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error[E0308]: `if` and `else` have incompatible types
--> $DIR/box-instead-of-dyn-fn.rs:10:9
|
LL | / if a % 2 == 0 {
LL | | move || println!("{a}")
| | -----------------------
| | |
| | the expected closure
| | expected because of this
LL | | } else {
LL | | Box::new(move || println!("{}", b))
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected closure, found `Box<[closure@box-instead-of-dyn-fn.rs:10:18]>`
LL | |
LL | | }
| |_____- `if` and `else` have incompatible types
|
= note: expected closure `[closure@$DIR/box-instead-of-dyn-fn.rs:8:9: 8:16]`
found struct `Box<[closure@$DIR/box-instead-of-dyn-fn.rs:10:18: 10:25]>`
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/box-instead-of-dyn-fn.rs:5:56
|
LL | fn print_on_or_the_other<'a>(a: i32, b: &'a String) -> dyn Fn() + 'a {
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= 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>
= note: if all the returned values were of the same type you could use `impl Fn() + 'a` as the return type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: you can create a new `enum` with a variant for each returned type
help: return a boxed trait object instead
|
LL | fn print_on_or_the_other<'a>(a: i32, b: &'a String) -> Box<dyn Fn() + 'a> {
| ++++ +
help: ... and box this value
|
LL | Box::new(move || println!("{a}"))
| +++++++++ +
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0308, E0746.
For more information about an error, try `rustc --explain E0308`.
|
