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SemaTemplateDeduction.cpp
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1 //===- SemaTemplateDeduction.cpp - Template Argument Deduction ------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements C++ template argument deduction.
10 //
11 //===----------------------------------------------------------------------===//
12 
14 #include "TreeTransform.h"
15 #include "TypeLocBuilder.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/ASTLambda.h"
18 #include "clang/AST/Decl.h"
20 #include "clang/AST/DeclBase.h"
21 #include "clang/AST/DeclCXX.h"
22 #include "clang/AST/DeclTemplate.h"
24 #include "clang/AST/Expr.h"
25 #include "clang/AST/ExprCXX.h"
27 #include "clang/AST/TemplateBase.h"
28 #include "clang/AST/TemplateName.h"
29 #include "clang/AST/Type.h"
30 #include "clang/AST/TypeLoc.h"
34 #include "clang/Basic/LLVM.h"
38 #include "clang/Basic/Specifiers.h"
39 #include "clang/Sema/Ownership.h"
40 #include "clang/Sema/Sema.h"
41 #include "clang/Sema/Template.h"
42 #include "llvm/ADT/APInt.h"
43 #include "llvm/ADT/APSInt.h"
44 #include "llvm/ADT/ArrayRef.h"
45 #include "llvm/ADT/DenseMap.h"
46 #include "llvm/ADT/FoldingSet.h"
47 #include "llvm/ADT/Optional.h"
48 #include "llvm/ADT/SmallBitVector.h"
49 #include "llvm/ADT/SmallPtrSet.h"
50 #include "llvm/ADT/SmallVector.h"
51 #include "llvm/Support/Casting.h"
52 #include "llvm/Support/Compiler.h"
53 #include "llvm/Support/ErrorHandling.h"
54 #include <algorithm>
55 #include <cassert>
56 #include <tuple>
57 #include <utility>
58 
59 namespace clang {
60 
61  /// Various flags that control template argument deduction.
62  ///
63  /// These flags can be bitwise-OR'd together.
65  /// No template argument deduction flags, which indicates the
66  /// strictest results for template argument deduction (as used for, e.g.,
67  /// matching class template partial specializations).
68  TDF_None = 0,
69 
70  /// Within template argument deduction from a function call, we are
71  /// matching with a parameter type for which the original parameter was
72  /// a reference.
74 
75  /// Within template argument deduction from a function call, we
76  /// are matching in a case where we ignore cv-qualifiers.
78 
79  /// Within template argument deduction from a function call,
80  /// we are matching in a case where we can perform template argument
81  /// deduction from a template-id of a derived class of the argument type.
83 
84  /// Allow non-dependent types to differ, e.g., when performing
85  /// template argument deduction from a function call where conversions
86  /// may apply.
88 
89  /// Whether we are performing template argument deduction for
90  /// parameters and arguments in a top-level template argument
92 
93  /// Within template argument deduction from overload resolution per
94  /// C++ [over.over] allow matching function types that are compatible in
95  /// terms of noreturn and default calling convention adjustments, or
96  /// similarly matching a declared template specialization against a
97  /// possible template, per C++ [temp.deduct.decl]. In either case, permit
98  /// deduction where the parameter is a function type that can be converted
99  /// to the argument type.
101 
102  /// Within template argument deduction for a conversion function, we are
103  /// matching with an argument type for which the original argument was
104  /// a reference.
106  };
107 }
108 
109 using namespace clang;
110 using namespace sema;
111 
112 /// Compare two APSInts, extending and switching the sign as
113 /// necessary to compare their values regardless of underlying type.
114 static bool hasSameExtendedValue(llvm::APSInt X, llvm::APSInt Y) {
115  if (Y.getBitWidth() > X.getBitWidth())
116  X = X.extend(Y.getBitWidth());
117  else if (Y.getBitWidth() < X.getBitWidth())
118  Y = Y.extend(X.getBitWidth());
119 
120  // If there is a signedness mismatch, correct it.
121  if (X.isSigned() != Y.isSigned()) {
122  // If the signed value is negative, then the values cannot be the same.
123  if ((Y.isSigned() && Y.isNegative()) || (X.isSigned() && X.isNegative()))
124  return false;
125 
126  Y.setIsSigned(true);
127  X.setIsSigned(true);
128  }
129 
130  return X == Y;
131 }
132 
135  TemplateParameterList *TemplateParams,
136  const TemplateArgument &Param,
137  TemplateArgument Arg,
138  TemplateDeductionInfo &Info,
140 
143  TemplateParameterList *TemplateParams,
144  QualType Param,
145  QualType Arg,
146  TemplateDeductionInfo &Info,
148  Deduced,
149  unsigned TDF,
150  bool PartialOrdering = false,
151  bool DeducedFromArrayBound = false);
152 
157  TemplateDeductionInfo &Info,
159  bool NumberOfArgumentsMustMatch);
160 
161 static void MarkUsedTemplateParameters(ASTContext &Ctx,
162  const TemplateArgument &TemplateArg,
163  bool OnlyDeduced, unsigned Depth,
164  llvm::SmallBitVector &Used);
165 
167  bool OnlyDeduced, unsigned Level,
168  llvm::SmallBitVector &Deduced);
169 
170 /// If the given expression is of a form that permits the deduction
171 /// of a non-type template parameter, return the declaration of that
172 /// non-type template parameter.
175  // If we are within an alias template, the expression may have undergone
176  // any number of parameter substitutions already.
177  while (true) {
178  if (ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(E))
179  E = IC->getSubExpr();
180  else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(E))
181  E = CE->getSubExpr();
182  else if (SubstNonTypeTemplateParmExpr *Subst =
183  dyn_cast<SubstNonTypeTemplateParmExpr>(E))
184  E = Subst->getReplacement();
185  else
186  break;
187  }
188 
189  if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
190  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl()))
191  if (NTTP->getDepth() == Info.getDeducedDepth())
192  return NTTP;
193 
194  return nullptr;
195 }
196 
197 /// Determine whether two declaration pointers refer to the same
198 /// declaration.
199 static bool isSameDeclaration(Decl *X, Decl *Y) {
200  if (NamedDecl *NX = dyn_cast<NamedDecl>(X))
201  X = NX->getUnderlyingDecl();
202  if (NamedDecl *NY = dyn_cast<NamedDecl>(Y))
203  Y = NY->getUnderlyingDecl();
204 
205  return X->getCanonicalDecl() == Y->getCanonicalDecl();
206 }
207 
208 /// Verify that the given, deduced template arguments are compatible.
209 ///
210 /// \returns The deduced template argument, or a NULL template argument if
211 /// the deduced template arguments were incompatible.
214  const DeducedTemplateArgument &X,
215  const DeducedTemplateArgument &Y) {
216  // We have no deduction for one or both of the arguments; they're compatible.
217  if (X.isNull())
218  return Y;
219  if (Y.isNull())
220  return X;
221 
222  // If we have two non-type template argument values deduced for the same
223  // parameter, they must both match the type of the parameter, and thus must
224  // match each other's type. As we're only keeping one of them, we must check
225  // for that now. The exception is that if either was deduced from an array
226  // bound, the type is permitted to differ.
229  if (!XType.isNull()) {
231  if (YType.isNull() || !Context.hasSameType(XType, YType))
232  return DeducedTemplateArgument();
233  }
234  }
235 
236  switch (X.getKind()) {
238  llvm_unreachable("Non-deduced template arguments handled above");
239 
241  // If two template type arguments have the same type, they're compatible.
242  if (Y.getKind() == TemplateArgument::Type &&
243  Context.hasSameType(X.getAsType(), Y.getAsType()))
244  return X;
245 
246  // If one of the two arguments was deduced from an array bound, the other
247  // supersedes it.
249  return X.wasDeducedFromArrayBound() ? Y : X;
250 
251  // The arguments are not compatible.
252  return DeducedTemplateArgument();
253 
255  // If we deduced a constant in one case and either a dependent expression or
256  // declaration in another case, keep the integral constant.
257  // If both are integral constants with the same value, keep that value.
262  return X.wasDeducedFromArrayBound() ? Y : X;
263 
264  // All other combinations are incompatible.
265  return DeducedTemplateArgument();
266 
268  if (Y.getKind() == TemplateArgument::Template &&
270  return X;
271 
272  // All other combinations are incompatible.
273  return DeducedTemplateArgument();
274 
279  return X;
280 
281  // All other combinations are incompatible.
282  return DeducedTemplateArgument();
283 
286  return checkDeducedTemplateArguments(Context, Y, X);
287 
288  // Compare the expressions for equality
289  llvm::FoldingSetNodeID ID1, ID2;
290  X.getAsExpr()->Profile(ID1, Context, true);
291  Y.getAsExpr()->Profile(ID2, Context, true);
292  if (ID1 == ID2)
293  return X.wasDeducedFromArrayBound() ? Y : X;
294 
295  // Differing dependent expressions are incompatible.
296  return DeducedTemplateArgument();
297  }
298 
300  assert(!X.wasDeducedFromArrayBound());
301 
302  // If we deduced a declaration and a dependent expression, keep the
303  // declaration.
305  return X;
306 
307  // If we deduced a declaration and an integral constant, keep the
308  // integral constant and whichever type did not come from an array
309  // bound.
310  if (Y.getKind() == TemplateArgument::Integral) {
311  if (Y.wasDeducedFromArrayBound())
312  return TemplateArgument(Context, Y.getAsIntegral(),
313  X.getParamTypeForDecl());
314  return Y;
315  }
316 
317  // If we deduced two declarations, make sure that they refer to the
318  // same declaration.
321  return X;
322 
323  // All other combinations are incompatible.
324  return DeducedTemplateArgument();
325 
327  // If we deduced a null pointer and a dependent expression, keep the
328  // null pointer.
330  return X;
331 
332  // If we deduced a null pointer and an integral constant, keep the
333  // integral constant.
335  return Y;
336 
337  // If we deduced two null pointers, they are the same.
339  return X;
340 
341  // All other combinations are incompatible.
342  return DeducedTemplateArgument();
343 
344  case TemplateArgument::Pack: {
345  if (Y.getKind() != TemplateArgument::Pack ||
346  X.pack_size() != Y.pack_size())
347  return DeducedTemplateArgument();
348 
351  XAEnd = X.pack_end(),
352  YA = Y.pack_begin();
353  XA != XAEnd; ++XA, ++YA) {
357  if (Merged.isNull())
358  return DeducedTemplateArgument();
359  NewPack.push_back(Merged);
360  }
361 
363  TemplateArgument::CreatePackCopy(Context, NewPack),
365  }
366  }
367 
368  llvm_unreachable("Invalid TemplateArgument Kind!");
369 }
370 
371 /// Deduce the value of the given non-type template parameter
372 /// as the given deduced template argument. All non-type template parameter
373 /// deduction is funneled through here.
375  Sema &S, TemplateParameterList *TemplateParams,
376  NonTypeTemplateParmDecl *NTTP, const DeducedTemplateArgument &NewDeduced,
377  QualType ValueType, TemplateDeductionInfo &Info,
379  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
380  "deducing non-type template argument with wrong depth");
381 
383  S.Context, Deduced[NTTP->getIndex()], NewDeduced);
384  if (Result.isNull()) {
385  Info.Param = NTTP;
386  Info.FirstArg = Deduced[NTTP->getIndex()];
387  Info.SecondArg = NewDeduced;
388  return Sema::TDK_Inconsistent;
389  }
390 
391  Deduced[NTTP->getIndex()] = Result;
392  if (!S.getLangOpts().CPlusPlus17)
393  return Sema::TDK_Success;
394 
395  if (NTTP->isExpandedParameterPack())
396  // FIXME: We may still need to deduce parts of the type here! But we
397  // don't have any way to find which slice of the type to use, and the
398  // type stored on the NTTP itself is nonsense. Perhaps the type of an
399  // expanded NTTP should be a pack expansion type?
400  return Sema::TDK_Success;
401 
402  // Get the type of the parameter for deduction. If it's a (dependent) array
403  // or function type, we will not have decayed it yet, so do that now.
404  QualType ParamType = S.Context.getAdjustedParameterType(NTTP->getType());
405  if (auto *Expansion = dyn_cast<PackExpansionType>(ParamType))
406  ParamType = Expansion->getPattern();
407 
408  // FIXME: It's not clear how deduction of a parameter of reference
409  // type from an argument (of non-reference type) should be performed.
410  // For now, we just remove reference types from both sides and let
411  // the final check for matching types sort out the mess.
413  S, TemplateParams, ParamType.getNonReferenceType(),
414  ValueType.getNonReferenceType(), Info, Deduced, TDF_SkipNonDependent,
415  /*PartialOrdering=*/false,
416  /*ArrayBound=*/NewDeduced.wasDeducedFromArrayBound());
417 }
418 
419 /// Deduce the value of the given non-type template parameter
420 /// from the given integral constant.
422  Sema &S, TemplateParameterList *TemplateParams,
423  NonTypeTemplateParmDecl *NTTP, const llvm::APSInt &Value,
424  QualType ValueType, bool DeducedFromArrayBound, TemplateDeductionInfo &Info,
427  S, TemplateParams, NTTP,
428  DeducedTemplateArgument(S.Context, Value, ValueType,
429  DeducedFromArrayBound),
430  ValueType, Info, Deduced);
431 }
432 
433 /// Deduce the value of the given non-type template parameter
434 /// from the given null pointer template argument type.
436  Sema &S, TemplateParameterList *TemplateParams,
437  NonTypeTemplateParmDecl *NTTP, QualType NullPtrType,
438  TemplateDeductionInfo &Info,
440  Expr *Value =
442  S.Context.NullPtrTy, NTTP->getLocation()),
443  NullPtrType, CK_NullToPointer)
444  .get();
445  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
447  Value->getType(), Info, Deduced);
448 }
449 
450 /// Deduce the value of the given non-type template parameter
451 /// from the given type- or value-dependent expression.
452 ///
453 /// \returns true if deduction succeeded, false otherwise.
455  Sema &S, TemplateParameterList *TemplateParams,
458  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
460  Value->getType(), Info, Deduced);
461 }
462 
463 /// Deduce the value of the given non-type template parameter
464 /// from the given declaration.
465 ///
466 /// \returns true if deduction succeeded, false otherwise.
468  Sema &S, TemplateParameterList *TemplateParams,
470  TemplateDeductionInfo &Info,
472  D = D ? cast<ValueDecl>(D->getCanonicalDecl()) : nullptr;
473  TemplateArgument New(D, T);
475  S, TemplateParams, NTTP, DeducedTemplateArgument(New), T, Info, Deduced);
476 }
477 
480  TemplateParameterList *TemplateParams,
481  TemplateName Param,
482  TemplateName Arg,
483  TemplateDeductionInfo &Info,
485  TemplateDecl *ParamDecl = Param.getAsTemplateDecl();
486  if (!ParamDecl) {
487  // The parameter type is dependent and is not a template template parameter,
488  // so there is nothing that we can deduce.
489  return Sema::TDK_Success;
490  }
491 
492  if (TemplateTemplateParmDecl *TempParam
493  = dyn_cast<TemplateTemplateParmDecl>(ParamDecl)) {
494  // If we're not deducing at this depth, there's nothing to deduce.
495  if (TempParam->getDepth() != Info.getDeducedDepth())
496  return Sema::TDK_Success;
497 
500  Deduced[TempParam->getIndex()],
501  NewDeduced);
502  if (Result.isNull()) {
503  Info.Param = TempParam;
504  Info.FirstArg = Deduced[TempParam->getIndex()];
505  Info.SecondArg = NewDeduced;
506  return Sema::TDK_Inconsistent;
507  }
508 
509  Deduced[TempParam->getIndex()] = Result;
510  return Sema::TDK_Success;
511  }
512 
513  // Verify that the two template names are equivalent.
514  if (S.Context.hasSameTemplateName(Param, Arg))
515  return Sema::TDK_Success;
516 
517  // Mismatch of non-dependent template parameter to argument.
518  Info.FirstArg = TemplateArgument(Param);
519  Info.SecondArg = TemplateArgument(Arg);
521 }
522 
523 /// Deduce the template arguments by comparing the template parameter
524 /// type (which is a template-id) with the template argument type.
525 ///
526 /// \param S the Sema
527 ///
528 /// \param TemplateParams the template parameters that we are deducing
529 ///
530 /// \param Param the parameter type
531 ///
532 /// \param Arg the argument type
533 ///
534 /// \param Info information about the template argument deduction itself
535 ///
536 /// \param Deduced the deduced template arguments
537 ///
538 /// \returns the result of template argument deduction so far. Note that a
539 /// "success" result means that template argument deduction has not yet failed,
540 /// but it may still fail, later, for other reasons.
543  TemplateParameterList *TemplateParams,
544  const TemplateSpecializationType *Param,
545  QualType Arg,
546  TemplateDeductionInfo &Info,
548  assert(Arg.isCanonical() && "Argument type must be canonical");
549 
550  // Treat an injected-class-name as its underlying template-id.
551  if (auto *Injected = dyn_cast<InjectedClassNameType>(Arg))
552  Arg = Injected->getInjectedSpecializationType();
553 
554  // Check whether the template argument is a dependent template-id.
555  if (const TemplateSpecializationType *SpecArg
556  = dyn_cast<TemplateSpecializationType>(Arg)) {
557  // Perform template argument deduction for the template name.
559  = DeduceTemplateArguments(S, TemplateParams,
560  Param->getTemplateName(),
561  SpecArg->getTemplateName(),
562  Info, Deduced))
563  return Result;
564 
565 
566  // Perform template argument deduction on each template
567  // argument. Ignore any missing/extra arguments, since they could be
568  // filled in by default arguments.
569  return DeduceTemplateArguments(S, TemplateParams,
570  Param->template_arguments(),
571  SpecArg->template_arguments(), Info, Deduced,
572  /*NumberOfArgumentsMustMatch=*/false);
573  }
574 
575  // If the argument type is a class template specialization, we
576  // perform template argument deduction using its template
577  // arguments.
578  const RecordType *RecordArg = dyn_cast<RecordType>(Arg);
579  if (!RecordArg) {
580  Info.FirstArg = TemplateArgument(QualType(Param, 0));
581  Info.SecondArg = TemplateArgument(Arg);
583  }
584 
586  = dyn_cast<ClassTemplateSpecializationDecl>(RecordArg->getDecl());
587  if (!SpecArg) {
588  Info.FirstArg = TemplateArgument(QualType(Param, 0));
589  Info.SecondArg = TemplateArgument(Arg);
591  }
592 
593  // Perform template argument deduction for the template name.
596  TemplateParams,
597  Param->getTemplateName(),
599  Info, Deduced))
600  return Result;
601 
602  // Perform template argument deduction for the template arguments.
603  return DeduceTemplateArguments(S, TemplateParams, Param->template_arguments(),
604  SpecArg->getTemplateArgs().asArray(), Info,
605  Deduced, /*NumberOfArgumentsMustMatch=*/true);
606 }
607 
608 /// Determines whether the given type is an opaque type that
609 /// might be more qualified when instantiated.
611  switch (T->getTypeClass()) {
612  case Type::TypeOfExpr:
613  case Type::TypeOf:
614  case Type::DependentName:
615  case Type::Decltype:
616  case Type::UnresolvedUsing:
617  case Type::TemplateTypeParm:
618  return true;
619 
620  case Type::ConstantArray:
621  case Type::IncompleteArray:
622  case Type::VariableArray:
623  case Type::DependentSizedArray:
625  cast<ArrayType>(T)->getElementType());
626 
627  default:
628  return false;
629  }
630 }
631 
632 /// Helper function to build a TemplateParameter when we don't
633 /// know its type statically.
635  if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(D))
636  return TemplateParameter(TTP);
637  if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D))
638  return TemplateParameter(NTTP);
639 
640  return TemplateParameter(cast<TemplateTemplateParmDecl>(D));
641 }
642 
643 /// If \p Param is an expanded parameter pack, get the number of expansions.
645  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param))
646  if (NTTP->isExpandedParameterPack())
647  return NTTP->getNumExpansionTypes();
648 
649  if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(Param))
650  if (TTP->isExpandedParameterPack())
651  return TTP->getNumExpansionTemplateParameters();
652 
653  return None;
654 }
655 
656 /// A pack that we're currently deducing.
658  // The index of the pack.
659  unsigned Index;
660 
661  // The old value of the pack before we started deducing it.
663 
664  // A deferred value of this pack from an inner deduction, that couldn't be
665  // deduced because this deduction hadn't happened yet.
667 
668  // The new value of the pack.
670 
671  // The outer deduction for this pack, if any.
672  DeducedPack *Outer = nullptr;
673 
674  DeducedPack(unsigned Index) : Index(Index) {}
675 };
676 
677 namespace {
678 
679 /// A scope in which we're performing pack deduction.
680 class PackDeductionScope {
681 public:
682  /// Prepare to deduce the packs named within Pattern.
683  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
686  : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
687  unsigned NumNamedPacks = addPacks(Pattern);
688  finishConstruction(NumNamedPacks);
689  }
690 
691  /// Prepare to directly deduce arguments of the parameter with index \p Index.
692  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
694  TemplateDeductionInfo &Info, unsigned Index)
695  : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
696  addPack(Index);
697  finishConstruction(1);
698  }
699 
700 private:
701  void addPack(unsigned Index) {
702  // Save the deduced template argument for the parameter pack expanded
703  // by this pack expansion, then clear out the deduction.
704  DeducedPack Pack(Index);
705  Pack.Saved = Deduced[Index];
706  Deduced[Index] = TemplateArgument();
707 
708  // FIXME: What if we encounter multiple packs with different numbers of
709  // pre-expanded expansions? (This should already have been diagnosed
710  // during substitution.)
711  if (Optional<unsigned> ExpandedPackExpansions =
712  getExpandedPackSize(TemplateParams->getParam(Index)))
713  FixedNumExpansions = ExpandedPackExpansions;
714 
715  Packs.push_back(Pack);
716  }
717 
718  unsigned addPacks(TemplateArgument Pattern) {
719  // Compute the set of template parameter indices that correspond to
720  // parameter packs expanded by the pack expansion.
721  llvm::SmallBitVector SawIndices(TemplateParams->size());
722 
723  auto AddPack = [&](unsigned Index) {
724  if (SawIndices[Index])
725  return;
726  SawIndices[Index] = true;
727  addPack(Index);
728  };
729 
730  // First look for unexpanded packs in the pattern.
732  S.collectUnexpandedParameterPacks(Pattern, Unexpanded);
733  for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
734  unsigned Depth, Index;
735  std::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]);
736  if (Depth == Info.getDeducedDepth())
737  AddPack(Index);
738  }
739  assert(!Packs.empty() && "Pack expansion without unexpanded packs?");
740 
741  unsigned NumNamedPacks = Packs.size();
742 
743  // We can also have deduced template parameters that do not actually
744  // appear in the pattern, but can be deduced by it (the type of a non-type
745  // template parameter pack, in particular). These won't have prevented us
746  // from partially expanding the pack.
747  llvm::SmallBitVector Used(TemplateParams->size());
748  MarkUsedTemplateParameters(S.Context, Pattern, /*OnlyDeduced*/true,
749  Info.getDeducedDepth(), Used);
750  for (int Index = Used.find_first(); Index != -1;
751  Index = Used.find_next(Index))
752  if (TemplateParams->getParam(Index)->isParameterPack())
753  AddPack(Index);
754 
755  return NumNamedPacks;
756  }
757 
758  void finishConstruction(unsigned NumNamedPacks) {
759  // Dig out the partially-substituted pack, if there is one.
760  const TemplateArgument *PartialPackArgs = nullptr;
761  unsigned NumPartialPackArgs = 0;
762  std::pair<unsigned, unsigned> PartialPackDepthIndex(-1u, -1u);
763  if (auto *Scope = S.CurrentInstantiationScope)
764  if (auto *Partial = Scope->getPartiallySubstitutedPack(
765  &PartialPackArgs, &NumPartialPackArgs))
766  PartialPackDepthIndex = getDepthAndIndex(Partial);
767 
768  // This pack expansion will have been partially or fully expanded if
769  // it only names explicitly-specified parameter packs (including the
770  // partially-substituted one, if any).
771  bool IsExpanded = true;
772  for (unsigned I = 0; I != NumNamedPacks; ++I) {
773  if (Packs[I].Index >= Info.getNumExplicitArgs()) {
774  IsExpanded = false;
775  IsPartiallyExpanded = false;
776  break;
777  }
778  if (PartialPackDepthIndex ==
779  std::make_pair(Info.getDeducedDepth(), Packs[I].Index)) {
780  IsPartiallyExpanded = true;
781  }
782  }
783 
784  // Skip over the pack elements that were expanded into separate arguments.
785  // If we partially expanded, this is the number of partial arguments.
786  if (IsPartiallyExpanded)
787  PackElements += NumPartialPackArgs;
788  else if (IsExpanded)
789  PackElements += *FixedNumExpansions;
790 
791  for (auto &Pack : Packs) {
792  if (Info.PendingDeducedPacks.size() > Pack.Index)
793  Pack.Outer = Info.PendingDeducedPacks[Pack.Index];
794  else
795  Info.PendingDeducedPacks.resize(Pack.Index + 1);
796  Info.PendingDeducedPacks[Pack.Index] = &Pack;
797 
798  if (PartialPackDepthIndex ==
799  std::make_pair(Info.getDeducedDepth(), Pack.Index)) {
800  Pack.New.append(PartialPackArgs, PartialPackArgs + NumPartialPackArgs);
801  // We pre-populate the deduced value of the partially-substituted
802  // pack with the specified value. This is not entirely correct: the
803  // value is supposed to have been substituted, not deduced, but the
804  // cases where this is observable require an exact type match anyway.
805  //
806  // FIXME: If we could represent a "depth i, index j, pack elem k"
807  // parameter, we could substitute the partially-substituted pack
808  // everywhere and avoid this.
809  if (!IsPartiallyExpanded)
810  Deduced[Pack.Index] = Pack.New[PackElements];
811  }
812  }
813  }
814 
815 public:
816  ~PackDeductionScope() {
817  for (auto &Pack : Packs)
818  Info.PendingDeducedPacks[Pack.Index] = Pack.Outer;
819  }
820 
821  /// Determine whether this pack has already been partially expanded into a
822  /// sequence of (prior) function parameters / template arguments.
823  bool isPartiallyExpanded() { return IsPartiallyExpanded; }
824 
825  /// Determine whether this pack expansion scope has a known, fixed arity.
826  /// This happens if it involves a pack from an outer template that has
827  /// (notionally) already been expanded.
828  bool hasFixedArity() { return FixedNumExpansions.hasValue(); }
829 
830  /// Determine whether the next element of the argument is still part of this
831  /// pack. This is the case unless the pack is already expanded to a fixed
832  /// length.
833  bool hasNextElement() {
834  return !FixedNumExpansions || *FixedNumExpansions > PackElements;
835  }
836 
837  /// Move to deducing the next element in each pack that is being deduced.
838  void nextPackElement() {
839  // Capture the deduced template arguments for each parameter pack expanded
840  // by this pack expansion, add them to the list of arguments we've deduced
841  // for that pack, then clear out the deduced argument.
842  for (auto &Pack : Packs) {
843  DeducedTemplateArgument &DeducedArg = Deduced[Pack.Index];
844  if (!Pack.New.empty() || !DeducedArg.isNull()) {
845  while (Pack.New.size() < PackElements)
846  Pack.New.push_back(DeducedTemplateArgument());
847  if (Pack.New.size() == PackElements)
848  Pack.New.push_back(DeducedArg);
849  else
850  Pack.New[PackElements] = DeducedArg;
851  DeducedArg = Pack.New.size() > PackElements + 1
852  ? Pack.New[PackElements + 1]
854  }
855  }
856  ++PackElements;
857  }
858 
859  /// Finish template argument deduction for a set of argument packs,
860  /// producing the argument packs and checking for consistency with prior
861  /// deductions.
863  finish(bool TreatNoDeductionsAsNonDeduced = true) {
864  // Build argument packs for each of the parameter packs expanded by this
865  // pack expansion.
866  for (auto &Pack : Packs) {
867  // Put back the old value for this pack.
868  Deduced[Pack.Index] = Pack.Saved;
869 
870  // If we are deducing the size of this pack even if we didn't deduce any
871  // values for it, then make sure we build a pack of the right size.
872  // FIXME: Should we always deduce the size, even if the pack appears in
873  // a non-deduced context?
874  if (!TreatNoDeductionsAsNonDeduced)
875  Pack.New.resize(PackElements);
876 
877  // Build or find a new value for this pack.
878  DeducedTemplateArgument NewPack;
879  if (PackElements && Pack.New.empty()) {
880  if (Pack.DeferredDeduction.isNull()) {
881  // We were not able to deduce anything for this parameter pack
882  // (because it only appeared in non-deduced contexts), so just
883  // restore the saved argument pack.
884  continue;
885  }
886 
887  NewPack = Pack.DeferredDeduction;
888  Pack.DeferredDeduction = TemplateArgument();
889  } else if (Pack.New.empty()) {
890  // If we deduced an empty argument pack, create it now.
892  } else {
893  TemplateArgument *ArgumentPack =
894  new (S.Context) TemplateArgument[Pack.New.size()];
895  std::copy(Pack.New.begin(), Pack.New.end(), ArgumentPack);
896  NewPack = DeducedTemplateArgument(
897  TemplateArgument(llvm::makeArrayRef(ArgumentPack, Pack.New.size())),
898  // FIXME: This is wrong, it's possible that some pack elements are
899  // deduced from an array bound and others are not:
900  // template<typename ...T, T ...V> void g(const T (&...p)[V]);
901  // g({1, 2, 3}, {{}, {}});
902  // ... should deduce T = {int, size_t (from array bound)}.
903  Pack.New[0].wasDeducedFromArrayBound());
904  }
905 
906  // Pick where we're going to put the merged pack.
908  if (Pack.Outer) {
909  if (Pack.Outer->DeferredDeduction.isNull()) {
910  // Defer checking this pack until we have a complete pack to compare
911  // it against.
912  Pack.Outer->DeferredDeduction = NewPack;
913  continue;
914  }
915  Loc = &Pack.Outer->DeferredDeduction;
916  } else {
917  Loc = &Deduced[Pack.Index];
918  }
919 
920  // Check the new pack matches any previous value.
921  DeducedTemplateArgument OldPack = *Loc;
922  DeducedTemplateArgument Result =
923  checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
924 
925  // If we deferred a deduction of this pack, check that one now too.
926  if (!Result.isNull() && !Pack.DeferredDeduction.isNull()) {
927  OldPack = Result;
928  NewPack = Pack.DeferredDeduction;
929  Result = checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
930  }
931 
932  NamedDecl *Param = TemplateParams->getParam(Pack.Index);
933  if (Result.isNull()) {
934  Info.Param = makeTemplateParameter(Param);
935  Info.FirstArg = OldPack;
936  Info.SecondArg = NewPack;
937  return Sema::TDK_Inconsistent;
938  }
939 
940  // If we have a pre-expanded pack and we didn't deduce enough elements
941  // for it, fail deduction.
942  if (Optional<unsigned> Expansions = getExpandedPackSize(Param)) {
943  if (*Expansions != PackElements) {
944  Info.Param = makeTemplateParameter(Param);
945  Info.FirstArg = Result;
947  }
948  }
949 
950  *Loc = Result;
951  }
952 
953  return Sema::TDK_Success;
954  }
955 
956 private:
957  Sema &S;
958  TemplateParameterList *TemplateParams;
960  TemplateDeductionInfo &Info;
961  unsigned PackElements = 0;
962  bool IsPartiallyExpanded = false;
963  /// The number of expansions, if we have a fully-expanded pack in this scope.
964  Optional<unsigned> FixedNumExpansions;
965 
967 };
968 
969 } // namespace
970 
971 /// Deduce the template arguments by comparing the list of parameter
972 /// types to the list of argument types, as in the parameter-type-lists of
973 /// function types (C++ [temp.deduct.type]p10).
974 ///
975 /// \param S The semantic analysis object within which we are deducing
976 ///
977 /// \param TemplateParams The template parameters that we are deducing
978 ///
979 /// \param Params The list of parameter types
980 ///
981 /// \param NumParams The number of types in \c Params
982 ///
983 /// \param Args The list of argument types
984 ///
985 /// \param NumArgs The number of types in \c Args
986 ///
987 /// \param Info information about the template argument deduction itself
988 ///
989 /// \param Deduced the deduced template arguments
990 ///
991 /// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
992 /// how template argument deduction is performed.
993 ///
994 /// \param PartialOrdering If true, we are performing template argument
995 /// deduction for during partial ordering for a call
996 /// (C++0x [temp.deduct.partial]).
997 ///
998 /// \returns the result of template argument deduction so far. Note that a
999 /// "success" result means that template argument deduction has not yet failed,
1000 /// but it may still fail, later, for other reasons.
1003  TemplateParameterList *TemplateParams,
1004  const QualType *Params, unsigned NumParams,
1005  const QualType *Args, unsigned NumArgs,
1006  TemplateDeductionInfo &Info,
1008  unsigned TDF,
1009  bool PartialOrdering = false) {
1010  // C++0x [temp.deduct.type]p10:
1011  // Similarly, if P has a form that contains (T), then each parameter type
1012  // Pi of the respective parameter-type- list of P is compared with the
1013  // corresponding parameter type Ai of the corresponding parameter-type-list
1014  // of A. [...]
1015  unsigned ArgIdx = 0, ParamIdx = 0;
1016  for (; ParamIdx != NumParams; ++ParamIdx) {
1017  // Check argument types.
1018  const PackExpansionType *Expansion
1019  = dyn_cast<PackExpansionType>(Params[ParamIdx]);
1020  if (!Expansion) {
1021  // Simple case: compare the parameter and argument types at this point.
1022 
1023  // Make sure we have an argument.
1024  if (ArgIdx >= NumArgs)
1026 
1027  if (isa<PackExpansionType>(Args[ArgIdx])) {
1028  // C++0x [temp.deduct.type]p22:
1029  // If the original function parameter associated with A is a function
1030  // parameter pack and the function parameter associated with P is not
1031  // a function parameter pack, then template argument deduction fails.
1033  }
1034 
1036  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1037  Params[ParamIdx], Args[ArgIdx],
1038  Info, Deduced, TDF,
1039  PartialOrdering))
1040  return Result;
1041 
1042  ++ArgIdx;
1043  continue;
1044  }
1045 
1046  // C++0x [temp.deduct.type]p10:
1047  // If the parameter-declaration corresponding to Pi is a function
1048  // parameter pack, then the type of its declarator- id is compared with
1049  // each remaining parameter type in the parameter-type-list of A. Each
1050  // comparison deduces template arguments for subsequent positions in the
1051  // template parameter packs expanded by the function parameter pack.
1052 
1053  QualType Pattern = Expansion->getPattern();
1054  PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
1055 
1056  // A pack scope with fixed arity is not really a pack any more, so is not
1057  // a non-deduced context.
1058  if (ParamIdx + 1 == NumParams || PackScope.hasFixedArity()) {
1059  for (; ArgIdx < NumArgs && PackScope.hasNextElement(); ++ArgIdx) {
1060  // Deduce template arguments from the pattern.
1062  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, Pattern,
1063  Args[ArgIdx], Info, Deduced,
1064  TDF, PartialOrdering))
1065  return Result;
1066 
1067  PackScope.nextPackElement();
1068  }
1069  } else {
1070  // C++0x [temp.deduct.type]p5:
1071  // The non-deduced contexts are:
1072  // - A function parameter pack that does not occur at the end of the
1073  // parameter-declaration-clause.
1074  //
1075  // FIXME: There is no wording to say what we should do in this case. We
1076  // choose to resolve this by applying the same rule that is applied for a
1077  // function call: that is, deduce all contained packs to their
1078  // explicitly-specified values (or to <> if there is no such value).
1079  //
1080  // This is seemingly-arbitrarily different from the case of a template-id
1081  // with a non-trailing pack-expansion in its arguments, which renders the
1082  // entire template-argument-list a non-deduced context.
1083 
1084  // If the parameter type contains an explicitly-specified pack that we
1085  // could not expand, skip the number of parameters notionally created
1086  // by the expansion.
1087  Optional<unsigned> NumExpansions = Expansion->getNumExpansions();
1088  if (NumExpansions && !PackScope.isPartiallyExpanded()) {
1089  for (unsigned I = 0; I != *NumExpansions && ArgIdx < NumArgs;
1090  ++I, ++ArgIdx)
1091  PackScope.nextPackElement();
1092  }
1093  }
1094 
1095  // Build argument packs for each of the parameter packs expanded by this
1096  // pack expansion.
1097  if (auto Result = PackScope.finish())
1098  return Result;
1099  }
1100 
1101  // Make sure we don't have any extra arguments.
1102  if (ArgIdx < NumArgs)
1104 
1105  return Sema::TDK_Success;
1106 }
1107 
1108 /// Determine whether the parameter has qualifiers that the argument
1109 /// lacks. Put another way, determine whether there is no way to add
1110 /// a deduced set of qualifiers to the ParamType that would result in
1111 /// its qualifiers matching those of the ArgType.
1113  QualType ArgType) {
1114  Qualifiers ParamQs = ParamType.getQualifiers();
1115  Qualifiers ArgQs = ArgType.getQualifiers();
1116 
1117  if (ParamQs == ArgQs)
1118  return false;
1119 
1120  // Mismatched (but not missing) Objective-C GC attributes.
1121  if (ParamQs.getObjCGCAttr() != ArgQs.getObjCGCAttr() &&
1122  ParamQs.hasObjCGCAttr())
1123  return true;
1124 
1125  // Mismatched (but not missing) address spaces.
1126  if (ParamQs.getAddressSpace() != ArgQs.getAddressSpace() &&
1127  ParamQs.hasAddressSpace())
1128  return true;
1129 
1130  // Mismatched (but not missing) Objective-C lifetime qualifiers.
1131  if (ParamQs.getObjCLifetime() != ArgQs.getObjCLifetime() &&
1132  ParamQs.hasObjCLifetime())
1133  return true;
1134 
1135  // CVR qualifiers inconsistent or a superset.
1136  return (ParamQs.getCVRQualifiers() & ~ArgQs.getCVRQualifiers()) != 0;
1137 }
1138 
1139 /// Compare types for equality with respect to possibly compatible
1140 /// function types (noreturn adjustment, implicit calling conventions). If any
1141 /// of parameter and argument is not a function, just perform type comparison.
1142 ///
1143 /// \param Param the template parameter type.
1144 ///
1145 /// \param Arg the argument type.
1147  CanQualType Arg) {
1148  const FunctionType *ParamFunction = Param->getAs<FunctionType>(),
1149  *ArgFunction = Arg->getAs<FunctionType>();
1150 
1151  // Just compare if not functions.
1152  if (!ParamFunction || !ArgFunction)
1153  return Param == Arg;
1154 
1155  // Noreturn and noexcept adjustment.
1156  QualType AdjustedParam;
1157  if (IsFunctionConversion(Param, Arg, AdjustedParam))
1158  return Arg == Context.getCanonicalType(AdjustedParam);
1159 
1160  // FIXME: Compatible calling conventions.
1161 
1162  return Param == Arg;
1163 }
1164 
1165 /// Get the index of the first template parameter that was originally from the
1166 /// innermost template-parameter-list. This is 0 except when we concatenate
1167 /// the template parameter lists of a class template and a constructor template
1168 /// when forming an implicit deduction guide.
1170  auto *Guide = dyn_cast<CXXDeductionGuideDecl>(FTD->getTemplatedDecl());
1171  if (!Guide || !Guide->isImplicit())
1172  return 0;
1173  return Guide->getDeducedTemplate()->getTemplateParameters()->size();
1174 }
1175 
1176 /// Determine whether a type denotes a forwarding reference.
1177 static bool isForwardingReference(QualType Param, unsigned FirstInnerIndex) {
1178  // C++1z [temp.deduct.call]p3:
1179  // A forwarding reference is an rvalue reference to a cv-unqualified
1180  // template parameter that does not represent a template parameter of a
1181  // class template.
1182  if (auto *ParamRef = Param->getAs<RValueReferenceType>()) {
1183  if (ParamRef->getPointeeType().getQualifiers())
1184  return false;
1185  auto *TypeParm = ParamRef->getPointeeType()->getAs<TemplateTypeParmType>();
1186  return TypeParm && TypeParm->getIndex() >= FirstInnerIndex;
1187  }
1188  return false;
1189 }
1190 
1191 /// Deduce the template arguments by comparing the parameter type and
1192 /// the argument type (C++ [temp.deduct.type]).
1193 ///
1194 /// \param S the semantic analysis object within which we are deducing
1195 ///
1196 /// \param TemplateParams the template parameters that we are deducing
1197 ///
1198 /// \param ParamIn the parameter type
1199 ///
1200 /// \param ArgIn the argument type
1201 ///
1202 /// \param Info information about the template argument deduction itself
1203 ///
1204 /// \param Deduced the deduced template arguments
1205 ///
1206 /// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
1207 /// how template argument deduction is performed.
1208 ///
1209 /// \param PartialOrdering Whether we're performing template argument deduction
1210 /// in the context of partial ordering (C++0x [temp.deduct.partial]).
1211 ///
1212 /// \returns the result of template argument deduction so far. Note that a
1213 /// "success" result means that template argument deduction has not yet failed,
1214 /// but it may still fail, later, for other reasons.
1217  TemplateParameterList *TemplateParams,
1218  QualType ParamIn, QualType ArgIn,
1219  TemplateDeductionInfo &Info,
1221  unsigned TDF,
1222  bool PartialOrdering,
1223  bool DeducedFromArrayBound) {
1224  // We only want to look at the canonical types, since typedefs and
1225  // sugar are not part of template argument deduction.
1226  QualType Param = S.Context.getCanonicalType(ParamIn);
1227  QualType Arg = S.Context.getCanonicalType(ArgIn);
1228 
1229  // If the argument type is a pack expansion, look at its pattern.
1230  // This isn't explicitly called out
1231  if (const PackExpansionType *ArgExpansion
1232  = dyn_cast<PackExpansionType>(Arg))
1233  Arg = ArgExpansion->getPattern();
1234 
1235  if (PartialOrdering) {
1236  // C++11 [temp.deduct.partial]p5:
1237  // Before the partial ordering is done, certain transformations are
1238  // performed on the types used for partial ordering:
1239  // - If P is a reference type, P is replaced by the type referred to.
1240  const ReferenceType *ParamRef = Param->getAs<ReferenceType>();
1241  if (ParamRef)
1242  Param = ParamRef->getPointeeType();
1243 
1244  // - If A is a reference type, A is replaced by the type referred to.
1245  const ReferenceType *ArgRef = Arg->getAs<ReferenceType>();
1246  if (ArgRef)
1247  Arg = ArgRef->getPointeeType();
1248 
1249  if (ParamRef && ArgRef && S.Context.hasSameUnqualifiedType(Param, Arg)) {
1250  // C++11 [temp.deduct.partial]p9:
1251  // If, for a given type, deduction succeeds in both directions (i.e.,
1252  // the types are identical after the transformations above) and both
1253  // P and A were reference types [...]:
1254  // - if [one type] was an lvalue reference and [the other type] was
1255  // not, [the other type] is not considered to be at least as
1256  // specialized as [the first type]
1257  // - if [one type] is more cv-qualified than [the other type],
1258  // [the other type] is not considered to be at least as specialized
1259  // as [the first type]
1260  // Objective-C ARC adds:
1261  // - [one type] has non-trivial lifetime, [the other type] has
1262  // __unsafe_unretained lifetime, and the types are otherwise
1263  // identical
1264  //
1265  // A is "considered to be at least as specialized" as P iff deduction
1266  // succeeds, so we model this as a deduction failure. Note that
1267  // [the first type] is P and [the other type] is A here; the standard
1268  // gets this backwards.
1269  Qualifiers ParamQuals = Param.getQualifiers();
1270  Qualifiers ArgQuals = Arg.getQualifiers();
1271  if ((ParamRef->isLValueReferenceType() &&
1272  !ArgRef->isLValueReferenceType()) ||
1273  ParamQuals.isStrictSupersetOf(ArgQuals) ||
1274  (ParamQuals.hasNonTrivialObjCLifetime() &&
1276  ParamQuals.withoutObjCLifetime() ==
1277  ArgQuals.withoutObjCLifetime())) {
1278  Info.FirstArg = TemplateArgument(ParamIn);
1279  Info.SecondArg = TemplateArgument(ArgIn);
1281  }
1282  }
1283 
1284  // C++11 [temp.deduct.partial]p7:
1285  // Remove any top-level cv-qualifiers:
1286  // - If P is a cv-qualified type, P is replaced by the cv-unqualified
1287  // version of P.
1288  Param = Param.getUnqualifiedType();
1289  // - If A is a cv-qualified type, A is replaced by the cv-unqualified
1290  // version of A.
1291  Arg = Arg.getUnqualifiedType();
1292  } else {
1293  // C++0x [temp.deduct.call]p4 bullet 1:
1294  // - If the original P is a reference type, the deduced A (i.e., the type
1295  // referred to by the reference) can be more cv-qualified than the
1296  // transformed A.
1297  if (TDF & TDF_ParamWithReferenceType) {
1298  Qualifiers Quals;
1299  QualType UnqualParam = S.Context.getUnqualifiedArrayType(Param, Quals);
1300  Quals.setCVRQualifiers(Quals.getCVRQualifiers() &
1301  Arg.getCVRQualifiers());
1302  Param = S.Context.getQualifiedType(UnqualParam, Quals);
1303  }
1304 
1305  if ((TDF & TDF_TopLevelParameterTypeList) && !Param->isFunctionType()) {
1306  // C++0x [temp.deduct.type]p10:
1307  // If P and A are function types that originated from deduction when
1308  // taking the address of a function template (14.8.2.2) or when deducing
1309  // template arguments from a function declaration (14.8.2.6) and Pi and
1310  // Ai are parameters of the top-level parameter-type-list of P and A,
1311  // respectively, Pi is adjusted if it is a forwarding reference and Ai
1312  // is an lvalue reference, in
1313  // which case the type of Pi is changed to be the template parameter
1314  // type (i.e., T&& is changed to simply T). [ Note: As a result, when
1315  // Pi is T&& and Ai is X&, the adjusted Pi will be T, causing T to be
1316  // deduced as X&. - end note ]
1317  TDF &= ~TDF_TopLevelParameterTypeList;
1318  if (isForwardingReference(Param, 0) && Arg->isLValueReferenceType())
1319  Param = Param->getPointeeType();
1320  }
1321  }
1322 
1323  // C++ [temp.deduct.type]p9:
1324  // A template type argument T, a template template argument TT or a
1325  // template non-type argument i can be deduced if P and A have one of
1326  // the following forms:
1327  //
1328  // T
1329  // cv-list T
1330  if (const TemplateTypeParmType *TemplateTypeParm
1331  = Param->getAs<TemplateTypeParmType>()) {
1332  // Just skip any attempts to deduce from a placeholder type or a parameter
1333  // at a different depth.
1334  if (Arg->isPlaceholderType() ||
1335  Info.getDeducedDepth() != TemplateTypeParm->getDepth())
1336  return Sema::TDK_Success;
1337 
1338  unsigned Index = TemplateTypeParm->getIndex();
1339  bool RecanonicalizeArg = false;
1340 
1341  // If the argument type is an array type, move the qualifiers up to the
1342  // top level, so they can be matched with the qualifiers on the parameter.
1343  if (isa<ArrayType>(Arg)) {
1344  Qualifiers Quals;
1345  Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
1346  if (Quals) {
1347  Arg = S.Context.getQualifiedType(Arg, Quals);
1348  RecanonicalizeArg = true;
1349  }
1350  }
1351 
1352  // The argument type can not be less qualified than the parameter
1353  // type.
1354  if (!(TDF & TDF_IgnoreQualifiers) &&
1356  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1357  Info.FirstArg = TemplateArgument(Param);
1358  Info.SecondArg = TemplateArgument(Arg);
1359  return Sema::TDK_Underqualified;
1360  }
1361 
1362  // Do not match a function type with a cv-qualified type.
1363  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1584
1364  if (Arg->isFunctionType() && Param.hasQualifiers()) {
1366  }
1367 
1368  assert(TemplateTypeParm->getDepth() == Info.getDeducedDepth() &&
1369  "saw template type parameter with wrong depth");
1370  assert(Arg != S.Context.OverloadTy && "Unresolved overloaded function");
1371  QualType DeducedType = Arg;
1372 
1373  // Remove any qualifiers on the parameter from the deduced type.
1374  // We checked the qualifiers for consistency above.
1375  Qualifiers DeducedQs = DeducedType.getQualifiers();
1376  Qualifiers ParamQs = Param.getQualifiers();
1377  DeducedQs.removeCVRQualifiers(ParamQs.getCVRQualifiers());
1378  if (ParamQs.hasObjCGCAttr())
1379  DeducedQs.removeObjCGCAttr();
1380  if (ParamQs.hasAddressSpace())
1381  DeducedQs.removeAddressSpace();
1382  if (ParamQs.hasObjCLifetime())
1383  DeducedQs.removeObjCLifetime();
1384 
1385  // Objective-C ARC:
1386  // If template deduction would produce a lifetime qualifier on a type
1387  // that is not a lifetime type, template argument deduction fails.
1388  if (ParamQs.hasObjCLifetime() && !DeducedType->isObjCLifetimeType() &&
1389  !DeducedType->isDependentType()) {
1390  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1391  Info.FirstArg = TemplateArgument(Param);
1392  Info.SecondArg = TemplateArgument(Arg);
1393  return Sema::TDK_Underqualified;
1394  }
1395 
1396  // Objective-C ARC:
1397  // If template deduction would produce an argument type with lifetime type
1398  // but no lifetime qualifier, the __strong lifetime qualifier is inferred.
1399  if (S.getLangOpts().ObjCAutoRefCount &&
1400  DeducedType->isObjCLifetimeType() &&
1401  !DeducedQs.hasObjCLifetime())
1403 
1404  DeducedType = S.Context.getQualifiedType(DeducedType.getUnqualifiedType(),
1405  DeducedQs);
1406 
1407  if (RecanonicalizeArg)
1408  DeducedType = S.Context.getCanonicalType(DeducedType);
1409 
1410  DeducedTemplateArgument NewDeduced(DeducedType, DeducedFromArrayBound);
1412  Deduced[Index],
1413  NewDeduced);
1414  if (Result.isNull()) {
1415  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1416  Info.FirstArg = Deduced[Index];
1417  Info.SecondArg = NewDeduced;
1418  return Sema::TDK_Inconsistent;
1419  }
1420 
1421  Deduced[Index] = Result;
1422  return Sema::TDK_Success;
1423  }
1424 
1425  // Set up the template argument deduction information for a failure.
1426  Info.FirstArg = TemplateArgument(ParamIn);
1427  Info.SecondArg = TemplateArgument(ArgIn);
1428 
1429  // If the parameter is an already-substituted template parameter
1430  // pack, do nothing: we don't know which of its arguments to look
1431  // at, so we have to wait until all of the parameter packs in this
1432  // expansion have arguments.
1433  if (isa<SubstTemplateTypeParmPackType>(Param))
1434  return Sema::TDK_Success;
1435 
1436  // Check the cv-qualifiers on the parameter and argument types.
1437  CanQualType CanParam = S.Context.getCanonicalType(Param);
1438  CanQualType CanArg = S.Context.getCanonicalType(Arg);
1439  if (!(TDF & TDF_IgnoreQualifiers)) {
1440  if (TDF & TDF_ParamWithReferenceType) {
1441  if (hasInconsistentOrSupersetQualifiersOf(Param, Arg))
1443  } else if (TDF & TDF_ArgWithReferenceType) {
1444  // C++ [temp.deduct.conv]p4:
1445  // If the original A is a reference type, A can be more cv-qualified
1446  // than the deduced A
1447  if (!Arg.getQualifiers().compatiblyIncludes(Param.getQualifiers()))
1449 
1450  // Strip out all extra qualifiers from the argument to figure out the
1451  // type we're converting to, prior to the qualification conversion.
1452  Qualifiers Quals;
1453  Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
1454  Arg = S.Context.getQualifiedType(Arg, Param.getQualifiers());
1455  } else if (!IsPossiblyOpaquelyQualifiedType(Param)) {
1456  if (Param.getCVRQualifiers() != Arg.getCVRQualifiers())
1458  }
1459 
1460  // If the parameter type is not dependent, there is nothing to deduce.
1461  if (!Param->isDependentType()) {
1462  if (!(TDF & TDF_SkipNonDependent)) {
1463  bool NonDeduced =
1465  ? !S.isSameOrCompatibleFunctionType(CanParam, CanArg)
1466  : Param != Arg;
1467  if (NonDeduced) {
1469  }
1470  }
1471  return Sema::TDK_Success;
1472  }
1473  } else if (!Param->isDependentType()) {
1474  CanQualType ParamUnqualType = CanParam.getUnqualifiedType(),
1475  ArgUnqualType = CanArg.getUnqualifiedType();
1476  bool Success =
1478  ? S.isSameOrCompatibleFunctionType(ParamUnqualType, ArgUnqualType)
1479  : ParamUnqualType == ArgUnqualType;
1480  if (Success)
1481  return Sema::TDK_Success;
1482  }
1483 
1484  switch (Param->getTypeClass()) {
1485  // Non-canonical types cannot appear here.
1486 #define NON_CANONICAL_TYPE(Class, Base) \
1487  case Type::Class: llvm_unreachable("deducing non-canonical type: " #Class);
1488 #define TYPE(Class, Base)
1489 #include "clang/AST/TypeNodes.def"
1490 
1491  case Type::TemplateTypeParm:
1492  case Type::SubstTemplateTypeParmPack:
1493  llvm_unreachable("Type nodes handled above");
1494 
1495  // These types cannot be dependent, so simply check whether the types are
1496  // the same.
1497  case Type::Builtin:
1498  case Type::VariableArray:
1499  case Type::Vector:
1500  case Type::FunctionNoProto:
1501  case Type::Record:
1502  case Type::Enum:
1503  case Type::ObjCObject:
1504  case Type::ObjCInterface:
1505  case Type::ObjCObjectPointer:
1506  if (TDF & TDF_SkipNonDependent)
1507  return Sema::TDK_Success;
1508 
1509  if (TDF & TDF_IgnoreQualifiers) {
1510  Param = Param.getUnqualifiedType();
1511  Arg = Arg.getUnqualifiedType();
1512  }
1513 
1514  return Param == Arg? Sema::TDK_Success : Sema::TDK_NonDeducedMismatch;
1515 
1516  // _Complex T [placeholder extension]
1517  case Type::Complex:
1518  if (const ComplexType *ComplexArg = Arg->getAs<ComplexType>())
1519  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1520  cast<ComplexType>(Param)->getElementType(),
1521  ComplexArg->getElementType(),
1522  Info, Deduced, TDF);
1523 
1525 
1526  // _Atomic T [extension]
1527  case Type::Atomic:
1528  if (const AtomicType *AtomicArg = Arg->getAs<AtomicType>())
1529  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1530  cast<AtomicType>(Param)->getValueType(),
1531  AtomicArg->getValueType(),
1532  Info, Deduced, TDF);
1533 
1535 
1536  // T *
1537  case Type::Pointer: {
1538  QualType PointeeType;
1539  if (const PointerType *PointerArg = Arg->getAs<PointerType>()) {
1540  PointeeType = PointerArg->getPointeeType();
1541  } else if (const ObjCObjectPointerType *PointerArg
1542  = Arg->getAs<ObjCObjectPointerType>()) {
1543  PointeeType = PointerArg->getPointeeType();
1544  } else {
1546  }
1547 
1548  unsigned SubTDF = TDF & (TDF_IgnoreQualifiers | TDF_DerivedClass);
1549  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1550  cast<PointerType>(Param)->getPointeeType(),
1551  PointeeType,
1552  Info, Deduced, SubTDF);
1553  }
1554 
1555  // T &
1556  case Type::LValueReference: {
1557  const LValueReferenceType *ReferenceArg =
1558  Arg->getAs<LValueReferenceType>();
1559  if (!ReferenceArg)
1561 
1562  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1563  cast<LValueReferenceType>(Param)->getPointeeType(),
1564  ReferenceArg->getPointeeType(), Info, Deduced, 0);
1565  }
1566 
1567  // T && [C++0x]
1568  case Type::RValueReference: {
1569  const RValueReferenceType *ReferenceArg =
1570  Arg->getAs<RValueReferenceType>();
1571  if (!ReferenceArg)
1573 
1574  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1575  cast<RValueReferenceType>(Param)->getPointeeType(),
1576  ReferenceArg->getPointeeType(),
1577  Info, Deduced, 0);
1578  }
1579 
1580  // T [] (implied, but not stated explicitly)
1581  case Type::IncompleteArray: {
1582  const IncompleteArrayType *IncompleteArrayArg =
1584  if (!IncompleteArrayArg)
1586 
1587  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1588  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1590  IncompleteArrayArg->getElementType(),
1591  Info, Deduced, SubTDF);
1592  }
1593 
1594  // T [integer-constant]
1595  case Type::ConstantArray: {
1596  const ConstantArrayType *ConstantArrayArg =
1598  if (!ConstantArrayArg)
1600 
1601  const ConstantArrayType *ConstantArrayParm =
1603  if (ConstantArrayArg->getSize() != ConstantArrayParm->getSize())
1604  return Sema::TDK_NonDeducedMismatch;
1605 
1606  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1607  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1608  ConstantArrayParm->getElementType(),
1609  ConstantArrayArg->getElementType(),
1610  Info, Deduced, SubTDF);
1611  }
1612 
1613  // type [i]
1614  case Type::DependentSizedArray: {
1615  const ArrayType *ArrayArg = S.Context.getAsArrayType(Arg);
1616  if (!ArrayArg)
1618 
1619  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1620 
1621  // Check the element type of the arrays
1622  const DependentSizedArrayType *DependentArrayParm
1625  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1626  DependentArrayParm->getElementType(),
1627  ArrayArg->getElementType(),
1628  Info, Deduced, SubTDF))
1629  return Result;
1630 
1631  // Determine the array bound is something we can deduce.
1633  = getDeducedParameterFromExpr(Info, DependentArrayParm->getSizeExpr());
1634  if (!NTTP)
1635  return Sema::TDK_Success;
1636 
1637  // We can perform template argument deduction for the given non-type
1638  // template parameter.
1639  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
1640  "saw non-type template parameter with wrong depth");
1641  if (const ConstantArrayType *ConstantArrayArg
1642  = dyn_cast<ConstantArrayType>(ArrayArg)) {
1643  llvm::APSInt Size(ConstantArrayArg->getSize());
1644  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, Size,
1645  S.Context.getSizeType(),
1646  /*ArrayBound=*/true,
1647  Info, Deduced);
1648  }
1649  if (const DependentSizedArrayType *DependentArrayArg
1650  = dyn_cast<DependentSizedArrayType>(ArrayArg))
1651  if (DependentArrayArg->getSizeExpr())
1652  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
1653  DependentArrayArg->getSizeExpr(),
1654  Info, Deduced);
1655 
1656  // Incomplete type does not match a dependently-sized array type
1658  }
1659 
1660  // type(*)(T)
1661  // T(*)()
1662  // T(*)(T)
1663  case Type::FunctionProto: {
1664  unsigned SubTDF = TDF & TDF_TopLevelParameterTypeList;
1665  const FunctionProtoType *FunctionProtoArg =
1666  dyn_cast<FunctionProtoType>(Arg);
1667  if (!FunctionProtoArg)
1669 
1670  const FunctionProtoType *FunctionProtoParam =
1671  cast<FunctionProtoType>(Param);
1672 
1673  if (FunctionProtoParam->getMethodQuals()
1674  != FunctionProtoArg->getMethodQuals() ||
1675  FunctionProtoParam->getRefQualifier()
1676  != FunctionProtoArg->getRefQualifier() ||
1677  FunctionProtoParam->isVariadic() != FunctionProtoArg->isVariadic())
1678  return Sema::TDK_NonDeducedMismatch;
1679 
1680  // Check return types.
1681  if (auto Result = DeduceTemplateArgumentsByTypeMatch(
1682  S, TemplateParams, FunctionProtoParam->getReturnType(),
1683  FunctionProtoArg->getReturnType(), Info, Deduced, 0))
1684  return Result;
1685 
1686  // Check parameter types.
1687  if (auto Result = DeduceTemplateArguments(
1688  S, TemplateParams, FunctionProtoParam->param_type_begin(),
1689  FunctionProtoParam->getNumParams(),
1690  FunctionProtoArg->param_type_begin(),
1691  FunctionProtoArg->getNumParams(), Info, Deduced, SubTDF))
1692  return Result;
1693 
1695  return Sema::TDK_Success;
1696 
1697  // FIXME: Per core-2016/10/1019 (no corresponding core issue yet), permit
1698  // deducing through the noexcept-specifier if it's part of the canonical
1699  // type. libstdc++ relies on this.
1700  Expr *NoexceptExpr = FunctionProtoParam->getNoexceptExpr();
1701  if (NonTypeTemplateParmDecl *NTTP =
1702  NoexceptExpr ? getDeducedParameterFromExpr(Info, NoexceptExpr)
1703  : nullptr) {
1704  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
1705  "saw non-type template parameter with wrong depth");
1706 
1707  llvm::APSInt Noexcept(1);
1708  switch (FunctionProtoArg->canThrow()) {
1709  case CT_Cannot:
1710  Noexcept = 1;
1711  LLVM_FALLTHROUGH;
1712 
1713  case CT_Can:
1714  // We give E in noexcept(E) the "deduced from array bound" treatment.
1715  // FIXME: Should we?
1717  S, TemplateParams, NTTP, Noexcept, S.Context.BoolTy,
1718  /*ArrayBound*/true, Info, Deduced);
1719 
1720  case CT_Dependent:
1721  if (Expr *ArgNoexceptExpr = FunctionProtoArg->getNoexceptExpr())
1723  S, TemplateParams, NTTP, ArgNoexceptExpr, Info, Deduced);
1724  // Can't deduce anything from throw(T...).
1725  break;
1726  }
1727  }
1728  // FIXME: Detect non-deduced exception specification mismatches?
1729  //
1730  // Careful about [temp.deduct.call] and [temp.deduct.conv], which allow
1731  // top-level differences in noexcept-specifications.
1732 
1733  return Sema::TDK_Success;
1734  }
1735 
1736  case Type::InjectedClassName:
1737  // Treat a template's injected-class-name as if the template
1738  // specialization type had been used.
1739  Param = cast<InjectedClassNameType>(Param)
1740  ->getInjectedSpecializationType();
1741  assert(isa<TemplateSpecializationType>(Param) &&
1742  "injected class name is not a template specialization type");
1743  LLVM_FALLTHROUGH;
1744 
1745  // template-name<T> (where template-name refers to a class template)
1746  // template-name<i>
1747  // TT<T>
1748  // TT<i>
1749  // TT<>
1750  case Type::TemplateSpecialization: {
1751  const TemplateSpecializationType *SpecParam =
1752  cast<TemplateSpecializationType>(Param);
1753 
1754  // When Arg cannot be a derived class, we can just try to deduce template
1755  // arguments from the template-id.
1756  const RecordType *RecordT = Arg->getAs<RecordType>();
1757  if (!(TDF & TDF_DerivedClass) || !RecordT)
1758  return DeduceTemplateArguments(S, TemplateParams, SpecParam, Arg, Info,
1759  Deduced);
1760 
1761  SmallVector<DeducedTemplateArgument, 8> DeducedOrig(Deduced.begin(),
1762  Deduced.end());
1763 
1765  S, TemplateParams, SpecParam, Arg, Info, Deduced);
1766 
1767  if (Result == Sema::TDK_Success)
1768  return Result;
1769 
1770  // We cannot inspect base classes as part of deduction when the type
1771  // is incomplete, so either instantiate any templates necessary to
1772  // complete the type, or skip over it if it cannot be completed.
1773  if (!S.isCompleteType(Info.getLocation(), Arg))
1774  return Result;
1775 
1776  // C++14 [temp.deduct.call] p4b3:
1777  // If P is a class and P has the form simple-template-id, then the
1778  // transformed A can be a derived class of the deduced A. Likewise if
1779  // P is a pointer to a class of the form simple-template-id, the
1780  // transformed A can be a pointer to a derived class pointed to by the
1781  // deduced A.
1782  //
1783  // These alternatives are considered only if type deduction would
1784  // otherwise fail. If they yield more than one possible deduced A, the
1785  // type deduction fails.
1786 
1787  // Reset the incorrectly deduced argument from above.
1788  Deduced = DeducedOrig;
1789 
1790  // Use data recursion to crawl through the list of base classes.
1791  // Visited contains the set of nodes we have already visited, while
1792  // ToVisit is our stack of records that we still need to visit.
1793  llvm::SmallPtrSet<const RecordType *, 8> Visited;
1795  ToVisit.push_back(RecordT);
1796  bool Successful = false;
1797  SmallVector<DeducedTemplateArgument, 8> SuccessfulDeduced;
1798  while (!ToVisit.empty()) {
1799  // Retrieve the next class in the inheritance hierarchy.
1800  const RecordType *NextT = ToVisit.pop_back_val();
1801 
1802  // If we have already seen this type, skip it.
1803  if (!Visited.insert(NextT).second)
1804  continue;
1805 
1806  // If this is a base class, try to perform template argument
1807  // deduction from it.
1808  if (NextT != RecordT) {
1809  TemplateDeductionInfo BaseInfo(Info.getLocation());
1811  DeduceTemplateArguments(S, TemplateParams, SpecParam,
1812  QualType(NextT, 0), BaseInfo, Deduced);
1813 
1814  // If template argument deduction for this base was successful,
1815  // note that we had some success. Otherwise, ignore any deductions
1816  // from this base class.
1817  if (BaseResult == Sema::TDK_Success) {
1818  // If we've already seen some success, then deduction fails due to
1819  // an ambiguity (temp.deduct.call p5).
1820  if (Successful)
1822 
1823  Successful = true;
1824  std::swap(SuccessfulDeduced, Deduced);
1825 
1826  Info.Param = BaseInfo.Param;
1827  Info.FirstArg = BaseInfo.FirstArg;
1828  Info.SecondArg = BaseInfo.SecondArg;
1829  }
1830 
1831  Deduced = DeducedOrig;
1832  }
1833 
1834  // Visit base classes
1835  CXXRecordDecl *Next = cast<CXXRecordDecl>(NextT->getDecl());
1836  for (const auto &Base : Next->bases()) {
1837  assert(Base.getType()->isRecordType() &&
1838  "Base class that isn't a record?");
1839  ToVisit.push_back(Base.getType()->getAs<RecordType>());
1840  }
1841  }
1842 
1843  if (Successful) {
1844  std::swap(SuccessfulDeduced, Deduced);
1845  return Sema::TDK_Success;
1846  }
1847 
1848  return Result;
1849  }
1850 
1851  // T type::*
1852  // T T::*
1853  // T (type::*)()
1854  // type (T::*)()
1855  // type (type::*)(T)
1856  // type (T::*)(T)
1857  // T (type::*)(T)
1858  // T (T::*)()
1859  // T (T::*)(T)
1860  case Type::MemberPointer: {
1861  const MemberPointerType *MemPtrParam = cast<MemberPointerType>(Param);
1862  const MemberPointerType *MemPtrArg = dyn_cast<MemberPointerType>(Arg);
1863  if (!MemPtrArg)
1865 
1866  QualType ParamPointeeType = MemPtrParam->getPointeeType();
1867  if (ParamPointeeType->isFunctionType())
1868  S.adjustMemberFunctionCC(ParamPointeeType, /*IsStatic=*/true,
1869  /*IsCtorOrDtor=*/false, Info.getLocation());
1870  QualType ArgPointeeType = MemPtrArg->getPointeeType();
1871  if (ArgPointeeType->isFunctionType())
1872  S.adjustMemberFunctionCC(ArgPointeeType, /*IsStatic=*/true,
1873  /*IsCtorOrDtor=*/false, Info.getLocation());
1874 
1876  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1877  ParamPointeeType,
1878  ArgPointeeType,
1879  Info, Deduced,
1880  TDF & TDF_IgnoreQualifiers))
1881  return Result;
1882 
1883  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1884  QualType(MemPtrParam->getClass(), 0),
1885  QualType(MemPtrArg->getClass(), 0),
1886  Info, Deduced,
1887  TDF & TDF_IgnoreQualifiers);
1888  }
1889 
1890  // (clang extension)
1891  //
1892  // type(^)(T)
1893  // T(^)()
1894  // T(^)(T)
1895  case Type::BlockPointer: {
1896  const BlockPointerType *BlockPtrParam = cast<BlockPointerType>(Param);
1897  const BlockPointerType *BlockPtrArg = dyn_cast<BlockPointerType>(Arg);
1898 
1899  if (!BlockPtrArg)
1901 
1902  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1903  BlockPtrParam->getPointeeType(),
1904  BlockPtrArg->getPointeeType(),
1905  Info, Deduced, 0);
1906  }
1907 
1908  // (clang extension)
1909  //
1910  // T __attribute__(((ext_vector_type(<integral constant>))))
1911  case Type::ExtVector: {
1912  const ExtVectorType *VectorParam = cast<ExtVectorType>(Param);
1913  if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
1914  // Make sure that the vectors have the same number of elements.
1915  if (VectorParam->getNumElements() != VectorArg->getNumElements())
1916  return Sema::TDK_NonDeducedMismatch;
1917 
1918  // Perform deduction on the element types.
1919  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1920  VectorParam->getElementType(),
1921  VectorArg->getElementType(),
1922  Info, Deduced, TDF);
1923  }
1924 
1925  if (const DependentSizedExtVectorType *VectorArg
1926  = dyn_cast<DependentSizedExtVectorType>(Arg)) {
1927  // We can't check the number of elements, since the argument has a
1928  // dependent number of elements. This can only occur during partial
1929  // ordering.
1930 
1931  // Perform deduction on the element types.
1932  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1933  VectorParam->getElementType(),
1934  VectorArg->getElementType(),
1935  Info, Deduced, TDF);
1936  }
1937 
1939  }
1940 
1941  case Type::DependentVector: {
1942  const auto *VectorParam = cast<DependentVectorType>(Param);
1943 
1944  if (const auto *VectorArg = dyn_cast<VectorType>(Arg)) {
1945  // Perform deduction on the element types.
1946  if (Sema::TemplateDeductionResult Result =
1948  S, TemplateParams, VectorParam->getElementType(),
1949  VectorArg->getElementType(), Info, Deduced, TDF))
1950  return Result;
1951 
1952  // Perform deduction on the vector size, if we can.
1953  NonTypeTemplateParmDecl *NTTP =
1954  getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
1955  if (!NTTP)
1956  return Sema::TDK_Success;
1957 
1958  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
1959  ArgSize = VectorArg->getNumElements();
1960  // Note that we use the "array bound" rules here; just like in that
1961  // case, we don't have any particular type for the vector size, but
1962  // we can provide one if necessary.
1963  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
1964  S.Context.UnsignedIntTy, true,
1965  Info, Deduced);
1966  }
1967 
1968  if (const auto *VectorArg = dyn_cast<DependentVectorType>(Arg)) {
1969  // Perform deduction on the element types.
1970  if (Sema::TemplateDeductionResult Result =
1972  S, TemplateParams, VectorParam->getElementType(),
1973  VectorArg->getElementType(), Info, Deduced, TDF))
1974  return Result;
1975 
1976  // Perform deduction on the vector size, if we can.
1978  Info, VectorParam->getSizeExpr());
1979  if (!NTTP)
1980  return Sema::TDK_Success;
1981 
1983  S, TemplateParams, NTTP, VectorArg->getSizeExpr(), Info, Deduced);
1984  }
1985 
1987  }
1988 
1989  // (clang extension)
1990  //
1991  // T __attribute__(((ext_vector_type(N))))
1992  case Type::DependentSizedExtVector: {
1993  const DependentSizedExtVectorType *VectorParam
1994  = cast<DependentSizedExtVectorType>(Param);
1995 
1996  if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
1997  // Perform deduction on the element types.
1999  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2000  VectorParam->getElementType(),
2001  VectorArg->getElementType(),
2002  Info, Deduced, TDF))
2003  return Result;
2004 
2005  // Perform deduction on the vector size, if we can.
2007  = getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2008  if (!NTTP)
2009  return Sema::TDK_Success;
2010 
2011  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
2012  ArgSize = VectorArg->getNumElements();
2013  // Note that we use the "array bound" rules here; just like in that
2014  // case, we don't have any particular type for the vector size, but
2015  // we can provide one if necessary.
2016  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
2017  S.Context.IntTy, true, Info,
2018  Deduced);
2019  }
2020 
2021  if (const DependentSizedExtVectorType *VectorArg
2022  = dyn_cast<DependentSizedExtVectorType>(Arg)) {
2023  // Perform deduction on the element types.
2025  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2026  VectorParam->getElementType(),
2027  VectorArg->getElementType(),
2028  Info, Deduced, TDF))
2029  return Result;
2030 
2031  // Perform deduction on the vector size, if we can.
2033  = getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2034  if (!NTTP)
2035  return Sema::TDK_Success;
2036 
2037  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2038  VectorArg->getSizeExpr(),
2039  Info, Deduced);
2040  }
2041 
2043  }
2044 
2045  // (clang extension)
2046  //
2047  // T __attribute__(((address_space(N))))
2048  case Type::DependentAddressSpace: {
2049  const DependentAddressSpaceType *AddressSpaceParam =
2050  cast<DependentAddressSpaceType>(Param);
2051 
2052  if (const DependentAddressSpaceType *AddressSpaceArg =
2053  dyn_cast<DependentAddressSpaceType>(Arg)) {
2054  // Perform deduction on the pointer type.
2055  if (Sema::TemplateDeductionResult Result =
2057  S, TemplateParams, AddressSpaceParam->getPointeeType(),
2058  AddressSpaceArg->getPointeeType(), Info, Deduced, TDF))
2059  return Result;
2060 
2061  // Perform deduction on the address space, if we can.
2063  Info, AddressSpaceParam->getAddrSpaceExpr());
2064  if (!NTTP)
2065  return Sema::TDK_Success;
2066 
2068  S, TemplateParams, NTTP, AddressSpaceArg->getAddrSpaceExpr(), Info,
2069  Deduced);
2070  }
2071 
2073  llvm::APSInt ArgAddressSpace(S.Context.getTypeSize(S.Context.IntTy),
2074  false);
2075  ArgAddressSpace = toTargetAddressSpace(Arg.getAddressSpace());
2076 
2077  // Perform deduction on the pointer types.
2078  if (Sema::TemplateDeductionResult Result =
2080  S, TemplateParams, AddressSpaceParam->getPointeeType(),
2081  S.Context.removeAddrSpaceQualType(Arg), Info, Deduced, TDF))
2082  return Result;
2083 
2084  // Perform deduction on the address space, if we can.
2086  Info, AddressSpaceParam->getAddrSpaceExpr());
2087  if (!NTTP)
2088  return Sema::TDK_Success;
2089 
2090  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2091  ArgAddressSpace, S.Context.IntTy,
2092  true, Info, Deduced);
2093  }
2094 
2096  }
2097 
2098  case Type::TypeOfExpr:
2099  case Type::TypeOf:
2100  case Type::DependentName:
2101  case Type::UnresolvedUsing:
2102  case Type::Decltype:
2103  case Type::UnaryTransform:
2104  case Type::Auto:
2105  case Type::DeducedTemplateSpecialization:
2106  case Type::DependentTemplateSpecialization:
2107  case Type::PackExpansion:
2108  case Type::Pipe:
2109  // No template argument deduction for these types
2110  return Sema::TDK_Success;
2111  }
2112 
2113  llvm_unreachable("Invalid Type Class!");
2114 }
2115 
2118  TemplateParameterList *TemplateParams,
2119  const TemplateArgument &Param,
2120  TemplateArgument Arg,
2121  TemplateDeductionInfo &Info,
2123  // If the template argument is a pack expansion, perform template argument
2124  // deduction against the pattern of that expansion. This only occurs during
2125  // partial ordering.
2126  if (Arg.isPackExpansion())
2127  Arg = Arg.getPackExpansionPattern();
2128 
2129  switch (Param.getKind()) {
2131  llvm_unreachable("Null template argument in parameter list");
2132 
2134  if (Arg.getKind() == TemplateArgument::Type)
2135  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2136  Param.getAsType(),
2137  Arg.getAsType(),
2138  Info, Deduced, 0);
2139  Info.FirstArg = Param;
2140  Info.SecondArg = Arg;
2142 
2144  if (Arg.getKind() == TemplateArgument::Template)
2145  return DeduceTemplateArguments(S, TemplateParams,
2146  Param.getAsTemplate(),
2147  Arg.getAsTemplate(), Info, Deduced);
2148  Info.FirstArg = Param;
2149  Info.SecondArg = Arg;
2151 
2153  llvm_unreachable("caller should handle pack expansions");
2154 
2156  if (Arg.getKind() == TemplateArgument::Declaration &&
2157  isSameDeclaration(Param.getAsDecl(), Arg.getAsDecl()))
2158  return Sema::TDK_Success;
2159 
2160  Info.FirstArg = Param;
2161  Info.SecondArg = Arg;
2163 
2165  if (Arg.getKind() == TemplateArgument::NullPtr &&
2167  return Sema::TDK_Success;
2168 
2169  Info.FirstArg = Param;
2170  Info.SecondArg = Arg;
2172 
2174  if (Arg.getKind() == TemplateArgument::Integral) {
2175  if (hasSameExtendedValue(Param.getAsIntegral(), Arg.getAsIntegral()))
2176  return Sema::TDK_Success;
2177 
2178  Info.FirstArg = Param;
2179  Info.SecondArg = Arg;
2181  }
2182 
2183  if (Arg.getKind() == TemplateArgument::Expression) {
2184  Info.FirstArg = Param;
2185  Info.SecondArg = Arg;
2187  }
2188 
2189  Info.FirstArg = Param;
2190  Info.SecondArg = Arg;
2192 
2194  if (NonTypeTemplateParmDecl *NTTP
2195  = getDeducedParameterFromExpr(Info, Param.getAsExpr())) {
2196  if (Arg.getKind() == TemplateArgument::Integral)
2197  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2198  Arg.getAsIntegral(),
2199  Arg.getIntegralType(),
2200  /*ArrayBound=*/false,
2201  Info, Deduced);
2202  if (Arg.getKind() == TemplateArgument::NullPtr)
2203  return DeduceNullPtrTemplateArgument(S, TemplateParams, NTTP,
2204  Arg.getNullPtrType(),
2205  Info, Deduced);
2207  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2208  Arg.getAsExpr(), Info, Deduced);
2210  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2211  Arg.getAsDecl(),
2212  Arg.getParamTypeForDecl(),
2213  Info, Deduced);
2214 
2215  Info.FirstArg = Param;
2216  Info.SecondArg = Arg;
2218  }
2219 
2220  // Can't deduce anything, but that's okay.
2221  return Sema::TDK_Success;
2222 
2224  llvm_unreachable("Argument packs should be expanded by the caller!");
2225  }
2226 
2227  llvm_unreachable("Invalid TemplateArgument Kind!");
2228 }
2229 
2230 /// Determine whether there is a template argument to be used for
2231 /// deduction.
2232 ///
2233 /// This routine "expands" argument packs in-place, overriding its input
2234 /// parameters so that \c Args[ArgIdx] will be the available template argument.
2235 ///
2236 /// \returns true if there is another template argument (which will be at
2237 /// \c Args[ArgIdx]), false otherwise.
2239  unsigned &ArgIdx) {
2240  if (ArgIdx == Args.size())
2241  return false;
2242 
2243  const TemplateArgument &Arg = Args[ArgIdx];
2244  if (Arg.getKind() != TemplateArgument::Pack)
2245  return true;
2246 
2247  assert(ArgIdx == Args.size() - 1 && "Pack not at the end of argument list?");
2248  Args = Arg.pack_elements();
2249  ArgIdx = 0;
2250  return ArgIdx < Args.size();
2251 }
2252 
2253 /// Determine whether the given set of template arguments has a pack
2254 /// expansion that is not the last template argument.
2256  bool FoundPackExpansion = false;
2257  for (const auto &A : Args) {
2258  if (FoundPackExpansion)
2259  return true;
2260 
2261  if (A.getKind() == TemplateArgument::Pack)
2262  return hasPackExpansionBeforeEnd(A.pack_elements());
2263 
2264  // FIXME: If this is a fixed-arity pack expansion from an outer level of
2265  // templates, it should not be treated as a pack expansion.
2266  if (A.isPackExpansion())
2267  FoundPackExpansion = true;
2268  }
2269 
2270  return false;
2271 }
2272 
2277  TemplateDeductionInfo &Info,
2279  bool NumberOfArgumentsMustMatch) {
2280  // C++0x [temp.deduct.type]p9:
2281  // If the template argument list of P contains a pack expansion that is not
2282  // the last template argument, the entire template argument list is a
2283  // non-deduced context.
2284  if (hasPackExpansionBeforeEnd(Params))
2285  return Sema::TDK_Success;
2286 
2287  // C++0x [temp.deduct.type]p9:
2288  // If P has a form that contains <T> or <i>, then each argument Pi of the
2289  // respective template argument list P is compared with the corresponding
2290  // argument Ai of the corresponding template argument list of A.
2291  unsigned ArgIdx = 0, ParamIdx = 0;
2292  for (; hasTemplateArgumentForDeduction(Params, ParamIdx); ++ParamIdx) {
2293  if (!Params[ParamIdx].isPackExpansion()) {
2294  // The simple case: deduce template arguments by matching Pi and Ai.
2295 
2296  // Check whether we have enough arguments.
2297  if (!hasTemplateArgumentForDeduction(Args, ArgIdx))
2298  return NumberOfArgumentsMustMatch
2301 
2302  // C++1z [temp.deduct.type]p9:
2303  // During partial ordering, if Ai was originally a pack expansion [and]
2304  // Pi is not a pack expansion, template argument deduction fails.
2305  if (Args[ArgIdx].isPackExpansion())
2307 
2308  // Perform deduction for this Pi/Ai pair.
2310  = DeduceTemplateArguments(S, TemplateParams,
2311  Params[ParamIdx], Args[ArgIdx],
2312  Info, Deduced))
2313  return Result;
2314 
2315  // Move to the next argument.
2316  ++ArgIdx;
2317  continue;
2318  }
2319 
2320  // The parameter is a pack expansion.
2321 
2322  // C++0x [temp.deduct.type]p9:
2323  // If Pi is a pack expansion, then the pattern of Pi is compared with
2324  // each remaining argument in the template argument list of A. Each
2325  // comparison deduces template arguments for subsequent positions in the
2326  // template parameter packs expanded by Pi.
2327  TemplateArgument Pattern = Params[ParamIdx].getPackExpansionPattern();
2328 
2329  // Prepare to deduce the packs within the pattern.
2330  PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
2331 
2332  // Keep track of the deduced template arguments for each parameter pack
2333  // expanded by this pack expansion (the outer index) and for each
2334  // template argument (the inner SmallVectors).
2335  for (; hasTemplateArgumentForDeduction(Args, ArgIdx) &&
2336  PackScope.hasNextElement();
2337  ++ArgIdx) {
2338  // Deduce template arguments from the pattern.
2340  = DeduceTemplateArguments(S, TemplateParams, Pattern, Args[ArgIdx],
2341  Info, Deduced))
2342  return Result;
2343 
2344  PackScope.nextPackElement();
2345  }
2346 
2347  // Build argument packs for each of the parameter packs expanded by this
2348  // pack expansion.
2349  if (auto Result = PackScope.finish())
2350  return Result;
2351  }
2352 
2353  return Sema::TDK_Success;
2354 }
2355 
2358  TemplateParameterList *TemplateParams,
2359  const TemplateArgumentList &ParamList,
2360  const TemplateArgumentList &ArgList,
2361  TemplateDeductionInfo &Info,
2363  return DeduceTemplateArguments(S, TemplateParams, ParamList.asArray(),
2364  ArgList.asArray(), Info, Deduced,
2365  /*NumberOfArgumentsMustMatch*/false);
2366 }
2367 
2368 /// Determine whether two template arguments are the same.
2369 static bool isSameTemplateArg(ASTContext &Context,
2371  const TemplateArgument &Y,
2372  bool PackExpansionMatchesPack = false) {
2373  // If we're checking deduced arguments (X) against original arguments (Y),
2374  // we will have flattened packs to non-expansions in X.
2375  if (PackExpansionMatchesPack && X.isPackExpansion() && !Y.isPackExpansion())
2376  X = X.getPackExpansionPattern();
2377 
2378  if (X.getKind() != Y.getKind())
2379  return false;
2380 
2381  switch (X.getKind()) {
2383  llvm_unreachable("Comparing NULL template argument");
2384 
2386  return Context.getCanonicalType(X.getAsType()) ==
2387  Context.getCanonicalType(Y.getAsType());
2388 
2390  return isSameDeclaration(X.getAsDecl(), Y.getAsDecl());
2391 
2393  return Context.hasSameType(X.getNullPtrType(), Y.getNullPtrType());
2394 
2397  return Context.getCanonicalTemplateName(
2398  X.getAsTemplateOrTemplatePattern()).getAsVoidPointer() ==
2399  Context.getCanonicalTemplateName(
2400  Y.getAsTemplateOrTemplatePattern()).getAsVoidPointer();
2401 
2404 
2406  llvm::FoldingSetNodeID XID, YID;
2407  X.getAsExpr()->Profile(XID, Context, true);
2408  Y.getAsExpr()->Profile(YID, Context, true);
2409  return XID == YID;
2410  }
2411 
2413  if (X.pack_size() != Y.pack_size())
2414  return false;
2415 
2417  XPEnd = X.pack_end(),
2418  YP = Y.pack_begin();
2419  XP != XPEnd; ++XP, ++YP)
2420  if (!isSameTemplateArg(Context, *XP, *YP, PackExpansionMatchesPack))
2421  return false;
2422 
2423  return true;
2424  }
2425 
2426  llvm_unreachable("Invalid TemplateArgument Kind!");
2427 }
2428 
2429 /// Allocate a TemplateArgumentLoc where all locations have
2430 /// been initialized to the given location.
2431 ///
2432 /// \param Arg The template argument we are producing template argument
2433 /// location information for.
2434 ///
2435 /// \param NTTPType For a declaration template argument, the type of
2436 /// the non-type template parameter that corresponds to this template
2437 /// argument. Can be null if no type sugar is available to add to the
2438 /// type from the template argument.
2439 ///
2440 /// \param Loc The source location to use for the resulting template
2441 /// argument.
2444  QualType NTTPType, SourceLocation Loc) {
2445  switch (Arg.getKind()) {
2447  llvm_unreachable("Can't get a NULL template argument here");
2448 
2450  return TemplateArgumentLoc(
2451  Arg, Context.getTrivialTypeSourceInfo(Arg.getAsType(), Loc));
2452 
2454  if (NTTPType.isNull())
2455  NTTPType = Arg.getParamTypeForDecl();
2456  Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
2457  .getAs<Expr>();
2458  return TemplateArgumentLoc(TemplateArgument(E), E);
2459  }
2460 
2462  if (NTTPType.isNull())
2463  NTTPType = Arg.getNullPtrType();
2464  Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
2465  .getAs<Expr>();
2466  return TemplateArgumentLoc(TemplateArgument(NTTPType, /*isNullPtr*/true),
2467  E);
2468  }
2469 
2471  Expr *E =
2472  BuildExpressionFromIntegralTemplateArgument(Arg, Loc).getAs<Expr>();
2473  return TemplateArgumentLoc(TemplateArgument(E), E);
2474  }
2475 
2479  TemplateName Template = Arg.getAsTemplate();
2480  if (DependentTemplateName *DTN = Template.getAsDependentTemplateName())
2481  Builder.MakeTrivial(Context, DTN->getQualifier(), Loc);
2482  else if (QualifiedTemplateName *QTN =
2483  Template.getAsQualifiedTemplateName())
2484  Builder.MakeTrivial(Context, QTN->getQualifier(), Loc);
2485 
2486  if (Arg.getKind() == TemplateArgument::Template)
2487  return TemplateArgumentLoc(Arg, Builder.getWithLocInContext(Context),
2488  Loc);
2489 
2490  return TemplateArgumentLoc(Arg, Builder.getWithLocInContext(Context),
2491  Loc, Loc);
2492  }
2493 
2495  return TemplateArgumentLoc(Arg, Arg.getAsExpr());
2496 
2499  }
2500 
2501  llvm_unreachable("Invalid TemplateArgument Kind!");
2502 }
2503 
2504 /// Convert the given deduced template argument and add it to the set of
2505 /// fully-converted template arguments.
2506 static bool
2509  NamedDecl *Template,
2510  TemplateDeductionInfo &Info,
2511  bool IsDeduced,
2513  auto ConvertArg = [&](DeducedTemplateArgument Arg,
2514  unsigned ArgumentPackIndex) {
2515  // Convert the deduced template argument into a template
2516  // argument that we can check, almost as if the user had written
2517  // the template argument explicitly.
2518  TemplateArgumentLoc ArgLoc =
2520 
2521  // Check the template argument, converting it as necessary.
2522  return S.CheckTemplateArgument(
2523  Param, ArgLoc, Template, Template->getLocation(),
2524  Template->getSourceRange().getEnd(), ArgumentPackIndex, Output,
2525  IsDeduced
2529  };
2530 
2531  if (Arg.getKind() == TemplateArgument::Pack) {
2532  // This is a template argument pack, so check each of its arguments against
2533  // the template parameter.
2534  SmallVector<TemplateArgument, 2> PackedArgsBuilder;
2535  for (const auto &P : Arg.pack_elements()) {
2536  // When converting the deduced template argument, append it to the
2537  // general output list. We need to do this so that the template argument
2538  // checking logic has all of the prior template arguments available.
2539  DeducedTemplateArgument InnerArg(P);
2541  assert(InnerArg.getKind() != TemplateArgument::Pack &&
2542  "deduced nested pack");
2543  if (P.isNull()) {
2544  // We deduced arguments for some elements of this pack, but not for
2545  // all of them. This happens if we get a conditionally-non-deduced
2546  // context in a pack expansion (such as an overload set in one of the
2547  // arguments).
2548  S.Diag(Param->getLocation(),
2549  diag::err_template_arg_deduced_incomplete_pack)
2550  << Arg << Param;
2551  return true;
2552  }
2553  if (ConvertArg(InnerArg, PackedArgsBuilder.size()))
2554  return true;
2555 
2556  // Move the converted template argument into our argument pack.
2557  PackedArgsBuilder.push_back(Output.pop_back_val());
2558  }
2559 
2560  // If the pack is empty, we still need to substitute into the parameter
2561  // itself, in case that substitution fails.
2562  if (PackedArgsBuilder.empty()) {
2565  MultiLevelTemplateArgumentList Args(TemplateArgs);
2566 
2567  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
2568  Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
2569  NTTP, Output,
2570  Template->getSourceRange());
2571  if (Inst.isInvalid() ||
2572  S.SubstType(NTTP->getType(), Args, NTTP->getLocation(),
2573  NTTP->getDeclName()).isNull())
2574  return true;
2575  } else if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(Param)) {
2576  Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
2577  TTP, Output,
2578  Template->getSourceRange());
2579  if (Inst.isInvalid() || !S.SubstDecl(TTP, S.CurContext, Args))
2580  return true;
2581  }
2582  // For type parameters, no substitution is ever required.
2583  }
2584 
2585  // Create the resulting argument pack.
2586  Output.push_back(
2587  TemplateArgument::CreatePackCopy(S.Context, PackedArgsBuilder));
2588  return false;
2589  }
2590 
2591  return ConvertArg(Arg, 0);
2592 }
2593 
2594 // FIXME: This should not be a template, but
2595 // ClassTemplatePartialSpecializationDecl sadly does not derive from
2596 // TemplateDecl.
2597 template<typename TemplateDeclT>
2599  Sema &S, TemplateDeclT *Template, bool IsDeduced,
2602  LocalInstantiationScope *CurrentInstantiationScope = nullptr,
2603  unsigned NumAlreadyConverted = 0, bool PartialOverloading = false) {
2604  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
2605 
2606  for (unsigned I = 0, N = TemplateParams->size(); I != N; ++I) {
2607  NamedDecl *Param = TemplateParams->getParam(I);
2608 
2609  // C++0x [temp.arg.explicit]p3:
2610  // A trailing template parameter pack (14.5.3) not otherwise deduced will
2611  // be deduced to an empty sequence of template arguments.
2612  // FIXME: Where did the word "trailing" come from?
2613  if (Deduced[I].isNull() && Param->isTemplateParameterPack()) {
2614  if (auto Result = PackDeductionScope(S, TemplateParams, Deduced, Info, I)
2615  .finish(/*TreatNoDeductionsAsNonDeduced*/false))
2616  return Result;
2617  }
2618 
2619  if (!Deduced[I].isNull()) {
2620  if (I < NumAlreadyConverted) {
2621  // We may have had explicitly-specified template arguments for a
2622  // template parameter pack (that may or may not have been extended
2623  // via additional deduced arguments).
2624  if (Param->isParameterPack() && CurrentInstantiationScope &&
2625  CurrentInstantiationScope->getPartiallySubstitutedPack() == Param) {
2626  // Forget the partially-substituted pack; its substitution is now
2627  // complete.
2628  CurrentInstantiationScope->ResetPartiallySubstitutedPack();
2629  // We still need to check the argument in case it was extended by
2630  // deduction.
2631  } else {
2632  // We have already fully type-checked and converted this
2633  // argument, because it was explicitly-specified. Just record the
2634  // presence of this argument.
2635  Builder.push_back(Deduced[I]);
2636  continue;
2637  }
2638  }
2639 
2640  // We may have deduced this argument, so it still needs to be
2641  // checked and converted.
2642  if (ConvertDeducedTemplateArgument(S, Param, Deduced[I], Template, Info,
2643  IsDeduced, Builder)) {
2644  Info.Param = makeTemplateParameter(Param);
2645  // FIXME: These template arguments are temporary. Free them!
2648  }
2649 
2650  continue;
2651  }
2652 
2653  // Substitute into the default template argument, if available.
2654  bool HasDefaultArg = false;
2655  TemplateDecl *TD = dyn_cast<TemplateDecl>(Template);
2656  if (!TD) {
2657  assert(isa<ClassTemplatePartialSpecializationDecl>(Template) ||
2658  isa<VarTemplatePartialSpecializationDecl>(Template));
2659  return Sema::TDK_Incomplete;
2660  }
2661 
2663  TD, TD->getLocation(), TD->getSourceRange().getEnd(), Param, Builder,
2664  HasDefaultArg);
2665 
2666  // If there was no default argument, deduction is incomplete.
2667  if (DefArg.getArgument().isNull()) {
2669  const_cast<NamedDecl *>(TemplateParams->getParam(I)));
2671  if (PartialOverloading) break;
2672 
2673  return HasDefaultArg ? Sema::TDK_SubstitutionFailure
2675  }
2676 
2677  // Check whether we can actually use the default argument.
2678  if (S.CheckTemplateArgument(Param, DefArg, TD, TD->getLocation(),
2679  TD->getSourceRange().getEnd(), 0, Builder,
2682  const_cast<NamedDecl *>(TemplateParams->getParam(I)));
2683  // FIXME: These template arguments are temporary. Free them!
2686  }
2687 
2688  // If we get here, we successfully used the default template argument.
2689  }
2690 
2691  return Sema::TDK_Success;
2692 }
2693 
2695  if (auto *DC = dyn_cast<DeclContext>(D))
2696  return DC;
2697  return D->getDeclContext();
2698 }
2699 
2700 template<typename T> struct IsPartialSpecialization {
2701  static constexpr bool value = false;
2702 };
2703 template<>
2705  static constexpr bool value = true;
2706 };
2707 template<>
2709  static constexpr bool value = true;
2710 };
2711 
2712 /// Complete template argument deduction for a partial specialization.
2713 template <typename T>
2714 static typename std::enable_if<IsPartialSpecialization<T>::value,
2717  Sema &S, T *Partial, bool IsPartialOrdering,
2718  const TemplateArgumentList &TemplateArgs,
2720  TemplateDeductionInfo &Info) {
2721  // Unevaluated SFINAE context.
2724  Sema::SFINAETrap Trap(S);
2725 
2726  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Partial));
2727 
2728  // C++ [temp.deduct.type]p2:
2729  // [...] or if any template argument remains neither deduced nor
2730  // explicitly specified, template argument deduction fails.
2732  if (auto Result = ConvertDeducedTemplateArguments(
2733  S, Partial, IsPartialOrdering, Deduced, Info, Builder))
2734  return Result;
2735 
2736  // Form the template argument list from the deduced template arguments.
2737  TemplateArgumentList *DeducedArgumentList
2739 
2740  Info.reset(DeducedArgumentList);
2741 
2742  // Substitute the deduced template arguments into the template
2743  // arguments of the class template partial specialization, and
2744  // verify that the instantiated template arguments are both valid
2745  // and are equivalent to the template arguments originally provided
2746  // to the class template.
2747  LocalInstantiationScope InstScope(S);
2748  auto *Template = Partial->getSpecializedTemplate();
2749  const ASTTemplateArgumentListInfo *PartialTemplArgInfo =
2750  Partial->getTemplateArgsAsWritten();
2751  const TemplateArgumentLoc *PartialTemplateArgs =
2752  PartialTemplArgInfo->getTemplateArgs();
2753 
2754  TemplateArgumentListInfo InstArgs(PartialTemplArgInfo->LAngleLoc,
2755  PartialTemplArgInfo->RAngleLoc);
2756 
2757  if (S.Subst(PartialTemplateArgs, PartialTemplArgInfo->NumTemplateArgs,
2758  InstArgs, MultiLevelTemplateArgumentList(*DeducedArgumentList))) {
2759  unsigned ArgIdx = InstArgs.size(), ParamIdx = ArgIdx;
2760  if (ParamIdx >= Partial->getTemplateParameters()->size())
2761  ParamIdx = Partial->getTemplateParameters()->size() - 1;
2762 
2763  Decl *Param = const_cast<NamedDecl *>(
2764  Partial->getTemplateParameters()->getParam(ParamIdx));
2765  Info.Param = makeTemplateParameter(Param);
2766  Info.FirstArg = PartialTemplateArgs[ArgIdx].getArgument();
2768  }
2769 
2770  SmallVector<TemplateArgument, 4> ConvertedInstArgs;
2771  if (S.CheckTemplateArgumentList(Template, Partial->getLocation(), InstArgs,
2772  false, ConvertedInstArgs))
2774 
2775  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
2776  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
2777  TemplateArgument InstArg = ConvertedInstArgs.data()[I];
2778  if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg)) {
2779  Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
2780  Info.FirstArg = TemplateArgs[I];
2781  Info.SecondArg = InstArg;
2783  }
2784  }
2785 
2786  if (Trap.hasErrorOccurred())
2788 
2789  return Sema::TDK_Success;
2790 }
2791 
2792 /// Complete template argument deduction for a class or variable template,
2793 /// when partial ordering against a partial specialization.
2794 // FIXME: Factor out duplication with partial specialization version above.
2796  Sema &S, TemplateDecl *Template, bool PartialOrdering,
2797  const TemplateArgumentList &TemplateArgs,
2799  TemplateDeductionInfo &Info) {
2800  // Unevaluated SFINAE context.
2803  Sema::SFINAETrap Trap(S);
2804 
2805  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Template));
2806 
2807  // C++ [temp.deduct.type]p2:
2808  // [...] or if any template argument remains neither deduced nor
2809  // explicitly specified, template argument deduction fails.
2811  if (auto Result = ConvertDeducedTemplateArguments(
2812  S, Template, /*IsDeduced*/PartialOrdering, Deduced, Info, Builder))
2813  return Result;
2814 
2815  // Check that we produced the correct argument list.
2816  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
2817  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
2818  TemplateArgument InstArg = Builder[I];
2819  if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg,
2820  /*PackExpansionMatchesPack*/true)) {
2821  Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
2822  Info.FirstArg = TemplateArgs[I];
2823  Info.SecondArg = InstArg;
2825  }
2826  }
2827 
2828  if (Trap.hasErrorOccurred())
2830 
2831  return Sema::TDK_Success;
2832 }
2833 
2834 
2835 /// Perform template argument deduction to determine whether
2836 /// the given template arguments match the given class template
2837 /// partial specialization per C++ [temp.class.spec.match].
2840  const TemplateArgumentList &TemplateArgs,
2841  TemplateDeductionInfo &Info) {
2842  if (Partial->isInvalidDecl())
2843  return TDK_Invalid;
2844 
2845  // C++ [temp.class.spec.match]p2:
2846  // A partial specialization matches a given actual template
2847  // argument list if the template arguments of the partial
2848  // specialization can be deduced from the actual template argument
2849  // list (14.8.2).
2850 
2851  // Unevaluated SFINAE context.
2854  SFINAETrap Trap(*this);
2855 
2857  Deduced.resize(Partial->getTemplateParameters()->size());
2858  if (TemplateDeductionResult Result
2859  = ::DeduceTemplateArguments(*this,
2860  Partial->getTemplateParameters(),
2861  Partial->getTemplateArgs(),
2862  TemplateArgs, Info, Deduced))
2863  return Result;
2864 
2865  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
2866  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
2867  Info);
2868  if (Inst.isInvalid())
2869  return TDK_InstantiationDepth;
2870 
2871  if (Trap.hasErrorOccurred())
2873 
2875  *this, Partial, /*PartialOrdering=*/false, TemplateArgs, Deduced, Info);
2876 }
2877 
2878 /// Perform template argument deduction to determine whether
2879 /// the given template arguments match the given variable template
2880 /// partial specialization per C++ [temp.class.spec.match].
2883  const TemplateArgumentList &TemplateArgs,
2884  TemplateDeductionInfo &Info) {
2885  if (Partial->isInvalidDecl())
2886  return TDK_Invalid;
2887 
2888  // C++ [temp.class.spec.match]p2:
2889  // A partial specialization matches a given actual template
2890  // argument list if the template arguments of the partial
2891  // specialization can be deduced from the actual template argument
2892  // list (14.8.2).
2893 
2894  // Unevaluated SFINAE context.
2897  SFINAETrap Trap(*this);
2898 
2900  Deduced.resize(Partial->getTemplateParameters()->size());
2902  *this, Partial->getTemplateParameters(), Partial->getTemplateArgs(),
2903  TemplateArgs, Info, Deduced))
2904  return Result;
2905 
2906  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
2907  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
2908  Info);
2909  if (Inst.isInvalid())
2910  return TDK_InstantiationDepth;
2911 
2912  if (Trap.hasErrorOccurred())
2914 
2916  *this, Partial, /*PartialOrdering=*/false, TemplateArgs, Deduced, Info);
2917 }
2918 
2919 /// Determine whether the given type T is a simple-template-id type.
2921  if (const TemplateSpecializationType *Spec
2923  return Spec->getTemplateName().getAsTemplateDecl() != nullptr;
2924 
2925  // C++17 [temp.local]p2:
2926  // the injected-class-name [...] is equivalent to the template-name followed
2927  // by the template-arguments of the class template specialization or partial
2928  // specialization enclosed in <>
2929  // ... which means it's equivalent to a simple-template-id.
2930  //
2931  // This only arises during class template argument deduction for a copy
2932  // deduction candidate, where it permits slicing.
2933  if (T->getAs<InjectedClassNameType>())
2934  return true;
2935 
2936  return false;
2937 }
2938 
2939 /// Substitute the explicitly-provided template arguments into the
2940 /// given function template according to C++ [temp.arg.explicit].
2941 ///
2942 /// \param FunctionTemplate the function template into which the explicit
2943 /// template arguments will be substituted.
2944 ///
2945 /// \param ExplicitTemplateArgs the explicitly-specified template
2946 /// arguments.
2947 ///
2948 /// \param Deduced the deduced template arguments, which will be populated
2949 /// with the converted and checked explicit template arguments.
2950 ///
2951 /// \param ParamTypes will be populated with the instantiated function
2952 /// parameters.
2953 ///
2954 /// \param FunctionType if non-NULL, the result type of the function template
2955 /// will also be instantiated and the pointed-to value will be updated with
2956 /// the instantiated function type.
2957 ///
2958 /// \param Info if substitution fails for any reason, this object will be
2959 /// populated with more information about the failure.
2960 ///
2961 /// \returns TDK_Success if substitution was successful, or some failure
2962 /// condition.
2965  FunctionTemplateDecl *FunctionTemplate,
2966  TemplateArgumentListInfo &ExplicitTemplateArgs,
2968  SmallVectorImpl<QualType> &ParamTypes,
2970  TemplateDeductionInfo &Info) {
2971  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
2972  TemplateParameterList *TemplateParams
2973  = FunctionTemplate->getTemplateParameters();
2974 
2975  if (ExplicitTemplateArgs.size() == 0) {
2976  // No arguments to substitute; just copy over the parameter types and
2977  // fill in the function type.
2978  for (auto P : Function->parameters())
2979  ParamTypes.push_back(P->getType());
2980 
2981  if (FunctionType)
2982  *FunctionType = Function->getType();
2983  return TDK_Success;
2984  }
2985 
2986  // Unevaluated SFINAE context.
2989  SFINAETrap Trap(*this);
2990 
2991  // C++ [temp.arg.explicit]p3:
2992  // Template arguments that are present shall be specified in the
2993  // declaration order of their corresponding template-parameters. The
2994  // template argument list shall not specify more template-arguments than
2995  // there are corresponding template-parameters.
2997 
2998  // Enter a new template instantiation context where we check the
2999  // explicitly-specified template arguments against this function template,
3000  // and then substitute them into the function parameter types.
3002  InstantiatingTemplate Inst(
3003  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3004  CodeSynthesisContext::ExplicitTemplateArgumentSubstitution, Info);
3005  if (Inst.isInvalid())
3006  return TDK_InstantiationDepth;
3007 
3008  if (CheckTemplateArgumentList(FunctionTemplate, SourceLocation(),
3009  ExplicitTemplateArgs, true, Builder, false) ||
3010  Trap.hasErrorOccurred()) {
3011  unsigned Index = Builder.size();
3012  if (Index >= TemplateParams->size())
3013  return TDK_SubstitutionFailure;
3014  Info.Param = makeTemplateParameter(TemplateParams->getParam(Index));
3015  return TDK_InvalidExplicitArguments;
3016  }
3017 
3018  // Form the template argument list from the explicitly-specified
3019  // template arguments.
3020  TemplateArgumentList *ExplicitArgumentList
3021  = TemplateArgumentList::CreateCopy(Context, Builder);
3022  Info.setExplicitArgs(ExplicitArgumentList);
3023 
3024  // Template argument deduction and the final substitution should be
3025  // done in the context of the templated declaration. Explicit
3026  // argument substitution, on the other hand, needs to happen in the
3027  // calling context.
3028  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3029 
3030  // If we deduced template arguments for a template parameter pack,
3031  // note that the template argument pack is partially substituted and record
3032  // the explicit template arguments. They'll be used as part of deduction
3033  // for this template parameter pack.
3034  unsigned PartiallySubstitutedPackIndex = -1u;
3035  if (!Builder.empty()) {
3036  const TemplateArgument &Arg = Builder.back();
3037  if (Arg.getKind() == TemplateArgument::Pack) {
3038  auto *Param = TemplateParams->getParam(Builder.size() - 1);
3039  // If this is a fully-saturated fixed-size pack, it should be
3040  // fully-substituted, not partially-substituted.
3041  Optional<unsigned> Expansions = getExpandedPackSize(Param);
3042  if (!Expansions || Arg.pack_size() < *Expansions) {
3043  PartiallySubstitutedPackIndex = Builder.size() - 1;
3044  CurrentInstantiationScope->SetPartiallySubstitutedPack(
3045  Param, Arg.pack_begin(), Arg.pack_size());
3046  }
3047  }
3048  }
3049 
3050  const FunctionProtoType *Proto
3051  = Function->getType()->getAs<FunctionProtoType>();
3052  assert(Proto && "Function template does not have a prototype?");
3053 
3054  // Isolate our substituted parameters from our caller.
3055  LocalInstantiationScope InstScope(*this, /*MergeWithOuterScope*/true);
3056 
3057  ExtParameterInfoBuilder ExtParamInfos;
3058 
3059  // Instantiate the types of each of the function parameters given the
3060  // explicitly-specified template arguments. If the function has a trailing
3061  // return type, substitute it after the arguments to ensure we substitute
3062  // in lexical order.
3063  if (Proto->hasTrailingReturn()) {
3064  if (SubstParmTypes(Function->getLocation(), Function->parameters(),
3065  Proto->getExtParameterInfosOrNull(),
3066  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3067  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3068  return TDK_SubstitutionFailure;
3069  }
3070 
3071  // Instantiate the return type.
3072  QualType ResultType;
3073  {
3074  // C++11 [expr.prim.general]p3:
3075  // If a declaration declares a member function or member function
3076  // template of a class X, the expression this is a prvalue of type
3077  // "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
3078  // and the end of the function-definition, member-declarator, or
3079  // declarator.
3080  Qualifiers ThisTypeQuals;
3081  CXXRecordDecl *ThisContext = nullptr;
3082  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Function)) {
3083  ThisContext = Method->getParent();
3084  ThisTypeQuals = Method->getMethodQualifiers();
3085  }
3086 
3087  CXXThisScopeRAII ThisScope(*this, ThisContext, ThisTypeQuals,
3088  getLangOpts().CPlusPlus11);
3089 
3090  ResultType =
3091  SubstType(Proto->getReturnType(),
3092  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3093  Function->getTypeSpecStartLoc(), Function->getDeclName());
3094  if (ResultType.isNull() || Trap.hasErrorOccurred())
3095  return TDK_SubstitutionFailure;
3096  }
3097 
3098  // Instantiate the types of each of the function parameters given the
3099  // explicitly-specified template arguments if we didn't do so earlier.
3100  if (!Proto->hasTrailingReturn() &&
3101  SubstParmTypes(Function->getLocation(), Function->parameters(),
3102  Proto->getExtParameterInfosOrNull(),
3103  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3104  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3105  return TDK_SubstitutionFailure;
3106 
3107  if (FunctionType) {
3108  auto EPI = Proto->getExtProtoInfo();
3109  EPI.ExtParameterInfos = ExtParamInfos.getPointerOrNull(ParamTypes.size());
3110 
3111  // In C++1z onwards, exception specifications are part of the function type,
3112  // so substitution into the type must also substitute into the exception
3113  // specification.
3114  SmallVector<QualType, 4> ExceptionStorage;
3115  if (getLangOpts().CPlusPlus17 &&
3116  SubstExceptionSpec(
3117  Function->getLocation(), EPI.ExceptionSpec, ExceptionStorage,
3118  MultiLevelTemplateArgumentList(*ExplicitArgumentList)))
3119  return TDK_SubstitutionFailure;
3120 
3121  *FunctionType = BuildFunctionType(ResultType, ParamTypes,
3122  Function->getLocation(),
3123  Function->getDeclName(),
3124  EPI);
3125  if (FunctionType->isNull() || Trap.hasErrorOccurred())
3126  return TDK_SubstitutionFailure;
3127  }
3128 
3129  // C++ [temp.arg.explicit]p2:
3130  // Trailing template arguments that can be deduced (14.8.2) may be
3131  // omitted from the list of explicit template-arguments. If all of the
3132  // template arguments can be deduced, they may all be omitted; in this
3133  // case, the empty template argument list <> itself may also be omitted.
3134  //
3135  // Take all of the explicitly-specified arguments and put them into
3136  // the set of deduced template arguments. The partially-substituted
3137  // parameter pack, however, will be set to NULL since the deduction
3138  // mechanism handles the partially-substituted argument pack directly.
3139  Deduced.reserve(TemplateParams->size());
3140  for (unsigned I = 0, N = ExplicitArgumentList->size(); I != N; ++I) {
3141  const TemplateArgument &Arg = ExplicitArgumentList->get(I);
3142  if (I == PartiallySubstitutedPackIndex)
3143  Deduced.push_back(DeducedTemplateArgument());
3144  else
3145  Deduced.push_back(Arg);
3146  }
3147 
3148  return TDK_Success;
3149 }
3150 
3151 /// Check whether the deduced argument type for a call to a function
3152 /// template matches the actual argument type per C++ [temp.deduct.call]p4.
3155  Sema::OriginalCallArg OriginalArg,
3156  QualType DeducedA) {
3157  ASTContext &Context = S.Context;
3158 
3159  auto Failed = [&]() -> Sema::TemplateDeductionResult {
3160  Info.FirstArg = TemplateArgument(DeducedA);
3161  Info.SecondArg = TemplateArgument(OriginalArg.OriginalArgType);
3162  Info.CallArgIndex = OriginalArg.ArgIdx;
3165  };
3166 
3167  QualType A = OriginalArg.OriginalArgType;
3168  QualType OriginalParamType = OriginalArg.OriginalParamType;
3169 
3170  // Check for type equality (top-level cv-qualifiers are ignored).
3171  if (Context.hasSameUnqualifiedType(A, DeducedA))
3172  return Sema::TDK_Success;
3173 
3174  // Strip off references on the argument types; they aren't needed for
3175  // the following checks.
3176  if (const ReferenceType *DeducedARef = DeducedA->getAs<ReferenceType>())
3177  DeducedA = DeducedARef->getPointeeType();
3178  if (const ReferenceType *ARef = A->getAs<ReferenceType>())
3179  A = ARef->getPointeeType();
3180 
3181  // C++ [temp.deduct.call]p4:
3182  // [...] However, there are three cases that allow a difference:
3183  // - If the original P is a reference type, the deduced A (i.e., the
3184  // type referred to by the reference) can be more cv-qualified than
3185  // the transformed A.
3186  if (const ReferenceType *OriginalParamRef
3187  = OriginalParamType->getAs<ReferenceType>()) {
3188  // We don't want to keep the reference around any more.
3189  OriginalParamType = OriginalParamRef->getPointeeType();
3190 
3191  // FIXME: Resolve core issue (no number yet): if the original P is a
3192  // reference type and the transformed A is function type "noexcept F",
3193  // the deduced A can be F.
3194  QualType Tmp;
3195  if (A->isFunctionType() && S.IsFunctionConversion(A, DeducedA, Tmp))
3196  return Sema::TDK_Success;
3197 
3198  Qualifiers AQuals = A.getQualifiers();
3199  Qualifiers DeducedAQuals = DeducedA.getQualifiers();
3200 
3201  // Under Objective-C++ ARC, the deduced type may have implicitly
3202  // been given strong or (when dealing with a const reference)
3203  // unsafe_unretained lifetime. If so, update the original
3204  // qualifiers to include this lifetime.
3205  if (S.getLangOpts().ObjCAutoRefCount &&
3206  ((DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_Strong &&
3207  AQuals.getObjCLifetime() == Qualifiers::OCL_None) ||
3208  (DeducedAQuals.hasConst() &&
3209  DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone))) {
3210  AQuals.setObjCLifetime(DeducedAQuals.getObjCLifetime());
3211  }
3212 
3213  if (AQuals == DeducedAQuals) {
3214  // Qualifiers match; there's nothing to do.
3215  } else if (!DeducedAQuals.compatiblyIncludes(AQuals)) {
3216  return Failed();
3217  } else {
3218  // Qualifiers are compatible, so have the argument type adopt the
3219  // deduced argument type's qualifiers as if we had performed the
3220  // qualification conversion.
3221  A = Context.getQualifiedType(A.getUnqualifiedType(), DeducedAQuals);
3222  }
3223  }
3224 
3225  // - The transformed A can be another pointer or pointer to member
3226  // type that can be converted to the deduced A via a function pointer
3227  // conversion and/or a qualification conversion.
3228  //
3229  // Also allow conversions which merely strip __attribute__((noreturn)) from
3230  // function types (recursively).
3231  bool ObjCLifetimeConversion = false;
3232  QualType ResultTy;
3233  if ((A->isAnyPointerType() || A->isMemberPointerType()) &&
3234  (S.IsQualificationConversion(A, DeducedA, false,
3235  ObjCLifetimeConversion) ||
3236  S.IsFunctionConversion(A, DeducedA, ResultTy)))
3237  return Sema::TDK_Success;
3238 
3239  // - If P is a class and P has the form simple-template-id, then the
3240  // transformed A can be a derived class of the deduced A. [...]
3241  // [...] Likewise, if P is a pointer to a class of the form
3242  // simple-template-id, the transformed A can be a pointer to a
3243  // derived class pointed to by the deduced A.
3244  if (const PointerType *OriginalParamPtr
3245  = OriginalParamType->getAs<PointerType>()) {
3246  if (const PointerType *DeducedAPtr = DeducedA->getAs<PointerType>()) {
3247  if (const PointerType *APtr = A->getAs<PointerType>()) {
3248  if (A->getPointeeType()->isRecordType()) {
3249  OriginalParamType = OriginalParamPtr->getPointeeType();
3250  DeducedA = DeducedAPtr->getPointeeType();
3251  A = APtr->getPointeeType();
3252  }
3253  }
3254  }
3255  }
3256 
3257  if (Context.hasSameUnqualifiedType(A, DeducedA))
3258  return Sema::TDK_Success;
3259 
3260  if (A->isRecordType() && isSimpleTemplateIdType(OriginalParamType) &&
3261  S.IsDerivedFrom(Info.getLocation(), A, DeducedA))
3262  return Sema::TDK_Success;
3263 
3264  return Failed();
3265 }
3266 
3267 /// Find the pack index for a particular parameter index in an instantiation of
3268 /// a function template with specific arguments.
3269 ///
3270 /// \return The pack index for whichever pack produced this parameter, or -1
3271 /// if this was not produced by a parameter. Intended to be used as the
3272 /// ArgumentPackSubstitutionIndex for further substitutions.
3273 // FIXME: We should track this in OriginalCallArgs so we don't need to
3274 // reconstruct it here.
3275 static unsigned getPackIndexForParam(Sema &S,
3276  FunctionTemplateDecl *FunctionTemplate,
3277  const MultiLevelTemplateArgumentList &Args,
3278  unsigned ParamIdx) {
3279  unsigned Idx = 0;
3280  for (auto *PD : FunctionTemplate->getTemplatedDecl()->parameters()) {
3281  if (PD->isParameterPack()) {
3282  unsigned NumExpansions =
3283  S.getNumArgumentsInExpansion(PD->getType(), Args).getValueOr(1);
3284  if (Idx + NumExpansions > ParamIdx)
3285  return ParamIdx - Idx;
3286  Idx += NumExpansions;
3287  } else {
3288  if (Idx == ParamIdx)
3289  return -1; // Not a pack expansion
3290  ++Idx;
3291  }
3292  }
3293 
3294  llvm_unreachable("parameter index would not be produced from template");
3295 }
3296 
3297 /// Finish template argument deduction for a function template,
3298 /// checking the deduced template arguments for completeness and forming
3299 /// the function template specialization.
3300 ///
3301 /// \param OriginalCallArgs If non-NULL, the original call arguments against
3302 /// which the deduced argument types should be compared.
3304  FunctionTemplateDecl *FunctionTemplate,
3306  unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
3307  TemplateDeductionInfo &Info,
3308  SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
3309  bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
3310  // Unevaluated SFINAE context.
3313  SFINAETrap Trap(*this);
3314 
3315  // Enter a new template instantiation context while we instantiate the
3316  // actual function declaration.
3317  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3318  InstantiatingTemplate Inst(
3319  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3320  CodeSynthesisContext::DeducedTemplateArgumentSubstitution, Info);
3321  if (Inst.isInvalid())
3322  return TDK_InstantiationDepth;
3323 
3324  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3325 
3326  // C++ [temp.deduct.type]p2:
3327  // [...] or if any template argument remains neither deduced nor
3328  // explicitly specified, template argument deduction fails.
3330  if (auto Result = ConvertDeducedTemplateArguments(
3331  *this, FunctionTemplate, /*IsDeduced*/true, Deduced, Info, Builder,
3332  CurrentInstantiationScope, NumExplicitlySpecified,
3333  PartialOverloading))
3334  return Result;
3335 
3336  // C++ [temp.deduct.call]p10: [DR1391]
3337  // If deduction succeeds for all parameters that contain
3338  // template-parameters that participate in template argument deduction,
3339  // and all template arguments are explicitly specified, deduced, or
3340  // obtained from default template arguments, remaining parameters are then
3341  // compared with the corresponding arguments. For each remaining parameter
3342  // P with a type that was non-dependent before substitution of any
3343  // explicitly-specified template arguments, if the corresponding argument
3344  // A cannot be implicitly converted to P, deduction fails.
3345  if (CheckNonDependent())
3346  return TDK_NonDependentConversionFailure;
3347 
3348  // Form the template argument list from the deduced template arguments.
3349  TemplateArgumentList *DeducedArgumentList
3350  = TemplateArgumentList::CreateCopy(Context, Builder);
3351  Info.reset(DeducedArgumentList);
3352 
3353  // Substitute the deduced template arguments into the function template
3354  // declaration to produce the function template specialization.
3355  DeclContext *Owner = FunctionTemplate->getDeclContext();
3356  if (FunctionTemplate->getFriendObjectKind())
3357  Owner = FunctionTemplate->getLexicalDeclContext();
3358  MultiLevelTemplateArgumentList SubstArgs(*DeducedArgumentList);
3359  Specialization = cast_or_null<FunctionDecl>(
3360  SubstDecl(FunctionTemplate->getTemplatedDecl(), Owner, SubstArgs));
3361  if (!Specialization || Specialization->isInvalidDecl())
3362  return TDK_SubstitutionFailure;
3363 
3364  assert(Specialization->getPrimaryTemplate()->getCanonicalDecl() ==
3365  FunctionTemplate->getCanonicalDecl());
3366 
3367  // If the template argument list is owned by the function template
3368  // specialization, release it.
3369  if (Specialization->getTemplateSpecializationArgs() == DeducedArgumentList &&
3370  !Trap.hasErrorOccurred())
3371  Info.take();
3372 
3373  // There may have been an error that did not prevent us from constructing a
3374  // declaration. Mark the declaration invalid and return with a substitution
3375  // failure.
3376  if (Trap.hasErrorOccurred()) {
3377  Specialization->setInvalidDecl(true);
3378  return TDK_SubstitutionFailure;
3379  }
3380 
3381  if (OriginalCallArgs) {
3382  // C++ [temp.deduct.call]p4:
3383  // In general, the deduction process attempts to find template argument
3384  // values that will make the deduced A identical to A (after the type A
3385  // is transformed as described above). [...]
3386  llvm::SmallDenseMap<std::pair<unsigned, QualType>, QualType> DeducedATypes;
3387  for (unsigned I = 0, N = OriginalCallArgs->size(); I != N; ++I) {
3388  OriginalCallArg OriginalArg = (*OriginalCallArgs)[I];
3389 
3390  auto ParamIdx = OriginalArg.ArgIdx;
3391  if (ParamIdx >= Specialization->getNumParams())
3392  // FIXME: This presumably means a pack ended up smaller than we
3393  // expected while deducing. Should this not result in deduction
3394  // failure? Can it even happen?
3395  continue;
3396 
3397  QualType DeducedA;
3398  if (!OriginalArg.DecomposedParam) {
3399  // P is one of the function parameters, just look up its substituted
3400  // type.
3401  DeducedA = Specialization->getParamDecl(ParamIdx)->getType();
3402  } else {
3403  // P is a decomposed element of a parameter corresponding to a
3404  // braced-init-list argument. Substitute back into P to find the
3405  // deduced A.
3406  QualType &CacheEntry =
3407  DeducedATypes[{ParamIdx, OriginalArg.OriginalParamType}];
3408  if (CacheEntry.isNull()) {
3410  *this, getPackIndexForParam(*this, FunctionTemplate, SubstArgs,
3411  ParamIdx));
3412  CacheEntry =
3413  SubstType(OriginalArg.OriginalParamType, SubstArgs,
3414  Specialization->getTypeSpecStartLoc(),
3415  Specialization->getDeclName());
3416  }
3417  DeducedA = CacheEntry;
3418  }
3419 
3420  if (auto TDK =
3421  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA))
3422  return TDK;
3423  }
3424  }
3425 
3426  // If we suppressed any diagnostics while performing template argument
3427  // deduction, and if we haven't already instantiated this declaration,
3428  // keep track of these diagnostics. They'll be emitted if this specialization
3429  // is actually used.
3430  if (Info.diag_begin() != Info.diag_end()) {
3431  SuppressedDiagnosticsMap::iterator
3432  Pos = SuppressedDiagnostics.find(Specialization->getCanonicalDecl());
3433  if (Pos == SuppressedDiagnostics.end())
3434  SuppressedDiagnostics[Specialization->getCanonicalDecl()]
3435  .append(Info.diag_begin(), Info.diag_end());
3436  }
3437 
3438  return TDK_Success;
3439 }
3440 
3441 /// Gets the type of a function for template-argument-deducton
3442 /// purposes when it's considered as part of an overload set.
3444  FunctionDecl *Fn) {
3445  // We may need to deduce the return type of the function now.
3446  if (S.getLangOpts().CPlusPlus14 && Fn->getReturnType()->isUndeducedType() &&
3447  S.DeduceReturnType(Fn, R.Expression->getExprLoc(), /*Diagnose*/ false))
3448  return {};
3449 
3450  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Fn))
3451  if (Method->isInstance()) {
3452  // An instance method that's referenced in a form that doesn't
3453  // look like a member pointer is just invalid.
3454  if (!R.HasFormOfMemberPointer)
3455  return {};
3456 
3457  return S.Context.getMemberPointerType(Fn->getType(),
3458  S.Context.getTypeDeclType(Method->getParent()).getTypePtr());
3459  }
3460 
3461  if (!R.IsAddressOfOperand) return Fn->getType();
3462  return S.Context.getPointerType(Fn->getType());
3463 }
3464 
3465 /// Apply the deduction rules for overload sets.
3466 ///
3467 /// \return the null type if this argument should be treated as an
3468 /// undeduced context
3469 static QualType
3471  Expr *Arg, QualType ParamType,
3472  bool ParamWasReference) {
3473 
3475 
3476  OverloadExpr *Ovl = R.Expression;
3477 
3478  // C++0x [temp.deduct.call]p4
3479  unsigned TDF = 0;
3480  if (ParamWasReference)
3482  if (R.IsAddressOfOperand)
3483  TDF |= TDF_IgnoreQualifiers;
3484 
3485  // C++0x [temp.deduct.call]p6:
3486  // When P is a function type, pointer to function type, or pointer
3487  // to member function type:
3488 
3489  if (!ParamType->isFunctionType() &&
3490  !ParamType->isFunctionPointerType() &&
3491  !ParamType->isMemberFunctionPointerType()) {
3492  if (Ovl->hasExplicitTemplateArgs()) {
3493  // But we can still look for an explicit specialization.
3494  if (FunctionDecl *ExplicitSpec
3496  return GetTypeOfFunction(S, R, ExplicitSpec);
3497  }
3498 
3499  DeclAccessPair DAP;
3500  if (FunctionDecl *Viable =
3502  return GetTypeOfFunction(S, R, Viable);
3503 
3504  return {};
3505  }
3506 
3507  // Gather the explicit template arguments, if any.
3508  TemplateArgumentListInfo ExplicitTemplateArgs;
3509  if (Ovl->hasExplicitTemplateArgs())
3510  Ovl->copyTemplateArgumentsInto(ExplicitTemplateArgs);
3511  QualType Match;
3512  for (UnresolvedSetIterator I = Ovl->decls_begin(),
3513  E = Ovl->decls_end(); I != E; ++I) {
3514  NamedDecl *D = (*I)->getUnderlyingDecl();
3515 
3516  if (FunctionTemplateDecl *FunTmpl = dyn_cast<FunctionTemplateDecl>(D)) {
3517  // - If the argument is an overload set containing one or more
3518  // function templates, the parameter is treated as a
3519  // non-deduced context.
3520  if (!Ovl->hasExplicitTemplateArgs())
3521  return {};
3522 
3523  // Otherwise, see if we can resolve a function type
3524  FunctionDecl *Specialization = nullptr;
3525  TemplateDeductionInfo Info(Ovl->getNameLoc());
3526  if (S.DeduceTemplateArguments(FunTmpl, &ExplicitTemplateArgs,
3527  Specialization, Info))
3528  continue;
3529 
3530  D = Specialization;
3531  }
3532 
3533  FunctionDecl *Fn = cast<FunctionDecl>(D);
3534  QualType ArgType = GetTypeOfFunction(S, R, Fn);
3535  if (ArgType.isNull()) continue;
3536 
3537  // Function-to-pointer conversion.
3538  if (!ParamWasReference && ParamType->isPointerType() &&
3539  ArgType->isFunctionType())
3540  ArgType = S.Context.getPointerType(ArgType);
3541 
3542  // - If the argument is an overload set (not containing function
3543  // templates), trial argument deduction is attempted using each
3544  // of the members of the set. If deduction succeeds for only one
3545  // of the overload set members, that member is used as the
3546  // argument value for the deduction. If deduction succeeds for
3547  // more than one member of the overload set the parameter is
3548  // treated as a non-deduced context.
3549 
3550  // We do all of this in a fresh context per C++0x [temp.deduct.type]p2:
3551  // Type deduction is done independently for each P/A pair, and
3552  // the deduced template argument values are then combined.
3553  // So we do not reject deductions which were made elsewhere.
3555  Deduced(TemplateParams->size());
3556  TemplateDeductionInfo Info(Ovl->getNameLoc());
3558  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
3559  ArgType, Info, Deduced, TDF);
3560  if (Result) continue;
3561  if (!Match.isNull())
3562  return {};
3563  Match = ArgType;
3564  }
3565 
3566  return Match;
3567 }
3568 
3569 /// Perform the adjustments to the parameter and argument types
3570 /// described in C++ [temp.deduct.call].
3571 ///
3572 /// \returns true if the caller should not attempt to perform any template
3573 /// argument deduction based on this P/A pair because the argument is an
3574 /// overloaded function set that could not be resolved.
3576  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3577  QualType &ParamType, QualType &ArgType, Expr *Arg, unsigned &TDF) {
3578  // C++0x [temp.deduct.call]p3:
3579  // If P is a cv-qualified type, the top level cv-qualifiers of P's type
3580  // are ignored for type deduction.
3581  if (ParamType.hasQualifiers())
3582  ParamType = ParamType.getUnqualifiedType();
3583 
3584  // [...] If P is a reference type, the type referred to by P is
3585  // used for type deduction.
3586  const ReferenceType *ParamRefType = ParamType->getAs<ReferenceType>();
3587  if (ParamRefType)
3588  ParamType = ParamRefType->getPointeeType();
3589 
3590  // Overload sets usually make this parameter an undeduced context,
3591  // but there are sometimes special circumstances. Typically
3592  // involving a template-id-expr.
3593  if (ArgType == S.Context.OverloadTy) {
3594  ArgType = ResolveOverloadForDeduction(S, TemplateParams,
3595  Arg, ParamType,
3596  ParamRefType != nullptr);
3597  if (ArgType.isNull())
3598  return true;
3599  }
3600 
3601  if (ParamRefType) {
3602  // If the argument has incomplete array type, try to complete its type.
3603  if (ArgType->isIncompleteArrayType()) {
3604  S.completeExprArrayBound(Arg);
3605  ArgType = Arg->getType();
3606  }
3607 
3608  // C++1z [temp.deduct.call]p3:
3609  // If P is a forwarding reference and the argument is an lvalue, the type
3610  // "lvalue reference to A" is used in place of A for type deduction.
3611  if (isForwardingReference(QualType(ParamRefType, 0), FirstInnerIndex) &&
3612  Arg->isLValue())
3613  ArgType = S.Context.getLValueReferenceType(ArgType);
3614  } else {
3615  // C++ [temp.deduct.call]p2:
3616  // If P is not a reference type:
3617  // - If A is an array type, the pointer type produced by the
3618  // array-to-pointer standard conversion (4.2) is used in place of
3619  // A for type deduction; otherwise,
3620  if (ArgType->isArrayType())
3621  ArgType = S.Context.getArrayDecayedType(ArgType);
3622  // - If A is a function type, the pointer type produced by the
3623  // function-to-pointer standard conversion (4.3) is used in place
3624  // of A for type deduction; otherwise,
3625  else if (ArgType->isFunctionType())
3626  ArgType = S.Context.getPointerType(ArgType);
3627  else {
3628  // - If A is a cv-qualified type, the top level cv-qualifiers of A's
3629  // type are ignored for type deduction.
3630  ArgType = ArgType.getUnqualifiedType();
3631  }
3632  }
3633 
3634  // C++0x [temp.deduct.call]p4:
3635  // In general, the deduction process attempts to find template argument
3636  // values that will make the deduced A identical to A (after the type A
3637  // is transformed as described above). [...]
3638  TDF = TDF_SkipNonDependent;
3639 
3640  // - If the original P is a reference type, the deduced A (i.e., the
3641  // type referred to by the reference) can be more cv-qualified than
3642  // the transformed A.
3643  if (ParamRefType)
3645  // - The transformed A can be another pointer or pointer to member
3646  // type that can be converted to the deduced A via a qualification
3647  // conversion (4.4).
3648  if (ArgType->isPointerType() || ArgType->isMemberPointerType() ||
3649  ArgType->isObjCObjectPointerType())
3650  TDF |= TDF_IgnoreQualifiers;
3651  // - If P is a class and P has the form simple-template-id, then the
3652  // transformed A can be a derived class of the deduced A. Likewise,
3653  // if P is a pointer to a class of the form simple-template-id, the
3654  // transformed A can be a pointer to a derived class pointed to by
3655  // the deduced A.
3656  if (isSimpleTemplateIdType(ParamType) ||
3657  (isa<PointerType>(ParamType) &&
3659  ParamType->getAs<PointerType>()->getPointeeType())))
3660  TDF |= TDF_DerivedClass;
3661 
3662  return false;
3663 }
3664 
3665 static bool
3667  QualType T);
3668 
3670  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3671  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
3673  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
3674  bool DecomposedParam, unsigned ArgIdx, unsigned TDF);
3675 
3676 /// Attempt template argument deduction from an initializer list
3677 /// deemed to be an argument in a function call.
3679  Sema &S, TemplateParameterList *TemplateParams, QualType AdjustedParamType,
3680  InitListExpr *ILE, TemplateDeductionInfo &Info,
3682  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs, unsigned ArgIdx,
3683  unsigned TDF) {
3684  // C++ [temp.deduct.call]p1: (CWG 1591)
3685  // If removing references and cv-qualifiers from P gives
3686  // std::initializer_list<P0> or P0[N] for some P0 and N and the argument is
3687  // a non-empty initializer list, then deduction is performed instead for
3688  // each element of the initializer list, taking P0 as a function template
3689  // parameter type and the initializer element as its argument
3690  //
3691  // We've already removed references and cv-qualifiers here.
3692  if (!ILE->getNumInits())
3693  return Sema::TDK_Success;
3694 
3695  QualType ElTy;
3696  auto *ArrTy = S.Context.getAsArrayType(AdjustedParamType);
3697  if (ArrTy)
3698  ElTy = ArrTy->getElementType();
3699  else if (!S.isStdInitializerList(AdjustedParamType, &ElTy)) {
3700  // Otherwise, an initializer list argument causes the parameter to be
3701  // considered a non-deduced context
3702  return Sema::TDK_Success;
3703  }
3704 
3705  // Deduction only needs to be done for dependent types.
3706  if (ElTy->isDependentType()) {
3707  for (Expr *E : ILE->inits()) {
3708  if (auto Result = DeduceTemplateArgumentsFromCallArgument(
3709  S, TemplateParams, 0, ElTy, E, Info, Deduced, OriginalCallArgs, true,
3710  ArgIdx, TDF))
3711  return Result;
3712  }
3713  }
3714 
3715  // in the P0[N] case, if N is a non-type template parameter, N is deduced
3716  // from the length of the initializer list.
3717  if (auto *DependentArrTy = dyn_cast_or_null<DependentSizedArrayType>(ArrTy)) {
3718  // Determine the array bound is something we can deduce.
3719  if (NonTypeTemplateParmDecl *NTTP =
3720  getDeducedParameterFromExpr(Info, DependentArrTy->getSizeExpr())) {
3721  // We can perform template argument deduction for the given non-type
3722  // template parameter.
3723  // C++ [temp.deduct.type]p13:
3724  // The type of N in the type T[N] is std::size_t.
3725  QualType T = S.Context.getSizeType();
3726  llvm::APInt Size(S.Context.getIntWidth(T), ILE->getNumInits());
3727  if (auto Result = DeduceNonTypeTemplateArgument(
3728  S, TemplateParams, NTTP, llvm::APSInt(Size), T,
3729  /*ArrayBound=*/true, Info, Deduced))
3730  return Result;
3731  }
3732  }
3733 
3734  return Sema::TDK_Success;
3735 }
3736 
3737 /// Perform template argument deduction per [temp.deduct.call] for a
3738 /// single parameter / argument pair.
3740  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3741  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
3743  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
3744  bool DecomposedParam, unsigned ArgIdx, unsigned TDF) {
3745  QualType ArgType = Arg->getType();
3746  QualType OrigParamType = ParamType;
3747 
3748  // If P is a reference type [...]
3749  // If P is a cv-qualified type [...]
3751  S, TemplateParams, FirstInnerIndex, ParamType, ArgType, Arg, TDF))
3752  return Sema::TDK_Success;
3753 
3754  // If [...] the argument is a non-empty initializer list [...]
3755  if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg))
3756  return DeduceFromInitializerList(S, TemplateParams, ParamType, ILE, Info,
3757  Deduced, OriginalCallArgs, ArgIdx, TDF);
3758 
3759  // [...] the deduction process attempts to find template argument values
3760  // that will make the deduced A identical to A
3761  //
3762  // Keep track of the argument type and corresponding parameter index,
3763  // so we can check for compatibility between the deduced A and A.
3764  OriginalCallArgs.push_back(
3765  Sema::OriginalCallArg(OrigParamType, DecomposedParam, ArgIdx, ArgType));
3766  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
3767  ArgType, Info, Deduced, TDF);
3768 }
3769 
3770 /// Perform template argument deduction from a function call
3771 /// (C++ [temp.deduct.call]).
3772 ///
3773 /// \param FunctionTemplate the function template for which we are performing
3774 /// template argument deduction.
3775 ///
3776 /// \param ExplicitTemplateArgs the explicit template arguments provided
3777 /// for this call.
3778 ///
3779 /// \param Args the function call arguments
3780 ///
3781 /// \param Specialization if template argument deduction was successful,
3782 /// this will be set to the function template specialization produced by
3783 /// template argument deduction.
3784 ///
3785 /// \param Info the argument will be updated to provide additional information
3786 /// about template argument deduction.
3787 ///
3788 /// \param CheckNonDependent A callback to invoke to check conversions for
3789 /// non-dependent parameters, between deduction and substitution, per DR1391.
3790 /// If this returns true, substitution will be skipped and we return
3791 /// TDK_NonDependentConversionFailure. The callback is passed the parameter
3792 /// types (after substituting explicit template arguments).
3793 ///
3794 /// \returns the result of template argument deduction.
3796  FunctionTemplateDecl *FunctionTemplate,
3797  TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
3798  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
3799  bool PartialOverloading,
3800  llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent) {
3801  if (FunctionTemplate->isInvalidDecl())
3802  return TDK_Invalid;
3803 
3804  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
3805  unsigned NumParams = Function->getNumParams();
3806 
3807  unsigned FirstInnerIndex = getFirstInnerIndex(FunctionTemplate);
3808 
3809  // C++ [temp.deduct.call]p1:
3810  // Template argument deduction is done by comparing each function template
3811  // parameter type (call it P) with the type of the corresponding argument
3812  // of the call (call it A) as described below.
3813  if (Args.size() < Function->getMinRequiredArguments() && !PartialOverloading)
3814  return TDK_TooFewArguments;
3815  else if (TooManyArguments(NumParams, Args.size(), PartialOverloading)) {
3816  const FunctionProtoType *Proto
3817  = Function->getType()->getAs<FunctionProtoType>();
3818  if (Proto->isTemplateVariadic())
3819  /* Do nothing */;
3820  else if (!Proto->isVariadic())
3821  return TDK_TooManyArguments;
3822  }
3823 
3824  // The types of the parameters from which we will perform template argument
3825  // deduction.
3826  LocalInstantiationScope InstScope(*this);
3827  TemplateParameterList *TemplateParams
3828  = FunctionTemplate->getTemplateParameters();
3830  SmallVector<QualType, 8> ParamTypes;
3831  unsigned NumExplicitlySpecified = 0;
3832  if (ExplicitTemplateArgs) {
3833  TemplateDeductionResult Result =
3834  SubstituteExplicitTemplateArguments(FunctionTemplate,
3835  *ExplicitTemplateArgs,
3836  Deduced,
3837  ParamTypes,
3838  nullptr,
3839  Info);
3840  if (Result)
3841  return Result;
3842 
3843  NumExplicitlySpecified = Deduced.size();
3844  } else {
3845  // Just fill in the parameter types from the function declaration.
3846  for (unsigned I = 0; I != NumParams; ++I)
3847  ParamTypes.push_back(Function->getParamDecl(I)->getType());
3848  }
3849 
3850  SmallVector<OriginalCallArg, 8> OriginalCallArgs;
3851 
3852  // Deduce an argument of type ParamType from an expression with index ArgIdx.
3853  auto DeduceCallArgument = [&](QualType ParamType, unsigned ArgIdx) {
3854  // C++ [demp.deduct.call]p1: (DR1391)
3855  // Template argument deduction is done by comparing each function template
3856  // parameter that contains template-parameters that participate in
3857  // template argument deduction ...
3858  if (!hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
3859  return Sema::TDK_Success;
3860 
3861  // ... with the type of the corresponding argument
3863  *this, TemplateParams, FirstInnerIndex, ParamType, Args[ArgIdx], Info, Deduced,
3864  OriginalCallArgs, /*Decomposed*/false, ArgIdx, /*TDF*/ 0);
3865  };
3866 
3867  // Deduce template arguments from the function parameters.
3868  Deduced.resize(TemplateParams->size());
3869  SmallVector<QualType, 8> ParamTypesForArgChecking;
3870  for (unsigned ParamIdx = 0, NumParamTypes = ParamTypes.size(), ArgIdx = 0;
3871  ParamIdx != NumParamTypes; ++ParamIdx) {
3872  QualType ParamType = ParamTypes[ParamIdx];
3873 
3874  const PackExpansionType *ParamExpansion =
3875  dyn_cast<PackExpansionType>(ParamType);
3876  if (!ParamExpansion) {
3877  // Simple case: matching a function parameter to a function argument.
3878  if (ArgIdx >= Args.size())
3879  break;
3880 
3881  ParamTypesForArgChecking.push_back(ParamType);
3882  if (auto Result = DeduceCallArgument(ParamType, ArgIdx++))
3883  return Result;
3884 
3885  continue;
3886  }
3887 
3888  QualType ParamPattern = ParamExpansion->getPattern();
3889  PackDeductionScope PackScope(*this, TemplateParams, Deduced, Info,
3890  ParamPattern);
3891 
3892  // C++0x [temp.deduct.call]p1:
3893  // For a function parameter pack that occurs at the end of the
3894  // parameter-declaration-list, the type A of each remaining argument of
3895  // the call is compared with the type P of the declarator-id of the
3896  // function parameter pack. Each comparison deduces template arguments
3897  // for subsequent positions in the template parameter packs expanded by
3898  // the function parameter pack. When a function parameter pack appears
3899  // in a non-deduced context [not at the end of the list], the type of
3900  // that parameter pack is never deduced.
3901  //
3902  // FIXME: The above rule allows the size of the parameter pack to change
3903  // after we skip it (in the non-deduced case). That makes no sense, so
3904  // we instead notionally deduce the pack against N arguments, where N is
3905  // the length of the explicitly-specified pack if it's expanded by the
3906  // parameter pack and 0 otherwise, and we treat each deduction as a
3907  // non-deduced context.
3908  if (ParamIdx + 1 == NumParamTypes || PackScope.hasFixedArity()) {
3909  for (; ArgIdx < Args.size() && PackScope.hasNextElement();
3910  PackScope.nextPackElement(), ++ArgIdx) {
3911  ParamTypesForArgChecking.push_back(ParamPattern);
3912  if (auto Result = DeduceCallArgument(ParamPattern, ArgIdx))
3913  return Result;
3914  }
3915  } else {
3916  // If the parameter type contains an explicitly-specified pack that we
3917  // could not expand, skip the number of parameters notionally created
3918  // by the expansion.
3919  Optional<unsigned> NumExpansions = ParamExpansion->getNumExpansions();
3920  if (NumExpansions && !PackScope.isPartiallyExpanded()) {
3921  for (unsigned I = 0; I != *NumExpansions && ArgIdx < Args.size();
3922  ++I, ++ArgIdx) {
3923  ParamTypesForArgChecking.push_back(ParamPattern);
3924  // FIXME: Should we add OriginalCallArgs for these? What if the
3925  // corresponding argument is a list?
3926  PackScope.nextPackElement();
3927  }
3928  }
3929  }
3930 
3931  // Build argument packs for each of the parameter packs expanded by this
3932  // pack expansion.
3933  if (auto Result = PackScope.finish())
3934  return Result;
3935  }
3936 
3937  // Capture the context in which the function call is made. This is the context
3938  // that is needed when the accessibility of template arguments is checked.
3939  DeclContext *CallingCtx = CurContext;
3940 
3942  FunctionTemplate, Deduced, NumExplicitlySpecified, Specialization, Info,
3943  &OriginalCallArgs, PartialOverloading, [&, CallingCtx]() {
3944  ContextRAII SavedContext(*this, CallingCtx);
3945  return CheckNonDependent(ParamTypesForArgChecking);
3946  });
3947 }
3948 
3951  bool AdjustExceptionSpec) {
3952  if (ArgFunctionType.isNull())
3953  return ArgFunctionType;
3954 
3955  const FunctionProtoType *FunctionTypeP =
3956  FunctionType->castAs<FunctionProtoType>();
3957  const FunctionProtoType *ArgFunctionTypeP =
3958  ArgFunctionType->getAs<FunctionProtoType>();
3959 
3960  FunctionProtoType::ExtProtoInfo EPI = ArgFunctionTypeP->getExtProtoInfo();
3961  bool Rebuild = false;
3962 
3963  CallingConv CC = FunctionTypeP->getCallConv();
3964  if (EPI.ExtInfo.getCC() != CC) {
3965  EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CC);
3966  Rebuild = true;
3967  }
3968 
3969  bool NoReturn = FunctionTypeP->getNoReturnAttr();
3970  if (EPI.ExtInfo.getNoReturn() != NoReturn) {
3971  EPI.ExtInfo = EPI.ExtInfo.withNoReturn(NoReturn);
3972  Rebuild = true;
3973  }
3974 
3975  if (AdjustExceptionSpec && (FunctionTypeP->hasExceptionSpec() ||
3976  ArgFunctionTypeP->hasExceptionSpec())) {
3977  EPI.ExceptionSpec = FunctionTypeP->getExtProtoInfo().ExceptionSpec;
3978  Rebuild = true;
3979  }
3980 
3981  if (!Rebuild)
3982  return ArgFunctionType;
3983 
3984  return Context.getFunctionType(ArgFunctionTypeP->getReturnType(),
3985  ArgFunctionTypeP->getParamTypes(), EPI);
3986 }
3987 
3988 /// Deduce template arguments when taking the address of a function
3989 /// template (C++ [temp.deduct.funcaddr]) or matching a specialization to
3990 /// a template.
3991 ///
3992 /// \param FunctionTemplate the function template for which we are performing
3993 /// template argument deduction.
3994 ///
3995 /// \param ExplicitTemplateArgs the explicitly-specified template
3996 /// arguments.
3997 ///
3998 /// \param ArgFunctionType the function type that will be used as the
3999 /// "argument" type (A) when performing template argument deduction from the
4000 /// function template's function type. This type may be NULL, if there is no
4001 /// argument type to compare against, in C++0x [temp.arg.explicit]p3.
4002 ///
4003 /// \param Specialization if template argument deduction was successful,
4004 /// this will be set to the function template specialization produced by
4005 /// template argument deduction.
4006 ///
4007 /// \param Info the argument will be updated to provide additional information
4008 /// about template argument deduction.
4009 ///
4010 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4011 /// the address of a function template per [temp.deduct.funcaddr] and
4012 /// [over.over]. If \c false, we are looking up a function template
4013 /// specialization based on its signature, per [temp.deduct.decl].
4014 ///
4015 /// \returns the result of template argument deduction.
4017  FunctionTemplateDecl *FunctionTemplate,
4018  TemplateArgumentListInfo *ExplicitTemplateArgs, QualType ArgFunctionType,
4019  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4020  bool IsAddressOfFunction) {
4021  if (FunctionTemplate->isInvalidDecl())
4022  return TDK_Invalid;
4023 
4024  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
4025  TemplateParameterList *TemplateParams
4026  = FunctionTemplate->getTemplateParameters();
4027  QualType FunctionType = Function->getType();
4028 
4029  // Substitute any explicit template arguments.
4030  LocalInstantiationScope InstScope(*this);
4032  unsigned NumExplicitlySpecified = 0;
4033  SmallVector<QualType, 4> ParamTypes;
4034  if (ExplicitTemplateArgs) {
4035  if (TemplateDeductionResult Result
4036  = SubstituteExplicitTemplateArguments(FunctionTemplate,
4037  *ExplicitTemplateArgs,
4038  Deduced, ParamTypes,
4039  &FunctionType, Info))
4040  return Result;
4041 
4042  NumExplicitlySpecified = Deduced.size();
4043  }
4044 
4045  // When taking the address of a function, we require convertibility of
4046  // the resulting function type. Otherwise, we allow arbitrary mismatches
4047  // of calling convention and noreturn.
4048  if (!IsAddressOfFunction)
4049  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, FunctionType,
4050  /*AdjustExceptionSpec*/false);
4051 
4052  // Unevaluated SFINAE context.
4055  SFINAETrap Trap(*this);
4056 
4057  Deduced.resize(TemplateParams->size());
4058 
4059  // If the function has a deduced return type, substitute it for a dependent
4060  // type so that we treat it as a non-deduced context in what follows. If we
4061  // are looking up by signature, the signature type should also have a deduced
4062  // return type, which we instead expect to exactly match.
4063  bool HasDeducedReturnType = false;
4064  if (getLangOpts().CPlusPlus14 && IsAddressOfFunction &&
4065  Function->getReturnType()->getContainedAutoType()) {
4066  FunctionType = SubstAutoType(FunctionType, Context.DependentTy);
4067  HasDeducedReturnType = true;
4068  }
4069 
4070  if (!ArgFunctionType.isNull()) {
4071  unsigned TDF =
4073  // Deduce template arguments from the function type.
4074  if (TemplateDeductionResult Result
4075  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4076  FunctionType, ArgFunctionType,
4077  Info, Deduced, TDF))
4078  return Result;
4079  }
4080 
4081  if (TemplateDeductionResult Result
4082  = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
4083  NumExplicitlySpecified,
4084  Specialization, Info))
4085  return Result;
4086 
4087  // If the function has a deduced return type, deduce it now, so we can check
4088  // that the deduced function type matches the requested type.
4089  if (HasDeducedReturnType &&
4090  Specialization->getReturnType()->isUndeducedType() &&
4091  DeduceReturnType(Specialization, Info.getLocation(), false))
4092  return TDK_MiscellaneousDeductionFailure;
4093 
4094  // If the function has a dependent exception specification, resolve it now,
4095  // so we can check that the exception specification matches.
4096  auto *SpecializationFPT =
4097  Specialization->getType()->castAs<FunctionProtoType>();
4098  if (getLangOpts().CPlusPlus17 &&
4099  isUnresolvedExceptionSpec(SpecializationFPT->getExceptionSpecType()) &&
4100  !ResolveExceptionSpec(Info.getLocation(), SpecializationFPT))
4101  return TDK_MiscellaneousDeductionFailure;
4102 
4103  // Adjust the exception specification of the argument to match the
4104  // substituted and resolved type we just formed. (Calling convention and
4105  // noreturn can't be dependent, so we don't actually need this for them
4106  // right now.)
4107  QualType SpecializationType = Specialization->getType();
4108  if (!IsAddressOfFunction)
4109  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, SpecializationType,
4110  /*AdjustExceptionSpec*/true);
4111 
4112  // If the requested function type does not match the actual type of the
4113  // specialization with respect to arguments of compatible pointer to function
4114  // types, template argument deduction fails.
4115  if (!ArgFunctionType.isNull()) {
4116  if (IsAddressOfFunction &&
4117  !isSameOrCompatibleFunctionType(
4118  Context.getCanonicalType(SpecializationType),
4119  Context.getCanonicalType(ArgFunctionType)))
4120  return TDK_MiscellaneousDeductionFailure;
4121 
4122  if (!IsAddressOfFunction &&
4123  !Context.hasSameType(SpecializationType, ArgFunctionType))
4124  return TDK_MiscellaneousDeductionFailure;
4125  }
4126 
4127  return TDK_Success;
4128 }
4129 
4130 /// Deduce template arguments for a templated conversion
4131 /// function (C++ [temp.deduct.conv]) and, if successful, produce a
4132 /// conversion function template specialization.
4135  QualType ToType,
4136  CXXConversionDecl *&Specialization,
4137  TemplateDeductionInfo &Info) {
4138  if (ConversionTemplate->isInvalidDecl())
4139  return TDK_Invalid;
4140 
4141  CXXConversionDecl *ConversionGeneric
4142  = cast<CXXConversionDecl>(ConversionTemplate->getTemplatedDecl());
4143 
4144  QualType FromType = ConversionGeneric->getConversionType();
4145 
4146  // Canonicalize the types for deduction.
4147  QualType P = Context.getCanonicalType(FromType);
4148  QualType A = Context.getCanonicalType(ToType);
4149 
4150  // C++0x [temp.deduct.conv]p2:
4151  // If P is a reference type, the type referred to by P is used for
4152  // type deduction.
4153  if (const ReferenceType *PRef = P->getAs<ReferenceType>())
4154  P = PRef->getPointeeType();
4155 
4156  // C++0x [temp.deduct.conv]p4:
4157  // [...] If A is a reference type, the type referred to by A is used
4158  // for type deduction.
4159  if (const ReferenceType *ARef = A->getAs<ReferenceType>()) {
4160  A = ARef->getPointeeType();
4161  // We work around a defect in the standard here: cv-qualifiers are also
4162  // removed from P and A in this case, unless P was a reference type. This
4163  // seems to mostly match what other compilers are doing.
4164  if (!FromType->getAs<ReferenceType>()) {
4165  A = A.getUnqualifiedType();
4166  P = P.getUnqualifiedType();
4167  }
4168 
4169  // C++ [temp.deduct.conv]p3:
4170  //
4171  // If A is not a reference type:
4172  } else {
4173  assert(!A->isReferenceType() && "Reference types were handled above");
4174 
4175  // - If P is an array type, the pointer type produced by the
4176  // array-to-pointer standard conversion (4.2) is used in place
4177  // of P for type deduction; otherwise,
4178  if (P->isArrayType())
4179  P = Context.getArrayDecayedType(P);
4180  // - If P is a function type, the pointer type produced by the
4181  // function-to-pointer standard conversion (4.3) is used in
4182  // place of P for type deduction; otherwise,
4183  else if (P->isFunctionType())
4184  P = Context.getPointerType(P);
4185  // - If P is a cv-qualified type, the top level cv-qualifiers of
4186  // P's type are ignored for type deduction.
4187  else
4188  P = P.getUnqualifiedType();
4189 
4190  // C++0x [temp.deduct.conv]p4:
4191  // If A is a cv-qualified type, the top level cv-qualifiers of A's
4192  // type are ignored for type deduction. If A is a reference type, the type
4193  // referred to by A is used for type deduction.
4194  A = A.getUnqualifiedType();
4195  }
4196 
4197  // Unevaluated SFINAE context.
4200  SFINAETrap Trap(*this);
4201 
4202  // C++ [temp.deduct.conv]p1:
4203  // Template argument deduction is done by comparing the return
4204  // type of the template conversion function (call it P) with the
4205  // type that is required as the result of the conversion (call it
4206  // A) as described in 14.8.2.4.
4207  TemplateParameterList *TemplateParams
4208  = ConversionTemplate->getTemplateParameters();
4210  Deduced.resize(TemplateParams->size());
4211 
4212  // C++0x [temp.deduct.conv]p4:
4213  // In general, the deduction process attempts to find template
4214  // argument values that will make the deduced A identical to
4215  // A. However, there are two cases that allow a difference:
4216  unsigned TDF = 0;
4217  // - If the original A is a reference type, A can be more
4218  // cv-qualified than the deduced A (i.e., the type referred to
4219  // by the reference)
4220  if (ToType->isReferenceType())
4221  TDF |= TDF_ArgWithReferenceType;
4222  // - The deduced A can be another pointer or pointer to member
4223  // type that can be converted to A via a qualification
4224  // conversion.
4225  //
4226  // (C++0x [temp.deduct.conv]p6 clarifies that this only happens when
4227  // both P and A are pointers or member pointers. In this case, we
4228  // just ignore cv-qualifiers completely).
4229  if ((P->isPointerType() && A->isPointerType()) ||
4231  TDF |= TDF_IgnoreQualifiers;
4232  if (TemplateDeductionResult Result
4233  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4234  P, A, Info, Deduced, TDF))
4235  return Result;
4236 
4237  // Create an Instantiation Scope for finalizing the operator.
4238  LocalInstantiationScope InstScope(*this);
4239  // Finish template argument deduction.
4240  FunctionDecl *ConversionSpecialized = nullptr;
4242  = FinishTemplateArgumentDeduction(ConversionTemplate, Deduced, 0,
4243  ConversionSpecialized, Info);
4244  Specialization = cast_or_null<CXXConversionDecl>(ConversionSpecialized);
4245  return Result;
4246 }
4247 
4248 /// Deduce template arguments for a function template when there is
4249 /// nothing to deduce against (C++0x [temp.arg.explicit]p3).
4250 ///
4251 /// \param FunctionTemplate the function template for which we are performing
4252 /// template argument deduction.
4253 ///
4254 /// \param ExplicitTemplateArgs the explicitly-specified template
4255 /// arguments.
4256 ///
4257 /// \param Specialization if template argument deduction was successful,
4258 /// this will be set to the function template specialization produced by
4259 /// template argument deduction.
4260 ///
4261 /// \param Info the argument will be updated to provide additional information
4262 /// about template argument deduction.
4263 ///
4264 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4265 /// the address of a function template in a context where we do not have a
4266 /// target type, per [over.over]. If \c false, we are looking up a function
4267 /// template specialization based on its signature, which only happens when
4268 /// deducing a function parameter type from an argument that is a template-id
4269 /// naming a function template specialization.
4270 ///
4271 /// \returns the result of template argument deduction.
4273  FunctionTemplateDecl *FunctionTemplate,
4274  TemplateArgumentListInfo *ExplicitTemplateArgs,
4275  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4276  bool IsAddressOfFunction) {
4277  return DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs,
4278  QualType(), Specialization, Info,
4279  IsAddressOfFunction);
4280 }
4281 
4282 namespace {
4283 
4284  /// Substitute the 'auto' specifier or deduced template specialization type
4285  /// specifier within a type for a given replacement type.
4286  class SubstituteDeducedTypeTransform :
4287  public TreeTransform<SubstituteDeducedTypeTransform> {
4288  QualType Replacement;
4289  bool UseTypeSugar;
4290 
4291  public:
4292  SubstituteDeducedTypeTransform(Sema &SemaRef, QualType Replacement,
4293  bool UseTypeSugar = true)
4295  Replacement(Replacement), UseTypeSugar(UseTypeSugar) {}
4296 
4297  QualType TransformDesugared(TypeLocBuilder &TLB, DeducedTypeLoc TL) {
4298  assert(isa<TemplateTypeParmType>(Replacement) &&
4299  "unexpected unsugared replacement kind");
4300  QualType Result = Replacement;
4302  NewTL.setNameLoc(TL.getNameLoc());
4303  return Result;
4304  }
4305 
4306  QualType TransformAutoType(TypeLocBuilder &TLB, AutoTypeLoc TL) {
4307  // If we're building the type pattern to deduce against, don't wrap the
4308  // substituted type in an AutoType. Certain template deduction rules
4309  // apply only when a template type parameter appears directly (and not if
4310  // the parameter is found through desugaring). For instance:
4311  // auto &&lref = lvalue;
4312  // must transform into "rvalue reference to T" not "rvalue reference to
4313  // auto type deduced as T" in order for [temp.deduct.call]p3 to apply.
4314  //
4315  // FIXME: Is this still necessary?
4316  if (!UseTypeSugar)
4317  return TransformDesugared(TLB, TL);
4318 
4319  QualType Result = SemaRef.Context.getAutoType(
4320  Replacement, TL.getTypePtr()->getKeyword(), Replacement.isNull());
4321  auto NewTL = TLB.push<AutoTypeLoc>(Result);
4322  NewTL.setNameLoc(TL.getNameLoc());
4323  return Result;
4324  }
4325 
4326  QualType TransformDeducedTemplateSpecializationType(
4328  if (!UseTypeSugar)
4329  return TransformDesugared(TLB, TL);
4330 
4332  TL.getTypePtr()->getTemplateName(),
4333  Replacement, Replacement.isNull());
4334  auto NewTL = TLB.push<DeducedTemplateSpecializationTypeLoc>(Result);
4335  NewTL.setNameLoc(TL.getNameLoc());
4336  return Result;
4337  }
4338 
4339  ExprResult TransformLambdaExpr(LambdaExpr *E) {
4340  // Lambdas never need to be transformed.
4341  return E;
4342  }
4343 
4344  QualType Apply(TypeLoc TL) {
4345  // Create some scratch storage for the transformed type locations.
4346  // FIXME: We're just going to throw this information away. Don't build it.
4347  TypeLocBuilder TLB;
4348  TLB.reserve(TL.getFullDataSize());
4349  return TransformType(TLB, TL);
4350  }
4351  };
4352 
4353 } // namespace
4354 
4357  Optional<unsigned> DependentDeductionDepth) {
4358  return DeduceAutoType(Type->getTypeLoc(), Init, Result,
4359  DependentDeductionDepth);
4360 }
4361 
4362 /// Attempt to produce an informative diagostic explaining why auto deduction
4363 /// failed.
4364 /// \return \c true if diagnosed, \c false if not.
4367  TemplateDeductionInfo &Info,
4368  ArrayRef<SourceRange> Ranges) {
4369  switch (TDK) {
4370  case Sema::TDK_Inconsistent: {
4371  // Inconsistent deduction means we were deducing from an initializer list.
4372  auto D = S.Diag(Info.getLocation(), diag::err_auto_inconsistent_deduction);
4373  D << Info.FirstArg << Info.SecondArg;
4374  for (auto R : Ranges)
4375  D << R;
4376  return true;
4377  }
4378 
4379  // FIXME: Are there other cases for which a custom diagnostic is more useful
4380  // than the basic "types don't match" diagnostic?
4381 
4382  default:
4383  return false;
4384  }
4385 }
4386 
4387 /// Deduce the type for an auto type-specifier (C++11 [dcl.spec.auto]p6)
4388 ///
4389 /// Note that this is done even if the initializer is dependent. (This is
4390 /// necessary to support partial ordering of templates using 'auto'.)
4391 /// A dependent type will be produced when deducing from a dependent type.
4392 ///
4393 /// \param Type the type pattern using the auto type-specifier.
4394 /// \param Init the initializer for the variable whose type is to be deduced.
4395 /// \param Result if type deduction was successful, this will be set to the
4396 /// deduced type.
4397 /// \param DependentDeductionDepth Set if we should permit deduction in
4398 /// dependent cases. This is necessary for template partial ordering with
4399 /// 'auto' template parameters. The value specified is the template
4400 /// parameter depth at which we should perform 'auto' deduction.
4403  Optional<unsigned> DependentDeductionDepth) {
4404  if (Init->getType()->isNonOverloadPlaceholderType()) {
4405  ExprResult NonPlaceholder = CheckPlaceholderExpr(Init);
4406  if (NonPlaceholder.isInvalid())
4407  return DAR_FailedAlreadyDiagnosed;
4408  Init = NonPlaceholder.get();
4409  }
4410 
4411  if (!DependentDeductionDepth &&
4412  (Type.getType()->isDependentType() || Init->isTypeDependent())) {
4413  Result = SubstituteDeducedTypeTransform(*this, QualType()).Apply(Type);
4414  assert(!Result.isNull() && "substituting DependentTy can't fail");
4415  return DAR_Succeeded;
4416  }
4417 
4418  // Find the depth of template parameter to synthesize.
4419  unsigned Depth = DependentDeductionDepth.getValueOr(0);
4420 
4421  // If this is a 'decltype(auto)' specifier, do the decltype dance.
4422  // Since 'decltype(auto)' can only occur at the top of the type, we
4423  // don't need to go digging for it.
4424  if (const AutoType *AT = Type.getType()->getAs<AutoType>()) {
4425  if (AT->isDecltypeAuto()) {
4426  if (isa<InitListExpr>(Init)) {
4427  Diag(Init->getBeginLoc(), diag::err_decltype_auto_initializer_list);
4428  return DAR_FailedAlreadyDiagnosed;
4429  }
4430 
4431  ExprResult ER = CheckPlaceholderExpr(Init);
4432  if (ER.isInvalid())
4433  return DAR_FailedAlreadyDiagnosed;
4434  Init = ER.get();
4435  QualType Deduced = BuildDecltypeType(Init, Init->getBeginLoc(), false);
4436  if (Deduced.isNull())
4437  return DAR_FailedAlreadyDiagnosed;
4438  // FIXME: Support a non-canonical deduced type for 'auto'.
4439  Deduced = Context.getCanonicalType(Deduced);
4440  Result = SubstituteDeducedTypeTransform(*this, Deduced).Apply(Type);
4441  if (Result.isNull())
4442  return DAR_FailedAlreadyDiagnosed;
4443  return DAR_Succeeded;
4444  } else if (!getLangOpts().CPlusPlus) {
4445  if (isa<InitListExpr>(Init)) {
4446  Diag(Init->getBeginLoc(), diag::err_auto_init_list_from_c);
4447  return DAR_FailedAlreadyDiagnosed;
4448  }
4449  }
4450  }
4451 
4452  SourceLocation Loc = Init->getExprLoc();
4453 
4454  LocalInstantiationScope InstScope(*this);
4455 
4456  // Build template<class TemplParam> void Func(FuncParam);
4458  Context, nullptr, SourceLocation(), Loc, Depth, 0, nullptr, false, false);
4459  QualType TemplArg = QualType(TemplParam->getTypeForDecl(), 0);
4460  NamedDecl *TemplParamPtr = TemplParam;
4462  Loc, Loc, TemplParamPtr, Loc, nullptr);
4463 
4464  QualType FuncParam =
4465  SubstituteDeducedTypeTransform(*this, TemplArg, /*UseTypeSugar*/false)
4466  .Apply(Type);
4467  assert(!FuncParam.isNull() &&
4468  "substituting template parameter for 'auto' failed");
4469 
4470  // Deduce type of TemplParam in Func(Init)
4472  Deduced.resize(1);
4473 
4474  TemplateDeductionInfo Info(Loc, Depth);
4475 
4476  // If deduction failed, don't diagnose if the initializer is dependent; it
4477  // might acquire a matching type in the instantiation.
4478  auto DeductionFailed = [&](TemplateDeductionResult TDK,
4480  if (Init->isTypeDependent()) {
4481  Result = SubstituteDeducedTypeTransform(*this, QualType()).Apply(Type);
4482  assert(!Result.isNull() && "substituting DependentTy can't fail");
4483  return DAR_Succeeded;
4484  }
4485  if (diagnoseAutoDeductionFailure(*this, TDK, Info, Ranges))
4486  return DAR_FailedAlreadyDiagnosed;
4487  return DAR_Failed;
4488  };
4489 
4490  SmallVector<OriginalCallArg, 4> OriginalCallArgs;
4491 
4492  InitListExpr *InitList = dyn_cast<InitListExpr>(Init);
4493  if (InitList) {
4494  // Notionally, we substitute std::initializer_list<T> for 'auto' and deduce
4495  // against that. Such deduction only succeeds if removing cv-qualifiers and
4496  // references results in std::initializer_list<T>.
4497  if (!Type.getType().getNonReferenceType()->getAs<AutoType>())
4498  return DAR_Failed;
4499 
4500  SourceRange DeducedFromInitRange;
4501  for (unsigned i = 0, e = InitList->getNumInits(); i < e; ++i) {
4502  Expr *Init = InitList->getInit(i);
4503 
4505  *this, TemplateParamsSt.get(), 0, TemplArg, Init,
4506  Info, Deduced, OriginalCallArgs, /*Decomposed*/ true,
4507  /*ArgIdx*/ 0, /*TDF*/ 0))
4508  return DeductionFailed(TDK, {DeducedFromInitRange,
4509  Init->getSourceRange()});
4510 
4511  if (DeducedFromInitRange.isInvalid() &&
4512  Deduced[0].getKind() != TemplateArgument::Null)
4513  DeducedFromInitRange = Init->getSourceRange();
4514  }
4515  } else {
4516  if (!getLangOpts().CPlusPlus && Init->refersToBitField()) {
4517  Diag(Loc, diag::err_auto_bitfield);
4518  return DAR_FailedAlreadyDiagnosed;
4519  }
4520 
4522  *this, TemplateParamsSt.get(), 0, FuncParam, Init, Info, Deduced,
4523  OriginalCallArgs, /*Decomposed*/ false, /*ArgIdx*/ 0, /*TDF*/ 0))
4524  return DeductionFailed(TDK, {});
4525  }
4526 
4527  // Could be null if somehow 'auto' appears in a non-deduced context.
4528  if (Deduced[0].getKind() != TemplateArgument::Type)
4529  return DeductionFailed(TDK_Incomplete, {});
4530 
4531  QualType DeducedType = Deduced[0].getAsType();
4532 
4533  if (InitList) {
4534  DeducedType = BuildStdInitializerList(DeducedType, Loc);
4535  if (DeducedType.isNull())
4536  return DAR_FailedAlreadyDiagnosed;
4537  }
4538 
4539  Result = SubstituteDeducedTypeTransform(*this, DeducedType).Apply(Type);
4540  if (Result.isNull())
4541  return DAR_FailedAlreadyDiagnosed;
4542 
4543  // Check that the deduced argument type is compatible with the original
4544  // argument type per C++ [temp.deduct.call]p4.
4545  QualType DeducedA = InitList ? Deduced[0].getAsType() : Result;
4546  for (const OriginalCallArg &OriginalArg : OriginalCallArgs) {
4547  assert((bool)InitList == OriginalArg.DecomposedParam &&
4548  "decomposed non-init-list in auto deduction?");
4549  if (auto TDK =
4550  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA)) {
4551  Result = QualType();
4552  return DeductionFailed(TDK, {});
4553  }
4554  }
4555 
4556  return DAR_Succeeded;
4557 }
4558 
4560  QualType TypeToReplaceAuto) {
4561  if (TypeToReplaceAuto->isDependentType())
4562  TypeToReplaceAuto = QualType();
4563  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4564  .TransformType(TypeWithAuto);
4565 }
4566 
4568  QualType TypeToReplaceAuto) {
4569  if (TypeToReplaceAuto->isDependentType())
4570  TypeToReplaceAuto = QualType();
4571  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4572  .TransformType(TypeWithAuto);
4573 }
4574 
4576  QualType TypeToReplaceAuto) {
4577  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
4578  /*UseTypeSugar*/ false)
4579  .TransformType(TypeWithAuto);
4580 }
4581 
4583  if (isa<InitListExpr>(Init))
4584  Diag(VDecl->getLocation(),
4585  VDecl->isInitCapture()
4586  ? diag::err_init_capture_deduction_failure_from_init_list
4587  : diag::err_auto_var_deduction_failure_from_init_list)
4588  << VDecl->getDeclName() << VDecl->getType() << Init->getSourceRange();
4589  else
4590  Diag(VDecl->getLocation(),
4591  VDecl->isInitCapture() ? diag::err_init_capture_deduction_failure
4592  : diag::err_auto_var_deduction_failure)
4593  << VDecl->getDeclName() << VDecl->getType() << Init->getType()
4594  << Init->getSourceRange();
4595 }
4596 
4598  bool Diagnose) {
4599  assert(FD->getReturnType()->isUndeducedType());
4600 
4601  // For a lambda's conversion operator, deduce any 'auto' or 'decltype(auto)'
4602  // within the return type from the call operator's type.
4603  if (isLambdaConversionOperator(FD)) {
4604  CXXRecordDecl *Lambda = cast<CXXMethodDecl>(FD)->getParent();
4605  FunctionDecl *CallOp = Lambda->getLambdaCallOperator();
4606 
4607  // For a generic lambda, instantiate the call operator if needed.
4608  if (auto *Args = FD->getTemplateSpecializationArgs()) {
4609  CallOp = InstantiateFunctionDeclaration(
4610  CallOp->getDescribedFunctionTemplate(), Args, Loc);
4611  if (!CallOp || CallOp->isInvalidDecl())
4612  return true;
4613 
4614  // We might need to deduce the return type by instantiating the definition
4615  // of the operator() function.
4616  if (CallOp->getReturnType()->isUndeducedType())
4617  InstantiateFunctionDefinition(Loc, CallOp);
4618  }
4619 
4620  if (CallOp->isInvalidDecl())
4621  return true;
4622  assert(!CallOp->getReturnType()->isUndeducedType() &&
4623  "failed to deduce lambda return type");
4624 
4625  // Build the new return type from scratch.
4626  QualType RetType = getLambdaConversionFunctionResultType(
4627  CallOp->getType()->castAs<FunctionProtoType>());
4628  if (FD->getReturnType()->getAs<PointerType>())
4629  RetType = Context.getPointerType(RetType);
4630  else {
4631  assert(FD->getReturnType()->getAs<BlockPointerType>());
4632  RetType = Context.getBlockPointerType(RetType);
4633  }
4634  Context.adjustDeducedFunctionResultType(FD, RetType);
4635  return false;
4636  }
4637 
4639  InstantiateFunctionDefinition(Loc, FD);
4640 
4641  bool StillUndeduced = FD->getReturnType()->isUndeducedType();
4642  if (StillUndeduced && Diagnose && !FD->isInvalidDecl()) {
4643  Diag(Loc, diag::err_auto_fn_used_before_defined) << FD;
4644  Diag(FD->getLocation(), diag::note_callee_decl) << FD;
4645  }
4646 
4647  return StillUndeduced;
4648 }
4649 
4650 /// If this is a non-static member function,
4651 static void
4653  CXXMethodDecl *Method,
4654  SmallVectorImpl<QualType> &ArgTypes) {
4655  // C++11 [temp.func.order]p3:
4656  // [...] The new parameter is of type "reference to cv A," where cv are
4657  // the cv-qualifiers of the function template (if any) and A is
4658  // the class of which the function template is a member.
4659  //
4660  // The standard doesn't say explicitly, but we pick the appropriate kind of
4661  // reference type based on [over.match.funcs]p4.
4662  QualType ArgTy = Context.getTypeDeclType(Method->getParent());
4663  ArgTy = Context.getQualifiedType(ArgTy, Method->getMethodQualifiers());
4664  if (Method->getRefQualifier() == RQ_RValue)
4665  ArgTy = Context.getRValueReferenceType(ArgTy);
4666  else
4667  ArgTy = Context.getLValueReferenceType(ArgTy);
4668  ArgTypes.push_back(ArgTy);
4669 }
4670 
4671 /// Determine whether the function template \p FT1 is at least as
4672 /// specialized as \p FT2.
4674  SourceLocation Loc,
4675  FunctionTemplateDecl *FT1,
4676  FunctionTemplateDecl *FT2,
4678  unsigned NumCallArguments1) {
4679  FunctionDecl *FD1 = FT1->getTemplatedDecl();
4680  FunctionDecl *FD2 = FT2->getTemplatedDecl();
4681  const FunctionProtoType *Proto1 = FD1->getType()->getAs<FunctionProtoType>();
4682  const FunctionProtoType *Proto2 = FD2->getType()->getAs<FunctionProtoType>();
4683 
4684  assert(Proto1 && Proto2 && "Function templates must have prototypes");
4685  TemplateParameterList *TemplateParams = FT2->getTemplateParameters();
4687  Deduced.resize(TemplateParams->size());
4688 
4689  // C++0x [temp.deduct.partial]p3:
4690  // The types used to determine the ordering depend on the context in which
4691  // the partial ordering is done:
4692  TemplateDeductionInfo Info(Loc);
4694  switch (TPOC) {
4695  case TPOC_Call: {
4696  // - In the context of a function call, the function parameter types are
4697  // used.
4698  CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
4699  CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
4700 
4701  // C++11 [temp.func.order]p3:
4702  // [...] If only one of the function templates is a non-static
4703  // member, that function template is considered to have a new
4704  // first parameter inserted in its function parameter list. The
4705  // new parameter is of type "reference to cv A," where cv are
4706  // the cv-qualifiers of the function template (if any) and A is
4707  // the class of which the function template is a member.
4708  //
4709  // Note that we interpret this to mean "if one of the function
4710  // templates is a non-static member and the other is a non-member";
4711  // otherwise, the ordering rules for static functions against non-static
4712  // functions don't make any sense.
4713  //
4714  // C++98/03 doesn't have this provision but we've extended DR532 to cover
4715  // it as wording was broken prior to it.
4717 
4718  unsigned NumComparedArguments = NumCallArguments1;
4719 
4720  if (!Method2 && Method1 && !Method1->isStatic()) {
4721  // Compare 'this' from Method1 against first parameter from Method2.
4722  AddImplicitObjectParameterType(S.Context, Method1, Args1);
4723  ++NumComparedArguments;
4724  } else if (!Method1 && Method2 && !Method2->isStatic()) {
4725  // Compare 'this' from Method2 against first parameter from Method1.
4726  AddImplicitObjectParameterType(S.Context, Method2, Args2);
4727  }
4728 
4729  Args1.insert(Args1.end(), Proto1->param_type_begin(),
4730  Proto1->param_type_end());
4731  Args2.insert(Args2.end(), Proto2->param_type_begin(),
4732  Proto2->param_type_end());
4733 
4734  // C++ [temp.func.order]p5:
4735  // The presence of unused ellipsis and default arguments has no effect on
4736  // the partial ordering of function templates.
4737  if (Args1.size() > NumComparedArguments)
4738  Args1.resize(NumComparedArguments);
4739  if (Args2.size() > NumComparedArguments)
4740  Args2.resize(NumComparedArguments);
4741  if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
4742  Args1.data(), Args1.size(), Info, Deduced,
4743  TDF_None, /*PartialOrdering=*/true))
4744  return false;
4745 
4746  break;
4747  }
4748 
4749  case TPOC_Conversion:
4750  // - In the context of a call to a conversion operator, the return types
4751  // of the conversion function templates are used.
4753  S, TemplateParams, Proto2->getReturnType(), Proto1->getReturnType(),
4754  Info, Deduced, TDF_None,
4755  /*PartialOrdering=*/true))
4756  return false;
4757  break;
4758 
4759  case TPOC_Other:
4760  // - In other contexts (14.6.6.2) the function template's function type
4761  // is used.
4762  if (DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
4763  FD2->getType(), FD1->getType(),
4764  Info, Deduced, TDF_None,
4765  /*PartialOrdering=*/true))
4766  return false;
4767  break;
4768  }
4769 
4770  // C++0x [temp.deduct.partial]p11:
4771  // In most cases, all template parameters must have values in order for
4772  // deduction to succeed, but for partial ordering purposes a template
4773  // parameter may remain without a value provided it is not used in the
4774  // types being used for partial ordering. [ Note: a template parameter used
4775  // in a non-deduced context is considered used. -end note]
4776  unsigned ArgIdx = 0, NumArgs = Deduced.size();
4777  for (; ArgIdx != NumArgs; ++ArgIdx)
4778  if (Deduced[ArgIdx].isNull())
4779  break;
4780 
4781  // FIXME: We fail to implement [temp.deduct.type]p1 along this path. We need
4782  // to substitute the deduced arguments back into the template and check that
4783  // we get the right type.
4784 
4785  if (ArgIdx == NumArgs) {
4786  // All template arguments were deduced. FT1 is at least as specialized
4787  // as FT2.
4788  return true;
4789  }
4790 
4791  // Figure out which template parameters were used.
4792  llvm::SmallBitVector UsedParameters(TemplateParams->size());
4793  switch (TPOC) {
4794  case TPOC_Call:
4795  for (unsigned I = 0, N = Args2.size(); I != N; ++I)
4796  ::MarkUsedTemplateParameters(S.Context, Args2[I], false,
4797  TemplateParams->getDepth(),
4798  UsedParameters);
4799  break;
4800 
4801  case TPOC_Conversion:
4802  ::MarkUsedTemplateParameters(S.Context, Proto2->getReturnType(), false,
4803  TemplateParams->getDepth(), UsedParameters);
4804  break;
4805 
4806  case TPOC_Other:
4807  ::MarkUsedTemplateParameters(S.Context, FD2->getType(), false,
4808  TemplateParams->getDepth(),
4809  UsedParameters);
4810  break;
4811  }
4812 
4813  for (; ArgIdx != NumArgs; ++ArgIdx)
4814  // If this argument had no value deduced but was used in one of the types
4815  // used for partial ordering, then deduction fails.
4816  if (Deduced[ArgIdx].isNull() && UsedParameters[ArgIdx])
4817  return false;
4818 
4819  return true;
4820 }
4821 
4822 /// Determine whether this a function template whose parameter-type-list
4823 /// ends with a function parameter pack.
4825  FunctionDecl *Function = FunTmpl->getTemplatedDecl();
4826  unsigned NumParams = Function->getNumParams();
4827  if (NumParams == 0)
4828  return false;
4829 
4830  ParmVarDecl *Last = Function->getParamDecl(NumParams - 1);
4831  if (!Last->isParameterPack())
4832  return false;
4833 
4834  // Make sure that no previous parameter is a parameter pack.
4835  while (--NumParams > 0) {
4836  if (Function->getParamDecl(NumParams - 1)->isParameterPack())
4837  return false;
4838  }
4839 
4840  return true;
4841 }
4842 
4843 /// Returns the more specialized function template according
4844 /// to the rules of function template partial ordering (C++ [temp.func.order]).
4845 ///
4846 /// \param FT1 the first function template
4847 ///
4848 /// \param FT2 the second function template
4849 ///
4850 /// \param TPOC the context in which we are performing partial ordering of
4851 /// function templates.
4852 ///
4853 /// \param NumCallArguments1 The number of arguments in the call to FT1, used
4854 /// only when \c TPOC is \c TPOC_Call.
4855 ///
4856 /// \param NumCallArguments2 The number of arguments in the call to FT2, used
4857 /// only when \c TPOC is \c TPOC_Call.
4858 ///
4859 /// \returns the more specialized function template. If neither
4860 /// template is more specialized, returns NULL.
4863  FunctionTemplateDecl *FT2,
4864  SourceLocation Loc,
4866  unsigned NumCallArguments1,
4867  unsigned NumCallArguments2) {
4868  bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
4869  NumCallArguments1);
4870  bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
4871  NumCallArguments2);
4872 
4873  if (Better1 != Better2) // We have a clear winner
4874  return Better1 ? FT1 : FT2;
4875 
4876  if (!Better1 && !Better2) // Neither is better than the other
4877  return nullptr;
4878 
4879  // FIXME: This mimics what GCC implements, but doesn't match up with the
4880  // proposed resolution for core issue 692. This area needs to be sorted out,
4881  // but for now we attempt to maintain compatibility.
4882  bool Variadic1 = isVariadicFunctionTemplate(FT1);
4883  bool Variadic2 = isVariadicFunctionTemplate(FT2);
4884  if (Variadic1 != Variadic2)
4885  return Variadic1? FT2 : FT1;
4886 
4887  return nullptr;
4888 }
4889 
4890 /// Determine if the two templates are equivalent.
4892  if (T1 == T2)
4893  return true;
4894 
4895  if (!T1 || !T2)
4896  return false;
4897 
4898  return T1->getCanonicalDecl() == T2->getCanonicalDecl();
4899 }
4900 
4901 /// Retrieve the most specialized of the given function template
4902 /// specializations.
4903 ///
4904 /// \param SpecBegin the start iterator of the function template
4905 /// specializations that we will be comparing.
4906 ///
4907 /// \param SpecEnd the end iterator of the function template
4908 /// specializations, paired with \p SpecBegin.
4909 ///
4910 /// \param Loc the location where the ambiguity or no-specializations
4911 /// diagnostic should occur.
4912 ///
4913 /// \param NoneDiag partial diagnostic used to diagnose cases where there are
4914 /// no matching candidates.
4915 ///
4916 /// \param AmbigDiag partial diagnostic used to diagnose an ambiguity, if one
4917 /// occurs.
4918 ///
4919 /// \param CandidateDiag partial diagnostic used for each function template
4920 /// specialization that is a candidate in the ambiguous ordering. One parameter
4921 /// in this diagnostic should be unbound, which will correspond to the string
4922 /// describing the template arguments for the function template specialization.
4923 ///
4924 /// \returns the most specialized function template specialization, if
4925 /// found. Otherwise, returns SpecEnd.
4927  UnresolvedSetIterator SpecBegin, UnresolvedSetIterator SpecEnd,
4928  TemplateSpecCandidateSet &FailedCandidates,
4929  SourceLocation Loc, const PartialDiagnostic &NoneDiag,
4930  const PartialDiagnostic &AmbigDiag, const PartialDiagnostic &CandidateDiag,
4931  bool Complain, QualType TargetType) {
4932  if (SpecBegin == SpecEnd) {
4933  if (Complain) {
4934  Diag(Loc, NoneDiag);
4935  FailedCandidates.NoteCandidates(*this, Loc);
4936  }
4937  return SpecEnd;
4938  }
4939 
4940  if (SpecBegin + 1 == SpecEnd)
4941  return SpecBegin;
4942 
4943  // Find the function template that is better than all of the templates it
4944  // has been compared to.
4945  UnresolvedSetIterator Best = SpecBegin;
4946  FunctionTemplateDecl *BestTemplate
4947  = cast<FunctionDecl>(*Best)->getPrimaryTemplate();
4948  assert(BestTemplate && "Not a function template specialization?");
4949  for (UnresolvedSetIterator I = SpecBegin + 1; I != SpecEnd; ++I) {
4950  FunctionTemplateDecl *Challenger
4951  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
4952  assert(Challenger && "Not a function template specialization?");
4953  if (isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
4954  Loc, TPOC_Other, 0, 0),
4955  Challenger)) {
4956  Best = I;
4957  BestTemplate = Challenger;
4958  }
4959  }
4960 
4961  // Make sure that the "best" function template is more specialized than all
4962  // of the others.
4963  bool Ambiguous = false;
4964  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
4965  FunctionTemplateDecl *Challenger
4966  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
4967  if (I != Best &&
4968  !isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
4969  Loc, TPOC_Other, 0, 0),
4970  BestTemplate)) {
4971  Ambiguous = true;
4972  break;
4973  }
4974  }
4975 
4976  if (!Ambiguous) {
4977  // We found an answer. Return it.
4978  return Best;
4979  }
4980 
4981  // Diagnose the ambiguity.
4982  if (Complain) {
4983  Diag(Loc, AmbigDiag);
4984 
4985  // FIXME: Can we order the candidates in some sane way?
4986  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
4987  PartialDiagnostic PD = CandidateDiag;
4988  const auto *FD = cast<FunctionDecl>(*I);
4989  PD << FD << getTemplateArgumentBindingsText(
4990  FD->getPrimaryTemplate()->getTemplateParameters(),
4991  *FD->getTemplateSpecializationArgs());
4992  if (!TargetType.isNull())
4993  HandleFunctionTypeMismatch(PD, FD->getType(), TargetType);
4994  Diag((*I)->getLocation(), PD);
4995  }
4996  }
4997 
4998  return SpecEnd;
4999 }
5000 
5001 /// Determine whether one partial specialization, P1, is at least as
5002 /// specialized than another, P2.
5003 ///
5004 /// \tparam TemplateLikeDecl The kind of P2, which must be a
5005 /// TemplateDecl or {Class,Var}TemplatePartialSpecializationDecl.
5006 /// \param T1 The injected-class-name of P1 (faked for a variable template).
5007 /// \param T2 The injected-class-name of P2 (faked for a variable template).
5008 template<typename TemplateLikeDecl>
5010  TemplateLikeDecl *P2,
5011  TemplateDeductionInfo &Info) {
5012  // C++ [temp.class.order]p1:
5013  // For two class template partial specializations, the first is at least as
5014  // specialized as the second if, given the following rewrite to two
5015  // function templates, the first function template is at least as
5016  // specialized as the second according to the ordering rules for function
5017  // templates (14.6.6.2):
5018  // - the first function template has the same template parameters as the
5019  // first partial specialization and has a single function parameter
5020  // whose type is a class template specialization with the template
5021  // arguments of the first partial specialization, and
5022  // - the second function template has the same template parameters as the
5023  // second partial specialization and has a single function parameter
5024  // whose type is a class template specialization with the template
5025  // arguments of the second partial specialization.
5026  //
5027  // Rather than synthesize function templates, we merely perform the
5028  // equivalent partial ordering by performing deduction directly on
5029  // the template arguments of the class template partial
5030  // specializations. This computation is slightly simpler than the
5031  // general problem of function template partial ordering, because
5032  // class template partial specializations are more constrained. We
5033  // know that every template parameter is deducible from the class
5034  // template partial specialization's template arguments, for
5035  // example.
5037 
5038  // Determine whether P1 is at least as specialized as P2.
5039  Deduced.resize(P2->getTemplateParameters()->size());
5040  if (DeduceTemplateArgumentsByTypeMatch(S, P2->getTemplateParameters(),
5041  T2, T1, Info, Deduced, TDF_None,
5042  /*PartialOrdering=*/true))
5043  return false;
5044 
5045  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(),
5046  Deduced.end());
5047  Sema::InstantiatingTemplate Inst(S, Info.getLocation(), P2, DeducedArgs,
5048  Info);
5049  auto *TST1 = T1->castAs<TemplateSpecializationType>();
5051  S, P2, /*PartialOrdering=*/true,
5053  TST1->template_arguments()),
5054  Deduced, Info))
5055  return false;
5056 
5057  return true;
5058 }
5059 
5060 /// Returns the more specialized class template partial specialization
5061 /// according to the rules of partial ordering of class template partial
5062 /// specializations (C++ [temp.class.order]).
5063 ///
5064 /// \param PS1 the first class template partial specialization
5065 ///
5066 /// \param PS2 the second class template partial specialization
5067 ///
5068 /// \returns the more specialized class template partial specialization. If
5069 /// neither partial specialization is more specialized, returns NULL.
5074  SourceLocation Loc) {
5077 
5078  TemplateDeductionInfo Info(Loc);
5079  bool Better1 = isAtLeastAsSpecializedAs(*this, PT1, PT2, PS2, Info);
5080  bool Better2 = isAtLeastAsSpecializedAs(*this, PT2, PT1, PS1, Info);
5081 
5082  if (Better1 == Better2)
5083  return nullptr;
5084 
5085  return Better1 ? PS1 : PS2;
5086 }
5087 
5090  ClassTemplateDecl *Primary = Spec->getSpecializedTemplate();
5091  QualType PrimaryT = Primary->getInjectedClassNameSpecialization();
5092  QualType PartialT = Spec->getInjectedSpecializationType();
5093  if (!isAtLeastAsSpecializedAs(*this, PartialT, PrimaryT, Primary, Info))
5094  return false;
5095  if (isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info)) {
5096  Info.clearSFINAEDiagnostic();
5097  return false;
5098  }
5099  return true;
5100 }
5101 
5106  // Pretend the variable template specializations are class template
5107  // specializations and form a fake injected class name type for comparison.
5108  assert(PS1->getSpecializedTemplate() == PS2->getSpecializedTemplate() &&
5109  "the partial specializations being compared should specialize"
5110  " the same template.");
5111  TemplateName Name(PS1->getSpecializedTemplate());
5112  TemplateName CanonTemplate = Context.getCanonicalTemplateName(Name);
5114  CanonTemplate, PS1->getTemplateArgs().asArray());
5116  CanonTemplate, PS2->getTemplateArgs().asArray());
5117 
5118  TemplateDeductionInfo Info(Loc);
5119  bool Better1 = isAtLeastAsSpecializedAs(*this, PT1, PT2, PS2, Info);
5120  bool Better2 = isAtLeastAsSpecializedAs(*this, PT2, PT1, PS1, Info);
5121 
5122  if (Better1 == Better2)
5123  return nullptr;
5124 
5125  return Better1 ? PS1 : PS2;
5126 }
5127 
5130  TemplateDecl *Primary = Spec->getSpecializedTemplate();
5131  // FIXME: Cache the injected template arguments rather than recomputing
5132  // them for each partial specialization.
5135  PrimaryArgs);
5136 
5137  TemplateName CanonTemplate =
5138  Context.getCanonicalTemplateName(TemplateName(Primary));
5139  QualType PrimaryT = Context.getTemplateSpecializationType(
5140  CanonTemplate, PrimaryArgs);
5141  QualType PartialT = Context.getTemplateSpecializationType(
5142  CanonTemplate, Spec->getTemplateArgs().asArray());
5143  if (!isAtLeastAsSpecializedAs(*this, PartialT, PrimaryT, Primary, Info))
5144  return false;
5145  if (isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info)) {
5146  Info.clearSFINAEDiagnostic();
5147  return false;
5148  }
5149  return true;
5150 }
5151 
5154  // C++1z [temp.arg.template]p4: (DR 150)
5155  // A template template-parameter P is at least as specialized as a
5156  // template template-argument A if, given the following rewrite to two
5157  // function templates...
5158 
5159  // Rather than synthesize function templates, we merely perform the
5160  // equivalent partial ordering by performing deduction directly on
5161  // the template parameter lists of the template template parameters.
5162  //
5163  // Given an invented class template X with the template parameter list of
5164  // A (including default arguments):
5167 
5168  // - Each function template has a single function parameter whose type is
5169  // a specialization of X with template arguments corresponding to the
5170  // template parameters from the respective function template
5172  Context.getInjectedTemplateArgs(A, AArgs);
5173 
5174  // Check P's arguments against A's parameter list. This will fill in default
5175  // template arguments as needed. AArgs are already correct by construction.
5176  // We can't just use CheckTemplateIdType because that will expand alias
5177  // templates.
5179  {
5180  SFINAETrap Trap(*this);
5181 
5182  Context.getInjectedTemplateArgs(P, PArgs);
5183  TemplateArgumentListInfo PArgList(P->getLAngleLoc(), P->getRAngleLoc());
5184  for (unsigned I = 0, N = P->size(); I != N; ++I) {
5185  // Unwrap packs that getInjectedTemplateArgs wrapped around pack
5186  // expansions, to form an "as written" argument list.
5187  TemplateArgument Arg = PArgs[I];
5188  if (Arg.getKind() == TemplateArgument::Pack) {
5189  assert(Arg.pack_size() == 1 && Arg.pack_begin()->isPackExpansion());
5190  Arg = *Arg.pack_begin();
5191  }
5192  PArgList.addArgument(getTrivialTemplateArgumentLoc(
5193  Arg, QualType(), P->getParam(I)->getLocation()));
5194  }
5195  PArgs.clear();
5196 
5197  // C++1z [temp.arg.template]p3:
5198  // If the rewrite produces an invalid type, then P is not at least as
5199  // specialized as A.
5200  if (CheckTemplateArgumentList(AArg, Loc, PArgList, false, PArgs) ||
5201  Trap.hasErrorOccurred())
5202  return false;
5203  }
5204 
5205  QualType AType = Context.getTemplateSpecializationType(X, AArgs);
5206  QualType PType = Context.getTemplateSpecializationType(X, PArgs);
5207 
5208  // ... the function template corresponding to P is at least as specialized
5209  // as the function template corresponding to A according to the partial
5210  // ordering rules for function templates.
5211  TemplateDeductionInfo Info(Loc, A->getDepth());
5212  return isAtLeastAsSpecializedAs(*this, PType, AType, AArg, Info);
5213 }
5214 
5215 /// Mark the template parameters that are used by the given
5216 /// expression.
5217 static void
5219  const Expr *E,
5220  bool OnlyDeduced,
5221  unsigned Depth,
5222  llvm::SmallBitVector &Used) {
5223  // We can deduce from a pack expansion.
5224  if (const PackExpansionExpr *Expansion = dyn_cast<PackExpansionExpr>(E))
5225  E = Expansion->getPattern();
5226 
5227  // Skip through any implicit casts we added while type-checking, and any
5228  // substitutions performed by template alias expansion.
5229  while (true) {
5230  if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E))
5231  E = ICE->getSubExpr();
5232  else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(E))
5233  E = CE->getSubExpr();
5234  else if (const SubstNonTypeTemplateParmExpr *Subst =
5235  dyn_cast<SubstNonTypeTemplateParmExpr>(E))
5236  E = Subst->getReplacement();
5237  else
5238  break;
5239  }
5240 
5241  // FIXME: if !OnlyDeduced, we have to walk the whole subexpression to
5242  // find other occurrences of template parameters.
5243  const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E);
5244  if (!DRE)
5245  return;
5246 
5247  const NonTypeTemplateParmDecl *NTTP
5248  = dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl());
5249  if (!NTTP)
5250  return;
5251 
5252  if (NTTP->getDepth() == Depth)
5253  Used[NTTP->getIndex()] = true;
5254 
5255  // In C++17 mode, additional arguments may be deduced from the type of a
5256  // non-type argument.
5257  if (Ctx.getLangOpts().CPlusPlus17)
5258  MarkUsedTemplateParameters(Ctx, NTTP->getType(), OnlyDeduced, Depth, Used);
5259 }
5260 
5261 /// Mark the template parameters that are used by the given
5262 /// nested name specifier.
5263 static void
5265  NestedNameSpecifier *NNS,
5266  bool OnlyDeduced,
5267  unsigned Depth,
5268  llvm::SmallBitVector &Used) {
5269  if (!NNS)
5270  return;
5271 
5272  MarkUsedTemplateParameters(Ctx, NNS->getPrefix(), OnlyDeduced, Depth,
5273  Used);
5275  OnlyDeduced, Depth, Used);
5276 }
5277 
5278 /// Mark the template parameters that are used by the given
5279 /// template name.
5280 static void
5282  TemplateName Name,
5283  bool OnlyDeduced,
5284  unsigned Depth,
5285  llvm::SmallBitVector &Used) {
5286  if (TemplateDecl *Template = Name.getAsTemplateDecl()) {
5287  if (TemplateTemplateParmDecl *TTP
5288  = dyn_cast<TemplateTemplateParmDecl>(Template)) {
5289  if (TTP->getDepth() == Depth)
5290  Used[TTP->getIndex()] = true;
5291  }
5292  return;
5293  }
5294 
5296  MarkUsedTemplateParameters(Ctx, QTN->getQualifier(), OnlyDeduced,
5297  Depth, Used);
5299  MarkUsedTemplateParameters(Ctx, DTN->getQualifier(), OnlyDeduced,
5300  Depth, Used);
5301 }
5302 
5303 /// Mark the template parameters that are used by the given
5304 /// type.
5305 static void
5307  bool OnlyDeduced,
5308  unsigned Depth,
5309  llvm::SmallBitVector &Used) {
5310  if (T.isNull())
5311  return;
5312 
5313  // Non-dependent types have nothing deducible
5314  if (!T->isDependentType())
5315  return;
5316 
5317  T = Ctx.getCanonicalType(T);
5318  switch (T->getTypeClass()) {
5319  case Type::Pointer:
5321  cast<PointerType>(T)->getPointeeType(),
5322  OnlyDeduced,
5323  Depth,
5324  Used);
5325  break;
5326 
5327  case Type::BlockPointer:
5329  cast<BlockPointerType>(T)->getPointeeType(),
5330  OnlyDeduced,
5331  Depth,
5332  Used);
5333  break;
5334 
5335  case Type::LValueReference:
5336  case Type::RValueReference:
5338  cast<ReferenceType>(T)->getPointeeType(),
5339  OnlyDeduced,
5340  Depth,
5341  Used);
5342  break;
5343 
5344  case Type::MemberPointer: {
5345  const MemberPointerType *MemPtr = cast<MemberPointerType>(T.getTypePtr());
5346  MarkUsedTemplateParameters(Ctx, MemPtr->getPointeeType(), OnlyDeduced,
5347  Depth, Used);
5348  MarkUsedTemplateParameters(Ctx, QualType(MemPtr->getClass(), 0),
5349  OnlyDeduced, Depth, Used);
5350  break;
5351  }
5352 
5353  case Type::DependentSizedArray:
5355  cast<DependentSizedArrayType>(T)->getSizeExpr(),
5356  OnlyDeduced, Depth, Used);
5357  // Fall through to check the element type
5358  LLVM_FALLTHROUGH;
5359 
5360  case Type::ConstantArray:
5361  case Type::IncompleteArray:
5363  cast<ArrayType>(T)->getElementType(),
5364  OnlyDeduced, Depth, Used);
5365  break;
5366 
5367  case Type::Vector:
5368  case Type::ExtVector:
5370  cast<VectorType>(T)->getElementType(),
5371  OnlyDeduced, Depth, Used);
5372  break;
5373 
5374  case Type::DependentVector: {
5375  const auto *VecType = cast<DependentVectorType>(T);
5376  MarkUsedTemplateParameters(Ctx, VecType->getElementType(), OnlyDeduced,
5377  Depth, Used);
5378  MarkUsedTemplateParameters(Ctx, VecType->getSizeExpr(), OnlyDeduced, Depth,
5379  Used);
5380  break;
5381  }
5382  case Type::DependentSizedExtVector: {
5383  const DependentSizedExtVectorType *VecType
5384  = cast<DependentSizedExtVectorType>(T);
5385  MarkUsedTemplateParameters(Ctx, VecType->getElementType(), OnlyDeduced,
5386  Depth, Used);
5387  MarkUsedTemplateParameters(Ctx, VecType->getSizeExpr(), OnlyDeduced,
5388  Depth, Used);
5389  break;
5390  }
5391 
5392  case Type::DependentAddressSpace: {
5393  const DependentAddressSpaceType *DependentASType =
5394  cast<DependentAddressSpaceType>(T);
5395  MarkUsedTemplateParameters(Ctx, DependentASType->getPointeeType(),
5396  OnlyDeduced, Depth, Used);
5398  DependentASType->getAddrSpaceExpr(),
5399  OnlyDeduced, Depth, Used);
5400  break;
5401  }
5402 
5403  case Type::FunctionProto: {
5404  const FunctionProtoType *Proto = cast<FunctionProtoType>(T);
5405  MarkUsedTemplateParameters(Ctx, Proto->getReturnType(), OnlyDeduced, Depth,
5406  Used);
5407  for (unsigned I = 0, N = Proto->getNumParams(); I != N; ++I) {
5408  // C++17 [temp.deduct.type]p5:
5409  // The non-deduced contexts are: [...]
5410  // -- A function parameter pack that does not occur at the end of the
5411  // parameter-declaration-list.
5412  if (!OnlyDeduced || I + 1 == N ||
5413  !Proto->getParamType(I)->getAs<PackExpansionType>()) {
5414  MarkUsedTemplateParameters(Ctx, Proto->getParamType(I), OnlyDeduced,
5415  Depth, Used);
5416  } else {
5417  // FIXME: C++17 [temp.deduct.call]p1:
5418  // When a function parameter pack appears in a non-deduced context,
5419  // the type of that pack is never deduced.
5420  //
5421  // We should also track a set of "never deduced" parameters, and
5422  // subtract that from the list of deduced parameters after marking.
5423  }
5424  }
5425  if (auto *E = Proto->getNoexceptExpr())
5426  MarkUsedTemplateParameters(Ctx, E, OnlyDeduced, Depth, Used);
5427  break;
5428  }
5429 
5430  case Type::TemplateTypeParm: {
5431  const TemplateTypeParmType *TTP = cast<TemplateTypeParmType>(T);
5432  if (TTP->getDepth() == Depth)
5433  Used[TTP->getIndex()] = true;
5434  break;
5435  }
5436 
5437  case Type::SubstTemplateTypeParmPack: {
5438  const SubstTemplateTypeParmPackType *Subst
5439  = cast<SubstTemplateTypeParmPackType>(T);
5441  QualType(Subst->getReplacedParameter(), 0),
5442  OnlyDeduced, Depth, Used);
5444  OnlyDeduced, Depth, Used);
5445  break;
5446  }
5447 
5448  case Type::InjectedClassName:
5449  T = cast<InjectedClassNameType>(T)->getInjectedSpecializationType();
5450  LLVM_FALLTHROUGH;
5451 
5452  case Type::TemplateSpecialization: {
5453  const TemplateSpecializationType *Spec
5454  = cast<TemplateSpecializationType>(T);
5455  MarkUsedTemplateParameters(Ctx, Spec->getTemplateName(), OnlyDeduced,
5456  Depth, Used);
5457 
5458  // C++0x [temp.deduct.type]p9:
5459  // If the template argument list of P contains a pack expansion that is
5460  // not the last template argument, the entire template argument list is a
5461  // non-deduced context.
5462  if (OnlyDeduced &&
5464  break;
5465 
5466  for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
5467  MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
5468  Used);
5469  break;
5470  }
5471 
5472  case Type::Complex:
5473  if (!OnlyDeduced)
5475  cast<ComplexType>(T)->getElementType(),
5476  OnlyDeduced, Depth, Used);
5477  break;
5478 
5479  case Type::Atomic:
5480  if (!OnlyDeduced)
5482  cast<AtomicType>(T)->getValueType(),
5483  OnlyDeduced, Depth, Used);
5484  break;
5485 
5486  case Type::DependentName:
5487  if (!OnlyDeduced)
5489  cast<DependentNameType>(T)->getQualifier(),
5490  OnlyDeduced, Depth, Used);
5491  break;
5492 
5493  case Type::DependentTemplateSpecialization: {
5494  // C++14 [temp.deduct.type]p5:
5495  // The non-deduced contexts are:
5496  // -- The nested-name-specifier of a type that was specified using a
5497  // qualified-id
5498  //
5499  // C++14 [temp.deduct.type]p6:
5500  // When a type name is specified in a way that includes a non-deduced
5501  // context, all of the types that comprise that type name are also
5502  // non-deduced.
5503  if (OnlyDeduced)
5504  break;
5505 
5507  = cast<DependentTemplateSpecializationType>(T);
5508 
5510  OnlyDeduced, Depth, Used);
5511 
5512  for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
5513  MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
5514  Used);
5515  break;
5516  }
5517 
5518  case Type::TypeOf:
5519  if (!OnlyDeduced)
5521  cast<TypeOfType>(T)->getUnderlyingType(),
5522  OnlyDeduced, Depth, Used);
5523  break;
5524 
5525  case Type::TypeOfExpr:
5526  if (!OnlyDeduced)
5528  cast<TypeOfExprType>(T)->getUnderlyingExpr(),
5529  OnlyDeduced, Depth, Used);
5530  break;
5531 
5532  case Type::Decltype:
5533  if (!OnlyDeduced)
5535  cast<DecltypeType>(T)->getUnderlyingExpr(),
5536  OnlyDeduced, Depth, Used);
5537  break;
5538 
5539  case Type::UnaryTransform:
5540  if (!OnlyDeduced)
5542  cast<UnaryTransformType>(T)->getUnderlyingType(),
5543  OnlyDeduced, Depth, Used);
5544  break;
5545