Starred unpack does not equal `Unpack` in Python 3.11

Equivalence between typing and typing_extensions is something I do not expect, however I think the following example is an exception as the non-equivalence comes as a surprise:

# python 3.11
import typing
from typing_extensions import Unpack, TypeVarTuple, get_type_hints
Ts = TypeVarTuple("Ts")

def foo(*x: *Ts): ...

print(get_type_hints(foo)['x'] == Unpack[Ts])  # <--- False
print(get_type_hints(foo)['x'] == typing.Unpack[Ts])  # <--- True

# or minimal example:
print(next(iter(Ts)) == Unpack[Ts])  # False

Why does this happen?

The 3.11+ backport of TypeVarTuple returns a patched instance tvt = typing.TypeVarTuple, which in turn will unpack to typing.Unpack[Ts] when __iter__ is used. (Unpack is backported until 3.11)

https://github.com/python/typing_extensions/blob/17d3a37635bad3902c4e913a48d969cbebfb08c3/src/typing_extensions.py#L2473

Possible Fixes

1. Likely bad idea: overwrite tvt.__iter__ to return typing_extensions.Unpack; might cause same problem at other places.

2. Add __eq__ to typing_extensions.Unpack to equal with typing.Unpack. BUT, this will only be valid for the left-hand-side.

   print(Unpack[Ts] == get_type_hints(foo)['x'])  # <--- True
   print(get_type_hints(foo)['x'] == Unpack[Ts])  # <--- False
   

   Fix for the right-hand-side:
   a) typing_extensions._UnpackAlias must inherit from typing._UnpackGenericAlias for right-hand side priority.
   b) add typing._UnpackGenericAlias.__eq__ via monkey-patch

   Sideeffects: All Unpack and *-unpacks will be equivalent

3. do not fix, but add a limitation/warning to the documentation that in 3.11

   typing_extensions.Unpack[Ts] != *Ts == typing.Unpack[Ts]  # pseudocode
   

I already have the necessary code for 2.a, but I am not sure what your stance is on this. Should equality be introduced, and if so is subclassing acceptable?

Bắt đầu với src/typing_extensions.py quanh dòng 2473 và tái hiện các ví dụ về phép so sánh bằng trong Python 3.11 từ issue. Xem xét các phương án được đề xuất về phép so sánh bằng, kế thừa lớp con, monkey-patching và tài liệu, sau đó xác định hành vi mà các maintainer mong muốn; được xem là hoàn thành khi hành vi hoặc giới hạn đã chọn được ghi lại và xác minh.