temporary objects are not allowed to be pass by ref anymore

[downs]

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.

To resolve this, let's consider two suspicions I have:

1) People use 'ref' for speed. Fairly obvious. I do it too. :)
2) People don't use 'out' for speed. This seems obvious, since 'out' does _more_ work than 'ref'.
2a) 'out' has stronger semantic meaning than 'ref'.

Because of this, I recommend allowing temporaries to be passed to 'ref' parameters, but not 'out' parameters. That way, you can still use 'out' to implement extraneous return values.