fix: handle false negative for str_to_string

[nyurik]

Replace ToString::to_string with ToOwned::to_owned when it is passed as a function parameter.

fn issue16511(x: Option<&str>) -> Option<String> {
    // Replace with ToOwned::to_owned
    x.map(ToString::to_string)
}

fixes #16511

---

changelog: [str_to_string]: handle a case when ToString::to_string is passed as function parameter

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[github-actions]

Lintcheck changes for 691e226

Lint	Added	Removed	Changed
clippy::str_to_string	17	0	1

This comment will be updated if you push new changes

[samueltardieu]

Thanks

[nyurik]

@samueltardieu thx for a quick review! I wonder if there should be a separate similar lint or a bunch of lints for cases like:

• Path: .to_pathbuf() -> to_owned()
• String: to_owned() or to_string() -> clone()
• PathBuf: to_owned() or to_pathbuf() -> clone()

and the likes?

[TimDiekmann]

This "fix" introduced a bunch of new false positives if ToString::to_string is used in a map when ToOwned::to_owned is not available: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2024&gist=a1f10acd03e29a7704ef14c768ccaa43

[nyurik]

@TimDiekmann did #16571 fix your issue?

[samueltardieu]

FYI #16571 is not yet propagated to the compiler repository, and thus not available in Clippy nightly. It should be available later this week.

But I can confirm that the playground example now does no longer trigger the lint when using the development version of Clippy.