Implement Array::concat function in C++....

test/mjsunit/array-concat.js

 // Copyright 2008 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 49 matching lines @@
   assertEquals("undefined", typeof(c[pos - 1]));
   assertEquals("foo", c[pos]);
   assertEquals("bar", c[pos + 1]);
 
   // When we take the number off the prototype it disappears from a, but
   // the concat put it in c itself.
   Array.prototype["123"] = undefined;
   assertEquals("undefined", typeof(a[123]));
   assertEquals("baz", c[123]);
 
+  // If the element of prototype is shadowed, the element on the instance
+  // should be copied, but not the one on the prototype.
+  Array.prototype[123] = 'baz';
+  a[123] = 'xyz';
+  assertEquals('xyz', a[123]);
+  c = a.concat(b);
+  assertEquals('xyz', c[123]);
+
   // Non-numeric properties on the prototype or the array shouldn't get
   // copied.
   Array.prototype.moe = 'joe';
   a.ben = 'jerry';
   assertEquals(a["moe"], 'joe');
   assertEquals(a["ben"], 'jerry');
   c = a.concat(b);
   // ben was not copied
   assertEquals("undefined", typeof(c.ben));
   // moe was not copied, but we can see it through the prototype
@@ skipping 12 matching lines @@
   assertEquals("undefined", typeof(c[0xffffffff]));
   assertEquals(c.length, a.length + 1);
 
 }
 
 a = [];
 c = a.concat('Hello');
 assertEquals(1, c.length);
 assertEquals("Hello", c[0]);
 assertEquals("Hello", c.toString());