Type ReactRef

Nothing out of the ordinary on this one.

src/isomorphic/classic/element/ReactElementType.js

@@ -23,7 +23,7 @@ export type ReactElement = {
   $$typeof: any,
   type: any,
   key: any,
-  ref: any,
+  ref: string | (elem: ?HTMLElement) => void,
   props: any,
   _owner: ReactInstance,
 

src/renderers/shared/stack/reconciler/ReactRef.js

@@ -7,12 +7,16 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule ReactRef
+ * @flow
  */
 
 'use strict';
 
 var ReactOwner = require('ReactOwner');
 
+import type { ReactInstance } from 'ReactInstanceType';
+import type { ReactElement } from 'ReactElementType';
+
 var ReactRef = {};
 
 function attachRef(ref, component, owner) {
@@ -33,7 +37,10 @@ function detachRef(ref, component, owner) {
   }
 }
 
-ReactRef.attachRefs = function(instance, element) {
+ReactRef.attachRefs = function(
+  instance: ReactInstance,
+  element: ReactElement,
+): void {
   if (element === null || element === false) {
     return;
   }
@@ -43,7 +50,10 @@ ReactRef.attachRefs = function(instance, element) {
   }
 };
 
-ReactRef.shouldUpdateRefs = function(prevElement, nextElement) {
+ReactRef.shouldUpdateRefs = function(
+  prevElement: ?ReactElement,
+  nextElement: ?ReactElement,
+): bool {
   // If either the owner or a `ref` has changed, make sure the newest owner
   // has stored a reference to `this`, and the previous owner (if different)
   // has forgotten the reference to `this`. We use the element instead
@@ -56,20 +66,21 @@ ReactRef.shouldUpdateRefs = function(prevElement, nextElement) {
   // is made. It probably belongs where the key checking and
   // instantiateReactComponent is done.
 
-  var prevEmpty = prevElement === null || prevElement === false;
-  var nextEmpty = nextElement === null || nextElement === false;
-
   return (
     // This has a few false positives w/r/t empty components.
-    prevEmpty || nextEmpty ||
+    prevElement == null || prevElement === false || // prevEmpty
+    nextElement == null || nextElement === false || // nextEmpty
     nextElement.ref !== prevElement.ref ||
     // If owner changes but we have an unchanged function ref, don't update refs
     (typeof nextElement.ref === 'string' &&
      nextElement._owner !== prevElement._owner)
   );
 };
 
-ReactRef.detachRefs = function(instance, element) {
+ReactRef.detachRefs = function(
+  instance: ReactInstance,
+  element: ReactElement,
+): void {
   if (element === null || element === false) {
     return;
   }