I was about to open an issue for this, but I see others are already having difficulties integrating this package into their TS projects. I had to copy the source code into my project and apply proper types.

Would it be too crazy to add "redux" as a dependency? I bet almost everyone who uses this is also using redux anyways.

The other more conservative approach is to copy the needed types straight from redux.
It's just 3: Reducer, Action, AnyAction

Let me know your thoughts. I'd be happy to make a pull request.

@OleksiiKuchma-Wix I tested your provided example code using my modifications and at the very least, I can confirm the types are accepted / there are no lint errors.

@OleksiiKuchma-Wix I have another version of this that may be slightly more future proof here: #38 Not sure how to best specify the dependency though

Using the redux reducer definition as suggested in #38, I find that passing

• more than one reducer, or
• an initial state and one or more reducers

to reduceReducers still gives type errors.

So I tried to re-type reduceReducers to be like combineReducers in redux:

import { Action, AnyAction, Reducer } from 'redux';

export default function reduceReducers<S, A extends Action = AnyAction>(
  initialState: S | null,
  ...reducers: Reducer<S, A>[]
): Reducer<S, A>;
export default function reduceReducers<S, A extends Action = AnyAction>(
  ...reducers: Reducer<S, A>[]
): Reducer<S, A>;

And that seems to have solved the type errors.