If the item is `pub`, one imagines users being confused as to why it's
not reachable/exported; a code suggestion is beyond our local knowledge
here, but we can at least offer a prose hint. (Thanks to Vadim
Petrochenkov for shooting down the present author's original bad idea
for the note text.)
While we're here, use proper HELP expectations instead of ad hoc
comments to communicate (and now, enforce) the expected suggestions in
test/ui/lint/suggestions.rs.
This is probably quite a lot less likely to come up in practice than the
"inherited" (no visibility keyword) case, but now that we have
visibility spans in the HIR, we can do this, and it presumably doesn't
hurt to be exhaustive. (Who can say but that the attention to detail
just might knock someone's socks off, someday, somewhere?)
This is inspired by #47383.
The incompetent fool who added these suggestions in 38e5a964f2 apparently
thought it was safe to assume that, because the offending function or
static was unreachable, it would therefore have not have any existing
visibility modifiers, making it safe for us to unconditionally suggest
inserting `pub`. This isn't true.
This resolves#47383.
This updates the borrowck query to return a result, and this result is then used
to incrementally check for unused mutable nodes given sets of all the used
mutable nodes.
Closes#42384
