import { Logger } from './log';
declare global {
    interface Promise<T> {
        /**
         * Logging the value between the promise chain.
         *
         * @return {Promise<T>}
         * A value which pass through within a promise
         *
         * @example
         * Promise.resolve(3)
         *   .log()
         *   .then(doSomething)
         * // return 3 in a promise, after logging
         */
        log(): Promise<T>;
        /**
         * Logging the value between the promise chain.
         *
         * @param {Function} [logger=console.log]
         * - a logger; default would be console.log
         *
         * @return {Promise<T>}
         * A value which pass through within a promise
         *
         * @example
         * Promise.resolve(true)
         *   .log(console.warn)
         *   .then(doSomething)
         * // return true in a promise, after logging
         */
        log(logger?: Logger): Promise<T>;
        /**
        * Logging the value between the promise chain.
        *
        * @param {Function} [logger=console.log]
        * - a logger; default would be console.log
        *
        * @param {...any[]} args[]
        * - additional arguments for logger
        *
        * @return {Promise<T>}
        * A value which pass through within a promise
        *
        * @example
        * Promise.resolve('a')
        *   .log(console.log, "my value:")
        *   .then(doSomething)
        * // return 'a' in a promise, after logging
        */
        log(logger?: Logger, ...args: any[]): Promise<T>;
    }
}