lib/Sema/SemaOverload.h - clang - Git at Google

 //===--- Overload.h - C++ Overloading ---------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines the data structures and types used in C++
 // overload resolution.
 //
 //===----------------------------------------------------------------------===//

 #ifndef LLVM_CLANG_SEMA_OVERLOAD_H
 #define LLVM_CLANG_SEMA_OVERLOAD_H

 #include "clang/AST/Decl.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/Type.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"

 namespace clang {
   class ASTContext;
   class CXXConstructorDecl;
   class CXXConversionDecl;
   class FunctionDecl;

   /// OverloadingResult - Capture the result of performing overload
   /// resolution.
   enum OverloadingResult {
     OR_Success,             ///< Overload resolution succeeded.
     OR_No_Viable_Function,  ///< No viable function found.
     OR_Ambiguous,           ///< Ambiguous candidates found.
     OR_Deleted              ///< Overload resoltuion refers to a deleted function.
   };

   /// ImplicitConversionKind - The kind of implicit conversion used to
   /// convert an argument to a parameter's type. The enumerator values
   /// match with Table 9 of (C++ 13.3.3.1.1) and are listed such that
   /// better conversion kinds have smaller values.
   enum ImplicitConversionKind {
     ICK_Identity = 0,          ///< Identity conversion (no conversion)
     ICK_Lvalue_To_Rvalue,      ///< Lvalue-to-rvalue conversion (C++ 4.1)
     ICK_Array_To_Pointer,      ///< Array-to-pointer conversion (C++ 4.2)
     ICK_Function_To_Pointer,   ///< Function-to-pointer (C++ 4.3)
     ICK_NoReturn_Adjustment,   ///< Removal of noreturn from a type (Clang)
     ICK_Qualification,         ///< Qualification conversions (C++ 4.4)
     ICK_Integral_Promotion,    ///< Integral promotions (C++ 4.5)
     ICK_Floating_Promotion,    ///< Floating point promotions (C++ 4.6)
     ICK_Complex_Promotion,     ///< Complex promotions (Clang extension)
     ICK_Integral_Conversion,   ///< Integral conversions (C++ 4.7)
     ICK_Floating_Conversion,   ///< Floating point conversions (C++ 4.8)
     ICK_Complex_Conversion,    ///< Complex conversions (C99 6.3.1.6)
     ICK_Floating_Integral,     ///< Floating-integral conversions (C++ 4.9)
     ICK_Pointer_Conversion,    ///< Pointer conversions (C++ 4.10)
     ICK_Pointer_Member,        ///< Pointer-to-member conversions (C++ 4.11)
     ICK_Boolean_Conversion,    ///< Boolean conversions (C++ 4.12)
     ICK_Compatible_Conversion, ///< Conversions between compatible types in C99
     ICK_Derived_To_Base,       ///< Derived-to-base (C++ [over.best.ics])
     ICK_Complex_Real,          ///< Complex-real conversions (C99 6.3.1.7)
     ICK_Num_Conversion_Kinds   ///< The number of conversion kinds
   };

   /// ImplicitConversionCategory - The category of an implicit
   /// conversion kind. The enumerator values match with Table 9 of
   /// (C++ 13.3.3.1.1) and are listed such that better conversion
   /// categories have smaller values.
   enum ImplicitConversionCategory {
     ICC_Identity = 0,              ///< Identity
     ICC_Lvalue_Transformation,     ///< Lvalue transformation
     ICC_Qualification_Adjustment,  ///< Qualification adjustment
     ICC_Promotion,                 ///< Promotion
     ICC_Conversion                 ///< Conversion
   };

   ImplicitConversionCategory
   GetConversionCategory(ImplicitConversionKind Kind);

   /// ImplicitConversionRank - The rank of an implicit conversion
   /// kind. The enumerator values match with Table 9 of (C++
   /// 13.3.3.1.1) and are listed such that better conversion ranks
   /// have smaller values.
   enum ImplicitConversionRank {
     ICR_Exact_Match = 0,        ///< Exact Match
     ICR_Promotion,              ///< Promotion
     ICR_Conversion,             ///< Conversion
     ICR_Complex_Real_Conversion ///< Complex <-> Real conversion
   };

   ImplicitConversionRank GetConversionRank(ImplicitConversionKind Kind);

   /// StandardConversionSequence - represents a standard conversion
   /// sequence (C++ 13.3.3.1.1). 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.
   struct 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.
     ImplicitConversionKind Third : 8;

     /// Deprecated - Whether this the deprecated conversion of a
     /// string literal to a pointer to non-const character data
     /// (C++ 4.2p2).
     bool DeprecatedStringLiteralToCharPtr : 1;

     /// IncompatibleObjC - Whether this is an Objective-C conversion
     /// that we should warn about (if we actually use it).
     bool IncompatibleObjC : 1;

     /// ReferenceBinding - True when this is a reference binding
     /// (C++ [over.ics.ref]).
     bool ReferenceBinding : 1;

     /// DirectBinding - True when this is a reference binding that is a
     /// direct binding (C++ [dcl.init.ref]).
     bool DirectBinding : 1;

     /// RRefBinding - True when this is a reference binding of an rvalue
     /// reference to an rvalue (C++0x [over.ics.rank]p3b4).
     bool RRefBinding : 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;

     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();
     ImplicitConversionRank getRank() const;
     bool isPointerConversionToBool() const;
     bool isPointerConversionToVoidPointer(ASTContext& Context) const;
     void DebugPrint() const;
   };

   /// UserDefinedConversionSequence - Represents a user-defined
   /// conversion sequence (C++ 13.3.3.1.2).
   struct UserDefinedConversionSequence {
     /// Before - Represents the standard conversion that occurs before
     /// the actual user-defined conversion. (C++ 13.3.3.1.2p1):
     ///
     ///   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 ... (elipsis) 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;

     /// 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.
     FunctionDecl* ConversionFunction;

     void DebugPrint() const;
   };

   /// Represents an ambiguous user-defined conversion sequence.
   struct AmbiguousConversionSequence {
     typedef llvm::SmallVector<FunctionDecl*, 4> ConversionSet;

     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(FunctionDecl *D) {
       conversions().push_back(D);
     }

     typedef ConversionSet::iterator iterator;
     iterator begin() { return conversions().begin(); }
     iterator end() { return conversions().end(); }

     typedef ConversionSet::const_iterator 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 {
       no_conversion,
       unrelated_class,
       suppressed_user,
       bad_qualifiers
     };

     // This can be null, e.g. for implicit object arguments.
     Expr *FromExpr;

     FailureKind Kind;

   private:
     // The type we're converting from (an opaque QualType).
     void *FromTy;

     // The type we're converting to (an opaque QualType).
     void *ToTy;

   public:
     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 = 0;
       setFromType(From);
       setToType(To);
     }

     QualType getFromType() const { return QualType::getFromOpaquePtr(FromTy); }
     QualType getToType() const { return QualType::getFromOpaquePtr(ToTy); }

     void setFromExpr(Expr *E) {
       FromExpr = E;
       setFromType(E->getType());
     }
     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++ 13.3.3.1.1), user-defined conversion sequence (C++ 13.3.3.1.2),
   /// or an ellipsis conversion sequence (C++ 13.3.3.1.3).
   struct 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 [over.best.ics]p10).
     enum Kind {
       StandardConversion = 0,
       UserDefinedConversion,
       AmbiguousConversion,
       EllipsisConversion,
       BadConversion
     };

   private:
     enum {
       Uninitialized = BadConversion + 1
     };

     /// ConversionKind - The kind of implicit conversion sequence.
     unsigned ConversionKind;

     void setKind(Kind K) {
       destruct();
       ConversionKind = K;
     }

     void destruct() {
       if (ConversionKind == AmbiguousConversion) Ambiguous.destruct();
     }

   public:
     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;
     };

     ImplicitConversionSequence() : ConversionKind(Uninitialized) {}
     ~ImplicitConversionSequence() {
       destruct();
     }
     ImplicitConversionSequence(const ImplicitConversionSequence &Other)
       : ConversionKind(Other.ConversionKind)
     {
       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) {
       destruct();
       new (this) ImplicitConversionSequence(Other);
       return *this;
     }

     Kind getKind() const {
       assert(isInitialized() && "querying uninitialized conversion");
       return Kind(ConversionKind);
     }
     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; }

     /// 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) {
       setKind(BadConversion);
       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) {
       setKind(BadConversion);
       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;
       Ambiguous.construct();
     }

     // 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 DebugPrint() const;
   };

   enum OverloadFailureKind {
     ovl_fail_too_many_arguments,
     ovl_fail_too_few_arguments,
     ovl_fail_bad_conversion,
     ovl_fail_bad_deduction,

     /// This conversion candidate was not considered because it
     /// duplicates the work of a trivial or derived-to-base
     /// conversion.
     ovl_fail_trivial_conversion,

     /// This conversion candidate is not viable because its result
     /// type is not implicitly convertible to the desired type.
     ovl_fail_bad_final_conversion
   };

   /// 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++ [over.call.object]).
     FunctionDecl *Function;

     // BuiltinTypes - Provides the return and parameter types of a
     // built-in overload candidate. Only valid when Function is NULL.
     struct {
       QualType ResultTy;
       QualType ParamTypes[3];
     } BuiltinTypes;

     /// Surrogate - The conversion function for which this candidate
     /// is a surrogate, but only if IsSurrogate is true.
     CXXConversionDecl *Surrogate;

     /// Conversions - The conversion sequences used to convert the
     /// function arguments to the function parameters.
     llvm::SmallVector<ImplicitConversionSequence, 4> Conversions;

     /// Viable - True to indicate that this overload candidate is viable.
     bool Viable;

     /// IsSurrogate - True to indicate that this candidate is a
     /// surrogate for a conversion to a function pointer or reference
     /// (C++ [over.call.object]).
     bool IsSurrogate;

     /// 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;

     /// FailureKind - The reason why this candidate is not viable.
     /// Actually an OverloadFailureKind.
     unsigned char FailureKind;

     /// PathAccess - The 'path access' to the given function/conversion.
     /// Actually an AccessSpecifier.
     unsigned Access;

     AccessSpecifier getAccess() const {
       return AccessSpecifier(Access);
     }

     /// A structure used to record information about a failed
     /// template argument deduction.
     struct DeductionFailureInfo {
       // A Sema::TemplateDeductionResult.
       unsigned Result;

       // A TemplateParameter.
       void *TemplateParameter;
     };

     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 (llvm::SmallVectorImpl<ImplicitConversionSequence>::const_iterator
              I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
         if (!I->isInitialized()) return false;
         if (I->isAmbiguous()) return true;
       }
       return false;
     }
   };

   /// OverloadCandidateSet - A set of overload candidates, used in C++
   /// overload resolution (C++ 13.3).
   class OverloadCandidateSet : public llvm::SmallVector<OverloadCandidate, 16> {
     typedef llvm::SmallVector<OverloadCandidate, 16> inherited;
     llvm::SmallPtrSet<Decl *, 16> Functions;

     SourceLocation Loc;
   public:
     OverloadCandidateSet(SourceLocation Loc) : Loc(Loc) {}

     SourceLocation getLocation() const { return Loc; }

     /// \brief Determine when this overload candidate will be new to the
     /// overload set.
     bool isNewCandidate(Decl *F) {
       return Functions.insert(F->getCanonicalDecl());
     }

     /// \brief Clear out all of the candidates.
     void clear() {
       inherited::clear();
       Functions.clear();
     }
   };
 } // end namespace clang

 #endif // LLVM_CLANG_SEMA_OVERLOAD_H
	//===--- Overload.h - C++ Overloading ---------------------------- C++ --===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file defines the data structures and types used in C++
	// overload resolution.
	//
	//===----------------------------------------------------------------------===//

	#ifndef LLVM_CLANG_SEMA_OVERLOAD_H
	#define LLVM_CLANG_SEMA_OVERLOAD_H

	#include "clang/AST/Decl.h"
	#include "clang/AST/Expr.h"
	#include "clang/AST/Type.h"
	#include "llvm/ADT/SmallPtrSet.h"
	#include "llvm/ADT/SmallVector.h"

	namespace clang {
	class ASTContext;
	class CXXConstructorDecl;
	class CXXConversionDecl;
	class FunctionDecl;

	/// OverloadingResult - Capture the result of performing overload
	/// resolution.
	enum OverloadingResult {
	OR_Success, ///< Overload resolution succeeded.
	OR_No_Viable_Function, ///< No viable function found.
	OR_Ambiguous, ///< Ambiguous candidates found.
	OR_Deleted ///< Overload resoltuion refers to a deleted function.
	};

	/// ImplicitConversionKind - The kind of implicit conversion used to
	/// convert an argument to a parameter's type. The enumerator values
	/// match with Table 9 of (C++ 13.3.3.1.1) and are listed such that
	/// better conversion kinds have smaller values.
	enum ImplicitConversionKind {
	ICK_Identity = 0, ///< Identity conversion (no conversion)
	ICK_Lvalue_To_Rvalue, ///< Lvalue-to-rvalue conversion (C++ 4.1)
	ICK_Array_To_Pointer, ///< Array-to-pointer conversion (C++ 4.2)
	ICK_Function_To_Pointer, ///< Function-to-pointer (C++ 4.3)
	ICK_NoReturn_Adjustment, ///< Removal of noreturn from a type (Clang)
	ICK_Qualification, ///< Qualification conversions (C++ 4.4)
	ICK_Integral_Promotion, ///< Integral promotions (C++ 4.5)
	ICK_Floating_Promotion, ///< Floating point promotions (C++ 4.6)
	ICK_Complex_Promotion, ///< Complex promotions (Clang extension)
	ICK_Integral_Conversion, ///< Integral conversions (C++ 4.7)
	ICK_Floating_Conversion, ///< Floating point conversions (C++ 4.8)
	ICK_Complex_Conversion, ///< Complex conversions (C99 6.3.1.6)
	ICK_Floating_Integral, ///< Floating-integral conversions (C++ 4.9)
	ICK_Pointer_Conversion, ///< Pointer conversions (C++ 4.10)
	ICK_Pointer_Member, ///< Pointer-to-member conversions (C++ 4.11)
	ICK_Boolean_Conversion, ///< Boolean conversions (C++ 4.12)
	ICK_Compatible_Conversion, ///< Conversions between compatible types in C99
	ICK_Derived_To_Base, ///< Derived-to-base (C++ [over.best.ics])
	ICK_Complex_Real, ///< Complex-real conversions (C99 6.3.1.7)
	ICK_Num_Conversion_Kinds ///< The number of conversion kinds
	};

	/// ImplicitConversionCategory - The category of an implicit
	/// conversion kind. The enumerator values match with Table 9 of
	/// (C++ 13.3.3.1.1) and are listed such that better conversion
	/// categories have smaller values.
	enum ImplicitConversionCategory {
	ICC_Identity = 0, ///< Identity
	ICC_Lvalue_Transformation, ///< Lvalue transformation
	ICC_Qualification_Adjustment, ///< Qualification adjustment
	ICC_Promotion, ///< Promotion
	ICC_Conversion ///< Conversion
	};

	ImplicitConversionCategory
	GetConversionCategory(ImplicitConversionKind Kind);

	/// ImplicitConversionRank - The rank of an implicit conversion
	/// kind. The enumerator values match with Table 9 of (C++
	/// 13.3.3.1.1) and are listed such that better conversion ranks
	/// have smaller values.
	enum ImplicitConversionRank {
	ICR_Exact_Match = 0, ///< Exact Match
	ICR_Promotion, ///< Promotion
	ICR_Conversion, ///< Conversion
	ICR_Complex_Real_Conversion ///< Complex <-> Real conversion
	};

	ImplicitConversionRank GetConversionRank(ImplicitConversionKind Kind);

	/// StandardConversionSequence - represents a standard conversion
	/// sequence (C++ 13.3.3.1.1). 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.
	struct 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.
	ImplicitConversionKind Third : 8;

	/// Deprecated - Whether this the deprecated conversion of a
	/// string literal to a pointer to non-const character data
	/// (C++ 4.2p2).
	bool DeprecatedStringLiteralToCharPtr : 1;

	/// IncompatibleObjC - Whether this is an Objective-C conversion
	/// that we should warn about (if we actually use it).
	bool IncompatibleObjC : 1;

	/// ReferenceBinding - True when this is a reference binding
	/// (C++ [over.ics.ref]).
	bool ReferenceBinding : 1;

	/// DirectBinding - True when this is a reference binding that is a
	/// direct binding (C++ [dcl.init.ref]).
	bool DirectBinding : 1;

	/// RRefBinding - True when this is a reference binding of an rvalue
	/// reference to an rvalue (C++0x [over.ics.rank]p3b4).
	bool RRefBinding : 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;

	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();
	ImplicitConversionRank getRank() const;
	bool isPointerConversionToBool() const;
	bool isPointerConversionToVoidPointer(ASTContext& Context) const;
	void DebugPrint() const;
	};

	/// UserDefinedConversionSequence - Represents a user-defined
	/// conversion sequence (C++ 13.3.3.1.2).
	struct UserDefinedConversionSequence {
	/// Before - Represents the standard conversion that occurs before
	/// the actual user-defined conversion. (C++ 13.3.3.1.2p1):
	///
	/// 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 ... (elipsis) 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;

	/// 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.
	FunctionDecl* ConversionFunction;

	void DebugPrint() const;
	};

	/// Represents an ambiguous user-defined conversion sequence.
	struct AmbiguousConversionSequence {
	typedef llvm::SmallVector<FunctionDecl*, 4> ConversionSet;

	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(FunctionDecl *D) {
	conversions().push_back(D);
	}

	typedef ConversionSet::iterator iterator;
	iterator begin() { return conversions().begin(); }
	iterator end() { return conversions().end(); }

	typedef ConversionSet::const_iterator 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 {
	no_conversion,
	unrelated_class,
	suppressed_user,
	bad_qualifiers
	};

	// This can be null, e.g. for implicit object arguments.
	Expr *FromExpr;

	FailureKind Kind;

	private:
	// The type we're converting from (an opaque QualType).
	void *FromTy;

	// The type we're converting to (an opaque QualType).
	void *ToTy;

	public:
	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 = 0;
	setFromType(From);
	setToType(To);
	}

	QualType getFromType() const { return QualType::getFromOpaquePtr(FromTy); }
	QualType getToType() const { return QualType::getFromOpaquePtr(ToTy); }

	void setFromExpr(Expr *E) {
	FromExpr = E;
	setFromType(E->getType());
	}
	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++ 13.3.3.1.1), user-defined conversion sequence (C++ 13.3.3.1.2),
	/// or an ellipsis conversion sequence (C++ 13.3.3.1.3).
	struct 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 [over.best.ics]p10).
	enum Kind {
	StandardConversion = 0,
	UserDefinedConversion,
	AmbiguousConversion,
	EllipsisConversion,
	BadConversion
	};

	private:
	enum {
	Uninitialized = BadConversion + 1
	};

	/// ConversionKind - The kind of implicit conversion sequence.
	unsigned ConversionKind;

	void setKind(Kind K) {
	destruct();
	ConversionKind = K;
	}

	void destruct() {
	if (ConversionKind == AmbiguousConversion) Ambiguous.destruct();
	}

	public:
	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;
	};

	ImplicitConversionSequence() : ConversionKind(Uninitialized) {}
	~ImplicitConversionSequence() {
	destruct();
	}
	ImplicitConversionSequence(const ImplicitConversionSequence &Other)
	: ConversionKind(Other.ConversionKind)
	{
	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) {
	destruct();
	new (this) ImplicitConversionSequence(Other);
	return *this;
	}

	Kind getKind() const {
	assert(isInitialized() && "querying uninitialized conversion");
	return Kind(ConversionKind);
	}
	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; }

	/// 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) {
	setKind(BadConversion);
	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) {
	setKind(BadConversion);
	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;
	Ambiguous.construct();
	}

	// 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 DebugPrint() const;
	};

	enum OverloadFailureKind {
	ovl_fail_too_many_arguments,
	ovl_fail_too_few_arguments,
	ovl_fail_bad_conversion,
	ovl_fail_bad_deduction,

	/// This conversion candidate was not considered because it
	/// duplicates the work of a trivial or derived-to-base
	/// conversion.
	ovl_fail_trivial_conversion,

	/// This conversion candidate is not viable because its result
	/// type is not implicitly convertible to the desired type.
	ovl_fail_bad_final_conversion
	};

	/// 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++ [over.call.object]).
	FunctionDecl *Function;

	// BuiltinTypes - Provides the return and parameter types of a
	// built-in overload candidate. Only valid when Function is NULL.
	struct {
	QualType ResultTy;
	QualType ParamTypes[3];
	} BuiltinTypes;

	/// Surrogate - The conversion function for which this candidate
	/// is a surrogate, but only if IsSurrogate is true.
	CXXConversionDecl *Surrogate;

	/// Conversions - The conversion sequences used to convert the
	/// function arguments to the function parameters.
	llvm::SmallVector<ImplicitConversionSequence, 4> Conversions;

	/// Viable - True to indicate that this overload candidate is viable.
	bool Viable;

	/// IsSurrogate - True to indicate that this candidate is a
	/// surrogate for a conversion to a function pointer or reference
	/// (C++ [over.call.object]).
	bool IsSurrogate;

	/// 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;

	/// FailureKind - The reason why this candidate is not viable.
	/// Actually an OverloadFailureKind.
	unsigned char FailureKind;

	/// PathAccess - The 'path access' to the given function/conversion.
	/// Actually an AccessSpecifier.
	unsigned Access;

	AccessSpecifier getAccess() const {
	return AccessSpecifier(Access);
	}

	/// A structure used to record information about a failed
	/// template argument deduction.
	struct DeductionFailureInfo {
	// A Sema::TemplateDeductionResult.
	unsigned Result;

	// A TemplateParameter.
	void *TemplateParameter;
	};

	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 (llvm::SmallVectorImpl<ImplicitConversionSequence>::const_iterator
	I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
	if (!I->isInitialized()) return false;
	if (I->isAmbiguous()) return true;
	}
	return false;
	}
	};

	/// OverloadCandidateSet - A set of overload candidates, used in C++
	/// overload resolution (C++ 13.3).
	class OverloadCandidateSet : public llvm::SmallVector<OverloadCandidate, 16> {
	typedef llvm::SmallVector<OverloadCandidate, 16> inherited;
	llvm::SmallPtrSet<Decl *, 16> Functions;

	SourceLocation Loc;
	public:
	OverloadCandidateSet(SourceLocation Loc) : Loc(Loc) {}

	SourceLocation getLocation() const { return Loc; }

	/// \brief Determine when this overload candidate will be new to the
	/// overload set.
	bool isNewCandidate(Decl *F) {
	return Functions.insert(F->getCanonicalDecl());
	}

	/// \brief Clear out all of the candidates.
	void clear() {
	inherited::clear();
	Functions.clear();
	}
	};
	} // end namespace clang

	#endif // LLVM_CLANG_SEMA_OVERLOAD_H