Proposal: user defined attributes

[Martin Nowak]

>>> Note that one library that did attempt runtime reflection capability
>>> (flectioned) does all this at runtime, and does some really funky shit,
>>> like opening /proc/self/map on Linux, or requiring you to pass an
>>> OPTLINK map file. I don't look at these as "innovations" as much as I  
>>> do
>>> as workarounds.
>>
>> Maybe there's a better approach than flectioned. Consider the language  
>> is frozen solid. How would you solve problems with it?
>
> I think the closest anyone has come is Jacob, with his orange library.   
> Maybe he can respond to this point.
>
> -Steve

Just showing this because it never comes up that one can already implement
runtime reflection using ModuleInfo.xgetMembers and  
TypeInfo_Struct.xgetMembers.

module a;
import std.stdio, std.variant;

void main()
{
     foreach(m; ModuleInfo)
     {
         if (m.name != "b") continue;
	// getMembers currently doesn't work for classes,
         // but it does for modules/structs
         auto get = cast(Variant function(string))m.xgetMembers;
         auto bfunc = get("bfunc").get!(size_t function());
         writeln(bfunc());
     }
}


module b;
import std.variant;

// a pointer to this method will end up in ModuleInfo xgetMembers
Variant getMembers(string name)
{
     Variant res;
     switch (name)
     {
     case "bfunc": return Variant(&bfunc);
     default: return Variant("member "~name~" not found");
     }
}

size_t bfunc()
{
     return 2;
}

It should be fairly easy to construct some helpers that make the compile  
time data digestible.