1 //===------- SemaTemplateInstantiate.cpp - C++ Template Instantiation ------===/
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //===----------------------------------------------------------------------===/
8 //
9 //  This file implements C++ template instantiation.
10 //
11 //===----------------------------------------------------------------------===/
12 
13 #include "clang/Sema/SemaInternal.h"
14 #include "TreeTransform.h"
15 #include "clang/AST/ASTConsumer.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/ASTLambda.h"
18 #include "clang/AST/DeclTemplate.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/Basic/LangOptions.h"
21 #include "clang/Sema/DeclSpec.h"
22 #include "clang/Sema/Initialization.h"
23 #include "clang/Sema/Lookup.h"
24 #include "clang/Sema/Template.h"
25 #include "clang/Sema/TemplateDeduction.h"
26 
27 using namespace clang;
28 using namespace sema;
29 
30 //===----------------------------------------------------------------------===/
31 // Template Instantiation Support
32 //===----------------------------------------------------------------------===/
33 
34 /// \brief Retrieve the template argument list(s) that should be used to
35 /// instantiate the definition of the given declaration.
36 ///
37 /// \param D the declaration for which we are computing template instantiation
38 /// arguments.
39 ///
40 /// \param Innermost if non-NULL, the innermost template argument list.
41 ///
42 /// \param RelativeToPrimary true if we should get the template
43 /// arguments relative to the primary template, even when we're
44 /// dealing with a specialization. This is only relevant for function
45 /// template specializations.
46 ///
47 /// \param Pattern If non-NULL, indicates the pattern from which we will be
48 /// instantiating the definition of the given declaration, \p D. This is
49 /// used to determine the proper set of template instantiation arguments for
50 /// friend function template specializations.
51 MultiLevelTemplateArgumentList
52 Sema::getTemplateInstantiationArgs(NamedDecl *D,
53                                    const TemplateArgumentList *Innermost,
54                                    bool RelativeToPrimary,
55                                    const FunctionDecl *Pattern) {
56   // Accumulate the set of template argument lists in this structure.
57   MultiLevelTemplateArgumentList Result;
58 
59   if (Innermost)
60     Result.addOuterTemplateArguments(Innermost);
61 
62   DeclContext *Ctx = dyn_cast<DeclContext>(D);
63   if (!Ctx) {
64     Ctx = D->getDeclContext();
65 
66     // Add template arguments from a variable template instantiation.
67     if (VarTemplateSpecializationDecl *Spec =
68             dyn_cast<VarTemplateSpecializationDecl>(D)) {
69       // We're done when we hit an explicit specialization.
70       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
71           !isa<VarTemplatePartialSpecializationDecl>(Spec))
72         return Result;
73 
74       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
75 
76       // If this variable template specialization was instantiated from a
77       // specialized member that is a variable template, we're done.
78       assert(Spec->getSpecializedTemplate() && "No variable template?");
79       llvm::PointerUnion<VarTemplateDecl*,
80                          VarTemplatePartialSpecializationDecl*> Specialized
81                              = Spec->getSpecializedTemplateOrPartial();
82       if (VarTemplatePartialSpecializationDecl *Partial =
83               Specialized.dyn_cast<VarTemplatePartialSpecializationDecl *>()) {
84         if (Partial->isMemberSpecialization())
85           return Result;
86       } else {
87         VarTemplateDecl *Tmpl = Specialized.get<VarTemplateDecl *>();
88         if (Tmpl->isMemberSpecialization())
89           return Result;
90       }
91     }
92 
93     // If we have a template template parameter with translation unit context,
94     // then we're performing substitution into a default template argument of
95     // this template template parameter before we've constructed the template
96     // that will own this template template parameter. In this case, we
97     // use empty template parameter lists for all of the outer templates
98     // to avoid performing any substitutions.
99     if (Ctx->isTranslationUnit()) {
100       if (TemplateTemplateParmDecl *TTP
101                                       = dyn_cast<TemplateTemplateParmDecl>(D)) {
102         for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
103           Result.addOuterTemplateArguments(None);
104         return Result;
105       }
106     }
107   }
108 
109   while (!Ctx->isFileContext()) {
110     // Add template arguments from a class template instantiation.
111     if (ClassTemplateSpecializationDecl *Spec
112           = dyn_cast<ClassTemplateSpecializationDecl>(Ctx)) {
113       // We're done when we hit an explicit specialization.
114       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
115           !isa<ClassTemplatePartialSpecializationDecl>(Spec))
116         break;
117 
118       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
119 
120       // If this class template specialization was instantiated from a
121       // specialized member that is a class template, we're done.
122       assert(Spec->getSpecializedTemplate() && "No class template?");
123       if (Spec->getSpecializedTemplate()->isMemberSpecialization())
124         break;
125     }
126     // Add template arguments from a function template specialization.
127     else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(Ctx)) {
128       if (!RelativeToPrimary &&
129           (Function->getTemplateSpecializationKind() ==
130                                                   TSK_ExplicitSpecialization &&
131            !Function->getClassScopeSpecializationPattern()))
132         break;
133 
134       if (const TemplateArgumentList *TemplateArgs
135             = Function->getTemplateSpecializationArgs()) {
136         // Add the template arguments for this specialization.
137         Result.addOuterTemplateArguments(TemplateArgs);
138 
139         // If this function was instantiated from a specialized member that is
140         // a function template, we're done.
141         assert(Function->getPrimaryTemplate() && "No function template?");
142         if (Function->getPrimaryTemplate()->isMemberSpecialization())
143           break;
144 
145         // If this function is a generic lambda specialization, we are done.
146         if (isGenericLambdaCallOperatorSpecialization(Function))
147           break;
148 
149       } else if (FunctionTemplateDecl *FunTmpl
150                                    = Function->getDescribedFunctionTemplate()) {
151         // Add the "injected" template arguments.
152         Result.addOuterTemplateArguments(FunTmpl->getInjectedTemplateArgs());
153       }
154 
155       // If this is a friend declaration and it declares an entity at
156       // namespace scope, take arguments from its lexical parent
157       // instead of its semantic parent, unless of course the pattern we're
158       // instantiating actually comes from the file's context!
159       if (Function->getFriendObjectKind() &&
160           Function->getDeclContext()->isFileContext() &&
161           (!Pattern || !Pattern->getLexicalDeclContext()->isFileContext())) {
162         Ctx = Function->getLexicalDeclContext();
163         RelativeToPrimary = false;
164         continue;
165       }
166     } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
167       if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
168         QualType T = ClassTemplate->getInjectedClassNameSpecialization();
169         const TemplateSpecializationType *TST =
170             cast<TemplateSpecializationType>(Context.getCanonicalType(T));
171         Result.addOuterTemplateArguments(
172             llvm::makeArrayRef(TST->getArgs(), TST->getNumArgs()));
173         if (ClassTemplate->isMemberSpecialization())
174           break;
175       }
176     }
177 
178     Ctx = Ctx->getParent();
179     RelativeToPrimary = false;
180   }
181 
182   return Result;
183 }
184 
185 bool Sema::ActiveTemplateInstantiation::isInstantiationRecord() const {
186   switch (Kind) {
187   case TemplateInstantiation:
188   case ExceptionSpecInstantiation:
189   case DefaultTemplateArgumentInstantiation:
190   case DefaultFunctionArgumentInstantiation:
191   case ExplicitTemplateArgumentSubstitution:
192   case DeducedTemplateArgumentSubstitution:
193   case PriorTemplateArgumentSubstitution:
194     return true;
195 
196   case DefaultTemplateArgumentChecking:
197     return false;
198   }
199 
200   llvm_unreachable("Invalid InstantiationKind!");
201 }
202 
203 Sema::InstantiatingTemplate::
204 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
205                       Decl *Entity,
206                       SourceRange InstantiationRange)
207   : SemaRef(SemaRef),
208     SavedInNonInstantiationSFINAEContext(
209                                         SemaRef.InNonInstantiationSFINAEContext)
210 {
211   Invalid = CheckInstantiationDepth(PointOfInstantiation,
212                                     InstantiationRange);
213   if (!Invalid) {
214     ActiveTemplateInstantiation Inst;
215     Inst.Kind = ActiveTemplateInstantiation::TemplateInstantiation;
216     Inst.PointOfInstantiation = PointOfInstantiation;
217     Inst.Entity = Entity;
218     Inst.TemplateArgs = 0;
219     Inst.NumTemplateArgs = 0;
220     Inst.InstantiationRange = InstantiationRange;
221     SemaRef.InNonInstantiationSFINAEContext = false;
222     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
223   }
224 }
225 
226 Sema::InstantiatingTemplate::
227 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
228                       FunctionDecl *Entity, ExceptionSpecification,
229                       SourceRange InstantiationRange)
230   : SemaRef(SemaRef),
231     SavedInNonInstantiationSFINAEContext(
232                                         SemaRef.InNonInstantiationSFINAEContext)
233 {
234   Invalid = CheckInstantiationDepth(PointOfInstantiation,
235                                     InstantiationRange);
236   if (!Invalid) {
237     ActiveTemplateInstantiation Inst;
238     Inst.Kind = ActiveTemplateInstantiation::ExceptionSpecInstantiation;
239     Inst.PointOfInstantiation = PointOfInstantiation;
240     Inst.Entity = Entity;
241     Inst.TemplateArgs = 0;
242     Inst.NumTemplateArgs = 0;
243     Inst.InstantiationRange = InstantiationRange;
244     SemaRef.InNonInstantiationSFINAEContext = false;
245     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
246   }
247 }
248 
249 Sema::InstantiatingTemplate::
250 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
251                       TemplateDecl *Template,
252                       ArrayRef<TemplateArgument> TemplateArgs,
253                       SourceRange InstantiationRange)
254   : SemaRef(SemaRef),
255     SavedInNonInstantiationSFINAEContext(
256                                      SemaRef.InNonInstantiationSFINAEContext)
257 {
258   Invalid = CheckInstantiationDepth(PointOfInstantiation,
259                                     InstantiationRange);
260   if (!Invalid) {
261     ActiveTemplateInstantiation Inst;
262     Inst.Kind
263       = ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation;
264     Inst.PointOfInstantiation = PointOfInstantiation;
265     Inst.Entity = Template;
266     Inst.TemplateArgs = TemplateArgs.data();
267     Inst.NumTemplateArgs = TemplateArgs.size();
268     Inst.InstantiationRange = InstantiationRange;
269     SemaRef.InNonInstantiationSFINAEContext = false;
270     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
271   }
272 }
273 
274 Sema::InstantiatingTemplate::
275 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
276                       FunctionTemplateDecl *FunctionTemplate,
277                       ArrayRef<TemplateArgument> TemplateArgs,
278                       ActiveTemplateInstantiation::InstantiationKind Kind,
279                       sema::TemplateDeductionInfo &DeductionInfo,
280                       SourceRange InstantiationRange)
281   : SemaRef(SemaRef),
282     SavedInNonInstantiationSFINAEContext(
283                                      SemaRef.InNonInstantiationSFINAEContext)
284 {
285   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
286   if (!Invalid) {
287     ActiveTemplateInstantiation Inst;
288     Inst.Kind = Kind;
289     Inst.PointOfInstantiation = PointOfInstantiation;
290     Inst.Entity = FunctionTemplate;
291     Inst.TemplateArgs = TemplateArgs.data();
292     Inst.NumTemplateArgs = TemplateArgs.size();
293     Inst.DeductionInfo = &DeductionInfo;
294     Inst.InstantiationRange = InstantiationRange;
295     SemaRef.InNonInstantiationSFINAEContext = false;
296     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
297 
298     if (!Inst.isInstantiationRecord())
299       ++SemaRef.NonInstantiationEntries;
300   }
301 }
302 
303 Sema::InstantiatingTemplate::
304 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
305                       ClassTemplatePartialSpecializationDecl *PartialSpec,
306                       ArrayRef<TemplateArgument> TemplateArgs,
307                       sema::TemplateDeductionInfo &DeductionInfo,
308                       SourceRange InstantiationRange)
309   : SemaRef(SemaRef),
310     SavedInNonInstantiationSFINAEContext(
311                                      SemaRef.InNonInstantiationSFINAEContext)
312 {
313   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
314   if (!Invalid) {
315     ActiveTemplateInstantiation Inst;
316     Inst.Kind = ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution;
317     Inst.PointOfInstantiation = PointOfInstantiation;
318     Inst.Entity = PartialSpec;
319     Inst.TemplateArgs = TemplateArgs.data();
320     Inst.NumTemplateArgs = TemplateArgs.size();
321     Inst.DeductionInfo = &DeductionInfo;
322     Inst.InstantiationRange = InstantiationRange;
323     SemaRef.InNonInstantiationSFINAEContext = false;
324     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
325   }
326 }
327 
328 Sema::InstantiatingTemplate::InstantiatingTemplate(
329     Sema &SemaRef, SourceLocation PointOfInstantiation,
330     VarTemplatePartialSpecializationDecl *PartialSpec,
331     ArrayRef<TemplateArgument> TemplateArgs,
332     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
333     : SemaRef(SemaRef), SavedInNonInstantiationSFINAEContext(
334                             SemaRef.InNonInstantiationSFINAEContext) {
335   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
336   if (!Invalid) {
337     ActiveTemplateInstantiation Inst;
338     Inst.Kind =
339         ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution;
340     Inst.PointOfInstantiation = PointOfInstantiation;
341     Inst.Entity = PartialSpec;
342     Inst.TemplateArgs = TemplateArgs.data();
343     Inst.NumTemplateArgs = TemplateArgs.size();
344     Inst.DeductionInfo = &DeductionInfo;
345     Inst.InstantiationRange = InstantiationRange;
346     SemaRef.InNonInstantiationSFINAEContext = false;
347     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
348   }
349 }
350 
351 Sema::InstantiatingTemplate::
352 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
353                       ParmVarDecl *Param,
354                       ArrayRef<TemplateArgument> TemplateArgs,
355                       SourceRange InstantiationRange)
356   : SemaRef(SemaRef),
357     SavedInNonInstantiationSFINAEContext(
358                                      SemaRef.InNonInstantiationSFINAEContext)
359 {
360   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
361   if (!Invalid) {
362     ActiveTemplateInstantiation Inst;
363     Inst.Kind
364       = ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation;
365     Inst.PointOfInstantiation = PointOfInstantiation;
366     Inst.Entity = Param;
367     Inst.TemplateArgs = TemplateArgs.data();
368     Inst.NumTemplateArgs = TemplateArgs.size();
369     Inst.InstantiationRange = InstantiationRange;
370     SemaRef.InNonInstantiationSFINAEContext = false;
371     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
372   }
373 }
374 
375 Sema::InstantiatingTemplate::
376 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
377                       NamedDecl *Template, NonTypeTemplateParmDecl *Param,
378                       ArrayRef<TemplateArgument> TemplateArgs,
379                       SourceRange InstantiationRange)
380   : SemaRef(SemaRef),
381     SavedInNonInstantiationSFINAEContext(
382                                      SemaRef.InNonInstantiationSFINAEContext)
383 {
384   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
385   if (!Invalid) {
386     ActiveTemplateInstantiation Inst;
387     Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
388     Inst.PointOfInstantiation = PointOfInstantiation;
389     Inst.Template = Template;
390     Inst.Entity = Param;
391     Inst.TemplateArgs = TemplateArgs.data();
392     Inst.NumTemplateArgs = TemplateArgs.size();
393     Inst.InstantiationRange = InstantiationRange;
394     SemaRef.InNonInstantiationSFINAEContext = false;
395     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
396   }
397 }
398 
399 Sema::InstantiatingTemplate::
400 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
401                       NamedDecl *Template, TemplateTemplateParmDecl *Param,
402                       ArrayRef<TemplateArgument> TemplateArgs,
403                       SourceRange InstantiationRange)
404   : SemaRef(SemaRef),
405     SavedInNonInstantiationSFINAEContext(
406                                      SemaRef.InNonInstantiationSFINAEContext)
407 {
408   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
409   if (!Invalid) {
410     ActiveTemplateInstantiation Inst;
411     Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
412     Inst.PointOfInstantiation = PointOfInstantiation;
413     Inst.Template = Template;
414     Inst.Entity = Param;
415     Inst.TemplateArgs = TemplateArgs.data();
416     Inst.NumTemplateArgs = TemplateArgs.size();
417     Inst.InstantiationRange = InstantiationRange;
418     SemaRef.InNonInstantiationSFINAEContext = false;
419     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
420   }
421 }
422 
423 Sema::InstantiatingTemplate::
424 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
425                       TemplateDecl *Template, NamedDecl *Param,
426                       ArrayRef<TemplateArgument> TemplateArgs,
427                       SourceRange InstantiationRange)
428   : SemaRef(SemaRef),
429     SavedInNonInstantiationSFINAEContext(
430                                      SemaRef.InNonInstantiationSFINAEContext)
431 {
432   Invalid = false;
433 
434   ActiveTemplateInstantiation Inst;
435   Inst.Kind = ActiveTemplateInstantiation::DefaultTemplateArgumentChecking;
436   Inst.PointOfInstantiation = PointOfInstantiation;
437   Inst.Template = Template;
438   Inst.Entity = Param;
439   Inst.TemplateArgs = TemplateArgs.data();
440   Inst.NumTemplateArgs = TemplateArgs.size();
441   Inst.InstantiationRange = InstantiationRange;
442   SemaRef.InNonInstantiationSFINAEContext = false;
443   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
444 
445   assert(!Inst.isInstantiationRecord());
446   ++SemaRef.NonInstantiationEntries;
447 }
448 
449 void Sema::InstantiatingTemplate::Clear() {
450   if (!Invalid) {
451     if (!SemaRef.ActiveTemplateInstantiations.back().isInstantiationRecord()) {
452       assert(SemaRef.NonInstantiationEntries > 0);
453       --SemaRef.NonInstantiationEntries;
454     }
455     SemaRef.InNonInstantiationSFINAEContext
456       = SavedInNonInstantiationSFINAEContext;
457 
458     // Name lookup no longer looks in this template's defining module.
459     assert(SemaRef.ActiveTemplateInstantiations.size() >=
460            SemaRef.ActiveTemplateInstantiationLookupModules.size() &&
461            "forgot to remove a lookup module for a template instantiation");
462     if (SemaRef.ActiveTemplateInstantiations.size() ==
463         SemaRef.ActiveTemplateInstantiationLookupModules.size()) {
464       if (Module *M = SemaRef.ActiveTemplateInstantiationLookupModules.back())
465         SemaRef.LookupModulesCache.erase(M);
466       SemaRef.ActiveTemplateInstantiationLookupModules.pop_back();
467     }
468 
469     SemaRef.ActiveTemplateInstantiations.pop_back();
470     Invalid = true;
471   }
472 }
473 
474 bool Sema::InstantiatingTemplate::CheckInstantiationDepth(
475                                         SourceLocation PointOfInstantiation,
476                                            SourceRange InstantiationRange) {
477   assert(SemaRef.NonInstantiationEntries <=
478                                    SemaRef.ActiveTemplateInstantiations.size());
479   if ((SemaRef.ActiveTemplateInstantiations.size() -
480           SemaRef.NonInstantiationEntries)
481         <= SemaRef.getLangOpts().InstantiationDepth)
482     return false;
483 
484   SemaRef.Diag(PointOfInstantiation,
485                diag::err_template_recursion_depth_exceeded)
486     << SemaRef.getLangOpts().InstantiationDepth
487     << InstantiationRange;
488   SemaRef.Diag(PointOfInstantiation, diag::note_template_recursion_depth)
489     << SemaRef.getLangOpts().InstantiationDepth;
490   return true;
491 }
492 
493 /// \brief Prints the current instantiation stack through a series of
494 /// notes.
495 void Sema::PrintInstantiationStack() {
496   // Determine which template instantiations to skip, if any.
497   unsigned SkipStart = ActiveTemplateInstantiations.size(), SkipEnd = SkipStart;
498   unsigned Limit = Diags.getTemplateBacktraceLimit();
499   if (Limit && Limit < ActiveTemplateInstantiations.size()) {
500     SkipStart = Limit / 2 + Limit % 2;
501     SkipEnd = ActiveTemplateInstantiations.size() - Limit / 2;
502   }
503 
504   // FIXME: In all of these cases, we need to show the template arguments
505   unsigned InstantiationIdx = 0;
506   for (SmallVectorImpl<ActiveTemplateInstantiation>::reverse_iterator
507          Active = ActiveTemplateInstantiations.rbegin(),
508          ActiveEnd = ActiveTemplateInstantiations.rend();
509        Active != ActiveEnd;
510        ++Active, ++InstantiationIdx) {
511     // Skip this instantiation?
512     if (InstantiationIdx >= SkipStart && InstantiationIdx < SkipEnd) {
513       if (InstantiationIdx == SkipStart) {
514         // Note that we're skipping instantiations.
515         Diags.Report(Active->PointOfInstantiation,
516                      diag::note_instantiation_contexts_suppressed)
517           << unsigned(ActiveTemplateInstantiations.size() - Limit);
518       }
519       continue;
520     }
521 
522     switch (Active->Kind) {
523     case ActiveTemplateInstantiation::TemplateInstantiation: {
524       Decl *D = Active->Entity;
525       if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(D)) {
526         unsigned DiagID = diag::note_template_member_class_here;
527         if (isa<ClassTemplateSpecializationDecl>(Record))
528           DiagID = diag::note_template_class_instantiation_here;
529         Diags.Report(Active->PointOfInstantiation, DiagID)
530           << Context.getTypeDeclType(Record)
531           << Active->InstantiationRange;
532       } else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
533         unsigned DiagID;
534         if (Function->getPrimaryTemplate())
535           DiagID = diag::note_function_template_spec_here;
536         else
537           DiagID = diag::note_template_member_function_here;
538         Diags.Report(Active->PointOfInstantiation, DiagID)
539           << Function
540           << Active->InstantiationRange;
541       } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
542         Diags.Report(Active->PointOfInstantiation,
543                      VD->isStaticDataMember()?
544                        diag::note_template_static_data_member_def_here
545                      : diag::note_template_variable_def_here)
546           << VD
547           << Active->InstantiationRange;
548       } else if (EnumDecl *ED = dyn_cast<EnumDecl>(D)) {
549         Diags.Report(Active->PointOfInstantiation,
550                      diag::note_template_enum_def_here)
551           << ED
552           << Active->InstantiationRange;
553       } else {
554         Diags.Report(Active->PointOfInstantiation,
555                      diag::note_template_type_alias_instantiation_here)
556           << cast<TypeAliasTemplateDecl>(D)
557           << Active->InstantiationRange;
558       }
559       break;
560     }
561 
562     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation: {
563       TemplateDecl *Template = cast<TemplateDecl>(Active->Entity);
564       SmallVector<char, 128> TemplateArgsStr;
565       llvm::raw_svector_ostream OS(TemplateArgsStr);
566       Template->printName(OS);
567       TemplateSpecializationType::PrintTemplateArgumentList(OS,
568                                                          Active->TemplateArgs,
569                                                       Active->NumTemplateArgs,
570                                                       getPrintingPolicy());
571       Diags.Report(Active->PointOfInstantiation,
572                    diag::note_default_arg_instantiation_here)
573         << OS.str()
574         << Active->InstantiationRange;
575       break;
576     }
577 
578     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution: {
579       FunctionTemplateDecl *FnTmpl = cast<FunctionTemplateDecl>(Active->Entity);
580       Diags.Report(Active->PointOfInstantiation,
581                    diag::note_explicit_template_arg_substitution_here)
582         << FnTmpl
583         << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
584                                            Active->TemplateArgs,
585                                            Active->NumTemplateArgs)
586         << Active->InstantiationRange;
587       break;
588     }
589 
590     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
591       if (ClassTemplatePartialSpecializationDecl *PartialSpec =
592             dyn_cast<ClassTemplatePartialSpecializationDecl>(Active->Entity)) {
593         Diags.Report(Active->PointOfInstantiation,
594                      diag::note_partial_spec_deduct_instantiation_here)
595           << Context.getTypeDeclType(PartialSpec)
596           << getTemplateArgumentBindingsText(
597                                          PartialSpec->getTemplateParameters(),
598                                              Active->TemplateArgs,
599                                              Active->NumTemplateArgs)
600           << Active->InstantiationRange;
601       } else {
602         FunctionTemplateDecl *FnTmpl
603           = cast<FunctionTemplateDecl>(Active->Entity);
604         Diags.Report(Active->PointOfInstantiation,
605                      diag::note_function_template_deduction_instantiation_here)
606           << FnTmpl
607           << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
608                                              Active->TemplateArgs,
609                                              Active->NumTemplateArgs)
610           << Active->InstantiationRange;
611       }
612       break;
613 
614     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation: {
615       ParmVarDecl *Param = cast<ParmVarDecl>(Active->Entity);
616       FunctionDecl *FD = cast<FunctionDecl>(Param->getDeclContext());
617 
618       SmallVector<char, 128> TemplateArgsStr;
619       llvm::raw_svector_ostream OS(TemplateArgsStr);
620       FD->printName(OS);
621       TemplateSpecializationType::PrintTemplateArgumentList(OS,
622                                                          Active->TemplateArgs,
623                                                       Active->NumTemplateArgs,
624                                                       getPrintingPolicy());
625       Diags.Report(Active->PointOfInstantiation,
626                    diag::note_default_function_arg_instantiation_here)
627         << OS.str()
628         << Active->InstantiationRange;
629       break;
630     }
631 
632     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution: {
633       NamedDecl *Parm = cast<NamedDecl>(Active->Entity);
634       std::string Name;
635       if (!Parm->getName().empty())
636         Name = std::string(" '") + Parm->getName().str() + "'";
637 
638       TemplateParameterList *TemplateParams = 0;
639       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
640         TemplateParams = Template->getTemplateParameters();
641       else
642         TemplateParams =
643           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
644                                                       ->getTemplateParameters();
645       Diags.Report(Active->PointOfInstantiation,
646                    diag::note_prior_template_arg_substitution)
647         << isa<TemplateTemplateParmDecl>(Parm)
648         << Name
649         << getTemplateArgumentBindingsText(TemplateParams,
650                                            Active->TemplateArgs,
651                                            Active->NumTemplateArgs)
652         << Active->InstantiationRange;
653       break;
654     }
655 
656     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking: {
657       TemplateParameterList *TemplateParams = 0;
658       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
659         TemplateParams = Template->getTemplateParameters();
660       else
661         TemplateParams =
662           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
663                                                       ->getTemplateParameters();
664 
665       Diags.Report(Active->PointOfInstantiation,
666                    diag::note_template_default_arg_checking)
667         << getTemplateArgumentBindingsText(TemplateParams,
668                                            Active->TemplateArgs,
669                                            Active->NumTemplateArgs)
670         << Active->InstantiationRange;
671       break;
672     }
673 
674     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
675       Diags.Report(Active->PointOfInstantiation,
676                    diag::note_template_exception_spec_instantiation_here)
677         << cast<FunctionDecl>(Active->Entity)
678         << Active->InstantiationRange;
679       break;
680     }
681   }
682 }
683 
684 Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
685   if (InNonInstantiationSFINAEContext)
686     return Optional<TemplateDeductionInfo *>(0);
687 
688   for (SmallVectorImpl<ActiveTemplateInstantiation>::const_reverse_iterator
689          Active = ActiveTemplateInstantiations.rbegin(),
690          ActiveEnd = ActiveTemplateInstantiations.rend();
691        Active != ActiveEnd;
692        ++Active)
693   {
694     switch(Active->Kind) {
695     case ActiveTemplateInstantiation::TemplateInstantiation:
696       // An instantiation of an alias template may or may not be a SFINAE
697       // context, depending on what else is on the stack.
698       if (isa<TypeAliasTemplateDecl>(Active->Entity))
699         break;
700       // Fall through.
701     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
702     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
703       // This is a template instantiation, so there is no SFINAE.
704       return None;
705 
706     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
707     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
708     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking:
709       // A default template argument instantiation and substitution into
710       // template parameters with arguments for prior parameters may or may
711       // not be a SFINAE context; look further up the stack.
712       break;
713 
714     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution:
715     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
716       // We're either substitution explicitly-specified template arguments
717       // or deduced template arguments, so SFINAE applies.
718       assert(Active->DeductionInfo && "Missing deduction info pointer");
719       return Active->DeductionInfo;
720     }
721   }
722 
723   return None;
724 }
725 
726 /// \brief Retrieve the depth and index of a parameter pack.
727 static std::pair<unsigned, unsigned>
728 getDepthAndIndex(NamedDecl *ND) {
729   if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(ND))
730     return std::make_pair(TTP->getDepth(), TTP->getIndex());
731 
732   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(ND))
733     return std::make_pair(NTTP->getDepth(), NTTP->getIndex());
734 
735   TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(ND);
736   return std::make_pair(TTP->getDepth(), TTP->getIndex());
737 }
738 
739 //===----------------------------------------------------------------------===/
740 // Template Instantiation for Types
741 //===----------------------------------------------------------------------===/
742 namespace {
743   class TemplateInstantiator : public TreeTransform<TemplateInstantiator> {
744     const MultiLevelTemplateArgumentList &TemplateArgs;
745     SourceLocation Loc;
746     DeclarationName Entity;
747 
748   public:
749     typedef TreeTransform<TemplateInstantiator> inherited;
750 
751     TemplateInstantiator(Sema &SemaRef,
752                          const MultiLevelTemplateArgumentList &TemplateArgs,
753                          SourceLocation Loc,
754                          DeclarationName Entity)
755       : inherited(SemaRef), TemplateArgs(TemplateArgs), Loc(Loc),
756         Entity(Entity) { }
757 
758     /// \brief Determine whether the given type \p T has already been
759     /// transformed.
760     ///
761     /// For the purposes of template instantiation, a type has already been
762     /// transformed if it is NULL or if it is not dependent.
763     bool AlreadyTransformed(QualType T);
764 
765     /// \brief Returns the location of the entity being instantiated, if known.
766     SourceLocation getBaseLocation() { return Loc; }
767 
768     /// \brief Returns the name of the entity being instantiated, if any.
769     DeclarationName getBaseEntity() { return Entity; }
770 
771     /// \brief Sets the "base" location and entity when that
772     /// information is known based on another transformation.
773     void setBase(SourceLocation Loc, DeclarationName Entity) {
774       this->Loc = Loc;
775       this->Entity = Entity;
776     }
777 
778     bool TryExpandParameterPacks(SourceLocation EllipsisLoc,
779                                  SourceRange PatternRange,
780                                  ArrayRef<UnexpandedParameterPack> Unexpanded,
781                                  bool &ShouldExpand, bool &RetainExpansion,
782                                  Optional<unsigned> &NumExpansions) {
783       return getSema().CheckParameterPacksForExpansion(EllipsisLoc,
784                                                        PatternRange, Unexpanded,
785                                                        TemplateArgs,
786                                                        ShouldExpand,
787                                                        RetainExpansion,
788                                                        NumExpansions);
789     }
790 
791     void ExpandingFunctionParameterPack(ParmVarDecl *Pack) {
792       SemaRef.CurrentInstantiationScope->MakeInstantiatedLocalArgPack(Pack);
793     }
794 
795     TemplateArgument ForgetPartiallySubstitutedPack() {
796       TemplateArgument Result;
797       if (NamedDecl *PartialPack
798             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
799         MultiLevelTemplateArgumentList &TemplateArgs
800           = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
801         unsigned Depth, Index;
802         llvm::tie(Depth, Index) = getDepthAndIndex(PartialPack);
803         if (TemplateArgs.hasTemplateArgument(Depth, Index)) {
804           Result = TemplateArgs(Depth, Index);
805           TemplateArgs.setArgument(Depth, Index, TemplateArgument());
806         }
807       }
808 
809       return Result;
810     }
811 
812     void RememberPartiallySubstitutedPack(TemplateArgument Arg) {
813       if (Arg.isNull())
814         return;
815 
816       if (NamedDecl *PartialPack
817             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
818         MultiLevelTemplateArgumentList &TemplateArgs
819         = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
820         unsigned Depth, Index;
821         llvm::tie(Depth, Index) = getDepthAndIndex(PartialPack);
822         TemplateArgs.setArgument(Depth, Index, Arg);
823       }
824     }
825 
826     /// \brief Transform the given declaration by instantiating a reference to
827     /// this declaration.
828     Decl *TransformDecl(SourceLocation Loc, Decl *D);
829 
830     void transformAttrs(Decl *Old, Decl *New) {
831       SemaRef.InstantiateAttrs(TemplateArgs, Old, New);
832     }
833 
834     void transformedLocalDecl(Decl *Old, Decl *New) {
835       SemaRef.CurrentInstantiationScope->InstantiatedLocal(Old, New);
836     }
837 
838     /// \brief Transform the definition of the given declaration by
839     /// instantiating it.
840     Decl *TransformDefinition(SourceLocation Loc, Decl *D);
841 
842     /// \brief Transform the first qualifier within a scope by instantiating the
843     /// declaration.
844     NamedDecl *TransformFirstQualifierInScope(NamedDecl *D, SourceLocation Loc);
845 
846     /// \brief Rebuild the exception declaration and register the declaration
847     /// as an instantiated local.
848     VarDecl *RebuildExceptionDecl(VarDecl *ExceptionDecl,
849                                   TypeSourceInfo *Declarator,
850                                   SourceLocation StartLoc,
851                                   SourceLocation NameLoc,
852                                   IdentifierInfo *Name);
853 
854     /// \brief Rebuild the Objective-C exception declaration and register the
855     /// declaration as an instantiated local.
856     VarDecl *RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
857                                       TypeSourceInfo *TSInfo, QualType T);
858 
859     /// \brief Check for tag mismatches when instantiating an
860     /// elaborated type.
861     QualType RebuildElaboratedType(SourceLocation KeywordLoc,
862                                    ElaboratedTypeKeyword Keyword,
863                                    NestedNameSpecifierLoc QualifierLoc,
864                                    QualType T);
865 
866     TemplateName TransformTemplateName(CXXScopeSpec &SS,
867                                        TemplateName Name,
868                                        SourceLocation NameLoc,
869                                        QualType ObjectType = QualType(),
870                                        NamedDecl *FirstQualifierInScope = 0);
871 
872     ExprResult TransformPredefinedExpr(PredefinedExpr *E);
873     ExprResult TransformDeclRefExpr(DeclRefExpr *E);
874     ExprResult TransformCXXDefaultArgExpr(CXXDefaultArgExpr *E);
875 
876     ExprResult TransformTemplateParmRefExpr(DeclRefExpr *E,
877                                             NonTypeTemplateParmDecl *D);
878     ExprResult TransformSubstNonTypeTemplateParmPackExpr(
879                                            SubstNonTypeTemplateParmPackExpr *E);
880 
881     /// \brief Rebuild a DeclRefExpr for a ParmVarDecl reference.
882     ExprResult RebuildParmVarDeclRefExpr(ParmVarDecl *PD, SourceLocation Loc);
883 
884     /// \brief Transform a reference to a function parameter pack.
885     ExprResult TransformFunctionParmPackRefExpr(DeclRefExpr *E,
886                                                 ParmVarDecl *PD);
887 
888     /// \brief Transform a FunctionParmPackExpr which was built when we couldn't
889     /// expand a function parameter pack reference which refers to an expanded
890     /// pack.
891     ExprResult TransformFunctionParmPackExpr(FunctionParmPackExpr *E);
892 
893     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
894                                         FunctionProtoTypeLoc TL);
895     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
896                                         FunctionProtoTypeLoc TL,
897                                         CXXRecordDecl *ThisContext,
898                                         unsigned ThisTypeQuals);
899 
900     ParmVarDecl *TransformFunctionTypeParam(ParmVarDecl *OldParm,
901                                             int indexAdjustment,
902                                             Optional<unsigned> NumExpansions,
903                                             bool ExpectParameterPack);
904 
905     /// \brief Transforms a template type parameter type by performing
906     /// substitution of the corresponding template type argument.
907     QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
908                                            TemplateTypeParmTypeLoc TL);
909 
910     /// \brief Transforms an already-substituted template type parameter pack
911     /// into either itself (if we aren't substituting into its pack expansion)
912     /// or the appropriate substituted argument.
913     QualType TransformSubstTemplateTypeParmPackType(TypeLocBuilder &TLB,
914                                            SubstTemplateTypeParmPackTypeLoc TL);
915 
916     ExprResult TransformCallExpr(CallExpr *CE) {
917       getSema().CallsUndergoingInstantiation.push_back(CE);
918       ExprResult Result =
919           TreeTransform<TemplateInstantiator>::TransformCallExpr(CE);
920       getSema().CallsUndergoingInstantiation.pop_back();
921       return Result;
922     }
923 
924     ExprResult TransformLambdaExpr(LambdaExpr *E) {
925       LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
926       return TreeTransform<TemplateInstantiator>::TransformLambdaExpr(E);
927     }
928 
929     ExprResult TransformLambdaScope(LambdaExpr *E,
930         CXXMethodDecl *NewCallOperator,
931         ArrayRef<InitCaptureInfoTy> InitCaptureExprsAndTypes) {
932       CXXMethodDecl *const OldCallOperator = E->getCallOperator();
933       // In the generic lambda case, we set the NewTemplate to be considered
934       // an "instantiation" of the OldTemplate.
935       if (FunctionTemplateDecl *const NewCallOperatorTemplate =
936             NewCallOperator->getDescribedFunctionTemplate()) {
937 
938         FunctionTemplateDecl *const OldCallOperatorTemplate =
939                               OldCallOperator->getDescribedFunctionTemplate();
940         NewCallOperatorTemplate->setInstantiatedFromMemberTemplate(
941                                                      OldCallOperatorTemplate);
942         // Mark the NewCallOperatorTemplate a specialization.
943         NewCallOperatorTemplate->setMemberSpecialization();
944       } else
945         // For a non-generic lambda we set the NewCallOperator to
946         // be an instantiation of the OldCallOperator.
947         NewCallOperator->setInstantiationOfMemberFunction(OldCallOperator,
948                                                     TSK_ImplicitInstantiation);
949 
950       return inherited::TransformLambdaScope(E, NewCallOperator,
951           InitCaptureExprsAndTypes);
952     }
953     TemplateParameterList *TransformTemplateParameterList(
954                               TemplateParameterList *OrigTPL)  {
955       if (!OrigTPL || !OrigTPL->size()) return OrigTPL;
956 
957       DeclContext *Owner = OrigTPL->getParam(0)->getDeclContext();
958       TemplateDeclInstantiator  DeclInstantiator(getSema(),
959                         /* DeclContext *Owner */ Owner, TemplateArgs);
960       return DeclInstantiator.SubstTemplateParams(OrigTPL);
961     }
962   private:
963     ExprResult transformNonTypeTemplateParmRef(NonTypeTemplateParmDecl *parm,
964                                                SourceLocation loc,
965                                                TemplateArgument arg);
966   };
967 }
968 
969 bool TemplateInstantiator::AlreadyTransformed(QualType T) {
970   if (T.isNull())
971     return true;
972 
973   if (T->isInstantiationDependentType() || T->isVariablyModifiedType())
974     return false;
975 
976   getSema().MarkDeclarationsReferencedInType(Loc, T);
977   return true;
978 }
979 
980 static TemplateArgument
981 getPackSubstitutedTemplateArgument(Sema &S, TemplateArgument Arg) {
982   assert(S.ArgumentPackSubstitutionIndex >= 0);
983   assert(S.ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
984   Arg = Arg.pack_begin()[S.ArgumentPackSubstitutionIndex];
985   if (Arg.isPackExpansion())
986     Arg = Arg.getPackExpansionPattern();
987   return Arg;
988 }
989 
990 Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
991   if (!D)
992     return 0;
993 
994   if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(D)) {
995     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
996       // If the corresponding template argument is NULL or non-existent, it's
997       // because we are performing instantiation from explicitly-specified
998       // template arguments in a function template, but there were some
999       // arguments left unspecified.
1000       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
1001                                             TTP->getPosition()))
1002         return D;
1003 
1004       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
1005 
1006       if (TTP->isParameterPack()) {
1007         assert(Arg.getKind() == TemplateArgument::Pack &&
1008                "Missing argument pack");
1009         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1010       }
1011 
1012       TemplateName Template = Arg.getAsTemplate();
1013       assert(!Template.isNull() && Template.getAsTemplateDecl() &&
1014              "Wrong kind of template template argument");
1015       return Template.getAsTemplateDecl();
1016     }
1017 
1018     // Fall through to find the instantiated declaration for this template
1019     // template parameter.
1020   }
1021 
1022   return SemaRef.FindInstantiatedDecl(Loc, cast<NamedDecl>(D), TemplateArgs);
1023 }
1024 
1025 Decl *TemplateInstantiator::TransformDefinition(SourceLocation Loc, Decl *D) {
1026   Decl *Inst = getSema().SubstDecl(D, getSema().CurContext, TemplateArgs);
1027   if (!Inst)
1028     return 0;
1029 
1030   getSema().CurrentInstantiationScope->InstantiatedLocal(D, Inst);
1031   return Inst;
1032 }
1033 
1034 NamedDecl *
1035 TemplateInstantiator::TransformFirstQualifierInScope(NamedDecl *D,
1036                                                      SourceLocation Loc) {
1037   // If the first part of the nested-name-specifier was a template type
1038   // parameter, instantiate that type parameter down to a tag type.
1039   if (TemplateTypeParmDecl *TTPD = dyn_cast_or_null<TemplateTypeParmDecl>(D)) {
1040     const TemplateTypeParmType *TTP
1041       = cast<TemplateTypeParmType>(getSema().Context.getTypeDeclType(TTPD));
1042 
1043     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
1044       // FIXME: This needs testing w/ member access expressions.
1045       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getIndex());
1046 
1047       if (TTP->isParameterPack()) {
1048         assert(Arg.getKind() == TemplateArgument::Pack &&
1049                "Missing argument pack");
1050 
1051         if (getSema().ArgumentPackSubstitutionIndex == -1)
1052           return 0;
1053 
1054         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1055       }
1056 
1057       QualType T = Arg.getAsType();
1058       if (T.isNull())
1059         return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
1060 
1061       if (const TagType *Tag = T->getAs<TagType>())
1062         return Tag->getDecl();
1063 
1064       // The resulting type is not a tag; complain.
1065       getSema().Diag(Loc, diag::err_nested_name_spec_non_tag) << T;
1066       return 0;
1067     }
1068   }
1069 
1070   return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
1071 }
1072 
1073 VarDecl *
1074 TemplateInstantiator::RebuildExceptionDecl(VarDecl *ExceptionDecl,
1075                                            TypeSourceInfo *Declarator,
1076                                            SourceLocation StartLoc,
1077                                            SourceLocation NameLoc,
1078                                            IdentifierInfo *Name) {
1079   VarDecl *Var = inherited::RebuildExceptionDecl(ExceptionDecl, Declarator,
1080                                                  StartLoc, NameLoc, Name);
1081   if (Var)
1082     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
1083   return Var;
1084 }
1085 
1086 VarDecl *TemplateInstantiator::RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
1087                                                         TypeSourceInfo *TSInfo,
1088                                                         QualType T) {
1089   VarDecl *Var = inherited::RebuildObjCExceptionDecl(ExceptionDecl, TSInfo, T);
1090   if (Var)
1091     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
1092   return Var;
1093 }
1094 
1095 QualType
1096 TemplateInstantiator::RebuildElaboratedType(SourceLocation KeywordLoc,
1097                                             ElaboratedTypeKeyword Keyword,
1098                                             NestedNameSpecifierLoc QualifierLoc,
1099                                             QualType T) {
1100   if (const TagType *TT = T->getAs<TagType>()) {
1101     TagDecl* TD = TT->getDecl();
1102 
1103     SourceLocation TagLocation = KeywordLoc;
1104 
1105     IdentifierInfo *Id = TD->getIdentifier();
1106 
1107     // TODO: should we even warn on struct/class mismatches for this?  Seems
1108     // like it's likely to produce a lot of spurious errors.
1109     if (Id && Keyword != ETK_None && Keyword != ETK_Typename) {
1110       TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForKeyword(Keyword);
1111       if (!SemaRef.isAcceptableTagRedeclaration(TD, Kind, /*isDefinition*/false,
1112                                                 TagLocation, *Id)) {
1113         SemaRef.Diag(TagLocation, diag::err_use_with_wrong_tag)
1114           << Id
1115           << FixItHint::CreateReplacement(SourceRange(TagLocation),
1116                                           TD->getKindName());
1117         SemaRef.Diag(TD->getLocation(), diag::note_previous_use);
1118       }
1119     }
1120   }
1121 
1122   return TreeTransform<TemplateInstantiator>::RebuildElaboratedType(KeywordLoc,
1123                                                                     Keyword,
1124                                                                   QualifierLoc,
1125                                                                     T);
1126 }
1127 
1128 TemplateName TemplateInstantiator::TransformTemplateName(CXXScopeSpec &SS,
1129                                                          TemplateName Name,
1130                                                          SourceLocation NameLoc,
1131                                                          QualType ObjectType,
1132                                              NamedDecl *FirstQualifierInScope) {
1133   if (TemplateTemplateParmDecl *TTP
1134        = dyn_cast_or_null<TemplateTemplateParmDecl>(Name.getAsTemplateDecl())) {
1135     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
1136       // If the corresponding template argument is NULL or non-existent, it's
1137       // because we are performing instantiation from explicitly-specified
1138       // template arguments in a function template, but there were some
1139       // arguments left unspecified.
1140       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
1141                                             TTP->getPosition()))
1142         return Name;
1143 
1144       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
1145 
1146       if (TTP->isParameterPack()) {
1147         assert(Arg.getKind() == TemplateArgument::Pack &&
1148                "Missing argument pack");
1149 
1150         if (getSema().ArgumentPackSubstitutionIndex == -1) {
1151           // We have the template argument pack to substitute, but we're not
1152           // actually expanding the enclosing pack expansion yet. So, just
1153           // keep the entire argument pack.
1154           return getSema().Context.getSubstTemplateTemplateParmPack(TTP, Arg);
1155         }
1156 
1157         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1158       }
1159 
1160       TemplateName Template = Arg.getAsTemplate();
1161       assert(!Template.isNull() && "Null template template argument");
1162 
1163       // We don't ever want to substitute for a qualified template name, since
1164       // the qualifier is handled separately. So, look through the qualified
1165       // template name to its underlying declaration.
1166       if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
1167         Template = TemplateName(QTN->getTemplateDecl());
1168 
1169       Template = getSema().Context.getSubstTemplateTemplateParm(TTP, Template);
1170       return Template;
1171     }
1172   }
1173 
1174   if (SubstTemplateTemplateParmPackStorage *SubstPack
1175       = Name.getAsSubstTemplateTemplateParmPack()) {
1176     if (getSema().ArgumentPackSubstitutionIndex == -1)
1177       return Name;
1178 
1179     TemplateArgument Arg = SubstPack->getArgumentPack();
1180     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1181     return Arg.getAsTemplate();
1182   }
1183 
1184   return inherited::TransformTemplateName(SS, Name, NameLoc, ObjectType,
1185                                           FirstQualifierInScope);
1186 }
1187 
1188 ExprResult
1189 TemplateInstantiator::TransformPredefinedExpr(PredefinedExpr *E) {
1190   if (!E->isTypeDependent())
1191     return SemaRef.Owned(E);
1192 
1193   return getSema().BuildPredefinedExpr(E->getLocation(), E->getIdentType());
1194 }
1195 
1196 ExprResult
1197 TemplateInstantiator::TransformTemplateParmRefExpr(DeclRefExpr *E,
1198                                                NonTypeTemplateParmDecl *NTTP) {
1199   // If the corresponding template argument is NULL or non-existent, it's
1200   // because we are performing instantiation from explicitly-specified
1201   // template arguments in a function template, but there were some
1202   // arguments left unspecified.
1203   if (!TemplateArgs.hasTemplateArgument(NTTP->getDepth(),
1204                                         NTTP->getPosition()))
1205     return SemaRef.Owned(E);
1206 
1207   TemplateArgument Arg = TemplateArgs(NTTP->getDepth(), NTTP->getPosition());
1208   if (NTTP->isParameterPack()) {
1209     assert(Arg.getKind() == TemplateArgument::Pack &&
1210            "Missing argument pack");
1211 
1212     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1213       // We have an argument pack, but we can't select a particular argument
1214       // out of it yet. Therefore, we'll build an expression to hold on to that
1215       // argument pack.
1216       QualType TargetType = SemaRef.SubstType(NTTP->getType(), TemplateArgs,
1217                                               E->getLocation(),
1218                                               NTTP->getDeclName());
1219       if (TargetType.isNull())
1220         return ExprError();
1221 
1222       return new (SemaRef.Context) SubstNonTypeTemplateParmPackExpr(TargetType,
1223                                                                     NTTP,
1224                                                               E->getLocation(),
1225                                                                     Arg);
1226     }
1227 
1228     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1229   }
1230 
1231   return transformNonTypeTemplateParmRef(NTTP, E->getLocation(), Arg);
1232 }
1233 
1234 ExprResult TemplateInstantiator::transformNonTypeTemplateParmRef(
1235                                                  NonTypeTemplateParmDecl *parm,
1236                                                  SourceLocation loc,
1237                                                  TemplateArgument arg) {
1238   ExprResult result;
1239   QualType type;
1240 
1241   // The template argument itself might be an expression, in which
1242   // case we just return that expression.
1243   if (arg.getKind() == TemplateArgument::Expression) {
1244     Expr *argExpr = arg.getAsExpr();
1245     result = SemaRef.Owned(argExpr);
1246     type = argExpr->getType();
1247 
1248   } else if (arg.getKind() == TemplateArgument::Declaration ||
1249              arg.getKind() == TemplateArgument::NullPtr) {
1250     ValueDecl *VD;
1251     if (arg.getKind() == TemplateArgument::Declaration) {
1252       VD = cast<ValueDecl>(arg.getAsDecl());
1253 
1254       // Find the instantiation of the template argument.  This is
1255       // required for nested templates.
1256       VD = cast_or_null<ValueDecl>(
1257              getSema().FindInstantiatedDecl(loc, VD, TemplateArgs));
1258       if (!VD)
1259         return ExprError();
1260     } else {
1261       // Propagate NULL template argument.
1262       VD = 0;
1263     }
1264 
1265     // Derive the type we want the substituted decl to have.  This had
1266     // better be non-dependent, or these checks will have serious problems.
1267     if (parm->isExpandedParameterPack()) {
1268       type = parm->getExpansionType(SemaRef.ArgumentPackSubstitutionIndex);
1269     } else if (parm->isParameterPack() &&
1270                isa<PackExpansionType>(parm->getType())) {
1271       type = SemaRef.SubstType(
1272                         cast<PackExpansionType>(parm->getType())->getPattern(),
1273                                      TemplateArgs, loc, parm->getDeclName());
1274     } else {
1275       type = SemaRef.SubstType(parm->getType(), TemplateArgs,
1276                                loc, parm->getDeclName());
1277     }
1278     assert(!type.isNull() && "type substitution failed for param type");
1279     assert(!type->isDependentType() && "param type still dependent");
1280     result = SemaRef.BuildExpressionFromDeclTemplateArgument(arg, type, loc);
1281 
1282     if (!result.isInvalid()) type = result.get()->getType();
1283   } else {
1284     result = SemaRef.BuildExpressionFromIntegralTemplateArgument(arg, loc);
1285 
1286     // Note that this type can be different from the type of 'result',
1287     // e.g. if it's an enum type.
1288     type = arg.getIntegralType();
1289   }
1290   if (result.isInvalid()) return ExprError();
1291 
1292   Expr *resultExpr = result.take();
1293   return SemaRef.Owned(new (SemaRef.Context)
1294                 SubstNonTypeTemplateParmExpr(type,
1295                                              resultExpr->getValueKind(),
1296                                              loc, parm, resultExpr));
1297 }
1298 
1299 ExprResult
1300 TemplateInstantiator::TransformSubstNonTypeTemplateParmPackExpr(
1301                                           SubstNonTypeTemplateParmPackExpr *E) {
1302   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1303     // We aren't expanding the parameter pack, so just return ourselves.
1304     return getSema().Owned(E);
1305   }
1306 
1307   TemplateArgument Arg = E->getArgumentPack();
1308   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1309   return transformNonTypeTemplateParmRef(E->getParameterPack(),
1310                                          E->getParameterPackLocation(),
1311                                          Arg);
1312 }
1313 
1314 ExprResult
1315 TemplateInstantiator::RebuildParmVarDeclRefExpr(ParmVarDecl *PD,
1316                                                 SourceLocation Loc) {
1317   DeclarationNameInfo NameInfo(PD->getDeclName(), Loc);
1318   return getSema().BuildDeclarationNameExpr(CXXScopeSpec(), NameInfo, PD);
1319 }
1320 
1321 ExprResult
1322 TemplateInstantiator::TransformFunctionParmPackExpr(FunctionParmPackExpr *E) {
1323   if (getSema().ArgumentPackSubstitutionIndex != -1) {
1324     // We can expand this parameter pack now.
1325     ParmVarDecl *D = E->getExpansion(getSema().ArgumentPackSubstitutionIndex);
1326     ValueDecl *VD = cast_or_null<ValueDecl>(TransformDecl(E->getExprLoc(), D));
1327     if (!VD)
1328       return ExprError();
1329     return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(VD), E->getExprLoc());
1330   }
1331 
1332   QualType T = TransformType(E->getType());
1333   if (T.isNull())
1334     return ExprError();
1335 
1336   // Transform each of the parameter expansions into the corresponding
1337   // parameters in the instantiation of the function decl.
1338   SmallVector<Decl *, 8> Parms;
1339   Parms.reserve(E->getNumExpansions());
1340   for (FunctionParmPackExpr::iterator I = E->begin(), End = E->end();
1341        I != End; ++I) {
1342     ParmVarDecl *D =
1343         cast_or_null<ParmVarDecl>(TransformDecl(E->getExprLoc(), *I));
1344     if (!D)
1345       return ExprError();
1346     Parms.push_back(D);
1347   }
1348 
1349   return FunctionParmPackExpr::Create(getSema().Context, T,
1350                                       E->getParameterPack(),
1351                                       E->getParameterPackLocation(), Parms);
1352 }
1353 
1354 ExprResult
1355 TemplateInstantiator::TransformFunctionParmPackRefExpr(DeclRefExpr *E,
1356                                                        ParmVarDecl *PD) {
1357   typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
1358   llvm::PointerUnion<Decl *, DeclArgumentPack *> *Found
1359     = getSema().CurrentInstantiationScope->findInstantiationOf(PD);
1360   assert(Found && "no instantiation for parameter pack");
1361 
1362   Decl *TransformedDecl;
1363   if (DeclArgumentPack *Pack = Found->dyn_cast<DeclArgumentPack *>()) {
1364     // If this is a reference to a function parameter pack which we can substitute
1365     // but can't yet expand, build a FunctionParmPackExpr for it.
1366     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1367       QualType T = TransformType(E->getType());
1368       if (T.isNull())
1369         return ExprError();
1370       return FunctionParmPackExpr::Create(getSema().Context, T, PD,
1371                                           E->getExprLoc(), *Pack);
1372     }
1373 
1374     TransformedDecl = (*Pack)[getSema().ArgumentPackSubstitutionIndex];
1375   } else {
1376     TransformedDecl = Found->get<Decl*>();
1377   }
1378 
1379   // We have either an unexpanded pack or a specific expansion.
1380   return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(TransformedDecl),
1381                                    E->getExprLoc());
1382 }
1383 
1384 ExprResult
1385 TemplateInstantiator::TransformDeclRefExpr(DeclRefExpr *E) {
1386   NamedDecl *D = E->getDecl();
1387 
1388   // Handle references to non-type template parameters and non-type template
1389   // parameter packs.
1390   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D)) {
1391     if (NTTP->getDepth() < TemplateArgs.getNumLevels())
1392       return TransformTemplateParmRefExpr(E, NTTP);
1393 
1394     // We have a non-type template parameter that isn't fully substituted;
1395     // FindInstantiatedDecl will find it in the local instantiation scope.
1396   }
1397 
1398   // Handle references to function parameter packs.
1399   if (ParmVarDecl *PD = dyn_cast<ParmVarDecl>(D))
1400     if (PD->isParameterPack())
1401       return TransformFunctionParmPackRefExpr(E, PD);
1402 
1403   return TreeTransform<TemplateInstantiator>::TransformDeclRefExpr(E);
1404 }
1405 
1406 ExprResult TemplateInstantiator::TransformCXXDefaultArgExpr(
1407     CXXDefaultArgExpr *E) {
1408   assert(!cast<FunctionDecl>(E->getParam()->getDeclContext())->
1409              getDescribedFunctionTemplate() &&
1410          "Default arg expressions are never formed in dependent cases.");
1411   return SemaRef.BuildCXXDefaultArgExpr(E->getUsedLocation(),
1412                            cast<FunctionDecl>(E->getParam()->getDeclContext()),
1413                                         E->getParam());
1414 }
1415 
1416 QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
1417                                                       FunctionProtoTypeLoc TL) {
1418   // We need a local instantiation scope for this function prototype.
1419   LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
1420   return inherited::TransformFunctionProtoType(TLB, TL);
1421 }
1422 
1423 QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
1424                                  FunctionProtoTypeLoc TL,
1425                                  CXXRecordDecl *ThisContext,
1426                                  unsigned ThisTypeQuals) {
1427   // We need a local instantiation scope for this function prototype.
1428   LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
1429   return inherited::TransformFunctionProtoType(TLB, TL, ThisContext,
1430                                                ThisTypeQuals);
1431 }
1432 
1433 ParmVarDecl *
1434 TemplateInstantiator::TransformFunctionTypeParam(ParmVarDecl *OldParm,
1435                                                  int indexAdjustment,
1436                                                Optional<unsigned> NumExpansions,
1437                                                  bool ExpectParameterPack) {
1438   return SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
1439                                   NumExpansions, ExpectParameterPack);
1440 }
1441 
1442 QualType
1443 TemplateInstantiator::TransformTemplateTypeParmType(TypeLocBuilder &TLB,
1444                                                 TemplateTypeParmTypeLoc TL) {
1445   const TemplateTypeParmType *T = TL.getTypePtr();
1446   if (T->getDepth() < TemplateArgs.getNumLevels()) {
1447     // Replace the template type parameter with its corresponding
1448     // template argument.
1449 
1450     // If the corresponding template argument is NULL or doesn't exist, it's
1451     // because we are performing instantiation from explicitly-specified
1452     // template arguments in a function template class, but there were some
1453     // arguments left unspecified.
1454     if (!TemplateArgs.hasTemplateArgument(T->getDepth(), T->getIndex())) {
1455       TemplateTypeParmTypeLoc NewTL
1456         = TLB.push<TemplateTypeParmTypeLoc>(TL.getType());
1457       NewTL.setNameLoc(TL.getNameLoc());
1458       return TL.getType();
1459     }
1460 
1461     TemplateArgument Arg = TemplateArgs(T->getDepth(), T->getIndex());
1462 
1463     if (T->isParameterPack()) {
1464       assert(Arg.getKind() == TemplateArgument::Pack &&
1465              "Missing argument pack");
1466 
1467       if (getSema().ArgumentPackSubstitutionIndex == -1) {
1468         // We have the template argument pack, but we're not expanding the
1469         // enclosing pack expansion yet. Just save the template argument
1470         // pack for later substitution.
1471         QualType Result
1472           = getSema().Context.getSubstTemplateTypeParmPackType(T, Arg);
1473         SubstTemplateTypeParmPackTypeLoc NewTL
1474           = TLB.push<SubstTemplateTypeParmPackTypeLoc>(Result);
1475         NewTL.setNameLoc(TL.getNameLoc());
1476         return Result;
1477       }
1478 
1479       Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1480     }
1481 
1482     assert(Arg.getKind() == TemplateArgument::Type &&
1483            "Template argument kind mismatch");
1484 
1485     QualType Replacement = Arg.getAsType();
1486 
1487     // TODO: only do this uniquing once, at the start of instantiation.
1488     QualType Result
1489       = getSema().Context.getSubstTemplateTypeParmType(T, Replacement);
1490     SubstTemplateTypeParmTypeLoc NewTL
1491       = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1492     NewTL.setNameLoc(TL.getNameLoc());
1493     return Result;
1494   }
1495 
1496   // The template type parameter comes from an inner template (e.g.,
1497   // the template parameter list of a member template inside the
1498   // template we are instantiating). Create a new template type
1499   // parameter with the template "level" reduced by one.
1500   TemplateTypeParmDecl *NewTTPDecl = 0;
1501   if (TemplateTypeParmDecl *OldTTPDecl = T->getDecl())
1502     NewTTPDecl = cast_or_null<TemplateTypeParmDecl>(
1503                                   TransformDecl(TL.getNameLoc(), OldTTPDecl));
1504 
1505   QualType Result
1506     = getSema().Context.getTemplateTypeParmType(T->getDepth()
1507                                                  - TemplateArgs.getNumLevels(),
1508                                                 T->getIndex(),
1509                                                 T->isParameterPack(),
1510                                                 NewTTPDecl);
1511   TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
1512   NewTL.setNameLoc(TL.getNameLoc());
1513   return Result;
1514 }
1515 
1516 QualType
1517 TemplateInstantiator::TransformSubstTemplateTypeParmPackType(
1518                                                             TypeLocBuilder &TLB,
1519                                          SubstTemplateTypeParmPackTypeLoc TL) {
1520   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1521     // We aren't expanding the parameter pack, so just return ourselves.
1522     SubstTemplateTypeParmPackTypeLoc NewTL
1523       = TLB.push<SubstTemplateTypeParmPackTypeLoc>(TL.getType());
1524     NewTL.setNameLoc(TL.getNameLoc());
1525     return TL.getType();
1526   }
1527 
1528   TemplateArgument Arg = TL.getTypePtr()->getArgumentPack();
1529   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1530   QualType Result = Arg.getAsType();
1531 
1532   Result = getSema().Context.getSubstTemplateTypeParmType(
1533                                       TL.getTypePtr()->getReplacedParameter(),
1534                                                           Result);
1535   SubstTemplateTypeParmTypeLoc NewTL
1536     = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1537   NewTL.setNameLoc(TL.getNameLoc());
1538   return Result;
1539 }
1540 
1541 /// \brief Perform substitution on the type T with a given set of template
1542 /// arguments.
1543 ///
1544 /// This routine substitutes the given template arguments into the
1545 /// type T and produces the instantiated type.
1546 ///
1547 /// \param T the type into which the template arguments will be
1548 /// substituted. If this type is not dependent, it will be returned
1549 /// immediately.
1550 ///
1551 /// \param Args the template arguments that will be
1552 /// substituted for the top-level template parameters within T.
1553 ///
1554 /// \param Loc the location in the source code where this substitution
1555 /// is being performed. It will typically be the location of the
1556 /// declarator (if we're instantiating the type of some declaration)
1557 /// or the location of the type in the source code (if, e.g., we're
1558 /// instantiating the type of a cast expression).
1559 ///
1560 /// \param Entity the name of the entity associated with a declaration
1561 /// being instantiated (if any). May be empty to indicate that there
1562 /// is no such entity (if, e.g., this is a type that occurs as part of
1563 /// a cast expression) or that the entity has no name (e.g., an
1564 /// unnamed function parameter).
1565 ///
1566 /// \returns If the instantiation succeeds, the instantiated
1567 /// type. Otherwise, produces diagnostics and returns a NULL type.
1568 TypeSourceInfo *Sema::SubstType(TypeSourceInfo *T,
1569                                 const MultiLevelTemplateArgumentList &Args,
1570                                 SourceLocation Loc,
1571                                 DeclarationName Entity) {
1572   assert(!ActiveTemplateInstantiations.empty() &&
1573          "Cannot perform an instantiation without some context on the "
1574          "instantiation stack");
1575 
1576   if (!T->getType()->isInstantiationDependentType() &&
1577       !T->getType()->isVariablyModifiedType())
1578     return T;
1579 
1580   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1581   return Instantiator.TransformType(T);
1582 }
1583 
1584 TypeSourceInfo *Sema::SubstType(TypeLoc TL,
1585                                 const MultiLevelTemplateArgumentList &Args,
1586                                 SourceLocation Loc,
1587                                 DeclarationName Entity) {
1588   assert(!ActiveTemplateInstantiations.empty() &&
1589          "Cannot perform an instantiation without some context on the "
1590          "instantiation stack");
1591 
1592   if (TL.getType().isNull())
1593     return 0;
1594 
1595   if (!TL.getType()->isInstantiationDependentType() &&
1596       !TL.getType()->isVariablyModifiedType()) {
1597     // FIXME: Make a copy of the TypeLoc data here, so that we can
1598     // return a new TypeSourceInfo. Inefficient!
1599     TypeLocBuilder TLB;
1600     TLB.pushFullCopy(TL);
1601     return TLB.getTypeSourceInfo(Context, TL.getType());
1602   }
1603 
1604   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1605   TypeLocBuilder TLB;
1606   TLB.reserve(TL.getFullDataSize());
1607   QualType Result = Instantiator.TransformType(TLB, TL);
1608   if (Result.isNull())
1609     return 0;
1610 
1611   return TLB.getTypeSourceInfo(Context, Result);
1612 }
1613 
1614 /// Deprecated form of the above.
1615 QualType Sema::SubstType(QualType T,
1616                          const MultiLevelTemplateArgumentList &TemplateArgs,
1617                          SourceLocation Loc, DeclarationName Entity) {
1618   assert(!ActiveTemplateInstantiations.empty() &&
1619          "Cannot perform an instantiation without some context on the "
1620          "instantiation stack");
1621 
1622   // If T is not a dependent type or a variably-modified type, there
1623   // is nothing to do.
1624   if (!T->isInstantiationDependentType() && !T->isVariablyModifiedType())
1625     return T;
1626 
1627   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc, Entity);
1628   return Instantiator.TransformType(T);
1629 }
1630 
1631 static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
1632   if (T->getType()->isInstantiationDependentType() ||
1633       T->getType()->isVariablyModifiedType())
1634     return true;
1635 
1636   TypeLoc TL = T->getTypeLoc().IgnoreParens();
1637   if (!TL.getAs<FunctionProtoTypeLoc>())
1638     return false;
1639 
1640   FunctionProtoTypeLoc FP = TL.castAs<FunctionProtoTypeLoc>();
1641   for (unsigned I = 0, E = FP.getNumParams(); I != E; ++I) {
1642     ParmVarDecl *P = FP.getParam(I);
1643 
1644     // This must be synthesized from a typedef.
1645     if (!P) continue;
1646 
1647     // The parameter's type as written might be dependent even if the
1648     // decayed type was not dependent.
1649     if (TypeSourceInfo *TSInfo = P->getTypeSourceInfo())
1650       if (TSInfo->getType()->isInstantiationDependentType())
1651         return true;
1652 
1653     // TODO: currently we always rebuild expressions.  When we
1654     // properly get lazier about this, we should use the same
1655     // logic to avoid rebuilding prototypes here.
1656     if (P->hasDefaultArg())
1657       return true;
1658   }
1659 
1660   return false;
1661 }
1662 
1663 /// A form of SubstType intended specifically for instantiating the
1664 /// type of a FunctionDecl.  Its purpose is solely to force the
1665 /// instantiation of default-argument expressions.
1666 TypeSourceInfo *Sema::SubstFunctionDeclType(TypeSourceInfo *T,
1667                                 const MultiLevelTemplateArgumentList &Args,
1668                                 SourceLocation Loc,
1669                                 DeclarationName Entity,
1670                                 CXXRecordDecl *ThisContext,
1671                                 unsigned ThisTypeQuals) {
1672   assert(!ActiveTemplateInstantiations.empty() &&
1673          "Cannot perform an instantiation without some context on the "
1674          "instantiation stack");
1675 
1676   if (!NeedsInstantiationAsFunctionType(T))
1677     return T;
1678 
1679   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1680 
1681   TypeLocBuilder TLB;
1682 
1683   TypeLoc TL = T->getTypeLoc();
1684   TLB.reserve(TL.getFullDataSize());
1685 
1686   QualType Result;
1687 
1688   if (FunctionProtoTypeLoc Proto = TL.getAs<FunctionProtoTypeLoc>()) {
1689     Result = Instantiator.TransformFunctionProtoType(TLB, Proto, ThisContext,
1690                                                      ThisTypeQuals);
1691   } else {
1692     Result = Instantiator.TransformType(TLB, TL);
1693   }
1694   if (Result.isNull())
1695     return 0;
1696 
1697   return TLB.getTypeSourceInfo(Context, Result);
1698 }
1699 
1700 ParmVarDecl *Sema::SubstParmVarDecl(ParmVarDecl *OldParm,
1701                             const MultiLevelTemplateArgumentList &TemplateArgs,
1702                                     int indexAdjustment,
1703                                     Optional<unsigned> NumExpansions,
1704                                     bool ExpectParameterPack) {
1705   TypeSourceInfo *OldDI = OldParm->getTypeSourceInfo();
1706   TypeSourceInfo *NewDI = 0;
1707 
1708   TypeLoc OldTL = OldDI->getTypeLoc();
1709   if (PackExpansionTypeLoc ExpansionTL = OldTL.getAs<PackExpansionTypeLoc>()) {
1710 
1711     // We have a function parameter pack. Substitute into the pattern of the
1712     // expansion.
1713     NewDI = SubstType(ExpansionTL.getPatternLoc(), TemplateArgs,
1714                       OldParm->getLocation(), OldParm->getDeclName());
1715     if (!NewDI)
1716       return 0;
1717 
1718     if (NewDI->getType()->containsUnexpandedParameterPack()) {
1719       // We still have unexpanded parameter packs, which means that
1720       // our function parameter is still a function parameter pack.
1721       // Therefore, make its type a pack expansion type.
1722       NewDI = CheckPackExpansion(NewDI, ExpansionTL.getEllipsisLoc(),
1723                                  NumExpansions);
1724     } else if (ExpectParameterPack) {
1725       // We expected to get a parameter pack but didn't (because the type
1726       // itself is not a pack expansion type), so complain. This can occur when
1727       // the substitution goes through an alias template that "loses" the
1728       // pack expansion.
1729       Diag(OldParm->getLocation(),
1730            diag::err_function_parameter_pack_without_parameter_packs)
1731         << NewDI->getType();
1732       return 0;
1733     }
1734   } else {
1735     NewDI = SubstType(OldDI, TemplateArgs, OldParm->getLocation(),
1736                       OldParm->getDeclName());
1737   }
1738 
1739   if (!NewDI)
1740     return 0;
1741 
1742   if (NewDI->getType()->isVoidType()) {
1743     Diag(OldParm->getLocation(), diag::err_param_with_void_type);
1744     return 0;
1745   }
1746 
1747   ParmVarDecl *NewParm = CheckParameter(Context.getTranslationUnitDecl(),
1748                                         OldParm->getInnerLocStart(),
1749                                         OldParm->getLocation(),
1750                                         OldParm->getIdentifier(),
1751                                         NewDI->getType(), NewDI,
1752                                         OldParm->getStorageClass());
1753   if (!NewParm)
1754     return 0;
1755 
1756   // Mark the (new) default argument as uninstantiated (if any).
1757   if (OldParm->hasUninstantiatedDefaultArg()) {
1758     Expr *Arg = OldParm->getUninstantiatedDefaultArg();
1759     NewParm->setUninstantiatedDefaultArg(Arg);
1760   } else if (OldParm->hasUnparsedDefaultArg()) {
1761     NewParm->setUnparsedDefaultArg();
1762     UnparsedDefaultArgInstantiations[OldParm].push_back(NewParm);
1763   } else if (Expr *Arg = OldParm->getDefaultArg())
1764     // FIXME: if we non-lazily instantiated non-dependent default args for
1765     // non-dependent parameter types we could remove a bunch of duplicate
1766     // conversion warnings for such arguments.
1767     NewParm->setUninstantiatedDefaultArg(Arg);
1768 
1769   NewParm->setHasInheritedDefaultArg(OldParm->hasInheritedDefaultArg());
1770 
1771   if (OldParm->isParameterPack() && !NewParm->isParameterPack()) {
1772     // Add the new parameter to the instantiated parameter pack.
1773     CurrentInstantiationScope->InstantiatedLocalPackArg(OldParm, NewParm);
1774   } else {
1775     // Introduce an Old -> New mapping
1776     CurrentInstantiationScope->InstantiatedLocal(OldParm, NewParm);
1777   }
1778 
1779   // FIXME: OldParm may come from a FunctionProtoType, in which case CurContext
1780   // can be anything, is this right ?
1781   NewParm->setDeclContext(CurContext);
1782 
1783   NewParm->setScopeInfo(OldParm->getFunctionScopeDepth(),
1784                         OldParm->getFunctionScopeIndex() + indexAdjustment);
1785 
1786   InstantiateAttrs(TemplateArgs, OldParm, NewParm);
1787 
1788   return NewParm;
1789 }
1790 
1791 /// \brief Substitute the given template arguments into the given set of
1792 /// parameters, producing the set of parameter types that would be generated
1793 /// from such a substitution.
1794 bool Sema::SubstParmTypes(SourceLocation Loc,
1795                           ParmVarDecl **Params, unsigned NumParams,
1796                           const MultiLevelTemplateArgumentList &TemplateArgs,
1797                           SmallVectorImpl<QualType> &ParamTypes,
1798                           SmallVectorImpl<ParmVarDecl *> *OutParams) {
1799   assert(!ActiveTemplateInstantiations.empty() &&
1800          "Cannot perform an instantiation without some context on the "
1801          "instantiation stack");
1802 
1803   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
1804                                     DeclarationName());
1805   return Instantiator.TransformFunctionTypeParams(Loc, Params, NumParams, 0,
1806                                                   ParamTypes, OutParams);
1807 }
1808 
1809 /// \brief Perform substitution on the base class specifiers of the
1810 /// given class template specialization.
1811 ///
1812 /// Produces a diagnostic and returns true on error, returns false and
1813 /// attaches the instantiated base classes to the class template
1814 /// specialization if successful.
1815 bool
1816 Sema::SubstBaseSpecifiers(CXXRecordDecl *Instantiation,
1817                           CXXRecordDecl *Pattern,
1818                           const MultiLevelTemplateArgumentList &TemplateArgs) {
1819   bool Invalid = false;
1820   SmallVector<CXXBaseSpecifier*, 4> InstantiatedBases;
1821   for (ClassTemplateSpecializationDecl::base_class_iterator
1822          Base = Pattern->bases_begin(), BaseEnd = Pattern->bases_end();
1823        Base != BaseEnd; ++Base) {
1824     if (!Base->getType()->isDependentType()) {
1825       if (const CXXRecordDecl *RD = Base->getType()->getAsCXXRecordDecl()) {
1826         if (RD->isInvalidDecl())
1827           Instantiation->setInvalidDecl();
1828       }
1829       InstantiatedBases.push_back(new (Context) CXXBaseSpecifier(*Base));
1830       continue;
1831     }
1832 
1833     SourceLocation EllipsisLoc;
1834     TypeSourceInfo *BaseTypeLoc;
1835     if (Base->isPackExpansion()) {
1836       // This is a pack expansion. See whether we should expand it now, or
1837       // wait until later.
1838       SmallVector<UnexpandedParameterPack, 2> Unexpanded;
1839       collectUnexpandedParameterPacks(Base->getTypeSourceInfo()->getTypeLoc(),
1840                                       Unexpanded);
1841       bool ShouldExpand = false;
1842       bool RetainExpansion = false;
1843       Optional<unsigned> NumExpansions;
1844       if (CheckParameterPacksForExpansion(Base->getEllipsisLoc(),
1845                                           Base->getSourceRange(),
1846                                           Unexpanded,
1847                                           TemplateArgs, ShouldExpand,
1848                                           RetainExpansion,
1849                                           NumExpansions)) {
1850         Invalid = true;
1851         continue;
1852       }
1853 
1854       // If we should expand this pack expansion now, do so.
1855       if (ShouldExpand) {
1856         for (unsigned I = 0; I != *NumExpansions; ++I) {
1857             Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, I);
1858 
1859           TypeSourceInfo *BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1860                                                   TemplateArgs,
1861                                               Base->getSourceRange().getBegin(),
1862                                                   DeclarationName());
1863           if (!BaseTypeLoc) {
1864             Invalid = true;
1865             continue;
1866           }
1867 
1868           if (CXXBaseSpecifier *InstantiatedBase
1869                 = CheckBaseSpecifier(Instantiation,
1870                                      Base->getSourceRange(),
1871                                      Base->isVirtual(),
1872                                      Base->getAccessSpecifierAsWritten(),
1873                                      BaseTypeLoc,
1874                                      SourceLocation()))
1875             InstantiatedBases.push_back(InstantiatedBase);
1876           else
1877             Invalid = true;
1878         }
1879 
1880         continue;
1881       }
1882 
1883       // The resulting base specifier will (still) be a pack expansion.
1884       EllipsisLoc = Base->getEllipsisLoc();
1885       Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
1886       BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1887                               TemplateArgs,
1888                               Base->getSourceRange().getBegin(),
1889                               DeclarationName());
1890     } else {
1891       BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1892                               TemplateArgs,
1893                               Base->getSourceRange().getBegin(),
1894                               DeclarationName());
1895     }
1896 
1897     if (!BaseTypeLoc) {
1898       Invalid = true;
1899       continue;
1900     }
1901 
1902     if (CXXBaseSpecifier *InstantiatedBase
1903           = CheckBaseSpecifier(Instantiation,
1904                                Base->getSourceRange(),
1905                                Base->isVirtual(),
1906                                Base->getAccessSpecifierAsWritten(),
1907                                BaseTypeLoc,
1908                                EllipsisLoc))
1909       InstantiatedBases.push_back(InstantiatedBase);
1910     else
1911       Invalid = true;
1912   }
1913 
1914   if (!Invalid &&
1915       AttachBaseSpecifiers(Instantiation, InstantiatedBases.data(),
1916                            InstantiatedBases.size()))
1917     Invalid = true;
1918 
1919   return Invalid;
1920 }
1921 
1922 // Defined via #include from SemaTemplateInstantiateDecl.cpp
1923 namespace clang {
1924   namespace sema {
1925     Attr *instantiateTemplateAttribute(const Attr *At, ASTContext &C, Sema &S,
1926                             const MultiLevelTemplateArgumentList &TemplateArgs);
1927   }
1928 }
1929 
1930 /// Determine whether we would be unable to instantiate this template (because
1931 /// it either has no definition, or is in the process of being instantiated).
1932 static bool DiagnoseUninstantiableTemplate(Sema &S,
1933                                            SourceLocation PointOfInstantiation,
1934                                            TagDecl *Instantiation,
1935                                            bool InstantiatedFromMember,
1936                                            TagDecl *Pattern,
1937                                            TagDecl *PatternDef,
1938                                            TemplateSpecializationKind TSK,
1939                                            bool Complain = true) {
1940   if (PatternDef && !PatternDef->isBeingDefined())
1941     return false;
1942 
1943   if (!Complain || (PatternDef && PatternDef->isInvalidDecl())) {
1944     // Say nothing
1945   } else if (PatternDef) {
1946     assert(PatternDef->isBeingDefined());
1947     S.Diag(PointOfInstantiation,
1948            diag::err_template_instantiate_within_definition)
1949       << (TSK != TSK_ImplicitInstantiation)
1950       << S.Context.getTypeDeclType(Instantiation);
1951     // Not much point in noting the template declaration here, since
1952     // we're lexically inside it.
1953     Instantiation->setInvalidDecl();
1954   } else if (InstantiatedFromMember) {
1955     S.Diag(PointOfInstantiation,
1956            diag::err_implicit_instantiate_member_undefined)
1957       << S.Context.getTypeDeclType(Instantiation);
1958     S.Diag(Pattern->getLocation(), diag::note_member_of_template_here);
1959   } else {
1960     S.Diag(PointOfInstantiation, diag::err_template_instantiate_undefined)
1961       << (TSK != TSK_ImplicitInstantiation)
1962       << S.Context.getTypeDeclType(Instantiation);
1963     S.Diag(Pattern->getLocation(), diag::note_template_decl_here);
1964   }
1965 
1966   // In general, Instantiation isn't marked invalid to get more than one
1967   // error for multiple undefined instantiations. But the code that does
1968   // explicit declaration -> explicit definition conversion can't handle
1969   // invalid declarations, so mark as invalid in that case.
1970   if (TSK == TSK_ExplicitInstantiationDeclaration)
1971     Instantiation->setInvalidDecl();
1972   return true;
1973 }
1974 
1975 /// \brief Instantiate the definition of a class from a given pattern.
1976 ///
1977 /// \param PointOfInstantiation The point of instantiation within the
1978 /// source code.
1979 ///
1980 /// \param Instantiation is the declaration whose definition is being
1981 /// instantiated. This will be either a class template specialization
1982 /// or a member class of a class template specialization.
1983 ///
1984 /// \param Pattern is the pattern from which the instantiation
1985 /// occurs. This will be either the declaration of a class template or
1986 /// the declaration of a member class of a class template.
1987 ///
1988 /// \param TemplateArgs The template arguments to be substituted into
1989 /// the pattern.
1990 ///
1991 /// \param TSK the kind of implicit or explicit instantiation to perform.
1992 ///
1993 /// \param Complain whether to complain if the class cannot be instantiated due
1994 /// to the lack of a definition.
1995 ///
1996 /// \returns true if an error occurred, false otherwise.
1997 bool
1998 Sema::InstantiateClass(SourceLocation PointOfInstantiation,
1999                        CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
2000                        const MultiLevelTemplateArgumentList &TemplateArgs,
2001                        TemplateSpecializationKind TSK,
2002                        bool Complain) {
2003   CXXRecordDecl *PatternDef
2004     = cast_or_null<CXXRecordDecl>(Pattern->getDefinition());
2005   if (DiagnoseUninstantiableTemplate(*this, PointOfInstantiation, Instantiation,
2006                                 Instantiation->getInstantiatedFromMemberClass(),
2007                                      Pattern, PatternDef, TSK, Complain))
2008     return true;
2009   Pattern = PatternDef;
2010 
2011   // \brief Record the point of instantiation.
2012   if (MemberSpecializationInfo *MSInfo
2013         = Instantiation->getMemberSpecializationInfo()) {
2014     MSInfo->setTemplateSpecializationKind(TSK);
2015     MSInfo->setPointOfInstantiation(PointOfInstantiation);
2016   } else if (ClassTemplateSpecializationDecl *Spec
2017         = dyn_cast<ClassTemplateSpecializationDecl>(Instantiation)) {
2018     Spec->setTemplateSpecializationKind(TSK);
2019     Spec->setPointOfInstantiation(PointOfInstantiation);
2020   }
2021 
2022   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2023   if (Inst.isInvalid())
2024     return true;
2025 
2026   // Enter the scope of this instantiation. We don't use
2027   // PushDeclContext because we don't have a scope.
2028   ContextRAII SavedContext(*this, Instantiation);
2029   EnterExpressionEvaluationContext EvalContext(*this,
2030                                                Sema::PotentiallyEvaluated);
2031 
2032   // If this is an instantiation of a local class, merge this local
2033   // instantiation scope with the enclosing scope. Otherwise, every
2034   // instantiation of a class has its own local instantiation scope.
2035   bool MergeWithParentScope = !Instantiation->isDefinedOutsideFunctionOrMethod();
2036   LocalInstantiationScope Scope(*this, MergeWithParentScope);
2037 
2038   // Pull attributes from the pattern onto the instantiation.
2039   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
2040 
2041   // Start the definition of this instantiation.
2042   Instantiation->startDefinition();
2043 
2044   Instantiation->setTagKind(Pattern->getTagKind());
2045 
2046   // Do substitution on the base class specifiers.
2047   if (SubstBaseSpecifiers(Instantiation, Pattern, TemplateArgs))
2048     Instantiation->setInvalidDecl();
2049 
2050   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
2051   SmallVector<Decl*, 4> Fields;
2052   SmallVector<std::pair<FieldDecl*, FieldDecl*>, 4>
2053     FieldsWithMemberInitializers;
2054   // Delay instantiation of late parsed attributes.
2055   LateInstantiatedAttrVec LateAttrs;
2056   Instantiator.enableLateAttributeInstantiation(&LateAttrs);
2057 
2058   for (RecordDecl::decl_iterator Member = Pattern->decls_begin(),
2059          MemberEnd = Pattern->decls_end();
2060        Member != MemberEnd; ++Member) {
2061     // Don't instantiate members not belonging in this semantic context.
2062     // e.g. for:
2063     // @code
2064     //    template <int i> class A {
2065     //      class B *g;
2066     //    };
2067     // @endcode
2068     // 'class B' has the template as lexical context but semantically it is
2069     // introduced in namespace scope.
2070     if ((*Member)->getDeclContext() != Pattern)
2071       continue;
2072 
2073     if ((*Member)->isInvalidDecl()) {
2074       Instantiation->setInvalidDecl();
2075       continue;
2076     }
2077 
2078     Decl *NewMember = Instantiator.Visit(*Member);
2079     if (NewMember) {
2080       if (FieldDecl *Field = dyn_cast<FieldDecl>(NewMember)) {
2081         Fields.push_back(Field);
2082         FieldDecl *OldField = cast<FieldDecl>(*Member);
2083         if (OldField->getInClassInitializer())
2084           FieldsWithMemberInitializers.push_back(std::make_pair(OldField,
2085                                                                 Field));
2086       } else if (EnumDecl *Enum = dyn_cast<EnumDecl>(NewMember)) {
2087         // C++11 [temp.inst]p1: The implicit instantiation of a class template
2088         // specialization causes the implicit instantiation of the definitions
2089         // of unscoped member enumerations.
2090         // Record a point of instantiation for this implicit instantiation.
2091         if (TSK == TSK_ImplicitInstantiation && !Enum->isScoped() &&
2092             Enum->isCompleteDefinition()) {
2093           MemberSpecializationInfo *MSInfo =Enum->getMemberSpecializationInfo();
2094           assert(MSInfo && "no spec info for member enum specialization");
2095           MSInfo->setTemplateSpecializationKind(TSK_ImplicitInstantiation);
2096           MSInfo->setPointOfInstantiation(PointOfInstantiation);
2097         }
2098       } else if (StaticAssertDecl *SA = dyn_cast<StaticAssertDecl>(NewMember)) {
2099         if (SA->isFailed()) {
2100           // A static_assert failed. Bail out; instantiating this
2101           // class is probably not meaningful.
2102           Instantiation->setInvalidDecl();
2103           break;
2104         }
2105       }
2106 
2107       if (NewMember->isInvalidDecl())
2108         Instantiation->setInvalidDecl();
2109     } else {
2110       // FIXME: Eventually, a NULL return will mean that one of the
2111       // instantiations was a semantic disaster, and we'll want to mark the
2112       // declaration invalid.
2113       // For now, we expect to skip some members that we can't yet handle.
2114     }
2115   }
2116 
2117   // Finish checking fields.
2118   ActOnFields(0, Instantiation->getLocation(), Instantiation, Fields,
2119               SourceLocation(), SourceLocation(), 0);
2120   CheckCompletedCXXClass(Instantiation);
2121 
2122   // Attach any in-class member initializers now the class is complete.
2123   // FIXME: We are supposed to defer instantiating these until they are needed.
2124   if (!FieldsWithMemberInitializers.empty()) {
2125     // C++11 [expr.prim.general]p4:
2126     //   Otherwise, if a member-declarator declares a non-static data member
2127     //  (9.2) of a class X, the expression this is a prvalue of type "pointer
2128     //  to X" within the optional brace-or-equal-initializer. It shall not
2129     //  appear elsewhere in the member-declarator.
2130     CXXThisScopeRAII ThisScope(*this, Instantiation, (unsigned)0);
2131 
2132     for (unsigned I = 0, N = FieldsWithMemberInitializers.size(); I != N; ++I) {
2133       FieldDecl *OldField = FieldsWithMemberInitializers[I].first;
2134       FieldDecl *NewField = FieldsWithMemberInitializers[I].second;
2135       Expr *OldInit = OldField->getInClassInitializer();
2136 
2137       ActOnStartCXXInClassMemberInitializer();
2138       ExprResult NewInit = SubstInitializer(OldInit, TemplateArgs,
2139                                             /*CXXDirectInit=*/false);
2140       Expr *Init = NewInit.take();
2141       assert((!Init || !isa<ParenListExpr>(Init)) &&
2142              "call-style init in class");
2143       ActOnFinishCXXInClassMemberInitializer(NewField, Init->getLocStart(),
2144                                              Init);
2145     }
2146   }
2147   // Instantiate late parsed attributes, and attach them to their decls.
2148   // See Sema::InstantiateAttrs
2149   for (LateInstantiatedAttrVec::iterator I = LateAttrs.begin(),
2150        E = LateAttrs.end(); I != E; ++I) {
2151     assert(CurrentInstantiationScope == Instantiator.getStartingScope());
2152     CurrentInstantiationScope = I->Scope;
2153 
2154     // Allow 'this' within late-parsed attributes.
2155     NamedDecl *ND = dyn_cast<NamedDecl>(I->NewDecl);
2156     CXXRecordDecl *ThisContext =
2157         dyn_cast_or_null<CXXRecordDecl>(ND->getDeclContext());
2158     CXXThisScopeRAII ThisScope(*this, ThisContext, /*TypeQuals*/0,
2159                                ND && ND->isCXXInstanceMember());
2160 
2161     Attr *NewAttr =
2162       instantiateTemplateAttribute(I->TmplAttr, Context, *this, TemplateArgs);
2163     I->NewDecl->addAttr(NewAttr);
2164     LocalInstantiationScope::deleteScopes(I->Scope,
2165                                           Instantiator.getStartingScope());
2166   }
2167   Instantiator.disableLateAttributeInstantiation();
2168   LateAttrs.clear();
2169 
2170   ActOnFinishDelayedMemberInitializers(Instantiation);
2171 
2172   if (TSK == TSK_ImplicitInstantiation) {
2173     Instantiation->setLocation(Pattern->getLocation());
2174     Instantiation->setLocStart(Pattern->getInnerLocStart());
2175     Instantiation->setRBraceLoc(Pattern->getRBraceLoc());
2176   }
2177 
2178   if (!Instantiation->isInvalidDecl()) {
2179     // Perform any dependent diagnostics from the pattern.
2180     PerformDependentDiagnostics(Pattern, TemplateArgs);
2181 
2182     // Instantiate any out-of-line class template partial
2183     // specializations now.
2184     for (TemplateDeclInstantiator::delayed_partial_spec_iterator
2185               P = Instantiator.delayed_partial_spec_begin(),
2186            PEnd = Instantiator.delayed_partial_spec_end();
2187          P != PEnd; ++P) {
2188       if (!Instantiator.InstantiateClassTemplatePartialSpecialization(
2189               P->first, P->second)) {
2190         Instantiation->setInvalidDecl();
2191         break;
2192       }
2193     }
2194 
2195     // Instantiate any out-of-line variable template partial
2196     // specializations now.
2197     for (TemplateDeclInstantiator::delayed_var_partial_spec_iterator
2198               P = Instantiator.delayed_var_partial_spec_begin(),
2199            PEnd = Instantiator.delayed_var_partial_spec_end();
2200          P != PEnd; ++P) {
2201       if (!Instantiator.InstantiateVarTemplatePartialSpecialization(
2202               P->first, P->second)) {
2203         Instantiation->setInvalidDecl();
2204         break;
2205       }
2206     }
2207   }
2208 
2209   // Exit the scope of this instantiation.
2210   SavedContext.pop();
2211 
2212   if (!Instantiation->isInvalidDecl()) {
2213     Consumer.HandleTagDeclDefinition(Instantiation);
2214 
2215     // Always emit the vtable for an explicit instantiation definition
2216     // of a polymorphic class template specialization.
2217     if (TSK == TSK_ExplicitInstantiationDefinition)
2218       MarkVTableUsed(PointOfInstantiation, Instantiation, true);
2219   }
2220 
2221   return Instantiation->isInvalidDecl();
2222 }
2223 
2224 /// \brief Instantiate the definition of an enum from a given pattern.
2225 ///
2226 /// \param PointOfInstantiation The point of instantiation within the
2227 ///        source code.
2228 /// \param Instantiation is the declaration whose definition is being
2229 ///        instantiated. This will be a member enumeration of a class
2230 ///        temploid specialization, or a local enumeration within a
2231 ///        function temploid specialization.
2232 /// \param Pattern The templated declaration from which the instantiation
2233 ///        occurs.
2234 /// \param TemplateArgs The template arguments to be substituted into
2235 ///        the pattern.
2236 /// \param TSK The kind of implicit or explicit instantiation to perform.
2237 ///
2238 /// \return \c true if an error occurred, \c false otherwise.
2239 bool Sema::InstantiateEnum(SourceLocation PointOfInstantiation,
2240                            EnumDecl *Instantiation, EnumDecl *Pattern,
2241                            const MultiLevelTemplateArgumentList &TemplateArgs,
2242                            TemplateSpecializationKind TSK) {
2243   EnumDecl *PatternDef = Pattern->getDefinition();
2244   if (DiagnoseUninstantiableTemplate(*this, PointOfInstantiation, Instantiation,
2245                                  Instantiation->getInstantiatedFromMemberEnum(),
2246                                      Pattern, PatternDef, TSK,/*Complain*/true))
2247     return true;
2248   Pattern = PatternDef;
2249 
2250   // Record the point of instantiation.
2251   if (MemberSpecializationInfo *MSInfo
2252         = Instantiation->getMemberSpecializationInfo()) {
2253     MSInfo->setTemplateSpecializationKind(TSK);
2254     MSInfo->setPointOfInstantiation(PointOfInstantiation);
2255   }
2256 
2257   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2258   if (Inst.isInvalid())
2259     return true;
2260 
2261   // Enter the scope of this instantiation. We don't use
2262   // PushDeclContext because we don't have a scope.
2263   ContextRAII SavedContext(*this, Instantiation);
2264   EnterExpressionEvaluationContext EvalContext(*this,
2265                                                Sema::PotentiallyEvaluated);
2266 
2267   LocalInstantiationScope Scope(*this, /*MergeWithParentScope*/true);
2268 
2269   // Pull attributes from the pattern onto the instantiation.
2270   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
2271 
2272   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
2273   Instantiator.InstantiateEnumDefinition(Instantiation, Pattern);
2274 
2275   // Exit the scope of this instantiation.
2276   SavedContext.pop();
2277 
2278   return Instantiation->isInvalidDecl();
2279 }
2280 
2281 namespace {
2282   /// \brief A partial specialization whose template arguments have matched
2283   /// a given template-id.
2284   struct PartialSpecMatchResult {
2285     ClassTemplatePartialSpecializationDecl *Partial;
2286     TemplateArgumentList *Args;
2287   };
2288 }
2289 
2290 bool Sema::InstantiateClassTemplateSpecialization(
2291     SourceLocation PointOfInstantiation,
2292     ClassTemplateSpecializationDecl *ClassTemplateSpec,
2293     TemplateSpecializationKind TSK, bool Complain) {
2294   // Perform the actual instantiation on the canonical declaration.
2295   ClassTemplateSpec = cast<ClassTemplateSpecializationDecl>(
2296                                          ClassTemplateSpec->getCanonicalDecl());
2297 
2298   // Check whether we have already instantiated or specialized this class
2299   // template specialization.
2300   if (ClassTemplateSpec->getSpecializationKind() != TSK_Undeclared) {
2301     if (ClassTemplateSpec->getSpecializationKind() ==
2302           TSK_ExplicitInstantiationDeclaration &&
2303         TSK == TSK_ExplicitInstantiationDefinition) {
2304       // An explicit instantiation definition follows an explicit instantiation
2305       // declaration (C++0x [temp.explicit]p10); go ahead and perform the
2306       // explicit instantiation.
2307       ClassTemplateSpec->setSpecializationKind(TSK);
2308 
2309       // If this is an explicit instantiation definition, mark the
2310       // vtable as used.
2311       if (TSK == TSK_ExplicitInstantiationDefinition &&
2312           !ClassTemplateSpec->isInvalidDecl())
2313         MarkVTableUsed(PointOfInstantiation, ClassTemplateSpec, true);
2314 
2315       return false;
2316     }
2317 
2318     // We can only instantiate something that hasn't already been
2319     // instantiated or specialized. Fail without any diagnostics: our
2320     // caller will provide an error message.
2321     return true;
2322   }
2323 
2324   if (ClassTemplateSpec->isInvalidDecl())
2325     return true;
2326 
2327   ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
2328   CXXRecordDecl *Pattern = 0;
2329 
2330   // C++ [temp.class.spec.match]p1:
2331   //   When a class template is used in a context that requires an
2332   //   instantiation of the class, it is necessary to determine
2333   //   whether the instantiation is to be generated using the primary
2334   //   template or one of the partial specializations. This is done by
2335   //   matching the template arguments of the class template
2336   //   specialization with the template argument lists of the partial
2337   //   specializations.
2338   typedef PartialSpecMatchResult MatchResult;
2339   SmallVector<MatchResult, 4> Matched;
2340   SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
2341   Template->getPartialSpecializations(PartialSpecs);
2342   TemplateSpecCandidateSet FailedCandidates(PointOfInstantiation);
2343   for (unsigned I = 0, N = PartialSpecs.size(); I != N; ++I) {
2344     ClassTemplatePartialSpecializationDecl *Partial = PartialSpecs[I];
2345     TemplateDeductionInfo Info(FailedCandidates.getLocation());
2346     if (TemplateDeductionResult Result
2347           = DeduceTemplateArguments(Partial,
2348                                     ClassTemplateSpec->getTemplateArgs(),
2349                                     Info)) {
2350       // Store the failed-deduction information for use in diagnostics, later.
2351       // TODO: Actually use the failed-deduction info?
2352       FailedCandidates.addCandidate()
2353           .set(Partial, MakeDeductionFailureInfo(Context, Result, Info));
2354       (void)Result;
2355     } else {
2356       Matched.push_back(PartialSpecMatchResult());
2357       Matched.back().Partial = Partial;
2358       Matched.back().Args = Info.take();
2359     }
2360   }
2361 
2362   // If we're dealing with a member template where the template parameters
2363   // have been instantiated, this provides the original template parameters
2364   // from which the member template's parameters were instantiated.
2365 
2366   if (Matched.size() >= 1) {
2367     SmallVectorImpl<MatchResult>::iterator Best = Matched.begin();
2368     if (Matched.size() == 1) {
2369       //   -- If exactly one matching specialization is found, the
2370       //      instantiation is generated from that specialization.
2371       // We don't need to do anything for this.
2372     } else {
2373       //   -- If more than one matching specialization is found, the
2374       //      partial order rules (14.5.4.2) are used to determine
2375       //      whether one of the specializations is more specialized
2376       //      than the others. If none of the specializations is more
2377       //      specialized than all of the other matching
2378       //      specializations, then the use of the class template is
2379       //      ambiguous and the program is ill-formed.
2380       for (SmallVectorImpl<MatchResult>::iterator P = Best + 1,
2381                                                PEnd = Matched.end();
2382            P != PEnd; ++P) {
2383         if (getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2384                                                     PointOfInstantiation)
2385               == P->Partial)
2386           Best = P;
2387       }
2388 
2389       // Determine if the best partial specialization is more specialized than
2390       // the others.
2391       bool Ambiguous = false;
2392       for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2393                                                PEnd = Matched.end();
2394            P != PEnd; ++P) {
2395         if (P != Best &&
2396             getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2397                                                     PointOfInstantiation)
2398               != Best->Partial) {
2399           Ambiguous = true;
2400           break;
2401         }
2402       }
2403 
2404       if (Ambiguous) {
2405         // Partial ordering did not produce a clear winner. Complain.
2406         ClassTemplateSpec->setInvalidDecl();
2407         Diag(PointOfInstantiation, diag::err_partial_spec_ordering_ambiguous)
2408           << ClassTemplateSpec;
2409 
2410         // Print the matching partial specializations.
2411         for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2412                                                  PEnd = Matched.end();
2413              P != PEnd; ++P)
2414           Diag(P->Partial->getLocation(), diag::note_partial_spec_match)
2415             << getTemplateArgumentBindingsText(
2416                                             P->Partial->getTemplateParameters(),
2417                                                *P->Args);
2418 
2419         return true;
2420       }
2421     }
2422 
2423     // Instantiate using the best class template partial specialization.
2424     ClassTemplatePartialSpecializationDecl *OrigPartialSpec = Best->Partial;
2425     while (OrigPartialSpec->getInstantiatedFromMember()) {
2426       // If we've found an explicit specialization of this class template,
2427       // stop here and use that as the pattern.
2428       if (OrigPartialSpec->isMemberSpecialization())
2429         break;
2430 
2431       OrigPartialSpec = OrigPartialSpec->getInstantiatedFromMember();
2432     }
2433 
2434     Pattern = OrigPartialSpec;
2435     ClassTemplateSpec->setInstantiationOf(Best->Partial, Best->Args);
2436   } else {
2437     //   -- If no matches are found, the instantiation is generated
2438     //      from the primary template.
2439     ClassTemplateDecl *OrigTemplate = Template;
2440     while (OrigTemplate->getInstantiatedFromMemberTemplate()) {
2441       // If we've found an explicit specialization of this class template,
2442       // stop here and use that as the pattern.
2443       if (OrigTemplate->isMemberSpecialization())
2444         break;
2445 
2446       OrigTemplate = OrigTemplate->getInstantiatedFromMemberTemplate();
2447     }
2448 
2449     Pattern = OrigTemplate->getTemplatedDecl();
2450   }
2451 
2452   bool Result = InstantiateClass(PointOfInstantiation, ClassTemplateSpec,
2453                                  Pattern,
2454                                 getTemplateInstantiationArgs(ClassTemplateSpec),
2455                                  TSK,
2456                                  Complain);
2457 
2458   return Result;
2459 }
2460 
2461 /// \brief Instantiates the definitions of all of the member
2462 /// of the given class, which is an instantiation of a class template
2463 /// or a member class of a template.
2464 void
2465 Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
2466                               CXXRecordDecl *Instantiation,
2467                         const MultiLevelTemplateArgumentList &TemplateArgs,
2468                               TemplateSpecializationKind TSK) {
2469   assert(
2470       (TSK == TSK_ExplicitInstantiationDefinition ||
2471        TSK == TSK_ExplicitInstantiationDeclaration ||
2472        (TSK == TSK_ImplicitInstantiation && Instantiation->isLocalClass())) &&
2473       "Unexpected template specialization kind!");
2474   for (DeclContext::decl_iterator D = Instantiation->decls_begin(),
2475                                DEnd = Instantiation->decls_end();
2476        D != DEnd; ++D) {
2477     bool SuppressNew = false;
2478     if (FunctionDecl *Function = dyn_cast<FunctionDecl>(*D)) {
2479       if (FunctionDecl *Pattern
2480             = Function->getInstantiatedFromMemberFunction()) {
2481         MemberSpecializationInfo *MSInfo
2482           = Function->getMemberSpecializationInfo();
2483         assert(MSInfo && "No member specialization information?");
2484         if (MSInfo->getTemplateSpecializationKind()
2485                                                  == TSK_ExplicitSpecialization)
2486           continue;
2487 
2488         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2489                                                    Function,
2490                                         MSInfo->getTemplateSpecializationKind(),
2491                                               MSInfo->getPointOfInstantiation(),
2492                                                    SuppressNew) ||
2493             SuppressNew)
2494           continue;
2495 
2496         if (Function->isDefined())
2497           continue;
2498 
2499         if (TSK == TSK_ExplicitInstantiationDefinition) {
2500           // C++0x [temp.explicit]p8:
2501           //   An explicit instantiation definition that names a class template
2502           //   specialization explicitly instantiates the class template
2503           //   specialization and is only an explicit instantiation definition
2504           //   of members whose definition is visible at the point of
2505           //   instantiation.
2506           if (!Pattern->isDefined())
2507             continue;
2508 
2509           Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2510 
2511           InstantiateFunctionDefinition(PointOfInstantiation, Function);
2512         } else {
2513           Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2514           if (TSK == TSK_ImplicitInstantiation)
2515             PendingLocalImplicitInstantiations.push_back(
2516                 std::make_pair(Function, PointOfInstantiation));
2517         }
2518       }
2519     } else if (VarDecl *Var = dyn_cast<VarDecl>(*D)) {
2520       if (isa<VarTemplateSpecializationDecl>(Var))
2521         continue;
2522 
2523       if (Var->isStaticDataMember()) {
2524         MemberSpecializationInfo *MSInfo = Var->getMemberSpecializationInfo();
2525         assert(MSInfo && "No member specialization information?");
2526         if (MSInfo->getTemplateSpecializationKind()
2527                                                  == TSK_ExplicitSpecialization)
2528           continue;
2529 
2530         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2531                                                    Var,
2532                                         MSInfo->getTemplateSpecializationKind(),
2533                                               MSInfo->getPointOfInstantiation(),
2534                                                    SuppressNew) ||
2535             SuppressNew)
2536           continue;
2537 
2538         if (TSK == TSK_ExplicitInstantiationDefinition) {
2539           // C++0x [temp.explicit]p8:
2540           //   An explicit instantiation definition that names a class template
2541           //   specialization explicitly instantiates the class template
2542           //   specialization and is only an explicit instantiation definition
2543           //   of members whose definition is visible at the point of
2544           //   instantiation.
2545           if (!Var->getInstantiatedFromStaticDataMember()
2546                                                      ->getOutOfLineDefinition())
2547             continue;
2548 
2549           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2550           InstantiateStaticDataMemberDefinition(PointOfInstantiation, Var);
2551         } else {
2552           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2553         }
2554       }
2555     } else if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(*D)) {
2556       // Always skip the injected-class-name, along with any
2557       // redeclarations of nested classes, since both would cause us
2558       // to try to instantiate the members of a class twice.
2559       if (Record->isInjectedClassName() || Record->getPreviousDecl())
2560         continue;
2561 
2562       MemberSpecializationInfo *MSInfo = Record->getMemberSpecializationInfo();
2563       assert(MSInfo && "No member specialization information?");
2564 
2565       if (MSInfo->getTemplateSpecializationKind()
2566                                                 == TSK_ExplicitSpecialization)
2567         continue;
2568 
2569       if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2570                                                  Record,
2571                                         MSInfo->getTemplateSpecializationKind(),
2572                                               MSInfo->getPointOfInstantiation(),
2573                                                  SuppressNew) ||
2574           SuppressNew)
2575         continue;
2576 
2577       CXXRecordDecl *Pattern = Record->getInstantiatedFromMemberClass();
2578       assert(Pattern && "Missing instantiated-from-template information");
2579 
2580       if (!Record->getDefinition()) {
2581         if (!Pattern->getDefinition()) {
2582           // C++0x [temp.explicit]p8:
2583           //   An explicit instantiation definition that names a class template
2584           //   specialization explicitly instantiates the class template
2585           //   specialization and is only an explicit instantiation definition
2586           //   of members whose definition is visible at the point of
2587           //   instantiation.
2588           if (TSK == TSK_ExplicitInstantiationDeclaration) {
2589             MSInfo->setTemplateSpecializationKind(TSK);
2590             MSInfo->setPointOfInstantiation(PointOfInstantiation);
2591           }
2592 
2593           continue;
2594         }
2595 
2596         InstantiateClass(PointOfInstantiation, Record, Pattern,
2597                          TemplateArgs,
2598                          TSK);
2599       } else {
2600         if (TSK == TSK_ExplicitInstantiationDefinition &&
2601             Record->getTemplateSpecializationKind() ==
2602                 TSK_ExplicitInstantiationDeclaration) {
2603           Record->setTemplateSpecializationKind(TSK);
2604           MarkVTableUsed(PointOfInstantiation, Record, true);
2605         }
2606       }
2607 
2608       Pattern = cast_or_null<CXXRecordDecl>(Record->getDefinition());
2609       if (Pattern)
2610         InstantiateClassMembers(PointOfInstantiation, Pattern, TemplateArgs,
2611                                 TSK);
2612     } else if (EnumDecl *Enum = dyn_cast<EnumDecl>(*D)) {
2613       MemberSpecializationInfo *MSInfo = Enum->getMemberSpecializationInfo();
2614       assert(MSInfo && "No member specialization information?");
2615 
2616       if (MSInfo->getTemplateSpecializationKind()
2617             == TSK_ExplicitSpecialization)
2618         continue;
2619 
2620       if (CheckSpecializationInstantiationRedecl(
2621             PointOfInstantiation, TSK, Enum,
2622             MSInfo->getTemplateSpecializationKind(),
2623             MSInfo->getPointOfInstantiation(), SuppressNew) ||
2624           SuppressNew)
2625         continue;
2626 
2627       if (Enum->getDefinition())
2628         continue;
2629 
2630       EnumDecl *Pattern = Enum->getInstantiatedFromMemberEnum();
2631       assert(Pattern && "Missing instantiated-from-template information");
2632 
2633       if (TSK == TSK_ExplicitInstantiationDefinition) {
2634         if (!Pattern->getDefinition())
2635           continue;
2636 
2637         InstantiateEnum(PointOfInstantiation, Enum, Pattern, TemplateArgs, TSK);
2638       } else {
2639         MSInfo->setTemplateSpecializationKind(TSK);
2640         MSInfo->setPointOfInstantiation(PointOfInstantiation);
2641       }
2642     }
2643   }
2644 }
2645 
2646 /// \brief Instantiate the definitions of all of the members of the
2647 /// given class template specialization, which was named as part of an
2648 /// explicit instantiation.
2649 void
2650 Sema::InstantiateClassTemplateSpecializationMembers(
2651                                            SourceLocation PointOfInstantiation,
2652                             ClassTemplateSpecializationDecl *ClassTemplateSpec,
2653                                                TemplateSpecializationKind TSK) {
2654   // C++0x [temp.explicit]p7:
2655   //   An explicit instantiation that names a class template
2656   //   specialization is an explicit instantion of the same kind
2657   //   (declaration or definition) of each of its members (not
2658   //   including members inherited from base classes) that has not
2659   //   been previously explicitly specialized in the translation unit
2660   //   containing the explicit instantiation, except as described
2661   //   below.
2662   InstantiateClassMembers(PointOfInstantiation, ClassTemplateSpec,
2663                           getTemplateInstantiationArgs(ClassTemplateSpec),
2664                           TSK);
2665 }
2666 
2667 StmtResult
2668 Sema::SubstStmt(Stmt *S, const MultiLevelTemplateArgumentList &TemplateArgs) {
2669   if (!S)
2670     return Owned(S);
2671 
2672   TemplateInstantiator Instantiator(*this, TemplateArgs,
2673                                     SourceLocation(),
2674                                     DeclarationName());
2675   return Instantiator.TransformStmt(S);
2676 }
2677 
2678 ExprResult
2679 Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
2680   if (!E)
2681     return Owned(E);
2682 
2683   TemplateInstantiator Instantiator(*this, TemplateArgs,
2684                                     SourceLocation(),
2685                                     DeclarationName());
2686   return Instantiator.TransformExpr(E);
2687 }
2688 
2689 ExprResult Sema::SubstInitializer(Expr *Init,
2690                           const MultiLevelTemplateArgumentList &TemplateArgs,
2691                           bool CXXDirectInit) {
2692   TemplateInstantiator Instantiator(*this, TemplateArgs,
2693                                     SourceLocation(),
2694                                     DeclarationName());
2695   return Instantiator.TransformInitializer(Init, CXXDirectInit);
2696 }
2697 
2698 bool Sema::SubstExprs(Expr **Exprs, unsigned NumExprs, bool IsCall,
2699                       const MultiLevelTemplateArgumentList &TemplateArgs,
2700                       SmallVectorImpl<Expr *> &Outputs) {
2701   if (NumExprs == 0)
2702     return false;
2703 
2704   TemplateInstantiator Instantiator(*this, TemplateArgs,
2705                                     SourceLocation(),
2706                                     DeclarationName());
2707   return Instantiator.TransformExprs(Exprs, NumExprs, IsCall, Outputs);
2708 }
2709 
2710 NestedNameSpecifierLoc
2711 Sema::SubstNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
2712                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2713   if (!NNS)
2714     return NestedNameSpecifierLoc();
2715 
2716   TemplateInstantiator Instantiator(*this, TemplateArgs, NNS.getBeginLoc(),
2717                                     DeclarationName());
2718   return Instantiator.TransformNestedNameSpecifierLoc(NNS);
2719 }
2720 
2721 /// \brief Do template substitution on declaration name info.
2722 DeclarationNameInfo
2723 Sema::SubstDeclarationNameInfo(const DeclarationNameInfo &NameInfo,
2724                          const MultiLevelTemplateArgumentList &TemplateArgs) {
2725   TemplateInstantiator Instantiator(*this, TemplateArgs, NameInfo.getLoc(),
2726                                     NameInfo.getName());
2727   return Instantiator.TransformDeclarationNameInfo(NameInfo);
2728 }
2729 
2730 TemplateName
2731 Sema::SubstTemplateName(NestedNameSpecifierLoc QualifierLoc,
2732                         TemplateName Name, SourceLocation Loc,
2733                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2734   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
2735                                     DeclarationName());
2736   CXXScopeSpec SS;
2737   SS.Adopt(QualifierLoc);
2738   return Instantiator.TransformTemplateName(SS, Name, Loc);
2739 }
2740 
2741 bool Sema::Subst(const TemplateArgumentLoc *Args, unsigned NumArgs,
2742                  TemplateArgumentListInfo &Result,
2743                  const MultiLevelTemplateArgumentList &TemplateArgs) {
2744   TemplateInstantiator Instantiator(*this, TemplateArgs, SourceLocation(),
2745                                     DeclarationName());
2746 
2747   return Instantiator.TransformTemplateArguments(Args, NumArgs, Result);
2748 }
2749 
2750 
2751 static const Decl* getCanonicalParmVarDecl(const Decl *D) {
2752   // When storing ParmVarDecls in the local instantiation scope, we always
2753   // want to use the ParmVarDecl from the canonical function declaration,
2754   // since the map is then valid for any redeclaration or definition of that
2755   // function.
2756   if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(D)) {
2757     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(PV->getDeclContext())) {
2758       unsigned i = PV->getFunctionScopeIndex();
2759       return FD->getCanonicalDecl()->getParamDecl(i);
2760     }
2761   }
2762   return D;
2763 }
2764 
2765 
2766 llvm::PointerUnion<Decl *, LocalInstantiationScope::DeclArgumentPack *> *
2767 LocalInstantiationScope::findInstantiationOf(const Decl *D) {
2768   D = getCanonicalParmVarDecl(D);
2769   for (LocalInstantiationScope *Current = this; Current;
2770        Current = Current->Outer) {
2771 
2772     // Check if we found something within this scope.
2773     const Decl *CheckD = D;
2774     do {
2775       LocalDeclsMap::iterator Found = Current->LocalDecls.find(CheckD);
2776       if (Found != Current->LocalDecls.end())
2777         return &Found->second;
2778 
2779       // If this is a tag declaration, it's possible that we need to look for
2780       // a previous declaration.
2781       if (const TagDecl *Tag = dyn_cast<TagDecl>(CheckD))
2782         CheckD = Tag->getPreviousDecl();
2783       else
2784         CheckD = 0;
2785     } while (CheckD);
2786 
2787     // If we aren't combined with our outer scope, we're done.
2788     if (!Current->CombineWithOuterScope)
2789       break;
2790   }
2791 
2792   // If we're performing a partial substitution during template argument
2793   // deduction, we may not have values for template parameters yet.
2794   if (isa<NonTypeTemplateParmDecl>(D) || isa<TemplateTypeParmDecl>(D) ||
2795       isa<TemplateTemplateParmDecl>(D))
2796     return 0;
2797 
2798   // If we didn't find the decl, then we either have a sema bug, or we have a
2799   // forward reference to a label declaration.  Return null to indicate that
2800   // we have an uninstantiated label.
2801   assert(isa<LabelDecl>(D) && "declaration not instantiated in this scope");
2802   return 0;
2803 }
2804 
2805 void LocalInstantiationScope::InstantiatedLocal(const Decl *D, Decl *Inst) {
2806   D = getCanonicalParmVarDecl(D);
2807   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2808   if (Stored.isNull())
2809     Stored = Inst;
2810   else if (DeclArgumentPack *Pack = Stored.dyn_cast<DeclArgumentPack *>())
2811     Pack->push_back(Inst);
2812   else
2813     assert(Stored.get<Decl *>() == Inst && "Already instantiated this local");
2814 }
2815 
2816 void LocalInstantiationScope::InstantiatedLocalPackArg(const Decl *D,
2817                                                        Decl *Inst) {
2818   D = getCanonicalParmVarDecl(D);
2819   DeclArgumentPack *Pack = LocalDecls[D].get<DeclArgumentPack *>();
2820   Pack->push_back(Inst);
2821 }
2822 
2823 void LocalInstantiationScope::MakeInstantiatedLocalArgPack(const Decl *D) {
2824   D = getCanonicalParmVarDecl(D);
2825   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2826   assert(Stored.isNull() && "Already instantiated this local");
2827   DeclArgumentPack *Pack = new DeclArgumentPack;
2828   Stored = Pack;
2829   ArgumentPacks.push_back(Pack);
2830 }
2831 
2832 void LocalInstantiationScope::SetPartiallySubstitutedPack(NamedDecl *Pack,
2833                                           const TemplateArgument *ExplicitArgs,
2834                                                     unsigned NumExplicitArgs) {
2835   assert((!PartiallySubstitutedPack || PartiallySubstitutedPack == Pack) &&
2836          "Already have a partially-substituted pack");
2837   assert((!PartiallySubstitutedPack
2838           || NumArgsInPartiallySubstitutedPack == NumExplicitArgs) &&
2839          "Wrong number of arguments in partially-substituted pack");
2840   PartiallySubstitutedPack = Pack;
2841   ArgsInPartiallySubstitutedPack = ExplicitArgs;
2842   NumArgsInPartiallySubstitutedPack = NumExplicitArgs;
2843 }
2844 
2845 NamedDecl *LocalInstantiationScope::getPartiallySubstitutedPack(
2846                                          const TemplateArgument **ExplicitArgs,
2847                                               unsigned *NumExplicitArgs) const {
2848   if (ExplicitArgs)
2849     *ExplicitArgs = 0;
2850   if (NumExplicitArgs)
2851     *NumExplicitArgs = 0;
2852 
2853   for (const LocalInstantiationScope *Current = this; Current;
2854        Current = Current->Outer) {
2855     if (Current->PartiallySubstitutedPack) {
2856       if (ExplicitArgs)
2857         *ExplicitArgs = Current->ArgsInPartiallySubstitutedPack;
2858       if (NumExplicitArgs)
2859         *NumExplicitArgs = Current->NumArgsInPartiallySubstitutedPack;
2860 
2861       return Current->PartiallySubstitutedPack;
2862     }
2863 
2864     if (!Current->CombineWithOuterScope)
2865       break;
2866   }
2867 
2868   return 0;
2869 }
2870