$target = new class {
    public function getMe() { return $this; }
};
$targetData = $serializer->normalize($target, null, [
    AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER => static fn($v) => is_object($v) ? get_class($v) : gettype($v)
]);

// Normalized data as expected:
// $targetData === ["me" => "class@anonymous\x00 ...."];

$target = new class implements \JsonSerializable {
    public function jsonSerialize() { return ['me' => $this]; }
};
$targetData = $serializer->normalize($target, null, [
    AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER => static fn($v) => is_object($v) ? get_class($v) : gettype($v)
]);

// Same result expected as above, but an exception will be thrown instead:
// Symfony\Component\Serializer\Exception\CircularReferenceException("A circular reference has been detected when serializing the object of class "JsonSerializable@anonymous" (configured limit: 1).")