Reference counted containers prototype

[Andrei Alexandrescu]

Hello,

I've been playing with a new approach to reference counting, in 
particular for the containers library.

A small prototype is at http://pastebin.com/WnSQY1Jw. The prototype 
features a simple doubly-linked list implementation DListImpl. That is 
not supposed to be manipulated directly (or it might, in case the user 
wants a simple garbage collected implementation - this is a point in the 
discussion).

DListImpl has only a couple of primitives implemented. The only 
interesting points that it tries to make are:

(a) the presence of the dispose() primitive, which deallocates all 
memory and brings the object back to its .init state

(b) the presence of the dup() primitive, which creates a full-blown 
duplicate of the object.

The interesting part of the sample is RefImpl, which has a couple of 
quite interesting details:

(a) All interaction with the held object is done via opDispatch. In fact 
opDispatch can be engineered to statically enforce no reference to the 
held object escapes.

(b) A const/immutable call against a non-existing is silently converted 
into a call against a default-initialized object.

(c) If a call works and returns the same type for a non-const and a 
const object, then the const version is preferred. This is to reduce the 
number of calls to ensureUnique().

Destroy.

Andrei