test/mjsunit/proto-accessor.js

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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 obj = {};
var obj2 = {};
desc.set.call(obj, obj2);
assertEquals(obj.__proto__, obj2);
assertEquals(desc.get.call(obj), obj2);


// 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);


var desc2 = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
assertEquals(desc2.get.call({}), 42);
assertDoesNotThrow("desc2.set.call({})");


Object.defineProperty(Object.prototype, "__proto__", { set:function(x){} });
var desc3 = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
assertDoesNotThrow("desc3.get.call({})");
assertDoesNotThrow("desc3.set.call({})");


Object.defineProperty(Object.prototype, "__proto__", { set: undefined });
assertThrows(function() {
  "use strict";
  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);