copy-ctor's

[Exil]

On Saturday, 25 May 2019 at 23:15:05 UTC, Manu wrote:
> So, it seems that if an object has a postblit and a copy 
> constructor, the postblit is preferred.
>
> It also seems that if an object has a copy constructor and a 
> MEMBER with a postblit, then object has a postblit generated 
> which calls through to the member, and that is preferred.
>
> I have also noticed that if you have a union containing an item 
> with a postblit, the postblit is always called, even if the 
> item in the union is not valid:
>
> struct S(T)
> {
>   union {
>     int x = 0;
>     T y = void;
>   }
>   bool isT = false;
> }
>
> S a;
> S b = a; // calls `y's postblit, even though it's `isT` is 
> false and
> the object is `void` initialised...
>
> So, it's very hard to craft a tool like 'S', when the supplied 
> T might have a postblit and ruin everything. What are my 
> options here?
>
> Also, `hasElaborateCopyConstructor` is broken now. It should 
> know about copy ctor's.

Seems a union also calls the postblit for every object in a 
union, which makes less sense, since only one of them should be 
valid at a time.

IIRC there was also a problem with copy constructors conflicting 
with the default constructor initalizers. Would probably be best 
to iron out all these bugs now before it gets used too much.