From aab3004482970776beccc2de86c93e99b83fe93b Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Sat, 8 Jun 2019 11:23:23 -0700
Subject: [PATCH] Eagerly reduce empty intersections to 'never'

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

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ff2360d57a..658eda5634 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9956,6 +9956,9 @@ namespace ts {
                 }
                 else {
                     result = createIntersectionType(typeSet, aliasSymbol, aliasTypeArguments);
+                    if (isEmptyIntersectionType(<IntersectionType>result)) {
+                        result = neverType;
+                    }
                 }
                 intersectionTypes.set(id, result);
             }