v8/test/mjsunit/es6/regress/regress-7706.js

// Copyright 2018 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

function toString(o) {
  %ToFastProperties(o.__proto__);
  return Object.prototype.toString.call(o);
}

class TestNumber extends Number {}
TestNumber.prototype[Symbol.toStringTag] = "TestNumber";
assertEquals("[object TestNumber]", toString(new TestNumber), "Try #1");
assertEquals("[object TestNumber]", toString(new TestNumber), "Try #2");

class TestBoolean extends Boolean {}
TestBoolean.prototype[Symbol.toStringTag] = "TestBoolean";
assertEquals("[object TestBoolean]", toString(new TestBoolean), "Try #1");
assertEquals("[object TestBoolean]", toString(new TestBoolean), "Try #2");

class TestString extends String {}
TestString.prototype[Symbol.toStringTag] = "TestString";
assertEquals("[object TestString]", toString(new TestString), "Try #1");
assertEquals("[object TestString]", toString(new TestString), "Try #2");

class base {}
class TestBigInt extends base {}
TestBigInt.prototype[Symbol.toStringTag] = 'TestBigInt';
var b = new TestBigInt();
b.__proto__.__proto__ = BigInt.prototype;
assertEquals("[object TestBigInt]", toString(b), "Try #1");
assertEquals("[object TestBigInt]", toString(b), "Try #2");

class TestSymbol extends base {}
TestSymbol.prototype[Symbol.toStringTag] = 'TestSymbol';
var sym = new TestSymbol();
sym.__proto__.__proto__ = Symbol.prototype;
assertEquals("[object TestSymbol]", toString(sym), "Try #1");
assertEquals("[object TestSymbol]", toString(sym), "Try #2");