From 98b6a5ad11f3ac8d0cec8c6358468b08079dbf90 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 15 Feb 2016 09:23:40 -0800
Subject: [PATCH] Make undefined and null assignable to each other

---
 src/compiler/checker.ts | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4667ff64d95..2de8c86e5fd 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -5415,8 +5415,7 @@ namespace ts {
                 }
 
                 if (isTypeAny(target)) return Ternary.True;
-                if (source === undefinedType) return Ternary.True;
-                if (source === nullType && target !== undefinedType) return Ternary.True;
+                if (source.flags & TypeFlags.Undefined) return Ternary.True;
                 if (source.flags & TypeFlags.Enum && target === numberType) return Ternary.True;
                 if (source.flags & TypeFlags.Enum && target.flags & TypeFlags.Enum) {
                     if (result = enumRelatedTo(source, target)) {