From 59b0095eba886d2db1833db673b6743634b3a4c4 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Sun, 27 Aug 2017 08:51:42 -0700
Subject: [PATCH] Clean up flags propagation for object literal types

---
 src/compiler/checker.ts | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 088cb4bb851..4c626b56483 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7834,7 +7834,9 @@ namespace ts {
                     members.set(leftProp.escapedName, getNonReadonlySymbol(leftProp));
                 }
             }
-            return createAnonymousType(undefined, members, emptyArray, emptyArray, stringIndexInfo, numberIndexInfo);
+            const result = createAnonymousType(undefined, members, emptyArray, emptyArray, stringIndexInfo, numberIndexInfo);
+            result.flags |= (left.flags | right.flags) & TypeFlags.PropagatingFlags;
+            return result;
         }
 
         function getNonReadonlySymbol(prop: Symbol) {
@@ -13534,7 +13536,6 @@ namespace ts {
             let propertiesTable = createSymbolTable();
             let propertiesArray: Symbol[] = [];
             let spread: Type = emptyObjectType;
-            let propagatedFlags: TypeFlags = 0;
 
             const contextualType = getApparentTypeOfContextualType(node);
             const contextualTypeHasPattern = contextualType && contextualType.pattern &&
@@ -13678,8 +13679,6 @@ namespace ts {
                     spread = getSpreadType(spread, createObjectLiteralType());
                 }
                 if (spread.flags & TypeFlags.Object) {
-                    // only set the symbol and flags if this is a (fresh) object type
-                    spread.flags |= propagatedFlags;
                     spread.flags |= TypeFlags.FreshLiteral;
                     (spread as ObjectType).objectFlags |= ObjectFlags.ObjectLiteral;
                     spread.symbol = node.symbol;
@@ -13702,9 +13701,6 @@ namespace ts {
                 if (inDestructuringPattern) {
                     result.pattern = node;
                 }
-                if (!(result.flags & TypeFlags.Nullable)) {
-                    propagatedFlags |= (result.flags & TypeFlags.PropagatingFlags);
-                }
                 return result;
             }
         }