Test [[IsHTMLDDA]] object as superclass

test/annexB/language/statements/class/subclass/superclass-emulates-undefined.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-runtime-semantics-classdefinitionevaluation
+description: >
+  [[IsHTMLDDA]] object as superclass: `null` check uses strict equality.
+  IsConstructor check is performed before "prototype" lookup.
+info: |
+  ClassDefinitionEvaluation
+
+  [...]
+  5. Else,
+    [...]
+    d. Let superclass be ? GetValue(superclassRef).
+    e. If superclass is null, then
+      [...]
+    f. Else if IsConstructor(superclass) is false, throw a TypeError exception.
+features: [class, IsHTMLDDA]
+---*/
+
+var superclass = $262.IsHTMLDDA;
+var prototypeGets = 0;
+Object.defineProperty(superclass, "prototype", {
+  get: function() {
+    prototypeGets += 1;
+  },
+});
+
+assert.throws(TypeError, function() {
+  class C extends superclass {}
+});
+
+assert.sameValue(prototypeGets, 0);