ES6: Tighten up Object.prototype.__proto__

test/mjsunit/proto-accessor.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --harmony-symbols
+
 var desc = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
-assertEquals("function", typeof desc.get);
-assertEquals("function", typeof desc.set);
-assertDoesNotThrow("desc.get.call({})");
-assertDoesNotThrow("desc.set.call({}, {})");
+var getProto = desc.get;
+var setProto = desc.set;
+
+function TestNoPoisonPill() {
+  assertEquals("function", typeof desc.get);
+  assertEquals("function", typeof desc.set);
+  assertDoesNotThrow("desc.get.call({})");
+  assertDoesNotThrow("desc.set.call({}, {})");
+
+  var obj = {};
+  var obj2 = {};
+  desc.set.call(obj, obj2);
+  assertEquals(obj.__proto__, obj2);
+  assertEquals(desc.get.call(obj), obj2);
+}
+TestNoPoisonPill();
 
 
-var obj = {};
-var obj2 = {};
-desc.set.call(obj, obj2);
-assertEquals(obj.__proto__, obj2);
-assertEquals(desc.get.call(obj), obj2);
+function TestRedefineObjectPrototypeProtoGetter() {
+  Object.defineProperty(Object.prototype, "__proto__", {
+    get: function() {
+      return 42;
+    }
+  });
+  assertEquals({}.__proto__, 42);
+  assertEquals(desc.get.call({}), Object.prototype);
+
+  var desc2 = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
+  assertEquals(desc2.get.call({}), 42);
+  assertEquals(desc2.set.call({}), undefined);
+
+  Object.defineProperty(Object.prototype, "__proto__", {
+    set: function(x) {}
+  });
+  var desc3 = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
+  assertEquals(desc3.get.call({}), 42);
+  assertEquals(desc3.set.call({}), undefined);
+}
+TestRedefineObjectPrototypeProtoGetter();
 
 
-// Check that any redefinition of the __proto__ accessor works.
-Object.defineProperty(Object.prototype, "__proto__", {
-  get: function() {
-    return 42;
-  }
-});
-assertEquals({}.__proto__, 42);
-assertEquals(desc.get.call({}), Object.prototype);
+function TestRedefineObjectPrototypeProtoSetter() {
+  Object.defineProperty(Object.prototype, "__proto__", { set: undefined });
+  assertThrows(function() {
+    "use strict";
+    var o = {};
+    var p = {};
+    o.__proto__ = p;
+  }, TypeError);
+}
+TestRedefineObjectPrototypeProtoSetter();
 
 
-var desc2 = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
-assertEquals(desc2.get.call({}), 42);
-assertDoesNotThrow("desc2.set.call({})");
+function TestGetProtoOfValues() {
+  assertEquals(getProto.call(1), Number.prototype);
+  assertEquals(getProto.call(true), Boolean.prototype);
+  assertEquals(getProto.call(false), Boolean.prototype);
+  assertEquals(getProto.call('s'), String.prototype);
+  assertEquals(getProto.call(Symbol()), Symbol.prototype);
+
+  assertThrows(function() { getProto.call(null); }, TypeError);
+  assertThrows(function() { getProto.call(undefined); }, TypeError);
+}
+TestGetProtoOfValues();
 
 
-Object.defineProperty(Object.prototype, "__proto__", { set:function(x){} });
-var desc3 = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
-assertDoesNotThrow("desc3.get.call({})");
-assertDoesNotThrow("desc3.set.call({})");
+var values = [1, true, false, 's', Symbol()];
 
 
-Object.defineProperty(Object.prototype, "__proto__", { set: undefined });
-assertThrows(function() {
-  "use strict";
+function TestSetProtoOfValues() {
+  for (var i = 0; i < values.length; i++) {
+    assertEquals(setProto.call(values[i], i), undefined);
+  }
+
+  assertThrows(function() { setProto.call(null, 7); }, TypeError);
+  assertThrows(function() { setProto.call(undefined, 8); }, TypeError);
+}
+TestSetProtoOfValues();
+
+
+function TestSetProtoToValue() {
+  var object = {};
+  var proto = {};
+  setProto.call(object, proto);
+
+  var valuesWithUndefined = values.concat(undefined);
+
+  for (var i = 0; i < valuesWithUndefined.length; i++) {
+    assertEquals(setProto.call(object, valuesWithUndefined[i]), undefined);
+    assertEquals(getProto.call(object), proto);
+  }
+
+  // null is the only valid value that can be used as a [[Prototype]].
+  assertEquals(setProto.call(object, null), undefined);
+  assertEquals(getProto.call(object), null);
+}
+TestSetProtoToValue();
+
+
+function TestDeleteProto() {
+  assertTrue(delete Object.prototype.__proto__);
   var o = {};
   var p = {};
   o.__proto__ = p;
-}, TypeError);
-
-
-assertTrue(delete Object.prototype.__proto__);
-var o = {};
-var p = {};
-o.__proto__ = p;
-assertEquals(Object.getPrototypeOf(o), Object.prototype);
-var desc4 = Object.getOwnPropertyDescriptor(o, "__proto__");
-assertTrue(desc4.configurable);
-assertTrue(desc4.enumerable);
-assertTrue(desc4.writable);
-assertEquals(desc4.value, p);
+  assertEquals(Object.getPrototypeOf(o), Object.prototype);
+  var desc4 = Object.getOwnPropertyDescriptor(o, "__proto__");
+  assertTrue(desc4.configurable);
+  assertTrue(desc4.enumerable);
+  assertTrue(desc4.writable);
+  assertEquals(desc4.value, p);
+}
+TestDeleteProto();