Copy Constructor DIP

[Jacob Carlborg]

On Friday, 13 July 2018 at 01:18:48 UTC, Andrei Alexandrescu 
wrote:
> On 7/12/18 2:30 PM, ag0aep6g wrote:

>> You're still potentially changing the semantics of existing 
>> code. `@implicit` can be a UDA today:
>> 
>> ----
>> enum implicit = 0;
>> struct C
>> {
>>      @implicit this(ref C another) {}
>> }
>> ----
>> 
>> Today, that's a normal constructor. With the DIP, it becomes a 
>> copy constructor.
>
> That is correct and a liability of the current DIP. That should 
> be mentioned in it.

That's easily fixed by implementing a compiler recognized UDA. 
That would mean that it would only be a copy constructor if 
"implicit" is defined in core.attribute. This would also avoid 
any special syntax in the parser. The already existing @selector 
is implemented like this.

--
/Jacob Carlborg