module FooBo
  class Bar
    a = 5 + foo
  end
end

-- -- --
s(:list,  [s(:module,  "FooBo",  [s(:class,  "Bar",  nil,  [s(:assign, 
  s(:name,  "a"), 
  s(:operator,  "+", 
    s(:int,  5), 
    s(:name,  "foo")))])])])