In the language definition <http://d-programming-language.org/struct.html>, it says:

> Struct assignment t=s is defined to be semantically equivalent to:
>   t = S.opAssign(s);
> where opAssign is a member function of S:
>   S* opAssign(S s)
>   {   ... bitcopy *this into tmp ...
>       ... bitcopy s into *this ...
>       ... call destructor on tmp ...
>       return this;
>   }

I'm struggling with this on 4 fronts:

1. What is `this`, when opAssign is called off of the type? (does it even make sense to call a member function without an instance?)
2. The return value of opAssign is `S*`, so it would seem that `t` is assigned a pointer value?
3. What is `tmp`, just another stack allocated instance of S?
4. What is the syntax for explicitly calling the destructor? (In C++, it is tmp.~S(), but in D would it be tmp.~this() or what?)

On Sat, 22 Oct 2011 03:21:09 +0000, Sean Silva wrote:

> I'm struggling with this on 4 fronts:
> 
> 1. What is `this`, when opAssign is called off of the type? (does it even make sense to call a member function without an instance?)

Please file a bug on http://d.puremagic.com/issues/

The example doesn't even compile:

Error: cannot implicitly convert expression (this) of type S to S*

> 2. The return value of opAssign is `S*`, so it would seem that `t` is assigned a pointer value?

The correct information is:

t=s is defined to be semantically equivalent to:

t.opAssign(s)

which means a signature of just

void opAssign(ref const S rhs) {
    //...
}

> 3. What is `tmp`, just another stack allocated instance of S?

I think it is just an example of something you might do.

> 4. What is the syntax for explicitly calling the destructor? (In C++, it
> is tmp.~S(), but in D would it be tmp.~this() or what?)

You don't. If you want to destroy use, clear(s);