Fix SplHeap::compare arginfo and tests

[morrisonlevi]

No description provided.

[carusogabriel]

(Stupid question): what does - do here?

[KalleZ]

The - prefix negates the return value, so if the right operand returns 8, then this will return -8

[carusogabriel]

This is a BC, isn't? 😕

[KalleZ]

Adding arginfo is BC

[petk]

BC breaks go to PHP 8 or is it something that PHP 7.4 can handle as well?

[carusogabriel]

@petk BC goes only in PHP 8. See #3443 for example, as well #74035 and #75958

[nikic]

The main thing I'd be concerned about is that a user implements compare with compare(Foo $a, Foo $b), which would no longer satisfy this signature (even with parameter contravariance -- this would need generics to work).

[carusogabriel]

This can be merged against master now :)

[krakjoe]

I'm not certain that Nikita's concern has been or is going to be addressed ?

What do you think about this now @nikic ?

[nikic]

I'm conflicted here. On the one hand, this change is going to make ergonomics worse, because people will no longer be able to typehint their compare() methods. On the other hand, the way this is currently achieved is through a dirty engine hack that probably shouldn't exist in the first place.

Overall I think we should merge this for PHP 8. Not a lot of people override this method and the current behavior is inconsistent with how PHP usually works.

We may also make availability of arginfo a hard requirement in future, in which case this would no longer work anyway.

[nikic]

Merged as 780bdcd into master.