Shouldn't this trigger a warning?

gistfile1.txt

09:21:58 dbrady@orthanc:~  ruby-2.0.0-p247 
∫ ruby -W4 temp.rb
true
09:22:05 dbrady@orthanc:~  ruby-2.0.0-p247 
∫ cat temp.rb
class Ponk
  def initialize(x)
    @x = x
  end

  def new_x?
    ! !! !! !!(@x)
  end
end

puts Ponk.new(nil).new_x?.inspect