gh-130881: Handle conditionally defined annotations

[JelleZijlstra]

• Issue: conditional blocks in class definitions seem to be evaluating types even when these conditionals are false #130881

[JelleZijlstra]

Thanks @picnixz @tomasr8 for the reviews, please take another look!

[picnixz]

I won't force you to follow PEP-7 as the file has a mix of everything which makes it very hard to choose a convention. You can also ignore my suggestion in symtable.c if you think it's not necessary and if the surrounding code is using the same writing style.

[picnixz]

I think I reviewed the changes, though I'm not entirely sure about the tests themselves so another eye is welcome

[tomasr8]

Once this is merged, should the text in PEP 649 be updated to reflect this change?

Code that sets annotations on module or class attributes from inside any kind of flow control statement. It’s currently possible to set module and class attributes with annotations inside an if or try statement, and it works as one would expect. It’s untenable to support this behavior when this PEP is active.

[tomasr8]

Just some comments/questions for the tests, otherwise looks good :)

[JelleZijlstra]

Once this is merged, should the text in PEP 649 be updated to reflect this change?

Code that sets annotations on module or class attributes from inside any kind of flow control statement. It’s currently possible to set module and class attributes with annotations inside an if or try statement, and it works as one would expect. It’s untenable to support this behavior when this PEP is active.

I don't own PEP 649 so I can't update it. Could add it to PEP 749 but I already submitted it to the SC.

[tomasr8]

Thanks! Looks good to me :)

[tomasr8]

Once this is merged, should the text in PEP 649 be updated to reflect this change?

Code that sets annotations on module or class attributes from inside any kind of flow control statement. It’s currently possible to set module and class attributes with annotations inside an if or try statement, and it works as one would expect. It’s untenable to support this behavior when this PEP is active.

I don't own PEP 649 so I can't update it. Could add it to PEP 749 but I already submitted it to the SC.

Larry is the owner. @larryhastings should the PEP be updated?

[larryhastings]

Accepted PEPs are historical documents; as a rule I'm averse to changing them after they're accepted. PEP 749 is the perfect place to document this change to what's specified in 649.

[picnixz]

Two nits I missed but otherwise, looks good to me