Issue with forward ranges which are reference types

[Mehrdad]

On 8/16/2011 9:05 PM, Jonathan M Davis wrote:
> Sorry that this is long, but it's very important IMHO, and I don't know how to
> make it much shorter and cover what it's supposed to cover.
>
> Okay. Your typical forward range is either an array a struct which is a value
> type (that is, copying it creates an independent range which points to the
> same elements and is not altered if the original range is altered - the
> elements that it points to aren't copied of course).<snip>
> Thoughts?
>
> - Jonathan M Davis
Funny, I was also thinking about this recently.

The trouble is that that's not the only issue. There's also the issue 
with polymorphism -- i.e., InputRangeObject is pretty much *useless* 
right now because no function ever checks for it (AFAIK... am I wrong?). 
So if you pass a random-access range object as an InputRange, the callee 
will just assume it's an InputRange and would reject it. So you're 
forced to downcast every time, which is really tedious. Things don't 
"just work" anymore.