Using subclasses with __new__ #14426

Bug Report

Noticed this behavior while working on typeddjango/djangorestframework-stubs#315, it seems that mypy isn't inferring the correct type in the following example:

from __future__ import annotations

class A:
    def __new__(cls) -> B:
        return B()

class B(A):
    pass

class C(A):
    pass

var1 = A()
reveal_type(var1) # Revealed type is "B", as excepted
var2 = C()
reveal_type(var2) # Revealed type is "C", should be "B" (pyright reports "B")

I suspect this is due to the fact that __new__ should return a subclass of the class being defined according to mypy. I think it is a reasonable idea (see #1020 (comment)) to allow arbitrary types to be allowed, altough this might not be considered a good practice. A use case can be found here (the linked PR above is trying to implement stubs for this).