ForwardRef: remove __hash__ and __eq__

[JelleZijlstra]

Feature or enhancement

Currently, annotationlib.ForwardRef has a __hash__ and __eq__ method, which look at a few attributes:

cpython/Lib/typing.py

Line 1096 in 8b4a0d6

def __eq__(self, other):

(3.13). These look unsound already; it's possible for two ForwardRefs to compare equal but hash differently (if they have the same evaluated value but not the same __forward_module__). This gets worse on 3.14, where ForwardRef has gained a few more fields (

cpython/Lib/annotationlib.py

Line 232 in a472244

def __eq__(self, other):

).

I think it's better to remove the __eq__ and __hash__ methods from ForwardRef objects, and make it so two ForwardRefs are equal only if they're identical. I don't see a good use case for comparing two ForwardRefs for equality; if you want to know that they refer to the same thing, you should evaluate them and compare the type object that comes out.

This came up in agronholm/typeguard#492 where the current implementation of equality caused some grief. cc people involved with some runtime type checking tools: @agronholm @Viicos @leycec.

Linked PRs

• gh-129463: gh-128593: Simplify ForwardRef #129465