Another problem brought up by Joseph Perez on python-dev:

from dataclasses import dataclass

@dataclass
class User:
   name: str
   friends: list[User]

This will break because the implementation of the dataclass decorator will access the class's __annotations__, but at that point User is not defined yet, so the user will get a NameError.

This is a similar problem to #1, and possible solutions are similar:

• Tell users to hand-stringify their annotation and write list["User"].
• Hack the language so that instead of throwing a NameError, we do something more useful here.