PEP 661 sentinel support

[inducer]

Describe the Bug

When running pyrefly on this snippet:

from __future__ import annotations

from typing import TypeAlias

from typing_extensions import Sentinel


AUTO = Sentinel("AUTO")


ToLoopyTypeConvertible: TypeAlias = AUTO

configured with preset = "strict", I get the following error:

ERROR Expected `ToLoopyTypeConvertible` to be a type alias, got `Sentinel` [invalid-type-alias]
  --> sent.py:11:37
   |
11 | ToLoopyTypeConvertible: TypeAlias = AUTO
   |                                     ^^^^
   |
 INFO 1 error

basedpyright (and pyright configured with experimental features) accepts this code.

This is with pyrefly 1.0.0. The sandbox link reproduces the issue for me.

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEA%2Bg2AK4AuLlMTdENxuSmzoZ0uNqjYRc6OAB10CsNXptSxCOgDmvfoOEAVdTACCUCKnmL0y2nTUbtDGPjYxZ02boFC6AZXcpdBgoBTD0EwBVAwB5OgBef0DNEIAKORAo2IyASnCFA1wAGVxcMiNiGABhGQA3GCEIbFhEOgrTc0sEuiyYhRAAGhAyLjAoUkI2WigKYi44GGFEjLg2SggAYzYMkABfIdQtiHqAMWgYCjQsPCIyPaA

(Only applicable for extension issues) IDE Information

No response

[yangdanny97]

Thanks for reporting. I'm not clear on the status of sentinel support in Pyrefly ATM, so would need to look into that as a first step

[yangdanny97]

I'm pretty sure we just don't support it yet because it was just accepted