gistfile1.scala

import scala.reflect.macros.Context
import scala.language.experimental.macros
import scala.annotation.StaticAnnotation

object builderMacro {
  def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
    import c.universe._
    import Flag._

    val optType = typeOf[Option[Any]]
    println(typeOf[String] <:< optType)

    val result = {
      annottees.map(_.tree).toList match {
        case q"case class $name(..$args)" :: Nil =>
          val props = args.collect {
            case q"$mods val $vname:$tpt = $expr" if tpt.tpe <:< typeOf[Option[_]] => 
              q"val $vname:$tpt = $expr"
            case vd: ValDef => vd
          }
          val newName = TypeName(name.decoded + "Builder")
          q"""
          case class $newName(..$props)
          """
      }
    }
    c.Expr[Any](result)
  }
}

class builder extends StaticAnnotation {
  def macroTransform(annottees: Any*) = macro builderMacro.impl
}


object Test extends App {
  @builder
  case class TestClass(x: Int = 4, y: Option[String] = Some("xx"))

  val x = TestClassBuilder()
  println(x.x)
  println(x.yValue)
}