Type class derivation in Scala 3

This repo contains the code to go with these slides: https://slides.com/cb372/type-class-derivation-in-scala-3

How to run the examples

Haskell

cd haskell/derivation-examples
stack run

Rust

cd rust/derivation-examples
cargo run

Scala 3 Show and Functor examples

sbt run

Scala 3 Mu gRPC server example

sbt muService/run

Notes on the Functor implementation

If you look carefully you'll see that Functor.derived is a given, which makes the use of derives completely redundant. Functor will be available even if the user doesn't bother to add derives Functor to their ADT, which is not great.

I wanted to rewrite Functor to follow the same pattern as Show, which is a lot simpler. It avoids the need for given, and it handles recursive datatypes nicely without the need for LazyWrapper. Unfortunately I couldn't quite get it to compile. You can see my attempt on the rewrite-functor branch.

PRs welcome :)