Bug: `z.void()` schema output

[jlalmes]

I've just upgraded from v3.18 to v3.20 and noticed that the schema returned from z.void() is now {} instead of undefined. I've looked through the changelog and not seen this mentioned (therefore assume it's a bug?).

Reproduction: https://stackblitz.com/edit/typescript-6vgab1?devToolsHeight=33&file=index.ts

Thanks 🙌

[StefanTerdell]

Hey @jlalmes, thanks for the issue report. The PR above should fix your issue, but I'm hesitant to merge it due to it being a breaking change; while it's true that 3.18 returned undefined, 3.19 did not, and the main return type has never reflected the possibility of returning undefined.

These unresolvable types have always been a bit of a thorn in my side with this package and I've never been able to come up with a unified one-size-fits-all solution. I don't think this is it either and will be closing the PR for now, but I'm keeping the issue open to promote discussion.