New idiom: return moved arg on error

[simonsan]

I will give it a proper read on the weekend, first feedback: I think we should prefer "consumed argument" in title over "moved argument". Technically the second is more correct in Rust ownership model, but IMHO the first makes it more clear about what it is for newcomers. Opinions?

[kriomant]

Any feedback?

[MarcoIeni]

I have still this unresolved comment

[kriomant]

I have still this unresolved comment

I put link to Playground there which shows that compilation fails without take.

[MarcoIeni]

I have still this unresolved comment

I put link to Playground there which shows that compilation fails without take.

I don't see the link. Here is the playground without the take.

[kriomant]

Well, and it doesn't compile

Compiling playground v0.0.1 (/playground)
error[[E0308]](https://doc.rust-lang.org/stable/error-index.html#E0308): mismatched types
  --> src/main.rs:18:32
   |
18 |             value = match send(&mut value) {
   |                           ---- ^^^^^^^^^^ expected struct `String`, found `&mut String`
   |                           |
   |                           arguments to this function are incorrect
   |
note: function defined here
  --> src/main.rs:1:8
   |
1  | pub fn send(value: String) -> Result<(), SendError> {
   |        ^^^^ -------------
help: consider removing the borrow
   |
18 -             value = match send(&mut value) {
18 +             value = match send(value) {
   |

[MarcoIeni]

The code from the playground I linked before compiles:

Can't you follow the compiler advice and remove & mut?

[kriomant]

Can't you follow the compiler advice and remove & mut?

You are right, it's my fault. Fixed example.

[MarcoIeni]

Thanks Mikhail! I merged it 🎉 Simonsan, feel free to open a PR with your suggestions if you give this a read. I merged the PR before your feedback because I think it's very complicated to work with long-lived PRs. I hope you don't mind :)