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