Using in as a parameter qualifier

[via Digitalmars-d-learn]

On Wednesday, 22 October 2014 at 19:44:49 UTC, Jonathan M Davis 
wrote:
> The only exception would be if the compiler determines that the 
> lvalue in question is never used after that call, in which 
> case, it might just move the object rather than copy it.

There's an additional restriction: local variables are guaranteed 
to live until the end of the scope they are declared in, and they 
will be destroyed in inverse order of declaration. A move can 
only happen if this guarantee wouldn't be violated. This is the 
case, for example, if the object doesn't have a destructor. If it 
does have one, it can still be moved if the call is at the end of 
the variable's scope, and the relative order of destruction of 
the other variables is unchanged. (The variable would then be 
destroyed on return inside the function, in an order depending on 
its position in the argument list.)

> So, you mean if draw was a member function of Bezier, and you 
> did something like
>
> Bezier(100, 100, 133, 200, 166, 200, 200, 200).draw()
>
> you want to know whether a copy of the Bezier object would be 
> made? The this member of a struct is a ref - in this case ref 
> Bezier - so it doesn't make a copy. The object would be 
> constructed in place and then be destroyed after it's used 
> (though exactly when it would be destroyed if the object were 
> created and called in a complex expression, I'm not sure - 
> possibly as soon as the function call terminated, possibly when 
> the statement completed).

AFAIK, always at the end of the entire statement, but I don't 
know about the order.