Fix #212 #214 (#215)

* fix(createClice) fix a bug with TS 3.6 (see #212)

* fix(types) fix feature detection for TS<3.5, make IsEmptyObj more accurate

* chore: any-cast NonInferred type

* Formatting

Author: phryneas

src/createSlice.ts

@@ -73,7 +73,7 @@ export interface CreateSliceOptions<
    * functions. These reducers should have existing action types used
    * as the keys, and action creators will _not_ be generated.
    */
-  extraReducers?: CaseReducers<State, any>
+  extraReducers?: CaseReducers<NoInfer<State>, any>
 }
 
 type PayloadActions<Types extends keyof any = string> = Record<
@@ -230,7 +230,7 @@ export function createSlice<
   })
 
   const finalCaseReducers = { ...extraReducers, ...sliceCaseReducersByType }
-  const reducer = createReducer(initialState, finalCaseReducers)
+  const reducer = createReducer(initialState, finalCaseReducers as any)
 
   return {
     name,

src/tsHelpers.ts

@@ -13,8 +13,8 @@ export type IsUnknown<T, True, False = never> = unknown extends T
   : False
 
 export type IsEmptyObj<T, True, False = never> = T extends any
-  ? {} extends T
-    ? IsUnknown<T, False, IsAny<T, False, True>>
+  ? keyof T extends never
+    ? IsUnknown<T, False, True>
     : False
   : never
 
@@ -24,11 +24,11 @@ export type IsEmptyObj<T, True, False = never> = T extends any
  * * versions below 3.5 will return `{}` for unresolvable interference
  * * versions above will return `unknown`
  * */
-export type AtLeastTS35<True, False> = IsUnknown<
+export type AtLeastTS35<True, False> = [True, False][IsUnknown<
   ReturnType<<T>() => T>,
-  True,
-  False
->
+  0,
+  1
+>]
 
 export type IsUnknownOrNonInferrable<T, True, False> = AtLeastTS35<
   IsUnknown<T, True, False>,

type-tests/files/createAction.typetest.ts

@@ -172,3 +172,16 @@ function expectType<T>(p: T): T {
   // typings:expect-error
   expectType<string>(strLenMetaAction('test').meta)
 }
+
+/*
+ * regression test for https://github.com/reduxjs/redux-starter-kit/issues/214
+ */
+{
+  const action = createAction<{ input?: string }>('ACTION')
+  const t: string|undefined = action({input: ""}).payload.input;
+  
+  // typings:expect-error
+  const u: number = action({input: ""}).payload.input;
+  // typings:expect-error
+  const v: number = action({input: 3}).payload.input;
+}