struct template constructors

[Boris-Barboris via Digitalmars-d-learn]

On Thursday, 22 June 2017 at 19:17:13 UTC, Ali Çehreli wrote:
> No time to think about the rest of the design but just to get 
> the code compiled, replace 'ref' with 'auto ref' like so:
>
>     this(DT)(scope auto ref UniquePtr!DT rhs)
>     {
>         // ...
>     }
>
> Ali

i added this static variable:

static int destcalls = 0;

changed constructor to:

     this(DT)(scope auto ref UniquePtr!DT rhs)
     {
         // here rhs releases pointer
         pragma(msg, typeof(rhs));
     }

wich prints "UniquePtr!(B)" on my machine,
and destructor:

     ~this() { destcalls++; }

Following code compiles and runs ok:

     class A {}
     class B: A {}
     UniquePtr!A a = UniquePtr!A.make();
     assert(destcalls == 0);
     UniquePtr!A b = UniquePtr!B.make();
     assert(destcalls == 1);

Destructor is called for the result of "UniquePtr!B.make();", and 
if it actually was passed by value (wich is indicated by pragma's 
output), b's internal pointer would refer to freed heap block.