I want to create my own Tuple type

[Ola Fosheim Grøstad]

I want to create my own Tuple type, and I don't like the messy 
implementation of the one in D's standard lib, or the one in 
Clang++'s standard lib. The concept is very simple so it is 
disheartening if it cannot be done in a simple way that does not 
impact compile times... :-/

The requirements are:

1. It should not lead to slower compile times than fixed arity 
templates (if so, then I would just list all sizes from 0..64 
instead).

2. If all types are similar then it should be implemented as a 
static array with indexing. If not, then all fields should have 
the names __0, __1 etc.


Something along the lines of, but not with fixed arity:


struct Tuple(){}

struct Tuple(T0){
     T0[1] __v;
     const ref opIndex(size_t i){ return __v[i]; }
}

struct Tuple(T0,T1){
     static if (is(T0==T1)) {
         T0[2] __v;
         this(T0 a, T1 b){__v[0]=a; __v[1]=b; }
         const ref opIndex(size_t i){ return __v[i]; }
     } else {
         T0 __0;
         T1 __1;
     }
}

auto _tuple(Ts...)(Ts args){
     return __Tuple!Ts(args);
}