Invariants for methods

[Walter Bright]

bearophile wrote:
> C#4 designers seem to have found a way to implement "old" (Prestate Values)
> correctly enough, so can't D2 adopt a similar solution?

C#'s designers did not implement contract inheritance, which is a rather 
critical feature. Without inheritance, contracts are little more than just a 
list of asserts, and you cannot do the inheritance with a library feature.