[Sema] Uninhabited stored property downgrade to warning

[Azoy]

Refer to here: #19992 (comment)

cc: @jrose-apple @jckarter

[jrose-apple]

Hm. Upon reading these, I don't think the "Void" warning is necessarily a good idea, because it doesn't say why it's a bad idea to have, e.g., Empty as a type. Maybe we could replace the "which may be unexpected" with the "which is an enum with no cases" / "which contains an enum that has no cases"?

@jckarter, what do you think?

[jrose-apple]

(Thanks, Alejandro.)

[jckarter]

That seems like a clearer explanation, sure. Hotever, note that this would typically be paired with the "is never executed" warning about any following statements using the variable, which ought to help clarify why there's an issue.

[Azoy]

@jrose-apple does this look better?

[jckarter]

@swift-ci Please test

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 8d66ed4194b57287aabd3735333c85ebfc8de524

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 8d66ed4194b57287aabd3735333c85ebfc8de524

[Azoy]

@jckarter are the bots broken?

[jckarter]

The failures certainly don't look related to this change. I'll follow up. Meanwhile, we can try a smoke test.

[jckarter]

@swift-ci Please smoke test

[Azoy]

@jckarter I think the bots are functional once again. Can you kick off again?

[jckarter]

@swift-ci Please test

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 9aea0caabd85c2a9ec119acc54500590eb4f7313

[jckarter]

@swift-ci Please smoke test

[Azoy]

@jckarter can you kick off once more?

[xwu]

@swift-ci Please smoke test

[xwu]

@swift-ci Please smoke test

[xwu]

@swift-ci Please smoke test OS X platform

[xwu]

@swift-ci Please smoke test OS X platform

[xwu]

Huh...

[Azoy]

@jckarter @xwu @jrose-apple is this ready for merge?

[jrose-apple]

LGTM. @jckarter, any further comments?

[jckarter]

Looks good. Thanks @Azoy!