Discover repository class from #[Entity] attribute on PHP 8

By doing it like this, we don't need to instantiate the object manager at all.

Unfortunately, BetterReflection doesn't support attributes yet so therefore we need to use native `ReflectionClass`.

See phpstan/phpstan#5863 (reply in thread)

Author: ruudk

src/Type/Doctrine/ObjectMetadataResolver.php

@@ -2,8 +2,10 @@
 
 namespace PHPStan\Type\Doctrine;
 
+use Doctrine\ORM\Mapping\Entity;
 use Doctrine\Persistence\ObjectManager;
 use PHPStan\Reflection\ReflectionProvider;
+use ReflectionClass;
 use function is_file;
 use function is_readable;
 
@@ -97,6 +99,17 @@ public function getResolvedRepositoryClass(): string
 
 	public function getRepositoryClass(string $className): string
 	{
+		if (PHP_MAJOR_VERSION >= 8 && $this->reflectionProvider->hasClass($className)) {
+			/** @phpstan-var class-string $className */
+			$reflector = new ReflectionClass($className);
+			if (method_exists($reflector, 'getAttributes')) {
+				$entityAttribute = $reflector->getAttributes(Entity::class)[0] ?? null;
+				if ($entityAttribute !== null) {
+					return $entityAttribute->newInstance()->repositoryClass;
+				}
+			}
+		}
+
 		$objectManager = $this->getObjectManager();
 		if ($objectManager === null) {
 			return $this->getResolvedRepositoryClass();