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/AST/ASTConsumer.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/ASTLambda.h"
18 #include "clang/AST/DeclTemplate.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/Basic/LangOptions.h"
21 #include "clang/Sema/DeclSpec.h"
22 #include "clang/Sema/Initialization.h"
23 #include "clang/Sema/Lookup.h"
24 #include "clang/Sema/Template.h"
25 #include "clang/Sema/TemplateDeduction.h"
26 
27 using namespace clang;
28 using namespace sema;
29 
30 //===----------------------------------------------------------------------===/
31 // Template Instantiation Support
32 //===----------------------------------------------------------------------===/
33 
34 /// \brief Retrieve the template argument list(s) that should be used to
35 /// instantiate the definition of the given declaration.
36 ///
37 /// \param D the declaration for which we are computing template instantiation
38 /// arguments.
39 ///
40 /// \param Innermost if non-NULL, the innermost template argument list.
41 ///
42 /// \param RelativeToPrimary true if we should get the template
43 /// arguments relative to the primary template, even when we're
44 /// dealing with a specialization. This is only relevant for function
45 /// template specializations.
46 ///
47 /// \param Pattern If non-NULL, indicates the pattern from which we will be
48 /// instantiating the definition of the given declaration, \p D. This is
49 /// used to determine the proper set of template instantiation arguments for
50 /// friend function template specializations.
51 MultiLevelTemplateArgumentList
52 Sema::getTemplateInstantiationArgs(NamedDecl *D,
53                                    const TemplateArgumentList *Innermost,
54                                    bool RelativeToPrimary,
55                                    const FunctionDecl *Pattern) {
56   // Accumulate the set of template argument lists in this structure.
57   MultiLevelTemplateArgumentList Result;
58 
59   if (Innermost)
60     Result.addOuterTemplateArguments(Innermost);
61 
62   DeclContext *Ctx = dyn_cast<DeclContext>(D);
63   if (!Ctx) {
64     Ctx = D->getDeclContext();
65 
66     // Add template arguments from a variable template instantiation.
67     if (VarTemplateSpecializationDecl *Spec =
68             dyn_cast<VarTemplateSpecializationDecl>(D)) {
69       // We're done when we hit an explicit specialization.
70       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
71           !isa<VarTemplatePartialSpecializationDecl>(Spec))
72         return Result;
73 
74       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
75 
76       // If this variable template specialization was instantiated from a
77       // specialized member that is a variable template, we're done.
78       assert(Spec->getSpecializedTemplate() && "No variable template?");
79       llvm::PointerUnion<VarTemplateDecl*,
80                          VarTemplatePartialSpecializationDecl*> Specialized
81                              = Spec->getSpecializedTemplateOrPartial();
82       if (VarTemplatePartialSpecializationDecl *Partial =
83               Specialized.dyn_cast<VarTemplatePartialSpecializationDecl *>()) {
84         if (Partial->isMemberSpecialization())
85           return Result;
86       } else {
87         VarTemplateDecl *Tmpl = Specialized.get<VarTemplateDecl *>();
88         if (Tmpl->isMemberSpecialization())
89           return Result;
90       }
91     }
92 
93     // If we have a template template parameter with translation unit context,
94     // then we're performing substitution into a default template argument of
95     // this template template parameter before we've constructed the template
96     // that will own this template template parameter. In this case, we
97     // use empty template parameter lists for all of the outer templates
98     // to avoid performing any substitutions.
99     if (Ctx->isTranslationUnit()) {
100       if (TemplateTemplateParmDecl *TTP
101                                       = dyn_cast<TemplateTemplateParmDecl>(D)) {
102         for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
103           Result.addOuterTemplateArguments(None);
104         return Result;
105       }
106     }
107   }
108 
109   while (!Ctx->isFileContext()) {
110     // Add template arguments from a class template instantiation.
111     if (ClassTemplateSpecializationDecl *Spec
112           = dyn_cast<ClassTemplateSpecializationDecl>(Ctx)) {
113       // We're done when we hit an explicit specialization.
114       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
115           !isa<ClassTemplatePartialSpecializationDecl>(Spec))
116         break;
117 
118       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
119 
120       // If this class template specialization was instantiated from a
121       // specialized member that is a class template, we're done.
122       assert(Spec->getSpecializedTemplate() && "No class template?");
123       if (Spec->getSpecializedTemplate()->isMemberSpecialization())
124         break;
125     }
126     // Add template arguments from a function template specialization.
127     else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(Ctx)) {
128       if (!RelativeToPrimary &&
129           (Function->getTemplateSpecializationKind() ==
130                                                   TSK_ExplicitSpecialization &&
131            !Function->getClassScopeSpecializationPattern()))
132         break;
133 
134       if (const TemplateArgumentList *TemplateArgs
135             = Function->getTemplateSpecializationArgs()) {
136         // Add the template arguments for this specialization.
137         Result.addOuterTemplateArguments(TemplateArgs);
138 
139         // If this function was instantiated from a specialized member that is
140         // a function template, we're done.
141         assert(Function->getPrimaryTemplate() && "No function template?");
142         if (Function->getPrimaryTemplate()->isMemberSpecialization())
143           break;
144 
145         // If this function is a generic lambda specialization, we are done.
146         if (isGenericLambdaCallOperatorSpecialization(Function))
147           break;
148 
149       } else if (FunctionTemplateDecl *FunTmpl
150                                    = Function->getDescribedFunctionTemplate()) {
151         // Add the "injected" template arguments.
152         Result.addOuterTemplateArguments(FunTmpl->getInjectedTemplateArgs());
153       }
154 
155       // If this is a friend declaration and it declares an entity at
156       // namespace scope, take arguments from its lexical parent
157       // instead of its semantic parent, unless of course the pattern we're
158       // instantiating actually comes from the file's context!
159       if (Function->getFriendObjectKind() &&
160           Function->getDeclContext()->isFileContext() &&
161           (!Pattern || !Pattern->getLexicalDeclContext()->isFileContext())) {
162         Ctx = Function->getLexicalDeclContext();
163         RelativeToPrimary = false;
164         continue;
165       }
166     } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
167       if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
168         QualType T = ClassTemplate->getInjectedClassNameSpecialization();
169         const TemplateSpecializationType *TST =
170             cast<TemplateSpecializationType>(Context.getCanonicalType(T));
171         Result.addOuterTemplateArguments(
172             llvm::makeArrayRef(TST->getArgs(), TST->getNumArgs()));
173         if (ClassTemplate->isMemberSpecialization())
174           break;
175       }
176     }
177 
178     Ctx = Ctx->getParent();
179     RelativeToPrimary = false;
180   }
181 
182   return Result;
183 }
184 
185 bool Sema::ActiveTemplateInstantiation::isInstantiationRecord() const {
186   switch (Kind) {
187   case TemplateInstantiation:
188   case ExceptionSpecInstantiation:
189   case DefaultTemplateArgumentInstantiation:
190   case DefaultFunctionArgumentInstantiation:
191   case ExplicitTemplateArgumentSubstitution:
192   case DeducedTemplateArgumentSubstitution:
193   case PriorTemplateArgumentSubstitution:
194     return true;
195 
196   case DefaultTemplateArgumentChecking:
197     return false;
198   }
199 
200   llvm_unreachable("Invalid InstantiationKind!");
201 }
202 
203 Sema::InstantiatingTemplate::InstantiatingTemplate(
204     Sema &SemaRef, ActiveTemplateInstantiation::InstantiationKind Kind,
205     SourceLocation PointOfInstantiation, SourceRange InstantiationRange,
206     Decl *Entity, NamedDecl *Template, ArrayRef<TemplateArgument> TemplateArgs,
207     sema::TemplateDeductionInfo *DeductionInfo)
208     : SemaRef(SemaRef), SavedInNonInstantiationSFINAEContext(
209                             SemaRef.InNonInstantiationSFINAEContext) {
210   // Don't allow further instantiation if a fatal error has occcured.  Any
211   // diagnostics we might have raised will not be visible.
212   if (SemaRef.Diags.hasFatalErrorOccurred()) {
213     Invalid = true;
214     return;
215   }
216   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
217   if (!Invalid) {
218     ActiveTemplateInstantiation Inst;
219     Inst.Kind = Kind;
220     Inst.PointOfInstantiation = PointOfInstantiation;
221     Inst.Entity = Entity;
222     Inst.Template = Template;
223     Inst.TemplateArgs = TemplateArgs.data();
224     Inst.NumTemplateArgs = TemplateArgs.size();
225     Inst.DeductionInfo = DeductionInfo;
226     Inst.InstantiationRange = InstantiationRange;
227     SemaRef.InNonInstantiationSFINAEContext = false;
228     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
229     if (!Inst.isInstantiationRecord())
230       ++SemaRef.NonInstantiationEntries;
231   }
232 }
233 
234 Sema::InstantiatingTemplate::InstantiatingTemplate(
235     Sema &SemaRef, SourceLocation PointOfInstantiation, Decl *Entity,
236     SourceRange InstantiationRange)
237     : InstantiatingTemplate(SemaRef,
238                             ActiveTemplateInstantiation::TemplateInstantiation,
239                             PointOfInstantiation, InstantiationRange, Entity) {}
240 
241 Sema::InstantiatingTemplate::InstantiatingTemplate(
242     Sema &SemaRef, SourceLocation PointOfInstantiation, FunctionDecl *Entity,
243     ExceptionSpecification, SourceRange InstantiationRange)
244     : InstantiatingTemplate(
245           SemaRef, ActiveTemplateInstantiation::ExceptionSpecInstantiation,
246           PointOfInstantiation, InstantiationRange, Entity) {}
247 
248 Sema::InstantiatingTemplate::InstantiatingTemplate(
249     Sema &SemaRef, SourceLocation PointOfInstantiation, TemplateDecl *Template,
250     ArrayRef<TemplateArgument> TemplateArgs, SourceRange InstantiationRange)
251     : InstantiatingTemplate(
252           SemaRef,
253           ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation,
254           PointOfInstantiation, InstantiationRange, Template, nullptr,
255           TemplateArgs) {}
256 
257 Sema::InstantiatingTemplate::InstantiatingTemplate(
258     Sema &SemaRef, SourceLocation PointOfInstantiation,
259     FunctionTemplateDecl *FunctionTemplate,
260     ArrayRef<TemplateArgument> TemplateArgs,
261     ActiveTemplateInstantiation::InstantiationKind Kind,
262     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
263     : InstantiatingTemplate(SemaRef, Kind, PointOfInstantiation,
264                             InstantiationRange, FunctionTemplate, nullptr,
265                             TemplateArgs, &DeductionInfo) {}
266 
267 Sema::InstantiatingTemplate::InstantiatingTemplate(
268     Sema &SemaRef, SourceLocation PointOfInstantiation,
269     ClassTemplatePartialSpecializationDecl *PartialSpec,
270     ArrayRef<TemplateArgument> TemplateArgs,
271     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
272     : InstantiatingTemplate(
273           SemaRef,
274           ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution,
275           PointOfInstantiation, InstantiationRange, PartialSpec, nullptr,
276           TemplateArgs, &DeductionInfo) {}
277 
278 Sema::InstantiatingTemplate::InstantiatingTemplate(
279     Sema &SemaRef, SourceLocation PointOfInstantiation,
280     VarTemplatePartialSpecializationDecl *PartialSpec,
281     ArrayRef<TemplateArgument> TemplateArgs,
282     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
283     : InstantiatingTemplate(
284           SemaRef,
285           ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution,
286           PointOfInstantiation, InstantiationRange, PartialSpec, nullptr,
287           TemplateArgs, &DeductionInfo) {}
288 
289 Sema::InstantiatingTemplate::InstantiatingTemplate(
290     Sema &SemaRef, SourceLocation PointOfInstantiation, ParmVarDecl *Param,
291     ArrayRef<TemplateArgument> TemplateArgs, SourceRange InstantiationRange)
292     : InstantiatingTemplate(
293           SemaRef,
294           ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation,
295           PointOfInstantiation, InstantiationRange, Param, nullptr,
296           TemplateArgs) {}
297 
298 Sema::InstantiatingTemplate::InstantiatingTemplate(
299     Sema &SemaRef, SourceLocation PointOfInstantiation, NamedDecl *Template,
300     NonTypeTemplateParmDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
301     SourceRange InstantiationRange)
302     : InstantiatingTemplate(
303           SemaRef,
304           ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution,
305           PointOfInstantiation, InstantiationRange, Param, Template,
306           TemplateArgs) {}
307 
308 Sema::InstantiatingTemplate::InstantiatingTemplate(
309     Sema &SemaRef, SourceLocation PointOfInstantiation, NamedDecl *Template,
310     TemplateTemplateParmDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
311     SourceRange InstantiationRange)
312     : InstantiatingTemplate(
313           SemaRef,
314           ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution,
315           PointOfInstantiation, InstantiationRange, Param, Template,
316           TemplateArgs) {}
317 
318 Sema::InstantiatingTemplate::InstantiatingTemplate(
319     Sema &SemaRef, SourceLocation PointOfInstantiation, TemplateDecl *Template,
320     NamedDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
321     SourceRange InstantiationRange)
322     : InstantiatingTemplate(
323           SemaRef, ActiveTemplateInstantiation::DefaultTemplateArgumentChecking,
324           PointOfInstantiation, InstantiationRange, Param, Template,
325           TemplateArgs) {}
326 
327 void Sema::InstantiatingTemplate::Clear() {
328   if (!Invalid) {
329     if (!SemaRef.ActiveTemplateInstantiations.back().isInstantiationRecord()) {
330       assert(SemaRef.NonInstantiationEntries > 0);
331       --SemaRef.NonInstantiationEntries;
332     }
333     SemaRef.InNonInstantiationSFINAEContext
334       = SavedInNonInstantiationSFINAEContext;
335 
336     // Name lookup no longer looks in this template's defining module.
337     assert(SemaRef.ActiveTemplateInstantiations.size() >=
338            SemaRef.ActiveTemplateInstantiationLookupModules.size() &&
339            "forgot to remove a lookup module for a template instantiation");
340     if (SemaRef.ActiveTemplateInstantiations.size() ==
341         SemaRef.ActiveTemplateInstantiationLookupModules.size()) {
342       if (Module *M = SemaRef.ActiveTemplateInstantiationLookupModules.back())
343         SemaRef.LookupModulesCache.erase(M);
344       SemaRef.ActiveTemplateInstantiationLookupModules.pop_back();
345     }
346 
347     SemaRef.ActiveTemplateInstantiations.pop_back();
348     Invalid = true;
349   }
350 }
351 
352 bool Sema::InstantiatingTemplate::CheckInstantiationDepth(
353                                         SourceLocation PointOfInstantiation,
354                                            SourceRange InstantiationRange) {
355   assert(SemaRef.NonInstantiationEntries <=
356                                    SemaRef.ActiveTemplateInstantiations.size());
357   if ((SemaRef.ActiveTemplateInstantiations.size() -
358           SemaRef.NonInstantiationEntries)
359         <= SemaRef.getLangOpts().InstantiationDepth)
360     return false;
361 
362   SemaRef.Diag(PointOfInstantiation,
363                diag::err_template_recursion_depth_exceeded)
364     << SemaRef.getLangOpts().InstantiationDepth
365     << InstantiationRange;
366   SemaRef.Diag(PointOfInstantiation, diag::note_template_recursion_depth)
367     << SemaRef.getLangOpts().InstantiationDepth;
368   return true;
369 }
370 
371 /// \brief Prints the current instantiation stack through a series of
372 /// notes.
373 void Sema::PrintInstantiationStack() {
374   // Determine which template instantiations to skip, if any.
375   unsigned SkipStart = ActiveTemplateInstantiations.size(), SkipEnd = SkipStart;
376   unsigned Limit = Diags.getTemplateBacktraceLimit();
377   if (Limit && Limit < ActiveTemplateInstantiations.size()) {
378     SkipStart = Limit / 2 + Limit % 2;
379     SkipEnd = ActiveTemplateInstantiations.size() - Limit / 2;
380   }
381 
382   // FIXME: In all of these cases, we need to show the template arguments
383   unsigned InstantiationIdx = 0;
384   for (SmallVectorImpl<ActiveTemplateInstantiation>::reverse_iterator
385          Active = ActiveTemplateInstantiations.rbegin(),
386          ActiveEnd = ActiveTemplateInstantiations.rend();
387        Active != ActiveEnd;
388        ++Active, ++InstantiationIdx) {
389     // Skip this instantiation?
390     if (InstantiationIdx >= SkipStart && InstantiationIdx < SkipEnd) {
391       if (InstantiationIdx == SkipStart) {
392         // Note that we're skipping instantiations.
393         Diags.Report(Active->PointOfInstantiation,
394                      diag::note_instantiation_contexts_suppressed)
395           << unsigned(ActiveTemplateInstantiations.size() - Limit);
396       }
397       continue;
398     }
399 
400     switch (Active->Kind) {
401     case ActiveTemplateInstantiation::TemplateInstantiation: {
402       Decl *D = Active->Entity;
403       if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(D)) {
404         unsigned DiagID = diag::note_template_member_class_here;
405         if (isa<ClassTemplateSpecializationDecl>(Record))
406           DiagID = diag::note_template_class_instantiation_here;
407         Diags.Report(Active->PointOfInstantiation, DiagID)
408           << Context.getTypeDeclType(Record)
409           << Active->InstantiationRange;
410       } else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
411         unsigned DiagID;
412         if (Function->getPrimaryTemplate())
413           DiagID = diag::note_function_template_spec_here;
414         else
415           DiagID = diag::note_template_member_function_here;
416         Diags.Report(Active->PointOfInstantiation, DiagID)
417           << Function
418           << Active->InstantiationRange;
419       } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
420         Diags.Report(Active->PointOfInstantiation,
421                      VD->isStaticDataMember()?
422                        diag::note_template_static_data_member_def_here
423                      : diag::note_template_variable_def_here)
424           << VD
425           << Active->InstantiationRange;
426       } else if (EnumDecl *ED = dyn_cast<EnumDecl>(D)) {
427         Diags.Report(Active->PointOfInstantiation,
428                      diag::note_template_enum_def_here)
429           << ED
430           << Active->InstantiationRange;
431       } else if (FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
432         Diags.Report(Active->PointOfInstantiation,
433                      diag::note_template_nsdmi_here)
434             << FD << Active->InstantiationRange;
435       } else {
436         Diags.Report(Active->PointOfInstantiation,
437                      diag::note_template_type_alias_instantiation_here)
438           << cast<TypeAliasTemplateDecl>(D)
439           << Active->InstantiationRange;
440       }
441       break;
442     }
443 
444     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation: {
445       TemplateDecl *Template = cast<TemplateDecl>(Active->Entity);
446       SmallVector<char, 128> TemplateArgsStr;
447       llvm::raw_svector_ostream OS(TemplateArgsStr);
448       Template->printName(OS);
449       TemplateSpecializationType::PrintTemplateArgumentList(OS,
450                                                          Active->TemplateArgs,
451                                                       Active->NumTemplateArgs,
452                                                       getPrintingPolicy());
453       Diags.Report(Active->PointOfInstantiation,
454                    diag::note_default_arg_instantiation_here)
455         << OS.str()
456         << Active->InstantiationRange;
457       break;
458     }
459 
460     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution: {
461       FunctionTemplateDecl *FnTmpl = cast<FunctionTemplateDecl>(Active->Entity);
462       Diags.Report(Active->PointOfInstantiation,
463                    diag::note_explicit_template_arg_substitution_here)
464         << FnTmpl
465         << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
466                                            Active->TemplateArgs,
467                                            Active->NumTemplateArgs)
468         << Active->InstantiationRange;
469       break;
470     }
471 
472     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
473       if (ClassTemplatePartialSpecializationDecl *PartialSpec =
474             dyn_cast<ClassTemplatePartialSpecializationDecl>(Active->Entity)) {
475         Diags.Report(Active->PointOfInstantiation,
476                      diag::note_partial_spec_deduct_instantiation_here)
477           << Context.getTypeDeclType(PartialSpec)
478           << getTemplateArgumentBindingsText(
479                                          PartialSpec->getTemplateParameters(),
480                                              Active->TemplateArgs,
481                                              Active->NumTemplateArgs)
482           << Active->InstantiationRange;
483       } else {
484         FunctionTemplateDecl *FnTmpl
485           = cast<FunctionTemplateDecl>(Active->Entity);
486         Diags.Report(Active->PointOfInstantiation,
487                      diag::note_function_template_deduction_instantiation_here)
488           << FnTmpl
489           << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
490                                              Active->TemplateArgs,
491                                              Active->NumTemplateArgs)
492           << Active->InstantiationRange;
493       }
494       break;
495 
496     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation: {
497       ParmVarDecl *Param = cast<ParmVarDecl>(Active->Entity);
498       FunctionDecl *FD = cast<FunctionDecl>(Param->getDeclContext());
499 
500       SmallVector<char, 128> TemplateArgsStr;
501       llvm::raw_svector_ostream OS(TemplateArgsStr);
502       FD->printName(OS);
503       TemplateSpecializationType::PrintTemplateArgumentList(OS,
504                                                          Active->TemplateArgs,
505                                                       Active->NumTemplateArgs,
506                                                       getPrintingPolicy());
507       Diags.Report(Active->PointOfInstantiation,
508                    diag::note_default_function_arg_instantiation_here)
509         << OS.str()
510         << Active->InstantiationRange;
511       break;
512     }
513 
514     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution: {
515       NamedDecl *Parm = cast<NamedDecl>(Active->Entity);
516       std::string Name;
517       if (!Parm->getName().empty())
518         Name = std::string(" '") + Parm->getName().str() + "'";
519 
520       TemplateParameterList *TemplateParams = nullptr;
521       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
522         TemplateParams = Template->getTemplateParameters();
523       else
524         TemplateParams =
525           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
526                                                       ->getTemplateParameters();
527       Diags.Report(Active->PointOfInstantiation,
528                    diag::note_prior_template_arg_substitution)
529         << isa<TemplateTemplateParmDecl>(Parm)
530         << Name
531         << getTemplateArgumentBindingsText(TemplateParams,
532                                            Active->TemplateArgs,
533                                            Active->NumTemplateArgs)
534         << Active->InstantiationRange;
535       break;
536     }
537 
538     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking: {
539       TemplateParameterList *TemplateParams = nullptr;
540       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
541         TemplateParams = Template->getTemplateParameters();
542       else
543         TemplateParams =
544           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
545                                                       ->getTemplateParameters();
546 
547       Diags.Report(Active->PointOfInstantiation,
548                    diag::note_template_default_arg_checking)
549         << getTemplateArgumentBindingsText(TemplateParams,
550                                            Active->TemplateArgs,
551                                            Active->NumTemplateArgs)
552         << Active->InstantiationRange;
553       break;
554     }
555 
556     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
557       Diags.Report(Active->PointOfInstantiation,
558                    diag::note_template_exception_spec_instantiation_here)
559         << cast<FunctionDecl>(Active->Entity)
560         << Active->InstantiationRange;
561       break;
562     }
563   }
564 }
565 
566 Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
567   if (InNonInstantiationSFINAEContext)
568     return Optional<TemplateDeductionInfo *>(nullptr);
569 
570   for (SmallVectorImpl<ActiveTemplateInstantiation>::const_reverse_iterator
571          Active = ActiveTemplateInstantiations.rbegin(),
572          ActiveEnd = ActiveTemplateInstantiations.rend();
573        Active != ActiveEnd;
574        ++Active)
575   {
576     switch(Active->Kind) {
577     case ActiveTemplateInstantiation::TemplateInstantiation:
578       // An instantiation of an alias template may or may not be a SFINAE
579       // context, depending on what else is on the stack.
580       if (isa<TypeAliasTemplateDecl>(Active->Entity))
581         break;
582       // Fall through.
583     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
584     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
585       // This is a template instantiation, so there is no SFINAE.
586       return None;
587 
588     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
589     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
590     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking:
591       // A default template argument instantiation and substitution into
592       // template parameters with arguments for prior parameters may or may
593       // not be a SFINAE context; look further up the stack.
594       break;
595 
596     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution:
597     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
598       // We're either substitution explicitly-specified template arguments
599       // or deduced template arguments, so SFINAE applies.
600       assert(Active->DeductionInfo && "Missing deduction info pointer");
601       return Active->DeductionInfo;
602     }
603   }
604 
605   return None;
606 }
607 
608 /// \brief Retrieve the depth and index of a parameter pack.
609 static std::pair<unsigned, unsigned>
610 getDepthAndIndex(NamedDecl *ND) {
611   if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(ND))
612     return std::make_pair(TTP->getDepth(), TTP->getIndex());
613 
614   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(ND))
615     return std::make_pair(NTTP->getDepth(), NTTP->getIndex());
616 
617   TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(ND);
618   return std::make_pair(TTP->getDepth(), TTP->getIndex());
619 }
620 
621 //===----------------------------------------------------------------------===/
622 // Template Instantiation for Types
623 //===----------------------------------------------------------------------===/
624 namespace {
625   class TemplateInstantiator : public TreeTransform<TemplateInstantiator> {
626     const MultiLevelTemplateArgumentList &TemplateArgs;
627     SourceLocation Loc;
628     DeclarationName Entity;
629 
630   public:
631     typedef TreeTransform<TemplateInstantiator> inherited;
632 
633     TemplateInstantiator(Sema &SemaRef,
634                          const MultiLevelTemplateArgumentList &TemplateArgs,
635                          SourceLocation Loc,
636                          DeclarationName Entity)
637       : inherited(SemaRef), TemplateArgs(TemplateArgs), Loc(Loc),
638         Entity(Entity) { }
639 
640     /// \brief Determine whether the given type \p T has already been
641     /// transformed.
642     ///
643     /// For the purposes of template instantiation, a type has already been
644     /// transformed if it is NULL or if it is not dependent.
645     bool AlreadyTransformed(QualType T);
646 
647     /// \brief Returns the location of the entity being instantiated, if known.
648     SourceLocation getBaseLocation() { return Loc; }
649 
650     /// \brief Returns the name of the entity being instantiated, if any.
651     DeclarationName getBaseEntity() { return Entity; }
652 
653     /// \brief Sets the "base" location and entity when that
654     /// information is known based on another transformation.
655     void setBase(SourceLocation Loc, DeclarationName Entity) {
656       this->Loc = Loc;
657       this->Entity = Entity;
658     }
659 
660     bool TryExpandParameterPacks(SourceLocation EllipsisLoc,
661                                  SourceRange PatternRange,
662                                  ArrayRef<UnexpandedParameterPack> Unexpanded,
663                                  bool &ShouldExpand, bool &RetainExpansion,
664                                  Optional<unsigned> &NumExpansions) {
665       return getSema().CheckParameterPacksForExpansion(EllipsisLoc,
666                                                        PatternRange, Unexpanded,
667                                                        TemplateArgs,
668                                                        ShouldExpand,
669                                                        RetainExpansion,
670                                                        NumExpansions);
671     }
672 
673     void ExpandingFunctionParameterPack(ParmVarDecl *Pack) {
674       SemaRef.CurrentInstantiationScope->MakeInstantiatedLocalArgPack(Pack);
675     }
676 
677     TemplateArgument ForgetPartiallySubstitutedPack() {
678       TemplateArgument Result;
679       if (NamedDecl *PartialPack
680             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
681         MultiLevelTemplateArgumentList &TemplateArgs
682           = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
683         unsigned Depth, Index;
684         std::tie(Depth, Index) = getDepthAndIndex(PartialPack);
685         if (TemplateArgs.hasTemplateArgument(Depth, Index)) {
686           Result = TemplateArgs(Depth, Index);
687           TemplateArgs.setArgument(Depth, Index, TemplateArgument());
688         }
689       }
690 
691       return Result;
692     }
693 
694     void RememberPartiallySubstitutedPack(TemplateArgument Arg) {
695       if (Arg.isNull())
696         return;
697 
698       if (NamedDecl *PartialPack
699             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
700         MultiLevelTemplateArgumentList &TemplateArgs
701         = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
702         unsigned Depth, Index;
703         std::tie(Depth, Index) = getDepthAndIndex(PartialPack);
704         TemplateArgs.setArgument(Depth, Index, Arg);
705       }
706     }
707 
708     /// \brief Transform the given declaration by instantiating a reference to
709     /// this declaration.
710     Decl *TransformDecl(SourceLocation Loc, Decl *D);
711 
712     void transformAttrs(Decl *Old, Decl *New) {
713       SemaRef.InstantiateAttrs(TemplateArgs, Old, New);
714     }
715 
716     void transformedLocalDecl(Decl *Old, Decl *New) {
717       SemaRef.CurrentInstantiationScope->InstantiatedLocal(Old, New);
718     }
719 
720     /// \brief Transform the definition of the given declaration by
721     /// instantiating it.
722     Decl *TransformDefinition(SourceLocation Loc, Decl *D);
723 
724     /// \brief Transform the first qualifier within a scope by instantiating the
725     /// declaration.
726     NamedDecl *TransformFirstQualifierInScope(NamedDecl *D, SourceLocation Loc);
727 
728     /// \brief Rebuild the exception declaration and register the declaration
729     /// as an instantiated local.
730     VarDecl *RebuildExceptionDecl(VarDecl *ExceptionDecl,
731                                   TypeSourceInfo *Declarator,
732                                   SourceLocation StartLoc,
733                                   SourceLocation NameLoc,
734                                   IdentifierInfo *Name);
735 
736     /// \brief Rebuild the Objective-C exception declaration and register the
737     /// declaration as an instantiated local.
738     VarDecl *RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
739                                       TypeSourceInfo *TSInfo, QualType T);
740 
741     /// \brief Check for tag mismatches when instantiating an
742     /// elaborated type.
743     QualType RebuildElaboratedType(SourceLocation KeywordLoc,
744                                    ElaboratedTypeKeyword Keyword,
745                                    NestedNameSpecifierLoc QualifierLoc,
746                                    QualType T);
747 
748     TemplateName
749     TransformTemplateName(CXXScopeSpec &SS, TemplateName Name,
750                           SourceLocation NameLoc,
751                           QualType ObjectType = QualType(),
752                           NamedDecl *FirstQualifierInScope = nullptr);
753 
754     const LoopHintAttr *TransformLoopHintAttr(const LoopHintAttr *LH);
755 
756     ExprResult TransformPredefinedExpr(PredefinedExpr *E);
757     ExprResult TransformDeclRefExpr(DeclRefExpr *E);
758     ExprResult TransformCXXDefaultArgExpr(CXXDefaultArgExpr *E);
759 
760     ExprResult TransformTemplateParmRefExpr(DeclRefExpr *E,
761                                             NonTypeTemplateParmDecl *D);
762     ExprResult TransformSubstNonTypeTemplateParmPackExpr(
763                                            SubstNonTypeTemplateParmPackExpr *E);
764 
765     /// \brief Rebuild a DeclRefExpr for a ParmVarDecl reference.
766     ExprResult RebuildParmVarDeclRefExpr(ParmVarDecl *PD, SourceLocation Loc);
767 
768     /// \brief Transform a reference to a function parameter pack.
769     ExprResult TransformFunctionParmPackRefExpr(DeclRefExpr *E,
770                                                 ParmVarDecl *PD);
771 
772     /// \brief Transform a FunctionParmPackExpr which was built when we couldn't
773     /// expand a function parameter pack reference which refers to an expanded
774     /// pack.
775     ExprResult TransformFunctionParmPackExpr(FunctionParmPackExpr *E);
776 
777     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
778                                         FunctionProtoTypeLoc TL) {
779       // Call the base version; it will forward to our overridden version below.
780       return inherited::TransformFunctionProtoType(TLB, TL);
781     }
782 
783     template<typename Fn>
784     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
785                                         FunctionProtoTypeLoc TL,
786                                         CXXRecordDecl *ThisContext,
787                                         unsigned ThisTypeQuals,
788                                         Fn TransformExceptionSpec);
789 
790     ParmVarDecl *TransformFunctionTypeParam(ParmVarDecl *OldParm,
791                                             int indexAdjustment,
792                                             Optional<unsigned> NumExpansions,
793                                             bool ExpectParameterPack);
794 
795     /// \brief Transforms a template type parameter type by performing
796     /// substitution of the corresponding template type argument.
797     QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
798                                            TemplateTypeParmTypeLoc TL);
799 
800     /// \brief Transforms an already-substituted template type parameter pack
801     /// into either itself (if we aren't substituting into its pack expansion)
802     /// or the appropriate substituted argument.
803     QualType TransformSubstTemplateTypeParmPackType(TypeLocBuilder &TLB,
804                                            SubstTemplateTypeParmPackTypeLoc TL);
805 
806     ExprResult TransformCallExpr(CallExpr *CE) {
807       getSema().CallsUndergoingInstantiation.push_back(CE);
808       ExprResult Result =
809           TreeTransform<TemplateInstantiator>::TransformCallExpr(CE);
810       getSema().CallsUndergoingInstantiation.pop_back();
811       return Result;
812     }
813 
814     ExprResult TransformLambdaExpr(LambdaExpr *E) {
815       LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
816       return TreeTransform<TemplateInstantiator>::TransformLambdaExpr(E);
817     }
818 
819     ExprResult TransformLambdaScope(LambdaExpr *E,
820         CXXMethodDecl *NewCallOperator,
821         ArrayRef<InitCaptureInfoTy> InitCaptureExprsAndTypes) {
822       CXXMethodDecl *const OldCallOperator = E->getCallOperator();
823       // In the generic lambda case, we set the NewTemplate to be considered
824       // an "instantiation" of the OldTemplate.
825       if (FunctionTemplateDecl *const NewCallOperatorTemplate =
826             NewCallOperator->getDescribedFunctionTemplate()) {
827 
828         FunctionTemplateDecl *const OldCallOperatorTemplate =
829                               OldCallOperator->getDescribedFunctionTemplate();
830         NewCallOperatorTemplate->setInstantiatedFromMemberTemplate(
831                                                      OldCallOperatorTemplate);
832       } else
833         // For a non-generic lambda we set the NewCallOperator to
834         // be an instantiation of the OldCallOperator.
835         NewCallOperator->setInstantiationOfMemberFunction(OldCallOperator,
836                                                     TSK_ImplicitInstantiation);
837 
838       return inherited::TransformLambdaScope(E, NewCallOperator,
839           InitCaptureExprsAndTypes);
840     }
841     TemplateParameterList *TransformTemplateParameterList(
842                               TemplateParameterList *OrigTPL)  {
843       if (!OrigTPL || !OrigTPL->size()) return OrigTPL;
844 
845       DeclContext *Owner = OrigTPL->getParam(0)->getDeclContext();
846       TemplateDeclInstantiator  DeclInstantiator(getSema(),
847                         /* DeclContext *Owner */ Owner, TemplateArgs);
848       return DeclInstantiator.SubstTemplateParams(OrigTPL);
849     }
850   private:
851     ExprResult transformNonTypeTemplateParmRef(NonTypeTemplateParmDecl *parm,
852                                                SourceLocation loc,
853                                                TemplateArgument arg);
854   };
855 }
856 
857 bool TemplateInstantiator::AlreadyTransformed(QualType T) {
858   if (T.isNull())
859     return true;
860 
861   if (T->isInstantiationDependentType() || T->isVariablyModifiedType())
862     return false;
863 
864   getSema().MarkDeclarationsReferencedInType(Loc, T);
865   return true;
866 }
867 
868 static TemplateArgument
869 getPackSubstitutedTemplateArgument(Sema &S, TemplateArgument Arg) {
870   assert(S.ArgumentPackSubstitutionIndex >= 0);
871   assert(S.ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
872   Arg = Arg.pack_begin()[S.ArgumentPackSubstitutionIndex];
873   if (Arg.isPackExpansion())
874     Arg = Arg.getPackExpansionPattern();
875   return Arg;
876 }
877 
878 Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
879   if (!D)
880     return nullptr;
881 
882   if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(D)) {
883     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
884       // If the corresponding template argument is NULL or non-existent, it's
885       // because we are performing instantiation from explicitly-specified
886       // template arguments in a function template, but there were some
887       // arguments left unspecified.
888       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
889                                             TTP->getPosition()))
890         return D;
891 
892       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
893 
894       if (TTP->isParameterPack()) {
895         assert(Arg.getKind() == TemplateArgument::Pack &&
896                "Missing argument pack");
897         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
898       }
899 
900       TemplateName Template = Arg.getAsTemplate();
901       assert(!Template.isNull() && Template.getAsTemplateDecl() &&
902              "Wrong kind of template template argument");
903       return Template.getAsTemplateDecl();
904     }
905 
906     // Fall through to find the instantiated declaration for this template
907     // template parameter.
908   }
909 
910   return SemaRef.FindInstantiatedDecl(Loc, cast<NamedDecl>(D), TemplateArgs);
911 }
912 
913 Decl *TemplateInstantiator::TransformDefinition(SourceLocation Loc, Decl *D) {
914   Decl *Inst = getSema().SubstDecl(D, getSema().CurContext, TemplateArgs);
915   if (!Inst)
916     return nullptr;
917 
918   getSema().CurrentInstantiationScope->InstantiatedLocal(D, Inst);
919   return Inst;
920 }
921 
922 NamedDecl *
923 TemplateInstantiator::TransformFirstQualifierInScope(NamedDecl *D,
924                                                      SourceLocation Loc) {
925   // If the first part of the nested-name-specifier was a template type
926   // parameter, instantiate that type parameter down to a tag type.
927   if (TemplateTypeParmDecl *TTPD = dyn_cast_or_null<TemplateTypeParmDecl>(D)) {
928     const TemplateTypeParmType *TTP
929       = cast<TemplateTypeParmType>(getSema().Context.getTypeDeclType(TTPD));
930 
931     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
932       // FIXME: This needs testing w/ member access expressions.
933       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getIndex());
934 
935       if (TTP->isParameterPack()) {
936         assert(Arg.getKind() == TemplateArgument::Pack &&
937                "Missing argument pack");
938 
939         if (getSema().ArgumentPackSubstitutionIndex == -1)
940           return nullptr;
941 
942         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
943       }
944 
945       QualType T = Arg.getAsType();
946       if (T.isNull())
947         return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
948 
949       if (const TagType *Tag = T->getAs<TagType>())
950         return Tag->getDecl();
951 
952       // The resulting type is not a tag; complain.
953       getSema().Diag(Loc, diag::err_nested_name_spec_non_tag) << T;
954       return nullptr;
955     }
956   }
957 
958   return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
959 }
960 
961 VarDecl *
962 TemplateInstantiator::RebuildExceptionDecl(VarDecl *ExceptionDecl,
963                                            TypeSourceInfo *Declarator,
964                                            SourceLocation StartLoc,
965                                            SourceLocation NameLoc,
966                                            IdentifierInfo *Name) {
967   VarDecl *Var = inherited::RebuildExceptionDecl(ExceptionDecl, Declarator,
968                                                  StartLoc, NameLoc, Name);
969   if (Var)
970     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
971   return Var;
972 }
973 
974 VarDecl *TemplateInstantiator::RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
975                                                         TypeSourceInfo *TSInfo,
976                                                         QualType T) {
977   VarDecl *Var = inherited::RebuildObjCExceptionDecl(ExceptionDecl, TSInfo, T);
978   if (Var)
979     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
980   return Var;
981 }
982 
983 QualType
984 TemplateInstantiator::RebuildElaboratedType(SourceLocation KeywordLoc,
985                                             ElaboratedTypeKeyword Keyword,
986                                             NestedNameSpecifierLoc QualifierLoc,
987                                             QualType T) {
988   if (const TagType *TT = T->getAs<TagType>()) {
989     TagDecl* TD = TT->getDecl();
990 
991     SourceLocation TagLocation = KeywordLoc;
992 
993     IdentifierInfo *Id = TD->getIdentifier();
994 
995     // TODO: should we even warn on struct/class mismatches for this?  Seems
996     // like it's likely to produce a lot of spurious errors.
997     if (Id && Keyword != ETK_None && Keyword != ETK_Typename) {
998       TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForKeyword(Keyword);
999       if (!SemaRef.isAcceptableTagRedeclaration(TD, Kind, /*isDefinition*/false,
1000                                                 TagLocation, *Id)) {
1001         SemaRef.Diag(TagLocation, diag::err_use_with_wrong_tag)
1002           << Id
1003           << FixItHint::CreateReplacement(SourceRange(TagLocation),
1004                                           TD->getKindName());
1005         SemaRef.Diag(TD->getLocation(), diag::note_previous_use);
1006       }
1007     }
1008   }
1009 
1010   return TreeTransform<TemplateInstantiator>::RebuildElaboratedType(KeywordLoc,
1011                                                                     Keyword,
1012                                                                   QualifierLoc,
1013                                                                     T);
1014 }
1015 
1016 TemplateName TemplateInstantiator::TransformTemplateName(CXXScopeSpec &SS,
1017                                                          TemplateName Name,
1018                                                          SourceLocation NameLoc,
1019                                                          QualType ObjectType,
1020                                              NamedDecl *FirstQualifierInScope) {
1021   if (TemplateTemplateParmDecl *TTP
1022        = dyn_cast_or_null<TemplateTemplateParmDecl>(Name.getAsTemplateDecl())) {
1023     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
1024       // If the corresponding template argument is NULL or non-existent, it's
1025       // because we are performing instantiation from explicitly-specified
1026       // template arguments in a function template, but there were some
1027       // arguments left unspecified.
1028       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
1029                                             TTP->getPosition()))
1030         return Name;
1031 
1032       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
1033 
1034       if (TTP->isParameterPack()) {
1035         assert(Arg.getKind() == TemplateArgument::Pack &&
1036                "Missing argument pack");
1037 
1038         if (getSema().ArgumentPackSubstitutionIndex == -1) {
1039           // We have the template argument pack to substitute, but we're not
1040           // actually expanding the enclosing pack expansion yet. So, just
1041           // keep the entire argument pack.
1042           return getSema().Context.getSubstTemplateTemplateParmPack(TTP, Arg);
1043         }
1044 
1045         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1046       }
1047 
1048       TemplateName Template = Arg.getAsTemplate();
1049       assert(!Template.isNull() && "Null template template argument");
1050 
1051       // We don't ever want to substitute for a qualified template name, since
1052       // the qualifier is handled separately. So, look through the qualified
1053       // template name to its underlying declaration.
1054       if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
1055         Template = TemplateName(QTN->getTemplateDecl());
1056 
1057       Template = getSema().Context.getSubstTemplateTemplateParm(TTP, Template);
1058       return Template;
1059     }
1060   }
1061 
1062   if (SubstTemplateTemplateParmPackStorage *SubstPack
1063       = Name.getAsSubstTemplateTemplateParmPack()) {
1064     if (getSema().ArgumentPackSubstitutionIndex == -1)
1065       return Name;
1066 
1067     TemplateArgument Arg = SubstPack->getArgumentPack();
1068     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1069     return Arg.getAsTemplate();
1070   }
1071 
1072   return inherited::TransformTemplateName(SS, Name, NameLoc, ObjectType,
1073                                           FirstQualifierInScope);
1074 }
1075 
1076 ExprResult
1077 TemplateInstantiator::TransformPredefinedExpr(PredefinedExpr *E) {
1078   if (!E->isTypeDependent())
1079     return E;
1080 
1081   return getSema().BuildPredefinedExpr(E->getLocation(), E->getIdentType());
1082 }
1083 
1084 ExprResult
1085 TemplateInstantiator::TransformTemplateParmRefExpr(DeclRefExpr *E,
1086                                                NonTypeTemplateParmDecl *NTTP) {
1087   // If the corresponding template argument is NULL or non-existent, it's
1088   // because we are performing instantiation from explicitly-specified
1089   // template arguments in a function template, but there were some
1090   // arguments left unspecified.
1091   if (!TemplateArgs.hasTemplateArgument(NTTP->getDepth(),
1092                                         NTTP->getPosition()))
1093     return E;
1094 
1095   TemplateArgument Arg = TemplateArgs(NTTP->getDepth(), NTTP->getPosition());
1096   if (NTTP->isParameterPack()) {
1097     assert(Arg.getKind() == TemplateArgument::Pack &&
1098            "Missing argument pack");
1099 
1100     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1101       // We have an argument pack, but we can't select a particular argument
1102       // out of it yet. Therefore, we'll build an expression to hold on to that
1103       // argument pack.
1104       QualType TargetType = SemaRef.SubstType(NTTP->getType(), TemplateArgs,
1105                                               E->getLocation(),
1106                                               NTTP->getDeclName());
1107       if (TargetType.isNull())
1108         return ExprError();
1109 
1110       return new (SemaRef.Context) SubstNonTypeTemplateParmPackExpr(TargetType,
1111                                                                     NTTP,
1112                                                               E->getLocation(),
1113                                                                     Arg);
1114     }
1115 
1116     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1117   }
1118 
1119   return transformNonTypeTemplateParmRef(NTTP, E->getLocation(), Arg);
1120 }
1121 
1122 const LoopHintAttr *
1123 TemplateInstantiator::TransformLoopHintAttr(const LoopHintAttr *LH) {
1124   Expr *TransformedExpr = getDerived().TransformExpr(LH->getValue()).get();
1125 
1126   if (TransformedExpr == LH->getValue())
1127     return LH;
1128 
1129   // Generate error if there is a problem with the value.
1130   if (getSema().CheckLoopHintExpr(TransformedExpr, LH->getLocation()))
1131     return LH;
1132 
1133   // Create new LoopHintValueAttr with integral expression in place of the
1134   // non-type template parameter.
1135   return LoopHintAttr::CreateImplicit(
1136       getSema().Context, LH->getSemanticSpelling(), LH->getOption(),
1137       LH->getState(), TransformedExpr, LH->getRange());
1138 }
1139 
1140 ExprResult TemplateInstantiator::transformNonTypeTemplateParmRef(
1141                                                  NonTypeTemplateParmDecl *parm,
1142                                                  SourceLocation loc,
1143                                                  TemplateArgument arg) {
1144   ExprResult result;
1145   QualType type;
1146 
1147   // The template argument itself might be an expression, in which
1148   // case we just return that expression.
1149   if (arg.getKind() == TemplateArgument::Expression) {
1150     Expr *argExpr = arg.getAsExpr();
1151     result = argExpr;
1152     type = argExpr->getType();
1153 
1154   } else if (arg.getKind() == TemplateArgument::Declaration ||
1155              arg.getKind() == TemplateArgument::NullPtr) {
1156     ValueDecl *VD;
1157     if (arg.getKind() == TemplateArgument::Declaration) {
1158       VD = cast<ValueDecl>(arg.getAsDecl());
1159 
1160       // Find the instantiation of the template argument.  This is
1161       // required for nested templates.
1162       VD = cast_or_null<ValueDecl>(
1163              getSema().FindInstantiatedDecl(loc, VD, TemplateArgs));
1164       if (!VD)
1165         return ExprError();
1166     } else {
1167       // Propagate NULL template argument.
1168       VD = nullptr;
1169     }
1170 
1171     // Derive the type we want the substituted decl to have.  This had
1172     // better be non-dependent, or these checks will have serious problems.
1173     if (parm->isExpandedParameterPack()) {
1174       type = parm->getExpansionType(SemaRef.ArgumentPackSubstitutionIndex);
1175     } else if (parm->isParameterPack() &&
1176                isa<PackExpansionType>(parm->getType())) {
1177       type = SemaRef.SubstType(
1178                         cast<PackExpansionType>(parm->getType())->getPattern(),
1179                                      TemplateArgs, loc, parm->getDeclName());
1180     } else {
1181       type = SemaRef.SubstType(parm->getType(), TemplateArgs,
1182                                loc, parm->getDeclName());
1183     }
1184     assert(!type.isNull() && "type substitution failed for param type");
1185     assert(!type->isDependentType() && "param type still dependent");
1186     result = SemaRef.BuildExpressionFromDeclTemplateArgument(arg, type, loc);
1187 
1188     if (!result.isInvalid()) type = result.get()->getType();
1189   } else {
1190     result = SemaRef.BuildExpressionFromIntegralTemplateArgument(arg, loc);
1191 
1192     // Note that this type can be different from the type of 'result',
1193     // e.g. if it's an enum type.
1194     type = arg.getIntegralType();
1195   }
1196   if (result.isInvalid()) return ExprError();
1197 
1198   Expr *resultExpr = result.get();
1199   return new (SemaRef.Context) SubstNonTypeTemplateParmExpr(
1200       type, resultExpr->getValueKind(), loc, parm, resultExpr);
1201 }
1202 
1203 ExprResult
1204 TemplateInstantiator::TransformSubstNonTypeTemplateParmPackExpr(
1205                                           SubstNonTypeTemplateParmPackExpr *E) {
1206   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1207     // We aren't expanding the parameter pack, so just return ourselves.
1208     return E;
1209   }
1210 
1211   TemplateArgument Arg = E->getArgumentPack();
1212   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1213   return transformNonTypeTemplateParmRef(E->getParameterPack(),
1214                                          E->getParameterPackLocation(),
1215                                          Arg);
1216 }
1217 
1218 ExprResult
1219 TemplateInstantiator::RebuildParmVarDeclRefExpr(ParmVarDecl *PD,
1220                                                 SourceLocation Loc) {
1221   DeclarationNameInfo NameInfo(PD->getDeclName(), Loc);
1222   return getSema().BuildDeclarationNameExpr(CXXScopeSpec(), NameInfo, PD);
1223 }
1224 
1225 ExprResult
1226 TemplateInstantiator::TransformFunctionParmPackExpr(FunctionParmPackExpr *E) {
1227   if (getSema().ArgumentPackSubstitutionIndex != -1) {
1228     // We can expand this parameter pack now.
1229     ParmVarDecl *D = E->getExpansion(getSema().ArgumentPackSubstitutionIndex);
1230     ValueDecl *VD = cast_or_null<ValueDecl>(TransformDecl(E->getExprLoc(), D));
1231     if (!VD)
1232       return ExprError();
1233     return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(VD), E->getExprLoc());
1234   }
1235 
1236   QualType T = TransformType(E->getType());
1237   if (T.isNull())
1238     return ExprError();
1239 
1240   // Transform each of the parameter expansions into the corresponding
1241   // parameters in the instantiation of the function decl.
1242   SmallVector<Decl *, 8> Parms;
1243   Parms.reserve(E->getNumExpansions());
1244   for (FunctionParmPackExpr::iterator I = E->begin(), End = E->end();
1245        I != End; ++I) {
1246     ParmVarDecl *D =
1247         cast_or_null<ParmVarDecl>(TransformDecl(E->getExprLoc(), *I));
1248     if (!D)
1249       return ExprError();
1250     Parms.push_back(D);
1251   }
1252 
1253   return FunctionParmPackExpr::Create(getSema().Context, T,
1254                                       E->getParameterPack(),
1255                                       E->getParameterPackLocation(), Parms);
1256 }
1257 
1258 ExprResult
1259 TemplateInstantiator::TransformFunctionParmPackRefExpr(DeclRefExpr *E,
1260                                                        ParmVarDecl *PD) {
1261   typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
1262   llvm::PointerUnion<Decl *, DeclArgumentPack *> *Found
1263     = getSema().CurrentInstantiationScope->findInstantiationOf(PD);
1264   assert(Found && "no instantiation for parameter pack");
1265 
1266   Decl *TransformedDecl;
1267   if (DeclArgumentPack *Pack = Found->dyn_cast<DeclArgumentPack *>()) {
1268     // If this is a reference to a function parameter pack which we can
1269     // substitute but can't yet expand, build a FunctionParmPackExpr for it.
1270     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1271       QualType T = TransformType(E->getType());
1272       if (T.isNull())
1273         return ExprError();
1274       return FunctionParmPackExpr::Create(getSema().Context, T, PD,
1275                                           E->getExprLoc(), *Pack);
1276     }
1277 
1278     TransformedDecl = (*Pack)[getSema().ArgumentPackSubstitutionIndex];
1279   } else {
1280     TransformedDecl = Found->get<Decl*>();
1281   }
1282 
1283   // We have either an unexpanded pack or a specific expansion.
1284   return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(TransformedDecl),
1285                                    E->getExprLoc());
1286 }
1287 
1288 ExprResult
1289 TemplateInstantiator::TransformDeclRefExpr(DeclRefExpr *E) {
1290   NamedDecl *D = E->getDecl();
1291 
1292   // Handle references to non-type template parameters and non-type template
1293   // parameter packs.
1294   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D)) {
1295     if (NTTP->getDepth() < TemplateArgs.getNumLevels())
1296       return TransformTemplateParmRefExpr(E, NTTP);
1297 
1298     // We have a non-type template parameter that isn't fully substituted;
1299     // FindInstantiatedDecl will find it in the local instantiation scope.
1300   }
1301 
1302   // Handle references to function parameter packs.
1303   if (ParmVarDecl *PD = dyn_cast<ParmVarDecl>(D))
1304     if (PD->isParameterPack())
1305       return TransformFunctionParmPackRefExpr(E, PD);
1306 
1307   return TreeTransform<TemplateInstantiator>::TransformDeclRefExpr(E);
1308 }
1309 
1310 ExprResult TemplateInstantiator::TransformCXXDefaultArgExpr(
1311     CXXDefaultArgExpr *E) {
1312   assert(!cast<FunctionDecl>(E->getParam()->getDeclContext())->
1313              getDescribedFunctionTemplate() &&
1314          "Default arg expressions are never formed in dependent cases.");
1315   return SemaRef.BuildCXXDefaultArgExpr(E->getUsedLocation(),
1316                            cast<FunctionDecl>(E->getParam()->getDeclContext()),
1317                                         E->getParam());
1318 }
1319 
1320 template<typename Fn>
1321 QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
1322                                  FunctionProtoTypeLoc TL,
1323                                  CXXRecordDecl *ThisContext,
1324                                  unsigned ThisTypeQuals,
1325                                  Fn TransformExceptionSpec) {
1326   // We need a local instantiation scope for this function prototype.
1327   LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
1328   return inherited::TransformFunctionProtoType(
1329       TLB, TL, ThisContext, ThisTypeQuals, TransformExceptionSpec);
1330 }
1331 
1332 ParmVarDecl *
1333 TemplateInstantiator::TransformFunctionTypeParam(ParmVarDecl *OldParm,
1334                                                  int indexAdjustment,
1335                                                Optional<unsigned> NumExpansions,
1336                                                  bool ExpectParameterPack) {
1337   return SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
1338                                   NumExpansions, ExpectParameterPack);
1339 }
1340 
1341 QualType
1342 TemplateInstantiator::TransformTemplateTypeParmType(TypeLocBuilder &TLB,
1343                                                 TemplateTypeParmTypeLoc TL) {
1344   const TemplateTypeParmType *T = TL.getTypePtr();
1345   if (T->getDepth() < TemplateArgs.getNumLevels()) {
1346     // Replace the template type parameter with its corresponding
1347     // template argument.
1348 
1349     // If the corresponding template argument is NULL or doesn't exist, it's
1350     // because we are performing instantiation from explicitly-specified
1351     // template arguments in a function template class, but there were some
1352     // arguments left unspecified.
1353     if (!TemplateArgs.hasTemplateArgument(T->getDepth(), T->getIndex())) {
1354       TemplateTypeParmTypeLoc NewTL
1355         = TLB.push<TemplateTypeParmTypeLoc>(TL.getType());
1356       NewTL.setNameLoc(TL.getNameLoc());
1357       return TL.getType();
1358     }
1359 
1360     TemplateArgument Arg = TemplateArgs(T->getDepth(), T->getIndex());
1361 
1362     if (T->isParameterPack()) {
1363       assert(Arg.getKind() == TemplateArgument::Pack &&
1364              "Missing argument pack");
1365 
1366       if (getSema().ArgumentPackSubstitutionIndex == -1) {
1367         // We have the template argument pack, but we're not expanding the
1368         // enclosing pack expansion yet. Just save the template argument
1369         // pack for later substitution.
1370         QualType Result
1371           = getSema().Context.getSubstTemplateTypeParmPackType(T, Arg);
1372         SubstTemplateTypeParmPackTypeLoc NewTL
1373           = TLB.push<SubstTemplateTypeParmPackTypeLoc>(Result);
1374         NewTL.setNameLoc(TL.getNameLoc());
1375         return Result;
1376       }
1377 
1378       Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1379     }
1380 
1381     assert(Arg.getKind() == TemplateArgument::Type &&
1382            "Template argument kind mismatch");
1383 
1384     QualType Replacement = Arg.getAsType();
1385 
1386     // TODO: only do this uniquing once, at the start of instantiation.
1387     QualType Result
1388       = getSema().Context.getSubstTemplateTypeParmType(T, Replacement);
1389     SubstTemplateTypeParmTypeLoc NewTL
1390       = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1391     NewTL.setNameLoc(TL.getNameLoc());
1392     return Result;
1393   }
1394 
1395   // The template type parameter comes from an inner template (e.g.,
1396   // the template parameter list of a member template inside the
1397   // template we are instantiating). Create a new template type
1398   // parameter with the template "level" reduced by one.
1399   TemplateTypeParmDecl *NewTTPDecl = nullptr;
1400   if (TemplateTypeParmDecl *OldTTPDecl = T->getDecl())
1401     NewTTPDecl = cast_or_null<TemplateTypeParmDecl>(
1402                                   TransformDecl(TL.getNameLoc(), OldTTPDecl));
1403 
1404   QualType Result
1405     = getSema().Context.getTemplateTypeParmType(T->getDepth()
1406                                                  - TemplateArgs.getNumLevels(),
1407                                                 T->getIndex(),
1408                                                 T->isParameterPack(),
1409                                                 NewTTPDecl);
1410   TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
1411   NewTL.setNameLoc(TL.getNameLoc());
1412   return Result;
1413 }
1414 
1415 QualType
1416 TemplateInstantiator::TransformSubstTemplateTypeParmPackType(
1417                                                             TypeLocBuilder &TLB,
1418                                          SubstTemplateTypeParmPackTypeLoc TL) {
1419   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1420     // We aren't expanding the parameter pack, so just return ourselves.
1421     SubstTemplateTypeParmPackTypeLoc NewTL
1422       = TLB.push<SubstTemplateTypeParmPackTypeLoc>(TL.getType());
1423     NewTL.setNameLoc(TL.getNameLoc());
1424     return TL.getType();
1425   }
1426 
1427   TemplateArgument Arg = TL.getTypePtr()->getArgumentPack();
1428   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1429   QualType Result = Arg.getAsType();
1430 
1431   Result = getSema().Context.getSubstTemplateTypeParmType(
1432                                       TL.getTypePtr()->getReplacedParameter(),
1433                                                           Result);
1434   SubstTemplateTypeParmTypeLoc NewTL
1435     = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1436   NewTL.setNameLoc(TL.getNameLoc());
1437   return Result;
1438 }
1439 
1440 /// \brief Perform substitution on the type T with a given set of template
1441 /// arguments.
1442 ///
1443 /// This routine substitutes the given template arguments into the
1444 /// type T and produces the instantiated type.
1445 ///
1446 /// \param T the type into which the template arguments will be
1447 /// substituted. If this type is not dependent, it will be returned
1448 /// immediately.
1449 ///
1450 /// \param Args the template arguments that will be
1451 /// substituted for the top-level template parameters within T.
1452 ///
1453 /// \param Loc the location in the source code where this substitution
1454 /// is being performed. It will typically be the location of the
1455 /// declarator (if we're instantiating the type of some declaration)
1456 /// or the location of the type in the source code (if, e.g., we're
1457 /// instantiating the type of a cast expression).
1458 ///
1459 /// \param Entity the name of the entity associated with a declaration
1460 /// being instantiated (if any). May be empty to indicate that there
1461 /// is no such entity (if, e.g., this is a type that occurs as part of
1462 /// a cast expression) or that the entity has no name (e.g., an
1463 /// unnamed function parameter).
1464 ///
1465 /// \returns If the instantiation succeeds, the instantiated
1466 /// type. Otherwise, produces diagnostics and returns a NULL type.
1467 TypeSourceInfo *Sema::SubstType(TypeSourceInfo *T,
1468                                 const MultiLevelTemplateArgumentList &Args,
1469                                 SourceLocation Loc,
1470                                 DeclarationName Entity) {
1471   assert(!ActiveTemplateInstantiations.empty() &&
1472          "Cannot perform an instantiation without some context on the "
1473          "instantiation stack");
1474 
1475   if (!T->getType()->isInstantiationDependentType() &&
1476       !T->getType()->isVariablyModifiedType())
1477     return T;
1478 
1479   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1480   return Instantiator.TransformType(T);
1481 }
1482 
1483 TypeSourceInfo *Sema::SubstType(TypeLoc TL,
1484                                 const MultiLevelTemplateArgumentList &Args,
1485                                 SourceLocation Loc,
1486                                 DeclarationName Entity) {
1487   assert(!ActiveTemplateInstantiations.empty() &&
1488          "Cannot perform an instantiation without some context on the "
1489          "instantiation stack");
1490 
1491   if (TL.getType().isNull())
1492     return nullptr;
1493 
1494   if (!TL.getType()->isInstantiationDependentType() &&
1495       !TL.getType()->isVariablyModifiedType()) {
1496     // FIXME: Make a copy of the TypeLoc data here, so that we can
1497     // return a new TypeSourceInfo. Inefficient!
1498     TypeLocBuilder TLB;
1499     TLB.pushFullCopy(TL);
1500     return TLB.getTypeSourceInfo(Context, TL.getType());
1501   }
1502 
1503   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1504   TypeLocBuilder TLB;
1505   TLB.reserve(TL.getFullDataSize());
1506   QualType Result = Instantiator.TransformType(TLB, TL);
1507   if (Result.isNull())
1508     return nullptr;
1509 
1510   return TLB.getTypeSourceInfo(Context, Result);
1511 }
1512 
1513 /// Deprecated form of the above.
1514 QualType Sema::SubstType(QualType T,
1515                          const MultiLevelTemplateArgumentList &TemplateArgs,
1516                          SourceLocation Loc, DeclarationName Entity) {
1517   assert(!ActiveTemplateInstantiations.empty() &&
1518          "Cannot perform an instantiation without some context on the "
1519          "instantiation stack");
1520 
1521   // If T is not a dependent type or a variably-modified type, there
1522   // is nothing to do.
1523   if (!T->isInstantiationDependentType() && !T->isVariablyModifiedType())
1524     return T;
1525 
1526   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc, Entity);
1527   return Instantiator.TransformType(T);
1528 }
1529 
1530 static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
1531   if (T->getType()->isInstantiationDependentType() ||
1532       T->getType()->isVariablyModifiedType())
1533     return true;
1534 
1535   TypeLoc TL = T->getTypeLoc().IgnoreParens();
1536   if (!TL.getAs<FunctionProtoTypeLoc>())
1537     return false;
1538 
1539   FunctionProtoTypeLoc FP = TL.castAs<FunctionProtoTypeLoc>();
1540   for (unsigned I = 0, E = FP.getNumParams(); I != E; ++I) {
1541     ParmVarDecl *P = FP.getParam(I);
1542 
1543     // This must be synthesized from a typedef.
1544     if (!P) continue;
1545 
1546     // The parameter's type as written might be dependent even if the
1547     // decayed type was not dependent.
1548     if (TypeSourceInfo *TSInfo = P->getTypeSourceInfo())
1549       if (TSInfo->getType()->isInstantiationDependentType())
1550         return true;
1551 
1552     // TODO: currently we always rebuild expressions.  When we
1553     // properly get lazier about this, we should use the same
1554     // logic to avoid rebuilding prototypes here.
1555     if (P->hasDefaultArg())
1556       return true;
1557   }
1558 
1559   return false;
1560 }
1561 
1562 /// A form of SubstType intended specifically for instantiating the
1563 /// type of a FunctionDecl.  Its purpose is solely to force the
1564 /// instantiation of default-argument expressions and to avoid
1565 /// instantiating an exception-specification.
1566 TypeSourceInfo *Sema::SubstFunctionDeclType(TypeSourceInfo *T,
1567                                 const MultiLevelTemplateArgumentList &Args,
1568                                 SourceLocation Loc,
1569                                 DeclarationName Entity,
1570                                 CXXRecordDecl *ThisContext,
1571                                 unsigned ThisTypeQuals) {
1572   assert(!ActiveTemplateInstantiations.empty() &&
1573          "Cannot perform an instantiation without some context on the "
1574          "instantiation stack");
1575 
1576   if (!NeedsInstantiationAsFunctionType(T))
1577     return T;
1578 
1579   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1580 
1581   TypeLocBuilder TLB;
1582 
1583   TypeLoc TL = T->getTypeLoc();
1584   TLB.reserve(TL.getFullDataSize());
1585 
1586   QualType Result;
1587 
1588   if (FunctionProtoTypeLoc Proto =
1589           TL.IgnoreParens().getAs<FunctionProtoTypeLoc>()) {
1590     // Instantiate the type, other than its exception specification. The
1591     // exception specification is instantiated in InitFunctionInstantiation
1592     // once we've built the FunctionDecl.
1593     // FIXME: Set the exception specification to EST_Uninstantiated here,
1594     // instead of rebuilding the function type again later.
1595     Result = Instantiator.TransformFunctionProtoType(
1596         TLB, Proto, ThisContext, ThisTypeQuals,
1597         [](FunctionProtoType::ExceptionSpecInfo &ESI,
1598            bool &Changed) { return false; });
1599   } else {
1600     Result = Instantiator.TransformType(TLB, TL);
1601   }
1602   if (Result.isNull())
1603     return nullptr;
1604 
1605   return TLB.getTypeSourceInfo(Context, Result);
1606 }
1607 
1608 void Sema::SubstExceptionSpec(FunctionDecl *New, const FunctionProtoType *Proto,
1609                               const MultiLevelTemplateArgumentList &Args) {
1610   FunctionProtoType::ExceptionSpecInfo ESI =
1611       Proto->getExtProtoInfo().ExceptionSpec;
1612   assert(ESI.Type != EST_Uninstantiated);
1613 
1614   TemplateInstantiator Instantiator(*this, Args, New->getLocation(),
1615                                     New->getDeclName());
1616 
1617   SmallVector<QualType, 4> ExceptionStorage;
1618   bool Changed = false;
1619   if (Instantiator.TransformExceptionSpec(
1620           New->getTypeSourceInfo()->getTypeLoc().getLocEnd(), ESI,
1621           ExceptionStorage, Changed))
1622     // On error, recover by dropping the exception specification.
1623     ESI.Type = EST_None;
1624 
1625   UpdateExceptionSpec(New, ESI);
1626 }
1627 
1628 ParmVarDecl *Sema::SubstParmVarDecl(ParmVarDecl *OldParm,
1629                             const MultiLevelTemplateArgumentList &TemplateArgs,
1630                                     int indexAdjustment,
1631                                     Optional<unsigned> NumExpansions,
1632                                     bool ExpectParameterPack) {
1633   TypeSourceInfo *OldDI = OldParm->getTypeSourceInfo();
1634   TypeSourceInfo *NewDI = nullptr;
1635 
1636   TypeLoc OldTL = OldDI->getTypeLoc();
1637   if (PackExpansionTypeLoc ExpansionTL = OldTL.getAs<PackExpansionTypeLoc>()) {
1638 
1639     // We have a function parameter pack. Substitute into the pattern of the
1640     // expansion.
1641     NewDI = SubstType(ExpansionTL.getPatternLoc(), TemplateArgs,
1642                       OldParm->getLocation(), OldParm->getDeclName());
1643     if (!NewDI)
1644       return nullptr;
1645 
1646     if (NewDI->getType()->containsUnexpandedParameterPack()) {
1647       // We still have unexpanded parameter packs, which means that
1648       // our function parameter is still a function parameter pack.
1649       // Therefore, make its type a pack expansion type.
1650       NewDI = CheckPackExpansion(NewDI, ExpansionTL.getEllipsisLoc(),
1651                                  NumExpansions);
1652     } else if (ExpectParameterPack) {
1653       // We expected to get a parameter pack but didn't (because the type
1654       // itself is not a pack expansion type), so complain. This can occur when
1655       // the substitution goes through an alias template that "loses" the
1656       // pack expansion.
1657       Diag(OldParm->getLocation(),
1658            diag::err_function_parameter_pack_without_parameter_packs)
1659         << NewDI->getType();
1660       return nullptr;
1661     }
1662   } else {
1663     NewDI = SubstType(OldDI, TemplateArgs, OldParm->getLocation(),
1664                       OldParm->getDeclName());
1665   }
1666 
1667   if (!NewDI)
1668     return nullptr;
1669 
1670   if (NewDI->getType()->isVoidType()) {
1671     Diag(OldParm->getLocation(), diag::err_param_with_void_type);
1672     return nullptr;
1673   }
1674 
1675   ParmVarDecl *NewParm = CheckParameter(Context.getTranslationUnitDecl(),
1676                                         OldParm->getInnerLocStart(),
1677                                         OldParm->getLocation(),
1678                                         OldParm->getIdentifier(),
1679                                         NewDI->getType(), NewDI,
1680                                         OldParm->getStorageClass());
1681   if (!NewParm)
1682     return nullptr;
1683 
1684   // Mark the (new) default argument as uninstantiated (if any).
1685   if (OldParm->hasUninstantiatedDefaultArg()) {
1686     Expr *Arg = OldParm->getUninstantiatedDefaultArg();
1687     NewParm->setUninstantiatedDefaultArg(Arg);
1688   } else if (OldParm->hasUnparsedDefaultArg()) {
1689     NewParm->setUnparsedDefaultArg();
1690     UnparsedDefaultArgInstantiations[OldParm].push_back(NewParm);
1691   } else if (Expr *Arg = OldParm->getDefaultArg())
1692     // FIXME: if we non-lazily instantiated non-dependent default args for
1693     // non-dependent parameter types we could remove a bunch of duplicate
1694     // conversion warnings for such arguments.
1695     NewParm->setUninstantiatedDefaultArg(Arg);
1696 
1697   NewParm->setHasInheritedDefaultArg(OldParm->hasInheritedDefaultArg());
1698 
1699   if (OldParm->isParameterPack() && !NewParm->isParameterPack()) {
1700     // Add the new parameter to the instantiated parameter pack.
1701     CurrentInstantiationScope->InstantiatedLocalPackArg(OldParm, NewParm);
1702   } else {
1703     // Introduce an Old -> New mapping
1704     CurrentInstantiationScope->InstantiatedLocal(OldParm, NewParm);
1705   }
1706 
1707   // FIXME: OldParm may come from a FunctionProtoType, in which case CurContext
1708   // can be anything, is this right ?
1709   NewParm->setDeclContext(CurContext);
1710 
1711   NewParm->setScopeInfo(OldParm->getFunctionScopeDepth(),
1712                         OldParm->getFunctionScopeIndex() + indexAdjustment);
1713 
1714   InstantiateAttrs(TemplateArgs, OldParm, NewParm);
1715 
1716   return NewParm;
1717 }
1718 
1719 /// \brief Substitute the given template arguments into the given set of
1720 /// parameters, producing the set of parameter types that would be generated
1721 /// from such a substitution.
1722 bool Sema::SubstParmTypes(SourceLocation Loc,
1723                           ParmVarDecl **Params, unsigned NumParams,
1724                           const MultiLevelTemplateArgumentList &TemplateArgs,
1725                           SmallVectorImpl<QualType> &ParamTypes,
1726                           SmallVectorImpl<ParmVarDecl *> *OutParams) {
1727   assert(!ActiveTemplateInstantiations.empty() &&
1728          "Cannot perform an instantiation without some context on the "
1729          "instantiation stack");
1730 
1731   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
1732                                     DeclarationName());
1733   return Instantiator.TransformFunctionTypeParams(Loc, Params, NumParams,
1734                                                   nullptr, ParamTypes,
1735                                                   OutParams);
1736 }
1737 
1738 /// \brief Perform substitution on the base class specifiers of the
1739 /// given class template specialization.
1740 ///
1741 /// Produces a diagnostic and returns true on error, returns false and
1742 /// attaches the instantiated base classes to the class template
1743 /// specialization if successful.
1744 bool
1745 Sema::SubstBaseSpecifiers(CXXRecordDecl *Instantiation,
1746                           CXXRecordDecl *Pattern,
1747                           const MultiLevelTemplateArgumentList &TemplateArgs) {
1748   bool Invalid = false;
1749   SmallVector<CXXBaseSpecifier*, 4> InstantiatedBases;
1750   for (const auto Base : Pattern->bases()) {
1751     if (!Base.getType()->isDependentType()) {
1752       if (const CXXRecordDecl *RD = Base.getType()->getAsCXXRecordDecl()) {
1753         if (RD->isInvalidDecl())
1754           Instantiation->setInvalidDecl();
1755       }
1756       InstantiatedBases.push_back(new (Context) CXXBaseSpecifier(Base));
1757       continue;
1758     }
1759 
1760     SourceLocation EllipsisLoc;
1761     TypeSourceInfo *BaseTypeLoc;
1762     if (Base.isPackExpansion()) {
1763       // This is a pack expansion. See whether we should expand it now, or
1764       // wait until later.
1765       SmallVector<UnexpandedParameterPack, 2> Unexpanded;
1766       collectUnexpandedParameterPacks(Base.getTypeSourceInfo()->getTypeLoc(),
1767                                       Unexpanded);
1768       bool ShouldExpand = false;
1769       bool RetainExpansion = false;
1770       Optional<unsigned> NumExpansions;
1771       if (CheckParameterPacksForExpansion(Base.getEllipsisLoc(),
1772                                           Base.getSourceRange(),
1773                                           Unexpanded,
1774                                           TemplateArgs, ShouldExpand,
1775                                           RetainExpansion,
1776                                           NumExpansions)) {
1777         Invalid = true;
1778         continue;
1779       }
1780 
1781       // If we should expand this pack expansion now, do so.
1782       if (ShouldExpand) {
1783         for (unsigned I = 0; I != *NumExpansions; ++I) {
1784             Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, I);
1785 
1786           TypeSourceInfo *BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
1787                                                   TemplateArgs,
1788                                               Base.getSourceRange().getBegin(),
1789                                                   DeclarationName());
1790           if (!BaseTypeLoc) {
1791             Invalid = true;
1792             continue;
1793           }
1794 
1795           if (CXXBaseSpecifier *InstantiatedBase
1796                 = CheckBaseSpecifier(Instantiation,
1797                                      Base.getSourceRange(),
1798                                      Base.isVirtual(),
1799                                      Base.getAccessSpecifierAsWritten(),
1800                                      BaseTypeLoc,
1801                                      SourceLocation()))
1802             InstantiatedBases.push_back(InstantiatedBase);
1803           else
1804             Invalid = true;
1805         }
1806 
1807         continue;
1808       }
1809 
1810       // The resulting base specifier will (still) be a pack expansion.
1811       EllipsisLoc = Base.getEllipsisLoc();
1812       Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
1813       BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
1814                               TemplateArgs,
1815                               Base.getSourceRange().getBegin(),
1816                               DeclarationName());
1817     } else {
1818       BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
1819                               TemplateArgs,
1820                               Base.getSourceRange().getBegin(),
1821                               DeclarationName());
1822     }
1823 
1824     if (!BaseTypeLoc) {
1825       Invalid = true;
1826       continue;
1827     }
1828 
1829     if (CXXBaseSpecifier *InstantiatedBase
1830           = CheckBaseSpecifier(Instantiation,
1831                                Base.getSourceRange(),
1832                                Base.isVirtual(),
1833                                Base.getAccessSpecifierAsWritten(),
1834                                BaseTypeLoc,
1835                                EllipsisLoc))
1836       InstantiatedBases.push_back(InstantiatedBase);
1837     else
1838       Invalid = true;
1839   }
1840 
1841   if (!Invalid &&
1842       AttachBaseSpecifiers(Instantiation, InstantiatedBases.data(),
1843                            InstantiatedBases.size()))
1844     Invalid = true;
1845 
1846   return Invalid;
1847 }
1848 
1849 // Defined via #include from SemaTemplateInstantiateDecl.cpp
1850 namespace clang {
1851   namespace sema {
1852     Attr *instantiateTemplateAttribute(const Attr *At, ASTContext &C, Sema &S,
1853                             const MultiLevelTemplateArgumentList &TemplateArgs);
1854   }
1855 }
1856 
1857 /// Determine whether we would be unable to instantiate this template (because
1858 /// it either has no definition, or is in the process of being instantiated).
1859 static bool DiagnoseUninstantiableTemplate(Sema &S,
1860                                            SourceLocation PointOfInstantiation,
1861                                            TagDecl *Instantiation,
1862                                            bool InstantiatedFromMember,
1863                                            TagDecl *Pattern,
1864                                            TagDecl *PatternDef,
1865                                            TemplateSpecializationKind TSK,
1866                                            bool Complain = true) {
1867   if (PatternDef && !PatternDef->isBeingDefined())
1868     return false;
1869 
1870   if (!Complain || (PatternDef && PatternDef->isInvalidDecl())) {
1871     // Say nothing
1872   } else if (PatternDef) {
1873     assert(PatternDef->isBeingDefined());
1874     S.Diag(PointOfInstantiation,
1875            diag::err_template_instantiate_within_definition)
1876       << (TSK != TSK_ImplicitInstantiation)
1877       << S.Context.getTypeDeclType(Instantiation);
1878     // Not much point in noting the template declaration here, since
1879     // we're lexically inside it.
1880     Instantiation->setInvalidDecl();
1881   } else if (InstantiatedFromMember) {
1882     S.Diag(PointOfInstantiation,
1883            diag::err_implicit_instantiate_member_undefined)
1884       << S.Context.getTypeDeclType(Instantiation);
1885     S.Diag(Pattern->getLocation(), diag::note_member_declared_at);
1886   } else {
1887     S.Diag(PointOfInstantiation, diag::err_template_instantiate_undefined)
1888       << (TSK != TSK_ImplicitInstantiation)
1889       << S.Context.getTypeDeclType(Instantiation);
1890     S.Diag(Pattern->getLocation(), diag::note_template_decl_here);
1891   }
1892 
1893   // In general, Instantiation isn't marked invalid to get more than one
1894   // error for multiple undefined instantiations. But the code that does
1895   // explicit declaration -> explicit definition conversion can't handle
1896   // invalid declarations, so mark as invalid in that case.
1897   if (TSK == TSK_ExplicitInstantiationDeclaration)
1898     Instantiation->setInvalidDecl();
1899   return true;
1900 }
1901 
1902 /// \brief Instantiate the definition of a class from a given pattern.
1903 ///
1904 /// \param PointOfInstantiation The point of instantiation within the
1905 /// source code.
1906 ///
1907 /// \param Instantiation is the declaration whose definition is being
1908 /// instantiated. This will be either a class template specialization
1909 /// or a member class of a class template specialization.
1910 ///
1911 /// \param Pattern is the pattern from which the instantiation
1912 /// occurs. This will be either the declaration of a class template or
1913 /// the declaration of a member class of a class template.
1914 ///
1915 /// \param TemplateArgs The template arguments to be substituted into
1916 /// the pattern.
1917 ///
1918 /// \param TSK the kind of implicit or explicit instantiation to perform.
1919 ///
1920 /// \param Complain whether to complain if the class cannot be instantiated due
1921 /// to the lack of a definition.
1922 ///
1923 /// \returns true if an error occurred, false otherwise.
1924 bool
1925 Sema::InstantiateClass(SourceLocation PointOfInstantiation,
1926                        CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
1927                        const MultiLevelTemplateArgumentList &TemplateArgs,
1928                        TemplateSpecializationKind TSK,
1929                        bool Complain) {
1930   CXXRecordDecl *PatternDef
1931     = cast_or_null<CXXRecordDecl>(Pattern->getDefinition());
1932   if (DiagnoseUninstantiableTemplate(*this, PointOfInstantiation, Instantiation,
1933                                 Instantiation->getInstantiatedFromMemberClass(),
1934                                      Pattern, PatternDef, TSK, Complain))
1935     return true;
1936   Pattern = PatternDef;
1937 
1938   // \brief Record the point of instantiation.
1939   if (MemberSpecializationInfo *MSInfo
1940         = Instantiation->getMemberSpecializationInfo()) {
1941     MSInfo->setTemplateSpecializationKind(TSK);
1942     MSInfo->setPointOfInstantiation(PointOfInstantiation);
1943   } else if (ClassTemplateSpecializationDecl *Spec
1944         = dyn_cast<ClassTemplateSpecializationDecl>(Instantiation)) {
1945     Spec->setTemplateSpecializationKind(TSK);
1946     Spec->setPointOfInstantiation(PointOfInstantiation);
1947   }
1948 
1949   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
1950   if (Inst.isInvalid())
1951     return true;
1952 
1953   // Enter the scope of this instantiation. We don't use
1954   // PushDeclContext because we don't have a scope.
1955   ContextRAII SavedContext(*this, Instantiation);
1956   EnterExpressionEvaluationContext EvalContext(*this,
1957                                                Sema::PotentiallyEvaluated);
1958 
1959   // If this is an instantiation of a local class, merge this local
1960   // instantiation scope with the enclosing scope. Otherwise, every
1961   // instantiation of a class has its own local instantiation scope.
1962   bool MergeWithParentScope = !Instantiation->isDefinedOutsideFunctionOrMethod();
1963   LocalInstantiationScope Scope(*this, MergeWithParentScope);
1964 
1965   // Pull attributes from the pattern onto the instantiation.
1966   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
1967 
1968   // Start the definition of this instantiation.
1969   Instantiation->startDefinition();
1970 
1971   // The instantiation is visible here, even if it was first declared in an
1972   // unimported module.
1973   Instantiation->setHidden(false);
1974 
1975   // FIXME: This loses the as-written tag kind for an explicit instantiation.
1976   Instantiation->setTagKind(Pattern->getTagKind());
1977 
1978   // Do substitution on the base class specifiers.
1979   if (SubstBaseSpecifiers(Instantiation, Pattern, TemplateArgs))
1980     Instantiation->setInvalidDecl();
1981 
1982   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
1983   SmallVector<Decl*, 4> Fields;
1984   // Delay instantiation of late parsed attributes.
1985   LateInstantiatedAttrVec LateAttrs;
1986   Instantiator.enableLateAttributeInstantiation(&LateAttrs);
1987 
1988   for (auto *Member : Pattern->decls()) {
1989     // Don't instantiate members not belonging in this semantic context.
1990     // e.g. for:
1991     // @code
1992     //    template <int i> class A {
1993     //      class B *g;
1994     //    };
1995     // @endcode
1996     // 'class B' has the template as lexical context but semantically it is
1997     // introduced in namespace scope.
1998     if (Member->getDeclContext() != Pattern)
1999       continue;
2000 
2001     if (Member->isInvalidDecl()) {
2002       Instantiation->setInvalidDecl();
2003       continue;
2004     }
2005 
2006     Decl *NewMember = Instantiator.Visit(Member);
2007     if (NewMember) {
2008       if (FieldDecl *Field = dyn_cast<FieldDecl>(NewMember)) {
2009         Fields.push_back(Field);
2010       } else if (EnumDecl *Enum = dyn_cast<EnumDecl>(NewMember)) {
2011         // C++11 [temp.inst]p1: The implicit instantiation of a class template
2012         // specialization causes the implicit instantiation of the definitions
2013         // of unscoped member enumerations.
2014         // Record a point of instantiation for this implicit instantiation.
2015         if (TSK == TSK_ImplicitInstantiation && !Enum->isScoped() &&
2016             Enum->isCompleteDefinition()) {
2017           MemberSpecializationInfo *MSInfo =Enum->getMemberSpecializationInfo();
2018           assert(MSInfo && "no spec info for member enum specialization");
2019           MSInfo->setTemplateSpecializationKind(TSK_ImplicitInstantiation);
2020           MSInfo->setPointOfInstantiation(PointOfInstantiation);
2021         }
2022       } else if (StaticAssertDecl *SA = dyn_cast<StaticAssertDecl>(NewMember)) {
2023         if (SA->isFailed()) {
2024           // A static_assert failed. Bail out; instantiating this
2025           // class is probably not meaningful.
2026           Instantiation->setInvalidDecl();
2027           break;
2028         }
2029       }
2030 
2031       if (NewMember->isInvalidDecl())
2032         Instantiation->setInvalidDecl();
2033     } else {
2034       // FIXME: Eventually, a NULL return will mean that one of the
2035       // instantiations was a semantic disaster, and we'll want to mark the
2036       // declaration invalid.
2037       // For now, we expect to skip some members that we can't yet handle.
2038     }
2039   }
2040 
2041   // Finish checking fields.
2042   ActOnFields(nullptr, Instantiation->getLocation(), Instantiation, Fields,
2043               SourceLocation(), SourceLocation(), nullptr);
2044   CheckCompletedCXXClass(Instantiation);
2045 
2046   // Instantiate late parsed attributes, and attach them to their decls.
2047   // See Sema::InstantiateAttrs
2048   for (LateInstantiatedAttrVec::iterator I = LateAttrs.begin(),
2049        E = LateAttrs.end(); I != E; ++I) {
2050     assert(CurrentInstantiationScope == Instantiator.getStartingScope());
2051     CurrentInstantiationScope = I->Scope;
2052 
2053     // Allow 'this' within late-parsed attributes.
2054     NamedDecl *ND = dyn_cast<NamedDecl>(I->NewDecl);
2055     CXXRecordDecl *ThisContext =
2056         dyn_cast_or_null<CXXRecordDecl>(ND->getDeclContext());
2057     CXXThisScopeRAII ThisScope(*this, ThisContext, /*TypeQuals*/0,
2058                                ND && ND->isCXXInstanceMember());
2059 
2060     Attr *NewAttr =
2061       instantiateTemplateAttribute(I->TmplAttr, Context, *this, TemplateArgs);
2062     I->NewDecl->addAttr(NewAttr);
2063     LocalInstantiationScope::deleteScopes(I->Scope,
2064                                           Instantiator.getStartingScope());
2065   }
2066   Instantiator.disableLateAttributeInstantiation();
2067   LateAttrs.clear();
2068 
2069   ActOnFinishDelayedMemberInitializers(Instantiation);
2070 
2071   // FIXME: We should do something similar for explicit instantiations so they
2072   // end up in the right module.
2073   if (TSK == TSK_ImplicitInstantiation) {
2074     Instantiation->setLocation(Pattern->getLocation());
2075     Instantiation->setLocStart(Pattern->getInnerLocStart());
2076     Instantiation->setRBraceLoc(Pattern->getRBraceLoc());
2077   }
2078 
2079   if (!Instantiation->isInvalidDecl()) {
2080     // Perform any dependent diagnostics from the pattern.
2081     PerformDependentDiagnostics(Pattern, TemplateArgs);
2082 
2083     // Instantiate any out-of-line class template partial
2084     // specializations now.
2085     for (TemplateDeclInstantiator::delayed_partial_spec_iterator
2086               P = Instantiator.delayed_partial_spec_begin(),
2087            PEnd = Instantiator.delayed_partial_spec_end();
2088          P != PEnd; ++P) {
2089       if (!Instantiator.InstantiateClassTemplatePartialSpecialization(
2090               P->first, P->second)) {
2091         Instantiation->setInvalidDecl();
2092         break;
2093       }
2094     }
2095 
2096     // Instantiate any out-of-line variable template partial
2097     // specializations now.
2098     for (TemplateDeclInstantiator::delayed_var_partial_spec_iterator
2099               P = Instantiator.delayed_var_partial_spec_begin(),
2100            PEnd = Instantiator.delayed_var_partial_spec_end();
2101          P != PEnd; ++P) {
2102       if (!Instantiator.InstantiateVarTemplatePartialSpecialization(
2103               P->first, P->second)) {
2104         Instantiation->setInvalidDecl();
2105         break;
2106       }
2107     }
2108   }
2109 
2110   // Exit the scope of this instantiation.
2111   SavedContext.pop();
2112 
2113   if (!Instantiation->isInvalidDecl()) {
2114     Consumer.HandleTagDeclDefinition(Instantiation);
2115 
2116     // Always emit the vtable for an explicit instantiation definition
2117     // of a polymorphic class template specialization.
2118     if (TSK == TSK_ExplicitInstantiationDefinition)
2119       MarkVTableUsed(PointOfInstantiation, Instantiation, true);
2120   }
2121 
2122   return Instantiation->isInvalidDecl();
2123 }
2124 
2125 /// \brief Instantiate the definition of an enum from a given pattern.
2126 ///
2127 /// \param PointOfInstantiation The point of instantiation within the
2128 ///        source code.
2129 /// \param Instantiation is the declaration whose definition is being
2130 ///        instantiated. This will be a member enumeration of a class
2131 ///        temploid specialization, or a local enumeration within a
2132 ///        function temploid specialization.
2133 /// \param Pattern The templated declaration from which the instantiation
2134 ///        occurs.
2135 /// \param TemplateArgs The template arguments to be substituted into
2136 ///        the pattern.
2137 /// \param TSK The kind of implicit or explicit instantiation to perform.
2138 ///
2139 /// \return \c true if an error occurred, \c false otherwise.
2140 bool Sema::InstantiateEnum(SourceLocation PointOfInstantiation,
2141                            EnumDecl *Instantiation, EnumDecl *Pattern,
2142                            const MultiLevelTemplateArgumentList &TemplateArgs,
2143                            TemplateSpecializationKind TSK) {
2144   EnumDecl *PatternDef = Pattern->getDefinition();
2145   if (DiagnoseUninstantiableTemplate(*this, PointOfInstantiation, Instantiation,
2146                                  Instantiation->getInstantiatedFromMemberEnum(),
2147                                      Pattern, PatternDef, TSK,/*Complain*/true))
2148     return true;
2149   Pattern = PatternDef;
2150 
2151   // Record the point of instantiation.
2152   if (MemberSpecializationInfo *MSInfo
2153         = Instantiation->getMemberSpecializationInfo()) {
2154     MSInfo->setTemplateSpecializationKind(TSK);
2155     MSInfo->setPointOfInstantiation(PointOfInstantiation);
2156   }
2157 
2158   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2159   if (Inst.isInvalid())
2160     return true;
2161 
2162   // The instantiation is visible here, even if it was first declared in an
2163   // unimported module.
2164   Instantiation->setHidden(false);
2165 
2166   // Enter the scope of this instantiation. We don't use
2167   // PushDeclContext because we don't have a scope.
2168   ContextRAII SavedContext(*this, Instantiation);
2169   EnterExpressionEvaluationContext EvalContext(*this,
2170                                                Sema::PotentiallyEvaluated);
2171 
2172   LocalInstantiationScope Scope(*this, /*MergeWithParentScope*/true);
2173 
2174   // Pull attributes from the pattern onto the instantiation.
2175   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
2176 
2177   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
2178   Instantiator.InstantiateEnumDefinition(Instantiation, Pattern);
2179 
2180   // Exit the scope of this instantiation.
2181   SavedContext.pop();
2182 
2183   return Instantiation->isInvalidDecl();
2184 }
2185 
2186 
2187 /// \brief Instantiate the definition of a field from the given pattern.
2188 ///
2189 /// \param PointOfInstantiation The point of instantiation within the
2190 ///        source code.
2191 /// \param Instantiation is the declaration whose definition is being
2192 ///        instantiated. This will be a class of a class temploid
2193 ///        specialization, or a local enumeration within a function temploid
2194 ///        specialization.
2195 /// \param Pattern The templated declaration from which the instantiation
2196 ///        occurs.
2197 /// \param TemplateArgs The template arguments to be substituted into
2198 ///        the pattern.
2199 ///
2200 /// \return \c true if an error occurred, \c false otherwise.
2201 bool Sema::InstantiateInClassInitializer(
2202     SourceLocation PointOfInstantiation, FieldDecl *Instantiation,
2203     FieldDecl *Pattern, const MultiLevelTemplateArgumentList &TemplateArgs) {
2204   // If there is no initializer, we don't need to do anything.
2205   if (!Pattern->hasInClassInitializer())
2206     return false;
2207 
2208   assert(Instantiation->getInClassInitStyle() ==
2209              Pattern->getInClassInitStyle() &&
2210          "pattern and instantiation disagree about init style");
2211 
2212   // Error out if we haven't parsed the initializer of the pattern yet because
2213   // we are waiting for the closing brace of the outer class.
2214   Expr *OldInit = Pattern->getInClassInitializer();
2215   if (!OldInit) {
2216     RecordDecl *PatternRD = Pattern->getParent();
2217     RecordDecl *OutermostClass = PatternRD->getOuterLexicalRecordContext();
2218     if (OutermostClass == PatternRD) {
2219       Diag(Pattern->getLocEnd(), diag::err_in_class_initializer_not_yet_parsed)
2220           << PatternRD << Pattern;
2221     } else {
2222       Diag(Pattern->getLocEnd(),
2223            diag::err_in_class_initializer_not_yet_parsed_outer_class)
2224           << PatternRD << OutermostClass << Pattern;
2225     }
2226     Instantiation->setInvalidDecl();
2227     return true;
2228   }
2229 
2230   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2231   if (Inst.isInvalid())
2232     return true;
2233 
2234   // Enter the scope of this instantiation. We don't use PushDeclContext because
2235   // we don't have a scope.
2236   ContextRAII SavedContext(*this, Instantiation->getParent());
2237   EnterExpressionEvaluationContext EvalContext(*this,
2238                                                Sema::PotentiallyEvaluated);
2239 
2240   LocalInstantiationScope Scope(*this);
2241 
2242   // Instantiate the initializer.
2243   ActOnStartCXXInClassMemberInitializer();
2244   CXXThisScopeRAII ThisScope(*this, Instantiation->getParent(), /*TypeQuals=*/0);
2245 
2246   ExprResult NewInit = SubstInitializer(OldInit, TemplateArgs,
2247                                         /*CXXDirectInit=*/false);
2248   Expr *Init = NewInit.get();
2249   assert((!Init || !isa<ParenListExpr>(Init)) && "call-style init in class");
2250   ActOnFinishCXXInClassMemberInitializer(
2251       Instantiation, Init ? Init->getLocStart() : SourceLocation(), Init);
2252 
2253   // Exit the scope of this instantiation.
2254   SavedContext.pop();
2255 
2256   // Return true if the in-class initializer is still missing.
2257   return !Instantiation->getInClassInitializer();
2258 }
2259 
2260 namespace {
2261   /// \brief A partial specialization whose template arguments have matched
2262   /// a given template-id.
2263   struct PartialSpecMatchResult {
2264     ClassTemplatePartialSpecializationDecl *Partial;
2265     TemplateArgumentList *Args;
2266   };
2267 }
2268 
2269 bool Sema::InstantiateClassTemplateSpecialization(
2270     SourceLocation PointOfInstantiation,
2271     ClassTemplateSpecializationDecl *ClassTemplateSpec,
2272     TemplateSpecializationKind TSK, bool Complain) {
2273   // Perform the actual instantiation on the canonical declaration.
2274   ClassTemplateSpec = cast<ClassTemplateSpecializationDecl>(
2275                                          ClassTemplateSpec->getCanonicalDecl());
2276 
2277   // Check whether we have already instantiated or specialized this class
2278   // template specialization.
2279   if (ClassTemplateSpec->getSpecializationKind() != TSK_Undeclared) {
2280     if (ClassTemplateSpec->getSpecializationKind() ==
2281           TSK_ExplicitInstantiationDeclaration &&
2282         TSK == TSK_ExplicitInstantiationDefinition) {
2283       // An explicit instantiation definition follows an explicit instantiation
2284       // declaration (C++0x [temp.explicit]p10); go ahead and perform the
2285       // explicit instantiation.
2286       ClassTemplateSpec->setSpecializationKind(TSK);
2287 
2288       // If this is an explicit instantiation definition, mark the
2289       // vtable as used.
2290       if (TSK == TSK_ExplicitInstantiationDefinition &&
2291           !ClassTemplateSpec->isInvalidDecl())
2292         MarkVTableUsed(PointOfInstantiation, ClassTemplateSpec, true);
2293 
2294       return false;
2295     }
2296 
2297     // We can only instantiate something that hasn't already been
2298     // instantiated or specialized. Fail without any diagnostics: our
2299     // caller will provide an error message.
2300     return true;
2301   }
2302 
2303   if (ClassTemplateSpec->isInvalidDecl())
2304     return true;
2305 
2306   ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
2307   CXXRecordDecl *Pattern = nullptr;
2308 
2309   // C++ [temp.class.spec.match]p1:
2310   //   When a class template is used in a context that requires an
2311   //   instantiation of the class, it is necessary to determine
2312   //   whether the instantiation is to be generated using the primary
2313   //   template or one of the partial specializations. This is done by
2314   //   matching the template arguments of the class template
2315   //   specialization with the template argument lists of the partial
2316   //   specializations.
2317   typedef PartialSpecMatchResult MatchResult;
2318   SmallVector<MatchResult, 4> Matched;
2319   SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
2320   Template->getPartialSpecializations(PartialSpecs);
2321   TemplateSpecCandidateSet FailedCandidates(PointOfInstantiation);
2322   for (unsigned I = 0, N = PartialSpecs.size(); I != N; ++I) {
2323     ClassTemplatePartialSpecializationDecl *Partial = PartialSpecs[I];
2324     TemplateDeductionInfo Info(FailedCandidates.getLocation());
2325     if (TemplateDeductionResult Result
2326           = DeduceTemplateArguments(Partial,
2327                                     ClassTemplateSpec->getTemplateArgs(),
2328                                     Info)) {
2329       // Store the failed-deduction information for use in diagnostics, later.
2330       // TODO: Actually use the failed-deduction info?
2331       FailedCandidates.addCandidate()
2332           .set(Partial, MakeDeductionFailureInfo(Context, Result, Info));
2333       (void)Result;
2334     } else {
2335       Matched.push_back(PartialSpecMatchResult());
2336       Matched.back().Partial = Partial;
2337       Matched.back().Args = Info.take();
2338     }
2339   }
2340 
2341   // If we're dealing with a member template where the template parameters
2342   // have been instantiated, this provides the original template parameters
2343   // from which the member template's parameters were instantiated.
2344 
2345   if (Matched.size() >= 1) {
2346     SmallVectorImpl<MatchResult>::iterator Best = Matched.begin();
2347     if (Matched.size() == 1) {
2348       //   -- If exactly one matching specialization is found, the
2349       //      instantiation is generated from that specialization.
2350       // We don't need to do anything for this.
2351     } else {
2352       //   -- If more than one matching specialization is found, the
2353       //      partial order rules (14.5.4.2) are used to determine
2354       //      whether one of the specializations is more specialized
2355       //      than the others. If none of the specializations is more
2356       //      specialized than all of the other matching
2357       //      specializations, then the use of the class template is
2358       //      ambiguous and the program is ill-formed.
2359       for (SmallVectorImpl<MatchResult>::iterator P = Best + 1,
2360                                                PEnd = Matched.end();
2361            P != PEnd; ++P) {
2362         if (getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2363                                                     PointOfInstantiation)
2364               == P->Partial)
2365           Best = P;
2366       }
2367 
2368       // Determine if the best partial specialization is more specialized than
2369       // the others.
2370       bool Ambiguous = false;
2371       for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2372                                                PEnd = Matched.end();
2373            P != PEnd; ++P) {
2374         if (P != Best &&
2375             getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2376                                                     PointOfInstantiation)
2377               != Best->Partial) {
2378           Ambiguous = true;
2379           break;
2380         }
2381       }
2382 
2383       if (Ambiguous) {
2384         // Partial ordering did not produce a clear winner. Complain.
2385         ClassTemplateSpec->setInvalidDecl();
2386         Diag(PointOfInstantiation, diag::err_partial_spec_ordering_ambiguous)
2387           << ClassTemplateSpec;
2388 
2389         // Print the matching partial specializations.
2390         for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2391                                                  PEnd = Matched.end();
2392              P != PEnd; ++P)
2393           Diag(P->Partial->getLocation(), diag::note_partial_spec_match)
2394             << getTemplateArgumentBindingsText(
2395                                             P->Partial->getTemplateParameters(),
2396                                                *P->Args);
2397 
2398         return true;
2399       }
2400     }
2401 
2402     // Instantiate using the best class template partial specialization.
2403     ClassTemplatePartialSpecializationDecl *OrigPartialSpec = Best->Partial;
2404     while (OrigPartialSpec->getInstantiatedFromMember()) {
2405       // If we've found an explicit specialization of this class template,
2406       // stop here and use that as the pattern.
2407       if (OrigPartialSpec->isMemberSpecialization())
2408         break;
2409 
2410       OrigPartialSpec = OrigPartialSpec->getInstantiatedFromMember();
2411     }
2412 
2413     Pattern = OrigPartialSpec;
2414     ClassTemplateSpec->setInstantiationOf(Best->Partial, Best->Args);
2415   } else {
2416     //   -- If no matches are found, the instantiation is generated
2417     //      from the primary template.
2418     ClassTemplateDecl *OrigTemplate = Template;
2419     while (OrigTemplate->getInstantiatedFromMemberTemplate()) {
2420       // If we've found an explicit specialization of this class template,
2421       // stop here and use that as the pattern.
2422       if (OrigTemplate->isMemberSpecialization())
2423         break;
2424 
2425       OrigTemplate = OrigTemplate->getInstantiatedFromMemberTemplate();
2426     }
2427 
2428     Pattern = OrigTemplate->getTemplatedDecl();
2429   }
2430 
2431   bool Result = InstantiateClass(PointOfInstantiation, ClassTemplateSpec,
2432                                  Pattern,
2433                                 getTemplateInstantiationArgs(ClassTemplateSpec),
2434                                  TSK,
2435                                  Complain);
2436 
2437   return Result;
2438 }
2439 
2440 /// \brief Instantiates the definitions of all of the member
2441 /// of the given class, which is an instantiation of a class template
2442 /// or a member class of a template.
2443 void
2444 Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
2445                               CXXRecordDecl *Instantiation,
2446                         const MultiLevelTemplateArgumentList &TemplateArgs,
2447                               TemplateSpecializationKind TSK) {
2448   // FIXME: We need to notify the ASTMutationListener that we did all of these
2449   // things, in case we have an explicit instantiation definition in a PCM, a
2450   // module, or preamble, and the declaration is in an imported AST.
2451   assert(
2452       (TSK == TSK_ExplicitInstantiationDefinition ||
2453        TSK == TSK_ExplicitInstantiationDeclaration ||
2454        (TSK == TSK_ImplicitInstantiation && Instantiation->isLocalClass())) &&
2455       "Unexpected template specialization kind!");
2456   for (auto *D : Instantiation->decls()) {
2457     bool SuppressNew = false;
2458     if (auto *Function = dyn_cast<FunctionDecl>(D)) {
2459       if (FunctionDecl *Pattern
2460             = Function->getInstantiatedFromMemberFunction()) {
2461         MemberSpecializationInfo *MSInfo
2462           = Function->getMemberSpecializationInfo();
2463         assert(MSInfo && "No member specialization information?");
2464         if (MSInfo->getTemplateSpecializationKind()
2465                                                  == TSK_ExplicitSpecialization)
2466           continue;
2467 
2468         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2469                                                    Function,
2470                                         MSInfo->getTemplateSpecializationKind(),
2471                                               MSInfo->getPointOfInstantiation(),
2472                                                    SuppressNew) ||
2473             SuppressNew)
2474           continue;
2475 
2476         // C++11 [temp.explicit]p8:
2477         //   An explicit instantiation definition that names a class template
2478         //   specialization explicitly instantiates the class template
2479         //   specialization and is only an explicit instantiation definition
2480         //   of members whose definition is visible at the point of
2481         //   instantiation.
2482         if (TSK == TSK_ExplicitInstantiationDefinition && !Pattern->isDefined())
2483           continue;
2484 
2485         Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2486 
2487         if (Function->isDefined()) {
2488           // Let the ASTConsumer know that this function has been explicitly
2489           // instantiated now, and its linkage might have changed.
2490           Consumer.HandleTopLevelDecl(DeclGroupRef(Function));
2491         } else if (TSK == TSK_ExplicitInstantiationDefinition) {
2492           InstantiateFunctionDefinition(PointOfInstantiation, Function);
2493         } else if (TSK == TSK_ImplicitInstantiation) {
2494           PendingLocalImplicitInstantiations.push_back(
2495               std::make_pair(Function, PointOfInstantiation));
2496         }
2497       }
2498     } else if (auto *Var = dyn_cast<VarDecl>(D)) {
2499       if (isa<VarTemplateSpecializationDecl>(Var))
2500         continue;
2501 
2502       if (Var->isStaticDataMember()) {
2503         MemberSpecializationInfo *MSInfo = Var->getMemberSpecializationInfo();
2504         assert(MSInfo && "No member specialization information?");
2505         if (MSInfo->getTemplateSpecializationKind()
2506                                                  == TSK_ExplicitSpecialization)
2507           continue;
2508 
2509         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2510                                                    Var,
2511                                         MSInfo->getTemplateSpecializationKind(),
2512                                               MSInfo->getPointOfInstantiation(),
2513                                                    SuppressNew) ||
2514             SuppressNew)
2515           continue;
2516 
2517         if (TSK == TSK_ExplicitInstantiationDefinition) {
2518           // C++0x [temp.explicit]p8:
2519           //   An explicit instantiation definition that names a class template
2520           //   specialization explicitly instantiates the class template
2521           //   specialization and is only an explicit instantiation definition
2522           //   of members whose definition is visible at the point of
2523           //   instantiation.
2524           if (!Var->getInstantiatedFromStaticDataMember()
2525                                                      ->getOutOfLineDefinition())
2526             continue;
2527 
2528           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2529           InstantiateStaticDataMemberDefinition(PointOfInstantiation, Var);
2530         } else {
2531           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2532         }
2533       }
2534     } else if (auto *Record = dyn_cast<CXXRecordDecl>(D)) {
2535       // Always skip the injected-class-name, along with any
2536       // redeclarations of nested classes, since both would cause us
2537       // to try to instantiate the members of a class twice.
2538       // Skip closure types; they'll get instantiated when we instantiate
2539       // the corresponding lambda-expression.
2540       if (Record->isInjectedClassName() || Record->getPreviousDecl() ||
2541           Record->isLambda())
2542         continue;
2543 
2544       MemberSpecializationInfo *MSInfo = Record->getMemberSpecializationInfo();
2545       assert(MSInfo && "No member specialization information?");
2546 
2547       if (MSInfo->getTemplateSpecializationKind()
2548                                                 == TSK_ExplicitSpecialization)
2549         continue;
2550 
2551       if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2552                                                  Record,
2553                                         MSInfo->getTemplateSpecializationKind(),
2554                                               MSInfo->getPointOfInstantiation(),
2555                                                  SuppressNew) ||
2556           SuppressNew)
2557         continue;
2558 
2559       CXXRecordDecl *Pattern = Record->getInstantiatedFromMemberClass();
2560       assert(Pattern && "Missing instantiated-from-template information");
2561 
2562       if (!Record->getDefinition()) {
2563         if (!Pattern->getDefinition()) {
2564           // C++0x [temp.explicit]p8:
2565           //   An explicit instantiation definition that names a class template
2566           //   specialization explicitly instantiates the class template
2567           //   specialization and is only an explicit instantiation definition
2568           //   of members whose definition is visible at the point of
2569           //   instantiation.
2570           if (TSK == TSK_ExplicitInstantiationDeclaration) {
2571             MSInfo->setTemplateSpecializationKind(TSK);
2572             MSInfo->setPointOfInstantiation(PointOfInstantiation);
2573           }
2574 
2575           continue;
2576         }
2577 
2578         InstantiateClass(PointOfInstantiation, Record, Pattern,
2579                          TemplateArgs,
2580                          TSK);
2581       } else {
2582         if (TSK == TSK_ExplicitInstantiationDefinition &&
2583             Record->getTemplateSpecializationKind() ==
2584                 TSK_ExplicitInstantiationDeclaration) {
2585           Record->setTemplateSpecializationKind(TSK);
2586           MarkVTableUsed(PointOfInstantiation, Record, true);
2587         }
2588       }
2589 
2590       Pattern = cast_or_null<CXXRecordDecl>(Record->getDefinition());
2591       if (Pattern)
2592         InstantiateClassMembers(PointOfInstantiation, Pattern, TemplateArgs,
2593                                 TSK);
2594     } else if (auto *Enum = dyn_cast<EnumDecl>(D)) {
2595       MemberSpecializationInfo *MSInfo = Enum->getMemberSpecializationInfo();
2596       assert(MSInfo && "No member specialization information?");
2597 
2598       if (MSInfo->getTemplateSpecializationKind()
2599             == TSK_ExplicitSpecialization)
2600         continue;
2601 
2602       if (CheckSpecializationInstantiationRedecl(
2603             PointOfInstantiation, TSK, Enum,
2604             MSInfo->getTemplateSpecializationKind(),
2605             MSInfo->getPointOfInstantiation(), SuppressNew) ||
2606           SuppressNew)
2607         continue;
2608 
2609       if (Enum->getDefinition())
2610         continue;
2611 
2612       EnumDecl *Pattern = Enum->getInstantiatedFromMemberEnum();
2613       assert(Pattern && "Missing instantiated-from-template information");
2614 
2615       if (TSK == TSK_ExplicitInstantiationDefinition) {
2616         if (!Pattern->getDefinition())
2617           continue;
2618 
2619         InstantiateEnum(PointOfInstantiation, Enum, Pattern, TemplateArgs, TSK);
2620       } else {
2621         MSInfo->setTemplateSpecializationKind(TSK);
2622         MSInfo->setPointOfInstantiation(PointOfInstantiation);
2623       }
2624     } else if (auto *Field = dyn_cast<FieldDecl>(D)) {
2625       // No need to instantiate in-class initializers during explicit
2626       // instantiation.
2627       if (Field->hasInClassInitializer() && TSK == TSK_ImplicitInstantiation) {
2628         CXXRecordDecl *ClassPattern =
2629             Instantiation->getTemplateInstantiationPattern();
2630         DeclContext::lookup_result Lookup =
2631             ClassPattern->lookup(Field->getDeclName());
2632         assert(Lookup.size() == 1);
2633         FieldDecl *Pattern = cast<FieldDecl>(Lookup[0]);
2634         InstantiateInClassInitializer(PointOfInstantiation, Field, Pattern,
2635                                       TemplateArgs);
2636       }
2637     }
2638   }
2639 }
2640 
2641 /// \brief Instantiate the definitions of all of the members of the
2642 /// given class template specialization, which was named as part of an
2643 /// explicit instantiation.
2644 void
2645 Sema::InstantiateClassTemplateSpecializationMembers(
2646                                            SourceLocation PointOfInstantiation,
2647                             ClassTemplateSpecializationDecl *ClassTemplateSpec,
2648                                                TemplateSpecializationKind TSK) {
2649   // C++0x [temp.explicit]p7:
2650   //   An explicit instantiation that names a class template
2651   //   specialization is an explicit instantion of the same kind
2652   //   (declaration or definition) of each of its members (not
2653   //   including members inherited from base classes) that has not
2654   //   been previously explicitly specialized in the translation unit
2655   //   containing the explicit instantiation, except as described
2656   //   below.
2657   InstantiateClassMembers(PointOfInstantiation, ClassTemplateSpec,
2658                           getTemplateInstantiationArgs(ClassTemplateSpec),
2659                           TSK);
2660 }
2661 
2662 StmtResult
2663 Sema::SubstStmt(Stmt *S, const MultiLevelTemplateArgumentList &TemplateArgs) {
2664   if (!S)
2665     return S;
2666 
2667   TemplateInstantiator Instantiator(*this, TemplateArgs,
2668                                     SourceLocation(),
2669                                     DeclarationName());
2670   return Instantiator.TransformStmt(S);
2671 }
2672 
2673 ExprResult
2674 Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
2675   if (!E)
2676     return E;
2677 
2678   TemplateInstantiator Instantiator(*this, TemplateArgs,
2679                                     SourceLocation(),
2680                                     DeclarationName());
2681   return Instantiator.TransformExpr(E);
2682 }
2683 
2684 ExprResult Sema::SubstInitializer(Expr *Init,
2685                           const MultiLevelTemplateArgumentList &TemplateArgs,
2686                           bool CXXDirectInit) {
2687   TemplateInstantiator Instantiator(*this, TemplateArgs,
2688                                     SourceLocation(),
2689                                     DeclarationName());
2690   return Instantiator.TransformInitializer(Init, CXXDirectInit);
2691 }
2692 
2693 bool Sema::SubstExprs(Expr **Exprs, unsigned NumExprs, bool IsCall,
2694                       const MultiLevelTemplateArgumentList &TemplateArgs,
2695                       SmallVectorImpl<Expr *> &Outputs) {
2696   if (NumExprs == 0)
2697     return false;
2698 
2699   TemplateInstantiator Instantiator(*this, TemplateArgs,
2700                                     SourceLocation(),
2701                                     DeclarationName());
2702   return Instantiator.TransformExprs(Exprs, NumExprs, IsCall, Outputs);
2703 }
2704 
2705 NestedNameSpecifierLoc
2706 Sema::SubstNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
2707                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2708   if (!NNS)
2709     return NestedNameSpecifierLoc();
2710 
2711   TemplateInstantiator Instantiator(*this, TemplateArgs, NNS.getBeginLoc(),
2712                                     DeclarationName());
2713   return Instantiator.TransformNestedNameSpecifierLoc(NNS);
2714 }
2715 
2716 /// \brief Do template substitution on declaration name info.
2717 DeclarationNameInfo
2718 Sema::SubstDeclarationNameInfo(const DeclarationNameInfo &NameInfo,
2719                          const MultiLevelTemplateArgumentList &TemplateArgs) {
2720   TemplateInstantiator Instantiator(*this, TemplateArgs, NameInfo.getLoc(),
2721                                     NameInfo.getName());
2722   return Instantiator.TransformDeclarationNameInfo(NameInfo);
2723 }
2724 
2725 TemplateName
2726 Sema::SubstTemplateName(NestedNameSpecifierLoc QualifierLoc,
2727                         TemplateName Name, SourceLocation Loc,
2728                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2729   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
2730                                     DeclarationName());
2731   CXXScopeSpec SS;
2732   SS.Adopt(QualifierLoc);
2733   return Instantiator.TransformTemplateName(SS, Name, Loc);
2734 }
2735 
2736 bool Sema::Subst(const TemplateArgumentLoc *Args, unsigned NumArgs,
2737                  TemplateArgumentListInfo &Result,
2738                  const MultiLevelTemplateArgumentList &TemplateArgs) {
2739   TemplateInstantiator Instantiator(*this, TemplateArgs, SourceLocation(),
2740                                     DeclarationName());
2741 
2742   return Instantiator.TransformTemplateArguments(Args, NumArgs, Result);
2743 }
2744 
2745 static const Decl *getCanonicalParmVarDecl(const Decl *D) {
2746   // When storing ParmVarDecls in the local instantiation scope, we always
2747   // want to use the ParmVarDecl from the canonical function declaration,
2748   // since the map is then valid for any redeclaration or definition of that
2749   // function.
2750   if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(D)) {
2751     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(PV->getDeclContext())) {
2752       unsigned i = PV->getFunctionScopeIndex();
2753       // This parameter might be from a freestanding function type within the
2754       // function and isn't necessarily referring to one of FD's parameters.
2755       if (FD->getParamDecl(i) == PV)
2756         return FD->getCanonicalDecl()->getParamDecl(i);
2757     }
2758   }
2759   return D;
2760 }
2761 
2762 
2763 llvm::PointerUnion<Decl *, LocalInstantiationScope::DeclArgumentPack *> *
2764 LocalInstantiationScope::findInstantiationOf(const Decl *D) {
2765   D = getCanonicalParmVarDecl(D);
2766   for (LocalInstantiationScope *Current = this; Current;
2767        Current = Current->Outer) {
2768 
2769     // Check if we found something within this scope.
2770     const Decl *CheckD = D;
2771     do {
2772       LocalDeclsMap::iterator Found = Current->LocalDecls.find(CheckD);
2773       if (Found != Current->LocalDecls.end())
2774         return &Found->second;
2775 
2776       // If this is a tag declaration, it's possible that we need to look for
2777       // a previous declaration.
2778       if (const TagDecl *Tag = dyn_cast<TagDecl>(CheckD))
2779         CheckD = Tag->getPreviousDecl();
2780       else
2781         CheckD = nullptr;
2782     } while (CheckD);
2783 
2784     // If we aren't combined with our outer scope, we're done.
2785     if (!Current->CombineWithOuterScope)
2786       break;
2787   }
2788 
2789   // If we're performing a partial substitution during template argument
2790   // deduction, we may not have values for template parameters yet.
2791   if (isa<NonTypeTemplateParmDecl>(D) || isa<TemplateTypeParmDecl>(D) ||
2792       isa<TemplateTemplateParmDecl>(D))
2793     return nullptr;
2794 
2795   // If we didn't find the decl, then we either have a sema bug, or we have a
2796   // forward reference to a label declaration.  Return null to indicate that
2797   // we have an uninstantiated label.
2798   assert(isa<LabelDecl>(D) && "declaration not instantiated in this scope");
2799   return nullptr;
2800 }
2801 
2802 void LocalInstantiationScope::InstantiatedLocal(const Decl *D, Decl *Inst) {
2803   D = getCanonicalParmVarDecl(D);
2804   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2805   if (Stored.isNull()) {
2806 #ifndef NDEBUG
2807     // It should not be present in any surrounding scope either.
2808     LocalInstantiationScope *Current = this;
2809     while (Current->CombineWithOuterScope && Current->Outer) {
2810       Current = Current->Outer;
2811       assert(Current->LocalDecls.find(D) == Current->LocalDecls.end() &&
2812              "Instantiated local in inner and outer scopes");
2813     }
2814 #endif
2815     Stored = Inst;
2816   } else if (DeclArgumentPack *Pack = Stored.dyn_cast<DeclArgumentPack *>()) {
2817     Pack->push_back(Inst);
2818   } else {
2819     assert(Stored.get<Decl *>() == Inst && "Already instantiated this local");
2820   }
2821 }
2822 
2823 void LocalInstantiationScope::InstantiatedLocalPackArg(const Decl *D,
2824                                                        Decl *Inst) {
2825   D = getCanonicalParmVarDecl(D);
2826   DeclArgumentPack *Pack = LocalDecls[D].get<DeclArgumentPack *>();
2827   Pack->push_back(Inst);
2828 }
2829 
2830 void LocalInstantiationScope::MakeInstantiatedLocalArgPack(const Decl *D) {
2831 #ifndef NDEBUG
2832   // This should be the first time we've been told about this decl.
2833   for (LocalInstantiationScope *Current = this;
2834        Current && Current->CombineWithOuterScope; Current = Current->Outer)
2835     assert(Current->LocalDecls.find(D) == Current->LocalDecls.end() &&
2836            "Creating local pack after instantiation of local");
2837 #endif
2838 
2839   D = getCanonicalParmVarDecl(D);
2840   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2841   DeclArgumentPack *Pack = new DeclArgumentPack;
2842   Stored = Pack;
2843   ArgumentPacks.push_back(Pack);
2844 }
2845 
2846 void LocalInstantiationScope::SetPartiallySubstitutedPack(NamedDecl *Pack,
2847                                           const TemplateArgument *ExplicitArgs,
2848                                                     unsigned NumExplicitArgs) {
2849   assert((!PartiallySubstitutedPack || PartiallySubstitutedPack == Pack) &&
2850          "Already have a partially-substituted pack");
2851   assert((!PartiallySubstitutedPack
2852           || NumArgsInPartiallySubstitutedPack == NumExplicitArgs) &&
2853          "Wrong number of arguments in partially-substituted pack");
2854   PartiallySubstitutedPack = Pack;
2855   ArgsInPartiallySubstitutedPack = ExplicitArgs;
2856   NumArgsInPartiallySubstitutedPack = NumExplicitArgs;
2857 }
2858 
2859 NamedDecl *LocalInstantiationScope::getPartiallySubstitutedPack(
2860                                          const TemplateArgument **ExplicitArgs,
2861                                               unsigned *NumExplicitArgs) const {
2862   if (ExplicitArgs)
2863     *ExplicitArgs = nullptr;
2864   if (NumExplicitArgs)
2865     *NumExplicitArgs = 0;
2866 
2867   for (const LocalInstantiationScope *Current = this; Current;
2868        Current = Current->Outer) {
2869     if (Current->PartiallySubstitutedPack) {
2870       if (ExplicitArgs)
2871         *ExplicitArgs = Current->ArgsInPartiallySubstitutedPack;
2872       if (NumExplicitArgs)
2873         *NumExplicitArgs = Current->NumArgsInPartiallySubstitutedPack;
2874 
2875       return Current->PartiallySubstitutedPack;
2876     }
2877 
2878     if (!Current->CombineWithOuterScope)
2879       break;
2880   }
2881 
2882   return nullptr;
2883 }
2884