The following error types exist right now within the core:

std::Error

Standard error types for the Kairo language

Classes

BaseError

Base class for all Kairo errors

NullValueError

Error thrown when a null value is encountered where a valid value is expected

RuntimeError

Error thrown for general runtime errors

StateMismatchError

Error thrown when an object is in an incorrect state for the requested operation

TypeMismatchError

Error thrown when a type mismatch occurs

you can either panic like this:

fn do_something(value: i32) -> i32 { /// since we are not returning an `i32?` this will throw
    panic std::Error::RuntimeError("This is a runtime error panic!");
}

// or we can return the error
fn do_something_else(value: i32) -> i32? { /// since we are returning an `i32?` we can return null on error
    return std::Error::RuntimeError("This is a runtime error return!");
}

// read the error/handle it
fn main() {
    // handling throw
    try {
        do_something(5); // this will throw and stop execution
    } catch (err: std::Error) {
        std::print(f"Caught an error from do_something: {err}");
    }

    // handling return
    let result: i32? = do_something_else(10);
    if (result == null) {
        std::print("do_something_else returned null");
    } else if (std::Error::RuntimeError in result) {
        std::print(f"Caught an error from do_something_else");
    } else {
        std::print(f"do_something_else returned: {*result}");
    }

    // remember to collapse quantom types when using them.
}

If you do want to explictly crash (like in the main funciton where a panic is not allowed):

fn main() {
    std::crash(std::Error::RuntimeError("This is a fatal runtime error crash!"));
}

This will immediately terminate the program and print the error message.