lib/Sema/Sema.h

//===--- Sema.h - Semantic Analysis & AST Building --------------*- 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 Sema class, which performs semantic analysis and
// builds ASTs.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_AST_SEMA_H
#define LLVM_CLANG_AST_SEMA_H

#include "IdentifierResolver.h"
#include "CXXFieldCollector.h"
#include "SemaOverload.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclObjC.h"
#include "clang/Parse/Action.h"
#include "clang/Sema/SemaDiagnostic.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/OwningPtr.h"
#include <string>
#include <vector>

namespace llvm {
  class APSInt;
}

namespace clang {
  class ASTContext;
  class ASTConsumer;
  class Preprocessor;
  class Decl;
  class DeclContext;
  class DeclSpec;
  class ExternalSemaSource;
  class NamedDecl;
  class Stmt;
  class Expr;
  class InitListExpr;
  class DesignatedInitExpr;
  class CallExpr;
  class DeclRefExpr;
  class VarDecl;
  class ParmVarDecl;
  class TypedefDecl;
  class FunctionDecl;
  class QualType;
  class LangOptions;
  class Token;
  class IntegerLiteral;
  class StringLiteral;
  class ArrayType;
  class LabelStmt;
  class SwitchStmt;
  class CXXTryStmt;
  class ExtVectorType;
  class TypedefDecl;
  class TemplateDecl;
  class TemplateArgument;
  class TemplateArgumentList;
  class TemplateParameterList;
  class TemplateTemplateParmDecl;
  class ClassTemplateDecl;
  class ObjCInterfaceDecl;
  class ObjCCompatibleAliasDecl;
  class ObjCProtocolDecl;
  class ObjCImplDecl;
  class ObjCImplementationDecl;
  class ObjCCategoryImplDecl;
  class ObjCCategoryDecl;
  class ObjCIvarDecl;
  class ObjCMethodDecl;
  class ObjCPropertyDecl;
  class ObjCContainerDecl;
  class BasePaths;
  struct MemberLookupCriteria;

/// BlockSemaInfo - When a block is being parsed, this contains information
/// about the block.  It is pointed to from Sema::CurBlock.
struct BlockSemaInfo {
  llvm::SmallVector<ParmVarDecl*, 8> Params;
  bool hasPrototype;
  bool isVariadic;
  bool hasBlockDeclRefExprs;
  
  BlockDecl *TheDecl;
  
  /// TheScope - This is the scope for the block itself, which contains
  /// arguments etc.
  Scope *TheScope;
  
  /// ReturnType - This will get set to block result type, by looking at
  /// return types, if any, in the block body.
  Type *ReturnType;
  
  /// LabelMap - This is a mapping from label identifiers to the LabelStmt for
  /// it (which acts like the label decl in some ways).  Forward referenced
  /// labels have a LabelStmt created for them with a null location & SubStmt.
  llvm::DenseMap<IdentifierInfo*, LabelStmt*> LabelMap;
  
  /// SwitchStack - This is the current set of active switch statements in the
  /// block.
  llvm::SmallVector<SwitchStmt*, 8> SwitchStack;
  
  /// SavedFunctionNeedsScopeChecking - This is the value of
  /// CurFunctionNeedsScopeChecking at the point when the block started.
  bool SavedFunctionNeedsScopeChecking;
  
  /// PrevBlockInfo - If this is nested inside another block, this points
  /// to the outer block.
  BlockSemaInfo *PrevBlockInfo;
};

/// Sema - This implements semantic analysis and AST building for C.
class Sema : public Action {
  Sema(const Sema&);           // DO NOT IMPLEMENT
  void operator=(const Sema&); // DO NOT IMPLEMENT
public:
  const LangOptions &LangOpts;
  Preprocessor &PP;
  ASTContext &Context;
  ASTConsumer &Consumer;
  Diagnostic &Diags;
  SourceManager &SourceMgr;

  /// \brief Source of additional semantic information.
  ExternalSemaSource *ExternalSource;

  /// CurContext - This is the current declaration context of parsing.
  DeclContext *CurContext;

  /// PreDeclaratorDC - Keeps the declaration context before switching to the
  /// context of a declarator's nested-name-specifier.
  DeclContext *PreDeclaratorDC;

  /// CurBlock - If inside of a block definition, this contains a pointer to
  /// the active block object that represents it.
  BlockSemaInfo *CurBlock;

  /// PackContext - Manages the stack for #pragma pack. An alignment
  /// of 0 indicates default alignment.
  void *PackContext; // Really a "PragmaPackStack*"

  /// FunctionLabelMap - This is a mapping from label identifiers to the
  /// LabelStmt for it (which acts like the label decl in some ways).  Forward
  /// referenced labels have a LabelStmt created for them with a null location &
  /// SubStmt.
  ///
  /// Note that this should always be accessed through getLabelMap() in order
  /// to handle blocks properly.
  llvm::DenseMap<IdentifierInfo*, LabelStmt*> FunctionLabelMap;
  
  /// FunctionSwitchStack - This is the current set of active switch statements
  /// in the top level function.  Clients should always use getSwitchStack() to
  /// handle the case when they are in a block.
  llvm::SmallVector<SwitchStmt*, 8> FunctionSwitchStack;

  /// ExprTemporaries - This is the stack of temporaries that are created by 
  /// the current full expression.
  llvm::SmallVector<CXXTempVarDecl*, 8> ExprTemporaries;

  /// CurFunctionNeedsScopeChecking - This is set to true when a function or
  /// ObjC method body contains a VLA or an ObjC try block, which introduce
  /// scopes that need to be checked for goto conditions.  If a function does
  /// not contain this, then it need not have the jump checker run on it.
  bool CurFunctionNeedsScopeChecking;
  
  /// ExtVectorDecls - This is a list all the extended vector types. This allows
  /// us to associate a raw vector type with one of the ext_vector type names.
  /// This is only necessary for issuing pretty diagnostics.
  llvm::SmallVector<TypedefDecl*, 24> ExtVectorDecls;

  /// ObjCCategoryImpls - Maintain a list of category implementations so 
  /// we can check for duplicates and find local method declarations.
  llvm::SmallVector<ObjCCategoryImplDecl*, 8> ObjCCategoryImpls;
  
  /// FieldCollector - Collects CXXFieldDecls during parsing of C++ classes.
  llvm::OwningPtr<CXXFieldCollector> FieldCollector;

  typedef llvm::SmallPtrSet<const CXXRecordDecl*, 8> RecordDeclSetTy;
  
  /// PureVirtualClassDiagSet - a set of class declarations which we have 
  /// emitted a list of pure virtual functions. Used to prevent emitting the
  /// same list more than once.
  llvm::OwningPtr<RecordDeclSetTy> PureVirtualClassDiagSet;
  
  /// \brief A mapping from external names to the most recent
  /// locally-scoped external declaration with that name.
  ///
  /// This map contains external declarations introduced in local
  /// scoped, e.g.,
  ///
  /// \code
  /// void f() {
  ///   void foo(int, int);
  /// }
  /// \endcode
  ///
  /// Here, the name "foo" will be associated with the declaration on
  /// "foo" within f. This name is not visible outside of
  /// "f". However, we still find it in two cases:
  ///
  ///   - If we are declaring another external with the name "foo", we
  ///     can find "foo" as a previous declaration, so that the types
  ///     of this external declaration can be checked for
  ///     compatibility.
  ///
  ///   - If we would implicitly declare "foo" (e.g., due to a call to
  ///     "foo" in C when no prototype or definition is visible), then
  ///     we find this declaration of "foo" and complain that it is
  ///     not visible.
  llvm::DenseMap<DeclarationName, NamedDecl *> LocallyScopedExternalDecls;

  /// \brief The set of tentative declarations seen so far in this
  /// translation unit for which no definition has been seen.
  ///
  /// The tentative declarations are indexed by the name of the
  /// declaration, and only the most recent tentative declaration for
  /// a given variable will be recorded here.
  llvm::DenseMap<DeclarationName, VarDecl *> TentativeDefinitions;

  IdentifierResolver IdResolver;

  /// Translation Unit Scope - useful to Objective-C actions that need
  /// to lookup file scope declarations in the "ordinary" C decl namespace.
  /// For example, user-defined classes, built-in "id" type, etc.
  Scope *TUScope;

  /// The C++ "std" namespace, where the standard library resides. Cached here
  /// by GetStdNamespace
  NamespaceDecl *StdNamespace;

  /// A flag to remember whether the implicit forms of operator new and delete
  /// have been declared.
  bool GlobalNewDeleteDeclared;

  /// \brief Whether the code handled by Sema should be considered a
  /// complete translation unit or not.
  ///
  /// When true (which is generally the case), Sema will perform
  /// end-of-translation-unit semantic tasks (such as creating
  /// initializers for tentative definitions in C) once parsing has
  /// completed. This flag will be false when building PCH files,
  /// since a PCH file is by definition not a complete translation
  /// unit.
  bool CompleteTranslationUnit;

  typedef llvm::DenseMap<Selector, ObjCMethodList> MethodPool;

  /// Instance/Factory Method Pools - allows efficient lookup when typechecking
  /// messages to "id". We need to maintain a list, since selectors can have
  /// differing signatures across classes. In Cocoa, this happens to be 
  /// extremely uncommon (only 1% of selectors are "overloaded").
  MethodPool InstanceMethodPool;
  MethodPool FactoryMethodPool;
  
  MethodPool::iterator ReadMethodPool(Selector Sel, bool isInstance);

  /// Private Helper predicate to check for 'self'.
  bool isSelfExpr(Expr *RExpr);
public:
  Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
       bool CompleteTranslationUnit = true);
  ~Sema() {
    if (PackContext) FreePackedContext();
  }
  
  const LangOptions &getLangOptions() const { return LangOpts; }
  Diagnostic &getDiagnostics() const { return Diags; }
  SourceManager &getSourceManager() const { return SourceMgr; }

  /// \brief Helper class that creates diagnostics with optional
  /// template instantiation stacks.
  ///
  /// This class provides a wrapper around the basic DiagnosticBuilder
  /// class that emits diagnostics. SemaDiagnosticBuilder is
  /// responsible for emitting the diagnostic (as DiagnosticBuilder
  /// does) and, if the diagnostic comes from inside a template
  /// instantiation, printing the template instantiation stack as
  /// well.
  class SemaDiagnosticBuilder : public DiagnosticBuilder {
    Sema &SemaRef;
    unsigned DiagID;

  public:
    SemaDiagnosticBuilder(DiagnosticBuilder &DB, Sema &SemaRef, unsigned DiagID)
      : DiagnosticBuilder(DB), SemaRef(SemaRef), DiagID(DiagID) { }

    ~SemaDiagnosticBuilder();
  };

  /// \brief Emit a diagnostic.
  SemaDiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID) {
    DiagnosticBuilder DB = Diags.Report(FullSourceLoc(Loc, SourceMgr), DiagID);
    return SemaDiagnosticBuilder(DB, *this, DiagID);
  }

  virtual void DeleteExpr(ExprTy *E);
  virtual void DeleteStmt(StmtTy *S);

  OwningExprResult Owned(Expr* E) { return OwningExprResult(*this, E); }
  OwningExprResult Owned(ExprResult R) {
    if (R.isInvalid())
      return ExprError();
    return OwningExprResult(*this, R.get());
  }
  OwningStmtResult Owned(Stmt* S) { return OwningStmtResult(*this, S); }

  virtual void ActOnEndOfTranslationUnit();

  /// getLabelMap() - Return the current label map.  If we're in a block, we
  /// return it.
  llvm::DenseMap<IdentifierInfo*, LabelStmt*> &getLabelMap() {
    return CurBlock ? CurBlock->LabelMap : FunctionLabelMap;
  }
  
  /// getSwitchStack - This is returns the switch stack for the current block or
  /// function.
  llvm::SmallVector<SwitchStmt*,8> &getSwitchStack() {
    return CurBlock ? CurBlock->SwitchStack : FunctionSwitchStack;
  }
  
  //===--------------------------------------------------------------------===//
  // Type Analysis / Processing: SemaType.cpp.
  //
  QualType adjustParameterType(QualType T);
  QualType ConvertDeclSpecToType(const DeclSpec &DS, SourceLocation DeclLoc,
                                 bool &IsInvalid);
  void ProcessTypeAttributeList(QualType &Result, const AttributeList *AL);
  QualType BuildPointerType(QualType T, unsigned Quals, 
                            SourceLocation Loc, DeclarationName Entity);
  QualType BuildReferenceType(QualType T, bool LValueRef, unsigned Quals,
                              SourceLocation Loc, DeclarationName Entity);
  QualType BuildArrayType(QualType T, ArrayType::ArraySizeModifier ASM,
                          Expr *ArraySize, unsigned Quals,
                          SourceLocation Loc, DeclarationName Entity);
  QualType BuildFunctionType(QualType T,
                             QualType *ParamTypes, unsigned NumParamTypes,
                             bool Variadic, unsigned Quals,
                             SourceLocation Loc, DeclarationName Entity);
  QualType GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip = 0);
  DeclarationName GetNameForDeclarator(Declarator &D);

  QualType ObjCGetTypeForMethodDefinition(DeclPtrTy D);

  bool UnwrapSimilarPointerTypes(QualType& T1, QualType& T2);

  virtual TypeResult ActOnTypeName(Scope *S, Declarator &D);

  bool RequireCompleteType(SourceLocation Loc, QualType T, unsigned diag,
                              SourceRange Range1 = SourceRange(),
                              SourceRange Range2 = SourceRange(),
                              QualType PrintType = QualType());

  QualType getQualifiedNameType(const CXXScopeSpec &SS, QualType T);

  //===--------------------------------------------------------------------===//
  // Symbol table / Decl tracking callbacks: SemaDecl.cpp.
  //

  /// getDeclName - Return a pretty name for the specified decl if possible, or
  /// an empty string if not.  This is used for pretty crash reporting. 
  virtual std::string getDeclName(DeclPtrTy D);
  
  DeclGroupPtrTy ConvertDeclToDeclGroup(DeclPtrTy Ptr);

  virtual TypeTy *getTypeName(IdentifierInfo &II, SourceLocation NameLoc, 
                              Scope *S, const CXXScopeSpec *SS);
  virtual DeclSpec::TST isTagName(IdentifierInfo &II, Scope *S);
  
  virtual DeclPtrTy ActOnDeclarator(Scope *S, Declarator &D) {
    return ActOnDeclarator(S, D, false);
  }
  DeclPtrTy ActOnDeclarator(Scope *S, Declarator &D, bool IsFunctionDefinition);
  void RegisterLocallyScopedExternCDecl(NamedDecl *ND, NamedDecl *PrevDecl,
                                        Scope *S);
  void DiagnoseFunctionSpecifiers(Declarator& D);
  NamedDecl* ActOnTypedefDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                                    QualType R, Decl* PrevDecl,
                                    bool &Redeclaration);
  NamedDecl* ActOnVariableDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                                     QualType R, NamedDecl* PrevDecl,
                                     bool &Redeclaration);
  void CheckVariableDeclaration(VarDecl *NewVD, NamedDecl *PrevDecl,
                                bool &Redeclaration);
  NamedDecl* ActOnFunctionDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                                     QualType R, NamedDecl* PrevDecl, 
                                     bool IsFunctionDefinition,
                                     bool &Redeclaration);
  void CheckFunctionDeclaration(FunctionDecl *NewFD, NamedDecl *&PrevDecl,
                                bool &Redeclaration, 
                                bool &OverloadableAttrRequired);
  virtual DeclPtrTy ActOnParamDeclarator(Scope *S, Declarator &D);
  virtual void ActOnParamDefaultArgument(DeclPtrTy param,
                                         SourceLocation EqualLoc,
                                         ExprArg defarg);
  virtual void ActOnParamUnparsedDefaultArgument(DeclPtrTy param, 
                                                 SourceLocation EqualLoc);
  virtual void ActOnParamDefaultArgumentError(DeclPtrTy param);
  virtual void AddInitializerToDecl(DeclPtrTy dcl, ExprArg init);
  void AddInitializerToDecl(DeclPtrTy dcl, ExprArg init, bool DirectInit);
  void ActOnUninitializedDecl(DeclPtrTy dcl);
  virtual void SetDeclDeleted(DeclPtrTy dcl, SourceLocation DelLoc);
  virtual DeclGroupPtrTy FinalizeDeclaratorGroup(Scope *S, DeclPtrTy *Group,
                                                 unsigned NumDecls);
  virtual void ActOnFinishKNRParamDeclarations(Scope *S, Declarator &D,
                                               SourceLocation LocAfterDecls);
  virtual DeclPtrTy ActOnStartOfFunctionDef(Scope *S, Declarator &D);
  virtual DeclPtrTy ActOnStartOfFunctionDef(Scope *S, DeclPtrTy D);
  virtual void ActOnStartOfObjCMethodDef(Scope *S, DeclPtrTy D);

  virtual DeclPtrTy ActOnFinishFunctionBody(DeclPtrTy Decl, StmtArg Body);
  DeclPtrTy ActOnFinishFunctionBody(DeclPtrTy Decl, StmtArg Body,
                                    bool IsInstantiation);
  void DiagnoseInvalidJumps(Stmt *Body);
  virtual DeclPtrTy ActOnFileScopeAsmDecl(SourceLocation Loc, ExprArg expr);

  /// Scope actions.
  virtual void ActOnPopScope(SourceLocation Loc, Scope *S);
  virtual void ActOnTranslationUnitScope(SourceLocation Loc, Scope *S);

  /// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
  /// no declarator (e.g. "struct foo;") is parsed.
  virtual DeclPtrTy ParsedFreeStandingDeclSpec(Scope *S, DeclSpec &DS);
  
  bool InjectAnonymousStructOrUnionMembers(Scope *S, DeclContext *Owner,
                                           RecordDecl *AnonRecord);
  virtual DeclPtrTy BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS, 
                                                RecordDecl *Record);

  bool isAcceptableTagRedeclaration(const TagDecl *Previous, 
                                    TagDecl::TagKind NewTag,
                                    SourceLocation NewTagLoc,
                                    const IdentifierInfo &Name);

  virtual DeclPtrTy ActOnTag(Scope *S, unsigned TagSpec, TagKind TK,
                             SourceLocation KWLoc, const CXXScopeSpec &SS,
                             IdentifierInfo *Name, SourceLocation NameLoc,
                             AttributeList *Attr, AccessSpecifier AS);
  
  virtual void ActOnDefs(Scope *S, DeclPtrTy TagD, SourceLocation DeclStart,
                         IdentifierInfo *ClassName,
                         llvm::SmallVectorImpl<DeclPtrTy> &Decls);
  virtual DeclPtrTy ActOnField(Scope *S, DeclPtrTy TagD,
                               SourceLocation DeclStart,
                               Declarator &D, ExprTy *BitfieldWidth);

  FieldDecl *HandleField(Scope *S, RecordDecl *TagD, SourceLocation DeclStart,
                         Declarator &D, Expr *BitfieldWidth,
                         AccessSpecifier AS);

  FieldDecl *CheckFieldDecl(DeclarationName Name, QualType T, 
                            RecordDecl *Record, SourceLocation Loc,
                            bool Mutable, Expr *BitfieldWidth,
                            AccessSpecifier AS, NamedDecl *PrevDecl,
                            Declarator *D = 0);
  
  virtual DeclPtrTy ActOnIvar(Scope *S, SourceLocation DeclStart,
                              Declarator &D, ExprTy *BitfieldWidth,
                              tok::ObjCKeywordKind visibility);

  // This is used for both record definitions and ObjC interface declarations.
  virtual void ActOnFields(Scope* S,
                           SourceLocation RecLoc, DeclPtrTy TagDecl,
                           DeclPtrTy *Fields, unsigned NumFields,
                           SourceLocation LBrac, SourceLocation RBrac,
                           AttributeList *AttrList);

  /// ActOnTagStartDefinition - Invoked when we have entered the
  /// scope of a tag's definition (e.g., for an enumeration, class,
  /// struct, or union).
  virtual void ActOnTagStartDefinition(Scope *S, DeclPtrTy TagDecl);

  /// ActOnTagFinishDefinition - Invoked once we have finished parsing
  /// the definition of a tag (enumeration, class, struct, or union).
  virtual void ActOnTagFinishDefinition(Scope *S, DeclPtrTy TagDecl);

  EnumConstantDecl *CheckEnumConstant(EnumDecl *Enum,
                                      EnumConstantDecl *LastEnumConst,
                                      SourceLocation IdLoc,
                                      IdentifierInfo *Id,
                                      ExprArg val);

  virtual DeclPtrTy ActOnEnumConstant(Scope *S, DeclPtrTy EnumDecl,
                                      DeclPtrTy LastEnumConstant,
                                      SourceLocation IdLoc, IdentifierInfo *Id,
                                      SourceLocation EqualLoc, ExprTy *Val);
  virtual void ActOnEnumBody(SourceLocation EnumLoc, SourceLocation LBraceLoc,
                             SourceLocation RBraceLoc, DeclPtrTy EnumDecl,
                             DeclPtrTy *Elements, unsigned NumElements);

  DeclContext *getContainingDC(DeclContext *DC);

  /// Set the current declaration context until it gets popped.
  void PushDeclContext(Scope *S, DeclContext *DC);
  void PopDeclContext();
  
  /// getCurFunctionDecl - If inside of a function body, this returns a pointer
  /// to the function decl for the function being parsed.  If we're currently
  /// in a 'block', this returns the containing context.
  FunctionDecl *getCurFunctionDecl();
  
  /// getCurMethodDecl - If inside of a method body, this returns a pointer to
  /// the method decl for the method being parsed.  If we're currently
  /// in a 'block', this returns the containing context.
  ObjCMethodDecl *getCurMethodDecl();

  /// getCurFunctionOrMethodDecl - Return the Decl for the current ObjC method
  /// or C function we're in, otherwise return null.  If we're currently
  /// in a 'block', this returns the containing context.
  NamedDecl *getCurFunctionOrMethodDecl();

  /// Add this decl to the scope shadowed decl chains.
  void PushOnScopeChains(NamedDecl *D, Scope *S);

  /// isDeclInScope - If 'Ctx' is a function/method, isDeclInScope returns true
  /// if 'D' is in Scope 'S', otherwise 'S' is ignored and isDeclInScope returns
  /// true if 'D' belongs to the given declaration context.
  bool isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S = 0) {
    return IdResolver.isDeclInScope(D, Ctx, Context, S);
  }


  /// Subroutines of ActOnDeclarator().
  TypedefDecl *ParseTypedefDecl(Scope *S, Declarator &D, QualType T);
  void MergeTypeDefDecl(TypedefDecl *New, Decl *Old);
  bool MergeFunctionDecl(FunctionDecl *New, Decl *Old);
  bool MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old);
  void MergeVarDecl(VarDecl *New, Decl *Old);
  bool MergeCXXFunctionDecl(FunctionDecl *New, FunctionDecl *Old);

  /// C++ Overloading.
  bool IsOverload(FunctionDecl *New, Decl* OldD, 
                  OverloadedFunctionDecl::function_iterator &MatchedDecl);
  ImplicitConversionSequence 
  TryImplicitConversion(Expr* From, QualType ToType,
                        bool SuppressUserConversions = false,
                        bool AllowExplicit = false,
                        bool ForceRValue = false);
  bool IsStandardConversion(Expr *From, QualType ToType, 
                            StandardConversionSequence& SCS);
  bool IsIntegralPromotion(Expr *From, QualType FromType, QualType ToType);
  bool IsFloatingPointPromotion(QualType FromType, QualType ToType);
  bool IsComplexPromotion(QualType FromType, QualType ToType);
  bool IsPointerConversion(Expr *From, QualType FromType, QualType ToType,
                           QualType& ConvertedType, bool &IncompatibleObjC);
  bool isObjCPointerConversion(QualType FromType, QualType ToType,
                               QualType& ConvertedType, bool &IncompatibleObjC);
  bool CheckPointerConversion(Expr *From, QualType ToType);
  bool IsMemberPointerConversion(Expr *From, QualType FromType, QualType ToType,
                                 QualType &ConvertedType);
  bool CheckMemberPointerConversion(Expr *From, QualType ToType);
  bool IsQualificationConversion(QualType FromType, QualType ToType);
  bool IsUserDefinedConversion(Expr *From, QualType ToType, 
                               UserDefinedConversionSequence& User,
                               bool AllowConversionFunctions,
                               bool AllowExplicit, bool ForceRValue);

  ImplicitConversionSequence::CompareKind 
  CompareImplicitConversionSequences(const ImplicitConversionSequence& ICS1,
                                     const ImplicitConversionSequence& ICS2);

  ImplicitConversionSequence::CompareKind 
  CompareStandardConversionSequences(const StandardConversionSequence& SCS1,
                                     const StandardConversionSequence& SCS2);

  ImplicitConversionSequence::CompareKind 
  CompareQualificationConversions(const StandardConversionSequence& SCS1,
                                  const StandardConversionSequence& SCS2);

  ImplicitConversionSequence::CompareKind
  CompareDerivedToBaseConversions(const StandardConversionSequence& SCS1,
                                  const StandardConversionSequence& SCS2);

  ImplicitConversionSequence 
  TryCopyInitialization(Expr* From, QualType ToType,
                        bool SuppressUserConversions = false,
                        bool ForceRValue = false);
  bool PerformCopyInitialization(Expr *&From, QualType ToType, 
                                 const char *Flavor, bool Elidable = false);

  ImplicitConversionSequence
  TryObjectArgumentInitialization(Expr *From, CXXMethodDecl *Method);
  bool PerformObjectArgumentInitialization(Expr *&From, CXXMethodDecl *Method);

  ImplicitConversionSequence TryContextuallyConvertToBool(Expr *From);
  bool PerformContextuallyConvertToBool(Expr *&From);

  /// 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.
  };

  typedef llvm::SmallPtrSet<FunctionDecl *, 16> FunctionSet;
  typedef llvm::SmallPtrSet<NamespaceDecl *, 16> AssociatedNamespaceSet;
  typedef llvm::SmallPtrSet<CXXRecordDecl *, 16> AssociatedClassSet;

  void AddOverloadCandidate(FunctionDecl *Function, 
                            Expr **Args, unsigned NumArgs,
                            OverloadCandidateSet& CandidateSet,
                            bool SuppressUserConversions = false,
                            bool ForceRValue = false);
  void AddFunctionCandidates(const FunctionSet &Functions,
                             Expr **Args, unsigned NumArgs,
                             OverloadCandidateSet& CandidateSet,
                             bool SuppressUserConversions = false);
  void AddMethodCandidate(CXXMethodDecl *Method,
                          Expr *Object, Expr **Args, unsigned NumArgs,
                          OverloadCandidateSet& CandidateSet,
                          bool SuppressUserConversions = false,
                          bool ForceRValue = false);
  void AddConversionCandidate(CXXConversionDecl *Conversion,
                              Expr *From, QualType ToType,
                              OverloadCandidateSet& CandidateSet);
  void AddSurrogateCandidate(CXXConversionDecl *Conversion,
                             const FunctionProtoType *Proto,
                             Expr *Object, Expr **Args, unsigned NumArgs,
                             OverloadCandidateSet& CandidateSet);
  void AddOperatorCandidates(OverloadedOperatorKind Op, Scope *S,
                             SourceLocation OpLoc,
                             Expr **Args, unsigned NumArgs,
                             OverloadCandidateSet& CandidateSet,
                             SourceRange OpRange = SourceRange());
  void AddMemberOperatorCandidates(OverloadedOperatorKind Op,
                                   SourceLocation OpLoc,
                                   Expr **Args, unsigned NumArgs,
                                   OverloadCandidateSet& CandidateSet,
                                   SourceRange OpRange = SourceRange());
  void AddBuiltinCandidate(QualType ResultTy, QualType *ParamTys, 
                           Expr **Args, unsigned NumArgs,
                           OverloadCandidateSet& CandidateSet,
                           bool IsAssignmentOperator = false,
                           unsigned NumContextualBoolArguments = 0);
  void AddBuiltinOperatorCandidates(OverloadedOperatorKind Op, 
                                    Expr **Args, unsigned NumArgs, 
                                    OverloadCandidateSet& CandidateSet);
  void AddArgumentDependentLookupCandidates(DeclarationName Name,
                                            Expr **Args, unsigned NumArgs,
                                            OverloadCandidateSet& CandidateSet);
  bool isBetterOverloadCandidate(const OverloadCandidate& Cand1,
                                 const OverloadCandidate& Cand2);
  OverloadingResult BestViableFunction(OverloadCandidateSet& CandidateSet,
                                       OverloadCandidateSet::iterator& Best);
  void PrintOverloadCandidates(OverloadCandidateSet& CandidateSet,
                               bool OnlyViable);
                               
  FunctionDecl *ResolveAddressOfOverloadedFunction(Expr *From, QualType ToType,
                                                   bool Complain);
  void FixOverloadedFunctionReference(Expr *E, FunctionDecl *Fn);

  FunctionDecl *ResolveOverloadedCallFn(Expr *Fn, NamedDecl *Callee,
                                        DeclarationName UnqualifiedName,
                                        SourceLocation LParenLoc,
                                        Expr **Args, unsigned NumArgs,
                                        SourceLocation *CommaLocs, 
                                        SourceLocation RParenLoc,
                                        bool &ArgumentDependentLookup);

  OwningExprResult CreateOverloadedUnaryOp(SourceLocation OpLoc,
                                           unsigned Opc,
                                           FunctionSet &Functions,
                                           ExprArg input);

  OwningExprResult CreateOverloadedBinOp(SourceLocation OpLoc,
                                         unsigned Opc,
                                         FunctionSet &Functions,
                                         Expr *LHS, Expr *RHS);

  ExprResult
  BuildCallToMemberFunction(Scope *S, Expr *MemExpr,
                            SourceLocation LParenLoc, Expr **Args, 
                            unsigned NumArgs, SourceLocation *CommaLocs,
                            SourceLocation RParenLoc);
  ExprResult 
  BuildCallToObjectOfClassType(Scope *S, Expr *Object, SourceLocation LParenLoc,
                               Expr **Args, unsigned NumArgs,
                               SourceLocation *CommaLocs, 
                               SourceLocation RParenLoc);

  ExprResult BuildOverloadedArrowExpr(Scope *S, Expr *Base, SourceLocation OpLoc,
                                      SourceLocation MemberLoc,
                                      IdentifierInfo &Member);
               
  /// Helpers for dealing with function parameters.
  bool CheckParmsForFunctionDef(FunctionDecl *FD);
  void CheckCXXDefaultArguments(FunctionDecl *FD);
  void CheckExtraCXXDefaultArguments(Declarator &D);

  Scope *getNonFieldDeclScope(Scope *S);

  /// \name Name lookup
  ///
  /// These routines provide name lookup that is used during semantic
  /// analysis to resolve the various kinds of names (identifiers,
  /// overloaded operator names, constructor names, etc.) into zero or
  /// more declarations within a particular scope. The major entry
  /// points are LookupName, which performs unqualified name lookup,
  /// and LookupQualifiedName, which performs qualified name lookup. 
  ///
  /// All name lookup is performed based on some specific criteria,
  /// which specify what names will be visible to name lookup and how
  /// far name lookup should work. These criteria are important both
  /// for capturing language semantics (certain lookups will ignore
  /// certain names, for example) and for performance, since name
  /// lookup is often a bottleneck in the compilation of C++. Name
  /// lookup criteria is specified via the LookupCriteria enumeration.
  ///
  /// The results of name lookup can vary based on the kind of name
  /// lookup performed, the current language, and the translation
  /// unit. In C, for example, name lookup will either return nothing
  /// (no entity found) or a single declaration. In C++, name lookup
  /// can additionally refer to a set of overloaded functions or
  /// result in an ambiguity. All of the possible results of name
  /// lookup are captured by the LookupResult class, which provides
  /// the ability to distinguish among them.
  //@{

  /// @brief Describes the kind of name lookup to perform.
  enum LookupNameKind {
    /// Ordinary name lookup, which finds ordinary names (functions,
    /// variables, typedefs, etc.) in C and most kinds of names
    /// (functions, variables, members, types, etc.) in C++.
    LookupOrdinaryName = 0,
    /// Tag name lookup, which finds the names of enums, classes,
    /// structs, and unions.
    LookupTagName,
    /// Member name lookup, which finds the names of
    /// class/struct/union members.
    LookupMemberName,
    // Look up of an operator name (e.g., operator+) for use with
    // operator overloading. This lookup is similar to ordinary name
    // lookup, but will ignore any declarations that are class
    // members.
    LookupOperatorName,
    /// Look up of a name that precedes the '::' scope resolution
    /// operator in C++. This lookup completely ignores operator,
    /// function, and enumerator names (C++ [basic.lookup.qual]p1).
    LookupNestedNameSpecifierName,
    /// Look up a namespace name within a C++ using directive or
    /// namespace alias definition, ignoring non-namespace names (C++
    /// [basic.lookup.udir]p1).
    LookupNamespaceName,
    /// Look up an ordinary name that is going to be redeclared as a
    /// name with linkage. This lookup ignores any declarations that
    /// are outside of the current scope unless they have linkage. See 
    /// C99 6.2.2p4-5 and C++ [basic.link]p6.
    LookupRedeclarationWithLinkage,
    /// Look up the name of an Objective-C protocol.
    LookupObjCProtocolName,
    /// Look up the name of an Objective-C implementation
    LookupObjCImplementationName,
    /// Look up the name of an Objective-C category implementation
    LookupObjCCategoryImplName
  };

  /// @brief Represents the results of name lookup.
  ///
  /// An instance of the LookupResult class captures the results of a
  /// single name lookup, which can return no result (nothing found),
  /// a single declaration, a set of overloaded functions, or an
  /// ambiguity. Use the getKind() method to determine which of these
  /// results occurred for a given lookup. 
  ///
  /// Any non-ambiguous lookup can be converted into a single
  /// (possibly NULL) @c NamedDecl* via a conversion function or the
  /// getAsDecl() method. This conversion permits the common-case
  /// usage in C and Objective-C where name lookup will always return
  /// a single declaration.
  struct LookupResult {
    /// The kind of entity that is actually stored within the
    /// LookupResult object.
    enum {
      /// First is a single declaration (a NamedDecl*), which may be NULL.
      SingleDecl,

      /// First is a single declaration (an OverloadedFunctionDecl*).
      OverloadedDeclSingleDecl,

      /// [First, Last) is an iterator range represented as opaque
      /// pointers used to reconstruct IdentifierResolver::iterators.
      OverloadedDeclFromIdResolver,

      /// [First, Last) is an iterator range represented as opaque
      /// pointers used to reconstruct DeclContext::lookup_iterators.
      OverloadedDeclFromDeclContext,

      /// First is a pointer to a BasePaths structure, which is owned
      /// by the LookupResult. Last is non-zero to indicate that the
      /// ambiguity is caused by two names found in base class
      /// subobjects of different types.
      AmbiguousLookupStoresBasePaths,

      /// [First, Last) is an iterator range represented as opaque
      /// pointers used to reconstruct new'ed Decl*[] array containing
      /// found ambiguous decls. LookupResult is owner of this array.
      AmbiguousLookupStoresDecls
    } StoredKind;

    /// The first lookup result, whose contents depend on the kind of
    /// lookup result. This may be a NamedDecl* (if StoredKind ==
    /// SingleDecl), OverloadedFunctionDecl* (if StoredKind ==
    /// OverloadedDeclSingleDecl), the opaque pointer from an
    /// IdentifierResolver::iterator (if StoredKind ==
    /// OverloadedDeclFromIdResolver), a DeclContext::lookup_iterator
    /// (if StoredKind == OverloadedDeclFromDeclContext), or a
    /// BasePaths pointer (if StoredKind == AmbiguousLookupStoresBasePaths).
    mutable uintptr_t First;

    /// The last lookup result, whose contents depend on the kind of
    /// lookup result. This may be unused (if StoredKind ==
    /// SingleDecl), it may have the same type as First (for
    /// overloaded function declarations), or is may be used as a
    /// Boolean value (if StoredKind == AmbiguousLookupStoresBasePaths).
    mutable uintptr_t Last;

    /// Context - The context in which we will build any
    /// OverloadedFunctionDecl nodes needed by the conversion to
    /// Decl*.
    ASTContext *Context;

    /// @brief The kind of entity found by name lookup.
    enum LookupKind {
      /// @brief No entity found met the criteria.
      NotFound = 0,

      /// @brief Name lookup found a single declaration that met the
      /// criteria. getAsDecl will return this declaration.
      Found,

      /// @brief Name lookup found a set of overloaded functions that
      /// met the criteria. getAsDecl will turn this set of overloaded
      /// functions into an OverloadedFunctionDecl.
      FoundOverloaded,

      /// Name lookup results in an ambiguity because multiple
      /// entities that meet the lookup criteria were found in
      /// subobjects of different types. For example:
      /// @code
      /// struct A { void f(int); }
      /// struct B { void f(double); }
      /// struct C : A, B { };
      /// void test(C c) { 
      ///   c.f(0); // error: A::f and B::f come from subobjects of different
      ///           // types. overload resolution is not performed.
      /// }
      /// @endcode
      AmbiguousBaseSubobjectTypes,

      /// Name lookup results in an ambiguity because multiple
      /// nonstatic entities that meet the lookup criteria were found
      /// in different subobjects of the same type. For example:
      /// @code
      /// struct A { int x; };
      /// struct B : A { };
      /// struct C : A { };
      /// struct D : B, C { };
      /// int test(D d) {
      ///   return d.x; // error: 'x' is found in two A subobjects (of B and C)
      /// }
      /// @endcode
      AmbiguousBaseSubobjects,

      /// Name lookup results in an ambiguity because multiple definitions
      /// of entity that meet the lookup criteria were found in different
      /// declaration contexts.
      /// @code
      /// namespace A {
      ///   int i;
      ///   namespace B { int i; }
      ///   int test() {
      ///     using namespace B;
      ///     return i; // error 'i' is found in namespace A and A::B
      ///    }
      /// }
      /// @endcode
      AmbiguousReference
    };

    static LookupResult CreateLookupResult(ASTContext &Context, NamedDecl *D);

    static LookupResult CreateLookupResult(ASTContext &Context, 
                                           IdentifierResolver::iterator F, 
                                           IdentifierResolver::iterator L);

    static LookupResult CreateLookupResult(ASTContext &Context, 
                                           DeclContext::lookup_iterator F, 
                                           DeclContext::lookup_iterator L);

    static LookupResult CreateLookupResult(ASTContext &Context, BasePaths *Paths, 
                                           bool DifferentSubobjectTypes) {
      LookupResult Result;
      Result.StoredKind = AmbiguousLookupStoresBasePaths;
      Result.First = reinterpret_cast<uintptr_t>(Paths);
      Result.Last = DifferentSubobjectTypes? 1 : 0;
      Result.Context = &Context;
      return Result;
    }

    template <typename Iterator>
    static LookupResult CreateLookupResult(ASTContext &Context,
                                           Iterator B, std::size_t Len) {
      NamedDecl ** Array = new NamedDecl*[Len];
      for (std::size_t Idx = 0; Idx < Len; ++Idx, ++B)
        Array[Idx] = *B;
      LookupResult Result;
      Result.StoredKind = AmbiguousLookupStoresDecls;
      Result.First = reinterpret_cast<uintptr_t>(Array);
      Result.Last = reinterpret_cast<uintptr_t>(Array + Len);
      Result.Context = &Context;
      return Result;
    }

    LookupKind getKind() const;

    /// @brief Determine whether name look found something.
    operator bool() const { return getKind() != NotFound; }

    /// @brief Determines whether the lookup resulted in an ambiguity.
    bool isAmbiguous() const {
      return StoredKind == AmbiguousLookupStoresBasePaths ||
             StoredKind == AmbiguousLookupStoresDecls;
    }

    /// @brief Allows conversion of a lookup result into a
    /// declaration, with the same behavior as getAsDecl.
    operator NamedDecl*() const { return getAsDecl(); }

    NamedDecl* getAsDecl() const;

    BasePaths *getBasePaths() const;

    /// \brief Iterate over the results of name lookup.
    ///
    /// The @c iterator class provides iteration over the results of a
    /// non-ambiguous name lookup.
    class iterator {
      /// The LookupResult structure we're iterating through.
      LookupResult *Result;

      /// The current position of this iterator within the sequence of
      /// results. This value will have the same representation as the
      /// @c First field in the LookupResult structure.
      mutable uintptr_t Current;

    public:
      typedef NamedDecl *                value_type;
      typedef NamedDecl *                reference;
      typedef NamedDecl *                pointer;
      typedef std::ptrdiff_t             difference_type;
      typedef std::forward_iterator_tag  iterator_category;

      iterator() : Result(0), Current(0) { }

      iterator(LookupResult *Res, uintptr_t Cur) : Result(Res), Current(Cur) { }

      reference operator*() const;

      pointer operator->() const { return **this; }

      iterator &operator++();

      iterator operator++(int) {
        iterator tmp(*this);
        ++(*this);
        return tmp;
      }

      friend inline bool operator==(iterator const& x, iterator const& y) {
        return x.Current == y.Current;
      }

      friend inline bool operator!=(iterator const& x, iterator const& y) {
        return x.Current != y.Current;
      }
    };
    friend class iterator;

    iterator begin();
    iterator end();

    /// \brief Free the memory associated with this lookup.
    void Destroy();
  };

private:
  typedef llvm::SmallVector<LookupResult, 3> LookupResultsVecTy;

  std::pair<bool, LookupResult> CppLookupName(Scope *S, DeclarationName Name,
                                              LookupNameKind NameKind,
                                              bool RedeclarationOnly);
  ObjCMethodDecl *FindMethodInNestedImplementations(
                                                const ObjCInterfaceDecl *IFace,
                                                const Selector &Sel);

public:
  /// Determines whether D is a suitable lookup result according to the
  /// lookup criteria.
  static bool isAcceptableLookupResult(NamedDecl *D, LookupNameKind NameKind,
                                       unsigned IDNS) {
    switch (NameKind) {
    case Sema::LookupOrdinaryName:
    case Sema::LookupTagName:
    case Sema::LookupMemberName:
    case Sema::LookupRedeclarationWithLinkage: // FIXME: check linkage, scoping
    case Sema::LookupObjCProtocolName:
    case Sema::LookupObjCImplementationName:
    case Sema::LookupObjCCategoryImplName:
      return D->isInIdentifierNamespace(IDNS);
      
    case Sema::LookupOperatorName:
      return D->isInIdentifierNamespace(IDNS) && 
             !D->getDeclContext()->isRecord();

    case Sema::LookupNestedNameSpecifierName:
      return isa<TypedefDecl>(D) || D->isInIdentifierNamespace(Decl::IDNS_Tag);
      
    case Sema::LookupNamespaceName:
      return isa<NamespaceDecl>(D) || isa<NamespaceAliasDecl>(D);
    }
    
    assert(false && 
           "isAcceptableLookupResult always returns before this point");
    return false;
  }

  LookupResult LookupName(Scope *S, DeclarationName Name, 
                          LookupNameKind NameKind, 
                          bool RedeclarationOnly = false,
                          bool AllowBuiltinCreation = true,
                          SourceLocation Loc = SourceLocation());
  LookupResult LookupQualifiedName(DeclContext *LookupCtx, DeclarationName Name,
                                   LookupNameKind NameKind, 
                                   bool RedeclarationOnly = false);
  LookupResult LookupParsedName(Scope *S, const CXXScopeSpec *SS, 
                                DeclarationName Name,
                                LookupNameKind NameKind, 
                                bool RedeclarationOnly = false,
                                bool AllowBuiltinCreation = true,
                                SourceLocation Loc = SourceLocation());

  ObjCProtocolDecl *LookupProtocol(IdentifierInfo *II);
  ObjCImplementationDecl *LookupObjCImplementation(IdentifierInfo *II);
  ObjCCategoryImplDecl *LookupObjCCategoryImpl(IdentifierInfo *II);

  void LookupOverloadedOperatorName(OverloadedOperatorKind Op, Scope *S,
                                    QualType T1, QualType T2, 
                                    FunctionSet &Functions);
                          
  void ArgumentDependentLookup(DeclarationName Name,
                               Expr **Args, unsigned NumArgs,
                               FunctionSet &Functions);

  void FindAssociatedClassesAndNamespaces(Expr **Args, unsigned NumArgs,
                                   AssociatedNamespaceSet &AssociatedNamespaces,
                                   AssociatedClassSet &AssociatedClasses);

  bool DiagnoseAmbiguousLookup(LookupResult &Result, DeclarationName Name,
                               SourceLocation NameLoc, 
                               SourceRange LookupRange = SourceRange());
  //@}
  
  ObjCInterfaceDecl *getObjCInterfaceDecl(IdentifierInfo *Id);
  NamedDecl *LazilyCreateBuiltin(IdentifierInfo *II, unsigned ID, 
                                 Scope *S, bool ForRedeclaration,
                                 SourceLocation Loc);
  NamedDecl *ImplicitlyDefineFunction(SourceLocation Loc, IdentifierInfo &II,
                                      Scope *S);
  void AddKnownFunctionAttributes(FunctionDecl *FD);

  // More parsing and symbol table subroutines.

  // Decl attributes - this routine is the top level dispatcher. 
  void ProcessDeclAttributes(Decl *D, const Declarator &PD);
  void ProcessDeclAttributeList(Decl *D, const AttributeList *AttrList);

  void WarnUndefinedMethod(SourceLocation ImpLoc, ObjCMethodDecl *method,
                           bool &IncompleteImpl);
  void WarnConflictingTypedMethods(ObjCMethodDecl *ImpMethod,
                                   ObjCMethodDecl *IntfMethod);
  bool QualifiedIdConformsQualifiedId(QualType LHS, QualType RHS);

  NamespaceDecl *GetStdNamespace();
  
  bool isPropertyReadonly(ObjCPropertyDecl *PropertyDecl,
                          ObjCInterfaceDecl *IDecl);
                           
  /// CheckProtocolMethodDefs - This routine checks unimplemented
  /// methods declared in protocol, and those referenced by it.
  /// \param IDecl - Used for checking for methods which may have been
  /// inherited.
  void CheckProtocolMethodDefs(SourceLocation ImpLoc,
                               ObjCProtocolDecl *PDecl,
                               bool& IncompleteImpl,
                               const llvm::DenseSet<Selector> &InsMap,
                               const llvm::DenseSet<Selector> &ClsMap,
                               ObjCInterfaceDecl *IDecl);
  
  /// CheckImplementationIvars - This routine checks if the instance variables
  /// listed in the implelementation match those listed in the interface. 
  void CheckImplementationIvars(ObjCImplementationDecl *ImpDecl,
                                ObjCIvarDecl **Fields, unsigned nIvars,
                                SourceLocation Loc);
  
  /// ImplMethodsVsClassMethods - This is main routine to warn if any method
  /// remains unimplemented in the class or category @implementation.
  void ImplMethodsVsClassMethods(ObjCImplDecl* IMPDecl, 
                                 ObjCContainerDecl* IDecl, 
                                 bool IncompleteImpl = false);
  
  /// MatchTwoMethodDeclarations - Checks if two methods' type match and returns
  /// true, or false, accordingly.
  bool MatchTwoMethodDeclarations(const ObjCMethodDecl *Method, 
                                  const ObjCMethodDecl *PrevMethod,
                                  bool matchBasedOnSizeAndAlignment = false); 

  /// MatchAllMethodDeclarations - Check methods declaraed in interface or
  /// or protocol against those declared in their implementations.
  void MatchAllMethodDeclarations(const llvm::DenseSet<Selector> &InsMap,
                                  const llvm::DenseSet<Selector> &ClsMap,
                                  llvm::DenseSet<Selector> &InsMapSeen,
                                  llvm::DenseSet<Selector> &ClsMapSeen,
                                  ObjCImplDecl* IMPDecl,
                                  ObjCContainerDecl* IDecl,
                                  bool &IncompleteImpl,
                                  bool ImmediateClass);

  /// AddInstanceMethodToGlobalPool - All instance methods in a translation
  /// unit are added to a global pool. This allows us to efficiently associate
  /// a selector with a method declaraation for purposes of typechecking
  /// messages sent to "id" (where the class of the object is unknown).
  void AddInstanceMethodToGlobalPool(ObjCMethodDecl *Method);
  
  /// LookupInstanceMethodInGlobalPool - Returns the method and warns if
  /// there are multiple signatures.
  ObjCMethodDecl *LookupInstanceMethodInGlobalPool(Selector Sel, SourceRange R);

  /// LookupFactoryMethodInGlobalPool - Returns the method and warns if
  /// there are multiple signatures.
  ObjCMethodDecl *LookupFactoryMethodInGlobalPool(Selector Sel, SourceRange R);
  
  /// AddFactoryMethodToGlobalPool - Same as above, but for factory methods.
  void AddFactoryMethodToGlobalPool(ObjCMethodDecl *Method);
  //===--------------------------------------------------------------------===//
  // Statement Parsing Callbacks: SemaStmt.cpp.
public:
  virtual OwningStmtResult ActOnExprStmt(FullExprArg Expr);

  virtual OwningStmtResult ActOnNullStmt(SourceLocation SemiLoc);
  virtual OwningStmtResult ActOnCompoundStmt(SourceLocation L, SourceLocation R,
                                             MultiStmtArg Elts,
                                             bool isStmtExpr);
  virtual OwningStmtResult ActOnDeclStmt(DeclGroupPtrTy Decl,
                                         SourceLocation StartLoc,
                                         SourceLocation EndLoc);
  virtual OwningStmtResult ActOnCaseStmt(SourceLocation CaseLoc, ExprArg LHSVal,
                                    SourceLocation DotDotDotLoc, ExprArg RHSVal,
                                    SourceLocation ColonLoc);
  virtual void ActOnCaseStmtBody(StmtTy *CaseStmt, StmtArg SubStmt);
  
  virtual OwningStmtResult ActOnDefaultStmt(SourceLocation DefaultLoc,
                                            SourceLocation ColonLoc,
                                            StmtArg SubStmt, Scope *CurScope);
  virtual OwningStmtResult ActOnLabelStmt(SourceLocation IdentLoc,
                                          IdentifierInfo *II,
                                          SourceLocation ColonLoc,
                                          StmtArg SubStmt);
  virtual OwningStmtResult ActOnIfStmt(SourceLocation IfLoc, 
                                       FullExprArg CondVal, StmtArg ThenVal, 
                                       SourceLocation ElseLoc, StmtArg ElseVal);
  virtual OwningStmtResult ActOnStartOfSwitchStmt(ExprArg Cond);
  virtual OwningStmtResult ActOnFinishSwitchStmt(SourceLocation SwitchLoc,
                                                 StmtArg Switch, StmtArg Body);
  virtual OwningStmtResult ActOnWhileStmt(SourceLocation WhileLoc, 
                                          FullExprArg Cond, StmtArg Body);
  virtual OwningStmtResult ActOnDoStmt(SourceLocation DoLoc, StmtArg Body,
                                       SourceLocation WhileLoc, ExprArg Cond);

  virtual OwningStmtResult ActOnForStmt(SourceLocation ForLoc,
                                        SourceLocation LParenLoc,
                                        StmtArg First, ExprArg Second,
                                        ExprArg Third, SourceLocation RParenLoc,
                                        StmtArg Body);
  virtual OwningStmtResult ActOnObjCForCollectionStmt(SourceLocation ForColLoc,
                                       SourceLocation LParenLoc,
                                       StmtArg First, ExprArg Second,
                                       SourceLocation RParenLoc, StmtArg Body);

  virtual OwningStmtResult ActOnGotoStmt(SourceLocation GotoLoc,
                                         SourceLocation LabelLoc,
                                         IdentifierInfo *LabelII);
  virtual OwningStmtResult ActOnIndirectGotoStmt(SourceLocation GotoLoc,
                                                 SourceLocation StarLoc,
                                                 ExprArg DestExp);
  virtual OwningStmtResult ActOnContinueStmt(SourceLocation ContinueLoc,
                                             Scope *CurScope);
  virtual OwningStmtResult ActOnBreakStmt(SourceLocation GotoLoc,
                                          Scope *CurScope);

  virtual OwningStmtResult ActOnReturnStmt(SourceLocation ReturnLoc,
                                           ExprArg RetValExp);
  OwningStmtResult ActOnBlockReturnStmt(SourceLocation ReturnLoc,
                                        Expr *RetValExp);

  virtual OwningStmtResult ActOnAsmStmt(SourceLocation AsmLoc,
                                        bool IsSimple,
                                        bool IsVolatile,
                                        unsigned NumOutputs,
                                        unsigned NumInputs,
                                        std::string *Names,
                                        MultiExprArg Constraints,
                                        MultiExprArg Exprs,
                                        ExprArg AsmString,
                                        MultiExprArg Clobbers,
                                        SourceLocation RParenLoc);

  virtual OwningStmtResult ActOnObjCAtCatchStmt(SourceLocation AtLoc,
                                                SourceLocation RParen,
                                                DeclPtrTy Parm, StmtArg Body,
                                                StmtArg CatchList);

  virtual OwningStmtResult ActOnObjCAtFinallyStmt(SourceLocation AtLoc,
                                                  StmtArg Body);

  virtual OwningStmtResult ActOnObjCAtTryStmt(SourceLocation AtLoc,
                                              StmtArg Try,
                                              StmtArg Catch, StmtArg Finally);

  virtual OwningStmtResult ActOnObjCAtThrowStmt(SourceLocation AtLoc,
                                                ExprArg Throw, 
                                                Scope *CurScope);
  virtual OwningStmtResult ActOnObjCAtSynchronizedStmt(SourceLocation AtLoc,
                                                       ExprArg SynchExpr,
                                                       StmtArg SynchBody);

  virtual DeclPtrTy ActOnExceptionDeclarator(Scope *S, Declarator &D);
  virtual OwningStmtResult ActOnCXXCatchBlock(SourceLocation CatchLoc,
                                              DeclPtrTy ExDecl,
                                              StmtArg HandlerBlock);
  virtual OwningStmtResult ActOnCXXTryBlock(SourceLocation TryLoc,
                                            StmtArg TryBlock,
                                            MultiStmtArg Handlers);
  void DiagnoseReturnInConstructorExceptionHandler(CXXTryStmt *TryBlock);

  //===--------------------------------------------------------------------===//
  // Expression Parsing Callbacks: SemaExpr.cpp.

  bool DiagnoseUseOfDecl(NamedDecl *D, SourceLocation Loc);
  bool DiagnosePropertyAccessorMismatch(ObjCPropertyDecl *PD, 
                                        ObjCMethodDecl *Getter,
                                        SourceLocation Loc);
  void DiagnoseSentinelCalls(NamedDecl *D, SourceLocation Loc,
                             Expr **Args, unsigned NumArgs);

  // Primary Expressions.
  virtual SourceRange getExprRange(ExprTy *E) const;

  virtual OwningExprResult ActOnIdentifierExpr(Scope *S, SourceLocation Loc,
                                               IdentifierInfo &II,
                                               bool HasTrailingLParen,
                                               const CXXScopeSpec *SS = 0,
                                               bool isAddressOfOperand = false);
  virtual OwningExprResult ActOnCXXOperatorFunctionIdExpr(Scope *S,
                                                    SourceLocation OperatorLoc,
                                                    OverloadedOperatorKind Op,
                                                    bool HasTrailingLParen,
                                                    const CXXScopeSpec &SS,
                                                    bool isAddressOfOperand);
  virtual OwningExprResult ActOnCXXConversionFunctionExpr(Scope *S,
                                                    SourceLocation OperatorLoc,
                                                    TypeTy *Ty,
                                                    bool HasTrailingLParen,
                                                    const CXXScopeSpec &SS,
                                                    bool isAddressOfOperand);
  DeclRefExpr *BuildDeclRefExpr(NamedDecl *D, QualType Ty, SourceLocation Loc,
                                bool TypeDependent, bool ValueDependent,
                                const CXXScopeSpec *SS = 0);
  VarDecl *BuildAnonymousStructUnionMemberPath(FieldDecl *Field,
                                    llvm::SmallVectorImpl<FieldDecl *> &Path);
  OwningExprResult
  BuildAnonymousStructUnionMemberReference(SourceLocation Loc,
                                           FieldDecl *Field,
                                           Expr *BaseObjectExpr = 0,
                                      SourceLocation OpLoc = SourceLocation());
  OwningExprResult ActOnDeclarationNameExpr(Scope *S, SourceLocation Loc,
                                            DeclarationName Name,
                                            bool HasTrailingLParen,
                                            const CXXScopeSpec *SS,
                                            bool isAddressOfOperand = false);

  virtual OwningExprResult ActOnPredefinedExpr(SourceLocation Loc,
                                               tok::TokenKind Kind);
  virtual OwningExprResult ActOnNumericConstant(const Token &);
  virtual OwningExprResult ActOnCharacterConstant(const Token &);
  virtual OwningExprResult ActOnParenExpr(SourceLocation L, SourceLocation R,
                                          ExprArg Val);

  /// ActOnStringLiteral - The specified tokens were lexed as pasted string
  /// fragments (e.g. "foo" "bar" L"baz").
  virtual OwningExprResult ActOnStringLiteral(const Token *Toks,
                                              unsigned NumToks);

  // Binary/Unary Operators.  'Tok' is the token for the operator.
  OwningExprResult CreateBuiltinUnaryOp(SourceLocation OpLoc,
                                        unsigned OpcIn, 
                                        ExprArg InputArg);
  virtual OwningExprResult ActOnUnaryOp(Scope *S, SourceLocation OpLoc,
                                        tok::TokenKind Op, ExprArg Input);

  OwningExprResult CreateSizeOfAlignOfExpr(QualType T, SourceLocation OpLoc, 
                                           bool isSizeOf, SourceRange R);
  OwningExprResult CreateSizeOfAlignOfExpr(Expr *E, SourceLocation OpLoc, 
                                           bool isSizeOf, SourceRange R);
  virtual OwningExprResult
    ActOnSizeOfAlignOfExpr(SourceLocation OpLoc, bool isSizeof, bool isType,
                           void *TyOrEx, const SourceRange &ArgRange);
                                           
  bool CheckAlignOfExpr(Expr *E, SourceLocation OpLoc, const SourceRange &R);
  bool CheckSizeOfAlignOfOperand(QualType type, SourceLocation OpLoc,
                                 const SourceRange &R, bool isSizeof);

  virtual OwningExprResult ActOnPostfixUnaryOp(Scope *S, SourceLocation OpLoc,
                                               tok::TokenKind Kind,
                                               ExprArg Input);

  virtual OwningExprResult ActOnArraySubscriptExpr(Scope *S, ExprArg Base,
                                                   SourceLocation LLoc,
                                                   ExprArg Idx,
                                                   SourceLocation RLoc);
  virtual OwningExprResult ActOnMemberReferenceExpr(Scope *S, ExprArg Base,
                                                    SourceLocation OpLoc,
                                                    tok::TokenKind OpKind,
                                                    SourceLocation MemberLoc,
                                                    IdentifierInfo &Member,
                                                    DeclPtrTy ImplDecl);
  bool ConvertArgumentsForCall(CallExpr *Call, Expr *Fn,
                               FunctionDecl *FDecl,
                               const FunctionProtoType *Proto,
                               Expr **Args, unsigned NumArgs,
                               SourceLocation RParenLoc);

  /// ActOnCallExpr - Handle a call to Fn with the specified array of arguments.
  /// This provides the location of the left/right parens and a list of comma
  /// locations.
  virtual OwningExprResult ActOnCallExpr(Scope *S, ExprArg Fn,
                                         SourceLocation LParenLoc,
                                         MultiExprArg Args,
                                         SourceLocation *CommaLocs,
                                         SourceLocation RParenLoc);

  virtual OwningExprResult ActOnCastExpr(SourceLocation LParenLoc, TypeTy *Ty,
                                         SourceLocation RParenLoc, ExprArg Op);

  virtual OwningExprResult ActOnCompoundLiteral(SourceLocation LParenLoc,
                                                TypeTy *Ty,
                                                SourceLocation RParenLoc,
                                                ExprArg Op);

  virtual OwningExprResult ActOnInitList(SourceLocation LParenLoc,
                                         MultiExprArg InitList,
                                         SourceLocation RParenLoc);

  virtual OwningExprResult ActOnDesignatedInitializer(Designation &Desig,
                                                      SourceLocation Loc,
                                                      bool GNUSyntax,
                                                      OwningExprResult Init);

  virtual OwningExprResult ActOnBinOp(Scope *S, SourceLocation TokLoc,
                                      tok::TokenKind Kind,
                                      ExprArg LHS, ExprArg RHS);
  OwningExprResult CreateBuiltinBinOp(SourceLocation TokLoc,
                                      unsigned Opc, Expr *lhs, Expr *rhs);

  /// ActOnConditionalOp - Parse a ?: operation.  Note that 'LHS' may be null
  /// in the case of a the GNU conditional expr extension.
  virtual OwningExprResult ActOnConditionalOp(SourceLocation QuestionLoc,
                                              SourceLocation ColonLoc,
                                              ExprArg Cond, ExprArg LHS,
                                              ExprArg RHS);

  /// ActOnAddrLabel - Parse the GNU address of label extension: "&&foo".
  virtual OwningExprResult ActOnAddrLabel(SourceLocation OpLoc,
                                          SourceLocation LabLoc,
                                          IdentifierInfo *LabelII);

  virtual OwningExprResult ActOnStmtExpr(SourceLocation LPLoc, StmtArg SubStmt,
                                         SourceLocation RPLoc); // "({..})"

  /// __builtin_offsetof(type, a.b[123][456].c)
  virtual OwningExprResult ActOnBuiltinOffsetOf(Scope *S,
                                                SourceLocation BuiltinLoc,
                                                SourceLocation TypeLoc,
                                                TypeTy *Arg1,
                                                OffsetOfComponent *CompPtr,
                                                unsigned NumComponents,
                                                SourceLocation RParenLoc);

  // __builtin_types_compatible_p(type1, type2)
  virtual OwningExprResult ActOnTypesCompatibleExpr(SourceLocation BuiltinLoc,
                                                    TypeTy *arg1, TypeTy *arg2,
                                                    SourceLocation RPLoc);

  // __builtin_choose_expr(constExpr, expr1, expr2)
  virtual OwningExprResult ActOnChooseExpr(SourceLocation BuiltinLoc,
                                           ExprArg cond, ExprArg expr1,
                                           ExprArg expr2, SourceLocation RPLoc);

  // __builtin_va_arg(expr, type)
  virtual OwningExprResult ActOnVAArg(SourceLocation BuiltinLoc,
                                      ExprArg expr, TypeTy *type,
                                      SourceLocation RPLoc);

  // __null
  virtual OwningExprResult ActOnGNUNullExpr(SourceLocation TokenLoc);

  //===------------------------- "Block" Extension ------------------------===//

  /// ActOnBlockStart - This callback is invoked when a block literal is
  /// started.
  virtual void ActOnBlockStart(SourceLocation CaretLoc, Scope *CurScope);

  /// ActOnBlockArguments - This callback allows processing of block arguments.
  /// If there are no arguments, this is still invoked.
  virtual void ActOnBlockArguments(Declarator &ParamInfo, Scope *CurScope);

  /// ActOnBlockError - If there is an error parsing a block, this callback
  /// is invoked to pop the information about the block from the action impl.
  virtual void ActOnBlockError(SourceLocation CaretLoc, Scope *CurScope);

  /// ActOnBlockStmtExpr - This is called when the body of a block statement
  /// literal was successfully completed.  ^(int x){...}
  virtual OwningExprResult ActOnBlockStmtExpr(SourceLocation CaretLoc,
                                              StmtArg Body, Scope *CurScope);

  //===---------------------------- C++ Features --------------------------===//

  // Act on C++ namespaces
  virtual DeclPtrTy ActOnStartNamespaceDef(Scope *S, SourceLocation IdentLoc,
                                           IdentifierInfo *Ident,
                                           SourceLocation LBrace);
  virtual void ActOnFinishNamespaceDef(DeclPtrTy Dcl, SourceLocation RBrace);

  virtual DeclPtrTy ActOnUsingDirective(Scope *CurScope,
                                        SourceLocation UsingLoc,
                                        SourceLocation NamespcLoc,
                                        const CXXScopeSpec &SS,
                                        SourceLocation IdentLoc,
                                        IdentifierInfo *NamespcName,
                                        AttributeList *AttrList);
  
  void PushUsingDirective(Scope *S, UsingDirectiveDecl *UDir);

  virtual DeclPtrTy ActOnNamespaceAliasDef(Scope *CurScope,
                                           SourceLocation NamespaceLoc,
                                           SourceLocation AliasLoc,
                                           IdentifierInfo *Alias,
                                           const CXXScopeSpec &SS,
                                           SourceLocation IdentLoc,
                                           IdentifierInfo *Ident);
  
  /// AddCXXDirectInitializerToDecl - This action is called immediately after 
  /// ActOnDeclarator, when a C++ direct initializer is present.
  /// e.g: "int x(1);"
  virtual void AddCXXDirectInitializerToDecl(DeclPtrTy Dcl,
                                             SourceLocation LParenLoc,
                                             MultiExprArg Exprs,
                                             SourceLocation *CommaLocs,
                                             SourceLocation RParenLoc);

  /// InitializeVarWithConstructor - Creates an CXXConstructExpr
  /// and sets it as the initializer for the the passed in VarDecl.
  void InitializeVarWithConstructor(VarDecl *VD, 
                                    CXXConstructorDecl *Constructor,
                                    QualType DeclInitType, 
                                    Expr **Exprs, unsigned NumExprs);
  
  /// InitializationKind - Represents which kind of C++ initialization
  /// [dcl.init] a routine is to perform.
  enum InitializationKind {
    IK_Direct, ///< Direct initialization
    IK_Copy,   ///< Copy initialization
    IK_Default ///< Default initialization
  };

  CXXConstructorDecl *
  PerformInitializationByConstructor(QualType ClassType,
                                     Expr **Args, unsigned NumArgs,
                                     SourceLocation Loc, SourceRange Range,
                                     DeclarationName InitEntity,
                                     InitializationKind Kind);

  /// ActOnCXXNamedCast - Parse {dynamic,static,reinterpret,const}_cast's.
  virtual OwningExprResult ActOnCXXNamedCast(SourceLocation OpLoc,
                                             tok::TokenKind Kind,
                                             SourceLocation LAngleBracketLoc,
                                             TypeTy *Ty,
                                             SourceLocation RAngleBracketLoc,
                                             SourceLocation LParenLoc,
                                             ExprArg E,
                                             SourceLocation RParenLoc);

  /// ActOnCXXTypeid - Parse typeid( something ).
  virtual OwningExprResult ActOnCXXTypeid(SourceLocation OpLoc,
                                          SourceLocation LParenLoc, bool isType,
                                          void *TyOrExpr,
                                          SourceLocation RParenLoc);

  //// ActOnCXXThis -  Parse 'this' pointer.
  virtual OwningExprResult ActOnCXXThis(SourceLocation ThisLoc);

  /// ActOnCXXBoolLiteral - Parse {true,false} literals.
  virtual OwningExprResult ActOnCXXBoolLiteral(SourceLocation OpLoc,
                                               tok::TokenKind Kind);

  /// ActOnCXXNullPtrLiteral - Parse 'nullptr'.
  virtual OwningExprResult ActOnCXXNullPtrLiteral(SourceLocation Loc);

  //// ActOnCXXThrow -  Parse throw expressions.
  virtual OwningExprResult ActOnCXXThrow(SourceLocation OpLoc,
                                         ExprArg expr);
  bool CheckCXXThrowOperand(SourceLocation ThrowLoc, Expr *&E);

  /// ActOnCXXTypeConstructExpr - Parse construction of a specified type.
  /// Can be interpreted either as function-style casting ("int(x)")
  /// or class type construction ("ClassType(x,y,z)")
  /// or creation of a value-initialized type ("int()").
  virtual OwningExprResult ActOnCXXTypeConstructExpr(SourceRange TypeRange,
                                                     TypeTy *TypeRep,
                                                     SourceLocation LParenLoc,
                                                     MultiExprArg Exprs,
                                                     SourceLocation *CommaLocs,
                                                     SourceLocation RParenLoc);

  /// ActOnCXXNew - Parsed a C++ 'new' expression.
  virtual OwningExprResult ActOnCXXNew(SourceLocation StartLoc, bool UseGlobal,
                                       SourceLocation PlacementLParen,
                                       MultiExprArg PlacementArgs,
                                       SourceLocation PlacementRParen,
                                       bool ParenTypeId, Declarator &D,
                                       SourceLocation ConstructorLParen,
                                       MultiExprArg ConstructorArgs,
                                       SourceLocation ConstructorRParen);
  bool CheckAllocatedType(QualType AllocType, const Declarator &D);
  bool FindAllocationFunctions(SourceLocation StartLoc, SourceRange Range,
                               bool UseGlobal, QualType AllocType, bool IsArray,
                               Expr **PlaceArgs, unsigned NumPlaceArgs,
                               FunctionDecl *&OperatorNew,
                               FunctionDecl *&OperatorDelete);
  bool FindAllocationOverload(SourceLocation StartLoc, SourceRange Range,
                              DeclarationName Name, Expr** Args,
                              unsigned NumArgs, DeclContext *Ctx,
                              bool AllowMissing, FunctionDecl *&Operator);
  void DeclareGlobalNewDelete();
  void DeclareGlobalAllocationFunction(DeclarationName Name, QualType Return,
                                       QualType Argument);

  /// ActOnCXXDelete - Parsed a C++ 'delete' expression
  virtual OwningExprResult ActOnCXXDelete(SourceLocation StartLoc,
                                          bool UseGlobal, bool ArrayForm,
                                          ExprArg Operand);

  /// ActOnCXXConditionDeclarationExpr - Parsed a condition declaration of a
  /// C++ if/switch/while/for statement.
  /// e.g: "if (int x = f()) {...}"
  virtual OwningExprResult ActOnCXXConditionDeclarationExpr(Scope *S,
                                                      SourceLocation StartLoc,
                                                      Declarator &D,
                                                      SourceLocation EqualLoc,
                                                      ExprArg AssignExprVal);

  /// ActOnUnaryTypeTrait - Parsed one of the unary type trait support
  /// pseudo-functions.
  virtual OwningExprResult ActOnUnaryTypeTrait(UnaryTypeTrait OTT,
                                               SourceLocation KWLoc,
                                               SourceLocation LParen,
                                               TypeTy *Ty,
                                               SourceLocation RParen);

  virtual OwningExprResult ActOnFinishFullExpr(ExprArg Expr);

  bool RequireCompleteDeclContext(const CXXScopeSpec &SS);
  
  DeclContext *computeDeclContext(const CXXScopeSpec &SS);
  bool isDependentScopeSpecifier(const CXXScopeSpec &SS);
  CXXRecordDecl *getCurrentInstantiationOf(NestedNameSpecifier *NNS);
  bool isUnknownSpecialization(const CXXScopeSpec &SS);

  /// ActOnCXXGlobalScopeSpecifier - Return the object that represents the
  /// global scope ('::').
  virtual CXXScopeTy *ActOnCXXGlobalScopeSpecifier(Scope *S,
                                                   SourceLocation CCLoc);

  /// ActOnCXXNestedNameSpecifier - Called during parsing of a
  /// nested-name-specifier. e.g. for "foo::bar::" we parsed "foo::" and now
  /// we want to resolve "bar::". 'SS' is empty or the previously parsed
  /// nested-name part ("foo::"), 'IdLoc' is the source location of 'bar',
  /// 'CCLoc' is the location of '::' and 'II' is the identifier for 'bar'.
  /// Returns a CXXScopeTy* object representing the C++ scope.
  virtual CXXScopeTy *ActOnCXXNestedNameSpecifier(Scope *S,
                                                  const CXXScopeSpec &SS,
                                                  SourceLocation IdLoc,
                                                  SourceLocation CCLoc,
                                                  IdentifierInfo &II);

  /// ActOnCXXNestedNameSpecifier - Called during parsing of a
  /// nested-name-specifier that involves a template-id, e.g.,
  /// "foo::bar<int, float>::", and now we need to build a scope
  /// specifier. \p SS is empty or the previously parsed nested-name
  /// part ("foo::"), \p Type is the already-parsed class template
  /// specialization (or other template-id that names a type), \p
  /// TypeRange is the source range where the type is located, and \p
  /// CCLoc is the location of the trailing '::'.
  virtual CXXScopeTy *ActOnCXXNestedNameSpecifier(Scope *S,
                                                  const CXXScopeSpec &SS,
                                                  TypeTy *Type,
                                                  SourceRange TypeRange,
                                                  SourceLocation CCLoc);

  /// ActOnCXXEnterDeclaratorScope - Called when a C++ scope specifier (global
  /// scope or nested-name-specifier) is parsed, part of a declarator-id.
  /// After this method is called, according to [C++ 3.4.3p3], names should be
  /// looked up in the declarator-id's scope, until the declarator is parsed and
  /// ActOnCXXExitDeclaratorScope is called.
  /// The 'SS' should be a non-empty valid CXXScopeSpec.
  virtual void ActOnCXXEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS);

  /// ActOnCXXExitDeclaratorScope - Called when a declarator that previously
  /// invoked ActOnCXXEnterDeclaratorScope(), is finished. 'SS' is the same
  /// CXXScopeSpec that was passed to ActOnCXXEnterDeclaratorScope as well.
  /// Used to indicate that names should revert to being looked up in the
  /// defining scope.
  virtual void ActOnCXXExitDeclaratorScope(Scope *S, const CXXScopeSpec &SS);

  // ParseObjCStringLiteral - Parse Objective-C string literals.
  virtual ExprResult ParseObjCStringLiteral(SourceLocation *AtLocs, 
                                            ExprTy **Strings,
                                            unsigned NumStrings);
  virtual ExprResult ParseObjCEncodeExpression(SourceLocation AtLoc,
                                               SourceLocation EncodeLoc,
                                               SourceLocation LParenLoc,
                                               TypeTy *Ty,
                                               SourceLocation RParenLoc);
  
  // ParseObjCSelectorExpression - Build selector expression for @selector
  virtual ExprResult ParseObjCSelectorExpression(Selector Sel,
                                                 SourceLocation AtLoc,
                                                 SourceLocation SelLoc,
                                                 SourceLocation LParenLoc,
                                                 SourceLocation RParenLoc);
  
  // ParseObjCProtocolExpression - Build protocol expression for @protocol
  virtual ExprResult ParseObjCProtocolExpression(IdentifierInfo * ProtocolName,
                                                 SourceLocation AtLoc,
                                                 SourceLocation ProtoLoc,
                                                 SourceLocation LParenLoc,
                                                 SourceLocation RParenLoc);

  //===--------------------------------------------------------------------===//
  // C++ Declarations
  //
  virtual DeclPtrTy ActOnStartLinkageSpecification(Scope *S,
                                                   SourceLocation ExternLoc,
                                                   SourceLocation LangLoc,
                                                   const char *Lang,
                                                   unsigned StrSize,
                                                   SourceLocation LBraceLoc);
  virtual DeclPtrTy ActOnFinishLinkageSpecification(Scope *S,
                                                    DeclPtrTy LinkageSpec,
                                                    SourceLocation RBraceLoc);


  //===--------------------------------------------------------------------===//
  // C++ Classes
  //
  virtual bool isCurrentClassName(const IdentifierInfo &II, Scope *S,
                                  const CXXScopeSpec *SS);

  virtual DeclPtrTy ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS,
                                             Declarator &D,
                                             ExprTy *BitfieldWidth,
                                             ExprTy *Init,
                                             bool Deleted = false);

  virtual MemInitResult ActOnMemInitializer(DeclPtrTy ConstructorD,
                                            Scope *S,
                                            IdentifierInfo *MemberOrBase,
                                            SourceLocation IdLoc,
                                            SourceLocation LParenLoc,
                                            ExprTy **Args, unsigned NumArgs,
                                            SourceLocation *CommaLocs,
                                            SourceLocation RParenLoc);

  void AddImplicitlyDeclaredMembersToClass(CXXRecordDecl *ClassDecl);

  virtual void ActOnMemInitializers(DeclPtrTy ConstructorDecl, 
                                    SourceLocation ColonLoc,
                                    MemInitTy **MemInits, unsigned NumMemInits);
  
  virtual void ActOnFinishCXXMemberSpecification(Scope* S, SourceLocation RLoc,
                                                 DeclPtrTy TagDecl,
                                                 SourceLocation LBrac,
                                                 SourceLocation RBrac);

  virtual void ActOnStartDelayedCXXMethodDeclaration(Scope *S,
                                                     DeclPtrTy Method);
  virtual void ActOnDelayedCXXMethodParameter(Scope *S, DeclPtrTy Param);
  virtual void ActOnFinishDelayedCXXMethodDeclaration(Scope *S,
                                                      DeclPtrTy Method);

  virtual DeclPtrTy ActOnStaticAssertDeclaration(SourceLocation AssertLoc, 
                                                 ExprArg AssertExpr,
                                                 ExprArg AssertMessageExpr);
  
  virtual bool ActOnFriendDecl(Scope *S, SourceLocation FriendLoc,
                               DeclPtrTy Dcl);

  QualType CheckConstructorDeclarator(Declarator &D, QualType R,
                                      FunctionDecl::StorageClass& SC);
  void CheckConstructor(CXXConstructorDecl *Constructor);
  QualType CheckDestructorDeclarator(Declarator &D,
                                     FunctionDecl::StorageClass& SC);
  void CheckConversionDeclarator(Declarator &D, QualType &R,
                                 FunctionDecl::StorageClass& SC);
  DeclPtrTy ActOnConversionDeclarator(CXXConversionDecl *Conversion);

  //===--------------------------------------------------------------------===//
  // C++ Derived Classes
  //

  /// ActOnBaseSpecifier - Parsed a base specifier
  CXXBaseSpecifier *CheckBaseSpecifier(CXXRecordDecl *Class,
                                       SourceRange SpecifierRange,
                                       bool Virtual, AccessSpecifier Access,
                                       QualType BaseType, 
                                       SourceLocation BaseLoc);
  virtual BaseResult ActOnBaseSpecifier(DeclPtrTy classdecl, 
                                        SourceRange SpecifierRange,
                                        bool Virtual, AccessSpecifier Access,
                                        TypeTy *basetype, SourceLocation 
                                        BaseLoc);

  bool AttachBaseSpecifiers(CXXRecordDecl *Class, CXXBaseSpecifier **Bases,
                            unsigned NumBases);
  virtual void ActOnBaseSpecifiers(DeclPtrTy ClassDecl, BaseTy **Bases, 
                                   unsigned NumBases);

  bool IsDerivedFrom(QualType Derived, QualType Base);
  bool IsDerivedFrom(QualType Derived, QualType Base, BasePaths &Paths);
  bool LookupInBases(CXXRecordDecl *Class, const MemberLookupCriteria& Criteria,
                     BasePaths &Paths);
  bool CheckDerivedToBaseConversion(QualType Derived, QualType Base,
                                    SourceLocation Loc, SourceRange Range);
  bool CheckDerivedToBaseConversion(QualType Derived, QualType Base,
                                    unsigned InaccessibleBaseID,
                                    unsigned AmbigiousBaseConvID,
                                    SourceLocation Loc, SourceRange Range,
                                    DeclarationName Name);
  
  std::string getAmbiguousPathsDisplayString(BasePaths &Paths);
  
  /// CheckReturnTypeCovariance - Checks whether two types are covariant, 
  /// according to C++ [class.virtual]p5.
  bool CheckOverridingFunctionReturnType(const CXXMethodDecl *New, 
                                         const CXXMethodDecl *Old);
  

  //===--------------------------------------------------------------------===//
  // C++ Access Control
  //
  
  bool SetMemberAccessSpecifier(NamedDecl *MemberDecl, 
                                NamedDecl *PrevMemberDecl,
                                AccessSpecifier LexicalAS);
  
  bool CheckBaseClassAccess(QualType Derived, QualType Base, 
                            unsigned InaccessibleBaseID,
                            BasePaths& Paths, SourceLocation AccessLoc,
                            DeclarationName Name);
  
  
  enum AbstractDiagSelID {
    AbstractNone = -1,
    AbstractReturnType,
    AbstractParamType,
    AbstractVariableType,
    AbstractFieldType
  };
  
  bool RequireNonAbstractType(SourceLocation Loc, QualType T, unsigned DiagID, 
                              AbstractDiagSelID SelID = AbstractNone,
                              const CXXRecordDecl *CurrentRD = 0);

  //===--------------------------------------------------------------------===//
  // C++ Overloaded Operators [C++ 13.5]
  //

  bool CheckOverloadedOperatorDeclaration(FunctionDecl *FnDecl);

  //===--------------------------------------------------------------------===//
  // C++ Templates [C++ 14]
  //
  virtual TemplateNameKind isTemplateName(const IdentifierInfo &II, Scope *S,
                                          TemplateTy &Template,
                                          const CXXScopeSpec *SS = 0);
  bool DiagnoseTemplateParameterShadow(SourceLocation Loc, Decl *PrevDecl);
  TemplateDecl *AdjustDeclIfTemplate(DeclPtrTy &Decl);

  virtual DeclPtrTy ActOnTypeParameter(Scope *S, bool Typename,
                                       SourceLocation KeyLoc,
                                       IdentifierInfo *ParamName,
                                       SourceLocation ParamNameLoc,
                                       unsigned Depth, unsigned Position);
  virtual void ActOnTypeParameterDefault(DeclPtrTy TypeParam, 
                                         SourceLocation EqualLoc,
                                         SourceLocation DefaultLoc,
                                         TypeTy *Default);

  QualType CheckNonTypeTemplateParameterType(QualType T, SourceLocation Loc);
  virtual DeclPtrTy ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
                                                  unsigned Depth,
                                                  unsigned Position);
  virtual void ActOnNonTypeTemplateParameterDefault(DeclPtrTy TemplateParam,
                                                    SourceLocation EqualLoc,
                                                    ExprArg Default);
  virtual DeclPtrTy ActOnTemplateTemplateParameter(Scope *S,
                                                   SourceLocation TmpLoc,
                                                   TemplateParamsTy *Params,
                                                   IdentifierInfo *ParamName,
                                                   SourceLocation ParamNameLoc,
                                                   unsigned Depth,
                                                   unsigned Position);
  virtual void ActOnTemplateTemplateParameterDefault(DeclPtrTy TemplateParam,
                                                     SourceLocation EqualLoc,
                                                     ExprArg Default);

  virtual TemplateParamsTy *
  ActOnTemplateParameterList(unsigned Depth,
                             SourceLocation ExportLoc,
                             SourceLocation TemplateLoc, 
                             SourceLocation LAngleLoc,
                             DeclPtrTy *Params, unsigned NumParams,
                             SourceLocation RAngleLoc);
  bool CheckTemplateParameterList(TemplateParameterList *NewParams,
                                  TemplateParameterList *OldParams);

  virtual DeclResult
  ActOnClassTemplate(Scope *S, unsigned TagSpec, TagKind TK,
                     SourceLocation KWLoc, const CXXScopeSpec &SS,
                     IdentifierInfo *Name, SourceLocation NameLoc,
                     AttributeList *Attr,
                     MultiTemplateParamsArg TemplateParameterLists,
                     AccessSpecifier AS);

  QualType CheckTemplateIdType(TemplateName Template,
                               SourceLocation TemplateLoc,
                               SourceLocation LAngleLoc,
                               const TemplateArgument *TemplateArgs,
                               unsigned NumTemplateArgs,
                               SourceLocation RAngleLoc);

  virtual TypeResult
  ActOnTemplateIdType(TemplateTy Template, SourceLocation TemplateLoc,
                      SourceLocation LAngleLoc,
                      ASTTemplateArgsPtr TemplateArgs,
                      SourceLocation *TemplateArgLocs,
                      SourceLocation RAngleLoc);
  
  virtual TemplateTy ActOnDependentTemplateName(SourceLocation TemplateKWLoc,
                                                const IdentifierInfo &Name,
                                                SourceLocation NameLoc,
                                                const CXXScopeSpec &SS);

  bool CheckClassTemplateSpecializationScope(ClassTemplateDecl *ClassTemplate,
                                    ClassTemplateSpecializationDecl *PrevDecl,
                                             SourceLocation TemplateNameLoc,
                                             SourceRange ScopeSpecifierRange,
                                             bool ExplicitInstantiation);

  virtual DeclResult
  ActOnClassTemplateSpecialization(Scope *S, unsigned TagSpec, TagKind TK,
                                   SourceLocation KWLoc, 
                                   const CXXScopeSpec &SS,
                                   TemplateTy Template,
                                   SourceLocation TemplateNameLoc,
                                   SourceLocation LAngleLoc,
                                   ASTTemplateArgsPtr TemplateArgs,
                                   SourceLocation *TemplateArgLocs,
                                   SourceLocation RAngleLoc,
                                   AttributeList *Attr,
                                 MultiTemplateParamsArg TemplateParameterLists);

  virtual DeclResult
  ActOnExplicitInstantiation(Scope *S, SourceLocation TemplateLoc,
                             unsigned TagSpec, 
                             SourceLocation KWLoc,
                             const CXXScopeSpec &SS,
                             TemplateTy Template,
                             SourceLocation TemplateNameLoc,
                             SourceLocation LAngleLoc,
                             ASTTemplateArgsPtr TemplateArgs,
                             SourceLocation *TemplateArgLocs,
                             SourceLocation RAngleLoc,
                             AttributeList *Attr);

  virtual DeclResult
  ActOnExplicitInstantiation(Scope *S, SourceLocation TemplateLoc,
                             unsigned TagSpec, 
                             SourceLocation KWLoc,
                             const CXXScopeSpec &SS,
                             IdentifierInfo *Name,
                             SourceLocation NameLoc,
                             AttributeList *Attr);

  bool CheckTemplateArgumentList(TemplateDecl *Template,
                                 SourceLocation TemplateLoc,
                                 SourceLocation LAngleLoc,
                                 const TemplateArgument *TemplateArgs,
                                 unsigned NumTemplateArgs,
                                 SourceLocation RAngleLoc,
                       llvm::SmallVectorImpl<TemplateArgument> &Converted);

  bool CheckTemplateArgument(TemplateTypeParmDecl *Param, QualType Arg,
                             SourceLocation ArgLoc);
  bool CheckTemplateArgumentAddressOfObjectOrFunction(Expr *Arg, 
                                                      NamedDecl *&Entity);
  bool CheckTemplateArgumentPointerToMember(Expr *Arg, NamedDecl *&Member);
  bool CheckTemplateArgument(NonTypeTemplateParmDecl *Param, 
                             QualType InstantiatedParamType, Expr *&Arg,
                       llvm::SmallVectorImpl<TemplateArgument> *Converted = 0);
  bool CheckTemplateArgument(TemplateTemplateParmDecl *Param, DeclRefExpr *Arg);
  bool TemplateParameterListsAreEqual(TemplateParameterList *New,
                                      TemplateParameterList *Old,
                                      bool Complain,
                                      bool IsTemplateTemplateParm = false,
                                      SourceLocation TemplateArgLoc
                                       = SourceLocation());
  
  bool CheckTemplateDeclScope(Scope *S, 
                              MultiTemplateParamsArg &TemplateParameterLists);

  /// \brief Called when the parser has parsed a C++ typename
  /// specifier, e.g., "typename T::type".
  ///
  /// \param TypenameLoc the location of the 'typename' keyword
  /// \param SS the nested-name-specifier following the typename (e.g., 'T::').
  /// \param II the identifier we're retrieving (e.g., 'type' in the example).
  /// \param IdLoc the location of the identifier.
  virtual TypeResult
  ActOnTypenameType(SourceLocation TypenameLoc, const CXXScopeSpec &SS,
                    const IdentifierInfo &II, SourceLocation IdLoc);

  /// \brief Called when the parser has parsed a C++ typename
  /// specifier that ends in a template-id, e.g., 
  /// "typename MetaFun::template apply<T1, T2>".
  ///
  /// \param TypenameLoc the location of the 'typename' keyword
  /// \param SS the nested-name-specifier following the typename (e.g., 'T::').
  /// \param TemplateLoc the location of the 'template' keyword, if any.
  /// \param Ty the type that the typename specifier refers to.
  virtual TypeResult
  ActOnTypenameType(SourceLocation TypenameLoc, const CXXScopeSpec &SS,
                    SourceLocation TemplateLoc, TypeTy *Ty);

  QualType CheckTypenameType(NestedNameSpecifier *NNS,
                             const IdentifierInfo &II,
                             SourceRange Range);
                             
  //===--------------------------------------------------------------------===//
  // C++ Template Instantiation
  //

  const TemplateArgumentList &getTemplateInstantiationArgs(NamedDecl *D);

  /// \brief A template instantiation that is currently in progress.
  struct ActiveTemplateInstantiation {
    /// \brief The kind of template instantiation we are performing
    enum {
      /// We are instantiating a template declaration. The entity is
      /// the declaration we're instantiating (e.g., a CXXRecordDecl).
      TemplateInstantiation,

      /// We are instantiating a default argument for a template
      /// parameter. The Entity is the template, and
      /// TemplateArgs/NumTemplateArguments provides the template
      /// arguments as specified.
      DefaultTemplateArgumentInstantiation
    } Kind;

    /// \brief The point of instantiation within the source code.
    SourceLocation PointOfInstantiation;

    /// \brief The entity that is being instantiated.
    uintptr_t Entity;

    // \brief If this the instantiation of a default template
    // argument, the list of template arguments.
    const TemplateArgument *TemplateArgs;

    /// \brief The number of template arguments in TemplateArgs.
    unsigned NumTemplateArgs;

    /// \brief The source range that covers the construct that cause
    /// the instantiation, e.g., the template-id that causes a class
    /// template instantiation.
    SourceRange InstantiationRange;

    friend bool operator==(const ActiveTemplateInstantiation &X,
                           const ActiveTemplateInstantiation &Y) {
      if (X.Kind != Y.Kind)
        return false;

      if (X.Entity != Y.Entity)
        return false;

      switch (X.Kind) {
      case TemplateInstantiation:
        return true;

      case DefaultTemplateArgumentInstantiation:
        return X.TemplateArgs == Y.TemplateArgs;
      }

      return true;
    }

    friend bool operator!=(const ActiveTemplateInstantiation &X,
                           const ActiveTemplateInstantiation &Y) {
      return !(X == Y);
    }
  };

  /// \brief List of active template instantiations.
  ///
  /// This vector is treated as a stack. As one template instantiation
  /// requires another template instantiation, additional
  /// instantiations are pushed onto the stack up to a
  /// user-configurable limit LangOptions::InstantiationDepth.
  llvm::SmallVector<ActiveTemplateInstantiation, 16> 
    ActiveTemplateInstantiations;

  /// \brief The last template from which a template instantiation
  /// error or warning was produced.
  ///
  /// This value is used to suppress printing of redundant template
  /// instantiation backtraces when there are multiple errors in the
  /// same instantiation. FIXME: Does this belong in Sema? It's tough
  /// to implement it anywhere else.
  ActiveTemplateInstantiation LastTemplateInstantiationErrorContext;

  /// \brief A stack object to be created when performing template
  /// instantiation.
  ///
  /// Construction of an object of type \c InstantiatingTemplate
  /// pushes the current instantiation onto the stack of active
  /// instantiations. If the size of this stack exceeds the maximum
  /// number of recursive template instantiations, construction
  /// produces an error and evaluates true.
  ///
  /// Destruction of this object will pop the named instantiation off
  /// the stack.
  struct InstantiatingTemplate {
    /// \brief Note that we are instantiating a class template,
    /// function template, or a member thereof.
    InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                          Decl *Entity,
                          SourceRange InstantiationRange = SourceRange());

    /// \brief Note that we are instantiating a default argument in a
    /// template-id.
    InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                          TemplateDecl *Template,
                          const TemplateArgument *TemplateArgs,
                          unsigned NumTemplateArgs,
                          SourceRange InstantiationRange = SourceRange());

    /// \brief Note that we have finished instantiating this template.
    void Clear();

    ~InstantiatingTemplate() { Clear(); }

    /// \brief Determines whether we have exceeded the maximum
    /// recursive template instantiations.
    operator bool() const { return Invalid; }

  private:
    Sema &SemaRef;
    bool Invalid;

    bool CheckInstantiationDepth(SourceLocation PointOfInstantiation,
                                 SourceRange InstantiationRange);

    InstantiatingTemplate(const InstantiatingTemplate&); // not implemented

    InstantiatingTemplate& 
    operator=(const InstantiatingTemplate&); // not implemented
  };

  void PrintInstantiationStack();

  /// \brief A stack-allocated class that identifies which local
  /// variable declaration instantiations are present in this scope.
  ///
  /// A new instance of this class type will be created whenever we
  /// instantiate a new function declaration, which will have its own
  /// set of parameter declarations.
  class LocalInstantiationScope {
    /// \brief Reference to the semantic analysis that is performing
    /// this template instantiation.
    Sema &SemaRef;

    /// \brief A mapping from local variable declarations that occur
    /// within a template to their instantiations.
    ///
    /// This mapping is used during instantiation to keep track of,
    /// e.g., function parameter and variable declarations. For example,
    /// given:
    ///
    /// \code
    ///   template<typename T> T add(T x, T y) { return x + y; }
    /// \endcode
    ///
    /// when we instantiate add<int>, we will introduce a mapping from
    /// the ParmVarDecl for 'x' that occurs in the template to the
    /// instantiated ParmVarDecl for 'x'.
    llvm::DenseMap<const VarDecl *, VarDecl *> LocalDecls;

    /// \brief The outer scope, in which contains local variable
    /// definitions from some other instantiation (that is not
    /// relevant to this particular scope).
    LocalInstantiationScope *Outer;

    // This class is non-copyable
    LocalInstantiationScope(const LocalInstantiationScope &);
    LocalInstantiationScope &operator=(const LocalInstantiationScope &);

  public:
    LocalInstantiationScope(Sema &SemaRef)
      : SemaRef(SemaRef), Outer(SemaRef.CurrentInstantiationScope) { 
      SemaRef.CurrentInstantiationScope = this;
    }

    ~LocalInstantiationScope() {
      SemaRef.CurrentInstantiationScope = Outer;
    }

    VarDecl *getInstantiationOf(const VarDecl *Var) {
      VarDecl *Result = LocalDecls[Var];
      assert(Result && "Variable was not instantiated in this scope!");
      return Result;
    }

    ParmVarDecl *getInstantiationOf(const ParmVarDecl *Var) {
      return cast<ParmVarDecl>(getInstantiationOf(cast<VarDecl>(Var)));
    }

    void InstantiatedLocal(const VarDecl *Var, VarDecl *VarInst) {
      VarDecl *&Stored = LocalDecls[Var];
      assert(!Stored && "Already instantiated this local variable");
      Stored = VarInst;
    }
  };

  /// \brief The current instantiation scope used to store local
  /// variables.
  LocalInstantiationScope *CurrentInstantiationScope;

  QualType InstantiateType(QualType T, const TemplateArgumentList &TemplateArgs,
                           SourceLocation Loc, DeclarationName Entity);

  OwningExprResult InstantiateExpr(Expr *E, 
                                   const TemplateArgumentList &TemplateArgs);

  OwningStmtResult InstantiateStmt(Stmt *S, 
                                   const TemplateArgumentList &TemplateArgs);

  Decl *InstantiateDecl(Decl *D, DeclContext *Owner,
                        const TemplateArgumentList &TemplateArgs);

  bool 
  InstantiateBaseSpecifiers(CXXRecordDecl *Instantiation,
                            CXXRecordDecl *Pattern,
                            const TemplateArgumentList &TemplateArgs);

  bool
  InstantiateClass(SourceLocation PointOfInstantiation,
                   CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
                   const TemplateArgumentList &TemplateArgs,
                   bool ExplicitInstantiation);

  bool 
  InstantiateClassTemplateSpecialization(
                           ClassTemplateSpecializationDecl *ClassTemplateSpec,
                           bool ExplicitInstantiation);

  void InstantiateClassMembers(SourceLocation PointOfInstantiation,
                               CXXRecordDecl *Instantiation,
                               const TemplateArgumentList &TemplateArgs);

  void InstantiateClassTemplateSpecializationMembers(
                                          SourceLocation PointOfInstantiation,
                           ClassTemplateSpecializationDecl *ClassTemplateSpec);

  NestedNameSpecifier *
  InstantiateNestedNameSpecifier(NestedNameSpecifier *NNS,
                                 SourceRange Range,
                                 const TemplateArgumentList &TemplateArgs);

  TemplateName
  InstantiateTemplateName(TemplateName Name, SourceLocation Loc,
                          const TemplateArgumentList &TemplateArgs);

  void InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
                                     FunctionDecl *Function);
  void InstantiateVariableDefinition(VarDecl *Var);

  // Simple function for cloning expressions.
  template<typename T> 
  OwningExprResult Clone(T *E) {
    assert(!E->isValueDependent() && !E->isTypeDependent() &&
           "expression is value or type dependent!");
    return Owned(E->Clone(Context));
  }
  
  // Objective-C declarations.
  virtual DeclPtrTy ActOnStartClassInterface(SourceLocation AtInterfaceLoc,
                                             IdentifierInfo *ClassName,
                                             SourceLocation ClassLoc,
                                             IdentifierInfo *SuperName,
                                             SourceLocation SuperLoc,
                                             const DeclPtrTy *ProtoRefs,
                                             unsigned NumProtoRefs,
                                             SourceLocation EndProtoLoc,
                                             AttributeList *AttrList);
  
  virtual DeclPtrTy ActOnCompatiblityAlias(
                    SourceLocation AtCompatibilityAliasLoc,
                    IdentifierInfo *AliasName,  SourceLocation AliasLocation,
                    IdentifierInfo *ClassName, SourceLocation ClassLocation);

  void CheckForwardProtocolDeclarationForCircularDependency(
    IdentifierInfo *PName,
    SourceLocation &PLoc, SourceLocation PrevLoc,
    const ObjCList<ObjCProtocolDecl> &PList);
                    
  virtual DeclPtrTy ActOnStartProtocolInterface(
                    SourceLocation AtProtoInterfaceLoc,
                    IdentifierInfo *ProtocolName, SourceLocation ProtocolLoc,
                    const DeclPtrTy *ProtoRefNames, unsigned NumProtoRefs,
                    SourceLocation EndProtoLoc,
                    AttributeList *AttrList);
  
  virtual DeclPtrTy ActOnStartCategoryInterface(SourceLocation AtInterfaceLoc,
                                                IdentifierInfo *ClassName,
                                                SourceLocation ClassLoc,
                                                IdentifierInfo *CategoryName,
                                                SourceLocation CategoryLoc,
                                                const DeclPtrTy *ProtoRefs,
                                                unsigned NumProtoRefs,
                                                SourceLocation EndProtoLoc);
  
  virtual DeclPtrTy ActOnStartClassImplementation(
                    SourceLocation AtClassImplLoc,
                    IdentifierInfo *ClassName, SourceLocation ClassLoc,
                    IdentifierInfo *SuperClassname, 
                    SourceLocation SuperClassLoc);
  
  virtual DeclPtrTy ActOnStartCategoryImplementation(
                                                  SourceLocation AtCatImplLoc,
                                                  IdentifierInfo *ClassName, 
                                                  SourceLocation ClassLoc,
                                                  IdentifierInfo *CatName,
                                                  SourceLocation CatLoc);
  
  virtual DeclPtrTy ActOnForwardClassDeclaration(SourceLocation Loc,
                                               IdentifierInfo **IdentList,
                                               unsigned NumElts);
  
  virtual DeclPtrTy ActOnForwardProtocolDeclaration(SourceLocation AtProtocolLoc,
                                            const IdentifierLocPair *IdentList,
                                                  unsigned NumElts,
                                                  AttributeList *attrList);
  
  virtual void FindProtocolDeclaration(bool WarnOnDeclarations,
                                       const IdentifierLocPair *ProtocolId,
                                       unsigned NumProtocols,
                                   llvm::SmallVectorImpl<DeclPtrTy> &Protocols);
  
  /// Ensure attributes are consistent with type. 
  /// \param [in, out] Attributes The attributes to check; they will
  /// be modified to be consistent with \arg PropertyTy.
  void CheckObjCPropertyAttributes(QualType PropertyTy, 
                                   SourceLocation Loc,
                                   unsigned &Attributes);
  void ProcessPropertyDecl(ObjCPropertyDecl *property, ObjCContainerDecl *DC);
  void DiagnosePropertyMismatch(ObjCPropertyDecl *Property, 
                                ObjCPropertyDecl *SuperProperty,
                                const IdentifierInfo *Name);
  void ComparePropertiesInBaseAndSuper(ObjCInterfaceDecl *IDecl);
  
  void MergeProtocolPropertiesIntoClass(Decl *CDecl,
                                        DeclPtrTy MergeProtocols);
  
  void DiagnoseClassExtensionDupMethods(ObjCCategoryDecl *CAT, 
                                        ObjCInterfaceDecl *ID);
  
  void MergeOneProtocolPropertiesIntoClass(Decl *CDecl,
                                           ObjCProtocolDecl *PDecl);
  
  virtual void ActOnAtEnd(SourceLocation AtEndLoc, DeclPtrTy classDecl,
                      DeclPtrTy *allMethods = 0, unsigned allNum = 0,
                      DeclPtrTy *allProperties = 0, unsigned pNum = 0,
                      DeclGroupPtrTy *allTUVars = 0, unsigned tuvNum = 0);
  
  virtual DeclPtrTy ActOnProperty(Scope *S, SourceLocation AtLoc,
                                  FieldDeclarator &FD, ObjCDeclSpec &ODS,
                                  Selector GetterSel, Selector SetterSel,
                                  DeclPtrTy ClassCategory,
                                  bool *OverridingProperty,
                                  tok::ObjCKeywordKind MethodImplKind);
  
  virtual DeclPtrTy ActOnPropertyImplDecl(SourceLocation AtLoc, 
                                          SourceLocation PropertyLoc,
                                          bool ImplKind,DeclPtrTy ClassImplDecl,
                                          IdentifierInfo *PropertyId,
                                          IdentifierInfo *PropertyIvar);
  
  virtual DeclPtrTy ActOnMethodDeclaration(
    SourceLocation BeginLoc, // location of the + or -.
    SourceLocation EndLoc,   // location of the ; or {.
    tok::TokenKind MethodType, 
    DeclPtrTy ClassDecl, ObjCDeclSpec &ReturnQT, TypeTy *ReturnType, 
    Selector Sel,
    // optional arguments. The number of types/arguments is obtained
    // from the Sel.getNumArgs().
    ObjCArgInfo *ArgInfo,
    llvm::SmallVectorImpl<Declarator> &Cdecls,
    AttributeList *AttrList, tok::ObjCKeywordKind MethodImplKind,
    bool isVariadic = false);

  // Helper method for ActOnClassMethod/ActOnInstanceMethod.
  // Will search "local" class/category implementations for a method decl.
  // Will also search in class's root looking for instance method.
  // Returns 0 if no method is found.
  ObjCMethodDecl *LookupPrivateClassMethod(Selector Sel, 
                                           ObjCInterfaceDecl *CDecl);
  ObjCMethodDecl *LookupPrivateInstanceMethod(Selector Sel,
                                              ObjCInterfaceDecl *ClassDecl);
  
  virtual OwningExprResult ActOnClassPropertyRefExpr(
    IdentifierInfo &receiverName,
    IdentifierInfo &propertyName,
    SourceLocation &receiverNameLoc,
    SourceLocation &propertyNameLoc);
  
  // ActOnClassMessage - used for both unary and keyword messages.
  // ArgExprs is optional - if it is present, the number of expressions
  // is obtained from NumArgs.
  virtual ExprResult ActOnClassMessage(
    Scope *S,
    IdentifierInfo *receivingClassName, Selector Sel, SourceLocation lbrac, 
    SourceLocation receiverLoc, SourceLocation selectorLoc,SourceLocation rbrac, 
    ExprTy **ArgExprs, unsigned NumArgs);

  // ActOnInstanceMessage - used for both unary and keyword messages.
  // ArgExprs is optional - if it is present, the number of expressions
  // is obtained from NumArgs.
  virtual ExprResult ActOnInstanceMessage(
    ExprTy *receiver, Selector Sel,
    SourceLocation lbrac, SourceLocation receiverLoc, SourceLocation rbrac, 
    ExprTy **ArgExprs, unsigned NumArgs);
  
  /// ActOnPragmaPack - Called on well formed #pragma pack(...).
  virtual void ActOnPragmaPack(PragmaPackKind Kind,
                               IdentifierInfo *Name,
                               ExprTy *Alignment,
                               SourceLocation PragmaLoc, 
                               SourceLocation LParenLoc,
                               SourceLocation RParenLoc);
  
  /// ActOnPragmaUnused - Called on well-formed '#pragma unused'.
  virtual void ActOnPragmaUnused(ExprTy **Exprs, unsigned NumExprs,
                                 SourceLocation PragmaLoc, 
                                 SourceLocation LParenLoc,
                                 SourceLocation RParenLoc);
  
  /// getPragmaPackAlignment() - Return the current alignment as specified by
  /// the current #pragma pack directive, or 0 if none is currently active.
  unsigned getPragmaPackAlignment() const;
  
  /// FreePackedContext - Deallocate and null out PackContext.
  void FreePackedContext();

  /// ImpCastExprToType - If Expr is not of type 'Type', insert an implicit
  /// cast.  If there is already an implicit cast, merge into the existing one.
  /// If isLvalue, the result of the cast is an lvalue.
  void ImpCastExprToType(Expr *&Expr, QualType Type, bool isLvalue = false);

  // UsualUnaryConversions - promotes integers (C99 6.3.1.1p2) and converts
  // functions and arrays to their respective pointers (C99 6.3.2.1).
  Expr *UsualUnaryConversions(Expr *&expr); 

  // DefaultFunctionArrayConversion - converts functions and arrays
  // to their respective pointers (C99 6.3.2.1). 
  void DefaultFunctionArrayConversion(Expr *&expr);
  
  // DefaultArgumentPromotion (C99 6.5.2.2p6). Used for function calls that
  // do not have a prototype. Integer promotions are performed on each 
  // argument, and arguments that have type float are promoted to double.
  void DefaultArgumentPromotion(Expr *&Expr);

  // Used for emitting the right warning by DefaultVariadicArgumentPromotion
  enum VariadicCallType {
    VariadicFunction,
    VariadicBlock,
    VariadicMethod
  };
  
  // DefaultVariadicArgumentPromotion - Like DefaultArgumentPromotion, but
  // will warn if the resulting type is not a POD type.
  bool DefaultVariadicArgumentPromotion(Expr *&Expr, VariadicCallType CT);
  
  // UsualArithmeticConversions - performs the UsualUnaryConversions on it's
  // operands and then handles various conversions that are common to binary
  // operators (C99 6.3.1.8). If both operands aren't arithmetic, this
  // routine returns the first non-arithmetic type found. The client is 
  // responsible for emitting appropriate error diagnostics.
  QualType UsualArithmeticConversions(Expr *&lExpr, Expr *&rExpr,
                                      bool isCompAssign = false);
  
  /// UsualArithmeticConversionsType - handles the various conversions
  /// that are common to binary operators (C99 6.3.1.8, C++ [expr]p9)
  /// and returns the result type of that conversion.
  QualType UsualArithmeticConversionsType(QualType lhs, QualType rhs);
                                          

  /// AssignConvertType - All of the 'assignment' semantic checks return this
  /// enum to indicate whether the assignment was allowed.  These checks are
  /// done for simple assignments, as well as initialization, return from
  /// function, argument passing, etc.  The query is phrased in terms of a
  /// source and destination type.
  enum AssignConvertType {
    /// Compatible - the types are compatible according to the standard.
    Compatible,
    
    /// PointerToInt - The assignment converts a pointer to an int, which we
    /// accept as an extension.
    PointerToInt,
    
    /// IntToPointer - The assignment converts an int to a pointer, which we
    /// accept as an extension.
    IntToPointer,
    
    /// FunctionVoidPointer - The assignment is between a function pointer and
    /// void*, which the standard doesn't allow, but we accept as an extension.
    FunctionVoidPointer,

    /// IncompatiblePointer - The assignment is between two pointers types that
    /// are not compatible, but we accept them as an extension.
    IncompatiblePointer,

    /// IncompatiblePointer - The assignment is between two pointers types which
    /// point to integers which have a different sign, but are otherwise identical.
    /// This is a subset of the above, but broken out because it's by far the most
    /// common case of incompatible pointers.
    IncompatiblePointerSign,

    /// CompatiblePointerDiscardsQualifiers - The assignment discards
    /// c/v/r qualifiers, which we accept as an extension.
    CompatiblePointerDiscardsQualifiers,

    /// IncompatibleVectors - The assignment is between two vector types that
    /// have the same size, which we accept as an extension.
    IncompatibleVectors,
    
    /// IntToBlockPointer - The assignment converts an int to a block 
    /// pointer. We disallow this.
    IntToBlockPointer,

    /// IncompatibleBlockPointer - The assignment is between two block 
    /// pointers types that are not compatible.
    IncompatibleBlockPointer,
    
    /// IncompatibleObjCQualifiedId - The assignment is between a qualified
    /// id type and something else (that is incompatible with it). For example,
    /// "id <XXX>" = "Foo *", where "Foo *" doesn't implement the XXX protocol.
    IncompatibleObjCQualifiedId,
    
    /// Incompatible - We reject this conversion outright, it is invalid to
    /// represent it in the AST.
    Incompatible
  };
  
  /// DiagnoseAssignmentResult - Emit a diagnostic, if required, for the
  /// assignment conversion type specified by ConvTy.  This returns true if the
  /// conversion was invalid or false if the conversion was accepted.
  bool DiagnoseAssignmentResult(AssignConvertType ConvTy,
                                SourceLocation Loc,
                                QualType DstType, QualType SrcType,
                                Expr *SrcExpr, const char *Flavor);
  
  /// CheckAssignmentConstraints - Perform type checking for assignment, 
  /// argument passing, variable initialization, and function return values. 
  /// This routine is only used by the following two methods. C99 6.5.16.
  AssignConvertType CheckAssignmentConstraints(QualType lhs, QualType rhs);
  
  // CheckSingleAssignmentConstraints - Currently used by 
  // CheckAssignmentOperands, and ActOnReturnStmt. Prior to type checking, 
  // this routine performs the default function/array converions.
  AssignConvertType CheckSingleAssignmentConstraints(QualType lhs, 
                                                     Expr *&rExpr);

  // \brief If the lhs type is a transparent union, check whether we
  // can initialize the transparent union with the given expression.
  AssignConvertType CheckTransparentUnionArgumentConstraints(QualType lhs, 
                                                             Expr *&rExpr);
  
  // Helper function for CheckAssignmentConstraints (C99 6.5.16.1p1)
  AssignConvertType CheckPointerTypesForAssignment(QualType lhsType, 
                                                   QualType rhsType);
                                                   
  // Helper function for CheckAssignmentConstraints involving two
  // block pointer types.
  AssignConvertType CheckBlockPointerTypesForAssignment(QualType lhsType, 
                                                        QualType rhsType);

  bool IsStringLiteralToNonConstPointerConversion(Expr *From, QualType ToType);

  bool PerformImplicitConversion(Expr *&From, QualType ToType, 
                                 const char *Flavor,
                                 bool AllowExplicit = false,
                                 bool Elidable = false);
  bool PerformImplicitConversion(Expr *&From, QualType ToType, 
                                 const ImplicitConversionSequence& ICS,
                                 const char *Flavor);
  bool PerformImplicitConversion(Expr *&From, QualType ToType,
                                 const StandardConversionSequence& SCS,
                                 const char *Flavor);

  /// the following "Check" methods will return a valid/converted QualType
  /// or a null QualType (indicating an error diagnostic was issued).

  /// type checking binary operators (subroutines of CreateBuiltinBinOp).
  QualType InvalidOperands(SourceLocation l, Expr *&lex, Expr *&rex);
  QualType CheckPointerToMemberOperands( // C++ 5.5
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, bool isIndirect);
  QualType CheckMultiplyDivideOperands( // C99 6.5.5
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, bool isCompAssign = false);
  QualType CheckRemainderOperands( // C99 6.5.5
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, bool isCompAssign = false);
  QualType CheckAdditionOperands( // C99 6.5.6
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, QualType* CompLHSTy = 0);
  QualType CheckSubtractionOperands( // C99 6.5.6
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, QualType* CompLHSTy = 0);
  QualType CheckShiftOperands( // C99 6.5.7
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, bool isCompAssign = false);
  QualType CheckCompareOperands( // C99 6.5.8/9
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, unsigned Opc, bool isRelational);
  QualType CheckBitwiseOperands( // C99 6.5.[10...12]
    Expr *&lex, Expr *&rex, SourceLocation OpLoc, bool isCompAssign = false);
  QualType CheckLogicalOperands( // C99 6.5.[13,14]
    Expr *&lex, Expr *&rex, SourceLocation OpLoc);
  // CheckAssignmentOperands is used for both simple and compound assignment.
  // For simple assignment, pass both expressions and a null converted type.
  // For compound assignment, pass both expressions and the converted type.
  QualType CheckAssignmentOperands( // C99 6.5.16.[1,2]
    Expr *lex, Expr *&rex, SourceLocation OpLoc, QualType convertedType);
  QualType CheckCommaOperands( // C99 6.5.17
    Expr *lex, Expr *&rex, SourceLocation OpLoc);
  QualType CheckConditionalOperands( // C99 6.5.15
    Expr *&cond, Expr *&lhs, Expr *&rhs, SourceLocation questionLoc);
  QualType CXXCheckConditionalOperands( // C++ 5.16
    Expr *&cond, Expr *&lhs, Expr *&rhs, SourceLocation questionLoc);
  QualType FindCompositePointerType(Expr *&E1, Expr *&E2); // C++ 5.9

  /// type checking for vector binary operators.
  inline QualType CheckVectorOperands(SourceLocation l, Expr *&lex, Expr *&rex);
  inline QualType CheckVectorCompareOperands(Expr *&lex, Expr *&rx,
                                             SourceLocation l, bool isRel);
  
  /// type checking unary operators (subroutines of ActOnUnaryOp).
  /// C99 6.5.3.1, 6.5.3.2, 6.5.3.4
  QualType CheckIncrementDecrementOperand(Expr *op, SourceLocation OpLoc,
                                          bool isInc);
  QualType CheckAddressOfOperand(Expr *op, SourceLocation OpLoc);
  QualType CheckIndirectionOperand(Expr *op, SourceLocation OpLoc);
  QualType CheckRealImagOperand(Expr *&Op, SourceLocation OpLoc, bool isReal);
  
  /// type checking primary expressions.
  QualType CheckExtVectorComponent(QualType baseType, SourceLocation OpLoc,
                                   IdentifierInfo &Comp, SourceLocation CmpLoc);
  
  /// type checking declaration initializers (C99 6.7.8)
  bool CheckInitializerTypes(Expr *&simpleInit_or_initList, QualType &declType,
                             SourceLocation InitLoc,DeclarationName InitEntity,
                             bool DirectInit);
  bool CheckInitList(InitListExpr *&InitList, QualType &DeclType);
  bool CheckForConstantInitializer(Expr *e, QualType t);
  
  bool CheckValueInitialization(QualType Type, SourceLocation Loc);

  // type checking C++ declaration initializers (C++ [dcl.init]).

  /// ReferenceCompareResult - Expresses the result of comparing two
  /// types (cv1 T1 and cv2 T2) to determine their compatibility for the
  /// purposes of initialization by reference (C++ [dcl.init.ref]p4).
  enum ReferenceCompareResult {
    /// Ref_Incompatible - The two types are incompatible, so direct
    /// reference binding is not possible.
    Ref_Incompatible = 0,
    /// Ref_Related - The two types are reference-related, which means
    /// that their unqualified forms (T1 and T2) are either the same
    /// or T1 is a base class of T2.
    Ref_Related,
    /// Ref_Compatible_With_Added_Qualification - The two types are
    /// reference-compatible with added qualification, meaning that
    /// they are reference-compatible and the qualifiers on T1 (cv1)
    /// are greater than the qualifiers on T2 (cv2).
    Ref_Compatible_With_Added_Qualification,
    /// Ref_Compatible - The two types are reference-compatible and
    /// have equivalent qualifiers (cv1 == cv2).
    Ref_Compatible
  };

  ReferenceCompareResult CompareReferenceRelationship(QualType T1, QualType T2,
                                                      bool& DerivedToBase);

  bool CheckReferenceInit(Expr *&simpleInit_or_initList, QualType declType,
                          ImplicitConversionSequence *ICS = 0,
                          bool SuppressUserConversions = false,
                          bool AllowExplicit = false,
                          bool ForceRValue = false);

  /// CheckCastTypes - Check type constraints for casting between types.
  bool CheckCastTypes(SourceRange TyRange, QualType CastTy, Expr *&CastExpr);
  
  // CheckVectorCast - check type constraints for vectors. 
  // Since vectors are an extension, there are no C standard reference for this.
  // We allow casting between vectors and integer datatypes of the same size.
  // returns true if the cast is invalid
  bool CheckVectorCast(SourceRange R, QualType VectorTy, QualType Ty);
  
  /// CheckMessageArgumentTypes - Check types in an Obj-C message send. 
  /// \param Method - May be null.
  /// \param [out] ReturnType - The return type of the send.
  /// \return true iff there were any incompatible types.
  bool CheckMessageArgumentTypes(Expr **Args, unsigned NumArgs, Selector Sel,
                                 ObjCMethodDecl *Method, bool isClassMessage,
                                 SourceLocation lbrac, SourceLocation rbrac,
                                 QualType &ReturnType);  

  /// CheckCXXBooleanCondition - Returns true if conversion to bool is invalid.
  bool CheckCXXBooleanCondition(Expr *&CondExpr);
                    
  /// ConvertIntegerToTypeWarnOnOverflow - Convert the specified APInt to have
  /// the specified width and sign.  If an overflow occurs, detect it and emit
  /// the specified diagnostic.
  void ConvertIntegerToTypeWarnOnOverflow(llvm::APSInt &OldVal, 
                                          unsigned NewWidth, bool NewSign,
                                          SourceLocation Loc, unsigned DiagID);
  
  bool ObjCQualifiedIdTypesAreCompatible(QualType LHS, QualType RHS,
                                         bool ForCompare);

  /// Checks that the Objective-C declaration is declared in the global scope.
  /// Emits an error and marks the declaration as invalid if it's not declared
  /// in the global scope.
  bool CheckObjCDeclScope(Decl *D);

  void InitBuiltinVaListType();

  /// VerifyIntegerConstantExpression - verifies that an expression is an ICE,
  /// and reports the appropriate diagnostics. Returns false on success.
  /// Can optionally return the value of the expression.
  bool VerifyIntegerConstantExpression(const Expr *E, llvm::APSInt *Result = 0);

  /// VerifyBitField - verifies that a bit field expression is an ICE and has
  /// the correct width, and that the field type is valid. 
  /// Returns false on success.
  bool VerifyBitField(SourceLocation FieldLoc, IdentifierInfo *FieldName, 
                      QualType FieldTy, const Expr *BitWidth);

  //===--------------------------------------------------------------------===//
  // Extra semantic analysis beyond the C type system
private:
  Action::OwningExprResult CheckFunctionCall(FunctionDecl *FDecl,
                                             CallExpr *TheCall);
  SourceLocation getLocationOfStringLiteralByte(const StringLiteral *SL,
                                                unsigned ByteNo) const;
  bool CheckObjCString(Expr *Arg);
  bool SemaBuiltinVAStart(CallExpr *TheCall);
  bool SemaBuiltinUnorderedCompare(CallExpr *TheCall);
  bool SemaBuiltinStackAddress(CallExpr *TheCall);
  Action::OwningExprResult SemaBuiltinShuffleVector(CallExpr *TheCall);
  bool SemaBuiltinPrefetch(CallExpr *TheCall); 
  bool SemaBuiltinObjectSize(CallExpr *TheCall);
  bool SemaBuiltinLongjmp(CallExpr *TheCall);
  bool SemaBuiltinAtomicOverloaded(CallExpr *TheCall);
  bool SemaCheckStringLiteral(const Expr *E, const CallExpr *TheCall,
                              bool HasVAListArg, unsigned format_idx,
                              unsigned firstDataArg);
  void CheckPrintfString(const StringLiteral *FExpr, const Expr *OrigFormatExpr,
                         const CallExpr *TheCall, bool HasVAListArg,
                         unsigned format_idx, unsigned firstDataArg);
  void CheckPrintfArguments(const CallExpr *TheCall, bool HasVAListArg, 
                            unsigned format_idx, unsigned firstDataArg);
  void CheckReturnStackAddr(Expr *RetValExp, QualType lhsType,
                            SourceLocation ReturnLoc);
  void CheckFloatComparison(SourceLocation loc, Expr* lex, Expr* rex);
};


//===--------------------------------------------------------------------===//
// Typed version of Parser::ExprArg (smart pointer for wrapping Expr pointers).
template <typename T>
class ExprOwningPtr : public Action::ExprArg {
public:
  ExprOwningPtr(Sema *S, T *expr) : Action::ExprArg(*S, expr) {}
  
  void reset(T* p) { Action::ExprArg::operator=(p); }
  T* get() const { return static_cast<T*>(Action::ExprArg::get()); }
  T* take() { return static_cast<T*>(Action::ExprArg::take()); }
  T* release() { return take(); }
  
  T& operator*() const { return *get(); }
  T* operator->() const { return get(); }
};
  
}  // end namespace clang

#endif