Custom operator affects prevoius operator.

[Totati]

Hi, I'm trying to make custom operators, but it messes up typings. What am I missing or doing wrong?
My operator looks like this:

export function isBlack(): OperatorFunction<Fruit | Fish, boolean> {
  return source => source.pipe(map(v => v.color === 'black'));
}

When i use it in a pipe, it messes up the previous tap's typing.
Stackblitz example

[raymonddavis]

The typing is incorrect on your custom operators.

export function isBlack(): OperatorFunction<Fruit | Fish, boolean> {
  return source => source.pipe(map(v => v.color === 'black'));
}

This implies that your operator will return Fruit | Fish.
What i think you want to do is this

export function isBlack<T extends Fruit | Fish>(): OperatorFunction<T, boolean> {
  return source => source.pipe(map(v => v.color === 'black'));
}

This allows Fruit | Fish to be passed in and whatever one is passed is also returned.

Your previous example will allow anything to be passed in and hard setting the return to a "new" type Fruit | Fish

Updated typing
Stackblitz example

[Totati]

Thank you, yes I wanted this :)