Compile time sequences

[drug]

I was incorrect with description of the problem. The problem is that 
there is no simple way to distinct types and symbols if symbols are 
private. Because private symbol is not accessible you can not get any 
info on it, including is it type or symbol or value. And you can not get 
protection for types and values, because they have no protection at all. 
So you can not get protection for types and values and can not check if 
alias is type, value and symbol because it is private/protected. Vicious 
circle.

Specific case https://run.dlang.io/is/CAoxXO

Honestly, if `isType` can recognize private members the problem would be 
solved. But I think `isSymbol` and `isValue` (working with private 
members) will make situation more consistent.


Current workaround with fields is using FieldNameTuple. But I fails to 
work around private enums.