pass-by-ref semantics for structs (was Deque impl.)

[Dmitry Olshansky]

31-Jan-2013 19:21, Andrei Alexandrescu пишет:
> On 1/31/13 10:18 AM, Steven Schveighoffer wrote:
>> On Thu, 31 Jan 2013 10:12:53 -0500, Andrei Alexandrescu
>>> As far as I can tell classes have the same problem.
>>
>> Nope.
>>
>> void foo(someclass aa, int x, int y)
>> {
>> aa[x] = y;
>> }
>>
>> void main()
>> {
>> someclass aa;
>> foo(aa, 1, 2); // segfault
>> ...
>> }
>
> We could easily arrange things to segfault just the same with a
> struct-based implementation.
>

Structs are quite borked in this regard e.g. without extra efforts the 
following:

somclass aa = someclass();
foor(aa, 1, 2); // segfault, surprize someclass() is someclass.init

The current workaround I find the most sensible is:
- @disable this();
- make all constructors private
- define opCall and forward it to private constructors. 0-arg versions 
have to pass dummy and/or default values to get struct constructed

- automate this boilerplate until something in language is fixed? :)

The advantage is that the following is illegal:
someclass aa;

and the following works as expected:
auto aa = someclass(); //create empty container damn it!

-- 
Dmitry Olshansky