custom attribute proposal (yeah, another one)

[Steven Schveighoffer]

On Fri, 06 Apr 2012 09:23:01 -0400, Steven Schveighoffer  
<schveiguy at yahoo.com> wrote:

> 7. One can lookup whether an attribute exists on a symbol using  
> __traits(hasAttribute, symbol).
> 8. One can retrieve the value of the CTFE result using  
> __traits(getAttribute, symbol).  If the CTFE function returns void, this  
> is a compiler error.

Boy, this was underspecified!

__traits(hasAttribute, attribute, symbol)
__traits(getAttribute, attribute, symbol)

> string serialize(T)(const ref T t) if (__traits(hasAttribute,  
> serializable) && __traits(getAttribute, serializable))

again:

if (__traits(hasAttribute, serializable, T) && __traits(getAttribute,  
serializable, T))

-Steve