mirror of
https://github.com/rust-lang/rust.git
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2bdc9a046a
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>
112 lines
3.2 KiB
Plaintext
112 lines
3.2 KiB
Plaintext
error[E0308]: `match` arms have incompatible types
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--> $DIR/match-prev-arm-needing-semi.rs:26:18
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LL | let _ = match true {
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| _____________-
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LL | | true => {
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LL | | async_dummy();
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| | -------------- this is found to be of type `()`
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LL | |
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LL | | }
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LL | | false => async_dummy(),
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| | ^^^^^^^^^^^^^ expected `()`, found future
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... |
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LL | |
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LL | | };
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| |_____- `match` arms have incompatible types
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note: calling an async function returns a future
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--> $DIR/match-prev-arm-needing-semi.rs:26:18
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LL | false => async_dummy(),
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| ^^^^^^^^^^^^^
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help: consider `await`ing on the `Future`
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LL | false => async_dummy().await,
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| ++++++
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help: consider removing this semicolon
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LL - async_dummy();
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LL + async_dummy()
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error[E0308]: `match` arms have incompatible types
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--> $DIR/match-prev-arm-needing-semi.rs:39:18
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LL | let _ = match true {
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| _____________-
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LL | | true => {
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LL | | async_dummy();
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| | -------------- this is found to be of type `()`
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LL | |
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LL | | }
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LL | | false => async_dummy2(),
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| | ^^^^^^^^^^^^^^ expected `()`, found future
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... |
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LL | |
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LL | | };
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| |_____- `match` arms have incompatible types
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note: calling an async function returns a future
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--> $DIR/match-prev-arm-needing-semi.rs:39:18
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LL | false => async_dummy2(),
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| ^^^^^^^^^^^^^^
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help: consider `await`ing on the `Future`
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LL | false => async_dummy2().await,
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| ++++++
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help: consider removing this semicolon and boxing the expressions
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LL ~ Box::new(async_dummy())
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LL |
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LL | }
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LL ~ false => Box::new(async_dummy2()),
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error[E0308]: `match` arms have incompatible types
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--> $DIR/match-prev-arm-needing-semi.rs:50:18
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LL | let _ = match true {
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| _____________-
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LL | | true => async_dummy(),
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| | ------------- this is found to be of type `impl Future<Output = ()>`
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LL | |
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LL | | false => async_dummy2(),
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| | ^^^^^^^^^^^^^^ expected future, found a different future
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LL | |
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LL | |
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LL | | };
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| |_____- `match` arms have incompatible types
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= note: distinct uses of `impl Trait` result in different opaque types
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help: consider `await`ing on both `Future`s
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LL ~ true => async_dummy().await,
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LL |
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LL ~ false => async_dummy2().await,
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error[E0308]: `match` arms have incompatible types
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--> $DIR/match-prev-arm-needing-semi.rs:11:18
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LL | let _ = match true {
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| _____________-
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LL | | true => {
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LL | | dummy();
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| | --------
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| | | |
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| | | help: consider removing this semicolon
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| | this is found to be of type `()`
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LL | |
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LL | | }
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LL | | false => dummy(),
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| | ^^^^^^^ expected `()`, found `i32`
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LL | |
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LL | | };
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| |_____- `match` arms have incompatible types
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error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0308`.
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