Expr.cpp

//===--- Expr.cpp - Expression AST Node Implementation --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Expr class and subclasses.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/Expr.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/TargetInfo.h"
#include <algorithm>
using namespace clang;

//===----------------------------------------------------------------------===//
// Primary Expressions.
//===----------------------------------------------------------------------===//

PredefinedExpr* PredefinedExpr::Clone(ASTContext &C) const {
  return new (C) PredefinedExpr(Loc, getType(), Type);
}

IntegerLiteral* IntegerLiteral::Clone(ASTContext &C) const {
  return new (C) IntegerLiteral(Value, getType(), Loc);
}

CharacterLiteral* CharacterLiteral::Clone(ASTContext &C) const {
  return new (C) CharacterLiteral(Value, IsWide, getType(), Loc);
}

FloatingLiteral* FloatingLiteral::Clone(ASTContext &C) const {
  bool exact = IsExact;
  return new (C) FloatingLiteral(Value, &exact, getType(), Loc);
}

ImaginaryLiteral* ImaginaryLiteral::Clone(ASTContext &C) const {
  // FIXME: Use virtual Clone(), once it is available
  Expr *ClonedVal = 0;
  if (const IntegerLiteral *IntLit = dyn_cast<IntegerLiteral>(Val))
    ClonedVal = IntLit->Clone(C);
  else
    ClonedVal = cast<FloatingLiteral>(Val)->Clone(C);
  return new (C) ImaginaryLiteral(ClonedVal, getType());
}

GNUNullExpr* GNUNullExpr::Clone(ASTContext &C) const {
  return new (C) GNUNullExpr(getType(), TokenLoc);
}

/// getValueAsApproximateDouble - This returns the value as an inaccurate
/// double.  Note that this may cause loss of precision, but is useful for
/// debugging dumps, etc.
double FloatingLiteral::getValueAsApproximateDouble() const {
  llvm::APFloat V = getValue();
  bool ignored;
  V.convert(llvm::APFloat::IEEEdouble, llvm::APFloat::rmNearestTiesToEven,
            &ignored);
  return V.convertToDouble();
}

StringLiteral *StringLiteral::Create(ASTContext &C, const char *StrData,
                                     unsigned ByteLength, bool Wide,
                                     QualType Ty,
                                     const SourceLocation *Loc, 
                                     unsigned NumStrs) {
  // Allocate enough space for the StringLiteral plus an array of locations for
  // any concatenated string tokens.
  void *Mem = C.Allocate(sizeof(StringLiteral)+
                         sizeof(SourceLocation)*(NumStrs-1),
                         llvm::alignof<StringLiteral>());
  StringLiteral *SL = new (Mem) StringLiteral(Ty);
  
  // OPTIMIZE: could allocate this appended to the StringLiteral.
  char *AStrData = new (C, 1) char[ByteLength];
  memcpy(AStrData, StrData, ByteLength);
  SL->StrData = AStrData;
  SL->ByteLength = ByteLength;
  SL->IsWide = Wide;
  SL->TokLocs[0] = Loc[0];
  SL->NumConcatenated = NumStrs;

  if (NumStrs != 1)
    memcpy(&SL->TokLocs[1], Loc+1, sizeof(SourceLocation)*(NumStrs-1));
  return SL;
}

StringLiteral *StringLiteral::CreateEmpty(ASTContext &C, unsigned NumStrs) {
  void *Mem = C.Allocate(sizeof(StringLiteral)+
                         sizeof(SourceLocation)*(NumStrs-1),
                         llvm::alignof<StringLiteral>());
  StringLiteral *SL = new (Mem) StringLiteral(QualType());
  SL->StrData = 0;
  SL->ByteLength = 0;
  SL->NumConcatenated = NumStrs;
  return SL;
}

StringLiteral* StringLiteral::Clone(ASTContext &C) const {
  return Create(C, StrData, ByteLength, IsWide, getType(),
                TokLocs, NumConcatenated);
}

void StringLiteral::Destroy(ASTContext &C) {
  C.Deallocate(const_cast<char*>(StrData));
  this->~StringLiteral();
  C.Deallocate(this);
}

void StringLiteral::setStrData(ASTContext &C, const char *Str, unsigned Len) {
  if (StrData)
    C.Deallocate(const_cast<char*>(StrData));

  char *AStrData = new (C, 1) char[Len];
  memcpy(AStrData, Str, Len);
  StrData = AStrData;
  ByteLength = Len;
}

/// getOpcodeStr - Turn an Opcode enum value into the punctuation char it
/// corresponds to, e.g. "sizeof" or "[pre]++".
const char *UnaryOperator::getOpcodeStr(Opcode Op) {
  switch (Op) {
  default: assert(0 && "Unknown unary operator");
  case PostInc: return "++";
  case PostDec: return "--";
  case PreInc:  return "++";
  case PreDec:  return "--";
  case AddrOf:  return "&";
  case Deref:   return "*";
  case Plus:    return "+";
  case Minus:   return "-";
  case Not:     return "~";
  case LNot:    return "!";
  case Real:    return "__real";
  case Imag:    return "__imag";
  case Extension: return "__extension__";
  case OffsetOf: return "__builtin_offsetof";
  }
}

UnaryOperator::Opcode 
UnaryOperator::getOverloadedOpcode(OverloadedOperatorKind OO, bool Postfix) {
  switch (OO) {
  default: assert(false && "No unary operator for overloaded function");
  case OO_PlusPlus:   return Postfix ? PostInc : PreInc;
  case OO_MinusMinus: return Postfix ? PostDec : PreDec;
  case OO_Amp:        return AddrOf;
  case OO_Star:       return Deref;
  case OO_Plus:       return Plus;
  case OO_Minus:      return Minus;
  case OO_Tilde:      return Not;
  case OO_Exclaim:    return LNot;
  }
}

OverloadedOperatorKind UnaryOperator::getOverloadedOperator(Opcode Opc) {
  switch (Opc) {
  case PostInc: case PreInc: return OO_PlusPlus;
  case PostDec: case PreDec: return OO_MinusMinus;
  case AddrOf: return OO_Amp;
  case Deref: return OO_Star;
  case Plus: return OO_Plus;
  case Minus: return OO_Minus;
  case Not: return OO_Tilde;
  case LNot: return OO_Exclaim;
  default: return OO_None;
  }
}


//===----------------------------------------------------------------------===//
// Postfix Operators.
//===----------------------------------------------------------------------===//

CallExpr::CallExpr(ASTContext& C, StmtClass SC, Expr *fn, Expr **args,
                   unsigned numargs, QualType t, SourceLocation rparenloc)
  : Expr(SC, t, 
         fn->isTypeDependent() || hasAnyTypeDependentArguments(args, numargs),
         fn->isValueDependent() || hasAnyValueDependentArguments(args,numargs)),
    NumArgs(numargs) {
      
  SubExprs = new (C) Stmt*[numargs+1];
  SubExprs[FN] = fn;
  for (unsigned i = 0; i != numargs; ++i)
    SubExprs[i+ARGS_START] = args[i];

  RParenLoc = rparenloc;
}

CallExpr::CallExpr(ASTContext& C, Expr *fn, Expr **args, unsigned numargs,
                   QualType t, SourceLocation rparenloc)
  : Expr(CallExprClass, t,
         fn->isTypeDependent() || hasAnyTypeDependentArguments(args, numargs),
         fn->isValueDependent() || hasAnyValueDependentArguments(args,numargs)),
    NumArgs(numargs) {

  SubExprs = new (C) Stmt*[numargs+1];
  SubExprs[FN] = fn;
  for (unsigned i = 0; i != numargs; ++i)
    SubExprs[i+ARGS_START] = args[i];

  RParenLoc = rparenloc;
}

CallExpr::CallExpr(ASTContext &C, EmptyShell Empty) 
  : Expr(CallExprClass, Empty), SubExprs(0), NumArgs(0) { 
  SubExprs = new (C) Stmt*[1];
}

void CallExpr::Destroy(ASTContext& C) {
  DestroyChildren(C);
  if (SubExprs) C.Deallocate(SubExprs);
  this->~CallExpr();
  C.Deallocate(this);
}

/// setNumArgs - This changes the number of arguments present in this call.
/// Any orphaned expressions are deleted by this, and any new operands are set
/// to null.
void CallExpr::setNumArgs(ASTContext& C, unsigned NumArgs) {
  // No change, just return.
  if (NumArgs == getNumArgs()) return;
  
  // If shrinking # arguments, just delete the extras and forgot them.
  if (NumArgs < getNumArgs()) {
    for (unsigned i = NumArgs, e = getNumArgs(); i != e; ++i)
      getArg(i)->Destroy(C);
    this->NumArgs = NumArgs;
    return;
  }

  // Otherwise, we are growing the # arguments.  New an bigger argument array.
  Stmt **NewSubExprs = new Stmt*[NumArgs+1];
  // Copy over args.
  for (unsigned i = 0; i != getNumArgs()+ARGS_START; ++i)
    NewSubExprs[i] = SubExprs[i];
  // Null out new args.
  for (unsigned i = getNumArgs()+ARGS_START; i != NumArgs+ARGS_START; ++i)
    NewSubExprs[i] = 0;
  
  if (SubExprs) C.Deallocate(SubExprs);
  SubExprs = NewSubExprs;
  this->NumArgs = NumArgs;
}

/// isBuiltinCall - If this is a call to a builtin, return the builtin ID.  If
/// not, return 0.
unsigned CallExpr::isBuiltinCall(ASTContext &Context) const {
  // All simple function calls (e.g. func()) are implicitly cast to pointer to
  // function. As a result, we try and obtain the DeclRefExpr from the 
  // ImplicitCastExpr.
  const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(getCallee());
  if (!ICE) // FIXME: deal with more complex calls (e.g. (func)(), (*func)()).
    return 0;
  
  const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(ICE->getSubExpr());
  if (!DRE)
    return 0;
  
  const FunctionDecl *FDecl = dyn_cast<FunctionDecl>(DRE->getDecl());
  if (!FDecl)
    return 0;
  
  if (!FDecl->getIdentifier())
    return 0;

  return FDecl->getBuiltinID(Context);
}

QualType CallExpr::getCallReturnType() const {
  QualType CalleeType = getCallee()->getType();
  if (const PointerType *FnTypePtr = CalleeType->getAsPointerType())
    CalleeType = FnTypePtr->getPointeeType();
  else if (const BlockPointerType *BPT = CalleeType->getAsBlockPointerType())
    CalleeType = BPT->getPointeeType();
  
  const FunctionType *FnType = CalleeType->getAsFunctionType();
  return FnType->getResultType();
}

/// getOpcodeStr - Turn an Opcode enum value into the punctuation char it
/// corresponds to, e.g. "<<=".
const char *BinaryOperator::getOpcodeStr(Opcode Op) {
  switch (Op) {
  case PtrMemD:   return ".*";
  case PtrMemI:   return "->*";
  case Mul:       return "*";
  case Div:       return "/";
  case Rem:       return "%";
  case Add:       return "+";
  case Sub:       return "-";
  case Shl:       return "<<";
  case Shr:       return ">>";
  case LT:        return "<";
  case GT:        return ">";
  case LE:        return "<=";
  case GE:        return ">=";
  case EQ:        return "==";
  case NE:        return "!=";
  case And:       return "&";
  case Xor:       return "^";
  case Or:        return "|";
  case LAnd:      return "&&";
  case LOr:       return "||";
  case Assign:    return "=";
  case MulAssign: return "*=";
  case DivAssign: return "/=";
  case RemAssign: return "%=";
  case AddAssign: return "+=";
  case SubAssign: return "-=";
  case ShlAssign: return "<<=";
  case ShrAssign: return ">>=";
  case AndAssign: return "&=";
  case XorAssign: return "^=";
  case OrAssign:  return "|=";
  case Comma:     return ",";
  }

  return "";
}

BinaryOperator::Opcode 
BinaryOperator::getOverloadedOpcode(OverloadedOperatorKind OO) {
  switch (OO) {
  default: assert(false && "Not an overloadable binary operator");
  case OO_Plus: return Add;
  case OO_Minus: return Sub;
  case OO_Star: return Mul;
  case OO_Slash: return Div;
  case OO_Percent: return Rem;
  case OO_Caret: return Xor;
  case OO_Amp: return And;
  case OO_Pipe: return Or;
  case OO_Equal: return Assign;
  case OO_Less: return LT;
  case OO_Greater: return GT;
  case OO_PlusEqual: return AddAssign;
  case OO_MinusEqual: return SubAssign;
  case OO_StarEqual: return MulAssign;
  case OO_SlashEqual: return DivAssign;
  case OO_PercentEqual: return RemAssign;
  case OO_CaretEqual: return XorAssign;
  case OO_AmpEqual: return AndAssign;
  case OO_PipeEqual: return OrAssign;
  case OO_LessLess: return Shl;
  case OO_GreaterGreater: return Shr;
  case OO_LessLessEqual: return ShlAssign;
  case OO_GreaterGreaterEqual: return ShrAssign;
  case OO_EqualEqual: return EQ;
  case OO_ExclaimEqual: return NE;
  case OO_LessEqual: return LE;
  case OO_GreaterEqual: return GE;
  case OO_AmpAmp: return LAnd;
  case OO_PipePipe: return LOr;
  case OO_Comma: return Comma;
  case OO_ArrowStar: return PtrMemI;
  }
}

OverloadedOperatorKind BinaryOperator::getOverloadedOperator(Opcode Opc) {
  static const OverloadedOperatorKind OverOps[] = {
    /* .* Cannot be overloaded */OO_None, OO_ArrowStar,
    OO_Star, OO_Slash, OO_Percent,
    OO_Plus, OO_Minus,
    OO_LessLess, OO_GreaterGreater,
    OO_Less, OO_Greater, OO_LessEqual, OO_GreaterEqual,
    OO_EqualEqual, OO_ExclaimEqual,
    OO_Amp,
    OO_Caret,
    OO_Pipe,
    OO_AmpAmp,
    OO_PipePipe,
    OO_Equal, OO_StarEqual,
    OO_SlashEqual, OO_PercentEqual,
    OO_PlusEqual, OO_MinusEqual,
    OO_LessLessEqual, OO_GreaterGreaterEqual,
    OO_AmpEqual, OO_CaretEqual,
    OO_PipeEqual,
    OO_Comma
  };
  return OverOps[Opc];
}

InitListExpr::InitListExpr(SourceLocation lbraceloc, 
                           Expr **initExprs, unsigned numInits,
                           SourceLocation rbraceloc)
  : Expr(InitListExprClass, QualType(),
         hasAnyTypeDependentArguments(initExprs, numInits),
         hasAnyValueDependentArguments(initExprs, numInits)),
    LBraceLoc(lbraceloc), RBraceLoc(rbraceloc), SyntacticForm(0), 
    UnionFieldInit(0), HadArrayRangeDesignator(false) {

  InitExprs.insert(InitExprs.end(), initExprs, initExprs+numInits);
}

void InitListExpr::reserveInits(unsigned NumInits) {
  if (NumInits > InitExprs.size())
    InitExprs.reserve(NumInits);
}

void InitListExpr::resizeInits(ASTContext &Context, unsigned NumInits) {
  for (unsigned Idx = NumInits, LastIdx = InitExprs.size();
       Idx < LastIdx; ++Idx)
    InitExprs[Idx]->Destroy(Context);
  InitExprs.resize(NumInits, 0);
}

Expr *InitListExpr::updateInit(unsigned Init, Expr *expr) {
  if (Init >= InitExprs.size()) {
    InitExprs.insert(InitExprs.end(), Init - InitExprs.size() + 1, 0);
    InitExprs.back() = expr;
    return 0;
  }
  
  Expr *Result = cast_or_null<Expr>(InitExprs[Init]);
  InitExprs[Init] = expr;
  return Result;
}

/// getFunctionType - Return the underlying function type for this block.
///
const FunctionType *BlockExpr::getFunctionType() const {
  return getType()->getAsBlockPointerType()->
                    getPointeeType()->getAsFunctionType();
}

SourceLocation BlockExpr::getCaretLocation() const { 
  return TheBlock->getCaretLocation(); 
}
const Stmt *BlockExpr::getBody() const { 
  return TheBlock->getBody();
}
Stmt *BlockExpr::getBody() { 
  return TheBlock->getBody(); 
}


//===----------------------------------------------------------------------===//
// Generic Expression Routines
//===----------------------------------------------------------------------===//

/// isUnusedResultAWarning - Return true if this immediate expression should
/// be warned about if the result is unused.  If so, fill in Loc and Ranges
/// with location to warn on and the source range[s] to report with the
/// warning.
bool Expr::isUnusedResultAWarning(SourceLocation &Loc, SourceRange &R1,
                                  SourceRange &R2) const {
  // Don't warn if the expr is type dependent. The type could end up
  // instantiating to void.
  if (isTypeDependent())
    return false;
  
  switch (getStmtClass()) {
  default:
    Loc = getExprLoc();
    R1 = getSourceRange();
    return true;
  case ParenExprClass:
    return cast<ParenExpr>(this)->getSubExpr()->
      isUnusedResultAWarning(Loc, R1, R2);
  case UnaryOperatorClass: {
    const UnaryOperator *UO = cast<UnaryOperator>(this);
    
    switch (UO->getOpcode()) {
    default: break;
    case UnaryOperator::PostInc:
    case UnaryOperator::PostDec:
    case UnaryOperator::PreInc:
    case UnaryOperator::PreDec:                 // ++/--
      return false;  // Not a warning.
    case UnaryOperator::Deref:
      // Dereferencing a volatile pointer is a side-effect.
      if (getType().isVolatileQualified())
        return false;
      break;
    case UnaryOperator::Real:
    case UnaryOperator::Imag:
      // accessing a piece of a volatile complex is a side-effect.
      if (UO->getSubExpr()->getType().isVolatileQualified())
        return false;
      break;
    case UnaryOperator::Extension:
      return UO->getSubExpr()->isUnusedResultAWarning(Loc, R1, R2);
    }
    Loc = UO->getOperatorLoc();
    R1 = UO->getSubExpr()->getSourceRange();
    return true;
  }
  case BinaryOperatorClass: {
    const BinaryOperator *BO = cast<BinaryOperator>(this);
    // Consider comma to have side effects if the LHS or RHS does.
    if (BO->getOpcode() == BinaryOperator::Comma)
      return BO->getRHS()->isUnusedResultAWarning(Loc, R1, R2) ||
             BO->getLHS()->isUnusedResultAWarning(Loc, R1, R2);
      
    if (BO->isAssignmentOp())
      return false;
    Loc = BO->getOperatorLoc();
    R1 = BO->getLHS()->getSourceRange();
    R2 = BO->getRHS()->getSourceRange();
    return true;
  }
  case CompoundAssignOperatorClass:
    return false;

  case ConditionalOperatorClass: {
    // The condition must be evaluated, but if either the LHS or RHS is a
    // warning, warn about them.
    const ConditionalOperator *Exp = cast<ConditionalOperator>(this);
    if (Exp->getLHS() && Exp->getLHS()->isUnusedResultAWarning(Loc, R1, R2))
      return true;
    return Exp->getRHS()->isUnusedResultAWarning(Loc, R1, R2);
  }

  case MemberExprClass:
    // If the base pointer or element is to a volatile pointer/field, accessing
    // it is a side effect.
    if (getType().isVolatileQualified())
      return false;
    Loc = cast<MemberExpr>(this)->getMemberLoc();
    R1 = SourceRange(Loc, Loc);
    R2 = cast<MemberExpr>(this)->getBase()->getSourceRange();
    return true;
      
  case ArraySubscriptExprClass:
    // If the base pointer or element is to a volatile pointer/field, accessing
    // it is a side effect.
    if (getType().isVolatileQualified())
      return false;
    Loc = cast<ArraySubscriptExpr>(this)->getRBracketLoc();
    R1 = cast<ArraySubscriptExpr>(this)->getLHS()->getSourceRange();
    R2 = cast<ArraySubscriptExpr>(this)->getRHS()->getSourceRange();
    return true;

  case CallExprClass:
  case CXXOperatorCallExprClass:
  case CXXMemberCallExprClass: {
    // If this is a direct call, get the callee.
    const CallExpr *CE = cast<CallExpr>(this);
    const Expr *CalleeExpr = CE->getCallee()->IgnoreParenCasts();
    if (const DeclRefExpr *CalleeDRE = dyn_cast<DeclRefExpr>(CalleeExpr)) {
      // If the callee has attribute pure, const, or warn_unused_result, warn
      // about it. void foo() { strlen("bar"); } should warn.
      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CalleeDRE->getDecl()))
        if (FD->getAttr<WarnUnusedResultAttr>() ||
            FD->getAttr<PureAttr>() || FD->getAttr<ConstAttr>()) {
          Loc = CE->getCallee()->getLocStart();
          R1 = CE->getCallee()->getSourceRange();
          
          if (unsigned NumArgs = CE->getNumArgs())
            R2 = SourceRange(CE->getArg(0)->getLocStart(),
                             CE->getArg(NumArgs-1)->getLocEnd());
          return true;
        }
    }
    return false;
  }
  case ObjCMessageExprClass:
    return false;
  case StmtExprClass: {
    // Statement exprs don't logically have side effects themselves, but are
    // sometimes used in macros in ways that give them a type that is unused.
    // For example ({ blah; foo(); }) will end up with a type if foo has a type.
    // however, if the result of the stmt expr is dead, we don't want to emit a
    // warning.
    const CompoundStmt *CS = cast<StmtExpr>(this)->getSubStmt();
    if (!CS->body_empty())
      if (const Expr *E = dyn_cast<Expr>(CS->body_back()))
        return E->isUnusedResultAWarning(Loc, R1, R2);
    
    Loc = cast<StmtExpr>(this)->getLParenLoc();
    R1 = getSourceRange();
    return true;
  }
  case CStyleCastExprClass:
    // If this is a cast to void, check the operand.  Otherwise, the result of
    // the cast is unused.
    if (getType()->isVoidType())
      return cast<CastExpr>(this)->getSubExpr()->isUnusedResultAWarning(Loc,
                                                                        R1, R2);
    Loc = cast<CStyleCastExpr>(this)->getLParenLoc();
    R1 = cast<CStyleCastExpr>(this)->getSubExpr()->getSourceRange();
    return true;
  case CXXFunctionalCastExprClass:
    // If this is a cast to void, check the operand.  Otherwise, the result of
    // the cast is unused.
    if (getType()->isVoidType())
      return cast<CastExpr>(this)->getSubExpr()->isUnusedResultAWarning(Loc,
                                                                        R1, R2);
    Loc = cast<CXXFunctionalCastExpr>(this)->getTypeBeginLoc();
    R1 = cast<CXXFunctionalCastExpr>(this)->getSubExpr()->getSourceRange();
    return true;
      
  case ImplicitCastExprClass:
    // Check the operand, since implicit casts are inserted by Sema
    return cast<ImplicitCastExpr>(this)
      ->getSubExpr()->isUnusedResultAWarning(Loc, R1, R2);

  case CXXDefaultArgExprClass:
    return cast<CXXDefaultArgExpr>(this)
      ->getExpr()->isUnusedResultAWarning(Loc, R1, R2);

  case CXXNewExprClass:
    // FIXME: In theory, there might be new expressions that don't have side
    // effects (e.g. a placement new with an uninitialized POD).
  case CXXDeleteExprClass:
    return false;
  case CXXExprWithTemporariesClass:
    return cast<CXXExprWithTemporaries>(this)
      ->getSubExpr()->isUnusedResultAWarning(Loc, R1, R2);
  }
}

/// DeclCanBeLvalue - Determine whether the given declaration can be
/// an lvalue. This is a helper routine for isLvalue.
static bool DeclCanBeLvalue(const NamedDecl *Decl, ASTContext &Ctx) {
  // C++ [temp.param]p6:
  //   A non-type non-reference template-parameter is not an lvalue.
  if (const NonTypeTemplateParmDecl *NTTParm 
        = dyn_cast<NonTypeTemplateParmDecl>(Decl))
    return NTTParm->getType()->isReferenceType();

  return isa<VarDecl>(Decl) || isa<FieldDecl>(Decl) ||
    // C++ 3.10p2: An lvalue refers to an object or function.
    (Ctx.getLangOptions().CPlusPlus &&
     (isa<FunctionDecl>(Decl) || isa<OverloadedFunctionDecl>(Decl)));
}

/// isLvalue - C99 6.3.2.1: an lvalue is an expression with an object type or an
/// incomplete type other than void. Nonarray expressions that can be lvalues:
///  - name, where name must be a variable
///  - e[i]
///  - (e), where e must be an lvalue
///  - e.name, where e must be an lvalue
///  - e->name
///  - *e, the type of e cannot be a function type
///  - string-constant
///  - (__real__ e) and (__imag__ e) where e is an lvalue  [GNU extension]
///  - reference type [C++ [expr]]
///
Expr::isLvalueResult Expr::isLvalue(ASTContext &Ctx) const {
  assert(!TR->isReferenceType() && "Expressions can't have reference type.");

  isLvalueResult Res = isLvalueInternal(Ctx);
  if (Res != LV_Valid || Ctx.getLangOptions().CPlusPlus)
    return Res;

  // first, check the type (C99 6.3.2.1). Expressions with function
  // type in C are not lvalues, but they can be lvalues in C++.
  if (TR->isFunctionType())
    return LV_NotObjectType;

  // Allow qualified void which is an incomplete type other than void (yuck).
  if (TR->isVoidType() && !Ctx.getCanonicalType(TR).getCVRQualifiers())
    return LV_IncompleteVoidType;

  return LV_Valid;
}

// Check whether the expression can be sanely treated like an l-value
Expr::isLvalueResult Expr::isLvalueInternal(ASTContext &Ctx) const {
  switch (getStmtClass()) {
  case StringLiteralClass:  // C99 6.5.1p4
  case ObjCEncodeExprClass: // @encode behaves like its string in every way.
    return LV_Valid;
  case ArraySubscriptExprClass: // C99 6.5.3p4 (e1[e2] == (*((e1)+(e2))))
    // For vectors, make sure base is an lvalue (i.e. not a function call).
    if (cast<ArraySubscriptExpr>(this)->getBase()->getType()->isVectorType())
      return cast<ArraySubscriptExpr>(this)->getBase()->isLvalue(Ctx);
    return LV_Valid;
  case DeclRefExprClass: 
  case QualifiedDeclRefExprClass: { // C99 6.5.1p2
    const NamedDecl *RefdDecl = cast<DeclRefExpr>(this)->getDecl();
    if (DeclCanBeLvalue(RefdDecl, Ctx))
      return LV_Valid;
    break;
  }
  case BlockDeclRefExprClass: {
    const BlockDeclRefExpr *BDR = cast<BlockDeclRefExpr>(this);
    if (isa<VarDecl>(BDR->getDecl()))
      return LV_Valid;
    break;
  }
  case MemberExprClass: { 
    const MemberExpr *m = cast<MemberExpr>(this);
    if (Ctx.getLangOptions().CPlusPlus) { // C++ [expr.ref]p4:
      NamedDecl *Member = m->getMemberDecl();
      // C++ [expr.ref]p4:
      //   If E2 is declared to have type "reference to T", then E1.E2
      //   is an lvalue.
      if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
        if (Value->getType()->isReferenceType())
          return LV_Valid;

      //   -- If E2 is a static data member [...] then E1.E2 is an lvalue.
      if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
        return LV_Valid;

      //   -- If E2 is a non-static data member [...]. If E1 is an
      //      lvalue, then E1.E2 is an lvalue.
      if (isa<FieldDecl>(Member))
        return m->isArrow() ? LV_Valid : m->getBase()->isLvalue(Ctx);

      //   -- If it refers to a static member function [...], then
      //      E1.E2 is an lvalue.
      //   -- Otherwise, if E1.E2 refers to a non-static member
      //      function [...], then E1.E2 is not an lvalue.
      if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
        return Method->isStatic()? LV_Valid : LV_MemberFunction;

      //   -- If E2 is a member enumerator [...], the expression E1.E2
      //      is not an lvalue.
      if (isa<EnumConstantDecl>(Member))
        return LV_InvalidExpression;

        // Not an lvalue.
      return LV_InvalidExpression;
    } 

    // C99 6.5.2.3p4
    return m->isArrow() ? LV_Valid : m->getBase()->isLvalue(Ctx);
  }
  case UnaryOperatorClass:
    if (cast<UnaryOperator>(this)->getOpcode() == UnaryOperator::Deref)
      return LV_Valid; // C99 6.5.3p4

    if (cast<UnaryOperator>(this)->getOpcode() == UnaryOperator::Real ||
        cast<UnaryOperator>(this)->getOpcode() == UnaryOperator::Imag ||
        cast<UnaryOperator>(this)->getOpcode() == UnaryOperator::Extension)
      return cast<UnaryOperator>(this)->getSubExpr()->isLvalue(Ctx);  // GNU.

    if (Ctx.getLangOptions().CPlusPlus && // C++ [expr.pre.incr]p1
        (cast<UnaryOperator>(this)->getOpcode() == UnaryOperator::PreInc ||
         cast<UnaryOperator>(this)->getOpcode() == UnaryOperator::PreDec))
      return LV_Valid;
    break;
  case ImplicitCastExprClass:
    return cast<ImplicitCastExpr>(this)->isLvalueCast()? LV_Valid 
                                                       : LV_InvalidExpression;
  case ParenExprClass: // C99 6.5.1p5
    return cast<ParenExpr>(this)->getSubExpr()->isLvalue(Ctx);
  case BinaryOperatorClass:
  case CompoundAssignOperatorClass: {
    const BinaryOperator *BinOp = cast<BinaryOperator>(this);

    if (Ctx.getLangOptions().CPlusPlus && // C++ [expr.comma]p1
        BinOp->getOpcode() == BinaryOperator::Comma)
      return BinOp->getRHS()->isLvalue(Ctx);

    // C++ [expr.mptr.oper]p6
    if ((BinOp->getOpcode() == BinaryOperator::PtrMemD ||
         BinOp->getOpcode() == BinaryOperator::PtrMemI) &&
        !BinOp->getType()->isFunctionType())
      return BinOp->getLHS()->isLvalue(Ctx);

    if (!BinOp->isAssignmentOp())
      return LV_InvalidExpression;

    if (Ctx.getLangOptions().CPlusPlus)
      // C++ [expr.ass]p1: 
      //   The result of an assignment operation [...] is an lvalue.
      return LV_Valid;


    // C99 6.5.16:
    //   An assignment expression [...] is not an lvalue.
    return LV_InvalidExpression;
  }
  case CallExprClass: 
  case CXXOperatorCallExprClass:
  case CXXMemberCallExprClass: {
    // C++0x [expr.call]p10
    //   A function call is an lvalue if and only if the result type
    //   is an lvalue reference.
    QualType ReturnType = cast<CallExpr>(this)->getCallReturnType();
    if (ReturnType->isLValueReferenceType())
      return LV_Valid;

    break;
  }
  case CompoundLiteralExprClass: // C99 6.5.2.5p5
    return LV_Valid;
  case ChooseExprClass:
    // __builtin_choose_expr is an lvalue if the selected operand is.
    return cast<ChooseExpr>(this)->getChosenSubExpr(Ctx)->isLvalue(Ctx);
  case ExtVectorElementExprClass:
    if (cast<ExtVectorElementExpr>(this)->containsDuplicateElements())
      return LV_DuplicateVectorComponents;
    return LV_Valid;
  case ObjCIvarRefExprClass: // ObjC instance variables are lvalues.
    return LV_Valid;
  case ObjCPropertyRefExprClass: // FIXME: check if read-only property.
    return LV_Valid;
  case ObjCKVCRefExprClass: // FIXME: check if read-only property.
    return LV_Valid;
  case PredefinedExprClass:
    return LV_Valid;
  case CXXDefaultArgExprClass:
    return cast<CXXDefaultArgExpr>(this)->getExpr()->isLvalue(Ctx);
  case CXXConditionDeclExprClass:
    return LV_Valid;
  case CStyleCastExprClass:
  case CXXFunctionalCastExprClass:
  case CXXStaticCastExprClass:
  case CXXDynamicCastExprClass:
  case CXXReinterpretCastExprClass:
  case CXXConstCastExprClass:
    // The result of an explicit cast is an lvalue if the type we are
    // casting to is an lvalue reference type. See C++ [expr.cast]p1,
    // C++ [expr.static.cast]p2, C++ [expr.dynamic.cast]p2,
    // C++ [expr.reinterpret.cast]p1, C++ [expr.const.cast]p1.
    if (cast<ExplicitCastExpr>(this)->getTypeAsWritten()->
          isLValueReferenceType())
      return LV_Valid;
    break;
  case CXXTypeidExprClass:
    // C++ 5.2.8p1: The result of a typeid expression is an lvalue of ...
    return LV_Valid;
  case ConditionalOperatorClass: {
    // Complicated handling is only for C++.
    if (!Ctx.getLangOptions().CPlusPlus)
      return LV_InvalidExpression;

    // Sema should have taken care to ensure that a CXXTemporaryObjectExpr is
    // everywhere there's an object converted to an rvalue. Also, any other
    // casts should be wrapped by ImplicitCastExprs. There's just the special
    // case involving throws to work out.
    const ConditionalOperator *Cond = cast<ConditionalOperator>(this);
    Expr *True = Cond->getTrueExpr();
    Expr *False = Cond->getFalseExpr();
    // C++0x 5.16p2
    //   If either the second or the third operand has type (cv) void, [...]
    //   the result [...] is an rvalue.
    if (True->getType()->isVoidType() || False->getType()->isVoidType())
      return LV_InvalidExpression;

    // Both sides must be lvalues for the result to be an lvalue.
    if (True->isLvalue(Ctx) != LV_Valid || False->isLvalue(Ctx) != LV_Valid)
      return LV_InvalidExpression;

    // That's it.
    return LV_Valid;
  }

  default:
    break;
  }
  return LV_InvalidExpression;
}

/// isModifiableLvalue - C99 6.3.2.1: an lvalue that does not have array type,
/// does not have an incomplete type, does not have a const-qualified type, and
/// if it is a structure or union, does not have any member (including, 
/// recursively, any member or element of all contained aggregates or unions)
/// with a const-qualified type.
Expr::isModifiableLvalueResult 
Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
  isLvalueResult lvalResult = isLvalue(Ctx);
    
  switch (lvalResult) {
  case LV_Valid: 
    // C++ 3.10p11: Functions cannot be modified, but pointers to
    // functions can be modifiable.
    if (Ctx.getLangOptions().CPlusPlus && TR->isFunctionType())
      return MLV_NotObjectType;
    break;

  case LV_NotObjectType: return MLV_NotObjectType;
  case LV_IncompleteVoidType: return MLV_IncompleteVoidType;
  case LV_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
  case LV_InvalidExpression:
    // If the top level is a C-style cast, and the subexpression is a valid
    // lvalue, then this is probably a use of the old-school "cast as lvalue"
    // GCC extension.  We don't support it, but we want to produce good
    // diagnostics when it happens so that the user knows why.
    if (const CStyleCastExpr *CE = dyn_cast<CStyleCastExpr>(IgnoreParens())) {
      if (CE->getSubExpr()->isLvalue(Ctx) == LV_Valid) {
        if (Loc)
          *Loc = CE->getLParenLoc();
        return MLV_LValueCast;
      }
    }
    return MLV_InvalidExpression;
  case LV_MemberFunction: return MLV_MemberFunction;
  }

  // The following is illegal:
  //   void takeclosure(void (^C)(void));
  //   void func() { int x = 1; takeclosure(^{ x = 7; }); }
  //
  if (isa<BlockDeclRefExpr>(this)) {
    const BlockDeclRefExpr *BDR = cast<BlockDeclRefExpr>(this);
    if (!BDR->isByRef() && isa<VarDecl>(BDR->getDecl()))
      return MLV_NotBlockQualified;
  }

  QualType CT = Ctx.getCanonicalType(getType());
  
  if (CT.isConstQualified())
    return MLV_ConstQualified;
  if (CT->isArrayType())
    return MLV_ArrayType;
  if (CT->isIncompleteType())
    return MLV_IncompleteType;
    
  if (const RecordType *r = CT->getAsRecordType()) {
    if (r->hasConstFields()) 
      return MLV_ConstQualified;
  }
  
  // Assigning to an 'implicit' property?
  else if (isa<ObjCKVCRefExpr>(this)) {
    const ObjCKVCRefExpr* KVCExpr = cast<ObjCKVCRefExpr>(this);
    if (KVCExpr->getSetterMethod() == 0)
      return MLV_NoSetterProperty;
  }
  return MLV_Valid;    
}

/// hasGlobalStorage - Return true if this expression has static storage
/// duration.  This means that the address of this expression is a link-time
/// constant.
bool Expr::hasGlobalStorage() const {
  switch (getStmtClass()) {
  default:
    return false;
  case BlockExprClass:
    return true;
  case ParenExprClass:
    return cast<ParenExpr>(this)->getSubExpr()->hasGlobalStorage();
  case ImplicitCastExprClass:
    return cast<ImplicitCastExpr>(this)->getSubExpr()->hasGlobalStorage();
  case CompoundLiteralExprClass:
    return cast<CompoundLiteralExpr>(this)->isFileScope();
  case DeclRefExprClass:
  case QualifiedDeclRefExprClass: {
    const Decl *D = cast<DeclRefExpr>(this)->getDecl();
    if (const VarDecl *VD = dyn_cast<VarDecl>(D))
      return VD->hasGlobalStorage();
    if (isa<FunctionDecl>(D))
      return true;
    return false;
  }
  case MemberExprClass: {
    const MemberExpr *M = cast<MemberExpr>(this);
    return !M->isArrow() && M->getBase()->hasGlobalStorage();
  }
  case ArraySubscriptExprClass:
    return cast<ArraySubscriptExpr>(this)->getBase()->hasGlobalStorage();
  case PredefinedExprClass:
    return true;
  case CXXDefaultArgExprClass:
    return cast<CXXDefaultArgExpr>(this)->getExpr()->hasGlobalStorage();
  }
}

/// isOBJCGCCandidate - Check if an expression is objc gc'able.
///
bool Expr::isOBJCGCCandidate(ASTContext &Ctx) const {
  switch (getStmtClass()) {
  default:
    return false;
  case ObjCIvarRefExprClass:
    return true;
  case Expr::UnaryOperatorClass:
    return cast<UnaryOperator>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
  case ParenExprClass:
    return cast<ParenExpr>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
  case ImplicitCastExprClass:
    return cast<ImplicitCastExpr>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
  case CStyleCastExprClass:
    return cast<CStyleCastExpr>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
  case DeclRefExprClass:
  case QualifiedDeclRefExprClass: {
    const Decl *D = cast<DeclRefExpr>(this)->getDecl();
    if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
      if (VD->hasGlobalStorage())
        return true;
      QualType T = VD->getType();
      // dereferencing to an object pointer is always a gc'able candidate
      if (T->isPointerType() && 
          Ctx.isObjCObjectPointerType(T->getAsPointerType()->getPointeeType()))
        return true;
        
    }
    return false;
  }
  case MemberExprClass: {
    const MemberExpr *M = cast<MemberExpr>(this);