text: //===- Type.h - C Language Family Type Representation -----------*- C++ -*-===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  /// \file
  /// C Language Family Type Representation
  ///
  /// This file defines the clang::Type interface and subclasses, used to
  /// represent types for languages in the C family.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_AST_TYPE_H
  #define LLVM_CLANG_AST_TYPE_H
  
  #include "clang/AST/NestedNameSpecifier.h"
  #include "clang/AST/TemplateName.h"
  #include "clang/Basic/AddressSpaces.h"
  #include "clang/Basic/AttrKinds.h"
  #include "clang/Basic/Diagnostic.h"
  #include "clang/Basic/ExceptionSpecificationType.h"
  #include "clang/Basic/LLVM.h"
  #include "clang/Basic/Linkage.h"
  #include "clang/Basic/PartialDiagnostic.h"
  #include "clang/Basic/SourceLocation.h"
  #include "clang/Basic/Specifiers.h"
  #include "clang/Basic/Visibility.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/APSInt.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/FoldingSet.h"
  #include "llvm/ADT/None.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/ADT/PointerIntPair.h"
  #include "llvm/ADT/PointerUnion.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/ADT/Twine.h"
  #include "llvm/ADT/iterator_range.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/PointerLikeTypeTraits.h"
  #include "llvm/Support/type_traits.h"
  #include "llvm/Support/TrailingObjects.h"
  #include <cassert>
  #include <cstddef>
  #include <cstdint>
  #include <cstring>
  #include <string>
  #include <type_traits>
  #include <utility>
  
  namespace clang {
  
  class ExtQuals;
  class QualType;
  class TagDecl;
  class Type;
  
  enum {
    TypeAlignmentInBits = 4,
    TypeAlignment = 1 << TypeAlignmentInBits
  };
  
  } // namespace clang
  
  namespace llvm {
  
    template <typename T>
    struct PointerLikeTypeTraits;
    template<>
    struct PointerLikeTypeTraits< ::clang::Type*> {
      static inline void *getAsVoidPointer(::clang::Type *P) { return P; }
  
      static inline ::clang::Type *getFromVoidPointer(void *P) {
        return static_cast< ::clang::Type*>(P);
      }
  
      enum { NumLowBitsAvailable = clang::TypeAlignmentInBits };
    };
  
    template<>
    struct PointerLikeTypeTraits< ::clang::ExtQuals*> {
      static inline void *getAsVoidPointer(::clang::ExtQuals *P) { return P; }
  
      static inline ::clang::ExtQuals *getFromVoidPointer(void *P) {
        return static_cast< ::clang::ExtQuals*>(P);
      }
  
      enum { NumLowBitsAvailable = clang::TypeAlignmentInBits };
    };
  
  } // namespace llvm
  
  namespace clang {
  
  class ASTContext;
  template <typename> class CanQual;
  class CXXRecordDecl;
  class DeclContext;
  class EnumDecl;
  class Expr;
  class ExtQualsTypeCommonBase;
  class FunctionDecl;
  class IdentifierInfo;
  class NamedDecl;
  class ObjCInterfaceDecl;
  class ObjCProtocolDecl;
  class ObjCTypeParamDecl;
  struct PrintingPolicy;
  class RecordDecl;
  class Stmt;
  class TagDecl;
  class TemplateArgument;
  class TemplateArgumentListInfo;
  class TemplateArgumentLoc;
  class TemplateTypeParmDecl;
  class TypedefNameDecl;
  class UnresolvedUsingTypenameDecl;
  
  using CanQualType = CanQual<Type>;
  
  // Provide forward declarations for all of the *Type classes.
  #define TYPE(Class, Base) class Class##Type;
  #include "clang/AST/TypeNodes.def"
  
  /// The collection of all-type qualifiers we support.
  /// Clang supports five independent qualifiers:
  /// * C99: const, volatile, and restrict
  /// * MS: __unaligned
  /// * Embedded C (TR18037): address spaces
  /// * Objective C: the GC attributes (none, weak, or strong)
  class Qualifiers {
  public:
    enum TQ { // NOTE: These flags must be kept in sync with DeclSpec::TQ.
      Const    = 0x1,
      Restrict = 0x2,
      Volatile = 0x4,
      CVRMask = Const | Volatile | Restrict
    };
  
    enum GC {
      GCNone = 0,
      Weak,
      Strong
    };
  
    enum ObjCLifetime {
      /// There is no lifetime qualification on this type.
      OCL_None,
  
      /// This object can be modified without requiring retains or
      /// releases.
      OCL_ExplicitNone,
  
      /// Assigning into this object requires the old value to be
      /// released and the new value to be retained.  The timing of the
      /// release of the old value is inexact: it may be moved to
      /// immediately after the last known point where the value is
      /// live.
      OCL_Strong,
  
      /// Reading or writing from this object requires a barrier call.
      OCL_Weak,
  
      /// Assigning into this object requires a lifetime extension.
      OCL_Autoreleasing
    };
  
    enum {
      /// The maximum supported address space number.
      /// 23 bits should be enough for anyone.
      MaxAddressSpace = 0x7fffffu,
  
      /// The width of the "fast" qualifier mask.
      FastWidth = 3,
  
      /// The fast qualifier mask.
      FastMask = (1 << FastWidth) - 1
    };
  
    /// Returns the common set of qualifiers while removing them from
    /// the given sets.
    static Qualifiers removeCommonQualifiers(Qualifiers &L, Qualifiers &R) {
      // If both are only CVR-qualified, bit operations are sufficient.
      if (!(L.Mask & ~CVRMask) && !(R.Mask & ~CVRMask)) {
        Qualifiers Q;
        Q.Mask = L.Mask & R.Mask;
        L.Mask &= ~Q.Mask;
        R.Mask &= ~Q.Mask;
        return Q;
      }
  
      Qualifiers Q;
      unsigned CommonCRV = L.getCVRQualifiers() & R.getCVRQualifiers();
      Q.addCVRQualifiers(CommonCRV);
      L.removeCVRQualifiers(CommonCRV);
      R.removeCVRQualifiers(CommonCRV);
  
      if (L.getObjCGCAttr() == R.getObjCGCAttr()) {
        Q.setObjCGCAttr(L.getObjCGCAttr());
        L.removeObjCGCAttr();
        R.removeObjCGCAttr();
      }
  
      if (L.getObjCLifetime() == R.getObjCLifetime()) {
        Q.setObjCLifetime(L.getObjCLifetime());
        L.removeObjCLifetime();
        R.removeObjCLifetime();
      }
  
      if (L.getAddressSpace() == R.getAddressSpace()) {
        Q.setAddressSpace(L.getAddressSpace());
        L.removeAddressSpace();
        R.removeAddressSpace();
      }
      return Q;
    }
  
    static Qualifiers fromFastMask(unsigned Mask) {
      Qualifiers Qs;
      Qs.addFastQualifiers(Mask);
      return Qs;
    }
  
    static Qualifiers fromCVRMask(unsigned CVR) {
      Qualifiers Qs;
      Qs.addCVRQualifiers(CVR);
      return Qs;
    }
  
    static Qualifiers fromCVRUMask(unsigned CVRU) {
      Qualifiers Qs;
      Qs.addCVRUQualifiers(CVRU);
      return Qs;
    }
  
    // Deserialize qualifiers from an opaque representation.
    static Qualifiers fromOpaqueValue(unsigned opaque) {
      Qualifiers Qs;
      Qs.Mask = opaque;
      return Qs;
    }
  
    // Serialize these qualifiers into an opaque representation.
    unsigned getAsOpaqueValue() const {
      return Mask;
    }
  
    bool hasConst() const { return Mask & Const; }
    bool hasOnlyConst() const { return Mask == Const; }
    void removeConst() { Mask &= ~Const; }
    void addConst() { Mask |= Const; }
  
    bool hasVolatile() const { return Mask & Volatile; }
    bool hasOnlyVolatile() const { return Mask == Volatile; }
    void removeVolatile() { Mask &= ~Volatile; }
    void addVolatile() { Mask |= Volatile; }
  
    bool hasRestrict() const { return Mask & Restrict; }
    bool hasOnlyRestrict() const { return Mask == Restrict; }
    void removeRestrict() { Mask &= ~Restrict; }
    void addRestrict() { Mask |= Restrict; }
  
    bool hasCVRQualifiers() const { return getCVRQualifiers(); }
    unsigned getCVRQualifiers() const { return Mask & CVRMask; }
    unsigned getCVRUQualifiers() const { return Mask & (CVRMask | UMask); }
  
    void setCVRQualifiers(unsigned mask) {
      assert(!(mask & ~CVRMask) && "bitmask contains non-CVR bits");
      Mask = (Mask & ~CVRMask) | mask;
    }
    void removeCVRQualifiers(unsigned mask) {
      assert(!(mask & ~CVRMask) && "bitmask contains non-CVR bits");
      Mask &= ~mask;
    }
    void removeCVRQualifiers() {
      removeCVRQualifiers(CVRMask);
    }
    void addCVRQualifiers(unsigned mask) {
      assert(!(mask & ~CVRMask) && "bitmask contains non-CVR bits");
      Mask |= mask;
    }
    void addCVRUQualifiers(unsigned mask) {
      assert(!(mask & ~CVRMask & ~UMask) && "bitmask contains non-CVRU bits");
      Mask |= mask;
    }
  
    bool hasUnaligned() const { return Mask & UMask; }
    void setUnaligned(bool flag) {
      Mask = (Mask & ~UMask) | (flag ? UMask : 0);
    }
    void removeUnaligned() { Mask &= ~UMask; }
    void addUnaligned() { Mask |= UMask; }
  
    bool hasObjCGCAttr() const { return Mask & GCAttrMask; }
    GC getObjCGCAttr() const { return GC((Mask & GCAttrMask) >> GCAttrShift); }
    void setObjCGCAttr(GC type) {
      Mask = (Mask & ~GCAttrMask) | (type << GCAttrShift);
    }
    void removeObjCGCAttr() { setObjCGCAttr(GCNone); }
    void addObjCGCAttr(GC type) {
      assert(type);
      setObjCGCAttr(type);
    }
    Qualifiers withoutObjCGCAttr() const {
      Qualifiers qs = *this;
      qs.removeObjCGCAttr();
      return qs;
    }
    Qualifiers withoutObjCLifetime() const {
      Qualifiers qs = *this;
      qs.removeObjCLifetime();
      return qs;
    }
    Qualifiers withoutAddressSpace() const {
      Qualifiers qs = *this;
      qs.removeAddressSpace();
      return qs;
    }
  
    bool hasObjCLifetime() const { return Mask & LifetimeMask; }
    ObjCLifetime getObjCLifetime() const {
      return ObjCLifetime((Mask & LifetimeMask) >> LifetimeShift);
    }
    void setObjCLifetime(ObjCLifetime type) {
      Mask = (Mask & ~LifetimeMask) | (type << LifetimeShift);
    }
    void removeObjCLifetime() { setObjCLifetime(OCL_None); }
    void addObjCLifetime(ObjCLifetime type) {
      assert(type);
      assert(!hasObjCLifetime());
      Mask |= (type << LifetimeShift);
    }
  
    /// True if the lifetime is neither None or ExplicitNone.
    bool hasNonTrivialObjCLifetime() const {
      ObjCLifetime lifetime = getObjCLifetime();
      return (lifetime > OCL_ExplicitNone);
    }
  
    /// True if the lifetime is either strong or weak.
    bool hasStrongOrWeakObjCLifetime() const {
      ObjCLifetime lifetime = getObjCLifetime();
      return (lifetime == OCL_Strong || lifetime == OCL_Weak);
    }
  
    bool hasAddressSpace() const { return Mask & AddressSpaceMask; }
    LangAS getAddressSpace() const {
      return static_cast<LangAS>(Mask >> AddressSpaceShift);
    }
    bool hasTargetSpecificAddressSpace() const {
      return isTargetAddressSpace(getAddressSpace());
    }
    /// Get the address space attribute value to be printed by diagnostics.
    unsigned getAddressSpaceAttributePrintValue() const {
      auto Addr = getAddressSpace();
      // This function is not supposed to be used with language specific
      // address spaces. If that happens, the diagnostic message should consider
      // printing the QualType instead of the address space value.
      assert(Addr == LangAS::Default || hasTargetSpecificAddressSpace());
      if (Addr != LangAS::Default)
        return toTargetAddressSpace(Addr);
      // TODO: The diagnostic messages where Addr may be 0 should be fixed
      // since it cannot differentiate the situation where 0 denotes the default
      // address space or user specified __attribute__((address_space(0))).
      return 0;
    }
    void setAddressSpace(LangAS space) {
      assert((unsigned)space <= MaxAddressSpace);
      Mask = (Mask & ~AddressSpaceMask)
           | (((uint32_t) space) << AddressSpaceShift);
    }
    void removeAddressSpace() { setAddressSpace(LangAS::Default); }
    void addAddressSpace(LangAS space) {
      assert(space != LangAS::Default);
      setAddressSpace(space);
    }
  
    // Fast qualifiers are those that can be allocated directly
    // on a QualType object.
    bool hasFastQualifiers() const { return getFastQualifiers(); }
    unsigned getFastQualifiers() const { return Mask & FastMask; }
    void setFastQualifiers(unsigned mask) {
      assert(!(mask & ~FastMask) && "bitmask contains non-fast qualifier bits");
      Mask = (Mask & ~FastMask) | mask;
    }
    void removeFastQualifiers(unsigned mask) {
      assert(!(mask & ~FastMask) && "bitmask contains non-fast qualifier bits");
      Mask &= ~mask;
    }
    void removeFastQualifiers() {
      removeFastQualifiers(FastMask);
    }
    void addFastQualifiers(unsigned mask) {
      assert(!(mask & ~FastMask) && "bitmask contains non-fast qualifier bits");
      Mask |= mask;
    }
  
    /// Return true if the set contains any qualifiers which require an ExtQuals
    /// node to be allocated.
    bool hasNonFastQualifiers() const { return Mask & ~FastMask; }
    Qualifiers getNonFastQualifiers() const {
      Qualifiers Quals = *this;
      Quals.setFastQualifiers(0);
      return Quals;
    }
  
    /// Return true if the set contains any qualifiers.
    bool hasQualifiers() const { return Mask; }
    bool empty() const { return !Mask; }
  
    /// Add the qualifiers from the given set to this set.
    void addQualifiers(Qualifiers Q) {
      // If the other set doesn't have any non-boolean qualifiers, just
      // bit-or it in.
      if (!(Q.Mask & ~CVRMask))
        Mask |= Q.Mask;
      else {
        Mask |= (Q.Mask & CVRMask);
        if (Q.hasAddressSpace())
          addAddressSpace(Q.getAddressSpace());
        if (Q.hasObjCGCAttr())
          addObjCGCAttr(Q.getObjCGCAttr());
        if (Q.hasObjCLifetime())
          addObjCLifetime(Q.getObjCLifetime());
      }
    }
  
    /// Remove the qualifiers from the given set from this set.
    void removeQualifiers(Qualifiers Q) {
      // If the other set doesn't have any non-boolean qualifiers, just
      // bit-and the inverse in.
      if (!(Q.Mask & ~CVRMask))
        Mask &= ~Q.Mask;
      else {
        Mask &= ~(Q.Mask & CVRMask);
        if (getObjCGCAttr() == Q.getObjCGCAttr())
          removeObjCGCAttr();
        if (getObjCLifetime() == Q.getObjCLifetime())
          removeObjCLifetime();
        if (getAddressSpace() == Q.getAddressSpace())
          removeAddressSpace();
      }
    }
  
    /// Add the qualifiers from the given set to this set, given that
    /// they don't conflict.
    void addConsistentQualifiers(Qualifiers qs) {
      assert(getAddressSpace() == qs.getAddressSpace() ||
             !hasAddressSpace() || !qs.hasAddressSpace());
      assert(getObjCGCAttr() == qs.getObjCGCAttr() ||
             !hasObjCGCAttr() || !qs.hasObjCGCAttr());
      assert(getObjCLifetime() == qs.getObjCLifetime() ||
             !hasObjCLifetime() || !qs.hasObjCLifetime());
      Mask |= qs.Mask;
    }
  
    /// Returns true if this address space is a superset of the other one.
    /// OpenCL v2.0 defines conversion rules (OpenCLC v2.0 s6.5.5) and notion of
    /// overlapping address spaces.
    /// CL1.1 or CL1.2:
    ///   every address space is a superset of itself.
    /// CL2.0 adds:
    ///   __generic is a superset of any address space except for __constant.
    bool isAddressSpaceSupersetOf(Qualifiers other) const {
      return
          // Address spaces must match exactly.
          getAddressSpace() == other.getAddressSpace() ||
          // Otherwise in OpenCLC v2.0 s6.5.5: every address space except
          // for __constant can be used as __generic.
          (getAddressSpace() == LangAS::opencl_generic &&
           other.getAddressSpace() != LangAS::opencl_constant);
    }
  
    /// Determines if these qualifiers compatibly include another set.
    /// Generally this answers the question of whether an object with the other
    /// qualifiers can be safely used as an object with these qualifiers.
    bool compatiblyIncludes(Qualifiers other) const {
      return isAddressSpaceSupersetOf(other) &&
             // ObjC GC qualifiers can match, be added, or be removed, but can't
             // be changed.
             (getObjCGCAttr() == other.getObjCGCAttr() || !hasObjCGCAttr() ||
              !other.hasObjCGCAttr()) &&
             // ObjC lifetime qualifiers must match exactly.
             getObjCLifetime() == other.getObjCLifetime() &&
             // CVR qualifiers may subset.
             (((Mask & CVRMask) | (other.Mask & CVRMask)) == (Mask & CVRMask)) &&
             // U qualifier may superset.
             (!other.hasUnaligned() || hasUnaligned());
    }
  
    /// Determines if these qualifiers compatibly include another set of
    /// qualifiers from the narrow perspective of Objective-C ARC lifetime.
    ///
    /// One set of Objective-C lifetime qualifiers compatibly includes the other
    /// if the lifetime qualifiers match, or if both are non-__weak and the
    /// including set also contains the 'const' qualifier, or both are non-__weak
    /// and one is None (which can only happen in non-ARC modes).
    bool compatiblyIncludesObjCLifetime(Qualifiers other) const {
      if (getObjCLifetime() == other.getObjCLifetime())
        return true;
  
      if (getObjCLifetime() == OCL_Weak || other.getObjCLifetime() == OCL_Weak)
        return false;
  
      if (getObjCLifetime() == OCL_None || other.getObjCLifetime() == OCL_None)
        return true;
  
      return hasConst();
    }
  
    /// Determine whether this set of qualifiers is a strict superset of
    /// another set of qualifiers, not considering qualifier compatibility.
    bool isStrictSupersetOf(Qualifiers Other) const;
  
    bool operator==(Qualifiers Other) const { return Mask == Other.Mask; }
    bool operator!=(Qualifiers Other) const { return Mask != Other.Mask; }
  
    explicit operator bool() const { return hasQualifiers(); }
  
    Qualifiers &operator+=(Qualifiers R) {
      addQualifiers(R);
      return *this;
    }
  
    // Union two qualifier sets.  If an enumerated qualifier appears
    // in both sets, use the one from the right.
    friend Qualifiers operator+(Qualifiers L, Qualifiers R) {
      L += R;
      return L;
    }
  
    Qualifiers &operator-=(Qualifiers R) {
      removeQualifiers(R);
      return *this;
    }
  
    /// Compute the difference between two qualifier sets.
    friend Qualifiers operator-(Qualifiers L, Qualifiers R) {
      L -= R;
      return L;
    }
  
    std::string getAsString() const;
    std::string getAsString(const PrintingPolicy &Policy) const;
  
    bool isEmptyWhenPrinted(const PrintingPolicy &Policy) const;
    void print(raw_ostream &OS, const PrintingPolicy &Policy,
               bool appendSpaceIfNonEmpty = false) const;
  
    void Profile(llvm::FoldingSetNodeID &ID) const {
      ID.AddInteger(Mask);
    }
  
  private:
    // bits:     |0 1 2|3|4 .. 5|6  ..  8|9   ...   31|
    //           |C R V|U|GCAttr|Lifetime|AddressSpace|
    uint32_t Mask = 0;
  
    static const uint32_t UMask = 0x8;
    static const uint32_t UShift = 3;
    static const uint32_t GCAttrMask = 0x30;
    static const uint32_t GCAttrShift = 4;
    static const uint32_t LifetimeMask = 0x1C0;
    static const uint32_t LifetimeShift = 6;
    static const uint32_t AddressSpaceMask =
        ~(CVRMask | UMask | GCAttrMask | LifetimeMask);
    static const uint32_t AddressSpaceShift = 9;
  };
  
  /// A std::pair-like structure for storing a qualified type split
  /// into its local qualifiers and its locally-unqualified type.
  struct SplitQualType {
    /// The locally-unqualified type.
    const Type *Ty = nullptr;
  
    /// The local qualifiers.
    Qualifiers Quals;
  
    SplitQualType() = default;
    SplitQualType(const Type *ty, Qualifiers qs) : Ty(ty), Quals(qs) {}
  
    SplitQualType getSingleStepDesugaredType() const; // end of this file
  
    // Make std::tie work.
    std::pair<const Type *,Qualifiers> asPair() const {
      return std::pair<const Type *, Qualifiers>(Ty, Quals);
    }
  
    friend bool operator==(SplitQualType a, SplitQualType b) {
      return a.Ty == b.Ty && a.Quals == b.Quals;
    }
    friend bool operator!=(SplitQualType a, SplitQualType b) {
      return a.Ty != b.Ty || a.Quals != b.Quals;
    }
  };
  
  /// The kind of type we are substituting Objective-C type arguments into.
  ///
  /// The kind of substitution affects the replacement of type parameters when
  /// no concrete type information is provided, e.g., when dealing with an
  /// unspecialized type.
  enum class ObjCSubstitutionContext {
    /// An ordinary type.
    Ordinary,
  
    /// The result type of a method or function.
    Result,
  
    /// The parameter type of a method or function.
    Parameter,
  
    /// The type of a property.
    Property,
  
    /// The superclass of a type.
    Superclass,
  };
  
  /// A (possibly-)qualified type.
  ///
  /// For efficiency, we don't store CV-qualified types as nodes on their
  /// own: instead each reference to a type stores the qualifiers.  This
  /// greatly reduces the number of nodes we need to allocate for types (for
  /// example we only need one for 'int', 'const int', 'volatile int',
  /// 'const volatile int', etc).
  ///
  /// As an added efficiency bonus, instead of making this a pair, we
  /// just store the two bits we care about in the low bits of the
  /// pointer.  To handle the packing/unpacking, we make QualType be a
  /// simple wrapper class that acts like a smart pointer.  A third bit
  /// indicates whether there are extended qualifiers present, in which
  /// case the pointer points to a special structure.
  class QualType {
    friend class QualifierCollector;
  
    // Thankfully, these are efficiently composable.
    llvm::PointerIntPair<llvm::PointerUnion<const Type *, const ExtQuals *>,
                         Qualifiers::FastWidth> Value;
  
    const ExtQuals *getExtQualsUnsafe() const {
      return Value.getPointer().get<const ExtQuals*>();
    }
  
    const Type *getTypePtrUnsafe() const {
      return Value.getPointer().get<const Type*>();
    }
  
    const ExtQualsTypeCommonBase *getCommonPtr() const {
      assert(!isNull() && "Cannot retrieve a NULL type pointer");
      auto CommonPtrVal = reinterpret_cast<uintptr_t>(Value.getOpaqueValue());
      CommonPtrVal &= ~(uintptr_t)((1 << TypeAlignmentInBits) - 1);
      return reinterpret_cast<ExtQualsTypeCommonBase*>(CommonPtrVal);
    }
  
  public:
    QualType() = default;
    QualType(const Type *Ptr, unsigned Quals) : Value(Ptr, Quals) {}
    QualType(const ExtQuals *Ptr, unsigned Quals) : Value(Ptr, Quals) {}
  
    unsigned getLocalFastQualifiers() const { return Value.getInt(); }
    void setLocalFastQualifiers(unsigned Quals) { Value.setInt(Quals); }
  
    /// Retrieves a pointer to the underlying (unqualified) type.
    ///
    /// This function requires that the type not be NULL. If the type might be
    /// NULL, use the (slightly less efficient) \c getTypePtrOrNull().
    const Type *getTypePtr() const;
  
    const Type *getTypePtrOrNull() const;
  
    /// Retrieves a pointer to the name of the base type.
    const IdentifierInfo *getBaseTypeIdentifier() const;
  
    /// Divides a QualType into its unqualified type and a set of local
    /// qualifiers.
    SplitQualType split() const;
  
    void *getAsOpaquePtr() const { return Value.getOpaqueValue(); }
  
    static QualType getFromOpaquePtr(const void *Ptr) {
      QualType T;
      T.Value.setFromOpaqueValue(const_cast<void*>(Ptr));
      return T;
    }
  
    const Type &operator*() const {
      return *getTypePtr();
    }
  
    const Type *operator->() const {
      return getTypePtr();
    }
  
    bool isCanonical() const;
    bool isCanonicalAsParam() const;
  
    /// Return true if this QualType doesn't point to a type yet.
    bool isNull() const {
      return Value.getPointer().isNull();
    }
  
    /// Determine whether this particular QualType instance has the
    /// "const" qualifier set, without looking through typedefs that may have
    /// added "const" at a different level.
    bool isLocalConstQualified() const {
      return (getLocalFastQualifiers() & Qualifiers::Const);
    }
  
    /// Determine whether this type is const-qualified.
    bool isConstQualified() const;
  
    /// Determine whether this particular QualType instance has the
    /// "restrict" qualifier set, without looking through typedefs that may have
    /// added "restrict" at a different level.
    bool isLocalRestrictQualified() const {
      return (getLocalFastQualifiers() & Qualifiers::Restrict);
    }
  
    /// Determine whether this type is restrict-qualified.
    bool isRestrictQualified() const;
  
    /// Determine whether this particular QualType instance has the
    /// "volatile" qualifier set, without looking through typedefs that may have
    /// added "volatile" at a different level.
    bool isLocalVolatileQualified() const {
      return (getLocalFastQualifiers() & Qualifiers::Volatile);
    }
  
    /// Determine whether this type is volatile-qualified.
    bool isVolatileQualified() const;
  
    /// Determine whether this particular QualType instance has any
    /// qualifiers, without looking through any typedefs that might add
    /// qualifiers at a different level.
    bool hasLocalQualifiers() const {
      return getLocalFastQualifiers() || hasLocalNonFastQualifiers();
    }
  
    /// Determine whether this type has any qualifiers.
    bool hasQualifiers() const;
  
    /// Determine whether this particular QualType instance has any
    /// "non-fast" qualifiers, e.g., those that are stored in an ExtQualType
    /// instance.
    bool hasLocalNonFastQualifiers() const {
      return Value.getPointer().is<const ExtQuals*>();
    }
  
    /// Retrieve the set of qualifiers local to this particular QualType
    /// instance, not including any qualifiers acquired through typedefs or
    /// other sugar.
    Qualifiers getLocalQualifiers() const;
  
    /// Retrieve the set of qualifiers applied to this type.
    Qualifiers getQualifiers() const;
  
    /// Retrieve the set of CVR (const-volatile-restrict) qualifiers
    /// local to this particular QualType instance, not including any qualifiers
    /// acquired through typedefs or other sugar.
    unsigned getLocalCVRQualifiers() const {
      return getLocalFastQualifiers();
    }
  
    /// Retrieve the set of CVR (const-volatile-restrict) qualifiers
    /// applied to this type.
    unsigned getCVRQualifiers() const;
  
    bool isConstant(const ASTContext& Ctx) const {
      return QualType::isConstant(*this, Ctx);
    }
  
    /// Determine whether this is a Plain Old Data (POD) type (C++ 3.9p10).
    bool isPODType(const ASTContext &Context) const;
  
    /// Return true if this is a POD type according to the rules of the C++98
    /// standard, regardless of the current compilation's language.
    bool isCXX98PODType(const ASTContext &Context) const;
  
    /// Return true if this is a POD type according to the more relaxed rules
    /// of the C++11 standard, regardless of the current compilation's language.
    /// (C++0x [basic.types]p9). Note that, unlike
    /// CXXRecordDecl::isCXX11StandardLayout, this takes DRs into account.
    bool isCXX11PODType(const ASTContext &Context) const;
  
    /// Return true if this is a trivial type per (C++0x [basic.types]p9)
    bool isTrivialType(const ASTContext &Context) const;
  
    /// Return true if this is a trivially copyable type (C++0x [basic.types]p9)
    bool isTriviallyCopyableType(const ASTContext &Context) const;
  
  
    /// Returns true if it is a class and it might be dynamic.
    bool mayBeDynamicClass() const;
  
    /// Returns true if it is not a class or if the class might not be dynamic.
    bool mayBeNotDynamicClass() const;
  
    // Don't promise in the API that anything besides 'const' can be
    // easily added.
  
    /// Add the `const` type qualifier to this QualType.
    void addConst() {
      addFastQualifiers(Qualifiers::Const);
    }
    QualType withConst() const {
      return withFastQualifiers(Qualifiers::Const);
    }
  
    /// Add the `volatile` type qualifier to this QualType.
    void addVolatile() {
      addFastQualifiers(Qualifiers::Volatile);
    }
    QualType withVolatile() const {
      return withFastQualifiers(Qualifiers::Volatile);
    }
  
    /// Add the `restrict` qualifier to this QualType.
    void addRestrict() {
      addFastQualifiers(Qualifiers::Restrict);
    }
    QualType withRestrict() const {
      return withFastQualifiers(Qualifiers::Restrict);
    }
  
    QualType withCVRQualifiers(unsigned CVR) const {
      return withFastQualifiers(CVR);
    }
  
    void addFastQualifiers(unsigned TQs) {
      assert(!(TQs & ~Qualifiers::FastMask)
             && "non-fast qualifier bits set in mask!");
      Value.setInt(Value.getInt() | TQs);
    }
  
    void removeLocalConst();
    void removeLocalVolatile();
    void removeLocalRestrict();
    void removeLocalCVRQualifiers(unsigned Mask);
  
    void removeLocalFastQualifiers() { Value.setInt(0); }
    void removeLocalFastQualifiers(unsigned Mask) {
      assert(!(Mask & ~Qualifiers::FastMask) && "mask has non-fast qualifiers");
      Value.setInt(Value.getInt() & ~Mask);
    }
  
    // Creates a type with the given qualifiers in addition to any
    // qualifiers already on this type.
    QualType withFastQualifiers(unsigned TQs) const {
      QualType T = *this;
      T.addFastQualifiers(TQs);
      return T;
    }
  
    // Creates a type with exactly the given fast qualifiers, removing
    // any existing fast qualifiers.
    QualType withExactLocalFastQualifiers(unsigned TQs) const {
      return withoutLocalFastQualifiers().withFastQualifiers(TQs);
    }
  
    // Removes fast qualifiers, but leaves any extended qualifiers in place.
    QualType withoutLocalFastQualifiers() const {
      QualType T = *this;
      T.removeLocalFastQualifiers();
      return T;
    }
  
    QualType getCanonicalType() const;
  
    /// Return this type with all of the instance-specific qualifiers
    /// removed, but without removing any qualifiers that may have been applied
    /// through typedefs.
    QualType getLocalUnqualifiedType() const { return QualType(getTypePtr(), 0); }
  
    /// Retrieve the unqualified variant of the given type,
    /// removing as little sugar as possible.
    ///
    /// This routine looks through various kinds of sugar to find the
    /// least-desugared type that is unqualified. For example, given:
    ///
    /// \code
    /// typedef int Integer;
    /// typedef const Integer CInteger;
    /// typedef CInteger DifferenceType;
    /// \endcode
    ///
    /// Executing \c getUnqualifiedType() on the type \c DifferenceType will
    /// desugar until we hit the type \c Integer, which has no qualifiers on it.
    ///
    /// The resulting type might still be qualified if it's sugar for an array
    /// type.  To strip qualifiers even from within a sugared array type, use
    /// ASTContext::getUnqualifiedArrayType.
    inline QualType getUnqualifiedType() const;
  
    /// Retrieve the unqualified variant of the given type, removing as little
    /// sugar as possible.
    ///
    /// Like getUnqualifiedType(), but also returns the set of
    /// qualifiers that were built up.
    ///
    /// The resulting type might still be qualified if it's sugar for an array
    /// type.  To strip qualifiers even from within a sugared array type, use
    /// ASTContext::getUnqualifiedArrayType.
    inline SplitQualType getSplitUnqualifiedType() const;
  
    /// Determine whether this type is more qualified than the other
    /// given type, requiring exact equality for non-CVR qualifiers.
    bool isMoreQualifiedThan(QualType Other) const;
  
    /// Determine whether this type is at least as qualified as the other
    /// given type, requiring exact equality for non-CVR qualifiers.
    bool isAtLeastAsQualifiedAs(QualType Other) const;
  
    QualType getNonReferenceType() const;
  
    /// Determine the type of a (typically non-lvalue) expression with the
    /// specified result type.
    ///
    /// This routine should be used for expressions for which the return type is
    /// explicitly specified (e.g., in a cast or call) and isn't necessarily
    /// an lvalue. It removes a top-level reference (since there are no
    /// expressions of reference type) and deletes top-level cvr-qualifiers
    /// from non-class types (in C++) or all types (in C).
    QualType getNonLValueExprType(const ASTContext &Context) const;
  
    /// Return the specified type with any "sugar" removed from
    /// the type.  This takes off typedefs, typeof's etc.  If the outer level of
    /// the type is already concrete, it returns it unmodified.  This is similar
    /// to getting the canonical type, but it doesn't remove *all* typedefs.  For
    /// example, it returns "T*" as "T*", (not as "int*"), because the pointer is
    /// concrete.
    ///
    /// Qualifiers are left in place.
    QualType getDesugaredType(const ASTContext &Context) const {
      return getDesugaredType(*this, Context);
    }
  
    SplitQualType getSplitDesugaredType() const {
      return getSplitDesugaredType(*this);
    }
  
    /// Return the specified type with one level of "sugar" removed from
    /// the type.
    ///
    /// This routine takes off the first typedef, typeof, etc. If the outer level
    /// of the type is already concrete, it returns it unmodified.
    QualType getSingleStepDesugaredType(const ASTContext &Context) const {
      return getSingleStepDesugaredTypeImpl(*this, Context);
    }
  
    /// Returns the specified type after dropping any
    /// outer-level parentheses.
    QualType IgnoreParens() const {
      if (isa<ParenType>(*this))
        return QualType::IgnoreParens(*this);
      return *this;
    }
  
    /// Indicate whether the specified types and qualifiers are identical.
    friend bool operator==(const QualType &LHS, const QualType &RHS) {
      return LHS.Value == RHS.Value;
    }
    friend bool operator!=(const QualType &LHS, const QualType &RHS) {
      return LHS.Value != RHS.Value;
    }
  
    static std::string getAsString(SplitQualType split,
                                   const PrintingPolicy &Policy) {
      return getAsString(split.Ty, split.Quals, Policy);
    }
    static std::string getAsString(const Type *ty, Qualifiers qs,
                                   const PrintingPolicy &Policy);
  
    std::string getAsString() const;
    std::string getAsString(const PrintingPolicy &Policy) const;
  
    void print(raw_ostream &OS, const PrintingPolicy &Policy,
               const Twine &PlaceHolder = Twine(),
               unsigned Indentation = 0) const;
  
    static void print(SplitQualType split, raw_ostream &OS,
                      const PrintingPolicy &policy, const Twine &PlaceHolder,
                      unsigned Indentation = 0) {
      return print(split.Ty, split.Quals, OS, policy, PlaceHolder, Indentation);
    }
  
    static void print(const Type *ty, Qualifiers qs,
                      raw_ostream &OS, const PrintingPolicy &policy,
                      const Twine &PlaceHolder,
                      unsigned Indentation = 0);
  
    void getAsStringInternal(std::string &Str,
                             const PrintingPolicy &Policy) const;
  
    static void getAsStringInternal(SplitQualType split, std::string &out,
                                    const PrintingPolicy &policy) {
      return getAsStringInternal(split.Ty, split.Quals, out, policy);
    }
  
    static void getAsStringInternal(const Type *ty, Qualifiers qs,
                                    std::string &out,
                                    const PrintingPolicy &policy);
  
    class StreamedQualTypeHelper {
      const QualType &T;
      const PrintingPolicy &Policy;
      const Twine &PlaceHolder;
      unsigned Indentation;
  
    public:
      StreamedQualTypeHelper(const QualType &T, const PrintingPolicy &Policy,
                             const Twine &PlaceHolder, unsigned Indentation)
          : T(T), Policy(Policy), PlaceHolder(PlaceHolder),
            Indentation(Indentation) {}
  
      friend raw_ostream &operator<<(raw_ostream &OS,
                                     const StreamedQualTypeHelper &SQT) {
        SQT.T.print(OS, SQT.Policy, SQT.PlaceHolder, SQT.Indentation);
        return OS;
      }
    };
  
    StreamedQualTypeHelper stream(const PrintingPolicy &Policy,
                                  const Twine &PlaceHolder = Twine(),
                                  unsigned Indentation = 0) const {
      return StreamedQualTypeHelper(*this, Policy, PlaceHolder, Indentation);
    }
  
    void dump(const char *s) const;
    void dump() const;
    void dump(llvm::raw_ostream &OS) const;
  
    void Profile(llvm::FoldingSetNodeID &ID) const {
      ID.AddPointer(getAsOpaquePtr());
    }
  
    /// Return the address space of this type.
    inline LangAS getAddressSpace() const;
  
    /// Returns gc attribute of this type.
    inline Qualifiers::GC getObjCGCAttr() const;
  
    /// true when Type is objc's weak.
    bool isObjCGCWeak() const {
      return getObjCGCAttr() == Qualifiers::Weak;
    }
  
    /// true when Type is objc's strong.
    bool isObjCGCStrong() const {
      return getObjCGCAttr() == Qualifiers::Strong;
    }
  
    /// Returns lifetime attribute of this type.
    Qualifiers::ObjCLifetime getObjCLifetime() const {
      return getQualifiers().getObjCLifetime();
    }
  
    bool hasNonTrivialObjCLifetime() const {
      return getQualifiers().hasNonTrivialObjCLifetime();
    }
  
    bool hasStrongOrWeakObjCLifetime() const {
      return getQualifiers().hasStrongOrWeakObjCLifetime();
    }
  
    // true when Type is objc's weak and weak is enabled but ARC isn't.
    bool isNonWeakInMRRWithObjCWeak(const ASTContext &Context) const;
  
    enum PrimitiveDefaultInitializeKind {
      /// The type does not fall into any of the following categories. Note that
      /// this case is zero-valued so that values of this enum can be used as a
      /// boolean condition for non-triviality.
      PDIK_Trivial,
  
      /// The type is an Objective-C retainable pointer type that is qualified
      /// with the ARC __strong qualifier.
      PDIK_ARCStrong,
  
      /// The type is an Objective-C retainable pointer type that is qualified
      /// with the ARC __weak qualifier.
      PDIK_ARCWeak,
  
      /// The type is a struct containing a field whose type is not PCK_Trivial.
      PDIK_Struct
    };
  
    /// Functions to query basic properties of non-trivial C struct types.
  
    /// Check if this is a non-trivial type that would cause a C struct
    /// transitively containing this type to be non-trivial to default initialize
    /// and return the kind.
    PrimitiveDefaultInitializeKind
    isNonTrivialToPrimitiveDefaultInitialize() const;
  
    enum PrimitiveCopyKind {
      /// The type does not fall into any of the following categories. Note that
      /// this case is zero-valued so that values of this enum can be used as a
      /// boolean condition for non-triviality.
      PCK_Trivial,
  
      /// The type would be trivial except that it is volatile-qualified. Types
      /// that fall into one of the other non-trivial cases may additionally be
      /// volatile-qualified.
      PCK_VolatileTrivial,
  
      /// The type is an Objective-C retainable pointer type that is qualified
      /// with the ARC __strong qualifier.
      PCK_ARCStrong,
  
      /// The type is an Objective-C retainable pointer type that is qualified
      /// with the ARC __weak qualifier.
      PCK_ARCWeak,
  
      /// The type is a struct containing a field whose type is neither
      /// PCK_Trivial nor PCK_VolatileTrivial.
      /// Note that a C++ struct type does not necessarily match this; C++ copying
      /// semantics are too complex to express here, in part because they depend
      /// on the exact constructor or assignment operator that is chosen by
      /// overload resolution to do the copy.
      PCK_Struct
    };
  
    /// Check if this is a non-trivial type that would cause a C struct
    /// transitively containing this type to be non-trivial. This function can be
    /// used to determine whether a field of this type can be declared inside a C
    /// union.
    bool isNonTrivialPrimitiveCType(const ASTContext &Ctx) const;
  
    /// Check if this is a non-trivial type that would cause a C struct
    /// transitively containing this type to be non-trivial to copy and return the
    /// kind.
    PrimitiveCopyKind isNonTrivialToPrimitiveCopy() const;
  
    /// Check if this is a non-trivial type that would cause a C struct
    /// transitively containing this type to be non-trivial to destructively
    /// move and return the kind. Destructive move in this context is a C++-style
    /// move in which the source object is placed in a valid but unspecified state
    /// after it is moved, as opposed to a truly destructive move in which the
    /// source object is placed in an uninitialized state.
    PrimitiveCopyKind isNonTrivialToPrimitiveDestructiveMove() const;
  
    enum DestructionKind {
      DK_none,
      DK_cxx_destructor,
      DK_objc_strong_lifetime,
      DK_objc_weak_lifetime,
      DK_nontrivial_c_struct
    };
  
    /// Returns a nonzero value if objects of this type require
    /// non-trivial work to clean up after.  Non-zero because it's
    /// conceivable that qualifiers (objc_gc(weak)?) could make
    /// something require destruction.
    DestructionKind isDestructedType() const {
      return isDestructedTypeImpl(*this);
    }
  
    /// Determine whether expressions of the given type are forbidden
    /// from being lvalues in C.
    ///
    /// The expression types that are forbidden to be lvalues are:
    ///   - 'void', but not qualified void
    ///   - function types
    ///
    /// The exact rule here is C99 6.3.2.1:
    ///   An lvalue is an expression with an object type or an incomplete
    ///   type other than void.
    bool isCForbiddenLValueType() const;
  
    /// Substitute type arguments for the Objective-C type parameters used in the
    /// subject type.
    ///
    /// \param ctx ASTContext in which the type exists.
    ///
    /// \param typeArgs The type arguments that will be substituted for the
    /// Objective-C type parameters in the subject type, which are generally
    /// computed via \c Type::getObjCSubstitutions. If empty, the type
    /// parameters will be replaced with their bounds or id/Class, as appropriate
    /// for the context.
    ///
    /// \param context The context in which the subject type was written.
    ///
    /// \returns the resulting type.
    QualType substObjCTypeArgs(ASTContext &ctx,
                               ArrayRef<QualType> typeArgs,
                               ObjCSubstitutionContext context) const;
  
    /// Substitute type arguments from an object type for the Objective-C type
    /// parameters used in the subject type.
    ///
    /// This operation combines the computation of type arguments for
    /// substitution (\c Type::getObjCSubstitutions) with the actual process of
    /// substitution (\c QualType::substObjCTypeArgs) for the convenience of
    /// callers that need to perform a single substitution in isolation.
    ///
    /// \param objectType The type of the object whose member type we're
    /// substituting into. For example, this might be the receiver of a message
    /// or the base of a property access.
    ///
    /// \param dc The declaration context from which the subject type was
    /// retrieved, which indicates (for example) which type parameters should
    /// be substituted.
    ///
    /// \param context The context in which the subject type was written.
    ///
    /// \returns the subject type after replacing all of the Objective-C type
    /// parameters with their corresponding arguments.
    QualType substObjCMemberType(QualType objectType,
                                 const DeclContext *dc,
                                 ObjCSubstitutionContext context) const;
  
    /// Strip Objective-C "__kindof" types from the given type.
    QualType stripObjCKindOfType(const ASTContext &ctx) const;
  
    /// Remove all qualifiers including _Atomic.
    QualType getAtomicUnqualifiedType() const;
  
  private:
    // These methods are implemented in a separate translation unit;
    // "static"-ize them to avoid creating temporary QualTypes in the
    // caller.
    static bool isConstant(QualType T, const ASTContext& Ctx);
    static QualType getDesugaredType(QualType T, const ASTContext &Context);
    static SplitQualType getSplitDesugaredType(QualType T);
    static SplitQualType getSplitUnqualifiedTypeImpl(QualType type);
    static QualType getSingleStepDesugaredTypeImpl(QualType type,
                                                   const ASTContext &C);
    static QualType IgnoreParens(QualType T);
    static DestructionKind isDestructedTypeImpl(QualType type);
  };
  
  } // namespace clang
  
  namespace llvm {
  
  /// Implement simplify_type for QualType, so that we can dyn_cast from QualType
  /// to a specific Type class.
  template<> struct simplify_type< ::clang::QualType> {
    using SimpleType = const ::clang::Type *;
  
    static SimpleType getSimplifiedValue(::clang::QualType Val) {
      return Val.getTypePtr();
    }
  };
  
  // Teach SmallPtrSet that QualType is "basically a pointer".
  template<>
  struct PointerLikeTypeTraits<clang::QualType> {
    static inline void *getAsVoidPointer(clang::QualType P) {
      return P.getAsOpaquePtr();
    }
  
    static inline clang::QualType getFromVoidPointer(void *P) {
      return clang::QualType::getFromOpaquePtr(P);
    }
  
    // Various qualifiers go in low bits.
    enum { NumLowBitsAvailable = 0 };
  };
  
  } // namespace llvm
  
  namespace clang {
  
  /// Base class that is common to both the \c ExtQuals and \c Type
  /// classes, which allows \c QualType to access the common fields between the
  /// two.
  class ExtQualsTypeCommonBase {
    friend class ExtQuals;
    friend class QualType;
    friend class Type;
  
    /// The "base" type of an extended qualifiers type (\c ExtQuals) or
    /// a self-referential pointer (for \c Type).
    ///
    /// This pointer allows an efficient mapping from a QualType to its
    /// underlying type pointer.
    const Type *const BaseType;
  
    /// The canonical type of this type.  A QualType.
    QualType CanonicalType;
  
    ExtQualsTypeCommonBase(const Type *baseType, QualType canon)
        : BaseType(baseType), CanonicalType(canon) {}
  };
  
  /// We can encode up to four bits in the low bits of a
  /// type pointer, but there are many more type qualifiers that we want
  /// to be able to apply to an arbitrary type.  Therefore we have this
  /// struct, intended to be heap-allocated and used by QualType to
  /// store qualifiers.
  ///
  /// The current design tags the 'const', 'restrict', and 'volatile' qualifiers
  /// in three low bits on the QualType pointer; a fourth bit records whether
  /// the pointer is an ExtQuals node. The extended qualifiers (address spaces,
  /// Objective-C GC attributes) are much more rare.
  class ExtQuals : public ExtQualsTypeCommonBase, public llvm::FoldingSetNode {
    // NOTE: changing the fast qualifiers should be straightforward as
    // long as you don't make 'const' non-fast.
    // 1. Qualifiers:
    //    a) Modify the bitmasks (Qualifiers::TQ and DeclSpec::TQ).
    //       Fast qualifiers must occupy the low-order bits.
    //    b) Update Qualifiers::FastWidth and FastMask.
    // 2. QualType:
    //    a) Update is{Volatile,Restrict}Qualified(), defined inline.
    //    b) Update remove{Volatile,Restrict}, defined near the end of
    //       this header.
    // 3. ASTContext:
    //    a) Update get{Volatile,Restrict}Type.
  
    /// The immutable set of qualifiers applied by this node. Always contains
    /// extended qualifiers.
    Qualifiers Quals;
  
    ExtQuals *this_() { return this; }
  
  public:
    ExtQuals(const Type *baseType, QualType canon, Qualifiers quals)
        : ExtQualsTypeCommonBase(baseType,
                                 canon.isNull() ? QualType(this_(), 0) : canon),
          Quals(quals) {
      assert(Quals.hasNonFastQualifiers()
             && "ExtQuals created with no fast qualifiers");
      assert(!Quals.hasFastQualifiers()
             && "ExtQuals created with fast qualifiers");
    }
  
    Qualifiers getQualifiers() const { return Quals; }
  
    bool hasObjCGCAttr() const { return Quals.hasObjCGCAttr(); }
    Qualifiers::GC getObjCGCAttr() const { return Quals.getObjCGCAttr(); }
  
    bool hasObjCLifetime() const { return Quals.hasObjCLifetime(); }
    Qualifiers::ObjCLifetime getObjCLifetime() const {
      return Quals.getObjCLifetime();
    }
  
    bool hasAddressSpace() const { return Quals.hasAddressSpace(); }
    LangAS getAddressSpace() const { return Quals.getAddressSpace(); }
  
    const Type *getBaseType() const { return BaseType; }
  
  public:
    void Profile(llvm::FoldingSetNodeID &ID) const {
      Profile(ID, getBaseType(), Quals);
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID,
                        const Type *BaseType,
                        Qualifiers Quals) {
      assert(!Quals.hasFastQualifiers() && "fast qualifiers in ExtQuals hash!");
      ID.AddPointer(BaseType);
      Quals.Profile(ID);
    }
  };
  
  /// The kind of C++11 ref-qualifier associated with a function type.
  /// This determines whether a member function's "this" object can be an
  /// lvalue, rvalue, or neither.
  enum RefQualifierKind {
    /// No ref-qualifier was provided.
    RQ_None = 0,
  
    /// An lvalue ref-qualifier was provided (\c &).
    RQ_LValue,
  
    /// An rvalue ref-qualifier was provided (\c &&).
    RQ_RValue
  };
  
  /// Which keyword(s) were used to create an AutoType.
  enum class AutoTypeKeyword {
    /// auto
    Auto,
  
    /// decltype(auto)
    DecltypeAuto,
  
    /// __auto_type (GNU extension)
    GNUAutoType
  };
  
  /// The base class of the type hierarchy.
  ///
  /// A central concept with types is that each type always has a canonical
  /// type.  A canonical type is the type with any typedef names stripped out
  /// of it or the types it references.  For example, consider:
  ///
  ///  typedef int  foo;
  ///  typedef foo* bar;
  ///    'int *'    'foo *'    'bar'
  ///
  /// There will be a Type object created for 'int'.  Since int is canonical, its
  /// CanonicalType pointer points to itself.  There is also a Type for 'foo' (a
  /// TypedefType).  Its CanonicalType pointer points to the 'int' Type.  Next
  /// there is a PointerType that represents 'int*', which, like 'int', is
  /// canonical.  Finally, there is a PointerType type for 'foo*' whose canonical
  /// type is 'int*', and there is a TypedefType for 'bar', whose canonical type
  /// is also 'int*'.
  ///
  /// Non-canonical types are useful for emitting diagnostics, without losing
  /// information about typedefs being used.  Canonical types are useful for type
  /// comparisons (they allow by-pointer equality tests) and useful for reasoning
  /// about whether something has a particular form (e.g. is a function type),
  /// because they implicitly, recursively, strip all typedefs out of a type.
  ///
  /// Types, once created, are immutable.
  ///
  class Type : public ExtQualsTypeCommonBase {
  public:
    enum TypeClass {
  #define TYPE(Class, Base) Class,
  #define LAST_TYPE(Class) TypeLast = Class,
  #define ABSTRACT_TYPE(Class, Base)
  #include "clang/AST/TypeNodes.def"
      TagFirst = Record, TagLast = Enum
    };
  
  private:
    /// Bitfields required by the Type class.
    class TypeBitfields {
      friend class Type;
      template <class T> friend class TypePropertyCache;
  
      /// TypeClass bitfield - Enum that specifies what subclass this belongs to.
      unsigned TC : 8;
  
      /// Whether this type is a dependent type (C++ [temp.dep.type]).
      unsigned Dependent : 1;
  
      /// Whether this type somehow involves a template parameter, even
      /// if the resolution of the type does not depend on a template parameter.
      unsigned InstantiationDependent : 1;
  
      /// Whether this type is a variably-modified type (C99 6.7.5).
      unsigned VariablyModified : 1;
  
      /// Whether this type contains an unexpanded parameter pack
      /// (for C++11 variadic templates).
      unsigned ContainsUnexpandedParameterPack : 1;
  
      /// True if the cache (i.e. the bitfields here starting with
      /// 'Cache') is valid.
      mutable unsigned CacheValid : 1;
  
      /// Linkage of this type.
      mutable unsigned CachedLinkage : 3;
  
      /// Whether this type involves and local or unnamed types.
      mutable unsigned CachedLocalOrUnnamed : 1;
  
      /// Whether this type comes from an AST file.
      mutable unsigned FromAST : 1;
  
      bool isCacheValid() const {
        return CacheValid;
      }
  
      Linkage getLinkage() const {
        assert(isCacheValid() && "getting linkage from invalid cache");
        return static_cast<Linkage>(CachedLinkage);
      }
  
      bool hasLocalOrUnnamedType() const {
        assert(isCacheValid() && "getting linkage from invalid cache");
        return CachedLocalOrUnnamed;
      }
    };
    enum { NumTypeBits = 18 };
  
  protected:
    // These classes allow subclasses to somewhat cleanly pack bitfields
    // into Type.
  
    class ArrayTypeBitfields {
      friend class ArrayType;
  
      unsigned : NumTypeBits;
  
      /// CVR qualifiers from declarations like
      /// 'int X[static restrict 4]'. For function parameters only.
      unsigned IndexTypeQuals : 3;
  
      /// Storage class qualifiers from declarations like
      /// 'int X[static restrict 4]'. For function parameters only.
      /// Actually an ArrayType::ArraySizeModifier.
      unsigned SizeModifier : 3;
    };
  
    class BuiltinTypeBitfields {
      friend class BuiltinType;
  
      unsigned : NumTypeBits;
  
      /// The kind (BuiltinType::Kind) of builtin type this is.
      unsigned Kind : 8;
    };
  
    /// FunctionTypeBitfields store various bits belonging to FunctionProtoType.
    /// Only common bits are stored here. Additional uncommon bits are stored
    /// in a trailing object after FunctionProtoType.
    class FunctionTypeBitfields {
      friend class FunctionProtoType;
      friend class FunctionType;
  
      unsigned : NumTypeBits;
  
      /// Extra information which affects how the function is called, like
      /// regparm and the calling convention.
      unsigned ExtInfo : 12;
  
      /// The ref-qualifier associated with a \c FunctionProtoType.
      ///
      /// This is a value of type \c RefQualifierKind.
      unsigned RefQualifier : 2;
  
      /// Used only by FunctionProtoType, put here to pack with the
      /// other bitfields.
      /// The qualifiers are part of FunctionProtoType because...
      ///
      /// C++ 8.3.5p4: The return type, the parameter type list and the
      /// cv-qualifier-seq, [...], are part of the function type.
      unsigned FastTypeQuals : Qualifiers::FastWidth;
      /// Whether this function has extended Qualifiers.
      unsigned HasExtQuals : 1;
  
      /// The number of parameters this function has, not counting '...'.
      /// According to [implimits] 8 bits should be enough here but this is
      /// somewhat easy to exceed with metaprogramming and so we would like to
      /// keep NumParams as wide as reasonably possible.
      unsigned NumParams : 16;
  
      /// The type of exception specification this function has.
      unsigned ExceptionSpecType : 4;
  
      /// Whether this function has extended parameter information.
      unsigned HasExtParameterInfos : 1;
  
      /// Whether the function is variadic.
      unsigned Variadic : 1;
  
      /// Whether this function has a trailing return type.
      unsigned HasTrailingReturn : 1;
    };
  
    class ObjCObjectTypeBitfields {
      friend class ObjCObjectType;
  
      unsigned : NumTypeBits;
  
      /// The number of type arguments stored directly on this object type.
      unsigned NumTypeArgs : 7;
  
      /// The number of protocols stored directly on this object type.
      unsigned NumProtocols : 6;
  
      /// Whether this is a "kindof" type.
      unsigned IsKindOf : 1;
    };
  
    class ReferenceTypeBitfields {
      friend class ReferenceType;
  
      unsigned : NumTypeBits;
  
      /// True if the type was originally spelled with an lvalue sigil.
      /// This is never true of rvalue references but can also be false
      /// on lvalue references because of C++0x [dcl.typedef]p9,
      /// as follows:
      ///
      ///   typedef int &ref;    // lvalue, spelled lvalue
      ///   typedef int &&rvref; // rvalue
      ///   ref &a;              // lvalue, inner ref, spelled lvalue
      ///   ref &&a;             // lvalue, inner ref
      ///   rvref &a;            // lvalue, inner ref, spelled lvalue
      ///   rvref &&a;           // rvalue, inner ref
      unsigned SpelledAsLValue : 1;
  
      /// True if the inner type is a reference type.  This only happens
      /// in non-canonical forms.
      unsigned InnerRef : 1;
    };
  
    class TypeWithKeywordBitfields {
      friend class TypeWithKeyword;
  
      unsigned : NumTypeBits;
  
      /// An ElaboratedTypeKeyword.  8 bits for efficient access.
      unsigned Keyword : 8;
    };
  
    enum { NumTypeWithKeywordBits = 8 };
  
    class ElaboratedTypeBitfields {
      friend class ElaboratedType;
  
      unsigned : NumTypeBits;
      unsigned : NumTypeWithKeywordBits;
  
      /// Whether the ElaboratedType has a trailing OwnedTagDecl.
      unsigned HasOwnedTagDecl : 1;
    };
  
    class VectorTypeBitfields {
      friend class VectorType;
      friend class DependentVectorType;
  
      unsigned : NumTypeBits;
  
      /// The kind of vector, either a generic vector type or some
      /// target-specific vector type such as for AltiVec or Neon.
      unsigned VecKind : 3;
  
      /// The number of elements in the vector.
      unsigned NumElements : 29 - NumTypeBits;
  
      enum { MaxNumElements = (1 << (29 - NumTypeBits)) - 1 };
    };
  
    class AttributedTypeBitfields {
      friend class AttributedType;
  
      unsigned : NumTypeBits;
  
      /// An AttributedType::Kind
      unsigned AttrKind : 32 - NumTypeBits;
    };
  
    class AutoTypeBitfields {
      friend class AutoType;
  
      unsigned : NumTypeBits;
  
      /// Was this placeholder type spelled as 'auto', 'decltype(auto)',
      /// or '__auto_type'?  AutoTypeKeyword value.
      unsigned Keyword : 2;
    };
  
    class SubstTemplateTypeParmPackTypeBitfields {
      friend class SubstTemplateTypeParmPackType;
  
      unsigned : NumTypeBits;
  
      /// The number of template arguments in \c Arguments, which is
      /// expected to be able to hold at least 1024 according to [implimits].
      /// However as this limit is somewhat easy to hit with template
      /// metaprogramming we'd prefer to keep it as large as possible.
      /// At the moment it has been left as a non-bitfield since this type
      /// safely fits in 64 bits as an unsigned, so there is no reason to
      /// introduce the performance impact of a bitfield.
      unsigned NumArgs;
    };
  
    class TemplateSpecializationTypeBitfields {
      friend class TemplateSpecializationType;
  
      unsigned : NumTypeBits;
  
      /// Whether this template specialization type is a substituted type alias.
      unsigned TypeAlias : 1;
  
      /// The number of template arguments named in this class template
      /// specialization, which is expected to be able to hold at least 1024
      /// according to [implimits]. However, as this limit is somewhat easy to
      /// hit with template metaprogramming we'd prefer to keep it as large
      /// as possible. At the moment it has been left as a non-bitfield since
      /// this type safely fits in 64 bits as an unsigned, so there is no reason
      /// to introduce the performance impact of a bitfield.
      unsigned NumArgs;
    };
  
    class DependentTemplateSpecializationTypeBitfields {
      friend class DependentTemplateSpecializationType;
  
      unsigned : NumTypeBits;
      unsigned : NumTypeWithKeywordBits;
  
      /// The number of template arguments named in this class template
      /// specialization, which is expected to be able to hold at least 1024
      /// according to [implimits]. However, as this limit is somewhat easy to
      /// hit with template metaprogramming we'd prefer to keep it as large
      /// as possible. At the moment it has been left as a non-bitfield since
      /// this type safely fits in 64 bits as an unsigned, so there is no reason
      /// to introduce the performance impact of a bitfield.
      unsigned NumArgs;
    };
  
    class PackExpansionTypeBitfields {
      friend class PackExpansionType;
  
      unsigned : NumTypeBits;
  
      /// The number of expansions that this pack expansion will
      /// generate when substituted (+1), which is expected to be able to
      /// hold at least 1024 according to [implimits]. However, as this limit
      /// is somewhat easy to hit with template metaprogramming we'd prefer to
      /// keep it as large as possible. At the moment it has been left as a
      /// non-bitfield since this type safely fits in 64 bits as an unsigned, so
      /// there is no reason to introduce the performance impact of a bitfield.
      ///
      /// This field will only have a non-zero value when some of the parameter
      /// packs that occur within the pattern have been substituted but others
      /// have not.
      unsigned NumExpansions;
    };
  
    union {
      TypeBitfields TypeBits;
      ArrayTypeBitfields ArrayTypeBits;
      AttributedTypeBitfields AttributedTypeBits;
      AutoTypeBitfields AutoTypeBits;
      BuiltinTypeBitfields BuiltinTypeBits;
      FunctionTypeBitfields FunctionTypeBits;
      ObjCObjectTypeBitfields ObjCObjectTypeBits;
      ReferenceTypeBitfields ReferenceTypeBits;
      TypeWithKeywordBitfields TypeWithKeywordBits;
      ElaboratedTypeBitfields ElaboratedTypeBits;
      VectorTypeBitfields VectorTypeBits;
      SubstTemplateTypeParmPackTypeBitfields SubstTemplateTypeParmPackTypeBits;
      TemplateSpecializationTypeBitfields TemplateSpecializationTypeBits;
      DependentTemplateSpecializationTypeBitfields
        DependentTemplateSpecializationTypeBits;
      PackExpansionTypeBitfields PackExpansionTypeBits;
  
      static_assert(sizeof(TypeBitfields) <= 8,
                    "TypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(ArrayTypeBitfields) <= 8,
                    "ArrayTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(AttributedTypeBitfields) <= 8,
                    "AttributedTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(AutoTypeBitfields) <= 8,
                    "AutoTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(BuiltinTypeBitfields) <= 8,
                    "BuiltinTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(FunctionTypeBitfields) <= 8,
                    "FunctionTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(ObjCObjectTypeBitfields) <= 8,
                    "ObjCObjectTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(ReferenceTypeBitfields) <= 8,
                    "ReferenceTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(TypeWithKeywordBitfields) <= 8,
                    "TypeWithKeywordBitfields is larger than 8 bytes!");
      static_assert(sizeof(ElaboratedTypeBitfields) <= 8,
                    "ElaboratedTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(VectorTypeBitfields) <= 8,
                    "VectorTypeBitfields is larger than 8 bytes!");
      static_assert(sizeof(SubstTemplateTypeParmPackTypeBitfields) <= 8,
                    "SubstTemplateTypeParmPackTypeBitfields is larger"
                    " than 8 bytes!");
      static_assert(sizeof(TemplateSpecializationTypeBitfields) <= 8,
                    "TemplateSpecializationTypeBitfields is larger"
                    " than 8 bytes!");
      static_assert(sizeof(DependentTemplateSpecializationTypeBitfields) <= 8,
                    "DependentTemplateSpecializationTypeBitfields is larger"
                    " than 8 bytes!");
      static_assert(sizeof(PackExpansionTypeBitfields) <= 8,
                    "PackExpansionTypeBitfields is larger than 8 bytes");
    };
  
  private:
    template <class T> friend class TypePropertyCache;
  
    /// Set whether this type comes from an AST file.
    void setFromAST(bool V = true) const {
      TypeBits.FromAST = V;
    }
  
  protected:
    friend class ASTContext;
  
    Type(TypeClass tc, QualType canon, bool Dependent,
         bool InstantiationDependent, bool VariablyModified,
         bool ContainsUnexpandedParameterPack)
        : ExtQualsTypeCommonBase(this,
                                 canon.isNull() ? QualType(this_(), 0) : canon) {
      TypeBits.TC = tc;
      TypeBits.Dependent = Dependent;
      TypeBits.InstantiationDependent = Dependent || InstantiationDependent;
      TypeBits.VariablyModified = VariablyModified;
      TypeBits.ContainsUnexpandedParameterPack = ContainsUnexpandedParameterPack;
      TypeBits.CacheValid = false;
      TypeBits.CachedLocalOrUnnamed = false;
      TypeBits.CachedLinkage = NoLinkage;
      TypeBits.FromAST = false;
    }
  
    // silence VC++ warning C4355: 'this' : used in base member initializer list
    Type *this_() { return this; }
  
    void setDependent(bool D = true) {
      TypeBits.Dependent = D;
      if (D)
        TypeBits.InstantiationDependent = true;
    }
  
    void setInstantiationDependent(bool D = true) {
      TypeBits.InstantiationDependent = D; }
  
    void setVariablyModified(bool VM = true) { TypeBits.VariablyModified = VM; }
  
    void setContainsUnexpandedParameterPack(bool PP = true) {
      TypeBits.ContainsUnexpandedParameterPack = PP;
    }
  
  public:
    friend class ASTReader;
    friend class ASTWriter;
  
    Type(const Type &) = delete;
    Type(Type &&) = delete;
    Type &operator=(const Type &) = delete;
    Type &operator=(Type &&) = delete;
  
    TypeClass getTypeClass() const { return static_cast<TypeClass>(TypeBits.TC); }
  
    /// Whether this type comes from an AST file.
    bool isFromAST() const { return TypeBits.FromAST; }
  
    /// Whether this type is or contains an unexpanded parameter
    /// pack, used to support C++0x variadic templates.
    ///
    /// A type that contains a parameter pack shall be expanded by the
    /// ellipsis operator at some point. For example, the typedef in the
    /// following example contains an unexpanded parameter pack 'T':
    ///
    /// \code
    /// template<typename ...T>
    /// struct X {
    ///   typedef T* pointer_types; // ill-formed; T is a parameter pack.
    /// };
    /// \endcode
    ///
    /// Note that this routine does not specify which
    bool containsUnexpandedParameterPack() const {
      return TypeBits.ContainsUnexpandedParameterPack;
    }
  
    /// Determines if this type would be canonical if it had no further
    /// qualification.
    bool isCanonicalUnqualified() const {
      return CanonicalType == QualType(this, 0);
    }
  
    /// Pull a single level of sugar off of this locally-unqualified type.
    /// Users should generally prefer SplitQualType::getSingleStepDesugaredType()
    /// or QualType::getSingleStepDesugaredType(const ASTContext&).
    QualType getLocallyUnqualifiedSingleStepDesugaredType() const;
  
    /// Types are partitioned into 3 broad categories (C99 6.2.5p1):
    /// object types, function types, and incomplete types.
  
    /// Return true if this is an incomplete type.
    /// A type that can describe objects, but which lacks information needed to
    /// determine its size (e.g. void, or a fwd declared struct). Clients of this
    /// routine will need to determine if the size is actually required.
    ///
    /// Def If non-null, and the type refers to some kind of declaration
    /// that can be completed (such as a C struct, C++ class, or Objective-C
    /// class), will be set to the declaration.
    bool isIncompleteType(NamedDecl **Def = nullptr) const;
  
    /// Return true if this is an incomplete or object
    /// type, in other words, not a function type.
    bool isIncompleteOrObjectType() const {
      return !isFunctionType();
    }
  
    /// Determine whether this type is an object type.
    bool isObjectType() const {
      // C++ [basic.types]p8:
      //   An object type is a (possibly cv-qualified) type that is not a
      //   function type, not a reference type, and not a void type.
      return !isReferenceType() && !isFunctionType() && !isVoidType();
    }
  
    /// Return true if this is a literal type
    /// (C++11 [basic.types]p10)
    bool isLiteralType(const ASTContext &Ctx) const;
  
    /// Test if this type is a standard-layout type.
    /// (C++0x [basic.type]p9)
    bool isStandardLayoutType() const;
  
    /// Helper methods to distinguish type categories. All type predicates
    /// operate on the canonical type, ignoring typedefs and qualifiers.
  
    /// Returns true if the type is a builtin type.
    bool isBuiltinType() const;
  
    /// Test for a particular builtin type.
    bool isSpecificBuiltinType(unsigned K) const;
  
    /// Test for a type which does not represent an actual type-system type but
    /// is instead used as a placeholder for various convenient purposes within
    /// Clang.  All such types are BuiltinTypes.
    bool isPlaceholderType() const;
    const BuiltinType *getAsPlaceholderType() const;
  
    /// Test for a specific placeholder type.
    bool isSpecificPlaceholderType(unsigned K) const;
  
    /// Test for a placeholder type other than Overload; see
    /// BuiltinType::isNonOverloadPlaceholderType.
    bool isNonOverloadPlaceholderType() const;
  
    /// isIntegerType() does *not* include complex integers (a GCC extension).
    /// isComplexIntegerType() can be used to test for complex integers.
    bool isIntegerType() const;     // C99 6.2.5p17 (int, char, bool, enum)
    bool isEnumeralType() const;
  
    /// Determine whether this type is a scoped enumeration type.
    bool isScopedEnumeralType() const;
    bool isBooleanType() const;
    bool isCharType() const;
    bool isWideCharType() const;
    bool isChar8Type() const;
    bool isChar16Type() const;
    bool isChar32Type() const;
    bool isAnyCharacterType() const;
    bool isIntegralType(const ASTContext &Ctx) const;
  
    /// Determine whether this type is an integral or enumeration type.
    bool isIntegralOrEnumerationType() const;
  
    /// Determine whether this type is an integral or unscoped enumeration type.
    bool isIntegralOrUnscopedEnumerationType() const;
  
    /// Floating point categories.
    bool isRealFloatingType() const; // C99 6.2.5p10 (float, double, long double)
    /// isComplexType() does *not* include complex integers (a GCC extension).
    /// isComplexIntegerType() can be used to test for complex integers.
    bool isComplexType() const;      // C99 6.2.5p11 (complex)
    bool isAnyComplexType() const;   // C99 6.2.5p11 (complex) + Complex Int.
    bool isFloatingType() const;     // C99 6.2.5p11 (real floating + complex)
    bool isHalfType() const;         // OpenCL 6.1.1.1, NEON (IEEE 754-2008 half)
    bool isFloat16Type() const;      // C11 extension ISO/IEC TS 18661
    bool isFloat128Type() const;
    bool isRealType() const;         // C99 6.2.5p17 (real floating + integer)
    bool isArithmeticType() const;   // C99 6.2.5p18 (integer + floating)
    bool isVoidType() const;         // C99 6.2.5p19
    bool isScalarType() const;       // C99 6.2.5p21 (arithmetic + pointers)
    bool isAggregateType() const;
    bool isFundamentalType() const;
    bool isCompoundType() const;
  
    // Type Predicates: Check to see if this type is structurally the specified
    // type, ignoring typedefs and qualifiers.
    bool isFunctionType() const;
    bool isFunctionNoProtoType() const { return getAs<FunctionNoProtoType>(); }
    bool isFunctionProtoType() const { return getAs<FunctionProtoType>(); }
    bool isPointerType() const;
    bool isAnyPointerType() const;   // Any C pointer or ObjC object pointer
    bool isBlockPointerType() const;
    bool isVoidPointerType() const;
    bool isReferenceType() const;
    bool isLValueReferenceType() const;
    bool isRValueReferenceType() const;
    bool isFunctionPointerType() const;
    bool isMemberPointerType() const;
    bool isMemberFunctionPointerType() const;
    bool isMemberDataPointerType() const;
    bool isArrayType() const;
    bool isConstantArrayType() const;
    bool isIncompleteArrayType() const;
    bool isVariableArrayType() const;
    bool isDependentSizedArrayType() const;
    bool isRecordType() const;
    bool isClassType() const;
    bool isStructureType() const;
    bool isObjCBoxableRecordType() const;
    bool isInterfaceType() const;
    bool isStructureOrClassType() const;
    bool isUnionType() const;
    bool isComplexIntegerType() const;            // GCC _Complex integer type.
    bool isVectorType() const;                    // GCC vector type.
    bool isExtVectorType() const;                 // Extended vector type.
    bool isDependentAddressSpaceType() const;     // value-dependent address space qualifier
    bool isObjCObjectPointerType() const;         // pointer to ObjC object
    bool isObjCRetainableType() const;            // ObjC object or block pointer
    bool isObjCLifetimeType() const;              // (array of)* retainable type
    bool isObjCIndirectLifetimeType() const;      // (pointer to)* lifetime type
    bool isObjCNSObjectType() const;              // __attribute__((NSObject))
    bool isObjCIndependentClassType() const;      // __attribute__((objc_independent_class))
    // FIXME: change this to 'raw' interface type, so we can used 'interface' type
    // for the common case.
    bool isObjCObjectType() const;                // NSString or typeof(*(id)0)
    bool isObjCQualifiedInterfaceType() const;    // NSString<foo>
    bool isObjCQualifiedIdType() const;           // id<foo>
    bool isObjCQualifiedClassType() const;        // Class<foo>
    bool isObjCObjectOrInterfaceType() const;
    bool isObjCIdType() const;                    // id
    bool isDecltypeType() const;
    /// Was this type written with the special inert-in-ARC __unsafe_unretained
    /// qualifier?
    ///
    /// This approximates the answer to the following question: if this
    /// translation unit were compiled in ARC, would this type be qualified
    /// with __unsafe_unretained?
    bool isObjCInertUnsafeUnretainedType() const {
      return hasAttr(attr::ObjCInertUnsafeUnretained);
    }
  
    /// Whether the type is Objective-C 'id' or a __kindof type of an
    /// object type, e.g., __kindof NSView * or __kindof id
    /// <NSCopying>.
    ///
    /// \param bound Will be set to the bound on non-id subtype types,
    /// which will be (possibly specialized) Objective-C class type, or
    /// null for 'id.
    bool isObjCIdOrObjectKindOfType(const ASTContext &ctx,
                                    const ObjCObjectType *&bound) const;
  
    bool isObjCClassType() const;                 // Class
  
    /// Whether the type is Objective-C 'Class' or a __kindof type of an
    /// Class type, e.g., __kindof Class <NSCopying>.
    ///
    /// Unlike \c isObjCIdOrObjectKindOfType, there is no relevant bound
    /// here because Objective-C's type system cannot express "a class
    /// object for a subclass of NSFoo".
    bool isObjCClassOrClassKindOfType() const;
  
    bool isBlockCompatibleObjCPointerType(ASTContext &ctx) const;
    bool isObjCSelType() const;                 // Class
    bool isObjCBuiltinType() const;               // 'id' or 'Class'
    bool isObjCARCBridgableType() const;
    bool isCARCBridgableType() const;
    bool isTemplateTypeParmType() const;          // C++ template type parameter
    bool isNullPtrType() const;                   // C++11 std::nullptr_t
    bool isAlignValT() const;                     // C++17 std::align_val_t
    bool isStdByteType() const;                   // C++17 std::byte
    bool isAtomicType() const;                    // C11 _Atomic()
  
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
    bool is##Id##Type() const;
  #include "clang/Basic/OpenCLImageTypes.def"
  
    bool isImageType() const;                     // Any OpenCL image type
  
    bool isSamplerT() const;                      // OpenCL sampler_t
    bool isEventT() const;                        // OpenCL event_t
    bool isClkEventT() const;                     // OpenCL clk_event_t
    bool isQueueT() const;                        // OpenCL queue_t
    bool isReserveIDT() const;                    // OpenCL reserve_id_t
  
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
    bool is##Id##Type() const;
  #include "clang/Basic/OpenCLExtensionTypes.def"
    // Type defined in cl_intel_device_side_avc_motion_estimation OpenCL extension
    bool isOCLIntelSubgroupAVCType() const;
    bool isOCLExtOpaqueType() const;              // Any OpenCL extension type
  
    bool isPipeType() const;                      // OpenCL pipe type
    bool isOpenCLSpecificType() const;            // Any OpenCL specific type
  
    /// Determines if this type, which must satisfy
    /// isObjCLifetimeType(), is implicitly __unsafe_unretained rather
    /// than implicitly __strong.
    bool isObjCARCImplicitlyUnretainedType() const;
  
    /// Return the implicit lifetime for this type, which must not be dependent.
    Qualifiers::ObjCLifetime getObjCARCImplicitLifetime() const;
  
    enum ScalarTypeKind {
      STK_CPointer,
      STK_BlockPointer,
      STK_ObjCObjectPointer,
      STK_MemberPointer,
      STK_Bool,
      STK_Integral,
      STK_Floating,
      STK_IntegralComplex,
      STK_FloatingComplex,
      STK_FixedPoint
    };
  
    /// Given that this is a scalar type, classify it.
    ScalarTypeKind getScalarTypeKind() const;
  
    /// Whether this type is a dependent type, meaning that its definition
    /// somehow depends on a template parameter (C++ [temp.dep.type]).
    bool isDependentType() const { return TypeBits.Dependent; }
  
    /// Determine whether this type is an instantiation-dependent type,
    /// meaning that the type involves a template parameter (even if the
    /// definition does not actually depend on the type substituted for that
    /// template parameter).
    bool isInstantiationDependentType() const {
      return TypeBits.InstantiationDependent;
    }
  
    /// Determine whether this type is an undeduced type, meaning that
    /// it somehow involves a C++11 'auto' type or similar which has not yet been
    /// deduced.
    bool isUndeducedType() const;
  
    /// Whether this type is a variably-modified type (C99 6.7.5).
    bool isVariablyModifiedType() const { return TypeBits.VariablyModified; }
  
    /// Whether this type involves a variable-length array type
    /// with a definite size.
    bool hasSizedVLAType() const;
  
    /// Whether this type is or contains a local or unnamed type.
    bool hasUnnamedOrLocalType() const;
  
    bool isOverloadableType() const;
  
    /// Determine wither this type is a C++ elaborated-type-specifier.
    bool isElaboratedTypeSpecifier() const;
  
    bool canDecayToPointerType() const;
  
    /// Whether this type is represented natively as a pointer.  This includes
    /// pointers, references, block pointers, and Objective-C interface,
    /// qualified id, and qualified interface types, as well as nullptr_t.
    bool hasPointerRepresentation() const;
  
    /// Whether this type can represent an objective pointer type for the
    /// purpose of GC'ability
    bool hasObjCPointerRepresentation() const;
  
    /// Determine whether this type has an integer representation
    /// of some sort, e.g., it is an integer type or a vector.
    bool hasIntegerRepresentation() const;
  
    /// Determine whether this type has an signed integer representation
    /// of some sort, e.g., it is an signed integer type or a vector.
    bool hasSignedIntegerRepresentation() const;
  
    /// Determine whether this type has an unsigned integer representation
    /// of some sort, e.g., it is an unsigned integer type or a vector.
    bool hasUnsignedIntegerRepresentation() const;
  
    /// Determine whether this type has a floating-point representation
    /// of some sort, e.g., it is a floating-point type or a vector thereof.
    bool hasFloatingRepresentation() const;
  
    // Type Checking Functions: Check to see if this type is structurally the
    // specified type, ignoring typedefs and qualifiers, and return a pointer to
    // the best type we can.
    const RecordType *getAsStructureType() const;
    /// NOTE: getAs*ArrayType are methods on ASTContext.
    const RecordType *getAsUnionType() const;
    const ComplexType *getAsComplexIntegerType() const; // GCC complex int type.
    const ObjCObjectType *getAsObjCInterfaceType() const;
  
    // The following is a convenience method that returns an ObjCObjectPointerType
    // for object declared using an interface.
    const ObjCObjectPointerType *getAsObjCInterfacePointerType() const;
    const ObjCObjectPointerType *getAsObjCQualifiedIdType() const;
    const ObjCObjectPointerType *getAsObjCQualifiedClassType() const;
    const ObjCObjectType *getAsObjCQualifiedInterfaceType() const;
  
    /// Retrieves the CXXRecordDecl that this type refers to, either
    /// because the type is a RecordType or because it is the injected-class-name
    /// type of a class template or class template partial specialization.
    CXXRecordDecl *getAsCXXRecordDecl() const;
  
    /// Retrieves the RecordDecl this type refers to.
    RecordDecl *getAsRecordDecl() const;
  
    /// Retrieves the TagDecl that this type refers to, either
    /// because the type is a TagType or because it is the injected-class-name
    /// type of a class template or class template partial specialization.
    TagDecl *getAsTagDecl() const;
  
    /// If this is a pointer or reference to a RecordType, return the
    /// CXXRecordDecl that the type refers to.
    ///
    /// If this is not a pointer or reference, or the type being pointed to does
    /// not refer to a CXXRecordDecl, returns NULL.
    const CXXRecordDecl *getPointeeCXXRecordDecl() const;
  
    /// Get the DeducedType whose type will be deduced for a variable with
    /// an initializer of this type. This looks through declarators like pointer
    /// types, but not through decltype or typedefs.
    DeducedType *getContainedDeducedType() const;
  
    /// Get the AutoType whose type will be deduced for a variable with
    /// an initializer of this type. This looks through declarators like pointer
    /// types, but not through decltype or typedefs.
    AutoType *getContainedAutoType() const {
      return dyn_cast_or_null<AutoType>(getContainedDeducedType());
    }
  
    /// Determine whether this type was written with a leading 'auto'
    /// corresponding to a trailing return type (possibly for a nested
    /// function type within a pointer to function type or similar).
    bool hasAutoForTrailingReturnType() const;
  
    /// Member-template getAs<specific type>'.  Look through sugar for
    /// an instance of \<specific type>.   This scheme will eventually
    /// replace the specific getAsXXXX methods above.
    ///
    /// There are some specializations of this member template listed
    /// immediately following this class.
    template <typename T> const T *getAs() const;
  
    /// Member-template getAsAdjusted<specific type>. Look through specific kinds
    /// of sugar (parens, attributes, etc) for an instance of \<specific type>.
    /// This is used when you need to walk over sugar nodes that represent some
    /// kind of type adjustment from a type that was written as a \<specific type>
    /// to another type that is still canonically a \<specific type>.
    template <typename T> const T *getAsAdjusted() const;
  
    /// A variant of getAs<> for array types which silently discards
    /// qualifiers from the outermost type.
    const ArrayType *getAsArrayTypeUnsafe() const;
  
    /// Member-template castAs<specific type>.  Look through sugar for
    /// the underlying instance of \<specific type>.
    ///
    /// This method has the same relationship to getAs<T> as cast<T> has
    /// to dyn_cast<T>; which is to say, the underlying type *must*
    /// have the intended type, and this method will never return null.
    template <typename T> const T *castAs() const;
  
    /// A variant of castAs<> for array type which silently discards
    /// qualifiers from the outermost type.
    const ArrayType *castAsArrayTypeUnsafe() const;
  
    /// Determine whether this type had the specified attribute applied to it
    /// (looking through top-level type sugar).
    bool hasAttr(attr::Kind AK) const;
  
    /// Get the base element type of this type, potentially discarding type
    /// qualifiers.  This should never be used when type qualifiers
    /// are meaningful.
    const Type *getBaseElementTypeUnsafe() const;
  
    /// If this is an array type, return the element type of the array,
    /// potentially with type qualifiers missing.
    /// This should never be used when type qualifiers are meaningful.
    const Type *getArrayElementTypeNoTypeQual() const;
  
    /// If this is a pointer type, return the pointee type.
    /// If this is an array type, return the array element type.
    /// This should never be used when type qualifiers are meaningful.
    const Type *getPointeeOrArrayElementType() const;
  
    /// If this is a pointer, ObjC object pointer, or block
    /// pointer, this returns the respective pointee.
    QualType getPointeeType() const;
  
    /// Return the specified type with any "sugar" removed from the type,
    /// removing any typedefs, typeofs, etc., as well as any qualifiers.
    const Type *getUnqualifiedDesugaredType() const;
  
    /// More type predicates useful for type checking/promotion
    bool isPromotableIntegerType() const; // C99 6.3.1.1p2
  
    /// Return true if this is an integer type that is
    /// signed, according to C99 6.2.5p4 [char, signed char, short, int, long..],
    /// or an enum decl which has a signed representation.
    bool isSignedIntegerType() const;
  
    /// Return true if this is an integer type that is
    /// unsigned, according to C99 6.2.5p6 [which returns true for _Bool],
    /// or an enum decl which has an unsigned representation.
    bool isUnsignedIntegerType() const;
  
    /// Determines whether this is an integer type that is signed or an
    /// enumeration types whose underlying type is a signed integer type.
    bool isSignedIntegerOrEnumerationType() const;
  
    /// Determines whether this is an integer type that is unsigned or an
    /// enumeration types whose underlying type is a unsigned integer type.
    bool isUnsignedIntegerOrEnumerationType() const;
  
    /// Return true if this is a fixed point type according to
    /// ISO/IEC JTC1 SC22 WG14 N1169.
    bool isFixedPointType() const;
  
    /// Return true if this is a fixed point or integer type.
    bool isFixedPointOrIntegerType() const;
  
    /// Return true if this is a saturated fixed point type according to
    /// ISO/IEC JTC1 SC22 WG14 N1169. This type can be signed or unsigned.
    bool isSaturatedFixedPointType() const;
  
    /// Return true if this is a saturated fixed point type according to
    /// ISO/IEC JTC1 SC22 WG14 N1169. This type can be signed or unsigned.
    bool isUnsaturatedFixedPointType() const;
  
    /// Return true if this is a fixed point type that is signed according
    /// to ISO/IEC JTC1 SC22 WG14 N1169. This type can also be saturated.
    bool isSignedFixedPointType() const;
  
    /// Return true if this is a fixed point type that is unsigned according
    /// to ISO/IEC JTC1 SC22 WG14 N1169. This type can also be saturated.
    bool isUnsignedFixedPointType() const;
  
    /// Return true if this is not a variable sized type,
    /// according to the rules of C99 6.7.5p3.  It is not legal to call this on
    /// incomplete types.
    bool isConstantSizeType() const;
  
    /// Returns true if this type can be represented by some
    /// set of type specifiers.
    bool isSpecifierType() const;
  
    /// Determine the linkage of this type.
    Linkage getLinkage() const;
  
    /// Determine the visibility of this type.
    Visibility getVisibility() const {
      return getLinkageAndVisibility().getVisibility();
    }
  
    /// Return true if the visibility was explicitly set is the code.
    bool isVisibilityExplicit() const {
      return getLinkageAndVisibility().isVisibilityExplicit();
    }
  
    /// Determine the linkage and visibility of this type.
    LinkageInfo getLinkageAndVisibility() const;
  
    /// True if the computed linkage is valid. Used for consistency
    /// checking. Should always return true.
    bool isLinkageValid() const;
  
    /// Determine the nullability of the given type.
    ///
    /// Note that nullability is only captured as sugar within the type
    /// system, not as part of the canonical type, so nullability will
    /// be lost by canonicalization and desugaring.
    Optional<NullabilityKind> getNullability(const ASTContext &context) const;
  
    /// Determine whether the given type can have a nullability
    /// specifier applied to it, i.e., if it is any kind of pointer type.
    ///
    /// \param ResultIfUnknown The value to return if we don't yet know whether
    ///        this type can have nullability because it is dependent.
    bool canHaveNullability(bool ResultIfUnknown = true) const;
  
    /// Retrieve the set of substitutions required when accessing a member
    /// of the Objective-C receiver type that is declared in the given context.
    ///
    /// \c *this is the type of the object we're operating on, e.g., the
    /// receiver for a message send or the base of a property access, and is
    /// expected to be of some object or object pointer type.
    ///
    /// \param dc The declaration context for which we are building up a
    /// substitution mapping, which should be an Objective-C class, extension,
    /// category, or method within.
    ///
    /// \returns an array of type arguments that can be substituted for
    /// the type parameters of the given declaration context in any type described
    /// within that context, or an empty optional to indicate that no
    /// substitution is required.
    Optional<ArrayRef<QualType>>
    getObjCSubstitutions(const DeclContext *dc) const;
  
    /// Determines if this is an ObjC interface type that may accept type
    /// parameters.
    bool acceptsObjCTypeParams() const;
  
    const char *getTypeClassName() const;
  
    QualType getCanonicalTypeInternal() const {
      return CanonicalType;
    }
  
    CanQualType getCanonicalTypeUnqualified() const; // in CanonicalType.h
    void dump() const;
    void dump(llvm::raw_ostream &OS) const;
  };
  
  /// This will check for a TypedefType by removing any existing sugar
  /// until it reaches a TypedefType or a non-sugared type.
  template <> const TypedefType *Type::getAs() const;
  
  /// This will check for a TemplateSpecializationType by removing any
  /// existing sugar until it reaches a TemplateSpecializationType or a
  /// non-sugared type.
  template <> const TemplateSpecializationType *Type::getAs() const;
  
  /// This will check for an AttributedType by removing any existing sugar
  /// until it reaches an AttributedType or a non-sugared type.
  template <> const AttributedType *Type::getAs() const;
  
  // We can do canonical leaf types faster, because we don't have to
  // worry about preserving child type decoration.
  #define TYPE(Class, Base)
  #define LEAF_TYPE(Class) \
  template <> inline const Class##Type *Type::getAs() const { \
    return dyn_cast<Class##Type>(CanonicalType); \
  } \
  template <> inline const Class##Type *Type::castAs() const { \
    return cast<Class##Type>(CanonicalType); \
  }
  #include "clang/AST/TypeNodes.def"
  
  /// This class is used for builtin types like 'int'.  Builtin
  /// types are always canonical and have a literal name field.
  class BuiltinType : public Type {
  public:
    enum Kind {
  // OpenCL image types
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) Id,
  #include "clang/Basic/OpenCLImageTypes.def"
  // OpenCL extension types
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) Id,
  #include "clang/Basic/OpenCLExtensionTypes.def"
  // All other builtin types
  #define BUILTIN_TYPE(Id, SingletonId) Id,
  #define LAST_BUILTIN_TYPE(Id) LastKind = Id
  #include "clang/AST/BuiltinTypes.def"
    };
  
  private:
    friend class ASTContext; // ASTContext creates these.
  
    BuiltinType(Kind K)
        : Type(Builtin, QualType(), /*Dependent=*/(K == Dependent),
               /*InstantiationDependent=*/(K == Dependent),
               /*VariablyModified=*/false,
               /*Unexpanded parameter pack=*/false) {
      BuiltinTypeBits.Kind = K;
    }
  
  public:
    Kind getKind() const { return static_cast<Kind>(BuiltinTypeBits.Kind); }
    StringRef getName(const PrintingPolicy &Policy) const;
  
    const char *getNameAsCString(const PrintingPolicy &Policy) const {
      // The StringRef is null-terminated.
      StringRef str = getName(Policy);
      assert(!str.empty() && str.data()[str.size()] == '\0');
      return str.data();
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    bool isInteger() const {
      return getKind() >= Bool && getKind() <= Int128;
    }
  
    bool isSignedInteger() const {
      return getKind() >= Char_S && getKind() <= Int128;
    }
  
    bool isUnsignedInteger() const {
      return getKind() >= Bool && getKind() <= UInt128;
    }
  
    bool isFloatingPoint() const {
      return getKind() >= Half && getKind() <= Float128;
    }
  
    /// Determines whether the given kind corresponds to a placeholder type.
    static bool isPlaceholderTypeKind(Kind K) {
      return K >= Overload;
    }
  
    /// Determines whether this type is a placeholder type, i.e. a type
    /// which cannot appear in arbitrary positions in a fully-formed
    /// expression.
    bool isPlaceholderType() const {
      return isPlaceholderTypeKind(getKind());
    }
  
    /// Determines whether this type is a placeholder type other than
    /// Overload.  Most placeholder types require only syntactic
    /// information about their context in order to be resolved (e.g.
    /// whether it is a call expression), which means they can (and
    /// should) be resolved in an earlier "phase" of analysis.
    /// Overload expressions sometimes pick up further information
    /// from their context, like whether the context expects a
    /// specific function-pointer type, and so frequently need
    /// special treatment.
    bool isNonOverloadPlaceholderType() const {
      return getKind() > Overload;
    }
  
    static bool classof(const Type *T) { return T->getTypeClass() == Builtin; }
  };
  
  /// Complex values, per C99 6.2.5p11.  This supports the C99 complex
  /// types (_Complex float etc) as well as the GCC integer complex extensions.
  class ComplexType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    QualType ElementType;
  
    ComplexType(QualType Element, QualType CanonicalPtr)
        : Type(Complex, CanonicalPtr, Element->isDependentType(),
               Element->isInstantiationDependentType(),
               Element->isVariablyModifiedType(),
               Element->containsUnexpandedParameterPack()),
          ElementType(Element) {}
  
  public:
    QualType getElementType() const { return ElementType; }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getElementType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Element) {
      ID.AddPointer(Element.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) { return T->getTypeClass() == Complex; }
  };
  
  /// Sugar for parentheses used when specifying types.
  class ParenType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    QualType Inner;
  
    ParenType(QualType InnerType, QualType CanonType)
        : Type(Paren, CanonType, InnerType->isDependentType(),
               InnerType->isInstantiationDependentType(),
               InnerType->isVariablyModifiedType(),
               InnerType->containsUnexpandedParameterPack()),
          Inner(InnerType) {}
  
  public:
    QualType getInnerType() const { return Inner; }
  
    bool isSugared() const { return true; }
    QualType desugar() const { return getInnerType(); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getInnerType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Inner) {
      Inner.Profile(ID);
    }
  
    static bool classof(const Type *T) { return T->getTypeClass() == Paren; }
  };
  
  /// PointerType - C99 6.7.5.1 - Pointer Declarators.
  class PointerType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    QualType PointeeType;
  
    PointerType(QualType Pointee, QualType CanonicalPtr)
        : Type(Pointer, CanonicalPtr, Pointee->isDependentType(),
               Pointee->isInstantiationDependentType(),
               Pointee->isVariablyModifiedType(),
               Pointee->containsUnexpandedParameterPack()),
          PointeeType(Pointee) {}
  
  public:
    QualType getPointeeType() const { return PointeeType; }
  
    /// Returns true if address spaces of pointers overlap.
    /// OpenCL v2.0 defines conversion rules for pointers to different
    /// address spaces (OpenCLC v2.0 s6.5.5) and notion of overlapping
    /// address spaces.
    /// CL1.1 or CL1.2:
    ///   address spaces overlap iff they are they same.
    /// CL2.0 adds:
    ///   __generic overlaps with any address space except for __constant.
    bool isAddressSpaceOverlapping(const PointerType &other) const {
      Qualifiers thisQuals = PointeeType.getQualifiers();
      Qualifiers otherQuals = other.getPointeeType().getQualifiers();
      // Address spaces overlap if at least one of them is a superset of another
      return thisQuals.isAddressSpaceSupersetOf(otherQuals) ||
             otherQuals.isAddressSpaceSupersetOf(thisQuals);
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getPointeeType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Pointee) {
      ID.AddPointer(Pointee.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) { return T->getTypeClass() == Pointer; }
  };
  
  /// Represents a type which was implicitly adjusted by the semantic
  /// engine for arbitrary reasons.  For example, array and function types can
  /// decay, and function types can have their calling conventions adjusted.
  class AdjustedType : public Type, public llvm::FoldingSetNode {
    QualType OriginalTy;
    QualType AdjustedTy;
  
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    AdjustedType(TypeClass TC, QualType OriginalTy, QualType AdjustedTy,
                 QualType CanonicalPtr)
        : Type(TC, CanonicalPtr, OriginalTy->isDependentType(),
               OriginalTy->isInstantiationDependentType(),
               OriginalTy->isVariablyModifiedType(),
               OriginalTy->containsUnexpandedParameterPack()),
          OriginalTy(OriginalTy), AdjustedTy(AdjustedTy) {}
  
  public:
    QualType getOriginalType() const { return OriginalTy; }
    QualType getAdjustedType() const { return AdjustedTy; }
  
    bool isSugared() const { return true; }
    QualType desugar() const { return AdjustedTy; }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, OriginalTy, AdjustedTy);
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Orig, QualType New) {
      ID.AddPointer(Orig.getAsOpaquePtr());
      ID.AddPointer(New.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == Adjusted || T->getTypeClass() == Decayed;
    }
  };
  
  /// Represents a pointer type decayed from an array or function type.
  class DecayedType : public AdjustedType {
    friend class ASTContext; // ASTContext creates these.
  
    inline
    DecayedType(QualType OriginalType, QualType Decayed, QualType Canonical);
  
  public:
    QualType getDecayedType() const { return getAdjustedType(); }
  
    inline QualType getPointeeType() const;
  
    static bool classof(const Type *T) { return T->getTypeClass() == Decayed; }
  };
  
  /// Pointer to a block type.
  /// This type is to represent types syntactically represented as
  /// "void (^)(int)", etc. Pointee is required to always be a function type.
  class BlockPointerType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    // Block is some kind of pointer type
    QualType PointeeType;
  
    BlockPointerType(QualType Pointee, QualType CanonicalCls)
        : Type(BlockPointer, CanonicalCls, Pointee->isDependentType(),
               Pointee->isInstantiationDependentType(),
               Pointee->isVariablyModifiedType(),
               Pointee->containsUnexpandedParameterPack()),
          PointeeType(Pointee) {}
  
  public:
    // Get the pointee type. Pointee is required to always be a function type.
    QualType getPointeeType() const { return PointeeType; }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
        Profile(ID, getPointeeType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Pointee) {
        ID.AddPointer(Pointee.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == BlockPointer;
    }
  };
  
  /// Base for LValueReferenceType and RValueReferenceType
  class ReferenceType : public Type, public llvm::FoldingSetNode {
    QualType PointeeType;
  
  protected:
    ReferenceType(TypeClass tc, QualType Referencee, QualType CanonicalRef,
                  bool SpelledAsLValue)
        : Type(tc, CanonicalRef, Referencee->isDependentType(),
               Referencee->isInstantiationDependentType(),
               Referencee->isVariablyModifiedType(),
               Referencee->containsUnexpandedParameterPack()),
          PointeeType(Referencee) {
      ReferenceTypeBits.SpelledAsLValue = SpelledAsLValue;
      ReferenceTypeBits.InnerRef = Referencee->isReferenceType();
    }
  
  public:
    bool isSpelledAsLValue() const { return ReferenceTypeBits.SpelledAsLValue; }
    bool isInnerRef() const { return ReferenceTypeBits.InnerRef; }
  
    QualType getPointeeTypeAsWritten() const { return PointeeType; }
  
    QualType getPointeeType() const {
      // FIXME: this might strip inner qualifiers; okay?
      const ReferenceType *T = this;
      while (T->isInnerRef())
        T = T->PointeeType->castAs<ReferenceType>();
      return T->PointeeType;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, PointeeType, isSpelledAsLValue());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID,
                        QualType Referencee,
                        bool SpelledAsLValue) {
      ID.AddPointer(Referencee.getAsOpaquePtr());
      ID.AddBoolean(SpelledAsLValue);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == LValueReference ||
             T->getTypeClass() == RValueReference;
    }
  };
  
  /// An lvalue reference type, per C++11 [dcl.ref].
  class LValueReferenceType : public ReferenceType {
    friend class ASTContext; // ASTContext creates these
  
    LValueReferenceType(QualType Referencee, QualType CanonicalRef,
                        bool SpelledAsLValue)
        : ReferenceType(LValueReference, Referencee, CanonicalRef,
                        SpelledAsLValue) {}
  
  public:
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == LValueReference;
    }
  };
  
  /// An rvalue reference type, per C++11 [dcl.ref].
  class RValueReferenceType : public ReferenceType {
    friend class ASTContext; // ASTContext creates these
  
    RValueReferenceType(QualType Referencee, QualType CanonicalRef)
         : ReferenceType(RValueReference, Referencee, CanonicalRef, false) {}
  
  public:
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == RValueReference;
    }
  };
  
  /// A pointer to member type per C++ 8.3.3 - Pointers to members.
  ///
  /// This includes both pointers to data members and pointer to member functions.
  class MemberPointerType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    QualType PointeeType;
  
    /// The class of which the pointee is a member. Must ultimately be a
    /// RecordType, but could be a typedef or a template parameter too.
    const Type *Class;
  
    MemberPointerType(QualType Pointee, const Type *Cls, QualType CanonicalPtr)
        : Type(MemberPointer, CanonicalPtr,
               Cls->isDependentType() || Pointee->isDependentType(),
               (Cls->isInstantiationDependentType() ||
                Pointee->isInstantiationDependentType()),
               Pointee->isVariablyModifiedType(),
               (Cls->containsUnexpandedParameterPack() ||
                Pointee->containsUnexpandedParameterPack())),
               PointeeType(Pointee), Class(Cls) {}
  
  public:
    QualType getPointeeType() const { return PointeeType; }
  
    /// Returns true if the member type (i.e. the pointee type) is a
    /// function type rather than a data-member type.
    bool isMemberFunctionPointer() const {
      return PointeeType->isFunctionProtoType();
    }
  
    /// Returns true if the member type (i.e. the pointee type) is a
    /// data type rather than a function type.
    bool isMemberDataPointer() const {
      return !PointeeType->isFunctionProtoType();
    }
  
    const Type *getClass() const { return Class; }
    CXXRecordDecl *getMostRecentCXXRecordDecl() const;
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getPointeeType(), getClass());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Pointee,
                        const Type *Class) {
      ID.AddPointer(Pointee.getAsOpaquePtr());
      ID.AddPointer(Class);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == MemberPointer;
    }
  };
  
  /// Represents an array type, per C99 6.7.5.2 - Array Declarators.
  class ArrayType : public Type, public llvm::FoldingSetNode {
  public:
    /// Capture whether this is a normal array (e.g. int X[4])
    /// an array with a static size (e.g. int X[static 4]), or an array
    /// with a star size (e.g. int X[*]).
    /// 'static' is only allowed on function parameters.
    enum ArraySizeModifier {
      Normal, Static, Star
    };
  
  private:
    /// The element type of the array.
    QualType ElementType;
  
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    // C++ [temp.dep.type]p1:
    //   A type is dependent if it is...
    //     - an array type constructed from any dependent type or whose
    //       size is specified by a constant expression that is
    //       value-dependent,
    ArrayType(TypeClass tc, QualType et, QualType can,
              ArraySizeModifier sm, unsigned tq,
              bool ContainsUnexpandedParameterPack)
        : Type(tc, can, et->isDependentType() || tc == DependentSizedArray,
               et->isInstantiationDependentType() || tc == DependentSizedArray,
               (tc == VariableArray || et->isVariablyModifiedType()),
               ContainsUnexpandedParameterPack),
          ElementType(et) {
      ArrayTypeBits.IndexTypeQuals = tq;
      ArrayTypeBits.SizeModifier = sm;
    }
  
  public:
    QualType getElementType() const { return ElementType; }
  
    ArraySizeModifier getSizeModifier() const {
      return ArraySizeModifier(ArrayTypeBits.SizeModifier);
    }
  
    Qualifiers getIndexTypeQualifiers() const {
      return Qualifiers::fromCVRMask(getIndexTypeCVRQualifiers());
    }
  
    unsigned getIndexTypeCVRQualifiers() const {
      return ArrayTypeBits.IndexTypeQuals;
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == ConstantArray ||
             T->getTypeClass() == VariableArray ||
             T->getTypeClass() == IncompleteArray ||
             T->getTypeClass() == DependentSizedArray;
    }
  };
  
  /// Represents the canonical version of C arrays with a specified constant size.
  /// For example, the canonical type for 'int A[4 + 4*100]' is a
  /// ConstantArrayType where the element type is 'int' and the size is 404.
  class ConstantArrayType : public ArrayType {
    llvm::APInt Size; // Allows us to unique the type.
  
    ConstantArrayType(QualType et, QualType can, const llvm::APInt &size,
                      ArraySizeModifier sm, unsigned tq)
        : ArrayType(ConstantArray, et, can, sm, tq,
                    et->containsUnexpandedParameterPack()),
          Size(size) {}
  
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    ConstantArrayType(TypeClass tc, QualType et, QualType can,
                      const llvm::APInt &size, ArraySizeModifier sm, unsigned tq)
        : ArrayType(tc, et, can, sm, tq, et->containsUnexpandedParameterPack()),
          Size(size) {}
  
  public:
    const llvm::APInt &getSize() const { return Size; }
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    /// Determine the number of bits required to address a member of
    // an array with the given element type and number of elements.
    static unsigned getNumAddressingBits(const ASTContext &Context,
                                         QualType ElementType,
                                         const llvm::APInt &NumElements);
  
    /// Determine the maximum number of active bits that an array's size
    /// can require, which limits the maximum size of the array.
    static unsigned getMaxSizeBits(const ASTContext &Context);
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getElementType(), getSize(),
              getSizeModifier(), getIndexTypeCVRQualifiers());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType ET,
                        const llvm::APInt &ArraySize, ArraySizeModifier SizeMod,
                        unsigned TypeQuals) {
      ID.AddPointer(ET.getAsOpaquePtr());
      ID.AddInteger(ArraySize.getZExtValue());
      ID.AddInteger(SizeMod);
      ID.AddInteger(TypeQuals);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == ConstantArray;
    }
  };
  
  /// Represents a C array with an unspecified size.  For example 'int A[]' has
  /// an IncompleteArrayType where the element type is 'int' and the size is
  /// unspecified.
  class IncompleteArrayType : public ArrayType {
    friend class ASTContext; // ASTContext creates these.
  
    IncompleteArrayType(QualType et, QualType can,
                        ArraySizeModifier sm, unsigned tq)
        : ArrayType(IncompleteArray, et, can, sm, tq,
                    et->containsUnexpandedParameterPack()) {}
  
  public:
    friend class StmtIteratorBase;
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == IncompleteArray;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getElementType(), getSizeModifier(),
              getIndexTypeCVRQualifiers());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType ET,
                        ArraySizeModifier SizeMod, unsigned TypeQuals) {
      ID.AddPointer(ET.getAsOpaquePtr());
      ID.AddInteger(SizeMod);
      ID.AddInteger(TypeQuals);
    }
  };
  
  /// Represents a C array with a specified size that is not an
  /// integer-constant-expression.  For example, 'int s[x+foo()]'.
  /// Since the size expression is an arbitrary expression, we store it as such.
  ///
  /// Note: VariableArrayType's aren't uniqued (since the expressions aren't) and
  /// should not be: two lexically equivalent variable array types could mean
  /// different things, for example, these variables do not have the same type
  /// dynamically:
  ///
  /// void foo(int x) {
  ///   int Y[x];
  ///   ++x;
  ///   int Z[x];
  /// }
  class VariableArrayType : public ArrayType {
    friend class ASTContext; // ASTContext creates these.
  
    /// An assignment-expression. VLA's are only permitted within
    /// a function block.
    Stmt *SizeExpr;
  
    /// The range spanned by the left and right array brackets.
    SourceRange Brackets;
  
    VariableArrayType(QualType et, QualType can, Expr *e,
                      ArraySizeModifier sm, unsigned tq,
                      SourceRange brackets)
        : ArrayType(VariableArray, et, can, sm, tq,
                    et->containsUnexpandedParameterPack()),
          SizeExpr((Stmt*) e), Brackets(brackets) {}
  
  public:
    friend class StmtIteratorBase;
  
    Expr *getSizeExpr() const {
      // We use C-style casts instead of cast<> here because we do not wish
      // to have a dependency of Type.h on Stmt.h/Expr.h.
      return (Expr*) SizeExpr;
    }
  
    SourceRange getBracketsRange() const { return Brackets; }
    SourceLocation getLBracketLoc() const { return Brackets.getBegin(); }
    SourceLocation getRBracketLoc() const { return Brackets.getEnd(); }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == VariableArray;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      llvm_unreachable("Cannot unique VariableArrayTypes.");
    }
  };
  
  /// Represents an array type in C++ whose size is a value-dependent expression.
  ///
  /// For example:
  /// \code
  /// template<typename T, int Size>
  /// class array {
  ///   T data[Size];
  /// };
  /// \endcode
  ///
  /// For these types, we won't actually know what the array bound is
  /// until template instantiation occurs, at which point this will
  /// become either a ConstantArrayType or a VariableArrayType.
  class DependentSizedArrayType : public ArrayType {
    friend class ASTContext; // ASTContext creates these.
  
    const ASTContext &Context;
  
    /// An assignment expression that will instantiate to the
    /// size of the array.
    ///
    /// The expression itself might be null, in which case the array
    /// type will have its size deduced from an initializer.
    Stmt *SizeExpr;
  
    /// The range spanned by the left and right array brackets.
    SourceRange Brackets;
  
    DependentSizedArrayType(const ASTContext &Context, QualType et, QualType can,
                            Expr *e, ArraySizeModifier sm, unsigned tq,
                            SourceRange brackets);
  
  public:
    friend class StmtIteratorBase;
  
    Expr *getSizeExpr() const {
      // We use C-style casts instead of cast<> here because we do not wish
      // to have a dependency of Type.h on Stmt.h/Expr.h.
      return (Expr*) SizeExpr;
    }
  
    SourceRange getBracketsRange() const { return Brackets; }
    SourceLocation getLBracketLoc() const { return Brackets.getBegin(); }
    SourceLocation getRBracketLoc() const { return Brackets.getEnd(); }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == DependentSizedArray;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, Context, getElementType(),
              getSizeModifier(), getIndexTypeCVRQualifiers(), getSizeExpr());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
                        QualType ET, ArraySizeModifier SizeMod,
                        unsigned TypeQuals, Expr *E);
  };
  
  /// Represents an extended address space qualifier where the input address space
  /// value is dependent. Non-dependent address spaces are not represented with a
  /// special Type subclass; they are stored on an ExtQuals node as part of a QualType.
  ///
  /// For example:
  /// \code
  /// template<typename T, int AddrSpace>
  /// class AddressSpace {
  ///   typedef T __attribute__((address_space(AddrSpace))) type;
  /// }
  /// \endcode
  class DependentAddressSpaceType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext;
  
    const ASTContext &Context;
    Expr *AddrSpaceExpr;
    QualType PointeeType;
    SourceLocation loc;
  
    DependentAddressSpaceType(const ASTContext &Context, QualType PointeeType,
                              QualType can, Expr *AddrSpaceExpr,
                              SourceLocation loc);
  
  public:
    Expr *getAddrSpaceExpr() const { return AddrSpaceExpr; }
    QualType getPointeeType() const { return PointeeType; }
    SourceLocation getAttributeLoc() const { return loc; }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == DependentAddressSpace;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, Context, getPointeeType(), getAddrSpaceExpr());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
                        QualType PointeeType, Expr *AddrSpaceExpr);
  };
  
  /// Represents an extended vector type where either the type or size is
  /// dependent.
  ///
  /// For example:
  /// \code
  /// template<typename T, int Size>
  /// class vector {
  ///   typedef T __attribute__((ext_vector_type(Size))) type;
  /// }
  /// \endcode
  class DependentSizedExtVectorType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext;
  
    const ASTContext &Context;
    Expr *SizeExpr;
  
    /// The element type of the array.
    QualType ElementType;
  
    SourceLocation loc;
  
    DependentSizedExtVectorType(const ASTContext &Context, QualType ElementType,
                                QualType can, Expr *SizeExpr, SourceLocation loc);
  
  public:
    Expr *getSizeExpr() const { return SizeExpr; }
    QualType getElementType() const { return ElementType; }
    SourceLocation getAttributeLoc() const { return loc; }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == DependentSizedExtVector;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, Context, getElementType(), getSizeExpr());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
                        QualType ElementType, Expr *SizeExpr);
  };
  
  
  /// Represents a GCC generic vector type. This type is created using
  /// __attribute__((vector_size(n)), where "n" specifies the vector size in
  /// bytes; or from an Altivec __vector or vector declaration.
  /// Since the constructor takes the number of vector elements, the
  /// client is responsible for converting the size into the number of elements.
  class VectorType : public Type, public llvm::FoldingSetNode {
  public:
    enum VectorKind {
      /// not a target-specific vector type
      GenericVector,
  
      /// is AltiVec vector
      AltiVecVector,
  
      /// is AltiVec 'vector Pixel'
      AltiVecPixel,
  
      /// is AltiVec 'vector bool ...'
      AltiVecBool,
  
      /// is ARM Neon vector
      NeonVector,
  
      /// is ARM Neon polynomial vector
      NeonPolyVector
    };
  
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    /// The element type of the vector.
    QualType ElementType;
  
    VectorType(QualType vecType, unsigned nElements, QualType canonType,
               VectorKind vecKind);
  
    VectorType(TypeClass tc, QualType vecType, unsigned nElements,
               QualType canonType, VectorKind vecKind);
  
  public:
    QualType getElementType() const { return ElementType; }
    unsigned getNumElements() const { return VectorTypeBits.NumElements; }
  
    static bool isVectorSizeTooLarge(unsigned NumElements) {
      return NumElements > VectorTypeBitfields::MaxNumElements;
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    VectorKind getVectorKind() const {
      return VectorKind(VectorTypeBits.VecKind);
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getElementType(), getNumElements(),
              getTypeClass(), getVectorKind());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType ElementType,
                        unsigned NumElements, TypeClass TypeClass,
                        VectorKind VecKind) {
      ID.AddPointer(ElementType.getAsOpaquePtr());
      ID.AddInteger(NumElements);
      ID.AddInteger(TypeClass);
      ID.AddInteger(VecKind);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == Vector || T->getTypeClass() == ExtVector;
    }
  };
  
  /// Represents a vector type where either the type or size is dependent.
  ////
  /// For example:
  /// \code
  /// template<typename T, int Size>
  /// class vector {
  ///   typedef T __attribute__((vector_size(Size))) type;
  /// }
  /// \endcode
  class DependentVectorType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext;
  
    const ASTContext &Context;
    QualType ElementType;
    Expr *SizeExpr;
    SourceLocation Loc;
  
    DependentVectorType(const ASTContext &Context, QualType ElementType,
                             QualType CanonType, Expr *SizeExpr,
                             SourceLocation Loc, VectorType::VectorKind vecKind);
  
  public:
    Expr *getSizeExpr() const { return SizeExpr; }
    QualType getElementType() const { return ElementType; }
    SourceLocation getAttributeLoc() const { return Loc; }
    VectorType::VectorKind getVectorKind() const {
      return VectorType::VectorKind(VectorTypeBits.VecKind);
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == DependentVector;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, Context, getElementType(), getSizeExpr(), getVectorKind());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
                        QualType ElementType, const Expr *SizeExpr,
                        VectorType::VectorKind VecKind);
  };
  
  /// ExtVectorType - Extended vector type. This type is created using
  /// __attribute__((ext_vector_type(n)), where "n" is the number of elements.
  /// Unlike vector_size, ext_vector_type is only allowed on typedef's. This
  /// class enables syntactic extensions, like Vector Components for accessing
  /// points (as .xyzw), colors (as .rgba), and textures (modeled after OpenGL
  /// Shading Language).
  class ExtVectorType : public VectorType {
    friend class ASTContext; // ASTContext creates these.
  
    ExtVectorType(QualType vecType, unsigned nElements, QualType canonType)
        : VectorType(ExtVector, vecType, nElements, canonType, GenericVector) {}
  
  public:
    static int getPointAccessorIdx(char c) {
      switch (c) {
      default: return -1;
      case 'x': case 'r': return 0;
      case 'y': case 'g': return 1;
      case 'z': case 'b': return 2;
      case 'w': case 'a': return 3;
      }
    }
  
    static int getNumericAccessorIdx(char c) {
      switch (c) {
        default: return -1;
        case '0': return 0;
        case '1': return 1;
        case '2': return 2;
        case '3': return 3;
        case '4': return 4;
        case '5': return 5;
        case '6': return 6;
        case '7': return 7;
        case '8': return 8;
        case '9': return 9;
        case 'A':
        case 'a': return 10;
        case 'B':
        case 'b': return 11;
        case 'C':
        case 'c': return 12;
        case 'D':
        case 'd': return 13;
        case 'E':
        case 'e': return 14;
        case 'F':
        case 'f': return 15;
      }
    }
  
    static int getAccessorIdx(char c, bool isNumericAccessor) {
      if (isNumericAccessor)
        return getNumericAccessorIdx(c);
      else
        return getPointAccessorIdx(c);
    }
  
    bool isAccessorWithinNumElements(char c, bool isNumericAccessor) const {
      if (int idx = getAccessorIdx(c, isNumericAccessor)+1)
        return unsigned(idx-1) < getNumElements();
      return false;
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == ExtVector;
    }
  };
  
  /// FunctionType - C99 6.7.5.3 - Function Declarators.  This is the common base
  /// class of FunctionNoProtoType and FunctionProtoType.
  class FunctionType : public Type {
    // The type returned by the function.
    QualType ResultType;
  
  public:
    /// Interesting information about a specific parameter that can't simply
    /// be reflected in parameter's type. This is only used by FunctionProtoType
    /// but is in FunctionType to make this class available during the
    /// specification of the bases of FunctionProtoType.
    ///
    /// It makes sense to model language features this way when there's some
    /// sort of parameter-specific override (such as an attribute) that
    /// affects how the function is called.  For example, the ARC ns_consumed
    /// attribute changes whether a parameter is passed at +0 (the default)
    /// or +1 (ns_consumed).  This must be reflected in the function type,
    /// but isn't really a change to the parameter type.
    ///
    /// One serious disadvantage of modelling language features this way is
    /// that they generally do not work with language features that attempt
    /// to destructure types.  For example, template argument deduction will
    /// not be able to match a parameter declared as
    ///   T (*)(U)
    /// against an argument of type
    ///   void (*)(__attribute__((ns_consumed)) id)
    /// because the substitution of T=void, U=id into the former will
    /// not produce the latter.
    class ExtParameterInfo {
      enum {
        ABIMask = 0x0F,
        IsConsumed = 0x10,
        HasPassObjSize = 0x20,
        IsNoEscape = 0x40,
      };
      unsigned char Data = 0;
  
    public:
      ExtParameterInfo() = default;
  
      /// Return the ABI treatment of this parameter.
      ParameterABI getABI() const { return ParameterABI(Data & ABIMask); }
      ExtParameterInfo withABI(ParameterABI kind) const {
        ExtParameterInfo copy = *this;
        copy.Data = (copy.Data & ~ABIMask) | unsigned(kind);
        return copy;
      }
  
      /// Is this parameter considered "consumed" by Objective-C ARC?
      /// Consumed parameters must have retainable object type.
      bool isConsumed() const { return (Data & IsConsumed); }
      ExtParameterInfo withIsConsumed(bool consumed) const {
        ExtParameterInfo copy = *this;
        if (consumed)
          copy.Data |= IsConsumed;
        else
          copy.Data &= ~IsConsumed;
        return copy;
      }
  
      bool hasPassObjectSize() const { return Data & HasPassObjSize; }
      ExtParameterInfo withHasPassObjectSize() const {
        ExtParameterInfo Copy = *this;
        Copy.Data |= HasPassObjSize;
        return Copy;
      }
  
      bool isNoEscape() const { return Data & IsNoEscape; }
      ExtParameterInfo withIsNoEscape(bool NoEscape) const {
        ExtParameterInfo Copy = *this;
        if (NoEscape)
          Copy.Data |= IsNoEscape;
        else
          Copy.Data &= ~IsNoEscape;
        return Copy;
      }
  
      unsigned char getOpaqueValue() const { return Data; }
      static ExtParameterInfo getFromOpaqueValue(unsigned char data) {
        ExtParameterInfo result;
        result.Data = data;
        return result;
      }
  
      friend bool operator==(ExtParameterInfo lhs, ExtParameterInfo rhs) {
        return lhs.Data == rhs.Data;
      }
  
      friend bool operator!=(ExtParameterInfo lhs, ExtParameterInfo rhs) {
        return lhs.Data != rhs.Data;
      }
    };
  
    /// A class which abstracts out some details necessary for
    /// making a call.
    ///
    /// It is not actually used directly for storing this information in
    /// a FunctionType, although FunctionType does currently use the
    /// same bit-pattern.
    ///
    // If you add a field (say Foo), other than the obvious places (both,
    // constructors, compile failures), what you need to update is
    // * Operator==
    // * getFoo
    // * withFoo
    // * functionType. Add Foo, getFoo.
    // * ASTContext::getFooType
    // * ASTContext::mergeFunctionTypes
    // * FunctionNoProtoType::Profile
    // * FunctionProtoType::Profile
    // * TypePrinter::PrintFunctionProto
    // * AST read and write
    // * Codegen
    class ExtInfo {
      friend class FunctionType;
  
      // Feel free to rearrange or add bits, but if you go over 12,
      // you'll need to adjust both the Bits field below and
      // Type::FunctionTypeBitfields.
  
      //   |  CC  |noreturn|produces|nocallersavedregs|regparm|nocfcheck|
      //   |0 .. 4|   5    |    6   |       7         |8 .. 10|    11   |
      //
      // regparm is either 0 (no regparm attribute) or the regparm value+1.
      enum { CallConvMask = 0x1F };
      enum { NoReturnMask = 0x20 };
      enum { ProducesResultMask = 0x40 };
      enum { NoCallerSavedRegsMask = 0x80 };
      enum { NoCfCheckMask = 0x800 };
      enum {
        RegParmMask = ~(CallConvMask | NoReturnMask | ProducesResultMask |
                        NoCallerSavedRegsMask | NoCfCheckMask),
        RegParmOffset = 8
      }; // Assumed to be the last field
      uint16_t Bits = CC_C;
  
      ExtInfo(unsigned Bits) : Bits(static_cast<uint16_t>(Bits)) {}
  
     public:
       // Constructor with no defaults. Use this when you know that you
       // have all the elements (when reading an AST file for example).
       ExtInfo(bool noReturn, bool hasRegParm, unsigned regParm, CallingConv cc,
               bool producesResult, bool noCallerSavedRegs, bool NoCfCheck) {
         assert((!hasRegParm || regParm < 7) && "Invalid regparm value");
         Bits = ((unsigned)cc) | (noReturn ? NoReturnMask : 0) |
                (producesResult ? ProducesResultMask : 0) |
                (noCallerSavedRegs ? NoCallerSavedRegsMask : 0) |
                (hasRegParm ? ((regParm + 1) << RegParmOffset) : 0) |
                (NoCfCheck ? NoCfCheckMask : 0);
      }
  
      // Constructor with all defaults. Use when for example creating a
      // function known to use defaults.
      ExtInfo() = default;
  
      // Constructor with just the calling convention, which is an important part
      // of the canonical type.
      ExtInfo(CallingConv CC) : Bits(CC) {}
  
      bool getNoReturn() const { return Bits & NoReturnMask; }
      bool getProducesResult() const { return Bits & ProducesResultMask; }
      bool getNoCallerSavedRegs() const { return Bits & NoCallerSavedRegsMask; }
      bool getNoCfCheck() const { return Bits & NoCfCheckMask; }
      bool getHasRegParm() const { return (Bits >> RegParmOffset) != 0; }
  
      unsigned getRegParm() const {
        unsigned RegParm = (Bits & RegParmMask) >> RegParmOffset;
        if (RegParm > 0)
          --RegParm;
        return RegParm;
      }
  
      CallingConv getCC() const { return CallingConv(Bits & CallConvMask); }
  
      bool operator==(ExtInfo Other) const {
        return Bits == Other.Bits;
      }
      bool operator!=(ExtInfo Other) const {
        return Bits != Other.Bits;
      }
  
      // Note that we don't have setters. That is by design, use
      // the following with methods instead of mutating these objects.
  
      ExtInfo withNoReturn(bool noReturn) const {
        if (noReturn)
          return ExtInfo(Bits | NoReturnMask);
        else
          return ExtInfo(Bits & ~NoReturnMask);
      }
  
      ExtInfo withProducesResult(bool producesResult) const {
        if (producesResult)
          return ExtInfo(Bits | ProducesResultMask);
        else
          return ExtInfo(Bits & ~ProducesResultMask);
      }
  
      ExtInfo withNoCallerSavedRegs(bool noCallerSavedRegs) const {
        if (noCallerSavedRegs)
          return ExtInfo(Bits | NoCallerSavedRegsMask);
        else
          return ExtInfo(Bits & ~NoCallerSavedRegsMask);
      }
  
      ExtInfo withNoCfCheck(bool noCfCheck) const {
        if (noCfCheck)
          return ExtInfo(Bits | NoCfCheckMask);
        else
          return ExtInfo(Bits & ~NoCfCheckMask);
      }
  
      ExtInfo withRegParm(unsigned RegParm) const {
        assert(RegParm < 7 && "Invalid regparm value");
        return ExtInfo((Bits & ~RegParmMask) |
                       ((RegParm + 1) << RegParmOffset));
      }
  
      ExtInfo withCallingConv(CallingConv cc) const {
        return ExtInfo((Bits & ~CallConvMask) | (unsigned) cc);
      }
  
      void Profile(llvm::FoldingSetNodeID &ID) const {
        ID.AddInteger(Bits);
      }
    };
  
    /// A simple holder for a QualType representing a type in an
    /// exception specification. Unfortunately needed by FunctionProtoType
    /// because TrailingObjects cannot handle repeated types.
    struct ExceptionType { QualType Type; };
  
    /// A simple holder for various uncommon bits which do not fit in
    /// FunctionTypeBitfields. Aligned to alignof(void *) to maintain the
    /// alignment of subsequent objects in TrailingObjects. You must update
    /// hasExtraBitfields in FunctionProtoType after adding extra data here.
    struct alignas(void *) FunctionTypeExtraBitfields {
      /// The number of types in the exception specification.
      /// A whole unsigned is not needed here and according to
      /// [implimits] 8 bits would be enough here.
      unsigned NumExceptionType;
    };
  
  protected:
    FunctionType(TypeClass tc, QualType res,
                 QualType Canonical, bool Dependent,
                 bool InstantiationDependent,
                 bool VariablyModified, bool ContainsUnexpandedParameterPack,
                 ExtInfo Info)
        : Type(tc, Canonical, Dependent, InstantiationDependent, VariablyModified,
               ContainsUnexpandedParameterPack),
          ResultType(res) {
      FunctionTypeBits.ExtInfo = Info.Bits;
    }
  
    Qualifiers getFastTypeQuals() const {
      return Qualifiers::fromFastMask(FunctionTypeBits.FastTypeQuals);
    }
  
  public:
    QualType getReturnType() const { return ResultType; }
  
    bool getHasRegParm() const { return getExtInfo().getHasRegParm(); }
    unsigned getRegParmType() const { return getExtInfo().getRegParm(); }
  
    /// Determine whether this function type includes the GNU noreturn
    /// attribute. The C++11 [[noreturn]] attribute does not affect the function
    /// type.
    bool getNoReturnAttr() const { return getExtInfo().getNoReturn(); }
  
    CallingConv getCallConv() const { return getExtInfo().getCC(); }
    ExtInfo getExtInfo() const { return ExtInfo(FunctionTypeBits.ExtInfo); }
  
    static_assert((~Qualifiers::FastMask & Qualifiers::CVRMask) == 0,
                  "Const, volatile and restrict are assumed to be a subset of "
                  "the fast qualifiers.");
  
    bool isConst() const { return getFastTypeQuals().hasConst(); }
    bool isVolatile() const { return getFastTypeQuals().hasVolatile(); }
    bool isRestrict() const { return getFastTypeQuals().hasRestrict(); }
  
    /// Determine the type of an expression that calls a function of
    /// this type.
    QualType getCallResultType(const ASTContext &Context) const {
      return getReturnType().getNonLValueExprType(Context);
    }
  
    static StringRef getNameForCallConv(CallingConv CC);
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == FunctionNoProto ||
             T->getTypeClass() == FunctionProto;
    }
  };
  
  /// Represents a K&R-style 'int foo()' function, which has
  /// no information available about its arguments.
  class FunctionNoProtoType : public FunctionType, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    FunctionNoProtoType(QualType Result, QualType Canonical, ExtInfo Info)
        : FunctionType(FunctionNoProto, Result, Canonical,
                       /*Dependent=*/false, /*InstantiationDependent=*/false,
                       Result->isVariablyModifiedType(),
                       /*ContainsUnexpandedParameterPack=*/false, Info) {}
  
  public:
    // No additional state past what FunctionType provides.
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getReturnType(), getExtInfo());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType ResultType,
                        ExtInfo Info) {
      Info.Profile(ID);
      ID.AddPointer(ResultType.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == FunctionNoProto;
    }
  };
  
  /// Represents a prototype with parameter type info, e.g.
  /// 'int foo(int)' or 'int foo(void)'.  'void' is represented as having no
  /// parameters, not as having a single void parameter. Such a type can have
  /// an exception specification, but this specification is not part of the
  /// canonical type. FunctionProtoType has several trailing objects, some of
  /// which optional. For more information about the trailing objects see
  /// the first comment inside FunctionProtoType.
  class FunctionProtoType final
      : public FunctionType,
        public llvm::FoldingSetNode,
        private llvm::TrailingObjects<
            FunctionProtoType, QualType, FunctionType::FunctionTypeExtraBitfields,
            FunctionType::ExceptionType, Expr *, FunctionDecl *,
            FunctionType::ExtParameterInfo, Qualifiers> {
    friend class ASTContext; // ASTContext creates these.
    friend TrailingObjects;
  
    // FunctionProtoType is followed by several trailing objects, some of
    // which optional. They are in order:
    //
    // * An array of getNumParams() QualType holding the parameter types.
    //   Always present. Note that for the vast majority of FunctionProtoType,
    //   these will be the only trailing objects.
    //
    // * Optionally if some extra data is stored in FunctionTypeExtraBitfields
    //   (see FunctionTypeExtraBitfields and FunctionTypeBitfields):
    //   a single FunctionTypeExtraBitfields. Present if and only if
    //   hasExtraBitfields() is true.
    //
    // * Optionally exactly one of:
    //   * an array of getNumExceptions() ExceptionType,
    //   * a single Expr *,
    //   * a pair of FunctionDecl *,
    //   * a single FunctionDecl *
    //   used to store information about the various types of exception
    //   specification. See getExceptionSpecSize for the details.
    //
    // * Optionally an array of getNumParams() ExtParameterInfo holding
    //   an ExtParameterInfo for each of the parameters. Present if and
    //   only if hasExtParameterInfos() is true.
    //
    // * Optionally a Qualifiers object to represent extra qualifiers that can't
    //   be represented by FunctionTypeBitfields.FastTypeQuals. Present if and only
    //   if hasExtQualifiers() is true.
    //
    // The optional FunctionTypeExtraBitfields has to be before the data
    // related to the exception specification since it contains the number
    // of exception types.
    //
    // We put the ExtParameterInfos last.  If all were equal, it would make
    // more sense to put these before the exception specification, because
    // it's much easier to skip past them compared to the elaborate switch
    // required to skip the exception specification.  However, all is not
    // equal; ExtParameterInfos are used to model very uncommon features,
    // and it's better not to burden the more common paths.
  
  public:
    /// Holds information about the various types of exception specification.
    /// ExceptionSpecInfo is not stored as such in FunctionProtoType but is
    /// used to group together the various bits of information about the
    /// exception specification.
    struct ExceptionSpecInfo {
      /// The kind of exception specification this is.
      ExceptionSpecificationType Type = EST_None;
  
      /// Explicitly-specified list of exception types.
      ArrayRef<QualType> Exceptions;
  
      /// Noexcept expression, if this is a computed noexcept specification.
      Expr *NoexceptExpr = nullptr;
  
      /// The function whose exception specification this is, for
      /// EST_Unevaluated and EST_Uninstantiated.
      FunctionDecl *SourceDecl = nullptr;
  
      /// The function template whose exception specification this is instantiated
      /// from, for EST_Uninstantiated.
      FunctionDecl *SourceTemplate = nullptr;
  
      ExceptionSpecInfo() = default;
  
      ExceptionSpecInfo(ExceptionSpecificationType EST) : Type(EST) {}
    };
  
    /// Extra information about a function prototype. ExtProtoInfo is not
    /// stored as such in FunctionProtoType but is used to group together
    /// the various bits of extra information about a function prototype.
    struct ExtProtoInfo {
      FunctionType::ExtInfo ExtInfo;
      bool Variadic : 1;
      bool HasTrailingReturn : 1;
      Qualifiers TypeQuals;
      RefQualifierKind RefQualifier = RQ_None;
      ExceptionSpecInfo ExceptionSpec;
      const ExtParameterInfo *ExtParameterInfos = nullptr;
  
      ExtProtoInfo() : Variadic(false), HasTrailingReturn(false) {}
  
      ExtProtoInfo(CallingConv CC)
          : ExtInfo(CC), Variadic(false), HasTrailingReturn(false) {}
  
      ExtProtoInfo withExceptionSpec(const ExceptionSpecInfo &ESI) {
        ExtProtoInfo Result(*this);
        Result.ExceptionSpec = ESI;
        return Result;
      }
    };
  
  private:
    unsigned numTrailingObjects(OverloadToken<QualType>) const {
      return getNumParams();
    }
  
    unsigned numTrailingObjects(OverloadToken<FunctionTypeExtraBitfields>) const {
      return hasExtraBitfields();
    }
  
    unsigned numTrailingObjects(OverloadToken<ExceptionType>) const {
      return getExceptionSpecSize().NumExceptionType;
    }
  
    unsigned numTrailingObjects(OverloadToken<Expr *>) const {
      return getExceptionSpecSize().NumExprPtr;
    }
  
    unsigned numTrailingObjects(OverloadToken<FunctionDecl *>) const {
      return getExceptionSpecSize().NumFunctionDeclPtr;
    }
  
    unsigned numTrailingObjects(OverloadToken<ExtParameterInfo>) const {
      return hasExtParameterInfos() ? getNumParams() : 0;
    }
  
    /// Determine whether there are any argument types that
    /// contain an unexpanded parameter pack.
    static bool containsAnyUnexpandedParameterPack(const QualType *ArgArray,
                                                   unsigned numArgs) {
      for (unsigned Idx = 0; Idx < numArgs; ++Idx)
        if (ArgArray[Idx]->containsUnexpandedParameterPack())
          return true;
  
      return false;
    }
  
    FunctionProtoType(QualType result, ArrayRef<QualType> params,
                      QualType canonical, const ExtProtoInfo &epi);
  
    /// This struct is returned by getExceptionSpecSize and is used to
    /// translate an ExceptionSpecificationType to the number and kind
    /// of trailing objects related to the exception specification.
    struct ExceptionSpecSizeHolder {
      unsigned NumExceptionType;
      unsigned NumExprPtr;
      unsigned NumFunctionDeclPtr;
    };
  
    /// Return the number and kind of trailing objects
    /// related to the exception specification.
    static ExceptionSpecSizeHolder
    getExceptionSpecSize(ExceptionSpecificationType EST, unsigned NumExceptions) {
      switch (EST) {
      case EST_None:
      case EST_DynamicNone:
      case EST_MSAny:
      case EST_BasicNoexcept:
      case EST_Unparsed:
        return {0, 0, 0};
  
      case EST_Dynamic:
        return {NumExceptions, 0, 0};
  
      case EST_DependentNoexcept:
      case EST_NoexceptFalse:
      case EST_NoexceptTrue:
        return {0, 1, 0};
  
      case EST_Uninstantiated:
        return {0, 0, 2};
  
      case EST_Unevaluated:
        return {0, 0, 1};
      }
      llvm_unreachable("bad exception specification kind");
    }
  
    /// Return the number and kind of trailing objects
    /// related to the exception specification.
    ExceptionSpecSizeHolder getExceptionSpecSize() const {
      return getExceptionSpecSize(getExceptionSpecType(), getNumExceptions());
    }
  
    /// Whether the trailing FunctionTypeExtraBitfields is present.
    static bool hasExtraBitfields(ExceptionSpecificationType EST) {
      // If the exception spec type is EST_Dynamic then we have > 0 exception
      // types and the exact number is stored in FunctionTypeExtraBitfields.
      return EST == EST_Dynamic;
    }
  
    /// Whether the trailing FunctionTypeExtraBitfields is present.
    bool hasExtraBitfields() const {
      return hasExtraBitfields(getExceptionSpecType());
    }
  
    bool hasExtQualifiers() const {
      return FunctionTypeBits.HasExtQuals;
    }
  
  public:
    unsigned getNumParams() const { return FunctionTypeBits.NumParams; }
  
    QualType getParamType(unsigned i) const {
      assert(i < getNumParams() && "invalid parameter index");
      return param_type_begin()[i];
    }
  
    ArrayRef<QualType> getParamTypes() const {
      return llvm::makeArrayRef(param_type_begin(), param_type_end());
    }
  
    ExtProtoInfo getExtProtoInfo() const {
      ExtProtoInfo EPI;
      EPI.ExtInfo = getExtInfo();
      EPI.Variadic = isVariadic();
      EPI.HasTrailingReturn = hasTrailingReturn();
      EPI.ExceptionSpec.Type = getExceptionSpecType();
      EPI.TypeQuals = getMethodQuals();
      EPI.RefQualifier = getRefQualifier();
      if (EPI.ExceptionSpec.Type == EST_Dynamic) {
        EPI.ExceptionSpec.Exceptions = exceptions();
      } else if (isComputedNoexcept(EPI.ExceptionSpec.Type)) {
        EPI.ExceptionSpec.NoexceptExpr = getNoexceptExpr();
      } else if (EPI.ExceptionSpec.Type == EST_Uninstantiated) {
        EPI.ExceptionSpec.SourceDecl = getExceptionSpecDecl();
        EPI.ExceptionSpec.SourceTemplate = getExceptionSpecTemplate();
      } else if (EPI.ExceptionSpec.Type == EST_Unevaluated) {
        EPI.ExceptionSpec.SourceDecl = getExceptionSpecDecl();
      }
      EPI.ExtParameterInfos = getExtParameterInfosOrNull();
      return EPI;
    }
  
    /// Get the kind of exception specification on this function.
    ExceptionSpecificationType getExceptionSpecType() const {
      return static_cast<ExceptionSpecificationType>(
          FunctionTypeBits.ExceptionSpecType);
    }
  
    /// Return whether this function has any kind of exception spec.
    bool hasExceptionSpec() const { return getExceptionSpecType() != EST_None; }
  
    /// Return whether this function has a dynamic (throw) exception spec.
    bool hasDynamicExceptionSpec() const {
      return isDynamicExceptionSpec(getExceptionSpecType());
    }
  
    /// Return whether this function has a noexcept exception spec.
    bool hasNoexceptExceptionSpec() const {
      return isNoexceptExceptionSpec(getExceptionSpecType());
    }
  
    /// Return whether this function has a dependent exception spec.
    bool hasDependentExceptionSpec() const;
  
    /// Return whether this function has an instantiation-dependent exception
    /// spec.
    bool hasInstantiationDependentExceptionSpec() const;
  
    /// Return the number of types in the exception specification.
    unsigned getNumExceptions() const {
      return getExceptionSpecType() == EST_Dynamic
                 ? getTrailingObjects<FunctionTypeExtraBitfields>()
                       ->NumExceptionType
                 : 0;
    }
  
    /// Return the ith exception type, where 0 <= i < getNumExceptions().
    QualType getExceptionType(unsigned i) const {
      assert(i < getNumExceptions() && "Invalid exception number!");
      return exception_begin()[i];
    }
  
    /// Return the expression inside noexcept(expression), or a null pointer
    /// if there is none (because the exception spec is not of this form).
    Expr *getNoexceptExpr() const {
      if (!isComputedNoexcept(getExceptionSpecType()))
        return nullptr;
      return *getTrailingObjects<Expr *>();
    }
  
    /// If this function type has an exception specification which hasn't
    /// been determined yet (either because it has not been evaluated or because
    /// it has not been instantiated), this is the function whose exception
    /// specification is represented by this type.
    FunctionDecl *getExceptionSpecDecl() const {
      if (getExceptionSpecType() != EST_Uninstantiated &&
          getExceptionSpecType() != EST_Unevaluated)
        return nullptr;
      return getTrailingObjects<FunctionDecl *>()[0];
    }
  
    /// If this function type has an uninstantiated exception
    /// specification, this is the function whose exception specification
    /// should be instantiated to find the exception specification for
    /// this type.
    FunctionDecl *getExceptionSpecTemplate() const {
      if (getExceptionSpecType() != EST_Uninstantiated)
        return nullptr;
      return getTrailingObjects<FunctionDecl *>()[1];
    }
  
    /// Determine whether this function type has a non-throwing exception
    /// specification.
    CanThrowResult canThrow() const;
  
    /// Determine whether this function type has a non-throwing exception
    /// specification. If this depends on template arguments, returns
    /// \c ResultIfDependent.
    bool isNothrow(bool ResultIfDependent = false) const {
      return ResultIfDependent ? canThrow() != CT_Can : canThrow() == CT_Cannot;
    }
  
    /// Whether this function prototype is variadic.
    bool isVariadic() const { return FunctionTypeBits.Variadic; }
  
    /// Determines whether this function prototype contains a
    /// parameter pack at the end.
    ///
    /// A function template whose last parameter is a parameter pack can be
    /// called with an arbitrary number of arguments, much like a variadic
    /// function.
    bool isTemplateVariadic() const;
  
    /// Whether this function prototype has a trailing return type.
    bool hasTrailingReturn() const { return FunctionTypeBits.HasTrailingReturn; }
  
    Qualifiers getMethodQuals() const {
      if (hasExtQualifiers())
        return *getTrailingObjects<Qualifiers>();
      else
        return getFastTypeQuals();
    }
  
    /// Retrieve the ref-qualifier associated with this function type.
    RefQualifierKind getRefQualifier() const {
      return static_cast<RefQualifierKind>(FunctionTypeBits.RefQualifier);
    }
  
    using param_type_iterator = const QualType *;
    using param_type_range = llvm::iterator_range<param_type_iterator>;
  
    param_type_range param_types() const {
      return param_type_range(param_type_begin(), param_type_end());
    }
  
    param_type_iterator param_type_begin() const {
      return getTrailingObjects<QualType>();
    }
  
    param_type_iterator param_type_end() const {
      return param_type_begin() + getNumParams();
    }
  
    using exception_iterator = const QualType *;
  
    ArrayRef<QualType> exceptions() const {
      return llvm::makeArrayRef(exception_begin(), exception_end());
    }
  
    exception_iterator exception_begin() const {
      return reinterpret_cast<exception_iterator>(
          getTrailingObjects<ExceptionType>());
    }
  
    exception_iterator exception_end() const {
      return exception_begin() + getNumExceptions();
    }
  
    /// Is there any interesting extra information for any of the parameters
    /// of this function type?
    bool hasExtParameterInfos() const {
      return FunctionTypeBits.HasExtParameterInfos;
    }
  
    ArrayRef<ExtParameterInfo> getExtParameterInfos() const {
      assert(hasExtParameterInfos());
      return ArrayRef<ExtParameterInfo>(getTrailingObjects<ExtParameterInfo>(),
                                        getNumParams());
    }
  
    /// Return a pointer to the beginning of the array of extra parameter
    /// information, if present, or else null if none of the parameters
    /// carry it.  This is equivalent to getExtProtoInfo().ExtParameterInfos.
    const ExtParameterInfo *getExtParameterInfosOrNull() const {
      if (!hasExtParameterInfos())
        return nullptr;
      return getTrailingObjects<ExtParameterInfo>();
    }
  
    ExtParameterInfo getExtParameterInfo(unsigned I) const {
      assert(I < getNumParams() && "parameter index out of range");
      if (hasExtParameterInfos())
        return getTrailingObjects<ExtParameterInfo>()[I];
      return ExtParameterInfo();
    }
  
    ParameterABI getParameterABI(unsigned I) const {
      assert(I < getNumParams() && "parameter index out of range");
      if (hasExtParameterInfos())
        return getTrailingObjects<ExtParameterInfo>()[I].getABI();
      return ParameterABI::Ordinary;
    }
  
    bool isParamConsumed(unsigned I) const {
      assert(I < getNumParams() && "parameter index out of range");
      if (hasExtParameterInfos())
        return getTrailingObjects<ExtParameterInfo>()[I].isConsumed();
      return false;
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void printExceptionSpecification(raw_ostream &OS,
                                     const PrintingPolicy &Policy) const;
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == FunctionProto;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Ctx);
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Result,
                        param_type_iterator ArgTys, unsigned NumArgs,
                        const ExtProtoInfo &EPI, const ASTContext &Context,
                        bool Canonical);
  };
  
  /// Represents the dependent type named by a dependently-scoped
  /// typename using declaration, e.g.
  ///   using typename Base<T>::foo;
  ///
  /// Template instantiation turns these into the underlying type.
  class UnresolvedUsingType : public Type {
    friend class ASTContext; // ASTContext creates these.
  
    UnresolvedUsingTypenameDecl *Decl;
  
    UnresolvedUsingType(const UnresolvedUsingTypenameDecl *D)
        : Type(UnresolvedUsing, QualType(), true, true, false,
               /*ContainsUnexpandedParameterPack=*/false),
          Decl(const_cast<UnresolvedUsingTypenameDecl*>(D)) {}
  
  public:
    UnresolvedUsingTypenameDecl *getDecl() const { return Decl; }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == UnresolvedUsing;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      return Profile(ID, Decl);
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID,
                        UnresolvedUsingTypenameDecl *D) {
      ID.AddPointer(D);
    }
  };
  
  class TypedefType : public Type {
    TypedefNameDecl *Decl;
  
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    TypedefType(TypeClass tc, const TypedefNameDecl *D, QualType can)
        : Type(tc, can, can->isDependentType(),
               can->isInstantiationDependentType(),
               can->isVariablyModifiedType(),
               /*ContainsUnexpandedParameterPack=*/false),
          Decl(const_cast<TypedefNameDecl*>(D)) {
      assert(!isa<TypedefType>(can) && "Invalid canonical type");
    }
  
  public:
    TypedefNameDecl *getDecl() const { return Decl; }
  
    bool isSugared() const { return true; }
    QualType desugar() const;
  
    static bool classof(const Type *T) { return T->getTypeClass() == Typedef; }
  };
  
  /// Sugar type that represents a type that was qualified by a qualifier written
  /// as a macro invocation.
  class MacroQualifiedType : public Type {
    friend class ASTContext; // ASTContext creates these.
  
    QualType UnderlyingTy;
    const IdentifierInfo *MacroII;
  
    MacroQualifiedType(QualType UnderlyingTy, QualType CanonTy,
                       const IdentifierInfo *MacroII)
        : Type(MacroQualified, CanonTy, UnderlyingTy->isDependentType(),
               UnderlyingTy->isInstantiationDependentType(),
               UnderlyingTy->isVariablyModifiedType(),
               UnderlyingTy->containsUnexpandedParameterPack()),
          UnderlyingTy(UnderlyingTy), MacroII(MacroII) {
      assert(isa<AttributedType>(UnderlyingTy) &&
             "Expected a macro qualified type to only wrap attributed types.");
    }
  
  public:
    const IdentifierInfo *getMacroIdentifier() const { return MacroII; }
    QualType getUnderlyingType() const { return UnderlyingTy; }
  
    /// Return this attributed type's modified type with no qualifiers attached to
    /// it.
    QualType getModifiedType() const;
  
    bool isSugared() const { return true; }
    QualType desugar() const;
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == MacroQualified;
    }
  };
  
  /// Represents a `typeof` (or __typeof__) expression (a GCC extension).
  class TypeOfExprType : public Type {
    Expr *TOExpr;
  
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    TypeOfExprType(Expr *E, QualType can = QualType());
  
  public:
    Expr *getUnderlyingExpr() const { return TOExpr; }
  
    /// Remove a single level of sugar.
    QualType desugar() const;
  
    /// Returns whether this type directly provides sugar.
    bool isSugared() const;
  
    static bool classof(const Type *T) { return T->getTypeClass() == TypeOfExpr; }
  };
  
  /// Internal representation of canonical, dependent
  /// `typeof(expr)` types.
  ///
  /// This class is used internally by the ASTContext to manage
  /// canonical, dependent types, only. Clients will only see instances
  /// of this class via TypeOfExprType nodes.
  class DependentTypeOfExprType
    : public TypeOfExprType, public llvm::FoldingSetNode {
    const ASTContext &Context;
  
  public:
    DependentTypeOfExprType(const ASTContext &Context, Expr *E)
        : TypeOfExprType(E), Context(Context) {}
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, Context, getUnderlyingExpr());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
                        Expr *E);
  };
  
  /// Represents `typeof(type)`, a GCC extension.
  class TypeOfType : public Type {
    friend class ASTContext; // ASTContext creates these.
  
    QualType TOType;
  
    TypeOfType(QualType T, QualType can)
        : Type(TypeOf, can, T->isDependentType(),
               T->isInstantiationDependentType(),
               T->isVariablyModifiedType(),
               T->containsUnexpandedParameterPack()),
          TOType(T) {
      assert(!isa<TypedefType>(can) && "Invalid canonical type");
    }
  
  public:
    QualType getUnderlyingType() const { return TOType; }
  
    /// Remove a single level of sugar.
    QualType desugar() const { return getUnderlyingType(); }
  
    /// Returns whether this type directly provides sugar.
    bool isSugared() const { return true; }
  
    static bool classof(const Type *T) { return T->getTypeClass() == TypeOf; }
  };
  
  /// Represents the type `decltype(expr)` (C++11).
  class DecltypeType : public Type {
    Expr *E;
    QualType UnderlyingType;
  
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    DecltypeType(Expr *E, QualType underlyingType, QualType can = QualType());
  
  public:
    Expr *getUnderlyingExpr() const { return E; }
    QualType getUnderlyingType() const { return UnderlyingType; }
  
    /// Remove a single level of sugar.
    QualType desugar() const;
  
    /// Returns whether this type directly provides sugar.
    bool isSugared() const;
  
    static bool classof(const Type *T) { return T->getTypeClass() == Decltype; }
  };
  
  /// Internal representation of canonical, dependent
  /// decltype(expr) types.
  ///
  /// This class is used internally by the ASTContext to manage
  /// canonical, dependent types, only. Clients will only see instances
  /// of this class via DecltypeType nodes.
  class DependentDecltypeType : public DecltypeType, public llvm::FoldingSetNode {
    const ASTContext &Context;
  
  public:
    DependentDecltypeType(const ASTContext &Context, Expr *E);
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, Context, getUnderlyingExpr());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
                        Expr *E);
  };
  
  /// A unary type transform, which is a type constructed from another.
  class UnaryTransformType : public Type {
  public:
    enum UTTKind {
      EnumUnderlyingType
    };
  
  private:
    /// The untransformed type.
    QualType BaseType;
  
    /// The transformed type if not dependent, otherwise the same as BaseType.
    QualType UnderlyingType;
  
    UTTKind UKind;
  
  protected:
    friend class ASTContext;
  
    UnaryTransformType(QualType BaseTy, QualType UnderlyingTy, UTTKind UKind,
                       QualType CanonicalTy);
  
  public:
    bool isSugared() const { return !isDependentType(); }
    QualType desugar() const { return UnderlyingType; }
  
    QualType getUnderlyingType() const { return UnderlyingType; }
    QualType getBaseType() const { return BaseType; }
  
    UTTKind getUTTKind() const { return UKind; }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == UnaryTransform;
    }
  };
  
  /// Internal representation of canonical, dependent
  /// __underlying_type(type) types.
  ///
  /// This class is used internally by the ASTContext to manage
  /// canonical, dependent types, only. Clients will only see instances
  /// of this class via UnaryTransformType nodes.
  class DependentUnaryTransformType : public UnaryTransformType,
                                      public llvm::FoldingSetNode {
  public:
    DependentUnaryTransformType(const ASTContext &C, QualType BaseType,
                                UTTKind UKind);
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getBaseType(), getUTTKind());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType BaseType,
                        UTTKind UKind) {
      ID.AddPointer(BaseType.getAsOpaquePtr());
      ID.AddInteger((unsigned)UKind);
    }
  };
  
  class TagType : public Type {
    friend class ASTReader;
  
    /// Stores the TagDecl associated with this type. The decl may point to any
    /// TagDecl that declares the entity.
    TagDecl *decl;
  
  protected:
    TagType(TypeClass TC, const TagDecl *D, QualType can);
  
  public:
    TagDecl *getDecl() const;
  
    /// Determines whether this type is in the process of being defined.
    bool isBeingDefined() const;
  
    static bool classof(const Type *T) {
      return T->getTypeClass() >= TagFirst && T->getTypeClass() <= TagLast;
    }
  };
  
  /// A helper class that allows the use of isa/cast/dyncast
  /// to detect TagType objects of structs/unions/classes.
  class RecordType : public TagType {
  protected:
    friend class ASTContext; // ASTContext creates these.
  
    explicit RecordType(const RecordDecl *D)
        : TagType(Record, reinterpret_cast<const TagDecl*>(D), QualType()) {}
    explicit RecordType(TypeClass TC, RecordDecl *D)
        : TagType(TC, reinterpret_cast<const TagDecl*>(D), QualType()) {}
  
  public:
    RecordDecl *getDecl() const {
      return reinterpret_cast<RecordDecl*>(TagType::getDecl());
    }
  
    /// Recursively check all fields in the record for const-ness. If any field
    /// is declared const, return true. Otherwise, return false.
    bool hasConstFields() const;
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) { return T->getTypeClass() == Record; }
  };
  
  /// A helper class that allows the use of isa/cast/dyncast
  /// to detect TagType objects of enums.
  class EnumType : public TagType {
    friend class ASTContext; // ASTContext creates these.
  
    explicit EnumType(const EnumDecl *D)
        : TagType(Enum, reinterpret_cast<const TagDecl*>(D), QualType()) {}
  
  public:
    EnumDecl *getDecl() const {
      return reinterpret_cast<EnumDecl*>(TagType::getDecl());
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) { return T->getTypeClass() == Enum; }
  };
  
  /// An attributed type is a type to which a type attribute has been applied.
  ///
  /// The "modified type" is the fully-sugared type to which the attributed
  /// type was applied; generally it is not canonically equivalent to the
  /// attributed type. The "equivalent type" is the minimally-desugared type
  /// which the type is canonically equivalent to.
  ///
  /// For example, in the following attributed type:
  ///     int32_t __attribute__((vector_size(16)))
  ///   - the modified type is the TypedefType for int32_t
  ///   - the equivalent type is VectorType(16, int32_t)
  ///   - the canonical type is VectorType(16, int)
  class AttributedType : public Type, public llvm::FoldingSetNode {
  public:
    using Kind = attr::Kind;
  
  private:
    friend class ASTContext; // ASTContext creates these
  
    QualType ModifiedType;
    QualType EquivalentType;
  
    AttributedType(QualType canon, attr::Kind attrKind, QualType modified,
                   QualType equivalent)
        : Type(Attributed, canon, equivalent->isDependentType(),
               equivalent->isInstantiationDependentType(),
               equivalent->isVariablyModifiedType(),
               equivalent->containsUnexpandedParameterPack()),
          ModifiedType(modified), EquivalentType(equivalent) {
      AttributedTypeBits.AttrKind = attrKind;
    }
  
  public:
    Kind getAttrKind() const {
      return static_cast<Kind>(AttributedTypeBits.AttrKind);
    }
  
    QualType getModifiedType() const { return ModifiedType; }
    QualType getEquivalentType() const { return EquivalentType; }
  
    bool isSugared() const { return true; }
    QualType desugar() const { return getEquivalentType(); }
  
    /// Does this attribute behave like a type qualifier?
    ///
    /// A type qualifier adjusts a type to provide specialized rules for
    /// a specific object, like the standard const and volatile qualifiers.
    /// This includes attributes controlling things like nullability,
    /// address spaces, and ARC ownership.  The value of the object is still
    /// largely described by the modified type.
    ///
    /// In contrast, many type attributes "rewrite" their modified type to
    /// produce a fundamentally different type, not necessarily related in any
    /// formalizable way to the original type.  For example, calling convention
    /// and vector attributes are not simple type qualifiers.
    ///
    /// Type qualifiers are often, but not always, reflected in the canonical
    /// type.
    bool isQualifier() const;
  
    bool isMSTypeSpec() const;
  
    bool isCallingConv() const;
  
    llvm::Optional<NullabilityKind> getImmediateNullability() const;
  
    /// Retrieve the attribute kind corresponding to the given
    /// nullability kind.
    static Kind getNullabilityAttrKind(NullabilityKind kind) {
      switch (kind) {
      case NullabilityKind::NonNull:
        return attr::TypeNonNull;
  
      case NullabilityKind::Nullable:
        return attr::TypeNullable;
  
      case NullabilityKind::Unspecified:
        return attr::TypeNullUnspecified;
      }
      llvm_unreachable("Unknown nullability kind.");
    }
  
    /// Strip off the top-level nullability annotation on the given
    /// type, if it's there.
    ///
    /// \param T The type to strip. If the type is exactly an
    /// AttributedType specifying nullability (without looking through
    /// type sugar), the nullability is returned and this type changed
    /// to the underlying modified type.
    ///
    /// \returns the top-level nullability, if present.
    static Optional<NullabilityKind> stripOuterNullability(QualType &T);
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getAttrKind(), ModifiedType, EquivalentType);
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, Kind attrKind,
                        QualType modified, QualType equivalent) {
      ID.AddInteger(attrKind);
      ID.AddPointer(modified.getAsOpaquePtr());
      ID.AddPointer(equivalent.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == Attributed;
    }
  };
  
  class TemplateTypeParmType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these
  
    // Helper data collector for canonical types.
    struct CanonicalTTPTInfo {
      unsigned Depth : 15;
      unsigned ParameterPack : 1;
      unsigned Index : 16;
    };
  
    union {
      // Info for the canonical type.
      CanonicalTTPTInfo CanTTPTInfo;
  
      // Info for the non-canonical type.
      TemplateTypeParmDecl *TTPDecl;
    };
  
    /// Build a non-canonical type.
    TemplateTypeParmType(TemplateTypeParmDecl *TTPDecl, QualType Canon)
        : Type(TemplateTypeParm, Canon, /*Dependent=*/true,
               /*InstantiationDependent=*/true,
               /*VariablyModified=*/false,
               Canon->containsUnexpandedParameterPack()),
          TTPDecl(TTPDecl) {}
  
    /// Build the canonical type.
    TemplateTypeParmType(unsigned D, unsigned I, bool PP)
        : Type(TemplateTypeParm, QualType(this, 0),
               /*Dependent=*/true,
               /*InstantiationDependent=*/true,
               /*VariablyModified=*/false, PP) {
      CanTTPTInfo.Depth = D;
      CanTTPTInfo.Index = I;
      CanTTPTInfo.ParameterPack = PP;
    }
  
    const CanonicalTTPTInfo& getCanTTPTInfo() const {
      QualType Can = getCanonicalTypeInternal();
      return Can->castAs<TemplateTypeParmType>()->CanTTPTInfo;
    }
  
  public:
    unsigned getDepth() const { return getCanTTPTInfo().Depth; }
    unsigned getIndex() const { return getCanTTPTInfo().Index; }
    bool isParameterPack() const { return getCanTTPTInfo().ParameterPack; }
  
    TemplateTypeParmDecl *getDecl() const {
      return isCanonicalUnqualified() ? nullptr : TTPDecl;
    }
  
    IdentifierInfo *getIdentifier() const;
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getDepth(), getIndex(), isParameterPack(), getDecl());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, unsigned Depth,
                        unsigned Index, bool ParameterPack,
                        TemplateTypeParmDecl *TTPDecl) {
      ID.AddInteger(Depth);
      ID.AddInteger(Index);
      ID.AddBoolean(ParameterPack);
      ID.AddPointer(TTPDecl);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == TemplateTypeParm;
    }
  };
  
  /// Represents the result of substituting a type for a template
  /// type parameter.
  ///
  /// Within an instantiated template, all template type parameters have
  /// been replaced with these.  They are used solely to record that a
  /// type was originally written as a template type parameter;
  /// therefore they are never canonical.
  class SubstTemplateTypeParmType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext;
  
    // The original type parameter.
    const TemplateTypeParmType *Replaced;
  
    SubstTemplateTypeParmType(const TemplateTypeParmType *Param, QualType Canon)
        : Type(SubstTemplateTypeParm, Canon, Canon->isDependentType(),
               Canon->isInstantiationDependentType(),
               Canon->isVariablyModifiedType(),
               Canon->containsUnexpandedParameterPack()),
          Replaced(Param) {}
  
  public:
    /// Gets the template parameter that was substituted for.
    const TemplateTypeParmType *getReplacedParameter() const {
      return Replaced;
    }
  
    /// Gets the type that was substituted for the template
    /// parameter.
    QualType getReplacementType() const {
      return getCanonicalTypeInternal();
    }
  
    bool isSugared() const { return true; }
    QualType desugar() const { return getReplacementType(); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getReplacedParameter(), getReplacementType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID,
                        const TemplateTypeParmType *Replaced,
                        QualType Replacement) {
      ID.AddPointer(Replaced);
      ID.AddPointer(Replacement.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == SubstTemplateTypeParm;
    }
  };
  
  /// Represents the result of substituting a set of types for a template
  /// type parameter pack.
  ///
  /// When a pack expansion in the source code contains multiple parameter packs
  /// and those parameter packs correspond to different levels of template
  /// parameter lists, this type node is used to represent a template type
  /// parameter pack from an outer level, which has already had its argument pack
  /// substituted but that still lives within a pack expansion that itself
  /// could not be instantiated. When actually performing a substitution into
  /// that pack expansion (e.g., when all template parameters have corresponding
  /// arguments), this type will be replaced with the \c SubstTemplateTypeParmType
  /// at the current pack substitution index.
  class SubstTemplateTypeParmPackType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext;
  
    /// The original type parameter.
    const TemplateTypeParmType *Replaced;
  
    /// A pointer to the set of template arguments that this
    /// parameter pack is instantiated with.
    const TemplateArgument *Arguments;
  
    SubstTemplateTypeParmPackType(const TemplateTypeParmType *Param,
                                  QualType Canon,
                                  const TemplateArgument &ArgPack);
  
  public:
    IdentifierInfo *getIdentifier() const { return Replaced->getIdentifier(); }
  
    /// Gets the template parameter that was substituted for.
    const TemplateTypeParmType *getReplacedParameter() const {
      return Replaced;
    }
  
    unsigned getNumArgs() const {
      return SubstTemplateTypeParmPackTypeBits.NumArgs;
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    TemplateArgument getArgumentPack() const;
  
    void Profile(llvm::FoldingSetNodeID &ID);
    static void Profile(llvm::FoldingSetNodeID &ID,
                        const TemplateTypeParmType *Replaced,
                        const TemplateArgument &ArgPack);
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == SubstTemplateTypeParmPack;
    }
  };
  
  /// Common base class for placeholders for types that get replaced by
  /// placeholder type deduction: C++11 auto, C++14 decltype(auto), C++17 deduced
  /// class template types, and (eventually) constrained type names from the C++
  /// Concepts TS.
  ///
  /// These types are usually a placeholder for a deduced type. However, before
  /// the initializer is attached, or (usually) if the initializer is
  /// type-dependent, there is no deduced type and the type is canonical. In
  /// the latter case, it is also a dependent type.
  class DeducedType : public Type {
  protected:
    DeducedType(TypeClass TC, QualType DeducedAsType, bool IsDependent,
                bool IsInstantiationDependent, bool ContainsParameterPack)
        : Type(TC,
               // FIXME: Retain the sugared deduced type?
               DeducedAsType.isNull() ? QualType(this, 0)
                                      : DeducedAsType.getCanonicalType(),
               IsDependent, IsInstantiationDependent,
               /*VariablyModified=*/false, ContainsParameterPack) {
      if (!DeducedAsType.isNull()) {
        if (DeducedAsType->isDependentType())
          setDependent();
        if (DeducedAsType->isInstantiationDependentType())
          setInstantiationDependent();
        if (DeducedAsType->containsUnexpandedParameterPack())
          setContainsUnexpandedParameterPack();
      }
    }
  
  public:
    bool isSugared() const { return !isCanonicalUnqualified(); }
    QualType desugar() const { return getCanonicalTypeInternal(); }
  
    /// Get the type deduced for this placeholder type, or null if it's
    /// either not been deduced or was deduced to a dependent type.
    QualType getDeducedType() const {
      return !isCanonicalUnqualified() ? getCanonicalTypeInternal() : QualType();
    }
    bool isDeduced() const {
      return !isCanonicalUnqualified() || isDependentType();
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == Auto ||
             T->getTypeClass() == DeducedTemplateSpecialization;
    }
  };
  
  /// Represents a C++11 auto or C++14 decltype(auto) type.
  class AutoType : public DeducedType, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these
  
    AutoType(QualType DeducedAsType, AutoTypeKeyword Keyword,
             bool IsDeducedAsDependent)
        : DeducedType(Auto, DeducedAsType, IsDeducedAsDependent,
                      IsDeducedAsDependent, /*ContainsPack=*/false) {
      AutoTypeBits.Keyword = (unsigned)Keyword;
    }
  
  public:
    bool isDecltypeAuto() const {
      return getKeyword() == AutoTypeKeyword::DecltypeAuto;
    }
  
    AutoTypeKeyword getKeyword() const {
      return (AutoTypeKeyword)AutoTypeBits.Keyword;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getDeducedType(), getKeyword(), isDependentType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Deduced,
                        AutoTypeKeyword Keyword, bool IsDependent) {
      ID.AddPointer(Deduced.getAsOpaquePtr());
      ID.AddInteger((unsigned)Keyword);
      ID.AddBoolean(IsDependent);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == Auto;
    }
  };
  
  /// Represents a C++17 deduced template specialization type.
  class DeducedTemplateSpecializationType : public DeducedType,
                                            public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these
  
    /// The name of the template whose arguments will be deduced.
    TemplateName Template;
  
    DeducedTemplateSpecializationType(TemplateName Template,
                                      QualType DeducedAsType,
                                      bool IsDeducedAsDependent)
        : DeducedType(DeducedTemplateSpecialization, DeducedAsType,
                      IsDeducedAsDependent || Template.isDependent(),
                      IsDeducedAsDependent || Template.isInstantiationDependent(),
                      Template.containsUnexpandedParameterPack()),
          Template(Template) {}
  
  public:
    /// Retrieve the name of the template that we are deducing.
    TemplateName getTemplateName() const { return Template;}
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getTemplateName(), getDeducedType(), isDependentType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, TemplateName Template,
                        QualType Deduced, bool IsDependent) {
      Template.Profile(ID);
      ID.AddPointer(Deduced.getAsOpaquePtr());
      ID.AddBoolean(IsDependent);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == DeducedTemplateSpecialization;
    }
  };
  
  /// Represents a type template specialization; the template
  /// must be a class template, a type alias template, or a template
  /// template parameter.  A template which cannot be resolved to one of
  /// these, e.g. because it is written with a dependent scope
  /// specifier, is instead represented as a
  /// @c DependentTemplateSpecializationType.
  ///
  /// A non-dependent template specialization type is always "sugar",
  /// typically for a \c RecordType.  For example, a class template
  /// specialization type of \c vector<int> will refer to a tag type for
  /// the instantiation \c std::vector<int, std::allocator<int>>
  ///
  /// Template specializations are dependent if either the template or
  /// any of the template arguments are dependent, in which case the
  /// type may also be canonical.
  ///
  /// Instances of this type are allocated with a trailing array of
  /// TemplateArguments, followed by a QualType representing the
  /// non-canonical aliased type when the template is a type alias
  /// template.
  class alignas(8) TemplateSpecializationType
      : public Type,
        public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these
  
    /// The name of the template being specialized.  This is
    /// either a TemplateName::Template (in which case it is a
    /// ClassTemplateDecl*, a TemplateTemplateParmDecl*, or a
    /// TypeAliasTemplateDecl*), a
    /// TemplateName::SubstTemplateTemplateParmPack, or a
    /// TemplateName::SubstTemplateTemplateParm (in which case the
    /// replacement must, recursively, be one of these).
    TemplateName Template;
  
    TemplateSpecializationType(TemplateName T,
                               ArrayRef<TemplateArgument> Args,
                               QualType Canon,
                               QualType Aliased);
  
  public:
    /// Determine whether any of the given template arguments are dependent.
    static bool anyDependentTemplateArguments(ArrayRef<TemplateArgumentLoc> Args,
                                              bool &InstantiationDependent);
  
    static bool anyDependentTemplateArguments(const TemplateArgumentListInfo &,
                                              bool &InstantiationDependent);
  
    /// True if this template specialization type matches a current
    /// instantiation in the context in which it is found.
    bool isCurrentInstantiation() const {
      return isa<InjectedClassNameType>(getCanonicalTypeInternal());
    }
  
    /// Determine if this template specialization type is for a type alias
    /// template that has been substituted.
    ///
    /// Nearly every template specialization type whose template is an alias
    /// template will be substituted. However, this is not the case when
    /// the specialization contains a pack expansion but the template alias
    /// does not have a corresponding parameter pack, e.g.,
    ///
    /// \code
    /// template<typename T, typename U, typename V> struct S;
    /// template<typename T, typename U> using A = S<T, int, U>;
    /// template<typename... Ts> struct X {
    ///   typedef A<Ts...> type; // not a type alias
    /// };
    /// \endcode
    bool isTypeAlias() const { return TemplateSpecializationTypeBits.TypeAlias; }
  
    /// Get the aliased type, if this is a specialization of a type alias
    /// template.
    QualType getAliasedType() const {
      assert(isTypeAlias() && "not a type alias template specialization");
      return *reinterpret_cast<const QualType*>(end());
    }
  
    using iterator = const TemplateArgument *;
  
    iterator begin() const { return getArgs(); }
    iterator end() const; // defined inline in TemplateBase.h
  
    /// Retrieve the name of the template that we are specializing.
    TemplateName getTemplateName() const { return Template; }
  
    /// Retrieve the template arguments.
    const TemplateArgument *getArgs() const {
      return reinterpret_cast<const TemplateArgument *>(this + 1);
    }
  
    /// Retrieve the number of template arguments.
    unsigned getNumArgs() const {
      return TemplateSpecializationTypeBits.NumArgs;
    }
  
    /// Retrieve a specific template argument as a type.
    /// \pre \c isArgType(Arg)
    const TemplateArgument &getArg(unsigned Idx) const; // in TemplateBase.h
  
    ArrayRef<TemplateArgument> template_arguments() const {
      return {getArgs(), getNumArgs()};
    }
  
    bool isSugared() const {
      return !isDependentType() || isCurrentInstantiation() || isTypeAlias();
    }
  
    QualType desugar() const {
      return isTypeAlias() ? getAliasedType() : getCanonicalTypeInternal();
    }
  
    void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Ctx) {
      Profile(ID, Template, template_arguments(), Ctx);
      if (isTypeAlias())
        getAliasedType().Profile(ID);
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, TemplateName T,
                        ArrayRef<TemplateArgument> Args,
                        const ASTContext &Context);
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == TemplateSpecialization;
    }
  };
  
  /// Print a template argument list, including the '<' and '>'
  /// enclosing the template arguments.
  void printTemplateArgumentList(raw_ostream &OS,
                                 ArrayRef<TemplateArgument> Args,
                                 const PrintingPolicy &Policy);
  
  void printTemplateArgumentList(raw_ostream &OS,
                                 ArrayRef<TemplateArgumentLoc> Args,
                                 const PrintingPolicy &Policy);
  
  void printTemplateArgumentList(raw_ostream &OS,
                                 const TemplateArgumentListInfo &Args,
                                 const PrintingPolicy &Policy);
  
  /// The injected class name of a C++ class template or class
  /// template partial specialization.  Used to record that a type was
  /// spelled with a bare identifier rather than as a template-id; the
  /// equivalent for non-templated classes is just RecordType.
  ///
  /// Injected class name types are always dependent.  Template
  /// instantiation turns these into RecordTypes.
  ///
  /// Injected class name types are always canonical.  This works
  /// because it is impossible to compare an injected class name type
  /// with the corresponding non-injected template type, for the same
  /// reason that it is impossible to directly compare template
  /// parameters from different dependent contexts: injected class name
  /// types can only occur within the scope of a particular templated
  /// declaration, and within that scope every template specialization
  /// will canonicalize to the injected class name (when appropriate
  /// according to the rules of the language).
  class InjectedClassNameType : public Type {
    friend class ASTContext; // ASTContext creates these.
    friend class ASTNodeImporter;
    friend class ASTReader; // FIXME: ASTContext::getInjectedClassNameType is not
                            // currently suitable for AST reading, too much
                            // interdependencies.
  
    CXXRecordDecl *Decl;
  
    /// The template specialization which this type represents.
    /// For example, in
    ///   template <class T> class A { ... };
    /// this is A<T>, whereas in
    ///   template <class X, class Y> class A<B<X,Y> > { ... };
    /// this is A<B<X,Y> >.
    ///
    /// It is always unqualified, always a template specialization type,
    /// and always dependent.
    QualType InjectedType;
  
    InjectedClassNameType(CXXRecordDecl *D, QualType TST)
        : Type(InjectedClassName, QualType(), /*Dependent=*/true,
               /*InstantiationDependent=*/true,
               /*VariablyModified=*/false,
               /*ContainsUnexpandedParameterPack=*/false),
          Decl(D), InjectedType(TST) {
      assert(isa<TemplateSpecializationType>(TST));
      assert(!TST.hasQualifiers());
      assert(TST->isDependentType());
    }
  
  public:
    QualType getInjectedSpecializationType() const { return InjectedType; }
  
    const TemplateSpecializationType *getInjectedTST() const {
      return cast<TemplateSpecializationType>(InjectedType.getTypePtr());
    }
  
    TemplateName getTemplateName() const {
      return getInjectedTST()->getTemplateName();
    }
  
    CXXRecordDecl *getDecl() const;
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == InjectedClassName;
    }
  };
  
  /// The kind of a tag type.
  enum TagTypeKind {
    /// The "struct" keyword.
    TTK_Struct,
  
    /// The "__interface" keyword.
    TTK_Interface,
  
    /// The "union" keyword.
    TTK_Union,
  
    /// The "class" keyword.
    TTK_Class,
  
    /// The "enum" keyword.
    TTK_Enum
  };
  
  /// The elaboration keyword that precedes a qualified type name or
  /// introduces an elaborated-type-specifier.
  enum ElaboratedTypeKeyword {
    /// The "struct" keyword introduces the elaborated-type-specifier.
    ETK_Struct,
  
    /// The "__interface" keyword introduces the elaborated-type-specifier.
    ETK_Interface,
  
    /// The "union" keyword introduces the elaborated-type-specifier.
    ETK_Union,
  
    /// The "class" keyword introduces the elaborated-type-specifier.
    ETK_Class,
  
    /// The "enum" keyword introduces the elaborated-type-specifier.
    ETK_Enum,
  
    /// The "typename" keyword precedes the qualified type name, e.g.,
    /// \c typename T::type.
    ETK_Typename,
  
    /// No keyword precedes the qualified type name.
    ETK_None
  };
  
  /// A helper class for Type nodes having an ElaboratedTypeKeyword.
  /// The keyword in stored in the free bits of the base class.
  /// Also provides a few static helpers for converting and printing
  /// elaborated type keyword and tag type kind enumerations.
  class TypeWithKeyword : public Type {
  protected:
    TypeWithKeyword(ElaboratedTypeKeyword Keyword, TypeClass tc,
                    QualType Canonical, bool Dependent,
                    bool InstantiationDependent, bool VariablyModified,
                    bool ContainsUnexpandedParameterPack)
        : Type(tc, Canonical, Dependent, InstantiationDependent, VariablyModified,
               ContainsUnexpandedParameterPack) {
      TypeWithKeywordBits.Keyword = Keyword;
    }
  
  public:
    ElaboratedTypeKeyword getKeyword() const {
      return static_cast<ElaboratedTypeKeyword>(TypeWithKeywordBits.Keyword);
    }
  
    /// Converts a type specifier (DeclSpec::TST) into an elaborated type keyword.
    static ElaboratedTypeKeyword getKeywordForTypeSpec(unsigned TypeSpec);
  
    /// Converts a type specifier (DeclSpec::TST) into a tag type kind.
    /// It is an error to provide a type specifier which *isn't* a tag kind here.
    static TagTypeKind getTagTypeKindForTypeSpec(unsigned TypeSpec);
  
    /// Converts a TagTypeKind into an elaborated type keyword.
    static ElaboratedTypeKeyword getKeywordForTagTypeKind(TagTypeKind Tag);
  
    /// Converts an elaborated type keyword into a TagTypeKind.
    /// It is an error to provide an elaborated type keyword
    /// which *isn't* a tag kind here.
    static TagTypeKind getTagTypeKindForKeyword(ElaboratedTypeKeyword Keyword);
  
    static bool KeywordIsTagTypeKind(ElaboratedTypeKeyword Keyword);
  
    static StringRef getKeywordName(ElaboratedTypeKeyword Keyword);
  
    static StringRef getTagTypeKindName(TagTypeKind Kind) {
      return getKeywordName(getKeywordForTagTypeKind(Kind));
    }
  
    class CannotCastToThisType {};
    static CannotCastToThisType classof(const Type *);
  };
  
  /// Represents a type that was referred to using an elaborated type
  /// keyword, e.g., struct S, or via a qualified name, e.g., N::M::type,
  /// or both.
  ///
  /// This type is used to keep track of a type name as written in the
  /// source code, including tag keywords and any nested-name-specifiers.
  /// The type itself is always "sugar", used to express what was written
  /// in the source code but containing no additional semantic information.
  class ElaboratedType final
      : public TypeWithKeyword,
        public llvm::FoldingSetNode,
        private llvm::TrailingObjects<ElaboratedType, TagDecl *> {
    friend class ASTContext; // ASTContext creates these
    friend TrailingObjects;
  
    /// The nested name specifier containing the qualifier.
    NestedNameSpecifier *NNS;
  
    /// The type that this qualified name refers to.
    QualType NamedType;
  
    /// The (re)declaration of this tag type owned by this occurrence is stored
    /// as a trailing object if there is one. Use getOwnedTagDecl to obtain
    /// it, or obtain a null pointer if there is none.
  
    ElaboratedType(ElaboratedTypeKeyword Keyword, NestedNameSpecifier *NNS,
                   QualType NamedType, QualType CanonType, TagDecl *OwnedTagDecl)
        : TypeWithKeyword(Keyword, Elaborated, CanonType,
                          NamedType->isDependentType(),
                          NamedType->isInstantiationDependentType(),
                          NamedType->isVariablyModifiedType(),
                          NamedType->containsUnexpandedParameterPack()),
          NNS(NNS), NamedType(NamedType) {
      ElaboratedTypeBits.HasOwnedTagDecl = false;
      if (OwnedTagDecl) {
        ElaboratedTypeBits.HasOwnedTagDecl = true;
        *getTrailingObjects<TagDecl *>() = OwnedTagDecl;
      }
      assert(!(Keyword == ETK_None && NNS == nullptr) &&
             "ElaboratedType cannot have elaborated type keyword "
             "and name qualifier both null.");
    }
  
  public:
    /// Retrieve the qualification on this type.
    NestedNameSpecifier *getQualifier() const { return NNS; }
  
    /// Retrieve the type named by the qualified-id.
    QualType getNamedType() const { return NamedType; }
  
    /// Remove a single level of sugar.
    QualType desugar() const { return getNamedType(); }
  
    /// Returns whether this type directly provides sugar.
    bool isSugared() const { return true; }
  
    /// Return the (re)declaration of this type owned by this occurrence of this
    /// type, or nullptr if there is none.
    TagDecl *getOwnedTagDecl() const {
      return ElaboratedTypeBits.HasOwnedTagDecl ? *getTrailingObjects<TagDecl *>()
                                                : nullptr;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getKeyword(), NNS, NamedType, getOwnedTagDecl());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, ElaboratedTypeKeyword Keyword,
                        NestedNameSpecifier *NNS, QualType NamedType,
                        TagDecl *OwnedTagDecl) {
      ID.AddInteger(Keyword);
      ID.AddPointer(NNS);
      NamedType.Profile(ID);
      ID.AddPointer(OwnedTagDecl);
    }
  
    static bool classof(const Type *T) { return T->getTypeClass() == Elaborated; }
  };
  
  /// Represents a qualified type name for which the type name is
  /// dependent.
  ///
  /// DependentNameType represents a class of dependent types that involve a
  /// possibly dependent nested-name-specifier (e.g., "T::") followed by a
  /// name of a type. The DependentNameType may start with a "typename" (for a
  /// typename-specifier), "class", "struct", "union", or "enum" (for a
  /// dependent elaborated-type-specifier), or nothing (in contexts where we
  /// know that we must be referring to a type, e.g., in a base class specifier).
  /// Typically the nested-name-specifier is dependent, but in MSVC compatibility
  /// mode, this type is used with non-dependent names to delay name lookup until
  /// instantiation.
  class DependentNameType : public TypeWithKeyword, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these
  
    /// The nested name specifier containing the qualifier.
    NestedNameSpecifier *NNS;
  
    /// The type that this typename specifier refers to.
    const IdentifierInfo *Name;
  
    DependentNameType(ElaboratedTypeKeyword Keyword, NestedNameSpecifier *NNS,
                      const IdentifierInfo *Name, QualType CanonType)
        : TypeWithKeyword(Keyword, DependentName, CanonType, /*Dependent=*/true,
                          /*InstantiationDependent=*/true,
                          /*VariablyModified=*/false,
                          NNS->containsUnexpandedParameterPack()),
          NNS(NNS), Name(Name) {}
  
  public:
    /// Retrieve the qualification on this type.
    NestedNameSpecifier *getQualifier() const { return NNS; }
  
    /// Retrieve the type named by the typename specifier as an identifier.
    ///
    /// This routine will return a non-NULL identifier pointer when the
    /// form of the original typename was terminated by an identifier,
    /// e.g., "typename T::type".
    const IdentifierInfo *getIdentifier() const {
      return Name;
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getKeyword(), NNS, Name);
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, ElaboratedTypeKeyword Keyword,
                        NestedNameSpecifier *NNS, const IdentifierInfo *Name) {
      ID.AddInteger(Keyword);
      ID.AddPointer(NNS);
      ID.AddPointer(Name);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == DependentName;
    }
  };
  
  /// Represents a template specialization type whose template cannot be
  /// resolved, e.g.
  ///   A<T>::template B<T>
  class alignas(8) DependentTemplateSpecializationType
      : public TypeWithKeyword,
        public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these
  
    /// The nested name specifier containing the qualifier.
    NestedNameSpecifier *NNS;
  
    /// The identifier of the template.
    const IdentifierInfo *Name;
  
    DependentTemplateSpecializationType(ElaboratedTypeKeyword Keyword,
                                        NestedNameSpecifier *NNS,
                                        const IdentifierInfo *Name,
                                        ArrayRef<TemplateArgument> Args,
                                        QualType Canon);
  
    const TemplateArgument *getArgBuffer() const {
      return reinterpret_cast<const TemplateArgument*>(this+1);
    }
  
    TemplateArgument *getArgBuffer() {
      return reinterpret_cast<TemplateArgument*>(this+1);
    }
  
  public:
    NestedNameSpecifier *getQualifier() const { return NNS; }
    const IdentifierInfo *getIdentifier() const { return Name; }
  
    /// Retrieve the template arguments.
    const TemplateArgument *getArgs() const {
      return getArgBuffer();
    }
  
    /// Retrieve the number of template arguments.
    unsigned getNumArgs() const {
      return DependentTemplateSpecializationTypeBits.NumArgs;
    }
  
    const TemplateArgument &getArg(unsigned Idx) const; // in TemplateBase.h
  
    ArrayRef<TemplateArgument> template_arguments() const {
      return {getArgs(), getNumArgs()};
    }
  
    using iterator = const TemplateArgument *;
  
    iterator begin() const { return getArgs(); }
    iterator end() const; // inline in TemplateBase.h
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context) {
      Profile(ID, Context, getKeyword(), NNS, Name, {getArgs(), getNumArgs()});
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID,
                        const ASTContext &Context,
                        ElaboratedTypeKeyword Keyword,
                        NestedNameSpecifier *Qualifier,
                        const IdentifierInfo *Name,
                        ArrayRef<TemplateArgument> Args);
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == DependentTemplateSpecialization;
    }
  };
  
  /// Represents a pack expansion of types.
  ///
  /// Pack expansions are part of C++11 variadic templates. A pack
  /// expansion contains a pattern, which itself contains one or more
  /// "unexpanded" parameter packs. When instantiated, a pack expansion
  /// produces a series of types, each instantiated from the pattern of
  /// the expansion, where the Ith instantiation of the pattern uses the
  /// Ith arguments bound to each of the unexpanded parameter packs. The
  /// pack expansion is considered to "expand" these unexpanded
  /// parameter packs.
  ///
  /// \code
  /// template<typename ...Types> struct tuple;
  ///
  /// template<typename ...Types>
  /// struct tuple_of_references {
  ///   typedef tuple<Types&...> type;
  /// };
  /// \endcode
  ///
  /// Here, the pack expansion \c Types&... is represented via a
  /// PackExpansionType whose pattern is Types&.
  class PackExpansionType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these
  
    /// The pattern of the pack expansion.
    QualType Pattern;
  
    PackExpansionType(QualType Pattern, QualType Canon,
                      Optional<unsigned> NumExpansions)
        : Type(PackExpansion, Canon, /*Dependent=*/Pattern->isDependentType(),
               /*InstantiationDependent=*/true,
               /*VariablyModified=*/Pattern->isVariablyModifiedType(),
               /*ContainsUnexpandedParameterPack=*/false),
          Pattern(Pattern) {
      PackExpansionTypeBits.NumExpansions =
          NumExpansions ? *NumExpansions + 1 : 0;
    }
  
  public:
    /// Retrieve the pattern of this pack expansion, which is the
    /// type that will be repeatedly instantiated when instantiating the
    /// pack expansion itself.
    QualType getPattern() const { return Pattern; }
  
    /// Retrieve the number of expansions that this pack expansion will
    /// generate, if known.
    Optional<unsigned> getNumExpansions() const {
      if (PackExpansionTypeBits.NumExpansions)
        return PackExpansionTypeBits.NumExpansions - 1;
      return None;
    }
  
    bool isSugared() const { return !Pattern->isDependentType(); }
    QualType desugar() const { return isSugared() ? Pattern : QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getPattern(), getNumExpansions());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType Pattern,
                        Optional<unsigned> NumExpansions) {
      ID.AddPointer(Pattern.getAsOpaquePtr());
      ID.AddBoolean(NumExpansions.hasValue());
      if (NumExpansions)
        ID.AddInteger(*NumExpansions);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == PackExpansion;
    }
  };
  
  /// This class wraps the list of protocol qualifiers. For types that can
  /// take ObjC protocol qualifers, they can subclass this class.
  template <class T>
  class ObjCProtocolQualifiers {
  protected:
    ObjCProtocolQualifiers() = default;
  
    ObjCProtocolDecl * const *getProtocolStorage() const {
      return const_cast<ObjCProtocolQualifiers*>(this)->getProtocolStorage();
    }
  
    ObjCProtocolDecl **getProtocolStorage() {
      return static_cast<T*>(this)->getProtocolStorageImpl();
    }
  
    void setNumProtocols(unsigned N) {
      static_cast<T*>(this)->setNumProtocolsImpl(N);
    }
  
    void initialize(ArrayRef<ObjCProtocolDecl *> protocols) {
      setNumProtocols(protocols.size());
      assert(getNumProtocols() == protocols.size() &&
             "bitfield overflow in protocol count");
      if (!protocols.empty())
        memcpy(getProtocolStorage(), protocols.data(),
               protocols.size() * sizeof(ObjCProtocolDecl*));
    }
  
  public:
    using qual_iterator = ObjCProtocolDecl * const *;
    using qual_range = llvm::iterator_range<qual_iterator>;
  
    qual_range quals() const { return qual_range(qual_begin(), qual_end()); }
    qual_iterator qual_begin() const { return getProtocolStorage(); }
    qual_iterator qual_end() const { return qual_begin() + getNumProtocols(); }
  
    bool qual_empty() const { return getNumProtocols() == 0; }
  
    /// Return the number of qualifying protocols in this type, or 0 if
    /// there are none.
    unsigned getNumProtocols() const {
      return static_cast<const T*>(this)->getNumProtocolsImpl();
    }
  
    /// Fetch a protocol by index.
    ObjCProtocolDecl *getProtocol(unsigned I) const {
      assert(I < getNumProtocols() && "Out-of-range protocol access");
      return qual_begin()[I];
    }
  
    /// Retrieve all of the protocol qualifiers.
    ArrayRef<ObjCProtocolDecl *> getProtocols() const {
      return ArrayRef<ObjCProtocolDecl *>(qual_begin(), getNumProtocols());
    }
  };
  
  /// Represents a type parameter type in Objective C. It can take
  /// a list of protocols.
  class ObjCTypeParamType : public Type,
                            public ObjCProtocolQualifiers<ObjCTypeParamType>,
                            public llvm::FoldingSetNode {
    friend class ASTContext;
    friend class ObjCProtocolQualifiers<ObjCTypeParamType>;
  
    /// The number of protocols stored on this type.
    unsigned NumProtocols : 6;
  
    ObjCTypeParamDecl *OTPDecl;
  
    /// The protocols are stored after the ObjCTypeParamType node. In the
    /// canonical type, the list of protocols are sorted alphabetically
    /// and uniqued.
    ObjCProtocolDecl **getProtocolStorageImpl();
  
    /// Return the number of qualifying protocols in this interface type,
    /// or 0 if there are none.
    unsigned getNumProtocolsImpl() const {
      return NumProtocols;
    }
  
    void setNumProtocolsImpl(unsigned N) {
      NumProtocols = N;
    }
  
    ObjCTypeParamType(const ObjCTypeParamDecl *D,
                      QualType can,
                      ArrayRef<ObjCProtocolDecl *> protocols);
  
  public:
    bool isSugared() const { return true; }
    QualType desugar() const { return getCanonicalTypeInternal(); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == ObjCTypeParam;
    }
  
    void Profile(llvm::FoldingSetNodeID &ID);
    static void Profile(llvm::FoldingSetNodeID &ID,
                        const ObjCTypeParamDecl *OTPDecl,
                        ArrayRef<ObjCProtocolDecl *> protocols);
  
    ObjCTypeParamDecl *getDecl() const { return OTPDecl; }
  };
  
  /// Represents a class type in Objective C.
  ///
  /// Every Objective C type is a combination of a base type, a set of
  /// type arguments (optional, for parameterized classes) and a list of
  /// protocols.
  ///
  /// Given the following declarations:
  /// \code
  ///   \@class C<T>;
  ///   \@protocol P;
  /// \endcode
  ///
  /// 'C' is an ObjCInterfaceType C.  It is sugar for an ObjCObjectType
  /// with base C and no protocols.
  ///
  /// 'C<P>' is an unspecialized ObjCObjectType with base C and protocol list [P].
  /// 'C<C*>' is a specialized ObjCObjectType with type arguments 'C*' and no
  /// protocol list.
  /// 'C<C*><P>' is a specialized ObjCObjectType with base C, type arguments 'C*',
  /// and protocol list [P].
  ///
  /// 'id' is a TypedefType which is sugar for an ObjCObjectPointerType whose
  /// pointee is an ObjCObjectType with base BuiltinType::ObjCIdType
  /// and no protocols.
  ///
  /// 'id<P>' is an ObjCObjectPointerType whose pointee is an ObjCObjectType
  /// with base BuiltinType::ObjCIdType and protocol list [P].  Eventually
  /// this should get its own sugar class to better represent the source.
  class ObjCObjectType : public Type,
                         public ObjCProtocolQualifiers<ObjCObjectType> {
    friend class ObjCProtocolQualifiers<ObjCObjectType>;
  
    // ObjCObjectType.NumTypeArgs - the number of type arguments stored
    // after the ObjCObjectPointerType node.
    // ObjCObjectType.NumProtocols - the number of protocols stored
    // after the type arguments of ObjCObjectPointerType node.
    //
    // These protocols are those written directly on the type.  If
    // protocol qualifiers ever become additive, the iterators will need
    // to get kindof complicated.
    //
    // In the canonical object type, these are sorted alphabetically
    // and uniqued.
  
    /// Either a BuiltinType or an InterfaceType or sugar for either.
    QualType BaseType;
  
    /// Cached superclass type.
    mutable llvm::PointerIntPair<const ObjCObjectType *, 1, bool>
      CachedSuperClassType;
  
    QualType *getTypeArgStorage();
    const QualType *getTypeArgStorage() const {
      return const_cast<ObjCObjectType *>(this)->getTypeArgStorage();
    }
  
    ObjCProtocolDecl **getProtocolStorageImpl();
    /// Return the number of qualifying protocols in this interface type,
    /// or 0 if there are none.
    unsigned getNumProtocolsImpl() const {
      return ObjCObjectTypeBits.NumProtocols;
    }
    void setNumProtocolsImpl(unsigned N) {
      ObjCObjectTypeBits.NumProtocols = N;
    }
  
  protected:
    enum Nonce_ObjCInterface { Nonce_ObjCInterface };
  
    ObjCObjectType(QualType Canonical, QualType Base,
                   ArrayRef<QualType> typeArgs,
                   ArrayRef<ObjCProtocolDecl *> protocols,
                   bool isKindOf);
  
    ObjCObjectType(enum Nonce_ObjCInterface)
          : Type(ObjCInterface, QualType(), false, false, false, false),
            BaseType(QualType(this_(), 0)) {
      ObjCObjectTypeBits.NumProtocols = 0;
      ObjCObjectTypeBits.NumTypeArgs = 0;
      ObjCObjectTypeBits.IsKindOf = 0;
    }
  
    void computeSuperClassTypeSlow() const;
  
  public:
    /// Gets the base type of this object type.  This is always (possibly
    /// sugar for) one of:
    ///  - the 'id' builtin type (as opposed to the 'id' type visible to the
    ///    user, which is a typedef for an ObjCObjectPointerType)
    ///  - the 'Class' builtin type (same caveat)
    ///  - an ObjCObjectType (currently always an ObjCInterfaceType)
    QualType getBaseType() const { return BaseType; }
  
    bool isObjCId() const {
      return getBaseType()->isSpecificBuiltinType(BuiltinType::ObjCId);
    }
  
    bool isObjCClass() const {
      return getBaseType()->isSpecificBuiltinType(BuiltinType::ObjCClass);
    }
  
    bool isObjCUnqualifiedId() const { return qual_empty() && isObjCId(); }
    bool isObjCUnqualifiedClass() const { return qual_empty() && isObjCClass(); }
    bool isObjCUnqualifiedIdOrClass() const {
      if (!qual_empty()) return false;
      if (const BuiltinType *T = getBaseType()->getAs<BuiltinType>())
        return T->getKind() == BuiltinType::ObjCId ||
               T->getKind() == BuiltinType::ObjCClass;
      return false;
    }
    bool isObjCQualifiedId() const { return !qual_empty() && isObjCId(); }
    bool isObjCQualifiedClass() const { return !qual_empty() && isObjCClass(); }
  
    /// Gets the interface declaration for this object type, if the base type
    /// really is an interface.
    ObjCInterfaceDecl *getInterface() const;
  
    /// Determine whether this object type is "specialized", meaning
    /// that it has type arguments.
    bool isSpecialized() const;
  
    /// Determine whether this object type was written with type arguments.
    bool isSpecializedAsWritten() const {
      return ObjCObjectTypeBits.NumTypeArgs > 0;
    }
  
    /// Determine whether this object type is "unspecialized", meaning
    /// that it has no type arguments.
    bool isUnspecialized() const { return !isSpecialized(); }
  
    /// Determine whether this object type is "unspecialized" as
    /// written, meaning that it has no type arguments.
    bool isUnspecializedAsWritten() const { return !isSpecializedAsWritten(); }
  
    /// Retrieve the type arguments of this object type (semantically).
    ArrayRef<QualType> getTypeArgs() const;
  
    /// Retrieve the type arguments of this object type as they were
    /// written.
    ArrayRef<QualType> getTypeArgsAsWritten() const {
      return llvm::makeArrayRef(getTypeArgStorage(),
                                ObjCObjectTypeBits.NumTypeArgs);
    }
  
    /// Whether this is a "__kindof" type as written.
    bool isKindOfTypeAsWritten() const { return ObjCObjectTypeBits.IsKindOf; }
  
    /// Whether this ia a "__kindof" type (semantically).
    bool isKindOfType() const;
  
    /// Retrieve the type of the superclass of this object type.
    ///
    /// This operation substitutes any type arguments into the
    /// superclass of the current class type, potentially producing a
    /// specialization of the superclass type. Produces a null type if
    /// there is no superclass.
    QualType getSuperClassType() const {
      if (!CachedSuperClassType.getInt())
        computeSuperClassTypeSlow();
  
      assert(CachedSuperClassType.getInt() && "Superclass not set?");
      return QualType(CachedSuperClassType.getPointer(), 0);
    }
  
    /// Strip off the Objective-C "kindof" type and (with it) any
    /// protocol qualifiers.
    QualType stripObjCKindOfTypeAndQuals(const ASTContext &ctx) const;
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == ObjCObject ||
             T->getTypeClass() == ObjCInterface;
    }
  };
  
  /// A class providing a concrete implementation
  /// of ObjCObjectType, so as to not increase the footprint of
  /// ObjCInterfaceType.  Code outside of ASTContext and the core type
  /// system should not reference this type.
  class ObjCObjectTypeImpl : public ObjCObjectType, public llvm::FoldingSetNode {
    friend class ASTContext;
  
    // If anyone adds fields here, ObjCObjectType::getProtocolStorage()
    // will need to be modified.
  
    ObjCObjectTypeImpl(QualType Canonical, QualType Base,
                       ArrayRef<QualType> typeArgs,
                       ArrayRef<ObjCProtocolDecl *> protocols,
                       bool isKindOf)
        : ObjCObjectType(Canonical, Base, typeArgs, protocols, isKindOf) {}
  
  public:
    void Profile(llvm::FoldingSetNodeID &ID);
    static void Profile(llvm::FoldingSetNodeID &ID,
                        QualType Base,
                        ArrayRef<QualType> typeArgs,
                        ArrayRef<ObjCProtocolDecl *> protocols,
                        bool isKindOf);
  };
  
  inline QualType *ObjCObjectType::getTypeArgStorage() {
    return reinterpret_cast<QualType *>(static_cast<ObjCObjectTypeImpl*>(this)+1);
  }
  
  inline ObjCProtocolDecl **ObjCObjectType::getProtocolStorageImpl() {
      return reinterpret_cast<ObjCProtocolDecl**>(
               getTypeArgStorage() + ObjCObjectTypeBits.NumTypeArgs);
  }
  
  inline ObjCProtocolDecl **ObjCTypeParamType::getProtocolStorageImpl() {
      return reinterpret_cast<ObjCProtocolDecl**>(
               static_cast<ObjCTypeParamType*>(this)+1);
  }
  
  /// Interfaces are the core concept in Objective-C for object oriented design.
  /// They basically correspond to C++ classes.  There are two kinds of interface
  /// types: normal interfaces like `NSString`, and qualified interfaces, which
  /// are qualified with a protocol list like `NSString<NSCopyable, NSAmazing>`.
  ///
  /// ObjCInterfaceType guarantees the following properties when considered
  /// as a subtype of its superclass, ObjCObjectType:
  ///   - There are no protocol qualifiers.  To reinforce this, code which
  ///     tries to invoke the protocol methods via an ObjCInterfaceType will
  ///     fail to compile.
  ///   - It is its own base type.  That is, if T is an ObjCInterfaceType*,
  ///     T->getBaseType() == QualType(T, 0).
  class ObjCInterfaceType : public ObjCObjectType {
    friend class ASTContext; // ASTContext creates these.
    friend class ASTReader;
    friend class ObjCInterfaceDecl;
  
    mutable ObjCInterfaceDecl *Decl;
  
    ObjCInterfaceType(const ObjCInterfaceDecl *D)
        : ObjCObjectType(Nonce_ObjCInterface),
          Decl(const_cast<ObjCInterfaceDecl*>(D)) {}
  
  public:
    /// Get the declaration of this interface.
    ObjCInterfaceDecl *getDecl() const { return Decl; }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == ObjCInterface;
    }
  
    // Nonsense to "hide" certain members of ObjCObjectType within this
    // class.  People asking for protocols on an ObjCInterfaceType are
    // not going to get what they want: ObjCInterfaceTypes are
    // guaranteed to have no protocols.
    enum {
      qual_iterator,
      qual_begin,
      qual_end,
      getNumProtocols,
      getProtocol
    };
  };
  
  inline ObjCInterfaceDecl *ObjCObjectType::getInterface() const {
    QualType baseType = getBaseType();
    while (const auto *ObjT = baseType->getAs<ObjCObjectType>()) {
      if (const auto *T = dyn_cast<ObjCInterfaceType>(ObjT))
        return T->getDecl();
  
      baseType = ObjT->getBaseType();
    }
  
    return nullptr;
  }
  
  /// Represents a pointer to an Objective C object.
  ///
  /// These are constructed from pointer declarators when the pointee type is
  /// an ObjCObjectType (or sugar for one).  In addition, the 'id' and 'Class'
  /// types are typedefs for these, and the protocol-qualified types 'id<P>'
  /// and 'Class<P>' are translated into these.
  ///
  /// Pointers to pointers to Objective C objects are still PointerTypes;
  /// only the first level of pointer gets it own type implementation.
  class ObjCObjectPointerType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    QualType PointeeType;
  
    ObjCObjectPointerType(QualType Canonical, QualType Pointee)
        : Type(ObjCObjectPointer, Canonical,
               Pointee->isDependentType(),
               Pointee->isInstantiationDependentType(),
               Pointee->isVariablyModifiedType(),
               Pointee->containsUnexpandedParameterPack()),
          PointeeType(Pointee) {}
  
  public:
    /// Gets the type pointed to by this ObjC pointer.
    /// The result will always be an ObjCObjectType or sugar thereof.
    QualType getPointeeType() const { return PointeeType; }
  
    /// Gets the type pointed to by this ObjC pointer.  Always returns non-null.
    ///
    /// This method is equivalent to getPointeeType() except that
    /// it discards any typedefs (or other sugar) between this
    /// type and the "outermost" object type.  So for:
    /// \code
    ///   \@class A; \@protocol P; \@protocol Q;
    ///   typedef A<P> AP;
    ///   typedef A A1;
    ///   typedef A1<P> A1P;
    ///   typedef A1P<Q> A1PQ;
    /// \endcode
    /// For 'A*', getObjectType() will return 'A'.
    /// For 'A<P>*', getObjectType() will return 'A<P>'.
    /// For 'AP*', getObjectType() will return 'A<P>'.
    /// For 'A1*', getObjectType() will return 'A'.
    /// For 'A1<P>*', getObjectType() will return 'A1<P>'.
    /// For 'A1P*', getObjectType() will return 'A1<P>'.
    /// For 'A1PQ*', getObjectType() will return 'A1<Q>', because
    ///   adding protocols to a protocol-qualified base discards the
    ///   old qualifiers (for now).  But if it didn't, getObjectType()
    ///   would return 'A1P<Q>' (and we'd have to make iterating over
    ///   qualifiers more complicated).
    const ObjCObjectType *getObjectType() const {
      return PointeeType->castAs<ObjCObjectType>();
    }
  
    /// If this pointer points to an Objective C
    /// \@interface type, gets the type for that interface.  Any protocol
    /// qualifiers on the interface are ignored.
    ///
    /// \return null if the base type for this pointer is 'id' or 'Class'
    const ObjCInterfaceType *getInterfaceType() const;
  
    /// If this pointer points to an Objective \@interface
    /// type, gets the declaration for that interface.
    ///
    /// \return null if the base type for this pointer is 'id' or 'Class'
    ObjCInterfaceDecl *getInterfaceDecl() const {
      return getObjectType()->getInterface();
    }
  
    /// True if this is equivalent to the 'id' type, i.e. if
    /// its object type is the primitive 'id' type with no protocols.
    bool isObjCIdType() const {
      return getObjectType()->isObjCUnqualifiedId();
    }
  
    /// True if this is equivalent to the 'Class' type,
    /// i.e. if its object tive is the primitive 'Class' type with no protocols.
    bool isObjCClassType() const {
      return getObjectType()->isObjCUnqualifiedClass();
    }
  
    /// True if this is equivalent to the 'id' or 'Class' type,
    bool isObjCIdOrClassType() const {
      return getObjectType()->isObjCUnqualifiedIdOrClass();
    }
  
    /// True if this is equivalent to 'id<P>' for some non-empty set of
    /// protocols.
    bool isObjCQualifiedIdType() const {
      return getObjectType()->isObjCQualifiedId();
    }
  
    /// True if this is equivalent to 'Class<P>' for some non-empty set of
    /// protocols.
    bool isObjCQualifiedClassType() const {
      return getObjectType()->isObjCQualifiedClass();
    }
  
    /// Whether this is a "__kindof" type.
    bool isKindOfType() const { return getObjectType()->isKindOfType(); }
  
    /// Whether this type is specialized, meaning that it has type arguments.
    bool isSpecialized() const { return getObjectType()->isSpecialized(); }
  
    /// Whether this type is specialized, meaning that it has type arguments.
    bool isSpecializedAsWritten() const {
      return getObjectType()->isSpecializedAsWritten();
    }
  
    /// Whether this type is unspecialized, meaning that is has no type arguments.
    bool isUnspecialized() const { return getObjectType()->isUnspecialized(); }
  
    /// Determine whether this object type is "unspecialized" as
    /// written, meaning that it has no type arguments.
    bool isUnspecializedAsWritten() const { return !isSpecializedAsWritten(); }
  
    /// Retrieve the type arguments for this type.
    ArrayRef<QualType> getTypeArgs() const {
      return getObjectType()->getTypeArgs();
    }
  
    /// Retrieve the type arguments for this type.
    ArrayRef<QualType> getTypeArgsAsWritten() const {
      return getObjectType()->getTypeArgsAsWritten();
    }
  
    /// An iterator over the qualifiers on the object type.  Provided
    /// for convenience.  This will always iterate over the full set of
    /// protocols on a type, not just those provided directly.
    using qual_iterator = ObjCObjectType::qual_iterator;
    using qual_range = llvm::iterator_range<qual_iterator>;
  
    qual_range quals() const { return qual_range(qual_begin(), qual_end()); }
  
    qual_iterator qual_begin() const {
      return getObjectType()->qual_begin();
    }
  
    qual_iterator qual_end() const {
      return getObjectType()->qual_end();
    }
  
    bool qual_empty() const { return getObjectType()->qual_empty(); }
  
    /// Return the number of qualifying protocols on the object type.
    unsigned getNumProtocols() const {
      return getObjectType()->getNumProtocols();
    }
  
    /// Retrieve a qualifying protocol by index on the object type.
    ObjCProtocolDecl *getProtocol(unsigned I) const {
      return getObjectType()->getProtocol(I);
    }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    /// Retrieve the type of the superclass of this object pointer type.
    ///
    /// This operation substitutes any type arguments into the
    /// superclass of the current class type, potentially producing a
    /// pointer to a specialization of the superclass type. Produces a
    /// null type if there is no superclass.
    QualType getSuperClassType() const;
  
    /// Strip off the Objective-C "kindof" type and (with it) any
    /// protocol qualifiers.
    const ObjCObjectPointerType *stripObjCKindOfTypeAndQuals(
                                   const ASTContext &ctx) const;
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getPointeeType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType T) {
      ID.AddPointer(T.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == ObjCObjectPointer;
    }
  };
  
  class AtomicType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    QualType ValueType;
  
    AtomicType(QualType ValTy, QualType Canonical)
        : Type(Atomic, Canonical, ValTy->isDependentType(),
               ValTy->isInstantiationDependentType(),
               ValTy->isVariablyModifiedType(),
               ValTy->containsUnexpandedParameterPack()),
          ValueType(ValTy) {}
  
  public:
    /// Gets the type contained by this atomic type, i.e.
    /// the type returned by performing an atomic load of this atomic type.
    QualType getValueType() const { return ValueType; }
  
    bool isSugared() const { return false; }
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getValueType());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType T) {
      ID.AddPointer(T.getAsOpaquePtr());
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == Atomic;
    }
  };
  
  /// PipeType - OpenCL20.
  class PipeType : public Type, public llvm::FoldingSetNode {
    friend class ASTContext; // ASTContext creates these.
  
    QualType ElementType;
    bool isRead;
  
    PipeType(QualType elemType, QualType CanonicalPtr, bool isRead)
        : Type(Pipe, CanonicalPtr, elemType->isDependentType(),
               elemType->isInstantiationDependentType(),
               elemType->isVariablyModifiedType(),
               elemType->containsUnexpandedParameterPack()),
          ElementType(elemType), isRead(isRead) {}
  
  public:
    QualType getElementType() const { return ElementType; }
  
    bool isSugared() const { return false; }
  
    QualType desugar() const { return QualType(this, 0); }
  
    void Profile(llvm::FoldingSetNodeID &ID) {
      Profile(ID, getElementType(), isReadOnly());
    }
  
    static void Profile(llvm::FoldingSetNodeID &ID, QualType T, bool isRead) {
      ID.AddPointer(T.getAsOpaquePtr());
      ID.AddBoolean(isRead);
    }
  
    static bool classof(const Type *T) {
      return T->getTypeClass() == Pipe;
    }
  
    bool isReadOnly() const { return isRead; }
  };
  
  /// A qualifier set is used to build a set of qualifiers.
  class QualifierCollector : public Qualifiers {
  public:
    QualifierCollector(Qualifiers Qs = Qualifiers()) : Qualifiers(Qs) {}
  
    /// Collect any qualifiers on the given type and return an
    /// unqualified type.  The qualifiers are assumed to be consistent
    /// with those already in the type.
    const Type *strip(QualType type) {
      addFastQualifiers(type.getLocalFastQualifiers());
      if (!type.hasLocalNonFastQualifiers())
        return type.getTypePtrUnsafe();
  
      const ExtQuals *extQuals = type.getExtQualsUnsafe();
      addConsistentQualifiers(extQuals->getQualifiers());
      return extQuals->getBaseType();
    }
  
    /// Apply the collected qualifiers to the given type.
    QualType apply(const ASTContext &Context, QualType QT) const;
  
    /// Apply the collected qualifiers to the given type.
    QualType apply(const ASTContext &Context, const Type* T) const;
  };
  
  // Inline function definitions.
  
  inline SplitQualType SplitQualType::getSingleStepDesugaredType() const {
    SplitQualType desugar =
      Ty->getLocallyUnqualifiedSingleStepDesugaredType().split();
    desugar.Quals.addConsistentQualifiers(Quals);
    return desugar;
  }
  
  inline const Type *QualType::getTypePtr() const {
    return getCommonPtr()->BaseType;
  }
  
  inline const Type *QualType::getTypePtrOrNull() const {
    return (isNull() ? nullptr : getCommonPtr()->BaseType);
  }
  
  inline SplitQualType QualType::split() const {
    if (!hasLocalNonFastQualifiers())
      return SplitQualType(getTypePtrUnsafe(),
                           Qualifiers::fromFastMask(getLocalFastQualifiers()));
  
    const ExtQuals *eq = getExtQualsUnsafe();
    Qualifiers qs = eq->getQualifiers();
    qs.addFastQualifiers(getLocalFastQualifiers());
    return SplitQualType(eq->getBaseType(), qs);
  }
  
  inline Qualifiers QualType::getLocalQualifiers() const {
    Qualifiers Quals;
    if (hasLocalNonFastQualifiers())
      Quals = getExtQualsUnsafe()->getQualifiers();
    Quals.addFastQualifiers(getLocalFastQualifiers());
    return Quals;
  }
  
  inline Qualifiers QualType::getQualifiers() const {
    Qualifiers quals = getCommonPtr()->CanonicalType.getLocalQualifiers();
    quals.addFastQualifiers(getLocalFastQualifiers());
    return quals;
  }
  
  inline unsigned QualType::getCVRQualifiers() const {
    unsigned cvr = getCommonPtr()->CanonicalType.getLocalCVRQualifiers();
    cvr |= getLocalCVRQualifiers();
    return cvr;
  }
  
  inline QualType QualType::getCanonicalType() const {
    QualType canon = getCommonPtr()->CanonicalType;
    return canon.withFastQualifiers(getLocalFastQualifiers());
  }
  
  inline bool QualType::isCanonical() const {
    return getTypePtr()->isCanonicalUnqualified();
  }
  
  inline bool QualType::isCanonicalAsParam() const {
    if (!isCanonical()) return false;
    if (hasLocalQualifiers()) return false;
  
    const Type *T = getTypePtr();
    if (T->isVariablyModifiedType() && T->hasSizedVLAType())
      return false;
  
    return !isa<FunctionType>(T) && !isa<ArrayType>(T);
  }
  
  inline bool QualType::isConstQualified() const {
    return isLocalConstQualified() ||
           getCommonPtr()->CanonicalType.isLocalConstQualified();
  }
  
  inline bool QualType::isRestrictQualified() const {
    return isLocalRestrictQualified() ||
           getCommonPtr()->CanonicalType.isLocalRestrictQualified();
  }
  
  
  inline bool QualType::isVolatileQualified() const {
    return isLocalVolatileQualified() ||
           getCommonPtr()->CanonicalType.isLocalVolatileQualified();
  }
  
  inline bool QualType::hasQualifiers() const {
    return hasLocalQualifiers() ||
           getCommonPtr()->CanonicalType.hasLocalQualifiers();
  }
  
  inline QualType QualType::getUnqualifiedType() const {
    if (!getTypePtr()->getCanonicalTypeInternal().hasLocalQualifiers())
      return QualType(getTypePtr(), 0);
  
    return QualType(getSplitUnqualifiedTypeImpl(*this).Ty, 0);
  }
  
  inline SplitQualType QualType::getSplitUnqualifiedType() const {
    if (!getTypePtr()->getCanonicalTypeInternal().hasLocalQualifiers())
      return split();
  
    return getSplitUnqualifiedTypeImpl(*this);
  }
  
  inline void QualType::removeLocalConst() {
    removeLocalFastQualifiers(Qualifiers::Const);
  }
  
  inline void QualType::removeLocalRestrict() {
    removeLocalFastQualifiers(Qualifiers::Restrict);
  }
  
  inline void QualType::removeLocalVolatile() {
    removeLocalFastQualifiers(Qualifiers::Volatile);
  }
  
  inline void QualType::removeLocalCVRQualifiers(unsigned Mask) {
    assert(!(Mask & ~Qualifiers::CVRMask) && "mask has non-CVR bits");
    static_assert((int)Qualifiers::CVRMask == (int)Qualifiers::FastMask,
                  "Fast bits differ from CVR bits!");
  
    // Fast path: we don't need to touch the slow qualifiers.
    removeLocalFastQualifiers(Mask);
  }
  
  /// Return the address space of this type.
  inline LangAS QualType::getAddressSpace() const {
    return getQualifiers().getAddressSpace();
  }
  
  /// Return the gc attribute of this type.
  inline Qualifiers::GC QualType::getObjCGCAttr() const {
    return getQualifiers().getObjCGCAttr();
  }
  
  inline FunctionType::ExtInfo getFunctionExtInfo(const Type &t) {
    if (const auto *PT = t.getAs<PointerType>()) {
      if (const auto *FT = PT->getPointeeType()->getAs<FunctionType>())
        return FT->getExtInfo();
    } else if (const auto *FT = t.getAs<FunctionType>())
      return FT->getExtInfo();
  
    return FunctionType::ExtInfo();
  }
  
  inline FunctionType::ExtInfo getFunctionExtInfo(QualType t) {
    return getFunctionExtInfo(*t);
  }
  
  /// Determine whether this type is more
  /// qualified than the Other type. For example, "const volatile int"
  /// is more qualified than "const int", "volatile int", and
  /// "int". However, it is not more qualified than "const volatile
  /// int".
  inline bool QualType::isMoreQualifiedThan(QualType other) const {
    Qualifiers MyQuals = getQualifiers();
    Qualifiers OtherQuals = other.getQualifiers();
    return (MyQuals != OtherQuals && MyQuals.compatiblyIncludes(OtherQuals));
  }
  
  /// Determine whether this type is at last
  /// as qualified as the Other type. For example, "const volatile
  /// int" is at least as qualified as "const int", "volatile int",
  /// "int", and "const volatile int".
  inline bool QualType::isAtLeastAsQualifiedAs(QualType other) const {
    Qualifiers OtherQuals = other.getQualifiers();
  
    // Ignore __unaligned qualifier if this type is a void.
    if (getUnqualifiedType()->isVoidType())
      OtherQuals.removeUnaligned();
  
    return getQualifiers().compatiblyIncludes(OtherQuals);
  }
  
  /// If Type is a reference type (e.g., const
  /// int&), returns the type that the reference refers to ("const
  /// int"). Otherwise, returns the type itself. This routine is used
  /// throughout Sema to implement C++ 5p6:
  ///
  ///   If an expression initially has the type "reference to T" (8.3.2,
  ///   8.5.3), the type is adjusted to "T" prior to any further
  ///   analysis, the expression designates the object or function
  ///   denoted by the reference, and the expression is an lvalue.
  inline QualType QualType::getNonReferenceType() const {
    if (const auto *RefType = (*this)->getAs<ReferenceType>())
      return RefType->getPointeeType();
    else
      return *this;
  }
  
  inline bool QualType::isCForbiddenLValueType() const {
    return ((getTypePtr()->isVoidType() && !hasQualifiers()) ||
            getTypePtr()->isFunctionType());
  }
  
  /// Tests whether the type is categorized as a fundamental type.
  ///
  /// \returns True for types specified in C++0x [basic.fundamental].
  inline bool Type::isFundamentalType() const {
    return isVoidType() ||
           // FIXME: It's really annoying that we don't have an
           // 'isArithmeticType()' which agrees with the standard definition.
           (isArithmeticType() && !isEnumeralType());
  }
  
  /// Tests whether the type is categorized as a compound type.
  ///
  /// \returns True for types specified in C++0x [basic.compound].
  inline bool Type::isCompoundType() const {
    // C++0x [basic.compound]p1:
    //   Compound types can be constructed in the following ways:
    //    -- arrays of objects of a given type [...];
    return isArrayType() ||
    //    -- functions, which have parameters of given types [...];
           isFunctionType() ||
    //    -- pointers to void or objects or functions [...];
           isPointerType() ||
    //    -- references to objects or functions of a given type. [...]
           isReferenceType() ||
    //    -- classes containing a sequence of objects of various types, [...];
           isRecordType() ||
    //    -- unions, which are classes capable of containing objects of different
    //               types at different times;
           isUnionType() ||
    //    -- enumerations, which comprise a set of named constant values. [...];
           isEnumeralType() ||
    //    -- pointers to non-static class members, [...].
           isMemberPointerType();
  }
  
  inline bool Type::isFunctionType() const {
    return isa<FunctionType>(CanonicalType);
  }
  
  inline bool Type::isPointerType() const {
    return isa<PointerType>(CanonicalType);
  }
  
  inline bool Type::isAnyPointerType() const {
    return isPointerType() || isObjCObjectPointerType();
  }
  
  inline bool Type::isBlockPointerType() const {
    return isa<BlockPointerType>(CanonicalType);
  }
  
  inline bool Type::isReferenceType() const {
    return isa<ReferenceType>(CanonicalType);
  }
  
  inline bool Type::isLValueReferenceType() const {
    return isa<LValueReferenceType>(CanonicalType);
  }
  
  inline bool Type::isRValueReferenceType() const {
    return isa<RValueReferenceType>(CanonicalType);
  }
  
  inline bool Type::isFunctionPointerType() const {
    if (const auto *T = getAs<PointerType>())
      return T->getPointeeType()->isFunctionType();
    else
      return false;
  }
  
  inline bool Type::isMemberPointerType() const {
    return isa<MemberPointerType>(CanonicalType);
  }
  
  inline bool Type::isMemberFunctionPointerType() const {
    if (const auto *T = getAs<MemberPointerType>())
      return T->isMemberFunctionPointer();
    else
      return false;
  }
  
  inline bool Type::isMemberDataPointerType() const {
    if (const auto *T = getAs<MemberPointerType>())
      return T->isMemberDataPointer();
    else
      return false;
  }
  
  inline bool Type::isArrayType() const {
    return isa<ArrayType>(CanonicalType);
  }
  
  inline bool Type::isConstantArrayType() const {
    return isa<ConstantArrayType>(CanonicalType);
  }
  
  inline bool Type::isIncompleteArrayType() const {
    return isa<IncompleteArrayType>(CanonicalType);
  }
  
  inline bool Type::isVariableArrayType() const {
    return isa<VariableArrayType>(CanonicalType);
  }
  
  inline bool Type::isDependentSizedArrayType() const {
    return isa<DependentSizedArrayType>(CanonicalType);
  }
  
  inline bool Type::isBuiltinType() const {
    return isa<BuiltinType>(CanonicalType);
  }
  
  inline bool Type::isRecordType() const {
    return isa<RecordType>(CanonicalType);
  }
  
  inline bool Type::isEnumeralType() const {
    return isa<EnumType>(CanonicalType);
  }
  
  inline bool Type::isAnyComplexType() const {
    return isa<ComplexType>(CanonicalType);
  }
  
  inline bool Type::isVectorType() const {
    return isa<VectorType>(CanonicalType);
  }
  
  inline bool Type::isExtVectorType() const {
    return isa<ExtVectorType>(CanonicalType);
  }
  
  inline bool Type::isDependentAddressSpaceType() const {
    return isa<DependentAddressSpaceType>(CanonicalType);
  }
  
  inline bool Type::isObjCObjectPointerType() const {
    return isa<ObjCObjectPointerType>(CanonicalType);
  }
  
  inline bool Type::isObjCObjectType() const {
    return isa<ObjCObjectType>(CanonicalType);
  }
  
  inline bool Type::isObjCObjectOrInterfaceType() const {
    return isa<ObjCInterfaceType>(CanonicalType) ||
      isa<ObjCObjectType>(CanonicalType);
  }
  
  inline bool Type::isAtomicType() const {
    return isa<AtomicType>(CanonicalType);
  }
  
  inline bool Type::isObjCQualifiedIdType() const {
    if (const auto *OPT = getAs<ObjCObjectPointerType>())
      return OPT->isObjCQualifiedIdType();
    return false;
  }
  
  inline bool Type::isObjCQualifiedClassType() const {
    if (const auto *OPT = getAs<ObjCObjectPointerType>())
      return OPT->isObjCQualifiedClassType();
    return false;
  }
  
  inline bool Type::isObjCIdType() const {
    if (const auto *OPT = getAs<ObjCObjectPointerType>())
      return OPT->isObjCIdType();
    return false;
  }
  
  inline bool Type::isObjCClassType() const {
    if (const auto *OPT = getAs<ObjCObjectPointerType>())
      return OPT->isObjCClassType();
    return false;
  }
  
  inline bool Type::isObjCSelType() const {
    if (const auto *OPT = getAs<PointerType>())
      return OPT->getPointeeType()->isSpecificBuiltinType(BuiltinType::ObjCSel);
    return false;
  }
  
  inline bool Type::isObjCBuiltinType() const {
    return isObjCIdType() || isObjCClassType() || isObjCSelType();
  }
  
  inline bool Type::isDecltypeType() const {
    return isa<DecltypeType>(this);
  }
  
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
    inline bool Type::is##Id##Type() const { \
      return isSpecificBuiltinType(BuiltinType::Id); \
    }
  #include "clang/Basic/OpenCLImageTypes.def"
  
  inline bool Type::isSamplerT() const {
    return isSpecificBuiltinType(BuiltinType::OCLSampler);
  }
  
  inline bool Type::isEventT() const {
    return isSpecificBuiltinType(BuiltinType::OCLEvent);
  }
  
  inline bool Type::isClkEventT() const {
    return isSpecificBuiltinType(BuiltinType::OCLClkEvent);
  }
  
  inline bool Type::isQueueT() const {
    return isSpecificBuiltinType(BuiltinType::OCLQueue);
  }
  
  inline bool Type::isReserveIDT() const {
    return isSpecificBuiltinType(BuiltinType::OCLReserveID);
  }
  
  inline bool Type::isImageType() const {
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) is##Id##Type() ||
    return
  #include "clang/Basic/OpenCLImageTypes.def"
        false; // end boolean or operation
  }
  
  inline bool Type::isPipeType() const {
    return isa<PipeType>(CanonicalType);
  }
  
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
    inline bool Type::is##Id##Type() const { \
      return isSpecificBuiltinType(BuiltinType::Id); \
    }
  #include "clang/Basic/OpenCLExtensionTypes.def"
  
  inline bool Type::isOCLIntelSubgroupAVCType() const {
  #define INTEL_SUBGROUP_AVC_TYPE(ExtType, Id) \
    isOCLIntelSubgroupAVC##Id##Type() ||
    return
  #include "clang/Basic/OpenCLExtensionTypes.def"
      false; // end of boolean or operation
  }
  
  inline bool Type::isOCLExtOpaqueType() const {
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) is##Id##Type() ||
    return
  #include "clang/Basic/OpenCLExtensionTypes.def"
      false; // end of boolean or operation
  }
  
  inline bool Type::isOpenCLSpecificType() const {
    return isSamplerT() || isEventT() || isImageType() || isClkEventT() ||
           isQueueT() || isReserveIDT() || isPipeType() || isOCLExtOpaqueType();
  }
  
  inline bool Type::isTemplateTypeParmType() const {
    return isa<TemplateTypeParmType>(CanonicalType);
  }
  
  inline bool Type::isSpecificBuiltinType(unsigned K) const {
    if (const BuiltinType *BT = getAs<BuiltinType>())
      if (BT->getKind() == (BuiltinType::Kind) K)
        return true;
    return false;
  }
  
  inline bool Type::isPlaceholderType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(this))
      return BT->isPlaceholderType();
    return false;
  }
  
  inline const BuiltinType *Type::getAsPlaceholderType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(this))
      if (BT->isPlaceholderType())
        return BT;
    return nullptr;
  }
  
  inline bool Type::isSpecificPlaceholderType(unsigned K) const {
    assert(BuiltinType::isPlaceholderTypeKind((BuiltinType::Kind) K));
    if (const auto *BT = dyn_cast<BuiltinType>(this))
      return (BT->getKind() == (BuiltinType::Kind) K);
    return false;
  }
  
  inline bool Type::isNonOverloadPlaceholderType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(this))
      return BT->isNonOverloadPlaceholderType();
    return false;
  }
  
  inline bool Type::isVoidType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() == BuiltinType::Void;
    return false;
  }
  
  inline bool Type::isHalfType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() == BuiltinType::Half;
    // FIXME: Should we allow complex __fp16? Probably not.
    return false;
  }
  
  inline bool Type::isFloat16Type() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() == BuiltinType::Float16;
    return false;
  }
  
  inline bool Type::isFloat128Type() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() == BuiltinType::Float128;
    return false;
  }
  
  inline bool Type::isNullPtrType() const {
    if (const auto *BT = getAs<BuiltinType>())
      return BT->getKind() == BuiltinType::NullPtr;
    return false;
  }
  
  bool IsEnumDeclComplete(EnumDecl *);
  bool IsEnumDeclScoped(EnumDecl *);
  
  inline bool Type::isIntegerType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() >= BuiltinType::Bool &&
             BT->getKind() <= BuiltinType::Int128;
    if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType)) {
      // Incomplete enum types are not treated as integer types.
      // FIXME: In C++, enum types are never integer types.
      return IsEnumDeclComplete(ET->getDecl()) &&
        !IsEnumDeclScoped(ET->getDecl());
    }
    return false;
  }
  
  inline bool Type::isFixedPointType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType)) {
      return BT->getKind() >= BuiltinType::ShortAccum &&
             BT->getKind() <= BuiltinType::SatULongFract;
    }
    return false;
  }
  
  inline bool Type::isFixedPointOrIntegerType() const {
    return isFixedPointType() || isIntegerType();
  }
  
  inline bool Type::isSaturatedFixedPointType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType)) {
      return BT->getKind() >= BuiltinType::SatShortAccum &&
             BT->getKind() <= BuiltinType::SatULongFract;
    }
    return false;
  }
  
  inline bool Type::isUnsaturatedFixedPointType() const {
    return isFixedPointType() && !isSaturatedFixedPointType();
  }
  
  inline bool Type::isSignedFixedPointType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType)) {
      return ((BT->getKind() >= BuiltinType::ShortAccum &&
               BT->getKind() <= BuiltinType::LongAccum) ||
              (BT->getKind() >= BuiltinType::ShortFract &&
               BT->getKind() <= BuiltinType::LongFract) ||
              (BT->getKind() >= BuiltinType::SatShortAccum &&
               BT->getKind() <= BuiltinType::SatLongAccum) ||
              (BT->getKind() >= BuiltinType::SatShortFract &&
               BT->getKind() <= BuiltinType::SatLongFract));
    }
    return false;
  }
  
  inline bool Type::isUnsignedFixedPointType() const {
    return isFixedPointType() && !isSignedFixedPointType();
  }
  
  inline bool Type::isScalarType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() > BuiltinType::Void &&
             BT->getKind() <= BuiltinType::NullPtr;
    if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
      // Enums are scalar types, but only if they are defined.  Incomplete enums
      // are not treated as scalar types.
      return IsEnumDeclComplete(ET->getDecl());
    return isa<PointerType>(CanonicalType) ||
           isa<BlockPointerType>(CanonicalType) ||
           isa<MemberPointerType>(CanonicalType) ||
           isa<ComplexType>(CanonicalType) ||
           isa<ObjCObjectPointerType>(CanonicalType);
  }
  
  inline bool Type::isIntegralOrEnumerationType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() >= BuiltinType::Bool &&
             BT->getKind() <= BuiltinType::Int128;
  
    // Check for a complete enum type; incomplete enum types are not properly an
    // enumeration type in the sense required here.
    if (const auto *ET = dyn_cast<EnumType>(CanonicalType))
      return IsEnumDeclComplete(ET->getDecl());
  
    return false;
  }
  
  inline bool Type::isBooleanType() const {
    if (const auto *BT = dyn_cast<BuiltinType>(CanonicalType))
      return BT->getKind() == BuiltinType::Bool;
    return false;
  }
  
  inline bool Type::isUndeducedType() const {
    auto *DT = getContainedDeducedType();
    return DT && !DT->isDeduced();
  }
  
  /// Determines whether this is a type for which one can define
  /// an overloaded operator.
  inline bool Type::isOverloadableType() const {
    return isDependentType() || isRecordType() || isEnumeralType();
  }
  
  /// Determines whether this type can decay to a pointer type.
  inline bool Type::canDecayToPointerType() const {
    return isFunctionType() || isArrayType();
  }
  
  inline bool Type::hasPointerRepresentation() const {
    return (isPointerType() || isReferenceType() || isBlockPointerType() ||
            isObjCObjectPointerType() || isNullPtrType());
  }
  
  inline bool Type::hasObjCPointerRepresentation() const {
    return isObjCObjectPointerType();
  }
  
  inline const Type *Type::getBaseElementTypeUnsafe() const {
    const Type *type = this;
    while (const ArrayType *arrayType = type->getAsArrayTypeUnsafe())
      type = arrayType->getElementType().getTypePtr();
    return type;
  }
  
  inline const Type *Type::getPointeeOrArrayElementType() const {
    const Type *type = this;
    if (type->isAnyPointerType())
      return type->getPointeeType().getTypePtr();
    else if (type->isArrayType())
      return type->getBaseElementTypeUnsafe();
    return type;
  }
  
  /// Insertion operator for diagnostics. This allows sending Qualifiers into a
  /// diagnostic with <<.
  inline const DiagnosticBuilder &operator<<(const DiagnosticBuilder &DB,
                                             Qualifiers Q) {
    DB.AddTaggedVal(Q.getAsOpaqueValue(),
                    DiagnosticsEngine::ArgumentKind::ak_qual);
    return DB;
  }
  
  /// Insertion operator for partial diagnostics. This allows sending Qualifiers
  /// into a diagnostic with <<.
  inline const PartialDiagnostic &operator<<(const PartialDiagnostic &PD,
                                             Qualifiers Q) {
    PD.AddTaggedVal(Q.getAsOpaqueValue(),
                    DiagnosticsEngine::ArgumentKind::ak_qual);
    return PD;
  }
  
  /// Insertion operator for diagnostics.  This allows sending QualType's into a
  /// diagnostic with <<.
  inline const DiagnosticBuilder &operator<<(const DiagnosticBuilder &DB,
                                             QualType T) {
    DB.AddTaggedVal(reinterpret_cast<intptr_t>(T.getAsOpaquePtr()),
                    DiagnosticsEngine::ak_qualtype);
    return DB;
  }
  
  /// Insertion operator for partial diagnostics.  This allows sending QualType's
  /// into a diagnostic with <<.
  inline const PartialDiagnostic &operator<<(const PartialDiagnostic &PD,
                                             QualType T) {
    PD.AddTaggedVal(reinterpret_cast<intptr_t>(T.getAsOpaquePtr()),
                    DiagnosticsEngine::ak_qualtype);
    return PD;
  }
  
  // Helper class template that is used by Type::getAs to ensure that one does
  // not try to look through a qualified type to get to an array type.
  template <typename T>
  using TypeIsArrayType =
      std::integral_constant<bool, std::is_same<T, ArrayType>::value ||
                                       std::is_base_of<ArrayType, T>::value>;
  
  // Member-template getAs<specific type>'.
  template <typename T> const T *Type::getAs() const {
    static_assert(!TypeIsArrayType<T>::value,
                  "ArrayType cannot be used with getAs!");
  
    // If this is directly a T type, return it.
    if (const auto *Ty = dyn_cast<T>(this))
      return Ty;
  
    // If the canonical form of this type isn't the right kind, reject it.
    if (!isa<T>(CanonicalType))
      return nullptr;
  
    // If this is a typedef for the type, strip the typedef off without
    // losing all typedef information.
    return cast<T>(getUnqualifiedDesugaredType());
  }
  
  template <typename T> const T *Type::getAsAdjusted() const {
    static_assert(!TypeIsArrayType<T>::value, "ArrayType cannot be used with getAsAdjusted!");
  
    // If this is directly a T type, return it.
    if (const auto *Ty = dyn_cast<T>(this))
      return Ty;
  
    // If the canonical form of this type isn't the right kind, reject it.
    if (!isa<T>(CanonicalType))
      return nullptr;
  
    // Strip off type adjustments that do not modify the underlying nature of the
    // type.
    const Type *Ty = this;
    while (Ty) {
      if (const auto *A = dyn_cast<AttributedType>(Ty))
        Ty = A->getModifiedType().getTypePtr();
      else if (const auto *E = dyn_cast<ElaboratedType>(Ty))
        Ty = E->desugar().getTypePtr();
      else if (const auto *P = dyn_cast<ParenType>(Ty))
        Ty = P->desugar().getTypePtr();
      else if (const auto *A = dyn_cast<AdjustedType>(Ty))
        Ty = A->desugar().getTypePtr();
      else if (const auto *M = dyn_cast<MacroQualifiedType>(Ty))
        Ty = M->desugar().getTypePtr();
      else
        break;
    }
  
    // Just because the canonical type is correct does not mean we can use cast<>,
    // since we may not have stripped off all the sugar down to the base type.
    return dyn_cast<T>(Ty);
  }
  
  inline const ArrayType *Type::getAsArrayTypeUnsafe() const {
    // If this is directly an array type, return it.
    if (const auto *arr = dyn_cast<ArrayType>(this))
      return arr;
  
    // If the canonical form of this type isn't the right kind, reject it.
    if (!isa<ArrayType>(CanonicalType))
      return nullptr;
  
    // If this is a typedef for the type, strip the typedef off without
    // losing all typedef information.
    return cast<ArrayType>(getUnqualifiedDesugaredType());
  }
  
  template <typename T> const T *Type::castAs() const {
    static_assert(!TypeIsArrayType<T>::value,
                  "ArrayType cannot be used with castAs!");
  
    if (const auto *ty = dyn_cast<T>(this)) return ty;
    assert(isa<T>(CanonicalType));
    return cast<T>(getUnqualifiedDesugaredType());
  }
  
  inline const ArrayType *Type::castAsArrayTypeUnsafe() const {
    assert(isa<ArrayType>(CanonicalType));
    if (const auto *arr = dyn_cast<ArrayType>(this)) return arr;
    return cast<ArrayType>(getUnqualifiedDesugaredType());
  }
  
  DecayedType::DecayedType(QualType OriginalType, QualType DecayedPtr,
                           QualType CanonicalPtr)
      : AdjustedType(Decayed, OriginalType, DecayedPtr, CanonicalPtr) {
  #ifndef NDEBUG
    QualType Adjusted = getAdjustedType();
    (void)AttributedType::stripOuterNullability(Adjusted);
    assert(isa<PointerType>(Adjusted));
  #endif
  }
  
  QualType DecayedType::getPointeeType() const {
    QualType Decayed = getDecayedType();
    (void)AttributedType::stripOuterNullability(Decayed);
    return cast<PointerType>(Decayed)->getPointeeType();
  }
  
  // Get the decimal string representation of a fixed point type, represented
  // as a scaled integer.
  // TODO: At some point, we should change the arguments to instead just accept an
  // APFixedPoint instead of APSInt and scale.
  void FixedPointValueToString(SmallVectorImpl<char> &Str, llvm::APSInt Val,
                               unsigned Scale);
  
  } // namespace clang
  
  #endif // LLVM_CLANG_AST_TYPE_H
  