Zero-arity unused functions Dialyzer patch

Dialyzer was not reporting unused functions with 0 arity. This was not
a real issue, until we found out that there could be cases where this
could lead to false warnings. This was the case in "no_local_return.erl".

7 files changed, 43 insertions, 32 deletions

diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index 8930054210..887b2dd049 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -316,27 +316,26 @@ analyze_module(Tree, Plt, Callgraph, Records, GetWarnings) ->
 
 analyze_loop(#state{callgraph = Callgraph, races = Races} = State) ->
   case state__get_work(State) of
-    none -> state__clean_not_called(State);
-    {Fun, NewState} ->
-      ArgTypes = state__get_args(Fun, NewState),
-      case any_none(ArgTypes) of
+    none -> State;
+    {Fun, NewState1} ->
+      {ArgTypes, IsCalled} = state__get_args_and_status(Fun, NewState1),
+      case not IsCalled of
 	true ->
-	  ?debug("Not handling1 ~w: ~s\n",
+	  ?debug("Not handling (not called) ~w: ~s\n",
 		 [state__lookup_name(get_label(Fun), State),
 		  t_to_string(t_product(ArgTypes))]),
-	  analyze_loop(NewState);
+	  analyze_loop(NewState1);
 	false ->
-	  case state__fun_env(Fun, NewState) of
+	  case state__fun_env(Fun, NewState1) of
 	    none ->
-	      ?debug("Not handling2 ~w: ~s\n",
+	      ?debug("Not handling (no env) ~w: ~s\n",
 		     [state__lookup_name(get_label(Fun), State),
 		      t_to_string(t_product(ArgTypes))]),
-	      analyze_loop(NewState);
+	      analyze_loop(NewState1);
 	    Map ->
 	      ?debug("Handling fun ~p: ~s\n",
 		     [state__lookup_name(get_label(Fun), State),
-		      t_to_string(state__fun_type(Fun, NewState))]),
-	      NewState1 = state__mark_fun_as_handled(NewState, Fun),
+		      t_to_string(state__fun_type(Fun, NewState1))]),
 	      Vars = cerl:fun_vars(Fun),
 	      Map1 = enter_type_lists(Vars, ArgTypes, Map),
 	      Body = cerl:fun_body(Fun),
@@ -2888,22 +2887,16 @@ state__new(Callgraph, Tree, Plt, Module, Records, BehaviourTranslations) ->
   TreeMap = build_tree_map(Tree),
   Funs = dict:fetch_keys(TreeMap),
   FunTab = init_fun_tab(Funs, dict:new(), TreeMap, Callgraph, Plt, Opaques),
-  Work = init_work([get_label(Tree)]),
-  Env = dict:store(top, map__new(), dict:new()),
+  ExportedFuns =
+    [Fun || Fun <- Funs--[top], dialyzer_callgraph:is_escaping(Fun, Callgraph)],
+  Work = init_work(ExportedFuns),
+  Env = lists:foldl(fun(Fun, Env) -> dict:store(Fun, map__new(), Env) end,
+		    dict:new(), Funs),
   #state{callgraph = Callgraph, envs = Env, fun_tab = FunTab, opaques = Opaques,
 	 plt = Plt, races = dialyzer_races:new(), records = Records,
 	 warning_mode = false, warnings = [], work = Work, tree_map = TreeMap,
 	 module = Module, behaviour_api_dict = BehaviourTranslations}.
 
-state__mark_fun_as_handled(#state{fun_tab = FunTab} = State, Fun0) ->
-  Fun = get_label(Fun0),
-  case dict:find(Fun, FunTab) of
-    {ok, {not_handled, Entry}} ->
-      State#state{fun_tab = dict:store(Fun, Entry, FunTab)};
-    {ok, {_, _}} ->
-      State
-  end.
-
 state__warning_mode(#state{warning_mode = WM}) ->
   WM.
 
@@ -2981,7 +2974,7 @@ state__get_warnings(#state{tree_map = TreeMap, fun_tab = FunTab,
 	{NotCalled, Ret} =
 	  case dict:fetch(get_label(Fun), FunTab) of
 	    {not_handled, {_Args0, Ret0}} -> {true, Ret0};
-	    {Args0, Ret0} -> {any_none(Args0), Ret0}
+	    {_Args0, Ret0} -> {false, Ret0}
 	  end,
 	case NotCalled of
 	  true ->
@@ -3075,11 +3068,11 @@ state__lookup_record(Tag, Arity, #state{records = Records}) ->
       error
   end.
 
-state__get_args(Tree, #state{fun_tab = FunTab}) ->
+state__get_args_and_status(Tree, #state{fun_tab = FunTab}) ->
   Fun = get_label(Tree),
   case dict:find(Fun, FunTab) of
-    {ok, {not_handled, {ArgTypes, _}}} -> ArgTypes;
-    {ok, {ArgTypes, _}} -> ArgTypes
+    {ok, {not_handled, {ArgTypes, _}}} -> {ArgTypes, false};
+    {ok, {ArgTypes, _}} -> {ArgTypes, true}
   end.
 
 build_tree_map(Tree) ->
@@ -3095,7 +3088,7 @@ build_tree_map(Tree) ->
   cerl_trees:fold(Fun, dict:new(), Tree).
 
 init_fun_tab([top|Left], Dict, TreeMap, Callgraph, Plt, Opaques) ->
-  NewDict = dict:store(top, {not_handled, {[], t_none()}}, Dict),
+  NewDict = dict:store(top, {[], t_none()}, Dict),
   init_fun_tab(Left, NewDict, TreeMap, Callgraph, Plt, Opaques);
 init_fun_tab([Fun|Left], Dict, TreeMap, Callgraph, Plt, Opaques) ->
   Arity = cerl:fun_arity(dict:fetch(Fun, TreeMap)),
@@ -3111,9 +3104,9 @@ init_fun_tab([Fun|Left], Dict, TreeMap, Callgraph, Plt, Opaques) ->
 	      false -> {Args, t_unit()}
 	    end
 	end;
-      false -> {lists:duplicate(Arity, t_none()), t_unit()}
+      false -> {not_handled, {lists:duplicate(Arity, t_none()), t_unit()}}
     end,
-  NewDict = dict:store(Fun, {not_handled, FunEntry}, Dict),
+  NewDict = dict:store(Fun, FunEntry, Dict),
   init_fun_tab(Left, NewDict, TreeMap, Callgraph, Plt, Opaques);
 init_fun_tab([], Dict, _TreeMap, _Callgraph, _Plt, _Opaques) ->
   Dict.
@@ -3137,7 +3130,8 @@ state__clean_not_called(#state{fun_tab = FunTab} = State) ->
 	     end, FunTab),
   State#state{fun_tab = NewFunTab}.
 
-state__all_fun_types(#state{fun_tab = FunTab}) ->
+state__all_fun_types(State) ->
+  #state{fun_tab = FunTab} = state__clean_not_called(State),
   Tab1 = dict:erase(top, FunTab),
   dict:map(fun(_Fun, {Args, Ret}) -> t_fun(Args, Ret)end, Tab1).
 
diff --git a/lib/dialyzer/test/options1_SUITE_data/results/compiler b/lib/dialyzer/test/options1_SUITE_data/results/compiler
index e82087ae86..6399e3e36b 100644
--- a/lib/dialyzer/test/options1_SUITE_data/results/compiler
+++ b/lib/dialyzer/test/options1_SUITE_data/results/compiler
@@ -20,6 +20,7 @@ cerl_inline.erl:2333: The pattern 'true' can never match the type 'false'
 cerl_inline.erl:2355: The pattern 'true' can never match the type 'false'
 cerl_inline.erl:238: The pattern 'true' can never match the type 'false'
 cerl_inline.erl:2436: Function filename/1 will never be called
+cerl_inline.erl:244: Function counter_stats/0 will never be called
 cerl_inline.erl:2700: The pattern 'true' can never match the type 'false'
 cerl_inline.erl:2730: The pattern <{F, L, D}, Vs> can never match the type <[1..255,...],[any()]>
 cerl_inline.erl:2738: The pattern <{F, L, D}, Vs> can never match the type <[1..255,...],[any()]>
diff --git a/lib/dialyzer/test/r9c_SUITE_data/results/inets b/lib/dialyzer/test/r9c_SUITE_data/results/inets
index 24cb39e52b..773525eb7f 100644
--- a/lib/dialyzer/test/r9c_SUITE_data/results/inets
+++ b/lib/dialyzer/test/r9c_SUITE_data/results/inets
@@ -8,6 +8,7 @@ http_lib.erl:424: The variable _ can never match since previous clauses complete
 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:660: Function exit_session_ok/2 has no local return
+httpc_handler.erl:676: Function format_time/0 will never be called
 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()}}
 httpc_manager.erl:478: The pattern {'error', Reason} can never match the type 'ok' | {number(),#session{clientclose::boolean(),pipeline::[],quelength::1}}
diff --git a/lib/dialyzer/test/small_SUITE_data/results/cerl_hipeify b/lib/dialyzer/test/small_SUITE_data/results/cerl_hipeify
index 87bf6f309f..06dc0d63ee 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/cerl_hipeify
+++ b/lib/dialyzer/test/small_SUITE_data/results/cerl_hipeify
@@ -1,4 +1,4 @@
 
 cerl_hipeify.erl:370: Function will never be called
-cerl_hipeify.erl:370: Guard test fun((none()) -> none()) =:= F::{_,_,_} | {_,_,_,_} | {_,_,_,_,_} | {_,_,_,_,_,_} | {_,_,_,_,_,_,_} can never succeed
+cerl_hipeify.erl:370: Guard test fun((none()) -> no_return()) =:= F::{_,_,_} | {_,_,_,_} | {_,_,_,_,_} | {_,_,_,_,_,_} | {_,_,_,_,_,_,_} can never succeed
 cerl_hipeify.erl:641: Function env__new_function_name/2 will never be called
diff --git a/lib/dialyzer/test/small_SUITE_data/results/inf_loop2 b/lib/dialyzer/test/small_SUITE_data/results/inf_loop2
index 7e9972ad98..142e4b2c37 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/inf_loop2
+++ b/lib/dialyzer/test/small_SUITE_data/results/inf_loop2
@@ -1,4 +1,4 @@
 
 inf_loop2.erl:18: Function test/0 has no local return
 inf_loop2.erl:19: The call lists:reverse('gazonk') will never return since it differs in the 1st argument from the success typing arguments: ([any()])
-inf_loop2.erl:22: Function loop/0 has no local return
+inf_loop2.erl:22: Function loop/0 will never be called
diff --git a/lib/dialyzer/test/small_SUITE_data/results/no_local_return b/lib/dialyzer/test/small_SUITE_data/results/no_local_return
new file mode 100644
index 0000000000..6ca1ed51d8
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/results/no_local_return
@@ -0,0 +1,3 @@
+
+no_local_return.erl:11: Function bar/1 will never be called
+no_local_return.erl:8: Function foo/0 will never be called
diff --git a/lib/dialyzer/test/small_SUITE_data/src/no_local_return.erl b/lib/dialyzer/test/small_SUITE_data/src/no_local_return.erl
new file mode 100644
index 0000000000..4e1a0b015a
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/no_local_return.erl
@@ -0,0 +1,12 @@
+-module(no_local_return).
+
+%% NOTE: No function is exported.  Dialyzer produced a bogus
+%%      'Function foo/0 has no local return' warning
+%% when in fact typer was finding correct return values for both
+%% these functions.
+
+foo() ->
+ bar(42).
+
+bar(X) ->
+ lists:duplicate(X, gazonk).