Declare incompatibility with `symfony/security-core` 6

[derrabus]

On the 6.0 branch, symfony/security-core has added return type declarations to the VoterInterface. Our implementation AclVoter is incompatible which is why our high-deps CI job is currently failing.

Since this incompatibility is not trivial to fix in a backwards-compatible manner, I propose to remove the 6.0 branch from the list of compatible versions.

[wouterj]

Unfortunately, doing this will break the symfony/symfony CI as it requires this component.

(we did this just before we made the previous release, which you corrected swiftly in https://github.com/symfony/security-acl/pull/92 )

[nicolas-grekas]

We'd better remove the return types on branch 6.0 I suppose.

[wouterj]

Maybe I'm missing something, but doesn't that mean that we must remove return types from all methods that are in classes that are not internal or final? That would be a real bummer...

[nicolas-grekas]

See my monolog on the topic at https://github.com/symfony/symfony/pull/42496 :)

[derrabus]

Well, for this library, it's actually one (!) method that causes us trouble. I'm convinced we can manage that without reverting every return type we've added so far. 😱

[nicolas-grekas]

We'd remove the return type only from VoterInterface::vote() then. The pain we feel now is the one the community will also feel very soon. Removing a few return types to reduce the migration cost looks worth it to me.

[derrabus]

We'd remove the return type only from VoterInterface::vote() then.

symfony/symfony#42901

[derrabus]

Closing because this has been resolved in Symfony.

[nicolas-grekas]

Linking to https://github.com/symfony/symfony/issues/43021 for history.