clang  13.0.0git
SemaTemplateDeduction.cpp
Go to the documentation of this file.
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 
3083  Deduced.resize(Partial->getTemplateParameters()->size());
3084  if (TemplateDeductionResult Result
3085  = ::DeduceTemplateArguments(*this,
3086  Partial->getTemplateParameters(),
3087  Partial->getTemplateArgs(),
3088  TemplateArgs, Info, Deduced))
3089  return Result;
3090 
3091  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3092  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
3093  Info);
3094  if (Inst.isInvalid())
3095  return TDK_InstantiationDepth;
3096 
3097  if (Trap.hasErrorOccurred())
3099 
3100  TemplateDeductionResult Result;
3102  Result = ::FinishTemplateArgumentDeduction(*this, Partial,
3103  /*IsPartialOrdering=*/false,
3104  TemplateArgs, Deduced, Info);
3105  });
3106  return Result;
3107 }
3108 
3109 /// Perform template argument deduction to determine whether
3110 /// the given template arguments match the given variable template
3111 /// partial specialization per C++ [temp.class.spec.match].
3114  const TemplateArgumentList &TemplateArgs,
3115  TemplateDeductionInfo &Info) {
3116  if (Partial->isInvalidDecl())
3117  return TDK_Invalid;
3118 
3119  // C++ [temp.class.spec.match]p2:
3120  // A partial specialization matches a given actual template
3121  // argument list if the template arguments of the partial
3122  // specialization can be deduced from the actual template argument
3123  // list (14.8.2).
3124 
3125  // Unevaluated SFINAE context.
3128  SFINAETrap Trap(*this);
3129 
3131  Deduced.resize(Partial->getTemplateParameters()->size());
3133  *this, Partial->getTemplateParameters(), Partial->getTemplateArgs(),
3134  TemplateArgs, Info, Deduced))
3135  return Result;
3136 
3137  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3138  InstantiatingTemplate Inst(*this, Info.getLocation(), Partial, DeducedArgs,
3139  Info);
3140  if (Inst.isInvalid())
3141  return TDK_InstantiationDepth;
3142 
3143  if (Trap.hasErrorOccurred())
3145 
3146  TemplateDeductionResult Result;
3148  Result = ::FinishTemplateArgumentDeduction(*this, Partial,
3149  /*IsPartialOrdering=*/false,
3150  TemplateArgs, Deduced, Info);
3151  });
3152  return Result;
3153 }
3154 
3155 /// Determine whether the given type T is a simple-template-id type.
3157  if (const TemplateSpecializationType *Spec
3159  return Spec->getTemplateName().getAsTemplateDecl() != nullptr;
3160 
3161  // C++17 [temp.local]p2:
3162  // the injected-class-name [...] is equivalent to the template-name followed
3163  // by the template-arguments of the class template specialization or partial
3164  // specialization enclosed in <>
3165  // ... which means it's equivalent to a simple-template-id.
3166  //
3167  // This only arises during class template argument deduction for a copy
3168  // deduction candidate, where it permits slicing.
3169  if (T->getAs<InjectedClassNameType>())
3170  return true;
3171 
3172  return false;
3173 }
3174 
3175 /// Substitute the explicitly-provided template arguments into the
3176 /// given function template according to C++ [temp.arg.explicit].
3177 ///
3178 /// \param FunctionTemplate the function template into which the explicit
3179 /// template arguments will be substituted.
3180 ///
3181 /// \param ExplicitTemplateArgs the explicitly-specified template
3182 /// arguments.
3183 ///
3184 /// \param Deduced the deduced template arguments, which will be populated
3185 /// with the converted and checked explicit template arguments.
3186 ///
3187 /// \param ParamTypes will be populated with the instantiated function
3188 /// parameters.
3189 ///
3190 /// \param FunctionType if non-NULL, the result type of the function template
3191 /// will also be instantiated and the pointed-to value will be updated with
3192 /// the instantiated function type.
3193 ///
3194 /// \param Info if substitution fails for any reason, this object will be
3195 /// populated with more information about the failure.
3196 ///
3197 /// \returns TDK_Success if substitution was successful, or some failure
3198 /// condition.
3201  FunctionTemplateDecl *FunctionTemplate,
3202  TemplateArgumentListInfo &ExplicitTemplateArgs,
3204  SmallVectorImpl<QualType> &ParamTypes,
3206  TemplateDeductionInfo &Info) {
3207  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
3208  TemplateParameterList *TemplateParams
3209  = FunctionTemplate->getTemplateParameters();
3210 
3211  if (ExplicitTemplateArgs.size() == 0) {
3212  // No arguments to substitute; just copy over the parameter types and
3213  // fill in the function type.
3214  for (auto P : Function->parameters())
3215  ParamTypes.push_back(P->getType());
3216 
3217  if (FunctionType)
3218  *FunctionType = Function->getType();
3219  return TDK_Success;
3220  }
3221 
3222  // Unevaluated SFINAE context.
3225  SFINAETrap Trap(*this);
3226 
3227  // C++ [temp.arg.explicit]p3:
3228  // Template arguments that are present shall be specified in the
3229  // declaration order of their corresponding template-parameters. The
3230  // template argument list shall not specify more template-arguments than
3231  // there are corresponding template-parameters.
3233 
3234  // Enter a new template instantiation context where we check the
3235  // explicitly-specified template arguments against this function template,
3236  // and then substitute them into the function parameter types.
3238  InstantiatingTemplate Inst(
3239  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3240  CodeSynthesisContext::ExplicitTemplateArgumentSubstitution, Info);
3241  if (Inst.isInvalid())
3242  return TDK_InstantiationDepth;
3243 
3244  if (CheckTemplateArgumentList(FunctionTemplate, SourceLocation(),
3245  ExplicitTemplateArgs, true, Builder, false) ||
3246  Trap.hasErrorOccurred()) {
3247  unsigned Index = Builder.size();
3248  if (Index >= TemplateParams->size())
3249  return TDK_SubstitutionFailure;
3250  Info.Param = makeTemplateParameter(TemplateParams->getParam(Index));
3251  return TDK_InvalidExplicitArguments;
3252  }
3253 
3254  // Form the template argument list from the explicitly-specified
3255  // template arguments.
3256  TemplateArgumentList *ExplicitArgumentList
3257  = TemplateArgumentList::CreateCopy(Context, Builder);
3258  Info.setExplicitArgs(ExplicitArgumentList);
3259 
3260  // Template argument deduction and the final substitution should be
3261  // done in the context of the templated declaration. Explicit
3262  // argument substitution, on the other hand, needs to happen in the
3263  // calling context.
3264  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3265 
3266  // If we deduced template arguments for a template parameter pack,
3267  // note that the template argument pack is partially substituted and record
3268  // the explicit template arguments. They'll be used as part of deduction
3269  // for this template parameter pack.
3270  unsigned PartiallySubstitutedPackIndex = -1u;
3271  if (!Builder.empty()) {
3272  const TemplateArgument &Arg = Builder.back();
3273  if (Arg.getKind() == TemplateArgument::Pack) {
3274  auto *Param = TemplateParams->getParam(Builder.size() - 1);
3275  // If this is a fully-saturated fixed-size pack, it should be
3276  // fully-substituted, not partially-substituted.
3277  Optional<unsigned> Expansions = getExpandedPackSize(Param);
3278  if (!Expansions || Arg.pack_size() < *Expansions) {
3279  PartiallySubstitutedPackIndex = Builder.size() - 1;
3280  CurrentInstantiationScope->SetPartiallySubstitutedPack(
3281  Param, Arg.pack_begin(), Arg.pack_size());
3282  }
3283  }
3284  }
3285 
3286  const FunctionProtoType *Proto
3287  = Function->getType()->getAs<FunctionProtoType>();
3288  assert(Proto && "Function template does not have a prototype?");
3289 
3290  // Isolate our substituted parameters from our caller.
3291  LocalInstantiationScope InstScope(*this, /*MergeWithOuterScope*/true);
3292 
3293  ExtParameterInfoBuilder ExtParamInfos;
3294 
3295  // Instantiate the types of each of the function parameters given the
3296  // explicitly-specified template arguments. If the function has a trailing
3297  // return type, substitute it after the arguments to ensure we substitute
3298  // in lexical order.
3299  if (Proto->hasTrailingReturn()) {
3300  if (SubstParmTypes(Function->getLocation(), Function->parameters(),
3301  Proto->getExtParameterInfosOrNull(),
3302  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3303  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3304  return TDK_SubstitutionFailure;
3305  }
3306 
3307  // Instantiate the return type.
3308  QualType ResultType;
3309  {
3310  // C++11 [expr.prim.general]p3:
3311  // If a declaration declares a member function or member function
3312  // template of a class X, the expression this is a prvalue of type
3313  // "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
3314  // and the end of the function-definition, member-declarator, or
3315  // declarator.
3316  Qualifiers ThisTypeQuals;
3317  CXXRecordDecl *ThisContext = nullptr;
3318  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Function)) {
3319  ThisContext = Method->getParent();
3320  ThisTypeQuals = Method->getMethodQualifiers();
3321  }
3322 
3323  CXXThisScopeRAII ThisScope(*this, ThisContext, ThisTypeQuals,
3324  getLangOpts().CPlusPlus11);
3325 
3326  ResultType =
3327  SubstType(Proto->getReturnType(),
3328  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3329  Function->getTypeSpecStartLoc(), Function->getDeclName());
3330  if (ResultType.isNull() || Trap.hasErrorOccurred())
3331  return TDK_SubstitutionFailure;
3332  // CUDA: Kernel function must have 'void' return type.
3333  if (getLangOpts().CUDA)
3334  if (Function->hasAttr<CUDAGlobalAttr>() && !ResultType->isVoidType()) {
3335  Diag(Function->getLocation(), diag::err_kern_type_not_void_return)
3336  << Function->getType() << Function->getSourceRange();
3337  return TDK_SubstitutionFailure;
3338  }
3339  }
3340 
3341  // Instantiate the types of each of the function parameters given the
3342  // explicitly-specified template arguments if we didn't do so earlier.
3343  if (!Proto->hasTrailingReturn() &&
3344  SubstParmTypes(Function->getLocation(), Function->parameters(),
3345  Proto->getExtParameterInfosOrNull(),
3346  MultiLevelTemplateArgumentList(*ExplicitArgumentList),
3347  ParamTypes, /*params*/ nullptr, ExtParamInfos))
3348  return TDK_SubstitutionFailure;
3349 
3350  if (FunctionType) {
3351  auto EPI = Proto->getExtProtoInfo();
3352  EPI.ExtParameterInfos = ExtParamInfos.getPointerOrNull(ParamTypes.size());
3353 
3354  // In C++1z onwards, exception specifications are part of the function type,
3355  // so substitution into the type must also substitute into the exception
3356  // specification.
3357  SmallVector<QualType, 4> ExceptionStorage;
3358  if (getLangOpts().CPlusPlus17 &&
3359  SubstExceptionSpec(
3360  Function->getLocation(), EPI.ExceptionSpec, ExceptionStorage,
3361  MultiLevelTemplateArgumentList(*ExplicitArgumentList)))
3362  return TDK_SubstitutionFailure;
3363 
3364  *FunctionType = BuildFunctionType(ResultType, ParamTypes,
3365  Function->getLocation(),
3366  Function->getDeclName(),
3367  EPI);
3368  if (FunctionType->isNull() || Trap.hasErrorOccurred())
3369  return TDK_SubstitutionFailure;
3370  }
3371 
3372  // C++ [temp.arg.explicit]p2:
3373  // Trailing template arguments that can be deduced (14.8.2) may be
3374  // omitted from the list of explicit template-arguments. If all of the
3375  // template arguments can be deduced, they may all be omitted; in this
3376  // case, the empty template argument list <> itself may also be omitted.
3377  //
3378  // Take all of the explicitly-specified arguments and put them into
3379  // the set of deduced template arguments. The partially-substituted
3380  // parameter pack, however, will be set to NULL since the deduction
3381  // mechanism handles the partially-substituted argument pack directly.
3382  Deduced.reserve(TemplateParams->size());
3383  for (unsigned I = 0, N = ExplicitArgumentList->size(); I != N; ++I) {
3384  const TemplateArgument &Arg = ExplicitArgumentList->get(I);
3385  if (I == PartiallySubstitutedPackIndex)
3386  Deduced.push_back(DeducedTemplateArgument());
3387  else
3388  Deduced.push_back(Arg);
3389  }
3390 
3391  return TDK_Success;
3392 }
3393 
3394 /// Check whether the deduced argument type for a call to a function
3395 /// template matches the actual argument type per C++ [temp.deduct.call]p4.
3398  Sema::OriginalCallArg OriginalArg,
3399  QualType DeducedA) {
3400  ASTContext &Context = S.Context;
3401 
3402  auto Failed = [&]() -> Sema::TemplateDeductionResult {
3403  Info.FirstArg = TemplateArgument(DeducedA);
3404  Info.SecondArg = TemplateArgument(OriginalArg.OriginalArgType);
3405  Info.CallArgIndex = OriginalArg.ArgIdx;
3408  };
3409 
3410  QualType A = OriginalArg.OriginalArgType;
3411  QualType OriginalParamType = OriginalArg.OriginalParamType;
3412 
3413  // Check for type equality (top-level cv-qualifiers are ignored).
3414  if (Context.hasSameUnqualifiedType(A, DeducedA))
3415  return Sema::TDK_Success;
3416 
3417  // Strip off references on the argument types; they aren't needed for
3418  // the following checks.
3419  if (const ReferenceType *DeducedARef = DeducedA->getAs<ReferenceType>())
3420  DeducedA = DeducedARef->getPointeeType();
3421  if (const ReferenceType *ARef = A->getAs<ReferenceType>())
3422  A = ARef->getPointeeType();
3423 
3424  // C++ [temp.deduct.call]p4:
3425  // [...] However, there are three cases that allow a difference:
3426  // - If the original P is a reference type, the deduced A (i.e., the
3427  // type referred to by the reference) can be more cv-qualified than
3428  // the transformed A.
3429  if (const ReferenceType *OriginalParamRef
3430  = OriginalParamType->getAs<ReferenceType>()) {
3431  // We don't want to keep the reference around any more.
3432  OriginalParamType = OriginalParamRef->getPointeeType();
3433 
3434  // FIXME: Resolve core issue (no number yet): if the original P is a
3435  // reference type and the transformed A is function type "noexcept F",
3436  // the deduced A can be F.
3437  QualType Tmp;
3438  if (A->isFunctionType() && S.IsFunctionConversion(A, DeducedA, Tmp))
3439  return Sema::TDK_Success;
3440 
3441  Qualifiers AQuals = A.getQualifiers();
3442  Qualifiers DeducedAQuals = DeducedA.getQualifiers();
3443 
3444  // Under Objective-C++ ARC, the deduced type may have implicitly
3445  // been given strong or (when dealing with a const reference)
3446  // unsafe_unretained lifetime. If so, update the original
3447  // qualifiers to include this lifetime.
3448  if (S.getLangOpts().ObjCAutoRefCount &&
3449  ((DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_Strong &&
3450  AQuals.getObjCLifetime() == Qualifiers::OCL_None) ||
3451  (DeducedAQuals.hasConst() &&
3452  DeducedAQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone))) {
3453  AQuals.setObjCLifetime(DeducedAQuals.getObjCLifetime());
3454  }
3455 
3456  if (AQuals == DeducedAQuals) {
3457  // Qualifiers match; there's nothing to do.
3458  } else if (!DeducedAQuals.compatiblyIncludes(AQuals)) {
3459  return Failed();
3460  } else {
3461  // Qualifiers are compatible, so have the argument type adopt the
3462  // deduced argument type's qualifiers as if we had performed the
3463  // qualification conversion.
3464  A = Context.getQualifiedType(A.getUnqualifiedType(), DeducedAQuals);
3465  }
3466  }
3467 
3468  // - The transformed A can be another pointer or pointer to member
3469  // type that can be converted to the deduced A via a function pointer
3470  // conversion and/or a qualification conversion.
3471  //
3472  // Also allow conversions which merely strip __attribute__((noreturn)) from
3473  // function types (recursively).
3474  bool ObjCLifetimeConversion = false;
3475  QualType ResultTy;
3476  if ((A->isAnyPointerType() || A->isMemberPointerType()) &&
3477  (S.IsQualificationConversion(A, DeducedA, false,
3478  ObjCLifetimeConversion) ||
3479  S.IsFunctionConversion(A, DeducedA, ResultTy)))
3480  return Sema::TDK_Success;
3481 
3482  // - If P is a class and P has the form simple-template-id, then the
3483  // transformed A can be a derived class of the deduced A. [...]
3484  // [...] Likewise, if P is a pointer to a class of the form
3485  // simple-template-id, the transformed A can be a pointer to a
3486  // derived class pointed to by the deduced A.
3487  if (const PointerType *OriginalParamPtr
3488  = OriginalParamType->getAs<PointerType>()) {
3489  if (const PointerType *DeducedAPtr = DeducedA->getAs<PointerType>()) {
3490  if (const PointerType *APtr = A->getAs<PointerType>()) {
3491  if (A->getPointeeType()->isRecordType()) {
3492  OriginalParamType = OriginalParamPtr->getPointeeType();
3493  DeducedA = DeducedAPtr->getPointeeType();
3494  A = APtr->getPointeeType();
3495  }
3496  }
3497  }
3498  }
3499 
3500  if (Context.hasSameUnqualifiedType(A, DeducedA))
3501  return Sema::TDK_Success;
3502 
3503  if (A->isRecordType() && isSimpleTemplateIdType(OriginalParamType) &&
3504  S.IsDerivedFrom(Info.getLocation(), A, DeducedA))
3505  return Sema::TDK_Success;
3506 
3507  return Failed();
3508 }
3509 
3510 /// Find the pack index for a particular parameter index in an instantiation of
3511 /// a function template with specific arguments.
3512 ///
3513 /// \return The pack index for whichever pack produced this parameter, or -1
3514 /// if this was not produced by a parameter. Intended to be used as the
3515 /// ArgumentPackSubstitutionIndex for further substitutions.
3516 // FIXME: We should track this in OriginalCallArgs so we don't need to
3517 // reconstruct it here.
3518 static unsigned getPackIndexForParam(Sema &S,
3519  FunctionTemplateDecl *FunctionTemplate,
3520  const MultiLevelTemplateArgumentList &Args,
3521  unsigned ParamIdx) {
3522  unsigned Idx = 0;
3523  for (auto *PD : FunctionTemplate->getTemplatedDecl()->parameters()) {
3524  if (PD->isParameterPack()) {
3525  unsigned NumExpansions =
3526  S.getNumArgumentsInExpansion(PD->getType(), Args).getValueOr(1);
3527  if (Idx + NumExpansions > ParamIdx)
3528  return ParamIdx - Idx;
3529  Idx += NumExpansions;
3530  } else {
3531  if (Idx == ParamIdx)
3532  return -1; // Not a pack expansion
3533  ++Idx;
3534  }
3535  }
3536 
3537  llvm_unreachable("parameter index would not be produced from template");
3538 }
3539 
3540 /// Finish template argument deduction for a function template,
3541 /// checking the deduced template arguments for completeness and forming
3542 /// the function template specialization.
3543 ///
3544 /// \param OriginalCallArgs If non-NULL, the original call arguments against
3545 /// which the deduced argument types should be compared.
3547  FunctionTemplateDecl *FunctionTemplate,
3549  unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
3550  TemplateDeductionInfo &Info,
3551  SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
3552  bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
3553  // Unevaluated SFINAE context.
3556  SFINAETrap Trap(*this);
3557 
3558  // Enter a new template instantiation context while we instantiate the
3559  // actual function declaration.
3560  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(), Deduced.end());
3561  InstantiatingTemplate Inst(
3562  *this, Info.getLocation(), FunctionTemplate, DeducedArgs,
3563  CodeSynthesisContext::DeducedTemplateArgumentSubstitution, Info);
3564  if (Inst.isInvalid())
3565  return TDK_InstantiationDepth;
3566 
3567  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
3568 
3569  // C++ [temp.deduct.type]p2:
3570  // [...] or if any template argument remains neither deduced nor
3571  // explicitly specified, template argument deduction fails.
3573  if (auto Result = ConvertDeducedTemplateArguments(
3574  *this, FunctionTemplate, /*IsDeduced*/true, Deduced, Info, Builder,
3575  CurrentInstantiationScope, NumExplicitlySpecified,
3576  PartialOverloading))
3577  return Result;
3578 
3579  // C++ [temp.deduct.call]p10: [DR1391]
3580  // If deduction succeeds for all parameters that contain
3581  // template-parameters that participate in template argument deduction,
3582  // and all template arguments are explicitly specified, deduced, or
3583  // obtained from default template arguments, remaining parameters are then
3584  // compared with the corresponding arguments. For each remaining parameter
3585  // P with a type that was non-dependent before substitution of any
3586  // explicitly-specified template arguments, if the corresponding argument
3587  // A cannot be implicitly converted to P, deduction fails.
3588  if (CheckNonDependent())
3589  return TDK_NonDependentConversionFailure;
3590 
3591  // Form the template argument list from the deduced template arguments.
3592  TemplateArgumentList *DeducedArgumentList
3593  = TemplateArgumentList::CreateCopy(Context, Builder);
3594  Info.reset(DeducedArgumentList);
3595 
3596  // Substitute the deduced template arguments into the function template
3597  // declaration to produce the function template specialization.
3598  DeclContext *Owner = FunctionTemplate->getDeclContext();
3599  if (FunctionTemplate->getFriendObjectKind())
3600  Owner = FunctionTemplate->getLexicalDeclContext();
3601  MultiLevelTemplateArgumentList SubstArgs(*DeducedArgumentList);
3602  Specialization = cast_or_null<FunctionDecl>(
3603  SubstDecl(FunctionTemplate->getTemplatedDecl(), Owner, SubstArgs));
3604  if (!Specialization || Specialization->isInvalidDecl())
3605  return TDK_SubstitutionFailure;
3606 
3607  assert(Specialization->getPrimaryTemplate()->getCanonicalDecl() ==
3608  FunctionTemplate->getCanonicalDecl());
3609 
3610  // If the template argument list is owned by the function template
3611  // specialization, release it.
3612  if (Specialization->getTemplateSpecializationArgs() == DeducedArgumentList &&
3613  !Trap.hasErrorOccurred())
3614  Info.take();
3615 
3616  // There may have been an error that did not prevent us from constructing a
3617  // declaration. Mark the declaration invalid and return with a substitution
3618  // failure.
3619  if (Trap.hasErrorOccurred()) {
3620  Specialization->setInvalidDecl(true);
3621  return TDK_SubstitutionFailure;
3622  }
3623 
3624  // C++2a [temp.deduct]p5
3625  // [...] When all template arguments have been deduced [...] all uses of
3626  // template parameters [...] are replaced with the corresponding deduced
3627  // or default argument values.
3628  // [...] If the function template has associated constraints
3629  // ([temp.constr.decl]), those constraints are checked for satisfaction
3630  // ([temp.constr.constr]). If the constraints are not satisfied, type
3631  // deduction fails.
3632  if (!PartialOverloading ||
3633  (Builder.size() == FunctionTemplate->getTemplateParameters()->size())) {
3634  if (CheckInstantiatedFunctionTemplateConstraints(Info.getLocation(),
3636  return TDK_MiscellaneousDeductionFailure;
3637 
3639  Info.reset(TemplateArgumentList::CreateCopy(Context, Builder));
3640  return TDK_ConstraintsNotSatisfied;
3641  }
3642  }
3643 
3644  if (OriginalCallArgs) {
3645  // C++ [temp.deduct.call]p4:
3646  // In general, the deduction process attempts to find template argument
3647  // values that will make the deduced A identical to A (after the type A
3648  // is transformed as described above). [...]
3649  llvm::SmallDenseMap<std::pair<unsigned, QualType>, QualType> DeducedATypes;
3650  for (unsigned I = 0, N = OriginalCallArgs->size(); I != N; ++I) {
3651  OriginalCallArg OriginalArg = (*OriginalCallArgs)[I];
3652 
3653  auto ParamIdx = OriginalArg.ArgIdx;
3654  if (ParamIdx >= Specialization->getNumParams())
3655  // FIXME: This presumably means a pack ended up smaller than we
3656  // expected while deducing. Should this not result in deduction
3657  // failure? Can it even happen?
3658  continue;
3659 
3660  QualType DeducedA;
3661  if (!OriginalArg.DecomposedParam) {
3662  // P is one of the function parameters, just look up its substituted
3663  // type.
3664  DeducedA = Specialization->getParamDecl(ParamIdx)->getType();
3665  } else {
3666  // P is a decomposed element of a parameter corresponding to a
3667  // braced-init-list argument. Substitute back into P to find the
3668  // deduced A.
3669  QualType &CacheEntry =
3670  DeducedATypes[{ParamIdx, OriginalArg.OriginalParamType}];
3671  if (CacheEntry.isNull()) {
3673  *this, getPackIndexForParam(*this, FunctionTemplate, SubstArgs,
3674  ParamIdx));
3675  CacheEntry =
3676  SubstType(OriginalArg.OriginalParamType, SubstArgs,
3677  Specialization->getTypeSpecStartLoc(),
3678  Specialization->getDeclName());
3679  }
3680  DeducedA = CacheEntry;
3681  }
3682 
3683  if (auto TDK =
3684  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA))
3685  return TDK;
3686  }
3687  }
3688 
3689  // If we suppressed any diagnostics while performing template argument
3690  // deduction, and if we haven't already instantiated this declaration,
3691  // keep track of these diagnostics. They'll be emitted if this specialization
3692  // is actually used.
3693  if (Info.diag_begin() != Info.diag_end()) {
3694  SuppressedDiagnosticsMap::iterator
3695  Pos = SuppressedDiagnostics.find(Specialization->getCanonicalDecl());
3696  if (Pos == SuppressedDiagnostics.end())
3697  SuppressedDiagnostics[Specialization->getCanonicalDecl()]
3698  .append(Info.diag_begin(), Info.diag_end());
3699  }
3700 
3701  return TDK_Success;
3702 }
3703 
3704 /// Gets the type of a function for template-argument-deducton
3705 /// purposes when it's considered as part of an overload set.
3707  FunctionDecl *Fn) {
3708  // We may need to deduce the return type of the function now.
3709  if (S.getLangOpts().CPlusPlus14 && Fn->getReturnType()->isUndeducedType() &&
3710  S.DeduceReturnType(Fn, R.Expression->getExprLoc(), /*Diagnose*/ false))
3711  return {};
3712 
3713  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Fn))
3714  if (Method->isInstance()) {
3715  // An instance method that's referenced in a form that doesn't
3716  // look like a member pointer is just invalid.
3717  if (!R.HasFormOfMemberPointer)
3718  return {};
3719 
3720  return S.Context.getMemberPointerType(Fn->getType(),
3721  S.Context.getTypeDeclType(Method->getParent()).getTypePtr());
3722  }
3723 
3724  if (!R.IsAddressOfOperand) return Fn->getType();
3725  return S.Context.getPointerType(Fn->getType());
3726 }
3727 
3728 /// Apply the deduction rules for overload sets.
3729 ///
3730 /// \return the null type if this argument should be treated as an
3731 /// undeduced context
3732 static QualType
3734  Expr *Arg, QualType ParamType,
3735  bool ParamWasReference) {
3736 
3738 
3739  OverloadExpr *Ovl = R.Expression;
3740 
3741  // C++0x [temp.deduct.call]p4
3742  unsigned TDF = 0;
3743  if (ParamWasReference)
3745  if (R.IsAddressOfOperand)
3746  TDF |= TDF_IgnoreQualifiers;
3747 
3748  // C++0x [temp.deduct.call]p6:
3749  // When P is a function type, pointer to function type, or pointer
3750  // to member function type:
3751 
3752  if (!ParamType->isFunctionType() &&
3753  !ParamType->isFunctionPointerType() &&
3754  !ParamType->isMemberFunctionPointerType()) {
3755  if (Ovl->hasExplicitTemplateArgs()) {
3756  // But we can still look for an explicit specialization.
3757  if (FunctionDecl *ExplicitSpec
3759  return GetTypeOfFunction(S, R, ExplicitSpec);
3760  }
3761 
3762  DeclAccessPair DAP;
3763  if (FunctionDecl *Viable =
3765  return GetTypeOfFunction(S, R, Viable);
3766 
3767  return {};
3768  }
3769 
3770  // Gather the explicit template arguments, if any.
3771  TemplateArgumentListInfo ExplicitTemplateArgs;
3772  if (Ovl->hasExplicitTemplateArgs())
3773  Ovl->copyTemplateArgumentsInto(ExplicitTemplateArgs);
3774  QualType Match;
3775  for (UnresolvedSetIterator I = Ovl->decls_begin(),
3776  E = Ovl->decls_end(); I != E; ++I) {
3777  NamedDecl *D = (*I)->getUnderlyingDecl();
3778 
3779  if (FunctionTemplateDecl *FunTmpl = dyn_cast<FunctionTemplateDecl>(D)) {
3780  // - If the argument is an overload set containing one or more
3781  // function templates, the parameter is treated as a
3782  // non-deduced context.
3783  if (!Ovl->hasExplicitTemplateArgs())
3784  return {};
3785 
3786  // Otherwise, see if we can resolve a function type
3787  FunctionDecl *Specialization = nullptr;
3788  TemplateDeductionInfo Info(Ovl->getNameLoc());
3789  if (S.DeduceTemplateArguments(FunTmpl, &ExplicitTemplateArgs,
3790  Specialization, Info))
3791  continue;
3792 
3793  D = Specialization;
3794  }
3795 
3796  FunctionDecl *Fn = cast<FunctionDecl>(D);
3797  QualType ArgType = GetTypeOfFunction(S, R, Fn);
3798  if (ArgType.isNull()) continue;
3799 
3800  // Function-to-pointer conversion.
3801  if (!ParamWasReference && ParamType->isPointerType() &&
3802  ArgType->isFunctionType())
3803  ArgType = S.Context.getPointerType(ArgType);
3804 
3805  // - If the argument is an overload set (not containing function
3806  // templates), trial argument deduction is attempted using each
3807  // of the members of the set. If deduction succeeds for only one
3808  // of the overload set members, that member is used as the
3809  // argument value for the deduction. If deduction succeeds for
3810  // more than one member of the overload set the parameter is
3811  // treated as a non-deduced context.
3812 
3813  // We do all of this in a fresh context per C++0x [temp.deduct.type]p2:
3814  // Type deduction is done independently for each P/A pair, and
3815  // the deduced template argument values are then combined.
3816  // So we do not reject deductions which were made elsewhere.
3818  Deduced(TemplateParams->size());
3819  TemplateDeductionInfo Info(Ovl->getNameLoc());
3821  = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
3822  ArgType, Info, Deduced, TDF);
3823  if (Result) continue;
3824  if (!Match.isNull())
3825  return {};
3826  Match = ArgType;
3827  }
3828 
3829  return Match;
3830 }
3831 
3832 /// Perform the adjustments to the parameter and argument types
3833 /// described in C++ [temp.deduct.call].
3834 ///
3835 /// \returns true if the caller should not attempt to perform any template
3836 /// argument deduction based on this P/A pair because the argument is an
3837 /// overloaded function set that could not be resolved.
3839  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3840  QualType &ParamType, QualType &ArgType, Expr *Arg, unsigned &TDF) {
3841  // C++0x [temp.deduct.call]p3:
3842  // If P is a cv-qualified type, the top level cv-qualifiers of P's type
3843  // are ignored for type deduction.
3844  if (ParamType.hasQualifiers())
3845  ParamType = ParamType.getUnqualifiedType();
3846 
3847  // [...] If P is a reference type, the type referred to by P is
3848  // used for type deduction.
3849  const ReferenceType *ParamRefType = ParamType->getAs<ReferenceType>();
3850  if (ParamRefType)
3851  ParamType = ParamRefType->getPointeeType();
3852 
3853  // Overload sets usually make this parameter an undeduced context,
3854  // but there are sometimes special circumstances. Typically
3855  // involving a template-id-expr.
3856  if (ArgType == S.Context.OverloadTy) {
3857  ArgType = ResolveOverloadForDeduction(S, TemplateParams,
3858  Arg, ParamType,
3859  ParamRefType != nullptr);
3860  if (ArgType.isNull())
3861  return true;
3862  }
3863 
3864  if (ParamRefType) {
3865  // If the argument has incomplete array type, try to complete its type.
3866  if (ArgType->isIncompleteArrayType())
3867  ArgType = S.getCompletedType(Arg);
3868 
3869  // C++1z [temp.deduct.call]p3:
3870  // If P is a forwarding reference and the argument is an lvalue, the type
3871  // "lvalue reference to A" is used in place of A for type deduction.
3872  if (isForwardingReference(QualType(ParamRefType, 0), FirstInnerIndex) &&
3873  Arg->isLValue()) {
3874  if (S.getLangOpts().OpenCL && !ArgType.hasAddressSpace())
3875  ArgType = S.Context.getAddrSpaceQualType(ArgType, LangAS::opencl_generic);
3876  ArgType = S.Context.getLValueReferenceType(ArgType);
3877  }
3878  } else {
3879  // C++ [temp.deduct.call]p2:
3880  // If P is not a reference type:
3881  // - If A is an array type, the pointer type produced by the
3882  // array-to-pointer standard conversion (4.2) is used in place of
3883  // A for type deduction; otherwise,
3884  if (ArgType->isArrayType())
3885  ArgType = S.Context.getArrayDecayedType(ArgType);
3886  // - If A is a function type, the pointer type produced by the
3887  // function-to-pointer standard conversion (4.3) is used in place
3888  // of A for type deduction; otherwise,
3889  else if (ArgType->isFunctionType())
3890  ArgType = S.Context.getPointerType(ArgType);
3891  else {
3892  // - If A is a cv-qualified type, the top level cv-qualifiers of A's
3893  // type are ignored for type deduction.
3894  ArgType = ArgType.getUnqualifiedType();
3895  }
3896  }
3897 
3898  // C++0x [temp.deduct.call]p4:
3899  // In general, the deduction process attempts to find template argument
3900  // values that will make the deduced A identical to A (after the type A
3901  // is transformed as described above). [...]
3902  TDF = TDF_SkipNonDependent;
3903 
3904  // - If the original P is a reference type, the deduced A (i.e., the
3905  // type referred to by the reference) can be more cv-qualified than
3906  // the transformed A.
3907  if (ParamRefType)
3909  // - The transformed A can be another pointer or pointer to member
3910  // type that can be converted to the deduced A via a qualification
3911  // conversion (4.4).
3912  if (ArgType->isPointerType() || ArgType->isMemberPointerType() ||
3913  ArgType->isObjCObjectPointerType())
3914  TDF |= TDF_IgnoreQualifiers;
3915  // - If P is a class and P has the form simple-template-id, then the
3916  // transformed A can be a derived class of the deduced A. Likewise,
3917  // if P is a pointer to a class of the form simple-template-id, the
3918  // transformed A can be a pointer to a derived class pointed to by
3919  // the deduced A.
3920  if (isSimpleTemplateIdType(ParamType) ||
3921  (isa<PointerType>(ParamType) &&
3923  ParamType->castAs<PointerType>()->getPointeeType())))
3924  TDF |= TDF_DerivedClass;
3925 
3926  return false;
3927 }
3928 
3929 static bool
3931  QualType T);
3932 
3934  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
3935  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
3936  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3937  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
3938  bool DecomposedParam, unsigned ArgIdx, unsigned TDF);
3939 
3940 /// Attempt template argument deduction from an initializer list
3941 /// deemed to be an argument in a function call.
3943  Sema &S, TemplateParameterList *TemplateParams, QualType AdjustedParamType,
3944  InitListExpr *ILE, TemplateDeductionInfo &Info,
3945  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
3946  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs, unsigned ArgIdx,
3947  unsigned TDF) {
3948  // C++ [temp.deduct.call]p1: (CWG 1591)
3949  // If removing references and cv-qualifiers from P gives
3950  // std::initializer_list<P0> or P0[N] for some P0 and N and the argument is
3951  // a non-empty initializer list, then deduction is performed instead for
3952  // each element of the initializer list, taking P0 as a function template
3953  // parameter type and the initializer element as its argument
3954  //
3955  // We've already removed references and cv-qualifiers here.
3956  if (!ILE->getNumInits())
3957  return Sema::TDK_Success;
3958 
3959  QualType ElTy;
3960  auto *ArrTy = S.Context.getAsArrayType(AdjustedParamType);
3961  if (ArrTy)
3962  ElTy = ArrTy->getElementType();
3963  else if (!S.isStdInitializerList(AdjustedParamType, &ElTy)) {
3964  // Otherwise, an initializer list argument causes the parameter to be
3965  // considered a non-deduced context
3966  return Sema::TDK_Success;
3967  }
3968 
3969  // Resolving a core issue: a braced-init-list containing any designators is
3970  // a non-deduced context.
3971  for (Expr *E : ILE->inits())
3972  if (isa<DesignatedInitExpr>(E))
3973  return Sema::TDK_Success;
3974 
3975  // Deduction only needs to be done for dependent types.
3976  if (ElTy->isDependentType()) {
3977  for (Expr *E : ILE->inits()) {
3978  if (auto Result = DeduceTemplateArgumentsFromCallArgument(
3979  S, TemplateParams, 0, ElTy, E, Info, Deduced, OriginalCallArgs, true,
3980  ArgIdx, TDF))
3981  return Result;
3982  }
3983  }
3984 
3985  // in the P0[N] case, if N is a non-type template parameter, N is deduced
3986  // from the length of the initializer list.
3987  if (auto *DependentArrTy = dyn_cast_or_null<DependentSizedArrayType>(ArrTy)) {
3988  // Determine the array bound is something we can deduce.
3989  if (const NonTypeTemplateParmDecl *NTTP =
3990  getDeducedParameterFromExpr(Info, DependentArrTy->getSizeExpr())) {
3991  // We can perform template argument deduction for the given non-type
3992  // template parameter.
3993  // C++ [temp.deduct.type]p13:
3994  // The type of N in the type T[N] is std::size_t.
3995  QualType T = S.Context.getSizeType();
3996  llvm::APInt Size(S.Context.getIntWidth(T), ILE->getNumInits());
3997  if (auto Result = DeduceNonTypeTemplateArgument(
3998  S, TemplateParams, NTTP, llvm::APSInt(Size), T,
3999  /*ArrayBound=*/true, Info, Deduced))
4000  return Result;
4001  }
4002  }
4003 
4004  return Sema::TDK_Success;
4005 }
4006 
4007 /// Perform template argument deduction per [temp.deduct.call] for a
4008 /// single parameter / argument pair.
4010  Sema &S, TemplateParameterList *TemplateParams, unsigned FirstInnerIndex,
4011  QualType ParamType, Expr *Arg, TemplateDeductionInfo &Info,
4012  SmallVectorImpl<DeducedTemplateArgument> &Deduced,
4013  SmallVectorImpl<Sema::OriginalCallArg> &OriginalCallArgs,
4014  bool DecomposedParam, unsigned ArgIdx, unsigned TDF) {
4015  QualType ArgType = Arg->getType();
4016  QualType OrigParamType = ParamType;
4017 
4018  // If P is a reference type [...]
4019  // If P is a cv-qualified type [...]
4021  S, TemplateParams, FirstInnerIndex, ParamType, ArgType, Arg, TDF))
4022  return Sema::TDK_Success;
4023 
4024  // If [...] the argument is a non-empty initializer list [...]
4025  if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg))
4026  return DeduceFromInitializerList(S, TemplateParams, ParamType, ILE, Info,
4027  Deduced, OriginalCallArgs, ArgIdx, TDF);
4028 
4029  // [...] the deduction process attempts to find template argument values
4030  // that will make the deduced A identical to A
4031  //
4032  // Keep track of the argument type and corresponding parameter index,
4033  // so we can check for compatibility between the deduced A and A.
4034  OriginalCallArgs.push_back(
4035  Sema::OriginalCallArg(OrigParamType, DecomposedParam, ArgIdx, ArgType));
4036  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
4037  ArgType, Info, Deduced, TDF);
4038 }
4039 
4040 /// Perform template argument deduction from a function call
4041 /// (C++ [temp.deduct.call]).
4042 ///
4043 /// \param FunctionTemplate the function template for which we are performing
4044 /// template argument deduction.
4045 ///
4046 /// \param ExplicitTemplateArgs the explicit template arguments provided
4047 /// for this call.
4048 ///
4049 /// \param Args the function call arguments
4050 ///
4051 /// \param Specialization if template argument deduction was successful,
4052 /// this will be set to the function template specialization produced by
4053 /// template argument deduction.
4054 ///
4055 /// \param Info the argument will be updated to provide additional information
4056 /// about template argument deduction.
4057 ///
4058 /// \param CheckNonDependent A callback to invoke to check conversions for
4059 /// non-dependent parameters, between deduction and substitution, per DR1391.
4060 /// If this returns true, substitution will be skipped and we return
4061 /// TDK_NonDependentConversionFailure. The callback is passed the parameter
4062 /// types (after substituting explicit template arguments).
4063 ///
4064 /// \returns the result of template argument deduction.
4066  FunctionTemplateDecl *FunctionTemplate,
4067  TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
4068  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4069  bool PartialOverloading,
4070  llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent) {
4071  if (FunctionTemplate->isInvalidDecl())
4072  return TDK_Invalid;
4073 
4074  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
4075  unsigned NumParams = Function->getNumParams();
4076 
4077  unsigned FirstInnerIndex = getFirstInnerIndex(FunctionTemplate);
4078 
4079  // C++ [temp.deduct.call]p1:
4080  // Template argument deduction is done by comparing each function template
4081  // parameter type (call it P) with the type of the corresponding argument
4082  // of the call (call it A) as described below.
4083  if (Args.size() < Function->getMinRequiredArguments() && !PartialOverloading)
4084  return TDK_TooFewArguments;
4085  else if (TooManyArguments(NumParams, Args.size(), PartialOverloading)) {
4086  const auto *Proto = Function->getType()->castAs<FunctionProtoType>();
4087  if (Proto->isTemplateVariadic())
4088  /* Do nothing */;
4089  else if (!Proto->isVariadic())
4090  return TDK_TooManyArguments;
4091  }
4092 
4093  // The types of the parameters from which we will perform template argument
4094  // deduction.
4095  LocalInstantiationScope InstScope(*this);
4096  TemplateParameterList *TemplateParams
4097  = FunctionTemplate->getTemplateParameters();
4099  SmallVector<QualType, 8> ParamTypes;
4100  unsigned NumExplicitlySpecified = 0;
4101  if (ExplicitTemplateArgs) {
4102  TemplateDeductionResult Result;
4104  Result = SubstituteExplicitTemplateArguments(
4105  FunctionTemplate, *ExplicitTemplateArgs, Deduced, ParamTypes, nullptr,
4106  Info);
4107  });
4108  if (Result)
4109  return Result;
4110 
4111  NumExplicitlySpecified = Deduced.size();
4112  } else {
4113  // Just fill in the parameter types from the function declaration.
4114  for (unsigned I = 0; I != NumParams; ++I)
4115  ParamTypes.push_back(Function->getParamDecl(I)->getType());
4116  }
4117 
4118  SmallVector<OriginalCallArg, 8> OriginalCallArgs;
4119 
4120  // Deduce an argument of type ParamType from an expression with index ArgIdx.
4121  auto DeduceCallArgument = [&](QualType ParamType, unsigned ArgIdx) {
4122  // C++ [demp.deduct.call]p1: (DR1391)
4123  // Template argument deduction is done by comparing each function template
4124  // parameter that contains template-parameters that participate in
4125  // template argument deduction ...
4126  if (!hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
4127  return Sema::TDK_Success;
4128 
4129  // ... with the type of the corresponding argument
4131  *this, TemplateParams, FirstInnerIndex, ParamType, Args[ArgIdx], Info, Deduced,
4132  OriginalCallArgs, /*Decomposed*/false, ArgIdx, /*TDF*/ 0);
4133  };
4134 
4135  // Deduce template arguments from the function parameters.
4136  Deduced.resize(TemplateParams->size());
4137  SmallVector<QualType, 8> ParamTypesForArgChecking;
4138  for (unsigned ParamIdx = 0, NumParamTypes = ParamTypes.size(), ArgIdx = 0;
4139  ParamIdx != NumParamTypes; ++ParamIdx) {
4140  QualType ParamType = ParamTypes[ParamIdx];
4141 
4142  const PackExpansionType *ParamExpansion =
4143  dyn_cast<PackExpansionType>(ParamType);
4144  if (!ParamExpansion) {
4145  // Simple case: matching a function parameter to a function argument.
4146  if (ArgIdx >= Args.size())
4147  break;
4148 
4149  ParamTypesForArgChecking.push_back(ParamType);
4150  if (auto Result = DeduceCallArgument(ParamType, ArgIdx++))
4151  return Result;
4152 
4153  continue;
4154  }
4155 
4156  QualType ParamPattern = ParamExpansion->getPattern();
4157  PackDeductionScope PackScope(*this, TemplateParams, Deduced, Info,
4158  ParamPattern);
4159 
4160  // C++0x [temp.deduct.call]p1:
4161  // For a function parameter pack that occurs at the end of the
4162  // parameter-declaration-list, the type A of each remaining argument of
4163  // the call is compared with the type P of the declarator-id of the
4164  // function parameter pack. Each comparison deduces template arguments
4165  // for subsequent positions in the template parameter packs expanded by
4166  // the function parameter pack. When a function parameter pack appears
4167  // in a non-deduced context [not at the end of the list], the type of
4168  // that parameter pack is never deduced.
4169  //
4170  // FIXME: The above rule allows the size of the parameter pack to change
4171  // after we skip it (in the non-deduced case). That makes no sense, so
4172  // we instead notionally deduce the pack against N arguments, where N is
4173  // the length of the explicitly-specified pack if it's expanded by the
4174  // parameter pack and 0 otherwise, and we treat each deduction as a
4175  // non-deduced context.
4176  if (ParamIdx + 1 == NumParamTypes || PackScope.hasFixedArity()) {
4177  for (; ArgIdx < Args.size() && PackScope.hasNextElement();
4178  PackScope.nextPackElement(), ++ArgIdx) {
4179  ParamTypesForArgChecking.push_back(ParamPattern);
4180  if (auto Result = DeduceCallArgument(ParamPattern, ArgIdx))
4181  return Result;
4182  }
4183  } else {
4184  // If the parameter type contains an explicitly-specified pack that we
4185  // could not expand, skip the number of parameters notionally created
4186  // by the expansion.
4187  Optional<unsigned> NumExpansions = ParamExpansion->getNumExpansions();
4188  if (NumExpansions && !PackScope.isPartiallyExpanded()) {
4189  for (unsigned I = 0; I != *NumExpansions && ArgIdx < Args.size();
4190  ++I, ++ArgIdx) {
4191  ParamTypesForArgChecking.push_back(ParamPattern);
4192  // FIXME: Should we add OriginalCallArgs for these? What if the
4193  // corresponding argument is a list?
4194  PackScope.nextPackElement();
4195  }
4196  }
4197  }
4198 
4199  // Build argument packs for each of the parameter packs expanded by this
4200  // pack expansion.
4201  if (auto Result = PackScope.finish())
4202  return Result;
4203  }
4204 
4205  // Capture the context in which the function call is made. This is the context
4206  // that is needed when the accessibility of template arguments is checked.
4207  DeclContext *CallingCtx = CurContext;
4208 
4209  TemplateDeductionResult Result;
4211  Result = FinishTemplateArgumentDeduction(
4212  FunctionTemplate, Deduced, NumExplicitlySpecified, Specialization, Info,
4213  &OriginalCallArgs, PartialOverloading, [&, CallingCtx]() {
4214  ContextRAII SavedContext(*this, CallingCtx);
4215  return CheckNonDependent(ParamTypesForArgChecking);
4216  });
4217  });
4218  return Result;
4219 }
4220 
4223  bool AdjustExceptionSpec) {
4224  if (ArgFunctionType.isNull())
4225  return ArgFunctionType;
4226 
4227  const auto *FunctionTypeP = FunctionType->castAs<FunctionProtoType>();
4228  const auto *ArgFunctionTypeP = ArgFunctionType->castAs<FunctionProtoType>();
4229  FunctionProtoType::ExtProtoInfo EPI = ArgFunctionTypeP->getExtProtoInfo();
4230  bool Rebuild = false;
4231 
4232  CallingConv CC = FunctionTypeP->getCallConv();
4233  if (EPI.ExtInfo.getCC() != CC) {
4234  EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CC);
4235  Rebuild = true;
4236  }
4237 
4238  bool NoReturn = FunctionTypeP->getNoReturnAttr();
4239  if (EPI.ExtInfo.getNoReturn() != NoReturn) {
4240  EPI.ExtInfo = EPI.ExtInfo.withNoReturn(NoReturn);
4241  Rebuild = true;
4242  }
4243 
4244  if (AdjustExceptionSpec && (FunctionTypeP->hasExceptionSpec() ||
4245  ArgFunctionTypeP->hasExceptionSpec())) {
4246  EPI.ExceptionSpec = FunctionTypeP->getExtProtoInfo().ExceptionSpec;
4247  Rebuild = true;
4248  }
4249 
4250  if (!Rebuild)
4251  return ArgFunctionType;
4252 
4253  return Context.getFunctionType(ArgFunctionTypeP->getReturnType(),
4254  ArgFunctionTypeP->getParamTypes(), EPI);
4255 }
4256 
4257 /// Deduce template arguments when taking the address of a function
4258 /// template (C++ [temp.deduct.funcaddr]) or matching a specialization to
4259 /// a template.
4260 ///
4261 /// \param FunctionTemplate the function template for which we are performing
4262 /// template argument deduction.
4263 ///
4264 /// \param ExplicitTemplateArgs the explicitly-specified template
4265 /// arguments.
4266 ///
4267 /// \param ArgFunctionType the function type that will be used as the
4268 /// "argument" type (A) when performing template argument deduction from the
4269 /// function template's function type. This type may be NULL, if there is no
4270 /// argument type to compare against, in C++0x [temp.arg.explicit]p3.
4271 ///
4272 /// \param Specialization if template argument deduction was successful,
4273 /// this will be set to the function template specialization produced by
4274 /// template argument deduction.
4275 ///
4276 /// \param Info the argument will be updated to provide additional information
4277 /// about template argument deduction.
4278 ///
4279 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4280 /// the address of a function template per [temp.deduct.funcaddr] and
4281 /// [over.over]. If \c false, we are looking up a function template
4282 /// specialization based on its signature, per [temp.deduct.decl].
4283 ///
4284 /// \returns the result of template argument deduction.
4286  FunctionTemplateDecl *FunctionTemplate,
4287  TemplateArgumentListInfo *ExplicitTemplateArgs, QualType ArgFunctionType,
4288  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4289  bool IsAddressOfFunction) {
4290  if (FunctionTemplate->isInvalidDecl())
4291  return TDK_Invalid;
4292 
4293  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
4294  TemplateParameterList *TemplateParams
4295  = FunctionTemplate->getTemplateParameters();
4296  QualType FunctionType = Function->getType();
4297 
4298  // Substitute any explicit template arguments.
4299  LocalInstantiationScope InstScope(*this);
4301  unsigned NumExplicitlySpecified = 0;
4302  SmallVector<QualType, 4> ParamTypes;
4303  if (ExplicitTemplateArgs) {
4304  TemplateDeductionResult Result;
4306  Result = SubstituteExplicitTemplateArguments(
4307  FunctionTemplate, *ExplicitTemplateArgs, Deduced, ParamTypes,
4308  &FunctionType, Info);
4309  });
4310  if (Result)
4311  return Result;
4312 
4313  NumExplicitlySpecified = Deduced.size();
4314  }
4315 
4316  // When taking the address of a function, we require convertibility of
4317  // the resulting function type. Otherwise, we allow arbitrary mismatches
4318  // of calling convention and noreturn.
4319  if (!IsAddressOfFunction)
4320  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, FunctionType,
4321  /*AdjustExceptionSpec*/false);
4322 
4323  // Unevaluated SFINAE context.
4326  SFINAETrap Trap(*this);
4327 
4328  Deduced.resize(TemplateParams->size());
4329 
4330  // If the function has a deduced return type, substitute it for a dependent
4331  // type so that we treat it as a non-deduced context in what follows. If we
4332  // are looking up by signature, the signature type should also have a deduced
4333  // return type, which we instead expect to exactly match.
4334  bool HasDeducedReturnType = false;
4335  if (getLangOpts().CPlusPlus14 && IsAddressOfFunction &&
4336  Function->getReturnType()->getContainedAutoType()) {
4338  HasDeducedReturnType = true;
4339  }
4340 
4341  if (!ArgFunctionType.isNull()) {
4342  unsigned TDF =
4344  // Deduce template arguments from the function type.
4345  if (TemplateDeductionResult Result
4346  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4347  FunctionType, ArgFunctionType,
4348  Info, Deduced, TDF))
4349  return Result;
4350  }
4351 
4352  TemplateDeductionResult Result;
4354  Result = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
4355  NumExplicitlySpecified,
4356  Specialization, Info);
4357  });
4358  if (Result)
4359  return Result;
4360 
4361  // If the function has a deduced return type, deduce it now, so we can check
4362  // that the deduced function type matches the requested type.
4363  if (HasDeducedReturnType &&
4364  Specialization->getReturnType()->isUndeducedType() &&
4367 
4368  // If the function has a dependent exception specification, resolve it now,
4369  // so we can check that the exception specification matches.
4370  auto *SpecializationFPT =
4371  Specialization->getType()->castAs<FunctionProtoType>();
4372  if (getLangOpts().CPlusPlus17 &&
4373  isUnresolvedExceptionSpec(SpecializationFPT->getExceptionSpecType()) &&
4374  !ResolveExceptionSpec(Info.getLocation(), SpecializationFPT))
4376 
4377  // Adjust the exception specification of the argument to match the
4378  // substituted and resolved type we just formed. (Calling convention and
4379  // noreturn can't be dependent, so we don't actually need this for them
4380  // right now.)
4381  QualType SpecializationType = Specialization->getType();
4382  if (!IsAddressOfFunction)
4383  ArgFunctionType = adjustCCAndNoReturn(ArgFunctionType, SpecializationType,
4384  /*AdjustExceptionSpec*/true);
4385 
4386  // If the requested function type does not match the actual type of the
4387  // specialization with respect to arguments of compatible pointer to function
4388  // types, template argument deduction fails.
4389  if (!ArgFunctionType.isNull()) {
4390  if (IsAddressOfFunction &&
4392  Context.getCanonicalType(SpecializationType),
4393  Context.getCanonicalType(ArgFunctionType)))
4395 
4396  if (!IsAddressOfFunction &&
4397  !Context.hasSameType(SpecializationType, ArgFunctionType))
4399  }
4400 
4401  return TDK_Success;
4402 }
4403 
4404 /// Deduce template arguments for a templated conversion
4405 /// function (C++ [temp.deduct.conv]) and, if successful, produce a
4406 /// conversion function template specialization.
4409  QualType ToType,
4410  CXXConversionDecl *&Specialization,
4411  TemplateDeductionInfo &Info) {
4412  if (ConversionTemplate->isInvalidDecl())
4413  return TDK_Invalid;
4414 
4415  CXXConversionDecl *ConversionGeneric
4416  = cast<CXXConversionDecl>(ConversionTemplate->getTemplatedDecl());
4417 
4418  QualType FromType = ConversionGeneric->getConversionType();
4419 
4420  // Canonicalize the types for deduction.
4421  QualType P = Context.getCanonicalType(FromType);
4422  QualType A = Context.getCanonicalType(ToType);
4423 
4424  // C++0x [temp.deduct.conv]p2:
4425  // If P is a reference type, the type referred to by P is used for
4426  // type deduction.
4427  if (const ReferenceType *PRef = P->getAs<ReferenceType>())
4428  P = PRef->getPointeeType();
4429 
4430  // C++0x [temp.deduct.conv]p4:
4431  // [...] If A is a reference type, the type referred to by A is used
4432  // for type deduction.
4433  if (const ReferenceType *ARef = A->getAs<ReferenceType>()) {
4434  A = ARef->getPointeeType();
4435  // We work around a defect in the standard here: cv-qualifiers are also
4436  // removed from P and A in this case, unless P was a reference type. This
4437  // seems to mostly match what other compilers are doing.
4438  if (!FromType->getAs<ReferenceType>()) {
4439  A = A.getUnqualifiedType();
4440  P = P.getUnqualifiedType();
4441  }
4442 
4443  // C++ [temp.deduct.conv]p3:
4444  //
4445  // If A is not a reference type:
4446  } else {
4447  assert(!A->isReferenceType() && "Reference types were handled above");
4448 
4449  // - If P is an array type, the pointer type produced by the
4450  // array-to-pointer standard conversion (4.2) is used in place
4451  // of P for type deduction; otherwise,
4452  if (P->isArrayType())
4454  // - If P is a function type, the pointer type produced by the
4455  // function-to-pointer standard conversion (4.3) is used in
4456  // place of P for type deduction; otherwise,
4457  else if (P->isFunctionType())
4459  // - If P is a cv-qualified type, the top level cv-qualifiers of
4460  // P's type are ignored for type deduction.
4461  else
4462  P = P.getUnqualifiedType();
4463 
4464  // C++0x [temp.deduct.conv]p4:
4465  // If A is a cv-qualified type, the top level cv-qualifiers of A's
4466  // type are ignored for type deduction. If A is a reference type, the type
4467  // referred to by A is used for type deduction.
4468  A = A.getUnqualifiedType();
4469  }
4470 
4471  // Unevaluated SFINAE context.
4474  SFINAETrap Trap(*this);
4475 
4476  // C++ [temp.deduct.conv]p1:
4477  // Template argument deduction is done by comparing the return
4478  // type of the template conversion function (call it P) with the
4479  // type that is required as the result of the conversion (call it
4480  // A) as described in 14.8.2.4.
4481  TemplateParameterList *TemplateParams
4482  = ConversionTemplate->getTemplateParameters();
4484  Deduced.resize(TemplateParams->size());
4485 
4486  // C++0x [temp.deduct.conv]p4:
4487  // In general, the deduction process attempts to find template
4488  // argument values that will make the deduced A identical to
4489  // A. However, there are two cases that allow a difference:
4490  unsigned TDF = 0;
4491  // - If the original A is a reference type, A can be more
4492  // cv-qualified than the deduced A (i.e., the type referred to
4493  // by the reference)
4494  if (ToType->isReferenceType())
4495  TDF |= TDF_ArgWithReferenceType;
4496  // - The deduced A can be another pointer or pointer to member
4497  // type that can be converted to A via a qualification
4498  // conversion.
4499  //
4500  // (C++0x [temp.deduct.conv]p6 clarifies that this only happens when
4501  // both P and A are pointers or member pointers. In this case, we
4502  // just ignore cv-qualifiers completely).
4503  if ((P->isPointerType() && A->isPointerType()) ||
4504  (P->isMemberPointerType() && A->isMemberPointerType()))
4505  TDF |= TDF_IgnoreQualifiers;
4506  if (TemplateDeductionResult Result
4507  = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
4508  P, A, Info, Deduced, TDF))
4509  return Result;
4510 
4511  // Create an Instantiation Scope for finalizing the operator.
4512  LocalInstantiationScope InstScope(*this);
4513  // Finish template argument deduction.
4514  FunctionDecl *ConversionSpecialized = nullptr;
4515  TemplateDeductionResult Result;
4517  Result = FinishTemplateArgumentDeduction(ConversionTemplate, Deduced, 0,
4518  ConversionSpecialized, Info);
4519  });
4520  Specialization = cast_or_null<CXXConversionDecl>(ConversionSpecialized);
4521  return Result;
4522 }
4523 
4524 /// Deduce template arguments for a function template when there is
4525 /// nothing to deduce against (C++0x [temp.arg.explicit]p3).
4526 ///
4527 /// \param FunctionTemplate the function template for which we are performing
4528 /// template argument deduction.
4529 ///
4530 /// \param ExplicitTemplateArgs the explicitly-specified template
4531 /// arguments.
4532 ///
4533 /// \param Specialization if template argument deduction was successful,
4534 /// this will be set to the function template specialization produced by
4535 /// template argument deduction.
4536 ///
4537 /// \param Info the argument will be updated to provide additional information
4538 /// about template argument deduction.
4539 ///
4540 /// \param IsAddressOfFunction If \c true, we are deducing as part of taking
4541 /// the address of a function template in a context where we do not have a
4542 /// target type, per [over.over]. If \c false, we are looking up a function
4543 /// template specialization based on its signature, which only happens when
4544 /// deducing a function parameter type from an argument that is a template-id
4545 /// naming a function template specialization.
4546 ///
4547 /// \returns the result of template argument deduction.
4549  FunctionTemplateDecl *FunctionTemplate,
4550  TemplateArgumentListInfo *ExplicitTemplateArgs,
4551  FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
4552  bool IsAddressOfFunction) {
4553  return DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs,
4554  QualType(), Specialization, Info,
4555  IsAddressOfFunction);
4556 }
4557 
4558 namespace {
4559  struct DependentAuto { bool IsPack; };
4560 
4561  /// Substitute the 'auto' specifier or deduced template specialization type
4562  /// specifier within a type for a given replacement type.
4563  class SubstituteDeducedTypeTransform :
4564  public TreeTransform<SubstituteDeducedTypeTransform> {
4565  QualType Replacement;
4566  bool ReplacementIsPack;
4567  bool UseTypeSugar;
4568 
4569  public:
4570  SubstituteDeducedTypeTransform(Sema &SemaRef, DependentAuto DA)
4571  : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef), Replacement(),
4572  ReplacementIsPack(DA.IsPack), UseTypeSugar(true) {}
4573 
4574  SubstituteDeducedTypeTransform(Sema &SemaRef, QualType Replacement,
4575  bool UseTypeSugar = true)
4576  : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef),
4577  Replacement(Replacement), ReplacementIsPack(false),
4578  UseTypeSugar(UseTypeSugar) {}
4579 
4580  QualType TransformDesugared(TypeLocBuilder &TLB, DeducedTypeLoc TL) {
4581  assert(isa<TemplateTypeParmType>(Replacement) &&
4582  "unexpected unsugared replacement kind");
4583  QualType Result = Replacement;
4585  NewTL.setNameLoc(TL.getNameLoc());
4586  return Result;
4587  }
4588 
4589  QualType TransformAutoType(TypeLocBuilder &TLB, AutoTypeLoc TL) {
4590  // If we're building the type pattern to deduce against, don't wrap the
4591  // substituted type in an AutoType. Certain template deduction rules
4592  // apply only when a template type parameter appears directly (and not if
4593  // the parameter is found through desugaring). For instance:
4594  // auto &&lref = lvalue;
4595  // must transform into "rvalue reference to T" not "rvalue reference to
4596  // auto type deduced as T" in order for [temp.deduct.call]p3 to apply.
4597  //
4598  // FIXME: Is this still necessary?
4599  if (!UseTypeSugar)
4600  return TransformDesugared(TLB, TL);
4601 
4602  QualType Result = SemaRef.Context.getAutoType(
4603  Replacement, TL.getTypePtr()->getKeyword(), Replacement.isNull(),
4604  ReplacementIsPack, TL.getTypePtr()->getTypeConstraintConcept(),
4606  auto NewTL = TLB.push<AutoTypeLoc>(Result);
4607  NewTL.copy(TL);
4608  return Result;
4609  }
4610 
4611  QualType TransformDeducedTemplateSpecializationType(
4613  if (!UseTypeSugar)
4614  return TransformDesugared(TLB, TL);
4615 
4616  QualType Result = SemaRef.Context.getDeducedTemplateSpecializationType(
4617  TL.getTypePtr()->getTemplateName(),
4618  Replacement, Replacement.isNull());
4619  auto NewTL = TLB.push<DeducedTemplateSpecializationTypeLoc>(Result);
4620  NewTL.setNameLoc(TL.getNameLoc());
4621  return Result;
4622  }
4623 
4624  ExprResult TransformLambdaExpr(LambdaExpr *E) {
4625  // Lambdas never need to be transformed.
4626  return E;
4627  }
4628 
4629  QualType Apply(TypeLoc TL) {
4630  // Create some scratch storage for the transformed type locations.
4631  // FIXME: We're just going to throw this information away. Don't build it.
4632  TypeLocBuilder TLB;
4633  TLB.reserve(TL.getFullDataSize());
4634  return TransformType(TLB, TL);
4635  }
4636  };
4637 
4638 } // namespace
4639 
4642  Optional<unsigned> DependentDeductionDepth,
4643  bool IgnoreConstraints) {
4644  return DeduceAutoType(Type->getTypeLoc(), Init, Result,
4645  DependentDeductionDepth, IgnoreConstraints);
4646 }
4647 
4648 /// Attempt to produce an informative diagostic explaining why auto deduction
4649 /// failed.
4650 /// \return \c true if diagnosed, \c false if not.
4653  TemplateDeductionInfo &Info,
4654  ArrayRef<SourceRange> Ranges) {
4655  switch (TDK) {
4656  case Sema::TDK_Inconsistent: {
4657  // Inconsistent deduction means we were deducing from an initializer list.
4658  auto D = S.Diag(Info.getLocation(), diag::err_auto_inconsistent_deduction);
4659  D << Info.FirstArg << Info.SecondArg;
4660  for (auto R : Ranges)
4661  D << R;
4662  return true;
4663  }
4664 
4665  // FIXME: Are there other cases for which a custom diagnostic is more useful
4666  // than the basic "types don't match" diagnostic?
4667 
4668  default:
4669  return false;
4670  }
4671 }
4672 
4675  AutoTypeLoc TypeLoc, QualType Deduced) {
4676  ConstraintSatisfaction Satisfaction;
4677  ConceptDecl *Concept = Type.getTypeConstraintConcept();
4678  TemplateArgumentListInfo TemplateArgs(TypeLoc.getLAngleLoc(),
4679  TypeLoc.getRAngleLoc());
4680  TemplateArgs.addArgument(
4683  Deduced, TypeLoc.getNameLoc())));
4684  for (unsigned I = 0, C = TypeLoc.getNumArgs(); I != C; ++I)
4685  TemplateArgs.addArgument(TypeLoc.getArgLoc(I));
4686 
4688  if (S.CheckTemplateArgumentList(Concept, SourceLocation(), TemplateArgs,
4689  /*PartialTemplateArgs=*/false, Converted))
4691  if (S.CheckConstraintSatisfaction(Concept, {Concept->getConstraintExpr()},
4692  Converted, TypeLoc.getLocalSourceRange(),
4693  Satisfaction))
4695  if (!Satisfaction.IsSatisfied) {
4696  std::string Buf;
4697  llvm::raw_string_ostream OS(Buf);
4698  OS << "'" << Concept->getName();
4699  if (TypeLoc.hasExplicitTemplateArgs()) {
4700  OS << "<";
4701  for (const auto &Arg : Type.getTypeConstraintArguments())
4702  Arg.print(S.getPrintingPolicy(), OS);
4703  OS << ">";
4704  }
4705  OS << "'";
4706  OS.flush();
4707  S.Diag(TypeLoc.getConceptNameLoc(),
4708  diag::err_placeholder_constraints_not_satisfied)
4709  << Deduced << Buf << TypeLoc.getLocalSourceRange();
4710  S.DiagnoseUnsatisfiedConstraint(Satisfaction);
4712  }
4713  return Sema::DAR_Succeeded;
4714 }
4715 
4716 /// Deduce the type for an auto type-specifier (C++11 [dcl.spec.auto]p6)
4717 ///
4718 /// Note that this is done even if the initializer is dependent. (This is
4719 /// necessary to support partial ordering of templates using 'auto'.)
4720 /// A dependent type will be produced when deducing from a dependent type.
4721 ///
4722 /// \param Type the type pattern using the auto type-specifier.
4723 /// \param Init the initializer for the variable whose type is to be deduced.
4724 /// \param Result if type deduction was successful, this will be set to the
4725 /// deduced type.
4726 /// \param DependentDeductionDepth Set if we should permit deduction in
4727 /// dependent cases. This is necessary for template partial ordering with
4728 /// 'auto' template parameters. The value specified is the template
4729 /// parameter depth at which we should perform 'auto' deduction.
4730 /// \param IgnoreConstraints Set if we should not fail if the deduced type does
4731 /// not satisfy the type-constraint in the auto type.
4734  Optional<unsigned> DependentDeductionDepth,
4735  bool IgnoreConstraints) {
4736  if (Init->containsErrors())
4738  if (Init->getType()->isNonOverloadPlaceholderType()) {
4739  ExprResult NonPlaceholder = CheckPlaceholderExpr(Init);
4740  if (NonPlaceholder.isInvalid())
4742  Init = NonPlaceholder.get();
4743  }
4744 
4745  DependentAuto DependentResult = {
4746  /*.IsPack = */ (bool)Type.getAs<PackExpansionTypeLoc>()};
4747 
4748  if (!DependentDeductionDepth &&
4749  (Type.getType()->isDependentType() || Init->isTypeDependent() ||
4750  Init->containsUnexpandedParameterPack())) {
4751  Result = SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
4752  assert(!Result.isNull() && "substituting DependentTy can't fail");
4753  return DAR_Succeeded;
4754  }
4755 
4756  // Find the depth of template parameter to synthesize.
4757  unsigned Depth = DependentDeductionDepth.getValueOr(0);
4758 
4759  // If this is a 'decltype(auto)' specifier, do the decltype dance.
4760  // Since 'decltype(auto)' can only occur at the top of the type, we
4761  // don't need to go digging for it.
4762  if (const AutoType *AT = Type.getType()->getAs<AutoType>()) {
4763  if (AT->isDecltypeAuto()) {
4764  if (isa<InitListExpr>(Init)) {
4765  Diag(Init->getBeginLoc(), diag::err_decltype_auto_initializer_list);
4767  }
4768 
4769  ExprResult ER = CheckPlaceholderExpr(Init);
4770  if (ER.isInvalid())
4772  Init = ER.get();
4773  QualType Deduced = BuildDecltypeType(Init, Init->getBeginLoc(), false);
4774  if (Deduced.isNull())
4776  // FIXME: Support a non-canonical deduced type for 'auto'.
4777  Deduced = Context.getCanonicalType(Deduced);
4778  if (AT->isConstrained() && !IgnoreConstraints) {
4779  auto ConstraintsResult =
4781  Type.getContainedAutoTypeLoc(),
4782  Deduced);
4783  if (ConstraintsResult != DAR_Succeeded)
4784  return ConstraintsResult;
4785  }
4786  Result = SubstituteDeducedTypeTransform(*this, Deduced).Apply(Type);
4787  if (Result.isNull())
4789  return DAR_Succeeded;
4790  } else if (!getLangOpts().CPlusPlus) {
4791  if (isa<InitListExpr>(Init)) {
4792  Diag(Init->getBeginLoc(), diag::err_auto_init_list_from_c);
4794  }
4795  }
4796  }
4797 
4798  SourceLocation Loc = Init->getExprLoc();
4799 
4800  LocalInstantiationScope InstScope(*this);
4801 
4802  // Build template<class TemplParam> void Func(FuncParam);
4804  Context, nullptr, SourceLocation(), Loc, Depth, 0, nullptr, false, false,
4805  false);
4806  QualType TemplArg = QualType(TemplParam->getTypeForDecl(), 0);
4807  NamedDecl *TemplParamPtr = TemplParam;
4809  Context, Loc, Loc, TemplParamPtr, Loc, nullptr);
4810 
4811  QualType FuncParam =
4812  SubstituteDeducedTypeTransform(*this, TemplArg, /*UseTypeSugar*/false)
4813  .Apply(Type);
4814  assert(!FuncParam.isNull() &&
4815  "substituting template parameter for 'auto' failed");
4816 
4817  // Deduce type of TemplParam in Func(Init)
4819  Deduced.resize(1);
4820 
4821  TemplateDeductionInfo Info(Loc, Depth);
4822 
4823  // If deduction failed, don't diagnose if the initializer is dependent; it
4824  // might acquire a matching type in the instantiation.
4825  auto DeductionFailed = [&](TemplateDeductionResult TDK,
4827  if (Init->isTypeDependent()) {
4828  Result =
4829  SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
4830  assert(!Result.isNull() && "substituting DependentTy can't fail");
4831  return DAR_Succeeded;
4832  }
4833  if (diagnoseAutoDeductionFailure(*this, TDK, Info, Ranges))
4835  return DAR_Failed;
4836  };
4837 
4838  SmallVector<OriginalCallArg, 4> OriginalCallArgs;
4839 
4840  InitListExpr *InitList = dyn_cast<InitListExpr>(Init);
4841  if (InitList) {
4842  // Notionally, we substitute std::initializer_list<T> for 'auto' and deduce
4843  // against that. Such deduction only succeeds if removing cv-qualifiers and
4844  // references results in std::initializer_list<T>.
4845  if (!Type.getType().getNonReferenceType()->getAs<AutoType>())
4846  return DAR_Failed;
4847 
4848  // Resolving a core issue: a braced-init-list containing any designators is
4849  // a non-deduced context.
4850  for (Expr *E : InitList->inits())
4851  if (isa<DesignatedInitExpr>(E))
4852  return DAR_Failed;
4853 
4854  SourceRange DeducedFromInitRange;
4855  for (unsigned i = 0, e = InitList->getNumInits(); i < e; ++i) {
4856  Expr *Init = InitList->getInit(i);
4857 
4859  *this, TemplateParamsSt.get(), 0, TemplArg, Init,
4860  Info, Deduced, OriginalCallArgs, /*Decomposed*/ true,
4861  /*ArgIdx*/ 0, /*TDF*/ 0))
4862  return DeductionFailed(TDK, {DeducedFromInitRange,
4863  Init->getSourceRange()});
4864 
4865  if (DeducedFromInitRange.isInvalid() &&
4866  Deduced[0].getKind() != TemplateArgument::Null)
4867  DeducedFromInitRange = Init->getSourceRange();
4868  }
4869  } else {
4870  if (!getLangOpts().CPlusPlus && Init->refersToBitField()) {
4871  Diag(Loc, diag::err_auto_bitfield);
4873  }
4874 
4876  *this, TemplateParamsSt.get(), 0, FuncParam, Init, Info, Deduced,
4877  OriginalCallArgs, /*Decomposed*/ false, /*ArgIdx*/ 0, /*TDF*/ 0))
4878  return DeductionFailed(TDK, {});
4879  }
4880 
4881  // Could be null if somehow 'auto' appears in a non-deduced context.
4882  if (Deduced[0].getKind() != TemplateArgument::Type)
4883  return DeductionFailed(TDK_Incomplete, {});
4884 
4885  QualType DeducedType = Deduced[0].getAsType();
4886 
4887  if (InitList) {
4889  if (DeducedType.isNull())
4891  }
4892 
4893  if (const auto *AT = Type.getType()->getAs<AutoType>()) {
4894  if (AT->isConstrained() && !IgnoreConstraints) {
4895  auto ConstraintsResult =
4897  Type.getContainedAutoTypeLoc(),
4898  DeducedType);
4899  if (ConstraintsResult != DAR_Succeeded)
4900  return ConstraintsResult;
4901  }
4902  }
4903 
4904  Result = SubstituteDeducedTypeTransform(*this, DeducedType).Apply(Type);
4905  if (Result.isNull())
4907 
4908  // Check that the deduced argument type is compatible with the original
4909  // argument type per C++ [temp.deduct.call]p4.
4910  QualType DeducedA = InitList ? Deduced[0].getAsType() : Result;
4911  for (const OriginalCallArg &OriginalArg : OriginalCallArgs) {
4912  assert((bool)InitList == OriginalArg.DecomposedParam &&
4913  "decomposed non-init-list in auto deduction?");
4914  if (auto TDK =
4915  CheckOriginalCallArgDeduction(*this, Info, OriginalArg, DeducedA)) {
4916  Result = QualType();
4917  return DeductionFailed(TDK, {});
4918  }
4919  }
4920 
4921  return DAR_Succeeded;
4922 }
4923 
4925  QualType TypeToReplaceAuto) {
4926  if (TypeToReplaceAuto->isDependentType())
4927  return SubstituteDeducedTypeTransform(
4928  *this, DependentAuto{
4929  TypeToReplaceAuto->containsUnexpandedParameterPack()})
4930  .TransformType(TypeWithAuto);
4931  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4932  .TransformType(TypeWithAuto);
4933 }
4934 
4936  QualType TypeToReplaceAuto) {
4937  if (TypeToReplaceAuto->isDependentType())
4938  return SubstituteDeducedTypeTransform(
4939  *this,
4940  DependentAuto{
4941  TypeToReplaceAuto->containsUnexpandedParameterPack()})
4942  .TransformType(TypeWithAuto);
4943  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
4944  .TransformType(TypeWithAuto);
4945 }
4946 
4948  QualType TypeToReplaceAuto) {
4949  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
4950  /*UseTypeSugar*/ false)
4951  .TransformType(TypeWithAuto);
4952 }
4953 
4955  QualType TypeToReplaceAuto) {
4956  return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto,
4957  /*UseTypeSugar*/ false)
4958  .TransformType(TypeWithAuto);
4959 }
4960 
4962  if (isa<InitListExpr>(Init))
4963  Diag(VDecl->getLocation(),
4964  VDecl->isInitCapture()
4965  ? diag::err_init_capture_deduction_failure_from_init_list
4966  : diag::err_auto_var_deduction_failure_from_init_list)
4967  << VDecl->getDeclName() << VDecl->getType() << Init->getSourceRange();
4968  else
4969  Diag(VDecl->getLocation(),
4970  VDecl->isInitCapture() ? diag::err_init_capture_deduction_failure
4971  : diag::err_auto_var_deduction_failure)
4972  << VDecl->getDeclName() << VDecl->getType() << Init->getType()
4973  << Init->getSourceRange();
4974 }
4975 
4977  bool Diagnose) {
4978  assert(FD->getReturnType()->isUndeducedType());
4979 
4980  // For a lambda's conversion operator, deduce any 'auto' or 'decltype(auto)'
4981  // within the return type from the call operator's type.
4982  if (isLambdaConversionOperator(FD)) {
4983  CXXRecordDecl *Lambda = cast<CXXMethodDecl>(FD)->getParent();
4984  FunctionDecl *CallOp = Lambda->getLambdaCallOperator();
4985 
4986  // For a generic lambda, instantiate the call operator if needed.
4987  if (auto *Args = FD->getTemplateSpecializationArgs()) {
4989  CallOp->getDescribedFunctionTemplate(), Args, Loc);
4990  if (!CallOp || CallOp->isInvalidDecl())
4991  return true;
4992 
4993  // We might need to deduce the return type by instantiating the definition
4994  // of the operator() function.
4995  if (CallOp->getReturnType()->isUndeducedType()) {
4996  runWithSufficientStackSpace(Loc, [&] {
4997  InstantiateFunctionDefinition(Loc, CallOp);
4998  });
4999  }
5000  }
5001 
5002  if (CallOp->isInvalidDecl())
5003  return true;
5004  assert(!CallOp->getReturnType()->isUndeducedType() &&
5005  "failed to deduce lambda return type");
5006 
5007  // Build the new return type from scratch.
5008  CallingConv RetTyCC = FD->getReturnType()
5009  ->getPointeeType()
5010  ->castAs<FunctionType>()
5011  ->getCallConv();
5013  CallOp->getType()->castAs<FunctionProtoType>(), RetTyCC);
5014  if (FD->getReturnType()->getAs<PointerType>())
5015  RetType = Context.getPointerType(RetType);
5016  else {
5017  assert(FD->getReturnType()->getAs<BlockPointerType>());
5018  RetType = Context.getBlockPointerType(RetType);
5019  }
5021  return false;
5022  }
5023 
5024  if (FD->getTemplateInstantiationPattern()) {
5025  runWithSufficientStackSpace(Loc, [&] {
5027  });
5028  }
5029 
5030  bool StillUndeduced = FD->getReturnType()->isUndeducedType();
5031  if (StillUndeduced && Diagnose && !FD->isInvalidDecl()) {
5032  Diag(Loc, diag::err_auto_fn_used_before_defined) << FD;
5033  Diag(FD->getLocation(), diag::note_callee_decl) << FD;
5034  }
5035 
5036  return StillUndeduced;
5037 }
5038 
5039 /// If this is a non-static member function,
5040 static void
5042  CXXMethodDecl *Method,
5043  SmallVectorImpl<QualType> &ArgTypes) {
5044  // C++11 [temp.func.order]p3:
5045  // [...] The new parameter is of type "reference to cv A," where cv are
5046  // the cv-qualifiers of the function template (if any) and A is
5047  // the class of which the function template is a member.
5048  //
5049  // The standard doesn't say explicitly, but we pick the appropriate kind of
5050  // reference type based on [over.match.funcs]p4.
5051  QualType ArgTy = Context.getTypeDeclType(Method->getParent());
5052  ArgTy = Context.getQualifiedType(ArgTy, Method->getMethodQualifiers());
5053  if (Method->getRefQualifier() == RQ_RValue)
5054  ArgTy = Context.getRValueReferenceType(ArgTy);
5055  else
5056  ArgTy = Context.getLValueReferenceType(ArgTy);
5057  ArgTypes.push_back(ArgTy);
5058 }
5059 
5060 /// Determine whether the function template \p FT1 is at least as
5061 /// specialized as \p FT2.
5063  SourceLocation Loc,
5064  FunctionTemplateDecl *FT1,
5065  FunctionTemplateDecl *FT2,
5067  unsigned NumCallArguments1,
5068  bool Reversed) {
5069  assert(!Reversed || TPOC == TPOC_Call);
5070 
5071  FunctionDecl *FD1 = FT1->getTemplatedDecl();
5072  FunctionDecl *FD2 = FT2->getTemplatedDecl();
5073  const FunctionProtoType *Proto1 = FD1->getType()->getAs<FunctionProtoType>();
5074  const FunctionProtoType *Proto2 = FD2->getType()->getAs<FunctionProtoType>();
5075 
5076  assert(Proto1 && Proto2 && "Function templates must have prototypes");
5077  TemplateParameterList *TemplateParams = FT2->getTemplateParameters();
5079  Deduced.resize(TemplateParams->size());
5080 
5081  // C++0x [temp.deduct.partial]p3:
5082  // The types used to determine the ordering depend on the context in which
5083  // the partial ordering is done:
5084  TemplateDeductionInfo Info(Loc);
5086  switch (TPOC) {
5087  case TPOC_Call: {
5088  // - In the context of a function call, the function parameter types are
5089  // used.
5090  CXXMethodDecl *Method1 = dyn_cast<CXXMethodDecl>(FD1);
5091  CXXMethodDecl *Method2 = dyn_cast<CXXMethodDecl>(FD2);
5092 
5093  // C++11 [temp.func.order]p3:
5094  // [...] If only one of the function templates is a non-static
5095  // member, that function template is considered to have a new
5096  // first parameter inserted in its function parameter list. The
5097  // new parameter is of type "reference to cv A," where cv are
5098  // the cv-qualifiers of the function template (if any) and A is
5099  // the class of which the function template is a member.
5100  //
5101  // Note that we interpret this to mean "if one of the function
5102  // templates is a non-static member and the other is a non-member";
5103  // otherwise, the ordering rules for static functions against non-static
5104  // functions don't make any sense.
5105  //
5106  // C++98/03 doesn't have this provision but we've extended DR532 to cover
5107  // it as wording was broken prior to it.
5109 
5110  unsigned NumComparedArguments = NumCallArguments1;
5111 
5112  if (!Method2 && Method1 && !Method1->isStatic()) {
5113  // Compare 'this' from Method1 against first parameter from Method2.
5114  AddImplicitObjectParameterType(S.Context, Method1, Args1);
5115  ++NumComparedArguments;
5116  } else if (!Method1 && Method2 && !Method2->isStatic()) {
5117  // Compare 'this' from Method2 against first parameter from Method1.
5118  AddImplicitObjectParameterType(S.Context, Method2, Args2);
5119  } else if (Method1 && Method2 && Reversed) {
5120  // Compare 'this' from Method1 against second parameter from Method2
5121  // and 'this' from Method2 against second parameter from Method1.
5122  AddImplicitObjectParameterType(S.Context, Method1, Args1);
5123  AddImplicitObjectParameterType(S.Context, Method2, Args2);
5124  ++NumComparedArguments;
5125  }
5126 
5127  Args1.insert(Args1.end(), Proto1->param_type_begin(),
5128  Proto1->param_type_end());
5129  Args2.insert(Args2.end(), Proto2->param_type_begin(),
5130  Proto2->param_type_end());
5131 
5132  // C++ [temp.func.order]p5:
5133  // The presence of unused ellipsis and default arguments has no effect on
5134  // the partial ordering of function templates.
5135  if (Args1.size() > NumComparedArguments)
5136  Args1.resize(NumComparedArguments);
5137  if (Args2.size() > NumComparedArguments)
5138  Args2.resize(NumComparedArguments);
5139  if (Reversed)
5140  std::reverse(Args2.begin(), Args2.end());
5141  if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
5142  Args1.data(), Args1.size(), Info, Deduced,
5143  TDF_None, /*PartialOrdering=*/true))
5144  return false;
5145 
5146  break;
5147  }
5148 
5149  case TPOC_Conversion:
5150  // - In the context of a call to a conversion operator, the return types
5151  // of the conversion function templates are used.
5153  S, TemplateParams, Proto2->getReturnType(), Proto1->getReturnType(),
5154  Info, Deduced, TDF_None,
5155  /*PartialOrdering=*/true))
5156  return false;
5157  break;
5158 
5159  case TPOC_Other:
5160  // - In other contexts (14.6.6.2) the function template's function type
5161  // is used.
5162  if (DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
5163  FD2->getType(), FD1->getType(),
5164  Info, Deduced, TDF_None,
5165  /*PartialOrdering=*/true))
5166  return false;
5167  break;
5168  }
5169 
5170  // C++0x [temp.deduct.partial]p11:
5171  // In most cases, all template parameters must have values in order for
5172  // deduction to succeed, but for partial ordering purposes a template
5173  // parameter may remain without a value provided it is not used in the
5174  // types being used for partial ordering. [ Note: a template parameter used
5175  // in a non-deduced context is considered used. -end note]
5176  unsigned ArgIdx = 0, NumArgs = Deduced.size();
5177  for (; ArgIdx != NumArgs; ++ArgIdx)
5178  if (Deduced[ArgIdx].isNull())
5179  break;
5180 
5181  // FIXME: We fail to implement [temp.deduct.type]p1 along this path. We need
5182  // to substitute the deduced arguments back into the template and check that
5183  // we get the right type.
5184 
5185  if (ArgIdx == NumArgs) {
5186  // All template arguments were deduced. FT1 is at least as specialized
5187  // as FT2.
5188  return true;
5189  }
5190 
5191  // Figure out which template parameters were used.
5192  llvm::SmallBitVector UsedParameters(TemplateParams->size());
5193  switch (TPOC) {
5194  case TPOC_Call:
5195  for (unsigned I = 0, N = Args2.size(); I != N; ++I)
5196  ::MarkUsedTemplateParameters(S.Context, Args2[I], false,
5197  TemplateParams->getDepth(),
5198  UsedParameters);
5199  break;
5200 
5201  case TPOC_Conversion:
5202  ::MarkUsedTemplateParameters(S.Context, Proto2->getReturnType(), false,
5203  TemplateParams->getDepth(), UsedParameters);
5204  break;
5205 
5206  case TPOC_Other:
5207  ::MarkUsedTemplateParameters(S.Context, FD2->getType(), false,
5208  TemplateParams->getDepth(),
5209  UsedParameters);
5210  break;
5211  }
5212 
5213  for (; ArgIdx != NumArgs; ++ArgIdx)
5214  // If this argument had no value deduced but was used in one of the types
5215  // used for partial ordering, then deduction fails.
5216  if (Deduced[ArgIdx].isNull() && UsedParameters[ArgIdx])
5217  return false;
5218 
5219  return true;
5220 }
5221 
5222 /// Determine whether this a function template whose parameter-type-list
5223 /// ends with a function parameter pack.
5225  FunctionDecl *Function = FunTmpl->getTemplatedDecl();
5226  unsigned NumParams = Function->getNumParams();
5227  if (NumParams == 0)
5228  return false;
5229 
5230  ParmVarDecl *Last = Function->getParamDecl(NumParams - 1);
5231  if (!Last->isParameterPack())
5232  return false;
5233 
5234  // Make sure that no previous parameter is a parameter pack.
5235  while (--NumParams > 0) {
5236  if (Function->getParamDecl(NumParams - 1)->isParameterPack())
5237  return false;
5238  }
5239 
5240  return true;
5241 }
5242 
5243 /// Returns the more specialized function template according
5244 /// to the rules of function template partial ordering (C++ [temp.func.order]).
5245 ///
5246 /// \param FT1 the first function template
5247 ///
5248 /// \param FT2 the second function template
5249 ///
5250 /// \param TPOC the context in which we are performing partial ordering of
5251 /// function templates.
5252 ///
5253 /// \param NumCallArguments1 The number of arguments in the call to FT1, used
5254 /// only when \c TPOC is \c TPOC_Call.
5255 ///
5256 /// \param NumCallArguments2 The number of arguments in the call to FT2, used
5257 /// only when \c TPOC is \c TPOC_Call.
5258 ///
5259 /// \param Reversed If \c true, exactly one of FT1 and FT2 is an overload
5260 /// candidate with a reversed parameter order. In this case, the corresponding
5261 /// P/A pairs between FT1 and FT2 are reversed.
5262 ///
5263 /// \returns the more specialized function template. If neither
5264 /// template is more specialized, returns NULL.
5267  FunctionTemplateDecl *FT2,
5268  SourceLocation Loc,
5270  unsigned NumCallArguments1,
5271  unsigned NumCallArguments2,
5272  bool Reversed) {
5273 
5274  auto JudgeByConstraints = [&] () -> FunctionTemplateDecl * {
5276  FT1->getAssociatedConstraints(AC1);
5277  FT2->getAssociatedConstraints(AC2);
5278  bool AtLeastAsConstrained1, AtLeastAsConstrained2;
5279  if (IsAtLeastAsConstrained(FT1, AC1, FT2, AC2, AtLeastAsConstrained1))
5280  return nullptr;
5281  if (IsAtLeastAsConstrained(FT2, AC2, FT1, AC1, AtLeastAsConstrained2))
5282  return nullptr;
5283  if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
5284  return nullptr;
5285  return AtLeastAsConstrained1 ? FT1 : FT2;
5286  };
5287 
5288  bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
5289  NumCallArguments1, Reversed);
5290  bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
5291  NumCallArguments2, Reversed);
5292 
5293  if (Better1 != Better2) // We have a clear winner
5294  return Better1 ? FT1 : FT2;
5295 
5296  if (!Better1 && !Better2) // Neither is better than the other
5297  return JudgeByConstraints();
5298 
5299  // FIXME: This mimics what GCC implements, but doesn't match up with the
5300  // proposed resolution for core issue 692. This area needs to be sorted out,
5301  // but for now we attempt to maintain compatibility.
5302  bool Variadic1 = isVariadicFunctionTemplate(FT1);
5303  bool Variadic2 = isVariadicFunctionTemplate(FT2);
5304  if (Variadic1 != Variadic2)
5305  return Variadic1? FT2 : FT1;
5306 
5307  return JudgeByConstraints();
5308 }
5309 
5310 /// Determine if the two templates are equivalent.
5312  if (T1 == T2)
5313  return true;
5314 
5315  if (!T1 || !T2)
5316  return false;
5317 
5318  return T1->getCanonicalDecl() == T2->getCanonicalDecl();
5319 }
5320 
5321 /// Retrieve the most specialized of the given function template
5322 /// specializations.
5323 ///
5324 /// \param SpecBegin the start iterator of the function template
5325 /// specializations that we will be comparing.
5326 ///
5327 /// \param SpecEnd the end iterator of the function template
5328 /// specializations, paired with \p SpecBegin.
5329 ///
5330 /// \param Loc the location where the ambiguity or no-specializations
5331 /// diagnostic should occur.
5332 ///
5333 /// \param NoneDiag partial diagnostic used to diagnose cases where there are
5334 /// no matching candidates.
5335 ///
5336 /// \param AmbigDiag partial diagnostic used to diagnose an ambiguity, if one
5337 /// occurs.
5338 ///
5339 /// \param CandidateDiag partial diagnostic used for each function template
5340 /// specialization that is a candidate in the ambiguous ordering. One parameter
5341 /// in this diagnostic should be unbound, which will correspond to the string
5342 /// describing the template arguments for the function template specialization.
5343 ///
5344 /// \returns the most specialized function template specialization, if
5345 /// found. Otherwise, returns SpecEnd.
5347  UnresolvedSetIterator SpecBegin, UnresolvedSetIterator SpecEnd,
5348  TemplateSpecCandidateSet &FailedCandidates,
5349  SourceLocation Loc, const PartialDiagnostic &NoneDiag,
5350  const PartialDiagnostic &AmbigDiag, const PartialDiagnostic &CandidateDiag,
5351  bool Complain, QualType TargetType) {
5352  if (SpecBegin == SpecEnd) {
5353  if (Complain) {
5354  Diag(Loc, NoneDiag);
5355  FailedCandidates.NoteCandidates(*this, Loc);
5356  }
5357  return SpecEnd;
5358  }
5359 
5360  if (SpecBegin + 1 == SpecEnd)
5361  return SpecBegin;
5362 
5363  // Find the function template that is better than all of the templates it
5364  // has been compared to.
5365  UnresolvedSetIterator Best = SpecBegin;
5366  FunctionTemplateDecl *BestTemplate
5367  = cast<FunctionDecl>(*Best)->getPrimaryTemplate();
5368  assert(BestTemplate && "Not a function template specialization?");
5369  for (UnresolvedSetIterator I = SpecBegin + 1; I != SpecEnd; ++I) {
5370  FunctionTemplateDecl *Challenger
5371  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
5372  assert(Challenger && "Not a function template specialization?");
5373  if (isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
5374  Loc, TPOC_Other, 0, 0),
5375  Challenger)) {
5376  Best = I;
5377  BestTemplate = Challenger;
5378  }
5379  }
5380 
5381  // Make sure that the "best" function template is more specialized than all
5382  // of the others.
5383  bool Ambiguous = false;
5384  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
5385  FunctionTemplateDecl *Challenger
5386  = cast<FunctionDecl>(*I)->getPrimaryTemplate();
5387  if (I != Best &&
5388  !isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
5389  Loc, TPOC_Other, 0, 0),
5390  BestTemplate)) {
5391  Ambiguous = true;
5392  break;
5393  }
5394  }
5395 
5396  if (!Ambiguous) {
5397  // We found an answer. Return it.
5398  return Best;
5399  }
5400 
5401  // Diagnose the ambiguity.
5402  if (Complain) {
5403  Diag(Loc, AmbigDiag);
5404 
5405  // FIXME: Can we order the candidates in some sane way?
5406  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
5407  PartialDiagnostic PD = CandidateDiag;
5408  const auto *FD = cast<FunctionDecl>(*I);
5409  PD << FD << getTemplateArgumentBindingsText(
5410  FD->getPrimaryTemplate()->getTemplateParameters(),
5411  *FD->getTemplateSpecializationArgs());
5412  if (!TargetType.isNull())
5413  HandleFunctionTypeMismatch(PD, FD->getType(), TargetType);
5414  Diag((*I)->getLocation(), PD);
5415  }
5416  }
5417 
5418  return SpecEnd;
5419 }
5420 
5421 /// Determine whether one partial specialization, P1, is at least as
5422 /// specialized than another, P2.
5423 ///
5424 /// \tparam TemplateLikeDecl The kind of P2, which must be a
5425 /// TemplateDecl or {Class,Var}TemplatePartialSpecializationDecl.
5426 /// \param T1 The injected-class-name of P1 (faked for a variable template).
5427 /// \param T2 The injected-class-name of P2 (faked for a variable template).
5428 template<typename TemplateLikeDecl>
5430  TemplateLikeDecl *P2,
5431  TemplateDeductionInfo &Info) {
5432  // C++ [temp.class.order]p1:
5433  // For two class template partial specializations, the first is at least as
5434  // specialized as the second if, given the following rewrite to two
5435  // function templates, the first function template is at least as
5436  // specialized as the second according to the ordering rules for function
5437  // templates (14.6.6.2):
5438  // - the first function template has the same template parameters as the
5439  // first partial specialization and has a single function parameter
5440  // whose type is a class template specialization with the template
5441  // arguments of the first partial specialization, and
5442  // - the second function template has the same template parameters as the
5443  // second partial specialization and has a single function parameter
5444  // whose type is a class template specialization with the template
5445  // arguments of the second partial specialization.
5446  //
5447  // Rather than synthesize function templates, we merely perform the
5448  // equivalent partial ordering by performing deduction directly on
5449  // the template arguments of the class template partial
5450  // specializations. This computation is slightly simpler than the
5451  // general problem of function template partial ordering, because
5452  // class template partial specializations are more constrained. We
5453  // know that every template parameter is deducible from the class
5454  // template partial specialization's template arguments, for
5455  // example.
5457 
5458  // Determine whether P1 is at least as specialized as P2.
5459  Deduced.resize(P2->getTemplateParameters()->size());
5460  if (DeduceTemplateArgumentsByTypeMatch(S, P2->getTemplateParameters(),
5461  T2, T1, Info, Deduced, TDF_None,
5462  /*PartialOrdering=*/true))
5463  return false;
5464 
5465  SmallVector<TemplateArgument, 4> DeducedArgs(Deduced.begin(),
5466  Deduced.end());
5467  Sema::InstantiatingTemplate Inst(S, Info.getLocation(), P2, DeducedArgs,
5468  Info);
5469  auto *TST1 = T1->