test/mjsunit/proto-poison.js

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// Check that the __proto__ accessor is properly poisoned when extracted
// from Object.prototype using the property descriptor.
var desc = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
assertEquals("function", typeof desc.get);
assertEquals("function", typeof desc.set);
assertDoesNotThrow("desc.get.call({})");
assertThrows("desc.set.call({})", TypeError);

// Check that any redefinition of the __proto__ accessor causes poising
// to cease and the accessor to be extracted normally.
Object.defineProperty(Object.prototype, "__proto__", { get:function(){} });
desc = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
assertDoesNotThrow("desc.get.call({})");
assertThrows("desc.set.call({})", TypeError);
Object.defineProperty(Object.prototype, "__proto__", { set:function(x){} });
desc = Object.getOwnPropertyDescriptor(Object.prototype, "__proto__");
assertDoesNotThrow("desc.get.call({})");
assertDoesNotThrow("desc.set.call({})");