From 2ee2ffb8e7a4a648461dec9acd061b9173505f97 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Thu, 11 Apr 2019 16:14:21 -1000
Subject: [PATCH] Use object identity check instead of IsTypeIdenticalTo

---
 src/compiler/checker.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index e3fda9e6e42..51b018fc5bf 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -10210,7 +10210,7 @@ namespace ts {
 
         function getConditionalTypeWorker(root: ConditionalRoot, mapper: TypeMapper | undefined, checkType: Type, extendsType: Type, trueType: Type, falseType: Type) {
             // Simplifications for types of the form `T extends U ? T : never` and `T extends U ? never : T`.
-            if (falseType.flags & TypeFlags.Never && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
+            if (falseType.flags & TypeFlags.Never && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
                 if (checkType.flags & TypeFlags.Any || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return trueType;
                 }
@@ -10218,7 +10218,7 @@ namespace ts {
                     return neverType;
                 }
             }
-            else if (trueType.flags & TypeFlags.Never && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
+            else if (trueType.flags & TypeFlags.Never && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
                 if (!(checkType.flags & TypeFlags.Any) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return neverType;
                 }