From 9598acd47702e2e8dee9a43d696d88b2730a2c6b Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 15 Jan 2018 15:31:43 -0800
Subject: [PATCH] Properly handle 'any' and 'never' as conditional check type

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

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 41717d4f0f7..6abe6ad04b0 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -8415,6 +8415,10 @@ namespace ts {
             if (checkType.flags & TypeFlags.Union) {
                 return getUnionType(map((<UnionType>checkType).types, t => getConditionalType(t, extendsType, mapper, trueType, falseType)));
             }
+            // Return union of trueType and falseType for any and never since they match anything
+            if (checkType.flags & (TypeFlags.Any | TypeFlags.Never)) {
+                return getUnionType([instantiateType(trueType, mapper), instantiateType(falseType, mapper)]);
+            }
             // Return trueType for a definitely true extends check
             if (isTypeAssignableTo(checkType, extendsType)) {
                 return instantiateType(trueType, mapper);