This is theoretically true and I am excited about LightTable but even then, there are many situations where automated refactoring simply isn't possible.

    var decoration = { topmargin: 10, bottommargin: 10 };
    ...
    function setMargin(where, value) {
        decoration[where + "margin"] = value;
    }
    ....
    setMargin("top", 20);

This is a hazard in pretty much any language though. At some point you're going to want to do something dynamic at run time just to get a particular feature to be possible- whether it's by using a built in feature of a language, or by importing an aircraft carrier to do it for you in Java. It's simply Godel's curse- every sufficiently powerful formal system has an escape port. Otherwise known as Greenspun's 10th rule.