aboutsummaryrefslogtreecommitdiffstats
path: root/lib/dialyzer/src/dialyzer_contracts.erl
blob: 2078e58ce8bc0421660ef426155ed90d9ded44e4 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
%% -*- erlang-indent-level: 2 -*-
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.

-module(dialyzer_contracts).

-export([check_contract/2,
	 check_contracts/4,
	 contracts_without_fun/3,
	 contract_to_string/1,
	 get_invalid_contract_warnings/4,
	 get_contract_args/1,
	 get_contract_return/1,
	 get_contract_return/2,
	 %% get_contract_signature/1,
	 is_overloaded/1,
	 process_contract_remote_types/2,
	 store_tmp_contract/5]).

-export_type([file_contract/0, plt_contracts/0]).

%%-----------------------------------------------------------------------

-include("dialyzer.hrl").

%%-----------------------------------------------------------------------
%% Types used in other parts of the system below
%%-----------------------------------------------------------------------

-type file_contract() :: {file_line(), #contract{}, Extra :: [_]}.

-type plt_contracts() :: orddict:orddict(mfa(), #contract{}).

%%-----------------------------------------------------------------------
%% Internal record for contracts whose components have not been processed
%% to expand records and/or remote types that they might contain.
%%-----------------------------------------------------------------------

-type cache() :: ets:tid().
-type tmp_contract_fun() ::
        fun((sets:set(mfa()), types(), cache()) -> contract_pair()).

-record(tmp_contract, {contract_funs = [] :: [tmp_contract_fun()],
		       forms	     = [] :: [{_, _}]}).

%%-----------------------------------------------------------------------

%%-define(DEBUG, true).

-ifdef(DEBUG).
-define(debug(X__, Y__), io:format(X__, Y__)).
-else.
-define(debug(X__, Y__), ok).
-endif.

%%-----------------------------------------------------------------------

-spec get_contract_return(#contract{}) -> erl_types:erl_type().

get_contract_return(#contract{contracts = Cs, args = GenArgs}) ->
  process_contracts(Cs, GenArgs).

-spec get_contract_return(#contract{}, [erl_types:erl_type()]) -> erl_types:erl_type().

get_contract_return(#contract{contracts = Cs}, Args) ->
  process_contracts(Cs, Args).

-spec get_contract_args(#contract{}) -> [erl_types:erl_type()].

get_contract_args(#contract{args = Args}) ->
  Args.

-spec get_contract_signature(#contract{}) -> erl_types:erl_type().

get_contract_signature(#contract{contracts = Cs, args = GeneralDomain}) ->
  Range = process_contracts(Cs, GeneralDomain),
  erl_types:t_fun(GeneralDomain, Range).

-spec is_overloaded(#contract{}) -> boolean().

is_overloaded(#contract{contracts = Cs}) ->
  case Cs of
    [_] -> true;
    [_,_|_] -> false
  end.

-spec contract_to_string(#contract{}) -> string().

contract_to_string(#contract{forms = Forms}) ->
  contract_to_string_1(Forms).

contract_to_string_1([{Contract, []}]) ->
  strip_fun(erl_types:t_form_to_string(Contract));
contract_to_string_1([{Contract, []}|Rest]) ->
  strip_fun(erl_types:t_form_to_string(Contract)) ++ "\n    ; "
    ++ contract_to_string_1(Rest);
contract_to_string_1([{Contract, Constraints}]) ->
  strip_fun(erl_types:t_form_to_string(Contract)) ++ " when "
    ++ constraints_to_string(Constraints);
contract_to_string_1([{Contract, Constraints}|Rest]) ->
  strip_fun(erl_types:t_form_to_string(Contract)) ++ " when "
    ++ constraints_to_string(Constraints) ++ ";" ++
    contract_to_string_1(Rest).

strip_fun("fun(" ++ String) ->
  butlast(String).

butlast([]) -> [];
butlast([_]) -> [];
butlast([H|T]) -> [H|butlast(T)].

constraints_to_string([]) ->
  "";
constraints_to_string([{type, _, constraint, [{atom, _, What}, Types]}|Rest]) ->
  S = constraint_to_string(What, Types),
  case Rest of
    [] -> S;
    _ -> S ++ ", " ++ constraints_to_string(Rest)
  end.

constraint_to_string(is_subtype, [{var, _, Var}, T]) ->
  atom_to_list(Var) ++ " :: " ++ erl_types:t_form_to_string(T);
constraint_to_string(What, Types) ->
  atom_to_list(What) ++ "("
    ++ sequence([erl_types:t_form_to_string(T) || T <- Types], ",")
    ++ ")".

sequence([], _Delimiter) -> "";
sequence([H], _Delimiter) -> H;
sequence([H|T], Delimiter) -> H ++ Delimiter ++ sequence(T, Delimiter).

-spec process_contract_remote_types(dialyzer_codeserver:codeserver(),
                                    erl_types:mod_records()) ->
                                       dialyzer_codeserver:codeserver().

process_contract_remote_types(CodeServer, RecordDict) ->
  Mods = dialyzer_codeserver:contracts_modules(CodeServer),
  ExpTypes = dialyzer_codeserver:get_exported_types(CodeServer),
  ContractFun =
    fun({{_M, _F, _A}=MFA, {File, TmpContract, Xtra}}, C0) ->
        #tmp_contract{contract_funs = CFuns, forms = Forms} = TmpContract,
        {NewCs, C2} = lists:mapfoldl(fun(CFun, C1) ->
                                         CFun(ExpTypes, RecordDict, C1)
                                     end, C0, CFuns),
        Args = general_domain(NewCs),
        Contract = #contract{contracts = NewCs, args = Args, forms = Forms},
        {{MFA, {File, Contract, Xtra}}, C2}
    end,
  ModuleFun =
    fun(ModuleName) ->
        Cache = erl_types:cache__new(),
        {ContractMap, CallbackMap} =
          dialyzer_codeserver:get_temp_contracts(ModuleName, CodeServer),
        {NewContractList, Cache1} =
          lists:mapfoldl(ContractFun, Cache, maps:to_list(ContractMap)),
        {NewCallbackList, _NewCache} =
          lists:mapfoldl(ContractFun, Cache1, maps:to_list(CallbackMap)),
        dialyzer_codeserver:store_contracts(ModuleName,
                                            maps:from_list(NewContractList),
                                            maps:from_list(NewCallbackList),
                                            CodeServer)
    end,
  lists:foreach(ModuleFun, Mods),
  dialyzer_codeserver:finalize_contracts(CodeServer).

-type opaques_fun() :: fun((module()) -> [erl_types:erl_type()]).

-type fun_types() :: dict:dict(label(), erl_types:type_table()).

-spec check_contracts([{mfa(), file_contract()}],
		      dialyzer_callgraph:callgraph(), fun_types(),
                      opaques_fun()) -> plt_contracts().

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, _Xtra}} ->
                Opaques = FindOpaques(M),
		case check_contract(Contract, Type, Opaques) of
		  ok ->
		    case erl_bif_types:is_known(M, F, A) of
		      true ->
			%% Disregard the contracts since
			%% this is a known function.
			NewContracts;
		      false ->
			[{MFA, Contract}|NewContracts]
		    end;
		  {error, _Error} -> NewContracts
		end;
	      error -> NewContracts
	    end;
	  error -> NewContracts
	end
    end,
  dict:fold(FoldFun, [], FunTypes).

%% Checks all components of a contract
-spec check_contract(#contract{}, erl_types:erl_type()) -> 'ok' | {'error', term()}.

check_contract(Contract, SuccType) ->
  check_contract(Contract, SuccType, 'universe').

check_contract(#contract{contracts = Contracts}, SuccType, Opaques) ->
  try
    Contracts1 = [{Contract, insert_constraints(Constraints)}
		  || {Contract, Constraints} <- Contracts],
    Contracts2 = [erl_types:t_subst(Contract, Map)
		  || {Contract, Map} <- Contracts1],
    GenDomains = [erl_types:t_fun_args(C) || C <- Contracts2],
    case check_domains(GenDomains) of
      error ->
	{error, {overlapping_contract, []}};
      ok ->
	InfList = [{Contract, erl_types:t_inf(Contract, SuccType, Opaques)}
		   || Contract <- Contracts2],
	case check_contract_inf_list(InfList, SuccType, Opaques) of
	  {error, _} = Invalid -> Invalid;
	  ok -> check_extraneous(Contracts2, SuccType)
	end
    end
  catch
    throw:{error, _} = Error -> Error
  end.

check_domains([_]) -> ok;
check_domains([Dom|Doms]) ->
  Fun = fun(D) ->
	    erl_types:any_none_or_unit(erl_types:t_inf_lists(Dom, D))
	end,
  case lists:all(Fun, Doms) of
    true -> check_domains(Doms);
    false -> error
  end.

%% 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(List, SuccType, Opaques) ->
  case check_contract_inf_list(List, SuccType, Opaques, []) of
    ok -> ok;
    {error, []} -> {error, invalid_contract};
    {error, [{SigRange, ContrRange}|_]} ->
      case erl_types:t_find_opaque_mismatch(SigRange, ContrRange, Opaques) of
        error -> {error, invalid_contract};
        {ok, _T1, T2} -> {error, {opaque_mismatch, T2}}
      end
  end.

check_contract_inf_list([{Contract, FunType}|Left], SuccType, Opaques, OM) ->
  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, Opaques, OM);
    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)) of
	    true ->
              CR = erl_types:t_fun_range(Contract),
              NewOM = [{STRange, CR}|OM],
              check_contract_inf_list(Left, SuccType, Opaques, NewOM);
	    false -> ok
	  end
      end
  end;
check_contract_inf_list([], _SuccType, _Opaques, OM) ->
  {error, OM}.

check_extraneous([], _SuccType) -> ok;
check_extraneous([C|Cs], SuccType) ->
  case check_extraneous_1(C, SuccType) of
    ok -> check_extraneous(Cs, SuccType);
    Error -> Error
  end.

check_extraneous_1(Contract, SuccType) ->
  CRng = erl_types:t_fun_range(Contract),
  CRngs = erl_types:t_elements(CRng),
  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))] of
    [] ->
      case bad_extraneous_list(CRng, STRng)
	orelse bad_extraneous_map(CRng, STRng)
      of
	true -> {error, invalid_contract};
	false -> ok
      end;
    CRs -> {error, {extra_range, erl_types:t_sup(CRs), STRng}}
  end.

bad_extraneous_list(CRng, STRng) ->
  CRngList = list_part(CRng),
  STRngList = list_part(STRng),
  case is_not_nil_list(CRngList) andalso is_not_nil_list(STRngList) of
    false -> false;
    true ->
      CRngElements = erl_types:t_list_elements(CRngList),
      STRngElements = erl_types:t_list_elements(STRngList),
      Inf = erl_types:t_inf(CRngElements, STRngElements),
      erl_types:t_is_none(Inf)
  end.

list_part(Type) ->
  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).

bad_extraneous_map(CRng, STRng) ->
  CRngMap = map_part(CRng),
  STRngMap = map_part(STRng),
  (not is_empty_map(CRngMap)) andalso (not is_empty_map(STRngMap))
    andalso is_empty_map(erl_types:t_inf(CRngMap, STRngMap)).

map_part(Type) ->
  erl_types:t_inf(erl_types:t_map(), Type).

is_empty_map(Type) ->
  erl_types:t_is_equal(Type, erl_types:t_from_term(#{})).

%% This is the heart of the "range function"
-spec process_contracts([contract_pair()], [erl_types:erl_type()]) ->
                           erl_types:erl_type().

process_contracts(OverContracts, Args) ->
  process_contracts(OverContracts, Args, erl_types:t_none()).

process_contracts([OverContract|Left], Args, AccRange) ->
  NewAccRange =
    case process_contract(OverContract, Args) of
      error -> AccRange;
      {ok, Range} -> erl_types:t_sup(AccRange, Range)
    end,
  process_contracts(Left, Args, NewAccRange);
process_contracts([], _Args, AccRange) ->
  AccRange.

-spec process_contract(contract_pair(), [erl_types:erl_type()]) ->
                          'error' | {'ok', erl_types:erl_type()}.

process_contract({Contract, Constraints}, CallTypes0) ->
  CallTypesFun = erl_types:t_fun(CallTypes0, erl_types:t_any()),
  ContArgsFun = erl_types:t_fun(erl_types:t_fun_args(Contract),
				erl_types:t_any()),
  ?debug("Instance: Contract:  ~s\n          Arguments: ~s\n",
	 [erl_types:t_to_string(ContArgsFun),
	  erl_types:t_to_string(CallTypesFun)]),
  case solve_constraints(ContArgsFun, CallTypesFun, Constraints) of
    {ok, VarMap} ->
      {ok, erl_types:t_subst(erl_types:t_fun_range(Contract), VarMap)};
    error -> error
  end.

solve_constraints(Contract, Call, Constraints) ->
  %% First make sure the call follows the constraints
  CMap = insert_constraints(Constraints),
  Contract1 = erl_types:t_subst(Contract, CMap),
  %% Just a safe over-approximation.
  %% TODO: Find the types for type variables properly
  ContrArgs = erl_types:t_fun_args(Contract1),
  CallArgs = erl_types:t_fun_args(Call),
  InfList = erl_types:t_inf_lists(ContrArgs, CallArgs),
  case erl_types:any_none_or_unit(InfList) of
    true -> error;
    false -> {ok, CMap}
  end.
  %%Inf = erl_types:t_inf(Contract1, Call),
  %% Then unify with the constrained call type.
  %%  ?debug("Call: ~s\n", [erl_types:t_to_string(Call)]),
  %%  ?debug("Contract: ~s\n", [erl_types:t_to_string(Contract)]),
  %%  ?debug("Contract1: ~s\n", [erl_types:t_to_string(Contract1)]),
  %%  ?debug("Inf: ~s\n", [erl_types:t_to_string(Inf)]),
  %%  erl_types:t_assign_variables_to_subtype(Contract, Inf).

-type contracts() :: dialyzer_codeserver:contracts().

%% Checks the contracts for functions that are not implemented
-spec contracts_without_fun(contracts(), [_], dialyzer_callgraph:callgraph()) ->
        [raw_warning()].

contracts_without_fun(Contracts, AllFuns0, Callgraph) ->
  AllFuns1 = [{dialyzer_callgraph:lookup_name(Label, Callgraph), Arity}
	      || {Label, Arity} <- AllFuns0],
  AllFuns2 = [{M, F, A} || {{ok, {M, F, _}}, A} <- AllFuns1],
  AllContractMFAs = maps:keys(Contracts),
  ErrorContractMFAs = AllContractMFAs -- AllFuns2,
  [warn_spec_missing_fun(MFA, Contracts) || MFA <- ErrorContractMFAs].

warn_spec_missing_fun({M, F, A} = MFA, Contracts) ->
  {{File, Line}, _Contract, _Xtra} = maps:get(MFA, Contracts),
  WarningInfo = {File, Line, MFA},
  {?WARN_CONTRACT_SYNTAX, WarningInfo, {spec_missing_fun, [M, F, A]}}.

%% This treats the "when" constraints. It will be extended, we hope.
insert_constraints(Constraints) ->
  insert_constraints(Constraints, maps:new()).

insert_constraints([{subtype, Type1, Type2}|Left], Map) ->
  case erl_types:t_is_var(Type1) of
    true ->
      Name = erl_types:t_var_name(Type1),
      Map1 = case maps:find(Name, Map) of
               error ->
                 maps:put(Name, Type2, Map);
               {ok, VarType} ->
                 maps:put(Name, erl_types:t_inf(VarType, Type2), Map)
             end,
      insert_constraints(Left, Map1);
    false ->
      %% A lot of things should change to add supertypes
      throw({error, io_lib:format("First argument of is_subtype constraint "
				  "must be a type variable: ~p\n", [Type1])})
  end;
insert_constraints([], Map) -> Map.

-type types() :: erl_types:type_table().

-type spec_data() :: {TypeSpec :: [_], Xtra:: [_]}.

-spec store_tmp_contract(mfa(), file_line(), spec_data(), contracts(), types()) ->
        contracts().

store_tmp_contract(MFA, FileLine, {TypeSpec, Xtra}, SpecMap, RecordsDict) ->
  %% io:format("contract from form: ~p\n", [TypeSpec]),
  TmpContract = contract_from_form(TypeSpec, MFA, RecordsDict, FileLine),
  %% io:format("contract: ~p\n", [TmpContract]),
  maps:put(MFA, {FileLine, TmpContract, Xtra}, SpecMap).

contract_from_form(Forms, MFA, RecDict, FileLine) ->
  {CFuns, Forms1} = contract_from_form(Forms, MFA, RecDict, FileLine, [], []),
  #tmp_contract{contract_funs = CFuns, forms = Forms1}.

contract_from_form([{type, _, 'fun', [_, _]} = Form | Left], MFA, RecDict,
		   FileLine, TypeAcc, FormAcc) ->
  TypeFun =
    fun(ExpTypes, AllRecords, Cache) ->
	{NewType, NewCache} =
	  try
            from_form_with_check(Form, ExpTypes, MFA, AllRecords, Cache)
	  catch
	    throw:{error, Msg} ->
	      {File, Line} = FileLine,
	      NewMsg = io_lib:format("~s:~p: ~s", [filename:basename(File),
                                                   Line, Msg]),
	      throw({error, NewMsg})
	  end,
        NewTypeNoVars = erl_types:subst_all_vars_to_any(NewType),
	{{NewTypeNoVars, []}, NewCache}
    end,
  NewTypeAcc = [TypeFun | TypeAcc],
  NewFormAcc = [{Form, []} | FormAcc],
  contract_from_form(Left, MFA, RecDict, FileLine, NewTypeAcc, NewFormAcc);
contract_from_form([{type, _L1, bounded_fun,
		     [{type, _L2, 'fun', [_, _]} = Form, Constr]}| Left],
		   MFA, RecDict, FileLine, TypeAcc, FormAcc) ->
  TypeFun =
    fun(ExpTypes, AllRecords, Cache) ->
	{Constr1, VarTable, Cache1} =
	  process_constraints(Constr, MFA, RecDict, ExpTypes, AllRecords,
                              Cache),
        {NewType, NewCache} =
          from_form_with_check(Form, ExpTypes, MFA, AllRecords,
                               VarTable, Cache1),
        NewTypeNoVars = erl_types:subst_all_vars_to_any(NewType),
	{{NewTypeNoVars, Constr1}, NewCache}
    end,
  NewTypeAcc = [TypeFun | TypeAcc],
  NewFormAcc = [{Form, Constr} | FormAcc],
  contract_from_form(Left, MFA, RecDict, FileLine, NewTypeAcc, NewFormAcc);
contract_from_form([], _MFA, _RecDict, _FileLine, TypeAcc, FormAcc) ->
  {lists:reverse(TypeAcc), lists:reverse(FormAcc)}.

process_constraints(Constrs, MFA, RecDict, ExpTypes, AllRecords, Cache) ->
  {Init0, NewCache} = initialize_constraints(Constrs, MFA, RecDict, ExpTypes,
                                             AllRecords, Cache),
  Init = remove_cycles(Init0),
  constraints_fixpoint(Init, MFA, RecDict, ExpTypes, AllRecords, NewCache).

initialize_constraints(Constrs, MFA, RecDict, ExpTypes, AllRecords, Cache) ->
  initialize_constraints(Constrs, MFA, RecDict, ExpTypes, AllRecords,
                         Cache, []).

initialize_constraints([], _MFA, _RecDict, _ExpTypes, _AllRecords,
                       Cache, Acc) ->
  {Acc, Cache};
initialize_constraints([Constr|Rest], MFA, RecDict, ExpTypes, AllRecords,
                       Cache, Acc) ->
  case Constr of
    {type, _, constraint, [{atom, _, is_subtype}, [Type1, Type2]]} ->
      VarTable = erl_types:var_table__new(),
      {T1, NewCache} =
        final_form(Type1, ExpTypes, MFA, AllRecords, VarTable, Cache),
      Entry = {T1, Type2},
      initialize_constraints(Rest, MFA, RecDict, ExpTypes, AllRecords,
                             NewCache, [Entry|Acc]);
    {type, _, constraint, [{atom,_,Name}, List]} ->
      N = length(List),
      throw({error,
	     io_lib:format("Unsupported type guard ~w/~w\n", [Name, N])})
  end.

constraints_fixpoint(Constrs, MFA, RecDict, ExpTypes, AllRecords, Cache) ->
  VarTable = erl_types:var_table__new(),
  {VarTab, NewCache} =
    constraints_to_dict(Constrs, MFA, RecDict, ExpTypes, AllRecords,
                        VarTable, Cache),
  constraints_fixpoint(VarTab, MFA, Constrs, RecDict, ExpTypes,
                       AllRecords, NewCache).

constraints_fixpoint(OldVarTab, MFA, Constrs, RecDict, ExpTypes,
                     AllRecords, Cache) ->
  {NewVarTab, NewCache} =
    constraints_to_dict(Constrs, MFA, RecDict, ExpTypes, AllRecords,
                        OldVarTab, Cache),
  case NewVarTab of
    OldVarTab ->
      Fun =
	fun(Key, Value, Acc) ->
	    [{subtype, erl_types:t_var(Key), Value}|Acc]
	end,
      FinalConstrs = maps:fold(Fun, [], NewVarTab),
      {FinalConstrs, NewVarTab, NewCache};
    _Other ->
      constraints_fixpoint(NewVarTab, MFA, Constrs, RecDict, ExpTypes,
                           AllRecords, NewCache)
  end.

final_form(Form, ExpTypes, MFA, AllRecords, VarTable, Cache) ->
  from_form_with_check(Form, ExpTypes, MFA, AllRecords, VarTable, Cache).

from_form_with_check(Form, ExpTypes, MFA, AllRecords, Cache) ->
  VarTable = erl_types:var_table__new(),
  from_form_with_check(Form, ExpTypes, MFA, AllRecords, VarTable, Cache).

from_form_with_check(Form, ExpTypes, MFA, AllRecords, VarTable, Cache) ->
  Site = {spec, MFA},
  C1 = erl_types:t_check_record_fields(Form, ExpTypes, Site, AllRecords,
                                       VarTable, Cache),
  erl_types:t_from_form(Form, ExpTypes, Site, AllRecords, VarTable, C1).

constraints_to_dict(Constrs, MFA, RecDict, ExpTypes, AllRecords,
                    VarTab, Cache) ->
  {Subtypes, NewCache} =
    constraints_to_subs(Constrs, MFA, RecDict, ExpTypes, AllRecords,
                        VarTab, Cache, []),
  {insert_constraints(Subtypes), NewCache}.

constraints_to_subs([], _MFA, _RecDict, _ExpTypes, _AllRecords,
                    _VarTab, Cache, Acc) ->
  {Acc, Cache};
constraints_to_subs([{T1, Form2}|Rest], MFA, RecDict, ExpTypes, AllRecords,
                    VarTab, Cache, Acc) ->
  {T2, NewCache} =
    final_form(Form2, ExpTypes, MFA, AllRecords, VarTab, Cache),
  NewAcc = [{subtype, T1, T2}|Acc],
  constraints_to_subs(Rest, MFA, RecDict, ExpTypes, AllRecords,
                      VarTab, NewCache, NewAcc).

%% Replaces variables with '_' when necessary to break up cycles among
%% the constraints.

remove_cycles(Constrs0) ->
  Uses = find_uses(Constrs0),
  G = digraph:new(),
  Vs0 = [V || {V, _} <- Uses] ++ [V || {_, V} <- Uses],
  Vs = lists:usort(Vs0),
  lists:foreach(fun(V) -> _ = digraph:add_vertex(G, V) end, Vs),
  lists:foreach(fun({From, To}) ->
                    _ = digraph:add_edge(G, {From, To}, From, To, [])
                end, Uses),
  ok = remove_cycles(G, Vs),
  ToRemove = ordsets:subtract(ordsets:from_list(Uses),
                              ordsets:from_list(digraph:edges(G))),
  Constrs = remove_uses(ToRemove, Constrs0),
  digraph:delete(G),
  Constrs.

find_uses([{Var, Form}|Constrs]) ->
  UsedVars = form_vars(Form, []),
  VarName = erl_types:t_var_name(Var),
  [{VarName, UsedVar} || UsedVar <- UsedVars] ++ find_uses(Constrs);
find_uses([]) ->
  [].

form_vars({var, _, '_'}, Vs) -> Vs;
form_vars({var, _, V}, Vs) -> [V|Vs];
form_vars(T, Vs) when is_tuple(T) ->
  form_vars(tuple_to_list(T), Vs);
form_vars([E|Es], Vs) ->
  form_vars(Es, form_vars(E, Vs));
form_vars(_, Vs) -> Vs.

remove_cycles(G, Vs) ->
  NumberOfEdges = digraph:no_edges(G),
  lists:foreach(fun(V) ->
                        case digraph:get_cycle(G, V) of
                          false -> true;
                          [V] -> digraph:del_edge(G, {V, V});
                          [V, V1|_] -> digraph:del_edge(G, {V, V1})
                        end
                    end, Vs),
  case digraph:no_edges(G) =:= NumberOfEdges of
    true -> ok;
    false -> remove_cycles(G, Vs)
  end.

remove_uses([], Constrs) -> Constrs;
remove_uses([{Var, Use}|ToRemove], Constrs0) ->
  Constrs = remove_uses(Var, Use, Constrs0),
  remove_uses(ToRemove, Constrs).

remove_uses(_Var, _Use, []) -> [];
remove_uses(Var, Use, [Constr|Constrs]) ->
  {V, Form} = Constr,
  NewConstr = case erl_types:t_var_name(V) =:= Var of
                true ->
                  {V, remove_use(Form, Use)};
                false ->
                  Constr
              end,
  [NewConstr|remove_uses(Var, Use, Constrs)].

remove_use({var, L, V}, V) -> {var, L, '_'};
remove_use(T, V) when is_tuple(T) ->
  list_to_tuple(remove_use(tuple_to_list(T), V));
remove_use([E|Es], V) ->
  [remove_use(E, V)|remove_use(Es, V)];
remove_use(T, _V) -> T.

%% Gets the most general domain of a list of domains of all
%% the overloaded contracts

general_domain(List) ->
  general_domain(List, erl_types:t_none()).

general_domain([{Sig, Constraints}|Left], AccSig) ->
  Map = insert_constraints(Constraints),
  Sig1 = erl_types:t_subst(Sig, Map),
  general_domain(Left, erl_types:t_sup(AccSig, Sig1));
general_domain([], AccSig) ->
  %% Get rid of all variables in the domain.
  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(),
                                    opaques_fun()) -> [raw_warning()].

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, FindOpaques, Acc) ->
  Contracts1 = dialyzer_codeserver:lookup_mod_contracts(Mod, CodeServer),
  Contracts2 = maps:to_list(Contracts1),
  Records = dialyzer_codeserver:lookup_mod_records(Mod, CodeServer),
  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, _Xtra}}|Left],
				   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, FindOpaques, Acc);
    {value, {Ret, Args}} ->
      Sig = erl_types:t_fun(Args, Ret),
      {M, _F, _A} = MFA,
      %% io:format("MFA ~p~n", [MFA]),
      Opaques = FindOpaques(M),
      {File, Line} = FileLine,
      WarningInfo = {File, Line, MFA},
      NewAcc =
	case check_contract(Contract, Sig, Opaques) of
	  {error, invalid_contract} ->
	    [invalid_contract_warning(MFA, WarningInfo, Sig, RecDict)|Acc];
          {error, {opaque_mismatch, T2}} ->
            W = contract_opaque_warning(MFA, WarningInfo, T2, Sig, RecDict),
            [W|Acc];
	  {error, {overlapping_contract, []}} ->
	    [overlapping_contract_warning(MFA, WarningInfo)|Acc];
	  {error, {extra_range, ExtraRanges, STRange}} ->
	    Warn =
	      case t_from_forms_without_remote(Contract#contract.forms,
					       MFA, RecDict) of
		{ok, NoRemoteType} ->
		  CRet = erl_types:t_fun_range(NoRemoteType),
		  erl_types:t_is_subtype(ExtraRanges, CRet);
		unsupported ->
		  true
	      end,
	    case Warn of
	      true ->
		[extra_range_warning(MFA, WarningInfo, ExtraRanges, STRange)|Acc];
	      false ->
		Acc
	    end;
	  {error, Msg} ->
	    [{?WARN_CONTRACT_SYNTAX, WarningInfo, Msg}|Acc];
	  ok ->
	    {M, F, A} = MFA,
	    CSig0 = get_contract_signature(Contract),
	    CSig = erl_types:subst_all_vars_to_any(CSig0),
	    case erl_bif_types:is_known(M, F, A) of
	      true ->
		%% This is strictly for contracts of functions also in
		%% erl_bif_types
		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, Opaques) of
		  {error, _} ->
		    [invalid_contract_warning(MFA, WarningInfo, BifSig, RecDict)
		     |Acc];
		  ok ->
		    picky_contract_check(CSig, BifSig, MFA, WarningInfo,
					 Contract, RecDict, Acc)
		end;
	      false ->
		picky_contract_check(CSig, Sig, MFA, WarningInfo, Contract,
				     RecDict, Acc)
	    end
	end,
      get_invalid_contract_warnings_funs(Left, Plt, RecDict, FindOpaques, NewAcc)
  end;
get_invalid_contract_warnings_funs([], _Plt, _RecDict, _FindOpaques, Acc) ->
  Acc.

invalid_contract_warning({M, F, A}, WarningInfo, SuccType, RecDict) ->
  SuccTypeStr = dialyzer_utils:format_sig(SuccType, RecDict),
  {?WARN_CONTRACT_TYPES, WarningInfo, {invalid_contract, [M, F, A, SuccTypeStr]}}.

contract_opaque_warning({M, F, A}, WarningInfo, OpType, SuccType, RecDict) ->
  OpaqueStr = erl_types:t_to_string(OpType),
  SuccTypeStr = dialyzer_utils:format_sig(SuccType, RecDict),
  {?WARN_CONTRACT_TYPES, WarningInfo,
   {contract_with_opaque, [M, F, A, OpaqueStr, SuccTypeStr]}}.

overlapping_contract_warning({M, F, A}, WarningInfo) ->
  {?WARN_CONTRACT_TYPES, WarningInfo, {overlapping_contract, [M, F, A]}}.

extra_range_warning({M, F, A}, WarningInfo, ExtraRanges, STRange) ->
  ERangesStr = erl_types:t_to_string(ExtraRanges),
  STRangeStr = erl_types:t_to_string(STRange),
  {?WARN_CONTRACT_SUPERTYPE, WarningInfo,
   {extra_range, [M, F, A, ERangesStr, STRangeStr]}}.

picky_contract_check(CSig0, Sig0, MFA, WarningInfo, Contract, RecDict, Acc) ->
  CSig = erl_types:t_abstract_records(CSig0, RecDict),
  Sig = erl_types:t_abstract_records(Sig0, RecDict),
  case erl_types:t_is_equal(CSig, Sig) of
    true -> Acc;
    false ->
      case (erl_types:t_is_none(erl_types:t_fun_range(Sig)) andalso
	    erl_types:t_is_unit(erl_types:t_fun_range(CSig))) of
	true -> Acc;
	false ->
	  case extra_contract_warning(MFA, WarningInfo, Contract,
				      CSig0, Sig0, RecDict) of
	    no_warning -> Acc;
	    {warning, Warning} -> [Warning|Acc]
	  end
      end
  end.

extra_contract_warning(MFA, WarningInfo, Contract, CSig, Sig, RecDict) ->
  {IsRemoteTypesRelated, SubtypeRelation} =
    is_remote_types_related(Contract, CSig, Sig, MFA, RecDict),
  case IsRemoteTypesRelated of
    true ->
      no_warning;
    false ->
      {M, F, A} = MFA,
      SigString = lists:flatten(dialyzer_utils:format_sig(Sig, RecDict)),
      ContractString = contract_to_string(Contract),
      {Tag, Msg} =
	case SubtypeRelation of
	  contract_is_subtype ->
	    {?WARN_CONTRACT_SUBTYPE,
	     {contract_subtype, [M, F, A, ContractString, SigString]}};
	  contract_is_supertype ->
	    {?WARN_CONTRACT_SUPERTYPE,
	     {contract_supertype, [M, F, A, ContractString, SigString]}};
	  neither ->
	    {?WARN_CONTRACT_NOT_EQUAL,
	     {contract_diff, [M, F, A, ContractString, SigString]}}
	end,
      {warning, {Tag, WarningInfo, Msg}}
  end.

is_remote_types_related(Contract, CSig, Sig, MFA, RecDict) ->
  case erl_types:t_is_subtype(CSig, Sig) of
    true ->
      {false, contract_is_subtype};
    false ->
      case erl_types:t_is_subtype(Sig, CSig) of
	true ->
	  case t_from_forms_without_remote(Contract#contract.forms, MFA,
                                           RecDict) of
	    {ok, NoRemoteTypeSig} ->
	      case blame_remote(CSig, NoRemoteTypeSig, Sig) of
		true ->
		  {true, neither};
		false ->
		  {false, contract_is_supertype}
	      end;
	    unsupported ->
	      {false, contract_is_supertype}
	  end;
	false ->
	  {false, neither}
      end
  end.

t_from_forms_without_remote([{FType, []}], MFA, RecDict) ->
  Site = {spec, MFA},
  {Type1, _} = erl_types:t_from_form_without_remote(FType, Site, RecDict),
  {ok, erl_types:subst_all_vars_to_any(Type1)};
t_from_forms_without_remote([{_FType, _Constrs}], _MFA, _RecDict) ->
  %% 'When' constraints
  unsupported;
t_from_forms_without_remote(_Forms, _MFA, _RecDict) ->
  %% Lots of forms
  unsupported.

blame_remote(ContractSig, NoRemoteContractSig, Sig) ->
  CArgs  = erl_types:t_fun_args(ContractSig),
  CRange = erl_types:t_fun_range(ContractSig),
  NRArgs = erl_types:t_fun_args(NoRemoteContractSig),
  NRRange = erl_types:t_fun_range(NoRemoteContractSig),
  SArgs = erl_types:t_fun_args(Sig),
  SRange = erl_types:t_fun_range(Sig),
  blame_remote_list([CRange|CArgs], [NRRange|NRArgs], [SRange|SArgs]).

blame_remote_list([], [], []) ->
  true;
blame_remote_list([CArg|CArgs], [NRArg|NRArgs], [SArg|SArgs]) ->
  case erl_types:t_is_equal(CArg, NRArg) of
    true ->
      case not erl_types:t_is_equal(CArg, SArg) of
	true  -> false;
	false -> blame_remote_list(CArgs, NRArgs, SArgs)
      end;
    false ->
      case erl_types:t_is_subtype(SArg, NRArg)
	andalso not erl_types:t_is_subtype(NRArg, SArg) of
	true  -> false;
	false -> blame_remote_list(CArgs, NRArgs, SArgs)
      end
  end.