import type { AsyncTransformFn } from '../../internal/function.js';
import { type Option } from './option.js';
/**
 *  Maps a `Option<T>` to `Option<U>` by applying a _transformer_ function
 *  to an contained `Some(T)` value, leaving an `None` value untouched.
 *
 *  This function can be used to compose the results of two functions.
 */
export declare function mapAsyncForOption<T, U>(input: Option<T>, transformer: AsyncTransformFn<T, U>): Promise<Option<U>>;