From e52ed1a23a470db3465704b8bc3c36dcead1eb4e Mon Sep 17 00:00:00 2001
From: gcnew <gcnew@abv.bg>
Date: Thu, 20 Jul 2017 02:48:30 +0300
Subject: [PATCH] Check the return type of type guard functions

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

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 70827becffe..253a8708f3a 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -17996,6 +17996,8 @@ namespace ts {
                 return;
             }
 
+            checkSourceElement(node.type);
+
             const { parameterName } = node;
             if (isThisTypePredicate(typePredicate)) {
                 getTypeFromThisTypeNode(parameterName as ThisTypeNode);