Follow jsc on not throwing when trying to add a property to a non-extensible object.

test/mjsunit/object-prevent-extensions.js

 // Copyright 2010 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
@@ skipping 17 matching lines @@
 // Tests the Object.preventExtensions method - ES 15.2.3.10
 
 
 var obj1 = {};
 // Extensible defaults to true.
 assertTrue(Object.isExtensible(obj1));
 Object.preventExtensions(obj1);
 
 // Make sure the is_extensible flag is set. 
 assertFalse(Object.isExtensible(obj1));
-// Try adding a new property.
-try {
-  obj1.x = 42;
-  assertUnreachable();
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
+obj1.x = 42;
 assertEquals(undefined, obj1.x);
 
 // Try adding a new element.
-try {
-  obj1[1] = 42;
-  assertUnreachable();
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
+obj1[1] = 42;
 assertEquals(undefined, obj1[1]);
 
 
 // Try when the object has an existing property.
 var obj2 = {};
 assertTrue(Object.isExtensible(obj2));
 obj2.x = 42;
 assertEquals(42, obj2.x);
 assertTrue(Object.isExtensible(obj2));
 
 Object.preventExtensions(obj2);
 assertEquals(42, obj2.x);
 
-try {
-  obj2.y = 42;
-  assertUnreachable();
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
-
+obj2.y = 42;
 // obj2.y should still be undefined.
 assertEquals(undefined, obj2.y);
 // Make sure we can still write values to obj.x.
 obj2.x = 43;
 assertEquals(43, obj2.x)
 
-try {
-  obj2.y = new function() { return 42; };
-  assertUnreachable();
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
+obj2.y = new function() { return 42; };
 // obj2.y should still be undefined.
 assertEquals(undefined, obj2.y);
 assertEquals(43, obj2.x)
 
 try {
   Object.defineProperty(obj2, "y", {value: 42});
 } catch (e) {
   assertTrue(/object is not extensible/.test(e));
 }
 
 // obj2.y should still be undefined.
 assertEquals(undefined, obj2.y);
 assertEquals(43, obj2.x);
 
-try {
-  obj2[1] = 42;
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
-
+obj2[1] = 42;
 assertEquals(undefined, obj2[1]);
 
 var arr = new Array();
 arr[1] = 10;
 
 Object.preventExtensions(arr);
 
-try {
-  arr[2] = 42;
-  assertUnreachable();
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
+arr[2] = 42;
 assertEquals(10, arr[1]);
 
 // We should still be able to change exiting elements.
 arr[1]= 42;
 assertEquals(42, arr[1]);
 
 
 // Test the the extensible flag is not inherited.
 var parent = {};
 parent.x = 42;
 Object.preventExtensions(parent);
 
 var child = Object.create(parent);
 
 // We should be able to add new properties to the child object.
 child.y = 42;
 
 // This should have no influence on the parent class.
-try {
-  parent.y = 29;
-  assertUnreachable();
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
+parent.y = 29;
 
 
 // Test that attributes on functions are also handled correctly.
 function foo() {
   return 42;
 }
 
 Object.preventExtensions(foo);
 
-try {
-  foo.x = 29;
-  assertUnreachable();
-} catch (e) {
-  assertTrue(/object is not extensible/.test(e));
-}
+foo.x = 29;
+assertEquals(undefined, foo.x);