Inconsistent error on generics

Bug report

For the following code with generics,

<?php declare(strict_types = 1);

/**
 * @template TKey
 * @template TValue
 */
class Collection
{
    ...
}

/**
  * @param Collection<int, string|null> $collection
  */
function testFunc(Collection $collection): void
{

}

$collection = new Collection([0 => 'foo', 1 => 'bar', 2 => null, 3 => 'baz']);

PHPStan reports the following inconsistent errors.

Parameter #1 $collection of function testFunc expects Collection<int, string|null>, Collection<int, string|null> given.

From my few attempts, this seems to happen when...

The value of the collection is nullable
Bleeding edge is enabled
PHPStan Level is less than 8

Code snippet that reproduces the problem

https://phpstan.org/r/6cb19ed5-8774-4178-a21b-a7e19d1934f9

Expected output

No errors.

Did PHPStan help you today? Did it make you happy in any way?

Yes, really helpful for finding bugs. Thank you so much! 😸

Having attempted somewhat, it seems that setting featureToggles.newRuleLevelHelper to false works around this problem for now 👀

@tamiroh

@tamiroh That's not a solution. This option will go away in 2.0 and everybody will get the same (new) behaviour.

@ondrejmirtes

@ondrejmirtes Yes, you are right. This is just a temporary work-around 😓. So I was just starting to think about how to fix it.

I must confirm this still happens, I, very unwillingly, bypassed it by removing the |null from the type, which shouldn't be needed. and it's inconsistent with the App class definition.

The App class defines @template TContainerInterface of (ContainerInterface|null),
now normally @param App<ContainerInterface|null> $app works, but not when you call function within the same class that has the same annotation as input:

<?php
class MyClass {
    /**
     * @param App<ContainerInterface|null> $app
     */
    public function registerSomething(App $app): void
    {
            $this->doRegister(
                app: $app,
                target: 'something',
            );
    }

    /**
     * @param App<ContainerInterface|null> $app
     */
    private function doRegister(App $app, string $target): void
    {
        $app->magic($target);
    }
}

I even tried to define a union type TContainerInterface on the class level as the App class does it and use App<TContainerInterface> - no still the same problem on the line calling ->doRegister(...:

Parameter $app of method MyClass<TContainerInterface of Psr\Container\ContainerInterface|null>::doRegister() expects
App<Psr\Container\ContainerInterface|null>, App<Psr\Container\ContainerInterface|null> given.

Note that I have the latest phpstan as of now - "2.1.14".

I mean the types are FQNs and EXACTLY the same.

This is the same issue than #9096 (comment)

Closed via merging phpstan/phpstan-src#6392

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.

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Inconsistent error on generics #11041

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Inconsistent error on generics #11041

Description

Bug report

Code snippet that reproduces the problem

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Did PHPStan help you today? Did it make you happy in any way?

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tamiroh commented on Sep 3, 2024

ondrejmirtes commented on Sep 3, 2024

tamiroh commented on Sep 3, 2024

realjjaveweb commented on May 5, 2025

VincentLanglet commented on Aug 2, 2025

phpstan-bot commented on Sep 10, 2026

github-actions commented on Oct 12, 2026

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