There are degrees of kludge.
Sample code at this answer, pasted below.
So as I was saying, the form of the name is in the spec at 4.6, 6.6.1. That is not ad-hoc. For every parameter pi , j with a default argument a method named f $default$n is generated which computes the default argument expression.
The lack of structured ability to access and reconstitute these generated names is a known issue (with a current thread on the ML).
import reflect._
import scala.reflect.runtime.{ currentMirror => cm }
import scala.reflect.runtime.universe._
// case class instance with default args
// Persons entering this site must be 18 or older, so assume that
case class Person(name: String, age: Int = 18) {
require(age >= 18)
}
object Test extends App {
// Person may have some default args, or not.
// normally, must Person(name = "Guy")
// we will Person(null, 18)
def newCase[A]()(implicit t: ClassTag[A]): A = {
val claas = cm classSymbol t.runtimeClass
val modul = claas.companionSymbol.asModule
val im = cm reflect (cm reflectModule modul).instance
defaut[A](im, "apply")
}
def defaut[A](im: InstanceMirror, name: String): A = {
val at = newTermName(name)
val ts = im.symbol.typeSignature
val method = (ts member at).asMethod
// either defarg or default val for type of p
def valueFor(p: Symbol, i: Int): Any = {
val defarg = ts member newTermName(s"$name$$default$$${i+1}")
if (defarg != NoSymbol) {
println(s"default $defarg")
(im reflectMethod defarg.asMethod)()
} else {
println(s"def val for $p")
p.typeSignature match {
case t if t =:= typeOf[String] => null
case t if t =:= typeOf[Int] => 0
case x => throw new IllegalArgumentException(x.toString)
}
}
}
val args = (for (ps <- method.paramss; p <- ps) yield p).zipWithIndex map (p => valueFor(p._1,p._2))
(im reflectMethod method)(args: _*).asInstanceOf[A]
}
assert(Person(name = null) == newCase[Person]())
}