DIP54 : revamp of Phobos tuple types

[Dicebot]

On Monday, 23 December 2013 at 01:39:26 UTC, Dicebot wrote:
> http://wiki.dlang.org/DIP54
>
> This is follow-up of several hot discussion threads that have 
> happened several months ago. It has become pretty clear that 
> there is no good way out of existing situation and least bad 
> needs to be picked just to move forward (because it still be 
> better than current horrible one)
>
> Linked proposal was discussed in short e-mail conversation with 
> Andrei (with silent observation with Walter) and is mostly 
> pre-approved. I am interested in general opinion of community 
> and suggestions for any smaller tweaks before starting to work 
> on pull requests.
>
> Thanks for your attention.

Small update on this.

I have chosen to go route of investigating compiler enhancement 
possibilities first to allow cleaner argument pack 
implementation. After some tweaks it was relatively easy to make 
work these two samples:

-----
struct X
{
     static int opSlice(size_t l, size_t u) { return l + u; }
}

pragma(msg, X[1..2]);
-----

and

-----
struct X
{
     // note the template args
     static auto opSlice(size_t l, size_t u)() { return l + u; }
}

pragma(msg, X[1..2]);
-----

However I am still struggling with more practical example:

-----
struct X(T...)
{
     static auto opSlice(size_t l, size_t u)() { return 
X!(T[l..u]); }
}

alias Y = (X!(1, 2, 3))[1..2];
-----

It seems to take completely different processing path, one that 
does not allow obvious syntax rewriting before semantic pass. I 
think I'll throw few more weeks into trying this and proceed with 
crappy alternative upon failure.