import type { AsyncTransformFn } from '../internal/function.js';
import { type Undefinable, type NotUndefined } from './undefinable.js';
/**
 *  Return the result of _transformer_ with using _input_ as an argument for it if _input_ is not `undefined`,
 *  Otherwise, return `undefined`.
 *
 *  * `U` must not be `Undefinable<*>`.
 *      * If you'd like return `Undefinable<*>` as `U`, use `andThen()`.
 *      * If the result of _transformer_ is `undefined`, this throw an `Error`.
 */
export declare function mapAsyncForUndefinable<T, U>(input: Undefinable<T>, transformer: AsyncTransformFn<T, NotUndefined<U>>): Promise<Undefinable<U>>;