error[E0277]: `?` couldn't convert the error to `()` --> $DIR/issue-32709.rs:4:11 | LL | fn a() -> Result { | --------------- expected `()` because of this LL | Err(5)?; | ^ the trait `From<{integer}>` is not implemented for `()` | = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait = help: the following other types implement trait `FromResidual`: as FromResidual>> as FromResidual>> = note: required because of the requirements on the impl of `FromResidual>` for `Result` error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.