From ba5b9c0af3d66a89b403edd05d94bc0470d84fea Mon Sep 17 00:00:00 2001
From: Andrew Clark <acdlite@fb.com>
Date: Tue, 31 Jan 2017 11:35:10 -0800
Subject: [PATCH] Add invariant

Defensive coding to prevent an infinite loop.
---
 src/renderers/shared/fiber/ReactFiberTreeReflection.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/renderers/shared/fiber/ReactFiberTreeReflection.js b/src/renderers/shared/fiber/ReactFiberTreeReflection.js
index c27f7ee97b..c7a51b036d 100644
--- a/src/renderers/shared/fiber/ReactFiberTreeReflection.js
+++ b/src/renderers/shared/fiber/ReactFiberTreeReflection.js
@@ -168,17 +168,24 @@ function findCurrentFiberUsingSlowPath(fiber : Fiber) : Fiber | null {
         child = parentB.child;
         while (child) {
           if (child === a) {
+            didFindChild = true;
             a = parentB;
             b = parentA;
             break;
           }
           if (child === b) {
+            didFindChild = true;
             b = parentB;
             a = parentA;
             break;
           }
           child = child.sibling;
         }
+        invariant(
+          didFindChild,
+          'Child was not found in either parent set. This indicates a bug ' +
+          'related to the return pointer.'
+        );
       }
     }