Proposal for exposing parameter names to case class toString or to any method

param-name-access-proposal.scala

trait NamedElementsProduct extends Product {
  def namedElements: Iterator[(String, Any)]
}

trait HaskellLikeToString extends NamedElementsProduct {
  override def toString: String = namedElements.map((p) => p._1 + "=" + p._2).mkString(productPrefix + "(", ",", ")")
}

case class A(a: Int, b: Int) extends NamedElementsProduct with HaskellLikeToString {
  def namedElements = List(("a", a), ("b", b)).iterator
}

// with compiler, or compiler plugin, support:
//case class A(a: Int, b: Int) extends HaskellLikeToString

assert(A(1, 2).toString == "A(a=1,b=2)")

trait FunctionManifest {
  trait ParamList {
    val isImplicit: Boolean
    val params: List[Param]
  }
  trait Param[T] {
    val name: String
    val default: Option[T]
    val synthetic: Boolean
  }
  
  def name: String
  def paramLists: List[ParamList]
}

// More generally, you could request an implicit manifest of the currenct function:
def a(a: Int)(implicit pm: FunctionManifest) = {
  "you called " + pm.name
}