From 6911acf80b712051db3833162eb68c3d3f79d13c Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Thu, 2 Nov 2017 14:28:46 -0700
Subject: [PATCH] Remove freshness from literal types in intersections

---
 src/compiler/checker.ts | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 09354d957a3..7c8386e5580 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7589,11 +7589,11 @@ namespace ts {
             }
         }
 
-        // Add the given types to the given type set. Order is preserved, duplicates are removed,
-        // and nested types of the given kind are flattened into the set.
+        // Add the given types to the given type set. Order is preserved, freshness is removed from literal
+        // types, duplicates are removed, and nested types of the given kind are flattened into the set.
         function addTypesToIntersection(typeSet: TypeSet, types: Type[]) {
             for (const type of types) {
-                addTypeToIntersection(typeSet, type);
+                addTypeToIntersection(typeSet, getRegularTypeOfLiteralType(type));
             }
         }