import std.typecons;
import std.traits;
import std.stdio;

class Update {
   this(string _id, string _m) {id = _id; message = _m;}
   string id;
   string message;
}

struct MessageHandler {}
struct Filter(alias f) if (isCallable!f)
{
   static bool check(Update u) { return f(u); }
}

class MyHandler {
   this() {}

   @MessageHandler
   @Filter!((Update u) => u.id == "ping" || u.id == "!ping")
   void ping(Update u) {
       writeln("pong: ", u.message);
   }

   @MessageHandler
   void all(Update u) {
       writeln("message received: ", u.message);
   }
}

class Dispather(HandlerType) {
   this(HandlerType _handler) {
       handler = _handler;
   }
   private HandlerType handler;
   void pullUpdate(Update u) {
       static foreach (handler_method; getSymbolsByUDA!(HandlerType, MessageHandler))
       {
           static if (hasUDA!(handler_method, Filter)) {
               alias filter = getUDAs!(handler_method, Filter)[0];
               if (filter.check(u)) {
                …

https://godbolt.org/z/jv6GxWb8c