Properly check mapped type constituents / Fix generic mapped type display

Author: ahejlsberg

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);
         }