Merge branch 'dev' into major

13 files changed, 151 insertions, 22 deletions

diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index 7137dbc036..8cb16d8f09 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -1414,6 +1414,17 @@ do_clause(C, Arg, ArgType0, OrigArgType, Map,
 			    false ->
 			      true
 			  end;
+			[Pat0, Pat1] -> % binary comprehension
+			  case cerl:is_c_cons(Pat0) of
+			    true ->
+			      not (cerl:is_c_var(cerl:cons_hd(Pat0)) andalso
+				   cerl:is_c_var(cerl:cons_tl(Pat0)) andalso
+                                   cerl:is_c_var(Pat1) andalso
+				   cerl:is_literal(Guard) andalso
+				   (cerl:concrete(Guard) =:= true));
+			    false ->
+			      true
+			  end;
 			_ -> true
 		      end;
 		    false ->
@@ -2915,7 +2926,7 @@ state__get_warnings(#state{tree_map = TreeMap, fun_tab = FunTab,
 	    {Warn, Msg} =
 	      case dialyzer_callgraph:lookup_name(FunLbl, Callgraph) of
 		error -> {true, {unused_fun, []}};
-		{ok, {_M, F, A}} = MFA ->
+		{ok, {_M, F, A} = MFA} ->
 		  {not sets:is_element(MFA, NoWarnUnused),
 		   {unused_fun, [F, A]}}
 	      end,
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/Makefile b/lib/dialyzer/test/Makefile
index 69a8fd742e..47deb17f1d 100644
--- a/lib/dialyzer/test/Makefile
+++ b/lib/dialyzer/test/Makefile
@@ -26,7 +26,7 @@ include $(ERL_TOP)/make/otp_release_targets.mk
 
 release_tests_spec:
 	$(INSTALL_DIR) $(RELSYSDIR)
-	chmod -f -R u+w $(RELSYSDIR)
+	chmod -R u+w $(RELSYSDIR)
 	$(INSTALL_DATA) $(AUXILIARY_FILES) $(RELSYSDIR)
 	@tar cf - *_SUITE_data | (cd $(RELSYSDIR); tar xf -)
 	cd $(RELSYSDIR);\
diff --git a/lib/dialyzer/test/r9c_SUITE_data/results/asn1 b/lib/dialyzer/test/r9c_SUITE_data/results/asn1
index ac83366bc8..571e562d0d 100644
--- a/lib/dialyzer/test/r9c_SUITE_data/results/asn1
+++ b/lib/dialyzer/test/r9c_SUITE_data/results/asn1
@@ -2,7 +2,7 @@
 asn1ct.erl:1500: The variable Err can never match since previous clauses completely covered the type #type{}
 asn1ct.erl:1596: The variable _ can never match since previous clauses completely covered the type 'ber_bin_v2'
 asn1ct.erl:1673: The pattern 'all' can never match the type 'asn1_module' | 'exclusive_decode' | 'partial_decode'
-asn1ct.erl:672: The pattern <{'false', Result}, _, _> can never match the type <{'true','true'},atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()],[any()]>
+asn1ct.erl:672: The pattern <{'false', Result}, _, _> can never match the type <{'true','true'},atom() | binary() | [atom() | [any()] | char()],[any()]>
 asn1ct.erl:909: Guard test is_atom(Ext::[49 | 97 | 98 | 100 | 110 | 115]) can never succeed
 asn1ct_check.erl:1698: The pattern {'error', _} can never match the type [any()]
 asn1ct_check.erl:2733: The pattern {'type', Tag, _, _, _, _} can never match the type 'ASN1_OPEN_TYPE' | {_,_} | {'fixedtypevaluefield',_,_}
diff --git a/lib/dialyzer/test/r9c_SUITE_data/results/inets b/lib/dialyzer/test/r9c_SUITE_data/results/inets
index fd5e36a3cd..6b16dba2ff 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()}}
@@ -27,7 +24,7 @@ httpd_manager.erl:933: Function acceptor_status/1 will never be called
 httpd_request_handler.erl:374: The call httpd_response:send_status(Info::#mod{parsed_header::maybe_improper_list()},417,[32 | 66 | 98 | 100 | 103 | 105 | 111 | 116 | 121,...]) will never return since it differs in the 2nd argument from the success typing arguments: (#mod{socket_type::'ip_comm' | {'ssl',_}},100 | 301 | 304 | 400 | 401 | 403 | 404 | 412 | 414 | 416 | 500 | 501 | 503,any())
 httpd_request_handler.erl:378: The call httpd_response:send_status(Info::#mod{parsed_header::maybe_improper_list()},417,[32 | 77 | 97 | 100 | 101 | 104 | 108 | 110 | 111 | 116 | 119,...]) will never return since it differs in the 2nd argument from the success typing arguments: (#mod{socket_type::'ip_comm' | {'ssl',_}},100 | 301 | 304 | 400 | 401 | 403 | 404 | 412 | 414 | 416 | 500 | 501 | 503,any())
 httpd_request_handler.erl:401: The call httpd_response:send_status(Info::#mod{parsed_header::maybe_improper_list()},417,[32 | 77 | 97 | 100 | 101 | 104 | 108 | 110 | 111 | 116 | 119,...]) will never return since it differs in the 2nd argument from the success typing arguments: (#mod{socket_type::'ip_comm' | {'ssl',_}},100 | 301 | 304 | 400 | 401 | 403 | 404 | 412 | 414 | 416 | 500 | 501 | 503,any())
-httpd_request_handler.erl:644: The call lists:reverse(Fields0::{'error',_} | {'ok',[[any()]]}) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
+httpd_request_handler.erl:644: The call lists:reverse(Fields0::{'error',_} | {'ok',_}) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
 httpd_request_handler.erl:645: Function will never be called
 httpd_sup.erl:63: The variable Else can never match since previous clauses completely covered the type {'error',_} | {'ok',[any()],_,_}
 httpd_sup.erl:88: The pattern {'error', Reason} can never match the type {'ok',_,_}
@@ -38,17 +35,17 @@ mod_auth_plain.erl:100: The variable _ can never match since previous clauses co
 mod_auth_plain.erl:159: The variable _ can never match since previous clauses completely covered the type [any()]
 mod_auth_plain.erl:83: The variable O can never match since previous clauses completely covered the type [any()]
 mod_cgi.erl:372: The pattern {'http_response', NewAccResponse} can never match the type 'ok'
-mod_dir.erl:101: The call lists:flatten(nonempty_improper_list(atom() | binary() | [any()] | char(),atom())) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
+mod_dir.erl:101: The call lists:flatten(nonempty_improper_list(atom() | [any()] | char(),atom())) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
 mod_dir.erl:72: The pattern {'error', Reason} can never match the type {'ok',[[[any()] | char()],...]}
-mod_get.erl:135: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | binary() | [any()] | char()]>
-mod_head.erl:80: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()]>
+mod_get.erl:135: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | [any()] | char()]>
+mod_head.erl:80: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | [any()] | char()]>
 mod_htaccess.erl:460: The pattern {'error', BadData} can never match the type {'ok',_}
-mod_include.erl:193: The pattern {_, Name, {[], []}} can never match the type {[any()],[any()],maybe_improper_list()}
-mod_include.erl:195: The pattern {_, Name, {PathInfo, []}} can never match the type {[any()],[any()],maybe_improper_list()}
-mod_include.erl:197: The pattern {_, Name, {PathInfo, QueryString}} can never match the type {[any()],[any()],maybe_improper_list()}
-mod_include.erl:201: The variable Gurka can never match since previous clauses completely covered the type {[any()],[any()],maybe_improper_list()}
-mod_include.erl:692: The pattern <{'read', Reason}, Info, Path> can never match the type <{'open',atom()},#mod{},atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()]>
-mod_include.erl:706: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()]>
+mod_include.erl:193: The pattern {_, Name, {[], []}} can never match the type {[any()],[any()],string()}
+mod_include.erl:195: The pattern {_, Name, {PathInfo, []}} can never match the type {[any()],[any()],string()}
+mod_include.erl:197: The pattern {_, Name, {PathInfo, QueryString}} can never match the type {[any()],[any()],string()}
+mod_include.erl:201: The variable Gurka can never match since previous clauses completely covered the type {[any()],[any()],string()}
+mod_include.erl:692: The pattern <{'read', Reason}, Info, Path> can never match the type <{'open',atom()},#mod{},atom() | binary() | [atom() | [any()] | char()]>
+mod_include.erl:706: The pattern <{'enfile', _}, _Info, Path> can never match the type <atom(),#mod{},atom() | binary() | [atom() | [any()] | char()]>
 mod_include.erl:716: Function read_error/3 will never be called
 mod_include.erl:719: Function read_error/4 will never be called
 mod_security_server.erl:386: The variable O can never match since previous clauses completely covered the type [any()]
diff --git a/lib/dialyzer/test/r9c_SUITE_data/results/mnesia b/lib/dialyzer/test/r9c_SUITE_data/results/mnesia
index e199581a0e..b0f4d12ae5 100644
--- a/lib/dialyzer/test/r9c_SUITE_data/results/mnesia
+++ b/lib/dialyzer/test/r9c_SUITE_data/results/mnesia
@@ -6,6 +6,9 @@ mnesia_bup.erl:111: The created fun has no local return
 mnesia_bup.erl:574: Function fallback_receiver/2 has no local return
 mnesia_bup.erl:967: Function uninstall_fallback_master/2 has no local return
 mnesia_checkpoint.erl:1014: The variable Error can never match since previous clauses completely covered the type {'ok',#checkpoint_args{nodes::[any()],retainers::[any(),...]}}
+mnesia_checkpoint.erl:1209: Function system_continue/3 has no local return
+mnesia_checkpoint.erl:792: Function retainer_loop/1 has no local return
+mnesia_checkpoint.erl:894: The call sys:handle_system_msg(Msg::any(),From::any(),'no_parent','mnesia_checkpoint',[],Cp::#checkpoint_args{}) breaks the contract (Msg,From,Parent,Module,Debug,Misc) -> Void when is_subtype(Msg,term()), is_subtype(From,{pid(),Tag::_}), is_subtype(Parent,pid()), is_subtype(Module,module()), is_subtype(Debug,[dbg_opt()]), is_subtype(Misc,term()), is_subtype(Void,term())
 mnesia_controller.erl:1666: The variable Tab can never match since previous clauses completely covered the type [any()]
 mnesia_controller.erl:1679: The pattern {'stop', Reason, Reply, State2} can never match the type {'noreply',_} | {'reply',_,_} | {'stop','shutdown',#state{}}
 mnesia_controller.erl:1685: The pattern {'noreply', State2, _Timeout} can never match the type {'reply',_,_}
@@ -15,6 +18,7 @@ mnesia_frag.erl:294: The call mnesia_frag:remote_collect(Ref::reference(),{'erro
 mnesia_frag.erl:304: The call mnesia_frag:remote_collect(Ref::reference(),{'error',{'node_not_running',_}},[],OldSelectFun::fun(() -> [any()])) will never return since it differs in the 2nd argument from the success typing arguments: (reference(),'ok',[any()],fun(() -> [any()]))
 mnesia_frag.erl:312: The call mnesia_frag:remote_collect(Ref::reference(),LocalRes::{'error',_},[],OldSelectFun::fun(() -> [any()])) will never return since it differs in the 2nd argument from the success typing arguments: (reference(),'ok',[any()],fun(() -> [any()]))
 mnesia_index.erl:52: The call mnesia_lib:other_val(Var::{_,'commit_work' | 'index' | 'setorbag' | 'storage_type' | {'index',_}},_ReASoN_::any()) will never return since it differs in the 1st argument from the success typing arguments: ({_,'active_replicas' | 'where_to_read' | 'where_to_write'},any())
+mnesia_lib.erl:1028: The pattern {'EXIT', Reason} can never match the type [any()] | {'error',_}
 mnesia_lib.erl:957: The pattern {'ok', {0, _}} can never match the type 'eof' | {'error',atom()} | {'ok',binary() | string()}
 mnesia_lib.erl:959: The pattern {'ok', {_, Bin}} can never match the type 'eof' | {'error',atom()} | {'ok',binary() | string()}
 mnesia_loader.erl:36: The call mnesia_lib:other_val(Var::{_,'access_mode' | 'cstruct' | 'db_nodes' | 'setorbag' | 'snmp' | 'storage_type'},Reason::any()) will never return since it differs in the 1st argument from the success typing arguments: ({_,'active_replicas' | 'where_to_read' | 'where_to_write'},any())
@@ -30,5 +34,6 @@ mnesia_schema.erl:1258: Guard test FromS::'disc_copies' | 'disc_only_copies' | '
 mnesia_schema.erl:1639: The pattern {'false', 'mandatory'} can never match the type {'false','optional'}
 mnesia_schema.erl:2434: The variable Reason can never match since previous clauses completely covered the type {'error',_} | {'ok',_}
 mnesia_schema.erl:451: Guard test UseDirAnyway::'false' == 'true' can never succeed
+mnesia_text.erl:180: The variable T can never match since previous clauses completely covered the type {'error',{integer(),atom() | tuple(),_}} | {'ok',_}
 mnesia_tm.erl:1522: Function commit_participant/5 has no local return
 mnesia_tm.erl:2169: Function system_terminate/4 has no local return
diff --git a/lib/dialyzer/test/race_SUITE_data/results/extract_translations b/lib/dialyzer/test/race_SUITE_data/results/extract_translations
index f7d5abc6f5..62aa1aa511 100644
--- a/lib/dialyzer/test/race_SUITE_data/results/extract_translations
+++ b/lib/dialyzer/test/race_SUITE_data/results/extract_translations
@@ -1,5 +1,5 @@
 
-extract_translations.erl:140: The call ets:insert('files',{atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()]}) might have an unintended effect due to a possible race condition caused by its combination with the ets:lookup('files',File::atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()]) call in extract_translations.erl on line 135
+extract_translations.erl:140: The call ets:insert('files',{atom() | binary() | [atom() | [any()] | char()]}) might have an unintended effect due to a possible race condition caused by its combination with the ets:lookup('files',File::atom() | binary() | [atom() | [any()] | char()]) call in extract_translations.erl on line 135
 extract_translations.erl:146: The call ets:insert('translations',{_,[]}) might have an unintended effect due to a possible race condition caused by its combination with the ets:lookup('translations',Str::any()) call in extract_translations.erl on line 126
-extract_translations.erl:152: The call ets:insert('files',{atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()]}) might have an unintended effect due to a possible race condition caused by its combination with the ets:lookup('files',File::atom() | binary() | [atom() | binary() | [atom() | binary() | [any()] | char()] | char()]) call in extract_translations.erl on line 148
+extract_translations.erl:152: The call ets:insert('files',{atom() | binary() | [atom() | [any()] | char()]}) might have an unintended effect due to a possible race condition caused by its combination with the ets:lookup('files',File::atom() | binary() | [atom() | [any()] | char()]) call in extract_translations.erl on line 148
 extract_translations.erl:154: The call ets:insert('translations',{_,[]}) might have an unintended effect due to a possible race condition caused by its combination with the ets:lookup('translations',Str::any()) call in extract_translations.erl on line 126
diff --git a/lib/dialyzer/test/small_SUITE_data/results/flatten b/lib/dialyzer/test/small_SUITE_data/results/flatten
index 4571214e49..8aa44dd002 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/flatten
+++ b/lib/dialyzer/test/small_SUITE_data/results/flatten
@@ -1,2 +1,2 @@
 
-flatten.erl:17: The call lists:flatten(nonempty_improper_list(atom() | binary() | [any()] | char(),atom())) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
+flatten.erl:17: The call lists:flatten(nonempty_improper_list(atom() | [any()] | char(),atom())) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
diff --git a/lib/dialyzer/test/small_SUITE_data/src/binary_lc_bug.erl b/lib/dialyzer/test/small_SUITE_data/src/binary_lc_bug.erl
new file mode 100644
index 0000000000..c1e82bfa59
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/binary_lc_bug.erl
@@ -0,0 +1,8 @@
+-module(test).
+
+-export([bin_compr/0]).
+
+bin_compr() ->
+%    [ 0 || {N, V} <- [{a, b}] ]. % Works ok
+    << <<>> || {A, B} <- [{a, b}] >>. % Complains
+%    << <<>> || X <- [{a, b}] >>. % Works ok
diff --git a/lib/dialyzer/test/small_SUITE_data/src/codec_can.erl b/lib/dialyzer/test/small_SUITE_data/src/codec_can.erl
new file mode 100644
index 0000000000..8abf872b37
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/codec_can.erl
@@ -0,0 +1,35 @@
+%%---------------------------------------------------------------------
+%% From: Peer Stritzinger
+%% Date: 1 May 2011
+%% Subject: Dialyzer v2.2.0 crash
+%%
+%% Binaries of the form <<_:N,_:_*M>> in specs resulted in a crash:
+%%     dialyzer: Analysis failed with error: {{case_clause,8},
+%%		 [{erl_types,t_form_to_string,1},
+%%		  {erl_types,t_form_to_string,1},
+%%		  {dialyzer_contracts,contract_to_string_1,1},
+%%		  {dialyzer_contracts,extra_contract_warning,6},
+%%		  {dialyzer_contracts,picky_contract_check,7},
+%% because function erl_types:t_form_to_string/1 was not the inverse
+%% of erl_types:t_to_string/2.
+%%
+%% Fixed on the same date and send to OTP for inclusion.
+%%---------------------------------------------------------------------
+-module(codec_can).
+
+-export([recv/3, decode/1]).
+
+-record(can_pkt, {id, data :: binary(), timestamp}).
+
+-type can_pkt() :: #can_pkt{}.
+-type channel() :: atom() | pid() | {atom(),_}.
+
+-spec recv(<<_:64,_:_*8>>, fun((can_pkt()) -> R), channel()) -> R.
+recv(Packet, Fun, Chan) ->
+  #can_pkt{id = Can_id, data = Can_data} = P = decode(Packet),
+  Fun(P).
+
+-spec decode(<<_:64,_:_*8>>) -> #can_pkt{id::<<_:11>>,timestamp::char()}.
+decode(<<_:12, Len:4, Timestamp:16, 0:3, Id:11/bitstring, 0:18,
+	 Data:Len/binary, _/binary>>) ->
+  #can_pkt{id = Id, data = Data, timestamp = Timestamp}.
diff --git a/lib/dialyzer/test/small_SUITE_data/src/list_to_bitstring.erl b/lib/dialyzer/test/small_SUITE_data/src/list_to_bitstring.erl
new file mode 100644
index 0000000000..2da708cb15
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/list_to_bitstring.erl
@@ -0,0 +1,21 @@
+%%=====================================================================
+%% From: Ken Robinson
+%% Date: 28/04/2011, 17:26
+%%
+%% Program that produced borus "Function has no local return" warnings
+%% due to erlang:list_to_bitstring/1 having erroneous hard coded type
+%% information, namely accepting iolist() instead of bitstrlist().
+%% Fixed 29/04/2011.
+%%=====================================================================
+
+-module(list_to_bitstring).
+
+-export([l2bs/0, l2bs_ok/0]).
+
+%% This function was producing a warning
+l2bs() ->
+    erlang:list_to_bitstring([<<42>>, <<42:13>>]).
+
+%% while this one was ok.
+l2bs_ok() ->
+    erlang:list_to_bitstring([<<42>>, <<42,42>>]).
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).
diff --git a/lib/dialyzer/test/small_SUITE_data/src/nowarnunused.erl b/lib/dialyzer/test/small_SUITE_data/src/nowarnunused.erl
new file mode 100644
index 0000000000..63daeee9e3
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/nowarnunused.erl
@@ -0,0 +1,7 @@
+-module(nowarnunused).
+
+-compile({nowarn_unused_function, return_error/2}).
+
+-spec return_error(integer(), any()) -> no_return().
+return_error(Line, Message) ->
+    throw({error, {Line, ?MODULE, Message}}).