Testing for template argument being result of takeExactly

[monarch_dodra]

On Saturday, 22 September 2012 at 23:53:28 UTC, Jonathan M Davis 
wrote:
> I'm trying to test...
> [SNIP]
> - Jonathan M Davis

I *kind of* see what you are doing with U, V, W, but what's wrong 
with just doing:

----
import std.range;

template Hello(R)
    if(is(typeof(R == typeof(takeExactly(R, 1)))))
{
    alias R Hello;
}

struct S;

void main( ) {
     Hello!(int[]) a; //OK
     Hello!S b;       //FAIL
}
----
?

It seems to work for me..., but I'm not 100% sure there isn't 
something illegal/unsafe in there.