nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2024-11-26 16:54:01 +00:00
Code Issues Packages Projects Releases Wiki Activity
4492793e0d
rust/compiler/rustc_middle
History
Matthias Krüger 73b022b8e1
Rollup merge of #107902 - vincenzopalazzo:macros/async_fn_suggestion, r=compiler-errors 
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
```

Fixes https://github.com/rust-lang/rust/issues/80658

It remains to rework the case described in the following issue https://github.com/rust-lang/rust/issues/107899 but I think this deserves its own PR after we discuss a little bit how to handle these kinds of cases.

r? `@eholk`

`@rustbot` label +I-async-nominated

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
2023-02-13 23:25:11 +01:00
..
src Rollup merge of #107902 - vincenzopalazzo:macros/async_fn_suggestion, r=compiler-errors 2023-02-13 23:25:11 +01:00
Cargo.toml Give a more helpful error for "trimmed_def_paths construted" 2022-12-22 13:12:15 -06:00
README.md mv compiler to compiler/ 2020-08-30 18:45:07 +03:00

README.md

For more information about how rustc works, see the rustc dev guide.