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Account for expected
dyn Trait
found impl Trait
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,18 @@ | ||
trait Trait {} | ||
struct Struct; | ||
impl Trait for Struct {} | ||
fn foo() -> impl Trait { | ||
Struct | ||
} | ||
fn main() { | ||
let a: Box<dyn Trait> = if true { | ||
Box::new(Struct) | ||
} else { | ||
foo() //~ ERROR E0308 | ||
}; | ||
let a: dyn Trait = if true { | ||
Struct //~ ERROR E0308 | ||
} else { | ||
foo() //~ ERROR E0308 | ||
}; | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,43 @@ | ||
error[E0308]: mismatched types | ||
--> $DIR/dyn-impl-type-mismatch.rs:11:9 | ||
| | ||
LL | fn foo() -> impl Trait { | ||
| ---------- the found opaque type | ||
... | ||
LL | foo() | ||
| ^^^^^ expected `Box<dyn Trait>`, found opaque type | ||
| | ||
= note: expected struct `Box<dyn Trait>` | ||
found opaque type `impl Trait` | ||
= 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(foo()) | ||
| +++++++++ + | ||
|
||
error[E0308]: mismatched types | ||
--> $DIR/dyn-impl-type-mismatch.rs:14:9 | ||
| | ||
LL | Struct | ||
| ^^^^^^ expected `dyn Trait`, found `Struct` | ||
| | ||
= note: expected trait object `dyn Trait` | ||
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[E0308]: mismatched types | ||
--> $DIR/dyn-impl-type-mismatch.rs:16:9 | ||
| | ||
LL | fn foo() -> impl Trait { | ||
| ---------- the found opaque type | ||
... | ||
LL | foo() | ||
| ^^^^^ expected `dyn Trait`, found opaque type | ||
| | ||
= note: expected trait object `dyn Trait` | ||
found opaque type `impl Trait` | ||
= help: you can box the `impl Trait` to coerce it to `Box<dyn Trait>`, but you'll have to change the expected type as well | ||
|
||
error: aborting due to 3 previous errors | ||
|
||
For more information about this error, try `rustc --explain E0308`. |