RFC: std.concepts

[Dicebot via Digitalmars-d]

It is important to leave possibility for compiler to verify that 
restricted types are used only in compliance with a concept. I am 
thinking about moving some basic primitives to druntime and 
designing it in a bit more light-weight way - for example, I 
don't like usage of Concept base class here.

Overall this is a very promising direction to develop but getting 
it to the point where it can be included into Phobos and 
advertised can be much more tricky. For now it can be useful as a 
dub package to experiment with.

I hope to provide more detailed feedback after investigating 
implementation closer.