declare type Modify<T, R> = Omit<T, keyof R> & R;
declare type Only<T, U> = {
    [P in keyof T]: T[P];
} & Omit<{
    [P in keyof U]?: never;
}, keyof T>;
declare type Either<T, U> = Only<T, U> | Only<U, T>;
export { Modify, Only, Either };