| // run-pass |
| |
| #[derive(Copy, Clone, Debug, PartialEq)] |
| struct BadNumErr; |
| |
| fn try_num(x: i32) -> Result<i32, BadNumErr> { |
| if x <= 5 { |
| Ok(x + 1) |
| } else { |
| Err(BadNumErr) |
| } |
| } |
| |
| type ResOpt = Result<Option<i32>, BadNumErr>; |
| type OptRes = Option<Result<i32, BadNumErr>>; |
| |
| fn main() { |
| let mut x: ResOpt = Ok(Some(5)); |
| let mut y: OptRes = Some(Ok(5)); |
| assert_eq!(x, y.transpose()); |
| assert_eq!(x.transpose(), y); |
| |
| x = Ok(None); |
| y = None; |
| assert_eq!(x, y.transpose()); |
| assert_eq!(x.transpose(), y); |
| |
| x = Err(BadNumErr); |
| y = Some(Err(BadNumErr)); |
| assert_eq!(x, y.transpose()); |
| assert_eq!(x.transpose(), y); |
| |
| let res: Result<Vec<i32>, BadNumErr> = |
| (0..10) |
| .map(|x| { |
| let y = try_num(x)?; |
| Ok(if y % 2 == 0 { |
| Some(y - 1) |
| } else { |
| None |
| }) |
| }) |
| .filter_map(Result::transpose) |
| .collect(); |
| |
| assert_eq!(res, Err(BadNumErr)) |
| } |