From e02dcf37447e2c4053920c1662b3216c90067be6 Mon Sep 17 00:00:00 2001
From: Nobuhiro Nakamura <lefb766@live.jp>
Date: Tue, 21 Mar 2017 02:40:25 +0900
Subject: [PATCH] Ensure createTupleType([]) to return singleton

---
 src/compiler/checker.ts | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 8f6fbed492372..661c470927366 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6210,7 +6210,13 @@ namespace ts {
             return tupleTypes[arity] || (tupleTypes[arity] = createTupleTypeOfArity(arity));
         }
 
-        function createTupleType(elementTypes: Type[]) {
+        function createTupleType(elementTypes: Type[]): TypeReference {
+            // We have to ensure that we get same instance for empty tuple type,
+            // because we use === in isTupleLikeType(type).
+            if (!elementTypes.length && emptyTupleType) {
+                return emptyTupleType;
+            }
+
             return createTypeReference(getTupleTypeOfArity(elementTypes.length), elementTypes);
         }