temporary objects are not allowed to be pass by ref anymore

[Mike Parker]

Denis Koroskin wrote:
> What's a rationale behind an issue described bug 2621?
> http://d.puremagic.com/issues/show_bug.cgi?id=2621
> 
> Why isn't it allowed anymore?
> 
> It broke quite a lot of my code. And while it is fixable by doing
> 
> auto tmp = someFunctionThatRetunsStruct();
> someMethodThatAcceptsStructByReference(tmp);
> 
> it looks ugly and unnecessary.

Yeah, I was recently caught by this when moving some code over to D2, 
thinking I'd take advantage of some const refs. I was quite surprised 
when my code wouldn't compile. Consider:

struct Foo
{
     int x;

     Foo opAdd(const ref Foo lhs)
     {
         Foo f = {x + lhs.x};
         return f;
     }

     ref Foo opAddAssign(const ref Foo lhs)
     {
         x += lhs.x;
         return f;
     }
}


Given Foo a, b and c, the following fails to compile:
c += a + b;

The work around is to add an overridden opAddAssign that takes a non-ref 
foo. Not pretty, especially when dealing with numerous methods. Rather 
defeats the purpose of const ref parameters, does it not? And it's far 
from intuitive, particularly when coming from C++.