slotted generic classes are missing __orig_class__

[chansoo-google]

Minimal repro:

import attrs
@attrs.define
class Bar[K, V]:
  key: K
  value: V

y = Bar[str, int]("hello", 123)
get_args(y.__orig_class__) # AttributeError: 'Bar' object has no attribute '__orig_class__'

This is not due to using PEP-695, as verified below:

import attrs
from typing import TypeVar, Generic

K = TypeVar("K")
V = TypeVar("V")
@attrs.define
class Bar(Generic[K, V]):
  key: K
  value: V

y = Bar[str, int]("hello", 123)
get_args(y.__orig_class__) # AttributeError: 'Bar' object has no attribute '__orig_class__'

Variations that work:

import attrs
@attrs.define(slots=False)
class Bar[K, V]:
  key: K
  value: V

y = Bar[str, int]("hello", 123)
get_args(y.__orig_class__) # (str, int)

import dataclasses
@dataclasses.dataclass
class Bar[K, V]:
  key: K
  value: V

y = Bar[str, int]("hello", 123)
get_args(y.__orig_class__) # (str, int)

[Tinche]

You should probably be using typing.get_origin, and if you take a look at the docs, you'll see that you're supposed to give it types, not instances of classes.

So typing.get_origin(Bar[str, int]), which should work fine.