IIRC, Scala's parser/compiler had to have a few little things added to support it even though Scala's syntax mostly supports it without messing with the internals. I could be wrong here, I am a bit fuzzy on the details. Also they sure put in a lot of effort in custom extractors and lots of other features to make it feel like the language supported it natively. But now Scala's XML support is a separate library that is not included with the distribution.