aren't you missing by default in this sentence ?

indeed ;) I will add it.

adding the typehint is a BC break as the class/method was not final. Non-updated child classes will trigger a deprecation warning (see https://3v4l.org/KO9T1), and updated child class will be incompatible with 3.4. So this BC break does not have an upgrade path

But there was a deprecation notice in 3.* and now it's 4.0 so we can broke the BC, right ?

And I agree there is no clean upgrade path. Users should just add this new type hint.

Do you think I should remove this?

Or we can bump symfony to PHP 7.2 to get https://wiki.php.net/rfc/parameter-no-type-variance :D

It should be possible to deprecate using something else than a SupportStrategyInterface in 3.4 and add this type-hint for 4.0, I don't see the problem 😕

@lyrixx:
To explain with more words:
Keep the add(Workflow $workflow, $supportStrategy) for 3.x, but starting from 3.4, you can add this code in the add function:

public function add(Workflow $workflow, $supportStrategy)
{
    if (!$supportStrategy instanceof SupportStrategyInterface) {
        @trigger_error('Using a strategy that does not implement '.SupportStrategyInterface::class.' is deprecated since version 3.4 and will be removed in 4.0.', E_USER_DEPRECATED);
    }
}

This is for 3.4

And for 4.0, you remove this deprecation and add the type-hint for SupportStrategyInterface.

That's all, it allows users that extend this method to be warned that the signature will be changed as of 4.0

@Pierstoval the issue about adding the typehint is not for people calling this code (this already has the proper deprecation). It is for people extending it (and indeed, this is solved on PHP 7.2+, which is a good news for our future)

1/ This is wrong. This is a real BC on 3.4 and this is strictly not possible to do that. We have to allow string argument to respect the BC promise

2/ There is already a deprecation notice in the 3.* branch

@Pierstoval the issue is that changing the typehint does not allow them to support both 3.4 and 4.0 at the same time in their child class => no continuous upgrade path)

I removed the new type hint, And I added it to the private method supports

4.0.0