---

name: maverick-rust-errors description: Rust error handling with Result, Error trait, anyhow, thiserror version: 1.0.0 triggers:

• Result
• "?"
• Error
• anyhow
• thiserror
• unwrap
• expect
• "Result<"

---

Rust Errors Skill

Result Type

Copyfn parse_number(s: &str) -> Result<i32, ParseIntError> {
    s.parse()
}

// Use ? operator for propagation
fn process() -> Result<(), Error> {
    let num = parse_number("42")?;
    Ok(())
}

Custom Errors with thiserror

Copyuse thiserror::Error;

#[derive(Error, Debug)]
pub enum MyError {
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),

    #[error("Parse error: {0}")]
    Parse(String),
}

Avoid unwrap/expect in Production

Copy// BAD
let value = some_option.unwrap();

// GOOD
let value = some_option.ok_or(MyError::MissingValue)?;

// OR provide default
let value = some_option.unwrap_or_default();

Review Severity

• CRITICAL: unwrap/expect without justification
• MAJOR: Missing error handling
• MINOR: Could use ? operator