Why do struct literals count as lvalues?

[kennytm]

Timon Gehr <timon.gehr at gmx.ch> wrote:

> auto ref currently treats struct literals as lvalues too. (therefore, as
> ref). And passing by value would be considerably less efficient for large structs.
> 
> As I understand it, the only issue with allowing literals and function
> results as lvalues is that generic code cannot detect if it is working
> with a temporary or not. I don't know if this would be useful in D though.
> 
> each code segment of the form:
> 
> void foo(ref S);
> ...
> foo(S(...));
> 
> is equivalent to one explicitly declaring the temporary:
> 
> {auto __temp=S(...); foo(__temp);}
> 
> The difference is that the first is more pleasant to write. If
> temporaries would become rvalues everyone would always have to write the
> second form manually. So imho it is just a syntax sugar issue.
> 
> I'd actually argue that ref-passing should work for arbitrary function results too.

Here I propose that we go a step further and abolish the notion of rvalue
and lvalue entirely, and let the compiler insert necessary temporary
variable when needed, so that we can finally write things like

    uint w;
    memcpy(w, &5.0f, w.sizeof);
    13u = w;

</joking>