download(artifact(...)=>url) broken

The download method that can be used to override the download URL for artifacts is broken since revision 663405 of the trunk.

Error message: undefined method `to_sym' for #<Buildr::Artifact:0xb74745ac>

My analysis of the problem is as follows.
The 'download' method in common.rb calls the 'file' method (e.g., "file(args.keys.first)").
The 'file' method in project.rb calls the path_to method (e.g., "Rake::FileTask.define_task(path_to(task_name))").
The 'path_to' method in project.rb calls the 'layout.expand' method (e.g., "File.expand_path(layout.expand(*names), base_dir)").
The 'expand' method in project.rb calls the 'to_sym' methods of its arguments, even though *args can be a one-element array containing a Buildr::Artifact instance that does not understand the 'to_sym' call (e.g., "args.compact.reject

.map(&:to_sym)").