1 //===- NestedNameSpecifier.cpp - C++ nested name specifiers ---------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //  This file defines the NestedNameSpecifier class, which represents
11 //  a C++ nested-name-specifier.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/AST/NestedNameSpecifier.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/Decl.h"
18 #include "clang/AST/DeclCXX.h"
19 #include "clang/AST/PrettyPrinter.h"
20 #include "clang/AST/TemplateName.h"
21 #include "clang/AST/Type.h"
22 #include "clang/AST/TypeLoc.h"
23 #include "clang/Basic/LLVM.h"
24 #include "clang/Basic/LangOptions.h"
25 #include "clang/Basic/SourceLocation.h"
26 #include "llvm/ADT/FoldingSet.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/Support/Casting.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include <algorithm>
33 #include <cassert>
34 #include <cstdlib>
35 #include <cstring>
36 
37 using namespace clang;
38 
39 NestedNameSpecifier *
40 NestedNameSpecifier::FindOrInsert(const ASTContext &Context,
41                                   const NestedNameSpecifier &Mockup) {
42   llvm::FoldingSetNodeID ID;
43   Mockup.Profile(ID);
44 
45   void *InsertPos = nullptr;
46   NestedNameSpecifier *NNS
47     = Context.NestedNameSpecifiers.FindNodeOrInsertPos(ID, InsertPos);
48   if (!NNS) {
49     NNS =
50         new (Context, alignof(NestedNameSpecifier)) NestedNameSpecifier(Mockup);
51     Context.NestedNameSpecifiers.InsertNode(NNS, InsertPos);
52   }
53 
54   return NNS;
55 }
56 
57 NestedNameSpecifier *
58 NestedNameSpecifier::Create(const ASTContext &Context,
59                             NestedNameSpecifier *Prefix, IdentifierInfo *II) {
60   assert(II && "Identifier cannot be NULL");
61   assert((!Prefix || Prefix->isDependent()) && "Prefix must be dependent");
62 
63   NestedNameSpecifier Mockup;
64   Mockup.Prefix.setPointer(Prefix);
65   Mockup.Prefix.setInt(StoredIdentifier);
66   Mockup.Specifier = II;
67   return FindOrInsert(Context, Mockup);
68 }
69 
70 NestedNameSpecifier *
71 NestedNameSpecifier::Create(const ASTContext &Context,
72                             NestedNameSpecifier *Prefix,
73                             const NamespaceDecl *NS) {
74   assert(NS && "Namespace cannot be NULL");
75   assert((!Prefix ||
76           (Prefix->getAsType() == nullptr &&
77            Prefix->getAsIdentifier() == nullptr)) &&
78          "Broken nested name specifier");
79   NestedNameSpecifier Mockup;
80   Mockup.Prefix.setPointer(Prefix);
81   Mockup.Prefix.setInt(StoredDecl);
82   Mockup.Specifier = const_cast<NamespaceDecl *>(NS);
83   return FindOrInsert(Context, Mockup);
84 }
85 
86 NestedNameSpecifier *
87 NestedNameSpecifier::Create(const ASTContext &Context,
88                             NestedNameSpecifier *Prefix,
89                             NamespaceAliasDecl *Alias) {
90   assert(Alias && "Namespace alias cannot be NULL");
91   assert((!Prefix ||
92           (Prefix->getAsType() == nullptr &&
93            Prefix->getAsIdentifier() == nullptr)) &&
94          "Broken nested name specifier");
95   NestedNameSpecifier Mockup;
96   Mockup.Prefix.setPointer(Prefix);
97   Mockup.Prefix.setInt(StoredDecl);
98   Mockup.Specifier = Alias;
99   return FindOrInsert(Context, Mockup);
100 }
101 
102 NestedNameSpecifier *
103 NestedNameSpecifier::Create(const ASTContext &Context,
104                             NestedNameSpecifier *Prefix,
105                             bool Template, const Type *T) {
106   assert(T && "Type cannot be NULL");
107   NestedNameSpecifier Mockup;
108   Mockup.Prefix.setPointer(Prefix);
109   Mockup.Prefix.setInt(Template? StoredTypeSpecWithTemplate : StoredTypeSpec);
110   Mockup.Specifier = const_cast<Type*>(T);
111   return FindOrInsert(Context, Mockup);
112 }
113 
114 NestedNameSpecifier *
115 NestedNameSpecifier::Create(const ASTContext &Context, IdentifierInfo *II) {
116   assert(II && "Identifier cannot be NULL");
117   NestedNameSpecifier Mockup;
118   Mockup.Prefix.setPointer(nullptr);
119   Mockup.Prefix.setInt(StoredIdentifier);
120   Mockup.Specifier = II;
121   return FindOrInsert(Context, Mockup);
122 }
123 
124 NestedNameSpecifier *
125 NestedNameSpecifier::GlobalSpecifier(const ASTContext &Context) {
126   if (!Context.GlobalNestedNameSpecifier)
127     Context.GlobalNestedNameSpecifier =
128         new (Context, alignof(NestedNameSpecifier)) NestedNameSpecifier();
129   return Context.GlobalNestedNameSpecifier;
130 }
131 
132 NestedNameSpecifier *
133 NestedNameSpecifier::SuperSpecifier(const ASTContext &Context,
134                                     CXXRecordDecl *RD) {
135   NestedNameSpecifier Mockup;
136   Mockup.Prefix.setPointer(nullptr);
137   Mockup.Prefix.setInt(StoredDecl);
138   Mockup.Specifier = RD;
139   return FindOrInsert(Context, Mockup);
140 }
141 
142 NestedNameSpecifier::SpecifierKind NestedNameSpecifier::getKind() const {
143   if (!Specifier)
144     return Global;
145 
146   switch (Prefix.getInt()) {
147   case StoredIdentifier:
148     return Identifier;
149 
150   case StoredDecl: {
151     NamedDecl *ND = static_cast<NamedDecl *>(Specifier);
152     if (isa<CXXRecordDecl>(ND))
153       return Super;
154     return isa<NamespaceDecl>(ND) ? Namespace : NamespaceAlias;
155   }
156 
157   case StoredTypeSpec:
158     return TypeSpec;
159 
160   case StoredTypeSpecWithTemplate:
161     return TypeSpecWithTemplate;
162   }
163 
164   llvm_unreachable("Invalid NNS Kind!");
165 }
166 
167 /// Retrieve the namespace stored in this nested name specifier.
168 NamespaceDecl *NestedNameSpecifier::getAsNamespace() const {
169   if (Prefix.getInt() == StoredDecl)
170     return dyn_cast<NamespaceDecl>(static_cast<NamedDecl *>(Specifier));
171 
172   return nullptr;
173 }
174 
175 /// Retrieve the namespace alias stored in this nested name specifier.
176 NamespaceAliasDecl *NestedNameSpecifier::getAsNamespaceAlias() const {
177   if (Prefix.getInt() == StoredDecl)
178     return dyn_cast<NamespaceAliasDecl>(static_cast<NamedDecl *>(Specifier));
179 
180   return nullptr;
181 }
182 
183 /// Retrieve the record declaration stored in this nested name specifier.
184 CXXRecordDecl *NestedNameSpecifier::getAsRecordDecl() const {
185   switch (Prefix.getInt()) {
186   case StoredIdentifier:
187     return nullptr;
188 
189   case StoredDecl:
190     return dyn_cast<CXXRecordDecl>(static_cast<NamedDecl *>(Specifier));
191 
192   case StoredTypeSpec:
193   case StoredTypeSpecWithTemplate:
194     return getAsType()->getAsCXXRecordDecl();
195   }
196 
197   llvm_unreachable("Invalid NNS Kind!");
198 }
199 
200 /// Whether this nested name specifier refers to a dependent
201 /// type or not.
202 bool NestedNameSpecifier::isDependent() const {
203   switch (getKind()) {
204   case Identifier:
205     // Identifier specifiers always represent dependent types
206     return true;
207 
208   case Namespace:
209   case NamespaceAlias:
210   case Global:
211     return false;
212 
213   case Super: {
214     CXXRecordDecl *RD = static_cast<CXXRecordDecl *>(Specifier);
215     for (const auto &Base : RD->bases())
216       if (Base.getType()->isDependentType())
217         return true;
218 
219     return false;
220   }
221 
222   case TypeSpec:
223   case TypeSpecWithTemplate:
224     return getAsType()->isDependentType();
225   }
226 
227   llvm_unreachable("Invalid NNS Kind!");
228 }
229 
230 /// Whether this nested name specifier refers to a dependent
231 /// type or not.
232 bool NestedNameSpecifier::isInstantiationDependent() const {
233   switch (getKind()) {
234   case Identifier:
235     // Identifier specifiers always represent dependent types
236     return true;
237 
238   case Namespace:
239   case NamespaceAlias:
240   case Global:
241   case Super:
242     return false;
243 
244   case TypeSpec:
245   case TypeSpecWithTemplate:
246     return getAsType()->isInstantiationDependentType();
247   }
248 
249   llvm_unreachable("Invalid NNS Kind!");
250 }
251 
252 bool NestedNameSpecifier::containsUnexpandedParameterPack() const {
253   switch (getKind()) {
254   case Identifier:
255     return getPrefix() && getPrefix()->containsUnexpandedParameterPack();
256 
257   case Namespace:
258   case NamespaceAlias:
259   case Global:
260   case Super:
261     return false;
262 
263   case TypeSpec:
264   case TypeSpecWithTemplate:
265     return getAsType()->containsUnexpandedParameterPack();
266   }
267 
268   llvm_unreachable("Invalid NNS Kind!");
269 }
270 
271 /// Print this nested name specifier to the given output
272 /// stream.
273 void
274 NestedNameSpecifier::print(raw_ostream &OS,
275                            const PrintingPolicy &Policy) const {
276   if (getPrefix())
277     getPrefix()->print(OS, Policy);
278 
279   switch (getKind()) {
280   case Identifier:
281     OS << getAsIdentifier()->getName();
282     break;
283 
284   case Namespace:
285     if (getAsNamespace()->isAnonymousNamespace())
286       return;
287 
288     OS << getAsNamespace()->getName();
289     break;
290 
291   case NamespaceAlias:
292     OS << getAsNamespaceAlias()->getName();
293     break;
294 
295   case Global:
296     break;
297 
298   case Super:
299     OS << "__super";
300     break;
301 
302   case TypeSpecWithTemplate:
303     OS << "template ";
304     // Fall through to print the type.
305     LLVM_FALLTHROUGH;
306 
307   case TypeSpec: {
308     const Type *T = getAsType();
309 
310     PrintingPolicy InnerPolicy(Policy);
311     InnerPolicy.SuppressScope = true;
312 
313     // Nested-name-specifiers are intended to contain minimally-qualified
314     // types. An actual ElaboratedType will not occur, since we'll store
315     // just the type that is referred to in the nested-name-specifier (e.g.,
316     // a TypedefType, TagType, etc.). However, when we are dealing with
317     // dependent template-id types (e.g., Outer<T>::template Inner<U>),
318     // the type requires its own nested-name-specifier for uniqueness, so we
319     // suppress that nested-name-specifier during printing.
320     assert(!isa<ElaboratedType>(T) &&
321            "Elaborated type in nested-name-specifier");
322     if (const TemplateSpecializationType *SpecType
323           = dyn_cast<TemplateSpecializationType>(T)) {
324       // Print the template name without its corresponding
325       // nested-name-specifier.
326       SpecType->getTemplateName().print(OS, InnerPolicy, true);
327 
328       // Print the template argument list.
329       printTemplateArgumentList(OS, SpecType->template_arguments(),
330                                 InnerPolicy);
331     } else {
332       // Print the type normally
333       QualType(T, 0).print(OS, InnerPolicy);
334     }
335     break;
336   }
337   }
338 
339   OS << "::";
340 }
341 
342 void NestedNameSpecifier::dump(const LangOptions &LO) const {
343   print(llvm::errs(), PrintingPolicy(LO));
344 }
345 
346 LLVM_DUMP_METHOD void NestedNameSpecifier::dump() const {
347   LangOptions LO;
348   print(llvm::errs(), PrintingPolicy(LO));
349 }
350 
351 unsigned
352 NestedNameSpecifierLoc::getLocalDataLength(NestedNameSpecifier *Qualifier) {
353   assert(Qualifier && "Expected a non-NULL qualifier");
354 
355   // Location of the trailing '::'.
356   unsigned Length = sizeof(unsigned);
357 
358   switch (Qualifier->getKind()) {
359   case NestedNameSpecifier::Global:
360     // Nothing more to add.
361     break;
362 
363   case NestedNameSpecifier::Identifier:
364   case NestedNameSpecifier::Namespace:
365   case NestedNameSpecifier::NamespaceAlias:
366   case NestedNameSpecifier::Super:
367     // The location of the identifier or namespace name.
368     Length += sizeof(unsigned);
369     break;
370 
371   case NestedNameSpecifier::TypeSpecWithTemplate:
372   case NestedNameSpecifier::TypeSpec:
373     // The "void*" that points at the TypeLoc data.
374     // Note: the 'template' keyword is part of the TypeLoc.
375     Length += sizeof(void *);
376     break;
377   }
378 
379   return Length;
380 }
381 
382 unsigned
383 NestedNameSpecifierLoc::getDataLength(NestedNameSpecifier *Qualifier) {
384   unsigned Length = 0;
385   for (; Qualifier; Qualifier = Qualifier->getPrefix())
386     Length += getLocalDataLength(Qualifier);
387   return Length;
388 }
389 
390 /// Load a (possibly unaligned) source location from a given address
391 /// and offset.
392 static SourceLocation LoadSourceLocation(void *Data, unsigned Offset) {
393   unsigned Raw;
394   memcpy(&Raw, static_cast<char *>(Data) + Offset, sizeof(unsigned));
395   return SourceLocation::getFromRawEncoding(Raw);
396 }
397 
398 /// Load a (possibly unaligned) pointer from a given address and
399 /// offset.
400 static void *LoadPointer(void *Data, unsigned Offset) {
401   void *Result;
402   memcpy(&Result, static_cast<char *>(Data) + Offset, sizeof(void*));
403   return Result;
404 }
405 
406 SourceRange NestedNameSpecifierLoc::getSourceRange() const {
407   if (!Qualifier)
408     return SourceRange();
409 
410   NestedNameSpecifierLoc First = *this;
411   while (NestedNameSpecifierLoc Prefix = First.getPrefix())
412     First = Prefix;
413 
414   return SourceRange(First.getLocalSourceRange().getBegin(),
415                      getLocalSourceRange().getEnd());
416 }
417 
418 SourceRange NestedNameSpecifierLoc::getLocalSourceRange() const {
419   if (!Qualifier)
420     return SourceRange();
421 
422   unsigned Offset = getDataLength(Qualifier->getPrefix());
423   switch (Qualifier->getKind()) {
424   case NestedNameSpecifier::Global:
425     return LoadSourceLocation(Data, Offset);
426 
427   case NestedNameSpecifier::Identifier:
428   case NestedNameSpecifier::Namespace:
429   case NestedNameSpecifier::NamespaceAlias:
430   case NestedNameSpecifier::Super:
431     return SourceRange(LoadSourceLocation(Data, Offset),
432                        LoadSourceLocation(Data, Offset + sizeof(unsigned)));
433 
434   case NestedNameSpecifier::TypeSpecWithTemplate:
435   case NestedNameSpecifier::TypeSpec: {
436     // The "void*" that points at the TypeLoc data.
437     // Note: the 'template' keyword is part of the TypeLoc.
438     void *TypeData = LoadPointer(Data, Offset);
439     TypeLoc TL(Qualifier->getAsType(), TypeData);
440     return SourceRange(TL.getBeginLoc(),
441                        LoadSourceLocation(Data, Offset + sizeof(void*)));
442   }
443   }
444 
445   llvm_unreachable("Invalid NNS Kind!");
446 }
447 
448 TypeLoc NestedNameSpecifierLoc::getTypeLoc() const {
449   assert((Qualifier->getKind() == NestedNameSpecifier::TypeSpec ||
450           Qualifier->getKind() == NestedNameSpecifier::TypeSpecWithTemplate) &&
451          "Nested-name-specifier location is not a type");
452 
453   // The "void*" that points at the TypeLoc data.
454   unsigned Offset = getDataLength(Qualifier->getPrefix());
455   void *TypeData = LoadPointer(Data, Offset);
456   return TypeLoc(Qualifier->getAsType(), TypeData);
457 }
458 
459 static void Append(char *Start, char *End, char *&Buffer, unsigned &BufferSize,
460               unsigned &BufferCapacity) {
461   if (Start == End)
462     return;
463 
464   if (BufferSize + (End - Start) > BufferCapacity) {
465     // Reallocate the buffer.
466     unsigned NewCapacity = std::max(
467         (unsigned)(BufferCapacity ? BufferCapacity * 2 : sizeof(void *) * 2),
468         (unsigned)(BufferSize + (End - Start)));
469     char *NewBuffer = static_cast<char *>(llvm::safe_malloc(NewCapacity));
470     if (BufferCapacity) {
471       memcpy(NewBuffer, Buffer, BufferSize);
472       free(Buffer);
473     }
474     Buffer = NewBuffer;
475     BufferCapacity = NewCapacity;
476   }
477 
478   memcpy(Buffer + BufferSize, Start, End - Start);
479   BufferSize += End-Start;
480 }
481 
482 /// Save a source location to the given buffer.
483 static void SaveSourceLocation(SourceLocation Loc, char *&Buffer,
484                                unsigned &BufferSize, unsigned &BufferCapacity) {
485   unsigned Raw = Loc.getRawEncoding();
486   Append(reinterpret_cast<char *>(&Raw),
487          reinterpret_cast<char *>(&Raw) + sizeof(unsigned),
488          Buffer, BufferSize, BufferCapacity);
489 }
490 
491 /// Save a pointer to the given buffer.
492 static void SavePointer(void *Ptr, char *&Buffer, unsigned &BufferSize,
493                         unsigned &BufferCapacity) {
494   Append(reinterpret_cast<char *>(&Ptr),
495          reinterpret_cast<char *>(&Ptr) + sizeof(void *),
496          Buffer, BufferSize, BufferCapacity);
497 }
498 
499 NestedNameSpecifierLocBuilder::
500 NestedNameSpecifierLocBuilder(const NestedNameSpecifierLocBuilder &Other)
501     : Representation(Other.Representation) {
502   if (!Other.Buffer)
503     return;
504 
505   if (Other.BufferCapacity == 0) {
506     // Shallow copy is okay.
507     Buffer = Other.Buffer;
508     BufferSize = Other.BufferSize;
509     return;
510   }
511 
512   // Deep copy
513   Append(Other.Buffer, Other.Buffer + Other.BufferSize, Buffer, BufferSize,
514          BufferCapacity);
515 }
516 
517 NestedNameSpecifierLocBuilder &
518 NestedNameSpecifierLocBuilder::
519 operator=(const NestedNameSpecifierLocBuilder &Other) {
520   Representation = Other.Representation;
521 
522   if (Buffer && Other.Buffer && BufferCapacity >= Other.BufferSize) {
523     // Re-use our storage.
524     BufferSize = Other.BufferSize;
525     memcpy(Buffer, Other.Buffer, BufferSize);
526     return *this;
527   }
528 
529   // Free our storage, if we have any.
530   if (BufferCapacity) {
531     free(Buffer);
532     BufferCapacity = 0;
533   }
534 
535   if (!Other.Buffer) {
536     // Empty.
537     Buffer = nullptr;
538     BufferSize = 0;
539     return *this;
540   }
541 
542   if (Other.BufferCapacity == 0) {
543     // Shallow copy is okay.
544     Buffer = Other.Buffer;
545     BufferSize = Other.BufferSize;
546     return *this;
547   }
548 
549   // Deep copy.
550   BufferSize = 0;
551   Append(Other.Buffer, Other.Buffer + Other.BufferSize, Buffer, BufferSize,
552          BufferCapacity);
553   return *this;
554 }
555 
556 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
557                                            SourceLocation TemplateKWLoc,
558                                            TypeLoc TL,
559                                            SourceLocation ColonColonLoc) {
560   Representation = NestedNameSpecifier::Create(Context, Representation,
561                                                TemplateKWLoc.isValid(),
562                                                TL.getTypePtr());
563 
564   // Push source-location info into the buffer.
565   SavePointer(TL.getOpaqueData(), Buffer, BufferSize, BufferCapacity);
566   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
567 }
568 
569 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
570                                            IdentifierInfo *Identifier,
571                                            SourceLocation IdentifierLoc,
572                                            SourceLocation ColonColonLoc) {
573   Representation = NestedNameSpecifier::Create(Context, Representation,
574                                                Identifier);
575 
576   // Push source-location info into the buffer.
577   SaveSourceLocation(IdentifierLoc, Buffer, BufferSize, BufferCapacity);
578   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
579 }
580 
581 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
582                                            NamespaceDecl *Namespace,
583                                            SourceLocation NamespaceLoc,
584                                            SourceLocation ColonColonLoc) {
585   Representation = NestedNameSpecifier::Create(Context, Representation,
586                                                Namespace);
587 
588   // Push source-location info into the buffer.
589   SaveSourceLocation(NamespaceLoc, Buffer, BufferSize, BufferCapacity);
590   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
591 }
592 
593 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
594                                            NamespaceAliasDecl *Alias,
595                                            SourceLocation AliasLoc,
596                                            SourceLocation ColonColonLoc) {
597   Representation = NestedNameSpecifier::Create(Context, Representation, Alias);
598 
599   // Push source-location info into the buffer.
600   SaveSourceLocation(AliasLoc, Buffer, BufferSize, BufferCapacity);
601   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
602 }
603 
604 void NestedNameSpecifierLocBuilder::MakeGlobal(ASTContext &Context,
605                                                SourceLocation ColonColonLoc) {
606   assert(!Representation && "Already have a nested-name-specifier!?");
607   Representation = NestedNameSpecifier::GlobalSpecifier(Context);
608 
609   // Push source-location info into the buffer.
610   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
611 }
612 
613 void NestedNameSpecifierLocBuilder::MakeSuper(ASTContext &Context,
614                                               CXXRecordDecl *RD,
615                                               SourceLocation SuperLoc,
616                                               SourceLocation ColonColonLoc) {
617   Representation = NestedNameSpecifier::SuperSpecifier(Context, RD);
618 
619   // Push source-location info into the buffer.
620   SaveSourceLocation(SuperLoc, Buffer, BufferSize, BufferCapacity);
621   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
622 }
623 
624 void NestedNameSpecifierLocBuilder::MakeTrivial(ASTContext &Context,
625                                                 NestedNameSpecifier *Qualifier,
626                                                 SourceRange R) {
627   Representation = Qualifier;
628 
629   // Construct bogus (but well-formed) source information for the
630   // nested-name-specifier.
631   BufferSize = 0;
632   SmallVector<NestedNameSpecifier *, 4> Stack;
633   for (NestedNameSpecifier *NNS = Qualifier; NNS; NNS = NNS->getPrefix())
634     Stack.push_back(NNS);
635   while (!Stack.empty()) {
636     NestedNameSpecifier *NNS = Stack.pop_back_val();
637     switch (NNS->getKind()) {
638       case NestedNameSpecifier::Identifier:
639       case NestedNameSpecifier::Namespace:
640       case NestedNameSpecifier::NamespaceAlias:
641         SaveSourceLocation(R.getBegin(), Buffer, BufferSize, BufferCapacity);
642         break;
643 
644       case NestedNameSpecifier::TypeSpec:
645       case NestedNameSpecifier::TypeSpecWithTemplate: {
646         TypeSourceInfo *TSInfo
647         = Context.getTrivialTypeSourceInfo(QualType(NNS->getAsType(), 0),
648                                            R.getBegin());
649         SavePointer(TSInfo->getTypeLoc().getOpaqueData(), Buffer, BufferSize,
650                     BufferCapacity);
651         break;
652       }
653 
654       case NestedNameSpecifier::Global:
655       case NestedNameSpecifier::Super:
656         break;
657     }
658 
659     // Save the location of the '::'.
660     SaveSourceLocation(Stack.empty()? R.getEnd() : R.getBegin(),
661                        Buffer, BufferSize, BufferCapacity);
662   }
663 }
664 
665 void NestedNameSpecifierLocBuilder::Adopt(NestedNameSpecifierLoc Other) {
666   if (BufferCapacity)
667     free(Buffer);
668 
669   if (!Other) {
670     Representation = nullptr;
671     BufferSize = 0;
672     return;
673   }
674 
675   // Rather than copying the data (which is wasteful), "adopt" the
676   // pointer (which points into the ASTContext) but set the capacity to zero to
677   // indicate that we don't own it.
678   Representation = Other.getNestedNameSpecifier();
679   Buffer = static_cast<char *>(Other.getOpaqueData());
680   BufferSize = Other.getDataLength();
681   BufferCapacity = 0;
682 }
683 
684 NestedNameSpecifierLoc
685 NestedNameSpecifierLocBuilder::getWithLocInContext(ASTContext &Context) const {
686   if (!Representation)
687     return NestedNameSpecifierLoc();
688 
689   // If we adopted our data pointer from elsewhere in the AST context, there's
690   // no need to copy the memory.
691   if (BufferCapacity == 0)
692     return NestedNameSpecifierLoc(Representation, Buffer);
693 
694   // FIXME: After copying the source-location information, should we free
695   // our (temporary) buffer and adopt the ASTContext-allocated memory?
696   // Doing so would optimize repeated calls to getWithLocInContext().
697   void *Mem = Context.Allocate(BufferSize, alignof(void *));
698   memcpy(Mem, Buffer, BufferSize);
699   return NestedNameSpecifierLoc(Representation, Mem);
700 }
701