/**
 * @license
 * Copyright 2017 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
export interface Resolver<R> {
    (value: R | Promise<R>): void;
}
export interface Rejecter {
    (reason?: Error): void;
}
export declare class Deferred<R = void> {
    promise: Promise<R>;
    resolve: Resolver<R>;
    reject: Rejecter;
    constructor();
}
/**
 * Takes an array of values and a function from a value to a Promise. The function is run on each
 * value sequentially, waiting for the previous promise to resolve before starting the next one.
 * The returned promise resolves once the function has been run on all values.
 */
export declare function sequence<T>(values: T[], fn: (value: T) => Promise<void>): Promise<void>;