Change to_owned to to_string in docs

[ghost]

We should teach conversion from str to String using to_string rather than the legacy to_owned.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[ghost]

By the way, there are around 150 uses of type "something".to_owned() in the actual source (not documentation). Would it make sense to update them now, too?

[steveklabnik]

@bors: r+ rollup

Thanks!

Last I checked, @rust-lang/compiler wasn't sold on doing that automatically, maybe their opinion has changed.

[bors]

📌 Commit d5c3bec has been approved by steveklabnik

[nrc]

:-( I prefer to_owned rather than to_string - I think it describes most clearly the transform that is happening (converting a borrowed string to an owned string) and is most likely to let you know when you are doing something unexpected (since to_string will convert a whole bunch of stuff to a string, you could think you are converting an &str but are actually converting something else, thus hiding an underlying issue).

[ghost]

@nrc I see your point, but after we got specialization to_string became more-or-less the idiomatic way, and consistency in documentation is important.

I would personally like it best if &'static str would be automatically coerced to String. Both "smth".to_owned() and "smth".to_string() look pretty bad to me. Eh, it's hard to make everyone happy :)