Helper method that returns methods that might have a problem when upgrading from Ruby 1.8 to Ruby 1.9 because of shadowing block variables. With a lot of false positives...

find_candidates.rb

# foo = 1
# 5.times do |foo|
#   puts foo
# end
# return foo #=> returns 5 in Ruby 1.8, but 1 in Ruby 1.9

def files
  Dir.glob('**/*.rb')
end

def methods(file)
  /(($\s+?)def.*?\2end)/m.match(File.read(file))
end

def candidate(method)
  /(\W(\w+)\W.*\|\2\|\W.*\W\2)/m.match(method)
end

files.each do |file|
  if ms = methods(file)
    ms.captures.each do |method|
      if candidate(method)
        puts "## #{file}"
        puts "#{method}\n\n"
      end
    end
  end
end