From 5a85fca0cd9db17b95e80068f17467b0c7f04fe5 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Wed, 26 Jul 2017 15:19:17 -0700
Subject: [PATCH] Properly check mapped type constituents / Fix generic mapped
 type display

---
 src/compiler/checker.ts | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2ff45ee0b73..ec9867fa9b7 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2558,10 +2558,8 @@ namespace ts {
                 }
 
                 function createTypeNodeFromObjectType(type: ObjectType): TypeNode {
-                    if (type.objectFlags & ObjectFlags.Mapped) {
-                        if (getConstraintTypeFromMappedType(<MappedType>type).flags & (TypeFlags.TypeParameter | TypeFlags.Index)) {
-                            return createMappedTypeNodeFromType(<MappedType>type);
-                        }
+                    if (isGenericMappedType(type)) {
+                        return createMappedTypeNodeFromType(<MappedType>type);
                     }
 
                     const resolved = resolveStructuredTypeMembers(type);
@@ -3464,11 +3462,9 @@ namespace ts {
                 }
 
                 function writeLiteralType(type: ObjectType, flags: TypeFormatFlags) {
-                    if (type.objectFlags & ObjectFlags.Mapped) {
-                        if (getConstraintTypeFromMappedType(<MappedType>type).flags & (TypeFlags.TypeParameter | TypeFlags.Index)) {
-                            writeMappedType(<MappedType>type);
-                            return;
-                        }
+                    if (isGenericMappedType(type)) {
+                        writeMappedType(<MappedType>type);
+                        return;
                     }
 
                     const resolved = resolveStructuredTypeMembers(type);
@@ -18641,6 +18637,8 @@ namespace ts {
         }
 
         function checkIndexedAccessType(node: IndexedAccessTypeNode) {
+            checkSourceElement(node.objectType);
+            checkSourceElement(node.indexType);
             checkIndexedAccessIndexType(getTypeFromIndexedAccessTypeNode(node), node);
         }