Out contracts: how to refer to objects' start state

[Andrej Mitrovic]

On 5/26/13, Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org> wrote:
> class A {
>    void fun()
>    in { auto oldLen = this.length; }
>    out { assert(this.length == oldLen + 1); }
>    body { ... }
> }
>
> That was technically difficult to do back then, and fell by the wayside.
> Today it would break too much code to introduce even if feasible.

Perhaps we could support this by allowing qualification of the in block:

out { assert(this.length == in.oldLen + 1); }

"in" is a keyword so it shouldn't break any existing code.