Error Handling

Many programs use mechanisms like exceptions for handling errors, but Rust takes a different approach. Rust doesn't have exceptions. Instead, it uses the Result type for recoverable errors and the panic! macro for unrecoverable errors. Similar to the Option enum we previously discussed, Result is another enum.

Result<T, E>

Result<T, E> is the type used for returning and propagating errors. Similar to Option, it has two variants: Ok(T), which represents success and contains a value, and Err(E), which represents an error and contains an error value. The T and E are generic type parameters that we'll discuss in more detail soon. For now, it's important to know that T represents the type of the value returned in a success case within the Ok variant, and E represents the type of the error returned in a failure case within the Err variant.

enum Result<T, E> {
   Ok(T),
   Err(E),
}

Additional Resources

Several sections in the Rust documentation thoroughly cover error handling.

Here are some useful links:

• Unrecoverable Errors with panic!: Useful information on how to troubleshoot code that panics.
• Recoverable Errors with Result: Deep dive into Result and general error handling.
• To panic! or Not to panic!: General guidelines on how to decide whether to panic in library code.
• The question mark operator: Useful for propagating errors to the calling function.¹