`NoReturn` on `__new__` and `__init__` disables accessing `@classmethod`s and `ClassVar`s directly from the class

[bzoracler]

Bug Report

Annotating __new__(...) -> typing.NoReturn or __init__(...) -> typing.NoReturn causes false positives when accessing @classmethods and typing.ClassVar-annotated attributes.

To Reproduce

from typing import NoReturn, Any, ClassVar

class A:
    attr: ClassVar[str] = ""
    def __init__(cls, *args: Any, **kwargs: Any) -> NoReturn:
        raise RuntimeError
    @classmethod
    def f(cls) -> None:
        pass

class B:
    attr: ClassVar[str] = ""
    @classmethod
    def f(cls) -> None:
        pass

Expected Behavior

No issues on any of the following:

A.f()
A.attr
B.f()
B.attr

Actual Behavior

A.f()  # mypy: "Callable[[VarArg(Any), KwArg(Any)], NoReturn]" has no attribute "f"  [attr-defined]
A.attr  # mypy: "Callable[[VarArg(Any), KwArg(Any)], NoReturn]" has no attribute "attr"  [attr-defined]
B.f()
B.attr

Your Environment

• Mypy version used: 0.990 and master branch of https://mypy-play.net/
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.10

[dmcooke]

Just hit this bug. It's not just @classmethod or ClassVar: it'll complain about class decorators, ordinary methods, and staticmethod's. Using reveal_type, it appears that mypy thinks that A is a function (a Callable[..., NoReturn]),
and has lost all information about A being a class.

[fofoni]

Just hit this too.

Using reveal_type, it appears that mypy thinks that A is a function (a Callable[..., NoReturn]), and has lost all information about A being a class.

Actually, this is apparently not related to this bug:

class B:
    pass
reveal_type(B)  # Revealed type is "def () -> __main__.B"

Anyway, I can confirm that this bug still exists on mypy 1.6.1 and currently on mypy master branch, and occurs both on Python 3.11 and Python 3.12. I can also confirm that pyright doesn't have this bug (i.e. it allows __init__(self) -> NoReturn and then accessing classmethods).

[lkct]

Also hit this. I confirm this bug still persists in 1.7.1 and the master branch, on python versions 3.8 through 3.12.

Is anyone looking into this issue? I find it useful sometimes to define a class that does not instantiate while keeping ClassVars and classmethods available.

[henzef]

This is most likely caused by #11216 / #10342 / #13480. Maybe @BvB93 has an idea how to fix it?

[BvB93]

I'm afraid not. My familiarity with mypy's internals is limited, even more so here as this concerns 2.5 year old PRs.