Narrow data type in Symfony NormalizerInterface implementations

[andyexeter]

Hey there,

The following, stripped down example of implementing the symfony/serializer package's NormalizerInterface currently triggers a incompatible-parameter-type error:

<?php declare(strict_types=1);

interface NormalizerInterface
{
    public function normalize(mixed $data): mixed;

    public function supportsNormalization(mixed $data): bool;
}

class MyNormalizer implements NormalizerInterface
{
    /**
     * @param object $data
     */
    public function normalize(mixed $data): mixed
    {
        return $data;
    }

    public function supportsNormalization(mixed $data): bool
    {
        return is_object($data);
    }
}

Playground link: https://mago.carthage.software/playground#019b4a8d-4bf3-a64f-8f82-9eb3e6b32e05

There is no error given in PHPStan.

We know that the $data argument given to normalize will always be an object, because normalize will only be called if supportsNormalization returns true.

I'm not sure if this is a bug per se, hence not reporting this as an issue - but how can I prevent Mago reporting this error?

[Bleksak]

you can use @var annotation to prevent this, or upgrade to symfony 7.4/8.0 where this should be fixed

[andyexeter]

@Bleksak I'm not seeing anything in the diff between 7.3 and 7.4 which would fix this in NormalizerInterface:

symfony/serializer@7.3..7.4#diff-42c85b22d0

[Bleksak]

Hmm I'm not sure if this is a place we missed or we couldn't do much about it. @azjezz can you check please?