I can probably find time to take a pass at the unparser, if you want.

> cls needs to be an expression node to allow for attribute lookups

That's why I suggested "identifier*"! Each identifier in the list would be one part of the dotted name, so we wouldn't need to worry about having arbitrary expressions:

Foo() -> MatchClass(["Foo"], [], [], [])
foo.bar.Baz() -> MatchClass(["foo", "bar", "Baz"], [], [], [])

Not a big deal, though.