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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"
28 #include "clang/AST/TemplateBase.h"
29 #include "clang/AST/TemplateName.h"
30 #include "clang/AST/Type.h"
31 #include "clang/AST/TypeLoc.h"
35 #include "clang/Basic/LLVM.h"
39 #include "clang/Basic/Specifiers.h"
40 #include "clang/Sema/Ownership.h"
41 #include "clang/Sema/Sema.h"
42 #include "clang/Sema/Template.h"
43 #include "llvm/ADT/APInt.h"
44 #include "llvm/ADT/APSInt.h"
45 #include "llvm/ADT/ArrayRef.h"
46 #include "llvm/ADT/DenseMap.h"
47 #include "llvm/ADT/FoldingSet.h"
48 #include "llvm/ADT/Optional.h"
49 #include "llvm/ADT/SmallBitVector.h"
50 #include "llvm/ADT/SmallPtrSet.h"
51 #include "llvm/ADT/SmallVector.h"
52 #include "llvm/Support/Casting.h"
53 #include "llvm/Support/Compiler.h"
54 #include "llvm/Support/ErrorHandling.h"
55 #include <algorithm>
56 #include <cassert>
57 #include <tuple>
58 #include <utility>
59 
60 namespace clang {
61 
62  /// Various flags that control template argument deduction.
63  ///
64  /// These flags can be bitwise-OR'd together.
66  /// No template argument deduction flags, which indicates the
67  /// strictest results for template argument deduction (as used for, e.g.,
68  /// matching class template partial specializations).
69  TDF_None = 0,
70 
71  /// Within template argument deduction from a function call, we are
72  /// matching with a parameter type for which the original parameter was
73  /// a reference.
75 
76  /// Within template argument deduction from a function call, we
77  /// are matching in a case where we ignore cv-qualifiers.
79 
80  /// Within template argument deduction from a function call,
81  /// we are matching in a case where we can perform template argument
82  /// deduction from a template-id of a derived class of the argument type.
84 
85  /// Allow non-dependent types to differ, e.g., when performing
86  /// template argument deduction from a function call where conversions
87  /// may apply.
89 
90  /// Whether we are performing template argument deduction for
91  /// parameters and arguments in a top-level template argument
93 
94  /// Within template argument deduction from overload resolution per
95  /// C++ [over.over] allow matching function types that are compatible in
96  /// terms of noreturn and default calling convention adjustments, or
97  /// similarly matching a declared template specialization against a
98  /// possible template, per C++ [temp.deduct.decl]. In either case, permit
99  /// deduction where the parameter is a function type that can be converted
100  /// to the argument type.
102 
103  /// Within template argument deduction for a conversion function, we are
104  /// matching with an argument type for which the original argument was
105  /// a reference.
107  };
108 }
109 
110 using namespace clang;
111 using namespace sema;
112 
113 /// Compare two APSInts, extending and switching the sign as
114 /// necessary to compare their values regardless of underlying type.
116  if (Y.getBitWidth() > X.getBitWidth())
117  X = X.extend(Y.getBitWidth());
118  else if (Y.getBitWidth() < X.getBitWidth())
119  Y = Y.extend(X.getBitWidth());
120 
121  // If there is a signedness mismatch, correct it.
122  if (X.isSigned() != Y.isSigned()) {
123  // If the signed value is negative, then the values cannot be the same.
124  if ((Y.isSigned() && Y.isNegative()) || (X.isSigned() && X.isNegative()))
125  return false;
126 
127  Y.setIsSigned(true);
128  X.setIsSigned(true);
129  }
130 
131  return X == Y;
132 }
133 
136  TemplateParameterList *TemplateParams,
137  const TemplateArgument &Param,
138  TemplateArgument Arg,
139  TemplateDeductionInfo &Info,
140  SmallVectorImpl<DeducedTemplateArgument> &Deduced);
141 
144  TemplateParameterList *TemplateParams,
145  QualType Param,
146  QualType Arg,
147  TemplateDeductionInfo &Info,
148  SmallVectorImpl<DeducedTemplateArgument> &
149  Deduced,
150  unsigned TDF,
151  bool PartialOrdering = false,
152  bool DeducedFromArrayBound = false);
153 
156  ArrayRef<TemplateArgument> Params,
157  ArrayRef<TemplateArgument> Args,
158  TemplateDeductionInfo &Info,
159  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
160  bool NumberOfArgumentsMustMatch);
161 
162 static void MarkUsedTemplateParameters(ASTContext &Ctx,
164  bool OnlyDeduced, unsigned Depth,
165  llvm::SmallBitVector &Used);
166 
168  bool OnlyDeduced, unsigned Level,
169  llvm::SmallBitVector &Deduced);
170 
171 /// If the given expression is of a form that permits the deduction
172 /// of a non-type template parameter, return the declaration of that
173 /// non-type template parameter.
174 static const NonTypeTemplateParmDecl *
176  // If we are within an alias template, the expression may have undergone
177  // any number of parameter substitutions already.
178  while (true) {
179  if (const auto *IC = dyn_cast<ImplicitCastExpr>(E))
180  E = IC->getSubExpr();
181  else if (const auto *CE = dyn_cast<ConstantExpr>(E))
182  E = CE->getSubExpr();
183  else if (const auto *Subst = dyn_cast<SubstNonTypeTemplateParmExpr>(E))
184  E = Subst->getReplacement();
185  else if (const auto *CCE = dyn_cast<CXXConstructExpr>(E)) {
186  // Look through implicit copy construction from an lvalue of the same type.
187  if (CCE->getParenOrBraceRange().isValid())
188  break;
189  // Note, there could be default arguments.
190  assert(CCE->getNumArgs() >= 1 && "implicit construct expr should have 1 arg");
191  E = CCE->getArg(0);
192  } else
193  break;
194  }
195 
196  if (const auto *DRE = dyn_cast<DeclRefExpr>(E))
197  if (const auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl()))
198  if (NTTP->getDepth() == Depth)
199  return NTTP;
200 
201  return nullptr;
202 }
203 
204 static const NonTypeTemplateParmDecl *
207 }
208 
209 /// Determine whether two declaration pointers refer to the same
210 /// declaration.
211 static bool isSameDeclaration(Decl *X, Decl *Y) {
212  if (NamedDecl *NX = dyn_cast<NamedDecl>(X))
213  X = NX->getUnderlyingDecl();
214  if (NamedDecl *NY = dyn_cast<NamedDecl>(Y))
215  Y = NY->getUnderlyingDecl();
216 
217  return X->getCanonicalDecl() == Y->getCanonicalDecl();
218 }
219 
220 /// Verify that the given, deduced template arguments are compatible.
221 ///
222 /// \returns The deduced template argument, or a NULL template argument if
223 /// the deduced template arguments were incompatible.
226  const DeducedTemplateArgument &X,
227  const DeducedTemplateArgument &Y) {
228  // We have no deduction for one or both of the arguments; they're compatible.
229  if (X.isNull())
230  return Y;
231  if (Y.isNull())
232  return X;
233 
234  // If we have two non-type template argument values deduced for the same
235  // parameter, they must both match the type of the parameter, and thus must
236  // match each other's type. As we're only keeping one of them, we must check
237  // for that now. The exception is that if either was deduced from an array
238  // bound, the type is permitted to differ.
241  if (!XType.isNull()) {
243  if (YType.isNull() || !Context.hasSameType(XType, YType))
244  return DeducedTemplateArgument();
245  }
246  }
247 
248  switch (X.getKind()) {
250  llvm_unreachable("Non-deduced template arguments handled above");
251 
253  // If two template type arguments have the same type, they're compatible.
254  if (Y.getKind() == TemplateArgument::Type &&
255  Context.hasSameType(X.getAsType(), Y.getAsType()))
256  return X;
257 
258  // If one of the two arguments was deduced from an array bound, the other
259  // supersedes it.
261  return X.wasDeducedFromArrayBound() ? Y : X;
262 
263  // The arguments are not compatible.
264  return DeducedTemplateArgument();
265 
267  // If we deduced a constant in one case and either a dependent expression or
268  // declaration in another case, keep the integral constant.
269  // If both are integral constants with the same value, keep that value.
274  return X.wasDeducedFromArrayBound() ? Y : X;
275 
276  // All other combinations are incompatible.
277  return DeducedTemplateArgument();
278 
280  if (Y.getKind() == TemplateArgument::Template &&
282  return X;
283 
284  // All other combinations are incompatible.
285  return DeducedTemplateArgument();
286 
291  return X;
292 
293  // All other combinations are incompatible.
294  return DeducedTemplateArgument();
295 
298  return checkDeducedTemplateArguments(Context, Y, X);
299 
300  // Compare the expressions for equality
301  llvm::FoldingSetNodeID ID1, ID2;
302  X.getAsExpr()->Profile(ID1, Context, true);
303  Y.getAsExpr()->Profile(ID2, Context, true);
304  if (ID1 == ID2)
305  return X.wasDeducedFromArrayBound() ? Y : X;
306 
307  // Differing dependent expressions are incompatible.
308  return DeducedTemplateArgument();
309  }
310 
312  assert(!X.wasDeducedFromArrayBound());
313 
314  // If we deduced a declaration and a dependent expression, keep the
315  // declaration.
317  return X;
318 
319  // If we deduced a declaration and an integral constant, keep the
320  // integral constant and whichever type did not come from an array
321  // bound.
322  if (Y.getKind() == TemplateArgument::Integral) {
323  if (Y.wasDeducedFromArrayBound())
324  return TemplateArgument(Context, Y.getAsIntegral(),
325  X.getParamTypeForDecl());
326  return Y;
327  }
328 
329  // If we deduced two declarations, make sure that they refer to the
330  // same declaration.
333  return X;
334 
335  // All other combinations are incompatible.
336  return DeducedTemplateArgument();
337 
339  // If we deduced a null pointer and a dependent expression, keep the
340  // null pointer.
342  return X;
343 
344  // If we deduced a null pointer and an integral constant, keep the
345  // integral constant.
347  return Y;
348 
349  // If we deduced two null pointers, they are the same.
351  return X;
352 
353  // All other combinations are incompatible.
354  return DeducedTemplateArgument();
355 
356  case TemplateArgument::Pack: {
357  if (Y.getKind() != TemplateArgument::Pack ||
358  X.pack_size() != Y.pack_size())
359  return DeducedTemplateArgument();
360 
363  XAEnd = X.pack_end(),
364  YA = Y.pack_begin();
365  XA != XAEnd; ++XA, ++YA) {
369  if (Merged.isNull() && !(XA->isNull() && YA->isNull()))
370  return DeducedTemplateArgument();
371  NewPack.push_back(Merged);
372  }
373 
375  TemplateArgument::CreatePackCopy(Context, NewPack),
377  }
378  }
379 
380  llvm_unreachable("Invalid TemplateArgument Kind!");
381 }
382 
383 /// Deduce the value of the given non-type template parameter
384 /// as the given deduced template argument. All non-type template parameter
385 /// deduction is funneled through here.
387  Sema &S, TemplateParameterList *TemplateParams,
388  const NonTypeTemplateParmDecl *NTTP, const DeducedTemplateArgument &NewDeduced,
389  QualType ValueType, TemplateDeductionInfo &Info,
390  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
391  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
392  "deducing non-type template argument with wrong depth");
393 
395  S.Context, Deduced[NTTP->getIndex()], NewDeduced);
396  if (Result.isNull()) {
397  Info.Param = const_cast<NonTypeTemplateParmDecl*>(NTTP);
398  Info.FirstArg = Deduced[NTTP->getIndex()];
399  Info.SecondArg = NewDeduced;
400  return Sema::TDK_Inconsistent;
401  }
402 
403  Deduced[NTTP->getIndex()] = Result;
404  if (!S.getLangOpts().CPlusPlus17)
405  return Sema::TDK_Success;
406 
407  if (NTTP->isExpandedParameterPack())
408  // FIXME: We may still need to deduce parts of the type here! But we
409  // don't have any way to find which slice of the type to use, and the
410  // type stored on the NTTP itself is nonsense. Perhaps the type of an
411  // expanded NTTP should be a pack expansion type?
412  return Sema::TDK_Success;
413 
414  // Get the type of the parameter for deduction. If it's a (dependent) array
415  // or function type, we will not have decayed it yet, so do that now.
416  QualType ParamType = S.Context.getAdjustedParameterType(NTTP->getType());
417  if (auto *Expansion = dyn_cast<PackExpansionType>(ParamType))
418  ParamType = Expansion->getPattern();
419 
420  // FIXME: It's not clear how deduction of a parameter of reference
421  // type from an argument (of non-reference type) should be performed.
422  // For now, we just remove reference types from both sides and let
423  // the final check for matching types sort out the mess.
424  ValueType = ValueType.getNonReferenceType();
425  if (ParamType->isReferenceType())
426  ParamType = ParamType.getNonReferenceType();
427  else
428  // Top-level cv-qualifiers are irrelevant for a non-reference type.
429  ValueType = ValueType.getUnqualifiedType();
430 
432  S, TemplateParams, ParamType, ValueType, Info, Deduced,
433  TDF_SkipNonDependent, /*PartialOrdering=*/false,
434  /*ArrayBound=*/NewDeduced.wasDeducedFromArrayBound());
435 }
436 
437 /// Deduce the value of the given non-type template parameter
438 /// from the given integral constant.
440  Sema &S, TemplateParameterList *TemplateParams,
441  const NonTypeTemplateParmDecl *NTTP, const llvm::APSInt &Value,
442  QualType ValueType, bool DeducedFromArrayBound, TemplateDeductionInfo &Info,
443  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
445  S, TemplateParams, NTTP,
446  DeducedTemplateArgument(S.Context, Value, ValueType,
447  DeducedFromArrayBound),
448  ValueType, Info, Deduced);
449 }
450 
451 /// Deduce the value of the given non-type template parameter
452 /// from the given null pointer template argument type.
454  Sema &S, TemplateParameterList *TemplateParams,
455  const NonTypeTemplateParmDecl *NTTP, QualType NullPtrType,
456  TemplateDeductionInfo &Info,
457  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
458  Expr *Value =
460  S.Context.NullPtrTy, NTTP->getLocation()),
461  NullPtrType, CK_NullToPointer)
462  .get();
463  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
465  Value->getType(), Info, Deduced);
466 }
467 
468 /// Deduce the value of the given non-type template parameter
469 /// from the given type- or value-dependent expression.
470 ///
471 /// \returns true if deduction succeeded, false otherwise.
473  Sema &S, TemplateParameterList *TemplateParams,
475  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
476  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
478  Value->getType(), Info, Deduced);
479 }
480 
481 /// Deduce the value of the given non-type template parameter
482 /// from the given declaration.
483 ///
484 /// \returns true if deduction succeeded, false otherwise.
486  Sema &S, TemplateParameterList *TemplateParams,
487  const NonTypeTemplateParmDecl *NTTP, ValueDecl *D, QualType T,
488  TemplateDeductionInfo &Info,
489  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
490  D = D ? cast<ValueDecl>(D->getCanonicalDecl()) : nullptr;
491  TemplateArgument New(D, T);
493  S, TemplateParams, NTTP, DeducedTemplateArgument(New), T, Info, Deduced);
494 }
495 
498  TemplateParameterList *TemplateParams,
499  TemplateName Param,
500  TemplateName Arg,
501  TemplateDeductionInfo &Info,
502  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
503  TemplateDecl *ParamDecl = Param.getAsTemplateDecl();
504  if (!ParamDecl) {
505  // The parameter type is dependent and is not a template template parameter,
506  // so there is nothing that we can deduce.
507  return Sema::TDK_Success;
508  }
509 
510  if (TemplateTemplateParmDecl *TempParam
511  = dyn_cast<TemplateTemplateParmDecl>(ParamDecl)) {
512  // If we're not deducing at this depth, there's nothing to deduce.
513  if (TempParam->getDepth() != Info.getDeducedDepth())
514  return Sema::TDK_Success;
515 
518  Deduced[TempParam->getIndex()],
519  NewDeduced);
520  if (Result.isNull()) {
521  Info.Param = TempParam;
522  Info.FirstArg = Deduced[TempParam->getIndex()];
523  Info.SecondArg = NewDeduced;
524  return Sema::TDK_Inconsistent;
525  }
526 
527  Deduced[TempParam->getIndex()] = Result;
528  return Sema::TDK_Success;
529  }
530 
531  // Verify that the two template names are equivalent.
532  if (S.Context.hasSameTemplateName(Param, Arg))
533  return Sema::TDK_Success;
534 
535  // Mismatch of non-dependent template parameter to argument.
536  Info.FirstArg = TemplateArgument(Param);
537  Info.SecondArg = TemplateArgument(Arg);
539 }
540 
541 /// Deduce the template arguments by comparing the template parameter
542 /// type (which is a template-id) with the template argument type.
543 ///
544 /// \param S the Sema
545 ///
546 /// \param TemplateParams the template parameters that we are deducing
547 ///
548 /// \param Param the parameter type
549 ///
550 /// \param Arg the argument type
551 ///
552 /// \param Info information about the template argument deduction itself
553 ///
554 /// \param Deduced the deduced template arguments
555 ///
556 /// \returns the result of template argument deduction so far. Note that a
557 /// "success" result means that template argument deduction has not yet failed,
558 /// but it may still fail, later, for other reasons.
561  TemplateParameterList *TemplateParams,
562  const TemplateSpecializationType *Param,
563  QualType Arg,
564  TemplateDeductionInfo &Info,
565  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
566  assert(Arg.isCanonical() && "Argument type must be canonical");
567 
568  // Treat an injected-class-name as its underlying template-id.
569  if (auto *Injected = dyn_cast<InjectedClassNameType>(Arg))
570  Arg = Injected->getInjectedSpecializationType();
571 
572  // Check whether the template argument is a dependent template-id.
573  if (const TemplateSpecializationType *SpecArg
574  = dyn_cast<TemplateSpecializationType>(Arg)) {
575  // Perform template argument deduction for the template name.
577  = DeduceTemplateArguments(S, TemplateParams,
578  Param->getTemplateName(),
579  SpecArg->getTemplateName(),
580  Info, Deduced))
581  return Result;
582 
583 
584  // Perform template argument deduction on each template
585  // argument. Ignore any missing/extra arguments, since they could be
586  // filled in by default arguments.
587  return DeduceTemplateArguments(S, TemplateParams,
588  Param->template_arguments(),
589  SpecArg->template_arguments(), Info, Deduced,
590  /*NumberOfArgumentsMustMatch=*/false);
591  }
592 
593  // If the argument type is a class template specialization, we
594  // perform template argument deduction using its template
595  // arguments.
596  const RecordType *RecordArg = dyn_cast<RecordType>(Arg);
597  if (!RecordArg) {
598  Info.FirstArg = TemplateArgument(QualType(Param, 0));
599  Info.SecondArg = TemplateArgument(Arg);
601  }
602 
604  = dyn_cast<ClassTemplateSpecializationDecl>(RecordArg->getDecl());
605  if (!SpecArg) {
606  Info.FirstArg = TemplateArgument(QualType(Param, 0));
607  Info.SecondArg = TemplateArgument(Arg);
609  }
610 
611  // Perform template argument deduction for the template name.
614  TemplateParams,
615  Param->getTemplateName(),
617  Info, Deduced))
618  return Result;
619 
620  // Perform template argument deduction for the template arguments.
621  return DeduceTemplateArguments(S, TemplateParams, Param->template_arguments(),
622  SpecArg->getTemplateArgs().asArray(), Info,
623  Deduced, /*NumberOfArgumentsMustMatch=*/true);
624 }
625 
626 /// Determines whether the given type is an opaque type that
627 /// might be more qualified when instantiated.
629  switch (T->getTypeClass()) {
630  case Type::TypeOfExpr:
631  case Type::TypeOf:
632  case Type::DependentName:
633  case Type::Decltype:
634  case Type::UnresolvedUsing:
635  case Type::TemplateTypeParm:
636  return true;
637 
638  case Type::ConstantArray:
639  case Type::IncompleteArray:
640  case Type::VariableArray:
641  case Type::DependentSizedArray:
643  cast<ArrayType>(T)->getElementType());
644 
645  default:
646  return false;
647  }
648 }
649 
650 /// Helper function to build a TemplateParameter when we don't
651 /// know its type statically.
653  if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(D))
654  return TemplateParameter(TTP);
655  if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D))
656  return TemplateParameter(NTTP);
657 
658  return TemplateParameter(cast<TemplateTemplateParmDecl>(D));
659 }
660 
661 /// If \p Param is an expanded parameter pack, get the number of expansions.
663  if (auto *TTP = dyn_cast<TemplateTypeParmDecl>(Param))
664  if (TTP->isExpandedParameterPack())
665  return TTP->getNumExpansionParameters();
666 
667  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param))
668  if (NTTP->isExpandedParameterPack())
669  return NTTP->getNumExpansionTypes();
670 
671  if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(Param))
672  if (TTP->isExpandedParameterPack())
673  return TTP->getNumExpansionTemplateParameters();
674 
675  return None;
676 }
677 
678 /// A pack that we're currently deducing.
680  // The index of the pack.
681  unsigned Index;
682 
683  // The old value of the pack before we started deducing it.
685 
686  // A deferred value of this pack from an inner deduction, that couldn't be
687  // deduced because this deduction hadn't happened yet.
689 
690  // The new value of the pack.
692 
693  // The outer deduction for this pack, if any.
694  DeducedPack *Outer = nullptr;
695 
696  DeducedPack(unsigned Index) : Index(Index) {}
697 };
698 
699 namespace {
700 
701 /// A scope in which we're performing pack deduction.
702 class PackDeductionScope {
703 public:
704  /// Prepare to deduce the packs named within Pattern.
705  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
708  : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
709  unsigned NumNamedPacks = addPacks(Pattern);
710  finishConstruction(NumNamedPacks);
711  }
712 
713  /// Prepare to directly deduce arguments of the parameter with index \p Index.
714  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
716  TemplateDeductionInfo &Info, unsigned Index)
717  : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
718  addPack(Index);
719  finishConstruction(1);
720  }
721 
722 private:
723  void addPack(unsigned Index) {
724  // Save the deduced template argument for the parameter pack expanded
725  // by this pack expansion, then clear out the deduction.
726  DeducedPack Pack(Index);
727  Pack.Saved = Deduced[Index];
728  Deduced[Index] = TemplateArgument();
729 
730  // FIXME: What if we encounter multiple packs with different numbers of
731  // pre-expanded expansions? (This should already have been diagnosed
732  // during substitution.)
733  if (Optional<unsigned> ExpandedPackExpansions =
734  getExpandedPackSize(TemplateParams->getParam(Index)))
735  FixedNumExpansions = ExpandedPackExpansions;
736 
737  Packs.push_back(Pack);
738  }
739 
740  unsigned addPacks(TemplateArgument Pattern) {
741  // Compute the set of template parameter indices that correspond to
742  // parameter packs expanded by the pack expansion.
743  llvm::SmallBitVector SawIndices(TemplateParams->size());
745 
746  auto AddPack = [&](unsigned Index) {
747  if (SawIndices[Index])
748  return;
749  SawIndices[Index] = true;
750  addPack(Index);
751 
752  // Deducing a parameter pack that is a pack expansion also constrains the
753  // packs appearing in that parameter to have the same deduced arity. Also,
754  // in C++17 onwards, deducing a non-type template parameter deduces its
755  // type, so we need to collect the pending deduced values for those packs.
756  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(
757  TemplateParams->getParam(Index))) {
758  if (!NTTP->isExpandedParameterPack())
759  if (auto *Expansion = dyn_cast<PackExpansionType>(NTTP->getType()))
760  ExtraDeductions.push_back(Expansion->getPattern());
761  }
762  // FIXME: Also collect the unexpanded packs in any type and template
763  // parameter packs that are pack expansions.
764  };
765 
766  auto Collect = [&](TemplateArgument Pattern) {
768  S.collectUnexpandedParameterPacks(Pattern, Unexpanded);
769  for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
770  unsigned Depth, Index;
771  std::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]);
772  if (Depth == Info.getDeducedDepth())
773  AddPack(Index);
774  }
775  };
776 
777  // Look for unexpanded packs in the pattern.
778  Collect(Pattern);
779  assert(!Packs.empty() && "Pack expansion without unexpanded packs?");
780 
781  unsigned NumNamedPacks = Packs.size();
782 
783  // Also look for unexpanded packs that are indirectly deduced by deducing
784  // the sizes of the packs in this pattern.
785  while (!ExtraDeductions.empty())
786  Collect(ExtraDeductions.pop_back_val());
787 
788  return NumNamedPacks;
789  }
790 
791  void finishConstruction(unsigned NumNamedPacks) {
792  // Dig out the partially-substituted pack, if there is one.
793  const TemplateArgument *PartialPackArgs = nullptr;
794  unsigned NumPartialPackArgs = 0;
795  std::pair<unsigned, unsigned> PartialPackDepthIndex(-1u, -1u);
796  if (auto *Scope = S.CurrentInstantiationScope)
797  if (auto *Partial = Scope->getPartiallySubstitutedPack(
798  &PartialPackArgs, &NumPartialPackArgs))
799  PartialPackDepthIndex = getDepthAndIndex(Partial);
800 
801  // This pack expansion will have been partially or fully expanded if
802  // it only names explicitly-specified parameter packs (including the
803  // partially-substituted one, if any).
804  bool IsExpanded = true;
805  for (unsigned I = 0; I != NumNamedPacks; ++I) {
806  if (Packs[I].Index >= Info.getNumExplicitArgs()) {
807  IsExpanded = false;
808  IsPartiallyExpanded = false;
809  break;
810  }
811  if (PartialPackDepthIndex ==
812  std::make_pair(Info.getDeducedDepth(), Packs[I].Index)) {
813  IsPartiallyExpanded = true;
814  }
815  }
816 
817  // Skip over the pack elements that were expanded into separate arguments.
818  // If we partially expanded, this is the number of partial arguments.
819  if (IsPartiallyExpanded)
820  PackElements += NumPartialPackArgs;
821  else if (IsExpanded)
822  PackElements += *FixedNumExpansions;
823 
824  for (auto &Pack : Packs) {
825  if (Info.PendingDeducedPacks.size() > Pack.Index)
826  Pack.Outer = Info.PendingDeducedPacks[Pack.Index];
827  else
828  Info.PendingDeducedPacks.resize(Pack.Index + 1);
829  Info.PendingDeducedPacks[Pack.Index] = &Pack;
830 
831  if (PartialPackDepthIndex ==
832  std::make_pair(Info.getDeducedDepth(), Pack.Index)) {
833  Pack.New.append(PartialPackArgs, PartialPackArgs + NumPartialPackArgs);
834  // We pre-populate the deduced value of the partially-substituted
835  // pack with the specified value. This is not entirely correct: the
836  // value is supposed to have been substituted, not deduced, but the
837  // cases where this is observable require an exact type match anyway.
838  //
839  // FIXME: If we could represent a "depth i, index j, pack elem k"
840  // parameter, we could substitute the partially-substituted pack
841  // everywhere and avoid this.
842  if (!IsPartiallyExpanded)
843  Deduced[Pack.Index] = Pack.New[PackElements];
844  }
845  }
846  }
847 
848 public:
849  ~PackDeductionScope() {
850  for (auto &Pack : Packs)
851  Info.PendingDeducedPacks[Pack.Index] = Pack.Outer;
852  }
853 
854  /// Determine whether this pack has already been partially expanded into a
855  /// sequence of (prior) function parameters / template arguments.
856  bool isPartiallyExpanded() { return IsPartiallyExpanded; }
857 
858  /// Determine whether this pack expansion scope has a known, fixed arity.
859  /// This happens if it involves a pack from an outer template that has
860  /// (notionally) already been expanded.
861  bool hasFixedArity() { return FixedNumExpansions.hasValue(); }
862 
863  /// Determine whether the next element of the argument is still part of this
864  /// pack. This is the case unless the pack is already expanded to a fixed
865  /// length.
866  bool hasNextElement() {
867  return !FixedNumExpansions || *FixedNumExpansions > PackElements;
868  }
869 
870  /// Move to deducing the next element in each pack that is being deduced.
871  void nextPackElement() {
872  // Capture the deduced template arguments for each parameter pack expanded
873  // by this pack expansion, add them to the list of arguments we've deduced
874  // for that pack, then clear out the deduced argument.
875  for (auto &Pack : Packs) {
876  DeducedTemplateArgument &DeducedArg = Deduced[Pack.Index];
877  if (!Pack.New.empty() || !DeducedArg.isNull()) {
878  while (Pack.New.size() < PackElements)
879  Pack.New.push_back(DeducedTemplateArgument());
880  if (Pack.New.size() == PackElements)
881  Pack.New.push_back(DeducedArg);
882  else
883  Pack.New[PackElements] = DeducedArg;
884  DeducedArg = Pack.New.size() > PackElements + 1
885  ? Pack.New[PackElements + 1]
887  }
888  }
889  ++PackElements;
890  }
891 
892  /// Finish template argument deduction for a set of argument packs,
893  /// producing the argument packs and checking for consistency with prior
894  /// deductions.
896  // Build argument packs for each of the parameter packs expanded by this
897  // pack expansion.
898  for (auto &Pack : Packs) {
899  // Put back the old value for this pack.
900  Deduced[Pack.Index] = Pack.Saved;
901 
902  // Always make sure the size of this pack is correct, even if we didn't
903  // deduce any values for it.
904  //
905  // FIXME: This isn't required by the normative wording, but substitution
906  // and post-substitution checking will always fail if the arity of any
907  // pack is not equal to the number of elements we processed. (Either that
908  // or something else has gone *very* wrong.) We're permitted to skip any
909  // hard errors from those follow-on steps by the intent (but not the
910  // wording) of C++ [temp.inst]p8:
911  //
912  // If the function selected by overload resolution can be determined
913  // without instantiating a class template definition, it is unspecified
914  // whether that instantiation actually takes place
915  Pack.New.resize(PackElements);
916 
917  // Build or find a new value for this pack.
918  DeducedTemplateArgument NewPack;
919  if (Pack.New.empty()) {
920  // If we deduced an empty argument pack, create it now.
922  } else {
923  TemplateArgument *ArgumentPack =
924  new (S.Context) TemplateArgument[Pack.New.size()];
925  std::copy(Pack.New.begin(), Pack.New.end(), ArgumentPack);
926  NewPack = DeducedTemplateArgument(
927  TemplateArgument(llvm::makeArrayRef(ArgumentPack, Pack.New.size())),
928  // FIXME: This is wrong, it's possible that some pack elements are
929  // deduced from an array bound and others are not:
930  // template<typename ...T, T ...V> void g(const T (&...p)[V]);
931  // g({1, 2, 3}, {{}, {}});
932  // ... should deduce T = {int, size_t (from array bound)}.
933  Pack.New[0].wasDeducedFromArrayBound());
934  }
935 
936  // Pick where we're going to put the merged pack.
938  if (Pack.Outer) {
939  if (Pack.Outer->DeferredDeduction.isNull()) {
940  // Defer checking this pack until we have a complete pack to compare
941  // it against.
942  Pack.Outer->DeferredDeduction = NewPack;
943  continue;
944  }
945  Loc = &Pack.Outer->DeferredDeduction;
946  } else {
947  Loc = &Deduced[Pack.Index];
948  }
949 
950  // Check the new pack matches any previous value.
951  DeducedTemplateArgument OldPack = *Loc;
952  DeducedTemplateArgument Result =
953  checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
954 
955  // If we deferred a deduction of this pack, check that one now too.
956  if (!Result.isNull() && !Pack.DeferredDeduction.isNull()) {
957  OldPack = Result;
958  NewPack = Pack.DeferredDeduction;
959  Result = checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
960  }
961 
962  NamedDecl *Param = TemplateParams->getParam(Pack.Index);
963  if (Result.isNull()) {
964  Info.Param = makeTemplateParameter(Param);
965  Info.FirstArg = OldPack;
966  Info.SecondArg = NewPack;
967  return Sema::TDK_Inconsistent;
968  }
969 
970  // If we have a pre-expanded pack and we didn't deduce enough elements
971  // for it, fail deduction.
972  if (Optional<unsigned> Expansions = getExpandedPackSize(Param)) {
973  if (*Expansions != PackElements) {
974  Info.Param = makeTemplateParameter(Param);
975  Info.FirstArg = Result;
977  }
978  }
979 
980  *Loc = Result;
981  }
982 
983  return Sema::TDK_Success;
984  }
985 
986 private:
987  Sema &S;
988  TemplateParameterList *TemplateParams;
990  TemplateDeductionInfo &Info;
991  unsigned PackElements = 0;
992  bool IsPartiallyExpanded = false;
993  /// The number of expansions, if we have a fully-expanded pack in this scope.
994  Optional<unsigned> FixedNumExpansions;
995 
997 };
998 
999 } // namespace
1000 
1001 /// Deduce the template arguments by comparing the list of parameter
1002 /// types to the list of argument types, as in the parameter-type-lists of
1003 /// function types (C++ [temp.deduct.type]p10).
1004 ///
1005 /// \param S The semantic analysis object within which we are deducing
1006 ///
1007 /// \param TemplateParams The template parameters that we are deducing
1008 ///
1009 /// \param Params The list of parameter types
1010 ///
1011 /// \param NumParams The number of types in \c Params
1012 ///
1013 /// \param Args The list of argument types
1014 ///
1015 /// \param NumArgs The number of types in \c Args
1016 ///
1017 /// \param Info information about the template argument deduction itself
1018 ///
1019 /// \param Deduced the deduced template arguments
1020 ///
1021 /// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
1022 /// how template argument deduction is performed.
1023 ///
1024 /// \param PartialOrdering If true, we are performing template argument
1025 /// deduction for during partial ordering for a call
1026 /// (C++0x [temp.deduct.partial]).
1027 ///
1028 /// \returns the result of template argument deduction so far. Note that a
1029 /// "success" result means that template argument deduction has not yet failed,
1030 /// but it may still fail, later, for other reasons.
1033  TemplateParameterList *TemplateParams,
1034  const QualType *Params, unsigned NumParams,
1035  const QualType *Args, unsigned NumArgs,
1036  TemplateDeductionInfo &Info,
1037  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
1038  unsigned TDF,
1039  bool PartialOrdering = false) {
1040  // C++0x [temp.deduct.type]p10:
1041  // Similarly, if P has a form that contains (T), then each parameter type
1042  // Pi of the respective parameter-type- list of P is compared with the
1043  // corresponding parameter type Ai of the corresponding parameter-type-list
1044  // of A. [...]
1045  unsigned ArgIdx = 0, ParamIdx = 0;
1046  for (; ParamIdx != NumParams; ++ParamIdx) {
1047  // Check argument types.
1048  const PackExpansionType *Expansion
1049  = dyn_cast<PackExpansionType>(Params[ParamIdx]);
1050  if (!Expansion) {
1051  // Simple case: compare the parameter and argument types at this point.
1052 
1053  // Make sure we have an argument.
1054  if (ArgIdx >= NumArgs)
1056 
1057  if (isa<PackExpansionType>(Args[ArgIdx])) {
1058  // C++0x [temp.deduct.type]p22:
1059  // If the original function parameter associated with A is a function
1060  // parameter pack and the function parameter associated with P is not
1061  // a function parameter pack, then template argument deduction fails.
1063  }
1064 
1066  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1067  Params[ParamIdx], Args[ArgIdx],
1068  Info, Deduced, TDF,
1069  PartialOrdering))
1070  return Result;
1071 
1072  ++ArgIdx;
1073  continue;
1074  }
1075 
1076  // C++0x [temp.deduct.type]p10:
1077  // If the parameter-declaration corresponding to Pi is a function
1078  // parameter pack, then the type of its declarator- id is compared with
1079  // each remaining parameter type in the parameter-type-list of A. Each
1080  // comparison deduces template arguments for subsequent positions in the
1081  // template parameter packs expanded by the function parameter pack.
1082 
1083  QualType Pattern = Expansion->getPattern();
1084  PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
1085 
1086  // A pack scope with fixed arity is not really a pack any more, so is not
1087  // a non-deduced context.
1088  if (ParamIdx + 1 == NumParams || PackScope.hasFixedArity()) {
1089  for (; ArgIdx < NumArgs && PackScope.hasNextElement(); ++ArgIdx) {
1090  // Deduce template arguments from the pattern.
1092  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, Pattern,
1093  Args[ArgIdx], Info, Deduced,
1094  TDF, PartialOrdering))
1095  return Result;
1096 
1097  PackScope.nextPackElement();
1098  }
1099  } else {
1100  // C++0x [temp.deduct.type]p5:
1101  // The non-deduced contexts are:
1102  // - A function parameter pack that does not occur at the end of the
1103  // parameter-declaration-clause.
1104  //
1105  // FIXME: There is no wording to say what we should do in this case. We
1106  // choose to resolve this by applying the same rule that is applied for a
1107  // function call: that is, deduce all contained packs to their
1108  // explicitly-specified values (or to <> if there is no such value).
1109  //
1110  // This is seemingly-arbitrarily different from the case of a template-id
1111  // with a non-trailing pack-expansion in its arguments, which renders the
1112  // entire template-argument-list a non-deduced context.
1113 
1114  // If the parameter type contains an explicitly-specified pack that we
1115  // could not expand, skip the number of parameters notionally created
1116  // by the expansion.
1117  Optional<unsigned> NumExpansions = Expansion->getNumExpansions();
1118  if (NumExpansions && !PackScope.isPartiallyExpanded()) {
1119  for (unsigned I = 0; I != *NumExpansions && ArgIdx < NumArgs;
1120  ++I, ++ArgIdx)
1121  PackScope.nextPackElement();
1122  }
1123  }
1124 
1125  // Build argument packs for each of the parameter packs expanded by this
1126  // pack expansion.
1127  if (auto Result = PackScope.finish())
1128  return Result;
1129  }
1130 
1131  // Make sure we don't have any extra arguments.
1132  if (ArgIdx < NumArgs)
1134 
1135  return Sema::TDK_Success;
1136 }
1137 
1138 /// Determine whether the parameter has qualifiers that the argument
1139 /// lacks. Put another way, determine whether there is no way to add
1140 /// a deduced set of qualifiers to the ParamType that would result in
1141 /// its qualifiers matching those of the ArgType.
1143  QualType ArgType) {
1144  Qualifiers ParamQs = ParamType.getQualifiers();
1145  Qualifiers ArgQs = ArgType.getQualifiers();
1146 
1147  if (ParamQs == ArgQs)
1148  return false;
1149 
1150  // Mismatched (but not missing) Objective-C GC attributes.
1151  if (ParamQs.getObjCGCAttr() != ArgQs.getObjCGCAttr() &&
1152  ParamQs.hasObjCGCAttr())
1153  return true;
1154 
1155  // Mismatched (but not missing) address spaces.
1156  if (ParamQs.getAddressSpace() != ArgQs.getAddressSpace() &&
1157  ParamQs.hasAddressSpace())
1158  return true;
1159 
1160  // Mismatched (but not missing) Objective-C lifetime qualifiers.
1161  if (ParamQs.getObjCLifetime() != ArgQs.getObjCLifetime() &&
1162  ParamQs.hasObjCLifetime())
1163  return true;
1164 
1165  // CVR qualifiers inconsistent or a superset.
1166  return (ParamQs.getCVRQualifiers() & ~ArgQs.getCVRQualifiers()) != 0;
1167 }
1168 
1169 /// Compare types for equality with respect to possibly compatible
1170 /// function types (noreturn adjustment, implicit calling conventions). If any
1171 /// of parameter and argument is not a function, just perform type comparison.
1172 ///
1173 /// \param Param the template parameter type.
1174 ///
1175 /// \param Arg the argument type.
1177  CanQualType Arg) {
1178  const FunctionType *ParamFunction = Param->getAs<FunctionType>(),
1179  *ArgFunction = Arg->getAs<FunctionType>();
1180 
1181  // Just compare if not functions.
1182  if (!ParamFunction || !ArgFunction)
1183  return Param == Arg;
1184 
1185  // Noreturn and noexcept adjustment.
1186  QualType AdjustedParam;
1187  if (IsFunctionConversion(Param, Arg, AdjustedParam))
1188  return Arg == Context.getCanonicalType(AdjustedParam);
1189 
1190  // FIXME: Compatible calling conventions.
1191 
1192  return Param == Arg;
1193 }
1194 
1195 /// Get the index of the first template parameter that was originally from the
1196 /// innermost template-parameter-list. This is 0 except when we concatenate
1197 /// the template parameter lists of a class template and a constructor template
1198 /// when forming an implicit deduction guide.
1200  auto *Guide = dyn_cast<CXXDeductionGuideDecl>(FTD->getTemplatedDecl());
1201  if (!Guide || !Guide->isImplicit())
1202  return 0;
1203  return Guide->getDeducedTemplate()->getTemplateParameters()->size();
1204 }
1205 
1206 /// Determine whether a type denotes a forwarding reference.
1207 static bool isForwardingReference(QualType Param, unsigned FirstInnerIndex) {
1208  // C++1z [temp.deduct.call]p3:
1209  // A forwarding reference is an rvalue reference to a cv-unqualified
1210  // template parameter that does not represent a template parameter of a
1211  // class template.
1212  if (auto *ParamRef = Param->getAs<RValueReferenceType>()) {
1213  if (ParamRef->getPointeeType().getQualifiers())
1214  return false;
1215  auto *TypeParm = ParamRef->getPointeeType()->getAs<TemplateTypeParmType>();
1216  return TypeParm && TypeParm->getIndex() >= FirstInnerIndex;
1217  }
1218  return false;
1219 }
1220 
1221 /// Attempt to deduce the template arguments by checking the base types
1222 /// according to (C++20 [temp.deduct.call] p4b3.
1223 ///
1224 /// \param S the semantic analysis object within which we are deducing.
1225 ///
1226 /// \param RecordT the top level record object we are deducing against.
1227 ///
1228 /// \param TemplateParams the template parameters that we are deducing.
1229 ///
1230 /// \param SpecParam the template specialization parameter type.
1231 ///
1232 /// \param Info information about the template argument deduction itself.
1233 ///
1234 /// \param Deduced the deduced template arguments.
1235 ///
1236 /// \returns the result of template argument deduction with the bases. "invalid"
1237 /// means no matches, "success" found a single item, and the
1238 /// "MiscellaneousDeductionFailure" result happens when the match is ambiguous.
1240  Sema &S, const RecordType *RecordT, TemplateParameterList *TemplateParams,
1241  const TemplateSpecializationType *SpecParam, TemplateDeductionInfo &Info,
1242  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
1243  // C++14 [temp.deduct.call] p4b3:
1244  // If P is a class and P has the form simple-template-id, then the
1245  // transformed A can be a derived class of the deduced A. Likewise if
1246  // P is a pointer to a class of the form simple-template-id, the
1247  // transformed A can be a pointer to a derived class pointed to by the
1248  // deduced A. However, if there is a class C that is a (direct or
1249  // indirect) base class of D and derived (directly or indirectly) from a
1250  // class B and that would be a valid deduced A, the deduced A cannot be
1251  // B or pointer to B, respectively.
1252  //
1253  // These alternatives are considered only if type deduction would
1254  // otherwise fail. If they yield more than one possible deduced A, the
1255  // type deduction fails.
1256 
1257  // Use a breadth-first search through the bases to collect the set of
1258  // successful matches. Visited contains the set of nodes we have already
1259  // visited, while ToVisit is our stack of records that we still need to
1260  // visit. Matches contains a list of matches that have yet to be
1261  // disqualified.
1264  // We iterate over this later, so we have to use MapVector to ensure
1265  // determinism.
1266  llvm::MapVector<const RecordType *, SmallVector<DeducedTemplateArgument, 8>>
1267  Matches;
1268 
1269  auto AddBases = [&Visited, &ToVisit](const RecordType *RT) {
1270  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1271  for (const auto &Base : RD->bases()) {
1272  assert(Base.getType()->isRecordType() &&
1273  "Base class that isn't a record?");
1274  const RecordType *RT = Base.getType()->getAs<RecordType>();
1275  if (Visited.insert(RT).second)
1276  ToVisit.push_back(Base.getType()->getAs<RecordType>());
1277  }
1278  };
1279 
1280  // Set up the loop by adding all the bases.
1281  AddBases(RecordT);
1282 
1283  // Search each path of bases until we either run into a successful match
1284  // (where all bases of it are invalid), or we run out of bases.
1285  while (!ToVisit.empty()) {
1286  const RecordType *NextT = ToVisit.pop_back_val();
1287 
1288  SmallVector<DeducedTemplateArgument, 8> DeducedCopy(Deduced.begin(),
1289  Deduced.end());
1292  DeduceTemplateArguments(S, TemplateParams, SpecParam,
1293  QualType(NextT, 0), BaseInfo, DeducedCopy);
1294 
1295  // If this was a successful deduction, add it to the list of matches,
1296  // otherwise we need to continue searching its bases.
1297  if (BaseResult == Sema::TDK_Success)
1298  Matches.insert({NextT, DeducedCopy});
1299  else
1300  AddBases(NextT);
1301  }
1302 
1303  // At this point, 'Matches' contains a list of seemingly valid bases, however
1304  // in the event that we have more than 1 match, it is possible that the base
1305  // of one of the matches might be disqualified for being a base of another
1306  // valid match. We can count on cyclical instantiations being invalid to
1307  // simplify the disqualifications. That is, if A & B are both matches, and B
1308  // inherits from A (disqualifying A), we know that A cannot inherit from B.
1309  if (Matches.size() > 1) {
1310  Visited.clear();
1311  for (const auto &Match : Matches)
1312  AddBases(Match.first);
1313 
1314  // We can give up once we have a single item (or have run out of things to
1315  // search) since cyclical inheritence isn't valid.
1316  while (Matches.size() > 1 && !ToVisit.empty()) {
1317  const RecordType *NextT = ToVisit.pop_back_val();
1318  Matches.erase(NextT);
1319 
1320  // Always add all bases, since the inheritence tree can contain
1321  // disqualifications for multiple matches.
1322  AddBases(NextT);
1323  }
1324  }
1325 
1326  if (Matches.empty())
1327  return Sema::TDK_Invalid;
1328  if (Matches.size() > 1)
1330 
1331  std::swap(Matches.front().second, Deduced);
1332  return Sema::TDK_Success;
1333 }
1334 
1335 /// Deduce the template arguments by comparing the parameter type and
1336 /// the argument type (C++ [temp.deduct.type]).
1337 ///
1338 /// \param S the semantic analysis object within which we are deducing
1339 ///
1340 /// \param TemplateParams the template parameters that we are deducing
1341 ///
1342 /// \param ParamIn the parameter type
1343 ///
1344 /// \param ArgIn the argument type
1345 ///
1346 /// \param Info information about the template argument deduction itself
1347 ///
1348 /// \param Deduced the deduced template arguments
1349 ///
1350 /// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
1351 /// how template argument deduction is performed.
1352 ///
1353 /// \param PartialOrdering Whether we're performing template argument deduction
1354 /// in the context of partial ordering (C++0x [temp.deduct.partial]).
1355 ///
1356 /// \returns the result of template argument deduction so far. Note that a
1357 /// "success" result means that template argument deduction has not yet failed,
1358 /// but it may still fail, later, for other reasons.
1361  TemplateParameterList *TemplateParams,
1362  QualType ParamIn, QualType ArgIn,
1363  TemplateDeductionInfo &Info,
1364  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
1365  unsigned TDF,
1366  bool PartialOrdering,
1367  bool DeducedFromArrayBound) {
1368  // We only want to look at the canonical types, since typedefs and
1369  // sugar are not part of template argument deduction.
1370  QualType Param = S.Context.getCanonicalType(ParamIn);
1371  QualType Arg = S.Context.getCanonicalType(ArgIn);
1372 
1373  // If the argument type is a pack expansion, look at its pattern.
1374  // This isn't explicitly called out
1375  if (const PackExpansionType *ArgExpansion
1376  = dyn_cast<PackExpansionType>(Arg))
1377  Arg = ArgExpansion->getPattern();
1378 
1379  if (PartialOrdering) {
1380  // C++11 [temp.deduct.partial]p5:
1381  // Before the partial ordering is done, certain transformations are
1382  // performed on the types used for partial ordering:
1383  // - If P is a reference type, P is replaced by the type referred to.
1384  const ReferenceType *ParamRef = Param->getAs<ReferenceType>();
1385  if (ParamRef)
1386  Param = ParamRef->getPointeeType();
1387 
1388  // - If A is a reference type, A is replaced by the type referred to.
1389  const ReferenceType *ArgRef = Arg->getAs<ReferenceType>();
1390  if (ArgRef)
1391  Arg = ArgRef->getPointeeType();
1392 
1393  if (ParamRef && ArgRef && S.Context.hasSameUnqualifiedType(Param, Arg)) {
1394  // C++11 [temp.deduct.partial]p9:
1395  // If, for a given type, deduction succeeds in both directions (i.e.,
1396  // the types are identical after the transformations above) and both
1397  // P and A were reference types [...]:
1398  // - if [one type] was an lvalue reference and [the other type] was
1399  // not, [the other type] is not considered to be at least as
1400  // specialized as [the first type]
1401  // - if [one type] is more cv-qualified than [the other type],
1402  // [the other type] is not considered to be at least as specialized
1403  // as [the first type]
1404  // Objective-C ARC adds:
1405  // - [one type] has non-trivial lifetime, [the other type] has
1406  // __unsafe_unretained lifetime, and the types are otherwise
1407  // identical
1408  //
1409  // A is "considered to be at least as specialized" as P iff deduction
1410  // succeeds, so we model this as a deduction failure. Note that
1411  // [the first type] is P and [the other type] is A here; the standard
1412  // gets this backwards.
1413  Qualifiers ParamQuals = Param.getQualifiers();
1414  Qualifiers ArgQuals = Arg.getQualifiers();
1415  if ((ParamRef->isLValueReferenceType() &&
1416  !ArgRef->isLValueReferenceType()) ||
1417  ParamQuals.isStrictSupersetOf(ArgQuals) ||
1418  (ParamQuals.hasNonTrivialObjCLifetime() &&
1420  ParamQuals.withoutObjCLifetime() ==
1421  ArgQuals.withoutObjCLifetime())) {
1422  Info.FirstArg = TemplateArgument(ParamIn);
1423  Info.SecondArg = TemplateArgument(ArgIn);
1425  }
1426  }
1427 
1428  // C++11 [temp.deduct.partial]p7:
1429  // Remove any top-level cv-qualifiers:
1430  // - If P is a cv-qualified type, P is replaced by the cv-unqualified
1431  // version of P.
1432  Param = Param.getUnqualifiedType();
1433  // - If A is a cv-qualified type, A is replaced by the cv-unqualified
1434  // version of A.
1435  Arg = Arg.getUnqualifiedType();
1436  } else {
1437  // C++0x [temp.deduct.call]p4 bullet 1:
1438  // - If the original P is a reference type, the deduced A (i.e., the type
1439  // referred to by the reference) can be more cv-qualified than the
1440  // transformed A.
1441  if (TDF & TDF_ParamWithReferenceType) {
1442  Qualifiers Quals;
1443  QualType UnqualParam = S.Context.getUnqualifiedArrayType(Param, Quals);
1444  Quals.setCVRQualifiers(Quals.getCVRQualifiers() &
1445  Arg.getCVRQualifiers());
1446  Param = S.Context.getQualifiedType(UnqualParam, Quals);
1447  }
1448 
1449  if ((TDF & TDF_TopLevelParameterTypeList) && !Param->isFunctionType()) {
1450  // C++0x [temp.deduct.type]p10:
1451  // If P and A are function types that originated from deduction when
1452  // taking the address of a function template (14.8.2.2) or when deducing
1453  // template arguments from a function declaration (14.8.2.6) and Pi and
1454  // Ai are parameters of the top-level parameter-type-list of P and A,
1455  // respectively, Pi is adjusted if it is a forwarding reference and Ai
1456  // is an lvalue reference, in
1457  // which case the type of Pi is changed to be the template parameter
1458  // type (i.e., T&& is changed to simply T). [ Note: As a result, when
1459  // Pi is T&& and Ai is X&, the adjusted Pi will be T, causing T to be
1460  // deduced as X&. - end note ]
1461  TDF &= ~TDF_TopLevelParameterTypeList;
1462  if (isForwardingReference(Param, 0) && Arg->isLValueReferenceType())
1463  Param = Param->getPointeeType();
1464  }
1465  }
1466 
1467  // C++ [temp.deduct.type]p9:
1468  // A template type argument T, a template template argument TT or a
1469  // template non-type argument i can be deduced if P and A have one of
1470  // the following forms:
1471  //
1472  // T
1473  // cv-list T
1474  if (const TemplateTypeParmType *TemplateTypeParm
1475  = Param->getAs<TemplateTypeParmType>()) {
1476  // Just skip any attempts to deduce from a placeholder type or a parameter
1477  // at a different depth.
1478  if (Arg->isPlaceholderType() ||
1479  Info.getDeducedDepth() != TemplateTypeParm->getDepth())
1480  return Sema::TDK_Success;
1481 
1482  unsigned Index = TemplateTypeParm->getIndex();
1483  bool RecanonicalizeArg = false;
1484 
1485  // If the argument type is an array type, move the qualifiers up to the
1486  // top level, so they can be matched with the qualifiers on the parameter.
1487  if (isa<ArrayType>(Arg)) {
1488  Qualifiers Quals;
1489  Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
1490  if (Quals) {
1491  Arg = S.Context.getQualifiedType(Arg, Quals);
1492  RecanonicalizeArg = true;
1493  }
1494  }
1495 
1496  // The argument type can not be less qualified than the parameter
1497  // type.
1498  if (!(TDF & TDF_IgnoreQualifiers) &&
1500  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1501  Info.FirstArg = TemplateArgument(Param);
1502  Info.SecondArg = TemplateArgument(Arg);
1503  return Sema::TDK_Underqualified;
1504  }
1505 
1506  // Do not match a function type with a cv-qualified type.
1507  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1584
1508  if (Arg->isFunctionType() && Param.hasQualifiers()) {
1510  }
1511 
1512  assert(TemplateTypeParm->getDepth() == Info.getDeducedDepth() &&
1513  "saw template type parameter with wrong depth");
1514  assert(Arg != S.Context.OverloadTy && "Unresolved overloaded function");
1515  QualType DeducedType = Arg;
1516 
1517  // Remove any qualifiers on the parameter from the deduced type.
1518  // We checked the qualifiers for consistency above.
1519  Qualifiers DeducedQs = DeducedType.getQualifiers();
1520  Qualifiers ParamQs = Param.getQualifiers();
1521  DeducedQs.removeCVRQualifiers(ParamQs.getCVRQualifiers());
1522  if (ParamQs.hasObjCGCAttr())
1523  DeducedQs.removeObjCGCAttr();
1524  if (ParamQs.hasAddressSpace())
1525  DeducedQs.removeAddressSpace();
1526  if (ParamQs.hasObjCLifetime())
1527  DeducedQs.removeObjCLifetime();
1528 
1529  // Objective-C ARC:
1530  // If template deduction would produce a lifetime qualifier on a type
1531  // that is not a lifetime type, template argument deduction fails.
1532  if (ParamQs.hasObjCLifetime() && !DeducedType->isObjCLifetimeType() &&
1533  !DeducedType->isDependentType()) {
1534  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1535  Info.FirstArg = TemplateArgument(Param);
1536  Info.SecondArg = TemplateArgument(Arg);
1537  return Sema::TDK_Underqualified;
1538  }
1539 
1540  // Objective-C ARC:
1541  // If template deduction would produce an argument type with lifetime type
1542  // but no lifetime qualifier, the __strong lifetime qualifier is inferred.
1543  if (S.getLangOpts().ObjCAutoRefCount &&
1544  DeducedType->isObjCLifetimeType() &&
1545  !DeducedQs.hasObjCLifetime())
1547 
1548  DeducedType = S.Context.getQualifiedType(DeducedType.getUnqualifiedType(),
1549  DeducedQs);
1550 
1551  if (RecanonicalizeArg)
1552  DeducedType = S.Context.getCanonicalType(DeducedType);
1553 
1554  DeducedTemplateArgument NewDeduced(DeducedType, DeducedFromArrayBound);
1556  Deduced[Index],
1557  NewDeduced);
1558  if (Result.isNull()) {
1559  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1560  Info.FirstArg = Deduced[Index];
1561  Info.SecondArg = NewDeduced;
1562  return Sema::TDK_Inconsistent;
1563  }
1564 
1565  Deduced[Index] = Result;
1566  return Sema::TDK_Success;
1567  }
1568 
1569  // Set up the template argument deduction information for a failure.
1570  Info.FirstArg = TemplateArgument(ParamIn);
1571  Info.SecondArg = TemplateArgument(ArgIn);
1572 
1573  // If the parameter is an already-substituted template parameter
1574  // pack, do nothing: we don't know which of its arguments to look
1575  // at, so we have to wait until all of the parameter packs in this
1576  // expansion have arguments.
1577  if (isa<SubstTemplateTypeParmPackType>(Param))
1578  return Sema::TDK_Success;
1579 
1580  // Check the cv-qualifiers on the parameter and argument types.
1581  CanQualType CanParam = S.Context.getCanonicalType(Param);
1582  CanQualType CanArg = S.Context.getCanonicalType(Arg);
1583  if (!(TDF & TDF_IgnoreQualifiers)) {
1584  if (TDF & TDF_ParamWithReferenceType) {
1585  if (hasInconsistentOrSupersetQualifiersOf(Param, Arg))
1587  } else if (TDF & TDF_ArgWithReferenceType) {
1588  // C++ [temp.deduct.conv]p4:
1589  // If the original A is a reference type, A can be more cv-qualified
1590  // than the deduced A
1591  if (!Arg.getQualifiers().compatiblyIncludes(Param.getQualifiers()))
1593 
1594  // Strip out all extra qualifiers from the argument to figure out the
1595  // type we're converting to, prior to the qualification conversion.
1596  Qualifiers Quals;
1597  Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
1598  Arg = S.Context.getQualifiedType(Arg, Param.getQualifiers());
1599  } else if (!IsPossiblyOpaquelyQualifiedType(Param)) {
1600  if (Param.getCVRQualifiers() != Arg.getCVRQualifiers())
1602  }
1603 
1604  // If the parameter type is not dependent, there is nothing to deduce.
1605  if (!Param->isDependentType()) {
1606  if (!(TDF & TDF_SkipNonDependent)) {
1607  bool NonDeduced =
1609  ? !S.isSameOrCompatibleFunctionType(CanParam, CanArg)
1610  : Param != Arg;
1611  if (NonDeduced) {
1613  }
1614  }
1615  return Sema::TDK_Success;
1616  }
1617  } else if (!Param->isDependentType()) {
1618  if (!(TDF & TDF_SkipNonDependent)) {
1619  CanQualType ParamUnqualType = CanParam.getUnqualifiedType(),
1620  ArgUnqualType = CanArg.getUnqualifiedType();
1621  bool Success =
1623  ? S.isSameOrCompatibleFunctionType(ParamUnqualType, ArgUnqualType)
1624  : ParamUnqualType == ArgUnqualType;
1625  if (Success)
1626  return Sema::TDK_Success;
1627  } else {
1628  return Sema::TDK_Success;
1629  }
1630  }
1631 
1632  switch (Param->getTypeClass()) {
1633  // Non-canonical types cannot appear here.
1634 #define NON_CANONICAL_TYPE(Class, Base) \
1635  case Type::Class: llvm_unreachable("deducing non-canonical type: " #Class);
1636 #define TYPE(Class, Base)
1637 #include "clang/AST/TypeNodes.inc"
1638 
1639  case Type::TemplateTypeParm:
1640  case Type::SubstTemplateTypeParmPack:
1641  llvm_unreachable("Type nodes handled above");
1642 
1643  // These types cannot be dependent, so simply check whether the types are
1644  // the same.
1645  case Type::Builtin:
1646  case Type::VariableArray:
1647  case Type::Vector:
1648  case Type::FunctionNoProto:
1649  case Type::Record:
1650  case Type::Enum:
1651  case Type::ObjCObject:
1652  case Type::ObjCInterface:
1653  case Type::ObjCObjectPointer:
1654  case Type::ExtInt:
1655  if (TDF & TDF_SkipNonDependent)
1656  return Sema::TDK_Success;
1657 
1658  if (TDF & TDF_IgnoreQualifiers) {
1659  Param = Param.getUnqualifiedType();
1660  Arg = Arg.getUnqualifiedType();
1661  }
1662 
1663  return Param == Arg? Sema::TDK_Success : Sema::TDK_NonDeducedMismatch;
1664 
1665  // _Complex T [placeholder extension]
1666  case Type::Complex:
1667  if (const ComplexType *ComplexArg = Arg->getAs<ComplexType>())
1668  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1669  cast<ComplexType>(Param)->getElementType(),
1670  ComplexArg->getElementType(),
1671  Info, Deduced, TDF);
1672 
1674 
1675  // _Atomic T [extension]
1676  case Type::Atomic:
1677  if (const AtomicType *AtomicArg = Arg->getAs<AtomicType>())
1678  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1679  cast<AtomicType>(Param)->getValueType(),
1680  AtomicArg->getValueType(),
1681  Info, Deduced, TDF);
1682 
1684 
1685  // T *
1686  case Type::Pointer: {
1687  QualType PointeeType;
1688  if (const PointerType *PointerArg = Arg->getAs<PointerType>()) {
1689  PointeeType = PointerArg->getPointeeType();
1690  } else if (const ObjCObjectPointerType *PointerArg
1691  = Arg->getAs<ObjCObjectPointerType>()) {
1692  PointeeType = PointerArg->getPointeeType();
1693  } else {
1695  }
1696 
1697  unsigned SubTDF = TDF & (TDF_IgnoreQualifiers | TDF_DerivedClass);
1698  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1699  cast<PointerType>(Param)->getPointeeType(),
1700  PointeeType,
1701  Info, Deduced, SubTDF);
1702  }
1703 
1704  // T &
1705  case Type::LValueReference: {
1706  const LValueReferenceType *ReferenceArg =
1707  Arg->getAs<LValueReferenceType>();
1708  if (!ReferenceArg)
1710 
1711  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1712  cast<LValueReferenceType>(Param)->getPointeeType(),
1713  ReferenceArg->getPointeeType(), Info, Deduced, 0);
1714  }
1715 
1716  // T && [C++0x]
1717  case Type::RValueReference: {
1718  const RValueReferenceType *ReferenceArg =
1719  Arg->getAs<RValueReferenceType>();
1720  if (!ReferenceArg)
1722 
1723  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1724  cast<RValueReferenceType>(Param)->getPointeeType(),
1725  ReferenceArg->getPointeeType(),
1726  Info, Deduced, 0);
1727  }
1728 
1729  // T [] (implied, but not stated explicitly)
1730  case Type::IncompleteArray: {
1731  const IncompleteArrayType *IncompleteArrayArg =
1733  if (!IncompleteArrayArg)
1735 
1736  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1737  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1739  IncompleteArrayArg->getElementType(),
1740  Info, Deduced, SubTDF);
1741  }
1742 
1743  // T [integer-constant]
1744  case Type::ConstantArray: {
1745  const ConstantArrayType *ConstantArrayArg =
1747  if (!ConstantArrayArg)
1749 
1750  const ConstantArrayType *ConstantArrayParm =
1752  if (ConstantArrayArg->getSize() != ConstantArrayParm->getSize())
1753  return Sema::TDK_NonDeducedMismatch;
1754 
1755  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1756  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1757  ConstantArrayParm->getElementType(),
1758  ConstantArrayArg->getElementType(),
1759  Info, Deduced, SubTDF);
1760  }
1761 
1762  // type [i]
1763  case Type::DependentSizedArray: {
1764  const ArrayType *ArrayArg = S.Context.getAsArrayType(Arg);
1765  if (!ArrayArg)
1767 
1768  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1769 
1770  // Check the element type of the arrays
1771  const DependentSizedArrayType *DependentArrayParm
1774  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1775  DependentArrayParm->getElementType(),
1776  ArrayArg->getElementType(),
1777  Info, Deduced, SubTDF))
1778  return Result;
1779 
1780  // Determine the array bound is something we can deduce.
1781  const NonTypeTemplateParmDecl *NTTP
1782  = getDeducedParameterFromExpr(Info, DependentArrayParm->getSizeExpr());
1783  if (!NTTP)
1784  return Sema::TDK_Success;
1785 
1786  // We can perform template argument deduction for the given non-type
1787  // template parameter.
1788  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
1789  "saw non-type template parameter with wrong depth");
1790  if (const ConstantArrayType *ConstantArrayArg
1791  = dyn_cast<ConstantArrayType>(ArrayArg)) {
1792  llvm::APSInt Size(ConstantArrayArg->getSize());
1793  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, Size,
1794  S.Context.getSizeType(),
1795  /*ArrayBound=*/true,
1796  Info, Deduced);
1797  }
1798  if (const DependentSizedArrayType *DependentArrayArg
1799  = dyn_cast<DependentSizedArrayType>(ArrayArg))
1800  if (DependentArrayArg->getSizeExpr())
1801  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
1802  DependentArrayArg->getSizeExpr(),
1803  Info, Deduced);
1804 
1805  // Incomplete type does not match a dependently-sized array type
1807  }
1808 
1809  // type(*)(T)
1810  // T(*)()
1811  // T(*)(T)
1812  case Type::FunctionProto: {
1813  unsigned SubTDF = TDF & TDF_TopLevelParameterTypeList;
1814  const FunctionProtoType *FunctionProtoArg =
1815  dyn_cast<FunctionProtoType>(Arg);
1816  if (!FunctionProtoArg)
1818 
1819  const FunctionProtoType *FunctionProtoParam =
1820  cast<FunctionProtoType>(Param);
1821 
1822  if (FunctionProtoParam->getMethodQuals()
1823  != FunctionProtoArg->getMethodQuals() ||
1824  FunctionProtoParam->getRefQualifier()
1825  != FunctionProtoArg->getRefQualifier() ||
1826  FunctionProtoParam->isVariadic() != FunctionProtoArg->isVariadic())
1827  return Sema::TDK_NonDeducedMismatch;
1828 
1829  // Check return types.
1830  if (auto Result = DeduceTemplateArgumentsByTypeMatch(
1831  S, TemplateParams, FunctionProtoParam->getReturnType(),
1832  FunctionProtoArg->getReturnType(), Info, Deduced, 0))
1833  return Result;
1834 
1835  // Check parameter types.
1836  if (auto Result = DeduceTemplateArguments(
1837  S, TemplateParams, FunctionProtoParam->param_type_begin(),
1838  FunctionProtoParam->getNumParams(),
1839  FunctionProtoArg->param_type_begin(),
1840  FunctionProtoArg->getNumParams(), Info, Deduced, SubTDF))
1841  return Result;
1842 
1844  return Sema::TDK_Success;
1845 
1846  // FIXME: Per core-2016/10/1019 (no corresponding core issue yet), permit
1847  // deducing through the noexcept-specifier if it's part of the canonical
1848  // type. libstdc++ relies on this.
1849  Expr *NoexceptExpr = FunctionProtoParam->getNoexceptExpr();
1850  if (const NonTypeTemplateParmDecl *NTTP =
1851  NoexceptExpr ? getDeducedParameterFromExpr(Info, NoexceptExpr)
1852  : nullptr) {
1853  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
1854  "saw non-type template parameter with wrong depth");
1855 
1856  llvm::APSInt Noexcept(1);
1857  switch (FunctionProtoArg->canThrow()) {
1858  case CT_Cannot:
1859  Noexcept = 1;
1860  LLVM_FALLTHROUGH;
1861 
1862  case CT_Can:
1863  // We give E in noexcept(E) the "deduced from array bound" treatment.
1864  // FIXME: Should we?
1866  S, TemplateParams, NTTP, Noexcept, S.Context.BoolTy,
1867  /*ArrayBound*/true, Info, Deduced);
1868 
1869  case CT_Dependent:
1870  if (Expr *ArgNoexceptExpr = FunctionProtoArg->getNoexceptExpr())
1872  S, TemplateParams, NTTP, ArgNoexceptExpr, Info, Deduced);
1873  // Can't deduce anything from throw(T...).
1874  break;
1875  }
1876  }
1877  // FIXME: Detect non-deduced exception specification mismatches?
1878  //
1879  // Careful about [temp.deduct.call] and [temp.deduct.conv], which allow
1880  // top-level differences in noexcept-specifications.
1881 
1882  return Sema::TDK_Success;
1883  }
1884 
1885  case Type::InjectedClassName:
1886  // Treat a template's injected-class-name as if the template
1887  // specialization type had been used.
1888  Param = cast<InjectedClassNameType>(Param)
1889  ->getInjectedSpecializationType();
1890  assert(isa<TemplateSpecializationType>(Param) &&
1891  "injected class name is not a template specialization type");
1892  LLVM_FALLTHROUGH;
1893 
1894  // template-name<T> (where template-name refers to a class template)
1895  // template-name<i>
1896  // TT<T>
1897  // TT<i>
1898  // TT<>
1899  case Type::TemplateSpecialization: {
1900  const TemplateSpecializationType *SpecParam =
1901  cast<TemplateSpecializationType>(Param);
1902 
1903  // When Arg cannot be a derived class, we can just try to deduce template
1904  // arguments from the template-id.
1905  const RecordType *RecordT = Arg->getAs<RecordType>();
1906  if (!(TDF & TDF_DerivedClass) || !RecordT)
1907  return DeduceTemplateArguments(S, TemplateParams, SpecParam, Arg, Info,
1908  Deduced);
1909 
1910  SmallVector<DeducedTemplateArgument, 8> DeducedOrig(Deduced.begin(),
1911  Deduced.end());
1912 
1914  S, TemplateParams, SpecParam, Arg, Info, Deduced);
1915 
1916  if (Result == Sema::TDK_Success)
1917  return Result;
1918 
1919  // We cannot inspect base classes as part of deduction when the type
1920  // is incomplete, so either instantiate any templates necessary to
1921  // complete the type, or skip over it if it cannot be completed.
1922  if (!S.isCompleteType(Info.getLocation(), Arg))
1923  return Result;
1924 
1925  // Reset the incorrectly deduced argument from above.
1926  Deduced = DeducedOrig;
1927 
1928  // Check bases according to C++14 [temp.deduct.call] p4b3:
1930  S, RecordT, TemplateParams, SpecParam, Info, Deduced);
1931 
1932  if (BaseResult != Sema::TDK_Invalid)
1933  return BaseResult;
1934  return Result;
1935  }
1936 
1937  // T type::*
1938  // T T::*
1939  // T (type::*)()
1940  // type (T::*)()
1941  // type (type::*)(T)
1942  // type (T::*)(T)
1943  // T (type::*)(T)
1944  // T (T::*)()
1945  // T (T::*)(T)
1946  case Type::MemberPointer: {
1947  const MemberPointerType *MemPtrParam = cast<MemberPointerType>(Param);
1948  const MemberPointerType *MemPtrArg = dyn_cast<MemberPointerType>(Arg);
1949  if (!MemPtrArg)
1951 
1952  QualType ParamPointeeType = MemPtrParam->getPointeeType();
1953  if (ParamPointeeType->isFunctionType())
1954  S.adjustMemberFunctionCC(ParamPointeeType, /*IsStatic=*/true,
1955  /*IsCtorOrDtor=*/false, Info.getLocation());
1956  QualType ArgPointeeType = MemPtrArg->getPointeeType();
1957  if (ArgPointeeType->isFunctionType())
1958  S.adjustMemberFunctionCC(ArgPointeeType, /*IsStatic=*/true,
1959  /*IsCtorOrDtor=*/false, Info.getLocation());
1960 
1962  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1963  ParamPointeeType,
1964  ArgPointeeType,
1965  Info, Deduced,
1966  TDF & TDF_IgnoreQualifiers))
1967  return Result;
1968 
1969  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1970  QualType(MemPtrParam->getClass(), 0),
1971  QualType(MemPtrArg->getClass(), 0),
1972  Info, Deduced,
1973  TDF & TDF_IgnoreQualifiers);
1974  }
1975 
1976  // (clang extension)
1977  //
1978  // type(^)(T)
1979  // T(^)()
1980  // T(^)(T)
1981  case Type::BlockPointer: {
1982  const BlockPointerType *BlockPtrParam = cast<BlockPointerType>(Param);
1983  const BlockPointerType *BlockPtrArg = dyn_cast<BlockPointerType>(Arg);
1984 
1985  if (!BlockPtrArg)
1987 
1988  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1989  BlockPtrParam->getPointeeType(),
1990  BlockPtrArg->getPointeeType(),
1991  Info, Deduced, 0);
1992  }
1993 
1994  // (clang extension)
1995  //
1996  // T __attribute__(((ext_vector_type(<integral constant>))))
1997  case Type::ExtVector: {
1998  const ExtVectorType *VectorParam = cast<ExtVectorType>(Param);
1999  if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
2000  // Make sure that the vectors have the same number of elements.
2001  if (VectorParam->getNumElements() != VectorArg->getNumElements())
2002  return Sema::TDK_NonDeducedMismatch;
2003 
2004  // Perform deduction on the element types.
2005  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2006  VectorParam->getElementType(),
2007  VectorArg->getElementType(),
2008  Info, Deduced, TDF);
2009  }
2010 
2011  if (const DependentSizedExtVectorType *VectorArg
2012  = dyn_cast<DependentSizedExtVectorType>(Arg)) {
2013  // We can't check the number of elements, since the argument has a
2014  // dependent number of elements. This can only occur during partial
2015  // ordering.
2016 
2017  // Perform deduction on the element types.
2018  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2019  VectorParam->getElementType(),
2020  VectorArg->getElementType(),
2021  Info, Deduced, TDF);
2022  }
2023 
2025  }
2026 
2027  case Type::DependentVector: {
2028  const auto *VectorParam = cast<DependentVectorType>(Param);
2029 
2030  if (const auto *VectorArg = dyn_cast<VectorType>(Arg)) {
2031  // Perform deduction on the element types.
2032  if (Sema::TemplateDeductionResult Result =
2034  S, TemplateParams, VectorParam->getElementType(),
2035  VectorArg->getElementType(), Info, Deduced, TDF))
2036  return Result;
2037 
2038  // Perform deduction on the vector size, if we can.
2039  const NonTypeTemplateParmDecl *NTTP =
2040  getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2041  if (!NTTP)
2042  return Sema::TDK_Success;
2043 
2044  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
2045  ArgSize = VectorArg->getNumElements();
2046  // Note that we use the "array bound" rules here; just like in that
2047  // case, we don't have any particular type for the vector size, but
2048  // we can provide one if necessary.
2049  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
2050  S.Context.UnsignedIntTy, true,
2051  Info, Deduced);
2052  }
2053 
2054  if (const auto *VectorArg = dyn_cast<DependentVectorType>(Arg)) {
2055  // Perform deduction on the element types.
2056  if (Sema::TemplateDeductionResult Result =
2058  S, TemplateParams, VectorParam->getElementType(),
2059  VectorArg->getElementType(), Info, Deduced, TDF))
2060  return Result;
2061 
2062  // Perform deduction on the vector size, if we can.
2064  Info, VectorParam->getSizeExpr());
2065  if (!NTTP)
2066  return Sema::TDK_Success;
2067 
2069  S, TemplateParams, NTTP, VectorArg->getSizeExpr(), Info, Deduced);
2070  }
2071 
2073  }
2074 
2075  // (clang extension)
2076  //
2077  // T __attribute__(((ext_vector_type(N))))
2078  case Type::DependentSizedExtVector: {
2079  const DependentSizedExtVectorType *VectorParam
2080  = cast<DependentSizedExtVectorType>(Param);
2081 
2082  if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
2083  // Perform deduction on the element types.
2085  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2086  VectorParam->getElementType(),
2087  VectorArg->getElementType(),
2088  Info, Deduced, TDF))
2089  return Result;
2090 
2091  // Perform deduction on the vector size, if we can.
2092  const NonTypeTemplateParmDecl *NTTP =
2093  getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2094  if (!NTTP)
2095  return Sema::TDK_Success;
2096 
2097  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
2098  ArgSize = VectorArg->getNumElements();
2099  // Note that we use the "array bound" rules here; just like in that
2100  // case, we don't have any particular type for the vector size, but
2101  // we can provide one if necessary.
2102  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
2103  S.Context.IntTy, true, Info,
2104  Deduced);
2105  }
2106 
2107  if (const DependentSizedExtVectorType *VectorArg
2108  = dyn_cast<DependentSizedExtVectorType>(Arg)) {
2109  // Perform deduction on the element types.
2111  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2112  VectorParam->getElementType(),
2113  VectorArg->getElementType(),
2114  Info, Deduced, TDF))
2115  return Result;
2116 
2117  // Perform deduction on the vector size, if we can.
2118  const NonTypeTemplateParmDecl *NTTP =
2119  getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2120  if (!NTTP)
2121  return Sema::TDK_Success;
2122 
2123  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2124  VectorArg->getSizeExpr(),
2125  Info, Deduced);
2126  }
2127 
2129  }
2130 
2131  // (clang extension)
2132  //
2133  // T __attribute__((matrix_type(<integral constant>,
2134  // <integral constant>)))
2135  case Type::ConstantMatrix: {
2136  const ConstantMatrixType *MatrixArg = dyn_cast<ConstantMatrixType>(Arg);
2137  if (!MatrixArg)
2139 
2140  const ConstantMatrixType *MatrixParam = cast<ConstantMatrixType>(Param);
2141  // Check that the dimensions are the same
2142  if (MatrixParam->getNumRows() != MatrixArg->getNumRows() ||
2143  MatrixParam->getNumColumns() != MatrixArg->getNumColumns()) {
2145  }
2146  // Perform deduction on element types.
2148  S, TemplateParams, MatrixParam->getElementType(),
2149  MatrixArg->getElementType(), Info, Deduced, TDF);
2150  }
2151 
2152  case Type::DependentSizedMatrix: {
2153  const MatrixType *MatrixArg = dyn_cast<MatrixType>(Arg);
2154  if (!MatrixArg)
2156 
2157  // Check the element type of the matrixes.
2158  const DependentSizedMatrixType *MatrixParam =
2159  cast<DependentSizedMatrixType>(Param);
2160  if (Sema::TemplateDeductionResult Result =
2162  S, TemplateParams, MatrixParam->getElementType(),
2163  MatrixArg->getElementType(), Info, Deduced, TDF))
2164  return Result;
2165 
2166  // Try to deduce a matrix dimension.
2167  auto DeduceMatrixArg =
2168  [&S, &Info, &Deduced, &TemplateParams](
2169  Expr *ParamExpr, const MatrixType *Arg,
2170  unsigned (ConstantMatrixType::*GetArgDimension)() const,
2171  Expr *(DependentSizedMatrixType::*GetArgDimensionExpr)() const) {
2172  const auto *ArgConstMatrix = dyn_cast<ConstantMatrixType>(Arg);
2173  const auto *ArgDepMatrix = dyn_cast<DependentSizedMatrixType>(Arg);
2174  if (!ParamExpr->isValueDependent()) {
2175  Optional<llvm::APSInt> ParamConst =
2176  ParamExpr->getIntegerConstantExpr(S.Context);
2177  if (!ParamConst)
2179 
2180  if (ArgConstMatrix) {
2181  if ((ArgConstMatrix->*GetArgDimension)() == *ParamConst)
2182  return Sema::TDK_Success;
2184  }
2185 
2186  Expr *ArgExpr = (ArgDepMatrix->*GetArgDimensionExpr)();
2187  if (!ArgExpr->isValueDependent())
2188  if (Optional<llvm::APSInt> ArgConst =
2189  ArgExpr->getIntegerConstantExpr(S.Context))
2190  if (*ArgConst == *ParamConst)
2191  return Sema::TDK_Success;
2193  }
2194 
2195  const NonTypeTemplateParmDecl *NTTP =
2196  getDeducedParameterFromExpr(Info, ParamExpr);
2197  if (!NTTP)
2198  return Sema::TDK_Success;
2199 
2200  if (ArgConstMatrix) {
2201  llvm::APSInt ArgConst(
2203  ArgConst = (ArgConstMatrix->*GetArgDimension)();
2205  S, TemplateParams, NTTP, ArgConst, S.Context.getSizeType(),
2206  /*ArrayBound=*/true, Info, Deduced);
2207  }
2208 
2210  S, TemplateParams, NTTP, (ArgDepMatrix->*GetArgDimensionExpr)(),
2211  Info, Deduced);
2212  };
2213 
2214  auto Result = DeduceMatrixArg(MatrixParam->getRowExpr(), MatrixArg,
2217  if (Result)
2218  return Result;
2219 
2220  return DeduceMatrixArg(MatrixParam->getColumnExpr(), MatrixArg,
2223  }
2224 
2225  // (clang extension)
2226  //
2227  // T __attribute__(((address_space(N))))
2228  case Type::DependentAddressSpace: {
2229  const DependentAddressSpaceType *AddressSpaceParam =
2230  cast<DependentAddressSpaceType>(Param);
2231 
2232  if (const DependentAddressSpaceType *AddressSpaceArg =
2233  dyn_cast<DependentAddressSpaceType>(Arg)) {
2234  // Perform deduction on the pointer type.
2235  if (Sema::TemplateDeductionResult Result =
2237  S, TemplateParams, AddressSpaceParam->getPointeeType(),
2238  AddressSpaceArg->getPointeeType(), Info, Deduced, TDF))
2239  return Result;
2240 
2241  // Perform deduction on the address space, if we can.
2243  Info, AddressSpaceParam->getAddrSpaceExpr());
2244  if (!NTTP)
2245  return Sema::TDK_Success;
2246 
2248  S, TemplateParams, NTTP, AddressSpaceArg->getAddrSpaceExpr(), Info,
2249  Deduced);
2250  }
2251 
2253  llvm::APSInt ArgAddressSpace(S.Context.getTypeSize(S.Context.IntTy),
2254  false);
2255  ArgAddressSpace = toTargetAddressSpace(Arg.getAddressSpace());
2256 
2257  // Perform deduction on the pointer types.
2258  if (Sema::TemplateDeductionResult Result =
2260  S, TemplateParams, AddressSpaceParam->getPointeeType(),
2261  S.Context.removeAddrSpaceQualType(Arg), Info, Deduced, TDF))
2262  return Result;
2263 
2264  // Perform deduction on the address space, if we can.
2266  Info, AddressSpaceParam->getAddrSpaceExpr());
2267  if (!NTTP)
2268  return Sema::TDK_Success;
2269 
2270  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2271  ArgAddressSpace, S.Context.IntTy,
2272  true, Info, Deduced);
2273  }
2274 
2276  }
2277  case Type::DependentExtInt: {
2278  const auto *IntParam = cast<DependentExtIntType>(Param);
2279 
2280  if (const auto *IntArg = dyn_cast<ExtIntType>(Arg)){
2281  if (IntParam->isUnsigned() != IntArg->isUnsigned())
2282  return Sema::TDK_NonDeducedMismatch;
2283 
2284  const NonTypeTemplateParmDecl *NTTP =
2285  getDeducedParameterFromExpr(Info, IntParam->getNumBitsExpr());
2286  if (!NTTP)
2287  return Sema::TDK_Success;
2288 
2289  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
2290  ArgSize = IntArg->getNumBits();
2291 
2292  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
2293  S.Context.IntTy, true, Info,
2294  Deduced);
2295  }
2296 
2297  if (const auto *IntArg = dyn_cast<DependentExtIntType>(Arg)) {
2298  if (IntParam->isUnsigned() != IntArg->isUnsigned())
2299  return Sema::TDK_NonDeducedMismatch;
2300  return Sema::TDK_Success;
2301  }
2303  }
2304 
2305  case Type::TypeOfExpr:
2306  case Type::TypeOf:
2307  case Type::DependentName:
2308  case Type::UnresolvedUsing:
2309  case Type::Decltype:
2310  case Type::UnaryTransform:
2311  case Type::Auto:
2312  case Type::DeducedTemplateSpecialization:
2313  case Type::DependentTemplateSpecialization:
2314  case Type::PackExpansion:
2315  case Type::Pipe:
2316  // No template argument deduction for these types
2317  return Sema::TDK_Success;
2318  }
2319 
2320  llvm_unreachable("Invalid Type Class!");
2321 }
2322 
2325  TemplateParameterList *TemplateParams,
2326  const TemplateArgument &Param,
2327  TemplateArgument Arg,
2328  TemplateDeductionInfo &Info,
2329  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
2330  // If the template argument is a pack expansion, perform template argument
2331  // deduction against the pattern of that expansion. This only occurs during
2332  // partial ordering.
2333  if (Arg.isPackExpansion())
2334  Arg = Arg.getPackExpansionPattern();
2335 
2336  switch (Param.getKind()) {
2338  llvm_unreachable("Null template argument in parameter list");
2339 
2341  if (Arg.getKind() == TemplateArgument::Type)
2342  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2343  Param.getAsType(),
2344  Arg.getAsType(),
2345  Info, Deduced, 0);
2346  Info.FirstArg = Param;
2347  Info.SecondArg = Arg;
2349 
2351  if (Arg.getKind() == TemplateArgument::Template)
2352  return DeduceTemplateArguments(S, TemplateParams,
2353  Param.getAsTemplate(),
2354  Arg.getAsTemplate(), Info, Deduced);
2355  Info.FirstArg = Param;
2356  Info.SecondArg = Arg;
2358 
2360  llvm_unreachable("caller should handle pack expansions");
2361 
2363  if (Arg.getKind() == TemplateArgument::Declaration &&
2364  isSameDeclaration(Param.getAsDecl(), Arg.getAsDecl()))
2365  return Sema::TDK_Success;
2366 
2367  Info.FirstArg = Param;
2368  Info.SecondArg = Arg;
2370 
2372  if (Arg.getKind() == TemplateArgument::NullPtr &&
2374  return Sema::TDK_Success;
2375 
2376  Info.FirstArg = Param;
2377  Info.SecondArg = Arg;
2379 
2381  if (Arg.getKind() == TemplateArgument::Integral) {
2382  if (hasSameExtendedValue(Param.getAsIntegral(), Arg.getAsIntegral()))
2383  return Sema::TDK_Success;
2384 
2385  Info.FirstArg = Param;
2386  Info.SecondArg = Arg;
2388  }
2389 
2390  if (Arg.getKind() == TemplateArgument::Expression) {
2391  Info.FirstArg = Param;
2392  Info.SecondArg = Arg;
2394  }
2395 
2396  Info.FirstArg = Param;
2397  Info.SecondArg = Arg;
2399 
2401  if (const NonTypeTemplateParmDecl *NTTP =
2402  getDeducedParameterFromExpr(Info, Param.getAsExpr())) {
2403  if (Arg.getKind() == TemplateArgument::Integral)
2404  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2405  Arg.getAsIntegral(),
2406  Arg.getIntegralType(),
2407  /*ArrayBound=*/false,
2408  Info, Deduced);
2409  if (Arg.getKind() == TemplateArgument::NullPtr)
2410  return DeduceNullPtrTemplateArgument(S, TemplateParams, NTTP,
2411  Arg.getNullPtrType(),
2412  Info, Deduced);
2414  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2415  Arg.getAsExpr(), Info, Deduced);
2417  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2418  Arg.getAsDecl(),
2419  Arg.getParamTypeForDecl(),
2420  Info, Deduced);
2421 
2422  Info.FirstArg = Param;
2423  Info.SecondArg = Arg;
2425  }
2426 
2427  // Can't deduce anything, but that's okay.
2428  return Sema::TDK_Success;
2429 
2431  llvm_unreachable("Argument packs should be expanded by the caller!");
2432  }
2433 
2434  llvm_unreachable("Invalid TemplateArgument Kind!");
2435 }
2436 
2437 /// Determine whether there is a template argument to be used for
2438 /// deduction.
2439 ///
2440 /// This routine "expands" argument packs in-place, overriding its input
2441 /// parameters so that \c Args[ArgIdx] will be the available template argument.
2442 ///
2443 /// \returns true if there is another template argument (which will be at
2444 /// \c Args[ArgIdx]), false otherwise.
2445 static bool hasTemplateArgumentForDeduction(ArrayRef<TemplateArgument> &Args,
2446  unsigned &ArgIdx) {
2447  if (ArgIdx == Args.size())
2448  return false;
2449 
2450  const TemplateArgument &Arg = Args[ArgIdx];
2451  if (Arg.getKind() != TemplateArgument::Pack)
2452  return true;
2453 
2454  assert(ArgIdx == Args.size() - 1 && "Pack not at the end of argument list?");
2455  Args = Arg.pack_elements();
2456  ArgIdx = 0;
2457  return ArgIdx < Args.size();
2458 }
2459 
2460 /// Determine whether the given set of template arguments has a pack
2461 /// expansion that is not the last template argument.
2462 static bool hasPackExpansionBeforeEnd(ArrayRef<TemplateArgument> Args) {
2463  bool FoundPackExpansion = false;
2464  for (const auto &A : Args) {
2465  if (FoundPackExpansion)
2466  return true;
2467 
2468  if (A.getKind() == TemplateArgument::Pack)
2469  return hasPackExpansionBeforeEnd(A.pack_elements());
2470 
2471  // FIXME: If this is a fixed-arity pack expansion from an outer level of
2472  // templates, it should not be treated as a pack expansion.
2473  if (A.isPackExpansion())
2474  FoundPackExpansion = true;
2475  }
2476 
2477  return false;
2478 }
2479 
2482  ArrayRef<TemplateArgument> Params,
2483  ArrayRef<TemplateArgument> Args,
2484  TemplateDeductionInfo &Info,
2485  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
2486  bool NumberOfArgumentsMustMatch) {
2487  // C++0x [temp.deduct.type]p9:
2488  // If the template argument list of P contains a pack expansion that is not
2489  // the last template argument, the entire template argument list is a
2490  // non-deduced context.
2491  if (hasPackExpansionBeforeEnd(Params))
2492  return Sema::TDK_Success;
2493 
2494  // C++0x [temp.deduct.type]p9:
2495  // If P has a form that contains <T> or <i>, then each argument Pi of the
2496  // respective template argument list P is compared with the corresponding
2497  // argument Ai of the corresponding template argument list of A.
2498  unsigned ArgIdx = 0, ParamIdx = 0;
2499  for (; hasTemplateArgumentForDeduction(Params, ParamIdx); ++ParamIdx) {
2500  if (!Params[ParamIdx].isPackExpansion()) {
2501  // The simple case: deduce template arguments by matching Pi and Ai.
2502 
2503  // Check whether we have enough arguments.
2504  if (!hasTemplateArgumentForDeduction(Args, ArgIdx))
2505  return NumberOfArgumentsMustMatch
2508 
2509  // C++1z [temp.deduct.type]p9:
2510  // During partial ordering, if Ai was originally a pack expansion [and]
2511  // Pi is not a pack expansion, template argument deduction fails.
2512  if (Args[ArgIdx].isPackExpansion())
2514 
2515  // Perform deduction for this Pi/Ai pair.
2517  = DeduceTemplateArguments(S, TemplateParams,
2518  Params[ParamIdx], Args[ArgIdx],
2519  Info, Deduced))
2520  return Result;
2521 
2522  // Move to the next argument.
2523  ++ArgIdx;
2524  continue;
2525  }
2526 
2527  // The parameter is a pack expansion.
2528 
2529  // C++0x [temp.deduct.type]p9:
2530  // If Pi is a pack expansion, then the pattern of Pi is compared with
2531  // each remaining argument in the template argument list of A. Each
2532  // comparison deduces template arguments for subsequent positions in the
2533  // template parameter packs expanded by Pi.
2535 
2536  // Prepare to deduce the packs within the pattern.
2537  PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
2538 
2539  // Keep track of the deduced template arguments for each parameter pack
2540  // expanded by this pack expansion (the outer index) and for each
2541  // template argument (the inner SmallVectors).
2542  for (; hasTemplateArgumentForDeduction(Args, ArgIdx) &&
2543  PackScope.hasNextElement();
2544  ++ArgIdx) {
2545  // Deduce template arguments from the pattern.
2547  = DeduceTemplateArguments(S, TemplateParams, Pattern, Args[ArgIdx],
2548  Info, Deduced))
2549  return Result;
2550 
2551  PackScope.nextPackElement();
2552  }
2553 
2554  // Build argument packs for each of the parameter packs expanded by this
2555  // pack expansion.
2556  if (auto Result = PackScope.finish())
2557  return Result;
2558  }
2559 
2560  return Sema::TDK_Success;
2561 }
2562 
2565  TemplateParameterList *TemplateParams,
2566  const TemplateArgumentList &ParamList,
2567  const TemplateArgumentList &ArgList,
2568  TemplateDeductionInfo &Info,
2569  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
2570  return DeduceTemplateArguments(S, TemplateParams, ParamList.asArray(),
2571  ArgList.asArray(), Info, Deduced,
2572  /*NumberOfArgumentsMustMatch*/false);
2573 }
2574 
2575 /// Determine whether two template arguments are the same.
2576 static bool isSameTemplateArg(ASTContext &Context,
2578  const TemplateArgument &Y,
2579  bool PackExpansionMatchesPack = false) {
2580  // If we're checking deduced arguments (X) against original arguments (Y),
2581  // we will have flattened packs to non-expansions in X.
2582  if (PackExpansionMatchesPack && X.isPackExpansion() && !Y.isPackExpansion())
2583  X = X.getPackExpansionPattern();
2584 
2585  if (X.getKind() != Y.getKind())
2586  return false;
2587 
2588  switch (X.getKind()) {
2590  llvm_unreachable("Comparing NULL template argument");
2591 
2593  return Context.getCanonicalType(X.getAsType()) ==
2594  Context.getCanonicalType(Y.getAsType());
2595 
2597  return isSameDeclaration(X.getAsDecl(), Y.getAsDecl());
2598 
2600  return Context.hasSameType(X.getNullPtrType(), Y.getNullPtrType());
2601 
2604  return Context.getCanonicalTemplateName(
2605  X.getAsTemplateOrTemplatePattern()).getAsVoidPointer() ==
2606  Context.getCanonicalTemplateName(
2607  Y.getAsTemplateOrTemplatePattern()).getAsVoidPointer();
2608 
2611 
2613  llvm::FoldingSetNodeID XID, YID;
2614  X.getAsExpr()->Profile(XID, Context, true);
2615  Y.getAsExpr()->Profile(YID, Context, true);
2616  return XID == YID;
2617  }
2618 
2620  if (X.pack_size() != Y.pack_size())
2621  return false;
2622 
2624  XPEnd = X.pack_end(),
2625  YP = Y.pack_begin();
2626  XP != XPEnd; ++XP, ++YP)
2627  if (!isSameTemplateArg(Context, *XP, *YP, PackExpansionMatchesPack))
2628  return false;
2629 
2630  return true;
2631  }
2632 
2633  llvm_unreachable("Invalid TemplateArgument Kind!");
2634 }
2635 
2636 /// Allocate a TemplateArgumentLoc where all locations have
2637 /// been initialized to the given location.
2638 ///
2639 /// \param Arg The template argument we are producing template argument
2640 /// location information for.
2641 ///
2642 /// \param NTTPType For a declaration template argument, the type of
2643 /// the non-type template parameter that corresponds to this template
2644 /// argument. Can be null if no type sugar is available to add to the
2645 /// type from the template argument.
2646 ///
2647 /// \param Loc The source location to use for the resulting template
2648 /// argument.
2651  QualType NTTPType, SourceLocation Loc) {
2652  switch (Arg.getKind()) {
2654  llvm_unreachable("Can't get a NULL template argument here");
2655 
2657  return TemplateArgumentLoc(
2658  Arg, Context.getTrivialTypeSourceInfo(Arg.getAsType(), Loc));
2659 
2661  if (NTTPType.isNull())
2662  NTTPType = Arg.getParamTypeForDecl();
2663  Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
2664  .getAs<Expr>();
2665  return TemplateArgumentLoc(TemplateArgument(E), E);
2666  }
2667 
2669  if (NTTPType.isNull())
2670  NTTPType = Arg.getNullPtrType();
2671  Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
2672  .getAs<Expr>();
2673  return TemplateArgumentLoc(TemplateArgument(NTTPType, /*isNullPtr*/true),
2674  E);
2675  }
2676 
2678  Expr *E =
2679  BuildExpressionFromIntegralTemplateArgument(Arg, Loc).getAs<Expr>();
2680  return TemplateArgumentLoc(TemplateArgument(E), E);
2681  }
2682 
2687  if (DependentTemplateName *DTN = Template.getAsDependentTemplateName())
2688  Builder.MakeTrivial(Context, DTN->getQualifier(), Loc);
2689  else if (QualifiedTemplateName *QTN =
2690  Template.getAsQualifiedTemplateName())
2691  Builder.MakeTrivial(Context, QTN->getQualifier(), Loc);
2692 
2693  if (Arg.getKind() == TemplateArgument::Template)
2694  return TemplateArgumentLoc(Context, Arg,
2695  Builder.getWithLocInContext(Context), Loc);
2696 
2697  return TemplateArgumentLoc(
2698  Context, Arg, Builder.getWithLocInContext(Context), Loc, Loc);
2699  }
2700 
2702  return TemplateArgumentLoc(Arg, Arg.getAsExpr());
2703 
2706  }
2707 
2708  llvm_unreachable("Invalid TemplateArgument Kind!");
2709 }
2710 
2713  SourceLocation Location) {
2714  return getTrivialTemplateArgumentLoc(
2715  Context.getInjectedTemplateArg(TemplateParm), QualType(), Location);
2716 }
2717 
2718 /// Convert the given deduced template argument and add it to the set of
2719 /// fully-converted template arguments.
2720 static bool
2723  NamedDecl *Template,
2724  TemplateDeductionInfo &Info,
2725  bool IsDeduced,
2726  SmallVectorImpl<TemplateArgument> &Output) {
2727  auto ConvertArg = [&](DeducedTemplateArgument Arg,
2728  unsigned ArgumentPackIndex) {
2729  // Convert the deduced template argument into a template
2730  // argument that we can check, almost as if the user had written
2731  // the template argument explicitly.
2732  TemplateArgumentLoc ArgLoc =
2734 
2735  // Check the template argument, converting it as necessary.
2736  return S.CheckTemplateArgument(
2737  Param, ArgLoc, Template, Template->getLocation(),
2738  Template->getSourceRange().getEnd(), ArgumentPackIndex, Output,
2739  IsDeduced
2743  };
2744 
2745  if (Arg.getKind() == TemplateArgument::Pack) {
2746  // This is a template argument pack, so check each of its arguments against
2747  // the template parameter.
2748  SmallVector<TemplateArgument, 2> PackedArgsBuilder;
2749  for (const auto &P : Arg.pack_elements()) {
2750  // When converting the deduced template argument, append it to the
2751  // general output list. We need to do this so that the template argument
2752  // checking logic has all of the prior template arguments available.
2753  DeducedTemplateArgument InnerArg(P);
2755  assert(InnerArg.getKind() != TemplateArgument::Pack &&
2756  "deduced nested pack");
2757  if (P.isNull()) {
2758  // We deduced arguments for some elements of this pack, but not for
2759  // all of them. This happens if we get a conditionally-non-deduced
2760  // context in a pack expansion (such as an overload set in one of the
2761  // arguments).
2762  S.Diag(Param->getLocation(),
2763  diag::err_template_arg_deduced_incomplete_pack)
2764  << Arg << Param;
2765  return true;
2766  }
2767  if (ConvertArg(InnerArg, PackedArgsBuilder.size()))
2768  return true;
2769 
2770  // Move the converted template argument into our argument pack.
2771  PackedArgsBuilder.push_back(Output.pop_back_val());
2772  }
2773 
2774  // If the pack is empty, we still need to substitute into the parameter
2775  // itself, in case that substitution fails.
2776  if (PackedArgsBuilder.empty()) {
2779  MultiLevelTemplateArgumentList Args(TemplateArgs);
2780 
2781  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
2782  Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
2783  NTTP, Output,
2784  Template->getSourceRange());
2785  if (Inst.isInvalid() ||
2786  S.SubstType(NTTP->getType(), Args, NTTP->getLocation(),
2787  NTTP->getDeclName()).isNull())
2788  return true;
2789  } else if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(Param)) {
2790  Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
2791  TTP, Output,
2792  Template->getSourceRange());
2793  if (Inst.isInvalid() || !S.SubstDecl(TTP, S.CurContext, Args))
2794  return true;
2795  }
2796  // For type parameters, no substitution is ever required.
2797  }
2798 
2799  // Create the resulting argument pack.
2800  Output.push_back(
2801  TemplateArgument::CreatePackCopy(S.Context, PackedArgsBuilder));
2802  return false;
2803  }
2804 
2805  return ConvertArg(Arg, 0);
2806 }
2807 
2808 // FIXME: This should not be a template, but
2809 // ClassTemplatePartialSpecializationDecl sadly does not derive from
2810 // TemplateDecl.
2811 template<typename TemplateDeclT>
2813  Sema &S, TemplateDeclT *Template, bool IsDeduced,
2814  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
2815  TemplateDeductionInfo &Info, SmallVectorImpl<TemplateArgument> &Builder,
2816  LocalInstantiationScope *CurrentInstantiationScope = nullptr,
2817  unsigned NumAlreadyConverted = 0, bool PartialOverloading = false) {
2818  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
2819 
2820  for (unsigned I = 0, N = TemplateParams->size(); I != N; ++I) {
2821  NamedDecl *Param = TemplateParams->getParam(I);
2822 
2823  // C++0x [temp.arg.explicit]p3:
2824  // A trailing template parameter pack (14.5.3) not otherwise deduced will
2825  // be deduced to an empty sequence of template arguments.
2826  // FIXME: Where did the word "trailing" come from?
2827  if (Deduced[I].isNull() && Param->isTemplateParameterPack()) {
2828  if (auto Result =
2829  PackDeductionScope(S, TemplateParams, Deduced, Info, I).finish())
2830  return Result;
2831  }
2832 
2833  if (!Deduced[I].isNull()) {
2834  if (I < NumAlreadyConverted) {
2835  // We may have had explicitly-specified template arguments for a
2836  // template parameter pack (that may or may not have been extended
2837  // via additional deduced arguments).
2838  if (Param->isParameterPack() && CurrentInstantiationScope &&
2839  CurrentInstantiationScope->getPartiallySubstitutedPack() == Param) {
2840  // Forget the partially-substituted pack; its substitution is now
2841  // complete.
2842  CurrentInstantiationScope->ResetPartiallySubstitutedPack();
2843  // We still need to check the argument in case it was extended by
2844  // deduction.
2845  } else {
2846  // We have already fully type-checked and converted this
2847  // argument, because it was explicitly-specified. Just record the
2848  // presence of this argument.
2849  Builder.push_back(Deduced[I]);
2850  continue;
2851  }
2852  }
2853 
2854  // We may have deduced this argument, so it still needs to be
2855  // checked and converted.
2856  if (ConvertDeducedTemplateArgument(S, Param, Deduced[I], Template, Info,
2857  IsDeduced, Builder)) {
2858  Info.Param = makeTemplateParameter(Param);
2859  // FIXME: These template arguments are temporary. Free them!
2862  }
2863 
2864  continue;
2865  }
2866 
2867  // Substitute into the default template argument, if available.
2868  bool HasDefaultArg = false;
2869  TemplateDecl *TD = dyn_cast<TemplateDecl>(Template);
2870  if (!TD) {
2871  assert(isa<ClassTemplatePartialSpecializationDecl>(Template) ||
2872  isa<VarTemplatePartialSpecializationDecl>(Template));
2873  return Sema::TDK_Incomplete;
2874  }
2875 
2877  TD, TD->getLocation(), TD->getSourceRange().getEnd(), Param, Builder,
2878  HasDefaultArg);
2879 
2880  // If there was no default argument, deduction is incomplete.
2881  if (DefArg.getArgument().isNull()) {
2883  const_cast<NamedDecl *>(TemplateParams->getParam(I)));
2885  if (PartialOverloading) break;
2886 
2887  return HasDefaultArg ? Sema::TDK_SubstitutionFailure
2889  }
2890 
2891  // Check whether we can actually use the default argument.
2892  if (S.CheckTemplateArgument(Param, DefArg, TD, TD->getLocation(),
2893  TD->getSourceRange().getEnd(), 0, Builder,
2896  const_cast<NamedDecl *>(TemplateParams->getParam(I)));
2897  // FIXME: These template arguments are temporary. Free them!
2900  }
2901 
2902  // If we get here, we successfully used the default template argument.
2903  }
2904 
2905  return Sema::TDK_Success;
2906 }
2907 
2909  if (auto *DC = dyn_cast<DeclContext>(D))
2910  return DC;
2911  return D->getDeclContext();
2912 }
2913 
2914 template<typename T> struct IsPartialSpecialization {
2915  static constexpr bool value = false;
2916 };
2917 template<>
2919  static constexpr bool value = true;
2920 };
2921 template<>
2923  static constexpr bool value = true;
2924 };
2925 
2926 template<typename TemplateDeclT>
2928 CheckDeducedArgumentConstraints(Sema& S, TemplateDeclT *Template,
2929  ArrayRef<TemplateArgument> DeducedArgs,
2930  TemplateDeductionInfo& Info) {
2931  llvm::SmallVector<const Expr *, 3> AssociatedConstraints;
2932  Template->getAssociatedConstraints(AssociatedConstraints);
2933  if (S.CheckConstraintSatisfaction(Template, AssociatedConstraints,
2934  DeducedArgs, Info.getLocation(),
2937  Info.reset(TemplateArgumentList::CreateCopy(S.Context, DeducedArgs));
2939  }
2940  return Sema::TDK_Success;
2941 }
2942 
2943 /// Complete template argument deduction for a partial specialization.
2944 template <typename T>
2945 static std::enable_if_t<IsPartialSpecialization<T>::value,
2948  Sema &S, T *Partial, bool IsPartialOrdering,
2949  const TemplateArgumentList &TemplateArgs,
2950  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
2951  TemplateDeductionInfo &Info) {
2952  // Unevaluated SFINAE context.
2955  Sema::SFINAETrap Trap(S);
2956 
2957  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Partial));
2958 
2959  // C++ [temp.deduct.type]p2:
2960  // [...] or if any template argument remains neither deduced nor
2961  // explicitly specified, template argument deduction fails.
2963  if (auto Result = ConvertDeducedTemplateArguments(
2964  S, Partial, IsPartialOrdering, Deduced, Info, Builder))
2965  return Result;
2966 
2967  // Form the template argument list from the deduced template arguments.
2968  TemplateArgumentList *DeducedArgumentList
2970 
2971  Info.reset(DeducedArgumentList);
2972 
2973  // Substitute the deduced template arguments into the template
2974  // arguments of the class template partial specialization, and
2975  // verify that the instantiated template arguments are both valid
2976  // and are equivalent to the template arguments originally provided
2977  // to the class template.
2978  LocalInstantiationScope InstScope(S);
2979  auto *Template = Partial->getSpecializedTemplate();
2980  const ASTTemplateArgumentListInfo *PartialTemplArgInfo =
2981  Partial->getTemplateArgsAsWritten();
2982  const TemplateArgumentLoc *PartialTemplateArgs =
2983  PartialTemplArgInfo->getTemplateArgs();
2984 
2985  TemplateArgumentListInfo InstArgs(PartialTemplArgInfo->LAngleLoc,
2986  PartialTemplArgInfo->RAngleLoc);
2987 
2988  if (S.Subst(PartialTemplateArgs, PartialTemplArgInfo->NumTemplateArgs,
2989  InstArgs, MultiLevelTemplateArgumentList(*DeducedArgumentList))) {
2990  unsigned ArgIdx = InstArgs.size(), ParamIdx = ArgIdx;
2991  if (ParamIdx >= Partial->getTemplateParameters()->size())
2992  ParamIdx = Partial->getTemplateParameters()->size() - 1;
2993 
2994  Decl *Param = const_cast<NamedDecl *>(
2995  Partial->getTemplateParameters()->getParam(ParamIdx));
2996  Info.Param = makeTemplateParameter(Param);
2997  Info.FirstArg = PartialTemplateArgs[ArgIdx].getArgument();
2999  }
3000 
3001  bool ConstraintsNotSatisfied;
3002  SmallVector<TemplateArgument, 4> ConvertedInstArgs;
3003  if (S.CheckTemplateArgumentList(Template, Partial->getLocation(), InstArgs,
3004  false, ConvertedInstArgs,
3005  /*UpdateArgsWithConversions=*/true,
3006  &ConstraintsNotSatisfied))
3007  return ConstraintsNotSatisfied ? Sema::TDK_ConstraintsNotSatisfied :
3009 
3010  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
3011  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
3012  TemplateArgument InstArg = ConvertedInstArgs.data()[I];
3013  if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg)) {
3014  Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
3015  Info.FirstArg = TemplateArgs[I];
3016  Info.SecondArg = InstArg;
3018  }
3019  }
3020 
3021  if (Trap.hasErrorOccurred())
3023 
3024  if (auto Result = CheckDeducedArgumentConstraints(S, Partial, Builder, Info))
3025  return Result;
3026 
3027  return Sema::TDK_Success;
3028 }
3029 
3030 /// Complete template argument deduction for a class or variable template,
3031 /// when partial ordering against a partial specialization.
3032 // FIXME: Factor out duplication with partial specialization version above.
3034  Sema &S, TemplateDecl *Template, bool PartialOrdering,
3035  const TemplateArgumentList &TemplateArgs,
3036  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3037  TemplateDeductionInfo &Info) {
3038  // Unevaluated SFINAE context.
3041  Sema::SFINAETrap Trap(S);
3042 
3043  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Template));
3044 
3045  // C++ [temp.deduct.type]p2:
3046  // [...] or if any template argument remains neither deduced nor
3047  // explicitly specified, template argument deduction fails.
3049  if (auto Result = ConvertDeducedTemplateArguments(
3050  S, Template, /*IsDeduced*/PartialOrdering, Deduced, Info, Builder))
3051  return Result;
3052 
3053  // Check that we produced the correct argument list.
3054  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
3055  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
3056  TemplateArgument InstArg = Builder[I];
3057  if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg,
3058  /*PackExpansionMatchesPack*/true)) {
3059  Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
3060  Info.FirstArg = TemplateArgs[I];
3061  Info.SecondArg = InstArg;
3063  }
3064  }
3065 
3066  if (Trap.hasErrorOccurred())
3068 
3069  if (auto Result = CheckDeducedArgumentConstraints(S, Template, Builder,
3070  Info))
3071  return Result;
3072 
3073  return Sema::TDK_Success;
3074 }
3075 
3076 /// Perform template argument deduction to determine whether
3077 /// the given template arguments match the given class template
3078 /// partial specialization per C++ [temp.class.spec.match].
3081  const TemplateArgumentList &TemplateArgs,
3082  TemplateDeductionInfo &Info) {
3083  if (Partial->isInvalidDecl())
3084  return TDK_Invalid;
3085 
3086  // C++ [temp.class.spec.match]p2:
3087  // A partial specialization matches a given actual template
3088  // argument list if the template arguments of the partial
3089  // specialization can be deduced from the actual template argument
3090  // list (14.8.2).
3091 
3092  // Unevaluated SFINAE context.
3095  SFINAETrap Trap(*this);
3096 
3098  Deduced.resize(Partial->getTemplateParameters()->size());
3099  if (TemplateDeductionResult Result
3100  = ::DeduceTemplateArguments(*this,
3101  Partial->getTemplateParameters(),
3102  Partial->getTemplateArgs(),
3103  TemplateArgs, Info, Deduced))
3104  return Result;
3105 
3106  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3107  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
3108  Info);
3109  if (Inst.isInvalid())
3110  return TDK_InstantiationDepth;
3111 
3112  if (Trap.hasErrorOccurred())
3114 
3115  TemplateDeductionResult Result;
3116  runWithSufficientStackSpace(Info.getLocation(), [&] {
3117  Result = ::FinishTemplateArgumentDeduction(*this, Partial,
3118  /*IsPartialOrdering=*/false,
3119  TemplateArgs, Deduced, Info);
3120  });
3121  return Result;
3122 }
3123 
3124 /// Perform template argument deduction to determine whether
3125 /// the given template arguments match the given variable template
3126 /// partial specialization per C++ [temp.class.spec.match].
3129  const TemplateArgumentList &TemplateArgs,
3130  TemplateDeductionInfo &Info) {
3131  if (Partial->isInvalidDecl())
3132  return TDK_Invalid;
3133 
3134  // C++ [temp.class.spec.match]p2:
3135  // A partial specialization matches a given actual template
3136  // argument list if the template arguments of the partial
3137  // specialization can be deduced from the actual template argument
3138  // list (14.8.2).
3139 
3140  // Unevaluated SFINAE context.
3143  SFINAETrap Trap(*this);
3144 
3146  Deduced.resize(Partial->getTemplateParameters()->size());
3148  *this, Partial->getTemplateParameters(), Partial->getTemplateArgs(),
3149  TemplateArgs, Info, Deduced))
3150  return Result;
3151 
3152  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3153  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
3154  Info);
3155  if (Inst.isInvalid())
3156  return TDK_InstantiationDepth;
3157 
3158  if (Trap.hasErrorOccurred())
3160 
3161  TemplateDeductionResult Result;
3162  runWithSufficientStackSpace(Info.getLocation(), [&] {
3163  Result = ::FinishTemplateArgumentDeduction(*this, Partial,
3164  /*IsPartialOrdering=*/false,
3165  TemplateArgs, Deduced, Info);
3166  });
3167  return Result;
3168 }
3169 
3170 /// Determine whether the given type T is a simple-template-id type.
3172  if (const TemplateSpecializationType *Spec
3174  return Spec->getTemplateName().getAsTemplateDecl() != nullptr;
3175 
3176  // C++17 [temp.local]p2:
3177  // the injected-class-name [...] is equivalent to the template-name followed
3178  // by the template-arguments of the class template specialization or partial
3179  // specialization enclosed in <>
3180  // ... which means it's equivalent to a simple-template-id.
3181  //
3182  // This only arises during class template argument deduction for a copy
3183  // deduction candidate, where it permits slicing.
3184  if (T->getAs<InjectedClassNameType>())
3185  return true;
3186 
3187  return false;
3188 }
3189 
3190 /// Substitute the explicitly-provided template arguments into the
3191 /// given function template according to C++ [temp.arg.explicit].
3192 ///
3193 /// \param FunctionTemplate the function template into which the explicit
3194 /// template arguments will be substituted.
3195 ///
3196 /// \param ExplicitTemplateArgs the explicitly-specified template
3197 /// arguments.
3198 ///
3199 /// \param Deduced the deduced template arguments, which will be populated
3200 /// with the converted and checked explicit template arguments.
3201 ///
3202 /// \param ParamTypes will be populated with the instantiated function
3203 /// parameters.
3204 ///
3205 /// \param FunctionType if non-NULL, the result type of the function template
3206 /// will also be instantiated and the pointed-to value will be updated with
3207 /// the instantiated function type.
3208 ///
3209 /// \param Info if substitution fails for any reason, this object will be
3210 /// populated with more information about the failure.
3211 ///
3212 /// \returns TDK_Success if substitution was successful, or some failure
3213 /// condition.
3216  FunctionTemplateDecl *FunctionTemplate,
3217  TemplateArgumentListInfo &ExplicitTemplateArgs,
3219  SmallVectorImpl<QualType> &ParamTypes,
3221  TemplateDeductionInfo &Info) {
3222  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
3223  TemplateParameterList *TemplateParams
3224  = FunctionTemplate->getTemplateParameters();
3225 
3226  if (ExplicitTemplateArgs.size() == 0) {
3227  // No arguments to substitute; just copy over the parameter types and
3228  // fill in the function type.
3229  for (auto P : Function->parameters())
3230  ParamTypes.push_back(P->getType());
3231 
3232  if (FunctionType)
3233  *FunctionType = Function->getType();
3234  return TDK_Success;
3235  }
3236 
3237  // Unevaluated SFINAE context.
3240  SFINAETrap Trap(*this);
3241 
3242  // C++ [temp.arg.explicit]p3:
3243  // Template arguments that are present shall be specified in the
3244  // declaration order of their corresponding template-parameters. The
3245  // template argument list shall not specify more template-arguments than
3246  // there are corresponding template-parameters.
3248 
3249  // Enter a new template instantiation context where we check the
3250  // explicitly-specified template arguments against this function template,
3251  // and then substitute them into the function parameter types.
3253  InstantiatingTemplate Inst(
3254  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3255  CodeSynthesisContext::ExplicitTemplateArgumentSubstitution, Info);
3256  if (Inst.isInvalid())
3257  return TDK_InstantiationDepth;
3258 
3259  if (CheckTemplateArgumentList(FunctionTemplate, SourceLocation(),
3260  ExplicitTemplateArgs, true, Builder, false) ||
3261  Trap.hasErrorOccurred()) {
3262  unsigned Index = Builder.size();
3263  if (Index >= TemplateParams->size())
3264  return TDK_SubstitutionFailure;
3265  Info.Param = makeTemplateParameter(TemplateParams->getParam(Index));
3266  return TDK_InvalidExplicitArguments;
3267  }
3268 
3269  // Form the template argument list from the explicitly-specified
3270  // template arguments.
3271  TemplateArgumentList *ExplicitArgumentList
3272  = TemplateArgumentList::CreateCopy(Context, Builder);
3273  Info.setExplicitArgs(ExplicitArgumentList);
3274 
3275  // Template argument deduction and the final substitution should be
3276  // done in the context of the templated declaration. Explicit
3277  // argument substitution, on the other hand, needs to happen in the
3278  // calling context.
3279  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3280 
3281  // If we deduced template arguments for a template parameter pack,
3282  // note that the template argument pack is partially substituted and record
3283  // the explicit template arguments. They'll be used as part of deduction
3284  // for this template parameter pack.
3285  unsigned PartiallySubstitutedPackIndex = -1u;
3286  if (!Builder.empty()) {
3287  const TemplateArgument &Arg = Builder.back();
3288  if (Arg.getKind() == TemplateArgument::Pack) {
3289  auto *Param = TemplateParams->getParam(Builder.size() - 1);
3290  // If this is a fully-saturated fixed-size pack, it should be
3291  // fully-substituted, not partially-substituted.
3292  Optional<unsigned> Expansions = getExpandedPackSize(Param);
3293  if (!Expansions || Arg.pack_size() < *Expansions) {
3294  PartiallySubstitutedPackIndex = Builder.size() - 1;
3295  CurrentInstantiationScope->SetPartiallySubstitutedPack(
3296  Param, Arg.pack_begin(), Arg.pack_size());
3297  }
3298  }
3299  }
3300 
3301  const FunctionProtoType *Proto
3302  = Function->getType()->getAs<FunctionProtoType>();
3303  assert(Proto && "Function template does not have a prototype?");
3304 
3305  // Isolate our substituted parameters from our caller.
3306  LocalInstantiationScope InstScope(*this, /*MergeWithOuterScope*/true);
3307 
3308  ExtParameterInfoBuilder ExtParamInfos;
3309 
3310  // Instantiate the types of each of the function parameters given the
3311  // explicitly-specified template arguments. If the function has a trailing
3312  // return type, substitute it after the arguments to ensure we substitute
3313  // in lexical order.
3314  if (Proto->hasTrailingReturn()) {
3315  if (SubstParmTypes(Function->getLocation(), Function->parameters(),
3316  Proto->getExtParameterInfosOrNull(),
3317  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3318  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3319  return TDK_SubstitutionFailure;
3320  }
3321 
3322  // Instantiate the return type.
3323  QualType ResultType;
3324  {
3325  // C++11 [expr.prim.general]p3:
3326  // If a declaration declares a member function or member function
3327  // template of a class X, the expression this is a prvalue of type
3328  // "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
3329  // and the end of the function-definition, member-declarator, or
3330  // declarator.
3331  Qualifiers ThisTypeQuals;
3332  CXXRecordDecl *ThisContext = nullptr;
3333  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Function)) {
3334  ThisContext = Method->getParent();
3335  ThisTypeQuals = Method->getMethodQualifiers();
3336  }
3337 
3338  CXXThisScopeRAII ThisScope(*this, ThisContext, ThisTypeQuals,
3339  getLangOpts().CPlusPlus11);
3340 
3341  ResultType =
3342  SubstType(Proto->getReturnType(),
3343  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3344  Function->getTypeSpecStartLoc(), Function->getDeclName());
3345  if (ResultType.isNull() || Trap.hasErrorOccurred())
3346  return TDK_SubstitutionFailure;
3347  // CUDA: Kernel function must have 'void' return type.
3348  if (getLangOpts().CUDA)
3349  if (Function->hasAttr<CUDAGlobalAttr>() && !ResultType->isVoidType()) {
3350  Diag(Function->getLocation(), diag::err_kern_type_not_void_return)
3351  << Function->getType() << Function->getSourceRange();
3352  return TDK_SubstitutionFailure;
3353  }
3354  }
3355 
3356  // Instantiate the types of each of the function parameters given the
3357  // explicitly-specified template arguments if we didn't do so earlier.
3358  if (!Proto->hasTrailingReturn() &&
3359  SubstParmTypes(Function->getLocation(), Function->parameters(),
3360  Proto->getExtParameterInfosOrNull(),
3361  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3362  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3363  return TDK_SubstitutionFailure;
3364 
3365  if (FunctionType) {
3366  auto EPI = Proto->getExtProtoInfo();
3367  EPI.ExtParameterInfos = ExtParamInfos.getPointerOrNull(ParamTypes.size());
3368 
3369  // In C++1z onwards, exception specifications are part of the function type,
3370  // so substitution into the type must also substitute into the exception
3371  // specification.
3372  SmallVector<QualType, 4> ExceptionStorage;
3373  if (getLangOpts().CPlusPlus17 &&
3374  SubstExceptionSpec(
3375  Function->getLocation(), EPI.ExceptionSpec, ExceptionStorage,
3376  MultiLevelTemplateArgumentList(*ExplicitArgumentList)))
3377  return TDK_SubstitutionFailure;
3378 
3379  *FunctionType = BuildFunctionType(ResultType, ParamTypes,
3380  Function->getLocation(),
3381  Function->getDeclName(),
3382  EPI);
3383  if (FunctionType->isNull() || Trap.hasErrorOccurred())
3384  return TDK_SubstitutionFailure;
3385  }
3386 
3387  // C++ [temp.arg.explicit]p2:
3388  // Trailing template arguments that can be deduced (14.8.2) may be
3389  // omitted from the list of explicit template-arguments. If all of the
3390  // template arguments can be deduced, they may all be omitted; in this
3391  // case, the empty template argument list <> itself may also be omitted.
3392  //
3393  // Take all of the explicitly-specified arguments and put them into
3394  // the set of deduced template arguments. The partially-substituted
3395  // parameter pack, however, will be set to NULL since the deduction
3396  // mechanism handles the partially-substituted argument pack directly.
3397  Deduced.reserve(TemplateParams->size());
3398  for (unsigned I = 0, N = ExplicitArgumentList->size(); I != N; ++I) {
3399  const TemplateArgument &Arg = ExplicitArgumentList->get(I);
3400  if (I == PartiallySubstitutedPackIndex)
3401  Deduced.push_back(DeducedTemplateArgument());
3402  else
3403  Deduced.push_back(Arg);
3404  }
3405 
3406  return TDK_Success;
3407 }
3408 
3409 /// Check whether the deduced argument type for a call to a function
3410 /// template matches the actual argument type per C++ [temp.deduct.call]p4.
3413  Sema::OriginalCallArg OriginalArg,
3414  QualType DeducedA) {
3415  ASTContext &Context = S.Context;
3416 
3417  auto Failed = [&]() -> Sema::TemplateDeductionResult {
3418  Info.FirstArg = TemplateArgument(DeducedA);
3419  Info.SecondArg = TemplateArgument(OriginalArg.OriginalArgType);
3420  Info.CallArgIndex = OriginalArg.ArgIdx;
3423  };
3424 
3425  QualType A = OriginalArg.OriginalArgType;
3426  QualType OriginalParamType = OriginalArg.OriginalParamType;
3427 
3428  // Check for type equality (top-level cv-qualifiers are ignored).
3429  if (Context.hasSameUnqualifiedType(A, DeducedA))
3430  return Sema::TDK_Success;
3431 
3432  // Strip off references on the argument types; they aren't needed for
3433  // the following checks.
3434  if (const ReferenceType *DeducedARef = DeducedA->getAs<ReferenceType>())
3435  DeducedA = DeducedARef->getPointeeType();
3436  if (const ReferenceType *ARef = A->getAs<ReferenceType>())
3437  A = ARef->getPointeeType();
3438 
3439  // C++ [temp.deduct.call]p4:
3440  // [...] However, there are three cases that allow a difference:
3441  // - If the original P is a reference type, the deduced A (i.e., the
3442  // type referred to by the reference) can be more cv-qualified than
3443  // the transformed A.
3444  if (const ReferenceType *OriginalParamRef
3445  = OriginalParamType->getAs<ReferenceType>()) {
3446  // We don't want to keep the reference around any more.
3447  OriginalParamType = OriginalParamRef->getPointeeType();
3448 
3449  // FIXME: Resolve core issue (no number yet): if the original P is a
3450  // reference type and the transformed A is function type "noexcept F",
3451  // the deduced A can be F.
3452  QualType Tmp;
3453  if (A->isFunctionType() && S.IsFunctionConversion(A, DeducedA, Tmp))
3454  return Sema::TDK_Success;
3455 
3456  Qualifiers AQuals = A.getQualifiers();
3457  Qualifiers DeducedAQuals = DeducedA.getQualifiers();
3458 
3459  // Under Objective-C++ ARC, the deduced type may have implicitly
3460  // been given strong or (when dealing with a const reference)
3461  // unsafe_unretained lifetime. If so, update the original
3462  // qualifiers to include this lifetime.
3463  if (S.getLangOpts().ObjCAutoRefCount &&
3464  ((DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_Strong &&
3465  AQuals.getObjCLifetime() == Qualifiers::OCL_None) ||
3466  (DeducedAQuals.hasConst() &&
3467  DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone))) {
3468  AQuals.setObjCLifetime(DeducedAQuals.getObjCLifetime());
3469  }
3470 
3471  if (AQuals == DeducedAQuals) {
3472  // Qualifiers match; there's nothing to do.
3473  } else if (!DeducedAQuals.compatiblyIncludes(AQuals)) {
3474  return Failed();
3475  } else {
3476  // Qualifiers are compatible, so have the argument type adopt the
3477  // deduced argument type's qualifiers as if we had performed the
3478  // qualification conversion.
3479  A = Context.getQualifiedType(A.getUnqualifiedType(), DeducedAQuals);
3480  }
3481  }
3482 
3483  // - The transformed A can be another pointer or pointer to member
3484  // type that can be converted to the deduced A via a function pointer
3485  // conversion and/or a qualification conversion.
3486  //
3487  // Also allow conversions which merely strip __attribute__((noreturn)) from
3488  // function types (recursively).
3489  bool ObjCLifetimeConversion = false;
3490  QualType ResultTy;
3491  if ((A->isAnyPointerType() || A->isMemberPointerType()) &&
3492  (S.IsQualificationConversion(A, DeducedA, false,
3493  ObjCLifetimeConversion) ||
3494  S.IsFunctionConversion(A, DeducedA, ResultTy)))
3495  return Sema::TDK_Success;
3496 
3497  // - If P is a class and P has the form simple-template-id, then the
3498  // transformed A can be a derived class of the deduced A. [...]
3499  // [...] Likewise, if P is a pointer to a class of the form
3500  // simple-template-id, the transformed A can be a pointer to a
3501  // derived class pointed to by the deduced A.
3502  if (const PointerType *OriginalParamPtr
3503  = OriginalParamType->getAs<PointerType>()) {
3504  if (const PointerType *DeducedAPtr = DeducedA->getAs<PointerType>()) {
3505  if (const PointerType *APtr = A->getAs<PointerType>()) {
3506  if (A->getPointeeType()->isRecordType()) {
3507  OriginalParamType = OriginalParamPtr->getPointeeType();
3508  DeducedA = DeducedAPtr->getPointeeType();
3509  A = APtr->getPointeeType();
3510  }
3511  }
3512  }
3513  }
3514 
3515  if (Context.hasSameUnqualifiedType(A, DeducedA))
3516  return Sema::TDK_Success;
3517 
3518  if (A->isRecordType() && isSimpleTemplateIdType(OriginalParamType) &&
3519  S.IsDerivedFrom(Info.getLocation(), A, DeducedA))
3520  return Sema::TDK_Success;
3521 
3522  return Failed();
3523 }
3524 
3525 /// Find the pack index for a particular parameter index in an instantiation of
3526 /// a function template with specific arguments.
3527 ///
3528 /// \return The pack index for whichever pack produced this parameter, or -1
3529 /// if this was not produced by a parameter. Intended to be used as the
3530 /// ArgumentPackSubstitutionIndex for further substitutions.
3531 // FIXME: We should track this in OriginalCallArgs so we don't need to
3532 // reconstruct it here.
3533 static unsigned getPackIndexForParam(Sema &S,
3534  FunctionTemplateDecl *FunctionTemplate,
3535  const MultiLevelTemplateArgumentList &Args,
3536  unsigned ParamIdx) {
3537  unsigned Idx = 0;
3538  for (auto *PD : FunctionTemplate->getTemplatedDecl()->parameters()) {
3539  if (PD->isParameterPack()) {
3540  unsigned NumExpansions =
3541  S.getNumArgumentsInExpansion(PD->getType(), Args).getValueOr(1);
3542  if (Idx + NumExpansions > ParamIdx)
3543  return ParamIdx - Idx;
3544  Idx += NumExpansions;
3545  } else {
3546  if (Idx == ParamIdx)
3547  return -1; // Not a pack expansion
3548  ++Idx;
3549  }
3550  }
3551 
3552  llvm_unreachable("parameter index would not be produced from template");
3553 }
3554 
3555 /// Finish template argument deduction for a function template,
3556 /// checking the deduced template arguments for completeness and forming
3557 /// the function template specialization.
3558 ///
3559 /// \param OriginalCallArgs If non-NULL, the original call arguments against
3560 /// which the deduced argument types should be compared.
3562  FunctionTemplateDecl *FunctionTemplate,
3564  unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
3565  TemplateDeductionInfo &Info,
3566  SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
3567  bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
3568  // Unevaluated SFINAE context.
3571  SFINAETrap Trap(*this);
3572 
3573  // Enter a new template instantiation context while we instantiate the
3574  // actual function declaration.
3575  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3576  InstantiatingTemplate Inst(
3577  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3578  CodeSynthesisContext::DeducedTemplateArgumentSubstitution, Info);
3579  if (Inst.isInvalid())
3580  return TDK_InstantiationDepth;
3581 
3582  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3583 
3584  // C++ [temp.deduct.type]p2:
3585  // [...] or if any template argument remains neither deduced nor
3586  // explicitly specified, template argument deduction fails.
3588  if (auto Result = ConvertDeducedTemplateArguments(
3589  *this, FunctionTemplate, /*IsDeduced*/true, Deduced, Info, Builder,
3590  CurrentInstantiationScope, NumExplicitlySpecified,
3591  PartialOverloading))
3592  return Result;
3593 
3594  // C++ [temp.deduct.call]p10: [DR1391]
3595  // If deduction succeeds for all parameters that contain
3596  // template-parameters that participate in template argument deduction,
3597  // and all template arguments are explicitly specified, deduced, or
3598  // obtained from default template arguments, remaining parameters are then
3599  // compared with the corresponding arguments. For each remaining parameter
3600  // P with a type that was non-dependent before substitution of any
3601  // explicitly-specified template arguments, if the corresponding argument
3602  // A cannot be implicitly converted to P, deduction fails.
3603  if (CheckNonDependent())
3604  return TDK_NonDependentConversionFailure;
3605 
3606  // Form the template argument list from the deduced template arguments.
3607  TemplateArgumentList *DeducedArgumentList
3608  = TemplateArgumentList::CreateCopy(Context, Builder);
3609  Info.reset(DeducedArgumentList);
3610 
3611  // Substitute the deduced template arguments into the function template
3612  // declaration to produce the function template specialization.
3613  DeclContext *Owner = FunctionTemplate->getDeclContext();
3614  if (FunctionTemplate->getFriendObjectKind())
3615  Owner = FunctionTemplate->getLexicalDeclContext();
3616  MultiLevelTemplateArgumentList SubstArgs(*DeducedArgumentList);
3617  Specialization = cast_or_null<FunctionDecl>(
3618  SubstDecl(FunctionTemplate->getTemplatedDecl(), Owner, SubstArgs));
3619  if (!Specialization || Specialization->isInvalidDecl())
3620  return TDK_SubstitutionFailure;
3621 
3622  assert(Specialization->getPrimaryTemplate()->getCanonicalDecl() ==
3623  FunctionTemplate->getCanonicalDecl());
3624 
3625  // If the template argument list is owned by the function template
3626  // specialization, release it.
3627  if (Specialization->getTemplateSpecializationArgs() == DeducedArgumentList &&
3628  !Trap.hasErrorOccurred())
3629  Info.take();
3630 
3631  // There may have been an error that did not prevent us from constructing a
3632  // declaration. Mark the declaration invalid and return with a substitution
3633  // failure.
3634  if (Trap.hasErrorOccurred()) {
3635  Specialization->setInvalidDecl(true);
3636  return TDK_SubstitutionFailure;
3637  }
3638 
3639  // C++2a [temp.deduct]p5
3640  // [...] When all template arguments have been deduced [...] all uses of
3641  // template parameters [...] are replaced with the corresponding deduced
3642  // or default argument values.
3643  // [...] If the function template has associated constraints
3644  // ([temp.constr.decl]), those constraints are checked for satisfaction
3645  // ([temp.constr.constr]). If the constraints are not satisfied, type
3646  // deduction fails.
3647  if (!PartialOverloading ||
3648  (Builder.size() == FunctionTemplate->getTemplateParameters()->size())) {
3649  if (CheckInstantiatedFunctionTemplateConstraints(Info.getLocation(),
3650  Specialization, Builder, Info.AssociatedConstraintsSatisfaction))
3651  return TDK_MiscellaneousDeductionFailure;
3652 
3654  Info.reset(TemplateArgumentList::CreateCopy(Context, Builder));
3655  return TDK_ConstraintsNotSatisfied;
3656  }
3657  }
3658 
3659  if (OriginalCallArgs) {
3660  // C++ [temp.deduct.call]p4:
3661  // In general, the deduction process attempts to find template argument
3662  // values that will make the deduced A identical to A (after the type A
3663  // is transformed as described above). [...]
3664  llvm::SmallDenseMap<std::pair<unsigned, QualType>, QualType> DeducedATypes;
3665  for (unsigned I = 0, N = OriginalCallArgs->size(); I != N; ++I) {
3666  OriginalCallArg OriginalArg = (*OriginalCallArgs)[I];
3667 
3668  auto ParamIdx = OriginalArg.ArgIdx;
3669  if (ParamIdx >= Specialization->getNumParams())
3670  // FIXME: This presumably means a pack ended up smaller than we
3671  // expected while deducing. Should this not result in deduction
3672  // failure? Can it even happen?
3673  continue;
3674 
3675  QualType DeducedA;
3676  if (!OriginalArg.DecomposedParam) {
3677  // P is one of the function parameters, just look up its substituted
3678  // type.
3679  DeducedA = Specialization->getParamDecl(ParamIdx)->getType();
3680  } else {
3681  // P is a decomposed element of a parameter corresponding to a
3682  // braced-init-list argument. Substitute back into P to find the
3683  // deduced A.
3684  QualType &CacheEntry =
3685  DeducedATypes[{ParamIdx, OriginalArg.OriginalParamType}];
3686  if (CacheEntry.isNull()) {
3688  *this, getPackIndexForParam(*this, FunctionTemplate, SubstArgs,
3689  ParamIdx));
3690  CacheEntry =
3691  SubstType(OriginalArg.OriginalParamType, SubstArgs,
3692  Specialization->getTypeSpecStartLoc(),
3693  Specialization->getDeclName());
3694  }
3695  DeducedA = CacheEntry;
3696  }
3697 
3698  if (auto TDK =
3699  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA))
3700  return TDK;
3701  }
3702  }
3703 
3704  // If we suppressed any diagnostics while performing template argument
3705  // deduction, and if we haven't already instantiated this declaration,
3706  // keep track of these diagnostics. They'll be emitted if this specialization
3707  // is actually used.
3708  if (Info.diag_begin() != Info.diag_end()) {
3709  SuppressedDiagnosticsMap::iterator
3710  Pos = SuppressedDiagnostics.find(Specialization->getCanonicalDecl());
3711  if (Pos == SuppressedDiagnostics.end())
3712  SuppressedDiagnostics[Specialization->getCanonicalDecl()]
3713  .append(Info.diag_begin(), Info.diag_end());
3714  }
3715 
3716  return TDK_Success;
3717 }
3718 
3719 /// Gets the type of a function for template-argument-deducton
3720 /// purposes when it's considered as part of an overload set.
3722  FunctionDecl *Fn) {
3723  // We may need to deduce the return type of the function now.
3724  if (S.getLangOpts().CPlusPlus14 && Fn->getReturnType()->isUndeducedType() &&
3725  S.DeduceReturnType(Fn, R.Expression->getExprLoc(), /*Diagnose*/ false))
3726  return {};
3727 
3728  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Fn))
3729  if (Method->isInstance()) {
3730  // An instance method that's referenced in a form that doesn't
3731  // look like a member pointer is just invalid.
3732  if (!R.HasFormOfMemberPointer)
3733  return {};
3734 
3735  return S.Context.getMemberPointerType(Fn->getType(),
3736  S.Context.getTypeDeclType(Method->getParent()).getTypePtr());
3737  }
3738 
3739  if (!R.IsAddressOfOperand) return Fn->getType();
3740  return S.Context.getPointerType(Fn->getType());
3741 }
3742 
3743 /// Apply the deduction rules for overload sets.
3744 ///
3745 /// \return the null type if this argument should be treated as an
3746 /// undeduced context
3747 static QualType
3749  Expr *Arg, QualType ParamType,
3750  bool ParamWasReference) {
3751 
3753 
3754  OverloadExpr *Ovl = R.Expression;
3755 
3756  // C++0x [temp.deduct.call]p4
3757  unsigned TDF = 0;
3758  if (ParamWasReference)
3760  if (R.IsAddressOfOperand)
3761  TDF |= TDF_IgnoreQualifiers;
3762 
3763  // C++0x [temp.deduct.call]p6:
3764  // When P is a function type, pointer to function type, or pointer
3765  // to member function type:
3766 
3767  if (!ParamType->isFunctionType() &&
3768  !ParamType->isFunctionPointerType() &&
3769  !ParamType->isMemberFunctionPointerType()) {
3770  if (Ovl->hasExplicitTemplateArgs()) {
3771  // But we can still look for an explicit specialization.
3772  if (FunctionDecl *ExplicitSpec
3774  return GetTypeOfFunction(S, R, ExplicitSpec);
3775  }
3776 
3777  DeclAccessPair DAP;
3778  if (FunctionDecl *Viable =
3780  return GetTypeOfFunction(S, R, Viable);
3781 
3782  return {};
3783  }
3784 
3785  // Gather the explicit template arguments, if any.
3786  TemplateArgumentListInfo ExplicitTemplateArgs;
3787  if (Ovl->hasExplicitTemplateArgs())
3788  Ovl->copyTemplateArgumentsInto(ExplicitTemplateArgs);
3789  QualType Match;
3790  for (UnresolvedSetIterator I = Ovl->decls_begin(),
3791  E = Ovl->decls_end(); I != E; ++I) {
3792  NamedDecl *D = (*I)->getUnderlyingDecl();
3793 
3794  if (FunctionTemplateDecl *FunTmpl = dyn_cast<FunctionTemplateDecl>(D)) {
3795  // - If the argument is an overload set containing one or more
3796  // function templates, the parameter is treated as a
3797  // non-deduced context.
3798  if (!Ovl->hasExplicitTemplateArgs())
3799  return {};
3800 
3801  // Otherwise, see if we can resolve a function type
3802  FunctionDecl *Specialization = nullptr;
3803  TemplateDeductionInfo Info(Ovl->getNameLoc());
3804  if (S.DeduceTemplateArguments(FunTmpl, &ExplicitTemplateArgs,
3805  Specialization, Info))
3806  continue;
3807 
3808  D = Specialization;
3809  }
3810 
3811  FunctionDecl *Fn = cast<FunctionDecl>(D);
3812  QualType ArgType = GetTypeOfFunction(S, R, Fn);
3813  if (ArgType.isNull()) continue;
3814 
3815  // Function-to-pointer conversion.
3816  if (!ParamWasReference && ParamType->isPointerType() &&
3817  ArgType->isFunctionType())
3818  ArgType = S.Context.getPointerType(ArgType);
3819 
3820  // - If the argument is an overload set (not containing function
3821  // templates), trial argument deduction is attempted using each
3822  // of the members of the set. If deduction succeeds for only one
3823  // of the overload set members, that member is used as the
3824  // argument value for the deduction. If deduction succeeds for
3825  // more than one member of the overload set the parameter is
3826  // treated as a non-deduced context.
3827 
3828  // We do all of this in a fresh context per C++0x [temp.deduct.type]p2:
3829  // Type deduction is done independently for each P/A pair, and
3830  // the deduced template argument values are then combined.
3831  // So we do not reject deductions which were made elsewhere.
3833  Deduced(TemplateParams->size());
3834  TemplateDeductionInfo Info(Ovl->getNameLoc());
3836  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
3837  ArgType, Info, Deduced, TDF);
3838  if (Result) continue;
3839  if (!Match.isNull())
3840  return {};
3841  Match = ArgType;
3842  }
3843 
3844  return Match;
3845 }
3846 
3847 /// Perform the adjustments to the parameter and argument types
3848 /// described in C++ [temp.deduct.call].
3849 ///
3850 /// \returns true if the caller should not attempt to perform any template
3851 /// argument deduction based on this P/A pair because the argument is an
3852 /// overloaded function set that could not be resolved.
3854  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3855  QualType &ParamType, QualType &ArgType, Expr *Arg, unsigned &TDF) {
3856  // C++0x [temp.deduct.call]p3:
3857  // If P is a cv-qualified type, the top level cv-qualifiers of P's type
3858  // are ignored for type deduction.
3859  if (ParamType.hasQualifiers())
3860  ParamType = ParamType.getUnqualifiedType();
3861 
3862  // [...] If P is a reference type, the type referred to by P is
3863  // used for type deduction.
3864  const ReferenceType *ParamRefType = ParamType->getAs<ReferenceType>();
3865  if (ParamRefType)
3866  ParamType = ParamRefType->getPointeeType();
3867 
3868  // Overload sets usually make this parameter an undeduced context,
3869  // but there are sometimes special circumstances. Typically
3870  // involving a template-id-expr.
3871  if (ArgType == S.Context.OverloadTy) {
3872  ArgType = ResolveOverloadForDeduction(S, TemplateParams,
3873  Arg, ParamType,
3874  ParamRefType != nullptr);
3875  if (ArgType.isNull())
3876  return true;
3877  }
3878 
3879  if (ParamRefType) {
3880  // If the argument has incomplete array type, try to complete its type.
3881  if (ArgType->isIncompleteArrayType()) {
3882  S.completeExprArrayBound(Arg);
3883  ArgType = Arg->getType();
3884  }
3885 
3886  // C++1z [temp.deduct.call]p3:
3887  // If P is a forwarding reference and the argument is an lvalue, the type
3888  // "lvalue reference to A" is used in place of A for type deduction.
3889  if (isForwardingReference(QualType(ParamRefType, 0), FirstInnerIndex) &&
3890  Arg->isLValue()) {
3891  if (S.getLangOpts().OpenCL)
3892  ArgType = S.Context.getAddrSpaceQualType(ArgType, LangAS::opencl_generic);
3893  ArgType = S.Context.getLValueReferenceType(ArgType);
3894  }
3895  } else {
3896  // C++ [temp.deduct.call]p2:
3897  // If P is not a reference type:
3898  // - If A is an array type, the pointer type produced by the
3899  // array-to-pointer standard conversion (4.2) is used in place of
3900  // A for type deduction; otherwise,
3901  if (ArgType->isArrayType())
3902  ArgType = S.Context.getArrayDecayedType(ArgType);
3903  // - If A is a function type, the pointer type produced by the
3904  // function-to-pointer standard conversion (4.3) is used in place
3905  // of A for type deduction; otherwise,
3906  else if (ArgType->isFunctionType())
3907  ArgType = S.Context.getPointerType(ArgType);
3908  else {
3909  // - If A is a cv-qualified type, the top level cv-qualifiers of A's
3910  // type are ignored for type deduction.
3911  ArgType = ArgType.getUnqualifiedType();
3912  }
3913  }
3914 
3915  // C++0x [temp.deduct.call]p4:
3916  // In general, the deduction process attempts to find template argument
3917  // values that will make the deduced A identical to A (after the type A
3918  // is transformed as described above). [...]
3919  TDF = TDF_SkipNonDependent;
3920 
3921  // - If the original P is a reference type, the deduced A (i.e., the
3922  // type referred to by the reference) can be more cv-qualified than
3923  // the transformed A.
3924  if (ParamRefType)
3926  // - The transformed A can be another pointer or pointer to member
3927  // type that can be converted to the deduced A via a qualification
3928  // conversion (4.4).
3929  if (ArgType->isPointerType() || ArgType->isMemberPointerType() ||
3930  ArgType->isObjCObjectPointerType())
3931  TDF |= TDF_IgnoreQualifiers;
3932  // - If P is a class and P has the form simple-template-id, then the
3933  // transformed A can be a derived class of the deduced A. Likewise,
3934  // if P is a pointer to a class of the form simple-template-id, the
3935  // transformed A can be a pointer to a derived class pointed to by
3936  // the deduced A.
3937  if (isSimpleTemplateIdType(ParamType) ||
3938  (isa<PointerType>(ParamType) &&
3940  ParamType->getAs<PointerType>()->getPointeeType())))
3941  TDF |= TDF_DerivedClass;
3942 
3943  return false;
3944 }
3945 
3946 static bool
3948  QualType T);
3949 
3951  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3952  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
3953  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3954  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
3955  bool DecomposedParam, unsigned ArgIdx, unsigned TDF);
3956 
3957 /// Attempt template argument deduction from an initializer list
3958 /// deemed to be an argument in a function call.
3960  Sema &S, TemplateParameterList *TemplateParams, QualType AdjustedParamType,
3961  InitListExpr *ILE, TemplateDeductionInfo &Info,
3962  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3963  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs, unsigned ArgIdx,
3964  unsigned TDF) {
3965  // C++ [temp.deduct.call]p1: (CWG 1591)
3966  // If removing references and cv-qualifiers from P gives
3967  // std::initializer_list<P0> or P0[N] for some P0 and N and the argument is
3968  // a non-empty initializer list, then deduction is performed instead for
3969  // each element of the initializer list, taking P0 as a function template
3970  // parameter type and the initializer element as its argument
3971  //
3972  // We've already removed references and cv-qualifiers here.
3973  if (!ILE->getNumInits())
3974  return Sema::TDK_Success;
3975 
3976  QualType ElTy;
3977  auto *ArrTy = S.Context.getAsArrayType(AdjustedParamType);
3978  if (ArrTy)
3979  ElTy = ArrTy->getElementType();
3980  else if (!S.isStdInitializerList(AdjustedParamType, &ElTy)) {
3981  // Otherwise, an initializer list argument causes the parameter to be
3982  // considered a non-deduced context
3983  return Sema::TDK_Success;
3984  }
3985 
3986  // Resolving a core issue: a braced-init-list containing any designators is
3987  // a non-deduced context.
3988  for (Expr *E : ILE->inits())
3989  if (isa<DesignatedInitExpr>(E))
3990  return Sema::TDK_Success;
3991 
3992  // Deduction only needs to be done for dependent types.
3993  if (ElTy->isDependentType()) {
3994  for (Expr *E : ILE->inits()) {
3995  if (auto Result = DeduceTemplateArgumentsFromCallArgument(
3996  S, TemplateParams, 0, ElTy, E, Info, Deduced, OriginalCallArgs, true,
3997  ArgIdx, TDF))
3998  return Result;
3999  }
4000  }
4001 
4002  // in the P0[N] case, if N is a non-type template parameter, N is deduced
4003  // from the length of the initializer list.
4004  if (auto *DependentArrTy = dyn_cast_or_null<DependentSizedArrayType>(ArrTy)) {
4005  // Determine the array bound is something we can deduce.
4006  if (const NonTypeTemplateParmDecl *NTTP =
4007  getDeducedParameterFromExpr(Info, DependentArrTy->getSizeExpr())) {
4008  // We can perform template argument deduction for the given non-type
4009  // template parameter.
4010  // C++ [temp.deduct.type]p13:
4011  // The type of N in the type T[N] is std::size_t.
4012  QualType T = S.Context.getSizeType();
4013  llvm::APInt Size(S.Context.getIntWidth(T), ILE->getNumInits());
4014  if (auto Result = DeduceNonTypeTemplateArgument(
4015  S, TemplateParams, NTTP, llvm::APSInt(Size), T,
4016  /*ArrayBound=*/true, Info, Deduced))
4017  return Result;
4018  }
4019  }
4020 
4021  return Sema::TDK_Success;
4022 }
4023 
4024 /// Perform template argument deduction per [temp.deduct.call] for a
4025 /// single parameter / argument pair.
4027  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
4028  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
4029  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
4030  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
4031  bool DecomposedParam, unsigned ArgIdx, unsigned TDF) {
4032  QualType ArgType = Arg->getType();
4033  QualType OrigParamType = ParamType;
4034 
4035  // If P is a reference type [...]
4036  // If P is a cv-qualified type [...]
4038  S, TemplateParams, FirstInnerIndex, ParamType, ArgType, Arg, TDF))
4039  return Sema::TDK_Success;
4040 
4041  // If [...] the argument is a non-empty initializer list [...]
4042  if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg))
4043  return DeduceFromInitializerList(S, TemplateParams, ParamType, ILE, Info,
4044  Deduced, OriginalCallArgs, ArgIdx, TDF);
4045 
4046  // [...] the deduction process attempts to find template argument values
4047  // that will make the deduced A identical to A
4048  //
4049  // Keep track of the argument type and corresponding parameter index,
4050  // so we can check for compatibility between the deduced A and A.
4051  OriginalCallArgs.push_back(
4052  Sema::OriginalCallArg(OrigParamType, DecomposedParam, ArgIdx, ArgType));
4053  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
4054  ArgType, Info, Deduced, TDF);
4055 }
4056 
4057 /// Perform template argument deduction from a function call
4058 /// (C++ [temp.deduct.call]).
4059 ///
4060 /// \param FunctionTemplate the function template for which we are performing
4061 /// template argument deduction.
4062 ///
4063 /// \param ExplicitTemplateArgs the explicit template arguments provided
4064 /// for this call.
4065 ///
4066 /// \param Args the function call arguments
4067 ///
4068 /// \param Specialization if template argument deduction was successful,
4069 /// this will be set to the function template specialization produced by
4070 /// template argument deduction.
4071 ///
4072 /// \param Info the argument will be updated to provide additional information
4073 /// about template argument deduction.
4074 ///
4075 /// \param CheckNonDependent A callback to invoke to check conversions for
4076 /// non-dependent parameters, between deduction and substitution, per DR1391.
4077 /// If this returns true, substitution will be skipped and we return
4078 /// TDK_NonDependentConversionFailure. The callback is passed the parameter
4079 /// types (after substituting explicit template arguments).
4080 ///
4081 /// \returns the result of template argument deduction.
4083  FunctionTemplateDecl *FunctionTemplate,
4084  TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
4085  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4086  bool PartialOverloading,
4087  llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent) {
4088  if (FunctionTemplate->isInvalidDecl())
4089  return TDK_Invalid;
4090 
4091  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
4092  unsigned NumParams = Function->getNumParams();
4093 
4094  unsigned FirstInnerIndex = getFirstInnerIndex(FunctionTemplate);
4095 
4096  // C++ [temp.deduct.call]p1:
4097  // Template argument deduction is done by comparing each function template
4098  // parameter type (call it P) with the type of the corresponding argument
4099  // of the call (call it A) as described below.
4100  if (Args.size() < Function->getMinRequiredArguments() && !PartialOverloading)
4101  return TDK_TooFewArguments;
4102  else if (TooManyArguments(NumParams, Args.size(), PartialOverloading)) {
4103  const auto *Proto = Function->getType()->castAs<FunctionProtoType>();
4104  if (Proto->isTemplateVariadic())
4105  /* Do nothing */;
4106  else if (!Proto->isVariadic())
4107  return TDK_TooManyArguments;
4108  }
4109 
4110  // The types of the parameters from which we will perform template argument
4111  // deduction.
4112  LocalInstantiationScope InstScope(*this);
4113  TemplateParameterList *TemplateParams
4114  = FunctionTemplate->getTemplateParameters();
4116  SmallVector<QualType, 8> ParamTypes;
4117  unsigned NumExplicitlySpecified = 0;
4118  if (ExplicitTemplateArgs) {
4119  TemplateDeductionResult Result;
4121  Result = SubstituteExplicitTemplateArguments(
4122  FunctionTemplate, *ExplicitTemplateArgs, Deduced, ParamTypes, nullptr,
4123  Info);
4124  });
4125  if (Result)
4126  return Result;
4127 
4128  NumExplicitlySpecified = Deduced.size();
4129  } else {
4130  // Just fill in the parameter types from the function declaration.
4131  for (unsigned I = 0; I != NumParams; ++I)
4132  ParamTypes.push_back(Function->getParamDecl(I)->getType());
4133  }
4134 
4135  SmallVector<OriginalCallArg, 8> OriginalCallArgs;
4136 
4137  // Deduce an argument of type ParamType from an expression with index ArgIdx.
4138  auto DeduceCallArgument = [&](QualType ParamType, unsigned ArgIdx) {
4139  // C++ [demp.deduct.call]p1: (DR1391)
4140  // Template argument deduction is done by comparing each function template
4141  // parameter that contains template-parameters that participate in
4142  // template argument deduction ...
4143  if (!hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
4144  return Sema::TDK_Success;
4145 
4146  // ... with the type of the corresponding argument
4148  *this, TemplateParams, FirstInnerIndex, ParamType, Args[ArgIdx], Info, Deduced,
4149  OriginalCallArgs, /*Decomposed*/false, ArgIdx, /*TDF*/ 0);
4150  };
4151 
4152  // Deduce template arguments from the function parameters.
4153  Deduced.resize(TemplateParams->size());
4154  SmallVector<QualType, 8> ParamTypesForArgChecking;
4155  for (unsigned ParamIdx = 0, NumParamTypes = ParamTypes.size(), ArgIdx = 0;
4156  ParamIdx != NumParamTypes; ++ParamIdx) {
4157  QualType ParamType = ParamTypes[ParamIdx];
4158 
4159  const PackExpansionType *ParamExpansion =
4160  dyn_cast<PackExpansionType>(ParamType);
4161  if (!ParamExpansion) {
4162  // Simple case: matching a function parameter to a function argument.
4163  if (ArgIdx >= Args.size())
4164  break;
4165 
4166  ParamTypesForArgChecking.push_back(ParamType);
4167  if (auto Result = DeduceCallArgument(ParamType, ArgIdx++))
4168  return Result;
4169 
4170  continue;
4171  }
4172 
4173  QualType ParamPattern = ParamExpansion->getPattern();
4174  PackDeductionScope PackScope(*this, TemplateParams, Deduced, Info,
4175  ParamPattern);
4176 
4177  // C++0x [temp.deduct.call]p1:
4178  // For a function parameter pack that occurs at the end of the
4179  // parameter-declaration-list, the type A of each remaining argument of
4180  // the call is compared with the type P of the declarator-id of the
4181  // function parameter pack. Each comparison deduces template arguments
4182  // for subsequent positions in the template parameter packs expanded by
4183  // the function parameter pack. When a function parameter pack appears
4184  // in a non-deduced context [not at the end of the list], the type of
4185  // that parameter pack is never deduced.
4186  //
4187  // FIXME: The above rule allows the size of the parameter pack to change
4188  // after we skip it (in the non-deduced case). That makes no sense, so
4189  // we instead notionally deduce the pack against N arguments, where N is
4190  // the length of the explicitly-specified pack if it's expanded by the
4191  // parameter pack and 0 otherwise, and we treat each deduction as a
4192  // non-deduced context.
4193  if (ParamIdx + 1 == NumParamTypes || PackScope.hasFixedArity()) {
4194  for (; ArgIdx < Args.size() && PackScope.hasNextElement();
4195  PackScope.nextPackElement(), ++ArgIdx) {
4196  ParamTypesForArgChecking.push_back(ParamPattern);
4197  if (auto Result = DeduceCallArgument(ParamPattern, ArgIdx))
4198  return Result;
4199  }
4200  } else {
4201  // If the parameter type contains an explicitly-specified pack that we
4202  // could not expand, skip the number of parameters notionally created
4203  // by the expansion.
4204  Optional<unsigned> NumExpansions = ParamExpansion->getNumExpansions();
4205  if (NumExpansions && !PackScope.isPartiallyExpanded()) {
4206  for (unsigned I = 0; I != *NumExpansions && ArgIdx < Args.size();
4207  ++I, ++ArgIdx) {
4208  ParamTypesForArgChecking.push_back(ParamPattern);
4209  // FIXME: Should we add OriginalCallArgs for these? What if the
4210  // corresponding argument is a list?
4211  PackScope.nextPackElement();
4212  }
4213  }
4214  }
4215 
4216  // Build argument packs for each of the parameter packs expanded by this
4217  // pack expansion.
4218  if (auto Result = PackScope.finish())
4219  return Result;
4220  }
4221 
4222  // Capture the context in which the function call is made. This is the context
4223  // that is needed when the accessibility of template arguments is checked.
4224  DeclContext *CallingCtx = CurContext;
4225 
4226  TemplateDeductionResult Result;
4229  FunctionTemplate, Deduced, NumExplicitlySpecified, Specialization, Info,
4230  &OriginalCallArgs, PartialOverloading, [&, CallingCtx]() {
4231  ContextRAII SavedContext(*this, CallingCtx);
4232  return CheckNonDependent(ParamTypesForArgChecking);
4233  });
4234  });
4235  return Result;
4236 }
4237 
4240  bool AdjustExceptionSpec) {
4241  if (ArgFunctionType.isNull())
4242  return ArgFunctionType;
4243 
4244  const auto *FunctionTypeP = FunctionType->castAs<FunctionProtoType>();
4245  const auto *ArgFunctionTypeP = ArgFunctionType->castAs<FunctionProtoType>();
4246  FunctionProtoType::ExtProtoInfo EPI = ArgFunctionTypeP->getExtProtoInfo();
4247  bool Rebuild = false;
4248 
4249  CallingConv CC = FunctionTypeP->getCallConv();
4250  if (EPI.ExtInfo.getCC() != CC) {
4251  EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CC);
4252  Rebuild = true;
4253  }
4254 
4255  bool NoReturn = FunctionTypeP->getNoReturnAttr();
4256  if (EPI.ExtInfo.getNoReturn() != NoReturn) {
4257  EPI.ExtInfo = EPI.ExtInfo.withNoReturn(NoReturn);
4258  Rebuild = true;
4259  }
4260 
4261  if (AdjustExceptionSpec && (FunctionTypeP->hasExceptionSpec() ||
4262  ArgFunctionTypeP->hasExceptionSpec())) {
4263  EPI.ExceptionSpec = FunctionTypeP->getExtProtoInfo().ExceptionSpec;
4264  Rebuild = true;
4265  }
4266 
4267  if (!Rebuild)
4268  return ArgFunctionType;
4269 
4270  return Context.getFunctionType(ArgFunctionTypeP->getReturnType(),
4271  ArgFunctionTypeP->getParamTypes(), EPI);
4272 }
4273 
4274 /// Deduce template arguments when taking the address of a function
4275 /// template (C++ [temp.deduct.funcaddr]) or matching a specialization to
4276 /// a template.
4277 ///
4278 /// \param FunctionTemplate the function template for which we are performing
4279 /// template argument deduction.
4280 ///
4281 /// \param ExplicitTemplateArgs the explicitly-specified template
4282 /// arguments.
4283 ///
4284 /// \param ArgFunctionType the function type that will be used as the
4285 /// "argument" type (A) when performing template argument deduction from the
4286 /// function template's function type. This type may be NULL, if there is no
4287 /// argument type to compare against, in C++0x [temp.arg.explicit]p3.
4288 ///
4289 /// \param Specialization if template argument deduction was successful,
4290 /// this will be set to the function template specialization produced by
4291 /// template argument deduction.
4292 ///
4293 /// \param Info the argument will be updated to provide additional information
4294 /// about template argument deduction.
4295 ///
4296 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4297 /// the address of a function template per [temp.deduct.funcaddr] and
4298 /// [over.over]. If \c false, we are looking up a function template
4299 /// specialization based on its signature, per [temp.deduct.decl].
4300 ///
4301 /// \returns the result of template argument deduction.
4303  FunctionTemplateDecl *FunctionTemplate,
4304  TemplateArgumentListInfo *ExplicitTemplateArgs, QualType ArgFunctionType,
4305  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4306  bool IsAddressOfFunction) {
4307  if (FunctionTemplate->isInvalidDecl())
4308  return TDK_Invalid;
4309 
4310  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
4311  TemplateParameterList *TemplateParams
4312  = FunctionTemplate->getTemplateParameters();
4313  QualType FunctionType = Function->getType();
4314 
4315  // Substitute any explicit template arguments.
4316  LocalInstantiationScope InstScope(*this);
4318  unsigned NumExplicitlySpecified = 0;
4319  SmallVector<QualType, 4> ParamTypes;
4320  if (ExplicitTemplateArgs) {
4321  TemplateDeductionResult Result;
4323  Result = SubstituteExplicitTemplateArguments(
4324  FunctionTemplate, *ExplicitTemplateArgs, Deduced, ParamTypes,
4325  &FunctionType, Info);
4326  });
4327  if (Result)
4328  return Result;
4329 
4330  NumExplicitlySpecified = Deduced.size();
4331  }
4332 
4333  // When taking the address of a function, we require convertibility of
4334  // the resulting function type. Otherwise, we allow arbitrary mismatches
4335  // of calling convention and noreturn.
4336  if (!IsAddressOfFunction)
4337  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, FunctionType,
4338  /*AdjustExceptionSpec*/false);
4339 
4340  // Unevaluated SFINAE context.
4343  SFINAETrap Trap(*this);
4344 
4345  Deduced.resize(TemplateParams->size());
4346 
4347  // If the function has a deduced return type, substitute it for a dependent
4348  // type so that we treat it as a non-deduced context in what follows. If we
4349  // are looking up by signature, the signature type should also have a deduced
4350  // return type, which we instead expect to exactly match.
4351  bool HasDeducedReturnType = false;
4352  if (getLangOpts().CPlusPlus14 && IsAddressOfFunction &&
4353  Function->getReturnType()->getContainedAutoType()) {
4354  FunctionType = SubstAutoType(FunctionType, Context.DependentTy);
4355  HasDeducedReturnType = true;
4356  }
4357 
4358  if (!ArgFunctionType.isNull()) {
4359  unsigned TDF =
4361  // Deduce template arguments from the function type.
4362  if (TemplateDeductionResult Result
4363  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4364  FunctionType, ArgFunctionType,
4365  Info, Deduced, TDF))
4366  return Result;
4367  }
4368 
4369  TemplateDeductionResult Result;
4371  Result = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
4372  NumExplicitlySpecified,
4373  Specialization, Info);
4374  });
4375  if (Result)
4376  return Result;
4377 
4378  // If the function has a deduced return type, deduce it now, so we can check
4379  // that the deduced function type matches the requested type.
4380  if (HasDeducedReturnType &&
4381  Specialization->getReturnType()->isUndeducedType() &&
4382  DeduceReturnType(Specialization, Info.getLocation(), false))
4383  return TDK_MiscellaneousDeductionFailure;
4384 
4385  // If the function has a dependent exception specification, resolve it now,
4386  // so we can check that the exception specification matches.
4387  auto *SpecializationFPT =
4388  Specialization->getType()->castAs<FunctionProtoType>();
4389  if (getLangOpts().CPlusPlus17 &&
4390  isUnresolvedExceptionSpec(SpecializationFPT->getExceptionSpecType()) &&
4391  !ResolveExceptionSpec(Info.getLocation(), SpecializationFPT))
4392  return TDK_MiscellaneousDeductionFailure;
4393 
4394  // Adjust the exception specification of the argument to match the
4395  // substituted and resolved type we just formed. (Calling convention and
4396  // noreturn can't be dependent, so we don't actually need this for them
4397  // right now.)
4398  QualType SpecializationType = Specialization->getType();
4399  if (!IsAddressOfFunction)
4400  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, SpecializationType,
4401  /*AdjustExceptionSpec*/true);
4402 
4403  // If the requested function type does not match the actual type of the
4404  // specialization with respect to arguments of compatible pointer to function
4405  // types, template argument deduction fails.
4406  if (!ArgFunctionType.isNull()) {
4407  if (IsAddressOfFunction &&
4408  !isSameOrCompatibleFunctionType(
4409  Context.getCanonicalType(SpecializationType),
4410  Context.getCanonicalType(ArgFunctionType)))
4411  return TDK_MiscellaneousDeductionFailure;
4412 
4413  if (!IsAddressOfFunction &&
4414  !Context.hasSameType(SpecializationType, ArgFunctionType))
4415  return TDK_MiscellaneousDeductionFailure;
4416  }
4417 
4418  return TDK_Success;
4419 }
4420 
4421 /// Deduce template arguments for a templated conversion
4422 /// function (C++ [temp.deduct.conv]) and, if successful, produce a
4423 /// conversion function template specialization.
4426  QualType ToType,
4427  CXXConversionDecl *&Specialization,
4428  TemplateDeductionInfo &Info) {
4429  if (ConversionTemplate->isInvalidDecl())
4430  return TDK_Invalid;
4431 
4432  CXXConversionDecl *ConversionGeneric
4433  = cast<CXXConversionDecl>(ConversionTemplate->getTemplatedDecl());
4434 
4435  QualType FromType = ConversionGeneric->getConversionType();
4436 
4437  // Canonicalize the types for deduction.
4438  QualType P = Context.getCanonicalType(FromType);
4439  QualType A = Context.getCanonicalType(ToType);
4440 
4441  // C++0x [temp.deduct.conv]p2:
4442  // If P is a reference type, the type referred to by P is used for
4443  // type deduction.
4444  if (const ReferenceType *PRef = P->getAs<ReferenceType>())
4445  P = PRef->getPointeeType();
4446 
4447  // C++0x [temp.deduct.conv]p4:
4448  // [...] If A is a reference type, the type referred to by A is used
4449  // for type deduction.
4450  if (const ReferenceType *ARef = A->getAs<ReferenceType>()) {
4451  A = ARef->getPointeeType();
4452  // We work around a defect in the standard here: cv-qualifiers are also
4453  // removed from P and A in this case, unless P was a reference type. This
4454  // seems to mostly match what other compilers are doing.
4455  if (!FromType->getAs<ReferenceType>()) {
4456  A = A.getUnqualifiedType();
4457  P = P.getUnqualifiedType();
4458  }
4459 
4460  // C++ [temp.deduct.conv]p3:
4461  //
4462  // If A is not a reference type:
4463  } else {
4464  assert(!A->isReferenceType() && "Reference types were handled above");
4465 
4466  // - If P is an array type, the pointer type produced by the
4467  // array-to-pointer standard conversion (4.2) is used in place
4468  // of P for type deduction; otherwise,
4469  if (P->isArrayType())
4470  P = Context.getArrayDecayedType(P);
4471  // - If P is a function type, the pointer type produced by the
4472  // function-to-pointer standard conversion (4.3) is used in
4473  // place of P for type deduction; otherwise,
4474  else if (P->isFunctionType())
4475  P = Context.getPointerType(P);
4476  // - If P is a cv-qualified type, the top level cv-qualifiers of
4477  // P's type are ignored for type deduction.
4478  else
4479  P = P.getUnqualifiedType();
4480 
4481  // C++0x [temp.deduct.conv]p4:
4482  // If A is a cv-qualified type, the top level cv-qualifiers of A's
4483  // type are ignored for type deduction. If A is a reference type, the type
4484  // referred to by A is used for type deduction.
4485  A = A.getUnqualifiedType();
4486  }
4487 
4488  // Unevaluated SFINAE context.
4491  SFINAETrap Trap(*this);
4492 
4493  // C++ [temp.deduct.conv]p1:
4494  // Template argument deduction is done by comparing the return
4495  // type of the template conversion function (call it P) with the
4496  // type that is required as the result of the conversion (call it
4497  // A) as described in 14.8.2.4.
4498  TemplateParameterList *TemplateParams
4499  = ConversionTemplate->getTemplateParameters();
4501  Deduced.resize(TemplateParams->size());
4502 
4503  // C++0x [temp.deduct.conv]p4:
4504  // In general, the deduction process attempts to find template
4505  // argument values that will make the deduced A identical to
4506  // A. However, there are two cases that allow a difference:
4507  unsigned TDF = 0;
4508  // - If the original A is a reference type, A can be more
4509  // cv-qualified than the deduced A (i.e., the type referred to
4510  // by the reference)
4511  if (ToType->isReferenceType())
4512  TDF |= TDF_ArgWithReferenceType;
4513  // - The deduced A can be another pointer or pointer to member
4514  // type that can be converted to A via a qualification
4515  // conversion.
4516  //
4517  // (C++0x [temp.deduct.conv]p6 clarifies that this only happens when
4518  // both P and A are pointers or member pointers. In this case, we
4519  // just ignore cv-qualifiers completely).
4520  if ((P->isPointerType() && A->isPointerType()) ||
4522  TDF |= TDF_IgnoreQualifiers;
4523  if (TemplateDeductionResult Result
4524  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4525  P, A, Info, Deduced, TDF))
4526  return Result;
4527 
4528  // Create an Instantiation Scope for finalizing the operator.
4529  LocalInstantiationScope InstScope(*this);
4530  // Finish template argument deduction.
4531  FunctionDecl *ConversionSpecialized = nullptr;
4532  TemplateDeductionResult Result;
4534  Result = FinishTemplateArgumentDeduction(ConversionTemplate, Deduced, 0,
4535  ConversionSpecialized, Info);
4536  });
4537  Specialization = cast_or_null<CXXConversionDecl>(ConversionSpecialized);
4538  return Result;
4539 }
4540 
4541 /// Deduce template arguments for a function template when there is
4542 /// nothing to deduce against (C++0x [temp.arg.explicit]p3).
4543 ///
4544 /// \param FunctionTemplate the function template for which we are performing
4545 /// template argument deduction.
4546 ///
4547 /// \param ExplicitTemplateArgs the explicitly-specified template
4548 /// arguments.
4549 ///
4550 /// \param Specialization if template argument deduction was successful,
4551 /// this will be set to the function template specialization produced by
4552 /// template argument deduction.
4553 ///
4554 /// \param Info the argument will be updated to provide additional information
4555 /// about template argument deduction.
4556 ///
4557 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4558 /// the address of a function template in a context where we do not have a
4559 /// target type, per [over.over]. If \c false, we are looking up a function
4560 /// template specialization based on its signature, which only happens when
4561 /// deducing a function parameter type from an argument that is a template-id
4562 /// naming a function template specialization.
4563 ///
4564 /// \returns the result of template argument deduction.
4566  FunctionTemplateDecl *FunctionTemplate,
4567  TemplateArgumentListInfo *ExplicitTemplateArgs,
4568  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4569  bool IsAddressOfFunction) {
4570  return DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs,
4571  QualType(), Specialization, Info,
4572  IsAddressOfFunction);
4573 }
4574 
4575 namespace {
4576  struct DependentAuto { bool IsPack; };
4577 
4578  /// Substitute the 'auto' specifier or deduced template specialization type
4579  /// specifier within a type for a given replacement type.
4580  class SubstituteDeducedTypeTransform :
4581  public TreeTransform<SubstituteDeducedTypeTransform> {
4582  QualType Replacement;
4583  bool ReplacementIsPack;
4584  bool UseTypeSugar;
4585 
4586  public:
4587  SubstituteDeducedTypeTransform(Sema &SemaRef, DependentAuto DA)
4588  : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef), Replacement(),
4589  ReplacementIsPack(DA.IsPack), UseTypeSugar(true) {}
4590 
4591  SubstituteDeducedTypeTransform(Sema &SemaRef, QualType Replacement,
4592  bool UseTypeSugar = true)
4594  Replacement(Replacement), ReplacementIsPack(false),
4595  UseTypeSugar(UseTypeSugar) {}
4596 
4597  QualType TransformDesugared(TypeLocBuilder &TLB, DeducedTypeLoc TL) {
4598  assert(isa<TemplateTypeParmType>(Replacement) &&
4599  "unexpected unsugared replacement kind");
4600  QualType Result = Replacement;
4602  NewTL.setNameLoc(TL.getNameLoc());
4603  return Result;
4604  }
4605 
4606  QualType TransformAutoType(TypeLocBuilder &TLB, AutoTypeLoc TL) {
4607  // If we're building the type pattern to deduce against, don't wrap the
4608  // substituted type in an AutoType. Certain template deduction rules
4609  // apply only when a template type parameter appears directly (and not if
4610  // the parameter is found through desugaring). For instance:
4611  // auto &&lref = lvalue;
4612  // must transform into "rvalue reference to T" not "rvalue reference to
4613  // auto type deduced as T" in order for [temp.deduct.call]p3 to apply.
4614  //
4615  // FIXME: Is this still necessary?
4616  if (!UseTypeSugar)
4617  return TransformDesugared(TLB, TL);
4618 
4619  QualType Result = SemaRef.Context.getAutoType(
4620  Replacement, TL.getTypePtr()->getKeyword(), Replacement.isNull(),
4621  ReplacementIsPack, TL.getTypePtr()->getTypeConstraintConcept(),
4623  auto NewTL = TLB.push<AutoTypeLoc>(Result);
4624  NewTL.copy(TL);
4625  return Result;
4626  }
4627 
4628  QualType TransformDeducedTemplateSpecializationType(
4630  if (!UseTypeSugar)
4631  return TransformDesugared(TLB, TL);
4632 
4634  TL.getTypePtr()->getTemplateName(),
4635  Replacement, Replacement.isNull());
4636  auto NewTL = TLB.push<DeducedTemplateSpecializationTypeLoc>(Result);
4637  NewTL.setNameLoc(TL.getNameLoc());
4638  return Result;
4639  }
4640 
4641  ExprResult TransformLambdaExpr(LambdaExpr *E) {
4642  // Lambdas never need to be transformed.
4643  return E;
4644  }
4645 
4646  QualType Apply(TypeLoc TL) {
4647  // Create some scratch storage for the transformed type locations.
4648  // FIXME: We're just going to throw this information away. Don't build it.
4649  TypeLocBuilder TLB;
4650  TLB.reserve(TL.getFullDataSize());
4651  return TransformType(TLB, TL);
4652  }
4653  };
4654 
4655 } // namespace
4656 
4659  Optional<unsigned> DependentDeductionDepth,
4660  bool IgnoreConstraints) {
4661  return DeduceAutoType(Type->getTypeLoc(), Init, Result,
4662  DependentDeductionDepth, IgnoreConstraints);
4663 }
4664 
4665 /// Attempt to produce an informative diagostic explaining why auto deduction
4666 /// failed.
4667 /// \return \c true if diagnosed, \c false if not.
4670  TemplateDeductionInfo &Info,
4671  ArrayRef<SourceRange> Ranges) {
4672  switch (TDK) {
4673  case Sema::TDK_Inconsistent: {
4674  // Inconsistent deduction means we were deducing from an initializer list.
4675  auto D = S.Diag(Info.getLocation(), diag::err_auto_inconsistent_deduction);
4676  D << Info.FirstArg << Info.SecondArg;
4677  for (auto R : Ranges)
4678  D << R;
4679  return true;
4680  }
4681 
4682  // FIXME: Are there other cases for which a custom diagnostic is more useful
4683  // than the basic "types don't match" diagnostic?
4684 
4685  default:
4686  return false;
4687  }
4688 }
4689 
4692  AutoTypeLoc TypeLoc, QualType Deduced) {
4693  ConstraintSatisfaction Satisfaction;
4694  ConceptDecl *Concept = Type.getTypeConstraintConcept();
4695  TemplateArgumentListInfo TemplateArgs(TypeLoc.getLAngleLoc(),
4696  TypeLoc.getRAngleLoc());
4697  TemplateArgs.addArgument(
4700  Deduced, TypeLoc.getNameLoc())));
4701  for (unsigned I = 0, C = TypeLoc.getNumArgs(); I != C; ++I)
4702  TemplateArgs.addArgument(TypeLoc.getArgLoc(I));
4703 
4705  if (S.CheckTemplateArgumentList(Concept, SourceLocation(), TemplateArgs,
4706  /*PartialTemplateArgs=*/false, Converted))
4708  if (S.CheckConstraintSatisfaction(Concept, {Concept->getConstraintExpr()},
4709  Converted, TypeLoc.getLocalSourceRange(),
4710  Satisfaction))
4712  if (!Satisfaction.IsSatisfied) {
4713  std::string Buf;
4714  llvm::raw_string_ostream OS(Buf);
4715  OS << "'" << Concept->getName();
4716  if (TypeLoc.hasExplicitTemplateArgs()) {
4717  OS << "<";
4718  for (const auto &Arg : Type.getTypeConstraintArguments())
4719  Arg.print(S.getPrintingPolicy(), OS);
4720  OS << ">";
4721  }
4722  OS << "'";
4723  OS.flush();
4724  S.Diag(TypeLoc.getConceptNameLoc(),
4725  diag::err_placeholder_constraints_not_satisfied)
4726  << Deduced << Buf << TypeLoc.getLocalSourceRange();
4727  S.DiagnoseUnsatisfiedConstraint(Satisfaction);
4729  }
4730  return Sema::DAR_Succeeded;
4731 }
4732 
4733 /// Deduce the type for an auto type-specifier (C++11 [dcl.spec.auto]p6)
4734 ///
4735 /// Note that this is done even if the initializer is dependent. (This is
4736 /// necessary to support partial ordering of templates using 'auto'.)
4737 /// A dependent type will be produced when deducing from a dependent type.
4738 ///
4739 /// \param Type the type pattern using the auto type-specifier.
4740 /// \param Init the initializer for the variable whose type is to be deduced.
4741 /// \param Result if type deduction was successful, this will be set to the
4742 /// deduced type.
4743 /// \param DependentDeductionDepth Set if we should permit deduction in
4744 /// dependent cases. This is necessary for template partial ordering with
4745 /// 'auto' template parameters. The value specified is the template
4746 /// parameter depth at which we should perform 'auto' deduction.
4747 /// \param IgnoreConstraints Set if we should not fail if the deduced type does
4748 /// not satisfy the type-constraint in the auto type.
4751  Optional<unsigned> DependentDeductionDepth,
4752  bool IgnoreConstraints) {
4753  if (Init->containsErrors())
4754  return DAR_FailedAlreadyDiagnosed;
4755  if (Init->getType()->isNonOverloadPlaceholderType()) {
4756  ExprResult NonPlaceholder = CheckPlaceholderExpr(Init);
4757  if (NonPlaceholder.isInvalid())
4758  return DAR_FailedAlreadyDiagnosed;
4759  Init = NonPlaceholder.get();
4760  }
4761 
4762  DependentAuto DependentResult = {
4763  /*.IsPack = */ (bool)Type.getAs<PackExpansionTypeLoc>()};
4764 
4765  if (!DependentDeductionDepth &&
4766  (Type.getType()->isDependentType() || Init->isTypeDependent() ||
4768  Result = SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
4769  assert(!Result.isNull() && "substituting DependentTy can't fail");
4770  return DAR_Succeeded;
4771  }
4772 
4773  // Find the depth of template parameter to synthesize.
4774  unsigned Depth = DependentDeductionDepth.getValueOr(0);
4775 
4776  // If this is a 'decltype(auto)' specifier, do the decltype dance.
4777  // Since 'decltype(auto)' can only occur at the top of the type, we
4778  // don't need to go digging for it.
4779  if (const AutoType *AT = Type.getType()->getAs<AutoType>()) {
4780  if (AT->isDecltypeAuto()) {
4781  if (isa<InitListExpr>(Init)) {
4782  Diag(Init->getBeginLoc(), diag::err_decltype_auto_initializer_list);
4783  return DAR_FailedAlreadyDiagnosed;
4784  }
4785 
4786  ExprResult ER = CheckPlaceholderExpr(Init);
4787  if (ER.isInvalid())
4788  return DAR_FailedAlreadyDiagnosed;
4789  Init = ER.get();
4790  QualType Deduced = BuildDecltypeType(Init, Init->getBeginLoc(), false);
4791  if (Deduced.isNull())
4792  return DAR_FailedAlreadyDiagnosed;
4793  // FIXME: Support a non-canonical deduced type for 'auto'.
4794  Deduced = Context.getCanonicalType(Deduced);
4795  if (AT->isConstrained() && !IgnoreConstraints) {
4796  auto ConstraintsResult =
4798  Type.getContainedAutoTypeLoc(),
4799  Deduced);
4800  if (ConstraintsResult != DAR_Succeeded)
4801  return ConstraintsResult;
4802  }
4803  Result = SubstituteDeducedTypeTransform(*this, Deduced).Apply(Type);
4804  if (Result.isNull())
4805  return DAR_FailedAlreadyDiagnosed;
4806  return DAR_Succeeded;
4807  } else if (!getLangOpts().CPlusPlus) {
4808  if (isa<InitListExpr>(Init)) {
4809  Diag(Init->getBeginLoc(), diag::err_auto_init_list_from_c);
4810  return DAR_FailedAlreadyDiagnosed;
4811  }
4812  }
4813  }
4814 
4815  SourceLocation Loc = Init->getExprLoc();
4816 
4817  LocalInstantiationScope InstScope(*this);
4818 
4819  // Build template<class TemplParam> void Func(FuncParam);
4821  Context, nullptr, SourceLocation(), Loc, Depth, 0, nullptr, false, false,
4822  false);
4823  QualType TemplArg = QualType(TemplParam->getTypeForDecl(), 0);
4824  NamedDecl *TemplParamPtr = TemplParam;
4826  Context, Loc, Loc, TemplParamPtr, Loc, nullptr);
4827 
4828  QualType FuncParam =
4829  SubstituteDeducedTypeTransform(*this, TemplArg, /*UseTypeSugar*/false)
4830  .Apply(Type);
4831  assert(!FuncParam.isNull() &&
4832  "substituting template parameter for 'auto' failed");
4833 
4834  // Deduce type of TemplParam in Func(Init)
4836  Deduced.resize(1);
4837 
4838  TemplateDeductionInfo Info(Loc, Depth);
4839 
4840  // If deduction failed, don't diagnose if the initializer is dependent; it
4841  // might acquire a matching type in the instantiation.
4842  auto DeductionFailed = [&](TemplateDeductionResult TDK,
4844  if (Init->isTypeDependent()) {
4845  Result =
4846  SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
4847  assert(!Result.isNull() && "substituting DependentTy can't fail");
4848  return DAR_Succeeded;
4849  }
4850  if (diagnoseAutoDeductionFailure(*this, TDK, Info, Ranges))
4851  return DAR_FailedAlreadyDiagnosed;
4852  return DAR_Failed;
4853  };
4854 
4855  SmallVector<OriginalCallArg, 4> OriginalCallArgs;
4856 
4857  InitListExpr *InitList = dyn_cast<InitListExpr>(Init);
4858  if (InitList) {
4859  // Notionally, we substitute std::initializer_list<T> for 'auto' and deduce
4860  // against that. Such deduction only succeeds if removing cv-qualifiers and
4861  // references results in std::initializer_list<T>.
4862  if (!Type.getType().getNonReferenceType()->getAs<AutoType>())
4863  return DAR_Failed;
4864 
4865  // Resolving a core issue: a braced-init-list containing any designators is
4866  // a non-deduced context.
4867  for (Expr *E : InitList->inits())
4868  if (isa<DesignatedInitExpr>(E))
4869  return DAR_Failed;
4870 
4871  SourceRange DeducedFromInitRange;
4872  for (unsigned i = 0, e = InitList->getNumInits(); i < e; ++i) {
4873  Expr *Init = InitList->getInit(i);
4874 
4876  *this, TemplateParamsSt.get(), 0, TemplArg, Init,
4877  Info, Deduced, OriginalCallArgs, /*Decomposed*/ true,
4878  /*ArgIdx*/ 0, /*TDF*/ 0))
4879  return DeductionFailed(TDK, {DeducedFromInitRange,
4880  Init->getSourceRange()});
4881 
4882  if (DeducedFromInitRange.isInvalid() &&
4883  Deduced[0].getKind() != TemplateArgument::Null)
4884  DeducedFromInitRange = Init->getSourceRange();
4885  }
4886  } else {
4887  if (!getLangOpts().CPlusPlus && Init->refersToBitField()) {
4888  Diag(Loc, diag::err_auto_bitfield);
4889  return DAR_FailedAlreadyDiagnosed;
4890  }
4891 
4893  *this, TemplateParamsSt.get(), 0, FuncParam, Init, Info, Deduced,
4894  OriginalCallArgs, /*Decomposed*/ false, /*ArgIdx*/ 0, /*TDF*/ 0))
4895  return DeductionFailed(TDK, {});
4896  }
4897 
4898  // Could be null if somehow 'auto' appears in a non-deduced context.
4899  if (Deduced[0].getKind() != TemplateArgument::Type)
4900  return DeductionFailed(TDK_Incomplete, {});
4901 
4902  QualType DeducedType = Deduced[0].getAsType();
4903 
4904  if (InitList) {
4905  DeducedType = BuildStdInitializerList(DeducedType, Loc);
4906  if (DeducedType.isNull())
4907  return DAR_FailedAlreadyDiagnosed;
4908  }
4909 
4910  if (const auto *AT = Type.getType()->getAs<AutoType>()) {
4911  if (AT->isConstrained() && !IgnoreConstraints) {
4912  auto ConstraintsResult =
4914  Type.getContainedAutoTypeLoc(),
4915  DeducedType);
4916  if (ConstraintsResult != DAR_Succeeded)
4917  return ConstraintsResult;
4918  }
4919  }
4920 
4921  Result = SubstituteDeducedTypeTransform(*this, DeducedType).Apply(Type);
4922  if (Result.isNull())
4923  return DAR_FailedAlreadyDiagnosed;
4924 
4925  // Check that the deduced argument type is compatible with the original
4926  // argument type per C++ [temp.deduct.call]p4.
4927  QualType DeducedA = InitList ? Deduced[0].getAsType() : Result;
4928  for (const OriginalCallArg &OriginalArg : OriginalCallArgs) {
4929  assert((bool)InitList == OriginalArg.DecomposedParam &&
4930  "decomposed non-init-list in auto deduction?");
4931  if (auto TDK =
4932  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA)) {
4933  Result = QualType();
4934  return DeductionFailed(TDK, {});
4935  }
4936  }
4937 
4938  return DAR_Succeeded;
4939 }
4940 
4942  QualType TypeToReplaceAuto) {
4943  if (TypeToReplaceAuto->isDependentType())
4944  return SubstituteDeducedTypeTransform(
4945  *this, DependentAuto{
4946  TypeToReplaceAuto->containsUnexpandedParameterPack()})
4947  .TransformType(TypeWithAuto);
4948  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4949  .TransformType(TypeWithAuto);
4950 }
4951 
4953  QualType TypeToReplaceAuto) {
4954  if (TypeToReplaceAuto->isDependentType())
4955  return SubstituteDeducedTypeTransform(
4956  *this,
4957  DependentAuto{
4958  TypeToReplaceAuto->containsUnexpandedParameterPack()})
4959  .TransformType(TypeWithAuto);
4960  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4961  .TransformType(TypeWithAuto);
4962 }
4963 
4965  QualType TypeToReplaceAuto) {
4966  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
4967  /*UseTypeSugar*/ false)
4968  .TransformType(TypeWithAuto);
4969 }
4970 
4972  QualType TypeToReplaceAuto) {
4973  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
4974  /*UseTypeSugar*/ false)
4975  .TransformType(TypeWithAuto);
4976 }
4977 
4979  if (isa<InitListExpr>(Init))
4980  Diag(VDecl->getLocation(),
4981  VDecl->isInitCapture()
4982  ? diag::err_init_capture_deduction_failure_from_init_list
4983  : diag::err_auto_var_deduction_failure_from_init_list)
4984  << VDecl->getDeclName() << VDecl->getType() << Init->getSourceRange();
4985  else
4986  Diag(VDecl->getLocation(),
4987  VDecl->isInitCapture() ? diag::err_init_capture_deduction_failure
4988  : diag::err_auto_var_deduction_failure)
4989  << VDecl->getDeclName() << VDecl->getType() << Init->getType()
4990  << Init->getSourceRange();
4991 }
4992 
4994  bool Diagnose) {
4995  assert(FD->getReturnType()->isUndeducedType());
4996 
4997  // For a lambda's conversion operator, deduce any 'auto' or 'decltype(auto)'
4998  // within the return type from the call operator's type.
4999  if (isLambdaConversionOperator(FD)) {
5000  CXXRecordDecl *Lambda = cast<CXXMethodDecl>(FD)->getParent();
5001  FunctionDecl *CallOp = Lambda->getLambdaCallOperator();
5002 
5003  // For a generic lambda, instantiate the call operator if needed.
5004  if (auto *Args = FD->getTemplateSpecializationArgs()) {
5005  CallOp = InstantiateFunctionDeclaration(
5006  CallOp->getDescribedFunctionTemplate(), Args, Loc);
5007  if (!CallOp || CallOp->isInvalidDecl())
5008  return true;
5009 
5010  // We might need to deduce the return type by instantiating the definition
5011  // of the operator() function.
5012  if (CallOp->getReturnType()->isUndeducedType()) {
5013  runWithSufficientStackSpace(Loc, [&] {
5014  InstantiateFunctionDefinition(Loc, CallOp);
5015  });
5016  }
5017  }
5018 
5019  if (CallOp->isInvalidDecl())
5020  return true;
5021  assert(!CallOp->getReturnType()->isUndeducedType() &&
5022  "failed to deduce lambda return type");
5023 
5024  // Build the new return type from scratch.
5025  CallingConv RetTyCC = FD->getReturnType()
5026  ->getPointeeType()
5027  ->castAs<FunctionType>()
5028  ->getCallConv();
5029  QualType RetType = getLambdaConversionFunctionResultType(
5030  CallOp->getType()->castAs<FunctionProtoType>(), RetTyCC);
5031  if (FD->getReturnType()->getAs<PointerType>())
5032  RetType = Context.getPointerType(RetType);
5033  else {
5034  assert(FD->getReturnType()->getAs<BlockPointerType>());
5035  RetType = Context.getBlockPointerType(RetType);
5036  }
5037  Context.adjustDeducedFunctionResultType(FD, RetType);
5038  return false;
5039  }
5040 
5041  if (FD->getTemplateInstantiationPattern()) {
5042  runWithSufficientStackSpace(Loc, [&] {
5043  InstantiateFunctionDefinition(Loc, FD);
5044  });
5045  }
5046 
5047  bool StillUndeduced = FD->getReturnType()->isUndeducedType();
5048  if (StillUndeduced && Diagnose && !FD->isInvalidDecl()) {
5049  Diag(Loc, diag::err_auto_fn_used_before_defined) << FD;
5050  Diag(FD->getLocation(), diag::note_callee_decl) << FD;
5051  }
5052 
5053  return StillUndeduced;
5054 }
5055 
5056 /// If this is a non-static member function,
5057 static void
5059  CXXMethodDecl *Method,
5060  SmallVectorImpl<QualType> &ArgTypes) {
5061  // C++11 [temp.func.order]p3:
5062  // [...] The new parameter is of type "reference to cv A," where cv are
5063  // the cv-qualifiers of the function template (if any) and A is
5064  // the class of which the function template is a member.
5065  //
5066  // The standard doesn't say explicitly, but we pick the appropriate kind of
5067  // reference type based on [over.match.funcs]p4.
5068  QualType ArgTy = Context.getTypeDeclType(Method->getParent());
5069  ArgTy = Context.getQualifiedType(ArgTy, Method->getMethodQualifiers());
5070  if (Method->getRefQualifier() == RQ_RValue)
5071  ArgTy = Context.getRValueReferenceType(ArgTy);
5072  else
5073  ArgTy = Context.getLValueReferenceType(ArgTy);
5074  ArgTypes.push_back(ArgTy);
5075 }
5076 
5077 /// Determine whether the function template \p FT1 is at least as
5078 /// specialized as \p FT2.
5080  SourceLocation Loc,
5081  FunctionTemplateDecl *FT1,
5082  FunctionTemplateDecl *FT2,
5084  unsigned NumCallArguments1,
5085  bool Reversed) {
5086  assert(!Reversed || TPOC == TPOC_Call);
5087 
5088  FunctionDecl *FD1 = FT1->getTemplatedDecl();
5089  FunctionDecl *FD2 = FT2->getTemplatedDecl();
5090  const FunctionProtoType *Proto1 = FD1->getType()->getAs<FunctionProtoType>();
5091  const FunctionProtoType *Proto2 = FD2->getType()->getAs<FunctionProtoType>();
5092 
5093  assert(Proto1 && Proto2 && "Function templates must have prototypes");
5094  TemplateParameterList *TemplateParams = FT2->getTemplateParameters();
5096  Deduced.resize(TemplateParams->size());
5097 
5098  // C++0x [temp.deduct.partial]p3:
5099  // The types used to determine the ordering depend on the context in which
5100  // the partial ordering is done:
5101  TemplateDeductionInfo Info(Loc);
5103  switch (TPOC) {
5104  case TPOC_Call: {
5105  // - In the context of a function call, the function parameter types are
5106  // used.
5107  CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
5108  CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
5109 
5110  // C++11 [temp.func.order]p3:
5111  // [...] If only one of the function templates is a non-static
5112  // member, that function template is considered to have a new
5113  // first parameter inserted in its function parameter list. The
5114  // new parameter is of type "reference to cv A," where cv are
5115  // the cv-qualifiers of the function template (if any) and A is
5116  // the class of which the function template is a member.
5117  //
5118  // Note that we interpret this to mean "if one of the function
5119  // templates is a non-static member and the other is a non-member";
5120  // otherwise, the ordering rules for static functions against non-static
5121  // functions don't make any sense.
5122  //
5123  // C++98/03 doesn't have this provision but we've extended DR532 to cover
5124  // it as wording was broken prior to it.
5126 
5127  unsigned NumComparedArguments = NumCallArguments1;
5128 
5129  if (!Method2 && Method1 && !Method1->isStatic()) {
5130  // Compare 'this' from Method1 against first parameter from Method2.
5131  AddImplicitObjectParameterType(S.Context, Method1, Args1);
5132  ++NumComparedArguments;
5133  } else if (!Method1 && Method2 && !Method2->isStatic()) {
5134  // Compare 'this' from Method2 against first parameter from Method1.
5135  AddImplicitObjectParameterType(S.Context, Method2, Args2);
5136  } else if (Method1 && Method2 && Reversed) {
5137  // Compare 'this' from Method1 against second parameter from Method2
5138  // and 'this' from Method2 against second parameter from Method1.
5139  AddImplicitObjectParameterType(S.Context, Method1, Args1);
5140  AddImplicitObjectParameterType(S.Context, Method2, Args2);
5141  ++NumComparedArguments;
5142  }
5143 
5144  Args1.insert(Args1.end(), Proto1->param_type_begin(),
5145  Proto1->param_type_end());
5146  Args2.insert(Args2.end(), Proto2->param_type_begin(),
5147  Proto2->param_type_end());
5148 
5149  // C++ [temp.func.order]p5:
5150  // The presence of unused ellipsis and default arguments has no effect on
5151  // the partial ordering of function templates.
5152  if (Args1.size() > NumComparedArguments)
5153  Args1.resize(NumComparedArguments);
5154  if (Args2.size() > NumComparedArguments)
5155  Args2.resize(NumComparedArguments);
5156  if (Reversed)
5157  std::reverse(Args2.begin(), Args2.end());
5158  if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
5159  Args1.data(), Args1.size(), Info, Deduced,
5160  TDF_None, /*PartialOrdering=*/true))
5161  return false;
5162 
5163  break;
5164  }
5165 
5166  case TPOC_Conversion:
5167  // - In the context of a call to a conversion operator, the return types
5168  // of the conversion function templates are used.
5170  S, TemplateParams, Proto2->getReturnType(), Proto1->getReturnType(),
5171  Info, Deduced, TDF_None,
5172  /*PartialOrdering=*/true))
5173  return false;
5174  break;
5175 
5176  case TPOC_Other:
5177  // - In other contexts (14.6.6.2) the function template's function type
5178  // is used.
5179  if (DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
5180  FD2->getType(), FD1->getType(),
5181  Info, Deduced, TDF_None,
5182  /*PartialOrdering=*/true))
5183  return false;
5184  break;
5185  }
5186 
5187  // C++0x [temp.deduct.partial]p11:
5188  // In most cases, all template parameters must have values in order for
5189  // deduction to succeed, but for partial ordering purposes a template
5190  // parameter may remain without a value provided it is not used in the
5191  // types being used for partial ordering. [ Note: a template parameter used
5192  // in a non-deduced context is considered used. -end note]
5193  unsigned ArgIdx = 0, NumArgs = Deduced.size();
5194  for (; ArgIdx != NumArgs; ++ArgIdx)
5195  if (Deduced[ArgIdx].isNull())
5196  break;
5197 
5198  // FIXME: We fail to implement [temp.deduct.type]p1 along this path. We need
5199  // to substitute the deduced arguments back into the template and check that
5200  // we get the right type.
5201 
5202  if (ArgIdx == NumArgs) {
5203  // All template arguments were deduced. FT1 is at least as specialized
5204  // as FT2.
5205  return true;
5206  }
5207 
5208  // Figure out which template parameters were used.
5209  llvm::SmallBitVector UsedParameters(TemplateParams->size());
5210  switch (TPOC) {
5211  case TPOC_Call:
5212  for (unsigned I = 0, N = Args2.size(); I != N; ++I)
5213  ::MarkUsedTemplateParameters(S.Context, Args2[I], false,
5214  TemplateParams->getDepth(),
5215  UsedParameters);
5216  break;
5217 
5218  case TPOC_Conversion:
5219  ::MarkUsedTemplateParameters(S.Context, Proto2->getReturnType(), false,
5220  TemplateParams->getDepth(), UsedParameters);
5221  break;
5222 
5223  case TPOC_Other:
5224  ::MarkUsedTemplateParameters(S.Context, FD2->getType(), false,
5225  TemplateParams->getDepth(),
5226  UsedParameters);
5227  break;
5228  }
5229 
5230  for (; ArgIdx != NumArgs; ++ArgIdx)
5231  // If this argument had no value deduced but was used in one of the types
5232  // used for partial ordering, then deduction fails.
5233  if (Deduced[ArgIdx].isNull() && UsedParameters[ArgIdx])
5234  return false;
5235 
5236  return true;
5237 }
5238 
5239 /// Determine whether this a function template whose parameter-type-list
5240 /// ends with a function parameter pack.
5242  FunctionDecl *Function = FunTmpl->getTemplatedDecl();
5243  unsigned NumParams = Function->getNumParams();
5244  if (NumParams == 0)
5245  return false;
5246 
5247  ParmVarDecl *Last = Function->getParamDecl(NumParams - 1);
5248  if (!Last->isParameterPack())
5249  return false;
5250 
5251  // Make sure that no previous parameter is a parameter pack.
5252  while (--NumParams > 0) {
5253  if (Function->getParamDecl(NumParams - 1)->isParameterPack())
5254  return false;
5255  }
5256 
5257  return true;
5258 }
5259 
5260 /// Returns the more specialized function template according
5261 /// to the rules of function template partial ordering (C++ [temp.func.order]).
5262 ///
5263 /// \param FT1 the first function template
5264 ///
5265 /// \param FT2 the second function template
5266 ///
5267 /// \param TPOC the context in which we are performing partial ordering of
5268 /// function templates.
5269 ///
5270 /// \param NumCallArguments1 The number of arguments in the call to FT1, used
5271 /// only when \c TPOC is \c TPOC_Call.
5272 ///
5273 /// \param NumCallArguments2 The number of arguments in the call to FT2, used
5274 /// only when \c TPOC is \c TPOC_Call.
5275 ///
5276 /// \param Reversed If \c true, exactly one of FT1 and FT2 is an overload
5277 /// candidate with a reversed parameter order. In this case, the corresponding
5278 /// P/A pairs between FT1 and FT2 are reversed.
5279 ///
5280 /// \returns the more specialized function template. If neither
5281 /// template is more specialized, returns NULL.
5284  FunctionTemplateDecl *FT2,
5285  SourceLocation Loc,
5287  unsigned NumCallArguments1,
5288  unsigned NumCallArguments2,
5289  bool Reversed) {
5290 
5291  auto JudgeByConstraints = [&] () -> FunctionTemplateDecl * {
5293  FT1->getAssociatedConstraints(AC1);
5294  FT2->getAssociatedConstraints(AC2);
5295  bool AtLeastAsConstrained1, AtLeastAsConstrained2;
5296  if (IsAtLeastAsConstrained(FT1, AC1, FT2, AC2, AtLeastAsConstrained1))
5297  return nullptr;
5298  if (IsAtLeastAsConstrained(FT2, AC2, FT1, AC1, AtLeastAsConstrained2))
5299  return nullptr;
5300  if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
5301  return nullptr;
5302  return AtLeastAsConstrained1 ? FT1 : FT2;
5303  };
5304 
5305  bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
5306  NumCallArguments1, Reversed);
5307  bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
5308  NumCallArguments2, Reversed);
5309 
5310  if (Better1 != Better2) // We have a clear winner
5311  return Better1 ? FT1 : FT2;
5312 
5313  if (!Better1 && !Better2) // Neither is better than the other
5314  return JudgeByConstraints();
5315 
5316  // FIXME: This mimics what GCC implements, but doesn't match up with the
5317  // proposed resolution for core issue 692. This area needs to be sorted out,
5318  // but for now we attempt to maintain compatibility.
5319  bool Variadic1 = isVariadicFunctionTemplate(FT1);
5320  bool Variadic2 = isVariadicFunctionTemplate(FT2);
5321  if (Variadic1 != Variadic2)
5322  return Variadic1? FT2 : FT1;
5323 
5324  return JudgeByConstraints();
5325 }
5326 
5327 /// Determine if the two templates are equivalent.
5329  if (T1 == T2)
5330  return true;
5331 
5332  if (!T1 || !T2)
5333  return false;
5334 
5335  return T1->getCanonicalDecl() == T2->getCanonicalDecl();
5336 }
5337 
5338 /// Retrieve the most specialized of the given function template
5339 /// specializations.
5340 ///
5341 /// \param SpecBegin the start iterator of the function template
5342 /// specializations that we will be comparing.
5343 ///
5344 /// \param SpecEnd the end iterator of the function template
5345 /// specializations, paired with \p SpecBegin.
5346 ///
5347 /// \param Loc the location where the ambiguity or no-specializations
5348 /// diagnostic should occur.
5349 ///
5350 /// \param NoneDiag partial diagnostic used to diagnose cases where there are
5351 /// no matching candidates.
5352 ///
5353 /// \param AmbigDiag partial diagnostic used to diagnose an ambiguity, if one
5354 /// occurs.
5355 ///
5356 /// \param CandidateDiag partial diagnostic used for each function template
5357 /// specialization that is a candidate in the ambiguous ordering. One parameter
5358 /// in this diagnostic should be unbound, which will correspond to the string
5359 /// describing the template arguments for the function template specialization.
5360 ///
5361 /// \returns the most specialized function template specialization, if
5362 /// found. Otherwise, returns SpecEnd.
5364  UnresolvedSetIterator SpecBegin, UnresolvedSetIterator SpecEnd,
5365  TemplateSpecCandidateSet &FailedCandidates,
5366  SourceLocation Loc, const PartialDiagnostic &NoneDiag,
5367  const PartialDiagnostic &AmbigDiag, const PartialDiagnostic &CandidateDiag,
5368  bool Complain, QualType TargetType) {
5369  if (SpecBegin == SpecEnd) {
5370  if (Complain) {
5371  Diag(Loc, NoneDiag);
5372  FailedCandidates.NoteCandidates(*this, Loc);
5373  }
5374  return SpecEnd;
5375  }
5376 
5377  if (SpecBegin + 1 == SpecEnd)
5378  return SpecBegin;
5379 
5380  // Find the function template that is better than all of the templates it
5381  // has been compared to.
5382  UnresolvedSetIterator Best = SpecBegin;
5383  FunctionTemplateDecl *BestTemplate
5384  = cast<FunctionDecl>(*Best)->getPrimaryTemplate();
5385  assert(BestTemplate && "Not a function template specialization?");
5386  for (UnresolvedSetIterator I = SpecBegin + 1; I != SpecEnd; ++I) {
5387  FunctionTemplateDecl *Challenger
5388  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
5389  assert(Challenger && "Not a function template specialization?");
5390  if (isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
5391  Loc, TPOC_Other, 0, 0),
5392  Challenger)) {
5393  Best = I;
5394  BestTemplate = Challenger;
5395  }
5396  }
5397 
5398  // Make sure that the "best" function template is more specialized than all
5399  // of the others.
5400  bool Ambiguous = false;
5401  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
5402  FunctionTemplateDecl *Challenger
5403  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
5404  if (I != Best &&
5405  !isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
5406  Loc, TPOC_Other, 0, 0),
5407  BestTemplate)) {
5408  Ambiguous = true;
5409  break;
5410  }
5411  }
5412 
5413  if (!Ambiguous) {
5414  // We found an answer. Return it.
5415  return Best;
5416  }
5417 
5418  // Diagnose the ambiguity.
5419  if (Complain) {
5420  Diag(Loc, AmbigDiag);
5421 
5422  // FIXME: Can we order the candidates in some sane way?
5423  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
5424  PartialDiagnostic PD = CandidateDiag;
5425  const auto *FD = cast<FunctionDecl>(*I);
5426  PD << FD << getTemplateArgumentBindingsText(
5427  FD->getPrimaryTemplate()->getTemplateParameters(),
5428  *FD->getTemplateSpecializationArgs());
5429  if (!TargetType.isNull())
5430  HandleFunctionTypeMismatch(PD, FD->getType(), TargetType);
5431  Diag((*I)->getLocation(), PD);
5432  }
5433  }
5434 
5435  return SpecEnd;
5436 }
5437 
5438 /// Determine whether one partial specialization, P1, is at least as
5439 /// specialized than another, P2.
5440 ///
5441 /// \tparam TemplateLikeDecl The kind of P2, which must be a
5442 /// TemplateDecl or {Class,Var}TemplatePartialSpecializationDecl.
5443 /// \param T1 The injected-class-name of P1 (faked for a variable template).
5444 /// \param T2 The injected-class-name of P2 (faked for a variable template).
5445 template<typename TemplateLikeDecl>
5447  TemplateLikeDecl *P2,
5448  TemplateDeductionInfo &Info) {
5449  // C++ [temp.class.order]p1:
5450  // For two class template partial specializations, the first is at least as
5451  // specialized as the second if, given the following rewrite to two
5452  // function templates, the first function template is at least as
5453  // specialized as the second according to the ordering rules for function
5454  // templates (14.6.6.2):
5455  // - the first function template has the same template parameters as the
5456  // first partial specialization and has a single function parameter
5457  // whose type is a class template specialization with the template
5458  // arguments of the first partial specialization, and
5459  // - the second function template has the same template parameters as the
5460  // second partial specialization and has a single function parameter
5461  // whose type is a class template specialization with the template
5462  // arguments of the second partial specialization.
5463  //
5464  // Rather than synthesize function templates, we merely perform the
5465  // equivalent partial ordering by performing deduction directly on
5466  // the template arguments of the class template partial
5467  // specializations. This computation is slightly simpler than the
5468  // general problem of function template partial ordering, because
5469  // class template partial specializations are more constrained. We
5470  // know that every template parameter is deducible from the class
5471  // template partial specialization's template arguments, for
5472  // example.
5474 
5475  // Determine whether P1 is at least as specialized as P2.
5476  Deduced.resize(P2->getTemplateParameters()->size());
5477  if (DeduceTemplateArgumentsByTypeMatch(S, P2->getTemplateParameters(),
5478  T2, T1, Info, Deduced, TDF_None,
5479  /*PartialOrdering=*/true))
5480  return false;
5481 
5482  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(),
5483  Deduced.end());
5484  Sema::InstantiatingTemplate Inst(S, Info.getLocation(), P2, DeducedArgs,
5485  Info);
5486  auto *TST1 = T1->castAs<TemplateSpecializationType>();
5487  bool AtLeastAsSpecialized;
5488  S.runWithSufficientStackSpace(Info.getLocation(), [&] {
5489  AtLeastAsSpecialized = !FinishTemplateArgumentDeduction(
5490  S, P2, /*IsPartialOrdering=*/true,
5492  TST1->template_arguments()),
5493  Deduced, Info);
5494  });
5495  return AtLeastAsSpecialized;
5496 }
5497 
5498 /// Returns the more specialized class template partial specialization
5499 /// according to the rules of partial ordering of class template partial
5500 /// specializations (C++ [temp.class.order]).
5501 ///
5502 /// \param PS1 the first class template partial specialization
5503 ///
5504 /// \param PS2 the second class template partial specialization
5505 ///
5506 /// \returns the more specialized class template partial specialization. If
5507 /// neither partial specialization is more specialized, returns NULL.
5512  SourceLocation Loc) {
5515 
5516  TemplateDeductionInfo Info(Loc);
5517  bool Better1 = isAtLeastAsSpecializedAs(*this, PT1, PT2, PS2, Info);
5518  bool Better2 = isAtLeastAsSpecializedAs(*this, PT2, PT1, PS1, Info);
5519 
5520  if (!Better1 && !Better2)
5521  return nullptr;
5522  if (Better1 && Better2) {
5524  PS1->getAssociatedConstraints(AC1);
5525  PS2->getAssociatedConstraints(AC2);
5526  bool AtLeastAsConstrained1, AtLeastAsConstrained2;
5527  if (IsAtLeastAsConstrained(PS1, AC1, PS2, AC2, AtLeastAsConstrained1))
5528  return nullptr;
5529  if (IsAtLeastAsConstrained(PS2, AC2, PS1, AC1, AtLeastAsConstrained2))
5530  return nullptr;
5531  if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
5532  return nullptr;
5533  return AtLeastAsConstrained1 ? PS1 : PS2;
5534  }
5535 
5536  return Better1 ? PS1 : PS2;
5537 }
5538 
5541  ClassTemplateDecl *Primary = Spec->