From a62b4d38ed133633f244c0e61fc19f12f2764c8b Mon Sep 17 00:00:00 2001
From: David Robles <drobles@yahoo-inc.com>
Date: Sun, 18 Dec 2016 21:20:47 -0800
Subject: [PATCH] Assert when attempting to set a nil background / overlay
 layout element.

---
 AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.mm | 1 +
 AsyncDisplayKit/Layout/ASOverlayLayoutSpec.mm    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.mm b/AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.mm
index a94c051a6b..51709a3977 100644
--- a/AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.mm
+++ b/AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.mm
@@ -67,6 +67,7 @@ - (ASLayout *)calculateLayoutThatFits:(ASSizeRange)constrainedSize
 
 - (void)setBackground:(id<ASLayoutElement>)background
 {
+  ASDisplayNodeAssertNotNil(background, @"Background cannot be nil");
   [super setChild:background atIndex:kBackgroundChildIndex];
 }
 
diff --git a/AsyncDisplayKit/Layout/ASOverlayLayoutSpec.mm b/AsyncDisplayKit/Layout/ASOverlayLayoutSpec.mm
index 8084b22746..3a40123330 100644
--- a/AsyncDisplayKit/Layout/ASOverlayLayoutSpec.mm
+++ b/AsyncDisplayKit/Layout/ASOverlayLayoutSpec.mm
@@ -43,6 +43,7 @@ - (instancetype)initWithChild:(id<ASLayoutElement>)child overlay:(id<ASLayoutEle
 
 - (void)setOverlay:(id<ASLayoutElement>)overlay
 {
+  ASDisplayNodeAssertNotNil(overlay, @"Overlay cannot be nil");
   [super setChild:overlay atIndex:kOverlayChildIndex];
 }