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Refactor and simplify the computation of implicit conversion sequences 

for reference binding. The code attempted to handle both the
computation of the ICS and the actual conversion, but the latter is an
anachronism: we now use InitializationSequence for that. 

Sema::CheckReferenceInit is now a static function TryReferenceInit
that's only use within overload resolution, and has been simplified
slightly. It still needs to be updated per C++ [over.ics.ref], by
eliminating more of the lvalue/rvalue checks.

llvm-svn: 101136
This commit is contained in:
Douglas Gregor 2010-04-13 16:31:36 +00:00
parent e5e775bc8e
commit 38ae6ab6bc
3 changed files with 334 additions and 493 deletions
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8
clang/lib/Sema/Sema.h
View File

@ -4182,14 +4182,6 @@ public:
QualType T1, QualType T2,
bool& DerivedToBase);
bool CheckReferenceInit(Expr *&simpleInit_or_initList, QualType declType,
SourceLocation DeclLoc,
bool SuppressUserConversions,
bool AllowExplicit,
bool ForceRValue,
ImplicitConversionSequence *ICS = 0,
bool IgnoreBaseAccess = false);
/// CheckCastTypes - Check type constraints for casting between types under
/// C semantics, or forward to CXXCheckCStyleCast in C++.
bool CheckCastTypes(SourceRange TyRange, QualType CastTy, Expr *&CastExpr,

468
clang/lib/Sema/SemaDeclCXX.cpp
View File

@ -4388,474 +4388,6 @@ Sema::CompleteConstructorCall(CXXConstructorDecl *Constructor,
return Invalid;
}
/// CompareReferenceRelationship - Compare the two types T1 and T2 to
/// determine whether they are reference-related,
/// reference-compatible, reference-compatible with added
/// qualification, or incompatible, for use in C++ initialization by
/// reference (C++ [dcl.ref.init]p4). Neither type can be a reference
/// type, and the first type (T1) is the pointee type of the reference
/// type being initialized.
Sema::ReferenceCompareResult
Sema::CompareReferenceRelationship(SourceLocation Loc,
QualType OrigT1, QualType OrigT2,
bool& DerivedToBase) {
assert(!OrigT1->isReferenceType() &&
"T1 must be the pointee type of the reference type");
assert(!OrigT2->isReferenceType() && "T2 cannot be a reference type");
QualType T1 = Context.getCanonicalType(OrigT1);
QualType T2 = Context.getCanonicalType(OrigT2);
Qualifiers T1Quals, T2Quals;
QualType UnqualT1 = Context.getUnqualifiedArrayType(T1, T1Quals);
QualType UnqualT2 = Context.getUnqualifiedArrayType(T2, T2Quals);
// C++ [dcl.init.ref]p4:
// Given types "cv1 T1" and "cv2 T2," "cv1 T1" is
// reference-related to "cv2 T2" if T1 is the same type as T2, or
// T1 is a base class of T2.
if (UnqualT1 == UnqualT2)
DerivedToBase = false;
else if (!RequireCompleteType(Loc, OrigT1, PDiag()) &&
!RequireCompleteType(Loc, OrigT2, PDiag()) &&
IsDerivedFrom(UnqualT2, UnqualT1))
DerivedToBase = true;
else
return Ref_Incompatible;
// At this point, we know that T1 and T2 are reference-related (at
// least).
// If the type is an array type, promote the element qualifiers to the type
// for comparison.
if (isa<ArrayType>(T1) && T1Quals)
T1 = Context.getQualifiedType(UnqualT1, T1Quals);
if (isa<ArrayType>(T2) && T2Quals)
T2 = Context.getQualifiedType(UnqualT2, T2Quals);
// C++ [dcl.init.ref]p4:
// "cv1 T1" is reference-compatible with "cv2 T2" if T1 is
// reference-related to T2 and cv1 is the same cv-qualification
// as, or greater cv-qualification than, cv2. For purposes of
// overload resolution, cases for which cv1 is greater
// cv-qualification than cv2 are identified as
// reference-compatible with added qualification (see 13.3.3.2).
if (T1Quals.getCVRQualifiers() == T2Quals.getCVRQualifiers())
return Ref_Compatible;
else if (T1.isMoreQualifiedThan(T2))
return Ref_Compatible_With_Added_Qualification;
else
return Ref_Related;
}
/// CheckReferenceInit - Check the initialization of a reference
/// variable with the given initializer (C++ [dcl.init.ref]). Init is
/// the initializer (either a simple initializer or an initializer
/// list), and DeclType is the type of the declaration. When ICS is
/// non-null, this routine will compute the implicit conversion
/// sequence according to C++ [over.ics.ref] and will not produce any
/// diagnostics; when ICS is null, it will emit diagnostics when any
/// errors are found. Either way, a return value of true indicates
/// that there was a failure, a return value of false indicates that
/// the reference initialization succeeded.
///
/// When @p SuppressUserConversions, user-defined conversions are
/// suppressed.
/// When @p AllowExplicit, we also permit explicit user-defined
/// conversion functions.
/// When @p ForceRValue, we unconditionally treat the initializer as an rvalue.
/// When @p IgnoreBaseAccess, we don't do access control on to-base conversion.
/// This is used when this is called from a C-style cast.
bool
Sema::CheckReferenceInit(Expr *&Init, QualType DeclType,
SourceLocation DeclLoc,
bool SuppressUserConversions,
bool AllowExplicit, bool ForceRValue,
ImplicitConversionSequence *ICS,
bool IgnoreBaseAccess) {
assert(DeclType->isReferenceType() && "Reference init needs a reference");
QualType T1 = DeclType->getAs<ReferenceType>()->getPointeeType();
QualType T2 = Init->getType();
// If the initializer is the address of an overloaded function, try
// to resolve the overloaded function. If all goes well, T2 is the
// type of the resulting function.
if (Context.getCanonicalType(T2) == Context.OverloadTy) {
DeclAccessPair Found;
FunctionDecl *Fn = ResolveAddressOfOverloadedFunction(Init, DeclType,
ICS != 0, Found);
if (Fn) {
// Since we're performing this reference-initialization for
// real, update the initializer with the resulting function.
if (!ICS) {
if (DiagnoseUseOfDecl(Fn, DeclLoc))
return true;
CheckAddressOfMemberAccess(Init, Found);
Init = FixOverloadedFunctionReference(Init, Found, Fn);
}
T2 = Fn->getType();
}
}
// Compute some basic properties of the types and the initializer.
bool isRValRef = DeclType->isRValueReferenceType();
bool DerivedToBase = false;
Expr::isLvalueResult InitLvalue = ForceRValue ? Expr::LV_InvalidExpression :
Init->isLvalue(Context);
ReferenceCompareResult RefRelationship
= CompareReferenceRelationship(DeclLoc, T1, T2, DerivedToBase);
// Most paths end in a failed conversion.
if (ICS) {
ICS->setBad(BadConversionSequence::no_conversion, Init, DeclType);
}
// C++ [dcl.init.ref]p5:
// A reference to type "cv1 T1" is initialized by an expression
// of type "cv2 T2" as follows:
// -- If the initializer expression
// Rvalue references cannot bind to lvalues (N2812).
// There is absolutely no situation where they can. In particular, note that
// this is ill-formed, even if B has a user-defined conversion to A&&:
// B b;
// A&& r = b;
if (isRValRef && InitLvalue == Expr::LV_Valid) {
if (!ICS)
Diag(DeclLoc, diag::err_lvalue_to_rvalue_ref)
<< Init->getSourceRange();
return true;
}
bool BindsDirectly = false;
// -- is an lvalue (but is not a bit-field), and "cv1 T1" is
// reference-compatible with "cv2 T2," or
//
// Note that the bit-field check is skipped if we are just computing
// the implicit conversion sequence (C++ [over.best.ics]p2).
if (InitLvalue == Expr::LV_Valid && (ICS || !Init->getBitField()) &&
RefRelationship >= Ref_Compatible_With_Added_Qualification) {
BindsDirectly = true;
if (ICS) {
// C++ [over.ics.ref]p1:
// When a parameter of reference type binds directly (8.5.3)
// to an argument expression, the implicit conversion sequence
// is the identity conversion, unless the argument expression
// has a type that is a derived class of the parameter type,
// in which case the implicit conversion sequence is a
// derived-to-base Conversion (13.3.3.1).
ICS->setStandard();
ICS->Standard.First = ICK_Identity;
ICS->Standard.Second = DerivedToBase? ICK_Derived_To_Base : ICK_Identity;
ICS->Standard.Third = ICK_Identity;
ICS->Standard.FromTypePtr = T2.getAsOpaquePtr();
ICS->Standard.setToType(0, T2);
ICS->Standard.setToType(1, T1);
ICS->Standard.setToType(2, T1);
ICS->Standard.ReferenceBinding = true;
ICS->Standard.DirectBinding = true;
ICS->Standard.RRefBinding = false;
ICS->Standard.CopyConstructor = 0;
// Nothing more to do: the inaccessibility/ambiguity check for
// derived-to-base conversions is suppressed when we're
// computing the implicit conversion sequence (C++
// [over.best.ics]p2).
return false;
} else {
// Perform the conversion.
CastExpr::CastKind CK = CastExpr::CK_NoOp;
if (DerivedToBase)
CK = CastExpr::CK_DerivedToBase;
else if(CheckExceptionSpecCompatibility(Init, T1))
return true;
ImpCastExprToType(Init, T1, CK, /*isLvalue=*/true);
}
}
// -- has a class type (i.e., T2 is a class type), where T1 is
// not reference-related to T2, and can be implicitly
// converted to an lvalue of type "cv3 T3," where "cv1 T1"
// is reference-compatible with "cv3 T3" 92) (this
// conversion is selected by enumerating the applicable
// conversion functions (13.3.1.6) and choosing the best
// one through overload resolution (13.3)),
if (!isRValRef && !SuppressUserConversions && T2->isRecordType() &&
!RequireCompleteType(DeclLoc, T2, 0) &&
RefRelationship == Ref_Incompatible) {
CXXRecordDecl *T2RecordDecl
= dyn_cast<CXXRecordDecl>(T2->getAs<RecordType>()->getDecl());
OverloadCandidateSet CandidateSet(DeclLoc);
const UnresolvedSetImpl *Conversions
= T2RecordDecl->getVisibleConversionFunctions();
for (UnresolvedSetImpl::iterator I = Conversions->begin(),
E = Conversions->end(); I != E; ++I) {
NamedDecl *D = *I;
CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
if (isa<UsingShadowDecl>(D))
D = cast<UsingShadowDecl>(D)->getTargetDecl();
FunctionTemplateDecl *ConvTemplate
= dyn_cast<FunctionTemplateDecl>(D);
CXXConversionDecl *Conv;
if (ConvTemplate)
Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
else
Conv = cast<CXXConversionDecl>(D);
// If the conversion function doesn't return a reference type,
// it can't be considered for this conversion.
if (Conv->getConversionType()->isLValueReferenceType() &&
(AllowExplicit || !Conv->isExplicit())) {
if (ConvTemplate)
AddTemplateConversionCandidate(ConvTemplate, I.getPair(), ActingDC,
Init, DeclType, CandidateSet);
else
AddConversionCandidate(Conv, I.getPair(), ActingDC, Init,
DeclType, CandidateSet);
}
}
OverloadCandidateSet::iterator Best;
switch (BestViableFunction(CandidateSet, DeclLoc, Best)) {
case OR_Success:
// C++ [over.ics.ref]p1:
//
// [...] If the parameter binds directly to the result of
// applying a conversion function to the argument
// expression, the implicit conversion sequence is a
// user-defined conversion sequence (13.3.3.1.2), with the
// second standard conversion sequence either an identity
// conversion or, if the conversion function returns an
// entity of a type that is a derived class of the parameter
// type, a derived-to-base Conversion.
if (!Best->FinalConversion.DirectBinding)
break;
// This is a direct binding.
BindsDirectly = true;
if (ICS) {
ICS->setUserDefined();
ICS->UserDefined.Before = Best->Conversions[0].Standard;
ICS->UserDefined.After = Best->FinalConversion;
ICS->UserDefined.ConversionFunction = Best->Function;
ICS->UserDefined.EllipsisConversion = false;
assert(ICS->UserDefined.After.ReferenceBinding &&
ICS->UserDefined.After.DirectBinding &&
"Expected a direct reference binding!");
return false;
} else {
OwningExprResult InitConversion =
BuildCXXCastArgument(DeclLoc, QualType(),
CastExpr::CK_UserDefinedConversion,
cast<CXXMethodDecl>(Best->Function),
Owned(Init));
Init = InitConversion.takeAs<Expr>();
if (CheckExceptionSpecCompatibility(Init, T1))
return true;
ImpCastExprToType(Init, T1, CastExpr::CK_UserDefinedConversion,
/*isLvalue=*/true);
}
break;
case OR_Ambiguous:
if (ICS) {
ICS->setAmbiguous();
for (OverloadCandidateSet::iterator Cand = CandidateSet.begin();
Cand != CandidateSet.end(); ++Cand)
if (Cand->Viable)
ICS->Ambiguous.addConversion(Cand->Function);
break;
}
Diag(DeclLoc, diag::err_ref_init_ambiguous) << DeclType << Init->getType()
<< Init->getSourceRange();
PrintOverloadCandidates(CandidateSet, OCD_ViableCandidates, &Init, 1);
return true;
case OR_No_Viable_Function:
case OR_Deleted:
// There was no suitable conversion, or we found a deleted
// conversion; continue with other checks.
break;
}
}
if (BindsDirectly) {
// C++ [dcl.init.ref]p4:
// [...] In all cases where the reference-related or
// reference-compatible relationship of two types is used to
// establish the validity of a reference binding, and T1 is a
// base class of T2, a program that necessitates such a binding
// is ill-formed if T1 is an inaccessible (clause 11) or
// ambiguous (10.2) base class of T2.
//
// Note that we only check this condition when we're allowed to
// complain about errors, because we should not be checking for
// ambiguity (or inaccessibility) unless the reference binding
// actually happens.
if (DerivedToBase)
return CheckDerivedToBaseConversion(T2, T1, DeclLoc,
Init->getSourceRange(),
IgnoreBaseAccess);
else
return false;
}
// -- Otherwise, the reference shall be to a non-volatile const
// type (i.e., cv1 shall be const), or the reference shall be an
// rvalue reference and the initializer expression shall be an rvalue.
if (!isRValRef && T1.getCVRQualifiers() != Qualifiers::Const) {
if (!ICS)
Diag(DeclLoc, diag::err_not_reference_to_const_init)
<< T1.isVolatileQualified()
<< T1 << int(InitLvalue != Expr::LV_Valid)
<< T2 << Init->getSourceRange();
return true;
}
// -- If the initializer expression is an rvalue, with T2 a
// class type, and "cv1 T1" is reference-compatible with
// "cv2 T2," the reference is bound in one of the
// following ways (the choice is implementation-defined):
//
// -- The reference is bound to the object represented by
// the rvalue (see 3.10) or to a sub-object within that
// object.
//
// -- A temporary of type "cv1 T2" [sic] is created, and
// a constructor is called to copy the entire rvalue
// object into the temporary. The reference is bound to
// the temporary or to a sub-object within the
// temporary.
//
// The constructor that would be used to make the copy
// shall be callable whether or not the copy is actually
// done.
//
// Note that C++0x [dcl.init.ref]p5 takes away this implementation
// freedom, so we will always take the first option and never build
// a temporary in this case. FIXME: We will, however, have to check
// for the presence of a copy constructor in C++98/03 mode.
if (InitLvalue != Expr::LV_Valid && T2->isRecordType() &&
RefRelationship >= Ref_Compatible_With_Added_Qualification) {
if (ICS) {
ICS->setStandard();
ICS->Standard.First = ICK_Identity;
ICS->Standard.Second = DerivedToBase? ICK_Derived_To_Base : ICK_Identity;
ICS->Standard.Third = ICK_Identity;
ICS->Standard.FromTypePtr = T2.getAsOpaquePtr();
ICS->Standard.setToType(0, T2);
ICS->Standard.setToType(1, T1);
ICS->Standard.setToType(2, T1);
ICS->Standard.ReferenceBinding = true;
ICS->Standard.DirectBinding = false;
ICS->Standard.RRefBinding = isRValRef;
ICS->Standard.CopyConstructor = 0;
} else {
CastExpr::CastKind CK = CastExpr::CK_NoOp;
if (DerivedToBase)
CK = CastExpr::CK_DerivedToBase;
else if(CheckExceptionSpecCompatibility(Init, T1))
return true;
ImpCastExprToType(Init, T1, CK, /*isLvalue=*/false);
}
return false;
}
// -- Otherwise, a temporary of type "cv1 T1" is created and
// initialized from the initializer expression using the
// rules for a non-reference copy initialization (8.5). The
// reference is then bound to the temporary. If T1 is
// reference-related to T2, cv1 must be the same
// cv-qualification as, or greater cv-qualification than,
// cv2; otherwise, the program is ill-formed.
if (RefRelationship == Ref_Related) {
// If cv1 == cv2 or cv1 is a greater cv-qualified than cv2, then
// we would be reference-compatible or reference-compatible with
// added qualification. But that wasn't the case, so the reference
// initialization fails.
if (!ICS)
Diag(DeclLoc, diag::err_reference_init_drops_quals)
<< T1 << int(InitLvalue != Expr::LV_Valid)
<< T2 << Init->getSourceRange();
return true;
}
// If at least one of the types is a class type, the types are not
// related, and we aren't allowed any user conversions, the
// reference binding fails. This case is important for breaking
// recursion, since TryImplicitConversion below will attempt to
// create a temporary through the use of a copy constructor.
if (SuppressUserConversions && RefRelationship == Ref_Incompatible &&
(T1->isRecordType() || T2->isRecordType())) {
if (!ICS)
Diag(DeclLoc, diag::err_typecheck_convert_incompatible)
<< DeclType << Init->getType() << AA_Initializing << Init->getSourceRange();
return true;
}
// Actually try to convert the initializer to T1.
if (ICS) {
// C++ [over.ics.ref]p2:
//
// When a parameter of reference type is not bound directly to
// an argument expression, the conversion sequence is the one
// required to convert the argument expression to the
// underlying type of the reference according to
// 13.3.3.1. Conceptually, this conversion sequence corresponds
// to copy-initializing a temporary of the underlying type with
// the argument expression. Any difference in top-level
// cv-qualification is subsumed by the initialization itself
// and does not constitute a conversion.
*ICS = TryImplicitConversion(Init, T1, SuppressUserConversions,
/*AllowExplicit=*/false,
/*ForceRValue=*/false,
/*InOverloadResolution=*/false);
// Of course, that's still a reference binding.
if (ICS->isStandard()) {
ICS->Standard.ReferenceBinding = true;
ICS->Standard.RRefBinding = isRValRef;
} else if (ICS->isUserDefined()) {
ICS->UserDefined.After.ReferenceBinding = true;
ICS->UserDefined.After.RRefBinding = isRValRef;
}
return ICS->isBad();
} else {
ImplicitConversionSequence Conversions;
bool badConversion = PerformImplicitConversion(Init, T1, AA_Initializing,
false, false,
Conversions);
if (badConversion) {
if (Conversions.isAmbiguous()) {
Diag(DeclLoc,
diag::err_lvalue_to_rvalue_ambig_ref) << Init->getSourceRange();
for (int j = Conversions.Ambiguous.conversions().size()-1;
j >= 0; j--) {
FunctionDecl *Func = Conversions.Ambiguous.conversions()[j];
NoteOverloadCandidate(Func);
}
}
else {
if (isRValRef)
Diag(DeclLoc, diag::err_lvalue_to_rvalue_ref)
<< Init->getSourceRange();
else
Diag(DeclLoc, diag::err_invalid_initialization)
<< DeclType << Init->getType() << Init->getSourceRange();
}
}
return badConversion;
}
}
static inline bool
CheckOperatorNewDeleteDeclarationScope(Sema &SemaRef,
const FunctionDecl *FnDecl) {

351
clang/lib/Sema/SemaOverload.cpp
View File

@ -2174,6 +2174,328 @@ Sema::CompareDerivedToBaseConversions(const StandardConversionSequence& SCS1,
return ImplicitConversionSequence::Indistinguishable;
}
/// CompareReferenceRelationship - Compare the two types T1 and T2 to
/// determine whether they are reference-related,
/// reference-compatible, reference-compatible with added
/// qualification, or incompatible, for use in C++ initialization by
/// reference (C++ [dcl.ref.init]p4). Neither type can be a reference
/// type, and the first type (T1) is the pointee type of the reference
/// type being initialized.
Sema::ReferenceCompareResult
Sema::CompareReferenceRelationship(SourceLocation Loc,
QualType OrigT1, QualType OrigT2,
bool& DerivedToBase) {
assert(!OrigT1->isReferenceType() &&
"T1 must be the pointee type of the reference type");
assert(!OrigT2->isReferenceType() && "T2 cannot be a reference type");
QualType T1 = Context.getCanonicalType(OrigT1);
QualType T2 = Context.getCanonicalType(OrigT2);
Qualifiers T1Quals, T2Quals;
QualType UnqualT1 = Context.getUnqualifiedArrayType(T1, T1Quals);
QualType UnqualT2 = Context.getUnqualifiedArrayType(T2, T2Quals);
// C++ [dcl.init.ref]p4:
// Given types "cv1 T1" and "cv2 T2," "cv1 T1" is
// reference-related to "cv2 T2" if T1 is the same type as T2, or
// T1 is a base class of T2.
if (UnqualT1 == UnqualT2)
DerivedToBase = false;
else if (!RequireCompleteType(Loc, OrigT1, PDiag()) &&
!RequireCompleteType(Loc, OrigT2, PDiag()) &&
IsDerivedFrom(UnqualT2, UnqualT1))
DerivedToBase = true;
else
return Ref_Incompatible;
// At this point, we know that T1 and T2 are reference-related (at
// least).
// If the type is an array type, promote the element qualifiers to the type
// for comparison.
if (isa<ArrayType>(T1) && T1Quals)
T1 = Context.getQualifiedType(UnqualT1, T1Quals);
if (isa<ArrayType>(T2) && T2Quals)
T2 = Context.getQualifiedType(UnqualT2, T2Quals);
// C++ [dcl.init.ref]p4:
// "cv1 T1" is reference-compatible with "cv2 T2" if T1 is
// reference-related to T2 and cv1 is the same cv-qualification
// as, or greater cv-qualification than, cv2. For purposes of
// overload resolution, cases for which cv1 is greater
// cv-qualification than cv2 are identified as
// reference-compatible with added qualification (see 13.3.3.2).
if (T1Quals.getCVRQualifiers() == T2Quals.getCVRQualifiers())
return Ref_Compatible;
else if (T1.isMoreQualifiedThan(T2))
return Ref_Compatible_With_Added_Qualification;
else
return Ref_Related;
}
/// \brief Compute an implicit conversion sequence for reference
/// initialization.
static ImplicitConversionSequence
TryReferenceInit(Sema &S, Expr *&Init, QualType DeclType,
SourceLocation DeclLoc,
bool SuppressUserConversions,
bool AllowExplicit, bool ForceRValue) {
assert(DeclType->isReferenceType() && "Reference init needs a reference");
// Most paths end in a failed conversion.
ImplicitConversionSequence ICS;
ICS.setBad(BadConversionSequence::no_conversion, Init, DeclType);
QualType T1 = DeclType->getAs<ReferenceType>()->getPointeeType();
QualType T2 = Init->getType();
// If the initializer is the address of an overloaded function, try
// to resolve the overloaded function. If all goes well, T2 is the
// type of the resulting function.
if (S.Context.getCanonicalType(T2) == S.Context.OverloadTy) {
DeclAccessPair Found;
if (FunctionDecl *Fn = S.ResolveAddressOfOverloadedFunction(Init, DeclType,
false, Found))
T2 = Fn->getType();
}
// Compute some basic properties of the types and the initializer.
bool isRValRef = DeclType->isRValueReferenceType();
bool DerivedToBase = false;
Expr::isLvalueResult InitLvalue = ForceRValue ? Expr::LV_InvalidExpression :
Init->isLvalue(S.Context);
Sema::ReferenceCompareResult RefRelationship
= S.CompareReferenceRelationship(DeclLoc, T1, T2, DerivedToBase);
// C++ [dcl.init.ref]p5:
// A reference to type "cv1 T1" is initialized by an expression
// of type "cv2 T2" as follows:
// -- If the initializer expression
// C++ [over.ics.ref]p3:
// Except for an implicit object parameter, for which see 13.3.1,
// a standard conversion sequence cannot be formed if it requires
// binding an lvalue reference to non-const to an rvalue or
// binding an rvalue reference to an lvalue.
if (isRValRef && InitLvalue == Expr::LV_Valid)
return ICS;
// -- is an lvalue (but is not a bit-field), and "cv1 T1" is
// reference-compatible with "cv2 T2," or
//
// Per C++ [over.ics.ref]p4, we don't check the bit-field property here.
if (InitLvalue == Expr::LV_Valid &&
RefRelationship >= Sema::Ref_Compatible_With_Added_Qualification) {
// C++ [over.ics.ref]p1:
// When a parameter of reference type binds directly (8.5.3)
// to an argument expression, the implicit conversion sequence
// is the identity conversion, unless the argument expression
// has a type that is a derived class of the parameter type,
// in which case the implicit conversion sequence is a
// derived-to-base Conversion (13.3.3.1).
ICS.setStandard();
ICS.Standard.First = ICK_Identity;
ICS.Standard.Second = DerivedToBase? ICK_Derived_To_Base : ICK_Identity;
ICS.Standard.Third = ICK_Identity;
ICS.Standard.FromTypePtr = T2.getAsOpaquePtr();
ICS.Standard.setToType(0, T2);
ICS.Standard.setToType(1, T1);
ICS.Standard.setToType(2, T1);
ICS.Standard.ReferenceBinding = true;
ICS.Standard.DirectBinding = true;
ICS.Standard.RRefBinding = false;
ICS.Standard.CopyConstructor = 0;
// Nothing more to do: the inaccessibility/ambiguity check for
// derived-to-base conversions is suppressed when we're
// computing the implicit conversion sequence (C++
// [over.best.ics]p2).
return ICS;
}
// -- has a class type (i.e., T2 is a class type), where T1 is
// not reference-related to T2, and can be implicitly
// converted to an lvalue of type "cv3 T3," where "cv1 T1"
// is reference-compatible with "cv3 T3" 92) (this
// conversion is selected by enumerating the applicable
// conversion functions (13.3.1.6) and choosing the best
// one through overload resolution (13.3)),
if (!isRValRef && !SuppressUserConversions && T2->isRecordType() &&
!S.RequireCompleteType(DeclLoc, T2, 0) &&
RefRelationship == Sema::Ref_Incompatible) {
CXXRecordDecl *T2RecordDecl
= dyn_cast<CXXRecordDecl>(T2->getAs<RecordType>()->getDecl());
OverloadCandidateSet CandidateSet(DeclLoc);
const UnresolvedSetImpl *Conversions
= T2RecordDecl->getVisibleConversionFunctions();
for (UnresolvedSetImpl::iterator I = Conversions->begin(),
E = Conversions->end(); I != E; ++I) {
NamedDecl *D = *I;
CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
if (isa<UsingShadowDecl>(D))
D = cast<UsingShadowDecl>(D)->getTargetDecl();
FunctionTemplateDecl *ConvTemplate
= dyn_cast<FunctionTemplateDecl>(D);
CXXConversionDecl *Conv;
if (ConvTemplate)
Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
else
Conv = cast<CXXConversionDecl>(D);
// If the conversion function doesn't return a reference type,
// it can't be considered for this conversion.
if (Conv->getConversionType()->isLValueReferenceType() &&
(AllowExplicit || !Conv->isExplicit())) {
if (ConvTemplate)
S.AddTemplateConversionCandidate(ConvTemplate, I.getPair(), ActingDC,
Init, DeclType, CandidateSet);
else
S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Init,
DeclType, CandidateSet);
}
}
OverloadCandidateSet::iterator Best;
switch (S.BestViableFunction(CandidateSet, DeclLoc, Best)) {
case OR_Success:
// C++ [over.ics.ref]p1:
//
// [...] If the parameter binds directly to the result of
// applying a conversion function to the argument
// expression, the implicit conversion sequence is a
// user-defined conversion sequence (13.3.3.1.2), with the
// second standard conversion sequence either an identity
// conversion or, if the conversion function returns an
// entity of a type that is a derived class of the parameter
// type, a derived-to-base Conversion.
if (!Best->FinalConversion.DirectBinding)
break;
ICS.setUserDefined();
ICS.UserDefined.Before = Best->Conversions[0].Standard;
ICS.UserDefined.After = Best->FinalConversion;
ICS.UserDefined.ConversionFunction = Best->Function;
ICS.UserDefined.EllipsisConversion = false;
assert(ICS.UserDefined.After.ReferenceBinding &&
ICS.UserDefined.After.DirectBinding &&
"Expected a direct reference binding!");
return ICS;
case OR_Ambiguous:
ICS.setAmbiguous();
for (OverloadCandidateSet::iterator Cand = CandidateSet.begin();
Cand != CandidateSet.end(); ++Cand)
if (Cand->Viable)
ICS.Ambiguous.addConversion(Cand->Function);
return ICS;
case OR_No_Viable_Function:
case OR_Deleted:
// There was no suitable conversion, or we found a deleted
// conversion; continue with other checks.
break;
}
}
// -- Otherwise, the reference shall be to a non-volatile const
// type (i.e., cv1 shall be const), or the reference shall be an
// rvalue reference and the initializer expression shall be an rvalue.
if (!isRValRef && T1.getCVRQualifiers() != Qualifiers::Const)
return ICS;
// -- If the initializer expression is an rvalue, with T2 a
// class type, and "cv1 T1" is reference-compatible with
// "cv2 T2," the reference is bound in one of the
// following ways (the choice is implementation-defined):
//
// -- The reference is bound to the object represented by
// the rvalue (see 3.10) or to a sub-object within that
// object.
//
// -- A temporary of type "cv1 T2" [sic] is created, and
// a constructor is called to copy the entire rvalue
// object into the temporary. The reference is bound to
// the temporary or to a sub-object within the
// temporary.
//
// The constructor that would be used to make the copy
// shall be callable whether or not the copy is actually
// done.
//
// Note that C++0x [dcl.init.ref]p5 takes away this implementation
// freedom, so we will always take the first option and never build
// a temporary in this case.
if (InitLvalue != Expr::LV_Valid && T2->isRecordType() &&
RefRelationship >= Sema::Ref_Compatible_With_Added_Qualification) {
ICS.setStandard();
ICS.Standard.First = ICK_Identity;
ICS.Standard.Second = DerivedToBase? ICK_Derived_To_Base : ICK_Identity;
ICS.Standard.Third = ICK_Identity;
ICS.Standard.FromTypePtr = T2.getAsOpaquePtr();
ICS.Standard.setToType(0, T2);
ICS.Standard.setToType(1, T1);
ICS.Standard.setToType(2, T1);
ICS.Standard.ReferenceBinding = true;
ICS.Standard.DirectBinding = false;
ICS.Standard.RRefBinding = isRValRef;
ICS.Standard.CopyConstructor = 0;
return ICS;
}
// -- Otherwise, a temporary of type "cv1 T1" is created and
// initialized from the initializer expression using the
// rules for a non-reference copy initialization (8.5). The
// reference is then bound to the temporary. If T1 is
// reference-related to T2, cv1 must be the same
// cv-qualification as, or greater cv-qualification than,
// cv2; otherwise, the program is ill-formed.
if (RefRelationship == Sema::Ref_Related) {
// If cv1 == cv2 or cv1 is a greater cv-qualified than cv2, then
// we would be reference-compatible or reference-compatible with
// added qualification. But that wasn't the case, so the reference
// initialization fails.
return ICS;
}
// If at least one of the types is a class type, the types are not
// related, and we aren't allowed any user conversions, the
// reference binding fails. This case is important for breaking
// recursion, since TryImplicitConversion below will attempt to
// create a temporary through the use of a copy constructor.
if (SuppressUserConversions && RefRelationship == Sema::Ref_Incompatible &&
(T1->isRecordType() || T2->isRecordType()))
return ICS;
// C++ [over.ics.ref]p2:
//
// When a parameter of reference type is not bound directly to
// an argument expression, the conversion sequence is the one
// required to convert the argument expression to the
// underlying type of the reference according to
// 13.3.3.1. Conceptually, this conversion sequence corresponds
// to copy-initializing a temporary of the underlying type with
// the argument expression. Any difference in top-level
// cv-qualification is subsumed by the initialization itself
// and does not constitute a conversion.
ICS = S.TryImplicitConversion(Init, T1, SuppressUserConversions,
/*AllowExplicit=*/false,
/*ForceRValue=*/false,
/*InOverloadResolution=*/false);
// Of course, that's still a reference binding.
if (ICS.isStandard()) {
ICS.Standard.ReferenceBinding = true;
ICS.Standard.RRefBinding = isRValRef;
} else if (ICS.isUserDefined()) {
ICS.UserDefined.After.ReferenceBinding = true;
ICS.UserDefined.After.RRefBinding = isRValRef;
}
return ICS;
}
/// TryCopyInitialization - Try to copy-initialize a value of type
/// ToType from the expression From. Return the implicit conversion
/// sequence required to pass this argument, which may be a bad
@ -2185,23 +2507,18 @@ ImplicitConversionSequence
Sema::TryCopyInitialization(Expr *From, QualType ToType,
bool SuppressUserConversions, bool ForceRValue,
bool InOverloadResolution) {
if (ToType->isReferenceType()) {
ImplicitConversionSequence ICS;
ICS.setBad(BadConversionSequence::no_conversion, From, ToType);
CheckReferenceInit(From, ToType,
/*FIXME:*/From->getLocStart(),
SuppressUserConversions,
/*AllowExplicit=*/false,
ForceRValue,
&ICS);
return ICS;
} else {
return TryImplicitConversion(From, ToType,
SuppressUserConversions,
/*AllowExplicit=*/false,
ForceRValue,
InOverloadResolution);
}
if (ToType->isReferenceType())
return TryReferenceInit(*this, From, ToType,
/*FIXME:*/From->getLocStart(),
SuppressUserConversions,
/*AllowExplicit=*/false,
ForceRValue);
return TryImplicitConversion(From, ToType,
SuppressUserConversions,
/*AllowExplicit=*/false,
ForceRValue,
InOverloadResolution);
}
/// TryObjectArgumentInitialization - Try to initialize the object