Consider this error:

$ cat t.rb
module M
   private
   def attr_accessor(*args); super; end
end

class C
   extend M
   attr_accessor :x
end

C.new.x = 1

$ ruby19 t.rb
t.rb:11:in `<main>': private method `x=' called for 
#<C:0x0000000091c670> (NoMethodError)


That looks very suspect, so I was about to file a bug report. But then I 
noticed that there is a warning reported with the -v switch:

$ ruby19 -v t.rb
ruby 1.9.2dev (2010-05-31) [x86_64-linux]
t.rb:3: warning: private attribute?
t.rb:11:in `<main>': private method `x=' called for 
#<C:0x000000012e5670> (NoMethodError)


Does anyone understand this warning? Is 'private' (without an argument) 
deprecated?