1 //===------- SemaTemplateInstantiate.cpp - C++ Template Instantiation ------===/
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 //  This file implements C++ template instantiation.
10 //
11 //===----------------------------------------------------------------------===/
12 
13 #include "clang/Sema/SemaInternal.h"
14 #include "TreeTransform.h"
15 #include "clang/Sema/DeclSpec.h"
16 #include "clang/Sema/Initialization.h"
17 #include "clang/Sema/Lookup.h"
18 #include "clang/Sema/Template.h"
19 #include "clang/Sema/TemplateDeduction.h"
20 #include "clang/AST/ASTConsumer.h"
21 #include "clang/AST/ASTContext.h"
22 #include "clang/AST/Expr.h"
23 #include "clang/AST/DeclTemplate.h"
24 #include "clang/Basic/LangOptions.h"
25 
26 using namespace clang;
27 using namespace sema;
28 
29 //===----------------------------------------------------------------------===/
30 // Template Instantiation Support
31 //===----------------------------------------------------------------------===/
32 
33 /// \brief Retrieve the template argument list(s) that should be used to
34 /// instantiate the definition of the given declaration.
35 ///
36 /// \param D the declaration for which we are computing template instantiation
37 /// arguments.
38 ///
39 /// \param Innermost if non-NULL, the innermost template argument list.
40 ///
41 /// \param RelativeToPrimary true if we should get the template
42 /// arguments relative to the primary template, even when we're
43 /// dealing with a specialization. This is only relevant for function
44 /// template specializations.
45 ///
46 /// \param Pattern If non-NULL, indicates the pattern from which we will be
47 /// instantiating the definition of the given declaration, \p D. This is
48 /// used to determine the proper set of template instantiation arguments for
49 /// friend function template specializations.
50 MultiLevelTemplateArgumentList
51 Sema::getTemplateInstantiationArgs(NamedDecl *D,
52                                    const TemplateArgumentList *Innermost,
53                                    bool RelativeToPrimary,
54                                    const FunctionDecl *Pattern) {
55   // Accumulate the set of template argument lists in this structure.
56   MultiLevelTemplateArgumentList Result;
57 
58   if (Innermost)
59     Result.addOuterTemplateArguments(Innermost);
60 
61   DeclContext *Ctx = dyn_cast<DeclContext>(D);
62   if (!Ctx) {
63     Ctx = D->getDeclContext();
64 
65     // If we have a template template parameter with translation unit context,
66     // then we're performing substitution into a default template argument of
67     // this template template parameter before we've constructed the template
68     // that will own this template template parameter. In this case, we
69     // use empty template parameter lists for all of the outer templates
70     // to avoid performing any substitutions.
71     if (Ctx->isTranslationUnit()) {
72       if (TemplateTemplateParmDecl *TTP
73                                       = dyn_cast<TemplateTemplateParmDecl>(D)) {
74         for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
75           Result.addOuterTemplateArguments(0, 0);
76         return Result;
77       }
78     }
79   }
80 
81   while (!Ctx->isFileContext()) {
82     // Add template arguments from a class template instantiation.
83     if (ClassTemplateSpecializationDecl *Spec
84           = dyn_cast<ClassTemplateSpecializationDecl>(Ctx)) {
85       // We're done when we hit an explicit specialization.
86       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
87           !isa<ClassTemplatePartialSpecializationDecl>(Spec))
88         break;
89 
90       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
91 
92       // If this class template specialization was instantiated from a
93       // specialized member that is a class template, we're done.
94       assert(Spec->getSpecializedTemplate() && "No class template?");
95       if (Spec->getSpecializedTemplate()->isMemberSpecialization())
96         break;
97     }
98     // Add template arguments from a function template specialization.
99     else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(Ctx)) {
100       if (!RelativeToPrimary &&
101           (Function->getTemplateSpecializationKind() ==
102                                                   TSK_ExplicitSpecialization &&
103            !Function->getClassScopeSpecializationPattern()))
104         break;
105 
106       if (const TemplateArgumentList *TemplateArgs
107             = Function->getTemplateSpecializationArgs()) {
108         // Add the template arguments for this specialization.
109         Result.addOuterTemplateArguments(TemplateArgs);
110 
111         // If this function was instantiated from a specialized member that is
112         // a function template, we're done.
113         assert(Function->getPrimaryTemplate() && "No function template?");
114         if (Function->getPrimaryTemplate()->isMemberSpecialization())
115           break;
116       } else if (FunctionTemplateDecl *FunTmpl
117                                    = Function->getDescribedFunctionTemplate()) {
118         // Add the "injected" template arguments.
119         std::pair<const TemplateArgument *, unsigned>
120           Injected = FunTmpl->getInjectedTemplateArgs();
121         Result.addOuterTemplateArguments(Injected.first, Injected.second);
122       }
123 
124       // If this is a friend declaration and it declares an entity at
125       // namespace scope, take arguments from its lexical parent
126       // instead of its semantic parent, unless of course the pattern we're
127       // instantiating actually comes from the file's context!
128       if (Function->getFriendObjectKind() &&
129           Function->getDeclContext()->isFileContext() &&
130           (!Pattern || !Pattern->getLexicalDeclContext()->isFileContext())) {
131         Ctx = Function->getLexicalDeclContext();
132         RelativeToPrimary = false;
133         continue;
134       }
135     } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
136       if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
137         QualType T = ClassTemplate->getInjectedClassNameSpecialization();
138         const TemplateSpecializationType *TST
139           = cast<TemplateSpecializationType>(Context.getCanonicalType(T));
140         Result.addOuterTemplateArguments(TST->getArgs(), TST->getNumArgs());
141         if (ClassTemplate->isMemberSpecialization())
142           break;
143       }
144     }
145 
146     Ctx = Ctx->getParent();
147     RelativeToPrimary = false;
148   }
149 
150   return Result;
151 }
152 
153 bool Sema::ActiveTemplateInstantiation::isInstantiationRecord() const {
154   switch (Kind) {
155   case TemplateInstantiation:
156   case DefaultTemplateArgumentInstantiation:
157   case DefaultFunctionArgumentInstantiation:
158     return true;
159 
160   case ExplicitTemplateArgumentSubstitution:
161   case DeducedTemplateArgumentSubstitution:
162   case PriorTemplateArgumentSubstitution:
163   case DefaultTemplateArgumentChecking:
164     return false;
165   }
166 
167   llvm_unreachable("Invalid InstantiationKind!");
168 }
169 
170 Sema::InstantiatingTemplate::
171 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
172                       Decl *Entity,
173                       SourceRange InstantiationRange)
174   : SemaRef(SemaRef),
175     SavedInNonInstantiationSFINAEContext(
176                                         SemaRef.InNonInstantiationSFINAEContext)
177 {
178   Invalid = CheckInstantiationDepth(PointOfInstantiation,
179                                     InstantiationRange);
180   if (!Invalid) {
181     ActiveTemplateInstantiation Inst;
182     Inst.Kind = ActiveTemplateInstantiation::TemplateInstantiation;
183     Inst.PointOfInstantiation = PointOfInstantiation;
184     Inst.Entity = reinterpret_cast<uintptr_t>(Entity);
185     Inst.TemplateArgs = 0;
186     Inst.NumTemplateArgs = 0;
187     Inst.InstantiationRange = InstantiationRange;
188     SemaRef.InNonInstantiationSFINAEContext = false;
189     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
190   }
191 }
192 
193 Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
194                                          SourceLocation PointOfInstantiation,
195                                          TemplateDecl *Template,
196                                          const TemplateArgument *TemplateArgs,
197                                          unsigned NumTemplateArgs,
198                                          SourceRange InstantiationRange)
199   : SemaRef(SemaRef),
200     SavedInNonInstantiationSFINAEContext(
201                                      SemaRef.InNonInstantiationSFINAEContext)
202 {
203   Invalid = CheckInstantiationDepth(PointOfInstantiation,
204                                     InstantiationRange);
205   if (!Invalid) {
206     ActiveTemplateInstantiation Inst;
207     Inst.Kind
208       = ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation;
209     Inst.PointOfInstantiation = PointOfInstantiation;
210     Inst.Entity = reinterpret_cast<uintptr_t>(Template);
211     Inst.TemplateArgs = TemplateArgs;
212     Inst.NumTemplateArgs = NumTemplateArgs;
213     Inst.InstantiationRange = InstantiationRange;
214     SemaRef.InNonInstantiationSFINAEContext = false;
215     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
216   }
217 }
218 
219 Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
220                                          SourceLocation PointOfInstantiation,
221                                       FunctionTemplateDecl *FunctionTemplate,
222                                         const TemplateArgument *TemplateArgs,
223                                                    unsigned NumTemplateArgs,
224                          ActiveTemplateInstantiation::InstantiationKind Kind,
225                                    sema::TemplateDeductionInfo &DeductionInfo,
226                                               SourceRange InstantiationRange)
227   : SemaRef(SemaRef),
228     SavedInNonInstantiationSFINAEContext(
229                                      SemaRef.InNonInstantiationSFINAEContext)
230 {
231   Invalid = CheckInstantiationDepth(PointOfInstantiation,
232                                     InstantiationRange);
233   if (!Invalid) {
234     ActiveTemplateInstantiation Inst;
235     Inst.Kind = Kind;
236     Inst.PointOfInstantiation = PointOfInstantiation;
237     Inst.Entity = reinterpret_cast<uintptr_t>(FunctionTemplate);
238     Inst.TemplateArgs = TemplateArgs;
239     Inst.NumTemplateArgs = NumTemplateArgs;
240     Inst.DeductionInfo = &DeductionInfo;
241     Inst.InstantiationRange = InstantiationRange;
242     SemaRef.InNonInstantiationSFINAEContext = false;
243     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
244 
245     if (!Inst.isInstantiationRecord())
246       ++SemaRef.NonInstantiationEntries;
247   }
248 }
249 
250 Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
251                                          SourceLocation PointOfInstantiation,
252                           ClassTemplatePartialSpecializationDecl *PartialSpec,
253                                          const TemplateArgument *TemplateArgs,
254                                          unsigned NumTemplateArgs,
255                                     sema::TemplateDeductionInfo &DeductionInfo,
256                                          SourceRange InstantiationRange)
257   : SemaRef(SemaRef),
258     SavedInNonInstantiationSFINAEContext(
259                                      SemaRef.InNonInstantiationSFINAEContext)
260 {
261   Invalid = false;
262 
263   ActiveTemplateInstantiation Inst;
264   Inst.Kind = ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution;
265   Inst.PointOfInstantiation = PointOfInstantiation;
266   Inst.Entity = reinterpret_cast<uintptr_t>(PartialSpec);
267   Inst.TemplateArgs = TemplateArgs;
268   Inst.NumTemplateArgs = NumTemplateArgs;
269   Inst.DeductionInfo = &DeductionInfo;
270   Inst.InstantiationRange = InstantiationRange;
271   SemaRef.InNonInstantiationSFINAEContext = false;
272   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
273 
274   assert(!Inst.isInstantiationRecord());
275   ++SemaRef.NonInstantiationEntries;
276 }
277 
278 Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
279                                           SourceLocation PointOfInstantiation,
280                                           ParmVarDecl *Param,
281                                           const TemplateArgument *TemplateArgs,
282                                           unsigned NumTemplateArgs,
283                                           SourceRange InstantiationRange)
284   : SemaRef(SemaRef),
285     SavedInNonInstantiationSFINAEContext(
286                                      SemaRef.InNonInstantiationSFINAEContext)
287 {
288   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
289 
290   if (!Invalid) {
291     ActiveTemplateInstantiation Inst;
292     Inst.Kind
293       = ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation;
294     Inst.PointOfInstantiation = PointOfInstantiation;
295     Inst.Entity = reinterpret_cast<uintptr_t>(Param);
296     Inst.TemplateArgs = TemplateArgs;
297     Inst.NumTemplateArgs = NumTemplateArgs;
298     Inst.InstantiationRange = InstantiationRange;
299     SemaRef.InNonInstantiationSFINAEContext = false;
300     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
301   }
302 }
303 
304 Sema::InstantiatingTemplate::
305 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
306                       NamedDecl *Template,
307                       NonTypeTemplateParmDecl *Param,
308                       const TemplateArgument *TemplateArgs,
309                       unsigned NumTemplateArgs,
310                       SourceRange InstantiationRange)
311   : SemaRef(SemaRef),
312     SavedInNonInstantiationSFINAEContext(
313                                      SemaRef.InNonInstantiationSFINAEContext)
314 {
315   Invalid = false;
316 
317   ActiveTemplateInstantiation Inst;
318   Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
319   Inst.PointOfInstantiation = PointOfInstantiation;
320   Inst.Template = Template;
321   Inst.Entity = reinterpret_cast<uintptr_t>(Param);
322   Inst.TemplateArgs = TemplateArgs;
323   Inst.NumTemplateArgs = NumTemplateArgs;
324   Inst.InstantiationRange = InstantiationRange;
325   SemaRef.InNonInstantiationSFINAEContext = false;
326   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
327 
328   assert(!Inst.isInstantiationRecord());
329   ++SemaRef.NonInstantiationEntries;
330 }
331 
332 Sema::InstantiatingTemplate::
333 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
334                       NamedDecl *Template,
335                       TemplateTemplateParmDecl *Param,
336                       const TemplateArgument *TemplateArgs,
337                       unsigned NumTemplateArgs,
338                       SourceRange InstantiationRange)
339   : SemaRef(SemaRef),
340     SavedInNonInstantiationSFINAEContext(
341                                      SemaRef.InNonInstantiationSFINAEContext)
342 {
343   Invalid = false;
344   ActiveTemplateInstantiation Inst;
345   Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
346   Inst.PointOfInstantiation = PointOfInstantiation;
347   Inst.Template = Template;
348   Inst.Entity = reinterpret_cast<uintptr_t>(Param);
349   Inst.TemplateArgs = TemplateArgs;
350   Inst.NumTemplateArgs = NumTemplateArgs;
351   Inst.InstantiationRange = InstantiationRange;
352   SemaRef.InNonInstantiationSFINAEContext = false;
353   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
354 
355   assert(!Inst.isInstantiationRecord());
356   ++SemaRef.NonInstantiationEntries;
357 }
358 
359 Sema::InstantiatingTemplate::
360 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
361                       TemplateDecl *Template,
362                       NamedDecl *Param,
363                       const TemplateArgument *TemplateArgs,
364                       unsigned NumTemplateArgs,
365                       SourceRange InstantiationRange)
366   : SemaRef(SemaRef),
367     SavedInNonInstantiationSFINAEContext(
368                                      SemaRef.InNonInstantiationSFINAEContext)
369 {
370   Invalid = false;
371 
372   ActiveTemplateInstantiation Inst;
373   Inst.Kind = ActiveTemplateInstantiation::DefaultTemplateArgumentChecking;
374   Inst.PointOfInstantiation = PointOfInstantiation;
375   Inst.Template = Template;
376   Inst.Entity = reinterpret_cast<uintptr_t>(Param);
377   Inst.TemplateArgs = TemplateArgs;
378   Inst.NumTemplateArgs = NumTemplateArgs;
379   Inst.InstantiationRange = InstantiationRange;
380   SemaRef.InNonInstantiationSFINAEContext = false;
381   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
382 
383   assert(!Inst.isInstantiationRecord());
384   ++SemaRef.NonInstantiationEntries;
385 }
386 
387 void Sema::InstantiatingTemplate::Clear() {
388   if (!Invalid) {
389     if (!SemaRef.ActiveTemplateInstantiations.back().isInstantiationRecord()) {
390       assert(SemaRef.NonInstantiationEntries > 0);
391       --SemaRef.NonInstantiationEntries;
392     }
393     SemaRef.InNonInstantiationSFINAEContext
394       = SavedInNonInstantiationSFINAEContext;
395     SemaRef.ActiveTemplateInstantiations.pop_back();
396     Invalid = true;
397   }
398 }
399 
400 bool Sema::InstantiatingTemplate::CheckInstantiationDepth(
401                                         SourceLocation PointOfInstantiation,
402                                            SourceRange InstantiationRange) {
403   assert(SemaRef.NonInstantiationEntries <=
404                                    SemaRef.ActiveTemplateInstantiations.size());
405   if ((SemaRef.ActiveTemplateInstantiations.size() -
406           SemaRef.NonInstantiationEntries)
407         <= SemaRef.getLangOptions().InstantiationDepth)
408     return false;
409 
410   SemaRef.Diag(PointOfInstantiation,
411                diag::err_template_recursion_depth_exceeded)
412     << SemaRef.getLangOptions().InstantiationDepth
413     << InstantiationRange;
414   SemaRef.Diag(PointOfInstantiation, diag::note_template_recursion_depth)
415     << SemaRef.getLangOptions().InstantiationDepth;
416   return true;
417 }
418 
419 /// \brief Prints the current instantiation stack through a series of
420 /// notes.
421 void Sema::PrintInstantiationStack() {
422   // Determine which template instantiations to skip, if any.
423   unsigned SkipStart = ActiveTemplateInstantiations.size(), SkipEnd = SkipStart;
424   unsigned Limit = Diags.getTemplateBacktraceLimit();
425   if (Limit && Limit < ActiveTemplateInstantiations.size()) {
426     SkipStart = Limit / 2 + Limit % 2;
427     SkipEnd = ActiveTemplateInstantiations.size() - Limit / 2;
428   }
429 
430   // FIXME: In all of these cases, we need to show the template arguments
431   unsigned InstantiationIdx = 0;
432   for (SmallVector<ActiveTemplateInstantiation, 16>::reverse_iterator
433          Active = ActiveTemplateInstantiations.rbegin(),
434          ActiveEnd = ActiveTemplateInstantiations.rend();
435        Active != ActiveEnd;
436        ++Active, ++InstantiationIdx) {
437     // Skip this instantiation?
438     if (InstantiationIdx >= SkipStart && InstantiationIdx < SkipEnd) {
439       if (InstantiationIdx == SkipStart) {
440         // Note that we're skipping instantiations.
441         Diags.Report(Active->PointOfInstantiation,
442                      diag::note_instantiation_contexts_suppressed)
443           << unsigned(ActiveTemplateInstantiations.size() - Limit);
444       }
445       continue;
446     }
447 
448     switch (Active->Kind) {
449     case ActiveTemplateInstantiation::TemplateInstantiation: {
450       Decl *D = reinterpret_cast<Decl *>(Active->Entity);
451       if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(D)) {
452         unsigned DiagID = diag::note_template_member_class_here;
453         if (isa<ClassTemplateSpecializationDecl>(Record))
454           DiagID = diag::note_template_class_instantiation_here;
455         Diags.Report(Active->PointOfInstantiation, DiagID)
456           << Context.getTypeDeclType(Record)
457           << Active->InstantiationRange;
458       } else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
459         unsigned DiagID;
460         if (Function->getPrimaryTemplate())
461           DiagID = diag::note_function_template_spec_here;
462         else
463           DiagID = diag::note_template_member_function_here;
464         Diags.Report(Active->PointOfInstantiation, DiagID)
465           << Function
466           << Active->InstantiationRange;
467       } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
468         Diags.Report(Active->PointOfInstantiation,
469                      diag::note_template_static_data_member_def_here)
470           << VD
471           << Active->InstantiationRange;
472       } else {
473         Diags.Report(Active->PointOfInstantiation,
474                      diag::note_template_type_alias_instantiation_here)
475           << cast<TypeAliasTemplateDecl>(D)
476           << Active->InstantiationRange;
477       }
478       break;
479     }
480 
481     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation: {
482       TemplateDecl *Template = cast<TemplateDecl>((Decl *)Active->Entity);
483       std::string TemplateArgsStr
484         = TemplateSpecializationType::PrintTemplateArgumentList(
485                                                          Active->TemplateArgs,
486                                                       Active->NumTemplateArgs,
487                                                       getPrintingPolicy());
488       Diags.Report(Active->PointOfInstantiation,
489                    diag::note_default_arg_instantiation_here)
490         << (Template->getNameAsString() + TemplateArgsStr)
491         << Active->InstantiationRange;
492       break;
493     }
494 
495     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution: {
496       FunctionTemplateDecl *FnTmpl
497         = cast<FunctionTemplateDecl>((Decl *)Active->Entity);
498       Diags.Report(Active->PointOfInstantiation,
499                    diag::note_explicit_template_arg_substitution_here)
500         << FnTmpl
501         << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
502                                            Active->TemplateArgs,
503                                            Active->NumTemplateArgs)
504         << Active->InstantiationRange;
505       break;
506     }
507 
508     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
509       if (ClassTemplatePartialSpecializationDecl *PartialSpec
510             = dyn_cast<ClassTemplatePartialSpecializationDecl>(
511                                                     (Decl *)Active->Entity)) {
512         Diags.Report(Active->PointOfInstantiation,
513                      diag::note_partial_spec_deduct_instantiation_here)
514           << Context.getTypeDeclType(PartialSpec)
515           << getTemplateArgumentBindingsText(
516                                          PartialSpec->getTemplateParameters(),
517                                              Active->TemplateArgs,
518                                              Active->NumTemplateArgs)
519           << Active->InstantiationRange;
520       } else {
521         FunctionTemplateDecl *FnTmpl
522           = cast<FunctionTemplateDecl>((Decl *)Active->Entity);
523         Diags.Report(Active->PointOfInstantiation,
524                      diag::note_function_template_deduction_instantiation_here)
525           << FnTmpl
526           << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
527                                              Active->TemplateArgs,
528                                              Active->NumTemplateArgs)
529           << Active->InstantiationRange;
530       }
531       break;
532 
533     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation: {
534       ParmVarDecl *Param = cast<ParmVarDecl>((Decl *)Active->Entity);
535       FunctionDecl *FD = cast<FunctionDecl>(Param->getDeclContext());
536 
537       std::string TemplateArgsStr
538         = TemplateSpecializationType::PrintTemplateArgumentList(
539                                                          Active->TemplateArgs,
540                                                       Active->NumTemplateArgs,
541                                                       getPrintingPolicy());
542       Diags.Report(Active->PointOfInstantiation,
543                    diag::note_default_function_arg_instantiation_here)
544         << (FD->getNameAsString() + TemplateArgsStr)
545         << Active->InstantiationRange;
546       break;
547     }
548 
549     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution: {
550       NamedDecl *Parm = cast<NamedDecl>((Decl *)Active->Entity);
551       std::string Name;
552       if (!Parm->getName().empty())
553         Name = std::string(" '") + Parm->getName().str() + "'";
554 
555       TemplateParameterList *TemplateParams = 0;
556       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
557         TemplateParams = Template->getTemplateParameters();
558       else
559         TemplateParams =
560           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
561                                                       ->getTemplateParameters();
562       Diags.Report(Active->PointOfInstantiation,
563                    diag::note_prior_template_arg_substitution)
564         << isa<TemplateTemplateParmDecl>(Parm)
565         << Name
566         << getTemplateArgumentBindingsText(TemplateParams,
567                                            Active->TemplateArgs,
568                                            Active->NumTemplateArgs)
569         << Active->InstantiationRange;
570       break;
571     }
572 
573     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking: {
574       TemplateParameterList *TemplateParams = 0;
575       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
576         TemplateParams = Template->getTemplateParameters();
577       else
578         TemplateParams =
579           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
580                                                       ->getTemplateParameters();
581 
582       Diags.Report(Active->PointOfInstantiation,
583                    diag::note_template_default_arg_checking)
584         << getTemplateArgumentBindingsText(TemplateParams,
585                                            Active->TemplateArgs,
586                                            Active->NumTemplateArgs)
587         << Active->InstantiationRange;
588       break;
589     }
590     }
591   }
592 }
593 
594 llvm::Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
595   if (InNonInstantiationSFINAEContext)
596     return llvm::Optional<TemplateDeductionInfo *>(0);
597 
598   for (SmallVector<ActiveTemplateInstantiation, 16>::const_reverse_iterator
599          Active = ActiveTemplateInstantiations.rbegin(),
600          ActiveEnd = ActiveTemplateInstantiations.rend();
601        Active != ActiveEnd;
602        ++Active)
603   {
604     switch(Active->Kind) {
605     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
606     case ActiveTemplateInstantiation::TemplateInstantiation:
607       // This is a template instantiation, so there is no SFINAE.
608       return llvm::Optional<TemplateDeductionInfo *>();
609 
610     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
611     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
612     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking:
613       // A default template argument instantiation and substitution into
614       // template parameters with arguments for prior parameters may or may
615       // not be a SFINAE context; look further up the stack.
616       break;
617 
618     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution:
619     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
620       // We're either substitution explicitly-specified template arguments
621       // or deduced template arguments, so SFINAE applies.
622       assert(Active->DeductionInfo && "Missing deduction info pointer");
623       return Active->DeductionInfo;
624     }
625   }
626 
627   return llvm::Optional<TemplateDeductionInfo *>();
628 }
629 
630 /// \brief Retrieve the depth and index of a parameter pack.
631 static std::pair<unsigned, unsigned>
632 getDepthAndIndex(NamedDecl *ND) {
633   if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(ND))
634     return std::make_pair(TTP->getDepth(), TTP->getIndex());
635 
636   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(ND))
637     return std::make_pair(NTTP->getDepth(), NTTP->getIndex());
638 
639   TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(ND);
640   return std::make_pair(TTP->getDepth(), TTP->getIndex());
641 }
642 
643 //===----------------------------------------------------------------------===/
644 // Template Instantiation for Types
645 //===----------------------------------------------------------------------===/
646 namespace {
647   class TemplateInstantiator : public TreeTransform<TemplateInstantiator> {
648     const MultiLevelTemplateArgumentList &TemplateArgs;
649     SourceLocation Loc;
650     DeclarationName Entity;
651 
652   public:
653     typedef TreeTransform<TemplateInstantiator> inherited;
654 
655     TemplateInstantiator(Sema &SemaRef,
656                          const MultiLevelTemplateArgumentList &TemplateArgs,
657                          SourceLocation Loc,
658                          DeclarationName Entity)
659       : inherited(SemaRef), TemplateArgs(TemplateArgs), Loc(Loc),
660         Entity(Entity) { }
661 
662     /// \brief Determine whether the given type \p T has already been
663     /// transformed.
664     ///
665     /// For the purposes of template instantiation, a type has already been
666     /// transformed if it is NULL or if it is not dependent.
667     bool AlreadyTransformed(QualType T);
668 
669     /// \brief Returns the location of the entity being instantiated, if known.
670     SourceLocation getBaseLocation() { return Loc; }
671 
672     /// \brief Returns the name of the entity being instantiated, if any.
673     DeclarationName getBaseEntity() { return Entity; }
674 
675     /// \brief Sets the "base" location and entity when that
676     /// information is known based on another transformation.
677     void setBase(SourceLocation Loc, DeclarationName Entity) {
678       this->Loc = Loc;
679       this->Entity = Entity;
680     }
681 
682     bool TryExpandParameterPacks(SourceLocation EllipsisLoc,
683                                  SourceRange PatternRange,
684                              llvm::ArrayRef<UnexpandedParameterPack> Unexpanded,
685                                  bool &ShouldExpand,
686                                  bool &RetainExpansion,
687                                  llvm::Optional<unsigned> &NumExpansions) {
688       return getSema().CheckParameterPacksForExpansion(EllipsisLoc,
689                                                        PatternRange, Unexpanded,
690                                                        TemplateArgs,
691                                                        ShouldExpand,
692                                                        RetainExpansion,
693                                                        NumExpansions);
694     }
695 
696     void ExpandingFunctionParameterPack(ParmVarDecl *Pack) {
697       SemaRef.CurrentInstantiationScope->MakeInstantiatedLocalArgPack(Pack);
698     }
699 
700     TemplateArgument ForgetPartiallySubstitutedPack() {
701       TemplateArgument Result;
702       if (NamedDecl *PartialPack
703             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
704         MultiLevelTemplateArgumentList &TemplateArgs
705           = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
706         unsigned Depth, Index;
707         llvm::tie(Depth, Index) = getDepthAndIndex(PartialPack);
708         if (TemplateArgs.hasTemplateArgument(Depth, Index)) {
709           Result = TemplateArgs(Depth, Index);
710           TemplateArgs.setArgument(Depth, Index, TemplateArgument());
711         }
712       }
713 
714       return Result;
715     }
716 
717     void RememberPartiallySubstitutedPack(TemplateArgument Arg) {
718       if (Arg.isNull())
719         return;
720 
721       if (NamedDecl *PartialPack
722             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
723         MultiLevelTemplateArgumentList &TemplateArgs
724         = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
725         unsigned Depth, Index;
726         llvm::tie(Depth, Index) = getDepthAndIndex(PartialPack);
727         TemplateArgs.setArgument(Depth, Index, Arg);
728       }
729     }
730 
731     /// \brief Transform the given declaration by instantiating a reference to
732     /// this declaration.
733     Decl *TransformDecl(SourceLocation Loc, Decl *D);
734 
735     void transformAttrs(Decl *Old, Decl *New) {
736       SemaRef.InstantiateAttrs(TemplateArgs, Old, New);
737     }
738 
739     void transformedLocalDecl(Decl *Old, Decl *New) {
740       SemaRef.CurrentInstantiationScope->InstantiatedLocal(Old, New);
741     }
742 
743     /// \brief Transform the definition of the given declaration by
744     /// instantiating it.
745     Decl *TransformDefinition(SourceLocation Loc, Decl *D);
746 
747     /// \bried Transform the first qualifier within a scope by instantiating the
748     /// declaration.
749     NamedDecl *TransformFirstQualifierInScope(NamedDecl *D, SourceLocation Loc);
750 
751     /// \brief Rebuild the exception declaration and register the declaration
752     /// as an instantiated local.
753     VarDecl *RebuildExceptionDecl(VarDecl *ExceptionDecl,
754                                   TypeSourceInfo *Declarator,
755                                   SourceLocation StartLoc,
756                                   SourceLocation NameLoc,
757                                   IdentifierInfo *Name);
758 
759     /// \brief Rebuild the Objective-C exception declaration and register the
760     /// declaration as an instantiated local.
761     VarDecl *RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
762                                       TypeSourceInfo *TSInfo, QualType T);
763 
764     /// \brief Check for tag mismatches when instantiating an
765     /// elaborated type.
766     QualType RebuildElaboratedType(SourceLocation KeywordLoc,
767                                    ElaboratedTypeKeyword Keyword,
768                                    NestedNameSpecifierLoc QualifierLoc,
769                                    QualType T);
770 
771     TemplateName TransformTemplateName(CXXScopeSpec &SS,
772                                        TemplateName Name,
773                                        SourceLocation NameLoc,
774                                        QualType ObjectType = QualType(),
775                                        NamedDecl *FirstQualifierInScope = 0);
776 
777     ExprResult TransformPredefinedExpr(PredefinedExpr *E);
778     ExprResult TransformDeclRefExpr(DeclRefExpr *E);
779     ExprResult TransformCXXDefaultArgExpr(CXXDefaultArgExpr *E);
780     ExprResult TransformTemplateParmRefExpr(DeclRefExpr *E,
781                                             NonTypeTemplateParmDecl *D);
782     ExprResult TransformSubstNonTypeTemplateParmPackExpr(
783                                            SubstNonTypeTemplateParmPackExpr *E);
784 
785     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
786                                         FunctionProtoTypeLoc TL);
787     ParmVarDecl *TransformFunctionTypeParam(ParmVarDecl *OldParm,
788                                             int indexAdjustment,
789                                         llvm::Optional<unsigned> NumExpansions,
790                                             bool ExpectParameterPack);
791 
792     /// \brief Transforms a template type parameter type by performing
793     /// substitution of the corresponding template type argument.
794     QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
795                                            TemplateTypeParmTypeLoc TL);
796 
797     /// \brief Transforms an already-substituted template type parameter pack
798     /// into either itself (if we aren't substituting into its pack expansion)
799     /// or the appropriate substituted argument.
800     QualType TransformSubstTemplateTypeParmPackType(TypeLocBuilder &TLB,
801                                            SubstTemplateTypeParmPackTypeLoc TL);
802 
803     ExprResult TransformCallExpr(CallExpr *CE) {
804       getSema().CallsUndergoingInstantiation.push_back(CE);
805       ExprResult Result =
806           TreeTransform<TemplateInstantiator>::TransformCallExpr(CE);
807       getSema().CallsUndergoingInstantiation.pop_back();
808       return move(Result);
809     }
810 
811   private:
812     ExprResult transformNonTypeTemplateParmRef(NonTypeTemplateParmDecl *parm,
813                                                SourceLocation loc,
814                                                const TemplateArgument &arg);
815   };
816 }
817 
818 bool TemplateInstantiator::AlreadyTransformed(QualType T) {
819   if (T.isNull())
820     return true;
821 
822   if (T->isInstantiationDependentType() || T->isVariablyModifiedType())
823     return false;
824 
825   getSema().MarkDeclarationsReferencedInType(Loc, T);
826   return true;
827 }
828 
829 Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
830   if (!D)
831     return 0;
832 
833   if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(D)) {
834     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
835       // If the corresponding template argument is NULL or non-existent, it's
836       // because we are performing instantiation from explicitly-specified
837       // template arguments in a function template, but there were some
838       // arguments left unspecified.
839       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
840                                             TTP->getPosition()))
841         return D;
842 
843       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
844 
845       if (TTP->isParameterPack()) {
846         assert(Arg.getKind() == TemplateArgument::Pack &&
847                "Missing argument pack");
848 
849         assert(getSema().ArgumentPackSubstitutionIndex >= 0);
850         assert(getSema().ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
851         Arg = Arg.pack_begin()[getSema().ArgumentPackSubstitutionIndex];
852       }
853 
854       TemplateName Template = Arg.getAsTemplate();
855       assert(!Template.isNull() && Template.getAsTemplateDecl() &&
856              "Wrong kind of template template argument");
857       return Template.getAsTemplateDecl();
858     }
859 
860     // Fall through to find the instantiated declaration for this template
861     // template parameter.
862   }
863 
864   return SemaRef.FindInstantiatedDecl(Loc, cast<NamedDecl>(D), TemplateArgs);
865 }
866 
867 Decl *TemplateInstantiator::TransformDefinition(SourceLocation Loc, Decl *D) {
868   Decl *Inst = getSema().SubstDecl(D, getSema().CurContext, TemplateArgs);
869   if (!Inst)
870     return 0;
871 
872   getSema().CurrentInstantiationScope->InstantiatedLocal(D, Inst);
873   return Inst;
874 }
875 
876 NamedDecl *
877 TemplateInstantiator::TransformFirstQualifierInScope(NamedDecl *D,
878                                                      SourceLocation Loc) {
879   // If the first part of the nested-name-specifier was a template type
880   // parameter, instantiate that type parameter down to a tag type.
881   if (TemplateTypeParmDecl *TTPD = dyn_cast_or_null<TemplateTypeParmDecl>(D)) {
882     const TemplateTypeParmType *TTP
883       = cast<TemplateTypeParmType>(getSema().Context.getTypeDeclType(TTPD));
884 
885     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
886       // FIXME: This needs testing w/ member access expressions.
887       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getIndex());
888 
889       if (TTP->isParameterPack()) {
890         assert(Arg.getKind() == TemplateArgument::Pack &&
891                "Missing argument pack");
892 
893         if (getSema().ArgumentPackSubstitutionIndex == -1)
894           return 0;
895 
896         assert(getSema().ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
897         Arg = Arg.pack_begin()[getSema().ArgumentPackSubstitutionIndex];
898       }
899 
900       QualType T = Arg.getAsType();
901       if (T.isNull())
902         return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
903 
904       if (const TagType *Tag = T->getAs<TagType>())
905         return Tag->getDecl();
906 
907       // The resulting type is not a tag; complain.
908       getSema().Diag(Loc, diag::err_nested_name_spec_non_tag) << T;
909       return 0;
910     }
911   }
912 
913   return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
914 }
915 
916 VarDecl *
917 TemplateInstantiator::RebuildExceptionDecl(VarDecl *ExceptionDecl,
918                                            TypeSourceInfo *Declarator,
919                                            SourceLocation StartLoc,
920                                            SourceLocation NameLoc,
921                                            IdentifierInfo *Name) {
922   VarDecl *Var = inherited::RebuildExceptionDecl(ExceptionDecl, Declarator,
923                                                  StartLoc, NameLoc, Name);
924   if (Var)
925     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
926   return Var;
927 }
928 
929 VarDecl *TemplateInstantiator::RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
930                                                         TypeSourceInfo *TSInfo,
931                                                         QualType T) {
932   VarDecl *Var = inherited::RebuildObjCExceptionDecl(ExceptionDecl, TSInfo, T);
933   if (Var)
934     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
935   return Var;
936 }
937 
938 QualType
939 TemplateInstantiator::RebuildElaboratedType(SourceLocation KeywordLoc,
940                                             ElaboratedTypeKeyword Keyword,
941                                             NestedNameSpecifierLoc QualifierLoc,
942                                             QualType T) {
943   if (const TagType *TT = T->getAs<TagType>()) {
944     TagDecl* TD = TT->getDecl();
945 
946     SourceLocation TagLocation = KeywordLoc;
947 
948     // FIXME: type might be anonymous.
949     IdentifierInfo *Id = TD->getIdentifier();
950 
951     // TODO: should we even warn on struct/class mismatches for this?  Seems
952     // like it's likely to produce a lot of spurious errors.
953     if (Keyword != ETK_None && Keyword != ETK_Typename) {
954       TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForKeyword(Keyword);
955       if (!SemaRef.isAcceptableTagRedeclaration(TD, Kind, /*isDefinition*/false,
956                                                 TagLocation, *Id)) {
957         SemaRef.Diag(TagLocation, diag::err_use_with_wrong_tag)
958           << Id
959           << FixItHint::CreateReplacement(SourceRange(TagLocation),
960                                           TD->getKindName());
961         SemaRef.Diag(TD->getLocation(), diag::note_previous_use);
962       }
963     }
964   }
965 
966   return TreeTransform<TemplateInstantiator>::RebuildElaboratedType(KeywordLoc,
967                                                                     Keyword,
968                                                                   QualifierLoc,
969                                                                     T);
970 }
971 
972 TemplateName TemplateInstantiator::TransformTemplateName(CXXScopeSpec &SS,
973                                                          TemplateName Name,
974                                                          SourceLocation NameLoc,
975                                                          QualType ObjectType,
976                                              NamedDecl *FirstQualifierInScope) {
977   if (TemplateTemplateParmDecl *TTP
978        = dyn_cast_or_null<TemplateTemplateParmDecl>(Name.getAsTemplateDecl())) {
979     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
980       // If the corresponding template argument is NULL or non-existent, it's
981       // because we are performing instantiation from explicitly-specified
982       // template arguments in a function template, but there were some
983       // arguments left unspecified.
984       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
985                                             TTP->getPosition()))
986         return Name;
987 
988       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
989 
990       if (TTP->isParameterPack()) {
991         assert(Arg.getKind() == TemplateArgument::Pack &&
992                "Missing argument pack");
993 
994         if (getSema().ArgumentPackSubstitutionIndex == -1) {
995           // We have the template argument pack to substitute, but we're not
996           // actually expanding the enclosing pack expansion yet. So, just
997           // keep the entire argument pack.
998           return getSema().Context.getSubstTemplateTemplateParmPack(TTP, Arg);
999         }
1000 
1001         assert(getSema().ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
1002         Arg = Arg.pack_begin()[getSema().ArgumentPackSubstitutionIndex];
1003       }
1004 
1005       TemplateName Template = Arg.getAsTemplate();
1006       assert(!Template.isNull() && "Null template template argument");
1007 
1008       // We don't ever want to substitute for a qualified template name, since
1009       // the qualifier is handled separately. So, look through the qualified
1010       // template name to its underlying declaration.
1011       if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
1012         Template = TemplateName(QTN->getTemplateDecl());
1013 
1014       Template = getSema().Context.getSubstTemplateTemplateParm(TTP, Template);
1015       return Template;
1016     }
1017   }
1018 
1019   if (SubstTemplateTemplateParmPackStorage *SubstPack
1020       = Name.getAsSubstTemplateTemplateParmPack()) {
1021     if (getSema().ArgumentPackSubstitutionIndex == -1)
1022       return Name;
1023 
1024     const TemplateArgument &ArgPack = SubstPack->getArgumentPack();
1025     assert(getSema().ArgumentPackSubstitutionIndex < (int)ArgPack.pack_size() &&
1026            "Pack substitution index out-of-range");
1027     return ArgPack.pack_begin()[getSema().ArgumentPackSubstitutionIndex]
1028     .getAsTemplate();
1029   }
1030 
1031   return inherited::TransformTemplateName(SS, Name, NameLoc, ObjectType,
1032                                           FirstQualifierInScope);
1033 }
1034 
1035 ExprResult
1036 TemplateInstantiator::TransformPredefinedExpr(PredefinedExpr *E) {
1037   if (!E->isTypeDependent())
1038     return SemaRef.Owned(E);
1039 
1040   FunctionDecl *currentDecl = getSema().getCurFunctionDecl();
1041   assert(currentDecl && "Must have current function declaration when "
1042                         "instantiating.");
1043 
1044   PredefinedExpr::IdentType IT = E->getIdentType();
1045 
1046   unsigned Length = PredefinedExpr::ComputeName(IT, currentDecl).length();
1047 
1048   llvm::APInt LengthI(32, Length + 1);
1049   QualType ResTy = getSema().Context.CharTy.withConst();
1050   ResTy = getSema().Context.getConstantArrayType(ResTy, LengthI,
1051                                                  ArrayType::Normal, 0);
1052   PredefinedExpr *PE =
1053     new (getSema().Context) PredefinedExpr(E->getLocation(), ResTy, IT);
1054   return getSema().Owned(PE);
1055 }
1056 
1057 ExprResult
1058 TemplateInstantiator::TransformTemplateParmRefExpr(DeclRefExpr *E,
1059                                                NonTypeTemplateParmDecl *NTTP) {
1060   // If the corresponding template argument is NULL or non-existent, it's
1061   // because we are performing instantiation from explicitly-specified
1062   // template arguments in a function template, but there were some
1063   // arguments left unspecified.
1064   if (!TemplateArgs.hasTemplateArgument(NTTP->getDepth(),
1065                                         NTTP->getPosition()))
1066     return SemaRef.Owned(E);
1067 
1068   TemplateArgument Arg = TemplateArgs(NTTP->getDepth(), NTTP->getPosition());
1069   if (NTTP->isParameterPack()) {
1070     assert(Arg.getKind() == TemplateArgument::Pack &&
1071            "Missing argument pack");
1072 
1073     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1074       // We have an argument pack, but we can't select a particular argument
1075       // out of it yet. Therefore, we'll build an expression to hold on to that
1076       // argument pack.
1077       QualType TargetType = SemaRef.SubstType(NTTP->getType(), TemplateArgs,
1078                                               E->getLocation(),
1079                                               NTTP->getDeclName());
1080       if (TargetType.isNull())
1081         return ExprError();
1082 
1083       return new (SemaRef.Context) SubstNonTypeTemplateParmPackExpr(TargetType,
1084                                                                     NTTP,
1085                                                               E->getLocation(),
1086                                                                     Arg);
1087     }
1088 
1089     assert(getSema().ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
1090     Arg = Arg.pack_begin()[getSema().ArgumentPackSubstitutionIndex];
1091   }
1092 
1093   return transformNonTypeTemplateParmRef(NTTP, E->getLocation(), Arg);
1094 }
1095 
1096 ExprResult TemplateInstantiator::transformNonTypeTemplateParmRef(
1097                                                  NonTypeTemplateParmDecl *parm,
1098                                                  SourceLocation loc,
1099                                                  const TemplateArgument &arg) {
1100   ExprResult result;
1101   QualType type;
1102 
1103   // The template argument itself might be an expression, in which
1104   // case we just return that expression.
1105   if (arg.getKind() == TemplateArgument::Expression) {
1106     Expr *argExpr = arg.getAsExpr();
1107     result = SemaRef.Owned(argExpr);
1108     type = argExpr->getType();
1109 
1110   } else if (arg.getKind() == TemplateArgument::Declaration) {
1111     ValueDecl *VD = cast<ValueDecl>(arg.getAsDecl());
1112 
1113     // Find the instantiation of the template argument.  This is
1114     // required for nested templates.
1115     VD = cast_or_null<ValueDecl>(
1116                        getSema().FindInstantiatedDecl(loc, VD, TemplateArgs));
1117     if (!VD)
1118       return ExprError();
1119 
1120     // Derive the type we want the substituted decl to have.  This had
1121     // better be non-dependent, or these checks will have serious problems.
1122     if (parm->isExpandedParameterPack()) {
1123       type = parm->getExpansionType(SemaRef.ArgumentPackSubstitutionIndex);
1124     } else if (parm->isParameterPack() &&
1125                isa<PackExpansionType>(parm->getType())) {
1126       type = SemaRef.SubstType(
1127                         cast<PackExpansionType>(parm->getType())->getPattern(),
1128                                      TemplateArgs, loc, parm->getDeclName());
1129     } else {
1130       type = SemaRef.SubstType(parm->getType(), TemplateArgs,
1131                                loc, parm->getDeclName());
1132     }
1133     assert(!type.isNull() && "type substitution failed for param type");
1134     assert(!type->isDependentType() && "param type still dependent");
1135     result = SemaRef.BuildExpressionFromDeclTemplateArgument(arg, type, loc);
1136 
1137     if (!result.isInvalid()) type = result.get()->getType();
1138   } else {
1139     result = SemaRef.BuildExpressionFromIntegralTemplateArgument(arg, loc);
1140 
1141     // Note that this type can be different from the type of 'result',
1142     // e.g. if it's an enum type.
1143     type = arg.getIntegralType();
1144   }
1145   if (result.isInvalid()) return ExprError();
1146 
1147   Expr *resultExpr = result.take();
1148   return SemaRef.Owned(new (SemaRef.Context)
1149                 SubstNonTypeTemplateParmExpr(type,
1150                                              resultExpr->getValueKind(),
1151                                              loc, parm, resultExpr));
1152 }
1153 
1154 ExprResult
1155 TemplateInstantiator::TransformSubstNonTypeTemplateParmPackExpr(
1156                                           SubstNonTypeTemplateParmPackExpr *E) {
1157   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1158     // We aren't expanding the parameter pack, so just return ourselves.
1159     return getSema().Owned(E);
1160   }
1161 
1162   const TemplateArgument &ArgPack = E->getArgumentPack();
1163   unsigned Index = (unsigned)getSema().ArgumentPackSubstitutionIndex;
1164   assert(Index < ArgPack.pack_size() && "Substitution index out-of-range");
1165 
1166   const TemplateArgument &Arg = ArgPack.pack_begin()[Index];
1167   return transformNonTypeTemplateParmRef(E->getParameterPack(),
1168                                          E->getParameterPackLocation(),
1169                                          Arg);
1170 }
1171 
1172 ExprResult
1173 TemplateInstantiator::TransformDeclRefExpr(DeclRefExpr *E) {
1174   NamedDecl *D = E->getDecl();
1175   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D)) {
1176     if (NTTP->getDepth() < TemplateArgs.getNumLevels())
1177       return TransformTemplateParmRefExpr(E, NTTP);
1178 
1179     // We have a non-type template parameter that isn't fully substituted;
1180     // FindInstantiatedDecl will find it in the local instantiation scope.
1181   }
1182 
1183   return TreeTransform<TemplateInstantiator>::TransformDeclRefExpr(E);
1184 }
1185 
1186 ExprResult TemplateInstantiator::TransformCXXDefaultArgExpr(
1187     CXXDefaultArgExpr *E) {
1188   assert(!cast<FunctionDecl>(E->getParam()->getDeclContext())->
1189              getDescribedFunctionTemplate() &&
1190          "Default arg expressions are never formed in dependent cases.");
1191   return SemaRef.BuildCXXDefaultArgExpr(E->getUsedLocation(),
1192                            cast<FunctionDecl>(E->getParam()->getDeclContext()),
1193                                         E->getParam());
1194 }
1195 
1196 QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
1197                                                       FunctionProtoTypeLoc TL) {
1198   // We need a local instantiation scope for this function prototype.
1199   LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
1200   return inherited::TransformFunctionProtoType(TLB, TL);
1201 }
1202 
1203 ParmVarDecl *
1204 TemplateInstantiator::TransformFunctionTypeParam(ParmVarDecl *OldParm,
1205                                                  int indexAdjustment,
1206                                        llvm::Optional<unsigned> NumExpansions,
1207                                                  bool ExpectParameterPack) {
1208   return SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
1209                                   NumExpansions, ExpectParameterPack);
1210 }
1211 
1212 QualType
1213 TemplateInstantiator::TransformTemplateTypeParmType(TypeLocBuilder &TLB,
1214                                                 TemplateTypeParmTypeLoc TL) {
1215   const TemplateTypeParmType *T = TL.getTypePtr();
1216   if (T->getDepth() < TemplateArgs.getNumLevels()) {
1217     // Replace the template type parameter with its corresponding
1218     // template argument.
1219 
1220     // If the corresponding template argument is NULL or doesn't exist, it's
1221     // because we are performing instantiation from explicitly-specified
1222     // template arguments in a function template class, but there were some
1223     // arguments left unspecified.
1224     if (!TemplateArgs.hasTemplateArgument(T->getDepth(), T->getIndex())) {
1225       TemplateTypeParmTypeLoc NewTL
1226         = TLB.push<TemplateTypeParmTypeLoc>(TL.getType());
1227       NewTL.setNameLoc(TL.getNameLoc());
1228       return TL.getType();
1229     }
1230 
1231     TemplateArgument Arg = TemplateArgs(T->getDepth(), T->getIndex());
1232 
1233     if (T->isParameterPack()) {
1234       assert(Arg.getKind() == TemplateArgument::Pack &&
1235              "Missing argument pack");
1236 
1237       if (getSema().ArgumentPackSubstitutionIndex == -1) {
1238         // We have the template argument pack, but we're not expanding the
1239         // enclosing pack expansion yet. Just save the template argument
1240         // pack for later substitution.
1241         QualType Result
1242           = getSema().Context.getSubstTemplateTypeParmPackType(T, Arg);
1243         SubstTemplateTypeParmPackTypeLoc NewTL
1244           = TLB.push<SubstTemplateTypeParmPackTypeLoc>(Result);
1245         NewTL.setNameLoc(TL.getNameLoc());
1246         return Result;
1247       }
1248 
1249       assert(getSema().ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
1250       Arg = Arg.pack_begin()[getSema().ArgumentPackSubstitutionIndex];
1251     }
1252 
1253     assert(Arg.getKind() == TemplateArgument::Type &&
1254            "Template argument kind mismatch");
1255 
1256     QualType Replacement = Arg.getAsType();
1257 
1258     // TODO: only do this uniquing once, at the start of instantiation.
1259     QualType Result
1260       = getSema().Context.getSubstTemplateTypeParmType(T, Replacement);
1261     SubstTemplateTypeParmTypeLoc NewTL
1262       = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1263     NewTL.setNameLoc(TL.getNameLoc());
1264     return Result;
1265   }
1266 
1267   // The template type parameter comes from an inner template (e.g.,
1268   // the template parameter list of a member template inside the
1269   // template we are instantiating). Create a new template type
1270   // parameter with the template "level" reduced by one.
1271   TemplateTypeParmDecl *NewTTPDecl = 0;
1272   if (TemplateTypeParmDecl *OldTTPDecl = T->getDecl())
1273     NewTTPDecl = cast_or_null<TemplateTypeParmDecl>(
1274                                   TransformDecl(TL.getNameLoc(), OldTTPDecl));
1275 
1276   QualType Result
1277     = getSema().Context.getTemplateTypeParmType(T->getDepth()
1278                                                  - TemplateArgs.getNumLevels(),
1279                                                 T->getIndex(),
1280                                                 T->isParameterPack(),
1281                                                 NewTTPDecl);
1282   TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
1283   NewTL.setNameLoc(TL.getNameLoc());
1284   return Result;
1285 }
1286 
1287 QualType
1288 TemplateInstantiator::TransformSubstTemplateTypeParmPackType(
1289                                                             TypeLocBuilder &TLB,
1290                                          SubstTemplateTypeParmPackTypeLoc TL) {
1291   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1292     // We aren't expanding the parameter pack, so just return ourselves.
1293     SubstTemplateTypeParmPackTypeLoc NewTL
1294       = TLB.push<SubstTemplateTypeParmPackTypeLoc>(TL.getType());
1295     NewTL.setNameLoc(TL.getNameLoc());
1296     return TL.getType();
1297   }
1298 
1299   const TemplateArgument &ArgPack = TL.getTypePtr()->getArgumentPack();
1300   unsigned Index = (unsigned)getSema().ArgumentPackSubstitutionIndex;
1301   assert(Index < ArgPack.pack_size() && "Substitution index out-of-range");
1302 
1303   QualType Result = ArgPack.pack_begin()[Index].getAsType();
1304   Result = getSema().Context.getSubstTemplateTypeParmType(
1305                                       TL.getTypePtr()->getReplacedParameter(),
1306                                                           Result);
1307   SubstTemplateTypeParmTypeLoc NewTL
1308     = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1309   NewTL.setNameLoc(TL.getNameLoc());
1310   return Result;
1311 }
1312 
1313 /// \brief Perform substitution on the type T with a given set of template
1314 /// arguments.
1315 ///
1316 /// This routine substitutes the given template arguments into the
1317 /// type T and produces the instantiated type.
1318 ///
1319 /// \param T the type into which the template arguments will be
1320 /// substituted. If this type is not dependent, it will be returned
1321 /// immediately.
1322 ///
1323 /// \param TemplateArgs the template arguments that will be
1324 /// substituted for the top-level template parameters within T.
1325 ///
1326 /// \param Loc the location in the source code where this substitution
1327 /// is being performed. It will typically be the location of the
1328 /// declarator (if we're instantiating the type of some declaration)
1329 /// or the location of the type in the source code (if, e.g., we're
1330 /// instantiating the type of a cast expression).
1331 ///
1332 /// \param Entity the name of the entity associated with a declaration
1333 /// being instantiated (if any). May be empty to indicate that there
1334 /// is no such entity (if, e.g., this is a type that occurs as part of
1335 /// a cast expression) or that the entity has no name (e.g., an
1336 /// unnamed function parameter).
1337 ///
1338 /// \returns If the instantiation succeeds, the instantiated
1339 /// type. Otherwise, produces diagnostics and returns a NULL type.
1340 TypeSourceInfo *Sema::SubstType(TypeSourceInfo *T,
1341                                 const MultiLevelTemplateArgumentList &Args,
1342                                 SourceLocation Loc,
1343                                 DeclarationName Entity) {
1344   assert(!ActiveTemplateInstantiations.empty() &&
1345          "Cannot perform an instantiation without some context on the "
1346          "instantiation stack");
1347 
1348   if (!T->getType()->isInstantiationDependentType() &&
1349       !T->getType()->isVariablyModifiedType())
1350     return T;
1351 
1352   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1353   return Instantiator.TransformType(T);
1354 }
1355 
1356 TypeSourceInfo *Sema::SubstType(TypeLoc TL,
1357                                 const MultiLevelTemplateArgumentList &Args,
1358                                 SourceLocation Loc,
1359                                 DeclarationName Entity) {
1360   assert(!ActiveTemplateInstantiations.empty() &&
1361          "Cannot perform an instantiation without some context on the "
1362          "instantiation stack");
1363 
1364   if (TL.getType().isNull())
1365     return 0;
1366 
1367   if (!TL.getType()->isInstantiationDependentType() &&
1368       !TL.getType()->isVariablyModifiedType()) {
1369     // FIXME: Make a copy of the TypeLoc data here, so that we can
1370     // return a new TypeSourceInfo. Inefficient!
1371     TypeLocBuilder TLB;
1372     TLB.pushFullCopy(TL);
1373     return TLB.getTypeSourceInfo(Context, TL.getType());
1374   }
1375 
1376   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1377   TypeLocBuilder TLB;
1378   TLB.reserve(TL.getFullDataSize());
1379   QualType Result = Instantiator.TransformType(TLB, TL);
1380   if (Result.isNull())
1381     return 0;
1382 
1383   return TLB.getTypeSourceInfo(Context, Result);
1384 }
1385 
1386 /// Deprecated form of the above.
1387 QualType Sema::SubstType(QualType T,
1388                          const MultiLevelTemplateArgumentList &TemplateArgs,
1389                          SourceLocation Loc, DeclarationName Entity) {
1390   assert(!ActiveTemplateInstantiations.empty() &&
1391          "Cannot perform an instantiation without some context on the "
1392          "instantiation stack");
1393 
1394   // If T is not a dependent type or a variably-modified type, there
1395   // is nothing to do.
1396   if (!T->isInstantiationDependentType() && !T->isVariablyModifiedType())
1397     return T;
1398 
1399   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc, Entity);
1400   return Instantiator.TransformType(T);
1401 }
1402 
1403 static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
1404   if (T->getType()->isInstantiationDependentType() ||
1405       T->getType()->isVariablyModifiedType())
1406     return true;
1407 
1408   TypeLoc TL = T->getTypeLoc().IgnoreParens();
1409   if (!isa<FunctionProtoTypeLoc>(TL))
1410     return false;
1411 
1412   FunctionProtoTypeLoc FP = cast<FunctionProtoTypeLoc>(TL);
1413   for (unsigned I = 0, E = FP.getNumArgs(); I != E; ++I) {
1414     ParmVarDecl *P = FP.getArg(I);
1415 
1416     // The parameter's type as written might be dependent even if the
1417     // decayed type was not dependent.
1418     if (TypeSourceInfo *TSInfo = P->getTypeSourceInfo())
1419       if (TSInfo->getType()->isInstantiationDependentType())
1420         return true;
1421 
1422     // TODO: currently we always rebuild expressions.  When we
1423     // properly get lazier about this, we should use the same
1424     // logic to avoid rebuilding prototypes here.
1425     if (P->hasDefaultArg())
1426       return true;
1427   }
1428 
1429   return false;
1430 }
1431 
1432 /// A form of SubstType intended specifically for instantiating the
1433 /// type of a FunctionDecl.  Its purpose is solely to force the
1434 /// instantiation of default-argument expressions.
1435 TypeSourceInfo *Sema::SubstFunctionDeclType(TypeSourceInfo *T,
1436                                 const MultiLevelTemplateArgumentList &Args,
1437                                 SourceLocation Loc,
1438                                 DeclarationName Entity) {
1439   assert(!ActiveTemplateInstantiations.empty() &&
1440          "Cannot perform an instantiation without some context on the "
1441          "instantiation stack");
1442 
1443   if (!NeedsInstantiationAsFunctionType(T))
1444     return T;
1445 
1446   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1447 
1448   TypeLocBuilder TLB;
1449 
1450   TypeLoc TL = T->getTypeLoc();
1451   TLB.reserve(TL.getFullDataSize());
1452 
1453   QualType Result = Instantiator.TransformType(TLB, TL);
1454   if (Result.isNull())
1455     return 0;
1456 
1457   return TLB.getTypeSourceInfo(Context, Result);
1458 }
1459 
1460 ParmVarDecl *Sema::SubstParmVarDecl(ParmVarDecl *OldParm,
1461                             const MultiLevelTemplateArgumentList &TemplateArgs,
1462                                     int indexAdjustment,
1463                                     llvm::Optional<unsigned> NumExpansions,
1464                                     bool ExpectParameterPack) {
1465   TypeSourceInfo *OldDI = OldParm->getTypeSourceInfo();
1466   TypeSourceInfo *NewDI = 0;
1467 
1468   TypeLoc OldTL = OldDI->getTypeLoc();
1469   if (isa<PackExpansionTypeLoc>(OldTL)) {
1470     PackExpansionTypeLoc ExpansionTL = cast<PackExpansionTypeLoc>(OldTL);
1471 
1472     // We have a function parameter pack. Substitute into the pattern of the
1473     // expansion.
1474     NewDI = SubstType(ExpansionTL.getPatternLoc(), TemplateArgs,
1475                       OldParm->getLocation(), OldParm->getDeclName());
1476     if (!NewDI)
1477       return 0;
1478 
1479     if (NewDI->getType()->containsUnexpandedParameterPack()) {
1480       // We still have unexpanded parameter packs, which means that
1481       // our function parameter is still a function parameter pack.
1482       // Therefore, make its type a pack expansion type.
1483       NewDI = CheckPackExpansion(NewDI, ExpansionTL.getEllipsisLoc(),
1484                                  NumExpansions);
1485     } else if (ExpectParameterPack) {
1486       // We expected to get a parameter pack but didn't (because the type
1487       // itself is not a pack expansion type), so complain. This can occur when
1488       // the substitution goes through an alias template that "loses" the
1489       // pack expansion.
1490       Diag(OldParm->getLocation(),
1491            diag::err_function_parameter_pack_without_parameter_packs)
1492         << NewDI->getType();
1493       return 0;
1494     }
1495   } else {
1496     NewDI = SubstType(OldDI, TemplateArgs, OldParm->getLocation(),
1497                       OldParm->getDeclName());
1498   }
1499 
1500   if (!NewDI)
1501     return 0;
1502 
1503   if (NewDI->getType()->isVoidType()) {
1504     Diag(OldParm->getLocation(), diag::err_param_with_void_type);
1505     return 0;
1506   }
1507 
1508   ParmVarDecl *NewParm = CheckParameter(Context.getTranslationUnitDecl(),
1509                                         OldParm->getInnerLocStart(),
1510                                         OldParm->getLocation(),
1511                                         OldParm->getIdentifier(),
1512                                         NewDI->getType(), NewDI,
1513                                         OldParm->getStorageClass(),
1514                                         OldParm->getStorageClassAsWritten());
1515   if (!NewParm)
1516     return 0;
1517 
1518   // Mark the (new) default argument as uninstantiated (if any).
1519   if (OldParm->hasUninstantiatedDefaultArg()) {
1520     Expr *Arg = OldParm->getUninstantiatedDefaultArg();
1521     NewParm->setUninstantiatedDefaultArg(Arg);
1522   } else if (OldParm->hasUnparsedDefaultArg()) {
1523     NewParm->setUnparsedDefaultArg();
1524     UnparsedDefaultArgInstantiations[OldParm].push_back(NewParm);
1525   } else if (Expr *Arg = OldParm->getDefaultArg())
1526     NewParm->setUninstantiatedDefaultArg(Arg);
1527 
1528   NewParm->setHasInheritedDefaultArg(OldParm->hasInheritedDefaultArg());
1529 
1530   if (OldParm->isParameterPack() && !NewParm->isParameterPack()) {
1531     // Add the new parameter to the instantiated parameter pack.
1532     CurrentInstantiationScope->InstantiatedLocalPackArg(OldParm, NewParm);
1533   } else {
1534     // Introduce an Old -> New mapping
1535     CurrentInstantiationScope->InstantiatedLocal(OldParm, NewParm);
1536   }
1537 
1538   // FIXME: OldParm may come from a FunctionProtoType, in which case CurContext
1539   // can be anything, is this right ?
1540   NewParm->setDeclContext(CurContext);
1541 
1542   NewParm->setScopeInfo(OldParm->getFunctionScopeDepth(),
1543                         OldParm->getFunctionScopeIndex() + indexAdjustment);
1544 
1545   return NewParm;
1546 }
1547 
1548 /// \brief Substitute the given template arguments into the given set of
1549 /// parameters, producing the set of parameter types that would be generated
1550 /// from such a substitution.
1551 bool Sema::SubstParmTypes(SourceLocation Loc,
1552                           ParmVarDecl **Params, unsigned NumParams,
1553                           const MultiLevelTemplateArgumentList &TemplateArgs,
1554                           SmallVectorImpl<QualType> &ParamTypes,
1555                           SmallVectorImpl<ParmVarDecl *> *OutParams) {
1556   assert(!ActiveTemplateInstantiations.empty() &&
1557          "Cannot perform an instantiation without some context on the "
1558          "instantiation stack");
1559 
1560   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
1561                                     DeclarationName());
1562   return Instantiator.TransformFunctionTypeParams(Loc, Params, NumParams, 0,
1563                                                   ParamTypes, OutParams);
1564 }
1565 
1566 /// \brief Perform substitution on the base class specifiers of the
1567 /// given class template specialization.
1568 ///
1569 /// Produces a diagnostic and returns true on error, returns false and
1570 /// attaches the instantiated base classes to the class template
1571 /// specialization if successful.
1572 bool
1573 Sema::SubstBaseSpecifiers(CXXRecordDecl *Instantiation,
1574                           CXXRecordDecl *Pattern,
1575                           const MultiLevelTemplateArgumentList &TemplateArgs) {
1576   bool Invalid = false;
1577   SmallVector<CXXBaseSpecifier*, 4> InstantiatedBases;
1578   for (ClassTemplateSpecializationDecl::base_class_iterator
1579          Base = Pattern->bases_begin(), BaseEnd = Pattern->bases_end();
1580        Base != BaseEnd; ++Base) {
1581     if (!Base->getType()->isDependentType()) {
1582       InstantiatedBases.push_back(new (Context) CXXBaseSpecifier(*Base));
1583       continue;
1584     }
1585 
1586     SourceLocation EllipsisLoc;
1587     TypeSourceInfo *BaseTypeLoc;
1588     if (Base->isPackExpansion()) {
1589       // This is a pack expansion. See whether we should expand it now, or
1590       // wait until later.
1591       SmallVector<UnexpandedParameterPack, 2> Unexpanded;
1592       collectUnexpandedParameterPacks(Base->getTypeSourceInfo()->getTypeLoc(),
1593                                       Unexpanded);
1594       bool ShouldExpand = false;
1595       bool RetainExpansion = false;
1596       llvm::Optional<unsigned> NumExpansions;
1597       if (CheckParameterPacksForExpansion(Base->getEllipsisLoc(),
1598                                           Base->getSourceRange(),
1599                                           Unexpanded,
1600                                           TemplateArgs, ShouldExpand,
1601                                           RetainExpansion,
1602                                           NumExpansions)) {
1603         Invalid = true;
1604         continue;
1605       }
1606 
1607       // If we should expand this pack expansion now, do so.
1608       if (ShouldExpand) {
1609         for (unsigned I = 0; I != *NumExpansions; ++I) {
1610             Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, I);
1611 
1612           TypeSourceInfo *BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1613                                                   TemplateArgs,
1614                                               Base->getSourceRange().getBegin(),
1615                                                   DeclarationName());
1616           if (!BaseTypeLoc) {
1617             Invalid = true;
1618             continue;
1619           }
1620 
1621           if (CXXBaseSpecifier *InstantiatedBase
1622                 = CheckBaseSpecifier(Instantiation,
1623                                      Base->getSourceRange(),
1624                                      Base->isVirtual(),
1625                                      Base->getAccessSpecifierAsWritten(),
1626                                      BaseTypeLoc,
1627                                      SourceLocation()))
1628             InstantiatedBases.push_back(InstantiatedBase);
1629           else
1630             Invalid = true;
1631         }
1632 
1633         continue;
1634       }
1635 
1636       // The resulting base specifier will (still) be a pack expansion.
1637       EllipsisLoc = Base->getEllipsisLoc();
1638       Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
1639       BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1640                               TemplateArgs,
1641                               Base->getSourceRange().getBegin(),
1642                               DeclarationName());
1643     } else {
1644       BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1645                               TemplateArgs,
1646                               Base->getSourceRange().getBegin(),
1647                               DeclarationName());
1648     }
1649 
1650     if (!BaseTypeLoc) {
1651       Invalid = true;
1652       continue;
1653     }
1654 
1655     if (CXXBaseSpecifier *InstantiatedBase
1656           = CheckBaseSpecifier(Instantiation,
1657                                Base->getSourceRange(),
1658                                Base->isVirtual(),
1659                                Base->getAccessSpecifierAsWritten(),
1660                                BaseTypeLoc,
1661                                EllipsisLoc))
1662       InstantiatedBases.push_back(InstantiatedBase);
1663     else
1664       Invalid = true;
1665   }
1666 
1667   if (!Invalid &&
1668       AttachBaseSpecifiers(Instantiation, InstantiatedBases.data(),
1669                            InstantiatedBases.size()))
1670     Invalid = true;
1671 
1672   return Invalid;
1673 }
1674 
1675 // Defined via #include from SemaTemplateInstantiateDecl.cpp
1676 namespace clang {
1677   namespace sema {
1678     Attr *instantiateTemplateAttribute(const Attr *At, ASTContext &C, Sema &S,
1679                             const MultiLevelTemplateArgumentList &TemplateArgs);
1680   }
1681 }
1682 
1683 /// \brief Instantiate the definition of a class from a given pattern.
1684 ///
1685 /// \param PointOfInstantiation The point of instantiation within the
1686 /// source code.
1687 ///
1688 /// \param Instantiation is the declaration whose definition is being
1689 /// instantiated. This will be either a class template specialization
1690 /// or a member class of a class template specialization.
1691 ///
1692 /// \param Pattern is the pattern from which the instantiation
1693 /// occurs. This will be either the declaration of a class template or
1694 /// the declaration of a member class of a class template.
1695 ///
1696 /// \param TemplateArgs The template arguments to be substituted into
1697 /// the pattern.
1698 ///
1699 /// \param TSK the kind of implicit or explicit instantiation to perform.
1700 ///
1701 /// \param Complain whether to complain if the class cannot be instantiated due
1702 /// to the lack of a definition.
1703 ///
1704 /// \returns true if an error occurred, false otherwise.
1705 bool
1706 Sema::InstantiateClass(SourceLocation PointOfInstantiation,
1707                        CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
1708                        const MultiLevelTemplateArgumentList &TemplateArgs,
1709                        TemplateSpecializationKind TSK,
1710                        bool Complain) {
1711   bool Invalid = false;
1712 
1713   CXXRecordDecl *PatternDef
1714     = cast_or_null<CXXRecordDecl>(Pattern->getDefinition());
1715   if (!PatternDef || PatternDef->isBeingDefined()) {
1716     if (!Complain || (PatternDef && PatternDef->isInvalidDecl())) {
1717       // Say nothing
1718     } else if (PatternDef) {
1719       assert(PatternDef->isBeingDefined());
1720       Diag(PointOfInstantiation,
1721            diag::err_template_instantiate_within_definition)
1722         << (TSK != TSK_ImplicitInstantiation)
1723         << Context.getTypeDeclType(Instantiation);
1724       // Not much point in noting the template declaration here, since
1725       // we're lexically inside it.
1726       Instantiation->setInvalidDecl();
1727     } else if (Pattern == Instantiation->getInstantiatedFromMemberClass()) {
1728       Diag(PointOfInstantiation,
1729            diag::err_implicit_instantiate_member_undefined)
1730         << Context.getTypeDeclType(Instantiation);
1731       Diag(Pattern->getLocation(), diag::note_member_of_template_here);
1732     } else {
1733       Diag(PointOfInstantiation, diag::err_template_instantiate_undefined)
1734         << (TSK != TSK_ImplicitInstantiation)
1735         << Context.getTypeDeclType(Instantiation);
1736       Diag(Pattern->getLocation(), diag::note_template_decl_here);
1737     }
1738 
1739     // In general, Instantiation isn't marked invalid to get more than one
1740     // error for multiple undefined instantiations. But the code that does
1741     // explicit declaration -> explicit definition conversion can't handle
1742     // invalid declarations, so mark as invalid in that case.
1743     if (TSK == TSK_ExplicitInstantiationDeclaration)
1744        Instantiation->setInvalidDecl();
1745     return true;
1746   }
1747   Pattern = PatternDef;
1748 
1749   // \brief Record the point of instantiation.
1750   if (MemberSpecializationInfo *MSInfo
1751         = Instantiation->getMemberSpecializationInfo()) {
1752     MSInfo->setTemplateSpecializationKind(TSK);
1753     MSInfo->setPointOfInstantiation(PointOfInstantiation);
1754   } else if (ClassTemplateSpecializationDecl *Spec
1755         = dyn_cast<ClassTemplateSpecializationDecl>(Instantiation)) {
1756     Spec->setTemplateSpecializationKind(TSK);
1757     Spec->setPointOfInstantiation(PointOfInstantiation);
1758   }
1759 
1760   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
1761   if (Inst)
1762     return true;
1763 
1764   // Enter the scope of this instantiation. We don't use
1765   // PushDeclContext because we don't have a scope.
1766   ContextRAII SavedContext(*this, Instantiation);
1767   EnterExpressionEvaluationContext EvalContext(*this,
1768                                                Sema::PotentiallyEvaluated);
1769 
1770   // If this is an instantiation of a local class, merge this local
1771   // instantiation scope with the enclosing scope. Otherwise, every
1772   // instantiation of a class has its own local instantiation scope.
1773   bool MergeWithParentScope = !Instantiation->isDefinedOutsideFunctionOrMethod();
1774   LocalInstantiationScope Scope(*this, MergeWithParentScope);
1775 
1776   // Pull attributes from the pattern onto the instantiation.
1777   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
1778 
1779   // Start the definition of this instantiation.
1780   Instantiation->startDefinition();
1781 
1782   Instantiation->setTagKind(Pattern->getTagKind());
1783 
1784   // Do substitution on the base class specifiers.
1785   if (SubstBaseSpecifiers(Instantiation, Pattern, TemplateArgs))
1786     Invalid = true;
1787 
1788   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
1789   SmallVector<Decl*, 4> Fields;
1790   SmallVector<std::pair<FieldDecl*, FieldDecl*>, 4>
1791     FieldsWithMemberInitializers;
1792   // Delay instantiation of late parsed attributes.
1793   LateInstantiatedAttrVec LateAttrs;
1794   Instantiator.enableLateAttributeInstantiation(&LateAttrs);
1795 
1796   for (RecordDecl::decl_iterator Member = Pattern->decls_begin(),
1797          MemberEnd = Pattern->decls_end();
1798        Member != MemberEnd; ++Member) {
1799     // Don't instantiate members not belonging in this semantic context.
1800     // e.g. for:
1801     // @code
1802     //    template <int i> class A {
1803     //      class B *g;
1804     //    };
1805     // @endcode
1806     // 'class B' has the template as lexical context but semantically it is
1807     // introduced in namespace scope.
1808     if ((*Member)->getDeclContext() != Pattern)
1809       continue;
1810 
1811     if ((*Member)->isInvalidDecl()) {
1812       Invalid = true;
1813       continue;
1814     }
1815 
1816     Decl *NewMember = Instantiator.Visit(*Member);
1817     if (NewMember) {
1818       if (FieldDecl *Field = dyn_cast<FieldDecl>(NewMember)) {
1819         Fields.push_back(Field);
1820         FieldDecl *OldField = cast<FieldDecl>(*Member);
1821         if (OldField->getInClassInitializer())
1822           FieldsWithMemberInitializers.push_back(std::make_pair(OldField,
1823                                                                 Field));
1824       } else if (NewMember->isInvalidDecl())
1825         Invalid = true;
1826     } else {
1827       // FIXME: Eventually, a NULL return will mean that one of the
1828       // instantiations was a semantic disaster, and we'll want to set Invalid =
1829       // true. For now, we expect to skip some members that we can't yet handle.
1830     }
1831   }
1832 
1833   // Finish checking fields.
1834   ActOnFields(0, Instantiation->getLocation(), Instantiation, Fields,
1835               SourceLocation(), SourceLocation(), 0);
1836   CheckCompletedCXXClass(Instantiation);
1837 
1838   // Attach any in-class member initializers now the class is complete.
1839   for (unsigned I = 0, N = FieldsWithMemberInitializers.size(); I != N; ++I) {
1840     FieldDecl *OldField = FieldsWithMemberInitializers[I].first;
1841     FieldDecl *NewField = FieldsWithMemberInitializers[I].second;
1842     Expr *OldInit = OldField->getInClassInitializer();
1843 
1844     ExprResult NewInit = SubstInitializer(OldInit, TemplateArgs,
1845                                           /*CXXDirectInit=*/false);
1846     if (NewInit.isInvalid())
1847       NewField->setInvalidDecl();
1848     else {
1849       Expr *Init = NewInit.take();
1850       assert(Init && "no-argument initializer in class");
1851       assert(!isa<ParenListExpr>(Init) && "call-style init in class");
1852       ActOnCXXInClassMemberInitializer(NewField,
1853                                        Init->getSourceRange().getBegin(), Init);
1854     }
1855   }
1856 
1857   // Instantiate late parsed attributes, and attach them to their decls.
1858   // See Sema::InstantiateAttrs
1859   for (LateInstantiatedAttrVec::iterator I = LateAttrs.begin(),
1860        E = LateAttrs.end(); I != E; ++I) {
1861     assert(CurrentInstantiationScope == Instantiator.getStartingScope());
1862     CurrentInstantiationScope = I->Scope;
1863     Attr *NewAttr =
1864       instantiateTemplateAttribute(I->TmplAttr, Context, *this, TemplateArgs);
1865     I->NewDecl->addAttr(NewAttr);
1866     LocalInstantiationScope::deleteScopes(I->Scope,
1867                                           Instantiator.getStartingScope());
1868   }
1869   Instantiator.disableLateAttributeInstantiation();
1870   LateAttrs.clear();
1871 
1872   if (!FieldsWithMemberInitializers.empty())
1873     ActOnFinishDelayedMemberInitializers(Instantiation);
1874 
1875   if (TSK == TSK_ImplicitInstantiation) {
1876     Instantiation->setLocation(Pattern->getLocation());
1877     Instantiation->setLocStart(Pattern->getInnerLocStart());
1878     Instantiation->setRBraceLoc(Pattern->getRBraceLoc());
1879   }
1880 
1881   if (Instantiation->isInvalidDecl())
1882     Invalid = true;
1883   else {
1884     // Instantiate any out-of-line class template partial
1885     // specializations now.
1886     for (TemplateDeclInstantiator::delayed_partial_spec_iterator
1887               P = Instantiator.delayed_partial_spec_begin(),
1888            PEnd = Instantiator.delayed_partial_spec_end();
1889          P != PEnd; ++P) {
1890       if (!Instantiator.InstantiateClassTemplatePartialSpecialization(
1891                                                                 P->first,
1892                                                                 P->second)) {
1893         Invalid = true;
1894         break;
1895       }
1896     }
1897   }
1898 
1899   // Exit the scope of this instantiation.
1900   SavedContext.pop();
1901 
1902   if (!Invalid) {
1903     Consumer.HandleTagDeclDefinition(Instantiation);
1904 
1905     // Always emit the vtable for an explicit instantiation definition
1906     // of a polymorphic class template specialization.
1907     if (TSK == TSK_ExplicitInstantiationDefinition)
1908       MarkVTableUsed(PointOfInstantiation, Instantiation, true);
1909   }
1910 
1911   return Invalid;
1912 }
1913 
1914 namespace {
1915   /// \brief A partial specialization whose template arguments have matched
1916   /// a given template-id.
1917   struct PartialSpecMatchResult {
1918     ClassTemplatePartialSpecializationDecl *Partial;
1919     TemplateArgumentList *Args;
1920   };
1921 }
1922 
1923 bool
1924 Sema::InstantiateClassTemplateSpecialization(
1925                            SourceLocation PointOfInstantiation,
1926                            ClassTemplateSpecializationDecl *ClassTemplateSpec,
1927                            TemplateSpecializationKind TSK,
1928                            bool Complain) {
1929   // Perform the actual instantiation on the canonical declaration.
1930   ClassTemplateSpec = cast<ClassTemplateSpecializationDecl>(
1931                                          ClassTemplateSpec->getCanonicalDecl());
1932 
1933   // Check whether we have already instantiated or specialized this class
1934   // template specialization.
1935   if (ClassTemplateSpec->getSpecializationKind() != TSK_Undeclared) {
1936     if (ClassTemplateSpec->getSpecializationKind() ==
1937           TSK_ExplicitInstantiationDeclaration &&
1938         TSK == TSK_ExplicitInstantiationDefinition) {
1939       // An explicit instantiation definition follows an explicit instantiation
1940       // declaration (C++0x [temp.explicit]p10); go ahead and perform the
1941       // explicit instantiation.
1942       ClassTemplateSpec->setSpecializationKind(TSK);
1943 
1944       // If this is an explicit instantiation definition, mark the
1945       // vtable as used.
1946       if (TSK == TSK_ExplicitInstantiationDefinition &&
1947           !ClassTemplateSpec->isInvalidDecl())
1948         MarkVTableUsed(PointOfInstantiation, ClassTemplateSpec, true);
1949 
1950       return false;
1951     }
1952 
1953     // We can only instantiate something that hasn't already been
1954     // instantiated or specialized. Fail without any diagnostics: our
1955     // caller will provide an error message.
1956     return true;
1957   }
1958 
1959   if (ClassTemplateSpec->isInvalidDecl())
1960     return true;
1961 
1962   ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
1963   CXXRecordDecl *Pattern = 0;
1964 
1965   // C++ [temp.class.spec.match]p1:
1966   //   When a class template is used in a context that requires an
1967   //   instantiation of the class, it is necessary to determine
1968   //   whether the instantiation is to be generated using the primary
1969   //   template or one of the partial specializations. This is done by
1970   //   matching the template arguments of the class template
1971   //   specialization with the template argument lists of the partial
1972   //   specializations.
1973   typedef PartialSpecMatchResult MatchResult;
1974   SmallVector<MatchResult, 4> Matched;
1975   SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
1976   Template->getPartialSpecializations(PartialSpecs);
1977   for (unsigned I = 0, N = PartialSpecs.size(); I != N; ++I) {
1978     ClassTemplatePartialSpecializationDecl *Partial = PartialSpecs[I];
1979     TemplateDeductionInfo Info(Context, PointOfInstantiation);
1980     if (TemplateDeductionResult Result
1981           = DeduceTemplateArguments(Partial,
1982                                     ClassTemplateSpec->getTemplateArgs(),
1983                                     Info)) {
1984       // FIXME: Store the failed-deduction information for use in
1985       // diagnostics, later.
1986       (void)Result;
1987     } else {
1988       Matched.push_back(PartialSpecMatchResult());
1989       Matched.back().Partial = Partial;
1990       Matched.back().Args = Info.take();
1991     }
1992   }
1993 
1994   // If we're dealing with a member template where the template parameters
1995   // have been instantiated, this provides the original template parameters
1996   // from which the member template's parameters were instantiated.
1997   SmallVector<const NamedDecl *, 4> InstantiatedTemplateParameters;
1998 
1999   if (Matched.size() >= 1) {
2000     SmallVector<MatchResult, 4>::iterator Best = Matched.begin();
2001     if (Matched.size() == 1) {
2002       //   -- If exactly one matching specialization is found, the
2003       //      instantiation is generated from that specialization.
2004       // We don't need to do anything for this.
2005     } else {
2006       //   -- If more than one matching specialization is found, the
2007       //      partial order rules (14.5.4.2) are used to determine
2008       //      whether one of the specializations is more specialized
2009       //      than the others. If none of the specializations is more
2010       //      specialized than all of the other matching
2011       //      specializations, then the use of the class template is
2012       //      ambiguous and the program is ill-formed.
2013       for (SmallVector<MatchResult, 4>::iterator P = Best + 1,
2014                                                     PEnd = Matched.end();
2015            P != PEnd; ++P) {
2016         if (getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2017                                                     PointOfInstantiation)
2018               == P->Partial)
2019           Best = P;
2020       }
2021 
2022       // Determine if the best partial specialization is more specialized than
2023       // the others.
2024       bool Ambiguous = false;
2025       for (SmallVector<MatchResult, 4>::iterator P = Matched.begin(),
2026                                                     PEnd = Matched.end();
2027            P != PEnd; ++P) {
2028         if (P != Best &&
2029             getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2030                                                     PointOfInstantiation)
2031               != Best->Partial) {
2032           Ambiguous = true;
2033           break;
2034         }
2035       }
2036 
2037       if (Ambiguous) {
2038         // Partial ordering did not produce a clear winner. Complain.
2039         ClassTemplateSpec->setInvalidDecl();
2040         Diag(PointOfInstantiation, diag::err_partial_spec_ordering_ambiguous)
2041           << ClassTemplateSpec;
2042 
2043         // Print the matching partial specializations.
2044         for (SmallVector<MatchResult, 4>::iterator P = Matched.begin(),
2045                                                       PEnd = Matched.end();
2046              P != PEnd; ++P)
2047           Diag(P->Partial->getLocation(), diag::note_partial_spec_match)
2048             << getTemplateArgumentBindingsText(
2049                                             P->Partial->getTemplateParameters(),
2050                                                *P->Args);
2051 
2052         return true;
2053       }
2054     }
2055 
2056     // Instantiate using the best class template partial specialization.
2057     ClassTemplatePartialSpecializationDecl *OrigPartialSpec = Best->Partial;
2058     while (OrigPartialSpec->getInstantiatedFromMember()) {
2059       // If we've found an explicit specialization of this class template,
2060       // stop here and use that as the pattern.
2061       if (OrigPartialSpec->isMemberSpecialization())
2062         break;
2063 
2064       OrigPartialSpec = OrigPartialSpec->getInstantiatedFromMember();
2065     }
2066 
2067     Pattern = OrigPartialSpec;
2068     ClassTemplateSpec->setInstantiationOf(Best->Partial, Best->Args);
2069   } else {
2070     //   -- If no matches are found, the instantiation is generated
2071     //      from the primary template.
2072     ClassTemplateDecl *OrigTemplate = Template;
2073     while (OrigTemplate->getInstantiatedFromMemberTemplate()) {
2074       // If we've found an explicit specialization of this class template,
2075       // stop here and use that as the pattern.
2076       if (OrigTemplate->isMemberSpecialization())
2077         break;
2078 
2079       OrigTemplate = OrigTemplate->getInstantiatedFromMemberTemplate();
2080     }
2081 
2082     Pattern = OrigTemplate->getTemplatedDecl();
2083   }
2084 
2085   bool Result = InstantiateClass(PointOfInstantiation, ClassTemplateSpec,
2086                                  Pattern,
2087                                 getTemplateInstantiationArgs(ClassTemplateSpec),
2088                                  TSK,
2089                                  Complain);
2090 
2091   return Result;
2092 }
2093 
2094 /// \brief Instantiates the definitions of all of the member
2095 /// of the given class, which is an instantiation of a class template
2096 /// or a member class of a template.
2097 void
2098 Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
2099                               CXXRecordDecl *Instantiation,
2100                         const MultiLevelTemplateArgumentList &TemplateArgs,
2101                               TemplateSpecializationKind TSK) {
2102   for (DeclContext::decl_iterator D = Instantiation->decls_begin(),
2103                                DEnd = Instantiation->decls_end();
2104        D != DEnd; ++D) {
2105     bool SuppressNew = false;
2106     if (FunctionDecl *Function = dyn_cast<FunctionDecl>(*D)) {
2107       if (FunctionDecl *Pattern
2108             = Function->getInstantiatedFromMemberFunction()) {
2109         MemberSpecializationInfo *MSInfo
2110           = Function->getMemberSpecializationInfo();
2111         assert(MSInfo && "No member specialization information?");
2112         if (MSInfo->getTemplateSpecializationKind()
2113                                                  == TSK_ExplicitSpecialization)
2114           continue;
2115 
2116         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2117                                                    Function,
2118                                         MSInfo->getTemplateSpecializationKind(),
2119                                               MSInfo->getPointOfInstantiation(),
2120                                                    SuppressNew) ||
2121             SuppressNew)
2122           continue;
2123 
2124         if (Function->isDefined())
2125           continue;
2126 
2127         if (TSK == TSK_ExplicitInstantiationDefinition) {
2128           // C++0x [temp.explicit]p8:
2129           //   An explicit instantiation definition that names a class template
2130           //   specialization explicitly instantiates the class template
2131           //   specialization and is only an explicit instantiation definition
2132           //   of members whose definition is visible at the point of
2133           //   instantiation.
2134           if (!Pattern->isDefined())
2135             continue;
2136 
2137           Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2138 
2139           InstantiateFunctionDefinition(PointOfInstantiation, Function);
2140         } else {
2141           Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2142         }
2143       }
2144     } else if (VarDecl *Var = dyn_cast<VarDecl>(*D)) {
2145       if (Var->isStaticDataMember()) {
2146         MemberSpecializationInfo *MSInfo = Var->getMemberSpecializationInfo();
2147         assert(MSInfo && "No member specialization information?");
2148         if (MSInfo->getTemplateSpecializationKind()
2149                                                  == TSK_ExplicitSpecialization)
2150           continue;
2151 
2152         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2153                                                    Var,
2154                                         MSInfo->getTemplateSpecializationKind(),
2155                                               MSInfo->getPointOfInstantiation(),
2156                                                    SuppressNew) ||
2157             SuppressNew)
2158           continue;
2159 
2160         if (TSK == TSK_ExplicitInstantiationDefinition) {
2161           // C++0x [temp.explicit]p8:
2162           //   An explicit instantiation definition that names a class template
2163           //   specialization explicitly instantiates the class template
2164           //   specialization and is only an explicit instantiation definition
2165           //   of members whose definition is visible at the point of
2166           //   instantiation.
2167           if (!Var->getInstantiatedFromStaticDataMember()
2168                                                      ->getOutOfLineDefinition())
2169             continue;
2170 
2171           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2172           InstantiateStaticDataMemberDefinition(PointOfInstantiation, Var);
2173         } else {
2174           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2175         }
2176       }
2177     } else if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(*D)) {
2178       // Always skip the injected-class-name, along with any
2179       // redeclarations of nested classes, since both would cause us
2180       // to try to instantiate the members of a class twice.
2181       if (Record->isInjectedClassName() || Record->getPreviousDecl())
2182         continue;
2183 
2184       MemberSpecializationInfo *MSInfo = Record->getMemberSpecializationInfo();
2185       assert(MSInfo && "No member specialization information?");
2186 
2187       if (MSInfo->getTemplateSpecializationKind()
2188                                                 == TSK_ExplicitSpecialization)
2189         continue;
2190 
2191       if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2192                                                  Record,
2193                                         MSInfo->getTemplateSpecializationKind(),
2194                                               MSInfo->getPointOfInstantiation(),
2195                                                  SuppressNew) ||
2196           SuppressNew)
2197         continue;
2198 
2199       CXXRecordDecl *Pattern = Record->getInstantiatedFromMemberClass();
2200       assert(Pattern && "Missing instantiated-from-template information");
2201 
2202       if (!Record->getDefinition()) {
2203         if (!Pattern->getDefinition()) {
2204           // C++0x [temp.explicit]p8:
2205           //   An explicit instantiation definition that names a class template
2206           //   specialization explicitly instantiates the class template
2207           //   specialization and is only an explicit instantiation definition
2208           //   of members whose definition is visible at the point of
2209           //   instantiation.
2210           if (TSK == TSK_ExplicitInstantiationDeclaration) {
2211             MSInfo->setTemplateSpecializationKind(TSK);
2212             MSInfo->setPointOfInstantiation(PointOfInstantiation);
2213           }
2214 
2215           continue;
2216         }
2217 
2218         InstantiateClass(PointOfInstantiation, Record, Pattern,
2219                          TemplateArgs,
2220                          TSK);
2221       } else {
2222         if (TSK == TSK_ExplicitInstantiationDefinition &&
2223             Record->getTemplateSpecializationKind() ==
2224                 TSK_ExplicitInstantiationDeclaration) {
2225           Record->setTemplateSpecializationKind(TSK);
2226           MarkVTableUsed(PointOfInstantiation, Record, true);
2227         }
2228       }
2229 
2230       Pattern = cast_or_null<CXXRecordDecl>(Record->getDefinition());
2231       if (Pattern)
2232         InstantiateClassMembers(PointOfInstantiation, Pattern, TemplateArgs,
2233                                 TSK);
2234     }
2235   }
2236 }
2237 
2238 /// \brief Instantiate the definitions of all of the members of the
2239 /// given class template specialization, which was named as part of an
2240 /// explicit instantiation.
2241 void
2242 Sema::InstantiateClassTemplateSpecializationMembers(
2243                                            SourceLocation PointOfInstantiation,
2244                             ClassTemplateSpecializationDecl *ClassTemplateSpec,
2245                                                TemplateSpecializationKind TSK) {
2246   // C++0x [temp.explicit]p7:
2247   //   An explicit instantiation that names a class template
2248   //   specialization is an explicit instantion of the same kind
2249   //   (declaration or definition) of each of its members (not
2250   //   including members inherited from base classes) that has not
2251   //   been previously explicitly specialized in the translation unit
2252   //   containing the explicit instantiation, except as described
2253   //   below.
2254   InstantiateClassMembers(PointOfInstantiation, ClassTemplateSpec,
2255                           getTemplateInstantiationArgs(ClassTemplateSpec),
2256                           TSK);
2257 }
2258 
2259 StmtResult
2260 Sema::SubstStmt(Stmt *S, const MultiLevelTemplateArgumentList &TemplateArgs) {
2261   if (!S)
2262     return Owned(S);
2263 
2264   TemplateInstantiator Instantiator(*this, TemplateArgs,
2265                                     SourceLocation(),
2266                                     DeclarationName());
2267   return Instantiator.TransformStmt(S);
2268 }
2269 
2270 ExprResult
2271 Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
2272   if (!E)
2273     return Owned(E);
2274 
2275   TemplateInstantiator Instantiator(*this, TemplateArgs,
2276                                     SourceLocation(),
2277                                     DeclarationName());
2278   return Instantiator.TransformExpr(E);
2279 }
2280 
2281 bool Sema::SubstExprs(Expr **Exprs, unsigned NumExprs, bool IsCall,
2282                       const MultiLevelTemplateArgumentList &TemplateArgs,
2283                       SmallVectorImpl<Expr *> &Outputs) {
2284   if (NumExprs == 0)
2285     return false;
2286 
2287   TemplateInstantiator Instantiator(*this, TemplateArgs,
2288                                     SourceLocation(),
2289                                     DeclarationName());
2290   return Instantiator.TransformExprs(Exprs, NumExprs, IsCall, Outputs);
2291 }
2292 
2293 NestedNameSpecifierLoc
2294 Sema::SubstNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
2295                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2296   if (!NNS)
2297     return NestedNameSpecifierLoc();
2298 
2299   TemplateInstantiator Instantiator(*this, TemplateArgs, NNS.getBeginLoc(),
2300                                     DeclarationName());
2301   return Instantiator.TransformNestedNameSpecifierLoc(NNS);
2302 }
2303 
2304 /// \brief Do template substitution on declaration name info.
2305 DeclarationNameInfo
2306 Sema::SubstDeclarationNameInfo(const DeclarationNameInfo &NameInfo,
2307                          const MultiLevelTemplateArgumentList &TemplateArgs) {
2308   TemplateInstantiator Instantiator(*this, TemplateArgs, NameInfo.getLoc(),
2309                                     NameInfo.getName());
2310   return Instantiator.TransformDeclarationNameInfo(NameInfo);
2311 }
2312 
2313 TemplateName
2314 Sema::SubstTemplateName(NestedNameSpecifierLoc QualifierLoc,
2315                         TemplateName Name, SourceLocation Loc,
2316                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2317   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
2318                                     DeclarationName());
2319   CXXScopeSpec SS;
2320   SS.Adopt(QualifierLoc);
2321   return Instantiator.TransformTemplateName(SS, Name, Loc);
2322 }
2323 
2324 bool Sema::Subst(const TemplateArgumentLoc *Args, unsigned NumArgs,
2325                  TemplateArgumentListInfo &Result,
2326                  const MultiLevelTemplateArgumentList &TemplateArgs) {
2327   TemplateInstantiator Instantiator(*this, TemplateArgs, SourceLocation(),
2328                                     DeclarationName());
2329 
2330   return Instantiator.TransformTemplateArguments(Args, NumArgs, Result);
2331 }
2332 
2333 llvm::PointerUnion<Decl *, LocalInstantiationScope::DeclArgumentPack *> *
2334 LocalInstantiationScope::findInstantiationOf(const Decl *D) {
2335   for (LocalInstantiationScope *Current = this; Current;
2336        Current = Current->Outer) {
2337 
2338     // Check if we found something within this scope.
2339     const Decl *CheckD = D;
2340     do {
2341       LocalDeclsMap::iterator Found = Current->LocalDecls.find(CheckD);
2342       if (Found != Current->LocalDecls.end())
2343         return &Found->second;
2344 
2345       // If this is a tag declaration, it's possible that we need to look for
2346       // a previous declaration.
2347       if (const TagDecl *Tag = dyn_cast<TagDecl>(CheckD))
2348         CheckD = Tag->getPreviousDecl();
2349       else
2350         CheckD = 0;
2351     } while (CheckD);
2352 
2353     // If we aren't combined with our outer scope, we're done.
2354     if (!Current->CombineWithOuterScope)
2355       break;
2356   }
2357 
2358   // If we didn't find the decl, then we either have a sema bug, or we have a
2359   // forward reference to a label declaration.  Return null to indicate that
2360   // we have an uninstantiated label.
2361   assert(isa<LabelDecl>(D) && "declaration not instantiated in this scope");
2362   return 0;
2363 }
2364 
2365 void LocalInstantiationScope::InstantiatedLocal(const Decl *D, Decl *Inst) {
2366   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2367   if (Stored.isNull())
2368     Stored = Inst;
2369   else if (Stored.is<Decl *>()) {
2370     assert(Stored.get<Decl *>() == Inst && "Already instantiated this local");
2371     Stored = Inst;
2372   } else
2373     LocalDecls[D].get<DeclArgumentPack *>()->push_back(Inst);
2374 }
2375 
2376 void LocalInstantiationScope::InstantiatedLocalPackArg(const Decl *D,
2377                                                        Decl *Inst) {
2378   DeclArgumentPack *Pack = LocalDecls[D].get<DeclArgumentPack *>();
2379   Pack->push_back(Inst);
2380 }
2381 
2382 void LocalInstantiationScope::MakeInstantiatedLocalArgPack(const Decl *D) {
2383   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2384   assert(Stored.isNull() && "Already instantiated this local");
2385   DeclArgumentPack *Pack = new DeclArgumentPack;
2386   Stored = Pack;
2387   ArgumentPacks.push_back(Pack);
2388 }
2389 
2390 void LocalInstantiationScope::SetPartiallySubstitutedPack(NamedDecl *Pack,
2391                                           const TemplateArgument *ExplicitArgs,
2392                                                     unsigned NumExplicitArgs) {
2393   assert((!PartiallySubstitutedPack || PartiallySubstitutedPack == Pack) &&
2394          "Already have a partially-substituted pack");
2395   assert((!PartiallySubstitutedPack
2396           || NumArgsInPartiallySubstitutedPack == NumExplicitArgs) &&
2397          "Wrong number of arguments in partially-substituted pack");
2398   PartiallySubstitutedPack = Pack;
2399   ArgsInPartiallySubstitutedPack = ExplicitArgs;
2400   NumArgsInPartiallySubstitutedPack = NumExplicitArgs;
2401 }
2402 
2403 NamedDecl *LocalInstantiationScope::getPartiallySubstitutedPack(
2404                                          const TemplateArgument **ExplicitArgs,
2405                                               unsigned *NumExplicitArgs) const {
2406   if (ExplicitArgs)
2407     *ExplicitArgs = 0;
2408   if (NumExplicitArgs)
2409     *NumExplicitArgs = 0;
2410 
2411   for (const LocalInstantiationScope *Current = this; Current;
2412        Current = Current->Outer) {
2413     if (Current->PartiallySubstitutedPack) {
2414       if (ExplicitArgs)
2415         *ExplicitArgs = Current->ArgsInPartiallySubstitutedPack;
2416       if (NumExplicitArgs)
2417         *NumExplicitArgs = Current->NumArgsInPartiallySubstitutedPack;
2418 
2419       return Current->PartiallySubstitutedPack;
2420     }
2421 
2422     if (!Current->CombineWithOuterScope)
2423       break;
2424   }
2425 
2426   return 0;
2427 }
2428