/**
 * This is a 'hacky' way to handle components which may have props either controlled or uncontrolled.
 *
 * Avoid using it if at all possible - generally it's better to write a controlled inner component
 * and simply make an uncontrolled version which wraps it.
 *
 * * If controlled, we mirror the prop state and propagate changes upwards via {@link propOnChange}.
 * * If uncontrolled, it is effectively a simple {@link useState()}.
 *
 * *Note: if mirroring, both `prop` and `propOnChange` **must** be provided.*
 *
 * @param prop the prop to be mirrored
 * @param propOnChange the handler to propagate changes from below back upwards
 * @param defaultVal the default value, only used if we aren't mirroring
 */
export declare function useMirrorProp<T>(prop: T | undefined, propOnChange: ((newVal: T) => void) | undefined, defaultVal: T | (() => T)): [T, (newVal: T) => void];