From the D Blog -- GSoC Report: Step

[ciechowoj via Digitalmars-d-announce]

On Friday, 9 September 2016 at 17:48:10 UTC, Andrej Mitrovic 
wrote:
> With regards to Sets missing from the language:
> [...]

Sure, but even if it is simple, there should be some standardized 
way to do this. To not force the people to invent the set 
interface in every project again and again. And newcomers will 
look for it in the standard docs, and not in ancient manuscripts. 
I mean it isn't obvious that one should use void[0][T]...

> I'm not sure about any special syntax which is expected for 
> languages which have built-in sets. It would probably be 
> overkill to add syntax support, but I'm not sure how often 
> people use set literals or not.

E.g. Python has build in literals for sets. C++ has sets in 
standard library. I see the points against adding something like 
this to the core of language, but it should be at least in the 
standard library.