new_contents: # test assigning to iterator within the loop
  for i in range(2):
      print(i)
      i = 2
  
  # test assigning to range parameter within the loop
  # (since we optimise for loops, this needs checking, currently it fails)
  #n = 2
  #for i in range(n):
  #    print(i)
  #    n = 0
  
subject: Add test for semantics of for-loop that optimisation can break.