import type { AnyFunction } from '../mod.ts';
/**
 * Returns function that calls original function only once.
 * All next calls will return result from first call.
 * @param fn Function.
 * @returns New wrapper function.
 */
export declare function once<T extends AnyFunction>(fn: T): (this: ThisParameterType<T>, ...args: Parameters<T>) => ReturnType<T>;