[bug] syntax_tool-1.6.5, injury data in erl_syntax_lib:map()

[Alexander Demidenko]

Hi,

Try to show on a synthetic example:

I have some source data:
1> X = {function,34,handle_event,2, [{clause,34,
[{var,34,'_'},{var,34,'_'}],[], [{cons,35,{tuple,35,[]},{nil,36}}]}]}.
{function,34,handle_event,2,
          [{clause,34,
                   [{var,34,'_'},{var,34,'_'}],
                   [],
                   [{cons,35,{tuple,35,[]},{nil,36}}]}]}

Now, I will try to traverse the data via erl_syntax_lib:map()

2> erl_syntax_lib:map(fun (El) -> io:format("~p~n",
[erl_syntax:revert(El)]), El end, X).
{atom,34,handle_event}
{var,34,'_'}
{var,34,'_'}
{tuple,35,[]}
{cons,35,{tuple,35,[]},{nil,35}}
{clause,34,[{var,34,'_'},{var,34,'_'}],[],[{cons,35,{tuple,35,[]},{nil,35}}]}
{function,34,handle_event,2,
          [{clause,34,
                   [{var,34,'_'},{var,34,'_'}],
                   [],
                   [{cons,35,{tuple,35,[]},{nil,35}}]}]}
{tree,function,
      {attr,34,[],none},
      {function,{tree,atom,{attr,34,[],none},handle_event},
                [{tree,clause,
                       {attr,34,[],none},
                       {clause,[{var,34,'_'},{var,34,'_'}],
                               none,
                               [{tree,list,
                                      {attr,35,[],none},
                                      {list,[{tuple,35,[]}],none}}]}}]}}


Ops, erl_syntax_lib vodoo magic, make unexpected change original
{nil,36} to {nil,35}
To test, make control measurements via erl_syntax_lib:fold()

3> erl_syntax_lib:fold(fun (El, Acc) -> io:format("~p~n", [El]) end, [], X).
{tree,atom,{attr,34,[],none},handle_event}
{var,34,'_'}
{var,34,'_'}
{tuple,35,[]}
{cons,35,{tuple,35,[]},{nil,36}}
{clause,34,[{var,34,'_'},{var,34,'_'}],[],[{cons,35,{tuple,35,[]},{nil,36}}]}
{function,34,handle_event,2,
          [{clause,34,
                   [{var,34,'_'},{var,34,'_'}],
                   [],
                   [{cons,35,{tuple,35,[]},{nil,36}}]}]}
ok

Unlike map(), fold() working correctly.


PS Test on Erlang R13B04 (erts-5.7.5) and Erlang R13B01 (erts-5.7.2)
with same results

--
---------------------------------------------
With best regards,
Alexander.