Add support for @template-contravariant

[autaut03]

Closes phpstan/phpstan#3960

[autaut03]

Should I also add some data sets to dataGetReferencedTypeArguments?

[autaut03]

Also, the tests are failing due to those errors missing. I haven't had time to debug why PHPStan doesn't report them, although I do believe they should be:

-94: Template type K is declared as contravariant, but occurs in invariant position in parameter l of method MethodSignatureVariance\B::a().
-127: Template type K is declared as contravariant, but occurs in invariant position in return type of method MethodSignatureVariance\B::l().
-130: Template type K is declared as contravariant, but occurs in invariant position in return type of method MethodSignatureVariance\B::m().

If somebody can help with those that'd be greatly appreciated :)

edit: Solved by adding the if($this->invariant()) return invariant(); check. Need to verify this is ok

[autaut03]

This change has broken some things. But is this change wrong?

[autaut03]

This change is in fact correct, this has also been a bug in PHPStan since 2019. Given the example from the test:

class Base {}
class Extended extends Base {}

/**
 * @template-contravariant K
 */
class B {
	/**
	 * @param Invariant<Out<In<K>>> $l
	 */
	function a($l) {}
}

/**
 * @param B<Extended> $b
 */
function f1($b) {}

/**
 * @param B<Base> $b
 */
function f2($b) {
    f1($b);
}

Without this change, PHPStan would effectively allow changing an invariant type parameter from Out<In<Extended>> to Out<In<Base>>, which is a bug.

@ondrejmirtes Can you verify I'm not wrong so I can fix the tests this has affected?

[ondrejmirtes]

this has also been a bug in PHPStan since 2019

Can you please show the bug on an existing code on phpstan.org/try? Your example uses @template-contravariant which is a new feature (so it couldn't be a bug in 2019).

[autaut03]

Sure thing. Here's a similar example with @template-covariant: https://phpstan.org/r/144953ee-3dfd-4606-a558-b373309ef9c5

It should have given the following error, but it currently passes: Template type K is declared as covariant, but occurs in invariant position in parameter a of method C::a().

[oprypkhantc]

Any updates on this @ondrejmirtes? I'd love to finish this PR and get it merged

[autaut03]

All the newly reported errors are technically all correct. It doesn't make sense that changing of variance for an extended class is allowed. It is currently covered by other PHPStan rules, but is there a point in doing that?

https://phpstan.org/r/fa55f2f8-8798-47fd-99d7-06c007e44be2

[ondrejmirtes]

Sorry, I can't review or merge this PR, the build is pretty broken. Please make it green first.

[autaut03]

Sorry, I can't review or merge this PR, the build is pretty broken. Please make it green first.

Sure. I was just waiting for a response in a thread above. I'll make it green.

[ondrejmirtes]

Yeah, at the same time I'm not sure about the failures, I need to see how the fixes look like. Is the code that causes the errors the added if ($this->invariant()) {? Does the @template-contravariant feature need that addition or not?

Maybe we could decouple that fix from the rest of the feature, it looks pretty blocking to me.

So maybe the build would be come green by removing the if ($this->invariant()) { and you could send another PR with that to have a discussion about that?

[autaut03]

Yeah, at the same time I'm not sure about the failures, I need to see how the fixes look like. Is the code that causes the errors the added if ($this->invariant()) {? Does the @template-contravariant feature need that addition or not?

Maybe we could decouple that fix from the rest of the feature, it looks pretty blocking to me.

So maybe the build would be come green by removing the if ($this->invariant()) { and you could send another PR with that to have a discussion about that?

Yeah, it's all caused by that change. Decoupling it sounds good, I'll do that.

[ondrejmirtes]

Awesome 👍

[ondrejmirtes]

Hi, I'm cleaning up old and stale PRs. Please send a new PR if you're still interested, thanks.