[timcameronryan]

As al_james metioned, in order to emulate a dynamic language, you have to take a lowest-common-denominator approach. Thus all objects are of the type JSObject, which has functions for get() set() invoke() etc.-- basically a glorified HashMap+Runnable.

However, you don't need to wrap objects for arithmetic operations. At the moment Mug can determine the result of some types of expressions. If you're adding two doubles, it doesn't wrap the numbers before adding them. If you're calling (10).toString(), then it will autobox the number just as defined in the ECMAScript spec (the [[ToObject]] operation).

Deterction currently only works where types are explicit (a number literal will always be a number, etc.) The next step is to do type analysis on local variables, which will allow loops like for (var i = 0; i < 10; i++) { ... } to be compiled without wrapping primitives at all, greatly improving speed.