DIP69 - Implement scope for escape proof references

[Steven Schveighoffer via Digitalmars-d]

On 12/5/14 3:55 PM, Walter Bright wrote:
> On 12/5/2014 7:27 AM, Steven Schveighoffer wrote:
>> Can someone who knows what this new feature is supposed to do give
>> some Ali
>> Çehreli-like description on the feature? Basically, let's strip out
>> the *proof*
>> in the DIP (the how it works and why we have it), and focus on how it
>> is to be
>> used.
>>
>> I still am having a hard time wrapping my head around the benefits and
>> when to
>> use scope, scope ref, why I would use it. I'm worried that we are
>> adding all
>> this complication and it will confuse the shit out of users, to the
>> point where
>> they won't use it.
>
> The tl;dr version is when a declaration is tagged with 'scope', the
> contents of that variable will not escape the lifetime of that declaration.
>
> It means that this code will be safe:
>
>     void foo(scope int* p);
>
>     p = malloc(n);
>     foo(p);
>     free(p);
>
> The rest is all the nuts and bolts of making that work.
>

This is not what I was asking for. What I wanted to know was, when I see 
scope ref, why is it there? When should I use it? When should I use 
scope? What nasty things are prevented if I use it? Examples would be 
preferable.

Note, in your example above, marking foo pure solves the problem already.

The rules and statements give an inferred benefit. I'd like that benefit 
to be more fully explained.

-Steve