Variadic grouping

[JS]

>>  alias T = Tuple!(int, int);
>>  alias Ts = Tuple!(T, T);
>>
>>  template A(S0..., S1...)
>>  {
>>      alias s0 = S0;
>>      alias s1 = S1;
>>  }
>>
>>  A!(Ts.init).s0 a;

so

alias T = Tuple!(int, int);
alias Ts = TupleSC!(T, T);

then Ts == ((int, int); (int, int))

and

alias T = TupleSC!(int, int);
alias Ts = Tuple!(T, T);

(int; int), (int; int))


and

alias T = TupleSC!(int, int);
alias Ts = TupleSC!(T, T);

(int; int); (int; int))

which all can be written longhand as TupleY!(TupleX!(int,int), 
TupleX!(int,int)).