pass by value && elide dtor + post-blit

[Ali Çehreli via Digitalmars-d-learn]

On 06/20/2015 02:09 PM, Xiaoxi wrote:
> When passing a struct by value:
>
> Is there any way to trick the compiler to elide unnecessary post-blit &
> dtor pair?
>
> Maybe using an union, somehow?
>

Can you show with an example please. I don't see either of those called 
for the following program:

import std.stdio;

struct S
{
     this(int)
     {
         writeln(__FUNCTION__);
     }

     this(this)
     {
         writeln(__FUNCTION__);
     }

     ~this()
     {
         writeln(__FUNCTION__);
     }
}

S foo()
{
     auto s = S(42);
     return s;
}

void main()
{
     writeln("before");
     auto s = foo();
     writeln("after");
}

The output:

before
deneme.S.this
after
deneme.S.~this

Ali