Merge pull request #781 from tlyu/advanced-errs
feature: advanced errors
This commit is contained in:
commit
c2ed98deb3
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@ -0,0 +1,98 @@
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// 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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@ -0,0 +1,203 @@
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// advanced_errs2.rs
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// This exercise demonstrates a few traits that are useful for custom error
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// types to implement, especially so that other code can consume the custom
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// error type more usefully.
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// Make this compile, and make the tests pass!
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// Execute `rustlings hint advanced_errs2` for hints.
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// Steps:
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// 1. Implement a missing trait so that `main()` will compile.
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// 2. Complete the partial implementation of `From` for
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// `ParseClimateError`.
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// 3. Handle the missing error cases in the `FromStr` implementation for
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// `Climate`.
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// 4. Complete the partial implementation of `Display` for
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// `ParseClimateError`.
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// I AM NOT DONE
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use std::error::Error;
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use std::fmt::{self, Display, Formatter};
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use std::num::{ParseFloatError, ParseIntError};
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use std::str::FromStr;
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// This is the custom error type that we will be using for the parser for
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// `Climate`.
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#[derive(Debug, PartialEq)]
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enum ParseClimateError {
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Empty,
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BadLen,
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NoCity,
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ParseInt(ParseIntError),
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ParseFloat(ParseFloatError),
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}
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// This `From` implementation allows the `?` operator to work on
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// `ParseIntError` values.
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impl From<ParseIntError> for ParseClimateError {
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fn from(e: ParseIntError) -> Self {
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Self::ParseInt(e)
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}
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}
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// This `From` implementation allows the `?` operator to work on
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// `ParseFloatError` values.
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impl From<ParseFloatError> for ParseClimateError {
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fn from(e: ParseFloatError) -> Self {
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// TODO: Complete this function
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}
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}
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// TODO: Implement a missing trait so that `main()` below will compile. It
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// is not necessary to implement any methods inside the missing trait.
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// The `Display` trait allows for other code to obtain the error formatted
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// as a user-visible string.
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impl Display for ParseClimateError {
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// TODO: Complete this function so that it produces the correct strings
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// for each error variant.
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fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
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// Imports the variants to make the following code more compact.
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use ParseClimateError::*;
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match self {
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NoCity => write!(f, "no city name"),
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ParseFloat(e) => write!(f, "error parsing temperature: {}", e),
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_ => write!(f, "unhandled error!"),
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}
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}
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}
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#[derive(Debug, PartialEq)]
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struct Climate {
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city: String,
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year: u32,
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temp: f32,
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}
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// Parser for `Climate`.
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// 1. Split the input string into 3 fields: city, year, temp.
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// 2. Return an error if the string is empty or has the wrong number of
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// fields.
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// 3. Return an error if the city name is empty.
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// 4. Parse the year as a `u32` and return an error if that fails.
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// 5. Parse the temp as a `f32` and return an error if that fails.
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// 6. Return an `Ok` value containing the completed `Climate` value.
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impl FromStr for Climate {
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type Err = ParseClimateError;
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// TODO: Complete this function by making it handle the missing error
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// cases.
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fn from_str(s: &str) -> Result<Self, Self::Err> {
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let v: Vec<_> = s.split(',').collect();
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let (city, year, temp) = match &v[..] {
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[city, year, temp] => (city.to_string(), year, temp),
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_ => return Err(ParseClimateError::BadLen),
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};
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let year: u32 = year.parse()?;
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let temp: f32 = temp.parse()?;
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Ok(Climate { city, year, temp })
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}
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}
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// Don't change anything below this line (other than to enable ignored
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// tests).
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fn main() -> Result<(), Box<dyn Error>> {
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println!("{:?}", "Hong Kong,1999,25.7".parse::<Climate>()?);
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println!("{:?}", "".parse::<Climate>()?);
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Ok(())
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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_empty() {
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let res = "".parse::<Climate>();
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assert_eq!(res, Err(ParseClimateError::Empty));
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assert_eq!(res.unwrap_err().to_string(), "empty input");
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}
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#[test]
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fn test_short() {
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let res = "Boston,1991".parse::<Climate>();
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assert_eq!(res, Err(ParseClimateError::BadLen));
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assert_eq!(res.unwrap_err().to_string(), "incorrect number of fields");
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}
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#[test]
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fn test_long() {
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let res = "Paris,1920,17.2,extra".parse::<Climate>();
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assert_eq!(res, Err(ParseClimateError::BadLen));
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assert_eq!(res.unwrap_err().to_string(), "incorrect number of fields");
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}
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#[test]
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fn test_no_city() {
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let res = ",1997,20.5".parse::<Climate>();
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assert_eq!(res, Err(ParseClimateError::NoCity));
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assert_eq!(res.unwrap_err().to_string(), "no city name");
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}
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#[test]
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fn test_parse_int_neg() {
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let res = "Barcelona,-25,22.3".parse::<Climate>();
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assert!(matches!(res, Err(ParseClimateError::ParseInt(_))));
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let err = res.unwrap_err();
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if let ParseClimateError::ParseInt(ref inner) = err {
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assert_eq!(
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err.to_string(),
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format!("error parsing year: {}", inner.to_string())
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);
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} else {
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unreachable!();
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};
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}
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#[test]
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fn test_parse_int_bad() {
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let res = "Beijing,foo,15.0".parse::<Climate>();
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assert!(matches!(res, Err(ParseClimateError::ParseInt(_))));
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let err = res.unwrap_err();
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if let ParseClimateError::ParseInt(ref inner) = err {
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assert_eq!(
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err.to_string(),
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format!("error parsing year: {}", inner.to_string())
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);
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} else {
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unreachable!();
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};
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}
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#[test]
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fn test_parse_float() {
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let res = "Manila,2001,bar".parse::<Climate>();
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assert!(matches!(res, Err(ParseClimateError::ParseFloat(_))));
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let err = res.unwrap_err();
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if let ParseClimateError::ParseFloat(ref inner) = err {
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assert_eq!(
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err.to_string(),
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format!("error parsing temperature: {}", inner.to_string())
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);
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} else {
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unreachable!();
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};
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}
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#[test]
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fn test_parse_good() {
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let res = "Munich,2015,23.1".parse::<Climate>();
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assert_eq!(
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res,
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Ok(Climate {
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city: "Munich".to_string(),
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year: 2015,
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temp: 23.1,
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})
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);
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}
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#[test]
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#[ignore]
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fn test_downcast() {
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let res = "São Paulo,-21,28.5".parse::<Climate>();
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assert!(matches!(res, Err(ParseClimateError::ParseInt(_))));
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let err = res.unwrap_err();
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let inner: Option<&(dyn Error + 'static)> = err.source();
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assert!(inner.is_some());
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assert!(inner.unwrap().is::<ParseIntError>());
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}
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}
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@ -1,16 +1,31 @@
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// This does practically the same thing that TryFrom<&str> does.
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// from_str.rs
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// This is similar to from_into.rs, but this time we'll implement `FromStr`
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// and return errors instead of falling back to a default value.
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// Additionally, upon implementing FromStr, you can use the `parse` method
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// on strings to generate an object of the implementor type.
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// You can read more about it at https://doc.rust-lang.org/std/str/trait.FromStr.html
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use std::error;
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use std::num::ParseIntError;
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use std::str::FromStr;
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#[derive(Debug)]
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#[derive(Debug, PartialEq)]
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struct Person {
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name: String,
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age: usize,
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}
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// We will use this error type for the `FromStr` implementation.
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#[derive(Debug, PartialEq)]
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enum ParsePersonError {
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// Empty input string
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Empty,
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// Incorrect number of fields
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BadLen,
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// Empty name field
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NoName,
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// Wrapped error from parse::<usize>()
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ParseInt(ParseIntError),
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}
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// I AM NOT DONE
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// Steps:
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@ -24,7 +39,7 @@ struct Person {
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// If everything goes well, then return a Result of a Person object
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impl FromStr for Person {
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type Err = Box<dyn error::Error>;
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type Err = ParsePersonError;
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fn from_str(s: &str) -> Result<Person, Self::Err> {
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}
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}
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@ -40,7 +55,7 @@ mod tests {
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#[test]
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fn empty_input() {
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assert!("".parse::<Person>().is_err());
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assert_eq!("".parse::<Person>(), Err(ParsePersonError::Empty));
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}
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#[test]
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fn good_input() {
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@ -52,41 +67,56 @@ mod tests {
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}
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#[test]
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fn missing_age() {
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assert!("John,".parse::<Person>().is_err());
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assert!(matches!(
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"John,".parse::<Person>(),
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Err(ParsePersonError::ParseInt(_))
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));
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}
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#[test]
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fn invalid_age() {
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assert!("John,twenty".parse::<Person>().is_err());
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assert!(matches!(
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"John,twenty".parse::<Person>(),
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Err(ParsePersonError::ParseInt(_))
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));
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}
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#[test]
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fn missing_comma_and_age() {
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assert!("John".parse::<Person>().is_err());
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assert_eq!("John".parse::<Person>(), Err(ParsePersonError::BadLen));
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}
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#[test]
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fn missing_name() {
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assert!(",1".parse::<Person>().is_err());
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assert_eq!(",1".parse::<Person>(), Err(ParsePersonError::NoName));
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}
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#[test]
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fn missing_name_and_age() {
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assert!(",".parse::<Person>().is_err());
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assert!(matches!(
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",".parse::<Person>(),
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Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
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));
|
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}
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|
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#[test]
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fn missing_name_and_invalid_age() {
|
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assert!(",one".parse::<Person>().is_err());
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assert!(matches!(
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",one".parse::<Person>(),
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Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
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));
|
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}
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|
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#[test]
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fn trailing_comma() {
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assert!("John,32,".parse::<Person>().is_err());
|
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assert_eq!("John,32,".parse::<Person>(), Err(ParsePersonError::BadLen));
|
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}
|
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|
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#[test]
|
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fn trailing_comma_and_some_string() {
|
||||
assert!("John,32,man".parse::<Person>().is_err());
|
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assert_eq!(
|
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"John,32,man".parse::<Person>(),
|
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Err(ParsePersonError::BadLen)
|
||||
);
|
||||
}
|
||||
}
|
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|
|
|
@ -1,9 +1,9 @@
|
|||
// try_from_into.rs
|
||||
// TryFrom is a simple and safe type conversion that may fail in a controlled way under some circumstances.
|
||||
// Basically, this is the same as From. The main difference is that this should return a Result type
|
||||
// instead of the target type itself.
|
||||
// You can read more about it at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
|
||||
use std::convert::{TryFrom, TryInto};
|
||||
use std::error;
|
||||
|
||||
#[derive(Debug, PartialEq)]
|
||||
struct Color {
|
||||
|
@ -12,12 +12,21 @@ struct Color {
|
|||
blue: u8,
|
||||
}
|
||||
|
||||
// We will use this error type for these `TryFrom` conversions.
|
||||
#[derive(Debug, PartialEq)]
|
||||
enum IntoColorError {
|
||||
// Incorrect length of slice
|
||||
BadLen,
|
||||
// Integer conversion error
|
||||
IntConversion,
|
||||
}
|
||||
|
||||
// I AM NOT DONE
|
||||
|
||||
// Your task is to complete this implementation
|
||||
// and return an Ok result of inner type Color.
|
||||
// You need to create an implementation for a tuple of three integers,
|
||||
// an array of three integers and a slice of integers.
|
||||
// an array of three integers, and a slice of integers.
|
||||
//
|
||||
// Note that the implementation for tuple and array will be checked at compile time,
|
||||
// but the slice implementation needs to check the slice length!
|
||||
|
@ -25,20 +34,23 @@ struct Color {
|
|||
|
||||
// Tuple implementation
|
||||
impl TryFrom<(i16, i16, i16)> for Color {
|
||||
type Error = Box<dyn error::Error>;
|
||||
fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {}
|
||||
type Error = IntoColorError;
|
||||
fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
|
||||
}
|
||||
}
|
||||
|
||||
// Array implementation
|
||||
impl TryFrom<[i16; 3]> for Color {
|
||||
type Error = Box<dyn error::Error>;
|
||||
fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {}
|
||||
type Error = IntoColorError;
|
||||
fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
|
||||
}
|
||||
}
|
||||
|
||||
// Slice implementation
|
||||
impl TryFrom<&[i16]> for Color {
|
||||
type Error = Box<dyn error::Error>;
|
||||
fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {}
|
||||
type Error = IntoColorError;
|
||||
fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
|
||||
}
|
||||
}
|
||||
|
||||
fn main() {
|
||||
|
@ -46,15 +58,15 @@ fn main() {
|
|||
let c1 = Color::try_from((183, 65, 14));
|
||||
println!("{:?}", c1);
|
||||
|
||||
// Since From is implemented for Color, we should be able to use Into
|
||||
// Since TryFrom is implemented for Color, we should be able to use TryInto
|
||||
let c2: Result<Color, _> = [183, 65, 14].try_into();
|
||||
println!("{:?}", c2);
|
||||
|
||||
let v = vec![183, 65, 14];
|
||||
// With slice we should use `from` function
|
||||
// With slice we should use `try_from` function
|
||||
let c3 = Color::try_from(&v[..]);
|
||||
println!("{:?}", c3);
|
||||
// or take slice within round brackets and use Into
|
||||
// or take slice within round brackets and use TryInto
|
||||
let c4: Result<Color, _> = (&v[..]).try_into();
|
||||
println!("{:?}", c4);
|
||||
}
|
||||
|
@ -65,15 +77,24 @@ mod tests {
|
|||
|
||||
#[test]
|
||||
fn test_tuple_out_of_range_positive() {
|
||||
assert!(Color::try_from((256, 1000, 10000)).is_err());
|
||||
assert_eq!(
|
||||
Color::try_from((256, 1000, 10000)),
|
||||
Err(IntoColorError::IntConversion)
|
||||
);
|
||||
}
|
||||
#[test]
|
||||
fn test_tuple_out_of_range_negative() {
|
||||
assert!(Color::try_from((-1, -10, -256)).is_err());
|
||||
assert_eq!(
|
||||
Color::try_from((-1, -10, -256)),
|
||||
Err(IntoColorError::IntConversion)
|
||||
);
|
||||
}
|
||||
#[test]
|
||||
fn test_tuple_sum() {
|
||||
assert!(Color::try_from((-1, 255, 255)).is_err());
|
||||
assert_eq!(
|
||||
Color::try_from((-1, 255, 255)),
|
||||
Err(IntoColorError::IntConversion)
|
||||
);
|
||||
}
|
||||
#[test]
|
||||
fn test_tuple_correct() {
|
||||
|
@ -91,17 +112,17 @@ mod tests {
|
|||
#[test]
|
||||
fn test_array_out_of_range_positive() {
|
||||
let c: Result<Color, _> = [1000, 10000, 256].try_into();
|
||||
assert!(c.is_err());
|
||||
assert_eq!(c, Err(IntoColorError::IntConversion));
|
||||
}
|
||||
#[test]
|
||||
fn test_array_out_of_range_negative() {
|
||||
let c: Result<Color, _> = [-10, -256, -1].try_into();
|
||||
assert!(c.is_err());
|
||||
assert_eq!(c, Err(IntoColorError::IntConversion));
|
||||
}
|
||||
#[test]
|
||||
fn test_array_sum() {
|
||||
let c: Result<Color, _> = [-1, 255, 255].try_into();
|
||||
assert!(c.is_err());
|
||||
assert_eq!(c, Err(IntoColorError::IntConversion));
|
||||
}
|
||||
#[test]
|
||||
fn test_array_correct() {
|
||||
|
@ -119,17 +140,26 @@ mod tests {
|
|||
#[test]
|
||||
fn test_slice_out_of_range_positive() {
|
||||
let arr = [10000, 256, 1000];
|
||||
assert!(Color::try_from(&arr[..]).is_err());
|
||||
assert_eq!(
|
||||
Color::try_from(&arr[..]),
|
||||
Err(IntoColorError::IntConversion)
|
||||
);
|
||||
}
|
||||
#[test]
|
||||
fn test_slice_out_of_range_negative() {
|
||||
let arr = [-256, -1, -10];
|
||||
assert!(Color::try_from(&arr[..]).is_err());
|
||||
assert_eq!(
|
||||
Color::try_from(&arr[..]),
|
||||
Err(IntoColorError::IntConversion)
|
||||
);
|
||||
}
|
||||
#[test]
|
||||
fn test_slice_sum() {
|
||||
let arr = [-1, 255, 255];
|
||||
assert!(Color::try_from(&arr[..]).is_err());
|
||||
assert_eq!(
|
||||
Color::try_from(&arr[..]),
|
||||
Err(IntoColorError::IntConversion)
|
||||
);
|
||||
}
|
||||
#[test]
|
||||
fn test_slice_correct() {
|
||||
|
@ -148,11 +178,11 @@ mod tests {
|
|||
#[test]
|
||||
fn test_slice_excess_length() {
|
||||
let v = vec![0, 0, 0, 0];
|
||||
assert!(Color::try_from(&v[..]).is_err());
|
||||
assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));
|
||||
}
|
||||
#[test]
|
||||
fn test_slice_insufficient_length() {
|
||||
let v = vec![0, 0];
|
||||
assert!(Color::try_from(&v[..]).is_err());
|
||||
assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));
|
||||
}
|
||||
}
|
||||
|
|
95
info.toml
95
info.toml
|
@ -941,6 +941,27 @@ mode = "test"
|
|||
hint = """
|
||||
Follow the steps provided right before the `From` implementation"""
|
||||
|
||||
[[exercises]]
|
||||
name = "from_str"
|
||||
path = "exercises/conversions/from_str.rs"
|
||||
mode = "test"
|
||||
hint = """
|
||||
The implementation of FromStr should return an Ok with a Person object,
|
||||
or an Err with an error if the string is not valid.
|
||||
|
||||
This is almost like the `from_into` exercise, but returning errors instead
|
||||
of falling back to a default value.
|
||||
|
||||
Hint: Look at the test cases to see which error variants to return.
|
||||
|
||||
Another hint: You can use the `map_err` method of `Result` with a function
|
||||
or a closure to wrap the error from `parse::<usize>`.
|
||||
|
||||
Yet another hint: If you would like to propagate errors by using the `?`
|
||||
operator in your solution, you might want to look at
|
||||
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/reenter_question_mark.html
|
||||
"""
|
||||
|
||||
[[exercises]]
|
||||
name = "try_from_into"
|
||||
path = "exercises/conversions/try_from_into.rs"
|
||||
|
@ -949,17 +970,19 @@ hint = """
|
|||
Follow the steps provided right before the `TryFrom` implementation.
|
||||
You can also use the example at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
|
||||
|
||||
You might want to look back at the exercise errors5 (or its hints) to remind
|
||||
yourself about how `Box<dyn Error>` works.
|
||||
Hint: Is there an implementation of `TryFrom` in the standard library that
|
||||
can both do the required integer conversion and check the range of the input?
|
||||
|
||||
If you're trying to return a string as an error, note that neither `str`
|
||||
nor `String` implements `error::Error`. However, there is an implementation
|
||||
of `From<&str>` for `Box<dyn Error>`. This means you can use `.into()` or
|
||||
the `?` operator to convert your string into the correct error type.
|
||||
Another hint: Look at the test cases to see which error variants to return.
|
||||
|
||||
If you're having trouble with using the `?` operator to convert an error string,
|
||||
recall that `?` works to convert `Err(something)` into the appropriate error
|
||||
type for returning from the function."""
|
||||
Yet another hint: You can use the `map_err` or `or` methods of `Result` to
|
||||
convert errors.
|
||||
|
||||
Yet another hint: If you would like to propagate errors by using the `?`
|
||||
operator in your solution, you might want to look at
|
||||
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/reenter_question_mark.html
|
||||
|
||||
Challenge: Can you make the `TryFrom` implementations generic over many integer types?"""
|
||||
|
||||
[[exercises]]
|
||||
name = "as_ref_mut"
|
||||
|
@ -968,14 +991,54 @@ mode = "test"
|
|||
hint = """
|
||||
Add AsRef<str> as a trait bound to the functions."""
|
||||
|
||||
# ADVANCED ERRORS
|
||||
|
||||
[[exercises]]
|
||||
name = "from_str"
|
||||
path = "exercises/conversions/from_str.rs"
|
||||
name = "advanced_errs1"
|
||||
path = "exercises/advanced_errors/advanced_errs1.rs"
|
||||
mode = "test"
|
||||
hint = """
|
||||
The implementation of FromStr should return an Ok with a Person object,
|
||||
or an Err with an error if the string is not valid.
|
||||
This is almost like the `try_from_into` exercise.
|
||||
This exercise uses an updated version of the code in errors6. The parsing
|
||||
code is now in an implementation of the `FromStr` trait. Note that the
|
||||
parsing code uses `?` directly, without any calls to `map_err()`. There is
|
||||
one partial implementation of the `From` trait example that you should
|
||||
complete.
|
||||
|
||||
If you're having trouble with returning the correct error type, see the
|
||||
hints for try_from_into."""
|
||||
Details: The `?` operator calls `From::from()` on the error type to convert
|
||||
it to the error type of the return type of the surrounding function.
|
||||
|
||||
Hint: You will need to write another implementation of `From` that has a
|
||||
different input type.
|
||||
"""
|
||||
|
||||
[[exercises]]
|
||||
name = "advanced_errs2"
|
||||
path = "exercises/advanced_errors/advanced_errs2.rs"
|
||||
mode = "test"
|
||||
hint = """
|
||||
This exercise demonstrates a few traits that are useful for custom error
|
||||
types to implement. These traits make it easier for other code to consume
|
||||
the custom error type.
|
||||
|
||||
Follow the steps in the comment near the top of the file. You will have to
|
||||
supply a missing trait implementation, and complete a few incomplete ones.
|
||||
|
||||
You may find these pages to be helpful references:
|
||||
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/define_error_type.html
|
||||
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/boxing_errors.html
|
||||
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/wrap_error.html
|
||||
|
||||
Hint: What trait must our error type have for `main()` to return the return
|
||||
type that it returns?
|
||||
|
||||
Another hint: It's not necessary to implement any methods inside the missing
|
||||
trait. (Some methods have default implementations that are supplied by the
|
||||
trait.)
|
||||
|
||||
Another hint: Consult the tests to determine which error variants (and which
|
||||
error message text) to produce for certain error conditions.
|
||||
|
||||
Challenge: There is one test that is marked `#[ignore]`. Can you supply the
|
||||
missing code that will make it pass? You may want to consult the standard
|
||||
library documentation for a certain trait for more hints.
|
||||
"""
|
||||
|
|
Loading…
Reference in New Issue