6eb48824da
Unless `try_trait_v2` is enabled, don't mention that `FromResidual` isn't implemented for a specific type when the implicit `From` conversion of a `?` fails. For the end user on stable, `?` might as well be a compiler intrinsic, so we remove that note to avoid further confusion and allowing other parts of the error to be more prominent.
```
error[E0277]: `?` couldn't convert the error to `u8`
--> $DIR/bad-interconversion.rs:4:20
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LL | fn result_to_result() -> Result<u64, u8> {
| --------------- expected `u8` because of this
LL | Ok(Err(123_i32)?)
| ------------^ the trait `From<i32>` is not implemented for `u8`
| |
| this can't be annotated with `?` because it has type `Result<_, i32>`
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= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
= help: the following other types implement trait `From<T>`:
`u8` implements `From<Char>`
`u8` implements `From<bool>`
```
63 lines
2.8 KiB
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63 lines
2.8 KiB
Plaintext
error[E0277]: `?` couldn't convert the error to `String`
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--> $DIR/question-mark-result-err-mismatch.rs:15:22
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LL | fn foo() -> Result<String, String> {
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| ---------------------- expected `String` because of this
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...
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LL | .map_err(|e| {
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| __________-
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LL | | e;
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| | - help: remove this semicolon
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LL | | })
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| |__________- this can't be annotated with `?` because it has type `Result<_, ()>`
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LL | .map(|()| "")?;
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| ^ the trait `From<()>` is not implemented for `String`
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= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
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= note: required for `Result<String, String>` to implement `FromResidual<Result<Infallible, ()>>`
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error[E0277]: `?` couldn't convert the error to `String`
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--> $DIR/question-mark-result-err-mismatch.rs:29:25
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LL | fn bar() -> Result<(), String> {
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| ------------------ expected `String` because of this
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LL | let x = foo();
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| ----- this has type `Result<_, String>`
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...
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LL | .map_err(|_| ())?;
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| ---------------^ the trait `From<()>` is not implemented for `String`
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| |
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| this can't be annotated with `?` because it has type `Result<_, ()>`
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= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
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= help: the following other types implement trait `From<T>`:
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`String` implements `From<&String>`
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`String` implements `From<&mut str>`
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`String` implements `From<&str>`
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`String` implements `From<Box<str>>`
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`String` implements `From<Cow<'_, str>>`
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`String` implements `From<char>`
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= note: required for `Result<(), String>` to implement `FromResidual<Result<Infallible, ()>>`
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error[E0277]: `?` couldn't convert the error to `String`
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--> $DIR/question-mark-result-err-mismatch.rs:49:11
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LL | fn baz() -> Result<String, String> {
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| ---------------------- expected `String` because of this
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...
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LL | .ok_or_else(|| {
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| __________-
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LL | | "Couldn't split the test string";
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| | - help: remove this semicolon
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LL | | })?;
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| | -^ the trait `From<()>` is not implemented for `String`
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| |__________|
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| this can't be annotated with `?` because it has type `Result<_, ()>`
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= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
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= note: required for `Result<String, String>` to implement `FromResidual<Result<Infallible, ()>>`
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0277`.
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