[PR] [react] useEffect callback returns nothing, or a function that returns nothing

Summary:
to match the changes in facebook/react#14119.

ran `make` and the tests, seemed ok?
Pull Request resolved: #7430

Reviewed By: bvaughn

Differential Revision: D13927998

Pulled By: jbrown215

fbshipit-source-id: 1bc0a6673d5f1bc9a58baa7ec30fdd6aace34813

Author: Sunil Pai

lib/react.js

@@ -305,7 +305,7 @@ declare module react {
     component: () => Promise<{ default: React$ComponentType<P> }>,
   ): React$ComponentType<P>;
 
-  declare type MaybeCleanUpFn = ?(() => mixed);
+  declare type MaybeCleanUpFn = void | (() => void);
 
   declare export function useContext<T>(
     context: React$Context<T>,

tests/react/react.exp

@@ -3423,6 +3423,42 @@ References:
                      ^^^^^^^^^^^^^^^^^^^^^ [2]
 
 
+Error ------------------------------------------------------------------------------------------ useEffect_hook.js:24:19
+
+Cannot call `React.useEffect` with async function bound to `create` because a callable signature is missing in
+`Promise` [1] but exists in function type [2] in the return value.
+
+   useEffect_hook.js:24:19
+    24|   React.useEffect(async () => {}) // Error: promise is incompatible with function return type
+                          ^^^^^^^^^^^^^^
+
+References:
+   useEffect_hook.js:24:30
+    24|   React.useEffect(async () => {}) // Error: promise is incompatible with function return type
+                                     ^ [1]
+   <BUILTINS>/react.js:308:41
+   308|   declare type MaybeCleanUpFn = void | (() => void);
+                                                ^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------ useEffect_hook.js:25:19
+
+Cannot call `React.useEffect` with function bound to `create` because number [1] is incompatible with undefined [2] in
+the return value of the return value.
+
+   useEffect_hook.js:25:19
+    25|   React.useEffect(() => () => 123) // Error: cleanup function should not return a value
+                          ^^^^^^^^^^^^^^^
+
+References:
+   useEffect_hook.js:25:31
+    25|   React.useEffect(() => () => 123) // Error: cleanup function should not return a value
+                                      ^^^ [1]
+   <BUILTINS>/react.js:308:47
+   308|   declare type MaybeCleanUpFn = void | (() => void);
+                                                      ^^^^ [2]
+
+
 Error ---------------------------------------------------------------------------------- useImperativeHandle_hook.js:6:3
 
 Cannot call `React.useImperativeHandle` because function [1] requires another argument.
@@ -3526,6 +3562,42 @@ References:
                      ^^^^^^^^^^^^^^^^^^^^^ [2]
 
 
+Error ------------------------------------------------------------------------------------ useLayoutEffect_hook.js:24:25
+
+Cannot call `React.useLayoutEffect` with async function bound to `create` because a callable signature is missing in
+`Promise` [1] but exists in function type [2] in the return value.
+
+   useLayoutEffect_hook.js:24:25
+    24|   React.useLayoutEffect(async () => {}) // Error: promise is incompatible with function return type
+                                ^^^^^^^^^^^^^^
+
+References:
+   useLayoutEffect_hook.js:24:36
+    24|   React.useLayoutEffect(async () => {}) // Error: promise is incompatible with function return type
+                                           ^ [1]
+   <BUILTINS>/react.js:308:41
+   308|   declare type MaybeCleanUpFn = void | (() => void);
+                                                ^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------ useLayoutEffect_hook.js:25:25
+
+Cannot call `React.useLayoutEffect` with function bound to `create` because number [1] is incompatible with
+undefined [2] in the return value of the return value.
+
+   useLayoutEffect_hook.js:25:25
+    25|   React.useLayoutEffect(() => () => 123) // Error: cleanup function should not return a value
+                                ^^^^^^^^^^^^^^^
+
+References:
+   useLayoutEffect_hook.js:25:37
+    25|   React.useLayoutEffect(() => () => 123) // Error: cleanup function should not return a value
+                                            ^^^ [1]
+   <BUILTINS>/react.js:308:47
+   308|   declare type MaybeCleanUpFn = void | (() => void);
+                                                      ^^^^ [2]
+
+
 Error ---------------------------------------------------------------------------------------------- useMemo_hook.js:6:3
 
 Cannot call `React.useMemo` because function [1] requires another argument.
@@ -4140,7 +4212,7 @@ References:
 
 
 
-Found 242 errors
+Found 246 errors
 
 Only showing the most relevant union/intersection branches.
 To see all branches, re-run Flow with --show-all-branches

tests/react/useEffect_hook.js

@@ -21,4 +21,6 @@ import React from 'react';
 {
   React.useEffect(1); // Error: number is incompatible with function type
   React.useEffect(() => {}, 1); // Error: number is incompatible with function react-only array
+  React.useEffect(async () => {}) // Error: promise is incompatible with function return type
+  React.useEffect(() => () => 123) // Error: cleanup function should not return a value
 }

tests/react/useLayoutEffect_hook.js

@@ -21,4 +21,6 @@ import React from 'react';
 {
   React.useLayoutEffect(1); // Error: number is incompatible with function type
   React.useLayoutEffect(() => {}, 1); // Error: number is incompatible with function react-only array
+  React.useLayoutEffect(async () => {}) // Error: promise is incompatible with function return type
+  React.useLayoutEffect(() => () => 123) // Error: cleanup function should not return a value
 }