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Revert "[SemaCXX] Implement CWG2137 (list-initialization from objects…
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… of the same type) (#77768)"

This reverts commit 924701311aa79180e86ad8ce43d253f27d25ec7d. Causes compilation
errors on valid code, see
llvm/llvm-project#77768 (comment).
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@DimitryAndric
DimitryAndric committed Jan 28, 2024
1 parent 1600828 commit 17a3106
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Showing 2 changed files with 20 additions and 58 deletions.
40 changes: 10 additions & 30 deletions contrib/llvm-project/clang/lib/Sema/SemaInit.cpp
View file
Expand Up @@ -4200,7 +4200,7 @@ static OverloadingResult ResolveConstructorOverload(
/// \param IsListInit Is this list-initialization?
/// \param IsInitListCopy Is this non-list-initialization resulting from a
/// list-initialization from {x} where x is the same
/// aggregate type as the entity?
/// type as the entity?
static void TryConstructorInitialization(Sema &S,
const InitializedEntity &Entity,
const InitializationKind &Kind,
Expand Down Expand Up @@ -4230,14 +4230,6 @@ static void TryConstructorInitialization(Sema &S,
Entity.getKind() !=
InitializedEntity::EK_LambdaToBlockConversionBlockElement);

bool CopyElisionPossible = false;
auto ElideConstructor = [&] {
// Convert qualifications if necessary.
Sequence.AddQualificationConversionStep(DestType, VK_PRValue);
if (ILE)
Sequence.RewrapReferenceInitList(DestType, ILE);
};

// C++17 [dcl.init]p17:
// - If the initializer expression is a prvalue and the cv-unqualified
// version of the source type is the same class as the class of the
Expand All @@ -4250,17 +4242,11 @@ static void TryConstructorInitialization(Sema &S,
if (S.getLangOpts().CPlusPlus17 && !RequireActualConstructor &&
UnwrappedArgs.size() == 1 && UnwrappedArgs[0]->isPRValue() &&
S.Context.hasSameUnqualifiedType(UnwrappedArgs[0]->getType(), DestType)) {
if (ILE && !DestType->isAggregateType()) {
// CWG2311: T{ prvalue_of_type_T } is not eligible for copy elision
// Make this an elision if this won't call an initializer-list
// constructor. (Always on an aggregate type or check constructors first.)
assert(!IsInitListCopy &&
"IsInitListCopy only possible with aggregate types");
CopyElisionPossible = true;
} else {
ElideConstructor();
return;
}
// Convert qualifications if necessary.
Sequence.AddQualificationConversionStep(DestType, VK_PRValue);
if (ILE)
Sequence.RewrapReferenceInitList(DestType, ILE);
return;
}

const RecordType *DestRecordType = DestType->getAs<RecordType>();
Expand Down Expand Up @@ -4305,12 +4291,6 @@ static void TryConstructorInitialization(Sema &S,
S, Kind.getLocation(), Args, CandidateSet, DestType, Ctors, Best,
CopyInitialization, AllowExplicit,
/*OnlyListConstructors=*/true, IsListInit, RequireActualConstructor);

if (CopyElisionPossible && Result == OR_No_Viable_Function) {
// No initializer list candidate
ElideConstructor();
return;
}
}

// C++11 [over.match.list]p1:
Expand Down Expand Up @@ -4592,9 +4572,9 @@ static void TryListInitialization(Sema &S,
return;
}

// C++11 [dcl.init.list]p3, per DR1467 and DR2137:
// - If T is an aggregate class and the initializer list has a single element
// of type cv U, where U is T or a class derived from T, the object is
// C++11 [dcl.init.list]p3, per DR1467:
// - If T is a class type and the initializer list has a single element of
// type cv U, where U is T or a class derived from T, the object is
// initialized from that element (by copy-initialization for
// copy-list-initialization, or by direct-initialization for
// direct-list-initialization).
Expand All @@ -4605,7 +4585,7 @@ static void TryListInitialization(Sema &S,
// - Otherwise, if T is an aggregate, [...] (continue below).
if (S.getLangOpts().CPlusPlus11 && InitList->getNumInits() == 1 &&
!IsDesignatedInit) {
if (DestType->isRecordType() && DestType->isAggregateType()) {
if (DestType->isRecordType()) {
QualType InitType = InitList->getInit(0)->getType();
if (S.Context.hasSameUnqualifiedType(InitType, DestType) ||
S.IsDerivedFrom(InitList->getBeginLoc(), InitType, DestType)) {
Expand Down
38 changes: 10 additions & 28 deletions contrib/llvm-project/clang/lib/Sema/SemaOverload.cpp
View file
Expand Up @@ -1568,37 +1568,19 @@ TryUserDefinedConversion(Sema &S, Expr *From, QualType ToType,
// called for those cases.
if (CXXConstructorDecl *Constructor
= dyn_cast<CXXConstructorDecl>(ICS.UserDefined.ConversionFunction)) {
QualType FromType;
SourceLocation FromLoc;
// C++11 [over.ics.list]p6, per DR2137:
// C++17 [over.ics.list]p6:
// If C is not an initializer-list constructor and the initializer list
// has a single element of type cv U, where U is X or a class derived
// from X, the implicit conversion sequence has Exact Match rank if U is
// X, or Conversion rank if U is derived from X.
if (const auto *InitList = dyn_cast<InitListExpr>(From);
InitList && InitList->getNumInits() == 1 &&
!S.isInitListConstructor(Constructor)) {
const Expr *SingleInit = InitList->getInit(0);
FromType = SingleInit->getType();
FromLoc = SingleInit->getBeginLoc();
} else {
FromType = From->getType();
FromLoc = From->getBeginLoc();
}
QualType FromCanon =
S.Context.getCanonicalType(FromType.getUnqualifiedType());
QualType FromCanon
= S.Context.getCanonicalType(From->getType().getUnqualifiedType());
QualType ToCanon
= S.Context.getCanonicalType(ToType).getUnqualifiedType();
if (Constructor->isCopyConstructor() &&
(FromCanon == ToCanon ||
S.IsDerivedFrom(FromLoc, FromCanon, ToCanon))) {
S.IsDerivedFrom(From->getBeginLoc(), FromCanon, ToCanon))) {
// Turn this into a "standard" conversion sequence, so that it
// gets ranked with standard conversion sequences.
DeclAccessPair Found = ICS.UserDefined.FoundConversionFunction;
ICS.setStandard();
ICS.Standard.setAsIdentityConversion();
ICS.Standard.setFromType(FromType);
ICS.Standard.setFromType(From->getType());
ICS.Standard.setAllToTypes(ToType);
ICS.Standard.CopyConstructor = Constructor;
ICS.Standard.FoundCopyConstructor = Found;
Expand Down Expand Up @@ -5324,18 +5306,18 @@ TryListConversion(Sema &S, InitListExpr *From, QualType ToType,
IsDesignatedInit)
return Result;

// Per DR1467 and DR2137:
// If the parameter type is an aggregate class X and the initializer list
// has a single element of type cv U, where U is X or a class derived from
// X, the implicit conversion sequence is the one required to convert the
// element to the parameter type.
// Per DR1467:
// If the parameter type is a class X and the initializer list has a single
// element of type cv U, where U is X or a class derived from X, the
// implicit conversion sequence is the one required to convert the element
// to the parameter type.
//
// Otherwise, if the parameter type is a character array [... ]
// and the initializer list has a single element that is an
// appropriately-typed string literal (8.5.2 [dcl.init.string]), the
// implicit conversion sequence is the identity conversion.
if (From->getNumInits() == 1 && !IsDesignatedInit) {
if (ToType->isRecordType() && ToType->isAggregateType()) {
if (ToType->isRecordType()) {
QualType InitType = From->getInit(0)->getType();
if (S.Context.hasSameUnqualifiedType(InitType, ToType) ||
S.IsDerivedFrom(From->getBeginLoc(), InitType, ToType))
Expand Down

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