From 67491414f1d343856c0fa8b032bd64b92566f3a5 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 18 Dec 2018 11:50:29 -0800
Subject: [PATCH] Handle intersection types in getWidenedType

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

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a5f1515b94a..c751c37c6d5 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13597,6 +13597,9 @@ namespace ts {
                     // union includes empty object types (e.g. reducing {} | string to just {}).
                     return getUnionType(widenedTypes, some(widenedTypes, isEmptyObjectType) ? UnionReduction.Subtype : UnionReduction.Literal);
                 }
+                if (type.flags & TypeFlags.Intersection) {
+                    return getIntersectionType(sameMap((<IntersectionType>type).types, getWidenedType));
+                }
                 if (isArrayType(type) || isTupleType(type)) {
                     return createTypeReference((<TypeReference>type).target, sameMap((<TypeReference>type).typeArguments, getWidenedType));
                 }