DIP 1018--The Copy Constructor--Community Review Round 1

[RazvanN]

On Wednesday, 9 January 2019 at 14:25:44 UTC, Atila Neves wrote:

> I didn't either until the example in the DIP:
>
> -----------
> struct C { this(ref C) {} }
> void fun(C c) {}
> void main() {
>     C c;
>     fun(c);
> }
> -----------
>
> c is moved before the DIP, and copied afterwards due to the 
> existing constructor being considered a copy constructor.

C is not moved in this situation. The following code:

struct C { this(this) { import std.stdio; writeln("postblit"); } }
void fun(C c) {}
void main()
{
     C c;
     fun(c);
}

prints "postblit". Am I missing something?

> I wasn't referring to opMove, no, but I think adding a `this(C 
> c)` constructor to the example would do it for rvalues?

The copy constructor is called solely on lvalues. `this(C c)` is 
a simple constructor that needs to be called explicitly.