From 1b07fbb2228e00c4dbfb1250333ab5c963707875 Mon Sep 17 00:00:00 2001
From: Herrington Darkholme <nonamesheep1@gmail.com>
Date: Thu, 21 Jul 2016 10:01:12 +0800
Subject: [PATCH] Fix #9843. IScriptSnapshot can return undefined

---
 src/services/services.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/services/services.ts b/src/services/services.ts
index 226d18f77dc..3124c78bd15 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -94,7 +94,7 @@ namespace ts {
          * change range cannot be determined.  However, in that case, incremental parsing will
          * not happen and the entire document will be re - parsed.
          */
-        getChangeRange(oldSnapshot: IScriptSnapshot): TextChangeRange;
+        getChangeRange(oldSnapshot: IScriptSnapshot): TextChangeRange | undefined;
 
         /** Releases all resources held by this script snapshot */
         dispose?(): void;