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dyn-trait-return-should-be-impl-trait.stderr
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dyn-trait-return-should-be-impl-trait.stderr
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error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:7:35
|
LL | fn fuz() -> (usize, Trait) { (42, Struct) }
| ^^^^^^ expected trait `Trait`, found struct `Struct`
|
= note: expected trait object `(dyn Trait + 'static)`
found struct `Struct`
error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:7:13
|
LL | fn fuz() -> (usize, Trait) { (42, Struct) }
| ^^^^^^^^^^^^^^ ------------ this returned value is of type `(usize, (dyn Trait + 'static))`
| |
| doesn't have a size known at compile-time
|
= help: within `(usize, (dyn Trait + 'static))`, the trait `std::marker::Sized` is not implemented for `(dyn Trait + 'static)`
= note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= note: required because it appears within the type `(usize, (dyn Trait + 'static))`
= note: the return type of a function must have a statically known size
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:10:39
|
LL | fn bar() -> (usize, dyn Trait) { (42, Struct) }
| ^^^^^^ expected trait `Trait`, found struct `Struct`
|
= note: expected trait object `(dyn Trait + 'static)`
found struct `Struct`
error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:10:13
|
LL | fn bar() -> (usize, dyn Trait) { (42, Struct) }
| ^^^^^^^^^^^^^^^^^^ ------------ this returned value is of type `(usize, (dyn Trait + 'static))`
| |
| doesn't have a size known at compile-time
|
= help: within `(usize, (dyn Trait + 'static))`, the trait `std::marker::Sized` is not implemented for `(dyn Trait + 'static)`
= note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= note: required because it appears within the type `(usize, (dyn Trait + 'static))`
= note: the return type of a function must have a statically known size
error[E0746]: return type cannot have a bare trait because it must be `Sized`
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:13:13
|
LL | fn bap() -> Trait { Struct }
| ^^^^^ doesn't have a size known at compile-time
|
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
help: you can use the `impl Trait` feature in the return type because all the return paths are of type `Struct`, which implements `dyn Trait`
|
LL | fn bap() -> impl Trait { Struct }
| ^^^^^^^^^^
error[E0746]: return type cannot have a bare trait because it must be `Sized`
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:15:13
|
LL | fn ban() -> dyn Trait { Struct }
| ^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
help: you can use the `impl Trait` feature in the return type because all the return paths are of type `Struct`, which implements `dyn Trait`
|
LL | fn ban() -> impl Trait { Struct }
| ^^^^^^^^^^
error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:17:13
|
LL | fn bak() -> dyn Trait { unimplemented!() }
| ^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `std::marker::Sized` is not implemented for `(dyn Trait + 'static)`
= note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= note: the return type of a function must have a statically known size
error[E0746]: return type cannot have a bare trait because it must be `Sized`
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:19:13
|
LL | fn bal() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
help: if all the returned values were of the same type you could use `impl Trait` as the return type
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:23:5
|
LL | return Struct;
| ^^^^^^
LL | }
LL | 42
| ^^
= help: alternatively, you can always create a new `enum` with a variant for each returned type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
help: if the performance implications are acceptable, you can return a trait object
|
LL | fn bal() -> Box<dyn Trait> {
LL | if true {
LL | return Box::new(Struct);
LL | }
LL | Box::new(42)
|
error[E0746]: return type cannot have a bare trait because it must be `Sized`
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:27:13
|
LL | fn bat() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
help: you can use the `impl Trait` feature in the return type because all the return paths are of type `{integer}`, which implements `dyn Trait`
|
LL | fn bat() -> impl Trait {
| ^^^^^^^^^^
error: aborting due to 9 previous errors
Some errors have detailed explanations: E0277, E0308, E0746.
For more information about an error, try `rustc --explain E0277`.