Deserializing JSON as an abstract type

[Chris]

So I'm trying to make a D wrapper for Telegram's JSON API using 
libtdjson. All results coming from the JSON API take the 
following structure:

{
   "@type": "className",
   "foo": "bar",
   "baz" {
     "@type": "otherClass"
   }
}

where every object, including nested ones, has a "@type" field 
which will correspond to a D class. There will be over 770 
possible types. So what I'm trying to figure out is how to 
deserialize the JSON so that it automatically gets parsed into 
the correct type.

I'm looking at asdf right now, but it doesn't seem like it has 
anything like that built in. Any ideas?