99 lines
2.6 KiB
Rust
99 lines
2.6 KiB
Rust
// advanced_errs1.rs
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// Remember back in errors6, we had multiple mapping functions so that we
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// could translate lower-level errors into our custom error type using
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// `map_err()`? What if we could use the `?` operator directly instead?
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// Make this code compile! Execute `rustlings hint advanced_errs1` for
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// hints :)
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// I AM NOT DONE
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use std::num::ParseIntError;
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use std::str::FromStr;
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// This is a custom error type that we will be using in the `FromStr`
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// implementation.
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#[derive(PartialEq, Debug)]
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enum ParsePosNonzeroError {
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Creation(CreationError),
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ParseInt(ParseIntError),
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}
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impl From<CreationError> for ParsePosNonzeroError {
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fn from(e: CreationError) -> Self {
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// TODO: complete this implementation so that the `?` operator will
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// work for `CreationError`
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}
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}
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// TODO: implement another instance of the `From` trait here so that the
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// `?` operator will work in the other place in the `FromStr`
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// implementation below.
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// Don't change anything below this line.
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impl FromStr for PositiveNonzeroInteger {
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type Err = ParsePosNonzeroError;
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fn from_str(s: &str) -> Result<PositiveNonzeroInteger, Self::Err> {
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let x: i64 = s.parse()?;
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Ok(PositiveNonzeroInteger::new(x)?)
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}
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}
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#[derive(PartialEq, Debug)]
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struct PositiveNonzeroInteger(u64);
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#[derive(PartialEq, Debug)]
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enum CreationError {
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Negative,
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Zero,
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}
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impl PositiveNonzeroInteger {
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fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
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match value {
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x if x < 0 => Err(CreationError::Negative),
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x if x == 0 => Err(CreationError::Zero),
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x => Ok(PositiveNonzeroInteger(x as u64)),
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}
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_parse_error() {
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// We can't construct a ParseIntError, so we have to pattern match.
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assert!(matches!(
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PositiveNonzeroInteger::from_str("not a number"),
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Err(ParsePosNonzeroError::ParseInt(_))
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));
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}
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#[test]
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fn test_negative() {
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assert_eq!(
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PositiveNonzeroInteger::from_str("-555"),
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Err(ParsePosNonzeroError::Creation(CreationError::Negative))
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);
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}
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#[test]
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fn test_zero() {
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assert_eq!(
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PositiveNonzeroInteger::from_str("0"),
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Err(ParsePosNonzeroError::Creation(CreationError::Zero))
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);
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}
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#[test]
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fn test_positive() {
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let x = PositiveNonzeroInteger::new(42);
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assert!(x.is_ok());
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assert_eq!(PositiveNonzeroInteger::from_str("42"), Ok(x.unwrap()));
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}
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}
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