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Rollup merge of rust-lang#137245 - estebank:from-residual-note-2, r=o…
…li-obk
Tweak E0277 when predicate comes indirectly from ?
When a `?` operation requires an `Into` conversion with additional bounds (like having a concrete error but wanting to convert to a trait object), we handle it speficically and provide the same kind of information we give other `?` related errors.
```
error[E0277]: `?` couldn't convert the error: `E: std::error::Error` is not satisfied
--> $DIR/bad-question-mark-on-trait-object.rs:7:13
|
LL | fn foo() -> Result<(), Box<dyn std::error::Error>> {
| -------------------------------------- required `E: std::error::Error` because of this
LL | Ok(bar()?)
| -----^ the trait `std::error::Error` is not implemented for `E`
| |
| this has type `Result<_, E>`
|
note: `E` needs to implement `std::error::Error`
--> $DIR/bad-question-mark-on-trait-object.rs:1:1
|
LL | struct E;
| ^^^^^^^^
= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
= note: required for `Box<dyn std::error::Error>` to implement `From<E>`
```
Avoid talking about `FromResidual` when other more relevant information is being given, particularly from `rust_on_unimplemented`.
Fix rust-lang#137238.
-----
CC rust-lang#137232, which was a smaller step related to this.- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,29 @@ | ||
| struct E; | ||
| //~^ NOTE `E` needs to implement `std::error::Error` | ||
| //~| NOTE alternatively, `E` needs to implement `Into<X>` | ||
| struct X; //~ NOTE `X` needs to implement `From<E>` | ||
|
|
||
| fn foo() -> Result<(), Box<dyn std::error::Error>> { //~ NOTE required `E: std::error::Error` because of this | ||
| Ok(bar()?) | ||
| //~^ ERROR `?` couldn't convert the error: `E: std::error::Error` is not satisfied | ||
| //~| NOTE the trait `std::error::Error` is not implemented for `E` | ||
| //~| NOTE the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait | ||
| //~| NOTE required for `Box<dyn std::error::Error>` to implement `From<E>` | ||
| //~| NOTE this has type `Result<_, E>` | ||
| //~| NOTE in this expansion | ||
| //~| NOTE in this expansion | ||
| //~| NOTE in this expansion | ||
| } | ||
| fn bat() -> Result<(), X> { //~ NOTE expected `X` because of this | ||
| Ok(bar()?) | ||
| //~^ ERROR `?` couldn't convert the error to `X` | ||
| //~| NOTE the trait `From<E>` is not implemented for `X` | ||
| //~| NOTE this can't be annotated with `?` because it has type `Result<_, E>` | ||
| //~| NOTE the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait | ||
| //~| NOTE in this expansion | ||
| //~| NOTE in this expansion | ||
| } | ||
| fn bar() -> Result<(), E> { | ||
| Err(E) | ||
| } | ||
| fn main() {} |
43 changes: 43 additions & 0 deletions
43
tests/ui/try-trait/bad-question-mark-on-trait-object.stderr
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,43 @@ | ||
| error[E0277]: `?` couldn't convert the error: `E: std::error::Error` is not satisfied | ||
| --> $DIR/bad-question-mark-on-trait-object.rs:7:13 | ||
| | | ||
| LL | fn foo() -> Result<(), Box<dyn std::error::Error>> { | ||
| | -------------------------------------- required `E: std::error::Error` because of this | ||
| LL | Ok(bar()?) | ||
| | -----^ the trait `std::error::Error` is not implemented for `E` | ||
| | | | ||
| | this has type `Result<_, E>` | ||
| | | ||
| note: `E` needs to implement `std::error::Error` | ||
| --> $DIR/bad-question-mark-on-trait-object.rs:1:1 | ||
| | | ||
| LL | struct E; | ||
| | ^^^^^^^^ | ||
| = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait | ||
| = note: required for `Box<dyn std::error::Error>` to implement `From<E>` | ||
|
|
||
| error[E0277]: `?` couldn't convert the error to `X` | ||
| --> $DIR/bad-question-mark-on-trait-object.rs:18:13 | ||
| | | ||
| LL | fn bat() -> Result<(), X> { | ||
| | ------------- expected `X` because of this | ||
| LL | Ok(bar()?) | ||
| | -----^ the trait `From<E>` is not implemented for `X` | ||
| | | | ||
| | this can't be annotated with `?` because it has type `Result<_, E>` | ||
| | | ||
| note: `X` needs to implement `From<E>` | ||
| --> $DIR/bad-question-mark-on-trait-object.rs:4:1 | ||
| | | ||
| LL | struct X; | ||
| | ^^^^^^^^ | ||
| note: alternatively, `E` needs to implement `Into<X>` | ||
| --> $DIR/bad-question-mark-on-trait-object.rs:1:1 | ||
| | | ||
| LL | struct E; | ||
| | ^^^^^^^^ | ||
| = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait | ||
|
|
||
| error: aborting due to 2 previous errors | ||
|
|
||
| For more information about this error, try `rustc --explain E0277`. |
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