Private fields

test/mjsunit/harmony/class-privates-proxy.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-private-class-fields
+
+var handler = {
+  getPrototypeOf(){ throw 'Called getPrototypeOf'; },
+  setPrototypeOf(){ throw 'Called setPrototypeOf'; },
+  isExtensible(){ throw 'Called isExtensible'; },
+  preventExtensions(){ throw 'Called preventExtensions'; },
+  getOwnPropertyDescriptor(){ throw 'Called getOwnPropertyDescriptor'; },
+  defineProperty(){ throw 'Called defineProperty'; },
+  has(){ throw 'Called has'; },
+  get(){ throw 'Called get'; },
+  set(){ throw 'Called set'; },
+  deleteProperty(){ throw 'Called deleteProperty'; },
+  ownKeys(){ throw 'Called ownKeys'; },
+  apply(){ throw 'Called apply'; },
+  construct(){ throw 'Called construct'; }
+};
+
+{
+  class Base {
+    constructor() {
+      return new Proxy({}, handler);
+    }
+  }
+
+  class Derived extends Base {
+    #x = 0;
+    static m(o){ return o.#x; }
+  }
+
+  assertEquals(0, Derived.m(new Derived));
+}