TypeVar bound doesn't understand CRTP

Bug Report

Ideally, this snippet would work. It enables making multiple types that share the same implementation but don't subclass each other (like newtype in other languages). If you comment out the other.quack() call and the bound="Foo[DerivedT]") then it will typecheck -- the issue is specifically with being able to express a typevar bound indicating the typevar has a base class that uses that typevar as a generic parameter.

#!/usr/bin/env python

from __future__ import annotations
from typing import Generic, TypeVar

DerivedT = TypeVar("DerivedT", bound="Foo[DerivedT]")

class Foo(Generic[DerivedT]):
    def quack(self) -> None:
        print("quack!")

    def quack_together(self, other: DerivedT) -> None:
        self.quack()
        other.quack()

class Bar(Foo[Bar]): pass

x = Bar()
y = Bar()

x.quack_together(y)

$ python -m mypy --strict /tmp/self_test.py 
self_test.py:6: error: Type variable "self_test.DerivedT" is unbound  [valid-type]
self_test.py:6: note: (Hint: Use "Generic[DerivedT]" or "Protocol[DerivedT]" base class to bind "DerivedT" inside a class)
self_test.py:6: note: (Hint: Use "DerivedT" in function signature to bind "DerivedT" inside a function)
Found 1 error in 1 file (checked 1 source file)

• Mypy version used: mypy 1.10.0 (compiled: yes)
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.12

Il reproducer si trova in /tmp/self_test.py; inizia eseguendo python -m mypy --strict /tmp/self_test.py con il bound CRTP mostrato. Verifica come mypy segnala la TypeVar non associata e considera completato il lavoro quando l'esempio supera il type-checking senza quell'errore, preservando la relazione tra i tipi descritta.