xref: /external/clang/include/clang/AST/Expr.h

//===--- Expr.h - Classes for representing expressions ----------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file defines the Expr interface and subclasses.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_AST_EXPR_H
#define LLVM_CLANG_AST_EXPR_H

#include "clang/AST/APValue.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/Type.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/SmallVector.h"
#include <vector>

namespace clang {
  class ASTContext;
  class APValue;
  class Decl;
  class IdentifierInfo;
  class ParmVarDecl;
  class NamedDecl;
  class ValueDecl;
  class BlockDecl;
  class CXXOperatorCallExpr;
  class CXXMemberCallExpr;

/// Expr - This represents one expression.  Note that Expr's are subclasses of
/// Stmt.  This allows an expression to be transparently used any place a Stmt
/// is required.
///
class Expr : public Stmt {
  QualType TR;

  /// TypeDependent - Whether this expression is type-dependent
  /// (C++ [temp.dep.expr]).
  bool TypeDependent : 1;

  /// ValueDependent - Whether this expression is value-dependent
  /// (C++ [temp.dep.constexpr]).
  bool ValueDependent : 1;

protected:
  // FIXME: Eventually, this constructor should go away and we should
  // require every subclass to provide type/value-dependence
  // information.
  Expr(StmtClass SC, QualType T)
    : Stmt(SC), TypeDependent(false), ValueDependent(false) {
    setType(T);
  }

  Expr(StmtClass SC, QualType T, bool TD, bool VD)
    : Stmt(SC), TypeDependent(TD), ValueDependent(VD) {
    setType(T);
  }

  /// \brief Construct an empty expression.
  explicit Expr(StmtClass SC, EmptyShell) : Stmt(SC) { }

public:
  QualType getType() const { return TR; }
  void setType(QualType t) {
    // In C++, the type of an expression is always adjusted so that it
    // will not have reference type an expression will never have
    // reference type (C++ [expr]p6). Use
    // QualType::getNonReferenceType() to retrieve the non-reference
    // type. Additionally, inspect Expr::isLvalue to determine whether
    // an expression that is adjusted in this manner should be
    // considered an lvalue.
    assert((TR.isNull() || !TR->isReferenceType()) &&
           "Expressions can't have reference type");

    TR = t;
  }

  /// isValueDependent - Determines whether this expression is
  /// value-dependent (C++ [temp.dep.constexpr]). For example, the
  /// array bound of "Chars" in the following example is
  /// value-dependent.
  /// @code
  /// template<int Size, char (&Chars)[Size]> struct meta_string;
  /// @endcode
  bool isValueDependent() const { return ValueDependent; }

  /// \brief Set whether this expression is value-dependent or not.
  void setValueDependent(bool VD) { ValueDependent = VD; }

  /// isTypeDependent - Determines whether this expression is
  /// type-dependent (C++ [temp.dep.expr]), which means that its type
  /// could change from one template instantiation to the next. For
  /// example, the expressions "x" and "x + y" are type-dependent in
  /// the following code, but "y" is not type-dependent:
  /// @code
  /// template<typename T>
  /// void add(T x, int y) {
  ///   x + y;
  /// }
  /// @endcode
  bool isTypeDependent() const { return TypeDependent; }

  /// \brief Set whether this expression is type-dependent or not.
  void setTypeDependent(bool TD) { TypeDependent = TD; }

  /// SourceLocation tokens are not useful in isolation - they are low level
  /// value objects created/interpreted by SourceManager. We assume AST
  /// clients will have a pointer to the respective SourceManager.
  virtual SourceRange getSourceRange() const = 0;

  /// getExprLoc - Return the preferred location for the arrow when diagnosing
  /// a problem with a generic expression.
  virtual SourceLocation getExprLoc() const { return getLocStart(); }

  /// 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 isUnusedResultAWarning(SourceLocation &Loc, SourceRange &R1,
                              SourceRange &R2) const;

  /// isLvalue - C99 6.3.2.1: an lvalue is an expression with an object type or
  /// 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
  ///  - reference type [C++ [expr]]
  ///  - b ? x : y, where x and y are lvalues of suitable types [C++]
  ///
  enum isLvalueResult {
    LV_Valid,
    LV_NotObjectType,
    LV_IncompleteVoidType,
    LV_DuplicateVectorComponents,
    LV_InvalidExpression,
    LV_MemberFunction
  };
  isLvalueResult isLvalue(ASTContext &Ctx) const;

  /// 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.
  ///
  /// \param Loc [in] [out] - A source location which *may* be filled
  /// in with the location of the expression making this a
  /// non-modifiable lvalue, if specified.
  enum isModifiableLvalueResult {
    MLV_Valid,
    MLV_NotObjectType,
    MLV_IncompleteVoidType,
    MLV_DuplicateVectorComponents,
    MLV_InvalidExpression,
    MLV_LValueCast,           // Specialized form of MLV_InvalidExpression.
    MLV_IncompleteType,
    MLV_ConstQualified,
    MLV_ArrayType,
    MLV_NotBlockQualified,
    MLV_ReadonlyProperty,
    MLV_NoSetterProperty,
    MLV_MemberFunction
  };
  isModifiableLvalueResult isModifiableLvalue(ASTContext &Ctx,
                                              SourceLocation *Loc = 0) const;

  bool isBitField();

  /// isIntegerConstantExpr - Return true if this expression is a valid integer
  /// constant expression, and, if so, return its value in Result.  If not a
  /// valid i-c-e, return false and fill in Loc (if specified) with the location
  /// of the invalid expression.
  bool isIntegerConstantExpr(llvm::APSInt &Result, ASTContext &Ctx,
                             SourceLocation *Loc = 0,
                             bool isEvaluated = true) const;
  bool isIntegerConstantExpr(ASTContext &Ctx, SourceLocation *Loc = 0) const {
    llvm::APSInt X;
    return isIntegerConstantExpr(X, Ctx, Loc);
  }
  /// isConstantInitializer - Returns true if this expression is a constant
  /// initializer, which can be emitted at compile-time.
  bool isConstantInitializer(ASTContext &Ctx) const;

  /// EvalResult is a struct with detailed info about an evaluated expression.
  struct EvalResult {
    /// Val - This is the value the expression can be folded to.
    APValue Val;

    /// HasSideEffects - Whether the evaluated expression has side effects.
    /// For example, (f() && 0) can be folded, but it still has side effects.
    bool HasSideEffects;

    /// Diag - If the expression is unfoldable, then Diag contains a note
    /// diagnostic indicating why it's not foldable. DiagLoc indicates a caret
    /// position for the error, and DiagExpr is the expression that caused
    /// the error.
    /// If the expression is foldable, but not an integer constant expression,
    /// Diag contains a note diagnostic that describes why it isn't an integer
    /// constant expression. If the expression *is* an integer constant
    /// expression, then Diag will be zero.
    unsigned Diag;
    const Expr *DiagExpr;
    SourceLocation DiagLoc;

    EvalResult() : HasSideEffects(false), Diag(0), DiagExpr(0) {}
  };

  /// Evaluate - Return true if this is a constant which we can fold using
  /// any crazy technique (that has nothing to do with language standards) that
  /// we want to.  If this function returns true, it returns the folded constant
  /// in Result.
  bool Evaluate(EvalResult &Result, ASTContext &Ctx) const;

  /// isEvaluatable - Call Evaluate to see if this expression can be constant
  /// folded, but discard the result.
  bool isEvaluatable(ASTContext &Ctx) const;

  /// EvaluateAsInt - Call Evaluate and return the folded integer. This
  /// must be called on an expression that constant folds to an integer.
  llvm::APSInt EvaluateAsInt(ASTContext &Ctx) const;

  /// EvaluateAsLValue - Evaluate an expression to see if it's a valid LValue.
  bool EvaluateAsLValue(EvalResult &Result, ASTContext &Ctx) const;

  /// isNullPointerConstant - C99 6.3.2.3p3 -  Return true if this is either an
  /// integer constant expression with the value zero, or if this is one that is
  /// cast to void*.
  bool isNullPointerConstant(ASTContext &Ctx) const;

  /// hasGlobalStorage - Return true if this expression has static storage
  /// duration.  This means that the address of this expression is a link-time
  /// constant.
  bool hasGlobalStorage() const;

  /// isOBJCGCCandidate - Return true if this expression may be used in a read/
  /// write barrier.
  bool isOBJCGCCandidate() const;

  /// IgnoreParens - Ignore parentheses.  If this Expr is a ParenExpr, return
  ///  its subexpression.  If that subexpression is also a ParenExpr,
  ///  then this method recursively returns its subexpression, and so forth.
  ///  Otherwise, the method returns the current Expr.
  Expr* IgnoreParens();

  /// IgnoreParenCasts - Ignore parentheses and casts.  Strip off any ParenExpr
  /// or CastExprs, returning their operand.
  Expr *IgnoreParenCasts();

  /// IgnoreParenNoopCasts - Ignore parentheses and casts that do not change the
  /// value (including ptr->int casts of the same size).  Strip off any
  /// ParenExpr or CastExprs, returning their operand.
  Expr *IgnoreParenNoopCasts(ASTContext &Ctx);

  const Expr* IgnoreParens() const {
    return const_cast<Expr*>(this)->IgnoreParens();
  }
  const Expr *IgnoreParenCasts() const {
    return const_cast<Expr*>(this)->IgnoreParenCasts();
  }
  const Expr *IgnoreParenNoopCasts(ASTContext &Ctx) const {
    return const_cast<Expr*>(this)->IgnoreParenNoopCasts(Ctx);
  }

  static bool hasAnyTypeDependentArguments(Expr** Exprs, unsigned NumExprs);
  static bool hasAnyValueDependentArguments(Expr** Exprs, unsigned NumExprs);

  static bool classof(const Stmt *T) {
    return T->getStmtClass() >= firstExprConstant &&
           T->getStmtClass() <= lastExprConstant;
  }
  static bool classof(const Expr *) { return true; }
};


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

/// DeclRefExpr - [C99 6.5.1p2] - A reference to a declared variable, function,
/// enum, etc.
class DeclRefExpr : public Expr {
  NamedDecl *D;
  SourceLocation Loc;

protected:
  // FIXME: Eventually, this constructor will go away and all subclasses
  // will have to provide the type- and value-dependent flags.
  DeclRefExpr(StmtClass SC, NamedDecl *d, QualType t, SourceLocation l) :
    Expr(SC, t), D(d), Loc(l) {}

  DeclRefExpr(StmtClass SC, NamedDecl *d, QualType t, SourceLocation l, bool TD,
              bool VD) :
    Expr(SC, t, TD, VD), D(d), Loc(l) {}

public:
  // FIXME: Eventually, this constructor will go away and all clients
  // will have to provide the type- and value-dependent flags.
  DeclRefExpr(NamedDecl *d, QualType t, SourceLocation l) :
    Expr(DeclRefExprClass, t), D(d), Loc(l) {}

  DeclRefExpr(NamedDecl *d, QualType t, SourceLocation l, bool TD, bool VD) :
    Expr(DeclRefExprClass, t, TD, VD), D(d), Loc(l) {}

  /// \brief Construct an empty declaration reference expression.
  explicit DeclRefExpr(EmptyShell Empty)
    : Expr(DeclRefExprClass, Empty) { }

  NamedDecl *getDecl() { return D; }
  const NamedDecl *getDecl() const { return D; }
  void setDecl(NamedDecl *NewD) { D = NewD; }

  SourceLocation getLocation() const { return Loc; }
  void setLocation(SourceLocation L) { Loc = L; }
  virtual SourceRange getSourceRange() const { return SourceRange(Loc); }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == DeclRefExprClass ||
           T->getStmtClass() == CXXConditionDeclExprClass ||
           T->getStmtClass() == QualifiedDeclRefExprClass;
  }
  static bool classof(const DeclRefExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// PredefinedExpr - [C99 6.4.2.2] - A predefined identifier such as __func__.
class PredefinedExpr : public Expr {
public:
  enum IdentType {
    Func,
    Function,
    PrettyFunction
  };

private:
  SourceLocation Loc;
  IdentType Type;
public:
  PredefinedExpr(SourceLocation l, QualType type, IdentType IT)
    : Expr(PredefinedExprClass, type), Loc(l), Type(IT) {}

  /// \brief Construct an empty predefined expression.
  explicit PredefinedExpr(EmptyShell Empty)
    : Expr(PredefinedExprClass, Empty) { }

  IdentType getIdentType() const { return Type; }
  void setIdentType(IdentType IT) { Type = IT; }

  SourceLocation getLocation() const { return Loc; }
  void setLocation(SourceLocation L) { Loc = L; }

  // FIXME: The logic for computing the value of a predefined expr should go
  // into a method here that takes the inner-most code decl (a block, function
  // or objc method) that the expr lives in.  This would allow sema and codegen
  // to be consistent for things like sizeof(__func__) etc.

  virtual SourceRange getSourceRange() const { return SourceRange(Loc); }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == PredefinedExprClass;
  }
  static bool classof(const PredefinedExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

class IntegerLiteral : public Expr {
  llvm::APInt Value;
  SourceLocation Loc;
public:
  // type should be IntTy, LongTy, LongLongTy, UnsignedIntTy, UnsignedLongTy,
  // or UnsignedLongLongTy
  IntegerLiteral(const llvm::APInt &V, QualType type, SourceLocation l)
    : Expr(IntegerLiteralClass, type), Value(V), Loc(l) {
    assert(type->isIntegerType() && "Illegal type in IntegerLiteral");
  }

  /// \brief Construct an empty integer literal.
  explicit IntegerLiteral(EmptyShell Empty)
    : Expr(IntegerLiteralClass, Empty) { }

  IntegerLiteral* Clone(ASTContext &C) const;

  const llvm::APInt &getValue() const { return Value; }
  virtual SourceRange getSourceRange() const { return SourceRange(Loc); }

  /// \brief Retrieve the location of the literal.
  SourceLocation getLocation() const { return Loc; }

  void setValue(const llvm::APInt &Val) { Value = Val; }
  void setLocation(SourceLocation Location) { Loc = Location; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == IntegerLiteralClass;
  }
  static bool classof(const IntegerLiteral *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

class CharacterLiteral : public Expr {
  unsigned Value;
  SourceLocation Loc;
  bool IsWide;
public:
  // type should be IntTy
  CharacterLiteral(unsigned value, bool iswide, QualType type, SourceLocation l)
    : Expr(CharacterLiteralClass, type), Value(value), Loc(l), IsWide(iswide) {
  }

  /// \brief Construct an empty character literal.
  CharacterLiteral(EmptyShell Empty) : Expr(CharacterLiteralClass, Empty) { }

  SourceLocation getLoc() const { return Loc; }
  bool isWide() const { return IsWide; }

  virtual SourceRange getSourceRange() const { return SourceRange(Loc); }

  unsigned getValue() const { return Value; }

  void setLocation(SourceLocation Location) { Loc = Location; }
  void setWide(bool W) { IsWide = W; }
  void setValue(unsigned Val) { Value = Val; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == CharacterLiteralClass;
  }
  static bool classof(const CharacterLiteral *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

class FloatingLiteral : public Expr {
  llvm::APFloat Value;
  bool IsExact : 1;
  SourceLocation Loc;
public:
  FloatingLiteral(const llvm::APFloat &V, bool* isexact,
                  QualType Type, SourceLocation L)
    : Expr(FloatingLiteralClass, Type), Value(V), IsExact(*isexact), Loc(L) {}

  /// \brief Construct an empty floating-point literal.
  FloatingLiteral(EmptyShell Empty)
    : Expr(FloatingLiteralClass, Empty), Value(0.0) { }

  const llvm::APFloat &getValue() const { return Value; }
  void setValue(const llvm::APFloat &Val) { Value = Val; }

  bool isExact() const { return IsExact; }
  void setExact(bool E) { IsExact = E; }

  /// 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 getValueAsApproximateDouble() const;

  SourceLocation getLocation() const { return Loc; }
  void setLocation(SourceLocation L) { Loc = L; }

  // FIXME: The logic for computing the value of a predefined expr should go
  // into a method here that takes the inner-most code decl (a block, function
  // or objc method) that the expr lives in.  This would allow sema and codegen
  // to be consistent for things like sizeof(__func__) etc.

  virtual SourceRange getSourceRange() const { return SourceRange(Loc); }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == FloatingLiteralClass;
  }
  static bool classof(const FloatingLiteral *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// ImaginaryLiteral - We support imaginary integer and floating point literals,
/// like "1.0i".  We represent these as a wrapper around FloatingLiteral and
/// IntegerLiteral classes.  Instances of this class always have a Complex type
/// whose element type matches the subexpression.
///
class ImaginaryLiteral : public Expr {
  Stmt *Val;
public:
  ImaginaryLiteral(Expr *val, QualType Ty)
    : Expr(ImaginaryLiteralClass, Ty), Val(val) {}

  /// \brief Build an empty imaginary literal.
  explicit ImaginaryLiteral(EmptyShell Empty)
    : Expr(ImaginaryLiteralClass, Empty) { }

  const Expr *getSubExpr() const { return cast<Expr>(Val); }
  Expr *getSubExpr() { return cast<Expr>(Val); }
  void setSubExpr(Expr *E) { Val = E; }

  virtual SourceRange getSourceRange() const { return Val->getSourceRange(); }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ImaginaryLiteralClass;
  }
  static bool classof(const ImaginaryLiteral *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// StringLiteral - This represents a string literal expression, e.g. "foo"
/// or L"bar" (wide strings).  The actual string is returned by getStrData()
/// is NOT null-terminated, and the length of the string is determined by
/// calling getByteLength().  The C type for a string is always a
/// ConstantArrayType.  In C++, the char type is const qualified, in C it is
/// not.
///
/// Note that strings in C can be formed by concatenation of multiple string
/// literal pptokens in translation phase #6.  This keeps track of the locations
/// of each of these pieces.
///
/// Strings in C can also be truncated and extended by assigning into arrays,
/// e.g. with constructs like:
///   char X[2] = "foobar";
/// In this case, getByteLength() will return 6, but the string literal will
/// have type "char[2]".
class StringLiteral : public Expr {
  const char *StrData;
  unsigned ByteLength;
  bool IsWide;
  unsigned NumConcatenated;
  SourceLocation TokLocs[1];

  StringLiteral(QualType Ty) : Expr(StringLiteralClass, Ty) {}
public:
  /// This is the "fully general" constructor that allows representation of
  /// strings formed from multiple concatenated tokens.
  static StringLiteral *Create(ASTContext &C, const char *StrData,
                               unsigned ByteLength, bool Wide, QualType Ty,
                               const SourceLocation *Loc, unsigned NumStrs);

  /// Simple constructor for string literals made from one token.
  static StringLiteral *Create(ASTContext &C, const char *StrData,
                               unsigned ByteLength,
                               bool Wide, QualType Ty, SourceLocation Loc) {
    return Create(C, StrData, ByteLength, Wide, Ty, &Loc, 1);
  }

  /// \brief Construct an empty string literal.
  static StringLiteral *CreateEmpty(ASTContext &C, unsigned NumStrs);

  StringLiteral* Clone(ASTContext &C) const;
  void Destroy(ASTContext &C);

  const char *getStrData() const { return StrData; }
  unsigned getByteLength() const { return ByteLength; }

  /// \brief Sets the string data to the given string data.
  void setStrData(ASTContext &C, const char *Str, unsigned Len);

  bool isWide() const { return IsWide; }
  void setWide(bool W) { IsWide = W; }

  bool containsNonAsciiOrNull() const {
    for (unsigned i = 0; i < getByteLength(); ++i)
      if (!isascii(getStrData()[i]) || !getStrData()[i])
        return true;
    return false;
  }
  /// getNumConcatenated - Get the number of string literal tokens that were
  /// concatenated in translation phase #6 to form this string literal.
  unsigned getNumConcatenated() const { return NumConcatenated; }

  SourceLocation getStrTokenLoc(unsigned TokNum) const {
    assert(TokNum < NumConcatenated && "Invalid tok number");
    return TokLocs[TokNum];
  }
  void setStrTokenLoc(unsigned TokNum, SourceLocation L) {
    assert(TokNum < NumConcatenated && "Invalid tok number");
    TokLocs[TokNum] = L;
  }

  typedef const SourceLocation *tokloc_iterator;
  tokloc_iterator tokloc_begin() const { return TokLocs; }
  tokloc_iterator tokloc_end() const { return TokLocs+NumConcatenated; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(TokLocs[0], TokLocs[NumConcatenated-1]);
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == StringLiteralClass;
  }
  static bool classof(const StringLiteral *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// ParenExpr - This represents a parethesized expression, e.g. "(1)".  This
/// AST node is only formed if full location information is requested.
class ParenExpr : public Expr {
  SourceLocation L, R;
  Stmt *Val;
public:
  ParenExpr(SourceLocation l, SourceLocation r, Expr *val)
    : Expr(ParenExprClass, val->getType(),
           val->isTypeDependent(), val->isValueDependent()),
      L(l), R(r), Val(val) {}

  /// \brief Construct an empty parenthesized expression.
  explicit ParenExpr(EmptyShell Empty)
    : Expr(ParenExprClass, Empty) { }

  const Expr *getSubExpr() const { return cast<Expr>(Val); }
  Expr *getSubExpr() { return cast<Expr>(Val); }
  void setSubExpr(Expr *E) { Val = E; }

  virtual SourceRange getSourceRange() const { return SourceRange(L, R); }

  /// \brief Get the location of the left parentheses '('.
  SourceLocation getLParen() const { return L; }
  void setLParen(SourceLocation Loc) { L = Loc; }

  /// \brief Get the location of the right parentheses ')'.
  SourceLocation getRParen() const { return R; }
  void setRParen(SourceLocation Loc) { R = Loc; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ParenExprClass;
  }
  static bool classof(const ParenExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};


/// UnaryOperator - This represents the unary-expression's (except sizeof and
/// alignof), the postinc/postdec operators from postfix-expression, and various
/// extensions.
///
/// Notes on various nodes:
///
/// Real/Imag - These return the real/imag part of a complex operand.  If
///   applied to a non-complex value, the former returns its operand and the
///   later returns zero in the type of the operand.
///
/// __builtin_offsetof(type, a.b[10]) is represented as a unary operator whose
///   subexpression is a compound literal with the various MemberExpr and
///   ArraySubscriptExpr's applied to it.
///
class UnaryOperator : public Expr {
public:
  // Note that additions to this should also update the StmtVisitor class.
  enum Opcode {
    PostInc, PostDec, // [C99 6.5.2.4] Postfix increment and decrement operators
    PreInc, PreDec,   // [C99 6.5.3.1] Prefix increment and decrement operators.
    AddrOf, Deref,    // [C99 6.5.3.2] Address and indirection operators.
    Plus, Minus,      // [C99 6.5.3.3] Unary arithmetic operators.
    Not, LNot,        // [C99 6.5.3.3] Unary arithmetic operators.
    Real, Imag,       // "__real expr"/"__imag expr" Extension.
    Extension,        // __extension__ marker.
    OffsetOf          // __builtin_offsetof
  };
private:
  Stmt *Val;
  Opcode Opc;
  SourceLocation Loc;
public:

  UnaryOperator(Expr *input, Opcode opc, QualType type, SourceLocation l)
    : Expr(UnaryOperatorClass, type,
           input->isTypeDependent() && opc != OffsetOf,
           input->isValueDependent()),
      Val(input), Opc(opc), Loc(l) {}

  /// \brief Build an empty unary operator.
  explicit UnaryOperator(EmptyShell Empty)
    : Expr(UnaryOperatorClass, Empty), Opc(AddrOf) { }

  Opcode getOpcode() const { return Opc; }
  void setOpcode(Opcode O) { Opc = O; }

  Expr *getSubExpr() const { return cast<Expr>(Val); }
  void setSubExpr(Expr *E) { Val = E; }

  /// getOperatorLoc - Return the location of the operator.
  SourceLocation getOperatorLoc() const { return Loc; }
  void setOperatorLoc(SourceLocation L) { Loc = L; }

  /// isPostfix - Return true if this is a postfix operation, like x++.
  static bool isPostfix(Opcode Op) {
    return Op == PostInc || Op == PostDec;
  }

  /// isPostfix - Return true if this is a prefix operation, like --x.
  static bool isPrefix(Opcode Op) {
    return Op == PreInc || Op == PreDec;
  }

  bool isPrefix() const { return isPrefix(Opc); }
  bool isPostfix() const { return isPostfix(Opc); }
  bool isIncrementOp() const {return Opc==PreInc || Opc==PostInc; }
  bool isIncrementDecrementOp() const { return Opc>=PostInc && Opc<=PreDec; }
  bool isOffsetOfOp() const { return Opc == OffsetOf; }
  static bool isArithmeticOp(Opcode Op) { return Op >= Plus && Op <= LNot; }

  /// getOpcodeStr - Turn an Opcode enum value into the punctuation char it
  /// corresponds to, e.g. "sizeof" or "[pre]++"
  static const char *getOpcodeStr(Opcode Op);

  /// \brief Retrieve the unary opcode that corresponds to the given
  /// overloaded operator.
  static Opcode getOverloadedOpcode(OverloadedOperatorKind OO, bool Postfix);

  /// \brief Retrieve the overloaded operator kind that corresponds to
  /// the given unary opcode.
  static OverloadedOperatorKind getOverloadedOperator(Opcode Opc);

  virtual SourceRange getSourceRange() const {
    if (isPostfix())
      return SourceRange(Val->getLocStart(), Loc);
    else
      return SourceRange(Loc, Val->getLocEnd());
  }
  virtual SourceLocation getExprLoc() const { return Loc; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == UnaryOperatorClass;
  }
  static bool classof(const UnaryOperator *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// SizeOfAlignOfExpr - [C99 6.5.3.4] - This is for sizeof/alignof, both of
/// types and expressions.
class SizeOfAlignOfExpr : public Expr {
  bool isSizeof : 1;  // true if sizeof, false if alignof.
  bool isType : 1;    // true if operand is a type, false if an expression
  union {
    void *Ty;
    Stmt *Ex;
  } Argument;
  SourceLocation OpLoc, RParenLoc;
public:
  SizeOfAlignOfExpr(bool issizeof, QualType T,
                    QualType resultType, SourceLocation op,
                    SourceLocation rp) :
      Expr(SizeOfAlignOfExprClass, resultType,
           false, // Never type-dependent (C++ [temp.dep.expr]p3).
           // Value-dependent if the argument is type-dependent.
           T->isDependentType()),
      isSizeof(issizeof), isType(true), OpLoc(op), RParenLoc(rp) {
    Argument.Ty = T.getAsOpaquePtr();
  }

  SizeOfAlignOfExpr(bool issizeof, Expr *E,
                    QualType resultType, SourceLocation op,
                    SourceLocation rp) :
      Expr(SizeOfAlignOfExprClass, resultType,
           false, // Never type-dependent (C++ [temp.dep.expr]p3).
           // Value-dependent if the argument is type-dependent.
           E->isTypeDependent()),
      isSizeof(issizeof), isType(false), OpLoc(op), RParenLoc(rp) {
    Argument.Ex = E;
  }

  /// \brief Construct an empty sizeof/alignof expression.
  explicit SizeOfAlignOfExpr(EmptyShell Empty)
    : Expr(SizeOfAlignOfExprClass, Empty) { }

  virtual void Destroy(ASTContext& C);

  bool isSizeOf() const { return isSizeof; }
  void setSizeof(bool S) { isSizeof = S; }

  bool isArgumentType() const { return isType; }
  QualType getArgumentType() const {
    assert(isArgumentType() && "calling getArgumentType() when arg is expr");
    return QualType::getFromOpaquePtr(Argument.Ty);
  }
  Expr *getArgumentExpr() {
    assert(!isArgumentType() && "calling getArgumentExpr() when arg is type");
    return static_cast<Expr*>(Argument.Ex);
  }
  const Expr *getArgumentExpr() const {
    return const_cast<SizeOfAlignOfExpr*>(this)->getArgumentExpr();
  }

  void setArgument(Expr *E) { Argument.Ex = E; isType = false; }
  void setArgument(QualType T) {
    Argument.Ty = T.getAsOpaquePtr();
    isType = true;
  }

  /// Gets the argument type, or the type of the argument expression, whichever
  /// is appropriate.
  QualType getTypeOfArgument() const {
    return isArgumentType() ? getArgumentType() : getArgumentExpr()->getType();
  }

  SourceLocation getOperatorLoc() const { return OpLoc; }
  void setOperatorLoc(SourceLocation L) { OpLoc = L; }

  SourceLocation getRParenLoc() const { return RParenLoc; }
  void setRParenLoc(SourceLocation L) { RParenLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(OpLoc, RParenLoc);
  }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == SizeOfAlignOfExprClass;
  }
  static bool classof(const SizeOfAlignOfExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

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

/// ArraySubscriptExpr - [C99 6.5.2.1] Array Subscripting.
class ArraySubscriptExpr : public Expr {
  enum { LHS, RHS, END_EXPR=2 };
  Stmt* SubExprs[END_EXPR];
  SourceLocation RBracketLoc;
public:
  ArraySubscriptExpr(Expr *lhs, Expr *rhs, QualType t,
                     SourceLocation rbracketloc)
  : Expr(ArraySubscriptExprClass, t,
         lhs->isTypeDependent() || rhs->isTypeDependent(),
         lhs->isValueDependent() || rhs->isValueDependent()),
    RBracketLoc(rbracketloc) {
    SubExprs[LHS] = lhs;
    SubExprs[RHS] = rhs;
  }

  /// \brief Create an empty array subscript expression.
  explicit ArraySubscriptExpr(EmptyShell Shell)
    : Expr(ArraySubscriptExprClass, Shell) { }

  /// An array access can be written A[4] or 4[A] (both are equivalent).
  /// - getBase() and getIdx() always present the normalized view: A[4].
  ///    In this case getBase() returns "A" and getIdx() returns "4".
  /// - getLHS() and getRHS() present the syntactic view. e.g. for
  ///    4[A] getLHS() returns "4".
  /// Note: Because vector element access is also written A[4] we must
  /// predicate the format conversion in getBase and getIdx only on the
  /// the type of the RHS, as it is possible for the LHS to be a vector of
  /// integer type
  Expr *getLHS() { return cast<Expr>(SubExprs[LHS]); }
  const Expr *getLHS() const { return cast<Expr>(SubExprs[LHS]); }
  void setLHS(Expr *E) { SubExprs[LHS] = E; }

  Expr *getRHS() { return cast<Expr>(SubExprs[RHS]); }
  const Expr *getRHS() const { return cast<Expr>(SubExprs[RHS]); }
  void setRHS(Expr *E) { SubExprs[RHS] = E; }

  Expr *getBase() {
    return cast<Expr>(getRHS()->getType()->isIntegerType() ? getLHS():getRHS());
  }

  const Expr *getBase() const {
    return cast<Expr>(getRHS()->getType()->isIntegerType() ? getLHS():getRHS());
  }

  Expr *getIdx() {
    return cast<Expr>(getRHS()->getType()->isIntegerType() ? getRHS():getLHS());
  }

  const Expr *getIdx() const {
    return cast<Expr>(getRHS()->getType()->isIntegerType() ? getRHS():getLHS());
  }

  virtual SourceRange getSourceRange() const {
    return SourceRange(getLHS()->getLocStart(), RBracketLoc);
  }

  SourceLocation getRBracketLoc() const { return RBracketLoc; }
  void setRBracketLoc(SourceLocation L) { RBracketLoc = L; }

  virtual SourceLocation getExprLoc() const { return getBase()->getExprLoc(); }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ArraySubscriptExprClass;
  }
  static bool classof(const ArraySubscriptExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};


/// CallExpr - Represents a function call (C99 6.5.2.2, C++ [expr.call]).
/// CallExpr itself represents a normal function call, e.g., "f(x, 2)",
/// while its subclasses may represent alternative syntax that (semantically)
/// results in a function call. For example, CXXOperatorCallExpr is
/// a subclass for overloaded operator calls that use operator syntax, e.g.,
/// "str1 + str2" to resolve to a function call.
class CallExpr : public Expr {
  enum { FN=0, ARGS_START=1 };
  Stmt **SubExprs;
  unsigned NumArgs;
  SourceLocation RParenLoc;

  // This version of the ctor is for deserialization.
  CallExpr(StmtClass SC, Stmt** subexprs, unsigned numargs, QualType t,
           SourceLocation rparenloc)
  : Expr(SC,t), SubExprs(subexprs),
    NumArgs(numargs), RParenLoc(rparenloc) {}

protected:
  // This version of the constructor is for derived classes.
  CallExpr(ASTContext& C, StmtClass SC, Expr *fn, Expr **args, unsigned numargs,
           QualType t, SourceLocation rparenloc);

public:
  CallExpr(ASTContext& C, Expr *fn, Expr **args, unsigned numargs, QualType t,
           SourceLocation rparenloc);

  /// \brief Build an empty call expression.
  CallExpr(ASTContext &C, EmptyShell Empty);

  ~CallExpr() {}

  void Destroy(ASTContext& C);

  const Expr *getCallee() const { return cast<Expr>(SubExprs[FN]); }
  Expr *getCallee() { return cast<Expr>(SubExprs[FN]); }
  void setCallee(Expr *F) { SubExprs[FN] = F; }

  /// getNumArgs - Return the number of actual arguments to this call.
  ///
  unsigned getNumArgs() const { return NumArgs; }

  /// getArg - Return the specified argument.
  Expr *getArg(unsigned Arg) {
    assert(Arg < NumArgs && "Arg access out of range!");
    return cast<Expr>(SubExprs[Arg+ARGS_START]);
  }
  const Expr *getArg(unsigned Arg) const {
    assert(Arg < NumArgs && "Arg access out of range!");
    return cast<Expr>(SubExprs[Arg+ARGS_START]);
  }

  /// setArg - Set the specified argument.
  void setArg(unsigned Arg, Expr *ArgExpr) {
    assert(Arg < NumArgs && "Arg access out of range!");
    SubExprs[Arg+ARGS_START] = ArgExpr;
  }

  /// 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 setNumArgs(ASTContext& C, unsigned NumArgs);

  typedef ExprIterator arg_iterator;
  typedef ConstExprIterator const_arg_iterator;

  arg_iterator arg_begin() { return SubExprs+ARGS_START; }
  arg_iterator arg_end() { return SubExprs+ARGS_START+getNumArgs(); }
  const_arg_iterator arg_begin() const { return SubExprs+ARGS_START; }
  const_arg_iterator arg_end() const { return SubExprs+ARGS_START+getNumArgs();}

  /// getNumCommas - Return the number of commas that must have been present in
  /// this function call.
  unsigned getNumCommas() const { return NumArgs ? NumArgs - 1 : 0; }

  /// isBuiltinCall - If this is a call to a builtin, return the builtin ID.  If
  /// not, return 0.
  unsigned isBuiltinCall(ASTContext &Context) const;

  SourceLocation getRParenLoc() const { return RParenLoc; }
  void setRParenLoc(SourceLocation L) { RParenLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(getCallee()->getLocStart(), RParenLoc);
  }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == CallExprClass ||
           T->getStmtClass() == CXXOperatorCallExprClass ||
           T->getStmtClass() == CXXMemberCallExprClass;
  }
  static bool classof(const CallExpr *) { return true; }
  static bool classof(const CXXOperatorCallExpr *) { return true; }
  static bool classof(const CXXMemberCallExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// MemberExpr - [C99 6.5.2.3] Structure and Union Members.  X->F and X.F.
///
class MemberExpr : public Expr {
  /// Base - the expression for the base pointer or structure references.  In
  /// X.F, this is "X".
  Stmt *Base;

  /// MemberDecl - This is the decl being referenced by the field/member name.
  /// In X.F, this is the decl referenced by F.
  NamedDecl *MemberDecl;

  /// MemberLoc - This is the location of the member name.
  SourceLocation MemberLoc;

  /// IsArrow - True if this is "X->F", false if this is "X.F".
  bool IsArrow;
public:
  MemberExpr(Expr *base, bool isarrow, NamedDecl *memberdecl, SourceLocation l,
             QualType ty)
    : Expr(MemberExprClass, ty),
      Base(base), MemberDecl(memberdecl), MemberLoc(l), IsArrow(isarrow) {}

  /// \brief Build an empty member reference expression.
  explicit MemberExpr(EmptyShell Empty) : Expr(MemberExprClass, Empty) { }

  void setBase(Expr *E) { Base = E; }
  Expr *getBase() const { return cast<Expr>(Base); }

  /// \brief Retrieve the member declaration to which this expression refers.
  ///
  /// The returned declaration will either be a FieldDecl or (in C++)
  /// a CXXMethodDecl.
  NamedDecl *getMemberDecl() const { return MemberDecl; }
  void setMemberDecl(NamedDecl *D) { MemberDecl = D; }

  bool isArrow() const { return IsArrow; }
  void setArrow(bool A) { IsArrow = A; }

  /// getMemberLoc - Return the location of the "member", in X->F, it is the
  /// location of 'F'.
  SourceLocation getMemberLoc() const { return MemberLoc; }
  void setMemberLoc(SourceLocation L) { MemberLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(getBase()->getLocStart(), MemberLoc);
  }

  virtual SourceLocation getExprLoc() const { return MemberLoc; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == MemberExprClass;
  }
  static bool classof(const MemberExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// CompoundLiteralExpr - [C99 6.5.2.5]
///
class CompoundLiteralExpr : public Expr {
  /// LParenLoc - If non-null, this is the location of the left paren in a
  /// compound literal like "(int){4}".  This can be null if this is a
  /// synthesized compound expression.
  SourceLocation LParenLoc;
  Stmt *Init;
  bool FileScope;
public:
  CompoundLiteralExpr(SourceLocation lparenloc, QualType ty, Expr *init,
                      bool fileScope)
    : Expr(CompoundLiteralExprClass, ty), LParenLoc(lparenloc), Init(init),
      FileScope(fileScope) {}

  /// \brief Construct an empty compound literal.
  explicit CompoundLiteralExpr(EmptyShell Empty)
    : Expr(CompoundLiteralExprClass, Empty) { }

  const Expr *getInitializer() const { return cast<Expr>(Init); }
  Expr *getInitializer() { return cast<Expr>(Init); }
  void setInitializer(Expr *E) { Init = E; }

  bool isFileScope() const { return FileScope; }
  void setFileScope(bool FS) { FileScope = FS; }

  SourceLocation getLParenLoc() const { return LParenLoc; }
  void setLParenLoc(SourceLocation L) { LParenLoc = L; }

  virtual SourceRange getSourceRange() const {
    // FIXME: Init should never be null.
    if (!Init)
      return SourceRange();
    if (LParenLoc.isInvalid())
      return Init->getSourceRange();
    return SourceRange(LParenLoc, Init->getLocEnd());
  }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == CompoundLiteralExprClass;
  }
  static bool classof(const CompoundLiteralExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// CastExpr - Base class for type casts, including both implicit
/// casts (ImplicitCastExpr) and explicit casts that have some
/// representation in the source code (ExplicitCastExpr's derived
/// classes).
class CastExpr : public Expr {
  Stmt *Op;
protected:
  CastExpr(StmtClass SC, QualType ty, Expr *op) :
    Expr(SC, ty,
         // Cast expressions are type-dependent if the type is
         // dependent (C++ [temp.dep.expr]p3).
         ty->isDependentType(),
         // Cast expressions are value-dependent if the type is
         // dependent or if the subexpression is value-dependent.
         ty->isDependentType() || (op && op->isValueDependent())),
    Op(op) {}

  /// \brief Construct an empty cast.
  CastExpr(StmtClass SC, EmptyShell Empty)
    : Expr(SC, Empty) { }

public:
  Expr *getSubExpr() { return cast<Expr>(Op); }
  const Expr *getSubExpr() const { return cast<Expr>(Op); }
  void setSubExpr(Expr *E) { Op = E; }

  static bool classof(const Stmt *T) {
    StmtClass SC = T->getStmtClass();
    if (SC >= CXXNamedCastExprClass && SC <= CXXFunctionalCastExprClass)
      return true;

    if (SC >= ImplicitCastExprClass && SC <= CStyleCastExprClass)
      return true;

    return false;
  }
  static bool classof(const CastExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// ImplicitCastExpr - Allows us to explicitly represent implicit type
/// conversions, which have no direct representation in the original
/// source code. For example: converting T[]->T*, void f()->void
/// (*f)(), float->double, short->int, etc.
///
/// In C, implicit casts always produce rvalues. However, in C++, an
/// implicit cast whose result is being bound to a reference will be
/// an lvalue. For example:
///
/// @code
/// class Base { };
/// class Derived : public Base { };
/// void f(Derived d) {
///   Base& b = d; // initializer is an ImplicitCastExpr to an lvalue of type Base
/// }
/// @endcode
class ImplicitCastExpr : public CastExpr {
  /// LvalueCast - Whether this cast produces an lvalue.
  bool LvalueCast;

public:
  ImplicitCastExpr(QualType ty, Expr *op, bool Lvalue) :
    CastExpr(ImplicitCastExprClass, ty, op), LvalueCast(Lvalue) { }

  /// \brief Construct an empty implicit cast.
  explicit ImplicitCastExpr(EmptyShell Shell)
    : CastExpr(ImplicitCastExprClass, Shell) { }


  virtual SourceRange getSourceRange() const {
    return getSubExpr()->getSourceRange();
  }

  /// isLvalueCast - Whether this cast produces an lvalue.
  bool isLvalueCast() const { return LvalueCast; }

  /// setLvalueCast - Set whether this cast produces an lvalue.
  void setLvalueCast(bool Lvalue) { LvalueCast = Lvalue; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ImplicitCastExprClass;
  }
  static bool classof(const ImplicitCastExpr *) { return true; }
};

/// ExplicitCastExpr - An explicit cast written in the source
/// code.
///
/// This class is effectively an abstract class, because it provides
/// the basic representation of an explicitly-written cast without
/// specifying which kind of cast (C cast, functional cast, static
/// cast, etc.) was written; specific derived classes represent the
/// particular style of cast and its location information.
///
/// Unlike implicit casts, explicit cast nodes have two different
/// types: the type that was written into the source code, and the
/// actual type of the expression as determined by semantic
/// analysis. These types may differ slightly. For example, in C++ one
/// can cast to a reference type, which indicates that the resulting
/// expression will be an lvalue. The reference type, however, will
/// not be used as the type of the expression.
class ExplicitCastExpr : public CastExpr {
  /// TypeAsWritten - The type that this expression is casting to, as
  /// written in the source code.
  QualType TypeAsWritten;

protected:
  ExplicitCastExpr(StmtClass SC, QualType exprTy, Expr *op, QualType writtenTy)
    : CastExpr(SC, exprTy, op), TypeAsWritten(writtenTy) {}

  /// \brief Construct an empty explicit cast.
  ExplicitCastExpr(StmtClass SC, EmptyShell Shell)
    : CastExpr(SC, Shell) { }

public:
  /// getTypeAsWritten - Returns the type that this expression is
  /// casting to, as written in the source code.
  QualType getTypeAsWritten() const { return TypeAsWritten; }
  void setTypeAsWritten(QualType T) { TypeAsWritten = T; }

  static bool classof(const Stmt *T) {
    StmtClass SC = T->getStmtClass();
    if (SC >= ExplicitCastExprClass && SC <= CStyleCastExprClass)
      return true;
    if (SC >= CXXNamedCastExprClass && SC <= CXXFunctionalCastExprClass)
      return true;

    return false;
  }
  static bool classof(const ExplicitCastExpr *) { return true; }
};

/// CStyleCastExpr - An explicit cast in C (C99 6.5.4) or a C-style
/// cast in C++ (C++ [expr.cast]), which uses the syntax
/// (Type)expr. For example: @c (int)f.
class CStyleCastExpr : public ExplicitCastExpr {
  SourceLocation LPLoc; // the location of the left paren
  SourceLocation RPLoc; // the location of the right paren
public:
  CStyleCastExpr(QualType exprTy, Expr *op, QualType writtenTy,
                    SourceLocation l, SourceLocation r) :
    ExplicitCastExpr(CStyleCastExprClass, exprTy, op, writtenTy),
    LPLoc(l), RPLoc(r) {}

  /// \brief Construct an empty C-style explicit cast.
  explicit CStyleCastExpr(EmptyShell Shell)
    : ExplicitCastExpr(CStyleCastExprClass, Shell) { }

  SourceLocation getLParenLoc() const { return LPLoc; }
  void setLParenLoc(SourceLocation L) { LPLoc = L; }

  SourceLocation getRParenLoc() const { return RPLoc; }
  void setRParenLoc(SourceLocation L) { RPLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(LPLoc, getSubExpr()->getSourceRange().getEnd());
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == CStyleCastExprClass;
  }
  static bool classof(const CStyleCastExpr *) { return true; }
};

/// \brief A builtin binary operation expression such as "x + y" or "x <= y".
///
/// This expression node kind describes a builtin binary operation,
/// such as "x + y" for integer values "x" and "y". The operands will
/// already have been converted to appropriate types (e.g., by
/// performing promotions or conversions).
///
/// In C++, where operators may be overloaded, a different kind of
/// expression node (CXXOperatorCallExpr) is used to express the
/// invocation of an overloaded operator with operator syntax. Within
/// a C++ template, whether BinaryOperator or CXXOperatorCallExpr is
/// used to store an expression "x + y" depends on the subexpressions
/// for x and y. If neither x or y is type-dependent, and the "+"
/// operator resolves to a built-in operation, BinaryOperator will be
/// used to express the computation (x and y may still be
/// value-dependent). If either x or y is type-dependent, or if the
/// "+" resolves to an overloaded operator, CXXOperatorCallExpr will
/// be used to express the computation.
class BinaryOperator : public Expr {
public:
  enum Opcode {
    // Operators listed in order of precedence.
    // Note that additions to this should also update the StmtVisitor class.
    PtrMemD, PtrMemI, // [C++ 5.5] Pointer-to-member operators.
    Mul, Div, Rem,    // [C99 6.5.5] Multiplicative operators.
    Add, Sub,         // [C99 6.5.6] Additive operators.
    Shl, Shr,         // [C99 6.5.7] Bitwise shift operators.
    LT, GT, LE, GE,   // [C99 6.5.8] Relational operators.
    EQ, NE,           // [C99 6.5.9] Equality operators.
    And,              // [C99 6.5.10] Bitwise AND operator.
    Xor,              // [C99 6.5.11] Bitwise XOR operator.
    Or,               // [C99 6.5.12] Bitwise OR operator.
    LAnd,             // [C99 6.5.13] Logical AND operator.
    LOr,              // [C99 6.5.14] Logical OR operator.
    Assign, MulAssign,// [C99 6.5.16] Assignment operators.
    DivAssign, RemAssign,
    AddAssign, SubAssign,
    ShlAssign, ShrAssign,
    AndAssign, XorAssign,
    OrAssign,
    Comma             // [C99 6.5.17] Comma operator.
  };
private:
  enum { LHS, RHS, END_EXPR };
  Stmt* SubExprs[END_EXPR];
  Opcode Opc;
  SourceLocation OpLoc;
public:

  BinaryOperator(Expr *lhs, Expr *rhs, Opcode opc, QualType ResTy,
                 SourceLocation opLoc)
    : Expr(BinaryOperatorClass, ResTy,
           lhs->isTypeDependent() || rhs->isTypeDependent(),
           lhs->isValueDependent() || rhs->isValueDependent()),
      Opc(opc), OpLoc(opLoc) {
    SubExprs[LHS] = lhs;
    SubExprs[RHS] = rhs;
    assert(!isCompoundAssignmentOp() &&
           "Use ArithAssignBinaryOperator for compound assignments");
  }

  /// \brief Construct an empty binary operator.
  explicit BinaryOperator(EmptyShell Empty)
    : Expr(BinaryOperatorClass, Empty), Opc(Comma) { }

  SourceLocation getOperatorLoc() const { return OpLoc; }
  void setOperatorLoc(SourceLocation L) { OpLoc = L; }

  Opcode getOpcode() const { return Opc; }
  void setOpcode(Opcode O) { Opc = O; }

  Expr *getLHS() const { return cast<Expr>(SubExprs[LHS]); }
  void setLHS(Expr *E) { SubExprs[LHS] = E; }
  Expr *getRHS() const { return cast<Expr>(SubExprs[RHS]); }
  void setRHS(Expr *E) { SubExprs[RHS] = E; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(getLHS()->getLocStart(), getRHS()->getLocEnd());
  }

  /// getOpcodeStr - Turn an Opcode enum value into the punctuation char it
  /// corresponds to, e.g. "<<=".
  static const char *getOpcodeStr(Opcode Op);

  /// \brief Retrieve the binary opcode that corresponds to the given
  /// overloaded operator.
  static Opcode getOverloadedOpcode(OverloadedOperatorKind OO);

  /// \brief Retrieve the overloaded operator kind that corresponds to
  /// the given binary opcode.
  static OverloadedOperatorKind getOverloadedOperator(Opcode Opc);

  /// predicates to categorize the respective opcodes.
  bool isMultiplicativeOp() const { return Opc >= Mul && Opc <= Rem; }
  bool isAdditiveOp() const { return Opc == Add || Opc == Sub; }
  bool isShiftOp() const { return Opc == Shl || Opc == Shr; }
  bool isBitwiseOp() const { return Opc >= And && Opc <= Or; }

  static bool isRelationalOp(Opcode Opc) { return Opc >= LT && Opc <= GE; }
  bool isRelationalOp() const { return isRelationalOp(Opc); }

  static bool isEqualityOp(Opcode Opc) { return Opc == EQ || Opc == NE; }
  bool isEqualityOp() const { return isEqualityOp(Opc); }

  static bool isLogicalOp(Opcode Opc) { return Opc == LAnd || Opc == LOr; }
  bool isLogicalOp() const { return isLogicalOp(Opc); }

  bool isAssignmentOp() const { return Opc >= Assign && Opc <= OrAssign; }
  bool isCompoundAssignmentOp() const { return Opc > Assign && Opc <= OrAssign;}
  bool isShiftAssignOp() const { return Opc == ShlAssign || Opc == ShrAssign; }

  static bool classof(const Stmt *S) {
    return S->getStmtClass() == BinaryOperatorClass ||
           S->getStmtClass() == CompoundAssignOperatorClass;
  }
  static bool classof(const BinaryOperator *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();

protected:
  BinaryOperator(Expr *lhs, Expr *rhs, Opcode opc, QualType ResTy,
                 SourceLocation oploc, bool dead)
    : Expr(CompoundAssignOperatorClass, ResTy), Opc(opc), OpLoc(oploc) {
    SubExprs[LHS] = lhs;
    SubExprs[RHS] = rhs;
  }

  BinaryOperator(StmtClass SC, EmptyShell Empty)
    : Expr(SC, Empty), Opc(MulAssign) { }
};

/// CompoundAssignOperator - For compound assignments (e.g. +=), we keep
/// track of the type the operation is performed in.  Due to the semantics of
/// these operators, the operands are promoted, the aritmetic performed, an
/// implicit conversion back to the result type done, then the assignment takes
/// place.  This captures the intermediate type which the computation is done
/// in.
class CompoundAssignOperator : public BinaryOperator {
  QualType ComputationLHSType;
  QualType ComputationResultType;
public:
  CompoundAssignOperator(Expr *lhs, Expr *rhs, Opcode opc,
                         QualType ResType, QualType CompLHSType,
                         QualType CompResultType,
                         SourceLocation OpLoc)
    : BinaryOperator(lhs, rhs, opc, ResType, OpLoc, true),
      ComputationLHSType(CompLHSType),
      ComputationResultType(CompResultType) {
    assert(isCompoundAssignmentOp() &&
           "Only should be used for compound assignments");
  }

  /// \brief Build an empty compound assignment operator expression.
  explicit CompoundAssignOperator(EmptyShell Empty)
    : BinaryOperator(CompoundAssignOperatorClass, Empty) { }

  // The two computation types are the type the LHS is converted
  // to for the computation and the type of the result; the two are
  // distinct in a few cases (specifically, int+=ptr and ptr-=ptr).
  QualType getComputationLHSType() const { return ComputationLHSType; }
  void setComputationLHSType(QualType T) { ComputationLHSType = T; }

  QualType getComputationResultType() const { return ComputationResultType; }
  void setComputationResultType(QualType T) { ComputationResultType = T; }

  static bool classof(const CompoundAssignOperator *) { return true; }
  static bool classof(const Stmt *S) {
    return S->getStmtClass() == CompoundAssignOperatorClass;
  }
};

/// ConditionalOperator - The ?: operator.  Note that LHS may be null when the
/// GNU "missing LHS" extension is in use.
///
class ConditionalOperator : public Expr {
  enum { COND, LHS, RHS, END_EXPR };
  Stmt* SubExprs[END_EXPR]; // Left/Middle/Right hand sides.
public:
  ConditionalOperator(Expr *cond, Expr *lhs, Expr *rhs, QualType t)
    : Expr(ConditionalOperatorClass, t,
           // FIXME: the type of the conditional operator doesn't
           // depend on the type of the conditional, but the standard
           // seems to imply that it could. File a bug!
           ((lhs && lhs->isTypeDependent()) || (rhs && rhs->isTypeDependent())),
           (cond->isValueDependent() ||
            (lhs && lhs->isValueDependent()) ||
            (rhs && rhs->isValueDependent()))) {
    SubExprs[COND] = cond;
    SubExprs[LHS] = lhs;
    SubExprs[RHS] = rhs;
  }

  /// \brief Build an empty conditional operator.
  explicit ConditionalOperator(EmptyShell Empty)
    : Expr(ConditionalOperatorClass, Empty) { }

  // getCond - Return the expression representing the condition for
  //  the ?: operator.
  Expr *getCond() const { return cast<Expr>(SubExprs[COND]); }
  void setCond(Expr *E) { SubExprs[COND] = E; }

  // getTrueExpr - Return the subexpression representing the value of the ?:
  //  expression if the condition evaluates to true.  In most cases this value
  //  will be the same as getLHS() except a GCC extension allows the left
  //  subexpression to be omitted, and instead of the condition be returned.
  //  e.g: x ?: y is shorthand for x ? x : y, except that the expression "x"
  //  is only evaluated once.
  Expr *getTrueExpr() const {
    return cast<Expr>(SubExprs[LHS] ? SubExprs[LHS] : SubExprs[COND]);
  }

  // getTrueExpr - Return the subexpression representing the value of the ?:
  // expression if the condition evaluates to false. This is the same as getRHS.
  Expr *getFalseExpr() const { return cast<Expr>(SubExprs[RHS]); }

  Expr *getLHS() const { return cast_or_null<Expr>(SubExprs[LHS]); }
  void setLHS(Expr *E) { SubExprs[LHS] = E; }

  Expr *getRHS() const { return cast<Expr>(SubExprs[RHS]); }
  void setRHS(Expr *E) { SubExprs[RHS] = E; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(getCond()->getLocStart(), getRHS()->getLocEnd());
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ConditionalOperatorClass;
  }
  static bool classof(const ConditionalOperator *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// AddrLabelExpr - The GNU address of label extension, representing &&label.
class AddrLabelExpr : public Expr {
  SourceLocation AmpAmpLoc, LabelLoc;
  LabelStmt *Label;
public:
  AddrLabelExpr(SourceLocation AALoc, SourceLocation LLoc, LabelStmt *L,
                QualType t)
    : Expr(AddrLabelExprClass, t), AmpAmpLoc(AALoc), LabelLoc(LLoc), Label(L) {}

  /// \brief Build an empty address of a label expression.
  explicit AddrLabelExpr(EmptyShell Empty)
    : Expr(AddrLabelExprClass, Empty) { }

  SourceLocation getAmpAmpLoc() const { return AmpAmpLoc; }
  void setAmpAmpLoc(SourceLocation L) { AmpAmpLoc = L; }
  SourceLocation getLabelLoc() const { return LabelLoc; }
  void setLabelLoc(SourceLocation L) { LabelLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(AmpAmpLoc, LabelLoc);
  }

  LabelStmt *getLabel() const { return Label; }
  void setLabel(LabelStmt *S) { Label = S; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == AddrLabelExprClass;
  }
  static bool classof(const AddrLabelExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// StmtExpr - This is the GNU Statement Expression extension: ({int X=4; X;}).
/// The StmtExpr contains a single CompoundStmt node, which it evaluates and
/// takes the value of the last subexpression.
class StmtExpr : public Expr {
  Stmt *SubStmt;
  SourceLocation LParenLoc, RParenLoc;
public:
  StmtExpr(CompoundStmt *substmt, QualType T,
           SourceLocation lp, SourceLocation rp) :
    Expr(StmtExprClass, T), SubStmt(substmt),  LParenLoc(lp), RParenLoc(rp) { }

  /// \brief Build an empty statement expression.
  explicit StmtExpr(EmptyShell Empty) : Expr(StmtExprClass, Empty) { }

  CompoundStmt *getSubStmt() { return cast<CompoundStmt>(SubStmt); }
  const CompoundStmt *getSubStmt() const { return cast<CompoundStmt>(SubStmt); }
  void setSubStmt(CompoundStmt *S) { SubStmt = S; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(LParenLoc, RParenLoc);
  }

  SourceLocation getLParenLoc() const { return LParenLoc; }
  void setLParenLoc(SourceLocation L) { LParenLoc = L; }
  SourceLocation getRParenLoc() const { return RParenLoc; }
  void setRParenLoc(SourceLocation L) { RParenLoc = L; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == StmtExprClass;
  }
  static bool classof(const StmtExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// TypesCompatibleExpr - GNU builtin-in function __builtin_type_compatible_p.
/// This AST node represents a function that returns 1 if two *types* (not
/// expressions) are compatible. The result of this built-in function can be
/// used in integer constant expressions.
class TypesCompatibleExpr : public Expr {
  QualType Type1;
  QualType Type2;
  SourceLocation BuiltinLoc, RParenLoc;
public:
  TypesCompatibleExpr(QualType ReturnType, SourceLocation BLoc,
                      QualType t1, QualType t2, SourceLocation RP) :
    Expr(TypesCompatibleExprClass, ReturnType), Type1(t1), Type2(t2),
    BuiltinLoc(BLoc), RParenLoc(RP) {}

  /// \brief Build an empty __builtin_type_compatible_p expression.
  explicit TypesCompatibleExpr(EmptyShell Empty)
    : Expr(TypesCompatibleExprClass, Empty) { }

  QualType getArgType1() const { return Type1; }
  void setArgType1(QualType T) { Type1 = T; }
  QualType getArgType2() const { return Type2; }
  void setArgType2(QualType T) { Type2 = T; }

  SourceLocation getBuiltinLoc() const { return BuiltinLoc; }
  void setBuiltinLoc(SourceLocation L) { BuiltinLoc = L; }

  SourceLocation getRParenLoc() const { return RParenLoc; }
  void setRParenLoc(SourceLocation L) { RParenLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(BuiltinLoc, RParenLoc);
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == TypesCompatibleExprClass;
  }
  static bool classof(const TypesCompatibleExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// ShuffleVectorExpr - clang-specific builtin-in function
/// __builtin_shufflevector.
/// This AST node represents a operator that does a constant
/// shuffle, similar to LLVM's shufflevector instruction. It takes
/// two vectors and a variable number of constant indices,
/// and returns the appropriately shuffled vector.
class ShuffleVectorExpr : public Expr {
  SourceLocation BuiltinLoc, RParenLoc;

  // SubExprs - the list of values passed to the __builtin_shufflevector
  // function. The first two are vectors, and the rest are constant
  // indices.  The number of values in this list is always
  // 2+the number of indices in the vector type.
  Stmt **SubExprs;
  unsigned NumExprs;

public:
  ShuffleVectorExpr(Expr **args, unsigned nexpr,
                    QualType Type, SourceLocation BLoc,
                    SourceLocation RP) :
    Expr(ShuffleVectorExprClass, Type), BuiltinLoc(BLoc),
    RParenLoc(RP), NumExprs(nexpr) {

    SubExprs = new Stmt*[nexpr];
    for (unsigned i = 0; i < nexpr; i++)
      SubExprs[i] = args[i];
  }

  /// \brief Build an empty vector-shuffle expression.
  explicit ShuffleVectorExpr(EmptyShell Empty)
    : Expr(ShuffleVectorExprClass, Empty), SubExprs(0) { }

  SourceLocation getBuiltinLoc() const { return BuiltinLoc; }
  void setBuiltinLoc(SourceLocation L) { BuiltinLoc = L; }

  SourceLocation getRParenLoc() const { return RParenLoc; }
  void setRParenLoc(SourceLocation L) { RParenLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(BuiltinLoc, RParenLoc);
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ShuffleVectorExprClass;
  }
  static bool classof(const ShuffleVectorExpr *) { return true; }

  ~ShuffleVectorExpr() {
    delete [] SubExprs;
  }

  /// getNumSubExprs - Return the size of the SubExprs array.  This includes the
  /// constant expression, the actual arguments passed in, and the function
  /// pointers.
  unsigned getNumSubExprs() const { return NumExprs; }

  /// getExpr - Return the Expr at the specified index.
  Expr *getExpr(unsigned Index) {
    assert((Index < NumExprs) && "Arg access out of range!");
    return cast<Expr>(SubExprs[Index]);
  }
  const Expr *getExpr(unsigned Index) const {
    assert((Index < NumExprs) && "Arg access out of range!");
    return cast<Expr>(SubExprs[Index]);
  }

  void setExprs(Expr ** Exprs, unsigned NumExprs);

  unsigned getShuffleMaskIdx(ASTContext &Ctx, unsigned N) {
    assert((N < NumExprs - 2) && "Shuffle idx out of range!");
    return getExpr(N+2)->EvaluateAsInt(Ctx).getZExtValue();
  }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// ChooseExpr - GNU builtin-in function __builtin_choose_expr.
/// This AST node is similar to the conditional operator (?:) in C, with
/// the following exceptions:
/// - the test expression must be a integer constant expression.
/// - the expression returned acts like the chosen subexpression in every
///   visible way: the type is the same as that of the chosen subexpression,
///   and all predicates (whether it's an l-value, whether it's an integer
///   constant expression, etc.) return the same result as for the chosen
///   sub-expression.
class ChooseExpr : public Expr {
  enum { COND, LHS, RHS, END_EXPR };
  Stmt* SubExprs[END_EXPR]; // Left/Middle/Right hand sides.
  SourceLocation BuiltinLoc, RParenLoc;
public:
  ChooseExpr(SourceLocation BLoc, Expr *cond, Expr *lhs, Expr *rhs, QualType t,
             SourceLocation RP)
    : Expr(ChooseExprClass, t),
      BuiltinLoc(BLoc), RParenLoc(RP) {
      SubExprs[COND] = cond;
      SubExprs[LHS] = lhs;
      SubExprs[RHS] = rhs;
    }

  /// \brief Build an empty __builtin_choose_expr.
  explicit ChooseExpr(EmptyShell Empty) : Expr(ChooseExprClass, Empty) { }

  /// isConditionTrue - Return whether the condition is true (i.e. not
  /// equal to zero).
  bool isConditionTrue(ASTContext &C) const;

  /// getChosenSubExpr - Return the subexpression chosen according to the
  /// condition.
  Expr *getChosenSubExpr(ASTContext &C) const {
    return isConditionTrue(C) ? getLHS() : getRHS();
  }

  Expr *getCond() const { return cast<Expr>(SubExprs[COND]); }
  void setCond(Expr *E) { SubExprs[COND] = E; }
  Expr *getLHS() const { return cast<Expr>(SubExprs[LHS]); }
  void setLHS(Expr *E) { SubExprs[LHS] = E; }
  Expr *getRHS() const { return cast<Expr>(SubExprs[RHS]); }
  void setRHS(Expr *E) { SubExprs[RHS] = E; }

  SourceLocation getBuiltinLoc() const { return BuiltinLoc; }
  void setBuiltinLoc(SourceLocation L) { BuiltinLoc = L; }

  SourceLocation getRParenLoc() const { return RParenLoc; }
  void setRParenLoc(SourceLocation L) { RParenLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(BuiltinLoc, RParenLoc);
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ChooseExprClass;
  }
  static bool classof(const ChooseExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// GNUNullExpr - Implements the GNU __null extension, which is a name
/// for a null pointer constant that has integral type (e.g., int or
/// long) and is the same size and alignment as a pointer. The __null
/// extension is typically only used by system headers, which define
/// NULL as __null in C++ rather than using 0 (which is an integer
/// that may not match the size of a pointer).
class GNUNullExpr : public Expr {
  /// TokenLoc - The location of the __null keyword.
  SourceLocation TokenLoc;

public:
  GNUNullExpr(QualType Ty, SourceLocation Loc)
    : Expr(GNUNullExprClass, Ty), TokenLoc(Loc) { }

  /// \brief Build an empty GNU __null expression.
  explicit GNUNullExpr(EmptyShell Empty) : Expr(GNUNullExprClass, Empty) { }

  /// getTokenLocation - The location of the __null token.
  SourceLocation getTokenLocation() const { return TokenLoc; }
  void setTokenLocation(SourceLocation L) { TokenLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(TokenLoc);
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == GNUNullExprClass;
  }
  static bool classof(const GNUNullExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// VAArgExpr, used for the builtin function __builtin_va_start.
class VAArgExpr : public Expr {
  Stmt *Val;
  SourceLocation BuiltinLoc, RParenLoc;
public:
  VAArgExpr(SourceLocation BLoc, Expr* e, QualType t, SourceLocation RPLoc)
    : Expr(VAArgExprClass, t),
      Val(e),
      BuiltinLoc(BLoc),
      RParenLoc(RPLoc) { }

  /// \brief Create an empty __builtin_va_start expression.
  explicit VAArgExpr(EmptyShell Empty) : Expr(VAArgExprClass, Empty) { }

  const Expr *getSubExpr() const { return cast<Expr>(Val); }
  Expr *getSubExpr() { return cast<Expr>(Val); }
  void setSubExpr(Expr *E) { Val = E; }

  SourceLocation getBuiltinLoc() const { return BuiltinLoc; }
  void setBuiltinLoc(SourceLocation L) { BuiltinLoc = L; }

  SourceLocation getRParenLoc() const { return RParenLoc; }
  void setRParenLoc(SourceLocation L) { RParenLoc = L; }

  virtual SourceRange getSourceRange() const {
    return SourceRange(BuiltinLoc, RParenLoc);
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == VAArgExprClass;
  }
  static bool classof(const VAArgExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// @brief Describes an C or C++ initializer list.
///
/// InitListExpr describes an initializer list, which can be used to
/// initialize objects of different types, including
/// struct/class/union types, arrays, and vectors. For example:
///
/// @code
/// struct foo x = { 1, { 2, 3 } };
/// @endcode
///
/// Prior to semantic analysis, an initializer list will represent the
/// initializer list as written by the user, but will have the
/// placeholder type "void". This initializer list is called the
/// syntactic form of the initializer, and may contain C99 designated
/// initializers (represented as DesignatedInitExprs), initializations
/// of subobject members without explicit braces, and so on. Clients
/// interested in the original syntax of the initializer list should
/// use the syntactic form of the initializer list.
///
/// After semantic analysis, the initializer list will represent the
/// semantic form of the initializer, where the initializations of all
/// subobjects are made explicit with nested InitListExpr nodes and
/// C99 designators have been eliminated by placing the designated
/// initializations into the subobject they initialize. Additionally,
/// any "holes" in the initialization, where no initializer has been
/// specified for a particular subobject, will be replaced with
/// implicitly-generated ImplicitValueInitExpr expressions that
/// value-initialize the subobjects. Note, however, that the
/// initializer lists may still have fewer initializers than there are
/// elements to initialize within the object.
///
/// Given the semantic form of the initializer list, one can retrieve
/// the original syntactic form of that initializer list (if it
/// exists) using getSyntacticForm(). Since many initializer lists
/// have the same syntactic and semantic forms, getSyntacticForm() may
/// return NULL, indicating that the current initializer list also
/// serves as its syntactic form.
class InitListExpr : public Expr {
  std::vector<Stmt *> InitExprs;
  SourceLocation LBraceLoc, RBraceLoc;

  /// Contains the initializer list that describes the syntactic form
  /// written in the source code.
  InitListExpr *SyntacticForm;

  /// If this initializer list initializes a union, specifies which
  /// field within the union will be initialized.
  FieldDecl *UnionFieldInit;

  /// Whether this initializer list originally had a GNU array-range
  /// designator in it. This is a temporary marker used by CodeGen.
  bool HadArrayRangeDesignator;

public:
  InitListExpr(SourceLocation lbraceloc, Expr **initexprs, unsigned numinits,
               SourceLocation rbraceloc);

  /// \brief Build an empty initializer list.
  explicit InitListExpr(EmptyShell Empty) : Expr(InitListExprClass, Empty) { }

  unsigned getNumInits() const { return InitExprs.size(); }

  const Expr* getInit(unsigned Init) const {
    assert(Init < getNumInits() && "Initializer access out of range!");
    return cast_or_null<Expr>(InitExprs[Init]);
  }

  Expr* getInit(unsigned Init) {
    assert(Init < getNumInits() && "Initializer access out of range!");
    return cast_or_null<Expr>(InitExprs[Init]);
  }

  void setInit(unsigned Init, Expr *expr) {
    assert(Init < getNumInits() && "Initializer access out of range!");
    InitExprs[Init] = expr;
  }

  /// \brief Reserve space for some number of initializers.
  void reserveInits(unsigned NumInits);

  /// @brief Specify the number of initializers
  ///
  /// If there are more than @p NumInits initializers, the remaining
  /// initializers will be destroyed. If there are fewer than @p
  /// NumInits initializers, NULL expressions will be added for the
  /// unknown initializers.
  void resizeInits(ASTContext &Context, unsigned NumInits);

  /// @brief Updates the initializer at index @p Init with the new
  /// expression @p expr, and returns the old expression at that
  /// location.
  ///
  /// When @p Init is out of range for this initializer list, the
  /// initializer list will be extended with NULL expressions to
  /// accomodate the new entry.
  Expr *updateInit(unsigned Init, Expr *expr);

  /// \brief If this initializes a union, specifies which field in the
  /// union to initialize.
  ///
  /// Typically, this field is the first named field within the
  /// union. However, a designated initializer can specify the
  /// initialization of a different field within the union.
  FieldDecl *getInitializedFieldInUnion() { return UnionFieldInit; }
  void setInitializedFieldInUnion(FieldDecl *FD) { UnionFieldInit = FD; }

  // Explicit InitListExpr's originate from source code (and have valid source
  // locations). Implicit InitListExpr's are created by the semantic analyzer.
  bool isExplicit() {
    return LBraceLoc.isValid() && RBraceLoc.isValid();
  }

  SourceLocation getLBraceLoc() const { return LBraceLoc; }
  void setLBraceLoc(SourceLocation Loc) { LBraceLoc = Loc; }
  SourceLocation getRBraceLoc() const { return RBraceLoc; }
  void setRBraceLoc(SourceLocation Loc) { RBraceLoc = Loc; }

  /// @brief Retrieve the initializer list that describes the
  /// syntactic form of the initializer.
  ///
  ///
  InitListExpr *getSyntacticForm() const { return SyntacticForm; }
  void setSyntacticForm(InitListExpr *Init) { SyntacticForm = Init; }

  bool hadArrayRangeDesignator() const { return HadArrayRangeDesignator; }
  void sawArrayRangeDesignator(bool ARD = true) {
    HadArrayRangeDesignator = ARD;
  }

  virtual SourceRange getSourceRange() const {
    return SourceRange(LBraceLoc, RBraceLoc);
  }
  static bool classof(const Stmt *T) {
    return T->getStmtClass() == InitListExprClass;
  }
  static bool classof(const InitListExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();

  typedef std::vector<Stmt *>::iterator iterator;
  typedef std::vector<Stmt *>::reverse_iterator reverse_iterator;

  iterator begin() { return InitExprs.begin(); }
  iterator end() { return InitExprs.end(); }
  reverse_iterator rbegin() { return InitExprs.rbegin(); }
  reverse_iterator rend() { return InitExprs.rend(); }
};

/// @brief Represents a C99 designated initializer expression.
///
/// A designated initializer expression (C99 6.7.8) contains one or
/// more designators (which can be field designators, array
/// designators, or GNU array-range designators) followed by an
/// expression that initializes the field or element(s) that the
/// designators refer to. For example, given:
///
/// @code
/// struct point {
///   double x;
///   double y;
/// };
/// struct point ptarray[10] = { [2].y = 1.0, [2].x = 2.0, [0].x = 1.0 };
/// @endcode
///
/// The InitListExpr contains three DesignatedInitExprs, the first of
/// which covers @c [2].y=1.0. This DesignatedInitExpr will have two
/// designators, one array designator for @c [2] followed by one field
/// designator for @c .y. The initalization expression will be 1.0.
class DesignatedInitExpr : public Expr {
public:
  /// \brief Forward declaration of the Designator class.
  class Designator;

private:
  /// The location of the '=' or ':' prior to the actual initializer
  /// expression.
  SourceLocation EqualOrColonLoc;

  /// Whether this designated initializer used the GNU deprecated
  /// syntax rather than the C99 '=' syntax.
  bool GNUSyntax : 1;

  /// The number of designators in this initializer expression.
  unsigned NumDesignators : 15;

  /// \brief The designators in this designated initialization
  /// expression.
  Designator *Designators;

  /// The number of subexpressions of this initializer expression,
  /// which contains both the initializer and any additional
  /// expressions used by array and array-range designators.
  unsigned NumSubExprs : 16;


  DesignatedInitExpr(QualType Ty, unsigned NumDesignators,
                     const Designator *Designators,
                     SourceLocation EqualOrColonLoc, bool GNUSyntax,
                     unsigned NumSubExprs);

  explicit DesignatedInitExpr(unsigned NumSubExprs)
    : Expr(DesignatedInitExprClass, EmptyShell()),
      NumDesignators(0), Designators(0), NumSubExprs(NumSubExprs) { }

public:
  /// A field designator, e.g., ".x".
  struct FieldDesignator {
    /// Refers to the field that is being initialized. The low bit
    /// of this field determines whether this is actually a pointer
    /// to an IdentifierInfo (if 1) or a FieldDecl (if 0). When
    /// initially constructed, a field designator will store an
    /// IdentifierInfo*. After semantic analysis has resolved that
    /// name, the field designator will instead store a FieldDecl*.
    uintptr_t NameOrField;

    /// The location of the '.' in the designated initializer.
    unsigned DotLoc;

    /// The location of the field name in the designated initializer.
    unsigned FieldLoc;
  };

  /// An array or GNU array-range designator, e.g., "[9]" or "[10..15]".
  struct ArrayOrRangeDesignator {
    /// Location of the first index expression within the designated
    /// initializer expression's list of subexpressions.
    unsigned Index;
    /// The location of the '[' starting the array range designator.
    unsigned LBracketLoc;
    /// The location of the ellipsis separating the start and end
    /// indices. Only valid for GNU array-range designators.
    unsigned EllipsisLoc;
    /// The location of the ']' terminating the array range designator.
    unsigned RBracketLoc;
  };

  /// @brief Represents a single C99 designator.
  ///
  /// @todo This class is infuriatingly similar to clang::Designator,
  /// but minor differences (storing indices vs. storing pointers)
  /// keep us from reusing it. Try harder, later, to rectify these
  /// differences.
  class Designator {
    /// @brief The kind of designator this describes.
    enum {
      FieldDesignator,
      ArrayDesignator,
      ArrayRangeDesignator
    } Kind;

    union {
      /// A field designator, e.g., ".x".
      struct FieldDesignator Field;
      /// An array or GNU array-range designator, e.g., "[9]" or "[10..15]".
      struct ArrayOrRangeDesignator ArrayOrRange;
    };
    friend class DesignatedInitExpr;

  public:
    Designator() {}

    /// @brief Initializes a field designator.
    Designator(const IdentifierInfo *FieldName, SourceLocation DotLoc,
               SourceLocation FieldLoc)
      : Kind(FieldDesignator) {
      Field.NameOrField = reinterpret_cast<uintptr_t>(FieldName) | 0x01;
      Field.DotLoc = DotLoc.getRawEncoding();
      Field.FieldLoc = FieldLoc.getRawEncoding();
    }

    /// @brief Initializes an array designator.
    Designator(unsigned Index, SourceLocation LBracketLoc,
               SourceLocation RBracketLoc)
      : Kind(ArrayDesignator) {
      ArrayOrRange.Index = Index;
      ArrayOrRange.LBracketLoc = LBracketLoc.getRawEncoding();
      ArrayOrRange.EllipsisLoc = SourceLocation().getRawEncoding();
      ArrayOrRange.RBracketLoc = RBracketLoc.getRawEncoding();
    }

    /// @brief Initializes a GNU array-range designator.
    Designator(unsigned Index, SourceLocation LBracketLoc,
               SourceLocation EllipsisLoc, SourceLocation RBracketLoc)
      : Kind(ArrayRangeDesignator) {
      ArrayOrRange.Index = Index;
      ArrayOrRange.LBracketLoc = LBracketLoc.getRawEncoding();
      ArrayOrRange.EllipsisLoc = EllipsisLoc.getRawEncoding();
      ArrayOrRange.RBracketLoc = RBracketLoc.getRawEncoding();
    }

    bool isFieldDesignator() const { return Kind == FieldDesignator; }
    bool isArrayDesignator() const { return Kind == ArrayDesignator; }
    bool isArrayRangeDesignator() const { return Kind == ArrayRangeDesignator; }

    IdentifierInfo * getFieldName();

    FieldDecl *getField() {
      assert(Kind == FieldDesignator && "Only valid on a field designator");
      if (Field.NameOrField & 0x01)
        return 0;
      else
        return reinterpret_cast<FieldDecl *>(Field.NameOrField);
    }

    void setField(FieldDecl *FD) {
      assert(Kind == FieldDesignator && "Only valid on a field designator");
      Field.NameOrField = reinterpret_cast<uintptr_t>(FD);
    }

    SourceLocation getDotLoc() const {
      assert(Kind == FieldDesignator && "Only valid on a field designator");
      return SourceLocation::getFromRawEncoding(Field.DotLoc);
    }

    SourceLocation getFieldLoc() const {
      assert(Kind == FieldDesignator && "Only valid on a field designator");
      return SourceLocation::getFromRawEncoding(Field.FieldLoc);
    }

    SourceLocation getLBracketLoc() const {
      assert((Kind == ArrayDesignator || Kind == ArrayRangeDesignator) &&
             "Only valid on an array or array-range designator");
      return SourceLocation::getFromRawEncoding(ArrayOrRange.LBracketLoc);
    }

    SourceLocation getRBracketLoc() const {
      assert((Kind == ArrayDesignator || Kind == ArrayRangeDesignator) &&
             "Only valid on an array or array-range designator");
      return SourceLocation::getFromRawEncoding(ArrayOrRange.RBracketLoc);
    }

    SourceLocation getEllipsisLoc() const {
      assert(Kind == ArrayRangeDesignator &&
             "Only valid on an array-range designator");
      return SourceLocation::getFromRawEncoding(ArrayOrRange.EllipsisLoc);
    }

    unsigned getFirstExprIndex() const {
      assert((Kind == ArrayDesignator || Kind == ArrayRangeDesignator) &&
             "Only valid on an array or array-range designator");
      return ArrayOrRange.Index;
    }

    SourceLocation getStartLocation() const {
      if (Kind == FieldDesignator)
        return getDotLoc().isInvalid()? getFieldLoc() : getDotLoc();
      else
        return getLBracketLoc();
    }
  };

  static DesignatedInitExpr *Create(ASTContext &C, Designator *Designators,
                                    unsigned NumDesignators,
                                    Expr **IndexExprs, unsigned NumIndexExprs,
                                    SourceLocation EqualOrColonLoc,
                                    bool GNUSyntax, Expr *Init);

  static DesignatedInitExpr *CreateEmpty(ASTContext &C, unsigned NumIndexExprs);

  /// @brief Returns the number of designators in this initializer.
  unsigned size() const { return NumDesignators; }

  // Iterator access to the designators.
  typedef Designator* designators_iterator;
  designators_iterator designators_begin() { return Designators; }
  designators_iterator designators_end() {
    return Designators + NumDesignators;
  }

  Designator *getDesignator(unsigned Idx) { return &designators_begin()[Idx]; }

  void setDesignators(const Designator *Desigs, unsigned NumDesigs);

  Expr *getArrayIndex(const Designator& D);
  Expr *getArrayRangeStart(const Designator& D);
  Expr *getArrayRangeEnd(const Designator& D);

  /// @brief Retrieve the location of the '=' that precedes the
  /// initializer value itself, if present.
  SourceLocation getEqualOrColonLoc() const { return EqualOrColonLoc; }
  void setEqualOrColonLoc(SourceLocation L) { EqualOrColonLoc = L; }

  /// @brief Determines whether this designated initializer used the
  /// deprecated GNU syntax for designated initializers.
  bool usesGNUSyntax() const { return GNUSyntax; }
  void setGNUSyntax(bool GNU) { GNUSyntax = GNU; }

  /// @brief Retrieve the initializer value.
  Expr *getInit() const {
    return cast<Expr>(*const_cast<DesignatedInitExpr*>(this)->child_begin());
  }

  void setInit(Expr *init) {
    *child_begin() = init;
  }

  /// \brief Retrieve the total number of subexpressions in this
  /// designated initializer expression, including the actual
  /// initialized value and any expressions that occur within array
  /// and array-range designators.
  unsigned getNumSubExprs() const { return NumSubExprs; }

  Expr *getSubExpr(unsigned Idx) {
    assert(Idx < NumSubExprs && "Subscript out of range");
    char* Ptr = static_cast<char*>(static_cast<void *>(this));
    Ptr += sizeof(DesignatedInitExpr);
    return reinterpret_cast<Expr**>(reinterpret_cast<void**>(Ptr))[Idx];
  }

  void setSubExpr(unsigned Idx, Expr *E) {
    assert(Idx < NumSubExprs && "Subscript out of range");
    char* Ptr = static_cast<char*>(static_cast<void *>(this));
    Ptr += sizeof(DesignatedInitExpr);
    reinterpret_cast<Expr**>(reinterpret_cast<void**>(Ptr))[Idx] = E;
  }

  /// \brief Replaces the designator at index @p Idx with the series
  /// of designators in [First, Last).
  void ExpandDesignator(unsigned Idx, const Designator *First,
                        const Designator *Last);

  virtual SourceRange getSourceRange() const;

  virtual void Destroy(ASTContext &C);

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == DesignatedInitExprClass;
  }
  static bool classof(const DesignatedInitExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// \brief Represents an implicitly-generated value initialization of
/// an object of a given type.
///
/// Implicit value initializations occur within semantic initializer
/// list expressions (InitListExpr) as placeholders for subobject
/// initializations not explicitly specified by the user.
///
/// \see InitListExpr
class ImplicitValueInitExpr : public Expr {
public:
  explicit ImplicitValueInitExpr(QualType ty)
    : Expr(ImplicitValueInitExprClass, ty) { }

  /// \brief Construct an empty implicit value initialization.
  explicit ImplicitValueInitExpr(EmptyShell Empty)
    : Expr(ImplicitValueInitExprClass, Empty) { }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ImplicitValueInitExprClass;
  }
  static bool classof(const ImplicitValueInitExpr *) { return true; }

  virtual SourceRange getSourceRange() const {
    return SourceRange();
  }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

//===----------------------------------------------------------------------===//
// Clang Extensions
//===----------------------------------------------------------------------===//


/// ExtVectorElementExpr - This represents access to specific elements of a
/// vector, and may occur on the left hand side or right hand side.  For example
/// the following is legal:  "V.xy = V.zw" if V is a 4 element extended vector.
///
/// Note that the base may have either vector or pointer to vector type, just
/// like a struct field reference.
///
class ExtVectorElementExpr : public Expr {
  Stmt *Base;
  IdentifierInfo *Accessor;
  SourceLocation AccessorLoc;
public:
  ExtVectorElementExpr(QualType ty, Expr *base, IdentifierInfo &accessor,
                       SourceLocation loc)
    : Expr(ExtVectorElementExprClass, ty),
      Base(base), Accessor(&accessor), AccessorLoc(loc) {}

  /// \brief Build an empty vector element expression.
  explicit ExtVectorElementExpr(EmptyShell Empty)
    : Expr(ExtVectorElementExprClass, Empty) { }

  const Expr *getBase() const { return cast<Expr>(Base); }
  Expr *getBase() { return cast<Expr>(Base); }
  void setBase(Expr *E) { Base = E; }

  IdentifierInfo &getAccessor() const { return *Accessor; }
  void setAccessor(IdentifierInfo *II) { Accessor = II; }

  SourceLocation getAccessorLoc() const { return AccessorLoc; }
  void setAccessorLoc(SourceLocation L) { AccessorLoc = L; }

  /// getNumElements - Get the number of components being selected.
  unsigned getNumElements() const;

  /// containsDuplicateElements - Return true if any element access is
  /// repeated.
  bool containsDuplicateElements() const;

  /// getEncodedElementAccess - Encode the elements accessed into an llvm
  /// aggregate Constant of ConstantInt(s).
  void getEncodedElementAccess(llvm::SmallVectorImpl<unsigned> &Elts) const;

  virtual SourceRange getSourceRange() const {
    return SourceRange(getBase()->getLocStart(), AccessorLoc);
  }

  /// isArrow - Return true if the base expression is a pointer to vector,
  /// return false if the base expression is a vector.
  bool isArrow() const;

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == ExtVectorElementExprClass;
  }
  static bool classof(const ExtVectorElementExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};


/// BlockExpr - Adaptor class for mixing a BlockDecl with expressions.
/// ^{ statement-body }   or   ^(int arg1, float arg2){ statement-body }
class BlockExpr : public Expr {
protected:
  BlockDecl *TheBlock;
  bool HasBlockDeclRefExprs;
public:
  BlockExpr(BlockDecl *BD, QualType ty, bool hasBlockDeclRefExprs)
    : Expr(BlockExprClass, ty),
      TheBlock(BD), HasBlockDeclRefExprs(hasBlockDeclRefExprs) {}

  /// \brief Build an empty block expression.
  explicit BlockExpr(EmptyShell Empty) : Expr(BlockExprClass, Empty) { }

  const BlockDecl *getBlockDecl() const { return TheBlock; }
  BlockDecl *getBlockDecl() { return TheBlock; }
  void setBlockDecl(BlockDecl *BD) { TheBlock = BD; }

  // Convenience functions for probing the underlying BlockDecl.
  SourceLocation getCaretLocation() const;
  const Stmt *getBody() const;
  Stmt *getBody();

  const Stmt *getBody(ASTContext &C) const { return getBody(); }
  Stmt *getBody(ASTContext &C) { return getBody(); }

  virtual SourceRange getSourceRange() const {
    return SourceRange(getCaretLocation(), getBody()->getLocEnd());
  }

  /// getFunctionType - Return the underlying function type for this block.
  const FunctionType *getFunctionType() const;

  /// hasBlockDeclRefExprs - Return true iff the block has BlockDeclRefExpr
  /// inside of the block that reference values outside the block.
  bool hasBlockDeclRefExprs() const { return HasBlockDeclRefExprs; }
  void setHasBlockDeclRefExprs(bool BDRE) { HasBlockDeclRefExprs = BDRE; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == BlockExprClass;
  }
  static bool classof(const BlockExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

/// BlockDeclRefExpr - A reference to a declared variable, function,
/// enum, etc.
class BlockDeclRefExpr : public Expr {
  ValueDecl *D;
  SourceLocation Loc;
  bool IsByRef;
public:
  BlockDeclRefExpr(ValueDecl *d, QualType t, SourceLocation l, bool ByRef) :
       Expr(BlockDeclRefExprClass, t), D(d), Loc(l), IsByRef(ByRef) {}

  // \brief Build an empty reference to a declared variable in a
  // block.
  explicit BlockDeclRefExpr(EmptyShell Empty)
    : Expr(BlockDeclRefExprClass, Empty) { }

  ValueDecl *getDecl() { return D; }
  const ValueDecl *getDecl() const { return D; }
  void setDecl(ValueDecl *VD) { D = VD; }

  SourceLocation getLocation() const { return Loc; }
  void setLocation(SourceLocation L) { Loc = L; }

  virtual SourceRange getSourceRange() const { return SourceRange(Loc); }

  bool isByRef() const { return IsByRef; }
  void setByRef(bool BR) { IsByRef = BR; }

  static bool classof(const Stmt *T) {
    return T->getStmtClass() == BlockDeclRefExprClass;
  }
  static bool classof(const BlockDeclRefExpr *) { return true; }

  // Iterators
  virtual child_iterator child_begin();
  virtual child_iterator child_end();
};

}  // end namespace clang

#endif