rust/tests/ui/impl-trait/dyn-trait-return-should-be-impl-trait.stderr
Esteban Küber 6efddac288 Provide more context on derived obligation error primary label
Expand the primary span of E0277 when the immediate unmet bound is not what the user wrote:

```
error[E0277]: the trait bound `i32: Bar` is not satisfied
 --> f100.rs:6:6
  |
6 |     <i32 as Foo>::foo();
  |      ^^^ the trait `Bar` is not implemented for `i32`, which is required by `i32: Foo`
  |
help: this trait has no implementations, consider adding one
 --> f100.rs:2:1
  |
2 | trait Bar {}
  | ^^^^^^^^^
note: required for `i32` to implement `Foo`
 --> f100.rs:3:14
  |
3 | impl<T: Bar> Foo for T {}
  |         ---  ^^^     ^
  |         |
  |         unsatisfied trait bound introduced here
```

Fix #40120.
2024-01-30 21:28:18 +00:00

302 lines
12 KiB
Plaintext

error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:7:35
|
LL | fn fuz() -> (usize, Trait) { (42, Struct) }
| ^^^^^^ expected `dyn Trait`, found `Struct`
|
= note: expected trait object `(dyn Trait + 'static)`
found struct `Struct`
= help: `Struct` implements `Trait` so you could box the found value and coerce it to the trait object `Box<dyn Trait>`, you will have to change the expected type as well
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 `Sized` is not implemented for `(dyn Trait + 'static)`, which is required by `(usize, (dyn Trait + 'static)): Sized`
= 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 `dyn Trait`, found `Struct`
|
= note: expected trait object `(dyn Trait + 'static)`
found struct `Struct`
= help: `Struct` implements `Trait` so you could box the found value and coerce it to the trait object `Box<dyn Trait>`, you will have to change the expected type as well
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 `Sized` is not implemented for `(dyn Trait + 'static)`, which is required by `(usize, (dyn Trait + 'static)): Sized`
= 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 an unboxed trait object
--> $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
|
help: box the return type, and wrap all of the returned values in `Box::new`
|
LL | fn bap() -> Box<Trait> { Box::new(Struct) }
| ++++ + +++++++++ +
error[E0746]: return type cannot have an unboxed trait object
--> $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
|
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
LL | fn ban() -> impl Trait { Struct }
| ~~~~
help: box the return type, and wrap all of the returned values in `Box::new`
|
LL | fn ban() -> Box<dyn Trait> { Box::new(Struct) }
| ++++ + +++++++++ +
error[E0746]: return type cannot have an unboxed trait object
--> $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: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
LL | fn bak() -> impl Trait { unimplemented!() }
| ~~~~
help: box the return type, and wrap all of the returned values in `Box::new`
|
LL | fn bak() -> Box<dyn Trait> { Box::new(unimplemented!()) }
| ++++ + +++++++++ +
error[E0746]: return type cannot have an unboxed trait object
--> $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: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
LL | fn bal() -> impl Trait {
| ~~~~
help: box the return type, and wrap all of the returned values in `Box::new`
|
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 an unboxed trait object
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:25:13
|
LL | fn bax() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
LL | fn bax() -> impl Trait {
| ~~~~
help: box the return type, and wrap all of the returned values in `Box::new`
|
LL ~ fn bax() -> Box<dyn Trait> {
LL | if true {
LL ~ Box::new(Struct)
LL | } else {
LL ~ Box::new(42)
|
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:34:16
|
LL | fn bam() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
LL | if true {
LL | return Struct;
| ^^^^^^ expected `Box<dyn Trait>`, found `Struct`
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found struct `Struct`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | return Box::new(Struct);
| +++++++++ +
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:36:5
|
LL | fn bam() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
...
LL | 42
| ^^ expected `Box<dyn Trait>`, found integer
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found type `{integer}`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | Box::new(42)
| +++++++++ +
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:40:16
|
LL | fn baq() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
LL | if true {
LL | return 0;
| ^ expected `Box<dyn Trait>`, found integer
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found type `{integer}`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | return Box::new(0);
| +++++++++ +
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:42:5
|
LL | fn baq() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
...
LL | 42
| ^^ expected `Box<dyn Trait>`, found integer
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found type `{integer}`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | Box::new(42)
| +++++++++ +
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:46:9
|
LL | fn baz() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
LL | if true {
LL | Struct
| ^^^^^^ expected `Box<dyn Trait>`, found `Struct`
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found struct `Struct`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | Box::new(Struct)
| +++++++++ +
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:48:9
|
LL | fn baz() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
...
LL | 42
| ^^ expected `Box<dyn Trait>`, found integer
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found type `{integer}`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | Box::new(42)
| +++++++++ +
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:53:9
|
LL | fn baw() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
LL | if true {
LL | 0
| ^ expected `Box<dyn Trait>`, found integer
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found type `{integer}`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | Box::new(0)
| +++++++++ +
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:55:9
|
LL | fn baw() -> Box<dyn Trait> {
| -------------- expected `Box<(dyn Trait + 'static)>` because of return type
...
LL | 42
| ^^ expected `Box<dyn Trait>`, found integer
|
= note: expected struct `Box<(dyn Trait + 'static)>`
found type `{integer}`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | Box::new(42)
| +++++++++ +
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:60:13
|
LL | fn bat() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
LL | fn bat() -> impl Trait {
| ~~~~
help: box the return type, and wrap all of the returned values in `Box::new`
|
LL ~ fn bat() -> Box<dyn Trait> {
LL | if true {
LL ~ return Box::new(0);
LL | }
LL ~ Box::new(42)
|
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:66:13
|
LL | fn bay() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
LL | fn bay() -> impl Trait {
| ~~~~
help: box the return type, and wrap all of the returned values in `Box::new`
|
LL ~ fn bay() -> Box<dyn Trait> {
LL | if true {
LL ~ Box::new(0)
LL | } else {
LL ~ Box::new(42)
|
error: aborting due to 19 previous errors
Some errors have detailed explanations: E0277, E0308, E0746.
For more information about an error, try `rustc --explain E0277`.