Update tests for classes extending null

Per https://github.com/tc39/ecma262/pull/781

test/language/statements/class/subclass/class-definition-null-proto-contains-return-override.js

@@ -4,18 +4,30 @@
 esid: sec-runtime-semantics-classdefinitionevaluation
 es6id: 14.5.14
 description: >
-    Runtime Semantics: ClassDefinitionEvaluation
+    The constructor of a null-extending class can contain an explicit return value.
+info: |
+  Runtime Semantics: ClassDefinitionEvaluation
 
-    If superclass is null, then
-      Let protoParent be null.
-      Let constructorParent be the intrinsic object %FunctionPrototype%.
+  [...]
+  15. If ClassHeritageopt is present, then set F's [[ConstructorKind]] internal slot to "derived".
+  [...]
+
+  9.2.2 [[Construct]]
+
+  [...]
+  13. If result.[[Type]] is return, then
+     a. If Type(result.[[Value]]) is Object, return NormalCompletion(result.[[Value]]).
+  [...]
 ---*/
+var obj;
+
 class Foo extends null {
   constructor() {
-    return {};
+    return obj = {};
   }
 }
 
 var f = new Foo();
 
+assert.sameValue(f, obj);
 assert.sameValue(Object.getPrototypeOf(f), Object.prototype);

test/language/statements/class/subclass/class-definition-null-proto-missing-return-override.js

@@ -3,12 +3,9 @@
 /*---
 esid: sec-runtime-semantics-classdefinitionevaluation
 description: >
-  The `this` value of a null-extending class is automatically initialized,
-  obviating the need for an explicit return value in the constructor.
+  The `this` value of a null-extending class isn't automatically initialized,
+  which makes it necessary to have an explicit return value in the constructor.
 info: |
-  The behavior under test was introduced in the "ES2017" revision of the
-  specification and conflicts with prior editions.
-
   Runtime Semantics: ClassDefinitionEvaluation
 
   [...]
@@ -18,24 +15,25 @@ info: |
      [...]
      b. Let superclass be the result of evaluating ClassHeritage.
   [...]
-  15. If ClassHeritageopt is present and superclass is not null, then set F's
-      [[ConstructorKind]] internal slot to "derived".
+  15. If ClassHeritageopt is present, then set F's [[ConstructorKind]] internal slot to "derived".
   [...]
 
   9.2.2 [[Construct]]
 
-  [...]
-  5. If kind is "base", then
-     a. Let thisArgument be ? OrdinaryCreateFromConstructor(newTarget,
-        "%ObjectPrototype%").
   [...]
   15. Return ? envRec.GetThisBinding().
+
+  8.1.1.3.4 GetThisBinding ( )
+  [...]
+  3. If envRec.[[ThisBindingStatus]] is "uninitialized", throw a ReferenceError exception.
+  [...]
 ---*/
 
 class Foo extends null {
-  constructor() {}
+  constructor() {
+  }
 }
 
-var foo = new Foo();
-
-assert.sameValue(Object.getPrototypeOf(foo), Foo.prototype);
+assert.throws(ReferenceError, function() {
+  new C();
+});

test/language/statements/class/subclass/class-definition-null-proto-super.js

@@ -3,8 +3,8 @@
 /*---
 esid: sec-runtime-semantics-classdefinitionevaluation
 description: >
-  The `this` value of a null-extending class is automatically initialized,
-  preventing the use of `super` from within the constructor.
+  Attempting to call `super()` in a null-extending class throws a TypeError,
+  because %FunctionPrototype% cannot be called as constructor function.
 info: |
   Runtime Semantics: ClassDefinitionEvaluation
 
@@ -14,17 +14,12 @@ info: |
   6. Else,
      [...]
      b. Let superclass be the result of evaluating ClassHeritage.
+     [...]
+     e. If superclass is null, then
+        [...]
+        ii. Let constructorParent be the intrinsic object %FunctionPrototype%.
   [...]
-  15. If ClassHeritageopt is present and superclass is not null, then set F's
-      [[ConstructorKind]] internal slot to "derived".
-  [...]
-
-  9.2.2 [[Construct]]
-
-  [...]
-  5. If kind is "base", then
-     a. Let thisArgument be ? OrdinaryCreateFromConstructor(newTarget,
-        "%ObjectPrototype%").
+  15. Let constructorInfo be the result of performing DefineMethod for constructor with arguments proto and constructorParent as the optional functionPrototype argument.
   [...]
 
   12.3.5.1 Runtime Semantics: Evaluation
@@ -32,17 +27,15 @@ info: |
   SuperCall : super Arguments
 
   [...]
-  6. Let result be ? Construct(func, argList, newTarget).
-  7. Let thisER be GetThisEnvironment( ).
-  8. Return ? thisER.BindThisValue(result).
+  3. Let func be ? GetSuperConstructor().
+  4. Let argList be ArgumentListEvaluation of Arguments.
+  [...]
 
-  8.1.1.3.1 BindThisValue
+  12.3.5.2 Runtime Semantics: GetSuperConstructor ( )
 
   [...]
-  3. If envRec.[[ThisBindingStatus]] is "initialized", throw a ReferenceError
-     exception.
-  4. Set envRec.[[ThisValue]] to V.
-  5. Set envRec.[[ThisBindingStatus]] to "initialized".
+  5. Let superConstructor be ! activeFunction.[[GetPrototypeOf]]().
+  6. If IsConstructor(superConstructor) is false, throw a TypeError exception.
   [...]
 ---*/
 
@@ -52,7 +45,7 @@ var reachable = 0;
 class C extends null {
   constructor() {
     reachable += 1;
-    super();
+    super(unreachable += 1);
     unreachable += 1;
   }
 }

test/language/statements/class/subclass/class-definition-null-proto-this.js

@@ -3,42 +3,37 @@
 /*---
 esid: sec-runtime-semantics-classdefinitionevaluation
 description: >
-  The `this` value of a null-extending class is automatically initialized
+  The `this` value of a null-extending class isn't automatically initialized
 info: |
-  The behavior under test was introduced in the "ES2017" revision of the
-  specification and conflicts with prior editions.
-
   Runtime Semantics: ClassDefinitionEvaluation
 
   [...]
-  5. If ClassHeritageopt is not present, then
-     [...]
-  6. Else,
-     [...]
-     b. Let superclass be the result of evaluating ClassHeritage.
-  [...]
-  15. If ClassHeritageopt is present and superclass is not null, then set F's
-      [[ConstructorKind]] internal slot to "derived".
+  15. If ClassHeritageopt is present, then set F's [[ConstructorKind]] internal slot to "derived".
   [...]
 
-  9.2.2 [[Construct]]
+  12.2.2.1 Runtime Semantics: Evaluation
+  PrimaryExpression : this
+  1. Return ? ResolveThisBinding( ).
 
+  8.3.4 ResolveThisBinding ( )
+  [...]
+  2. Return ? envRec.GetThisBinding().
+  
+  8.1.1.3.4 GetThisBinding ( )
   [...]
-  5. If kind is "base", then
-     a. Let thisArgument be ? OrdinaryCreateFromConstructor(newTarget,
-        "%ObjectPrototype%").
+  3. If envRec.[[ThisBindingStatus]] is "uninitialized", throw a ReferenceError exception.
   [...]
 ---*/
 
-var thisVal, instance;
-
 class C extends null {
   constructor() {
-    thisVal = this;
+    // Use an arrow function to access the `this` binding of the class constructor.
+    assert.throws(ReferenceError, () => {
+      this;
+    });
   }
 }
 
-instance = new C();
-
-assert.sameValue(instance instanceof C, true);
-assert.sameValue(instance, thisVal);
+assert.throws(ReferenceError, function() {
+  new C();
+});

test/language/statements/class/subclass/class-definition-null-proto.js

@@ -4,32 +4,21 @@
 esid: sec-runtime-semantics-classdefinitionevaluation
 es6id: 14.5.14
 description: >
-  When a null-extending class does not specify a `constructor` method
-  definition, a method with zero parameters and an empty body is used
+  The prototype of a null-extending class is %FunctionPrototype%, the prototype of
+  its "prototype" property is `null`.
 info: |
-  The behavior under test was introduced in the "ES2017" revision of the
-  specification and conflicts with prior editions.
-
   Runtime Semantics: ClassDefinitionEvaluation
 
+  [...]
   5. If ClassHeritageopt is not present, then
      [...]
   6. Else,
      [...]
      b. Let superclass be the result of evaluating ClassHeritage.
      [...]
-  7. Let proto be ObjectCreate(protoParent).
-  8. If ClassBodyopt is not present, let constructor be empty.
-  9. Else, let constructor be ConstructorMethod of ClassBody.
-  10. If constructor is empty, then
-      a. If ClassHeritageopt is present and superclass is not null, then
-         [...]
-      b. Else,
-         i. Let constructor be the result of parsing the source text
-
-              constructor( ){ }
-
-            using the syntactic grammar with the goal symbol MethodDefinition.
+     e. If superclass is null, then
+         i. Let protoParent be null.
+        ii. Let constructorParent be the intrinsic object %FunctionPrototype%.
   [...]
 ---*/
 
@@ -37,3 +26,4 @@ class Foo extends null {}
 
 assert.sameValue(Object.getPrototypeOf(Foo.prototype), null);
 assert.sameValue(Object.getPrototypeOf(Foo.prototype.constructor), Function.prototype);
+assert.sameValue(Foo, Foo.prototype.constructor);