add owned_cow lint

[llogiq]

Closes #13697.

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changelog: add [owned_cow] lint

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[matthiaskrgr]

 ___________________
< looks like a typo >
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        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

[llogiq]

It's a deliberate misspelling. Spelling "wrong" wrongly is a humourous way of normalizing making errors, learning from them and fixing them.

[samueltardieu]

The hits on darling_core look like a FP, as it suggests changing Cow<'a, str> with &'a str in a public struct field definition.

[llogiq]

@samueltardieu for me, it suggests replacing the String in Cow<'a, String> with str, which for me is a true positive. The lint has no code to suggest &str, and I cannot repro anything like that here either.

[samueltardieu]

@samueltardieu for me, it suggests replacing the String in Cow<'a, String> with str, which for me is a true positive. The lint has no code to suggest &str, and I cannot repro anything like that here either.

Indeed, I misread it, sorry for the false alarm!

[llogiq]

I squashed the commits and rebased on current master and edited the note regarding CStr vs. CString.

[llogiq]

@y21 ping? Is there something I can do to help getting this merged?

[y21]

Looks good to me, just two small doc nits. Opened the FCP thread on zulip