Problem with generics and extends

[nikophil]

Support question

Hello,

i'm trying to solve a "contravariance problem" with generics.

I reproduced my problem in phpstan's playground: https://phpstan.org/r/74032d14-212e-4d02-9871-dc2e80ec2808

I don't understand why in the context of my object ChildGenericClass contextualized on Model, i cannot pass to its parent's constructor a generics contextualized on Model as well.

thanks for your help and amazing work :)

[ondrejmirtes]

parent::__construct doesn't currently work correctly from generics point of view. There's definitely an issue about that already, but I'm gonna keep this one open too.

[nikophil]

ok perfect, thanks :)

i don't know how complicated the fix would be, but i would definitely be interested to try to help on this

[mvorisek]

not sure if related, but the following code does not work in playground:

<?php declare(strict_types = 1);

/**
 * @template T
 */
abstract class A
{
}

/**
 * @template T
 * @extends parent<T>
 */
class B extends A
{
}

there is probably some infinity recursion, which makes even the Share button to not work (code should be shareable even if phpstan did not finish).

[nikophil]

shouldn't you do this way?

<?php 

declare(strict_types = 1);

/**
 * @template T
 */
abstract class A
{
}

/**
 * @template T
 * @extends A<T>
 */
class B extends A
{
}

[mvorisek]

@nikophil I already did it that way, but that code is very dangerous as it can be very easily missed to be renamed when copying to another child class - thus parent<T> should work.

[phpstan-bot]

@nikophil After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-20: Parameter #1 $otherGenericClass of method GenericClass<BaseModel>::__construct() expects OtherGenericClass<BaseModel>, OtherGenericClass<Model> given.
+No errors

[github-actions]

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