import type { TransformFn } from '../internal/function.js';
import { type NotNull, type Nullable } from './nullable.js';
/**
 *  Return the result of _transformer_ with using _input_ as an argument for it if _input_ is not `null`.
 *  Otherwise, return _defaultValue_.
 *
 *  Basically, this operation is a combination `map()` and `unwrapOr()`.
 *
 *  * `U` must not be `Nullable<*>`.
 *      * If the result of _transformer_ is `null`, this throw an `Error`.
 *      * If the result of _defaultValue_ is `null`, this throw an `Error`.
 *  * If you'd like to accept `Nullable<*>` as `U`, use a combination `andThen()` and `or()`.
 */
export declare function mapOrForNullable<T, U>(input: Nullable<T>, defaultValue: NotNull<U>, transformer: TransformFn<T, NotNull<U>>): NotNull<U>;