problems with ParseTree

[Josh]

I've been having some problems with the latest git revision.
Ultimately, I have a stack trace like:

>> Tweet.select { 'something' }
ArgumentError: wrong number of arguments (4 for 3)
from /Library/Ruby/Gems/1.8/gems/ParseTree-2.0.1/lib/
parse_tree.rb:156:in `parse_tree_for_meth'
from /Library/Ruby/Gems/1.8/gems/ParseTree-2.0.1/lib/
parse_tree.rb:156:in `parse_tree_for_method'
from /Library/Ruby/Gems/1.8/gems/ParseTree-2.0.1/lib/
parse_tree.rb:68:in `translate'
from /Library/Ruby/Gems/1.8/gems/ambition-0.5.1/lib/ambition/
sexp_translator.rb:10:in `translate'
from /Library/Ruby/Gems/1.8/gems/ambition-0.5.1/lib/ambition/
processors/base.rb:85:in `to_s'
from /Library/Ruby/Gems/1.8/gems/ambition-0.5.1/lib/ambition/
context.rb:33:in `<<'
from /Library/Ruby/Gems/1.8/gems/ambition-0.5.1/lib/ambition/
api.rb:9:in `select'

The Rakefile specifies ParseTree 2.0.1.

I tried setting it to 2.1.1, and it seems to work after that.