xref: /minix3/external/bsd/llvm/dist/clang/lib/Sema/SemaTemplateInstantiate.cpp (revision ebfedea0ce5bbe81e252ddf32d732e40fb633fae)
1 //===------- SemaTemplateInstantiate.cpp - C++ Template Instantiation ------===/
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //===----------------------------------------------------------------------===/
8 //
9 //  This file implements C++ template instantiation.
10 //
11 //===----------------------------------------------------------------------===/
12 
13 #include "clang/Sema/SemaInternal.h"
14 #include "TreeTransform.h"
15 #include "clang/AST/ASTConsumer.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/ASTLambda.h"
18 #include "clang/AST/DeclTemplate.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/Basic/LangOptions.h"
21 #include "clang/Sema/DeclSpec.h"
22 #include "clang/Sema/Initialization.h"
23 #include "clang/Sema/Lookup.h"
24 #include "clang/Sema/Template.h"
25 #include "clang/Sema/TemplateDeduction.h"
26 
27 using namespace clang;
28 using namespace sema;
29 
30 //===----------------------------------------------------------------------===/
31 // Template Instantiation Support
32 //===----------------------------------------------------------------------===/
33 
34 /// \brief Retrieve the template argument list(s) that should be used to
35 /// instantiate the definition of the given declaration.
36 ///
37 /// \param D the declaration for which we are computing template instantiation
38 /// arguments.
39 ///
40 /// \param Innermost if non-NULL, the innermost template argument list.
41 ///
42 /// \param RelativeToPrimary true if we should get the template
43 /// arguments relative to the primary template, even when we're
44 /// dealing with a specialization. This is only relevant for function
45 /// template specializations.
46 ///
47 /// \param Pattern If non-NULL, indicates the pattern from which we will be
48 /// instantiating the definition of the given declaration, \p D. This is
49 /// used to determine the proper set of template instantiation arguments for
50 /// friend function template specializations.
51 MultiLevelTemplateArgumentList
52 Sema::getTemplateInstantiationArgs(NamedDecl *D,
53                                    const TemplateArgumentList *Innermost,
54                                    bool RelativeToPrimary,
55                                    const FunctionDecl *Pattern) {
56   // Accumulate the set of template argument lists in this structure.
57   MultiLevelTemplateArgumentList Result;
58 
59   if (Innermost)
60     Result.addOuterTemplateArguments(Innermost);
61 
62   DeclContext *Ctx = dyn_cast<DeclContext>(D);
63   if (!Ctx) {
64     Ctx = D->getDeclContext();
65 
66     // Add template arguments from a variable template instantiation.
67     if (VarTemplateSpecializationDecl *Spec =
68             dyn_cast<VarTemplateSpecializationDecl>(D)) {
69       // We're done when we hit an explicit specialization.
70       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
71           !isa<VarTemplatePartialSpecializationDecl>(Spec))
72         return Result;
73 
74       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
75 
76       // If this variable template specialization was instantiated from a
77       // specialized member that is a variable template, we're done.
78       assert(Spec->getSpecializedTemplate() && "No variable template?");
79       if (Spec->getSpecializedTemplate()->isMemberSpecialization())
80         return Result;
81     }
82 
83     // If we have a template template parameter with translation unit context,
84     // then we're performing substitution into a default template argument of
85     // this template template parameter before we've constructed the template
86     // that will own this template template parameter. In this case, we
87     // use empty template parameter lists for all of the outer templates
88     // to avoid performing any substitutions.
89     if (Ctx->isTranslationUnit()) {
90       if (TemplateTemplateParmDecl *TTP
91                                       = dyn_cast<TemplateTemplateParmDecl>(D)) {
92         for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
93           Result.addOuterTemplateArguments(None);
94         return Result;
95       }
96     }
97   }
98 
99   while (!Ctx->isFileContext()) {
100     // Add template arguments from a class template instantiation.
101     if (ClassTemplateSpecializationDecl *Spec
102           = dyn_cast<ClassTemplateSpecializationDecl>(Ctx)) {
103       // We're done when we hit an explicit specialization.
104       if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
105           !isa<ClassTemplatePartialSpecializationDecl>(Spec))
106         break;
107 
108       Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
109 
110       // If this class template specialization was instantiated from a
111       // specialized member that is a class template, we're done.
112       assert(Spec->getSpecializedTemplate() && "No class template?");
113       if (Spec->getSpecializedTemplate()->isMemberSpecialization())
114         break;
115     }
116     // Add template arguments from a function template specialization.
117     else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(Ctx)) {
118       if (!RelativeToPrimary &&
119           (Function->getTemplateSpecializationKind() ==
120                                                   TSK_ExplicitSpecialization &&
121            !Function->getClassScopeSpecializationPattern()))
122         break;
123 
124       if (const TemplateArgumentList *TemplateArgs
125             = Function->getTemplateSpecializationArgs()) {
126         // Add the template arguments for this specialization.
127         Result.addOuterTemplateArguments(TemplateArgs);
128 
129         // If this function was instantiated from a specialized member that is
130         // a function template, we're done.
131         assert(Function->getPrimaryTemplate() && "No function template?");
132         if (Function->getPrimaryTemplate()->isMemberSpecialization())
133           break;
134 
135         // If this function is a generic lambda specialization, we are done.
136         if (isGenericLambdaCallOperatorSpecialization(Function))
137           break;
138 
139       } else if (FunctionTemplateDecl *FunTmpl
140                                    = Function->getDescribedFunctionTemplate()) {
141         // Add the "injected" template arguments.
142         Result.addOuterTemplateArguments(FunTmpl->getInjectedTemplateArgs());
143       }
144 
145       // If this is a friend declaration and it declares an entity at
146       // namespace scope, take arguments from its lexical parent
147       // instead of its semantic parent, unless of course the pattern we're
148       // instantiating actually comes from the file's context!
149       if (Function->getFriendObjectKind() &&
150           Function->getDeclContext()->isFileContext() &&
151           (!Pattern || !Pattern->getLexicalDeclContext()->isFileContext())) {
152         Ctx = Function->getLexicalDeclContext();
153         RelativeToPrimary = false;
154         continue;
155       }
156     } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
157       if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
158         QualType T = ClassTemplate->getInjectedClassNameSpecialization();
159         const TemplateSpecializationType *TST =
160             cast<TemplateSpecializationType>(Context.getCanonicalType(T));
161         Result.addOuterTemplateArguments(
162             llvm::makeArrayRef(TST->getArgs(), TST->getNumArgs()));
163         if (ClassTemplate->isMemberSpecialization())
164           break;
165       }
166     }
167 
168     Ctx = Ctx->getParent();
169     RelativeToPrimary = false;
170   }
171 
172   return Result;
173 }
174 
175 bool Sema::ActiveTemplateInstantiation::isInstantiationRecord() const {
176   switch (Kind) {
177   case TemplateInstantiation:
178   case ExceptionSpecInstantiation:
179   case DefaultTemplateArgumentInstantiation:
180   case DefaultFunctionArgumentInstantiation:
181   case ExplicitTemplateArgumentSubstitution:
182   case DeducedTemplateArgumentSubstitution:
183   case PriorTemplateArgumentSubstitution:
184     return true;
185 
186   case DefaultTemplateArgumentChecking:
187     return false;
188   }
189 
190   llvm_unreachable("Invalid InstantiationKind!");
191 }
192 
193 Sema::InstantiatingTemplate::
194 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
195                       Decl *Entity,
196                       SourceRange InstantiationRange)
197   : SemaRef(SemaRef),
198     SavedInNonInstantiationSFINAEContext(
199                                         SemaRef.InNonInstantiationSFINAEContext)
200 {
201   Invalid = CheckInstantiationDepth(PointOfInstantiation,
202                                     InstantiationRange);
203   if (!Invalid) {
204     ActiveTemplateInstantiation Inst;
205     Inst.Kind = ActiveTemplateInstantiation::TemplateInstantiation;
206     Inst.PointOfInstantiation = PointOfInstantiation;
207     Inst.Entity = Entity;
208     Inst.TemplateArgs = 0;
209     Inst.NumTemplateArgs = 0;
210     Inst.InstantiationRange = InstantiationRange;
211     SemaRef.InNonInstantiationSFINAEContext = false;
212     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
213   }
214 }
215 
216 Sema::InstantiatingTemplate::
217 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
218                       FunctionDecl *Entity, ExceptionSpecification,
219                       SourceRange InstantiationRange)
220   : SemaRef(SemaRef),
221     SavedInNonInstantiationSFINAEContext(
222                                         SemaRef.InNonInstantiationSFINAEContext)
223 {
224   Invalid = CheckInstantiationDepth(PointOfInstantiation,
225                                     InstantiationRange);
226   if (!Invalid) {
227     ActiveTemplateInstantiation Inst;
228     Inst.Kind = ActiveTemplateInstantiation::ExceptionSpecInstantiation;
229     Inst.PointOfInstantiation = PointOfInstantiation;
230     Inst.Entity = Entity;
231     Inst.TemplateArgs = 0;
232     Inst.NumTemplateArgs = 0;
233     Inst.InstantiationRange = InstantiationRange;
234     SemaRef.InNonInstantiationSFINAEContext = false;
235     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
236   }
237 }
238 
239 Sema::InstantiatingTemplate::
240 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
241                       TemplateDecl *Template,
242                       ArrayRef<TemplateArgument> TemplateArgs,
243                       SourceRange InstantiationRange)
244   : SemaRef(SemaRef),
245     SavedInNonInstantiationSFINAEContext(
246                                      SemaRef.InNonInstantiationSFINAEContext)
247 {
248   Invalid = CheckInstantiationDepth(PointOfInstantiation,
249                                     InstantiationRange);
250   if (!Invalid) {
251     ActiveTemplateInstantiation Inst;
252     Inst.Kind
253       = ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation;
254     Inst.PointOfInstantiation = PointOfInstantiation;
255     Inst.Entity = Template;
256     Inst.TemplateArgs = TemplateArgs.data();
257     Inst.NumTemplateArgs = TemplateArgs.size();
258     Inst.InstantiationRange = InstantiationRange;
259     SemaRef.InNonInstantiationSFINAEContext = false;
260     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
261   }
262 }
263 
264 Sema::InstantiatingTemplate::
265 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
266                       FunctionTemplateDecl *FunctionTemplate,
267                       ArrayRef<TemplateArgument> TemplateArgs,
268                       ActiveTemplateInstantiation::InstantiationKind Kind,
269                       sema::TemplateDeductionInfo &DeductionInfo,
270                       SourceRange InstantiationRange)
271   : SemaRef(SemaRef),
272     SavedInNonInstantiationSFINAEContext(
273                                      SemaRef.InNonInstantiationSFINAEContext)
274 {
275   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
276   if (!Invalid) {
277     ActiveTemplateInstantiation Inst;
278     Inst.Kind = Kind;
279     Inst.PointOfInstantiation = PointOfInstantiation;
280     Inst.Entity = FunctionTemplate;
281     Inst.TemplateArgs = TemplateArgs.data();
282     Inst.NumTemplateArgs = TemplateArgs.size();
283     Inst.DeductionInfo = &DeductionInfo;
284     Inst.InstantiationRange = InstantiationRange;
285     SemaRef.InNonInstantiationSFINAEContext = false;
286     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
287 
288     if (!Inst.isInstantiationRecord())
289       ++SemaRef.NonInstantiationEntries;
290   }
291 }
292 
293 Sema::InstantiatingTemplate::
294 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
295                       ClassTemplatePartialSpecializationDecl *PartialSpec,
296                       ArrayRef<TemplateArgument> TemplateArgs,
297                       sema::TemplateDeductionInfo &DeductionInfo,
298                       SourceRange InstantiationRange)
299   : SemaRef(SemaRef),
300     SavedInNonInstantiationSFINAEContext(
301                                      SemaRef.InNonInstantiationSFINAEContext)
302 {
303   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
304   if (!Invalid) {
305     ActiveTemplateInstantiation Inst;
306     Inst.Kind = ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution;
307     Inst.PointOfInstantiation = PointOfInstantiation;
308     Inst.Entity = PartialSpec;
309     Inst.TemplateArgs = TemplateArgs.data();
310     Inst.NumTemplateArgs = TemplateArgs.size();
311     Inst.DeductionInfo = &DeductionInfo;
312     Inst.InstantiationRange = InstantiationRange;
313     SemaRef.InNonInstantiationSFINAEContext = false;
314     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
315   }
316 }
317 
318 Sema::InstantiatingTemplate::InstantiatingTemplate(
319     Sema &SemaRef, SourceLocation PointOfInstantiation,
320     VarTemplatePartialSpecializationDecl *PartialSpec,
321     ArrayRef<TemplateArgument> TemplateArgs,
322     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
323     : SemaRef(SemaRef), SavedInNonInstantiationSFINAEContext(
324                             SemaRef.InNonInstantiationSFINAEContext) {
325   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
326   if (!Invalid) {
327     ActiveTemplateInstantiation Inst;
328     Inst.Kind =
329         ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution;
330     Inst.PointOfInstantiation = PointOfInstantiation;
331     Inst.Entity = PartialSpec;
332     Inst.TemplateArgs = TemplateArgs.data();
333     Inst.NumTemplateArgs = TemplateArgs.size();
334     Inst.DeductionInfo = &DeductionInfo;
335     Inst.InstantiationRange = InstantiationRange;
336     SemaRef.InNonInstantiationSFINAEContext = false;
337     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
338   }
339 }
340 
341 Sema::InstantiatingTemplate::
342 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
343                       ParmVarDecl *Param,
344                       ArrayRef<TemplateArgument> TemplateArgs,
345                       SourceRange InstantiationRange)
346   : SemaRef(SemaRef),
347     SavedInNonInstantiationSFINAEContext(
348                                      SemaRef.InNonInstantiationSFINAEContext)
349 {
350   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
351   if (!Invalid) {
352     ActiveTemplateInstantiation Inst;
353     Inst.Kind
354       = ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation;
355     Inst.PointOfInstantiation = PointOfInstantiation;
356     Inst.Entity = Param;
357     Inst.TemplateArgs = TemplateArgs.data();
358     Inst.NumTemplateArgs = TemplateArgs.size();
359     Inst.InstantiationRange = InstantiationRange;
360     SemaRef.InNonInstantiationSFINAEContext = false;
361     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
362   }
363 }
364 
365 Sema::InstantiatingTemplate::
366 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
367                       NamedDecl *Template, NonTypeTemplateParmDecl *Param,
368                       ArrayRef<TemplateArgument> TemplateArgs,
369                       SourceRange InstantiationRange)
370   : SemaRef(SemaRef),
371     SavedInNonInstantiationSFINAEContext(
372                                      SemaRef.InNonInstantiationSFINAEContext)
373 {
374   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
375   if (!Invalid) {
376     ActiveTemplateInstantiation Inst;
377     Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
378     Inst.PointOfInstantiation = PointOfInstantiation;
379     Inst.Template = Template;
380     Inst.Entity = Param;
381     Inst.TemplateArgs = TemplateArgs.data();
382     Inst.NumTemplateArgs = TemplateArgs.size();
383     Inst.InstantiationRange = InstantiationRange;
384     SemaRef.InNonInstantiationSFINAEContext = false;
385     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
386   }
387 }
388 
389 Sema::InstantiatingTemplate::
390 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
391                       NamedDecl *Template, TemplateTemplateParmDecl *Param,
392                       ArrayRef<TemplateArgument> TemplateArgs,
393                       SourceRange InstantiationRange)
394   : SemaRef(SemaRef),
395     SavedInNonInstantiationSFINAEContext(
396                                      SemaRef.InNonInstantiationSFINAEContext)
397 {
398   Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
399   if (!Invalid) {
400     ActiveTemplateInstantiation Inst;
401     Inst.Kind = ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution;
402     Inst.PointOfInstantiation = PointOfInstantiation;
403     Inst.Template = Template;
404     Inst.Entity = Param;
405     Inst.TemplateArgs = TemplateArgs.data();
406     Inst.NumTemplateArgs = TemplateArgs.size();
407     Inst.InstantiationRange = InstantiationRange;
408     SemaRef.InNonInstantiationSFINAEContext = false;
409     SemaRef.ActiveTemplateInstantiations.push_back(Inst);
410   }
411 }
412 
413 Sema::InstantiatingTemplate::
414 InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
415                       TemplateDecl *Template, NamedDecl *Param,
416                       ArrayRef<TemplateArgument> TemplateArgs,
417                       SourceRange InstantiationRange)
418   : SemaRef(SemaRef),
419     SavedInNonInstantiationSFINAEContext(
420                                      SemaRef.InNonInstantiationSFINAEContext)
421 {
422   Invalid = false;
423 
424   ActiveTemplateInstantiation Inst;
425   Inst.Kind = ActiveTemplateInstantiation::DefaultTemplateArgumentChecking;
426   Inst.PointOfInstantiation = PointOfInstantiation;
427   Inst.Template = Template;
428   Inst.Entity = Param;
429   Inst.TemplateArgs = TemplateArgs.data();
430   Inst.NumTemplateArgs = TemplateArgs.size();
431   Inst.InstantiationRange = InstantiationRange;
432   SemaRef.InNonInstantiationSFINAEContext = false;
433   SemaRef.ActiveTemplateInstantiations.push_back(Inst);
434 
435   assert(!Inst.isInstantiationRecord());
436   ++SemaRef.NonInstantiationEntries;
437 }
438 
439 void Sema::InstantiatingTemplate::Clear() {
440   if (!Invalid) {
441     if (!SemaRef.ActiveTemplateInstantiations.back().isInstantiationRecord()) {
442       assert(SemaRef.NonInstantiationEntries > 0);
443       --SemaRef.NonInstantiationEntries;
444     }
445     SemaRef.InNonInstantiationSFINAEContext
446       = SavedInNonInstantiationSFINAEContext;
447 
448     // Name lookup no longer looks in this template's defining module.
449     assert(SemaRef.ActiveTemplateInstantiations.size() >=
450            SemaRef.ActiveTemplateInstantiationLookupModules.size() &&
451            "forgot to remove a lookup module for a template instantiation");
452     if (SemaRef.ActiveTemplateInstantiations.size() ==
453         SemaRef.ActiveTemplateInstantiationLookupModules.size()) {
454       if (Module *M = SemaRef.ActiveTemplateInstantiationLookupModules.back())
455         SemaRef.LookupModulesCache.erase(M);
456       SemaRef.ActiveTemplateInstantiationLookupModules.pop_back();
457     }
458 
459     SemaRef.ActiveTemplateInstantiations.pop_back();
460     Invalid = true;
461   }
462 }
463 
464 bool Sema::InstantiatingTemplate::CheckInstantiationDepth(
465                                         SourceLocation PointOfInstantiation,
466                                            SourceRange InstantiationRange) {
467   assert(SemaRef.NonInstantiationEntries <=
468                                    SemaRef.ActiveTemplateInstantiations.size());
469   if ((SemaRef.ActiveTemplateInstantiations.size() -
470           SemaRef.NonInstantiationEntries)
471         <= SemaRef.getLangOpts().InstantiationDepth)
472     return false;
473 
474   SemaRef.Diag(PointOfInstantiation,
475                diag::err_template_recursion_depth_exceeded)
476     << SemaRef.getLangOpts().InstantiationDepth
477     << InstantiationRange;
478   SemaRef.Diag(PointOfInstantiation, diag::note_template_recursion_depth)
479     << SemaRef.getLangOpts().InstantiationDepth;
480   return true;
481 }
482 
483 /// \brief Prints the current instantiation stack through a series of
484 /// notes.
485 void Sema::PrintInstantiationStack() {
486   // Determine which template instantiations to skip, if any.
487   unsigned SkipStart = ActiveTemplateInstantiations.size(), SkipEnd = SkipStart;
488   unsigned Limit = Diags.getTemplateBacktraceLimit();
489   if (Limit && Limit < ActiveTemplateInstantiations.size()) {
490     SkipStart = Limit / 2 + Limit % 2;
491     SkipEnd = ActiveTemplateInstantiations.size() - Limit / 2;
492   }
493 
494   // FIXME: In all of these cases, we need to show the template arguments
495   unsigned InstantiationIdx = 0;
496   for (SmallVectorImpl<ActiveTemplateInstantiation>::reverse_iterator
497          Active = ActiveTemplateInstantiations.rbegin(),
498          ActiveEnd = ActiveTemplateInstantiations.rend();
499        Active != ActiveEnd;
500        ++Active, ++InstantiationIdx) {
501     // Skip this instantiation?
502     if (InstantiationIdx >= SkipStart && InstantiationIdx < SkipEnd) {
503       if (InstantiationIdx == SkipStart) {
504         // Note that we're skipping instantiations.
505         Diags.Report(Active->PointOfInstantiation,
506                      diag::note_instantiation_contexts_suppressed)
507           << unsigned(ActiveTemplateInstantiations.size() - Limit);
508       }
509       continue;
510     }
511 
512     switch (Active->Kind) {
513     case ActiveTemplateInstantiation::TemplateInstantiation: {
514       Decl *D = Active->Entity;
515       if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(D)) {
516         unsigned DiagID = diag::note_template_member_class_here;
517         if (isa<ClassTemplateSpecializationDecl>(Record))
518           DiagID = diag::note_template_class_instantiation_here;
519         Diags.Report(Active->PointOfInstantiation, DiagID)
520           << Context.getTypeDeclType(Record)
521           << Active->InstantiationRange;
522       } else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
523         unsigned DiagID;
524         if (Function->getPrimaryTemplate())
525           DiagID = diag::note_function_template_spec_here;
526         else
527           DiagID = diag::note_template_member_function_here;
528         Diags.Report(Active->PointOfInstantiation, DiagID)
529           << Function
530           << Active->InstantiationRange;
531       } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
532         Diags.Report(Active->PointOfInstantiation,
533                      VD->isStaticDataMember()?
534                        diag::note_template_static_data_member_def_here
535                      : diag::note_template_variable_def_here)
536           << VD
537           << Active->InstantiationRange;
538       } else if (EnumDecl *ED = dyn_cast<EnumDecl>(D)) {
539         Diags.Report(Active->PointOfInstantiation,
540                      diag::note_template_enum_def_here)
541           << ED
542           << Active->InstantiationRange;
543       } else {
544         Diags.Report(Active->PointOfInstantiation,
545                      diag::note_template_type_alias_instantiation_here)
546           << cast<TypeAliasTemplateDecl>(D)
547           << Active->InstantiationRange;
548       }
549       break;
550     }
551 
552     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation: {
553       TemplateDecl *Template = cast<TemplateDecl>(Active->Entity);
554       SmallVector<char, 128> TemplateArgsStr;
555       llvm::raw_svector_ostream OS(TemplateArgsStr);
556       Template->printName(OS);
557       TemplateSpecializationType::PrintTemplateArgumentList(OS,
558                                                          Active->TemplateArgs,
559                                                       Active->NumTemplateArgs,
560                                                       getPrintingPolicy());
561       Diags.Report(Active->PointOfInstantiation,
562                    diag::note_default_arg_instantiation_here)
563         << OS.str()
564         << Active->InstantiationRange;
565       break;
566     }
567 
568     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution: {
569       FunctionTemplateDecl *FnTmpl = cast<FunctionTemplateDecl>(Active->Entity);
570       Diags.Report(Active->PointOfInstantiation,
571                    diag::note_explicit_template_arg_substitution_here)
572         << FnTmpl
573         << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
574                                            Active->TemplateArgs,
575                                            Active->NumTemplateArgs)
576         << Active->InstantiationRange;
577       break;
578     }
579 
580     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
581       if (ClassTemplatePartialSpecializationDecl *PartialSpec =
582             dyn_cast<ClassTemplatePartialSpecializationDecl>(Active->Entity)) {
583         Diags.Report(Active->PointOfInstantiation,
584                      diag::note_partial_spec_deduct_instantiation_here)
585           << Context.getTypeDeclType(PartialSpec)
586           << getTemplateArgumentBindingsText(
587                                          PartialSpec->getTemplateParameters(),
588                                              Active->TemplateArgs,
589                                              Active->NumTemplateArgs)
590           << Active->InstantiationRange;
591       } else {
592         FunctionTemplateDecl *FnTmpl
593           = cast<FunctionTemplateDecl>(Active->Entity);
594         Diags.Report(Active->PointOfInstantiation,
595                      diag::note_function_template_deduction_instantiation_here)
596           << FnTmpl
597           << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
598                                              Active->TemplateArgs,
599                                              Active->NumTemplateArgs)
600           << Active->InstantiationRange;
601       }
602       break;
603 
604     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation: {
605       ParmVarDecl *Param = cast<ParmVarDecl>(Active->Entity);
606       FunctionDecl *FD = cast<FunctionDecl>(Param->getDeclContext());
607 
608       SmallVector<char, 128> TemplateArgsStr;
609       llvm::raw_svector_ostream OS(TemplateArgsStr);
610       FD->printName(OS);
611       TemplateSpecializationType::PrintTemplateArgumentList(OS,
612                                                          Active->TemplateArgs,
613                                                       Active->NumTemplateArgs,
614                                                       getPrintingPolicy());
615       Diags.Report(Active->PointOfInstantiation,
616                    diag::note_default_function_arg_instantiation_here)
617         << OS.str()
618         << Active->InstantiationRange;
619       break;
620     }
621 
622     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution: {
623       NamedDecl *Parm = cast<NamedDecl>(Active->Entity);
624       std::string Name;
625       if (!Parm->getName().empty())
626         Name = std::string(" '") + Parm->getName().str() + "'";
627 
628       TemplateParameterList *TemplateParams = 0;
629       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
630         TemplateParams = Template->getTemplateParameters();
631       else
632         TemplateParams =
633           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
634                                                       ->getTemplateParameters();
635       Diags.Report(Active->PointOfInstantiation,
636                    diag::note_prior_template_arg_substitution)
637         << isa<TemplateTemplateParmDecl>(Parm)
638         << Name
639         << getTemplateArgumentBindingsText(TemplateParams,
640                                            Active->TemplateArgs,
641                                            Active->NumTemplateArgs)
642         << Active->InstantiationRange;
643       break;
644     }
645 
646     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking: {
647       TemplateParameterList *TemplateParams = 0;
648       if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
649         TemplateParams = Template->getTemplateParameters();
650       else
651         TemplateParams =
652           cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
653                                                       ->getTemplateParameters();
654 
655       Diags.Report(Active->PointOfInstantiation,
656                    diag::note_template_default_arg_checking)
657         << getTemplateArgumentBindingsText(TemplateParams,
658                                            Active->TemplateArgs,
659                                            Active->NumTemplateArgs)
660         << Active->InstantiationRange;
661       break;
662     }
663 
664     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
665       Diags.Report(Active->PointOfInstantiation,
666                    diag::note_template_exception_spec_instantiation_here)
667         << cast<FunctionDecl>(Active->Entity)
668         << Active->InstantiationRange;
669       break;
670     }
671   }
672 }
673 
674 Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
675   if (InNonInstantiationSFINAEContext)
676     return Optional<TemplateDeductionInfo *>(0);
677 
678   for (SmallVectorImpl<ActiveTemplateInstantiation>::const_reverse_iterator
679          Active = ActiveTemplateInstantiations.rbegin(),
680          ActiveEnd = ActiveTemplateInstantiations.rend();
681        Active != ActiveEnd;
682        ++Active)
683   {
684     switch(Active->Kind) {
685     case ActiveTemplateInstantiation::TemplateInstantiation:
686       // An instantiation of an alias template may or may not be a SFINAE
687       // context, depending on what else is on the stack.
688       if (isa<TypeAliasTemplateDecl>(Active->Entity))
689         break;
690       // Fall through.
691     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
692     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
693       // This is a template instantiation, so there is no SFINAE.
694       return None;
695 
696     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
697     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
698     case ActiveTemplateInstantiation::DefaultTemplateArgumentChecking:
699       // A default template argument instantiation and substitution into
700       // template parameters with arguments for prior parameters may or may
701       // not be a SFINAE context; look further up the stack.
702       break;
703 
704     case ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution:
705     case ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution:
706       // We're either substitution explicitly-specified template arguments
707       // or deduced template arguments, so SFINAE applies.
708       assert(Active->DeductionInfo && "Missing deduction info pointer");
709       return Active->DeductionInfo;
710     }
711   }
712 
713   return None;
714 }
715 
716 /// \brief Retrieve the depth and index of a parameter pack.
717 static std::pair<unsigned, unsigned>
718 getDepthAndIndex(NamedDecl *ND) {
719   if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(ND))
720     return std::make_pair(TTP->getDepth(), TTP->getIndex());
721 
722   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(ND))
723     return std::make_pair(NTTP->getDepth(), NTTP->getIndex());
724 
725   TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(ND);
726   return std::make_pair(TTP->getDepth(), TTP->getIndex());
727 }
728 
729 //===----------------------------------------------------------------------===/
730 // Template Instantiation for Types
731 //===----------------------------------------------------------------------===/
732 namespace {
733   class TemplateInstantiator : public TreeTransform<TemplateInstantiator> {
734     const MultiLevelTemplateArgumentList &TemplateArgs;
735     SourceLocation Loc;
736     DeclarationName Entity;
737 
738   public:
739     typedef TreeTransform<TemplateInstantiator> inherited;
740 
741     TemplateInstantiator(Sema &SemaRef,
742                          const MultiLevelTemplateArgumentList &TemplateArgs,
743                          SourceLocation Loc,
744                          DeclarationName Entity)
745       : inherited(SemaRef), TemplateArgs(TemplateArgs), Loc(Loc),
746         Entity(Entity) { }
747 
748     /// \brief Determine whether the given type \p T has already been
749     /// transformed.
750     ///
751     /// For the purposes of template instantiation, a type has already been
752     /// transformed if it is NULL or if it is not dependent.
753     bool AlreadyTransformed(QualType T);
754 
755     /// \brief Returns the location of the entity being instantiated, if known.
756     SourceLocation getBaseLocation() { return Loc; }
757 
758     /// \brief Returns the name of the entity being instantiated, if any.
759     DeclarationName getBaseEntity() { return Entity; }
760 
761     /// \brief Sets the "base" location and entity when that
762     /// information is known based on another transformation.
763     void setBase(SourceLocation Loc, DeclarationName Entity) {
764       this->Loc = Loc;
765       this->Entity = Entity;
766     }
767 
768     bool TryExpandParameterPacks(SourceLocation EllipsisLoc,
769                                  SourceRange PatternRange,
770                                  ArrayRef<UnexpandedParameterPack> Unexpanded,
771                                  bool &ShouldExpand, bool &RetainExpansion,
772                                  Optional<unsigned> &NumExpansions) {
773       return getSema().CheckParameterPacksForExpansion(EllipsisLoc,
774                                                        PatternRange, Unexpanded,
775                                                        TemplateArgs,
776                                                        ShouldExpand,
777                                                        RetainExpansion,
778                                                        NumExpansions);
779     }
780 
781     void ExpandingFunctionParameterPack(ParmVarDecl *Pack) {
782       SemaRef.CurrentInstantiationScope->MakeInstantiatedLocalArgPack(Pack);
783     }
784 
785     TemplateArgument ForgetPartiallySubstitutedPack() {
786       TemplateArgument Result;
787       if (NamedDecl *PartialPack
788             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
789         MultiLevelTemplateArgumentList &TemplateArgs
790           = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
791         unsigned Depth, Index;
792         llvm::tie(Depth, Index) = getDepthAndIndex(PartialPack);
793         if (TemplateArgs.hasTemplateArgument(Depth, Index)) {
794           Result = TemplateArgs(Depth, Index);
795           TemplateArgs.setArgument(Depth, Index, TemplateArgument());
796         }
797       }
798 
799       return Result;
800     }
801 
802     void RememberPartiallySubstitutedPack(TemplateArgument Arg) {
803       if (Arg.isNull())
804         return;
805 
806       if (NamedDecl *PartialPack
807             = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
808         MultiLevelTemplateArgumentList &TemplateArgs
809         = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
810         unsigned Depth, Index;
811         llvm::tie(Depth, Index) = getDepthAndIndex(PartialPack);
812         TemplateArgs.setArgument(Depth, Index, Arg);
813       }
814     }
815 
816     /// \brief Transform the given declaration by instantiating a reference to
817     /// this declaration.
818     Decl *TransformDecl(SourceLocation Loc, Decl *D);
819 
820     void transformAttrs(Decl *Old, Decl *New) {
821       SemaRef.InstantiateAttrs(TemplateArgs, Old, New);
822     }
823 
824     void transformedLocalDecl(Decl *Old, Decl *New) {
825       SemaRef.CurrentInstantiationScope->InstantiatedLocal(Old, New);
826     }
827 
828     /// \brief Transform the definition of the given declaration by
829     /// instantiating it.
830     Decl *TransformDefinition(SourceLocation Loc, Decl *D);
831 
832     /// \brief Transform the first qualifier within a scope by instantiating the
833     /// declaration.
834     NamedDecl *TransformFirstQualifierInScope(NamedDecl *D, SourceLocation Loc);
835 
836     /// \brief Rebuild the exception declaration and register the declaration
837     /// as an instantiated local.
838     VarDecl *RebuildExceptionDecl(VarDecl *ExceptionDecl,
839                                   TypeSourceInfo *Declarator,
840                                   SourceLocation StartLoc,
841                                   SourceLocation NameLoc,
842                                   IdentifierInfo *Name);
843 
844     /// \brief Rebuild the Objective-C exception declaration and register the
845     /// declaration as an instantiated local.
846     VarDecl *RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
847                                       TypeSourceInfo *TSInfo, QualType T);
848 
849     /// \brief Check for tag mismatches when instantiating an
850     /// elaborated type.
851     QualType RebuildElaboratedType(SourceLocation KeywordLoc,
852                                    ElaboratedTypeKeyword Keyword,
853                                    NestedNameSpecifierLoc QualifierLoc,
854                                    QualType T);
855 
856     TemplateName TransformTemplateName(CXXScopeSpec &SS,
857                                        TemplateName Name,
858                                        SourceLocation NameLoc,
859                                        QualType ObjectType = QualType(),
860                                        NamedDecl *FirstQualifierInScope = 0);
861 
862     ExprResult TransformPredefinedExpr(PredefinedExpr *E);
863     ExprResult TransformDeclRefExpr(DeclRefExpr *E);
864     ExprResult TransformCXXDefaultArgExpr(CXXDefaultArgExpr *E);
865 
866     ExprResult TransformTemplateParmRefExpr(DeclRefExpr *E,
867                                             NonTypeTemplateParmDecl *D);
868     ExprResult TransformSubstNonTypeTemplateParmPackExpr(
869                                            SubstNonTypeTemplateParmPackExpr *E);
870 
871     /// \brief Rebuild a DeclRefExpr for a ParmVarDecl reference.
872     ExprResult RebuildParmVarDeclRefExpr(ParmVarDecl *PD, SourceLocation Loc);
873 
874     /// \brief Transform a reference to a function parameter pack.
875     ExprResult TransformFunctionParmPackRefExpr(DeclRefExpr *E,
876                                                 ParmVarDecl *PD);
877 
878     /// \brief Transform a FunctionParmPackExpr which was built when we couldn't
879     /// expand a function parameter pack reference which refers to an expanded
880     /// pack.
881     ExprResult TransformFunctionParmPackExpr(FunctionParmPackExpr *E);
882 
883     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
884                                         FunctionProtoTypeLoc TL);
885     QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
886                                         FunctionProtoTypeLoc TL,
887                                         CXXRecordDecl *ThisContext,
888                                         unsigned ThisTypeQuals);
889 
890     ParmVarDecl *TransformFunctionTypeParam(ParmVarDecl *OldParm,
891                                             int indexAdjustment,
892                                             Optional<unsigned> NumExpansions,
893                                             bool ExpectParameterPack);
894 
895     /// \brief Transforms a template type parameter type by performing
896     /// substitution of the corresponding template type argument.
897     QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
898                                            TemplateTypeParmTypeLoc TL);
899 
900     /// \brief Transforms an already-substituted template type parameter pack
901     /// into either itself (if we aren't substituting into its pack expansion)
902     /// or the appropriate substituted argument.
903     QualType TransformSubstTemplateTypeParmPackType(TypeLocBuilder &TLB,
904                                            SubstTemplateTypeParmPackTypeLoc TL);
905 
906     ExprResult TransformCallExpr(CallExpr *CE) {
907       getSema().CallsUndergoingInstantiation.push_back(CE);
908       ExprResult Result =
909           TreeTransform<TemplateInstantiator>::TransformCallExpr(CE);
910       getSema().CallsUndergoingInstantiation.pop_back();
911       return Result;
912     }
913 
914     ExprResult TransformLambdaExpr(LambdaExpr *E) {
915       LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
916       return TreeTransform<TemplateInstantiator>::TransformLambdaExpr(E);
917     }
918 
919     ExprResult TransformLambdaScope(LambdaExpr *E,
920                                     CXXMethodDecl *NewCallOperator) {
921       CXXMethodDecl *const OldCallOperator = E->getCallOperator();
922       // In the generic lambda case, we set the NewTemplate to be considered
923       // an "instantiation" of the OldTemplate.
924       if (FunctionTemplateDecl *const NewCallOperatorTemplate =
925             NewCallOperator->getDescribedFunctionTemplate()) {
926 
927         FunctionTemplateDecl *const OldCallOperatorTemplate =
928                               OldCallOperator->getDescribedFunctionTemplate();
929         NewCallOperatorTemplate->setInstantiatedFromMemberTemplate(
930                                                      OldCallOperatorTemplate);
931         // Mark the NewCallOperatorTemplate a specialization.
932         NewCallOperatorTemplate->setMemberSpecialization();
933       } else
934         // For a non-generic lambda we set the NewCallOperator to
935         // be an instantiation of the OldCallOperator.
936         NewCallOperator->setInstantiationOfMemberFunction(OldCallOperator,
937                                                     TSK_ImplicitInstantiation);
938 
939       return inherited::TransformLambdaScope(E, NewCallOperator);
940     }
941     TemplateParameterList *TransformTemplateParameterList(
942                               TemplateParameterList *OrigTPL)  {
943       if (!OrigTPL || !OrigTPL->size()) return OrigTPL;
944 
945       DeclContext *Owner = OrigTPL->getParam(0)->getDeclContext();
946       TemplateDeclInstantiator  DeclInstantiator(getSema(),
947                         /* DeclContext *Owner */ Owner, TemplateArgs);
948       return DeclInstantiator.SubstTemplateParams(OrigTPL);
949     }
950   private:
951     ExprResult transformNonTypeTemplateParmRef(NonTypeTemplateParmDecl *parm,
952                                                SourceLocation loc,
953                                                TemplateArgument arg);
954   };
955 }
956 
957 bool TemplateInstantiator::AlreadyTransformed(QualType T) {
958   if (T.isNull())
959     return true;
960 
961   if (T->isInstantiationDependentType() || T->isVariablyModifiedType())
962     return false;
963 
964   getSema().MarkDeclarationsReferencedInType(Loc, T);
965   return true;
966 }
967 
968 static TemplateArgument
969 getPackSubstitutedTemplateArgument(Sema &S, TemplateArgument Arg) {
970   assert(S.ArgumentPackSubstitutionIndex >= 0);
971   assert(S.ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
972   Arg = Arg.pack_begin()[S.ArgumentPackSubstitutionIndex];
973   if (Arg.isPackExpansion())
974     Arg = Arg.getPackExpansionPattern();
975   return Arg;
976 }
977 
978 Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
979   if (!D)
980     return 0;
981 
982   if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(D)) {
983     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
984       // If the corresponding template argument is NULL or non-existent, it's
985       // because we are performing instantiation from explicitly-specified
986       // template arguments in a function template, but there were some
987       // arguments left unspecified.
988       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
989                                             TTP->getPosition()))
990         return D;
991 
992       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
993 
994       if (TTP->isParameterPack()) {
995         assert(Arg.getKind() == TemplateArgument::Pack &&
996                "Missing argument pack");
997         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
998       }
999 
1000       TemplateName Template = Arg.getAsTemplate();
1001       assert(!Template.isNull() && Template.getAsTemplateDecl() &&
1002              "Wrong kind of template template argument");
1003       return Template.getAsTemplateDecl();
1004     }
1005 
1006     // Fall through to find the instantiated declaration for this template
1007     // template parameter.
1008   }
1009 
1010   return SemaRef.FindInstantiatedDecl(Loc, cast<NamedDecl>(D), TemplateArgs);
1011 }
1012 
1013 Decl *TemplateInstantiator::TransformDefinition(SourceLocation Loc, Decl *D) {
1014   Decl *Inst = getSema().SubstDecl(D, getSema().CurContext, TemplateArgs);
1015   if (!Inst)
1016     return 0;
1017 
1018   getSema().CurrentInstantiationScope->InstantiatedLocal(D, Inst);
1019   return Inst;
1020 }
1021 
1022 NamedDecl *
1023 TemplateInstantiator::TransformFirstQualifierInScope(NamedDecl *D,
1024                                                      SourceLocation Loc) {
1025   // If the first part of the nested-name-specifier was a template type
1026   // parameter, instantiate that type parameter down to a tag type.
1027   if (TemplateTypeParmDecl *TTPD = dyn_cast_or_null<TemplateTypeParmDecl>(D)) {
1028     const TemplateTypeParmType *TTP
1029       = cast<TemplateTypeParmType>(getSema().Context.getTypeDeclType(TTPD));
1030 
1031     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
1032       // FIXME: This needs testing w/ member access expressions.
1033       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getIndex());
1034 
1035       if (TTP->isParameterPack()) {
1036         assert(Arg.getKind() == TemplateArgument::Pack &&
1037                "Missing argument pack");
1038 
1039         if (getSema().ArgumentPackSubstitutionIndex == -1)
1040           return 0;
1041 
1042         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1043       }
1044 
1045       QualType T = Arg.getAsType();
1046       if (T.isNull())
1047         return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
1048 
1049       if (const TagType *Tag = T->getAs<TagType>())
1050         return Tag->getDecl();
1051 
1052       // The resulting type is not a tag; complain.
1053       getSema().Diag(Loc, diag::err_nested_name_spec_non_tag) << T;
1054       return 0;
1055     }
1056   }
1057 
1058   return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
1059 }
1060 
1061 VarDecl *
1062 TemplateInstantiator::RebuildExceptionDecl(VarDecl *ExceptionDecl,
1063                                            TypeSourceInfo *Declarator,
1064                                            SourceLocation StartLoc,
1065                                            SourceLocation NameLoc,
1066                                            IdentifierInfo *Name) {
1067   VarDecl *Var = inherited::RebuildExceptionDecl(ExceptionDecl, Declarator,
1068                                                  StartLoc, NameLoc, Name);
1069   if (Var)
1070     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
1071   return Var;
1072 }
1073 
1074 VarDecl *TemplateInstantiator::RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
1075                                                         TypeSourceInfo *TSInfo,
1076                                                         QualType T) {
1077   VarDecl *Var = inherited::RebuildObjCExceptionDecl(ExceptionDecl, TSInfo, T);
1078   if (Var)
1079     getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
1080   return Var;
1081 }
1082 
1083 QualType
1084 TemplateInstantiator::RebuildElaboratedType(SourceLocation KeywordLoc,
1085                                             ElaboratedTypeKeyword Keyword,
1086                                             NestedNameSpecifierLoc QualifierLoc,
1087                                             QualType T) {
1088   if (const TagType *TT = T->getAs<TagType>()) {
1089     TagDecl* TD = TT->getDecl();
1090 
1091     SourceLocation TagLocation = KeywordLoc;
1092 
1093     IdentifierInfo *Id = TD->getIdentifier();
1094 
1095     // TODO: should we even warn on struct/class mismatches for this?  Seems
1096     // like it's likely to produce a lot of spurious errors.
1097     if (Id && Keyword != ETK_None && Keyword != ETK_Typename) {
1098       TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForKeyword(Keyword);
1099       if (!SemaRef.isAcceptableTagRedeclaration(TD, Kind, /*isDefinition*/false,
1100                                                 TagLocation, *Id)) {
1101         SemaRef.Diag(TagLocation, diag::err_use_with_wrong_tag)
1102           << Id
1103           << FixItHint::CreateReplacement(SourceRange(TagLocation),
1104                                           TD->getKindName());
1105         SemaRef.Diag(TD->getLocation(), diag::note_previous_use);
1106       }
1107     }
1108   }
1109 
1110   return TreeTransform<TemplateInstantiator>::RebuildElaboratedType(KeywordLoc,
1111                                                                     Keyword,
1112                                                                   QualifierLoc,
1113                                                                     T);
1114 }
1115 
1116 TemplateName TemplateInstantiator::TransformTemplateName(CXXScopeSpec &SS,
1117                                                          TemplateName Name,
1118                                                          SourceLocation NameLoc,
1119                                                          QualType ObjectType,
1120                                              NamedDecl *FirstQualifierInScope) {
1121   if (TemplateTemplateParmDecl *TTP
1122        = dyn_cast_or_null<TemplateTemplateParmDecl>(Name.getAsTemplateDecl())) {
1123     if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
1124       // If the corresponding template argument is NULL or non-existent, it's
1125       // because we are performing instantiation from explicitly-specified
1126       // template arguments in a function template, but there were some
1127       // arguments left unspecified.
1128       if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
1129                                             TTP->getPosition()))
1130         return Name;
1131 
1132       TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
1133 
1134       if (TTP->isParameterPack()) {
1135         assert(Arg.getKind() == TemplateArgument::Pack &&
1136                "Missing argument pack");
1137 
1138         if (getSema().ArgumentPackSubstitutionIndex == -1) {
1139           // We have the template argument pack to substitute, but we're not
1140           // actually expanding the enclosing pack expansion yet. So, just
1141           // keep the entire argument pack.
1142           return getSema().Context.getSubstTemplateTemplateParmPack(TTP, Arg);
1143         }
1144 
1145         Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1146       }
1147 
1148       TemplateName Template = Arg.getAsTemplate();
1149       assert(!Template.isNull() && "Null template template argument");
1150 
1151       // We don't ever want to substitute for a qualified template name, since
1152       // the qualifier is handled separately. So, look through the qualified
1153       // template name to its underlying declaration.
1154       if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
1155         Template = TemplateName(QTN->getTemplateDecl());
1156 
1157       Template = getSema().Context.getSubstTemplateTemplateParm(TTP, Template);
1158       return Template;
1159     }
1160   }
1161 
1162   if (SubstTemplateTemplateParmPackStorage *SubstPack
1163       = Name.getAsSubstTemplateTemplateParmPack()) {
1164     if (getSema().ArgumentPackSubstitutionIndex == -1)
1165       return Name;
1166 
1167     TemplateArgument Arg = SubstPack->getArgumentPack();
1168     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1169     return Arg.getAsTemplate();
1170   }
1171 
1172   return inherited::TransformTemplateName(SS, Name, NameLoc, ObjectType,
1173                                           FirstQualifierInScope);
1174 }
1175 
1176 ExprResult
1177 TemplateInstantiator::TransformPredefinedExpr(PredefinedExpr *E) {
1178   if (!E->isTypeDependent())
1179     return SemaRef.Owned(E);
1180 
1181   return getSema().BuildPredefinedExpr(E->getLocation(), E->getIdentType());
1182 }
1183 
1184 ExprResult
1185 TemplateInstantiator::TransformTemplateParmRefExpr(DeclRefExpr *E,
1186                                                NonTypeTemplateParmDecl *NTTP) {
1187   // If the corresponding template argument is NULL or non-existent, it's
1188   // because we are performing instantiation from explicitly-specified
1189   // template arguments in a function template, but there were some
1190   // arguments left unspecified.
1191   if (!TemplateArgs.hasTemplateArgument(NTTP->getDepth(),
1192                                         NTTP->getPosition()))
1193     return SemaRef.Owned(E);
1194 
1195   TemplateArgument Arg = TemplateArgs(NTTP->getDepth(), NTTP->getPosition());
1196   if (NTTP->isParameterPack()) {
1197     assert(Arg.getKind() == TemplateArgument::Pack &&
1198            "Missing argument pack");
1199 
1200     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1201       // We have an argument pack, but we can't select a particular argument
1202       // out of it yet. Therefore, we'll build an expression to hold on to that
1203       // argument pack.
1204       QualType TargetType = SemaRef.SubstType(NTTP->getType(), TemplateArgs,
1205                                               E->getLocation(),
1206                                               NTTP->getDeclName());
1207       if (TargetType.isNull())
1208         return ExprError();
1209 
1210       return new (SemaRef.Context) SubstNonTypeTemplateParmPackExpr(TargetType,
1211                                                                     NTTP,
1212                                                               E->getLocation(),
1213                                                                     Arg);
1214     }
1215 
1216     Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1217   }
1218 
1219   return transformNonTypeTemplateParmRef(NTTP, E->getLocation(), Arg);
1220 }
1221 
1222 ExprResult TemplateInstantiator::transformNonTypeTemplateParmRef(
1223                                                  NonTypeTemplateParmDecl *parm,
1224                                                  SourceLocation loc,
1225                                                  TemplateArgument arg) {
1226   ExprResult result;
1227   QualType type;
1228 
1229   // The template argument itself might be an expression, in which
1230   // case we just return that expression.
1231   if (arg.getKind() == TemplateArgument::Expression) {
1232     Expr *argExpr = arg.getAsExpr();
1233     result = SemaRef.Owned(argExpr);
1234     type = argExpr->getType();
1235 
1236   } else if (arg.getKind() == TemplateArgument::Declaration ||
1237              arg.getKind() == TemplateArgument::NullPtr) {
1238     ValueDecl *VD;
1239     if (arg.getKind() == TemplateArgument::Declaration) {
1240       VD = cast<ValueDecl>(arg.getAsDecl());
1241 
1242       // Find the instantiation of the template argument.  This is
1243       // required for nested templates.
1244       VD = cast_or_null<ValueDecl>(
1245              getSema().FindInstantiatedDecl(loc, VD, TemplateArgs));
1246       if (!VD)
1247         return ExprError();
1248     } else {
1249       // Propagate NULL template argument.
1250       VD = 0;
1251     }
1252 
1253     // Derive the type we want the substituted decl to have.  This had
1254     // better be non-dependent, or these checks will have serious problems.
1255     if (parm->isExpandedParameterPack()) {
1256       type = parm->getExpansionType(SemaRef.ArgumentPackSubstitutionIndex);
1257     } else if (parm->isParameterPack() &&
1258                isa<PackExpansionType>(parm->getType())) {
1259       type = SemaRef.SubstType(
1260                         cast<PackExpansionType>(parm->getType())->getPattern(),
1261                                      TemplateArgs, loc, parm->getDeclName());
1262     } else {
1263       type = SemaRef.SubstType(parm->getType(), TemplateArgs,
1264                                loc, parm->getDeclName());
1265     }
1266     assert(!type.isNull() && "type substitution failed for param type");
1267     assert(!type->isDependentType() && "param type still dependent");
1268     result = SemaRef.BuildExpressionFromDeclTemplateArgument(arg, type, loc);
1269 
1270     if (!result.isInvalid()) type = result.get()->getType();
1271   } else {
1272     result = SemaRef.BuildExpressionFromIntegralTemplateArgument(arg, loc);
1273 
1274     // Note that this type can be different from the type of 'result',
1275     // e.g. if it's an enum type.
1276     type = arg.getIntegralType();
1277   }
1278   if (result.isInvalid()) return ExprError();
1279 
1280   Expr *resultExpr = result.take();
1281   return SemaRef.Owned(new (SemaRef.Context)
1282                 SubstNonTypeTemplateParmExpr(type,
1283                                              resultExpr->getValueKind(),
1284                                              loc, parm, resultExpr));
1285 }
1286 
1287 ExprResult
1288 TemplateInstantiator::TransformSubstNonTypeTemplateParmPackExpr(
1289                                           SubstNonTypeTemplateParmPackExpr *E) {
1290   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1291     // We aren't expanding the parameter pack, so just return ourselves.
1292     return getSema().Owned(E);
1293   }
1294 
1295   TemplateArgument Arg = E->getArgumentPack();
1296   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1297   return transformNonTypeTemplateParmRef(E->getParameterPack(),
1298                                          E->getParameterPackLocation(),
1299                                          Arg);
1300 }
1301 
1302 ExprResult
1303 TemplateInstantiator::RebuildParmVarDeclRefExpr(ParmVarDecl *PD,
1304                                                 SourceLocation Loc) {
1305   DeclarationNameInfo NameInfo(PD->getDeclName(), Loc);
1306   return getSema().BuildDeclarationNameExpr(CXXScopeSpec(), NameInfo, PD);
1307 }
1308 
1309 ExprResult
1310 TemplateInstantiator::TransformFunctionParmPackExpr(FunctionParmPackExpr *E) {
1311   if (getSema().ArgumentPackSubstitutionIndex != -1) {
1312     // We can expand this parameter pack now.
1313     ParmVarDecl *D = E->getExpansion(getSema().ArgumentPackSubstitutionIndex);
1314     ValueDecl *VD = cast_or_null<ValueDecl>(TransformDecl(E->getExprLoc(), D));
1315     if (!VD)
1316       return ExprError();
1317     return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(VD), E->getExprLoc());
1318   }
1319 
1320   QualType T = TransformType(E->getType());
1321   if (T.isNull())
1322     return ExprError();
1323 
1324   // Transform each of the parameter expansions into the corresponding
1325   // parameters in the instantiation of the function decl.
1326   SmallVector<Decl *, 8> Parms;
1327   Parms.reserve(E->getNumExpansions());
1328   for (FunctionParmPackExpr::iterator I = E->begin(), End = E->end();
1329        I != End; ++I) {
1330     ParmVarDecl *D =
1331         cast_or_null<ParmVarDecl>(TransformDecl(E->getExprLoc(), *I));
1332     if (!D)
1333       return ExprError();
1334     Parms.push_back(D);
1335   }
1336 
1337   return FunctionParmPackExpr::Create(getSema().Context, T,
1338                                       E->getParameterPack(),
1339                                       E->getParameterPackLocation(), Parms);
1340 }
1341 
1342 ExprResult
1343 TemplateInstantiator::TransformFunctionParmPackRefExpr(DeclRefExpr *E,
1344                                                        ParmVarDecl *PD) {
1345   typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
1346   llvm::PointerUnion<Decl *, DeclArgumentPack *> *Found
1347     = getSema().CurrentInstantiationScope->findInstantiationOf(PD);
1348   assert(Found && "no instantiation for parameter pack");
1349 
1350   Decl *TransformedDecl;
1351   if (DeclArgumentPack *Pack = Found->dyn_cast<DeclArgumentPack *>()) {
1352     // If this is a reference to a function parameter pack which we can substitute
1353     // but can't yet expand, build a FunctionParmPackExpr for it.
1354     if (getSema().ArgumentPackSubstitutionIndex == -1) {
1355       QualType T = TransformType(E->getType());
1356       if (T.isNull())
1357         return ExprError();
1358       return FunctionParmPackExpr::Create(getSema().Context, T, PD,
1359                                           E->getExprLoc(), *Pack);
1360     }
1361 
1362     TransformedDecl = (*Pack)[getSema().ArgumentPackSubstitutionIndex];
1363   } else {
1364     TransformedDecl = Found->get<Decl*>();
1365   }
1366 
1367   // We have either an unexpanded pack or a specific expansion.
1368   return RebuildParmVarDeclRefExpr(cast<ParmVarDecl>(TransformedDecl),
1369                                    E->getExprLoc());
1370 }
1371 
1372 ExprResult
1373 TemplateInstantiator::TransformDeclRefExpr(DeclRefExpr *E) {
1374   NamedDecl *D = E->getDecl();
1375 
1376   // Handle references to non-type template parameters and non-type template
1377   // parameter packs.
1378   if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D)) {
1379     if (NTTP->getDepth() < TemplateArgs.getNumLevels())
1380       return TransformTemplateParmRefExpr(E, NTTP);
1381 
1382     // We have a non-type template parameter that isn't fully substituted;
1383     // FindInstantiatedDecl will find it in the local instantiation scope.
1384   }
1385 
1386   // Handle references to function parameter packs.
1387   if (ParmVarDecl *PD = dyn_cast<ParmVarDecl>(D))
1388     if (PD->isParameterPack())
1389       return TransformFunctionParmPackRefExpr(E, PD);
1390 
1391   return TreeTransform<TemplateInstantiator>::TransformDeclRefExpr(E);
1392 }
1393 
1394 ExprResult TemplateInstantiator::TransformCXXDefaultArgExpr(
1395     CXXDefaultArgExpr *E) {
1396   assert(!cast<FunctionDecl>(E->getParam()->getDeclContext())->
1397              getDescribedFunctionTemplate() &&
1398          "Default arg expressions are never formed in dependent cases.");
1399   return SemaRef.BuildCXXDefaultArgExpr(E->getUsedLocation(),
1400                            cast<FunctionDecl>(E->getParam()->getDeclContext()),
1401                                         E->getParam());
1402 }
1403 
1404 QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
1405                                                       FunctionProtoTypeLoc TL) {
1406   // We need a local instantiation scope for this function prototype.
1407   LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
1408   return inherited::TransformFunctionProtoType(TLB, TL);
1409 }
1410 
1411 QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
1412                                  FunctionProtoTypeLoc TL,
1413                                  CXXRecordDecl *ThisContext,
1414                                  unsigned ThisTypeQuals) {
1415   // We need a local instantiation scope for this function prototype.
1416   LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
1417   return inherited::TransformFunctionProtoType(TLB, TL, ThisContext,
1418                                                ThisTypeQuals);
1419 }
1420 
1421 ParmVarDecl *
1422 TemplateInstantiator::TransformFunctionTypeParam(ParmVarDecl *OldParm,
1423                                                  int indexAdjustment,
1424                                                Optional<unsigned> NumExpansions,
1425                                                  bool ExpectParameterPack) {
1426   return SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
1427                                   NumExpansions, ExpectParameterPack);
1428 }
1429 
1430 QualType
1431 TemplateInstantiator::TransformTemplateTypeParmType(TypeLocBuilder &TLB,
1432                                                 TemplateTypeParmTypeLoc TL) {
1433   const TemplateTypeParmType *T = TL.getTypePtr();
1434   if (T->getDepth() < TemplateArgs.getNumLevels()) {
1435     // Replace the template type parameter with its corresponding
1436     // template argument.
1437 
1438     // If the corresponding template argument is NULL or doesn't exist, it's
1439     // because we are performing instantiation from explicitly-specified
1440     // template arguments in a function template class, but there were some
1441     // arguments left unspecified.
1442     if (!TemplateArgs.hasTemplateArgument(T->getDepth(), T->getIndex())) {
1443       TemplateTypeParmTypeLoc NewTL
1444         = TLB.push<TemplateTypeParmTypeLoc>(TL.getType());
1445       NewTL.setNameLoc(TL.getNameLoc());
1446       return TL.getType();
1447     }
1448 
1449     TemplateArgument Arg = TemplateArgs(T->getDepth(), T->getIndex());
1450 
1451     if (T->isParameterPack()) {
1452       assert(Arg.getKind() == TemplateArgument::Pack &&
1453              "Missing argument pack");
1454 
1455       if (getSema().ArgumentPackSubstitutionIndex == -1) {
1456         // We have the template argument pack, but we're not expanding the
1457         // enclosing pack expansion yet. Just save the template argument
1458         // pack for later substitution.
1459         QualType Result
1460           = getSema().Context.getSubstTemplateTypeParmPackType(T, Arg);
1461         SubstTemplateTypeParmPackTypeLoc NewTL
1462           = TLB.push<SubstTemplateTypeParmPackTypeLoc>(Result);
1463         NewTL.setNameLoc(TL.getNameLoc());
1464         return Result;
1465       }
1466 
1467       Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1468     }
1469 
1470     assert(Arg.getKind() == TemplateArgument::Type &&
1471            "Template argument kind mismatch");
1472 
1473     QualType Replacement = Arg.getAsType();
1474 
1475     // TODO: only do this uniquing once, at the start of instantiation.
1476     QualType Result
1477       = getSema().Context.getSubstTemplateTypeParmType(T, Replacement);
1478     SubstTemplateTypeParmTypeLoc NewTL
1479       = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1480     NewTL.setNameLoc(TL.getNameLoc());
1481     return Result;
1482   }
1483 
1484   // The template type parameter comes from an inner template (e.g.,
1485   // the template parameter list of a member template inside the
1486   // template we are instantiating). Create a new template type
1487   // parameter with the template "level" reduced by one.
1488   TemplateTypeParmDecl *NewTTPDecl = 0;
1489   if (TemplateTypeParmDecl *OldTTPDecl = T->getDecl())
1490     NewTTPDecl = cast_or_null<TemplateTypeParmDecl>(
1491                                   TransformDecl(TL.getNameLoc(), OldTTPDecl));
1492 
1493   QualType Result
1494     = getSema().Context.getTemplateTypeParmType(T->getDepth()
1495                                                  - TemplateArgs.getNumLevels(),
1496                                                 T->getIndex(),
1497                                                 T->isParameterPack(),
1498                                                 NewTTPDecl);
1499   TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
1500   NewTL.setNameLoc(TL.getNameLoc());
1501   return Result;
1502 }
1503 
1504 QualType
1505 TemplateInstantiator::TransformSubstTemplateTypeParmPackType(
1506                                                             TypeLocBuilder &TLB,
1507                                          SubstTemplateTypeParmPackTypeLoc TL) {
1508   if (getSema().ArgumentPackSubstitutionIndex == -1) {
1509     // We aren't expanding the parameter pack, so just return ourselves.
1510     SubstTemplateTypeParmPackTypeLoc NewTL
1511       = TLB.push<SubstTemplateTypeParmPackTypeLoc>(TL.getType());
1512     NewTL.setNameLoc(TL.getNameLoc());
1513     return TL.getType();
1514   }
1515 
1516   TemplateArgument Arg = TL.getTypePtr()->getArgumentPack();
1517   Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
1518   QualType Result = Arg.getAsType();
1519 
1520   Result = getSema().Context.getSubstTemplateTypeParmType(
1521                                       TL.getTypePtr()->getReplacedParameter(),
1522                                                           Result);
1523   SubstTemplateTypeParmTypeLoc NewTL
1524     = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
1525   NewTL.setNameLoc(TL.getNameLoc());
1526   return Result;
1527 }
1528 
1529 /// \brief Perform substitution on the type T with a given set of template
1530 /// arguments.
1531 ///
1532 /// This routine substitutes the given template arguments into the
1533 /// type T and produces the instantiated type.
1534 ///
1535 /// \param T the type into which the template arguments will be
1536 /// substituted. If this type is not dependent, it will be returned
1537 /// immediately.
1538 ///
1539 /// \param Args the template arguments that will be
1540 /// substituted for the top-level template parameters within T.
1541 ///
1542 /// \param Loc the location in the source code where this substitution
1543 /// is being performed. It will typically be the location of the
1544 /// declarator (if we're instantiating the type of some declaration)
1545 /// or the location of the type in the source code (if, e.g., we're
1546 /// instantiating the type of a cast expression).
1547 ///
1548 /// \param Entity the name of the entity associated with a declaration
1549 /// being instantiated (if any). May be empty to indicate that there
1550 /// is no such entity (if, e.g., this is a type that occurs as part of
1551 /// a cast expression) or that the entity has no name (e.g., an
1552 /// unnamed function parameter).
1553 ///
1554 /// \returns If the instantiation succeeds, the instantiated
1555 /// type. Otherwise, produces diagnostics and returns a NULL type.
1556 TypeSourceInfo *Sema::SubstType(TypeSourceInfo *T,
1557                                 const MultiLevelTemplateArgumentList &Args,
1558                                 SourceLocation Loc,
1559                                 DeclarationName Entity) {
1560   assert(!ActiveTemplateInstantiations.empty() &&
1561          "Cannot perform an instantiation without some context on the "
1562          "instantiation stack");
1563 
1564   if (!T->getType()->isInstantiationDependentType() &&
1565       !T->getType()->isVariablyModifiedType())
1566     return T;
1567 
1568   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1569   return Instantiator.TransformType(T);
1570 }
1571 
1572 TypeSourceInfo *Sema::SubstType(TypeLoc TL,
1573                                 const MultiLevelTemplateArgumentList &Args,
1574                                 SourceLocation Loc,
1575                                 DeclarationName Entity) {
1576   assert(!ActiveTemplateInstantiations.empty() &&
1577          "Cannot perform an instantiation without some context on the "
1578          "instantiation stack");
1579 
1580   if (TL.getType().isNull())
1581     return 0;
1582 
1583   if (!TL.getType()->isInstantiationDependentType() &&
1584       !TL.getType()->isVariablyModifiedType()) {
1585     // FIXME: Make a copy of the TypeLoc data here, so that we can
1586     // return a new TypeSourceInfo. Inefficient!
1587     TypeLocBuilder TLB;
1588     TLB.pushFullCopy(TL);
1589     return TLB.getTypeSourceInfo(Context, TL.getType());
1590   }
1591 
1592   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1593   TypeLocBuilder TLB;
1594   TLB.reserve(TL.getFullDataSize());
1595   QualType Result = Instantiator.TransformType(TLB, TL);
1596   if (Result.isNull())
1597     return 0;
1598 
1599   return TLB.getTypeSourceInfo(Context, Result);
1600 }
1601 
1602 /// Deprecated form of the above.
1603 QualType Sema::SubstType(QualType T,
1604                          const MultiLevelTemplateArgumentList &TemplateArgs,
1605                          SourceLocation Loc, DeclarationName Entity) {
1606   assert(!ActiveTemplateInstantiations.empty() &&
1607          "Cannot perform an instantiation without some context on the "
1608          "instantiation stack");
1609 
1610   // If T is not a dependent type or a variably-modified type, there
1611   // is nothing to do.
1612   if (!T->isInstantiationDependentType() && !T->isVariablyModifiedType())
1613     return T;
1614 
1615   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc, Entity);
1616   return Instantiator.TransformType(T);
1617 }
1618 
1619 static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
1620   if (T->getType()->isInstantiationDependentType() ||
1621       T->getType()->isVariablyModifiedType())
1622     return true;
1623 
1624   TypeLoc TL = T->getTypeLoc().IgnoreParens();
1625   if (!TL.getAs<FunctionProtoTypeLoc>())
1626     return false;
1627 
1628   FunctionProtoTypeLoc FP = TL.castAs<FunctionProtoTypeLoc>();
1629   for (unsigned I = 0, E = FP.getNumArgs(); I != E; ++I) {
1630     ParmVarDecl *P = FP.getArg(I);
1631 
1632     // This must be synthesized from a typedef.
1633     if (!P) continue;
1634 
1635     // The parameter's type as written might be dependent even if the
1636     // decayed type was not dependent.
1637     if (TypeSourceInfo *TSInfo = P->getTypeSourceInfo())
1638       if (TSInfo->getType()->isInstantiationDependentType())
1639         return true;
1640 
1641     // TODO: currently we always rebuild expressions.  When we
1642     // properly get lazier about this, we should use the same
1643     // logic to avoid rebuilding prototypes here.
1644     if (P->hasDefaultArg())
1645       return true;
1646   }
1647 
1648   return false;
1649 }
1650 
1651 /// A form of SubstType intended specifically for instantiating the
1652 /// type of a FunctionDecl.  Its purpose is solely to force the
1653 /// instantiation of default-argument expressions.
1654 TypeSourceInfo *Sema::SubstFunctionDeclType(TypeSourceInfo *T,
1655                                 const MultiLevelTemplateArgumentList &Args,
1656                                 SourceLocation Loc,
1657                                 DeclarationName Entity,
1658                                 CXXRecordDecl *ThisContext,
1659                                 unsigned ThisTypeQuals) {
1660   assert(!ActiveTemplateInstantiations.empty() &&
1661          "Cannot perform an instantiation without some context on the "
1662          "instantiation stack");
1663 
1664   if (!NeedsInstantiationAsFunctionType(T))
1665     return T;
1666 
1667   TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
1668 
1669   TypeLocBuilder TLB;
1670 
1671   TypeLoc TL = T->getTypeLoc();
1672   TLB.reserve(TL.getFullDataSize());
1673 
1674   QualType Result;
1675 
1676   if (FunctionProtoTypeLoc Proto = TL.getAs<FunctionProtoTypeLoc>()) {
1677     Result = Instantiator.TransformFunctionProtoType(TLB, Proto, ThisContext,
1678                                                      ThisTypeQuals);
1679   } else {
1680     Result = Instantiator.TransformType(TLB, TL);
1681   }
1682   if (Result.isNull())
1683     return 0;
1684 
1685   return TLB.getTypeSourceInfo(Context, Result);
1686 }
1687 
1688 ParmVarDecl *Sema::SubstParmVarDecl(ParmVarDecl *OldParm,
1689                             const MultiLevelTemplateArgumentList &TemplateArgs,
1690                                     int indexAdjustment,
1691                                     Optional<unsigned> NumExpansions,
1692                                     bool ExpectParameterPack) {
1693   TypeSourceInfo *OldDI = OldParm->getTypeSourceInfo();
1694   TypeSourceInfo *NewDI = 0;
1695 
1696   TypeLoc OldTL = OldDI->getTypeLoc();
1697   if (PackExpansionTypeLoc ExpansionTL = OldTL.getAs<PackExpansionTypeLoc>()) {
1698 
1699     // We have a function parameter pack. Substitute into the pattern of the
1700     // expansion.
1701     NewDI = SubstType(ExpansionTL.getPatternLoc(), TemplateArgs,
1702                       OldParm->getLocation(), OldParm->getDeclName());
1703     if (!NewDI)
1704       return 0;
1705 
1706     if (NewDI->getType()->containsUnexpandedParameterPack()) {
1707       // We still have unexpanded parameter packs, which means that
1708       // our function parameter is still a function parameter pack.
1709       // Therefore, make its type a pack expansion type.
1710       NewDI = CheckPackExpansion(NewDI, ExpansionTL.getEllipsisLoc(),
1711                                  NumExpansions);
1712     } else if (ExpectParameterPack) {
1713       // We expected to get a parameter pack but didn't (because the type
1714       // itself is not a pack expansion type), so complain. This can occur when
1715       // the substitution goes through an alias template that "loses" the
1716       // pack expansion.
1717       Diag(OldParm->getLocation(),
1718            diag::err_function_parameter_pack_without_parameter_packs)
1719         << NewDI->getType();
1720       return 0;
1721     }
1722   } else {
1723     NewDI = SubstType(OldDI, TemplateArgs, OldParm->getLocation(),
1724                       OldParm->getDeclName());
1725   }
1726 
1727   if (!NewDI)
1728     return 0;
1729 
1730   if (NewDI->getType()->isVoidType()) {
1731     Diag(OldParm->getLocation(), diag::err_param_with_void_type);
1732     return 0;
1733   }
1734 
1735   ParmVarDecl *NewParm = CheckParameter(Context.getTranslationUnitDecl(),
1736                                         OldParm->getInnerLocStart(),
1737                                         OldParm->getLocation(),
1738                                         OldParm->getIdentifier(),
1739                                         NewDI->getType(), NewDI,
1740                                         OldParm->getStorageClass());
1741   if (!NewParm)
1742     return 0;
1743 
1744   // Mark the (new) default argument as uninstantiated (if any).
1745   if (OldParm->hasUninstantiatedDefaultArg()) {
1746     Expr *Arg = OldParm->getUninstantiatedDefaultArg();
1747     NewParm->setUninstantiatedDefaultArg(Arg);
1748   } else if (OldParm->hasUnparsedDefaultArg()) {
1749     NewParm->setUnparsedDefaultArg();
1750     UnparsedDefaultArgInstantiations[OldParm].push_back(NewParm);
1751   } else if (Expr *Arg = OldParm->getDefaultArg())
1752     // FIXME: if we non-lazily instantiated non-dependent default args for
1753     // non-dependent parameter types we could remove a bunch of duplicate
1754     // conversion warnings for such arguments.
1755     NewParm->setUninstantiatedDefaultArg(Arg);
1756 
1757   NewParm->setHasInheritedDefaultArg(OldParm->hasInheritedDefaultArg());
1758 
1759   if (OldParm->isParameterPack() && !NewParm->isParameterPack()) {
1760     // Add the new parameter to the instantiated parameter pack.
1761     CurrentInstantiationScope->InstantiatedLocalPackArg(OldParm, NewParm);
1762   } else {
1763     // Introduce an Old -> New mapping
1764     CurrentInstantiationScope->InstantiatedLocal(OldParm, NewParm);
1765   }
1766 
1767   // FIXME: OldParm may come from a FunctionProtoType, in which case CurContext
1768   // can be anything, is this right ?
1769   NewParm->setDeclContext(CurContext);
1770 
1771   NewParm->setScopeInfo(OldParm->getFunctionScopeDepth(),
1772                         OldParm->getFunctionScopeIndex() + indexAdjustment);
1773 
1774   InstantiateAttrs(TemplateArgs, OldParm, NewParm);
1775 
1776   return NewParm;
1777 }
1778 
1779 /// \brief Substitute the given template arguments into the given set of
1780 /// parameters, producing the set of parameter types that would be generated
1781 /// from such a substitution.
1782 bool Sema::SubstParmTypes(SourceLocation Loc,
1783                           ParmVarDecl **Params, unsigned NumParams,
1784                           const MultiLevelTemplateArgumentList &TemplateArgs,
1785                           SmallVectorImpl<QualType> &ParamTypes,
1786                           SmallVectorImpl<ParmVarDecl *> *OutParams) {
1787   assert(!ActiveTemplateInstantiations.empty() &&
1788          "Cannot perform an instantiation without some context on the "
1789          "instantiation stack");
1790 
1791   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
1792                                     DeclarationName());
1793   return Instantiator.TransformFunctionTypeParams(Loc, Params, NumParams, 0,
1794                                                   ParamTypes, OutParams);
1795 }
1796 
1797 /// \brief Perform substitution on the base class specifiers of the
1798 /// given class template specialization.
1799 ///
1800 /// Produces a diagnostic and returns true on error, returns false and
1801 /// attaches the instantiated base classes to the class template
1802 /// specialization if successful.
1803 bool
1804 Sema::SubstBaseSpecifiers(CXXRecordDecl *Instantiation,
1805                           CXXRecordDecl *Pattern,
1806                           const MultiLevelTemplateArgumentList &TemplateArgs) {
1807   bool Invalid = false;
1808   SmallVector<CXXBaseSpecifier*, 4> InstantiatedBases;
1809   for (ClassTemplateSpecializationDecl::base_class_iterator
1810          Base = Pattern->bases_begin(), BaseEnd = Pattern->bases_end();
1811        Base != BaseEnd; ++Base) {
1812     if (!Base->getType()->isDependentType()) {
1813       if (const CXXRecordDecl *RD = Base->getType()->getAsCXXRecordDecl()) {
1814         if (RD->isInvalidDecl())
1815           Instantiation->setInvalidDecl();
1816       }
1817       InstantiatedBases.push_back(new (Context) CXXBaseSpecifier(*Base));
1818       continue;
1819     }
1820 
1821     SourceLocation EllipsisLoc;
1822     TypeSourceInfo *BaseTypeLoc;
1823     if (Base->isPackExpansion()) {
1824       // This is a pack expansion. See whether we should expand it now, or
1825       // wait until later.
1826       SmallVector<UnexpandedParameterPack, 2> Unexpanded;
1827       collectUnexpandedParameterPacks(Base->getTypeSourceInfo()->getTypeLoc(),
1828                                       Unexpanded);
1829       bool ShouldExpand = false;
1830       bool RetainExpansion = false;
1831       Optional<unsigned> NumExpansions;
1832       if (CheckParameterPacksForExpansion(Base->getEllipsisLoc(),
1833                                           Base->getSourceRange(),
1834                                           Unexpanded,
1835                                           TemplateArgs, ShouldExpand,
1836                                           RetainExpansion,
1837                                           NumExpansions)) {
1838         Invalid = true;
1839         continue;
1840       }
1841 
1842       // If we should expand this pack expansion now, do so.
1843       if (ShouldExpand) {
1844         for (unsigned I = 0; I != *NumExpansions; ++I) {
1845             Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, I);
1846 
1847           TypeSourceInfo *BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1848                                                   TemplateArgs,
1849                                               Base->getSourceRange().getBegin(),
1850                                                   DeclarationName());
1851           if (!BaseTypeLoc) {
1852             Invalid = true;
1853             continue;
1854           }
1855 
1856           if (CXXBaseSpecifier *InstantiatedBase
1857                 = CheckBaseSpecifier(Instantiation,
1858                                      Base->getSourceRange(),
1859                                      Base->isVirtual(),
1860                                      Base->getAccessSpecifierAsWritten(),
1861                                      BaseTypeLoc,
1862                                      SourceLocation()))
1863             InstantiatedBases.push_back(InstantiatedBase);
1864           else
1865             Invalid = true;
1866         }
1867 
1868         continue;
1869       }
1870 
1871       // The resulting base specifier will (still) be a pack expansion.
1872       EllipsisLoc = Base->getEllipsisLoc();
1873       Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
1874       BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1875                               TemplateArgs,
1876                               Base->getSourceRange().getBegin(),
1877                               DeclarationName());
1878     } else {
1879       BaseTypeLoc = SubstType(Base->getTypeSourceInfo(),
1880                               TemplateArgs,
1881                               Base->getSourceRange().getBegin(),
1882                               DeclarationName());
1883     }
1884 
1885     if (!BaseTypeLoc) {
1886       Invalid = true;
1887       continue;
1888     }
1889 
1890     if (CXXBaseSpecifier *InstantiatedBase
1891           = CheckBaseSpecifier(Instantiation,
1892                                Base->getSourceRange(),
1893                                Base->isVirtual(),
1894                                Base->getAccessSpecifierAsWritten(),
1895                                BaseTypeLoc,
1896                                EllipsisLoc))
1897       InstantiatedBases.push_back(InstantiatedBase);
1898     else
1899       Invalid = true;
1900   }
1901 
1902   if (!Invalid &&
1903       AttachBaseSpecifiers(Instantiation, InstantiatedBases.data(),
1904                            InstantiatedBases.size()))
1905     Invalid = true;
1906 
1907   return Invalid;
1908 }
1909 
1910 // Defined via #include from SemaTemplateInstantiateDecl.cpp
1911 namespace clang {
1912   namespace sema {
1913     Attr *instantiateTemplateAttribute(const Attr *At, ASTContext &C, Sema &S,
1914                             const MultiLevelTemplateArgumentList &TemplateArgs);
1915   }
1916 }
1917 
1918 /// Determine whether we would be unable to instantiate this template (because
1919 /// it either has no definition, or is in the process of being instantiated).
1920 static bool DiagnoseUninstantiableTemplate(Sema &S,
1921                                            SourceLocation PointOfInstantiation,
1922                                            TagDecl *Instantiation,
1923                                            bool InstantiatedFromMember,
1924                                            TagDecl *Pattern,
1925                                            TagDecl *PatternDef,
1926                                            TemplateSpecializationKind TSK,
1927                                            bool Complain = true) {
1928   if (PatternDef && !PatternDef->isBeingDefined())
1929     return false;
1930 
1931   if (!Complain || (PatternDef && PatternDef->isInvalidDecl())) {
1932     // Say nothing
1933   } else if (PatternDef) {
1934     assert(PatternDef->isBeingDefined());
1935     S.Diag(PointOfInstantiation,
1936            diag::err_template_instantiate_within_definition)
1937       << (TSK != TSK_ImplicitInstantiation)
1938       << S.Context.getTypeDeclType(Instantiation);
1939     // Not much point in noting the template declaration here, since
1940     // we're lexically inside it.
1941     Instantiation->setInvalidDecl();
1942   } else if (InstantiatedFromMember) {
1943     S.Diag(PointOfInstantiation,
1944            diag::err_implicit_instantiate_member_undefined)
1945       << S.Context.getTypeDeclType(Instantiation);
1946     S.Diag(Pattern->getLocation(), diag::note_member_of_template_here);
1947   } else {
1948     S.Diag(PointOfInstantiation, diag::err_template_instantiate_undefined)
1949       << (TSK != TSK_ImplicitInstantiation)
1950       << S.Context.getTypeDeclType(Instantiation);
1951     S.Diag(Pattern->getLocation(), diag::note_template_decl_here);
1952   }
1953 
1954   // In general, Instantiation isn't marked invalid to get more than one
1955   // error for multiple undefined instantiations. But the code that does
1956   // explicit declaration -> explicit definition conversion can't handle
1957   // invalid declarations, so mark as invalid in that case.
1958   if (TSK == TSK_ExplicitInstantiationDeclaration)
1959     Instantiation->setInvalidDecl();
1960   return true;
1961 }
1962 
1963 /// \brief Instantiate the definition of a class from a given pattern.
1964 ///
1965 /// \param PointOfInstantiation The point of instantiation within the
1966 /// source code.
1967 ///
1968 /// \param Instantiation is the declaration whose definition is being
1969 /// instantiated. This will be either a class template specialization
1970 /// or a member class of a class template specialization.
1971 ///
1972 /// \param Pattern is the pattern from which the instantiation
1973 /// occurs. This will be either the declaration of a class template or
1974 /// the declaration of a member class of a class template.
1975 ///
1976 /// \param TemplateArgs The template arguments to be substituted into
1977 /// the pattern.
1978 ///
1979 /// \param TSK the kind of implicit or explicit instantiation to perform.
1980 ///
1981 /// \param Complain whether to complain if the class cannot be instantiated due
1982 /// to the lack of a definition.
1983 ///
1984 /// \returns true if an error occurred, false otherwise.
1985 bool
1986 Sema::InstantiateClass(SourceLocation PointOfInstantiation,
1987                        CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
1988                        const MultiLevelTemplateArgumentList &TemplateArgs,
1989                        TemplateSpecializationKind TSK,
1990                        bool Complain) {
1991   CXXRecordDecl *PatternDef
1992     = cast_or_null<CXXRecordDecl>(Pattern->getDefinition());
1993   if (DiagnoseUninstantiableTemplate(*this, PointOfInstantiation, Instantiation,
1994                                 Instantiation->getInstantiatedFromMemberClass(),
1995                                      Pattern, PatternDef, TSK, Complain))
1996     return true;
1997   Pattern = PatternDef;
1998 
1999   // \brief Record the point of instantiation.
2000   if (MemberSpecializationInfo *MSInfo
2001         = Instantiation->getMemberSpecializationInfo()) {
2002     MSInfo->setTemplateSpecializationKind(TSK);
2003     MSInfo->setPointOfInstantiation(PointOfInstantiation);
2004   } else if (ClassTemplateSpecializationDecl *Spec
2005         = dyn_cast<ClassTemplateSpecializationDecl>(Instantiation)) {
2006     Spec->setTemplateSpecializationKind(TSK);
2007     Spec->setPointOfInstantiation(PointOfInstantiation);
2008   }
2009 
2010   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2011   if (Inst.isInvalid())
2012     return true;
2013 
2014   // Enter the scope of this instantiation. We don't use
2015   // PushDeclContext because we don't have a scope.
2016   ContextRAII SavedContext(*this, Instantiation);
2017   EnterExpressionEvaluationContext EvalContext(*this,
2018                                                Sema::PotentiallyEvaluated);
2019 
2020   // If this is an instantiation of a local class, merge this local
2021   // instantiation scope with the enclosing scope. Otherwise, every
2022   // instantiation of a class has its own local instantiation scope.
2023   bool MergeWithParentScope = !Instantiation->isDefinedOutsideFunctionOrMethod();
2024   LocalInstantiationScope Scope(*this, MergeWithParentScope);
2025 
2026   // Pull attributes from the pattern onto the instantiation.
2027   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
2028 
2029   // Start the definition of this instantiation.
2030   Instantiation->startDefinition();
2031 
2032   Instantiation->setTagKind(Pattern->getTagKind());
2033 
2034   // Do substitution on the base class specifiers.
2035   if (SubstBaseSpecifiers(Instantiation, Pattern, TemplateArgs))
2036     Instantiation->setInvalidDecl();
2037 
2038   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
2039   SmallVector<Decl*, 4> Fields;
2040   SmallVector<std::pair<FieldDecl*, FieldDecl*>, 4>
2041     FieldsWithMemberInitializers;
2042   // Delay instantiation of late parsed attributes.
2043   LateInstantiatedAttrVec LateAttrs;
2044   Instantiator.enableLateAttributeInstantiation(&LateAttrs);
2045 
2046   for (RecordDecl::decl_iterator Member = Pattern->decls_begin(),
2047          MemberEnd = Pattern->decls_end();
2048        Member != MemberEnd; ++Member) {
2049     // Don't instantiate members not belonging in this semantic context.
2050     // e.g. for:
2051     // @code
2052     //    template <int i> class A {
2053     //      class B *g;
2054     //    };
2055     // @endcode
2056     // 'class B' has the template as lexical context but semantically it is
2057     // introduced in namespace scope.
2058     if ((*Member)->getDeclContext() != Pattern)
2059       continue;
2060 
2061     if ((*Member)->isInvalidDecl()) {
2062       Instantiation->setInvalidDecl();
2063       continue;
2064     }
2065 
2066     Decl *NewMember = Instantiator.Visit(*Member);
2067     if (NewMember) {
2068       if (FieldDecl *Field = dyn_cast<FieldDecl>(NewMember)) {
2069         Fields.push_back(Field);
2070         FieldDecl *OldField = cast<FieldDecl>(*Member);
2071         if (OldField->getInClassInitializer())
2072           FieldsWithMemberInitializers.push_back(std::make_pair(OldField,
2073                                                                 Field));
2074       } else if (EnumDecl *Enum = dyn_cast<EnumDecl>(NewMember)) {
2075         // C++11 [temp.inst]p1: The implicit instantiation of a class template
2076         // specialization causes the implicit instantiation of the definitions
2077         // of unscoped member enumerations.
2078         // Record a point of instantiation for this implicit instantiation.
2079         if (TSK == TSK_ImplicitInstantiation && !Enum->isScoped() &&
2080             Enum->isCompleteDefinition()) {
2081           MemberSpecializationInfo *MSInfo =Enum->getMemberSpecializationInfo();
2082           assert(MSInfo && "no spec info for member enum specialization");
2083           MSInfo->setTemplateSpecializationKind(TSK_ImplicitInstantiation);
2084           MSInfo->setPointOfInstantiation(PointOfInstantiation);
2085         }
2086       } else if (StaticAssertDecl *SA = dyn_cast<StaticAssertDecl>(NewMember)) {
2087         if (SA->isFailed()) {
2088           // A static_assert failed. Bail out; instantiating this
2089           // class is probably not meaningful.
2090           Instantiation->setInvalidDecl();
2091           break;
2092         }
2093       }
2094 
2095       if (NewMember->isInvalidDecl())
2096         Instantiation->setInvalidDecl();
2097     } else {
2098       // FIXME: Eventually, a NULL return will mean that one of the
2099       // instantiations was a semantic disaster, and we'll want to mark the
2100       // declaration invalid.
2101       // For now, we expect to skip some members that we can't yet handle.
2102     }
2103   }
2104 
2105   // Finish checking fields.
2106   ActOnFields(0, Instantiation->getLocation(), Instantiation, Fields,
2107               SourceLocation(), SourceLocation(), 0);
2108   CheckCompletedCXXClass(Instantiation);
2109 
2110   // Attach any in-class member initializers now the class is complete.
2111   // FIXME: We are supposed to defer instantiating these until they are needed.
2112   if (!FieldsWithMemberInitializers.empty()) {
2113     // C++11 [expr.prim.general]p4:
2114     //   Otherwise, if a member-declarator declares a non-static data member
2115     //  (9.2) of a class X, the expression this is a prvalue of type "pointer
2116     //  to X" within the optional brace-or-equal-initializer. It shall not
2117     //  appear elsewhere in the member-declarator.
2118     CXXThisScopeRAII ThisScope(*this, Instantiation, (unsigned)0);
2119 
2120     for (unsigned I = 0, N = FieldsWithMemberInitializers.size(); I != N; ++I) {
2121       FieldDecl *OldField = FieldsWithMemberInitializers[I].first;
2122       FieldDecl *NewField = FieldsWithMemberInitializers[I].second;
2123       Expr *OldInit = OldField->getInClassInitializer();
2124 
2125       ExprResult NewInit = SubstInitializer(OldInit, TemplateArgs,
2126                                             /*CXXDirectInit=*/false);
2127       if (NewInit.isInvalid())
2128         NewField->setInvalidDecl();
2129       else {
2130         Expr *Init = NewInit.take();
2131         assert(Init && "no-argument initializer in class");
2132         assert(!isa<ParenListExpr>(Init) && "call-style init in class");
2133         ActOnCXXInClassMemberInitializer(NewField, Init->getLocStart(), Init);
2134       }
2135     }
2136   }
2137   // Instantiate late parsed attributes, and attach them to their decls.
2138   // See Sema::InstantiateAttrs
2139   for (LateInstantiatedAttrVec::iterator I = LateAttrs.begin(),
2140        E = LateAttrs.end(); I != E; ++I) {
2141     assert(CurrentInstantiationScope == Instantiator.getStartingScope());
2142     CurrentInstantiationScope = I->Scope;
2143 
2144     // Allow 'this' within late-parsed attributes.
2145     NamedDecl *ND = dyn_cast<NamedDecl>(I->NewDecl);
2146     CXXRecordDecl *ThisContext =
2147         dyn_cast_or_null<CXXRecordDecl>(ND->getDeclContext());
2148     CXXThisScopeRAII ThisScope(*this, ThisContext, /*TypeQuals*/0,
2149                                ND && ND->isCXXInstanceMember());
2150 
2151     Attr *NewAttr =
2152       instantiateTemplateAttribute(I->TmplAttr, Context, *this, TemplateArgs);
2153     I->NewDecl->addAttr(NewAttr);
2154     LocalInstantiationScope::deleteScopes(I->Scope,
2155                                           Instantiator.getStartingScope());
2156   }
2157   Instantiator.disableLateAttributeInstantiation();
2158   LateAttrs.clear();
2159 
2160   ActOnFinishDelayedMemberInitializers(Instantiation);
2161 
2162   if (TSK == TSK_ImplicitInstantiation) {
2163     Instantiation->setLocation(Pattern->getLocation());
2164     Instantiation->setLocStart(Pattern->getInnerLocStart());
2165     Instantiation->setRBraceLoc(Pattern->getRBraceLoc());
2166   }
2167 
2168   if (!Instantiation->isInvalidDecl()) {
2169     // Perform any dependent diagnostics from the pattern.
2170     PerformDependentDiagnostics(Pattern, TemplateArgs);
2171 
2172     // Instantiate any out-of-line class template partial
2173     // specializations now.
2174     for (TemplateDeclInstantiator::delayed_partial_spec_iterator
2175               P = Instantiator.delayed_partial_spec_begin(),
2176            PEnd = Instantiator.delayed_partial_spec_end();
2177          P != PEnd; ++P) {
2178       if (!Instantiator.InstantiateClassTemplatePartialSpecialization(
2179               P->first, P->second)) {
2180         Instantiation->setInvalidDecl();
2181         break;
2182       }
2183     }
2184 
2185     // Instantiate any out-of-line variable template partial
2186     // specializations now.
2187     for (TemplateDeclInstantiator::delayed_var_partial_spec_iterator
2188               P = Instantiator.delayed_var_partial_spec_begin(),
2189            PEnd = Instantiator.delayed_var_partial_spec_end();
2190          P != PEnd; ++P) {
2191       if (!Instantiator.InstantiateVarTemplatePartialSpecialization(
2192               P->first, P->second)) {
2193         Instantiation->setInvalidDecl();
2194         break;
2195       }
2196     }
2197   }
2198 
2199   // Exit the scope of this instantiation.
2200   SavedContext.pop();
2201 
2202   if (!Instantiation->isInvalidDecl()) {
2203     Consumer.HandleTagDeclDefinition(Instantiation);
2204 
2205     // Always emit the vtable for an explicit instantiation definition
2206     // of a polymorphic class template specialization.
2207     if (TSK == TSK_ExplicitInstantiationDefinition)
2208       MarkVTableUsed(PointOfInstantiation, Instantiation, true);
2209   }
2210 
2211   return Instantiation->isInvalidDecl();
2212 }
2213 
2214 /// \brief Instantiate the definition of an enum from a given pattern.
2215 ///
2216 /// \param PointOfInstantiation The point of instantiation within the
2217 ///        source code.
2218 /// \param Instantiation is the declaration whose definition is being
2219 ///        instantiated. This will be a member enumeration of a class
2220 ///        temploid specialization, or a local enumeration within a
2221 ///        function temploid specialization.
2222 /// \param Pattern The templated declaration from which the instantiation
2223 ///        occurs.
2224 /// \param TemplateArgs The template arguments to be substituted into
2225 ///        the pattern.
2226 /// \param TSK The kind of implicit or explicit instantiation to perform.
2227 ///
2228 /// \return \c true if an error occurred, \c false otherwise.
2229 bool Sema::InstantiateEnum(SourceLocation PointOfInstantiation,
2230                            EnumDecl *Instantiation, EnumDecl *Pattern,
2231                            const MultiLevelTemplateArgumentList &TemplateArgs,
2232                            TemplateSpecializationKind TSK) {
2233   EnumDecl *PatternDef = Pattern->getDefinition();
2234   if (DiagnoseUninstantiableTemplate(*this, PointOfInstantiation, Instantiation,
2235                                  Instantiation->getInstantiatedFromMemberEnum(),
2236                                      Pattern, PatternDef, TSK,/*Complain*/true))
2237     return true;
2238   Pattern = PatternDef;
2239 
2240   // Record the point of instantiation.
2241   if (MemberSpecializationInfo *MSInfo
2242         = Instantiation->getMemberSpecializationInfo()) {
2243     MSInfo->setTemplateSpecializationKind(TSK);
2244     MSInfo->setPointOfInstantiation(PointOfInstantiation);
2245   }
2246 
2247   InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
2248   if (Inst.isInvalid())
2249     return true;
2250 
2251   // Enter the scope of this instantiation. We don't use
2252   // PushDeclContext because we don't have a scope.
2253   ContextRAII SavedContext(*this, Instantiation);
2254   EnterExpressionEvaluationContext EvalContext(*this,
2255                                                Sema::PotentiallyEvaluated);
2256 
2257   LocalInstantiationScope Scope(*this, /*MergeWithParentScope*/true);
2258 
2259   // Pull attributes from the pattern onto the instantiation.
2260   InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
2261 
2262   TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
2263   Instantiator.InstantiateEnumDefinition(Instantiation, Pattern);
2264 
2265   // Exit the scope of this instantiation.
2266   SavedContext.pop();
2267 
2268   return Instantiation->isInvalidDecl();
2269 }
2270 
2271 namespace {
2272   /// \brief A partial specialization whose template arguments have matched
2273   /// a given template-id.
2274   struct PartialSpecMatchResult {
2275     ClassTemplatePartialSpecializationDecl *Partial;
2276     TemplateArgumentList *Args;
2277   };
2278 }
2279 
2280 bool Sema::InstantiateClassTemplateSpecialization(
2281     SourceLocation PointOfInstantiation,
2282     ClassTemplateSpecializationDecl *ClassTemplateSpec,
2283     TemplateSpecializationKind TSK, bool Complain) {
2284   // Perform the actual instantiation on the canonical declaration.
2285   ClassTemplateSpec = cast<ClassTemplateSpecializationDecl>(
2286                                          ClassTemplateSpec->getCanonicalDecl());
2287 
2288   // Check whether we have already instantiated or specialized this class
2289   // template specialization.
2290   if (ClassTemplateSpec->getSpecializationKind() != TSK_Undeclared) {
2291     if (ClassTemplateSpec->getSpecializationKind() ==
2292           TSK_ExplicitInstantiationDeclaration &&
2293         TSK == TSK_ExplicitInstantiationDefinition) {
2294       // An explicit instantiation definition follows an explicit instantiation
2295       // declaration (C++0x [temp.explicit]p10); go ahead and perform the
2296       // explicit instantiation.
2297       ClassTemplateSpec->setSpecializationKind(TSK);
2298 
2299       // If this is an explicit instantiation definition, mark the
2300       // vtable as used.
2301       if (TSK == TSK_ExplicitInstantiationDefinition &&
2302           !ClassTemplateSpec->isInvalidDecl())
2303         MarkVTableUsed(PointOfInstantiation, ClassTemplateSpec, true);
2304 
2305       return false;
2306     }
2307 
2308     // We can only instantiate something that hasn't already been
2309     // instantiated or specialized. Fail without any diagnostics: our
2310     // caller will provide an error message.
2311     return true;
2312   }
2313 
2314   if (ClassTemplateSpec->isInvalidDecl())
2315     return true;
2316 
2317   ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
2318   CXXRecordDecl *Pattern = 0;
2319 
2320   // C++ [temp.class.spec.match]p1:
2321   //   When a class template is used in a context that requires an
2322   //   instantiation of the class, it is necessary to determine
2323   //   whether the instantiation is to be generated using the primary
2324   //   template or one of the partial specializations. This is done by
2325   //   matching the template arguments of the class template
2326   //   specialization with the template argument lists of the partial
2327   //   specializations.
2328   typedef PartialSpecMatchResult MatchResult;
2329   SmallVector<MatchResult, 4> Matched;
2330   SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
2331   Template->getPartialSpecializations(PartialSpecs);
2332   TemplateSpecCandidateSet FailedCandidates(PointOfInstantiation);
2333   for (unsigned I = 0, N = PartialSpecs.size(); I != N; ++I) {
2334     ClassTemplatePartialSpecializationDecl *Partial = PartialSpecs[I];
2335     TemplateDeductionInfo Info(FailedCandidates.getLocation());
2336     if (TemplateDeductionResult Result
2337           = DeduceTemplateArguments(Partial,
2338                                     ClassTemplateSpec->getTemplateArgs(),
2339                                     Info)) {
2340       // Store the failed-deduction information for use in diagnostics, later.
2341       // TODO: Actually use the failed-deduction info?
2342       FailedCandidates.addCandidate()
2343           .set(Partial, MakeDeductionFailureInfo(Context, Result, Info));
2344       (void)Result;
2345     } else {
2346       Matched.push_back(PartialSpecMatchResult());
2347       Matched.back().Partial = Partial;
2348       Matched.back().Args = Info.take();
2349     }
2350   }
2351 
2352   // If we're dealing with a member template where the template parameters
2353   // have been instantiated, this provides the original template parameters
2354   // from which the member template's parameters were instantiated.
2355   SmallVector<const NamedDecl *, 4> InstantiatedTemplateParameters;
2356 
2357   if (Matched.size() >= 1) {
2358     SmallVectorImpl<MatchResult>::iterator Best = Matched.begin();
2359     if (Matched.size() == 1) {
2360       //   -- If exactly one matching specialization is found, the
2361       //      instantiation is generated from that specialization.
2362       // We don't need to do anything for this.
2363     } else {
2364       //   -- If more than one matching specialization is found, the
2365       //      partial order rules (14.5.4.2) are used to determine
2366       //      whether one of the specializations is more specialized
2367       //      than the others. If none of the specializations is more
2368       //      specialized than all of the other matching
2369       //      specializations, then the use of the class template is
2370       //      ambiguous and the program is ill-formed.
2371       for (SmallVectorImpl<MatchResult>::iterator P = Best + 1,
2372                                                PEnd = Matched.end();
2373            P != PEnd; ++P) {
2374         if (getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2375                                                     PointOfInstantiation)
2376               == P->Partial)
2377           Best = P;
2378       }
2379 
2380       // Determine if the best partial specialization is more specialized than
2381       // the others.
2382       bool Ambiguous = false;
2383       for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2384                                                PEnd = Matched.end();
2385            P != PEnd; ++P) {
2386         if (P != Best &&
2387             getMoreSpecializedPartialSpecialization(P->Partial, Best->Partial,
2388                                                     PointOfInstantiation)
2389               != Best->Partial) {
2390           Ambiguous = true;
2391           break;
2392         }
2393       }
2394 
2395       if (Ambiguous) {
2396         // Partial ordering did not produce a clear winner. Complain.
2397         ClassTemplateSpec->setInvalidDecl();
2398         Diag(PointOfInstantiation, diag::err_partial_spec_ordering_ambiguous)
2399           << ClassTemplateSpec;
2400 
2401         // Print the matching partial specializations.
2402         for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
2403                                                  PEnd = Matched.end();
2404              P != PEnd; ++P)
2405           Diag(P->Partial->getLocation(), diag::note_partial_spec_match)
2406             << getTemplateArgumentBindingsText(
2407                                             P->Partial->getTemplateParameters(),
2408                                                *P->Args);
2409 
2410         return true;
2411       }
2412     }
2413 
2414     // Instantiate using the best class template partial specialization.
2415     ClassTemplatePartialSpecializationDecl *OrigPartialSpec = Best->Partial;
2416     while (OrigPartialSpec->getInstantiatedFromMember()) {
2417       // If we've found an explicit specialization of this class template,
2418       // stop here and use that as the pattern.
2419       if (OrigPartialSpec->isMemberSpecialization())
2420         break;
2421 
2422       OrigPartialSpec = OrigPartialSpec->getInstantiatedFromMember();
2423     }
2424 
2425     Pattern = OrigPartialSpec;
2426     ClassTemplateSpec->setInstantiationOf(Best->Partial, Best->Args);
2427   } else {
2428     //   -- If no matches are found, the instantiation is generated
2429     //      from the primary template.
2430     ClassTemplateDecl *OrigTemplate = Template;
2431     while (OrigTemplate->getInstantiatedFromMemberTemplate()) {
2432       // If we've found an explicit specialization of this class template,
2433       // stop here and use that as the pattern.
2434       if (OrigTemplate->isMemberSpecialization())
2435         break;
2436 
2437       OrigTemplate = OrigTemplate->getInstantiatedFromMemberTemplate();
2438     }
2439 
2440     Pattern = OrigTemplate->getTemplatedDecl();
2441   }
2442 
2443   bool Result = InstantiateClass(PointOfInstantiation, ClassTemplateSpec,
2444                                  Pattern,
2445                                 getTemplateInstantiationArgs(ClassTemplateSpec),
2446                                  TSK,
2447                                  Complain);
2448 
2449   return Result;
2450 }
2451 
2452 /// \brief Instantiates the definitions of all of the member
2453 /// of the given class, which is an instantiation of a class template
2454 /// or a member class of a template.
2455 void
2456 Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
2457                               CXXRecordDecl *Instantiation,
2458                         const MultiLevelTemplateArgumentList &TemplateArgs,
2459                               TemplateSpecializationKind TSK) {
2460   for (DeclContext::decl_iterator D = Instantiation->decls_begin(),
2461                                DEnd = Instantiation->decls_end();
2462        D != DEnd; ++D) {
2463     bool SuppressNew = false;
2464     if (FunctionDecl *Function = dyn_cast<FunctionDecl>(*D)) {
2465       if (FunctionDecl *Pattern
2466             = Function->getInstantiatedFromMemberFunction()) {
2467         MemberSpecializationInfo *MSInfo
2468           = Function->getMemberSpecializationInfo();
2469         assert(MSInfo && "No member specialization information?");
2470         if (MSInfo->getTemplateSpecializationKind()
2471                                                  == TSK_ExplicitSpecialization)
2472           continue;
2473 
2474         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2475                                                    Function,
2476                                         MSInfo->getTemplateSpecializationKind(),
2477                                               MSInfo->getPointOfInstantiation(),
2478                                                    SuppressNew) ||
2479             SuppressNew)
2480           continue;
2481 
2482         if (Function->isDefined())
2483           continue;
2484 
2485         if (TSK == TSK_ExplicitInstantiationDefinition) {
2486           // C++0x [temp.explicit]p8:
2487           //   An explicit instantiation definition that names a class template
2488           //   specialization explicitly instantiates the class template
2489           //   specialization and is only an explicit instantiation definition
2490           //   of members whose definition is visible at the point of
2491           //   instantiation.
2492           if (!Pattern->isDefined())
2493             continue;
2494 
2495           Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2496 
2497           InstantiateFunctionDefinition(PointOfInstantiation, Function);
2498         } else {
2499           Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2500         }
2501       }
2502     } else if (VarDecl *Var = dyn_cast<VarDecl>(*D)) {
2503       if (isa<VarTemplateSpecializationDecl>(Var))
2504         continue;
2505 
2506       if (Var->isStaticDataMember()) {
2507         MemberSpecializationInfo *MSInfo = Var->getMemberSpecializationInfo();
2508         assert(MSInfo && "No member specialization information?");
2509         if (MSInfo->getTemplateSpecializationKind()
2510                                                  == TSK_ExplicitSpecialization)
2511           continue;
2512 
2513         if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2514                                                    Var,
2515                                         MSInfo->getTemplateSpecializationKind(),
2516                                               MSInfo->getPointOfInstantiation(),
2517                                                    SuppressNew) ||
2518             SuppressNew)
2519           continue;
2520 
2521         if (TSK == TSK_ExplicitInstantiationDefinition) {
2522           // C++0x [temp.explicit]p8:
2523           //   An explicit instantiation definition that names a class template
2524           //   specialization explicitly instantiates the class template
2525           //   specialization and is only an explicit instantiation definition
2526           //   of members whose definition is visible at the point of
2527           //   instantiation.
2528           if (!Var->getInstantiatedFromStaticDataMember()
2529                                                      ->getOutOfLineDefinition())
2530             continue;
2531 
2532           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2533           InstantiateStaticDataMemberDefinition(PointOfInstantiation, Var);
2534         } else {
2535           Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
2536         }
2537       }
2538     } else if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(*D)) {
2539       // Always skip the injected-class-name, along with any
2540       // redeclarations of nested classes, since both would cause us
2541       // to try to instantiate the members of a class twice.
2542       if (Record->isInjectedClassName() || Record->getPreviousDecl())
2543         continue;
2544 
2545       MemberSpecializationInfo *MSInfo = Record->getMemberSpecializationInfo();
2546       assert(MSInfo && "No member specialization information?");
2547 
2548       if (MSInfo->getTemplateSpecializationKind()
2549                                                 == TSK_ExplicitSpecialization)
2550         continue;
2551 
2552       if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
2553                                                  Record,
2554                                         MSInfo->getTemplateSpecializationKind(),
2555                                               MSInfo->getPointOfInstantiation(),
2556                                                  SuppressNew) ||
2557           SuppressNew)
2558         continue;
2559 
2560       CXXRecordDecl *Pattern = Record->getInstantiatedFromMemberClass();
2561       assert(Pattern && "Missing instantiated-from-template information");
2562 
2563       if (!Record->getDefinition()) {
2564         if (!Pattern->getDefinition()) {
2565           // C++0x [temp.explicit]p8:
2566           //   An explicit instantiation definition that names a class template
2567           //   specialization explicitly instantiates the class template
2568           //   specialization and is only an explicit instantiation definition
2569           //   of members whose definition is visible at the point of
2570           //   instantiation.
2571           if (TSK == TSK_ExplicitInstantiationDeclaration) {
2572             MSInfo->setTemplateSpecializationKind(TSK);
2573             MSInfo->setPointOfInstantiation(PointOfInstantiation);
2574           }
2575 
2576           continue;
2577         }
2578 
2579         InstantiateClass(PointOfInstantiation, Record, Pattern,
2580                          TemplateArgs,
2581                          TSK);
2582       } else {
2583         if (TSK == TSK_ExplicitInstantiationDefinition &&
2584             Record->getTemplateSpecializationKind() ==
2585                 TSK_ExplicitInstantiationDeclaration) {
2586           Record->setTemplateSpecializationKind(TSK);
2587           MarkVTableUsed(PointOfInstantiation, Record, true);
2588         }
2589       }
2590 
2591       Pattern = cast_or_null<CXXRecordDecl>(Record->getDefinition());
2592       if (Pattern)
2593         InstantiateClassMembers(PointOfInstantiation, Pattern, TemplateArgs,
2594                                 TSK);
2595     } else if (EnumDecl *Enum = dyn_cast<EnumDecl>(*D)) {
2596       MemberSpecializationInfo *MSInfo = Enum->getMemberSpecializationInfo();
2597       assert(MSInfo && "No member specialization information?");
2598 
2599       if (MSInfo->getTemplateSpecializationKind()
2600             == TSK_ExplicitSpecialization)
2601         continue;
2602 
2603       if (CheckSpecializationInstantiationRedecl(
2604             PointOfInstantiation, TSK, Enum,
2605             MSInfo->getTemplateSpecializationKind(),
2606             MSInfo->getPointOfInstantiation(), SuppressNew) ||
2607           SuppressNew)
2608         continue;
2609 
2610       if (Enum->getDefinition())
2611         continue;
2612 
2613       EnumDecl *Pattern = Enum->getInstantiatedFromMemberEnum();
2614       assert(Pattern && "Missing instantiated-from-template information");
2615 
2616       if (TSK == TSK_ExplicitInstantiationDefinition) {
2617         if (!Pattern->getDefinition())
2618           continue;
2619 
2620         InstantiateEnum(PointOfInstantiation, Enum, Pattern, TemplateArgs, TSK);
2621       } else {
2622         MSInfo->setTemplateSpecializationKind(TSK);
2623         MSInfo->setPointOfInstantiation(PointOfInstantiation);
2624       }
2625     }
2626   }
2627 }
2628 
2629 /// \brief Instantiate the definitions of all of the members of the
2630 /// given class template specialization, which was named as part of an
2631 /// explicit instantiation.
2632 void
2633 Sema::InstantiateClassTemplateSpecializationMembers(
2634                                            SourceLocation PointOfInstantiation,
2635                             ClassTemplateSpecializationDecl *ClassTemplateSpec,
2636                                                TemplateSpecializationKind TSK) {
2637   // C++0x [temp.explicit]p7:
2638   //   An explicit instantiation that names a class template
2639   //   specialization is an explicit instantion of the same kind
2640   //   (declaration or definition) of each of its members (not
2641   //   including members inherited from base classes) that has not
2642   //   been previously explicitly specialized in the translation unit
2643   //   containing the explicit instantiation, except as described
2644   //   below.
2645   InstantiateClassMembers(PointOfInstantiation, ClassTemplateSpec,
2646                           getTemplateInstantiationArgs(ClassTemplateSpec),
2647                           TSK);
2648 }
2649 
2650 StmtResult
2651 Sema::SubstStmt(Stmt *S, const MultiLevelTemplateArgumentList &TemplateArgs) {
2652   if (!S)
2653     return Owned(S);
2654 
2655   TemplateInstantiator Instantiator(*this, TemplateArgs,
2656                                     SourceLocation(),
2657                                     DeclarationName());
2658   return Instantiator.TransformStmt(S);
2659 }
2660 
2661 ExprResult
2662 Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
2663   if (!E)
2664     return Owned(E);
2665 
2666   TemplateInstantiator Instantiator(*this, TemplateArgs,
2667                                     SourceLocation(),
2668                                     DeclarationName());
2669   return Instantiator.TransformExpr(E);
2670 }
2671 
2672 ExprResult Sema::SubstInitializer(Expr *Init,
2673                           const MultiLevelTemplateArgumentList &TemplateArgs,
2674                           bool CXXDirectInit) {
2675   TemplateInstantiator Instantiator(*this, TemplateArgs,
2676                                     SourceLocation(),
2677                                     DeclarationName());
2678   return Instantiator.TransformInitializer(Init, CXXDirectInit);
2679 }
2680 
2681 bool Sema::SubstExprs(Expr **Exprs, unsigned NumExprs, bool IsCall,
2682                       const MultiLevelTemplateArgumentList &TemplateArgs,
2683                       SmallVectorImpl<Expr *> &Outputs) {
2684   if (NumExprs == 0)
2685     return false;
2686 
2687   TemplateInstantiator Instantiator(*this, TemplateArgs,
2688                                     SourceLocation(),
2689                                     DeclarationName());
2690   return Instantiator.TransformExprs(Exprs, NumExprs, IsCall, Outputs);
2691 }
2692 
2693 NestedNameSpecifierLoc
2694 Sema::SubstNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
2695                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2696   if (!NNS)
2697     return NestedNameSpecifierLoc();
2698 
2699   TemplateInstantiator Instantiator(*this, TemplateArgs, NNS.getBeginLoc(),
2700                                     DeclarationName());
2701   return Instantiator.TransformNestedNameSpecifierLoc(NNS);
2702 }
2703 
2704 /// \brief Do template substitution on declaration name info.
2705 DeclarationNameInfo
2706 Sema::SubstDeclarationNameInfo(const DeclarationNameInfo &NameInfo,
2707                          const MultiLevelTemplateArgumentList &TemplateArgs) {
2708   TemplateInstantiator Instantiator(*this, TemplateArgs, NameInfo.getLoc(),
2709                                     NameInfo.getName());
2710   return Instantiator.TransformDeclarationNameInfo(NameInfo);
2711 }
2712 
2713 TemplateName
2714 Sema::SubstTemplateName(NestedNameSpecifierLoc QualifierLoc,
2715                         TemplateName Name, SourceLocation Loc,
2716                         const MultiLevelTemplateArgumentList &TemplateArgs) {
2717   TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
2718                                     DeclarationName());
2719   CXXScopeSpec SS;
2720   SS.Adopt(QualifierLoc);
2721   return Instantiator.TransformTemplateName(SS, Name, Loc);
2722 }
2723 
2724 bool Sema::Subst(const TemplateArgumentLoc *Args, unsigned NumArgs,
2725                  TemplateArgumentListInfo &Result,
2726                  const MultiLevelTemplateArgumentList &TemplateArgs) {
2727   TemplateInstantiator Instantiator(*this, TemplateArgs, SourceLocation(),
2728                                     DeclarationName());
2729 
2730   return Instantiator.TransformTemplateArguments(Args, NumArgs, Result);
2731 }
2732 
2733 
2734 static const Decl* getCanonicalParmVarDecl(const Decl *D) {
2735   // When storing ParmVarDecls in the local instantiation scope, we always
2736   // want to use the ParmVarDecl from the canonical function declaration,
2737   // since the map is then valid for any redeclaration or definition of that
2738   // function.
2739   if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(D)) {
2740     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(PV->getDeclContext())) {
2741       unsigned i = PV->getFunctionScopeIndex();
2742       return FD->getCanonicalDecl()->getParamDecl(i);
2743     }
2744   }
2745   return D;
2746 }
2747 
2748 
2749 llvm::PointerUnion<Decl *, LocalInstantiationScope::DeclArgumentPack *> *
2750 LocalInstantiationScope::findInstantiationOf(const Decl *D) {
2751   D = getCanonicalParmVarDecl(D);
2752   for (LocalInstantiationScope *Current = this; Current;
2753        Current = Current->Outer) {
2754 
2755     // Check if we found something within this scope.
2756     const Decl *CheckD = D;
2757     do {
2758       LocalDeclsMap::iterator Found = Current->LocalDecls.find(CheckD);
2759       if (Found != Current->LocalDecls.end())
2760         return &Found->second;
2761 
2762       // If this is a tag declaration, it's possible that we need to look for
2763       // a previous declaration.
2764       if (const TagDecl *Tag = dyn_cast<TagDecl>(CheckD))
2765         CheckD = Tag->getPreviousDecl();
2766       else
2767         CheckD = 0;
2768     } while (CheckD);
2769 
2770     // If we aren't combined with our outer scope, we're done.
2771     if (!Current->CombineWithOuterScope)
2772       break;
2773   }
2774 
2775   // If we're performing a partial substitution during template argument
2776   // deduction, we may not have values for template parameters yet.
2777   if (isa<NonTypeTemplateParmDecl>(D) || isa<TemplateTypeParmDecl>(D) ||
2778       isa<TemplateTemplateParmDecl>(D))
2779     return 0;
2780 
2781   // If we didn't find the decl, then we either have a sema bug, or we have a
2782   // forward reference to a label declaration.  Return null to indicate that
2783   // we have an uninstantiated label.
2784   assert(isa<LabelDecl>(D) && "declaration not instantiated in this scope");
2785   return 0;
2786 }
2787 
2788 void LocalInstantiationScope::InstantiatedLocal(const Decl *D, Decl *Inst) {
2789   D = getCanonicalParmVarDecl(D);
2790   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2791   if (Stored.isNull())
2792     Stored = Inst;
2793   else if (DeclArgumentPack *Pack = Stored.dyn_cast<DeclArgumentPack *>())
2794     Pack->push_back(Inst);
2795   else
2796     assert(Stored.get<Decl *>() == Inst && "Already instantiated this local");
2797 }
2798 
2799 void LocalInstantiationScope::InstantiatedLocalPackArg(const Decl *D,
2800                                                        Decl *Inst) {
2801   D = getCanonicalParmVarDecl(D);
2802   DeclArgumentPack *Pack = LocalDecls[D].get<DeclArgumentPack *>();
2803   Pack->push_back(Inst);
2804 }
2805 
2806 void LocalInstantiationScope::MakeInstantiatedLocalArgPack(const Decl *D) {
2807   D = getCanonicalParmVarDecl(D);
2808   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
2809   assert(Stored.isNull() && "Already instantiated this local");
2810   DeclArgumentPack *Pack = new DeclArgumentPack;
2811   Stored = Pack;
2812   ArgumentPacks.push_back(Pack);
2813 }
2814 
2815 void LocalInstantiationScope::SetPartiallySubstitutedPack(NamedDecl *Pack,
2816                                           const TemplateArgument *ExplicitArgs,
2817                                                     unsigned NumExplicitArgs) {
2818   assert((!PartiallySubstitutedPack || PartiallySubstitutedPack == Pack) &&
2819          "Already have a partially-substituted pack");
2820   assert((!PartiallySubstitutedPack
2821           || NumArgsInPartiallySubstitutedPack == NumExplicitArgs) &&
2822          "Wrong number of arguments in partially-substituted pack");
2823   PartiallySubstitutedPack = Pack;
2824   ArgsInPartiallySubstitutedPack = ExplicitArgs;
2825   NumArgsInPartiallySubstitutedPack = NumExplicitArgs;
2826 }
2827 
2828 NamedDecl *LocalInstantiationScope::getPartiallySubstitutedPack(
2829                                          const TemplateArgument **ExplicitArgs,
2830                                               unsigned *NumExplicitArgs) const {
2831   if (ExplicitArgs)
2832     *ExplicitArgs = 0;
2833   if (NumExplicitArgs)
2834     *NumExplicitArgs = 0;
2835 
2836   for (const LocalInstantiationScope *Current = this; Current;
2837        Current = Current->Outer) {
2838     if (Current->PartiallySubstitutedPack) {
2839       if (ExplicitArgs)
2840         *ExplicitArgs = Current->ArgsInPartiallySubstitutedPack;
2841       if (NumExplicitArgs)
2842         *NumExplicitArgs = Current->NumArgsInPartiallySubstitutedPack;
2843 
2844       return Current->PartiallySubstitutedPack;
2845     }
2846 
2847     if (!Current->CombineWithOuterScope)
2848       break;
2849   }
2850 
2851   return 0;
2852 }
2853