classfields: PrivateFieldAdd TypeError test

test/language/statements/class/privatefieldadd-typeerror.js

+// Copyright (C) 2017 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: Class construction should error if attempting to add private field twice
+esid: sec-ecmascript-function-objects-construct-argumentslist-newtarget
+info: |
+  [[Construct]] ( argumentsList, newTarget)
+    ...
+    8. If kind is "base", then
+      a. Perform OrdinaryCallBindThis(F, calleeContext, thisArgument).
+      b. Let result be InitializeInstanceFields(thisArgument, F).
+      c. If result is an abrupt completion, then
+        i. Remove calleeContext from execution context stack and restore callerContext as the running execution context.
+        ii. Return Completion(result).
+
+  InitializeInstanceFields ( O, constructor )
+    1. Assert: Type ( O ) is Object.
+    2. Assert: Assert constructor is an ECMAScript function object.
+    3. Let fieldRecords be the value of constructor's [[Fields]] internal slot.
+    4. For each item fieldRecord in order from fieldRecords,
+      a. If fieldRecord.[[static]] is false, then
+        i. Perform ? DefineField(O, fieldRecord).
+
+  DefineField(receiver, fieldRecord)
+    ...
+    8. If fieldName is a Private Name,
+      a. Perform ? PrivateFieldAdd(fieldName, receiver, initValue).
+
+  PrivateFieldAdd (P, O, value)
+    1. Assert: P is a Private Name value.
+    2. If O is not an object, throw a TypeError exception.
+    3. Let entry be PrivateFieldFind(P, O).
+    4. If entry is not empty, throw a TypeError exception.
+
+features: [class-fields]
+---*/
+
+
+class A {
+  constructor(arg) {
+    return arg;
+  }
+}
+
+class C extends A {
+  #x;
+
+  constructor(arg) {
+    super(arg);
+  }
+}
+
+var containsprivatex = new C();
+
+assert.throws(TypeError, function() {
+  // After the super call in C's constructor, the `this` value in C will
+  // already have "#x" in it's [[PrivateFieldValues]]
+  new C(containsprivatex);
+})