Usually when something is called "meta" it means that it is special and does not compose.

I had someone explaining D templates to me on an Idris meetup, but it's been a few years, so I might very well be wrong here and not remember correctly. I'm happy to be corrected.

My next question would be: can I write those meta templates myself and modify them with themselves? In the same way that I could have a type-level function that applies another type-level function twice and then apply it on itself to get a new type-level function that applies another type-level function four times.