import { RefinedSource } from '../source-elements/refined-source';
import { SourceQueryElement } from './source-query-element';
import type { SourceDesc } from '../types/source-desc';
import type { IncludeItem } from './include-item';
/**
 * An element which represents adding source extensions to a
 * query or source using the `extend` operator. This element
 * cannot be treated as a query.
 *
 * e.g. `flights extend { rename: carrier2 is carrier }`
 */
export declare class SQExtend extends SourceQueryElement {
    readonly sqSrc: SourceQueryElement;
    readonly extend: SourceDesc;
    readonly includeList: IncludeItem[] | undefined;
    elementType: string;
    asSource?: RefinedSource;
    constructor(sqSrc: SourceQueryElement, extend: SourceDesc, includeList: IncludeItem[] | undefined);
    getSource(): RefinedSource | undefined;
    isSource(): boolean;
}