This is part 2 in a series of blog posts on macro metaprogramming in Scala 3. (Click here for part 1) In the previous part I have introduced the two macro APIs as well as several related concepts of metaprogramming with type families and implicits. If you haven’t read it already, you should do so now as the rest of the article won’t be understandable without it. In this second part, we will apply all our knowledge to a practical example and learn how to generate new classes with macros. Quite a bit of arcane magic is necessary to make this possible and it is my goal of this blog series to share with you all the tricks that I have worked out to maneuver around limitations of the compiler.
With the release of Scala 3, one of the biggest changes to the language revolves around metaprogramming: Inline-functions, match types, generic-programming tools like tuple types and Mirrors, as well as a new macro API have been added to make code generation a major concern of Scala. Naturally, one of the first things you may want to do is generate new classes, which is much harder than it sounds. My goal for this series of blog posts is to teach you all of the secret tricks to work around macro limitations and obtain the forbidden fruit (or something close to it). Part 2 can be found here.