The following code doesn’t work:

let observable: Observable<{ key: number }> = of({ key: 123 });
observable.pipe(
    distinctUntilChanged(undefined, v => v.key)
);

eventough there is an overload export function distinctUntilChanged<T, K>( comparator?: (previous: K, current: K) => boolean, keySelector: (value: T) => K = identity as (value: T) => K ): MonoTypeOperatorFunction<T>.

What’s the reason for it?