Inconsistent error on generics

[tamiroh]

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! 😸