An introduction to Typeclass Metaprogramming

"Typeclass metaprogramming is a powerful technique available to Haskell programmers to automatically generate term-level code from static type information. It has been used to great effect in several popular Haskell libraries (such as the servant ecosystem), and it is the core mechanism used to implement generic programming via GHC generics. Despite this, remarkably little material exists that explains the technique, relegating it to folk knowledge known only to advanced Haskell programmers." https://lexi-lambda.github.io/blog/2021/03/25/an-introduction-to-typeclass-metaprogramming/