Errors Are Values

Rust

Handle missing values and failures with Option and Result. Propagate errors with ?, define useful error types, and decide when a panic is appropriate.

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0 / 4 correct

How can ? propagate ParseIntError from a function returning Result<i32, MyErr>?

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use std::num::ParseIntError;

#[derive(Debug)]
struct MyErr(ParseIntError);

impl From<ParseIntError> for MyErr {
    fn from(error: ParseIntError) -> Self {
        MyErr(error)
    }
}

fn parse(s: &str) -> Result<i32, MyErr> {
    Ok(s.parse::<i32>()?)
}

fn main() {
    println!("{:?}", parse("21"));
    if let Err(MyErr(error)) = parse("x") {
        println!("parse error: {error}");
    }
}

Question 1 of 4