False positive on DateTime(Immutable)

[Tobion]

Bug report

Phpstan does not seem to understand that there are only two implementations of DateTimeInterface.
The following code

public function __construct(\DateTimeInterface $date)
{
	$this->date = $date instanceof \DateTimeImmutable ? $date : \DateTimeImmutable::createFromMutable($date);
}

results in wrong error

Parameter #1 $object of static method DateTimeImmutable::createFromMutable() expects DateTime, DateTimeInterface given.

Code snippet that reproduces the problem

https://phpstan.org/r/6db83755-bca0-4294-a457-3d38a503aaac

[ondrejmirtes]

This is expected error, PHPStan does not have hardcoded knowledge there's only two implementations of DateTimeInterface. Use union of the two types instead (in PHPDoc if you're on PHP 7.x): https://phpstan.org/r/0e8fa65d-202a-41d0-9e1e-01941886341a

[Tobion]

But I think phpstan should have this hardcoded knowledge. Custom implementations of DateTimeInterface are not possible. False positive errors should be avoided as much as possible because those are hurting phpstan usability the most.

[Tobion]

Also changing to union types won't help. The DateTimeInterface is coming from a long chain of other code and even third party code.
So just changing to union types will create a different false positive

Parameter ... of class ... constructor expects DateTime|DateTimeImmutable, DateTimeInterface given.

[Tobion]

@ondrejmirtes any chance to reconsider this?

[ondrejmirtes]

@Tobion I'm not promising PHPStan will understand this in every scenario, but I did a simple fix for your case: phpstan/phpstan-src@5eb96f5

[Tobion]

Cool, thank you.

[github-actions]

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