Generalized Stephen's patch from http://codereview.chromium.org/7044100/ and

test/mjsunit/not.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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+function testNot(x) {
+  // The VM constant folds so we use that to check the result.
+  var expected = eval("!(" + x + ")");
+  var actual = !x;
+  assertEquals(expected, actual, "x: " + x);
+}
+
+testNot(0);
+testNot(1);
+testNot(-1);
+testNot(-0);
+
+testNot(NaN);
+testNot(Infinity);
+testNot(-Infinity);
+
+testNot(true);
+testNot(false);
+
+assertTrue(!"");
+assertFalse(!"foo");
+
+assertFalse(![]);
+assertFalse(![1]);
+assertFalse(![1,2]);
+
+assertFalse(!{});
+assertFalse(!{foo:1});
+assertFalse(!{foo:1,bar:2});
+
+assertFalse(!!0);
+assertTrue(!!1);