summaryrefslogtreecommitdiff
path: root/src/elaborate.sml
blob: 9c96060d9d163e19be029bbf9f7c89f694a73a05 (plain)
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
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
(* Copyright (c) 2008, Adam Chlipala
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * - The names of contributors may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *)

structure Elaborate :> ELABORATE = struct

structure P = Prim
structure L = Source
structure L' = Elab
structure E = ElabEnv
structure U = ElabUtil

open Print
open ElabPrint

fun elabExplicitness e =
    case e of
        L.Explicit => L'.Explicit
      | L.Implicit => L'.Implicit

fun occursKind r =
    U.Kind.exists (fn L'.KUnif (_, r') => r = r'
                    | _ => false)

datatype kunify_error =
         KOccursCheckFailed of L'.kind * L'.kind
       | KIncompatible of L'.kind * L'.kind

exception KUnify' of kunify_error

fun kunifyError err =
    case err of
        KOccursCheckFailed (k1, k2) =>
        eprefaces "Kind occurs check failed"
        [("Kind 1", p_kind k1),
         ("Kind 2", p_kind k2)]
      | KIncompatible (k1, k2) =>
        eprefaces "Incompatible kinds"
        [("Kind 1", p_kind k1),
         ("Kind 2", p_kind k2)]

fun unifyKinds' (k1All as (k1, _)) (k2All as (k2, _)) =
    let
        fun err f = raise KUnify' (f (k1All, k2All))
    in
        case (k1, k2) of
            (L'.KType, L'.KType) => ()
          | (L'.KArrow (d1, r1), L'.KArrow (d2, r2)) =>
            (unifyKinds' d1 d2;
             unifyKinds' r1 r2)
          | (L'.KName, L'.KName) => ()
          | (L'.KRecord k1, L'.KRecord k2) => unifyKinds' k1 k2

          | (L'.KError, _) => ()
          | (_, L'.KError) => ()

          | (L'.KUnif (_, ref (SOME k1All)), _) => unifyKinds' k1All k2All
          | (_, L'.KUnif (_, ref (SOME k2All))) => unifyKinds' k1All k2All

          | (L'.KUnif (_, r1), L'.KUnif (_, r2)) =>
            if r1 = r2 then
                ()
            else
                r1 := SOME k2All

          | (L'.KUnif (_, r), _) =>
            if occursKind r k2All then
                err KOccursCheckFailed
            else
                r := SOME k2All
          | (_, L'.KUnif (_, r)) =>
            if occursKind r k1All then
                err KOccursCheckFailed
            else
                r := SOME k1All

          | _ => err KIncompatible
    end

exception KUnify of L'.kind * L'.kind * kunify_error

fun unifyKinds k1 k2 =
    unifyKinds' k1 k2
    handle KUnify' err => raise KUnify (k1, k2, err)

datatype con_error =
         UnboundCon of ErrorMsg.span * string
       | UnboundStrInCon of ErrorMsg.span * string
       | WrongKind of L'.con * L'.kind * L'.kind * kunify_error

fun conError env err =
    case err of
        UnboundCon (loc, s) =>
        ErrorMsg.errorAt loc ("Unbound constructor variable " ^ s)
      | UnboundStrInCon (loc, s) =>
        ErrorMsg.errorAt loc ("Unbound structure " ^ s)
      | WrongKind (c, k1, k2, kerr) =>
        (ErrorMsg.errorAt (#2 c) "Wrong kind";
         eprefaces' [("Constructor", p_con env c),
                     ("Have kind", p_kind k1),
                     ("Need kind", p_kind k2)];
         kunifyError kerr)

fun checkKind env c k1 k2 =
    unifyKinds k1 k2
    handle KUnify (k1, k2, err) =>
           conError env (WrongKind (c, k1, k2, err))

val dummy = ErrorMsg.dummySpan

val ktype = (L'.KType, dummy)
val kname = (L'.KName, dummy)
val ktype_record = (L'.KRecord ktype, dummy)

val cerror = (L'.CError, dummy)
val kerror = (L'.KError, dummy)
val eerror = (L'.EError, dummy)
val sgnerror = (L'.SgnError, dummy)
val strerror = (L'.StrError, dummy)

local
    val count = ref 0
in

fun resetKunif () = count := 0

fun kunif () =
    let
        val n = !count
        val s = if n <= 26 then
                    str (chr (ord #"A" + n))
                else
                    "U" ^ Int.toString (n - 26)
    in
        count := n + 1;
        (L'.KUnif (s, ref NONE), dummy)
    end

end

local
    val count = ref 0
in

fun resetCunif () = count := 0

fun cunif k =
    let
        val n = !count
        val s = if n <= 26 then
                    str (chr (ord #"A" + n))
                else
                    "U" ^ Int.toString (n - 26)
    in
        count := n + 1;
        (L'.CUnif (k, s, ref NONE), dummy)
    end

end

fun elabKind (k, loc) =
    case k of
        L.KType => (L'.KType, loc)
      | L.KArrow (k1, k2) => (L'.KArrow (elabKind k1, elabKind k2), loc)
      | L.KName => (L'.KName, loc)
      | L.KRecord k => (L'.KRecord (elabKind k), loc)
      | L.KWild => kunif ()

fun elabCon env (c, loc) =
    case c of
        L.CAnnot (c, k) =>
        let
            val k' = elabKind k
            val (c', ck) = elabCon env c
        in
            checkKind env c' ck k';
            (c', k')
        end

      | L.TFun (t1, t2) =>
        let
            val (t1', k1) = elabCon env t1
            val (t2', k2) = elabCon env t2
        in
            checkKind env t1' k1 ktype;
            checkKind env t2' k2 ktype;
            ((L'.TFun (t1', t2'), loc), ktype)
        end
      | L.TCFun (e, x, k, t) =>
        let
            val e' = elabExplicitness e
            val k' = elabKind k
            val env' = E.pushCRel env x k'
            val (t', tk) = elabCon env' t
        in
            checkKind env t' tk ktype;
            ((L'.TCFun (e', x, k', t'), loc), ktype)
        end
      | L.TRecord c =>
        let
            val (c', ck) = elabCon env c
            val k = (L'.KRecord ktype, loc)
        in
            checkKind env c' ck k;
            ((L'.TRecord c', loc), ktype)
        end

      | L.CVar ([], s) =>
        (case E.lookupC env s of
             E.NotBound =>
             (conError env (UnboundCon (loc, s));
              (cerror, kerror))
           | E.Rel (n, k) =>
             ((L'.CRel n, loc), k)
           | E.Named (n, k) =>
             ((L'.CNamed n, loc), k))
      | L.CVar (m1 :: ms, s) =>
        (case E.lookupStr env m1 of
             NONE => (conError env (UnboundStrInCon (loc, m1));
                      (cerror, kerror))
           | SOME (n, sgn) =>
             let
                 val (str, sgn) = foldl (fn (m, (str, sgn)) =>
                                     case E.projectStr env {sgn = sgn, str = str, field = m} of
                                         NONE => (conError env (UnboundStrInCon (loc, m));
                                                  (strerror, sgnerror))
                                       | SOME sgn => ((L'.StrProj (str, m), loc), sgn))
                                  ((L'.StrVar n, loc), sgn) ms

                 val k = case E.projectCon env {sgn = sgn, str = str, field = s} of
                             NONE => (conError env (UnboundCon (loc, s));
                                      kerror)
                           | SOME (k, _) => k
             in
                 ((L'.CModProj (n, ms, s), loc), k)
             end)
                                                                       
      | L.CApp (c1, c2) =>
        let
            val (c1', k1) = elabCon env c1
            val (c2', k2) = elabCon env c2
            val dom = kunif ()
            val ran = kunif ()
        in
            checkKind env c1' k1 (L'.KArrow (dom, ran), loc);
            checkKind env c2' k2 dom;
            ((L'.CApp (c1', c2'), loc), ran)
        end
      | L.CAbs (x, k, t) =>
        let
            val k' = elabKind k
            val env' = E.pushCRel env x k'
            val (t', tk) = elabCon env' t
        in
            ((L'.CAbs (x, k', t'), loc),
             (L'.KArrow (k', tk), loc))
        end

      | L.CName s =>
        ((L'.CName s, loc), kname)

      | L.CRecord xcs =>
        let
            val k = kunif ()

            val xcs' = map (fn (x, c) =>
                               let
                                   val (x', xk) = elabCon env x
                                   val (c', ck) = elabCon env c
                               in
                                   checkKind env x' xk kname;
                                   checkKind env c' ck k;
                                   (x', c')
                               end) xcs
        in
            ((L'.CRecord (k, xcs'), loc), (L'.KRecord k, loc))
        end
      | L.CConcat (c1, c2) =>
        let
            val (c1', k1) = elabCon env c1
            val (c2', k2) = elabCon env c2
            val ku = kunif ()
            val k = (L'.KRecord ku, loc)
        in
            checkKind env c1' k1 k;
            checkKind env c2' k2 k;
            ((L'.CConcat (c1', c2'), loc), k)
        end

      | L.CWild k =>
        let
            val k' = elabKind k
        in
            (cunif k', k')
        end

fun kunifsRemain k =
    case k of
        L'.KUnif (_, ref NONE) => true
      | _ => false
fun cunifsRemain c =
    case c of
        L'.CUnif (_, _, ref NONE) => true
      | _ => false

val kunifsInKind = U.Kind.exists kunifsRemain
val kunifsInCon = U.Con.exists {kind = kunifsRemain,
                                con = fn _ => false}
val kunifsInExp = U.Exp.exists {kind = kunifsRemain,
                                con = fn _ => false,
                                exp = fn _ => false}

val cunifsInCon = U.Con.exists {kind = fn _ => false,
                                con = cunifsRemain}
val cunifsInExp = U.Exp.exists {kind = fn _ => false,
                                con = cunifsRemain,
                                exp = fn _ => false}

fun occursCon r =
    U.Con.exists {kind = fn _ => false,
                  con = fn L'.CUnif (_, _, r') => r = r'
                         | _ => false}

datatype cunify_error =
         CKind of L'.kind * L'.kind * kunify_error
       | COccursCheckFailed of L'.con * L'.con
       | CIncompatible of L'.con * L'.con
       | CExplicitness of L'.con * L'.con
       | CKindof of L'.con
       | CRecordFailure

exception CUnify' of cunify_error

fun cunifyError env err =
    case err of
        CKind (k1, k2, kerr) =>
        (eprefaces "Kind unification failure"
                   [("Kind 1", p_kind k1),
                    ("Kind 2", p_kind k2)];
         kunifyError kerr)
      | COccursCheckFailed (c1, c2) =>
        eprefaces "Constructor occurs check failed"
                  [("Con 1", p_con env c1),
                   ("Con 2", p_con env c2)]
      | CIncompatible (c1, c2) =>
        eprefaces "Incompatible constructors"
                  [("Con 1", p_con env c1),
                   ("Con 2", p_con env c2)]
      | CExplicitness (c1, c2) =>
        eprefaces "Differing constructor function explicitness"
                  [("Con 1", p_con env c1),
                   ("Con 2", p_con env c2)]
      | CKindof c =>
        eprefaces "Kind unification variable blocks kindof calculation"
                  [("Con", p_con env c)]
      | CRecordFailure =>
        eprefaces "Can't unify record constructors" []

exception SynUnif = E.SynUnif
val liftConInCon = E.liftConInCon

val subConInCon =
    U.Con.mapB {kind = fn k => k,
                con = fn (xn, rep) => fn c =>
                                  case c of
                                      L'.CRel xn' =>
                                      if xn = xn' then
                                          #1 rep
                                      else
                                          c
                                    (*| L'.CUnif _ => raise SynUnif*)
                                    | _ => c,
                bind = fn ((xn, rep), U.Con.Rel _) => (xn+1, liftConInCon 0 rep)
                        | (ctx, _) => ctx}

type record_summary = {
     fields : (L'.con * L'.con) list,
     unifs : (L'.con * L'.con option ref) list,
     others : L'.con list
}

fun summaryToCon {fields, unifs, others} =
    let
        val c = (L'.CRecord (ktype, []), dummy)
        val c = List.foldr (fn (c', c) => (L'.CConcat (c', c), dummy)) c others
        val c = List.foldr (fn ((c', _), c) => (L'.CConcat (c', c), dummy)) c unifs
    in
        (L'.CConcat ((L'.CRecord (ktype, fields), dummy), c), dummy)
    end

fun p_summary env s = p_con env (summaryToCon s)

exception CUnify of L'.con * L'.con * cunify_error

fun hnormKind (kAll as (k, _)) =
    case k of
        L'.KUnif (_, ref (SOME k)) => hnormKind k
      | _ => kAll

fun kindof env (c, loc) =
    case c of
        L'.TFun _ => ktype
      | L'.TCFun _ => ktype
      | L'.TRecord _ => ktype

      | L'.CRel xn => #2 (E.lookupCRel env xn)
      | L'.CNamed xn => #2 (E.lookupCNamed env xn)
      | L'.CModProj (n, ms, x) =>
        let
            val (_, sgn) = E.lookupStrNamed env n
            val (str, sgn) = foldl (fn (m, (str, sgn)) =>
                                       case E.projectStr env {sgn = sgn, str = str, field = m} of
                                           NONE => raise Fail "kindof: Unknown substructure"
                                         | SOME sgn => ((L'.StrProj (str, m), loc), sgn))
                             ((L'.StrVar n, loc), sgn) ms
        in
            case E.projectCon env {sgn = sgn, str = str, field = x} of
                NONE => raise Fail "kindof: Unknown con in structure"
              | SOME (k, _) => k
        end

      | L'.CApp (c, _) =>
        (case #1 (hnormKind (kindof env c)) of
             L'.KArrow (_, k) => k
           | L'.KError => kerror
           | _ => raise CUnify' (CKindof c))
      | L'.CAbs (x, k, c) => (L'.KArrow (k, kindof (E.pushCRel env x k) c), loc)

      | L'.CName _ => kname

      | L'.CRecord (k, _) => (L'.KRecord k, loc)
      | L'.CConcat (c, _) => kindof env c

      | L'.CError => kerror
      | L'.CUnif (k, _, _) => k

fun unifyRecordCons env (c1, c2) =
    let
        val k1 = kindof env c1
        val k2 = kindof env c2
    in
        unifyKinds k1 k2;
        unifySummaries env (k1, recordSummary env c1, recordSummary env c2)
    end

and recordSummary env c : record_summary =
    case hnormCon env c of
        (L'.CRecord (_, xcs), _) => {fields = xcs, unifs = [], others = []}
      | (L'.CConcat (c1, c2), _) =>
        let
            val s1 = recordSummary env c1
            val s2 = recordSummary env c2
        in
            {fields = #fields s1 @ #fields s2,
             unifs = #unifs s1 @ #unifs s2,
             others = #others s1 @ #others s2}
        end
      | (L'.CUnif (_, _, ref (SOME c)), _) => recordSummary env c
      | c' as (L'.CUnif (_, _, r), _) => {fields = [], unifs = [(c', r)], others = []}
      | c' => {fields = [], unifs = [], others = [c']}

and consEq env (c1, c2) =
    (unifyCons env c1 c2;
     true)
    handle CUnify _ => false

and unifySummaries env (k, s1 : record_summary, s2 : record_summary) =
    let
        (*val () = eprefaces "Summaries" [("#1", p_summary env s1),
                                          ("#2", p_summary env s2)]*)

        fun eatMatching p (ls1, ls2) =
            let
                fun em (ls1, ls2, passed1) =
                    case ls1 of
                        [] => (rev passed1, ls2)
                      | h1 :: t1 =>
                        let
                            fun search (ls2', passed2) =
                                case ls2' of
                                    [] => em (t1, ls2, h1 :: passed1)
                                  | h2 :: t2 =>
                                    if p (h1, h2) then
                                        em (t1, List.revAppend (passed2, t2), passed1)
                                    else
                                        search (t2, h2 :: passed2)
                        in
                            search (ls2, [])
                        end
            in
                em (ls1, ls2, [])
            end

        val (fs1, fs2) = eatMatching (fn ((x1, c1), (x2, c2)) =>
                                         if consEq env (x1, x2) then
                                             (unifyCons env c1 c2;
                                              true)
                                         else
                                             false) (#fields s1, #fields s2)
        (*val () = eprefaces "Summaries2" [("#1", p_summary env {fields = fs1, unifs = #unifs s1, others = #others s1}),
                                           ("#2", p_summary env {fields = fs2, unifs = #unifs s2, others = #others s2})]*)
        val (unifs1, unifs2) = eatMatching (fn ((_, r1), (_, r2)) => r1 = r2) (#unifs s1, #unifs s2)
        val (others1, others2) = eatMatching (consEq env) (#others s1, #others s2)

        fun unifFields (fs, others, unifs) =
            case (fs, others, unifs) of
                ([], [], _) => ([], [], unifs)
              | (_, _, []) => (fs, others, [])
              | (_, _, (_, r) :: rest) =>
                let
                    val r' = ref NONE
                    val cr' = (L'.CUnif (k, "recd", r'), dummy)

                    val prefix = case (fs, others) of
                                     ([], other :: others) =>
                                     List.foldl (fn (other, c) =>
                                                    (L'.CConcat (c, other), dummy))
                                                other others
                                   | (fs, []) =>
                                     (L'.CRecord (k, fs), dummy)
                                   | (fs, others) =>
                                     List.foldl (fn (other, c) =>
                                                    (L'.CConcat (c, other), dummy))
                                                (L'.CRecord (k, fs), dummy) others
                in
                    r := SOME (L'.CConcat (prefix, cr'), dummy);
                    ([], [], (cr', r') :: rest)
                end

        val (fs1, others1, unifs2) = unifFields (fs1, others1, unifs2)
        val (fs2, others2, unifs1) = unifFields (fs2, others2, unifs1)

        val clear1 = case (fs1, others1) of
                         ([], []) => true
                       | _ => false
        val clear2 = case (fs2, others2) of
                         ([], []) => true
                       | _ => false
        val empty = (L'.CRecord (k, []), dummy)
        fun pairOffUnifs (unifs1, unifs2) =
            case (unifs1, unifs2) of
                ([], _) =>
                if clear1 then
                    List.app (fn (_, r) => r := SOME empty) unifs2
                else
                    raise CUnify' CRecordFailure
              | (_, []) =>
                if clear2 then
                    List.app (fn (_, r) => r := SOME empty) unifs1
                else
                    raise CUnify' CRecordFailure
              | ((c1, _) :: rest1, (_, r2) :: rest2) =>
                (r2 := SOME c1;
                 pairOffUnifs (rest1, rest2))
    in
        pairOffUnifs (unifs1, unifs2)
    end

and hnormCon env (cAll as (c, loc)) =
    case c of
        L'.CUnif (_, _, ref (SOME c)) => hnormCon env c

      | L'.CNamed xn =>
        (case E.lookupCNamed env xn of
             (_, _, SOME c') => hnormCon env c'
           | _ => cAll)

      | L'.CModProj (n, ms, x) =>
        let
            val (_, sgn) = E.lookupStrNamed env n
            val (str, sgn) = foldl (fn (m, (str, sgn)) =>
                                       case E.projectStr env {sgn = sgn, str = str, field = m} of
                                           NONE => raise Fail "hnormCon: Unknown substructure"
                                         | SOME sgn => ((L'.StrProj (str, m), loc), sgn))
                             ((L'.StrVar n, loc), sgn) ms
        in
            case E.projectCon env {sgn = sgn, str = str, field = x} of
                NONE => raise Fail "kindof: Unknown con in structure"
              | SOME (_, NONE) => cAll
              | SOME (_, SOME c) => hnormCon env c
        end

      | L'.CApp (c1, c2) =>
        (case hnormCon env c1 of
             (L'.CAbs (_, _, cb), _) =>
             ((hnormCon env (subConInCon (0, c2) cb))
              handle SynUnif => cAll)
           | _ => cAll)

      | L'.CConcat (c1, c2) =>
        (case (hnormCon env c1, hnormCon env c2) of
             ((L'.CRecord (k, xcs1), loc), (L'.CRecord (_, xcs2), _)) =>
             (L'.CRecord (k, xcs1 @ xcs2), loc)
           | _ => cAll)

      | _ => cAll

and unifyCons' env c1 c2 =
    unifyCons'' env (hnormCon env c1) (hnormCon env c2)
    
and unifyCons'' env (c1All as (c1, _)) (c2All as (c2, _)) =
    let
        fun err f = raise CUnify' (f (c1All, c2All))

        fun isRecord () = unifyRecordCons env (c1All, c2All)
    in
        case (c1, c2) of
            (L'.TFun (d1, r1), L'.TFun (d2, r2)) =>
            (unifyCons' env d1 d2;
             unifyCons' env r1 r2)
          | (L'.TCFun (expl1, x1, d1, r1), L'.TCFun (expl2, _, d2, r2)) =>
            if expl1 <> expl2 then
                err CExplicitness
            else
                (unifyKinds d1 d2;
                 unifyCons' (E.pushCRel env x1 d1) r1 r2)
          | (L'.TRecord r1, L'.TRecord r2) => unifyCons' env r1 r2

          | (L'.CRel n1, L'.CRel n2) =>
            if n1 = n2 then
                ()
            else
                err CIncompatible
          | (L'.CNamed n1, L'.CNamed n2) =>
            if n1 = n2 then
                ()
            else
                err CIncompatible

          | (L'.CApp (d1, r1), L'.CApp (d2, r2)) =>
            (unifyCons' env d1 d2;
             unifyCons' env r1 r2)
          | (L'.CAbs (x1, k1, c1), L'.CAbs (_, k2, c2)) =>
            (unifyKinds k1 k2;
             unifyCons' (E.pushCRel env x1 k1) c1 c2)

          | (L'.CName n1, L'.CName n2) =>
            if n1 = n2 then
                ()
            else
                err CIncompatible

          | (L'.CModProj (n1, ms1, x1), L'.CModProj (n2, ms2, x2)) =>
            if n1 = n2 andalso ms1 = ms2 andalso x1 = x2 then
                ()
            else
                err CIncompatible

          | (L'.CError, _) => ()
          | (_, L'.CError) => ()

          | (L'.CUnif (_, _, ref (SOME c1All)), _) => unifyCons' env c1All c2All
          | (_, L'.CUnif (_, _, ref (SOME c2All))) => unifyCons' env c1All c2All

          | (L'.CUnif (k1, _, r1), L'.CUnif (k2, _, r2)) =>
            if r1 = r2 then
                ()
            else
                (unifyKinds k1 k2;
                 r1 := SOME c2All)

          | (L'.CUnif (_, _, r), _) =>
            if occursCon r c2All then
                err COccursCheckFailed
            else
                r := SOME c2All
          | (_, L'.CUnif (_, _, r)) =>
            if occursCon r c1All then
                err COccursCheckFailed
            else
                r := SOME c1All

          | (L'.CRecord _, _) => isRecord ()
          | (_, L'.CRecord _) => isRecord ()
          | (L'.CConcat _, _) => isRecord ()
          | (_, L'.CConcat _) => isRecord ()

          | _ => err CIncompatible
    end

and unifyCons env c1 c2 =
    unifyCons' env c1 c2
    handle CUnify' err => raise CUnify (c1, c2, err)
         | KUnify args => raise CUnify (c1, c2, CKind args)

datatype exp_error =
       UnboundExp of ErrorMsg.span * string
     | UnboundStrInExp of ErrorMsg.span * string
     | Unify of L'.exp * L'.con * L'.con * cunify_error
     | Unif of string * L'.con
     | WrongForm of string * L'.exp * L'.con

fun expError env err =
    case err of
        UnboundExp (loc, s) =>
        ErrorMsg.errorAt loc ("Unbound expression variable " ^ s)
      | UnboundStrInExp (loc, s) =>
        ErrorMsg.errorAt loc ("Unbound structure " ^ s)
      | Unify (e, c1, c2, uerr) =>
        (ErrorMsg.errorAt (#2 e) "Unification failure";
         eprefaces' [("Expression", p_exp env e),
                     ("Have con", p_con env c1),
                     ("Need con", p_con env c2)];
         cunifyError env uerr)
      | Unif (action, c) =>
        (ErrorMsg.errorAt (#2 c) ("Unification variable blocks " ^ action);
         eprefaces' [("Con", p_con env c)])
      | WrongForm (variety, e, t) =>
        (ErrorMsg.errorAt (#2 e) ("Expression is not a " ^ variety);
         eprefaces' [("Expression", p_exp env e),
                     ("Type", p_con env t)])

fun checkCon env e c1 c2 =
    unifyCons env c1 c2
    handle CUnify (c1, c2, err) =>
           expError env (Unify (e, c1, c2, err))

fun primType env p =
    let
        val s = case p of
                    P.Int _ => "int"
                  | P.Float _ => "float"
                  | P.String _ => "string"
    in
        case E.lookupC env s of
            E.NotBound => raise Fail ("Primitive type " ^ s ^ " unbound")
          | E.Rel _ => raise Fail ("Primitive type " ^ s ^ " bound as relative")
          | E.Named (n, (L'.KType, _)) => L'.CNamed n
          | E.Named _ => raise Fail ("Primitive type " ^ s ^ " bound at non-Type kind")
    end

fun typeof env (e, loc) =
    case e of
        L'.EPrim p => (primType env p, loc)
      | L'.ERel n => #2 (E.lookupERel env n)
      | L'.ENamed n => #2 (E.lookupENamed env n)
      | L'.EModProj (n, ms, x) =>
        let
            val (_, sgn) = E.lookupStrNamed env n
            val (str, sgn) = foldl (fn (m, (str, sgn)) =>
                                       case E.projectStr env {sgn = sgn, str = str, field = m} of
                                           NONE => raise Fail "kindof: Unknown substructure"
                                         | SOME sgn => ((L'.StrProj (str, m), loc), sgn))
                             ((L'.StrVar n, loc), sgn) ms
        in
            case E.projectVal env {sgn = sgn, str = str, field = x} of
                NONE => raise Fail "typeof: Unknown val in structure"
              | SOME t => t
        end

      | L'.EApp (e1, _) =>
        (case #1 (typeof env e1) of
             L'.TFun (_, c) => c
           | _ => raise Fail "typeof: Bad EApp")
      | L'.EAbs (_, _, ran, _) => ran
      | L'.ECApp (e1, c) =>
        (case #1 (typeof env e1) of
             L'.TCFun (_, _, _, c1) => subConInCon (0, c) c1
           | _ => raise Fail "typeof: Bad ECApp")
      | L'.ECAbs (expl, x, k, e1) => (L'.TCFun (expl, x, k, typeof (E.pushCRel env x k) e1), loc)

      | L'.ERecord xes => (L'.TRecord (L'.CRecord (ktype, map (fn (x, _, t) => (x, t)) xes), loc), loc)
      | L'.EField (_, _, {field, ...}) => field

      | L'.EError => cerror

fun elabHead env (e as (_, loc)) t =
    let
        fun unravel (t, e) =
            case hnormCon env t of
                (L'.TCFun (L'.Implicit, x, k, t'), _) =>
                let
                    val u = cunif k
                in
                    unravel (subConInCon (0, u) t',
                             (L'.ECApp (e, u), loc))
                end
              | _ => (e, t)
    in
        unravel (t, e)
    end

fun elabExp env (e, loc) =
    case e of
        L.EAnnot (e, t) =>
        let
            val (e', et) = elabExp env e
            val (t', _) = elabCon env t
        in
            checkCon env e' et t';
            (e', t')
        end

      | L.EPrim p => ((L'.EPrim p, loc), (primType env p, loc))
      | L.EVar ([], s) =>
        (case E.lookupE env s of
             E.NotBound =>
             (expError env (UnboundExp (loc, s));
              (eerror, cerror))
           | E.Rel (n, t) => ((L'.ERel n, loc), t)
           | E.Named (n, t) => ((L'.ENamed n, loc), t))
      | L.EVar (m1 :: ms, s) =>
        (case E.lookupStr env m1 of
             NONE => (expError env (UnboundStrInExp (loc, m1));
                      (eerror, cerror))
           | SOME (n, sgn) =>
             let
                 val (str, sgn) = foldl (fn (m, (str, sgn)) =>
                                     case E.projectStr env {sgn = sgn, str = str, field = m} of
                                         NONE => (conError env (UnboundStrInCon (loc, m));
                                                  (strerror, sgnerror))
                                       | SOME sgn => ((L'.StrProj (str, m), loc), sgn))
                                  ((L'.StrVar n, loc), sgn) ms

                 val t = case E.projectVal env {sgn = sgn, str = str, field = s} of
                             NONE => (expError env (UnboundExp (loc, s));
                                      cerror)
                           | SOME t => t
             in
                 ((L'.EModProj (n, ms, s), loc), t)
             end)

      | L.EApp (e1, e2) =>
        let
            val (e1', t1) = elabExp env e1
            val (e1', t1) = elabHead env e1' t1
            val (e2', t2) = elabExp env e2

            val dom = cunif ktype
            val ran = cunif ktype
            val t = (L'.TFun (dom, ran), dummy)
        in
            checkCon env e1' t1 t;
            checkCon env e2' t2 dom;
            ((L'.EApp (e1', e2'), loc), ran)
        end
      | L.EAbs (x, to, e) =>
        let
            val t' = case to of
                         NONE => cunif ktype
                       | SOME t =>
                         let
                             val (t', tk) = elabCon env t
                         in
                             checkKind env t' tk ktype;
                             t'
                         end
            val (e', et) = elabExp (E.pushERel env x t') e
        in
            ((L'.EAbs (x, t', et, e'), loc),
             (L'.TFun (t', et), loc))
        end
      | L.ECApp (e, c) =>
        let
            val (e', et) = elabExp env e
            val (e', et) = elabHead env e' et
            val (c', ck) = elabCon env c
        in
            case #1 (hnormCon env et) of
                L'.CError => (eerror, cerror)
              | L'.TCFun (_, _, k, eb) =>
                let
                    val () = checkKind env c' ck k
                    val eb' = subConInCon (0, c') eb
                              handle SynUnif => (expError env (Unif ("substitution", eb));
                                                 cerror)
                in
                    ((L'.ECApp (e', c'), loc), eb')
                end

              | L'.CUnif _ =>
                (expError env (Unif ("application", et));
                 (eerror, cerror))

              | _ =>
                (expError env (WrongForm ("constructor function", e', et));
                 (eerror, cerror))
        end
      | L.ECAbs (expl, x, k, e) =>
        let
            val expl' = elabExplicitness expl
            val k' = elabKind k
            val (e', et) = elabExp (E.pushCRel env x k') e
        in
            ((L'.ECAbs (expl', x, k', e'), loc),
             (L'.TCFun (expl', x, k', et), loc))
        end

      | L.ERecord xes =>
        let
            val xes' = map (fn (x, e) =>
                               let
                                   val (x', xk) = elabCon env x
                                   val (e', et) = elabExp env e
                               in
                                   checkKind env x' xk kname;
                                   (x', e', et)
                               end) xes
        in
            ((L'.ERecord xes', loc),
             (L'.TRecord (L'.CRecord (ktype, map (fn (x', _, et) => (x', et)) xes'), loc), loc))
        end

      | L.EField (e, c) =>
        let
            val (e', et) = elabExp env e
            val (c', ck) = elabCon env c

            val ft = cunif ktype
            val rest = cunif ktype_record
        in
            checkKind env c' ck kname;
            checkCon env e' et (L'.TRecord (L'.CConcat ((L'.CRecord (ktype, [(c', ft)]), loc), rest), loc), loc);
            ((L'.EField (e', c', {field = ft, rest = rest}), loc), ft)
        end
            

datatype decl_error =
         KunifsRemainKind of ErrorMsg.span * L'.kind
       | KunifsRemainCon of ErrorMsg.span * L'.con
       | KunifsRemainExp of ErrorMsg.span * L'.exp
       | CunifsRemainCon of ErrorMsg.span * L'.con
       | CunifsRemainExp of ErrorMsg.span * L'.exp

fun declError env err =
    case err of
        KunifsRemainKind (loc, k) =>
        (ErrorMsg.errorAt loc "Some kind unification variables are undetermined in kind";
         eprefaces' [("Kind", p_kind k)])
      | KunifsRemainCon (loc, c) =>
        (ErrorMsg.errorAt loc "Some kind unification variables are undetermined in constructor";
         eprefaces' [("Constructor", p_con env c)])
      | KunifsRemainExp (loc, e) =>
        (ErrorMsg.errorAt loc "Some kind unification variables are undetermined in expression";
         eprefaces' [("Expression", p_exp env e)])
      | CunifsRemainCon (loc, c) =>
        (ErrorMsg.errorAt loc "Some constructor unification variables are undetermined in constructor";
         eprefaces' [("Constructor", p_con env c)])
      | CunifsRemainExp (loc, e) =>
        (ErrorMsg.errorAt loc "Some constructor unification variables are undetermined in expression";
         eprefaces' [("Expression", p_exp env e)])

datatype sgn_error =
         UnboundSgn of ErrorMsg.span * string
       | UnmatchedSgi of L'.sgn_item
       | SgiWrongKind of L'.sgn_item * L'.kind * L'.sgn_item * L'.kind * kunify_error
       | SgiWrongCon of L'.sgn_item * L'.con * L'.sgn_item * L'.con * cunify_error
       | SgnWrongForm of L'.sgn * L'.sgn
       | UnWhereable of L'.sgn * string

fun sgnError env err =
    case err of
        UnboundSgn (loc, s) =>
        ErrorMsg.errorAt loc ("Unbound signature variable " ^ s)
      | UnmatchedSgi (sgi as (_, loc)) =>
        (ErrorMsg.errorAt loc "Unmatched signature item";
         eprefaces' [("Item", p_sgn_item env sgi)])
      | SgiWrongKind (sgi1, k1, sgi2, k2, kerr) =>
        (ErrorMsg.errorAt (#2 sgi1) "Kind unification failure in signature matching:";
         eprefaces' [("Item 1", p_sgn_item env sgi1),
                     ("Item 2", p_sgn_item env sgi2),
                     ("Kind 1", p_kind k1),
                     ("Kind 2", p_kind k2)];
         kunifyError kerr)
      | SgiWrongCon (sgi1, c1, sgi2, c2, cerr) =>
        (ErrorMsg.errorAt (#2 sgi1) "Constructor unification failure in signature matching:";
         eprefaces' [("Item 1", p_sgn_item env sgi1),
                     ("Item 2", p_sgn_item env sgi2),
                     ("Con 1", p_con env c1),
                     ("Con 2", p_con env c2)];
         cunifyError env cerr)
      | SgnWrongForm (sgn1, sgn2) =>
        (ErrorMsg.errorAt (#2 sgn1) "Incompatible signatures:";
         eprefaces' [("Sig 1", p_sgn env sgn1),
                     ("Sig 2", p_sgn env sgn2)])
      | UnWhereable (sgn, x) =>
        (ErrorMsg.errorAt (#2 sgn) "Unavailable field for 'where'";
         eprefaces' [("Signature", p_sgn env sgn),
                     ("Field", PD.string x)])

datatype str_error =
         UnboundStr of ErrorMsg.span * string

fun strError env err =
    case err of
        UnboundStr (loc, s) =>
        ErrorMsg.errorAt loc ("Unbound structure variable " ^ s)

val hnormSgn = E.hnormSgn

fun elabSgn_item ((sgi, loc), env) =
    let
        
    in
        resetKunif ();
        resetCunif ();
        case sgi of
            L.SgiConAbs (x, k) =>
            let
                val k' = elabKind k

                val (env', n) = E.pushCNamed env x k' NONE
            in
                if ErrorMsg.anyErrors () then
                    ()
                else (
                    if kunifsInKind k' then
                        declError env (KunifsRemainKind (loc, k'))
                    else
                        ()
                    );

                ((L'.SgiConAbs (x, n, k'), loc), env')
            end

          | L.SgiCon (x, ko, c) =>
            let
                val k' = case ko of
                             NONE => kunif ()
                           | SOME k => elabKind k

                val (c', ck) = elabCon env c
                val (env', n) = E.pushCNamed env x k' (SOME c')
            in
                checkKind env c' ck k';

                if ErrorMsg.anyErrors () then
                    ()
                else (
                    if kunifsInKind k' then
                        declError env (KunifsRemainKind (loc, k'))
                    else
                        ();

                    if kunifsInCon c' then
                        declError env (KunifsRemainCon (loc, c'))
                    else
                        ()
                    );

                ((L'.SgiCon (x, n, k', c'), loc), env')
            end

          | L.SgiVal (x, c) =>
            let
                val (c', ck) = elabCon env c

                val (env', n) = E.pushENamed env x c'
            in
                unifyKinds ck ktype;

                if ErrorMsg.anyErrors () then
                    ()
                else (
                    if kunifsInCon c' then
                        declError env (KunifsRemainCon (loc, c'))
                    else
                        ()
                    );

                ((L'.SgiVal (x, n, c'), loc), env')
            end

          | L.SgiStr (x, sgn) =>
            let
                val sgn' = elabSgn env sgn
                val (env', n) = E.pushStrNamed env x sgn'
            in
                ((L'.SgiStr (x, n, sgn'), loc), env')
            end
            
    end

and elabSgn env (sgn, loc) =
    case sgn of
        L.SgnConst sgis =>
        let
            val (sgis', _) = ListUtil.foldlMap elabSgn_item env sgis
        in
            (L'.SgnConst sgis', loc)
        end
      | L.SgnVar x =>
        (case E.lookupSgn env x of
             NONE =>
             (sgnError env (UnboundSgn (loc, x));
              (L'.SgnError, loc))
           | SOME (n, sgis) => (L'.SgnVar n, loc))
      | L.SgnFun (m, dom, ran) =>
        let
            val dom' = elabSgn env dom
            val (env', n) = E.pushStrNamed env m dom'
            val ran' = elabSgn env' ran
        in
            (L'.SgnFun (m, n, dom', ran'), loc)
        end
      | L.SgnWhere (sgn, x, c) =>
        let
            val sgn' = elabSgn env sgn
            val (c', ck) = elabCon env c
        in
            case #1 (hnormSgn env sgn') of
                L'.SgnError => sgnerror
              | L'.SgnConst sgis =>
                if List.exists (fn (L'.SgiConAbs (x, _, k), _) =>
                                   (unifyKinds k ck;
                                    true)
                                 | _ => false) sgis then
                    (L'.SgnWhere (sgn', x, c'), loc)
                else
                    (sgnError env (UnWhereable (sgn', x));
                     sgnerror)
              | _ => (sgnError env (UnWhereable (sgn', x));
                      sgnerror)
        end

fun sgiOfDecl (d, loc) =
    case d of
        L'.DCon (x, n, k, c) => SOME (L'.SgiCon (x, n, k, c), loc)
      | L'.DVal (x, n, t, _) => SOME (L'.SgiVal (x, n, t), loc)
      | L'.DSgn _ => NONE
      | L'.DStr (x, n, sgn, _) => SOME (L'.SgiStr (x, n, sgn), loc)

fun subSgn env sgn1 (sgn2 as (_, loc2)) =
    case (#1 (hnormSgn env sgn1), #1 (hnormSgn env sgn2)) of
        (L'.SgnError, _) => ()
      | (_, L'.SgnError) => ()

      | (L'.SgnConst sgis1, L'.SgnConst sgis2) =>
        let
            fun folder (sgi2All as (sgi, _), env) =
                let
                    fun seek p =
                        let
                            fun seek env ls =
                                case ls of
                                    [] => (sgnError env (UnmatchedSgi sgi2All);
                                           env)
                                  | h :: t =>
                                    case p h of
                                        NONE => seek (E.sgiBinds env h) t
                                      | SOME env => env
                        in
                            seek env sgis1
                        end
                in
                    case sgi of
                        L'.SgiConAbs (x, n2, k2) =>
                        seek (fn sgi1All as (sgi1, _) =>
                                 let
                                     fun found (x', n1, k1, co1) =
                                         if x = x' then
                                             let
                                                 val () = unifyKinds k1 k2
                                                     handle KUnify (k1, k2, err) =>
                                                            sgnError env (SgiWrongKind (sgi1All, k1, sgi2All, k2, err))
                                                 val env = E.pushCNamedAs env x n1 k1 co1
                                             in
                                                 SOME (if n1 = n2 then
                                                           env
                                                       else
                                                           E.pushCNamedAs env x n2 k2 (SOME (L'.CNamed n1, loc2)))
                                             end
                                         else
                                             NONE
                                 in
                                     case sgi1 of
                                         L'.SgiConAbs (x', n1, k1) => found (x', n1, k1, NONE)
                                       | L'.SgiCon (x', n1, k1, c1) => found (x', n1, k1, SOME c1)
                                       | _ => NONE
                                 end)

                      | L'.SgiCon (x, n2, k2, c2) =>
                        seek (fn sgi1All as (sgi1, _) =>
                                 case sgi1 of
                                     L'.SgiCon (x', n1, k1, c1) =>
                                     if x = x' then
                                         let
                                             val () = unifyCons env c1 c2
                                                 handle CUnify (c1, c2, err) =>
                                                        sgnError env (SgiWrongCon (sgi1All, c1, sgi2All, c2, err))
                                         in
                                             SOME (E.pushCNamedAs env x n2 k2 (SOME c2))
                                         end
                                     else
                                         NONE
                                   | _ => NONE)

                      | L'.SgiVal (x, n2, c2) =>
                        seek (fn sgi1All as (sgi1, _) =>
                                 case sgi1 of
                                     L'.SgiVal (x', n1, c1) =>
                                     if x = x' then
                                         let
                                             val () = unifyCons env c1 c2
                                                 handle CUnify (c1, c2, err) =>
                                                        sgnError env (SgiWrongCon (sgi1All, c1, sgi2All, c2, err))
                                         in
                                             SOME env
                                         end
                                     else
                                         NONE
                                   | _ => NONE)

                      | L'.SgiStr (x, n2, sgn2) =>
                        seek (fn sgi1All as (sgi1, _) =>
                                 case sgi1 of
                                     L'.SgiStr (x', n1, sgn1) =>
                                     if x = x' then
                                         (subSgn env sgn1 sgn2;
                                          SOME env)
                                     else
                                         NONE
                                   | _ => NONE)
                        (* Add type equations between structures here some day. *)
                end
        in
            ignore (foldl folder env sgis2)
        end

      | (L'.SgnFun (m1, n1, dom1, ran1), L'.SgnFun (m2, n2, dom2, ran2)) =>
        (subSgn env dom2 dom1;
         subSgn env ran1 ran2)

      | _ => sgnError env (SgnWrongForm (sgn1, sgn2))

fun selfify env {str, strs, sgn} =
    case #1 (hnormSgn env sgn) of
        L'.SgnError => sgn
      | L'.SgnVar _ => sgn

      | L'.SgnConst sgis =>
        (L'.SgnConst (map (fn (L'.SgiConAbs (x, n, k), loc) =>
                              (L'.SgiCon (x, n, k, (L'.CModProj (str, strs, x), loc)), loc)
                            | (L'.SgiStr (x, n, sgn), loc) =>
                              (L'.SgiStr (x, n, selfify env {str = str, strs = strs @ [x], sgn = sgn}), loc)
                            | x => x) sgis), #2 sgn)
      | L'.SgnFun _ => sgn
      | L'.SgnWhere _ => sgn

fun elabDecl ((d, loc), env) =
    let
        
    in
        resetKunif ();
        resetCunif ();
        case d of
            L.DCon (x, ko, c) =>
            let
                val k' = case ko of
                             NONE => kunif ()
                           | SOME k => elabKind k

                val (c', ck) = elabCon env c
                val (env', n) = E.pushCNamed env x k' (SOME c')
            in
                checkKind env c' ck k';

                if ErrorMsg.anyErrors () then
                    ()
                else (
                    if kunifsInKind k' then
                        declError env (KunifsRemainKind (loc, k'))
                    else
                        ();

                    if kunifsInCon c' then
                        declError env (KunifsRemainCon (loc, c'))
                    else
                        ()
                    );

                ((L'.DCon (x, n, k', c'), loc), env')
            end
          | L.DVal (x, co, e) =>
            let
                val (c', ck) = case co of
                                   NONE => (cunif ktype, ktype)
                                 | SOME c => elabCon env c

                val (e', et) = elabExp env e
                val (env', n) = E.pushENamed env x c'
            in
                checkCon env e' et c';

                if ErrorMsg.anyErrors () then
                    ()
                else (
                    if kunifsInCon c' then
                        declError env (KunifsRemainCon (loc, c'))
                    else
                        ();

                    if cunifsInCon c' then
                        declError env (CunifsRemainCon (loc, c'))
                    else
                        ();

                    if kunifsInExp e' then
                        declError env (KunifsRemainExp (loc, e'))
                    else
                        ();

                    if cunifsInExp e' then
                        declError env (CunifsRemainExp (loc, e'))
                    else
                        ());

                ((L'.DVal (x, n, c', e'), loc), env')
            end

          | L.DSgn (x, sgn) =>
            let
                val sgn' = elabSgn env sgn
                val (env', n) = E.pushSgnNamed env x sgn'
            in
                ((L'.DSgn (x, n, sgn'), loc), env')
            end

          | L.DStr (x, sgno, str) =>
            let
                val formal = Option.map (elabSgn env) sgno
                val (str', actual) = elabStr env str

                fun self (str, _) =
                    case str of
                        L'.StrVar x => SOME (x, [])
                      | L'.StrProj (str, x) =>
                        (case self str of
                             NONE => NONE
                           | SOME (m, ms) => SOME (m, ms @ [x]))
                      | _ => NONE

                val sgn' = case formal of
                               NONE =>
                               (case self str' of
                                    NONE => actual
                                  | SOME (str, strs) => selfify env {sgn = actual, str = str, strs = strs})
                             | SOME formal =>
                               (subSgn env actual formal;
                                formal)

                val (env', n) = E.pushStrNamed env x sgn'
            in
                ((L'.DStr (x, n, sgn', str'), loc), env')
            end
    end

and elabStr env (str, loc) =
    case str of
        L.StrConst ds =>
        let
            val (ds', env') = ListUtil.foldlMap elabDecl env ds
            val sgis = List.mapPartial sgiOfDecl ds'
        in
            ((L'.StrConst ds', loc), (L'.SgnConst sgis, loc))
        end
      | L.StrVar x =>
        (case E.lookupStr env x of
             NONE =>
             (strError env (UnboundStr (loc, x));
              (strerror, sgnerror))
           | SOME (n, sgn) => ((L'.StrVar n, loc), sgn))
      | L.StrProj (str, x) =>
        let
            val (str', sgn) = elabStr env str
        in
            case E.projectStr env {str = str', sgn = sgn, field = x} of
                NONE => (strError env (UnboundStr (loc, x));
                         (strerror, sgnerror))
              | SOME sgn => ((L'.StrProj (str', x), loc), sgn)
        end
      | L.StrFun (m, dom, ranO, str) =>
        let
            val dom' = elabSgn env dom
            val (env', n) = E.pushStrNamed env m dom'
            val (str', actual) = elabStr env' str

            val formal =
                case ranO of
                    NONE => actual
                  | SOME ran =>
                    let
                        val ran' = elabSgn env' ran
                    in
                        subSgn env' actual ran';
                        ran'
                    end
        in
            ((L'.StrFun (m, n, dom', formal, str'), loc),
             (L'.SgnFun (m, n, dom', formal), loc))
        end

val elabFile = ListUtil.foldlMap elabDecl

end