Verify tuple is a tuple of class objects?

[Steven Schveighoffer]

On Fri, 18 Feb 2011 16:15:16 -0500, Sean Eskapp <eatingstaples at gmail.com>  
wrote:

> Is there a way to "run" a template at compile time, without using a  
> member?
> What I'm trying to do is verify that every element of a tuple is a class  
> type,
> and so far, I've been doing this:
>
> template VerifyTuple(Type, Types...)
> {
> 	static assert(is(Type : Object), Type.stringof ~ " is not a class  
> type.");
>
> 	static if(Types.length == 0)
> 		alias void dummy;
> 	else
> 		alias VerifyTuple!(Types).dummy dummy;
> }
>
> and to use it, I have to do this:
> class Foo(T...)
> {
>     alias VerifyTuple!(T).dummy dummy;
> }
>
> Is there any way to just "run" the template, without bothering to use the
> dummy aliases?

eponymous should help (also cleaned up some of your code):

template VerifyTuple(Types...)
{
    static if(Types.length == 0)
       enum bool VerifyTuple = true;
    else
       enum bool VerifyTuple == is(Type : Object) &&  
VerifyTuple!(Types[1..$]);
}

class Foo(T...)
{
    static assert(VerifyTuple!(T...), "one of types in " ~ T.stringof ~ "  
is not a class");
}

It doesn't identify the specific type that isn't a class, but that could  
be done with a separate template.

-Steve