Generics inheritance raises errors

[remi-san]

Bug report

Using v0.12.31

When declaring type implementing or extending a generic type, when this type is passed as a parameter or as a return, it is not considered a subclass of the generic type it implements or extend.

Code snippet that reproduces the problem

<?php

declare(strict_types=1);

interface Entity{}

final class Dish implements Entity
{
}

/**
 * @template T of Entity
 */
interface Filter {}

/**
 * @extends Filter<Dish>
 */
interface DishFilter extends Filter {}

/**
 * @extends SearchDoctrineRepository<Dish>
 */
final class DishDoctrineRepository extends SearchDoctrineRepository
{
    /**
     * @return array<Dish>
     */
    public function filter(DishFilter $filter): array
    {
        return parent::filterEntities($filter);
    }
}

/**
 * @template T of Entity
 */
abstract class SearchDoctrineRepository
{
    /**
     * @param Filter<T>     $filter
     *
     * @return array<T>
     */
    public function filterEntities(Filter $filter): array
    {
        return [];
    }
}

This code raises the following errors:

• Method DishDoctrineRepository::filter() should return array<Dish> but returns array<Entity>.
• Parameter #1 $filter of method SearchDoctrineRepository<Entity>::filterEntities() expects Filter<Entity>, DishFilter given.

It can be found here https://phpstan.org/r/5200477a-9300-454d-bca8-59511b8c51d3

Expected output

Given that DishDoctrineRepository extends SearchDoctrineRepository<Dish> I expect the return type of filterEntities() to be array<Dish> and not array<Entity> as it is detected.

And because DishFilter extends Filter<Dish>, when the method expects Filter<Dish>, it should allow to get a DishFilter.

Am I doing something wrong here?

[hultberg]

I think I may have the same issue with @extends. I have an example in https://phpstan.org/r/952f7013-2b00-4cb4-9e26-353a9924f3b3 where I attempt to extend AnimalCollection to accept the same as AnimalCollection does, but it seems that phpstan thinks AnimalQueue only ever contain an "Animal" and not "Dog" as the AnimalQueue was created with. I have tried several combinations with covariant without luck.

In this playground https://phpstan.org/r/8e09eb41-fa34-4714-9996-994c911d8910 I have removed T of Animal, and I get no error, but the usage of getName() inside AnimalCollection is not detected it seems.

[ondrejmirtes]

@hultberg Your error isn't related to OP but rather to #2735. Repeating the constructor in the child class will work for you now: https://phpstan.org/r/8edeab32-683a-4b49-86fa-5213bd955b10

[phpstan-bot]

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

@@ @@
-31: Method DishDoctrineRepository::filter() should return array<Dish> but returns array<Entity>.
 31: Parameter #1 $filter of method SearchDoctrineRepository<Entity>::filterEntities() expects Filter<Entity>, DishFilter given.

Full report

Line	Error
31	Parameter #1 $filter of method SearchDoctrineRepository<Entity>::filterEntities() expects Filter<Entity>, DishFilter given.

[ondrejmirtes]

Fixed: phpstan/phpstan-src@4acbc6c

You can get rid of the remaining error with @template-covariant: https://phpstan.org/r/c4bc2358-d836-4dca-9222-02ebc82d34e3

[github-actions]

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