Closing only over final variables is deliberately a requirement because closing over non-final variables can lead to confusing situations. I discussed this in m

Closing only over final variables is deliberately a requirement because closing over non-final variables can lead to confusing situations. I discussed this in more detail in a previous thread: http://news.ycombinator.com/item?id=1257599 http://news.ycombinator.com/item?id=1257599 Good point regarding the effect on interoperability. I don't have an answer for that.