fix(devtools): improve type inference for Devtools initializer (#3511)

* fix(devtools): improve type inference for Devtools initializer

* fix(devtools): enhance type inference for Devtools initializer

* test(types): add devtools inference regression for #3510

* Rename options parameter to devtoolsOptions

* test(types): fix lint in devtools #3510 regression case

* test(types): simplify lint-safe ts-expect-error expression

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Daishi Kato <dai-shi@users.noreply.github.com>

Author: 3 people

src/middleware/devtools.ts

@@ -96,7 +96,7 @@ type Devtools = <
 >(
   initializer: StateCreator<T, [...Mps, ['zustand/devtools', never]], Mcs, U>,
   devtoolsOptions?: DevtoolsOptions,
-) => StateCreator<T, Mps, [['zustand/devtools', never], ...Mcs]>
+) => StateCreator<T, Mps, [['zustand/devtools', never], ...Mcs], U>
 
 type DevtoolsImpl = <T>(
   storeInitializer: StateCreator<T, [], []>,

tests/middlewareTypes.test.tsx

@@ -198,6 +198,28 @@ describe('counter state spec (single middleware)', () => {
     expect(useStoreD).toBeDefined()
   })
 
+  it('devtools #3510', () => {
+    type MyState = {
+      count: number
+      inc: () => void
+    }
+
+    const useBoundStore = create<MyState>()(
+      devtools((set, get) => ({
+        count: 0,
+        inc: () => {
+          set({ count: get().count + 1 }, false, 'inc')
+          // @ts-expect-error `get` should be inferred as `MyState`.
+          void get().foo
+          // @ts-expect-error `set` should enforce `count` as number.
+          set({ count: '1' })
+        },
+      })),
+    )
+
+    expect(useBoundStore).toBeDefined()
+  })
+
   it('subscribeWithSelector', () => {
     const useBoundStore = create<CounterState>()(
       subscribeWithSelector((set, get) => ({