Implement C++ DR1391 (wg21.link/cwg1391)
Check for implicit conversion sequences for non-dependent function
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 re-commits r290808, reverted in r290811 and r291412, with a couple of
fixes for handling of explicitly-specified non-trailing template argument
packs.
llvm-svn: 291427
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index c0321d3..41f4fa7 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -590,7 +590,6 @@
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:
@@ -646,6 +645,10 @@
Result.HasDiagnostic = true;
}
break;
+
+ case Sema::TDK_Success:
+ case Sema::TDK_NonDependentConversionFailure:
+ llvm_unreachable("not a deduction failure");
}
return Result;
@@ -661,6 +664,7 @@
case Sema::TDK_TooFewArguments:
case Sema::TDK_InvalidExplicitArguments:
case Sema::TDK_CUDATargetMismatch:
+ case Sema::TDK_NonDependentConversionFailure:
break;
case Sema::TDK_Inconsistent:
@@ -705,6 +709,7 @@
case Sema::TDK_DeducedMismatchNested:
case Sema::TDK_NonDeducedMismatch:
case Sema::TDK_CUDATargetMismatch:
+ case Sema::TDK_NonDependentConversionFailure:
return TemplateParameter();
case Sema::TDK_Incomplete:
@@ -736,6 +741,7 @@
case Sema::TDK_Underqualified:
case Sema::TDK_NonDeducedMismatch:
case Sema::TDK_CUDATargetMismatch:
+ case Sema::TDK_NonDependentConversionFailure:
return nullptr;
case Sema::TDK_DeducedMismatch:
@@ -764,6 +770,7 @@
case Sema::TDK_InvalidExplicitArguments:
case Sema::TDK_SubstitutionFailure:
case Sema::TDK_CUDATargetMismatch:
+ case Sema::TDK_NonDependentConversionFailure:
return nullptr;
case Sema::TDK_Inconsistent:
@@ -792,6 +799,7 @@
case Sema::TDK_InvalidExplicitArguments:
case Sema::TDK_SubstitutionFailure:
case Sema::TDK_CUDATargetMismatch:
+ case Sema::TDK_NonDependentConversionFailure:
return nullptr;
case Sema::TDK_Inconsistent:
@@ -822,8 +830,8 @@
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();
}
@@ -5860,7 +5868,8 @@
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");
@@ -5876,10 +5885,11 @@
// function, e.g., X::f(). We use an empty type for the implied
// object argument (C++ [over.call.func]p3), and the acting context
// is irrelevant.
- AddMethodCandidate(Method, FoundDecl, Method->getParent(),
- QualType(), Expr::Classification::makeSimpleLValue(),
+ AddMethodCandidate(Method, FoundDecl, Method->getParent(), QualType(),
+ Expr::Classification::makeSimpleLValue(),
/*ThisArg=*/nullptr, Args, CandidateSet,
- SuppressUserConversions, PartialOverloading);
+ SuppressUserConversions, PartialOverloading,
+ EarlyConversions);
return;
}
// We treat a constructor like a non-member function, since its object
@@ -5912,7 +5922,8 @@
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;
@@ -5976,7 +5987,10 @@
// 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
@@ -6414,7 +6428,8 @@
Expr *ThisArg, 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");
@@ -6435,7 +6450,8 @@
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;
@@ -6497,7 +6513,10 @@
// 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
@@ -6562,19 +6581,30 @@
// 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, [&](ArrayRef<QualType> ParamTypes) {
+ return CheckNonDependentConversions(
+ MethodTmpl, ParamTypes, 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;
}
@@ -6586,7 +6616,7 @@
AddMethodCandidate(cast<CXXMethodDecl>(Specialization), FoundDecl,
ActingContext, ObjectType, ObjectClassification,
/*ThisArg=*/ThisArg, Args, CandidateSet,
- SuppressUserConversions, PartialOverloading);
+ SuppressUserConversions, PartialOverloading, Conversions);
}
/// \brief Add a C++ function template specialization as a candidate
@@ -6614,19 +6644,29 @@
// 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, [&](ArrayRef<QualType> ParamTypes) {
+ return CheckNonDependentConversions(FunctionTemplate, ParamTypes,
+ 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;
}
@@ -6634,7 +6674,64 @@
// 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<QualType> ParamTypes,
+ 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(ParamTypes.size(), Args.size()); I != N;
+ ++I) {
+ QualType ParamType = ParamTypes[I];
+ 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
@@ -8875,8 +8972,8 @@
// 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]);
@@ -10099,7 +10196,7 @@
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);
@@ -10168,12 +10265,12 @@
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 {
@@ -10186,9 +10283,7 @@
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;
@@ -10208,7 +10303,8 @@
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:
@@ -10311,11 +10407,11 @@
// 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])) {
@@ -10364,7 +10460,8 @@
}
/// 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);
@@ -10377,30 +10474,24 @@
// 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 FunctionProtoType* Proto;
- unsigned ArgIdx = ConvIdx;
+ const FunctionProtoType *Proto;
+ unsigned ArgIdx = 0;
if (Cand->IsSurrogate) {
QualType ConvType
@@ -10408,40 +10499,56 @@
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();
}
}