"Asserted type does not narrow down the type" when using assertions with generics

[chris54721]

Bug report

When using assertions such as @phpstan-assert-if-true with generics, if the extending class specifies the same type specified in the "upper bound" of the generic (in the example: @template TAttribute of string and @extends Voter<string, Post>), the assert.alreadyNarrowedType error is returned.

As a workaround, I am using @extends Voter<non-empty-string, Post>.

The Voter class in the example is adapted from the phpstan/phpstan-symfony stub.

Can reproduce only with PHPStan 1.10.58 (not <=1.10.57)

Code snippet that reproduces the problem

https://phpstan.org/r/d2eb8124-32b6-4d5f-8d75-536c7357a17f

Expected output

It should not report the error as not narrowing the type is a valid thing to do.

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[RobertMe]

As a second work-a-round. Personally I just prefer to be explicit with TAttribute, i.e. like this: https://phpstan.org/r/2842e234-4c51-4a80-b87b-e49ec8cad94a
Not solely because of the error it now gives (calling with aaa while it only accepts POST_READ). But if you have a voter which supports multiple attributes (which you can union, like 'POST_READ'|'POST_WRITE') then PHPStan will also automatically error when you have a match or switch which doesn't handle all cases, like this: https://phpstan.org/r/ea859beb-bfc8-4b3f-8f28-402732816720 / https://phpstan.org/r/884e8030-fd93-4a79-9f57-2b4c8e30ddda

So being explicit in the supported attributes means that you get even better static analyses.

@ondrejmirtes I guess this is due to phpstan/phpstan-src#2909? As then it will then read the same attribute on the inherited instance as if it was written by hand. So do you have any hint for a fix? As I would obviously like to resolve the bug I created with my fix. But not sure how the rule giving this "new" error could determine whether the assert tag is inherited or handwritten.

[ondrejmirtes]

Fixed: phpstan/phpstan-src@299df51

[floviolleau]

Hi,

I have this issue with phpstan 1.10.58 and not with 1.10.57.
I saw that you fixed it on 1.11 branch. Will it be fixed on 1.10 branch?

Thanks a lot

[ondrejmirtes]

It's fixed on 1.10.x. It's going to be released in matter of days.

[ondrejmirtes]

Released: https://github.com/phpstan/phpstan/releases/tag/1.10.59

[github-actions]

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