module app; 

void main()

{

    auto n = new Node(); 

    auto r = new RootNode(); 

    auto s = new SpriteNode(); 

    auto nt = new NotTagged(); 

    auto un = new Unique(); 

​

    workFunction(nt); 

    workFunction(un); 

    workFunction(n); 

    workFunction(r); 

    workFunction(s); 

}

​

class NotTagged : Node{}

​

/* https://issues.dlang.org/show_bug.cgi?id=18718

static foreach(m; __traits(allMembers, mixin("app")))

{

    pragma(msg, m); 

}

*/

​

@Node class Node{}

​

@RootNode class RootNode : Node{}

​

@SpriteNode class SpriteNode : Node{}

​

@Node @Unique class Unique : Node{}

​

template isSpecified(T)

{

    bool isSpecified(U)()

    {

        return is(T == U); 

    } 

}

​

void workFunction(T)(T object)

{

    import std.meta : anySatisfy, staticIndexOf; 

    import std.stdio : writeln; 

    /*

    case for non exclusive tags, the else branch handle an abstract, untagged case. 

    */ 

    static if(__traits(getAttributes, T).length)

    {

        static if(anySatisfy!(isSpecified!SpriteNode, __traits(getAttributes, T)))

        {

            writeln("got SpriteNode");

        }

        static if(anySatisfy!(isSpecified!RootNode, __traits(getAttributes, T)))

        {

            writeln("got RootNode");

        }

        // nothing happens, when there is a tag, which is not explicitely described. 

    }   

    else

    {

        writeln("got something abstract");

        writeln(__traits(getAttributes, T).stringof);

    }

​

    /*

    case for exclusive tags, there can be only one, because of "else static if's".

    Case "without a tag" is asserted as false. 

    */ 

    static if(__traits(getAttributes, T).length)

    {

        static if(staticIndexOf!(SpriteNode, __traits(getAttributes, T)) > -1)

        {

            writeln("got SpriteNode");

        }

        else static if(staticIndexOf!(RootNode, __traits(getAttributes, T)) > -1)

        {

            writeln("got RootNode");

        }

        else

        {

            writeln("got something abstract");

            writeln(__traits(getAttributes, T).stringof);

        }

    }

    else

    {

        writeln("got an untagged class");

    }

}