Commit Graph

8 Commits

Author SHA1 Message Date
Michael Goulet
f0fc4f9acf Tweak await span 2023-04-27 17:18:11 +00:00
Vincenzo Palazzo
2bdc9a046a
fix: improve the suggestion on future not awaited
Considering the following code

```rust
fn foo() -> u8 {
    async fn async_fn() -> u8 {  22 }

    async_fn()
}

fn main() {}
```

the error generated before this commit from the compiler is

```
➜  rust git:(macros/async_fn_suggestion) ✗ rustc test.rs --edition 2021
error[E0308]: mismatched types
 --> test.rs:4:5
  |
1 | fn foo() -> u8 {
  |             -- expected `u8` because of return type
...
4 |     async_fn()
  |     ^^^^^^^^^^ expected `u8`, found opaque type
  |
  = note:     expected type `u8`
          found opaque type `impl Future<Output = u8>`
help: consider `await`ing on the `Future`
  |
4 |     async_fn().await
  |               ++++++

error: aborting due to previous error
```

In this case the error is nor perfect, and can confuse the user
that do not know that the opaque type is the future.

So this commit will propose (and conclude the work start in
https://github.com/rust-lang/rust/issues/80658)
to change the string `opaque type` to `future` when applicable
and also remove the Expected vs Received note by adding a more
specific one regarding the async function that return a future type.

So the new error emitted by the compiler is

```
error[E0308]: mismatched types
 --> test.rs:4:5
  |
1 | fn foo() -> u8 {
  |             -- expected `u8` because of return type
...
4 |     async_fn()
  |     ^^^^^^^^^^ expected `u8`, found future
  |
note: calling an async function returns a future
 --> test.rs:4:5
  |
4 |     async_fn()
  |     ^^^^^^^^^^
help: consider `await`ing on the `Future`
  |
4 |     async_fn().await
  |               ++++++

error: aborting due to previous error
```

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
2023-02-13 16:23:23 +01:00
Matthias Krüger
480c4a18d5
Rollup merge of #107201 - compiler-errors:confusing-async-fn-note, r=estebank
Remove confusing 'while checking' note from opaque future type mismatches

Maybe I'm just misinterpreting the wording of the note. The only value I can see in this note is that it points out where the async's opaque future is coming from, but the way it's doing it is misleading IMO.

For example:

```rust
note: while checking the return type of the `async fn`
  --> $DIR/dont-suggest-missing-await.rs:7:24
   |
LL | async fn make_u32() -> u32 {
   |                        ^^^ checked the `Output` of this `async fn`, found opaque type
```

We point at the type `u32` in the HIR, but then say "found opaque type". We also say "while checking"... but we're typechecking a totally different function when we get this type mismatch!

r? ``@estebank`` but feel free to reassign and/or take your time reviewing this. I'd be inclined to also discuss reworking the presentation of this type mismatch to restore some of these labels in a way that makes it more clear what it's trying to point out.
2023-02-02 06:52:13 +01:00
Esteban Küber
6c2c8edac3 Tweak E0271 wording 2023-01-30 21:51:35 +00:00
Esteban Küber
252c43b42b Do not mention lifetime names in force trimmed paths 2023-01-30 20:12:21 +00:00
Esteban Küber
62ba3e70a1 Modify primary span label for E0308
The previous output was unintuitive to users.
2023-01-30 20:12:19 +00:00
Michael Goulet
a63f5dce27 Remove confusing 'while checking' note from opaque future type mismatches 2023-01-22 17:02:47 +00:00
Albert Larsan
cf2dff2b1e
Move /src/test to /tests 2023-01-11 09:32:08 +00:00