scala.xml.Node toString does not allow extending the Node class

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With Scala 2.9.2 you could extend a scala.xml.Node and create your own class. When you use toString, the default case would print out the custom Node much like an Elem, since this was the catch all implementation.

Since this commit (see src/library/scala/xml/Utility.scala): scala/scala@e7ea29c

The behavior changed to printing Elem and throwing an exception when it was not one of the known sub-classes of Node.

This means the user can no longer extend the XML hierarchy with his own classes and use toString, since any XML tree that includes custom classes extending Node will throw exceptions on a toString.

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Imported From: https://issues.scala-lang.org/browse/SI-6800?orig=1
Reporter: Thomas Santana (nebulorum)
Affected Versions: 2.10.0-RC5

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@SethTisue said:
The scala-xml library is now community-maintained. Issues with it are now tracked at https://github.com/scala/scala-xml/issues instead of here in the Scala JIRA.

Interested community members: if you consider this issue significant, feel free to open a new issue for it on GitHub, with links in both directions.