Stregthen a spec

src/proper.erl

@@ -1,4 +1,4 @@
-%%% Copyright 2010-2011 Manolis Papadakis <manopapad@gmail.com>,
+%%% Copyright 2010-2013 Manolis Papadakis <manopapad@gmail.com>,
 %%%                     Eirini Arvaniti <eirinibob@gmail.com>
 %%%                 and Kostis Sagonas <kostis@cs.ntua.gr>
 %%%
@@ -17,7 +17,7 @@
 %%% You should have received a copy of the GNU General Public License
 %%% along with PropEr.  If not, see <http://www.gnu.org/licenses/>.
 
-%%% @copyright 2010-2011 Manolis Papadakis, Eirini Arvaniti and Kostis Sagonas
+%%% @copyright 2010-2013 Manolis Papadakis, Eirini Arvaniti and Kostis Sagonas
 %%% @version {@version}
 %%% @author Manolis Papadakis
 
@@ -657,13 +657,13 @@ global_state_erase() ->
     ok.
 
 %% @private
--spec spawn_link_migrate(fun(() -> _)) -> pid().
+-spec spawn_link_migrate(fun(() -> 'ok')) -> pid().
 spawn_link_migrate(ActualFun) ->
     PDictStuff = get(),
     Fun = fun() ->
 	      lists:foreach(fun({K,V}) -> put(K,V) end, PDictStuff),
 	      proper_arith:rand_reseed(),
-	      ActualFun()
+	      ok = ActualFun()
 	  end,
     spawn_link(Fun).