Dialyzer bug or some problem with my code

Anthony Molinaro <>
Tue Mar 22 00:51:28 CET 2011


  Not sure if this is a bug or not, but the attached file exhibits the

% erlc tmp.erl
% erl -eval 'tmp:test(), init:stop()' -noshell
  All 2 tests passed.
% dialyzer -Wno_opaque tmp.erl
  Checking whether the PLT /Users/molinaro/.dialyzer_plt is up-to-date... yes
  Proceeding with analysis...
tmp.erl:19: Function key_in_dict/2 has no local return
Unknown functions:
 done in 0m0.63s
done (warnings were emitted)

Using R14B02.  As far as I can tell the key_in_dict function always returns
so I'm not sure why it would have no local return.  I can always work around
with -Wno_return but I already don't like the fact that I have to work around
dict being an opaque type with -Wno_opaque (is that ever going to get fixed?).


Anthony Molinaro                           <>
-------------- next part --------------
-module (tmp).

-export ([in_thing/2]).


-spec in_thing(_,_) -> boolean().
in_thing (A, B) ->
  case B of
    Dict when is_tuple (B) andalso element (1, B) =:= dict ->
      key_in_dict (A, Dict);
    List when is_list (B) ->
      key_in_list (A, List);
    _ ->

-spec key_in_dict(list(),dict()) -> boolean().
key_in_dict (Key, Dict) when is_list (Key) ->
  dict:is_key (Key, Dict)
    orelse dict:is_key (list_to_binary(Key), Dict)
    orelse dict:is_key (list_to_atom(Key), Dict).

-spec key_in_list(list(),[{any(),any()}]) -> boolean().
key_in_list (Key, List) when is_list (Key), is_list (List) ->
  proplists:is_defined (Key, List)
    orelse proplists:is_defined (list_to_binary(Key), List)
    orelse proplists:is_defined (list_to_atom(Key), List).


-define(ALIST1, [{"A","B"},{"C","D"}]).
-define(ALIST2, [{'A',"B"},{'C',"D"}]).
-define(ALIST3, [{<<"A">>,"B"},{<<"C">>,"D"}]).

in_thing_dict_test () ->
  ?assertEqual (in_thing("A",dict:from_list (?ALIST1)), true),
  ?assertEqual (in_thing("A",dict:from_list (?ALIST2)), true),
  ?assertEqual (in_thing("A",dict:from_list (?ALIST3)), true),
  ?assertEqual (in_thing("B",dict:from_list (?ALIST1)), false),
  ?assertEqual (in_thing("B",dict:from_list (?ALIST2)), false),
  ?assertEqual (in_thing("B",dict:from_list (?ALIST3)), false).

in_thing_list_test () ->
  ?assertEqual (in_thing("A",?ALIST1), true),
  ?assertEqual (in_thing("A",?ALIST2), true),
  ?assertEqual (in_thing("A",?ALIST3), true),
  ?assertEqual (in_thing("B",?ALIST1), false),
  ?assertEqual (in_thing("B",?ALIST2), false),
  ?assertEqual (in_thing("B",?ALIST3), false).


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