var o1 =
  {
    get property() { print("gotten!"); return "get"; },
    set property(v) { print("sotten!  " + v); }
  };
var v1 = o1.property; // prints "gotten!", v1 === "get"
o1.property = "new"; // prints "sotten!"

…and programmatic:

var o2 = {};
o2.__defineGetter__("property", function() { print("gotten!"); return "get"; });
o2.__defineSetter__("property", function() { print("sotten!"); });
var v2 = o2.property; // prints "gotten!", v2 === "get"
o2.property = "new"; // prints "sotten!"

The two examples are slightly different. The first example should have printed “sotten! new” and the second example will only print “sotten!”. I’m sure this was just a casual oversight, but it might be good to update it for future readers.

And for what it’s worth, stack traces include line numbers, so it’s not like you’re totally hosed if functions don’t have names, nor is it the case that names are essential to debugging.

I’ve not actually tested the accessor-literal syntax, either, just heard so over IRC, so… maybe.

Forcing getters and setters to have the right number arguments sounds sane to me, since you can’t sensibly access them except via the expression/assignment syntax, so there shouldn’t have been much sense in allowing things that would have been unusable. (I’m also specifically ignoring the possibility of looking them up then calling them with the wrong number of arguments, of course, since that’s obtuse enough that you might as well have an inner function in that case.)

Object.defineProperty = function(object, name, desc) {
 if (!desc.enumerable) throw "Non-enumerable properties not supported";
 if (!desc.configurable) throw "Non-configurable properties not supported";
 if (typeof desc.value !== "undefined") {
  if (desc.get || desc.set) throw "Descriptor value not compatible with getter/setter";
  object[name] = value;
 }
 else {
  if (!(desc.get || desc.set)) throw "Descriptor must have value, getter or setter";
  if (desc.get) object.__defineGetter__(name, desc.get);
  if (desc.set) object.__defineSetter__(name, desc.set);
 }
 return object;
}