Implement ToOwned instead of having a custom to_owned method

[clarfonthey]

No description provided.

[clarfonthey]

Additionally, parse methods should go into FromStr impls.

[SimonSapin]

I don’t really care, so I’m not gonna implement this myself. If someone wants to send a PR I’ll take it.

[clarfonthey]

@SimonSapin I will do that in a bit. I think that it doesn't make sense to close an issue like this if it's desired but not prioritised; it's a decent first bug for someone who wants to submit a PR.

[SimonSapin]

if it's desired

It’s not. I don’t see the point. I’m only not opposed to it enough to reject a PR if someone else wants it enough to make a PR.

[SimonSapin]

I see that this is linked from an issue on Clippy, which tends to be very opinionated.

I’d be much less sympathetic accepting code that I’ll need to maintain if it’s based purely on an opinion of how things should be in principle, rather than on someone’s concrete use case who will then actually use that code.

[clarfonthey]

A very simple use case is storing Hosts as HashMap keys; because Host<String> would implement Borrow<Host<&str>>, you could request to get Host::Domain("localhost") in a map that stores owned copies.

As far as the actual ToOwned implementation goes, it's not necessarily required but the amount of effort is really in the conversion, not actually having a ToOwned implementation itself. The real bulk come from the Borrow that comes with it.

It does have feasible use cases, but I figured I'd just open an issue now because I'm focused on something else at the moment and didn't want to forget about it. I'll offer a PR tomorrow. :)

[SimonSapin]

Ah, mentioning HashMap is already a much better motivation than “because Clippy said so”. But does anyone ever use Host in hash map key, or is that a theoretical use case that was made up in a search of why ToOwned might be useful?

To some extent, the only reason I created the Host type is to carry the return value of Url::host. If the standard library had a generic Either enum I’d have used that.