test if the alias of a template is a literal

[Gianni Pisetta via Digitalmars-d-learn]

Hi all,
I have an AliasSeq composed of literal strings, variables and 
delegates. I want to build a template Optimize that will return 
an AliasSeq that have all adjacent literals concatenated into 
one. So i writed something like this:

template isStringLiteral(alias V) {
    enum bool isStringLiteral = ( is( typeof( V ) == string ) );
}

template Optimize(Os...) {
    static if ( Os.length < 2 )
        alias Optimize = Os;
    else {
        alias Optimized = Optimize!(Os[1..$]);

        static if ( isStringLiteral!(Os[0]) && 
isStringLiteral!(Optimized[0]) ) {
            enum string First = Os[0] ~ Optimized[0];
            alias Rest = Optimized[1..$];
        }
        else {
            alias First = AliasSeq!(Os[0]);
            alias Rest = Optimized;
        }
        alias Optimize = AliasSeq!(First, Rest);
    }
}

but at the moment isStringLiteral will return true even with 
variables of type string. So i searched for a metod to check if 
an alias is a literal value, but found nothing. Anyone have any 
clue on how can be done?

Thanks,
Gianni Pisetta