Another 2.9.0 regression

https://issues.scala-lang.org/browse/SI-4586?focusedCommentId=53227#comment-53227
IIUC Debasish hit this one first, in a much more rarefied context, so it presumably didn't seem so serious a few days ago... But my colleague found a much more basic issue that I've added as a comment to #4586, because it seems to result in the same stack trace, although it may not be the same underlying issue.
In short, this crashes in 2.9.0.final:

object T4586 { 
  { val x = classOf[List[_]] }
}

But this doesn't (i.e. there's no val definition)

object T4586_Nope1 { 
  { classOf[List[_]] }
}

Nor does this (note that the declaration is in the outer scope)

object T4586_Nope2 { 
  val x = classOf[List[_]]
}

-0xe1a