SemaDeclCXX.cpp

//===------ SemaDeclCXX.cpp - Semantic Analysis for C++ Declarations ------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements semantic analysis for C++ declarations.
//
//===----------------------------------------------------------------------===//

#include "Sema.h"
#include "SemaInherit.h"
#include "clang/AST/ASTConsumer.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclVisitor.h"
#include "clang/AST/TypeOrdering.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Parse/DeclSpec.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Compiler.h"
#include <algorithm> // for std::equal
#include <map>

using namespace clang;

//===----------------------------------------------------------------------===//
// CheckDefaultArgumentVisitor
//===----------------------------------------------------------------------===//

namespace {
  /// CheckDefaultArgumentVisitor - C++ [dcl.fct.default] Traverses
  /// the default argument of a parameter to determine whether it
  /// contains any ill-formed subexpressions. For example, this will
  /// diagnose the use of local variables or parameters within the
  /// default argument expression.
  class VISIBILITY_HIDDEN CheckDefaultArgumentVisitor 
    : public StmtVisitor<CheckDefaultArgumentVisitor, bool> {
    Expr *DefaultArg;
    Sema *S;

  public:
    CheckDefaultArgumentVisitor(Expr *defarg, Sema *s) 
      : DefaultArg(defarg), S(s) {}

    bool VisitExpr(Expr *Node);
    bool VisitDeclRefExpr(DeclRefExpr *DRE);
    bool VisitCXXThisExpr(CXXThisExpr *ThisE);
  };

  /// VisitExpr - Visit all of the children of this expression.
  bool CheckDefaultArgumentVisitor::VisitExpr(Expr *Node) {
    bool IsInvalid = false;
    for (Stmt::child_iterator I = Node->child_begin(), 
         E = Node->child_end(); I != E; ++I)
      IsInvalid |= Visit(*I);
    return IsInvalid;
  }

  /// VisitDeclRefExpr - Visit a reference to a declaration, to
  /// determine whether this declaration can be used in the default
  /// argument expression.
  bool CheckDefaultArgumentVisitor::VisitDeclRefExpr(DeclRefExpr *DRE) {
    NamedDecl *Decl = DRE->getDecl();
    if (ParmVarDecl *Param = dyn_cast<ParmVarDecl>(Decl)) {
      // C++ [dcl.fct.default]p9
      //   Default arguments are evaluated each time the function is
      //   called. The order of evaluation of function arguments is
      //   unspecified. Consequently, parameters of a function shall not
      //   be used in default argument expressions, even if they are not
      //   evaluated. Parameters of a function declared before a default
      //   argument expression are in scope and can hide namespace and
      //   class member names.
      return S->Diag(DRE->getSourceRange().getBegin(), 
                     diag::err_param_default_argument_references_param)
         << Param->getDeclName() << DefaultArg->getSourceRange();
    } else if (VarDecl *VDecl = dyn_cast<VarDecl>(Decl)) {
      // C++ [dcl.fct.default]p7
      //   Local variables shall not be used in default argument
      //   expressions.
      if (VDecl->isBlockVarDecl())
        return S->Diag(DRE->getSourceRange().getBegin(), 
                       diag::err_param_default_argument_references_local)
          << VDecl->getDeclName() << DefaultArg->getSourceRange();
    }

    return false;
  }

  /// VisitCXXThisExpr - Visit a C++ "this" expression.
  bool CheckDefaultArgumentVisitor::VisitCXXThisExpr(CXXThisExpr *ThisE) {
    // C++ [dcl.fct.default]p8:
    //   The keyword this shall not be used in a default argument of a
    //   member function.
    return S->Diag(ThisE->getSourceRange().getBegin(),
                   diag::err_param_default_argument_references_this)
               << ThisE->getSourceRange();
  }
}

/// ActOnParamDefaultArgument - Check whether the default argument
/// provided for a function parameter is well-formed. If so, attach it
/// to the parameter declaration.
void
Sema::ActOnParamDefaultArgument(DeclPtrTy param, SourceLocation EqualLoc, 
                                ExprArg defarg) {
  ParmVarDecl *Param = cast<ParmVarDecl>(param.getAs<Decl>());
  ExprOwningPtr<Expr> DefaultArg(this, (Expr *)defarg.release());
  QualType ParamType = Param->getType();

  // Default arguments are only permitted in C++
  if (!getLangOptions().CPlusPlus) {
    Diag(EqualLoc, diag::err_param_default_argument)
      << DefaultArg->getSourceRange();
    Param->setInvalidDecl();
    return;
  }

  // C++ [dcl.fct.default]p5
  //   A default argument expression is implicitly converted (clause
  //   4) to the parameter type. The default argument expression has
  //   the same semantic constraints as the initializer expression in
  //   a declaration of a variable of the parameter type, using the
  //   copy-initialization semantics (8.5).
  Expr *DefaultArgPtr = DefaultArg.get();
  bool DefaultInitFailed = CheckInitializerTypes(DefaultArgPtr, ParamType,
                                                 EqualLoc,
                                                 Param->getDeclName(),
                                                 /*DirectInit=*/false);
  if (DefaultArgPtr != DefaultArg.get()) {
    DefaultArg.take();
    DefaultArg.reset(DefaultArgPtr);
  }
  if (DefaultInitFailed) {
    return;
  }

  // Check that the default argument is well-formed
  CheckDefaultArgumentVisitor DefaultArgChecker(DefaultArg.get(), this);
  if (DefaultArgChecker.Visit(DefaultArg.get())) {
    Param->setInvalidDecl();
    return;
  }

  // Okay: add the default argument to the parameter
  Param->setDefaultArg(DefaultArg.take());
}

/// ActOnParamUnparsedDefaultArgument - We've seen a default
/// argument for a function parameter, but we can't parse it yet
/// because we're inside a class definition. Note that this default
/// argument will be parsed later.
void Sema::ActOnParamUnparsedDefaultArgument(DeclPtrTy param, 
                                             SourceLocation EqualLoc) {
  ParmVarDecl *Param = cast<ParmVarDecl>(param.getAs<Decl>());
  if (Param)
    Param->setUnparsedDefaultArg();
}

/// ActOnParamDefaultArgumentError - Parsing or semantic analysis of
/// the default argument for the parameter param failed.
void Sema::ActOnParamDefaultArgumentError(DeclPtrTy param) {
  cast<ParmVarDecl>(param.getAs<Decl>())->setInvalidDecl();
}

/// CheckExtraCXXDefaultArguments - Check for any extra default
/// arguments in the declarator, which is not a function declaration
/// or definition and therefore is not permitted to have default
/// arguments. This routine should be invoked for every declarator
/// that is not a function declaration or definition.
void Sema::CheckExtraCXXDefaultArguments(Declarator &D) {
  // C++ [dcl.fct.default]p3
  //   A default argument expression shall be specified only in the
  //   parameter-declaration-clause of a function declaration or in a
  //   template-parameter (14.1). It shall not be specified for a
  //   parameter pack. If it is specified in a
  //   parameter-declaration-clause, it shall not occur within a
  //   declarator or abstract-declarator of a parameter-declaration.
  for (unsigned i = 0, e = D.getNumTypeObjects(); i != e; ++i) {
    DeclaratorChunk &chunk = D.getTypeObject(i);
    if (chunk.Kind == DeclaratorChunk::Function) {
      for (unsigned argIdx = 0, e = chunk.Fun.NumArgs; argIdx != e; ++argIdx) {
        ParmVarDecl *Param =
          cast<ParmVarDecl>(chunk.Fun.ArgInfo[argIdx].Param.getAs<Decl>());
        if (Param->hasUnparsedDefaultArg()) {
          CachedTokens *Toks = chunk.Fun.ArgInfo[argIdx].DefaultArgTokens;
          Diag(Param->getLocation(), diag::err_param_default_argument_nonfunc)
            << SourceRange((*Toks)[1].getLocation(), Toks->back().getLocation());
          delete Toks;
          chunk.Fun.ArgInfo[argIdx].DefaultArgTokens = 0;
        } else if (Param->getDefaultArg()) {
          Diag(Param->getLocation(), diag::err_param_default_argument_nonfunc)
            << Param->getDefaultArg()->getSourceRange();
          Param->setDefaultArg(0);
        }
      }
    }
  }
}

// MergeCXXFunctionDecl - Merge two declarations of the same C++
// function, once we already know that they have the same
// type. Subroutine of MergeFunctionDecl. Returns true if there was an
// error, false otherwise.
bool Sema::MergeCXXFunctionDecl(FunctionDecl *New, FunctionDecl *Old) {
  bool Invalid = false;

  // C++ [dcl.fct.default]p4:
  //
  //   For non-template functions, default arguments can be added in
  //   later declarations of a function in the same
  //   scope. Declarations in different scopes have completely
  //   distinct sets of default arguments. That is, declarations in
  //   inner scopes do not acquire default arguments from
  //   declarations in outer scopes, and vice versa. In a given
  //   function declaration, all parameters subsequent to a
  //   parameter with a default argument shall have default
  //   arguments supplied in this or previous declarations. A
  //   default argument shall not be redefined by a later
  //   declaration (not even to the same value).
  for (unsigned p = 0, NumParams = Old->getNumParams(); p < NumParams; ++p) {
    ParmVarDecl *OldParam = Old->getParamDecl(p);
    ParmVarDecl *NewParam = New->getParamDecl(p);

    if(OldParam->getDefaultArg() && NewParam->getDefaultArg()) {
      Diag(NewParam->getLocation(), 
           diag::err_param_default_argument_redefinition)
        << NewParam->getDefaultArg()->getSourceRange();
      Diag(OldParam->getLocation(), diag::note_previous_definition);
      Invalid = true;
    } else if (OldParam->getDefaultArg()) {
      // Merge the old default argument into the new parameter
      NewParam->setDefaultArg(OldParam->getDefaultArg());
    }
  }

  return Invalid;
}

/// CheckCXXDefaultArguments - Verify that the default arguments for a
/// function declaration are well-formed according to C++
/// [dcl.fct.default].
void Sema::CheckCXXDefaultArguments(FunctionDecl *FD) {
  unsigned NumParams = FD->getNumParams();
  unsigned p;

  // Find first parameter with a default argument
  for (p = 0; p < NumParams; ++p) {
    ParmVarDecl *Param = FD->getParamDecl(p);
    if (Param->getDefaultArg())
      break;
  }

  // C++ [dcl.fct.default]p4:
  //   In a given function declaration, all parameters
  //   subsequent to a parameter with a default argument shall
  //   have default arguments supplied in this or previous
  //   declarations. A default argument shall not be redefined
  //   by a later declaration (not even to the same value).
  unsigned LastMissingDefaultArg = 0;
  for(; p < NumParams; ++p) {
    ParmVarDecl *Param = FD->getParamDecl(p);
    if (!Param->getDefaultArg()) {
      if (Param->isInvalidDecl())
        /* We already complained about this parameter. */;
      else if (Param->getIdentifier())
        Diag(Param->getLocation(), 
             diag::err_param_default_argument_missing_name)
          << Param->getIdentifier();
      else
        Diag(Param->getLocation(), 
             diag::err_param_default_argument_missing);
    
      LastMissingDefaultArg = p;
    }
  }

  if (LastMissingDefaultArg > 0) {
    // Some default arguments were missing. Clear out all of the
    // default arguments up to (and including) the last missing
    // default argument, so that we leave the function parameters
    // in a semantically valid state.
    for (p = 0; p <= LastMissingDefaultArg; ++p) {
      ParmVarDecl *Param = FD->getParamDecl(p);
      if (Param->getDefaultArg()) {
        if (!Param->hasUnparsedDefaultArg())
          Param->getDefaultArg()->Destroy(Context);
        Param->setDefaultArg(0);
      }
    }
  }
}

/// isCurrentClassName - Determine whether the identifier II is the
/// name of the class type currently being defined. In the case of
/// nested classes, this will only return true if II is the name of
/// the innermost class.
bool Sema::isCurrentClassName(const IdentifierInfo &II, Scope *,
                              const CXXScopeSpec *SS) {
  CXXRecordDecl *CurDecl;
  if (SS && SS->isSet() && !SS->isInvalid()) {
    DeclContext *DC = computeDeclContext(*SS);
    CurDecl = dyn_cast_or_null<CXXRecordDecl>(DC);
  } else
    CurDecl = dyn_cast_or_null<CXXRecordDecl>(CurContext);

  if (CurDecl)
    return &II == CurDecl->getIdentifier();
  else
    return false;
}

/// \brief Check the validity of a C++ base class specifier. 
///
/// \returns a new CXXBaseSpecifier if well-formed, emits diagnostics
/// and returns NULL otherwise.
CXXBaseSpecifier *
Sema::CheckBaseSpecifier(CXXRecordDecl *Class,
                         SourceRange SpecifierRange,
                         bool Virtual, AccessSpecifier Access,
                         QualType BaseType, 
                         SourceLocation BaseLoc) {
  // C++ [class.union]p1:
  //   A union shall not have base classes.
  if (Class->isUnion()) {
    Diag(Class->getLocation(), diag::err_base_clause_on_union)
      << SpecifierRange;
    return 0;
  }

  if (BaseType->isDependentType())
    return new CXXBaseSpecifier(SpecifierRange, Virtual, 
                                Class->getTagKind() == RecordDecl::TK_class,
                                Access, BaseType);

  // Base specifiers must be record types.
  if (!BaseType->isRecordType()) {
    Diag(BaseLoc, diag::err_base_must_be_class) << SpecifierRange;
    return 0;
  }

  // C++ [class.union]p1:
  //   A union shall not be used as a base class.
  if (BaseType->isUnionType()) {
    Diag(BaseLoc, diag::err_union_as_base_class) << SpecifierRange;
    return 0;
  }

  // C++ [class.derived]p2:
  //   The class-name in a base-specifier shall not be an incompletely
  //   defined class.
  if (RequireCompleteType(BaseLoc, BaseType, diag::err_incomplete_base_class,
                          SpecifierRange))
    return 0;

  // If the base class is polymorphic, the new one is, too.
  RecordDecl *BaseDecl = BaseType->getAsRecordType()->getDecl();
  assert(BaseDecl && "Record type has no declaration");
  BaseDecl = BaseDecl->getDefinition(Context);
  assert(BaseDecl && "Base type is not incomplete, but has no definition");
  if (cast<CXXRecordDecl>(BaseDecl)->isPolymorphic())
    Class->setPolymorphic(true);

  // C++ [dcl.init.aggr]p1:
  //   An aggregate is [...] a class with [...] no base classes [...].
  Class->setAggregate(false);
  Class->setPOD(false);

  // Create the base specifier.
  // FIXME: Allocate via ASTContext?
  return new CXXBaseSpecifier(SpecifierRange, Virtual, 
                              Class->getTagKind() == RecordDecl::TK_class, 
                              Access, BaseType);
}

/// ActOnBaseSpecifier - Parsed a base specifier. A base specifier is
/// one entry in the base class list of a class specifier, for
/// example: 
///    class foo : public bar, virtual private baz { 
/// 'public bar' and 'virtual private baz' are each base-specifiers.
Sema::BaseResult 
Sema::ActOnBaseSpecifier(DeclPtrTy classdecl, SourceRange SpecifierRange,
                         bool Virtual, AccessSpecifier Access,
                         TypeTy *basetype, SourceLocation BaseLoc) {
  AdjustDeclIfTemplate(classdecl);
  CXXRecordDecl *Class = cast<CXXRecordDecl>(classdecl.getAs<Decl>());
  QualType BaseType = QualType::getFromOpaquePtr(basetype);
  if (CXXBaseSpecifier *BaseSpec = CheckBaseSpecifier(Class, SpecifierRange,
                                                      Virtual, Access,
                                                      BaseType, BaseLoc))
    return BaseSpec;
  
  return true;
}

/// \brief Performs the actual work of attaching the given base class
/// specifiers to a C++ class.
bool Sema::AttachBaseSpecifiers(CXXRecordDecl *Class, CXXBaseSpecifier **Bases,
                                unsigned NumBases) {
 if (NumBases == 0)
    return false;

  // Used to keep track of which base types we have already seen, so
  // that we can properly diagnose redundant direct base types. Note
  // that the key is always the unqualified canonical type of the base
  // class.
  std::map<QualType, CXXBaseSpecifier*, QualTypeOrdering> KnownBaseTypes;

  // Copy non-redundant base specifiers into permanent storage.
  unsigned NumGoodBases = 0;
  bool Invalid = false;
  for (unsigned idx = 0; idx < NumBases; ++idx) {
    QualType NewBaseType 
      = Context.getCanonicalType(Bases[idx]->getType());
    NewBaseType = NewBaseType.getUnqualifiedType();

    if (KnownBaseTypes[NewBaseType]) {
      // C++ [class.mi]p3:
      //   A class shall not be specified as a direct base class of a
      //   derived class more than once.
      Diag(Bases[idx]->getSourceRange().getBegin(),
           diag::err_duplicate_base_class)
        << KnownBaseTypes[NewBaseType]->getType()
        << Bases[idx]->getSourceRange();

      // Delete the duplicate base class specifier; we're going to
      // overwrite its pointer later.
      delete Bases[idx];

      Invalid = true;
    } else {
      // Okay, add this new base class.
      KnownBaseTypes[NewBaseType] = Bases[idx];
      Bases[NumGoodBases++] = Bases[idx];
    }
  }

  // Attach the remaining base class specifiers to the derived class.
  Class->setBases(Bases, NumGoodBases);

  // Delete the remaining (good) base class specifiers, since their
  // data has been copied into the CXXRecordDecl.
  for (unsigned idx = 0; idx < NumGoodBases; ++idx)
    delete Bases[idx];

  return Invalid;
}

/// ActOnBaseSpecifiers - Attach the given base specifiers to the
/// class, after checking whether there are any duplicate base
/// classes.
void Sema::ActOnBaseSpecifiers(DeclPtrTy ClassDecl, BaseTy **Bases, 
                               unsigned NumBases) {
  if (!ClassDecl || !Bases || !NumBases)
    return;

  AdjustDeclIfTemplate(ClassDecl);
  AttachBaseSpecifiers(cast<CXXRecordDecl>(ClassDecl.getAs<Decl>()),
                       (CXXBaseSpecifier**)(Bases), NumBases);
}

//===----------------------------------------------------------------------===//
// C++ class member Handling
//===----------------------------------------------------------------------===//

/// ActOnCXXMemberDeclarator - This is invoked when a C++ class member
/// declarator is parsed. 'AS' is the access specifier, 'BW' specifies the
/// bitfield width if there is one and 'InitExpr' specifies the initializer if
/// any.
Sema::DeclPtrTy
Sema::ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS, Declarator &D,
                               ExprTy *BW, ExprTy *InitExpr, bool Deleted) {
  const DeclSpec &DS = D.getDeclSpec();
  DeclarationName Name = GetNameForDeclarator(D);
  Expr *BitWidth = static_cast<Expr*>(BW);
  Expr *Init = static_cast<Expr*>(InitExpr);
  SourceLocation Loc = D.getIdentifierLoc();

  bool isFunc = D.isFunctionDeclarator();

  // C++ 9.2p6: A member shall not be declared to have automatic storage
  // duration (auto, register) or with the extern storage-class-specifier.
  // C++ 7.1.1p8: The mutable specifier can be applied only to names of class
  // data members and cannot be applied to names declared const or static,
  // and cannot be applied to reference members.
  switch (DS.getStorageClassSpec()) {
    case DeclSpec::SCS_unspecified:
    case DeclSpec::SCS_typedef:
    case DeclSpec::SCS_static:
      // FALL THROUGH.
      break;
    case DeclSpec::SCS_mutable:
      if (isFunc) {
        if (DS.getStorageClassSpecLoc().isValid())
          Diag(DS.getStorageClassSpecLoc(), diag::err_mutable_function);
        else
          Diag(DS.getThreadSpecLoc(), diag::err_mutable_function);
        
        // FIXME: It would be nicer if the keyword was ignored only for this
        // declarator. Otherwise we could get follow-up errors.
        D.getMutableDeclSpec().ClearStorageClassSpecs();
      } else {
        QualType T = GetTypeForDeclarator(D, S);
        diag::kind err = static_cast<diag::kind>(0);
        if (T->isReferenceType())
          err = diag::err_mutable_reference;
        else if (T.isConstQualified())
          err = diag::err_mutable_const;
        if (err != 0) {
          if (DS.getStorageClassSpecLoc().isValid())
            Diag(DS.getStorageClassSpecLoc(), err);
          else
            Diag(DS.getThreadSpecLoc(), err);
          // FIXME: It would be nicer if the keyword was ignored only for this
          // declarator. Otherwise we could get follow-up errors.
          D.getMutableDeclSpec().ClearStorageClassSpecs();
        }
      }
      break;
    default:
      if (DS.getStorageClassSpecLoc().isValid())
        Diag(DS.getStorageClassSpecLoc(),
             diag::err_storageclass_invalid_for_member);
      else
        Diag(DS.getThreadSpecLoc(), diag::err_storageclass_invalid_for_member);
      D.getMutableDeclSpec().ClearStorageClassSpecs();
  }

  if (!isFunc &&
      D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_typename &&
      D.getNumTypeObjects() == 0) {
    // Check also for this case:
    //
    // typedef int f();
    // f a;
    //
    QualType TDType = QualType::getFromOpaquePtr(DS.getTypeRep());
    isFunc = TDType->isFunctionType();
  }

  bool isInstField = ((DS.getStorageClassSpec() == DeclSpec::SCS_unspecified ||
                       DS.getStorageClassSpec() == DeclSpec::SCS_mutable) &&
                      !isFunc);

  Decl *Member;
  if (isInstField) {
    Member = HandleField(S, cast<CXXRecordDecl>(CurContext), Loc, D, BitWidth,
                         AS);
    assert(Member && "HandleField never returns null");
  } else {
    Member = ActOnDeclarator(S, D).getAs<Decl>();
    if (!Member) {
      if (BitWidth) DeleteExpr(BitWidth);
      return DeclPtrTy();
    }

    // Non-instance-fields can't have a bitfield.
    if (BitWidth) {
      if (Member->isInvalidDecl()) {
        // don't emit another diagnostic.
      } else if (isa<VarDecl>(Member)) {
        // C++ 9.6p3: A bit-field shall not be a static member.
        // "static member 'A' cannot be a bit-field"
        Diag(Loc, diag::err_static_not_bitfield)
          << Name << BitWidth->getSourceRange();
      } else if (isa<TypedefDecl>(Member)) {
        // "typedef member 'x' cannot be a bit-field"
        Diag(Loc, diag::err_typedef_not_bitfield)
          << Name << BitWidth->getSourceRange();
      } else {
        // A function typedef ("typedef int f(); f a;").
        // C++ 9.6p3: A bit-field shall have integral or enumeration type.
        Diag(Loc, diag::err_not_integral_type_bitfield)
          << Name << cast<ValueDecl>(Member)->getType() 
          << BitWidth->getSourceRange();
      }
      
      DeleteExpr(BitWidth);
      BitWidth = 0;
      Member->setInvalidDecl();
    }

    Member->setAccess(AS);
  }

  assert((Name || isInstField) && "No identifier for non-field ?");

  if (Init)
    AddInitializerToDecl(DeclPtrTy::make(Member), ExprArg(*this, Init), false);
  if (Deleted) // FIXME: Source location is not very good.
    SetDeclDeleted(DeclPtrTy::make(Member), D.getSourceRange().getBegin());

  if (isInstField) {
    FieldCollector->Add(cast<FieldDecl>(Member));
    return DeclPtrTy();
  }
  return DeclPtrTy::make(Member);
}

/// ActOnMemInitializer - Handle a C++ member initializer.
Sema::MemInitResult 
Sema::ActOnMemInitializer(DeclPtrTy ConstructorD,
                          Scope *S,
                          IdentifierInfo *MemberOrBase,
                          SourceLocation IdLoc,
                          SourceLocation LParenLoc,
                          ExprTy **Args, unsigned NumArgs,
                          SourceLocation *CommaLocs,
                          SourceLocation RParenLoc) {
  CXXConstructorDecl *Constructor 
    = dyn_cast<CXXConstructorDecl>(ConstructorD.getAs<Decl>());
  if (!Constructor) {
    // The user wrote a constructor initializer on a function that is
    // not a C++ constructor. Ignore the error for now, because we may
    // have more member initializers coming; we'll diagnose it just
    // once in ActOnMemInitializers.
    return true;
  }

  CXXRecordDecl *ClassDecl = Constructor->getParent();

  // C++ [class.base.init]p2:
  //   Names in a mem-initializer-id are looked up in the scope of the
  //   constructor’s class and, if not found in that scope, are looked
  //   up in the scope containing the constructor’s
  //   definition. [Note: if the constructor’s class contains a member
  //   with the same name as a direct or virtual base class of the
  //   class, a mem-initializer-id naming the member or base class and
  //   composed of a single identifier refers to the class member. A
  //   mem-initializer-id for the hidden base class may be specified
  //   using a qualified name. ]
  // Look for a member, first.
  FieldDecl *Member = 0;
  DeclContext::lookup_result Result 
    = ClassDecl->lookup(Context, MemberOrBase);
  if (Result.first != Result.second)
    Member = dyn_cast<FieldDecl>(*Result.first);

  // FIXME: Handle members of an anonymous union.

  if (Member) {
    // FIXME: Perform direct initialization of the member.
    return new CXXBaseOrMemberInitializer(Member, (Expr **)Args, NumArgs);
  }

  // It didn't name a member, so see if it names a class.
  TypeTy *BaseTy = getTypeName(*MemberOrBase, IdLoc, S, 0/*SS*/);
  if (!BaseTy)
    return Diag(IdLoc, diag::err_mem_init_not_member_or_class)
      << MemberOrBase << SourceRange(IdLoc, RParenLoc);
  
  QualType BaseType = QualType::getFromOpaquePtr(BaseTy);
  if (!BaseType->isRecordType())
    return Diag(IdLoc, diag::err_base_init_does_not_name_class)
      << BaseType << SourceRange(IdLoc, RParenLoc);

  // C++ [class.base.init]p2:
  //   [...] Unless the mem-initializer-id names a nonstatic data
  //   member of the constructor’s class or a direct or virtual base
  //   of that class, the mem-initializer is ill-formed. A
  //   mem-initializer-list can initialize a base class using any
  //   name that denotes that base class type.
  
  // First, check for a direct base class.
  const CXXBaseSpecifier *DirectBaseSpec = 0;
  for (CXXRecordDecl::base_class_const_iterator Base = ClassDecl->bases_begin();
       Base != ClassDecl->bases_end(); ++Base) {
    if (Context.getCanonicalType(BaseType).getUnqualifiedType() == 
        Context.getCanonicalType(Base->getType()).getUnqualifiedType()) {
      // We found a direct base of this type. That's what we're
      // initializing.
      DirectBaseSpec = &*Base;
      break;
    }
  }
  
  // Check for a virtual base class.
  // FIXME: We might be able to short-circuit this if we know in
  // advance that there are no virtual bases.
  const CXXBaseSpecifier *VirtualBaseSpec = 0;
  if (!DirectBaseSpec || !DirectBaseSpec->isVirtual()) {
    // We haven't found a base yet; search the class hierarchy for a
    // virtual base class.
    BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
                    /*DetectVirtual=*/false);
    if (IsDerivedFrom(Context.getTypeDeclType(ClassDecl), BaseType, Paths)) {
      for (BasePaths::paths_iterator Path = Paths.begin(); 
           Path != Paths.end(); ++Path) {
        if (Path->back().Base->isVirtual()) {
          VirtualBaseSpec = Path->back().Base;
          break;
        }
      }
    }
  }

  // C++ [base.class.init]p2:
  //   If a mem-initializer-id is ambiguous because it designates both
  //   a direct non-virtual base class and an inherited virtual base
  //   class, the mem-initializer is ill-formed.
  if (DirectBaseSpec && VirtualBaseSpec)
    return Diag(IdLoc, diag::err_base_init_direct_and_virtual)
      << MemberOrBase << SourceRange(IdLoc, RParenLoc);

  return new CXXBaseOrMemberInitializer(BaseType, (Expr **)Args, NumArgs);
}

void Sema::ActOnMemInitializers(DeclPtrTy ConstructorDecl, 
                                SourceLocation ColonLoc,
                                MemInitTy **MemInits, unsigned NumMemInits) {
  CXXConstructorDecl *Constructor = 
  dyn_cast<CXXConstructorDecl>(ConstructorDecl.getAs<Decl>());
  
  if (!Constructor) {
    Diag(ColonLoc, diag::err_only_constructors_take_base_inits);
    return;
  }
}

namespace {
  /// PureVirtualMethodCollector - traverses a class and its superclasses
  /// and determines if it has any pure virtual methods.
  class VISIBILITY_HIDDEN PureVirtualMethodCollector {
    ASTContext &Context;

  public:
    typedef llvm::SmallVector<const CXXMethodDecl*, 8> MethodList;

  private:
    MethodList Methods;
    
    void Collect(const CXXRecordDecl* RD, MethodList& Methods);
    
  public:
    PureVirtualMethodCollector(ASTContext &Ctx, const CXXRecordDecl* RD) 
      : Context(Ctx) {
        
      MethodList List;
      Collect(RD, List);
        
      // Copy the temporary list to methods, and make sure to ignore any
      // null entries.
      for (size_t i = 0, e = List.size(); i != e; ++i) {
        if (List[i])
          Methods.push_back(List[i]);
      }          
    }
    
    bool empty() const { return Methods.empty(); }
    
    MethodList::const_iterator methods_begin() { return Methods.begin(); }
    MethodList::const_iterator methods_end() { return Methods.end(); }
  };
  
  void PureVirtualMethodCollector::Collect(const CXXRecordDecl* RD, 
                                           MethodList& Methods) {
    // First, collect the pure virtual methods for the base classes.
    for (CXXRecordDecl::base_class_const_iterator Base = RD->bases_begin(),
         BaseEnd = RD->bases_end(); Base != BaseEnd; ++Base) {
      if (const RecordType *RT = Base->getType()->getAsRecordType()) {
        const CXXRecordDecl *BaseDecl = cast<CXXRecordDecl>(RT->getDecl());
        if (BaseDecl && BaseDecl->isAbstract())
          Collect(BaseDecl, Methods);
      }
    }
    
    // Next, zero out any pure virtual methods that this class overrides.
    for (size_t i = 0, e = Methods.size(); i != e; ++i) {
      const CXXMethodDecl *VMD = dyn_cast_or_null<CXXMethodDecl>(Methods[i]);
      if (!VMD)
        continue;
      
      DeclContext::lookup_const_iterator I, E;
      for (llvm::tie(I, E) = RD->lookup(Context, VMD->getDeclName()); 
           I != E; ++I) {
        if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(*I)) {
          if (Context.getCanonicalType(MD->getType()) == 
              Context.getCanonicalType(VMD->getType())) {
            // We did find a matching method, which means that this is not a
            // pure virtual method in the current class. Zero it out.
            Methods[i] = 0;
          }
        }
      }
    }
    
    // Finally, add pure virtual methods from this class.
    for (RecordDecl::decl_iterator i = RD->decls_begin(Context), 
                                   e = RD->decls_end(Context); 
         i != e; ++i) {
      if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(*i)) {
        if (MD->isPure())
          Methods.push_back(MD);
      }
    }
  }
}

bool Sema::RequireNonAbstractType(SourceLocation Loc, QualType T, 
                                  unsigned DiagID, AbstractDiagSelID SelID,
                                  const CXXRecordDecl *CurrentRD) {
  
  if (!getLangOptions().CPlusPlus)
    return false;
  
  if (const ArrayType *AT = Context.getAsArrayType(T))
    return RequireNonAbstractType(Loc, AT->getElementType(), DiagID, SelID,
                                  CurrentRD);
  
  if (const PointerType *PT = T->getAsPointerType()) {
    // Find the innermost pointer type.
    while (const PointerType *T = PT->getPointeeType()->getAsPointerType())
      PT = T;
    
    if (const ArrayType *AT = Context.getAsArrayType(PT->getPointeeType()))
      return RequireNonAbstractType(Loc, AT->getElementType(), DiagID, SelID,
                                    CurrentRD);
  }
  
  const RecordType *RT = T->getAsRecordType();
  if (!RT)
    return false;
  
  const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(RT->getDecl());
  if (!RD)
    return false;

  if (CurrentRD && CurrentRD != RD)
    return false;
  
  if (!RD->isAbstract())
    return false;
  
  Diag(Loc, DiagID) << RD->getDeclName() << SelID;
  
  // Check if we've already emitted the list of pure virtual functions for this
  // class.
  if (PureVirtualClassDiagSet && PureVirtualClassDiagSet->count(RD))
    return true;
  
  PureVirtualMethodCollector Collector(Context, RD);
  
  for (PureVirtualMethodCollector::MethodList::const_iterator I = 
       Collector.methods_begin(), E = Collector.methods_end(); I != E; ++I) {
    const CXXMethodDecl *MD = *I;
    
    Diag(MD->getLocation(), diag::note_pure_virtual_function) << 
      MD->getDeclName();
  }

  if (!PureVirtualClassDiagSet)
    PureVirtualClassDiagSet.reset(new RecordDeclSetTy);
  PureVirtualClassDiagSet->insert(RD);
  
  return true;
}

namespace {
  class VISIBILITY_HIDDEN AbstractClassUsageDiagnoser 
    : public DeclVisitor<AbstractClassUsageDiagnoser, bool> {
    Sema &SemaRef;
    CXXRecordDecl *AbstractClass;
  
    bool VisitDeclContext(const DeclContext *DC) {
      bool Invalid = false;

      for (CXXRecordDecl::decl_iterator I = DC->decls_begin(SemaRef.Context),
           E = DC->decls_end(SemaRef.Context); I != E; ++I)
        Invalid |= Visit(*I);

      return Invalid;
    }
      
  public:
    AbstractClassUsageDiagnoser(Sema& SemaRef, CXXRecordDecl *ac)
      : SemaRef(SemaRef), AbstractClass(ac) {
        Visit(SemaRef.Context.getTranslationUnitDecl());
    }

    bool VisitFunctionDecl(const FunctionDecl *FD) {
      if (FD->isThisDeclarationADefinition()) {
        // No need to do the check if we're in a definition, because it requires
        // that the return/param types are complete.
        // because that requires 
        return VisitDeclContext(FD);
      }
      
      // Check the return type.
      QualType RTy = FD->getType()->getAsFunctionType()->getResultType();
      bool Invalid = 
        SemaRef.RequireNonAbstractType(FD->getLocation(), RTy,
                                       diag::err_abstract_type_in_decl,
                                       Sema::AbstractReturnType,
                                       AbstractClass);

      for (FunctionDecl::param_const_iterator I = FD->param_begin(), 
           E = FD->param_end(); I != E; ++I) {
        const ParmVarDecl *VD = *I;
        Invalid |= 
          SemaRef.RequireNonAbstractType(VD->getLocation(),
                                         VD->getOriginalType(), 
                                         diag::err_abstract_type_in_decl, 
                                         Sema::AbstractParamType,
                                         AbstractClass);
      }

      return Invalid;
    }
    
    bool VisitDecl(const Decl* D) {
      if (const DeclContext *DC = dyn_cast<DeclContext>(D))
        return VisitDeclContext(DC);
      
      return false;
    }
  };
}

void Sema::ActOnFinishCXXMemberSpecification(Scope* S, SourceLocation RLoc,
                                             DeclPtrTy TagDecl,
                                             SourceLocation LBrac,
                                             SourceLocation RBrac) {
  TemplateDecl *Template = AdjustDeclIfTemplate(TagDecl);
  ActOnFields(S, RLoc, TagDecl,
              (DeclPtrTy*)FieldCollector->getCurFields(),
              FieldCollector->getCurNumFields(), LBrac, RBrac, 0);

  CXXRecordDecl *RD = cast<CXXRecordDecl>(TagDecl.getAs<Decl>());
  if (!RD->isAbstract()) {
    // Collect all the pure virtual methods and see if this is an abstract
    // class after all.
    PureVirtualMethodCollector Collector(Context, RD);
    if (!Collector.empty()) 
      RD->setAbstract(true);
  }
  
  if (RD->isAbstract()) 
    AbstractClassUsageDiagnoser(*this, RD);
    
  if (!Template)
    AddImplicitlyDeclaredMembersToClass(RD);
}

/// AddImplicitlyDeclaredMembersToClass - Adds any implicitly-declared
/// special functions, such as the default constructor, copy
/// constructor, or destructor, to the given C++ class (C++
/// [special]p1).  This routine can only be executed just before the
/// definition of the class is complete.
void Sema::AddImplicitlyDeclaredMembersToClass(CXXRecordDecl *ClassDecl) {
  QualType ClassType = Context.getTypeDeclType(ClassDecl);
  ClassType = Context.getCanonicalType(ClassType);

  if (!ClassDecl->hasUserDeclaredConstructor()) {
    // C++ [class.ctor]p5:
    //   A default constructor for a class X is a constructor of class X
    //   that can be called without an argument. If there is no
    //   user-declared constructor for class X, a default constructor is
    //   implicitly declared. An implicitly-declared default constructor
    //   is an inline public member of its class.
    DeclarationName Name 
      = Context.DeclarationNames.getCXXConstructorName(ClassType);
    CXXConstructorDecl *DefaultCon = 
      CXXConstructorDecl::Create(Context, ClassDecl,
                                 ClassDecl->getLocation(), Name,
                                 Context.getFunctionType(Context.VoidTy,
                                                         0, 0, false, 0),
                                 /*isExplicit=*/false,
                                 /*isInline=*/true,
                                 /*isImplicitlyDeclared=*/true);
    DefaultCon->setAccess(AS_public);
    DefaultCon->setImplicit();
    ClassDecl->addDecl(Context, DefaultCon);

    // Notify the class that we've added a constructor.
    ClassDecl->addedConstructor(Context, DefaultCon);
  }

  if (!ClassDecl->hasUserDeclaredCopyConstructor()) {
    // C++ [class.copy]p4:
    //   If the class definition does not explicitly declare a copy
    //   constructor, one is declared implicitly.

    // C++ [class.copy]p5:
    //   The implicitly-declared copy constructor for a class X will
    //   have the form
    //
    //       X::X(const X&)
    //
    //   if
    bool HasConstCopyConstructor = true;

    //     -- each direct or virtual base class B of X has a copy
    //        constructor whose first parameter is of type const B& or
    //        const volatile B&, and
    for (CXXRecordDecl::base_class_iterator Base = ClassDecl->bases_begin();
         HasConstCopyConstructor && Base != ClassDecl->bases_end(); ++Base) {
      const CXXRecordDecl *BaseClassDecl