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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,
163  const TemplateArgument &TemplateArg,
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.
239  if (!X.wasDeducedFromArrayBound() && !Y.wasDeducedFromArrayBound()) {
240  QualType XType = X.getNonTypeTemplateArgumentType();
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.
260  if (X.wasDeducedFromArrayBound() != Y.wasDeducedFromArrayBound())
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.
273  hasSameExtendedValue(X.getAsIntegral(), Y.getAsIntegral())))
274  return X.wasDeducedFromArrayBound() ? Y : X;
275 
276  // All other combinations are incompatible.
277  return DeducedTemplateArgument();
278 
280  if (Y.getKind() == TemplateArgument::Template &&
281  Context.hasSameTemplateName(X.getAsTemplate(), Y.getAsTemplate()))
282  return X;
283 
284  // All other combinations are incompatible.
285  return DeducedTemplateArgument();
286 
289  Context.hasSameTemplateName(X.getAsTemplateOrTemplatePattern(),
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.
332  isSameDeclaration(X.getAsDecl(), Y.getAsDecl()))
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 
362  for (TemplateArgument::pack_iterator XA = X.pack_begin(),
363  XAEnd = X.pack_end(),
364  YA = Y.pack_begin();
365  XA != XAEnd; ++XA, ++YA) {
367  Context, DeducedTemplateArgument(*XA, X.wasDeducedFromArrayBound()),
369  if (Merged.isNull() && !(XA->isNull() && YA->isNull()))
370  return DeducedTemplateArgument();
371  NewPack.push_back(Merged);
372  }
373 
375  TemplateArgument::CreatePackCopy(Context, NewPack),
376  X.wasDeducedFromArrayBound() && Y.wasDeducedFromArrayBound());
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) {
460  NTTP->getLocation()),
461  NullPtrType,
462  NullPtrType->isMemberPointerType() ? CK_NullToMemberPointer
463  : CK_NullToPointer)
464  .get();
465  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
467  Value->getType(), Info, Deduced);
468 }
469 
470 /// Deduce the value of the given non-type template parameter
471 /// from the given type- or value-dependent expression.
472 ///
473 /// \returns true if deduction succeeded, false otherwise.
475  Sema &S, TemplateParameterList *TemplateParams,
477  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
478  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
480  Value->getType(), Info, Deduced);
481 }
482 
483 /// Deduce the value of the given non-type template parameter
484 /// from the given declaration.
485 ///
486 /// \returns true if deduction succeeded, false otherwise.
488  Sema &S, TemplateParameterList *TemplateParams,
489  const NonTypeTemplateParmDecl *NTTP, ValueDecl *D, QualType T,
490  TemplateDeductionInfo &Info,
491  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
492  D = D ? cast<ValueDecl>(D->getCanonicalDecl()) : nullptr;
493  TemplateArgument New(D, T);
495  S, TemplateParams, NTTP, DeducedTemplateArgument(New), T, Info, Deduced);
496 }
497 
500  TemplateParameterList *TemplateParams,
501  TemplateName Param,
502  TemplateName Arg,
503  TemplateDeductionInfo &Info,
504  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
505  TemplateDecl *ParamDecl = Param.getAsTemplateDecl();
506  if (!ParamDecl) {
507  // The parameter type is dependent and is not a template template parameter,
508  // so there is nothing that we can deduce.
509  return Sema::TDK_Success;
510  }
511 
512  if (TemplateTemplateParmDecl *TempParam
513  = dyn_cast<TemplateTemplateParmDecl>(ParamDecl)) {
514  // If we're not deducing at this depth, there's nothing to deduce.
515  if (TempParam->getDepth() != Info.getDeducedDepth())
516  return Sema::TDK_Success;
517 
520  Deduced[TempParam->getIndex()],
521  NewDeduced);
522  if (Result.isNull()) {
523  Info.Param = TempParam;
524  Info.FirstArg = Deduced[TempParam->getIndex()];
525  Info.SecondArg = NewDeduced;
526  return Sema::TDK_Inconsistent;
527  }
528 
529  Deduced[TempParam->getIndex()] = Result;
530  return Sema::TDK_Success;
531  }
532 
533  // Verify that the two template names are equivalent.
534  if (S.Context.hasSameTemplateName(Param, Arg))
535  return Sema::TDK_Success;
536 
537  // Mismatch of non-dependent template parameter to argument.
538  Info.FirstArg = TemplateArgument(Param);
539  Info.SecondArg = TemplateArgument(Arg);
541 }
542 
543 /// Deduce the template arguments by comparing the template parameter
544 /// type (which is a template-id) with the template argument type.
545 ///
546 /// \param S the Sema
547 ///
548 /// \param TemplateParams the template parameters that we are deducing
549 ///
550 /// \param Param the parameter type
551 ///
552 /// \param Arg the argument type
553 ///
554 /// \param Info information about the template argument deduction itself
555 ///
556 /// \param Deduced the deduced template arguments
557 ///
558 /// \returns the result of template argument deduction so far. Note that a
559 /// "success" result means that template argument deduction has not yet failed,
560 /// but it may still fail, later, for other reasons.
563  TemplateParameterList *TemplateParams,
564  const TemplateSpecializationType *Param,
565  QualType Arg,
566  TemplateDeductionInfo &Info,
567  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
568  assert(Arg.isCanonical() && "Argument type must be canonical");
569 
570  // Treat an injected-class-name as its underlying template-id.
571  if (auto *Injected = dyn_cast<InjectedClassNameType>(Arg))
572  Arg = Injected->getInjectedSpecializationType();
573 
574  // Check whether the template argument is a dependent template-id.
575  if (const TemplateSpecializationType *SpecArg
576  = dyn_cast<TemplateSpecializationType>(Arg)) {
577  // Perform template argument deduction for the template name.
579  = DeduceTemplateArguments(S, TemplateParams,
580  Param->getTemplateName(),
581  SpecArg->getTemplateName(),
582  Info, Deduced))
583  return Result;
584 
585 
586  // Perform template argument deduction on each template
587  // argument. Ignore any missing/extra arguments, since they could be
588  // filled in by default arguments.
589  return DeduceTemplateArguments(S, TemplateParams,
590  Param->template_arguments(),
591  SpecArg->template_arguments(), Info, Deduced,
592  /*NumberOfArgumentsMustMatch=*/false);
593  }
594 
595  // If the argument type is a class template specialization, we
596  // perform template argument deduction using its template
597  // arguments.
598  const RecordType *RecordArg = dyn_cast<RecordType>(Arg);
599  if (!RecordArg) {
600  Info.FirstArg = TemplateArgument(QualType(Param, 0));
601  Info.SecondArg = TemplateArgument(Arg);
603  }
604 
606  = dyn_cast<ClassTemplateSpecializationDecl>(RecordArg->getDecl());
607  if (!SpecArg) {
608  Info.FirstArg = TemplateArgument(QualType(Param, 0));
609  Info.SecondArg = TemplateArgument(Arg);
611  }
612 
613  // Perform template argument deduction for the template name.
616  TemplateParams,
617  Param->getTemplateName(),
619  Info, Deduced))
620  return Result;
621 
622  // Perform template argument deduction for the template arguments.
623  return DeduceTemplateArguments(S, TemplateParams, Param->template_arguments(),
624  SpecArg->getTemplateArgs().asArray(), Info,
625  Deduced, /*NumberOfArgumentsMustMatch=*/true);
626 }
627 
628 /// Determines whether the given type is an opaque type that
629 /// might be more qualified when instantiated.
631  switch (T->getTypeClass()) {
632  case Type::TypeOfExpr:
633  case Type::TypeOf:
634  case Type::DependentName:
635  case Type::Decltype:
636  case Type::UnresolvedUsing:
637  case Type::TemplateTypeParm:
638  return true;
639 
640  case Type::ConstantArray:
641  case Type::IncompleteArray:
642  case Type::VariableArray:
643  case Type::DependentSizedArray:
645  cast<ArrayType>(T)->getElementType());
646 
647  default:
648  return false;
649  }
650 }
651 
652 /// Helper function to build a TemplateParameter when we don't
653 /// know its type statically.
655  if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(D))
656  return TemplateParameter(TTP);
657  if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D))
658  return TemplateParameter(NTTP);
659 
660  return TemplateParameter(cast<TemplateTemplateParmDecl>(D));
661 }
662 
663 /// A pack that we're currently deducing.
665  // The index of the pack.
666  unsigned Index;
667 
668  // The old value of the pack before we started deducing it.
670 
671  // A deferred value of this pack from an inner deduction, that couldn't be
672  // deduced because this deduction hadn't happened yet.
674 
675  // The new value of the pack.
677 
678  // The outer deduction for this pack, if any.
679  DeducedPack *Outer = nullptr;
680 
681  DeducedPack(unsigned Index) : Index(Index) {}
682 };
683 
684 namespace {
685 
686 /// A scope in which we're performing pack deduction.
687 class PackDeductionScope {
688 public:
689  /// Prepare to deduce the packs named within Pattern.
690  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
691  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
693  : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
694  unsigned NumNamedPacks = addPacks(Pattern);
695  finishConstruction(NumNamedPacks);
696  }
697 
698  /// Prepare to directly deduce arguments of the parameter with index \p Index.
699  PackDeductionScope(Sema &S, TemplateParameterList *TemplateParams,
700  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
701  TemplateDeductionInfo &Info, unsigned Index)
702  : S(S), TemplateParams(TemplateParams), Deduced(Deduced), Info(Info) {
703  addPack(Index);
704  finishConstruction(1);
705  }
706 
707 private:
708  void addPack(unsigned Index) {
709  // Save the deduced template argument for the parameter pack expanded
710  // by this pack expansion, then clear out the deduction.
711  DeducedPack Pack(Index);
712  Pack.Saved = Deduced[Index];
713  Deduced[Index] = TemplateArgument();
714 
715  // FIXME: What if we encounter multiple packs with different numbers of
716  // pre-expanded expansions? (This should already have been diagnosed
717  // during substitution.)
718  if (Optional<unsigned> ExpandedPackExpansions =
719  getExpandedPackSize(TemplateParams->getParam(Index)))
720  FixedNumExpansions = ExpandedPackExpansions;
721 
722  Packs.push_back(Pack);
723  }
724 
725  unsigned addPacks(TemplateArgument Pattern) {
726  // Compute the set of template parameter indices that correspond to
727  // parameter packs expanded by the pack expansion.
728  llvm::SmallBitVector SawIndices(TemplateParams->size());
730 
731  auto AddPack = [&](unsigned Index) {
732  if (SawIndices[Index])
733  return;
734  SawIndices[Index] = true;
735  addPack(Index);
736 
737  // Deducing a parameter pack that is a pack expansion also constrains the
738  // packs appearing in that parameter to have the same deduced arity. Also,
739  // in C++17 onwards, deducing a non-type template parameter deduces its
740  // type, so we need to collect the pending deduced values for those packs.
741  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(
742  TemplateParams->getParam(Index))) {
743  if (!NTTP->isExpandedParameterPack())
744  if (auto *Expansion = dyn_cast<PackExpansionType>(NTTP->getType()))
745  ExtraDeductions.push_back(Expansion->getPattern());
746  }
747  // FIXME: Also collect the unexpanded packs in any type and template
748  // parameter packs that are pack expansions.
749  };
750 
751  auto Collect = [&](TemplateArgument Pattern) {
753  S.collectUnexpandedParameterPacks(Pattern, Unexpanded);
754  for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
755  unsigned Depth, Index;
756  std::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]);
757  if (Depth == Info.getDeducedDepth())
758  AddPack(Index);
759  }
760  };
761 
762  // Look for unexpanded packs in the pattern.
763  Collect(Pattern);
764  assert(!Packs.empty() && "Pack expansion without unexpanded packs?");
765 
766  unsigned NumNamedPacks = Packs.size();
767 
768  // Also look for unexpanded packs that are indirectly deduced by deducing
769  // the sizes of the packs in this pattern.
770  while (!ExtraDeductions.empty())
771  Collect(ExtraDeductions.pop_back_val());
772 
773  return NumNamedPacks;
774  }
775 
776  void finishConstruction(unsigned NumNamedPacks) {
777  // Dig out the partially-substituted pack, if there is one.
778  const TemplateArgument *PartialPackArgs = nullptr;
779  unsigned NumPartialPackArgs = 0;
780  std::pair<unsigned, unsigned> PartialPackDepthIndex(-1u, -1u);
781  if (auto *Scope = S.CurrentInstantiationScope)
782  if (auto *Partial = Scope->getPartiallySubstitutedPack(
783  &PartialPackArgs, &NumPartialPackArgs))
784  PartialPackDepthIndex = getDepthAndIndex(Partial);
785 
786  // This pack expansion will have been partially or fully expanded if
787  // it only names explicitly-specified parameter packs (including the
788  // partially-substituted one, if any).
789  bool IsExpanded = true;
790  for (unsigned I = 0; I != NumNamedPacks; ++I) {
791  if (Packs[I].Index >= Info.getNumExplicitArgs()) {
792  IsExpanded = false;
793  IsPartiallyExpanded = false;
794  break;
795  }
796  if (PartialPackDepthIndex ==
797  std::make_pair(Info.getDeducedDepth(), Packs[I].Index)) {
798  IsPartiallyExpanded = true;
799  }
800  }
801 
802  // Skip over the pack elements that were expanded into separate arguments.
803  // If we partially expanded, this is the number of partial arguments.
804  if (IsPartiallyExpanded)
805  PackElements += NumPartialPackArgs;
806  else if (IsExpanded)
807  PackElements += *FixedNumExpansions;
808 
809  for (auto &Pack : Packs) {
810  if (Info.PendingDeducedPacks.size() > Pack.Index)
811  Pack.Outer = Info.PendingDeducedPacks[Pack.Index];
812  else
813  Info.PendingDeducedPacks.resize(Pack.Index + 1);
814  Info.PendingDeducedPacks[Pack.Index] = &Pack;
815 
816  if (PartialPackDepthIndex ==
817  std::make_pair(Info.getDeducedDepth(), Pack.Index)) {
818  Pack.New.append(PartialPackArgs, PartialPackArgs + NumPartialPackArgs);
819  // We pre-populate the deduced value of the partially-substituted
820  // pack with the specified value. This is not entirely correct: the
821  // value is supposed to have been substituted, not deduced, but the
822  // cases where this is observable require an exact type match anyway.
823  //
824  // FIXME: If we could represent a "depth i, index j, pack elem k"
825  // parameter, we could substitute the partially-substituted pack
826  // everywhere and avoid this.
827  if (!IsPartiallyExpanded)
828  Deduced[Pack.Index] = Pack.New[PackElements];
829  }
830  }
831  }
832 
833 public:
834  ~PackDeductionScope() {
835  for (auto &Pack : Packs)
836  Info.PendingDeducedPacks[Pack.Index] = Pack.Outer;
837  }
838 
839  /// Determine whether this pack has already been partially expanded into a
840  /// sequence of (prior) function parameters / template arguments.
841  bool isPartiallyExpanded() { return IsPartiallyExpanded; }
842 
843  /// Determine whether this pack expansion scope has a known, fixed arity.
844  /// This happens if it involves a pack from an outer template that has
845  /// (notionally) already been expanded.
846  bool hasFixedArity() { return FixedNumExpansions.hasValue(); }
847 
848  /// Determine whether the next element of the argument is still part of this
849  /// pack. This is the case unless the pack is already expanded to a fixed
850  /// length.
851  bool hasNextElement() {
852  return !FixedNumExpansions || *FixedNumExpansions > PackElements;
853  }
854 
855  /// Move to deducing the next element in each pack that is being deduced.
856  void nextPackElement() {
857  // Capture the deduced template arguments for each parameter pack expanded
858  // by this pack expansion, add them to the list of arguments we've deduced
859  // for that pack, then clear out the deduced argument.
860  for (auto &Pack : Packs) {
861  DeducedTemplateArgument &DeducedArg = Deduced[Pack.Index];
862  if (!Pack.New.empty() || !DeducedArg.isNull()) {
863  while (Pack.New.size() < PackElements)
864  Pack.New.push_back(DeducedTemplateArgument());
865  if (Pack.New.size() == PackElements)
866  Pack.New.push_back(DeducedArg);
867  else
868  Pack.New[PackElements] = DeducedArg;
869  DeducedArg = Pack.New.size() > PackElements + 1
870  ? Pack.New[PackElements + 1]
872  }
873  }
874  ++PackElements;
875  }
876 
877  /// Finish template argument deduction for a set of argument packs,
878  /// producing the argument packs and checking for consistency with prior
879  /// deductions.
881  // Build argument packs for each of the parameter packs expanded by this
882  // pack expansion.
883  for (auto &Pack : Packs) {
884  // Put back the old value for this pack.
885  Deduced[Pack.Index] = Pack.Saved;
886 
887  // Always make sure the size of this pack is correct, even if we didn't
888  // deduce any values for it.
889  //
890  // FIXME: This isn't required by the normative wording, but substitution
891  // and post-substitution checking will always fail if the arity of any
892  // pack is not equal to the number of elements we processed. (Either that
893  // or something else has gone *very* wrong.) We're permitted to skip any
894  // hard errors from those follow-on steps by the intent (but not the
895  // wording) of C++ [temp.inst]p8:
896  //
897  // If the function selected by overload resolution can be determined
898  // without instantiating a class template definition, it is unspecified
899  // whether that instantiation actually takes place
900  Pack.New.resize(PackElements);
901 
902  // Build or find a new value for this pack.
903  DeducedTemplateArgument NewPack;
904  if (Pack.New.empty()) {
905  // If we deduced an empty argument pack, create it now.
907  } else {
908  TemplateArgument *ArgumentPack =
909  new (S.Context) TemplateArgument[Pack.New.size()];
910  std::copy(Pack.New.begin(), Pack.New.end(), ArgumentPack);
911  NewPack = DeducedTemplateArgument(
912  TemplateArgument(llvm::makeArrayRef(ArgumentPack, Pack.New.size())),
913  // FIXME: This is wrong, it's possible that some pack elements are
914  // deduced from an array bound and others are not:
915  // template<typename ...T, T ...V> void g(const T (&...p)[V]);
916  // g({1, 2, 3}, {{}, {}});
917  // ... should deduce T = {int, size_t (from array bound)}.
918  Pack.New[0].wasDeducedFromArrayBound());
919  }
920 
921  // Pick where we're going to put the merged pack.
923  if (Pack.Outer) {
924  if (Pack.Outer->DeferredDeduction.isNull()) {
925  // Defer checking this pack until we have a complete pack to compare
926  // it against.
927  Pack.Outer->DeferredDeduction = NewPack;
928  continue;
929  }
930  Loc = &Pack.Outer->DeferredDeduction;
931  } else {
932  Loc = &Deduced[Pack.Index];
933  }
934 
935  // Check the new pack matches any previous value.
936  DeducedTemplateArgument OldPack = *Loc;
937  DeducedTemplateArgument Result =
938  checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
939 
940  // If we deferred a deduction of this pack, check that one now too.
941  if (!Result.isNull() && !Pack.DeferredDeduction.isNull()) {
942  OldPack = Result;
943  NewPack = Pack.DeferredDeduction;
944  Result = checkDeducedTemplateArguments(S.Context, OldPack, NewPack);
945  }
946 
947  NamedDecl *Param = TemplateParams->getParam(Pack.Index);
948  if (Result.isNull()) {
949  Info.Param = makeTemplateParameter(Param);
950  Info.FirstArg = OldPack;
951  Info.SecondArg = NewPack;
952  return Sema::TDK_Inconsistent;
953  }
954 
955  // If we have a pre-expanded pack and we didn't deduce enough elements
956  // for it, fail deduction.
957  if (Optional<unsigned> Expansions = getExpandedPackSize(Param)) {
958  if (*Expansions != PackElements) {
959  Info.Param = makeTemplateParameter(Param);
960  Info.FirstArg = Result;
962  }
963  }
964 
965  *Loc = Result;
966  }
967 
968  return Sema::TDK_Success;
969  }
970 
971 private:
972  Sema &S;
973  TemplateParameterList *TemplateParams;
974  SmallVectorImpl<DeducedTemplateArgument> &Deduced;
975  TemplateDeductionInfo &Info;
976  unsigned PackElements = 0;
977  bool IsPartiallyExpanded = false;
978  /// The number of expansions, if we have a fully-expanded pack in this scope.
979  Optional<unsigned> FixedNumExpansions;
980 
982 };
983 
984 } // namespace
985 
986 /// Deduce the template arguments by comparing the list of parameter
987 /// types to the list of argument types, as in the parameter-type-lists of
988 /// function types (C++ [temp.deduct.type]p10).
989 ///
990 /// \param S The semantic analysis object within which we are deducing
991 ///
992 /// \param TemplateParams The template parameters that we are deducing
993 ///
994 /// \param Params The list of parameter types
995 ///
996 /// \param NumParams The number of types in \c Params
997 ///
998 /// \param Args The list of argument types
999 ///
1000 /// \param NumArgs The number of types in \c Args
1001 ///
1002 /// \param Info information about the template argument deduction itself
1003 ///
1004 /// \param Deduced the deduced template arguments
1005 ///
1006 /// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
1007 /// how template argument deduction is performed.
1008 ///
1009 /// \param PartialOrdering If true, we are performing template argument
1010 /// deduction for during partial ordering for a call
1011 /// (C++0x [temp.deduct.partial]).
1012 ///
1013 /// \returns the result of template argument deduction so far. Note that a
1014 /// "success" result means that template argument deduction has not yet failed,
1015 /// but it may still fail, later, for other reasons.
1018  TemplateParameterList *TemplateParams,
1019  const QualType *Params, unsigned NumParams,
1020  const QualType *Args, unsigned NumArgs,
1021  TemplateDeductionInfo &Info,
1022  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
1023  unsigned TDF,
1024  bool PartialOrdering = false) {
1025  // C++0x [temp.deduct.type]p10:
1026  // Similarly, if P has a form that contains (T), then each parameter type
1027  // Pi of the respective parameter-type- list of P is compared with the
1028  // corresponding parameter type Ai of the corresponding parameter-type-list
1029  // of A. [...]
1030  unsigned ArgIdx = 0, ParamIdx = 0;
1031  for (; ParamIdx != NumParams; ++ParamIdx) {
1032  // Check argument types.
1033  const PackExpansionType *Expansion
1034  = dyn_cast<PackExpansionType>(Params[ParamIdx]);
1035  if (!Expansion) {
1036  // Simple case: compare the parameter and argument types at this point.
1037 
1038  // Make sure we have an argument.
1039  if (ArgIdx >= NumArgs)
1041 
1042  if (isa<PackExpansionType>(Args[ArgIdx])) {
1043  // C++0x [temp.deduct.type]p22:
1044  // If the original function parameter associated with A is a function
1045  // parameter pack and the function parameter associated with P is not
1046  // a function parameter pack, then template argument deduction fails.
1048  }
1049 
1051  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1052  Params[ParamIdx], Args[ArgIdx],
1053  Info, Deduced, TDF,
1054  PartialOrdering))
1055  return Result;
1056 
1057  ++ArgIdx;
1058  continue;
1059  }
1060 
1061  // C++0x [temp.deduct.type]p10:
1062  // If the parameter-declaration corresponding to Pi is a function
1063  // parameter pack, then the type of its declarator- id is compared with
1064  // each remaining parameter type in the parameter-type-list of A. Each
1065  // comparison deduces template arguments for subsequent positions in the
1066  // template parameter packs expanded by the function parameter pack.
1067 
1068  QualType Pattern = Expansion->getPattern();
1069  PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
1070 
1071  // A pack scope with fixed arity is not really a pack any more, so is not
1072  // a non-deduced context.
1073  if (ParamIdx + 1 == NumParams || PackScope.hasFixedArity()) {
1074  for (; ArgIdx < NumArgs && PackScope.hasNextElement(); ++ArgIdx) {
1075  // Deduce template arguments from the pattern.
1077  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, Pattern,
1078  Args[ArgIdx], Info, Deduced,
1079  TDF, PartialOrdering))
1080  return Result;
1081 
1082  PackScope.nextPackElement();
1083  }
1084  } else {
1085  // C++0x [temp.deduct.type]p5:
1086  // The non-deduced contexts are:
1087  // - A function parameter pack that does not occur at the end of the
1088  // parameter-declaration-clause.
1089  //
1090  // FIXME: There is no wording to say what we should do in this case. We
1091  // choose to resolve this by applying the same rule that is applied for a
1092  // function call: that is, deduce all contained packs to their
1093  // explicitly-specified values (or to <> if there is no such value).
1094  //
1095  // This is seemingly-arbitrarily different from the case of a template-id
1096  // with a non-trailing pack-expansion in its arguments, which renders the
1097  // entire template-argument-list a non-deduced context.
1098 
1099  // If the parameter type contains an explicitly-specified pack that we
1100  // could not expand, skip the number of parameters notionally created
1101  // by the expansion.
1102  Optional<unsigned> NumExpansions = Expansion->getNumExpansions();
1103  if (NumExpansions && !PackScope.isPartiallyExpanded()) {
1104  for (unsigned I = 0; I != *NumExpansions && ArgIdx < NumArgs;
1105  ++I, ++ArgIdx)
1106  PackScope.nextPackElement();
1107  }
1108  }
1109 
1110  // Build argument packs for each of the parameter packs expanded by this
1111  // pack expansion.
1112  if (auto Result = PackScope.finish())
1113  return Result;
1114  }
1115 
1116  // Make sure we don't have any extra arguments.
1117  if (ArgIdx < NumArgs)
1119 
1120  return Sema::TDK_Success;
1121 }
1122 
1123 /// Determine whether the parameter has qualifiers that the argument
1124 /// lacks. Put another way, determine whether there is no way to add
1125 /// a deduced set of qualifiers to the ParamType that would result in
1126 /// its qualifiers matching those of the ArgType.
1128  QualType ArgType) {
1129  Qualifiers ParamQs = ParamType.getQualifiers();
1130  Qualifiers ArgQs = ArgType.getQualifiers();
1131 
1132  if (ParamQs == ArgQs)
1133  return false;
1134 
1135  // Mismatched (but not missing) Objective-C GC attributes.
1136  if (ParamQs.getObjCGCAttr() != ArgQs.getObjCGCAttr() &&
1137  ParamQs.hasObjCGCAttr())
1138  return true;
1139 
1140  // Mismatched (but not missing) address spaces.
1141  if (ParamQs.getAddressSpace() != ArgQs.getAddressSpace() &&
1142  ParamQs.hasAddressSpace())
1143  return true;
1144 
1145  // Mismatched (but not missing) Objective-C lifetime qualifiers.
1146  if (ParamQs.getObjCLifetime() != ArgQs.getObjCLifetime() &&
1147  ParamQs.hasObjCLifetime())
1148  return true;
1149 
1150  // CVR qualifiers inconsistent or a superset.
1151  return (ParamQs.getCVRQualifiers() & ~ArgQs.getCVRQualifiers()) != 0;
1152 }
1153 
1154 /// Compare types for equality with respect to possibly compatible
1155 /// function types (noreturn adjustment, implicit calling conventions). If any
1156 /// of parameter and argument is not a function, just perform type comparison.
1157 ///
1158 /// \param Param the template parameter type.
1159 ///
1160 /// \param Arg the argument type.
1162  CanQualType Arg) {
1163  const FunctionType *ParamFunction = Param->getAs<FunctionType>(),
1164  *ArgFunction = Arg->getAs<FunctionType>();
1165 
1166  // Just compare if not functions.
1167  if (!ParamFunction || !ArgFunction)
1168  return Param == Arg;
1169 
1170  // Noreturn and noexcept adjustment.
1171  QualType AdjustedParam;
1172  if (IsFunctionConversion(Param, Arg, AdjustedParam))
1173  return Arg == Context.getCanonicalType(AdjustedParam);
1174 
1175  // FIXME: Compatible calling conventions.
1176 
1177  return Param == Arg;
1178 }
1179 
1180 /// Get the index of the first template parameter that was originally from the
1181 /// innermost template-parameter-list. This is 0 except when we concatenate
1182 /// the template parameter lists of a class template and a constructor template
1183 /// when forming an implicit deduction guide.
1185  auto *Guide = dyn_cast<CXXDeductionGuideDecl>(FTD->getTemplatedDecl());
1186  if (!Guide || !Guide->isImplicit())
1187  return 0;
1188  return Guide->getDeducedTemplate()->getTemplateParameters()->size();
1189 }
1190 
1191 /// Determine whether a type denotes a forwarding reference.
1192 static bool isForwardingReference(QualType Param, unsigned FirstInnerIndex) {
1193  // C++1z [temp.deduct.call]p3:
1194  // A forwarding reference is an rvalue reference to a cv-unqualified
1195  // template parameter that does not represent a template parameter of a
1196  // class template.
1197  if (auto *ParamRef = Param->getAs<RValueReferenceType>()) {
1198  if (ParamRef->getPointeeType().getQualifiers())
1199  return false;
1200  auto *TypeParm = ParamRef->getPointeeType()->getAs<TemplateTypeParmType>();
1201  return TypeParm && TypeParm->getIndex() >= FirstInnerIndex;
1202  }
1203  return false;
1204 }
1205 
1206 /// Attempt to deduce the template arguments by checking the base types
1207 /// according to (C++20 [temp.deduct.call] p4b3.
1208 ///
1209 /// \param S the semantic analysis object within which we are deducing.
1210 ///
1211 /// \param RecordT the top level record object we are deducing against.
1212 ///
1213 /// \param TemplateParams the template parameters that we are deducing.
1214 ///
1215 /// \param SpecParam the template specialization parameter type.
1216 ///
1217 /// \param Info information about the template argument deduction itself.
1218 ///
1219 /// \param Deduced the deduced template arguments.
1220 ///
1221 /// \returns the result of template argument deduction with the bases. "invalid"
1222 /// means no matches, "success" found a single item, and the
1223 /// "MiscellaneousDeductionFailure" result happens when the match is ambiguous.
1225  Sema &S, const RecordType *RecordT, TemplateParameterList *TemplateParams,
1226  const TemplateSpecializationType *SpecParam, TemplateDeductionInfo &Info,
1227  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
1228  // C++14 [temp.deduct.call] p4b3:
1229  // If P is a class and P has the form simple-template-id, then the
1230  // transformed A can be a derived class of the deduced A. Likewise if
1231  // P is a pointer to a class of the form simple-template-id, the
1232  // transformed A can be a pointer to a derived class pointed to by the
1233  // deduced A. However, if there is a class C that is a (direct or
1234  // indirect) base class of D and derived (directly or indirectly) from a
1235  // class B and that would be a valid deduced A, the deduced A cannot be
1236  // B or pointer to B, respectively.
1237  //
1238  // These alternatives are considered only if type deduction would
1239  // otherwise fail. If they yield more than one possible deduced A, the
1240  // type deduction fails.
1241 
1242  // Use a breadth-first search through the bases to collect the set of
1243  // successful matches. Visited contains the set of nodes we have already
1244  // visited, while ToVisit is our stack of records that we still need to
1245  // visit. Matches contains a list of matches that have yet to be
1246  // disqualified.
1249  // We iterate over this later, so we have to use MapVector to ensure
1250  // determinism.
1251  llvm::MapVector<const RecordType *, SmallVector<DeducedTemplateArgument, 8>>
1252  Matches;
1253 
1254  auto AddBases = [&Visited, &ToVisit](const RecordType *RT) {
1255  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1256  for (const auto &Base : RD->bases()) {
1257  assert(Base.getType()->isRecordType() &&
1258  "Base class that isn't a record?");
1259  const RecordType *RT = Base.getType()->getAs<RecordType>();
1260  if (Visited.insert(RT).second)
1261  ToVisit.push_back(Base.getType()->getAs<RecordType>());
1262  }
1263  };
1264 
1265  // Set up the loop by adding all the bases.
1266  AddBases(RecordT);
1267 
1268  // Search each path of bases until we either run into a successful match
1269  // (where all bases of it are invalid), or we run out of bases.
1270  while (!ToVisit.empty()) {
1271  const RecordType *NextT = ToVisit.pop_back_val();
1272 
1273  SmallVector<DeducedTemplateArgument, 8> DeducedCopy(Deduced.begin(),
1274  Deduced.end());
1277  DeduceTemplateArguments(S, TemplateParams, SpecParam,
1278  QualType(NextT, 0), BaseInfo, DeducedCopy);
1279 
1280  // If this was a successful deduction, add it to the list of matches,
1281  // otherwise we need to continue searching its bases.
1283  Matches.insert({NextT, DeducedCopy});
1284  else
1285  AddBases(NextT);
1286  }
1287 
1288  // At this point, 'Matches' contains a list of seemingly valid bases, however
1289  // in the event that we have more than 1 match, it is possible that the base
1290  // of one of the matches might be disqualified for being a base of another
1291  // valid match. We can count on cyclical instantiations being invalid to
1292  // simplify the disqualifications. That is, if A & B are both matches, and B
1293  // inherits from A (disqualifying A), we know that A cannot inherit from B.
1294  if (Matches.size() > 1) {
1295  Visited.clear();
1296  for (const auto &Match : Matches)
1297  AddBases(Match.first);
1298 
1299  // We can give up once we have a single item (or have run out of things to
1300  // search) since cyclical inheritence isn't valid.
1301  while (Matches.size() > 1 && !ToVisit.empty()) {
1302  const RecordType *NextT = ToVisit.pop_back_val();
1303  Matches.erase(NextT);
1304 
1305  // Always add all bases, since the inheritence tree can contain
1306  // disqualifications for multiple matches.
1307  AddBases(NextT);
1308  }
1309  }
1310 
1311  if (Matches.empty())
1312  return Sema::TDK_Invalid;
1313  if (Matches.size() > 1)
1315 
1316  std::swap(Matches.front().second, Deduced);
1317  return Sema::TDK_Success;
1318 }
1319 
1320 /// Deduce the template arguments by comparing the parameter type and
1321 /// the argument type (C++ [temp.deduct.type]).
1322 ///
1323 /// \param S the semantic analysis object within which we are deducing
1324 ///
1325 /// \param TemplateParams the template parameters that we are deducing
1326 ///
1327 /// \param ParamIn the parameter type
1328 ///
1329 /// \param ArgIn the argument type
1330 ///
1331 /// \param Info information about the template argument deduction itself
1332 ///
1333 /// \param Deduced the deduced template arguments
1334 ///
1335 /// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
1336 /// how template argument deduction is performed.
1337 ///
1338 /// \param PartialOrdering Whether we're performing template argument deduction
1339 /// in the context of partial ordering (C++0x [temp.deduct.partial]).
1340 ///
1341 /// \returns the result of template argument deduction so far. Note that a
1342 /// "success" result means that template argument deduction has not yet failed,
1343 /// but it may still fail, later, for other reasons.
1346  TemplateParameterList *TemplateParams,
1347  QualType ParamIn, QualType ArgIn,
1348  TemplateDeductionInfo &Info,
1349  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
1350  unsigned TDF,
1351  bool PartialOrdering,
1352  bool DeducedFromArrayBound) {
1353  // We only want to look at the canonical types, since typedefs and
1354  // sugar are not part of template argument deduction.
1355  QualType Param = S.Context.getCanonicalType(ParamIn);
1356  QualType Arg = S.Context.getCanonicalType(ArgIn);
1357 
1358  // If the argument type is a pack expansion, look at its pattern.
1359  // This isn't explicitly called out
1360  if (const PackExpansionType *ArgExpansion
1361  = dyn_cast<PackExpansionType>(Arg))
1362  Arg = ArgExpansion->getPattern();
1363 
1364  if (PartialOrdering) {
1365  // C++11 [temp.deduct.partial]p5:
1366  // Before the partial ordering is done, certain transformations are
1367  // performed on the types used for partial ordering:
1368  // - If P is a reference type, P is replaced by the type referred to.
1369  const ReferenceType *ParamRef = Param->getAs<ReferenceType>();
1370  if (ParamRef)
1371  Param = ParamRef->getPointeeType();
1372 
1373  // - If A is a reference type, A is replaced by the type referred to.
1374  const ReferenceType *ArgRef = Arg->getAs<ReferenceType>();
1375  if (ArgRef)
1376  Arg = ArgRef->getPointeeType();
1377 
1378  if (ParamRef && ArgRef && S.Context.hasSameUnqualifiedType(Param, Arg)) {
1379  // C++11 [temp.deduct.partial]p9:
1380  // If, for a given type, deduction succeeds in both directions (i.e.,
1381  // the types are identical after the transformations above) and both
1382  // P and A were reference types [...]:
1383  // - if [one type] was an lvalue reference and [the other type] was
1384  // not, [the other type] is not considered to be at least as
1385  // specialized as [the first type]
1386  // - if [one type] is more cv-qualified than [the other type],
1387  // [the other type] is not considered to be at least as specialized
1388  // as [the first type]
1389  // Objective-C ARC adds:
1390  // - [one type] has non-trivial lifetime, [the other type] has
1391  // __unsafe_unretained lifetime, and the types are otherwise
1392  // identical
1393  //
1394  // A is "considered to be at least as specialized" as P iff deduction
1395  // succeeds, so we model this as a deduction failure. Note that
1396  // [the first type] is P and [the other type] is A here; the standard
1397  // gets this backwards.
1398  Qualifiers ParamQuals = Param.getQualifiers();
1399  Qualifiers ArgQuals = Arg.getQualifiers();
1400  if ((ParamRef->isLValueReferenceType() &&
1401  !ArgRef->isLValueReferenceType()) ||
1402  ParamQuals.isStrictSupersetOf(ArgQuals) ||
1403  (ParamQuals.hasNonTrivialObjCLifetime() &&
1405  ParamQuals.withoutObjCLifetime() ==
1406  ArgQuals.withoutObjCLifetime())) {
1407  Info.FirstArg = TemplateArgument(ParamIn);
1408  Info.SecondArg = TemplateArgument(ArgIn);
1410  }
1411  }
1412 
1413  // C++11 [temp.deduct.partial]p7:
1414  // Remove any top-level cv-qualifiers:
1415  // - If P is a cv-qualified type, P is replaced by the cv-unqualified
1416  // version of P.
1417  Param = Param.getUnqualifiedType();
1418  // - If A is a cv-qualified type, A is replaced by the cv-unqualified
1419  // version of A.
1420  Arg = Arg.getUnqualifiedType();
1421  } else {
1422  // C++0x [temp.deduct.call]p4 bullet 1:
1423  // - If the original P is a reference type, the deduced A (i.e., the type
1424  // referred to by the reference) can be more cv-qualified than the
1425  // transformed A.
1426  if (TDF & TDF_ParamWithReferenceType) {
1427  Qualifiers Quals;
1428  QualType UnqualParam = S.Context.getUnqualifiedArrayType(Param, Quals);
1429  Quals.setCVRQualifiers(Quals.getCVRQualifiers() &
1430  Arg.getCVRQualifiers());
1431  Param = S.Context.getQualifiedType(UnqualParam, Quals);
1432  }
1433 
1434  if ((TDF & TDF_TopLevelParameterTypeList) && !Param->isFunctionType()) {
1435  // C++0x [temp.deduct.type]p10:
1436  // If P and A are function types that originated from deduction when
1437  // taking the address of a function template (14.8.2.2) or when deducing
1438  // template arguments from a function declaration (14.8.2.6) and Pi and
1439  // Ai are parameters of the top-level parameter-type-list of P and A,
1440  // respectively, Pi is adjusted if it is a forwarding reference and Ai
1441  // is an lvalue reference, in
1442  // which case the type of Pi is changed to be the template parameter
1443  // type (i.e., T&& is changed to simply T). [ Note: As a result, when
1444  // Pi is T&& and Ai is X&, the adjusted Pi will be T, causing T to be
1445  // deduced as X&. - end note ]
1447  if (isForwardingReference(Param, 0) && Arg->isLValueReferenceType())
1448  Param = Param->getPointeeType();
1449  }
1450  }
1451 
1452  // C++ [temp.deduct.type]p9:
1453  // A template type argument T, a template template argument TT or a
1454  // template non-type argument i can be deduced if P and A have one of
1455  // the following forms:
1456  //
1457  // T
1458  // cv-list T
1459  if (const TemplateTypeParmType *TemplateTypeParm
1460  = Param->getAs<TemplateTypeParmType>()) {
1461  // Just skip any attempts to deduce from a placeholder type or a parameter
1462  // at a different depth.
1463  if (Arg->isPlaceholderType() ||
1464  Info.getDeducedDepth() != TemplateTypeParm->getDepth())
1465  return Sema::TDK_Success;
1466 
1467  unsigned Index = TemplateTypeParm->getIndex();
1468  bool RecanonicalizeArg = false;
1469 
1470  // If the argument type is an array type, move the qualifiers up to the
1471  // top level, so they can be matched with the qualifiers on the parameter.
1472  if (isa<ArrayType>(Arg)) {
1473  Qualifiers Quals;
1474  Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
1475  if (Quals) {
1476  Arg = S.Context.getQualifiedType(Arg, Quals);
1477  RecanonicalizeArg = true;
1478  }
1479  }
1480 
1481  // The argument type can not be less qualified than the parameter
1482  // type.
1483  if (!(TDF & TDF_IgnoreQualifiers) &&
1485  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1486  Info.FirstArg = TemplateArgument(Param);
1487  Info.SecondArg = TemplateArgument(Arg);
1488  return Sema::TDK_Underqualified;
1489  }
1490 
1491  // Do not match a function type with a cv-qualified type.
1492  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1584
1493  if (Arg->isFunctionType() && Param.hasQualifiers()) {
1495  }
1496 
1497  assert(TemplateTypeParm->getDepth() == Info.getDeducedDepth() &&
1498  "saw template type parameter with wrong depth");
1499  assert(Arg != S.Context.OverloadTy && "Unresolved overloaded function");
1500  QualType DeducedType = Arg;
1501 
1502  // Remove any qualifiers on the parameter from the deduced type.
1503  // We checked the qualifiers for consistency above.
1504  Qualifiers DeducedQs = DeducedType.getQualifiers();
1505  Qualifiers ParamQs = Param.getQualifiers();
1506  DeducedQs.removeCVRQualifiers(ParamQs.getCVRQualifiers());
1507  if (ParamQs.hasObjCGCAttr())
1508  DeducedQs.removeObjCGCAttr();
1509  if (ParamQs.hasAddressSpace())
1510  DeducedQs.removeAddressSpace();
1511  if (ParamQs.hasObjCLifetime())
1512  DeducedQs.removeObjCLifetime();
1513 
1514  // Objective-C ARC:
1515  // If template deduction would produce a lifetime qualifier on a type
1516  // that is not a lifetime type, template argument deduction fails.
1517  if (ParamQs.hasObjCLifetime() && !DeducedType->isObjCLifetimeType() &&
1519  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1520  Info.FirstArg = TemplateArgument(Param);
1521  Info.SecondArg = TemplateArgument(Arg);
1522  return Sema::TDK_Underqualified;
1523  }
1524 
1525  // Objective-C ARC:
1526  // If template deduction would produce an argument type with lifetime type
1527  // but no lifetime qualifier, the __strong lifetime qualifier is inferred.
1528  if (S.getLangOpts().ObjCAutoRefCount &&
1530  !DeducedQs.hasObjCLifetime())
1532 
1533  DeducedType = S.Context.getQualifiedType(DeducedType.getUnqualifiedType(),
1534  DeducedQs);
1535 
1536  if (RecanonicalizeArg)
1538 
1539  DeducedTemplateArgument NewDeduced(DeducedType, DeducedFromArrayBound);
1541  Deduced[Index],
1542  NewDeduced);
1543  if (Result.isNull()) {
1544  Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
1545  Info.FirstArg = Deduced[Index];
1546  Info.SecondArg = NewDeduced;
1547  return Sema::TDK_Inconsistent;
1548  }
1549 
1550  Deduced[Index] = Result;
1551  return Sema::TDK_Success;
1552  }
1553 
1554  // Set up the template argument deduction information for a failure.
1555  Info.FirstArg = TemplateArgument(ParamIn);
1556  Info.SecondArg = TemplateArgument(ArgIn);
1557 
1558  // If the parameter is an already-substituted template parameter
1559  // pack, do nothing: we don't know which of its arguments to look
1560  // at, so we have to wait until all of the parameter packs in this
1561  // expansion have arguments.
1562  if (isa<SubstTemplateTypeParmPackType>(Param))
1563  return Sema::TDK_Success;
1564 
1565  // Check the cv-qualifiers on the parameter and argument types.
1566  CanQualType CanParam = S.Context.getCanonicalType(Param);
1567  CanQualType CanArg = S.Context.getCanonicalType(Arg);
1568  if (!(TDF & TDF_IgnoreQualifiers)) {
1569  if (TDF & TDF_ParamWithReferenceType) {
1570  if (hasInconsistentOrSupersetQualifiersOf(Param, Arg))
1572  } else if (TDF & TDF_ArgWithReferenceType) {
1573  // C++ [temp.deduct.conv]p4:
1574  // If the original A is a reference type, A can be more cv-qualified
1575  // than the deduced A
1576  if (!Arg.getQualifiers().compatiblyIncludes(Param.getQualifiers()))
1578 
1579  // Strip out all extra qualifiers from the argument to figure out the
1580  // type we're converting to, prior to the qualification conversion.
1581  Qualifiers Quals;
1582  Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
1583  Arg = S.Context.getQualifiedType(Arg, Param.getQualifiers());
1584  } else if (!IsPossiblyOpaquelyQualifiedType(Param)) {
1585  if (Param.getCVRQualifiers() != Arg.getCVRQualifiers())
1587  }
1588 
1589  // If the parameter type is not dependent, there is nothing to deduce.
1590  if (!Param->isDependentType()) {
1591  if (!(TDF & TDF_SkipNonDependent)) {
1592  bool NonDeduced =
1594  ? !S.isSameOrCompatibleFunctionType(CanParam, CanArg)
1595  : Param != Arg;
1596  if (NonDeduced) {
1598  }
1599  }
1600  return Sema::TDK_Success;
1601  }
1602  } else if (!Param->isDependentType()) {
1603  if (!(TDF & TDF_SkipNonDependent)) {
1604  CanQualType ParamUnqualType = CanParam.getUnqualifiedType(),
1605  ArgUnqualType = CanArg.getUnqualifiedType();
1606  bool Success =
1608  ? S.isSameOrCompatibleFunctionType(ParamUnqualType, ArgUnqualType)
1609  : ParamUnqualType == ArgUnqualType;
1610  if (Success)
1611  return Sema::TDK_Success;
1612  } else {
1613  return Sema::TDK_Success;
1614  }
1615  }
1616 
1617  switch (Param->getTypeClass()) {
1618  // Non-canonical types cannot appear here.
1619 #define NON_CANONICAL_TYPE(Class, Base) \
1620  case Type::Class: llvm_unreachable("deducing non-canonical type: " #Class);
1621 #define TYPE(Class, Base)
1622 #include "clang/AST/TypeNodes.inc"
1623 
1624  case Type::TemplateTypeParm:
1625  case Type::SubstTemplateTypeParmPack:
1626  llvm_unreachable("Type nodes handled above");
1627 
1628  // These types cannot be dependent, so simply check whether the types are
1629  // the same.
1630  case Type::Builtin:
1631  case Type::VariableArray:
1632  case Type::Vector:
1633  case Type::FunctionNoProto:
1634  case Type::Record:
1635  case Type::Enum:
1636  case Type::ObjCObject:
1637  case Type::ObjCInterface:
1638  case Type::ObjCObjectPointer:
1639  case Type::ExtInt:
1640  if (TDF & TDF_SkipNonDependent)
1641  return Sema::TDK_Success;
1642 
1643  if (TDF & TDF_IgnoreQualifiers) {
1644  Param = Param.getUnqualifiedType();
1645  Arg = Arg.getUnqualifiedType();
1646  }
1647 
1648  return Param == Arg? Sema::TDK_Success : Sema::TDK_NonDeducedMismatch;
1649 
1650  // _Complex T [placeholder extension]
1651  case Type::Complex:
1652  if (const ComplexType *ComplexArg = Arg->getAs<ComplexType>())
1653  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1654  cast<ComplexType>(Param)->getElementType(),
1655  ComplexArg->getElementType(),
1656  Info, Deduced, TDF);
1657 
1659 
1660  // _Atomic T [extension]
1661  case Type::Atomic:
1662  if (const AtomicType *AtomicArg = Arg->getAs<AtomicType>())
1663  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1664  cast<AtomicType>(Param)->getValueType(),
1665  AtomicArg->getValueType(),
1666  Info, Deduced, TDF);
1667 
1669 
1670  // T *
1671  case Type::Pointer: {
1672  QualType PointeeType;
1673  if (const PointerType *PointerArg = Arg->getAs<PointerType>()) {
1674  PointeeType = PointerArg->getPointeeType();
1675  } else if (const ObjCObjectPointerType *PointerArg
1676  = Arg->getAs<ObjCObjectPointerType>()) {
1677  PointeeType = PointerArg->getPointeeType();
1678  } else {
1680  }
1681 
1682  unsigned SubTDF = TDF & (TDF_IgnoreQualifiers | TDF_DerivedClass);
1683  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1684  cast<PointerType>(Param)->getPointeeType(),
1685  PointeeType,
1686  Info, Deduced, SubTDF);
1687  }
1688 
1689  // T &
1690  case Type::LValueReference: {
1691  const LValueReferenceType *ReferenceArg =
1692  Arg->getAs<LValueReferenceType>();
1693  if (!ReferenceArg)
1695 
1696  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1697  cast<LValueReferenceType>(Param)->getPointeeType(),
1698  ReferenceArg->getPointeeType(), Info, Deduced, 0);
1699  }
1700 
1701  // T && [C++0x]
1702  case Type::RValueReference: {
1703  const RValueReferenceType *ReferenceArg =
1704  Arg->getAs<RValueReferenceType>();
1705  if (!ReferenceArg)
1707 
1708  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1709  cast<RValueReferenceType>(Param)->getPointeeType(),
1710  ReferenceArg->getPointeeType(),
1711  Info, Deduced, 0);
1712  }
1713 
1714  // T [] (implied, but not stated explicitly)
1715  case Type::IncompleteArray: {
1716  const IncompleteArrayType *IncompleteArrayArg =
1718  if (!IncompleteArrayArg)
1720 
1721  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1722  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1724  IncompleteArrayArg->getElementType(),
1725  Info, Deduced, SubTDF);
1726  }
1727 
1728  // T [integer-constant]
1729  case Type::ConstantArray: {
1730  const ConstantArrayType *ConstantArrayArg =
1732  if (!ConstantArrayArg)
1734 
1735  const ConstantArrayType *ConstantArrayParm =
1737  if (ConstantArrayArg->getSize() != ConstantArrayParm->getSize())
1739 
1740  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1741  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1742  ConstantArrayParm->getElementType(),
1743  ConstantArrayArg->getElementType(),
1744  Info, Deduced, SubTDF);
1745  }
1746 
1747  // type [i]
1748  case Type::DependentSizedArray: {
1749  const ArrayType *ArrayArg = S.Context.getAsArrayType(Arg);
1750  if (!ArrayArg)
1752 
1753  unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
1754 
1755  // Check the element type of the arrays
1756  const DependentSizedArrayType *DependentArrayParm
1759  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1760  DependentArrayParm->getElementType(),
1761  ArrayArg->getElementType(),
1762  Info, Deduced, SubTDF))
1763  return Result;
1764 
1765  // Determine the array bound is something we can deduce.
1766  const NonTypeTemplateParmDecl *NTTP
1767  = getDeducedParameterFromExpr(Info, DependentArrayParm->getSizeExpr());
1768  if (!NTTP)
1769  return Sema::TDK_Success;
1770 
1771  // We can perform template argument deduction for the given non-type
1772  // template parameter.
1773  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
1774  "saw non-type template parameter with wrong depth");
1775  if (const ConstantArrayType *ConstantArrayArg
1776  = dyn_cast<ConstantArrayType>(ArrayArg)) {
1777  llvm::APSInt Size(ConstantArrayArg->getSize());
1778  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, Size,
1779  S.Context.getSizeType(),
1780  /*ArrayBound=*/true,
1781  Info, Deduced);
1782  }
1783  if (const DependentSizedArrayType *DependentArrayArg
1784  = dyn_cast<DependentSizedArrayType>(ArrayArg))
1785  if (DependentArrayArg->getSizeExpr())
1786  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
1787  DependentArrayArg->getSizeExpr(),
1788  Info, Deduced);
1789 
1790  // Incomplete type does not match a dependently-sized array type
1792  }
1793 
1794  // type(*)(T)
1795  // T(*)()
1796  // T(*)(T)
1797  case Type::FunctionProto: {
1798  unsigned SubTDF = TDF & TDF_TopLevelParameterTypeList;
1799  const FunctionProtoType *FunctionProtoArg =
1800  dyn_cast<FunctionProtoType>(Arg);
1801  if (!FunctionProtoArg)
1803 
1804  const FunctionProtoType *FunctionProtoParam =
1805  cast<FunctionProtoType>(Param);
1806 
1807  if (FunctionProtoParam->getMethodQuals()
1808  != FunctionProtoArg->getMethodQuals() ||
1809  FunctionProtoParam->getRefQualifier()
1810  != FunctionProtoArg->getRefQualifier() ||
1811  FunctionProtoParam->isVariadic() != FunctionProtoArg->isVariadic())
1813 
1814  // Check return types.
1815  if (auto Result = DeduceTemplateArgumentsByTypeMatch(
1816  S, TemplateParams, FunctionProtoParam->getReturnType(),
1817  FunctionProtoArg->getReturnType(), Info, Deduced, 0))
1818  return Result;
1819 
1820  // Check parameter types.
1821  if (auto Result = DeduceTemplateArguments(
1822  S, TemplateParams, FunctionProtoParam->param_type_begin(),
1823  FunctionProtoParam->getNumParams(),
1824  FunctionProtoArg->param_type_begin(),
1825  FunctionProtoArg->getNumParams(), Info, Deduced, SubTDF))
1826  return Result;
1827 
1829  return Sema::TDK_Success;
1830 
1831  // FIXME: Per core-2016/10/1019 (no corresponding core issue yet), permit
1832  // deducing through the noexcept-specifier if it's part of the canonical
1833  // type. libstdc++ relies on this.
1834  Expr *NoexceptExpr = FunctionProtoParam->getNoexceptExpr();
1835  if (const NonTypeTemplateParmDecl *NTTP =
1836  NoexceptExpr ? getDeducedParameterFromExpr(Info, NoexceptExpr)
1837  : nullptr) {
1838  assert(NTTP->getDepth() == Info.getDeducedDepth() &&
1839  "saw non-type template parameter with wrong depth");
1840 
1841  llvm::APSInt Noexcept(1);
1842  switch (FunctionProtoArg->canThrow()) {
1843  case CT_Cannot:
1844  Noexcept = 1;
1845  LLVM_FALLTHROUGH;
1846 
1847  case CT_Can:
1848  // We give E in noexcept(E) the "deduced from array bound" treatment.
1849  // FIXME: Should we?
1851  S, TemplateParams, NTTP, Noexcept, S.Context.BoolTy,
1852  /*ArrayBound*/true, Info, Deduced);
1853 
1854  case CT_Dependent:
1855  if (Expr *ArgNoexceptExpr = FunctionProtoArg->getNoexceptExpr())
1857  S, TemplateParams, NTTP, ArgNoexceptExpr, Info, Deduced);
1858  // Can't deduce anything from throw(T...).
1859  break;
1860  }
1861  }
1862  // FIXME: Detect non-deduced exception specification mismatches?
1863  //
1864  // Careful about [temp.deduct.call] and [temp.deduct.conv], which allow
1865  // top-level differences in noexcept-specifications.
1866 
1867  return Sema::TDK_Success;
1868  }
1869 
1870  case Type::InjectedClassName:
1871  // Treat a template's injected-class-name as if the template
1872  // specialization type had been used.
1873  Param = cast<InjectedClassNameType>(Param)
1874  ->getInjectedSpecializationType();
1875  assert(isa<TemplateSpecializationType>(Param) &&
1876  "injected class name is not a template specialization type");
1877  LLVM_FALLTHROUGH;
1878 
1879  // template-name<T> (where template-name refers to a class template)
1880  // template-name<i>
1881  // TT<T>
1882  // TT<i>
1883  // TT<>
1884  case Type::TemplateSpecialization: {
1885  const TemplateSpecializationType *SpecParam =
1886  cast<TemplateSpecializationType>(Param);
1887 
1888  // When Arg cannot be a derived class, we can just try to deduce template
1889  // arguments from the template-id.
1890  const RecordType *RecordT = Arg->getAs<RecordType>();
1891  if (!(TDF & TDF_DerivedClass) || !RecordT)
1892  return DeduceTemplateArguments(S, TemplateParams, SpecParam, Arg, Info,
1893  Deduced);
1894 
1895  SmallVector<DeducedTemplateArgument, 8> DeducedOrig(Deduced.begin(),
1896  Deduced.end());
1897 
1899  S, TemplateParams, SpecParam, Arg, Info, Deduced);
1900 
1901  if (Result == Sema::TDK_Success)
1902  return Result;
1903 
1904  // We cannot inspect base classes as part of deduction when the type
1905  // is incomplete, so either instantiate any templates necessary to
1906  // complete the type, or skip over it if it cannot be completed.
1907  if (!S.isCompleteType(Info.getLocation(), Arg))
1908  return Result;
1909 
1910  // Reset the incorrectly deduced argument from above.
1911  Deduced = DeducedOrig;
1912 
1913  // Check bases according to C++14 [temp.deduct.call] p4b3:
1915  S, RecordT, TemplateParams, SpecParam, Info, Deduced);
1916 
1918  return BaseResult;
1919  return Result;
1920  }
1921 
1922  // T type::*
1923  // T T::*
1924  // T (type::*)()
1925  // type (T::*)()
1926  // type (type::*)(T)
1927  // type (T::*)(T)
1928  // T (type::*)(T)
1929  // T (T::*)()
1930  // T (T::*)(T)
1931  case Type::MemberPointer: {
1932  const MemberPointerType *MemPtrParam = cast<MemberPointerType>(Param);
1933  const MemberPointerType *MemPtrArg = dyn_cast<MemberPointerType>(Arg);
1934  if (!MemPtrArg)
1936 
1937  QualType ParamPointeeType = MemPtrParam->getPointeeType();
1938  if (ParamPointeeType->isFunctionType())
1939  S.adjustMemberFunctionCC(ParamPointeeType, /*IsStatic=*/true,
1940  /*IsCtorOrDtor=*/false, Info.getLocation());
1941  QualType ArgPointeeType = MemPtrArg->getPointeeType();
1942  if (ArgPointeeType->isFunctionType())
1943  S.adjustMemberFunctionCC(ArgPointeeType, /*IsStatic=*/true,
1944  /*IsCtorOrDtor=*/false, Info.getLocation());
1945 
1947  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1948  ParamPointeeType,
1949  ArgPointeeType,
1950  Info, Deduced,
1951  TDF & TDF_IgnoreQualifiers))
1952  return Result;
1953 
1954  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1955  QualType(MemPtrParam->getClass(), 0),
1956  QualType(MemPtrArg->getClass(), 0),
1957  Info, Deduced,
1958  TDF & TDF_IgnoreQualifiers);
1959  }
1960 
1961  // (clang extension)
1962  //
1963  // type(^)(T)
1964  // T(^)()
1965  // T(^)(T)
1966  case Type::BlockPointer: {
1967  const BlockPointerType *BlockPtrParam = cast<BlockPointerType>(Param);
1968  const BlockPointerType *BlockPtrArg = dyn_cast<BlockPointerType>(Arg);
1969 
1970  if (!BlockPtrArg)
1972 
1973  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1974  BlockPtrParam->getPointeeType(),
1975  BlockPtrArg->getPointeeType(),
1976  Info, Deduced, 0);
1977  }
1978 
1979  // (clang extension)
1980  //
1981  // T __attribute__(((ext_vector_type(<integral constant>))))
1982  case Type::ExtVector: {
1983  const ExtVectorType *VectorParam = cast<ExtVectorType>(Param);
1984  if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
1985  // Make sure that the vectors have the same number of elements.
1986  if (VectorParam->getNumElements() != VectorArg->getNumElements())
1988 
1989  // Perform deduction on the element types.
1990  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
1991  VectorParam->getElementType(),
1992  VectorArg->getElementType(),
1993  Info, Deduced, TDF);
1994  }
1995 
1996  if (const DependentSizedExtVectorType *VectorArg
1997  = dyn_cast<DependentSizedExtVectorType>(Arg)) {
1998  // We can't check the number of elements, since the argument has a
1999  // dependent number of elements. This can only occur during partial
2000  // ordering.
2001 
2002  // Perform deduction on the element types.
2003  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2004  VectorParam->getElementType(),
2005  VectorArg->getElementType(),
2006  Info, Deduced, TDF);
2007  }
2008 
2010  }
2011 
2012  case Type::DependentVector: {
2013  const auto *VectorParam = cast<DependentVectorType>(Param);
2014 
2015  if (const auto *VectorArg = dyn_cast<VectorType>(Arg)) {
2016  // Perform deduction on the element types.
2017  if (Sema::TemplateDeductionResult Result =
2019  S, TemplateParams, VectorParam->getElementType(),
2020  VectorArg->getElementType(), Info, Deduced, TDF))
2021  return Result;
2022 
2023  // Perform deduction on the vector size, if we can.
2024  const NonTypeTemplateParmDecl *NTTP =
2025  getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2026  if (!NTTP)
2027  return Sema::TDK_Success;
2028 
2029  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
2030  ArgSize = VectorArg->getNumElements();
2031  // Note that we use the "array bound" rules here; just like in that
2032  // case, we don't have any particular type for the vector size, but
2033  // we can provide one if necessary.
2034  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
2035  S.Context.UnsignedIntTy, true,
2036  Info, Deduced);
2037  }
2038 
2039  if (const auto *VectorArg = dyn_cast<DependentVectorType>(Arg)) {
2040  // Perform deduction on the element types.
2041  if (Sema::TemplateDeductionResult Result =
2043  S, TemplateParams, VectorParam->getElementType(),
2044  VectorArg->getElementType(), Info, Deduced, TDF))
2045  return Result;
2046 
2047  // Perform deduction on the vector size, if we can.
2049  Info, VectorParam->getSizeExpr());
2050  if (!NTTP)
2051  return Sema::TDK_Success;
2052 
2054  S, TemplateParams, NTTP, VectorArg->getSizeExpr(), Info, Deduced);
2055  }
2056 
2058  }
2059 
2060  // (clang extension)
2061  //
2062  // T __attribute__(((ext_vector_type(N))))
2063  case Type::DependentSizedExtVector: {
2064  const DependentSizedExtVectorType *VectorParam
2065  = cast<DependentSizedExtVectorType>(Param);
2066 
2067  if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
2068  // Perform deduction on the element types.
2070  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2071  VectorParam->getElementType(),
2072  VectorArg->getElementType(),
2073  Info, Deduced, TDF))
2074  return Result;
2075 
2076  // Perform deduction on the vector size, if we can.
2077  const NonTypeTemplateParmDecl *NTTP =
2078  getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2079  if (!NTTP)
2080  return Sema::TDK_Success;
2081 
2082  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
2083  ArgSize = VectorArg->getNumElements();
2084  // Note that we use the "array bound" rules here; just like in that
2085  // case, we don't have any particular type for the vector size, but
2086  // we can provide one if necessary.
2087  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
2088  S.Context.IntTy, true, Info,
2089  Deduced);
2090  }
2091 
2092  if (const DependentSizedExtVectorType *VectorArg
2093  = dyn_cast<DependentSizedExtVectorType>(Arg)) {
2094  // Perform deduction on the element types.
2096  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2097  VectorParam->getElementType(),
2098  VectorArg->getElementType(),
2099  Info, Deduced, TDF))
2100  return Result;
2101 
2102  // Perform deduction on the vector size, if we can.
2103  const NonTypeTemplateParmDecl *NTTP =
2104  getDeducedParameterFromExpr(Info, VectorParam->getSizeExpr());
2105  if (!NTTP)
2106  return Sema::TDK_Success;
2107 
2108  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2109  VectorArg->getSizeExpr(),
2110  Info, Deduced);
2111  }
2112 
2114  }
2115 
2116  // (clang extension)
2117  //
2118  // T __attribute__((matrix_type(<integral constant>,
2119  // <integral constant>)))
2120  case Type::ConstantMatrix: {
2121  const ConstantMatrixType *MatrixArg = dyn_cast<ConstantMatrixType>(Arg);
2122  if (!MatrixArg)
2124 
2125  const ConstantMatrixType *MatrixParam = cast<ConstantMatrixType>(Param);
2126  // Check that the dimensions are the same
2127  if (MatrixParam->getNumRows() != MatrixArg->getNumRows() ||
2128  MatrixParam->getNumColumns() != MatrixArg->getNumColumns()) {
2130  }
2131  // Perform deduction on element types.
2133  S, TemplateParams, MatrixParam->getElementType(),
2134  MatrixArg->getElementType(), Info, Deduced, TDF);
2135  }
2136 
2137  case Type::DependentSizedMatrix: {
2138  const MatrixType *MatrixArg = dyn_cast<MatrixType>(Arg);
2139  if (!MatrixArg)
2141 
2142  // Check the element type of the matrixes.
2143  const DependentSizedMatrixType *MatrixParam =
2144  cast<DependentSizedMatrixType>(Param);
2145  if (Sema::TemplateDeductionResult Result =
2147  S, TemplateParams, MatrixParam->getElementType(),
2148  MatrixArg->getElementType(), Info, Deduced, TDF))
2149  return Result;
2150 
2151  // Try to deduce a matrix dimension.
2152  auto DeduceMatrixArg =
2153  [&S, &Info, &Deduced, &TemplateParams](
2154  Expr *ParamExpr, const MatrixType *Arg,
2155  unsigned (ConstantMatrixType::*GetArgDimension)() const,
2156  Expr *(DependentSizedMatrixType::*GetArgDimensionExpr)() const) {
2157  const auto *ArgConstMatrix = dyn_cast<ConstantMatrixType>(Arg);
2158  const auto *ArgDepMatrix = dyn_cast<DependentSizedMatrixType>(Arg);
2159  if (!ParamExpr->isValueDependent()) {
2160  Optional<llvm::APSInt> ParamConst =
2161  ParamExpr->getIntegerConstantExpr(S.Context);
2162  if (!ParamConst)
2164 
2165  if (ArgConstMatrix) {
2166  if ((ArgConstMatrix->*GetArgDimension)() == *ParamConst)
2167  return Sema::TDK_Success;
2169  }
2170 
2171  Expr *ArgExpr = (ArgDepMatrix->*GetArgDimensionExpr)();
2172  if (!ArgExpr->isValueDependent())
2173  if (Optional<llvm::APSInt> ArgConst =
2174  ArgExpr->getIntegerConstantExpr(S.Context))
2175  if (*ArgConst == *ParamConst)
2176  return Sema::TDK_Success;
2178  }
2179 
2180  const NonTypeTemplateParmDecl *NTTP =
2181  getDeducedParameterFromExpr(Info, ParamExpr);
2182  if (!NTTP)
2183  return Sema::TDK_Success;
2184 
2185  if (ArgConstMatrix) {
2186  llvm::APSInt ArgConst(
2188  ArgConst = (ArgConstMatrix->*GetArgDimension)();
2190  S, TemplateParams, NTTP, ArgConst, S.Context.getSizeType(),
2191  /*ArrayBound=*/true, Info, Deduced);
2192  }
2193 
2195  S, TemplateParams, NTTP, (ArgDepMatrix->*GetArgDimensionExpr)(),
2196  Info, Deduced);
2197  };
2198 
2199  auto Result = DeduceMatrixArg(MatrixParam->getRowExpr(), MatrixArg,
2202  if (Result)
2203  return Result;
2204 
2205  return DeduceMatrixArg(MatrixParam->getColumnExpr(), MatrixArg,
2208  }
2209 
2210  // (clang extension)
2211  //
2212  // T __attribute__(((address_space(N))))
2213  case Type::DependentAddressSpace: {
2214  const DependentAddressSpaceType *AddressSpaceParam =
2215  cast<DependentAddressSpaceType>(Param);
2216 
2217  if (const DependentAddressSpaceType *AddressSpaceArg =
2218  dyn_cast<DependentAddressSpaceType>(Arg)) {
2219  // Perform deduction on the pointer type.
2220  if (Sema::TemplateDeductionResult Result =
2222  S, TemplateParams, AddressSpaceParam->getPointeeType(),
2223  AddressSpaceArg->getPointeeType(), Info, Deduced, TDF))
2224  return Result;
2225 
2226  // Perform deduction on the address space, if we can.
2228  Info, AddressSpaceParam->getAddrSpaceExpr());
2229  if (!NTTP)
2230  return Sema::TDK_Success;
2231 
2233  S, TemplateParams, NTTP, AddressSpaceArg->getAddrSpaceExpr(), Info,
2234  Deduced);
2235  }
2236 
2238  llvm::APSInt ArgAddressSpace(S.Context.getTypeSize(S.Context.IntTy),
2239  false);
2240  ArgAddressSpace = toTargetAddressSpace(Arg.getAddressSpace());
2241 
2242  // Perform deduction on the pointer types.
2243  if (Sema::TemplateDeductionResult Result =
2245  S, TemplateParams, AddressSpaceParam->getPointeeType(),
2246  S.Context.removeAddrSpaceQualType(Arg), Info, Deduced, TDF))
2247  return Result;
2248 
2249  // Perform deduction on the address space, if we can.
2251  Info, AddressSpaceParam->getAddrSpaceExpr());
2252  if (!NTTP)
2253  return Sema::TDK_Success;
2254 
2255  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2256  ArgAddressSpace, S.Context.IntTy,
2257  true, Info, Deduced);
2258  }
2259 
2261  }
2262  case Type::DependentExtInt: {
2263  const auto *IntParam = cast<DependentExtIntType>(Param);
2264 
2265  if (const auto *IntArg = dyn_cast<ExtIntType>(Arg)){
2266  if (IntParam->isUnsigned() != IntArg->isUnsigned())
2268 
2269  const NonTypeTemplateParmDecl *NTTP =
2270  getDeducedParameterFromExpr(Info, IntParam->getNumBitsExpr());
2271  if (!NTTP)
2272  return Sema::TDK_Success;
2273 
2274  llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
2275  ArgSize = IntArg->getNumBits();
2276 
2277  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
2278  S.Context.IntTy, true, Info,
2279  Deduced);
2280  }
2281 
2282  if (const auto *IntArg = dyn_cast<DependentExtIntType>(Arg)) {
2283  if (IntParam->isUnsigned() != IntArg->isUnsigned())
2285  return Sema::TDK_Success;
2286  }
2288  }
2289 
2290  case Type::TypeOfExpr:
2291  case Type::TypeOf:
2292  case Type::DependentName:
2293  case Type::UnresolvedUsing:
2294  case Type::Decltype:
2295  case Type::UnaryTransform:
2296  case Type::Auto:
2297  case Type::DeducedTemplateSpecialization:
2298  case Type::DependentTemplateSpecialization:
2299  case Type::PackExpansion:
2300  case Type::Pipe:
2301  // No template argument deduction for these types
2302  return Sema::TDK_Success;
2303  }
2304 
2305  llvm_unreachable("Invalid Type Class!");
2306 }
2307 
2310  TemplateParameterList *TemplateParams,
2311  const TemplateArgument &Param,
2312  TemplateArgument Arg,
2313  TemplateDeductionInfo &Info,
2314  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
2315  // If the template argument is a pack expansion, perform template argument
2316  // deduction against the pattern of that expansion. This only occurs during
2317  // partial ordering.
2318  if (Arg.isPackExpansion())
2319  Arg = Arg.getPackExpansionPattern();
2320 
2321  switch (Param.getKind()) {
2323  llvm_unreachable("Null template argument in parameter list");
2324 
2326  if (Arg.getKind() == TemplateArgument::Type)
2327  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
2328  Param.getAsType(),
2329  Arg.getAsType(),
2330  Info, Deduced, 0);
2331  Info.FirstArg = Param;
2332  Info.SecondArg = Arg;
2334 
2336  if (Arg.getKind() == TemplateArgument::Template)
2337  return DeduceTemplateArguments(S, TemplateParams,
2338  Param.getAsTemplate(),
2339  Arg.getAsTemplate(), Info, Deduced);
2340  Info.FirstArg = Param;
2341  Info.SecondArg = Arg;
2343 
2345  llvm_unreachable("caller should handle pack expansions");
2346 
2348  if (Arg.getKind() == TemplateArgument::Declaration &&
2349  isSameDeclaration(Param.getAsDecl(), Arg.getAsDecl()))
2350  return Sema::TDK_Success;
2351 
2352  Info.FirstArg = Param;
2353  Info.SecondArg = Arg;
2355 
2357  if (Arg.getKind() == TemplateArgument::NullPtr &&
2359  return Sema::TDK_Success;
2360 
2361  Info.FirstArg = Param;
2362  Info.SecondArg = Arg;
2364 
2366  if (Arg.getKind() == TemplateArgument::Integral) {
2367  if (hasSameExtendedValue(Param.getAsIntegral(), Arg.getAsIntegral()))
2368  return Sema::TDK_Success;
2369 
2370  Info.FirstArg = Param;
2371  Info.SecondArg = Arg;
2373  }
2374 
2375  if (Arg.getKind() == TemplateArgument::Expression) {
2376  Info.FirstArg = Param;
2377  Info.SecondArg = Arg;
2379  }
2380 
2381  Info.FirstArg = Param;
2382  Info.SecondArg = Arg;
2384 
2386  if (const NonTypeTemplateParmDecl *NTTP =
2387  getDeducedParameterFromExpr(Info, Param.getAsExpr())) {
2388  if (Arg.getKind() == TemplateArgument::Integral)
2389  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2390  Arg.getAsIntegral(),
2391  Arg.getIntegralType(),
2392  /*ArrayBound=*/false,
2393  Info, Deduced);
2394  if (Arg.getKind() == TemplateArgument::NullPtr)
2395  return DeduceNullPtrTemplateArgument(S, TemplateParams, NTTP,
2396  Arg.getNullPtrType(),
2397  Info, Deduced);
2399  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2400  Arg.getAsExpr(), Info, Deduced);
2402  return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP,
2403  Arg.getAsDecl(),
2404  Arg.getParamTypeForDecl(),
2405  Info, Deduced);
2406 
2407  Info.FirstArg = Param;
2408  Info.SecondArg = Arg;
2410  }
2411 
2412  // Can't deduce anything, but that's okay.
2413  return Sema::TDK_Success;
2414 
2416  llvm_unreachable("Argument packs should be expanded by the caller!");
2417  }
2418 
2419  llvm_unreachable("Invalid TemplateArgument Kind!");
2420 }
2421 
2422 /// Determine whether there is a template argument to be used for
2423 /// deduction.
2424 ///
2425 /// This routine "expands" argument packs in-place, overriding its input
2426 /// parameters so that \c Args[ArgIdx] will be the available template argument.
2427 ///
2428 /// \returns true if there is another template argument (which will be at
2429 /// \c Args[ArgIdx]), false otherwise.
2430 static bool hasTemplateArgumentForDeduction(ArrayRef<TemplateArgument> &Args,
2431  unsigned &ArgIdx) {
2432  if (ArgIdx == Args.size())
2433  return false;
2434 
2435  const TemplateArgument &Arg = Args[ArgIdx];
2436  if (Arg.getKind() != TemplateArgument::Pack)
2437  return true;
2438 
2439  assert(ArgIdx == Args.size() - 1 && "Pack not at the end of argument list?");
2440  Args = Arg.pack_elements();
2441  ArgIdx = 0;
2442  return ArgIdx < Args.size();
2443 }
2444 
2445 /// Determine whether the given set of template arguments has a pack
2446 /// expansion that is not the last template argument.
2447 static bool hasPackExpansionBeforeEnd(ArrayRef<TemplateArgument> Args) {
2448  bool FoundPackExpansion = false;
2449  for (const auto &A : Args) {
2450  if (FoundPackExpansion)
2451  return true;
2452 
2453  if (A.getKind() == TemplateArgument::Pack)
2454  return hasPackExpansionBeforeEnd(A.pack_elements());
2455 
2456  // FIXME: If this is a fixed-arity pack expansion from an outer level of
2457  // templates, it should not be treated as a pack expansion.
2458  if (A.isPackExpansion())
2459  FoundPackExpansion = true;
2460  }
2461 
2462  return false;
2463 }
2464 
2467  ArrayRef<TemplateArgument> Params,
2468  ArrayRef<TemplateArgument> Args,
2469  TemplateDeductionInfo &Info,
2470  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
2471  bool NumberOfArgumentsMustMatch) {
2472  // C++0x [temp.deduct.type]p9:
2473  // If the template argument list of P contains a pack expansion that is not
2474  // the last template argument, the entire template argument list is a
2475  // non-deduced context.
2476  if (hasPackExpansionBeforeEnd(Params))
2477  return Sema::TDK_Success;
2478 
2479  // C++0x [temp.deduct.type]p9:
2480  // If P has a form that contains <T> or <i>, then each argument Pi of the
2481  // respective template argument list P is compared with the corresponding
2482  // argument Ai of the corresponding template argument list of A.
2483  unsigned ArgIdx = 0, ParamIdx = 0;
2484  for (; hasTemplateArgumentForDeduction(Params, ParamIdx); ++ParamIdx) {
2485  if (!Params[ParamIdx].isPackExpansion()) {
2486  // The simple case: deduce template arguments by matching Pi and Ai.
2487 
2488  // Check whether we have enough arguments.
2489  if (!hasTemplateArgumentForDeduction(Args, ArgIdx))
2490  return NumberOfArgumentsMustMatch
2493 
2494  // C++1z [temp.deduct.type]p9:
2495  // During partial ordering, if Ai was originally a pack expansion [and]
2496  // Pi is not a pack expansion, template argument deduction fails.
2497  if (Args[ArgIdx].isPackExpansion())
2499 
2500  // Perform deduction for this Pi/Ai pair.
2502  = DeduceTemplateArguments(S, TemplateParams,
2503  Params[ParamIdx], Args[ArgIdx],
2504  Info, Deduced))
2505  return Result;
2506 
2507  // Move to the next argument.
2508  ++ArgIdx;
2509  continue;
2510  }
2511 
2512  // The parameter is a pack expansion.
2513 
2514  // C++0x [temp.deduct.type]p9:
2515  // If Pi is a pack expansion, then the pattern of Pi is compared with
2516  // each remaining argument in the template argument list of A. Each
2517  // comparison deduces template arguments for subsequent positions in the
2518  // template parameter packs expanded by Pi.
2520 
2521  // Prepare to deduce the packs within the pattern.
2522  PackDeductionScope PackScope(S, TemplateParams, Deduced, Info, Pattern);
2523 
2524  // Keep track of the deduced template arguments for each parameter pack
2525  // expanded by this pack expansion (the outer index) and for each
2526  // template argument (the inner SmallVectors).
2527  for (; hasTemplateArgumentForDeduction(Args, ArgIdx) &&
2528  PackScope.hasNextElement();
2529  ++ArgIdx) {
2530  // Deduce template arguments from the pattern.
2532  = DeduceTemplateArguments(S, TemplateParams, Pattern, Args[ArgIdx],
2533  Info, Deduced))
2534  return Result;
2535 
2536  PackScope.nextPackElement();
2537  }
2538 
2539  // Build argument packs for each of the parameter packs expanded by this
2540  // pack expansion.
2541  if (auto Result = PackScope.finish())
2542  return Result;
2543  }
2544 
2545  return Sema::TDK_Success;
2546 }
2547 
2550  TemplateParameterList *TemplateParams,
2551  const TemplateArgumentList &ParamList,
2552  const TemplateArgumentList &ArgList,
2553  TemplateDeductionInfo &Info,
2554  SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
2555  return DeduceTemplateArguments(S, TemplateParams, ParamList.asArray(),
2556  ArgList.asArray(), Info, Deduced,
2557  /*NumberOfArgumentsMustMatch*/false);
2558 }
2559 
2560 /// Determine whether two template arguments are the same.
2561 static bool isSameTemplateArg(ASTContext &Context,
2563  const TemplateArgument &Y,
2564  bool PackExpansionMatchesPack = false) {
2565  // If we're checking deduced arguments (X) against original arguments (Y),
2566  // we will have flattened packs to non-expansions in X.
2567  if (PackExpansionMatchesPack && X.isPackExpansion() && !Y.isPackExpansion())
2568  X = X.getPackExpansionPattern();
2569 
2570  if (X.getKind() != Y.getKind())
2571  return false;
2572 
2573  switch (X.getKind()) {
2575  llvm_unreachable("Comparing NULL template argument");
2576 
2578  return Context.getCanonicalType(X.getAsType()) ==
2579  Context.getCanonicalType(Y.getAsType());
2580 
2582  return isSameDeclaration(X.getAsDecl(), Y.getAsDecl());
2583 
2585  return Context.hasSameType(X.getNullPtrType(), Y.getNullPtrType());
2586 
2589  return Context.getCanonicalTemplateName(
2590  X.getAsTemplateOrTemplatePattern()).getAsVoidPointer() ==
2591  Context.getCanonicalTemplateName(
2593 
2595  return hasSameExtendedValue(X.getAsIntegral(), Y.getAsIntegral());
2596 
2598  llvm::FoldingSetNodeID XID, YID;
2599  X.getAsExpr()->Profile(XID, Context, true);
2600  Y.getAsExpr()->Profile(YID, Context, true);
2601  return XID == YID;
2602  }
2603 
2605  if (X.pack_size() != Y.pack_size())
2606  return false;
2607 
2608  for (TemplateArgument::pack_iterator XP = X.pack_begin(),
2609  XPEnd = X.pack_end(),
2610  YP = Y.pack_begin();
2611  XP != XPEnd; ++XP, ++YP)
2612  if (!isSameTemplateArg(Context, *XP, *YP, PackExpansionMatchesPack))
2613  return false;
2614 
2615  return true;
2616  }
2617 
2618  llvm_unreachable("Invalid TemplateArgument Kind!");
2619 }
2620 
2621 /// Allocate a TemplateArgumentLoc where all locations have
2622 /// been initialized to the given location.
2623 ///
2624 /// \param Arg The template argument we are producing template argument
2625 /// location information for.
2626 ///
2627 /// \param NTTPType For a declaration template argument, the type of
2628 /// the non-type template parameter that corresponds to this template
2629 /// argument. Can be null if no type sugar is available to add to the
2630 /// type from the template argument.
2631 ///
2632 /// \param Loc The source location to use for the resulting template
2633 /// argument.
2636  QualType NTTPType, SourceLocation Loc) {
2637  switch (Arg.getKind()) {
2639  llvm_unreachable("Can't get a NULL template argument here");
2640 
2642  return TemplateArgumentLoc(
2643  Arg, Context.getTrivialTypeSourceInfo(Arg.getAsType(), Loc));
2644 
2646  if (NTTPType.isNull())
2647  NTTPType = Arg.getParamTypeForDecl();
2648  Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
2649  .getAs<Expr>();
2650  return TemplateArgumentLoc(TemplateArgument(E), E);
2651  }
2652 
2654  if (NTTPType.isNull())
2655  NTTPType = Arg.getNullPtrType();
2656  Expr *E = BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
2657  .getAs<Expr>();
2658  return TemplateArgumentLoc(TemplateArgument(NTTPType, /*isNullPtr*/true),
2659  E);
2660  }
2661 
2663  Expr *E =
2664  BuildExpressionFromIntegralTemplateArgument(Arg, Loc).getAs<Expr>();
2665  return TemplateArgumentLoc(TemplateArgument(E), E);
2666  }
2667 
2672  if (DependentTemplateName *DTN = Template.getAsDependentTemplateName())
2673  Builder.MakeTrivial(Context, DTN->getQualifier(), Loc);
2674  else if (QualifiedTemplateName *QTN =
2675  Template.getAsQualifiedTemplateName())
2676  Builder.MakeTrivial(Context, QTN->getQualifier(), Loc);
2677 
2678  if (Arg.getKind() == TemplateArgument::Template)
2679  return TemplateArgumentLoc(Context, Arg,
2680  Builder.getWithLocInContext(Context), Loc);
2681 
2682  return TemplateArgumentLoc(
2683  Context, Arg, Builder.getWithLocInContext(Context), Loc, Loc);
2684  }
2685 
2687  return TemplateArgumentLoc(Arg, Arg.getAsExpr());
2688 
2691  }
2692 
2693  llvm_unreachable("Invalid TemplateArgument Kind!");
2694 }
2695 
2698  SourceLocation Location) {
2699  return getTrivialTemplateArgumentLoc(
2700  Context.getInjectedTemplateArg(TemplateParm), QualType(), Location);
2701 }
2702 
2703 /// Convert the given deduced template argument and add it to the set of
2704 /// fully-converted template arguments.
2705 static bool
2708  NamedDecl *Template,
2709  TemplateDeductionInfo &Info,
2710  bool IsDeduced,
2711  SmallVectorImpl<TemplateArgument> &Output) {
2712  auto ConvertArg = [&](DeducedTemplateArgument Arg,
2713  unsigned ArgumentPackIndex) {
2714  // Convert the deduced template argument into a template
2715  // argument that we can check, almost as if the user had written
2716  // the template argument explicitly.
2717  TemplateArgumentLoc ArgLoc =
2719 
2720  // Check the template argument, converting it as necessary.
2721  return S.CheckTemplateArgument(
2722  Param, ArgLoc, Template, Template->getLocation(),
2723  Template->getSourceRange().getEnd(), ArgumentPackIndex, Output,
2724  IsDeduced
2728  };
2729 
2730  if (Arg.getKind() == TemplateArgument::Pack) {
2731  // This is a template argument pack, so check each of its arguments against
2732  // the template parameter.
2733  SmallVector<TemplateArgument, 2> PackedArgsBuilder;
2734  for (const auto &P : Arg.pack_elements()) {
2735  // When converting the deduced template argument, append it to the
2736  // general output list. We need to do this so that the template argument
2737  // checking logic has all of the prior template arguments available.
2738  DeducedTemplateArgument InnerArg(P);
2740  assert(InnerArg.getKind() != TemplateArgument::Pack &&
2741  "deduced nested pack");
2742  if (P.isNull()) {
2743  // We deduced arguments for some elements of this pack, but not for
2744  // all of them. This happens if we get a conditionally-non-deduced
2745  // context in a pack expansion (such as an overload set in one of the
2746  // arguments).
2747  S.Diag(Param->getLocation(),
2748  diag::err_template_arg_deduced_incomplete_pack)
2749  << Arg << Param;
2750  return true;
2751  }
2752  if (ConvertArg(InnerArg, PackedArgsBuilder.size()))
2753  return true;
2754 
2755  // Move the converted template argument into our argument pack.
2756  PackedArgsBuilder.push_back(Output.pop_back_val());
2757  }
2758 
2759  // If the pack is empty, we still need to substitute into the parameter
2760  // itself, in case that substitution fails.
2761  if (PackedArgsBuilder.empty()) {
2764  MultiLevelTemplateArgumentList Args(TemplateArgs);
2765 
2766  if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
2767  Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
2768  NTTP, Output,
2769  Template->getSourceRange());
2770  if (Inst.isInvalid() ||
2771  S.SubstType(NTTP->getType(), Args, NTTP->getLocation(),
2772  NTTP->getDeclName()).isNull())
2773  return true;
2774  } else if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(Param)) {
2775  Sema::InstantiatingTemplate Inst(S, Template->getLocation(), Template,
2776  TTP, Output,
2777  Template->getSourceRange());
2778  if (Inst.isInvalid() || !S.SubstDecl(TTP, S.CurContext, Args))
2779  return true;
2780  }
2781  // For type parameters, no substitution is ever required.
2782  }
2783 
2784  // Create the resulting argument pack.
2785  Output.push_back(
2786  TemplateArgument::CreatePackCopy(S.Context, PackedArgsBuilder));
2787  return false;
2788  }
2789 
2790  return ConvertArg(Arg, 0);
2791 }
2792 
2793 // FIXME: This should not be a template, but
2794 // ClassTemplatePartialSpecializationDecl sadly does not derive from
2795 // TemplateDecl.
2796 template<typename TemplateDeclT>
2798  Sema &S, TemplateDeclT *Template, bool IsDeduced,
2799  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
2800  TemplateDeductionInfo &Info, SmallVectorImpl<TemplateArgument> &Builder,
2801  LocalInstantiationScope *CurrentInstantiationScope = nullptr,
2802  unsigned NumAlreadyConverted = 0, bool PartialOverloading = false) {
2803  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
2804 
2805  for (unsigned I = 0, N = TemplateParams->size(); I != N; ++I) {
2806  NamedDecl *Param = TemplateParams->getParam(I);
2807 
2808  // C++0x [temp.arg.explicit]p3:
2809  // A trailing template parameter pack (14.5.3) not otherwise deduced will
2810  // be deduced to an empty sequence of template arguments.
2811  // FIXME: Where did the word "trailing" come from?
2812  if (Deduced[I].isNull() && Param->isTemplateParameterPack()) {
2813  if (auto Result =
2814  PackDeductionScope(S, TemplateParams, Deduced, Info, I).finish())
2815  return Result;
2816  }
2817 
2818  if (!Deduced[I].isNull()) {
2819  if (I < NumAlreadyConverted) {
2820  // We may have had explicitly-specified template arguments for a
2821  // template parameter pack (that may or may not have been extended
2822  // via additional deduced arguments).
2823  if (Param->isParameterPack() && CurrentInstantiationScope &&
2824  CurrentInstantiationScope->getPartiallySubstitutedPack() == Param) {
2825  // Forget the partially-substituted pack; its substitution is now
2826  // complete.
2827  CurrentInstantiationScope->ResetPartiallySubstitutedPack();
2828  // We still need to check the argument in case it was extended by
2829  // deduction.
2830  } else {
2831  // We have already fully type-checked and converted this
2832  // argument, because it was explicitly-specified. Just record the
2833  // presence of this argument.
2834  Builder.push_back(Deduced[I]);
2835  continue;
2836  }
2837  }
2838 
2839  // We may have deduced this argument, so it still needs to be
2840  // checked and converted.
2841  if (ConvertDeducedTemplateArgument(S, Param, Deduced[I], Template, Info,
2842  IsDeduced, Builder)) {
2843  Info.Param = makeTemplateParameter(Param);
2844  // FIXME: These template arguments are temporary. Free them!
2847  }
2848 
2849  continue;
2850  }
2851 
2852  // Substitute into the default template argument, if available.
2853  bool HasDefaultArg = false;
2854  TemplateDecl *TD = dyn_cast<TemplateDecl>(Template);
2855  if (!TD) {
2856  assert(isa<ClassTemplatePartialSpecializationDecl>(Template) ||
2857  isa<VarTemplatePartialSpecializationDecl>(Template));
2858  return Sema::TDK_Incomplete;
2859  }
2860 
2862  TD, TD->getLocation(), TD->getSourceRange().getEnd(), Param, Builder,
2863  HasDefaultArg);
2864 
2865  // If there was no default argument, deduction is incomplete.
2866  if (DefArg.getArgument().isNull()) {
2868  const_cast<NamedDecl *>(TemplateParams->getParam(I)));
2870  if (PartialOverloading) break;
2871 
2872  return HasDefaultArg ? Sema::TDK_SubstitutionFailure
2874  }
2875 
2876  // Check whether we can actually use the default argument.
2877  if (S.CheckTemplateArgument(Param, DefArg, TD, TD->getLocation(),
2878  TD->getSourceRange().getEnd(), 0, Builder,
2881  const_cast<NamedDecl *>(TemplateParams->getParam(I)));
2882  // FIXME: These template arguments are temporary. Free them!
2885  }
2886 
2887  // If we get here, we successfully used the default template argument.
2888  }
2889 
2890  return Sema::TDK_Success;
2891 }
2892 
2894  if (auto *DC = dyn_cast<DeclContext>(D))
2895  return DC;
2896  return D->getDeclContext();
2897 }
2898 
2899 template<typename T> struct IsPartialSpecialization {
2900  static constexpr bool value = false;
2901 };
2902 template<>
2904  static constexpr bool value = true;
2905 };
2906 template<>
2908  static constexpr bool value = true;
2909 };
2910 
2911 template<typename TemplateDeclT>
2913 CheckDeducedArgumentConstraints(Sema& S, TemplateDeclT *Template,
2914  ArrayRef<TemplateArgument> DeducedArgs,
2915  TemplateDeductionInfo& Info) {
2916  llvm::SmallVector<const Expr *, 3> AssociatedConstraints;
2917  Template->getAssociatedConstraints(AssociatedConstraints);
2918  if (S.CheckConstraintSatisfaction(Template, AssociatedConstraints,
2919  DeducedArgs, Info.getLocation(),
2922  Info.reset(TemplateArgumentList::CreateCopy(S.Context, DeducedArgs));
2924  }
2925  return Sema::TDK_Success;
2926 }
2927 
2928 /// Complete template argument deduction for a partial specialization.
2929 template <typename T>
2930 static std::enable_if_t<IsPartialSpecialization<T>::value,
2933  Sema &S, T *Partial, bool IsPartialOrdering,
2934  const TemplateArgumentList &TemplateArgs,
2935  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
2936  TemplateDeductionInfo &Info) {
2937  // Unevaluated SFINAE context.
2940  Sema::SFINAETrap Trap(S);
2941 
2942  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Partial));
2943 
2944  // C++ [temp.deduct.type]p2:
2945  // [...] or if any template argument remains neither deduced nor
2946  // explicitly specified, template argument deduction fails.
2948  if (auto Result = ConvertDeducedTemplateArguments(
2949  S, Partial, IsPartialOrdering, Deduced, Info, Builder))
2950  return Result;
2951 
2952  // Form the template argument list from the deduced template arguments.
2953  TemplateArgumentList *DeducedArgumentList
2955 
2956  Info.reset(DeducedArgumentList);
2957 
2958  // Substitute the deduced template arguments into the template
2959  // arguments of the class template partial specialization, and
2960  // verify that the instantiated template arguments are both valid
2961  // and are equivalent to the template arguments originally provided
2962  // to the class template.
2963  LocalInstantiationScope InstScope(S);
2964  auto *Template = Partial->getSpecializedTemplate();
2965  const ASTTemplateArgumentListInfo *PartialTemplArgInfo =
2966  Partial->getTemplateArgsAsWritten();
2967  const TemplateArgumentLoc *PartialTemplateArgs =
2968  PartialTemplArgInfo->getTemplateArgs();
2969 
2970  TemplateArgumentListInfo InstArgs(PartialTemplArgInfo->LAngleLoc,
2971  PartialTemplArgInfo->RAngleLoc);
2972 
2973  if (S.Subst(PartialTemplateArgs, PartialTemplArgInfo->NumTemplateArgs,
2974  InstArgs, MultiLevelTemplateArgumentList(*DeducedArgumentList))) {
2975  unsigned ArgIdx = InstArgs.size(), ParamIdx = ArgIdx;
2976  if (ParamIdx >= Partial->getTemplateParameters()->size())
2977  ParamIdx = Partial->getTemplateParameters()->size() - 1;
2978 
2979  Decl *Param = const_cast<NamedDecl *>(
2980  Partial->getTemplateParameters()->getParam(ParamIdx));
2981  Info.Param = makeTemplateParameter(Param);
2982  Info.FirstArg = PartialTemplateArgs[ArgIdx].getArgument();
2984  }
2985 
2986  bool ConstraintsNotSatisfied;
2987  SmallVector<TemplateArgument, 4> ConvertedInstArgs;
2988  if (S.CheckTemplateArgumentList(Template, Partial->getLocation(), InstArgs,
2989  false, ConvertedInstArgs,
2990  /*UpdateArgsWithConversions=*/true,
2991  &ConstraintsNotSatisfied))
2992  return ConstraintsNotSatisfied ? Sema::TDK_ConstraintsNotSatisfied :
2994 
2995  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
2996  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
2997  TemplateArgument InstArg = ConvertedInstArgs.data()[I];
2998  if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg)) {
2999  Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
3000  Info.FirstArg = TemplateArgs[I];
3001  Info.SecondArg = InstArg;
3003  }
3004  }
3005 
3006  if (Trap.hasErrorOccurred())
3008 
3009  if (auto Result = CheckDeducedArgumentConstraints(S, Partial, Builder, Info))
3010  return Result;
3011 
3012  return Sema::TDK_Success;
3013 }
3014 
3015 /// Complete template argument deduction for a class or variable template,
3016 /// when partial ordering against a partial specialization.
3017 // FIXME: Factor out duplication with partial specialization version above.
3019  Sema &S, TemplateDecl *Template, bool PartialOrdering,
3020  const TemplateArgumentList &TemplateArgs,
3021  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3022  TemplateDeductionInfo &Info) {
3023  // Unevaluated SFINAE context.
3026  Sema::SFINAETrap Trap(S);
3027 
3028  Sema::ContextRAII SavedContext(S, getAsDeclContextOrEnclosing(Template));
3029 
3030  // C++ [temp.deduct.type]p2:
3031  // [...] or if any template argument remains neither deduced nor
3032  // explicitly specified, template argument deduction fails.
3034  if (auto Result = ConvertDeducedTemplateArguments(
3035  S, Template, /*IsDeduced*/PartialOrdering, Deduced, Info, Builder))
3036  return Result;
3037 
3038  // Check that we produced the correct argument list.
3039  TemplateParameterList *TemplateParams = Template->getTemplateParameters();
3040  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
3041  TemplateArgument InstArg = Builder[I];
3042  if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg,
3043  /*PackExpansionMatchesPack*/true)) {
3044  Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
3045  Info.FirstArg = TemplateArgs[I];
3046  Info.SecondArg = InstArg;
3048  }
3049  }
3050 
3051  if (Trap.hasErrorOccurred())
3053 
3054  if (auto Result = CheckDeducedArgumentConstraints(S, Template, Builder,
3055  Info))
3056  return Result;
3057 
3058  return Sema::TDK_Success;
3059 }
3060 
3061 /// Perform template argument deduction to determine whether
3062 /// the given template arguments match the given class template
3063 /// partial specialization per C++ [temp.class.spec.match].
3066  const TemplateArgumentList &TemplateArgs,
3067  TemplateDeductionInfo &Info) {
3068  if (Partial->isInvalidDecl())
3069  return TDK_Invalid;
3070 
3071  // C++ [temp.class.spec.match]p2:
3072  // A partial specialization matches a given actual template
3073  // argument list if the template arguments of the partial
3074  // specialization can be deduced from the actual template argument
3075  // list (14.8.2).
3076 
3077  // Unevaluated SFINAE context.
3080  SFINAETrap Trap(*this);
3081 
3082  // This deduction has no relation to any outer instantiation we might be
3083  // performing.
3084  LocalInstantiationScope InstantiationScope(*this);
3085 
3087  Deduced.resize(Partial->getTemplateParameters()->size());
3088  if (TemplateDeductionResult Result
3089  = ::DeduceTemplateArguments(*this,
3090  Partial->getTemplateParameters(),
3091  Partial->getTemplateArgs(),
3092  TemplateArgs, Info, Deduced))
3093  return Result;
3094 
3095  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3096  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
3097  Info);
3098  if (Inst.isInvalid())
3099  return TDK_InstantiationDepth;
3100 
3101  if (Trap.hasErrorOccurred())
3103 
3104  TemplateDeductionResult Result;
3106  Result = ::FinishTemplateArgumentDeduction(*this, Partial,
3107  /*IsPartialOrdering=*/false,
3108  TemplateArgs, Deduced, Info);
3109  });
3110  return Result;
3111 }
3112 
3113 /// Perform template argument deduction to determine whether
3114 /// the given template arguments match the given variable template
3115 /// partial specialization per C++ [temp.class.spec.match].
3118  const TemplateArgumentList &TemplateArgs,
3119  TemplateDeductionInfo &Info) {
3120  if (Partial->isInvalidDecl())
3121  return TDK_Invalid;
3122 
3123  // C++ [temp.class.spec.match]p2:
3124  // A partial specialization matches a given actual template
3125  // argument list if the template arguments of the partial
3126  // specialization can be deduced from the actual template argument
3127  // list (14.8.2).
3128 
3129  // Unevaluated SFINAE context.
3132  SFINAETrap Trap(*this);
3133 
3134  // This deduction has no relation to any outer instantiation we might be
3135  // performing.
3136  LocalInstantiationScope InstantiationScope(*this);
3137 
3139  Deduced.resize(Partial->getTemplateParameters()->size());
3141  *this, Partial->getTemplateParameters(), Partial->getTemplateArgs(),
3142  TemplateArgs, Info, Deduced))
3143  return Result;
3144 
3145  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3146  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
3147  Info);
3148  if (Inst.isInvalid())
3149  return TDK_InstantiationDepth;
3150 
3151  if (Trap.hasErrorOccurred())
3153 
3154  TemplateDeductionResult Result;
3156  Result = ::FinishTemplateArgumentDeduction(*this, Partial,
3157  /*IsPartialOrdering=*/false,
3158  TemplateArgs, Deduced, Info);
3159  });
3160  return Result;
3161 }
3162 
3163 /// Determine whether the given type T is a simple-template-id type.
3165  if (const TemplateSpecializationType *Spec
3167  return Spec->getTemplateName().getAsTemplateDecl() != nullptr;
3168 
3169  // C++17 [temp.local]p2:
3170  // the injected-class-name [...] is equivalent to the template-name followed
3171  // by the template-arguments of the class template specialization or partial
3172  // specialization enclosed in <>
3173  // ... which means it's equivalent to a simple-template-id.
3174  //
3175  // This only arises during class template argument deduction for a copy
3176  // deduction candidate, where it permits slicing.
3177  if (T->getAs<InjectedClassNameType>())
3178  return true;
3179 
3180  return false;
3181 }
3182 
3183 /// Substitute the explicitly-provided template arguments into the
3184 /// given function template according to C++ [temp.arg.explicit].
3185 ///
3186 /// \param FunctionTemplate the function template into which the explicit
3187 /// template arguments will be substituted.
3188 ///
3189 /// \param ExplicitTemplateArgs the explicitly-specified template
3190 /// arguments.
3191 ///
3192 /// \param Deduced the deduced template arguments, which will be populated
3193 /// with the converted and checked explicit template arguments.
3194 ///
3195 /// \param ParamTypes will be populated with the instantiated function
3196 /// parameters.
3197 ///
3198 /// \param FunctionType if non-NULL, the result type of the function template
3199 /// will also be instantiated and the pointed-to value will be updated with
3200 /// the instantiated function type.
3201 ///
3202 /// \param Info if substitution fails for any reason, this object will be
3203 /// populated with more information about the failure.
3204 ///
3205 /// \returns TDK_Success if substitution was successful, or some failure
3206 /// condition.
3209  FunctionTemplateDecl *FunctionTemplate,
3210  TemplateArgumentListInfo &ExplicitTemplateArgs,
3212  SmallVectorImpl<QualType> &ParamTypes,
3214  TemplateDeductionInfo &Info) {
3215  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
3216  TemplateParameterList *TemplateParams
3217  = FunctionTemplate->getTemplateParameters();
3218 
3219  if (ExplicitTemplateArgs.size() == 0) {
3220  // No arguments to substitute; just copy over the parameter types and
3221  // fill in the function type.
3222  for (auto P : Function->parameters())
3223  ParamTypes.push_back(P->getType());
3224 
3225  if (FunctionType)
3226  *FunctionType = Function->getType();
3227  return TDK_Success;
3228  }
3229 
3230  // Unevaluated SFINAE context.
3233  SFINAETrap Trap(*this);
3234 
3235  // C++ [temp.arg.explicit]p3:
3236  // Template arguments that are present shall be specified in the
3237  // declaration order of their corresponding template-parameters. The
3238  // template argument list shall not specify more template-arguments than
3239  // there are corresponding template-parameters.
3241 
3242  // Enter a new template instantiation context where we check the
3243  // explicitly-specified template arguments against this function template,
3244  // and then substitute them into the function parameter types.
3246  InstantiatingTemplate Inst(
3247  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3248  CodeSynthesisContext::ExplicitTemplateArgumentSubstitution, Info);
3249  if (Inst.isInvalid())
3250  return TDK_InstantiationDepth;
3251 
3252  if (CheckTemplateArgumentList(FunctionTemplate, SourceLocation(),
3253  ExplicitTemplateArgs, true, Builder, false) ||
3254  Trap.hasErrorOccurred()) {
3255  unsigned Index = Builder.size();
3256  if (Index >= TemplateParams->size())
3257  return TDK_SubstitutionFailure;
3258  Info.Param = makeTemplateParameter(TemplateParams->getParam(Index));
3259  return TDK_InvalidExplicitArguments;
3260  }
3261 
3262  // Form the template argument list from the explicitly-specified
3263  // template arguments.
3264  TemplateArgumentList *ExplicitArgumentList
3265  = TemplateArgumentList::CreateCopy(Context, Builder);
3266  Info.setExplicitArgs(ExplicitArgumentList);
3267 
3268  // Template argument deduction and the final substitution should be
3269  // done in the context of the templated declaration. Explicit
3270  // argument substitution, on the other hand, needs to happen in the
3271  // calling context.
3272  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3273 
3274  // If we deduced template arguments for a template parameter pack,
3275  // note that the template argument pack is partially substituted and record
3276  // the explicit template arguments. They'll be used as part of deduction
3277  // for this template parameter pack.
3278  unsigned PartiallySubstitutedPackIndex = -1u;
3279  if (!Builder.empty()) {
3280  const TemplateArgument &Arg = Builder.back();
3281  if (Arg.getKind() == TemplateArgument::Pack) {
3282  auto *Param = TemplateParams->getParam(Builder.size() - 1);
3283  // If this is a fully-saturated fixed-size pack, it should be
3284  // fully-substituted, not partially-substituted.
3285  Optional<unsigned> Expansions = getExpandedPackSize(Param);
3286  if (!Expansions || Arg.pack_size() < *Expansions) {
3287  PartiallySubstitutedPackIndex = Builder.size() - 1;
3288  CurrentInstantiationScope->SetPartiallySubstitutedPack(
3289  Param, Arg.pack_begin(), Arg.pack_size());
3290  }
3291  }
3292  }
3293 
3294  const FunctionProtoType *Proto
3295  = Function->getType()->getAs<FunctionProtoType>();
3296  assert(Proto && "Function template does not have a prototype?");
3297 
3298  // Isolate our substituted parameters from our caller.
3299  LocalInstantiationScope InstScope(*this, /*MergeWithOuterScope*/true);
3300 
3301  ExtParameterInfoBuilder ExtParamInfos;
3302 
3303  // Instantiate the types of each of the function parameters given the
3304  // explicitly-specified template arguments. If the function has a trailing
3305  // return type, substitute it after the arguments to ensure we substitute
3306  // in lexical order.
3307  if (Proto->hasTrailingReturn()) {
3308  if (SubstParmTypes(Function->getLocation(), Function->parameters(),
3309  Proto->getExtParameterInfosOrNull(),
3310  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3311  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3312  return TDK_SubstitutionFailure;
3313  }
3314 
3315  // Instantiate the return type.
3316  QualType ResultType;
3317  {
3318  // C++11 [expr.prim.general]p3:
3319  // If a declaration declares a member function or member function
3320  // template of a class X, the expression this is a prvalue of type
3321  // "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
3322  // and the end of the function-definition, member-declarator, or
3323  // declarator.
3324  Qualifiers ThisTypeQuals;
3325  CXXRecordDecl *ThisContext = nullptr;
3326  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Function)) {
3327  ThisContext = Method->getParent();
3328  ThisTypeQuals = Method->getMethodQualifiers();
3329  }
3330 
3331  CXXThisScopeRAII ThisScope(*this, ThisContext, ThisTypeQuals,
3332  getLangOpts().CPlusPlus11);
3333 
3334  ResultType =
3335  SubstType(Proto->getReturnType(),
3336  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3337  Function->getTypeSpecStartLoc(), Function->getDeclName());
3338  if (ResultType.isNull() || Trap.hasErrorOccurred())
3339  return TDK_SubstitutionFailure;
3340  // CUDA: Kernel function must have 'void' return type.
3341  if (getLangOpts().CUDA)
3342  if (Function->hasAttr<CUDAGlobalAttr>() && !ResultType->isVoidType()) {
3343  Diag(Function->getLocation(), diag::err_kern_type_not_void_return)
3344  << Function->getType() << Function->getSourceRange();
3345  return TDK_SubstitutionFailure;
3346  }
3347  }
3348 
3349  // Instantiate the types of each of the function parameters given the
3350  // explicitly-specified template arguments if we didn't do so earlier.
3351  if (!Proto->hasTrailingReturn() &&
3352  SubstParmTypes(Function->getLocation(), Function->parameters(),
3353  Proto->getExtParameterInfosOrNull(),
3354  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3355  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3356  return TDK_SubstitutionFailure;
3357 
3358  if (FunctionType) {
3359  auto EPI = Proto->getExtProtoInfo();
3360  EPI.ExtParameterInfos = ExtParamInfos.getPointerOrNull(ParamTypes.size());
3361 
3362  // In C++1z onwards, exception specifications are part of the function type,
3363  // so substitution into the type must also substitute into the exception
3364  // specification.
3365  SmallVector<QualType, 4> ExceptionStorage;
3366  if (getLangOpts().CPlusPlus17 &&
3367  SubstExceptionSpec(
3368  Function->getLocation(), EPI.ExceptionSpec, ExceptionStorage,
3369  MultiLevelTemplateArgumentList(*ExplicitArgumentList)))
3370  return TDK_SubstitutionFailure;
3371 
3372  *FunctionType = BuildFunctionType(ResultType, ParamTypes,
3373  Function->getLocation(),
3374  Function->getDeclName(),
3375  EPI);
3376  if (FunctionType->isNull() || Trap.hasErrorOccurred())
3377  return TDK_SubstitutionFailure;
3378  }
3379 
3380  // C++ [temp.arg.explicit]p2:
3381  // Trailing template arguments that can be deduced (14.8.2) may be
3382  // omitted from the list of explicit template-arguments. If all of the
3383  // template arguments can be deduced, they may all be omitted; in this
3384  // case, the empty template argument list <> itself may also be omitted.
3385  //
3386  // Take all of the explicitly-specified arguments and put them into
3387  // the set of deduced template arguments. The partially-substituted
3388  // parameter pack, however, will be set to NULL since the deduction
3389  // mechanism handles the partially-substituted argument pack directly.
3390  Deduced.reserve(TemplateParams->size());
3391  for (unsigned I = 0, N = ExplicitArgumentList->size(); I != N; ++I) {
3392  const TemplateArgument &Arg = ExplicitArgumentList->get(I);
3393  if (I == PartiallySubstitutedPackIndex)
3394  Deduced.push_back(DeducedTemplateArgument());
3395  else
3396  Deduced.push_back(Arg);
3397  }
3398 
3399  return TDK_Success;
3400 }
3401 
3402 /// Check whether the deduced argument type for a call to a function
3403 /// template matches the actual argument type per C++ [temp.deduct.call]p4.
3406  Sema::OriginalCallArg OriginalArg,
3407  QualType DeducedA) {
3408  ASTContext &Context = S.Context;
3409 
3410  auto Failed = [&]() -> Sema::TemplateDeductionResult {
3411  Info.FirstArg = TemplateArgument(DeducedA);
3412  Info.SecondArg = TemplateArgument(OriginalArg.OriginalArgType);
3413  Info.CallArgIndex = OriginalArg.ArgIdx;
3416  };
3417 
3418  QualType A = OriginalArg.OriginalArgType;
3419  QualType OriginalParamType = OriginalArg.OriginalParamType;
3420 
3421  // Check for type equality (top-level cv-qualifiers are ignored).
3422  if (Context.hasSameUnqualifiedType(A, DeducedA))
3423  return Sema::TDK_Success;
3424 
3425  // Strip off references on the argument types; they aren't needed for
3426  // the following checks.
3427  if (const ReferenceType *DeducedARef = DeducedA->getAs<ReferenceType>())
3428  DeducedA = DeducedARef->getPointeeType();
3429  if (const ReferenceType *ARef = A->getAs<ReferenceType>())
3430  A = ARef->getPointeeType();
3431 
3432  // C++ [temp.deduct.call]p4:
3433  // [...] However, there are three cases that allow a difference:
3434  // - If the original P is a reference type, the deduced A (i.e., the
3435  // type referred to by the reference) can be more cv-qualified than
3436  // the transformed A.
3437  if (const ReferenceType *OriginalParamRef
3438  = OriginalParamType->getAs<ReferenceType>()) {
3439  // We don't want to keep the reference around any more.
3440  OriginalParamType = OriginalParamRef->getPointeeType();
3441 
3442  // FIXME: Resolve core issue (no number yet): if the original P is a
3443  // reference type and the transformed A is function type "noexcept F",
3444  // the deduced A can be F.
3445  QualType Tmp;
3446  if (A->isFunctionType() && S.IsFunctionConversion(A, DeducedA, Tmp))
3447  return Sema::TDK_Success;
3448 
3449  Qualifiers AQuals = A.getQualifiers();
3450  Qualifiers DeducedAQuals = DeducedA.getQualifiers();
3451 
3452  // Under Objective-C++ ARC, the deduced type may have implicitly
3453  // been given strong or (when dealing with a const reference)
3454  // unsafe_unretained lifetime. If so, update the original
3455  // qualifiers to include this lifetime.
3456  if (S.getLangOpts().ObjCAutoRefCount &&
3457  ((DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_Strong &&
3458  AQuals.getObjCLifetime() == Qualifiers::OCL_None) ||
3459  (DeducedAQuals.hasConst() &&
3460  DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone))) {
3461  AQuals.setObjCLifetime(DeducedAQuals.getObjCLifetime());
3462  }
3463 
3464  if (AQuals == DeducedAQuals) {
3465  // Qualifiers match; there's nothing to do.
3466  } else if (!DeducedAQuals.compatiblyIncludes(AQuals)) {
3467  return Failed();
3468  } else {
3469  // Qualifiers are compatible, so have the argument type adopt the
3470  // deduced argument type's qualifiers as if we had performed the
3471  // qualification conversion.
3472  A = Context.getQualifiedType(A.getUnqualifiedType(), DeducedAQuals);
3473  }
3474  }
3475 
3476  // - The transformed A can be another pointer or pointer to member
3477  // type that can be converted to the deduced A via a function pointer
3478  // conversion and/or a qualification conversion.
3479  //
3480  // Also allow conversions which merely strip __attribute__((noreturn)) from
3481  // function types (recursively).
3482  bool ObjCLifetimeConversion = false;
3483  QualType ResultTy;
3484  if ((A->isAnyPointerType() || A->isMemberPointerType()) &&
3485  (S.IsQualificationConversion(A, DeducedA, false,
3486  ObjCLifetimeConversion) ||
3487  S.IsFunctionConversion(A, DeducedA, ResultTy)))
3488  return Sema::TDK_Success;
3489 
3490  // - If P is a class and P has the form simple-template-id, then the
3491  // transformed A can be a derived class of the deduced A. [...]
3492  // [...] Likewise, if P is a pointer to a class of the form
3493  // simple-template-id, the transformed A can be a pointer to a
3494  // derived class pointed to by the deduced A.
3495  if (const PointerType *OriginalParamPtr
3496  = OriginalParamType->getAs<PointerType>()) {
3497  if (const PointerType *DeducedAPtr = DeducedA->getAs<PointerType>()) {
3498  if (const PointerType *APtr = A->getAs<PointerType>()) {
3499  if (A->getPointeeType()->isRecordType()) {
3500  OriginalParamType = OriginalParamPtr->getPointeeType();
3501  DeducedA = DeducedAPtr->getPointeeType();
3502  A = APtr->getPointeeType();
3503  }
3504  }
3505  }
3506  }
3507 
3508  if (Context.hasSameUnqualifiedType(A, DeducedA))
3509  return Sema::TDK_Success;
3510 
3511  if (A->isRecordType() && isSimpleTemplateIdType(OriginalParamType) &&
3512  S.IsDerivedFrom(Info.getLocation(), A, DeducedA))
3513  return Sema::TDK_Success;
3514 
3515  return Failed();
3516 }
3517 
3518 /// Find the pack index for a particular parameter index in an instantiation of
3519 /// a function template with specific arguments.
3520 ///
3521 /// \return The pack index for whichever pack produced this parameter, or -1
3522 /// if this was not produced by a parameter. Intended to be used as the
3523 /// ArgumentPackSubstitutionIndex for further substitutions.
3524 // FIXME: We should track this in OriginalCallArgs so we don't need to
3525 // reconstruct it here.
3526 static unsigned getPackIndexForParam(Sema &S,
3527  FunctionTemplateDecl *FunctionTemplate,
3528  const MultiLevelTemplateArgumentList &Args,
3529  unsigned ParamIdx) {
3530  unsigned Idx = 0;
3531  for (auto *PD : FunctionTemplate->getTemplatedDecl()->parameters()) {
3532  if (PD->isParameterPack()) {
3533  unsigned NumExpansions =
3534  S.getNumArgumentsInExpansion(PD->getType(), Args).getValueOr(1);
3535  if (Idx + NumExpansions > ParamIdx)
3536  return ParamIdx - Idx;
3537  Idx += NumExpansions;
3538  } else {
3539  if (Idx == ParamIdx)
3540  return -1; // Not a pack expansion
3541  ++Idx;
3542  }
3543  }
3544 
3545  llvm_unreachable("parameter index would not be produced from template");
3546 }
3547 
3548 /// Finish template argument deduction for a function template,
3549 /// checking the deduced template arguments for completeness and forming
3550 /// the function template specialization.
3551 ///
3552 /// \param OriginalCallArgs If non-NULL, the original call arguments against
3553 /// which the deduced argument types should be compared.
3555  FunctionTemplateDecl *FunctionTemplate,
3557  unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
3558  TemplateDeductionInfo &Info,
3559  SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
3560  bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
3561  // Unevaluated SFINAE context.
3564  SFINAETrap Trap(*this);
3565 
3566  // Enter a new template instantiation context while we instantiate the
3567  // actual function declaration.
3568  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3569  InstantiatingTemplate Inst(
3570  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3571  CodeSynthesisContext::DeducedTemplateArgumentSubstitution, Info);
3572  if (Inst.isInvalid())
3573  return TDK_InstantiationDepth;
3574 
3575  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3576 
3577  // C++ [temp.deduct.type]p2:
3578  // [...] or if any template argument remains neither deduced nor
3579  // explicitly specified, template argument deduction fails.
3581  if (auto Result = ConvertDeducedTemplateArguments(
3582  *this, FunctionTemplate, /*IsDeduced*/true, Deduced, Info, Builder,
3583  CurrentInstantiationScope, NumExplicitlySpecified,
3584  PartialOverloading))
3585  return Result;
3586 
3587  // C++ [temp.deduct.call]p10: [DR1391]
3588  // If deduction succeeds for all parameters that contain
3589  // template-parameters that participate in template argument deduction,
3590  // and all template arguments are explicitly specified, deduced, or
3591  // obtained from default template arguments, remaining parameters are then
3592  // compared with the corresponding arguments. For each remaining parameter
3593  // P with a type that was non-dependent before substitution of any
3594  // explicitly-specified template arguments, if the corresponding argument
3595  // A cannot be implicitly converted to P, deduction fails.
3596  if (CheckNonDependent())
3597  return TDK_NonDependentConversionFailure;
3598 
3599  // Form the template argument list from the deduced template arguments.
3600  TemplateArgumentList *DeducedArgumentList
3601  = TemplateArgumentList::CreateCopy(Context, Builder);
3602  Info.reset(DeducedArgumentList);
3603 
3604  // Substitute the deduced template arguments into the function template
3605  // declaration to produce the function template specialization.
3606  DeclContext *Owner = FunctionTemplate->getDeclContext();
3607  if (FunctionTemplate->getFriendObjectKind())
3608  Owner = FunctionTemplate->getLexicalDeclContext();
3609  MultiLevelTemplateArgumentList SubstArgs(*DeducedArgumentList);
3610  Specialization = cast_or_null<FunctionDecl>(
3611  SubstDecl(FunctionTemplate->getTemplatedDecl(), Owner, SubstArgs));
3612  if (!Specialization || Specialization->isInvalidDecl())
3613  return TDK_SubstitutionFailure;
3614 
3615  assert(Specialization->getPrimaryTemplate()->getCanonicalDecl() ==
3616  FunctionTemplate->getCanonicalDecl());
3617 
3618  // If the template argument list is owned by the function template
3619  // specialization, release it.
3620  if (Specialization->getTemplateSpecializationArgs() == DeducedArgumentList &&
3621  !Trap.hasErrorOccurred())
3622  Info.take();
3623 
3624  // There may have been an error that did not prevent us from constructing a
3625  // declaration. Mark the declaration invalid and return with a substitution
3626  // failure.
3627  if (Trap.hasErrorOccurred()) {
3628  Specialization->setInvalidDecl(true);
3629  return TDK_SubstitutionFailure;
3630  }
3631 
3632  // C++2a [temp.deduct]p5
3633  // [...] When all template arguments have been deduced [...] all uses of
3634  // template parameters [...] are replaced with the corresponding deduced
3635  // or default argument values.
3636  // [...] If the function template has associated constraints
3637  // ([temp.constr.decl]), those constraints are checked for satisfaction
3638  // ([temp.constr.constr]). If the constraints are not satisfied, type
3639  // deduction fails.
3640  if (!PartialOverloading ||
3641  (Builder.size() == FunctionTemplate->getTemplateParameters()->size())) {
3642  if (CheckInstantiatedFunctionTemplateConstraints(Info.getLocation(),
3644  return TDK_MiscellaneousDeductionFailure;
3645 
3647  Info.reset(TemplateArgumentList::CreateCopy(Context, Builder));
3648  return TDK_ConstraintsNotSatisfied;
3649  }
3650  }
3651 
3652  if (OriginalCallArgs) {
3653  // C++ [temp.deduct.call]p4:
3654  // In general, the deduction process attempts to find template argument
3655  // values that will make the deduced A identical to A (after the type A
3656  // is transformed as described above). [...]
3657  llvm::SmallDenseMap<std::pair<unsigned, QualType>, QualType> DeducedATypes;
3658  for (unsigned I = 0, N = OriginalCallArgs->size(); I != N; ++I) {
3659  OriginalCallArg OriginalArg = (*OriginalCallArgs)[I];
3660 
3661  auto ParamIdx = OriginalArg.ArgIdx;
3662  if (ParamIdx >= Specialization->getNumParams())
3663  // FIXME: This presumably means a pack ended up smaller than we
3664  // expected while deducing. Should this not result in deduction
3665  // failure? Can it even happen?
3666  continue;
3667 
3668  QualType DeducedA;
3669  if (!OriginalArg.DecomposedParam) {
3670  // P is one of the function parameters, just look up its substituted
3671  // type.
3672  DeducedA = Specialization->getParamDecl(ParamIdx)->getType();
3673  } else {
3674  // P is a decomposed element of a parameter corresponding to a
3675  // braced-init-list argument. Substitute back into P to find the
3676  // deduced A.
3677  QualType &CacheEntry =
3678  DeducedATypes[{ParamIdx, OriginalArg.OriginalParamType}];
3679  if (CacheEntry.isNull()) {
3681  *this, getPackIndexForParam(*this, FunctionTemplate, SubstArgs,
3682  ParamIdx));
3683  CacheEntry =
3684  SubstType(OriginalArg.OriginalParamType, SubstArgs,
3685  Specialization->getTypeSpecStartLoc(),
3686  Specialization->getDeclName());
3687  }
3688  DeducedA = CacheEntry;
3689  }
3690 
3691  if (auto TDK =
3692  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA))
3693  return TDK;
3694  }
3695  }
3696 
3697  // If we suppressed any diagnostics while performing template argument
3698  // deduction, and if we haven't already instantiated this declaration,
3699  // keep track of these diagnostics. They'll be emitted if this specialization
3700  // is actually used.
3701  if (Info.diag_begin() != Info.diag_end()) {
3702  SuppressedDiagnosticsMap::iterator
3703  Pos = SuppressedDiagnostics.find(Specialization->getCanonicalDecl());
3704  if (Pos == SuppressedDiagnostics.end())
3705  SuppressedDiagnostics[Specialization->getCanonicalDecl()]
3706  .append(Info.diag_begin(), Info.diag_end());
3707  }
3708 
3709  return TDK_Success;
3710 }
3711 
3712 /// Gets the type of a function for template-argument-deducton
3713 /// purposes when it's considered as part of an overload set.
3715  FunctionDecl *Fn) {
3716  // We may need to deduce the return type of the function now.
3717  if (S.getLangOpts().CPlusPlus14 && Fn->getReturnType()->isUndeducedType() &&
3718  S.DeduceReturnType(Fn, R.Expression->getExprLoc(), /*Diagnose*/ false))
3719  return {};
3720 
3721  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Fn))
3722  if (Method->isInstance()) {
3723  // An instance method that's referenced in a form that doesn't
3724  // look like a member pointer is just invalid.
3725  if (!R.HasFormOfMemberPointer)
3726  return {};
3727 
3728  return S.Context.getMemberPointerType(Fn->getType(),
3729  S.Context.getTypeDeclType(Method->getParent()).getTypePtr());
3730  }
3731 
3732  if (!R.IsAddressOfOperand) return Fn->getType();
3733  return S.Context.getPointerType(Fn->getType());
3734 }
3735 
3736 /// Apply the deduction rules for overload sets.
3737 ///
3738 /// \return the null type if this argument should be treated as an
3739 /// undeduced context
3740 static QualType
3742  Expr *Arg, QualType ParamType,
3743  bool ParamWasReference) {
3744 
3746 
3747  OverloadExpr *Ovl = R.Expression;
3748 
3749  // C++0x [temp.deduct.call]p4
3750  unsigned TDF = 0;
3751  if (ParamWasReference)
3753  if (R.IsAddressOfOperand)
3754  TDF |= TDF_IgnoreQualifiers;
3755 
3756  // C++0x [temp.deduct.call]p6:
3757  // When P is a function type, pointer to function type, or pointer
3758  // to member function type:
3759 
3760  if (!ParamType->isFunctionType() &&
3761  !ParamType->isFunctionPointerType() &&
3762  !ParamType->isMemberFunctionPointerType()) {
3763  if (Ovl->hasExplicitTemplateArgs()) {
3764  // But we can still look for an explicit specialization.
3765  if (FunctionDecl *ExplicitSpec
3767  return GetTypeOfFunction(S, R, ExplicitSpec);
3768  }
3769 
3770  DeclAccessPair DAP;
3771  if (FunctionDecl *Viable =
3773  return GetTypeOfFunction(S, R, Viable);
3774 
3775  return {};
3776  }
3777 
3778  // Gather the explicit template arguments, if any.
3779  TemplateArgumentListInfo ExplicitTemplateArgs;
3780  if (Ovl->hasExplicitTemplateArgs())
3781  Ovl->copyTemplateArgumentsInto(ExplicitTemplateArgs);
3782  QualType Match;
3783  for (UnresolvedSetIterator I = Ovl->decls_begin(),
3784  E = Ovl->decls_end(); I != E; ++I) {
3785  NamedDecl *D = (*I)->getUnderlyingDecl();
3786 
3787  if (FunctionTemplateDecl *FunTmpl = dyn_cast<FunctionTemplateDecl>(D)) {
3788  // - If the argument is an overload set containing one or more
3789  // function templates, the parameter is treated as a
3790  // non-deduced context.
3791  if (!Ovl->hasExplicitTemplateArgs())
3792  return {};
3793 
3794  // Otherwise, see if we can resolve a function type
3795  FunctionDecl *Specialization = nullptr;
3796  TemplateDeductionInfo Info(Ovl->getNameLoc());
3797  if (S.DeduceTemplateArguments(FunTmpl, &ExplicitTemplateArgs,
3798  Specialization, Info))
3799  continue;
3800 
3801  D = Specialization;
3802  }
3803 
3804  FunctionDecl *Fn = cast<FunctionDecl>(D);
3805  QualType ArgType = GetTypeOfFunction(S, R, Fn);
3806  if (ArgType.isNull()) continue;
3807 
3808  // Function-to-pointer conversion.
3809  if (!ParamWasReference && ParamType->isPointerType() &&
3810  ArgType->isFunctionType())
3811  ArgType = S.Context.getPointerType(ArgType);
3812 
3813  // - If the argument is an overload set (not containing function
3814  // templates), trial argument deduction is attempted using each
3815  // of the members of the set. If deduction succeeds for only one
3816  // of the overload set members, that member is used as the
3817  // argument value for the deduction. If deduction succeeds for
3818  // more than one member of the overload set the parameter is
3819  // treated as a non-deduced context.
3820 
3821  // We do all of this in a fresh context per C++0x [temp.deduct.type]p2:
3822  // Type deduction is done independently for each P/A pair, and
3823  // the deduced template argument values are then combined.
3824  // So we do not reject deductions which were made elsewhere.
3826  Deduced(TemplateParams->size());
3827  TemplateDeductionInfo Info(Ovl->getNameLoc());
3829  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
3830  ArgType, Info, Deduced, TDF);
3831  if (Result) continue;
3832  if (!Match.isNull())
3833  return {};
3834  Match = ArgType;
3835  }
3836 
3837  return Match;
3838 }
3839 
3840 /// Perform the adjustments to the parameter and argument types
3841 /// described in C++ [temp.deduct.call].
3842 ///
3843 /// \returns true if the caller should not attempt to perform any template
3844 /// argument deduction based on this P/A pair because the argument is an
3845 /// overloaded function set that could not be resolved.
3847  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3848  QualType &ParamType, QualType &ArgType, Expr *Arg, unsigned &TDF) {
3849  // C++0x [temp.deduct.call]p3:
3850  // If P is a cv-qualified type, the top level cv-qualifiers of P's type
3851  // are ignored for type deduction.
3852  if (ParamType.hasQualifiers())
3853  ParamType = ParamType.getUnqualifiedType();
3854 
3855  // [...] If P is a reference type, the type referred to by P is
3856  // used for type deduction.
3857  const ReferenceType *ParamRefType = ParamType->getAs<ReferenceType>();
3858  if (ParamRefType)
3859  ParamType = ParamRefType->getPointeeType();
3860 
3861  // Overload sets usually make this parameter an undeduced context,
3862  // but there are sometimes special circumstances. Typically
3863  // involving a template-id-expr.
3864  if (ArgType == S.Context.OverloadTy) {
3865  ArgType = ResolveOverloadForDeduction(S, TemplateParams,
3866  Arg, ParamType,
3867  ParamRefType != nullptr);
3868  if (ArgType.isNull())
3869  return true;
3870  }
3871 
3872  if (ParamRefType) {
3873  // If the argument has incomplete array type, try to complete its type.
3874  if (ArgType->isIncompleteArrayType())
3875  ArgType = S.getCompletedType(Arg);
3876 
3877  // C++1z [temp.deduct.call]p3:
3878  // If P is a forwarding reference and the argument is an lvalue, the type
3879  // "lvalue reference to A" is used in place of A for type deduction.
3880  if (isForwardingReference(QualType(ParamRefType, 0), FirstInnerIndex) &&
3881  Arg->isLValue()) {
3882  if (S.getLangOpts().OpenCL && !ArgType.hasAddressSpace())
3883  ArgType = S.Context.getAddrSpaceQualType(ArgType, LangAS::opencl_generic);
3884  ArgType = S.Context.getLValueReferenceType(ArgType);
3885  }
3886  } else {
3887  // C++ [temp.deduct.call]p2:
3888  // If P is not a reference type:
3889  // - If A is an array type, the pointer type produced by the
3890  // array-to-pointer standard conversion (4.2) is used in place of
3891  // A for type deduction; otherwise,
3892  if (ArgType->isArrayType())
3893  ArgType = S.Context.getArrayDecayedType(ArgType);
3894  // - If A is a function type, the pointer type produced by the
3895  // function-to-pointer standard conversion (4.3) is used in place
3896  // of A for type deduction; otherwise,
3897  else if (ArgType->isFunctionType())
3898  ArgType = S.Context.getPointerType(ArgType);
3899  else {
3900  // - If A is a cv-qualified type, the top level cv-qualifiers of A's
3901  // type are ignored for type deduction.
3902  ArgType = ArgType.getUnqualifiedType();
3903  }
3904  }
3905 
3906  // C++0x [temp.deduct.call]p4:
3907  // In general, the deduction process attempts to find template argument
3908  // values that will make the deduced A identical to A (after the type A
3909  // is transformed as described above). [...]
3910  TDF = TDF_SkipNonDependent;
3911 
3912  // - If the original P is a reference type, the deduced A (i.e., the
3913  // type referred to by the reference) can be more cv-qualified than
3914  // the transformed A.
3915  if (ParamRefType)
3917  // - The transformed A can be another pointer or pointer to member
3918  // type that can be converted to the deduced A via a qualification
3919  // conversion (4.4).
3920  if (ArgType->isPointerType() || ArgType->isMemberPointerType() ||
3921  ArgType->isObjCObjectPointerType())
3922  TDF |= TDF_IgnoreQualifiers;
3923  // - If P is a class and P has the form simple-template-id, then the
3924  // transformed A can be a derived class of the deduced A. Likewise,
3925  // if P is a pointer to a class of the form simple-template-id, the
3926  // transformed A can be a pointer to a derived class pointed to by
3927  // the deduced A.
3928  if (isSimpleTemplateIdType(ParamType) ||
3929  (isa<PointerType>(ParamType) &&
3931  ParamType->castAs<PointerType>()->getPointeeType())))
3932  TDF |= TDF_DerivedClass;
3933 
3934  return false;
3935 }
3936 
3937 static bool
3939  QualType T);
3940 
3942  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3943  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
3944  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3945  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
3946  bool DecomposedParam, unsigned ArgIdx, unsigned TDF);
3947 
3948 /// Attempt template argument deduction from an initializer list
3949 /// deemed to be an argument in a function call.
3951  Sema &S, TemplateParameterList *TemplateParams, QualType AdjustedParamType,
3952  InitListExpr *ILE, TemplateDeductionInfo &Info,
3953  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3954  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs, unsigned ArgIdx,
3955  unsigned TDF) {
3956  // C++ [temp.deduct.call]p1: (CWG 1591)
3957  // If removing references and cv-qualifiers from P gives
3958  // std::initializer_list<P0> or P0[N] for some P0 and N and the argument is
3959  // a non-empty initializer list, then deduction is performed instead for
3960  // each element of the initializer list, taking P0 as a function template
3961  // parameter type and the initializer element as its argument
3962  //
3963  // We've already removed references and cv-qualifiers here.
3964  if (!ILE->getNumInits())
3965  return Sema::TDK_Success;
3966 
3967  QualType ElTy;
3968  auto *ArrTy = S.Context.getAsArrayType(AdjustedParamType);
3969  if (ArrTy)
3970  ElTy = ArrTy->getElementType();
3971  else if (!S.isStdInitializerList(AdjustedParamType, &ElTy)) {
3972  // Otherwise, an initializer list argument causes the parameter to be
3973  // considered a non-deduced context
3974  return Sema::TDK_Success;
3975  }
3976 
3977  // Resolving a core issue: a braced-init-list containing any designators is
3978  // a non-deduced context.
3979  for (Expr *E : ILE->inits())
3980  if (isa<DesignatedInitExpr>(E))
3981  return Sema::TDK_Success;
3982 
3983  // Deduction only needs to be done for dependent types.
3984  if (ElTy->isDependentType()) {
3985  for (Expr *E : ILE->inits()) {
3986  if (auto Result = DeduceTemplateArgumentsFromCallArgument(
3987  S, TemplateParams, 0, ElTy, E, Info, Deduced, OriginalCallArgs, true,
3988  ArgIdx, TDF))
3989  return Result;
3990  }
3991  }
3992 
3993  // in the P0[N] case, if N is a non-type template parameter, N is deduced
3994  // from the length of the initializer list.
3995  if (auto *DependentArrTy = dyn_cast_or_null<DependentSizedArrayType>(ArrTy)) {
3996  // Determine the array bound is something we can deduce.
3997  if (const NonTypeTemplateParmDecl *NTTP =
3998  getDeducedParameterFromExpr(Info, DependentArrTy->getSizeExpr())) {
3999  // We can perform template argument deduction for the given non-type
4000  // template parameter.
4001  // C++ [temp.deduct.type]p13:
4002  // The type of N in the type T[N] is std::size_t.
4003  QualType T = S.Context.getSizeType();
4004  llvm::APInt Size(S.Context.getIntWidth(T), ILE->getNumInits());
4005  if (auto Result = DeduceNonTypeTemplateArgument(
4006  S, TemplateParams, NTTP, llvm::APSInt(Size), T,
4007  /*ArrayBound=*/true, Info, Deduced))
4008  return Result;
4009  }
4010  }
4011 
4012  return Sema::TDK_Success;
4013 }
4014 
4015 /// Perform template argument deduction per [temp.deduct.call] for a
4016 /// single parameter / argument pair.
4018  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
4019  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
4020  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
4021  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
4022  bool DecomposedParam, unsigned ArgIdx, unsigned TDF) {
4023  QualType ArgType = Arg->getType();
4024  QualType OrigParamType = ParamType;
4025 
4026  // If P is a reference type [...]
4027  // If P is a cv-qualified type [...]
4029  S, TemplateParams, FirstInnerIndex, ParamType, ArgType, Arg, TDF))
4030  return Sema::TDK_Success;
4031 
4032  // If [...] the argument is a non-empty initializer list [...]
4033  if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg))
4034  return DeduceFromInitializerList(S, TemplateParams, ParamType, ILE, Info,
4035  Deduced, OriginalCallArgs, ArgIdx, TDF);
4036 
4037  // [...] the deduction process attempts to find template argument values
4038  // that will make the deduced A identical to A
4039  //
4040  // Keep track of the argument type and corresponding parameter index,
4041  // so we can check for compatibility between the deduced A and A.
4042  OriginalCallArgs.push_back(
4043  Sema::OriginalCallArg(OrigParamType, DecomposedParam, ArgIdx, ArgType));
4044  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
4045  ArgType, Info, Deduced, TDF);
4046 }
4047 
4048 /// Perform template argument deduction from a function call
4049 /// (C++ [temp.deduct.call]).
4050 ///
4051 /// \param FunctionTemplate the function template for which we are performing
4052 /// template argument deduction.
4053 ///
4054 /// \param ExplicitTemplateArgs the explicit template arguments provided
4055 /// for this call.
4056 ///
4057 /// \param Args the function call arguments
4058 ///
4059 /// \param Specialization if template argument deduction was successful,
4060 /// this will be set to the function template specialization produced by
4061 /// template argument deduction.
4062 ///
4063 /// \param Info the argument will be updated to provide additional information
4064 /// about template argument deduction.
4065 ///
4066 /// \param CheckNonDependent A callback to invoke to check conversions for
4067 /// non-dependent parameters, between deduction and substitution, per DR1391.
4068 /// If this returns true, substitution will be skipped and we return
4069 /// TDK_NonDependentConversionFailure. The callback is passed the parameter
4070 /// types (after substituting explicit template arguments).
4071 ///
4072 /// \returns the result of template argument deduction.
4074  FunctionTemplateDecl *FunctionTemplate,
4075  TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
4076  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4077  bool PartialOverloading,
4078  llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent) {
4079  if (FunctionTemplate->isInvalidDecl())
4080  return TDK_Invalid;
4081 
4082  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
4083  unsigned NumParams = Function->getNumParams();
4084 
4085  unsigned FirstInnerIndex = getFirstInnerIndex(FunctionTemplate);
4086 
4087  // C++ [temp.deduct.call]p1:
4088  // Template argument deduction is done by comparing each function template
4089  // parameter type (call it P) with the type of the corresponding argument
4090  // of the call (call it A) as described below.
4091  if (Args.size() < Function->getMinRequiredArguments() && !PartialOverloading)
4092  return TDK_TooFewArguments;
4093  else if (TooManyArguments(NumParams, Args.size(), PartialOverloading)) {
4094  const auto *Proto = Function->getType()->castAs<FunctionProtoType>();
4095  if (Proto->isTemplateVariadic())
4096  /* Do nothing */;
4097  else if (!Proto->isVariadic())
4098  return TDK_TooManyArguments;
4099  }
4100 
4101  // The types of the parameters from which we will perform template argument
4102  // deduction.
4103  LocalInstantiationScope InstScope(*this);
4104  TemplateParameterList *TemplateParams
4105  = FunctionTemplate->getTemplateParameters();
4107  SmallVector<QualType, 8> ParamTypes;
4108  unsigned NumExplicitlySpecified = 0;
4109  if (ExplicitTemplateArgs) {
4110  TemplateDeductionResult Result;
4112  Result = SubstituteExplicitTemplateArguments(
4113  FunctionTemplate, *ExplicitTemplateArgs, Deduced, ParamTypes, nullptr,
4114  Info);
4115  });
4116  if (Result)
4117  return Result;
4118 
4119  NumExplicitlySpecified = Deduced.size();
4120  } else {
4121  // Just fill in the parameter types from the function declaration.
4122  for (unsigned I = 0; I != NumParams; ++I)
4123  ParamTypes.push_back(Function->getParamDecl(I)->getType());
4124  }
4125 
4126  SmallVector<OriginalCallArg, 8> OriginalCallArgs;
4127 
4128  // Deduce an argument of type ParamType from an expression with index ArgIdx.
4129  auto DeduceCallArgument = [&](QualType ParamType, unsigned ArgIdx) {
4130  // C++ [demp.deduct.call]p1: (DR1391)
4131  // Template argument deduction is done by comparing each function template
4132  // parameter that contains template-parameters that participate in
4133  // template argument deduction ...
4134  if (!hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
4135  return Sema::TDK_Success;
4136 
4137  // ... with the type of the corresponding argument
4139  *this, TemplateParams, FirstInnerIndex, ParamType, Args[ArgIdx], Info, Deduced,
4140  OriginalCallArgs, /*Decomposed*/false, ArgIdx, /*TDF*/ 0);
4141  };
4142 
4143  // Deduce template arguments from the function parameters.
4144  Deduced.resize(TemplateParams->size());
4145  SmallVector<QualType, 8> ParamTypesForArgChecking;
4146  for (unsigned ParamIdx = 0, NumParamTypes = ParamTypes.size(), ArgIdx = 0;
4147  ParamIdx != NumParamTypes; ++ParamIdx) {
4148  QualType ParamType = ParamTypes[ParamIdx];
4149 
4150  const PackExpansionType *ParamExpansion =
4151  dyn_cast<PackExpansionType>(ParamType);
4152  if (!ParamExpansion) {
4153  // Simple case: matching a function parameter to a function argument.
4154  if (ArgIdx >= Args.size())
4155  break;
4156 
4157  ParamTypesForArgChecking.push_back(ParamType);
4158  if (auto Result = DeduceCallArgument(ParamType, ArgIdx++))
4159  return Result;
4160 
4161  continue;
4162  }
4163 
4164  QualType ParamPattern = ParamExpansion->getPattern();
4165  PackDeductionScope PackScope(*this, TemplateParams, Deduced, Info,
4166  ParamPattern);
4167 
4168  // C++0x [temp.deduct.call]p1:
4169  // For a function parameter pack that occurs at the end of the
4170  // parameter-declaration-list, the type A of each remaining argument of
4171  // the call is compared with the type P of the declarator-id of the
4172  // function parameter pack. Each comparison deduces template arguments
4173  // for subsequent positions in the template parameter packs expanded by
4174  // the function parameter pack. When a function parameter pack appears
4175  // in a non-deduced context [not at the end of the list], the type of
4176  // that parameter pack is never deduced.
4177  //
4178  // FIXME: The above rule allows the size of the parameter pack to change
4179  // after we skip it (in the non-deduced case). That makes no sense, so
4180  // we instead notionally deduce the pack against N arguments, where N is
4181  // the length of the explicitly-specified pack if it's expanded by the
4182  // parameter pack and 0 otherwise, and we treat each deduction as a
4183  // non-deduced context.
4184  if (ParamIdx + 1 == NumParamTypes || PackScope.hasFixedArity()) {
4185  for (; ArgIdx < Args.size() && PackScope.hasNextElement();
4186  PackScope.nextPackElement(), ++ArgIdx) {
4187  ParamTypesForArgChecking.push_back(ParamPattern);
4188  if (auto Result = DeduceCallArgument(ParamPattern, ArgIdx))
4189  return Result;
4190  }
4191  } else {
4192  // If the parameter type contains an explicitly-specified pack that we
4193  // could not expand, skip the number of parameters notionally created
4194  // by the expansion.
4195  Optional<unsigned> NumExpansions = ParamExpansion->getNumExpansions();
4196  if (NumExpansions && !PackScope.isPartiallyExpanded()) {
4197  for (unsigned I = 0; I != *NumExpansions && ArgIdx < Args.size();
4198  ++I, ++ArgIdx) {
4199  ParamTypesForArgChecking.push_back(ParamPattern);
4200  // FIXME: Should we add OriginalCallArgs for these? What if the
4201  // corresponding argument is a list?
4202  PackScope.nextPackElement();
4203  }
4204  }
4205  }
4206 
4207  // Build argument packs for each of the parameter packs expanded by this
4208  // pack expansion.
4209  if (auto Result = PackScope.finish())
4210  return Result;
4211  }
4212 
4213  // Capture the context in which the function call is made. This is the context
4214  // that is needed when the accessibility of template arguments is checked.
4215  DeclContext *CallingCtx = CurContext;
4216 
4217  TemplateDeductionResult Result;
4219  Result = FinishTemplateArgumentDeduction(
4220  FunctionTemplate, Deduced, NumExplicitlySpecified, Specialization, Info,
4221  &OriginalCallArgs, PartialOverloading, [&, CallingCtx]() {
4222  ContextRAII SavedContext(*this, CallingCtx);
4223  return CheckNonDependent(ParamTypesForArgChecking);
4224  });
4225  });
4226  return Result;
4227 }
4228 
4231  bool AdjustExceptionSpec) {
4232  if (ArgFunctionType.isNull())
4233  return ArgFunctionType;
4234 
4235  const auto *FunctionTypeP = FunctionType->castAs<FunctionProtoType>();
4236  const auto *ArgFunctionTypeP = ArgFunctionType->castAs<FunctionProtoType>();
4237  FunctionProtoType::ExtProtoInfo EPI = ArgFunctionTypeP->getExtProtoInfo();
4238  bool Rebuild = false;
4239 
4240  CallingConv CC = FunctionTypeP->getCallConv();
4241  if (EPI.ExtInfo.getCC() != CC) {
4242  EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CC);
4243  Rebuild = true;
4244  }
4245 
4246  bool NoReturn = FunctionTypeP->getNoReturnAttr();
4247  if (EPI.ExtInfo.getNoReturn() != NoReturn) {
4248  EPI.ExtInfo = EPI.ExtInfo.withNoReturn(NoReturn);
4249  Rebuild = true;
4250  }
4251 
4252  if (AdjustExceptionSpec && (FunctionTypeP->hasExceptionSpec() ||
4253  ArgFunctionTypeP->hasExceptionSpec())) {
4254  EPI.ExceptionSpec = FunctionTypeP->getExtProtoInfo().ExceptionSpec;
4255  Rebuild = true;
4256  }
4257 
4258  if (!Rebuild)
4259  return ArgFunctionType;
4260 
4261  return Context.getFunctionType(ArgFunctionTypeP->getReturnType(),
4262  ArgFunctionTypeP->getParamTypes(), EPI);
4263 }
4264 
4265 /// Deduce template arguments when taking the address of a function
4266 /// template (C++ [temp.deduct.funcaddr]) or matching a specialization to
4267 /// a template.
4268 ///
4269 /// \param FunctionTemplate the function template for which we are performing
4270 /// template argument deduction.
4271 ///
4272 /// \param ExplicitTemplateArgs the explicitly-specified template
4273 /// arguments.
4274 ///
4275 /// \param ArgFunctionType the function type that will be used as the
4276 /// "argument" type (A) when performing template argument deduction from the
4277 /// function template's function type. This type may be NULL, if there is no
4278 /// argument type to compare against, in C++0x [temp.arg.explicit]p3.
4279 ///
4280 /// \param Specialization if template argument deduction was successful,
4281 /// this will be set to the function template specialization produced by
4282 /// template argument deduction.
4283 ///
4284 /// \param Info the argument will be updated to provide additional information
4285 /// about template argument deduction.
4286 ///
4287 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4288 /// the address of a function template per [temp.deduct.funcaddr] and
4289 /// [over.over]. If \c false, we are looking up a function template
4290 /// specialization based on its signature, per [temp.deduct.decl].
4291 ///
4292 /// \returns the result of template argument deduction.
4294  FunctionTemplateDecl *FunctionTemplate,
4295  TemplateArgumentListInfo *ExplicitTemplateArgs, QualType ArgFunctionType,
4296  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4297  bool IsAddressOfFunction) {
4298  if (FunctionTemplate->isInvalidDecl())
4299  return TDK_Invalid;
4300 
4301  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
4302  TemplateParameterList *TemplateParams
4303  = FunctionTemplate->getTemplateParameters();
4304  QualType FunctionType = Function->getType();
4305 
4306  // Substitute any explicit template arguments.
4307  LocalInstantiationScope InstScope(*this);
4309  unsigned NumExplicitlySpecified = 0;
4310  SmallVector<QualType, 4> ParamTypes;
4311  if (ExplicitTemplateArgs) {
4312  TemplateDeductionResult Result;
4314  Result = SubstituteExplicitTemplateArguments(
4315  FunctionTemplate, *ExplicitTemplateArgs, Deduced, ParamTypes,
4316  &FunctionType, Info);
4317  });
4318  if (Result)
4319  return Result;
4320 
4321  NumExplicitlySpecified = Deduced.size();
4322  }
4323 
4324  // When taking the address of a function, we require convertibility of
4325  // the resulting function type. Otherwise, we allow arbitrary mismatches
4326  // of calling convention and noreturn.
4327  if (!IsAddressOfFunction)
4328  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, FunctionType,
4329  /*AdjustExceptionSpec*/false);
4330 
4331  // Unevaluated SFINAE context.
4334  SFINAETrap Trap(*this);
4335 
4336  Deduced.resize(TemplateParams->size());
4337 
4338  // If the function has a deduced return type, substitute it for a dependent
4339  // type so that we treat it as a non-deduced context in what follows. If we
4340  // are looking up by signature, the signature type should also have a deduced
4341  // return type, which we instead expect to exactly match.
4342  bool HasDeducedReturnType = false;
4343  if (getLangOpts().CPlusPlus14 && IsAddressOfFunction &&
4344  Function->getReturnType()->getContainedAutoType()) {
4346  HasDeducedReturnType = true;
4347  }
4348 
4349  if (!ArgFunctionType.isNull()) {
4350  unsigned TDF =
4352  // Deduce template arguments from the function type.
4353  if (TemplateDeductionResult Result
4354  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4355  FunctionType, ArgFunctionType,
4356  Info, Deduced, TDF))
4357  return Result;
4358  }
4359 
4360  TemplateDeductionResult Result;
4362  Result = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
4363  NumExplicitlySpecified,
4364  Specialization, Info);
4365  });
4366  if (Result)
4367  return Result;
4368 
4369  // If the function has a deduced return type, deduce it now, so we can check
4370  // that the deduced function type matches the requested type.
4371  if (HasDeducedReturnType &&
4372  Specialization->getReturnType()->isUndeducedType() &&
4375 
4376  // If the function has a dependent exception specification, resolve it now,
4377  // so we can check that the exception specification matches.
4378  auto *SpecializationFPT =
4379  Specialization->getType()->castAs<FunctionProtoType>();
4380  if (getLangOpts().CPlusPlus17 &&
4381  isUnresolvedExceptionSpec(SpecializationFPT->getExceptionSpecType()) &&
4382  !ResolveExceptionSpec(Info.getLocation(), SpecializationFPT))
4384 
4385  // Adjust the exception specification of the argument to match the
4386  // substituted and resolved type we just formed. (Calling convention and
4387  // noreturn can't be dependent, so we don't actually need this for them
4388  // right now.)
4389  QualType SpecializationType = Specialization->getType();
4390  if (!IsAddressOfFunction)
4391  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, SpecializationType,
4392  /*AdjustExceptionSpec*/true);
4393 
4394  // If the requested function type does not match the actual type of the
4395  // specialization with respect to arguments of compatible pointer to function
4396  // types, template argument deduction fails.
4397  if (!ArgFunctionType.isNull()) {
4398  if (IsAddressOfFunction &&
4400  Context.getCanonicalType(SpecializationType),
4401  Context.getCanonicalType(ArgFunctionType)))
4403 
4404  if (!IsAddressOfFunction &&
4405  !Context.hasSameType(SpecializationType, ArgFunctionType))
4407  }
4408 
4409  return TDK_Success;
4410 }
4411 
4412 /// Deduce template arguments for a templated conversion
4413 /// function (C++ [temp.deduct.conv]) and, if successful, produce a
4414 /// conversion function template specialization.
4417  QualType ToType,
4418  CXXConversionDecl *&Specialization,
4419  TemplateDeductionInfo &Info) {
4420  if (ConversionTemplate->isInvalidDecl())
4421  return TDK_Invalid;
4422 
4423  CXXConversionDecl *ConversionGeneric
4424  = cast<CXXConversionDecl>(ConversionTemplate->getTemplatedDecl());
4425 
4426  QualType FromType = ConversionGeneric->getConversionType();
4427 
4428  // Canonicalize the types for deduction.
4429  QualType P = Context.getCanonicalType(FromType);
4430  QualType A = Context.getCanonicalType(ToType);
4431 
4432  // C++0x [temp.deduct.conv]p2:
4433  // If P is a reference type, the type referred to by P is used for
4434  // type deduction.
4435  if (const ReferenceType *PRef = P->getAs<ReferenceType>())
4436  P = PRef->getPointeeType();
4437 
4438  // C++0x [temp.deduct.conv]p4:
4439  // [...] If A is a reference type, the type referred to by A is used
4440  // for type deduction.
4441  if (const ReferenceType *ARef = A->getAs<ReferenceType>()) {
4442  A = ARef->getPointeeType();
4443  // We work around a defect in the standard here: cv-qualifiers are also
4444  // removed from P and A in this case, unless P was a reference type. This
4445  // seems to mostly match what other compilers are doing.
4446  if (!FromType->getAs<ReferenceType>()) {
4447  A = A.getUnqualifiedType();
4448  P = P.getUnqualifiedType();
4449  }
4450 
4451  // C++ [temp.deduct.conv]p3:
4452  //
4453  // If A is not a reference type:
4454  } else {
4455  assert(!A->isReferenceType() && "Reference types were handled above");
4456 
4457  // - If P is an array type, the pointer type produced by the
4458  // array-to-pointer standard conversion (4.2) is used in place
4459  // of P for type deduction; otherwise,
4460  if (P->isArrayType())
4462  // - If P is a function type, the pointer type produced by the
4463  // function-to-pointer standard conversion (4.3) is used in
4464  // place of P for type deduction; otherwise,
4465  else if (P->isFunctionType())
4467  // - If P is a cv-qualified type, the top level cv-qualifiers of
4468  // P's type are ignored for type deduction.
4469  else
4470  P = P.getUnqualifiedType();
4471 
4472  // C++0x [temp.deduct.conv]p4:
4473  // If A is a cv-qualified type, the top level cv-qualifiers of A's
4474  // type are ignored for type deduction. If A is a reference type, the type
4475  // referred to by A is used for type deduction.
4476  A = A.getUnqualifiedType();
4477  }
4478 
4479  // Unevaluated SFINAE context.
4482  SFINAETrap Trap(*this);
4483 
4484  // C++ [temp.deduct.conv]p1:
4485  // Template argument deduction is done by comparing the return
4486  // type of the template conversion function (call it P) with the
4487  // type that is required as the result of the conversion (call it
4488  // A) as described in 14.8.2.4.
4489  TemplateParameterList *TemplateParams
4490  = ConversionTemplate->getTemplateParameters();
4492  Deduced.resize(TemplateParams->size());
4493 
4494  // C++0x [temp.deduct.conv]p4:
4495  // In general, the deduction process attempts to find template
4496  // argument values that will make the deduced A identical to
4497  // A. However, there are two cases that allow a difference:
4498  unsigned TDF = 0;
4499  // - If the original A is a reference type, A can be more
4500  // cv-qualified than the deduced A (i.e., the type referred to
4501  // by the reference)
4502  if (ToType->isReferenceType())
4503  TDF |= TDF_ArgWithReferenceType;
4504  // - The deduced A can be another pointer or pointer to member
4505  // type that can be converted to A via a qualification
4506  // conversion.
4507  //
4508  // (C++0x [temp.deduct.conv]p6 clarifies that this only happens when
4509  // both P and A are pointers or member pointers. In this case, we
4510  // just ignore cv-qualifiers completely).
4511  if ((P->isPointerType() && A->isPointerType()) ||
4512  (P->isMemberPointerType() && A->isMemberPointerType()))
4513  TDF |= TDF_IgnoreQualifiers;
4514  if (TemplateDeductionResult Result
4515  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4516  P, A, Info, Deduced, TDF))
4517  return Result;
4518 
4519  // Create an Instantiation Scope for finalizing the operator.
4520  LocalInstantiationScope InstScope(*this);
4521  // Finish template argument deduction.
4522  FunctionDecl *ConversionSpecialized = nullptr;
4523  TemplateDeductionResult Result;
4525  Result = FinishTemplateArgumentDeduction(ConversionTemplate, Deduced, 0,
4526  ConversionSpecialized, Info);
4527  });
4528  Specialization = cast_or_null<CXXConversionDecl>(ConversionSpecialized);
4529  return Result;
4530 }
4531 
4532 /// Deduce template arguments for a function template when there is
4533 /// nothing to deduce against (C++0x [temp.arg.explicit]p3).
4534 ///
4535 /// \param FunctionTemplate the function template for which we are performing
4536 /// template argument deduction.
4537 ///
4538 /// \param ExplicitTemplateArgs the explicitly-specified template
4539 /// arguments.
4540 ///
4541 /// \param Specialization if template argument deduction was successful,
4542 /// this will be set to the function template specialization produced by
4543 /// template argument deduction.
4544 ///
4545 /// \param Info the argument will be updated to provide additional information
4546 /// about template argument deduction.
4547 ///
4548 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4549 /// the address of a function template in a context where we do not have a
4550 /// target type, per [over.over]. If \c false, we are looking up a function
4551 /// template specialization based on its signature, which only happens when
4552 /// deducing a function parameter type from an argument that is a template-id
4553 /// naming a function template specialization.
4554 ///
4555 /// \returns the result of template argument deduction.
4557  FunctionTemplateDecl *FunctionTemplate,
4558  TemplateArgumentListInfo *ExplicitTemplateArgs,
4559  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4560  bool IsAddressOfFunction) {
4561  return DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs,
4562  QualType(), Specialization, Info,
4563  IsAddressOfFunction);
4564 }
4565 
4566 namespace {
4567  struct DependentAuto { bool IsPack; };
4568 
4569  /// Substitute the 'auto' specifier or deduced template specialization type
4570  /// specifier within a type for a given replacement type.
4571  class SubstituteDeducedTypeTransform :
4572  public TreeTransform<SubstituteDeducedTypeTransform> {
4573  QualType Replacement;
4574  bool ReplacementIsPack;
4575  bool UseTypeSugar;
4576 
4577  public:
4578  SubstituteDeducedTypeTransform(Sema &SemaRef, DependentAuto DA)
4579  : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef), Replacement(),
4580  ReplacementIsPack(DA.IsPack), UseTypeSugar(true) {}
4581 
4582  SubstituteDeducedTypeTransform(Sema &SemaRef, QualType Replacement,
4583  bool UseTypeSugar = true)
4584  : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef),
4585  Replacement(Replacement), ReplacementIsPack(false),
4586  UseTypeSugar(UseTypeSugar) {}
4587 
4588  QualType TransformDesugared(TypeLocBuilder &TLB, DeducedTypeLoc TL) {
4589  assert(isa<TemplateTypeParmType>(Replacement) &&
4590  "unexpected unsugared replacement kind");
4591  QualType Result = Replacement;
4593  NewTL.setNameLoc(TL.getNameLoc());
4594  return Result;
4595  }
4596 
4597  QualType TransformAutoType(TypeLocBuilder &TLB, AutoTypeLoc TL) {
4598  // If we're building the type pattern to deduce against, don't wrap the
4599  // substituted type in an AutoType. Certain template deduction rules
4600  // apply only when a template type parameter appears directly (and not if
4601  // the parameter is found through desugaring). For instance:
4602  // auto &&lref = lvalue;
4603  // must transform into "rvalue reference to T" not "rvalue reference to
4604  // auto type deduced as T" in order for [temp.deduct.call]p3 to apply.
4605  //
4606  // FIXME: Is this still necessary?
4607  if (!UseTypeSugar)
4608  return TransformDesugared(TLB, TL);
4609 
4610  QualType Result = SemaRef.Context.getAutoType(
4611  Replacement, TL.getTypePtr()->getKeyword(), Replacement.isNull(),
4612  ReplacementIsPack, TL.getTypePtr()->getTypeConstraintConcept(),
4614  auto NewTL = TLB.push<AutoTypeLoc>(Result);
4615  NewTL.copy(TL);
4616  return Result;
4617  }
4618 
4619  QualType TransformDeducedTemplateSpecializationType(
4621  if (!UseTypeSugar)
4622  return TransformDesugared(TLB, TL);
4623 
4624  QualType Result = SemaRef.Context.getDeducedTemplateSpecializationType(
4625  TL.getTypePtr()->getTemplateName(),
4626  Replacement, Replacement.isNull());
4627  auto NewTL = TLB.push<DeducedTemplateSpecializationTypeLoc>(Result);
4628  NewTL.setNameLoc(TL.getNameLoc());
4629  return Result;
4630  }
4631 
4632  ExprResult TransformLambdaExpr(LambdaExpr *E) {
4633  // Lambdas never need to be transformed.
4634  return E;
4635  }
4636 
4637  QualType Apply(TypeLoc TL) {
4638  // Create some scratch storage for the transformed type locations.
4639  // FIXME: We're just going to throw this information away. Don't build it.
4640  TypeLocBuilder TLB;
4641  TLB.reserve(TL.getFullDataSize());
4642  return TransformType(TLB, TL);
4643  }
4644  };
4645 
4646 } // namespace
4647 
4650  Optional<unsigned> DependentDeductionDepth,
4651  bool IgnoreConstraints) {
4652  return DeduceAutoType(Type->getTypeLoc(), Init, Result,
4653  DependentDeductionDepth, IgnoreConstraints);
4654 }
4655 
4656 /// Attempt to produce an informative diagostic explaining why auto deduction
4657 /// failed.
4658 /// \return \c true if diagnosed, \c false if not.
4661  TemplateDeductionInfo &Info,
4662  ArrayRef<SourceRange> Ranges) {
4663  switch (TDK) {
4664  case Sema::TDK_Inconsistent: {
4665  // Inconsistent deduction means we were deducing from an initializer list.
4666  auto D = S.Diag(Info.getLocation(), diag::err_auto_inconsistent_deduction);
4667  D << Info.FirstArg << Info.SecondArg;
4668  for (auto R : Ranges)
4669  D << R;
4670  return true;
4671  }
4672 
4673  // FIXME: Are there other cases for which a custom diagnostic is more useful
4674  // than the basic "types don't match" diagnostic?
4675 
4676  default:
4677  return false;
4678  }
4679 }
4680 
4683  AutoTypeLoc TypeLoc, QualType Deduced) {
4684  ConstraintSatisfaction Satisfaction;
4685  ConceptDecl *Concept = Type.getTypeConstraintConcept();
4686  TemplateArgumentListInfo TemplateArgs(TypeLoc.getLAngleLoc(),
4687  TypeLoc.getRAngleLoc());
4688  TemplateArgs.addArgument(
4691  Deduced, TypeLoc.getNameLoc())));
4692  for (unsigned I = 0, C = TypeLoc.getNumArgs(); I != C; ++I)
4693  TemplateArgs.addArgument(TypeLoc.getArgLoc(I));
4694 
4696  if (S.CheckTemplateArgumentList(Concept, SourceLocation(), TemplateArgs,
4697  /*PartialTemplateArgs=*/false, Converted))
4699  if (S.CheckConstraintSatisfaction(Concept, {Concept->getConstraintExpr()},
4700  Converted, TypeLoc.getLocalSourceRange(),
4701  Satisfaction))
4703  if (!Satisfaction.IsSatisfied) {
4704  std::string Buf;
4705  llvm::raw_string_ostream OS(Buf);
4706  OS << "'" << Concept->getName();
4707  if (TypeLoc.hasExplicitTemplateArgs()) {
4709  OS, Type.getTypeConstraintArguments(), S.getPrintingPolicy(),
4710  Type.getTypeConstraintConcept()->getTemplateParameters());
4711  }
4712  OS << "'";
4713  OS.flush();
4714  S.Diag(TypeLoc.getConceptNameLoc(),
4715  diag::err_placeholder_constraints_not_satisfied)
4716  << Deduced << Buf << TypeLoc.getLocalSourceRange();
4717  S.DiagnoseUnsatisfiedConstraint(Satisfaction);
4719  }
4720  return Sema::DAR_Succeeded;
4721 }
4722 
4723 /// Deduce the type for an auto type-specifier (C++11 [dcl.spec.auto]p6)
4724 ///
4725 /// Note that this is done even if the initializer is dependent. (This is
4726 /// necessary to support partial ordering of templates using 'auto'.)
4727 /// A dependent type will be produced when deducing from a dependent type.
4728 ///
4729 /// \param Type the type pattern using the auto type-specifier.
4730 /// \param Init the initializer for the variable whose type is to be deduced.
4731 /// \param Result if type deduction was successful, this will be set to the
4732 /// deduced type.
4733 /// \param DependentDeductionDepth Set if we should permit deduction in
4734 /// dependent cases. This is necessary for template partial ordering with
4735 /// 'auto' template parameters. The value specified is the template
4736 /// parameter depth at which we should perform 'auto' deduction.
4737 /// \param IgnoreConstraints Set if we should not fail if the deduced type does
4738 /// not satisfy the type-constraint in the auto type.
4741  Optional<unsigned> DependentDeductionDepth,
4742  bool IgnoreConstraints) {
4743  if (Init->containsErrors())
4745  if (Init->getType()->isNonOverloadPlaceholderType()) {
4746  ExprResult NonPlaceholder = CheckPlaceholderExpr(Init);
4747  if (NonPlaceholder.isInvalid())
4749  Init = NonPlaceholder.get();
4750  }
4751 
4752  DependentAuto DependentResult = {
4753  /*.IsPack = */ (bool)Type.getAs<PackExpansionTypeLoc>()};
4754 
4755  if (!DependentDeductionDepth &&
4756  (Type.getType()->isDependentType() || Init->isTypeDependent() ||
4757  Init->containsUnexpandedParameterPack())) {
4758  Result = SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
4759  assert(!Result.isNull() && "substituting DependentTy can't fail");
4760  return DAR_Succeeded;
4761  }
4762 
4763  // Find the depth of template parameter to synthesize.
4764  unsigned Depth = DependentDeductionDepth.getValueOr(0);
4765 
4766  // If this is a 'decltype(auto)' specifier, do the decltype dance.
4767  // Since 'decltype(auto)' can only occur at the top of the type, we
4768  // don't need to go digging for it.
4769  if (const AutoType *AT = Type.getType()->getAs<AutoType>()) {
4770  if (AT->isDecltypeAuto()) {
4771  if (isa<InitListExpr>(Init)) {
4772  Diag(Init->getBeginLoc(), diag::err_decltype_auto_initializer_list);
4774  }
4775 
4776  ExprResult ER = CheckPlaceholderExpr(Init);
4777  if (ER.isInvalid())
4779  Init = ER.get();
4780  QualType Deduced = BuildDecltypeType(Init, Init->getBeginLoc(), false);
4781  if (Deduced.isNull())
4783  // FIXME: Support a non-canonical deduced type for 'auto'.
4784  Deduced = Context.getCanonicalType(Deduced);
4785  if (AT->isConstrained() && !IgnoreConstraints) {
4786  auto ConstraintsResult =
4788  Type.getContainedAutoTypeLoc(),
4789  Deduced);
4790  if (ConstraintsResult != DAR_Succeeded)
4791  return ConstraintsResult;
4792  }
4793  Result = SubstituteDeducedTypeTransform(*this, Deduced).Apply(Type);
4794  if (Result.isNull())
4796  return DAR_Succeeded;
4797  } else if (!getLangOpts().CPlusPlus) {
4798  if (isa<InitListExpr>(Init)) {
4799  Diag(Init->getBeginLoc(), diag::err_auto_init_list_from_c);
4801  }
4802  }
4803  }
4804 
4805  SourceLocation Loc = Init->getExprLoc();
4806 
4807  LocalInstantiationScope InstScope(*this);
4808 
4809  // Build template<class TemplParam> void Func(FuncParam);
4811  Context, nullptr, SourceLocation(), Loc, Depth, 0, nullptr, false, false,
4812  false);
4813  QualType TemplArg = QualType(TemplParam->getTypeForDecl(), 0);
4814  NamedDecl *TemplParamPtr = TemplParam;
4816  Context, Loc, Loc, TemplParamPtr, Loc, nullptr);
4817 
4818  QualType FuncParam =
4819  SubstituteDeducedTypeTransform(*this, TemplArg, /*UseTypeSugar*/false)
4820  .Apply(Type);
4821  assert(!FuncParam.isNull() &&
4822  "substituting template parameter for 'auto' failed");
4823 
4824  // Deduce type of TemplParam in Func(Init)
4826  Deduced.resize(1);
4827 
4828  TemplateDeductionInfo Info(Loc, Depth);
4829 
4830  // If deduction failed, don't diagnose if the initializer is dependent; it
4831  // might acquire a matching type in the instantiation.
4832  auto DeductionFailed = [&](TemplateDeductionResult TDK,
4834  if (Init->isTypeDependent()) {
4835  Result =
4836  SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
4837  assert(!Result.isNull() && "substituting DependentTy can't fail");
4838  return DAR_Succeeded;
4839  }
4840  if (diagnoseAutoDeductionFailure(*this, TDK, Info, Ranges))
4842  return DAR_Failed;
4843  };
4844 
4845  SmallVector<OriginalCallArg, 4> OriginalCallArgs;
4846 
4847  InitListExpr *InitList = dyn_cast<InitListExpr>(Init);
4848  if (InitList) {
4849  // Notionally, we substitute std::initializer_list<T> for 'auto' and deduce
4850  // against that. Such deduction only succeeds if removing cv-qualifiers and
4851  // references results in std::initializer_list<T>.
4852  if (!Type.getType().getNonReferenceType()->getAs<AutoType>())
4853  return DAR_Failed;
4854 
4855  // Resolving a core issue: a braced-init-list containing any designators is
4856  // a non-deduced context.
4857  for (Expr *E : InitList->inits())
4858  if (isa<DesignatedInitExpr>(E))
4859  return DAR_Failed;
4860 
4861  SourceRange DeducedFromInitRange;
4862  for (unsigned i = 0, e = InitList->getNumInits(); i < e; ++i) {
4863  Expr *Init = InitList->getInit(i);
4864 
4866  *this, TemplateParamsSt.get(), 0, TemplArg, Init,
4867  Info, Deduced, OriginalCallArgs, /*Decomposed*/ true,
4868  /*ArgIdx*/ 0, /*TDF*/ 0))
4869  return DeductionFailed(TDK, {DeducedFromInitRange,
4870  Init->getSourceRange()});
4871 
4872  if (DeducedFromInitRange.isInvalid() &&
4873  Deduced[0].getKind() != TemplateArgument::Null)
4874  DeducedFromInitRange = Init->getSourceRange();
4875  }
4876  } else {
4877  if (!getLangOpts().CPlusPlus && Init->refersToBitField()) {
4878  Diag(Loc, diag::err_auto_bitfield);
4880  }
4881 
4883  *this, TemplateParamsSt.get(), 0, FuncParam, Init, Info, Deduced,
4884  OriginalCallArgs, /*Decomposed*/ false, /*ArgIdx*/ 0, /*TDF*/ 0))
4885  return DeductionFailed(TDK, {});
4886  }
4887 
4888  // Could be null if somehow 'auto' appears in a non-deduced context.
4889  if (Deduced[0].getKind() != TemplateArgument::Type)
4890  return DeductionFailed(TDK_Incomplete, {});
4891 
4892  QualType DeducedType = Deduced[0].getAsType();
4893 
4894  if (InitList) {
4896  if (DeducedType.isNull())
4898  }
4899 
4900  if (const auto *AT = Type.getType()->getAs<AutoType>()) {
4901  if (AT->isConstrained() && !IgnoreConstraints) {
4902  auto ConstraintsResult =
4904  Type.getContainedAutoTypeLoc(),
4905  DeducedType);
4906  if (ConstraintsResult != DAR_Succeeded)
4907  return ConstraintsResult;
4908  }
4909  }
4910 
4911  Result = SubstituteDeducedTypeTransform(*this, DeducedType).Apply(Type);
4912  if (Result.isNull())
4914 
4915  // Check that the deduced argument type is compatible with the original
4916  // argument type per C++ [temp.deduct.call]p4.
4917  QualType DeducedA = InitList ? Deduced[0].getAsType() : Result;
4918  for (const OriginalCallArg &OriginalArg : OriginalCallArgs) {
4919  assert((bool)InitList == OriginalArg.DecomposedParam &&
4920  "decomposed non-init-list in auto deduction?");
4921  if (auto TDK =
4922  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA)) {
4923  Result = QualType();
4924  return DeductionFailed(TDK, {});
4925  }
4926  }
4927 
4928  return DAR_Succeeded;
4929 }
4930 
4932  QualType TypeToReplaceAuto) {
4933  if (TypeToReplaceAuto->isDependentType())
4934  return SubstituteDeducedTypeTransform(
4935  *this, DependentAuto{
4936  TypeToReplaceAuto->containsUnexpandedParameterPack()})
4937  .TransformType(TypeWithAuto);
4938  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4939  .TransformType(TypeWithAuto);
4940 }
4941 
4943  QualType TypeToReplaceAuto) {
4944  if (TypeToReplaceAuto->isDependentType())
4945  return SubstituteDeducedTypeTransform(
4946  *this,
4947  DependentAuto{
4948  TypeToReplaceAuto->containsUnexpandedParameterPack()})
4949  .TransformType(TypeWithAuto);
4950  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4951  .TransformType(TypeWithAuto);
4952 }
4953 
4955  QualType TypeToReplaceAuto) {
4956  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
4957  /*UseTypeSugar*/ false)
4958  .TransformType(TypeWithAuto);
4959 }
4960 
4962  QualType TypeToReplaceAuto) {
4963  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
4964  /*UseTypeSugar*/ false)
4965  .TransformType(TypeWithAuto);
4966 }
4967 
4969  if (isa<InitListExpr>(Init))
4970  Diag(VDecl->getLocation(),
4971  VDecl->isInitCapture()
4972  ? diag::err_init_capture_deduction_failure_from_init_list
4973  : diag::err_auto_var_deduction_failure_from_init_list)
4974  << VDecl->getDeclName() << VDecl->getType() << Init->getSourceRange();
4975  else
4976  Diag(VDecl->getLocation(),
4977  VDecl->isInitCapture() ? diag::err_init_capture_deduction_failure
4978  : diag::err_auto_var_deduction_failure)
4979  << VDecl->getDeclName() << VDecl->getType() << Init->getType()
4980  << Init->getSourceRange();
4981 }
4982 
4984  bool Diagnose) {
4985  assert(FD->getReturnType()->isUndeducedType());
4986 
4987  // For a lambda's conversion operator, deduce any 'auto' or 'decltype(auto)'
4988  // within the return type from the call operator's type.
4989  if (isLambdaConversionOperator(FD)) {
4990  CXXRecordDecl *Lambda = cast<CXXMethodDecl>(FD)->getParent();
4991  FunctionDecl *CallOp = Lambda->getLambdaCallOperator();
4992 
4993  // For a generic lambda, instantiate the call operator if needed.
4994  if (auto *Args = FD->getTemplateSpecializationArgs()) {
4996  CallOp->getDescribedFunctionTemplate(), Args, Loc);
4997  if (!CallOp || CallOp->isInvalidDecl())
4998  return true;
4999 
5000  // We might need to deduce the return type by instantiating the definition
5001  // of the operator() function.
5002  if (CallOp->getReturnType()->isUndeducedType()) {
5003  runWithSufficientStackSpace(Loc, [&] {
5004  InstantiateFunctionDefinition(Loc, CallOp);
5005  });
5006  }
5007  }
5008 
5009  if (CallOp->isInvalidDecl())
5010  return true;
5011  assert(!CallOp->getReturnType()->isUndeducedType() &&
5012  "failed to deduce lambda return type");
5013 
5014  // Build the new return type from scratch.
5015  CallingConv RetTyCC = FD->getReturnType()
5016  ->getPointeeType()
5017  ->castAs<FunctionType>()
5018  ->getCallConv();
5020  CallOp->getType()->castAs<FunctionProtoType>(), RetTyCC);
5021  if (FD->getReturnType()->getAs<PointerType>())
5022  RetType = Context.getPointerType(RetType);
5023  else {
5024  assert(FD->getReturnType()->getAs<BlockPointerType>());
5025  RetType = Context.getBlockPointerType(RetType);
5026  }
5028  return false;
5029  }
5030 
5031  if (FD->getTemplateInstantiationPattern()) {
5032  runWithSufficientStackSpace(Loc, [&] {
5034  });
5035  }
5036 
5037  bool StillUndeduced = FD->getReturnType()->isUndeducedType();
5038  if (StillUndeduced && Diagnose && !FD->isInvalidDecl()) {
5039  Diag(Loc, diag::err_auto_fn_used_before_defined) << FD;
5040  Diag(FD->getLocation(), diag::note_callee_decl) << FD;
5041  }
5042 
5043  return StillUndeduced;
5044 }
5045 
5046 /// If this is a non-static member function,
5047 static void
5049  CXXMethodDecl *Method,
5050  SmallVectorImpl<QualType> &ArgTypes) {
5051  // C++11 [temp.func.order]p3:
5052  // [...] The new parameter is of type "reference to cv A," where cv are
5053  // the cv-qualifiers of the function template (if any) and A is
5054  // the class of which the function template is a member.
5055  //
5056  // The standard doesn't say explicitly, but we pick the appropriate kind of
5057  // reference type based on [over.match.funcs]p4.
5058  QualType ArgTy = Context.getTypeDeclType(Method->getParent());
5059  ArgTy = Context.getQualifiedType(ArgTy, Method->getMethodQualifiers());
5060  if (Method->getRefQualifier() == RQ_RValue)
5061  ArgTy = Context.getRValueReferenceType(ArgTy);
5062  else
5063  ArgTy = Context.getLValueReferenceType(ArgTy);
5064  ArgTypes.push_back(ArgTy);
5065 }
5066 
5067 /// Determine whether the function template \p FT1 is at least as
5068 /// specialized as \p FT2.
5070  SourceLocation Loc,
5071  FunctionTemplateDecl *FT1,
5072  FunctionTemplateDecl *FT2,
5074  unsigned NumCallArguments1,
5075  bool Reversed) {
5076  assert(!Reversed || TPOC == TPOC_Call);
5077 
5078  FunctionDecl *FD1 = FT1->getTemplatedDecl();
5079  FunctionDecl *FD2 = FT2->getTemplatedDecl();
5080  const FunctionProtoType *Proto1 = FD1->getType()->getAs<FunctionProtoType>();
5081  const FunctionProtoType *Proto2 = FD2->getType()->getAs<FunctionProtoType>();
5082 
5083  assert(Proto1 && Proto2 && "Function templates must have prototypes");
5084  TemplateParameterList *TemplateParams = FT2->getTemplateParameters();
5086  Deduced.resize(TemplateParams->size());
5087 
5088  // C++0x [temp.deduct.partial]p3:
5089  // The types used to determine the ordering depend on the context in which
5090  // the partial ordering is done:
5091  TemplateDeductionInfo Info(Loc);
5093  switch (TPOC) {
5094  case TPOC_Call: {
5095  // - In the context of a function call, the function parameter types are
5096  // used.
5097  CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
5098  CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
5099 
5100  // C++11 [temp.func.order]p3:
5101  // [...] If only one of the function templates is a non-static
5102  // member, that function template is considered to have a new
5103  // first parameter inserted in its function parameter list. The
5104  // new parameter is of type "reference to cv A," where cv are
5105  // the cv-qualifiers of the function template (if any) and A is
5106  // the class of which the function template is a member.
5107  //
5108  // Note that we interpret this to mean "if one of the function
5109  // templates is a non-static member and the other is a non-member";
5110  // otherwise, the ordering rules for static functions against non-static
5111  // functions don't make any sense.
5112  //
5113  // C++98/03 doesn't have this provision but we've extended DR532 to cover
5114  // it as wording was broken prior to it.
5116 
5117  unsigned NumComparedArguments = NumCallArguments1;
5118 
5119  if (!Method2 && Method1 && !Method1->isStatic()) {
5120  // Compare 'this' from Method1 against first parameter from Method2.
5121  AddImplicitObjectParameterType(S.Context, Method1, Args1);
5122  ++NumComparedArguments;
5123  } else if (!Method1 && Method2 && !Method2->isStatic()) {
5124  // Compare 'this' from Method2 against first parameter from Method1.
5125  AddImplicitObjectParameterType(S.Context, Method2, Args2);
5126  } else if (Method1 && Method2 && Reversed) {
5127  // Compare 'this' from Method1 against second parameter from Method2
5128  // and 'this' from Method2 against second parameter from Method1.
5129  AddImplicitObjectParameterType(S.Context, Method1, Args1);
5130  AddImplicitObjectParameterType(S.Context, Method2, Args2);
5131  ++NumComparedArguments;
5132  }
5133 
5134  Args1.insert(Args1.end(), Proto1->param_type_begin(),
5135  Proto1->param_type_end());
5136  Args2.insert(Args2.end(), Proto2->param_type_begin(),
5137  Proto2->param_type_end());
5138 
5139  // C++ [temp.func.order]p5:
5140  // The presence of unused ellipsis and default arguments has no effect on
5141  // the partial ordering of function templates.
5142  if (Args1.size() > NumComparedArguments)
5143  Args1.resize(NumComparedArguments);
5144  if (Args2.size() > NumComparedArguments)
5145  Args2.resize(NumComparedArguments);
5146  if (Reversed)
5147  std::reverse(Args2.begin(), Args2.end());
5148  if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
5149  Args1.data(), Args1.size(), Info, Deduced,
5150  TDF_None, /*PartialOrdering=*/true))
5151  return false;
5152 
5153  break;
5154  }
5155 
5156  case TPOC_Conversion:
5157  // - In the context of a call to a conversion operator, the return types
5158  // of the conversion function templates are used.
5160  S, TemplateParams, Proto2->getReturnType(), Proto1->getReturnType(),
5161  Info, Deduced, TDF_None,
5162  /*PartialOrdering=*/true))
5163  return false;
5164  break;
5165 
5166  case TPOC_Other:
5167  // - In other contexts (14.6.6.2) the function template's function type
5168  // is used.
5169  if (DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
5170  FD2->getType(), FD1->getType(),
5171  Info, Deduced, TDF_None,
5172  /*PartialOrdering=*/true))
5173  return false;
5174  break;
5175  }
5176 
5177  // C++0x [temp.deduct.partial]p11:
5178  // In most cases, all template parameters must have values in order for
5179  // deduction to succeed, but for partial ordering purposes a template
5180  // parameter may remain without a value provided it is not used in the
5181  // types being used for partial ordering. [ Note: a template parameter used
5182  // in a non-deduced context is considered used. -end note]
5183  unsigned ArgIdx = 0, NumArgs = Deduced.size();
5184  for (; ArgIdx != NumArgs; ++ArgIdx)
5185  if (Deduced[ArgIdx].isNull())
5186  break;
5187 
5188  // FIXME: We fail to implement [temp.deduct.type]p1 along this path. We need
5189  // to substitute the deduced arguments back into the template and check that
5190  // we get the right type.
5191 
5192  if (ArgIdx == NumArgs) {
5193  // All template arguments were deduced. FT1 is at least as specialized
5194  // as FT2.
5195  return true;
5196  }
5197 
5198  // Figure out which template parameters were used.
5199  llvm::SmallBitVector UsedParameters(TemplateParams->size());
5200  switch (TPOC) {
5201  case TPOC_Call:
5202  for (unsigned I = 0, N = Args2.size(); I != N; ++I)
5203  ::MarkUsedTemplateParameters(S.Context, Args2[I], false,
5204  TemplateParams->getDepth(),
5205  UsedParameters);
5206  break;
5207 
5208  case TPOC_Conversion:
5209  ::MarkUsedTemplateParameters(S.Context, Proto2->getReturnType(), false,
5210  TemplateParams->getDepth(), UsedParameters);
5211  break;
5212 
5213  case TPOC_Other:
5214  ::MarkUsedTemplateParameters(S.Context, FD2->getType(), false,
5215  TemplateParams->getDepth(),
5216  UsedParameters);
5217  break;
5218  }
5219 
5220  for (; ArgIdx != NumArgs; ++ArgIdx)
5221  // If this argument had no value deduced but was used in one of the types
5222  // used for partial ordering, then deduction fails.
5223  if (Deduced[ArgIdx].isNull() && UsedParameters[ArgIdx])
5224  return false;
5225 
5226  return true;
5227 }
5228 
5229 /// Determine whether this a function template whose parameter-type-list
5230 /// ends with a function parameter pack.
5232  FunctionDecl *Function = FunTmpl->getTemplatedDecl();
5233  unsigned NumParams = Function->getNumParams();
5234  if (NumParams == 0)
5235  return false;
5236 
5237  ParmVarDecl *Last = Function->getParamDecl(NumParams - 1);
5238  if (!Last->isParameterPack())
5239  return false;
5240 
5241  // Make sure that no previous parameter is a parameter pack.
5242  while (--NumParams > 0) {
5243  if (Function->getParamDecl(NumParams - 1)->isParameterPack())
5244  return false;
5245  }
5246 
5247  return true;
5248 }
5249 
5250 /// Returns the more specialized function template according
5251 /// to the rules of function template partial ordering (C++ [temp.func.order]).
5252 ///
5253 /// \param FT1 the first function template
5254 ///
5255 /// \param FT2 the second function template
5256 ///
5257 /// \param TPOC the context in which we are performing partial ordering of
5258 /// function templates.
5259 ///
5260 /// \param NumCallArguments1 The number of arguments in the call to FT1, used
5261 /// only when \c TPOC is \c TPOC_Call.
5262 ///
5263 /// \param NumCallArguments2 The number of arguments in the call to FT2, used
5264 /// only when \c TPOC is \c TPOC_Call.
5265 ///
5266 /// \param Reversed If \c true, exactly one of FT1 and FT2 is an overload
5267 /// candidate with a reversed parameter order. In this case, the corresponding
5268 /// P/A pairs between FT1 and FT2 are reversed.
5269 ///
5270 /// \returns the more specialized function template. If neither
5271 /// template is more specialized, returns NULL.
5274  FunctionTemplateDecl *FT2,
5275  SourceLocation Loc,
5277  unsigned NumCallArguments1,
5278  unsigned NumCallArguments2,
5279  bool Reversed) {
5280 
5281  auto JudgeByConstraints = [&] () -> FunctionTemplateDecl * {
5283  FT1->getAssociatedConstraints(AC1);
5284  FT2->getAssociatedConstraints(AC2);
5285  bool AtLeastAsConstrained1, AtLeastAsConstrained2;
5286  if (IsAtLeastAsConstrained(FT1, AC1, FT2, AC2, AtLeastAsConstrained1))
5287  return nullptr;
5288  if (IsAtLeastAsConstrained(FT2, AC2, FT1, AC1, AtLeastAsConstrained2))
5289  return nullptr;
5290  if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
5291  return nullptr;
5292  return AtLeastAsConstrained1 ? FT1 : FT2;
5293  };
5294 
5295  bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
5296  NumCallArguments1, Reversed);
5297  bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
5298  NumCallArguments2, Reversed);
5299 
5300  if (Better1 != Better2) // We have a clear winner
5301  return Better1 ? FT1 : FT2;
5302 
5303  if (!Better1 && !Better2) // Neither is better than the other
5304  return JudgeByConstraints();
5305 
5306  // FIXME: This mimics what GCC implements, but doesn't match up with the
5307  // proposed resolution for core issue 692. This area needs to be sorted out,
5308  // but for now we attempt to maintain compatibility.
5309  bool Variadic1 = isVariadicFunctionTemplate(FT1);
5310  bool Variadic2 = isVariadicFunctionTemplate(FT2);
5311  if (Variadic1 != Variadic2)
5312  return Variadic1? FT2 : FT1;
5313 
5314  return JudgeByConstraints();
5315 }
5316 
5317 /// Determine if the two templates are equivalent.
5319  if (T1 == T2)
5320  return true;
5321 
5322  if (!T1 || !T2)
5323  return false;
5324 
5325  return T1->getCanonicalDecl() == T2->getCanonicalDecl();
5326 }
5327 
5328 /// Retrieve the most specialized of the given function template
5329 /// specializations.
5330 ///
5331 /// \param SpecBegin the start iterator of the function template
5332 /// specializations that we will be comparing.
5333 ///
5334 /// \param SpecEnd the end iterator of the function template
5335 /// specializations, paired with \p SpecBegin.
5336 ///
5337 /// \param Loc the location where the ambiguity or no-specializations
5338 /// diagnostic should occur.
5339 ///
5340 /// \param NoneDiag partial diagnostic used to diagnose cases where there are
5341 /// no matching candidates.
5342 ///
5343 /// \param AmbigDiag partial diagnostic used to diagnose an ambiguity, if one
5344 /// occurs.
5345 ///
5346 /// \param CandidateDiag partial diagnostic used for each function template
5347 /// specialization that is a candidate in the ambiguous ordering. One parameter
5348 /// in this diagnostic should be unbound, which will correspond to the string
5349 /// describing the template arguments for the function template specialization.
5350 ///
5351 /// \returns the most specialized function template specialization, if
5352 /// found. Otherwise, returns SpecEnd.
5354  UnresolvedSetIterator SpecBegin, UnresolvedSetIterator SpecEnd,
5355  TemplateSpecCandidateSet &FailedCandidates,
5356  SourceLocation Loc, const PartialDiagnostic &NoneDiag,
5357  const PartialDiagnostic &AmbigDiag, const PartialDiagnostic &CandidateDiag,
5358  bool Complain, QualType TargetType) {
5359  if (SpecBegin == SpecEnd) {
5360  if (Complain) {
5361  Diag(Loc, NoneDiag);
5362  FailedCandidates.NoteCandidates(*this, Loc);
5363  }
5364  return SpecEnd;
5365  }
5366 
5367  if (SpecBegin + 1 == SpecEnd)
5368  return SpecBegin;
5369 
5370  // Find the function template that is better than all of the templates it
5371  // has been compared to.
5372  UnresolvedSetIterator Best = SpecBegin;
5373  FunctionTemplateDecl *BestTemplate
5374  = cast<FunctionDecl>(*Best)->getPrimaryTemplate();
5375  assert(BestTemplate && "Not a function template specialization?");
5376  for (UnresolvedSetIterator I = SpecBegin + 1; I != SpecEnd; ++I) {
5377  FunctionTemplateDecl *Challenger
5378  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
5379  assert(Challenger && "Not a function template specialization?");
5380  if (isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
5381  Loc, TPOC_Other, 0, 0),
5382  Challenger)) {
5383  Best = I;
5384  BestTemplate = Challenger;
5385  }
5386  }
5387 
5388  // Make sure that the "best" function template is more specialized than all
5389  // of the others.
5390  bool Ambiguous = false;
5391  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
5392  FunctionTemplateDecl *Challenger
5393  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
5394  if (I != Best &&
5395  !isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
5396  Loc, TPOC_Other, 0, 0),
5397  BestTemplate)) {
5398  Ambiguous = true;
5399  break;
5400  }
5401  }
5402 
5403  if (!Ambiguous) {
5404  // We found an answer. Return it.
5405  return Best;
5406  }
5407 
5408  // Diagnose the ambiguity.
5409  if (Complain) {
5410  Diag(Loc, AmbigDiag);
5411 
5412  // FIXME: Can we order the candidates in some sane way?
5413  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
5414  PartialDiagnostic PD = CandidateDiag;
5415  const auto *FD = cast<FunctionDecl>(*I);
5416  PD << FD << getTemplateArgumentBindingsText(
5417  FD->getPrimaryTemplate()->getTemplateParameters(),
5418  *FD->getTemplateSpecializationArgs());
5419  if (!TargetType.isNull())
5420  HandleFunctionTypeMismatch(PD, FD->getType(), TargetType);
5421  Diag((*I)->getLocation(), PD);
5422  }
5423  }
5424 
5425  return SpecEnd;
5426 }
5427 
5428 /// Determine whether one partial specialization, P1, is at least as
5429 /// specialized than another, P2.
5430 ///
5431 /// \tparam TemplateLikeDecl The kind of P2, which must be a
5432 /// TemplateDecl or {Class,Var}TemplatePartialSpecializationDecl.
5433 /// \param T1 The injected-class-name of P1 (faked for a variable template).
5434 /// \param T2 The injected-class-name of P2 (faked for a variable template).
5435 template<typename TemplateLikeDecl>
5437  TemplateLikeDecl *P2,
5438  TemplateDeductionInfo &Info) {
5439  // C++ [temp.class.order]p1:
5440  // For two class template partial specializations, the first is at least as
5441  // specialized as the second if, given the following rewrite to two
5442  // function templates, the first function template is at least as
5443  // specialized as the second according to the ordering rules for function
5444  // templates (14.6.6.2):
5445  // - the first function template has the same template parameters as the
5446  // first partial specialization and has a single function parameter
5447  // whose type is a class template specialization with the template
5448  // arguments of the first partial specialization, and
5449  // - the second function template has the same template parameters as the
5450  // second partial specialization and has a single function parameter
5451  // whose type is a class template specialization with the template
5452  // arguments of the second partial specialization.
5453  //
5454  // Rather than synthesize function templates, we merely perform the
5455  // equivalent partial ordering by performing deduction directly on
5456  // the template arguments of the class template partial
5457  // specializations. This computation is slightly simpler than the
5458  // general problem of function template partial ordering, because
5459  // class template partial specializations are more constrained. We
5460  // know that every template parameter is deducible from the class
5461  // template partial specialization's template arguments, for
5462  // example.
5464 
5465  // Determine whether P1 is at least as specialized as P2.
5466  Deduced.resize(P2->getTemplateParameters()->size());
5467  if (DeduceTemplateArgumentsByTypeMatch(S, P2->getTemplateParameters(),
5468  T2, T1, Info, Deduced, TDF_None,
5469  /*PartialOrdering=*/true))
5470