Added Flow type to keep hooks dispatchers in-sync (#14599)

* Added Flow type to keep hooks dispatchers in-sync

Author: bvaughn

Diff for: packages/react-debug-tools/src/ReactDebugHooks.js

@@ -10,6 +10,7 @@
 import type {ReactContext, ReactProviderType} from 'shared/ReactTypes';
 import type {Fiber} from 'react-reconciler/src/ReactFiber';
 import type {Hook} from 'react-reconciler/src/ReactFiberHooks';
+import typeof {Dispatcher as DispatcherType} from 'react-reconciler/src/ReactFiberDispatcher';
 
 import ErrorStackParser from 'error-stack-parser';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
@@ -209,7 +210,7 @@ function useMemo<T>(
   return value;
 }
 
-const Dispatcher = {
+const Dispatcher: DispatcherType = {
   readContext,
   useCallback,
   useContext,

Diff for: packages/react-dom/src/server/ReactPartialRendererHooks.js

@@ -7,6 +7,7 @@
  * @flow
  */
 
+import typeof {Dispatcher as DispatcherType} from 'react-reconciler/src/ReactFiberDispatcher';
 import type {ThreadID} from './ReactThreadIDAllocator';
 import type {ReactContext} from 'shared/ReactTypes';
 import areHookInputsEqual from 'shared/areHookInputsEqual';
@@ -326,27 +327,31 @@ function dispatchAction<A>(
   }
 }
 
-function noop(): void {}
-function identity(fn: Function): Function {
-  return fn;
+export function useCallback<T>(
+  callback: T,
+  inputs: Array<mixed> | void | null,
+): T {
+  // Callbacks are passed as they are in the server environment.
+  return callback;
 }
 
+function noop(): void {}
+
 export let currentThreadID: ThreadID = 0;
 
 export function setCurrentThreadID(threadID: ThreadID) {
   currentThreadID = threadID;
 }
 
-export const Dispatcher = {
+export const Dispatcher: DispatcherType = {
   readContext,
   useContext,
   useMemo,
   useReducer,
   useRef,
   useState,
   useLayoutEffect,
-  // Callbacks are passed as they are in the server environment.
-  useCallback: identity,
+  useCallback,
   // useImperativeHandle is not run in the server environment
   useImperativeHandle: noop,
   // Effects are not run in the server environment.