scala: FOO cannot be cast to FOO

Question

In Scala, I am incredibly confused by this fairly tautological error message:

java.lang.ClassCastException: FOO cannot be cast to FOO

I would e

Answer 1

I've run into similar issue, and I've converted my code to use IMain#mostRecentVar introduced in Scala 2.9. Here's from CompilerMatcher I wrote:

  val main = new IMain(s)
  main.compileSources(files.map(toSourceFile(_)): _*)
  code map { c => main.interpret(c) match {
    case IR.Error => error("Error interpreting %s" format (c))
    case _ => 
  }}
  val recent = main.mostRecentVar
  val holder = main.valueOfTerm(recent)
  if (holder != Some(expected))
    println("actual: " + holder.map(_.toString).getOrElse{"None"})