Result, Option & the ? Operator in Rust

From the Rust cheat sheet · Error Handling · verified Jul 2026

Result, Option & the ? Operator

Propagate errors idiomatically with Result<T, E> and the ? operator.

rust

// Result<T, E> — success or error
fn parse_port(s: &str) -> Result<u16, std::num::ParseIntError> {
    let port = s.parse::<u16>()?;   // ? returns early on error
    Ok(port)
}

// Handle Result
match parse_port("8080") {
    Ok(port) => println!("Port: {port}"),
    Err(e) => eprintln!("Error: {e}"),
}

// ? chains multiple fallible operations
fn read_config() -> Result<String, std::io::Error> {
    let contents = std::fs::read_to_string("config.toml")?;
    Ok(contents)
}

💡 The ? operator replaces verbose match/unwrap patterns — it's the idiomatic way to propagate errors

⚡ Implement From<OtherError> for your error type — then ? auto-converts between error types

📌 Use Box<dyn Error> as a quick return type when you don't want a custom error enum

🟢 In production, use the anyhow crate for applications and thiserror for libraries

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