handleActions return Typing for functions not respected

[dannycochran]

It looks like functions in handleActions aren't properly propagating the Generic type passed in, for instance:

interface MyInterface {
  foo: number;
  bar: string;
}

const export default handleActions<MyInterface, {}>({
  [SOME_ACTION]: (state, payload) => ({
    notFoo: 'bar'
  });
});

The value return from the SOME_ACTION function should give a Typescript warning but it's not, unless you specifically type the return type in the reducer function. Looking at how handleActions is typed, though, I'm not sure why this is happening:

...
export function handleActions<State, Payload>(
    reducerMap: ReducerMap<State, Payload>,
    initialState: State
): Reducer<State, Payload>;
...
export interface ReducerMap<State, Payload> {
    [actionType: string]: Reducer<State, Payload> | ReducerNextThrow<State, Payload>;
}
...
export interface ReducerNextThrow<State, Payload> {
    next?(state: State, action: Action<Payload>): State;
    throw?(state: State, action: Action<Payload>): State;
}
...
export type Reducer<State, Payload> = (state: State, action: Action<Payload>) => State;

It seems like "MyInterface" should be properly propagated as the return type for reducer functions?