The Tor Browser / file revision

 // obj.defineProperty throws if a value, getter, or setter is not a debuggee value.

 load(libdir + "asserts.js");

 var g = newGlobal();

 var dbg = new Debugger;

 var gobj = dbg.addDebuggee(g);

 assertThrowsInstanceOf(function () { gobj.defineProperty('x', {value: {}}); }, TypeError);

 assertThrowsInstanceOf(function () { gobj.defineProperty('x', {get: Number}); }, TypeError);

 assertThrowsInstanceOf(function () { gobj.defineProperty('x', {get: gobj, set: Number}) },

                        TypeError);