/**
 * Returns the input **value** if it is not null or undefined, else an error is thrown.
 */
export declare function unpack<T, O>(value: T | null | undefined): T;
/**
 * Returns the input **value** if it is not null or undefined, else the **instead** value will be returned.
 */
export declare function unpack<T, O>(value: T | null | undefined, instead: O): T | O;