throw

The throw keyword raises an error, transferring control to the nearest enclosing catch (or propagating out of the function if none handles it). It also triggers any defer statements registered in the scopes being exited.

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Syntax & Example

fn lookup(key: string): i64 {
    if key == "" {
        throw Error("empty key");
    }
    return 0;
}

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Use Cases

• Signaling that an operation cannot proceed normally.
• Propagating failures up to a layer that can handle them.
• Combining with try/catch for structured error handling.

See also: try, catch, Error Handling.