anchor.diff:        | Unary(_, t)
         | Label(_, t)
         | Convert(_, t) 
  -      | Function(_, _, t) -> f t
  +      | FunctionFast(_, _, t) -> 
  +        f t
         
         | Comma(a, b)
         | While(_, a, b)
  
positive.code:         | Some c -> f c
          | None -> ()
  
          
        | For(_, a, b, c, d) ->
          f a
          f b
  
negative.code:     | New of Tree * Tree list
      | Return of Tree
      | Function of string option * Scope * Tree
      | FunctionFast of string option * Scope ref * Tree
      | Invoke of Tree * Tree list
      | Label of string * Tree
      | For of string option * Tree * Tree * Tree * Tree
  