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Standard conversion sequences now have a CopyConstructor field, to 

cope with the case where a user-defined conversion is actually a copy
construction, and therefore can be compared against other standard
conversion sequences. While I called this a hack before, now I'm
convinced that it's the right way to go.

Compare overloads based on derived-to-base conversions that invoke
copy constructors. 

Suppress user-defined conversions when attempting to call a
user-defined conversion.

llvm-svn: 58629
This commit is contained in:
Douglas Gregor 2008-11-03 19:09:14 +00:00
parent 4d0549e3be
commit 2fe9883a96
7 changed files with 106 additions and 46 deletions
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17
clang/lib/Sema/Sema.h
View File

@ -370,7 +370,9 @@ private:
/// C++ Overloading.
bool IsOverload(FunctionDecl *New, Decl* OldD,
OverloadedFunctionDecl::function_iterator &MatchedDecl);
ImplicitConversionSequence TryImplicitConversion(Expr* From, QualType ToType);
ImplicitConversionSequence
TryImplicitConversion(Expr* From, QualType ToType,
bool SuppressUserConversions = false);
bool IsStandardConversion(Expr *From, QualType ToType,
StandardConversionSequence& SCS);
bool IsIntegralPromotion(Expr *From, QualType FromType, QualType ToType);
@ -398,7 +400,9 @@ private:
CompareDerivedToBaseConversions(const StandardConversionSequence& SCS1,
const StandardConversionSequence& SCS2);
ImplicitConversionSequence TryCopyInitialization(Expr* From, QualType ToType);
ImplicitConversionSequence
TryCopyInitialization(Expr* From, QualType ToType,
bool SuppressUserConversions = false);
bool PerformCopyInitialization(Expr *&From, QualType ToType,
const char *Flavor);
@ -412,10 +416,12 @@ private:
void AddOverloadCandidate(FunctionDecl *Function,
Expr **Args, unsigned NumArgs,
OverloadCandidateSet& CandidateSet);
OverloadCandidateSet& CandidateSet,
bool SuppressUserConversions = false);
void AddOverloadCandidates(OverloadedFunctionDecl *Ovl,
Expr **Args, unsigned NumArgs,
OverloadCandidateSet& CandidateSet);
OverloadCandidateSet& CandidateSet,
bool SuppressUserConversions = false);
bool isBetterOverloadCandidate(const OverloadCandidate& Cand1,
const OverloadCandidate& Cand2);
OverloadingResult BestViableFunction(OverloadCandidateSet& CandidateSet,
@ -1165,7 +1171,8 @@ private:
bool& DerivedToBase);
bool CheckReferenceInit(Expr *&simpleInit_or_initList, QualType &declType,
ImplicitConversionSequence *ICS = 0);
ImplicitConversionSequence *ICS = 0,
bool SuppressUserConversions = false);
/// CheckCastTypes - Check type constraints for casting between types.
bool CheckCastTypes(SourceRange TyRange, QualType CastTy, Expr *&CastExpr);

8
clang/lib/Sema/SemaDeclCXX.cpp
View File

@ -931,9 +931,13 @@ Sema::CompareReferenceRelationship(QualType T1, QualType T2,
/// 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.
bool
Sema::CheckReferenceInit(Expr *&Init, QualType &DeclType,
ImplicitConversionSequence *ICS) {
ImplicitConversionSequence *ICS,
bool SuppressUserConversions) {
assert(DeclType->isReferenceType() && "Reference init needs a reference");
QualType T1 = DeclType->getAsReferenceType()->getPointeeType();
@ -1114,7 +1118,7 @@ Sema::CheckReferenceInit(Expr *&Init, QualType &DeclType,
/// 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);
*ICS = TryImplicitConversion(Init, T1, SuppressUserConversions);
return ICS->ConversionKind == ImplicitConversionSequence::BadConversion;
} else {
return PerformImplicitConversion(Init, T1);

14
clang/lib/Sema/SemaExprCXX.cpp
View File

@ -929,6 +929,13 @@ Sema::PerformImplicitConversion(Expr *&From, QualType ToType,
// anything here.
QualType FromType = From->getType();
if (SCS.CopyConstructor) {
// FIXME: Create a temporary object by calling the copy
// constructor.
ImpCastExprToType(From, ToType);
return false;
}
// Perform the first implicit conversion.
switch (SCS.First) {
case ICK_Identity:
@ -982,13 +989,6 @@ Sema::PerformImplicitConversion(Expr *&From, QualType ToType,
ImpCastExprToType(From, FromType);
break;
case ICK_Derived_To_Base:
// FIXME: This should never happen. It's a consequence of
// pretending that a user-defined conversion via copy constructor
// is actually a standard conversion.
ImpCastExprToType(From, ToType);
break;
default:
assert(false && "Improper second standard conversion");
break;

91
clang/lib/Sema/SemaOverload.cpp
View File

@ -99,6 +99,7 @@ void StandardConversionSequence::setAsIdentityConversion() {
Deprecated = false;
ReferenceBinding = false;
DirectBinding = false;
CopyConstructor = 0;
}
/// getRank - Retrieve the rank of this standard conversion sequence
@ -174,6 +175,14 @@ void StandardConversionSequence::DebugPrint() const {
fprintf(stderr, " -> ");
}
fprintf(stderr, "%s", GetImplicitConversionName(Second));
if (CopyConstructor) {
fprintf(stderr, " (by copy constructor)");
} else if (DirectBinding) {
fprintf(stderr, " (direct reference binding)");
} else if (ReferenceBinding) {
fprintf(stderr, " (reference binding)");
}
PrintedSomething = true;
}
@ -344,13 +353,18 @@ Sema::IsOverload(FunctionDecl *New, Decl* OldD,
/// it will not produce any diagnostics if no conversion is available,
/// but will instead return an implicit conversion sequence of kind
/// "BadConversion".
///
/// If @p SuppressUserConversions, then user-defined conversions are
/// not permitted.
ImplicitConversionSequence
Sema::TryImplicitConversion(Expr* From, QualType ToType)
Sema::TryImplicitConversion(Expr* From, QualType ToType,
bool SuppressUserConversions)
{
ImplicitConversionSequence ICS;
if (IsStandardConversion(From, ToType, ICS.Standard))
ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
else if (IsUserDefinedConversion(From, ToType, ICS.UserDefined)) {
else if (!SuppressUserConversions &&
IsUserDefinedConversion(From, ToType, ICS.UserDefined)) {
ICS.ConversionKind = ImplicitConversionSequence::UserDefinedConversion;
// C++ [over.ics.user]p4:
// A conversion of an expression of class type to the same class
@ -362,15 +376,13 @@ Sema::TryImplicitConversion(Expr* From, QualType ToType)
if (CXXConstructorDecl *Constructor
= dyn_cast<CXXConstructorDecl>(ICS.UserDefined.ConversionFunction)) {
if (Constructor->isCopyConstructor(Context)) {
// FIXME: This is a temporary hack to give copy-constructor
// calls the appropriate rank (Exact Match or Conversion) by
// making them into standard conversions. To really fix this, we
// need to tweak the rank-checking logic to deal with ranking
// different kinds of user conversions.
// Turn this into a "standard" conversion sequence, so that it
// gets ranked with standard conversion sequences.
ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
ICS.Standard.setAsIdentityConversion();
ICS.Standard.FromTypePtr = From->getType().getAsOpaquePtr();
ICS.Standard.ToTypePtr = ToType.getAsOpaquePtr();
ICS.Standard.CopyConstructor = Constructor;
if (IsDerivedFrom(From->getType().getUnqualifiedType(),
ToType.getUnqualifiedType()))
ICS.Standard.Second = ICK_Derived_To_Base;
@ -403,6 +415,7 @@ Sema::IsStandardConversion(Expr* From, QualType ToType,
// Standard conversions (C++ [conv])
SCS.Deprecated = false;
SCS.FromTypePtr = FromType.getAsOpaquePtr();
SCS.CopyConstructor = 0;
// The first conversion can be an lvalue-to-rvalue conversion,
// array-to-pointer conversion, or function-to-pointer conversion
@ -536,13 +549,6 @@ Sema::IsStandardConversion(Expr* From, QualType ToType,
// [...] Any difference in top-level cv-qualification is
// subsumed by the initialization itself and does not constitute
// a conversion. [...]
// C++ [dcl.init]p14 last bullet:
// [ Note: an expression of type "cv1 T" can initialize an object
// of type “cv2 T” independently of the cv-qualifiers cv1 and
// cv2. -- end note]
//
// FIXME: Where is the normative text?
CanonFrom = Context.getCanonicalType(FromType);
CanonTo = Context.getCanonicalType(ToType);
if (CanonFrom.getUnqualifiedType() == CanonTo.getUnqualifiedType() &&
@ -881,8 +887,8 @@ bool Sema::IsUserDefinedConversion(Expr *From, QualType ToType,
func != Constructors->function_end(); ++func) {
CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(*func);
if (Constructor->isConvertingConstructor())
// FIXME: Suppress user-defined conversions in here!
AddOverloadCandidate(Constructor, &From, 1, CandidateSet);
AddOverloadCandidate(Constructor, &From, 1, CandidateSet,
/*SuppressUserConversions=*/true);
}
}
@ -1259,9 +1265,9 @@ Sema::CompareDerivedToBaseConversions(const StandardConversionSequence& SCS1,
return ImplicitConversionSequence::Worse;
}
// -- binding of an expression of type B to a reference of type
// A& is better than binding an expression of type C to a
// reference of type A&,
// -- binding of an expression of type B to a reference of type
// A& is better than binding an expression of type C to a
// reference of type A&,
if (FromType1.getUnqualifiedType() != FromType2.getUnqualifiedType() &&
ToType1.getUnqualifiedType() == ToType2.getUnqualifiedType()) {
if (IsDerivedFrom(FromType2, FromType1))
@ -1278,9 +1284,26 @@ Sema::CompareDerivedToBaseConversions(const StandardConversionSequence& SCS1,
// FIXME: conversion of B::* to C::* is better than conversion of
// A::* to C::*, and
// FIXME: conversion of C to B is better than conversion of C to A,
if (SCS1.CopyConstructor && SCS2.CopyConstructor &&
SCS1.Second == ICK_Derived_To_Base) {
// -- conversion of C to B is better than conversion of C to A,
if (FromType1.getUnqualifiedType() == FromType2.getUnqualifiedType() &&
ToType1.getUnqualifiedType() != ToType2.getUnqualifiedType()) {
if (IsDerivedFrom(ToType1, ToType2))
return ImplicitConversionSequence::Better;
else if (IsDerivedFrom(ToType2, ToType1))
return ImplicitConversionSequence::Worse;
}
// FIXME: conversion of B to A is better than conversion of C to A.
// -- conversion of B to A is better than conversion of C to A.
if (FromType1.getUnqualifiedType() != FromType2.getUnqualifiedType() &&
ToType1.getUnqualifiedType() == ToType2.getUnqualifiedType()) {
if (IsDerivedFrom(FromType2, FromType1))
return ImplicitConversionSequence::Better;
else if (IsDerivedFrom(FromType1, FromType2))
return ImplicitConversionSequence::Worse;
}
}
return ImplicitConversionSequence::Indistinguishable;
}
@ -1289,9 +1312,11 @@ Sema::CompareDerivedToBaseConversions(const StandardConversionSequence& SCS1,
/// ToType from the expression From. Return the implicit conversion
/// sequence required to pass this argument, which may be a bad
/// conversion sequence (meaning that the argument cannot be passed to
/// a parameter of this type). This is user for argument passing,
/// a parameter of this type). If @p SuppressUserConversions, then we
/// do not permit any user-defined conversion sequences.
ImplicitConversionSequence
Sema::TryCopyInitialization(Expr *From, QualType ToType) {
Sema::TryCopyInitialization(Expr *From, QualType ToType,
bool SuppressUserConversions) {
if (!getLangOptions().CPlusPlus) {
// In C, copy initialization is the same as performing an assignment.
AssignConvertType ConvTy =
@ -1305,10 +1330,10 @@ Sema::TryCopyInitialization(Expr *From, QualType ToType) {
return ICS;
} else if (ToType->isReferenceType()) {
ImplicitConversionSequence ICS;
CheckReferenceInit(From, ToType, &ICS);
CheckReferenceInit(From, ToType, &ICS, SuppressUserConversions);
return ICS;
} else {
return TryImplicitConversion(From, ToType);
return TryImplicitConversion(From, ToType, SuppressUserConversions);
}
}
@ -1340,11 +1365,14 @@ bool Sema::PerformCopyInitialization(Expr *&From, QualType ToType,
}
/// AddOverloadCandidate - Adds the given function to the set of
/// candidate functions, using the given function call arguments.
/// candidate functions, using the given function call arguments. If
/// @p SuppressUserConversions, then don't allow user-defined
/// conversions via constructors or conversion operators.
void
Sema::AddOverloadCandidate(FunctionDecl *Function,
Expr **Args, unsigned NumArgs,
OverloadCandidateSet& CandidateSet)
OverloadCandidateSet& CandidateSet,
bool SuppressUserConversions)
{
const FunctionTypeProto* Proto
= dyn_cast<FunctionTypeProto>(Function->getType()->getAsFunctionType());
@ -1389,7 +1417,8 @@ Sema::AddOverloadCandidate(FunctionDecl *Function,
// parameter of F.
QualType ParamType = Proto->getArgType(ArgIdx);
Candidate.Conversions[ArgIdx]
= TryCopyInitialization(Args[ArgIdx], ParamType);
= TryCopyInitialization(Args[ArgIdx], ParamType,
SuppressUserConversions);
if (Candidate.Conversions[ArgIdx].ConversionKind
== ImplicitConversionSequence::BadConversion)
Candidate.Viable = false;
@ -1408,11 +1437,13 @@ Sema::AddOverloadCandidate(FunctionDecl *Function,
void
Sema::AddOverloadCandidates(OverloadedFunctionDecl *Ovl,
Expr **Args, unsigned NumArgs,
OverloadCandidateSet& CandidateSet)
OverloadCandidateSet& CandidateSet,
bool SuppressUserConversions)
{
for (OverloadedFunctionDecl::function_iterator Func = Ovl->function_begin();
Func != Ovl->function_end(); ++Func)
AddOverloadCandidate(*Func, Args, NumArgs, CandidateSet);
AddOverloadCandidate(*Func, Args, NumArgs, CandidateSet,
SuppressUserConversions);
}
/// isBetterOverloadCandidate - Determines whether the first overload

8
clang/lib/Sema/SemaOverload.h
View File

@ -18,6 +18,7 @@
#include "llvm/ADT/SmallVector.h"
namespace clang {
class CXXConstructorDecl;
class FunctionDecl;
/// ImplicitConversionKind - The kind of implicit conversion used to
@ -114,6 +115,13 @@ namespace clang {
/// is an opaque pointer that can be translated into a QualType.
void *ToTypePtr;
/// CopyConstructor - The copy constructor that is used to perform
/// this conversion, when the conversion is actually just the
/// initialization of an object via copy constructor. Such
/// conversions are either identity conversions or derived-to-base
/// conversions.
CXXConstructorDecl *CopyConstructor;
void setAsIdentityConversion();
ImplicitConversionRank getRank() const;
bool isPointerConversionToBool() const;

4
clang/test/SemaCXX/converting-constructor.cpp
View File

@ -1,4 +1,4 @@
// RUN: clang -fsyntax-only %s
// RUN: clang -fsyntax-only -verify %s
class Z { };
class Y {
@ -18,6 +18,6 @@ void g(short s, Y y, Z z) {
f(s);
f(1.0f);
f(y);
f(z); // expected-error{{incompatible}}
f(z); // expected-error{{incompatible type passing 'class Z', expected 'class X'}}
}

10
clang/test/SemaCXX/overload-call-copycon.cpp
View File

@ -36,3 +36,13 @@ void test_copycon3(B b, const B bc) {
int& i1 = copycon3(b);
float& f1 = copycon3(bc);
}
class C : public B { };
float& copycon4(A a);
int& copycon4(B b);
void test_copycon4(C c) {
int& i = copycon4(c);
};