anchor.diff:          | Some c -> f c
           | None -> ()
   
  -        
         | For(_, a, b, c, d) ->
           f a
           f b
  
positive.code:         f c
  
        | Object xs -> 
          for _, x in xs do f x
  
        | Switch(t, xs) -> 
          f t
  
negative.code: 
        | Block xs
        | Array xs -> 
          for x in xs do 
            f x
  
        | ForIn(_, a, b, c)
        | Ternary(a, b, c) -> 
  