more type fixes

test/applyMiddleware.spec.ts

@@ -28,10 +28,10 @@ describe('applyMiddleware', () => {
   })
 
   it('wraps dispatch method with middleware once', () => {
-    function test(spyOnMethods: any) {
-      return (methods: any) => {
+    function test(spyOnMethods: any): Middleware {
+      return methods => {
         spyOnMethods(methods)
-        return (next: Dispatch) => (action: Action) => next(action)
+        return next => action => next(action)
       }
     }
 
@@ -53,8 +53,8 @@ describe('applyMiddleware', () => {
   })
 
   it('passes recursive dispatches through the middleware chain', () => {
-    function test(spyOnMethods: any) {
-      return () => (next: Dispatch) => (action: Action) => {
+    function test(spyOnMethods: any): Middleware {
+      return () => next => action => {
         spyOnMethods(action)
         return next(action)
       }
@@ -146,8 +146,7 @@ describe('applyMiddleware', () => {
     }
 
     function dummyMiddleware({ dispatch }: MiddlewareAPI) {
-      return (_next: Dispatch) => (action: Action) =>
-        dispatch(action, testCallArgs)
+      return (_next: unknown) => (action: any) => dispatch(action, testCallArgs)
     }
 
     const store = createStore(

test/helpers/middleware.ts

@@ -1,13 +1,9 @@
-import { MiddlewareAPI, Dispatch, AnyAction } from 'redux'
+import { Dispatch, Middleware } from 'redux'
 
-type ThunkAction<T extends any = any> = T extends AnyAction
-  ? AnyAction
-  : T extends Function
-  ? T
-  : never
-
-export function thunk({ dispatch, getState }: MiddlewareAPI) {
-  return (next: Dispatch) =>
-    <_>(action: ThunkAction) =>
-      typeof action === 'function' ? action(dispatch, getState) : next(action)
-}
+export const thunk: Middleware<{
+  <R>(thunk: (dispatch: Dispatch, getState: () => any) => R): R
+}> =
+  ({ dispatch, getState }) =>
+  next =>
+  action =>
+    typeof action === 'function' ? action(dispatch, getState) : next(action)