1 error[E0277]: `?` couldn't convert the error to `u8`
2 --> $DIR/bad-interconversion.rs:6:20
4 LL | fn result_to_result() -> Result<u64, u8> {
5 | --------------- expected `u8` because of this
7 | ^ the trait `From<i32>` is not implemented for `u8`
9 = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
10 = help: the following other types implement trait `From<T>`:
20 = note: required for `Result<u64, u8>` to implement `FromResidual<Result<Infallible, i32>>`
22 error[E0277]: the `?` operator can only be used on `Result`s, not `Option`s, in a function that returns `Result`
23 --> $DIR/bad-interconversion.rs:11:12
25 LL | fn option_to_result() -> Result<u64, String> {
26 | -------------------------------------------- this function returns a `Result`
28 | ^ use `.ok_or(...)?` to provide an error compatible with `Result<u64, String>`
30 = help: the trait `FromResidual<Option<Infallible>>` is not implemented for `Result<u64, String>`
31 = help: the following other types implement trait `FromResidual<R>`:
32 <Result<T, F> as FromResidual<Result<Infallible, E>>>
33 <Result<T, F> as FromResidual<Yeet<E>>>
35 error[E0277]: the `?` operator can only be used on `Result`s in a function that returns `Result`
36 --> $DIR/bad-interconversion.rs:17:31
38 LL | fn control_flow_to_result() -> Result<u64, String> {
39 | -------------------------------------------------- this function returns a `Result`
40 LL | Ok(ControlFlow::Break(123)?)
41 | ^ this `?` produces `ControlFlow<{integer}, Infallible>`, which is incompatible with `Result<u64, String>`
43 = help: the trait `FromResidual<ControlFlow<{integer}, Infallible>>` is not implemented for `Result<u64, String>`
44 = help: the following other types implement trait `FromResidual<R>`:
45 <Result<T, F> as FromResidual<Result<Infallible, E>>>
46 <Result<T, F> as FromResidual<Yeet<E>>>
48 error[E0277]: the `?` operator can only be used on `Option`s, not `Result`s, in a function that returns `Option`
49 --> $DIR/bad-interconversion.rs:22:22
51 LL | fn result_to_option() -> Option<u16> {
52 | ------------------------------------ this function returns an `Option`
53 LL | Some(Err("hello")?)
54 | ^ use `.ok()?` if you want to discard the `Result<Infallible, &str>` error information
56 = help: the trait `FromResidual<Result<Infallible, &str>>` is not implemented for `Option<u16>`
57 = help: the following other types implement trait `FromResidual<R>`:
58 <Option<T> as FromResidual<Yeet<()>>>
59 <Option<T> as FromResidual>
61 error[E0277]: the `?` operator can only be used on `Option`s in a function that returns `Option`
62 --> $DIR/bad-interconversion.rs:27:33
64 LL | fn control_flow_to_option() -> Option<u64> {
65 | ------------------------------------------ this function returns an `Option`
66 LL | Some(ControlFlow::Break(123)?)
67 | ^ this `?` produces `ControlFlow<{integer}, Infallible>`, which is incompatible with `Option<u64>`
69 = help: the trait `FromResidual<ControlFlow<{integer}, Infallible>>` is not implemented for `Option<u64>`
70 = help: the following other types implement trait `FromResidual<R>`:
71 <Option<T> as FromResidual<Yeet<()>>>
72 <Option<T> as FromResidual>
74 error[E0277]: the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
75 --> $DIR/bad-interconversion.rs:32:39
77 LL | fn result_to_control_flow() -> ControlFlow<String> {
78 | -------------------------------------------------- this function returns a `ControlFlow`
79 LL | ControlFlow::Continue(Err("hello")?)
80 | ^ this `?` produces `Result<Infallible, &str>`, which is incompatible with `ControlFlow<String>`
82 = help: the trait `FromResidual<Result<Infallible, &str>>` is not implemented for `ControlFlow<String>`
83 = help: the trait `FromResidual` is implemented for `ControlFlow<B, C>`
85 error[E0277]: the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
86 --> $DIR/bad-interconversion.rs:37:12
88 LL | fn option_to_control_flow() -> ControlFlow<u64> {
89 | ----------------------------------------------- this function returns a `ControlFlow`
91 | ^ this `?` produces `Option<Infallible>`, which is incompatible with `ControlFlow<u64>`
93 = help: the trait `FromResidual<Option<Infallible>>` is not implemented for `ControlFlow<u64>`
94 = help: the trait `FromResidual` is implemented for `ControlFlow<B, C>`
96 error[E0277]: the `?` operator in a function that returns `ControlFlow<B, _>` can only be used on other `ControlFlow<B, _>`s (with the same Break type)
97 --> $DIR/bad-interconversion.rs:43:29
99 LL | fn control_flow_to_control_flow() -> ControlFlow<i64> {
100 | ----------------------------------------------------- this function returns a `ControlFlow`
101 LL | ControlFlow::Break(4_u8)?;
102 | ^ this `?` produces `ControlFlow<u8, Infallible>`, which is incompatible with `ControlFlow<i64>`
104 = help: the trait `FromResidual<ControlFlow<u8, Infallible>>` is not implemented for `ControlFlow<i64>`
105 = note: unlike `Result`, there's no `From`-conversion performed for `ControlFlow`
106 = help: the trait `FromResidual` is implemented for `ControlFlow<B, C>`
108 error: aborting due to 8 previous errors
110 For more information about this error, try `rustc --explain E0277`.