Fix server loop detection

Dialyzer does not normally emit warnings for functions that
implement non-terminating server loops. This detection failed
when some of the elements in an SCC terminated normally (being
for example list comprehensions or other generic anonymous
functions that were included in the SCC). This patch fixes that.

3 files changed, 48 insertions, 6 deletions

diff --git a/lib/dialyzer/src/dialyzer_typesig.erl b/lib/dialyzer/src/dialyzer_typesig.erl
index c45615d670..65c2ff76bb 100644
--- a/lib/dialyzer/src/dialyzer_typesig.erl
+++ b/lib/dialyzer/src/dialyzer_typesig.erl
@@ -1684,11 +1684,14 @@ solve_scc(SCC, Map, State, TryingUnit) ->
     true ->
       ?debug("SCC ~w reached fixpoint\n", [SCC]),
       NewTypes = unsafe_lookup_type_list(Funs, Map2),
-      case lists:all(fun(T) -> t_is_none(t_fun_range(T)) end, NewTypes)
+      case erl_types:any_none([t_fun_range(T) || T <- NewTypes])
 	andalso TryingUnit =:= false of
 	true ->
-	  UnitTypes = [t_fun(state__fun_arity(F, State), t_unit())
-		       || F <- Funs],
+	  UnitTypes =
+	    [case t_is_none(t_fun_range(T)) of
+	       false -> T;
+	       true -> t_fun(t_fun_args(T), t_unit())
+	     end || T <- NewTypes],
 	  Map3 = enter_type_lists(Funs, UnitTypes, Map2),
 	  solve_scc(SCC, Map3, State, true);
 	false ->
diff --git a/lib/dialyzer/test/r9c_SUITE_data/results/inets b/lib/dialyzer/test/r9c_SUITE_data/results/inets
index fd5e36a3cd..a0551e10d7 100644
--- a/lib/dialyzer/test/r9c_SUITE_data/results/inets
+++ b/lib/dialyzer/test/r9c_SUITE_data/results/inets
@@ -7,9 +7,6 @@ http_lib.erl:286: The call http_lib:close('ip_comm' | {'ssl',_},any()) will neve
 http_lib.erl:424: The variable _ can never match since previous clauses completely covered the type any()
 http_lib.erl:438: The variable _ can never match since previous clauses completely covered the type any()
 http_lib.erl:99: Function getHeaderValue/2 will never be called
-httpc_handler.erl:322: Function status_continue/2 has no local return
-httpc_handler.erl:37: Function init_connection/2 has no local return
-httpc_handler.erl:65: Function next_response_with_request/2 has no local return
 httpc_handler.erl:660: Function exit_session_ok/2 has no local return
 httpc_manager.erl:145: The pattern {ErrorReply, State2} can never match the type {{'ok',number()},number(),#state{reqid::number()}}
 httpc_manager.erl:160: The pattern {ErrorReply, State2} can never match the type {{'ok',number()},number(),#state{reqid::number()}}
diff --git a/lib/dialyzer/test/small_SUITE_data/src/no_return_bug.erl b/lib/dialyzer/test/small_SUITE_data/src/no_return_bug.erl
new file mode 100644
index 0000000000..5c24902590
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/no_return_bug.erl
@@ -0,0 +1,42 @@
+%% Dialyzer couldn't infer that monitor_diskspace would go in an infinite loop
+%% instead of crashing due to the existence of list comprehensions that have a
+%% normal success typing. These were added to the monitor_diskspace's SCC and
+%% dialyzer_typesig didn't try to assign unit() to monitor_diskspace, as it
+%% required all the members of the SCC to return none().
+%%
+%% Testcase was submitted in erlang-questions mailing list by Prashanth Mundkur
+%% (http://erlang.org/pipermail/erlang-questions/2011-May/058063.html)
+
+-module(no_return_bug).
+-export([diskspace/1, monitor_diskspace/2, refresh_tags/1, monitor_launch/0]).
+
+-type diskinfo() :: {non_neg_integer(), non_neg_integer()}.
+
+-spec diskspace(nonempty_string()) -> {'ok', diskinfo()} | {'error', term()}.
+diskspace(Path) ->
+    case Path of
+        "a" -> {ok, {0,0}};
+        _ -> {error, error}
+    end.
+
+-spec monitor_diskspace(nonempty_string(),
+                        [{diskinfo(), nonempty_string()}]) ->
+                               no_return().
+monitor_diskspace(Root, Vols) ->
+    Df = fun(VolName) ->
+                 diskspace(filename:join([Root, VolName]))
+         end,
+    NewVols = [{Space, VolName}
+               || {VolName, {ok, Space}}
+                      <- [{VolName, Df(VolName)}
+                          || {_OldSpace, VolName} <- Vols]],
+    monitor_diskspace(Root, NewVols).
+
+-spec refresh_tags(nonempty_string()) -> no_return().
+refresh_tags(Root) ->
+    {ok, _} = diskspace(Root),
+    refresh_tags(Root).
+
+monitor_launch() ->
+    spawn_link(fun() -> refresh_tags("abc") end),
+    spawn_link(fun() -> monitor_diskspace("root", [{{0,0}, "a"}]) end).