I'm a very lazy (oops) language implementer. Every time but one when I've implemented closures, I took the quick approach of just copying the entire frame to the heap.
The other time, I was able to do more data flow analysis, but it also resulted in a bunch of annoying fiddly bugs and took more maintenance.
I'm not suggesting the v8 team took the 'easy way' out, but doing the deep introspection is hard, and in an environment such as a browser, I can see trading a pathological case such as this for what must be 1,000,000,000 inappropriate aggressive gc bugs.
The other time, I was able to do more data flow analysis, but it also resulted in a bunch of annoying fiddly bugs and took more maintenance.
I'm not suggesting the v8 team took the 'easy way' out, but doing the deep introspection is hard, and in an environment such as a browser, I can see trading a pathological case such as this for what must be 1,000,000,000 inappropriate aggressive gc bugs.
(See the recent discussion over RubyMotion for examples of the opposite problem: http://news.ycombinator.com/item?id=5949072)