[johnfn]

If you use discriminated union types - e.g. give them both a type key which is a unique string, then you don't need type guards as typescript is smart enough to understand that checking the type key does the type discrimination.

[vanwalj]

Sure, but you don't always have control over an external module or service, and it still something flow is better at

[johnfn]

Yeah, that's true. I don't know why you've been downvoted. You have a legitimate answer.