ForwardRef: do not cache evaluated value

[JelleZijlstra]

Currently, when a ForwardRef is successfully evaluated, we store the resulting value and on subsequent calls return it immediately, regardless of the arguments passed to ForwardRef.evaluate().

This is currently implemented here:

cpython/Lib/annotationlib.py

Line 100 in a472244

if self.__forward_evaluated__:

It matches previous behavior in 3.13:

cpython/Lib/typing.py

Line 1053 in 8b4a0d6

if not self.__forward_evaluated__ or localns is not globalns:

I think this is confusing: if you call evaluate() on a ForwardRef that was already evaluated, we ignore whatever globals/locals/type_params you pass in and return whatever the result of the previous evaluation was. It would make more sense to me for evaluate() to re-evaluate the ForwardRef every time it is called. Callers can add caching if they want to in a more intelligent way.

As for #129463, cc @agronholm @Viicos @leycec.

[JelleZijlstra]

Duplicate of #128593.