address feedback

src/compiler/transformers/es2015.ts

@@ -3338,7 +3338,11 @@ namespace ts {
         priority: 0,
         text: `
             var __extends = (this && this.__extends) || function (d, b) {
-                Object.setPrototypeOf(d, b);
+                if (typeof Object.setPrototypeOf === "function") {
+                    Object.setPrototypeOf(d, b);
+                } else {
+                    d.__proto__ = b;
+                }
                 function __() { this.constructor = d; }
                 d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
             };`

tests/baselines/reference/ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js

@@ -22,7 +22,11 @@ module A {
 
 //// [ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/ExportClassWithInaccessibleTypeInTypeParameterConstraint.js

@@ -26,7 +26,11 @@ module A {
 
 //// [ExportClassWithInaccessibleTypeInTypeParameterConstraint.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/abstractClassInLocalScope.js

@@ -9,7 +9,11 @@
 
 //// [abstractClassInLocalScope.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/abstractClassInLocalScopeIsAbstract.js

@@ -9,7 +9,11 @@
 
 //// [abstractClassInLocalScopeIsAbstract.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/abstractProperty.js

@@ -23,7 +23,11 @@ class C extends B {
 
 //// [abstractProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/abstractPropertyNegative.js

@@ -45,7 +45,11 @@ abstract class AbstractAccessorMismatch {
 
 //// [abstractPropertyNegative.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/accessOverriddenBaseClassMember1.js

@@ -17,7 +17,11 @@ class ColoredPoint extends Point {
 
 //// [accessOverriddenBaseClassMember1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

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

@@ -26,7 +26,11 @@ class LanguageSpec_section_4_5_inference {
 
 //// [accessors_spec_section-4.5_inference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInAccessorsOfClass.js

@@ -38,7 +38,11 @@ exports.Model = Model;
 //// [aliasUsage1_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInArray.js

@@ -32,7 +32,11 @@ exports.Model = Model;
 //// [aliasUsageInArray_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInFunctionExpression.js

@@ -31,7 +31,11 @@ exports.Model = Model;
 //// [aliasUsageInFunctionExpression_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInGenericFunction.js

@@ -35,7 +35,11 @@ exports.Model = Model;
 //// [aliasUsageInGenericFunction_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInIndexerOfClass.js

@@ -37,7 +37,11 @@ exports.Model = Model;
 //// [aliasUsageInIndexerOfClass_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInObjectLiteral.js

@@ -32,7 +32,11 @@ exports.Model = Model;
 //// [aliasUsageInObjectLiteral_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInOrExpression.js

@@ -35,7 +35,11 @@ exports.Model = Model;
 //// [aliasUsageInOrExpression_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInTypeArgumentOfExtendsClause.js

@@ -35,7 +35,11 @@ exports.Model = Model;
 //// [aliasUsageInTypeArgumentOfExtendsClause_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -51,7 +55,11 @@ exports.VisualizationModel = VisualizationModel;
 //// [aliasUsageInTypeArgumentOfExtendsClause_main.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/aliasUsageInVarAssignment.js

@@ -31,7 +31,11 @@ exports.Model = Model;
 //// [aliasUsageInVarAssignment_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/ambiguousOverloadResolution.js

@@ -10,7 +10,11 @@ var t: number = f(x, x); // Not an error
 
 //// [ambiguousOverloadResolution.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/apparentTypeSubtyping.js

@@ -25,7 +25,11 @@ class Derived2<U extends String> extends Base2 { // error because of the prototy
 // subtype checks use the apparent type of the target type
 // S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S:
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/apparentTypeSupertype.js

@@ -15,7 +15,11 @@ class Derived<U extends String> extends Base { // error
 // subtype checks use the apparent type of the target type
 // S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S:
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrayAssignmentTest1.js

@@ -87,7 +87,11 @@ arr_any = i1; // should be an error - is
 
 //// [arrayAssignmentTest1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrayAssignmentTest2.js

@@ -61,7 +61,11 @@ arr_any = i1; // should be an error - is
 
 //// [arrayAssignmentTest2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrayBestCommonTypes.js

@@ -109,7 +109,11 @@ module NonEmptyTypes {
 
 //// [arrayBestCommonTypes.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrayLiteralTypeInference.js

@@ -53,7 +53,11 @@ var z3: { id: number }[] =
 
 //// [arrayLiteralTypeInference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrayLiterals.js

@@ -39,7 +39,11 @@ var context4: Base[] = [new Derived1(), new Derived1()];
 //// [arrayLiterals.js]
 // Empty array literal with no contextual type has type Undefined[]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrayLiteralsWithRecursiveGenerics.js

@@ -27,7 +27,11 @@ var as = [list, myDerivedList]; // List<number>[]
 
 //// [arrayLiteralsWithRecursiveGenerics.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrayOfSubtypeIsAssignableToReadonlyArray.js

@@ -21,7 +21,11 @@ rrb = cra; // error: 'A' is not assignable to 'B'
 
 //// [arrayOfSubtypeIsAssignableToReadonlyArray.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/arrowFunctionContexts.js

@@ -98,7 +98,11 @@ var asserted2: any;
 
 //// [arrowFunctionContexts.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithCallSignatures3.js

@@ -102,7 +102,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithCallSignatures3.js]
 // these are all permitted with the current rules, since we do not do contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithCallSignatures4.js

@@ -101,7 +101,11 @@ module Errors {
 //// [assignmentCompatWithCallSignatures4.js]
 // These are mostly permitted with the current loose rules. All ok unless otherwise noted.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithCallSignatures5.js

@@ -68,7 +68,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithCallSignatures5.js]
 // checking assignment compat for function types. No errors in this file
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithCallSignatures6.js

@@ -45,7 +45,11 @@ b16 = x.a16;
 //// [assignmentCompatWithCallSignatures6.js]
 // checking assignment compatibility relations for function types. All valid
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithConstructSignatures3.js

@@ -102,7 +102,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithConstructSignatures3.js]
 // checking assignment compatibility relations for function types. All of these are valid.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithConstructSignatures4.js

@@ -101,7 +101,11 @@ module Errors {
 //// [assignmentCompatWithConstructSignatures4.js]
 // checking assignment compatibility relations for function types.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithConstructSignatures5.js

@@ -68,7 +68,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithConstructSignatures5.js]
 // checking assignment compat for function types. All valid
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithConstructSignatures6.js

@@ -45,7 +45,11 @@ b16 = x.a16;
 //// [assignmentCompatWithConstructSignatures6.js]
 // checking assignment compatibility relations for function types. All valid.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithNumericIndexer.js

@@ -46,7 +46,11 @@ module Generics {
 //// [assignmentCompatWithNumericIndexer.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithNumericIndexer3.js

@@ -43,7 +43,11 @@ module Generics {
 //// [assignmentCompatWithNumericIndexer3.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithObjectMembers4.js

@@ -94,7 +94,11 @@ module WithBase {
 //// [assignmentCompatWithObjectMembers4.js]
 // members N and M of types S and T have the same name, same accessibility, same optionality, and N is not assignable M
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithObjectMembersOptionality.js

@@ -91,7 +91,11 @@ module SourceHasOptional {
 //// [assignmentCompatWithObjectMembersOptionality.js]
 // Derived member is not optional but base member is, should be ok
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithObjectMembersOptionality2.js

@@ -93,7 +93,11 @@ module SourceHasOptional {
 // M is optional and S contains no property with the same name as M
 // N is optional and T contains no property with the same name as N
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentCompatWithStringIndexer.js

@@ -56,7 +56,11 @@ module Generics {
 //// [assignmentCompatWithStringIndexer.js]
 // index signatures must be compatible in assignments
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/assignmentLHSIsValue.js

@@ -72,7 +72,11 @@ foo() = value;
 
 //// [assignmentLHSIsValue.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/asyncImportedPromise_es5.js

@@ -12,7 +12,11 @@ class Test {
 //// [task.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/autolift4.js

@@ -25,7 +25,11 @@ class Point3D extends Point {
 
 //// [autolift4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/baseCheck.js

@@ -31,7 +31,11 @@ function f() {
 
 //// [baseCheck.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/baseIndexSignatureResolution.js

@@ -26,7 +26,11 @@ var z: Derived = b.foo();
 
 //// [baseIndexSignatureResolution.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/baseTypeOrderChecking.js

@@ -38,7 +38,11 @@ class Class4<T> extends Class3<T>
 
 //// [baseTypeOrderChecking.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/baseTypeWrappingInstantiationChain.js

@@ -29,7 +29,11 @@ class C<T1> extends CBase<T1> {
 
 //// [baseTypeWrappingInstantiationChain.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/bases.js

@@ -22,7 +22,11 @@ new C().y;
 
 //// [bases.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/bestCommonTypeOfConditionalExpressions.js

@@ -30,7 +30,11 @@ function foo5<T, U>(t: T, u: U): Object {
 // conditional expressions return the best common type of the branches plus contextual type (using the first candidate if multiple BCTs exist)
 // no errors expected here
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/bestCommonTypeOfConditionalExpressions2.js

@@ -28,7 +28,11 @@ function foo3<T extends U, U extends V, V>(t: T, u: U) {
 // conditional expressions return the best common type of the branches plus contextual type (using the first candidate if multiple BCTs exist)
 // these are errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/bestCommonTypeOfTuple2.js

@@ -24,7 +24,11 @@ var e51 = t5[2]; // {}
 
 //// [bestCommonTypeOfTuple2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/callSignatureAssignabilityInInheritance2.js

@@ -72,7 +72,11 @@ interface I extends A {
 //// [callSignatureAssignabilityInInheritance2.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/callSignatureAssignabilityInInheritance3.js

@@ -117,7 +117,11 @@ module Errors {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // error cases
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/callSignatureAssignabilityInInheritance4.js

@@ -52,7 +52,11 @@ interface I extends A {
 //// [callSignatureAssignabilityInInheritance4.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/callSignatureAssignabilityInInheritance5.js

@@ -52,7 +52,11 @@ interface I extends B {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // same as subtypingWithCallSignatures2 just with an extra level of indirection in the inheritance chain
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/callSignatureAssignabilityInInheritance6.js

@@ -55,7 +55,11 @@ interface I9<T> extends A {
 // same as subtypingWithCallSignatures4 but using class type parameters instead of generic signatures
 // all are errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/callWithSpread.js

@@ -60,7 +60,11 @@ class D extends C {
 
 //// [callWithSpread.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/captureThisInSuperCall.js

@@ -10,7 +10,11 @@ class B extends A {
 
 //// [captureThisInSuperCall.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/castingTuple.js

@@ -34,7 +34,11 @@ t4[2] = 10;
 
 //// [castingTuple.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/chainedAssignment3.js

@@ -24,7 +24,11 @@ a = b = new A();
 
 //// [chainedAssignment3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js

@@ -21,7 +21,11 @@ class C extends B {
 
 //// [chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkForObjectTooStrict.js

@@ -33,7 +33,11 @@ class Baz extends Object {
 
 //// [checkForObjectTooStrict.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing1.js

@@ -12,7 +12,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing2.js

@@ -12,7 +12,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing3.js

@@ -17,7 +17,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing4.js

@@ -21,7 +21,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing5.js

@@ -9,7 +9,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing6.js

@@ -12,7 +12,11 @@ class Super extends Base {
 
 //// [checkSuperCallBeforeThisAccessing6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing7.js

@@ -11,7 +11,11 @@ class Super extends Base {
 
 //// [checkSuperCallBeforeThisAccessing7.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/checkSuperCallBeforeThisAccessing8.js

@@ -12,7 +12,11 @@ class Super extends Base {
 
 //// [checkSuperCallBeforeThisAccessing8.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/circularImportAlias.js

@@ -22,7 +22,11 @@ var c = new B.a.C();
 //// [circularImportAlias.js]
 // expected no error
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/circularTypeofWithFunctionModule.js

@@ -15,7 +15,11 @@ namespace maker {
 //// [circularTypeofWithFunctionModule.js]
 // Repro from #6072
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractConstructorAssignability.js

@@ -16,7 +16,11 @@ new CC;
 
 //// [classAbstractConstructorAssignability.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractCrashedOnce.js

@@ -12,7 +12,11 @@ var x = new bar();
 
 //// [classAbstractCrashedOnce.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractExtends.js

@@ -18,7 +18,11 @@ class E extends B {
 
 //// [classAbstractExtends.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractFactoryFunction.js

@@ -19,7 +19,11 @@ NewB(B);
 
 //// [classAbstractFactoryFunction.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractGeneric.js

@@ -27,7 +27,11 @@ class G<T> extends A<T> {
 
 //// [classAbstractGeneric.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractInAModule.js

@@ -9,7 +9,11 @@ new M.B;
 
 //// [classAbstractInAModule.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractInheritance.js

@@ -23,7 +23,11 @@ abstract class GG extends CC {}
 
 //// [classAbstractInheritance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractInstantiations1.js

@@ -29,7 +29,11 @@ c = new B;
 // Calling new with (non)abstract classes.
 //
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractInstantiations2.js

@@ -53,7 +53,11 @@ class H { // error -- not declared abstract
 
 //// [classAbstractInstantiations2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractOverrideWithAbstract.js

@@ -25,7 +25,11 @@ class DD extends BB {
 
 //// [classAbstractOverrideWithAbstract.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractSuperCalls.js

@@ -29,7 +29,11 @@ abstract class BB extends AA {
 
 //// [classAbstractSuperCalls.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractUsingAbstractMethod1.js

@@ -19,7 +19,11 @@ a.foo();
 
 //// [classAbstractUsingAbstractMethod1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classAbstractUsingAbstractMethods2.js

@@ -29,7 +29,11 @@ class DD extends AA {
 
 //// [classAbstractUsingAbstractMethods2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classConstructorAccessibility2.js

@@ -48,7 +48,11 @@ var dc = new DerivedC(1);
 
 //// [classConstructorAccessibility2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classConstructorAccessibility4.js

@@ -32,7 +32,11 @@ class D {
 
 //// [classConstructorAccessibility4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classConstructorAccessibility5.js

@@ -13,7 +13,11 @@ class Unrelated {
 
 //// [classConstructorAccessibility5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classConstructorParametersAccessibility.js

@@ -28,7 +28,11 @@ class Derived extends C3 {
 
 //// [classConstructorParametersAccessibility.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classConstructorParametersAccessibility2.js

@@ -28,7 +28,11 @@ class Derived extends C3 {
 
 //// [classConstructorParametersAccessibility2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classConstructorParametersAccessibility3.js

@@ -15,7 +15,11 @@ d.p;  // public, OK
 
 //// [classConstructorParametersAccessibility3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classDeclarationMergedInModuleWithContinuation.js

@@ -13,7 +13,11 @@ module M {
 
 //// [classDeclarationMergedInModuleWithContinuation.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classDeclaredBeforeClassFactory.js

@@ -9,7 +9,11 @@ function makeBaseClass() {
 
 //// [classDeclaredBeforeClassFactory.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classDoesNotDependOnBaseTypes.js

@@ -14,7 +14,11 @@ class StringTreeCollection extends StringTreeCollectionBase { }
 
 //// [classDoesNotDependOnBaseTypes.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classExpression2.js

@@ -4,7 +4,11 @@ var v = class C extends D {};
 
 //// [classExpression2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classExpression3.js

@@ -8,7 +8,11 @@ c.c;
 
 //// [classExpression3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };

tests/baselines/reference/classExpressionExtendingAbstractClass.js

@@ -10,7 +10,11 @@ var C = class extends A {     // no error reported!
 
 //// [classExpressionExtendingAbstractClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };