import { ServiceIdentifier } from './interfaces';
declare const defaultUndefinedValue: unique symbol;
/**
 * > NOTE: does not support Changing dependencies without `@inject`.
 */
declare class Optional {
    identifier: ServiceIdentifier<any>;
    constructor(identifier: ServiceIdentifier<any>);
    get key(): symbol;
}
export { Optional, defaultUndefinedValue };
//# sourceMappingURL=optional.d.ts.map