borrowed pointers vs ref

[Steven Schveighoffer via Digitalmars-d]

On Tue, 13 May 2014 09:50:12 -0400, Dicebot <public at dicebot.lv> wrote:

> On Tuesday, 13 May 2014 at 13:40:42 UTC, Jacob Carlborg wrote:
>> On 13/05/14 15:36, Dicebot wrote:
>>
>>> There are 2 `scope` uses to think about. One is storage class and in
>>> that context `scope` is more of owned / unique pointer. Other is
>>> parameter qualifier and that one is closer to ref / borrowed pointer.
>>>
>>> Main problem about making `ref` borrowed pointer is that you will need
>>> to prohibit storing it in function transitively. This will need to
>>> become invalid code:
>>>
>>> struct A
>>> {
>>>     int* ptr;
>>> }
>>>
>>> int* gptr;
>>>
>>> void foo(ref A a)
>>> {
>>>     gptr = a.ptr; // error, can't leak borrowed a.ptr into global  
>>> context
>>> }
>>>
>>> This feels like too much of a breakage, this is why `scope` (or `scope
>>> ref`) feels more appropriate.
>>
>> I always though "scope" would behave like that.
>
> Walter's initial post implies that he wanted to re-used `ref` for  
> borrowed pointer (which would mean same semantics as `scope` parameter  
> qualifier)

Yes, the difference here is that scope is a storage class, and only  
affects the "head", whereas borrowed would have to be transitive.

-Steve