Avoid AnyAction in return type, clarify docs

README.md

@@ -206,7 +206,7 @@ composing reducers for which initial state is unnecessary.
 Note that since the type of the state cannot be inferred from the initial state,
 it must be provided as a type parameter:
 
-```javascript
+```ts
 const reducer = reducerWithoutInitialState<State>()
     .case(setName, setNameHandler)
     .case(addBalance, addBalanceHandler)
@@ -394,7 +394,8 @@ There are two reasons you may want to do this:
     separate NPM packages, you may run into type errors since the exported
     reducer has type `ReducerBuilder`, which the consuming package does not
     recognize unless it also depends on `typescript-fsa-reducers`. This is
-    avoided by returning a plain function instead.
+    avoided by calling `.build()`, whose return type is a plain function
+    instead.
 
 Example usage:
 

src/index.ts

@@ -70,12 +70,13 @@ export interface ReducerBuilder<InS, OutS = InS, PassedS = InS | undefined> {
         ) => ReducerBuilder<InS, OutS, PassedS>,
     ): ReducerBuilder<InS, OutS, PassedS>;
 
-    // Intentionally avoid AnyAction in return type so packages can export reducers
-    // created using .default() or .build() without requiring a dependency on typescript-fsa.
+    // Intentionally avoid AnyAction in return type so packages can export
+    // reducers created using .default() or .build() without consumers requiring
+    // a dependency on typescript-fsa.
     default(
         defaultHandler: Handler<InS, OutS, AnyAction>,
-    ): (state: PassedS, action: AnyAction) => OutS;
-    build(): (state: PassedS, action: AnyAction) => OutS;
+    ): (state: PassedS, action: { type: any }) => OutS;
+    build(): (state: PassedS, action: { type: any }) => OutS;
     (state: PassedS, action: AnyAction): OutS;
 }