import { ValidationRule } from './ValidationRule';
export declare const IS_UNDEFINED: 'IS_UNDEFINED';
export declare type IsUndefined = Readonly<{
    type: 'IS_UNDEFINED';
}>;
export declare const Undefineds: {
    notUndefined<P>(): ValidationRule<P | undefined, Readonly<{
        type: "IS_UNDEFINED";
    }>, P, []>;
    optional<P, E, A, M extends any[]>(validationRule: ValidationRule<P, E, A, M>): ValidationRule<P | undefined, E, A | undefined, M>;
};