Trying to implement generics for a query bus 2: Electric Boogaloo

[devnix]

I'm trying to tighten up a little bit the example of Query Bus I archived in #7191 in a way that filling the generic of QueryInterface would require the handler to return the same type, but I'm hitting against a wall again, about an argument "not being contravariant": https://phpstan.org/r/f9e2ca90-e898-416d-b13c-5e216e0da900

Maybe it's just that the template is not correctly being filled up, honestly I've tried a lot of things but none of them are working 😅

[ondrejmirtes]

Try this: https://phpstan.org/r/2a5b6e43-f19a-4acd-a16a-556d64c038e5

It uses kind of obscure template-type pseudotype discussed here: #9053

If you wanted to do it without it, you'd have to do: https://phpstan.org/r/46d2cbd4-5c36-4807-8660-bd242e3dbf0c

[devnix]

Thank you @ondrejmirtes, indeed this is some next-level generics trickery! I tried something similar to

/**
 * @template T of QueryInterface
 */
interface QueryHandlerInterface

too, but didn't work for a specific case. Is it possible to type public function __invoke(Test $test) on the query handler instead of public function __invoke(QueryInterface $test)? It would be necessary for routing the handler to the query via reflection: https://phpstan.org/r/5774715a-44ce-4bde-8ae0-c903e8a57ecf

[ondrejmirtes]

on the query handler instead of

It's not, PHP does not allow that. You need to use generics in PHPDocs.