error[E0277]: `?` couldn't convert the error to `()` --> $DIR/try-on-option.rs:7:6 | LL | x?; | ^ the trait `std::convert::From` is not implemented for `()` | = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait = note: required by `std::convert::From::from` error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`) --> $DIR/try-on-option.rs:13:5 | LL | / fn bar() -> u32 { LL | | let x: Option = None; LL | | x?; | | ^^ cannot use the `?` operator in a function that returns `u32` LL | | 22 LL | | } | |_- this function should return `Result` or `Option` to accept `?` | = help: the trait `std::ops::Try` is not implemented for `u32` = note: required by `std::ops::Try::from_error` error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.