import React from "react";
type RefCallback<T> = (instance: T | null) => void;
type Empty = null | undefined;
type InputRef<I> = React.Ref<I> | Empty;
type Result<I> = RefCallback<I> | null;
/**
 * Merges refs into a single memoized callback ref or `null`.
 * This makes sure multiple refs are updated together and have the same value.
 *
 * This function accepts up to four refs. If you need to merge more, or have an unspecified number of refs to merge,
 * use `useMergeRefsN` instead.
 */
export declare function useMergeRefs<I>(a: InputRef<I>, b: InputRef<I>): Result<I>;
export declare function useMergeRefs<I>(a: InputRef<I>, b: InputRef<I>, c: InputRef<I>): Result<I>;
export declare function useMergeRefs<I>(a: InputRef<I>, b: InputRef<I>, c: InputRef<I>, d: InputRef<I>): Result<I>;
/**
 * Merges an array of refs into a single memoized callback ref or `null`.
 *
 * If you need to merge a fixed number (up to four) of refs, use `useMergeRefs` instead for better performance.
 */
export declare function useMergeRefsN<I>(refs: InputRef<I>[]): Result<I>;
export {};