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//===- Overload.h - C++ Overloading -----------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file defines the data structures and types used in C++
// overload resolution.
#include "clang/AST/Decl.h"
#include "clang/AST/DeclAccessPair.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/Type.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Sema/SemaFixItUtils.h"
#include "clang/Sema/TemplateDeduction.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/AlignOf.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <utility>
namespace clang {
class APValue;
class ASTContext;
class Sema;
/// OverloadingResult - Capture the result of performing overload
/// resolution.
enum OverloadingResult {
/// Overload resolution succeeded.
/// No viable function found.
/// Ambiguous candidates found.
/// Succeeded, but refers to a deleted function.
enum OverloadCandidateDisplayKind {
/// Requests that all candidates be shown. Viable candidates will
/// be printed first.
/// Requests that only viable candidates be shown.
/// The parameter ordering that will be used for the candidate. This is
/// used to represent C++20 binary operator rewrites that reverse the order
/// of the arguments. If the parameter ordering is Reversed, the Args list is
/// reversed (but obviously the ParamDecls for the function are not).
/// After forming an OverloadCandidate with reversed parameters, the list
/// of conversions will (as always) be indexed by argument, so will be
/// in reverse parameter order.
enum class OverloadCandidateParamOrder : char { Normal, Reversed };
/// The kinds of rewrite we perform on overload candidates. Note that the
/// values here are chosen to serve as both bitflags and as a rank (lower
/// values are preferred by overload resolution).
enum OverloadCandidateRewriteKind : unsigned {
/// Candidate is not a rewritten candidate.
CRK_None = 0x0,
/// Candidate is a rewritten candidate with a different operator name.
CRK_DifferentOperator = 0x1,
/// Candidate is a rewritten candidate with a reversed order of parameters.
CRK_Reversed = 0x2,
/// ImplicitConversionKind - The kind of implicit conversion used to
/// convert an argument to a parameter's type. The enumerator values
/// match with the table titled 'Conversions' in [over.ics.scs] and are listed
/// such that better conversion kinds have smaller values.
enum ImplicitConversionKind {
/// Identity conversion (no conversion)
ICK_Identity = 0,
/// Lvalue-to-rvalue conversion (C++ [conv.lval])
/// Array-to-pointer conversion (C++ [conv.array])
/// Function-to-pointer (C++ [conv.array])
/// Function pointer conversion (C++17 [conv.fctptr])
/// Qualification conversions (C++ [conv.qual])
/// Integral promotions (C++ [conv.prom])
/// Floating point promotions (C++ [conv.fpprom])
/// Complex promotions (Clang extension)
/// Integral conversions (C++ [conv.integral])
/// Floating point conversions (C++ [conv.double]
/// Complex conversions (C99
/// Floating-integral conversions (C++ [conv.fpint])
/// Pointer conversions (C++ [conv.ptr])
/// Pointer-to-member conversions (C++ [conv.mem])
/// Boolean conversions (C++ [conv.bool])
/// Conversions between compatible types in C99
/// Derived-to-base (C++ [])
/// Vector conversions
/// A vector splat from an arithmetic type
/// Complex-real conversions (C99
/// Block Pointer conversions
/// Transparent Union Conversions
/// Objective-C ARC writeback conversion
/// Zero constant to event (OpenCL1.2 6.12.10)
/// Zero constant to queue
/// Conversions allowed in C, but not C++
/// C-only conversion between pointers with incompatible types
/// The number of conversion kinds
/// ImplicitConversionRank - The rank of an implicit conversion
/// kind. The enumerator values match with Table 9 of (C++
/// and are listed such that better conversion ranks
/// have smaller values.
enum ImplicitConversionRank {
/// Exact Match
ICR_Exact_Match = 0,
/// Promotion
/// Conversion
/// OpenCL Scalar Widening
/// Complex <-> Real conversion
/// ObjC ARC writeback conversion
/// Conversion only allowed in the C standard (e.g. void* to char*).
/// Conversion not allowed by the C standard, but that we accept as an
/// extension anyway.
ImplicitConversionRank GetConversionRank(ImplicitConversionKind Kind);
/// NarrowingKind - The kind of narrowing conversion being performed by a
/// standard conversion sequence according to C++11 [dcl.init.list]p7.
enum NarrowingKind {
/// Not a narrowing conversion.
/// A narrowing conversion by virtue of the source and destination types.
/// A narrowing conversion, because a constant expression got narrowed.
/// A narrowing conversion, because a non-constant-expression variable might
/// have got narrowed.
/// Cannot tell whether this is a narrowing conversion because the
/// expression is value-dependent.
/// StandardConversionSequence - represents a standard conversion
/// sequence (C++ A standard conversion sequence
/// contains between zero and three conversions. If a particular
/// conversion is not needed, it will be set to the identity conversion
/// (ICK_Identity). Note that the three conversions are
/// specified as separate members (rather than in an array) so that
/// we can keep the size of a standard conversion sequence to a
/// single word.
class StandardConversionSequence {
/// First -- The first conversion can be an lvalue-to-rvalue
/// conversion, array-to-pointer conversion, or
/// function-to-pointer conversion.
ImplicitConversionKind First : 8;
/// Second - The second conversion can be an integral promotion,
/// floating point promotion, integral conversion, floating point
/// conversion, floating-integral conversion, pointer conversion,
/// pointer-to-member conversion, or boolean conversion.
ImplicitConversionKind Second : 8;
/// Third - The third conversion can be a qualification conversion
/// or a function conversion.
ImplicitConversionKind Third : 8;
/// Whether this is the deprecated conversion of a
/// string literal to a pointer to non-const character data
/// (C++ 4.2p2).
unsigned DeprecatedStringLiteralToCharPtr : 1;
/// Whether the qualification conversion involves a change in the
/// Objective-C lifetime (for automatic reference counting).
unsigned QualificationIncludesObjCLifetime : 1;
/// IncompatibleObjC - Whether this is an Objective-C conversion
/// that we should warn about (if we actually use it).
unsigned IncompatibleObjC : 1;
/// ReferenceBinding - True when this is a reference binding
/// (C++ [over.ics.ref]).
unsigned ReferenceBinding : 1;
/// DirectBinding - True when this is a reference binding that is a
/// direct binding (C++ [dcl.init.ref]).
unsigned DirectBinding : 1;
/// Whether this is an lvalue reference binding (otherwise, it's
/// an rvalue reference binding).
unsigned IsLvalueReference : 1;
/// Whether we're binding to a function lvalue.
unsigned BindsToFunctionLvalue : 1;
/// Whether we're binding to an rvalue.
unsigned BindsToRvalue : 1;
/// Whether this binds an implicit object argument to a
/// non-static member function without a ref-qualifier.
unsigned BindsImplicitObjectArgumentWithoutRefQualifier : 1;
/// Whether this binds a reference to an object with a different
/// Objective-C lifetime qualifier.
unsigned ObjCLifetimeConversionBinding : 1;
/// FromType - The type that this conversion is converting
/// from. This is an opaque pointer that can be translated into a
/// QualType.
void *FromTypePtr;
/// ToType - The types that this conversion is converting to in
/// each step. This is an opaque pointer that can be translated
/// into a QualType.
void *ToTypePtrs[3];
/// 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;
DeclAccessPair FoundCopyConstructor;
void setFromType(QualType T) { FromTypePtr = T.getAsOpaquePtr(); }
void setToType(unsigned Idx, QualType T) {
assert(Idx < 3 && "To type index is out of range");
ToTypePtrs[Idx] = T.getAsOpaquePtr();
void setAllToTypes(QualType T) {
ToTypePtrs[0] = T.getAsOpaquePtr();
ToTypePtrs[1] = ToTypePtrs[0];
ToTypePtrs[2] = ToTypePtrs[0];
QualType getFromType() const {
return QualType::getFromOpaquePtr(FromTypePtr);
QualType getToType(unsigned Idx) const {
assert(Idx < 3 && "To type index is out of range");
return QualType::getFromOpaquePtr(ToTypePtrs[Idx]);
void setAsIdentityConversion();
bool isIdentityConversion() const {
return Second == ICK_Identity && Third == ICK_Identity;
ImplicitConversionRank getRank() const;
getNarrowingKind(ASTContext &Context, const Expr *Converted,
APValue &ConstantValue, QualType &ConstantType,
bool IgnoreFloatToIntegralConversion = false) const;
bool isPointerConversionToBool() const;
bool isPointerConversionToVoidPointer(ASTContext& Context) const;
void dump() const;
/// UserDefinedConversionSequence - Represents a user-defined
/// conversion sequence (C++
struct UserDefinedConversionSequence {
/// Represents the standard conversion that occurs before
/// the actual user-defined conversion.
/// C++11
/// If the user-defined conversion is specified by a constructor
/// (12.3.1), the initial standard conversion sequence converts
/// the source type to the type required by the argument of the
/// constructor. If the user-defined conversion is specified by
/// a conversion function (12.3.2), the initial standard
/// conversion sequence converts the source type to the implicit
/// object parameter of the conversion function.
StandardConversionSequence Before;
/// EllipsisConversion - When this is true, it means user-defined
/// conversion sequence starts with a ... (ellipsis) conversion, instead of
/// a standard conversion. In this case, 'Before' field must be ignored.
// FIXME. I much rather put this as the first field. But there seems to be
// a gcc code gen. bug which causes a crash in a test. Putting it here seems
// to work around the crash.
bool EllipsisConversion : 1;
/// HadMultipleCandidates - When this is true, it means that the
/// conversion function was resolved from an overloaded set having
/// size greater than 1.
bool HadMultipleCandidates : 1;
/// After - Represents the standard conversion that occurs after
/// the actual user-defined conversion.
StandardConversionSequence After;
/// ConversionFunction - The function that will perform the
/// user-defined conversion. Null if the conversion is an
/// aggregate initialization from an initializer list.
FunctionDecl* ConversionFunction;
/// The declaration that we found via name lookup, which might be
/// the same as \c ConversionFunction or it might be a using declaration
/// that refers to \c ConversionFunction.
DeclAccessPair FoundConversionFunction;
void dump() const;
/// Represents an ambiguous user-defined conversion sequence.
struct AmbiguousConversionSequence {
using ConversionSet =
SmallVector<std::pair<NamedDecl *, FunctionDecl *>, 4>;
void *FromTypePtr;
void *ToTypePtr;
char Buffer[sizeof(ConversionSet)];
QualType getFromType() const {
return QualType::getFromOpaquePtr(FromTypePtr);
QualType getToType() const {
return QualType::getFromOpaquePtr(ToTypePtr);
void setFromType(QualType T) { FromTypePtr = T.getAsOpaquePtr(); }
void setToType(QualType T) { ToTypePtr = T.getAsOpaquePtr(); }
ConversionSet &conversions() {
return *reinterpret_cast<ConversionSet*>(Buffer);
const ConversionSet &conversions() const {
return *reinterpret_cast<const ConversionSet*>(Buffer);
void addConversion(NamedDecl *Found, FunctionDecl *D) {
conversions().push_back(std::make_pair(Found, D));
using iterator = ConversionSet::iterator;
iterator begin() { return conversions().begin(); }
iterator end() { return conversions().end(); }
using const_iterator = ConversionSet::const_iterator;
const_iterator begin() const { return conversions().begin(); }
const_iterator end() const { return conversions().end(); }
void construct();
void destruct();
void copyFrom(const AmbiguousConversionSequence &);
/// BadConversionSequence - Records information about an invalid
/// conversion sequence.
struct BadConversionSequence {
enum FailureKind {
// This can be null, e.g. for implicit object arguments.
Expr *FromExpr;
FailureKind Kind;
// The type we're converting from (an opaque QualType).
void *FromTy;
// The type we're converting to (an opaque QualType).
void *ToTy;
void init(FailureKind K, Expr *From, QualType To) {
init(K, From->getType(), To);
FromExpr = From;
void init(FailureKind K, QualType From, QualType To) {
Kind = K;
FromExpr = nullptr;
QualType getFromType() const { return QualType::getFromOpaquePtr(FromTy); }
QualType getToType() const { return QualType::getFromOpaquePtr(ToTy); }
void setFromExpr(Expr *E) {
FromExpr = E;
void setFromType(QualType T) { FromTy = T.getAsOpaquePtr(); }
void setToType(QualType T) { ToTy = T.getAsOpaquePtr(); }
/// ImplicitConversionSequence - Represents an implicit conversion
/// sequence, which may be a standard conversion sequence
/// (C++, user-defined conversion sequence (C++,
/// or an ellipsis conversion sequence (C++
class ImplicitConversionSequence {
/// Kind - The kind of implicit conversion sequence. BadConversion
/// specifies that there is no conversion from the source type to
/// the target type. AmbiguousConversion represents the unique
/// ambiguous conversion (C++0x []p10).
enum Kind {
StandardConversion = 0,
enum {
Uninitialized = BadConversion + 1
/// ConversionKind - The kind of implicit conversion sequence.
unsigned ConversionKind : 30;
/// Whether the target is really a std::initializer_list, and the
/// sequence only represents the worst element conversion.
unsigned StdInitializerListElement : 1;
void setKind(Kind K) {
ConversionKind = K;
void destruct() {
if (ConversionKind == AmbiguousConversion) Ambiguous.destruct();
union {
/// When ConversionKind == StandardConversion, provides the
/// details of the standard conversion sequence.
StandardConversionSequence Standard;
/// When ConversionKind == UserDefinedConversion, provides the
/// details of the user-defined conversion sequence.
UserDefinedConversionSequence UserDefined;
/// When ConversionKind == AmbiguousConversion, provides the
/// details of the ambiguous conversion.
AmbiguousConversionSequence Ambiguous;
/// When ConversionKind == BadConversion, provides the details
/// of the bad conversion.
BadConversionSequence Bad;
: ConversionKind(Uninitialized), StdInitializerListElement(false) {
ImplicitConversionSequence(const ImplicitConversionSequence &Other)
: ConversionKind(Other.ConversionKind),
StdInitializerListElement(Other.StdInitializerListElement) {
switch (ConversionKind) {
case Uninitialized: break;
case StandardConversion: Standard = Other.Standard; break;
case UserDefinedConversion: UserDefined = Other.UserDefined; break;
case AmbiguousConversion: Ambiguous.copyFrom(Other.Ambiguous); break;
case EllipsisConversion: break;
case BadConversion: Bad = Other.Bad; break;
ImplicitConversionSequence &
operator=(const ImplicitConversionSequence &Other) {
new (this) ImplicitConversionSequence(Other);
return *this;
~ImplicitConversionSequence() {
Kind getKind() const {
assert(isInitialized() && "querying uninitialized conversion");
return Kind(ConversionKind);
/// Return a ranking of the implicit conversion sequence
/// kind, where smaller ranks represent better conversion
/// sequences.
/// In particular, this routine gives user-defined conversion
/// sequences and ambiguous conversion sequences the same rank,
/// per C++ []p10.
unsigned getKindRank() const {
switch (getKind()) {
case StandardConversion:
return 0;
case UserDefinedConversion:
case AmbiguousConversion:
return 1;
case EllipsisConversion:
return 2;
case BadConversion:
return 3;
llvm_unreachable("Invalid ImplicitConversionSequence::Kind!");
bool isBad() const { return getKind() == BadConversion; }
bool isStandard() const { return getKind() == StandardConversion; }
bool isEllipsis() const { return getKind() == EllipsisConversion; }
bool isAmbiguous() const { return getKind() == AmbiguousConversion; }
bool isUserDefined() const { return getKind() == UserDefinedConversion; }
bool isFailure() const { return isBad() || isAmbiguous(); }
/// Determines whether this conversion sequence has been
/// initialized. Most operations should never need to query
/// uninitialized conversions and should assert as above.
bool isInitialized() const { return ConversionKind != Uninitialized; }
/// Sets this sequence as a bad conversion for an explicit argument.
void setBad(BadConversionSequence::FailureKind Failure,
Expr *FromExpr, QualType ToType) {
Bad.init(Failure, FromExpr, ToType);
/// Sets this sequence as a bad conversion for an implicit argument.
void setBad(BadConversionSequence::FailureKind Failure,
QualType FromType, QualType ToType) {
Bad.init(Failure, FromType, ToType);
void setStandard() { setKind(StandardConversion); }
void setEllipsis() { setKind(EllipsisConversion); }
void setUserDefined() { setKind(UserDefinedConversion); }
void setAmbiguous() {
if (ConversionKind == AmbiguousConversion) return;
ConversionKind = AmbiguousConversion;
void setAsIdentityConversion(QualType T) {
/// Whether the target is really a std::initializer_list, and the
/// sequence only represents the worst element conversion.
bool isStdInitializerListElement() const {
return StdInitializerListElement;
void setStdInitializerListElement(bool V = true) {
StdInitializerListElement = V;
// The result of a comparison between implicit conversion
// sequences. Use Sema::CompareImplicitConversionSequences to
// actually perform the comparison.
enum CompareKind {
Better = -1,
Indistinguishable = 0,
Worse = 1
void DiagnoseAmbiguousConversion(Sema &S,
SourceLocation CaretLoc,
const PartialDiagnostic &PDiag) const;
void dump() const;
enum OverloadFailureKind {
/// This conversion candidate was not considered because it
/// duplicates the work of a trivial or derived-to-base
/// conversion.
/// This conversion candidate was not considered because it is
/// an illegal instantiation of a constructor temploid: it is
/// callable with one argument, we only have one argument, and
/// its first parameter type is exactly the type of the class.
/// Defining such a constructor directly is illegal, and
/// template-argument deduction is supposed to ignore such
/// instantiations, but we can still get one with the right
/// kind of implicit instantiation.
/// This conversion candidate is not viable because its result
/// type is not implicitly convertible to the desired type.
/// This conversion function template specialization candidate is not
/// viable because the final conversion was not an exact match.
/// (CUDA) This candidate was not viable because the callee
/// was not accessible from the caller's target (i.e. host->device,
/// global->host, device->host).
/// This candidate function was not viable because an enable_if
/// attribute disabled it.
/// This candidate constructor or conversion fonction
/// is used implicitly but the explicit(bool) specifier
/// was resolved to true
/// This candidate was not viable because its address could not be taken.
/// This candidate was not viable because its OpenCL extension is disabled.
/// This inherited constructor is not viable because it would slice the
/// argument.
/// This candidate was not viable because it is a non-default multiversioned
/// function.
/// This constructor/conversion candidate fail due to an address space
/// mismatch between the object being constructed and the overload
/// candidate.
/// A list of implicit conversion sequences for the arguments of an
/// OverloadCandidate.
using ConversionSequenceList =
/// OverloadCandidate - A single candidate in an overload set (C++ 13.3).
struct OverloadCandidate {
/// Function - The actual function that this candidate
/// represents. When NULL, this is a built-in candidate
/// (C++ [over.oper]) or a surrogate for a conversion to a
/// function pointer or reference (C++ []).
FunctionDecl *Function;
/// FoundDecl - The original declaration that was looked up /
/// invented / otherwise found, together with its access.
/// Might be a UsingShadowDecl or a FunctionTemplateDecl.
DeclAccessPair FoundDecl;
/// BuiltinParamTypes - Provides the parameter types of a built-in overload
/// candidate. Only valid when Function is NULL.
QualType BuiltinParamTypes[3];
/// Surrogate - The conversion function for which this candidate
/// is a surrogate, but only if IsSurrogate is true.
CXXConversionDecl *Surrogate;
/// The conversion sequences used to convert the function arguments
/// to the function parameters. Note that these are indexed by argument,
/// so may not match the parameter order of Function.
ConversionSequenceList Conversions;
/// The FixIt hints which can be used to fix the Bad candidate.
ConversionFixItGenerator Fix;
/// Viable - True to indicate that this overload candidate is viable.
bool Viable : 1;
/// IsSurrogate - True to indicate that this candidate is a
/// surrogate for a conversion to a function pointer or reference
/// (C++ []).
bool IsSurrogate : 1;
/// IgnoreObjectArgument - True to indicate that the first
/// argument's conversion, which for this function represents the
/// implicit object argument, should be ignored. This will be true
/// when the candidate is a static member function (where the
/// implicit object argument is just a placeholder) or a
/// non-static member function when the call doesn't have an
/// object argument.
bool IgnoreObjectArgument : 1;
/// True if the candidate was found using ADL.
CallExpr::ADLCallKind IsADLCandidate : 1;
/// Whether this is a rewritten candidate, and if so, of what kind?
OverloadCandidateRewriteKind RewriteKind : 2;
/// FailureKind - The reason why this candidate is not viable.
/// Actually an OverloadFailureKind.
unsigned char FailureKind;
/// The number of call arguments that were explicitly provided,
/// to be used while performing partial ordering of function templates.
unsigned ExplicitCallArguments;
union {
DeductionFailureInfo DeductionFailure;
/// FinalConversion - For a conversion function (where Function is
/// a CXXConversionDecl), the standard conversion that occurs
/// after the call to the overload candidate to convert the result
/// of calling the conversion function to the required type.
StandardConversionSequence FinalConversion;
/// hasAmbiguousConversion - Returns whether this overload
/// candidate requires an ambiguous conversion or not.
bool hasAmbiguousConversion() const {
for (auto &C : Conversions) {
if (!C.isInitialized()) return false;
if (C.isAmbiguous()) return true;
return false;
bool TryToFixBadConversion(unsigned Idx, Sema &S) {
bool CanFix = Fix.tryToFixConversion(
Conversions[Idx].Bad.getToType(), S);
// If at least one conversion fails, the candidate cannot be fixed.
if (!CanFix)
return CanFix;
unsigned getNumParams() const {
if (IsSurrogate) {
QualType STy = Surrogate->getConversionType();
while (STy->isPointerType() || STy->isReferenceType())
STy = STy->getPointeeType();
return STy->castAs<FunctionProtoType>()->getNumParams();
if (Function)
return Function->getNumParams();
return ExplicitCallArguments;
friend class OverloadCandidateSet;
: IsADLCandidate(CallExpr::NotADL), RewriteKind(CRK_None) {}
/// OverloadCandidateSet - A set of overload candidates, used in C++
/// overload resolution (C++ 13.3).
class OverloadCandidateSet {
enum CandidateSetKind {
/// Normal lookup.
/// C++ [over.match.oper]:
/// Lookup of operator function candidates in a call using operator
/// syntax. Candidates that have no parameters of class type will be
/// skipped unless there is a parameter of (reference to) enum type and
/// the corresponding argument is of the same enum type.
/// C++ [over.match.copy]:
/// Copy-initialization of an object of class type by user-defined
/// conversion.
/// C++ [over.match.ctor], [over.match.list]
/// Initialization of an object of class type by constructor,
/// using either a parenthesized or braced list of arguments.
/// Information about operator rewrites to consider when adding operator
/// functions to a candidate set.
struct OperatorRewriteInfo {
: OriginalOperator(OO_None), AllowRewrittenCandidates(false) {}
OperatorRewriteInfo(OverloadedOperatorKind Op, bool AllowRewritten)
: OriginalOperator(Op), AllowRewrittenCandidates(AllowRewritten) {}
/// The original operator as written in the source.
OverloadedOperatorKind OriginalOperator;
/// Whether we should include rewritten candidates in the overload set.
bool AllowRewrittenCandidates;
/// Would use of this function result in a rewrite using a different
/// operator?
bool isRewrittenOperator(const FunctionDecl *FD) {
return OriginalOperator &&
FD->getDeclName().getCXXOverloadedOperator() != OriginalOperator;
bool isAcceptableCandidate(const FunctionDecl *FD) {
return AllowRewrittenCandidates || !isRewrittenOperator(FD);
/// Determine the kind of rewrite that should be performed for this
/// candidate.
getRewriteKind(const FunctionDecl *FD, OverloadCandidateParamOrder PO) {
OverloadCandidateRewriteKind CRK = CRK_None;
if (isRewrittenOperator(FD))
CRK = OverloadCandidateRewriteKind(CRK | CRK_DifferentOperator);
if (PO == OverloadCandidateParamOrder::Reversed)
CRK = OverloadCandidateRewriteKind(CRK | CRK_Reversed);
return CRK;
/// Determine whether we should consider looking for and adding reversed
/// candidates for operator Op.
bool shouldAddReversed(OverloadedOperatorKind Op);
/// Determine whether we should add a rewritten candidate for \p FD with
/// reversed parameter order.
bool shouldAddReversed(ASTContext &Ctx, const FunctionDecl *FD);
SmallVector<OverloadCandidate, 16> Candidates;
llvm::SmallPtrSet<uintptr_t, 16> Functions;
// Allocator for ConversionSequenceLists. We store the first few of these
// inline to avoid allocation for small sets.
llvm::BumpPtrAllocator SlabAllocator;
SourceLocation Loc;
CandidateSetKind Kind;
OperatorRewriteInfo RewriteInfo;
constexpr static unsigned NumInlineBytes =
24 * sizeof(ImplicitConversionSequence);
unsigned NumInlineBytesUsed = 0;
alignas(void *) char InlineSpace[NumInlineBytes];
// Address space of the object being constructed.
LangAS DestAS = LangAS::Default;
/// If we have space, allocates from inline storage. Otherwise, allocates
/// from the slab allocator.
/// FIXME: It would probably be nice to have a SmallBumpPtrAllocator
/// instead.
/// FIXME: Now that this only allocates ImplicitConversionSequences, do we
/// want to un-generalize this?
template <typename T>
T *slabAllocate(unsigned N) {
// It's simpler if this doesn't need to consider alignment.
static_assert(alignof(T) == alignof(void *),
"Only works for pointer-aligned types.");
static_assert(std::is_trivial<T>::value ||
std::is_same<ImplicitConversionSequence, T>::value,
"Add destruction logic to OverloadCandidateSet::clear().");
unsigned NBytes = sizeof(T) * N;
if (NBytes > NumInlineBytes - NumInlineBytesUsed)
return SlabAllocator.Allocate<T>(N);
char *FreeSpaceStart = InlineSpace + NumInlineBytesUsed;
assert(uintptr_t(FreeSpaceStart) % alignof(void *) == 0 &&
"Misaligned storage!");
NumInlineBytesUsed += NBytes;
return reinterpret_cast<T *>(FreeSpaceStart);
void destroyCandidates();
OverloadCandidateSet(SourceLocation Loc, CandidateSetKind CSK,
OperatorRewriteInfo RewriteInfo = {})
: Loc(Loc), Kind(CSK), RewriteInfo(RewriteInfo) {}
OverloadCandidateSet(const OverloadCandidateSet &) = delete;
OverloadCandidateSet &operator=(const OverloadCandidateSet &) = delete;
~OverloadCandidateSet() { destroyCandidates(); }
SourceLocation getLocation() const { return Loc; }
CandidateSetKind getKind() const { return Kind; }
OperatorRewriteInfo getRewriteInfo() const { return RewriteInfo; }
/// Determine when this overload candidate will be new to the
/// overload set.
bool isNewCandidate(Decl *F, OverloadCandidateParamOrder PO =
OverloadCandidateParamOrder::Normal) {
uintptr_t Key = reinterpret_cast<uintptr_t>(F->getCanonicalDecl());
Key |= static_cast<uintptr_t>(PO);
return Functions.insert(Key).second;
/// Clear out all of the candidates.
void clear(CandidateSetKind CSK);
using iterator = SmallVectorImpl<OverloadCandidate>::iterator;
iterator begin() { return Candidates.begin(); }
iterator end() { return Candidates.end(); }
size_t size() const { return Candidates.size(); }
bool empty() const { return Candidates.empty(); }
/// Allocate storage for conversion sequences for NumConversions
/// conversions.
allocateConversionSequences(unsigned NumConversions) {
ImplicitConversionSequence *Conversions =
// Construct the new objects.
for (unsigned I = 0; I != NumConversions; ++I)
new (&Conversions[I]) ImplicitConversionSequence();
return ConversionSequenceList(Conversions, NumConversions);
/// 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");
OverloadCandidate &C = Candidates.back();
C.Conversions = Conversions.empty()
? allocateConversionSequences(NumConversions)
: Conversions;
return C;
/// Find the best viable function on this overload set, if it exists.
OverloadingResult BestViableFunction(Sema &S, SourceLocation Loc,
OverloadCandidateSet::iterator& Best);
SmallVector<OverloadCandidate *, 32> CompleteCandidates(
Sema &S, OverloadCandidateDisplayKind OCD, ArrayRef<Expr *> Args,
SourceLocation OpLoc = SourceLocation(),
llvm::function_ref<bool(OverloadCandidate &)> Filter =
[](OverloadCandidate &) { return true; });
void NoteCandidates(
PartialDiagnosticAt PA, Sema &S, OverloadCandidateDisplayKind OCD,
ArrayRef<Expr *> Args, StringRef Opc = "",
SourceLocation Loc = SourceLocation(),
llvm::function_ref<bool(OverloadCandidate &)> Filter =
[](OverloadCandidate &) { return true; });
void NoteCandidates(Sema &S, ArrayRef<Expr *> Args,
ArrayRef<OverloadCandidate *> Cands,
StringRef Opc = "",
SourceLocation OpLoc = SourceLocation());
LangAS getDestAS() { return DestAS; }
void setDestAS(LangAS AS) {
assert((Kind == CSK_InitByConstructor ||
Kind == CSK_InitByUserDefinedConversion) &&
"can't set the destination address space when not constructing an "
DestAS = AS;
bool isBetterOverloadCandidate(Sema &S,
const OverloadCandidate &Cand1,
const OverloadCandidate &Cand2,
SourceLocation Loc,
OverloadCandidateSet::CandidateSetKind Kind);
struct ConstructorInfo {
DeclAccessPair FoundDecl;
CXXConstructorDecl *Constructor;
FunctionTemplateDecl *ConstructorTmpl;
explicit operator bool() const { return Constructor; }
// FIXME: Add an AddOverloadCandidate / AddTemplateOverloadCandidate overload
// that takes one of these.
inline ConstructorInfo getConstructorInfo(NamedDecl *ND) {
if (isa<UsingDecl>(ND))
return ConstructorInfo{};
// For constructors, the access check is performed against the underlying
// declaration, not the found declaration.
auto *D = ND->getUnderlyingDecl();
ConstructorInfo Info = {DeclAccessPair::make(ND, D->getAccess()), nullptr,
Info.ConstructorTmpl = dyn_cast<FunctionTemplateDecl>(D);
if (Info.ConstructorTmpl)
D = Info.ConstructorTmpl->getTemplatedDecl();
Info.Constructor = dyn_cast<CXXConstructorDecl>(D);
return Info;
} // namespace clang