Example of simplified macro definition that could be made possible by a compiler plugin running before namer and typer

Macro TransformBeforeTyper.scala

// Absolutely need to annotate return type!
@extend(URL) def secure: URL = macro 
  reify(new URL(s"https://${self.splice.getHost}${self.splice.getPath}"))
  
// Gets desugared to:

import scala.language.experimental.macros
import scala.reflect.macros.Context
implicit class secure(self: URL) {
  def secure = macro secureImpl.secureImpl
}
object secureImpl {
  def secureImpl(c: Context): c.Expr[URL] = {
    import c.universe._
    val Apply(_, List(selfTree)) = c.prefix.tree
    val self = c.Expr[URL](selfTree)
    reify(new URL(s"https://${self.splice.getHost}${self.splice.getPath}"))
  }
}