scalafix_ccc.scala

// Fake Scalafix rule to rewrite Scala to CCC
// Just so that you catch the idea
final case class CCCRule(index: SemanticdbIndex) extends SemanticRule(index, "CCCRule") {

  def convertSubTree(ctx: RuleCtx, v: Tree, tree: Tree): Tree = {
    tree match {
      // the identity morphism
      case t@q"$x => ${y: Term.Name}" if (x.name.isEqual(y)) =>
        q"""K.id[${x.decltpe.get}]"""
        
      // the plus function completely hardcoded and supposing we have CCC & CCCNumExt in the context
      case t@q"$px => $py => $x + $y" =>
        q"""○(addC)(⨂(exl[${x.decltpe.get}, ${x.decltpe.get}])(exr[${px.decltpe.get}, ${py.decltpe.get}]))"""

  }
  override def fix(ctx: RuleCtx): Patch = {
    val trees = convertTree(ctx, ctx.tree)
    trees.map { case (tree, newTree) => ctx.replaceTree(tree, newTree.toString) }.asPatch
  }
}