static if check for array and AA

[BCS]

Kirk McDonald wrote:
> I'm fairly certain I've seen this come up before, but I can't seem to 
> rediscover the thread.
> 
> I'm trying to write a static if condition to check whether a certain 
> type is an array, and another check for an associative array. The former 
> proved to be moderately simple:
> 
> bool isArray(T) () {
>     static if (is(typeof(T.init[0])[] == T)) {
>         return true;
>     } else {
>         return false;
>     }
> }
> 
> Note that this only checks for dynamic arrays.
> 
> Associative arrays are harder. The above trick can't quite work as the 
> type of the key can't be relied upon. It's easy enough to do the check 
> using RTTI:
> 
> bool isAA(T) () {
>     TypeInfo t = typeid(T);
>     if (cast(TypeInfo_AssociativeArray) t) {
>         return true;
>     } else {
>         return false;
>     }
> }
> 
> But of course that is a runtime check, and this should really be a 
> compile-time check. (Also, the various subclasses of TypeInfo are 
> undocumented, so I'm not sure if it's a good idea to rely on them.)
> 
> Anyone else have some template judo to share?
> 
> -Kirk McDonald


template isAA(T)
{
	const isAA = is((cast(T)null).keys);
}

???

or something like that