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| author | Esteban Küber <esteban@kuber.com.ar> | 2023-10-06 19:07:05 +0000 |
|---|---|---|
| committer | Esteban Küber <esteban@kuber.com.ar> | 2023-12-05 22:22:08 +0000 |
| commit | 6c3879d1f154bb6f18562d29aa30fbc03239c66f (patch) | |
| tree | 8094277f80e32194cb2cf688d86d60469e5396fd /tests/ui/try-trait | |
| parent | ec94480d9877e9c7ccf1255ab592dfc85d07ec50 (diff) | |
| download | rust-6c3879d1f154bb6f18562d29aa30fbc03239c66f.tar.gz rust-6c3879d1f154bb6f18562d29aa30fbc03239c66f.zip | |
Provide context when `?` can't be called because of `Result<_, E>`
When a method chain ending in `?` causes an E0277 because the
expression's `Result::Err` variant doesn't have a type that can be
converted to the `Result<_, E>` type parameter in the return type,
provide additional context of which parts of the chain can and can't
support the `?` operator.
```
error[E0277]: `?` couldn't convert the error to `String`
--> $DIR/question-mark-result-err-mismatch.rs:28:25
|
LL | fn bar() -> Result<(), String> {
| ------------------ expected `String` because of this
LL | let x = foo();
| ----- this can be annotated with `?` because it has type `Result<String, String>`
LL | let one = x
LL | .map(|s| ())
| ----------- this can be annotated with `?` because it has type `Result<(), String>`
LL | .map_err(|_| ())?;
| ---------------^ the trait `From<()>` is not implemented for `String`
| |
| this can't be annotated with `?` because it has type `Result<(), ()>`
|
= 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>`:
<String as From<char>>
<String as From<Box<str>>>
<String as From<Cow<'a, str>>>
<String as From<&str>>
<String as From<&mut str>>
<String as From<&String>>
= note: required for `Result<(), String>` to implement `FromResidual<Result<Infallible, ()>>`
```
Fix #72124.
Diffstat (limited to 'tests/ui/try-trait')
| -rw-r--r-- | tests/ui/try-trait/bad-interconversion.stderr | 4 | ||||
| -rw-r--r-- | tests/ui/try-trait/issue-32709.stderr | 4 |
2 files changed, 6 insertions, 2 deletions
diff --git a/tests/ui/try-trait/bad-interconversion.stderr b/tests/ui/try-trait/bad-interconversion.stderr index d8b9431becc..97fbbdbf8f8 100644 --- a/tests/ui/try-trait/bad-interconversion.stderr +++ b/tests/ui/try-trait/bad-interconversion.stderr @@ -4,7 +4,9 @@ error[E0277]: `?` couldn't convert the error to `u8` 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` + | ------------^ the trait `From<i32>` is not implemented for `u8` + | | + | this can't be annotated with `?` because it has type `Result<_, i32>` | = 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>`: diff --git a/tests/ui/try-trait/issue-32709.stderr b/tests/ui/try-trait/issue-32709.stderr index 46798f5dcfd..b155b3ff663 100644 --- a/tests/ui/try-trait/issue-32709.stderr +++ b/tests/ui/try-trait/issue-32709.stderr @@ -4,7 +4,9 @@ error[E0277]: `?` couldn't convert the error to `()` LL | fn a() -> Result<i32, ()> { | --------------- expected `()` because of this LL | Err(5)?; - | ^ the trait `From<{integer}>` is not implemented for `()` + | ------^ the trait `From<{integer}>` is not implemented for `()` + | | + | this can't be annotated with `?` because it has type `Result<_, {integer}>` | = 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>`: |