aboutsummaryrefslogtreecommitdiffstats
path: root/include/clang/ASTMatchers/ASTMatchersInternal.h
blob: b1bb0bfa3218373074eb391d7cbdc6e158b8270b (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
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
//===- ASTMatchersInternal.h - Structural query framework -------*- 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
//
//===----------------------------------------------------------------------===//
//
//  Implements the base layer of the matcher framework.
//
//  Matchers are methods that return a Matcher<T> which provides a method
//  Matches(...) which is a predicate on an AST node. The Matches method's
//  parameters define the context of the match, which allows matchers to recurse
//  or store the current node as bound to a specific string, so that it can be
//  retrieved later.
//
//  In general, matchers have two parts:
//  1. A function Matcher<T> MatcherName(<arguments>) which returns a Matcher<T>
//     based on the arguments and optionally on template type deduction based
//     on the arguments. Matcher<T>s form an implicit reverse hierarchy
//     to clang's AST class hierarchy, meaning that you can use a Matcher<Base>
//     everywhere a Matcher<Derived> is required.
//  2. An implementation of a class derived from MatcherInterface<T>.
//
//  The matcher functions are defined in ASTMatchers.h. To make it possible
//  to implement both the matcher function and the implementation of the matcher
//  interface in one place, ASTMatcherMacros.h defines macros that allow
//  implementing a matcher in a single place.
//
//  This file contains the base classes needed to construct the actual matchers.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_ASTMATCHERS_ASTMATCHERSINTERNAL_H
#define LLVM_CLANG_ASTMATCHERS_ASTMATCHERSINTERNAL_H

#include "clang/AST/ASTTypeTraits.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclFriend.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/NestedNameSpecifier.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/TemplateName.h"
#include "clang/AST/Type.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/OperatorKinds.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/IntrusiveRefCntPtr.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/iterator.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ManagedStatic.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <map>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

namespace clang {

class ASTContext;

namespace ast_matchers {

class BoundNodes;

namespace internal {

/// Variadic function object.
///
/// Most of the functions below that use VariadicFunction could be implemented
/// using plain C++11 variadic functions, but the function object allows us to
/// capture it on the dynamic matcher registry.
template <typename ResultT, typename ArgT,
          ResultT (*Func)(ArrayRef<const ArgT *>)>
struct VariadicFunction {
  ResultT operator()() const { return Func(None); }

  template <typename... ArgsT>
  ResultT operator()(const ArgT &Arg1, const ArgsT &... Args) const {
    return Execute(Arg1, static_cast<const ArgT &>(Args)...);
  }

  // We also allow calls with an already created array, in case the caller
  // already had it.
  ResultT operator()(ArrayRef<ArgT> Args) const {
    SmallVector<const ArgT*, 8> InnerArgs;
    for (const ArgT &Arg : Args)
      InnerArgs.push_back(&Arg);
    return Func(InnerArgs);
  }

private:
  // Trampoline function to allow for implicit conversions to take place
  // before we make the array.
  template <typename... ArgsT> ResultT Execute(const ArgsT &... Args) const {
    const ArgT *const ArgsArray[] = {&Args...};
    return Func(ArrayRef<const ArgT *>(ArgsArray, sizeof...(ArgsT)));
  }
};

/// Unifies obtaining the underlying type of a regular node through
/// `getType` and a TypedefNameDecl node through `getUnderlyingType`.
inline QualType getUnderlyingType(const Expr &Node) { return Node.getType(); }

inline QualType getUnderlyingType(const ValueDecl &Node) {
  return Node.getType();
}
inline QualType getUnderlyingType(const TypedefNameDecl &Node) {
  return Node.getUnderlyingType();
}
inline QualType getUnderlyingType(const FriendDecl &Node) {
  if (const TypeSourceInfo *TSI = Node.getFriendType())
    return TSI->getType();
  return QualType();
}

/// Unifies obtaining the FunctionProtoType pointer from both
/// FunctionProtoType and FunctionDecl nodes..
inline const FunctionProtoType *
getFunctionProtoType(const FunctionProtoType &Node) {
  return &Node;
}

inline const FunctionProtoType *getFunctionProtoType(const FunctionDecl &Node) {
  return Node.getType()->getAs<FunctionProtoType>();
}

/// Internal version of BoundNodes. Holds all the bound nodes.
class BoundNodesMap {
public:
  /// Adds \c Node to the map with key \c ID.
  ///
  /// The node's base type should be in NodeBaseType or it will be unaccessible.
  void addNode(StringRef ID, const ast_type_traits::DynTypedNode& DynNode) {
    NodeMap[ID] = DynNode;
  }

  /// Returns the AST node bound to \c ID.
  ///
  /// Returns NULL if there was no node bound to \c ID or if there is a node but
  /// it cannot be converted to the specified type.
  template <typename T>
  const T *getNodeAs(StringRef ID) const {
    IDToNodeMap::const_iterator It = NodeMap.find(ID);
    if (It == NodeMap.end()) {
      return nullptr;
    }
    return It->second.get<T>();
  }

  ast_type_traits::DynTypedNode getNode(StringRef ID) const {
    IDToNodeMap::const_iterator It = NodeMap.find(ID);
    if (It == NodeMap.end()) {
      return ast_type_traits::DynTypedNode();
    }
    return It->second;
  }

  /// Imposes an order on BoundNodesMaps.
  bool operator<(const BoundNodesMap &Other) const {
    return NodeMap < Other.NodeMap;
  }

  /// A map from IDs to the bound nodes.
  ///
  /// Note that we're using std::map here, as for memoization:
  /// - we need a comparison operator
  /// - we need an assignment operator
  using IDToNodeMap = std::map<std::string, ast_type_traits::DynTypedNode>;

  const IDToNodeMap &getMap() const {
    return NodeMap;
  }

  /// Returns \c true if this \c BoundNodesMap can be compared, i.e. all
  /// stored nodes have memoization data.
  bool isComparable() const {
    for (const auto &IDAndNode : NodeMap) {
      if (!IDAndNode.second.getMemoizationData())
        return false;
    }
    return true;
  }

private:
  IDToNodeMap NodeMap;
};

/// Creates BoundNodesTree objects.
///
/// The tree builder is used during the matching process to insert the bound
/// nodes from the Id matcher.
class BoundNodesTreeBuilder {
public:
  /// A visitor interface to visit all BoundNodes results for a
  /// BoundNodesTree.
  class Visitor {
  public:
    virtual ~Visitor() = default;

    /// Called multiple times during a single call to VisitMatches(...).
    ///
    /// 'BoundNodesView' contains the bound nodes for a single match.
    virtual void visitMatch(const BoundNodes& BoundNodesView) = 0;
  };

  /// Add a binding from an id to a node.
  void setBinding(StringRef Id, const ast_type_traits::DynTypedNode &DynNode) {
    if (Bindings.empty())
      Bindings.emplace_back();
    for (BoundNodesMap &Binding : Bindings)
      Binding.addNode(Id, DynNode);
  }

  /// Adds a branch in the tree.
  void addMatch(const BoundNodesTreeBuilder &Bindings);

  /// Visits all matches that this BoundNodesTree represents.
  ///
  /// The ownership of 'ResultVisitor' remains at the caller.
  void visitMatches(Visitor* ResultVisitor);

  template <typename ExcludePredicate>
  bool removeBindings(const ExcludePredicate &Predicate) {
    Bindings.erase(std::remove_if(Bindings.begin(), Bindings.end(), Predicate),
                   Bindings.end());
    return !Bindings.empty();
  }

  /// Imposes an order on BoundNodesTreeBuilders.
  bool operator<(const BoundNodesTreeBuilder &Other) const {
    return Bindings < Other.Bindings;
  }

  /// Returns \c true if this \c BoundNodesTreeBuilder can be compared,
  /// i.e. all stored node maps have memoization data.
  bool isComparable() const {
    for (const BoundNodesMap &NodesMap : Bindings) {
      if (!NodesMap.isComparable())
        return false;
    }
    return true;
  }

private:
  SmallVector<BoundNodesMap, 1> Bindings;
};

class ASTMatchFinder;

/// Generic interface for all matchers.
///
/// Used by the implementation of Matcher<T> and DynTypedMatcher.
/// In general, implement MatcherInterface<T> or SingleNodeMatcherInterface<T>
/// instead.
class DynMatcherInterface
    : public llvm::ThreadSafeRefCountedBase<DynMatcherInterface> {
public:
  virtual ~DynMatcherInterface() = default;

  /// Returns true if \p DynNode can be matched.
  ///
  /// May bind \p DynNode to an ID via \p Builder, or recurse into
  /// the AST via \p Finder.
  virtual bool dynMatches(const ast_type_traits::DynTypedNode &DynNode,
                          ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const = 0;
};

/// Generic interface for matchers on an AST node of type T.
///
/// Implement this if your matcher may need to inspect the children or
/// descendants of the node or bind matched nodes to names. If you are
/// writing a simple matcher that only inspects properties of the
/// current node and doesn't care about its children or descendants,
/// implement SingleNodeMatcherInterface instead.
template <typename T>
class MatcherInterface : public DynMatcherInterface {
public:
  /// Returns true if 'Node' can be matched.
  ///
  /// May bind 'Node' to an ID via 'Builder', or recurse into
  /// the AST via 'Finder'.
  virtual bool matches(const T &Node,
                       ASTMatchFinder *Finder,
                       BoundNodesTreeBuilder *Builder) const = 0;

  bool dynMatches(const ast_type_traits::DynTypedNode &DynNode,
                  ASTMatchFinder *Finder,
                  BoundNodesTreeBuilder *Builder) const override {
    return matches(DynNode.getUnchecked<T>(), Finder, Builder);
  }
};

/// Interface for matchers that only evaluate properties on a single
/// node.
template <typename T>
class SingleNodeMatcherInterface : public MatcherInterface<T> {
public:
  /// Returns true if the matcher matches the provided node.
  ///
  /// A subclass must implement this instead of Matches().
  virtual bool matchesNode(const T &Node) const = 0;

private:
  /// Implements MatcherInterface::Matches.
  bool matches(const T &Node,
               ASTMatchFinder * /* Finder */,
               BoundNodesTreeBuilder * /*  Builder */) const override {
    return matchesNode(Node);
  }
};

template <typename> class Matcher;

/// Matcher that works on a \c DynTypedNode.
///
/// It is constructed from a \c Matcher<T> object and redirects most calls to
/// underlying matcher.
/// It checks whether the \c DynTypedNode is convertible into the type of the
/// underlying matcher and then do the actual match on the actual node, or
/// return false if it is not convertible.
class DynTypedMatcher {
public:
  /// Takes ownership of the provided implementation pointer.
  template <typename T>
  DynTypedMatcher(MatcherInterface<T> *Implementation)
      : SupportedKind(ast_type_traits::ASTNodeKind::getFromNodeKind<T>()),
        RestrictKind(SupportedKind), Implementation(Implementation) {}

  /// Construct from a variadic function.
  enum VariadicOperator {
    /// Matches nodes for which all provided matchers match.
    VO_AllOf,

    /// Matches nodes for which at least one of the provided matchers
    /// matches.
    VO_AnyOf,

    /// Matches nodes for which at least one of the provided matchers
    /// matches, but doesn't stop at the first match.
    VO_EachOf,

    /// Matches nodes that do not match the provided matcher.
    ///
    /// Uses the variadic matcher interface, but fails if
    /// InnerMatchers.size() != 1.
    VO_UnaryNot
  };

  static DynTypedMatcher
  constructVariadic(VariadicOperator Op,
                    ast_type_traits::ASTNodeKind SupportedKind,
                    std::vector<DynTypedMatcher> InnerMatchers);

  /// Get a "true" matcher for \p NodeKind.
  ///
  /// It only checks that the node is of the right kind.
  static DynTypedMatcher trueMatcher(ast_type_traits::ASTNodeKind NodeKind);

  void setAllowBind(bool AB) { AllowBind = AB; }

  /// Check whether this matcher could ever match a node of kind \p Kind.
  /// \return \c false if this matcher will never match such a node. Otherwise,
  /// return \c true.
  bool canMatchNodesOfKind(ast_type_traits::ASTNodeKind Kind) const;

  /// Return a matcher that points to the same implementation, but
  ///   restricts the node types for \p Kind.
  DynTypedMatcher dynCastTo(const ast_type_traits::ASTNodeKind Kind) const;

  /// Returns true if the matcher matches the given \c DynNode.
  bool matches(const ast_type_traits::DynTypedNode &DynNode,
               ASTMatchFinder *Finder, BoundNodesTreeBuilder *Builder) const;

  /// Same as matches(), but skips the kind check.
  ///
  /// It is faster, but the caller must ensure the node is valid for the
  /// kind of this matcher.
  bool matchesNoKindCheck(const ast_type_traits::DynTypedNode &DynNode,
                          ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const;

  /// Bind the specified \p ID to the matcher.
  /// \return A new matcher with the \p ID bound to it if this matcher supports
  ///   binding. Otherwise, returns an empty \c Optional<>.
  llvm::Optional<DynTypedMatcher> tryBind(StringRef ID) const;

  /// Returns a unique \p ID for the matcher.
  ///
  /// Casting a Matcher<T> to Matcher<U> creates a matcher that has the
  /// same \c Implementation pointer, but different \c RestrictKind. We need to
  /// include both in the ID to make it unique.
  ///
  /// \c MatcherIDType supports operator< and provides strict weak ordering.
  using MatcherIDType = std::pair<ast_type_traits::ASTNodeKind, uint64_t>;
  MatcherIDType getID() const {
    /// FIXME: Document the requirements this imposes on matcher
    /// implementations (no new() implementation_ during a Matches()).
    return std::make_pair(RestrictKind,
                          reinterpret_cast<uint64_t>(Implementation.get()));
  }

  /// Returns the type this matcher works on.
  ///
  /// \c matches() will always return false unless the node passed is of this
  /// or a derived type.
  ast_type_traits::ASTNodeKind getSupportedKind() const {
    return SupportedKind;
  }

  /// Returns \c true if the passed \c DynTypedMatcher can be converted
  ///   to a \c Matcher<T>.
  ///
  /// This method verifies that the underlying matcher in \c Other can process
  /// nodes of types T.
  template <typename T> bool canConvertTo() const {
    return canConvertTo(ast_type_traits::ASTNodeKind::getFromNodeKind<T>());
  }
  bool canConvertTo(ast_type_traits::ASTNodeKind To) const;

  /// Construct a \c Matcher<T> interface around the dynamic matcher.
  ///
  /// This method asserts that \c canConvertTo() is \c true. Callers
  /// should call \c canConvertTo() first to make sure that \c this is
  /// compatible with T.
  template <typename T> Matcher<T> convertTo() const {
    assert(canConvertTo<T>());
    return unconditionalConvertTo<T>();
  }

  /// Same as \c convertTo(), but does not check that the underlying
  ///   matcher can handle a value of T.
  ///
  /// If it is not compatible, then this matcher will never match anything.
  template <typename T> Matcher<T> unconditionalConvertTo() const;

private:
 DynTypedMatcher(ast_type_traits::ASTNodeKind SupportedKind,
                 ast_type_traits::ASTNodeKind RestrictKind,
                 IntrusiveRefCntPtr<DynMatcherInterface> Implementation)
     : SupportedKind(SupportedKind), RestrictKind(RestrictKind),
       Implementation(std::move(Implementation)) {}

  bool AllowBind = false;
  ast_type_traits::ASTNodeKind SupportedKind;

  /// A potentially stricter node kind.
  ///
  /// It allows to perform implicit and dynamic cast of matchers without
  /// needing to change \c Implementation.
  ast_type_traits::ASTNodeKind RestrictKind;
  IntrusiveRefCntPtr<DynMatcherInterface> Implementation;
};

/// Wrapper base class for a wrapping matcher.
///
/// This is just a container for a DynTypedMatcher that can be used as a base
/// class for another matcher.
template <typename T>
class WrapperMatcherInterface : public MatcherInterface<T> {
protected:
  explicit WrapperMatcherInterface(DynTypedMatcher &&InnerMatcher)
      : InnerMatcher(std::move(InnerMatcher)) {}

  const DynTypedMatcher InnerMatcher;
};

/// Wrapper of a MatcherInterface<T> *that allows copying.
///
/// A Matcher<Base> can be used anywhere a Matcher<Derived> is
/// required. This establishes an is-a relationship which is reverse
/// to the AST hierarchy. In other words, Matcher<T> is contravariant
/// with respect to T. The relationship is built via a type conversion
/// operator rather than a type hierarchy to be able to templatize the
/// type hierarchy instead of spelling it out.
template <typename T>
class Matcher {
public:
  /// Takes ownership of the provided implementation pointer.
  explicit Matcher(MatcherInterface<T> *Implementation)
      : Implementation(Implementation) {}

  /// Implicitly converts \c Other to a Matcher<T>.
  ///
  /// Requires \c T to be derived from \c From.
  template <typename From>
  Matcher(const Matcher<From> &Other,
          typename std::enable_if<std::is_base_of<From, T>::value &&
                               !std::is_same<From, T>::value>::type * = nullptr)
      : Implementation(restrictMatcher(Other.Implementation)) {
    assert(Implementation.getSupportedKind().isSame(
        ast_type_traits::ASTNodeKind::getFromNodeKind<T>()));
  }

  /// Implicitly converts \c Matcher<Type> to \c Matcher<QualType>.
  ///
  /// The resulting matcher is not strict, i.e. ignores qualifiers.
  template <typename TypeT>
  Matcher(const Matcher<TypeT> &Other,
          typename std::enable_if<
            std::is_same<T, QualType>::value &&
            std::is_same<TypeT, Type>::value>::type* = nullptr)
      : Implementation(new TypeToQualType<TypeT>(Other)) {}

  /// Convert \c this into a \c Matcher<T> by applying dyn_cast<> to the
  /// argument.
  /// \c To must be a base class of \c T.
  template <typename To>
  Matcher<To> dynCastTo() const {
    static_assert(std::is_base_of<To, T>::value, "Invalid dynCast call.");
    return Matcher<To>(Implementation);
  }

  /// Forwards the call to the underlying MatcherInterface<T> pointer.
  bool matches(const T &Node,
               ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const {
    return Implementation.matches(ast_type_traits::DynTypedNode::create(Node),
                                  Finder, Builder);
  }

  /// Returns an ID that uniquely identifies the matcher.
  DynTypedMatcher::MatcherIDType getID() const {
    return Implementation.getID();
  }

  /// Extract the dynamic matcher.
  ///
  /// The returned matcher keeps the same restrictions as \c this and remembers
  /// that it is meant to support nodes of type \c T.
  operator DynTypedMatcher() const { return Implementation; }

  /// Allows the conversion of a \c Matcher<Type> to a \c
  /// Matcher<QualType>.
  ///
  /// Depending on the constructor argument, the matcher is either strict, i.e.
  /// does only matches in the absence of qualifiers, or not, i.e. simply
  /// ignores any qualifiers.
  template <typename TypeT>
  class TypeToQualType : public WrapperMatcherInterface<QualType> {
  public:
    TypeToQualType(const Matcher<TypeT> &InnerMatcher)
        : TypeToQualType::WrapperMatcherInterface(InnerMatcher) {}

    bool matches(const QualType &Node, ASTMatchFinder *Finder,
                 BoundNodesTreeBuilder *Builder) const override {
      if (Node.isNull())
        return false;
      return this->InnerMatcher.matches(
          ast_type_traits::DynTypedNode::create(*Node), Finder, Builder);
    }
  };

private:
  // For Matcher<T> <=> Matcher<U> conversions.
  template <typename U> friend class Matcher;

  // For DynTypedMatcher::unconditionalConvertTo<T>.
  friend class DynTypedMatcher;

  static DynTypedMatcher restrictMatcher(const DynTypedMatcher &Other) {
    return Other.dynCastTo(ast_type_traits::ASTNodeKind::getFromNodeKind<T>());
  }

  explicit Matcher(const DynTypedMatcher &Implementation)
      : Implementation(restrictMatcher(Implementation)) {
    assert(this->Implementation.getSupportedKind()
               .isSame(ast_type_traits::ASTNodeKind::getFromNodeKind<T>()));
  }

  DynTypedMatcher Implementation;
};  // class Matcher

/// A convenient helper for creating a Matcher<T> without specifying
/// the template type argument.
template <typename T>
inline Matcher<T> makeMatcher(MatcherInterface<T> *Implementation) {
  return Matcher<T>(Implementation);
}

/// Specialization of the conversion functions for QualType.
///
/// This specialization provides the Matcher<Type>->Matcher<QualType>
/// conversion that the static API does.
template <>
inline Matcher<QualType> DynTypedMatcher::convertTo<QualType>() const {
  assert(canConvertTo<QualType>());
  const ast_type_traits::ASTNodeKind SourceKind = getSupportedKind();
  if (SourceKind.isSame(
          ast_type_traits::ASTNodeKind::getFromNodeKind<Type>())) {
    // We support implicit conversion from Matcher<Type> to Matcher<QualType>
    return unconditionalConvertTo<Type>();
  }
  return unconditionalConvertTo<QualType>();
}

/// Finds the first node in a range that matches the given matcher.
template <typename MatcherT, typename IteratorT>
bool matchesFirstInRange(const MatcherT &Matcher, IteratorT Start,
                         IteratorT End, ASTMatchFinder *Finder,
                         BoundNodesTreeBuilder *Builder) {
  for (IteratorT I = Start; I != End; ++I) {
    BoundNodesTreeBuilder Result(*Builder);
    if (Matcher.matches(*I, Finder, &Result)) {
      *Builder = std::move(Result);
      return true;
    }
  }
  return false;
}

/// Finds the first node in a pointer range that matches the given
/// matcher.
template <typename MatcherT, typename IteratorT>
bool matchesFirstInPointerRange(const MatcherT &Matcher, IteratorT Start,
                                IteratorT End, ASTMatchFinder *Finder,
                                BoundNodesTreeBuilder *Builder) {
  for (IteratorT I = Start; I != End; ++I) {
    BoundNodesTreeBuilder Result(*Builder);
    if (Matcher.matches(**I, Finder, &Result)) {
      *Builder = std::move(Result);
      return true;
    }
  }
  return false;
}

// Metafunction to determine if type T has a member called getDecl.
template <typename Ty>
class has_getDecl {
  using yes = char[1];
  using no = char[2];

  template <typename Inner>
  static yes& test(Inner *I, decltype(I->getDecl()) * = nullptr);

  template <typename>
  static no& test(...);

public:
  static const bool value = sizeof(test<Ty>(nullptr)) == sizeof(yes);
};

/// Matches overloaded operators with a specific name.
///
/// The type argument ArgT is not used by this matcher but is used by
/// PolymorphicMatcherWithParam1 and should be StringRef.
template <typename T, typename ArgT>
class HasOverloadedOperatorNameMatcher : public SingleNodeMatcherInterface<T> {
  static_assert(std::is_same<T, CXXOperatorCallExpr>::value ||
                std::is_base_of<FunctionDecl, T>::value,
                "unsupported class for matcher");
  static_assert(std::is_same<ArgT, StringRef>::value,
                "argument type must be StringRef");

public:
  explicit HasOverloadedOperatorNameMatcher(const StringRef Name)
      : SingleNodeMatcherInterface<T>(), Name(Name) {}

  bool matchesNode(const T &Node) const override {
    return matchesSpecialized(Node);
  }

private:

  /// CXXOperatorCallExpr exist only for calls to overloaded operators
  /// so this function returns true if the call is to an operator of the given
  /// name.
  bool matchesSpecialized(const CXXOperatorCallExpr &Node) const {
    return getOperatorSpelling(Node.getOperator()) == Name;
  }

  /// Returns true only if CXXMethodDecl represents an overloaded
  /// operator and has the given operator name.
  bool matchesSpecialized(const FunctionDecl &Node) const {
    return Node.isOverloadedOperator() &&
           getOperatorSpelling(Node.getOverloadedOperator()) == Name;
  }

  std::string Name;
};

/// Matches named declarations with a specific name.
///
/// See \c hasName() and \c hasAnyName() in ASTMatchers.h for details.
class HasNameMatcher : public SingleNodeMatcherInterface<NamedDecl> {
 public:
  explicit HasNameMatcher(std::vector<std::string> Names);

  bool matchesNode(const NamedDecl &Node) const override;

 private:
  /// Unqualified match routine.
  ///
  /// It is much faster than the full match, but it only works for unqualified
  /// matches.
  bool matchesNodeUnqualified(const NamedDecl &Node) const;

  /// Full match routine
  ///
  /// Fast implementation for the simple case of a named declaration at
  /// namespace or RecordDecl scope.
  /// It is slower than matchesNodeUnqualified, but faster than
  /// matchesNodeFullSlow.
  bool matchesNodeFullFast(const NamedDecl &Node) const;

  /// Full match routine
  ///
  /// It generates the fully qualified name of the declaration (which is
  /// expensive) before trying to match.
  /// It is slower but simple and works on all cases.
  bool matchesNodeFullSlow(const NamedDecl &Node) const;

  const bool UseUnqualifiedMatch;
  const std::vector<std::string> Names;
};

/// Trampoline function to use VariadicFunction<> to construct a
///        HasNameMatcher.
Matcher<NamedDecl> hasAnyNameFunc(ArrayRef<const StringRef *> NameRefs);

/// Trampoline function to use VariadicFunction<> to construct a
///        hasAnySelector matcher.
Matcher<ObjCMessageExpr> hasAnySelectorFunc(
    ArrayRef<const StringRef *> NameRefs);

/// Matches declarations for QualType and CallExpr.
///
/// Type argument DeclMatcherT is required by PolymorphicMatcherWithParam1 but
/// not actually used.
template <typename T, typename DeclMatcherT>
class HasDeclarationMatcher : public WrapperMatcherInterface<T> {
  static_assert(std::is_same<DeclMatcherT, Matcher<Decl>>::value,
                "instantiated with wrong types");

public:
  explicit HasDeclarationMatcher(const Matcher<Decl> &InnerMatcher)
      : HasDeclarationMatcher::WrapperMatcherInterface(InnerMatcher) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    return matchesSpecialized(Node, Finder, Builder);
  }

private:
  /// Forwards to matching on the underlying type of the QualType.
  bool matchesSpecialized(const QualType &Node, ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    if (Node.isNull())
      return false;

    return matchesSpecialized(*Node, Finder, Builder);
  }

  /// Finds the best declaration for a type and returns whether the inner
  /// matcher matches on it.
  bool matchesSpecialized(const Type &Node, ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    // DeducedType does not have declarations of its own, so
    // match the deduced type instead.
    const Type *EffectiveType = &Node;
    if (const auto *S = dyn_cast<DeducedType>(&Node)) {
      EffectiveType = S->getDeducedType().getTypePtrOrNull();
      if (!EffectiveType)
        return false;
    }

    // First, for any types that have a declaration, extract the declaration and
    // match on it.
    if (const auto *S = dyn_cast<TagType>(EffectiveType)) {
      return matchesDecl(S->getDecl(), Finder, Builder);
    }
    if (const auto *S = dyn_cast<InjectedClassNameType>(EffectiveType)) {
      return matchesDecl(S->getDecl(), Finder, Builder);
    }
    if (const auto *S = dyn_cast<TemplateTypeParmType>(EffectiveType)) {
      return matchesDecl(S->getDecl(), Finder, Builder);
    }
    if (const auto *S = dyn_cast<TypedefType>(EffectiveType)) {
      return matchesDecl(S->getDecl(), Finder, Builder);
    }
    if (const auto *S = dyn_cast<UnresolvedUsingType>(EffectiveType)) {
      return matchesDecl(S->getDecl(), Finder, Builder);
    }
    if (const auto *S = dyn_cast<ObjCObjectType>(EffectiveType)) {
      return matchesDecl(S->getInterface(), Finder, Builder);
    }

    // A SubstTemplateTypeParmType exists solely to mark a type substitution
    // on the instantiated template. As users usually want to match the
    // template parameter on the uninitialized template, we can always desugar
    // one level without loss of expressivness.
    // For example, given:
    //   template<typename T> struct X { T t; } class A {}; X<A> a;
    // The following matcher will match, which otherwise would not:
    //   fieldDecl(hasType(pointerType())).
    if (const auto *S = dyn_cast<SubstTemplateTypeParmType>(EffectiveType)) {
      return matchesSpecialized(S->getReplacementType(), Finder, Builder);
    }

    // For template specialization types, we want to match the template
    // declaration, as long as the type is still dependent, and otherwise the
    // declaration of the instantiated tag type.
    if (const auto *S = dyn_cast<TemplateSpecializationType>(EffectiveType)) {
      if (!S->isTypeAlias() && S->isSugared()) {
        // If the template is non-dependent, we want to match the instantiated
        // tag type.
        // For example, given:
        //   template<typename T> struct X {}; X<int> a;
        // The following matcher will match, which otherwise would not:
        //   templateSpecializationType(hasDeclaration(cxxRecordDecl())).
        return matchesSpecialized(*S->desugar(), Finder, Builder);
      }
      // If the template is dependent or an alias, match the template
      // declaration.
      return matchesDecl(S->getTemplateName().getAsTemplateDecl(), Finder,
                         Builder);
    }

    // FIXME: We desugar elaborated types. This makes the assumption that users
    // do never want to match on whether a type is elaborated - there are
    // arguments for both sides; for now, continue desugaring.
    if (const auto *S = dyn_cast<ElaboratedType>(EffectiveType)) {
      return matchesSpecialized(S->desugar(), Finder, Builder);
    }
    return false;
  }

  /// Extracts the Decl the DeclRefExpr references and returns whether
  /// the inner matcher matches on it.
  bool matchesSpecialized(const DeclRefExpr &Node, ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getDecl(), Finder, Builder);
  }

  /// Extracts the Decl of the callee of a CallExpr and returns whether
  /// the inner matcher matches on it.
  bool matchesSpecialized(const CallExpr &Node, ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getCalleeDecl(), Finder, Builder);
  }

  /// Extracts the Decl of the constructor call and returns whether the
  /// inner matcher matches on it.
  bool matchesSpecialized(const CXXConstructExpr &Node,
                          ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getConstructor(), Finder, Builder);
  }

  bool matchesSpecialized(const ObjCIvarRefExpr &Node,
                          ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getDecl(), Finder, Builder);
  }

  /// Extracts the operator new of the new call and returns whether the
  /// inner matcher matches on it.
  bool matchesSpecialized(const CXXNewExpr &Node,
                          ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getOperatorNew(), Finder, Builder);
  }

  /// Extracts the \c ValueDecl a \c MemberExpr refers to and returns
  /// whether the inner matcher matches on it.
  bool matchesSpecialized(const MemberExpr &Node,
                          ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getMemberDecl(), Finder, Builder);
  }

  /// Extracts the \c LabelDecl a \c AddrLabelExpr refers to and returns
  /// whether the inner matcher matches on it.
  bool matchesSpecialized(const AddrLabelExpr &Node,
                          ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getLabel(), Finder, Builder);
  }

  /// Extracts the declaration of a LabelStmt and returns whether the
  /// inner matcher matches on it.
  bool matchesSpecialized(const LabelStmt &Node, ASTMatchFinder *Finder,
                          BoundNodesTreeBuilder *Builder) const {
    return matchesDecl(Node.getDecl(), Finder, Builder);
  }

  /// Returns whether the inner matcher \c Node. Returns false if \c Node
  /// is \c NULL.
  bool matchesDecl(const Decl *Node, ASTMatchFinder *Finder,
                   BoundNodesTreeBuilder *Builder) const {
    return Node != nullptr &&
           this->InnerMatcher.matches(
               ast_type_traits::DynTypedNode::create(*Node), Finder, Builder);
  }
};

/// IsBaseType<T>::value is true if T is a "base" type in the AST
/// node class hierarchies.
template <typename T>
struct IsBaseType {
  static const bool value =
      std::is_same<T, Decl>::value ||
      std::is_same<T, Stmt>::value ||
      std::is_same<T, QualType>::value ||
      std::is_same<T, Type>::value ||
      std::is_same<T, TypeLoc>::value ||
      std::is_same<T, NestedNameSpecifier>::value ||
      std::is_same<T, NestedNameSpecifierLoc>::value ||
      std::is_same<T, CXXCtorInitializer>::value;
};
template <typename T>
const bool IsBaseType<T>::value;

/// Interface that allows matchers to traverse the AST.
/// FIXME: Find a better name.
///
/// This provides three entry methods for each base node type in the AST:
/// - \c matchesChildOf:
///   Matches a matcher on every child node of the given node. Returns true
///   if at least one child node could be matched.
/// - \c matchesDescendantOf:
///   Matches a matcher on all descendant nodes of the given node. Returns true
///   if at least one descendant matched.
/// - \c matchesAncestorOf:
///   Matches a matcher on all ancestors of the given node. Returns true if
///   at least one ancestor matched.
///
/// FIXME: Currently we only allow Stmt and Decl nodes to start a traversal.
/// In the future, we want to implement this for all nodes for which it makes
/// sense. In the case of matchesAncestorOf, we'll want to implement it for
/// all nodes, as all nodes have ancestors.
class ASTMatchFinder {
public:

  /// Defines how bindings are processed on recursive matches.
  enum BindKind {
    /// Stop at the first match and only bind the first match.
    BK_First,

    /// Create results for all combinations of bindings that match.
    BK_All
  };

  /// Defines which ancestors are considered for a match.
  enum AncestorMatchMode {
    /// All ancestors.
    AMM_All,

    /// Direct parent only.
    AMM_ParentOnly
  };

  virtual ~ASTMatchFinder() = default;

  /// Returns true if the given class is directly or indirectly derived
  /// from a base type matching \c base.
  ///
  /// A class is considered to be also derived from itself.
  virtual bool classIsDerivedFrom(const CXXRecordDecl *Declaration,
                                  const Matcher<NamedDecl> &Base,
                                  BoundNodesTreeBuilder *Builder) = 0;

  template <typename T>
  bool matchesChildOf(const T &Node, const DynTypedMatcher &Matcher,
                      BoundNodesTreeBuilder *Builder,
                      ast_type_traits::TraversalKind Traverse, BindKind Bind) {
    static_assert(std::is_base_of<Decl, T>::value ||
                  std::is_base_of<Stmt, T>::value ||
                  std::is_base_of<NestedNameSpecifier, T>::value ||
                  std::is_base_of<NestedNameSpecifierLoc, T>::value ||
                  std::is_base_of<TypeLoc, T>::value ||
                  std::is_base_of<QualType, T>::value,
                  "unsupported type for recursive matching");
    return matchesChildOf(ast_type_traits::DynTypedNode::create(Node),
                          Matcher, Builder, Traverse, Bind);
  }

  template <typename T>
  bool matchesDescendantOf(const T &Node,
                           const DynTypedMatcher &Matcher,
                           BoundNodesTreeBuilder *Builder,
                           BindKind Bind) {
    static_assert(std::is_base_of<Decl, T>::value ||
                  std::is_base_of<Stmt, T>::value ||
                  std::is_base_of<NestedNameSpecifier, T>::value ||
                  std::is_base_of<NestedNameSpecifierLoc, T>::value ||
                  std::is_base_of<TypeLoc, T>::value ||
                  std::is_base_of<QualType, T>::value,
                  "unsupported type for recursive matching");
    return matchesDescendantOf(ast_type_traits::DynTypedNode::create(Node),
                               Matcher, Builder, Bind);
  }

  // FIXME: Implement support for BindKind.
  template <typename T>
  bool matchesAncestorOf(const T &Node,
                         const DynTypedMatcher &Matcher,
                         BoundNodesTreeBuilder *Builder,
                         AncestorMatchMode MatchMode) {
    static_assert(std::is_base_of<Decl, T>::value ||
                      std::is_base_of<NestedNameSpecifierLoc, T>::value ||
                      std::is_base_of<Stmt, T>::value ||
                      std::is_base_of<TypeLoc, T>::value,
                  "type not allowed for recursive matching");
    return matchesAncestorOf(ast_type_traits::DynTypedNode::create(Node),
                             Matcher, Builder, MatchMode);
  }

  virtual ASTContext &getASTContext() const = 0;

protected:
  virtual bool matchesChildOf(const ast_type_traits::DynTypedNode &Node,
                              const DynTypedMatcher &Matcher,
                              BoundNodesTreeBuilder *Builder,
                              ast_type_traits::TraversalKind Traverse,
                              BindKind Bind) = 0;

  virtual bool matchesDescendantOf(const ast_type_traits::DynTypedNode &Node,
                                   const DynTypedMatcher &Matcher,
                                   BoundNodesTreeBuilder *Builder,
                                   BindKind Bind) = 0;

  virtual bool matchesAncestorOf(const ast_type_traits::DynTypedNode &Node,
                                 const DynTypedMatcher &Matcher,
                                 BoundNodesTreeBuilder *Builder,
                                 AncestorMatchMode MatchMode) = 0;
};

/// A type-list implementation.
///
/// A "linked list" of types, accessible by using the ::head and ::tail
/// typedefs.
template <typename... Ts> struct TypeList {}; // Empty sentinel type list.

template <typename T1, typename... Ts> struct TypeList<T1, Ts...> {
  /// The first type on the list.
  using head = T1;

  /// A sublist with the tail. ie everything but the head.
  ///
  /// This type is used to do recursion. TypeList<>/EmptyTypeList indicates the
  /// end of the list.
  using tail = TypeList<Ts...>;
};

/// The empty type list.
using EmptyTypeList = TypeList<>;

/// Helper meta-function to determine if some type \c T is present or
///   a parent type in the list.
template <typename AnyTypeList, typename T>
struct TypeListContainsSuperOf {
  static const bool value =
      std::is_base_of<typename AnyTypeList::head, T>::value ||
      TypeListContainsSuperOf<typename AnyTypeList::tail, T>::value;
};
template <typename T>
struct TypeListContainsSuperOf<EmptyTypeList, T> {
  static const bool value = false;
};

/// A "type list" that contains all types.
///
/// Useful for matchers like \c anything and \c unless.
using AllNodeBaseTypes =
    TypeList<Decl, Stmt, NestedNameSpecifier, NestedNameSpecifierLoc, QualType,
             Type, TypeLoc, CXXCtorInitializer>;

/// Helper meta-function to extract the argument out of a function of
///   type void(Arg).
///
/// See AST_POLYMORPHIC_SUPPORTED_TYPES for details.
template <class T> struct ExtractFunctionArgMeta;
template <class T> struct ExtractFunctionArgMeta<void(T)> {
  using type = T;
};

/// Default type lists for ArgumentAdaptingMatcher matchers.
using AdaptativeDefaultFromTypes = AllNodeBaseTypes;
using AdaptativeDefaultToTypes =
    TypeList<Decl, Stmt, NestedNameSpecifier, NestedNameSpecifierLoc, TypeLoc,
             QualType>;

/// All types that are supported by HasDeclarationMatcher above.
using HasDeclarationSupportedTypes =
    TypeList<CallExpr, CXXConstructExpr, CXXNewExpr, DeclRefExpr, EnumType,
             ElaboratedType, InjectedClassNameType, LabelStmt, AddrLabelExpr,
             MemberExpr, QualType, RecordType, TagType,
             TemplateSpecializationType, TemplateTypeParmType, TypedefType,
             UnresolvedUsingType, ObjCIvarRefExpr>;

/// Converts a \c Matcher<T> to a matcher of desired type \c To by
/// "adapting" a \c To into a \c T.
///
/// The \c ArgumentAdapterT argument specifies how the adaptation is done.
///
/// For example:
///   \c ArgumentAdaptingMatcher<HasMatcher, T>(InnerMatcher);
/// Given that \c InnerMatcher is of type \c Matcher<T>, this returns a matcher
/// that is convertible into any matcher of type \c To by constructing
/// \c HasMatcher<To, T>(InnerMatcher).
///
/// If a matcher does not need knowledge about the inner type, prefer to use
/// PolymorphicMatcherWithParam1.
template <template <typename ToArg, typename FromArg> class ArgumentAdapterT,
          typename FromTypes = AdaptativeDefaultFromTypes,
          typename ToTypes = AdaptativeDefaultToTypes>
struct ArgumentAdaptingMatcherFunc {
  template <typename T> class Adaptor {
  public:
    explicit Adaptor(const Matcher<T> &InnerMatcher)
        : InnerMatcher(InnerMatcher) {}

    using ReturnTypes = ToTypes;

    template <typename To> operator Matcher<To>() const {
      return Matcher<To>(new ArgumentAdapterT<To, T>(InnerMatcher));
    }

  private:
    const Matcher<T> InnerMatcher;
  };

  template <typename T>
  static Adaptor<T> create(const Matcher<T> &InnerMatcher) {
    return Adaptor<T>(InnerMatcher);
  }

  template <typename T>
  Adaptor<T> operator()(const Matcher<T> &InnerMatcher) const {
    return create(InnerMatcher);
  }
};

/// A PolymorphicMatcherWithParamN<MatcherT, P1, ..., PN> object can be
/// created from N parameters p1, ..., pN (of type P1, ..., PN) and
/// used as a Matcher<T> where a MatcherT<T, P1, ..., PN>(p1, ..., pN)
/// can be constructed.
///
/// For example:
/// - PolymorphicMatcherWithParam0<IsDefinitionMatcher>()
///   creates an object that can be used as a Matcher<T> for any type T
///   where an IsDefinitionMatcher<T>() can be constructed.
/// - PolymorphicMatcherWithParam1<ValueEqualsMatcher, int>(42)
///   creates an object that can be used as a Matcher<T> for any type T
///   where a ValueEqualsMatcher<T, int>(42) can be constructed.
template <template <typename T> class MatcherT,
          typename ReturnTypesF = void(AllNodeBaseTypes)>
class PolymorphicMatcherWithParam0 {
public:
  using ReturnTypes = typename ExtractFunctionArgMeta<ReturnTypesF>::type;

  template <typename T>
  operator Matcher<T>() const {
    static_assert(TypeListContainsSuperOf<ReturnTypes, T>::value,
                  "right polymorphic conversion");
    return Matcher<T>(new MatcherT<T>());
  }
};

template <template <typename T, typename P1> class MatcherT,
          typename P1,
          typename ReturnTypesF = void(AllNodeBaseTypes)>
class PolymorphicMatcherWithParam1 {
public:
  explicit PolymorphicMatcherWithParam1(const P1 &Param1)
      : Param1(Param1) {}

  using ReturnTypes = typename ExtractFunctionArgMeta<ReturnTypesF>::type;

  template <typename T>
  operator Matcher<T>() const {
    static_assert(TypeListContainsSuperOf<ReturnTypes, T>::value,
                  "right polymorphic conversion");
    return Matcher<T>(new MatcherT<T, P1>(Param1));
  }

private:
  const P1 Param1;
};

template <template <typename T, typename P1, typename P2> class MatcherT,
          typename P1, typename P2,
          typename ReturnTypesF = void(AllNodeBaseTypes)>
class PolymorphicMatcherWithParam2 {
public:
  PolymorphicMatcherWithParam2(const P1 &Param1, const P2 &Param2)
      : Param1(Param1), Param2(Param2) {}

  using ReturnTypes = typename ExtractFunctionArgMeta<ReturnTypesF>::type;

  template <typename T>
  operator Matcher<T>() const {
    static_assert(TypeListContainsSuperOf<ReturnTypes, T>::value,
                  "right polymorphic conversion");
    return Matcher<T>(new MatcherT<T, P1, P2>(Param1, Param2));
  }

private:
  const P1 Param1;
  const P2 Param2;
};

/// Matches any instance of the given NodeType.
///
/// This is useful when a matcher syntactically requires a child matcher,
/// but the context doesn't care. See for example: anything().
class TrueMatcher {
public:
  using ReturnTypes = AllNodeBaseTypes;

  template <typename T>
  operator Matcher<T>() const {
    return DynTypedMatcher::trueMatcher(
               ast_type_traits::ASTNodeKind::getFromNodeKind<T>())
        .template unconditionalConvertTo<T>();
  }
};

/// A Matcher that allows binding the node it matches to an id.
///
/// BindableMatcher provides a \a bind() method that allows binding the
/// matched node to an id if the match was successful.
template <typename T>
class BindableMatcher : public Matcher<T> {
public:
  explicit BindableMatcher(const Matcher<T> &M) : Matcher<T>(M) {}
  explicit BindableMatcher(MatcherInterface<T> *Implementation)
    : Matcher<T>(Implementation) {}

  /// Returns a matcher that will bind the matched node on a match.
  ///
  /// The returned matcher is equivalent to this matcher, but will
  /// bind the matched node on a match.
  Matcher<T> bind(StringRef ID) const {
    return DynTypedMatcher(*this)
        .tryBind(ID)
        ->template unconditionalConvertTo<T>();
  }

  /// Same as Matcher<T>'s conversion operator, but enables binding on
  /// the returned matcher.
  operator DynTypedMatcher() const {
    DynTypedMatcher Result = static_cast<const Matcher<T>&>(*this);
    Result.setAllowBind(true);
    return Result;
  }
};

/// Matches nodes of type T that have child nodes of type ChildT for
/// which a specified child matcher matches.
///
/// ChildT must be an AST base type.
template <typename T, typename ChildT>
class HasMatcher : public WrapperMatcherInterface<T> {
public:
  explicit HasMatcher(const Matcher<ChildT> &ChildMatcher)
      : HasMatcher::WrapperMatcherInterface(ChildMatcher) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    return Finder->matchesChildOf(Node, this->InnerMatcher, Builder,
                                  ast_type_traits::TraversalKind::TK_AsIs,
                                  ASTMatchFinder::BK_First);
  }
};

/// Matches nodes of type T that have child nodes of type ChildT for
/// which a specified child matcher matches. ChildT must be an AST base
/// type.
/// As opposed to the HasMatcher, the ForEachMatcher will produce a match
/// for each child that matches.
template <typename T, typename ChildT>
class ForEachMatcher : public WrapperMatcherInterface<T> {
  static_assert(IsBaseType<ChildT>::value,
                "for each only accepts base type matcher");

 public:
   explicit ForEachMatcher(const Matcher<ChildT> &ChildMatcher)
       : ForEachMatcher::WrapperMatcherInterface(ChildMatcher) {}

  bool matches(const T& Node, ASTMatchFinder* Finder,
               BoundNodesTreeBuilder* Builder) const override {
    return Finder->matchesChildOf(
        Node, this->InnerMatcher, Builder,
        ast_type_traits::TraversalKind::TK_IgnoreImplicitCastsAndParentheses,
        ASTMatchFinder::BK_All);
  }
};

/// VariadicOperatorMatcher related types.
/// @{

/// Polymorphic matcher object that uses a \c
/// DynTypedMatcher::VariadicOperator operator.
///
/// Input matchers can have any type (including other polymorphic matcher
/// types), and the actual Matcher<T> is generated on demand with an implicit
/// coversion operator.
template <typename... Ps> class VariadicOperatorMatcher {
public:
  VariadicOperatorMatcher(DynTypedMatcher::VariadicOperator Op, Ps &&... Params)
      : Op(Op), Params(std::forward<Ps>(Params)...) {}

  template <typename T> operator Matcher<T>() const {
    return DynTypedMatcher::constructVariadic(
               Op, ast_type_traits::ASTNodeKind::getFromNodeKind<T>(),
               getMatchers<T>(llvm::index_sequence_for<Ps...>()))
        .template unconditionalConvertTo<T>();
  }

private:
  // Helper method to unpack the tuple into a vector.
  template <typename T, std::size_t... Is>
  std::vector<DynTypedMatcher> getMatchers(llvm::index_sequence<Is...>) const {
    return {Matcher<T>(std::get<Is>(Params))...};
  }

  const DynTypedMatcher::VariadicOperator Op;
  std::tuple<Ps...> Params;
};

/// Overloaded function object to generate VariadicOperatorMatcher
///   objects from arbitrary matchers.
template <unsigned MinCount, unsigned MaxCount>
struct VariadicOperatorMatcherFunc {
  DynTypedMatcher::VariadicOperator Op;

  template <typename... Ms>
  VariadicOperatorMatcher<Ms...> operator()(Ms &&... Ps) const {
    static_assert(MinCount <= sizeof...(Ms) && sizeof...(Ms) <= MaxCount,
                  "invalid number of parameters for variadic matcher");
    return VariadicOperatorMatcher<Ms...>(Op, std::forward<Ms>(Ps)...);
  }
};

/// @}

template <typename T>
inline Matcher<T> DynTypedMatcher::unconditionalConvertTo() const {
  return Matcher<T>(*this);
}

/// Creates a Matcher<T> that matches if all inner matchers match.
template<typename T>
BindableMatcher<T> makeAllOfComposite(
    ArrayRef<const Matcher<T> *> InnerMatchers) {
  // For the size() == 0 case, we return a "true" matcher.
  if (InnerMatchers.empty()) {
    return BindableMatcher<T>(TrueMatcher());
  }
  // For the size() == 1 case, we simply return that one matcher.
  // No need to wrap it in a variadic operation.
  if (InnerMatchers.size() == 1) {
    return BindableMatcher<T>(*InnerMatchers[0]);
  }

  using PI = llvm::pointee_iterator<const Matcher<T> *const *>;

  std::vector<DynTypedMatcher> DynMatchers(PI(InnerMatchers.begin()),
                                           PI(InnerMatchers.end()));
  return BindableMatcher<T>(
      DynTypedMatcher::constructVariadic(
          DynTypedMatcher::VO_AllOf,
          ast_type_traits::ASTNodeKind::getFromNodeKind<T>(),
          std::move(DynMatchers))
          .template unconditionalConvertTo<T>());
}

/// Creates a Matcher<T> that matches if
/// T is dyn_cast'able into InnerT and all inner matchers match.
///
/// Returns BindableMatcher, as matchers that use dyn_cast have
/// the same object both to match on and to run submatchers on,
/// so there is no ambiguity with what gets bound.
template<typename T, typename InnerT>
BindableMatcher<T> makeDynCastAllOfComposite(
    ArrayRef<const Matcher<InnerT> *> InnerMatchers) {
  return BindableMatcher<T>(
      makeAllOfComposite(InnerMatchers).template dynCastTo<T>());
}

/// Matches nodes of type T that have at least one descendant node of
/// type DescendantT for which the given inner matcher matches.
///
/// DescendantT must be an AST base type.
template <typename T, typename DescendantT>
class HasDescendantMatcher : public WrapperMatcherInterface<T> {
  static_assert(IsBaseType<DescendantT>::value,
                "has descendant only accepts base type matcher");

public:
  explicit HasDescendantMatcher(const Matcher<DescendantT> &DescendantMatcher)
      : HasDescendantMatcher::WrapperMatcherInterface(DescendantMatcher) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    return Finder->matchesDescendantOf(Node, this->InnerMatcher, Builder,
                                       ASTMatchFinder::BK_First);
  }
};

/// Matches nodes of type \c T that have a parent node of type \c ParentT
/// for which the given inner matcher matches.
///
/// \c ParentT must be an AST base type.
template <typename T, typename ParentT>
class HasParentMatcher : public WrapperMatcherInterface<T> {
  static_assert(IsBaseType<ParentT>::value,
                "has parent only accepts base type matcher");

public:
  explicit HasParentMatcher(const Matcher<ParentT> &ParentMatcher)
      : HasParentMatcher::WrapperMatcherInterface(ParentMatcher) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    return Finder->matchesAncestorOf(Node, this->InnerMatcher, Builder,
                                     ASTMatchFinder::AMM_ParentOnly);
  }
};

/// Matches nodes of type \c T that have at least one ancestor node of
/// type \c AncestorT for which the given inner matcher matches.
///
/// \c AncestorT must be an AST base type.
template <typename T, typename AncestorT>
class HasAncestorMatcher : public WrapperMatcherInterface<T> {
  static_assert(IsBaseType<AncestorT>::value,
                "has ancestor only accepts base type matcher");

public:
  explicit HasAncestorMatcher(const Matcher<AncestorT> &AncestorMatcher)
      : HasAncestorMatcher::WrapperMatcherInterface(AncestorMatcher) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    return Finder->matchesAncestorOf(Node, this->InnerMatcher, Builder,
                                     ASTMatchFinder::AMM_All);
  }
};

/// Matches nodes of type T that have at least one descendant node of
/// type DescendantT for which the given inner matcher matches.
///
/// DescendantT must be an AST base type.
/// As opposed to HasDescendantMatcher, ForEachDescendantMatcher will match
/// for each descendant node that matches instead of only for the first.
template <typename T, typename DescendantT>
class ForEachDescendantMatcher : public WrapperMatcherInterface<T> {
  static_assert(IsBaseType<DescendantT>::value,
                "for each descendant only accepts base type matcher");

public:
  explicit ForEachDescendantMatcher(
      const Matcher<DescendantT> &DescendantMatcher)
      : ForEachDescendantMatcher::WrapperMatcherInterface(DescendantMatcher) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    return Finder->matchesDescendantOf(Node, this->InnerMatcher, Builder,
                                       ASTMatchFinder::BK_All);
  }
};

/// Matches on nodes that have a getValue() method if getValue() equals
/// the value the ValueEqualsMatcher was constructed with.
template <typename T, typename ValueT>
class ValueEqualsMatcher : public SingleNodeMatcherInterface<T> {
  static_assert(std::is_base_of<CharacterLiteral, T>::value ||
                std::is_base_of<CXXBoolLiteralExpr, T>::value ||
                std::is_base_of<FloatingLiteral, T>::value ||
                std::is_base_of<IntegerLiteral, T>::value,
                "the node must have a getValue method");

public:
  explicit ValueEqualsMatcher(const ValueT &ExpectedValue)
      : ExpectedValue(ExpectedValue) {}

  bool matchesNode(const T &Node) const override {
    return Node.getValue() == ExpectedValue;
  }

private:
  const ValueT ExpectedValue;
};

/// Template specializations to easily write matchers for floating point
/// literals.
template <>
inline bool ValueEqualsMatcher<FloatingLiteral, double>::matchesNode(
    const FloatingLiteral &Node) const {
  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEsingle())
    return Node.getValue().convertToFloat() == ExpectedValue;
  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEdouble())
    return Node.getValue().convertToDouble() == ExpectedValue;
  return false;
}
template <>
inline bool ValueEqualsMatcher<FloatingLiteral, float>::matchesNode(
    const FloatingLiteral &Node) const {
  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEsingle())
    return Node.getValue().convertToFloat() == ExpectedValue;
  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEdouble())
    return Node.getValue().convertToDouble() == ExpectedValue;
  return false;
}
template <>
inline bool ValueEqualsMatcher<FloatingLiteral, llvm::APFloat>::matchesNode(
    const FloatingLiteral &Node) const {
  return ExpectedValue.compare(Node.getValue()) == llvm::APFloat::cmpEqual;
}

/// A VariadicDynCastAllOfMatcher<SourceT, TargetT> object is a
/// variadic functor that takes a number of Matcher<TargetT> and returns a
/// Matcher<SourceT> that matches TargetT nodes that are matched by all of the
/// given matchers, if SourceT can be dynamically casted into TargetT.
///
/// For example:
///   const VariadicDynCastAllOfMatcher<Decl, CXXRecordDecl> record;
/// Creates a functor record(...) that creates a Matcher<Decl> given
/// a variable number of arguments of type Matcher<CXXRecordDecl>.
/// The returned matcher matches if the given Decl can by dynamically
/// casted to CXXRecordDecl and all given matchers match.
template <typename SourceT, typename TargetT>
class VariadicDynCastAllOfMatcher
    : public VariadicFunction<BindableMatcher<SourceT>, Matcher<TargetT>,
                              makeDynCastAllOfComposite<SourceT, TargetT>> {
public:
  VariadicDynCastAllOfMatcher() {}
};

/// A \c VariadicAllOfMatcher<T> object is a variadic functor that takes
/// a number of \c Matcher<T> and returns a \c Matcher<T> that matches \c T
/// nodes that are matched by all of the given matchers.
///
/// For example:
///   const VariadicAllOfMatcher<NestedNameSpecifier> nestedNameSpecifier;
/// Creates a functor nestedNameSpecifier(...) that creates a
/// \c Matcher<NestedNameSpecifier> given a variable number of arguments of type
/// \c Matcher<NestedNameSpecifier>.
/// The returned matcher matches if all given matchers match.
template <typename T>
class VariadicAllOfMatcher
    : public VariadicFunction<BindableMatcher<T>, Matcher<T>,
                              makeAllOfComposite<T>> {
public:
  VariadicAllOfMatcher() {}
};

/// Matches nodes of type \c TLoc for which the inner
/// \c Matcher<T> matches.
template <typename TLoc, typename T>
class LocMatcher : public WrapperMatcherInterface<TLoc> {
public:
  explicit LocMatcher(const Matcher<T> &InnerMatcher)
      : LocMatcher::WrapperMatcherInterface(InnerMatcher) {}

  bool matches(const TLoc &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    if (!Node)
      return false;
    return this->InnerMatcher.matches(extract(Node), Finder, Builder);
  }

private:
  static ast_type_traits::DynTypedNode
  extract(const NestedNameSpecifierLoc &Loc) {
    return ast_type_traits::DynTypedNode::create(*Loc.getNestedNameSpecifier());
  }
};

/// Matches \c TypeLocs based on an inner matcher matching a certain
/// \c QualType.
///
/// Used to implement the \c loc() matcher.
class TypeLocTypeMatcher : public WrapperMatcherInterface<TypeLoc> {
public:
  explicit TypeLocTypeMatcher(const Matcher<QualType> &InnerMatcher)
      : TypeLocTypeMatcher::WrapperMatcherInterface(InnerMatcher) {}

  bool matches(const TypeLoc &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    if (!Node)
      return false;
    return this->InnerMatcher.matches(
        ast_type_traits::DynTypedNode::create(Node.getType()), Finder, Builder);
  }
};

/// Matches nodes of type \c T for which the inner matcher matches on a
/// another node of type \c T that can be reached using a given traverse
/// function.
template <typename T>
class TypeTraverseMatcher : public WrapperMatcherInterface<T> {
public:
  explicit TypeTraverseMatcher(const Matcher<QualType> &InnerMatcher,
                               QualType (T::*TraverseFunction)() const)
      : TypeTraverseMatcher::WrapperMatcherInterface(InnerMatcher),
        TraverseFunction(TraverseFunction) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    QualType NextNode = (Node.*TraverseFunction)();
    if (NextNode.isNull())
      return false;
    return this->InnerMatcher.matches(
        ast_type_traits::DynTypedNode::create(NextNode), Finder, Builder);
  }

private:
  QualType (T::*TraverseFunction)() const;
};

/// Matches nodes of type \c T in a ..Loc hierarchy, for which the inner
/// matcher matches on a another node of type \c T that can be reached using a
/// given traverse function.
template <typename T>
class TypeLocTraverseMatcher : public WrapperMatcherInterface<T> {
public:
  explicit TypeLocTraverseMatcher(const Matcher<TypeLoc> &InnerMatcher,
                                  TypeLoc (T::*TraverseFunction)() const)
      : TypeLocTraverseMatcher::WrapperMatcherInterface(InnerMatcher),
        TraverseFunction(TraverseFunction) {}

  bool matches(const T &Node, ASTMatchFinder *Finder,
               BoundNodesTreeBuilder *Builder) const override {
    TypeLoc NextNode = (Node.*TraverseFunction)();
    if (!NextNode)
      return false;
    return this->InnerMatcher.matches(
        ast_type_traits::DynTypedNode::create(NextNode), Finder, Builder);
  }

private:
  TypeLoc (T::*TraverseFunction)() const;
};

/// Converts a \c Matcher<InnerT> to a \c Matcher<OuterT>, where
/// \c OuterT is any type that is supported by \c Getter.
///
/// \code Getter<OuterT>::value() \endcode returns a
/// \code InnerTBase (OuterT::*)() \endcode, which is used to adapt a \c OuterT
/// object into a \c InnerT
template <typename InnerTBase,
          template <typename OuterT> class Getter,
          template <typename OuterT> class MatcherImpl,
          typename ReturnTypesF>
class TypeTraversePolymorphicMatcher {
private:
  using Self = TypeTraversePolymorphicMatcher<InnerTBase, Getter, MatcherImpl,
                                              ReturnTypesF>;

  static Self create(ArrayRef<const Matcher<InnerTBase> *> InnerMatchers);

public:
  using ReturnTypes = typename ExtractFunctionArgMeta<ReturnTypesF>::type;

  explicit TypeTraversePolymorphicMatcher(
      ArrayRef<const Matcher<InnerTBase> *> InnerMatchers)
      : InnerMatcher(makeAllOfComposite(InnerMatchers)) {}

  template <typename OuterT> operator Matcher<OuterT>() const {
    return Matcher<OuterT>(
        new MatcherImpl<OuterT>(InnerMatcher, Getter<OuterT>::value()));
  }

  struct Func
      : public VariadicFunction<Self, Matcher<InnerTBase>, &Self::create> {
    Func() {}
  };

private:
  const Matcher<InnerTBase> InnerMatcher;
};

/// A simple memoizer of T(*)() functions.
///
/// It will call the passed 'Func' template parameter at most once.
/// Used to support AST_MATCHER_FUNCTION() macro.
template <typename Matcher, Matcher (*Func)()> class MemoizedMatcher {
  struct Wrapper {
    Wrapper() : M(Func()) {}

    Matcher M;
  };

public:
  static const Matcher &getInstance() {
    static llvm::ManagedStatic<Wrapper> Instance;
    return Instance->M;
  }
};

// Define the create() method out of line to silence a GCC warning about
// the struct "Func" having greater visibility than its base, which comes from
// using the flag -fvisibility-inlines-hidden.
template <typename InnerTBase, template <typename OuterT> class Getter,
          template <typename OuterT> class MatcherImpl, typename ReturnTypesF>
TypeTraversePolymorphicMatcher<InnerTBase, Getter, MatcherImpl, ReturnTypesF>
TypeTraversePolymorphicMatcher<
    InnerTBase, Getter, MatcherImpl,
    ReturnTypesF>::create(ArrayRef<const Matcher<InnerTBase> *> InnerMatchers) {
  return Self(InnerMatchers);
}

// FIXME: unify ClassTemplateSpecializationDecl and TemplateSpecializationType's
// APIs for accessing the template argument list.
inline ArrayRef<TemplateArgument>
getTemplateSpecializationArgs(const ClassTemplateSpecializationDecl &D) {
  return D.getTemplateArgs().asArray();
}

inline ArrayRef<TemplateArgument>
getTemplateSpecializationArgs(const TemplateSpecializationType &T) {
  return llvm::makeArrayRef(T.getArgs(), T.getNumArgs());
}

inline ArrayRef<TemplateArgument>
getTemplateSpecializationArgs(const FunctionDecl &FD) {
  if (const auto* TemplateArgs = FD.getTemplateSpecializationArgs())
    return TemplateArgs->asArray();
  return ArrayRef<TemplateArgument>();
}

struct NotEqualsBoundNodePredicate {
  bool operator()(const internal::BoundNodesMap &Nodes) const {
    return Nodes.getNode(ID) != Node;
  }

  std::string ID;
  ast_type_traits::DynTypedNode Node;
};

template <typename Ty>
struct GetBodyMatcher {
  static const Stmt *get(const Ty &Node) {
    return Node.getBody();
  }
};

template <>
inline const Stmt *GetBodyMatcher<FunctionDecl>::get(const FunctionDecl &Node) {
  return Node.doesThisDeclarationHaveABody() ? Node.getBody() : nullptr;
}

template <typename Ty>
struct HasSizeMatcher {
  static bool hasSize(const Ty &Node, unsigned int N) {
    return Node.getSize() == N;
  }
};

template <>
inline bool HasSizeMatcher<StringLiteral>::hasSize(
    const StringLiteral &Node, unsigned int N) {
  return Node.getLength() == N;
}

template <typename Ty>
struct GetSourceExpressionMatcher {
  static const Expr *get(const Ty &Node) {
    return Node.getSubExpr();
  }
};

template <>
inline const Expr *GetSourceExpressionMatcher<OpaqueValueExpr>::get(
    const OpaqueValueExpr &Node) {
  return Node.getSourceExpr();
}

template <typename Ty>
struct CompoundStmtMatcher {
  static const CompoundStmt *get(const Ty &Node) {
    return &Node;
  }
};

template <>
inline const CompoundStmt *
CompoundStmtMatcher<StmtExpr>::get(const StmtExpr &Node) {
  return Node.getSubStmt();
}

} // namespace internal

} // namespace ast_matchers

} // namespace clang

#endif // LLVM_CLANG_ASTMATCHERS_ASTMATCHERSINTERNAL_H