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Comment by maxfurman | Hacker News Reader

Wow. More impressive work by the Typescript team!

AFAICT this will have the most impact on folks using Typescript with Redux stores and similar dispatchers.I know I would have liked having this feature back when I was doing that work.

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FWIW, our standard recommended Redux usage patterns for the last couple years have specifically _not_ needed switch statements to determine how to handle an action, because our official Redux Toolkit package has a `createSlice` API that lets you define case reducers as simple functions in an object. `createSlice` then generates all the action types internally, generates corresponding action creator functions, and handles calling the right case reducer when that action is dispatched.

Additionally, RTK has been designed to work great with TypeScript. Typically all you need to declare is the type of the state for that slice, and the payload for each reducer's action, and everything else is inferred.

See our Redux docs tutorials for details:

https://redux.js.org/tutorials/essentials/part-2-app-structu...

https://redux.js.org/tutorials/fundamentals/part-8-modern-re...

https://redux.js.org/tutorials/typescript-quick-start

I believe this will also obviate a common recommendation to not destructure when using React Query: https://tkdodo.eu/blog/react-query-and-type-script#type-narr...

Thanks for sharing this. I literally ran into the same issue yesterday, and was wondering why TS can't understand that I am discriminating on the isSucces property.

I’ll definitely update that article once the new TS version is released :)

Note that this already worked fine by just operating on the field.

Like `if (action.kind === 'x')` / `switch (action.kind)`.

This "only" extends support to destructured discriminators.

Definitely nice to have, but of limited impact.

Definitely a help. It should make it easier to use with payloads in postMessage too.

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