fix replaceReducer type

index.d.ts

@@ -326,7 +326,9 @@ export interface Store<S = any, A extends Action = AnyAction> {
    *
    * @param nextReducer The reducer for the store to use instead.
    */
-  replaceReducer(nextReducer: Reducer<S, A>): void
+  replaceReducer<NewState = S, NewActions extends A = A>(
+    nextReducer: Reducer<NewState, NewActions>
+  ): Store<NewState, NewActions>
 
   /**
    * Interoperability point for observable/reactive libraries.
@@ -667,3 +669,9 @@ export function compose<R>(
 ): (...args: any[]) => R
 
 export function compose<R>(...funcs: Function[]): (...args: any[]) => R
+
+export const __DO_NOT_USE__ActionTypes: {
+  INIT: string
+  REPLACE: string
+  PROBE_UNKNOWN_ACTION: () => string
+}

src/createStore.js

@@ -238,6 +238,7 @@ export default function createStore(reducer, preloadedState, enhancer) {
     // will receive the previous state. This effectively populates
     // the new state tree with any relevant data from the old one.
     dispatch({ type: ActionTypes.REPLACE })
+    return store
   }
 
   /**
@@ -284,11 +285,12 @@ export default function createStore(reducer, preloadedState, enhancer) {
   // the initial state tree.
   dispatch({ type: ActionTypes.INIT })
 
-  return {
+  const store = {
     dispatch,
     subscribe,
     getState,
     replaceReducer,
     [$$observable]: observable
   }
+  return store
 }