Merge pull request #3524 from Microsoft/extendsNull

Support null in __extends helper

src/compiler/emitter.ts

@@ -21,8 +21,7 @@ namespace ts {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };`;
 
         // emit output for the __decorate helper function

tests/baselines/reference/ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js

@@ -24,8 +24,7 @@ module A {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A;
 (function (A) {

tests/baselines/reference/ExportClassWithInaccessibleTypeInTypeParameterConstraint.js

@@ -28,8 +28,7 @@ module A {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A;
 (function (A) {

tests/baselines/reference/accessOverriddenBaseClassMember1.js

@@ -19,8 +19,7 @@ class ColoredPoint extends Point {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Point = (function () {
     function Point(x, y) {

tests/baselines/reference/accessors_spec_section-4.5_inference.js

@@ -28,8 +28,7 @@ class LanguageSpec_section_4_5_inference {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/aliasUsageInAccessorsOfClass.js

@@ -38,8 +38,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsage1_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/aliasUsageInArray.js

@@ -32,8 +32,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInArray_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/aliasUsageInFunctionExpression.js

@@ -31,8 +31,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInFunctionExpression_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/aliasUsageInGenericFunction.js

@@ -35,8 +35,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInGenericFunction_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/aliasUsageInIndexerOfClass.js

@@ -37,8 +37,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInIndexerOfClass_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/aliasUsageInObjectLiteral.js

@@ -32,8 +32,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInObjectLiteral_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/aliasUsageInOrExpression.js

@@ -35,8 +35,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInOrExpression_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/aliasUsageInTypeArgumentOfExtendsClause.js

@@ -35,8 +35,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInTypeArgumentOfExtendsClause_backbone");
 var VisualizationModel = (function (_super) {
@@ -51,8 +50,7 @@ exports.VisualizationModel = VisualizationModel;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var moduleA = require("aliasUsageInTypeArgumentOfExtendsClause_moduleA");
 var C = (function () {

tests/baselines/reference/aliasUsageInVarAssignment.js

@@ -31,8 +31,7 @@ exports.Model = Model;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Backbone = require("aliasUsageInVarAssignment_backbone");
 var VisualizationModel = (function (_super) {

tests/baselines/reference/ambiguousOverloadResolution.js

@@ -12,8 +12,7 @@ var t: number = f(x, x); // Not an error
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/apparentTypeSubtyping.js

@@ -27,8 +27,7 @@ class Derived2<U extends String> extends Base2 { // error because of the prototy
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/apparentTypeSupertype.js

@@ -17,8 +17,7 @@ class Derived<U extends String> extends Base { // error
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/arrayAssignmentTest1.js

@@ -89,8 +89,7 @@ arr_any = i1; // should be an error - is
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C1 = (function () {
     function C1() {

tests/baselines/reference/arrayAssignmentTest2.js

@@ -63,8 +63,7 @@ arr_any = i1; // should be an error - is
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C1 = (function () {
     function C1() {

tests/baselines/reference/arrayBestCommonTypes.js

@@ -111,8 +111,7 @@ module NonEmptyTypes {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var EmptyTypes;
 (function (EmptyTypes) {

tests/baselines/reference/arrayLiteralTypeInference.js

@@ -55,8 +55,7 @@ var z3: { id: number }[] =
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Action = (function () {
     function Action() {

tests/baselines/reference/arrayLiterals.js

@@ -41,8 +41,7 @@ var context4: Base[] = [new Derived1(), new Derived1()];
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var arr1 = [[], [1], ['']];
 var arr2 = [[null], [1], ['']];

tests/baselines/reference/arrayLiteralsWithRecursiveGenerics.js

@@ -29,8 +29,7 @@ var as = [list, myDerivedList]; // List<number>[]
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var List = (function () {
     function List() {

tests/baselines/reference/arrowFunctionContexts.js

@@ -100,8 +100,7 @@ var asserted2: any;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 // Arrow function used in with statement
 with (window) {

tests/baselines/reference/assignmentCompatWithCallSignatures3.js

@@ -104,8 +104,7 @@ b18 = a18; // ok
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithCallSignatures4.js

@@ -103,8 +103,7 @@ module Errors {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Errors;
 (function (Errors) {

tests/baselines/reference/assignmentCompatWithCallSignatures5.js

@@ -70,8 +70,7 @@ b18 = a18; // ok
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithCallSignatures6.js

@@ -47,8 +47,7 @@ b16 = x.a16;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithConstructSignatures3.js

@@ -104,8 +104,7 @@ b18 = a18; // ok
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithConstructSignatures4.js

@@ -103,8 +103,7 @@ module Errors {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Errors;
 (function (Errors) {

tests/baselines/reference/assignmentCompatWithConstructSignatures5.js

@@ -70,8 +70,7 @@ b18 = a18; // ok
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithConstructSignatures6.js

@@ -47,8 +47,7 @@ b16 = x.a16;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithNumericIndexer.js

@@ -48,8 +48,7 @@ module Generics {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/assignmentCompatWithNumericIndexer3.js

@@ -45,8 +45,7 @@ module Generics {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/assignmentCompatWithObjectMembers4.js

@@ -96,8 +96,7 @@ module WithBase {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var OnlyDerived;
 (function (OnlyDerived) {

tests/baselines/reference/assignmentCompatWithObjectMembersOptionality.js

@@ -93,8 +93,7 @@ module SourceHasOptional {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithObjectMembersOptionality2.js

@@ -95,8 +95,7 @@ module SourceHasOptional {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/assignmentCompatWithStringIndexer.js

@@ -58,8 +58,7 @@ module Generics {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/assignmentLHSIsValue.js

@@ -74,8 +74,7 @@ foo() = value;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 // expected error for all the LHS of assignments
 var value;

tests/baselines/reference/autolift4.js

@@ -27,8 +27,7 @@ class Point3D extends Point {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Point = (function () {
     function Point(x, y) {

tests/baselines/reference/baseCheck.js

@@ -33,8 +33,7 @@ function f() {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function () {
     function C(x, y) {

tests/baselines/reference/baseIndexSignatureResolution.js

@@ -28,8 +28,7 @@ var z: Derived = b.foo();
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/baseTypeOrderChecking.js

@@ -40,8 +40,7 @@ class Class4<T> extends Class3<T>
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var someVariable;
 var Class1 = (function () {

tests/baselines/reference/baseTypeWrappingInstantiationChain.js

@@ -30,8 +30,7 @@ class Wrapper<T5> {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function (_super) {
     __extends(C, _super);

tests/baselines/reference/bases.js

@@ -24,8 +24,7 @@ new C().y;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var B = (function () {
     function B() {

tests/baselines/reference/bestCommonTypeOfConditionalExpressions.js

@@ -32,8 +32,7 @@ function foo5<T, U>(t: T, u: U): Object {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var a;
 var b;

tests/baselines/reference/bestCommonTypeOfConditionalExpressions2.js

@@ -30,8 +30,7 @@ function foo3<T extends U, U extends V, V>(t: T, u: U) {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/bestCommonTypeOfTuple2.js

@@ -26,8 +26,7 @@ var e51 = t5[2]; // {}
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function () {
     function C() {

tests/baselines/reference/callSignatureAssignabilityInInheritance2.js

@@ -74,8 +74,7 @@ interface I extends A {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/callSignatureAssignabilityInInheritance3.js

@@ -119,8 +119,7 @@ module Errors {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Errors;
 (function (Errors) {

tests/baselines/reference/callSignatureAssignabilityInInheritance4.js

@@ -54,8 +54,7 @@ interface I extends A {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/callSignatureAssignabilityInInheritance5.js

@@ -54,8 +54,7 @@ interface I extends B {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/callSignatureAssignabilityInInheritance6.js

@@ -57,8 +57,7 @@ interface I9<T> extends A {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/callWithSpread.js

@@ -54,8 +54,7 @@ class D extends C {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 function foo(x, y) {
     var z = [];

tests/baselines/reference/captureThisInSuperCall.js

@@ -12,8 +12,7 @@ class B extends A {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A(p) {

tests/baselines/reference/castingTuple.js

@@ -36,8 +36,7 @@ t4[2] = 10;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/chainedAssignment3.js

@@ -26,8 +26,7 @@ a = b = new A();
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js

@@ -23,8 +23,7 @@ class C extends B {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Chain = (function () {
     function Chain(value) {

tests/baselines/reference/checkForObjectTooStrict.js

@@ -35,8 +35,7 @@ class Baz extends Object {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Foo;
 (function (Foo) {

tests/baselines/reference/circularImportAlias.js

@@ -24,8 +24,7 @@ var c = new B.a.C();
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var B;
 (function (B) {

tests/baselines/reference/classConstructorParametersAccessibility.js

@@ -30,8 +30,7 @@ class Derived extends C3 {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C1 = (function () {
     function C1(x) {

tests/baselines/reference/classConstructorParametersAccessibility2.js

@@ -30,8 +30,7 @@ class Derived extends C3 {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C1 = (function () {
     function C1(x) {

tests/baselines/reference/classConstructorParametersAccessibility3.js

@@ -17,8 +17,7 @@ d.p;  // public, OK
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base(p) {

tests/baselines/reference/classDeclarationMergedInModuleWithContinuation.js

@@ -15,8 +15,7 @@ module M {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var M;
 (function (M) {

tests/baselines/reference/classDoesNotDependOnBaseTypes.js

@@ -16,8 +16,7 @@ class StringTreeCollection extends StringTreeCollectionBase { }
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var x;
 if (typeof x !== "string") {

tests/baselines/reference/classExtendingClass.js

@@ -35,8 +35,7 @@ var r8 = D2.other(1);
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function () {
     function C() {

tests/baselines/reference/classExtendingPrimitive.js

@@ -19,8 +19,7 @@ class C8 extends E { }
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function (_super) {
     __extends(C, _super);

tests/baselines/reference/classExtendingPrimitive2.js

@@ -9,8 +9,7 @@ class C5a extends null { }
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C4a = (function () {
     function C4a() {

tests/baselines/reference/classExtendingQualifiedName.js

@@ -11,8 +11,7 @@ module M {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var M;
 (function (M) {

tests/baselines/reference/classExtendingQualifiedName2.js

@@ -11,8 +11,7 @@ module M {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var M;
 (function (M) {

tests/baselines/reference/classExtendsClauseClassMergedWithModuleNotReferingConstructor.js

@@ -17,8 +17,7 @@ module Foo {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classExtendsClauseClassNotReferringConstructor.js

@@ -10,8 +10,7 @@ module Foo {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classExtendsEveryObjectType.js

@@ -20,8 +20,7 @@ class C6 extends []{ } // error
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function (_super) {
     __extends(C, _super);

tests/baselines/reference/classExtendsEveryObjectType2.js

@@ -7,8 +7,7 @@ class C6 extends []{ } // error
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C2 = (function (_super) {
     __extends(C2, _super);

tests/baselines/reference/classExtendsInterface.js

@@ -12,8 +12,7 @@ class B2<T> implements Comparable2<T> {}
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function (_super) {
     __extends(A, _super);

tests/baselines/reference/classExtendsItself.js

@@ -9,8 +9,7 @@ class E<T> extends E<string> { } // error
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function (_super) {
     __extends(C, _super);

tests/baselines/reference/classExtendsItselfIndirectly.js

@@ -15,8 +15,7 @@ class E2<T> extends D2<T> { baz: T; }
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function (_super) {
     __extends(C, _super);

tests/baselines/reference/classExtendsItselfIndirectly2.js

@@ -26,8 +26,7 @@ module O {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function (_super) {
     __extends(C, _super);

tests/baselines/reference/classExtendsItselfIndirectly3.js

@@ -22,8 +22,7 @@ class E2<T> extends D2<T> { baz: T; }
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function (_super) {
     __extends(C, _super);
@@ -36,8 +35,7 @@ var C = (function (_super) {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var D = (function (_super) {
     __extends(D, _super);
@@ -50,8 +48,7 @@ var D = (function (_super) {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var E = (function (_super) {
     __extends(E, _super);
@@ -64,8 +61,7 @@ var E = (function (_super) {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C2 = (function (_super) {
     __extends(C2, _super);
@@ -78,8 +74,7 @@ var C2 = (function (_super) {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var D2 = (function (_super) {
     __extends(D2, _super);
@@ -92,8 +87,7 @@ var D2 = (function (_super) {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var E2 = (function (_super) {
     __extends(E2, _super);

tests/baselines/reference/classExtendsMultipleBaseClasses.js

@@ -7,8 +7,7 @@ class C extends A,B { }
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classExtendsShadowedConstructorFunction.js

@@ -12,8 +12,7 @@ module M {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function () {
     function C() {

tests/baselines/reference/classExtendsValidConstructorFunction.js

@@ -9,8 +9,7 @@ class C extends foo { } // error, cannot extend it though
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 function foo() { }
 var x = new foo(); // can be used as a constructor function

tests/baselines/reference/classHeritageWithTrailingSeparator.js

@@ -7,8 +7,7 @@ class D extends C, {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function () {
     function C() {

tests/baselines/reference/classImplementsClass2.js

@@ -17,8 +17,7 @@ c2 = c;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classImplementsClass3.js

@@ -18,8 +18,7 @@ c2 = c;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classImplementsClass4.js

@@ -20,8 +20,7 @@ c2 = c;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classImplementsClass5.js

@@ -21,8 +21,7 @@ c2 = c;
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classImplementsClass6.js

@@ -25,8 +25,7 @@ c2.bar(); // should error
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classIndexer3.js

@@ -14,8 +14,7 @@ class D123 extends C123 {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C123 = (function () {
     function C123() {

tests/baselines/reference/classInheritence.js

@@ -6,8 +6,7 @@ class A extends A { }
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var B = (function (_super) {
     __extends(B, _super);

tests/baselines/reference/classIsSubtypeOfBaseType.js

@@ -19,8 +19,7 @@ class Derived2 extends Base<{ bar: string; }> {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base() {

tests/baselines/reference/classOrder2.js

@@ -23,8 +23,7 @@ a.foo();
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function (_super) {
     __extends(A, _super);

tests/baselines/reference/classOrderBug.js

@@ -19,8 +19,7 @@ class foo extends baz {}
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var bar = (function () {
     function bar() {

tests/baselines/reference/classSideInheritance1.js

@@ -19,8 +19,7 @@ C2.bar(); // valid
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A() {

tests/baselines/reference/classSideInheritance2.js

@@ -24,8 +24,7 @@ class TextBase implements IText {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var SubText = (function (_super) {
     __extends(SubText, _super);

tests/baselines/reference/classSideInheritance3.js

@@ -22,8 +22,7 @@ var r3: typeof A = C; // ok
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var A = (function () {
     function A(x) {

tests/baselines/reference/classUpdateTests.js

@@ -117,8 +117,7 @@ class R {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 //
 // test codegen for instance properties

tests/baselines/reference/classWithBaseClassButNoConstructor.js

@@ -44,8 +44,7 @@ var d6 = new D(1); // ok
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var Base = (function () {
     function Base(x) {

tests/baselines/reference/classWithConstructors.js

@@ -53,8 +53,7 @@ module Generics {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var NonGeneric;
 (function (NonGeneric) {

tests/baselines/reference/classWithProtectedProperty.js

@@ -32,8 +32,7 @@ class D extends C {
 var __extends = (this && this.__extends) || function (d, b) {
     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
     function __() { this.constructor = d; }
-    __.prototype = b.prototype;
-    d.prototype = new __();
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
 var C = (function () {
     function C() {