Copy Constructor DIP and implementation

[Jonathan M Davis]

On Monday, September 17, 2018 7:30:24 AM MDT rmc via Digitalmars-d-announce 
wrote:
> On Wednesday, 12 September 2018 at 16:40:45 UTC, Jonathan M Davis
>
> wrote:
> > [snip]
> > Personally, I'd rather that we just risk the code breakage
> > caused by not having an attribute for copy constructors than
> > use either @implicit or @copy, since it really only risks
> > breaking code using constructors that were intended to be copy
> > constructors but had to be called explicitly, and that code
> > would almost certainly be fine if copy constructors then became
> > implicit, but Andrei seems unwilling to do that. [snip]
> > - Jonathan M Davis
>
> I'd also vote for no attribute for copy constructors and have a
> tool to warn us of changes across compiler versions that can
> detect constructors that look like copy constructors.
>
> If dub keeps track of the dmd compiler version we could even have
> automated warnings for all dub packages.
>
> This would also start us on the road towards a tool that allows
> us to make breaking changes. At first the tool could just warn
> us. Then we could slowly add automated code transforms.
>
> Pretty sure this sort of tool has been mentioned before. This
> seems like a good use-case.

At minimum, we could use a transitionary compiler flag like we have with
other DIPs.

- Jonathan M Davis