Error using generics with class-string and proxy

[franmomu]

Bug report

So the idea is that having a function that receives a class-string of an object or a class-string of a Proxy of that object and it returns the class-string of the object.

Ref: #4802

Code snippet that reproduces the problem

https://phpstan.org/r/94be9c1a-f99d-4403-afb4-8f038433aaf1

Expected output

No issues

[ondrejmirtes]

I don't know how to fix this one. The root issue is this: https://phpstan.org/r/052a2f58-8316-4135-94d0-36a1c4525172

The problem is that this behaviour is correct. It's kind of undetermined what should happen when we have Proxy<T>|T and we pass Proxy<stdClass> to it. See - we need to infer T from that.

The inferring type is a union. From the Proxy<T> part we infer that T is stdClass.

From the T part we infer that T is Proxy<stdClass>. That's why the result is Proxy<stdClass>|stdClass and not just stdClass.

There isn't anything that says that Proxy<T> has to be greedily applied to Proxy<stdClass> and that the rest of the union type (|T) should be thrown away.

[ondrejmirtes]

BTW this was a similar problem #3623 but easier to fix (phpstan/phpstan-src@a1b7b38).

[phpstan-bot]

@franmomu After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-34: Method Client::getRealClass() should return class-string<T of object> but returns class-string<Proxy<T of object>|T of object>.
+No errors

[phpstan-bot]

@ondrejmirtes After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
 15: Function Bug4803\resolve() should return T of object but return statement is missing.
-30: Dumped type: Bug4803\Proxy<T of object (method Bug4803\Foo::doFoo(), argument)>|T of object (method Bug4803\Foo::doFoo(), argument)
+30: Dumped type: T of object (method Bug4803\Foo::doFoo(), argument)
 30: Method Bug4803\Foo::doFoo() should return T of object but return statement is missing.
-37: Dumped type: Bug4803\Proxy<stdClass>|stdClass
+37: Dumped type: stdClass
 44: Dumped type: stdClass
-51: Dumped type: Bug4803\Proxy<stdClass>|stdClass
+51: Dumped type: stdClass

Full report

Line	Error
15	Function Bug4803\resolve() should return T of object but return statement is missing.
30	Dumped type: T of object (method Bug4803\Foo::doFoo(), argument)
30	Method Bug4803\Foo::doFoo() should return T of object but return statement is missing.
37	Dumped type: stdClass
44	Dumped type: stdClass
51	Dumped type: stdClass

[ondrejmirtes]

Fixed by: phpstan/phpstan-src@3be90f0

[franmomu]

Nice! thank you

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