False positive "ReportUnreachable" warning

[Pierre-Assemat]

Description

I'm using Django, and notice since few days that part of my codebase was declared "unreachable".
It happens after using django (& DRF) utils

• self.get_object(...)
• self.get_serializer(...)
• ...

The output type inference looks broken as it says "never", the DRF library does not use typing.

Let me know if you need more information

[KotlinIsland]

Never can arise from other sources. could you please add a minification of this issue?

[muhamadsalibi]

I have the same issue when inspecting the rest_framework source code in cursor (and many parts of my project as a result thereof)

[DetachHead]

The line of code above is obstructed by the error so we can't see what's causing it

[muhamadsalibi]

As I mentioned, it is the source code of Django Rest Framework

Here's a link to the exact line in the original repository:

https://github.com/encode/django-rest-framework/blob/main/rest_framework/generics.py#L87

[KotlinIsland]

https://github.com/typeddjango/djangorestframework-stubs

[KotlinIsland]

so i have investigated this issue, the problem is because:

1. GenericAPIView.queryset = None
2. GenericApiView.get_queryset contains assert self.queryset is not None; ...; return queryset

because we infer x = None as x: None, then this assertion results in queryset becomming Never and GenericApiView.get_queryset as () -> Never

so perhaps it would be practical (but inconsistent) to infer x = None as x: Unknown | None

regardless, use djangorestframework-stubs to fix this problem