rustlings/exercises/error_handling/errors4.rs

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// errors4.rs
//
// Execute `rustlings hint errors4` or use the `hint` watch subcommand for a
// hint.
#[derive(PartialEq, Debug)]
struct PositiveNonzeroInteger(u64);
#[derive(PartialEq, Debug)]
enum CreationError {
Negative,
Zero,
}
impl PositiveNonzeroInteger {
fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
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match value.signum() {
-1 => Err(CreationError::Negative),
0 => Err(CreationError::Zero),
_ => Ok(PositiveNonzeroInteger(value as u64))
}
}
}
#[test]
fn test_creation() {
assert!(PositiveNonzeroInteger::new(10).is_ok());
assert_eq!(
Err(CreationError::Negative),
PositiveNonzeroInteger::new(-10)
);
assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0));
}