anchor.diff:  
   %%@hidden
   erl_prettypr_format_nl(Form) ->
  -    [erl_prettypr:format(Form), "\n"].
  +    with_increased_backtrace_depth(
  +      fun() -> [erl_prettypr:format(Form), "\n"] end).
   
   %%@hidden
   runtime_fn_transform(FnName, FnParseTree) ->
  
positive.code:         atom -> {atom, erl_syntax:atom_value(Node)};
          _    -> non_atom
      end.
  
negative.code: 
  %%@hidden
  runtime_fn_transform(FnName, FnParseTree, Transforms) ->
      with_increased_backtrace_depth(
        fun() ->
                Clauses = erl_syntax:function_clauses(FnParseTree),
                erl_syntax:revert(
                  apply_transforms(
                    erl_syntax:function(erl_syntax:atom(FnName), Clauses),
                    Transforms ++ [{replace_term, call_self, FnName}]))
        end).
  
  %%@hidden
  runtime_expr_transform(ExprParseTree) ->
  