Question

I have the following scenario:

sealed abstract class Type(val inUse: Boolean)

case class IntTy(override val inUse: Boolean) extends Type(inUse)

case class TupleTy(override val inUse: Boolean, elems: Type*) extends Type(inUse) {
  def this(elems: Type*) = this(false, elems:_*)
}

In Scala 2.8.0 this works just fine and I can create a new TupleTy instance with:

TupleTy(IntTy(false))

However, I’ve just updated to Scala 2.9.1 final and it no longer works. I now get the following error:

error: type mismatch;
found   : IntTy
required: Boolean
              TupleTy(IntTy(false))
                           ^

Is this a bug or am I missing somehing?

Answer 1

I’m not sure that it works in 2.8.0.

You have defined an additional constructor, but not an additional factory method.

new TupleTy(IntTy(false)) // works as expected

EDIT

Here is a possible workaround

case class TupleTy(override val inUse: Boolean = false)(elems: Type*) extends Type(inUse)

Now you can do ugly things like this, but you shouldn’t. No really, you shouldn’t.

TupleTy()(IntTy(false))