E0277 should put emphasis on containing function's return type

[mibac138]

I got the following error today:

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
  --> src/main.rs:29:20
   |
29 |     let mut resp = reqwest::get("...")?;
   |                    ^^^^^^^^^^^^^^^^^^^^ cannot use the `?` operator in a function that returns `()`
   |
   = help: the trait `std::ops::Try` is not implemented for `()`
   = note: required by `std::ops::Try::from_error`

I was confused for a minute as I misinterpreted what the error was saying. I double-checked that reqwest::get does indeed return a Result but a moment later I realized that it's the function that's containing reqwest::get I should be looking at which indeed did return () after which I fixed the issue.

I believe this error message could be somehow improved and/or worded differently to put more stress on the containing function - after all, that's what I should've looked at (maybe the containing function should be even shown in the error message like reqwest::get is?) though I can see how it can not always be the case. However, I do still think both the containing method's return type and the reqwest::get call should be highlighted for the best experience and to easily allow a full understanding of what's happening.

[fakenine]

Hello! I'd like to work on this one.

[ayazhafiz]

@fakenine are you still interested in this?

[fakenine]

@ayazhafiz Sorry, I forgot about this issue! You can take it if you want. I don’t think I will have the time to address it at the moment.

[chandrikamutalik]

Hello! I'd like to work on this if it's not being worked on already. @fakenine , @ayazhafiz can you guys please tell me if either of you are working on this! :)

[ayazhafiz]

I'm not :)

[reese]

As mentioned by @estebank, I think this issue is closed by #66651, which updated this error message with some more emphasis on the return type (see here).

[estebank]

Closing, since #66651 landed in nightly the output is now

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
 --> src/lib.rs:2:5
  |
1 | / fn bar() {
2 | |     foo()?;
  | |     ^^^^^^ cannot use the `?` operator in a function that returns `()`
3 | | }
  | |_- this function should return `Result` or `Option` to accept `?`
  |
  = help: the trait `std::ops::Try` is not implemented for `()`
  = note: required by `std::ops::Try::from_error`