gistfile1.rb

require 'warnings'

class Foo
  include Warnings

  def some_call
    $-w = %w[ -shadowed ]
    list = []
    while true
      list = 1 # no warning
    end
  end

  # or this
  def some_other_call
    no_warn("shadowed") do
      list = []
      while true
        list = 1 # no warning
      end   
    end
  end

  # or this for explicitly requiring warnings
  def some_new_call
    warn("shadowed") do
      list = []
      while true
        list = 1 # this warns
      end   
    end
  end
end