auto ref is on the docket

[Andrei Alexandrescu via Digitalmars-d]

On 6/21/15 10:25 PM, Walter Bright wrote:
> On 6/21/2015 10:08 PM, Steven Schveighoffer wrote:
>> On 6/22/15 12:11 AM, Andrei Alexandrescu wrote:
>>> Walter and I discussed what auto ref for templates
>>
>> You mean *non-templates*? auto ref for templates has a very well
>> defined meaning.
>>
>> And reading your post, I'm unclear what exactly happens. Does this
>> generate 2
>> functions from one, and then call the wrapper for auto-ref?
>>
>> So for instance:
>>
>> ref int fun(auto ref int x);
>>
>> What happens here?
>>
>> auto x = &fun;
>> x(5);
>>
>> -Steve
>>
>
> The idea is that fun(5) would be lowered to:
>
>     auto tmp = 5;
>     fun(tmp);

I don't think that lowering is recommended - it prolongs the lifetime of 
the temporary through the end of the caller. But that may be actually a 
good thing.

> But when talking to Andrei I didn't realize that it would be subtly
> different behavior than 'auto ref' for template functions, which makes
> me concerned that this is not a good idea.

That's fine.

> Note that one can always rewrite:
>
>      ref int fun(ref int x);
>
> into:
>
>      ref int fun()(auto ref int x);
>
> if auto ref is desired.

I don't understand this. My lowering scheme doesn't allow for that.


Andrei