DIP69 - Implement scope for escape proof references

[Dicebot via Digitalmars-d]

On Saturday, 13 December 2014 at 00:10:07 UTC, Walter Bright 
wrote:
> The proposal provides escape proof passing of arguments. This 
> is necessary in order to make rc safe, for example.
>
> What are you looking for?

I am looking for a tool to prevent escaping references to 
user-defined entities / resources from specific scope. RC case is 
not interesting at all to me though I recognize the potential 
benefits of tweaking the scope system to help with it. But there 
is a big difference between tweak for one specific use case or 
designing feature around it (so it becomes almost useless in 
other cases).

I have already provided you an example of code I want to be 
enforced with scope and two major issues with existing proposal 
that make it lacking. This example is akin to litmus test for any 
scope proposal - if it doesn't allow to express such design, that 
proposal is simply not good enough.

In case you have forgotten, I am reminding about two critical 
points that are necessary to make it fly:

1) inout analog for scope to be able to deduce borrowship of 
return values based on borrowship of input arguments. Current 
system is conservative and results in template bloat (complicated 
by the fact that it is storage class thus not actually part of a 
type)

2) at least optional transitivity to be able to express to 
protect with scope data referenced by slice or owned linked list 
referenced from root node.

------

In your tree example I would have never wanted scope protection 
of one specific node of such tree - but a transitive scope 
protection of whole tree view available through on of node 
pointers/references. It doesn't matter who and how owns the data 
for borrowship implementation - only thing that matters that _it 
is not me_.