v8/test/mjsunit/regress/regress-5638b.js

// Copyright 2017 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: --allow-natives-syntax

class A {
  constructor(arg) {
    assertEquals(123, arg);
    assertSame(observer, new.target);
    superclass_counter++;
  }
}

class B extends A {
  constructor() {
    super(123);
    construction_counter++;
  }
}
%PrepareFunctionForOptimization(B);

var superclass_counter = 0;

var construction_counter = 0;

var observation_counter = 0;

var observer = new Proxy(A, {
  get(target, property, receiver) {
    if (property === 'prototype') {
      %DeoptimizeFunction(B);
      observation_counter++;
    }
    return Reflect.get(target, property, receiver);
  }
});

Reflect.construct(B, [], observer);
Reflect.construct(B, [], observer);
%OptimizeFunctionOnNextCall(B);
Reflect.construct(B, [], observer);
assertEquals(3, observation_counter);
assertEquals(3, construction_counter);
assertEquals(3, superclass_counter);