old_contents: 'test iterating over a string'
  
  __pychecker__ = 'stringiter'
  
  def func1():
      'should generate a warning'
      s = 'string'
      for c in s:
          print 'oops', c[0]
  
  def func2():
      'should generate a warning'
      f = open('/dev/null')
      s = f.read()
      for c in s:
          print 'oops', c[0]
  
  def func3():
      'should not generate a warning'
      for i in []:
          print 'ok', i
      for i in ():
          print 'ok', i
  
  def func4():
      'should not generate a warning'
      v = []
      for i in v:
          print 'ok', i
      v = ()
      for i in v:
          print 'ok', i
  
  
new_contents: 'test iterating over a string'
  
  __pychecker__ = 'stringiter'
  
  def func1():
      'should generate a warning'
      s = 'string'
      for c in s:
          print 'oops', c[0]
  
  def func2():
      'should generate a warning'
      f = open('/dev/null')
      s = f.read()
      for c in s:
          print 'oops', c[0]
  
  def func3():
      'should not generate a warning'
      for i in []:
          print 'ok', i
      for i in ():
          print 'ok', i
  
  def func4():
      'should not generate a warning'
      v = []
      for i in v:
          print 'ok', i
      w = ()
      for i in w:
          print 'ok', i
  
  
subject: use different vars for different types