Using assertions with generics / template types

[RobertMe]

Hi,

I'm getting a confusing error in relation to using a type assertion mixed with a generic, and I'm uncertain whether I'm using this correctly. I've created a reproducer in the playground: https://phpstan.org/r/c8276a36-06ea-4fe6-9617-f88a70f1ece6

My expectation would be that the second dumpType would still result in FooDescription, while it actually is FooDescription&TDescription of Description<TItem of ItemInterface (class UserInterface, parameter)> (class UserInterface, parameter) (not sure what the meaning of the additional (class UserInterface, parameter) is those two times). This while TDescription is set to FooDescription, so I would expect this to be resolved into FooDescription&FooDescription aka FooDescription.

Futhermore in my actual code the return value of this do() method is another generic which uses TDescription as well and is created with $description. And this then also fails because the type doesn't comply, like this extended playground example: https://phpstan.org/r/ad9838f8-eabf-43c6-99f0-7db736a70186

Furthermore in my actual code I'm using this generic as input for another generic which is determined based on the nested type TItem for which a Description<TItem> is used. And this also fails because the intersection doesn't comply. This this playground example: https://phpstan.org/r/fae7d444-e733-42cd-80fb-1abbf68cdb51 .

So my question is whether I am using the assertion correctly, or whether this is a bug. (Obvious workaround would be to drop the @phpstan-assert-if-true annotation :), which fixes my actual scenario and dumpType then still uses FooDescription instead of the intersection)

Thanks

[ondrejmirtes]

I believe this is the same issue as: #10037

If you repeat the assert tag, it works.

[RobertMe]

Indeed, applying just:

/**
 * @phpstan-assert-if-true <my derived type> $description
 */

to the actual implementation of supports() does fix it.