Incorrect Space difference in pattern matching exhaustivity

[abeln]

Details here: #4869 (comment)

[liufengyun]

More specifically, the following code should get a warning, but it doesn't:

abstract class AbstractFile
class PlainFile(path: String) extends AbstractFile
class VirtualFile(name: String) extends AbstractFile
abstract class ZipArchive(path: String) extends AbstractFile {
  sealed abstract class Entry(name: String) extends VirtualFile(name)
  class DirEntry(path: String) extends Entry(path)
}

object Test {
  def foo(file: AbstractFile) =  file match {
    case ze: ZipArchive#Entry =>
  }
}

[abeln]

Just to keep track of things, this is blocking #4869

[liufengyun]

I'll work on this during the weekend to unblock #4869.