From 14e23dbb5fd0d87c4387287c289e1b28e43d01c3 Mon Sep 17 00:00:00 2001
From: Andy Hanson <anhans@microsoft.com>
Date: Thu, 17 May 2018 09:15:47 -0700
Subject: [PATCH] Reduce map lookups

---
 src/compiler/checker.ts | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d0780406f1186..cec14246a04ba 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15366,10 +15366,11 @@ namespace ts {
                 links.resolvedSignatures = createMap();
             }
             const cacheKey = "" + getTypeId(valueType);
-            if (links.resolvedSignatures.get(cacheKey) && links.resolvedSignatures.get(cacheKey) !== resolvingSignaturesArray) {
-                signatures = links.resolvedSignatures.get(cacheKey);
+            const cachedResolved = links.resolvedSignatures.get(cacheKey);
+            if (cachedResolved && cachedResolved !== resolvingSignaturesArray) {
+                signatures = cachedResolved;
             }
-            else if (!links.resolvedSignatures.get(cacheKey)) {
+            else if (!cachedResolved) {
                 links.resolvedSignatures.set(cacheKey, resolvingSignaturesArray);
                 links.resolvedSignatures.set(cacheKey, signatures = instantiateJsxSignatures(context, signatures));
             }