Compile time iota

[Dicebot via Digitalmars-d]

Things like std.typetuple, while not being as broken as std.json 
implementation-wise, deal good amount of damage being a technical 
debt. It simply unpleasant to build anything on top of it and 
Phobos lacks quite many metaprogramming utilities. It is also a 
small but important step in simplifying related learning curve.

I agree it shouldn't be considered a priority but if there is a 
work done already there - why not?