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the-dr-lazy / deox

Functional Type-safe Flux Standard Utilities
https://deox.js.org
MIT License
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createReducer has wrong type for action arg. #96

Closed anilanar closed 5 years ago

anilanar commented 5 years ago

A reducer created with createReducer can be called with any action that has a (string?) type property. However, createReducer limits its action argument to those that are specifically handled by it.

Due to contravariance, (state: State, action: SpecificActions) => State does not extend (state: State, action: AnyAction) => State.

I know why createReducer is typed in such a way, but I wonder if some conditional type magic can allow us to encode handled action types + any action except those that are handled?

anilanar commented 5 years ago

Actually, even if we had the type I propose above, it wouldn't make the reducer extend from one that allows AnyAction argument; again due to contravariance. I guess all functions/types that work with deox reducers need to know about all action types too, inconvenient but necessary.