This issue was reported by Emilian Bold via nashorn-dev list:

http://mail.openjdk.java.net/pipermail/nashorn-dev/2016-May/006142.html

Few Tree nodes expose names - like label in ContinueTree, BreakTree, name of variable in VariableTree, name of function in FunctionDeclarationTree, name of property in MemberSelectTree etc. It makes it difficult to get offsets [for editors etc.]. Would be nice if there is a way to get offsets - perhaps exposed as IdentifierTree when possible.