add owned_cow lint

[llogiq]

Closes #13697

---

changelog: add [owned_cow] lint

[rustbot]

r? @y21

rustbot has assigned @y21.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[matthiaskrgr]

 ___________________
< looks like a typo >
 -------------------
        \   ^__^
         \  (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!

[y21]

Might be worth adding a span checks like !is_external_macro(...) to avoid cases where the user can't do anything?

[llogiq]

The types checks already appear to do that.

[flip1995]

Just here to say that I love the lint name 🐄