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Provide better suggestions when encountering a bare trait as a type
Add the following suggestions: ``` error[E0782]: trait objects must include the `dyn` keyword --> $DIR/not-on-bare-trait-2021.rs:11:11 | LL | fn bar(x: Foo) -> Foo { | ^^^ | help: use a generic type parameter, constrained by the trait `Foo` | LL | fn bar<T: Foo>(x: T) -> Foo { | ++++++++ ~ help: you can also use `impl Foo`, but users won't be able to specify the type paramer when calling the `fn`, having to rely exclusively on type inference | LL | fn bar(x: impl Foo) -> Foo { | ++++ help: alternatively, use a trait object to accept any type that implements `Foo`, accessing its methods at runtime using dynamic dispatch | LL | fn bar(x: &dyn Foo) -> Foo { | ++++ error[E0782]: trait objects must include the `dyn` keyword --> $DIR/not-on-bare-trait-2021.rs:11:19 | LL | fn bar(x: Foo) -> Foo { | ^^^ | help: use `impl Foo` to return an opaque type, as long as you return a single underlying type | LL | fn bar(x: Foo) -> impl Foo { | ++++ help: alternatively, you can return an owned trait object | LL | fn bar(x: Foo) -> Box<dyn Foo> { | +++++++ + ```
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,17 @@ | ||
// edition:2021 | ||
trait Foo { | ||
fn dummy(&self) {} | ||
} | ||
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// This should emit the less confusing error, not the more confusing one. | ||
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fn foo(_x: Foo + Send) { | ||
//~^ ERROR trait objects must include the `dyn` keyword | ||
} | ||
fn bar(x: Foo) -> Foo { | ||
//~^ ERROR trait objects must include the `dyn` keyword | ||
//~| ERROR trait objects must include the `dyn` keyword | ||
x | ||
} | ||
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fn main() {} |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,56 @@ | ||
error[E0782]: trait objects must include the `dyn` keyword | ||
--> $DIR/not-on-bare-trait-2021.rs:8:12 | ||
| | ||
LL | fn foo(_x: Foo + Send) { | ||
| ^^^^^^^^^^ | ||
| | ||
help: use a new generic type parameter, constrained by `Foo + Send` | ||
| | ||
LL | fn foo<T: Foo + Send>(_x: T) { | ||
| +++++++++++++++ ~ | ||
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference | ||
| | ||
LL | fn foo(_x: impl Foo + Send) { | ||
| ++++ | ||
help: alternatively, use a trait object to accept any type that implements `Foo + Send`, accessing its methods at runtime using dynamic dispatch | ||
| | ||
LL | fn foo(_x: &(dyn Foo + Send)) { | ||
| +++++ + | ||
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error[E0782]: trait objects must include the `dyn` keyword | ||
--> $DIR/not-on-bare-trait-2021.rs:11:11 | ||
| | ||
LL | fn bar(x: Foo) -> Foo { | ||
| ^^^ | ||
| | ||
help: use a new generic type parameter, constrained by `Foo` | ||
| | ||
LL | fn bar<T: Foo>(x: T) -> Foo { | ||
| ++++++++ ~ | ||
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference | ||
| | ||
LL | fn bar(x: impl Foo) -> Foo { | ||
| ++++ | ||
help: alternatively, use a trait object to accept any type that implements `Foo`, accessing its methods at runtime using dynamic dispatch | ||
| | ||
LL | fn bar(x: &dyn Foo) -> Foo { | ||
| ++++ | ||
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error[E0782]: trait objects must include the `dyn` keyword | ||
--> $DIR/not-on-bare-trait-2021.rs:11:19 | ||
| | ||
LL | fn bar(x: Foo) -> Foo { | ||
| ^^^ | ||
| | ||
help: use `impl Foo` to return an opaque type, as long as you return a single underlying type | ||
| | ||
LL | fn bar(x: Foo) -> impl Foo { | ||
| ++++ | ||
help: alternatively, you can return an owned trait object | ||
| | ||
LL | fn bar(x: Foo) -> Box<dyn Foo> { | ||
| +++++++ + | ||
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error: aborting due to 3 previous errors | ||
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For more information about this error, try `rustc --explain E0782`. |
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