From 84d747a89cca17e70ff797754f34bc14807f8f03 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Fri, 1 Dec 2017 14:48:59 -0800
Subject: [PATCH] Simplify mappedTypeStack cache key

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

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index f0cb233cb7..c77f9dd652 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -11395,7 +11395,7 @@ namespace ts {
                         // such that direct inferences to T get priority over inferences to Partial<T>, for example.
                         const inference = getInferenceInfoForType((<IndexType>constraintType).type);
                         if (inference && !inference.isFixed) {
-                            const key = (source.symbol ? getSymbolId(source.symbol) : "no symbol") + "," + getSymbolId(target.symbol);
+                            const key = (source.symbol ? getSymbolId(source.symbol) + "," : "") + getSymbolId(target.symbol);
                             if (contains(mappedTypeStack, key)) {
                                 return;
                             }