Merge branch 'hb/dialyzer/opaque_types_fixes/OTP-10397'

* hb/dialyzer/opaque_types_fixes/OTP-10397:
  [dialyzer] Re-work the handling of opaque types

40 files changed, 6452 insertions, 2335 deletions

diff --git a/lib/dialyzer/src/dialyzer.erl b/lib/dialyzer/src/dialyzer.erl
index 35156afff2..bb7e39dfda 100644
--- a/lib/dialyzer/src/dialyzer.erl
+++ b/lib/dialyzer/src/dialyzer.erl
@@ -423,6 +423,9 @@ message_to_string({call_without_opaque, [M, F, Args, ExpectedTriples]}) ->
 message_to_string({opaque_eq, [Type, _Op, OpaqueType]}) ->
   io_lib:format("Attempt to test for equality between a term of type ~s"
 		" and a term of opaque type ~s\n", [Type, OpaqueType]);
+message_to_string({opaque_guard, [Arg1, Infix, Arg2, ArgNs]}) ->
+  io_lib:format("Guard test ~s ~s ~s contains ~s\n",
+		[Arg1, Infix, Arg2, form_positions(ArgNs)]);
 message_to_string({opaque_guard, [Guard, Args]}) ->
   io_lib:format("Guard test ~w~s breaks the opaqueness of its argument\n",
 		[Guard, Args]);
@@ -435,8 +438,16 @@ message_to_string({opaque_match, [Pat, OpaqueType, OpaqueTerm]}) ->
 message_to_string({opaque_neq, [Type, _Op, OpaqueType]}) ->
   io_lib:format("Attempt to test for inequality between a term of type ~s"
 		" and a term of opaque type ~s\n", [Type, OpaqueType]);
-message_to_string({opaque_type_test, [Fun, Opaque]}) ->
-  io_lib:format("The type test ~s(~s) breaks the opaqueness of the term ~s\n", [Fun, Opaque, Opaque]);
+message_to_string({opaque_type_test, [Fun, Args, Arg, ArgType]}) ->
+  io_lib:format("The type test ~s~s breaks the opaqueness of the term ~s~s\n",
+                [Fun, Args, Arg, ArgType]);
+message_to_string({opaque_size, [SizeType, Size]}) ->
+  io_lib:format("The size ~s breaks the opaqueness of ~s\n",
+                [SizeType, Size]);
+message_to_string({opaque_call, [M, F, Args, Culprit, OpaqueType]}) ->
+  io_lib:format("The call ~s:~s~s breaks the opaqueness of the term ~s :: ~s\n",
+                [M, F, Args, Culprit, OpaqueType]);
+
 %%----- Warnings for concurrency errors --------------------
 message_to_string({race_condition, [M, F, Args, Reason]}) ->
   io_lib:format("The call ~w:~w~s ~s\n", [M, F, Args, Reason]);
diff --git a/lib/dialyzer/src/dialyzer_cl.erl b/lib/dialyzer/src/dialyzer_cl.erl
index 365c0b36d4..a7be6e0d05 100644
--- a/lib/dialyzer/src/dialyzer_cl.erl
+++ b/lib/dialyzer/src/dialyzer_cl.erl
@@ -2,7 +2,7 @@
 %%-------------------------------------------------------------------
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2006-2013. All Rights Reserved.
+%% Copyright Ericsson AB 2006-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -613,7 +613,7 @@ cl_loop(State, LogCache) ->
 -spec failed_anal_msg(string(), [_]) -> nonempty_string().
 
 failed_anal_msg(Reason, LogCache) ->
-  Msg = "Analysis failed with error:\n" ++ Reason ++ "\n",
+  Msg = "Analysis failed with error:\n" ++ lists:flatten(Reason) ++ "\n",
   case LogCache =:= [] of
     true -> Msg;
     false ->
@@ -640,7 +640,7 @@ store_unknown_behaviours(#cl_state{unknown_behaviours = Behs} = St, Beh) ->
 -spec cl_error(string()) -> no_return().
 
 cl_error(Msg) ->
-  throw({dialyzer_error, Msg}).
+  throw({dialyzer_error, lists:flatten(Msg)}).
 
 -spec cl_error(#cl_state{}, string()) -> no_return().
 
@@ -650,7 +650,7 @@ cl_error(State, Msg) ->
     Outfile -> io:format(Outfile, "\n~s\n", [Msg])
   end,
   maybe_close_output_file(State),
-  throw({dialyzer_error, Msg}).
+  throw({dialyzer_error, lists:flatten(Msg)}).
 
 return_value(State = #cl_state{erlang_mode = ErlangMode,
 			       mod_deps = ModDeps,
diff --git a/lib/dialyzer/src/dialyzer_contracts.erl b/lib/dialyzer/src/dialyzer_contracts.erl
index 332a326b0d..3467ab4e65 100644
--- a/lib/dialyzer/src/dialyzer_contracts.erl
+++ b/lib/dialyzer/src/dialyzer_contracts.erl
@@ -2,7 +2,7 @@
 %%-----------------------------------------------------------------------
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2007-2013. All Rights Reserved.
+%% Copyright Ericsson AB 2007-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -21,10 +21,10 @@
 -module(dialyzer_contracts).
 
 -export([check_contract/2,
-	 check_contracts/3,
+	 check_contracts/4,
 	 contracts_without_fun/3,
 	 contract_to_string/1,
-	 get_invalid_contract_warnings/3,
+	 get_invalid_contract_warnings/4,
 	 get_contract_args/1,
 	 get_contract_return/1,
 	 get_contract_return/2,
@@ -160,17 +160,22 @@ process_contract_remote_types(CodeServer) ->
   dialyzer_codeserver:finalize_contracts(NewContractDict, NewCallbackDict,
 					 CodeServer).
 
+-type opaques() :: [erl_types:erl_type()] | 'universe'.
+-type opaques_fun() :: fun((module()) -> opaques()).
+
 -spec check_contracts([{mfa(), file_contract()}],
-		      dialyzer_callgraph:callgraph(), dict()) -> plt_contracts().
+		      dialyzer_callgraph:callgraph(), dict(),
+                      opaques_fun()) -> plt_contracts().
 
-check_contracts(Contracts, Callgraph, FunTypes) ->
+check_contracts(Contracts, Callgraph, FunTypes, FindOpaques) ->
   FoldFun =
     fun(Label, Type, NewContracts) ->
 	case dialyzer_callgraph:lookup_name(Label, Callgraph) of
 	  {ok, {M,F,A} = MFA} ->
 	    case orddict:find(MFA, Contracts) of
 	      {ok, {_FileLine, Contract}} ->
-		case check_contract(Contract, Type) of
+                Opaques = FindOpaques(M),
+		case check_contract(Contract, Type, Opaques) of
 		  ok ->
 		    case erl_bif_types:is_known(M, F, A) of
 		      true ->
@@ -192,7 +197,10 @@ check_contracts(Contracts, Callgraph, FunTypes) ->
 %% Checks all components of a contract
 -spec check_contract(#contract{}, erl_types:erl_type()) -> 'ok' | {'error', term()}.
 
-check_contract(#contract{contracts = Contracts}, SuccType) ->
+check_contract(Contract, SuccType) ->
+  check_contract(Contract, SuccType, 'universe').
+
+check_contract(#contract{contracts = Contracts}, SuccType, Opaques) ->
   try
     Contracts1 = [{Contract, insert_constraints(Constraints, dict:new())}
 		  || {Contract, Constraints} <- Contracts],
@@ -203,9 +211,9 @@ check_contract(#contract{contracts = Contracts}, SuccType) ->
       error ->
 	{error, {overlapping_contract, []}};
       ok ->
-	InfList = [erl_types:t_inf(Contract, SuccType, opaque)
+	InfList = [erl_types:t_inf(Contract, SuccType, Opaques)
 		   || Contract <- Contracts2],
-	case check_contract_inf_list(InfList, SuccType) of
+	case check_contract_inf_list(InfList, SuccType, Opaques) of
 	  {error, _} = Invalid -> Invalid;
 	  ok -> check_extraneous(Contracts2, SuccType)
 	end
@@ -217,7 +225,7 @@ check_contract(#contract{contracts = Contracts}, SuccType) ->
 check_domains([_]) -> ok;
 check_domains([Dom|Doms]) ->
   Fun = fun(D) ->
-	    erl_types:any_none_or_unit(erl_types:t_inf_lists(Dom, D, opaque))
+	    erl_types:any_none_or_unit(erl_types:t_inf_lists(Dom, D))
 	end,
   case lists:all(Fun, Doms) of
     true -> check_domains(Doms);
@@ -227,23 +235,23 @@ check_domains([Dom|Doms]) ->
 %% Allow a contract if one of the overloaded contracts is possible.
 %% We used to be more strict, e.g., all overloaded contracts had to be
 %% possible.
-check_contract_inf_list([FunType|Left], SuccType) ->
+check_contract_inf_list([FunType|Left], SuccType, Opaques) ->
   FunArgs = erl_types:t_fun_args(FunType),
   case lists:any(fun erl_types:t_is_none_or_unit/1, FunArgs) of
-    true -> check_contract_inf_list(Left, SuccType);
+    true -> check_contract_inf_list(Left, SuccType, Opaques);
     false ->
       STRange = erl_types:t_fun_range(SuccType),
       case erl_types:t_is_none_or_unit(STRange) of
 	true -> ok;
 	false ->
 	  Range = erl_types:t_fun_range(FunType),
-	  case erl_types:t_is_none(erl_types:t_inf(STRange, Range, opaque)) of
-	    true -> check_contract_inf_list(Left, SuccType);
+	  case erl_types:t_is_none(erl_types:t_inf(STRange, Range)) of
+	    true -> check_contract_inf_list(Left, SuccType, Opaques);
 	    false -> ok
 	  end
       end
   end;
-check_contract_inf_list([], _SuccType) ->
+check_contract_inf_list([], _SuccType, _Opaques) ->
   {error, invalid_contract}.
 
 check_extraneous([], _SuccType) -> ok;
@@ -259,7 +267,7 @@ check_extraneous_1(Contract, SuccType) ->
   STRng = erl_types:t_fun_range(SuccType),
   ?debug("CR = ~p\nSR = ~p\n", [CRngs, STRng]),
   case [CR || CR <- CRngs,
-              erl_types:t_is_none(erl_types:t_inf(CR, STRng, opaque))] of
+              erl_types:t_is_none(erl_types:t_inf(CR, STRng))] of
     [] ->
       CRngList = list_part(CRng),
       STRngList = list_part(STRng),
@@ -268,7 +276,7 @@ check_extraneous_1(Contract, SuccType) ->
         true ->
           CRngElements = erl_types:t_list_elements(CRngList),
           STRngElements = erl_types:t_list_elements(STRngList),
-          Inf = erl_types:t_inf(CRngElements, STRngElements, opaque),
+          Inf = erl_types:t_inf(CRngElements, STRngElements),
           case erl_types:t_is_none(Inf) of
             true -> {error, invalid_contract};
             false -> ok
@@ -278,7 +286,7 @@ check_extraneous_1(Contract, SuccType) ->
   end.
 
 list_part(Type) ->
-  erl_types:t_inf(erl_types:t_list(), Type, opaque).
+  erl_types:t_inf(erl_types:t_list(), Type).
 
 is_not_nil_list(Type) ->
   erl_types:t_is_list(Type) andalso not erl_types:t_is_nil(Type).
@@ -374,7 +382,7 @@ insert_constraints([], Dict) -> Dict.
 store_tmp_contract(MFA, FileLine, TypeSpec, SpecDict, RecordsDict) ->
   %% io:format("contract from form: ~p\n", [TypeSpec]),
   TmpContract = contract_from_form(TypeSpec, RecordsDict, FileLine),
-  %% io:format("contract: ~p\n", [Contract]),
+  %% io:format("contract: ~p\n", [TmpContract]),
   dict:store(MFA, {FileLine, TmpContract}, SpecDict).
 
 contract_from_form(Forms, RecDict, FileLine) ->
@@ -494,30 +502,35 @@ general_domain([], AccSig) ->
   AccSig1 = erl_types:subst_all_vars_to_any(AccSig),
   erl_types:t_fun_args(AccSig1).
 
--spec get_invalid_contract_warnings([module()], dialyzer_codeserver:codeserver(), dialyzer_plt:plt()) -> [dial_warning()].
+-spec get_invalid_contract_warnings([module()],
+                                    dialyzer_codeserver:codeserver(),
+                                    dialyzer_plt:plt(),
+                                    opaques_fun()) -> [dial_warning()].
 
-get_invalid_contract_warnings(Modules, CodeServer, Plt) ->
-  get_invalid_contract_warnings_modules(Modules, CodeServer, Plt, []).
+get_invalid_contract_warnings(Modules, CodeServer, Plt, FindOpaques) ->
+  get_invalid_contract_warnings_modules(Modules, CodeServer, Plt, FindOpaques, []).
 
-get_invalid_contract_warnings_modules([Mod|Mods], CodeServer, Plt, Acc) ->
+get_invalid_contract_warnings_modules([Mod|Mods], CodeServer, Plt, FindOpaques, Acc) ->
   Contracts1 = dialyzer_codeserver:lookup_mod_contracts(Mod, CodeServer),
   Contracts2 = dict:to_list(Contracts1),
   Records = dialyzer_codeserver:lookup_mod_records(Mod, CodeServer),
-  NewAcc = get_invalid_contract_warnings_funs(Contracts2, Plt, Records, Acc),
-  get_invalid_contract_warnings_modules(Mods, CodeServer, Plt, NewAcc);
-get_invalid_contract_warnings_modules([], _CodeServer, _Plt, Acc) ->
+  NewAcc = get_invalid_contract_warnings_funs(Contracts2, Plt, Records, FindOpaques, Acc),
+  get_invalid_contract_warnings_modules(Mods, CodeServer, Plt, FindOpaques, NewAcc);
+get_invalid_contract_warnings_modules([], _CodeServer, _Plt, _FindOpaques, Acc) ->
   Acc.
 
 get_invalid_contract_warnings_funs([{MFA, {FileLine, Contract}}|Left],
-				   Plt, RecDict, Acc) ->
+				   Plt, RecDict, FindOpaques, Acc) ->
   case dialyzer_plt:lookup(Plt, MFA) of
     none ->
       %% This must be a contract for a non-available function. Just accept it.
-      get_invalid_contract_warnings_funs(Left, Plt, RecDict, Acc);
+      get_invalid_contract_warnings_funs(Left, Plt, RecDict, FindOpaques, Acc);
     {value, {Ret, Args}} ->
       Sig = erl_types:t_fun(Args, Ret),
+      {M, _F, _A} = MFA,
+      Opaques = FindOpaques(M),
       NewAcc =
-	case check_contract(Contract, Sig) of
+	case check_contract(Contract, Sig, Opaques) of
 	  {error, invalid_contract} ->
 	    [invalid_contract_warning(MFA, FileLine, Sig, RecDict)|Acc];
 	  {error, {overlapping_contract, []}} ->
@@ -551,7 +564,7 @@ get_invalid_contract_warnings_funs([{MFA, {FileLine, Contract}}|Left],
 		BifArgs = erl_bif_types:arg_types(M, F, A),
 		BifRet = erl_bif_types:type(M, F, A),
 		BifSig = erl_types:t_fun(BifArgs, BifRet),
-		case check_contract(Contract, BifSig) of
+		case check_contract(Contract, BifSig, Opaques) of
 		  {error, _} ->
 		    [invalid_contract_warning(MFA, FileLine, BifSig, RecDict)
 		     |Acc];
@@ -564,9 +577,9 @@ get_invalid_contract_warnings_funs([{MFA, {FileLine, Contract}}|Left],
 				     RecDict, Acc)
 	    end
 	end,
-      get_invalid_contract_warnings_funs(Left, Plt, RecDict, NewAcc)
+      get_invalid_contract_warnings_funs(Left, Plt, RecDict, FindOpaques, NewAcc)
   end;
-get_invalid_contract_warnings_funs([], _Plt, _RecDict, Acc) ->
+get_invalid_contract_warnings_funs([], _Plt, _RecDict, _FindOpaques, Acc) ->
   Acc.
 
 invalid_contract_warning({M, F, A}, FileLine, SuccType, RecDict) ->
@@ -601,16 +614,23 @@ picky_contract_check(CSig0, Sig0, MFA, FileLine, Contract, RecDict, Acc) ->
   end.
 
 extra_contract_warning({M, F, A}, FileLine, Contract, CSig, Sig, RecDict) ->
-  SigString = lists:flatten(dialyzer_utils:format_sig(Sig, RecDict)),
-  ContractString0 = lists:flatten(dialyzer_utils:format_sig(CSig, RecDict)),
+  %% We do not want to depend upon erl_types:t_to_string() possibly
+  %% hiding the contents of opaque types.
+  SigUnopaque = erl_types:t_unopaque(Sig),
+  CSigUnopaque = erl_types:t_unopaque(CSig),
+  SigString0 =
+    lists:flatten(dialyzer_utils:format_sig(SigUnopaque, RecDict)),
+  ContractString0 =
+    lists:flatten(dialyzer_utils:format_sig(CSigUnopaque, RecDict)),
   %% The only difference is in record fields containing 'undefined' or not.
-  IsUndefRecordFieldsRelated = SigString =:= ContractString0,
+  IsUndefRecordFieldsRelated = SigString0 =:= ContractString0,
   {IsRemoteTypesRelated, SubtypeRelation} =
     is_remote_types_related(Contract, CSig, Sig, RecDict),
   case IsUndefRecordFieldsRelated orelse IsRemoteTypesRelated of
     true ->
       no_warning;
     false ->
+      SigString = lists:flatten(dialyzer_utils:format_sig(Sig, RecDict)),
       ContractString = contract_to_string(Contract),
       {Tag, Msg} =
 	case SubtypeRelation of
diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index 922ccad599..3591d5be8e 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -2,7 +2,7 @@
 %%--------------------------------------------------------------------
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2006-2012. All Rights Reserved.
+%% Copyright Ericsson AB 2006-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -41,27 +41,33 @@
 
 -include("dialyzer.hrl").
 
+%%-import(helper, %% 'helper' could be any module doing sanity checks...
 -import(erl_types,
-	[any_none/1, t_any/0, t_atom/0, t_atom/1, t_atom_vals/1,
+        [t_inf/2, t_inf/3, t_inf_lists/2, t_inf_lists/3,
+         t_inf_lists/3, t_is_equal/2, t_is_subtype/2, t_subtract/2,
+         t_sup/1, t_sup/2]).
+
+-import(erl_types,
+	[any_none/1, t_any/0, t_atom/0, t_atom/1, t_atom_vals/1, t_atom_vals/2,
 	 t_binary/0, t_boolean/0,
 	 t_bitstr/0, t_bitstr/2, t_bitstr_concat/1, t_bitstr_match/2,
-	 t_cons/0, t_cons/2, t_cons_hd/1, t_cons_tl/1, t_contains_opaque/1,
+	 t_cons/0, t_cons/2, t_cons_hd/2, t_cons_tl/2,
+         t_contains_opaque/2,
 	 t_find_opaque_mismatch/2, t_float/0, t_from_range/2, t_from_term/1,
-	 t_fun/0, t_fun/2, t_fun_args/1, t_fun_range/1,
-	 t_inf/2, t_inf/3, t_inf_lists/2, t_inf_lists/3, t_inf_lists_masked/3,
-	 t_integer/0, t_integers/1,
-	 t_is_any/1, t_is_atom/1, t_is_atom/2, t_is_boolean/1, t_is_equal/2,
-	 t_is_integer/1, t_is_nil/1, t_is_none/1, t_is_none_or_unit/1,
-	 t_is_number/1, t_is_reference/1, t_is_pid/1, t_is_port/1,
-	 t_is_subtype/2, t_is_unit/1,
+	 t_fun/0, t_fun/2, t_fun_args/1, t_fun_args/2, t_fun_range/1,
+	 t_fun_range/2, t_integer/0, t_integers/1,
+	 t_is_any/1, t_is_atom/1, t_is_atom/2, t_is_any_atom/3,
+         t_is_boolean/2,
+	 t_is_integer/2, t_is_nil/2, t_is_none/1, t_is_none_or_unit/1,
+	 t_is_number/2, t_is_reference/2, t_is_pid/2, t_is_port/2,
+         t_is_unit/1,
 	 t_limit/2, t_list/0, t_maybe_improper_list/0, t_module/0,
-	 t_none/0, t_non_neg_integer/0, t_number/0, t_number_vals/1,
-	 t_opaque_match_atom/2, t_opaque_match_record/2,
-	 t_opaque_matching_structure/2,
+	 t_none/0, t_non_neg_integer/0, t_number/0, t_number_vals/2,
 	 t_pid/0, t_port/0, t_product/1, t_reference/0,
-	 t_sup/1, t_sup/2, t_subtract/2, t_to_string/2, t_to_tlist/1,
-	 t_tuple/0, t_tuple/1, t_tuple_args/1, t_tuple_subtypes/1,
-	 t_unit/0, t_unopaque/1]).
+         t_to_string/2, t_to_tlist/1,
+	 t_tuple/0, t_tuple/1, t_tuple_args/1, t_tuple_args/2,
+         t_tuple_subtypes/2,
+	 t_unit/0, t_unopaque/2]).
 
 %%-define(DEBUG, true).
 %%-define(DEBUG_PP, true).
@@ -204,7 +210,7 @@ analyze_loop(State) ->
 
 traverse(Tree, Map, State) ->
   ?debug("Handling ~p\n", [cerl:type(Tree)]),
-  %%debug_pp_map(Map),
+  %% debug_pp_map(Map),
   case cerl:type(Tree) of
     alias ->
       %% This only happens when checking for illegal record patterns
@@ -256,12 +262,7 @@ traverse(Tree, Map, State) ->
       case cerl:unfold_literal(Tree) of
 	Tree ->
 	  Type = literal_type(Tree),
-	  NewType =
-	    case erl_types:t_opaque_match_atom(Type, State#state.opaques) of
-	      [Opaque] -> Opaque;
-	      _ -> Type
-	    end,
-	  {State, Map, NewType};
+	  {State, Map, Type};
 	NewTree -> traverse(NewTree, Map, State)
       end;
     module ->
@@ -286,8 +287,11 @@ traverse(Tree, Map, State) ->
 	  SMA;
 	false ->
 	  State2 =
-	    case (t_is_any(ArgType) orelse t_is_simple(ArgType)
-		                    orelse is_call_to_send(Arg)) of
+	    case
+              t_is_any(ArgType)
+              orelse t_is_simple(ArgType, State)
+              orelse is_call_to_send(Arg)
+            of
 	      true -> % do not warn in these cases
 		State1;
 	      false ->
@@ -311,15 +315,7 @@ traverse(Tree, Map, State) ->
       case state__lookup_type_for_letrec(Tree, State) of
 	error ->
 	  LType = lookup_type(Tree, Map),
-	  Opaques = State#state.opaques,
-	  case t_opaque_match_record(LType, Opaques) of
-	    [Opaque] -> {State, Map, Opaque};
-	    _ ->
-	      case t_opaque_match_atom(LType, Opaques) of
-		[Opaque] -> {State, Map, Opaque};
-		_ -> {State, Map, LType}
-	      end
-	  end;
+          {State, Map, LType};
 	{ok, Type} -> {State, Map, Type}
       end;
     Other ->
@@ -367,7 +363,8 @@ handle_apply(Tree, Map, State) ->
 					  Tree, Msg),
 	      {State3, Map2, t_none()};
 	    false ->
-	      NewArgs = t_inf_lists(ArgTypes, t_fun_args(OpType1)),
+	      NewArgs = t_inf_lists(ArgTypes,
+                                    t_fun_args(OpType1, 'universe')),
 	      case any_none(NewArgs) of
 		true ->
 		  Msg = {fun_app_args,
@@ -378,7 +375,7 @@ handle_apply(Tree, Map, State) ->
 		  {State3, enter_type(Op, OpType1, Map2), t_none()};
 		false ->
 		  Map3 = enter_type_lists(Args, NewArgs, Map2),
-		  Range0 = t_fun_range(OpType1),
+		  Range0 = t_fun_range(OpType1, 'universe'),
 		  Range =
 		    case t_is_unit(Range0) of
 		      true  -> t_none();
@@ -423,83 +420,55 @@ handle_apply_or_call([{TypeOfApply, {Fun, Sig, Contr, LocalRet}}|Left],
 	{M, F, A} = Fun,
 	case erl_bif_types:is_known(M, F, A) of
 	  true ->
-	    IsBIF = true,
 	    BArgs = erl_bif_types:arg_types(M, F, A),
 	    BRange =
 	      fun(FunArgs) ->
-		  ArgPos = erl_bif_types:structure_inspecting_args(M, F, A),
-		  NewFunArgs =
-		    case ArgPos =:= [] of
-		      true -> FunArgs;
-		      false -> % some positions need to be un-opaqued
-			N = length(FunArgs),
-			PFs = lists:zip(lists:seq(1, N), FunArgs),
-			[case ordsets:is_element(P, ArgPos) of
-			   true  -> erl_types:t_unopaque(FArg, Opaques);
-			   false -> FArg
-			 end || {P, FArg} <- PFs]
-		    end,
-		  erl_bif_types:type(M, F, A, NewFunArgs)
+		  erl_bif_types:type(M, F, A, FunArgs, Opaques)
 	      end,
 	    {BArgs, BRange};
-	  false -> IsBIF = false, GenSig
+          false ->
+            GenSig
 	end;
-      local -> IsBIF = false, GenSig
+      local -> GenSig
     end,
   {SigArgs, SigRange} =
-    %% if there is hard-coded or contract information with opaque types,
-    %% the checking for possible type violations needs to take place w.r.t.
-    %% this information and not w.r.t. the structure-based success typing.
-    case prefer_opaque_types(CArgs, BifArgs) of
-      true -> {AnyArgs, t_any()}; % effectively forgets the success typing
-      false ->
-	case Sig of
-	  {value, {SR, SA}} -> {SA, SR};
-	  none -> {AnyArgs, t_any()}
-	end
-    end,
-  ArgModeMask = [case lists:member(Arg, Opaques) of
-                   true -> opaque;
-                   false -> structured
-                 end || Arg <- ArgTypes],
-  NewArgsSig = t_inf_lists_masked(SigArgs, ArgTypes, ArgModeMask),
-  NewArgsContract = t_inf_lists_masked(CArgs, ArgTypes, ArgModeMask),
-  NewArgsBif = t_inf_lists_masked(BifArgs, ArgTypes, ArgModeMask),
-  NewArgTypes0 = t_inf_lists_masked(NewArgsSig, NewArgsContract, ArgModeMask),
-  NewArgTypes = t_inf_lists_masked(NewArgTypes0, NewArgsBif, ArgModeMask),
-  BifRet = BifRange(NewArgTypes),
-  {TmpArgTypes, TmpArgsContract} =
-    case (TypeOfApply =:= remote) andalso (not IsBIF) of
-      true ->
-	List1 = lists:zip(CArgs, NewArgTypes),
-	List2 = lists:zip(CArgs, NewArgsContract),
-	{[erl_types:t_unopaque_on_mismatch(T1, T2, Opaques)
-	  || {T1, T2} <- List1],
-	 [erl_types:t_unopaque_on_mismatch(T1, T2, Opaques)
-	  || {T1, T2} <- List2]};
-      false  -> {NewArgTypes, NewArgsContract}
-    end,
-  ContrRet = CRange(TmpArgTypes),
-  RetMode =
-    case t_contains_opaque(ContrRet) orelse t_contains_opaque(BifRet) of
-      true  -> opaque;
-      false -> structured
+    case Sig of
+      {value, {SR, SA}} -> {SA, SR};
+      none -> {AnyArgs, t_any()}
     end,
-  RetWithoutContr = t_inf(SigRange, BifRet, RetMode),
-  RetWithoutLocal = t_inf(ContrRet, RetWithoutContr, RetMode),
+
   ?debug("--------------------------------------------------------\n", []),
-  ?debug("Fun: ~p\n", [Fun]),
-  ?debug("Args: ~s\n", [erl_types:t_to_string(t_product(ArgTypes))]),
+  ?debug("Fun: ~p\n", [state__lookup_name(Fun, State)]),
+  ?debug("Module ~p\n", [State#state.module]),
+  ?debug("CArgs ~s\n", [erl_types:t_to_string(t_product(CArgs))]),
+  ?debug("ArgTypes ~s\n", [erl_types:t_to_string(t_product(ArgTypes))]),
+  ?debug("BifArgs ~p\n", [erl_types:t_to_string(t_product(BifArgs))]),
+
+  NewArgsSig = t_inf_lists(SigArgs, ArgTypes, Opaques),
+  ?debug("SigArgs ~s\n", [erl_types:t_to_string(t_product(SigArgs))]),
   ?debug("NewArgsSig: ~s\n", [erl_types:t_to_string(t_product(NewArgsSig))]),
+  NewArgsContract = t_inf_lists(CArgs, ArgTypes, Opaques),
   ?debug("NewArgsContract: ~s\n",
 	 [erl_types:t_to_string(t_product(NewArgsContract))]),
+  NewArgsBif = t_inf_lists(BifArgs, ArgTypes, Opaques),
   ?debug("NewArgsBif: ~s\n", [erl_types:t_to_string(t_product(NewArgsBif))]),
-  ?debug("NewArgTypes: ~s\n", [erl_types:t_to_string(t_product(NewArgTypes))]),
+  NewArgTypes0 = t_inf_lists(NewArgsSig, NewArgsContract),
+  NewArgTypes = t_inf_lists(NewArgTypes0, NewArgsBif, Opaques),
+  ?debug("NewArgTypes ~s\n", [erl_types:t_to_string(t_product(NewArgTypes))]),
+  ?debug("\n", []),
+
+  BifRet = BifRange(NewArgTypes),
+  ContrRet = CRange(NewArgTypes),
+  RetWithoutContr = t_inf(SigRange, BifRet),
+  RetWithoutLocal = t_inf(ContrRet, RetWithoutContr),
+
   ?debug("RetWithoutContr: ~s\n",[erl_types:t_to_string(RetWithoutContr)]),
   ?debug("RetWithoutLocal: ~s\n", [erl_types:t_to_string(RetWithoutLocal)]),
   ?debug("BifRet: ~s\n", [erl_types:t_to_string(BifRange(NewArgTypes))]),
-  ?debug("ContrRet: ~s\n", [erl_types:t_to_string(CRange(TmpArgTypes))]),
-  ?debug("SigRet: ~s\n", [erl_types:t_to_string(SigRange)]),
+  ?debug("SigRange: ~s\n", [erl_types:t_to_string(SigRange)]),
+  ?debug("ContrRet: ~s\n", [erl_types:t_to_string(CRange(NewArgTypes))]),
+  ?debug("LocalRet: ~s\n", [erl_types:t_to_string(LocalRet)]),
+
   State1 =
     case is_race_analysis_enabled(State) of
       true ->
@@ -513,6 +482,9 @@ handle_apply_or_call([{TypeOfApply, {Fun, Sig, Contr, LocalRet}}|Left],
   FailedConj = any_none([RetWithoutLocal|NewArgTypes]),
   IsFailBif = t_is_none(BifRange(BifArgs)),
   IsFailSig = t_is_none(SigRange),
+  ?debug("FailedConj: ~p~n", [FailedConj]),
+  ?debug("IsFailBif: ~p~n", [IsFailBif]),
+  ?debug("IsFailSig: ~p~n", [IsFailSig]),
   State2 =
     case FailedConj andalso not (IsFailBif orelse IsFailSig) of
       true ->
@@ -532,14 +504,14 @@ handle_apply_or_call([{TypeOfApply, {Fun, Sig, Contr, LocalRet}}|Left],
 	  false ->
 	    FailedSig = any_none(NewArgsSig),
 	    FailedContract =
-	      any_none([CRange(TmpArgsContract)|NewArgsContract]),
+	      any_none([CRange(NewArgsContract)|NewArgsContract]),
 	    FailedBif = any_none([BifRange(NewArgsBif)|NewArgsBif]),
 	    InfSig = t_inf(t_fun(SigArgs, SigRange),
-			   t_fun(BifArgs, BifRange(BifArgs))),
+                           t_fun(BifArgs, BifRange(BifArgs))),
 	    FailReason =
 	      apply_fail_reason(FailedSig, FailedBif, FailedContract),
 	    Msg = get_apply_fail_msg(Fun, Args, ArgTypes, NewArgTypes, InfSig,
-				     Contr, CArgs, State1, FailReason),
+				     Contr, CArgs, State1, FailReason, Opaques),
 	    WarnType = case Msg of
 			 {call, _} -> ?WARN_FAILING_CALL;
 			 {apply, _} -> ?WARN_FAILING_CALL;
@@ -547,7 +519,8 @@ handle_apply_or_call([{TypeOfApply, {Fun, Sig, Contr, LocalRet}}|Left],
 			 {call_without_opaque, _} -> ?WARN_OPAQUE;
 			 {opaque_type_test, _} -> ?WARN_OPAQUE
 		       end,
-	    state__add_warning(State1, WarnType, Tree, Msg)
+            Frc = {erlang, is_record, 3} =:= state__lookup_name(Fun, State),
+	    state__add_warning(State1, WarnType, Tree, Msg, Frc)
 	end;
       false -> State1
     end,
@@ -571,7 +544,7 @@ handle_apply_or_call([{TypeOfApply, {Fun, Sig, Contr, LocalRet}}|Left],
   TotalRet =
     case t_is_none(LocalRet) andalso t_is_unit(RetWithoutLocal) of
       true -> RetWithoutLocal;
-      false -> t_inf(RetWithoutLocal, LocalRet, opaque)
+      false -> t_inf(RetWithoutLocal, LocalRet)
     end,
   NewAccRet = t_sup(AccRet, TotalRet),
   ?debug("NewAccRet: ~s\n", [t_to_string(NewAccRet)]),
@@ -590,7 +563,7 @@ apply_fail_reason(FailedSig, FailedBif, FailedContract) ->
   end.
 
 get_apply_fail_msg(Fun, Args, ArgTypes, NewArgTypes,
-		   Sig, Contract, ContrArgs, State, FailReason) ->
+		   Sig, Contract, ContrArgs, State, FailReason, Opaques) ->
   ArgStrings = format_args(Args, ArgTypes, State),
   ContractInfo =
     case Contract of
@@ -599,44 +572,52 @@ get_apply_fail_msg(Fun, Args, ArgTypes, NewArgTypes,
 	 dialyzer_contracts:contract_to_string(C)};
       none -> {false, none}
     end,
-  EnumArgTypes =
-    case NewArgTypes of
-      [] -> [];
-      _ -> lists:zip(lists:seq(1, length(NewArgTypes)), NewArgTypes)
-    end,
+  EnumArgTypes = lists:zip(lists:seq(1, length(NewArgTypes)), NewArgTypes),
   ArgNs = [Arg || {Arg, Type} <- EnumArgTypes, t_is_none(Type)],
   case state__lookup_name(Fun, State) of
-    {M, F, _A} ->
-      case is_opaque_type_test_problem(Fun, NewArgTypes, State) of
-	true ->
-	  [Opaque] = NewArgTypes,
-	  {opaque_type_test, [atom_to_list(F), erl_types:t_to_string(Opaque)]};
-	false ->
+    {M, F, A} ->
+      case is_opaque_type_test_problem(Fun, Args, NewArgTypes, State) of
+	{yes, Arg, ArgType} ->
+	  {opaque_type_test, [atom_to_list(F), ArgStrings,
+                              format_arg(Arg), format_type(ArgType, State)]};
+	no ->
 	  SigArgs = t_fun_args(Sig),
-	  case is_opaque_related_problem(ArgNs, ArgTypes) of
-	    true ->  %% an opaque term is used where a structured term is expected
-	      ExpectedArgs =
-		case FailReason of
-		  only_sig -> SigArgs;
-		  _ -> ContrArgs
-		end,
-	      {call_with_opaque, [M, F, ArgStrings, ArgNs, ExpectedArgs]};
-	    false ->
-	      case is_opaque_related_problem(ArgNs, SigArgs) orelse
-		is_opaque_related_problem(ArgNs, ContrArgs) of
-		true ->  %% a structured term is used where an opaque is expected
-		  ExpectedTriples =
-		    case FailReason of
-		      only_sig -> expected_arg_triples(ArgNs, SigArgs, State);
-		      _ -> expected_arg_triples(ArgNs, ContrArgs, State)
-		    end,
-		  {call_without_opaque, [M, F, ArgStrings, ExpectedTriples]};
-		false -> %% there is a structured term clash in some argument
-		  {call, [M, F, ArgStrings,
-			  ArgNs, FailReason,
-			  format_sig_args(Sig, State),
-			  format_type(t_fun_range(Sig), State),
-			  ContractInfo]}
+          BadOpaque =
+            opaque_problems([SigArgs, ContrArgs], ArgTypes, Opaques, ArgNs),
+          %% In fact *both* 'call_with_opaque' and
+          %% 'call_without_opaque' are possible.
+          case lists:keyfind(decl, 1, BadOpaque) of
+            {decl, BadArgs} ->
+              %% a structured term is used where an opaque is expected
+              ExpectedTriples =
+                case FailReason of
+                  only_sig -> expected_arg_triples(BadArgs, SigArgs, State);
+                  _ -> expected_arg_triples(BadArgs, ContrArgs, State)
+                end,
+              {call_without_opaque, [M, F, ArgStrings, ExpectedTriples]};
+            false ->
+              case lists:keyfind(use, 1, BadOpaque) of
+                {use, BadArgs} ->
+                  %% an opaque term is used where a structured term is expected
+                  ExpectedArgs =
+                    case FailReason of
+                      only_sig -> SigArgs;
+                      _ -> ContrArgs
+                    end,
+                  {call_with_opaque, [M, F, ArgStrings, BadArgs, ExpectedArgs]};
+                false ->
+                  case
+                    erl_bif_types:opaque_args(M, F, A, ArgTypes, Opaques)
+                  of
+                    [] ->  %% there is a structured term clash in some argument
+                      {call, [M, F, ArgStrings,
+                              ArgNs, FailReason,
+                              format_sig_args(Sig, State),
+                              format_type(t_fun_range(Sig), State),
+                              ContractInfo]};
+                    Ns ->
+                      {call_with_opaque, [M, F, ArgStrings, Ns, ContrArgs]}
+                  end
 	      end
 	  end
       end;
@@ -648,20 +629,28 @@ get_apply_fail_msg(Fun, Args, ArgTypes, NewArgTypes,
 	       ContractInfo]}
   end.
 
-%% returns 'true' if we are running with opaque on (not checked yet),
-%% and there is either a contract or hard-coded type information with
-%% opaque types
-%% TODO: check that we are running with opaque types
-%% TODO: check the return type also
-prefer_opaque_types(CArgs, BifArgs) ->
-  t_contains_opaque(t_product(CArgs))
-    orelse t_contains_opaque(t_product(BifArgs)).
-
-is_opaque_related_problem(ArgNs, ArgTypes) ->
-  Fun = fun (N) -> erl_types:t_contains_opaque(lists:nth(N, ArgTypes)) end,
-  ArgNs =/= [] andalso lists:all(Fun, ArgNs).
-
-is_opaque_type_test_problem(Fun, ArgTypes, State) ->
+%% -> [{ElementI, [ArgN]}] where [ArgN] is a non-empty list of
+%% arguments containing unknown opaque types and Element is 1 or 2.
+opaque_problems(ContractOrSigList, ArgTypes, Opaques, ArgNs) ->
+  ArgElementList = find_unknown(ContractOrSigList, ArgTypes, Opaques, ArgNs),
+  F = fun(1) -> decl; (2) -> use end,
+  [{F(ElementI), lists:usort([ArgN || {ArgN, EI} <- ArgElementList,
+                                      EI =:= ElementI])} ||
+    ElementI <- lists:usort([EI || {_, EI} <- ArgElementList])].
+
+%% -> [{ArgN, ElementI}] where ElementI = 1 means there is an unknown
+%% opaque type in argument ArgN of the the contract/signature,
+%% and ElementI = 2 means that there is an unknown opaque type in
+%% argument ArgN of the the (current) argument types.
+find_unknown(ContractOrSigList, ArgTypes, Opaques, NoneArgNs) ->
+  ArgNs = lists:seq(1, length(ArgTypes)),
+  [{ArgN, ElementI} ||
+    ContractOrSig <- ContractOrSigList,
+    {E1, E2, ArgN} <- lists:zip3(ContractOrSig, ArgTypes, ArgNs),
+    lists:member(ArgN, NoneArgNs),
+    ElementI <- erl_types:t_find_unknown_opaque(E1, E2, Opaques)].
+
+is_opaque_type_test_problem(Fun, Args, ArgTypes, State) ->
   case Fun of
     {erlang, FN, 1} when FN =:= is_atom;      FN =:= is_boolean;
 			 FN =:= is_binary;    FN =:= is_bitstring;
@@ -669,10 +658,18 @@ is_opaque_type_test_problem(Fun, ArgTypes, State) ->
 			 FN =:= is_integer;   FN =:= is_list;
 			 FN =:= is_number;    FN =:= is_pid; FN =:= is_port;
 			 FN =:= is_reference; FN =:= is_tuple ->
-      [Type] = ArgTypes,
-      erl_types:t_is_opaque(Type) andalso
-	not lists:member(Type, State#state.opaques);
-    _ -> false
+      type_test_opaque_arg(Args, ArgTypes, State#state.opaques);
+    {erlang, FN, 2} when FN =:= is_function ->
+      type_test_opaque_arg(Args, ArgTypes, State#state.opaques);
+    _ -> no
+  end.
+
+type_test_opaque_arg([], [], _Opaques) ->
+  no;
+type_test_opaque_arg([Arg|Args], [ArgType|ArgTypes], Opaques) ->
+  case erl_types:t_has_opaque_subtype(ArgType, Opaques) of
+    true -> {yes, Arg, ArgType};
+    false -> type_test_opaque_arg(Args, ArgTypes, Opaques)
   end.
 
 expected_arg_triples(ArgNs, ArgTypes, State) ->
@@ -683,47 +680,56 @@ expected_arg_triples(ArgNs, ArgTypes, State) ->
 
 add_bif_warnings({erlang, Op, 2}, [T1, T2] = Ts, Tree, State)
   when Op =:= '=:='; Op =:= '==' ->
-  Type1 = erl_types:t_unopaque(T1, State#state.opaques),
-  Type2 = erl_types:t_unopaque(T2, State#state.opaques),
-  Inf = t_inf(T1, T2),
-  Inf1 = t_inf(Type1, Type2),
-  case t_is_none(Inf) andalso t_is_none(Inf1) andalso(not any_none(Ts))
-    andalso (not is_int_float_eq_comp(T1, Op, T2)) of
+  Opaques = State#state.opaques,
+  Inf = t_inf(T1, T2, Opaques),
+  case
+    t_is_none(Inf) andalso (not any_none(Ts))
+    andalso (not is_int_float_eq_comp(T1, Op, T2, Opaques))
+  of
     true ->
-      Args = case erl_types:t_is_opaque(T1) of
-	       true  -> [format_type(T2, State), Op, format_type(T1, State)];
-	       false -> [format_type(T1, State), Op, format_type(T2, State)]
-	     end,
-      case any_opaque(Ts) of
-	true ->
-	  state__add_warning(State, ?WARN_OPAQUE, Tree, {opaque_eq, Args});
-	false ->
-	  state__add_warning(State, ?WARN_MATCHING, Tree, {exact_eq, Args})
+      %% Give priority to opaque warning (as usual).
+      case erl_types:t_find_unknown_opaque(T1, T2, Opaques) of
+        [] ->
+          Args = comp_format_args([], T1, Op, T2, State),
+          state__add_warning(State, ?WARN_MATCHING, Tree, {exact_eq, Args});
+        Ns ->
+          Args = comp_format_args(Ns, T1, Op, T2, State),
+	  state__add_warning(State, ?WARN_OPAQUE, Tree, {opaque_eq, Args})
       end;
     false ->
       State
   end;
 add_bif_warnings({erlang, Op, 2}, [T1, T2] = Ts, Tree, State)
   when Op =:= '=/='; Op =:= '/=' ->
-  Inf = t_inf(T1, T2),
-  case t_is_none(Inf) andalso (not any_none(Ts))
-    andalso (not is_int_float_eq_comp(T1, Op, T2)) andalso any_opaque(Ts) of
+  Opaques = State#state.opaques,
+  case
+    (not any_none(Ts))
+    andalso (not is_int_float_eq_comp(T1, Op, T2, Opaques))
+  of
     true ->
-      Args = case erl_types:t_is_opaque(T1) of
-	       true  -> [format_type(T2, State), Op, format_type(T1, State)];
-	       false -> [format_type(T1, State), Op, format_type(T2, State)]
-	     end,
-      state__add_warning(State, ?WARN_OPAQUE, Tree, {opaque_neq, Args});
+      case erl_types:t_find_unknown_opaque(T1, T2, Opaques) of
+        [] -> State;
+        Ns ->
+          Args = comp_format_args(Ns, T1, Op, T2, State),
+	  state__add_warning(State, ?WARN_OPAQUE, Tree, {opaque_neq, Args})
+      end;
     false ->
       State
   end;
 add_bif_warnings(_, _, _, State) ->
   State.
 
-is_int_float_eq_comp(T1, Op, T2) ->
+is_int_float_eq_comp(T1, Op, T2, Opaques) ->
   (Op =:= '==' orelse Op =:= '/=') andalso
-    ((erl_types:t_is_float(T1) andalso erl_types:t_is_integer(T2)) orelse
-     (erl_types:t_is_integer(T1) andalso erl_types:t_is_float(T2))).
+    ((erl_types:t_is_float(T1, Opaques)
+      andalso t_is_integer(T2, Opaques)) orelse
+     (t_is_integer(T1, Opaques)
+      andalso erl_types:t_is_float(T2, Opaques))).
+
+comp_format_args([1|_], T1, Op, T2, State) ->
+  [format_type(T2, State), Op, format_type(T1, State)];
+comp_format_args(_, T1, Op, T2, State) ->
+  [format_type(T1, State), Op, format_type(T2, State)].
 
 %%----------------------------------------
 
@@ -784,16 +790,27 @@ handle_bitstr(Tree, Map, State) ->
 	  {State3, Map2, t_none()};
 	false ->
 	  UnitVal = cerl:concrete(cerl:bitstr_unit(Tree)),
-	  Type =
-	    case t_number_vals(SizeType) of
-	      [OneSize] -> t_bitstr(0, OneSize * UnitVal);
-	      _ ->
-		MinSize = erl_types:number_min(SizeType),
-		t_bitstr(UnitVal, UnitVal * MinSize)
-	    end,
+          Opaques = State2#state.opaques,
+          NumberVals = t_number_vals(SizeType, Opaques),
+          {State3, Type} =
+            case t_contains_opaque(SizeType, Opaques) of
+              true ->
+                Msg = {opaque_size, [format_type(SizeType, State2),
+                                     format_cerl(Size)]},
+                {state__add_warning(State2, ?WARN_OPAQUE, Size, Msg),
+                 t_none()};
+              false ->
+                case NumberVals of
+                  [OneSize] -> {State2, t_bitstr(0, OneSize * UnitVal)};
+                  unknown -> {State2, t_bitstr()};
+                  _ ->
+                    MinSize = erl_types:number_min(SizeType, Opaques),
+                    {State2, t_bitstr(UnitVal, UnitVal * MinSize)}
+                end
+            end,
 	  Map3 = enter_type_lists([Val, Size, Tree],
 				  [ValType, SizeType, Type], Map2),
-	  {State2, Map3, Type}
+	  {State3, Map3, Type}
       end
   end.
 
@@ -805,34 +822,47 @@ handle_call(Tree, Map, State) ->
   Args = cerl:call_args(Tree),
   MFAList = [M, F|Args],
   {State1, Map1, [MType0, FType0|As]} = traverse_list(MFAList, Map, State),
-  %% Module and function names should be treated as *structured terms*
-  %% even if they happen to be identical to an atom (or tuple) which
-  %% is also involved in the definition of an opaque data type.
-  MType = t_inf(t_module(), t_unopaque(MType0)),
-  FType = t_inf(t_atom(), t_unopaque(FType0)),
+  Opaques = State#state.opaques,
+  MType = t_inf(t_module(), MType0, Opaques),
+  FType = t_inf(t_atom(), FType0, Opaques),
   Map2 = enter_type_lists([M, F], [MType, FType], Map1),
+  MOpaque = t_is_none(MType) andalso (not t_is_none(MType0)),
+  FOpaque = t_is_none(FType) andalso (not t_is_none(FType0)),
   case any_none([MType, FType|As]) of
     true ->
       State2 =
-	case t_is_none(MType) andalso (not t_is_none(MType0)) of
-	  true -> % This is a problem we just detected; not a known one
-	    MS = format_cerl(M),
-	    Msg = {app_call, [MS, format_cerl(F),
-			      format_args(Args, As, State1),
-			      MS, format_type(t_module(), State1),
-			      format_type(MType0, State1)]},
-	    state__add_warning(State1, ?WARN_FAILING_CALL, Tree, Msg);
-	  false ->
-	    case t_is_none(FType) andalso (not t_is_none(FType0)) of
-	      true ->
-		FS = format_cerl(F),
-		Msg = {app_call, [format_cerl(M), FS,
-				  format_args(Args, As, State1),
-				  FS, format_type(t_atom(), State1),
-				  format_type(FType0, State1)]},
-		state__add_warning(State1, ?WARN_FAILING_CALL, Tree, Msg);
-	      false -> State1
-	    end
+        if
+          MOpaque -> % This is a problem we just detected; not a known one
+            MS = format_cerl(M),
+            case t_is_none(t_inf(t_module(), MType0)) of
+              true ->
+                Msg = {app_call, [MS, format_cerl(F),
+                                  format_args(Args, As, State1),
+                                  MS, format_type(t_module(), State1),
+                                  format_type(MType0, State1)]},
+                state__add_warning(State1, ?WARN_FAILING_CALL, Tree, Msg);
+              false ->
+                Msg = {opaque_call, [MS, format_cerl(F),
+                                     format_args(Args, As, State1),
+                                     MS, format_type(MType0, State1)]},
+                state__add_warning(State1, ?WARN_FAILING_CALL, Tree, Msg)
+            end;
+          FOpaque ->
+            FS = format_cerl(F),
+            case t_is_none(t_inf(t_atom(), FType0)) of
+              true ->
+                Msg = {app_call, [format_cerl(M), FS,
+                                  format_args(Args, As, State1),
+                                  FS, format_type(t_atom(), State1),
+                                  format_type(FType0, State1)]},
+                state__add_warning(State1, ?WARN_FAILING_CALL, Tree, Msg);
+              false ->
+                Msg = {opaque_call, [format_cerl(M), FS,
+                                     format_args(Args, As, State1),
+                                     FS, format_type(FType0, State1)]},
+                state__add_warning(State1, ?WARN_FAILING_CALL, Tree, Msg)
+            end;
+          true -> State1
 	end,
       {State2, Map2, t_none()};
     false ->
@@ -874,7 +904,7 @@ handle_case(Tree, Map, State) ->
 	handle_clauses(Clauses, Arg, ArgType, ArgType, State2,
 		       [], Map2, [], []),
       Map3 = join_maps_end(MapList, Map2),
-      debug_pp_map(Map2),
+      debug_pp_map(Map3),
       {State3, Map3, Type}
   end.
 
@@ -886,7 +916,7 @@ handle_cons(Tree, Map, State) ->
   {State1, Map1, HdType} = traverse(Hd, Map, State),
   {State2, Map2, TlType} = traverse(Tl, Map1, State1),
   State3 =
-    case t_is_none(t_inf(TlType, t_list())) of
+    case t_is_none(t_inf(TlType, t_list(), State2#state.opaques)) of
       true ->
 	Msg = {improper_list_constr, [format_type(TlType, State2)]},
 	state__add_warning(State2, ?WARN_NON_PROPER_LIST, Tree, Msg);
@@ -979,8 +1009,9 @@ handle_receive(Tree, Map, State) ->
                    [], []),
   Map1 = join_maps(MapList, Map),
   {State3, Map2, TimeoutType} = traverse(Timeout, Map1, State2),
-  case (t_is_atom(TimeoutType) andalso
-	(t_atom_vals(TimeoutType) =:= ['infinity'])) of
+  Opaques = State3#state.opaques,
+  case (t_is_atom(TimeoutType, Opaques) andalso
+	(t_atom_vals(TimeoutType, Opaques) =:= ['infinity'])) of
     true ->
       {State3, Map2, ReceiveType};
     false ->
@@ -1031,55 +1062,46 @@ handle_tuple(Tree, Map, State) ->
     true ->
       {State1, Map1, t_none()};
     false ->
-      %% Let's find out if this is a record or opaque construction.
+      %% Let's find out if this is a record
       case Elements of
 	[Tag|Left] ->
 	  case cerl:is_c_atom(Tag) of
 	    true ->
 	      TagVal = cerl:atom_val(Tag),
-	      case t_opaque_match_record(TupleType, State1#state.opaques) of
-		[Opaque] ->
-		  RecStruct = t_opaque_matching_structure(TupleType, Opaque),
-		  RecFields = t_tuple_args(RecStruct),
-		  case bind_pat_vars(Elements, RecFields, [], Map1, State1) of
-		    {error, _, ErrorPat, ErrorType, _} ->
-		      Msg = {record_constr,
-			     [TagVal, format_patterns(ErrorPat),
-			      format_type(ErrorType, State1)]},
-		      State2 = state__add_warning(State1, ?WARN_MATCHING,
-						  Tree, Msg),
-		      {State2, Map1, t_none()};
-		    {Map2, _ETypes} ->
-		      {State1, Map2, Opaque}
-		  end;
-		_ ->
-		  case state__lookup_record(TagVal, length(Left), State1) of
-		    error -> {State1, Map1, TupleType};
-		    {ok, RecType} ->
-		      InfTupleType = t_inf(RecType, TupleType),
-		      case t_is_none(InfTupleType) of
-			true ->
-			  RecC = format_type(TupleType, State1),
-			  FieldDiffs = format_field_diffs(TupleType, State1),
-			  Msg = {record_constr, [RecC, FieldDiffs]},
-			  State2 = state__add_warning(State1, ?WARN_MATCHING,
-						      Tree, Msg),
-			  {State2, Map1, t_none()};
-			false ->
-			  case bind_pat_vars(Elements, t_tuple_args(RecType),
-					     [], Map1, State1) of
-			    {error, bind, ErrorPat, ErrorType, _} ->
-			      Msg = {record_constr,
-				     [TagVal, format_patterns(ErrorPat),
-				      format_type(ErrorType, State1)]},
-			      State2 = state__add_warning(State1, ?WARN_MATCHING,
-							  Tree, Msg),
-			      {State2, Map1, t_none()};
-			    {Map2, ETypes} ->
-			      {State1, Map2, t_tuple(ETypes)}
-			  end
-		      end
-		  end
+              case state__lookup_record(TagVal, length(Left), State1) of
+                error -> {State1, Map1, TupleType};
+                {ok, RecType} ->
+                  InfTupleType = t_inf(RecType, TupleType),
+                  case t_is_none(InfTupleType) of
+                    true ->
+                      RecC = format_type(TupleType, State1),
+                      FieldDiffs = format_field_diffs(TupleType, State1),
+                      Msg = {record_constr, [RecC, FieldDiffs]},
+                      State2 = state__add_warning(State1, ?WARN_MATCHING,
+                                                  Tree, Msg),
+                      {State2, Map1, t_none()};
+                    false ->
+                      case bind_pat_vars(Elements, t_tuple_args(RecType),
+                                         [], Map1, State1) of
+                        {error, bind, ErrorPat, ErrorType, _} ->
+                          Msg = {record_constr,
+                                 [TagVal, format_patterns(ErrorPat),
+                                  format_type(ErrorType, State1)]},
+                          State2 = state__add_warning(State1, ?WARN_MATCHING,
+                                                      Tree, Msg),
+                          {State2, Map1, t_none()};
+                        {error, opaque, ErrorPat, ErrorType, OpaqueType} ->
+                          Msg = {opaque_match,
+                                 [format_patterns(ErrorPat),
+                                  format_type(ErrorType, State1),
+                                  format_type(OpaqueType, State1)]},
+                          State2 = state__add_warning(State1, ?WARN_OPAQUE,
+                                                      Tree, Msg),
+                          {State2, Map1, t_none()};
+                        {Map2, ETypes} ->
+                          {State1, Map2, t_tuple(ETypes)}
+                      end
+                  end
 	      end;
 	    false ->
 	      {State1, Map1, t_tuple(EsType)}
@@ -1356,7 +1378,9 @@ bind_pat_vars_reverse(Pats, Types, Acc, Map, State) ->
   end.
 
 bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
-  ?debug("Binding pat: ~w to ~s\n", [cerl:type(Pat), format_type(Type, State)]),
+  ?debug("Binding pat: ~w to ~s\n", [cerl:type(Pat), format_type(Type, State)]
+),
+  Opaques = State#state.opaques,
   {NewMap, TypeOut} =
     case cerl:type(Pat) of
       alias ->
@@ -1372,9 +1396,15 @@ bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
 	case Rev of
 	  true -> {Map, t_bitstr()};
 	  false ->
-	    BinType = t_inf(t_bitstr(), Type),
+	    BinType = t_inf(t_bitstr(), Type, Opaques),
 	    case t_is_none(BinType) of
-	      true -> bind_error([Pat], Type, t_none(), bind);
+	      true ->
+                case t_find_opaque_mismatch(t_bitstr(), Type) of
+                  {ok, T1, T2}  ->
+                    bind_error([Pat], T1, T2, opaque);
+                  error ->
+                    bind_error([Pat], Type, t_none(), bind)
+                end;
 	      false ->
 		Segs = cerl:binary_segments(Pat),
 		{Map1, SegTypes} = bind_bin_segs(Segs, BinType, Map, State),
@@ -1382,28 +1412,24 @@ bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
 	    end
 	end;
       cons ->
-	Cons = t_inf(Type, t_cons()),
+	Cons = t_inf(Type, t_cons(), Opaques),
 	case t_is_none(Cons) of
 	  true ->
 	    bind_opaque_pats(t_cons(), Type, Pat, Map, State, Rev);
 	  false ->
 	    {Map1, [HdType, TlType]} =
 	      bind_pat_vars([cerl:cons_hd(Pat), cerl:cons_tl(Pat)],
-			    [t_cons_hd(Cons), t_cons_tl(Cons)],
+			    [t_cons_hd(Cons, Opaques),
+                             t_cons_tl(Cons, Opaques)],
 			    [], Map, State, Rev),
 	    {Map1, t_cons(HdType, TlType)}
 	end;
       literal ->
 	Literal = literal_type(Pat),
-	LiteralOrOpaque =
-	  case t_opaque_match_atom(Literal, State#state.opaques) of
-	    [Opaque] -> Opaque;
-	    _ -> Literal
-	  end,
-	case t_is_none(t_inf(LiteralOrOpaque, Type)) of
+	case t_is_none(t_inf(Literal, Type, Opaques)) of
 	  true ->
 	    bind_opaque_pats(Literal, Type, Pat, Map, State, Rev);
-	  false -> {Map, LiteralOrOpaque}
+	  false -> {Map, Literal}
 	end;
       tuple ->
 	Es = cerl:tuple_es(Pat),
@@ -1419,27 +1445,28 @@ bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
 		    {ok, Record} ->
 		      [_Head|AnyTail] = [t_any() || _ <- Es],
 		      UntypedRecord = t_tuple([t_atom(TagAtom)|AnyTail]),
-		      {not erl_types:t_is_equal(Record, UntypedRecord), Record}
+		      {not t_is_equal(Record, UntypedRecord), Record}
 		  end;
 		false -> {false, t_tuple(length(Es))}
 	      end
 	  end,
-	Tuple = t_inf(Prototype, Type),
+	Tuple = t_inf(Prototype, Type, Opaques),
 	case t_is_none(Tuple) of
 	  true ->
 	    bind_opaque_pats(Prototype, Type, Pat, Map, State, Rev);
 	  false ->
-	    SubTuples = t_tuple_subtypes(Tuple),
+	    SubTuples = t_tuple_subtypes(Tuple, Opaques),
 	    %% Need to call the top function to get the try-catch wrapper
             MapJ = join_maps_begin(Map),
 	    Results =
 	      case Rev of
 		true ->
-		  [bind_pat_vars_reverse(Es, t_tuple_args(SubTuple), [],
-					 MapJ, State)
+		  [bind_pat_vars_reverse(Es, t_tuple_args(SubTuple, Opaques),
+                                         [], MapJ, State)
 		   || SubTuple <- SubTuples];
 		false ->
-		  [bind_pat_vars(Es, t_tuple_args(SubTuple), [], MapJ, State)
+		  [bind_pat_vars(Es, t_tuple_args(SubTuple, Opaques), [],
+                                 MapJ, State)
 		   || SubTuple <- SubTuples]
 	      end,
 	    case lists:keyfind(opaque, 2, Results) of
@@ -1466,37 +1493,14 @@ bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
 	  bind_pat_vars(Es, t_to_tlist(Type), [], Map, State, Rev),
 	{Map1, t_product(EsTypes)};
       var ->
-	Opaques = State#state.opaques,
 	VarType1 =
 	  case state__lookup_type_for_letrec(Pat, State) of
-	    error ->
-	      LType = lookup_type(Pat, Map),
-	      case t_opaque_match_record(LType, Opaques) of
-		[Opaque] -> Opaque;
-		_ ->
-		  case t_opaque_match_atom(LType, Opaques) of
-		    [Opaque] -> Opaque;
-		    _ ->  LType
-		  end
-	      end;
+	    error -> lookup_type(Pat, Map);
 	    {ok, RecType} -> RecType
 	  end,
 	%% Must do inf when binding args to pats. Vars in pats are fresh.
-	VarType2 = t_inf(VarType1, Type),
-	VarType3 =
-	  case Opaques =/= [] of
-	    true ->
-	      case t_opaque_match_record(VarType2, Opaques) of
-		[OpaqueRec] -> OpaqueRec;
-		_ ->
-		  case t_opaque_match_atom(VarType2, Opaques) of
-		    [OpaqueAtom] -> OpaqueAtom;
-		    _ -> VarType2
-		  end
-	      end;
-	    false -> VarType2
-	  end,
-	case t_is_none(VarType3) of
+	VarType2 = t_inf(VarType1, Type, Opaques),
+	case t_is_none(VarType2) of
 	  true ->
 	    case t_find_opaque_mismatch(VarType1, Type) of
 	      {ok, T1, T2}  ->
@@ -1505,8 +1509,8 @@ bind_pat_vars([Pat|PatLeft], [Type|TypeLeft], Acc, Map, State, Rev) ->
 		bind_error([Pat], Type, t_none(), bind)
 	    end;
 	  false ->
-	    Map1 = enter_type(Pat, VarType3, Map),
-	    {Map1, VarType3}
+	    Map1 = enter_type(Pat, VarType2, Map),
+	    {Map1, VarType2}
 	end;
       _Other ->
 	%% Catch all is needed when binding args to pats
@@ -1529,7 +1533,8 @@ bind_bin_segs([Seg|Segs], BinType, Acc, Map, State) ->
       binary = SegType, [] = Segs, %% just an assert
       T = t_inf(t_bitstr(UnitVal, 0), BinType),
       {Map1, [Type]} = bind_pat_vars([Val], [T], [], Map, State, false),
-      bind_bin_segs(Segs, t_bitstr(0, 0), [Type|Acc], Map1, State);
+      Type1 = remove_local_opaque_types(Type, State#state.opaques),
+      bind_bin_segs(Segs, t_bitstr(0, 0), [Type1|Acc], Map1, State);
     utf -> % XXX: possibly can be strengthened
       true = lists:member(SegType, [utf8, utf16, utf32]),
       {Map1, [_]} = bind_pat_vars([Val], [t_integer()], [], Map, State, false),
@@ -1539,11 +1544,17 @@ bind_bin_segs([Seg|Segs], BinType, Acc, Map, State) ->
       Size = cerl:bitstr_size(Seg),
       {Map1, [SizeType]} =
 	bind_pat_vars([Size], [t_non_neg_integer()], [], Map, State, false),
+      Opaques = State#state.opaques,
+      NumberVals = t_number_vals(SizeType, Opaques),
+      case t_contains_opaque(SizeType, Opaques) of
+        true -> bind_error([Seg], SizeType, t_none(), opaque);
+        false -> ok
+      end,
       Type =
-	case t_number_vals(SizeType) of
+	case NumberVals of
 	  [OneSize] -> t_bitstr(0, UnitVal * OneSize);
-	  _ ->
-	    MinSize = erl_types:number_min(SizeType),
+	  _ -> % 'unknown' too
+	    MinSize = erl_types:number_min(SizeType, Opaques),
 	    t_bitstr(UnitVal, UnitVal * MinSize)
 	end,
       ValConstr =
@@ -1551,7 +1562,7 @@ bind_bin_segs([Seg|Segs], BinType, Acc, Map, State) ->
 	  binary -> Type; %% The same constraints as for the whole bitstr
 	  float -> t_float();
 	  integer ->
-	    case t_number_vals(SizeType) of
+	    case NumberVals of
 	      unknown -> t_integer();
 	      List ->
 		SizeVal = lists:max(List),
@@ -1579,7 +1590,7 @@ bind_error(Pats, Type, OpaqueType, Error) ->
 bind_opaque_pats(GenType, Type, Pat, Map, State, Rev) ->
   case t_find_opaque_mismatch(GenType, Type) of
     {ok, T1, T2}  ->
-      case lists:member(T2, State#state.opaques) of
+      case erl_types:is_opaque_type(T2, State#state.opaques) of
 	true ->
 	  NewType = erl_types:t_struct_from_opaque(Type, [T2]),
 	  {Map1, _} =
@@ -1700,19 +1711,9 @@ handle_guard_call(Guard, Map, Env, Eval, State) ->
 
 handle_guard_gen_fun({M, F, A}, Guard, Map, Env, Eval, State) ->
   Args = cerl:call_args(Guard),
-  {Map1, As0} = bind_guard_list(Args, Map, Env, dont_know, State),
-  MapFun = fun(Type) ->
-	       case lists:member(Type, State#state.opaques) of
-		 true -> erl_types:t_opaque_structure(Type);
-		 false -> Type
-	       end
-	   end,
-  As = lists:map(MapFun, As0),
-  Mode = case As =:= As0 of
-	   true -> structured;
-	   false -> opaque
-	 end,
-  BifRet = erl_bif_types:type(M, F, A, As),
+  {Map1, As} = bind_guard_list(Args, Map, Env, dont_know, State),
+  Opaques = State#state.opaques,
+  BifRet = erl_bif_types:type(M, F, A, As, Opaques),
   case t_is_none(BifRet) of
     true ->
       %% Is this an error-bif?
@@ -1721,11 +1722,8 @@ handle_guard_gen_fun({M, F, A}, Guard, Map, Env, Eval, State) ->
 	false -> signal_guard_fatal_fail(Eval, Guard, As, State)
       end;
     false ->
-      BifArgs = case erl_bif_types:arg_types(M, F, A) of
-		  unknown -> lists:duplicate(A, t_any());
-		  List -> List
-		end,
-      Map2 = enter_type_lists(Args, t_inf_lists(BifArgs, As0, Mode), Map1),
+      BifArgs = bif_args(M, F, A),
+      Map2 = enter_type_lists(Args, t_inf_lists(BifArgs, As, Opaques), Map1),
       Ret =
 	case Eval of
 	  pos -> t_inf(t_atom(true), BifRet);
@@ -1771,29 +1769,19 @@ bind_type_test(Eval, TypeTest, ArgType, State) ->
 	   is_reference -> t_reference();
 	   is_tuple -> t_tuple()
 	 end,
-  Mode = determine_mode(ArgType, State#state.opaques),
   case Eval of
     pos ->
-      Inf = t_inf(Type, ArgType, Mode),
+      Inf = t_inf(Type, ArgType, State#state.opaques),
       case t_is_none(Inf) of
 	true -> error;
 	false -> {ok, Inf, t_atom(true)}
       end;
     neg ->
-      case Mode of
-	opaque ->
-	  Struct = erl_types:t_opaque_structure(ArgType),
-	  case t_is_none(t_subtract(Struct, Type)) of
-	    true -> error;
-	    false  -> {ok, ArgType, t_atom(false)}
-	  end;
-	structured ->
-	  Sub = t_subtract(ArgType, Type),
-	  case t_is_none(Sub) of
-	    true -> error;
-	    false -> {ok, Sub, t_atom(false)}
-	  end
-	end;
+      Sub = t_subtract(ArgType, Type),
+      case t_is_none(Sub) of
+        true -> error;
+        false -> {ok, Sub, t_atom(false)}
+      end;
     dont_know ->
       {ok, ArgType, t_boolean()}
   end.
@@ -1802,9 +1790,10 @@ handle_guard_comp(Guard, Comp, Map, Env, Eval, State) ->
   Args = cerl:call_args(Guard),
   [Arg1, Arg2] = Args,
   {Map1, ArgTypes} = bind_guard_list(Args, Map, Env, dont_know, State),
+  Opaques = State#state.opaques,
   [Type1, Type2] = ArgTypes,
-  IsInt1 = t_is_integer(Type1),
-  IsInt2 = t_is_integer(Type2),
+  IsInt1 = t_is_integer(Type1, Opaques),
+  IsInt2 = t_is_integer(Type2, Opaques),
   case {cerl:type(Arg1), cerl:type(Arg2)} of
     {literal, literal} ->
       case erlang:Comp(cerl:concrete(Arg1), cerl:concrete(Arg2)) of
@@ -1817,12 +1806,13 @@ handle_guard_comp(Guard, Comp, Map, Env, Eval, State) ->
 	false when Eval =:= neg ->       {Map, t_atom(false)}
       end;
     {literal, var} when IsInt1 andalso IsInt2 andalso (Eval =:= pos) ->
-      case bind_comp_literal_var(Arg1, Arg2, Type2, Comp, Map1) of
+      case bind_comp_literal_var(Arg1, Arg2, Type2, Comp, Map1, Opaques) of
 	error -> signal_guard_fail(Eval, Guard, ArgTypes, State);
 	{ok, NewMap} -> {NewMap, t_atom(true)}
       end;
     {var, literal} when IsInt1 andalso IsInt2 andalso (Eval =:= pos) ->
-      case bind_comp_literal_var(Arg2, Arg1, Type1, invert_comp(Comp), Map1) of
+      case bind_comp_literal_var(Arg2, Arg1, Type1, invert_comp(Comp),
+                                 Map1, Opaques) of
 	error -> signal_guard_fail(Eval, Guard, ArgTypes, State);
 	{ok, NewMap} -> {NewMap, t_atom(true)}
       end;
@@ -1835,10 +1825,10 @@ invert_comp('<')  -> '>';
 invert_comp('>=') -> '=<';
 invert_comp('>')  -> '<'.
 
-bind_comp_literal_var(Lit, Var, VarType, CompOp, Map) ->
+bind_comp_literal_var(Lit, Var, VarType, CompOp, Map, Opaques) ->
   LitVal = cerl:concrete(Lit),
   NewVarType =
-    case t_number_vals(VarType) of
+    case t_number_vals(VarType, Opaques) of
       unknown ->
 	Range =
 	  case CompOp of
@@ -1847,7 +1837,7 @@ bind_comp_literal_var(Lit, Var, VarType, CompOp, Map) ->
 	    '>=' -> t_from_range(neg_inf, LitVal);
 	    '>'  -> t_from_range(neg_inf, LitVal - 1)
 	  end,
-	t_inf(Range, VarType);
+	t_inf(Range, VarType, Opaques);
       NumberVals ->
 	NewNumberVals = [X || X <- NumberVals, erlang:CompOp(LitVal, X)],
 	t_integers(NewNumberVals)
@@ -1861,17 +1851,18 @@ handle_guard_is_function(Guard, Map, Env, Eval, State) ->
   Args = cerl:call_args(Guard),
   {Map1, ArgTypes0} = bind_guard_list(Args, Map, Env, dont_know, State),
   [FunType0, ArityType0] = ArgTypes0,
-  ArityType = t_inf(ArityType0, t_integer()),
+  Opaques = State#state.opaques,
+  ArityType = t_inf(ArityType0, t_integer(), Opaques),
   case t_is_none(ArityType) of
     true -> signal_guard_fail(Eval, Guard, ArgTypes0, State);
     false ->
       FunTypeConstr =
-	case t_number_vals(ArityType) of
+	case t_number_vals(ArityType, State#state.opaques) of
 	  unknown -> t_fun();
 	  Vals ->
 	    t_sup([t_fun(lists:duplicate(X, t_any()), t_any()) || X <- Vals])
 	end,
-      FunType = t_inf(FunType0, FunTypeConstr),
+      FunType = t_inf(FunType0, FunTypeConstr, Opaques),
       case t_is_none(FunType) of
 	true ->
 	  case Eval of
@@ -1896,33 +1887,45 @@ handle_guard_is_record(Guard, Map, Env, Eval, State) ->
   Arity = cerl:int_val(Arity0),
   {Map1, RecType} = bind_guard(Rec, Map, Env, dont_know, State),
   ArityMin1 = Arity - 1,
-  TupleType =
-    case state__lookup_record(Tag, ArityMin1, State) of
-      error -> t_tuple([t_atom(Tag)|lists:duplicate(ArityMin1, t_any())]);
-      {ok, Prototype} -> Prototype
-    end,
-  Mode = determine_mode(RecType, State#state.opaques),
-  NewTupleType =
-    case t_opaque_match_record(TupleType, State#state.opaques) of
-      [Opaque] -> Opaque;
-      _ -> TupleType
-    end,
-  Type = t_inf(NewTupleType, RecType, Mode),
-  case t_is_none(Type) of
+  Opaques = State#state.opaques,
+  Tuple = t_tuple([t_atom(Tag)|lists:duplicate(ArityMin1, t_any())]),
+  case t_is_none(t_inf(Tuple, RecType, Opaques)) of
     true ->
-      case Eval of
-	pos -> signal_guard_fail(Eval, Guard,
-				 [RecType, t_from_term(Tag),
-				  t_from_term(Arity)],
-				 State);
-	neg -> {Map1, t_atom(false)};
-	dont_know -> {Map1, t_atom(false)}
+      case erl_types:t_has_opaque_subtype(RecType, Opaques) of
+        true ->
+          signal_guard_fail(Eval, Guard,
+                            [RecType, t_from_term(Tag),
+                             t_from_term(Arity)],
+                            State);
+        false ->
+          case Eval of
+            pos -> signal_guard_fail(Eval, Guard,
+                                     [RecType, t_from_term(Tag),
+                                      t_from_term(Arity)],
+                                     State);
+            neg -> {Map1, t_atom(false)};
+            dont_know -> {Map1, t_atom(false)}
+          end
       end;
     false ->
-      case Eval of
-	pos -> {enter_type(Rec, Type, Map1), t_atom(true)};
-	neg -> {Map1, t_atom(false)};
-	dont_know -> {Map1, t_boolean()}
+      TupleType =
+        case state__lookup_record(Tag, ArityMin1, State) of
+          error -> Tuple;
+          {ok, Prototype} -> Prototype
+        end,
+      Type = t_inf(TupleType, RecType, State#state.opaques),
+      case t_is_none(Type) of
+        true ->
+          %% No special handling of opaque errors.
+          FArgs = "record " ++ format_type(RecType, State),
+          Msg = {record_matching, [FArgs, Tag]},
+          throw({fail, {Guard, Msg}});
+        false ->
+          case Eval of
+            pos -> {enter_type(Rec, Type, Map1), t_atom(true)};
+            neg -> {Map1, t_atom(false)};
+            dont_know -> {Map1, t_boolean()}
+          end
       end
   end.
 
@@ -1975,14 +1978,24 @@ handle_guard_eq(Guard, Map, Env, Eval, State) ->
 bind_eq_guard(Guard, Arg1, Arg2, Map, Env, Eval, State) ->
   {Map1, Type1} = bind_guard(Arg1, Map, Env, dont_know, State),
   {Map2, Type2} = bind_guard(Arg2, Map1, Env, dont_know, State),
-  case (t_is_nil(Type1) orelse t_is_nil(Type2) orelse
-	t_is_atom(Type1) orelse t_is_atom(Type2)) of
+  Opaques = State#state.opaques,
+  case
+    t_is_nil(Type1, Opaques) orelse t_is_nil(Type2, Opaques)
+    orelse t_is_atom(Type1, Opaques) orelse t_is_atom(Type2, Opaques)
+  of
     true -> bind_eqeq_guard(Guard, Arg1, Arg2, Map, Env, Eval, State);
     false ->
-      case Eval of
-	pos -> {Map2, t_atom(true)};
-	neg -> {Map2, t_atom(false)};
-	dont_know -> {Map2, t_boolean()}
+      %% XXX. Is this test OK?
+      OpArgs = erl_types:t_find_unknown_opaque(Type1, Type2, Opaques),
+      case OpArgs =:= [] of
+        true ->
+          case Eval of
+            pos -> {Map2, t_atom(true)};
+            neg -> {Map2, t_atom(false)};
+            dont_know -> {Map2, t_boolean()}
+          end;
+        false ->
+          signal_guard_fail(Eval, Guard, [Type1, Type2], State)
       end
   end.
 
@@ -2021,44 +2034,52 @@ bind_eqeq_guard(Guard, Arg1, Arg2, Map, Env, Eval, State) ->
   {Map2, Type2} = bind_guard(Arg2, Map1, Env, dont_know, State),
   ?debug("Types are:~s =:= ~s\n", [t_to_string(Type1),
 				   t_to_string(Type2)]),
-  Inf = t_inf(Type1, Type2),
+  Opaques = State#state.opaques,
+  Inf = t_inf(Type1, Type2, Opaques),
   case t_is_none(Inf) of
     true ->
-      case Eval of
-	neg -> {Map2, t_atom(false)};
-	dont_know -> {Map2, t_atom(false)};
-	pos -> signal_guard_fail(Eval, Guard, [Type1, Type2], State)
+      OpArgs = erl_types:t_find_unknown_opaque(Type1, Type2, Opaques),
+      case OpArgs =:= [] of
+        true ->
+          case Eval of
+            neg -> {Map2, t_atom(false)};
+            dont_know -> {Map2, t_atom(false)};
+            pos -> signal_guard_fail(Eval, Guard, [Type1, Type2], State)
+          end;
+        false ->
+          signal_guard_fail(Eval, Guard, [Type1, Type2], State)
       end;
     false ->
       case Eval of
-	pos ->
-	  case {cerl:type(Arg1), cerl:type(Arg2)} of
-	    {var, var} ->
-	      Map3 = enter_subst(Arg1, Arg2, Map2),
-	      Map4 = enter_type(Arg2, Inf, Map3),
-	      {Map4, t_atom(true)};
-	    {var, _} ->
-	      Map3 = enter_type(Arg1, Inf, Map2),
-	      {Map3, t_atom(true)};
-	    {_, var} ->
-	      Map3 = enter_type(Arg2, Inf, Map2),
-	      {Map3, t_atom(true)};
-	    {_, _} ->
-	      {Map2, t_atom(true)}
-	  end;
-	neg ->
-	  {Map2, t_atom(false)};
-	dont_know ->
-	  {Map2, t_boolean()}
+        pos ->
+          case {cerl:type(Arg1), cerl:type(Arg2)} of
+            {var, var} ->
+              Map3 = enter_subst(Arg1, Arg2, Map2),
+              Map4 = enter_type(Arg2, Inf, Map3),
+              {Map4, t_atom(true)};
+            {var, _} ->
+              Map3 = enter_type(Arg1, Inf, Map2),
+              {Map3, t_atom(true)};
+            {_, var} ->
+              Map3 = enter_type(Arg2, Inf, Map2),
+              {Map3, t_atom(true)};
+            {_, _} ->
+              {Map2, t_atom(true)}
+          end;
+        neg ->
+          {Map2, t_atom(false)};
+        dont_know ->
+          {Map2, t_boolean()}
       end
   end.
 
 bind_eqeq_guard_lit_other(Guard, Arg1, Arg2, Map, Env, State) ->
   Eval = dont_know,
+  Opaques = State#state.opaques,
   case cerl:concrete(Arg1) of
     true ->
       {_, Type} = MT = bind_guard(Arg2, Map, Env, pos, State),
-      case t_is_atom(true, Type) of
+      case t_is_any_atom(true, Type, Opaques) of
 	true -> MT;
 	false ->
 	  {_, Type0} = bind_guard(Arg2, Map, Env, Eval, State),
@@ -2066,7 +2087,7 @@ bind_eqeq_guard_lit_other(Guard, Arg1, Arg2, Map, Env, State) ->
       end;
     false ->
       {Map1, Type} = bind_guard(Arg2, Map, Env, neg, State),
-      case t_is_atom(false, Type) of
+      case t_is_any_atom(false, Type, Opaques) of
 	true -> {Map1, t_atom(true)};
 	false ->
 	  {_, Type0} = bind_guard(Arg2, Map, Env, Eval, State),
@@ -2087,14 +2108,15 @@ bind_eqeq_guard_lit_other(Guard, Arg1, Arg2, Map, Env, State) ->
 
 handle_guard_and(Guard, Map, Env, Eval, State) ->
   [Arg1, Arg2] = cerl:call_args(Guard),
+  Opaques = State#state.opaques,
   case Eval of
     pos ->
       {Map1, Type1} = bind_guard(Arg1, Map, Env, Eval, State),
-      case t_is_atom(true, Type1) of
+      case t_is_any_atom(true, Type1, Opaques) of
 	false -> signal_guard_fail(Eval, Guard, [Type1, t_any()], State);
 	true ->
 	  {Map2, Type2} = bind_guard(Arg2, Map1, Env, Eval, State),
-	  case t_is_atom(true, Type2) of
+	  case t_is_any_atom(true, Type2, Opaques) of
 	    false -> signal_guard_fail(Eval, Guard, [Type1, Type2], State);
 	    true -> {Map2, t_atom(true)}
 	  end
@@ -2109,7 +2131,10 @@ handle_guard_and(Guard, Map, Env, Eval, State) ->
 	try bind_guard(Arg2, MapJ, Env, neg, State)
 	catch throw:{fail, _} -> bind_guard(Arg1, MapJ, Env, pos, State)
 	end,
-      case t_is_atom(false, Type1) orelse t_is_atom(false, Type2) of
+      case
+        t_is_any_atom(false, Type1, Opaques)
+        orelse t_is_any_atom(false, Type2, Opaques)
+      of
 	true -> {join_maps_end([Map1, Map2], MapJ), t_atom(false)};
 	false -> signal_guard_fail(Eval, Guard, [Type1, Type2], State)
       end;
@@ -2124,11 +2149,16 @@ handle_guard_and(Guard, Map, Env, Eval, State) ->
 	false ->
 	  NewMap = join_maps_end([Map1, Map2], MapJ),
 	  NewType =
-	    case {t_atom_vals(Bool1), t_atom_vals(Bool2)} of
+	    case {t_atom_vals(Bool1, Opaques), t_atom_vals(Bool2, Opaques)} of
 	      {['true'] , ['true'] } -> t_atom(true);
 	      {['false'], _        } -> t_atom(false);
 	      {_        , ['false']} -> t_atom(false);
+              {unknown  , _        } ->
+                signal_guard_fail(Eval, Guard, [Type1, Type2], State);
+              {_        , unknown  } ->
+                signal_guard_fail(Eval, Guard, [Type1, Type2], State);
 	      {_        , _        } -> t_boolean()
+
 	    end,
 	  {NewMap, NewType}
       end
@@ -2136,6 +2166,7 @@ handle_guard_and(Guard, Map, Env, Eval, State) ->
 
 handle_guard_or(Guard, Map, Env, Eval, State) ->
   [Arg1, Arg2] = cerl:call_args(Guard),
+  Opaques = State#state.opaques,
   case Eval of
     pos ->
       MapJ = join_maps_begin(Map),
@@ -2149,19 +2180,23 @@ handle_guard_or(Guard, Map, Env, Eval, State) ->
 	catch
 	  throw:{fail,_} -> bind_guard(Arg2, MapJ, Env, dont_know, State)
 	end,
-      case ((t_is_atom(true, Bool1) andalso t_is_boolean(Bool2))
-	    orelse
-	    (t_is_atom(true, Bool2) andalso t_is_boolean(Bool1))) of
+      case
+        ((t_is_any_atom(true, Bool1, Opaques)
+          andalso t_is_boolean(Bool2, Opaques))
+         orelse
+           (t_is_any_atom(true, Bool2, Opaques)
+            andalso t_is_boolean(Bool1, Opaques)))
+      of
 	true -> {join_maps_end([Map1, Map2], MapJ), t_atom(true)};
 	false -> signal_guard_fail(Eval, Guard, [Bool1, Bool2], State)
       end;
     neg ->
       {Map1, Type1} = bind_guard(Arg1, Map, Env, neg, State),
-      case t_is_atom(false, Type1) of
+      case t_is_any_atom(false, Type1, Opaques) of
 	false -> signal_guard_fail(Eval, Guard, [Type1, t_any()], State);
 	true ->
 	  {Map2, Type2} = bind_guard(Arg2, Map1, Env, neg, State),
-	  case t_is_atom(false, Type2) of
+	  case t_is_any_atom(false, Type2, Opaques) of
 	    false -> signal_guard_fail(Eval, Guard, [Type1, Type2], State);
 	    true -> {Map2, t_atom(false)}
 	  end
@@ -2177,10 +2212,14 @@ handle_guard_or(Guard, Map, Env, Eval, State) ->
 	false ->
 	  NewMap = join_maps_end([Map1, Map2], MapJ),
 	  NewType =
-	    case {t_atom_vals(Bool1), t_atom_vals(Bool2)} of
+	    case {t_atom_vals(Bool1, Opaques), t_atom_vals(Bool2, Opaques)} of
 	      {['false'], ['false']} -> t_atom(false);
 	      {['true'] , _        } -> t_atom(true);
 	      {_        , ['true'] } -> t_atom(true);
+              {unknown  , _        } ->
+                signal_guard_fail(Eval, Guard, [Type1, Type2], State);
+              {_        , unknown  } ->
+                signal_guard_fail(Eval, Guard, [Type1, Type2], State);
 	      {_        , _        } -> t_boolean()
 	    end,
 	  {NewMap, NewType}
@@ -2189,10 +2228,11 @@ handle_guard_or(Guard, Map, Env, Eval, State) ->
 
 handle_guard_not(Guard, Map, Env, Eval, State) ->
   [Arg] = cerl:call_args(Guard),
+  Opaques = State#state.opaques,
   case Eval of
     neg ->
       {Map1, Type} = bind_guard(Arg, Map, Env, pos, State),
-      case t_is_atom(true, Type) of
+      case t_is_any_atom(true, Type, Opaques) of
 	true -> {Map1, t_atom(false)};
 	false ->
 	  {_, Type0} = bind_guard(Arg, Map, Env, Eval, State),
@@ -2200,7 +2240,7 @@ handle_guard_not(Guard, Map, Env, Eval, State) ->
       end;
     pos ->
       {Map1, Type} = bind_guard(Arg, Map, Env, neg, State),
-      case t_is_atom(false, Type) of
+      case t_is_any_atom(false, Type, Opaques) of
 	true -> {Map1, t_atom(true)};
 	false ->
 	  {_, Type0} = bind_guard(Arg, Map, Env, Eval, State),
@@ -2212,10 +2252,11 @@ handle_guard_not(Guard, Map, Env, Eval, State) ->
       case t_is_none(Bool) of
 	true -> throw({fatal_fail, none});
 	false ->
-	  case t_atom_vals(Bool) of
+	  case t_atom_vals(Bool, Opaques) of
 	    ['true'] -> {Map1, t_atom(false)};
 	    ['false'] -> {Map1, t_atom(true)};
-	    [_, _] -> {Map1, Bool}
+	    [_, _] -> {Map1, Bool};
+            unknown -> signal_guard_fail(Eval, Guard, [Type], State)
 	  end
       end
   end.
@@ -2235,27 +2276,40 @@ bind_guard_list([], Map, _Env, _Eval, _State, Acc) ->
 			state()) -> no_return().
 
 signal_guard_fail(Eval, Guard, ArgTypes, State) ->
+  signal_guard_failure(Eval, Guard, ArgTypes, fail, State).
+
+signal_guard_fatal_fail(Eval, Guard, ArgTypes, State) ->
+  signal_guard_failure(Eval, Guard, ArgTypes, fatal_fail, State).
+
+signal_guard_failure(Eval, Guard, ArgTypes, Tag, State) ->
   Args = cerl:call_args(Guard),
   F = cerl:atom_val(cerl:call_name(Guard)),
-  MFA = {cerl:atom_val(cerl:call_module(Guard)), F, length(Args)},
-  Msg =
+  {M, F, A} = MFA = {cerl:atom_val(cerl:call_module(Guard)), F, length(Args)},
+  Opaques = State#state.opaques,
+  {Kind, XInfo} =
+    case erl_bif_types:opaque_args(M, F, A, ArgTypes, Opaques) of
+      [] ->
+        {case Eval of
+           neg -> neg_guard_fail;
+           pos -> guard_fail;
+           dont_know -> guard_fail
+         end,
+         []};
+      Ns -> {opaque_guard, [Ns]}
+    end,
+  FArgs =
     case is_infix_op(MFA) of
       true ->
 	[ArgType1, ArgType2] = ArgTypes,
 	[Arg1, Arg2] = Args,
-	Kind = 
-	  case Eval of
-	    neg -> neg_guard_fail;
-	    pos -> guard_fail;
-	    dont_know -> guard_fail
-	  end,
-	{Kind, [format_args_1([Arg1], [ArgType1], State),
-		atom_to_list(F),
-		format_args_1([Arg2], [ArgType2], State)]};
+	[format_args_1([Arg1], [ArgType1], State),
+         atom_to_list(F),
+         format_args_1([Arg2], [ArgType2], State)] ++ XInfo;
       false ->
-	mk_guard_msg(Eval, F, Args, ArgTypes, State)
+        [F, format_args(Args, ArgTypes, State)]
     end,
-  throw({fail, {Guard, Msg}}).
+  Msg = {Kind, FArgs},
+  throw({Tag, {Guard, Msg}}).
 
 is_infix_op({erlang, '=:=', 2}) -> true;
 is_infix_op({erlang, '==', 2}) -> true;
@@ -2268,25 +2322,10 @@ is_infix_op({erlang, '>=', 2}) -> true;
 is_infix_op({M, F, A}) when is_atom(M), is_atom(F),
 			    is_integer(A), 0 =< A, A =< 255 -> false.
 
--spec signal_guard_fatal_fail(eval(), cerl:c_call(), [erl_types:erl_type()],
-			      state()) -> no_return().
-
-signal_guard_fatal_fail(Eval, Guard, ArgTypes, State) ->
-  Args = cerl:call_args(Guard),
-  F = cerl:atom_val(cerl:call_name(Guard)),
-  Msg = mk_guard_msg(Eval, F, Args, ArgTypes, State),
-  throw({fatal_fail, {Guard, Msg}}).
-
-mk_guard_msg(Eval, F, Args, ArgTypes, State) ->
-  FArgs = [F, format_args(Args, ArgTypes, State)],
-  case any_has_opaque_subtype(ArgTypes) of
-    true -> {opaque_guard, FArgs};
-    false ->
-      case Eval of
-	neg -> {neg_guard_fail, FArgs};
-	pos -> {guard_fail, FArgs};
-	dont_know -> {guard_fail, FArgs}
-      end
+bif_args(M, F, A) ->
+  case erl_bif_types:arg_types(M, F, A) of
+    unknown -> lists:duplicate(A, t_any());
+    List -> List
   end.
 
 bind_guard_case_clauses(Arg, Clauses, Map0, Env, Eval, State) ->
@@ -2366,14 +2405,15 @@ bind_guard_case_clauses(GenArgType, GenMap, ArgExpr, [Clause|Left],
 	  end,
 	  {NewMap3, CType} = bind_guard(cerl:clause_body(Clause), NewMap2,
 					Env, Eval, State),
+          Opaques = State#state.opaques,
 	  case Eval of
 	    pos ->
-	      case t_is_atom(true, CType) of
+	      case t_is_any_atom(true, CType, Opaques) of
 		true -> ok;
 		false -> throw({fail, none})
 	      end;
 	    neg ->
-	      case t_is_atom(false, CType) of
+	      case t_is_any_atom(false, CType, Opaques) of
 		true -> ok;
 		false -> throw({fail, none})
 	      end;
@@ -2501,8 +2541,11 @@ enter_type(Key, Val, MS) ->
 	    error ->
 	      ?debug("Entering ~p :: ~s\n", [KeyLabel, t_to_string(Val)]),
 	      case dict:find(KeyLabel, Dict) of
-		{ok, Val} -> MS;
-		{ok, _OldVal} -> store_map(KeyLabel, Val, MS);
+		{ok, Value} ->
+                  case erl_types:t_is_equal(Val, Value) of
+                    true -> MS;
+                    false -> store_map(KeyLabel, Val, MS)
+                  end;
 		error -> store_map(KeyLabel, Val, MS)
 	      end
 	  end
@@ -2611,10 +2654,15 @@ get_label(L) when is_integer(L) ->
 get_label(T) ->
   cerl_trees:get_label(T).
 
-t_is_simple(ArgType) ->
-  t_is_atom(ArgType) orelse t_is_number(ArgType) orelse t_is_port(ArgType)
-    orelse t_is_pid(ArgType) orelse t_is_reference(ArgType)
-    orelse t_is_nil(ArgType).
+t_is_simple(ArgType, State) ->
+  Opaques = State#state.opaques,
+  t_is_atom(ArgType, Opaques) orelse t_is_number(ArgType, Opaques)
+    orelse t_is_port(ArgType, Opaques)
+    orelse t_is_pid(ArgType, Opaques) orelse t_is_reference(ArgType, Opaques)
+    orelse t_is_nil(ArgType, Opaques).
+
+remove_local_opaque_types(Type, Opaques) ->
+  t_unopaque(Type, Opaques).
 
 %% t_is_structured(ArgType) ->
 %%   case t_is_nil(ArgType) of
@@ -2638,12 +2686,6 @@ is_call_to_send(Tree) ->
 	andalso (Arity =:= 2)
   end.
 
-any_opaque(Ts) ->
-  lists:any(fun erl_types:t_is_opaque/1, Ts).
-
-any_has_opaque_subtype(Ts) ->
-  lists:any(fun erl_types:t_has_opaque_subtype/1, Ts).
-
 filter_match_fail([Clause] = Cls) ->
   Body = cerl:clause_body(Clause),
   case cerl:type(Body) of
@@ -2662,12 +2704,6 @@ filter_match_fail([]) ->
   %%      receive after 1 -> ok end
   [].
 
-determine_mode(Type, Opaques) ->
-  case lists:member(Type, Opaques) of
-    true  -> opaque;
-    false -> structured
-  end.
-
 %%% ===========================================================================
 %%%
 %%%  The State.
@@ -2679,7 +2715,7 @@ state__new(Callgraph, Tree, Plt, Module, Records) ->
     erl_types:t_opaque_from_records(Records),
   TreeMap = build_tree_map(Tree),
   Funs = dict:fetch_keys(TreeMap),
-  FunTab = init_fun_tab(Funs, dict:new(), TreeMap, Callgraph, Plt, Opaques),
+  FunTab = init_fun_tab(Funs, dict:new(), TreeMap, Callgraph, Plt),
   ExportedFuns =
     [Fun || Fun <- Funs--[top], dialyzer_callgraph:is_escaping(Fun, Callgraph)],
   Work = init_work(ExportedFuns),
@@ -2740,12 +2776,14 @@ state__add_warning(#state{warnings = Warnings, warning_mode = true} = State,
   case Force of
     true ->
       Warn = {Tag, {get_file(Ann), abs(get_line(Ann))}, Msg},
+      ?debug("MSG ~s\n", [dialyzer:format_warning(Warn)]),
       State#state{warnings = [Warn|Warnings]};
     false ->
       case is_compiler_generated(Ann) of
 	true -> State;
 	false ->
 	  Warn = {Tag, {get_file(Ann), get_line(Ann)}, Msg},
+          ?debug("MSG ~s\n", [dialyzer:format_warning(Warn)]),
 	  State#state{warnings = [Warn|Warnings]}
       end
   end.
@@ -2875,10 +2913,10 @@ build_tree_map(Tree) ->
     end,
   cerl_trees:fold(Fun, dict:new(), Tree).
 
-init_fun_tab([top|Left], Dict, TreeMap, Callgraph, Plt, Opaques) ->
+init_fun_tab([top|Left], Dict, TreeMap, Callgraph, Plt) ->
   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) ->
+  init_fun_tab(Left, NewDict, TreeMap, Callgraph, Plt);
+init_fun_tab([Fun|Left], Dict, TreeMap, Callgraph, Plt) ->
   Arity = cerl:fun_arity(dict:fetch(Fun, TreeMap)),
   FunEntry =
     case dialyzer_callgraph:is_escaping(Fun, Callgraph) of
@@ -2895,8 +2933,8 @@ init_fun_tab([Fun|Left], Dict, TreeMap, Callgraph, Plt, Opaques) ->
       false -> {not_handled, {lists:duplicate(Arity, t_none()), t_unit()}}
     end,
   NewDict = dict:store(Fun, FunEntry, Dict),
-  init_fun_tab(Left, NewDict, TreeMap, Callgraph, Plt, Opaques);
-init_fun_tab([], Dict, _TreeMap, _Callgraph, _Plt, _Opaques) ->
+  init_fun_tab(Left, NewDict, TreeMap, Callgraph, Plt);
+init_fun_tab([], Dict, _TreeMap, _Callgraph, _Plt) ->
   ?debug("DICT:~p\n",[dict:to_list(Dict)]),
   Dict.
 
@@ -2945,34 +2983,27 @@ state__update_fun_entry(Tree, ArgTypes, Out0,
     if Fun =:= top -> Out0;
        true ->
 	case lookup_fun_sig(Fun, CG, Plt) of
-	  {value, {SigRet, _}} -> t_inf(SigRet, Out0, opaque);
+	  {value, {SigRet, _}} -> t_inf(SigRet, Out0);
 	  none -> Out0
 	end
     end,
   Out = t_limit(Out1, ?TYPE_LIMIT),
-  case dict:find(Fun, FunTab) of
-    {ok, {ArgTypes, OldOut}} ->
-      case t_is_equal(OldOut, Out) of
-	true ->
-	  ?debug("Fixpoint for ~w: ~s\n",
-		 [state__lookup_name(Fun, State),
-		  t_to_string(t_fun(ArgTypes, Out))]),
-	  State;
-	false ->
-	  NewEntry = {ArgTypes, Out},
-	  ?debug("New Entry for ~w: ~s\n",
-		 [state__lookup_name(Fun, State),
-		  t_to_string(t_fun(ArgTypes, Out))]),
-	  NewFunTab = dict:store(Fun, NewEntry, FunTab),
-	  State1 = State#state{fun_tab = NewFunTab},
-	  state__add_work_from_fun(Tree, State1)
-      end;
-    {ok, {NewArgTypes, _OldOut}} ->
-      %% Can only happen in self-recursive functions. Only update the out type.
-      NewEntry = {NewArgTypes, Out},
+  {ok, {OldArgTypes, OldOut}} = dict:find(Fun, FunTab),
+  SameArgs = lists:all(fun({A, B}) -> erl_types:t_is_equal(A, B)
+                       end, lists:zip(OldArgTypes, ArgTypes)),
+  SameOut = t_is_equal(OldOut, Out),
+  if
+    SameArgs, SameOut ->
+      ?debug("Fixpoint for ~w: ~s\n",
+	     [state__lookup_name(Fun, State),
+	      t_to_string(t_fun(ArgTypes, Out))]),
+      State;
+    true ->
+      %% Can only happen in self-recursive functions.
+      NewEntry = {OldArgTypes, Out},
       ?debug("New Entry for ~w: ~s\n",
 	     [state__lookup_name(Fun, State),
-	      t_to_string(t_fun(NewArgTypes, Out))]),
+	      t_to_string(t_fun(OldArgTypes, Out))]),
       NewFunTab = dict:store(Fun, NewEntry, FunTab),
       State1 = State#state{fun_tab = NewFunTab},
       state__add_work_from_fun(Tree, State1)
@@ -2993,7 +3024,7 @@ state__add_work_from_fun(Tree, #state{callgraph = Callgraph,
 	  %% Must filter the result for results in this module.
 	  FilteredList = [L || {ok, L} <- LabelList, dict:is_key(L, TreeMap)],
 	  ?debug("~w: Will try to add:~w\n",
-		 [state__lookup_name(get_label(Tree), State), MFAList]),
+		 [state__lookup_name(Label, State), MFAList]),
 	  lists:foldl(fun(L, AccState) ->
 			  state__add_work(L, AccState)
 		      end, State, FilteredList)
@@ -3054,7 +3085,8 @@ forward_args(Fun, ArgTypes, #state{work = Work, fun_tab = FunTab} = State) ->
   case Fixpoint of
     true -> State;
     false ->
-      NewArgTypes = [t_sup(X, Y) || {X, Y} <- lists:zip(ArgTypes, OldArgTypes)],
+      NewArgTypes = [t_sup(X, Y) ||
+                      {X, Y} <- lists:zip(ArgTypes, OldArgTypes)],
       NewWork = add_work(Fun, Work),
       ?debug("~w: forwarding args ~s\n",
 	     [state__lookup_name(Fun, State),
@@ -3238,13 +3270,13 @@ format_field_diffs(RecConstruction, #state{records = R}) ->
 
 -spec format_sig_args(erl_types:erl_type(), state()) -> string().
 
-format_sig_args(Type, #state{records = R}) ->
-  SigArgs = t_fun_args(Type),
+format_sig_args(Type, #state{opaques = Opaques} = State) ->
+  SigArgs = t_fun_args(Type, Opaques),
   case SigArgs of
     [] -> "()";
     [SArg|SArgs] ->
-      lists:flatten("(" ++ t_to_string(SArg, R)
-		        ++ ["," ++ t_to_string(T, R) || T <- SArgs] ++ ")")
+      lists:flatten("(" ++ format_type(SArg, State)
+		        ++ ["," ++ format_type(T, State) || T <- SArgs] ++ ")")
     end.
 
 format_cerl(Tree) ->
diff --git a/lib/dialyzer/src/dialyzer_succ_typings.erl b/lib/dialyzer/src/dialyzer_succ_typings.erl
index 84379642bf..f0488b5ee3 100644
--- a/lib/dialyzer/src/dialyzer_succ_typings.erl
+++ b/lib/dialyzer/src/dialyzer_succ_typings.erl
@@ -2,7 +2,7 @@
 %%-----------------------------------------------------------------------
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2006-2012. All Rights Reserved.
+%% Copyright Ericsson AB 2006-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -149,8 +149,10 @@ get_warnings(Callgraph, Plt, DocPlt, Codeserver,
   NewState = InitState#st{no_warn_unused = NoWarnUnused},
   Mods = dialyzer_callgraph:modules(NewState#st.callgraph),
   MiniPlt = NewState#st.plt,
+  FindOpaques = lookup_and_find_opaques_fun(Codeserver),
   CWarns =
-    dialyzer_contracts:get_invalid_contract_warnings(Mods, Codeserver, MiniPlt),
+    dialyzer_contracts:get_invalid_contract_warnings(Mods, Codeserver,
+                                                     MiniPlt, FindOpaques),
   MiniDocPlt = dialyzer_plt:get_mini_plt(DocPlt),
   ModWarns =
     ?timing(TimingServer, "warning",
@@ -261,7 +263,16 @@ refine_one_module(M, {CodeServer, Callgraph, Plt, _Solvers}) ->
   FunTypes = get_fun_types_from_plt(AllFuns, Callgraph, Plt),
   NewFunTypes =
     dialyzer_dataflow:get_fun_types(ModCode, Plt, Callgraph, Records),
-  case reached_fixpoint(FunTypes, NewFunTypes) of
+  Contracts1 = dialyzer_codeserver:lookup_mod_contracts(M, CodeServer),
+  Contracts = orddict:from_list(dict:to_list(Contracts1)),
+  FindOpaques = find_opaques_fun(Records),
+  DecoratedFunTypes =
+    decorate_succ_typings(Contracts, Callgraph, NewFunTypes, FindOpaques),
+  %% ?debug("NewFunTypes       ~p\n   ~n", [dict:to_list(NewFunTypes)]),
+  %% ?debug("refine DecoratedFunTypes ~p\n   ~n", [dict:to_list(DecoratedFunTypes)]),
+  debug_pp_functions("Refine", NewFunTypes, DecoratedFunTypes, Callgraph),
+
+  case reached_fixpoint(FunTypes, DecoratedFunTypes) of
     true -> [];
     {false, NotFixpoint} ->
       ?debug("Not fixpoint\n", []),
@@ -357,9 +368,16 @@ find_succ_types_for_scc(SCC, {Codeserver, Callgraph, Plt, Solvers}) ->
   AllFunSet = sets:from_list([X || {X, _} <- AllFuns]),
   FilteredFunTypes =
     dict:filter(fun(X, _) -> sets:is_element(X, AllFunSet) end, FunTypes),
+  FindOpaques = lookup_and_find_opaques_fun(Codeserver),
+  DecoratedFunTypes =
+    decorate_succ_typings(Contracts3, Callgraph, FilteredFunTypes, FindOpaques),
   %% Check contracts
   PltContracts =
-    dialyzer_contracts:check_contracts(Contracts3, Callgraph, FilteredFunTypes),
+    dialyzer_contracts:check_contracts(Contracts3, Callgraph,
+                                       DecoratedFunTypes, FindOpaques),
+  %% ?debug("FilteredFunTypes ~p\n   ~n", [dict:to_list(FilteredFunTypes)]),
+  %% ?debug("SCC DecoratedFunTypes ~p\n   ~n", [dict:to_list(DecoratedFunTypes)]),
+  debug_pp_functions("SCC", FilteredFunTypes, DecoratedFunTypes, Callgraph),
   ContractFixpoint =
     lists:all(fun({MFA, _C}) ->
 		  %% Check the non-deleted PLT
@@ -368,16 +386,47 @@ find_succ_types_for_scc(SCC, {Codeserver, Callgraph, Plt, Solvers}) ->
 		    {value, _} -> true
 		  end
 	      end, PltContracts),
-  Plt = insert_into_plt(FilteredFunTypes, Callgraph, Plt),
+  Plt = insert_into_plt(DecoratedFunTypes, Callgraph, Plt),
   Plt = dialyzer_plt:insert_contract_list(Plt, PltContracts),
   case (ContractFixpoint andalso 
-	reached_fixpoint_strict(PropTypes, FilteredFunTypes)) of
+	reached_fixpoint_strict(PropTypes, DecoratedFunTypes)) of
     true -> [];
     false ->
       ?debug("Not fixpoint for: ~w\n", [AllFuns]),
       [Fun || {Fun, _Arity} <- AllFuns]
   end.
 
+decorate_succ_typings(Contracts, Callgraph, FunTypes, FindOpaques) ->
+  F = fun(Label, Type) ->
+          case dialyzer_callgraph:lookup_name(Label, Callgraph) of
+            {ok, MFA} ->
+              case orddict:find(MFA, Contracts) of
+                {ok, {_FileLine, Contract}} ->
+                  Args = dialyzer_contracts:get_contract_args(Contract),
+                  Ret = dialyzer_contracts:get_contract_return(Contract),
+                  C = erl_types:t_fun(Args, Ret),
+                  {M, _, _} = MFA,
+                  Opaques = FindOpaques(M),
+                  erl_types:t_decorate_with_opaque(Type, C, Opaques);
+                error -> Type
+              end;
+            error -> Type
+          end
+      end,
+  dict:map(F, FunTypes).
+
+lookup_and_find_opaques_fun(Codeserver) ->
+  fun(Module) ->
+      Records = dialyzer_codeserver:lookup_mod_records(Module, Codeserver),
+      (find_opaques_fun(Records))(Module)
+  end.
+
+find_opaques_fun(Records) ->
+  fun(Module) ->
+      erl_types:module_builtin_opaques(Module) ++
+      erl_types:t_opaque_from_records(Records)
+  end.
+
 get_fun_types_from_plt(FunList, Callgraph, Plt) ->
   get_fun_types_from_plt(FunList, Callgraph, Plt, dict:new()).
 
@@ -443,9 +492,30 @@ debug_pp_succ_typings(SuccTypes) ->
    || {MFA, {contract, RetFun, ArgT}} <- SuccTypes],
   ?debug("\n", []),
   ok.
+
+debug_pp_functions(Header, FunTypes, DecoratedFunTypes, Callgraph) ->
+  ?debug("FunTypes (~s)\n", [Header]),
+  FTypes = lists:keysort(1, dict:to_list(FunTypes)),
+  DTypes = lists:keysort(1, dict:to_list(DecoratedFunTypes)),
+  Fun = fun({{Label, Type},{Label, DecoratedType}}) ->
+            Name = lookup_name(Label, Callgraph),
+            ?debug("~w (~w): ~s\n",
+                   [Name, Label, erl_types:t_to_string(Type)]),
+            case erl_types:t_is_equal(Type, DecoratedType) of
+              true -> ok;
+              false ->
+                ?debug("  With opaque types: ~s\n",
+                       [erl_types:t_to_string(DecoratedType)])
+            end
+        end,
+  lists:foreach(Fun, lists:zip(FTypes, DTypes)),
+  ?debug("\n", []).
 -else.
 debug_pp_succ_typings(_) ->
   ok.
+
+debug_pp_functions(_, _, _, _) ->
+  ok.
 -endif.
 
 lookup_name(F, CG) ->
diff --git a/lib/dialyzer/src/dialyzer_typesig.erl b/lib/dialyzer/src/dialyzer_typesig.erl
index a418a11e65..db7875704a 100644
--- a/lib/dialyzer/src/dialyzer_typesig.erl
+++ b/lib/dialyzer/src/dialyzer_typesig.erl
@@ -2,7 +2,7 @@
 %%-----------------------------------------------------------------------
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2006-2013. All Rights Reserved.
+%% Copyright Ericsson AB 2006-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -31,28 +31,30 @@
 -export([analyze_scc/6]).
 -export([get_safe_underapprox/2]).
 
+%%-import(helper, %% 'helper' could be any module doing sanity checks...
+-import(erl_types,
+        [t_has_var/1, t_inf/2, t_is_equal/2, t_is_subtype/2,
+        t_subtract/2, t_subtract_list/2, t_sup/1, t_sup/2,t_unify/2]).
+
 -import(erl_types,
 	[t_any/0, t_atom/0, t_atom_vals/1,
 	 t_binary/0, t_bitstr/0, t_bitstr/2, t_bitstr_concat/1, t_boolean/0,
 	 t_collect_vars/1, t_cons/2, t_cons_hd/1, t_cons_tl/1,
 	 t_float/0, t_from_range/2, t_from_term/1,
 	 t_fun/0, t_fun/2, t_fun_args/1, t_fun_range/1,
-	 t_has_var/1,
-	 t_inf/2, t_inf/3, t_integer/0,
-	 t_is_any/1, t_is_atom/1, t_is_atom/2, t_is_cons/1, t_is_equal/2,
+         t_integer/0,
+	 t_is_any/1, t_is_atom/1, t_is_any_atom/2, t_is_cons/1,
 	 t_is_float/1, t_is_fun/1,
 	 t_is_integer/1, t_non_neg_integer/0,
 	 t_is_list/1, t_is_nil/1, t_is_none/1, t_is_number/1,
 
-	 t_is_subtype/2, t_limit/2, t_list/0, t_list/1,
+         t_limit/2, t_list/0, t_list/1,
 	 t_list_elements/1, t_nonempty_list/1, t_maybe_improper_list/0,
 	 t_module/0, t_number/0, t_number_vals/1,
-	 t_opaque_match_record/2, t_opaque_matching_structure/2,
-	 t_opaque_from_records/1,
 	 t_pid/0, t_port/0, t_product/1, t_reference/0,
-	 t_subst/2, t_subtract/2, t_subtract_list/2, t_sup/1, t_sup/2,
+	 t_subst/2,
 	 t_timeout/0, t_tuple/0, t_tuple/1,
-	 t_unify/3, t_var/1, t_var_name/1,
+         t_var/1, t_var_name/1,
 	 t_none/0, t_unit/0]).
 
 -include("dialyzer.hrl").
@@ -105,11 +107,10 @@
 		module                          :: module(),
 		name_map    = dict:new()        :: dict(),
 		next_label  = 0                 :: label(),
-		self_rec                        :: erl_types:erl_type(),
+		self_rec                        :: 'false' | erl_types:erl_type(),
 		plt                             :: dialyzer_plt:plt(),
 		prop_types  = {'d', dict:new()} :: dict_or_ets(),
 		records     = dict:new()        :: dict(),
-		opaques     = []                :: [erl_types:erl_type()],
 		scc         = []                :: [type_var()],
 		mfas                            :: [tuple()],
                 solvers     = []                :: [solver()]
@@ -192,11 +193,10 @@ solvers(Solvers) -> Solvers.
 %%
 %% ============================================================================
 
-traverse_scc([{MFA, Def, Rec}|Left], DefSet, AccState) ->
+traverse_scc([{_MFA, Def, Rec}|Left], DefSet, AccState) ->
   TmpState1 = state__set_rec_dict(AccState, Rec),
-  TmpState2 = state__set_opaques(TmpState1, MFA),
   DummyLetrec = cerl:c_letrec([Def], cerl:c_atom(foo)),
-  {NewAccState, _} = traverse(DummyLetrec, DefSet, TmpState2),
+  {NewAccState, _} = traverse(DummyLetrec, DefSet, TmpState1),
   traverse_scc(Left, DefSet, NewAccState);
 traverse_scc([], _DefSet, AccState) ->
   AccState.
@@ -386,12 +386,7 @@ traverse(Tree, DefinedVars, State) ->
       case cerl:unfold_literal(Tree) of
 	Tree ->
 	  Type = t_from_term(cerl:concrete(Tree)),
-	  NewType =
-	    case erl_types:t_opaque_match_atom(Type, State#state.opaques) of
-	      [Opaque] -> Opaque;
-	      _ -> Type
-	    end,
-	  {State, NewType};
+	  {State, Type};
 	NewTree -> traverse(NewTree, DefinedVars, State)
       end;
     module ->
@@ -462,25 +457,17 @@ traverse(Tree, DefinedVars, State) ->
 	[Tag|Fields] ->
 	  case cerl:is_c_atom(Tag) of
 	    true ->
-	      %% Check if an opaque term is constructed.
-	      case t_opaque_match_record(TupleType, State#state.opaques) of
-		[Opaque] ->
-		  OpStruct = t_opaque_matching_structure(TupleType, Opaque),
-		  State3 = state__store_conj(TupleType, sub, OpStruct, State2),
-		  {State3, Opaque};
-		%% Check if a record is constructed.
-		_ ->
-		  Arity = length(Fields),
-		  Records = State2#state.records,
-		  case lookup_record(Records, cerl:atom_val(Tag), Arity) of
-		    error -> {State2, TupleType};
-		    {ok, RecType} ->
-		      State3 = state__store_conj(TupleType, sub, RecType, State2),
-		      {State3, TupleType}
-		  end
-	      end;
+              %% Check if a record is constructed.
+              Arity = length(Fields),
+              Records = State2#state.records,
+              case lookup_record(Records, cerl:atom_val(Tag), Arity) of
+                error -> {State2, TupleType};
+                {ok, RecType} ->
+                  State3 = state__store_conj(TupleType, sub, RecType, State2),
+                  {State3, TupleType}
+              end;
 	    false -> {State2, TupleType}
-	  end;
+          end;
 	[] -> {State2, TupleType}
       end;
     values ->
@@ -591,9 +578,13 @@ handle_try(Tree, DefinedVars, State) ->
   case state__is_in_guard(State) of
     true ->
       Conj1 = mk_conj_constraint_list([ArgBodyCs,
-				       mk_constraint(BodyVar, eq, TreeVar)]),
+				       mk_constraint(BodyVar,
+                                                     eq,
+                                                     TreeVar)]),
       Disj = mk_disj_constraint_list([Conj1,
-				      mk_constraint(HandlerVar, eq, TreeVar)]),
+				      mk_constraint(HandlerVar,
+                                                    eq,
+                                                    TreeVar)]),
       NewState1 = state__new_constraint_context(HandlerState),
       Conj2 = mk_conj_constraint_list([OldCs, Disj]),
       NewState2 = state__store_conj(Conj2, NewState1),
@@ -604,19 +595,27 @@ handle_try(Tree, DefinedVars, State) ->
 	  {false, false} ->
 	    Conj1 =
 	      mk_conj_constraint_list([ArgBodyCs,
-				       mk_constraint(TreeVar, eq, BodyVar)]),
+				       mk_constraint(TreeVar,
+                                                     eq,
+                                                     BodyVar)]),
 	    Conj2 =
 	      mk_conj_constraint_list([HandlerCs,
-				       mk_constraint(TreeVar, eq, HandlerVar)]),
+				       mk_constraint(TreeVar,
+                                                     eq,
+                                                     HandlerVar)]),
 	    Disj = mk_disj_constraint_list([Conj1, Conj2]),
 	    {Disj, TreeVar};
 	  {false, true} ->
 	    {mk_conj_constraint_list([ArgBodyCs,
-				      mk_constraint(TreeVar, eq, BodyVar)]),
+				      mk_constraint(TreeVar,
+                                                    eq,
+                                                    BodyVar)]),
 	     BodyVar};
 	  {true, false} ->
 	    {mk_conj_constraint_list([HandlerCs,
-				      mk_constraint(TreeVar, eq, HandlerVar)]),
+				      mk_constraint(TreeVar,
+                                                    eq,
+                                                    HandlerVar)]),
 	     HandlerVar};
 	  {true, true} ->
 	    ?debug("Throw failed\n", []),
@@ -668,10 +667,7 @@ handle_call(Call, DefinedVars, State) ->
 get_plt_constr(MFA, Dst, ArgVars, State) ->
   Plt = state__plt(State),
   PltRes = dialyzer_plt:lookup(Plt, MFA),
-  Opaques = State#state.opaques,
-  Module = State#state.module,
   SCCMFAs = State#state.mfas,
-  {FunModule, _, _} = MFA,
   Contract =
     case lists:member(MFA, SCCMFAs) of
       true -> none;
@@ -691,28 +687,24 @@ get_plt_constr(MFA, Dst, ArgVars, State) ->
 	  none ->
 	    {?mk_fun_var(fun(Map) ->
 			     ArgTypes = lookup_type_list(ArgVars, Map),
-			     dialyzer_contracts:get_contract_return(C, ArgTypes)
+                             get_contract_return(C, ArgTypes)
 			 end, ArgVars), GenArgs};
 	  {value, {PltRetType, PltArgTypes}} ->
 	    %% Need to combine the contract with the success typing.
 	    {?mk_fun_var(
 		fun(Map) ->
-		    ArgTypes0 = lookup_type_list(ArgVars, Map),
-		    ArgTypes = case FunModule =:= Module of
-				 false ->
-				   List = lists:zip(PltArgTypes, ArgTypes0),
-				   [erl_types:t_unopaque_on_mismatch(T1, T2, Opaques)
-				    || {T1, T2} <- List];
-				 true -> ArgTypes0
-			       end,
-		    CRet = dialyzer_contracts:get_contract_return(C, ArgTypes),
-		    t_inf(CRet, PltRetType, opaque)
+		    ArgTypes = lookup_type_list(ArgVars, Map),
+                    CRet = get_contract_return(C, ArgTypes),
+		    t_inf(CRet, PltRetType)
 		end, ArgVars),
-	     [t_inf(X, Y, opaque) || {X, Y} <- lists:zip(GenArgs, PltArgTypes)]}
+	     [t_inf(X, Y) || {X, Y} <- lists:zip(GenArgs, PltArgTypes)]}
 	end,
       state__store_conj_lists([Dst|ArgVars], sub, [RetType|ArgCs], State)
   end.
 
+get_contract_return(C, ArgTypes) ->
+  dialyzer_contracts:get_contract_return(C, ArgTypes).
+
 filter_match_fail([Clause] = Cls) ->
   Body = cerl:clause_body(Clause),
   case cerl:type(Body) of
@@ -1086,7 +1078,7 @@ get_bif_constr({erlang, Op, 2}, Dst, Args = [Arg1, Arg2], _State)
   when Op =:= '+'; Op =:= '-'; Op =:= '*' ->
   ReturnType = ?mk_fun_var(fun(Map) ->
 			       TmpArgTypes = lookup_type_list(Args, Map),
-			       erl_bif_types:type(erlang, Op, 2, TmpArgTypes)
+			       bif_return(erlang, Op, 2, TmpArgTypes)
 			   end, Args),
   ArgFun =
     fun(A, Pos) ->
@@ -1128,8 +1120,8 @@ get_bif_constr({erlang, Op, 2}, Dst, [Arg1, Arg2] = Args, _State)
     fun(LocalArg1, LocalArg2, LocalOp) ->
 	fun(Map) ->
 	    DstType = lookup_type(Dst, Map),
-	    IsTrue = t_is_atom(true, DstType),
-	    IsFalse = t_is_atom(false, DstType),
+	    IsTrue = t_is_any_atom(true, DstType),
+	    IsFalse = t_is_any_atom(false, DstType),
 	    case IsTrue orelse IsFalse of
 	      true ->
 		Arg1Type = lookup_type(LocalArg1, Map),
@@ -1176,7 +1168,7 @@ get_bif_constr({erlang, Op, 2}, Dst, [Arg1, Arg2] = Args, _State)
   Arg2Var = ?mk_fun_var(Arg2Fun, DstArgs),
   DstVar = ?mk_fun_var(fun(Map) ->
 			   TmpArgTypes = lookup_type_list(Args, Map),
-			   erl_bif_types:type(erlang, Op, 2, TmpArgTypes)
+			   bif_return(erlang, Op, 2, TmpArgTypes)
 		       end, Args),
   mk_conj_constraint_list([mk_constraint(Dst, sub, DstVar),
 			   mk_constraint(Arg1, sub, Arg1Var),
@@ -1218,7 +1210,7 @@ get_bif_constr({erlang, '++', 2}, Dst, [Hd, Tl] = Args, _State) ->
   ArgTypes = erl_bif_types:arg_types(erlang, '++', 2),
   ReturnType = ?mk_fun_var(fun(Map) ->
 			       TmpArgTypes = lookup_type_list(Args, Map),
-			       erl_bif_types:type(erlang, '++', 2, TmpArgTypes)
+			       bif_return(erlang, '++', 2, TmpArgTypes)
 			   end, Args),
   Cs = mk_constraints(Args, sub, ArgTypes),
   mk_conj_constraint_list([mk_constraint(Dst, sub, ReturnType),
@@ -1240,7 +1232,7 @@ get_bif_constr({erlang, is_function, 1}, Dst, [Arg], State) ->
 get_bif_constr({erlang, is_function, 2}, Dst, [Fun, Arity], _State) ->
   ArgFun = fun(Map) ->
 	       DstType = lookup_type(Dst, Map),
-	       case t_is_atom(true, DstType) of
+	       case t_is_any_atom(true, DstType) of
 		 true ->
 		   ArityType = lookup_type(Arity, Map),
 		   case t_number_vals(ArityType) of
@@ -1268,7 +1260,7 @@ get_bif_constr({erlang, is_reference, 1}, Dst, [Arg], State) ->
   get_bif_test_constr(Dst, Arg, t_reference(), State);
 get_bif_constr({erlang, is_record, 2}, Dst, [Var, Tag] = Args, _State) ->
   ArgFun = fun(Map) ->
-	       case t_is_atom(true, lookup_type(Dst, Map)) of
+	       case t_is_any_atom(true, lookup_type(Dst, Map)) of
 		 true -> t_tuple();
 		 false -> t_any()
 	       end
@@ -1276,7 +1268,7 @@ get_bif_constr({erlang, is_record, 2}, Dst, [Var, Tag] = Args, _State) ->
   ArgV = ?mk_fun_var(ArgFun, [Dst]),
   DstFun = fun(Map) ->
 	       TmpArgTypes = lookup_type_list(Args, Map),
-	       erl_bif_types:type(erlang, is_record, 2, TmpArgTypes)
+	       bif_return(erlang, is_record, 2, TmpArgTypes)
 	   end,
   DstV = ?mk_fun_var(DstFun, Args),
   mk_conj_constraint_list([mk_constraint(Dst, sub, DstV),
@@ -1285,10 +1277,9 @@ get_bif_constr({erlang, is_record, 2}, Dst, [Var, Tag] = Args, _State) ->
 get_bif_constr({erlang, is_record, 3}, Dst, [Var, Tag, Arity] = Args, State) ->
   %% TODO: Revise this to make it precise for Tag and Arity.
   Records = State#state.records,
-  AllOpaques = State#state.opaques,
   ArgFun =
     fun(Map) ->
-	case t_is_atom(true, lookup_type(Dst, Map)) of
+	case t_is_any_atom(true, lookup_type(Dst, Map)) of
 	  true ->
 	    ArityType = lookup_type(Arity, Map),
 	    case t_is_integer(ArityType) of
@@ -1304,10 +1295,7 @@ get_bif_constr({erlang, is_record, 3}, Dst, [Var, Tag, Arity] = Args, State) ->
 			  [TagVal] ->
 			    case lookup_record(Records, TagVal, ArityVal - 1) of
 			      {ok, Type} ->
-				case t_opaque_match_record(Type, AllOpaques) of
-				  [Opaque] -> Opaque;
-				  _ -> Type
-				end;
+                                Type;
 			      error -> GenRecord
 			    end;
 			  _ -> GenRecord
@@ -1323,38 +1311,9 @@ get_bif_constr({erlang, is_record, 3}, Dst, [Var, Tag, Arity] = Args, State) ->
     end,
   ArgV = ?mk_fun_var(ArgFun, [Tag, Arity, Dst]),
   DstFun = fun(Map) ->
-	       [TmpVar, TmpTag, TmpArity] = TmpArgTypes = lookup_type_list(Args, Map),
-	       TmpArgTypes2 =
-		 case lists:member(TmpVar, AllOpaques) of
-		   true ->
-		     case t_is_integer(TmpArity) of
-		       true ->
-			 case t_number_vals(TmpArity) of
-			   [TmpArityVal] ->
-			     case t_is_atom(TmpTag) of
-			       true ->
-				 case t_atom_vals(TmpTag) of
-				   [TmpTagVal] ->
-				     case lookup_record(Records, TmpTagVal,
-							TmpArityVal - 1) of
-				       {ok, TmpType} ->
-					 case t_is_none(t_inf(TmpType, TmpVar, opaque)) of
-					   true  -> TmpArgTypes;
-					   false -> [TmpType, TmpTag, TmpArity]
-					 end;
-				       error -> TmpArgTypes
-				     end;
-				   _ -> TmpArgTypes
-				 end;
-			       false -> TmpArgTypes
-			     end;
-			   _ -> TmpArgTypes
-			 end;
-		       false -> TmpArgTypes
-		     end;
-		   false -> TmpArgTypes
-		 end,
-	       erl_bif_types:type(erlang, is_record, 3, TmpArgTypes2)
+	       [TmpVar, TmpTag, TmpArity] = lookup_type_list(Args, Map),
+               TmpArgTypes = [TmpVar,TmpTag,TmpArity],
+	       bif_return(erlang, is_record, 3, TmpArgTypes)
 	   end,
   DstV = ?mk_fun_var(DstFun, Args),
   mk_conj_constraint_list([mk_constraint(Dst, sub, DstV),
@@ -1369,12 +1328,14 @@ get_bif_constr({erlang, 'and', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
   ArgFun = fun(Var) ->
 	       fun(Map) ->
 		   DstType = lookup_type(Dst, Map),
-		   case t_is_atom(true, DstType) of
+		   case t_is_any_atom(true, DstType) of
 		     true -> True;
 		     false ->
-		       case t_is_atom(false, DstType) of
+		       case t_is_any_atom(false, DstType) of
 			 true ->
-			   case t_is_atom(true, lookup_type(Var, Map)) of
+			   case
+                             t_is_any_atom(true, lookup_type(Var, Map))
+                           of
 			     true -> False;
 			     false -> t_boolean()
 			   end;
@@ -1386,15 +1347,15 @@ get_bif_constr({erlang, 'and', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
 	   end,
   DstFun = fun(Map) ->
 	       Arg1Type = lookup_type(Arg1, Map),
-	       case t_is_atom(false, Arg1Type) of
+	       case t_is_any_atom(false, Arg1Type) of
 		 true -> False;
 		 false ->
 		   Arg2Type = lookup_type(Arg2, Map),
-		   case t_is_atom(false, Arg2Type) of
+		   case t_is_any_atom(false, Arg2Type) of
 		     true -> False;
 		     false ->
-		       case (t_is_atom(true, Arg1Type)
-			     andalso t_is_atom(true, Arg2Type)) of
+		       case (t_is_any_atom(true, Arg1Type)
+			     andalso t_is_any_atom(true, Arg2Type)) of
 			 true -> True;
 			 false -> t_boolean()
 		       end
@@ -1413,12 +1374,14 @@ get_bif_constr({erlang, 'or', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
   ArgFun = fun(Var) ->
 	       fun(Map) ->
 		   DstType = lookup_type(Dst, Map),
-		   case t_is_atom(false, DstType) of
+		   case t_is_any_atom(false, DstType) of
 		     true -> False;
 		     false ->
-		       case t_is_atom(true, DstType) of
+		       case t_is_any_atom(true, DstType) of
 			 true ->
-			   case t_is_atom(false, lookup_type(Var, Map)) of
+			   case
+                             t_is_any_atom(false, lookup_type(Var, Map))
+                           of
 			     true -> True;
 			     false -> t_boolean()
 			   end;
@@ -1430,15 +1393,15 @@ get_bif_constr({erlang, 'or', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
 	   end,
   DstFun = fun(Map) ->
 	       Arg1Type = lookup_type(Arg1, Map),
-	       case t_is_atom(true, Arg1Type) of
+	       case t_is_any_atom(true, Arg1Type) of
 		 true -> True;
 		 false ->
 		   Arg2Type = lookup_type(Arg2, Map),
-		   case t_is_atom(true, Arg2Type) of
+		   case t_is_any_atom(true, Arg2Type) of
 		     true -> True;
 		     false ->
-		       case (t_is_atom(false, Arg1Type)
-			     andalso t_is_atom(false, Arg2Type)) of
+		       case (t_is_any_atom(false, Arg1Type)
+			     andalso t_is_any_atom(false, Arg2Type)) of
 			 true -> False;
 			 false -> t_boolean()
 		       end
@@ -1465,10 +1428,10 @@ get_bif_constr({erlang, 'not', 1}, Dst, [Arg] = Args, _State) ->
   Fun = fun(Var) ->
 	    fun(Map) ->
 		Type = lookup_type(Var, Map),
-		case t_is_atom(true, Type) of
+		case t_is_any_atom(true, Type) of
 		  true -> False;
 		  false ->
-		    case t_is_atom(false, Type) of
+		    case t_is_any_atom(false, Type) of
 		      true -> True;
 		      false -> t_boolean()
 		    end
@@ -1485,10 +1448,10 @@ get_bif_constr({erlang, '=:=', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
 	fun(Map) ->
 	    DstType = lookup_type(Dst, Map),
 	    OtherVarType = lookup_type(OtherVar, Map),
-	    case t_is_atom(true, DstType) of
+	    case t_is_any_atom(true, DstType) of
 	      true -> OtherVarType;
 	      false ->
-		case t_is_atom(false, DstType) of
+		case t_is_any_atom(false, DstType) of
 		  true ->
 		    case is_singleton_type(OtherVarType) of
 		      true -> t_subtract(lookup_type(Self, Map), OtherVarType);
@@ -1518,7 +1481,7 @@ get_bif_constr({erlang, '=:=', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
 get_bif_constr({erlang, '==', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
   DstFun = fun(Map) ->
 	       TmpArgTypes = lookup_type_list(Args, Map),
-	       erl_bif_types:type(erlang, '==', 2, TmpArgTypes)
+	       bif_return(erlang, '==', 2, TmpArgTypes)
 	   end,
   ArgFun =
     fun(Var, Self) ->
@@ -1527,16 +1490,16 @@ get_bif_constr({erlang, '==', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
 	    DstType = lookup_type(Dst, Map),
 	    case is_singleton_non_number_type(VarType) of
 	      true ->
-		case t_is_atom(true, DstType) of
+		case t_is_any_atom(true, DstType) of
 		  true -> VarType;
 		  false ->
-		    case t_is_atom(false, DstType) of
+		    case t_is_any_atom(false, DstType) of
 		      true -> t_subtract(lookup_type(Self, Map), VarType);
 		      false -> t_any()
 		    end
 		end;
 	      false ->
-		case t_is_atom(true, DstType) of
+		case t_is_any_atom(true, DstType) of
 		  true ->
 		    case t_is_number(VarType) of
 		      true -> t_number();
@@ -1560,18 +1523,14 @@ get_bif_constr({erlang, '==', 2}, Dst, [Arg1, Arg2] = Args, _State) ->
 			   mk_constraint(Arg1, sub, ArgV1),
 			   mk_constraint(Arg2, sub, ArgV2)]);
 get_bif_constr({erlang, element, 2} = _BIF, Dst, Args,
-               #state{cs = Constrs, opaques = Opaques}) ->
+               #state{cs = Constrs}) ->
   GenType = erl_bif_types:type(erlang, element, 2),
   case t_is_none(GenType) of
     true -> ?debug("Bif: ~w failed\n", [_BIF]), throw(error);
     false ->
       Fun = fun(Map) ->
-		[I, T] = ATs = lookup_type_list(Args, Map),
-		ATs2 = case lists:member(T, Opaques) of
-			 true -> [I, erl_types:t_opaque_structure(T)];
-			 false -> ATs
-		       end,
-		erl_bif_types:type(erlang, element, 2, ATs2)
+		ATs2 = lookup_type_list(Args, Map),
+		bif_return(erlang, element, 2, ATs2)
 	    end,
       ReturnType = ?mk_fun_var(Fun, Args),
       ArgTypes = erl_bif_types:arg_types(erlang, element, 2),
@@ -1583,22 +1542,14 @@ get_bif_constr({erlang, element, 2} = _BIF, Dst, Args,
         end,
       mk_conj_constraint_list([mk_constraint(Dst, sub, ReturnType)|NewCs])
   end;
-get_bif_constr({M, F, A} = _BIF, Dst, Args, State) ->
+get_bif_constr({M, F, A} = _BIF, Dst, Args, _State) ->
   GenType = erl_bif_types:type(M, F, A),
-  Opaques = State#state.opaques,
   case t_is_none(GenType) of
     true -> ?debug("Bif: ~w failed\n", [_BIF]), throw(error);
     false ->
-      UnopaqueFun =
-	fun(T) -> case lists:member(T, Opaques)  of
-		    true -> erl_types:t_unopaque(T, [T]);
-		    false -> T
-		  end
-	end,
       ReturnType = ?mk_fun_var(fun(Map) ->
-				  TmpArgTypes0 = lookup_type_list(Args, Map),
-				  TmpArgTypes = [UnopaqueFun(T) || T<- TmpArgTypes0],
-				  erl_bif_types:type(M, F, A, TmpArgTypes)
+                                  TmpArgTypes = lookup_type_list(Args, Map),
+                                  bif_return(M, F, A, TmpArgTypes)
 			      end, Args),
       case erl_bif_types:is_known(M, F, A) of
 	false ->
@@ -1616,12 +1567,12 @@ get_bif_constr({M, F, A} = _BIF, Dst, Args, State) ->
   end.
 
 eval_inv_arith('+', _Pos, Dst, Arg) ->
-  erl_bif_types:type(erlang, '-', 2, [Dst, Arg]);
+  bif_return(erlang, '-', 2, [Dst, Arg]);
 eval_inv_arith('*', _Pos, Dst, Arg) ->
   case t_number_vals(Arg) of
     [0] -> t_integer();
     _ ->
-      TmpRet = erl_bif_types:type(erlang, 'div', 2, [Dst, Arg]),
+      TmpRet = bif_return(erlang, 'div', 2, [Dst, Arg]),
       Zero = t_from_term(0),
       %% If 0 is not part of the result, it cannot be part of the argument.
       case t_is_subtype(Zero, Dst) of
@@ -1630,9 +1581,9 @@ eval_inv_arith('*', _Pos, Dst, Arg) ->
       end
   end;
 eval_inv_arith('-', 1, Dst, Arg) ->
-  erl_bif_types:type(erlang, '-', 2, [Arg, Dst]);
+  bif_return(erlang, '-', 2, [Arg, Dst]);
 eval_inv_arith('-', 2, Dst, Arg) ->
-  erl_bif_types:type(erlang, '+', 2, [Arg, Dst]).
+  bif_return(erlang, '+', 2, [Arg, Dst]).
 
 range_inc(neg_inf) -> neg_inf;
 range_inc(pos_inf) -> pos_inf;
@@ -1642,33 +1593,20 @@ range_dec(neg_inf) -> neg_inf;
 range_dec(pos_inf) -> pos_inf;
 range_dec(Int) when is_integer(Int) -> Int - 1.
 
-get_bif_test_constr(Dst, Arg, Type, State) ->
+get_bif_test_constr(Dst, Arg, Type, _State) ->
   ArgFun = fun(Map) ->
 	       DstType = lookup_type(Dst, Map),
-	       case t_is_atom(true, DstType) of
+	       case t_is_any_atom(true, DstType) of
 		 true -> Type;
 		 false -> t_any()
 	       end
 	   end,
   ArgV = ?mk_fun_var(ArgFun, [Dst]),
-  Opaques = State#state.opaques,
   DstFun = fun(Map) ->
 	       ArgType = lookup_type(Arg, Map),
 	       case t_is_none(t_inf(ArgType, Type)) of
 		 true ->
-		   case lists:member(ArgType, Opaques) of
-		     true ->
-		       OpaqueStruct = erl_types:t_opaque_structure(ArgType),
-		       case t_is_none(t_inf(OpaqueStruct, Type)) of
-			 true -> t_from_term(false);
-			 false ->
-			   case t_is_subtype(ArgType, Type) of
-			     true -> t_from_term(true);
-			     false -> t_boolean()
-			   end
-		       end;
-		     false ->  t_from_term(false)
-		   end;
+                   t_from_term(false);
 		 false ->
 		   case t_is_subtype(ArgType, Type) of
 		     true -> t_from_term(true);
@@ -1784,7 +1722,6 @@ minimize_state(#state{
 		  fun_arities = FunArities,
 		  self_rec    = SelfRec,
 		  prop_types  = {d, PropTypes},
-		  opaques     = Opaques,
                   solvers     = Solvers
 		 }) ->
   Opts = [{read_concurrency, true}],
@@ -1798,7 +1735,6 @@ minimize_state(#state{
      fun_arities = FunArities,
      self_rec    = SelfRec,
      prop_types  = {e, ETSPropTypes},
-     opaques     = Opaques,
      solvers     = Solvers
     }.
 
@@ -1956,8 +1892,7 @@ v2_solve_ref(Fun, Map, State) ->
   {ok, NewMap}.
 
 v2_solve(#constraint{}=C, Map, V2State) ->
-  State = V2State#v2_state.state,
-  case solve_one_c(C, Map, State#state.opaques) of
+  case solve_one_c(C, Map) of
     error ->
       report_failed_constraint(C, Map),
       {error, V2State};
@@ -2031,7 +1966,7 @@ v2_solve_self_recursive(Cs, Map, Id, RecType0, V2State0) ->
     {ok, NewMap, V2State, U} ->
       pp_map("recursive finished", NewMap),
       NewRecType = unsafe_lookup_type(Id, NewMap),
-      case t_is_equal(NewRecType, RecType0) of
+      case is_equal(NewRecType, RecType0) of
 	true ->
           {NewMap2, U1} = enter_var_type(RecVar, NewRecType, NewMap),
 	  {ok, NewMap2, V2State, lists:umerge(U, U1)};
@@ -2397,7 +2332,7 @@ solve_self_recursive(Cs, Map, MapDict, Id, RecType0, State) ->
     {ok, NewMapDict, NewMap} ->
       pp_map("NewMap", NewMap),
       NewRecType = unsafe_lookup_type(Id, NewMap),
-      case t_is_equal(NewRecType, RecType0) of
+      case is_equal(NewRecType, RecType0) of
 	true ->
 	  {ok, NewMapDict, enter_type(RecVar, NewRecType, NewMap)};
 	false ->
@@ -2447,7 +2382,7 @@ solve_cs([#constraint_list{} = C|Tail], Map, MapDict, State) ->
     {error, _NewMapDict} = Error -> Error
   end;
 solve_cs([#constraint{} = C|Tail], Map, MapDict, State) ->
-  case solve_one_c(C, Map, State#state.opaques) of
+  case solve_one_c(C, Map) of
     error ->
       report_failed_constraint(C, Map),
       {error, MapDict};
@@ -2457,10 +2392,10 @@ solve_cs([#constraint{} = C|Tail], Map, MapDict, State) ->
 solve_cs([], Map, MapDict, _State) ->
   {ok, MapDict, Map}.
 
-solve_one_c(#constraint{lhs = Lhs, rhs = Rhs, op = Op}, Map, Opaques) ->
+solve_one_c(#constraint{lhs = Lhs, rhs = Rhs, op = Op}, Map) ->
   LhsType = lookup_type(Lhs, Map),
   RhsType = lookup_type(Rhs, Map),
-  Inf = t_inf(LhsType, RhsType, opaque),
+  Inf = t_inf(LhsType, RhsType),
   ?debug("Solving: ~s :: ~s ~w ~s :: ~s\n\tInf: ~s\n",
 	 [format_type(Lhs), format_type(LhsType), Op,
 	  format_type(Rhs), format_type(RhsType), format_type(Inf)]),
@@ -2468,12 +2403,12 @@ solve_one_c(#constraint{lhs = Lhs, rhs = Rhs, op = Op}, Map, Opaques) ->
     true -> error;
     false ->
       case Op of
-	sub -> solve_subtype(Lhs, Inf, Map, Opaques);
+	sub -> solve_subtype(Lhs, Inf, Map);
 	eq ->
-	  case solve_subtype(Lhs, Inf, Map, Opaques) of
+	  case solve_subtype(Lhs, Inf, Map) of
 	    error -> error;
 	    {ok, {Map1, U1}} ->
-              case solve_subtype(Rhs, Inf, Map1, Opaques) of
+              case solve_subtype(Rhs, Inf, Map1) of
                 error -> error;
                 {ok, {Map2, U2}} -> {ok, {Map2, lists:umerge(U1, U2)}}
               end
@@ -2481,7 +2416,7 @@ solve_one_c(#constraint{lhs = Lhs, rhs = Rhs, op = Op}, Map, Opaques) ->
       end
   end.
 
-solve_subtype(Type, Inf, Map, Opaques) ->
+solve_subtype(Type, Inf, Map) ->
   %% case cerl:is_literal(Type) of
   %%   true ->
   %%     case t_is_subtype(t_from_term(cerl:concrete(Type)), Inf) of
@@ -2489,7 +2424,7 @@ solve_subtype(Type, Inf, Map, Opaques) ->
   %%	false -> error
   %%     end;
   %%   false ->
-      try t_unify(Type, Inf, Opaques) of
+      try t_unify(Type, Inf) of
 	{_, List} -> {ok, enter_type_list(List, Map)}
       catch
 	throw:{mismatch, _T1, _T2} ->
@@ -2540,7 +2475,7 @@ join_one_key(Key, [Map|Maps], Type) ->
     true -> Type;
     false ->
       NewType = lookup_type(Key, Map),
-      case t_is_equal(NewType, Type) of
+      case is_equal(NewType, Type) of
 	true  -> join_one_key(Key, Maps, Type);
 	false -> join_one_key(Key, Maps, t_sup(NewType, Type))
       end
@@ -2555,7 +2490,7 @@ maps_are_equal(Map1, Map2, Deps) ->
 maps_are_equal_1(Map1, Map2, [H|Tail]) ->
   T1 = lookup_type(H, Map1),
   T2 = lookup_type(H, Map2),
-  case t_is_equal(T1, T2) of
+  case is_equal(T1, T2) of
     true -> maps_are_equal_1(Map1, Map2, Tail);
     false ->
       ?debug("~w: ~s =/= ~s\n", [H, format_type(T1), format_type(T2)]),
@@ -2587,14 +2522,20 @@ prune_keys(Map1, Map2, Deps) ->
 
 enter_type(Key, Val, Map) when is_integer(Key) ->
   ?debug("Entering ~s :: ~s\n", [format_type(t_var(Key)), format_type(Val)]),
-  case t_is_any(Val) of
+  %% Keep any() in the map if it is opaque:
+  case is_equal(Val, t_any()) of
     true ->
       erase_type(Key, Map);
     false ->
       LimitedVal = t_limit(Val, ?INTERNAL_TYPE_LIMIT),
+      [?debug("LimitedVal ~s\n", [format_type(LimitedVal)]) ||
+        not is_equal(LimitedVal, Val)],
       case dict:find(Key, Map) of
-	{ok, LimitedVal} -> Map;
-	{ok, _} -> map_store(Key, LimitedVal, Map);
+        {ok, Value} ->
+          case is_equal(Value, LimitedVal) of
+            true -> Map;
+            false -> map_store(Key, LimitedVal, Map)
+          end;
 	error -> map_store(Key, LimitedVal, Map)
       end
   end;
@@ -2681,7 +2622,10 @@ updated_vars_only(U, OldMap, NewMap) ->
   [V || V <- U, not is_same(V, OldMap, NewMap)].
 
 is_same(Key, Map1, Map2) ->
-  t_is_equal(lookup_type(Key, Map1), lookup_type(Key, Map2)).
+  is_equal(lookup_type(Key, Map1), lookup_type(Key, Map2)).
+
+is_equal(Type1, Type2) ->
+  t_is_equal(Type1, Type2).
 
 pp_map(_S, _Map) ->
   ?debug("\t~s: ~p\n",
@@ -2716,11 +2660,6 @@ new_state(SCC0, NextLabel, CallGraph, Plt, PropTypes, Solvers) ->
 state__set_rec_dict(State, RecDict) ->
   State#state{records = RecDict}.
 
-state__set_opaques(#state{records = RecDict} = State, {M, _F, _A}) ->
-  Opaques =
-    erl_types:module_builtin_opaques(M) ++ t_opaque_from_records(RecDict),
-  State#state{opaques = Opaques, module = M}.
-
 state__set_in_match(State, Bool) ->
   State#state{in_match = Bool}.
 
@@ -2760,7 +2699,8 @@ state__lookup_undef_var(Tree, #state{callgraph = CG, plt = Plt}) ->
     {ok, MFA} ->
       case dialyzer_plt:lookup(Plt, MFA) of
 	none -> error;
-	{value, {RetType, ArgTypes}} -> {ok, t_fun(ArgTypes, RetType)}
+	{value, {RetType, ArgTypes}} ->
+          {ok, t_fun(ArgTypes, RetType)}
       end
   end.
 
@@ -2897,7 +2837,7 @@ state__get_cs(Var, #state{cmap = {d, Dict}}) ->
   dict:fetch(Var, Dict).
 
 state__is_self_rec(Fun, #state{self_rec = SelfRec}) ->
-  Fun =:= SelfRec.
+  not (SelfRec =:= 'false') andalso is_equal(Fun, SelfRec).
 
 state__store_funs(Vars0, Funs0, #state{fun_map = Map} = State) ->
   debug_make_name_map(Vars0, Funs0),
@@ -2923,7 +2863,9 @@ state__finalize(State) ->
 %%
 %% ============================================================================
 
--spec mk_constraint(erl_types:erl_type(), constr_op(), fvar_or_type()) -> #constraint{}.
+-spec mk_constraint(erl_types:erl_type(),
+                    constr_op(),
+                    fvar_or_type()) -> #constraint{}.
 
 mk_constraint(Lhs, Op, Rhs) ->
   case t_is_any(Lhs) orelse constraint_opnd_is_any(Rhs) of
@@ -2934,9 +2876,9 @@ mk_constraint(Lhs, Op, Rhs) ->
       case Deps =:= [] of
 	true ->
 	  %% This constraint is constant. Solve it immediately.
-	  case solve_one_c(C, map_new(), []) of
+	  case solve_one_c(C, map_new()) of
 	    error -> throw(error);
-	    _ ->
+	    _R ->
 	      %% This is always true, keep it anyway for logistic reasons
 	      C
 	  end;
@@ -2944,10 +2886,13 @@ mk_constraint(Lhs, Op, Rhs) ->
 	  C
       end;
     true ->
-      C = mk_constraint_1(t_any(), Op, t_any()),
-      C#constraint{deps = []}
+      mk_constraint_any(Op)
   end.
 
+mk_constraint_any(Op) ->
+  C = mk_constraint_1(t_any(), Op, t_any()),
+  C#constraint{deps = []}.
+
 %% the following function is used so that we do not call
 %% erl_types:t_is_any/1 with a term other than an erl_type()
 -spec constraint_opnd_is_any(fvar_or_type()) -> boolean().
@@ -3002,7 +2947,8 @@ mk_constraint_1(Lhs, Op, Rhs) ->
   #constraint{lhs = Lhs, op = Op, rhs = Rhs}.
 
 mk_constraints([Lhs|LhsTail], Op, [Rhs|RhsTail]) ->
-  [mk_constraint(Lhs, Op, Rhs)|mk_constraints(LhsTail, Op, RhsTail)];
+  [mk_constraint(Lhs, Op, Rhs) |
+   mk_constraints(LhsTail, Op, RhsTail)];
 mk_constraints([], _Op, []) ->
   [].
 
@@ -3017,7 +2963,7 @@ mk_constraint_list(Type, List) ->
   Deps = calculate_deps(List2),
   case Deps =:= [] of
     true -> #constraint_list{type = conj,
-			     list = [mk_constraint(t_any(), eq, t_any())],
+			     list = [mk_constraint_any(eq)],
 			     deps = []};
     false -> #constraint_list{type = Type, list = List2, deps = Deps}
   end.
@@ -3236,6 +3182,9 @@ calculate_masks([], _I, L) ->
 %%
 %% ============================================================================
 
+bif_return(M, F, A, Xs) ->
+  erl_bif_types:type(M, F, A, Xs).
+
 is_singleton_non_number_type(Type) ->
   case t_is_number(Type) of
     true -> false;
@@ -3265,7 +3214,7 @@ is_singleton_type(Type) ->
 
 find_element(Args, Cs) ->
   [Pos, Tuple] = Args,
-  case erl_types:t_is_number(Pos) of
+  case t_is_number(Pos) of
     true ->
       case erl_types:t_number_vals(Pos) of
         'unknown' -> 'unknown';
@@ -3301,8 +3250,10 @@ find_constraint(Tuple, [_|Cs]) ->
 lookup_record(Records, Tag, Arity) ->
   case erl_types:lookup_record(Tag, Arity, Records) of
     {ok, Fields} ->
-      {ok, t_tuple([t_from_term(Tag)|
-		    [FieldType || {_FieldName, FieldType} <- Fields]])};
+      RecType =
+        t_tuple([t_from_term(Tag)|
+                 [FieldType || {_FieldName, FieldType} <- Fields]]),
+      {ok, RecType};
     error ->
       error
   end.
diff --git a/lib/dialyzer/test/Makefile b/lib/dialyzer/test/Makefile
index 9f8a3f1194..27cabc8ef8 100644
--- a/lib/dialyzer/test/Makefile
+++ b/lib/dialyzer/test/Makefile
@@ -7,6 +7,7 @@ include $(ERL_TOP)/make/$(TARGET)/otp.mk
 
 AUXILIARY_FILES=\
 	dialyzer.spec\
+	dialyzer.cover\
 	dialyzer_test_constants.hrl\
 	dialyzer_common.erl\
 	file_utils.erl\
diff --git a/lib/dialyzer/test/dialyzer.cover b/lib/dialyzer/test/dialyzer.cover
new file mode 100644
index 0000000000..cc61ea1901
--- /dev/null
+++ b/lib/dialyzer/test/dialyzer.cover
@@ -0,0 +1,3 @@
+%% -*- erlang -*-
+{incl_app,dialyzer,details}.
+%{incl_mods,dialyzer,[erl_types,erl_bif_types]}.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/crash b/lib/dialyzer/test/opaque_SUITE_data/results/crash
index 1ddae5149f..69bdc00257 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/crash
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/crash
@@ -1,6 +1,6 @@
 
 crash_1.erl:45: Record construction #targetlist{list::[]} violates the declared type of field list::'undefined' | crash_1:target()
-crash_1.erl:48: The call crash_1:get_using_branch2(Branch::maybe_improper_list(),L::'undefined' | crash_1:target()) contains an opaque term as 2nd argument when terms of different types are expected in these positions
+crash_1.erl:48: The call crash_1:get_using_branch2(Branch::maybe_improper_list(),L::'undefined' | crash_1:target()) will never return since it differs in the 2nd argument from the success typing arguments: (any(),maybe_improper_list())
 crash_1.erl:50: The pattern <_Branch, []> can never match the type <maybe_improper_list(),'undefined' | crash_1:target()>
 crash_1.erl:52: The pattern <Branch, [H = {'target', _, _} | _T]> can never match the type <maybe_improper_list(),'undefined' | crash_1:target()>
 crash_1.erl:54: The pattern <Branch, [{'target', _, _} | T]> can never match the type <maybe_improper_list(),'undefined' | crash_1:target()>
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/ets b/lib/dialyzer/test/opaque_SUITE_data/results/ets
index 5498ba1538..e79696bc30 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/ets
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/ets
@@ -1,3 +1,4 @@
 
 ets_use.erl:12: Guard test is_integer(T::atom() | tid()) breaks the opaqueness of its argument
+ets_use.erl:20: The type test is_integer(atom() | tid()) breaks the opaqueness of the term atom() | tid()
 ets_use.erl:7: Guard test is_integer(T::tid()) breaks the opaqueness of its argument
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/ewgi b/lib/dialyzer/test/opaque_SUITE_data/results/ewgi
index 3c8cfb59f8..5bc6b87fbb 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/ewgi
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/ewgi
@@ -1,4 +1,4 @@
 
 ewgi_api.erl:55: The call gb_trees:to_list({non_neg_integer(),'nil' | {_,_,_,_}}) does not have an opaque term of type gb_tree() as 1st argument
-ewgi_testapp.erl:35: The call ewgi_testapp:htmlise_data("request_data",{non_neg_integer(),'nil' | {_,_,_,_}}) will never return since it differs in the 2nd argument from the success typing arguments: ([95 | 97 | 100 | 101 | 104 | 112 | 113 | 114 | 115 | 116 | 117,...],[{_,_}])
+ewgi_testapp.erl:35: The call ewgi_testapp:htmlise_data("request_data",{non_neg_integer(),'nil' | {_,_,_,_}}) does not have a term of type [{_,_}] | gb_tree() (with opaque subterms) as 2nd argument
 ewgi_testapp.erl:43: The call gb_trees:to_list(T::{non_neg_integer(),'nil' | {_,_,_,_}}) does not have an opaque term of type gb_tree() as 1st argument
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/inf_loop1 b/lib/dialyzer/test/opaque_SUITE_data/results/inf_loop1
index eb8f304905..4fe5fcfe2d 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/inf_loop1
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/inf_loop1
@@ -2,4 +2,4 @@
 inf_loop1.erl:119: The pattern [{_, LNorms}] can never match the type []
 inf_loop1.erl:121: The pattern [{LinksA, LNormA}, {LinksB, LNormB}] can never match the type []
 inf_loop1.erl:129: The pattern [{_, Norm} | _] can never match the type []
-inf_loop1.erl:71: The call gb_trees:get(Edge::any(),Etab::array()) contains an opaque term as 2nd argument when terms of different types are expected in these positions
+inf_loop1.erl:71: The call gb_trees:get(Edge::any(),Etab::array()) does not have an opaque term of type gb_tree() as 2nd argument
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/inf_loop2 b/lib/dialyzer/test/opaque_SUITE_data/results/inf_loop2
new file mode 100644
index 0000000000..4f0b79eb35
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/inf_loop2
@@ -0,0 +1,5 @@
+
+inf_loop2.erl:122: The pattern [{_, LNorms}] can never match the type []
+inf_loop2.erl:124: The pattern [{LinksA, LNormA}, {LinksB, LNormB}] can never match the type []
+inf_loop2.erl:132: The pattern [{_, Norm} | _] can never match the type []
+inf_loop2.erl:74: The call gb_trees:get(Edge::any(),Etab::array()) does not have an opaque term of type gb_tree() as 2nd argument
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/int b/lib/dialyzer/test/opaque_SUITE_data/results/int
index 3ee4def34b..dc806fa12c 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/int
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/int
@@ -1,3 +1,3 @@
 
-int_adt.erl:28: Invalid type specification for function int_adt:add_f/2. The success typing is (number(),float()) -> number()
-int_adt.erl:32: Invalid type specification for function int_adt:div_f/2. The success typing is (number(),number()) -> float()
+int_adt.erl:28: Invalid type specification for function int_adt:add_f/2. The success typing is (number() | int_adt:int(),float()) -> number() | int_adt:int()
+int_adt.erl:32: Invalid type specification for function int_adt:div_f/2. The success typing is (number() | int_adt:int(),number() | int_adt:int()) -> float()
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/mixed_opaque b/lib/dialyzer/test/opaque_SUITE_data/results/mixed_opaque
index ab850b613e..0363be544d 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/mixed_opaque
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/mixed_opaque
@@ -1,2 +1,2 @@
 
-mixed_opaque_use.erl:31: The call mixed_opaque_rec_adt:get_a(Q::mixed_opaque_queue_adt:my_queue()) contains an opaque term as 1st argument when an opaque term of type mixed_opaque_rec_adt:rec() is expected
+mixed_opaque_use.erl:31: The call mixed_opaque_rec_adt:get_a(Q::mixed_opaque_queue_adt:my_queue()) does not have an opaque term of type mixed_opaque_rec_adt:rec() as 1st argument
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/modules b/lib/dialyzer/test/opaque_SUITE_data/results/modules
new file mode 100644
index 0000000000..f71334b9de
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/modules
@@ -0,0 +1,3 @@
+
+opaque_digraph.erl:353: Cons will produce an improper list since its 2nd argument is number()
+opaque_digraph.erl:365: Cons will produce an improper list since its 2nd argument is number()
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/my_queue b/lib/dialyzer/test/opaque_SUITE_data/results/my_queue
index 2860b91084..1f25a6f9c3 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/my_queue
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/my_queue
@@ -4,4 +4,4 @@ my_queue_use.erl:19: The call my_queue_adt:add(42,Q0::[]) does not have an opaqu
 my_queue_use.erl:24: The attempt to match a term of type my_queue_adt:my_queue() against the pattern [42 | Q2] breaks the opaqueness of the term
 my_queue_use.erl:30: Attempt to test for equality between a term of type [] and a term of opaque type my_queue_adt:my_queue()
 my_queue_use.erl:34: Cons will produce an improper list since its 2nd argument is my_queue_adt:my_queue()
-my_queue_use.erl:34: The call my_queue_adt:dequeue(nonempty_improper_list(42,my_queue_adt:my_queue())) does not have an opaque term of type my_queue_adt:my_queue() as 1st argument
+my_queue_use.erl:34: The call my_queue_adt:dequeue(nonempty_maybe_improper_list(42,my_queue_adt:my_queue())) does not have an opaque term of type my_queue_adt:my_queue() as 1st argument
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/opaque b/lib/dialyzer/test/opaque_SUITE_data/results/opaque
index ca76f57b54..5747f9061f 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/opaque
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/opaque
@@ -1,2 +1,3 @@
 
+opaque_bug3.erl:19: The pattern 'a' can never match the type #c{}
 opaque_bug4.erl:20: The attempt to match a term of type opaque_adt:abc() against the pattern 'a' breaks the opaqueness of the term
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/queue b/lib/dialyzer/test/opaque_SUITE_data/results/queue
index c3f04ea64d..59ce33f098 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/queue
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/queue
@@ -5,7 +5,6 @@ queue_use.erl:27: The attempt to match a term of type queue() against the patter
 queue_use.erl:33: Attempt to test for equality between a term of type {[42,...],[]} and a term of opaque type queue()
 queue_use.erl:36: The attempt to match a term of type queue() against the pattern {F, _R} breaks the opaqueness of the term
 queue_use.erl:40: The call queue:out({[42,...],[]}) does not have an opaque term of type queue() as 1st argument
-queue_use.erl:48: The call queue_use:add_unique(42,#db{p::[],q::queue()}) contains an opaque term as 2nd argument when terms of different types are expected in these positions
 queue_use.erl:51: The call queue_use:is_in_queue(E::42,DB::#db{p::[],q::queue()}) contains an opaque term as 2nd argument when terms of different types are expected in these positions
 queue_use.erl:56: The attempt to match a term of type #db{p::[],q::queue()} against the pattern {'db', _, {L1, L2}} breaks the opaqueness of queue()
 queue_use.erl:62: The call queue_use:tuple_queue({42,'gazonk'}) does not have a term of type {_,queue()} (with opaque subterms) as 1st argument
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/simple b/lib/dialyzer/test/opaque_SUITE_data/results/simple
new file mode 100644
index 0000000000..f55b384cbe
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/simple
@@ -0,0 +1,87 @@
+
+exact_api.erl:17: The call exact_api:set_type(A::#digraph{vtab::'notable',etab::'notable',ntab::'notable',cyclic::'true'}) does not have an opaque term of type digraph() as 1st argument
+exact_api.erl:23: The call digraph:delete(G::#digraph{vtab::'notable',etab::'notable',ntab::'notable',cyclic::'true'}) does not have an opaque term of type digraph() as 1st argument
+exact_api.erl:55: The attempt to match a term of type exact_adt:exact_adt() against the pattern {'exact_adt'} breaks the opaqueness of the term
+exact_api.erl:59: The call exact_adt:exact_adt_set_type2(A::#exact_adt{}) does not have an opaque term of type exact_adt:exact_adt() as 1st argument
+is_rec.erl:10: The call erlang:is_record(simple1_adt:d1(),'r',2) contains an opaque term as 1st argument when terms of different types are expected in these positions
+is_rec.erl:15: The call erlang:is_record(A::simple1_adt:d1(),'r',I::1 | 2 | 3) contains an opaque term as 1st argument when terms of different types are expected in these positions
+is_rec.erl:19: Guard test is_record(A::simple1_adt:d1(),'r',2) breaks the opaqueness of its argument
+is_rec.erl:23: Guard test is_record({simple1_adt:d1(),1},'r',2) breaks the opaqueness of its argument
+is_rec.erl:41: The call erlang:is_record(A::simple1_adt:d1(),R::'a') contains an opaque term as 1st argument when terms of different types are expected in these positions
+is_rec.erl:45: The call erlang:is_record(A::simple1_adt:d1(),A::simple1_adt:d1(),1) contains an opaque term as 2nd argument when terms of different types are expected in these positions
+is_rec.erl:49: The call erlang:is_record(A::simple1_adt:d1(),any(),1) contains an opaque term as 1st argument when terms of different types are expected in these positions
+is_rec.erl:53: The call erlang:is_record(A::simple1_adt:d1(),A::simple1_adt:d1(),any()) contains an opaque term as 2nd argument when terms of different types are expected in these positions
+is_rec.erl:57: Guard test is_record(A::simple1_adt:d1(),'r',2) breaks the opaqueness of its argument
+is_rec.erl:61: The record #r{f1::simple1_adt:d1()} violates the declared type for #r{}
+is_rec.erl:65: The call erlang:is_record({simple1_adt:d1(),1},'r',2) contains an opaque term as 1st argument when terms of different types are expected in these positions
+rec_api.erl:22: Record construction #r1{f1::10} violates the declared type of field f1::'undefined' | rec_api:a()
+rec_api.erl:23: The pattern {'r1', 10} violates the declared type for #r1{}
+rec_api.erl:27: The attempt to match a term of type rec_adt:r1() against the pattern {'r1', 'a'} breaks the opaqueness of the term
+rec_api.erl:29: Invalid type specification for function rec_api:adt_t1/1. The success typing is (#r1{f1::'a'}) -> #r1{f1::'a'}
+rec_api.erl:34: Invalid type specification for function rec_api:adt_r1/0. The success typing is () -> #r1{f1::'a'}
+rec_api.erl:77: The attempt to match a term of type rec_api:f() against the variable _ breaks the opaqueness of the term
+simple1_api.erl:113: The test simple1_api:d1() =:= simple1_api:d2() can never evaluate to 'true'
+simple1_api.erl:118: Guard test simple1_api:d2() =:= A::simple1_api:d1() can never succeed
+simple1_api.erl:142: Attempt to test for equality between a term of type simple1_adt:o2() and a term of opaque type simple1_adt:o1()
+simple1_api.erl:148: Guard test simple1_adt:o2() =:= A::simple1_adt:o1() contains an opaque term as 1st argument
+simple1_api.erl:154: Attempt to test for inequality between a term of type simple1_adt:o2() and a term of opaque type simple1_adt:o1()
+simple1_api.erl:160: Attempt to test for inequality between a term of type simple1_adt:o2() and a term of opaque type simple1_adt:o1()
+simple1_api.erl:165: Attempt to test for equality between a term of type simple1_adt:c2() and a term of opaque type simple1_adt:c1()
+simple1_api.erl:181: Guard test A::simple1_adt:d1() =< B::simple1_adt:d2() contains an opaque term as 1st argument
+simple1_api.erl:185: Guard test 'a' =< B::simple1_adt:d2() contains an opaque term as 2nd argument
+simple1_api.erl:189: Guard test A::simple1_adt:d1() =< 'd' contains an opaque term as 1st argument
+simple1_api.erl:197: The type test is_integer(A::simple1_adt:d1()) breaks the opaqueness of the term A::simple1_adt:d1()
+simple1_api.erl:221: Guard test A::simple1_api:i1() > 3 can never succeed
+simple1_api.erl:225: Guard test A::simple1_adt:i1() > 3 contains an opaque term as 1st argument
+simple1_api.erl:233: Guard test A::simple1_adt:i1() < 3 contains an opaque term as 1st argument
+simple1_api.erl:239: Guard test A::1 > 3 can never succeed
+simple1_api.erl:243: Guard test A::1 > 3 can never succeed
+simple1_api.erl:257: Guard test is_function(T::simple1_api:o1()) can never succeed
+simple1_api.erl:265: Guard test is_function(T::simple1_adt:o1()) breaks the opaqueness of its argument
+simple1_api.erl:269: The type test is_function(T::simple1_adt:o1()) breaks the opaqueness of the term T::simple1_adt:o1()
+simple1_api.erl:274: Guard test is_function(T::simple1_api:o1(),A::simple1_api:i1()) can never succeed
+simple1_api.erl:284: Guard test is_function(T::simple1_adt:o1(),A::simple1_adt:i1()) breaks the opaqueness of its argument
+simple1_api.erl:289: The type test is_function(T::simple1_adt:o1(),A::simple1_adt:i1()) breaks the opaqueness of the term T::simple1_adt:o1()
+simple1_api.erl:294: The call erlang:is_function(T::simple1_api:o1(),A::simple1_adt:i1()) contains an opaque term as 2nd argument when terms of different types are expected in these positions
+simple1_api.erl:300: The type test is_function(T::simple1_adt:o1(),A::simple1_api:i1()) breaks the opaqueness of the term T::simple1_adt:o1()
+simple1_api.erl:306: Guard test B::simple1_api:b2() =:= 'true' can never succeed
+simple1_api.erl:315: Guard test A::simple1_api:b1() =:= 'false' can never succeed
+simple1_api.erl:319: Guard test not('and'('true','true')) can never succeed
+simple1_api.erl:337: Clause guard cannot succeed.
+simple1_api.erl:342: Guard test B::simple1_adt:b2() =:= 'true' contains an opaque term as 1st argument
+simple1_api.erl:347: Guard test A::simple1_adt:b1() =:= 'true' contains an opaque term as 1st argument
+simple1_api.erl:355: Invalid type specification for function simple1_api:bool_adt_t6/1. The success typing is ('true') -> 1
+simple1_api.erl:365: Clause guard cannot succeed.
+simple1_api.erl:368: Invalid type specification for function simple1_api:bool_adt_t8/2. The success typing is (boolean(),boolean()) -> 1
+simple1_api.erl:378: Clause guard cannot succeed.
+simple1_api.erl:381: Invalid type specification for function simple1_api:bool_adt_t9/2. The success typing is ('false','false') -> 1
+simple1_api.erl:407: The size simple1_adt:i1() breaks the opaqueness of A
+simple1_api.erl:418: The attempt to match a term of type non_neg_integer() against the variable A breaks the opaqueness of simple1_adt:i1()
+simple1_api.erl:425: The attempt to match a term of type non_neg_integer() against the variable B breaks the opaqueness of simple1_adt:i1()
+simple1_api.erl:432: The attempt to match a term of type non_neg_integer() against the variable B breaks the opaqueness of simple1_api:o1()
+simple1_api.erl:448: The attempt to match a term of type non_neg_integer() against the variable Sz breaks the opaqueness of simple1_adt:i1()
+simple1_api.erl:460: The attempt to match a term of type simple1_adt:bit1() against the pattern <<_/binary-unit:8>> breaks the opaqueness of the term
+simple1_api.erl:478: The call 'foo':A(A::simple1_adt:a()) breaks the opaqueness of the term A :: simple1_adt:a()
+simple1_api.erl:486: The call A:'foo'(A::simple1_adt:a()) breaks the opaqueness of the term A :: simple1_adt:a()
+simple1_api.erl:499: The call 'foo':A(A::simple1_api:i()) requires that A is of type atom() not simple1_api:i()
+simple1_api.erl:503: The call 'foo':A(A::simple1_adt:i()) requires that A is of type atom() not simple1_adt:i()
+simple1_api.erl:507: The call A:'foo'(A::simple1_api:i()) requires that A is of type atom() | tuple() not simple1_api:i()
+simple1_api.erl:511: The call A:'foo'(A::simple1_adt:i()) requires that A is of type atom() | tuple() not simple1_adt:i()
+simple1_api.erl:519: Guard test A::simple1_adt:d2() == B::simple1_adt:d1() contains an opaque term as 1st argument
+simple1_api.erl:534: Guard test A::simple1_adt:d1() >= 3 contains an opaque term as 1st argument
+simple1_api.erl:536: Guard test A::simple1_adt:d1() == 3 contains an opaque term as 1st argument
+simple1_api.erl:538: Guard test A::simple1_adt:d1() =:= 3 contains an opaque term as 1st argument
+simple1_api.erl:548: The call erlang:'<'(A::simple1_adt:d1(),3) contains an opaque term as 1st argument when terms of different types are expected in these positions
+simple1_api.erl:558: The call erlang:'=<'(A::simple1_adt:d1(),B::simple1_adt:d2()) contains an opaque term as 1st argument when terms of different types are expected in these positions
+simple1_api.erl:565: Guard test {digraph(),3} > {digraph(),atom() | tid()} contains an opaque term as 2nd argument
+simple1_api.erl:91: Invalid type specification for function simple1_api:tup/0. The success typing is () -> {'a','b'}
+simple2_api.erl:100: The call lists:flatten(A::simple1_adt:tuple1()) contains an opaque term as 1st argument when a structured term of type [any()] is expected
+simple2_api.erl:116: The call lists:flatten({simple1_adt:tuple1()}) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
+simple2_api.erl:121: Guard test {simple1_adt:d1(),3} > {simple1_adt:d1(),simple1_adt:tuple1()} contains an opaque term as 2nd argument
+simple2_api.erl:125: The call erlang:tuple_to_list(B::simple1_adt:tuple1()) contains an opaque term as 1st argument when a structured term of type tuple() is expected
+simple2_api.erl:31: The call erlang:'!'(A::simple1_adt:d1(),'foo') contains an opaque term as 1st argument when terms of different types are expected in these positions
+simple2_api.erl:35: The call erlang:send(A::simple1_adt:d1(),'foo') contains an opaque term as 1st argument when terms of different types are expected in these positions
+simple2_api.erl:51: The call erlang:'<'(A::simple1_adt:d1(),3) contains an opaque term as 1st argument when terms of different types are expected in these positions
+simple2_api.erl:59: The call lists:keysearch(1,A::simple1_adt:d1(),[]) contains an opaque term as 2nd argument when terms of different types are expected in these positions
+simple2_api.erl:67: The call lists:keysearch('key',1,A::simple1_adt:tuple1()) contains an opaque term as 3rd argument when terms of different types are expected in these positions
+simple2_api.erl:96: The call lists:keyreplace('a',1,[{1, 2}],A::simple1_adt:tuple1()) contains an opaque term as 4th argument when terms of different types are expected in these positions
diff --git a/lib/dialyzer/test/opaque_SUITE_data/results/wings b/lib/dialyzer/test/opaque_SUITE_data/results/wings
index a9571441f8..0ca91ae331 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/results/wings
+++ b/lib/dialyzer/test/opaque_SUITE_data/results/wings
@@ -4,7 +4,7 @@ wings_dissolve.erl:19: Guard test is_list(Faces::gb_set()) breaks the opaqueness
 wings_dissolve.erl:272: Guard test is_list(Faces::gb_set()) breaks the opaqueness of its argument
 wings_dissolve.erl:31: The call gb_sets:is_empty(Faces::[any(),...]) does not have an opaque term of type gb_set() as 1st argument
 wings_edge.erl:205: The pattern <Edge, 'hard', Htab> can never match the type <_,'soft',_>
-wings_edge_cmd.erl:30: The call gb_trees:size(P::gb_set()) contains an opaque term as 1st argument when an opaque term of type gb_tree() is expected
+wings_edge_cmd.erl:30: The call gb_trees:size(P::gb_set()) does not have an opaque term of type gb_tree() as 1st argument
 wings_edge_cmd.erl:32: The pattern [_ | Parts] can never match the type []
 wings_edge_cmd.erl:32: The pattern [{_, P} | _] can never match the type []
 wings_io.erl:30: The attempt to match a term of type {'empty',queue()} against the pattern {'empty', {In, Out}} breaks the opaqueness of queue()
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/ets/ets_use.erl b/lib/dialyzer/test/opaque_SUITE_data/src/ets/ets_use.erl
index d65af0af4e..4eb202f16a 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/src/ets/ets_use.erl
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/ets/ets_use.erl
@@ -1,5 +1,5 @@
 -module(ets_use).
--export([t1/0, t2/0]).
+-export([t1/0, t2/0, t3/0, t4/0]).
 
 t1() ->
     case n() of
@@ -13,4 +13,10 @@ t2() ->
 	T when is_atom(T) -> atm
     end.
 
-n() -> ets:new(n, [named_table]).
+t3() ->
+    is_atom(n()). % no warning since atom() is possible
+
+t4() ->
+    is_integer(n()). % opaque warning since tid() is opaque
+
+n() -> ets:new(n, [named_table]). % -> atom() | tid()
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/inf_loop2.erl b/lib/dialyzer/test/opaque_SUITE_data/src/inf_loop2.erl
new file mode 100644
index 0000000000..659ccaf015
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/inf_loop2.erl
@@ -0,0 +1,175 @@
+%% -*- erlang-indent-level: 2 -*-
+%%----------------------------------------------------------------------------
+%% Copy of inf_loop1.erl, where the calls mentioned below have been
+%% restored.
+
+%% Non-sensical (i.e., stripped-down) program that sends the analysis
+%% into an infinite loop. The #we.es field was originally a gb_tree()
+%% but the programmer declared it as an array in order to change it to
+%% that data type instead. In the file, there are two calls to function
+%% gb_trees:get/2 which seem to be the ones responsible for sending the
+%% analysis into an infinite loop. Currently, these calls are marked and
+%% have been changed to gbee_trees:get/2 in order to be able to see that
+%% the analysis works if these two calls are taken out of the picture.
+%%----------------------------------------------------------------------------
+-module(inf_loop2).
+
+-export([command/1]).
+
+-record(we, {id,
+	     es = array:new() :: array(),
+	     vp,
+	     mirror = none}).
+-record(edge, {vs,ve,a = none,b = none,lf,rf,ltpr,ltsu,rtpr,rtsu}).
+
+command(St) ->
+  State = drag_mode(offset_region),
+  SetupSt = wings_sel_conv:more(St),
+  Tvs = wings_sel:fold(fun(Faces, #we{id = Id} = We, Acc) ->
+			   FaceRegions = wings_sel:face_regions(Faces, We),
+			   {AllVs0,VsData} =
+			     collect_offset_regions_data(FaceRegions, We, [], []),
+			   AllVs = ordsets:from_list(AllVs0),
+			   [{Id,{AllVs,offset_regions_fun(VsData, State)}}|Acc]
+                       end,
+                       [],
+                       SetupSt),
+    wings_drag:setup(Tvs, 42, [], St).
+
+drag_mode(Type) ->
+    {Mode,Norm} = wings_pref:get_value(Type, {average,loop}),
+    {Type,Mode,Norm}.
+
+collect_offset_regions_data([Faces|Regions], We, AllVs, VsData) ->
+  {FaceNormTab,OuterEdges,RegVs} =
+    some_fake_module:faces_data_0(Faces, We, [], [], []),
+  {LoopNorm,LoopVsData,LoopVs} =
+    offset_regions_loop_data(OuterEdges, Faces, We, FaceNormTab),
+  Vs = RegVs -- LoopVs,
+  RegVsData = vertex_normals(Vs, FaceNormTab, We, LoopVsData),
+  collect_offset_regions_data(Regions, We, RegVs ++ AllVs,
+			      [{LoopNorm,RegVsData}|VsData]);
+collect_offset_regions_data([], _, AllVs, VsData) ->
+  {AllVs,VsData}.
+
+offset_regions_loop_data(Edges, Faces, We, FNtab) ->
+  EdgeSet = gb_sets:from_list(Edges),
+  offset_loop_data_0(EdgeSet, Faces, We, FNtab, [], [], []).
+
+offset_loop_data_0(EdgeSet0, Faces, We, FNtab, LNorms, VData0, Vs0) ->
+  case gb_sets:is_empty(EdgeSet0) of
+    false ->
+      {Edge,EdgeSet1} = gb_sets:take_smallest(EdgeSet0),
+      {EdgeSet,VData,Links,LoopNorm,Vs} =
+	offset_loop_data_1(Edge, EdgeSet1, Faces, We, FNtab, VData0, Vs0),
+      offset_loop_data_0(EdgeSet, Faces, We, FNtab,
+			 [{Links,LoopNorm}|LNorms], VData, Vs);
+    true ->
+      AvgLoopNorm = average_loop_norm(LNorms),
+      {AvgLoopNorm,VData0,Vs0}
+  end.
+
+offset_loop_data_1(Edge, EdgeSet, _Faces,
+                   #we{es = Etab, vp = Vtab} = We, FNtab, VData, Vs) ->
+  #edge{vs = Va, ve = Vb, lf = Lf, ltsu = NextLeft} = gb_trees:get(Edge, Etab),
+  VposA = gb_trees:get(Va, Vtab),
+  VposB = gb_trees:get(Vb, Vtab),
+  VDir = e3d_vec:sub(VposB, VposA),
+  FNorm = wings_face:normal(Lf, We),
+  EdgeData = gb_trees:get(NextLeft, Etab),
+  offset_loop_data_2(NextLeft, EdgeData, Va, VposA, Lf, Edge, We, FNtab,
+		     EdgeSet, VDir, [], [FNorm], VData, [], Vs, 0).
+
+offset_loop_data_2(CurE, #edge{vs = Va, ve = Vb, lf = PrevFace,
+			       rtsu = NextEdge, ltsu = IfCurIsMember},
+                   Vb, VposB, PrevFace, LastE,
+                   #we{mirror = M} = We,
+                   FNtab, EdgeSet0, VDir, EDir0, VNorms0, VData0, VPs0, Vs0,
+                   Links) ->
+  Mirror = M == PrevFace,
+  offset_loop_is_member(Mirror, Vb, Va, VposB, CurE, IfCurIsMember, VNorms0,
+			NextEdge, EdgeSet0, VDir, EDir0, FNtab, PrevFace,
+			LastE, We, VData0, VPs0, Vs0, Links).
+
+offset_loop_is_member(Mirror, V1, V2, Vpos1, CurE, NextE, VNorms0, NEdge,
+                      EdgeSet0, VDir, EDir0, FNtab, PFace, LastE, We,
+                      VData0, VPs0, Vs0, Links) ->
+  #we{es = Etab, vp = Vtab} = We,
+  Vpos2 = gb_trees:get(V2, Vtab),
+  Dir = e3d_vec:sub(Vpos2, Vpos1),
+  NextVDir = e3d_vec:neg(Dir),
+  EdgeSet = gb_sets:delete(CurE, EdgeSet0),
+  EdgeData = gb_trees:get(NextE, Etab), %% HERE
+  [FNorm|_] = VNorms0,
+  VData = offset_loop_data_3(Mirror, V1, Vpos1, VNorms0, NEdge, VDir,
+			     Dir, EDir0, FNtab, We, VData0),
+  VPs = [Vpos1|VPs0],
+  Vs = [V1|Vs0],
+  offset_loop_data_2(NextE, EdgeData, V2, Vpos2, PFace, LastE, We, FNtab,
+		     EdgeSet, NextVDir, [], [FNorm], VData, VPs, Vs, Links + 1).
+
+offset_loop_data_3(false, V, Vpos, VNorms0, NextEdge,
+                   VDir, Dir, EDir0, FNtab, We, VData0) ->
+  #we{es = Etab} = We,
+  VNorm = e3d_vec:norm(e3d_vec:add(VNorms0)),
+  NV = wings_vertex:other(V, gb_trees:get(NextEdge, Etab)), %% HERE
+  ANorm = vertex_normal(NV, FNtab, We),
+  EDir = some_fake_module:average_edge_dir(VNorm, VDir, Dir, EDir0),
+  AvgDir = some_fake_module:evaluate_vdata(VDir, Dir, VNorm),
+  ScaledDir = some_fake_module:along_edge_scale_factor(VDir, Dir, EDir, ANorm),
+  [{V,{Vpos,AvgDir,EDir,ScaledDir}}|VData0].
+
+average_loop_norm([{_,LNorms}]) ->
+  e3d_vec:norm(LNorms);
+average_loop_norm([{LinksA,LNormA},{LinksB,LNormB}]) ->
+  case LinksA < LinksB of
+    true ->
+      e3d_vec:norm(e3d_vec:add(e3d_vec:neg(LNormA), LNormB));
+    false ->
+      e3d_vec:norm(e3d_vec:add(e3d_vec:neg(LNormB), LNormA))
+  end;
+average_loop_norm(LNorms) ->
+  LoopNorms = [Norm || {_,Norm} <- LNorms],
+  e3d_vec:norm(e3d_vec:neg(e3d_vec:add(LoopNorms))).
+
+vertex_normals([V|Vs], FaceNormTab, #we{vp = Vtab, mirror = M} = We, Acc) ->
+  FaceNorms =
+    wings_vertex:fold(fun(_, Face, _, A) when Face == M ->
+			  [e3d_vec:neg(wings_face:normal(M, We))|A];
+			 (_, Face, _, A) ->
+			  [gb_trees:get(Face, FaceNormTab)|A]
+		      end, [], V, We),
+  VNorm = e3d_vec:norm(e3d_vec:add(FaceNorms)),
+  Vpos = gb_trees:get(V, Vtab),
+  vertex_normals(Vs, FaceNormTab, We, [{V,{Vpos,VNorm}}|Acc]);
+vertex_normals([], _, _, Acc) ->
+  Acc.
+
+vertex_normal(V, FaceNormTab, #we{mirror = M} = We) ->
+  wings_vertex:fold(fun(_, Face, _, A) when Face == M ->
+			[e3d_vec:neg(wings_face:normal(Face, We))|A];
+		       (_, Face, _, A) ->
+			N = gb_trees:get(Face, FaceNormTab),
+			case e3d_vec:is_zero(N) of
+			  true -> A;
+			  false -> [N|A]
+			end
+		    end, [], V, We).
+
+offset_regions_fun(OffsetData, {_,Solution,_} = State) ->
+  fun(new_mode_data, {NewState,_}) ->
+      offset_regions_fun(OffsetData, NewState);
+     ([Dist,_,_,Bump|_], A) ->
+      lists:foldl(fun({LoopNormal,VsData}, VsAcc0) ->
+		      lists:foldl(fun({V,{Vpos0,VNorm}}, VsAcc) ->
+				      [{V,Vpos0}|VsAcc];
+				     ({V,{Vpos0,Dir,EDir,ScaledEDir}}, VsAcc) ->
+				      Vec = case Solution of
+					      average -> Dir;
+					      along_edges -> EDir;
+					      scaled -> ScaledEDir
+					    end,
+				      [{V,Vpos0}|VsAcc]
+				  end, VsAcc0, VsData)
+		  end, A, OffsetData)
+  end.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/modules/opaque_digraph.erl b/lib/dialyzer/test/opaque_SUITE_data/src/modules/opaque_digraph.erl
new file mode 100644
index 0000000000..09d4229e28
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/modules/opaque_digraph.erl
@@ -0,0 +1,655 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1996-2014. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+
+%%% The Erlang scanner. All types are opaque, which puts some stress
+%%% on Dialyzer.
+
+-module(opaque_digraph).
+
+-export([new/0, new/1, delete/1, info/1]).
+
+-export([add_vertex/1, add_vertex/2, add_vertex/3]).
+-export([del_vertex/2, del_vertices/2]).
+-export([vertex/2, no_vertices/1, vertices/1]).
+-export([source_vertices/1, sink_vertices/1]).
+
+-export([add_edge/3, add_edge/4, add_edge/5]).
+-export([del_edge/2, del_edges/2, del_path/3]).
+-export([edge/2, no_edges/1, edges/1]).
+
+-export([out_neighbours/2, in_neighbours/2]).
+-export([out_edges/2, in_edges/2, edges/2]).
+-export([out_degree/2, in_degree/2]).
+-export([get_path/3, get_cycle/2]).
+
+-export([get_short_path/3, get_short_cycle/2]).
+
+-export_type([local_digraph/0, d_type/0, vertex/0]).
+
+-record(digraph, {vtab = notable :: ets:tab(),
+		  etab = notable :: ets:tab(),
+		  ntab = notable :: ets:tab(),
+	          cyclic = true  :: boolean()}).
+
+-opaque local_digraph() :: #digraph{}.
+
+-export_type([edge/0, label/0, add_edge_err_rsn/0,
+              d_protection/0, d_cyclicity/0]).
+
+-opaque edge()    :: term().
+-opaque label()   :: term().
+-opaque vertex()  :: term().
+
+-opaque add_edge_err_rsn() :: {'bad_edge', Path :: [vertex()]}
+                          | {'bad_vertex', V :: vertex()}.
+
+%%
+%% Type is a list of
+%%  protected | private
+%%  acyclic | cyclic
+%%
+%%  default is [cyclic,protected]
+%%
+-opaque d_protection() :: 'private' | 'protected'.
+-opaque d_cyclicity()  :: 'acyclic' | 'cyclic'.
+-opaque d_type()       :: d_cyclicity() | d_protection().
+
+-spec new() -> local_digraph().
+
+new() -> new([]).
+
+-spec new(Type) -> local_digraph() when
+      Type :: [d_type()].
+
+new(Type) ->
+    case check_type(Type, protected, []) of
+	{Access, Ts} ->
+	    V = ets:new(vertices, [set, Access]),
+	    E = ets:new(edges, [set, Access]),
+	    N = ets:new(neighbours, [bag, Access]),
+	    ets:insert(N, [{'$vid', 0}, {'$eid', 0}]),
+	    set_type(Ts, #digraph{vtab=V, etab=E, ntab=N});
+	error ->
+	    erlang:error(badarg)
+    end.
+
+%%
+%% Check type of graph
+%%
+%-spec check_type([d_type()], d_protection(), [{'cyclic', boolean()}]) ->
+%       	{d_protection(), [{'cyclic', boolean()}]}.
+
+check_type([acyclic|Ts], A, L) ->
+    check_type(Ts, A,[{cyclic,false} | L]);
+check_type([cyclic | Ts], A, L) ->
+    check_type(Ts, A, [{cyclic,true} | L]);
+check_type([protected | Ts], _, L) ->
+    check_type(Ts, protected, L);
+check_type([private | Ts], _, L) ->
+    check_type(Ts, private, L);
+check_type([], A, L) -> {A, L};
+check_type(_, _, _) -> error.
+
+%%
+%% Set graph type
+%%
+-spec set_type([{'cyclic', boolean()}], local_digraph()) -> local_digraph().
+
+set_type([{cyclic,V} | Ks], G) ->
+    set_type(Ks, G#digraph{cyclic = V});
+set_type([], G) -> G.
+
+
+%% Data access functions
+
+-spec delete(G) -> 'true' when
+      G :: local_digraph().
+
+delete(G) ->
+    ets:delete(G#digraph.vtab),
+    ets:delete(G#digraph.etab),
+    ets:delete(G#digraph.ntab).
+
+-spec info(G) -> InfoList when
+      G :: local_digraph(),
+      InfoList :: [{'cyclicity', Cyclicity :: d_cyclicity()} |
+                   {'memory', NoWords :: non_neg_integer()} |
+                   {'protection', Protection :: d_protection()}].
+
+info(G) ->
+    VT = G#digraph.vtab,
+    ET = G#digraph.etab,
+    NT = G#digraph.ntab,
+    Cyclicity = case G#digraph.cyclic of
+		    true  -> cyclic;
+		    false -> acyclic
+		end,
+    Protection = ets:info(VT, protection),
+    Memory = ets:info(VT, memory) + ets:info(ET, memory) + ets:info(NT, memory),
+    [{cyclicity, Cyclicity}, {memory, Memory}, {protection, Protection}].
+
+-spec add_vertex(G) -> vertex() when
+      G :: local_digraph().
+
+add_vertex(G) ->
+    do_add_vertex({new_vertex_id(G), []}, G).
+
+-spec add_vertex(G, V) -> vertex() when
+      G :: local_digraph(),
+      V :: vertex().
+
+add_vertex(G, V) ->
+    do_add_vertex({V, []}, G).
+
+-spec add_vertex(G, V, Label) -> vertex() when
+      G :: local_digraph(),
+      V :: vertex(),
+      Label :: label().
+
+add_vertex(G, V, D) ->
+    do_add_vertex({V, D}, G).
+
+-spec del_vertex(G, V) -> 'true' when
+      G :: local_digraph(),
+      V :: vertex().
+
+del_vertex(G, V) ->
+    do_del_vertex(V, G).
+
+-spec del_vertices(G, Vertices) -> 'true' when
+      G :: local_digraph(),
+      Vertices :: [vertex()].
+
+del_vertices(G, Vs) ->
+    do_del_vertices(Vs, G).
+
+-spec vertex(G, V) -> {V, Label} | 'false' when
+      G :: local_digraph(),
+      V :: vertex(),
+      Label :: label().
+
+vertex(G, V) ->
+    case ets:lookup(G#digraph.vtab, V) of
+	[] -> false;
+	[Vertex] -> Vertex
+    end.
+
+-spec no_vertices(G) -> non_neg_integer() when
+      G :: local_digraph().
+
+no_vertices(G) ->
+    ets:info(G#digraph.vtab, size).
+
+-spec vertices(G) -> Vertices when
+      G :: local_digraph(),
+      Vertices :: [vertex()].
+
+vertices(G) ->
+    ets:select(G#digraph.vtab, [{{'$1', '_'}, [], ['$1']}]).
+
+-spec source_vertices(local_digraph()) -> [vertex()].
+
+source_vertices(G) ->
+    collect_vertices(G, in).
+
+-spec sink_vertices(local_digraph()) -> [vertex()].
+
+sink_vertices(G) ->
+    collect_vertices(G, out).
+
+-spec in_degree(G, V) -> non_neg_integer() when
+      G :: local_digraph(),
+      V :: vertex().
+
+in_degree(G, V) ->
+    length(ets:lookup(G#digraph.ntab, {in, V})).
+
+-spec in_neighbours(G, V) -> Vertex when
+      G :: local_digraph(),
+      V :: vertex(),
+      Vertex :: [vertex()].
+
+in_neighbours(G, V) ->
+    ET = G#digraph.etab,
+    NT = G#digraph.ntab,
+    collect_elems(ets:lookup(NT, {in, V}), ET, 2).
+
+-spec in_edges(G, V) -> Edges when
+      G :: local_digraph(),
+      V :: vertex(),
+      Edges :: [edge()].
+
+in_edges(G, V) ->
+    ets:select(G#digraph.ntab, [{{{in, V}, '$1'}, [], ['$1']}]).
+
+-spec out_degree(G, V) -> non_neg_integer() when
+      G :: local_digraph(),
+      V :: vertex().
+
+out_degree(G, V) ->
+    length(ets:lookup(G#digraph.ntab, {out, V})).
+
+-spec out_neighbours(G, V) -> Vertices when
+      G :: local_digraph(),
+      V :: vertex(),
+      Vertices :: [vertex()].
+
+out_neighbours(G, V) ->
+    ET = G#digraph.etab,
+    NT = G#digraph.ntab,
+    collect_elems(ets:lookup(NT, {out, V}), ET, 3).
+
+-spec out_edges(G, V) -> Edges when
+      G :: local_digraph(),
+      V :: vertex(),
+      Edges :: [edge()].
+
+out_edges(G, V) ->
+    ets:select(G#digraph.ntab, [{{{out, V}, '$1'}, [], ['$1']}]).
+
+-spec add_edge(G, V1, V2) -> edge() | {'error', add_edge_err_rsn()} when
+      G :: local_digraph(),
+      V1 :: vertex(),
+      V2 :: vertex().
+
+add_edge(G, V1, V2) ->
+    do_add_edge({new_edge_id(G), V1, V2, []}, G).
+
+-spec add_edge(G, V1, V2, Label) -> edge() | {'error', add_edge_err_rsn()} when
+      G :: local_digraph(),
+      V1 :: vertex(),
+      V2 :: vertex(),
+      Label :: label().
+
+add_edge(G, V1, V2, D) ->
+    do_add_edge({new_edge_id(G), V1, V2, D}, G).
+
+-spec add_edge(G, E, V1, V2, Label) -> edge() | {'error', add_edge_err_rsn()} when
+      G :: local_digraph(),
+      E :: edge(),
+      V1 :: vertex(),
+      V2 :: vertex(),
+      Label :: label().
+
+add_edge(G, E, V1, V2, D) ->
+    do_add_edge({E, V1, V2, D}, G).
+
+-spec del_edge(G, E) -> 'true' when
+      G :: local_digraph(),
+      E :: edge().
+
+del_edge(G, E) ->
+    do_del_edges([E], G).
+
+-spec del_edges(G, Edges) -> 'true' when
+      G :: local_digraph(),
+      Edges :: [edge()].
+
+del_edges(G, Es) ->
+    do_del_edges(Es, G).
+
+-spec no_edges(G) -> non_neg_integer() when
+      G :: local_digraph().
+
+no_edges(G) ->
+    ets:info(G#digraph.etab, size).
+
+-spec edges(G) -> Edges when
+      G :: local_digraph(),
+      Edges :: [edge()].
+
+edges(G) ->
+    ets:select(G#digraph.etab, [{{'$1', '_', '_', '_'}, [], ['$1']}]).
+
+-spec edges(G, V) -> Edges when
+      G :: local_digraph(),
+      V :: vertex(),
+      Edges :: [edge()].
+
+edges(G, V) ->
+    ets:select(G#digraph.ntab, [{{{out, V},'$1'}, [], ['$1']},
+				{{{in, V}, '$1'}, [], ['$1']}]).
+
+-spec edge(G, E) -> {E, V1, V2, Label} | 'false' when
+      G :: local_digraph(),
+      E :: edge(),
+      V1 :: vertex(),
+      V2 :: vertex(),
+      Label :: label().
+
+edge(G, E) ->
+    case ets:lookup(G#digraph.etab,E) of
+	[] -> false;
+	[Edge] -> Edge
+    end.
+
+%%
+%% Generate a "unique" edge identifier (relative to this graph)
+%%
+-spec new_edge_id(local_digraph()) -> edge().
+
+new_edge_id(G) ->
+    NT = G#digraph.ntab,
+    [{'$eid', K}] = ets:lookup(NT, '$eid'),
+    true = ets:delete(NT, '$eid'),
+    true = ets:insert(NT, {'$eid', K+1}),
+    ['$e' | K].
+
+%%
+%% Generate a "unique" vertex identifier (relative to this graph)
+%%
+-spec new_vertex_id(local_digraph()) -> vertex().
+
+new_vertex_id(G) ->
+    NT = G#digraph.ntab,
+    [{'$vid', K}] = ets:lookup(NT, '$vid'),
+    true = ets:delete(NT, '$vid'),
+    true = ets:insert(NT, {'$vid', K+1}),
+    ['$v' | K].
+
+%%
+%% Collect elements for a index in a tuple
+%%
+collect_elems(Keys, Table, Index) ->
+    collect_elems(Keys, Table, Index, []).
+
+collect_elems([{_,Key}|Keys], Table, Index, Acc) ->
+    collect_elems(Keys, Table, Index,
+		  [ets:lookup_element(Table, Key, Index)|Acc]);
+collect_elems([], _, _, Acc) -> Acc.
+
+-spec do_add_vertex({vertex(), label()}, local_digraph()) -> vertex().
+
+do_add_vertex({V, _Label} = VL, G) ->
+    ets:insert(G#digraph.vtab, VL),
+    V.
+
+%%
+%% Collect either source or sink vertices.
+%%
+collect_vertices(G, Type) ->
+    Vs = vertices(G),
+    lists:foldl(fun(V, A) ->
+			case ets:member(G#digraph.ntab, {Type, V}) of
+			    true -> A;
+			    false -> [V|A]
+			end
+		end, [], Vs).
+
+%%
+%% Delete vertices
+%%
+do_del_vertices([V | Vs], G) ->
+    do_del_vertex(V, G),
+    do_del_vertices(Vs, G);
+do_del_vertices([], #digraph{}) -> true.
+
+do_del_vertex(V, G) ->
+    do_del_nedges(ets:lookup(G#digraph.ntab, {in, V}), G),
+    do_del_nedges(ets:lookup(G#digraph.ntab, {out, V}), G),
+    ets:delete(G#digraph.vtab, V).
+
+do_del_nedges([{_, E}|Ns], G) ->
+    case ets:lookup(G#digraph.etab, E) of
+	[{E, V1, V2, _}] ->
+	    do_del_edge(E, V1, V2, G),
+	    do_del_nedges(Ns, G);
+	[] -> % cannot happen
+	    do_del_nedges(Ns, G)
+    end;
+do_del_nedges([], #digraph{}) -> true.
+
+%%
+%% Delete edges
+%%
+do_del_edges([E|Es], G) ->
+    case ets:lookup(G#digraph.etab, E) of
+	[{E,V1,V2,_}] ->
+	    do_del_edge(E,V1,V2,G),
+	    do_del_edges(Es, G);
+	[] ->
+	    do_del_edges(Es, G)
+    end;
+do_del_edges([], #digraph{}) -> true.
+
+do_del_edge(E, V1, V2, G) ->
+    ets:select_delete(G#digraph.ntab, [{{{in, V2}, E}, [], [true]},
+				       {{{out,V1}, E}, [], [true]}]),
+    ets:delete(G#digraph.etab, E).
+
+-spec rm_edges([vertex(),...], local_digraph()) -> 'true'.
+
+rm_edges([V1, V2|Vs], G) ->
+    rm_edge(V1, V2, G),
+    rm_edges([V2|Vs], G);
+rm_edges(_, _) -> true.
+
+-spec rm_edge(vertex(), vertex(), local_digraph()) -> 'ok'.
+
+rm_edge(V1, V2, G) ->
+    Es = out_edges(G, V1),
+    rm_edge_0(Es, V1, V2, G).
+
+rm_edge_0([E|Es], V1, V2, G) ->
+    case ets:lookup(G#digraph.etab, E) of
+	[{E, V1, V2, _}]  ->
+            do_del_edge(E, V1, V2, G),
+	    rm_edge_0(Es, V1, V2, G);
+	_ ->
+	    rm_edge_0(Es, V1, V2, G)
+    end;
+rm_edge_0([], _, _, #digraph{}) -> ok.
+
+%%
+%% Check that endpoints exist
+%%
+-spec do_add_edge({edge(), vertex(), vertex(), label()}, local_digraph()) ->
+	edge() | {'error', add_edge_err_rsn()}.
+
+do_add_edge({E, V1, V2, Label}, G) ->
+    case ets:member(G#digraph.vtab, V1) of
+	false -> {error, {bad_vertex, V1}};
+	true  ->
+	    case ets:member(G#digraph.vtab, V2) of
+		false -> {error, {bad_vertex, V2}};
+                true ->
+                    case other_edge_exists(G, E, V1, V2) of
+                        true -> {error, {bad_edge, [V1, V2]}};
+                        false when G#digraph.cyclic =:= false ->
+                            acyclic_add_edge(E, V1, V2, Label, G);
+                        false ->
+                            do_insert_edge(E, V1, V2, Label, G)
+                    end
+	    end
+    end.
+
+other_edge_exists(#digraph{etab = ET}, E, V1, V2) ->
+    case ets:lookup(ET, E) of
+        [{E, Vert1, Vert2, _}] when Vert1 =/= V1; Vert2 =/= V2 ->
+            true;
+        _ ->
+            false
+    end.
+
+-spec do_insert_edge(edge(), vertex(), vertex(), label(), local_digraph()) -> edge().
+
+do_insert_edge(E, V1, V2, Label, #digraph{ntab=NT, etab=ET}) ->
+    ets:insert(NT, [{{out, V1}, E}, {{in, V2}, E}]),
+    ets:insert(ET, {E, V1, V2, Label}),
+    E.
+
+-spec acyclic_add_edge(edge(), vertex(), vertex(), label(), local_digraph()) ->
+	edge() | {'error', {'bad_edge', [vertex()]}}.
+
+acyclic_add_edge(_E, V1, V2, _L, _G) when V1 =:= V2 ->
+    {error, {bad_edge, [V1, V2]}};
+acyclic_add_edge(E, V1, V2, Label, G) ->
+    case get_path(G, V2, V1) of
+	false -> do_insert_edge(E, V1, V2, Label, G);
+	Path -> {error, {bad_edge, Path}}
+    end.
+
+%%
+%% Delete all paths from vertex V1 to vertex V2
+%%
+
+-spec del_path(G, V1, V2) -> 'true' when
+      G :: local_digraph(),
+      V1 :: vertex(),
+      V2 :: vertex().
+
+del_path(G, V1, V2) ->
+    case get_path(G, V1, V2) of
+	false -> true;
+	Path ->
+	    rm_edges(Path, G),
+	    del_path(G, V1, V2)
+    end.
+
+%%
+%% Find a cycle through V
+%% return the cycle as list of vertices [V ... V]
+%% if no cycle exists false is returned
+%% if only a cycle of length one exists it will be
+%% returned as [V] but only after longer cycles have
+%% been searched.
+%%
+
+-spec get_cycle(G, V) -> Vertices | 'false' when
+      G :: local_digraph(),
+      V :: vertex(),
+      Vertices :: [vertex(),...].
+
+get_cycle(G, V) ->
+    case one_path(out_neighbours(G, V), V, [], [V], [V], 2, G, 1) of
+	false ->
+	    case lists:member(V, out_neighbours(G, V)) of
+		true -> [V];
+		false -> false
+	    end;
+	Vs -> Vs
+    end.
+
+%%
+%% Find a path from V1 to V2
+%% return the path as list of vertices [V1 ... V2]
+%% if no path exists false is returned
+%%
+
+-spec get_path(G, V1, V2) -> Vertices | 'false' when
+      G :: local_digraph(),
+      V1 :: vertex(),
+      V2 :: vertex(),
+      Vertices :: [vertex(),...].
+
+get_path(G, V1, V2) ->
+    one_path(out_neighbours(G, V1), V2, [], [V1], [V1], 1, G, 1).
+
+%%
+%% prune_short_path (evaluate conditions on path)
+%% short : if path is too short
+%% ok    : if path is ok
+%%
+prune_short_path(Counter, Min) when Counter < Min ->
+    short;
+prune_short_path(_Counter, _Min) ->
+    ok.
+
+one_path([W|Ws], W, Cont, Xs, Ps, Prune, G, Counter) ->
+    case prune_short_path(Counter, Prune) of
+	short -> one_path(Ws, W, Cont, Xs, Ps, Prune, G, Counter);
+	ok -> lists:reverse([W|Ps])
+    end;
+one_path([V|Vs], W, Cont, Xs, Ps, Prune, G, Counter) ->
+    case lists:member(V, Xs) of
+	true ->  one_path(Vs, W, Cont, Xs, Ps, Prune, G, Counter);
+	false -> one_path(out_neighbours(G, V), W,
+			  [{Vs,Ps} | Cont], [V|Xs], [V|Ps],
+			  Prune, G, Counter+1)
+    end;
+one_path([], W, [{Vs,Ps}|Cont], Xs, _, Prune, G, Counter) ->
+    one_path(Vs, W, Cont, Xs, Ps, Prune, G, Counter-1);
+one_path([], _, [], _, _, _, _, _Counter) -> false.
+
+%%
+%% Like get_cycle/2, but a cycle of length one is preferred.
+%%
+
+-spec get_short_cycle(G, V) -> Vertices | 'false' when
+      G :: local_digraph(),
+      V :: vertex(),
+      Vertices :: [vertex(),...].
+
+get_short_cycle(G, V) ->
+    get_short_path(G, V, V).
+
+%%
+%% Like get_path/3, but using a breadth-first search makes it possible
+%% to find a short path.
+%%
+
+-spec get_short_path(G, V1, V2) -> Vertices | 'false' when
+      G :: local_digraph(),
+      V1 :: vertex(),
+      V2 :: vertex(),
+      Vertices :: [vertex(),...].
+
+get_short_path(G, V1, V2) ->
+    T = new(),
+    add_vertex(T, V1),
+    Q = queue:new(),
+    Q1 = queue_out_neighbours(V1, G, Q),
+    L = spath(Q1, G, V2, T),
+    delete(T),
+    L.
+
+spath(Q, G, Sink, T) ->
+    case queue:out(Q) of
+	{{value, E}, Q1} ->
+	    {_E, V1, V2, _Label} = edge(G, E),
+	    if
+		Sink =:= V2 ->
+		    follow_path(V1, T, [V2]);
+		true ->
+		    case vertex(T, V2) of
+			false ->
+			    add_vertex(T, V2),
+			    add_edge(T, V2, V1),
+			    NQ = queue_out_neighbours(V2, G, Q1),
+			    spath(NQ, G, Sink, T);
+			_V ->
+			    spath(Q1, G, Sink, T)
+		    end
+	    end;
+	{empty, _Q1} ->
+	    false
+    end.
+
+follow_path(V, T, P) ->
+    P1 = [V | P],
+    case out_neighbours(T, V) of
+	[N] ->
+	    follow_path(N, T, P1);
+	[] ->
+	    P1
+    end.
+
+queue_out_neighbours(V, G, Q0) ->
+    lists:foldl(fun(E, Q) -> queue:in(E, Q) end, Q0, out_edges(G, V)).
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/modules/opaque_erl_scan.erl b/lib/dialyzer/test/opaque_SUITE_data/src/modules/opaque_erl_scan.erl
new file mode 100644
index 0000000000..9ecd4f92a1
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/modules/opaque_erl_scan.erl
@@ -0,0 +1,1300 @@
+%% -*- coding: utf-8 -*-
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1996-2014. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+
+%%% The Erlang scanner. All types are opaque, which puts some stress
+%%% on Dialyzer.
+
+-module(opaque_erl_scan).
+
+%%% External exports
+
+-export([string/1,string/2,string/3,tokens/3,tokens/4,
+         format_error/1,reserved_word/1,
+         token_info/1,token_info/2,
+         attributes_info/1,attributes_info/2,set_attribute/3]).
+
+%%% Private
+-export([continuation_location/1]).
+
+-export_type([error_info/0,
+              line/0,
+              location/0,
+              options/0,
+              return_cont/0,
+              token/0,
+              tokens_result/0]).
+
+%%%
+%%% Defines and type definitions
+%%%
+
+-define(COLUMN(C), (is_integer(C) andalso C >= 1)).
+%% Line numbers less than zero have always been allowed:
+-define(ALINE(L), is_integer(L)).
+-define(STRING(S), is_list(S)).
+-define(RESWORDFUN(F), is_function(F, 1)).
+-define(SETATTRFUN(F), is_function(F, 1)).
+
+-export_type([category/0, column/0, resword_fun/0, option/0, symbol/0,
+              info_line/0, attributes_data/0, attributes/0, tokens/0,
+              error_description/0, char_spec/0, cont_fun/0,
+              attribute_item/0, info_location/0, attribute_info/0,
+              token_item/0, token_info/0]).
+
+-opaque category() :: atom().
+-opaque column() :: pos_integer().
+-opaque line() :: integer().
+-opaque location() :: line() | {line(),column()}.
+-opaque resword_fun() :: fun((atom()) -> boolean()).
+-opaque option() :: 'return' | 'return_white_spaces' | 'return_comments'
+                | 'text' | {'reserved_word_fun', resword_fun()}.
+-opaque options() :: option() | [option()].
+-opaque symbol() :: atom() | float() | integer() | string().
+-opaque info_line() :: integer() | term().
+-opaque attributes_data()
+       :: [{'column', column()} | {'line', info_line()} | {'text', string()}]
+        |  {line(), column()}.
+%% The fact that {line(),column()} is a possible attributes() type
+%% is hidden.
+-opaque attributes() :: line() | attributes_data().
+-opaque token() :: {category(), attributes(), symbol()}
+               | {category(), attributes()}.
+-opaque tokens() :: [token()].
+-opaque error_description() :: term().
+-opaque error_info() :: {location(), module(), error_description()}.
+
+%%% Local record.
+-record(erl_scan,
+        {resword_fun = fun reserved_word/1 :: resword_fun(),
+         ws          = false               :: boolean(),
+         comment     = false               :: boolean(),
+         text        = false               :: boolean()}).
+
+%%----------------------------------------------------------------------------
+
+-spec format_error(ErrorDescriptor) -> string() when
+      ErrorDescriptor :: error_description().
+format_error({string,Quote,Head}) ->
+    lists:flatten(["unterminated " ++ string_thing(Quote) ++
+                   " starting with " ++
+                   io_lib:write_string(Head, Quote)]);
+format_error({illegal,Type}) ->
+    lists:flatten(io_lib:fwrite("illegal ~w", [Type]));
+format_error(char) -> "unterminated character";
+format_error({base,Base}) ->
+    lists:flatten(io_lib:fwrite("illegal base '~w'", [Base]));
+format_error(Other) ->
+    lists:flatten(io_lib:write(Other)).
+
+-spec string(String) -> Return when
+      String :: string(),
+      Return :: {'ok', Tokens :: tokens(), EndLocation}
+              | {'error', ErrorInfo :: error_info(), ErrorLocation},
+      EndLocation :: location(),
+      ErrorLocation :: location().
+string(String) ->
+    string(String, 1, []).
+
+-spec string(String, StartLocation) -> Return when
+      String :: string(),
+      Return :: {'ok', Tokens :: tokens(), EndLocation}
+              | {'error', ErrorInfo :: error_info(), ErrorLocation},
+      StartLocation :: location(),
+      EndLocation :: location(),
+      ErrorLocation :: location().
+string(String, StartLocation) ->
+    string(String, StartLocation, []).
+
+-spec string(String, StartLocation, Options) -> Return when
+      String :: string(),
+      Options :: options(),
+      Return :: {'ok', Tokens :: tokens(), EndLocation}
+              | {'error', ErrorInfo :: error_info(), ErrorLocation},
+      StartLocation :: location(),
+      EndLocation :: location(),
+      ErrorLocation :: location().
+string(String, Line, Options) when ?STRING(String), ?ALINE(Line) ->
+    string1(String, options(Options), Line, no_col, []);
+string(String, {Line,Column}, Options) when ?STRING(String),
+                                            ?ALINE(Line),
+                                            ?COLUMN(Column) ->
+    string1(String, options(Options), Line, Column, []).
+
+-opaque char_spec() :: string() | 'eof'.
+-opaque cont_fun() :: fun((char_spec(), #erl_scan{}, line(), column(),
+                         tokens(), any()) -> any()).
+-opaque return_cont() :: {erl_scan_continuation,
+                          string(), column(), tokens(), line(),
+                          #erl_scan{}, any(), cont_fun()}.
+-opaque tokens_result() :: {'ok', Tokens :: tokens(), EndLocation :: location()}
+                       | {'eof', EndLocation :: location()}
+                       | {'error', ErrorInfo :: error_info(),
+                          EndLocation :: location()}.
+
+-spec tokens(Continuation, CharSpec, StartLocation) -> Return when
+      Continuation :: return_cont() | [],
+      CharSpec :: char_spec(),
+      StartLocation :: location(),
+      Return :: {'done',Result :: tokens_result(),LeftOverChars :: char_spec()}
+              | {'more', Continuation1 :: return_cont()}.
+tokens(Cont, CharSpec, StartLocation) ->
+    tokens(Cont, CharSpec, StartLocation, []).
+
+-spec tokens(Continuation, CharSpec, StartLocation, Options) -> Return when
+      Continuation :: return_cont() | [],
+      CharSpec :: char_spec(),
+      StartLocation :: location(),
+      Options :: options(),
+      Return :: {'done',Result :: tokens_result(),LeftOverChars :: char_spec()}
+              | {'more', Continuation1 :: return_cont()}.
+tokens([], CharSpec, Line, Options) when ?ALINE(Line) ->
+    tokens1(CharSpec, options(Options), Line, no_col, [], fun scan/6, []);
+tokens([], CharSpec, {Line,Column}, Options) when ?ALINE(Line),
+                                                  ?COLUMN(Column) ->
+    tokens1(CharSpec, options(Options), Line, Column, [], fun scan/6, []);
+tokens({erl_scan_continuation,Cs,Col,Toks,Line,St,Any,Fun},
+       CharSpec, _Loc, _Opts) ->
+    tokens1(Cs++CharSpec, St, Line, Col, Toks, Fun, Any).
+
+continuation_location({erl_scan_continuation,_,no_col,_,Line,_,_,_}) ->
+    Line;
+continuation_location({erl_scan_continuation,_,Col,_,Line,_,_,_}) ->
+    {Line,Col}.
+
+-opaque attribute_item() :: 'column' | 'length' | 'line'
+                        | 'location' | 'text'.
+-opaque info_location() :: location() | term().
+-opaque attribute_info() :: {'column', column()}| {'length', pos_integer()}
+                        | {'line', info_line()}
+                        | {'location', info_location()}
+                        | {'text', string()}.
+-opaque token_item() :: 'category' | 'symbol' | attribute_item().
+-opaque token_info() :: {'category', category()} | {'symbol', symbol()}
+                    | attribute_info().
+
+-spec token_info(Token) -> TokenInfo when
+      Token :: token(),
+      TokenInfo :: [TokenInfoTuple :: token_info()].
+token_info(Token) ->
+    Items = [category,column,length,line,symbol,text], % undefined order
+    token_info(Token, Items).
+
+-spec token_info(Token, TokenItem) -> TokenInfoTuple | 'undefined' when
+                     Token :: token(),
+                     TokenItem :: token_item(),
+                     TokenInfoTuple :: token_info();
+                (Token, TokenItems) -> TokenInfo when
+                     Token :: token(),
+                     TokenItems :: [TokenItem :: token_item()],
+                     TokenInfo :: [TokenInfoTuple :: token_info()].
+token_info(_Token, []) ->
+    [];
+token_info(Token, [Item|Items]) when is_atom(Item) ->
+    case token_info(Token, Item) of
+        undefined ->
+            token_info(Token, Items);
+        TokenInfo when is_tuple(TokenInfo) ->
+            [TokenInfo|token_info(Token, Items)]
+    end;
+token_info({Category,_Attrs}, category=Item) ->
+    {Item,Category};
+token_info({Category,_Attrs,_Symbol}, category=Item) ->
+    {Item,Category};
+token_info({Category,_Attrs}, symbol=Item) ->
+    {Item,Category};
+token_info({_Category,_Attrs,Symbol}, symbol=Item) ->
+    {Item,Symbol};
+token_info({_Category,Attrs}, Item) ->
+    attributes_info(Attrs, Item);
+token_info({_Category,Attrs,_Symbol}, Item) ->
+    attributes_info(Attrs, Item).
+
+-spec attributes_info(Attributes) -> AttributesInfo when
+      Attributes :: attributes(),
+      AttributesInfo :: [AttributeInfoTuple :: attribute_info()].
+attributes_info(Attributes) ->
+    Items = [column,length,line,text], % undefined order
+    attributes_info(Attributes, Items).
+
+-spec attributes_info
+        (Attributes, AttributeItem) -> AttributeInfoTuple | 'undefined' when
+             Attributes :: attributes(),
+             AttributeItem :: attribute_item(),
+             AttributeInfoTuple :: attribute_info();
+        (Attributes, AttributeItems) -> AttributeInfo when
+             Attributes :: attributes(),
+             AttributeItems :: [AttributeItem :: attribute_item()],
+             AttributeInfo :: [AttributeInfoTuple :: attribute_info()].
+attributes_info(_Attrs, []) ->
+    [];
+attributes_info(Attrs, [A|As]) when is_atom(A) ->
+    case attributes_info(Attrs, A) of
+        undefined ->
+            attributes_info(Attrs, As);
+        AttributeInfo when is_tuple(AttributeInfo) ->
+            [AttributeInfo|attributes_info(Attrs, As)]
+    end;
+attributes_info({Line,Column}, column=Item) when ?ALINE(Line),
+                                                 ?COLUMN(Column) ->
+    {Item,Column};
+attributes_info(Line, column) when ?ALINE(Line) ->
+    undefined;
+attributes_info(Attrs, column=Item) ->
+    attr_info(Attrs, Item);
+attributes_info(Attrs, length=Item) ->
+    case attributes_info(Attrs, text) of
+        undefined ->
+            undefined;
+        {text,Text} ->
+            {Item,length(Text)}
+    end;
+attributes_info(Line, line=Item) when ?ALINE(Line) ->
+    {Item,Line};
+attributes_info({Line,Column}, line=Item) when ?ALINE(Line),
+                                               ?COLUMN(Column) ->
+    {Item,Line};
+attributes_info(Attrs, line=Item) ->
+    attr_info(Attrs, Item);
+attributes_info({Line,Column}=Location, location=Item) when ?ALINE(Line),
+                                                            ?COLUMN(Column) ->
+    {Item,Location};
+attributes_info(Line, location=Item) when ?ALINE(Line) ->
+    {Item,Line};
+attributes_info(Attrs, location=Item) ->
+    {line,Line} = attributes_info(Attrs, line), % assume line is present
+    case attributes_info(Attrs, column) of
+        undefined ->
+            %% If set_attribute() has assigned a term such as {17,42}
+            %% to 'line', then Line will look like {Line,Column}. One
+            %% should not use 'location' but 'line' and 'column' in
+            %% such special cases.
+            {Item,Line};
+        {column,Column} ->
+            {Item,{Line,Column}}
+    end;
+attributes_info({Line,Column}, text) when ?ALINE(Line), ?COLUMN(Column) ->
+    undefined;
+attributes_info(Line, text) when ?ALINE(Line) ->
+    undefined;
+attributes_info(Attrs, text=Item) ->
+    attr_info(Attrs, Item);
+attributes_info(T1, T2) ->
+    erlang:error(badarg, [T1,T2]).
+
+-spec set_attribute(AttributeItem, Attributes, SetAttributeFun) -> Attributes when
+      AttributeItem :: 'line',
+      Attributes :: attributes(),
+      SetAttributeFun :: fun((info_line()) -> info_line()).
+set_attribute(Tag, Attributes, Fun) when ?SETATTRFUN(Fun) ->
+    set_attr(Tag, Attributes, Fun).
+
+%%%
+%%% Local functions
+%%%
+
+string_thing($') -> "atom";   %' Stupid Emacs
+string_thing(_) -> "string".
+
+-define(WHITE_SPACE(C),
+        is_integer(C) andalso
+         (C >= $\000 andalso C =< $\s orelse C >= $\200 andalso C =< $\240)).
+-define(DIGIT(C), C >= $0, C =< $9).
+-define(CHAR(C), is_integer(C), C >= 0).
+-define(UNICODE(C),
+        is_integer(C) andalso
+         (C >= 0 andalso C < 16#D800 orelse
+          C > 16#DFFF andalso C < 16#FFFE orelse
+          C > 16#FFFF andalso C =< 16#10FFFF)).
+
+-define(UNI255(C), C >= 0, C =< 16#ff).
+
+options(Opts0) when is_list(Opts0) ->
+    Opts = lists:foldr(fun expand_opt/2, [], Opts0),
+    [RW_fun] =
+        case opts(Opts, [reserved_word_fun], []) of
+            badarg ->
+                erlang:error(badarg, [Opts0]);
+            R ->
+                R
+        end,
+    Comment = proplists:get_bool(return_comments, Opts),
+    WS = proplists:get_bool(return_white_spaces, Opts),
+    Txt = proplists:get_bool(text, Opts),
+    #erl_scan{resword_fun = RW_fun,
+              comment     = Comment,
+              ws          = WS,
+              text        = Txt};
+options(Opt) ->
+    options([Opt]).
+
+opts(Options, [Key|Keys], L) ->
+    V = case lists:keyfind(Key, 1, Options) of
+            {reserved_word_fun,F} when ?RESWORDFUN(F) ->
+                {ok,F};
+            {Key,_} ->
+                badarg;
+            false ->
+                {ok,default_option(Key)}
+        end,
+    case V of
+        badarg ->
+            badarg;
+        {ok,Value} ->
+            opts(Options, Keys, [Value|L])
+    end;
+opts(_Options, [], L) ->
+    lists:reverse(L).
+
+default_option(reserved_word_fun) ->
+    fun reserved_word/1.
+
+expand_opt(return, Os) ->
+    [return_comments,return_white_spaces|Os];
+expand_opt(O, Os) ->
+    [O|Os].
+
+attr_info(Attrs, Item) ->
+    try lists:keyfind(Item, 1, Attrs) of
+        {_Item, _Value} = T ->
+            T;
+        false ->
+            undefined
+    catch
+	_:_ ->
+            erlang:error(badarg, [Attrs, Item])
+    end.
+
+-spec set_attr('line', attributes(), fun((line()) -> line())) -> attributes().
+
+set_attr(line, Line, Fun) when ?ALINE(Line) ->
+    Ln = Fun(Line),
+    if
+        ?ALINE(Ln) ->
+            Ln;
+        true ->
+            [{line,Ln}]
+    end;
+set_attr(line, {Line,Column}, Fun) when ?ALINE(Line), ?COLUMN(Column) ->
+    Ln = Fun(Line),
+    if
+        ?ALINE(Ln) ->
+            {Ln,Column};
+        true ->
+            [{line,Ln},{column,Column}]
+    end;
+set_attr(line=Tag, Attrs, Fun) when is_list(Attrs) ->
+    {line,Line} = lists:keyfind(Tag, 1, Attrs),
+    case lists:keyreplace(Tag, 1, Attrs, {line,Fun(Line)}) of
+        [{line,Ln}] when ?ALINE(Ln) ->
+            Ln;
+        As ->
+            As
+    end;
+set_attr(T1, T2, T3) ->
+    erlang:error(badarg, [T1,T2,T3]).
+
+tokens1(Cs, St, Line, Col, Toks, Fun, Any) when ?STRING(Cs); Cs =:= eof ->
+    case Fun(Cs, St, Line, Col, Toks, Any) of
+        {more,{Cs0,Ncol,Ntoks,Nline,Nany,Nfun}} ->
+            {more,{erl_scan_continuation,Cs0,Ncol,Ntoks,Nline,St,Nany,Nfun}};
+        {ok,Toks0,eof,Nline,Ncol} ->
+            Res = case Toks0 of
+                      [] ->
+                          {eof,location(Nline, Ncol)};
+                      _ ->
+                          {ok,lists:reverse(Toks0),location(Nline,Ncol)}
+                  end,
+            {done,Res,eof};
+        {ok,Toks0,Rest,Nline,Ncol} ->
+            {done,{ok,lists:reverse(Toks0),location(Nline, Ncol)},Rest};
+        {{error,_,_}=Error,Rest} ->
+            {done,Error,Rest}
+    end.
+
+string1(Cs, St, Line, Col, Toks) ->
+    case scan1(Cs, St, Line, Col, Toks) of
+        {more,{Cs0,Ncol,Ntoks,Nline,Any,Fun}} ->
+            case Fun(Cs0++eof, St, Nline, Ncol, Ntoks, Any) of
+                {ok,Toks1,_Rest,Line2,Col2} ->
+                    {ok,lists:reverse(Toks1),location(Line2, Col2)};
+                {{error,_,_}=Error,_Rest} ->
+                    Error
+            end;
+        {ok,Ntoks,[_|_]=Rest,Nline,Ncol} ->
+            string1(Rest, St, Nline, Ncol, Ntoks);
+        {ok,Ntoks,_,Nline,Ncol} ->
+            {ok,lists:reverse(Ntoks),location(Nline, Ncol)};
+        {{error,_,_}=Error,_Rest} ->
+            Error
+    end.
+
+scan(Cs, St, Line, Col, Toks, _) ->
+    scan1(Cs, St, Line, Col, Toks).
+
+scan1([$\s|Cs], St, Line, Col, Toks) when St#erl_scan.ws ->
+    scan_spcs(Cs, St, Line, Col, Toks, 1);
+scan1([$\s|Cs], St, Line, Col, Toks) ->
+    skip_white_space(Cs, St, Line, Col, Toks, 1);
+scan1([$\n|Cs], St, Line, Col, Toks) when St#erl_scan.ws ->
+    scan_newline(Cs, St, Line, Col, Toks);
+scan1([$\n|Cs], St, Line, Col, Toks) ->
+    skip_white_space(Cs, St, Line+1, new_column(Col, 1), Toks, 0);
+scan1([C|Cs], St, Line, Col, Toks) when C >= $A, C =< $Z ->
+    scan_variable(Cs, St, Line, Col, Toks, [C]);
+scan1([C|Cs], St, Line, Col, Toks) when C >= $a, C =< $z ->
+    scan_atom(Cs, St, Line, Col, Toks, [C]);
+%% Optimization: some very common punctuation characters:
+scan1([$,|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ",", ',', 1);
+scan1([$(|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "(", '(', 1);
+scan1([$)|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ")", ')', 1);
+scan1([${|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "{", '{', 1);
+scan1([$}|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "}", '}', 1);
+scan1([$[|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "[", '[', 1);
+scan1([$]|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "]", ']', 1);
+scan1([$;|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ";", ';', 1);
+scan1([$_=C|Cs], St, Line, Col, Toks) ->
+    scan_variable(Cs, St, Line, Col, Toks, [C]);
+%% More punctuation characters below.
+scan1([$\%|Cs], St, Line, Col, Toks) when not St#erl_scan.comment ->
+    skip_comment(Cs, St, Line, Col, Toks, 1);
+scan1([$\%=C|Cs], St, Line, Col, Toks) ->
+    scan_comment(Cs, St, Line, Col, Toks, [C]);
+scan1([C|Cs], St, Line, Col, Toks) when ?DIGIT(C) ->
+    scan_number(Cs, St, Line, Col, Toks, [C]);
+scan1("..."++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "...", '...', 3);
+scan1(".."=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+scan1(".."++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "..", '..', 2);
+scan1("."=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+scan1([$.=C|Cs], St, Line, Col, Toks) ->
+    scan_dot(Cs, St, Line, Col, Toks, [C]);
+scan1([$"|Cs], St, Line, Col, Toks) -> %" Emacs
+    State0 = {[],[],Line,Col},
+    scan_string(Cs, St, Line, incr_column(Col, 1), Toks, State0);
+scan1([$'|Cs], St, Line, Col, Toks) -> %' Emacs
+    State0 = {[],[],Line,Col},
+    scan_qatom(Cs, St, Line, incr_column(Col, 1), Toks, State0);
+scan1([$$|Cs], St, Line, Col, Toks) ->
+    scan_char(Cs, St, Line, Col, Toks);
+scan1([$\r|Cs], St, Line, Col, Toks) when St#erl_scan.ws ->
+    white_space_end(Cs, St, Line, Col, Toks, 1, "\r");
+scan1([C|Cs], St, Line, Col, Toks) when C >= $ß, C =< $ÿ, C =/= $÷ ->
+    scan_atom(Cs, St, Line, Col, Toks, [C]);
+scan1([C|Cs], St, Line, Col, Toks) when C >= $À, C =< $Þ, C /= $× ->
+    scan_variable(Cs, St, Line, Col, Toks, [C]);
+scan1([$\t|Cs], St, Line, Col, Toks) when St#erl_scan.ws ->
+    scan_tabs(Cs, St, Line, Col, Toks, 1);
+scan1([$\t|Cs], St, Line, Col, Toks) ->
+    skip_white_space(Cs, St, Line, Col, Toks, 1);
+scan1([C|Cs], St, Line, Col, Toks) when ?WHITE_SPACE(C) ->
+    case St#erl_scan.ws of
+        true ->
+            scan_white_space(Cs, St, Line, Col, Toks, [C]);
+        false ->
+            skip_white_space(Cs, St, Line, Col, Toks, 1)
+    end;
+%% Punctuation characters and operators, first recognise multiples.
+%% << <- <=
+scan1("<<"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "<<", '<<', 2);
+scan1("<-"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "<-", '<-', 2);
+scan1("<="++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "<=", '<=', 2);
+scan1("<"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% >> >=
+scan1(">>"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ">>", '>>', 2);
+scan1(">="++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ">=", '>=', 2);
+scan1(">"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% -> --
+scan1("->"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "->", '->', 2);
+scan1("--"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "--", '--', 2);
+scan1("-"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% ++
+scan1("++"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "++", '++', 2);
+scan1("+"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% =:= =/= =< ==
+scan1("=:="++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "=:=", '=:=', 3);
+scan1("=:"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+scan1("=/="++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "=/=", '=/=', 3);
+scan1("=/"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+scan1("=<"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "=<", '=<', 2);
+scan1("=="++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "==", '==', 2);
+scan1("="=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% /=
+scan1("/="++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "/=", '/=', 2);
+scan1("/"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% ||
+scan1("||"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "||", '||', 2);
+scan1("|"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% :-
+scan1(":-"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ":-", ':-', 2);
+%% :: for typed records
+scan1("::"++Cs, St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "::", '::', 2);
+scan1(":"=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+%% Optimization: punctuation characters less than 127:
+scan1([$=|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "=", '=', 1);
+scan1([$:|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ":", ':', 1);
+scan1([$||Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "|", '|', 1);
+scan1([$#|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "#", '#', 1);
+scan1([$/|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "/", '/', 1);
+scan1([$?|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "?", '?', 1);
+scan1([$-|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "-", '-', 1);
+scan1([$+|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "+", '+', 1);
+scan1([$*|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "*", '*', 1);
+scan1([$<|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "<", '<', 1);
+scan1([$>|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, ">", '>', 1);
+scan1([$!|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "!", '!', 1);
+scan1([$@|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "@", '@', 1);
+scan1([$\\|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "\\", '\\', 1);
+scan1([$^|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "^", '^', 1);
+scan1([$`|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "`", '`', 1);
+scan1([$~|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "~", '~', 1);
+scan1([$&|Cs], St, Line, Col, Toks) ->
+    tok2(Cs, St, Line, Col, Toks, "&", '&', 1);
+%% End of optimization.
+scan1([C|Cs], St, Line, Col, Toks) when ?UNI255(C) ->
+    Str = [C],
+    tok2(Cs, St, Line, Col, Toks, Str, list_to_atom(Str), 1);
+scan1([C|Cs], _St, Line, Col, _Toks) when ?CHAR(C) ->
+    Ncol = incr_column(Col, 1),
+    scan_error({illegal,character}, Line, Col, Line, Ncol, Cs);
+scan1([]=Cs, _St, Line, Col, Toks) ->
+    {more,{Cs,Col,Toks,Line,[],fun scan/6}};
+scan1(eof=Cs, _St, Line, Col, Toks) ->
+    {ok,Toks,Cs,Line,Col}.
+
+scan_atom(Cs0, St, Line, Col, Toks, Ncs0) ->
+    case scan_name(Cs0, Ncs0) of
+        {more,Ncs} ->
+            {more,{[],Col,Toks,Line,Ncs,fun scan_atom/6}};
+        {Wcs,Cs} ->
+            case catch list_to_atom(Wcs) of
+                Name when is_atom(Name) ->
+                    case (St#erl_scan.resword_fun)(Name) of
+                        true ->
+                            tok2(Cs, St, Line, Col, Toks, Wcs, Name);
+                        false ->
+                            tok3(Cs, St, Line, Col, Toks, atom, Wcs, Name)
+                    end;
+                _Error ->
+                    Ncol = incr_column(Col, length(Wcs)),
+                    scan_error({illegal,atom}, Line, Col, Line, Ncol, Cs)
+            end
+    end.
+
+scan_variable(Cs0, St, Line, Col, Toks, Ncs0) ->
+    case scan_name(Cs0, Ncs0) of
+        {more,Ncs} ->
+            {more,{[],Col,Toks,Line,Ncs,fun scan_variable/6}};
+        {Wcs,Cs} ->
+            case catch list_to_atom(Wcs) of
+                Name when is_atom(Name) ->
+                    tok3(Cs, St, Line, Col, Toks, var, Wcs, Name);
+                _Error ->
+                    Ncol = incr_column(Col, length(Wcs)),
+                    scan_error({illegal,var}, Line, Col, Line, Ncol, Cs)
+            end
+    end.
+
+scan_name([C|Cs], Ncs) when C >= $a, C =< $z ->
+    scan_name(Cs, [C|Ncs]);
+scan_name([C|Cs], Ncs) when C >= $A, C =< $Z ->
+    scan_name(Cs, [C|Ncs]);
+scan_name([$_=C|Cs], Ncs) ->
+    scan_name(Cs, [C|Ncs]);
+scan_name([C|Cs], Ncs) when ?DIGIT(C) ->
+    scan_name(Cs, [C|Ncs]);
+scan_name([$@=C|Cs], Ncs) ->
+    scan_name(Cs, [C|Ncs]);
+scan_name([C|Cs], Ncs) when C >= $ß, C =< $ÿ, C =/= $÷ ->
+    scan_name(Cs, [C|Ncs]);
+scan_name([C|Cs], Ncs) when C >= $À, C =< $Þ, C =/= $× ->
+    scan_name(Cs, [C|Ncs]);
+scan_name([], Ncs) ->
+    {more,Ncs};
+scan_name(Cs, Ncs) ->
+    {lists:reverse(Ncs),Cs}.
+
+-define(STR(St, S), if St#erl_scan.text -> S; true -> [] end).
+
+scan_dot([$%|_]=Cs, St, Line, Col, Toks, Ncs) ->
+    Attrs = attributes(Line, Col, St, Ncs),
+    {ok,[{dot,Attrs}|Toks],Cs,Line,incr_column(Col, 1)};
+scan_dot([$\n=C|Cs], St, Line, Col, Toks, Ncs) ->
+    Attrs = attributes(Line, Col, St, ?STR(St, Ncs++[C])),
+    {ok,[{dot,Attrs}|Toks],Cs,Line+1,new_column(Col, 1)};
+scan_dot([C|Cs], St, Line, Col, Toks, Ncs) when ?WHITE_SPACE(C) ->
+    Attrs = attributes(Line, Col, St, ?STR(St, Ncs++[C])),
+    {ok,[{dot,Attrs}|Toks],Cs,Line,incr_column(Col, 2)};
+scan_dot(eof=Cs, St, Line, Col, Toks, Ncs) ->
+    Attrs = attributes(Line, Col, St, Ncs),
+    {ok,[{dot,Attrs}|Toks],Cs,Line,incr_column(Col, 1)};
+scan_dot(Cs, St, Line, Col, Toks, Ncs) ->
+    tok2(Cs, St, Line, Col, Toks, Ncs, '.', 1).
+
+%%% White space characters are very common, so it is worthwhile to
+%%% scan them fast and store them compactly. (The words "whitespace"
+%%% and "white space" usually mean the same thing. The Erlang
+%%% specification denotes the characters with ASCII code in the
+%%% interval 0 to 32 as "white space".)
+%%%
+%%% Convention: if there is a white newline ($\n) it will always be
+%%% the first character in the text string. As a consequence, there
+%%% cannot be more than one newline in a white_space token string.
+%%%
+%%% Some common combinations are recognized, some are not. Examples
+%%% of the latter are tab(s) followed by space(s), like "\t  ".
+%%% (They will be represented by two (or more) tokens.)
+%%%
+%%% Note: the character sequence "\r\n" is *not* recognized since it
+%%% would violate the property that $\n will always be the first
+%%% character. (But since "\r\n\r\n" is common, it pays off to
+%%% recognize "\n\r".)
+
+scan_newline([$\s|Cs], St, Line, Col, Toks) ->
+    scan_nl_spcs(Cs, St, Line, Col, Toks, 2);
+scan_newline([$\t|Cs], St, Line, Col, Toks) ->
+    scan_nl_tabs(Cs, St, Line, Col, Toks, 2);
+scan_newline([$\r|Cs], St, Line, Col, Toks) ->
+    newline_end(Cs, St, Line, Col, Toks, 2, "\n\r");
+scan_newline([$\f|Cs], St, Line, Col, Toks) ->
+    newline_end(Cs, St, Line, Col, Toks, 2, "\n\f");
+scan_newline([], _St, Line, Col, Toks) ->
+    {more,{[$\n],Col,Toks,Line,[],fun scan/6}};
+scan_newline(Cs, St, Line, Col, Toks) ->
+    scan_nl_white_space(Cs, St, Line, Col, Toks, "\n").
+
+scan_nl_spcs([$\s|Cs], St, Line, Col, Toks, N) when N < 17 ->
+    scan_nl_spcs(Cs, St, Line, Col, Toks, N+1);
+scan_nl_spcs([]=Cs, _St, Line, Col, Toks, N) ->
+    {more,{Cs,Col,Toks,Line,N,fun scan_nl_spcs/6}};
+scan_nl_spcs(Cs, St, Line, Col, Toks, N) ->
+    newline_end(Cs, St, Line, Col, Toks, N, nl_spcs(N)).
+
+scan_nl_tabs([$\t|Cs], St, Line, Col, Toks, N) when N < 11 ->
+    scan_nl_tabs(Cs, St, Line, Col, Toks, N+1);
+scan_nl_tabs([]=Cs, _St, Line, Col, Toks, N) ->
+    {more,{Cs,Col,Toks,Line,N,fun scan_nl_tabs/6}};
+scan_nl_tabs(Cs, St, Line, Col, Toks, N) ->
+    newline_end(Cs, St, Line, Col, Toks, N, nl_tabs(N)).
+
+%% Note: returning {more,Cont} is meaningless here; one could just as
+%% well return several tokens. But since tokens() scans up to a full
+%% stop anyway, nothing is gained by not collecting all white spaces.
+scan_nl_white_space([$\n|Cs], #erl_scan{text = false}=St, Line, no_col=Col,
+                    Toks0, Ncs) ->
+    Toks = [{white_space,Line,lists:reverse(Ncs)}|Toks0],
+    scan_newline(Cs, St, Line+1, Col, Toks);
+scan_nl_white_space([$\n|Cs], St, Line, Col, Toks, Ncs0) ->
+    Ncs = lists:reverse(Ncs0),
+    Attrs = attributes(Line, Col, St, Ncs),
+    Token = {white_space,Attrs,Ncs},
+    scan_newline(Cs, St, Line+1, new_column(Col, length(Ncs)), [Token|Toks]);
+scan_nl_white_space([C|Cs], St, Line, Col, Toks, Ncs) when ?WHITE_SPACE(C) ->
+    scan_nl_white_space(Cs, St, Line, Col, Toks, [C|Ncs]);
+scan_nl_white_space([]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_nl_white_space/6}};
+scan_nl_white_space(Cs, #erl_scan{text = false}=St, Line, no_col=Col,
+                    Toks, Ncs) ->
+    scan1(Cs, St, Line+1, Col, [{white_space,Line,lists:reverse(Ncs)}|Toks]);
+scan_nl_white_space(Cs, St, Line, Col, Toks, Ncs0) ->
+    Ncs = lists:reverse(Ncs0),
+    Attrs = attributes(Line, Col, St, Ncs),
+    Token = {white_space,Attrs,Ncs},
+    scan1(Cs, St, Line+1, new_column(Col, length(Ncs)), [Token|Toks]).
+
+newline_end(Cs, #erl_scan{text = false}=St, Line, no_col=Col,
+            Toks, _N, Ncs) ->
+    scan1(Cs, St, Line+1, Col, [{white_space,Line,Ncs}|Toks]);
+newline_end(Cs, St, Line, Col, Toks, N, Ncs) ->
+    Attrs = attributes(Line, Col, St, Ncs),
+    scan1(Cs, St, Line+1, new_column(Col, N), [{white_space,Attrs,Ncs}|Toks]).
+
+scan_spcs([$\s|Cs], St, Line, Col, Toks, N) when N < 16 ->
+    scan_spcs(Cs, St, Line, Col, Toks, N+1);
+scan_spcs([]=Cs, _St, Line, Col, Toks, N) ->
+    {more,{Cs,Col,Toks,Line,N,fun scan_spcs/6}};
+scan_spcs(Cs, St, Line, Col, Toks, N) ->
+    white_space_end(Cs, St, Line, Col, Toks, N, spcs(N)).
+
+scan_tabs([$\t|Cs], St, Line, Col, Toks, N) when N < 10 ->
+    scan_tabs(Cs, St, Line, Col, Toks, N+1);
+scan_tabs([]=Cs, _St, Line, Col, Toks, N) ->
+    {more,{Cs,Col,Toks,Line,N,fun scan_tabs/6}};
+scan_tabs(Cs, St, Line, Col, Toks, N) ->
+    white_space_end(Cs, St, Line, Col, Toks, N, tabs(N)).
+
+skip_white_space([$\n|Cs], St, Line, Col, Toks, _N) ->
+    skip_white_space(Cs, St, Line+1, new_column(Col, 1), Toks, 0);
+skip_white_space([C|Cs], St, Line, Col, Toks, N) when ?WHITE_SPACE(C) ->
+    skip_white_space(Cs, St, Line, Col, Toks, N+1);
+skip_white_space([]=Cs, _St, Line, Col, Toks, N) ->
+    {more,{Cs,Col,Toks,Line,N,fun skip_white_space/6}};
+skip_white_space(Cs, St, Line, Col, Toks, N) ->
+    scan1(Cs, St, Line, incr_column(Col, N), Toks).
+
+%% Maybe \t and \s should break the loop.
+scan_white_space([$\n|_]=Cs, St, Line, Col, Toks, Ncs) ->
+    white_space_end(Cs, St, Line, Col, Toks, length(Ncs), lists:reverse(Ncs));
+scan_white_space([C|Cs], St, Line, Col, Toks, Ncs) when ?WHITE_SPACE(C) ->
+    scan_white_space(Cs, St, Line, Col, Toks, [C|Ncs]);
+scan_white_space([]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_white_space/6}};
+scan_white_space(Cs, St, Line, Col, Toks, Ncs) ->
+    white_space_end(Cs, St, Line, Col, Toks, length(Ncs), lists:reverse(Ncs)).
+
+-compile({inline,[white_space_end/7]}).
+
+white_space_end(Cs, St, Line, Col, Toks, N, Ncs) ->
+    tok3(Cs, St, Line, Col, Toks, white_space, Ncs, Ncs, N).
+
+scan_char([$\\|Cs]=Cs0, St, Line, Col, Toks) ->
+    case scan_escape(Cs, incr_column(Col, 2)) of
+        more ->
+            {more,{[$$|Cs0],Col,Toks,Line,[],fun scan/6}};
+        {error,Ncs,Error,Ncol} ->
+            scan_error(Error, Line, Col, Line, Ncol, Ncs);
+        {eof,Ncol} ->
+            scan_error(char, Line, Col, Line, Ncol, eof);
+        {nl,Val,Str,Ncs,Ncol} ->
+            Attrs = attributes(Line, Col, St, ?STR(St, "$\\"++Str)), %"
+            Ntoks = [{char,Attrs,Val}|Toks],
+            scan1(Ncs, St, Line+1, Ncol, Ntoks);
+        {Val,Str,Ncs,Ncol} ->
+            Attrs = attributes(Line, Col, St, ?STR(St, "$\\"++Str)), %"
+            Ntoks = [{char,Attrs,Val}|Toks],
+            scan1(Ncs, St, Line, Ncol, Ntoks)
+    end;
+scan_char([$\n=C|Cs], St, Line, Col, Toks) ->
+    Attrs = attributes(Line, Col, St, ?STR(St, [$$,C])),
+    scan1(Cs, St, Line+1, new_column(Col, 1), [{char,Attrs,C}|Toks]);
+scan_char([C|Cs], St, Line, Col, Toks) when ?UNICODE(C) ->
+    Attrs = attributes(Line, Col, St, ?STR(St, [$$,C])),
+    scan1(Cs, St, Line, incr_column(Col, 2), [{char,Attrs,C}|Toks]);
+scan_char([C|_Cs], _St, Line, Col, _Toks) when ?CHAR(C) ->
+    scan_error({illegal,character}, Line, Col, Line, incr_column(Col, 1), eof);
+scan_char([], _St, Line, Col, Toks) ->
+    {more,{[$$],Col,Toks,Line,[],fun scan/6}};
+scan_char(eof, _St, Line, Col, _Toks) ->
+    scan_error(char, Line, Col, Line, incr_column(Col, 1), eof).
+
+scan_string(Cs, St, Line, Col, Toks, {Wcs,Str,Line0,Col0}) ->
+    case scan_string0(Cs, St, Line, Col, $\", Str, Wcs) of %"
+        {more,Ncs,Nline,Ncol,Nstr,Nwcs} ->
+            State = {Nwcs,Nstr,Line0,Col0},
+            {more,{Ncs,Ncol,Toks,Nline,State,fun scan_string/6}};
+        {char_error,Ncs,Error,Nline,Ncol,EndCol} ->
+            scan_error(Error, Nline, Ncol, Nline, EndCol, Ncs);
+        {error,Nline,Ncol,Nwcs,Ncs} ->
+            Estr = string:substr(Nwcs, 1, 16), % Expanded escape chars.
+            scan_error({string,$\",Estr}, Line0, Col0, Nline, Ncol, Ncs); %"
+        {Ncs,Nline,Ncol,Nstr,Nwcs} ->
+            Attrs = attributes(Line0, Col0, St, Nstr),
+            scan1(Ncs, St, Nline, Ncol, [{string,Attrs,Nwcs}|Toks])
+    end.
+
+scan_qatom(Cs, St, Line, Col, Toks, {Wcs,Str,Line0,Col0}) ->
+    case scan_string0(Cs, St, Line, Col, $\', Str, Wcs) of %'
+        {more,Ncs,Nline,Ncol,Nstr,Nwcs} ->
+            State = {Nwcs,Nstr,Line0,Col0},
+            {more,{Ncs,Ncol,Toks,Nline,State,fun scan_qatom/6}};
+        {char_error,Ncs,Error,Nline,Ncol,EndCol} ->
+            scan_error(Error, Nline, Ncol, Nline, EndCol, Ncs);
+        {error,Nline,Ncol,Nwcs,Ncs} ->
+            Estr = string:substr(Nwcs, 1, 16), % Expanded escape chars.
+            scan_error({string,$\',Estr}, Line0, Col0, Nline, Ncol, Ncs); %'
+        {Ncs,Nline,Ncol,Nstr,Nwcs} ->
+            case catch list_to_atom(Nwcs) of
+                A when is_atom(A) ->
+                    Attrs = attributes(Line0, Col0, St, Nstr),
+                    scan1(Ncs, St, Nline, Ncol, [{atom,Attrs,A}|Toks]);
+                _ ->
+                    scan_error({illegal,atom}, Line0, Col0, Nline, Ncol, Ncs)
+            end
+    end.
+
+scan_string0(Cs, #erl_scan{text=false}, Line, no_col=Col, Q, [], Wcs) ->
+    scan_string_no_col(Cs, Line, Col, Q, Wcs);
+scan_string0(Cs, #erl_scan{text=true}, Line, no_col=Col, Q, Str, Wcs) ->
+    scan_string1(Cs, Line, Col, Q, Str, Wcs);
+scan_string0(Cs, St, Line, Col, Q, [], Wcs) ->
+    scan_string_col(Cs, St, Line, Col, Q, Wcs);
+scan_string0(Cs, _St, Line, Col, Q, Str, Wcs) ->
+    scan_string1(Cs, Line, Col, Q, Str, Wcs).
+
+%% Optimization. Col =:= no_col.
+scan_string_no_col([Q|Cs], Line, Col, Q, Wcs) ->
+    {Cs,Line,Col,_DontCare=[],lists:reverse(Wcs)};
+scan_string_no_col([$\n=C|Cs], Line, Col, Q, Wcs) ->
+    scan_string_no_col(Cs, Line+1, Col, Q, [C|Wcs]);
+scan_string_no_col([C|Cs], Line, Col, Q, Wcs) when C =/= $\\, ?UNICODE(C) ->
+    scan_string_no_col(Cs, Line, Col, Q, [C|Wcs]);
+scan_string_no_col(Cs, Line, Col, Q, Wcs) ->
+    scan_string1(Cs, Line, Col, Q, Wcs, Wcs).
+
+%% Optimization. Col =/= no_col.
+scan_string_col([Q|Cs], St, Line, Col, Q, Wcs0) ->
+    Wcs = lists:reverse(Wcs0),
+    Str = ?STR(St, [Q|Wcs++[Q]]),
+    {Cs,Line,Col+1,Str,Wcs};
+scan_string_col([$\n=C|Cs], St, Line, _xCol, Q, Wcs) ->
+    scan_string_col(Cs, St, Line+1, 1, Q, [C|Wcs]);
+scan_string_col([C|Cs], St, Line, Col, Q, Wcs) when C =/= $\\, ?UNICODE(C) ->
+    scan_string_col(Cs, St, Line, Col+1, Q, [C|Wcs]);
+scan_string_col(Cs, _St, Line, Col, Q, Wcs) ->
+    scan_string1(Cs, Line, Col, Q, Wcs, Wcs).
+
+%% Note: in those cases when a 'char_error' tuple is returned below it
+%% is tempting to skip over characters up to the first Q character,
+%% but then the end location of the error tuple would not correspond
+%% to the start location of the returned Rest string. (Maybe the end
+%% location could be modified, but that too is ugly.)
+scan_string1([Q|Cs], Line, Col, Q, Str0, Wcs0) ->
+    Wcs = lists:reverse(Wcs0),
+    Str = [Q|lists:reverse(Str0, [Q])],
+    {Cs,Line,incr_column(Col, 1),Str,Wcs};
+scan_string1([$\n=C|Cs], Line, Col, Q, Str, Wcs) ->
+    Ncol = new_column(Col, 1),
+    scan_string1(Cs, Line+1, Ncol, Q, [C|Str], [C|Wcs]);
+scan_string1([$\\|Cs]=Cs0, Line, Col, Q, Str, Wcs) ->
+    case scan_escape(Cs, Col) of
+        more ->
+            {more,Cs0,Line,Col,Str,Wcs};
+        {error,Ncs,Error,Ncol} ->
+            {char_error,Ncs,Error,Line,Col,incr_column(Ncol, 1)};
+        {eof,Ncol} ->
+            {error,Line,incr_column(Ncol, 1),lists:reverse(Wcs),eof};
+        {nl,Val,ValStr,Ncs,Ncol} ->
+            Nstr = lists:reverse(ValStr, [$\\|Str]),
+            Nwcs = [Val|Wcs],
+            scan_string1(Ncs, Line+1, Ncol, Q, Nstr, Nwcs);
+        {Val,ValStr,Ncs,Ncol} ->
+            Nstr = lists:reverse(ValStr, [$\\|Str]),
+            Nwcs = [Val|Wcs],
+            scan_string1(Ncs, Line, incr_column(Ncol, 1), Q, Nstr, Nwcs)
+    end;
+scan_string1([C|Cs], Line, no_col=Col, Q, Str, Wcs) when ?UNICODE(C) ->
+    scan_string1(Cs, Line, Col, Q, [C|Str], [C|Wcs]);
+scan_string1([C|Cs], Line, Col, Q, Str, Wcs) when ?UNICODE(C) ->
+    scan_string1(Cs, Line, Col+1, Q, [C|Str], [C|Wcs]);
+scan_string1([C|Cs], Line, Col, _Q, _Str, _Wcs) when ?CHAR(C) ->
+    {char_error,Cs,{illegal,character},Line,Col,incr_column(Col, 1)};
+scan_string1([]=Cs, Line, Col, _Q, Str, Wcs) ->
+    {more,Cs,Line,Col,Str,Wcs};
+scan_string1(eof, Line, Col, _Q, _Str, Wcs) ->
+    {error,Line,Col,lists:reverse(Wcs),eof}.
+
+-define(OCT(C), C >= $0, C =< $7).
+-define(HEX(C), C >= $0 andalso C =< $9 orelse
+                C >= $A andalso C =< $F orelse
+                C >= $a andalso C =< $f).
+
+%% \<1-3> octal digits
+scan_escape([O1,O2,O3|Cs], Col) when ?OCT(O1), ?OCT(O2), ?OCT(O3) ->
+    Val = (O1*8 + O2)*8 + O3 - 73*$0,
+    {Val,[O1,O2,O3],Cs,incr_column(Col, 3)};
+scan_escape([O1,O2], _Col) when ?OCT(O1), ?OCT(O2) ->
+    more;
+scan_escape([O1,O2|Cs], Col) when ?OCT(O1), ?OCT(O2) ->
+    Val = (O1*8 + O2) - 9*$0,
+    {Val,[O1,O2],Cs,incr_column(Col, 2)};
+scan_escape([O1], _Col) when ?OCT(O1) ->
+    more;
+scan_escape([O1|Cs], Col) when ?OCT(O1) ->
+    {O1 - $0,[O1],Cs,incr_column(Col, 1)};
+%% \x{<hex digits>}
+scan_escape([$x,${|Cs], Col) ->
+    scan_hex(Cs, incr_column(Col, 2), []);
+scan_escape([$x], _Col) ->
+    more;
+scan_escape([$x|eof], Col) ->
+    {eof,incr_column(Col, 1)};
+%% \x<2> hexadecimal digits
+scan_escape([$x,H1,H2|Cs], Col) when ?HEX(H1), ?HEX(H2) ->
+    Val = erlang:list_to_integer([H1,H2], 16),
+    {Val,[$x,H1,H2],Cs,incr_column(Col, 3)};
+scan_escape([$x,H1], _Col) when ?HEX(H1) ->
+    more;
+scan_escape([$x|Cs], Col) ->
+    {error,Cs,{illegal,character},incr_column(Col, 1)};
+%% \^X -> CTL-X
+scan_escape([$^=C0,$\n=C|Cs], Col) ->
+    {nl,C,[C0,C],Cs,new_column(Col, 1)};
+scan_escape([$^=C0,C|Cs], Col) when ?CHAR(C) ->
+    Val = C band 31,
+    {Val,[C0,C],Cs,incr_column(Col, 2)};
+scan_escape([$^], _Col) ->
+    more;
+scan_escape([$^|eof], Col) ->
+    {eof,incr_column(Col, 1)};
+scan_escape([$\n=C|Cs], Col) ->
+    {nl,C,[C],Cs,new_column(Col, 1)};
+scan_escape([C0|Cs], Col) when ?UNICODE(C0) ->
+    C = escape_char(C0),
+    {C,[C0],Cs,incr_column(Col, 1)};
+scan_escape([C|Cs], Col) when ?CHAR(C) ->
+    {error,Cs,{illegal,character},incr_column(Col, 1)};
+scan_escape([], _Col) ->
+    more;
+scan_escape(eof, Col) ->
+    {eof,Col}.
+
+scan_hex([C|Cs], no_col=Col, Wcs) when ?HEX(C) ->
+    scan_hex(Cs, Col, [C|Wcs]);
+scan_hex([C|Cs], Col, Wcs) when ?HEX(C) ->
+    scan_hex(Cs, Col+1, [C|Wcs]);
+scan_hex(Cs, Col, Wcs) ->
+    scan_esc_end(Cs, Col, Wcs, 16, "x{").
+
+scan_esc_end([$}|Cs], Col, Wcs0, B, Str0) ->
+    Wcs = lists:reverse(Wcs0),
+    case catch erlang:list_to_integer(Wcs, B) of
+        Val when ?UNICODE(Val) ->
+            {Val,Str0++Wcs++[$}],Cs,incr_column(Col, 1)};
+        _ ->
+            {error,Cs,{illegal,character},incr_column(Col, 1)}
+    end;
+scan_esc_end([], _Col, _Wcs, _B, _Str0) ->
+    more;
+scan_esc_end(eof, Col, _Wcs, _B, _Str0) ->
+    {eof,Col};
+scan_esc_end(Cs, Col, _Wcs, _B, _Str0) ->
+    {error,Cs,{illegal,character},Col}.
+
+escape_char($n) -> $\n;                         % \n = LF
+escape_char($r) -> $\r;                         % \r = CR
+escape_char($t) -> $\t;                         % \t = TAB
+escape_char($v) -> $\v;                         % \v = VT
+escape_char($b) -> $\b;                         % \b = BS
+escape_char($f) -> $\f;                         % \f = FF
+escape_char($e) -> $\e;                         % \e = ESC
+escape_char($s) -> $\s;                         % \s = SPC
+escape_char($d) -> $\d;                         % \d = DEL
+escape_char(C) -> C.
+
+scan_number([C|Cs], St, Line, Col, Toks, Ncs) when ?DIGIT(C) ->
+    scan_number(Cs, St, Line, Col, Toks, [C|Ncs]);
+scan_number([$.,C|Cs], St, Line, Col, Toks, Ncs) when ?DIGIT(C) ->
+    scan_fraction(Cs, St, Line, Col, Toks, [C,$.|Ncs]);
+scan_number([$.]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_number/6}};
+scan_number([$#|Cs]=Cs0, St, Line, Col, Toks, Ncs0) ->
+    Ncs = lists:reverse(Ncs0),
+    case catch list_to_integer(Ncs) of
+        B when B >= 2, B =< 1+$Z-$A+10 ->
+            Bcs = ?STR(St, Ncs++[$#]),
+            scan_based_int(Cs, St, Line, Col, Toks, {B,[],Bcs});
+        B ->
+            Len = length(Ncs),
+            scan_error({base,B}, Line, Col, Line, incr_column(Col, Len), Cs0)
+    end;
+scan_number([]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_number/6}};
+scan_number(Cs, St, Line, Col, Toks, Ncs0) ->
+    Ncs = lists:reverse(Ncs0),
+    case catch list_to_integer(Ncs) of
+        N when is_integer(N) ->
+            tok3(Cs, St, Line, Col, Toks, integer, Ncs, N);
+        _ ->
+            Ncol = incr_column(Col, length(Ncs)),
+            scan_error({illegal,integer}, Line, Col, Line, Ncol, Cs)
+    end.
+
+scan_based_int([C|Cs], St, Line, Col, Toks, {B,Ncs,Bcs})
+    when ?DIGIT(C), C < $0+B ->
+    scan_based_int(Cs, St, Line, Col, Toks, {B,[C|Ncs],Bcs});
+scan_based_int([C|Cs], St, Line, Col, Toks, {B,Ncs,Bcs})
+    when C >= $A, B > 10, C < $A+B-10 ->
+    scan_based_int(Cs, St, Line, Col, Toks, {B,[C|Ncs],Bcs});
+scan_based_int([C|Cs], St, Line, Col, Toks, {B,Ncs,Bcs})
+    when C >= $a, B > 10, C < $a+B-10 ->
+    scan_based_int(Cs, St, Line, Col, Toks, {B,[C|Ncs],Bcs});
+scan_based_int([]=Cs, _St, Line, Col, Toks, State) ->
+    {more,{Cs,Col,Toks,Line,State,fun scan_based_int/6}};
+scan_based_int(Cs, St, Line, Col, Toks, {B,Ncs0,Bcs}) ->
+    Ncs = lists:reverse(Ncs0),
+    case catch erlang:list_to_integer(Ncs, B) of
+        N when is_integer(N) ->
+            tok3(Cs, St, Line, Col, Toks, integer, ?STR(St, Bcs++Ncs), N);
+        _ ->
+            Len = length(Bcs)+length(Ncs),
+            Ncol = incr_column(Col, Len),
+            scan_error({illegal,integer}, Line, Col, Line, Ncol, Cs)
+    end.
+
+scan_fraction([C|Cs], St, Line, Col, Toks, Ncs) when ?DIGIT(C) ->
+    scan_fraction(Cs, St, Line, Col, Toks, [C|Ncs]);
+scan_fraction([E|Cs], St, Line, Col, Toks, Ncs) when E =:= $e; E =:= $E ->
+    scan_exponent_sign(Cs, St, Line, Col, Toks, [E|Ncs]);
+scan_fraction([]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_fraction/6}};
+scan_fraction(Cs, St, Line, Col, Toks, Ncs) ->
+    float_end(Cs, St, Line, Col, Toks, Ncs).
+
+scan_exponent_sign([C|Cs], St, Line, Col, Toks, Ncs) when C =:= $+; C =:= $- ->
+    scan_exponent(Cs, St, Line, Col, Toks, [C|Ncs]);
+scan_exponent_sign([]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_exponent_sign/6}};
+scan_exponent_sign(Cs, St, Line, Col, Toks, Ncs) ->
+    scan_exponent(Cs, St, Line, Col, Toks, Ncs).
+
+scan_exponent([C|Cs], St, Line, Col, Toks, Ncs) when ?DIGIT(C) ->
+    scan_exponent(Cs, St, Line, Col, Toks, [C|Ncs]);
+scan_exponent([]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_exponent/6}};
+scan_exponent(Cs, St, Line, Col, Toks, Ncs) ->
+    float_end(Cs, St, Line, Col, Toks, Ncs).
+
+float_end(Cs, St, Line, Col, Toks, Ncs0) ->
+    Ncs = lists:reverse(Ncs0),
+    case catch list_to_float(Ncs) of
+        F when is_float(F) ->
+            tok3(Cs, St, Line, Col, Toks, float, Ncs, F);
+        _ ->
+            Ncol = incr_column(Col, length(Ncs)),
+            scan_error({illegal,float}, Line, Col, Line, Ncol, Cs)
+    end.
+
+skip_comment([C|Cs], St, Line, Col, Toks, N) when C =/= $\n, ?CHAR(C) ->
+    case ?UNICODE(C) of
+        true ->
+            skip_comment(Cs, St, Line, Col, Toks, N+1);
+        false ->
+            Ncol = incr_column(Col, N+1),
+            scan_error({illegal,character}, Line, Col, Line, Ncol, Cs)
+    end;
+skip_comment([]=Cs, _St, Line, Col, Toks, N) ->
+    {more,{Cs,Col,Toks,Line,N,fun skip_comment/6}};
+skip_comment(Cs, St, Line, Col, Toks, N) ->
+    scan1(Cs, St, Line, incr_column(Col, N), Toks).
+
+scan_comment([C|Cs], St, Line, Col, Toks, Ncs) when C =/= $\n, ?CHAR(C) ->
+    case ?UNICODE(C) of
+        true ->
+            scan_comment(Cs, St, Line, Col, Toks, [C|Ncs]);
+        false ->
+            Ncol = incr_column(Col, length(Ncs)+1),
+            scan_error({illegal,character}, Line, Col, Line, Ncol, Cs)
+    end;
+scan_comment([]=Cs, _St, Line, Col, Toks, Ncs) ->
+    {more,{Cs,Col,Toks,Line,Ncs,fun scan_comment/6}};
+scan_comment(Cs, St, Line, Col, Toks, Ncs0) ->
+    Ncs = lists:reverse(Ncs0),
+    tok3(Cs, St, Line, Col, Toks, comment, Ncs, Ncs).
+
+tok2(Cs, #erl_scan{text = false}=St, Line, no_col=Col, Toks, _Wcs, P) ->
+    scan1(Cs, St, Line, Col, [{P,Line}|Toks]);
+tok2(Cs, St, Line, Col, Toks, Wcs, P) ->
+    Attrs = attributes(Line, Col, St, Wcs),
+    scan1(Cs, St, Line, incr_column(Col, length(Wcs)), [{P,Attrs}|Toks]).
+
+tok2(Cs, #erl_scan{text = false}=St, Line, no_col=Col, Toks, _Wcs, P, _N) ->
+    scan1(Cs, St, Line, Col, [{P,Line}|Toks]);
+tok2(Cs, St, Line, Col, Toks, Wcs, P, N) ->
+    Attrs = attributes(Line, Col, St, Wcs),
+    scan1(Cs, St, Line, incr_column(Col, N), [{P,Attrs}|Toks]).
+
+tok3(Cs, #erl_scan{text = false}=St, Line, no_col=Col, Toks, Item, _S, Sym) ->
+    scan1(Cs, St, Line, Col, [{Item,Line,Sym}|Toks]);
+tok3(Cs, St, Line, Col, Toks, Item, String, Sym) ->
+    Token = {Item,attributes(Line, Col, St, String),Sym},
+    scan1(Cs, St, Line, incr_column(Col, length(String)), [Token|Toks]).
+
+tok3(Cs, #erl_scan{text = false}=St, Line, no_col=Col, Toks, Item,
+     _String, Sym, _Length) ->
+    scan1(Cs, St, Line, Col, [{Item,Line,Sym}|Toks]);
+tok3(Cs, St, Line, Col, Toks, Item, String, Sym, Length) ->
+    Token = {Item,attributes(Line, Col, St, String),Sym},
+    scan1(Cs, St, Line, incr_column(Col, Length), [Token|Toks]).
+
+scan_error(Error, Line, Col, EndLine, EndCol, Rest) ->
+    Loc = location(Line, Col),
+    EndLoc = location(EndLine, EndCol),
+    scan_error(Error, Loc, EndLoc, Rest).
+
+scan_error(Error, ErrorLoc, EndLoc, Rest) ->
+    {{error,{ErrorLoc,?MODULE,Error},EndLoc},Rest}.
+
+-compile({inline,[attributes/4]}).
+
+attributes(Line, no_col, #erl_scan{text = false}, _String) ->
+    Line;
+attributes(Line, no_col, #erl_scan{text = true}, String) ->
+    [{line,Line},{text,String}];
+attributes(Line, Col, #erl_scan{text = false}, _String) ->
+    {Line,Col};
+attributes(Line, Col, #erl_scan{text = true}, String) ->
+    [{line,Line},{column,Col},{text,String}].
+
+location(Line, no_col) ->
+    Line;
+location(Line, Col) when is_integer(Col) ->
+    {Line,Col}.
+
+-compile({inline,[incr_column/2,new_column/2]}).
+
+incr_column(no_col=Col, _N) ->
+    Col;
+incr_column(Col, N) when is_integer(Col) ->
+    Col + N.
+
+new_column(no_col=Col, _Ncol) ->
+    Col;
+new_column(Col, Ncol) when is_integer(Col) ->
+    Ncol.
+
+nl_spcs(2)  -> "\n ";
+nl_spcs(3)  -> "\n  ";
+nl_spcs(4)  -> "\n   ";
+nl_spcs(5)  -> "\n    ";
+nl_spcs(6)  -> "\n     ";
+nl_spcs(7)  -> "\n      ";
+nl_spcs(8)  -> "\n       ";
+nl_spcs(9)  -> "\n        ";
+nl_spcs(10) -> "\n         ";
+nl_spcs(11) -> "\n          ";
+nl_spcs(12) -> "\n           ";
+nl_spcs(13) -> "\n            ";
+nl_spcs(14) -> "\n             ";
+nl_spcs(15) -> "\n              ";
+nl_spcs(16) -> "\n               ";
+nl_spcs(17) -> "\n                ".
+
+spcs(1)  -> " ";
+spcs(2)  -> "  ";
+spcs(3)  -> "   ";
+spcs(4)  -> "    ";
+spcs(5)  -> "     ";
+spcs(6)  -> "      ";
+spcs(7)  -> "       ";
+spcs(8)  -> "        ";
+spcs(9)  -> "         ";
+spcs(10) -> "          ";
+spcs(11) -> "           ";
+spcs(12) -> "            ";
+spcs(13) -> "             ";
+spcs(14) -> "              ";
+spcs(15) -> "               ";
+spcs(16) -> "                ".
+
+nl_tabs(2)  -> "\n\t";
+nl_tabs(3)  -> "\n\t\t";
+nl_tabs(4)  -> "\n\t\t\t";
+nl_tabs(5)  -> "\n\t\t\t\t";
+nl_tabs(6)  -> "\n\t\t\t\t\t";
+nl_tabs(7)  -> "\n\t\t\t\t\t\t";
+nl_tabs(8)  -> "\n\t\t\t\t\t\t\t";
+nl_tabs(9)  -> "\n\t\t\t\t\t\t\t\t";
+nl_tabs(10) -> "\n\t\t\t\t\t\t\t\t\t";
+nl_tabs(11) -> "\n\t\t\t\t\t\t\t\t\t\t".
+
+tabs(1)  ->  "\t";
+tabs(2)  ->  "\t\t";
+tabs(3)  ->  "\t\t\t";
+tabs(4)  ->  "\t\t\t\t";
+tabs(5)  ->  "\t\t\t\t\t";
+tabs(6)  ->  "\t\t\t\t\t\t";
+tabs(7)  ->  "\t\t\t\t\t\t\t";
+tabs(8)  ->  "\t\t\t\t\t\t\t\t";
+tabs(9)  ->  "\t\t\t\t\t\t\t\t\t";
+tabs(10) ->  "\t\t\t\t\t\t\t\t\t\t".
+
+-spec reserved_word(Atom :: atom()) -> boolean().
+reserved_word('after') -> true;
+reserved_word('begin') -> true;
+reserved_word('case') -> true;
+reserved_word('try') -> true;
+reserved_word('cond') -> true;
+reserved_word('catch') -> true;
+reserved_word('andalso') -> true;
+reserved_word('orelse') -> true;
+reserved_word('end') -> true;
+reserved_word('fun') -> true;
+reserved_word('if') -> true;
+reserved_word('let') -> true;
+reserved_word('of') -> true;
+reserved_word('receive') -> true;
+reserved_word('when') -> true;
+reserved_word('bnot') -> true;
+reserved_word('not') -> true;
+reserved_word('div') -> true;
+reserved_word('rem') -> true;
+reserved_word('band') -> true;
+reserved_word('and') -> true;
+reserved_word('bor') -> true;
+reserved_word('bxor') -> true;
+reserved_word('bsl') -> true;
+reserved_word('bsr') -> true;
+reserved_word('or') -> true;
+reserved_word('xor') -> true;
+reserved_word(_) -> false.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/opaque/opaque_adt.erl b/lib/dialyzer/test/opaque_SUITE_data/src/opaque/opaque_adt.erl
index 3456f0e9c6..cdcaa5f9e8 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/src/opaque/opaque_adt.erl
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/opaque/opaque_adt.erl
@@ -3,6 +3,8 @@
 
 -opaque abc() :: 'a' | 'b' | 'c'.
 
+-spec atom_or_list(_) -> abc() | list().
+
 atom_or_list(1) -> a;
 atom_or_list(2) -> b;
 atom_or_list(3) -> c;
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/exact_adt.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/exact_adt.erl
new file mode 100644
index 0000000000..7103847ae7
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/exact_adt.erl
@@ -0,0 +1,17 @@
+-module(exact_adt).
+
+-export([exact_adt_set_type/1, exact_adt_set_type2/1]).
+
+-export_type([exact_adt/0]).
+
+-record(exact_adt, {}).
+
+-opaque exact_adt() :: #exact_adt{}.
+
+-spec exact_adt_set_type(_) -> exact_adt().
+
+exact_adt_set_type(G) -> G.
+
+-spec exact_adt_set_type2(exact_adt()) -> exact_adt().
+
+exact_adt_set_type2(G) -> G.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/exact_api.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/exact_api.erl
new file mode 100644
index 0000000000..5f7ab4f3aa
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/exact_api.erl
@@ -0,0 +1,60 @@
+-module(exact_api).
+
+-export([new/0, exact_api_test/1, exact_api_new/1,
+         exact_adt_test/1, exact_adt_new/1]).
+
+-export_type([exact_api/0]).
+
+-record(digraph, {vtab = notable :: ets:tab(),
+		  etab = notable :: ets:tab(),
+		  ntab = notable :: ets:tab(),
+	          cyclic = true  :: boolean()}).
+
+-spec new() -> digraph().
+
+new() ->
+    A = #digraph{},
+    set_type(A), % does not have an opaque term as 1st argument
+    A.
+
+-spec set_type(digraph()) -> true.
+
+set_type(G) ->
+    digraph:delete(G).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%% The derived spec of exact_api_new() is
+%%% -spec exact_api_new(exact_api:exact_api()) -> exact_api:exact_api().
+%%% This won't happen unless dialyzer_typesig uses
+%%% t_is_exactly_equal() rather than t_is_equal().
+%%% [As of R17B the latter considers two types equal if nothing but
+%%%  their ?opaque tags differ.]
+
+-record(exact_api, {}).
+
+-opaque exact_api() :: #exact_api{}.
+
+exact_api_test(X) ->
+    #exact_api{} = exact_api_set_type(X). % OK
+
+exact_api_new(A) ->
+    A = #exact_api{},
+    _ = exact_api_set_type(A), % OK (the opaque type is local)
+    A.
+
+-spec exact_api_set_type(exact_api()) -> exact_api().
+
+exact_api_set_type(#exact_api{}=E) -> E.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+-record(exact_adt, {}).
+
+exact_adt_test(X) ->
+    #exact_adt{} = exact_adt:exact_adt_set_type(X). % breaks the opaqueness
+
+exact_adt_new(A) ->
+    A = #exact_adt{},
+    _ = exact_adt:exact_adt_set_type2(A), % does not have an opaque term as 1st argument
+    A.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/is_rec.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/is_rec.erl
new file mode 100644
index 0000000000..2b157483bc
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/is_rec.erl
@@ -0,0 +1,65 @@
+-module(is_rec).
+
+-export([ri1/0, ri11/0, ri13/0, ri14/0, ri2/0, ri3/0, ri4/0, ri5/0,
+         ri6/0, ri7/0, ri8/0]).
+
+-record(r, {f1 :: integer()}).
+
+ri1() ->
+    A = simple1_adt:d1(),
+    is_record(A, r). % opaque term 1
+
+ri11() ->
+    A = simple1_adt:d1(),
+    I = '1-3'(),
+    is_record(A, r, I). % opaque term 1
+
+ri13() ->
+    A = simple1_adt:d1(),
+    if is_record(A, r) -> true end. % breaks the opaqueness
+
+ri14() ->
+    A = simple1_adt:d1(),
+    if is_record({A, 1}, r) -> true end. % breaks the opaqueness
+
+-type '1-3-t'() :: 1..3.
+
+-spec '1-3'() -> '1-3-t'().
+
+'1-3'() ->
+    random:uniform(3).
+
+
+-spec 'Atom'() -> atom().
+
+'Atom'() ->
+    a.
+
+ri2() ->
+    A = simple1_adt:d1(),
+    R = 'Atom'(),
+    is_record(A, R). % opaque term 1
+
+ri3() ->
+    A = simple1_adt:d1(),
+    is_record(A, A, 1). % opaque term 2
+
+ri4() ->
+    A = simple1_adt:d1(),
+    is_record(A, hipp:hopp(), 1). % opaque term 1
+
+ri5() ->
+    A = simple1_adt:d1(),
+    is_record(A, A, hipp:hopp()). % opaque term 2
+
+ri6() ->
+    A = simple1_adt:d1(),
+    if is_record(A, r) -> true end. % breaks opaqueness
+
+ri7() ->
+    A = simple1_adt:d1(),
+    if is_record({r, A}, r) -> true end. % A violates #r{}
+
+ri8() ->
+    A = simple1_adt:d1(),
+    is_record({A, 1}, r). % opaque term 1
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/rec_adt.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/rec_adt.erl
new file mode 100644
index 0000000000..ff80d6e99b
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/rec_adt.erl
@@ -0,0 +1,28 @@
+-module(rec_adt).
+
+-export([f/0, r1/0]).
+
+-export_type([r1/0]).
+
+-export_type([f/0, op_t/0, a/0]).
+
+-opaque a() :: a | b.
+
+-record(r1,
+        {f1 :: a()}).
+
+-opaque r1() :: #r1{}.
+
+-opaque f() :: fun((_) -> _).
+
+-opaque op_t() :: integer().
+
+-spec f() -> f().
+
+f() ->
+    fun(_) -> 3 end.
+
+-spec r1() -> r1().
+
+r1() ->
+    #r1{f1 = a}.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/rec_api.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/rec_api.erl
new file mode 100644
index 0000000000..d9b1d59f0c
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/rec_api.erl
@@ -0,0 +1,77 @@
+-module(rec_api).
+
+-export([t1/0, t2/0, adt_t1/0, adt_t1/1, adt_r1/0,
+         t/1, t_adt/0, r/0, r_adt/0]).
+
+-export_type([{a,0},{r1,0}]).
+
+-export_type([f/0, op_t/0, r/0, tup/0]).
+
+-opaque a() :: a | b.
+
+-record(r1,
+        {f1 :: a()}).
+
+-opaque r1() :: #r1{}.
+
+t1() ->
+    A = #r1{f1 = a},
+    {r1, a} = A.
+
+t2() ->
+    A = {r1, 10}, % violates the type of #r1{}
+    {r1, 10} = A. % violates the type of #r1{}
+
+adt_t1() ->
+    R = rec_adt:r1(),
+    {r1, a} = R. % breaks the opaqueness
+
+-spec adt_t1(rec_adt:r1()) -> rec_adt:r1(). % invalid type spec
+
+adt_t1(R) ->
+    {r1, a} = R.
+
+-spec adt_r1() -> rec_adt:r1(). % invalid type spec
+
+adt_r1() ->
+    #r1{f1 = a}.
+
+-opaque f() :: fun((_) -> _).
+
+-opaque op_t() :: integer().
+
+-spec t(f()) -> _.
+
+t(A) ->
+    T = term(),
+    %% 3(T), % cannot test this: dialyzer_dep deliberately crashes
+    A(T).
+
+-spec term() -> op_t().
+
+term() ->
+    3.
+
+t_adt() ->
+    A = rec_adt:f(),
+    T = term(),
+    A(T).
+
+-record(r, {f = fun(_) -> 3 end :: f(), o = 1 :: op_t()}).
+
+-opaque r() :: #r{}.
+
+-opaque tup() :: {'r', f(), op_t()}.
+
+-spec r() -> _.
+
+r() ->
+    {r, f(), 2}. % OK, f() is a local opaque type
+
+-spec f() -> f().
+
+f() ->
+    fun(_) -> 3 end.
+
+r_adt() ->
+    {r, rec_adt:f(), 2}. % breaks the opaqueness
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_adt.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_adt.erl
new file mode 100644
index 0000000000..21a277c1e9
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_adt.erl
@@ -0,0 +1,138 @@
+-module(simple1_adt).
+
+-export([d1/0, d2/0, i/0, n1/0, n2/0, o1/0, o2/0,
+         c1/0, c2/0, bit1/0, a/0, i1/0, tuple/0,
+         b1/0, b2/0, ty_i1/0]).
+
+-export_type([o1/0, o2/0, d1/0, d2/0]).
+
+-export_type([i1/0, i2/0, di1/0, di2/0]).
+
+-export_type([ty_i1/0, c1/0, c2/0]).
+
+-export_type([b1/0, b2/0]).
+
+-export_type([bit1/0]).
+
+-export_type([tuple1/0, a/0, i/0]).
+
+%% Equal:
+
+-opaque o1() :: a | b | c.
+
+-opaque o2() :: a | b | c.
+
+%% Disjoint:
+
+-opaque d1() :: a | b | c.
+
+-opaque d2() :: d | e | f.
+
+%% One common element:
+
+-opaque c1() :: a | b | c.
+
+-opaque c2() :: c | e | f.
+
+%% Equal integer range:
+
+-opaque i1() :: 1 | 2.
+
+-opaque i2() :: 1 | 2.
+
+%% Disjoint integer range:
+
+-opaque di1() :: 1 | 2.
+
+-opaque di2() :: 3 | 4.
+
+
+-type ty_i1() :: 1 | 2.
+
+%% Boolean types
+
+-opaque b1() :: boolean().
+
+-opaque b2() :: boolean().
+
+%% Binary types
+
+-opaque bit1() :: binary().
+
+%% Tuple types
+
+-opaque tuple1() :: tuple().
+
+%% Atom type
+
+-opaque a() :: atom().
+
+-opaque i() :: integer().
+
+-spec d1() -> d1().
+
+d1() -> a.
+
+-spec d2() -> d2().
+
+d2() -> d.
+
+-spec i() -> i().
+
+i() ->
+    1.
+
+-spec n1() -> o1().
+
+n1() -> a.
+
+-spec n2() -> o2().
+
+n2() -> a.
+
+-spec o1() -> o1().
+
+o1() -> a.
+
+-spec o2() -> o2().
+
+o2() -> a.
+
+-spec c1() -> c1().
+
+c1() -> a.
+
+-spec c2() -> c2().
+
+c2() -> e.
+
+-spec bit1() -> bit1().
+
+bit1() ->
+    <<"hej">>.
+
+-spec a() -> a().
+
+a() ->
+    e.
+
+-spec i1() -> i1().
+
+i1() -> 1.
+
+-spec tuple() -> tuple1().
+
+tuple() -> {1,2}.
+
+-spec b1() -> b1().
+
+b1() -> true.
+
+-spec b2() -> b2().
+
+b2() -> false.
+
+-spec ty_i1() -> ty_i1().
+
+ty_i1() ->
+    1.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_api.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_api.erl
new file mode 100644
index 0000000000..5135eb8e59
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_api.erl
@@ -0,0 +1,571 @@
+-module(simple1_api).
+
+-export([t1/1, adt_t1/1, t2/1, adt_t2/1, tup/0, t3/0, t4/0, t5/0, t6/0, t7/0,
+         t8/0, adt_t3/0, adt_t4/0, adt_t7/0, adt_t8/0, adt_t5/0,
+         c1/2, c2/2, c2/0, c3/0, c4/0, tt1/0, tt2/0,
+         cmp1/0, cmp2/0, cmp3/0, cmp4/0,
+         ty_cmp1/0, ty_cmp2/0, ty_cmp3/0, ty_cmp4/0,
+         f1/0, f2/0, adt_f1/0, adt_f2/0, f3/0, f4/0, adt_f3/0, adt_f4/0,
+         adt_f4_a/0, adt_f4_b/0,
+         bool_t1/0, bool_t2/0, bool_t3/0, bool_t4/0, bool_t5/1, bool_t6/1,
+         bool_t7/0, bool_adt_t1/0, bool_adt_t2/0, bool_adt_t5/1,
+         bool_adt_t6/1, bool_t8/0, bool_adt_t8/2, bool_t9/0, bool_adt_t9/2,
+         bit_t1/0, bit_adt_t1/0, bit_t3/1, bit_adt_t2/0, bit_adt_t3/1,
+         bit_t5/1, bit_t4/1, bit_adt_t4/1, bit_t5/0, bit_adt_t5/0,
+         call_f/1, call_f_adt/1, call_m_adt/1, call_m/1, call_f_i/1,
+         call_m_i/1, call_m_adt_i/1, call_f_adt_i/1,
+         eq1/0, eq2/0, c5/0, c6/2, c7/2, c8/0]).
+
+%%% Equal opaque types
+
+-export_type([o1/0, o2/0]).
+
+-export_type([d1/0, d2/0]).
+
+-opaque o1() :: a | b | c.
+
+-opaque o2() :: a | b | c.
+
+-export_type([i1/0, i2/0, di1/0, di2/0]).
+
+-export_type([b1/0, b2/0]).
+
+-export_type([bit1/0]).
+
+-export_type([a/0, i/0]).
+
+%% The derived spec is
+%%  -spec t1('a' | 'b') -> simple1_api:o1('a') | simple1_api:o2('a').
+%% but that is not tested...
+
+t1(a) ->
+    o1();
+t1(b) ->
+    o2().
+
+-spec o1() -> o1().
+
+o1() -> a.
+
+-spec o2() -> o2().
+
+o2() -> a.
+
+%% The derived spec is
+%% -spec adt_t1('a' | 'b') -> simple1_adt:o1('a') | simple1_adt:o2('a').
+%% but that is not tested...
+
+adt_t1(a) ->
+    simple1_adt:o1();
+adt_t1(b) ->
+    simple1_adt:o2().
+
+%%% Disjunct opaque types
+
+-opaque d1() :: a | b | c.
+
+-opaque d2() :: d | e | f.
+
+%% -spec t2('a' | 'b') -> simple1_api:d1('a') | simple1_api:d2('d').
+
+t2(a) ->
+    d1();
+t2(b) ->
+    d2().
+
+-spec d1() -> d1().
+
+d1() -> a.
+
+-spec d2() -> d2().
+
+d2() -> d.
+
+%% -spec adt_t2('a' | 'b') -> simple1_adt:d1('a') | simple1_adt:d2('d').
+
+adt_t2(a) ->
+    simple1_adt:d1();
+adt_t2(b) ->
+    simple1_adt:d2().
+
+-spec tup() -> simple1_adt:tuple1(). % invalid type spec
+
+tup() ->
+    {a, b}.
+
+%%% Matching equal opaque types with different names
+
+t3() ->
+    A = n1(),
+    B = n2(),
+    A = A, % OK, of course
+    A = B. % OK since o1() and o2() are local opaque types
+
+t4() ->
+    A = n1(),
+    B = n2(),
+    true = A =:= A, % OK, of course
+    A =:= B. % OK since o1() and o2() are local opaque types
+
+t5() ->
+    A = d1(),
+    B = d2(),
+    A =:= B. % can never evaluate to true
+
+t6() ->
+    A = d1(),
+    B = d2(),
+    A = B. % can never succeed
+
+t7() ->
+    A = d1(),
+    B = d2(),
+    A =/= B. % OK (always true?)
+
+t8() ->
+    A = d1(),
+    B = d2(),
+    A /= B. % OK (always true?)
+
+-spec n1() -> o1().
+
+n1() -> a.
+
+-spec n2() -> o2().
+
+n2() -> a.
+
+adt_t3() ->
+    A = simple1_adt:n1(),
+    B = simple1_adt:n2(),
+    true = A =:= A, % OK.
+    A =:= B. % opaque test, not OK
+
+adt_t4() ->
+    A = simple1_adt:n1(),
+    B = simple1_adt:n2(),
+    A = A, % OK
+    A = B. % opaque term
+
+adt_t7() ->
+    A = simple1_adt:n1(),
+    B = simple1_adt:n2(),
+    false = A =/= A, % OK
+    A =/= B. % opaque test, not OK
+
+adt_t8() ->
+    A = simple1_adt:n1(),
+    B = simple1_adt:n2(),
+    false = A /= A, % OK
+    A /= B. % opaque test, not OK
+
+adt_t5() ->
+    A = simple1_adt:c1(),
+    B = simple1_adt:c2(),
+    A =:= B. % opaque test, not OK
+
+%% Comparison in guard
+
+-spec c1(simple1_adt:d1(), simple1_adt:d2()) -> boolean().
+
+c1(A, B) when A =< B -> true. % succ type of A and B is any() (type spec is OK)
+
+-spec c2(simple1_adt:d1(), simple1_adt:d2()) -> boolean().
+
+c2(A, B) ->
+    if A =< B -> true end. % succ type of A and B is any() (type spec is OK)
+
+c2() ->
+    A = simple1_adt:d1(),
+    B = simple1_adt:d2(),
+    if A =< B -> ok end. % opaque term
+
+c3() ->
+    B = simple1_adt:d2(),
+    if a =< B -> ok end. % opaque term
+
+c4() ->
+    A = simple1_adt:d1(),
+    if A =< d -> ok end. % opaque term
+
+tt1() ->
+    A = o1(),
+    is_integer(A). % OK
+
+tt2() ->
+    A = simple1_adt:d1(),
+    is_integer(A). % breaks the opaqueness
+
+%% Comparison with integers
+
+-opaque i1() :: 1 | 2.
+
+-opaque i2() :: 1 | 2.
+
+-opaque di1() :: 1 | 2.
+
+-opaque di2() :: 3 | 4.
+
+-spec i1() -> i1().
+
+i1() -> 1.
+
+-type ty_i1() :: 1 | 2.
+
+-spec ty_i1() -> ty_i1().
+
+ty_i1() -> 1.
+
+cmp1() ->
+    A = i1(),
+    if A > 3 -> ok end. % can never succeed
+
+cmp2() ->
+    A = simple1_adt:i1(),
+    if A > 3 -> ok end. % opaque term
+
+cmp3() ->
+    A = i1(),
+    if A < 3 -> ok end.
+
+cmp4() ->
+    A = simple1_adt:i1(),
+    if A < 3 -> ok end. % opaque term
+
+%% -type
+
+ty_cmp1() ->
+    A = ty_i1(),
+    if A > 3 -> ok end. % can never succeed
+
+ty_cmp2() ->
+    A = simple1_adt:ty_i1(),
+    if A > 3 -> ok end. % can never succeed
+
+ty_cmp3() ->
+    A = ty_i1(),
+    if A < 3 -> ok end.
+
+ty_cmp4() ->
+    A = simple1_adt:ty_i1(),
+    if A < 3 -> ok end.
+
+%% is_function
+
+f1() ->
+    T = n1(),
+    if is_function(T) -> ok end. % can never succeed
+
+f2() ->
+    T = n1(),
+    is_function(T). % ok
+
+adt_f1() ->
+    T = simple1_adt:n1(),
+    if is_function(T) -> ok end. % breaks the opaqueness
+
+adt_f2() ->
+    T = simple1_adt:n1(),
+    is_function(T). % breaks the opaqueness
+
+f3() ->
+    A = i1(),
+    T = n1(),
+    if is_function(T, A) -> ok end. % can never succeed
+
+f4() ->
+    A = i1(),
+    T = n1(),
+    is_function(T, A). % ok
+
+adt_f3() ->
+    A = simple1_adt:i1(),
+    T = simple1_adt:n1(),
+    if is_function(T, A) -> ok end. % breaks the opaqueness
+
+adt_f4() ->
+    A = simple1_adt:i1(),
+    T = simple1_adt:n1(),
+    is_function(T, A). % breaks the opaqueness
+
+adt_f4_a() ->
+    A = simple1_adt:i1(),
+    T = n1(),
+    is_function(T, A). % opaque term
+
+
+adt_f4_b() ->
+    A = i1(),
+    T = simple1_adt:n1(),
+    is_function(T, A). % breaks the opaqueness
+
+%% A few Boolean examples
+
+bool_t1() ->
+    B = b2(),
+    if B -> ok end. % B =:= true can never succeed
+
+bool_t2() ->
+    A = b1(),
+    B = b2(),
+    if A and not B -> ok end.
+
+bool_t3() ->
+    A = b1(),
+    if not A -> ok end. % can never succeed
+
+bool_t4() ->
+    A = n1(),
+    if not ((A >= 1) and not (A < 1)) -> ok end. % can never succeed
+
+-spec bool_t5(i1()) -> integer().
+
+bool_t5(A) ->
+    if [not (A > 1)] =:=
+       [false]-> 1 end.
+
+-spec bool_t6(b1()) -> integer().
+
+bool_t6(A) ->
+    if [not A] =:=
+       [false]-> 1 end.
+
+-spec bool_t7() -> integer().
+
+bool_t7() ->
+    A = i1(),
+    if [not A] =:= % cannot succeed
+       [false]-> 1 end.
+
+bool_adt_t1() ->
+    B = simple1_adt:b2(),
+    if B -> ok end. % opaque term
+
+bool_adt_t2() ->
+    A = simple1_adt:b1(),
+    B = simple1_adt:b2(),
+    if A and not B -> ok end. % opaque term
+
+-spec bool_adt_t5(simple1_adt:i1()) -> integer().
+
+bool_adt_t5(A) ->
+    if [not (A > 1)] =:= % succ type of A is any() (type spec is OK)
+       [false]-> 1 end.
+
+-spec bool_adt_t6(simple1_adt:b1()) -> integer(). % invalid type spec
+
+bool_adt_t6(A) ->
+    if [not A] =:= % succ type of A is 'true'
+       [false]-> 1 end.
+
+-spec bool_t8() -> integer().
+
+bool_t8() ->
+    A = i1(),
+    if [A and A] =:= % cannot succeed
+       [false]-> 1 end.
+
+-spec bool_adt_t8(simple1_adt:b1(), simple1_adt:b2()) -> integer(). % invalid
+
+bool_adt_t8(A, B) ->
+    if [A and B] =:=
+       [false]-> 1 end.
+
+-spec bool_t9() -> integer().
+
+bool_t9() ->
+    A = i1(),
+    if [A or A] =:= % cannot succeed
+       [false]-> 1 end.
+
+-spec bool_adt_t9(simple1_adt:b1(), simple1_adt:b2()) -> integer(). % invalid
+
+bool_adt_t9(A, B) ->
+    if [A or B] =:=
+       [false]-> 1 end.
+
+-opaque b1() :: boolean().
+
+-opaque b2() :: boolean().
+
+-spec b1() -> b1().
+
+b1() -> true.
+
+-spec b2() -> b2().
+
+b2() -> false.
+
+%% Few (very few...) examples with bit syntax
+
+bit_t1() ->
+    A = i1(),
+    <<100:(A)>>.
+
+bit_adt_t1() ->
+    A = simple1_adt:i1(),
+    <<100:(A)>>. % breaks the opaqueness
+
+bit_t3(A) ->
+    B = i1(),
+    case none:none() of
+        <<A:B>> -> 1
+    end.
+
+bit_adt_t2() ->
+    A = simple1_adt:i1(),
+    case <<"hej">> of
+        <<_:A>> -> ok % breaks the opaqueness (but the message is strange)
+    end.
+
+
+bit_adt_t3(A) ->
+    B = simple1_adt:i1(),
+    case none:none() of
+        <<A:  % breaks the opaqueness (the message is less than perfect)
+          B>> -> 1
+    end.
+
+bit_t5(A) ->
+    B = o1(),
+    case none:none() of
+        <<A:B>> -> 1 % breaks the opaqueness
+    end.
+
+-spec bit_t4(<<_:1>>) -> integer().
+
+bit_t4(A) ->
+    Sz = i1(),
+    case A of
+        <<_:Sz>> -> 1
+    end.
+
+-spec bit_adt_t4(<<_:1>>) -> integer().
+
+bit_adt_t4(A) ->
+    Sz = simple1_adt:i1(),
+    case A of
+        <<_:Sz>> -> 1 % breaks the opaqueness
+    end.
+
+bit_t5() ->
+    A = bit1(),
+    case A of
+        <<_/binary>> -> 1
+    end.
+
+bit_adt_t5() ->
+    A = simple1_adt:bit1(),
+    case A of
+        <<_/binary>> -> 1 % breaks the opaqueness
+    end.
+
+-opaque bit1() :: binary().
+
+-spec bit1() -> bit1().
+
+bit1() ->
+    <<"hej">>.
+
+%% Calls with variable module or function
+
+call_f(A) ->
+    A = a(),
+    foo:A(A).
+
+call_f_adt(A) ->
+    A = simple1_adt:a(),
+    foo:A(A). % breaks the opaqueness
+
+call_m(A) ->
+    A = a(),
+    A:foo(A).
+
+call_m_adt(A) ->
+    A = simple1_adt:a(),
+    A:foo(A). % breaks the opaqueness
+
+-opaque a() :: atom().
+
+-opaque i() :: integer().
+
+-spec a() -> a().
+
+a() ->
+    e.
+
+call_f_i(A) ->
+    A = i(),
+    foo:A(A). % A is not atom() but i()
+
+call_f_adt_i(A) ->
+    A = simple1_adt:i(),
+    foo:A(A). % A is not atom() but simple1_adt:i()
+
+call_m_i(A) ->
+    A = i(),
+    A:foo(A). % A is not atom() but i()
+
+call_m_adt_i(A) ->
+    A = simple1_adt:i(),
+    A:foo(A). % A is not atom() but simple1_adt:i()
+
+-spec eq1() -> integer().
+
+eq1() ->
+    A = simple1_adt:d2(),
+    B = simple1_adt:d1(),
+    if
+        A == B -> % opaque term
+            0;
+        A == A ->
+            1;
+        A =:= A -> % compiler finds this one cannot match
+            2;
+        true -> % compiler finds this one cannot match
+            3
+    end.
+
+eq2() ->
+    A = simple1_adt:d1(),
+    if
+        {A} >= {A} ->
+            1;
+        A >= 3 -> % opaque term
+            2;
+        A == 3 -> % opaque term
+            3;
+        A =:= 3 -> % opaque term
+            4;
+        A == A ->
+            5;
+        A =:= A -> % compiler finds this one cannot match
+            6
+    end.
+
+c5() ->
+    A = simple1_adt:d1(),
+    A < 3. % opaque term
+
+c6(A, B) ->
+    A = simple1_adt:d1(),
+    B = simple1_adt:d1(),
+    A =< B. % same type - no warning
+
+c7(A, B) ->
+    A = simple1_adt:d1(),
+    B = simple1_adt:d2(),
+    A =< B. % opaque term
+
+c8() ->
+    D = digraph:new(),
+    E = ets:new(foo, []),
+    if {D, a} > {D, E} -> true; % OK
+       {1.0, 2} > {{D}, {E}} -> true; % OK
+       {D, 3} > {D, E} -> true  % opaque term 2
+    end.
+
+-spec i() -> i().
+
+i() ->
+    1.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple2_api.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple2_api.erl
new file mode 100644
index 0000000000..c86f6fd0b5
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple2_api.erl
@@ -0,0 +1,125 @@
+-module(simple2_api).
+
+-export([c1/2, c2/0, c3/0, c4/1, c5/1, c6/0, c6_b/0, c7/0, c7_b/0,
+         c7_c/0, c8/0, c9/0, c10/0, c11/0, c12/0, c13/0, c14/0, c15/0,
+         c16/0, c17/0, c18/0, c19/0, c20/0, c21/0, c22/0, c23/0,
+         c24/0, c25/0, c26/0]).
+
+-spec c1(simple1_adt:d1(), simple1_adt:d2()) -> boolean().
+
+c1(A, B) ->
+    {A} =< {B}. % succ type of A and B is any()
+
+c2() ->
+    A = simple1_adt:d1(),
+    erlang:make_tuple(1, A). % ok
+
+c3() ->
+    A = simple1_adt:d1(),
+    setelement(1, {A}, A). % ok
+
+c4(_) ->
+    A = simple1_adt:d1(),
+    halt(A). % ok (BIF fails...)
+
+c5(_) ->
+    A = simple1_adt:d1(),
+    [A] -- [A]. % ok
+
+c6() ->
+    A = simple1_adt:d1(),
+    A ! foo. % opaque term
+
+c6_b() ->
+    A = simple1_adt:d1(),
+    erlang:send(A, foo). % opaque term
+
+c7() ->
+    A = simple1_adt:d1(),
+    foo ! A. % ok
+
+c7_b() ->
+    A = simple1_adt:d1(),
+    erlang:send(foo, A). % ok
+
+c7_c() ->
+    A = simple1_adt:d1(),
+    erlang:send(foo, A, []). % ok
+
+c8() ->
+    A = simple1_adt:d1(),
+    A < 3. % opaque term
+
+c9() ->
+    A = simple1_adt:d1(),
+    lists:keysearch(A, 1, []). % ok
+
+c10() ->
+    A = simple1_adt:d1(),
+    lists:keysearch(1, A, []). % opaque term 2
+
+c11() ->
+    A = simple1_adt:tuple(),
+    lists:keysearch(key, 1, [A]). % ok
+
+c12() ->
+    A = simple1_adt:tuple(),
+    lists:keysearch(key, 1, A). % opaque term 3
+
+c13() ->
+    A = simple1_adt:tuple(),
+    lists:keysearch(key, 1, [{A,2}]). % ok
+
+c14() ->
+    A = simple1_adt:tuple(),
+    lists:keysearch(key, 1, [{2,A}]). % ok
+
+c15() ->
+    A = simple1_adt:d1(),
+    lists:keysearch(key, 1, [A]). % ok
+
+c16() ->
+    A = simple1_adt:tuple(),
+    erlang:send(foo, A). % ok
+
+c17() ->
+    A = simple1_adt:tuple(),
+    lists:reverse([A]). % ok
+
+c18() ->
+    A = simple1_adt:tuple(),
+    lists:keyreplace(a, 1, [A], {1,2}). % ok
+
+c19() ->
+    A = simple1_adt:tuple(),
+    %% Problem. The spec says argument 4 is a tuple(). Fix that!
+    lists:keyreplace(a, 1, [{1,2}], A). % opaque term 4
+
+c20() ->
+    A = simple1_adt:tuple(),
+    lists:flatten(A). % opaque term 1
+
+c21() ->
+    A = simple1_adt:tuple(),
+    lists:flatten([[{A}]]). % ok
+
+c22() ->
+    A = simple1_adt:tuple(),
+    lists:flatten([[A]]). % ok
+
+c23() ->
+    A = simple1_adt:tuple(),
+    lists:flatten([A]). % ok
+
+c24() ->
+    A = simple1_adt:tuple(),
+    lists:flatten({A}). % will never return
+
+c25() ->
+    A = simple1_adt:d1(),
+    B = simple1_adt:tuple(),
+    if {A,3} > {A,B} -> true end. % opaque 2nd argument
+
+c26() ->
+    B = simple1_adt:tuple(),
+    tuple_to_list(B). % opaque term 1
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/union/union_adt.erl b/lib/dialyzer/test/opaque_SUITE_data/src/union/union_adt.erl
index 5ca3202bba..d88f238190 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/src/union/union_adt.erl
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/union/union_adt.erl
@@ -1,10 +1,15 @@
 -module(union_adt).
 -export([new/1, new_a/1, new_rec/1]).
 
+%% Now (R17) that opaque types are no longer recognized by their shape
+%% this test case is rather meaningless.
+
 -record(rec, {x = 42 :: integer()}).
 
 -opaque u() :: 'aaa' | 'bbb' | #rec{}.
 
+-spec new(_) -> u().
+
 new(a) -> aaa;
 new(b) -> bbb;
 new(X) when is_integer(X) ->
@@ -13,7 +18,11 @@ new(X) when is_integer(X) ->
 %% the following two functions (and their uses in union_use.erl) test
 %% that the return type is the opaque one and not just a subtype of it
 
+-spec new_a(_) -> u().
+
 new_a(a) -> aaa.
 
+-spec new_rec(_) -> u().
+
 new_rec(X) when is_integer(X) ->
   #rec{x = X}.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/zoltan_adt.erl b/lib/dialyzer/test/opaque_SUITE_data/src/zoltan_adt.erl
new file mode 100644
index 0000000000..c742990c6a
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/zoltan_adt.erl
@@ -0,0 +1,5 @@
+-module(zoltan_adt).
+
+-export_type([id/0]).
+
+-opaque id() :: string().
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/zoltan_kis3.erl b/lib/dialyzer/test/opaque_SUITE_data/src/zoltan_kis3.erl
index b62b9de576..07c9f0a270 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/src/zoltan_kis3.erl
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/zoltan_kis3.erl
@@ -2,13 +2,13 @@
 
 -export([f/0, gen/0]).
 
--opaque id() :: string().
+%-opaque id() :: string().
 
 -spec f() -> char().
 
 %% List pattern matching issue
 f() -> [H|_T] = gen(), H.
 
--spec gen() -> id().
+-spec gen() -> zoltan_adt:id().
 
 gen() -> "Dummy".
diff --git a/lib/dialyzer/vsn.mk b/lib/dialyzer/vsn.mk
index af32c5b901..95d2464e1d 100644
--- a/lib/dialyzer/vsn.mk
+++ b/lib/dialyzer/vsn.mk
@@ -1 +1 @@
-DIALYZER_VSN = 2.6.1
+DIALYZER_VSN = 2.7
diff --git a/lib/hipe/cerl/erl_bif_types.erl b/lib/hipe/cerl/erl_bif_types.erl
index 42c7e360c1..32a502e212 100644
--- a/lib/hipe/cerl/erl_bif_types.erl
+++ b/lib/hipe/cerl/erl_bif_types.erl
@@ -30,19 +30,17 @@
 
 %-define(BITS, (hipe_rtl_arch:word_size() * 8) - ?TAG_IMMED1_SIZE).
 -define(BITS, 128). %This is only in bsl to convert answer to pos_inf/neg_inf.
--define(TAG_IMMED1_SIZE, 4).
+-export([type/3, type/4, type/5, arg_types/3,
+	 is_known/3, opaque_args/5, infinity_add/2]).
 
--export([type/3, type/4, arg_types/3, 
-	 is_known/3, structure_inspecting_args/3, infinity_add/2]).
-
--import(erl_types, [number_max/1,
-		    number_min/1,
+-import(erl_types, [number_max/2,
+		    number_min/2,
 		    t_any/0,
 		    t_arity/0,
 		    t_atom/0,
 		    t_atom/1,
 		    t_atoms/1,
-		    t_atom_vals/1,
+		    t_atom_vals/2,
 		    t_binary/0,
 		    t_bitstr/0,
 		    t_boolean/0,
@@ -60,10 +58,11 @@
 		    t_from_term/1,
 		    t_fun/0,
 		    t_fun/2,
-		    t_fun_args/1,
-		    t_fun_range/1,
+		    t_fun_args/2,
+		    t_fun_range/2,
 		    t_identifier/0,
-		    t_inf/2,
+                    t_has_opaque_subtype/2,
+                    t_inf/3,
 		    t_integer/0,
 		    t_integer/1,
 		    t_non_neg_fixnum/0,
@@ -71,30 +70,28 @@
 		    t_pos_integer/0,
 		    t_integers/1,
 		    t_is_any/1,
-		    t_is_atom/1,
-		    t_is_binary/1,
-		    t_is_bitstr/1,
-		    t_is_boolean/1,
-		    t_is_cons/1,
-		    t_is_float/1,
-		    t_is_float/1,
-		    t_is_fun/1,
-		    t_is_integer/1,
-		    t_is_integer/1,
-		    t_is_nil/1,
+		    t_is_atom/2,
+		    t_is_binary/2,
+		    t_is_bitstr/2,
+		    t_is_boolean/2,
+		    t_is_cons/2,
+		    t_is_float/2,
+		    t_is_fun/2,
+		    t_is_integer/2,
+		    t_is_nil/1, t_is_nil/2,
 		    t_is_none/1,
 		    t_is_none_or_unit/1,
-		    t_is_number/1,
-		    t_is_pid/1,
-		    t_is_port/1,
-		    t_is_maybe_improper_list/1,
-		    t_is_reference/1,
+		    t_is_number/2,
+		    t_is_pid/2,
+		    t_is_port/2,
+		    t_is_maybe_improper_list/2,
+		    t_is_reference/2,
 		    t_is_string/1,
 		    t_is_subtype/2,
-		    t_is_tuple/1,
+		    t_is_tuple/2,
 		    t_list/0,
 		    t_list/1,
-		    t_list_elements/1,
+		    t_list_elements/2,
 		    t_list_termination/1,
 		    t_mfa/0,
 		    t_module/0,
@@ -104,7 +101,7 @@
 		    t_nonempty_list/0,
 		    t_nonempty_list/1,
 		    t_number/0,
-		    t_number_vals/1,
+		    t_number_vals/2,
 		    t_pid/0,
 		    t_port/0,
 		    t_maybe_improper_list/0,
@@ -115,9 +112,9 @@
 		    t_sup/2,
 		    t_tuple/0,
 		    t_tuple/1,
-		    t_tuple_args/1,
-		    t_tuple_size/1,
-		    t_tuple_subtypes/1
+		    t_tuple_args/2,
+		    t_tuple_size/2,
+		    t_tuple_subtypes/2
 		   ]).
 
 -ifdef(DO_ERL_BIF_TYPES_TEST).
@@ -129,47 +126,61 @@
 -spec type(atom(), atom(), arity()) -> erl_types:erl_type().
 
 type(M, F, A) ->
-  type(M, F, A, any_list(A)).
+  type(M, F, A, any_list(A), []).
 
 %% Arguments should be checked for undefinedness, so we do not make
 %% unnecessary overapproximations.
 
 -spec type(atom(), atom(), arity(), [erl_types:erl_type()]) -> erl_types:erl_type().
 
+type(M, F, A, Xs) ->
+  type(M, F, A, Xs, 'universe').
+
+-type opaques() :: 'universe' | [erl_types:erl_type()].
+
+-type arg_types() :: [erl_types:erl_type()].
+
+-spec type(atom(), atom(), arity(), arg_types(), opaques()) ->
+              erl_types:erl_type().
+
 %%-- erlang -------------------------------------------------------------------
-type(erlang, halt, 0, _) -> t_none();
-type(erlang, halt, 1, _) -> t_none();
-type(erlang, halt, 2, _) -> t_none();
-type(erlang, exit, 1, _) -> t_none();
-type(erlang, error, 1, _) -> t_none();
-type(erlang, error, 2, _) -> t_none();
-type(erlang, throw, 1, _) -> t_none();
-type(erlang, '==', 2, Xs = [X1, X2]) ->
-  case t_is_atom(X1) andalso t_is_atom(X2) of
-    true -> type(erlang, '=:=', 2, Xs);
+type(erlang, halt, 0, _, _) -> t_none();
+type(erlang, halt, 1, _, _) -> t_none();
+type(erlang, halt, 2, _, _) -> t_none();
+type(erlang, exit, 1, _, _) -> t_none();
+type(erlang, error, 1, _, _) -> t_none();
+type(erlang, error, 2, _, _) -> t_none();
+type(erlang, throw, 1, _, _) -> t_none();
+type(erlang, '==', 2, Xs = [X1, X2], Opaques) ->
+  case
+    t_is_atom(X1, Opaques) andalso t_is_atom(X2, Opaques)
+  of
+    true -> type(erlang, '=:=', 2, Xs, Opaques);
     false ->
-      case t_is_integer(X1) andalso t_is_integer(X2) of
-	true -> type(erlang, '=:=', 2, Xs);
-	false -> strict(Xs, t_boolean())
+      case t_is_integer(X1, Opaques) andalso t_is_integer(X2, Opaques) of
+	true -> type(erlang, '=:=', 2, Xs, Opaques);
+	false -> strict2(Xs, t_boolean())
       end
   end;
-type(erlang, '/=', 2, Xs = [X1, X2]) -> 
-  case t_is_atom(X1) andalso t_is_atom(X2) of
-    true -> type(erlang, '=/=', 2, Xs);
+type(erlang, '/=', 2, Xs = [X1, X2], Opaques) ->
+  case
+    t_is_atom(X1, Opaques) andalso t_is_atom(X2, Opaques)
+  of
+    true -> type(erlang, '=/=', 2, Xs, Opaques);
     false ->
-      case t_is_integer(X1) andalso t_is_integer(X2) of
-	true -> type(erlang, '=/=', 2, Xs);
-	false -> strict(Xs, t_boolean())
+      case t_is_integer(X1, Opaques) andalso t_is_integer(X2, Opaques) of
+	true -> type(erlang, '=/=', 2, Xs, Opaques);
+	false -> strict2(Xs, t_boolean())
       end
   end;
-type(erlang, '=:=', 2, Xs = [Lhs, Rhs]) -> 
+type(erlang, '=:=', 2, Xs = [Lhs, Rhs], Opaques) ->
   Ans =
-    case t_is_none(t_inf(Lhs, Rhs)) of
+    case t_is_none(t_inf(Lhs, Rhs, Opaques)) of
       true -> t_atom('false');
       false ->
-	case t_is_atom(Lhs) andalso t_is_atom(Rhs) of
+	case t_is_atom(Lhs, Opaques) andalso t_is_atom(Rhs, Opaques) of
 	  true ->
-	    case {t_atom_vals(Lhs), t_atom_vals(Rhs)} of
+	    case {t_atom_vals(Lhs, Opaques), t_atom_vals(Rhs, Opaques)} of
 	      {unknown, _} -> t_boolean();
 	      {_, unknown} -> t_boolean();
 	      {[X], [X]} -> t_atom('true');
@@ -181,16 +192,20 @@ type(erlang, '=:=', 2, Xs = [Lhs, Rhs]) ->
 		end
 	    end;
 	  false ->
-	    case t_is_integer(Lhs) andalso t_is_integer(Rhs) of
+	    case
+              t_is_integer(Lhs, Opaques) andalso t_is_integer(Rhs, Opaques)
+            of
 	      false -> t_boolean();
 	      true ->
-		case {t_number_vals(Lhs), t_number_vals(Rhs)} of
+		case
+                  {t_number_vals(Lhs, Opaques), t_number_vals(Rhs, Opaques)}
+                of
 		  {[X], [X]} when is_integer(X) -> t_atom('true');
 		  _ ->
-		    LhsMax = number_max(Lhs),
-		    LhsMin = number_min(Lhs),
-		    RhsMax = number_max(Rhs),
-		    RhsMin = number_min(Rhs),
+		    LhsMax = number_max(Lhs, Opaques),
+		    LhsMin = number_min(Lhs, Opaques),
+		    RhsMax = number_max(Rhs, Opaques),
+		    RhsMin = number_min(Rhs, Opaques),
 		    Ans1 = (is_integer(LhsMin) 
 			    andalso is_integer(RhsMax)
 			    andalso (LhsMin > RhsMax)),
@@ -205,15 +220,15 @@ type(erlang, '=:=', 2, Xs = [Lhs, Rhs]) ->
 	    end
 	end
     end,
-  strict(Xs, Ans);
-type(erlang, '=/=', 2, Xs = [Lhs, Rhs]) ->
+  strict2(Xs, Ans);
+type(erlang, '=/=', 2, Xs = [Lhs, Rhs], Opaques) ->
   Ans =
-    case t_is_none(t_inf(Lhs, Rhs)) of
+    case t_is_none(t_inf(Lhs, Rhs, Opaques)) of
       true -> t_atom('true');
       false ->
-	case t_is_atom(Lhs) andalso t_is_atom(Rhs) of
+	case t_is_atom(Lhs, Opaques) andalso t_is_atom(Rhs, Opaques) of
 	  true ->
-	    case {t_atom_vals(Lhs), t_atom_vals(Rhs)} of
+	    case {t_atom_vals(Lhs, Opaques), t_atom_vals(Rhs, Opaques)} of
 	      {unknown, _} -> t_boolean();
 	      {_, unknown} -> t_boolean();
 	      {[Val], [Val]} -> t_atom('false');
@@ -221,13 +236,15 @@ type(erlang, '=/=', 2, Xs = [Lhs, Rhs]) ->
 		t_sup([t_from_term(X =/= Y) || X <- LhsVals, Y <- RhsVals])
 	    end;
 	  false ->
-	    case t_is_integer(Lhs) andalso t_is_integer(Rhs) of
+	    case
+              t_is_integer(Lhs, Opaques) andalso t_is_integer(Rhs, Opaques)
+            of
 	      false -> t_boolean();
 	      true ->
-		LhsMax = number_max(Lhs),
-		LhsMin = number_min(Lhs),
-		RhsMax = number_max(Rhs),
-		RhsMin = number_min(Rhs),
+		LhsMax = number_max(Lhs, Opaques),
+		LhsMin = number_min(Lhs, Opaques),
+		RhsMax = number_max(Rhs, Opaques),
+		RhsMin = number_min(Rhs, Opaques),
 		Ans1 = (is_integer(LhsMin) andalso is_integer(RhsMax)
 			andalso (LhsMin > RhsMax)),
 		Ans2 = (is_integer(LhsMax) andalso is_integer(RhsMin)
@@ -244,15 +261,15 @@ type(erlang, '=/=', 2, Xs = [Lhs, Rhs]) ->
 	    end
 	end
     end,
-  strict(Xs, Ans);
-type(erlang, '>', 2, Xs = [Lhs, Rhs]) -> 
+  strict2(Xs, Ans);
+type(erlang, '>', 2, Xs = [Lhs, Rhs], Opaques) ->
   Ans =
-    case t_is_integer(Lhs) andalso t_is_integer(Rhs) of
+    case t_is_integer(Lhs, Opaques) andalso t_is_integer(Rhs, Opaques) of
       true ->
-	LhsMax = number_max(Lhs),
-	LhsMin = number_min(Lhs),
-	RhsMax = number_max(Rhs),
-	RhsMin = number_min(Rhs),
+	LhsMax = number_max(Lhs, Opaques),
+	LhsMin = number_min(Lhs, Opaques),
+	RhsMax = number_max(Rhs, Opaques),
+	RhsMin = number_min(Rhs, Opaques),
 	T = t_atom('true'),
 	F = t_atom('false'),
 	if 
@@ -260,17 +277,17 @@ type(erlang, '>', 2, Xs = [Lhs, Rhs]) ->
 	  is_integer(LhsMax), is_integer(RhsMin), RhsMin >= LhsMax -> F;
 	  true -> t_boolean()
 	end;
-      false -> compare('>', Lhs, Rhs)
+      false -> compare('>', Lhs, Rhs, Opaques)
     end,
-  strict(Xs, Ans);
-type(erlang, '>=', 2, Xs = [Lhs, Rhs]) ->
+  strict2(Xs, Ans);
+type(erlang, '>=', 2, Xs = [Lhs, Rhs], Opaques) ->
   Ans =
-    case t_is_integer(Lhs) andalso t_is_integer(Rhs) of
+    case t_is_integer(Lhs, Opaques) andalso t_is_integer(Rhs, Opaques) of
       true ->
-	LhsMax = number_max(Lhs),
-	LhsMin = number_min(Lhs),
-	RhsMax = number_max(Rhs),
-	RhsMin = number_min(Rhs),
+	LhsMax = number_max(Lhs, Opaques),
+	LhsMin = number_min(Lhs, Opaques),
+	RhsMax = number_max(Rhs, Opaques),
+	RhsMin = number_min(Rhs, Opaques),
 	T = t_atom('true'),
 	F = t_atom('false'),
 	if 
@@ -278,17 +295,17 @@ type(erlang, '>=', 2, Xs = [Lhs, Rhs]) ->
 	  is_integer(LhsMax), is_integer(RhsMin), RhsMin > LhsMax -> F;
 	  true -> t_boolean()
 	end;
-      false -> compare('>=', Lhs, Rhs)
+      false -> compare('>=', Lhs, Rhs, Opaques)
     end,
-  strict(Xs, Ans);
-type(erlang, '<', 2, Xs = [Lhs, Rhs]) ->
+  strict2(Xs, Ans);
+type(erlang, '<', 2, Xs = [Lhs, Rhs], Opaques) ->
   Ans =
-    case t_is_integer(Lhs) andalso t_is_integer(Rhs) of
+    case t_is_integer(Lhs, Opaques) andalso t_is_integer(Rhs, Opaques) of
       true ->
-	LhsMax = number_max(Lhs),
-	LhsMin = number_min(Lhs),
-	RhsMax = number_max(Rhs),
-	RhsMin = number_min(Rhs),
+	LhsMax = number_max(Lhs, Opaques),
+	LhsMin = number_min(Lhs, Opaques),
+	RhsMax = number_max(Rhs, Opaques),
+	RhsMin = number_min(Rhs, Opaques),
 	T = t_atom('true'),
 	F = t_atom('false'),
 	if 
@@ -296,17 +313,17 @@ type(erlang, '<', 2, Xs = [Lhs, Rhs]) ->
 	  is_integer(LhsMin), is_integer(RhsMax), RhsMax =< LhsMin -> F;
 	  true -> t_boolean()
 	end;
-      false -> compare('<', Lhs, Rhs)
+      false -> compare('<', Lhs, Rhs, Opaques)
     end,
-  strict(Xs, Ans);
-type(erlang, '=<', 2, Xs = [Lhs, Rhs]) ->
+  strict2(Xs, Ans);
+type(erlang, '=<', 2, Xs = [Lhs, Rhs], Opaques) ->
   Ans =
-    case t_is_integer(Lhs) andalso t_is_integer(Rhs) of
+    case t_is_integer(Lhs, Opaques) andalso t_is_integer(Rhs, Opaques) of
       true ->
-	LhsMax = number_max(Lhs),
-	LhsMin = number_min(Lhs),
-	RhsMax = number_max(Rhs),
-	RhsMin = number_min(Rhs),
+	LhsMax = number_max(Lhs, Opaques),
+	LhsMin = number_min(Lhs, Opaques),
+	RhsMax = number_max(Rhs, Opaques),
+	RhsMin = number_min(Rhs, Opaques),
 	T = t_atom('true'),
 	F = t_atom('false'),
 	if 
@@ -314,232 +331,237 @@ type(erlang, '=<', 2, Xs = [Lhs, Rhs]) ->
 	  is_integer(LhsMin), is_integer(RhsMax), RhsMax < LhsMin -> F;
 	  true -> t_boolean()
 	end;
-      false -> compare('=<', Lhs, Rhs)
+      false -> compare('=<', Lhs, Rhs, Opaques)
     end,
-  strict(Xs, Ans);
-type(erlang, '+', 1, Xs) ->
-  strict(arg_types(erlang, '+', 1), Xs, 
-	 fun ([X]) -> X end);
-type(erlang, '-', 1, Xs) ->
-  strict(arg_types(erlang, '-', 1), Xs, 
+  strict2(Xs, Ans);
+type(erlang, '+', 1, Xs, Opaques) ->
+  strict(erlang, '+', 1, Xs, fun ([X]) -> X end, Opaques);
+type(erlang, '-', 1, Xs, Opaques) ->
+  strict(erlang, '-', 1, Xs,
 	 fun ([X]) -> 
-	     case t_is_integer(X) of
+	     case t_is_integer(X, Opaques) of
 	       true -> type(erlang, '-', 2, [t_integer(0), X]);
 	       false -> X
 	     end
-	 end);
-type(erlang, '!', 2, Xs) ->
-  strict(arg_types(erlang, '!', 2), Xs, fun ([_, X2]) -> X2 end);
-type(erlang, '+', 2, Xs) ->
-  strict(arg_types(erlang, '+', 2), Xs,
+	 end, Opaques);
+type(erlang, '!', 2, Xs, Opaques) ->
+  strict(erlang, '!', 2, Xs, fun ([_, X2]) -> X2 end, Opaques);
+type(erlang, '+', 2, Xs, Opaques) ->
+  strict(erlang, '+', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('+', X1, X2) of
+	     case arith('+', X1, X2, Opaques) of
 	       {ok, T} -> T;
 	       error ->
-		 case t_is_float(X1) orelse t_is_float(X2) of
+		 case
+                   t_is_float(X1, Opaques) orelse t_is_float(X2, Opaques)
+                 of
 		   true -> t_float();
 		   false -> t_number()
 		 end
 	     end
-	 end);
-type(erlang, '-', 2, Xs) ->
-  strict(arg_types(erlang, '-', 2), Xs,
+	 end, Opaques);
+type(erlang, '-', 2, Xs, Opaques) ->
+  strict(erlang, '-', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('-', X1, X2) of
+	     case arith('-', X1, X2, Opaques) of
 	       {ok, T} -> T;
 	       error ->
-		 case t_is_float(X1) orelse t_is_float(X2) of
+		 case
+                   t_is_float(X1, Opaques) orelse t_is_float(X2, Opaques)
+                 of
 		   true -> t_float();
 		   false -> t_number()
 		 end
 	     end
-	 end);
-type(erlang, '*', 2, Xs) ->
-  strict(arg_types(erlang, '*', 2), Xs,
+	 end, Opaques);
+type(erlang, '*', 2, Xs, Opaques) ->
+  strict(erlang, '*', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('*', X1, X2) of
+	     case arith('*', X1, X2, Opaques) of
 	       {ok, T} -> T;
 	       error ->
-		 case t_is_float(X1) orelse t_is_float(X2) of
+		 case
+                   t_is_float(X1, Opaques) orelse t_is_float(X2, Opaques)
+                 of
 		   true -> t_float();
 		   false -> t_number()
 		 end
 	     end
-	 end);
-type(erlang, '/', 2, Xs) ->
-  strict(arg_types(erlang, '/', 2), Xs,
-	 fun (_) -> t_float() end);
-type(erlang, 'div', 2, Xs) ->
-  strict(arg_types(erlang, 'div', 2), Xs,
+	 end, Opaques);
+type(erlang, '/', 2, Xs, Opaques) ->
+  strict(erlang, '/', 2, Xs, fun (_) -> t_float() end, Opaques);
+type(erlang, 'div', 2, Xs, Opaques) ->
+  strict(erlang, 'div', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('div', X1, X2) of
+	     case arith('div', X1, X2, Opaques) of
 	       error -> t_integer();
 	       {ok, T} -> T
 	     end
-	 end);
-type(erlang, 'rem', 2, Xs) ->
-  strict(arg_types(erlang, 'rem', 2), Xs,
+	 end, Opaques);
+type(erlang, 'rem', 2, Xs, Opaques) ->
+  strict(erlang, 'rem', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('rem', X1, X2) of
+	     case arith('rem', X1, X2, Opaques) of
 	       error -> t_non_neg_integer();
 	       {ok, T} -> T
 	     end
-	 end);
-type(erlang, '++', 2, Xs) ->
-  strict(arg_types(erlang, '++', 2), Xs,
+	 end, Opaques);
+type(erlang, '++', 2, Xs, Opaques) ->
+  strict(erlang, '++', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case t_is_nil(X1) of
+	     case t_is_nil(X1, Opaques) of
 	       true  -> X2;    % even if X2 is not a list
 	       false ->
-		 case t_is_nil(X2) of
+		 case t_is_nil(X2, Opaques) of
 		   true  -> X1;
 		   false ->
-		     E1 = t_list_elements(X1),
-		     case t_is_cons(X1) of
+		     E1 = t_list_elements(X1, Opaques),
+		     case t_is_cons(X1, Opaques) of
 		       true -> t_cons(E1, X2);
 		       false ->
 			 t_sup(X2, t_cons(E1, X2))
 		     end
 		 end
 	     end
-	 end);
-type(erlang, '--', 2, Xs) ->
+	 end, Opaques);
+type(erlang, '--', 2, Xs, Opaques) ->
   %% We don't know which elements (if any) in X2 will be found and
   %% removed from X1, even if they would have the same type. Thus, we
   %% must assume that X1 can remain unchanged. However, if we succeed,
   %% we know that X1 must be a proper list, but the result could
   %% possibly be empty even if X1 is nonempty.
-  strict(arg_types(erlang, '--', 2), Xs,
+  strict(erlang, '--', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case t_is_nil(X1) of
+	     case t_is_nil(X1, Opaques) of
 	       true  -> t_nil();
 	       false ->
-		 case t_is_nil(X2) of
+		 case t_is_nil(X2, Opaques) of
 		   true  -> X1;
-		   false -> t_list(t_list_elements(X1))
+		   false -> t_list(t_list_elements(X1, Opaques))
 		 end
 	     end
-	 end);
-type(erlang, 'and', 2, Xs) ->
-  strict(arg_types(erlang, 'and', 2), Xs, fun (_) -> t_boolean() end);
-type(erlang, 'or', 2, Xs) ->
-  strict(arg_types(erlang, 'or', 2), Xs, fun (_) -> t_boolean() end);
-type(erlang, 'xor', 2, Xs) ->
-  strict(arg_types(erlang, 'xor', 2), Xs, fun (_) -> t_boolean() end);
-type(erlang, 'not', 1, Xs) ->
-  strict(arg_types(erlang, 'not', 1), Xs, fun (_) -> t_boolean() end);
-type(erlang, 'band', 2, Xs) ->
-  strict(arg_types(erlang, 'band', 2), Xs,
+	 end, Opaques);
+type(erlang, 'and', 2, Xs, Opaques) ->
+  strict(erlang, 'and', 2, Xs, fun (_) -> t_boolean() end, Opaques);
+type(erlang, 'or', 2, Xs, Opaques) ->
+  strict(erlang, 'or', 2, Xs, fun (_) -> t_boolean() end, Opaques);
+type(erlang, 'xor', 2, Xs, Opaques) ->
+  strict(erlang, 'xor', 2, Xs, fun (_) -> t_boolean() end, Opaques);
+type(erlang, 'not', 1, Xs, Opaques) ->
+  strict(erlang, 'not', 1, Xs, fun (_) -> t_boolean() end, Opaques);
+type(erlang, 'band', 2, Xs, Opaques) ->
+  strict(erlang, 'band', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('band', X1, X2) of
+	     case arith('band', X1, X2, Opaques) of
 	       error -> t_integer();
 	       {ok, T} -> T
 	     end
-	 end);
+	 end, Opaques);
 %% The result is not wider than the smallest argument. We need to
 %% kill any value-sets in the result.
-%%  strict(arg_types(erlang, 'band', 2), Xs,
-%%	 fun ([X1, X2]) -> t_sup(t_inf(X1, X2), t_byte()) end);
-type(erlang, 'bor', 2, Xs) ->
-  strict(arg_types(erlang, 'bor', 2), Xs,
+%%  strict(erlang, 'band', 2, Xs,
+%%	 fun ([X1, X2]) -> t_sup(t_inf(X1, X2, Opaques), t_byte()) end, Opaques);
+type(erlang, 'bor', 2, Xs, Opaques) ->
+  strict(erlang, 'bor', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('bor', X1, X2) of
+	     case arith('bor', X1, X2, Opaques) of
 	       error -> t_integer();
 	       {ok, T} -> T
 	     end
-	 end);
+	 end, Opaques);
 %% The result is not wider than the largest argument. We need to
 %% kill any value-sets in the result.
-%%  strict(arg_types(erlang, 'bor', 2), Xs,
-%%	 fun ([X1, X2]) -> t_sup(t_sup(X1, X2), t_byte()) end);
-type(erlang, 'bxor', 2, Xs) ->
-  strict(arg_types(erlang, 'bxor', 2), Xs,
+%%  strict(erlang, 'bor', 2, Xs,
+%%	 fun ([X1, X2]) -> t_sup(t_sup(X1, X2), t_byte()) end, Opaques);
+type(erlang, 'bxor', 2, Xs, Opaques) ->
+  strict(erlang, 'bxor', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('bxor', X1, X2) of
+	     case arith('bxor', X1, X2, Opaques) of
 	       error -> t_integer();
 	       {ok, T} -> T
 	     end
-	 end);
+	 end, Opaques);
 %% The result is not wider than the largest argument. We need to
 %% kill any value-sets in the result.
-%%  strict(arg_types(erlang, 'bxor', 2), Xs,
-%%	 fun ([X1, X2]) -> t_sup(t_sup(X1, X2), t_byte()) end);
-type(erlang, 'bsr', 2, Xs) ->
-  strict(arg_types(erlang, 'bsr', 2), Xs,
+%%  strict(erlang, 'bxor', 2, Xs,
+%%	 fun ([X1, X2]) -> t_sup(t_sup(X1, X2), t_byte()) end, Opaques);
+type(erlang, 'bsr', 2, Xs, Opaques) ->
+  strict(erlang, 'bsr', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('bsr', X1, X2) of
+	     case arith('bsr', X1, X2, Opaques) of
 	       error -> t_integer();
 	       {ok, T} -> T
 	     end
-	 end);
+	 end, Opaques);
 %% If the first argument is unsigned (which is the case for
 %% characters and bytes), the result is never wider. We need to kill
 %% any value-sets in the result.
-%%  strict(arg_types(erlang, 'bsr', 2), Xs,
-%%	 fun ([X, _]) -> t_sup(X, t_byte()) end);
-type(erlang, 'bsl', 2, Xs) ->
-  strict(arg_types(erlang, 'bsl', 2), Xs,
+%%  strict(erlang, 'bsr', 2, Xs,
+%%	 fun ([X, _]) -> t_sup(X, t_byte()) end, Opaques);
+type(erlang, 'bsl', 2, Xs, Opaques) ->
+  strict(erlang, 'bsl', 2, Xs,
 	 fun ([X1, X2]) ->
-	     case arith('bsl', X1, X2) of
+	     case arith('bsl', X1, X2, Opaques) of
 	       error -> t_integer();
 	       {ok, T} -> T
 	     end
-	 end);
+	 end, Opaques);
 %% Not worth doing anything special here.
-%%  strict(arg_types(erlang, 'bsl', 2), Xs, fun (_) -> t_integer() end);
-type(erlang, 'bnot', 1, Xs) ->
- strict(arg_types(erlang, 'bnot', 1), Xs,
+%%  strict(erlang, 'bsl', 2, Xs, fun (_) -> t_integer() end, Opaques);
+type(erlang, 'bnot', 1, Xs, Opaques) ->
+ strict(erlang, 'bnot', 1, Xs,
 	 fun ([X1]) ->
-	     case arith('bnot', X1) of
+	     case arith('bnot', X1, Opaques) of
 	       error -> t_integer();
 	       {ok, T} -> T
 	     end
-	 end);
+	 end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, abs, 1, Xs) ->
-  strict(arg_types(erlang, abs, 1), Xs, fun ([X]) -> X end);
+type(erlang, abs, 1, Xs, Opaques) ->
+  strict(erlang, abs, 1, Xs, fun ([X]) -> X end, Opaques);
 %% This returns (-X)-1, so it often gives a negative result.
-%%  strict(arg_types(erlang, 'bnot', 1), Xs, fun (_) -> t_integer() end);
-type(erlang, append, 2, Xs) -> type(erlang, '++', 2, Xs); % alias
-type(erlang, apply, 2, Xs) ->
+%%  strict(erlang, 'bnot', 1, Xs, fun (_) -> t_integer() end, Opaques);
+type(erlang, append, 2, Xs, _Opaques) -> type(erlang, '++', 2, Xs); % alias
+type(erlang, apply, 2, Xs, Opaques) ->
   Fun = fun ([X, _Y]) -> 
-	    case t_is_fun(X) of
+	    case t_is_fun(X, Opaques) of
 	      true ->
-		t_fun_range(X);
+		t_fun_range(X, Opaques);
 	      false ->
 		t_any() 
 	    end
 	end,
-  strict(arg_types(erlang, apply, 2), Xs, Fun);
-type(erlang, apply, 3, Xs) ->
-  strict(arg_types(erlang, apply, 3), Xs, fun (_) -> t_any() end);
+  strict(erlang, apply, 2, Xs, Fun, Opaques);
+type(erlang, apply, 3, Xs, Opaques) ->
+  strict(erlang, apply, 3, Xs, fun (_) -> t_any() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, binary_part, 2, Xs) ->
-  strict(arg_types(erlang, binary_part, 2), Xs, fun (_) -> t_binary() end);
+type(erlang, binary_part, 2, Xs, Opaques) ->
+  strict(erlang, binary_part, 2, Xs, fun (_) -> t_binary() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, binary_part, 3, Xs) ->
-  strict(arg_types(erlang, binary_part, 3), Xs, fun (_) -> t_binary() end);
+type(erlang, binary_part, 3, Xs, Opaques) ->
+  strict(erlang, binary_part, 3, Xs, fun (_) -> t_binary() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, bit_size, 1, Xs) ->
-  strict(arg_types(erlang, bit_size, 1), Xs,
-	 fun (_) -> t_non_neg_integer() end);
+type(erlang, bit_size, 1, Xs, Opaques) ->
+  strict(erlang, bit_size, 1, Xs,
+	 fun (_) -> t_non_neg_integer() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, byte_size, 1, Xs) ->
-  strict(arg_types(erlang, byte_size, 1), Xs,
-	 fun (_) -> t_non_neg_integer() end);
-type(erlang, disconnect_node, 1, Xs) ->
-  strict(arg_types(erlang, disconnect_node, 1), Xs, fun (_) -> t_sup([t_boolean(), t_atom('ignored')]) end);
+type(erlang, byte_size, 1, Xs, Opaques) ->
+  strict(erlang, byte_size, 1, Xs,
+	 fun (_) -> t_non_neg_integer() end, Opaques);
+type(erlang, disconnect_node, 1, Xs, Opaques) ->
+  strict(erlang, disconnect_node, 1, Xs,
+         fun (_) -> t_sup([t_boolean(), t_atom('ignored')]) end, Opaques);
 %% Guard bif, needs to be here.
 %% Also much more expressive than anything you could write in a spec...
-type(erlang, element, 2, Xs) ->
-  strict(arg_types(erlang, element, 2), Xs,
+type(erlang, element, 2, Xs, Opaques) ->
+  strict(erlang, element, 2, Xs,
 	 fun ([X1, X2]) ->
-	     case t_tuple_subtypes(X2) of
+	     case t_tuple_subtypes(X2, Opaques) of
 	       unknown -> t_any();
 	       [_] ->
-		 Sz = t_tuple_size(X2),
-		 As = t_tuple_args(X2),
-		 case t_number_vals(X1) of
+		 Sz = t_tuple_size(X2, Opaques),
+		 As = t_tuple_args(X2, Opaques),
+		 case t_number_vals(X1, Opaques) of
 		   unknown -> t_sup(As);
 		   Ns when is_list(Ns) ->
 		     Fun = fun 
@@ -553,165 +575,161 @@ type(erlang, element, 2, Xs) ->
 	       Ts when is_list(Ts) ->
 		 t_sup([type(erlang, element, 2, [X1, Y]) || Y <- Ts])
 	     end
-	 end);
+	 end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, float, 1, Xs) ->
-  strict(arg_types(erlang, float, 1), Xs, fun (_) -> t_float() end);
-type(erlang, fun_info, 1, Xs) ->
-  strict(arg_types(erlang, fun_info, 1), Xs,
-	 fun (_) -> t_list(t_tuple([t_atom(), t_any()])) end);
-type(erlang, get_cookie, 0, _) -> t_atom();  % | t_atom('nocookie')
+type(erlang, float, 1, Xs, Opaques) ->
+  strict(erlang, float, 1, Xs, fun (_) -> t_float() end, Opaques);
+type(erlang, fun_info, 1, Xs, Opaques) ->
+  strict(erlang, fun_info, 1, Xs,
+	 fun (_) -> t_list(t_tuple([t_atom(), t_any()])) end, Opaques);
+type(erlang, get_cookie, 0, _, _Opaques) -> t_atom();  % | t_atom('nocookie')
 %% Guard bif, needs to be here.
-type(erlang, hd, 1, Xs) ->
-  strict(arg_types(erlang, hd, 1), Xs, fun ([X]) -> t_cons_hd(X) end);
-type(erlang, integer_to_list, 2, Xs) ->
-  strict(arg_types(erlang, integer_to_list, 2), Xs,
-	 fun (_) -> t_string() end);
-type(erlang, info, 1, Xs) -> type(erlang, system_info, 1, Xs); % alias
+type(erlang, hd, 1, Xs, Opaques) ->
+  strict(erlang, hd, 1, Xs, fun ([X]) -> t_cons_hd(X) end, Opaques);
+type(erlang, integer_to_list, 2, Xs, Opaques) ->
+  strict(erlang, integer_to_list, 2, Xs,
+	 fun (_) -> t_string() end, Opaques);
+type(erlang, info, 1, Xs, _) -> type(erlang, system_info, 1, Xs); % alias
 %% All type tests are guard BIF's and may be implemented in ways that
 %% cannot be expressed in a type spec, why they are kept in erl_bif_types.
-type(erlang, is_atom, 1, Xs) ->   
-  Fun = fun (X) -> check_guard(X, fun (Y) -> t_is_atom(Y) end, t_atom()) end,
-  strict(arg_types(erlang, is_atom, 1), Xs, Fun);
-type(erlang, is_binary, 1, Xs) ->
+type(erlang, is_atom, 1, Xs, Opaques) ->
+  Fun = fun (X) ->
+            check_guard(X, fun (Y) -> t_is_atom(Y, Opaques) end,
+                        t_atom(), Opaques)
+        end,
+  strict(erlang, is_atom, 1, Xs, Fun, Opaques);
+type(erlang, is_binary, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_binary(Y) end, t_binary())
+	    check_guard(X, fun (Y) -> t_is_binary(Y, Opaques) end,
+                        t_binary(), Opaques)
 	end,
-  strict(arg_types(erlang, is_binary, 1), Xs, Fun);
-type(erlang, is_bitstring, 1, Xs) ->
+  strict(erlang, is_binary, 1, Xs, Fun, Opaques);
+type(erlang, is_bitstring, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_bitstr(Y) end, t_bitstr())
+	    check_guard(X, fun (Y) -> t_is_bitstr(Y, Opaques) end,
+                        t_bitstr(), Opaques)
 	end,
-  strict(arg_types(erlang, is_bitstring, 1), Xs, Fun);
-type(erlang, is_boolean, 1, Xs) ->
+  strict(erlang, is_bitstring, 1, Xs, Fun, Opaques);
+type(erlang, is_boolean, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_boolean(Y) end, t_boolean())
+	    check_guard(X, fun (Y) -> t_is_boolean(Y, Opaques) end,
+                        t_boolean(), Opaques)
 	end,
-  strict(arg_types(erlang, is_boolean, 1), Xs, Fun);
-type(erlang, is_float, 1, Xs) ->
+  strict(erlang, is_boolean, 1, Xs, Fun, Opaques);
+type(erlang, is_float, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_float(Y) end, t_float())
+	    check_guard(X, fun (Y) -> t_is_float(Y, Opaques) end,
+                        t_float(), Opaques)
 	end,
-  strict(arg_types(erlang, is_float, 1), Xs, Fun);
-type(erlang, is_function, 1, Xs) ->
-  Fun = fun (X) -> check_guard(X, fun (Y) -> t_is_fun(Y) end, t_fun()) end,
-  strict(arg_types(erlang, is_function, 1), Xs, Fun);
-type(erlang, is_function, 2, Xs) ->
+  strict(erlang, is_float, 1, Xs, Fun, Opaques);
+type(erlang, is_function, 1, Xs, Opaques) ->
+  Fun = fun (X) ->
+            check_guard(X, fun (Y) -> t_is_fun(Y, Opaques) end,
+                        t_fun(), Opaques)
+        end,
+  strict(erlang, is_function, 1, Xs, Fun, Opaques);
+type(erlang, is_function, 2, Xs, Opaques) ->
   Fun = fun ([FunType, ArityType]) -> 
-	    case t_number_vals(ArityType) of
+	    case t_number_vals(ArityType, Opaques) of
 	      unknown -> t_boolean();
 	      [Val] -> 
 		FunConstr = t_fun(any_list(Val), t_any()),
 		Fun2 = fun (X) ->
 			   t_is_subtype(X, FunConstr) andalso (not t_is_none(X))
 		       end,
-		check_guard_single(FunType, Fun2, FunConstr);
+		check_guard_single(FunType, Fun2, FunConstr, Opaques);
 	      IntList when is_list(IntList) -> t_boolean() %% true?
 	    end
 	end,
-  strict(arg_types(erlang, is_function, 2), Xs, Fun);
-type(erlang, is_integer, 1, Xs) ->
+  strict(erlang, is_function, 2, Xs, Fun, Opaques);
+type(erlang, is_integer, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_integer(Y) end, t_integer())
+	    check_guard(X, fun (Y) -> t_is_integer(Y, Opaques) end,
+                        t_integer(), Opaques)
 	end,
-  strict(arg_types(erlang, is_integer, 1), Xs, Fun);
-type(erlang, is_list, 1, Xs) ->
+  strict(erlang, is_integer, 1, Xs, Fun, Opaques);
+type(erlang, is_list, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    Fun2 = fun (Y) -> t_is_maybe_improper_list(Y) end,
-	    check_guard(X, Fun2, t_maybe_improper_list())
+	    Fun2 = fun (Y) -> t_is_maybe_improper_list(Y, Opaques) end,
+	    check_guard(X, Fun2, t_maybe_improper_list(), Opaques)
 	end,
-  strict(arg_types(erlang, is_list, 1), Xs, Fun);
-type(erlang, is_number, 1, Xs) ->
+  strict(erlang, is_list, 1, Xs, Fun, Opaques);
+type(erlang, is_number, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_number(Y) end, t_number())
+	    check_guard(X, fun (Y) -> t_is_number(Y, Opaques) end,
+                        t_number(), Opaques)
 	end,
-  strict(arg_types(erlang, is_number, 1), Xs, Fun);
-type(erlang, is_pid, 1, Xs) ->
-  Fun = fun (X) -> check_guard(X, fun (Y) -> t_is_pid(Y) end, t_pid()) end,
-  strict(arg_types(erlang, is_pid, 1), Xs, Fun);
-type(erlang, is_port, 1, Xs) ->
-  Fun = fun (X) -> check_guard(X, fun (Y) -> t_is_port(Y) end, t_port()) end,
-  strict(arg_types(erlang, is_port, 1), Xs, Fun);
-type(erlang, is_record, 2, Xs) ->
+  strict(erlang, is_number, 1, Xs, Fun, Opaques);
+type(erlang, is_pid, 1, Xs, Opaques) ->
+  Fun = fun (X) ->
+            check_guard(X, fun (Y) -> t_is_pid(Y, Opaques) end,
+                        t_pid(), Opaques)
+        end,
+  strict(erlang, is_pid, 1, Xs, Fun, Opaques);
+type(erlang, is_port, 1, Xs, Opaques) ->
+  Fun = fun (X) ->
+            check_guard(X, fun (Y) -> t_is_port(Y, Opaques) end,
+                        t_port(), Opaques)
+        end,
+  strict(erlang, is_port, 1, Xs, Fun, Opaques);
+type(erlang, is_record, 2, Xs, Opaques) ->
   Fun = fun ([X, Y]) ->
-	    case t_is_tuple(X) of
+	    case t_is_tuple(X, Opaques) of
 	      false ->
-		case t_is_none(t_inf(t_tuple(), X)) of
-		  true -> t_atom('false');
+		case t_is_none(t_inf(t_tuple(), X, Opaques)) of
+		  true ->
+                    case t_has_opaque_subtype(X, Opaques) of
+                      true -> t_none();
+                      false -> t_atom('false')
+                    end;
 		  false -> t_boolean()
 		end;
 	      true ->
-		case t_tuple_subtypes(X) of
+		case t_tuple_subtypes(X, Opaques) of
 		  unknown -> t_boolean();
 		  [Tuple] ->
-		    case t_tuple_args(Tuple) of
+		    case t_tuple_args(Tuple, Opaques) of
 		      %% any -> t_boolean();
-		      [Tag|_] ->
-			case t_is_atom(Tag) of
-			  false ->
-			    TagAtom = t_inf(Tag, t_atom()),
-			    case t_is_none(TagAtom) of
-			      true -> t_atom('false');
-			      false -> t_boolean()
-			    end;
-			  true ->
-			    case t_atom_vals(Tag) of
-			      [RealTag] -> 
-				case t_atom_vals(Y) of
-				  [RealTag] -> t_atom('true');
-				  _ -> t_boolean() 
-				end;
-			      _ -> t_boolean()
-			    end
-			end
+		      [Tag|_] -> check_record_tag(Tag, Y, Opaques)
 		    end;
 		  List when length(List) >= 2 ->
 		    t_sup([type(erlang, is_record, 2, [T, Y]) || T <- List])
 		end
 	    end
 	end,
-  strict(arg_types(erlang, is_record, 2), Xs, Fun);
-type(erlang, is_record, 3, Xs) ->
+  strict(erlang, is_record, 2, Xs, Fun, Opaques);
+type(erlang, is_record, 3, Xs, Opaques) ->
   Fun = fun ([X, Y, Z]) ->
-	    Arity = t_number_vals(Z),
-	    case t_is_tuple(X) of
+	    Arity = t_number_vals(Z, Opaques),
+	    case t_is_tuple(X, Opaques) of
 	      false when length(Arity) =:= 1 ->
 		[RealArity] = Arity,
-		case t_is_none(t_inf(t_tuple(RealArity), X)) of
-		  true -> t_atom('false');
+		case t_is_none(t_inf(t_tuple(RealArity), X, Opaques)) of
+		  true ->
+                    case t_has_opaque_subtype(X, Opaques) of
+                      true -> t_none();
+                      false -> t_atom('false')
+                    end;
 		  false -> t_boolean()
 		end;
 	      false ->
-		case t_is_none(t_inf(t_tuple(), X)) of
-		  true -> t_atom('false');
+		case t_is_none(t_inf(t_tuple(), X, Opaques)) of
+		  true ->
+                    case t_has_opaque_subtype(X, Opaques) of
+                      true -> t_none();
+                      false -> t_atom('false')
+                    end;
 		  false -> t_boolean()
 		end;
 	      true when length(Arity) =:= 1 ->
 		[RealArity] = Arity,
-		case t_tuple_subtypes(X) of
+		case t_tuple_subtypes(X, Opaques) of
 		  unknown -> t_boolean();
 		  [Tuple] ->
-		    case t_tuple_args(Tuple) of
+		    case t_tuple_args(Tuple, Opaques) of
 		      %% any -> t_boolean();
 		      Args when length(Args) =:= RealArity ->
-			Tag = hd(Args),
-			case t_is_atom(Tag) of
-			  false ->
-			    TagAtom = t_inf(Tag, t_atom()),
-			    case t_is_none(TagAtom) of
-			      true -> t_atom('false');
-			      false -> t_boolean()
-			    end;
-			  true ->
-			    case t_atom_vals(Tag) of
-			      [RealTag] -> 
-				case t_atom_vals(Y) of
-				  [RealTag] -> t_atom('true');
-				  _ -> t_boolean()
-				end;
-			      _ -> t_boolean()
-			    end
-			end;
+                        check_record_tag(hd(Args), Y, Opaques);
 		      Args when length(Args) =/= RealArity ->
 			t_atom('false')
 		    end;
@@ -722,62 +740,66 @@ type(erlang, is_record, 3, Xs) ->
 		t_boolean()
 	    end
 	end,
-  strict(arg_types(erlang, is_record, 3), Xs, Fun);
-type(erlang, is_reference, 1, Xs) ->
+  strict(erlang, is_record, 3, Xs, Fun, Opaques);
+type(erlang, is_reference, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_reference(Y) end, t_reference())
+	    check_guard(X, fun (Y) -> t_is_reference(Y, Opaques) end,
+                        t_reference(), Opaques)
 	end,
-  strict(arg_types(erlang, is_reference, 1), Xs, Fun);
-type(erlang, is_tuple, 1, Xs) ->
+  strict(erlang, is_reference, 1, Xs, Fun, Opaques);
+type(erlang, is_tuple, 1, Xs, Opaques) ->
   Fun = fun (X) ->
-	    check_guard(X, fun (Y) -> t_is_tuple(Y) end, t_tuple())
+	    check_guard(X, fun (Y) -> t_is_tuple(Y, Opaques) end,
+                        t_tuple(), Opaques)
 	end,
-  strict(arg_types(erlang, is_tuple, 1), Xs, Fun);
+  strict(erlang, is_tuple, 1, Xs, Fun, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, length, 1, Xs) ->
-  strict(arg_types(erlang, length, 1), Xs, fun (_) -> t_non_neg_fixnum() end);
-type(erlang, make_tuple, 2, Xs) ->
-  strict(arg_types(erlang, make_tuple, 2), Xs,
+type(erlang, length, 1, Xs, Opaques) ->
+  strict(erlang, length, 1, Xs, fun (_) -> t_non_neg_fixnum() end, Opaques);
+type(erlang, make_tuple, 2, Xs, Opaques) ->
+  strict(erlang, make_tuple, 2, Xs,
 	 fun ([Int, _]) ->
-	     case t_number_vals(Int) of
+	     case t_number_vals(Int, Opaques) of
 	       [N] when is_integer(N), N >= 0 -> t_tuple(N);
 	       _Other -> t_tuple()
 	     end
-	 end);
-type(erlang, make_tuple, 3, Xs) ->
-  strict(arg_types(erlang, make_tuple, 3), Xs,
+	 end, Opaques);
+type(erlang, make_tuple, 3, Xs, Opaques) ->
+  strict(erlang, make_tuple, 3, Xs,
 	 fun ([Int, _, _]) ->
-	     case t_number_vals(Int) of
+	     case t_number_vals(Int, Opaques) of
 	       [N] when is_integer(N), N >= 0 -> t_tuple(N);
 	       _Other -> t_tuple()
 	     end
-	 end);
-type(erlang, memory, 0, _) -> t_list(t_tuple([t_atom(), t_non_neg_fixnum()]));
-type(erlang, nif_error, 1, _) ->
-  t_any();   % this BIF and the next one are stubs for NIFs and never return
-type(erlang, nif_error, 2, Xs) ->
-  strict(arg_types(erlang, nif_error, 2), Xs, fun (_) -> t_any() end);
+	 end, Opaques);
+type(erlang, memory, 0, _, _Opaques) ->
+  t_list(t_tuple([t_atom(), t_non_neg_fixnum()]));
+type(erlang, nif_error, 1, Xs, Opaques) ->
+  %% this BIF and the next one are stubs for NIFs and never return
+  strict(erlang, nif_error, 1, Xs, fun (_) -> t_any() end, Opaques);
+type(erlang, nif_error, 2, Xs, Opaques) ->
+  strict(erlang, nif_error, 2, Xs, fun (_) -> t_any() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, node, 0, _) -> t_node();
+type(erlang, node, 0, _, _Opaques) -> t_node();
 %% Guard bif, needs to be here.
-type(erlang, node, 1, Xs) ->
-  strict(arg_types(erlang, node, 1), Xs, fun (_) -> t_node() end);
+type(erlang, node, 1, Xs, Opaques) ->
+  strict(erlang, node, 1, Xs, fun (_) -> t_node() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, round, 1, Xs) ->
-  strict(arg_types(erlang, round, 1), Xs, fun (_) -> t_integer() end);
+type(erlang, round, 1, Xs, Opaques) ->
+  strict(erlang, round, 1, Xs, fun (_) -> t_integer() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, self, 0, _) -> t_pid();
-type(erlang, set_cookie, 2, Xs) ->
-  strict(arg_types(erlang, set_cookie, 2), Xs, fun (_) -> t_atom('true') end);
-type(erlang, setelement, 3, Xs) ->
-  strict(arg_types(erlang, setelement, 3), Xs,
+type(erlang, self, 0, _, _Opaques) -> t_pid();
+type(erlang, set_cookie, 2, Xs, Opaques) ->
+  strict(erlang, set_cookie, 2, Xs, fun (_) -> t_atom('true') end, Opaques);
+type(erlang, setelement, 3, Xs, Opaques) ->
+  strict(erlang, setelement, 3, Xs,
 	 fun ([X1, X2, X3]) ->
-	     case t_tuple_subtypes(X2) of
+	     case t_tuple_subtypes(X2, Opaques) of
 	       unknown -> t_tuple();
 	       [_] ->
-		 Sz = t_tuple_size(X2),
-		 As = t_tuple_args(X2),
-		 case t_number_vals(X1) of
+		 Sz = t_tuple_size(X2, Opaques),
+		 As = t_tuple_args(X2, Opaques),
+		 case t_number_vals(X1, Opaques) of
 		   unknown ->
 		     t_tuple([t_sup(X, X3) || X <- As]);
 		   [N] when is_integer(N), 1 =< N, N =< Sz ->
@@ -799,29 +821,29 @@ type(erlang, setelement, 3, Xs) ->
 	       Ts when is_list(Ts) ->
 		 t_sup([type(erlang, setelement, 3, [X1, Y, X3]) || Y <- Ts])
 	     end
-	 end);
+	 end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, size, 1, Xs) ->
-  strict(arg_types(erlang, size, 1), Xs, fun (_) -> t_non_neg_integer() end);
-type(erlang, spawn, 1, Xs) ->
-  strict(arg_types(erlang, spawn, 1), Xs, fun (_) -> t_pid() end);
-type(erlang, spawn, 2, Xs) ->
-  strict(arg_types(erlang, spawn, 2), Xs, fun (_) -> t_pid() end);
-type(erlang, spawn, 4, Xs) ->
-  strict(arg_types(erlang, spawn, 4), Xs, fun (_) -> t_pid() end);
-type(erlang, spawn_link, 1, Xs) -> type(erlang, spawn, 1, Xs);  % same
-type(erlang, spawn_link, 2, Xs) -> type(erlang, spawn, 2, Xs);  % same
-type(erlang, spawn_link, 4, Xs) -> type(erlang, spawn, 4, Xs);  % same
-type(erlang, subtract, 2, Xs) -> type(erlang, '--', 2, Xs); % alias
-type(erlang, suspend_process, 1, Xs) ->
-  strict(arg_types(erlang, suspend_process, 1), Xs,
-	 fun (_) -> t_atom('true') end);
-type(erlang, system_info, 1, Xs) ->
-  strict(arg_types(erlang, system_info, 1), Xs,
+type(erlang, size, 1, Xs, Opaques) ->
+  strict(erlang, size, 1, Xs, fun (_) -> t_non_neg_integer() end, Opaques);
+type(erlang, spawn, 1, Xs, Opaques) ->
+  strict(erlang, spawn, 1, Xs, fun (_) -> t_pid() end, Opaques);
+type(erlang, spawn, 2, Xs, Opaques) ->
+  strict(erlang, spawn, 2, Xs, fun (_) -> t_pid() end, Opaques);
+type(erlang, spawn, 4, Xs, Opaques) ->
+  strict(erlang, spawn, 4, Xs, fun (_) -> t_pid() end, Opaques);
+type(erlang, spawn_link, 1, Xs, _) -> type(erlang, spawn, 1, Xs);  % same
+type(erlang, spawn_link, 2, Xs, _) -> type(erlang, spawn, 2, Xs);  % same
+type(erlang, spawn_link, 4, Xs, _) -> type(erlang, spawn, 4, Xs);  % same
+type(erlang, subtract, 2, Xs, _Opaques) -> type(erlang, '--', 2, Xs); % alias
+type(erlang, suspend_process, 1, Xs, Opaques) ->
+  strict(erlang, suspend_process, 1, Xs,
+	 fun (_) -> t_atom('true') end, Opaques);
+type(erlang, system_info, 1, Xs, Opaques) ->
+  strict(erlang, system_info, 1, Xs,
 	 fun ([Type]) ->
-	     case t_is_atom(Type) of
+	     case t_is_atom(Type, Opaques) of
 	       true ->
-		 case t_atom_vals(Type) of
+		 case t_atom_vals(Type, Opaques) of
 		   ['allocated_areas'] ->
 		     t_list(t_sup([t_tuple([t_atom(),t_non_neg_integer()]),
 				   t_tuple([t_atom(),
@@ -936,26 +958,28 @@ type(erlang, system_info, 1, Xs) ->
 	       false ->  %% This currently handles only {allocator, Alloc}
 		 t_any() %% overapproximation as the return value might change
 	     end
-	 end);
+	 end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, tl, 1, Xs) ->
-  strict(arg_types(erlang, tl, 1), Xs, fun ([X]) -> t_cons_tl(X) end);
+type(erlang, tl, 1, Xs, Opaques) ->
+  strict(erlang, tl, 1, Xs, fun ([X]) -> t_cons_tl(X) end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, trunc, 1, Xs) ->
-  strict(arg_types(erlang, trunc, 1), Xs, fun (_) -> t_integer() end);
+type(erlang, trunc, 1, Xs, Opaques) ->
+  strict(erlang, trunc, 1, Xs, fun (_) -> t_integer() end, Opaques);
 %% Guard bif, needs to be here.
-type(erlang, tuple_size, 1, Xs) ->
-  strict(arg_types(erlang, tuple_size, 1), Xs, fun (_) -> t_non_neg_integer() end);
-type(erlang, tuple_to_list, 1, Xs) ->
-  strict(arg_types(erlang, tuple_to_list, 1), Xs,
+type(erlang, tuple_size, 1, Xs, Opaques) ->
+  strict(erlang, tuple_size, 1, Xs,
+         fun (_) -> t_non_neg_integer() end, Opaques);
+type(erlang, tuple_to_list, 1, Xs, Opaques) ->
+  strict(erlang, tuple_to_list, 1, Xs,
 	 fun ([X]) ->
-	     case t_tuple_subtypes(X) of
+	     case t_tuple_subtypes(X, Opaques) of
 	       unknown -> t_list();
 	       SubTypes -> 
-		 Args = lists:flatten([t_tuple_args(ST) || ST <- SubTypes]),
+                 Args = lists:append([t_tuple_args(ST, Opaques) ||
+                                       ST <- SubTypes]),
 		 %% Can be nil if the tuple can be {}
 		 case lists:any(fun (T) ->
-				    t_tuple_size(T) =:= 0
+				    t_tuple_size(T, Opaques) =:= 0
 				end, SubTypes) of
 		   true ->
 		     %% Be careful here. If we had only {} we need to
@@ -965,279 +989,284 @@ type(erlang, tuple_to_list, 1, Xs) ->
 		     t_nonempty_list(t_sup(Args))
 		 end
 	     end
-	 end);
-type(erlang, yield, 0, _) -> t_atom('true');
+	 end, Opaques);
+type(erlang, yield, 0, _, _Opaques) -> t_atom('true');
 %%-- ets ----------------------------------------------------------------------
-type(ets, rename, 2, Xs) ->
-  strict(arg_types(ets, rename, 2), Xs, fun ([_, Name]) -> Name end);
+type(ets, rename, 2, Xs, Opaques) ->
+  strict(ets, rename, 2, Xs, fun ([_, Name]) -> Name end, Opaques);
 %%-- hipe_bifs ----------------------------------------------------------------
-type(hipe_bifs, add_ref, 2, Xs) ->
-  strict(arg_types(hipe_bifs, add_ref, 2), Xs, fun (_) -> t_nil() end);
-type(hipe_bifs, alloc_data, 2, Xs) ->
-  strict(arg_types(hipe_bifs, alloc_data, 2), Xs,
-	 fun (_) -> t_integer() end); % address
-type(hipe_bifs, array, 2, Xs) ->
-  strict(arg_types(hipe_bifs, array, 2), Xs, fun (_) -> t_immarray() end);
-type(hipe_bifs, array_length, 1, Xs) ->
-  strict(arg_types(hipe_bifs, array_length, 1), Xs,
-	 fun (_) -> t_non_neg_fixnum() end);
-type(hipe_bifs, array_sub, 2, Xs) ->
-  strict(arg_types(hipe_bifs, array_sub, 2), Xs, fun (_) -> t_immediate() end);
-type(hipe_bifs, array_update, 3, Xs) ->
-  strict(arg_types(hipe_bifs, array_update, 3), Xs,
-	 fun (_) -> t_immarray() end);
-type(hipe_bifs, atom_to_word, 1, Xs) ->
-  strict(arg_types(hipe_bifs, atom_to_word, 1), Xs,
-	 fun (_) -> t_integer() end);
-type(hipe_bifs, bif_address, 3, Xs) ->
-  strict(arg_types(hipe_bifs, bif_address, 3), Xs,
-	 fun (_) -> t_sup(t_integer(), t_atom('false')) end);
-type(hipe_bifs, bitarray, 2, Xs) ->
-  strict(arg_types(hipe_bifs, bitarray, 2), Xs, fun (_) -> t_bitarray() end);
-type(hipe_bifs, bitarray_sub, 2, Xs) ->
-  strict(arg_types(hipe_bifs, bitarray_sub, 2), Xs, fun (_) -> t_boolean() end);
-type(hipe_bifs, bitarray_update, 3, Xs) ->
-  strict(arg_types(hipe_bifs, bitarray_update, 3), Xs,
-	 fun (_) -> t_bitarray() end);
-type(hipe_bifs, bytearray, 2, Xs) ->
-  strict(arg_types(hipe_bifs, bytearray, 2), Xs, fun (_) -> t_bytearray() end);
-type(hipe_bifs, bytearray_sub, 2, Xs) ->
-  strict(arg_types(hipe_bifs, bytearray_sub, 2), Xs, fun (_) -> t_byte() end);
-type(hipe_bifs, bytearray_update, 3, Xs) ->
-  strict(arg_types(hipe_bifs, bytearray_update, 3), Xs,
-	 fun (_) -> t_bytearray() end);
-type(hipe_bifs, call_count_clear, 1, Xs) ->
-  strict(arg_types(hipe_bifs, call_count_clear, 1), Xs,
-	 fun (_) -> t_sup(t_non_neg_integer(), t_atom('false')) end);
-type(hipe_bifs, call_count_get, 1, Xs) ->
-  strict(arg_types(hipe_bifs, call_count_get, 1), Xs,
-	 fun (_) -> t_sup(t_non_neg_integer(), t_atom('false')) end);
-type(hipe_bifs, call_count_off, 1, Xs) ->
-  strict(arg_types(hipe_bifs, call_count_off, 1), Xs,
-	 fun (_) -> t_sup(t_non_neg_integer(), t_atom('false')) end);
-type(hipe_bifs, call_count_on, 1, Xs) ->
-  strict(arg_types(hipe_bifs, call_count_on, 1), Xs,
-	 fun (_) -> t_sup(t_atom('true'), t_nil()) end);
-type(hipe_bifs, check_crc, 1, Xs) ->
-  strict(arg_types(hipe_bifs, check_crc, 1), Xs, fun (_) -> t_boolean() end);
-type(hipe_bifs, enter_code, 2, Xs) ->
-  strict(arg_types(hipe_bifs, enter_code, 2), Xs,
+type(hipe_bifs, add_ref, 2, Xs, Opaques) ->
+  strict(hipe_bifs, add_ref, 2, Xs, fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, alloc_data, 2, Xs, Opaques) ->
+  strict(hipe_bifs, alloc_data, 2, Xs,
+	 fun (_) -> t_integer() end, Opaques); % address
+type(hipe_bifs, array, 2, Xs, Opaques) ->
+  strict(hipe_bifs, array, 2, Xs, fun (_) -> t_immarray() end, Opaques);
+type(hipe_bifs, array_length, 1, Xs, Opaques) ->
+  strict(hipe_bifs, array_length, 1, Xs,
+	 fun (_) -> t_non_neg_fixnum() end, Opaques);
+type(hipe_bifs, array_sub, 2, Xs, Opaques) ->
+  strict(hipe_bifs, array_sub, 2, Xs, fun (_) -> t_immediate() end, Opaques);
+type(hipe_bifs, array_update, 3, Xs, Opaques) ->
+  strict(hipe_bifs, array_update, 3, Xs,
+	 fun (_) -> t_immarray() end, Opaques);
+type(hipe_bifs, atom_to_word, 1, Xs, Opaques) ->
+  strict(hipe_bifs, atom_to_word, 1, Xs,
+	 fun (_) -> t_integer() end, Opaques);
+type(hipe_bifs, bif_address, 3, Xs, Opaques) ->
+  strict(hipe_bifs, bif_address, 3, Xs,
+	 fun (_) -> t_sup(t_integer(), t_atom('false')) end, Opaques);
+type(hipe_bifs, bitarray, 2, Xs, Opaques) ->
+  strict(hipe_bifs, bitarray, 2, Xs, fun (_) -> t_bitarray() end, Opaques);
+type(hipe_bifs, bitarray_sub, 2, Xs, Opaques) ->
+  strict(hipe_bifs, bitarray_sub, 2, Xs,
+         fun (_) -> t_boolean() end, Opaques);
+type(hipe_bifs, bitarray_update, 3, Xs, Opaques) ->
+  strict(hipe_bifs, bitarray_update, 3, Xs,
+	 fun (_) -> t_bitarray() end, Opaques);
+type(hipe_bifs, bytearray, 2, Xs, Opaques) ->
+  strict(hipe_bifs, bytearray, 2, Xs, fun (_) -> t_bytearray() end, Opaques);
+type(hipe_bifs, bytearray_sub, 2, Xs, Opaques) ->
+  strict(hipe_bifs, bytearray_sub, 2, Xs, fun (_) -> t_byte() end, Opaques);
+type(hipe_bifs, bytearray_update, 3, Xs, Opaques) ->
+  strict(hipe_bifs, bytearray_update, 3, Xs,
+	 fun (_) -> t_bytearray() end, Opaques);
+type(hipe_bifs, call_count_clear, 1, Xs, Opaques) ->
+  strict(hipe_bifs, call_count_clear, 1, Xs,
+	 fun (_) -> t_sup(t_non_neg_integer(), t_atom('false')) end, Opaques);
+type(hipe_bifs, call_count_get, 1, Xs, Opaques) ->
+  strict(hipe_bifs, call_count_get, 1, Xs,
+	 fun (_) -> t_sup(t_non_neg_integer(), t_atom('false')) end, Opaques);
+type(hipe_bifs, call_count_off, 1, Xs, Opaques) ->
+  strict(hipe_bifs, call_count_off, 1, Xs,
+	 fun (_) -> t_sup(t_non_neg_integer(), t_atom('false')) end, Opaques);
+type(hipe_bifs, call_count_on, 1, Xs, Opaques) ->
+  strict(hipe_bifs, call_count_on, 1, Xs,
+	 fun (_) -> t_sup(t_atom('true'), t_nil()) end, Opaques);
+type(hipe_bifs, check_crc, 1, Xs, Opaques) ->
+  strict(hipe_bifs, check_crc, 1, Xs, fun (_) -> t_boolean() end, Opaques);
+type(hipe_bifs, enter_code, 2, Xs, Opaques) ->
+  strict(hipe_bifs, enter_code, 2, Xs,
 	 fun (_) -> t_tuple([t_integer(),
 			     %% XXX: The tuple below contains integers and
 			     %% is of size same as the length of the MFA list
-			     t_sup(t_nil(), t_binary())]) end);
-type(hipe_bifs, enter_sdesc, 1, Xs) ->
-  strict(arg_types(hipe_bifs, enter_sdesc, 1), Xs, fun (_) -> t_nil() end);
-type(hipe_bifs, find_na_or_make_stub, 2, Xs) ->
-  strict(arg_types(hipe_bifs, find_na_or_make_stub, 2), Xs,
-	 fun (_) -> t_integer() end); % address
-type(hipe_bifs, fun_to_address, 1, Xs) ->
-  strict(arg_types(hipe_bifs, fun_to_address, 1), Xs,
-	 fun (_) -> t_integer() end);
-%% type(hipe_bifs, get_emu_address, 1, Xs) ->
-%%    strict(arg_types(hipe_bifs, get_emu_address, 1), Xs,
-%%	   fun (_) -> t_integer() end); % address
-type(hipe_bifs, get_rts_param, 1, Xs) ->
-  strict(arg_types(hipe_bifs, get_rts_param, 1), Xs,
-	 fun (_) -> t_sup(t_integer(), t_nil()) end);
-type(hipe_bifs, invalidate_funinfo_native_addresses, 1, Xs) ->
-  strict(arg_types(hipe_bifs, invalidate_funinfo_native_addresses, 1), Xs,
-	 fun (_) -> t_nil() end);
-type(hipe_bifs, make_fe, 3, Xs) ->
-  strict(arg_types(hipe_bifs, make_fe, 3), Xs, fun (_) -> t_integer() end);
-%% type(hipe_bifs, make_native_stub, 2, Xs) ->
-%%    strict(arg_types(hipe_bifs, make_native_stub, 2), Xs,
-%%	   fun (_) -> t_integer() end); % address
-type(hipe_bifs, mark_referred_from, 1, Xs) ->
-  strict(arg_types(hipe_bifs, mark_referred_from, 1), Xs,
-	 fun (_) -> t_nil() end);
-type(hipe_bifs, merge_term, 1, Xs) ->
-  strict(arg_types(hipe_bifs, merge_term, 1), Xs, fun ([X]) -> X end);
-type(hipe_bifs, nstack_used_size, 0, _) ->
+			     t_sup(t_nil(), t_binary())]) end, Opaques);
+type(hipe_bifs, enter_sdesc, 1, Xs, Opaques) ->
+  strict(hipe_bifs, enter_sdesc, 1, Xs, fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, find_na_or_make_stub, 2, Xs, Opaques) ->
+  strict(hipe_bifs, find_na_or_make_stub, 2, Xs,
+	 fun (_) -> t_integer() end, Opaques); % address
+type(hipe_bifs, fun_to_address, 1, Xs, Opaques) ->
+  strict(hipe_bifs, fun_to_address, 1, Xs,
+	 fun (_) -> t_integer() end, Opaques);
+%% type(hipe_bifs, get_emu_address, 1, Xs, Opaques) ->
+%%    strict(hipe_bifs, get_emu_address, 1, Xs,
+%%	   fun (_) -> t_integer() end, Opaques); % address
+type(hipe_bifs, get_rts_param, 1, Xs, Opaques) ->
+  strict(hipe_bifs, get_rts_param, 1, Xs,
+	 fun (_) -> t_sup(t_integer(), t_nil()) end, Opaques);
+type(hipe_bifs, invalidate_funinfo_native_addresses, 1, Xs, Opaques) ->
+  strict(hipe_bifs, invalidate_funinfo_native_addresses, 1, Xs,
+	 fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, make_fe, 3, Xs, Opaques) ->
+  strict(hipe_bifs, make_fe, 3, Xs, fun (_) -> t_integer() end, Opaques);
+%% type(hipe_bifs, make_native_stub, 2, Xs, Opaques) ->
+%%    strict(hipe_bifs, make_native_stub, 2, Xs,
+%%	   fun (_) -> t_integer() end, Opaques); % address
+type(hipe_bifs, mark_referred_from, 1, Xs, Opaques) ->
+  strict(hipe_bifs, mark_referred_from, 1, Xs,
+	 fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, merge_term, 1, Xs, Opaques) ->
+  strict(hipe_bifs, merge_term, 1, Xs, fun ([X]) -> X end, Opaques);
+type(hipe_bifs, nstack_used_size, 0, _, _Opaques) ->
   t_non_neg_fixnum();
-type(hipe_bifs, patch_call, 3, Xs) ->
-  strict(arg_types(hipe_bifs, patch_call, 3), Xs, fun (_) -> t_nil() end);
-type(hipe_bifs, patch_insn, 3, Xs) ->
-  strict(arg_types(hipe_bifs, patch_insn, 3), Xs, fun (_) -> t_nil() end);
-type(hipe_bifs, primop_address, 1, Xs) ->
-  strict(arg_types(hipe_bifs, primop_address, 1), Xs,
-	 fun (_) -> t_sup(t_integer(), t_atom('false')) end);
-type(hipe_bifs, redirect_referred_from, 1, Xs) ->
-  strict(arg_types(hipe_bifs, redirect_referred_from, 1), Xs,
-	 fun (_) -> t_nil() end);
-type(hipe_bifs, ref, 1, Xs) ->
-  strict(arg_types(hipe_bifs, ref, 1), Xs, fun (_) -> t_immarray() end);
-type(hipe_bifs, ref_get, 1, Xs) ->
-  strict(arg_types(hipe_bifs, ref_get, 1), Xs, fun (_) -> t_immediate() end);
-type(hipe_bifs, ref_set, 2, Xs) ->
-  strict(arg_types(hipe_bifs, ref_set, 2), Xs, fun (_) -> t_nil() end);
-type(hipe_bifs, remove_refs_from, 1, Xs) ->
-  strict(arg_types(hipe_bifs, remove_refs_from, 1), Xs,
-	 fun (_) -> t_atom('ok') end);
-type(hipe_bifs, set_funinfo_native_address, 3, Xs) ->
-  strict(arg_types(hipe_bifs, set_funinfo_native_address, 3), Xs,
-	 fun (_) -> t_nil() end);
-type(hipe_bifs, set_native_address, 3, Xs) ->
-  strict(arg_types(hipe_bifs, set_native_address, 3), Xs,
-	 fun (_) -> t_nil() end);
-type(hipe_bifs, system_crc, 1, Xs) ->
-  strict(arg_types(hipe_bifs, system_crc, 1), Xs, fun (_) -> t_crc32() end);
-type(hipe_bifs, term_to_word, 1, Xs) ->
-  strict(arg_types(hipe_bifs, term_to_word, 1), Xs,
-	 fun (_) -> t_integer() end);
-type(hipe_bifs, update_code_size, 3, Xs) ->
-  strict(arg_types(hipe_bifs, update_code_size, 3), Xs,
-	 fun (_) -> t_nil() end);
-type(hipe_bifs, write_u8, 2, Xs) ->
-  strict(arg_types(hipe_bifs, write_u8, 2), Xs, fun (_) -> t_nil() end);
-type(hipe_bifs, write_u32, 2, Xs) ->
-  strict(arg_types(hipe_bifs, write_u32, 2), Xs, fun (_) -> t_nil() end);
-type(hipe_bifs, write_u64, 2, Xs) ->
-  strict(arg_types(hipe_bifs, write_u64, 2), Xs, fun (_) -> t_nil() end);
+type(hipe_bifs, patch_call, 3, Xs, Opaques) ->
+  strict(hipe_bifs, patch_call, 3, Xs, fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, patch_insn, 3, Xs, Opaques) ->
+  strict(hipe_bifs, patch_insn, 3, Xs, fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, primop_address, 1, Xs, Opaques) ->
+  strict(hipe_bifs, primop_address, 1, Xs,
+	 fun (_) -> t_sup(t_integer(), t_atom('false')) end, Opaques);
+type(hipe_bifs, redirect_referred_from, 1, Xs, Opaques) ->
+  strict(hipe_bifs, redirect_referred_from, 1, Xs,
+	 fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, ref, 1, Xs, Opaques) ->
+  strict(hipe_bifs, ref, 1, Xs, fun (_) -> t_immarray() end, Opaques);
+type(hipe_bifs, ref_get, 1, Xs, Opaques) ->
+  strict(hipe_bifs, ref_get, 1, Xs, fun (_) -> t_immediate() end, Opaques);
+type(hipe_bifs, ref_set, 2, Xs, Opaques) ->
+  strict(hipe_bifs, ref_set, 2, Xs, fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, remove_refs_from, 1, Xs, Opaques) ->
+  strict(hipe_bifs, remove_refs_from, 1, Xs,
+	 fun (_) -> t_atom('ok') end, Opaques);
+type(hipe_bifs, set_funinfo_native_address, 3, Xs, Opaques) ->
+  strict(hipe_bifs, set_funinfo_native_address, 3, Xs,
+	 fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, set_native_address, 3, Xs, Opaques) ->
+  strict(hipe_bifs, set_native_address, 3, Xs,
+	 fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, system_crc, 1, Xs, Opaques) ->
+  strict(hipe_bifs, system_crc, 1, Xs, fun (_) -> t_crc32() end, Opaques);
+type(hipe_bifs, term_to_word, 1, Xs, Opaques) ->
+  strict(hipe_bifs, term_to_word, 1, Xs,
+	 fun (_) -> t_integer() end, Opaques);
+type(hipe_bifs, update_code_size, 3, Xs, Opaques) ->
+  strict(hipe_bifs, update_code_size, 3, Xs,
+	 fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, write_u8, 2, Xs, Opaques) ->
+  strict(hipe_bifs, write_u8, 2, Xs, fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, write_u32, 2, Xs, Opaques) ->
+  strict(hipe_bifs, write_u32, 2, Xs, fun (_) -> t_nil() end, Opaques);
+type(hipe_bifs, write_u64, 2, Xs, Opaques) ->
+  strict(hipe_bifs, write_u64, 2, Xs, fun (_) -> t_nil() end, Opaques);
 %%-- lists --------------------------------------------------------------------
-type(lists, all, 2, Xs) ->
-  strict(arg_types(lists, all, 2), Xs, 
+type(lists, all, 2, Xs, Opaques) ->
+  strict(lists, all, 2, Xs,
 	 fun ([F, L]) -> 
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> t_atom('true');
 	       false ->
-		 El = t_list_elements(L),
-		 case check_fun_application(F, [El]) of
+		 El = t_list_elements(L, Opaques),
+		 case check_fun_application(F, [El], Opaques) of
 		   ok -> 
-		     case t_is_cons(L) of
-		       true -> t_fun_range(F);
+		     case t_is_cons(L, Opaques) of
+		       true -> t_fun_range(F, Opaques);
 		       false -> 
 			 %% The list can be empty.
-			 t_sup(t_atom('true'), t_fun_range(F))
+			 t_sup(t_atom('true'), t_fun_range(F, Opaques))
 		     end;
 		   error ->
-		     case t_is_cons(L) of
+		     case t_is_cons(L, Opaques) of
 		       true -> t_none();
-		       false -> t_fun_range(F)
+		       false -> t_fun_range(F, Opaques)
 		     end
 		 end
 	     end
-	 end);
-type(lists, any, 2, Xs) ->
-  strict(arg_types(lists, any, 2), Xs, 
+	 end, Opaques);
+type(lists, any, 2, Xs, Opaques) ->
+  strict(lists, any, 2, Xs,
 	 fun ([F, L]) -> 
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> t_atom('false');
 	       false ->
-		 El = t_list_elements(L),
-		 case check_fun_application(F, [El]) of
+		 El = t_list_elements(L, Opaques),
+		 case check_fun_application(F, [El], Opaques) of
 		   ok -> 
-		     case t_is_cons(L) of
-		       true -> t_fun_range(F);
+		     case t_is_cons(L, Opaques) of
+		       true -> t_fun_range(F, Opaques);
 		       false -> 
 			 %% The list can be empty
-			 t_sup(t_atom('false'), t_fun_range(F))
+			 t_sup(t_atom('false'), t_fun_range(F, Opaques))
 		     end;
 		   error ->
-		     case t_is_cons(L) of
+		     case t_is_cons(L, Opaques) of
 		       true -> t_none();
-		       false -> t_fun_range(F)
+		       false -> t_fun_range(F, Opaques)
 		     end
 		 end
 	     end
-	 end);
-type(lists, append, 2, Xs) -> type(erlang, '++', 2, Xs);  % alias
-type(lists, delete, 2, Xs) ->
-  strict(arg_types(lists, delete, 2), Xs, 
+	 end, Opaques);
+type(lists, append, 2, Xs, _Opaques) -> type(erlang, '++', 2, Xs);  % alias
+type(lists, delete, 2, Xs, Opaques) ->
+  strict(lists, delete, 2, Xs,
 	 fun ([_, List]) -> 
-	     case t_is_cons(List) of
+	     case t_is_cons(List, Opaques) of
 	       true -> t_cons_tl(List);
 	       false -> List
 	     end
-	 end);
-type(lists, dropwhile, 2, Xs) -> 
-  strict(arg_types(lists, dropwhile, 2), Xs,
+	 end, Opaques);
+type(lists, dropwhile, 2, Xs, Opaques) ->
+  strict(lists, dropwhile, 2, Xs,
 	 fun ([F, X]) -> 
-	     case t_is_nil(X) of
+	     case t_is_nil(X, Opaques) of
 	       true -> t_nil();
 	       false ->
-		 X1 = t_list_elements(X),
-		 case check_fun_application(F, [X1]) of
+		 X1 = t_list_elements(X, Opaques),
+		 case check_fun_application(F, [X1], Opaques) of
 		   ok ->
-		     case t_atom_vals(t_fun_range(F)) of
+		     case t_atom_vals(t_fun_range(F, Opaques), Opaques) of
 		       ['true'] ->
-			 case t_is_none(t_inf(t_list(), X)) of
+			 case t_is_none(t_inf(t_list(), X, Opaques)) of
 			   true -> t_none();
 			   false -> t_nil()
 			 end;
 		       ['false'] -> 
-			 case t_is_none(t_inf(t_list(), X)) of
+			 case t_is_none(t_inf(t_list(), X, Opaques)) of
 			   true -> t_none();
 			   false -> X
 			 end;
 		       _ -> 
-			 t_inf(t_cons_tl(t_inf(X, t_cons())), 
-			       t_maybe_improper_list())
+			 t_inf(t_cons_tl(t_inf(X, t_cons(), Opaques)),
+                             t_maybe_improper_list(), Opaques)
 		     end;
 		   error ->
-		     case t_is_cons(X) of
+		     case t_is_cons(X, Opaques) of
 		       true -> t_none();
 		       false -> t_nil()
 		     end
 		 end
 	     end
-	 end);
-type(lists, filter, 2, Xs) ->
-  strict(arg_types(lists, filter, 2), Xs,
+	 end, Opaques);
+type(lists, filter, 2, Xs, Opaques) ->
+  strict(lists, filter, 2, Xs,
 	 fun ([F, L]) -> 
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> t_nil();
 	       false ->
-		 T = t_list_elements(L),
-		 case check_fun_application(F, [T]) of
+		 T = t_list_elements(L, Opaques),
+		 case check_fun_application(F, [T], Opaques) of
 		   ok ->
-		     case t_atom_vals(t_fun_range(F)) =:= ['false'] of
+                     RangeVals = t_atom_vals(t_fun_range(F, Opaques), Opaques),
+		     case RangeVals =:= ['false'] of
 		       true -> t_nil();
 		       false -> 
-			 case t_atom_vals(t_fun_range(F)) =:= ['true'] of
+			 case RangeVals =:= ['true'] of
 			   true -> L;
 			   false -> t_list(T)
 			 end
 		     end;
 		   error ->
-		     case t_is_cons(L) of
+		     case t_is_cons(L, Opaques) of
 		       true -> t_none();
 		       false -> t_nil()
 		     end
 		 end
 	     end
-	 end);
-type(lists, flatten, 1, Xs) ->
-  strict(arg_types(lists, flatten, 1), Xs,
+	 end, Opaques);
+type(lists, flatten, 1, Xs, Opaques) ->
+  strict(lists, flatten, 1, Xs,
 	 fun ([L]) ->
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> L;    % (nil has undefined elements)
 	       false ->
 		 %% Avoiding infinite recursion is tricky
-		 X1 = t_list_elements(L),
+		 X1 = t_list_elements(L, Opaques),
 		 case t_is_any(X1) of
 		   true -> 
 		     t_list();
 		   false ->
-		     X2 = type(lists, flatten, 1, [t_inf(X1, t_list())]),
+		     X2 = type(lists, flatten, 1, [t_inf(X1, t_list(), Opaques)]),
 		     t_sup(t_list(t_subtract(X1, t_list())), X2)
 		 end
 	     end
-	 end);
-type(lists, flatmap, 2, Xs) ->
-  strict(arg_types(lists, flatmap, 2), Xs,
+	 end, Opaques);
+type(lists, flatmap, 2, Xs, Opaques) ->
+  strict(lists, flatmap, 2, Xs,
 	 fun ([F, List]) -> 
-	     case t_is_nil(List) of
+	     case t_is_nil(List, Opaques) of
 	       true -> t_nil();
 	       false ->
-		 case check_fun_application(F, [t_list_elements(List)]) of
+		 case
+                   check_fun_application(F, [t_list_elements(List, Opaques)],
+                                         Opaques)
+                 of
 		   ok ->
-		     R = t_fun_range(F),
+		     R = t_fun_range(F, Opaques),
 		     case t_is_nil(R) of
 		       true -> t_nil();
 		       false ->
-			 Elems = t_list_elements(R),
-			 case t_is_cons(List) of
+			 Elems = t_list_elements(R, Opaques),
+			 case t_is_cons(List, Opaques) of
 			   true ->
 			     case t_is_subtype(t_nil(), R) of
 			       true -> t_list(Elems);
@@ -1247,58 +1276,65 @@ type(lists, flatmap, 2, Xs) ->
 			 end
 		     end;
 		   error ->
-		     case t_is_cons(List) of
+		     case t_is_cons(List, Opaques) of
 		       true -> t_none();
 		       false -> t_nil()
 		     end
 		 end
  	     end
-	 end);
-type(lists, foreach, 2, Xs) ->
-  strict(arg_types(lists, foreach, 2), Xs,
+	 end, Opaques);
+type(lists, foreach, 2, Xs, Opaques) ->
+  strict(lists, foreach, 2, Xs,
 	 fun ([F, List]) ->
-	     case t_is_cons(List) of
+	     case t_is_cons(List, Opaques) of
 	       true ->
-		 case check_fun_application(F, [t_list_elements(List)]) of
+		 case
+                   check_fun_application(F, [t_list_elements(List, Opaques)],
+                                         Opaques)
+                 of
 		   ok -> t_atom('ok');
 		   error -> t_none()
 		 end;
 	       false ->
 		 t_atom('ok')
 	     end
-	 end);
-type(lists, foldl, 3, Xs) ->
-  strict(arg_types(lists, foldl, 3), Xs,
+	 end, Opaques);
+type(lists, foldl, 3, Xs, Opaques) ->
+  strict(lists, foldl, 3, Xs,
 	 fun ([F, Acc, List]) ->
-	     case t_is_nil(List) of
+	     case t_is_nil(List, Opaques) of
 	       true -> Acc;
 	       false ->
-		 case check_fun_application(F, [t_list_elements(List), Acc]) of
+		 case
+                   check_fun_application(F,
+                                         [t_list_elements(List, Opaques),Acc],
+                                         Opaques)
+                 of
 		   ok ->
-		     case t_is_cons(List) of
-		       true -> t_fun_range(F);
-		       false -> t_sup(t_fun_range(F), Acc)
+		     case t_is_cons(List, Opaques) of
+		       true -> t_fun_range(F, Opaques);
+		       false -> t_sup(t_fun_range(F, Opaques), Acc)
 		     end;
 		   error ->
-		     case t_is_cons(List) of
+		     case t_is_cons(List, Opaques) of
 		       true -> t_none();
 		       false -> Acc
 		     end
 		 end
 	     end
-	 end);
-type(lists, foldr, 3, Xs) -> type(lists, foldl, 3, Xs);    % same
-type(lists, keydelete, 3, Xs) ->
-  strict(arg_types(lists, keydelete, 3), Xs, 
+	 end, Opaques);
+type(lists, foldr, 3, Xs, _Opaques) -> type(lists, foldl, 3, Xs);  % same
+type(lists, keydelete, 3, Xs, Opaques) ->
+  strict(lists, keydelete, 3, Xs,
 	 fun ([_, _, L]) ->
 	     Term = t_list_termination(L),
 	     t_sup(Term, erl_types:lift_list_to_pos_empty(L))
-	 end);
-type(lists, keyfind, 3, Xs) ->
-  strict(arg_types(lists, keyfind, 3), Xs,
+	 end, Opaques);
+type(lists, keyfind, 3, Xs, Opaques) ->
+  strict(lists, keyfind, 3, Xs,
 	 fun ([X, Y, Z]) ->
-	     ListEs = t_list_elements(Z),
-	     Tuple = t_inf(t_tuple(), ListEs),
+	     ListEs = t_list_elements(Z, Opaques),
+	     Tuple = t_inf(t_tuple(), ListEs, Opaques),
 	     case t_is_none(Tuple) of
 	       true -> t_atom('false');
 	       false ->
@@ -1308,58 +1344,61 @@ type(lists, keyfind, 3, Xs) ->
 		 case t_is_any(X) of
 		   true -> Ret;
 		   false ->
-		     case t_tuple_subtypes(Tuple) of
+		     case t_tuple_subtypes(Tuple, Opaques) of
 		       unknown -> Ret;
 		       List ->
-			 case key_comparisons_fail(X, Y, List) of
+			 case key_comparisons_fail(X, Y, List, Opaques) of
 			   true -> t_atom('false');
 			   false -> Ret
 			 end
 		     end
 		 end
 	     end
-	 end);
-type(lists, keymap, 3, Xs) ->
-  strict(arg_types(lists, keymap, 3), Xs,
+	 end, Opaques);
+type(lists, keymap, 3, Xs, Opaques) ->
+  strict(lists, keymap, 3, Xs,
 	 fun ([F, _I, L]) ->
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> L;
-	       false -> t_list(t_sup(t_fun_range(F), t_list_elements(L)))
+	       false -> t_list(t_sup(t_fun_range(F, Opaques),
+                                     t_list_elements(L, Opaques)))
 	     end
-	 end);
-type(lists, keymember, 3, Xs) ->
-  strict(arg_types(lists, keymember, 3), Xs,
+	 end, Opaques);
+type(lists, keymember, 3, Xs, Opaques) ->
+  strict(lists, keymember, 3, Xs,
 	 fun ([X, Y, Z]) ->
-	     ListEs = t_list_elements(Z),
-	     Tuple = t_inf(t_tuple(), ListEs),
+	     ListEs = t_list_elements(Z, Opaques),
+	     Tuple = t_inf(t_tuple(), ListEs, Opaques),
 	     case t_is_none(Tuple) of
 	       true -> t_atom('false');
 	       false ->
 		 case t_is_any(X) of
 		   true -> t_boolean();
 		   false ->
-		     case t_tuple_subtypes(Tuple) of
+		     case t_tuple_subtypes(Tuple, Opaques) of
 		       unknown -> t_boolean();
 		       List ->
-			 case key_comparisons_fail(X, Y, List) of
+			 case key_comparisons_fail(X, Y, List, Opaques) of
 			   true -> t_atom('false');
 			   false -> t_boolean()
 			 end
 		     end
 		 end
 	     end
-	 end);
-type(lists, keymerge, 3, Xs) ->
-  strict(arg_types(lists, keymerge, 3), Xs,
-	 fun ([_I, L1, L2]) -> type(lists, merge, 2, [L1, L2]) end);
-type(lists, keyreplace, 4, Xs) ->
-  strict(arg_types(lists, keyreplace, 4), Xs,
-	 fun ([_K, _I, L, T]) -> t_list(t_sup(t_list_elements(L), T)) end);
-type(lists, keysearch, 3, Xs) ->
-  strict(arg_types(lists, keysearch, 3), Xs,
+	 end, Opaques);
+type(lists, keymerge, 3, Xs, Opaques) ->
+  strict(lists, keymerge, 3, Xs,
+	 fun ([_I, L1, L2]) -> type(lists, merge, 2, [L1, L2]) end, Opaques);
+type(lists, keyreplace, 4, Xs, Opaques) ->
+  strict(lists, keyreplace, 4, Xs,
+	 fun ([_K, _I, L, T]) ->
+             t_list(t_sup(t_list_elements(L, Opaques), T))
+         end, Opaques);
+type(lists, keysearch, 3, Xs, Opaques) ->
+  strict(lists, keysearch, 3, Xs,
 	 fun ([X, Y, Z]) ->
-	     ListEs = t_list_elements(Z),
-	     Tuple = t_inf(t_tuple(), ListEs),
+	     ListEs = t_list_elements(Z, Opaques),
+	     Tuple = t_inf(t_tuple(), ListEs, Opaques),
 	     case t_is_none(Tuple) of
 	       true -> t_atom('false');
 	       false ->
@@ -1368,91 +1407,93 @@ type(lists, keysearch, 3, Xs) ->
 		 case t_is_any(X) of
 		   true -> Ret;
 		   false ->
-		     case t_tuple_subtypes(Tuple) of
+		     case t_tuple_subtypes(Tuple, Opaques) of
 		       unknown -> Ret;
 		       List ->
-			 case key_comparisons_fail(X, Y, List) of
+			 case key_comparisons_fail(X, Y, List, Opaques) of
 			   true -> t_atom('false');
 			   false -> Ret
 			 end
 		     end
 		 end
 	     end
-	 end);
-type(lists, keysort, 2, Xs) ->
-  strict(arg_types(lists, keysort, 2), Xs, fun ([_, L]) -> L end);
-type(lists, last, 1, Xs) ->
-  strict(arg_types(lists, last, 1), Xs, fun ([L]) -> t_list_elements(L) end);
-type(lists, map, 2, Xs) ->
-  strict(arg_types(lists, map, 2), Xs,
+	 end, Opaques);
+type(lists, keysort, 2, Xs, Opaques) ->
+  strict(lists, keysort, 2, Xs, fun ([_, L]) -> L end, Opaques);
+type(lists, last, 1, Xs, Opaques) ->
+  strict(lists, last, 1, Xs,
+         fun ([L]) -> t_list_elements(L, Opaques) end, Opaques);
+type(lists, map, 2, Xs, Opaques) ->
+  strict(lists, map, 2, Xs,
 	 fun ([F, L]) -> 
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> L;
 	       false ->
-		 El = t_list_elements(L),
-		 case t_is_cons(L) of
+		 El = t_list_elements(L, Opaques),
+		 case t_is_cons(L, Opaques) of
 		   true ->
-		     case check_fun_application(F, [El]) of
-		       ok -> t_nonempty_list(t_fun_range(F));
+		     case check_fun_application(F, [El], Opaques) of
+		       ok -> t_nonempty_list(t_fun_range(F, Opaques));
 		       error -> t_none()
 		     end;
 		   false ->
-		     case check_fun_application(F, [El]) of
-		       ok -> t_list(t_fun_range(F));
+		     case check_fun_application(F, [El], Opaques) of
+		       ok -> t_list(t_fun_range(F, Opaques));
 		       error -> t_nil()
 		     end
 		 end
 	     end
-	 end);
-type(lists, mapfoldl, 3, Xs) ->
-  strict(arg_types(lists, mapfoldl, 3), Xs,
+	 end, Opaques);
+type(lists, mapfoldl, 3, Xs, Opaques) ->
+  strict(lists, mapfoldl, 3, Xs,
 	 fun ([F, Acc, List]) ->
-	     case t_is_nil(List) of
+	     case t_is_nil(List, Opaques) of
 	       true -> t_tuple([List, Acc]);
 	       false ->
-		 El = t_list_elements(List),
-		 R = t_fun_range(F),
-		 case t_is_cons(List) of
+		 El = t_list_elements(List, Opaques),
+		 R = t_fun_range(F, Opaques),
+		 case t_is_cons(List, Opaques) of
 		   true ->
-		     case check_fun_application(F, [El, Acc]) of
+		     case check_fun_application(F, [El, Acc], Opaques) of
 		       ok ->
 			 Fun = fun (RangeTuple) ->
-				   [T1, T2] = t_tuple_args(RangeTuple),
+				   [T1, T2] = t_tuple_args(RangeTuple, Opaques),
 				   t_tuple([t_nonempty_list(T1), T2])
 			       end,
-			 t_sup([Fun(ST) || ST <- t_tuple_subtypes(R)]);
+			 t_sup([Fun(ST) || ST <- t_tuple_subtypes(R, Opaques)]);
 		       error -> 
 			 t_none()
 		     end;
 		   false ->
-		     case check_fun_application(F, [El, Acc]) of
+		     case check_fun_application(F, [El, Acc], Opaques) of
 		       ok ->
 			 Fun = fun (RangeTuple) ->
-				   [T1, T2] = t_tuple_args(RangeTuple),
+				   [T1, T2] = t_tuple_args(RangeTuple, Opaques),
 				   t_tuple([t_list(T1), t_sup(Acc, T2)])
 			       end,
-			 t_sup([Fun(ST) || ST <- t_tuple_subtypes(R)]);
+			 t_sup([Fun(ST) || ST <- t_tuple_subtypes(R, Opaques)]);
 		       error ->
 			 t_tuple([t_nil(), Acc])
 		     end
 		 end
 	     end
-	 end);
-type(lists, mapfoldr, 3, Xs) -> type(lists, mapfoldl, 3, Xs);    % same
-type(lists, max, 1, Xs) ->
-  strict(arg_types(lists, max, 1), Xs, fun ([L]) -> t_list_elements(L) end);
-type(lists, member, 2, Xs) ->
-  strict(arg_types(lists, member, 2), Xs,
+	 end, Opaques);
+type(lists, mapfoldr, 3, Xs, _Opaques) -> type(lists, mapfoldl, 3, Xs); % same
+type(lists, max, 1, Xs, Opaques) ->
+  strict(lists, max, 1, Xs,
+         fun ([L]) -> t_list_elements(L, Opaques) end, Opaques);
+type(lists, member, 2, Xs, Opaques) ->
+  strict(lists, member, 2, Xs,
 	 fun ([X, Y]) ->
-	     Y1 = t_list_elements(Y),
-	     case t_is_none(t_inf(Y1, X)) of
+	     Y1 = t_list_elements(Y, Opaques),
+	     case t_is_none(t_inf(Y1, X, Opaques)) of
 	       true -> t_atom('false');
 	       false -> t_boolean()
 	     end
-	 end);
-%% type(lists, merge, 1, Xs) ->
-type(lists, merge, 2, Xs) ->
-  strict(arg_types(lists, merge, 2), Xs,
+	 end, Opaques);
+%% type(lists, merge, 1, Xs, Opaques) ->
+type(lists, merge, 2, Xs, Opaques) ->
+  strict(lists, merge, 2, Xs,
 	 fun ([L1, L2]) ->
 	     case t_is_none(L1) of
 	       true -> L2;
@@ -1462,30 +1503,31 @@ type(lists, merge, 2, Xs) ->
 		   false -> t_sup(L1, L2)
 		 end
 	     end
-	 end);
-type(lists, min, 1, Xs) ->
-  strict(arg_types(lists, min, 1), Xs, fun ([L]) -> t_list_elements(L) end);
-type(lists, nth, 2, Xs) ->
-  strict(arg_types(lists, nth, 2), Xs,
-	 fun ([_, Y]) -> t_list_elements(Y) end);
-type(lists, nthtail, 2, Xs) ->
-  strict(arg_types(lists, nthtail, 2), Xs,
-	 fun ([_, Y]) -> t_sup(Y, t_list()) end);
-type(lists, partition, 2, Xs) ->
-  strict(arg_types(lists, partition, 2), Xs,
+	 end, Opaques);
+type(lists, min, 1, Xs, Opaques) ->
+  strict(lists, min, 1, Xs,
+         fun ([L]) -> t_list_elements(L, Opaques) end, Opaques);
+type(lists, nth, 2, Xs, Opaques) ->
+  strict(lists, nth, 2, Xs,
+	 fun ([_, Y]) -> t_list_elements(Y, Opaques) end, Opaques);
+type(lists, nthtail, 2, Xs, Opaques) ->
+  strict(lists, nthtail, 2, Xs,
+	 fun ([_, Y]) -> t_sup(Y, t_list()) end, Opaques);
+type(lists, partition, 2, Xs, Opaques) ->
+  strict(lists, partition, 2, Xs,
 	 fun ([F, L]) ->
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> t_tuple([L,L]);
 	       false ->
-		 El = t_list_elements(L),
-		 case check_fun_application(F, [El]) of
+		 El = t_list_elements(L, Opaques),
+		 case check_fun_application(F, [El], Opaques) of
 		   error -> 
-		     case t_is_cons(L) of
+		     case t_is_cons(L, Opaques) of
 		       true -> t_none();
 		       false -> t_tuple([t_nil(), t_nil()])
 		     end;
 		   ok ->
-		     case t_atom_vals(t_fun_range(F)) of
+		     case t_atom_vals(t_fun_range(F, Opaques), Opaques) of
 		       ['true'] -> t_tuple([L, t_nil()]);
 		       ['false'] -> t_tuple([t_nil(), L]);
 		       [_, _] ->
@@ -1494,123 +1536,131 @@ type(lists, partition, 2, Xs) ->
 		     end
 		 end
 	     end
-	 end);
-type(lists, reverse, 1, Xs) ->
-  strict(arg_types(lists, reverse, 1), Xs, fun ([X]) -> X end);
-type(lists, reverse, 2, Xs) ->
+	 end, Opaques);
+type(lists, reverse, 1, Xs, Opaques) ->
+  strict(lists, reverse, 1, Xs, fun ([X]) -> X end, Opaques);
+type(lists, reverse, 2, Xs, _Opaques) ->
   type(erlang, '++', 2, Xs);    % reverse-onto is just like append
-type(lists, sort, 1, Xs) ->
-  strict(arg_types(lists, sort, 1), Xs, fun ([X]) -> X end);
-type(lists, sort, 2, Xs) ->
-  strict(arg_types(lists, sort, 2), Xs,
+type(lists, sort, 1, Xs, Opaques) ->
+  strict(lists, sort, 1, Xs, fun ([X]) -> X end, Opaques);
+type(lists, sort, 2, Xs, Opaques) ->
+  strict(lists, sort, 2, Xs,
 	 fun ([F, L]) ->
-	     R = t_fun_range(F),
-	     case t_is_boolean(R) of
+	     R = t_fun_range(F, Opaques),
+	     case t_is_boolean(R, Opaques) of
 	       true -> L;
 	       false ->
-		 case t_is_nil(L) of
+		 case t_is_nil(L, Opaques) of
 		   true -> t_nil();
 		   false -> t_none()
 		 end
 	     end
-	 end);
-type(lists, split, 2, Xs) ->
-  strict(arg_types(lists, split, 2), Xs,
+	 end, Opaques);
+type(lists, split, 2, Xs, Opaques) ->
+  strict(lists, split, 2, Xs,
 	 fun ([_, L]) ->
-	     case t_is_nil(L) of
+	     case t_is_nil(L, Opaques) of
 	       true -> t_tuple([L, L]);
 	       false ->
-		 T = t_list_elements(L),
+		 T = t_list_elements(L, Opaques),
 		 t_tuple([t_list(T), t_list(T)])
 	     end
-	 end);
-type(lists, splitwith, 2, Xs) -> 
+	 end, Opaques);
+type(lists, splitwith, 2, Xs, _Opaques) ->
   T1 = type(lists, takewhile, 2, Xs),
   T2 = type(lists, dropwhile, 2, Xs),
   case t_is_none(T1) orelse t_is_none(T2) of
     true -> t_none();
     false -> t_tuple([T1, T2])
   end;
-type(lists, subtract, 2, Xs) -> type(erlang, '--', 2, Xs);  % alias
-type(lists, takewhile, 2, Xs) ->
-  strict(arg_types(lists, takewhile, 2), Xs,
+type(lists, subtract, 2, Xs, _Opaques) -> type(erlang, '--', 2, Xs);  % alias
+type(lists, takewhile, 2, Xs, Opaques) ->
+  strict(lists, takewhile, 2, Xs,
 	 fun([F, L]) ->
-	     case t_is_none(t_inf(t_list(), L)) of
+	     case t_is_none(t_inf(t_list(), L, Opaques)) of
 	       false -> type(lists, filter, 2, Xs);
 	       true ->
 		 %% This works for non-proper lists as well.
-		 El = t_list_elements(L),
+		 El = t_list_elements(L, Opaques),
 		 type(lists, filter, 2, [F, t_list(El)])
 	     end
-	 end);
-type(lists, usort, 1, Xs) -> type(lists, sort, 1, Xs); % same
-type(lists, usort, 2, Xs) -> type(lists, sort, 2, Xs); % same
-type(lists, unzip, 1, Xs) ->
-  strict(arg_types(lists, unzip, 1), Xs, 
+	 end, Opaques);
+type(lists, usort, 1, Xs, _Opaques) -> type(lists, sort, 1, Xs); % same
+type(lists, usort, 2, Xs, _Opaques) -> type(lists, sort, 2, Xs); % same
+type(lists, unzip, 1, Xs, Opaques) ->
+  strict(lists, unzip, 1, Xs,
  	 fun ([Ps]) ->
-	     case t_is_nil(Ps) of
+	     case t_is_nil(Ps, Opaques) of
 	       true ->
 		 t_tuple([t_nil(), t_nil()]);
 	       false -> % Ps is a proper list of pairs
-		 TupleTypes = t_tuple_subtypes(t_list_elements(Ps)),
+		 TupleTypes = t_tuple_subtypes(t_list_elements(Ps, Opaques),
+                                               Opaques),
 		 lists:foldl(fun(Tuple, Acc) ->
-				 [A, B] = t_tuple_args(Tuple),
+				 [A, B] = t_tuple_args(Tuple, Opaques),
 				 t_sup(t_tuple([t_list(A), t_list(B)]), Acc)
 			     end, t_none(), TupleTypes)
 	     end
- 	 end);
-type(lists, unzip3, 1, Xs) ->
-  strict(arg_types(lists, unzip3, 1), Xs, 
+         end, Opaques);
+type(lists, unzip3, 1, Xs, Opaques) ->
+  strict(lists, unzip3, 1, Xs,
  	 fun ([Ts]) ->
-	     case t_is_nil(Ts) of
+	     case t_is_nil(Ts, Opaques) of
 	       true ->
 		 t_tuple([t_nil(), t_nil(), t_nil()]);
 	       false -> % Ps is a proper list of triples
-		 TupleTypes = t_tuple_subtypes(t_list_elements(Ts)),
+		 TupleTypes = t_tuple_subtypes(t_list_elements(Ts, Opaques),
+                                              Opaques),
 		 lists:foldl(fun(T, Acc) ->
-				 [A, B, C] = t_tuple_args(T),
+				 [A, B, C] = t_tuple_args(T, Opaques),
 				 t_sup(t_tuple([t_list(A), 
 						t_list(B), 
 						t_list(C)]),
 				       Acc)
 			     end, t_none(), TupleTypes)
 	     end
- 	 end);
-type(lists, zip, 2, Xs) ->
-  strict(arg_types(lists, zip, 2), Xs,
+         end, Opaques);
+type(lists, zip, 2, Xs, Opaques) ->
+  strict(lists, zip, 2, Xs,
 	 fun ([As, Bs]) ->
-	     case (t_is_nil(As) orelse t_is_nil(Bs)) of
+	     case (t_is_nil(As, Opaques) orelse t_is_nil(Bs, Opaques)) of
 	       true -> t_nil();
 	       false ->
-		 A = t_list_elements(As),
-		 B = t_list_elements(Bs),
+		 A = t_list_elements(As, Opaques),
+		 B = t_list_elements(Bs, Opaques),
 		 t_list(t_tuple([A, B]))
 	     end
-	 end);
-type(lists, zip3, 3, Xs) ->
-  strict(arg_types(lists, zip3, 3), Xs,
+	 end, Opaques);
+type(lists, zip3, 3, Xs, Opaques) ->
+  strict(lists, zip3, 3, Xs,
 	 fun ([As, Bs, Cs]) ->
-	     case (t_is_nil(As) orelse t_is_nil(Bs) orelse t_is_nil(Cs)) of
+	     case
+               (t_is_nil(As, Opaques)
+                orelse t_is_nil(Bs, Opaques)
+                orelse t_is_nil(Cs, Opaques))
+             of
 	       true -> t_nil();
 	       false ->
-		 A = t_list_elements(As),
-		 B = t_list_elements(Bs),
-		 C = t_list_elements(Cs),
+		 A = t_list_elements(As, Opaques),
+		 B = t_list_elements(Bs, Opaques),
+		 C = t_list_elements(Cs, Opaques),
 		 t_list(t_tuple([A, B, C]))
 	     end
-	 end);
-type(lists, zipwith, 3, Xs) ->
-  strict(arg_types(lists, zipwith, 3), Xs,
-	 fun ([F, _As, _Bs]) -> t_sup(t_list(t_fun_range(F)), t_nil()) end);
-type(lists, zipwith3, 4, Xs) ->
-  strict(arg_types(lists, zipwith3, 4), Xs,
-	 fun ([F,_As,_Bs,_Cs]) -> t_sup(t_list(t_fun_range(F)), t_nil()) end);
+	 end, Opaques);
+type(lists, zipwith, 3, Xs, Opaques) ->
+  strict(lists, zipwith, 3, Xs,
+	 fun ([F, _As, _Bs]) -> t_sup(t_list(t_fun_range(F, Opaques)),
+                                      t_nil()) end, Opaques);
+type(lists, zipwith3, 4, Xs, Opaques) ->
+  strict(lists, zipwith3, 4, Xs,
+	 fun ([F,_As,_Bs,_Cs]) -> t_sup(t_list(t_fun_range(F, Opaques)),
+                                        t_nil()) end, Opaques);
 
 %%-- string -------------------------------------------------------------------
-type(string, chars, 2, Xs) ->  % NOTE: added to avoid loss of information
-  strict(arg_types(string, chars, 2), Xs, fun (_) -> t_string() end);
-type(string, chars, 3, Xs) ->  % NOTE: added to avoid loss of information
-  strict(arg_types(string, chars, 3), Xs,
+type(string, chars, 2, Xs, Opaques) ->  % NOTE: added to avoid loss of info
+  strict(string, chars, 2, Xs, fun (_) -> t_string() end, Opaques);
+type(string, chars, 3, Xs, Opaques) -> % NOTE: added to avoid loss of info
+  strict(string, chars, 3, Xs,
 	 fun ([Char, N, Tail]) ->
 	     case t_is_nil(Tail) of
 	       true ->
@@ -1623,10 +1673,10 @@ type(string, chars, 3, Xs) ->  % NOTE: added to avoid loss of information
 		     t_sup(t_sup(t_string(), Tail), t_cons(Char, Tail))
 		 end
 	     end
-	 end);
+	 end, Opaques);
 
 %%-----------------------------------------------------------------------------
-type(M, F, A, Xs) when is_atom(M), is_atom(F),
+type(M, F, A, Xs, _O) when is_atom(M), is_atom(F),
 		       is_integer(A), 0 =< A, A =< 255 ->
   strict(Xs, t_any()).  % safe approximation for all functions.
 
@@ -1635,13 +1685,20 @@ type(M, F, A, Xs) when is_atom(M), is_atom(F),
 %% Auxiliary functions
 %%-----------------------------------------------------------------------------
 
-strict(Xs, Ts, F) ->
-  %% io:format("inf lists arg~n1:~p~n2:~p ~n", [Xs, Ts]),
-  Xs1 = inf_lists(Xs, Ts),
+strict(M, F, A, Xs, Fun, Opaques) ->
+  Ts = arg_types(M, F, A),
+  %% io:format("inf lists arg~nXs: ~p~nTs: ~p ~n", [Xs, Ts]),
+  Xs1 = inf_lists(Xs, Ts, Opaques),
   %% io:format("inf lists return ~p ~n", [Xs1]),
   case any_is_none_or_unit(Xs1) of
     true -> t_none();
-    false -> F(Xs1)
+    false -> Fun(Xs1)
+  end.
+
+strict2(Xs, X) ->
+  case any_is_none_or_unit(Xs) of
+    true -> t_none();
+    false -> X
   end.
 
 strict(Xs, X) ->
@@ -1650,9 +1707,9 @@ strict(Xs, X) ->
     false -> X
   end.
 
-inf_lists([X | Xs], [T | Ts]) ->
-  [t_inf(X, T) | inf_lists(Xs, Ts)];
-inf_lists([], []) ->
+inf_lists([X | Xs], [T | Ts], Opaques) ->
+  [t_inf(X, T, Opaques) | inf_lists(Xs, Ts, Opaques)];
+inf_lists([], [], _Opaques) ->
   [].
 
 any_list(N) -> any_list(N, t_any()).
@@ -1670,20 +1727,43 @@ list_replace(1, E, [_X | Xs]) ->
 any_is_none_or_unit(Ts) ->
   lists:any(fun erl_types:t_is_none_or_unit/1, Ts).
 
-check_guard([X], Test, Type) ->
-  check_guard_single(X, Test, Type).
+check_guard([X], Test, Type, Opaques) ->
+  check_guard_single(X, Test, Type, Opaques).
 
-check_guard_single(X, Test, Type) ->
+check_guard_single(X, Test, Type, Opaques) ->
   case Test(X) of
     true -> t_atom('true');
     false ->
-      case erl_types:t_is_opaque(X) of
-	true -> t_none();
-	false ->
-	  case t_is_none(t_inf(Type, X)) of
-	    true -> t_atom('false');
-	    false -> t_boolean()
-	  end
+      case t_is_none(t_inf(Type, X, Opaques)) of
+        true ->
+          case t_has_opaque_subtype(X, Opaques) of
+            true -> t_none();
+            false -> t_atom('false')
+          end;
+        false -> t_boolean()
+      end
+  end.
+
+check_record_tag(Tag, Y, Opaques) ->
+  case t_is_atom(Tag, Opaques) of
+    false ->
+      TagAtom = t_inf(Tag, t_atom(), Opaques),
+      case t_is_none(TagAtom) of
+        true ->
+          case t_has_opaque_subtype(Tag, Opaques) of
+            true -> t_none();
+            false -> t_atom('false')
+          end;
+        false -> t_boolean()
+      end;
+    true ->
+      case t_atom_vals(Tag, Opaques) of
+        [RealTag] ->
+          case t_atom_vals(Y, Opaques) of
+            [RealTag] -> t_atom('true');
+            _ -> t_boolean()
+          end;
+        _ -> t_boolean()
       end
   end.
 
@@ -1828,12 +1908,12 @@ negwidth(X, N) ->
     false -> negwidth(X, N+1)
   end.
 
-arith('bnot', X1) ->
-  case t_is_integer(X1) of
+arith('bnot', X1, Opaques) ->
+  case t_is_integer(X1, Opaques) of
     false -> error;
     true ->
-      Min1 = number_min(X1),
-      Max1 = number_max(X1),
+      Min1 = number_min(X1, Opaques),
+      Max1 = number_max(X1, Opaques),
       {ok, t_from_range(infinity_add(infinity_inv(Max1), -1),
 			infinity_add(infinity_inv(Min1), -1))}
   end.
@@ -1907,13 +1987,13 @@ arith_bor_range_set({Min, Max}, [Int|IntList]) ->
 	      IntList),
   {infinity_bor(Min, SafeAnd), infinity_bor(Max, SafeAnd)}.
 	      
-arith_band(X1, X2) ->
-  L1 = t_number_vals(X1), 
-  L2 = t_number_vals(X2),
-  Min1 = number_min(X1),
-  Max1 = number_max(X1),
-  Min2 = number_min(X2),
-  Max2 = number_max(X2),
+arith_band(X1, X2, Opaques) ->
+  L1 = t_number_vals(X1, Opaques),
+  L2 = t_number_vals(X2, Opaques),
+  Min1 = number_min(X1, Opaques),
+  Max1 = number_max(X1, Opaques),
+  Min2 = number_min(X2, Opaques),
+  Max2 = number_max(X2, Opaques),
   case {L1 =:= unknown, L2 =:= unknown} of
     {true, false} ->
       arith_band_range_set(arith_band_ranges(Min1, Max1, Min2, Max2), L2);
@@ -1923,13 +2003,13 @@ arith_band(X1, X2) ->
       arith_band_ranges(Min1, Max1, Min2, Max2)
   end.
 
-arith_bor(X1, X2) ->
-  L1 = t_number_vals(X1), 
-  L2 = t_number_vals(X2),
-  Min1 = number_min(X1),
-  Max1 = number_max(X1),
-  Min2 = number_min(X2),
-  Max2 = number_max(X2),
+arith_bor(X1, X2, Opaques) ->
+  L1 = t_number_vals(X1, Opaques),
+  L2 = t_number_vals(X2, Opaques),
+  Min1 = number_min(X1, Opaques),
+  Max1 = number_max(X1, Opaques),
+  Min2 = number_min(X2, Opaques),
+  Max2 = number_max(X2, Opaques),
   case {L1 =:= unknown, L2 =:= unknown} of
     {true, false} ->
       arith_bor_range_set(arith_bor_ranges(Min1, Max1, Min2, Max2), L2);
@@ -1967,19 +2047,19 @@ arith_bor_ranges(Min1, Max1, Min2, Max2) ->
     end,
   {Min, Max}.
 
-arith(Op, X1, X2) ->
+arith(Op, X1, X2, Opaques) ->
   %% io:format("arith ~p ~p ~p~n", [Op, X1, X2]),
-  case t_is_integer(X1) andalso t_is_integer(X2) of
+  case t_is_integer(X1, Opaques) andalso t_is_integer(X2, Opaques) of
     false -> error;
     true ->
-      L1 = t_number_vals(X1), 
-      L2 = t_number_vals(X2),
+      L1 = t_number_vals(X1, Opaques),
+      L2 = t_number_vals(X2, Opaques),
       case (L1 =:= unknown) orelse (L2 =:= unknown) of
 	true ->
-	  Min1 = number_min(X1),
-	  Max1 = number_max(X1),
-	  Min2 = number_min(X2),
-	  Max2 = number_max(X2),
+	  Min1 = number_min(X1, Opaques),
+	  Max1 = number_max(X1, Opaques),
+	  Min2 = number_min(X2, Opaques),
+	  Max2 = number_max(X2, Opaques),
 	  {NewMin, NewMax} =
 	    case Op of
 	      '+'    -> {infinity_add(Min1, Min2), infinity_add(Max1, Max2)};
@@ -1992,8 +2072,8 @@ arith(Op, X1, X2) ->
 	      'bsr'  -> NewMin2 = infinity_inv(Max2),
 			NewMax2 = infinity_inv(Min2),
 			arith_bsl(Min1, Max1, NewMin2, NewMax2);
-	      'band' -> arith_band(X1, X2);
-	      'bor'  -> arith_bor(X1, X2);
+	      'band' -> arith_band(X1, X2, Opaques);
+	      'bor'  -> arith_bor(X1, X2, Opaques);
 	      'bxor' -> arith_bor_ranges(Min1, Max1, Min2, Max2) %% overaprox.
 	    end,
 	  %% io:format("done arith ~p = ~p~n", [Op, {NewMin, NewMax}]),
@@ -2025,58 +2105,62 @@ arith(Op, X1, X2) ->
 %% Comparison of terms
 %%=============================================================================
 
-compare(Op, Lhs, Rhs) ->
-  case t_is_none(t_inf(Lhs, Rhs)) of
+compare(Op, Lhs, Rhs, Opaques) ->
+  case t_is_none(t_inf(Lhs, Rhs, Opaques)) of
     false -> t_boolean();
     true ->
-      case Op of
-	'<' -> always_smaller(Lhs, Rhs);
-	'>' -> always_smaller(Rhs, Lhs);
-	'=<' -> always_smaller(Lhs, Rhs);
-	'>=' -> always_smaller(Rhs, Lhs)
+      case opaque_args(erlang, Op, 2, [Lhs, Rhs], Opaques) =:= [] of
+        true ->
+          case Op of
+            '<' -> always_smaller(Lhs, Rhs, Opaques);
+            '>' -> always_smaller(Rhs, Lhs, Opaques);
+            '=<' -> always_smaller(Lhs, Rhs, Opaques);
+            '>=' -> always_smaller(Rhs, Lhs, Opaques)
+          end;
+        false -> t_none()
       end
   end.
 
-always_smaller(Type1, Type2) ->
-  {Min1, Max1} = type_ranks(Type1),
-  {Min2, Max2} = type_ranks(Type2),
+always_smaller(Type1, Type2, Opaques) ->
+  {Min1, Max1} = type_ranks(Type1, Opaques),
+  {Min2, Max2} = type_ranks(Type2, Opaques),
   if Max1 < Min2 -> t_atom('true');
      Min1 > Max2 -> t_atom('false');
      true        -> t_boolean()
   end.
 
-type_ranks(Type) ->
-  type_ranks(Type, 1, 0, 0, type_order()).
+type_ranks(Type, Opaques) ->
+  type_ranks(Type, 1, 0, 0, type_order(), Opaques).
 
-type_ranks(_Type, _I, Min, Max, []) -> {Min, Max};
-type_ranks(Type, I, Min, Max, [TypeClass|Rest]) ->
+type_ranks(_Type, _I, Min, Max, [], _Opaques) -> {Min, Max};
+type_ranks(Type, I, Min, Max, [TypeClass|Rest], Opaques) ->
   {NewMin, NewMax} =
-    case t_is_none(t_inf(Type, TypeClass)) of
+    case t_is_none(t_inf(Type, TypeClass, Opaques)) of
       true  -> {Min, Max};
       false -> case Min of
 		 0 -> {I, I};
 		 _ -> {Min, I}
 	       end
     end,
-  type_ranks(Type, I+1, NewMin, NewMax, Rest).
+  type_ranks(Type, I+1, NewMin, NewMax, Rest, Opaques).
 
 type_order() ->
   [t_number(), t_atom(), t_reference(), t_fun(), t_port(), t_pid(), t_tuple(),
    t_list(), t_binary()].
 
-key_comparisons_fail(X0, KeyPos, TupleList) ->
-  X = case t_is_number(t_inf(X0, t_number())) of
+key_comparisons_fail(X0, KeyPos, TupleList, Opaques) ->
+  X = case t_is_number(t_inf(X0, t_number(), Opaques), Opaques) of
 	false -> X0;
 	true -> t_number()
       end,
   lists:all(fun(Tuple) ->
 		Key = type(erlang, element, 2, [KeyPos, Tuple]),
-		t_is_none(t_inf(Key, X))
+		t_is_none(t_inf(Key, X, Opaques))
 	    end, TupleList).
 
 %%=============================================================================
 
--spec arg_types(atom(), atom(), arity()) -> [erl_types:erl_type()] | 'unknown'.
+-spec arg_types(atom(), atom(), arity()) -> arg_types() | 'unknown'.
 
 %%------- erlang --------------------------------------------------------------
 arg_types(erlang, '!', 2) ->
@@ -2508,47 +2592,78 @@ arg_types(M, F, A) when is_atom(M), is_atom(F),
   unknown.                     % safe approximation for all functions.
 
 
--spec is_known(atom(), atom(), arity()) -> boolean().
+-spec is_known(module(), atom(), arity()) -> boolean().
 
 is_known(M, F, A) ->
   arg_types(M, F, A) =/= unknown.
 
+-spec opaque_args(module(), atom(), arity(),
+                  arg_types(), opaques()) -> [pos_integer()].
+
+%% Use this function to find out which argument caused empty type.
+
+opaque_args(_M, _F, _A, _Xs, 'universe') -> [];
+opaque_args(M, F, A, Xs, Opaques) ->
+  case kind_of_check(M, F, A) of
+    record ->
+      [X,Y|_] = Xs,
+      [1 ||
+        case t_is_tuple(X, Opaques) of
+          true ->
+            case t_tuple_subtypes(X, Opaques) of
+              unknown -> false;
+              List when length(List) >= 1 -> opaque_recargs(List, Y, Opaques)
+            end;
+          false -> t_has_opaque_subtype(X, Opaques)
+        end];
+    subtype ->
+      [N ||
+        {N, X} <- lists:zip(lists:seq(1, length(Xs)), Xs),
+        t_has_opaque_subtype(X, Opaques)];
+    find_unknown ->
+      [L, R] = Xs,
+      erl_types:t_find_unknown_opaque(L, R, Opaques);
+    no_check -> []
+  end.
 
--spec structure_inspecting_args(atom(), atom(), arity()) -> [1..255].
-
-structure_inspecting_args(erlang, element, 2) -> [2];
-structure_inspecting_args(erlang, is_atom, 1) -> [1];
-structure_inspecting_args(erlang, is_boolean, 1) -> [1];
-structure_inspecting_args(erlang, is_binary, 1) -> [1];
-structure_inspecting_args(erlang, is_bitstring, 1) -> [1];
-structure_inspecting_args(erlang, is_float, 1) -> [1];
-structure_inspecting_args(erlang, is_function, 1) -> [1];
-structure_inspecting_args(erlang, is_integer, 1) -> [1];
-structure_inspecting_args(erlang, is_list, 1) -> [1];
-structure_inspecting_args(erlang, is_number, 1) -> [1];
-structure_inspecting_args(erlang, is_pid, 1) -> [1];
-structure_inspecting_args(erlang, is_port, 1) -> [1];
-structure_inspecting_args(erlang, is_reference, 1) -> [1];
-structure_inspecting_args(erlang, is_tuple, 1) -> [1];
-structure_inspecting_args(erlang, length, 1) -> [1];
-%%structure_inspecting_args(erlang, setelement, 3) -> [2].
-structure_inspecting_args(_, _, _) -> []. % XXX: assume no arg needs inspection
-
-
-check_fun_application(Fun, Args) ->
-  case t_is_fun(Fun) of
+kind_of_check(erlang, is_record, 3) ->
+  record;
+kind_of_check(erlang, is_record, 2) ->
+  record;
+kind_of_check(erlang, F, A) ->
+  case erl_internal:guard_bif(F, A) orelse erl_internal:bool_op(F, A) of
+    true -> subtype;
+    false ->
+      case erl_internal:comp_op(F, A) of
+        true -> find_unknown;
+        false -> no_check
+      end
+  end;
+kind_of_check(_M, _F, _A) -> no_check.
+
+opaque_recargs(Tuples, Y, Opaques) ->
+  Fun = fun(Tuple) ->
+            case t_tuple_args(Tuple, Opaques) of
+              [Tag|_] -> t_is_none(check_record_tag(Tag, Y, Opaques));
+              _ -> false
+            end
+        end,
+  lists:all(Fun, Tuples).
+
+check_fun_application(Fun, Args, Opaques) ->
+  case t_is_fun(Fun, Opaques) of
     true ->
-      case t_fun_args(Fun) of
+      case t_fun_args(Fun, Opaques) of
 	unknown ->
-	  case t_is_none_or_unit(t_fun_range(Fun)) of
+	  case t_is_none_or_unit(t_fun_range(Fun, Opaques)) of
 	    true -> error;
 	    false -> ok
 	  end;
 	FunDom when length(FunDom) =:= length(Args) ->
-	  case any_is_none_or_unit(inf_lists(FunDom, Args)) of
+	  case any_is_none_or_unit(inf_lists(FunDom, Args, Opaques)) of
 	    true -> error;
 	    false ->
-	      case t_is_none_or_unit(t_fun_range(Fun)) of
+	      case t_is_none_or_unit(t_fun_range(Fun, Opaques)) of
 		true -> error;
 		false -> ok
 	      end
diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index d7d8a878c5..cfa72d85b7 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -2,7 +2,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2003-2013. All Rights Reserved.
+%% Copyright Ericsson AB 2003-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -42,15 +42,15 @@
 	 max/2,
 	 module_builtin_opaques/1,
 	 min/2,
-	 number_max/1,
-	 number_min/1,
+	 number_max/1, number_max/2,
+	 number_min/1, number_min/2,
 	 t_abstract_records/2,
 	 t_any/0,
 	 t_arity/0,
 	 t_atom/0,
 	 t_atom/1,
 	 t_atoms/1,
-	 t_atom_vals/1,
+	 t_atom_vals/1, t_atom_vals/2,
 	 t_binary/0,
 	 t_bitstr/0,
 	 t_bitstr/2,
@@ -66,12 +66,14 @@
 	 t_collect_vars/1,
 	 t_cons/0,
 	 t_cons/2,
-	 t_cons_hd/1,
-	 t_cons_tl/1,
+	 t_cons_hd/1, t_cons_hd/2,
+	 t_cons_tl/1, t_cons_tl/2,
 	 t_constant/0,
-	 t_contains_opaque/1,
+         t_contains_opaque/1, t_contains_opaque/2,
+         t_decorate_with_opaque/3,
 	 t_elements/1,
 	 t_find_opaque_mismatch/2,
+         t_find_unknown_opaque/3,
 	 t_fixnum/0,
 	 t_map/2,
 	 t_non_neg_fixnum/0,
@@ -87,18 +89,18 @@
 	 t_fun/0,
 	 t_fun/1,
 	 t_fun/2,
-	 t_fun_args/1,
-	 t_fun_arity/1,
-	 t_fun_range/1,
-	 t_has_opaque_subtype/1,
+	 t_fun_args/1, t_fun_args/2,
+	 t_fun_arity/1, t_fun_arity/2,
+	 t_fun_range/1, t_fun_range/2,
+	 t_has_opaque_subtype/2,
 	 t_has_var/1,
 	 t_identifier/0,
 	 %% t_improper_list/2,
-	 t_inf/2,
-	 t_inf/3,
-	 t_inf_lists/2,
-	 t_inf_lists/3,
-	 t_inf_lists_masked/3,
+         t_inf/1,
+         t_inf/2,
+         t_inf/3,
+         t_inf_lists/2,
+         t_inf_lists/3,
 	 t_integer/0,
 	 t_integer/1,
 	 t_non_neg_integer/0,
@@ -107,44 +109,44 @@
 	 t_iodata/0,
 	 t_iolist/0,
 	 t_is_any/1,
-	 t_is_atom/1,
-	 t_is_atom/2,
-	 t_is_binary/1,
-	 t_is_bitstr/1,
+	 t_is_atom/1, t_is_atom/2,
+	 t_is_any_atom/2, t_is_any_atom/3,
+	 t_is_binary/1, t_is_binary/2,
+	 t_is_bitstr/1, t_is_bitstr/2,
 	 t_is_bitwidth/1,
-	 t_is_boolean/1,
+	 t_is_boolean/1, t_is_boolean/2,
 	 %% t_is_byte/1,
 	 %% t_is_char/1,
-	 t_is_cons/1,
+	 t_is_cons/1, t_is_cons/2,
 	 t_is_constant/1,
 	 t_is_equal/2,
 	 t_is_fixnum/1,
-	 t_is_float/1,
-	 t_is_fun/1,
+	 t_is_float/1, t_is_float/2,
+	 t_is_fun/1, t_is_fun/2,
 	 t_is_instance/2,
-	 t_is_integer/1,
+	 t_is_integer/1, t_is_integer/2,
 	 t_is_list/1,
 	 t_is_matchstate/1,
-	 t_is_nil/1,
+	 t_is_nil/1, t_is_nil/2,
 	 t_is_non_neg_integer/1,
 	 t_is_none/1,
 	 t_is_none_or_unit/1,
-	 t_is_number/1,
-	 t_is_opaque/1,
-	 t_is_pid/1,
-	 t_is_port/1,
-	 t_is_maybe_improper_list/1,
-	 t_is_reference/1,
+	 t_is_number/1, t_is_number/2,
+	 t_is_opaque/1, t_is_opaque/2,
+	 t_is_pid/1, t_is_pid/2,
+	 t_is_port/1, t_is_port/2,
+	 t_is_maybe_improper_list/1, t_is_maybe_improper_list/2,
+	 t_is_reference/1, t_is_reference/2,
 	 t_is_remote/1,
 	 t_is_string/1,
 	 t_is_subtype/2,
-	 t_is_tuple/1,
+	 t_is_tuple/1, t_is_tuple/2,
 	 t_is_unit/1,
 	 t_is_var/1,
 	 t_limit/2,
 	 t_list/0,
 	 t_list/1,
-	 t_list_elements/1,
+	 t_list_elements/1, t_list_elements/2,
 	 t_list_termination/1,
 	 t_matchstate/0,
 	 t_matchstate/2,
@@ -163,11 +165,8 @@
 	 t_nonempty_string/0,
 	 t_number/0,
 	 t_number/1,
-	 t_number_vals/1,
+	 t_number_vals/1, t_number_vals/2,
 	 t_opaque_from_records/1,
-	 t_opaque_match_atom/2,
-	 t_opaque_match_record/2,
-	 t_opaque_matching_structure/2,
 	 t_opaque_structure/1,
 	 %% t_parameterized_module/0,
 	 t_pid/0,
@@ -192,16 +191,14 @@
 	 t_to_tlist/1,
 	 t_tuple/0,
 	 t_tuple/1,
-	 t_tuple_args/1,
-	 t_tuple_size/1,
+	 t_tuple_args/1, t_tuple_args/2,
+	 t_tuple_size/1, t_tuple_size/2,
 	 t_tuple_sizes/1,
 	 t_tuple_subtypes/1,
+         t_tuple_subtypes/2,
 	 t_unify/2,
-	 t_unify/3,
 	 t_unit/0,
-	 t_unopaque/1,
-	 t_unopaque/2,
-	 t_unopaque_on_mismatch/3,
+	 t_unopaque/1, t_unopaque/2,
 	 t_var/1,
 	 t_var_name/1,
 	 %% t_assign_variables_to_subtype/2,
@@ -209,6 +206,7 @@
 	 record_field_diffs_to_string/2,
 	 subst_all_vars_to_any/1,
 	 lift_list_to_pos_empty/1,
+         is_opaque_type/2,
 	 is_erl_type/1,
 	 atom_to_string/1
 	]).
@@ -228,6 +226,14 @@
 
 -export_type([erl_type/0]).
 
+%%-define(DEBUG, true).
+
+-ifdef(DEBUG).
+-define(debug(__A), __A).
+-else.
+-define(debug(__A), ok).
+-endif.
+
 %%=============================================================================
 %%
 %% Definition of the type structure
@@ -310,6 +316,9 @@
 
 -record(int_set, {set :: [integer()]}).
 -record(int_rng, {from :: rng_elem(), to :: rng_elem()}).
+%% Note: the definition of #opaque{} was changed to 'mod' and 'name';
+%% it used to be an ordsets of {Mod, Name} pairs. The Dialyzer version
+%% was updated to 2.7 due to this change.
 -record(opaque,  {mod :: module(), name :: atom(),
 		  args = [] :: [erl_type()], struct :: erl_type()}).
 -record(remote,  {mod:: module(), name :: atom(), args = [] :: [erl_type()]}).
@@ -346,6 +355,8 @@
 -define(integer_non_neg,           ?int_range(0, pos_inf)).
 -define(integer_neg,               ?int_range(neg_inf, -1)).
 
+-type opaques() :: [erl_type()] | 'universe'.
+
 %%-----------------------------------------------------------------------------
 %% Unions
 %%
@@ -384,8 +395,11 @@ t_any() ->
 
 -spec t_is_any(erl_type()) -> boolean().
 
-t_is_any(?any) -> true;
-t_is_any(_) -> false.
+t_is_any(Type) ->
+  do_opaque(Type, 'universe', fun is_any/1).
+
+is_any(?any) -> true;
+is_any(_) -> false.
 
 -spec t_none() -> erl_type().
 
@@ -407,16 +421,25 @@ t_opaque(Mod, Name, Args, Struct) ->
   O = #opaque{mod = Mod, name = Name, args = Args, struct = Struct},
   ?opaque(set_singleton(O)).
 
+-spec t_is_opaque(erl_type(), [erl_type()]) -> boolean().
+
+t_is_opaque(?opaque(_) = Type, Opaques) ->
+  not is_opaque_type(Type, Opaques);
+t_is_opaque(_Type, _Opaques) -> false.
+
 -spec t_is_opaque(erl_type()) -> boolean().
 
 t_is_opaque(?opaque(_)) -> true;
 t_is_opaque(_) -> false.
 
--spec t_has_opaque_subtype(erl_type()) -> boolean().
+-spec t_has_opaque_subtype(erl_type(), opaques()) -> boolean().
+
+t_has_opaque_subtype(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun has_opaque_subtype/1).
 
-t_has_opaque_subtype(?union(Ts)) ->
+has_opaque_subtype(?union(Ts)) ->
   lists:any(fun t_is_opaque/1, Ts);
-t_has_opaque_subtype(T) ->
+has_opaque_subtype(T) ->
   t_is_opaque(T).
 
 -spec t_opaque_structure(erl_type()) -> erl_type().
@@ -424,74 +447,62 @@ t_has_opaque_subtype(T) ->
 t_opaque_structure(?opaque(Elements)) ->
   t_sup([Struct || #opaque{struct = Struct} <- ordsets:to_list(Elements)]).
 
--spec t_opaque_module(erl_type()) -> module().
+-spec t_opaque_modules(erl_type()) -> [module()].
 
-t_opaque_module(?opaque(Elements)) ->
+t_opaque_modules(?opaque(Elements)) ->
   case ordsets:size(Elements) of
     1 ->
-      [#opaque{mod = Module}] = ordsets:to_list(Elements),
-      Module;
+      [#opaque{mod = Mod}] = set_to_list(Elements),
+      [Mod];
     _ -> throw({error, "Unexpected multiple opaque types"})
   end.
 
-%% This only makes sense if we know that Type matches Opaque
--spec t_opaque_matching_structure(erl_type(), erl_type()) -> erl_type().
-
-t_opaque_matching_structure(Type, Opaque) ->
-  OpaqueStruct = t_opaque_structure(Opaque),
-  case OpaqueStruct of
-    ?union(L1) ->
-      case Type of
-	?union(_L2) -> OpaqueStruct;
-	_OtherType -> t_opaque_matching_structure_list(Type, L1)
-      end;
-    ?tuple_set(_Set1) = TupleSet ->
-      case Type of
-	?tuple_set(_Set2) -> OpaqueStruct;
-	_ -> t_opaque_matching_structure_list(Type, t_tuple_subtypes(TupleSet))
-      end;
-    _Other -> OpaqueStruct
-  end.
-
-t_opaque_matching_structure_list(Type, List) ->
-  NewList = [t_inf(Element, Type) || Element <- List],
-  Results = [NotNone || NotNone <- NewList, NotNone =/= ?none],
-  case Results of
-    [] -> ?none;
-    [First|_] -> First
-  end.
-
 -spec t_contains_opaque(erl_type()) -> boolean().
 
-t_contains_opaque(?any)                     -> false;
-t_contains_opaque(?none)                    -> false;
-t_contains_opaque(?unit)                    -> false;
-t_contains_opaque(?atom(_Set))              -> false;
-t_contains_opaque(?bitstr(_Unit, _Base))    -> false;
-t_contains_opaque(?float)                   -> false;
-t_contains_opaque(?function(Domain, Range)) ->
-  t_contains_opaque(Domain) orelse t_contains_opaque(Range);
-t_contains_opaque(?identifier(_Types))      -> false;
-t_contains_opaque(?integer(_Types))         -> false;
-t_contains_opaque(?int_range(_From, _To))   -> false;
-t_contains_opaque(?int_set(_Set))           -> false;
-t_contains_opaque(?list(Type, _, _))        -> t_contains_opaque(Type);
-t_contains_opaque(?matchstate(_P, _Slots))  -> false;
-t_contains_opaque(?nil)                     -> false;
-t_contains_opaque(?number(_Set, _Tag))      -> false;
-t_contains_opaque(?opaque(_))               -> true;
-t_contains_opaque(?product(Types))          -> list_contains_opaque(Types);
-t_contains_opaque(?tuple(?any, _, _))       -> false;
-t_contains_opaque(?tuple(Types, _, _))      -> list_contains_opaque(Types);
-t_contains_opaque(?tuple_set(_Set) = T)     ->
-  list_contains_opaque(t_tuple_subtypes(T));
-t_contains_opaque(?union(List))             -> list_contains_opaque(List);
-t_contains_opaque(?var(_Id))                -> false.
-
--spec list_contains_opaque([erl_type()]) -> boolean().
-
-list_contains_opaque(List) ->
-  lists:any(fun t_contains_opaque/1, List).
+t_contains_opaque(Type) ->
+  t_contains_opaque(Type, []).
+
+%% Returns 'true' iff there is an opaque type that is *not* one of
+%% the types of the second argument.
+
+-spec t_contains_opaque(erl_type(), [erl_type()]) -> boolean().
+
+t_contains_opaque(?any, _Opaques) -> false;
+t_contains_opaque(?none, _Opaques) -> false;
+t_contains_opaque(?unit, _Opaques) -> false;
+t_contains_opaque(?atom(_Set), _Opaques) -> false;
+t_contains_opaque(?bitstr(_Unit, _Base), _Opaques) -> false;
+t_contains_opaque(?float, _Opaques) -> false;
+t_contains_opaque(?function(Domain, Range), Opaques) ->
+  t_contains_opaque(Domain, Opaques)
+  orelse t_contains_opaque(Range, Opaques);
+t_contains_opaque(?identifier(_Types), _Opaques) -> false;
+t_contains_opaque(?integer(_Types), _Opaques) -> false;
+t_contains_opaque(?int_range(_From, _To), _Opaques) -> false;
+t_contains_opaque(?int_set(_Set), _Opaques) -> false;
+t_contains_opaque(?list(Type, Tail, _), Opaques) ->
+  t_contains_opaque(Type, Opaques) orelse t_contains_opaque(Tail, Opaques);
+t_contains_opaque(?matchstate(_P, _Slots), _Opaques) -> false;
+t_contains_opaque(?nil, _Opaques) -> false;
+t_contains_opaque(?number(_Set, _Tag), _Opaques) -> false;
+t_contains_opaque(?opaque(_)=T, Opaques) ->
+  not is_opaque_type(T, Opaques)
+  orelse t_contains_opaque(t_opaque_structure(T));
+t_contains_opaque(?product(Types), Opaques) ->
+  list_contains_opaque(Types, Opaques);
+t_contains_opaque(?tuple(?any, _, _), _Opaques) -> false;
+t_contains_opaque(?tuple(Types, _, _), Opaques) ->
+  list_contains_opaque(Types, Opaques);
+t_contains_opaque(?tuple_set(_Set) = T, Opaques) ->
+  list_contains_opaque(t_tuple_subtypes(T), Opaques);
+t_contains_opaque(?union(List), Opaques) ->
+  list_contains_opaque(List, Opaques);
+t_contains_opaque(?var(_Id), _Opaques) -> false.
+
+-spec list_contains_opaque([erl_type()], [erl_type()]) -> boolean().
+
+list_contains_opaque(List, Opaques) ->
+  lists:any(fun(E) -> t_contains_opaque(E, Opaques) end, List).
 
 %% t_find_opaque_mismatch/2 of two types should only be used if their
 %% t_inf is t_none() due to some opaque type violation.
@@ -506,9 +517,12 @@ t_find_opaque_mismatch(T1, T2) ->
 
 t_find_opaque_mismatch(?any, _Type, _TopType) -> error;
 t_find_opaque_mismatch(?none, _Type, _TopType) -> error;
-t_find_opaque_mismatch(?list(T1, _, _), ?list(T2, _, _), TopType) ->
-  t_find_opaque_mismatch(T1, T2, TopType);
+t_find_opaque_mismatch(?list(T1, Tl1, _), ?list(T2, Tl2, _), TopType) ->
+  t_find_opaque_mismatch_ordlists([T1, Tl1], [T2, Tl2], TopType);
 t_find_opaque_mismatch(_T1, ?opaque(_) = T2, TopType) -> {ok, TopType, T2};
+t_find_opaque_mismatch(?opaque(_) = T1, _T2, TopType) ->
+  %% The generated message is somewhat misleading:
+  {ok, TopType, T1};
 t_find_opaque_mismatch(?product(T1), ?product(T2), TopType) ->
   t_find_opaque_mismatch_ordlists(T1, T2, TopType);
 t_find_opaque_mismatch(?tuple(T1, Arity, _), ?tuple(T2, Arity, _), TopType) ->
@@ -538,6 +552,166 @@ t_find_opaque_mismatch_list([H|T]) ->
     error -> t_find_opaque_mismatch_list(T)
   end.
 
+-spec t_find_unknown_opaque(erl_type(), erl_type(), opaques()) ->
+                               [pos_integer()].
+
+%% The nice thing about using two types and t_inf() as compared to
+%% calling t_contains_opaque/2 is that the traversal stops when
+%% there is a mismatch which means that unknown opaque types "below"
+%% the mismatch are not found.
+%% XXX. Returns one element even if both oparands contain opaque types.
+%% XXX. Slow since t_inf() is called but the results are ignored.
+t_find_unknown_opaque(_T1, _T2, 'universe') -> [];
+t_find_unknown_opaque(T1, T2, Opaques) ->
+  try t_inf(T1, T2, {match, Opaques}) of
+    _ -> []
+  catch throw:N when is_integer(N) -> [N]
+  end.
+
+-spec t_decorate_with_opaque(erl_type(), erl_type(), [erl_type()]) -> erl_type().
+
+%% The first argument can contain opaque types. The second argument
+%% is assumed to be taken from the contract.
+
+t_decorate_with_opaque(T1, T2, Opaques) ->
+  case t_is_equal(T1, T2) orelse not t_contains_opaque(T2) of
+    true -> T1;
+    false ->
+      T = t_inf(T1, T2),
+      case t_contains_opaque(T) of
+        false -> T1;
+        true ->
+          R = decorate(T1, T, Opaques),
+          ?debug(case catch t_is_equal(t_unopaque(R), t_unopaque(T1)) of
+                   true -> ok;
+                   false ->
+                     io:format("T1 = ~p,\n", [T1]),
+                     io:format("T2 = ~p,\n", [T2]),
+                     io:format("O = ~p,\n", [Opaques]),
+                     io:format("erl_types:t_decorate_with_opaque(T1,T2,O).\n"),
+                     throw({error, "Failed to handle opaque types"})
+                 end),
+          R
+      end
+  end.
+
+decorate(?none=Type, _, _Opaques) -> Type;
+decorate(?function(Domain, Range), ?function(D, R), Opaques) ->
+  ?function(decorate(Domain, D, Opaques), decorate(Range, R, Opaques));
+decorate(?list(Types, Tail, Size), ?list(Ts, Tl, _Sz), Opaques) ->
+  ?list(decorate(Types, Ts, Opaques), decorate(Tail, Tl, Opaques), Size);
+decorate(?product(Types), ?product(Ts), Opaques) ->
+  ?product(list_decorate(Types, Ts, Opaques));
+decorate(?tuple(_, _, _)=T, ?tuple(?any, _, _), _Opaques) -> T;
+decorate(?tuple(?any, _, _)=T, ?tuple(_, _, _), _Opaques) -> T;
+decorate(?tuple(Types, Arity, Tag), ?tuple(Ts, Arity, _), Opaques) ->
+  ?tuple(list_decorate(Types, Ts, Opaques), Arity, Tag);
+decorate(?tuple_set(List), ?tuple(_, Arity, _) = T, Opaques) ->
+  decorate_tuple_sets(List, [{Arity, [T]}], Opaques);
+decorate(?tuple_set(List), ?tuple_set(L), Opaques) ->
+  decorate_tuple_sets(List, L, Opaques);
+decorate(?union(List), T, Opaques) when T =/= ?any ->
+  ?union(L) = force_union(T),
+  union_decorate(List, L, Opaques);
+decorate(?opaque(_)=T, _, _Opaques) -> T;
+decorate(T, ?union(L), Opaques) when T =/= ?any ->
+  ?union(List) = force_union(T),
+  union_decorate(List, L, Opaques);
+decorate(Type, ?opaque(_)=T, Opaques) ->
+  decorate_with_opaque(Type, T, Opaques);
+decorate(Type, _T, _Opaques) -> Type.
+
+%% Note: it is important that #opaque.struct is a subtype of the
+%% opaque type.
+decorate_with_opaque(Type, ?opaque(Set2), Opaques) ->
+  case decoration(set_to_list(Set2), Type, Opaques, [], false) of
+    {[], false} -> Type;
+    {List, All} when List =/= [] ->
+      NewType = ?opaque(ordsets:from_list(List)),
+      case All of
+        true -> NewType;
+        false -> t_sup(NewType, Type)
+      end
+  end.
+
+decoration([#opaque{struct = S} = Opaque|OpaqueTypes], Type, Opaques,
+           NewOpaqueTypes, All) ->
+  IsOpaque = is_opaque_type2(Opaque, Opaques),
+  I = t_inf(Type, S),
+  case not IsOpaque orelse t_is_none(I = t_inf(Type, S)) of
+    true -> decoration(OpaqueTypes, Type, Opaques, NewOpaqueTypes, All);
+    false ->
+      NewOpaque = Opaque#opaque{struct = decorate(I, S, Opaques)},
+      NewAll = All orelse t_is_equal(I, Type),
+      decoration(OpaqueTypes, Type, Opaques, [NewOpaque|NewOpaqueTypes], NewAll)
+  end;
+decoration([], _Type, _Opaques, NewOpaqueTypes, All) ->
+  {NewOpaqueTypes, All}.
+
+-spec list_decorate([erl_type()], [erl_type()], opaques()) -> [erl_type()].
+
+list_decorate(List, L, Opaques) ->
+  [decorate(Elem, E, Opaques) || {Elem, E} <- lists:zip(List, L)].
+
+union_decorate(U1, U2, Opaques) ->
+  Union = union_decorate(U1, U2, Opaques, 0, []),
+  [A,B,F,I,L,N,T,M,_,_R] = U1,
+  [_,_,_,_,_,_,_,_,Opaque,_] = U2,
+  List = [A,B,F,I,L,N,T,M],
+  DecList = [Dec ||
+              E <- List,
+              not t_is_none(Dec = decorate(E, Opaque, Opaques))],
+  t_sup([Union|DecList]).
+
+union_decorate([?none|Left1], [_|Left2], Opaques, N, Acc) ->
+  union_decorate(Left1, Left2, Opaques, N, [?none|Acc]);
+union_decorate([T1|Left1], [?none|Left2], Opaques, N, Acc) ->
+  union_decorate(Left1, Left2, Opaques, N+1, [T1|Acc]);
+union_decorate([T1|Left1], [T2|Left2], Opaques, N, Acc) ->
+  union_decorate(Left1, Left2, Opaques, N+1, [decorate(T1, T2, Opaques)|Acc]);
+union_decorate([], [], _Opaques, N, Acc) ->
+  if N =:= 0 -> ?none;
+     N =:= 1 ->
+      [Type] = [T || T <- Acc, T =/= ?none],
+      Type;
+     N >= 2  -> ?union(lists:reverse(Acc))
+  end.
+
+decorate_tuple_sets(List, L, Opaques) ->
+  decorate_tuple_sets(List, L, Opaques, []).
+
+decorate_tuple_sets([{Arity, Tuples}|List], [{Arity, Ts}|L], Opaques, Acc) ->
+  DecTs = decorate_tuples_in_sets(Tuples, Ts, Opaques),
+  decorate_tuple_sets(List, L, Opaques, [{Arity, DecTs}|Acc]);
+decorate_tuple_sets([ArTup|List], L, Opaques, Acc) ->
+  decorate_tuple_sets(List, L, Opaques, [ArTup|Acc]);
+decorate_tuple_sets([], _L, _Opaques, Acc) ->
+  ?tuple_set(lists:reverse(Acc)).
+
+decorate_tuples_in_sets([?tuple(Elements, _, ?any)], Ts, Opaques) ->
+  NewList = [list_decorate(Elements, Es, Opaques) || ?tuple(Es, _, _) <- Ts],
+  case t_sup([t_tuple(Es) || Es <- NewList]) of
+    ?tuple_set([{_Arity, Tuples}]) -> Tuples;
+    ?tuple(_, _, _)=Tuple -> [Tuple]
+  end;
+decorate_tuples_in_sets(Tuples, Ts, Opaques) ->
+  decorate_tuples_in_sets(Tuples, Ts, Opaques, []).
+
+decorate_tuples_in_sets([?tuple(Elements, Arity, Tag1) = T1|Tuples] = L1,
+                        [?tuple(Es, Arity, Tag2)|Ts] = L2, Opaques, Acc) ->
+  if
+    Tag1 < Tag2   -> decorate_tuples_in_sets(Tuples, L2, Opaques, [T1|Acc]);
+    Tag1 > Tag2   -> decorate_tuples_in_sets(L1, Ts, Opaques, Acc);
+    Tag1 =:= Tag2 ->
+      NewElements = list_decorate(Elements, Es, Opaques),
+      NewAcc = [?tuple(NewElements, Arity, Tag1)|Acc],
+      decorate_tuples_in_sets(Tuples, Ts, Opaques, NewAcc)
+  end;
+decorate_tuples_in_sets([T1|Tuples], L2, Opaques, Acc) ->
+  decorate_tuples_in_sets(Tuples, L2, Opaques, [T1|Acc]);
+decorate_tuples_in_sets([], _L, _Opaques, Acc) ->
+  lists:reverse(Acc).
+
 -spec t_opaque_from_records(dict()) -> [erl_type()].
 
 t_opaque_from_records(RecDict) ->
@@ -559,44 +733,6 @@ t_opaque_from_records(RecDict) ->
 	     end, OpaqueRecDict),
   [OpaqueType || {_Key, OpaqueType} <- dict:to_list(OpaqueTypeDict)].
 
--spec t_opaque_match_atom(erl_type(), [erl_type()]) -> [erl_type()].
-
-t_opaque_match_atom(?atom(_) = Atom,  Opaques) ->
-  case t_atom_vals(Atom) of
-    unknown -> [];
-    _  -> [O || O <- Opaques, t_inf(Atom, O, opaque) =/= ?none,
-		t_opaque_atom_vals(t_opaque_structure(O)) =/= unknown]
-  end;
-t_opaque_match_atom(_, _) -> [].
-
--spec t_opaque_atom_vals(erl_type()) -> 'unknown' | [atom(),...].
-
-t_opaque_atom_vals(OpaqueStruct) ->
-  case OpaqueStruct of
-    ?atom(_) -> t_atom_vals(OpaqueStruct);
-    ?union([Atom,_,_,_,_,_,_,_,_,_]) -> t_atom_vals(Atom);
-    _ -> unknown
-  end.
-	  
--spec t_opaque_match_record(erl_type(), [erl_type()]) -> [erl_type()].
-
-t_opaque_match_record(?tuple([?atom(_) = Tag|_Fields], _, _) = Rec, Opaques) ->
-  [O || O <- Opaques, t_inf(Rec, O, opaque) =/= ?none,
-	lists:member(Tag, t_opaque_tuple_tags(t_opaque_structure(O)))];
-t_opaque_match_record(_, _) -> [].
-
--spec t_opaque_tuple_tags(erl_type()) -> [erl_type()].
-
-t_opaque_tuple_tags(OpaqueStruct) ->
-  case OpaqueStruct of
-    ?tuple([?atom(_) = Tag|_Fields], _, _) -> [Tag];
-    ?tuple_set(_) = TupleSet ->
-      Tuples = t_tuple_subtypes(TupleSet),
-      lists:flatten([t_opaque_tuple_tags(T) || T <- Tuples]);
-    ?union([_,_,_,_,_,_,Tuples,_,_,_]) -> t_opaque_tuple_tags(Tuples);
-    _ -> []
-  end.
-
 %% Decompose opaque instances of type arg2 to structured types, in arg1
 %% XXX: Same as t_unopaque
 -spec t_struct_from_opaque(erl_type(), [erl_type()]) -> erl_type().
@@ -605,9 +741,10 @@ t_struct_from_opaque(?function(Domain, Range), Opaques) ->
   ?function(t_struct_from_opaque(Domain, Opaques),
 	    t_struct_from_opaque(Range, Opaques));
 t_struct_from_opaque(?list(Types, Term, Size), Opaques) ->
-  ?list(t_struct_from_opaque(Types, Opaques), Term, Size);
+  ?list(t_struct_from_opaque(Types, Opaques),
+        t_struct_from_opaque(Term, Opaques), Size);
 t_struct_from_opaque(?opaque(_) = T, Opaques) ->
-  case lists:member(T, Opaques) of
+  case is_opaque_type(T, Opaques) of
     true  -> t_opaque_structure(T);
     false -> T
   end;
@@ -627,24 +764,10 @@ t_struct_from_opaque(Type, _Opaques) -> Type.
 list_struct_from_opaque(Types, Opaques) ->
   [t_struct_from_opaque(Type, Opaques) || Type <- Types].
 
--spec t_unopaque_on_mismatch(erl_type(), erl_type(), [erl_type()]) -> erl_type().
-
-t_unopaque_on_mismatch(GenType, Type, Opaques) ->
-  case t_inf(GenType, Type) of
-    ?none ->
-      Unopaqued = t_unopaque(Type, Opaques),
-      %% XXX: Unions might be a problem, must investigate.
-      case t_inf(GenType, Unopaqued) of
-	?none -> Type;
-	_ -> Unopaqued
-      end;
-     _ -> Type
-  end.
-
 -spec module_builtin_opaques(module()) -> [erl_type()].
 
 module_builtin_opaques(Module) ->
-  [O || O <- all_opaque_builtins(), t_opaque_module(O) =:= Module].
+  [O || O <- all_opaque_builtins(), lists:member(Module, t_opaque_modules(O))].
 
 %%-----------------------------------------------------------------------------
 %% Remote types: these types are used for preprocessing;
@@ -657,8 +780,11 @@ t_remote(Mod, Name, Args) ->
 
 -spec t_is_remote(erl_type()) -> boolean().
 
-t_is_remote(?remote(_)) -> true;
-t_is_remote(_) -> false.
+t_is_remote(Type) ->
+  do_opaque(Type, 'universe', fun is_remote/1).
+
+is_remote(?remote(_)) -> true;
+is_remote(_) -> false.
 
 -spec t_solve_remote(erl_type(), set(), dict()) -> erl_type().
 
@@ -827,40 +953,75 @@ t_atoms(List) when is_list(List) ->
 
 -spec t_atom_vals(erl_type()) -> 'unknown' | [atom(),...].
 
-t_atom_vals(?atom(?any)) -> unknown;
-t_atom_vals(?atom(Set)) -> set_to_list(Set);
-t_atom_vals(Other) ->
+t_atom_vals(Type) ->
+  t_atom_vals(Type, 'universe').
+
+-spec t_atom_vals(erl_type(), opaques()) -> 'unknown' | [atom(),...].
+
+t_atom_vals(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun atom_vals/1).
+
+atom_vals(?atom(?any)) -> unknown;
+atom_vals(?atom(Set)) -> set_to_list(Set);
+atom_vals(?opaque(_)) -> unknown;
+atom_vals(Other) ->
   ?atom(_) = Atm = t_inf(t_atom(), Other),
-  t_atom_vals(Atm).
+  atom_vals(Atm).
 
 -spec t_is_atom(erl_type()) -> boolean().
 
-t_is_atom(?atom(_)) -> true;
-t_is_atom(_) -> false.
+t_is_atom(Type) ->
+  t_is_atom(Type, 'universe').
+
+-spec t_is_atom(erl_type(), opaques()) -> boolean().
+
+t_is_atom(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_atom1/1).
+
+is_atom1(?atom(_)) -> true;
+is_atom1(_) -> false.
 
--spec t_is_atom(atom(), erl_type()) -> boolean().
+-spec t_is_any_atom(atom(), erl_type()) -> boolean().
 
-t_is_atom(Atom, ?atom(?any)) when is_atom(Atom) -> false;
-t_is_atom(Atom, ?atom(Set)) when is_atom(Atom) -> set_is_singleton(Atom, Set);
-t_is_atom(Atom, _) when is_atom(Atom) -> false.
+t_is_any_atom(Atom, SomeAtomsType) ->
+  t_is_any_atom(Atom, SomeAtomsType, 'universe').
+
+-spec t_is_any_atom(atom(), erl_type(), opaques()) -> boolean().
+
+t_is_any_atom(Atom, SomeAtomsType, Opaques) ->
+  do_opaque(SomeAtomsType, Opaques,
+            fun(AtomsType) -> is_any_atom(Atom, AtomsType) end).
+
+is_any_atom(Atom, ?atom(?any)) when is_atom(Atom) -> false;
+is_any_atom(Atom, ?atom(Set)) when is_atom(Atom) ->
+  set_is_singleton(Atom, Set);
+is_any_atom(Atom, _) when is_atom(Atom) -> false.
 
 %%------------------------------------
 
+-spec t_is_boolean(erl_type()) -> boolean().
+
+t_is_boolean(Type) ->
+  t_is_boolean(Type, 'universe').
+
+-spec t_is_boolean(erl_type(), opaques()) -> boolean().
+
+t_is_boolean(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_boolean/1).
+
 -spec t_boolean() -> erl_type().
 
 t_boolean() ->
   ?atom(set_from_list([false, true])).
 
--spec t_is_boolean(erl_type()) -> boolean().
-
-t_is_boolean(?atom(?any)) -> false;
-t_is_boolean(?atom(Set)) ->
+is_boolean(?atom(?any)) -> false;
+is_boolean(?atom(Set)) ->
   case set_size(Set) of
     1 -> set_is_element(true, Set) orelse set_is_element(false, Set);
     2 -> set_is_element(true, Set) andalso set_is_element(false, Set);
     N when is_integer(N), N > 2 -> false
   end;
-t_is_boolean(_) -> false.
+is_boolean(_) -> false.
 
 %%-----------------------------------------------------------------------------
 %% Binaries
@@ -873,9 +1034,17 @@ t_binary() ->
 
 -spec t_is_binary(erl_type()) -> boolean().
 
-t_is_binary(?bitstr(U, B)) -> 
+t_is_binary(Type) ->
+  t_is_binary(Type, 'universe').
+
+-spec t_is_binary(erl_type(), opaques()) -> boolean().
+
+t_is_binary(Type, Opaques) ->
+    do_opaque(Type, Opaques, fun is_binary/1).
+
+is_binary(?bitstr(U, B)) ->
   ((U rem 8) =:= 0) andalso ((B rem 8) =:= 0);
-t_is_binary(_) -> false.
+is_binary(_) -> false.
 
 %%-----------------------------------------------------------------------------
 %% Bitstrings
@@ -922,19 +1091,27 @@ t_bitstr_concat_1([], Acc) ->
 t_bitstr_concat(T1, T2) ->
   T1p = t_inf(t_bitstr(), T1),
   T2p = t_inf(t_bitstr(), T2),
-  bitstr_concat(T1p, T2p).
+  bitstr_concat(t_unopaque(T1p), t_unopaque(T2p)).
 
 -spec t_bitstr_match(erl_type(), erl_type()) -> erl_type().
 
 t_bitstr_match(T1, T2) ->
   T1p = t_inf(t_bitstr(), T1),
   T2p = t_inf(t_bitstr(), T2),
-  bitstr_match(T1p, T2p).
+  bitstr_match(t_unopaque(T1p), t_unopaque(T2p)).
 
 -spec t_is_bitstr(erl_type()) -> boolean().
 
-t_is_bitstr(?bitstr(_, _)) -> true;
-t_is_bitstr(_) -> false.
+t_is_bitstr(Type) ->
+  t_is_bitstr(Type, 'universe').
+
+-spec t_is_bitstr(erl_type(), opaques()) -> boolean().
+
+t_is_bitstr(Type, Opaques) ->
+    do_opaque(Type, Opaques, fun is_bitstr/1).
+
+is_bitstr(?bitstr(_, _)) -> true;
+is_bitstr(_) -> false.
 
 %%-----------------------------------------------------------------------------
 %% Matchstates
@@ -1045,27 +1222,59 @@ t_fun(Arity, Range) when is_integer(Arity), 0 =< Arity, Arity =< 255 ->
 
 -spec t_fun_args(erl_type()) -> 'unknown' | [erl_type()].
 
-t_fun_args(?function(?any, _)) ->
+t_fun_args(Type) ->
+  t_fun_args(Type, 'universe').
+
+-spec t_fun_args(erl_type(), opaques()) -> 'unknown' | [erl_type()].
+
+t_fun_args(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun fun_args/1).
+
+fun_args(?function(?any, _)) ->
   unknown;
-t_fun_args(?function(?product(Domain), _)) when is_list(Domain) ->
+fun_args(?function(?product(Domain), _)) when is_list(Domain) ->
   Domain.
 
 -spec t_fun_arity(erl_type()) -> 'unknown' | non_neg_integer().
 
-t_fun_arity(?function(?any, _)) ->
+t_fun_arity(Type) ->
+  t_fun_arity(Type, 'universe').
+
+-spec t_fun_arity(erl_type(), opaques()) -> 'unknown' | non_neg_integer().
+
+t_fun_arity(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun fun_arity/1).
+
+fun_arity(?function(?any, _)) ->
   unknown;
-t_fun_arity(?function(?product(Domain), _)) ->
+fun_arity(?function(?product(Domain), _)) ->
   length(Domain).
 
 -spec t_fun_range(erl_type()) -> erl_type().
 
-t_fun_range(?function(_, Range)) ->
+t_fun_range(Type) ->
+  t_fun_range(Type, 'universe').
+
+-spec t_fun_range(erl_type(), opaques()) -> erl_type().
+
+t_fun_range(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun fun_range/1).
+
+fun_range(?function(_, Range)) ->
   Range.
 
 -spec t_is_fun(erl_type()) -> boolean().
 
-t_is_fun(?function(_, _)) -> true;
-t_is_fun(_) -> false.
+t_is_fun(Type) ->
+  t_is_fun(Type, 'universe').
+
+-spec t_is_fun(erl_type(), opaques()) -> boolean().
+
+t_is_fun(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_fun/1).
+
+is_fun(?function(_, _)) -> true;
+is_fun(_) -> false.
 
 %%-----------------------------------------------------------------------------
 %% Identifiers. Includes ports, pids and refs.
@@ -1092,9 +1301,17 @@ t_port() ->
 
 -spec t_is_port(erl_type()) -> boolean().
 
-t_is_port(?identifier(?any)) -> false;
-t_is_port(?identifier(Set)) -> set_is_singleton(?port_qual, Set);
-t_is_port(_) -> false.
+t_is_port(Type) ->
+  t_is_port(Type, 'universe').
+
+-spec t_is_port(erl_type(), opaques()) -> boolean().
+
+t_is_port(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_port1/1).
+
+is_port1(?identifier(?any)) -> false;
+is_port1(?identifier(Set)) -> set_is_singleton(?port_qual, Set);
+is_port1(_) -> false.
 
 %%------------------------------------
 
@@ -1105,9 +1322,17 @@ t_pid() ->
 
 -spec t_is_pid(erl_type()) -> boolean().
 
-t_is_pid(?identifier(?any)) -> false;
-t_is_pid(?identifier(Set)) -> set_is_singleton(?pid_qual, Set);
-t_is_pid(_) -> false.
+t_is_pid(Type) ->
+  t_is_pid(Type, 'universe').
+
+-spec t_is_pid(erl_type(), opaques()) -> boolean().
+
+t_is_pid(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_pid1/1).
+
+is_pid1(?identifier(?any)) -> false;
+is_pid1(?identifier(Set)) -> set_is_singleton(?pid_qual, Set);
+is_pid1(_) -> false.
 
 %%------------------------------------
 
@@ -1118,9 +1343,17 @@ t_reference() ->
 
 -spec t_is_reference(erl_type()) -> boolean().
 
-t_is_reference(?identifier(?any)) -> false;
-t_is_reference(?identifier(Set)) -> set_is_singleton(?reference_qual, Set);
-t_is_reference(_) -> false.
+t_is_reference(Type) ->
+  t_is_reference(Type, 'universe').
+
+-spec t_is_reference(erl_type(), opaques()) -> boolean().
+
+t_is_reference(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_reference1/1).
+
+is_reference1(?identifier(?any)) -> false;
+is_reference1(?identifier(Set)) -> set_is_singleton(?reference_qual, Set);
+is_reference1(_) -> false.
 
 %%-----------------------------------------------------------------------------
 %% Numbers are divided into floats, integers, chars and bytes.
@@ -1138,21 +1371,39 @@ t_number(X) when is_integer(X) ->
 
 -spec t_is_number(erl_type()) -> boolean().
 
-t_is_number(?number(_, _)) -> true;
-t_is_number(_) -> false.
+t_is_number(Type) ->
+  t_is_number(Type, 'universe').
+
+-spec t_is_number(erl_type(), opaques()) -> boolean().
+
+t_is_number(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_number/1).
+
+is_number(?number(_, _)) -> true;
+is_number(_) -> false.
 
 %% Currently, the type system collapses all floats to ?float and does
 %% not keep any information about their values. As a result, the list
 %% that this function returns contains only integers.
+
 -spec t_number_vals(erl_type()) -> 'unknown' | [integer(),...].
 
-t_number_vals(?int_set(?any)) -> unknown;
-t_number_vals(?int_set(Set)) -> set_to_list(Set);
-t_number_vals(?number(_, _)) -> unknown;
-t_number_vals(Other) ->
+t_number_vals(Type) ->
+  t_number_vals(Type, 'universe').
+
+-spec t_number_vals(erl_type(), opaques()) -> 'unknown' | [integer(),...].
+
+t_number_vals(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun number_vals/1).
+
+number_vals(?int_set(?any)) -> unknown;
+number_vals(?int_set(Set)) -> set_to_list(Set);
+number_vals(?number(_, _)) -> unknown;
+number_vals(?opaque(_)) -> unknown;
+number_vals(Other) ->
   Inf = t_inf(Other, t_number()),
   false = t_is_none(Inf), % sanity check
-  t_number_vals(Inf).
+  number_vals(Inf).
 
 %%------------------------------------
 
@@ -1163,8 +1414,16 @@ t_float() ->
 
 -spec t_is_float(erl_type()) -> boolean().
 
-t_is_float(?float) -> true;
-t_is_float(_) -> false.
+t_is_float(Type) ->
+  t_is_float(Type, 'universe').
+
+-spec t_is_float(erl_type(), opaques()) -> boolean().
+
+t_is_float(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_float1/1).
+
+is_float1(?float) -> true;
+is_float1(_) -> false.
 
 %%------------------------------------
 
@@ -1185,8 +1444,16 @@ t_integers(List) when is_list(List) ->
 
 -spec t_is_integer(erl_type()) -> boolean().
 
-t_is_integer(?integer(_)) -> true;
-t_is_integer(_) -> false.
+t_is_integer(Type) ->
+  t_is_integer(Type, 'universe').
+
+-spec t_is_integer(erl_type(), opaques()) -> boolean().
+
+t_is_integer(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_integer1/1).
+
+is_integer1(?integer(_)) -> true;
+is_integer1(_) -> false.
 
 %%------------------------------------
 
@@ -1250,7 +1517,7 @@ t_cons(Hd, ?nil) ->
 t_cons(Hd, ?list(Contents, Termination, _)) ->
   ?nonempty_list(t_sup(Contents, Hd), Termination);
 t_cons(Hd, Tail) ->
-  case t_inf(Tail, t_maybe_improper_list()) of
+  case cons_tail(t_inf(Tail, t_maybe_improper_list())) of
     ?list(Contents, Termination, _Size) ->
       %% Collapse the list part of the termination but keep the
       %% non-list part intact.
@@ -1262,18 +1529,45 @@ t_cons(Hd, Tail) ->
     ?unit -> ?none
   end.
 
+cons_tail(Type) ->
+  do_opaque(Type, 'universe', fun(T) -> T end).
+
 -spec t_is_cons(erl_type()) -> boolean().
 
-t_is_cons(?nonempty_list(_, _)) -> true;
-t_is_cons(_) -> false.  
+t_is_cons(Type) ->
+  t_is_cons(Type, 'universe').
+
+-spec t_is_cons(erl_type(), opaques()) -> boolean().
+
+t_is_cons(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_cons/1).
+
+is_cons(?nonempty_list(_, _)) -> true;
+is_cons(_) -> false.
 
 -spec t_cons_hd(erl_type()) -> erl_type().
 
-t_cons_hd(?nonempty_list(Contents, _Termination)) -> Contents.
+t_cons_hd(Type) ->
+  t_cons_hd(Type, 'universe').
+
+-spec t_cons_hd(erl_type(), opaques()) -> erl_type().
+
+t_cons_hd(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun cons_hd/1).
+
+cons_hd(?nonempty_list(Contents, _Termination)) -> Contents.
 
 -spec t_cons_tl(erl_type()) -> erl_type().
 
-t_cons_tl(?nonempty_list(_Contents, Termination) = T) ->
+t_cons_tl(Type) ->
+  t_cons_tl(Type, 'universe').
+
+-spec t_cons_tl(erl_type(), opaques()) -> erl_type().
+
+t_cons_tl(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun cons_tl/1).
+
+cons_tl(?nonempty_list(_Contents, Termination) = T) ->
   t_sup(Termination, T).
 
 -spec t_nil() -> erl_type().
@@ -1283,8 +1577,16 @@ t_nil() ->
 
 -spec t_is_nil(erl_type()) -> boolean().
 
-t_is_nil(?nil) -> true;
-t_is_nil(_) -> false.
+t_is_nil(Type) ->
+  t_is_nil(Type, 'universe').
+
+-spec t_is_nil(erl_type(), opaques()) -> boolean().
+
+t_is_nil(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_nil/1).
+
+is_nil(?nil) -> true;
+is_nil(_) -> false.
 
 -spec t_list() -> erl_type().
 
@@ -1300,8 +1602,16 @@ t_list(Contents) ->
 
 -spec t_list_elements(erl_type()) -> erl_type().
 
-t_list_elements(?list(Contents, _, _)) -> Contents;
-t_list_elements(?nil) -> ?none.
+t_list_elements(Type) ->
+  t_list_elements(Type, 'universe').
+
+-spec t_list_elements(erl_type(), opaques()) -> erl_type().
+
+t_list_elements(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun list_elements/1).
+
+list_elements(?list(Contents, _, _)) -> Contents;
+list_elements(?nil) -> ?none.
 
 -spec t_list_termination(erl_type()) -> erl_type().
 
@@ -1356,9 +1666,17 @@ t_maybe_improper_list(Content, Termination) ->
 
 -spec t_is_maybe_improper_list(erl_type()) -> boolean().
 
-t_is_maybe_improper_list(?list(_, _, _)) -> true;
-t_is_maybe_improper_list(?nil) -> true;
-t_is_maybe_improper_list(_) -> false.
+t_is_maybe_improper_list(Type) ->
+  t_is_maybe_improper_list(Type, 'universe').
+
+-spec t_is_maybe_improper_list(erl_type(), opaques()) -> boolean().
+
+t_is_maybe_improper_list(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_maybe_improper_list/1).
+
+is_maybe_improper_list(?list(_, _, _)) -> true;
+is_maybe_improper_list(?nil) -> true;
+is_maybe_improper_list(_) -> false.
 
 %% %% Should only be used if you know what you are doing. See t_cons/2
 %% -spec t_improper_list(erl_type(), erl_type()) -> erl_type().
@@ -1405,32 +1723,77 @@ t_tuple(List) ->
 
 -spec get_tuple_tags([erl_type()]) -> [erl_type(),...].
 
-get_tuple_tags([?atom(?any)|_]) -> [?any];
-get_tuple_tags([?atom(Set)|_]) ->
+get_tuple_tags([Tag|_]) ->
+  do_opaque(Tag, 'universe', fun tuple_tags/1);
+get_tuple_tags(_) -> [?any].
+
+tuple_tags(?atom(?any)) -> [?any];
+tuple_tags(?atom(Set)) ->
   case set_size(Set) > ?TUPLE_TAG_LIMIT of
     true -> [?any];
     false -> [t_atom(A) || A <- set_to_list(Set)]
   end;
-get_tuple_tags(_) -> [?any].
+tuple_tags(_) -> [?any].
 
 %% to be used for a tuple with known types for its arguments (not ?any)
 -spec t_tuple_args(erl_type()) -> [erl_type()].
 
-t_tuple_args(?tuple(Args, _, _)) when is_list(Args) -> Args.
+t_tuple_args(Type) ->
+  t_tuple_args(Type, 'universe').
+
+%% to be used for a tuple with known types for its arguments (not ?any)
+-spec t_tuple_args(erl_type(), opaques()) -> [erl_type()].
+
+t_tuple_args(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun tuple_args/1).
+
+tuple_args(?tuple(Args, _, _)) when is_list(Args) -> Args.
 
 %% to be used for a tuple with a known size (not ?any)
 -spec t_tuple_size(erl_type()) -> non_neg_integer().
 
-t_tuple_size(?tuple(_, Size, _)) when is_integer(Size) -> Size.
+t_tuple_size(Type) ->
+  t_tuple_size(Type, 'universe').
+
+%% to be used for a tuple with a known size (not ?any)
+-spec t_tuple_size(erl_type(), opaques()) -> non_neg_integer().
+
+t_tuple_size(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun tuple_size1/1).
+
+tuple_size1(?tuple(_, Size, _)) when is_integer(Size) -> Size.
 
 -spec t_tuple_sizes(erl_type()) -> 'unknown' | [non_neg_integer(),...].
 
-t_tuple_sizes(?tuple(?any, ?any, ?any)) -> unknown;
-t_tuple_sizes(?tuple(_, Size, _)) when is_integer(Size) -> [Size];
-t_tuple_sizes(?tuple_set(List)) -> [Size || {Size, _} <- List].
+t_tuple_sizes(Type) ->
+  do_opaque(Type, 'universe', fun tuple_sizes/1).
+
+tuple_sizes(?tuple(?any, ?any, ?any)) -> unknown;
+tuple_sizes(?tuple(_, Size, _)) when is_integer(Size) -> [Size];
+tuple_sizes(?tuple_set(List)) -> [Size || {Size, _} <- List].
+
+-spec t_tuple_subtypes(erl_type(), opaques()) ->
+         'unknown' | [erl_type(),...].
+
+t_tuple_subtypes(Type, Opaques) ->
+  Fun = fun(?tuple_set(List)) ->
+            t_tuple_subtypes_tuple_list(List, Opaques);
+           (?opaque(_)) -> unknown;
+           (T) -> t_tuple_subtypes(T)
+        end,
+  do_opaque(Type, Opaques, Fun).
+
+t_tuple_subtypes_tuple_list(List, Opaques) ->
+  lists:append([t_tuple_subtypes_list(Tuples, Opaques) ||
+                 {_Size, Tuples} <- List]).
+
+t_tuple_subtypes_list(List, Opaques) ->
+  ListOfLists = [t_tuple_subtypes(E, Opaques) || E <- List, E =/= ?none],
+  lists:append([L || L <- ListOfLists, L =/= 'unknown']).
 
 -spec t_tuple_subtypes(erl_type()) -> 'unknown' | [erl_type(),...].
 
+%% XXX. Not the same as t_tuple_subtypes(T, 'universe')...
 t_tuple_subtypes(?tuple(?any, ?any, ?any)) -> unknown;
 t_tuple_subtypes(?tuple(_, _, _) = T) -> [T];
 t_tuple_subtypes(?tuple_set(List)) ->
@@ -1438,9 +1801,17 @@ t_tuple_subtypes(?tuple_set(List)) ->
 
 -spec t_is_tuple(erl_type()) -> boolean().
 
-t_is_tuple(?tuple(_, _, _)) -> true;
-t_is_tuple(?tuple_set(_)) -> true;
-t_is_tuple(_) -> false.
+t_is_tuple(Type) ->
+  t_is_tuple(Type, 'universe').
+
+-spec t_is_tuple(erl_type(), opaques()) -> boolean().
+
+t_is_tuple(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun is_tuple1/1).
+
+is_tuple1(?tuple(_, _, _)) -> true;
+is_tuple1(?tuple_set(_)) -> true;
+is_tuple1(_) -> false.
 
 %%-----------------------------------------------------------------------------
 %% Non-primitive types, including some handy syntactic sugar types
@@ -1451,6 +1822,7 @@ t_is_tuple(_) -> false.
 t_bitstrlist() ->
   t_iolist(1, t_bitstr()).
 
+%% XXX. To be removed.
 -spec t_constant() -> erl_type().
 
 t_constant() ->
@@ -1555,7 +1927,8 @@ t_timeout() ->
 t_array() ->
   t_opaque(array, array, [],
 	   t_tuple([t_atom('array'),
-		    t_non_neg_integer(), t_non_neg_integer(),
+		    t_sup([t_atom('undefined'), t_non_neg_integer()]),
+                    t_sup([t_atom('undefined'), t_non_neg_integer()]),
 		    t_any(), t_any()])).
 
 -spec t_dict() -> erl_type().
@@ -1566,7 +1939,8 @@ t_dict() ->
 		    t_non_neg_integer(), t_non_neg_integer(),
 		    t_non_neg_integer(), t_non_neg_integer(),
 		    t_non_neg_integer(), t_non_neg_integer(),
-		    t_tuple(), t_tuple()])).
+                    t_sup([t_atom('undefined'), t_tuple()]),
+                    t_sup([t_atom('undefined'), t_tuple()])])).
 
 -spec t_digraph() -> erl_type().
 
@@ -1601,7 +1975,9 @@ t_set() ->
   t_opaque(sets, set, [],
 	   t_tuple([t_atom('set'), t_non_neg_integer(), t_non_neg_integer(),
 		    t_pos_integer(), t_non_neg_integer(), t_non_neg_integer(),
-		    t_non_neg_integer(), t_tuple(), t_tuple()])).
+		    t_non_neg_integer(),
+                    t_sup([t_atom('undefined'), t_tuple()]),
+                    t_sup([t_atom('undefined'), t_tuple()])])).
 
 -spec t_tid() -> erl_type().
 
@@ -1673,8 +2049,11 @@ t_has_var(?tuple(Elements, _, _)) ->
   t_has_var_list(Elements);
 t_has_var(?tuple_set(_) = T) ->
   t_has_var_list(t_tuple_subtypes(T));
+%% t_has_var(?opaque(_)=T) ->
+%%   %% "Polymorphic opaque types not supported yet"
+%%   t_has_var(t_opaque_structure(T));
 %% t_has_var(?union(_) = U) ->
-%% exit(lists:flatten(io_lib:format("Union happens in t_has_var/1 ~p\n",[U])));
+%% exit(flat_format("Union happens in t_has_var/1 ~p\n",[U]));
 t_has_var(_) -> false.
 
 -spec t_has_var_list([erl_type()]) -> boolean().
@@ -1705,6 +2084,9 @@ t_collect_vars(?tuple(Types, _, _), Acc) ->
 t_collect_vars(?tuple_set(_) = TS, Acc) ->
   lists:foldl(fun(T, TmpAcc) -> t_collect_vars(T, TmpAcc) end, Acc, 
 	      t_tuple_subtypes(TS));
+%% t_collect_vars(?opaque(_)=T, Acc) ->
+%%   %% "Polymorphic opaque types not supported yet"
+%%   t_collect_vars(t_opaque_structure(T), Acc);
 t_collect_vars(_, Acc) ->
   Acc.
 
@@ -1827,15 +2209,31 @@ t_is_bitwidth(_) -> false.
 
 -spec number_min(erl_type()) -> rng_elem().
 
-number_min(?int_range(From, _)) -> From;
-number_min(?int_set(Set)) -> set_min(Set);
-number_min(?number(?any, _Tag)) -> neg_inf.
+number_min(Type) ->
+  number_min(Type, 'universe').
+
+-spec number_min(erl_type(), opaques()) -> rng_elem().
+
+number_min(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun number_min2/1).
+
+number_min2(?int_range(From, _)) -> From;
+number_min2(?int_set(Set)) -> set_min(Set);
+number_min2(?number(?any, _Tag)) -> neg_inf.
 
 -spec number_max(erl_type()) -> rng_elem().
 
-number_max(?int_range(_, To)) -> To;
-number_max(?int_set(Set)) -> set_max(Set);
-number_max(?number(?any, _Tag)) -> pos_inf.
+number_max(Type) ->
+  number_max(Type, 'universe').
+
+-spec number_max(erl_type(), opaques()) -> rng_elem().
+
+number_max(Type, Opaques) ->
+  do_opaque(Type, Opaques, fun number_max2/1).
+
+number_max2(?int_range(_, To)) -> To;
+number_max2(?int_set(Set)) -> set_max(Set);
+number_max2(?number(?any, _Tag)) -> pos_inf.
 
 %% -spec int_range(rgn_elem(), rng_elem()) -> erl_type().
 %%
@@ -1917,7 +2315,7 @@ t_sup(?function(Domain1, Range1), ?function(Domain2, Range2)) ->
 t_sup(?identifier(Set1), ?identifier(Set2)) ->
   ?identifier(set_union(Set1, Set2));
 t_sup(?opaque(Set1), ?opaque(Set2)) ->
-  ?opaque(set_union_no_limit(Set1, Set2));
+  sup_opaque(set_to_list(ordsets:union(Set1, Set2)));
 %%Disallow unions with opaque types
 %%t_sup(T1=?opaque(_,_,_), T2) ->
 %%  io:format("Debug: t_sup executed with args ~w and ~w~n",[T1, T2]), ?none;
@@ -2005,6 +2403,27 @@ t_sup(T1, T2) ->
   ?union(U2) = force_union(T2),
   sup_union(U1, U2).
 
+sup_opaque([]) -> ?none;
+sup_opaque(List) ->
+  L = sup_opaq(List),
+  ?opaque(ordsets:from_list(L)).
+
+sup_opaq(L0) ->
+  L1 = [{{Mod,Name}, T} ||
+           #opaque{mod = Mod, name = Name}=T <- L0],
+  F = family(L1),
+  [supl(Ts) || {_, Ts} <- F].
+
+supl([O]) -> O;
+supl(Ts) -> supl(Ts, t_none()).
+
+supl([#opaque{struct = S}=O|L], S0) ->
+  S1 = t_sup(S, S0),
+  case L =:= [] of
+    true -> O#opaque{struct = S1};
+    false -> supl(L, S1)
+  end.
+
 -spec t_sup_lists([erl_type()], [erl_type()]) -> [erl_type()].
 
 t_sup_lists([T1|Left1], [T2|Left2]) ->
@@ -2132,19 +2551,26 @@ t_elements(?number(_, _) = T) ->
     ?int_set(Set) ->
       [t_integer(I) || I <- Set]
   end;
-t_elements(?opaque(_) = T) -> [T];
+t_elements(?opaque(_) = T) ->
+  do_elements(T);
 t_elements(?tuple(_, _, _) = T) -> [T];
 t_elements(?tuple_set(_) = TS) ->
   case t_tuple_subtypes(TS) of
     unknown -> [];
     Elems -> Elems
   end;
-t_elements(?union(List)) ->
-  lists:append([t_elements(T) || T <- List]);
+t_elements(?union(_) = T) ->
+  do_elements(T);
 t_elements(?var(_)) -> [?any].  %% yes, vars exist -- what else to do here?
 %% t_elements(T) ->
 %%   io:format("T_ELEMENTS => ~p\n", [T]).
 
+do_elements(Type0) ->
+  case do_opaque(Type0, 'universe', fun(T) -> T end) of
+    ?union(List) -> lists:append([t_elements(T) || T <- List]);
+    Type -> t_elements(Type)
+  end.
+
 %%-----------------------------------------------------------------------------
 %% Infimum
 %%
@@ -2162,74 +2588,77 @@ t_inf([]) -> ?none.
 -spec t_inf(erl_type(), erl_type()) -> erl_type().
 
 t_inf(T1, T2) ->
-  t_inf(T1, T2, structured).
-
--type t_inf_mode() :: 'opaque' | 'structured'.
--spec t_inf(erl_type(), erl_type(), t_inf_mode()) -> erl_type().
-
-t_inf(?var(_), ?var(_), _Mode) -> ?any;
-t_inf(?var(_), T, _Mode) -> subst_all_vars_to_any(T);
-t_inf(T, ?var(_), _Mode) -> subst_all_vars_to_any(T);
-t_inf(?any, T, _Mode) -> subst_all_vars_to_any(T);
-t_inf(T, ?any, _Mode) -> subst_all_vars_to_any(T);
-t_inf(?none, _, _Mode) -> ?none;
-t_inf(_, ?none, _Mode) -> ?none;
-t_inf(?unit, _, _Mode) -> ?unit;	% ?unit cases should appear below ?none
-t_inf(_, ?unit, _Mode) -> ?unit;
-t_inf(T, T, _Mode) -> subst_all_vars_to_any(T);
+  t_inf(T1, T2, 'universe').
+
+%% 'match' should be used from t_find_unknown_opaque() only
+-type t_inf_opaques() :: 'universe'
+                       | [erl_type()] | {'match', [erl_type() | 'universe']}.
+
+-spec t_inf(erl_type(), erl_type(), t_inf_opaques()) -> erl_type().
+
+t_inf(?var(_), ?var(_), _Opaques) -> ?any;
+t_inf(?var(_), T, _Opaques) -> subst_all_vars_to_any(T);
+t_inf(T, ?var(_), _Opaques) -> subst_all_vars_to_any(T);
+t_inf(?any, T, _Opaques) -> subst_all_vars_to_any(T);
+t_inf(T, ?any, _Opaques) -> subst_all_vars_to_any(T);
+t_inf(?none, _, _Opaques) -> ?none;
+t_inf(_, ?none, _Opaques) -> ?none;
+t_inf(?unit, _, _Opaques) -> ?unit;	% ?unit cases should appear below ?none
+t_inf(_, ?unit, _Opaques) -> ?unit;
+t_inf(T, T, _Opaques) -> subst_all_vars_to_any(T);
 t_inf(?atom(Set1), ?atom(Set2), _) ->
   case set_intersection(Set1, Set2) of
     ?none ->  ?none;
     NewSet -> ?atom(NewSet)
   end;
-t_inf(?bitstr(U1, B1), ?bitstr(0, B2), _Mode) ->
+t_inf(?bitstr(U1, B1), ?bitstr(0, B2), _Opaques) ->
   if B2 >= B1 andalso (B2-B1) rem U1 =:= 0 -> t_bitstr(0, B2);
      true -> ?none
   end;
-t_inf(?bitstr(0, B1), ?bitstr(U2, B2), _Mode) ->
+t_inf(?bitstr(0, B1), ?bitstr(U2, B2), _Opaques) ->
   if B1 >= B2 andalso (B1-B2) rem U2 =:= 0 -> t_bitstr(0, B1);
      true -> ?none
   end;
-t_inf(?bitstr(U1, B1), ?bitstr(U1, B1), _Mode) ->
+t_inf(?bitstr(U1, B1), ?bitstr(U1, B1), _Opaques) ->
   t_bitstr(U1, B1);
-t_inf(?bitstr(U1, B1), ?bitstr(U2, B2), _Mode) when U2 > U1 ->
+t_inf(?bitstr(U1, B1), ?bitstr(U2, B2), _Opaques) when U2 > U1 ->
   inf_bitstr(U2, B2, U1, B1);
-t_inf(?bitstr(U1, B1), ?bitstr(U2, B2), _Mode) ->
+t_inf(?bitstr(U1, B1), ?bitstr(U2, B2), _Opaques) ->
   inf_bitstr(U1, B1, U2, B2);
-t_inf(?function(Domain1, Range1), ?function(Domain2, Range2), Mode) ->
-  case t_inf(Domain1, Domain2, Mode) of
+t_inf(?function(Domain1, Range1), ?function(Domain2, Range2), Opaques) ->
+  case t_inf(Domain1, Domain2, Opaques) of
     ?none -> ?none;
-    Domain -> ?function(Domain, t_inf(Range1, Range2, Mode))
+    Domain -> ?function(Domain, t_inf(Range1, Range2, Opaques))
   end;
-t_inf(?identifier(Set1), ?identifier(Set2), _Mode) ->
+t_inf(?identifier(Set1), ?identifier(Set2), _Opaques) ->
   case set_intersection(Set1, Set2) of
     ?none -> ?none;
     Set -> ?identifier(Set)
   end;
-t_inf(?matchstate(Pres1, Slots1), ?matchstate(Pres2, Slots2), _Mode) ->
+t_inf(?matchstate(Pres1, Slots1), ?matchstate(Pres2, Slots2), _Opaques) ->
   ?matchstate(t_inf(Pres1, Pres2), t_inf(Slots1, Slots2));
-t_inf(?nil, ?nil, _Mode) -> ?nil;
-t_inf(?nil, ?nonempty_list(_, _), _Mode) ->
+t_inf(?nil, ?nil, _Opaques) -> ?nil;
+t_inf(?nil, ?nonempty_list(_, _), _Opaques) ->
   ?none;
-t_inf(?nonempty_list(_, _), ?nil, _Mode) ->
+t_inf(?nonempty_list(_, _), ?nil, _Opaques) ->
   ?none;
-t_inf(?nil, ?list(_Contents, Termination, _), Mode) ->
-  t_inf(?nil, Termination, Mode);
-t_inf(?list(_Contents, Termination, _), ?nil, Mode) ->
-  t_inf(?nil, Termination, Mode);
+t_inf(?nil, ?list(_Contents, Termination, _), Opaques) ->
+  t_inf(?nil, t_unopaque(Termination), Opaques);
+t_inf(?list(_Contents, Termination, _), ?nil, Opaques) ->
+  t_inf(?nil, t_unopaque(Termination), Opaques);
 t_inf(?list(Contents1, Termination1, Size1),
-      ?list(Contents2, Termination2, Size2), Mode) ->  
-  case t_inf(Termination1, Termination2, Mode) of
+      ?list(Contents2, Termination2, Size2), Opaques) ->
+  case t_inf(Termination1, Termination2, Opaques) of
     ?none -> ?none;
     Termination ->
-      case t_inf(Contents1, Contents2, Mode) of
-	?none -> 
+      case t_inf(Contents1, Contents2, Opaques) of
+	?none ->
 	  %% If none of the lists are nonempty, then the infimum is nil.
 	  case (Size1 =:= ?unknown_qual) andalso (Size2 =:= ?unknown_qual) of
 	    true -> t_nil();
 	    false -> ?none
 	  end;
-	Contents -> 
+	Contents ->
 	  Size =
 	    case {Size1, Size2} of
 	      {?unknown_qual, ?unknown_qual} -> ?unknown_qual;
@@ -2240,7 +2669,7 @@ t_inf(?list(Contents1, Termination1, Size1),
 	  ?list(Contents, Termination, Size)
       end
   end;
-t_inf(?number(_, _) = T1, ?number(_, _) = T2, _Mode) ->
+t_inf(?number(_, _) = T1, ?number(_, _) = T2, _Opaques) ->
   case {T1, T2} of
     {T, T}                            -> T;
     {_, ?number(?any, ?unknown_qual)} -> T1;
@@ -2249,16 +2678,16 @@ t_inf(?number(_, _) = T1, ?number(_, _) = T2, _Mode) ->
     {?integer(_), ?float}             -> ?none;
     {?integer(?any), ?integer(_)}     -> T2;
     {?integer(_), ?integer(?any)}     -> T1;
-    {?int_set(Set1), ?int_set(Set2)}  -> 
+    {?int_set(Set1), ?int_set(Set2)}  ->
       case set_intersection(Set1, Set2) of
 	?none -> ?none;
 	Set -> ?int_set(Set)
       end;
-    {?int_range(From1, To1), ?int_range(From2, To2)} -> 
+    {?int_range(From1, To1), ?int_range(From2, To2)} ->
       t_from_range(max(From1, From2), min(To1, To2));
     {Range = ?int_range(_, _), ?int_set(Set)} ->
       %% io:format("t_inf range, set args ~p ~p ~n", [T1, T2]),
-      Ans2 = 
+      Ans2 =
 	case set_filter(fun(X) -> in_range(X, Range) end, Set) of
 	  ?none -> ?none;
 	  NewSet -> ?int_set(NewSet)
@@ -2271,193 +2700,253 @@ t_inf(?number(_, _) = T1, ?number(_, _) = T2, _Mode) ->
 	NewSet -> ?int_set(NewSet)
       end
   end;
-t_inf(?product(Types1), ?product(Types2), Mode) ->
+t_inf(?product(Types1), ?product(Types2), Opaques) ->
   L1 = length(Types1),
   L2 = length(Types2),
-  if L1 =:= L2 -> ?product(t_inf_lists(Types1, Types2, Mode));
+  if L1 =:= L2 -> ?product(t_inf_lists(Types1, Types2, Opaques));
      true -> ?none
   end;
-t_inf(?product(_), _, _Mode) ->
+t_inf(?product(_), _, _Opaques) ->
   ?none;
-t_inf(_, ?product(_), _Mode) ->
+t_inf(_, ?product(_), _Opaques) ->
   ?none;
-t_inf(?tuple(?any, ?any, ?any), ?tuple(_, _, _) = T, _Mode) ->
+t_inf(?tuple(?any, ?any, ?any), ?tuple(_, _, _) = T, _Opaques) ->
   subst_all_vars_to_any(T);
-t_inf(?tuple(_, _, _) = T, ?tuple(?any, ?any, ?any), _Mode) ->
+t_inf(?tuple(_, _, _) = T, ?tuple(?any, ?any, ?any), _Opaques) ->
   subst_all_vars_to_any(T);
-t_inf(?tuple(?any, ?any, ?any), ?tuple_set(_) = T, _Mode) ->
+t_inf(?tuple(?any, ?any, ?any), ?tuple_set(_) = T, _Opaques) ->
   subst_all_vars_to_any(T);
-t_inf(?tuple_set(_) = T, ?tuple(?any, ?any, ?any), _Mode) ->
+t_inf(?tuple_set(_) = T, ?tuple(?any, ?any, ?any), _Opaques) ->
   subst_all_vars_to_any(T);
-t_inf(?tuple(Elements1, Arity, _Tag1), ?tuple(Elements2, Arity, _Tag2), Mode) ->
-  case t_inf_lists_strict(Elements1, Elements2, Mode) of
+t_inf(?tuple(Elements1, Arity, _Tag1), ?tuple(Elements2, Arity, _Tag2), Opaques) ->
+  case t_inf_lists_strict(Elements1, Elements2, Opaques) of
     bottom -> ?none;
     NewElements -> t_tuple(NewElements)
   end;
-t_inf(?tuple_set(List1), ?tuple_set(List2), Mode) ->
-  inf_tuple_sets(List1, List2, Mode);
-t_inf(?tuple_set(List), ?tuple(_, Arity, _) = T, Mode) ->
-  inf_tuple_sets(List, [{Arity, [T]}], Mode);
-t_inf(?tuple(_, Arity, _) = T, ?tuple_set(List), Mode) ->
-  inf_tuple_sets(List, [{Arity, [T]}], Mode);
+t_inf(?tuple_set(List1), ?tuple_set(List2), Opaques) ->
+  inf_tuple_sets(List1, List2, Opaques);
+t_inf(?tuple_set(List), ?tuple(_, Arity, _) = T, Opaques) ->
+  inf_tuple_sets(List, [{Arity, [T]}], Opaques);
+t_inf(?tuple(_, Arity, _) = T, ?tuple_set(List), Opaques) ->
+  inf_tuple_sets(List, [{Arity, [T]}], Opaques);
 %% be careful: here and in the next clause T can be ?opaque
-t_inf(?union(U1), T, Mode) ->
+t_inf(?union(U1), T, Opaques) ->
   ?union(U2) = force_union(T),
-  inf_union(U1, U2, Mode);
-t_inf(T, ?union(U2), Mode) ->
+  inf_union(U1, U2, Opaques);
+t_inf(T, ?union(U2), Opaques) ->
   ?union(U1) = force_union(T),
-  inf_union(U1, U2, Mode);
+  inf_union(U1, U2, Opaques);
+t_inf(?opaque(Set1), ?opaque(Set2), Opaques) ->
+  inf_opaque(Set1, Set2, Opaques);
+t_inf(?opaque(_) = T1, T2, Opaques) ->
+  inf_opaque1(T2, T1, 1, Opaques);
+t_inf(T1, ?opaque(_) = T2, Opaques) ->
+  inf_opaque1(T1, T2, 2, Opaques);
 %% and as a result, the cases for ?opaque should appear *after* ?union
-t_inf(?opaque(Set1) = T1, ?opaque(Set2) = T2, Mode) ->
-  case set_intersection(Set1, Set2) of
-    ?none ->
-      case Mode =:= opaque of
-	true ->
-	  Struct1 = t_opaque_structure(T1),
-	  case t_inf(Struct1, T2) of
-	    ?none ->
-	      Struct2 = t_opaque_structure(T2),
-	      case t_inf(Struct2, T1) of
-		?none -> ?none;
-		_ -> T2
-	      end;
-	    _ -> T1
-	  end;
-	false -> ?none
-      end;
-    NewSet -> ?opaque(NewSet)
-  end;
-t_inf(?opaque(_) = T1, T2, opaque) ->
-  case t_inf(t_opaque_structure(T1), T2, structured) of
-    ?none -> ?none;
-    _Type -> T1
-  end;
-t_inf(T1, ?opaque(_) = T2, opaque) ->
-  case t_inf(T1, t_opaque_structure(T2), structured) of
-    ?none -> ?none;
-    _Type -> T2
-  end;
 t_inf(#c{}, #c{}, _) ->
   ?none.
 
+inf_opaque1(T1, ?opaque(Set2)=T2, Pos, Opaques) ->
+  case Opaques =:= 'universe' orelse inf_is_opaque_type(T2, Pos, Opaques) of
+    false -> ?none;
+    true ->
+      List2 = set_to_list(Set2),
+      case inf_collect(T1, List2, Opaques, []) of
+        [] -> ?none;
+        OpL -> ?opaque(ordsets:from_list(OpL))
+      end
+  end.
+
+inf_is_opaque_type(T, Pos, {match, Opaques}) ->
+  is_opaque_type(T, Opaques) orelse throw(Pos);
+inf_is_opaque_type(T, _Pos, Opaques) ->
+  is_opaque_type(T, Opaques).
+
+inf_collect(T1, [T2|List2], Opaques, OpL) ->
+  #opaque{struct = S2} = T2,
+  case t_inf(T1, S2, Opaques) of
+    ?none -> inf_collect(T1, List2, Opaques, OpL);
+    Inf ->
+      Op = T2#opaque{struct = Inf},
+      inf_collect(T1, List2, Opaques, [Op|OpL])
+  end;
+inf_collect(_T1, [], _Opaques, OpL) ->
+  OpL.
+
+combine(S, T1, T2) ->
+  #opaque{mod = Mod1, name = Name1} = T1,
+  #opaque{mod = Mod2, name = Name2} = T2,
+  case {Mod1, Name1} =:= {Mod2, Name2} of
+    true  -> [comb(Mod1, Name1, S, T1)];
+    false -> [comb(Mod1, Name1, S, T1), comb(Mod2, Name2, S, T2)]
+  end.
+
+comb(Mod, Name, S, T) ->
+  case is_same_name(Mod, Name, S) of
+    true -> S;
+    false -> T#opaque{struct = S}
+  end.
+
+is_same_name(Mod, Name, ?opaque([#opaque{mod = Mod, name = Name}])) -> true;
+is_same_name(_Mod, _Name, _Opaque) -> false.
+
+%% Combining two lists this way can be very time consuming...
+inf_opaque(Set1, Set2, Opaques) ->
+  List1 = inf_look_up(Set1, 1, Opaques),
+  List2 = inf_look_up(Set2, 2, Opaques),
+  List0 = [combine(Inf, T1, T2) ||
+            {Is1, ModName1, T1} <- List1,
+            {Is2, ModName2, T2} <- List2,
+            not t_is_none(Inf = inf_opaque_types(Is1, ModName1, T1,
+                                                 Is2, ModName2, T2,
+                                                 Opaques))],
+  List = lists:sort(lists:append(List0)),
+  sup_opaque(List).
+
+%% Optimization: do just one lookup.
+inf_look_up(Set, Pos, Opaques) ->
+  [{Opaques =:= 'universe' orelse inf_is_opaque_type2(T, Pos, Opaques),
+    {M, N}, T} ||
+    #opaque{mod = M, name = N} = T <- set_to_list(Set)].
+
+inf_is_opaque_type2(T, Pos, {match, Opaques}) ->
+  is_opaque_type2(T, Opaques) orelse throw(Pos);
+inf_is_opaque_type2(T, _Pos, Opaques) ->
+  is_opaque_type2(T, Opaques).
+
+inf_opaque_types(IsOpaque1, ModName1, T1, IsOpaque2, ModName2, T2, Opaques) ->
+  #opaque{struct = S1}=T1,
+  #opaque{struct = S2}=T2,
+  case Opaques =:= 'universe' orelse ModName1 =:= ModName2 of
+    true -> t_inf(S1, S2, Opaques);
+    false ->
+      case {IsOpaque1, IsOpaque2} of
+        {true, true}   -> t_inf(S1, S2, Opaques);
+        {true, false}  -> t_inf(S1, ?opaque(set_singleton(T2)), Opaques);
+        {false, true}  -> t_inf(?opaque(set_singleton(T1)), S2, Opaques);
+        {false, false} -> t_none()
+      end
+  end.
+
 -spec t_inf_lists([erl_type()], [erl_type()]) -> [erl_type()].
 
 t_inf_lists(L1, L2) ->
-  t_inf_lists(L1, L2, structured).
+  t_inf_lists(L1, L2, 'universe').
 
--spec t_inf_lists([erl_type()], [erl_type()], t_inf_mode()) -> [erl_type()].
+-spec t_inf_lists([erl_type()], [erl_type()], t_inf_opaques()) -> [erl_type()].
 
-t_inf_lists(L1, L2, Mode) ->
-  t_inf_lists(L1, L2, [], Mode).
+t_inf_lists(L1, L2, Opaques) ->
+  t_inf_lists(L1, L2, [], Opaques).
 
--spec t_inf_lists([erl_type()], [erl_type()], [erl_type()], t_inf_mode()) -> [erl_type()].
+-spec t_inf_lists([erl_type()], [erl_type()], [erl_type()], [erl_type()]) -> [erl_type()].
 
-t_inf_lists([T1|Left1], [T2|Left2], Acc, Mode) ->
-  t_inf_lists(Left1, Left2, [t_inf(T1, T2, Mode)|Acc], Mode);
-t_inf_lists([], [], Acc, _Mode) ->
+t_inf_lists([T1|Left1], [T2|Left2], Acc, Opaques) ->
+  t_inf_lists(Left1, Left2, [t_inf(T1, T2, Opaques)|Acc], Opaques);
+t_inf_lists([], [], Acc, _Opaques) ->
   lists:reverse(Acc).
 
 %% Infimum of lists with strictness.
 %% If any element is the ?none type, the value 'bottom' is returned.
 
--spec t_inf_lists_strict([erl_type()], [erl_type()], t_inf_mode()) -> 'bottom' | [erl_type()].
+-spec t_inf_lists_strict([erl_type()], [erl_type()], [erl_type()]) -> 'bottom' | [erl_type()].
 
-t_inf_lists_strict(L1, L2, Mode) ->
-  t_inf_lists_strict(L1, L2, [], Mode).
+t_inf_lists_strict(L1, L2, Opaques) ->
+  t_inf_lists_strict(L1, L2, [], Opaques).
 
--spec t_inf_lists_strict([erl_type()], [erl_type()], [erl_type()], t_inf_mode()) -> 'bottom' | [erl_type()].
+-spec t_inf_lists_strict([erl_type()], [erl_type()], [erl_type()], [erl_type()]) -> 'bottom' | [erl_type()].
 
-t_inf_lists_strict([T1|Left1], [T2|Left2], Acc, Mode) ->
-  case t_inf(T1, T2, Mode) of
+t_inf_lists_strict([T1|Left1], [T2|Left2], Acc, Opaques) ->
+  case t_inf(T1, T2, Opaques) of
     ?none -> bottom;
-    T -> t_inf_lists_strict(Left1, Left2, [T|Acc], Mode)
+    T -> t_inf_lists_strict(Left1, Left2, [T|Acc], Opaques)
   end;
-t_inf_lists_strict([], [], Acc, _Mode) ->
+t_inf_lists_strict([], [], Acc, _Opaques) ->
   lists:reverse(Acc).
 
--spec t_inf_lists_masked([erl_type()], [erl_type()], [t_inf_mode()]) -> [erl_type()].
-
-t_inf_lists_masked(List1, List2, Mask) ->
-  List = lists:zip3(List1, List2, Mask),
-  [t_inf(T1, T2, Mode) || {T1, T2, Mode} <- List].
-
-inf_tuple_sets(L1, L2, Mode) ->
-  case inf_tuple_sets(L1, L2, [], Mode) of
+inf_tuple_sets(L1, L2, Opaques) ->
+  case inf_tuple_sets(L1, L2, [], Opaques) of
     [] -> ?none;
     [{_Arity, [?tuple(_, _, _) = OneTuple]}] -> OneTuple;
     List -> ?tuple_set(List)
   end.
 
-inf_tuple_sets([{Arity, Tuples1}|Ts1], [{Arity, Tuples2}|Ts2], Acc, Mode) ->
-  case inf_tuples_in_sets(Tuples1, Tuples2, Mode) of
-    [] -> inf_tuple_sets(Ts1, Ts2, Acc, Mode);
+inf_tuple_sets([{Arity, Tuples1}|Ts1], [{Arity, Tuples2}|Ts2], Acc, Opaques) ->
+  case inf_tuples_in_sets(Tuples1, Tuples2, Opaques) of
+    [] -> inf_tuple_sets(Ts1, Ts2, Acc, Opaques);
     [?tuple_set([{Arity, NewTuples}])] ->
-      inf_tuple_sets(Ts1, Ts2, [{Arity, NewTuples}|Acc], Mode);
-    NewTuples -> inf_tuple_sets(Ts1, Ts2, [{Arity, NewTuples}|Acc], Mode)
+      inf_tuple_sets(Ts1, Ts2, [{Arity, NewTuples}|Acc], Opaques);
+    NewTuples -> inf_tuple_sets(Ts1, Ts2, [{Arity, NewTuples}|Acc], Opaques)
   end;
-inf_tuple_sets([{Arity1, _}|Ts1] = L1, [{Arity2, _}|Ts2] = L2, Acc, Mode) ->
-  if Arity1 < Arity2 -> inf_tuple_sets(Ts1, L2, Acc, Mode);
-     Arity1 > Arity2 -> inf_tuple_sets(L1, Ts2, Acc, Mode)
+inf_tuple_sets([{Arity1, _}|Ts1] = L1, [{Arity2, _}|Ts2] = L2, Acc, Opaques) ->
+  if Arity1 < Arity2 -> inf_tuple_sets(Ts1, L2, Acc, Opaques);
+     Arity1 > Arity2 -> inf_tuple_sets(L1, Ts2, Acc, Opaques)
   end;
-inf_tuple_sets([], _, Acc, _Mode) -> lists:reverse(Acc);
-inf_tuple_sets(_, [], Acc, _Mode) -> lists:reverse(Acc).
-      
-inf_tuples_in_sets([?tuple(Elements1, _, ?any)], L2, Mode) ->
-  NewList = [t_inf_lists_strict(Elements1, Elements2, Mode)
+inf_tuple_sets([], _, Acc, _Opaques) -> lists:reverse(Acc);
+inf_tuple_sets(_, [], Acc, _Opaques) -> lists:reverse(Acc).
+
+inf_tuples_in_sets([?tuple(Elements1, _, ?any)], L2, Opaques) ->
+  NewList = [t_inf_lists_strict(Elements1, Elements2, Opaques)
 	     || ?tuple(Elements2, _, _) <- L2],
   [t_tuple(Es) || Es <- NewList, Es =/= bottom];
-inf_tuples_in_sets(L1, [?tuple(Elements2, _, ?any)], Mode) ->
-  NewList = [t_inf_lists_strict(Elements1, Elements2, Mode)
+inf_tuples_in_sets(L1, [?tuple(Elements2, _, ?any)], Opaques) ->
+  NewList = [t_inf_lists_strict(Elements1, Elements2, Opaques)
 	     || ?tuple(Elements1, _, _) <- L1],
   [t_tuple(Es) || Es <- NewList, Es =/= bottom];
-inf_tuples_in_sets(L1, L2, Mode) ->
-  inf_tuples_in_sets(L1, L2, [], Mode).
+inf_tuples_in_sets(L1, L2, Opaques) ->
+  inf_tuples_in_sets2(L1, L2, [], Opaques).
 
-inf_tuples_in_sets([?tuple(Elements1, Arity, Tag)|Ts1],
-		   [?tuple(Elements2, Arity, Tag)|Ts2], Acc, Mode) ->
-  case t_inf_lists_strict(Elements1, Elements2, Mode) of
-    bottom -> inf_tuples_in_sets(Ts1, Ts2, Acc, Mode);
+inf_tuples_in_sets2([?tuple(Elements1, Arity, Tag)|Ts1],
+                    [?tuple(Elements2, Arity, Tag)|Ts2], Acc, Opaques) ->
+  case t_inf_lists_strict(Elements1, Elements2, Opaques) of
+    bottom -> inf_tuples_in_sets2(Ts1, Ts2, Acc, Opaques);
     NewElements ->
-      inf_tuples_in_sets(Ts1, Ts2, [?tuple(NewElements, Arity, Tag)|Acc], Mode)
+      inf_tuples_in_sets2(Ts1, Ts2, [?tuple(NewElements, Arity, Tag)|Acc],
+                          Opaques)
+  end;
+inf_tuples_in_sets2([?tuple(_, _, Tag1)|Ts1] = L1,
+                    [?tuple(_, _, Tag2)|Ts2] = L2, Acc, Opaques) ->
+  if Tag1 < Tag2 -> inf_tuples_in_sets2(Ts1, L2, Acc, Opaques);
+     Tag1 > Tag2 -> inf_tuples_in_sets2(L1, Ts2, Acc, Opaques)
   end;
-inf_tuples_in_sets([?tuple(_, _, Tag1)|Ts1] = L1,
-		   [?tuple(_, _, Tag2)|Ts2] = L2, Acc, Mode) ->
-  if Tag1 < Tag2 -> inf_tuples_in_sets(Ts1, L2, Acc, Mode);
-     Tag1 > Tag2 -> inf_tuples_in_sets(L1, Ts2, Acc, Mode)
+inf_tuples_in_sets2([], _, Acc, _Opaques) -> lists:reverse(Acc);
+inf_tuples_in_sets2(_, [], Acc, _Opaques) -> lists:reverse(Acc).
+
+inf_union(U1, U2, Opaques) ->
+  OpaqueFun =
+    fun(Union1, Union2, InfFun) ->
+	[_,_,_,_,_,_,_,_,Opaque,_] = Union1,
+        [A,B,F,I,L,N,T,M,_,_R] = Union2,
+        List = [A,B,F,I,L,N,T,M],
+        inf_union_collect(List, Opaque, InfFun, [], [])
+    end,
+  O1 = OpaqueFun(U1, U2, fun(E, Opaque) -> t_inf(Opaque, E, Opaques) end),
+  O2 = OpaqueFun(U2, U1, fun(E, Opaque) -> t_inf(E, Opaque, Opaques) end),
+  Union = inf_union(U1, U2, 0, [], Opaques),
+  t_sup([O1, O2, Union]).
+
+inf_union_collect([], _Opaque, _InfFun, InfList, ThrowList) ->
+  case t_sup(InfList) of
+    ?none when ThrowList =/= [] -> throw(hd(lists:flatten(ThrowList)));
+    Sup -> Sup
   end;
-inf_tuples_in_sets([], _, Acc, _Mode) -> lists:reverse(Acc);
-inf_tuples_in_sets(_, [], Acc, _Mode) -> lists:reverse(Acc).
-
-inf_union(U1, U2, opaque) ->
-%%---------------------------------------------------------------------
-%%                          Under Testing
-%%----------------------------------------------------------------------
-%%   OpaqueFun = 
-%%     fun(Union1, Union2) ->
-%% 	[_,_,_,_,_,_,_,_,Opaque,_] = Union1,
-%% 	[A,B,F,I,L,N,T,M,_,_R] = Union2,
-%% 	List = [A,B,F,I,L,N,T,M],
-%%         case [T || T <- List, t_inf(T, Opaque, opaque) =/= ?none] of
-%% 	  [] -> ?none;
-%% 	  _  -> Opaque
-%% 	end
-%%     end,
-%%   O1 = OpaqueFun(U1, U2),
-%%   O2 = OpaqueFun(U2, U1),
-%%   Union = inf_union(U1, U2, 0, [], opaque),
-%%   t_sup([O1, O2, Union]);
-  inf_union(U1, U2, 0, [], opaque);
-inf_union(U1, U2, OtherMode) ->
-  inf_union(U1, U2, 0, [], OtherMode).
-
-inf_union([?none|Left1], [?none|Left2], N, Acc, Mode) ->
-  inf_union(Left1, Left2, N, [?none|Acc], Mode);
-inf_union([T1|Left1], [T2|Left2], N, Acc, Mode) ->
-  case t_inf(T1, T2, Mode) of
-    ?none -> inf_union(Left1, Left2, N, [?none|Acc], Mode);
-    T     -> inf_union(Left1, Left2, N+1, [T|Acc], Mode)
+inf_union_collect([?none|L], Opaque, InfFun, InfList, ThrowList) ->
+  inf_union_collect(L, Opaque, InfFun, [?none|InfList], ThrowList);
+inf_union_collect([E|L], Opaque, InfFun, InfList, ThrowList) ->
+  try InfFun(E, Opaque)of
+    Inf ->
+      inf_union_collect(L, Opaque, InfFun, [Inf|InfList], ThrowList)
+  catch throw:N when is_integer(N) ->
+      inf_union_collect(L, Opaque, InfFun, InfList, [N|ThrowList])
+  end.
+
+inf_union([?none|Left1], [?none|Left2], N, Acc, Opaques) ->
+  inf_union(Left1, Left2, N, [?none|Acc], Opaques);
+inf_union([T1|Left1], [T2|Left2], N, Acc, Opaques) ->
+  case t_inf(T1, T2, Opaques) of
+    ?none -> inf_union(Left1, Left2, N, [?none|Acc], Opaques);
+    T     -> inf_union(Left1, Left2, N+1, [T|Acc], Opaques)
   end;
-inf_union([], [], N, Acc, _Mode) ->
+inf_union([], [], N, Acc, _Opaques) ->
   if N =:= 0 -> ?none;
      N =:= 1 ->
       [Type] = [T || T <- Acc, T =/= ?none],
@@ -2536,6 +3025,11 @@ t_subst_dict(?tuple(Elements, _Arity, _Tag), Dict) ->
   t_tuple([t_subst_dict(E, Dict) || E <- Elements]);
 t_subst_dict(?tuple_set(_) = TS, Dict) ->
   t_sup([t_subst_dict(T, Dict) || T <- t_tuple_subtypes(TS)]);
+%% t_subst_dict(?opaque(Es), Dict) ->
+%%   %% "Polymorphic opaque types not supported yet"
+%%   List = [Opaque#opaque{struct = t_subst_dict(S, Dict)} ||
+%%            Opaque = #opaque{struct = S} <- set_to_list(Es)],
+%%   ?opaque(ordsets:from_list(List));
 t_subst_dict(T, _Dict) ->
   T.
 
@@ -2578,6 +3072,11 @@ t_subst_aux(?tuple(Elements, _Arity, _Tag), VarMap) ->
   t_tuple([t_subst_aux(E, VarMap) || E <- Elements]);
 t_subst_aux(?tuple_set(_) = TS, VarMap) ->
   t_sup([t_subst_aux(T, VarMap) || T <- t_tuple_subtypes(TS)]);
+%% t_subst_aux(?opaque(Es), VarMap) ->
+%%   %% "Polymorphic opaque types not supported yet"
+%%   List = [Opaque#opaque{struct = t_subst_aux(S, VarMap)} ||
+%%            Opaque = #opaque{struct = S} <- set_to_list(Es)],
+%%   ?opaque(ordsets:from_list(List));
 t_subst_aux(T, _VarMap) ->
   T.
 	      
@@ -2590,112 +3089,147 @@ t_subst_aux(T, _VarMap) ->
 -spec t_unify(erl_type(), erl_type()) -> t_unify_ret().
 
 t_unify(T1, T2) ->
-  t_unify(T1, T2, []).
-
--spec t_unify(erl_type(), erl_type(), [erl_type()]) -> t_unify_ret().
-
-t_unify(T1, T2, Opaques) ->
-  {T, VarMap} = t_unify(T1, T2, [], Opaques),
+  {T, VarMap} = t_unify(T1, T2, []),
   {t_subst_kv(T, VarMap), lists:keysort(1, VarMap)}.
 
-t_unify(?var(Id) = T, ?var(Id), VarMap, _Opaques) ->
+t_unify(?var(Id) = T, ?var(Id), VarMap) ->
   {T, VarMap};
-t_unify(?var(Id1) = T, ?var(Id2), VarMap, Opaques) ->
+t_unify(?var(Id1) = T, ?var(Id2), VarMap) ->
   case lists:keyfind(Id1, 1, VarMap) of
     false ->
       case lists:keyfind(Id2, 1, VarMap) of
 	false -> {T, [{Id2, T} | VarMap]};
-	{Id2, Type} -> t_unify(T, Type, VarMap, Opaques)
+	{Id2, Type} -> t_unify(T, Type, VarMap)
       end;
     {Id1, Type1} ->
       case lists:keyfind(Id2, 1, VarMap) of
 	false -> {Type1, [{Id2, T} | VarMap]};
-	{Id2, Type2} -> t_unify(Type1, Type2, VarMap, Opaques)
+	{Id2, Type2} -> t_unify(Type1, Type2, VarMap)
       end
   end;
-t_unify(?var(Id), Type, VarMap, Opaques) ->
+t_unify(?var(Id), Type, VarMap) ->
   case lists:keyfind(Id, 1, VarMap) of
     false -> {Type, [{Id, Type} | VarMap]};
-    {Id, VarType} -> t_unify(VarType, Type, VarMap, Opaques)
+    {Id, VarType} -> t_unify(VarType, Type, VarMap)
   end;
-t_unify(Type, ?var(Id), VarMap, Opaques) ->
+t_unify(Type, ?var(Id), VarMap) ->
   case lists:keyfind(Id, 1, VarMap) of
     false -> {Type, [{Id, Type} | VarMap]};
-    {Id, VarType} -> t_unify(VarType, Type, VarMap, Opaques)
+    {Id, VarType} -> t_unify(VarType, Type, VarMap)
   end;
-t_unify(?function(Domain1, Range1), ?function(Domain2, Range2), VarMap, Opaques) ->
-  {Domain, VarMap1} = t_unify(Domain1, Domain2, VarMap, Opaques),
-  {Range, VarMap2} = t_unify(Range1, Range2, VarMap1, Opaques),
+t_unify(?function(Domain1, Range1), ?function(Domain2, Range2), VarMap) ->
+  {Domain, VarMap1} = t_unify(Domain1, Domain2, VarMap),
+  {Range, VarMap2} = t_unify(Range1, Range2, VarMap1),
   {?function(Domain, Range), VarMap2};
 t_unify(?list(Contents1, Termination1, Size), 
-	?list(Contents2, Termination2, Size), VarMap, Opaques) ->
-  {Contents, VarMap1} = t_unify(Contents1, Contents2, VarMap, Opaques),
-  {Termination, VarMap2} = t_unify(Termination1, Termination2, VarMap1, Opaques),
+	?list(Contents2, Termination2, Size), VarMap) ->
+  {Contents, VarMap1} = t_unify(Contents1, Contents2, VarMap),
+  {Termination, VarMap2} = t_unify(Termination1, Termination2, VarMap1),
   {?list(Contents, Termination, Size), VarMap2};
-t_unify(?product(Types1), ?product(Types2), VarMap, Opaques) ->
-  {Types, VarMap1} = unify_lists(Types1, Types2, VarMap, Opaques),
+t_unify(?product(Types1), ?product(Types2), VarMap) ->
+  {Types, VarMap1} = unify_lists(Types1, Types2, VarMap),
   {?product(Types), VarMap1};
-t_unify(?tuple(?any, ?any, ?any) = T, ?tuple(?any, ?any, ?any), VarMap, _Opaques) ->
+t_unify(?tuple(?any, ?any, ?any) = T, ?tuple(?any, ?any, ?any), VarMap) ->
   {T, VarMap};
 t_unify(?tuple(Elements1, Arity, _), 
-	?tuple(Elements2, Arity, _), VarMap, Opaques) when Arity =/= ?any ->
-  {NewElements, VarMap1} = unify_lists(Elements1, Elements2, VarMap, Opaques),
+	?tuple(Elements2, Arity, _), VarMap) when Arity =/= ?any ->
+  {NewElements, VarMap1} = unify_lists(Elements1, Elements2, VarMap),
   {t_tuple(NewElements), VarMap1};
 t_unify(?tuple_set([{Arity, _}]) = T1, 
-	?tuple(_, Arity, _) = T2, VarMap, Opaques) when Arity =/= ?any ->
-  unify_tuple_set_and_tuple(T1, T2, VarMap, Opaques);
+	?tuple(_, Arity, _) = T2, VarMap) when Arity =/= ?any ->
+  unify_tuple_set_and_tuple1(T1, T2, VarMap);
 t_unify(?tuple(_, Arity, _) = T1,
-	?tuple_set([{Arity, _}]) = T2, VarMap, Opaques) when Arity =/= ?any ->
-  unify_tuple_set_and_tuple(T2, T1, VarMap, Opaques);
-t_unify(?tuple_set(List1), ?tuple_set(List2), VarMap, Opaques) ->
-  {Tuples, NewVarMap} =
-    unify_lists(lists:append([T || {_Arity, T} <- List1]), 
-		lists:append([T || {_Arity, T} <- List2]), VarMap, Opaques),
-  {t_sup(Tuples), NewVarMap};
-t_unify(?opaque(Elements) = T, ?opaque(Elements), VarMap, _Opaques) ->
-  {T, VarMap};
-t_unify(?opaque(_) = T1, ?opaque(_) = T2, _VarMap, _Opaques) ->
-  throw({mismatch, T1, T2});
-t_unify(Type, ?opaque(_) = OpType, VarMap, Opaques) ->
-  t_unify_with_opaque(Type, OpType, VarMap, Opaques);
-t_unify(?opaque(_) = OpType, Type, VarMap, Opaques) ->
-  t_unify_with_opaque(Type, OpType, VarMap, Opaques);
-t_unify(T, T, VarMap, _Opaques) ->
+	?tuple_set([{Arity, _}]) = T2, VarMap) when Arity =/= ?any ->
+  unify_tuple_set_and_tuple2(T1, T2, VarMap);
+t_unify(?tuple_set(List1) = T1, ?tuple_set(List2) = T2, VarMap) ->
+  try
+    unify_lists(lists:append([T || {_Arity, T} <- List1]),
+                lists:append([T || {_Arity, T} <- List2]), VarMap)
+  of
+    {Tuples, NewVarMap} -> {t_sup(Tuples), NewVarMap}
+  catch _:_ -> throw({mismatch, T1, T2})
+  end;
+t_unify(?opaque(_) = T1, ?opaque(_) = T2, VarMap) ->
+  t_unify(t_opaque_structure(T1), t_opaque_structure(T2), VarMap);
+t_unify(T1, ?opaque(_) = T2, VarMap) ->
+  t_unify(T1, t_opaque_structure(T2), VarMap);
+t_unify(?opaque(_) = T1, T2, VarMap) ->
+  t_unify(t_opaque_structure(T1), T2, VarMap);
+t_unify(T, T, VarMap) ->
   {T, VarMap};
-t_unify(T1, T2, _, _) ->
+t_unify(?union(_)=T1, ?union(_)=T2, VarMap) ->
+  {Type1, Type2} = unify_union2(T1, T2),
+  t_unify(Type1, Type2, VarMap);
+t_unify(?union(_)=T1, T2, VarMap) ->
+  t_unify(unify_union1(T1, T1, T2), T2, VarMap);
+t_unify(T1, ?union(_)=T2, VarMap) ->
+  t_unify(T1, unify_union1(T2, T1, T2), VarMap);
+t_unify(T1, T2, _) ->
   throw({mismatch, T1, T2}).
 
-t_unify_with_opaque(Type, OpType, VarMap, Opaques) ->
-  case lists:member(OpType, Opaques) of
+unify_union2(?union(List1)=T1, ?union(List2)=T2) ->
+  case {unify_union(List1), unify_union(List2)} of
+    {{yes, Type1}, {yes, Type2}} -> {Type1, Type2};
+    {{yes, Type1}, no} -> {Type1, T2};
+    {no, {yes, Type2}} -> {T1, Type2};
+    {no, no} -> throw({mismatch, T1, T2})
+  end.
+
+unify_union1(?union(List), T1, T2) ->
+  case unify_union(List) of
+    {yes, Type} -> Type;
+    no -> throw({mismatch, T1, T2})
+  end.
+
+unify_union(List) ->
+  [A,B,F,I,L,N,T,M,O,R] = List,
+  if O =:= ?none -> no;
     true ->
-      Struct = t_opaque_structure(OpType),
-      try t_unify(Type, Struct, VarMap, Opaques) of
-	{_T, VarMap1} -> {OpType, VarMap1}
-      catch
-	throw:{mismatch, _T1, _T2} ->
-	  case t_inf(OpType, Type, opaque) of
-	    ?none -> throw({mismatch, Type, OpType});
-	    _ -> {OpType, VarMap}
-	  end
-      end;
-    false ->
-      throw({mismatch, Type, OpType})
+      S = t_opaque_structure(O),
+      {yes, t_sup([A,B,F,I,L,N,T,M,S,R])}
   end.
 
-unify_tuple_set_and_tuple(?tuple_set([{Arity, List}]), 
-			  ?tuple(Elements2, Arity, _), VarMap, Opaques) ->
+-spec is_opaque_type(erl_type(), [erl_type()]) -> boolean().
+
+%% An opaque type is a union of types. Returns true iff any of the type
+%% names (Module and Name) of the first argument (the opaque type to
+%% check) occurs in any of the opaque types of the second argument.
+is_opaque_type(?opaque(Elements), Opaques) ->
+  lists:any(fun(Opaque) -> is_opaque_type2(Opaque, Opaques) end, Elements).
+
+is_opaque_type2(#opaque{mod = Mod1, name = Name1}, Opaques) ->
+  F1 = fun(?opaque(Es)) ->
+           F2 = fun(#opaque{mod = Mod, name = Name}) ->
+                    Mod1 =:= Mod andalso Name1 =:= Name
+                end,
+           lists:any(F2, Es)
+       end,
+  lists:any(F1, Opaques).
+
+%% Two functions since t_unify is not symmetric.
+unify_tuple_set_and_tuple1(?tuple_set([{Arity, List}]),
+                           ?tuple(Elements2, Arity, _), VarMap) ->
+  %% Can only work if the single tuple has variables at correct places.
+  %% Collapse the tuple set.
+  {NewElements, VarMap1} =
+    unify_lists(sup_tuple_elements(List), Elements2, VarMap),
+  {t_tuple(NewElements), VarMap1}.
+
+unify_tuple_set_and_tuple2(?tuple(Elements2, Arity, _),
+                           ?tuple_set([{Arity, List}]), VarMap) ->
   %% Can only work if the single tuple has variables at correct places.
   %% Collapse the tuple set.
-  {NewElements, VarMap1} = unify_lists(sup_tuple_elements(List), Elements2, VarMap, Opaques),
+  {NewElements, VarMap1} =
+    unify_lists(Elements2, sup_tuple_elements(List), VarMap),
   {t_tuple(NewElements), VarMap1}.
 
-unify_lists(L1, L2, VarMap, Opaques) ->
-  unify_lists(L1, L2, VarMap, [], Opaques).
+unify_lists(L1, L2, VarMap) ->
+  unify_lists(L1, L2, VarMap, []).
 
-unify_lists([T1|Left1], [T2|Left2], VarMap, Acc, Opaques) ->
-  {NewT, NewVarMap} = t_unify(T1, T2, VarMap, Opaques),
-  unify_lists(Left1, Left2, NewVarMap, [NewT|Acc], Opaques);
-unify_lists([], [], VarMap, Acc, _Opaques) ->
+unify_lists([T1|Left1], [T2|Left2], VarMap, Acc) ->
+  {NewT, NewVarMap} = t_unify(T1, T2, VarMap),
+  unify_lists(Left1, Left2, NewVarMap, [NewT|Acc]);
+unify_lists([], [], VarMap, Acc) ->
   {lists:reverse(Acc), VarMap}.
 
 %%t_assign_variables_to_subtype(T1, T2) ->
@@ -2837,11 +3371,12 @@ t_subtract(?identifier(Set1), ?identifier(Set2)) ->
     ?none -> ?none;
     Set -> ?identifier(Set)
   end;
-t_subtract(?opaque(Set1), ?opaque(Set2)) ->
-  case set_subtract(Set1, Set2) of
-    ?none -> ?none;
-    Set -> ?opaque(Set)
-  end;
+t_subtract(?opaque(_)=T1, ?opaque(_)=T2) ->
+  opaque_subtract(T1, t_opaque_structure(T2));
+t_subtract(?opaque(_)=T1, T2) ->
+  opaque_subtract(T1, T2);
+t_subtract(T1, ?opaque(_)=T2) ->
+  t_subtract(T1, t_opaque_structure(T2));
 t_subtract(?matchstate(Pres1, Slots1), ?matchstate(Pres2, _Slots2)) ->
   Pres = t_subtract(Pres1, Pres2),
   case t_is_none(Pres) of
@@ -2976,6 +3511,17 @@ t_subtract(T1, T2) ->
   ?union(U2) = force_union(T2),
   subtract_union(U1, U2).
 
+-spec opaque_subtract(erl_type(), erl_type()) -> erl_type().
+
+opaque_subtract(?opaque(Set1), T2) ->
+  List = [T1#opaque{struct = Sub} ||
+           #opaque{struct = S1}=T1 <- set_to_list(Set1),
+           not t_is_none(Sub = t_subtract(S1, T2))],
+  case List of
+    [] -> ?none;
+    _ -> ?opaque(ordsets:from_list(List))
+  end.
+
 -spec t_subtract_lists([erl_type()], [erl_type()]) -> [erl_type()].
 
 t_subtract_lists(L1, L2) ->
@@ -2991,7 +3537,18 @@ t_subtract_lists([], [], Acc) ->
 -spec subtract_union([erl_type(),...], [erl_type(),...]) -> erl_type().
 
 subtract_union(U1, U2) ->
-  subtract_union(U1, U2, 0, []).
+  [A1,B1,F1,I1,L1,N1,T1,M1,O1,R1] = U1,
+  [A2,B2,F2,I2,L2,N2,T2,M2,O2,R2] = U2,
+  List1 = [A1,B1,F1,I1,L1,N1,T1,M1,?none,R1],
+  List2 = [A2,B2,F2,I2,L2,N2,T2,M2,?none,R2],
+  Sub1 = subtract_union(List1, List2, 0, []),
+  O = if O1 =:= ?none -> O1;
+         true -> t_subtract(O1, ?union(U2))
+      end,
+  Sub2 = if O2 =:= ?none -> Sub1;
+            true -> t_subtract(Sub1, t_opaque_structure(O2))
+         end,
+  t_sup(O, Sub2).
 
 -spec subtract_union([erl_type()], [erl_type()], non_neg_integer(), [erl_type()]) -> erl_type().
 
@@ -3052,10 +3609,24 @@ t_is_equal(_, _) -> false.
 
 t_is_subtype(T1, T2) ->
   Inf = t_inf(T1, T2),
-  t_is_equal(T1, Inf).
+  subtype_is_equal(T1, Inf).
+
+%% The subtype relation has to behave correctly irrespective of opaque
+%% types.
+subtype_is_equal(T, T)   -> true;
+subtype_is_equal(T1, T2) ->
+  t_is_equal(case t_contains_opaque(T1) of
+               true  -> t_unopaque(T1);
+               false -> T1
+             end,
+             case t_contains_opaque(T2) of
+               true  -> t_unopaque(T2);
+               false -> T2
+             end).
 
 -spec t_is_instance(erl_type(), erl_type()) -> boolean().
 
+%% XXX. To be removed.
 t_is_instance(ConcreteType, Type) ->
   t_is_subtype(ConcreteType, t_unopaque(Type)).
 
@@ -3067,12 +3638,12 @@ t_unopaque(T) ->
 -spec t_unopaque(erl_type(), 'universe' | [erl_type()]) -> erl_type().
 
 t_unopaque(?opaque(_) = T, Opaques) ->
-  case Opaques =:= universe orelse lists:member(T, Opaques) of
+  case Opaques =:= 'universe' orelse is_opaque_type(T, Opaques) of
     true -> t_unopaque(t_opaque_structure(T), Opaques);
     false -> T  % XXX: needs revision for parametric opaque data types
   end;
 t_unopaque(?list(ElemT, Termination, Sz), Opaques) ->
-  ?list(t_unopaque(ElemT, Opaques), Termination, Sz);
+  ?list(t_unopaque(ElemT, Opaques), t_unopaque(Termination, Opaques), Sz);
 t_unopaque(?tuple(?any, _, _) = T, _) -> T;
 t_unopaque(?tuple(ArgTs, Sz, Tag), Opaques) when is_list(ArgTs) ->
   NewArgTs = [t_unopaque(A, Opaques) || A <- ArgTs],
@@ -3081,14 +3652,19 @@ t_unopaque(?tuple_set(Set), Opaques) ->
   NewSet = [{Sz, [t_unopaque(T, Opaques) || T <- Tuples]}
 	    || {Sz, Tuples} <- Set],
   ?tuple_set(NewSet);
+t_unopaque(?product(Types), Opaques) ->
+  ?product([t_unopaque(T, Opaques) || T <- Types]);
+t_unopaque(?function(Domain, Range), Opaques) ->
+  ?function(t_unopaque(Domain, Opaques), t_unopaque(Range, Opaques));
 t_unopaque(?union([A,B,F,I,L,N,T,M,O,R]), Opaques) ->
   UL = t_unopaque(L, Opaques),
   UT = t_unopaque(T, Opaques),
-  UO = case O of
-	 ?none -> [];
-	 ?opaque(Os) -> [t_unopaque(S, Opaques) || #opaque{struct = S} <- Os]
-       end,
-  t_sup([?union([A,B,F,I,UL,N,UT,M,?none,R])|UO]);
+  UF = t_unopaque(F, Opaques),
+  {OF,UO} = case t_unopaque(O, Opaques) of
+              ?opaque(_) = O1 -> {O1, []};
+              Type -> {?none, [Type]}
+            end,
+  t_sup([?union([A,B,UF,I,UL,N,UT,M,OF,R])|UO]);
 t_unopaque(T, _) ->
   T.
 
@@ -3134,6 +3710,12 @@ t_limit_k(?product(Elements), K) ->
   ?product([t_limit_k(X, K - 1) || X <- Elements]);
 t_limit_k(?union(Elements), K) ->
   ?union([t_limit_k(X, K) || X <- Elements]);
+t_limit_k(?opaque(Es), K) ->
+  List = [begin
+            NewS = t_limit_k(S, K),
+            Opaque#opaque{struct = NewS}
+          end || #opaque{struct = S} = Opaque <- set_to_list(Es)],
+  ?opaque(ordsets:from_list(List));
 t_limit_k(T, _K) -> T.
 
 %%============================================================================
@@ -3167,7 +3749,7 @@ t_abstract_records(?union(Types), RecDict) ->
 t_abstract_records(?tuple(?any, ?any, ?any) = T, _RecDict) ->
   T;
 t_abstract_records(?tuple(Elements, Arity, ?atom(_) = Tag), RecDict) ->
-  [TagAtom] = t_atom_vals(Tag),
+  [TagAtom] = atom_vals(Tag),
   case lookup_record(TagAtom, Arity - 1, RecDict) of
     error -> t_tuple([t_abstract_records(E, RecDict) || E <- Elements]);
     {ok, Fields} -> t_tuple([Tag|[T || {_Name, T} <- Fields]])
@@ -3176,6 +3758,8 @@ t_abstract_records(?tuple(Elements, _Arity, _Tag), RecDict) ->
   t_tuple([t_abstract_records(E, RecDict) || E <- Elements]);
 t_abstract_records(?tuple_set(_) = Tuples, RecDict) ->
   t_sup([t_abstract_records(T, RecDict) || T <- t_tuple_subtypes(Tuples)]);
+t_abstract_records(?opaque(_)=Type, RecDict) ->
+  t_abstract_records(t_opaque_structure(Type), RecDict);
 t_abstract_records(T, _RecDict) -> 
   T.
 
@@ -3198,6 +3782,14 @@ t_map(Fun, ?tuple(Elements, _Arity, _Tag)) ->
   Fun(t_tuple([t_map(Fun, E) || E <- Elements]));
 t_map(Fun, ?tuple_set(_) = Tuples) ->
   Fun(t_sup([t_map(Fun, T) || T <- t_tuple_subtypes(Tuples)]));
+t_map(Fun, ?opaque(Set)) ->
+  L = [Opaque#opaque{struct = NewS} ||
+        #opaque{struct = S} = Opaque <- set_to_list(Set),
+        not t_is_none(NewS = t_map(Fun, S))],
+  Fun(case L of
+        [] -> ?none;
+        _ -> ?opaque(ordsets:from_list(L))
+      end);
 t_map(Fun, T) ->
   Fun(T).
 
@@ -3239,11 +3831,11 @@ t_to_string(?bitstr(8, 0), _RecDict) ->
 t_to_string(?bitstr(1, 0), _RecDict) ->
   "bitstring()";
 t_to_string(?bitstr(0, B), _RecDict) ->
-  lists:flatten(io_lib:format("<<_:~w>>", [B]));
+  flat_format("<<_:~w>>", [B]);
 t_to_string(?bitstr(U, 0), _RecDict) ->
-  lists:flatten(io_lib:format("<<_:_*~w>>", [U]));
+  flat_format("<<_:_*~w>>", [U]);
 t_to_string(?bitstr(U, B), _RecDict) ->
-  lists:flatten(io_lib:format("<<_:~w,_:_*~w>>", [B, U]));
+  flat_format("<<_:~w,_:_*~w>>", [B, U]);
 t_to_string(?function(?any, ?any), _RecDict) ->
   "fun()";
 t_to_string(?function(?any, Range), RecDict) ->
@@ -3255,18 +3847,16 @@ t_to_string(?identifier(Set), _RecDict) ->
   case Set of
     ?any -> "identifier()";
     _ ->
-      string:join([io_lib:format("~w()", [T]) || T <- set_to_list(Set)], " | ")
+      string:join([flat_format("~w()", [T]) || T <- set_to_list(Set)], " | ")
   end;
-t_to_string(?opaque(Set), _RecDict) ->
-  string:join([case is_opaque_builtin(Mod, Name) of
-		 true  -> io_lib:format("~w()", [Name]);
-		 false -> io_lib:format("~w:~w()", [Mod, Name])
-	       end
-	       || #opaque{mod = Mod, name = Name} <- set_to_list(Set)],
+t_to_string(?opaque(Set), RecDict) ->
+  string:join([opaque_type(Mod, Name, S, RecDict) ||
+                #opaque{mod = Mod, name = Name, struct = S}
+                  <- set_to_list(Set)],
 	      " | ");
 t_to_string(?matchstate(Pres, Slots), RecDict) ->
-  io_lib:format("ms(~s,~s)", [t_to_string(Pres, RecDict),
-			      t_to_string(Slots,RecDict)]);
+  flat_format("ms(~s,~s)", [t_to_string(Pres, RecDict),
+                            t_to_string(Slots,RecDict)]);
 t_to_string(?nil, _RecDict) ->
   "[]";
 t_to_string(?nonempty_list(Contents, Termination), RecDict) ->
@@ -3282,7 +3872,9 @@ t_to_string(?nonempty_list(Contents, Termination), RecDict) ->
       case Contents =:= ?any of
 	true -> ok;
 	false ->
-	  erlang:error({illegal_list, ?nonempty_list(Contents, Termination)})
+          %% XXX. See comment below.
+          %% erlang:error({illegal_list, ?nonempty_list(Contents, Termination)})
+          ok
       end,
       "nonempty_maybe_improper_list()";
     _ ->
@@ -3305,11 +3897,14 @@ t_to_string(?list(Contents, Termination, ?unknown_qual), RecDict) ->
       end;
     ?any ->
       %% Just a safety check.      
+      %% XXX. Types such as "maybe_improper_list(integer(), any())"
+      %% are OK, but cannot be printed!?
       case Contents =:= ?any of
 	true -> ok;
 	false ->
-	  L = ?list(Contents, Termination, ?unknown_qual),
-	  erlang:error({illegal_list, L})
+          ok
+          %% L = ?list(Contents, Termination, ?unknown_qual),
+          %% erlang:error({illegal_list, L})
       end,
       "maybe_improper_list()";
     _ -> 
@@ -3330,7 +3925,7 @@ t_to_string(?integer_pos, _RecDict) -> "pos_integer()";
 t_to_string(?integer_non_neg, _RecDict) -> "non_neg_integer()";
 t_to_string(?integer_neg, _RecDict) -> "neg_integer()";
 t_to_string(?int_range(From, To), _RecDict) ->
-  lists:flatten(io_lib:format("~w..~w", [From, To]));
+  flat_format("~w..~w", [From, To]);
 t_to_string(?integer(?any), _RecDict) -> "integer()";
 t_to_string(?float, _RecDict) -> "float()";
 t_to_string(?number(?any, ?unknown_qual), _RecDict) -> "number()";
@@ -3338,10 +3933,10 @@ t_to_string(?product(List), RecDict) ->
   "<" ++ comma_sequence(List, RecDict) ++ ">";
 t_to_string(?remote(Set), RecDict) ->
   string:join([case Args =:= [] of
-		 true  -> io_lib:format("~w:~w()", [Mod, Name]);
+		 true  -> flat_format("~w:~w()", [Mod, Name]);
 		 false ->
 		   ArgString = comma_sequence(Args, RecDict),
-		   io_lib:format("~w:~w(~s)", [Mod, Name, ArgString])
+		   flat_format("~w:~w(~s)", [Mod, Name, ArgString])
 	       end
 	       || #remote{mod = Mod, name = Name, args = Args} <-
 		    set_to_list(Set)],
@@ -3350,7 +3945,7 @@ t_to_string(?tuple(?any, ?any, ?any), _RecDict) -> "tuple()";
 t_to_string(?tuple(Elements, _Arity, ?any), RecDict) ->   
   "{" ++ comma_sequence(Elements, RecDict) ++ "}";
 t_to_string(?tuple(Elements, Arity, Tag), RecDict) ->
-  [TagAtom] = t_atom_vals(Tag),
+  [TagAtom] = atom_vals(Tag),
   case lookup_record(TagAtom, Arity-1, RecDict) of
     error -> "{" ++ comma_sequence(Elements, RecDict) ++ "}";
     {ok, FieldNames} ->
@@ -3361,9 +3956,9 @@ t_to_string(?tuple_set(_) = T, RecDict) ->
 t_to_string(?union(Types), RecDict) ->
   union_sequence([T || T <- Types, T =/= ?none], RecDict);
 t_to_string(?var(Id), _RecDict) when is_atom(Id) ->
-  io_lib:format("~s", [atom_to_list(Id)]);
+  flat_format("~s", [atom_to_list(Id)]);
 t_to_string(?var(Id), _RecDict) when is_integer(Id) ->
-  io_lib:format("var(~w)", [Id]).
+  flat_format("var(~w)", [Id]).
 
 record_to_string(Tag, [_|Fields], FieldNames, RecDict) ->
   FieldStrings = record_fields_to_string(Fields, FieldNames, RecDict, []),
@@ -3371,7 +3966,7 @@ record_to_string(Tag, [_|Fields], FieldNames, RecDict) ->
 
 record_fields_to_string([F|Fs], [{FName, _DefType}|FDefs], RecDict, Acc) ->
   NewAcc =
-    case t_is_any(F) orelse t_is_atom('undefined', F) of
+    case t_is_equal(F, t_any()) orelse t_is_any_atom('undefined', F) of
       true -> Acc;
       false ->
 	StrFV = atom_to_string(FName) ++ "::" ++ t_to_string(F, RecDict),
@@ -3389,13 +3984,14 @@ record_fields_to_string([], [], _RecDict, Acc) ->
 -spec record_field_diffs_to_string(erl_type(), dict()) -> string().
 
 record_field_diffs_to_string(?tuple([_|Fs], Arity, Tag), RecDict) ->
-  [TagAtom] = t_atom_vals(Tag),
+  [TagAtom] = atom_vals(Tag),
   {ok, FieldNames} = lookup_record(TagAtom, Arity-1, RecDict),
   %% io:format("RecCElems = ~p\nRecTypes = ~p\n", [Fs, FieldNames]),
   FieldDiffs = field_diffs(Fs, FieldNames, RecDict, []),
   string:join(FieldDiffs, " and ").
 
 field_diffs([F|Fs], [{FName, DefType}|FDefs], RecDict, Acc) ->
+  %% Don't care about opaqueness for now.
   NewAcc =
     case not t_is_none(t_inf(F, DefType)) of
       true -> Acc;
@@ -3418,6 +4014,24 @@ union_sequence(Types, RecDict) ->
   List = [t_to_string(T, RecDict) || T <- Types], 
   string:join(List, " | ").
 
+-ifdef(DEBUG).
+opaque_type(Mod, Name, S, RecDict) ->
+  opaque_name(Mod, Name, t_to_string(S, RecDict)).
+-else.
+opaque_type(Mod, Name, _S, _RecDict) ->
+  opaque_name(Mod, Name, "").
+-endif.
+
+opaque_name(Mod, Name, Extra) ->
+  S = mod_name(Mod, Name),
+  flat_format("~s(~s)", [S, Extra]).
+
+mod_name(Mod, Name) ->
+  case is_opaque_builtin(Mod, Name) of
+    true  -> flat_format("~w", [Name]);
+    false -> flat_format("~w:~w", [Mod, Name])
+  end.
+
 %%=============================================================================
 %% 
 %% Build a type from parse forms.
@@ -3437,246 +4051,197 @@ t_from_form(Form, RecDict) ->
 -spec t_from_form(parse_form(), dict(), dict()) -> erl_type().
 
 t_from_form(Form, RecDict, VarDict) ->
-  {T, _R} = t_from_form(Form, [], false, RecDict, VarDict),
+  {T, _R} = t_from_form(Form, [], RecDict, VarDict),
   T.
 
 -type type_names() :: [{'type' | 'opaque' | 'record', atom()}].
--spec t_from_form(parse_form(), type_names(), boolean(), dict(), dict()) ->
+-spec t_from_form(parse_form(), type_names(), dict(), dict()) ->
                      {erl_type(), type_names()}.
 
-t_from_form({var, _L, '_'}, _TypeNames, _InOpaque, _RecDict, _VarDict) ->
+t_from_form({var, _L, '_'}, _TypeNames, _RecDict, _VarDict) ->
   {t_any(), []};
-t_from_form({var, _L, Name}, _TypeNames, _InOpaque, _RecDict, VarDict) ->
+t_from_form({var, _L, Name}, _TypeNames, _RecDict, VarDict) ->
   case dict:find(Name, VarDict) of
     error -> {t_var(Name), []};
     {ok, Val} -> {Val, []}
   end;
-t_from_form({ann_type, _L, [_Var, Type]}, TypeNames, InOpaque, RecDict,
-            VarDict) ->
-  t_from_form(Type, TypeNames, InOpaque, RecDict, VarDict);
-t_from_form({paren_type, _L, [Type]}, TypeNames, InOpaque, RecDict,
-            VarDict) ->
-  t_from_form(Type, TypeNames, InOpaque, RecDict, VarDict);
+t_from_form({ann_type, _L, [_Var, Type]}, TypeNames, RecDict, VarDict) ->
+  t_from_form(Type, TypeNames, RecDict, VarDict);
+t_from_form({paren_type, _L, [Type]}, TypeNames, RecDict, VarDict) ->
+  t_from_form(Type, TypeNames, RecDict, VarDict);
 t_from_form({remote_type, _L, [{atom, _, Module}, {atom, _, Type}, Args]},
-	    TypeNames, InOpaque, RecDict, VarDict) ->
-  {L, R} = list_from_form(Args, TypeNames, InOpaque, RecDict, VarDict),
+	    TypeNames, RecDict, VarDict) ->
+  {L, R} = list_from_form(Args, TypeNames, RecDict, VarDict),
   {t_remote(Module, Type, L), R};
-t_from_form({atom, _L, Atom}, _TypeNames, _InOpaque, _RecDict, _VarDict) ->
+t_from_form({atom, _L, Atom}, _TypeNames, _RecDict, _VarDict) ->
   {t_atom(Atom), []};
-t_from_form({integer, _L, Int}, _TypeNames, _InOpaque, _RecDict, _VarDict) ->
+t_from_form({integer, _L, Int}, _TypeNames, _RecDict, _VarDict) ->
   {t_integer(Int), []};
-t_from_form({op, _L, _Op, _Arg} = Op, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({op, _L, _Op, _Arg} = Op, _TypeNames, _RecDict, _VarDict) ->
   case erl_eval:partial_eval(Op) of
     {integer, _, Val} ->
       {t_integer(Val), []};
     _ -> throw({error, io_lib:format("Unable to evaluate type ~w\n", [Op])})
   end;
-t_from_form({op, _L, _Op, _Arg1, _Arg2} = Op, _TypeNames, _InOpaque,
+t_from_form({op, _L, _Op, _Arg1, _Arg2} = Op, _TypeNames,
             _RecDict, _VarDict) ->
   case erl_eval:partial_eval(Op) of
     {integer, _, Val} ->
       {t_integer(Val), []};
     _ -> throw({error, io_lib:format("Unable to evaluate type ~w\n", [Op])})
   end;
-t_from_form({type, _L, any, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, any, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_any(), []};
-t_from_form({type, _L, arity, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, arity, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_arity(), []};
-t_from_form({type, _L, array, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, array, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_array(), []};
-t_from_form({type, _L, atom, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, atom, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_atom(), []};
-t_from_form({type, _L, binary, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, binary, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_binary(), []};
 t_from_form({type, _L, binary, [Base, Unit]} = Type,
-	    _TypeNames, _InOpaque, _RecDict, _VarDict) ->
+	    _TypeNames, _RecDict, _VarDict) ->
   case {erl_eval:partial_eval(Base), erl_eval:partial_eval(Unit)} of
     {{integer, _, B}, {integer, _, U}} when B >= 0, U >= 0 ->
       {t_bitstr(U, B), []};
     _ -> throw({error, io_lib:format("Unable to evaluate type ~w\n", [Type])})
   end;
-t_from_form({type, _L, bitstring, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, bitstring, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_bitstr(), []};
-t_from_form({type, _L, bool, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, bool, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_boolean(), []};	% XXX: Temporarily
-t_from_form({type, _L, boolean, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, boolean, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_boolean(), []};
-t_from_form({type, _L, byte, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, byte, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_byte(), []};
-t_from_form({type, _L, char, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, char, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_char(), []};
-t_from_form({type, _L, dict, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, dict, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_dict(), []};
-t_from_form({type, _L, digraph, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, digraph, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_digraph(), []};
-t_from_form({type, _L, float, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, float, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_float(), []};
-t_from_form({type, _L, function, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, function, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_fun(), []};
-t_from_form({type, _L, 'fun', []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, 'fun', []}, _TypeNames, _RecDict, _VarDict) ->
   {t_fun(), []};
 t_from_form({type, _L, 'fun', [{type, _, any}, Range]}, TypeNames,
-            InOpaque, RecDict, VarDict) ->
-  {T, R} = t_from_form(Range, TypeNames, InOpaque, RecDict, VarDict),
+            RecDict, VarDict) ->
+  {T, R} = t_from_form(Range, TypeNames, RecDict, VarDict),
   {t_fun(T), R};
 t_from_form({type, _L, 'fun', [{type, _, product, Domain}, Range]},
-            TypeNames, InOpaque, RecDict, VarDict) ->
-  {L, R1} = list_from_form(Domain, TypeNames, InOpaque, RecDict, VarDict),
-  {T, R2} = t_from_form(Range, TypeNames, InOpaque, RecDict, VarDict),
+            TypeNames, RecDict, VarDict) ->
+  {L, R1} = list_from_form(Domain, TypeNames, RecDict, VarDict),
+  {T, R2} = t_from_form(Range, TypeNames, RecDict, VarDict),
   {t_fun(L, T), R1 ++ R2};
-t_from_form({type, _L, gb_set, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, gb_set, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_gb_set(), []};
-t_from_form({type, _L, gb_tree, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, gb_tree, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_gb_tree(), []};
-t_from_form({type, _L, identifier, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, identifier, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_identifier(), []};
-t_from_form({type, _L, integer, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, integer, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_integer(), []};
-t_from_form({type, _L, iodata, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, iodata, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_iodata(), []};
-t_from_form({type, _L, iolist, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, iolist, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_iolist(), []};
-t_from_form({type, _L, list, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, list, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_list(), []};
-t_from_form({type, _L, list, [Type]}, TypeNames, InOpaque, RecDict,
-            VarDict) ->
-  {T, R} = t_from_form(Type, TypeNames, InOpaque, RecDict, VarDict),
+t_from_form({type, _L, list, [Type]}, TypeNames, RecDict,  VarDict) ->
+  {T, R} = t_from_form(Type, TypeNames, RecDict, VarDict),
   {t_list(T), R};
-t_from_form({type, _L, mfa, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, mfa, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_mfa(), []};
-t_from_form({type, _L, module, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, module, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_module(), []};
-t_from_form({type, _L, nil, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, nil, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_nil(), []};
-t_from_form({type, _L, neg_integer, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, neg_integer, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_neg_integer(), []};
-t_from_form({type, _L, non_neg_integer, []}, _TypeNames, _InOpaque, _RecDict,
+t_from_form({type, _L, non_neg_integer, []}, _TypeNames, _RecDict,
             _VarDict) ->
   {t_non_neg_integer(), []};
-t_from_form({type, _L, no_return, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, no_return, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_unit(), []};
-t_from_form({type, _L, node, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, node, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_node(), []};
-t_from_form({type, _L, none, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, none, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_none(), []};
-t_from_form({type, _L, nonempty_list, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, nonempty_list, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_nonempty_list(), []};
-t_from_form({type, _L, nonempty_list, [Type]}, TypeNames, InOpaque, RecDict,
-            VarDict) ->
-  {T, R} = t_from_form(Type, TypeNames, InOpaque, RecDict, VarDict),
+t_from_form({type, _L, nonempty_list, [Type]}, TypeNames, RecDict, VarDict) ->
+  {T, R} = t_from_form(Type, TypeNames, RecDict, VarDict),
   {t_nonempty_list(T), R};
 t_from_form({type, _L, nonempty_improper_list, [Cont, Term]}, TypeNames,
-            InOpaque, RecDict, VarDict) ->
-  {T1, R1} = t_from_form(Cont, TypeNames, InOpaque, RecDict, VarDict),
-  {T2, R2} = t_from_form(Term, TypeNames, InOpaque, RecDict, VarDict),
+            RecDict, VarDict) ->
+  {T1, R1} = t_from_form(Cont, TypeNames, RecDict, VarDict),
+  {T2, R2} = t_from_form(Term, TypeNames, RecDict, VarDict),
   {t_cons(T1, T2), R1 ++ R2};
 t_from_form({type, _L, nonempty_maybe_improper_list, []}, _TypeNames,
-            _InOpaque, _RecDict, _VarDict) ->
+            _RecDict, _VarDict) ->
   {t_cons(?any, ?any), []};
 t_from_form({type, _L, nonempty_maybe_improper_list, [Cont, Term]},
-            TypeNames, InOpaque, RecDict, VarDict) ->
-  {T1, R1} = t_from_form(Cont, TypeNames, InOpaque, RecDict, VarDict),
-  {T2, R2} = t_from_form(Term, TypeNames, InOpaque, RecDict, VarDict),
+            TypeNames, RecDict, VarDict) ->
+  {T1, R1} = t_from_form(Cont, TypeNames, RecDict, VarDict),
+  {T2, R2} = t_from_form(Term, TypeNames, RecDict, VarDict),
   {t_cons(T1, T2), R1 ++ R2};
-t_from_form({type, _L, nonempty_string, []}, _TypeNames, _InOpaque, _RecDict,
+t_from_form({type, _L, nonempty_string, []}, _TypeNames, _RecDict,
             _VarDict) ->
   {t_nonempty_string(), []};
-t_from_form({type, _L, number, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, number, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_number(), []};
-t_from_form({type, _L, pid, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, pid, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_pid(), []};
-t_from_form({type, _L, port, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, port, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_port(), []};
-t_from_form({type, _L, pos_integer, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, pos_integer, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_pos_integer(), []};
-t_from_form({type, _L, maybe_improper_list, []}, _TypeNames, _InOpaque,
+t_from_form({type, _L, maybe_improper_list, []}, _TypeNames,
             _RecDict, _VarDict) ->
   {t_maybe_improper_list(), []};
 t_from_form({type, _L, maybe_improper_list, [Content, Termination]},
-            TypeNames, InOpaque, RecDict, VarDict) ->
-  {T1, R1} = t_from_form(Content, TypeNames, InOpaque, RecDict, VarDict),
-  {T2, R2} = t_from_form(Termination, TypeNames, InOpaque, RecDict, VarDict),
+            TypeNames, RecDict, VarDict) ->
+  {T1, R1} = t_from_form(Content, TypeNames, RecDict, VarDict),
+  {T2, R2} = t_from_form(Termination, TypeNames, RecDict, VarDict),
   {t_maybe_improper_list(T1, T2), R1 ++ R2};
-t_from_form({type, _L, product, Elements}, TypeNames, InOpaque, RecDict,
-            VarDict) ->
-  {L, R} = list_from_form(Elements, TypeNames, InOpaque, RecDict, VarDict),
+t_from_form({type, _L, product, Elements}, TypeNames, RecDict, VarDict) ->
+  {L, R} = list_from_form(Elements, TypeNames, RecDict, VarDict),
   {t_product(L), R};
-t_from_form({type, _L, queue, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, queue, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_queue(), []};
 t_from_form({type, _L, range, [From, To]} = Type,
-	    _TypeNames, _InOpaque, _RecDict, _VarDict) ->
+	    _TypeNames, _RecDict, _VarDict) ->
   case {erl_eval:partial_eval(From), erl_eval:partial_eval(To)} of
     {{integer, _, FromVal}, {integer, _, ToVal}} ->
       {t_from_range(FromVal, ToVal), []};
     _ -> throw({error, io_lib:format("Unable to evaluate type ~w\n", [Type])})
   end;
-t_from_form({type, _L, record, [Name|Fields]}, TypeNames, InOpaque, RecDict,
-            VarDict) ->
-  record_from_form(Name, Fields, TypeNames, InOpaque, RecDict, VarDict);
-t_from_form({type, _L, reference, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, record, [Name|Fields]}, TypeNames, RecDict, VarDict) ->
+  record_from_form(Name, Fields, TypeNames, RecDict, VarDict);
+t_from_form({type, _L, reference, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_reference(), []};
-t_from_form({type, _L, set, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, set, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_set(), []};
-t_from_form({type, _L, string, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, string, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_string(), []};
-t_from_form({type, _L, term, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, term, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_any(), []};
-t_from_form({type, _L, tid, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, tid, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_tid(), []};
-t_from_form({type, _L, timeout, []}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, timeout, []}, _TypeNames, _RecDict, _VarDict) ->
   {t_timeout(), []};
-t_from_form({type, _L, tuple, any}, _TypeNames, _InOpaque, _RecDict,
-            _VarDict) ->
+t_from_form({type, _L, tuple, any}, _TypeNames, _RecDict, _VarDict) ->
   {t_tuple(), []};
-t_from_form({type, _L, tuple, Args}, TypeNames, InOpaque, RecDict, VarDict) ->
-  {L, R} = list_from_form(Args, TypeNames, InOpaque, RecDict, VarDict),
+t_from_form({type, _L, tuple, Args}, TypeNames, RecDict, VarDict) ->
+  {L, R} = list_from_form(Args, TypeNames, RecDict, VarDict),
   {t_tuple(L), R};
-t_from_form({type, _L, union, Args}, TypeNames, InOpaque, RecDict, VarDict) ->
-  {L, R} = list_from_form(Args, TypeNames, InOpaque, RecDict, VarDict),
+t_from_form({type, _L, union, Args}, TypeNames, RecDict, VarDict) ->
+  {L, R} = list_from_form(Args, TypeNames, RecDict, VarDict),
   {t_sup(L), R};
-t_from_form({type, _L, Name, Args}, TypeNames, InOpaque, RecDict, VarDict) ->
+t_from_form({type, _L, Name, Args}, TypeNames, RecDict, VarDict) ->
   ArgsLen = length(Args),
   case lookup_type(Name, ArgsLen, RecDict) of
     {type, {_Module, Type, ArgNames}} ->
@@ -3685,13 +4250,12 @@ t_from_form({type, _L, Name, Args}, TypeNames, InOpaque, RecDict, VarDict) ->
           List = lists:zipwith(
                    fun(ArgName, ArgType) ->
                        {Ttemp, _R} = t_from_form(ArgType, TypeNames,
-                                                 InOpaque, RecDict,
-                                                 VarDict),
+                                                 RecDict, VarDict),
                        {ArgName, Ttemp}
                    end,
                    ArgNames, Args),
           TmpVarDict = dict:from_list(List),
-          {T, R} = t_from_form(Type, [{type, Name}|TypeNames], InOpaque,
+          {T, R} = t_from_form(Type, [{type, Name}|TypeNames],
                                RecDict, TmpVarDict),
           case lists:member({type, Name}, R) of
             true -> {t_limit(T, ?REC_TYPE_LIMIT), R};
@@ -3706,13 +4270,12 @@ t_from_form({type, _L, Name, Args}, TypeNames, InOpaque, RecDict, VarDict) ->
             List = lists:zipwith(
                      fun(ArgName, ArgType) ->
                          {Ttemp, _R} = t_from_form(ArgType, TypeNames,
-                                                   InOpaque, RecDict,
-                                                   VarDict),
+                                                   RecDict, VarDict),
                          {ArgName, Ttemp}
                      end,
                      ArgNames, Args),
             TmpVarDict = dict:from_list(List),
-            {T, R} = t_from_form(Type, [{opaque, Name}|TypeNames], true,
+            {T, R} = t_from_form(Type, [{opaque, Name}|TypeNames],
                                  RecDict, TmpVarDict),
             case lists:member({opaque, Name}, R) of
               true -> {t_limit(T, ?REC_TYPE_LIMIT), R};
@@ -3720,27 +4283,21 @@ t_from_form({type, _L, Name, Args}, TypeNames, InOpaque, RecDict, VarDict) ->
             end;
           false -> {t_any(), [{opaque, Name}]}
         end,
-      Tret =
-        case InOpaque of
-          true -> Rep;
-          false ->
-            t_from_form({opaque, -1, Name, {Module, Args, Rep}},
-                        RecDict, VarDict)
-          end,
+      Tret = t_from_form({opaque, -1, Name, {Module, Args, Rep}},
+                         RecDict, VarDict),
       {Tret, Rret};
     error ->
       Msg = io_lib:format("Unable to find type ~w/~w\n", [Name, ArgsLen]),
       throw({error, Msg})
   end;
-t_from_form({opaque, _L, Name, {Mod, Args, Rep}}, _TypeNames, _InOpaque,
+t_from_form({opaque, _L, Name, {Mod, Args, Rep}}, _TypeNames,
             _RecDict, _VarDict) ->
   case Args of
     [] -> {t_opaque(Mod, Name, Args, Rep), []};
     _ -> throw({error, "Polymorphic opaque types not supported yet"})
   end.
 
-record_from_form({atom, _, Name}, ModFields, TypeNames, InOpaque, RecDict,
-                 VarDict) ->
+record_from_form({atom, _, Name}, ModFields, TypeNames, RecDict, VarDict) ->
   case can_unfold_more({record, Name}, TypeNames) of
     true ->
       case lookup_record(Name, RecDict) of
@@ -3751,11 +4308,11 @@ record_from_form({atom, _, Name}, ModFields, TypeNames, InOpaque, RecDict,
           {DeclFields1, R1} =
             case lists:all(fun(Elem) -> Elem end, AreTyped) of
               true -> {DeclFields, []};
-              false -> fields_from_form(DeclFields, TypeNames1, InOpaque,
+              false -> fields_from_form(DeclFields, TypeNames1,
                                         RecDict, dict:new())
             end,
           {GetModRec, R2} = get_mod_record(ModFields, DeclFields1,
-                                           TypeNames1, InOpaque,
+                                           TypeNames1,
                                            RecDict, VarDict),
           case GetModRec of
             {error, FieldName} ->
@@ -3772,13 +4329,11 @@ record_from_form({atom, _, Name}, ModFields, TypeNames, InOpaque, RecDict,
     false -> {t_any(), []}
   end.
 
-get_mod_record([], DeclFields, _TypeNames, _InOpaque, _RecDict,
-               _VarDict) ->
+get_mod_record([], DeclFields, _TypeNames, _RecDict, _VarDict) ->
   {{ok, DeclFields}, []};
-get_mod_record(ModFields, DeclFields, TypeNames, InOpaque, RecDict,
-               VarDict) ->
+get_mod_record(ModFields, DeclFields, TypeNames, RecDict, VarDict) ->
   DeclFieldsDict = orddict:from_list(DeclFields),
-  {ModFieldsDict, R} = build_field_dict(ModFields, TypeNames, InOpaque,
+  {ModFieldsDict, R} = build_field_dict(ModFields, TypeNames,
                                         RecDict, VarDict),
   case get_mod_record(DeclFieldsDict, ModFieldsDict, []) of
     {error, _FieldName} = Error -> {Error, R};
@@ -3788,17 +4343,16 @@ get_mod_record(ModFields, DeclFields, TypeNames, InOpaque, RecDict,
        R}
   end.
 
-build_field_dict(FieldTypes, TypeNames, InOpaque, RecDict, VarDict) ->
-  build_field_dict(FieldTypes, TypeNames, InOpaque, RecDict, VarDict, []).
+build_field_dict(FieldTypes, TypeNames, RecDict, VarDict) ->
+  build_field_dict(FieldTypes, TypeNames, RecDict, VarDict, []).
 
 build_field_dict([{type, _, field_type, [{atom, _, Name}, Type]}|Left], 
-		 TypeNames, InOpaque, RecDict, VarDict, Acc) ->
-  {T, R1} = t_from_form(Type, TypeNames, InOpaque, RecDict, VarDict),
+		 TypeNames, RecDict, VarDict, Acc) ->
+  {T, R1} = t_from_form(Type, TypeNames, RecDict, VarDict),
   NewAcc = [{Name, T}|Acc],
-  {D, R2} = build_field_dict(Left, TypeNames, InOpaque, RecDict, VarDict,
-                             NewAcc),
+  {D, R2} = build_field_dict(Left, TypeNames, RecDict, VarDict, NewAcc),
   {D, R1 ++ R2};
-build_field_dict([], _TypeNames, _InOpaque, _RecDict, _VarDict, Acc) ->
+build_field_dict([], _TypeNames, _RecDict, _VarDict, Acc) ->
   {orddict:from_list(Acc), []}.
 
 get_mod_record([{FieldName, DeclType}|Left1], 
@@ -3817,19 +4371,19 @@ get_mod_record(DeclFields, [], Acc) ->
 get_mod_record(_, [{FieldName2, _ModType}|_], _Acc) ->
   {error, FieldName2}.
 
-fields_from_form([], _TypeNames, _InOpaque, _RecDict, _VarDict) ->
+fields_from_form([], _TypeNames, _RecDict, _VarDict) ->
   {[], []};
-fields_from_form([{Name, Type}|Tail], TypeNames, InOpaque, RecDict,
+fields_from_form([{Name, Type}|Tail], TypeNames, RecDict,
                  VarDict) ->
-  {T, R1} = t_from_form(Type, TypeNames, InOpaque, RecDict, VarDict),
-  {F, R2} = fields_from_form(Tail, TypeNames, InOpaque, RecDict, VarDict),
+  {T, R1} = t_from_form(Type, TypeNames, RecDict, VarDict),
+  {F, R2} = fields_from_form(Tail, TypeNames, RecDict, VarDict),
   {[{Name, T}|F], R1 ++ R2}.
 
-list_from_form([], _TypeNames, _InOpaque, _RecDict, _VarDict) ->
+list_from_form([], _TypeNames, _RecDict, _VarDict) ->
   {[], []};
-list_from_form([H|Tail], TypeNames, InOpaque, RecDict, VarDict) ->
-  {T, R1} = t_from_form(H, TypeNames, InOpaque, RecDict, VarDict),
-  {L, R2} = list_from_form(Tail, TypeNames, InOpaque, RecDict, VarDict),
+list_from_form([H|Tail], TypeNames, RecDict, VarDict) ->
+  {T, R1} = t_from_form(H, TypeNames, RecDict, VarDict),
+  {L, R2} = list_from_form(Tail, TypeNames, RecDict, VarDict),
   {[T|L], R1 ++ R2}.
 
 -spec t_form_to_string(parse_form()) -> string().
@@ -3852,10 +4406,10 @@ t_form_to_string({op, _L, _Op, _Arg1, _Arg2} = Op) ->
 t_form_to_string({ann_type, _L, [Var, Type]}) ->
   t_form_to_string(Var) ++ "::" ++ t_form_to_string(Type);
 t_form_to_string({paren_type, _L, [Type]}) ->
-  io_lib:format("(~s)", [t_form_to_string(Type)]);
+  flat_format("(~s)", [t_form_to_string(Type)]);
 t_form_to_string({remote_type, _L, [{atom, _, Mod}, {atom, _, Name}, Args]}) ->
   ArgString = "(" ++ string:join(t_form_to_string_list(Args), ",") ++ ")",
-  io_lib:format("~w:~w", [Mod, Name]) ++ ArgString;
+  flat_format("~w:~w", [Mod, Name]) ++ ArgString;
 t_form_to_string({type, _L, arity, []}) -> "arity()";
 t_form_to_string({type, _L, binary, []}) -> "binary()";
 t_form_to_string({type, _L, binary, [Base, Unit]} = Type) ->
@@ -3866,9 +4420,9 @@ t_form_to_string({type, _L, binary, [Base, Unit]} = Type) ->
 	{0, 0} -> "<<>>";
 	{8, 0} -> "binary()";
 	{1, 0} -> "bitstring()";
-	{0, B} -> lists:flatten(io_lib:format("<<_:~w>>", [B]));
-	{U, 0} -> lists:flatten(io_lib:format("<<_:_*~w>>", [U]));
-	{U, B} -> lists:flatten(io_lib:format("<<_:~w,_:_*~w>>", [B, U]))
+	{0, B} -> flat_format("<<_:~w>>", [B]);
+	{U, 0} -> flat_format("<<_:_*~w>>", [U]);
+	{U, B} -> flat_format("<<_:~w,_:_*~w>>", [B, U])
       end;
     _ -> io_lib:format("Badly formed bitstr type ~w", [Type])
   end;
@@ -3894,16 +4448,16 @@ t_form_to_string({type, _L, product, Elements}) ->
 t_form_to_string({type, _L, range, [From, To]} = Type) ->
   case {erl_eval:partial_eval(From), erl_eval:partial_eval(To)} of
     {{integer, _, FromVal}, {integer, _, ToVal}} ->
-      io_lib:format("~w..~w", [FromVal, ToVal]);
-    _ -> io_lib:format("Badly formed type ~w",[Type])
+      flat_format("~w..~w", [FromVal, ToVal]);
+    _ -> flat_format("Badly formed type ~w",[Type])
   end;
 t_form_to_string({type, _L, record, [{atom, _, Name}]}) ->
-  io_lib:format("#~w{}", [Name]);
+  flat_format("#~w{}", [Name]);
 t_form_to_string({type, _L, record, [{atom, _, Name}|Fields]}) ->
   FieldString = string:join(t_form_to_string_list(Fields), ","),
-  io_lib:format("#~w{~s}", [Name, FieldString]);
+  flat_format("#~w{~s}", [Name, FieldString]);
 t_form_to_string({type, _L, field_type, [{atom, _, Name}, Type]}) ->
-  io_lib:format("~w::~s", [Name, t_form_to_string(Type)]);
+  flat_format("~w::~s", [Name, t_form_to_string(Type)]);
 t_form_to_string({type, _L, term, []}) -> "term()";
 t_form_to_string({type, _L, timeout, []}) -> "timeout()";
 t_form_to_string({type, _L, tuple, any}) -> "tuple()";
@@ -3916,8 +4470,8 @@ t_form_to_string({type, _L, Name, []} = T) ->
   catch throw:{error, _} -> atom_to_string(Name) ++ "()"
   end;
 t_form_to_string({type, _L, Name, List}) -> 
-  io_lib:format("~w(~s)",
-		[Name, string:join(t_form_to_string_list(List), ",")]).
+  flat_format("~w(~s)",
+              [Name, string:join(t_form_to_string_list(List), ",")]).
 
 t_form_to_string_list(List) ->
   t_form_to_string_list(List, []).
@@ -3930,7 +4484,7 @@ t_form_to_string_list([], Acc) ->
 -spec atom_to_string(atom()) -> string().
 
 atom_to_string(Atom) ->
-  lists:flatten(io_lib:format("~w", [Atom])).
+  flat_format("~w", [Atom]).
 
 %%=============================================================================
 %% 
@@ -4002,6 +4556,29 @@ can_unfold_more(TypeName, TypeNames) ->
   Fun = fun(E, Acc) -> case E of TypeName -> Acc + 1; _ -> Acc end end,
   lists:foldl(Fun, 0, TypeNames) < ?REC_TYPE_LIMIT.
 
+-spec do_opaque(erl_type(), opaques(), fun((_) -> T)) -> T.
+
+%% Probably a little faster than calling t_unopaque/2.
+%% Unions that are due to opaque types are unopaqued.
+do_opaque(?opaque(_) = Type, Opaques, Pred) ->
+  case Opaques =:= 'universe' orelse is_opaque_type(Type, Opaques) of
+    true -> do_opaque(t_opaque_structure(Type), Opaques, Pred);
+    false -> Pred(Type)
+  end;
+do_opaque(?union(List) = Type, Opaques, Pred) ->
+  [A,B,F,I,L,N,T,M,O,R] = List,
+  if O =:= ?none -> Pred(Type);
+    true ->
+      case Opaques =:= 'universe' orelse is_opaque_type(O, Opaques) of
+        true ->
+          S = t_opaque_structure(O),
+          do_opaque(t_sup([A,B,F,I,L,N,T,M,S,R]), Opaques, Pred);
+        false -> Pred(Type)
+      end
+  end;
+do_opaque(Type, _Opaques, Pred) ->
+  Pred(Type).
+
 %% -----------------------------------
 %% Set
 %%
@@ -4068,7 +4645,7 @@ set_size(Set) ->
 set_to_string(Set) ->
   L = [case is_atom(X) of
 	 true -> io_lib:write_string(atom_to_list(X), $'); % stupid emacs '
-	 false -> io_lib:format("~w", [X])
+	 false -> flat_format("~w", [X])
        end || X <- set_to_list(Set)],
   string:join(L, " | ").
 
@@ -4077,6 +4654,9 @@ set_min([H|_]) -> H.
 set_max(Set) ->
   hd(lists:reverse(Set)).
 
+flat_format(F, S) ->
+  lists:flatten(io_lib:format(F, S)).
+
 %%=============================================================================
 %% 
 %% Utilities for the binary type
@@ -4131,6 +4711,11 @@ handle_base(Unit, Pos) when Pos >= 0 ->
 handle_base(Unit, Neg) ->
   (Unit+(Neg rem Unit)) rem Unit.
   
+family(L) ->
+  R = sofs:relation(L),
+  F = sofs:relation_to_family(R),
+  sofs:to_external(F).
+
 %%=============================================================================
 %% Consistency-testing function(s) below
 %%=============================================================================