Template bound type throws invalid bound type error when referencing another type of the same templated class

[ste93cry]

Bug report

When a type of the template is bound to a generic type that references another template type, the following (false-positive) errors are thrown:

PHPDoc tag @template ... for class ... has invalid bound type ....
PHPDoc tag @template ... for interface ... has invalid bound type ....

I see at least two issues here: the first one is that the same error is thrown twice (for the same line) like if the analysis was done twice, not sure why (one time for the class and another for the interface, even though the line it's referring to is just the latter). The second and most severe issue is that PHPStan is not recognizing that the bound type is referencing another type of the same templated class.

Code snippet that reproduces the problem

https://phpstan.org/r/175d8c1a-3159-4d28-b761-7d1bb8d80bb2

Expected output

No error expected

[dakur]

It looks like our query bus implementation actually. Just getting rid of baselined errors and this one remains. 🙂

[ste93cry]

That's exactly my use-case, I also tried implementing the feature into PHPStan but could not get it working

[MartinMystikJonas]

I too stumbled upon this. My use case is passing Entity and EntityCollection types to generic ORM mapper.

[ondrejmirtes]

Hi, I'm trying to wrap my head around what are the expectations here. In which case this alternative doesn't work for you? https://phpstan.org/r/7fbb37b7-54bd-4578-97ba-f90272a6719b

[ste93cry]

In your example the TResult param of QueryHandlerInterface is not bound anymore to the TResult param of QueryInterface, therefore you lose the security that the value returned by the handler is of the type expected when using its query. For example, assuming that to the execution of the FooQuery query gets you back a FooQueryResult object, with my use-case you get an error if you try to use an handler that returns BarQueryResult while with yours you don't. Psalm supports this, but it looks like it's not easy to implement according to its internals.

[ondrejmirtes]

@ste93cry A code sample is worth a 1000 words, so I'd like a phpstan.org example with expected output so that I'm sure we're on the same page :)

[ste93cry]

I don't know how I could express this better than the following example with a few comments added. Since the generics are a PHPStan's thing there is no way to assert that the returned value is of the expected type using plain PHP, but ideally the tool should warn me when something is wrong

https://phpstan.org/r/0aa9a099-3d52-4e6d-8875-b510bd8ef66d

Below you can find also the same example with Psalm which works as expected, maybe that's better than any broken example I can get with the PHPStan playground

https://psalm.dev/r/bd6495a1e2

Thank you for trying to understand the issue, I know you said you're busy and this is not a priority on your list but having it work or trying to come up with the solution together would be nice

[ondrejmirtes]

Implemented: phpstan/phpstan-src@e671cc0

I still have some failing tests around this (phpstan/phpstan-src@f5cb727) that I'll resolve before the release is out.

Please test the hell out of this :)

[ste93cry]

Wow, thank you very much for taking the time to implement this, I appreciate this so much!

[ondrejmirtes]

You're welcome :) Feel free to check out the implementation to see what was needed.

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