Scala macro for assigned value label in apply method

Question

From object Naming below (adapted from answer in Scala macro get enclosing line), which gathers the label associated to a value,

val x = Naming.apply("")
x: String = x

would like to modify the apply method so that it would deliver a new Naming instance where assignedName takes the assigned value label, namely,

val x = Naming()
assert( x.assignedName == "x")

In the code that follows, a naîve change like this

def apply(s: String): String = Naming( macro impl )

cannot work. Any working approach to instantiate assignedName is much valued.

case class Naming(var assignedName: String = "") {
  val m = collection.mutable.Map[String,Int]()
}

object Naming {

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

  def apply(s: String): String = macro impl 

  def impl(c: Context)(s: c.Expr[String]): c.Expr[String] = {
    import c.universe._

    c.enclosingClass.collect {
      case ValDef(_, name, _, rhs) if rhs.pos == c.macroApplication.pos =>
        c.literal(name.decoded)
    }.headOption.getOrElse(
      c.literal("")
    )
  }

}

Update In apply method, reify'ing the Naming instance with assisgnedName updated might be a solution. If viable, how could this be implemented ?