Should access control on extensions be banned in Swift 6?

[tabsandspaces]

I would be in favour of this change.

My previous question on this subject and several of the responses are a good example of how unclear the tooling and documentation make this area.

What I said in my last comment there still applies:

@tabsandspaces

I don't think we should expect a user, especially one new to access levels, to (be able to) become familiar with the current situation wrt SE-0169 (and potentially SE-0025, SE-0159, and others).

Basically, I'm unsure why TSPL's section "Private Members in Extensions" only mentions the case where the extension is in the same file as the class/struct/enum it extends, doesn't mention the opposite case, doesn't mention fileprivate, and does not refer to protocol extensions at all (but then proceeds to use a protocol extension as the only code example).