Const transitivity is bad sometimes

[Robert Fraser]

naryl wrote:
> I've found several similar cases. It happens when short-lived invariant 
> object has reference to long-lived mutable object, but not the object 
> itself. When one object creates, contains and finalizes another it is 
> logical to make contained object invariant if container is invariant. 
> But when (as in example) invariant Message is used only to deliver 
> notifier to several subscribers, transitive const doesn't fit. Of course 
> I can cast it away, but on http://www.digitalmars.com/d/const3.html it 
> states that "modification after casting away const" [is] "undefined 
> behavior".

I think in this case it should be okay as long as at least one mutable 
reference to the object exists, since the referenced object can't be 
treated as invariant.