From 3ee89f5ead985bf85b54f6cbc9bcb1d4fcbc5c3c Mon Sep 17 00:00:00 2001
From: Johannes Rieken <johannes.rieken@gmail.com>
Date: Mon, 4 Sep 2017 16:52:54 +0200
Subject: [PATCH] double cancel dummy cancellation token

---
 src/vs/base/common/cancellation.ts | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/vs/base/common/cancellation.ts b/src/vs/base/common/cancellation.ts
index cfd7feae295..b05c8880c54 100644
--- a/src/vs/base/common/cancellation.ts
+++ b/src/vs/base/common/cancellation.ts
@@ -84,8 +84,10 @@ export class CancellationTokenSource {
 			// cancelled token when cancellation happens
 			// before someone asks for the token
 			this._token = CancellationToken.Cancelled;
-		} else {
-			(<MutableToken>this._token).cancel();
+
+		} else if (this._token instanceof MutableToken) {
+			// actually cancel
+			this._token.cancel();
 		}
 	}