Any way to get rid of the val values = findValues boilerplate?

[i-am-the-slime]

Hey there,

Nice library!
Wouldn't it be possible to eliminate the need for
val values = findValues by simply extending EnumEntry?
Why is this needed?

[lloydmeta]

Hey,

Thanks for the feedback :)

I'm afraid I don't quite understand how extending EnumEntry would help get rid of that piece of boilerplate. Can you show me an example of what you had in mind?

[bertderbecker]

Hey,
I have written a little macro annotation with scalameta:

class AutoFindValues extends StaticAnnotation {

  inline def apply(defn: Any): Any = meta {
    defn match {
      case obj @ Defn.Object(mods, name, templ) =>
        obj.copy(templ = templ.copy(stats = templ.stats.map(_ :+ q"val values = findValues;")))
      case _ =>
        println(defn.structure)
        abort("@AutoFindValues must annotate an object.")
    }
  }
}

Does it work for you?

[i-am-the-slime]

Hmm, seems like I understood this wrong. I thought there could just be a default implementation in EnumEntry which is lazy val values = findValues.

[i-am-the-slime]

@bertderbecker Looks good to me.

[lloydmeta]

@i-am-the-slime ah yeah, unfortunately we can't put findValues as a lazy val on the base class because the macro expansion gets invoked, at which point the macro doesn't know what the implementing superclass will be. If I remember correctly, I've experimented with this in the past and it seems to work if I make it a def values = findValues instead, but that means a new list gets constructed on every call, which seems wasteful.

@bertderbecker that's a neat trick :)