llvm.org GIT mirror llvm / 04dcbb5 include / llvm / Support / YAMLTraits.h
04dcbb5

Tree @04dcbb5 (Download .tar.gz)

YAMLTraits.h @04dcbb5raw · history · 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
 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
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
//===- llvm/Support/YAMLTraits.h --------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_YAMLTRAITS_H
#define LLVM_SUPPORT_YAMLTRAITS_H

#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/AlignOf.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Regex.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/YAMLParser.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cctype>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <map>
#include <memory>
#include <new>
#include <string>
#include <system_error>
#include <type_traits>
#include <vector>

namespace llvm {
namespace yaml {

enum class NodeKind : uint8_t {
  Scalar,
  Map,
  Sequence,
};

struct EmptyContext {};

/// This class should be specialized by any type that needs to be converted
/// to/from a YAML mapping.  For example:
///
///     struct MappingTraits<MyStruct> {
///       static void mapping(IO &io, MyStruct &s) {
///         io.mapRequired("name", s.name);
///         io.mapRequired("size", s.size);
///         io.mapOptional("age",  s.age);
///       }
///     };
template<class T>
struct MappingTraits {
  // Must provide:
  // static void mapping(IO &io, T &fields);
  // Optionally may provide:
  // static StringRef validate(IO &io, T &fields);
  //
  // The optional flow flag will cause generated YAML to use a flow mapping
  // (e.g. { a: 0, b: 1 }):
  // static const bool flow = true;
};

/// This class is similar to MappingTraits<T> but allows you to pass in
/// additional context for each map operation.  For example:
///
///     struct MappingContextTraits<MyStruct, MyContext> {
///       static void mapping(IO &io, MyStruct &s, MyContext &c) {
///         io.mapRequired("name", s.name);
///         io.mapRequired("size", s.size);
///         io.mapOptional("age",  s.age);
///         ++c.TimesMapped;
///       }
///     };
template <class T, class Context> struct MappingContextTraits {
  // Must provide:
  // static void mapping(IO &io, T &fields, Context &Ctx);
  // Optionally may provide:
  // static StringRef validate(IO &io, T &fields, Context &Ctx);
  //
  // The optional flow flag will cause generated YAML to use a flow mapping
  // (e.g. { a: 0, b: 1 }):
  // static const bool flow = true;
};

/// This class should be specialized by any integral type that converts
/// to/from a YAML scalar where there is a one-to-one mapping between
/// in-memory values and a string in YAML.  For example:
///
///     struct ScalarEnumerationTraits<Colors> {
///         static void enumeration(IO &io, Colors &value) {
///           io.enumCase(value, "red",   cRed);
///           io.enumCase(value, "blue",  cBlue);
///           io.enumCase(value, "green", cGreen);
///         }
///       };
template <typename T, typename Enable = void> struct ScalarEnumerationTraits {
  // Must provide:
  // static void enumeration(IO &io, T &value);
};

/// This class should be specialized by any integer type that is a union
/// of bit values and the YAML representation is a flow sequence of
/// strings.  For example:
///
///      struct ScalarBitSetTraits<MyFlags> {
///        static void bitset(IO &io, MyFlags &value) {
///          io.bitSetCase(value, "big",   flagBig);
///          io.bitSetCase(value, "flat",  flagFlat);
///          io.bitSetCase(value, "round", flagRound);
///        }
///      };
template <typename T, typename Enable = void> struct ScalarBitSetTraits {
  // Must provide:
  // static void bitset(IO &io, T &value);
};

/// Describe which type of quotes should be used when quoting is necessary.
/// Some non-printable characters need to be double-quoted, while some others
/// are fine with simple-quoting, and some don't need any quoting.
enum class QuotingType { None, Single, Double };

/// This class should be specialized by type that requires custom conversion
/// to/from a yaml scalar.  For example:
///
///    template<>
///    struct ScalarTraits<MyType> {
///      static void output(const MyType &val, void*, llvm::raw_ostream &out) {
///        // stream out custom formatting
///        out << llvm::format("%x", val);
///      }
///      static StringRef input(StringRef scalar, void*, MyType &value) {
///        // parse scalar and set `value`
///        // return empty string on success, or error string
///        return StringRef();
///      }
///      static QuotingType mustQuote(StringRef) { return QuotingType::Single; }
///    };
template <typename T, typename Enable = void> struct ScalarTraits {
  // Must provide:
  //
  // Function to write the value as a string:
  // static void output(const T &value, void *ctxt, llvm::raw_ostream &out);
  //
  // Function to convert a string to a value.  Returns the empty
  // StringRef on success or an error string if string is malformed:
  // static StringRef input(StringRef scalar, void *ctxt, T &value);
  //
  // Function to determine if the value should be quoted.
  // static QuotingType mustQuote(StringRef);
};

/// This class should be specialized by type that requires custom conversion
/// to/from a YAML literal block scalar. For example:
///
///    template <>
///    struct BlockScalarTraits<MyType> {
///      static void output(const MyType &Value, void*, llvm::raw_ostream &Out)
///      {
///        // stream out custom formatting
///        Out << Value;
///      }
///      static StringRef input(StringRef Scalar, void*, MyType &Value) {
///        // parse scalar and set `value`
///        // return empty string on success, or error string
///        return StringRef();
///      }
///    };
template <typename T>
struct BlockScalarTraits {
  // Must provide:
  //
  // Function to write the value as a string:
  // static void output(const T &Value, void *ctx, llvm::raw_ostream &Out);
  //
  // Function to convert a string to a value.  Returns the empty
  // StringRef on success or an error string if string is malformed:
  // static StringRef input(StringRef Scalar, void *ctxt, T &Value);
  //
  // Optional:
  // static StringRef inputTag(T &Val, std::string Tag)
  // static void outputTag(const T &Val, raw_ostream &Out)
};

/// This class should be specialized by type that requires custom conversion
/// to/from a YAML scalar with optional tags. For example:
///
///    template <>
///    struct TaggedScalarTraits<MyType> {
///      static void output(const MyType &Value, void*, llvm::raw_ostream
///      &ScalarOut, llvm::raw_ostream &TagOut)
///      {
///        // stream out custom formatting including optional Tag
///        Out << Value;
///      }
///      static StringRef input(StringRef Scalar, StringRef Tag, void*, MyType
///      &Value) {
///        // parse scalar and set `value`
///        // return empty string on success, or error string
///        return StringRef();
///      }
///      static QuotingType mustQuote(const MyType &Value, StringRef) {
///        return QuotingType::Single;
///      }
///    };
template <typename T> struct TaggedScalarTraits {
  // Must provide:
  //
  // Function to write the value and tag as strings:
  // static void output(const T &Value, void *ctx, llvm::raw_ostream &ScalarOut,
  // llvm::raw_ostream &TagOut);
  //
  // Function to convert a string to a value.  Returns the empty
  // StringRef on success or an error string if string is malformed:
  // static StringRef input(StringRef Scalar, StringRef Tag, void *ctxt, T
  // &Value);
  //
  // Function to determine if the value should be quoted.
  // static QuotingType mustQuote(const T &Value, StringRef Scalar);
};

/// This class should be specialized by any type that needs to be converted
/// to/from a YAML sequence.  For example:
///
///    template<>
///    struct SequenceTraits<MyContainer> {
///      static size_t size(IO &io, MyContainer &seq) {
///        return seq.size();
///      }
///      static MyType& element(IO &, MyContainer &seq, size_t index) {
///        if ( index >= seq.size() )
///          seq.resize(index+1);
///        return seq[index];
///      }
///    };
template<typename T, typename EnableIf = void>
struct SequenceTraits {
  // Must provide:
  // static size_t size(IO &io, T &seq);
  // static T::value_type& element(IO &io, T &seq, size_t index);
  //
  // The following is option and will cause generated YAML to use
  // a flow sequence (e.g. [a,b,c]).
  // static const bool flow = true;
};

/// This class should be specialized by any type for which vectors of that
/// type need to be converted to/from a YAML sequence.
template<typename T, typename EnableIf = void>
struct SequenceElementTraits {
  // Must provide:
  // static const bool flow;
};

/// This class should be specialized by any type that needs to be converted
/// to/from a list of YAML documents.
template<typename T>
struct DocumentListTraits {
  // Must provide:
  // static size_t size(IO &io, T &seq);
  // static T::value_type& element(IO &io, T &seq, size_t index);
};

/// This class should be specialized by any type that needs to be converted
/// to/from a YAML mapping in the case where the names of the keys are not known
/// in advance, e.g. a string map.
template <typename T>
struct CustomMappingTraits {
  // static void inputOne(IO &io, StringRef key, T &elem);
  // static void output(IO &io, T &elem);
};

/// This class should be specialized by any type that can be represented as
/// a scalar, map, or sequence, decided dynamically. For example:
///
///    typedef std::unique_ptr<MyBase> MyPoly;
///
///    template<>
///    struct PolymorphicTraits<MyPoly> {
///      static NodeKind getKind(const MyPoly &poly) {
///        return poly->getKind();
///      }
///      static MyScalar& getAsScalar(MyPoly &poly) {
///        if (!poly || !isa<MyScalar>(poly))
///          poly.reset(new MyScalar());
///        return *cast<MyScalar>(poly.get());
///      }
///      // ...
///    };
template <typename T> struct PolymorphicTraits {
  // Must provide:
  // static NodeKind getKind(const T &poly);
  // static scalar_type &getAsScalar(T &poly);
  // static map_type &getAsMap(T &poly);
  // static sequence_type &getAsSequence(T &poly);
};

// Only used for better diagnostics of missing traits
template <typename T>
struct MissingTrait;

// Test if ScalarEnumerationTraits<T> is defined on type T.
template <class T>
struct has_ScalarEnumerationTraits
{
  using Signature_enumeration = void (*)(class IO&, T&);

  template <typename U>
  static char test(SameType<Signature_enumeration, &U::enumeration>*);

  template <typename U>
  static double test(...);

  static bool const value =
    (sizeof(test<ScalarEnumerationTraits<T>>(nullptr)) == 1);
};

// Test if ScalarBitSetTraits<T> is defined on type T.
template <class T>
struct has_ScalarBitSetTraits
{
  using Signature_bitset = void (*)(class IO&, T&);

  template <typename U>
  static char test(SameType<Signature_bitset, &U::bitset>*);

  template <typename U>
  static double test(...);

  static bool const value = (sizeof(test<ScalarBitSetTraits<T>>(nullptr)) == 1);
};

// Test if ScalarTraits<T> is defined on type T.
template <class T>
struct has_ScalarTraits
{
  using Signature_input = StringRef (*)(StringRef, void*, T&);
  using Signature_output = void (*)(const T&, void*, raw_ostream&);
  using Signature_mustQuote = QuotingType (*)(StringRef);

  template <typename U>
  static char test(SameType<Signature_input, &U::input> *,
                   SameType<Signature_output, &U::output> *,
                   SameType<Signature_mustQuote, &U::mustQuote> *);

  template <typename U>
  static double test(...);

  static bool const value =
      (sizeof(test<ScalarTraits<T>>(nullptr, nullptr, nullptr)) == 1);
};

// Test if BlockScalarTraits<T> is defined on type T.
template <class T>
struct has_BlockScalarTraits
{
  using Signature_input = StringRef (*)(StringRef, void *, T &);
  using Signature_output = void (*)(const T &, void *, raw_ostream &);

  template <typename U>
  static char test(SameType<Signature_input, &U::input> *,
                   SameType<Signature_output, &U::output> *);

  template <typename U>
  static double test(...);

  static bool const value =
      (sizeof(test<BlockScalarTraits<T>>(nullptr, nullptr)) == 1);
};

// Test if TaggedScalarTraits<T> is defined on type T.
template <class T> struct has_TaggedScalarTraits {
  using Signature_input = StringRef (*)(StringRef, StringRef, void *, T &);
  using Signature_output = void (*)(const T &, void *, raw_ostream &,
                                    raw_ostream &);
  using Signature_mustQuote = QuotingType (*)(const T &, StringRef);

  template <typename U>
  static char test(SameType<Signature_input, &U::input> *,
                   SameType<Signature_output, &U::output> *,
                   SameType<Signature_mustQuote, &U::mustQuote> *);

  template <typename U> static double test(...);

  static bool const value =
      (sizeof(test<TaggedScalarTraits<T>>(nullptr, nullptr, nullptr)) == 1);
};

// Test if MappingContextTraits<T> is defined on type T.
template <class T, class Context> struct has_MappingTraits {
  using Signature_mapping = void (*)(class IO &, T &, Context &);

  template <typename U>
  static char test(SameType<Signature_mapping, &U::mapping>*);

  template <typename U>
  static double test(...);

  static bool const value =
      (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
};

// Test if MappingTraits<T> is defined on type T.
template <class T> struct has_MappingTraits<T, EmptyContext> {
  using Signature_mapping = void (*)(class IO &, T &);

  template <typename U>
  static char test(SameType<Signature_mapping, &U::mapping> *);

  template <typename U> static double test(...);

  static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
};

// Test if MappingContextTraits<T>::validate() is defined on type T.
template <class T, class Context> struct has_MappingValidateTraits {
  using Signature_validate = StringRef (*)(class IO &, T &, Context &);

  template <typename U>
  static char test(SameType<Signature_validate, &U::validate>*);

  template <typename U>
  static double test(...);

  static bool const value =
      (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
};

// Test if MappingTraits<T>::validate() is defined on type T.
template <class T> struct has_MappingValidateTraits<T, EmptyContext> {
  using Signature_validate = StringRef (*)(class IO &, T &);

  template <typename U>
  static char test(SameType<Signature_validate, &U::validate> *);

  template <typename U> static double test(...);

  static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
};

// Test if SequenceTraits<T> is defined on type T.
template <class T>
struct has_SequenceMethodTraits
{
  using Signature_size = size_t (*)(class IO&, T&);

  template <typename U>
  static char test(SameType<Signature_size, &U::size>*);

  template <typename U>
  static double test(...);

  static bool const value =  (sizeof(test<SequenceTraits<T>>(nullptr)) == 1);
};

// Test if CustomMappingTraits<T> is defined on type T.
template <class T>
struct has_CustomMappingTraits
{
  using Signature_input = void (*)(IO &io, StringRef key, T &v);

  template <typename U>
  static char test(SameType<Signature_input, &U::inputOne>*);

  template <typename U>
  static double test(...);

  static bool const value =
      (sizeof(test<CustomMappingTraits<T>>(nullptr)) == 1);
};

// has_FlowTraits<int> will cause an error with some compilers because
// it subclasses int.  Using this wrapper only instantiates the
// real has_FlowTraits only if the template type is a class.
template <typename T, bool Enabled = std::is_class<T>::value>
class has_FlowTraits
{
public:
   static const bool value = false;
};

// Some older gcc compilers don't support straight forward tests
// for members, so test for ambiguity cause by the base and derived
// classes both defining the member.
template <class T>
struct has_FlowTraits<T, true>
{
  struct Fallback { bool flow; };
  struct Derived : T, Fallback { };

  template<typename C>
  static char (&f(SameType<bool Fallback::*, &C::flow>*))[1];

  template<typename C>
  static char (&f(...))[2];

  static bool const value = sizeof(f<Derived>(nullptr)) == 2;
};

// Test if SequenceTraits<T> is defined on type T
template<typename T>
struct has_SequenceTraits : public std::integral_constant<bool,
                                      has_SequenceMethodTraits<T>::value > { };

// Test if DocumentListTraits<T> is defined on type T
template <class T>
struct has_DocumentListTraits
{
  using Signature_size = size_t (*)(class IO &, T &);

  template <typename U>
  static char test(SameType<Signature_size, &U::size>*);

  template <typename U>
  static double test(...);

  static bool const value = (sizeof(test<DocumentListTraits<T>>(nullptr))==1);
};

template <class T> struct has_PolymorphicTraits {
  using Signature_getKind = NodeKind (*)(const T &);

  template <typename U>
  static char test(SameType<Signature_getKind, &U::getKind> *);

  template <typename U> static double test(...);

  static bool const value = (sizeof(test<PolymorphicTraits<T>>(nullptr)) == 1);
};

inline bool isNumeric(StringRef S) {
  const static auto skipDigits = [](StringRef Input) {
    return Input.drop_front(
        std::min(Input.find_first_not_of("0123456789"), Input.size()));
  };

  // Make S.front() and S.drop_front().front() (if S.front() is [+-]) calls
  // safe.
  if (S.empty() || S.equals("+") || S.equals("-"))
    return false;

  if (S.equals(".nan") || S.equals(".NaN") || S.equals(".NAN"))
    return true;

  // Infinity and decimal numbers can be prefixed with sign.
  StringRef Tail = (S.front() == '-' || S.front() == '+') ? S.drop_front() : S;

  // Check for infinity first, because checking for hex and oct numbers is more
  // expensive.
  if (Tail.equals(".inf") || Tail.equals(".Inf") || Tail.equals(".INF"))
    return true;

  // Section 10.3.2 Tag Resolution
  // YAML 1.2 Specification prohibits Base 8 and Base 16 numbers prefixed with
  // [-+], so S should be used instead of Tail.
  if (S.startswith("0o"))
    return S.size() > 2 &&
           S.drop_front(2).find_first_not_of("01234567") == StringRef::npos;

  if (S.startswith("0x"))
    return S.size() > 2 && S.drop_front(2).find_first_not_of(
                               "0123456789abcdefABCDEF") == StringRef::npos;

  // Parse float: [-+]? (\. [0-9]+ | [0-9]+ (\. [0-9]* )?) ([eE] [-+]? [0-9]+)?
  S = Tail;

  // Handle cases when the number starts with '.' and hence needs at least one
  // digit after dot (as opposed by number which has digits before the dot), but
  // doesn't have one.
  if (S.startswith(".") &&
      (S.equals(".") ||
       (S.size() > 1 && std::strchr("0123456789", S[1]) == nullptr)))
    return false;

  if (S.startswith("E") || S.startswith("e"))
    return false;

  enum ParseState {
    Default,
    FoundDot,
    FoundExponent,
  };
  ParseState State = Default;

  S = skipDigits(S);

  // Accept decimal integer.
  if (S.empty())
    return true;

  if (S.front() == '.') {
    State = FoundDot;
    S = S.drop_front();
  } else if (S.front() == 'e' || S.front() == 'E') {
    State = FoundExponent;
    S = S.drop_front();
  } else {
    return false;
  }

  if (State == FoundDot) {
    S = skipDigits(S);
    if (S.empty())
      return true;

    if (S.front() == 'e' || S.front() == 'E') {
      State = FoundExponent;
      S = S.drop_front();
    } else {
      return false;
    }
  }

  assert(State == FoundExponent && "Should have found exponent at this point.");
  if (S.empty())
    return false;

  if (S.front() == '+' || S.front() == '-') {
    S = S.drop_front();
    if (S.empty())
      return false;
  }

  return skipDigits(S).empty();
}

inline bool isNull(StringRef S) {
  return S.equals("null") || S.equals("Null") || S.equals("NULL") ||
         S.equals("~");
}

inline bool isBool(StringRef S) {
  return S.equals("true") || S.equals("True") || S.equals("TRUE") ||
         S.equals("false") || S.equals("False") || S.equals("FALSE");
}

// 5.1. Character Set
// The allowed character range explicitly excludes the C0 control block #x0-#x1F
// (except for TAB #x9, LF #xA, and CR #xD which are allowed), DEL #x7F, the C1
// control block #x80-#x9F (except for NEL #x85 which is allowed), the surrogate
// block #xD800-#xDFFF, #xFFFE, and #xFFFF.
inline QuotingType needsQuotes(StringRef S) {
  if (S.empty())
    return QuotingType::Single;
  if (isspace(S.front()) || isspace(S.back()))
    return QuotingType::Single;
  if (isNull(S))
    return QuotingType::Single;
  if (isBool(S))
    return QuotingType::Single;
  if (isNumeric(S))
    return QuotingType::Single;

  // 7.3.3 Plain Style
  // Plain scalars must not begin with most indicators, as this would cause
  // ambiguity with other YAML constructs.
  static constexpr char Indicators[] = R"(-?:\,[]{}#&*!|>'"%@`)";
  if (S.find_first_of(Indicators) == 0)
    return QuotingType::Single;

  QuotingType MaxQuotingNeeded = QuotingType::None;
  for (unsigned char C : S) {
    // Alphanum is safe.
    if (isAlnum(C))
      continue;

    switch (C) {
    // Safe scalar characters.
    case '_':
    case '-':
    case '^':
    case '.':
    case ',':
    case ' ':
    // TAB (0x9) is allowed in unquoted strings.
    case 0x9:
      continue;
    // LF(0xA) and CR(0xD) may delimit values and so require at least single
    // quotes.
    case 0xA:
    case 0xD:
      MaxQuotingNeeded = QuotingType::Single;
      continue;
    // DEL (0x7F) are excluded from the allowed character range.
    case 0x7F:
      return QuotingType::Double;
    // Forward slash is allowed to be unquoted, but we quote it anyway.  We have
    // many tests that use FileCheck against YAML output, and this output often
    // contains paths.  If we quote backslashes but not forward slashes then
    // paths will come out either quoted or unquoted depending on which platform
    // the test is run on, making FileCheck comparisons difficult.
    case '/':
    default: {
      // C0 control block (0x0 - 0x1F) is excluded from the allowed character
      // range.
      if (C <= 0x1F)
        return QuotingType::Double;

      // Always double quote UTF-8.
      if ((C & 0x80) != 0)
        return QuotingType::Double;

      // The character is not safe, at least simple quoting needed.
      MaxQuotingNeeded = QuotingType::Single;
    }
    }
  }

  return MaxQuotingNeeded;
}

template <typename T, typename Context>
struct missingTraits
    : public std::integral_constant<bool,
                                    !has_ScalarEnumerationTraits<T>::value &&
                                        !has_ScalarBitSetTraits<T>::value &&
                                        !has_ScalarTraits<T>::value &&
                                        !has_BlockScalarTraits<T>::value &&
                                        !has_TaggedScalarTraits<T>::value &&
                                        !has_MappingTraits<T, Context>::value &&
                                        !has_SequenceTraits<T>::value &&
                                        !has_CustomMappingTraits<T>::value &&
                                        !has_DocumentListTraits<T>::value &&
                                        !has_PolymorphicTraits<T>::value> {};

template <typename T, typename Context>
struct validatedMappingTraits
    : public std::integral_constant<
          bool, has_MappingTraits<T, Context>::value &&
                    has_MappingValidateTraits<T, Context>::value> {};

template <typename T, typename Context>
struct unvalidatedMappingTraits
    : public std::integral_constant<
          bool, has_MappingTraits<T, Context>::value &&
                    !has_MappingValidateTraits<T, Context>::value> {};

// Base class for Input and Output.
class IO {
public:
  IO(void *Ctxt = nullptr);
  virtual ~IO();

  virtual bool outputting() = 0;

  virtual unsigned beginSequence() = 0;
  virtual bool preflightElement(unsigned, void *&) = 0;
  virtual void postflightElement(void*) = 0;
  virtual void endSequence() = 0;
  virtual bool canElideEmptySequence() = 0;

  virtual unsigned beginFlowSequence() = 0;
  virtual bool preflightFlowElement(unsigned, void *&) = 0;
  virtual void postflightFlowElement(void*) = 0;
  virtual void endFlowSequence() = 0;

  virtual bool mapTag(StringRef Tag, bool Default=false) = 0;
  virtual void beginMapping() = 0;
  virtual void endMapping() = 0;
  virtual bool preflightKey(const char*, bool, bool, bool &, void *&) = 0;
  virtual void postflightKey(void*) = 0;
  virtual std::vector<StringRef> keys() = 0;

  virtual void beginFlowMapping() = 0;
  virtual void endFlowMapping() = 0;

  virtual void beginEnumScalar() = 0;
  virtual bool matchEnumScalar(const char*, bool) = 0;
  virtual bool matchEnumFallback() = 0;
  virtual void endEnumScalar() = 0;

  virtual bool beginBitSetScalar(bool &) = 0;
  virtual bool bitSetMatch(const char*, bool) = 0;
  virtual void endBitSetScalar() = 0;

  virtual void scalarString(StringRef &, QuotingType) = 0;
  virtual void blockScalarString(StringRef &) = 0;
  virtual void scalarTag(std::string &) = 0;

  virtual NodeKind getNodeKind() = 0;

  virtual void setError(const Twine &) = 0;

  template <typename T>
  void enumCase(T &Val, const char* Str, const T ConstVal) {
    if ( matchEnumScalar(Str, outputting() && Val == ConstVal) ) {
      Val = ConstVal;
    }
  }

  // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
  template <typename T>
  void enumCase(T &Val, const char* Str, const uint32_t ConstVal) {
    if ( matchEnumScalar(Str, outputting() && Val == static_cast<T>(ConstVal)) ) {
      Val = ConstVal;
    }
  }

  template <typename FBT, typename T>
  void enumFallback(T &Val) {
    if (matchEnumFallback()) {
      EmptyContext Context;
      // FIXME: Force integral conversion to allow strong typedefs to convert.
      FBT Res = static_cast<typename FBT::BaseType>(Val);
      yamlize(*this, Res, true, Context);
      Val = static_cast<T>(static_cast<typename FBT::BaseType>(Res));
    }
  }

  template <typename T>
  void bitSetCase(T &Val, const char* Str, const T ConstVal) {
    if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
      Val = static_cast<T>(Val | ConstVal);
    }
  }

  // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
  template <typename T>
  void bitSetCase(T &Val, const char* Str, const uint32_t ConstVal) {
    if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
      Val = static_cast<T>(Val | ConstVal);
    }
  }

  template <typename T>
  void maskedBitSetCase(T &Val, const char *Str, T ConstVal, T Mask) {
    if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
      Val = Val | ConstVal;
  }

  template <typename T>
  void maskedBitSetCase(T &Val, const char *Str, uint32_t ConstVal,
                        uint32_t Mask) {
    if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
      Val = Val | ConstVal;
  }

  void *getContext();
  void setContext(void *);

  template <typename T> void mapRequired(const char *Key, T &Val) {
    EmptyContext Ctx;
    this->processKey(Key, Val, true, Ctx);
  }

  template <typename T, typename Context>
  void mapRequired(const char *Key, T &Val, Context &Ctx) {
    this->processKey(Key, Val, true, Ctx);
  }

  template <typename T> void mapOptional(const char *Key, T &Val) {
    EmptyContext Ctx;
    mapOptionalWithContext(Key, Val, Ctx);
  }

  template <typename T, typename DefaultT>
  void mapOptional(const char *Key, T &Val, const DefaultT &Default) {
    EmptyContext Ctx;
    mapOptionalWithContext(Key, Val, Default, Ctx);
  }

  template <typename T, typename Context>
  typename std::enable_if<has_SequenceTraits<T>::value, void>::type
  mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
    // omit key/value instead of outputting empty sequence
    if (this->canElideEmptySequence() && !(Val.begin() != Val.end()))
      return;
    this->processKey(Key, Val, false, Ctx);
  }

  template <typename T, typename Context>
  void mapOptionalWithContext(const char *Key, Optional<T> &Val, Context &Ctx) {
    this->processKeyWithDefault(Key, Val, Optional<T>(), /*Required=*/false,
                                Ctx);
  }

  template <typename T, typename Context>
  typename std::enable_if<!has_SequenceTraits<T>::value, void>::type
  mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
    this->processKey(Key, Val, false, Ctx);
  }

  template <typename T, typename Context, typename DefaultT>
  void mapOptionalWithContext(const char *Key, T &Val, const DefaultT &Default,
                              Context &Ctx) {
    static_assert(std::is_convertible<DefaultT, T>::value,
                  "Default type must be implicitly convertible to value type!");
    this->processKeyWithDefault(Key, Val, static_cast<const T &>(Default),
                                false, Ctx);
  }

private:
  template <typename T, typename Context>
  void processKeyWithDefault(const char *Key, Optional<T> &Val,
                             const Optional<T> &DefaultValue, bool Required,
                             Context &Ctx) {
    assert(DefaultValue.hasValue() == false &&
           "Optional<T> shouldn't have a value!");
    void *SaveInfo;
    bool UseDefault = true;
    const bool sameAsDefault = outputting() && !Val.hasValue();
    if (!outputting() && !Val.hasValue())
      Val = T();
    if (Val.hasValue() &&
        this->preflightKey(Key, Required, sameAsDefault, UseDefault,
                           SaveInfo)) {
      yamlize(*this, Val.getValue(), Required, Ctx);
      this->postflightKey(SaveInfo);
    } else {
      if (UseDefault)
        Val = DefaultValue;
    }
  }

  template <typename T, typename Context>
  void processKeyWithDefault(const char *Key, T &Val, const T &DefaultValue,
                             bool Required, Context &Ctx) {
    void *SaveInfo;
    bool UseDefault;
    const bool sameAsDefault = outputting() && Val == DefaultValue;
    if ( this->preflightKey(Key, Required, sameAsDefault, UseDefault,
                                                                  SaveInfo) ) {
      yamlize(*this, Val, Required, Ctx);
      this->postflightKey(SaveInfo);
    }
    else {
      if ( UseDefault )
        Val = DefaultValue;
    }
  }

  template <typename T, typename Context>
  void processKey(const char *Key, T &Val, bool Required, Context &Ctx) {
    void *SaveInfo;
    bool UseDefault;
    if ( this->preflightKey(Key, Required, false, UseDefault, SaveInfo) ) {
      yamlize(*this, Val, Required, Ctx);
      this->postflightKey(SaveInfo);
    }
  }

private:
  void *Ctxt;
};

namespace detail {

template <typename T, typename Context>
void doMapping(IO &io, T &Val, Context &Ctx) {
  MappingContextTraits<T, Context>::mapping(io, Val, Ctx);
}

template <typename T> void doMapping(IO &io, T &Val, EmptyContext &Ctx) {
  MappingTraits<T>::mapping(io, Val);
}

} // end namespace detail

template <typename T>
typename std::enable_if<has_ScalarEnumerationTraits<T>::value, void>::type
yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
  io.beginEnumScalar();
  ScalarEnumerationTraits<T>::enumeration(io, Val);
  io.endEnumScalar();
}

template <typename T>
typename std::enable_if<has_ScalarBitSetTraits<T>::value, void>::type
yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
  bool DoClear;
  if ( io.beginBitSetScalar(DoClear) ) {
    if ( DoClear )
      Val = T();
    ScalarBitSetTraits<T>::bitset(io, Val);
    io.endBitSetScalar();
  }
}

template <typename T>
typename std::enable_if<has_ScalarTraits<T>::value, void>::type
yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
  if ( io.outputting() ) {
    std::string Storage;
    raw_string_ostream Buffer(Storage);
    ScalarTraits<T>::output(Val, io.getContext(), Buffer);
    StringRef Str = Buffer.str();
    io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
  }
  else {
    StringRef Str;
    io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
    StringRef Result = ScalarTraits<T>::input(Str, io.getContext(), Val);
    if ( !Result.empty() ) {
      io.setError(Twine(Result));
    }
  }
}

template <typename T>
typename std::enable_if<has_BlockScalarTraits<T>::value, void>::type
yamlize(IO &YamlIO, T &Val, bool, EmptyContext &Ctx) {
  if (YamlIO.outputting()) {
    std::string Storage;
    raw_string_ostream Buffer(Storage);
    BlockScalarTraits<T>::output(Val, YamlIO.getContext(), Buffer);
    StringRef Str = Buffer.str();
    YamlIO.blockScalarString(Str);
  } else {
    StringRef Str;
    YamlIO.blockScalarString(Str);
    StringRef Result =
        BlockScalarTraits<T>::input(Str, YamlIO.getContext(), Val);
    if (!Result.empty())
      YamlIO.setError(Twine(Result));
  }
}

template <typename T>
typename std::enable_if<has_TaggedScalarTraits<T>::value, void>::type
yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
  if (io.outputting()) {
    std::string ScalarStorage, TagStorage;
    raw_string_ostream ScalarBuffer(ScalarStorage), TagBuffer(TagStorage);
    TaggedScalarTraits<T>::output(Val, io.getContext(), ScalarBuffer,
                                  TagBuffer);
    io.scalarTag(TagBuffer.str());
    StringRef ScalarStr = ScalarBuffer.str();
    io.scalarString(ScalarStr,
                    TaggedScalarTraits<T>::mustQuote(Val, ScalarStr));
  } else {
    std::string Tag;
    io.scalarTag(Tag);
    StringRef Str;
    io.scalarString(Str, QuotingType::None);
    StringRef Result =
        TaggedScalarTraits<T>::input(Str, Tag, io.getContext(), Val);
    if (!Result.empty()) {
      io.setError(Twine(Result));
    }
  }
}

template <typename T, typename Context>
typename std::enable_if<validatedMappingTraits<T, Context>::value, void>::type
yamlize(IO &io, T &Val, bool, Context &Ctx) {
  if (has_FlowTraits<MappingTraits<T>>::value)
    io.beginFlowMapping();
  else
    io.beginMapping();
  if (io.outputting()) {
    StringRef Err = MappingTraits<T>::validate(io, Val);
    if (!Err.empty()) {
      errs() << Err << "\n";
      assert(Err.empty() && "invalid struct trying to be written as yaml");
    }
  }
  detail::doMapping(io, Val, Ctx);
  if (!io.outputting()) {
    StringRef Err = MappingTraits<T>::validate(io, Val);
    if (!Err.empty())
      io.setError(Err);
  }
  if (has_FlowTraits<MappingTraits<T>>::value)
    io.endFlowMapping();
  else
    io.endMapping();
}

template <typename T, typename Context>
typename std::enable_if<unvalidatedMappingTraits<T, Context>::value, void>::type
yamlize(IO &io, T &Val, bool, Context &Ctx) {
  if (has_FlowTraits<MappingTraits<T>>::value) {
    io.beginFlowMapping();
    detail::doMapping(io, Val, Ctx);
    io.endFlowMapping();
  } else {
    io.beginMapping();
    detail::doMapping(io, Val, Ctx);
    io.endMapping();
  }
}

template <typename T>
typename std::enable_if<has_CustomMappingTraits<T>::value, void>::type
yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
  if ( io.outputting() ) {
    io.beginMapping();
    CustomMappingTraits<T>::output(io, Val);
    io.endMapping();
  } else {
    io.beginMapping();
    for (StringRef key : io.keys())
      CustomMappingTraits<T>::inputOne(io, key, Val);
    io.endMapping();
  }
}

template <typename T>
typename std::enable_if<has_PolymorphicTraits<T>::value, void>::type
yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
  switch (io.outputting() ? PolymorphicTraits<T>::getKind(Val)
                          : io.getNodeKind()) {
  case NodeKind::Scalar:
    return yamlize(io, PolymorphicTraits<T>::getAsScalar(Val), true, Ctx);
  case NodeKind::Map:
    return yamlize(io, PolymorphicTraits<T>::getAsMap(Val), true, Ctx);
  case NodeKind::Sequence:
    return yamlize(io, PolymorphicTraits<T>::getAsSequence(Val), true, Ctx);
  }
}

template <typename T>
typename std::enable_if<missingTraits<T, EmptyContext>::value, void>::type
yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
}

template <typename T, typename Context>
typename std::enable_if<has_SequenceTraits<T>::value, void>::type
yamlize(IO &io, T &Seq, bool, Context &Ctx) {
  if ( has_FlowTraits< SequenceTraits<T>>::value ) {
    unsigned incnt = io.beginFlowSequence();
    unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
    for(unsigned i=0; i < count; ++i) {
      void *SaveInfo;
      if ( io.preflightFlowElement(i, SaveInfo) ) {
        yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
        io.postflightFlowElement(SaveInfo);
      }
    }
    io.endFlowSequence();
  }
  else {
    unsigned incnt = io.beginSequence();
    unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
    for(unsigned i=0; i < count; ++i) {
      void *SaveInfo;
      if ( io.preflightElement(i, SaveInfo) ) {
        yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
        io.postflightElement(SaveInfo);
      }
    }
    io.endSequence();
  }
}

template<>
struct ScalarTraits<bool> {
  static void output(const bool &, void* , raw_ostream &);
  static StringRef input(StringRef, void *, bool &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<StringRef> {
  static void output(const StringRef &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, StringRef &);
  static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
};

template<>
struct ScalarTraits<std::string> {
  static void output(const std::string &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, std::string &);
  static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
};

template<>
struct ScalarTraits<uint8_t> {
  static void output(const uint8_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, uint8_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<uint16_t> {
  static void output(const uint16_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, uint16_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<uint32_t> {
  static void output(const uint32_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, uint32_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<uint64_t> {
  static void output(const uint64_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, uint64_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<int8_t> {
  static void output(const int8_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, int8_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<int16_t> {
  static void output(const int16_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, int16_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<int32_t> {
  static void output(const int32_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, int32_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<int64_t> {
  static void output(const int64_t &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, int64_t &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<float> {
  static void output(const float &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, float &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<double> {
  static void output(const double &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, double &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

// For endian types, we use existing scalar Traits class for the underlying
// type.  This way endian aware types are supported whenever the traits are
// defined for the underlying type.
template <typename value_type, support::endianness endian, size_t alignment>
struct ScalarTraits<
    support::detail::packed_endian_specific_integral<value_type, endian,
                                                     alignment>,
    typename std::enable_if<has_ScalarTraits<value_type>::value>::type> {
  using endian_type =
      support::detail::packed_endian_specific_integral<value_type, endian,
                                                       alignment>;

  static void output(const endian_type &E, void *Ctx, raw_ostream &Stream) {
    ScalarTraits<value_type>::output(static_cast<value_type>(E), Ctx, Stream);
  }

  static StringRef input(StringRef Str, void *Ctx, endian_type &E) {
    value_type V;
    auto R = ScalarTraits<value_type>::input(Str, Ctx, V);
    E = static_cast<endian_type>(V);
    return R;
  }

  static QuotingType mustQuote(StringRef Str) {
    return ScalarTraits<value_type>::mustQuote(Str);
  }
};

template <typename value_type, support::endianness endian, size_t alignment>
struct ScalarEnumerationTraits<
    support::detail::packed_endian_specific_integral<value_type, endian,
                                                     alignment>,
    typename std::enable_if<
        has_ScalarEnumerationTraits<value_type>::value>::type> {
  using endian_type =
      support::detail::packed_endian_specific_integral<value_type, endian,
                                                       alignment>;

  static void enumeration(IO &io, endian_type &E) {
    value_type V = E;
    ScalarEnumerationTraits<value_type>::enumeration(io, V);
    E = V;
  }
};

template <typename value_type, support::endianness endian, size_t alignment>
struct ScalarBitSetTraits<
    support::detail::packed_endian_specific_integral<value_type, endian,
                                                     alignment>,
    typename std::enable_if<has_ScalarBitSetTraits<value_type>::value>::type> {
  using endian_type =
      support::detail::packed_endian_specific_integral<value_type, endian,
                                                       alignment>;
  static void bitset(IO &io, endian_type &E) {
    value_type V = E;
    ScalarBitSetTraits<value_type>::bitset(io, V);
    E = V;
  }
};

// Utility for use within MappingTraits<>::mapping() method
// to [de]normalize an object for use with YAML conversion.
template <typename TNorm, typename TFinal>
struct MappingNormalization {
  MappingNormalization(IO &i_o, TFinal &Obj)
      : io(i_o), BufPtr(nullptr), Result(Obj) {
    if ( io.outputting() ) {
      BufPtr = new (&Buffer) TNorm(io, Obj);
    }
    else {
      BufPtr = new (&Buffer) TNorm(io);
    }
  }

  ~MappingNormalization() {
    if ( ! io.outputting() ) {
      Result = BufPtr->denormalize(io);
    }
    BufPtr->~TNorm();
  }

  TNorm* operator->() { return BufPtr; }

private:
  using Storage = AlignedCharArrayUnion<TNorm>;

  Storage       Buffer;
  IO           &io;
  TNorm        *BufPtr;
  TFinal       &Result;
};

// Utility for use within MappingTraits<>::mapping() method
// to [de]normalize an object for use with YAML conversion.
template <typename TNorm, typename TFinal>
struct MappingNormalizationHeap {
  MappingNormalizationHeap(IO &i_o, TFinal &Obj, BumpPtrAllocator *allocator)
    : io(i_o), Result(Obj) {
    if ( io.outputting() ) {
      BufPtr = new (&Buffer) TNorm(io, Obj);
    }
    else if (allocator) {
      BufPtr = allocator->Allocate<TNorm>();
      new (BufPtr) TNorm(io);
    } else {
      BufPtr = new TNorm(io);
    }
  }

  ~MappingNormalizationHeap() {
    if ( io.outputting() ) {
      BufPtr->~TNorm();
    }
    else {
      Result = BufPtr->denormalize(io);
    }
  }

  TNorm* operator->() { return BufPtr; }

private:
  using Storage = AlignedCharArrayUnion<TNorm>;

  Storage       Buffer;
  IO           &io;
  TNorm        *BufPtr = nullptr;
  TFinal       &Result;
};

///
/// The Input class is used to parse a yaml document into in-memory structs
/// and vectors.
///
/// It works by using YAMLParser to do a syntax parse of the entire yaml
/// document, then the Input class builds a graph of HNodes which wraps
/// each yaml Node.  The extra layer is buffering.  The low level yaml
/// parser only lets you look at each node once.  The buffering layer lets
/// you search and interate multiple times.  This is necessary because
/// the mapRequired() method calls may not be in the same order
/// as the keys in the document.
///
class Input : public IO {
public:
  // Construct a yaml Input object from a StringRef and optional
  // user-data. The DiagHandler can be specified to provide
  // alternative error reporting.
  Input(StringRef InputContent,
        void *Ctxt = nullptr,
        SourceMgr::DiagHandlerTy DiagHandler = nullptr,
        void *DiagHandlerCtxt = nullptr);
  Input(MemoryBufferRef Input,
        void *Ctxt = nullptr,
        SourceMgr::DiagHandlerTy DiagHandler = nullptr,
        void *DiagHandlerCtxt = nullptr);
  ~Input() override;

  // Check if there was an syntax or semantic error during parsing.
  std::error_code error();

private:
  bool outputting() override;
  bool mapTag(StringRef, bool) override;
  void beginMapping() override;
  void endMapping() override;
  bool preflightKey(const char *, bool, bool, bool &, void *&) override;
  void postflightKey(void *) override;
  std::vector<StringRef> keys() override;
  void beginFlowMapping() override;
  void endFlowMapping() override;
  unsigned beginSequence() override;
  void endSequence() override;
  bool preflightElement(unsigned index, void *&) override;
  void postflightElement(void *) override;
  unsigned beginFlowSequence() override;
  bool preflightFlowElement(unsigned , void *&) override;
  void postflightFlowElement(void *) override;
  void endFlowSequence() override;
  void beginEnumScalar() override;
  bool matchEnumScalar(const char*, bool) override;
  bool matchEnumFallback() override;
  void endEnumScalar() override;
  bool beginBitSetScalar(bool &) override;
  bool bitSetMatch(const char *, bool ) override;
  void endBitSetScalar() override;
  void scalarString(StringRef &, QuotingType) override;
  void blockScalarString(StringRef &) override;
  void scalarTag(std::string &) override;
  NodeKind getNodeKind() override;
  void setError(const Twine &message) override;
  bool canElideEmptySequence() override;

  class HNode {
    virtual void anchor();

  public:
    HNode(Node *n) : _node(n) { }
    virtual ~HNode() = default;

    static bool classof(const HNode *) { return true; }

    Node *_node;
  };

  class EmptyHNode : public HNode {
    void anchor() override;

  public:
    EmptyHNode(Node *n) : HNode(n) { }

    static bool classof(const HNode *n) { return NullNode::classof(n->_node); }

    static bool classof(const EmptyHNode *) { return true; }
  };

  class ScalarHNode : public HNode {
    void anchor() override;

  public:
    ScalarHNode(Node *n, StringRef s) : HNode(n), _value(s) { }

    StringRef value() const { return _value; }

    static bool classof(const HNode *n) {
      return ScalarNode::classof(n->_node) ||
             BlockScalarNode::classof(n->_node);
    }

    static bool classof(const ScalarHNode *) { return true; }

  protected:
    StringRef _value;
  };

  class MapHNode : public HNode {
    void anchor() override;

  public:
    MapHNode(Node *n) : HNode(n) { }

    static bool classof(const HNode *n) {
      return MappingNode::classof(n->_node);
    }

    static bool classof(const MapHNode *) { return true; }

    using NameToNode = StringMap<std::unique_ptr<HNode>>;

    NameToNode Mapping;
    SmallVector<std::string, 6> ValidKeys;
  };

  class SequenceHNode : public HNode {
    void anchor() override;

  public:
    SequenceHNode(Node *n) : HNode(n) { }

    static bool classof(const HNode *n) {
      return SequenceNode::classof(n->_node);
    }

    static bool classof(const SequenceHNode *) { return true; }

    std::vector<std::unique_ptr<HNode>> Entries;
  };

  std::unique_ptr<Input::HNode> createHNodes(Node *node);
  void setError(HNode *hnode, const Twine &message);
  void setError(Node *node, const Twine &message);

public:
  // These are only used by operator>>. They could be private
  // if those templated things could be made friends.
  bool setCurrentDocument();
  bool nextDocument();

  /// Returns the current node that's being parsed by the YAML Parser.
  const Node *getCurrentNode() const;

private:
  SourceMgr                           SrcMgr; // must be before Strm
  std::unique_ptr<llvm::yaml::Stream> Strm;
  std::unique_ptr<HNode>              TopNode;
  std::error_code                     EC;
  BumpPtrAllocator                    StringAllocator;
  document_iterator                   DocIterator;
  std::vector<bool>                   BitValuesUsed;
  HNode *CurrentNode = nullptr;
  bool                                ScalarMatchFound;
};

///
/// The Output class is used to generate a yaml document from in-memory structs
/// and vectors.
///
class Output : public IO {
public:
  Output(raw_ostream &, void *Ctxt = nullptr, int WrapColumn = 70);
  ~Output() override;

  /// Set whether or not to output optional values which are equal
  /// to the default value.  By default, when outputting if you attempt
  /// to write a value that is equal to the default, the value gets ignored.
  /// Sometimes, it is useful to be able to see these in the resulting YAML
  /// anyway.
  void setWriteDefaultValues(bool Write) { WriteDefaultValues = Write; }

  bool outputting() override;
  bool mapTag(StringRef, bool) override;
  void beginMapping() override;
  void endMapping() override;
  bool preflightKey(const char *key, bool, bool, bool &, void *&) override;
  void postflightKey(void *) override;
  std::vector<StringRef> keys() override;
  void beginFlowMapping() override;
  void endFlowMapping() override;
  unsigned beginSequence() override;
  void endSequence() override;
  bool preflightElement(unsigned, void *&) override;
  void postflightElement(void *) override;
  unsigned beginFlowSequence() override;
  bool preflightFlowElement(unsigned, void *&) override;
  void postflightFlowElement(void *) override;
  void endFlowSequence() override;
  void beginEnumScalar() override;
  bool matchEnumScalar(const char*, bool) override;
  bool matchEnumFallback() override;
  void endEnumScalar() override;
  bool beginBitSetScalar(bool &) override;
  bool bitSetMatch(const char *, bool ) override;
  void endBitSetScalar() override;
  void scalarString(StringRef &, QuotingType) override;
  void blockScalarString(StringRef &) override;
  void scalarTag(std::string &) override;
  NodeKind getNodeKind() override;
  void setError(const Twine &message) override;
  bool canElideEmptySequence() override;

  // These are only used by operator<<. They could be private
  // if that templated operator could be made a friend.
  void beginDocuments();
  bool preflightDocument(unsigned);
  void postflightDocument();
  void endDocuments();

private:
  void output(StringRef s);
  void outputUpToEndOfLine(StringRef s);
  void newLineCheck();
  void outputNewLine();
  void paddedKey(StringRef key);
  void flowKey(StringRef Key);

  enum InState {
    inSeqFirstElement,
    inSeqOtherElement,
    inFlowSeqFirstElement,
    inFlowSeqOtherElement,
    inMapFirstKey,
    inMapOtherKey,
    inFlowMapFirstKey,
    inFlowMapOtherKey
  };

  static bool inSeqAnyElement(InState State);
  static bool inFlowSeqAnyElement(InState State);
  static bool inMapAnyKey(InState State);
  static bool inFlowMapAnyKey(InState State);

  raw_ostream &Out;
  int WrapColumn;
  SmallVector<InState, 8> StateStack;
  int Column = 0;
  int ColumnAtFlowStart = 0;
  int ColumnAtMapFlowStart = 0;
  bool NeedBitValueComma = false;
  bool NeedFlowSequenceComma = false;
  bool EnumerationMatchFound = false;
  bool NeedsNewLine = false;
  bool WriteDefaultValues = false;
};

/// YAML I/O does conversion based on types. But often native data types
/// are just a typedef of built in intergral types (e.g. int).  But the C++
/// type matching system sees through the typedef and all the typedefed types
/// look like a built in type. This will cause the generic YAML I/O conversion
/// to be used. To provide better control over the YAML conversion, you can
/// use this macro instead of typedef.  It will create a class with one field
/// and automatic conversion operators to and from the base type.
/// Based on BOOST_STRONG_TYPEDEF
#define LLVM_YAML_STRONG_TYPEDEF(_base, _type)                                 \
    struct _type {                                                             \
        _type() = default;                                                     \
        _type(const _base v) : value(v) {}                                     \
        _type(const _type &v) = default;                                       \
        _type &operator=(const _type &rhs) = default;                          \
        _type &operator=(const _base &rhs) { value = rhs; return *this; }      \
        operator const _base & () const { return value; }                      \
        bool operator==(const _type &rhs) const { return value == rhs.value; } \
        bool operator==(const _base &rhs) const { return value == rhs; }       \
        bool operator<(const _type &rhs) const { return value < rhs.value; }   \
        _base value;                                                           \
        using BaseType = _base;                                                \
    };

///
/// Use these types instead of uintXX_t in any mapping to have
/// its yaml output formatted as hexadecimal.
///
LLVM_YAML_STRONG_TYPEDEF(uint8_t, Hex8)
LLVM_YAML_STRONG_TYPEDEF(uint16_t, Hex16)
LLVM_YAML_STRONG_TYPEDEF(uint32_t, Hex32)
LLVM_YAML_STRONG_TYPEDEF(uint64_t, Hex64)

template<>
struct ScalarTraits<Hex8> {
  static void output(const Hex8 &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, Hex8 &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<Hex16> {
  static void output(const Hex16 &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, Hex16 &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<Hex32> {
  static void output(const Hex32 &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, Hex32 &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

template<>
struct ScalarTraits<Hex64> {
  static void output(const Hex64 &, void *, raw_ostream &);
  static StringRef input(StringRef, void *, Hex64 &);
  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
};

// Define non-member operator>> so that Input can stream in a document list.
template <typename T>
inline
typename std::enable_if<has_DocumentListTraits<T>::value, Input &>::type
operator>>(Input &yin, T &docList) {
  int i = 0;
  EmptyContext Ctx;
  while ( yin.setCurrentDocument() ) {
    yamlize(yin, DocumentListTraits<T>::element(yin, docList, i), true, Ctx);
    if ( yin.error() )
      return yin;
    yin.nextDocument();
    ++i;
  }
  return yin;
}

// Define non-member operator>> so that Input can stream in a map as a document.
template <typename T>
inline typename std::enable_if<has_MappingTraits<T, EmptyContext>::value,
                               Input &>::type
operator>>(Input &yin, T &docMap) {
  EmptyContext Ctx;
  yin.setCurrentDocument();
  yamlize(yin, docMap, true, Ctx);
  return yin;
}

// Define non-member operator>> so that Input can stream in a sequence as
// a document.
template <typename T>
inline
typename std::enable_if<has_SequenceTraits<T>::value, Input &>::type
operator>>(Input &yin, T &docSeq) {
  EmptyContext Ctx;
  if (yin.setCurrentDocument())
    yamlize(yin, docSeq, true, Ctx);
  return yin;
}

// Define non-member operator>> so that Input can stream in a block scalar.
template <typename T>
inline
typename std::enable_if<has_BlockScalarTraits<T>::value, Input &>::type
operator>>(Input &In, T &Val) {
  EmptyContext Ctx;
  if (In.setCurrentDocument())
    yamlize(In, Val, true, Ctx);
  return In;
}

// Define non-member operator>> so that Input can stream in a string map.
template <typename T>
inline
typename std::enable_if<has_CustomMappingTraits<T>::value, Input &>::type
operator>>(Input &In, T &Val) {
  EmptyContext Ctx;
  if (In.setCurrentDocument())
    yamlize(In, Val, true, Ctx);
  return In;
}

// Define non-member operator>> so that Input can stream in a polymorphic type.
template <typename T>
inline typename std::enable_if<has_PolymorphicTraits<T>::value, Input &>::type
operator>>(Input &In, T &Val) {
  EmptyContext Ctx;
  if (In.setCurrentDocument())
    yamlize(In, Val, true, Ctx);
  return In;
}

// Provide better error message about types missing a trait specialization
template <typename T>
inline typename std::enable_if<missingTraits<T, EmptyContext>::value,
                               Input &>::type
operator>>(Input &yin, T &docSeq) {
  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
  return yin;
}

// Define non-member operator<< so that Output can stream out document list.
template <typename T>
inline
typename std::enable_if<has_DocumentListTraits<T>::value, Output &>::type
operator<<(Output &yout, T &docList) {
  EmptyContext Ctx;
  yout.beginDocuments();
  const size_t count = DocumentListTraits<T>::size(yout, docList);
  for(size_t i=0; i < count; ++i) {
    if ( yout.preflightDocument(i) ) {
      yamlize(yout, DocumentListTraits<T>::element(yout, docList, i), true,
              Ctx);
      yout.postflightDocument();
    }
  }
  yout.endDocuments();
  return yout;
}

// Define non-member operator<< so that Output can stream out a map.
template <typename T>
inline typename std::enable_if<has_MappingTraits<T, EmptyContext>::value,
                               Output &>::type
operator<<(Output &yout, T &map) {
  EmptyContext Ctx;
  yout.beginDocuments();
  if ( yout.preflightDocument(0) ) {
    yamlize(yout, map, true, Ctx);
    yout.postflightDocument();
  }
  yout.endDocuments();
  return yout;
}

// Define non-member operator<< so that Output can stream out a sequence.
template <typename T>
inline
typename std::enable_if<has_SequenceTraits<T>::value, Output &>::type
operator<<(Output &yout, T &seq) {
  EmptyContext Ctx;
  yout.beginDocuments();
  if ( yout.preflightDocument(0) ) {
    yamlize(yout, seq, true, Ctx);
    yout.postflightDocument();
  }
  yout.endDocuments();
  return yout;
}

// Define non-member operator<< so that Output can stream out a block scalar.
template <typename T>
inline
typename std::enable_if<has_BlockScalarTraits<T>::value, Output &>::type
operator<<(Output &Out, T &Val) {
  EmptyContext Ctx;
  Out.beginDocuments();
  if (Out.preflightDocument(0)) {
    yamlize(Out, Val, true, Ctx);
    Out.postflightDocument();
  }
  Out.endDocuments();
  return Out;
}

// Define non-member operator<< so that Output can stream out a string map.
template <typename T>
inline
typename std::enable_if<has_CustomMappingTraits<T>::value, Output &>::type
operator<<(Output &Out, T &Val) {
  EmptyContext Ctx;
  Out.beginDocuments();
  if (Out.preflightDocument(0)) {
    yamlize(Out, Val, true, Ctx);
    Out.postflightDocument();
  }
  Out.endDocuments();
  return Out;
}

// Define non-member operator<< so that Output can stream out a polymorphic
// type.
template <typename T>
inline typename std::enable_if<has_PolymorphicTraits<T>::value, Output &>::type
operator<<(Output &Out, T &Val) {
  EmptyContext Ctx;
  Out.beginDocuments();
  if (Out.preflightDocument(0)) {
    // FIXME: The parser does not support explicit documents terminated with a
    // plain scalar; the end-marker is included as part of the scalar token.
    assert(PolymorphicTraits<T>::getKind(Val) != NodeKind::Scalar && "plain scalar documents are not supported");
    yamlize(Out, Val, true, Ctx);
    Out.postflightDocument();
  }
  Out.endDocuments();
  return Out;
}

// Provide better error message about types missing a trait specialization
template <typename T>
inline typename std::enable_if<missingTraits<T, EmptyContext>::value,
                               Output &>::type
operator<<(Output &yout, T &seq) {
  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
  return yout;
}

template <bool B> struct IsFlowSequenceBase {};
template <> struct IsFlowSequenceBase<true> { static const bool flow = true; };

template <typename T, bool Flow>
struct SequenceTraitsImpl : IsFlowSequenceBase<Flow> {
private:
  using type = typename T::value_type;

public:
  static size_t size(IO &io, T &seq) { return seq.size(); }

  static type &element(IO &io, T &seq, size_t index) {
    if (index >= seq.size())
      seq.resize(index + 1);
    return seq[index];
  }
};

// Simple helper to check an expression can be used as a bool-valued template
// argument.
template <bool> struct CheckIsBool { static const bool value = true; };

// If T has SequenceElementTraits, then vector<T> and SmallVector<T, N> have
// SequenceTraits that do the obvious thing.
template <typename T>
struct SequenceTraits<std::vector<T>,
                      typename std::enable_if<CheckIsBool<
                          SequenceElementTraits<T>::flow>::value>::type>
    : SequenceTraitsImpl<std::vector<T>, SequenceElementTraits<T>::flow> {};
template <typename T, unsigned N>
struct SequenceTraits<SmallVector<T, N>,
                      typename std::enable_if<CheckIsBool<
                          SequenceElementTraits<T>::flow>::value>::type>
    : SequenceTraitsImpl<SmallVector<T, N>, SequenceElementTraits<T>::flow> {};
template <typename T>
struct SequenceTraits<SmallVectorImpl<T>,
                      typename std::enable_if<CheckIsBool<
                          SequenceElementTraits<T>::flow>::value>::type>
    : SequenceTraitsImpl<SmallVectorImpl<T>, SequenceElementTraits<T>::flow> {};

// Sequences of fundamental types use flow formatting.
template <typename T>
struct SequenceElementTraits<
    T, typename std::enable_if<std::is_fundamental<T>::value>::type> {
  static const bool flow = true;
};

// Sequences of strings use block formatting.
template<> struct SequenceElementTraits<std::string> {
  static const bool flow = false;
};
template<> struct SequenceElementTraits<StringRef> {
  static const bool flow = false;
};
template<> struct SequenceElementTraits<std::pair<std::string, std::string>> {
  static const bool flow = false;
};

/// Implementation of CustomMappingTraits for std::map<std::string, T>.
template <typename T> struct StdMapStringCustomMappingTraitsImpl {
  using map_type = std::map<std::string, T>;

  static void inputOne(IO &io, StringRef key, map_type &v) {
    io.mapRequired(key.str().c_str(), v[key]);
  }

  static void output(IO &io, map_type &v) {
    for (auto &p : v)
      io.mapRequired(p.first.c_str(), p.second);
  }
};

} // end namespace yaml
} // end namespace llvm

#define LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(TYPE, FLOW)                          \
  namespace llvm {                                                             \
  namespace yaml {                                                             \
  static_assert(                                                               \
      !std::is_fundamental<TYPE>::value &&                                     \
      !std::is_same<TYPE, std::string>::value &&                               \
      !std::is_same<TYPE, llvm::StringRef>::value,                             \
      "only use LLVM_YAML_IS_SEQUENCE_VECTOR for types you control");          \
  template <> struct SequenceElementTraits<TYPE> {                             \
    static const bool flow = FLOW;                                             \
  };                                                                           \
  }                                                                            \
  }

/// Utility for declaring that a std::vector of a particular type
/// should be considered a YAML sequence.
#define LLVM_YAML_IS_SEQUENCE_VECTOR(type)                                     \
  LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, false)

/// Utility for declaring that a std::vector of a particular type
/// should be considered a YAML flow sequence.
#define LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(type)                                \
  LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, true)

#define LLVM_YAML_DECLARE_MAPPING_TRAITS(Type)                                 \
  namespace llvm {                                                             \
  namespace yaml {                                                             \
  template <> struct MappingTraits<Type> {                                     \
    static void mapping(IO &IO, Type &Obj);                                    \
  };                                                                           \
  }                                                                            \
  }

#define LLVM_YAML_DECLARE_ENUM_TRAITS(Type)                                    \
  namespace llvm {                                                             \
  namespace yaml {                                                             \
  template <> struct ScalarEnumerationTraits<Type> {                           \
    static void enumeration(IO &io, Type &Value);                              \
  };                                                                           \
  }                                                                            \
  }

#define LLVM_YAML_DECLARE_BITSET_TRAITS(Type)                                  \
  namespace llvm {                                                             \
  namespace yaml {                                                             \
  template <> struct ScalarBitSetTraits<Type> {                                \
    static void bitset(IO &IO, Type &Options);                                 \
  };                                                                           \
  }                                                                            \
  }

#define LLVM_YAML_DECLARE_SCALAR_TRAITS(Type, MustQuote)                       \
  namespace llvm {                                                             \
  namespace yaml {                                                             \
  template <> struct ScalarTraits<Type> {                                      \
    static void output(const Type &Value, void *ctx, raw_ostream &Out);        \
    static StringRef input(StringRef Scalar, void *ctxt, Type &Value);         \
    static QuotingType mustQuote(StringRef) { return MustQuote; }              \
  };                                                                           \
  }                                                                            \
  }

/// Utility for declaring that a std::vector of a particular type
/// should be considered a YAML document list.
#define LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(_type)                               \
  namespace llvm {                                                             \
  namespace yaml {                                                             \
  template <unsigned N>                                                        \
  struct DocumentListTraits<SmallVector<_type, N>>                             \
      : public SequenceTraitsImpl<SmallVector<_type, N>, false> {};            \
  template <>                                                                  \
  struct DocumentListTraits<std::vector<_type>>                                \
      : public SequenceTraitsImpl<std::vector<_type>, false> {};               \
  }                                                                            \
  }

/// Utility for declaring that std::map<std::string, _type> should be considered
/// a YAML map.
#define LLVM_YAML_IS_STRING_MAP(_type)                                         \
  namespace llvm {                                                             \
  namespace yaml {                                                             \
  template <>                                                                  \
  struct CustomMappingTraits<std::map<std::string, _type>>                     \
      : public StdMapStringCustomMappingTraitsImpl<_type> {};                  \
  }                                                                            \
  }

#endif // LLVM_SUPPORT_YAMLTRAITS_H