lib/Sema/SemaExprObjC.cpp

//===--- SemaExprObjC.cpp - Semantic Analysis for ObjC Expressions --------===//
//
//                     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 Objective-C expressions.
//
//===----------------------------------------------------------------------===//

#include "Sema.h"
#include "Lookup.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/ExprObjC.h"
#include "llvm/ADT/SmallString.h"
#include "clang/Lex/Preprocessor.h"

using namespace clang;

Sema::ExprResult Sema::ParseObjCStringLiteral(SourceLocation *AtLocs,
                                              ExprTy **strings,
                                              unsigned NumStrings) {
  StringLiteral **Strings = reinterpret_cast<StringLiteral**>(strings);

  // Most ObjC strings are formed out of a single piece.  However, we *can*
  // have strings formed out of multiple @ strings with multiple pptokens in
  // each one, e.g. @"foo" "bar" @"baz" "qux"   which need to be turned into one
  // StringLiteral for ObjCStringLiteral to hold onto.
  StringLiteral *S = Strings[0];

  // If we have a multi-part string, merge it all together.
  if (NumStrings != 1) {
    // Concatenate objc strings.
    llvm::SmallString<128> StrBuf;
    llvm::SmallVector<SourceLocation, 8> StrLocs;

    for (unsigned i = 0; i != NumStrings; ++i) {
      S = Strings[i];

      // ObjC strings can't be wide.
      if (S->isWide()) {
        Diag(S->getLocStart(), diag::err_cfstring_literal_not_string_constant)
          << S->getSourceRange();
        return true;
      }

      // Get the string data.
      StrBuf.append(S->getStrData(), S->getStrData()+S->getByteLength());

      // Get the locations of the string tokens.
      StrLocs.append(S->tokloc_begin(), S->tokloc_end());

      // Free the temporary string.
      S->Destroy(Context);
    }

    // Create the aggregate string with the appropriate content and location
    // information.
    S = StringLiteral::Create(Context, &StrBuf[0], StrBuf.size(), false,
                              Context.getPointerType(Context.CharTy),
                              &StrLocs[0], StrLocs.size());
  }

  // Verify that this composite string is acceptable for ObjC strings.
  if (CheckObjCString(S))
    return true;

  // Initialize the constant string interface lazily. This assumes
  // the NSString interface is seen in this translation unit. Note: We
  // don't use NSConstantString, since the runtime team considers this
  // interface private (even though it appears in the header files).
  QualType Ty = Context.getObjCConstantStringInterface();
  if (!Ty.isNull()) {
    Ty = Context.getObjCObjectPointerType(Ty);
  } else {
    IdentifierInfo *NSIdent = &Context.Idents.get("NSString");
    NamedDecl *IF = LookupSingleName(TUScope, NSIdent, AtLocs[0],
                                     LookupOrdinaryName);
    if (ObjCInterfaceDecl *StrIF = dyn_cast_or_null<ObjCInterfaceDecl>(IF)) {
      Context.setObjCConstantStringInterface(StrIF);
      Ty = Context.getObjCConstantStringInterface();
      Ty = Context.getObjCObjectPointerType(Ty);
    } else {
      // If there is no NSString interface defined then treat constant
      // strings as untyped objects and let the runtime figure it out later.
      Ty = Context.getObjCIdType();
    }
  }

  return new (Context) ObjCStringLiteral(S, Ty, AtLocs[0]);
}

Expr *Sema::BuildObjCEncodeExpression(SourceLocation AtLoc,
                                      TypeSourceInfo *EncodedTypeInfo,
                                      SourceLocation RParenLoc) {
  QualType EncodedType = EncodedTypeInfo->getType();
  QualType StrTy;
  if (EncodedType->isDependentType())
    StrTy = Context.DependentTy;
  else {
    std::string Str;
    Context.getObjCEncodingForType(EncodedType, Str);

    // The type of @encode is the same as the type of the corresponding string,
    // which is an array type.
    StrTy = Context.CharTy;
    // A C++ string literal has a const-qualified element type (C++ 2.13.4p1).
    if (getLangOptions().CPlusPlus || getLangOptions().ConstStrings)
      StrTy.addConst();
    StrTy = Context.getConstantArrayType(StrTy, llvm::APInt(32, Str.size()+1),
                                         ArrayType::Normal, 0);
  }

  return new (Context) ObjCEncodeExpr(StrTy, EncodedTypeInfo, AtLoc, RParenLoc);
}

Sema::ExprResult Sema::ParseObjCEncodeExpression(SourceLocation AtLoc,
                                                 SourceLocation EncodeLoc,
                                                 SourceLocation LParenLoc,
                                                 TypeTy *ty,
                                                 SourceLocation RParenLoc) {
  // FIXME: Preserve type source info ?
  TypeSourceInfo *TInfo;
  QualType EncodedType = GetTypeFromParser(ty, &TInfo);
  if (!TInfo)
    TInfo = Context.getTrivialTypeSourceInfo(EncodedType,
                                             PP.getLocForEndOfToken(LParenLoc));

  return BuildObjCEncodeExpression(AtLoc, TInfo, RParenLoc);
}

Sema::ExprResult Sema::ParseObjCSelectorExpression(Selector Sel,
                                                   SourceLocation AtLoc,
                                                   SourceLocation SelLoc,
                                                   SourceLocation LParenLoc,
                                                   SourceLocation RParenLoc) {
  ObjCMethodDecl *Method = LookupInstanceMethodInGlobalPool(Sel,
                             SourceRange(LParenLoc, RParenLoc), false);
  if (!Method)
    Method = LookupFactoryMethodInGlobalPool(Sel,
                                          SourceRange(LParenLoc, RParenLoc));
  if (!Method)
    Diag(SelLoc, diag::warn_undeclared_selector) << Sel;

  QualType Ty = Context.getObjCSelType();
  return new (Context) ObjCSelectorExpr(Ty, Sel, AtLoc, RParenLoc);
}

Sema::ExprResult Sema::ParseObjCProtocolExpression(IdentifierInfo *ProtocolId,
                                                   SourceLocation AtLoc,
                                                   SourceLocation ProtoLoc,
                                                   SourceLocation LParenLoc,
                                                   SourceLocation RParenLoc) {
  ObjCProtocolDecl* PDecl = LookupProtocol(ProtocolId, ProtoLoc);
  if (!PDecl) {
    Diag(ProtoLoc, diag::err_undeclared_protocol) << ProtocolId;
    return true;
  }

  QualType Ty = Context.getObjCProtoType();
  if (Ty.isNull())
    return true;
  Ty = Context.getObjCObjectPointerType(Ty);
  return new (Context) ObjCProtocolExpr(Ty, PDecl, AtLoc, RParenLoc);
}

bool Sema::CheckMessageArgumentTypes(Expr **Args, unsigned NumArgs,
                                     Selector Sel, ObjCMethodDecl *Method,
                                     bool isClassMessage,
                                     SourceLocation lbrac, SourceLocation rbrac,
                                     QualType &ReturnType) {
  if (!Method) {
    // Apply default argument promotion as for (C99 6.5.2.2p6).
    for (unsigned i = 0; i != NumArgs; i++)
      DefaultArgumentPromotion(Args[i]);

    unsigned DiagID = isClassMessage ? diag::warn_class_method_not_found :
                                       diag::warn_inst_method_not_found;
    Diag(lbrac, DiagID)
      << Sel << isClassMessage << SourceRange(lbrac, rbrac);
    ReturnType = Context.getObjCIdType();
    return false;
  }

  ReturnType = Method->getResultType();

  unsigned NumNamedArgs = Sel.getNumArgs();
  // Method might have more arguments than selector indicates. This is due
  // to addition of c-style arguments in method.
  if (Method->param_size() > Sel.getNumArgs())
    NumNamedArgs = Method->param_size();
  // FIXME. This need be cleaned up.
  if (NumArgs < NumNamedArgs) {
    Diag(lbrac, diag::err_typecheck_call_too_few_args) << 2
    << NumNamedArgs << NumArgs;
    return false;
  }

  bool IsError = false;
  for (unsigned i = 0; i < NumNamedArgs; i++) {
    Expr *argExpr = Args[i];
    assert(argExpr && "CheckMessageArgumentTypes(): missing expression");

    QualType lhsType = Method->param_begin()[i]->getType();
    QualType rhsType = argExpr->getType();

    // If necessary, apply function/array conversion. C99 6.7.5.3p[7,8].
    if (lhsType->isArrayType())
      lhsType = Context.getArrayDecayedType(lhsType);
    else if (lhsType->isFunctionType())
      lhsType = Context.getPointerType(lhsType);

    AssignConvertType Result =
      CheckSingleAssignmentConstraints(lhsType, argExpr);
    if (Result == Incompatible && !getLangOptions().CPlusPlus &&
        CheckTransparentUnionArgumentConstraints(lhsType, argExpr)
        == Sema::Compatible)
      Result = Compatible;
        
    if (Args[i] != argExpr) // The expression was converted.
      Args[i] = argExpr; // Make sure we store the converted expression.

    IsError |=
      DiagnoseAssignmentResult(Result, argExpr->getLocStart(), lhsType, rhsType,
                               argExpr, AA_Sending);
  }

  // Promote additional arguments to variadic methods.
  if (Method->isVariadic()) {
    for (unsigned i = NumNamedArgs; i < NumArgs; ++i)
      IsError |= DefaultVariadicArgumentPromotion(Args[i], VariadicMethod);
  } else {
    // Check for extra arguments to non-variadic methods.
    if (NumArgs != NumNamedArgs) {
      Diag(Args[NumNamedArgs]->getLocStart(),
           diag::err_typecheck_call_too_many_args)
        << 2 /*method*/ << NumNamedArgs << NumArgs
        << Method->getSourceRange()
        << SourceRange(Args[NumNamedArgs]->getLocStart(),
                       Args[NumArgs-1]->getLocEnd());
    }
  }

  return IsError;
}

bool Sema::isSelfExpr(Expr *RExpr) {
  if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(RExpr))
    if (DRE->getDecl()->getIdentifier() == &Context.Idents.get("self"))
      return true;
  return false;
}

// Helper method for ActOnClassMethod/ActOnInstanceMethod.
// Will search "local" class/category implementations for a method decl.
// If failed, then we search in class's root for an instance method.
// Returns 0 if no method is found.
ObjCMethodDecl *Sema::LookupPrivateClassMethod(Selector Sel,
                                          ObjCInterfaceDecl *ClassDecl) {
  ObjCMethodDecl *Method = 0;
  // lookup in class and all superclasses
  while (ClassDecl && !Method) {
    if (ObjCImplementationDecl *ImpDecl = ClassDecl->getImplementation())
      Method = ImpDecl->getClassMethod(Sel);

    // Look through local category implementations associated with the class.
    if (!Method)
      Method = ClassDecl->getCategoryClassMethod(Sel);

    // Before we give up, check if the selector is an instance method.
    // But only in the root. This matches gcc's behaviour and what the
    // runtime expects.
    if (!Method && !ClassDecl->getSuperClass()) {
      Method = ClassDecl->lookupInstanceMethod(Sel);
      // Look through local category implementations associated
      // with the root class.
      if (!Method)
        Method = LookupPrivateInstanceMethod(Sel, ClassDecl);
    }

    ClassDecl = ClassDecl->getSuperClass();
  }
  return Method;
}

ObjCMethodDecl *Sema::LookupPrivateInstanceMethod(Selector Sel,
                                              ObjCInterfaceDecl *ClassDecl) {
  ObjCMethodDecl *Method = 0;
  while (ClassDecl && !Method) {
    // If we have implementations in scope, check "private" methods.
    if (ObjCImplementationDecl *ImpDecl = ClassDecl->getImplementation())
      Method = ImpDecl->getInstanceMethod(Sel);

    // Look through local category implementations associated with the class.
    if (!Method)
      Method = ClassDecl->getCategoryInstanceMethod(Sel);
    ClassDecl = ClassDecl->getSuperClass();
  }
  return Method;
}

/// HandleExprPropertyRefExpr - Handle foo.bar where foo is a pointer to an
/// objective C interface.  This is a property reference expression.
Action::OwningExprResult Sema::
HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,
                          Expr *BaseExpr, DeclarationName MemberName,
                          SourceLocation MemberLoc) {
  const ObjCInterfaceType *IFaceT = OPT->getInterfaceType();
  ObjCInterfaceDecl *IFace = IFaceT->getDecl();
  IdentifierInfo *Member = MemberName.getAsIdentifierInfo();

  // Search for a declared property first.
  if (ObjCPropertyDecl *PD = IFace->FindPropertyDeclaration(Member)) {
    // Check whether we can reference this property.
    if (DiagnoseUseOfDecl(PD, MemberLoc))
      return ExprError();
    QualType ResTy = PD->getType();
    Selector Sel = PP.getSelectorTable().getNullarySelector(Member);
    ObjCMethodDecl *Getter = IFace->lookupInstanceMethod(Sel);
    if (DiagnosePropertyAccessorMismatch(PD, Getter, MemberLoc))
      ResTy = Getter->getResultType();
    return Owned(new (Context) ObjCPropertyRefExpr(PD, ResTy,
                                                   MemberLoc, BaseExpr));
  }
  // Check protocols on qualified interfaces.
  for (ObjCObjectPointerType::qual_iterator I = OPT->qual_begin(),
       E = OPT->qual_end(); I != E; ++I)
    if (ObjCPropertyDecl *PD = (*I)->FindPropertyDeclaration(Member)) {
      // Check whether we can reference this property.
      if (DiagnoseUseOfDecl(PD, MemberLoc))
        return ExprError();

      return Owned(new (Context) ObjCPropertyRefExpr(PD, PD->getType(),
                                                     MemberLoc, BaseExpr));
    }
  // If that failed, look for an "implicit" property by seeing if the nullary
  // selector is implemented.

  // FIXME: The logic for looking up nullary and unary selectors should be
  // shared with the code in ActOnInstanceMessage.

  Selector Sel = PP.getSelectorTable().getNullarySelector(Member);
  ObjCMethodDecl *Getter = IFace->lookupInstanceMethod(Sel);

  // If this reference is in an @implementation, check for 'private' methods.
  if (!Getter)
    Getter = IFace->lookupPrivateInstanceMethod(Sel);

  // Look through local category implementations associated with the class.
  if (!Getter)
    Getter = IFace->getCategoryInstanceMethod(Sel);
  if (Getter) {
    // Check if we can reference this property.
    if (DiagnoseUseOfDecl(Getter, MemberLoc))
      return ExprError();
  }
  // If we found a getter then this may be a valid dot-reference, we
  // will look for the matching setter, in case it is needed.
  Selector SetterSel =
    SelectorTable::constructSetterName(PP.getIdentifierTable(),
                                       PP.getSelectorTable(), Member);
  ObjCMethodDecl *Setter = IFace->lookupInstanceMethod(SetterSel);
  if (!Setter) {
    // If this reference is in an @implementation, also check for 'private'
    // methods.
    Setter = IFace->lookupPrivateInstanceMethod(SetterSel);
  }
  // Look through local category implementations associated with the class.
  if (!Setter)
    Setter = IFace->getCategoryInstanceMethod(SetterSel);

  if (Setter && DiagnoseUseOfDecl(Setter, MemberLoc))
    return ExprError();

  if (Getter) {
    QualType PType;
    PType = Getter->getResultType();
    return Owned(new (Context) ObjCImplicitSetterGetterRefExpr(Getter, PType,
                                    Setter, MemberLoc, BaseExpr));
  }

  // Attempt to correct for typos in property names.
  LookupResult Res(*this, MemberName, MemberLoc, LookupOrdinaryName);
  if (CorrectTypo(Res, 0, 0, IFace, false, CTC_NoKeywords, OPT) &&
      Res.getAsSingle<ObjCPropertyDecl>()) {
    DeclarationName TypoResult = Res.getLookupName();
    Diag(MemberLoc, diag::err_property_not_found_suggest)
      << MemberName << QualType(OPT, 0) << TypoResult
      << FixItHint::CreateReplacement(MemberLoc, TypoResult.getAsString());
    ObjCPropertyDecl *Property = Res.getAsSingle<ObjCPropertyDecl>();
    Diag(Property->getLocation(), diag::note_previous_decl)
      << Property->getDeclName();
    return HandleExprPropertyRefExpr(OPT, BaseExpr, TypoResult, MemberLoc);
  }
  
  Diag(MemberLoc, diag::err_property_not_found)
    << MemberName << QualType(OPT, 0);
  if (Setter && !Getter)
    Diag(Setter->getLocation(), diag::note_getter_unavailable)
      << MemberName << BaseExpr->getSourceRange();
  return ExprError();
}



Action::OwningExprResult Sema::
ActOnClassPropertyRefExpr(IdentifierInfo &receiverName,
                          IdentifierInfo &propertyName,
                          SourceLocation receiverNameLoc,
                          SourceLocation propertyNameLoc) {

  IdentifierInfo *receiverNamePtr = &receiverName;
  ObjCInterfaceDecl *IFace = getObjCInterfaceDecl(receiverNamePtr,
                                                  receiverNameLoc);
  if (IFace == 0) {
    // If the "receiver" is 'super' in a method, handle it as an expression-like
    // property reference.
    if (ObjCMethodDecl *CurMethod = getCurMethodDecl())
      if (receiverNamePtr->isStr("super")) {
        if (CurMethod->isInstanceMethod()) {
          QualType T = 
            Context.getObjCInterfaceType(CurMethod->getClassInterface());
          T = Context.getObjCObjectPointerType(T);
          Expr *SuperExpr = new (Context) ObjCSuperExpr(receiverNameLoc, T);
        
          return HandleExprPropertyRefExpr(T->getAsObjCInterfacePointerType(),
                                           SuperExpr, &propertyName,
                                           propertyNameLoc);
        }

        // Otherwise, if this is a class method, try dispatching to our
        // superclass.
        IFace = CurMethod->getClassInterface()->getSuperClass();
      }
    
    if (IFace == 0) {
      Diag(receiverNameLoc, diag::err_expected_ident_or_lparen);
      return ExprError();
    }
  }

  // Search for a declared property first.
  Selector Sel = PP.getSelectorTable().getNullarySelector(&propertyName);
  ObjCMethodDecl *Getter = IFace->lookupClassMethod(Sel);

  // If this reference is in an @implementation, check for 'private' methods.
  if (!Getter)
    if (ObjCMethodDecl *CurMeth = getCurMethodDecl())
      if (ObjCInterfaceDecl *ClassDecl = CurMeth->getClassInterface())
        if (ObjCImplementationDecl *ImpDecl = ClassDecl->getImplementation())
          Getter = ImpDecl->getClassMethod(Sel);

  if (Getter) {
    // FIXME: refactor/share with ActOnMemberReference().
    // Check if we can reference this property.
    if (DiagnoseUseOfDecl(Getter, propertyNameLoc))
      return ExprError();
  }

  // Look for the matching setter, in case it is needed.
  Selector SetterSel =
    SelectorTable::constructSetterName(PP.getIdentifierTable(),
                                       PP.getSelectorTable(), &propertyName);

  ObjCMethodDecl *Setter = IFace->lookupClassMethod(SetterSel);
  if (!Setter) {
    // If this reference is in an @implementation, also check for 'private'
    // methods.
    if (ObjCMethodDecl *CurMeth = getCurMethodDecl())
      if (ObjCInterfaceDecl *ClassDecl = CurMeth->getClassInterface())
        if (ObjCImplementationDecl *ImpDecl = ClassDecl->getImplementation())
          Setter = ImpDecl->getClassMethod(SetterSel);
  }
  // Look through local category implementations associated with the class.
  if (!Setter)
    Setter = IFace->getCategoryClassMethod(SetterSel);

  if (Setter && DiagnoseUseOfDecl(Setter, propertyNameLoc))
    return ExprError();

  if (Getter || Setter) {
    QualType PType;

    if (Getter)
      PType = Getter->getResultType();
    else {
      for (ObjCMethodDecl::param_iterator PI = Setter->param_begin(),
           E = Setter->param_end(); PI != E; ++PI)
        PType = (*PI)->getType();
    }
    return Owned(new (Context) ObjCImplicitSetterGetterRefExpr(
                                  Getter, PType, Setter,
                                  propertyNameLoc, IFace, receiverNameLoc));
  }
  return ExprError(Diag(propertyNameLoc, diag::err_property_not_found)
                     << &propertyName << Context.getObjCInterfaceType(IFace));
}

Sema::ObjCMessageKind Sema::getObjCMessageKind(Scope *S,
                                               IdentifierInfo *&Name,
                                               SourceLocation NameLoc,
                                               bool IsSuper,
                                               bool HasTrailingDot) {
  // If the identifier is "super" and there is no trailing dot, we're
  // messaging super.
  if (IsSuper && !HasTrailingDot && S->isInObjcMethodScope())
    return ObjCSuperMessage;
  
  LookupResult Result(*this, Name, NameLoc, LookupOrdinaryName);
  LookupName(Result, S);
  
  switch (Result.getResultKind()) {
  case LookupResult::NotFound:
    // Normal name lookup didn't find anything. If we're in an
    // Objective-C method, look for ivars. If we find one, we're done!
    // FIXME: This is a hack. Ivar lookup should be part of normal lookup.
    if (ObjCMethodDecl *Method = getCurMethodDecl()) {
      ObjCInterfaceDecl *ClassDeclared;
      if (Method->getClassInterface()->lookupInstanceVariable(Name, 
                                                              ClassDeclared))
        return ObjCInstanceMessage;
    }
      
    // Break out; we'll perform typo correction below.
    break;

  case LookupResult::NotFoundInCurrentInstantiation:
  case LookupResult::FoundOverloaded:
  case LookupResult::FoundUnresolvedValue:
  case LookupResult::Ambiguous:
    Result.suppressDiagnostics();
    return ObjCInstanceMessage;

  case LookupResult::Found: {
    // We found something. If it's a type, then we have a class
    // message. Otherwise, it's an instance message.
    NamedDecl *ND = Result.getFoundDecl();
    if (isa<ObjCInterfaceDecl>(ND) || isa<TypeDecl>(ND) || 
        isa<UnresolvedUsingTypenameDecl>(ND))
      return ObjCClassMessage;

    return ObjCInstanceMessage;
  }
  }

  // Determine our typo-correction context.
  CorrectTypoContext CTC = CTC_Expression;
  if (ObjCMethodDecl *Method = getCurMethodDecl())
    if (Method->getClassInterface() &&
        Method->getClassInterface()->getSuperClass())
      CTC = CTC_ObjCMessageReceiver;
      
  if (DeclarationName Corrected = CorrectTypo(Result, S, 0, 0, false, CTC)) {
    if (Result.isSingleResult()) {
      // If we found a declaration, correct when it refers to an Objective-C
      // class.
      NamedDecl *ND = Result.getFoundDecl();
      if (isa<ObjCInterfaceDecl>(ND)) {
        Diag(NameLoc, diag::err_unknown_receiver_suggest)
          << Name << Result.getLookupName()
          << FixItHint::CreateReplacement(SourceRange(NameLoc),
                                          ND->getNameAsString());
        Diag(ND->getLocation(), diag::note_previous_decl)
          << Corrected;

        Name = ND->getIdentifier();
        return ObjCClassMessage;
      }
    } else if (Result.empty() && Corrected.getAsIdentifierInfo() &&
               Corrected.getAsIdentifierInfo()->isStr("super")) {
      // If we've found the keyword "super", this is a send to super.
      Diag(NameLoc, diag::err_unknown_receiver_suggest)
        << Name << Corrected
        << FixItHint::CreateReplacement(SourceRange(NameLoc), "super");
      Name = Corrected.getAsIdentifierInfo();
      return ObjCSuperMessage;
    }
  }
  
  // Fall back: let the parser try to parse it as an instance message.
  return ObjCInstanceMessage;
}

// ActOnClassMessage - used for both unary and keyword messages.
// ArgExprs is optional - if it is present, the number of expressions
// is obtained from Sel.getNumArgs().
Sema::ExprResult Sema::
ActOnClassMessage(Scope *S, IdentifierInfo *receiverName, Selector Sel,
                  SourceLocation lbrac, SourceLocation receiverLoc,
                  SourceLocation selectorLoc, SourceLocation rbrac,
                  ExprTy **Args, unsigned NumArgs) {
  assert(receiverName && "missing receiver class name");

  Expr **ArgExprs = reinterpret_cast<Expr **>(Args);
  ObjCInterfaceDecl *ClassDecl = 0;
  bool isSuper = false;

  // Special case a message to super, which can be either a class message or an
  // instance message, depending on what CurMethodDecl is.
  if (receiverName->isStr("super")) {
    if (ObjCMethodDecl *CurMethod = getCurMethodDecl()) {
      ObjCInterfaceDecl *OID = CurMethod->getClassInterface();
      if (!OID)
        return Diag(lbrac, diag::error_no_super_class_message)
                      << CurMethod->getDeclName();
      ClassDecl = OID->getSuperClass();
      if (ClassDecl == 0)
        return Diag(lbrac, diag::error_no_super_class) << OID->getDeclName();
      if (CurMethod->isInstanceMethod()) {
        QualType superTy = Context.getObjCInterfaceType(ClassDecl);
        superTy = Context.getObjCObjectPointerType(superTy);
        ExprResult ReceiverExpr = new (Context) ObjCSuperExpr(SourceLocation(),
                                                              superTy);
        // We are really in an instance method, redirect.
        return ActOnInstanceMessage(ReceiverExpr.get(), Sel, lbrac,
                                    selectorLoc, rbrac, Args, NumArgs);
      }
      
      // Otherwise, if this is a class method, try dispatching to our
      // superclass, which is in ClassDecl.
      isSuper = true;
    }
  }
  
  if (ClassDecl == 0)
    ClassDecl = getObjCInterfaceDecl(receiverName, receiverLoc, true);

  // The following code allows for the following GCC-ism:
  //
  //  typedef XCElementDisplayRect XCElementGraphicsRect;
  //
  //  @implementation XCRASlice
  //  - whatever { // Note that XCElementGraphicsRect is a typedef name.
  //    _sGraphicsDelegate =[[XCElementGraphicsRect alloc] init];
  //  }
  //
  // If necessary, the following lookup could move to getObjCInterfaceDecl().
  if (!ClassDecl) {
    NamedDecl *IDecl
      = LookupSingleName(TUScope, receiverName, receiverLoc, 
                         LookupOrdinaryName);
    if (TypedefDecl *OCTD = dyn_cast_or_null<TypedefDecl>(IDecl))
      if (const ObjCInterfaceType *OCIT
                      = OCTD->getUnderlyingType()->getAs<ObjCInterfaceType>())
        ClassDecl = OCIT->getDecl();

    if (!ClassDecl) {
      // Give a better error message for invalid use of super.
      if (receiverName->isStr("super"))
        Diag(receiverLoc, diag::err_invalid_receiver_to_message_super);
      else
        Diag(receiverLoc, diag::err_invalid_receiver_to_message);
      return true;
    }
  }
  assert(ClassDecl && "missing interface declaration");
  ObjCMethodDecl *Method = 0;
  QualType returnType;
  if (ClassDecl->isForwardDecl()) {
    // A forward class used in messaging is tread as a 'Class'
    Diag(lbrac, diag::warn_receiver_forward_class) << ClassDecl->getDeclName();
    Method = LookupFactoryMethodInGlobalPool(Sel, SourceRange(lbrac,rbrac));
    if (Method)
      Diag(Method->getLocation(), diag::note_method_sent_forward_class)
        << Method->getDeclName();
  }
  if (!Method)
    Method = ClassDecl->lookupClassMethod(Sel);

  // If we have an implementation in scope, check "private" methods.
  if (!Method)
    Method = LookupPrivateClassMethod(Sel, ClassDecl);

  if (Method && DiagnoseUseOfDecl(Method, receiverLoc))
    return true;

  if (CheckMessageArgumentTypes(ArgExprs, NumArgs, Sel, Method, true,
                                lbrac, rbrac, returnType))
    return true;

  returnType = returnType.getNonReferenceType();

  // FIXME: need to do a better job handling 'super' usage within a class.  For
  // now, we simply pass the "super" identifier through (which isn't consistent
  // with instance methods.
  if (isSuper)
    return new (Context) ObjCMessageExpr(Context, receiverName, receiverLoc,
                                         Sel, returnType, Method, lbrac, rbrac,
                                         ArgExprs, NumArgs);
  
  // If we have the ObjCInterfaceDecl* for the class that is receiving the
  // message, use that to construct the ObjCMessageExpr.  Otherwise pass on the
  // IdentifierInfo* for the class.
  return new (Context) ObjCMessageExpr(Context, ClassDecl, receiverLoc,
                                       Sel, returnType, Method, lbrac, rbrac, 
                                       ArgExprs, NumArgs);
}

// ActOnInstanceMessage - used for both unary and keyword messages.
// ArgExprs is optional - if it is present, the number of expressions
// is obtained from Sel.getNumArgs().
Sema::ExprResult Sema::ActOnInstanceMessage(ExprTy *receiver, Selector Sel,
                                            SourceLocation lbrac,
                                            SourceLocation receiverLoc,
                                            SourceLocation rbrac,
                                            ExprTy **Args, unsigned NumArgs) {
  assert(receiver && "missing receiver expression");

  Expr **ArgExprs = reinterpret_cast<Expr **>(Args);
  Expr *RExpr = static_cast<Expr *>(receiver);

  // If necessary, apply function/array conversion to the receiver.
  // C99 6.7.5.3p[7,8].
  DefaultFunctionArrayLvalueConversion(RExpr);

  QualType returnType;
  QualType ReceiverCType =
    Context.getCanonicalType(RExpr->getType()).getUnqualifiedType();

  // Handle messages to id.
  if (ReceiverCType->isObjCIdType() || ReceiverCType->isBlockPointerType() ||
      Context.isObjCNSObjectType(RExpr->getType())) {
    ObjCMethodDecl *Method = LookupInstanceMethodInGlobalPool(
                               Sel, SourceRange(lbrac,rbrac));
    if (!Method)
      Method = LookupFactoryMethodInGlobalPool(Sel, SourceRange(lbrac, rbrac));
    if (CheckMessageArgumentTypes(ArgExprs, NumArgs, Sel, Method, false,
                                  lbrac, rbrac, returnType))
      return true;
    returnType = returnType.getNonReferenceType();
    return new (Context) ObjCMessageExpr(Context, RExpr, Sel, returnType,
                                         Method, lbrac, rbrac,
                                         ArgExprs, NumArgs);
  }

  // Handle messages to Class.
  if (ReceiverCType->isObjCClassType() ||
      ReceiverCType->isObjCQualifiedClassType()) {
    ObjCMethodDecl *Method = 0;

    if (ObjCMethodDecl *CurMeth = getCurMethodDecl()) {
      if (ObjCInterfaceDecl *ClassDecl = CurMeth->getClassInterface()) {
        // First check the public methods in the class interface.
        Method = ClassDecl->lookupClassMethod(Sel);

        if (!Method)
          Method = LookupPrivateClassMethod(Sel, ClassDecl);

        // FIXME: if we still haven't found a method, we need to look in
        // protocols (if we have qualifiers).
      }
      if (Method && DiagnoseUseOfDecl(Method, receiverLoc))
        return true;
    }
    if (!Method) {
      // If not messaging 'self', look for any factory method named 'Sel'.
      if (!isSelfExpr(RExpr)) {
        Method = LookupFactoryMethodInGlobalPool(Sel, SourceRange(lbrac,rbrac));
        if (!Method) {
          // If no class (factory) method was found, check if an _instance_
          // method of the same name exists in the root class only.
          Method = LookupInstanceMethodInGlobalPool(
                                   Sel, SourceRange(lbrac,rbrac));
          if (Method)
              if (const ObjCInterfaceDecl *ID =
                dyn_cast<ObjCInterfaceDecl>(Method->getDeclContext())) {
              if (ID->getSuperClass())
                Diag(lbrac, diag::warn_root_inst_method_not_found)
                  << Sel << SourceRange(lbrac, rbrac);
            }
        }
      }
    }
    if (CheckMessageArgumentTypes(ArgExprs, NumArgs, Sel, Method, false,
                                  lbrac, rbrac, returnType))
      return true;
    returnType = returnType.getNonReferenceType();
    return new (Context) ObjCMessageExpr(Context, RExpr, Sel, returnType,
                                         Method, lbrac, rbrac,
                                         ArgExprs, NumArgs);
  }

  ObjCMethodDecl *Method = 0;
  ObjCInterfaceDecl* ClassDecl = 0;

  // We allow sending a message to a qualified ID ("id<foo>"), which is ok as
  // long as one of the protocols implements the selector (if not, warn).
  if (const ObjCObjectPointerType *QIdTy =
        ReceiverCType->getAsObjCQualifiedIdType()) {
    // Search protocols for instance methods.
    for (ObjCObjectPointerType::qual_iterator I = QIdTy->qual_begin(),
         E = QIdTy->qual_end(); I != E; ++I) {
      ObjCProtocolDecl *PDecl = *I;
      if (PDecl && (Method = PDecl->lookupInstanceMethod(Sel)))
        break;
      // Since we aren't supporting "Class<foo>", look for a class method.
      if (PDecl && (Method = PDecl->lookupClassMethod(Sel)))
        break;
    }
  } else if (const ObjCObjectPointerType *OCIType =
                ReceiverCType->getAsObjCInterfacePointerType()) {
    // We allow sending a message to a pointer to an interface (an object).

    ClassDecl = OCIType->getInterfaceDecl();
    // FIXME: consider using LookupInstanceMethodInGlobalPool, since it will be
    // faster than the following method (which can do *many* linear searches).
    // The idea is to add class info to InstanceMethodPool.
    Method = ClassDecl->lookupInstanceMethod(Sel);

    if (!Method) {
      // Search protocol qualifiers.
      for (ObjCObjectPointerType::qual_iterator QI = OCIType->qual_begin(),
           E = OCIType->qual_end(); QI != E; ++QI) {
        if ((Method = (*QI)->lookupInstanceMethod(Sel)))
          break;
      }
    }
    if (!Method) {
      // If we have implementations in scope, check "private" methods.
      Method = LookupPrivateInstanceMethod(Sel, ClassDecl);

      if (!Method && !isSelfExpr(RExpr)) {
        // If we still haven't found a method, look in the global pool. This
        // behavior isn't very desirable, however we need it for GCC
        // compatibility. FIXME: should we deviate??
        if (OCIType->qual_empty()) {
          Method = LookupInstanceMethodInGlobalPool(
                               Sel, SourceRange(lbrac,rbrac));
          if (Method && !OCIType->getInterfaceDecl()->isForwardDecl())
            Diag(lbrac, diag::warn_maynot_respond)
              << OCIType->getInterfaceDecl()->getIdentifier() << Sel;
        }
      }
    }
    if (Method && DiagnoseUseOfDecl(Method, receiverLoc))
      return true;
  } else if (!Context.getObjCIdType().isNull() &&
             (ReceiverCType->isPointerType() ||
              (ReceiverCType->isIntegerType() &&
               ReceiverCType->isScalarType()))) {
    // Implicitly convert integers and pointers to 'id' but emit a warning.
    Diag(lbrac, diag::warn_bad_receiver_type)
      << RExpr->getType() << RExpr->getSourceRange();
    if (ReceiverCType->isPointerType())
      ImpCastExprToType(RExpr, Context.getObjCIdType(), CastExpr::CK_BitCast);
    else
      ImpCastExprToType(RExpr, Context.getObjCIdType(),
                        CastExpr::CK_IntegralToPointer);
  } else {
    // Reject other random receiver types (e.g. structs).
    Diag(lbrac, diag::err_bad_receiver_type)
      << RExpr->getType() << RExpr->getSourceRange();
    return true;
  }

  if (Method)
    DiagnoseSentinelCalls(Method, receiverLoc, ArgExprs, NumArgs);
  if (CheckMessageArgumentTypes(ArgExprs, NumArgs, Sel, Method, false,
                                lbrac, rbrac, returnType))
    return true;
  returnType = returnType.getNonReferenceType();
  return new (Context) ObjCMessageExpr(Context, RExpr, Sel, returnType, Method,
                                       lbrac, rbrac, ArgExprs, NumArgs);
}