import type { FilterFn, TypePredicateFn } from '../internal/function.js';
import { type Nullable, type NotNull } from './nullable.js';
/**
 *  Returns `null` if the _input_ is `null`,
 *  otherwise calls _predicate_ with the _input_ `T` and returns:
 *
 *      * `T` if _predicate_ returns `true`.
 *      * `null` if _predicate_ returns `false`.
 */
export declare function filterForNullable<T>(input: Nullable<T>, predicate: FilterFn<T>): Nullable<T>;
/**
 *  Returns `null` if the _input_ is `null`,
 *  otherwise calls _predicate_ with the _input_ `T` and returns:
 *
 *      * The input value as `U` if _predicate_ returns `true` which means that _predicate_ says the input value is U.
 *      * `null` if _predicate_ returns `false`.
 *
 *  Please use {@link filterForNullable} generally if you don't have to narrow the type.
 */
export declare function filterWithEnsureTypeForNullable<T, U extends T>(input: Nullable<T>, predicate: TypePredicateFn<T, NotNull<U>>): Nullable<U>;