export declare const is: {
    available: <X>(x: X) => x is NonNullable<X>;
    unavailable: (x: any) => x is (undefined | null);
    /** @deprecated use `unavailable` instead */
    void: (x: any) => x is (undefined | null);
    /** @deprecated use `available` instead */
    defined: <X>(x: X) => x is NonNullable<X>;
    boolean: (x: any) => x is boolean;
    number: (x: any) => x is number;
    string: (x: any) => x is string;
    bigint: (x: any) => x is bigint;
    object: <X>(x: X) => x is object & NonNullable<X>;
    array: (x: any | any[]) => x is any[];
};