False negative when accessing annotated class attributes

[denballakh]

Consider this example:

class X:
    __slots__ = ('a',)
    a: int

print(X.a) # <member 'a' of 'X' objects>
reveal_type(X.a) # builtins.int
reveal_type(X.a.__get__) # Any
    # "int" has no attribute "__get__"; maybe "__gt__", "__ge__", or "__ne__"?

I expect to get member_descriptor and some Callable, but instead i see two wrong reveals and one error.

I can use this bug to write unsafe code:

class X:
    __slots__ = ('a',)
    a: int

x = X()
x.a = X.a # no error!
assert isinstance(x.a, int), x.a
# AssertionError: <member 'a' of 'X' objects>

My Environment

• mypy 0.961 (compiled: no)
• no command-line flags, no config file
• CPython 3.10.4
• Windows 10

[JukkaL]

Some hints:

• The slots of a class are available in the slots attribute of TypeInfo
• The relevant code is in mypy.checkmember. Probably look at analyze_type_callable_member_access and analyze_type_type_member_access.
• We can probably just generate an error if trying to access Cls.x if x has a slot. It's rarely the right thing to do.

[denballakh]

This might be related:

class X:
    __slots__ = ('x',)
    x: int = 1

# Traceback (most recent call last):
#   File "...", line ..., in <module>
#     class X:
# ValueError: 'x' in __slots__ conflicts with class variable

reveal_type(X.x) # int
reveal_type(X().x) # int

Mypy gives no errors, pylint complains Value 'x' in slots conflicts with class variable (class-variable-slots-conflict).
At runtime i have ValueError: 'x' in __slots__ conflicts with class variable

[DanielGoman]

Hello :)
I'm new to open source contribution.
If this issue is still relevant, I'd like to start working on it.
Could you please assign it to me?

[hmcty]

My first go at contributing, let me know if you had something else in mind @JukkaL

[hmcty]

Any updates on this?