import type { AsyncTransformFn } from '../internal/function.js';
import { type Nullable } from './nullable.js';
export type NullableAsyncTryTransformFn<in T, out U> = AsyncTransformFn<T, Nullable<U>>;
/**
 *  Returns `null` if the _input_ is `null`,
 *  otherwise calls _transformer_ with the value and returns the result.
 *
 *  XXX:
 *  Some languages call this operation flatmap.
 *  But we don't provide `flatMap()` as alias of this function.
 *  because it's too hard to undarstand that "flatMap" operation for `T | null`
 */
export declare function andThenAsyncForNullable<T, U>(input: Nullable<T>, transformer: NullableAsyncTryTransformFn<T, U>): Promise<Nullable<U>>;