Class fields, part 3 (backends)

test/mjsunit/harmony/class-fields-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-class-fields
+
+{
+  let effects = [];
+  let handler = {
+    defineProperty(){
+      effects.push(0);
+      return true;
+    },
+    get(){
+      throw 'called get';
+    },
+    set(){
+      throw 'called set';
+    }
+  };
+
+  class Base {
+    constructor(){
+      return new Proxy({}, handler);
+    }
+  }
+
+  class Derived extends Base {
+    a = 0;
+  }
+
+  new Derived;
+  assertArrayEquals([0], effects);
+}
+
+{
+  let handler = {
+    defineProperty(){
+      throw new Error;
+    }
+  };
+
+  class Base {
+    constructor(){
+      return new Proxy({}, handler);
+    }
+  }
+
+  class Derived extends Base {
+    a = 0;
+  }
+
+  assertThrows(() => new Derived);
+}