Why is 'scope' so weak?

[Lars T. Kyllingstad]

On Wed, 24 Nov 2010 10:34:10 -0600, Andrei Alexandrescu wrote:

> On 11/24/10 5:06 AM, Lars T. Kyllingstad wrote:
>> On Tue, 23 Nov 2010 23:26:54 -0500, Robert Jacques wrote:
>>
>>> On Tue, 23 Nov 2010 07:59:27 -0500, Lars T. Kyllingstad
>>> <public at kyllingen.nospamnet>  wrote:
>>>
>>>> If I've understood things correctly, by marking a delegate parameter
>>>> with 'scope' you tell the compiler not to create a true closure for
>>>> the delegate.  Effectively you're saying "I promise not to escape
>>>> this delegate, so you don't need to copy its context to the heap".
>>>>
>>>> In brief, my question is:  Why doesn't the compiler enforce this
>>>> promise?  In particular, why is 'scope' not a type constructor?
>>>
>>> For scope to be a type constructor, D requires some form of
>>> ownership-types&  local escape analysis. Just like mutable and
>>> immutable data needs const, I think stack/thread-local/shared data
>>> needs scope. (There is an old proposal on the wiki about the technical
>>> implementation, though it's badly worded) But my understanding is that
>>> all things ownership related are relegated to D3.
>>
>> Well, I think something needs to be done about it in D2 as well,
>> because right now 'scope' allows memory corruption to happen even in
>> safe mode, as demonstrated by this slightly modified example:
> [snip]
> 
> This is a bug. Could you please file it as major?


http://d.puremagic.com/issues/show_bug.cgi?id=5270

I'm curious to see what the solution to this will be.

-Lars