Follow-up to a pre-existing regression test.

test/mjsunit/regress/regress-1530.js

 // Copyright 2011 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 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Test that redefining the 'prototype' property of a function object
 // does actually set the internal value and does not screw up any
 // shadowing between said property and the internal value.
 
 var f = function() {};
 
 // Verify that normal assignment of 'prototype' property works properly
 // and updates the internal value.
-var x = { foo: 'bar' };
-f.prototype = x;
-assertSame(f.prototype, x);
+var a = { foo: 'bar' };
+f.prototype = a;
+assertSame(f.prototype, a);
 assertSame(f.prototype.foo, 'bar');
 assertSame(new f().foo, 'bar');
-assertSame(Object.getPrototypeOf(new f()), x);
-assertSame(Object.getOwnPropertyDescriptor(f, 'prototype').value, x);
+assertSame(Object.getPrototypeOf(new f()), a);
+assertSame(Object.getOwnPropertyDescriptor(f, 'prototype').value, a);
+assertTrue(Object.getOwnPropertyDescriptor(f, 'prototype').writable);
 
 // Verify that 'prototype' behaves like a data property when it comes to
 // redefining with Object.defineProperty() and the internal value gets
 // updated.
-var y = { foo: 'baz' };
-Object.defineProperty(f, 'prototype', { value: y, writable: true });
-assertSame(f.prototype, y);
+var b = { foo: 'baz' };
+Object.defineProperty(f, 'prototype', { value: b, writable: true });
+assertSame(f.prototype, b);
 assertSame(f.prototype.foo, 'baz');
 assertSame(new f().foo, 'baz');
-assertSame(Object.getPrototypeOf(new f()), y);
-assertSame(Object.getOwnPropertyDescriptor(f, 'prototype').value, y);
+assertSame(Object.getPrototypeOf(new f()), b);
+assertSame(Object.getOwnPropertyDescriptor(f, 'prototype').value, b);
+assertTrue(Object.getOwnPropertyDescriptor(f, 'prototype').writable);
 
 // Verify that the previous redefinition didn't screw up callbacks and
 // the internal value still gets updated.
-var z = { foo: 'other' };
-f.prototype = z;
-assertSame(f.prototype, z);
+var c = { foo: 'other' };
+f.prototype = c;
+assertSame(f.prototype, c);
 assertSame(f.prototype.foo, 'other');
 assertSame(new f().foo, 'other');
-assertSame(Object.getPrototypeOf(new f()), z);
-assertSame(Object.getOwnPropertyDescriptor(f, 'prototype').value, z);
+assertSame(Object.getPrototypeOf(new f()), c);
+assertSame(Object.getOwnPropertyDescriptor(f, 'prototype').value, c);
+assertTrue(Object.getOwnPropertyDescriptor(f, 'prototype').writable);
+
+// Verify that 'prototype' can be redefined to contain a different value
+// and have a different writability attribute at the same time.
+var d = { foo: 'final' };
+Object.defineProperty(f, 'prototype', { value: d, writable: false });
+assertSame(f.prototype, d);
+assertSame(f.prototype.foo, 'final');
+assertSame(new f().foo, 'final');
+assertSame(Object.getPrototypeOf(new f()), d);
+assertSame(Object.getOwnPropertyDescriptor(f, 'prototype').value, d);
+assertFalse(Object.getOwnPropertyDescriptor(f, 'prototype').writable);
+
+// Verify that non-writability of redefined 'prototype' is respected.
+assertThrows("'use strict'; f.prototype = {}");
+assertThrows("Object.defineProperty(f, 'prototype', { value: {} })");
 
 // Verify that non-writability of other properties is respected.
 assertThrows("Object.defineProperty(f, 'name', { value: {} })");
 assertThrows("Object.defineProperty(f, 'length', { value: {} })");
 assertThrows("Object.defineProperty(f, 'caller', { value: {} })");
 assertThrows("Object.defineProperty(f, 'arguments', { value: {} })");