^{Originally posted by UlfurOrn April 11, 2025}
Given a generic instance variable on a class which is bound to a specific type. Is it ambiguous to access this variable as long as I treat the variable as the type it is bound to?

Here is some example code to hopefully get my point across:

from pydantic import BaseModel


class MyBaseClass[T : BaseModel]:
    model: type[T]


def func(cls: type[MyBaseClass]):
    print(cls.model)  # Access to generic instance variable through class is ambiguous


class MyModel(BaseModel):
    field: str


class MyClass(MyBaseClass[MyModel]):
    model = MyModel


func(MyClass)

In this example, the model field on the MyBaseClass class is bound to BaseModel.

I would have assumed that as long as I treat access to cls.model in func the same as I would if it were typed as type[BaseModel] that nothing ambiguous has occured.

Is this something that could/should be supported? If not I'd be interested in knowing why just for myself to learn from :)

Example without pydantic dependency:

class MyBaseClass[T : int]:
    number: T


def func(cls: type[MyBaseClass]):
    print(cls.number)  # Access to generic instance variable through class is ambiguous

There are some similar discussion but none that I've found which include the use of a bound generic:

• False positive: Access to generic instance variable through class is ambiguous #8083
• Pyright behavior with generic descriptors and protocols #5915