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/ASTMutationListener.h"
19 #include "clang/AST/DeclTemplate.h"
20 #include "clang/AST/Expr.h"
21 #include "clang/Basic/LangOptions.h"
22 #include "clang/Sema/DeclSpec.h"
23 #include "clang/Sema/Initialization.h"
24 #include "clang/Sema/Lookup.h"
25 #include "clang/Sema/PrettyDeclStackTrace.h"
26 #include "clang/Sema/Template.h"
27 #include "clang/Sema/TemplateDeduction.h"
28 
29 using namespace clang;
30 using namespace sema;
31 
32 //===----------------------------------------------------------------------===/
33 // Template Instantiation Support
34 //===----------------------------------------------------------------------===/
35 
36 /// \brief Retrieve the template argument list(s) that should be used to
37 /// instantiate the definition of the given declaration.
38 ///
39 /// \param D the declaration for which we are computing template instantiation
40 /// arguments.
41 ///
42 /// \param Innermost if non-NULL, the innermost template argument list.
43 ///
44 /// \param RelativeToPrimary true if we should get the template
45 /// arguments relative to the primary template, even when we're
46 /// dealing with a specialization. This is only relevant for function
47 /// template specializations.
48 ///
49 /// \param Pattern If non-NULL, indicates the pattern from which we will be
50 /// instantiating the definition of the given declaration, \p D. This is
51 /// used to determine the proper set of template instantiation arguments for
52 /// friend function template specializations.
53 MultiLevelTemplateArgumentList
54 Sema::getTemplateInstantiationArgs(NamedDecl *D,
55                                    const TemplateArgumentList *Innermost,
56                                    bool RelativeToPrimary,
57                                    const FunctionDecl *Pattern) {
58   // Accumulate the set of template argument lists in this structure.
59   MultiLevelTemplateArgumentList Result;
60 
61   if (Innermost)
62     Result.addOuterTemplateArguments(Innermost);
63 
64   DeclContext *Ctx = dyn_cast<DeclContext>(D);
65   if (!Ctx) {
66     Ctx = D->getDeclContext();
67 
68     // Add template arguments from a variable template instantiation.
69     if (VarTemplateSpecializationDecl *Spec =
70             dyn_cast<VarTemplateSpecializationDecl>(D)) {
71       // We're done when we hit an explicit specialization.
72       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
73           !isa<VarTemplatePartialSpecializationDecl>(Spec))
74         return Result;
75 
76       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
77 
78       // If this variable template specialization was instantiated from a
79       // specialized member that is a variable template, we're done.
80       assert(Spec->getSpecializedTemplate() && "No variable template?");
81       llvm::PointerUnion<VarTemplateDecl*,
82                          VarTemplatePartialSpecializationDecl*> Specialized
83                              = Spec->getSpecializedTemplateOrPartial();
84       if (VarTemplatePartialSpecializationDecl *Partial =
85               Specialized.dyn_cast<VarTemplatePartialSpecializationDecl *>()) {
86         if (Partial->isMemberSpecialization())
87           return Result;
88       } else {
89         VarTemplateDecl *Tmpl = Specialized.get<VarTemplateDecl *>();
90         if (Tmpl->isMemberSpecialization())
91           return Result;
92       }
93     }
94 
95     // If we have a template template parameter with translation unit context,
96     // then we're performing substitution into a default template argument of
97     // this template template parameter before we've constructed the template
98     // that will own this template template parameter. In this case, we
99     // use empty template parameter lists for all of the outer templates
100     // to avoid performing any substitutions.
101     if (Ctx->isTranslationUnit()) {
102       if (TemplateTemplateParmDecl *TTP
103                                       = dyn_cast<TemplateTemplateParmDecl>(D)) {
104         for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
105           Result.addOuterTemplateArguments(None);
106         return Result;
107       }
108     }
109   }
110 
111   while (!Ctx->isFileContext()) {
112     // Add template arguments from a class template instantiation.
113     if (ClassTemplateSpecializationDecl *Spec
114           = dyn_cast<ClassTemplateSpecializationDecl>(Ctx)) {
115       // We're done when we hit an explicit specialization.
116       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
117           !isa<ClassTemplatePartialSpecializationDecl>(Spec))
118         break;
119 
120       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
121 
122       // If this class template specialization was instantiated from a
123       // specialized member that is a class template, we're done.
124       assert(Spec->getSpecializedTemplate() && "No class template?");
125       if (Spec->getSpecializedTemplate()->isMemberSpecialization())
126         break;
127     }
128     // Add template arguments from a function template specialization.
129     else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(Ctx)) {
130       if (!RelativeToPrimary &&
131           (Function->getTemplateSpecializationKind() ==
132                                                   TSK_ExplicitSpecialization &&
133            !Function->getClassScopeSpecializationPattern()))
134         break;
135 
136       if (const TemplateArgumentList *TemplateArgs
137             = Function->getTemplateSpecializationArgs()) {
138         // Add the template arguments for this specialization.
139         Result.addOuterTemplateArguments(TemplateArgs);
140 
141         // If this function was instantiated from a specialized member that is
142         // a function template, we're done.
143         assert(Function->getPrimaryTemplate() && "No function template?");
144         if (Function->getPrimaryTemplate()->isMemberSpecialization())
145           break;
146 
147         // If this function is a generic lambda specialization, we are done.
148         if (isGenericLambdaCallOperatorSpecialization(Function))
149           break;
150 
151       } else if (FunctionTemplateDecl *FunTmpl
152                                    = Function->getDescribedFunctionTemplate()) {
153         // Add the "injected" template arguments.
154         Result.addOuterTemplateArguments(FunTmpl->getInjectedTemplateArgs());
155       }
156 
157       // If this is a friend declaration and it declares an entity at
158       // namespace scope, take arguments from its lexical parent
159       // instead of its semantic parent, unless of course the pattern we're
160       // instantiating actually comes from the file's context!
161       if (Function->getFriendObjectKind() &&
162           Function->getDeclContext()->isFileContext() &&
163           (!Pattern || !Pattern->getLexicalDeclContext()->isFileContext())) {
164         Ctx = Function->getLexicalDeclContext();
165         RelativeToPrimary = false;
166         continue;
167       }
168     } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
169       if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
170         QualType T = ClassTemplate->getInjectedClassNameSpecialization();
171         const TemplateSpecializationType *TST =
172             cast<TemplateSpecializationType>(Context.getCanonicalType(T));
173         Result.addOuterTemplateArguments(
174             llvm::makeArrayRef(TST->getArgs(), TST->getNumArgs()));
175         if (ClassTemplate->isMemberSpecialization())
176           break;
177       }
178     }
179 
180     Ctx = Ctx->getParent();
181     RelativeToPrimary = false;
182   }
183 
184   return Result;
185 }
186 
187 bool Sema::ActiveTemplateInstantiation::isInstantiationRecord() const {
188   switch (Kind) {
189   case TemplateInstantiation:
190   case ExceptionSpecInstantiation:
191   case DefaultTemplateArgumentInstantiation:
192   case DefaultFunctionArgumentInstantiation:
193   case ExplicitTemplateArgumentSubstitution:
194   case DeducedTemplateArgumentSubstitution:
195   case PriorTemplateArgumentSubstitution:
196     return true;
197 
198   case DefaultTemplateArgumentChecking:
199     return false;
200   }
201 
202   llvm_unreachable("Invalid InstantiationKind!");
203 }
204 
205 Sema::InstantiatingTemplate::InstantiatingTemplate(
206     Sema &SemaRef, ActiveTemplateInstantiation::InstantiationKind Kind,
207     SourceLocation PointOfInstantiation, SourceRange InstantiationRange,
208     Decl *Entity, NamedDecl *Template, ArrayRef<TemplateArgument> TemplateArgs,
209     sema::TemplateDeductionInfo *DeductionInfo)
210     : SemaRef(SemaRef), SavedInNonInstantiationSFINAEContext(
211                             SemaRef.InNonInstantiationSFINAEContext) {
212   // Don't allow further instantiation if a fatal error has occcured.  Any
213   // diagnostics we might have raised will not be visible.
214   if (SemaRef.Diags.hasFatalErrorOccurred()) {
215     Invalid = true;
216     return;
217   }
218   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
219   if (!Invalid) {
220     ActiveTemplateInstantiation Inst;
221     Inst.Kind = Kind;
222     Inst.PointOfInstantiation = PointOfInstantiation;
223     Inst.Entity = Entity;
224     Inst.Template = Template;
225     Inst.TemplateArgs = TemplateArgs.data();
226     Inst.NumTemplateArgs = TemplateArgs.size();
227     Inst.DeductionInfo = DeductionInfo;
228     Inst.InstantiationRange = InstantiationRange;
229     AlreadyInstantiating =
230         !SemaRef.InstantiatingSpecializations
231              .insert(std::make_pair(Inst.Entity->getCanonicalDecl(), Inst.Kind))
232              .second;
233     SemaRef.InNonInstantiationSFINAEContext = false;
234     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
235     if (!Inst.isInstantiationRecord())
236       ++SemaRef.NonInstantiationEntries;
237   }
238 }
239 
240 Sema::InstantiatingTemplate::InstantiatingTemplate(
241     Sema &SemaRef, SourceLocation PointOfInstantiation, Decl *Entity,
242     SourceRange InstantiationRange)
243     : InstantiatingTemplate(SemaRef,
244                             ActiveTemplateInstantiation::TemplateInstantiation,
245                             PointOfInstantiation, InstantiationRange, Entity) {}
246 
247 Sema::InstantiatingTemplate::InstantiatingTemplate(
248     Sema &SemaRef, SourceLocation PointOfInstantiation, FunctionDecl *Entity,
249     ExceptionSpecification, SourceRange InstantiationRange)
250     : InstantiatingTemplate(
251           SemaRef, ActiveTemplateInstantiation::ExceptionSpecInstantiation,
252           PointOfInstantiation, InstantiationRange, Entity) {}
253 
254 Sema::InstantiatingTemplate::InstantiatingTemplate(
255     Sema &SemaRef, SourceLocation PointOfInstantiation, TemplateParameter Param,
256     TemplateDecl *Template, ArrayRef<TemplateArgument> TemplateArgs,
257     SourceRange InstantiationRange)
258     : InstantiatingTemplate(
259           SemaRef,
260           ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation,
261           PointOfInstantiation, InstantiationRange, getAsNamedDecl(Param),
262           Template, TemplateArgs) {}
263 
264 Sema::InstantiatingTemplate::InstantiatingTemplate(
265     Sema &SemaRef, SourceLocation PointOfInstantiation,
266     FunctionTemplateDecl *FunctionTemplate,
267     ArrayRef<TemplateArgument> TemplateArgs,
268     ActiveTemplateInstantiation::InstantiationKind Kind,
269     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
270     : InstantiatingTemplate(SemaRef, Kind, PointOfInstantiation,
271                             InstantiationRange, FunctionTemplate, nullptr,
272                             TemplateArgs, &DeductionInfo) {
273   assert(
274     Kind == ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution ||
275     Kind == ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution);
276 }
277 
278 Sema::InstantiatingTemplate::InstantiatingTemplate(
279     Sema &SemaRef, SourceLocation PointOfInstantiation,
280     ClassTemplatePartialSpecializationDecl *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,
291     VarTemplatePartialSpecializationDecl *PartialSpec,
292     ArrayRef<TemplateArgument> TemplateArgs,
293     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
294     : InstantiatingTemplate(
295           SemaRef,
296           ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution,
297           PointOfInstantiation, InstantiationRange, PartialSpec, nullptr,
298           TemplateArgs, &DeductionInfo) {}
299 
300 Sema::InstantiatingTemplate::InstantiatingTemplate(
301     Sema &SemaRef, SourceLocation PointOfInstantiation, ParmVarDecl *Param,
302     ArrayRef<TemplateArgument> TemplateArgs, SourceRange InstantiationRange)
303     : InstantiatingTemplate(
304           SemaRef,
305           ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation,
306           PointOfInstantiation, InstantiationRange, Param, nullptr,
307           TemplateArgs) {}
308 
309 Sema::InstantiatingTemplate::InstantiatingTemplate(
310     Sema &SemaRef, SourceLocation PointOfInstantiation, NamedDecl *Template,
311     NonTypeTemplateParmDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
312     SourceRange InstantiationRange)
313     : InstantiatingTemplate(
314           SemaRef,
315           ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution,
316           PointOfInstantiation, InstantiationRange, Param, Template,
317           TemplateArgs) {}
318 
319 Sema::InstantiatingTemplate::InstantiatingTemplate(
320     Sema &SemaRef, SourceLocation PointOfInstantiation, NamedDecl *Template,
321     TemplateTemplateParmDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
322     SourceRange InstantiationRange)
323     : InstantiatingTemplate(
324           SemaRef,
325           ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution,
326           PointOfInstantiation, InstantiationRange, Param, Template,
327           TemplateArgs) {}
328 
329 Sema::InstantiatingTemplate::InstantiatingTemplate(
330     Sema &SemaRef, SourceLocation PointOfInstantiation, TemplateDecl *Template,
331     NamedDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
332     SourceRange InstantiationRange)
333     : InstantiatingTemplate(
334           SemaRef, ActiveTemplateInstantiation::DefaultTemplateArgumentChecking,
335           PointOfInstantiation, InstantiationRange, Param, Template,
336           TemplateArgs) {}
337 
338 void Sema::InstantiatingTemplate::Clear() {
339   if (!Invalid) {
340     auto &Active = SemaRef.ActiveTemplateInstantiations.back();
341     if (!Active.isInstantiationRecord()) {
342       assert(SemaRef.NonInstantiationEntries > 0);
343       --SemaRef.NonInstantiationEntries;
344     }
345     SemaRef.InNonInstantiationSFINAEContext
346       = SavedInNonInstantiationSFINAEContext;
347 
348     // Name lookup no longer looks in this template's defining module.
349     assert(SemaRef.ActiveTemplateInstantiations.size() >=
350            SemaRef.ActiveTemplateInstantiationLookupModules.size() &&
351            "forgot to remove a lookup module for a template instantiation");
352     if (SemaRef.ActiveTemplateInstantiations.size() ==
353         SemaRef.ActiveTemplateInstantiationLookupModules.size()) {
354       if (Module *M = SemaRef.ActiveTemplateInstantiationLookupModules.back())
355         SemaRef.LookupModulesCache.erase(M);
356       SemaRef.ActiveTemplateInstantiationLookupModules.pop_back();
357     }
358 
359     if (!AlreadyInstantiating)
360       SemaRef.InstantiatingSpecializations.erase(
361           std::make_pair(Active.Entity, Active.Kind));
362 
363     SemaRef.ActiveTemplateInstantiations.pop_back();
364     Invalid = true;
365   }
366 }
367 
368 bool Sema::InstantiatingTemplate::CheckInstantiationDepth(
369                                         SourceLocation PointOfInstantiation,
370                                            SourceRange InstantiationRange) {
371   assert(SemaRef.NonInstantiationEntries <=
372                                    SemaRef.ActiveTemplateInstantiations.size());
373   if ((SemaRef.ActiveTemplateInstantiations.size() -
374           SemaRef.NonInstantiationEntries)
375         <= SemaRef.getLangOpts().InstantiationDepth)
376     return false;
377 
378   SemaRef.Diag(PointOfInstantiation,
379                diag::err_template_recursion_depth_exceeded)
380     << SemaRef.getLangOpts().InstantiationDepth
381     << InstantiationRange;
382   SemaRef.Diag(PointOfInstantiation, diag::note_template_recursion_depth)
383     << SemaRef.getLangOpts().InstantiationDepth;
384   return true;
385 }
386 
387 /// \brief Prints the current instantiation stack through a series of
388 /// notes.
389 void Sema::PrintInstantiationStack() {
390   // Determine which template instantiations to skip, if any.
391   unsigned SkipStart = ActiveTemplateInstantiations.size(), SkipEnd = SkipStart;
392   unsigned Limit = Diags.getTemplateBacktraceLimit();
393   if (Limit && Limit < ActiveTemplateInstantiations.size()) {
394     SkipStart = Limit / 2 + Limit % 2;
395     SkipEnd = ActiveTemplateInstantiations.size() - Limit / 2;
396   }
397 
398   // FIXME: In all of these cases, we need to show the template arguments
399   unsigned InstantiationIdx = 0;
400   for (SmallVectorImpl<ActiveTemplateInstantiation>::reverse_iterator
401          Active = ActiveTemplateInstantiations.rbegin(),
402          ActiveEnd = ActiveTemplateInstantiations.rend();
403        Active != ActiveEnd;
404        ++Active, ++InstantiationIdx) {
405     // Skip this instantiation?
406     if (InstantiationIdx >= SkipStart && InstantiationIdx < SkipEnd) {
407       if (InstantiationIdx == SkipStart) {
408         // Note that we're skipping instantiations.
409         Diags.Report(Active->PointOfInstantiation,
410                      diag::note_instantiation_contexts_suppressed)
411           << unsigned(ActiveTemplateInstantiations.size() - Limit);
412       }
413       continue;
414     }
415 
416     switch (Active->Kind) {
417     case ActiveTemplateInstantiation::TemplateInstantiation: {
418       Decl *D = Active->Entity;
419       if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(D)) {
420         unsigned DiagID = diag::note_template_member_class_here;
421         if (isa<ClassTemplateSpecializationDecl>(Record))
422           DiagID = diag::note_template_class_instantiation_here;
423         Diags.Report(Active->PointOfInstantiation, DiagID)
424           << Context.getTypeDeclType(Record)
425           << Active->InstantiationRange;
426       } else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
427         unsigned DiagID;
428         if (Function->getPrimaryTemplate())
429           DiagID = diag::note_function_template_spec_here;
430         else
431           DiagID = diag::note_template_member_function_here;
432         Diags.Report(Active->PointOfInstantiation, DiagID)
433           << Function
434           << Active->InstantiationRange;
435       } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
436         Diags.Report(Active->PointOfInstantiation,
437                      VD->isStaticDataMember()?
438                        diag::note_template_static_data_member_def_here
439                      : diag::note_template_variable_def_here)
440           << VD
441           << Active->InstantiationRange;
442       } else if (EnumDecl *ED = dyn_cast<EnumDecl>(D)) {
443         Diags.Report(Active->PointOfInstantiation,
444                      diag::note_template_enum_def_here)
445           << ED
446           << Active->InstantiationRange;
447       } else if (FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
448         Diags.Report(Active->PointOfInstantiation,
449                      diag::note_template_nsdmi_here)
450             << FD << Active->InstantiationRange;
451       } else {
452         Diags.Report(Active->PointOfInstantiation,
453                      diag::note_template_type_alias_instantiation_here)
454           << cast<TypeAliasTemplateDecl>(D)
455           << Active->InstantiationRange;
456       }
457       break;
458     }
459 
460     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation: {
461       TemplateDecl *Template = cast<TemplateDecl>(Active->Template);
462       SmallVector<char, 128> TemplateArgsStr;
463       llvm::raw_svector_ostream OS(TemplateArgsStr);
464       Template->printName(OS);
465       TemplateSpecializationType::PrintTemplateArgumentList(
466           OS, Active->template_arguments(), getPrintingPolicy());
467       Diags.Report(Active->PointOfInstantiation,
468                    diag::note_default_arg_instantiation_here)
469         << OS.str()
470         << Active->InstantiationRange;
471       break;
472     }
473 
474     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution: {
475       FunctionTemplateDecl *FnTmpl = cast<FunctionTemplateDecl>(Active->Entity);
476       Diags.Report(Active->PointOfInstantiation,
477                    diag::note_explicit_template_arg_substitution_here)
478         << FnTmpl
479         << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
480                                            Active->TemplateArgs,
481                                            Active->NumTemplateArgs)
482         << Active->InstantiationRange;
483       break;
484     }
485 
486     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
487       if (ClassTemplatePartialSpecializationDecl *PartialSpec =
488             dyn_cast<ClassTemplatePartialSpecializationDecl>(Active->Entity)) {
489         Diags.Report(Active->PointOfInstantiation,
490                      diag::note_partial_spec_deduct_instantiation_here)
491           << Context.getTypeDeclType(PartialSpec)
492           << getTemplateArgumentBindingsText(
493                                          PartialSpec->getTemplateParameters(),
494                                              Active->TemplateArgs,
495                                              Active->NumTemplateArgs)
496           << Active->InstantiationRange;
497       } else {
498         FunctionTemplateDecl *FnTmpl
499           = cast<FunctionTemplateDecl>(Active->Entity);
500         Diags.Report(Active->PointOfInstantiation,
501                      diag::note_function_template_deduction_instantiation_here)
502           << FnTmpl
503           << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
504                                              Active->TemplateArgs,
505                                              Active->NumTemplateArgs)
506           << Active->InstantiationRange;
507       }
508       break;
509 
510     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation: {
511       ParmVarDecl *Param = cast<ParmVarDecl>(Active->Entity);
512       FunctionDecl *FD = cast<FunctionDecl>(Param->getDeclContext());
513 
514       SmallVector<char, 128> TemplateArgsStr;
515       llvm::raw_svector_ostream OS(TemplateArgsStr);
516       FD->printName(OS);
517       TemplateSpecializationType::PrintTemplateArgumentList(
518           OS, Active->template_arguments(), getPrintingPolicy());
519       Diags.Report(Active->PointOfInstantiation,
520                    diag::note_default_function_arg_instantiation_here)
521         << OS.str()
522         << Active->InstantiationRange;
523       break;
524     }
525 
526     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution: {
527       NamedDecl *Parm = cast<NamedDecl>(Active->Entity);
528       std::string Name;
529       if (!Parm->getName().empty())
530         Name = std::string(" '") + Parm->getName().str() + "'";
531 
532       TemplateParameterList *TemplateParams = nullptr;
533       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
534         TemplateParams = Template->getTemplateParameters();
535       else
536         TemplateParams =
537           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
538                                                       ->getTemplateParameters();
539       Diags.Report(Active->PointOfInstantiation,
540                    diag::note_prior_template_arg_substitution)
541         << isa<TemplateTemplateParmDecl>(Parm)
542         << Name
543         << getTemplateArgumentBindingsText(TemplateParams,
544                                            Active->TemplateArgs,
545                                            Active->NumTemplateArgs)
546         << Active->InstantiationRange;
547       break;
548     }
549 
550     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking: {
551       TemplateParameterList *TemplateParams = nullptr;
552       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
553         TemplateParams = Template->getTemplateParameters();
554       else
555         TemplateParams =
556           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
557                                                       ->getTemplateParameters();
558 
559       Diags.Report(Active->PointOfInstantiation,
560                    diag::note_template_default_arg_checking)
561         << getTemplateArgumentBindingsText(TemplateParams,
562                                            Active->TemplateArgs,
563                                            Active->NumTemplateArgs)
564         << Active->InstantiationRange;
565       break;
566     }
567 
568     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
569       Diags.Report(Active->PointOfInstantiation,
570                    diag::note_template_exception_spec_instantiation_here)
571         << cast<FunctionDecl>(Active->Entity)
572         << Active->InstantiationRange;
573       break;
574     }
575   }
576 }
577 
578 Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
579   if (InNonInstantiationSFINAEContext)
580     return Optional<TemplateDeductionInfo *>(nullptr);
581 
582   for (SmallVectorImpl<ActiveTemplateInstantiation>::const_reverse_iterator
583          Active = ActiveTemplateInstantiations.rbegin(),
584          ActiveEnd = ActiveTemplateInstantiations.rend();
585        Active != ActiveEnd;
586        ++Active)
587   {
588     switch(Active->Kind) {
589     case ActiveTemplateInstantiation::TemplateInstantiation:
590       // An instantiation of an alias template may or may not be a SFINAE
591       // context, depending on what else is on the stack.
592       if (isa<TypeAliasTemplateDecl>(Active->Entity))
593         break;
594       // Fall through.
595     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
596     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
597       // This is a template instantiation, so there is no SFINAE.
598       return None;
599 
600     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
601     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
602     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking:
603       // A default template argument instantiation and substitution into
604       // template parameters with arguments for prior parameters may or may
605       // not be a SFINAE context; look further up the stack.
606       break;
607 
608     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution:
609     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
610       // We're either substitution explicitly-specified template arguments
611       // or deduced template arguments, so SFINAE applies.
612       assert(Active->DeductionInfo && "Missing deduction info pointer");
613       return Active->DeductionInfo;
614     }
615   }
616 
617   return None;
618 }
619 
620 /// \brief Retrieve the depth and index of a parameter pack.
621 static std::pair<unsigned, unsigned>
622 getDepthAndIndex(NamedDecl *ND) {
623   if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(ND))
624     return std::make_pair(TTP->getDepth(), TTP->getIndex());
625 
626   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(ND))
627     return std::make_pair(NTTP->getDepth(), NTTP->getIndex());
628 
629   TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(ND);
630   return std::make_pair(TTP->getDepth(), TTP->getIndex());
631 }
632 
633 //===----------------------------------------------------------------------===/
634 // Template Instantiation for Types
635 //===----------------------------------------------------------------------===/
636 namespace {
637   class TemplateInstantiator : public TreeTransform<TemplateInstantiator> {
638     const MultiLevelTemplateArgumentList &TemplateArgs;
639     SourceLocation Loc;
640     DeclarationName Entity;
641 
642   public:
643     typedef TreeTransform<TemplateInstantiator> inherited;
644 
645     TemplateInstantiator(Sema &SemaRef,
646                          const MultiLevelTemplateArgumentList &TemplateArgs,
647                          SourceLocation Loc,
648                          DeclarationName Entity)
649       : inherited(SemaRef), TemplateArgs(TemplateArgs), Loc(Loc),
650         Entity(Entity) { }
651 
652     /// \brief Determine whether the given type \p T has already been
653     /// transformed.
654     ///
655     /// For the purposes of template instantiation, a type has already been
656     /// transformed if it is NULL or if it is not dependent.
657     bool AlreadyTransformed(QualType T);
658 
659     /// \brief Returns the location of the entity being instantiated, if known.
660     SourceLocation getBaseLocation() { return Loc; }
661 
662     /// \brief Returns the name of the entity being instantiated, if any.
663     DeclarationName getBaseEntity() { return Entity; }
664 
665     /// \brief Sets the "base" location and entity when that
666     /// information is known based on another transformation.
667     void setBase(SourceLocation Loc, DeclarationName Entity) {
668       this->Loc = Loc;
669       this->Entity = Entity;
670     }
671 
672     bool TryExpandParameterPacks(SourceLocation EllipsisLoc,
673                                  SourceRange PatternRange,
674                                  ArrayRef<UnexpandedParameterPack> Unexpanded,
675                                  bool &ShouldExpand, bool &RetainExpansion,
676                                  Optional<unsigned> &NumExpansions) {
677       return getSema().CheckParameterPacksForExpansion(EllipsisLoc,
678                                                        PatternRange, Unexpanded,
679                                                        TemplateArgs,
680                                                        ShouldExpand,
681                                                        RetainExpansion,
682                                                        NumExpansions);
683     }
684 
685     void ExpandingFunctionParameterPack(ParmVarDecl *Pack) {
686       SemaRef.CurrentInstantiationScope->MakeInstantiatedLocalArgPack(Pack);
687     }
688 
689     TemplateArgument ForgetPartiallySubstitutedPack() {
690       TemplateArgument Result;
691       if (NamedDecl *PartialPack
692             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
693         MultiLevelTemplateArgumentList &TemplateArgs
694           = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
695         unsigned Depth, Index;
696         std::tie(Depth, Index) = getDepthAndIndex(PartialPack);
697         if (TemplateArgs.hasTemplateArgument(Depth, Index)) {
698           Result = TemplateArgs(Depth, Index);
699           TemplateArgs.setArgument(Depth, Index, TemplateArgument());
700         }
701       }
702 
703       return Result;
704     }
705 
706     void RememberPartiallySubstitutedPack(TemplateArgument Arg) {
707       if (Arg.isNull())
708         return;
709 
710       if (NamedDecl *PartialPack
711             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
712         MultiLevelTemplateArgumentList &TemplateArgs
713         = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
714         unsigned Depth, Index;
715         std::tie(Depth, Index) = getDepthAndIndex(PartialPack);
716         TemplateArgs.setArgument(Depth, Index, Arg);
717       }
718     }
719 
720     /// \brief Transform the given declaration by instantiating a reference to
721     /// this declaration.
722     Decl *TransformDecl(SourceLocation Loc, Decl *D);
723 
724     void transformAttrs(Decl *Old, Decl *New) {
725       SemaRef.InstantiateAttrs(TemplateArgs, Old, New);
726     }
727 
728     void transformedLocalDecl(Decl *Old, Decl *New) {
729       // If we've instantiated the call operator of a lambda or the call
730       // operator template of a generic lambda, update the "instantiation of"
731       // information.
732       auto *NewMD = dyn_cast<CXXMethodDecl>(New);
733       if (NewMD && isLambdaCallOperator(NewMD)) {
734         auto *OldMD = dyn_cast<CXXMethodDecl>(Old);
735         if (auto *NewTD = NewMD->getDescribedFunctionTemplate())
736           NewTD->setInstantiatedFromMemberTemplate(
737               OldMD->getDescribedFunctionTemplate());
738         else
739           NewMD->setInstantiationOfMemberFunction(OldMD,
740                                                   TSK_ImplicitInstantiation);
741       }
742 
743       SemaRef.CurrentInstantiationScope->InstantiatedLocal(Old, New);
744 
745       // We recreated a local declaration, but not by instantiating it. There
746       // may be pending dependent diagnostics to produce.
747       if (auto *DC = dyn_cast<DeclContext>(Old))
748         SemaRef.PerformDependentDiagnostics(DC, TemplateArgs);
749     }
750 
751     /// \brief Transform the definition of the given declaration by
752     /// instantiating it.
753     Decl *TransformDefinition(SourceLocation Loc, Decl *D);
754 
755     /// \brief Transform the first qualifier within a scope by instantiating the
756     /// declaration.
757     NamedDecl *TransformFirstQualifierInScope(NamedDecl *D, SourceLocation Loc);
758 
759     /// \brief Rebuild the exception declaration and register the declaration
760     /// as an instantiated local.
761     VarDecl *RebuildExceptionDecl(VarDecl *ExceptionDecl,
762                                   TypeSourceInfo *Declarator,
763                                   SourceLocation StartLoc,
764                                   SourceLocation NameLoc,
765                                   IdentifierInfo *Name);
766 
767     /// \brief Rebuild the Objective-C exception declaration and register the
768     /// declaration as an instantiated local.
769     VarDecl *RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
770                                       TypeSourceInfo *TSInfo, QualType T);
771 
772     /// \brief Check for tag mismatches when instantiating an
773     /// elaborated type.
774     QualType RebuildElaboratedType(SourceLocation KeywordLoc,
775                                    ElaboratedTypeKeyword Keyword,
776                                    NestedNameSpecifierLoc QualifierLoc,
777                                    QualType T);
778 
779     TemplateName
780     TransformTemplateName(CXXScopeSpec &SS, TemplateName Name,
781                           SourceLocation NameLoc,
782                           QualType ObjectType = QualType(),
783                           NamedDecl *FirstQualifierInScope = nullptr);
784 
785     const LoopHintAttr *TransformLoopHintAttr(const LoopHintAttr *LH);
786 
787     ExprResult TransformPredefinedExpr(PredefinedExpr *E);
788     ExprResult TransformDeclRefExpr(DeclRefExpr *E);
789     ExprResult TransformCXXDefaultArgExpr(CXXDefaultArgExpr *E);
790 
791     ExprResult TransformTemplateParmRefExpr(DeclRefExpr *E,
792                                             NonTypeTemplateParmDecl *D);
793     ExprResult TransformSubstNonTypeTemplateParmPackExpr(
794                                            SubstNonTypeTemplateParmPackExpr *E);
795 
796     /// \brief Rebuild a DeclRefExpr for a ParmVarDecl reference.
797     ExprResult RebuildParmVarDeclRefExpr(ParmVarDecl *PD, SourceLocation Loc);
798 
799     /// \brief Transform a reference to a function parameter pack.
800     ExprResult TransformFunctionParmPackRefExpr(DeclRefExpr *E,
801                                                 ParmVarDecl *PD);
802 
803     /// \brief Transform a FunctionParmPackExpr which was built when we couldn't
804     /// expand a function parameter pack reference which refers to an expanded
805     /// pack.
806     ExprResult TransformFunctionParmPackExpr(FunctionParmPackExpr *E);
807 
808     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
809                                         FunctionProtoTypeLoc TL) {
810       // Call the base version; it will forward to our overridden version below.
811       return inherited::TransformFunctionProtoType(TLB, TL);
812     }
813 
814     template<typename Fn>
815     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
816                                         FunctionProtoTypeLoc TL,
817                                         CXXRecordDecl *ThisContext,
818                                         unsigned ThisTypeQuals,
819                                         Fn TransformExceptionSpec);
820 
821     ParmVarDecl *TransformFunctionTypeParam(ParmVarDecl *OldParm,
822                                             int indexAdjustment,
823                                             Optional<unsigned> NumExpansions,
824                                             bool ExpectParameterPack);
825 
826     /// \brief Transforms a template type parameter type by performing
827     /// substitution of the corresponding template type argument.
828     QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
829                                            TemplateTypeParmTypeLoc TL);
830 
831     /// \brief Transforms an already-substituted template type parameter pack
832     /// into either itself (if we aren't substituting into its pack expansion)
833     /// or the appropriate substituted argument.
834     QualType TransformSubstTemplateTypeParmPackType(TypeLocBuilder &TLB,
835                                            SubstTemplateTypeParmPackTypeLoc TL);
836 
837     ExprResult TransformLambdaExpr(LambdaExpr *E) {
838       LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
839       return TreeTransform<TemplateInstantiator>::TransformLambdaExpr(E);
840     }
841 
842     TemplateParameterList *TransformTemplateParameterList(
843                               TemplateParameterList *OrigTPL)  {
844       if (!OrigTPL || !OrigTPL->size()) return OrigTPL;
845 
846       DeclContext *Owner = OrigTPL->getParam(0)->getDeclContext();
847       TemplateDeclInstantiator  DeclInstantiator(getSema(),
848                         /* DeclContext *Owner */ Owner, TemplateArgs);
849       return DeclInstantiator.SubstTemplateParams(OrigTPL);
850     }
851   private:
852     ExprResult transformNonTypeTemplateParmRef(NonTypeTemplateParmDecl *parm,
853                                                SourceLocation loc,
854                                                TemplateArgument arg);
855   };
856 }
857 
858 bool TemplateInstantiator::AlreadyTransformed(QualType T) {
859   if (T.isNull())
860     return true;
861 
862   if (T->isInstantiationDependentType() || T->isVariablyModifiedType())
863     return false;
864 
865   getSema().MarkDeclarationsReferencedInType(Loc, T);
866   return true;
867 }
868 
869 static TemplateArgument
870 getPackSubstitutedTemplateArgument(Sema &S, TemplateArgument Arg) {
871   assert(S.ArgumentPackSubstitutionIndex >= 0);
872   assert(S.ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
873   Arg = Arg.pack_begin()[S.ArgumentPackSubstitutionIndex];
874   if (Arg.isPackExpansion())
875     Arg = Arg.getPackExpansionPattern();
876   return Arg;
877 }
878 
879 Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
880   if (!D)
881     return nullptr;
882 
883   if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(D)) {
884     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
885       // If the corresponding template argument is NULL or non-existent, it's
886       // because we are performing instantiation from explicitly-specified
887       // template arguments in a function template, but there were some
888       // arguments left unspecified.
889       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
890                                             TTP->getPosition()))
891         return D;
892 
893       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
894 
895       if (TTP->isParameterPack()) {
896         assert(Arg.getKind() == TemplateArgument::Pack &&
897                "Missing argument pack");
898         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
899       }
900 
901       TemplateName Template = Arg.getAsTemplate();
902       assert(!Template.isNull() && Template.getAsTemplateDecl() &&
903              "Wrong kind of template template argument");
904       return Template.getAsTemplateDecl();
905     }
906 
907     // Fall through to find the instantiated declaration for this template
908     // template parameter.
909   }
910 
911   return SemaRef.FindInstantiatedDecl(Loc, cast<NamedDecl>(D), TemplateArgs);
912 }
913 
914 Decl *TemplateInstantiator::TransformDefinition(SourceLocation Loc, Decl *D) {
915   Decl *Inst = getSema().SubstDecl(D, getSema().CurContext, TemplateArgs);
916   if (!Inst)
917     return nullptr;
918 
919   getSema().CurrentInstantiationScope->InstantiatedLocal(D, Inst);
920   return Inst;
921 }
922 
923 NamedDecl *
924 TemplateInstantiator::TransformFirstQualifierInScope(NamedDecl *D,
925                                                      SourceLocation Loc) {
926   // If the first part of the nested-name-specifier was a template type
927   // parameter, instantiate that type parameter down to a tag type.
928   if (TemplateTypeParmDecl *TTPD = dyn_cast_or_null<TemplateTypeParmDecl>(D)) {
929     const TemplateTypeParmType *TTP
930       = cast<TemplateTypeParmType>(getSema().Context.getTypeDeclType(TTPD));
931 
932     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
933       // FIXME: This needs testing w/ member access expressions.
934       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getIndex());
935 
936       if (TTP->isParameterPack()) {
937         assert(Arg.getKind() == TemplateArgument::Pack &&
938                "Missing argument pack");
939 
940         if (getSema().ArgumentPackSubstitutionIndex == -1)
941           return nullptr;
942 
943         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
944       }
945 
946       QualType T = Arg.getAsType();
947       if (T.isNull())
948         return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
949 
950       if (const TagType *Tag = T->getAs<TagType>())
951         return Tag->getDecl();
952 
953       // The resulting type is not a tag; complain.
954       getSema().Diag(Loc, diag::err_nested_name_spec_non_tag) << T;
955       return nullptr;
956     }
957   }
958 
959   return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
960 }
961 
962 VarDecl *
963 TemplateInstantiator::RebuildExceptionDecl(VarDecl *ExceptionDecl,
964                                            TypeSourceInfo *Declarator,
965                                            SourceLocation StartLoc,
966                                            SourceLocation NameLoc,
967                                            IdentifierInfo *Name) {
968   VarDecl *Var = inherited::RebuildExceptionDecl(ExceptionDecl, Declarator,
969                                                  StartLoc, NameLoc, Name);
970   if (Var)
971     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
972   return Var;
973 }
974 
975 VarDecl *TemplateInstantiator::RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
976                                                         TypeSourceInfo *TSInfo,
977                                                         QualType T) {
978   VarDecl *Var = inherited::RebuildObjCExceptionDecl(ExceptionDecl, TSInfo, T);
979   if (Var)
980     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
981   return Var;
982 }
983 
984 QualType
985 TemplateInstantiator::RebuildElaboratedType(SourceLocation KeywordLoc,
986                                             ElaboratedTypeKeyword Keyword,
987                                             NestedNameSpecifierLoc QualifierLoc,
988                                             QualType T) {
989   if (const TagType *TT = T->getAs<TagType>()) {
990     TagDecl* TD = TT->getDecl();
991 
992     SourceLocation TagLocation = KeywordLoc;
993 
994     IdentifierInfo *Id = TD->getIdentifier();
995 
996     // TODO: should we even warn on struct/class mismatches for this?  Seems
997     // like it's likely to produce a lot of spurious errors.
998     if (Id && Keyword != ETK_None && Keyword != ETK_Typename) {
999       TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForKeyword(Keyword);
1000       if (!SemaRef.isAcceptableTagRedeclaration(TD, Kind, /*isDefinition*/false,
1001                                                 TagLocation, Id)) {
1002         SemaRef.Diag(TagLocation, diag::err_use_with_wrong_tag)
1003           << Id
1004           << FixItHint::CreateReplacement(SourceRange(TagLocation),
1005                                           TD->getKindName());
1006         SemaRef.Diag(TD->getLocation(), diag::note_previous_use);
1007       }
1008     }
1009   }
1010 
1011   return TreeTransform<TemplateInstantiator>::RebuildElaboratedType(KeywordLoc,
1012                                                                     Keyword,
1013                                                                   QualifierLoc,
1014                                                                     T);
1015 }
1016 
1017 TemplateName TemplateInstantiator::TransformTemplateName(CXXScopeSpec &SS,
1018                                                          TemplateName Name,
1019                                                          SourceLocation NameLoc,
1020                                                          QualType ObjectType,
1021                                              NamedDecl *FirstQualifierInScope) {
1022   if (TemplateTemplateParmDecl *TTP
1023        = dyn_cast_or_null<TemplateTemplateParmDecl>(Name.getAsTemplateDecl())) {
1024     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
1025       // If the corresponding template argument is NULL or non-existent, it's
1026       // because we are performing instantiation from explicitly-specified
1027       // template arguments in a function template, but there were some
1028       // arguments left unspecified.
1029       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
1030                                             TTP->getPosition()))
1031         return Name;
1032 
1033       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
1034 
1035       if (TTP->isParameterPack()) {
1036         assert(Arg.getKind() == TemplateArgument::Pack &&
1037                "Missing argument pack");
1038 
1039         if (getSema().ArgumentPackSubstitutionIndex == -1) {
1040           // We have the template argument pack to substitute, but we're not
1041           // actually expanding the enclosing pack expansion yet. So, just
1042           // keep the entire argument pack.
1043           return getSema().Context.getSubstTemplateTemplateParmPack(TTP, Arg);
1044         }
1045 
1046         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1047       }
1048 
1049       TemplateName Template = Arg.getAsTemplate();
1050       assert(!Template.isNull() && "Null template template argument");
1051 
1052       // We don't ever want to substitute for a qualified template name, since
1053       // the qualifier is handled separately. So, look through the qualified
1054       // template name to its underlying declaration.
1055       if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
1056         Template = TemplateName(QTN->getTemplateDecl());
1057 
1058       Template = getSema().Context.getSubstTemplateTemplateParm(TTP, Template);
1059       return Template;
1060     }
1061   }
1062 
1063   if (SubstTemplateTemplateParmPackStorage *SubstPack
1064       = Name.getAsSubstTemplateTemplateParmPack()) {
1065     if (getSema().ArgumentPackSubstitutionIndex == -1)
1066       return Name;
1067 
1068     TemplateArgument Arg = SubstPack->getArgumentPack();
1069     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1070     return Arg.getAsTemplate();
1071   }
1072 
1073   return inherited::TransformTemplateName(SS, Name, NameLoc, ObjectType,
1074                                           FirstQualifierInScope);
1075 }
1076 
1077 ExprResult
1078 TemplateInstantiator::TransformPredefinedExpr(PredefinedExpr *E) {
1079   if (!E->isTypeDependent())
1080     return E;
1081 
1082   return getSema().BuildPredefinedExpr(E->getLocation(), E->getIdentType());
1083 }
1084 
1085 ExprResult
1086 TemplateInstantiator::TransformTemplateParmRefExpr(DeclRefExpr *E,
1087                                                NonTypeTemplateParmDecl *NTTP) {
1088   // If the corresponding template argument is NULL or non-existent, it's
1089   // because we are performing instantiation from explicitly-specified
1090   // template arguments in a function template, but there were some
1091   // arguments left unspecified.
1092   if (!TemplateArgs.hasTemplateArgument(NTTP->getDepth(),
1093                                         NTTP->getPosition()))
1094     return E;
1095 
1096   TemplateArgument Arg = TemplateArgs(NTTP->getDepth(), NTTP->getPosition());
1097   if (NTTP->isParameterPack()) {
1098     assert(Arg.getKind() == TemplateArgument::Pack &&
1099            "Missing argument pack");
1100 
1101     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1102       // We have an argument pack, but we can't select a particular argument
1103       // out of it yet. Therefore, we'll build an expression to hold on to that
1104       // argument pack.
1105       QualType TargetType = SemaRef.SubstType(NTTP->getType(), TemplateArgs,
1106                                               E->getLocation(),
1107                                               NTTP->getDeclName());
1108       if (TargetType.isNull())
1109         return ExprError();
1110 
1111       return new (SemaRef.Context) SubstNonTypeTemplateParmPackExpr(TargetType,
1112                                                                     NTTP,
1113                                                               E->getLocation(),
1114                                                                     Arg);
1115     }
1116 
1117     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1118   }
1119 
1120   return transformNonTypeTemplateParmRef(NTTP, E->getLocation(), Arg);
1121 }
1122 
1123 const LoopHintAttr *
1124 TemplateInstantiator::TransformLoopHintAttr(const LoopHintAttr *LH) {
1125   Expr *TransformedExpr = getDerived().TransformExpr(LH->getValue()).get();
1126 
1127   if (TransformedExpr == LH->getValue())
1128     return LH;
1129 
1130   // Generate error if there is a problem with the value.
1131   if (getSema().CheckLoopHintExpr(TransformedExpr, LH->getLocation()))
1132     return LH;
1133 
1134   // Create new LoopHintValueAttr with integral expression in place of the
1135   // non-type template parameter.
1136   return LoopHintAttr::CreateImplicit(
1137       getSema().Context, LH->getSemanticSpelling(), LH->getOption(),
1138       LH->getState(), TransformedExpr, LH->getRange());
1139 }
1140 
1141 ExprResult TemplateInstantiator::transformNonTypeTemplateParmRef(
1142                                                  NonTypeTemplateParmDecl *parm,
1143                                                  SourceLocation loc,
1144                                                  TemplateArgument arg) {
1145   ExprResult result;
1146   QualType type;
1147 
1148   // The template argument itself might be an expression, in which
1149   // case we just return that expression.
1150   if (arg.getKind() == TemplateArgument::Expression) {
1151     Expr *argExpr = arg.getAsExpr();
1152     result = argExpr;
1153     type = argExpr->getType();
1154 
1155   } else if (arg.getKind() == TemplateArgument::Declaration ||
1156              arg.getKind() == TemplateArgument::NullPtr) {
1157     ValueDecl *VD;
1158     if (arg.getKind() == TemplateArgument::Declaration) {
1159       VD = cast<ValueDecl>(arg.getAsDecl());
1160 
1161       // Find the instantiation of the template argument.  This is
1162       // required for nested templates.
1163       VD = cast_or_null<ValueDecl>(
1164              getSema().FindInstantiatedDecl(loc, VD, TemplateArgs));
1165       if (!VD)
1166         return ExprError();
1167     } else {
1168       // Propagate NULL template argument.
1169       VD = nullptr;
1170     }
1171 
1172     // Derive the type we want the substituted decl to have.  This had
1173     // better be non-dependent, or these checks will have serious problems.
1174     if (parm->isExpandedParameterPack()) {
1175       type = parm->getExpansionType(SemaRef.ArgumentPackSubstitutionIndex);
1176     } else if (parm->isParameterPack() &&
1177                isa<PackExpansionType>(parm->getType())) {
1178       type = SemaRef.SubstType(
1179                         cast<PackExpansionType>(parm->getType())->getPattern(),
1180                                      TemplateArgs, loc, parm->getDeclName());
1181     } else {
1182       type = SemaRef.SubstType(parm->getType(), TemplateArgs,
1183                                loc, parm->getDeclName());
1184     }
1185     assert(!type.isNull() && "type substitution failed for param type");
1186     assert(!type->isDependentType() && "param type still dependent");
1187     result = SemaRef.BuildExpressionFromDeclTemplateArgument(arg, type, loc);
1188 
1189     if (!result.isInvalid()) type = result.get()->getType();
1190   } else {
1191     result = SemaRef.BuildExpressionFromIntegralTemplateArgument(arg, loc);
1192 
1193     // Note that this type can be different from the type of 'result',
1194     // e.g. if it's an enum type.
1195     type = arg.getIntegralType();
1196   }
1197   if (result.isInvalid()) return ExprError();
1198 
1199   Expr *resultExpr = result.get();
1200   return new (SemaRef.Context) SubstNonTypeTemplateParmExpr(
1201       type, resultExpr->getValueKind(), loc, parm, resultExpr);
1202 }
1203 
1204 ExprResult
1205 TemplateInstantiator::TransformSubstNonTypeTemplateParmPackExpr(
1206                                           SubstNonTypeTemplateParmPackExpr *E) {
1207   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1208     // We aren't expanding the parameter pack, so just return ourselves.
1209     return E;
1210   }
1211 
1212   TemplateArgument Arg = E->getArgumentPack();
1213   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1214   return transformNonTypeTemplateParmRef(E->getParameterPack(),
1215                                          E->getParameterPackLocation(),
1216                                          Arg);
1217 }
1218 
1219 ExprResult
1220 TemplateInstantiator::RebuildParmVarDeclRefExpr(ParmVarDecl *PD,
1221                                                 SourceLocation Loc) {
1222   DeclarationNameInfo NameInfo(PD->getDeclName(), Loc);
1223   return getSema().BuildDeclarationNameExpr(CXXScopeSpec(), NameInfo, PD);
1224 }
1225 
1226 ExprResult
1227 TemplateInstantiator::TransformFunctionParmPackExpr(FunctionParmPackExpr *E) {
1228   if (getSema().ArgumentPackSubstitutionIndex != -1) {
1229     // We can expand this parameter pack now.
1230     ParmVarDecl *D = E->getExpansion(getSema().ArgumentPackSubstitutionIndex);
1231     ValueDecl *VD = cast_or_null<ValueDecl>(TransformDecl(E->getExprLoc(), D));
1232     if (!VD)
1233       return ExprError();
1234     return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(VD), E->getExprLoc());
1235   }
1236 
1237   QualType T = TransformType(E->getType());
1238   if (T.isNull())
1239     return ExprError();
1240 
1241   // Transform each of the parameter expansions into the corresponding
1242   // parameters in the instantiation of the function decl.
1243   SmallVector<ParmVarDecl *, 8> Parms;
1244   Parms.reserve(E->getNumExpansions());
1245   for (FunctionParmPackExpr::iterator I = E->begin(), End = E->end();
1246        I != End; ++I) {
1247     ParmVarDecl *D =
1248         cast_or_null<ParmVarDecl>(TransformDecl(E->getExprLoc(), *I));
1249     if (!D)
1250       return ExprError();
1251     Parms.push_back(D);
1252   }
1253 
1254   return FunctionParmPackExpr::Create(getSema().Context, T,
1255                                       E->getParameterPack(),
1256                                       E->getParameterPackLocation(), Parms);
1257 }
1258 
1259 ExprResult
1260 TemplateInstantiator::TransformFunctionParmPackRefExpr(DeclRefExpr *E,
1261                                                        ParmVarDecl *PD) {
1262   typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
1263   llvm::PointerUnion<Decl *, DeclArgumentPack *> *Found
1264     = getSema().CurrentInstantiationScope->findInstantiationOf(PD);
1265   assert(Found && "no instantiation for parameter pack");
1266 
1267   Decl *TransformedDecl;
1268   if (DeclArgumentPack *Pack = Found->dyn_cast<DeclArgumentPack *>()) {
1269     // If this is a reference to a function parameter pack which we can
1270     // substitute but can't yet expand, build a FunctionParmPackExpr for it.
1271     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1272       QualType T = TransformType(E->getType());
1273       if (T.isNull())
1274         return ExprError();
1275       return FunctionParmPackExpr::Create(getSema().Context, T, PD,
1276                                           E->getExprLoc(), *Pack);
1277     }
1278 
1279     TransformedDecl = (*Pack)[getSema().ArgumentPackSubstitutionIndex];
1280   } else {
1281     TransformedDecl = Found->get<Decl*>();
1282   }
1283 
1284   // We have either an unexpanded pack or a specific expansion.
1285   return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(TransformedDecl),
1286                                    E->getExprLoc());
1287 }
1288 
1289 ExprResult
1290 TemplateInstantiator::TransformDeclRefExpr(DeclRefExpr *E) {
1291   NamedDecl *D = E->getDecl();
1292 
1293   // Handle references to non-type template parameters and non-type template
1294   // parameter packs.
1295   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D)) {
1296     if (NTTP->getDepth() < TemplateArgs.getNumLevels())
1297       return TransformTemplateParmRefExpr(E, NTTP);
1298 
1299     // We have a non-type template parameter that isn't fully substituted;
1300     // FindInstantiatedDecl will find it in the local instantiation scope.
1301   }
1302 
1303   // Handle references to function parameter packs.
1304   if (ParmVarDecl *PD = dyn_cast<ParmVarDecl>(D))
1305     if (PD->isParameterPack())
1306       return TransformFunctionParmPackRefExpr(E, PD);
1307 
1308   return TreeTransform<TemplateInstantiator>::TransformDeclRefExpr(E);
1309 }
1310 
1311 ExprResult TemplateInstantiator::TransformCXXDefaultArgExpr(
1312     CXXDefaultArgExpr *E) {
1313   assert(!cast<FunctionDecl>(E->getParam()->getDeclContext())->
1314              getDescribedFunctionTemplate() &&
1315          "Default arg expressions are never formed in dependent cases.");
1316   return SemaRef.BuildCXXDefaultArgExpr(E->getUsedLocation(),
1317                            cast<FunctionDecl>(E->getParam()->getDeclContext()),
1318                                         E->getParam());
1319 }
1320 
1321 template<typename Fn>
1322 QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
1323                                  FunctionProtoTypeLoc TL,
1324                                  CXXRecordDecl *ThisContext,
1325                                  unsigned ThisTypeQuals,
1326                                  Fn TransformExceptionSpec) {
1327   // We need a local instantiation scope for this function prototype.
1328   LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
1329   return inherited::TransformFunctionProtoType(
1330       TLB, TL, ThisContext, ThisTypeQuals, TransformExceptionSpec);
1331 }
1332 
1333 ParmVarDecl *
1334 TemplateInstantiator::TransformFunctionTypeParam(ParmVarDecl *OldParm,
1335                                                  int indexAdjustment,
1336                                                Optional<unsigned> NumExpansions,
1337                                                  bool ExpectParameterPack) {
1338   return SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
1339                                   NumExpansions, ExpectParameterPack);
1340 }
1341 
1342 QualType
1343 TemplateInstantiator::TransformTemplateTypeParmType(TypeLocBuilder &TLB,
1344                                                 TemplateTypeParmTypeLoc TL) {
1345   const TemplateTypeParmType *T = TL.getTypePtr();
1346   if (T->getDepth() < TemplateArgs.getNumLevels()) {
1347     // Replace the template type parameter with its corresponding
1348     // template argument.
1349 
1350     // If the corresponding template argument is NULL or doesn't exist, it's
1351     // because we are performing instantiation from explicitly-specified
1352     // template arguments in a function template class, but there were some
1353     // arguments left unspecified.
1354     if (!TemplateArgs.hasTemplateArgument(T->getDepth(), T->getIndex())) {
1355       TemplateTypeParmTypeLoc NewTL
1356         = TLB.push<TemplateTypeParmTypeLoc>(TL.getType());
1357       NewTL.setNameLoc(TL.getNameLoc());
1358       return TL.getType();
1359     }
1360 
1361     TemplateArgument Arg = TemplateArgs(T->getDepth(), T->getIndex());
1362 
1363     if (T->isParameterPack()) {
1364       assert(Arg.getKind() == TemplateArgument::Pack &&
1365              "Missing argument pack");
1366 
1367       if (getSema().ArgumentPackSubstitutionIndex == -1) {
1368         // We have the template argument pack, but we're not expanding the
1369         // enclosing pack expansion yet. Just save the template argument
1370         // pack for later substitution.
1371         QualType Result
1372           = getSema().Context.getSubstTemplateTypeParmPackType(T, Arg);
1373         SubstTemplateTypeParmPackTypeLoc NewTL
1374           = TLB.push<SubstTemplateTypeParmPackTypeLoc>(Result);
1375         NewTL.setNameLoc(TL.getNameLoc());
1376         return Result;
1377       }
1378 
1379       Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1380     }
1381 
1382     assert(Arg.getKind() == TemplateArgument::Type &&
1383            "Template argument kind mismatch");
1384 
1385     QualType Replacement = Arg.getAsType();
1386 
1387     // TODO: only do this uniquing once, at the start of instantiation.
1388     QualType Result
1389       = getSema().Context.getSubstTemplateTypeParmType(T, Replacement);
1390     SubstTemplateTypeParmTypeLoc NewTL
1391       = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1392     NewTL.setNameLoc(TL.getNameLoc());
1393     return Result;
1394   }
1395 
1396   // The template type parameter comes from an inner template (e.g.,
1397   // the template parameter list of a member template inside the
1398   // template we are instantiating). Create a new template type
1399   // parameter with the template "level" reduced by one.
1400   TemplateTypeParmDecl *NewTTPDecl = nullptr;
1401   if (TemplateTypeParmDecl *OldTTPDecl = T->getDecl())
1402     NewTTPDecl = cast_or_null<TemplateTypeParmDecl>(
1403                                   TransformDecl(TL.getNameLoc(), OldTTPDecl));
1404 
1405   QualType Result
1406     = getSema().Context.getTemplateTypeParmType(T->getDepth()
1407                                                  - TemplateArgs.getNumLevels(),
1408                                                 T->getIndex(),
1409                                                 T->isParameterPack(),
1410                                                 NewTTPDecl);
1411   TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
1412   NewTL.setNameLoc(TL.getNameLoc());
1413   return Result;
1414 }
1415 
1416 QualType
1417 TemplateInstantiator::TransformSubstTemplateTypeParmPackType(
1418                                                             TypeLocBuilder &TLB,
1419                                          SubstTemplateTypeParmPackTypeLoc TL) {
1420   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1421     // We aren't expanding the parameter pack, so just return ourselves.
1422     SubstTemplateTypeParmPackTypeLoc NewTL
1423       = TLB.push<SubstTemplateTypeParmPackTypeLoc>(TL.getType());
1424     NewTL.setNameLoc(TL.getNameLoc());
1425     return TL.getType();
1426   }
1427 
1428   TemplateArgument Arg = TL.getTypePtr()->getArgumentPack();
1429   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1430   QualType Result = Arg.getAsType();
1431 
1432   Result = getSema().Context.getSubstTemplateTypeParmType(
1433                                       TL.getTypePtr()->getReplacedParameter(),
1434                                                           Result);
1435   SubstTemplateTypeParmTypeLoc NewTL
1436     = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1437   NewTL.setNameLoc(TL.getNameLoc());
1438   return Result;
1439 }
1440 
1441 /// \brief Perform substitution on the type T with a given set of template
1442 /// arguments.
1443 ///
1444 /// This routine substitutes the given template arguments into the
1445 /// type T and produces the instantiated type.
1446 ///
1447 /// \param T the type into which the template arguments will be
1448 /// substituted. If this type is not dependent, it will be returned
1449 /// immediately.
1450 ///
1451 /// \param Args the template arguments that will be
1452 /// substituted for the top-level template parameters within T.
1453 ///
1454 /// \param Loc the location in the source code where this substitution
1455 /// is being performed. It will typically be the location of the
1456 /// declarator (if we're instantiating the type of some declaration)
1457 /// or the location of the type in the source code (if, e.g., we're
1458 /// instantiating the type of a cast expression).
1459 ///
1460 /// \param Entity the name of the entity associated with a declaration
1461 /// being instantiated (if any). May be empty to indicate that there
1462 /// is no such entity (if, e.g., this is a type that occurs as part of
1463 /// a cast expression) or that the entity has no name (e.g., an
1464 /// unnamed function parameter).
1465 ///
1466 /// \returns If the instantiation succeeds, the instantiated
1467 /// type. Otherwise, produces diagnostics and returns a NULL type.
1468 TypeSourceInfo *Sema::SubstType(TypeSourceInfo *T,
1469                                 const MultiLevelTemplateArgumentList &Args,
1470                                 SourceLocation Loc,
1471                                 DeclarationName Entity) {
1472   assert(!ActiveTemplateInstantiations.empty() &&
1473          "Cannot perform an instantiation without some context on the "
1474          "instantiation stack");
1475 
1476   if (!T->getType()->isInstantiationDependentType() &&
1477       !T->getType()->isVariablyModifiedType())
1478     return T;
1479 
1480   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1481   return Instantiator.TransformType(T);
1482 }
1483 
1484 TypeSourceInfo *Sema::SubstType(TypeLoc TL,
1485                                 const MultiLevelTemplateArgumentList &Args,
1486                                 SourceLocation Loc,
1487                                 DeclarationName Entity) {
1488   assert(!ActiveTemplateInstantiations.empty() &&
1489          "Cannot perform an instantiation without some context on the "
1490          "instantiation stack");
1491 
1492   if (TL.getType().isNull())
1493     return nullptr;
1494 
1495   if (!TL.getType()->isInstantiationDependentType() &&
1496       !TL.getType()->isVariablyModifiedType()) {
1497     // FIXME: Make a copy of the TypeLoc data here, so that we can
1498     // return a new TypeSourceInfo. Inefficient!
1499     TypeLocBuilder TLB;
1500     TLB.pushFullCopy(TL);
1501     return TLB.getTypeSourceInfo(Context, TL.getType());
1502   }
1503 
1504   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1505   TypeLocBuilder TLB;
1506   TLB.reserve(TL.getFullDataSize());
1507   QualType Result = Instantiator.TransformType(TLB, TL);
1508   if (Result.isNull())
1509     return nullptr;
1510 
1511   return TLB.getTypeSourceInfo(Context, Result);
1512 }
1513 
1514 /// Deprecated form of the above.
1515 QualType Sema::SubstType(QualType T,
1516                          const MultiLevelTemplateArgumentList &TemplateArgs,
1517                          SourceLocation Loc, DeclarationName Entity) {
1518   assert(!ActiveTemplateInstantiations.empty() &&
1519          "Cannot perform an instantiation without some context on the "
1520          "instantiation stack");
1521 
1522   // If T is not a dependent type or a variably-modified type, there
1523   // is nothing to do.
1524   if (!T->isInstantiationDependentType() && !T->isVariablyModifiedType())
1525     return T;
1526 
1527   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc, Entity);
1528   return Instantiator.TransformType(T);
1529 }
1530 
1531 static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
1532   if (T->getType()->isInstantiationDependentType() ||
1533       T->getType()->isVariablyModifiedType())
1534     return true;
1535 
1536   TypeLoc TL = T->getTypeLoc().IgnoreParens();
1537   if (!TL.getAs<FunctionProtoTypeLoc>())
1538     return false;
1539 
1540   FunctionProtoTypeLoc FP = TL.castAs<FunctionProtoTypeLoc>();
1541   for (ParmVarDecl *P : FP.getParams()) {
1542     // This must be synthesized from a typedef.
1543     if (!P) continue;
1544 
1545     // If there are any parameters, a new TypeSourceInfo that refers to the
1546     // instantiated parameters must be built.
1547     return true;
1548   }
1549 
1550   return false;
1551 }
1552 
1553 /// A form of SubstType intended specifically for instantiating the
1554 /// type of a FunctionDecl.  Its purpose is solely to force the
1555 /// instantiation of default-argument expressions and to avoid
1556 /// instantiating an exception-specification.
1557 TypeSourceInfo *Sema::SubstFunctionDeclType(TypeSourceInfo *T,
1558                                 const MultiLevelTemplateArgumentList &Args,
1559                                 SourceLocation Loc,
1560                                 DeclarationName Entity,
1561                                 CXXRecordDecl *ThisContext,
1562                                 unsigned ThisTypeQuals) {
1563   assert(!ActiveTemplateInstantiations.empty() &&
1564          "Cannot perform an instantiation without some context on the "
1565          "instantiation stack");
1566 
1567   if (!NeedsInstantiationAsFunctionType(T))
1568     return T;
1569 
1570   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1571 
1572   TypeLocBuilder TLB;
1573 
1574   TypeLoc TL = T->getTypeLoc();
1575   TLB.reserve(TL.getFullDataSize());
1576 
1577   QualType Result;
1578 
1579   if (FunctionProtoTypeLoc Proto =
1580           TL.IgnoreParens().getAs<FunctionProtoTypeLoc>()) {
1581     // Instantiate the type, other than its exception specification. The
1582     // exception specification is instantiated in InitFunctionInstantiation
1583     // once we've built the FunctionDecl.
1584     // FIXME: Set the exception specification to EST_Uninstantiated here,
1585     // instead of rebuilding the function type again later.
1586     Result = Instantiator.TransformFunctionProtoType(
1587         TLB, Proto, ThisContext, ThisTypeQuals,
1588         [](FunctionProtoType::ExceptionSpecInfo &ESI,
1589            bool &Changed) { return false; });
1590   } else {
1591     Result = Instantiator.TransformType(TLB, TL);
1592   }
1593   if (Result.isNull())
1594     return nullptr;
1595 
1596   return TLB.getTypeSourceInfo(Context, Result);
1597 }
1598 
1599 void Sema::SubstExceptionSpec(FunctionDecl *New, const FunctionProtoType *Proto,
1600                               const MultiLevelTemplateArgumentList &Args) {
1601   FunctionProtoType::ExceptionSpecInfo ESI =
1602       Proto->getExtProtoInfo().ExceptionSpec;
1603   assert(ESI.Type != EST_Uninstantiated);
1604 
1605   TemplateInstantiator Instantiator(*this, Args, New->getLocation(),
1606                                     New->getDeclName());
1607 
1608   SmallVector<QualType, 4> ExceptionStorage;
1609   bool Changed = false;
1610   if (Instantiator.TransformExceptionSpec(
1611           New->getTypeSourceInfo()->getTypeLoc().getLocEnd(), ESI,
1612           ExceptionStorage, Changed))
1613     // On error, recover by dropping the exception specification.
1614     ESI.Type = EST_None;
1615 
1616   UpdateExceptionSpec(New, ESI);
1617 }
1618 
1619 ParmVarDecl *Sema::SubstParmVarDecl(ParmVarDecl *OldParm,
1620                             const MultiLevelTemplateArgumentList &TemplateArgs,
1621                                     int indexAdjustment,
1622                                     Optional<unsigned> NumExpansions,
1623                                     bool ExpectParameterPack) {
1624   TypeSourceInfo *OldDI = OldParm->getTypeSourceInfo();
1625   TypeSourceInfo *NewDI = nullptr;
1626 
1627   TypeLoc OldTL = OldDI->getTypeLoc();
1628   if (PackExpansionTypeLoc ExpansionTL = OldTL.getAs<PackExpansionTypeLoc>()) {
1629 
1630     // We have a function parameter pack. Substitute into the pattern of the
1631     // expansion.
1632     NewDI = SubstType(ExpansionTL.getPatternLoc(), TemplateArgs,
1633                       OldParm->getLocation(), OldParm->getDeclName());
1634     if (!NewDI)
1635       return nullptr;
1636 
1637     if (NewDI->getType()->containsUnexpandedParameterPack()) {
1638       // We still have unexpanded parameter packs, which means that
1639       // our function parameter is still a function parameter pack.
1640       // Therefore, make its type a pack expansion type.
1641       NewDI = CheckPackExpansion(NewDI, ExpansionTL.getEllipsisLoc(),
1642                                  NumExpansions);
1643     } else if (ExpectParameterPack) {
1644       // We expected to get a parameter pack but didn't (because the type
1645       // itself is not a pack expansion type), so complain. This can occur when
1646       // the substitution goes through an alias template that "loses" the
1647       // pack expansion.
1648       Diag(OldParm->getLocation(),
1649            diag::err_function_parameter_pack_without_parameter_packs)
1650         << NewDI->getType();
1651       return nullptr;
1652     }
1653   } else {
1654     NewDI = SubstType(OldDI, TemplateArgs, OldParm->getLocation(),
1655                       OldParm->getDeclName());
1656   }
1657 
1658   if (!NewDI)
1659     return nullptr;
1660 
1661   if (NewDI->getType()->isVoidType()) {
1662     Diag(OldParm->getLocation(), diag::err_param_with_void_type);
1663     return nullptr;
1664   }
1665 
1666   ParmVarDecl *NewParm = CheckParameter(Context.getTranslationUnitDecl(),
1667                                         OldParm->getInnerLocStart(),
1668                                         OldParm->getLocation(),
1669                                         OldParm->getIdentifier(),
1670                                         NewDI->getType(), NewDI,
1671                                         OldParm->getStorageClass());
1672   if (!NewParm)
1673     return nullptr;
1674 
1675   // Mark the (new) default argument as uninstantiated (if any).
1676   if (OldParm->hasUninstantiatedDefaultArg()) {
1677     Expr *Arg = OldParm->getUninstantiatedDefaultArg();
1678     NewParm->setUninstantiatedDefaultArg(Arg);
1679   } else if (OldParm->hasUnparsedDefaultArg()) {
1680     NewParm->setUnparsedDefaultArg();
1681     UnparsedDefaultArgInstantiations[OldParm].push_back(NewParm);
1682   } else if (Expr *Arg = OldParm->getDefaultArg()) {
1683     FunctionDecl *OwningFunc = cast<FunctionDecl>(OldParm->getDeclContext());
1684     if (OwningFunc->isLexicallyWithinFunctionOrMethod()) {
1685       // Instantiate default arguments for methods of local classes (DR1484)
1686       // and non-defining declarations.
1687       Sema::ContextRAII SavedContext(*this, OwningFunc);
1688       LocalInstantiationScope Local(*this);
1689       ExprResult NewArg = SubstExpr(Arg, TemplateArgs);
1690       if (NewArg.isUsable()) {
1691         // It would be nice if we still had this.
1692         SourceLocation EqualLoc = NewArg.get()->getLocStart();
1693         SetParamDefaultArgument(NewParm, NewArg.get(), EqualLoc);
1694       }
1695     } else {
1696       // FIXME: if we non-lazily instantiated non-dependent default args for
1697       // non-dependent parameter types we could remove a bunch of duplicate
1698       // conversion warnings for such arguments.
1699       NewParm->setUninstantiatedDefaultArg(Arg);
1700     }
1701   }
1702 
1703   NewParm->setHasInheritedDefaultArg(OldParm->hasInheritedDefaultArg());
1704 
1705   if (OldParm->isParameterPack() && !NewParm->isParameterPack()) {
1706     // Add the new parameter to the instantiated parameter pack.
1707     CurrentInstantiationScope->InstantiatedLocalPackArg(OldParm, NewParm);
1708   } else {
1709     // Introduce an Old -> New mapping
1710     CurrentInstantiationScope->InstantiatedLocal(OldParm, NewParm);
1711   }
1712 
1713   // FIXME: OldParm may come from a FunctionProtoType, in which case CurContext
1714   // can be anything, is this right ?
1715   NewParm->setDeclContext(CurContext);
1716 
1717   NewParm->setScopeInfo(OldParm->getFunctionScopeDepth(),
1718                         OldParm->getFunctionScopeIndex() + indexAdjustment);
1719 
1720   InstantiateAttrs(TemplateArgs, OldParm, NewParm);
1721 
1722   return NewParm;
1723 }
1724 
1725 /// \brief Substitute the given template arguments into the given set of
1726 /// parameters, producing the set of parameter types that would be generated
1727 /// from such a substitution.
1728 bool Sema::SubstParmTypes(
1729     SourceLocation Loc, ArrayRef<ParmVarDecl *> Params,
1730     const FunctionProtoType::ExtParameterInfo *ExtParamInfos,
1731     const MultiLevelTemplateArgumentList &TemplateArgs,
1732     SmallVectorImpl<QualType> &ParamTypes,
1733     SmallVectorImpl<ParmVarDecl *> *OutParams,
1734     ExtParameterInfoBuilder &ParamInfos) {
1735   assert(!ActiveTemplateInstantiations.empty() &&
1736          "Cannot perform an instantiation without some context on the "
1737          "instantiation stack");
1738 
1739   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
1740                                     DeclarationName());
1741   return Instantiator.TransformFunctionTypeParams(
1742       Loc, Params, nullptr, ExtParamInfos, ParamTypes, OutParams, ParamInfos);
1743 }
1744 
1745 /// \brief Perform substitution on the base class specifiers of the
1746 /// given class template specialization.
1747 ///
1748 /// Produces a diagnostic and returns true on error, returns false and
1749 /// attaches the instantiated base classes to the class template
1750 /// specialization if successful.
1751 bool
1752 Sema::SubstBaseSpecifiers(CXXRecordDecl *Instantiation,
1753                           CXXRecordDecl *Pattern,
1754                           const MultiLevelTemplateArgumentList &TemplateArgs) {
1755   bool Invalid = false;
1756   SmallVector<CXXBaseSpecifier*, 4> InstantiatedBases;
1757   for (const auto &Base : Pattern->bases()) {
1758     if (!Base.getType()->isDependentType()) {
1759       if (const CXXRecordDecl *RD = Base.getType()->getAsCXXRecordDecl()) {
1760         if (RD->isInvalidDecl())
1761           Instantiation->setInvalidDecl();
1762       }
1763       InstantiatedBases.push_back(new (Context) CXXBaseSpecifier(Base));
1764       continue;
1765     }
1766 
1767     SourceLocation EllipsisLoc;
1768     TypeSourceInfo *BaseTypeLoc;
1769     if (Base.isPackExpansion()) {
1770       // This is a pack expansion. See whether we should expand it now, or
1771       // wait until later.
1772       SmallVector<UnexpandedParameterPack, 2> Unexpanded;
1773       collectUnexpandedParameterPacks(Base.getTypeSourceInfo()->getTypeLoc(),
1774                                       Unexpanded);
1775       bool ShouldExpand = false;
1776       bool RetainExpansion = false;
1777       Optional<unsigned> NumExpansions;
1778       if (CheckParameterPacksForExpansion(Base.getEllipsisLoc(),
1779                                           Base.getSourceRange(),
1780                                           Unexpanded,
1781                                           TemplateArgs, ShouldExpand,
1782                                           RetainExpansion,
1783                                           NumExpansions)) {
1784         Invalid = true;
1785         continue;
1786       }
1787 
1788       // If we should expand this pack expansion now, do so.
1789       if (ShouldExpand) {
1790         for (unsigned I = 0; I != *NumExpansions; ++I) {
1791             Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, I);
1792 
1793           TypeSourceInfo *BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
1794                                                   TemplateArgs,
1795                                               Base.getSourceRange().getBegin(),
1796                                                   DeclarationName());
1797           if (!BaseTypeLoc) {
1798             Invalid = true;
1799             continue;
1800           }
1801 
1802           if (CXXBaseSpecifier *InstantiatedBase
1803                 = CheckBaseSpecifier(Instantiation,
1804                                      Base.getSourceRange(),
1805                                      Base.isVirtual(),
1806                                      Base.getAccessSpecifierAsWritten(),
1807                                      BaseTypeLoc,
1808                                      SourceLocation()))
1809             InstantiatedBases.push_back(InstantiatedBase);
1810           else
1811             Invalid = true;
1812         }
1813 
1814         continue;
1815       }
1816 
1817       // The resulting base specifier will (still) be a pack expansion.
1818       EllipsisLoc = Base.getEllipsisLoc();
1819       Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
1820       BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
1821                               TemplateArgs,
1822                               Base.getSourceRange().getBegin(),
1823                               DeclarationName());
1824     } else {
1825       BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
1826                               TemplateArgs,
1827                               Base.getSourceRange().getBegin(),
1828                               DeclarationName());
1829     }
1830 
1831     if (!BaseTypeLoc) {
1832       Invalid = true;
1833       continue;
1834     }
1835 
1836     if (CXXBaseSpecifier *InstantiatedBase
1837           = CheckBaseSpecifier(Instantiation,
1838                                Base.getSourceRange(),
1839                                Base.isVirtual(),
1840                                Base.getAccessSpecifierAsWritten(),
1841                                BaseTypeLoc,
1842                                EllipsisLoc))
1843       InstantiatedBases.push_back(InstantiatedBase);
1844     else
1845       Invalid = true;
1846   }
1847 
1848   if (!Invalid && AttachBaseSpecifiers(Instantiation, InstantiatedBases))
1849     Invalid = true;
1850 
1851   return Invalid;
1852 }
1853 
1854 // Defined via #include from SemaTemplateInstantiateDecl.cpp
1855 namespace clang {
1856   namespace sema {
1857     Attr *instantiateTemplateAttribute(const Attr *At, ASTContext &C, Sema &S,
1858                             const MultiLevelTemplateArgumentList &TemplateArgs);
1859   }
1860 }
1861 
1862 /// \brief Instantiate the definition of a class from a given pattern.
1863 ///
1864 /// \param PointOfInstantiation The point of instantiation within the
1865 /// source code.
1866 ///
1867 /// \param Instantiation is the declaration whose definition is being
1868 /// instantiated. This will be either a class template specialization
1869 /// or a member class of a class template specialization.
1870 ///
1871 /// \param Pattern is the pattern from which the instantiation
1872 /// occurs. This will be either the declaration of a class template or
1873 /// the declaration of a member class of a class template.
1874 ///
1875 /// \param TemplateArgs The template arguments to be substituted into
1876 /// the pattern.
1877 ///
1878 /// \param TSK the kind of implicit or explicit instantiation to perform.
1879 ///
1880 /// \param Complain whether to complain if the class cannot be instantiated due
1881 /// to the lack of a definition.
1882 ///
1883 /// \returns true if an error occurred, false otherwise.
1884 bool
1885 Sema::InstantiateClass(SourceLocation PointOfInstantiation,
1886                        CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
1887                        const MultiLevelTemplateArgumentList &TemplateArgs,
1888                        TemplateSpecializationKind TSK,
1889                        bool Complain) {
1890   CXXRecordDecl *PatternDef
1891     = cast_or_null<CXXRecordDecl>(Pattern->getDefinition());
1892   if (DiagnoseUninstantiableTemplate(PointOfInstantiation, Instantiation,
1893                                 Instantiation->getInstantiatedFromMemberClass(),
1894                                      Pattern, PatternDef, TSK, Complain))
1895     return true;
1896   Pattern = PatternDef;
1897 
1898   // \brief Record the point of instantiation.
1899   if (MemberSpecializationInfo *MSInfo
1900         = Instantiation->getMemberSpecializationInfo()) {
1901     MSInfo->setTemplateSpecializationKind(TSK);
1902     MSInfo->setPointOfInstantiation(PointOfInstantiation);
1903   } else if (ClassTemplateSpecializationDecl *Spec
1904         = dyn_cast<ClassTemplateSpecializationDecl>(Instantiation)) {
1905     Spec->setTemplateSpecializationKind(TSK);
1906     Spec->setPointOfInstantiation(PointOfInstantiation);
1907   }
1908 
1909   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
1910   if (Inst.isInvalid())
1911     return true;
1912   assert(!Inst.isAlreadyInstantiating() && "should have been caught by caller");
1913   PrettyDeclStackTraceEntry CrashInfo(*this, Instantiation, SourceLocation(),
1914                                       "instantiating class definition");
1915 
1916   // Enter the scope of this instantiation. We don't use
1917   // PushDeclContext because we don't have a scope.
1918   ContextRAII SavedContext(*this, Instantiation);
1919   EnterExpressionEvaluationContext EvalContext(*this,
1920                                                Sema::PotentiallyEvaluated);
1921 
1922   // If this is an instantiation of a local class, merge this local
1923   // instantiation scope with the enclosing scope. Otherwise, every
1924   // instantiation of a class has its own local instantiation scope.
1925   bool MergeWithParentScope = !Instantiation->isDefinedOutsideFunctionOrMethod();
1926   LocalInstantiationScope Scope(*this, MergeWithParentScope);
1927 
1928   // All dllexported classes created during instantiation should be fully
1929   // emitted after instantiation completes. We may not be ready to emit any
1930   // delayed classes already on the stack, so save them away and put them back
1931   // later.
1932   decltype(DelayedDllExportClasses) ExportedClasses;
1933   std::swap(ExportedClasses, DelayedDllExportClasses);
1934 
1935   // Pull attributes from the pattern onto the instantiation.
1936   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
1937 
1938   // Start the definition of this instantiation.
1939   Instantiation->startDefinition();
1940 
1941   // The instantiation is visible here, even if it was first declared in an
1942   // unimported module.
1943   Instantiation->setHidden(false);
1944 
1945   // FIXME: This loses the as-written tag kind for an explicit instantiation.
1946   Instantiation->setTagKind(Pattern->getTagKind());
1947 
1948   // Do substitution on the base class specifiers.
1949   if (SubstBaseSpecifiers(Instantiation, Pattern, TemplateArgs))
1950     Instantiation->setInvalidDecl();
1951 
1952   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
1953   SmallVector<Decl*, 4> Fields;
1954   // Delay instantiation of late parsed attributes.
1955   LateInstantiatedAttrVec LateAttrs;
1956   Instantiator.enableLateAttributeInstantiation(&LateAttrs);
1957 
1958   for (auto *Member : Pattern->decls()) {
1959     // Don't instantiate members not belonging in this semantic context.
1960     // e.g. for:
1961     // @code
1962     //    template <int i> class A {
1963     //      class B *g;
1964     //    };
1965     // @endcode
1966     // 'class B' has the template as lexical context but semantically it is
1967     // introduced in namespace scope.
1968     if (Member->getDeclContext() != Pattern)
1969       continue;
1970 
1971     if (Member->isInvalidDecl()) {
1972       Instantiation->setInvalidDecl();
1973       continue;
1974     }
1975 
1976     Decl *NewMember = Instantiator.Visit(Member);
1977     if (NewMember) {
1978       if (FieldDecl *Field = dyn_cast<FieldDecl>(NewMember)) {
1979         Fields.push_back(Field);
1980       } else if (EnumDecl *Enum = dyn_cast<EnumDecl>(NewMember)) {
1981         // C++11 [temp.inst]p1: The implicit instantiation of a class template
1982         // specialization causes the implicit instantiation of the definitions
1983         // of unscoped member enumerations.
1984         // Record a point of instantiation for this implicit instantiation.
1985         if (TSK == TSK_ImplicitInstantiation && !Enum->isScoped() &&
1986             Enum->isCompleteDefinition()) {
1987           MemberSpecializationInfo *MSInfo =Enum->getMemberSpecializationInfo();
1988           assert(MSInfo && "no spec info for member enum specialization");
1989           MSInfo->setTemplateSpecializationKind(TSK_ImplicitInstantiation);
1990           MSInfo->setPointOfInstantiation(PointOfInstantiation);
1991         }
1992       } else if (StaticAssertDecl *SA = dyn_cast<StaticAssertDecl>(NewMember)) {
1993         if (SA->isFailed()) {
1994           // A static_assert failed. Bail out; instantiating this
1995           // class is probably not meaningful.
1996           Instantiation->setInvalidDecl();
1997           break;
1998         }
1999       }
2000 
2001       if (NewMember->isInvalidDecl())
2002         Instantiation->setInvalidDecl();
2003     } else {
2004       // FIXME: Eventually, a NULL return will mean that one of the
2005       // instantiations was a semantic disaster, and we'll want to mark the
2006       // declaration invalid.
2007       // For now, we expect to skip some members that we can't yet handle.
2008     }
2009   }
2010 
2011   // Finish checking fields.
2012   ActOnFields(nullptr, Instantiation->getLocation(), Instantiation, Fields,
2013               SourceLocation(), SourceLocation(), nullptr);
2014   CheckCompletedCXXClass(Instantiation);
2015 
2016   // Default arguments are parsed, if not instantiated. We can go instantiate
2017   // default arg exprs for default constructors if necessary now.
2018   ActOnFinishCXXNonNestedClass(Instantiation);
2019 
2020   // Put back the delayed exported classes that we moved out of the way.
2021   std::swap(ExportedClasses, DelayedDllExportClasses);
2022 
2023   // Instantiate late parsed attributes, and attach them to their decls.
2024   // See Sema::InstantiateAttrs
2025   for (LateInstantiatedAttrVec::iterator I = LateAttrs.begin(),
2026        E = LateAttrs.end(); I != E; ++I) {
2027     assert(CurrentInstantiationScope == Instantiator.getStartingScope());
2028     CurrentInstantiationScope = I->Scope;
2029 
2030     // Allow 'this' within late-parsed attributes.
2031     NamedDecl *ND = dyn_cast<NamedDecl>(I->NewDecl);
2032     CXXRecordDecl *ThisContext =
2033         dyn_cast_or_null<CXXRecordDecl>(ND->getDeclContext());
2034     CXXThisScopeRAII ThisScope(*this, ThisContext, /*TypeQuals*/0,
2035                                ND && ND->isCXXInstanceMember());
2036 
2037     Attr *NewAttr =
2038       instantiateTemplateAttribute(I->TmplAttr, Context, *this, TemplateArgs);
2039     I->NewDecl->addAttr(NewAttr);
2040     LocalInstantiationScope::deleteScopes(I->Scope,
2041                                           Instantiator.getStartingScope());
2042   }
2043   Instantiator.disableLateAttributeInstantiation();
2044   LateAttrs.clear();
2045 
2046   ActOnFinishDelayedMemberInitializers(Instantiation);
2047 
2048   // FIXME: We should do something similar for explicit instantiations so they
2049   // end up in the right module.
2050   if (TSK == TSK_ImplicitInstantiation) {
2051     Instantiation->setLocation(Pattern->getLocation());
2052     Instantiation->setLocStart(Pattern->getInnerLocStart());
2053     Instantiation->setBraceRange(Pattern->getBraceRange());
2054   }
2055 
2056   if (!Instantiation->isInvalidDecl()) {
2057     // Perform any dependent diagnostics from the pattern.
2058     PerformDependentDiagnostics(Pattern, TemplateArgs);
2059 
2060     // Instantiate any out-of-line class template partial
2061     // specializations now.
2062     for (TemplateDeclInstantiator::delayed_partial_spec_iterator
2063               P = Instantiator.delayed_partial_spec_begin(),
2064            PEnd = Instantiator.delayed_partial_spec_end();
2065          P != PEnd; ++P) {
2066       if (!Instantiator.InstantiateClassTemplatePartialSpecialization(
2067               P->first, P->second)) {
2068         Instantiation->setInvalidDecl();
2069         break;
2070       }
2071     }
2072 
2073     // Instantiate any out-of-line variable template partial
2074     // specializations now.
2075     for (TemplateDeclInstantiator::delayed_var_partial_spec_iterator
2076               P = Instantiator.delayed_var_partial_spec_begin(),
2077            PEnd = Instantiator.delayed_var_partial_spec_end();
2078          P != PEnd; ++P) {
2079       if (!Instantiator.InstantiateVarTemplatePartialSpecialization(
2080               P->first, P->second)) {
2081         Instantiation->setInvalidDecl();
2082         break;
2083       }
2084     }
2085   }
2086 
2087   // Exit the scope of this instantiation.
2088   SavedContext.pop();
2089 
2090   if (!Instantiation->isInvalidDecl()) {
2091     Consumer.HandleTagDeclDefinition(Instantiation);
2092 
2093     // Always emit the vtable for an explicit instantiation definition
2094     // of a polymorphic class template specialization.
2095     if (TSK == TSK_ExplicitInstantiationDefinition)
2096       MarkVTableUsed(PointOfInstantiation, Instantiation, true);
2097   }
2098 
2099   return Instantiation->isInvalidDecl();
2100 }
2101 
2102 /// \brief Instantiate the definition of an enum from a given pattern.
2103 ///
2104 /// \param PointOfInstantiation The point of instantiation within the
2105 ///        source code.
2106 /// \param Instantiation is the declaration whose definition is being
2107 ///        instantiated. This will be a member enumeration of a class
2108 ///        temploid specialization, or a local enumeration within a
2109 ///        function temploid specialization.
2110 /// \param Pattern The templated declaration from which the instantiation
2111 ///        occurs.
2112 /// \param TemplateArgs The template arguments to be substituted into
2113 ///        the pattern.
2114 /// \param TSK The kind of implicit or explicit instantiation to perform.
2115 ///
2116 /// \return \c true if an error occurred, \c false otherwise.
2117 bool Sema::InstantiateEnum(SourceLocation PointOfInstantiation,
2118                            EnumDecl *Instantiation, EnumDecl *Pattern,
2119                            const MultiLevelTemplateArgumentList &TemplateArgs,
2120                            TemplateSpecializationKind TSK) {
2121   EnumDecl *PatternDef = Pattern->getDefinition();
2122   if (DiagnoseUninstantiableTemplate(PointOfInstantiation, Instantiation,
2123                                  Instantiation->getInstantiatedFromMemberEnum(),
2124                                      Pattern, PatternDef, TSK,/*Complain*/true))
2125     return true;
2126   Pattern = PatternDef;
2127 
2128   // Record the point of instantiation.
2129   if (MemberSpecializationInfo *MSInfo
2130         = Instantiation->getMemberSpecializationInfo()) {
2131     MSInfo->setTemplateSpecializationKind(TSK);
2132     MSInfo->setPointOfInstantiation(PointOfInstantiation);
2133   }
2134 
2135   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2136   if (Inst.isInvalid())
2137     return true;
2138   if (Inst.isAlreadyInstantiating())
2139     return false;
2140   PrettyDeclStackTraceEntry CrashInfo(*this, Instantiation, SourceLocation(),
2141                                       "instantiating enum definition");
2142 
2143   // The instantiation is visible here, even if it was first declared in an
2144   // unimported module.
2145   Instantiation->setHidden(false);
2146 
2147   // Enter the scope of this instantiation. We don't use
2148   // PushDeclContext because we don't have a scope.
2149   ContextRAII SavedContext(*this, Instantiation);
2150   EnterExpressionEvaluationContext EvalContext(*this,
2151                                                Sema::PotentiallyEvaluated);
2152 
2153   LocalInstantiationScope Scope(*this, /*MergeWithParentScope*/true);
2154 
2155   // Pull attributes from the pattern onto the instantiation.
2156   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
2157 
2158   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
2159   Instantiator.InstantiateEnumDefinition(Instantiation, Pattern);
2160 
2161   // Exit the scope of this instantiation.
2162   SavedContext.pop();
2163 
2164   return Instantiation->isInvalidDecl();
2165 }
2166 
2167 
2168 /// \brief Instantiate the definition of a field from the given pattern.
2169 ///
2170 /// \param PointOfInstantiation The point of instantiation within the
2171 ///        source code.
2172 /// \param Instantiation is the declaration whose definition is being
2173 ///        instantiated. This will be a class of a class temploid
2174 ///        specialization, or a local enumeration within a function temploid
2175 ///        specialization.
2176 /// \param Pattern The templated declaration from which the instantiation
2177 ///        occurs.
2178 /// \param TemplateArgs The template arguments to be substituted into
2179 ///        the pattern.
2180 ///
2181 /// \return \c true if an error occurred, \c false otherwise.
2182 bool Sema::InstantiateInClassInitializer(
2183     SourceLocation PointOfInstantiation, FieldDecl *Instantiation,
2184     FieldDecl *Pattern, const MultiLevelTemplateArgumentList &TemplateArgs) {
2185   // If there is no initializer, we don't need to do anything.
2186   if (!Pattern->hasInClassInitializer())
2187     return false;
2188 
2189   assert(Instantiation->getInClassInitStyle() ==
2190              Pattern->getInClassInitStyle() &&
2191          "pattern and instantiation disagree about init style");
2192 
2193   // Error out if we haven't parsed the initializer of the pattern yet because
2194   // we are waiting for the closing brace of the outer class.
2195   Expr *OldInit = Pattern->getInClassInitializer();
2196   if (!OldInit) {
2197     RecordDecl *PatternRD = Pattern->getParent();
2198     RecordDecl *OutermostClass = PatternRD->getOuterLexicalRecordContext();
2199     if (OutermostClass == PatternRD) {
2200       Diag(Pattern->getLocEnd(), diag::err_in_class_initializer_not_yet_parsed)
2201           << PatternRD << Pattern;
2202     } else {
2203       Diag(Pattern->getLocEnd(),
2204            diag::err_in_class_initializer_not_yet_parsed_outer_class)
2205           << PatternRD << OutermostClass << Pattern;
2206     }
2207     Instantiation->setInvalidDecl();
2208     return true;
2209   }
2210 
2211   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2212   if (Inst.isInvalid())
2213     return true;
2214   if (Inst.isAlreadyInstantiating()) {
2215     // Error out if we hit an instantiation cycle for this initializer.
2216     Diag(PointOfInstantiation, diag::err_in_class_initializer_cycle)
2217       << Instantiation;
2218     return true;
2219   }
2220   PrettyDeclStackTraceEntry CrashInfo(*this, Instantiation, SourceLocation(),
2221                                       "instantiating default member init");
2222 
2223   // Enter the scope of this instantiation. We don't use PushDeclContext because
2224   // we don't have a scope.
2225   ContextRAII SavedContext(*this, Instantiation->getParent());
2226   EnterExpressionEvaluationContext EvalContext(*this,
2227                                                Sema::PotentiallyEvaluated);
2228 
2229   LocalInstantiationScope Scope(*this, true);
2230 
2231   // Instantiate the initializer.
2232   ActOnStartCXXInClassMemberInitializer();
2233   CXXThisScopeRAII ThisScope(*this, Instantiation->getParent(), /*TypeQuals=*/0);
2234 
2235   ExprResult NewInit = SubstInitializer(OldInit, TemplateArgs,
2236                                         /*CXXDirectInit=*/false);
2237   Expr *Init = NewInit.get();
2238   assert((!Init || !isa<ParenListExpr>(Init)) && "call-style init in class");
2239   ActOnFinishCXXInClassMemberInitializer(
2240       Instantiation, Init ? Init->getLocStart() : SourceLocation(), Init);
2241 
2242   if (auto *L = getASTMutationListener())
2243     L->DefaultMemberInitializerInstantiated(Instantiation);
2244 
2245   // Exit the scope of this instantiation.
2246   SavedContext.pop();
2247 
2248   // Return true if the in-class initializer is still missing.
2249   return !Instantiation->getInClassInitializer();
2250 }
2251 
2252 namespace {
2253   /// \brief A partial specialization whose template arguments have matched
2254   /// a given template-id.
2255   struct PartialSpecMatchResult {
2256     ClassTemplatePartialSpecializationDecl *Partial;
2257     TemplateArgumentList *Args;
2258   };
2259 }
2260 
2261 bool Sema::InstantiateClassTemplateSpecialization(
2262     SourceLocation PointOfInstantiation,
2263     ClassTemplateSpecializationDecl *ClassTemplateSpec,
2264     TemplateSpecializationKind TSK, bool Complain) {
2265   // Perform the actual instantiation on the canonical declaration.
2266   ClassTemplateSpec = cast<ClassTemplateSpecializationDecl>(
2267                                          ClassTemplateSpec->getCanonicalDecl());
2268   if (ClassTemplateSpec->isInvalidDecl())
2269     return true;
2270 
2271   ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
2272   CXXRecordDecl *Pattern = nullptr;
2273 
2274   // C++ [temp.class.spec.match]p1:
2275   //   When a class template is used in a context that requires an
2276   //   instantiation of the class, it is necessary to determine
2277   //   whether the instantiation is to be generated using the primary
2278   //   template or one of the partial specializations. This is done by
2279   //   matching the template arguments of the class template
2280   //   specialization with the template argument lists of the partial
2281   //   specializations.
2282   typedef PartialSpecMatchResult MatchResult;
2283   SmallVector<MatchResult, 4> Matched;
2284   SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
2285   Template->getPartialSpecializations(PartialSpecs);
2286   TemplateSpecCandidateSet FailedCandidates(PointOfInstantiation);
2287   for (unsigned I = 0, N = PartialSpecs.size(); I != N; ++I) {
2288     ClassTemplatePartialSpecializationDecl *Partial = PartialSpecs[I];
2289     TemplateDeductionInfo Info(FailedCandidates.getLocation());
2290     if (TemplateDeductionResult Result
2291           = DeduceTemplateArguments(Partial,
2292                                     ClassTemplateSpec->getTemplateArgs(),
2293                                     Info)) {
2294       // Store the failed-deduction information for use in diagnostics, later.
2295       // TODO: Actually use the failed-deduction info?
2296       FailedCandidates.addCandidate().set(
2297           DeclAccessPair::make(Template, AS_public), Partial,
2298           MakeDeductionFailureInfo(Context, Result, Info));
2299       (void)Result;
2300     } else {
2301       Matched.push_back(PartialSpecMatchResult());
2302       Matched.back().Partial = Partial;
2303       Matched.back().Args = Info.take();
2304     }
2305   }
2306 
2307   // If we're dealing with a member template where the template parameters
2308   // have been instantiated, this provides the original template parameters
2309   // from which the member template's parameters were instantiated.
2310 
2311   if (Matched.size() >= 1) {
2312     SmallVectorImpl<MatchResult>::iterator Best = Matched.begin();
2313     if (Matched.size() == 1) {
2314       //   -- If exactly one matching specialization is found, the
2315       //      instantiation is generated from that specialization.
2316       // We don't need to do anything for this.
2317     } else {
2318       //   -- If more than one matching specialization is found, the
2319       //      partial order rules (14.5.4.2) are used to determine
2320       //      whether one of the specializations is more specialized
2321       //      than the others. If none of the specializations is more
2322       //      specialized than all of the other matching
2323       //      specializations, then the use of the class template is
2324       //      ambiguous and the program is ill-formed.
2325       for (SmallVectorImpl<MatchResult>::iterator P = Best + 1,
2326                                                PEnd = Matched.end();
2327            P != PEnd; ++P) {
2328         if (getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2329                                                     PointOfInstantiation)
2330               == P->Partial)
2331           Best = P;
2332       }
2333 
2334       // Determine if the best partial specialization is more specialized than
2335       // the others.
2336       bool Ambiguous = false;
2337       for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2338                                                PEnd = Matched.end();
2339            P != PEnd; ++P) {
2340         if (P != Best &&
2341             getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2342                                                     PointOfInstantiation)
2343               != Best->Partial) {
2344           Ambiguous = true;
2345           break;
2346         }
2347       }
2348 
2349       if (Ambiguous) {
2350         // Partial ordering did not produce a clear winner. Complain.
2351         ClassTemplateSpec->setInvalidDecl();
2352         Diag(PointOfInstantiation, diag::err_partial_spec_ordering_ambiguous)
2353           << ClassTemplateSpec;
2354 
2355         // Print the matching partial specializations.
2356         for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2357                                                  PEnd = Matched.end();
2358              P != PEnd; ++P)
2359           Diag(P->Partial->getLocation(), diag::note_partial_spec_match)
2360             << getTemplateArgumentBindingsText(
2361                                             P->Partial->getTemplateParameters(),
2362                                                *P->Args);
2363 
2364         return true;
2365       }
2366     }
2367 
2368     // Instantiate using the best class template partial specialization.
2369     ClassTemplatePartialSpecializationDecl *OrigPartialSpec = Best->Partial;
2370     while (OrigPartialSpec->getInstantiatedFromMember()) {
2371       // If we've found an explicit specialization of this class template,
2372       // stop here and use that as the pattern.
2373       if (OrigPartialSpec->isMemberSpecialization())
2374         break;
2375 
2376       OrigPartialSpec = OrigPartialSpec->getInstantiatedFromMember();
2377     }
2378 
2379     Pattern = OrigPartialSpec;
2380     ClassTemplateSpec->setInstantiationOf(Best->Partial, Best->Args);
2381   } else {
2382     //   -- If no matches are found, the instantiation is generated
2383     //      from the primary template.
2384     ClassTemplateDecl *OrigTemplate = Template;
2385     while (OrigTemplate->getInstantiatedFromMemberTemplate()) {
2386       // If we've found an explicit specialization of this class template,
2387       // stop here and use that as the pattern.
2388       if (OrigTemplate->isMemberSpecialization())
2389         break;
2390 
2391       OrigTemplate = OrigTemplate->getInstantiatedFromMemberTemplate();
2392     }
2393 
2394     Pattern = OrigTemplate->getTemplatedDecl();
2395   }
2396 
2397   bool Result = InstantiateClass(PointOfInstantiation, ClassTemplateSpec,
2398                                  Pattern,
2399                                 getTemplateInstantiationArgs(ClassTemplateSpec),
2400                                  TSK,
2401                                  Complain);
2402 
2403   return Result;
2404 }
2405 
2406 /// \brief Instantiates the definitions of all of the member
2407 /// of the given class, which is an instantiation of a class template
2408 /// or a member class of a template.
2409 void
2410 Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
2411                               CXXRecordDecl *Instantiation,
2412                         const MultiLevelTemplateArgumentList &TemplateArgs,
2413                               TemplateSpecializationKind TSK) {
2414   // FIXME: We need to notify the ASTMutationListener that we did all of these
2415   // things, in case we have an explicit instantiation definition in a PCM, a
2416   // module, or preamble, and the declaration is in an imported AST.
2417   assert(
2418       (TSK == TSK_ExplicitInstantiationDefinition ||
2419        TSK == TSK_ExplicitInstantiationDeclaration ||
2420        (TSK == TSK_ImplicitInstantiation && Instantiation->isLocalClass())) &&
2421       "Unexpected template specialization kind!");
2422   for (auto *D : Instantiation->decls()) {
2423     bool SuppressNew = false;
2424     if (auto *Function = dyn_cast<FunctionDecl>(D)) {
2425       if (FunctionDecl *Pattern
2426             = Function->getInstantiatedFromMemberFunction()) {
2427         MemberSpecializationInfo *MSInfo
2428           = Function->getMemberSpecializationInfo();
2429         assert(MSInfo && "No member specialization information?");
2430         if (MSInfo->getTemplateSpecializationKind()
2431                                                  == TSK_ExplicitSpecialization)
2432           continue;
2433 
2434         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2435                                                    Function,
2436                                         MSInfo->getTemplateSpecializationKind(),
2437                                               MSInfo->getPointOfInstantiation(),
2438                                                    SuppressNew) ||
2439             SuppressNew)
2440           continue;
2441 
2442         // C++11 [temp.explicit]p8:
2443         //   An explicit instantiation definition that names a class template
2444         //   specialization explicitly instantiates the class template
2445         //   specialization and is only an explicit instantiation definition
2446         //   of members whose definition is visible at the point of
2447         //   instantiation.
2448         if (TSK == TSK_ExplicitInstantiationDefinition && !Pattern->isDefined())
2449           continue;
2450 
2451         Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2452 
2453         if (Function->isDefined()) {
2454           // Let the ASTConsumer know that this function has been explicitly
2455           // instantiated now, and its linkage might have changed.
2456           Consumer.HandleTopLevelDecl(DeclGroupRef(Function));
2457         } else if (TSK == TSK_ExplicitInstantiationDefinition) {
2458           InstantiateFunctionDefinition(PointOfInstantiation, Function);
2459         } else if (TSK == TSK_ImplicitInstantiation) {
2460           PendingLocalImplicitInstantiations.push_back(
2461               std::make_pair(Function, PointOfInstantiation));
2462         }
2463       }
2464     } else if (auto *Var = dyn_cast<VarDecl>(D)) {
2465       if (isa<VarTemplateSpecializationDecl>(Var))
2466         continue;
2467 
2468       if (Var->isStaticDataMember()) {
2469         MemberSpecializationInfo *MSInfo = Var->getMemberSpecializationInfo();
2470         assert(MSInfo && "No member specialization information?");
2471         if (MSInfo->getTemplateSpecializationKind()
2472                                                  == TSK_ExplicitSpecialization)
2473           continue;
2474 
2475         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2476                                                    Var,
2477                                         MSInfo->getTemplateSpecializationKind(),
2478                                               MSInfo->getPointOfInstantiation(),
2479                                                    SuppressNew) ||
2480             SuppressNew)
2481           continue;
2482 
2483         if (TSK == TSK_ExplicitInstantiationDefinition) {
2484           // C++0x [temp.explicit]p8:
2485           //   An explicit instantiation definition that names a class template
2486           //   specialization explicitly instantiates the class template
2487           //   specialization and is only an explicit instantiation definition
2488           //   of members whose definition is visible at the point of
2489           //   instantiation.
2490           if (!Var->getInstantiatedFromStaticDataMember()->getDefinition())
2491             continue;
2492 
2493           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2494           InstantiateStaticDataMemberDefinition(PointOfInstantiation, Var);
2495         } else {
2496           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2497         }
2498       }
2499     } else if (auto *Record = dyn_cast<CXXRecordDecl>(D)) {
2500       // Always skip the injected-class-name, along with any
2501       // redeclarations of nested classes, since both would cause us
2502       // to try to instantiate the members of a class twice.
2503       // Skip closure types; they'll get instantiated when we instantiate
2504       // the corresponding lambda-expression.
2505       if (Record->isInjectedClassName() || Record->getPreviousDecl() ||
2506           Record->isLambda())
2507         continue;
2508 
2509       MemberSpecializationInfo *MSInfo = Record->getMemberSpecializationInfo();
2510       assert(MSInfo && "No member specialization information?");
2511 
2512       if (MSInfo->getTemplateSpecializationKind()
2513                                                 == TSK_ExplicitSpecialization)
2514         continue;
2515 
2516       if (Context.getTargetInfo().getCXXABI().isMicrosoft() &&
2517           TSK == TSK_ExplicitInstantiationDeclaration) {
2518         // In MSVC mode, explicit instantiation decl of the outer class doesn't
2519         // affect the inner class.
2520         continue;
2521       }
2522 
2523       if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2524                                                  Record,
2525                                         MSInfo->getTemplateSpecializationKind(),
2526                                               MSInfo->getPointOfInstantiation(),
2527                                                  SuppressNew) ||
2528           SuppressNew)
2529         continue;
2530 
2531       CXXRecordDecl *Pattern = Record->getInstantiatedFromMemberClass();
2532       assert(Pattern && "Missing instantiated-from-template information");
2533 
2534       if (!Record->getDefinition()) {
2535         if (!Pattern->getDefinition()) {
2536           // C++0x [temp.explicit]p8:
2537           //   An explicit instantiation definition that names a class template
2538           //   specialization explicitly instantiates the class template
2539           //   specialization and is only an explicit instantiation definition
2540           //   of members whose definition is visible at the point of
2541           //   instantiation.
2542           if (TSK == TSK_ExplicitInstantiationDeclaration) {
2543             MSInfo->setTemplateSpecializationKind(TSK);
2544             MSInfo->setPointOfInstantiation(PointOfInstantiation);
2545           }
2546 
2547           continue;
2548         }
2549 
2550         InstantiateClass(PointOfInstantiation, Record, Pattern,
2551                          TemplateArgs,
2552                          TSK);
2553       } else {
2554         if (TSK == TSK_ExplicitInstantiationDefinition &&
2555             Record->getTemplateSpecializationKind() ==
2556                 TSK_ExplicitInstantiationDeclaration) {
2557           Record->setTemplateSpecializationKind(TSK);
2558           MarkVTableUsed(PointOfInstantiation, Record, true);
2559         }
2560       }
2561 
2562       Pattern = cast_or_null<CXXRecordDecl>(Record->getDefinition());
2563       if (Pattern)
2564         InstantiateClassMembers(PointOfInstantiation, Pattern, TemplateArgs,
2565                                 TSK);
2566     } else if (auto *Enum = dyn_cast<EnumDecl>(D)) {
2567       MemberSpecializationInfo *MSInfo = Enum->getMemberSpecializationInfo();
2568       assert(MSInfo && "No member specialization information?");
2569 
2570       if (MSInfo->getTemplateSpecializationKind()
2571             == TSK_ExplicitSpecialization)
2572         continue;
2573 
2574       if (CheckSpecializationInstantiationRedecl(
2575             PointOfInstantiation, TSK, Enum,
2576             MSInfo->getTemplateSpecializationKind(),
2577             MSInfo->getPointOfInstantiation(), SuppressNew) ||
2578           SuppressNew)
2579         continue;
2580 
2581       if (Enum->getDefinition())
2582         continue;
2583 
2584       EnumDecl *Pattern = Enum->getTemplateInstantiationPattern();
2585       assert(Pattern && "Missing instantiated-from-template information");
2586 
2587       if (TSK == TSK_ExplicitInstantiationDefinition) {
2588         if (!Pattern->getDefinition())
2589           continue;
2590 
2591         InstantiateEnum(PointOfInstantiation, Enum, Pattern, TemplateArgs, TSK);
2592       } else {
2593         MSInfo->setTemplateSpecializationKind(TSK);
2594         MSInfo->setPointOfInstantiation(PointOfInstantiation);
2595       }
2596     } else if (auto *Field = dyn_cast<FieldDecl>(D)) {
2597       // No need to instantiate in-class initializers during explicit
2598       // instantiation.
2599       if (Field->hasInClassInitializer() && TSK == TSK_ImplicitInstantiation) {
2600         CXXRecordDecl *ClassPattern =
2601             Instantiation->getTemplateInstantiationPattern();
2602         DeclContext::lookup_result Lookup =
2603             ClassPattern->lookup(Field->getDeclName());
2604         FieldDecl *Pattern = cast<FieldDecl>(Lookup.front());
2605         InstantiateInClassInitializer(PointOfInstantiation, Field, Pattern,
2606                                       TemplateArgs);
2607       }
2608     }
2609   }
2610 }
2611 
2612 /// \brief Instantiate the definitions of all of the members of the
2613 /// given class template specialization, which was named as part of an
2614 /// explicit instantiation.
2615 void
2616 Sema::InstantiateClassTemplateSpecializationMembers(
2617                                            SourceLocation PointOfInstantiation,
2618                             ClassTemplateSpecializationDecl *ClassTemplateSpec,
2619                                                TemplateSpecializationKind TSK) {
2620   // C++0x [temp.explicit]p7:
2621   //   An explicit instantiation that names a class template
2622   //   specialization is an explicit instantion of the same kind
2623   //   (declaration or definition) of each of its members (not
2624   //   including members inherited from base classes) that has not
2625   //   been previously explicitly specialized in the translation unit
2626   //   containing the explicit instantiation, except as described
2627   //   below.
2628   InstantiateClassMembers(PointOfInstantiation, ClassTemplateSpec,
2629                           getTemplateInstantiationArgs(ClassTemplateSpec),
2630                           TSK);
2631 }
2632 
2633 StmtResult
2634 Sema::SubstStmt(Stmt *S, const MultiLevelTemplateArgumentList &TemplateArgs) {
2635   if (!S)
2636     return S;
2637 
2638   TemplateInstantiator Instantiator(*this, TemplateArgs,
2639                                     SourceLocation(),
2640                                     DeclarationName());
2641   return Instantiator.TransformStmt(S);
2642 }
2643 
2644 ExprResult
2645 Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
2646   if (!E)
2647     return E;
2648 
2649   TemplateInstantiator Instantiator(*this, TemplateArgs,
2650                                     SourceLocation(),
2651                                     DeclarationName());
2652   return Instantiator.TransformExpr(E);
2653 }
2654 
2655 ExprResult Sema::SubstInitializer(Expr *Init,
2656                           const MultiLevelTemplateArgumentList &TemplateArgs,
2657                           bool CXXDirectInit) {
2658   TemplateInstantiator Instantiator(*this, TemplateArgs,
2659                                     SourceLocation(),
2660                                     DeclarationName());
2661   return Instantiator.TransformInitializer(Init, CXXDirectInit);
2662 }
2663 
2664 bool Sema::SubstExprs(ArrayRef<Expr *> Exprs, bool IsCall,
2665                       const MultiLevelTemplateArgumentList &TemplateArgs,
2666                       SmallVectorImpl<Expr *> &Outputs) {
2667   if (Exprs.empty())
2668     return false;
2669 
2670   TemplateInstantiator Instantiator(*this, TemplateArgs,
2671                                     SourceLocation(),
2672                                     DeclarationName());
2673   return Instantiator.TransformExprs(Exprs.data(), Exprs.size(),
2674                                      IsCall, Outputs);
2675 }
2676 
2677 NestedNameSpecifierLoc
2678 Sema::SubstNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
2679                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2680   if (!NNS)
2681     return NestedNameSpecifierLoc();
2682 
2683   TemplateInstantiator Instantiator(*this, TemplateArgs, NNS.getBeginLoc(),
2684                                     DeclarationName());
2685   return Instantiator.TransformNestedNameSpecifierLoc(NNS);
2686 }
2687 
2688 /// \brief Do template substitution on declaration name info.
2689 DeclarationNameInfo
2690 Sema::SubstDeclarationNameInfo(const DeclarationNameInfo &NameInfo,
2691                          const MultiLevelTemplateArgumentList &TemplateArgs) {
2692   TemplateInstantiator Instantiator(*this, TemplateArgs, NameInfo.getLoc(),
2693                                     NameInfo.getName());
2694   return Instantiator.TransformDeclarationNameInfo(NameInfo);
2695 }
2696 
2697 TemplateName
2698 Sema::SubstTemplateName(NestedNameSpecifierLoc QualifierLoc,
2699                         TemplateName Name, SourceLocation Loc,
2700                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2701   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
2702                                     DeclarationName());
2703   CXXScopeSpec SS;
2704   SS.Adopt(QualifierLoc);
2705   return Instantiator.TransformTemplateName(SS, Name, Loc);
2706 }
2707 
2708 bool Sema::Subst(const TemplateArgumentLoc *Args, unsigned NumArgs,
2709                  TemplateArgumentListInfo &Result,
2710                  const MultiLevelTemplateArgumentList &TemplateArgs) {
2711   TemplateInstantiator Instantiator(*this, TemplateArgs, SourceLocation(),
2712                                     DeclarationName());
2713 
2714   return Instantiator.TransformTemplateArguments(Args, NumArgs, Result);
2715 }
2716 
2717 static const Decl *getCanonicalParmVarDecl(const Decl *D) {
2718   // When storing ParmVarDecls in the local instantiation scope, we always
2719   // want to use the ParmVarDecl from the canonical function declaration,
2720   // since the map is then valid for any redeclaration or definition of that
2721   // function.
2722   if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(D)) {
2723     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(PV->getDeclContext())) {
2724       unsigned i = PV->getFunctionScopeIndex();
2725       // This parameter might be from a freestanding function type within the
2726       // function and isn't necessarily referring to one of FD's parameters.
2727       if (FD->getParamDecl(i) == PV)
2728         return FD->getCanonicalDecl()->getParamDecl(i);
2729     }
2730   }
2731   return D;
2732 }
2733 
2734 
2735 llvm::PointerUnion<Decl *, LocalInstantiationScope::DeclArgumentPack *> *
2736 LocalInstantiationScope::findInstantiationOf(const Decl *D) {
2737   D = getCanonicalParmVarDecl(D);
2738   for (LocalInstantiationScope *Current = this; Current;
2739        Current = Current->Outer) {
2740 
2741     // Check if we found something within this scope.
2742     const Decl *CheckD = D;
2743     do {
2744       LocalDeclsMap::iterator Found = Current->LocalDecls.find(CheckD);
2745       if (Found != Current->LocalDecls.end())
2746         return &Found->second;
2747 
2748       // If this is a tag declaration, it's possible that we need to look for
2749       // a previous declaration.
2750       if (const TagDecl *Tag = dyn_cast<TagDecl>(CheckD))
2751         CheckD = Tag->getPreviousDecl();
2752       else
2753         CheckD = nullptr;
2754     } while (CheckD);
2755 
2756     // If we aren't combined with our outer scope, we're done.
2757     if (!Current->CombineWithOuterScope)
2758       break;
2759   }
2760 
2761   // If we're performing a partial substitution during template argument
2762   // deduction, we may not have values for template parameters yet.
2763   if (isa<NonTypeTemplateParmDecl>(D) || isa<TemplateTypeParmDecl>(D) ||
2764       isa<TemplateTemplateParmDecl>(D))
2765     return nullptr;
2766 
2767   // Local types referenced prior to definition may require instantiation.
2768   if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D))
2769     if (RD->isLocalClass())
2770       return nullptr;
2771 
2772   // Enumeration types referenced prior to definition may appear as a result of
2773   // error recovery.
2774   if (isa<EnumDecl>(D))
2775     return nullptr;
2776 
2777   // If we didn't find the decl, then we either have a sema bug, or we have a
2778   // forward reference to a label declaration.  Return null to indicate that
2779   // we have an uninstantiated label.
2780   assert(isa<LabelDecl>(D) && "declaration not instantiated in this scope");
2781   return nullptr;
2782 }
2783 
2784 void LocalInstantiationScope::InstantiatedLocal(const Decl *D, Decl *Inst) {
2785   D = getCanonicalParmVarDecl(D);
2786   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2787   if (Stored.isNull()) {
2788 #ifndef NDEBUG
2789     // It should not be present in any surrounding scope either.
2790     LocalInstantiationScope *Current = this;
2791     while (Current->CombineWithOuterScope && Current->Outer) {
2792       Current = Current->Outer;
2793       assert(Current->LocalDecls.find(D) == Current->LocalDecls.end() &&
2794              "Instantiated local in inner and outer scopes");
2795     }
2796 #endif
2797     Stored = Inst;
2798   } else if (DeclArgumentPack *Pack = Stored.dyn_cast<DeclArgumentPack *>()) {
2799     Pack->push_back(cast<ParmVarDecl>(Inst));
2800   } else {
2801     assert(Stored.get<Decl *>() == Inst && "Already instantiated this local");
2802   }
2803 }
2804 
2805 void LocalInstantiationScope::InstantiatedLocalPackArg(const Decl *D,
2806                                                        ParmVarDecl *Inst) {
2807   D = getCanonicalParmVarDecl(D);
2808   DeclArgumentPack *Pack = LocalDecls[D].get<DeclArgumentPack *>();
2809   Pack->push_back(Inst);
2810 }
2811 
2812 void LocalInstantiationScope::MakeInstantiatedLocalArgPack(const Decl *D) {
2813 #ifndef NDEBUG
2814   // This should be the first time we've been told about this decl.
2815   for (LocalInstantiationScope *Current = this;
2816        Current && Current->CombineWithOuterScope; Current = Current->Outer)
2817     assert(Current->LocalDecls.find(D) == Current->LocalDecls.end() &&
2818            "Creating local pack after instantiation of local");
2819 #endif
2820 
2821   D = getCanonicalParmVarDecl(D);
2822   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2823   DeclArgumentPack *Pack = new DeclArgumentPack;
2824   Stored = Pack;
2825   ArgumentPacks.push_back(Pack);
2826 }
2827 
2828 void LocalInstantiationScope::SetPartiallySubstitutedPack(NamedDecl *Pack,
2829                                           const TemplateArgument *ExplicitArgs,
2830                                                     unsigned NumExplicitArgs) {
2831   assert((!PartiallySubstitutedPack || PartiallySubstitutedPack == Pack) &&
2832          "Already have a partially-substituted pack");
2833   assert((!PartiallySubstitutedPack
2834           || NumArgsInPartiallySubstitutedPack == NumExplicitArgs) &&
2835          "Wrong number of arguments in partially-substituted pack");
2836   PartiallySubstitutedPack = Pack;
2837   ArgsInPartiallySubstitutedPack = ExplicitArgs;
2838   NumArgsInPartiallySubstitutedPack = NumExplicitArgs;
2839 }
2840 
2841 NamedDecl *LocalInstantiationScope::getPartiallySubstitutedPack(
2842                                          const TemplateArgument **ExplicitArgs,
2843                                               unsigned *NumExplicitArgs) const {
2844   if (ExplicitArgs)
2845     *ExplicitArgs = nullptr;
2846   if (NumExplicitArgs)
2847     *NumExplicitArgs = 0;
2848 
2849   for (const LocalInstantiationScope *Current = this; Current;
2850        Current = Current->Outer) {
2851     if (Current->PartiallySubstitutedPack) {
2852       if (ExplicitArgs)
2853         *ExplicitArgs = Current->ArgsInPartiallySubstitutedPack;
2854       if (NumExplicitArgs)
2855         *NumExplicitArgs = Current->NumArgsInPartiallySubstitutedPack;
2856 
2857       return Current->PartiallySubstitutedPack;
2858     }
2859 
2860     if (!Current->CombineWithOuterScope)
2861       break;
2862   }
2863 
2864   return nullptr;
2865 }
2866