Restrict return type further

Author: acdlite

packages/react-debug-tools/src/ReactDebugHooks.js

@@ -142,7 +142,7 @@ function useRef<T>(initialValue: T): {current: T} {
 }
 
 function useLayoutEffect(
-  create: () => mixed,
+  create: () => (() => void) | void,
   inputs: Array<mixed> | void | null,
 ): void {
   nextHook();
@@ -154,7 +154,7 @@ function useLayoutEffect(
 }
 
 function useEffect(
-  create: () => mixed,
+  create: () => (() => void) | void,
   inputs: Array<mixed> | void | null,
 ): void {
   nextHook();

packages/react-dom/src/server/ReactPartialRendererHooks.js

@@ -329,7 +329,7 @@ function useRef<T>(initialValue: T): {current: T} {
 }
 
 export function useLayoutEffect(
-  create: () => mixed,
+  create: () => (() => void) | void,
   inputs: Array<mixed> | void | null,
 ) {
   if (__DEV__) {

packages/react-reconciler/src/ReactFiberHooks.js

@@ -66,8 +66,8 @@ export type Hook = {
 
 type Effect = {
   tag: HookEffectTag,
-  create: () => mixed,
-  destroy: (() => mixed) | null,
+  create: () => (() => void) | void,
+  destroy: (() => void) | null,
   deps: Array<mixed> | null,
   next: Effect,
 };
@@ -608,7 +608,7 @@ export function useRef<T>(initialValue: T): {current: T} {
 }
 
 export function useLayoutEffect(
-  create: () => mixed,
+  create: () => (() => void) | void,
   deps: Array<mixed> | void | null,
 ): void {
   if (__DEV__) {
@@ -618,7 +618,7 @@ export function useLayoutEffect(
 }
 
 export function useEffect(
-  create: () => mixed,
+  create: () => (() => void) | void,
   deps: Array<mixed> | void | null,
 ): void {
   if (__DEV__) {
@@ -679,7 +679,9 @@ export function useImperativeHandle<T>(
       const refCallback = ref;
       const inst = create();
       refCallback(inst);
-      return () => refCallback(null);
+      return () => {
+        refCallback(null);
+      };
     } else if (ref !== null && ref !== undefined) {
       const refObject = ref;
       const inst = create();

packages/react/src/ReactHooks.js

@@ -71,15 +71,15 @@ export function useRef<T>(initialValue: T): {current: T} {
 }
 
 export function useEffect(
-  create: () => mixed,
+  create: () => (() => void) | void,
   inputs: Array<mixed> | void | null,
 ) {
   const dispatcher = resolveDispatcher();
   return dispatcher.useEffect(create, inputs);
 }
 
 export function useLayoutEffect(
-  create: () => mixed,
+  create: () => (() => void) | void,
   inputs: Array<mixed> | void | null,
 ) {
   const dispatcher = resolveDispatcher();