68d3ac567c
Add new exercises errors5 and errors6, to introduce boxed errors and custom error enums more gently. Delete errorsn, because it tried to do too much too soon.
87 lines
2.1 KiB
Rust
87 lines
2.1 KiB
Rust
// errors6.rs
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// Using catch-all error types like `Box<dyn error::Error>` isn't recommended
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// for library code, where callers might want to make decisions based on the
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// error content, instead of printing it out or propagating it further. Here,
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// we define a custom error type to make it possible for callers to decide
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// what to do next when our function returns an error.
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// Make these tests pass! Execute `rustlings hint errors6` for hints :)
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// I AM NOT DONE
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// This is a custom error type that we will be using in `parse_pos_nonzero()`.
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#[derive(PartialEq, Debug)]
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enum ParsePosNonzeroError {
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CreationError,
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ParseIntError
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}
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fn parse_pos_nonzero(s: &str)
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-> Result<PositiveNonzeroInteger, ParsePosNonzeroError>
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{
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// TODO: change this to return an appropriate error instead of panicking
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// when `parse()` returns an error.
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let x: i64 = s.parse().unwrap();
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PositiveNonzeroInteger::new(x)
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.or(Err(ParsePosNonzeroError::CreationError))
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}
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// Don't change anything below this line.
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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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assert_eq!(
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parse_pos_nonzero("not a number"),
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Err(ParsePosNonzeroError::ParseIntError)
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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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parse_pos_nonzero("-555"),
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Err(ParsePosNonzeroError::CreationError)
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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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parse_pos_nonzero("0"),
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Err(ParsePosNonzeroError::CreationError)
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);
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}
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#[test]
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fn test_positive() {
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assert_eq!(
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parse_pos_nonzero("42"),
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Ok(PositiveNonzeroInteger(42))
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);
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}
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}
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