Really interesting talk.
According to the Groovy devcon 2 report at http://javanicus.com/blog2/items/191-index.html "no agreement was reached on [...] whether we should have any syntax denoting the difference between a true lexical Closure and one of these Builder blocks. The historical reasons go back to Builder blocks looking just like Closures, and I'm afraid this long standing mistake must be removed from the language before any true progress can be made, as no sensible specification rules can be applied while the dichotomy exists. I headed back to London with a very disappointed James Strachan"
In Groovy language creator Strachan's last ever email on its mailing list 2 days later at http://groovy.329449.n5.nabble.com/Paris-write-up-tt395560.h... "Note that no other dynamic language I'm aware of has any concept of dynamic name resolution in the way you suggest; names are always statically bound to objects in a sensible way in all dynamic languages I'm aware of (lisp, smalltalk, python, ruby etc). I see no argument yet for why we have to throw away decades of language research and development with respect to name resolution across the language as a whole"