]> granicus.if.org Git - clang/commitdiff
DR1391: Check for implicit conversion sequences for non-dependent function
authorRichard Smith <richard-llvm@metafoo.co.uk>
Mon, 2 Jan 2017 02:42:17 +0000 (02:42 +0000)
committerRichard Smith <richard-llvm@metafoo.co.uk>
Mon, 2 Jan 2017 02:42:17 +0000 (02:42 +0000)
template parameters between deduction and substitution. The idea is to accept
as many cases as possible, on the basis that substitution failure outside
the immediate context is much more common during substitution than during
implicit conversion sequence formation.

This does not implement the partial ordering portion of DR1391, which so
far appears to be misguided.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290808 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Sema/Overload.h
include/clang/Sema/Sema.h
lib/Sema/SemaOverload.cpp
lib/Sema/SemaTemplateDeduction.cpp
test/CXX/drs/dr13xx.cpp
test/Misc/diag-template-diffing.cpp
test/SemaCXX/overload-call.cpp
test/SemaCXX/overload-member-call.cpp
www/cxx_dr_status.html

index 376db92d03bd5265cae79cdea7f4f40c1481fba1..0d74816dfd068311c30a9a910f87c1b643067b3e 100644 (file)
@@ -531,6 +531,13 @@ namespace clang {
       Ambiguous.construct();
     }
 
+    void setAsIdentityConversion(QualType T) {
+      setStandard();
+      Standard.setAsIdentityConversion();
+      Standard.setFromType(T);
+      Standard.setAllToTypes(T);
+    }
+
     /// \brief Whether the target is really a std::initializer_list, and the
     /// sequence only represents the worst element conversion.
     bool isStdInitializerListElement() const {
@@ -603,6 +610,11 @@ namespace clang {
     ovl_fail_ext_disabled,
   };
 
+  /// A list of implicit conversion sequences for the arguments of an
+  /// OverloadCandidate.
+  typedef llvm::MutableArrayRef<ImplicitConversionSequence>
+      ConversionSequenceList;
+
   /// OverloadCandidate - A single candidate in an overload set (C++ 13.3).
   struct OverloadCandidate {
     /// Function - The actual function that this candidate
@@ -627,18 +639,13 @@ namespace clang {
     /// is a surrogate, but only if IsSurrogate is true.
     CXXConversionDecl *Surrogate;
 
-    /// Conversions - The conversion sequences used to convert the
-    /// function arguments to the function parameters, the pointer points to a
-    /// fixed size array with NumConversions elements. The memory is owned by
-    /// the OverloadCandidateSet.
-    ImplicitConversionSequence *Conversions;
+    /// The conversion sequences used to convert the function arguments
+    /// to the function parameters.
+    ConversionSequenceList Conversions;
 
     /// The FixIt hints which can be used to fix the Bad candidate.
     ConversionFixItGenerator Fix;
 
-    /// NumConversions - The number of elements in the Conversions array.
-    unsigned NumConversions;
-
     /// Viable - True to indicate that this overload candidate is viable.
     bool Viable;
 
@@ -677,9 +684,9 @@ namespace clang {
     /// hasAmbiguousConversion - Returns whether this overload
     /// candidate requires an ambiguous conversion or not.
     bool hasAmbiguousConversion() const {
-      for (unsigned i = 0, e = NumConversions; i != e; ++i) {
-        if (!Conversions[i].isInitialized()) return false;
-        if (Conversions[i].isAmbiguous()) return true;
+      for (auto &C : Conversions) {
+        if (!C.isInitialized()) return false;
+        if (C.isAmbiguous()) return true;
       }
       return false;
     }
@@ -728,7 +735,7 @@ namespace clang {
     SmallVector<OverloadCandidate, 16> Candidates;
     llvm::SmallPtrSet<Decl *, 16> Functions;
 
-    // Allocator for OverloadCandidate::Conversions. We store the first few
+    // Allocator for ConversionSequenceLists. We store the first few
     // elements inline to avoid allocation for small sets.
     llvm::BumpPtrAllocator ConversionSequenceAllocator;
 
@@ -769,30 +776,45 @@ namespace clang {
     size_t size() const { return Candidates.size(); }
     bool empty() const { return Candidates.empty(); }
 
-    /// \brief Add a new candidate with NumConversions conversion sequence slots
-    /// to the overload set.
-    OverloadCandidate &addCandidate(unsigned NumConversions = 0) {
-      Candidates.push_back(OverloadCandidate());
-      OverloadCandidate &C = Candidates.back();
+    /// \brief Allocate storage for conversion sequences for NumConversions
+    /// conversions.
+    ConversionSequenceList
+    allocateConversionSequences(unsigned NumConversions) {
+      ImplicitConversionSequence *Conversions;
 
       // Assign space from the inline array if there are enough free slots
       // available.
       if (NumConversions + NumInlineSequences <= 16) {
         ImplicitConversionSequence *I =
             (ImplicitConversionSequence *)InlineSpace.buffer;
-        C.Conversions = &I[NumInlineSequences];
+        Conversions = &I[NumInlineSequences];
         NumInlineSequences += NumConversions;
       } else {
         // Otherwise get memory from the allocator.
-        C.Conversions = ConversionSequenceAllocator
-                          .Allocate<ImplicitConversionSequence>(NumConversions);
+        Conversions =
+            ConversionSequenceAllocator.Allocate<ImplicitConversionSequence>(
+                NumConversions);
       }
 
       // Construct the new objects.
-      for (unsigned i = 0; i != NumConversions; ++i)
-        new (&C.Conversions[i]) ImplicitConversionSequence();
+      for (unsigned I = 0; I != NumConversions; ++I)
+        new (&Conversions[I]) ImplicitConversionSequence();
+
+      return ConversionSequenceList(Conversions, NumConversions);
+    }
+
+    /// \brief Add a new candidate with NumConversions conversion sequence slots
+    /// to the overload set.
+    OverloadCandidate &addCandidate(unsigned NumConversions = 0,
+                                    ConversionSequenceList Conversions = None) {
+      assert((Conversions.empty() || Conversions.size() == NumConversions) &&
+             "preallocated conversion sequence has wrong length");
 
-      C.NumConversions = NumConversions;
+      Candidates.push_back(OverloadCandidate());
+      OverloadCandidate &C = Candidates.back();
+      C.Conversions = Conversions.empty()
+                          ? allocateConversionSequences(NumConversions)
+                          : Conversions;
       return C;
     }
 
index 82caaeb24ae72ff2d579ebc58ca87d26831d0c98..a7e563d3b86b8ffb46a8bf09e358d417671bc310 100644 (file)
@@ -119,6 +119,7 @@ namespace clang {
   class FunctionProtoType;
   class FunctionTemplateDecl;
   class ImplicitConversionSequence;
+  typedef MutableArrayRef<ImplicitConversionSequence> ConversionSequenceList;
   class InitListExpr;
   class InitializationKind;
   class InitializationSequence;
@@ -2510,10 +2511,11 @@ public:
   void AddOverloadCandidate(FunctionDecl *Function,
                             DeclAccessPair FoundDecl,
                             ArrayRef<Expr *> Args,
-                            OverloadCandidateSetCandidateSet,
+                            OverloadCandidateSet &CandidateSet,
                             bool SuppressUserConversions = false,
                             bool PartialOverloading = false,
-                            bool AllowExplicit = false);
+                            bool AllowExplicit = false,
+                            ConversionSequenceList EarlyConversions = None);
   void AddFunctionCandidates(const UnresolvedSetImpl &Functions,
                       ArrayRef<Expr *> Args,
                       OverloadCandidateSet &CandidateSet,
@@ -2533,7 +2535,8 @@ public:
                           ArrayRef<Expr *> Args,
                           OverloadCandidateSet& CandidateSet,
                           bool SuppressUserConversions = false,
-                          bool PartialOverloading = false);
+                          bool PartialOverloading = false,
+                          ConversionSequenceList EarlyConversions = None);
   void AddMethodTemplateCandidate(FunctionTemplateDecl *MethodTmpl,
                                   DeclAccessPair FoundDecl,
                                   CXXRecordDecl *ActingContext,
@@ -2551,6 +2554,15 @@ public:
                                     OverloadCandidateSet& CandidateSet,
                                     bool SuppressUserConversions = false,
                                     bool PartialOverloading = false);
+  bool CheckNonDependentConversions(FunctionTemplateDecl *FunctionTemplate,
+                                    ArrayRef<Expr *> Args,
+                                    OverloadCandidateSet &CandidateSet,
+                                    ConversionSequenceList &Conversions,
+                                    bool SuppressUserConversions,
+                                    CXXRecordDecl *ActingContext = nullptr,
+                                    QualType ObjectType = QualType(),
+                                    Expr::Classification
+                                        ObjectClassification = {});
   void AddConversionCandidate(CXXConversionDecl *Conversion,
                               DeclAccessPair FoundDecl,
                               CXXRecordDecl *ActingContext,
@@ -6579,6 +6591,8 @@ public:
     /// \brief The arguments included an overloaded function name that could
     /// not be resolved to a suitable function.
     TDK_FailedOverloadResolution,
+    /// \brief Checking non-dependent argument conversions failed.
+    TDK_NonDependentConversionFailure,
     /// \brief Deduction failed; that's all we know.
     TDK_MiscellaneousDeductionFailure,
     /// \brief CUDA Target attributes do not match.
@@ -6616,14 +6630,14 @@ public:
     QualType OriginalArgType;
   };
 
-  TemplateDeductionResult
-  FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
-                      SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                                  unsigned NumExplicitlySpecified,
-                                  FunctionDecl *&Specialization,
-                                  sema::TemplateDeductionInfo &Info,
-           SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs = nullptr,
-                                  bool PartialOverloading = false);
+  TemplateDeductionResult FinishTemplateArgumentDeduction(
+      FunctionTemplateDecl *FunctionTemplate,
+      SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+      unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
+      sema::TemplateDeductionInfo &Info,
+      SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs = nullptr,
+      bool PartialOverloading = false,
+      llvm::function_ref<bool()> CheckNonDependent = []{ return false; });
 
   TemplateDeductionResult
   DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
@@ -6631,7 +6645,8 @@ public:
                           ArrayRef<Expr *> Args,
                           FunctionDecl *&Specialization,
                           sema::TemplateDeductionInfo &Info,
-                          bool PartialOverloading = false);
+                          bool PartialOverloading,
+                          llvm::function_ref<bool()> CheckNonDependent);
 
   TemplateDeductionResult
   DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
index 47e3df20d9111fb36ec02aeff13fe8d84b98b318..a2ee2b00ecfc6c4778e33f5384f039f900829cb3 100644 (file)
@@ -589,7 +589,6 @@ clang::MakeDeductionFailureInfo(ASTContext &Context,
   Result.Result = static_cast<unsigned>(TDK);
   Result.HasDiagnostic = false;
   switch (TDK) {
-  case Sema::TDK_Success:
   case Sema::TDK_Invalid:
   case Sema::TDK_InstantiationDepth:
   case Sema::TDK_TooManyArguments:
@@ -648,6 +647,10 @@ clang::MakeDeductionFailureInfo(ASTContext &Context,
   case Sema::TDK_FailedOverloadResolution:
     Result.Data = Info.Expression;
     break;
+
+  case Sema::TDK_Success:
+  case Sema::TDK_NonDependentConversionFailure:
+    llvm_unreachable("not a deduction failure");
   }
 
   return Result;
@@ -664,6 +667,7 @@ void DeductionFailureInfo::Destroy() {
   case Sema::TDK_InvalidExplicitArguments:
   case Sema::TDK_FailedOverloadResolution:
   case Sema::TDK_CUDATargetMismatch:
+  case Sema::TDK_NonDependentConversionFailure:
     break;
 
   case Sema::TDK_Inconsistent:
@@ -707,6 +711,7 @@ TemplateParameter DeductionFailureInfo::getTemplateParameter() {
   case Sema::TDK_NonDeducedMismatch:
   case Sema::TDK_FailedOverloadResolution:
   case Sema::TDK_CUDATargetMismatch:
+  case Sema::TDK_NonDependentConversionFailure:
     return TemplateParameter();
 
   case Sema::TDK_Incomplete:
@@ -739,6 +744,7 @@ TemplateArgumentList *DeductionFailureInfo::getTemplateArgumentList() {
   case Sema::TDK_NonDeducedMismatch:
   case Sema::TDK_FailedOverloadResolution:
   case Sema::TDK_CUDATargetMismatch:
+  case Sema::TDK_NonDependentConversionFailure:
     return nullptr;
 
   case Sema::TDK_DeducedMismatch:
@@ -767,6 +773,7 @@ const TemplateArgument *DeductionFailureInfo::getFirstArg() {
   case Sema::TDK_SubstitutionFailure:
   case Sema::TDK_FailedOverloadResolution:
   case Sema::TDK_CUDATargetMismatch:
+  case Sema::TDK_NonDependentConversionFailure:
     return nullptr;
 
   case Sema::TDK_Inconsistent:
@@ -795,6 +802,7 @@ const TemplateArgument *DeductionFailureInfo::getSecondArg() {
   case Sema::TDK_SubstitutionFailure:
   case Sema::TDK_FailedOverloadResolution:
   case Sema::TDK_CUDATargetMismatch:
+  case Sema::TDK_NonDependentConversionFailure:
     return nullptr;
 
   case Sema::TDK_Inconsistent:
@@ -829,8 +837,8 @@ llvm::Optional<unsigned> DeductionFailureInfo::getCallArgIndex() {
 
 void OverloadCandidateSet::destroyCandidates() {
   for (iterator i = begin(), e = end(); i != e; ++i) {
-    for (unsigned ii = 0, ie = i->NumConversions; ii != ie; ++ii)
-      i->Conversions[ii].~ImplicitConversionSequence();
+    for (auto &C : i->Conversions)
+      C.~ImplicitConversionSequence();
     if (!i->Viable && i->FailureKind == ovl_fail_bad_deduction)
       i->DeductionFailure.Destroy();
   }
@@ -5837,7 +5845,8 @@ Sema::AddOverloadCandidate(FunctionDecl *Function,
                            OverloadCandidateSet &CandidateSet,
                            bool SuppressUserConversions,
                            bool PartialOverloading,
-                           bool AllowExplicit) {
+                           bool AllowExplicit,
+                           ConversionSequenceList EarlyConversions) {
   const FunctionProtoType *Proto
     = dyn_cast<FunctionProtoType>(Function->getType()->getAs<FunctionType>());
   assert(Proto && "Functions without a prototype cannot be overloaded");
@@ -5856,7 +5865,7 @@ Sema::AddOverloadCandidate(FunctionDecl *Function,
       AddMethodCandidate(Method, FoundDecl, Method->getParent(),
                          QualType(), Expr::Classification::makeSimpleLValue(),
                          Args, CandidateSet, SuppressUserConversions,
-                         PartialOverloading);
+                         PartialOverloading, EarlyConversions);
       return;
     }
     // We treat a constructor like a non-member function, since its object
@@ -5889,7 +5898,8 @@ Sema::AddOverloadCandidate(FunctionDecl *Function,
   EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
 
   // Add this candidate
-  OverloadCandidate &Candidate = CandidateSet.addCandidate(Args.size());
+  OverloadCandidate &Candidate =
+      CandidateSet.addCandidate(Args.size(), EarlyConversions);
   Candidate.FoundDecl = FoundDecl;
   Candidate.Function = Function;
   Candidate.Viable = true;
@@ -5953,7 +5963,10 @@ Sema::AddOverloadCandidate(FunctionDecl *Function,
   // Determine the implicit conversion sequences for each of the
   // arguments.
   for (unsigned ArgIdx = 0; ArgIdx < Args.size(); ++ArgIdx) {
-    if (ArgIdx < NumParams) {
+    if (Candidate.Conversions[ArgIdx].isInitialized()) {
+      // We already formed a conversion sequence for this parameter during
+      // template argument deduction.
+    } else if (ArgIdx < NumParams) {
       // (C++ 13.3.2p3): for F to be a viable function, there shall
       // exist for each argument an implicit conversion sequence
       // (13.3.3.1) that converts that argument to the corresponding
@@ -6262,7 +6275,8 @@ Sema::AddMethodCandidate(CXXMethodDecl *Method, DeclAccessPair FoundDecl,
                          ArrayRef<Expr *> Args,
                          OverloadCandidateSet &CandidateSet,
                          bool SuppressUserConversions,
-                         bool PartialOverloading) {
+                         bool PartialOverloading,
+                         ConversionSequenceList EarlyConversions) {
   const FunctionProtoType *Proto
     = dyn_cast<FunctionProtoType>(Method->getType()->getAs<FunctionType>());
   assert(Proto && "Methods without a prototype cannot be overloaded");
@@ -6283,7 +6297,8 @@ Sema::AddMethodCandidate(CXXMethodDecl *Method, DeclAccessPair FoundDecl,
   EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
 
   // Add this candidate
-  OverloadCandidate &Candidate = CandidateSet.addCandidate(Args.size() + 1);
+  OverloadCandidate &Candidate =
+      CandidateSet.addCandidate(Args.size() + 1, EarlyConversions);
   Candidate.FoundDecl = FoundDecl;
   Candidate.Function = Method;
   Candidate.IsSurrogate = false;
@@ -6345,7 +6360,10 @@ Sema::AddMethodCandidate(CXXMethodDecl *Method, DeclAccessPair FoundDecl,
   // Determine the implicit conversion sequences for each of the
   // arguments.
   for (unsigned ArgIdx = 0; ArgIdx < Args.size(); ++ArgIdx) {
-    if (ArgIdx < NumParams) {
+    if (Candidate.Conversions[ArgIdx + 1].isInitialized()) {
+      // We already formed a conversion sequence for this parameter during
+      // template argument deduction.
+    } else if (ArgIdx < NumParams) {
       // (C++ 13.3.2p3): for F to be a viable function, there shall
       // exist for each argument an implicit conversion sequence
       // (13.3.3.1) that converts that argument to the corresponding
@@ -6406,19 +6424,30 @@ Sema::AddMethodTemplateCandidate(FunctionTemplateDecl *MethodTmpl,
   //   functions.
   TemplateDeductionInfo Info(CandidateSet.getLocation());
   FunctionDecl *Specialization = nullptr;
-  if (TemplateDeductionResult Result
-      = DeduceTemplateArguments(MethodTmpl, ExplicitTemplateArgs, Args,
-                                Specialization, Info, PartialOverloading)) {
-    OverloadCandidate &Candidate = CandidateSet.addCandidate();
+  ConversionSequenceList Conversions;
+  if (TemplateDeductionResult Result = DeduceTemplateArguments(
+          MethodTmpl, ExplicitTemplateArgs, Args, Specialization, Info,
+          PartialOverloading, [&]() {
+            return CheckNonDependentConversions(
+                MethodTmpl, Args, CandidateSet, Conversions,
+                SuppressUserConversions, ActingContext, ObjectType,
+                ObjectClassification);
+          })) {
+    OverloadCandidate &Candidate =
+        CandidateSet.addCandidate(Conversions.size(), Conversions);
     Candidate.FoundDecl = FoundDecl;
     Candidate.Function = MethodTmpl->getTemplatedDecl();
     Candidate.Viable = false;
-    Candidate.FailureKind = ovl_fail_bad_deduction;
     Candidate.IsSurrogate = false;
     Candidate.IgnoreObjectArgument = false;
     Candidate.ExplicitCallArguments = Args.size();
-    Candidate.DeductionFailure = MakeDeductionFailureInfo(Context, Result,
-                                                          Info);
+    if (Result == TDK_NonDependentConversionFailure)
+      Candidate.FailureKind = ovl_fail_bad_conversion;
+    else {
+      Candidate.FailureKind = ovl_fail_bad_deduction;
+      Candidate.DeductionFailure = MakeDeductionFailureInfo(Context, Result,
+                                                            Info);
+    }
     return;
   }
 
@@ -6429,7 +6458,8 @@ Sema::AddMethodTemplateCandidate(FunctionTemplateDecl *MethodTmpl,
          "Specialization is not a member function?");
   AddMethodCandidate(cast<CXXMethodDecl>(Specialization), FoundDecl,
                      ActingContext, ObjectType, ObjectClassification, Args,
-                     CandidateSet, SuppressUserConversions, PartialOverloading);
+                     CandidateSet, SuppressUserConversions, PartialOverloading,
+                     Conversions);
 }
 
 /// \brief Add a C++ function template specialization as a candidate
@@ -6457,19 +6487,29 @@ Sema::AddTemplateOverloadCandidate(FunctionTemplateDecl *FunctionTemplate,
   //   functions.
   TemplateDeductionInfo Info(CandidateSet.getLocation());
   FunctionDecl *Specialization = nullptr;
-  if (TemplateDeductionResult Result
-        = DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs, Args,
-                                  Specialization, Info, PartialOverloading)) {
-    OverloadCandidate &Candidate = CandidateSet.addCandidate();
+  ConversionSequenceList Conversions;
+  if (TemplateDeductionResult Result = DeduceTemplateArguments(
+          FunctionTemplate, ExplicitTemplateArgs, Args, Specialization, Info,
+          PartialOverloading, [&]() {
+            return CheckNonDependentConversions(FunctionTemplate, Args,
+                                                CandidateSet, Conversions,
+                                                SuppressUserConversions);
+          })) {
+    OverloadCandidate &Candidate =
+        CandidateSet.addCandidate(Conversions.size(), Conversions);
     Candidate.FoundDecl = FoundDecl;
     Candidate.Function = FunctionTemplate->getTemplatedDecl();
     Candidate.Viable = false;
-    Candidate.FailureKind = ovl_fail_bad_deduction;
     Candidate.IsSurrogate = false;
     Candidate.IgnoreObjectArgument = false;
     Candidate.ExplicitCallArguments = Args.size();
-    Candidate.DeductionFailure = MakeDeductionFailureInfo(Context, Result,
-                                                          Info);
+    if (Result == TDK_NonDependentConversionFailure)
+      Candidate.FailureKind = ovl_fail_bad_conversion;
+    else {
+      Candidate.FailureKind = ovl_fail_bad_deduction;
+      Candidate.DeductionFailure = MakeDeductionFailureInfo(Context, Result,
+                                                            Info);
+    }
     return;
   }
 
@@ -6477,7 +6517,64 @@ Sema::AddTemplateOverloadCandidate(FunctionTemplateDecl *FunctionTemplate,
   // deduction as a candidate.
   assert(Specialization && "Missing function template specialization?");
   AddOverloadCandidate(Specialization, FoundDecl, Args, CandidateSet,
-                       SuppressUserConversions, PartialOverloading);
+                       SuppressUserConversions, PartialOverloading,
+                       /*AllowExplicit*/false, Conversions);
+}
+
+/// Check that implicit conversion sequences can be formed for each argument
+/// whose corresponding parameter has a non-dependent type, per DR1391's
+/// [temp.deduct.call]p10.
+bool Sema::CheckNonDependentConversions(
+    FunctionTemplateDecl *FunctionTemplate, ArrayRef<Expr *> Args,
+    OverloadCandidateSet &CandidateSet, ConversionSequenceList &Conversions,
+    bool SuppressUserConversions, CXXRecordDecl *ActingContext,
+    QualType ObjectType, Expr::Classification ObjectClassification) {
+  // FIXME: The cases in which we allow explicit conversions for constructor
+  // arguments never consider calling a constructor template. It's not clear
+  // that is correct.
+  const bool AllowExplicit = false;
+
+  auto *FD = FunctionTemplate->getTemplatedDecl();
+  auto *Method = dyn_cast<CXXMethodDecl>(FD);
+  bool HasThisConversion = Method && !isa<CXXConstructorDecl>(Method);
+  unsigned ThisConversions = HasThisConversion ? 1 : 0;
+
+  Conversions =
+      CandidateSet.allocateConversionSequences(ThisConversions + Args.size());
+
+  // Overload resolution is always an unevaluated context.
+  EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
+
+  // For a method call, check the 'this' conversion here too. DR1391 doesn't
+  // require that, but this check should never result in a hard error, and
+  // overload resolution is permitted to sidestep instantiations.
+  if (HasThisConversion && !cast<CXXMethodDecl>(FD)->isStatic() &&
+      !ObjectType.isNull()) {
+    Conversions[0] = TryObjectArgumentInitialization(
+        *this, CandidateSet.getLocation(), ObjectType, ObjectClassification,
+        Method, ActingContext);
+    if (Conversions[0].isBad())
+      return true;
+  }
+
+
+  for (unsigned I = 0, N = std::min<unsigned>(FD->getNumParams(), Args.size());
+       I != N; ++I) {
+    QualType ParamType = FD->getParamDecl(I)->getType();
+    if (!ParamType->isDependentType()) {
+      Conversions[ThisConversions + I]
+        = TryCopyInitialization(*this, Args[I], ParamType,
+                                SuppressUserConversions,
+                                /*InOverloadResolution=*/true,
+                                /*AllowObjCWritebackConversion=*/
+                                  getLangOpts().ObjCAutoRefCount,
+                                AllowExplicit);
+      if (Conversions[ThisConversions + I].isBad())
+        return true;
+    }
+  }
+
+  return false;
 }
 
 /// Determine whether this is an allowable conversion from the result
@@ -8716,8 +8813,8 @@ bool clang::isBetterOverloadCandidate(Sema &S, const OverloadCandidate &Cand1,
 
   // Define functions that don't require ill-formed conversions for a given
   // argument to be better candidates than functions that do.
-  unsigned NumArgs = Cand1.NumConversions;
-  assert(Cand2.NumConversions == NumArgs && "Overload candidate mismatch");
+  unsigned NumArgs = Cand1.Conversions.size();
+  assert(Cand2.Conversions.size() == NumArgs && "Overload candidate mismatch");
   bool HasBetterConversion = false;
   for (unsigned ArgIdx = StartArg; ArgIdx < NumArgs; ++ArgIdx) {
     bool Cand1Bad = IsIllFormedConversion(Cand1.Conversions[ArgIdx]);
@@ -9924,7 +10021,7 @@ static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
 
   case ovl_fail_bad_conversion: {
     unsigned I = (Cand->IgnoreObjectArgument ? 1 : 0);
-    for (unsigned N = Cand->NumConversions; I != N; ++I)
+    for (unsigned N = Cand->Conversions.size(); I != N; ++I)
       if (Cand->Conversions[I].isBad())
         return DiagnoseBadConversion(S, Cand, I, TakingCandidateAddress);
 
@@ -9987,12 +10084,12 @@ static void NoteSurrogateCandidate(Sema &S, OverloadCandidate *Cand) {
 static void NoteBuiltinOperatorCandidate(Sema &S, StringRef Opc,
                                          SourceLocation OpLoc,
                                          OverloadCandidate *Cand) {
-  assert(Cand->NumConversions <= 2 && "builtin operator is not binary");
+  assert(Cand->Conversions.size() <= 2 && "builtin operator is not binary");
   std::string TypeStr("operator");
   TypeStr += Opc;
   TypeStr += "(";
   TypeStr += Cand->BuiltinTypes.ParamTypes[0].getAsString();
-  if (Cand->NumConversions == 1) {
+  if (Cand->Conversions.size() == 1) {
     TypeStr += ")";
     S.Diag(OpLoc, diag::note_ovl_builtin_unary_candidate) << TypeStr;
   } else {
@@ -10005,9 +10102,7 @@ static void NoteBuiltinOperatorCandidate(Sema &S, StringRef Opc,
 
 static void NoteAmbiguousUserConversions(Sema &S, SourceLocation OpLoc,
                                          OverloadCandidate *Cand) {
-  unsigned NoOperands = Cand->NumConversions;
-  for (unsigned ArgIdx = 0; ArgIdx < NoOperands; ++ArgIdx) {
-    const ImplicitConversionSequence &ICS = Cand->Conversions[ArgIdx];
+  for (const ImplicitConversionSequence &ICS : Cand->Conversions) {
     if (ICS.isBad()) break; // all meaningless after first invalid
     if (!ICS.isAmbiguous()) continue;
 
@@ -10027,7 +10122,8 @@ static SourceLocation GetLocationForCandidate(const OverloadCandidate *Cand) {
 static unsigned RankDeductionFailure(const DeductionFailureInfo &DFI) {
   switch ((Sema::TemplateDeductionResult)DFI.Result) {
   case Sema::TDK_Success:
-    llvm_unreachable("TDK_success while diagnosing bad deduction");
+  case Sema::TDK_NonDependentConversionFailure:
+    llvm_unreachable("non-deduction failure while diagnosing bad deduction");
 
   case Sema::TDK_Invalid:
   case Sema::TDK_Incomplete:
@@ -10130,11 +10226,11 @@ struct CompareOverloadCandidatesForDisplay {
 
         // If there's any ordering between the defined conversions...
         // FIXME: this might not be transitive.
-        assert(L->NumConversions == R->NumConversions);
+        assert(L->Conversions.size() == R->Conversions.size());
 
         int leftBetter = 0;
         unsigned I = (L->IgnoreObjectArgument || R->IgnoreObjectArgument);
-        for (unsigned E = L->NumConversions; I != E; ++I) {
+        for (unsigned E = L->Conversions.size(); I != E; ++I) {
           switch (CompareImplicitConversionSequences(S, Loc,
                                                      L->Conversions[I],
                                                      R->Conversions[I])) {
@@ -10183,7 +10279,8 @@ struct CompareOverloadCandidatesForDisplay {
 }
 
 /// CompleteNonViableCandidate - Normally, overload resolution only
-/// computes up to the first. Produces the FixIt set if possible.
+/// computes up to the first bad conversion. Produces the FixIt set if
+/// possible.
 static void CompleteNonViableCandidate(Sema &S, OverloadCandidate *Cand,
                                        ArrayRef<Expr *> Args) {
   assert(!Cand->Viable);
@@ -10196,30 +10293,24 @@ static void CompleteNonViableCandidate(Sema &S, OverloadCandidate *Cand,
   // Use a implicit copy initialization to check conversion fixes.
   Cand->Fix.setConversionChecker(TryCopyInitialization);
 
-  // Skip forward to the first bad conversion.
-  unsigned ConvIdx = (Cand->IgnoreObjectArgument ? 1 : 0);
-  unsigned ConvCount = Cand->NumConversions;
-  while (true) {
+  // Attempt to fix the bad conversion.
+  unsigned ConvCount = Cand->Conversions.size();
+  for (unsigned ConvIdx = (Cand->IgnoreObjectArgument ? 1 : 0); /**/;
+       ++ConvIdx) {
     assert(ConvIdx != ConvCount && "no bad conversion in candidate");
-    ConvIdx++;
-    if (Cand->Conversions[ConvIdx - 1].isBad()) {
-      Unfixable = !Cand->TryToFixBadConversion(ConvIdx - 1, S);
+    if (Cand->Conversions[ConvIdx].isInitialized() &&
+        Cand->Conversions[ConvIdx].isBad()) {
+      Unfixable = !Cand->TryToFixBadConversion(ConvIdx, S);
       break;
     }
   }
 
-  if (ConvIdx == ConvCount)
-    return;
-
-  assert(!Cand->Conversions[ConvIdx].isInitialized() &&
-         "remaining conversion is initialized?");
-
   // FIXME: this should probably be preserved from the overload
   // operation somehow.
   bool SuppressUserConversions = false;
 
-  const FunctionProtoTypeProto;
-  unsigned ArgIdx = ConvIdx;
+  const FunctionProtoType *Proto;
+  unsigned ArgIdx = 0;
 
   if (Cand->IsSurrogate) {
     QualType ConvType
@@ -10227,40 +10318,56 @@ static void CompleteNonViableCandidate(Sema &S, OverloadCandidate *Cand,
     if (const PointerType *ConvPtrType = ConvType->getAs<PointerType>())
       ConvType = ConvPtrType->getPointeeType();
     Proto = ConvType->getAs<FunctionProtoType>();
-    ArgIdx--;
+    ArgIdx = 1;
   } else if (Cand->Function) {
     Proto = Cand->Function->getType()->getAs<FunctionProtoType>();
     if (isa<CXXMethodDecl>(Cand->Function) &&
         !isa<CXXConstructorDecl>(Cand->Function))
-      ArgIdx--;
+      ArgIdx = 1;
   } else {
     // Builtin binary operator with a bad first conversion.
     assert(ConvCount <= 3);
-    for (; ConvIdx != ConvCount; ++ConvIdx)
-      Cand->Conversions[ConvIdx]
-        = TryCopyInitialization(S, Args[ConvIdx],
-                                Cand->BuiltinTypes.ParamTypes[ConvIdx],
-                                SuppressUserConversions,
-                                /*InOverloadResolution*/ true,
-                                /*AllowObjCWritebackConversion=*/
-                                  S.getLangOpts().ObjCAutoRefCount);
+    for (unsigned ConvIdx = (Cand->IgnoreObjectArgument ? 1 : 0);
+         ConvIdx != ConvCount; ++ConvIdx) {
+      if (Cand->Conversions[ConvIdx].isInitialized())
+        continue;
+      if (Cand->BuiltinTypes.ParamTypes[ConvIdx]->isDependentType())
+        Cand->Conversions[ConvIdx].setAsIdentityConversion(
+            Args[ConvIdx]->getType());
+      else
+        Cand->Conversions[ConvIdx] = TryCopyInitialization(
+            S, Args[ConvIdx], Cand->BuiltinTypes.ParamTypes[ConvIdx],
+            SuppressUserConversions,
+            /*InOverloadResolution*/ true,
+            /*AllowObjCWritebackConversion=*/
+            S.getLangOpts().ObjCAutoRefCount);
+      // FIXME: If the conversion is bad, try to fix it.
+    }
     return;
   }
 
   // Fill in the rest of the conversions.
   unsigned NumParams = Proto->getNumParams();
-  for (; ConvIdx != ConvCount; ++ConvIdx, ++ArgIdx) {
-    if (ArgIdx < NumParams) {
-      Cand->Conversions[ConvIdx] = TryCopyInitialization(
-          S, Args[ArgIdx], Proto->getParamType(ArgIdx), SuppressUserConversions,
-          /*InOverloadResolution=*/true,
-          /*AllowObjCWritebackConversion=*/
-          S.getLangOpts().ObjCAutoRefCount);
-      // Store the FixIt in the candidate if it exists.
-      if (!Unfixable && Cand->Conversions[ConvIdx].isBad())
-        Unfixable = !Cand->TryToFixBadConversion(ConvIdx, S);
-    }
-    else
+  for (unsigned ConvIdx = (Cand->IgnoreObjectArgument ? 1 : 0);
+       ConvIdx != ConvCount; ++ConvIdx, ++ArgIdx) {
+    if (Cand->Conversions[ConvIdx].isInitialized()) {
+      // Found the bad conversion.
+    } else if (ArgIdx < NumParams) {
+      if (Proto->getParamType(ArgIdx)->isDependentType())
+        Cand->Conversions[ConvIdx].setAsIdentityConversion(
+            Args[ArgIdx]->getType());
+      else {
+        Cand->Conversions[ConvIdx] =
+            TryCopyInitialization(S, Args[ArgIdx], Proto->getParamType(ArgIdx),
+                                  SuppressUserConversions,
+                                  /*InOverloadResolution=*/true,
+                                  /*AllowObjCWritebackConversion=*/
+                                  S.getLangOpts().ObjCAutoRefCount);
+        // Store the FixIt in the candidate if it exists.
+        if (!Unfixable && Cand->Conversions[ConvIdx].isBad())
+          Unfixable = !Cand->TryToFixBadConversion(ConvIdx, S);
+      }
+    } else
       Cand->Conversions[ConvIdx].setEllipsis();
   }
 }
index 0bc85a2f2635bd68c05ce96d5f6638a9a0ae9605..dc291836fb94db78415070c1afda0cbf2bd351c6 100644 (file)
@@ -2849,14 +2849,13 @@ CheckOriginalCallArgDeduction(Sema &S, Sema::OriginalCallArg OriginalArg,
 ///
 /// \param OriginalCallArgs If non-NULL, the original call arguments against
 /// which the deduced argument types should be compared.
-Sema::TemplateDeductionResult
-Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
-                       SmallVectorImpl<DeducedTemplateArgument> &Deduced,
-                                      unsigned NumExplicitlySpecified,
-                                      FunctionDecl *&Specialization,
-                                      TemplateDeductionInfo &Info,
-        SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
-                                      bool PartialOverloading) {
+Sema::TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
+    FunctionTemplateDecl *FunctionTemplate,
+    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+    unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
+    TemplateDeductionInfo &Info,
+    SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
+    bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
   // Unevaluated SFINAE context.
   EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
   SFINAETrap Trap(*this);
@@ -2883,6 +2882,18 @@ Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
           PartialOverloading))
     return Result;
 
+  // C++ [temp.deduct.call]p10: [DR1391]
+  //   If deduction succeeds for all parameters that contain
+  //   template-parameters that participate in template argument deduction,
+  //   and all template arguments are explicitly specified, deduced, or
+  //   obtained from default template arguments, remaining parameters are then
+  //   compared with the corresponding arguments. For each remaining parameter
+  //   P with a type that was non-dependent before substitution of any
+  //   explicitly-specified template arguments, if the corresponding argument
+  //   A cannot be implicitly converted to P, deduction fails.
+  if (CheckNonDependent())
+    return TDK_NonDependentConversionFailure;
+
   // Form the template argument list from the deduced template arguments.
   TemplateArgumentList *DeducedArgumentList
     = TemplateArgumentList::CreateCopy(Context, Builder);
@@ -3307,12 +3318,17 @@ DeduceTemplateArgumentByListElement(Sema &S,
 /// \param Info the argument will be updated to provide additional information
 /// about template argument deduction.
 ///
+/// \param CheckNonDependent A callback to invoke to check conversions for
+/// non-dependent parameters, between deduction and substitution, per DR1391.
+/// If this returns true, substitution will be skipped and we return
+/// TDK_NonDependentConversionFailure.
+///
 /// \returns the result of template argument deduction.
 Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
     FunctionTemplateDecl *FunctionTemplate,
     TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
     FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
-    bool PartialOverloading) {
+    bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
   if (FunctionTemplate->isInvalidDecl())
     return TDK_Invalid;
 
@@ -3496,7 +3512,7 @@ Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
   return FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
                                          NumExplicitlySpecified, Specialization,
                                          Info, &OriginalCallArgs,
-                                         PartialOverloading);
+                                         PartialOverloading, CheckNonDependent);
 }
 
 QualType Sema::adjustCCAndNoReturn(QualType ArgFunctionType,
index 28bebcbb607e64228b677117c85b8c95cb45d8e0..b9be5ca821c5c5f6380c4227254ed77912fcd839 100644 (file)
@@ -174,3 +174,81 @@ namespace dr1359 { // dr1359: 3.5
   constexpr Y y = Y(); // expected-error {{no matching}}
 #endif
 }
+
+namespace dr1391 { // dr1391: partial
+  struct A {}; struct B : A {};
+  template<typename T> struct C { C(int); typename T::error error; }; // expected-error 2{{'::'}}
+  template<typename T> struct D {};
+
+  // No deduction is performed for parameters with no deducible template-parameters, therefore types do not need to match.
+  template<typename T> void a(T, int T::*);
+  void test_a(int A::*p) { a(A(), p); } // ok, type of second parameter does not need to match
+
+  namespace dr_example_1 {
+    template<typename T, typename U> void f(C<T>);
+    template<typename T> void f(D<T>);
+
+    void g(D<int> d) {
+      f(d); // ok, first 'f' eliminated by deduction failure
+      f<int>(d); // ok, first 'f' eliminated because 'U' cannot be deduced
+    }
+  }
+
+  namespace dr_example_2 {
+    template<typename T> typename C<T>::error f(int, T);
+    template<typename T> T f(T, T);
+
+    void g(A a) {
+      f(a, a); // ok, no conversion from A to int for first parameter of first candidate
+    }
+  }
+
+  namespace std_example {
+    template<typename T> struct Z {
+      typedef typename T::x xx;
+    };
+    template<typename T> typename Z<T>::xx f(void *, T);
+    template<typename T> void f(int, T);
+    struct A {} a;
+    void g() { f(1, a); }
+  }
+
+  template<typename T> void b(C<int> ci, T *p);
+  void b(...);
+  void test_b() {
+    b(0, 0); // ok, deduction fails prior to forming a conversion sequence and instantiating C<int>
+    // FIXME: The "while substituting" note should point at the overload candidate.
+    b<int>(0, 0); // expected-note {{instantiation of}} expected-note {{while substituting}}
+  }
+
+  template<typename T> struct Id { typedef T type; };
+  template<typename T> void c(T, typename Id<C<T> >::type);
+  void test_c() {
+    // Implicit conversion sequences for dependent types are checked later.
+    c(0.0, 0); // expected-note {{instantiation of}}
+  }
+
+  namespace partial_ordering {
+    // FIXME: Second template should be considered more specialized because non-dependent parameter is ignored.
+    template<typename T> int a(T, short) = delete; // expected-error 0-1{{extension}} expected-note {{candidate}}
+    template<typename T> int a(T*, char); // expected-note {{candidate}}
+    int test_a = a((int*)0, 0); // FIXME: expected-error {{ambiguous}}
+
+    // FIXME: Second template should be considered more specialized:
+    // deducing #1 from #2 ignores the second P/A pair, so deduction succeeds,
+    // deducing #2 from #1 fails to deduce T, so deduction fails.
+    template<typename T> int b(T, int) = delete; // expected-error 0-1{{extension}} expected-note {{candidate}}
+    template<typename T, typename U> int b(T*, U); // expected-note {{candidate}}
+    int test_b = b((int*)0, 0); // FIXME: expected-error {{ambiguous}}
+
+    // Unintended consequences: because partial ordering does not consider
+    // explicit template arguments, and deduction from a non-dependent type
+    // vacuously succeeds, a non-dependent template is less specialized than
+    // anything else!
+    // According to DR1391, this is ambiguous!
+    template<typename T> int c(int);
+    template<typename T> int c(T);
+    int test_c1 = c(0); // ok
+    int test_c2 = c<int>(0); // FIXME: apparently ambiguous
+  }
+}
index 78083989928244430bd0148ae261ba002789b23f..2192223191bb5131edc383564fc06aa7b56064f2 100644 (file)
@@ -1401,7 +1401,7 @@ void run() {
   f(1, integral_constant<bool, true>{});
 }
 // CHECK-ELIDE-NOTREE: error: no matching function for call to 'f'
-// CHECK-ELIDE-NOTREE: note: candidate function [with T = int] not viable: no known conversion from 'integral_constant<[...], true>' to 'integral_constant<[...], false>' for 2nd argument
+// CHECK-ELIDE-NOTREE: note: candidate function not viable: no known conversion from 'integral_constant<[...], true>' to 'integral_constant<[...], false>' for 2nd argument
 }
 
 namespace ZeroArgs {
index 3a01bf24b31afd78f325d8deea881076313bdb4b..0e3a9ee50bb241a0daac3f0231bf00ee303e3e13 100644 (file)
@@ -338,7 +338,7 @@ namespace PR5756 {
 
 // Tests the exact text used to note the candidates
 namespace test1 {
-  template <class T> void foo(T t, unsigned N); // expected-note {{candidate function [with T = int] not viable: no known conversion from 'const char [6]' to 'unsigned int' for 2nd argument}}
+  template <class T> void foo(T t, unsigned N); // expected-note {{candidate function not viable: no known conversion from 'const char [6]' to 'unsigned int' for 2nd argument}}
   void foo(int n, char N); // expected-note {{candidate function not viable: no known conversion from 'const char [6]' to 'char' for 2nd argument}} 
   void foo(int n, const char *s, int t); // expected-note {{candidate function not viable: requires 3 arguments, but 2 were provided}}
   void foo(int n, const char *s, int t, ...); // expected-note {{candidate function not viable: requires at least 3 arguments, but 2 were provided}}
index e0f34d937f6f1989bee57c91b984058fa8058574..6e64b25d6b532e1aa3c312bbb8472b703eaa624e 100644 (file)
@@ -70,7 +70,7 @@ void test_X2(X2 *x2p, const X2 *cx2p) {
 // Tests the exact text used to note the candidates
 namespace test1 {
   class A {
-    template <class T> void foo(T t, unsigned N); // expected-note {{candidate function [with T = int] not viable: no known conversion from 'const char [6]' to 'unsigned int' for 2nd argument}}
+    template <class T> void foo(T t, unsigned N); // expected-note {{candidate function not viable: no known conversion from 'const char [6]' to 'unsigned int' for 2nd argument}}
     void foo(int n, char N); // expected-note {{candidate function not viable: no known conversion from 'const char [6]' to 'char' for 2nd argument}} 
     void foo(int n, const char *s, int t); // expected-note {{candidate function not viable: requires 3 arguments, but 2 were provided}}
     void foo(int n, const char *s, int t, ...); // expected-note {{candidate function not viable: requires at least 3 arguments, but 2 were provided}}
index b4936eed3b3562968c420a7e8ef4bb76cae60c9f..90176314403f69fc6b6ef038bbe8dd7aef25d323 100644 (file)
@@ -8161,7 +8161,7 @@ and <I>POD class</I></td>
     <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1391">1391</a></td>
     <td>DRWP</td>
     <td>Conversions to parameter types with non-deduced template arguments</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="partial" align="center">Partial</td>
   </tr>
   <tr id="1392">
     <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1392">1392</a></td>