataFixtures/ORM/Main/User/LookupData.php:42
{ProjectNs}/Bundle/DataFixturesBundle/DataFixtures/ORM/Main/User/LookupData->load() at D:/projects/{projectname}/vendor/doctrine/data-fixtures/lib/Doctrine/Common/DataFixtures/Executor/AbstractExecutor.php:120
Doctrine/Common/DataFixtures/Executor/AbstractExecutor->load() at D:/projects/{projectname}/vendor/doctrine/data-fixtures/lib/Doctrine/Common/DataFixtures/Executor/ORMExecutor.php:83
Doctrine/Common/DataFixtures/Executor/ORMExecutor->Doctrine/Common/DataFixtures/Executor/{closure}() at n/a:n/a
call_user_func() at D:/projects/{projectname}/vendor/doctrine/orm/lib/Doctrine/ORM/EntityManager.php:223
Doctrine/ORM/EntityManager->transactional() at D:/projects/{projectname}/var/cache/apps/web/local/jms_diextra/doctrine/EntityManager_50ffafed6b09f.php:31
EntityManager50ffafed6b09f_546a8d27f194334ee012bfe64f629947b07e4919/__CG__/Doctrine/ORM/EntityManager->transactional() at D:/projects/{projectname}/vendor/doctrine/data-fixtures/lib/Doctrine/Common/DataFixtures/Executor/ORMExecutor.php:85
Doctrine/Common/DataFixtures/Executor/ORMExecutor->execute() at D:/projects/{projectname}/vendor/doctrine/doctrine-fixtures-bundle/Doctrine/Bundle/FixturesBundle/Command/LoadDataFixturesDoctrineCommand.php:106
Doctrine/Bundle/FixturesBundle/Command/LoadDataFixturesDoctrineCommand->execute() at D:/projects/{projectname}/vendor/symfony/symfony/src/Symfony/Component/Console/Command/Command.php:238
Symfony/Component/Console/Command/Command->run() at D:/projects/{projectname}/vendor/symfony/symfony/src/Symfony/Component/Console/Application.php:192
Symfony/Component/Console/Application->doRun() at D:/projects/{projectname}/vendor/symfony/symfony/src/Symfony/Bundle/FrameworkBundle/Console/Application.php:78
Symfony/Bundle/FrameworkBundle/Console/Application->doRun() at D:/projects/{projectname}/vendor/symfony/symfony/src/Symfony/Component/Console/Application.php:105
Symfony/Component/Console/Application->run() at D:/projects/{projectname}/bin/console.php:17
This works in this recent commit here, 0864ab8adac5c31d5ba97f0eb6792e5431a75b70. Should have worked before as well. Can you verify?
Related to DDC-1998, tests this behavior