1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/try-operator-on-main.rs:7:31
|
LL | fn main() {
| --------- this function should return `Result` or `Option` to accept `?`
LL | // error for a `Try` type on a non-`Try` fn
LL | std::fs::File::open("foo")?;
| ^ cannot use the `?` operator in a function that returns `()`
|
help: consider adding return type
|
LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
LL | // error for a `Try` type on a non-`Try` fn
...
LL | try_trait_generic::<()>();
LL + Ok(())
|
error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/try-operator-on-main.rs:10:5
|
LL | ()?;
| ^^^ the `?` operator cannot be applied to type `()`
|
= help: the trait `Try` is not implemented for `()`
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
--> $DIR/try-operator-on-main.rs:10:7
|
LL | fn main() {
| --------- this function should return `Result` or `Option` to accept `?`
...
LL | ()?;
| ^ cannot use the `?` operator in a function that returns `()`
error[E0277]: the trait bound `(): Try` is not satisfied
--> $DIR/try-operator-on-main.rs:14:25
|
LL | try_trait_generic::<()>();
| ^^ the trait `Try` is not implemented for `()`
|
note: required by a bound in `try_trait_generic`
--> $DIR/try-operator-on-main.rs:17:25
|
LL | fn try_trait_generic<T: Try>() -> T {
| ^^^ required by this bound in `try_trait_generic`
error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/try-operator-on-main.rs:19:5
|
LL | ()?;
| ^^^ the `?` operator cannot be applied to type `()`
|
= help: the trait `Try` is not implemented for `()`
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0277`.
|
