Why does the Scala compiler say that copy is not a member of my case class?

Question

First, this is in Scala 2.8, so it should be there! =)

I'm working on Lift's Javascript objects and I want to have the following:

case class JsVar(varName: String, andThen: String*) extends JsExp {
  // ...
  def -&(right: String) = copy(andThen=(right :: andThen.toList.reverse).reverse :_*)
}

Unfortunately, I get the following compiler error:

[error] Lift/framework/web/webkit/src/main/scala/net/liftweb/http/js/JsCommands.scala:452: not found: value copy
[error]     def -&(right: String) = copy(andThen=(right :: andThen.toList.reverse).reverse :_*)
[error]

The case class has properties, so there should be a copy method, right?

If I try this.copy I get practically the same error:

[error] Lift/framework/web/webkit/src/main/scala/net/liftweb/http/js/JsCommands.scala:452: value copy is not a member of net.liftweb.http.js.JE.JsVar
[error]     def -&(right: String) = this.copy(andThen=(right :: andThen.toList.reverse).reverse :_*)
[error]

Why is this and how can I use copy in my case class method? Or is the idea that copy is something the compiler adds after declaring my methods?

Should I just do this?

case class JsVar(varName: String, andThen: String*) extends JsExp {
  // ...
  def -&(right: String) = JsVar(varName, (right :: andThen.toList.reverse).reverse :_*)
}

Answer 1

The specification is silent on this regard, but this is actually expected. The copy method depends on default parameters, and default parameters are not allowed for repeated paramters (varargs):

It is not allowed to define any default arguments in a parameter section with a repeated parameter.

(Scala Reference, section 4.6.2 - Repeated Parameters)

scala> def f(xs: Int*) = xs
f: (xs: Int*)Int*

scala> def f(xs: Int* = List(1, 2, 3)) = xs
<console>:24: error: type mismatch;
 found   : List[Int]
 required: Int*
       def f(xs: Int* = List(1, 2, 3)) = xs
                            ^
<console>:24: error: a parameter section with a `*'-parameter is not allowed to have default arguments
       def f(xs: Int* = List(1, 2, 3)) = xs
           ^