%%---------------------------------------------------------------------------
%% From: Nicolas Tranger <[email protected]>
%% Date: 10/11/2110
%%
%% After adding spec statements to my module, Dialyzer failed on execution
%% though. I've been trying to create a minimal reproducible case and
%% reduced the code to something similar of about 80 LOC. As noted in the
%% comments, commenting out some lines makes Dialyzer parse and analyze
%% the file correctly. The code executes correctly and as expected.
%%
%% I'm not sure what causes the issue. parse_result is polymorphic in its
%% return type, but statically typed based on the type of the 3th argument
%% (well, that's how I see things from a Haskell background).
%%---------------------------------------------------------------------------
%% This was a bug in erl_types:t_subtract/2 which was not handling the case
%% of free variables in prameterized types. Fixed 15/10/2010.
%%---------------------------------------------------------------------------
-module(param_types_crash).
-export([test/0]).
-type socket_error() :: 'connection_closed' | 'timeout'.
-type app_error() :: 'no_magic' | 'unknown_failure'.
-type resulthandler_result(T) :: {'ok', T} | socket_error() | app_error().
-type resulthandler(T) :: fun((binary()) -> resulthandler_result(T)).
test() ->
Data = <<0:32/little-unsigned, 1:8/little, 1:8/little-unsigned>>,
case parse_result(Data, get_option(fun get_bool/1)) of
%% Removing the next 2 lines makes
%% dialyzer param_types_crash.erl -Wunmatched_returns -Wunderspecs
%% succeed. With these lines, it fails.
{ok, none} -> none;
{ok, {some, Value}} -> Value;
Reply -> {error, Reply}
end.
-spec parse_result(binary(), resulthandler(T)) -> resulthandler_result(T).
parse_result(<<ResultCode:32/little-unsigned, Rest/binary>>, ResultHandler) ->
case ResultCode of
0 -> ResultHandler(Rest);
1 -> no_magic;
2 -> unknown_failure
end.
-spec get_bool(binary()) -> {'ok', boolean()} | socket_error().
get_bool(Data) ->
case get_data(Data, 1, size(Data)) of
{<<Value:8/little-unsigned>>, <<>>} -> {ok, (Value =:= 1)};
Other -> Other
end.
-spec get_option(resulthandler(T)) -> resulthandler('none' | {'some', T}).
get_option(Fun) ->
fun(Data) ->
case get_data(Data, 1, size(Data)) of
{<<HasValue:8/little>>, Rest} ->
case HasValue of
0 -> {ok, none};
1 -> {ok, Value} = Fun(Rest),
{ok, {some, Value}}
end;
Other -> Other
end
end.
-spec get_data(binary(), non_neg_integer(), non_neg_integer()) ->
{binary(), binary()} | socket_error().
get_data(Data, Length, Received) when Length > Received ->
case Data of
<<>> -> connection_closed;
_ -> timeout
end;
get_data(Data, Length, _) ->
<<Bin:Length/binary, Rest/binary>> = Data,
{Bin, Rest}.
