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