d.erl

-module(d).

-export([sum_user/0]).

-spec sum_user() -> {ok, [{binary(), integer()}]}
                        | {error, term()}.
sum_user() ->
    BucketUsages = [maybe_sum_bucket()],
    {ok, BucketUsages}.

-spec maybe_sum_bucket() ->
                              {string(), string()} |
                              {string(), [{string(), integer()}]}.
maybe_sum_bucket() ->
    Bucket = <<"binary">>,
    case sum_bucket() of
        {struct, _} = BucketUsage -> {Bucket, BucketUsage};

        {error, _} = E ->
            {Bucket, iolist_to_binary(io_lib:format("~p", [E]))}
    end.

-spec sum_bucket() ->
                        {struct, [{binary(), non_neg_integer()}]} |
                        {error, term()}.
sum_bucket() ->
    {ok, Results} = {ok, [{1, [{int(), int()}]}]},
    {1, [{Objects, Bytes}]} = lists:keyfind(1, 1, Results),
    {struct, [{<<"Objects">>, Objects},
              {<<"Bytes">>, Bytes}]}.

-spec int() -> non_neg_integer().
int() -> 23.
     

gistfile1.txt

$ erlc  +debug_info d.erl && dialyzer --build_plt d.beam
d.erl:32: Warning: this clause cannot match because a previous clause at line 28 always matches
  Creating PLT /home/kuenishi/.dialyzer_plt ... done in 0m0.14s
done (passed successfully)
$ dialyzer .
  Checking whether the PLT /home/kuenishi/.dialyzer_plt is up-to-date... yes
  Proceeding with analysis...
d.erl:5: Invalid type specification for function d:sum_user/0. The success typing is () -> {'ok',[{<<_:48>>,{_,_}},...]}
d.erl:11: Invalid type specification for function d:maybe_sum_bucket/0. The success typing is () -> {<<_:48>>,{'struct',[{_,_},...]}}
d.erl:19: The pattern E = {'error', _} can never match the type {'struct',[{<<_:40,_:_*16>>,23},...]}
d.erl:32: The pattern {'error', Error} can never match the type {'ok',[{1,[{23,23},...]},...]}
 done in 0m0.14s
done (warnings were emitted)