export type None = null | undefined;
export type Just<T> = T;
export type Maybe<T> = Just<T> | None;
export declare function just<T>(maybe: Maybe<T>, errorMessage?: string): asserts maybe is Just<T>;
export declare function isJust<T>(maybe: Maybe<T>): maybe is Just<T>;
export declare function isNone<T>(maybe: Maybe<T>): maybe is None;
export declare function withDefault<T, K>(v: Maybe<T>, alternative: K): K | NonNullable<T>;
export declare const _: undefined;