It seems like $this->authGateway->wikiSessionId() can also be of type null; however, parameter $identifier of App\Src\UseCases\Domain\...mousUser::__construct() does only seem to accept string, maybe add an additional type check?
(
Ignorable by Annotation
)
If this is a false-positive, you can also ignore this issue in your code via the ignore-type annotation
40
return new AnonymousUser(/** @scrutinizer ignore-type */ $this->authGateway->wikiSessionId());