Contracts (feature request)

Hi all,

I'm quite new to Scala and like a lot its approach to support programmer.
It has obviously a focus on scalable component programming 
(provided/required services and mixin composition). That's why I would 
almost expect to see contracts integrated into the language.
By contracts I mean pre- and post conditions for methods and a class 
invariant, which all are checked at runtime (precondition and class 
invariant before invocation of the body of the method and postcondition 
and class invariant after leaving the method).
The reason why I think those are important, is that seperating the 
contract from body makes the code a bit less burdensome to read. For 
instance, pre and post have different meaning, they're not just any 
asserts. Also postcondition test is not needed in different exit paths 
of method (wrapping method call isn't a good alternative either).
One big advantage is that the conditions are spread to subclasses 
automatically by compiler.

Is there any plans for this, or am I just dreaming of a thing that just 
don't fit in Scala?

Example:

def fun(x: Int): Int
  pre{
    x >= 0 && x < 10
  }
  post(result){
    result < x
  }
  = {
    -x
  }

Thanks for very interesting language!
Sincerely, Henrik