Boost.ScopeExit based on D's scope(exit)

[Christopher Wright]

Andrei Alexandrescu wrote:
> Same about introducing default-isolation in D. 
> Bartosz was extremely opposed to it in the beginning, I remember a huge 
> debate about it at Kahili. A couple of months later, it was almost his 
> idea :o). I'm no more lucid. Every once in a while I need to remind 
> myself that local instantiation, a very cool feature unique to D, was 
> Walter's idea that I merely stumbled upon. Neither of us initially knew 
> how good it was...

These last two receive far less attention than const. What is default 
isolation? What is local instantiation?