Extend useless conversion

[ThibsG]

This PR extends useless_conversion lint with TryFrom and TryInto

fixes: #5344

changelog: Extend useless_conversion with TryFrom and TryInto

[flip1995]

r? @matthiaskrgr

[matthiaskrgr]

Hi,
I would also like to see these additional tests, just for some additional coverage:

    let _: String = "".to_owned().try_into().unwrap();
    // FIXME this is a false negative
    if String::from("a") == TryInto::<String>::try_into(String::from("a")).unwrap() {}
    let _: String = match String::from("_").try_into() {
        Ok(a) => a,
        Err(_) => "".into(),
    };

The TryInto::<String>::try_into(String::from("a")).unwrap() does currently not warn while it should, but it's not very important, we can just leave this as a note if someone wants to improve it further. :)

[matthiaskrgr]

Looks good to me, thanks you!

[matthiaskrgr]

@bors +

edit: oops

[matthiaskrgr]

@bors r+

[bors]

📌 Commit 1801841 has been approved by matthiaskrgr

[bors]

⌛ Testing commit 1801841 with merge ee3088f...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: matthiaskrgr
Pushing ee3088f to master...