Aspect Oriented Programming?
mgreenbe: AOP was the next big thing five years ago.  I've never heard of a serious, non-dog-food project written in any (pointcut-rich) implementation of aspects.The fundamental problem with aspect-oriented programming is that it makes it impossible to reason compositionally: any part of your program could be affected by an aspect, so it can be quite hard to know what your code is doing.I think instrumentation, as a technique, is vital.  But having instrumentation as a language-level feature seems like a bad idea to me.  As a programmer, I instrument code to understand its behavior, not to define it.