From fcdd5bd7826321be178b3f83ac5c17ef96065dfd Mon Sep 17 00:00:00 2001
From: Ben Lichtman <belichtm@microsoft.com>
Date: Thu, 10 Oct 2019 16:28:41 -0700
Subject: [PATCH] Add assertion when classification has unexpected length

---
 src/services/classifier.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/services/classifier.ts b/src/services/classifier.ts
index 443555c2bbd..22955d04cbc 100644
--- a/src/services/classifier.ts
+++ b/src/services/classifier.ts
@@ -499,8 +499,10 @@ namespace ts {
         return { spans, endOfLineState: EndOfLineState.None };
 
         function pushClassification(start: number, end: number, type: ClassificationType): void {
+            const length = end - start;
+            Debug.assert(length >= 0, `Classification had non-positive length of ${length}`);
             spans.push(start);
-            spans.push(end - start);
+            spans.push(length);
             spans.push(type);
         }
     }