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 //===--- ItaniumDemangle.h -----------*- mode:c++;eval:(read-only-mode) -*-===//
 //       Do not edit! See README.txt.
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // Generic itanium demangler library.
 // There are two copies of this file in the source tree.  The one under
 // libcxxabi is the original and the one under llvm is the copy.  Use
 // cp-to-llvm.sh to update the copy.  See README.txt for more details.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef DEMANGLE_ITANIUMDEMANGLE_H
 #define DEMANGLE_ITANIUMDEMANGLE_H
 
 #include "DemangleConfig.h"
 #include "StringViewExtras.h"
 #include "Utility.h"
 #include <algorithm>
 #include <cctype>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
 #include <limits>
 #include <new>
 #include <string_view>
 #include <type_traits>
 #include <utility>
 
 #if defined(__clang__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-template"
 #endif
 
 DEMANGLE_NAMESPACE_BEGIN
 
 template <class T, size_t N> class PODSmallVector {
   static_assert(std::is_trivial<T>::value,
                 "T is required to be a trivial type");
   T *First = nullptr;
   T *Last = nullptr;
   T *Cap = nullptr;
   T Inline[N] = {};
 
   bool isInline() const { return First == Inline; }
 
   void clearInline() {
     First = Inline;
     Last = Inline;
     Cap = Inline + N;
   }
 
   void reserve(size_t NewCap) {
     size_t S = size();
     if (isInline()) {
       auto *Tmp = static_cast<T *>(std::malloc(NewCap * sizeof(T)));
       if (Tmp == nullptr)
         std::abort();
       std::copy(First, Last, Tmp);
       First = Tmp;
     } else {
       First = static_cast<T *>(std::realloc(First, NewCap * sizeof(T)));
       if (First == nullptr)
         std::abort();
     }
     Last = First + S;
     Cap = First + NewCap;
   }
 
 public:
   PODSmallVector() : First(Inline), Last(First), Cap(Inline + N) {}
 
   PODSmallVector(const PODSmallVector &) = delete;
   PODSmallVector &operator=(const PODSmallVector &) = delete;
 
   PODSmallVector(PODSmallVector &&Other) : PODSmallVector() {
     if (Other.isInline()) {
       std::copy(Other.begin(), Other.end(), First);
       Last = First + Other.size();
       Other.clear();
       return;
     }
 
     First = Other.First;
     Last = Other.Last;
     Cap = Other.Cap;
     Other.clearInline();
   }
 
   PODSmallVector &operator=(PODSmallVector &&Other) {
     if (Other.isInline()) {
       if (!isInline()) {
         std::free(First);
         clearInline();
       }
       std::copy(Other.begin(), Other.end(), First);
       Last = First + Other.size();
       Other.clear();
       return *this;
     }
 
     if (isInline()) {
       First = Other.First;
       Last = Other.Last;
       Cap = Other.Cap;
       Other.clearInline();
       return *this;
     }
 
     std::swap(First, Other.First);
     std::swap(Last, Other.Last);
     std::swap(Cap, Other.Cap);
     Other.clear();
     return *this;
   }
 
   // NOLINTNEXTLINE(readability-identifier-naming)
   void push_back(const T &Elem) {
     if (Last == Cap)
       reserve(size() * 2);
     *Last++ = Elem;
   }
 
   // NOLINTNEXTLINE(readability-identifier-naming)
   void pop_back() {
     DEMANGLE_ASSERT(Last != First, "Popping empty vector!");
     --Last;
   }
 
   void shrinkToSize(size_t Index) {
     DEMANGLE_ASSERT(Index <= size(), "shrinkToSize() can't expand!");
     Last = First + Index;
   }
 
   T *begin() { return First; }
   T *end() { return Last; }
 
   bool empty() const { return First == Last; }
   size_t size() const { return static_cast<size_t>(Last - First); }
   T &back() {
     DEMANGLE_ASSERT(Last != First, "Calling back() on empty vector!");
     return *(Last - 1);
   }
   T &operator[](size_t Index) {
     DEMANGLE_ASSERT(Index < size(), "Invalid access!");
     return *(begin() + Index);
   }
   void clear() { Last = First; }
 
   ~PODSmallVector() {
     if (!isInline())
       std::free(First);
   }
 };
 
 class NodeArray;
 
 // Base class of all AST nodes. The AST is built by the parser, then is
 // traversed by the printLeft/Right functions to produce a demangled string.
 class Node {
 public:
   enum Kind : unsigned char {
 #define NODE(NodeKind) K##NodeKind,
 #include "ItaniumNodes.def"
   };
 
   /// Three-way bool to track a cached value. Unknown is possible if this node
   /// has an unexpanded parameter pack below it that may affect this cache.
   enum class Cache : unsigned char { Yes, No, Unknown, };
 
   /// Operator precedence for expression nodes. Used to determine required
   /// parens in expression emission.
   enum class Prec {
     Primary,
     Postfix,
     Unary,
     Cast,
     PtrMem,
     Multiplicative,
     Additive,
     Shift,
     Spaceship,
     Relational,
     Equality,
     And,
     Xor,
     Ior,
     AndIf,
     OrIf,
     Conditional,
     Assign,
     Comma,
     Default,
   };
 
 private:
   Kind K;
 
   Prec Precedence : 6;
 
 protected:
   /// Tracks if this node has a component on its right side, in which case we
   /// need to call printRight.
   Cache RHSComponentCache : 2;
 
   /// Track if this node is a (possibly qualified) array type. This can affect
   /// how we format the output string.
   Cache ArrayCache : 2;
 
   /// Track if this node is a (possibly qualified) function type. This can
   /// affect how we format the output string.
   Cache FunctionCache : 2;
 
 public:
   Node(Kind K_, Prec Precedence_ = Prec::Primary,
        Cache RHSComponentCache_ = Cache::No, Cache ArrayCache_ = Cache::No,
        Cache FunctionCache_ = Cache::No)
       : K(K_), Precedence(Precedence_), RHSComponentCache(RHSComponentCache_),
         ArrayCache(ArrayCache_), FunctionCache(FunctionCache_) {}
   Node(Kind K_, Cache RHSComponentCache_, Cache ArrayCache_ = Cache::No,
        Cache FunctionCache_ = Cache::No)
       : Node(K_, Prec::Primary, RHSComponentCache_, ArrayCache_,
              FunctionCache_) {}
 
   /// Visit the most-derived object corresponding to this object.
   template<typename Fn> void visit(Fn F) const;
 
   // The following function is provided by all derived classes:
   //
   // Call F with arguments that, when passed to the constructor of this node,
   // would construct an equivalent node.
   //template<typename Fn> void match(Fn F) const;
 
   bool hasRHSComponent(OutputBuffer &OB) const {
     if (RHSComponentCache != Cache::Unknown)
       return RHSComponentCache == Cache::Yes;
     return hasRHSComponentSlow(OB);
   }
 
   bool hasArray(OutputBuffer &OB) const {
     if (ArrayCache != Cache::Unknown)
       return ArrayCache == Cache::Yes;
     return hasArraySlow(OB);
   }
 
   bool hasFunction(OutputBuffer &OB) const {
     if (FunctionCache != Cache::Unknown)
       return FunctionCache == Cache::Yes;
     return hasFunctionSlow(OB);
   }
 
   Kind getKind() const { return K; }
 
   Prec getPrecedence() const { return Precedence; }
   Cache getRHSComponentCache() const { return RHSComponentCache; }
   Cache getArrayCache() const { return ArrayCache; }
   Cache getFunctionCache() const { return FunctionCache; }
 
   virtual bool hasRHSComponentSlow(OutputBuffer &) const { return false; }
   virtual bool hasArraySlow(OutputBuffer &) const { return false; }
   virtual bool hasFunctionSlow(OutputBuffer &) const { return false; }
 
   // Dig through "glue" nodes like ParameterPack and ForwardTemplateReference to
   // get at a node that actually represents some concrete syntax.
   virtual const Node *getSyntaxNode(OutputBuffer &) const { return this; }
 
   // Print this node as an expression operand, surrounding it in parentheses if
   // its precedence is [Strictly] weaker than P.
   void printAsOperand(OutputBuffer &OB, Prec P = Prec::Default,
                       bool StrictlyWorse = false) const {
     bool Paren =
         unsigned(getPrecedence()) >= unsigned(P) + unsigned(StrictlyWorse);
     if (Paren)
       OB.printOpen();
     print(OB);
     if (Paren)
       OB.printClose();
   }
 
   void print(OutputBuffer &OB) const {
     printLeft(OB);
     if (RHSComponentCache != Cache::No)
       printRight(OB);
   }
 
   // Print the "left" side of this Node into OutputBuffer.
   virtual void printLeft(OutputBuffer &) const = 0;
 
   // Print the "right". This distinction is necessary to represent C++ types
   // that appear on the RHS of their subtype, such as arrays or functions.
   // Since most types don't have such a component, provide a default
   // implementation.
   virtual void printRight(OutputBuffer &) const {}
 
   // Print an initializer list of this type. Returns true if we printed a custom
   // representation, false if nothing has been printed and the default
   // representation should be used.
   virtual bool printInitListAsType(OutputBuffer &, const NodeArray &) const {
     return false;
   }
 
   virtual std::string_view getBaseName() const { return {}; }
 
   // Silence compiler warnings, this dtor will never be called.
   virtual ~Node() = default;
 
 #ifndef NDEBUG
   DEMANGLE_DUMP_METHOD void dump() const;
 #endif
 };
 
 class NodeArray {
   Node **Elements;
   size_t NumElements;
 
 public:
   NodeArray() : Elements(nullptr), NumElements(0) {}
   NodeArray(Node **Elements_, size_t NumElements_)
       : Elements(Elements_), NumElements(NumElements_) {}
 
   bool empty() const { return NumElements == 0; }
   size_t size() const { return NumElements; }
 
   Node **begin() const { return Elements; }
   Node **end() const { return Elements + NumElements; }
 
   Node *operator[](size_t Idx) const { return Elements[Idx]; }
 
   void printWithComma(OutputBuffer &OB) const {
     bool FirstElement = true;
     for (size_t Idx = 0; Idx != NumElements; ++Idx) {
       size_t BeforeComma = OB.getCurrentPosition();
       if (!FirstElement)
         OB += ", ";
       size_t AfterComma = OB.getCurrentPosition();
       Elements[Idx]->printAsOperand(OB, Node::Prec::Comma);
 
       // Elements[Idx] is an empty parameter pack expansion, we should erase the
       // comma we just printed.
       if (AfterComma == OB.getCurrentPosition()) {
         OB.setCurrentPosition(BeforeComma);
         continue;
       }
 
       FirstElement = false;
     }
   }
 
   // Print an array of integer literals as a string literal. Returns whether we
   // could do so.
   bool printAsString(OutputBuffer &OB) const;
 };
 
 struct NodeArrayNode : Node {
   NodeArray Array;
   NodeArrayNode(NodeArray Array_) : Node(KNodeArrayNode), Array(Array_) {}
 
   template<typename Fn> void match(Fn F) const { F(Array); }
 
   void printLeft(OutputBuffer &OB) const override { Array.printWithComma(OB); }
 };
 
 class DotSuffix final : public Node {
   const Node *Prefix;
   const std::string_view Suffix;
 
 public:
   DotSuffix(const Node *Prefix_, std::string_view Suffix_)
       : Node(KDotSuffix), Prefix(Prefix_), Suffix(Suffix_) {}
 
   template<typename Fn> void match(Fn F) const { F(Prefix, Suffix); }
 
   void printLeft(OutputBuffer &OB) const override {
     Prefix->print(OB);
     OB += " (";
     OB += Suffix;
     OB += ")";
   }
 };
 
 class VendorExtQualType final : public Node {
   const Node *Ty;
   std::string_view Ext;
   const Node *TA;
 
 public:
   VendorExtQualType(const Node *Ty_, std::string_view Ext_, const Node *TA_)
       : Node(KVendorExtQualType), Ty(Ty_), Ext(Ext_), TA(TA_) {}
 
   const Node *getTy() const { return Ty; }
   std::string_view getExt() const { return Ext; }
   const Node *getTA() const { return TA; }
 
   template <typename Fn> void match(Fn F) const { F(Ty, Ext, TA); }
 
   void printLeft(OutputBuffer &OB) const override {
     Ty->print(OB);
     OB += " ";
     OB += Ext;
     if (TA != nullptr)
       TA->print(OB);
   }
 };
 
 enum FunctionRefQual : unsigned char {
   FrefQualNone,
   FrefQualLValue,
   FrefQualRValue,
 };
 
 enum Qualifiers {
   QualNone = 0,
   QualConst = 0x1,
   QualVolatile = 0x2,
   QualRestrict = 0x4,
 };
 
 inline Qualifiers operator|=(Qualifiers &Q1, Qualifiers Q2) {
   return Q1 = static_cast<Qualifiers>(Q1 | Q2);
 }
 
 class QualType final : public Node {
 protected:
   const Qualifiers Quals;
   const Node *Child;
 
   void printQuals(OutputBuffer &OB) const {
     if (Quals & QualConst)
       OB += " const";
     if (Quals & QualVolatile)
       OB += " volatile";
     if (Quals & QualRestrict)
       OB += " restrict";
   }
 
 public:
   QualType(const Node *Child_, Qualifiers Quals_)
       : Node(KQualType, Child_->getRHSComponentCache(), Child_->getArrayCache(),
              Child_->getFunctionCache()),
         Quals(Quals_), Child(Child_) {}
 
   Qualifiers getQuals() const { return Quals; }
   const Node *getChild() const { return Child; }
 
   template<typename Fn> void match(Fn F) const { F(Child, Quals); }
 
   bool hasRHSComponentSlow(OutputBuffer &OB) const override {
     return Child->hasRHSComponent(OB);
   }
   bool hasArraySlow(OutputBuffer &OB) const override {
     return Child->hasArray(OB);
   }
   bool hasFunctionSlow(OutputBuffer &OB) const override {
     return Child->hasFunction(OB);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     Child->printLeft(OB);
     printQuals(OB);
   }
 
   void printRight(OutputBuffer &OB) const override { Child->printRight(OB); }
 };
 
 class ConversionOperatorType final : public Node {
   const Node *Ty;
 
 public:
   ConversionOperatorType(const Node *Ty_)
       : Node(KConversionOperatorType), Ty(Ty_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "operator ";
     Ty->print(OB);
   }
 };
 
 class PostfixQualifiedType final : public Node {
   const Node *Ty;
   const std::string_view Postfix;
 
 public:
   PostfixQualifiedType(const Node *Ty_, std::string_view Postfix_)
       : Node(KPostfixQualifiedType), Ty(Ty_), Postfix(Postfix_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Postfix); }
 
   void printLeft(OutputBuffer &OB) const override {
     Ty->printLeft(OB);
     OB += Postfix;
   }
 };
 
 class NameType final : public Node {
   const std::string_view Name;
 
 public:
   NameType(std::string_view Name_) : Node(KNameType), Name(Name_) {}
 
   template<typename Fn> void match(Fn F) const { F(Name); }
 
   std::string_view getName() const { return Name; }
   std::string_view getBaseName() const override { return Name; }
 
   void printLeft(OutputBuffer &OB) const override { OB += Name; }
 };
 
 class BitIntType final : public Node {
   const Node *Size;
   bool Signed;
 
 public:
   BitIntType(const Node *Size_, bool Signed_)
       : Node(KBitIntType), Size(Size_), Signed(Signed_) {}
 
   template <typename Fn> void match(Fn F) const { F(Size, Signed); }
 
   void printLeft(OutputBuffer &OB) const override {
     if (!Signed)
       OB += "unsigned ";
     OB += "_BitInt";
     OB.printOpen();
     Size->printAsOperand(OB);
     OB.printClose();
   }
 };
 
 class ElaboratedTypeSpefType : public Node {
   std::string_view Kind;
   Node *Child;
 public:
   ElaboratedTypeSpefType(std::string_view Kind_, Node *Child_)
       : Node(KElaboratedTypeSpefType), Kind(Kind_), Child(Child_) {}
 
   template<typename Fn> void match(Fn F) const { F(Kind, Child); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += Kind;
     OB += ' ';
     Child->print(OB);
   }
 };
 
 class TransformedType : public Node {
   std::string_view Transform;
   Node *BaseType;
 public:
   TransformedType(std::string_view Transform_, Node *BaseType_)
       : Node(KTransformedType), Transform(Transform_), BaseType(BaseType_) {}
 
   template<typename Fn> void match(Fn F) const { F(Transform, BaseType); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += Transform;
     OB += '(';
     BaseType->print(OB);
     OB += ')';
   }
 };
 
 struct AbiTagAttr : Node {
   Node *Base;
   std::string_view Tag;
 
   AbiTagAttr(Node *Base_, std::string_view Tag_)
       : Node(KAbiTagAttr, Base_->getRHSComponentCache(), Base_->getArrayCache(),
              Base_->getFunctionCache()),
         Base(Base_), Tag(Tag_) {}
 
   template<typename Fn> void match(Fn F) const { F(Base, Tag); }
 
   std::string_view getBaseName() const override { return Base->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Base->printLeft(OB);
     OB += "[abi:";
     OB += Tag;
     OB += "]";
   }
 };
 
 class EnableIfAttr : public Node {
   NodeArray Conditions;
 public:
   EnableIfAttr(NodeArray Conditions_)
       : Node(KEnableIfAttr), Conditions(Conditions_) {}
 
   template<typename Fn> void match(Fn F) const { F(Conditions); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += " [enable_if:";
     Conditions.printWithComma(OB);
     OB += ']';
   }
 };
 
 class ObjCProtoName : public Node {
   const Node *Ty;
   std::string_view Protocol;
 
   friend class PointerType;
 
 public:
   ObjCProtoName(const Node *Ty_, std::string_view Protocol_)
       : Node(KObjCProtoName), Ty(Ty_), Protocol(Protocol_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Protocol); }
 
   bool isObjCObject() const {
     return Ty->getKind() == KNameType &&
            static_cast<const NameType *>(Ty)->getName() == "objc_object";
   }
 
   void printLeft(OutputBuffer &OB) const override {
     Ty->print(OB);
     OB += "<";
     OB += Protocol;
     OB += ">";
   }
 };
 
 class PointerType final : public Node {
   const Node *Pointee;
 
 public:
   PointerType(const Node *Pointee_)
       : Node(KPointerType, Pointee_->getRHSComponentCache()),
         Pointee(Pointee_) {}
 
   const Node *getPointee() const { return Pointee; }
 
   template<typename Fn> void match(Fn F) const { F(Pointee); }
 
   bool hasRHSComponentSlow(OutputBuffer &OB) const override {
     return Pointee->hasRHSComponent(OB);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     // We rewrite objc_object<SomeProtocol>* into id<SomeProtocol>.
     if (Pointee->getKind() != KObjCProtoName ||
         !static_cast<const ObjCProtoName *>(Pointee)->isObjCObject()) {
       Pointee->printLeft(OB);
       if (Pointee->hasArray(OB))
         OB += " ";
       if (Pointee->hasArray(OB) || Pointee->hasFunction(OB))
         OB += "(";
       OB += "*";
     } else {
       const auto *objcProto = static_cast<const ObjCProtoName *>(Pointee);
       OB += "id<";
       OB += objcProto->Protocol;
       OB += ">";
     }
   }
 
   void printRight(OutputBuffer &OB) const override {
     if (Pointee->getKind() != KObjCProtoName ||
         !static_cast<const ObjCProtoName *>(Pointee)->isObjCObject()) {
       if (Pointee->hasArray(OB) || Pointee->hasFunction(OB))
         OB += ")";
       Pointee->printRight(OB);
     }
   }
 };
 
 enum class ReferenceKind {
   LValue,
   RValue,
 };
 
 // Represents either a LValue or an RValue reference type.
 class ReferenceType : public Node {
   const Node *Pointee;
   ReferenceKind RK;
 
   mutable bool Printing = false;
 
   // Dig through any refs to refs, collapsing the ReferenceTypes as we go. The
   // rule here is rvalue ref to rvalue ref collapses to a rvalue ref, and any
   // other combination collapses to a lvalue ref.
   //
   // A combination of a TemplateForwardReference and a back-ref Substitution
   // from an ill-formed string may have created a cycle; use cycle detection to
   // avoid looping forever.
   std::pair<ReferenceKind, const Node *> collapse(OutputBuffer &OB) const {
     auto SoFar = std::make_pair(RK, Pointee);
     // Track the chain of nodes for the Floyd's 'tortoise and hare'
     // cycle-detection algorithm, since getSyntaxNode(S) is impure
     PODSmallVector<const Node *, 8> Prev;
     for (;;) {
       const Node *SN = SoFar.second->getSyntaxNode(OB);
       if (SN->getKind() != KReferenceType)
         break;
       auto *RT = static_cast<const ReferenceType *>(SN);
       SoFar.second = RT->Pointee;
       SoFar.first = std::min(SoFar.first, RT->RK);
 
       // The middle of Prev is the 'slow' pointer moving at half speed
       Prev.push_back(SoFar.second);
       if (Prev.size() > 1 && SoFar.second == Prev[(Prev.size() - 1) / 2]) {
         // Cycle detected
         SoFar.second = nullptr;
         break;
       }
     }
     return SoFar;
   }
 
 public:
   ReferenceType(const Node *Pointee_, ReferenceKind RK_)
       : Node(KReferenceType, Pointee_->getRHSComponentCache()),
         Pointee(Pointee_), RK(RK_) {}
 
   template<typename Fn> void match(Fn F) const { F(Pointee, RK); }
 
   bool hasRHSComponentSlow(OutputBuffer &OB) const override {
     return Pointee->hasRHSComponent(OB);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     if (Printing)
       return;
     ScopedOverride<bool> SavePrinting(Printing, true);
     std::pair<ReferenceKind, const Node *> Collapsed = collapse(OB);
     if (!Collapsed.second)
       return;
     Collapsed.second->printLeft(OB);
     if (Collapsed.second->hasArray(OB))
       OB += " ";
     if (Collapsed.second->hasArray(OB) || Collapsed.second->hasFunction(OB))
       OB += "(";
 
     OB += (Collapsed.first == ReferenceKind::LValue ? "&" : "&&");
   }
   void printRight(OutputBuffer &OB) const override {
     if (Printing)
       return;
     ScopedOverride<bool> SavePrinting(Printing, true);
     std::pair<ReferenceKind, const Node *> Collapsed = collapse(OB);
     if (!Collapsed.second)
       return;
     if (Collapsed.second->hasArray(OB) || Collapsed.second->hasFunction(OB))
       OB += ")";
     Collapsed.second->printRight(OB);
   }
 };
 
 class PointerToMemberType final : public Node {
   const Node *ClassType;
   const Node *MemberType;
 
 public:
   PointerToMemberType(const Node *ClassType_, const Node *MemberType_)
       : Node(KPointerToMemberType, MemberType_->getRHSComponentCache()),
         ClassType(ClassType_), MemberType(MemberType_) {}
 
   template<typename Fn> void match(Fn F) const { F(ClassType, MemberType); }
 
   bool hasRHSComponentSlow(OutputBuffer &OB) const override {
     return MemberType->hasRHSComponent(OB);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     MemberType->printLeft(OB);
     if (MemberType->hasArray(OB) || MemberType->hasFunction(OB))
       OB += "(";
     else
       OB += " ";
     ClassType->print(OB);
     OB += "::*";
   }
 
   void printRight(OutputBuffer &OB) const override {
     if (MemberType->hasArray(OB) || MemberType->hasFunction(OB))
       OB += ")";
     MemberType->printRight(OB);
   }
 };
 
 class ArrayType final : public Node {
   const Node *Base;
   Node *Dimension;
 
 public:
   ArrayType(const Node *Base_, Node *Dimension_)
       : Node(KArrayType,
              /*RHSComponentCache=*/Cache::Yes,
              /*ArrayCache=*/Cache::Yes),
         Base(Base_), Dimension(Dimension_) {}
 
   template<typename Fn> void match(Fn F) const { F(Base, Dimension); }
 
   bool hasRHSComponentSlow(OutputBuffer &) const override { return true; }
   bool hasArraySlow(OutputBuffer &) const override { return true; }
 
   void printLeft(OutputBuffer &OB) const override { Base->printLeft(OB); }
 
   void printRight(OutputBuffer &OB) const override {
     if (OB.back() != ']')
       OB += " ";
     OB += "[";
     if (Dimension)
       Dimension->print(OB);
     OB += "]";
     Base->printRight(OB);
   }
 
   bool printInitListAsType(OutputBuffer &OB,
                            const NodeArray &Elements) const override {
     if (Base->getKind() == KNameType &&
         static_cast<const NameType *>(Base)->getName() == "char") {
       return Elements.printAsString(OB);
     }
     return false;
   }
 };
 
 class FunctionType final : public Node {
   const Node *Ret;
   NodeArray Params;
   Qualifiers CVQuals;
   FunctionRefQual RefQual;
   const Node *ExceptionSpec;
 
 public:
   FunctionType(const Node *Ret_, NodeArray Params_, Qualifiers CVQuals_,
                FunctionRefQual RefQual_, const Node *ExceptionSpec_)
       : Node(KFunctionType,
              /*RHSComponentCache=*/Cache::Yes, /*ArrayCache=*/Cache::No,
              /*FunctionCache=*/Cache::Yes),
         Ret(Ret_), Params(Params_), CVQuals(CVQuals_), RefQual(RefQual_),
         ExceptionSpec(ExceptionSpec_) {}
 
   template<typename Fn> void match(Fn F) const {
     F(Ret, Params, CVQuals, RefQual, ExceptionSpec);
   }
 
   bool hasRHSComponentSlow(OutputBuffer &) const override { return true; }
   bool hasFunctionSlow(OutputBuffer &) const override { return true; }
 
   // Handle C++'s ... quirky decl grammar by using the left & right
   // distinction. Consider:
   //   int (*f(float))(char) {}
   // f is a function that takes a float and returns a pointer to a function
   // that takes a char and returns an int. If we're trying to print f, start
   // by printing out the return types's left, then print our parameters, then
   // finally print right of the return type.
   void printLeft(OutputBuffer &OB) const override {
     Ret->printLeft(OB);
     OB += " ";
   }
 
   void printRight(OutputBuffer &OB) const override {
     OB.printOpen();
     Params.printWithComma(OB);
     OB.printClose();
     Ret->printRight(OB);
 
     if (CVQuals & QualConst)
       OB += " const";
     if (CVQuals & QualVolatile)
       OB += " volatile";
     if (CVQuals & QualRestrict)
       OB += " restrict";
 
     if (RefQual == FrefQualLValue)
       OB += " &";
     else if (RefQual == FrefQualRValue)
       OB += " &&";
 
     if (ExceptionSpec != nullptr) {
       OB += ' ';
       ExceptionSpec->print(OB);
     }
   }
 };
 
 class NoexceptSpec : public Node {
   const Node *E;
 public:
   NoexceptSpec(const Node *E_) : Node(KNoexceptSpec), E(E_) {}
 
   template<typename Fn> void match(Fn F) const { F(E); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "noexcept";
     OB.printOpen();
     E->printAsOperand(OB);
     OB.printClose();
   }
 };
 
 class DynamicExceptionSpec : public Node {
   NodeArray Types;
 public:
   DynamicExceptionSpec(NodeArray Types_)
       : Node(KDynamicExceptionSpec), Types(Types_) {}
 
   template<typename Fn> void match(Fn F) const { F(Types); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "throw";
     OB.printOpen();
     Types.printWithComma(OB);
     OB.printClose();
   }
 };
 
 /// Represents the explicitly named object parameter.
 /// E.g.,
 /// \code{.cpp}
 ///   struct Foo {
 ///     void bar(this Foo && self);
 ///   };
 /// \endcode
 class ExplicitObjectParameter final : public Node {
   Node *Base;
 
 public:
   ExplicitObjectParameter(Node *Base_)
       : Node(KExplicitObjectParameter), Base(Base_) {
     DEMANGLE_ASSERT(
         Base != nullptr,
         "Creating an ExplicitObjectParameter without a valid Base Node.");
   }
 
   template <typename Fn> void match(Fn F) const { F(Base); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "this ";
     Base->print(OB);
   }
 };
 
 class FunctionEncoding final : public Node {
   const Node *Ret;
   const Node *Name;
   NodeArray Params;
   const Node *Attrs;
   const Node *Requires;
   Qualifiers CVQuals;
   FunctionRefQual RefQual;
 
 public:
   FunctionEncoding(const Node *Ret_, const Node *Name_, NodeArray Params_,
                    const Node *Attrs_, const Node *Requires_,
                    Qualifiers CVQuals_, FunctionRefQual RefQual_)
       : Node(KFunctionEncoding,
              /*RHSComponentCache=*/Cache::Yes, /*ArrayCache=*/Cache::No,
              /*FunctionCache=*/Cache::Yes),
         Ret(Ret_), Name(Name_), Params(Params_), Attrs(Attrs_),
         Requires(Requires_), CVQuals(CVQuals_), RefQual(RefQual_) {}
 
   template<typename Fn> void match(Fn F) const {
     F(Ret, Name, Params, Attrs, Requires, CVQuals, RefQual);
   }
 
   Qualifiers getCVQuals() const { return CVQuals; }
   FunctionRefQual getRefQual() const { return RefQual; }
   NodeArray getParams() const { return Params; }
   const Node *getReturnType() const { return Ret; }
 
   bool hasRHSComponentSlow(OutputBuffer &) const override { return true; }
   bool hasFunctionSlow(OutputBuffer &) const override { return true; }
 
   const Node *getName() const { return Name; }
 
   void printLeft(OutputBuffer &OB) const override {
     if (Ret) {
       Ret->printLeft(OB);
       if (!Ret->hasRHSComponent(OB))
         OB += " ";
     }
     Name->print(OB);
   }
 
   void printRight(OutputBuffer &OB) const override {
     OB.printOpen();
     Params.printWithComma(OB);
     OB.printClose();
     if (Ret)
       Ret->printRight(OB);
 
     if (CVQuals & QualConst)
       OB += " const";
     if (CVQuals & QualVolatile)
       OB += " volatile";
     if (CVQuals & QualRestrict)
       OB += " restrict";
 
     if (RefQual == FrefQualLValue)
       OB += " &";
     else if (RefQual == FrefQualRValue)
       OB += " &&";
 
     if (Attrs != nullptr)
       Attrs->print(OB);
 
     if (Requires != nullptr) {
       OB += " requires ";
       Requires->print(OB);
     }
   }
 };
 
 class LiteralOperator : public Node {
   const Node *OpName;
 
 public:
   LiteralOperator(const Node *OpName_)
       : Node(KLiteralOperator), OpName(OpName_) {}
 
   template<typename Fn> void match(Fn F) const { F(OpName); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "operator\"\" ";
     OpName->print(OB);
   }
 };
 
 class SpecialName final : public Node {
   const std::string_view Special;
   const Node *Child;
 
 public:
   SpecialName(std::string_view Special_, const Node *Child_)
       : Node(KSpecialName), Special(Special_), Child(Child_) {}
 
   template<typename Fn> void match(Fn F) const { F(Special, Child); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += Special;
     Child->print(OB);
   }
 };
 
 class CtorVtableSpecialName final : public Node {
   const Node *FirstType;
   const Node *SecondType;
 
 public:
   CtorVtableSpecialName(const Node *FirstType_, const Node *SecondType_)
       : Node(KCtorVtableSpecialName),
         FirstType(FirstType_), SecondType(SecondType_) {}
 
   template<typename Fn> void match(Fn F) const { F(FirstType, SecondType); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "construction vtable for ";
     FirstType->print(OB);
     OB += "-in-";
     SecondType->print(OB);
   }
 };
 
 struct NestedName : Node {
   Node *Qual;
   Node *Name;
 
   NestedName(Node *Qual_, Node *Name_)
       : Node(KNestedName), Qual(Qual_), Name(Name_) {}
 
   template<typename Fn> void match(Fn F) const { F(Qual, Name); }
 
   std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Qual->print(OB);
     OB += "::";
     Name->print(OB);
   }
 };
 
 struct MemberLikeFriendName : Node {
   Node *Qual;
   Node *Name;
 
   MemberLikeFriendName(Node *Qual_, Node *Name_)
       : Node(KMemberLikeFriendName), Qual(Qual_), Name(Name_) {}
 
   template<typename Fn> void match(Fn F) const { F(Qual, Name); }
 
   std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Qual->print(OB);
     OB += "::friend ";
     Name->print(OB);
   }
 };
 
 struct ModuleName : Node {
   ModuleName *Parent;
   Node *Name;
   bool IsPartition;
 
   ModuleName(ModuleName *Parent_, Node *Name_, bool IsPartition_ = false)
       : Node(KModuleName), Parent(Parent_), Name(Name_),
         IsPartition(IsPartition_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Parent, Name, IsPartition);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     if (Parent)
       Parent->print(OB);
     if (Parent || IsPartition)
       OB += IsPartition ? ':' : '.';
     Name->print(OB);
   }
 };
 
 struct ModuleEntity : Node {
   ModuleName *Module;
   Node *Name;
 
   ModuleEntity(ModuleName *Module_, Node *Name_)
       : Node(KModuleEntity), Module(Module_), Name(Name_) {}
 
   template <typename Fn> void match(Fn F) const { F(Module, Name); }
 
   std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Name->print(OB);
     OB += '@';
     Module->print(OB);
   }
 };
 
 struct LocalName : Node {
   Node *Encoding;
   Node *Entity;
 
   LocalName(Node *Encoding_, Node *Entity_)
       : Node(KLocalName), Encoding(Encoding_), Entity(Entity_) {}
 
   template<typename Fn> void match(Fn F) const { F(Encoding, Entity); }
 
   void printLeft(OutputBuffer &OB) const override {
     Encoding->print(OB);
     OB += "::";
     Entity->print(OB);
   }
 };
 
 class QualifiedName final : public Node {
   // qualifier::name
   const Node *Qualifier;
   const Node *Name;
 
 public:
   QualifiedName(const Node *Qualifier_, const Node *Name_)
       : Node(KQualifiedName), Qualifier(Qualifier_), Name(Name_) {}
 
   template<typename Fn> void match(Fn F) const { F(Qualifier, Name); }
 
   std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Qualifier->print(OB);
     OB += "::";
     Name->print(OB);
   }
 };
 
 class VectorType final : public Node {
   const Node *BaseType;
   const Node *Dimension;
 
 public:
   VectorType(const Node *BaseType_, const Node *Dimension_)
       : Node(KVectorType), BaseType(BaseType_), Dimension(Dimension_) {}
 
   const Node *getBaseType() const { return BaseType; }
   const Node *getDimension() const { return Dimension; }
 
   template<typename Fn> void match(Fn F) const { F(BaseType, Dimension); }
 
   void printLeft(OutputBuffer &OB) const override {
     BaseType->print(OB);
     OB += " vector[";
     if (Dimension)
       Dimension->print(OB);
     OB += "]";
   }
 };
 
 class PixelVectorType final : public Node {
   const Node *Dimension;
 
 public:
   PixelVectorType(const Node *Dimension_)
       : Node(KPixelVectorType), Dimension(Dimension_) {}
 
   template<typename Fn> void match(Fn F) const { F(Dimension); }
 
   void printLeft(OutputBuffer &OB) const override {
     // FIXME: This should demangle as "vector pixel".
     OB += "pixel vector[";
     Dimension->print(OB);
     OB += "]";
   }
 };
 
 class BinaryFPType final : public Node {
   const Node *Dimension;
 
 public:
   BinaryFPType(const Node *Dimension_)
       : Node(KBinaryFPType), Dimension(Dimension_) {}
 
   template<typename Fn> void match(Fn F) const { F(Dimension); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "_Float";
     Dimension->print(OB);
   }
 };
 
 enum class TemplateParamKind { Type, NonType, Template };
 
 /// An invented name for a template parameter for which we don't have a
 /// corresponding template argument.
 ///
 /// This node is created when parsing the <lambda-sig> for a lambda with
 /// explicit template arguments, which might be referenced in the parameter
 /// types appearing later in the <lambda-sig>.
 class SyntheticTemplateParamName final : public Node {
   TemplateParamKind Kind;
   unsigned Index;
 
 public:
   SyntheticTemplateParamName(TemplateParamKind Kind_, unsigned Index_)
       : Node(KSyntheticTemplateParamName), Kind(Kind_), Index(Index_) {}
 
   template<typename Fn> void match(Fn F) const { F(Kind, Index); }
 
   void printLeft(OutputBuffer &OB) const override {
     switch (Kind) {
     case TemplateParamKind::Type:
       OB += "$T";
       break;
     case TemplateParamKind::NonType:
       OB += "$N";
       break;
     case TemplateParamKind::Template:
       OB += "$TT";
       break;
     }
     if (Index > 0)
       OB << Index - 1;
   }
 };
 
 class TemplateParamQualifiedArg final : public Node {
   Node *Param;
   Node *Arg;
 
 public:
   TemplateParamQualifiedArg(Node *Param_, Node *Arg_)
       : Node(KTemplateParamQualifiedArg), Param(Param_), Arg(Arg_) {}
 
   template <typename Fn> void match(Fn F) const { F(Param, Arg); }
 
   Node *getArg() { return Arg; }
 
   void printLeft(OutputBuffer &OB) const override {
     // Don't print Param to keep the output consistent.
     Arg->print(OB);
   }
 };
 
 /// A template type parameter declaration, 'typename T'.
 class TypeTemplateParamDecl final : public Node {
   Node *Name;
 
 public:
   TypeTemplateParamDecl(Node *Name_)
       : Node(KTypeTemplateParamDecl, Cache::Yes), Name(Name_) {}
 
   template<typename Fn> void match(Fn F) const { F(Name); }
 
   void printLeft(OutputBuffer &OB) const override { OB += "typename "; }
 
   void printRight(OutputBuffer &OB) const override { Name->print(OB); }
 };
 
 /// A constrained template type parameter declaration, 'C<U> T'.
 class ConstrainedTypeTemplateParamDecl final : public Node {
   Node *Constraint;
   Node *Name;
 
 public:
   ConstrainedTypeTemplateParamDecl(Node *Constraint_, Node *Name_)
       : Node(KConstrainedTypeTemplateParamDecl, Cache::Yes),
         Constraint(Constraint_), Name(Name_) {}
 
   template<typename Fn> void match(Fn F) const { F(Constraint, Name); }
 
   void printLeft(OutputBuffer &OB) const override {
     Constraint->print(OB);
     OB += " ";
   }
 
   void printRight(OutputBuffer &OB) const override { Name->print(OB); }
 };
 
 /// A non-type template parameter declaration, 'int N'.
 class NonTypeTemplateParamDecl final : public Node {
   Node *Name;
   Node *Type;
 
 public:
   NonTypeTemplateParamDecl(Node *Name_, Node *Type_)
       : Node(KNonTypeTemplateParamDecl, Cache::Yes), Name(Name_), Type(Type_) {}
 
   template<typename Fn> void match(Fn F) const { F(Name, Type); }
 
   void printLeft(OutputBuffer &OB) const override {
     Type->printLeft(OB);
     if (!Type->hasRHSComponent(OB))
       OB += " ";
   }
 
   void printRight(OutputBuffer &OB) const override {
     Name->print(OB);
     Type->printRight(OB);
   }
 };
 
 /// A template template parameter declaration,
 /// 'template<typename T> typename N'.
 class TemplateTemplateParamDecl final : public Node {
   Node *Name;
   NodeArray Params;
   Node *Requires;
 
 public:
   TemplateTemplateParamDecl(Node *Name_, NodeArray Params_, Node *Requires_)
       : Node(KTemplateTemplateParamDecl, Cache::Yes), Name(Name_),
         Params(Params_), Requires(Requires_) {}
 
   template <typename Fn> void match(Fn F) const { F(Name, Params, Requires); }
 
   void printLeft(OutputBuffer &OB) const override {
     ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
     OB += "template<";
     Params.printWithComma(OB);
     OB += "> typename ";
   }
 
   void printRight(OutputBuffer &OB) const override {
     Name->print(OB);
     if (Requires != nullptr) {
       OB += " requires ";
       Requires->print(OB);
     }
   }
 };
 
 /// A template parameter pack declaration, 'typename ...T'.
 class TemplateParamPackDecl final : public Node {
   Node *Param;
 
 public:
   TemplateParamPackDecl(Node *Param_)
       : Node(KTemplateParamPackDecl, Cache::Yes), Param(Param_) {}
 
   template<typename Fn> void match(Fn F) const { F(Param); }
 
   void printLeft(OutputBuffer &OB) const override {
     Param->printLeft(OB);
     OB += "...";
   }
 
   void printRight(OutputBuffer &OB) const override { Param->printRight(OB); }
 };
 
 /// An unexpanded parameter pack (either in the expression or type context). If
 /// this AST is correct, this node will have a ParameterPackExpansion node above
 /// it.
 ///
 /// This node is created when some <template-args> are found that apply to an
 /// <encoding>, and is stored in the TemplateParams table. In order for this to
 /// appear in the final AST, it has to referenced via a <template-param> (ie,
 /// T_).
 class ParameterPack final : public Node {
   NodeArray Data;
 
   // Setup OutputBuffer for a pack expansion, unless we're already expanding
   // one.
   void initializePackExpansion(OutputBuffer &OB) const {
     if (OB.CurrentPackMax == std::numeric_limits<unsigned>::max()) {
       OB.CurrentPackMax = static_cast<unsigned>(Data.size());
       OB.CurrentPackIndex = 0;
     }
   }
 
 public:
   ParameterPack(NodeArray Data_) : Node(KParameterPack), Data(Data_) {
     ArrayCache = FunctionCache = RHSComponentCache = Cache::Unknown;
     if (std::all_of(Data.begin(), Data.end(),
                     [](Node *P) { return P->getArrayCache() == Cache::No; }))
       ArrayCache = Cache::No;
     if (std::all_of(Data.begin(), Data.end(),
                     [](Node *P) { return P->getFunctionCache() == Cache::No; }))
       FunctionCache = Cache::No;
     if (std::all_of(Data.begin(), Data.end(), [](Node *P) {
           return P->getRHSComponentCache() == Cache::No;
         }))
       RHSComponentCache = Cache::No;
   }
 
   template<typename Fn> void match(Fn F) const { F(Data); }
 
   bool hasRHSComponentSlow(OutputBuffer &OB) const override {
     initializePackExpansion(OB);
     size_t Idx = OB.CurrentPackIndex;
     return Idx < Data.size() && Data[Idx]->hasRHSComponent(OB);
   }
   bool hasArraySlow(OutputBuffer &OB) const override {
     initializePackExpansion(OB);
     size_t Idx = OB.CurrentPackIndex;
     return Idx < Data.size() && Data[Idx]->hasArray(OB);
   }
   bool hasFunctionSlow(OutputBuffer &OB) const override {
     initializePackExpansion(OB);
     size_t Idx = OB.CurrentPackIndex;
     return Idx < Data.size() && Data[Idx]->hasFunction(OB);
   }
   const Node *getSyntaxNode(OutputBuffer &OB) const override {
     initializePackExpansion(OB);
     size_t Idx = OB.CurrentPackIndex;
     return Idx < Data.size() ? Data[Idx]->getSyntaxNode(OB) : this;
   }
 
   void printLeft(OutputBuffer &OB) const override {
     initializePackExpansion(OB);
     size_t Idx = OB.CurrentPackIndex;
     if (Idx < Data.size())
       Data[Idx]->printLeft(OB);
   }
   void printRight(OutputBuffer &OB) const override {
     initializePackExpansion(OB);
     size_t Idx = OB.CurrentPackIndex;
     if (Idx < Data.size())
       Data[Idx]->printRight(OB);
   }
 };
 
 /// A variadic template argument. This node represents an occurrence of
 /// J<something>E in some <template-args>. It isn't itself unexpanded, unless
 /// one of its Elements is. The parser inserts a ParameterPack into the
 /// TemplateParams table if the <template-args> this pack belongs to apply to an
 /// <encoding>.
 class TemplateArgumentPack final : public Node {
   NodeArray Elements;
 public:
   TemplateArgumentPack(NodeArray Elements_)
       : Node(KTemplateArgumentPack), Elements(Elements_) {}
 
   template<typename Fn> void match(Fn F) const { F(Elements); }
 
   NodeArray getElements() const { return Elements; }
 
   void printLeft(OutputBuffer &OB) const override {
     Elements.printWithComma(OB);
   }
 };
 
 /// A pack expansion. Below this node, there are some unexpanded ParameterPacks
 /// which each have Child->ParameterPackSize elements.
 class ParameterPackExpansion final : public Node {
   const Node *Child;
 
 public:
   ParameterPackExpansion(const Node *Child_)
       : Node(KParameterPackExpansion), Child(Child_) {}
 
   template<typename Fn> void match(Fn F) const { F(Child); }
 
   const Node *getChild() const { return Child; }
 
   void printLeft(OutputBuffer &OB) const override {
     constexpr unsigned Max = std::numeric_limits<unsigned>::max();
     ScopedOverride<unsigned> SavePackIdx(OB.CurrentPackIndex, Max);
     ScopedOverride<unsigned> SavePackMax(OB.CurrentPackMax, Max);
     size_t StreamPos = OB.getCurrentPosition();
 
     // Print the first element in the pack. If Child contains a ParameterPack,
     // it will set up S.CurrentPackMax and print the first element.
     Child->print(OB);
 
     // No ParameterPack was found in Child. This can occur if we've found a pack
     // expansion on a <function-param>.
     if (OB.CurrentPackMax == Max) {
       OB += "...";
       return;
     }
 
     // We found a ParameterPack, but it has no elements. Erase whatever we may
     // of printed.
     if (OB.CurrentPackMax == 0) {
       OB.setCurrentPosition(StreamPos);
       return;
     }
 
     // Else, iterate through the rest of the elements in the pack.
     for (unsigned I = 1, E = OB.CurrentPackMax; I < E; ++I) {
       OB += ", ";
       OB.CurrentPackIndex = I;
       Child->print(OB);
     }
   }
 };
 
 class TemplateArgs final : public Node {
   NodeArray Params;
   Node *Requires;
 
 public:
   TemplateArgs(NodeArray Params_, Node *Requires_)
       : Node(KTemplateArgs), Params(Params_), Requires(Requires_) {}
 
   template<typename Fn> void match(Fn F) const { F(Params, Requires); }
 
   NodeArray getParams() { return Params; }
 
   void printLeft(OutputBuffer &OB) const override {
     ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
     OB += "<";
     Params.printWithComma(OB);
     OB += ">";
     // Don't print the requires clause to keep the output simple.
   }
 };
 
 /// A forward-reference to a template argument that was not known at the point
 /// where the template parameter name was parsed in a mangling.
 ///
 /// This is created when demangling the name of a specialization of a
 /// conversion function template:
 ///
 /// \code
 /// struct A {
 ///   template<typename T> operator T*();
 /// };
 /// \endcode
 ///
 /// When demangling a specialization of the conversion function template, we
 /// encounter the name of the template (including the \c T) before we reach
 /// the template argument list, so we cannot substitute the parameter name
 /// for the corresponding argument while parsing. Instead, we create a
 /// \c ForwardTemplateReference node that is resolved after we parse the
 /// template arguments.
 struct ForwardTemplateReference : Node {
   size_t Index;
   Node *Ref = nullptr;
 
   // If we're currently printing this node. It is possible (though invalid) for
   // a forward template reference to refer to itself via a substitution. This
   // creates a cyclic AST, which will stack overflow printing. To fix this, bail
   // out if more than one print* function is active.
   mutable bool Printing = false;
 
   ForwardTemplateReference(size_t Index_)
       : Node(KForwardTemplateReference, Cache::Unknown, Cache::Unknown,
              Cache::Unknown),
         Index(Index_) {}
 
   // We don't provide a matcher for these, because the value of the node is
   // not determined by its construction parameters, and it generally needs
   // special handling.
   template<typename Fn> void match(Fn F) const = delete;
 
   bool hasRHSComponentSlow(OutputBuffer &OB) const override {
     if (Printing)
       return false;
     ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->hasRHSComponent(OB);
   }
   bool hasArraySlow(OutputBuffer &OB) const override {
     if (Printing)
       return false;
     ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->hasArray(OB);
   }
   bool hasFunctionSlow(OutputBuffer &OB) const override {
     if (Printing)
       return false;
     ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->hasFunction(OB);
   }
   const Node *getSyntaxNode(OutputBuffer &OB) const override {
     if (Printing)
       return this;
     ScopedOverride<bool> SavePrinting(Printing, true);
     return Ref->getSyntaxNode(OB);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     if (Printing)
       return;
     ScopedOverride<bool> SavePrinting(Printing, true);
     Ref->printLeft(OB);
   }
   void printRight(OutputBuffer &OB) const override {
     if (Printing)
       return;
     ScopedOverride<bool> SavePrinting(Printing, true);
     Ref->printRight(OB);
   }
 };
 
 struct NameWithTemplateArgs : Node {
   // name<template_args>
   Node *Name;
   Node *TemplateArgs;
 
   NameWithTemplateArgs(Node *Name_, Node *TemplateArgs_)
       : Node(KNameWithTemplateArgs), Name(Name_), TemplateArgs(TemplateArgs_) {}
 
   template<typename Fn> void match(Fn F) const { F(Name, TemplateArgs); }
 
   std::string_view getBaseName() const override { return Name->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     Name->print(OB);
     TemplateArgs->print(OB);
   }
 };
 
 class GlobalQualifiedName final : public Node {
   Node *Child;
 
 public:
   GlobalQualifiedName(Node* Child_)
       : Node(KGlobalQualifiedName), Child(Child_) {}
 
   template<typename Fn> void match(Fn F) const { F(Child); }
 
   std::string_view getBaseName() const override { return Child->getBaseName(); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "::";
     Child->print(OB);
   }
 };
 
 enum class SpecialSubKind {
   allocator,
   basic_string,
   string,
   istream,
   ostream,
   iostream,
 };
 
 class SpecialSubstitution;
 class ExpandedSpecialSubstitution : public Node {
 protected:
   SpecialSubKind SSK;
 
   ExpandedSpecialSubstitution(SpecialSubKind SSK_, Kind K_)
       : Node(K_), SSK(SSK_) {}
 public:
   ExpandedSpecialSubstitution(SpecialSubKind SSK_)
       : ExpandedSpecialSubstitution(SSK_, KExpandedSpecialSubstitution) {}
   inline ExpandedSpecialSubstitution(SpecialSubstitution const *);
 
   template<typename Fn> void match(Fn F) const { F(SSK); }
 
 protected:
   bool isInstantiation() const {
     return unsigned(SSK) >= unsigned(SpecialSubKind::string);
   }
 
   std::string_view getBaseName() const override {
     switch (SSK) {
     case SpecialSubKind::allocator:
       return {"allocator"};
     case SpecialSubKind::basic_string:
       return {"basic_string"};
     case SpecialSubKind::string:
       return {"basic_string"};
     case SpecialSubKind::istream:
       return {"basic_istream"};
     case SpecialSubKind::ostream:
       return {"basic_ostream"};
     case SpecialSubKind::iostream:
       return {"basic_iostream"};
     }
     DEMANGLE_UNREACHABLE;
   }
 
 private:
   void printLeft(OutputBuffer &OB) const override {
     OB << "std::" << getBaseName();
     if (isInstantiation()) {
       OB << "<char, std::char_traits<char>";
       if (SSK == SpecialSubKind::string)
         OB << ", std::allocator<char>";
       OB << ">";
     }
   }
 };
 
 class SpecialSubstitution final : public ExpandedSpecialSubstitution {
 public:
   SpecialSubstitution(SpecialSubKind SSK_)
       : ExpandedSpecialSubstitution(SSK_, KSpecialSubstitution) {}
 
   template<typename Fn> void match(Fn F) const { F(SSK); }
 
   std::string_view getBaseName() const override {
     std::string_view SV = ExpandedSpecialSubstitution::getBaseName();
     if (isInstantiation()) {
       // The instantiations are typedefs that drop the "basic_" prefix.
       DEMANGLE_ASSERT(starts_with(SV, "basic_"), "");
       SV.remove_prefix(sizeof("basic_") - 1);
     }
     return SV;
   }
 
   void printLeft(OutputBuffer &OB) const override {
     OB << "std::" << getBaseName();
   }
 };
 
 inline ExpandedSpecialSubstitution::ExpandedSpecialSubstitution(
     SpecialSubstitution const *SS)
     : ExpandedSpecialSubstitution(SS->SSK) {}
 
 class CtorDtorName final : public Node {
   const Node *Basename;
   const bool IsDtor;
   const int Variant;
 
 public:
   CtorDtorName(const Node *Basename_, bool IsDtor_, int Variant_)
       : Node(KCtorDtorName), Basename(Basename_), IsDtor(IsDtor_),
         Variant(Variant_) {}
 
   template<typename Fn> void match(Fn F) const { F(Basename, IsDtor, Variant); }
 
   void printLeft(OutputBuffer &OB) const override {
     if (IsDtor)
       OB += "~";
     OB += Basename->getBaseName();
   }
 };
 
 class DtorName : public Node {
   const Node *Base;
 
 public:
   DtorName(const Node *Base_) : Node(KDtorName), Base(Base_) {}
 
   template<typename Fn> void match(Fn F) const { F(Base); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "~";
     Base->printLeft(OB);
   }
 };
 
 class UnnamedTypeName : public Node {
   const std::string_view Count;
 
 public:
   UnnamedTypeName(std::string_view Count_)
       : Node(KUnnamedTypeName), Count(Count_) {}
 
   template<typename Fn> void match(Fn F) const { F(Count); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "'unnamed";
     OB += Count;
     OB += "\'";
   }
 };
 
 class ClosureTypeName : public Node {
   NodeArray TemplateParams;
   const Node *Requires1;
   NodeArray Params;
   const Node *Requires2;
   std::string_view Count;
 
 public:
   ClosureTypeName(NodeArray TemplateParams_, const Node *Requires1_,
                   NodeArray Params_, const Node *Requires2_,
                   std::string_view Count_)
       : Node(KClosureTypeName), TemplateParams(TemplateParams_),
         Requires1(Requires1_), Params(Params_), Requires2(Requires2_),
         Count(Count_) {}
 
   template<typename Fn> void match(Fn F) const {
     F(TemplateParams, Requires1, Params, Requires2, Count);
   }
 
   void printDeclarator(OutputBuffer &OB) const {
     if (!TemplateParams.empty()) {
       ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
       OB += "<";
       TemplateParams.printWithComma(OB);
       OB += ">";
     }
     if (Requires1 != nullptr) {
       OB += " requires ";
       Requires1->print(OB);
       OB += " ";
     }
     OB.printOpen();
     Params.printWithComma(OB);
     OB.printClose();
     if (Requires2 != nullptr) {
       OB += " requires ";
       Requires2->print(OB);
     }
   }
 
   void printLeft(OutputBuffer &OB) const override {
     // FIXME: This demangling is not particularly readable.
     OB += "\'lambda";
     OB += Count;
     OB += "\'";
     printDeclarator(OB);
   }
 };
 
 class StructuredBindingName : public Node {
   NodeArray Bindings;
 public:
   StructuredBindingName(NodeArray Bindings_)
       : Node(KStructuredBindingName), Bindings(Bindings_) {}
 
   template<typename Fn> void match(Fn F) const { F(Bindings); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB.printOpen('[');
     Bindings.printWithComma(OB);
     OB.printClose(']');
   }
 };
 
 // -- Expression Nodes --
 
 class BinaryExpr : public Node {
   const Node *LHS;
   const std::string_view InfixOperator;
   const Node *RHS;
 
 public:
   BinaryExpr(const Node *LHS_, std::string_view InfixOperator_,
              const Node *RHS_, Prec Prec_)
       : Node(KBinaryExpr, Prec_), LHS(LHS_), InfixOperator(InfixOperator_),
         RHS(RHS_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(LHS, InfixOperator, RHS, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     bool ParenAll = OB.isGtInsideTemplateArgs() &&
                     (InfixOperator == ">" || InfixOperator == ">>");
     if (ParenAll)
       OB.printOpen();
     // Assignment is right associative, with special LHS precedence.
     bool IsAssign = getPrecedence() == Prec::Assign;
     LHS->printAsOperand(OB, IsAssign ? Prec::OrIf : getPrecedence(), !IsAssign);
     // No space before comma operator
     if (!(InfixOperator == ","))
       OB += " ";
     OB += InfixOperator;
     OB += " ";
     RHS->printAsOperand(OB, getPrecedence(), IsAssign);
     if (ParenAll)
       OB.printClose();
   }
 };
 
 class ArraySubscriptExpr : public Node {
   const Node *Op1;
   const Node *Op2;
 
 public:
   ArraySubscriptExpr(const Node *Op1_, const Node *Op2_, Prec Prec_)
       : Node(KArraySubscriptExpr, Prec_), Op1(Op1_), Op2(Op2_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Op1, Op2, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     Op1->printAsOperand(OB, getPrecedence());
     OB.printOpen('[');
     Op2->printAsOperand(OB);
     OB.printClose(']');
   }
 };
 
 class PostfixExpr : public Node {
   const Node *Child;
   const std::string_view Operator;
 
 public:
   PostfixExpr(const Node *Child_, std::string_view Operator_, Prec Prec_)
       : Node(KPostfixExpr, Prec_), Child(Child_), Operator(Operator_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Child, Operator, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     Child->printAsOperand(OB, getPrecedence(), true);
     OB += Operator;
   }
 };
 
 class ConditionalExpr : public Node {
   const Node *Cond;
   const Node *Then;
   const Node *Else;
 
 public:
   ConditionalExpr(const Node *Cond_, const Node *Then_, const Node *Else_,
                   Prec Prec_)
       : Node(KConditionalExpr, Prec_), Cond(Cond_), Then(Then_), Else(Else_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Cond, Then, Else, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     Cond->printAsOperand(OB, getPrecedence());
     OB += " ? ";
     Then->printAsOperand(OB);
     OB += " : ";
     Else->printAsOperand(OB, Prec::Assign, true);
   }
 };
 
 class MemberExpr : public Node {
   const Node *LHS;
   const std::string_view Kind;
   const Node *RHS;
 
 public:
   MemberExpr(const Node *LHS_, std::string_view Kind_, const Node *RHS_,
              Prec Prec_)
       : Node(KMemberExpr, Prec_), LHS(LHS_), Kind(Kind_), RHS(RHS_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(LHS, Kind, RHS, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     LHS->printAsOperand(OB, getPrecedence(), true);
     OB += Kind;
     RHS->printAsOperand(OB, getPrecedence(), false);
   }
 };
 
 class SubobjectExpr : public Node {
   const Node *Type;
   const Node *SubExpr;
   std::string_view Offset;
   NodeArray UnionSelectors;
   bool OnePastTheEnd;
 
 public:
   SubobjectExpr(const Node *Type_, const Node *SubExpr_,
                 std::string_view Offset_, NodeArray UnionSelectors_,
                 bool OnePastTheEnd_)
       : Node(KSubobjectExpr), Type(Type_), SubExpr(SubExpr_), Offset(Offset_),
         UnionSelectors(UnionSelectors_), OnePastTheEnd(OnePastTheEnd_) {}
 
   template<typename Fn> void match(Fn F) const {
     F(Type, SubExpr, Offset, UnionSelectors, OnePastTheEnd);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     SubExpr->print(OB);
     OB += ".<";
     Type->print(OB);
     OB += " at offset ";
     if (Offset.empty()) {
       OB += "0";
     } else if (Offset[0] == 'n') {
       OB += "-";
       OB += std::string_view(Offset.data() + 1, Offset.size() - 1);
     } else {
       OB += Offset;
     }
     OB += ">";
   }
 };
 
 class EnclosingExpr : public Node {
   const std::string_view Prefix;
   const Node *Infix;
   const std::string_view Postfix;
 
 public:
   EnclosingExpr(std::string_view Prefix_, const Node *Infix_,
                 Prec Prec_ = Prec::Primary)
       : Node(KEnclosingExpr, Prec_), Prefix(Prefix_), Infix(Infix_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Prefix, Infix, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += Prefix;
     OB.printOpen();
     Infix->print(OB);
     OB.printClose();
     OB += Postfix;
   }
 };
 
 class CastExpr : public Node {
   // cast_kind<to>(from)
   const std::string_view CastKind;
   const Node *To;
   const Node *From;
 
 public:
   CastExpr(std::string_view CastKind_, const Node *To_, const Node *From_,
            Prec Prec_)
       : Node(KCastExpr, Prec_), CastKind(CastKind_), To(To_), From(From_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(CastKind, To, From, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += CastKind;
     {
       ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
       OB += "<";
       To->printLeft(OB);
       OB += ">";
     }
     OB.printOpen();
     From->printAsOperand(OB);
     OB.printClose();
   }
 };
 
 class SizeofParamPackExpr : public Node {
   const Node *Pack;
 
 public:
   SizeofParamPackExpr(const Node *Pack_)
       : Node(KSizeofParamPackExpr), Pack(Pack_) {}
 
   template<typename Fn> void match(Fn F) const { F(Pack); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "sizeof...";
     OB.printOpen();
     ParameterPackExpansion PPE(Pack);
     PPE.printLeft(OB);
     OB.printClose();
   }
 };
 
 class CallExpr : public Node {
   const Node *Callee;
   NodeArray Args;
   bool IsParen; // (func)(args ...) ?
 
 public:
   CallExpr(const Node *Callee_, NodeArray Args_, bool IsParen_, Prec Prec_)
       : Node(KCallExpr, Prec_), Callee(Callee_), Args(Args_),
         IsParen(IsParen_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Callee, Args, IsParen, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     if (IsParen)
       OB.printOpen();
     Callee->print(OB);
     if (IsParen)
       OB.printClose();
     OB.printOpen();
     Args.printWithComma(OB);
     OB.printClose();
   }
 };
 
 class NewExpr : public Node {
   // new (expr_list) type(init_list)
   NodeArray ExprList;
   Node *Type;
   NodeArray InitList;
   bool IsGlobal; // ::operator new ?
   bool IsArray;  // new[] ?
 public:
   NewExpr(NodeArray ExprList_, Node *Type_, NodeArray InitList_, bool IsGlobal_,
           bool IsArray_, Prec Prec_)
       : Node(KNewExpr, Prec_), ExprList(ExprList_), Type(Type_),
         InitList(InitList_), IsGlobal(IsGlobal_), IsArray(IsArray_) {}
 
   template<typename Fn> void match(Fn F) const {
     F(ExprList, Type, InitList, IsGlobal, IsArray, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     if (IsGlobal)
       OB += "::";
     OB += "new";
     if (IsArray)
       OB += "[]";
     if (!ExprList.empty()) {
       OB.printOpen();
       ExprList.printWithComma(OB);
       OB.printClose();
     }
     OB += " ";
     Type->print(OB);
     if (!InitList.empty()) {
       OB.printOpen();
       InitList.printWithComma(OB);
       OB.printClose();
     }
   }
 };
 
 class DeleteExpr : public Node {
   Node *Op;
   bool IsGlobal;
   bool IsArray;
 
 public:
   DeleteExpr(Node *Op_, bool IsGlobal_, bool IsArray_, Prec Prec_)
       : Node(KDeleteExpr, Prec_), Op(Op_), IsGlobal(IsGlobal_),
         IsArray(IsArray_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Op, IsGlobal, IsArray, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     if (IsGlobal)
       OB += "::";
     OB += "delete";
     if (IsArray)
       OB += "[]";
     OB += ' ';
     Op->print(OB);
   }
 };
 
 class PrefixExpr : public Node {
   std::string_view Prefix;
   Node *Child;
 
 public:
   PrefixExpr(std::string_view Prefix_, Node *Child_, Prec Prec_)
       : Node(KPrefixExpr, Prec_), Prefix(Prefix_), Child(Child_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Prefix, Child, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += Prefix;
     Child->printAsOperand(OB, getPrecedence());
   }
 };
 
 class FunctionParam : public Node {
   std::string_view Number;
 
 public:
   FunctionParam(std::string_view Number_)
       : Node(KFunctionParam), Number(Number_) {}
 
   template<typename Fn> void match(Fn F) const { F(Number); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "fp";
     OB += Number;
   }
 };
 
 class ConversionExpr : public Node {
   const Node *Type;
   NodeArray Expressions;
 
 public:
   ConversionExpr(const Node *Type_, NodeArray Expressions_, Prec Prec_)
       : Node(KConversionExpr, Prec_), Type(Type_), Expressions(Expressions_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Type, Expressions, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     OB.printOpen();
     Type->print(OB);
     OB.printClose();
     OB.printOpen();
     Expressions.printWithComma(OB);
     OB.printClose();
   }
 };
 
 class PointerToMemberConversionExpr : public Node {
   const Node *Type;
   const Node *SubExpr;
   std::string_view Offset;
 
 public:
   PointerToMemberConversionExpr(const Node *Type_, const Node *SubExpr_,
                                 std::string_view Offset_, Prec Prec_)
       : Node(KPointerToMemberConversionExpr, Prec_), Type(Type_),
         SubExpr(SubExpr_), Offset(Offset_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Type, SubExpr, Offset, getPrecedence());
   }
 
   void printLeft(OutputBuffer &OB) const override {
     OB.printOpen();
     Type->print(OB);
     OB.printClose();
     OB.printOpen();
     SubExpr->print(OB);
     OB.printClose();
   }
 };
 
 class InitListExpr : public Node {
   const Node *Ty;
   NodeArray Inits;
 public:
   InitListExpr(const Node *Ty_, NodeArray Inits_)
       : Node(KInitListExpr), Ty(Ty_), Inits(Inits_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Inits); }
 
   void printLeft(OutputBuffer &OB) const override {
     if (Ty) {
       if (Ty->printInitListAsType(OB, Inits))
         return;
       Ty->print(OB);
     }
     OB += '{';
     Inits.printWithComma(OB);
     OB += '}';
   }
 };
 
 class BracedExpr : public Node {
   const Node *Elem;
   const Node *Init;
   bool IsArray;
 public:
   BracedExpr(const Node *Elem_, const Node *Init_, bool IsArray_)
       : Node(KBracedExpr), Elem(Elem_), Init(Init_), IsArray(IsArray_) {}
 
   template<typename Fn> void match(Fn F) const { F(Elem, Init, IsArray); }
 
   void printLeft(OutputBuffer &OB) const override {
     if (IsArray) {
       OB += '[';
       Elem->print(OB);
       OB += ']';
     } else {
       OB += '.';
       Elem->print(OB);
     }
     if (Init->getKind() != KBracedExpr && Init->getKind() != KBracedRangeExpr)
       OB += " = ";
     Init->print(OB);
   }
 };
 
 class BracedRangeExpr : public Node {
   const Node *First;
   const Node *Last;
   const Node *Init;
 public:
   BracedRangeExpr(const Node *First_, const Node *Last_, const Node *Init_)
       : Node(KBracedRangeExpr), First(First_), Last(Last_), Init(Init_) {}
 
   template<typename Fn> void match(Fn F) const { F(First, Last, Init); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += '[';
     First->print(OB);
     OB += " ... ";
     Last->print(OB);
     OB += ']';
     if (Init->getKind() != KBracedExpr && Init->getKind() != KBracedRangeExpr)
       OB += " = ";
     Init->print(OB);
   }
 };
 
 class FoldExpr : public Node {
   const Node *Pack, *Init;
   std::string_view OperatorName;
   bool IsLeftFold;
 
 public:
   FoldExpr(bool IsLeftFold_, std::string_view OperatorName_, const Node *Pack_,
            const Node *Init_)
       : Node(KFoldExpr), Pack(Pack_), Init(Init_), OperatorName(OperatorName_),
         IsLeftFold(IsLeftFold_) {}
 
   template<typename Fn> void match(Fn F) const {
     F(IsLeftFold, OperatorName, Pack, Init);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     auto PrintPack = [&] {
       OB.printOpen();
       ParameterPackExpansion(Pack).print(OB);
       OB.printClose();
     };
 
     OB.printOpen();
     // Either '[init op ]... op pack' or 'pack op ...[ op init]'
     // Refactored to '[(init|pack) op ]...[ op (pack|init)]'
     // Fold expr operands are cast-expressions
     if (!IsLeftFold || Init != nullptr) {
       // '(init|pack) op '
       if (IsLeftFold)
         Init->printAsOperand(OB, Prec::Cast, true);
       else
         PrintPack();
       OB << " " << OperatorName << " ";
     }
     OB << "...";
     if (IsLeftFold || Init != nullptr) {
       // ' op (init|pack)'
       OB << " " << OperatorName << " ";
       if (IsLeftFold)
         PrintPack();
       else
         Init->printAsOperand(OB, Prec::Cast, true);
     }
     OB.printClose();
   }
 };
 
 class ThrowExpr : public Node {
   const Node *Op;
 
 public:
   ThrowExpr(const Node *Op_) : Node(KThrowExpr), Op(Op_) {}
 
   template<typename Fn> void match(Fn F) const { F(Op); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "throw ";
     Op->print(OB);
   }
 };
 
 class BoolExpr : public Node {
   bool Value;
 
 public:
   BoolExpr(bool Value_) : Node(KBoolExpr), Value(Value_) {}
 
   template<typename Fn> void match(Fn F) const { F(Value); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += Value ? std::string_view("true") : std::string_view("false");
   }
 };
 
 class StringLiteral : public Node {
   const Node *Type;
 
 public:
   StringLiteral(const Node *Type_) : Node(KStringLiteral), Type(Type_) {}
 
   template<typename Fn> void match(Fn F) const { F(Type); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "\"<";
     Type->print(OB);
     OB += ">\"";
   }
 };
 
 class LambdaExpr : public Node {
   const Node *Type;
 
 public:
   LambdaExpr(const Node *Type_) : Node(KLambdaExpr), Type(Type_) {}
 
   template<typename Fn> void match(Fn F) const { F(Type); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "[]";
     if (Type->getKind() == KClosureTypeName)
       static_cast<const ClosureTypeName *>(Type)->printDeclarator(OB);
     OB += "{...}";
   }
 };
 
 class EnumLiteral : public Node {
   // ty(integer)
   const Node *Ty;
   std::string_view Integer;
 
 public:
   EnumLiteral(const Node *Ty_, std::string_view Integer_)
       : Node(KEnumLiteral), Ty(Ty_), Integer(Integer_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Integer); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB.printOpen();
     Ty->print(OB);
     OB.printClose();
 
     if (Integer[0] == 'n')
       OB << '-' << std::string_view(Integer.data() + 1, Integer.size() - 1);
     else
       OB << Integer;
   }
 };
 
 class IntegerLiteral : public Node {
   std::string_view Type;
   std::string_view Value;
 
 public:
   IntegerLiteral(std::string_view Type_, std::string_view Value_)
       : Node(KIntegerLiteral), Type(Type_), Value(Value_) {}
 
   template<typename Fn> void match(Fn F) const { F(Type, Value); }
 
   void printLeft(OutputBuffer &OB) const override {
     if (Type.size() > 3) {
       OB.printOpen();
       OB += Type;
       OB.printClose();
     }
 
     if (Value[0] == 'n')
       OB << '-' << std::string_view(Value.data() + 1, Value.size() - 1);
     else
       OB += Value;
 
     if (Type.size() <= 3)
       OB += Type;
   }
 
   std::string_view value() const { return Value; }
 };
 
 class RequiresExpr : public Node {
   NodeArray Parameters;
   NodeArray Requirements;
 public:
   RequiresExpr(NodeArray Parameters_, NodeArray Requirements_)
       : Node(KRequiresExpr), Parameters(Parameters_),
         Requirements(Requirements_) {}
 
   template<typename Fn> void match(Fn F) const { F(Parameters, Requirements); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += "requires";
     if (!Parameters.empty()) {
       OB += ' ';
       OB.printOpen();
       Parameters.printWithComma(OB);
       OB.printClose();
     }
     OB += ' ';
     OB.printOpen('{');
     for (const Node *Req : Requirements) {
       Req->print(OB);
     }
     OB += ' ';
     OB.printClose('}');
   }
 };
 
 class ExprRequirement : public Node {
   const Node *Expr;
   bool IsNoexcept;
   const Node *TypeConstraint;
 public:
   ExprRequirement(const Node *Expr_, bool IsNoexcept_,
                   const Node *TypeConstraint_)
       : Node(KExprRequirement), Expr(Expr_), IsNoexcept(IsNoexcept_),
         TypeConstraint(TypeConstraint_) {}
 
   template <typename Fn> void match(Fn F) const {
     F(Expr, IsNoexcept, TypeConstraint);
   }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += " ";
     if (IsNoexcept || TypeConstraint)
       OB.printOpen('{');
     Expr->print(OB);
     if (IsNoexcept || TypeConstraint)
       OB.printClose('}');
     if (IsNoexcept)
       OB += " noexcept";
     if (TypeConstraint) {
       OB += " -> ";
       TypeConstraint->print(OB);
     }
     OB += ';';
   }
 };
 
 class TypeRequirement : public Node {
   const Node *Type;
 public:
   TypeRequirement(const Node *Type_)
       : Node(KTypeRequirement), Type(Type_) {}
 
   template <typename Fn> void match(Fn F) const { F(Type); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += " typename ";
     Type->print(OB);
     OB += ';';
   }
 };
 
 class NestedRequirement : public Node {
   const Node *Constraint;
 public:
   NestedRequirement(const Node *Constraint_)
       : Node(KNestedRequirement), Constraint(Constraint_) {}
 
   template <typename Fn> void match(Fn F) const { F(Constraint); }
 
   void printLeft(OutputBuffer &OB) const override {
     OB += " requires ";
     Constraint->print(OB);
     OB += ';';
   }
 };
 
 template <class Float> struct FloatData;
 
 namespace float_literal_impl {
 constexpr Node::Kind getFloatLiteralKind(float *) {
   return Node::KFloatLiteral;
 }
 constexpr Node::Kind getFloatLiteralKind(double *) {
   return Node::KDoubleLiteral;
 }
 constexpr Node::Kind getFloatLiteralKind(long double *) {
   return Node::KLongDoubleLiteral;
 }
 }
 
 template <class Float> class FloatLiteralImpl : public Node {
   const std::string_view Contents;
 
   static constexpr Kind KindForClass =
       float_literal_impl::getFloatLiteralKind((Float *)nullptr);
 
 public:
   FloatLiteralImpl(std::string_view Contents_)
       : Node(KindForClass), Contents(Contents_) {}
 
   template<typename Fn> void match(Fn F) const { F(Contents); }
 
   void printLeft(OutputBuffer &OB) const override {
     const size_t N = FloatData<Float>::mangled_size;
     if (Contents.size() >= N) {
       union {
         Float value;
         char buf[sizeof(Float)];
       };
       const char *t = Contents.data();
       const char *last = t + N;
       char *e = buf;
       for (; t != last; ++t, ++e) {
         unsigned d1 = isdigit(*t) ? static_cast<unsigned>(*t - '0')
                                   : static_cast<unsigned>(*t - 'a' + 10);
         ++t;
         unsigned d0 = isdigit(*t) ? static_cast<unsigned>(*t - '0')
                                   : static_cast<unsigned>(*t - 'a' + 10);
         *e = static_cast<char>((d1 << 4) + d0);
       }
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
       std::reverse(buf, e);
 #endif
       char num[FloatData<Float>::max_demangled_size] = {0};
       int n = snprintf(num, sizeof(num), FloatData<Float>::spec, value);
       OB += std::string_view(num, n);
     }
   }
 };
 
 using FloatLiteral = FloatLiteralImpl<float>;
 using DoubleLiteral = FloatLiteralImpl<double>;
 using LongDoubleLiteral = FloatLiteralImpl<long double>;
 
 /// Visit the node. Calls \c F(P), where \c P is the node cast to the
 /// appropriate derived class.
 template<typename Fn>
 void Node::visit(Fn F) const {
   switch (K) {
 #define NODE(X)                                                                \
   case K##X:                                                                   \
     return F(static_cast<const X *>(this));
 #include "ItaniumNodes.def"
   }
   DEMANGLE_ASSERT(0, "unknown mangling node kind");
 }
 
 /// Determine the kind of a node from its type.
 template<typename NodeT> struct NodeKind;
 #define NODE(X)                                                                \
   template <> struct NodeKind<X> {                                             \
     static constexpr Node::Kind Kind = Node::K##X;                             \
     static constexpr const char *name() { return #X; }                         \
   };
 #include "ItaniumNodes.def"
 
 inline bool NodeArray::printAsString(OutputBuffer &OB) const {
   auto StartPos = OB.getCurrentPosition();
   auto Fail = [&OB, StartPos] {
     OB.setCurrentPosition(StartPos);
     return false;
   };
 
   OB += '"';
   bool LastWasNumericEscape = false;
   for (const Node *Element : *this) {
     if (Element->getKind() != Node::KIntegerLiteral)
       return Fail();
     int integer_value = 0;
     for (char c : static_cast<const IntegerLiteral *>(Element)->value()) {
       if (c < '0' || c > '9' || integer_value > 25)
         return Fail();
       integer_value *= 10;
       integer_value += c - '0';
     }
     if (integer_value > 255)
       return Fail();
 
     // Insert a `""` to avoid accidentally extending a numeric escape.
     if (LastWasNumericEscape) {
       if ((integer_value >= '0' && integer_value <= '9') ||
           (integer_value >= 'a' && integer_value <= 'f') ||
           (integer_value >= 'A' && integer_value <= 'F')) {
         OB += "\"\"";
       }
     }
 
     LastWasNumericEscape = false;
 
     // Determine how to print this character.
     switch (integer_value) {
     case '\a':
       OB += "\\a";
       break;
     case '\b':
       OB += "\\b";
       break;
     case '\f':
       OB += "\\f";
       break;
     case '\n':
       OB += "\\n";
       break;
     case '\r':
       OB += "\\r";
       break;
     case '\t':
       OB += "\\t";
       break;
     case '\v':
       OB += "\\v";
       break;
 
     case '"':
       OB += "\\\"";
       break;
     case '\\':
       OB += "\\\\";
       break;
 
     default:
       // We assume that the character is ASCII, and use a numeric escape for all
       // remaining non-printable ASCII characters.
       if (integer_value < 32 || integer_value == 127) {
         constexpr char Hex[] = "0123456789ABCDEF";
         OB += '\\';
         if (integer_value > 7)
           OB += 'x';
         if (integer_value >= 16)
           OB += Hex[integer_value >> 4];
         OB += Hex[integer_value & 0xF];
         LastWasNumericEscape = true;
         break;
       }
 
       // Assume all remaining characters are directly printable.
       OB += (char)integer_value;
       break;
     }
   }
   OB += '"';
   return true;
 }
 
 template <typename Derived, typename Alloc> struct AbstractManglingParser {
   const char *First;
   const char *Last;
 
   // Name stack, this is used by the parser to hold temporary names that were
   // parsed. The parser collapses multiple names into new nodes to construct
   // the AST. Once the parser is finished, names.size() == 1.
   PODSmallVector<Node *, 32> Names;
 
   // Substitution table. Itanium supports name substitutions as a means of
   // compression. The string "S42_" refers to the 44nd entry (base-36) in this
   // table.
   PODSmallVector<Node *, 32> Subs;
 
   // A list of template argument values corresponding to a template parameter
   // list.
   using TemplateParamList = PODSmallVector<Node *, 8>;
 
   class ScopedTemplateParamList {
     AbstractManglingParser *Parser;
     size_t OldNumTemplateParamLists;
     TemplateParamList Params;
 
   public:
     ScopedTemplateParamList(AbstractManglingParser *TheParser)
         : Parser(TheParser),
           OldNumTemplateParamLists(TheParser->TemplateParams.size()) {
       Parser->TemplateParams.push_back(&Params);
     }
     ~ScopedTemplateParamList() {
       DEMANGLE_ASSERT(Parser->TemplateParams.size() >= OldNumTemplateParamLists,
                       "");
       Parser->TemplateParams.shrinkToSize(OldNumTemplateParamLists);
     }
     TemplateParamList *params() { return &Params; }
   };
 
   // Template parameter table. Like the above, but referenced like "T42_".
   // This has a smaller size compared to Subs and Names because it can be
   // stored on the stack.
   TemplateParamList OuterTemplateParams;
 
   // Lists of template parameters indexed by template parameter depth,
   // referenced like "TL2_4_". If nonempty, element 0 is always
   // OuterTemplateParams; inner elements are always template parameter lists of
   // lambda expressions. For a generic lambda with no explicit template
   // parameter list, the corresponding parameter list pointer will be null.
   PODSmallVector<TemplateParamList *, 4> TemplateParams;
 
   class SaveTemplateParams {
     AbstractManglingParser *Parser;
     decltype(TemplateParams) OldParams;
     decltype(OuterTemplateParams) OldOuterParams;
 
   public:
     SaveTemplateParams(AbstractManglingParser *TheParser) : Parser(TheParser) {
       OldParams = std::move(Parser->TemplateParams);
       OldOuterParams = std::move(Parser->OuterTemplateParams);
       Parser->TemplateParams.clear();
       Parser->OuterTemplateParams.clear();
     }
     ~SaveTemplateParams() {
       Parser->TemplateParams = std::move(OldParams);
       Parser->OuterTemplateParams = std::move(OldOuterParams);
     }
   };
 
   // Set of unresolved forward <template-param> references. These can occur in a
   // conversion operator's type, and are resolved in the enclosing <encoding>.
   PODSmallVector<ForwardTemplateReference *, 4> ForwardTemplateRefs;
 
   bool TryToParseTemplateArgs = true;
   bool PermitForwardTemplateReferences = false;
   bool HasIncompleteTemplateParameterTracking = false;
   size_t ParsingLambdaParamsAtLevel = (size_t)-1;
 
   unsigned NumSyntheticTemplateParameters[3] = {};
 
   Alloc ASTAllocator;
 
   AbstractManglingParser(const char *First_, const char *Last_)
       : First(First_), Last(Last_) {}
 
   Derived &getDerived() { return static_cast<Derived &>(*this); }
 
   void reset(const char *First_, const char *Last_) {
     First = First_;
     Last = Last_;
     Names.clear();
     Subs.clear();
     TemplateParams.clear();
     ParsingLambdaParamsAtLevel = (size_t)-1;
     TryToParseTemplateArgs = true;
     PermitForwardTemplateReferences = false;
     for (int I = 0; I != 3; ++I)
       NumSyntheticTemplateParameters[I] = 0;
     ASTAllocator.reset();
   }
 
   template <class T, class... Args> Node *make(Args &&... args) {
     return ASTAllocator.template makeNode<T>(std::forward<Args>(args)...);
   }
 
   template <class It> NodeArray makeNodeArray(It begin, It end) {
     size_t sz = static_cast<size_t>(end - begin);
     void *mem = ASTAllocator.allocateNodeArray(sz);
     Node **data = new (mem) Node *[sz];
     std::copy(begin, end, data);
     return NodeArray(data, sz);
   }
 
   NodeArray popTrailingNodeArray(size_t FromPosition) {
     DEMANGLE_ASSERT(FromPosition <= Names.size(), "");
     NodeArray res =
         makeNodeArray(Names.begin() + (long)FromPosition, Names.end());
     Names.shrinkToSize(FromPosition);
     return res;
   }
 
   bool consumeIf(std::string_view S) {
     if (starts_with(std::string_view(First, Last - First), S)) {
       First += S.size();
       return true;
     }
     return false;
   }
 
   bool consumeIf(char C) {
     if (First != Last && *First == C) {
       ++First;
       return true;
     }
     return false;
   }
 
   char consume() { return First != Last ? *First++ : '\0'; }
 
   char look(unsigned Lookahead = 0) const {
     if (static_cast<size_t>(Last - First) <= Lookahead)
       return '\0';
     return First[Lookahead];
   }
 
   size_t numLeft() const { return static_cast<size_t>(Last - First); }
 
   std::string_view parseNumber(bool AllowNegative = false);
   Qualifiers parseCVQualifiers();
   bool parsePositiveInteger(size_t *Out);
   std::string_view parseBareSourceName();
 
   bool parseSeqId(size_t *Out);
   Node *parseSubstitution();
   Node *parseTemplateParam();
   Node *parseTemplateParamDecl(TemplateParamList *Params);
   Node *parseTemplateArgs(bool TagTemplates = false);
   Node *parseTemplateArg();
 
   bool isTemplateParamDecl() {
     return look() == 'T' &&
            std::string_view("yptnk").find(look(1)) != std::string_view::npos;
   }
 
   /// Parse the <expression> production.
   Node *parseExpr();
   Node *parsePrefixExpr(std::string_view Kind, Node::Prec Prec);
   Node *parseBinaryExpr(std::string_view Kind, Node::Prec Prec);
   Node *parseIntegerLiteral(std::string_view Lit);
   Node *parseExprPrimary();
   template <class Float> Node *parseFloatingLiteral();
   Node *parseFunctionParam();
   Node *parseConversionExpr();
   Node *parseBracedExpr();
   Node *parseFoldExpr();
   Node *parsePointerToMemberConversionExpr(Node::Prec Prec);
   Node *parseSubobjectExpr();
   Node *parseConstraintExpr();
   Node *parseRequiresExpr();
 
   /// Parse the <type> production.
   Node *parseType();
   Node *parseFunctionType();
   Node *parseVectorType();
   Node *parseDecltype();
   Node *parseArrayType();
   Node *parsePointerToMemberType();
   Node *parseClassEnumType();
   Node *parseQualifiedType();
 
   Node *parseEncoding(bool ParseParams = true);
   bool parseCallOffset();
   Node *parseSpecialName();
 
   /// Holds some extra information about a <name> that is being parsed. This
   /// information is only pertinent if the <name> refers to an <encoding>.
   struct NameState {
     bool CtorDtorConversion = false;
     bool EndsWithTemplateArgs = false;
     Qualifiers CVQualifiers = QualNone;
     FunctionRefQual ReferenceQualifier = FrefQualNone;
     size_t ForwardTemplateRefsBegin;
     bool HasExplicitObjectParameter = false;
 
     NameState(AbstractManglingParser *Enclosing)
         : ForwardTemplateRefsBegin(Enclosing->ForwardTemplateRefs.size()) {}
   };
 
   bool resolveForwardTemplateRefs(NameState &State) {
     size_t I = State.ForwardTemplateRefsBegin;
     size_t E = ForwardTemplateRefs.size();
     for (; I < E; ++I) {
       size_t Idx = ForwardTemplateRefs[I]->Index;
       if (TemplateParams.empty() || !TemplateParams[0] ||
           Idx >= TemplateParams[0]->size())
         return true;
       ForwardTemplateRefs[I]->Ref = (*TemplateParams[0])[Idx];
     }
     ForwardTemplateRefs.shrinkToSize(State.ForwardTemplateRefsBegin);
     return false;
   }
 
   /// Parse the <name> production>
   Node *parseName(NameState *State = nullptr);
   Node *parseLocalName(NameState *State);
   Node *parseOperatorName(NameState *State);
   bool parseModuleNameOpt(ModuleName *&Module);
   Node *parseUnqualifiedName(NameState *State, Node *Scope, ModuleName *Module);
   Node *parseUnnamedTypeName(NameState *State);
   Node *parseSourceName(NameState *State);
   Node *parseUnscopedName(NameState *State, bool *isSubstName);
   Node *parseNestedName(NameState *State);
   Node *parseCtorDtorName(Node *&SoFar, NameState *State);
 
   Node *parseAbiTags(Node *N);
 
   struct OperatorInfo {
     enum OIKind : unsigned char {
       Prefix,      // Prefix unary: @ expr
       Postfix,     // Postfix unary: expr @
       Binary,      // Binary: lhs @ rhs
       Array,       // Array index:  lhs [ rhs ]
       Member,      // Member access: lhs @ rhs
       New,         // New
       Del,         // Delete
       Call,        // Function call: expr (expr*)
       CCast,       // C cast: (type)expr
       Conditional, // Conditional: expr ? expr : expr
       NameOnly,    // Overload only, not allowed in expression.
       // Below do not have operator names
       NamedCast, // Named cast, @<type>(expr)
       OfIdOp,    // alignof, sizeof, typeid
 
       Unnameable = NamedCast,
     };
     char Enc[2];      // Encoding
     OIKind Kind;      // Kind of operator
     bool Flag : 1;    // Entry-specific flag
     Node::Prec Prec : 7; // Precedence
     const char *Name; // Spelling
 
   public:
     constexpr OperatorInfo(const char (&E)[3], OIKind K, bool F, Node::Prec P,
                            const char *N)
         : Enc{E[0], E[1]}, Kind{K}, Flag{F}, Prec{P}, Name{N} {}
 
   public:
     bool operator<(const OperatorInfo &Other) const {
       return *this < Other.Enc;
     }
     bool operator<(const char *Peek) const {
       return Enc[0] < Peek[0] || (Enc[0] == Peek[0] && Enc[1] < Peek[1]);
     }
     bool operator==(const char *Peek) const {
       return Enc[0] == Peek[0] && Enc[1] == Peek[1];
     }
     bool operator!=(const char *Peek) const { return !this->operator==(Peek); }
 
   public:
     std::string_view getSymbol() const {
       std::string_view Res = Name;
       if (Kind < Unnameable) {
         DEMANGLE_ASSERT(starts_with(Res, "operator"),
                         "operator name does not start with 'operator'");
         Res.remove_prefix(sizeof("operator") - 1);
         if (starts_with(Res, ' '))
           Res.remove_prefix(1);
       }
       return Res;
     }
     std::string_view getName() const { return Name; }
     OIKind getKind() const { return Kind; }
     bool getFlag() const { return Flag; }
     Node::Prec getPrecedence() const { return Prec; }
   };
   static const OperatorInfo Ops[];
   static const size_t NumOps;
   const OperatorInfo *parseOperatorEncoding();
 
   /// Parse the <unresolved-name> production.
   Node *parseUnresolvedName(bool Global);
   Node *parseSimpleId();
   Node *parseBaseUnresolvedName();
   Node *parseUnresolvedType();
   Node *parseDestructorName();
 
   /// Top-level entry point into the parser.
   Node *parse(bool ParseParams = true);
 };
 
 const char* parse_discriminator(const char* first, const char* last);
 
 // <name> ::= <nested-name> // N
 //        ::= <local-name> # See Scope Encoding below  // Z
 //        ::= <unscoped-template-name> <template-args>
 //        ::= <unscoped-name>
 //
 // <unscoped-template-name> ::= <unscoped-name>
 //                          ::= <substitution>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseName(NameState *State) {
   if (look() == 'N')
     return getDerived().parseNestedName(State);
   if (look() == 'Z')
     return getDerived().parseLocalName(State);
 
   Node *Result = nullptr;
   bool IsSubst = false;
 
   Result = getDerived().parseUnscopedName(State, &IsSubst);
   if (!Result)
     return nullptr;
 
   if (look() == 'I') {
     //        ::= <unscoped-template-name> <template-args>
     if (!IsSubst)
       // An unscoped-template-name is substitutable.
       Subs.push_back(Result);
     Node *TA = getDerived().parseTemplateArgs(State != nullptr);
     if (TA == nullptr)
       return nullptr;
     if (State)
       State->EndsWithTemplateArgs = true;
     Result = make<NameWithTemplateArgs>(Result, TA);
   } else if (IsSubst) {
     // The substitution case must be followed by <template-args>.
     return nullptr;
   }
 
   return Result;
 }
 
 // <local-name> := Z <function encoding> E <entity name> [<discriminator>]
 //              := Z <function encoding> E s [<discriminator>]
 //              := Z <function encoding> Ed [ <parameter number> ] _ <entity name>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseLocalName(NameState *State) {
   if (!consumeIf('Z'))
     return nullptr;
   Node *Encoding = getDerived().parseEncoding();
   if (Encoding == nullptr || !consumeIf('E'))
     return nullptr;
 
   if (consumeIf('s')) {
     First = parse_discriminator(First, Last);
     auto *StringLitName = make<NameType>("string literal");
     if (!StringLitName)
       return nullptr;
     return make<LocalName>(Encoding, StringLitName);
   }
 
   // The template parameters of the inner name are unrelated to those of the
   // enclosing context.
   SaveTemplateParams SaveTemplateParamsScope(this);
 
   if (consumeIf('d')) {
     parseNumber(true);
     if (!consumeIf('_'))
       return nullptr;
     Node *N = getDerived().parseName(State);
     if (N == nullptr)
       return nullptr;
     return make<LocalName>(Encoding, N);
   }
 
   Node *Entity = getDerived().parseName(State);
   if (Entity == nullptr)
     return nullptr;
   First = parse_discriminator(First, Last);
   return make<LocalName>(Encoding, Entity);
 }
 
 // <unscoped-name> ::= <unqualified-name>
 //                 ::= St <unqualified-name>   # ::std::
 // [*] extension
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseUnscopedName(NameState *State,
                                                           bool *IsSubst) {
 
   Node *Std = nullptr;
   if (consumeIf("St")) {
     Std = make<NameType>("std");
     if (Std == nullptr)
       return nullptr;
   }
 
   Node *Res = nullptr;
   ModuleName *Module = nullptr;
   if (look() == 'S') {
     Node *S = getDerived().parseSubstitution();
     if (!S)
       return nullptr;
     if (S->getKind() == Node::KModuleName)
       Module = static_cast<ModuleName *>(S);
     else if (IsSubst && Std == nullptr) {
       Res = S;
       *IsSubst = true;
     } else {
       return nullptr;
     }
   }
 
   if (Res == nullptr || Std != nullptr) {
     Res = getDerived().parseUnqualifiedName(State, Std, Module);
   }
 
   return Res;
 }
 
 // <unqualified-name> ::= [<module-name>] F? L? <operator-name> [<abi-tags>]
 //                    ::= [<module-name>] <ctor-dtor-name> [<abi-tags>]
 //                    ::= [<module-name>] F? L? <source-name> [<abi-tags>]
 //                    ::= [<module-name>] L? <unnamed-type-name> [<abi-tags>]
 //          # structured binding declaration
 //                    ::= [<module-name>] L? DC <source-name>+ E
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseUnqualifiedName(
     NameState *State, Node *Scope, ModuleName *Module) {
   if (getDerived().parseModuleNameOpt(Module))
     return nullptr;
 
   bool IsMemberLikeFriend = Scope && consumeIf('F');
 
   consumeIf('L');
 
   Node *Result;
   if (look() >= '1' && look() <= '9') {
     Result = getDerived().parseSourceName(State);
   } else if (look() == 'U') {
     Result = getDerived().parseUnnamedTypeName(State);
   } else if (consumeIf("DC")) {
     // Structured binding
     size_t BindingsBegin = Names.size();
     do {
       Node *Binding = getDerived().parseSourceName(State);
       if (Binding == nullptr)
         return nullptr;
       Names.push_back(Binding);
     } while (!consumeIf('E'));
     Result = make<StructuredBindingName>(popTrailingNodeArray(BindingsBegin));
   } else if (look() == 'C' || look() == 'D') {
     // A <ctor-dtor-name>.
     if (Scope == nullptr || Module != nullptr)
       return nullptr;
     Result = getDerived().parseCtorDtorName(Scope, State);
   } else {
     Result = getDerived().parseOperatorName(State);
   }
 
   if (Result != nullptr && Module != nullptr)
     Result = make<ModuleEntity>(Module, Result);
   if (Result != nullptr)
     Result = getDerived().parseAbiTags(Result);
   if (Result != nullptr && IsMemberLikeFriend)
     Result = make<MemberLikeFriendName>(Scope, Result);
   else if (Result != nullptr && Scope != nullptr)
     Result = make<NestedName>(Scope, Result);
 
   return Result;
 }
 
 // <module-name> ::= <module-subname>
 //       ::= <module-name> <module-subname>
 //       ::= <substitution>  # passed in by caller
 // <module-subname> ::= W <source-name>
 //          ::= W P <source-name>
 template <typename Derived, typename Alloc>
 bool AbstractManglingParser<Derived, Alloc>::parseModuleNameOpt(
     ModuleName *&Module) {
   while (consumeIf('W')) {
     bool IsPartition = consumeIf('P');
     Node *Sub = getDerived().parseSourceName(nullptr);
     if (!Sub)
       return true;
     Module =
         static_cast<ModuleName *>(make<ModuleName>(Module, Sub, IsPartition));
     Subs.push_back(Module);
   }
 
   return false;
 }
 
 // <unnamed-type-name> ::= Ut [<nonnegative number>] _
 //                     ::= <closure-type-name>
 //
 // <closure-type-name> ::= Ul <lambda-sig> E [ <nonnegative number> ] _
 //
 // <lambda-sig> ::= <template-param-decl>* [Q <requires-clause expression>]
 //                  <parameter type>+  # or "v" if the lambda has no parameters
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseUnnamedTypeName(NameState *State) {
   // <template-params> refer to the innermost <template-args>. Clear out any
   // outer args that we may have inserted into TemplateParams.
   if (State != nullptr)
     TemplateParams.clear();
 
   if (consumeIf("Ut")) {
     std::string_view Count = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<UnnamedTypeName>(Count);
   }
   if (consumeIf("Ul")) {
     ScopedOverride<size_t> SwapParams(ParsingLambdaParamsAtLevel,
                                       TemplateParams.size());
     ScopedTemplateParamList LambdaTemplateParams(this);
 
     size_t ParamsBegin = Names.size();
     while (getDerived().isTemplateParamDecl()) {
       Node *T =
           getDerived().parseTemplateParamDecl(LambdaTemplateParams.params());
       if (T == nullptr)
         return nullptr;
       Names.push_back(T);
     }
     NodeArray TempParams = popTrailingNodeArray(ParamsBegin);
 
     // FIXME: If TempParams is empty and none of the function parameters
     // includes 'auto', we should remove LambdaTemplateParams from the
     // TemplateParams list. Unfortunately, we don't find out whether there are
     // any 'auto' parameters until too late in an example such as:
     //
     //   template<typename T> void f(
     //       decltype([](decltype([]<typename T>(T v) {}),
     //                   auto) {})) {}
     //   template<typename T> void f(
     //       decltype([](decltype([]<typename T>(T w) {}),
     //                   int) {})) {}
     //
     // Here, the type of v is at level 2 but the type of w is at level 1. We
     // don't find this out until we encounter the type of the next parameter.
     //
     // However, compilers can't actually cope with the former example in
     // practice, and it's likely to be made ill-formed in future, so we don't
     // need to support it here.
     //
     // If we encounter an 'auto' in the function parameter types, we will
     // recreate a template parameter scope for it, but any intervening lambdas
     // will be parsed in the 'wrong' template parameter depth.
     if (TempParams.empty())
       TemplateParams.pop_back();
 
     Node *Requires1 = nullptr;
     if (consumeIf('Q')) {
       Requires1 = getDerived().parseConstraintExpr();
       if (Requires1 == nullptr)
         return nullptr;
     }
 
     if (!consumeIf("v")) {
       do {
         Node *P = getDerived().parseType();
         if (P == nullptr)
           return nullptr;
         Names.push_back(P);
       } while (look() != 'E' && look() != 'Q');
     }
     NodeArray Params = popTrailingNodeArray(ParamsBegin);
 
     Node *Requires2 = nullptr;
     if (consumeIf('Q')) {
       Requires2 = getDerived().parseConstraintExpr();
       if (Requires2 == nullptr)
         return nullptr;
     }
 
     if (!consumeIf('E'))
       return nullptr;
 
     std::string_view Count = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<ClosureTypeName>(TempParams, Requires1, Params, Requires2,
                                  Count);
   }
   if (consumeIf("Ub")) {
     (void)parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<NameType>("'block-literal'");
   }
   return nullptr;
 }
 
 // <source-name> ::= <positive length number> <identifier>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseSourceName(NameState *) {
   size_t Length = 0;
   if (parsePositiveInteger(&Length))
     return nullptr;
   if (numLeft() < Length || Length == 0)
     return nullptr;
   std::string_view Name(First, Length);
   First += Length;
   if (starts_with(Name, "_GLOBAL__N"))
     return make<NameType>("(anonymous namespace)");
   return make<NameType>(Name);
 }
 
 // Operator encodings
 template <typename Derived, typename Alloc>
 const typename AbstractManglingParser<
     Derived, Alloc>::OperatorInfo AbstractManglingParser<Derived,
                                                          Alloc>::Ops[] = {
     // Keep ordered by encoding
     {"aN", OperatorInfo::Binary, false, Node::Prec::Assign, "operator&="},
     {"aS", OperatorInfo::Binary, false, Node::Prec::Assign, "operator="},
     {"aa", OperatorInfo::Binary, false, Node::Prec::AndIf, "operator&&"},
     {"ad", OperatorInfo::Prefix, false, Node::Prec::Unary, "operator&"},
     {"an", OperatorInfo::Binary, false, Node::Prec::And, "operator&"},
     {"at", OperatorInfo::OfIdOp, /*Type*/ true, Node::Prec::Unary, "alignof "},
     {"aw", OperatorInfo::NameOnly, false, Node::Prec::Primary,
      "operator co_await"},
     {"az", OperatorInfo::OfIdOp, /*Type*/ false, Node::Prec::Unary, "alignof "},
     {"cc", OperatorInfo::NamedCast, false, Node::Prec::Postfix, "const_cast"},
     {"cl", OperatorInfo::Call, /*Paren*/ false, Node::Prec::Postfix,
      "operator()"},
     {"cm", OperatorInfo::Binary, false, Node::Prec::Comma, "operator,"},
     {"co", OperatorInfo::Prefix, false, Node::Prec::Unary, "operator~"},
     {"cp", OperatorInfo::Call, /*Paren*/ true, Node::Prec::Postfix,
      "operator()"},
     {"cv", OperatorInfo::CCast, false, Node::Prec::Cast, "operator"}, // C Cast
     {"dV", OperatorInfo::Binary, false, Node::Prec::Assign, "operator/="},
     {"da", OperatorInfo::Del, /*Ary*/ true, Node::Prec::Unary,
      "operator delete[]"},
     {"dc", OperatorInfo::NamedCast, false, Node::Prec::Postfix, "dynamic_cast"},
     {"de", OperatorInfo::Prefix, false, Node::Prec::Unary, "operator*"},
     {"dl", OperatorInfo::Del, /*Ary*/ false, Node::Prec::Unary,
      "operator delete"},
     {"ds", OperatorInfo::Member, /*Named*/ false, Node::Prec::PtrMem,
      "operator.*"},
     {"dt", OperatorInfo::Member, /*Named*/ false, Node::Prec::Postfix,
      "operator."},
     {"dv", OperatorInfo::Binary, false, Node::Prec::Assign, "operator/"},
     {"eO", OperatorInfo::Binary, false, Node::Prec::Assign, "operator^="},
     {"eo", OperatorInfo::Binary, false, Node::Prec::Xor, "operator^"},
     {"eq", OperatorInfo::Binary, false, Node::Prec::Equality, "operator=="},
     {"ge", OperatorInfo::Binary, false, Node::Prec::Relational, "operator>="},
     {"gt", OperatorInfo::Binary, false, Node::Prec::Relational, "operator>"},
     {"ix", OperatorInfo::Array, false, Node::Prec::Postfix, "operator[]"},
     {"lS", OperatorInfo::Binary, false, Node::Prec::Assign, "operator<<="},
     {"le", OperatorInfo::Binary, false, Node::Prec::Relational, "operator<="},
     {"ls", OperatorInfo::Binary, false, Node::Prec::Shift, "operator<<"},
     {"lt", OperatorInfo::Binary, false, Node::Prec::Relational, "operator<"},
     {"mI", OperatorInfo::Binary, false, Node::Prec::Assign, "operator-="},
     {"mL", OperatorInfo::Binary, false, Node::Prec::Assign, "operator*="},
     {"mi", OperatorInfo::Binary, false, Node::Prec::Additive, "operator-"},
     {"ml", OperatorInfo::Binary, false, Node::Prec::Multiplicative,
      "operator*"},
     {"mm", OperatorInfo::Postfix, false, Node::Prec::Postfix, "operator--"},
     {"na", OperatorInfo::New, /*Ary*/ true, Node::Prec::Unary,
      "operator new[]"},
     {"ne", OperatorInfo::Binary, false, Node::Prec::Equality, "operator!="},
     {"ng", OperatorInfo::Prefix, false, Node::Prec::Unary, "operator-"},
     {"nt", OperatorInfo::Prefix, false, Node::Prec::Unary, "operator!"},
     {"nw", OperatorInfo::New, /*Ary*/ false, Node::Prec::Unary, "operator new"},
     {"oR", OperatorInfo::Binary, false, Node::Prec::Assign, "operator|="},
     {"oo", OperatorInfo::Binary, false, Node::Prec::OrIf, "operator||"},
     {"or", OperatorInfo::Binary, false, Node::Prec::Ior, "operator|"},
     {"pL", OperatorInfo::Binary, false, Node::Prec::Assign, "operator+="},
     {"pl", OperatorInfo::Binary, false, Node::Prec::Additive, "operator+"},
     {"pm", OperatorInfo::Member, /*Named*/ false, Node::Prec::PtrMem,
      "operator->*"},
     {"pp", OperatorInfo::Postfix, false, Node::Prec::Postfix, "operator++"},
     {"ps", OperatorInfo::Prefix, false, Node::Prec::Unary, "operator+"},
     {"pt", OperatorInfo::Member, /*Named*/ true, Node::Prec::Postfix,
      "operator->"},
     {"qu", OperatorInfo::Conditional, false, Node::Prec::Conditional,
      "operator?"},
     {"rM", OperatorInfo::Binary, false, Node::Prec::Assign, "operator%="},
     {"rS", OperatorInfo::Binary, false, Node::Prec::Assign, "operator>>="},
     {"rc", OperatorInfo::NamedCast, false, Node::Prec::Postfix,
      "reinterpret_cast"},
     {"rm", OperatorInfo::Binary, false, Node::Prec::Multiplicative,
      "operator%"},
     {"rs", OperatorInfo::Binary, false, Node::Prec::Shift, "operator>>"},
     {"sc", OperatorInfo::NamedCast, false, Node::Prec::Postfix, "static_cast"},
     {"ss", OperatorInfo::Binary, false, Node::Prec::Spaceship, "operator<=>"},
     {"st", OperatorInfo::OfIdOp, /*Type*/ true, Node::Prec::Unary, "sizeof "},
     {"sz", OperatorInfo::OfIdOp, /*Type*/ false, Node::Prec::Unary, "sizeof "},
     {"te", OperatorInfo::OfIdOp, /*Type*/ false, Node::Prec::Postfix,
      "typeid "},
     {"ti", OperatorInfo::OfIdOp, /*Type*/ true, Node::Prec::Postfix, "typeid "},
 };
 template <typename Derived, typename Alloc>
 const size_t AbstractManglingParser<Derived, Alloc>::NumOps = sizeof(Ops) /
                                                               sizeof(Ops[0]);
 
 // If the next 2 chars are an operator encoding, consume them and return their
 // OperatorInfo.  Otherwise return nullptr.
 template <typename Derived, typename Alloc>
 const typename AbstractManglingParser<Derived, Alloc>::OperatorInfo *
 AbstractManglingParser<Derived, Alloc>::parseOperatorEncoding() {
   if (numLeft() < 2)
     return nullptr;
 
   // We can't use lower_bound as that can link to symbols in the C++ library,
   // and this must remain independent of that.
   size_t lower = 0u, upper = NumOps - 1; // Inclusive bounds.
   while (upper != lower) {
     size_t middle = (upper + lower) / 2;
     if (Ops[middle] < First)
       lower = middle + 1;
     else
       upper = middle;
   }
   if (Ops[lower] != First)
     return nullptr;
 
   First += 2;
   return &Ops[lower];
 }
 
 //   <operator-name> ::= See parseOperatorEncoding()
 //                   ::= li <source-name>  # operator ""
 //                   ::= v <digit> <source-name>  # vendor extended operator
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseOperatorName(NameState *State) {
   if (const auto *Op = parseOperatorEncoding()) {
     if (Op->getKind() == OperatorInfo::CCast) {
       //              ::= cv <type>    # (cast)
       ScopedOverride<bool> SaveTemplate(TryToParseTemplateArgs, false);
       // If we're parsing an encoding, State != nullptr and the conversion
       // operators' <type> could have a <template-param> that refers to some
       // <template-arg>s further ahead in the mangled name.
       ScopedOverride<bool> SavePermit(PermitForwardTemplateReferences,
                                       PermitForwardTemplateReferences ||
                                           State != nullptr);
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
       if (State) State->CtorDtorConversion = true;
       return make<ConversionOperatorType>(Ty);
     }
 
     if (Op->getKind() >= OperatorInfo::Unnameable)
       /* Not a nameable operator.  */
       return nullptr;
     if (Op->getKind() == OperatorInfo::Member && !Op->getFlag())
       /* Not a nameable MemberExpr */
       return nullptr;
 
     return make<NameType>(Op->getName());
   }
 
   if (consumeIf("li")) {
     //                   ::= li <source-name>  # operator ""
     Node *SN = getDerived().parseSourceName(State);
     if (SN == nullptr)
       return nullptr;
     return make<LiteralOperator>(SN);
   }
 
   if (consumeIf('v')) {
     // ::= v <digit> <source-name>        # vendor extended operator
     if (look() >= '0' && look() <= '9') {
       First++;
       Node *SN = getDerived().parseSourceName(State);
       if (SN == nullptr)
         return nullptr;
       return make<ConversionOperatorType>(SN);
     }
     return nullptr;
   }
 
   return nullptr;
 }
 
 // <ctor-dtor-name> ::= C1  # complete object constructor
 //                  ::= C2  # base object constructor
 //                  ::= C3  # complete object allocating constructor
 //   extension      ::= C4  # gcc old-style "[unified]" constructor
 //   extension      ::= C5  # the COMDAT used for ctors
 //                  ::= D0  # deleting destructor
 //                  ::= D1  # complete object destructor
 //                  ::= D2  # base object destructor
 //   extension      ::= D4  # gcc old-style "[unified]" destructor
 //   extension      ::= D5  # the COMDAT used for dtors
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseCtorDtorName(Node *&SoFar,
                                                           NameState *State) {
   if (SoFar->getKind() == Node::KSpecialSubstitution) {
     // Expand the special substitution.
     SoFar = make<ExpandedSpecialSubstitution>(
         static_cast<SpecialSubstitution *>(SoFar));
     if (!SoFar)
       return nullptr;
   }
 
   if (consumeIf('C')) {
     bool IsInherited = consumeIf('I');
     if (look() != '1' && look() != '2' && look() != '3' && look() != '4' &&
         look() != '5')
       return nullptr;
     int Variant = look() - '0';
     ++First;
     if (State) State->CtorDtorConversion = true;
     if (IsInherited) {
       if (getDerived().parseName(State) == nullptr)
         return nullptr;
     }
     return make<CtorDtorName>(SoFar, /*IsDtor=*/false, Variant);
   }
 
   if (look() == 'D' && (look(1) == '0' || look(1) == '1' || look(1) == '2' ||
                         look(1) == '4' || look(1) == '5')) {
     int Variant = look(1) - '0';
     First += 2;
     if (State) State->CtorDtorConversion = true;
     return make<CtorDtorName>(SoFar, /*IsDtor=*/true, Variant);
   }
 
   return nullptr;
 }
 
 // <nested-name> ::= N [<CV-Qualifiers>] [<ref-qualifier>] <prefix>
 //          <unqualified-name> E
 //               ::= N [<CV-Qualifiers>] [<ref-qualifier>] <template-prefix>
 //                  <template-args> E
 //
 // <prefix> ::= <prefix> <unqualified-name>
 //          ::= <template-prefix> <template-args>
 //          ::= <template-param>
 //          ::= <decltype>
 //          ::= # empty
 //          ::= <substitution>
 //          ::= <prefix> <data-member-prefix>
 // [*] extension
 //
 // <data-member-prefix> := <member source-name> [<template-args>] M
 //
 // <template-prefix> ::= <prefix> <template unqualified-name>
 //                   ::= <template-param>
 //                   ::= <substitution>
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseNestedName(NameState *State) {
   if (!consumeIf('N'))
     return nullptr;
 
   // 'H' specifies that the encoding that follows
   // has an explicit object parameter.
   if (!consumeIf('H')) {
     Qualifiers CVTmp = parseCVQualifiers();
     if (State)
       State->CVQualifiers = CVTmp;
 
     if (consumeIf('O')) {
       if (State)
         State->ReferenceQualifier = FrefQualRValue;
     } else if (consumeIf('R')) {
       if (State)
         State->ReferenceQualifier = FrefQualLValue;
     } else {
       if (State)
         State->ReferenceQualifier = FrefQualNone;
     }
   } else if (State) {
     State->HasExplicitObjectParameter = true;
   }
 
   Node *SoFar = nullptr;
   while (!consumeIf('E')) {
     if (State)
       // Only set end-with-template on the case that does that.
       State->EndsWithTemplateArgs = false;
 
     if (look() == 'T') {
       //          ::= <template-param>
       if (SoFar != nullptr)
         return nullptr; // Cannot have a prefix.
       SoFar = getDerived().parseTemplateParam();
     } else if (look() == 'I') {
       //          ::= <template-prefix> <template-args>
       if (SoFar == nullptr)
         return nullptr; // Must have a prefix.
       Node *TA = getDerived().parseTemplateArgs(State != nullptr);
       if (TA == nullptr)
         return nullptr;
       if (SoFar->getKind() == Node::KNameWithTemplateArgs)
         // Semantically <template-args> <template-args> cannot be generated by a
         // C++ entity.  There will always be [something like] a name between
         // them.
         return nullptr;
       if (State)
         State->EndsWithTemplateArgs = true;
       SoFar = make<NameWithTemplateArgs>(SoFar, TA);
     } else if (look() == 'D' && (look(1) == 't' || look(1) == 'T')) {
       //          ::= <decltype>
       if (SoFar != nullptr)
         return nullptr; // Cannot have a prefix.
       SoFar = getDerived().parseDecltype();
     } else {
       ModuleName *Module = nullptr;
 
       if (look() == 'S') {
         //          ::= <substitution>
         Node *S = nullptr;
         if (look(1) == 't') {
           First += 2;
           S = make<NameType>("std");
         } else {
           S = getDerived().parseSubstitution();
         }
         if (!S)
           return nullptr;
         if (S->getKind() == Node::KModuleName) {
           Module = static_cast<ModuleName *>(S);
         } else if (SoFar != nullptr) {
           return nullptr; // Cannot have a prefix.
         } else {
           SoFar = S;
           continue; // Do not push a new substitution.
         }
       }
 
       //          ::= [<prefix>] <unqualified-name>
       SoFar = getDerived().parseUnqualifiedName(State, SoFar, Module);
     }
 
     if (SoFar == nullptr)
       return nullptr;
     Subs.push_back(SoFar);
 
     // No longer used.
     // <data-member-prefix> := <member source-name> [<template-args>] M
     consumeIf('M');
   }
 
   if (SoFar == nullptr || Subs.empty())
     return nullptr;
 
   Subs.pop_back();
   return SoFar;
 }
 
 // <simple-id> ::= <source-name> [ <template-args> ]
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseSimpleId() {
   Node *SN = getDerived().parseSourceName(/*NameState=*/nullptr);
   if (SN == nullptr)
     return nullptr;
   if (look() == 'I') {
     Node *TA = getDerived().parseTemplateArgs();
     if (TA == nullptr)
       return nullptr;
     return make<NameWithTemplateArgs>(SN, TA);
   }
   return SN;
 }
 
 // <destructor-name> ::= <unresolved-type>  # e.g., ~T or ~decltype(f())
 //                   ::= <simple-id>        # e.g., ~A<2*N>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseDestructorName() {
   Node *Result;
   if (std::isdigit(look()))
     Result = getDerived().parseSimpleId();
   else
     Result = getDerived().parseUnresolvedType();
   if (Result == nullptr)
     return nullptr;
   return make<DtorName>(Result);
 }
 
 // <unresolved-type> ::= <template-param>
 //                   ::= <decltype>
 //                   ::= <substitution>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseUnresolvedType() {
   if (look() == 'T') {
     Node *TP = getDerived().parseTemplateParam();
     if (TP == nullptr)
       return nullptr;
     Subs.push_back(TP);
     return TP;
   }
   if (look() == 'D') {
     Node *DT = getDerived().parseDecltype();
     if (DT == nullptr)
       return nullptr;
     Subs.push_back(DT);
     return DT;
   }
   return getDerived().parseSubstitution();
 }
 
 // <base-unresolved-name> ::= <simple-id>                                # unresolved name
 //          extension     ::= <operator-name>                            # unresolved operator-function-id
 //          extension     ::= <operator-name> <template-args>            # unresolved operator template-id
 //                        ::= on <operator-name>                         # unresolved operator-function-id
 //                        ::= on <operator-name> <template-args>         # unresolved operator template-id
 //                        ::= dn <destructor-name>                       # destructor or pseudo-destructor;
 //                                                                         # e.g. ~X or ~X<N-1>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseBaseUnresolvedName() {
   if (std::isdigit(look()))
     return getDerived().parseSimpleId();
 
   if (consumeIf("dn"))
     return getDerived().parseDestructorName();
 
   consumeIf("on");
 
   Node *Oper = getDerived().parseOperatorName(/*NameState=*/nullptr);
   if (Oper == nullptr)
     return nullptr;
   if (look() == 'I') {
     Node *TA = getDerived().parseTemplateArgs();
     if (TA == nullptr)
       return nullptr;
     return make<NameWithTemplateArgs>(Oper, TA);
   }
   return Oper;
 }
 
 // <unresolved-name>
 //  extension        ::= srN <unresolved-type> [<template-args>] <unresolved-qualifier-level>* E <base-unresolved-name>
 //                   ::= [gs] <base-unresolved-name>                     # x or (with "gs") ::x
 //                   ::= [gs] sr <unresolved-qualifier-level>+ E <base-unresolved-name>
 //                                                                       # A::x, N::y, A<T>::z; "gs" means leading "::"
 // [gs] has been parsed by caller.
 //                   ::= sr <unresolved-type> <base-unresolved-name>     # T::x / decltype(p)::x
 //  extension        ::= sr <unresolved-type> <template-args> <base-unresolved-name>
 //                                                                       # T::N::x /decltype(p)::N::x
 //  (ignored)        ::= srN <unresolved-type>  <unresolved-qualifier-level>+ E <base-unresolved-name>
 //
 // <unresolved-qualifier-level> ::= <simple-id>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseUnresolvedName(bool Global) {
   Node *SoFar = nullptr;
 
   // srN <unresolved-type> [<template-args>] <unresolved-qualifier-level>* E <base-unresolved-name>
   // srN <unresolved-type>                   <unresolved-qualifier-level>+ E <base-unresolved-name>
   if (consumeIf("srN")) {
     SoFar = getDerived().parseUnresolvedType();
     if (SoFar == nullptr)
       return nullptr;
 
     if (look() == 'I') {
       Node *TA = getDerived().parseTemplateArgs();
       if (TA == nullptr)
         return nullptr;
       SoFar = make<NameWithTemplateArgs>(SoFar, TA);
       if (!SoFar)
         return nullptr;
     }
 
     while (!consumeIf('E')) {
       Node *Qual = getDerived().parseSimpleId();
       if (Qual == nullptr)
         return nullptr;
       SoFar = make<QualifiedName>(SoFar, Qual);
       if (!SoFar)
         return nullptr;
     }
 
     Node *Base = getDerived().parseBaseUnresolvedName();
     if (Base == nullptr)
       return nullptr;
     return make<QualifiedName>(SoFar, Base);
   }
 
   // [gs] <base-unresolved-name>                     # x or (with "gs") ::x
   if (!consumeIf("sr")) {
     SoFar = getDerived().parseBaseUnresolvedName();
     if (SoFar == nullptr)
       return nullptr;
     if (Global)
       SoFar = make<GlobalQualifiedName>(SoFar);
     return SoFar;
   }
 
   // [gs] sr <unresolved-qualifier-level>+ E   <base-unresolved-name>
   if (std::isdigit(look())) {
     do {
       Node *Qual = getDerived().parseSimpleId();
       if (Qual == nullptr)
         return nullptr;
       if (SoFar)
         SoFar = make<QualifiedName>(SoFar, Qual);
       else if (Global)
         SoFar = make<GlobalQualifiedName>(Qual);
       else
         SoFar = Qual;
       if (!SoFar)
         return nullptr;
     } while (!consumeIf('E'));
   }
   //      sr <unresolved-type>                 <base-unresolved-name>
   //      sr <unresolved-type> <template-args> <base-unresolved-name>
   else {
     SoFar = getDerived().parseUnresolvedType();
     if (SoFar == nullptr)
       return nullptr;
 
     if (look() == 'I') {
       Node *TA = getDerived().parseTemplateArgs();
       if (TA == nullptr)
         return nullptr;
       SoFar = make<NameWithTemplateArgs>(SoFar, TA);
       if (!SoFar)
         return nullptr;
     }
   }
 
   DEMANGLE_ASSERT(SoFar != nullptr, "");
 
   Node *Base = getDerived().parseBaseUnresolvedName();
   if (Base == nullptr)
     return nullptr;
   return make<QualifiedName>(SoFar, Base);
 }
 
 // <abi-tags> ::= <abi-tag> [<abi-tags>]
 // <abi-tag> ::= B <source-name>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseAbiTags(Node *N) {
   while (consumeIf('B')) {
     std::string_view SN = parseBareSourceName();
     if (SN.empty())
       return nullptr;
     N = make<AbiTagAttr>(N, SN);
     if (!N)
       return nullptr;
   }
   return N;
 }
 
 // <number> ::= [n] <non-negative decimal integer>
 template <typename Alloc, typename Derived>
 std::string_view
 AbstractManglingParser<Alloc, Derived>::parseNumber(bool AllowNegative) {
   const char *Tmp = First;
   if (AllowNegative)
     consumeIf('n');
   if (numLeft() == 0 || !std::isdigit(*First))
     return std::string_view();
   while (numLeft() != 0 && std::isdigit(*First))
     ++First;
   return std::string_view(Tmp, First - Tmp);
 }
 
 // <positive length number> ::= [0-9]*
 template <typename Alloc, typename Derived>
 bool AbstractManglingParser<Alloc, Derived>::parsePositiveInteger(size_t *Out) {
   *Out = 0;
   if (look() < '0' || look() > '9')
     return true;
   while (look() >= '0' && look() <= '9') {
     *Out *= 10;
     *Out += static_cast<size_t>(consume() - '0');
   }
   return false;
 }
 
 template <typename Alloc, typename Derived>
 std::string_view AbstractManglingParser<Alloc, Derived>::parseBareSourceName() {
   size_t Int = 0;
   if (parsePositiveInteger(&Int) || numLeft() < Int)
     return {};
   std::string_view R(First, Int);
   First += Int;
   return R;
 }
 
 // <function-type> ::= [<CV-qualifiers>] [<exception-spec>] [Dx] F [Y] <bare-function-type> [<ref-qualifier>] E
 //
 // <exception-spec> ::= Do                # non-throwing exception-specification (e.g., noexcept, throw())
 //                  ::= DO <expression> E # computed (instantiation-dependent) noexcept
 //                  ::= Dw <type>+ E      # dynamic exception specification with instantiation-dependent types
 //
 // <ref-qualifier> ::= R                   # & ref-qualifier
 // <ref-qualifier> ::= O                   # && ref-qualifier
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseFunctionType() {
   Qualifiers CVQuals = parseCVQualifiers();
 
   Node *ExceptionSpec = nullptr;
   if (consumeIf("Do")) {
     ExceptionSpec = make<NameType>("noexcept");
     if (!ExceptionSpec)
       return nullptr;
   } else if (consumeIf("DO")) {
     Node *E = getDerived().parseExpr();
     if (E == nullptr || !consumeIf('E'))
       return nullptr;
     ExceptionSpec = make<NoexceptSpec>(E);
     if (!ExceptionSpec)
       return nullptr;
   } else if (consumeIf("Dw")) {
     size_t SpecsBegin = Names.size();
     while (!consumeIf('E')) {
       Node *T = getDerived().parseType();
       if (T == nullptr)
         return nullptr;
       Names.push_back(T);
     }
     ExceptionSpec =
       make<DynamicExceptionSpec>(popTrailingNodeArray(SpecsBegin));
     if (!ExceptionSpec)
       return nullptr;
   }
 
   consumeIf("Dx"); // transaction safe
 
   if (!consumeIf('F'))
     return nullptr;
   consumeIf('Y'); // extern "C"
   Node *ReturnType = getDerived().parseType();
   if (ReturnType == nullptr)
     return nullptr;
 
   FunctionRefQual ReferenceQualifier = FrefQualNone;
   size_t ParamsBegin = Names.size();
   while (true) {
     if (consumeIf('E'))
       break;
     if (consumeIf('v'))
       continue;
     if (consumeIf("RE")) {
       ReferenceQualifier = FrefQualLValue;
       break;
     }
     if (consumeIf("OE")) {
       ReferenceQualifier = FrefQualRValue;
       break;
     }
     Node *T = getDerived().parseType();
     if (T == nullptr)
       return nullptr;
     Names.push_back(T);
   }
 
   NodeArray Params = popTrailingNodeArray(ParamsBegin);
   return make<FunctionType>(ReturnType, Params, CVQuals,
                             ReferenceQualifier, ExceptionSpec);
 }
 
 // extension:
 // <vector-type>           ::= Dv <positive dimension number> _ <extended element type>
 //                         ::= Dv [<dimension expression>] _ <element type>
 // <extended element type> ::= <element type>
 //                         ::= p # AltiVec vector pixel
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseVectorType() {
   if (!consumeIf("Dv"))
     return nullptr;
   if (look() >= '1' && look() <= '9') {
     Node *DimensionNumber = make<NameType>(parseNumber());
     if (!DimensionNumber)
       return nullptr;
     if (!consumeIf('_'))
       return nullptr;
     if (consumeIf('p'))
       return make<PixelVectorType>(DimensionNumber);
     Node *ElemType = getDerived().parseType();
     if (ElemType == nullptr)
       return nullptr;
     return make<VectorType>(ElemType, DimensionNumber);
   }
 
   if (!consumeIf('_')) {
     Node *DimExpr = getDerived().parseExpr();
     if (!DimExpr)
       return nullptr;
     if (!consumeIf('_'))
       return nullptr;
     Node *ElemType = getDerived().parseType();
     if (!ElemType)
       return nullptr;
     return make<VectorType>(ElemType, DimExpr);
   }
   Node *ElemType = getDerived().parseType();
   if (!ElemType)
     return nullptr;
   return make<VectorType>(ElemType, /*Dimension=*/nullptr);
 }
 
 // <decltype>  ::= Dt <expression> E  # decltype of an id-expression or class member access (C++0x)
 //             ::= DT <expression> E  # decltype of an expression (C++0x)
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseDecltype() {
   if (!consumeIf('D'))
     return nullptr;
   if (!consumeIf('t') && !consumeIf('T'))
     return nullptr;
   Node *E = getDerived().parseExpr();
   if (E == nullptr)
     return nullptr;
   if (!consumeIf('E'))
     return nullptr;
   return make<EnclosingExpr>("decltype", E);
 }
 
 // <array-type> ::= A <positive dimension number> _ <element type>
 //              ::= A [<dimension expression>] _ <element type>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseArrayType() {
   if (!consumeIf('A'))
     return nullptr;
 
   Node *Dimension = nullptr;
 
   if (std::isdigit(look())) {
     Dimension = make<NameType>(parseNumber());
     if (!Dimension)
       return nullptr;
     if (!consumeIf('_'))
       return nullptr;
   } else if (!consumeIf('_')) {
     Node *DimExpr = getDerived().parseExpr();
     if (DimExpr == nullptr)
       return nullptr;
     if (!consumeIf('_'))
       return nullptr;
     Dimension = DimExpr;
   }
 
   Node *Ty = getDerived().parseType();
   if (Ty == nullptr)
     return nullptr;
   return make<ArrayType>(Ty, Dimension);
 }
 
 // <pointer-to-member-type> ::= M <class type> <member type>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parsePointerToMemberType() {
   if (!consumeIf('M'))
     return nullptr;
   Node *ClassType = getDerived().parseType();
   if (ClassType == nullptr)
     return nullptr;
   Node *MemberType = getDerived().parseType();
   if (MemberType == nullptr)
     return nullptr;
   return make<PointerToMemberType>(ClassType, MemberType);
 }
 
 // <class-enum-type> ::= <name>     # non-dependent type name, dependent type name, or dependent typename-specifier
 //                   ::= Ts <name>  # dependent elaborated type specifier using 'struct' or 'class'
 //                   ::= Tu <name>  # dependent elaborated type specifier using 'union'
 //                   ::= Te <name>  # dependent elaborated type specifier using 'enum'
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseClassEnumType() {
   std::string_view ElabSpef;
   if (consumeIf("Ts"))
     ElabSpef = "struct";
   else if (consumeIf("Tu"))
     ElabSpef = "union";
   else if (consumeIf("Te"))
     ElabSpef = "enum";
 
   Node *Name = getDerived().parseName();
   if (Name == nullptr)
     return nullptr;
 
   if (!ElabSpef.empty())
     return make<ElaboratedTypeSpefType>(ElabSpef, Name);
 
   return Name;
 }
 
 // <qualified-type>     ::= <qualifiers> <type>
 // <qualifiers> ::= <extended-qualifier>* <CV-qualifiers>
 // <extended-qualifier> ::= U <source-name> [<template-args>] # vendor extended type qualifier
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseQualifiedType() {
   if (consumeIf('U')) {
     std::string_view Qual = parseBareSourceName();
     if (Qual.empty())
       return nullptr;
 
     // extension            ::= U <objc-name> <objc-type>  # objc-type<identifier>
     if (starts_with(Qual, "objcproto")) {
       constexpr size_t Len = sizeof("objcproto") - 1;
       std::string_view ProtoSourceName(Qual.data() + Len, Qual.size() - Len);
       std::string_view Proto;
       {
         ScopedOverride<const char *> SaveFirst(First, ProtoSourceName.data()),
             SaveLast(Last, &*ProtoSourceName.rbegin() + 1);
         Proto = parseBareSourceName();
       }
       if (Proto.empty())
         return nullptr;
       Node *Child = getDerived().parseQualifiedType();
       if (Child == nullptr)
         return nullptr;
       return make<ObjCProtoName>(Child, Proto);
     }
 
     Node *TA = nullptr;
     if (look() == 'I') {
       TA = getDerived().parseTemplateArgs();
       if (TA == nullptr)
         return nullptr;
     }
 
     Node *Child = getDerived().parseQualifiedType();
     if (Child == nullptr)
       return nullptr;
     return make<VendorExtQualType>(Child, Qual, TA);
   }
 
   Qualifiers Quals = parseCVQualifiers();
   Node *Ty = getDerived().parseType();
   if (Ty == nullptr)
     return nullptr;
   if (Quals != QualNone)
     Ty = make<QualType>(Ty, Quals);
   return Ty;
 }
 
 // <type>      ::= <builtin-type>
 //             ::= <qualified-type>
 //             ::= <function-type>
 //             ::= <class-enum-type>
 //             ::= <array-type>
 //             ::= <pointer-to-member-type>
 //             ::= <template-param>
 //             ::= <template-template-param> <template-args>
 //             ::= <decltype>
 //             ::= P <type>        # pointer
 //             ::= R <type>        # l-value reference
 //             ::= O <type>        # r-value reference (C++11)
 //             ::= C <type>        # complex pair (C99)
 //             ::= G <type>        # imaginary (C99)
 //             ::= <substitution>  # See Compression below
 // extension   ::= U <objc-name> <objc-type>  # objc-type<identifier>
 // extension   ::= <vector-type> # <vector-type> starts with Dv
 //
 // <objc-name> ::= <k0 number> objcproto <k1 number> <identifier>  # k0 = 9 + <number of digits in k1> + k1
 // <objc-type> ::= <source-name>  # PU<11+>objcproto 11objc_object<source-name> 11objc_object -> id<source-name>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseType() {
   Node *Result = nullptr;
 
   switch (look()) {
   //             ::= <qualified-type>
   case 'r':
   case 'V':
   case 'K': {
     unsigned AfterQuals = 0;
     if (look(AfterQuals) == 'r') ++AfterQuals;
     if (look(AfterQuals) == 'V') ++AfterQuals;
     if (look(AfterQuals) == 'K') ++AfterQuals;
 
     if (look(AfterQuals) == 'F' ||
         (look(AfterQuals) == 'D' &&
          (look(AfterQuals + 1) == 'o' || look(AfterQuals + 1) == 'O' ||
           look(AfterQuals + 1) == 'w' || look(AfterQuals + 1) == 'x'))) {
       Result = getDerived().parseFunctionType();
       break;
     }
     DEMANGLE_FALLTHROUGH;
   }
   case 'U': {
     Result = getDerived().parseQualifiedType();
     break;
   }
   // <builtin-type> ::= v    # void
   case 'v':
     ++First;
     return make<NameType>("void");
   //                ::= w    # wchar_t
   case 'w':
     ++First;
     return make<NameType>("wchar_t");
   //                ::= b    # bool
   case 'b':
     ++First;
     return make<NameType>("bool");
   //                ::= c    # char
   case 'c':
     ++First;
     return make<NameType>("char");
   //                ::= a    # signed char
   case 'a':
     ++First;
     return make<NameType>("signed char");
   //                ::= h    # unsigned char
   case 'h':
     ++First;
     return make<NameType>("unsigned char");
   //                ::= s    # short
   case 's':
     ++First;
     return make<NameType>("short");
   //                ::= t    # unsigned short
   case 't':
     ++First;
     return make<NameType>("unsigned short");
   //                ::= i    # int
   case 'i':
     ++First;
     return make<NameType>("int");
   //                ::= j    # unsigned int
   case 'j':
     ++First;
     return make<NameType>("unsigned int");
   //                ::= l    # long
   case 'l':
     ++First;
     return make<NameType>("long");
   //                ::= m    # unsigned long
   case 'm':
     ++First;
     return make<NameType>("unsigned long");
   //                ::= x    # long long, __int64
   case 'x':
     ++First;
     return make<NameType>("long long");
   //                ::= y    # unsigned long long, __int64
   case 'y':
     ++First;
     return make<NameType>("unsigned long long");
   //                ::= n    # __int128
   case 'n':
     ++First;
     return make<NameType>("__int128");
   //                ::= o    # unsigned __int128
   case 'o':
     ++First;
     return make<NameType>("unsigned __int128");
   //                ::= f    # float
   case 'f':
     ++First;
     return make<NameType>("float");
   //                ::= d    # double
   case 'd':
     ++First;
     return make<NameType>("double");
   //                ::= e    # long double, __float80
   case 'e':
     ++First;
     return make<NameType>("long double");
   //                ::= g    # __float128
   case 'g':
     ++First;
     return make<NameType>("__float128");
   //                ::= z    # ellipsis
   case 'z':
     ++First;
     return make<NameType>("...");
 
   // <builtin-type> ::= u <source-name>    # vendor extended type
   case 'u': {
     ++First;
     std::string_view Res = parseBareSourceName();
     if (Res.empty())
       return nullptr;
     // Typically, <builtin-type>s are not considered substitution candidates,
     // but the exception to that exception is vendor extended types (Itanium C++
     // ABI 5.9.1).
     if (consumeIf('I')) {
       Node *BaseType = parseType();
       if (BaseType == nullptr)
         return nullptr;
       if (!consumeIf('E'))
         return nullptr;
       Result = make<TransformedType>(Res, BaseType);
     } else
       Result = make<NameType>(Res);
     break;
   }
   case 'D':
     switch (look(1)) {
     //                ::= Dd   # IEEE 754r decimal floating point (64 bits)
     case 'd':
       First += 2;
       return make<NameType>("decimal64");
     //                ::= De   # IEEE 754r decimal floating point (128 bits)
     case 'e':
       First += 2;
       return make<NameType>("decimal128");
     //                ::= Df   # IEEE 754r decimal floating point (32 bits)
     case 'f':
       First += 2;
       return make<NameType>("decimal32");
     //                ::= Dh   # IEEE 754r half-precision floating point (16 bits)
     case 'h':
       First += 2;
       return make<NameType>("half");
     //       ::= DF16b         # C++23 std::bfloat16_t
     //       ::= DF <number> _ # ISO/IEC TS 18661 binary floating point (N bits)
     case 'F': {
       First += 2;
       if (consumeIf("16b"))
         return make<NameType>("std::bfloat16_t");
       Node *DimensionNumber = make<NameType>(parseNumber());
       if (!DimensionNumber)
         return nullptr;
       if (!consumeIf('_'))
         return nullptr;
       return make<BinaryFPType>(DimensionNumber);
     }
     //                ::= [DS] DA  # N1169 fixed-point [_Sat] T _Accum
     //                ::= [DS] DR  # N1169 fixed-point [_Sat] T _Frac
     // <fixed-point-size>
     //                ::= s # short
     //                ::= t # unsigned short
     //                ::= i # plain
     //                ::= j # unsigned
     //                ::= l # long
     //                ::= m # unsigned long
     case 'A': {
       char c = look(2);
       First += 3;
       switch (c) {
       case 's':
         return make<NameType>("short _Accum");
       case 't':
         return make<NameType>("unsigned short _Accum");
       case 'i':
         return make<NameType>("_Accum");
       case 'j':
         return make<NameType>("unsigned _Accum");
       case 'l':
         return make<NameType>("long _Accum");
       case 'm':
         return make<NameType>("unsigned long _Accum");
       default:
         return nullptr;
       }
     }
     case 'R': {
       char c = look(2);
       First += 3;
       switch (c) {
       case 's':
         return make<NameType>("short _Fract");
       case 't':
         return make<NameType>("unsigned short _Fract");
       case 'i':
         return make<NameType>("_Fract");
       case 'j':
         return make<NameType>("unsigned _Fract");
       case 'l':
         return make<NameType>("long _Fract");
       case 'm':
         return make<NameType>("unsigned long _Fract");
       default:
         return nullptr;
       }
     }
     case 'S': {
       First += 2;
       if (look() != 'D')
         return nullptr;
       if (look(1) == 'A') {
         char c = look(2);
         First += 3;
         switch (c) {
         case 's':
           return make<NameType>("_Sat short _Accum");
         case 't':
           return make<NameType>("_Sat unsigned short _Accum");
         case 'i':
           return make<NameType>("_Sat _Accum");
         case 'j':
           return make<NameType>("_Sat unsigned _Accum");
         case 'l':
           return make<NameType>("_Sat long _Accum");
         case 'm':
           return make<NameType>("_Sat unsigned long _Accum");
         default:
           return nullptr;
         }
       }
       if (look(1) == 'R') {
         char c = look(2);
         First += 3;
         switch (c) {
         case 's':
           return make<NameType>("_Sat short _Fract");
         case 't':
           return make<NameType>("_Sat unsigned short _Fract");
         case 'i':
           return make<NameType>("_Sat _Fract");
         case 'j':
           return make<NameType>("_Sat unsigned _Fract");
         case 'l':
           return make<NameType>("_Sat long _Fract");
         case 'm':
           return make<NameType>("_Sat unsigned long _Fract");
         default:
           return nullptr;
         }
       }
       return nullptr;
     }
     //                ::= DB <number> _                             # C23 signed _BitInt(N)
     //                ::= DB <instantiation-dependent expression> _ # C23 signed _BitInt(N)
     //                ::= DU <number> _                             # C23 unsigned _BitInt(N)
     //                ::= DU <instantiation-dependent expression> _ # C23 unsigned _BitInt(N)
     case 'B':
     case 'U': {
       bool Signed = look(1) == 'B';
       First += 2;
       Node *Size = std::isdigit(look()) ? make<NameType>(parseNumber())
                                         : getDerived().parseExpr();
       if (!Size)
         return nullptr;
       if (!consumeIf('_'))
         return nullptr;
       return make<BitIntType>(Size, Signed);
     }
     //                ::= Di   # char32_t
     case 'i':
       First += 2;
       return make<NameType>("char32_t");
     //                ::= Ds   # char16_t
     case 's':
       First += 2;
       return make<NameType>("char16_t");
     //                ::= Du   # char8_t (C++2a, not yet in the Itanium spec)
     case 'u':
       First += 2;
       return make<NameType>("char8_t");
     //                ::= Da   # auto (in dependent new-expressions)
     case 'a':
       First += 2;
       return make<NameType>("auto");
     //                ::= Dc   # decltype(auto)
     case 'c':
       First += 2;
       return make<NameType>("decltype(auto)");
     //                ::= Dk <type-constraint> # constrained auto
     //                ::= DK <type-constraint> # constrained decltype(auto)
     case 'k':
     case 'K': {
       std::string_view Kind = look(1) == 'k' ? " auto" : " decltype(auto)";
       First += 2;
       Node *Constraint = getDerived().parseName();
       if (!Constraint)
         return nullptr;
       return make<PostfixQualifiedType>(Constraint, Kind);
     }
     //                ::= Dn   # std::nullptr_t (i.e., decltype(nullptr))
     case 'n':
       First += 2;
       return make<NameType>("std::nullptr_t");
 
     //             ::= <decltype>
     case 't':
     case 'T': {
       Result = getDerived().parseDecltype();
       break;
     }
     // extension   ::= <vector-type> # <vector-type> starts with Dv
     case 'v': {
       Result = getDerived().parseVectorType();
       break;
     }
     //           ::= Dp <type>       # pack expansion (C++0x)
     case 'p': {
       First += 2;
       Node *Child = getDerived().parseType();
       if (!Child)
         return nullptr;
       Result = make<ParameterPackExpansion>(Child);
       break;
     }
     // Exception specifier on a function type.
     case 'o':
     case 'O':
     case 'w':
     // Transaction safe function type.
     case 'x':
       Result = getDerived().parseFunctionType();
       break;
     }
     break;
   //             ::= <function-type>
   case 'F': {
     Result = getDerived().parseFunctionType();
     break;
   }
   //             ::= <array-type>
   case 'A': {
     Result = getDerived().parseArrayType();
     break;
   }
   //             ::= <pointer-to-member-type>
   case 'M': {
     Result = getDerived().parsePointerToMemberType();
     break;
   }
   //             ::= <template-param>
   case 'T': {
     // This could be an elaborate type specifier on a <class-enum-type>.
     if (look(1) == 's' || look(1) == 'u' || look(1) == 'e') {
       Result = getDerived().parseClassEnumType();
       break;
     }
 
     Result = getDerived().parseTemplateParam();
     if (Result == nullptr)
       return nullptr;
 
     // Result could be either of:
     //   <type>        ::= <template-param>
     //   <type>        ::= <template-template-param> <template-args>
     //
     //   <template-template-param> ::= <template-param>
     //                             ::= <substitution>
     //
     // If this is followed by some <template-args>, and we're permitted to
     // parse them, take the second production.
 
     if (TryToParseTemplateArgs && look() == 'I') {
       Subs.push_back(Result);
       Node *TA = getDerived().parseTemplateArgs();
       if (TA == nullptr)
         return nullptr;
       Result = make<NameWithTemplateArgs>(Result, TA);
     }
     break;
   }
   //             ::= P <type>        # pointer
   case 'P': {
     ++First;
     Node *Ptr = getDerived().parseType();
     if (Ptr == nullptr)
       return nullptr;
     Result = make<PointerType>(Ptr);
     break;
   }
   //             ::= R <type>        # l-value reference
   case 'R': {
     ++First;
     Node *Ref = getDerived().parseType();
     if (Ref == nullptr)
       return nullptr;
     Result = make<ReferenceType>(Ref, ReferenceKind::LValue);
     break;
   }
   //             ::= O <type>        # r-value reference (C++11)
   case 'O': {
     ++First;
     Node *Ref = getDerived().parseType();
     if (Ref == nullptr)
       return nullptr;
     Result = make<ReferenceType>(Ref, ReferenceKind::RValue);
     break;
   }
   //             ::= C <type>        # complex pair (C99)
   case 'C': {
     ++First;
     Node *P = getDerived().parseType();
     if (P == nullptr)
       return nullptr;
     Result = make<PostfixQualifiedType>(P, " complex");
     break;
   }
   //             ::= G <type>        # imaginary (C99)
   case 'G': {
     ++First;
     Node *P = getDerived().parseType();
     if (P == nullptr)
       return P;
     Result = make<PostfixQualifiedType>(P, " imaginary");
     break;
   }
   //             ::= <substitution>  # See Compression below
   case 'S': {
     if (look(1) != 't') {
       bool IsSubst = false;
       Result = getDerived().parseUnscopedName(nullptr, &IsSubst);
       if (!Result)
         return nullptr;
 
       // Sub could be either of:
       //   <type>        ::= <substitution>
       //   <type>        ::= <template-template-param> <template-args>
       //
       //   <template-template-param> ::= <template-param>
       //                             ::= <substitution>
       //
       // If this is followed by some <template-args>, and we're permitted to
       // parse them, take the second production.
 
       if (look() == 'I' && (!IsSubst || TryToParseTemplateArgs)) {
         if (!IsSubst)
           Subs.push_back(Result);
         Node *TA = getDerived().parseTemplateArgs();
         if (TA == nullptr)
           return nullptr;
         Result = make<NameWithTemplateArgs>(Result, TA);
       } else if (IsSubst) {
         // If all we parsed was a substitution, don't re-insert into the
         // substitution table.
         return Result;
       }
       break;
     }
     DEMANGLE_FALLTHROUGH;
   }
   //        ::= <class-enum-type>
   default: {
     Result = getDerived().parseClassEnumType();
     break;
   }
   }
 
   // If we parsed a type, insert it into the substitution table. Note that all
   // <builtin-type>s and <substitution>s have already bailed out, because they
   // don't get substitutions.
   if (Result != nullptr)
     Subs.push_back(Result);
   return Result;
 }
 
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parsePrefixExpr(std::string_view Kind,
                                                         Node::Prec Prec) {
   Node *E = getDerived().parseExpr();
   if (E == nullptr)
     return nullptr;
   return make<PrefixExpr>(Kind, E, Prec);
 }
 
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseBinaryExpr(std::string_view Kind,
                                                         Node::Prec Prec) {
   Node *LHS = getDerived().parseExpr();
   if (LHS == nullptr)
     return nullptr;
   Node *RHS = getDerived().parseExpr();
   if (RHS == nullptr)
     return nullptr;
   return make<BinaryExpr>(LHS, Kind, RHS, Prec);
 }
 
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseIntegerLiteral(
     std::string_view Lit) {
   std::string_view Tmp = parseNumber(true);
   if (!Tmp.empty() && consumeIf('E'))
     return make<IntegerLiteral>(Lit, Tmp);
   return nullptr;
 }
 
 // <CV-Qualifiers> ::= [r] [V] [K]
 template <typename Alloc, typename Derived>
 Qualifiers AbstractManglingParser<Alloc, Derived>::parseCVQualifiers() {
   Qualifiers CVR = QualNone;
   if (consumeIf('r'))
     CVR |= QualRestrict;
   if (consumeIf('V'))
     CVR |= QualVolatile;
   if (consumeIf('K'))
     CVR |= QualConst;
   return CVR;
 }
 
 // <function-param> ::= fp <top-level CV-Qualifiers> _                                     # L == 0, first parameter
 //                  ::= fp <top-level CV-Qualifiers> <parameter-2 non-negative number> _   # L == 0, second and later parameters
 //                  ::= fL <L-1 non-negative number> p <top-level CV-Qualifiers> _         # L > 0, first parameter
 //                  ::= fL <L-1 non-negative number> p <top-level CV-Qualifiers> <parameter-2 non-negative number> _   # L > 0, second and later parameters
 //                  ::= fpT      # 'this' expression (not part of standard?)
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseFunctionParam() {
   if (consumeIf("fpT"))
     return make<NameType>("this");
   if (consumeIf("fp")) {
     parseCVQualifiers();
     std::string_view Num = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<FunctionParam>(Num);
   }
   if (consumeIf("fL")) {
     if (parseNumber().empty())
       return nullptr;
     if (!consumeIf('p'))
       return nullptr;
     parseCVQualifiers();
     std::string_view Num = parseNumber();
     if (!consumeIf('_'))
       return nullptr;
     return make<FunctionParam>(Num);
   }
   return nullptr;
 }
 
 // cv <type> <expression>                               # conversion with one argument
 // cv <type> _ <expression>* E                          # conversion with a different number of arguments
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseConversionExpr() {
   if (!consumeIf("cv"))
     return nullptr;
   Node *Ty;
   {
     ScopedOverride<bool> SaveTemp(TryToParseTemplateArgs, false);
     Ty = getDerived().parseType();
   }
 
   if (Ty == nullptr)
     return nullptr;
 
   if (consumeIf('_')) {
     size_t ExprsBegin = Names.size();
     while (!consumeIf('E')) {
       Node *E = getDerived().parseExpr();
       if (E == nullptr)
         return E;
       Names.push_back(E);
     }
     NodeArray Exprs = popTrailingNodeArray(ExprsBegin);
     return make<ConversionExpr>(Ty, Exprs);
   }
 
   Node *E[1] = {getDerived().parseExpr()};
   if (E[0] == nullptr)
     return nullptr;
   return make<ConversionExpr>(Ty, makeNodeArray(E, E + 1));
 }
 
 // <expr-primary> ::= L <type> <value number> E                          # integer literal
 //                ::= L <type> <value float> E                           # floating literal
 //                ::= L <string type> E                                  # string literal
 //                ::= L <nullptr type> E                                 # nullptr literal (i.e., "LDnE")
 //                ::= L <lambda type> E                                  # lambda expression
 // FIXME:         ::= L <type> <real-part float> _ <imag-part float> E   # complex floating point literal (C 2000)
 //                ::= L <mangled-name> E                                 # external name
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseExprPrimary() {
   if (!consumeIf('L'))
     return nullptr;
   switch (look()) {
   case 'w':
     ++First;
     return getDerived().parseIntegerLiteral("wchar_t");
   case 'b':
     if (consumeIf("b0E"))
       return make<BoolExpr>(0);
     if (consumeIf("b1E"))
       return make<BoolExpr>(1);
     return nullptr;
   case 'c':
     ++First;
     return getDerived().parseIntegerLiteral("char");
   case 'a':
     ++First;
     return getDerived().parseIntegerLiteral("signed char");
   case 'h':
     ++First;
     return getDerived().parseIntegerLiteral("unsigned char");
   case 's':
     ++First;
     return getDerived().parseIntegerLiteral("short");
   case 't':
     ++First;
     return getDerived().parseIntegerLiteral("unsigned short");
   case 'i':
     ++First;
     return getDerived().parseIntegerLiteral("");
   case 'j':
     ++First;
     return getDerived().parseIntegerLiteral("u");
   case 'l':
     ++First;
     return getDerived().parseIntegerLiteral("l");
   case 'm':
     ++First;
     return getDerived().parseIntegerLiteral("ul");
   case 'x':
     ++First;
     return getDerived().parseIntegerLiteral("ll");
   case 'y':
     ++First;
     return getDerived().parseIntegerLiteral("ull");
   case 'n':
     ++First;
     return getDerived().parseIntegerLiteral("__int128");
   case 'o':
     ++First;
     return getDerived().parseIntegerLiteral("unsigned __int128");
   case 'f':
     ++First;
     return getDerived().template parseFloatingLiteral<float>();
   case 'd':
     ++First;
     return getDerived().template parseFloatingLiteral<double>();
   case 'e':
     ++First;
 #if defined(__powerpc__) || defined(__s390__)
     // Handle cases where long doubles encoded with e have the same size
     // and representation as doubles.
     return getDerived().template parseFloatingLiteral<double>();
 #else
     return getDerived().template parseFloatingLiteral<long double>();
 #endif
   case '_':
     if (consumeIf("_Z")) {
       Node *R = getDerived().parseEncoding();
       if (R != nullptr && consumeIf('E'))
         return R;
     }
     return nullptr;
   case 'A': {
     Node *T = getDerived().parseType();
     if (T == nullptr)
       return nullptr;
     // FIXME: We need to include the string contents in the mangling.
     if (consumeIf('E'))
       return make<StringLiteral>(T);
     return nullptr;
   }
   case 'D':
     if (consumeIf("Dn") && (consumeIf('0'), consumeIf('E')))
       return make<NameType>("nullptr");
     return nullptr;
   case 'T':
     // Invalid mangled name per
     //   http://sourcerytools.com/pipermail/cxx-abi-dev/2011-August/002422.html
     return nullptr;
   case 'U': {
     // FIXME: Should we support LUb... for block literals?
     if (look(1) != 'l')
       return nullptr;
     Node *T = parseUnnamedTypeName(nullptr);
     if (!T || !consumeIf('E'))
       return nullptr;
     return make<LambdaExpr>(T);
   }
   default: {
     // might be named type
     Node *T = getDerived().parseType();
     if (T == nullptr)
       return nullptr;
     std::string_view N = parseNumber(/*AllowNegative=*/true);
     if (N.empty())
       return nullptr;
     if (!consumeIf('E'))
       return nullptr;
     return make<EnumLiteral>(T, N);
   }
   }
 }
 
 // <braced-expression> ::= <expression>
 //                     ::= di <field source-name> <braced-expression>    # .name = expr
 //                     ::= dx <index expression> <braced-expression>     # [expr] = expr
 //                     ::= dX <range begin expression> <range end expression> <braced-expression>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseBracedExpr() {
   if (look() == 'd') {
     switch (look(1)) {
     case 'i': {
       First += 2;
       Node *Field = getDerived().parseSourceName(/*NameState=*/nullptr);
       if (Field == nullptr)
         return nullptr;
       Node *Init = getDerived().parseBracedExpr();
       if (Init == nullptr)
         return nullptr;
       return make<BracedExpr>(Field, Init, /*isArray=*/false);
     }
     case 'x': {
       First += 2;
       Node *Index = getDerived().parseExpr();
       if (Index == nullptr)
         return nullptr;
       Node *Init = getDerived().parseBracedExpr();
       if (Init == nullptr)
         return nullptr;
       return make<BracedExpr>(Index, Init, /*isArray=*/true);
     }
     case 'X': {
       First += 2;
       Node *RangeBegin = getDerived().parseExpr();
       if (RangeBegin == nullptr)
         return nullptr;
       Node *RangeEnd = getDerived().parseExpr();
       if (RangeEnd == nullptr)
         return nullptr;
       Node *Init = getDerived().parseBracedExpr();
       if (Init == nullptr)
         return nullptr;
       return make<BracedRangeExpr>(RangeBegin, RangeEnd, Init);
     }
     }
   }
   return getDerived().parseExpr();
 }
 
 // (not yet in the spec)
 // <fold-expr> ::= fL <binary-operator-name> <expression> <expression>
 //             ::= fR <binary-operator-name> <expression> <expression>
 //             ::= fl <binary-operator-name> <expression>
 //             ::= fr <binary-operator-name> <expression>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseFoldExpr() {
   if (!consumeIf('f'))
     return nullptr;
 
   bool IsLeftFold = false, HasInitializer = false;
   switch (look()) {
   default:
     return nullptr;
   case 'L':
     IsLeftFold = true;
     HasInitializer = true;
     break;
   case 'R':
     HasInitializer = true;
     break;
   case 'l':
     IsLeftFold = true;
     break;
   case 'r':
     break;
   }
   ++First;
 
   const auto *Op = parseOperatorEncoding();
   if (!Op)
     return nullptr;
   if (!(Op->getKind() == OperatorInfo::Binary
         || (Op->getKind() == OperatorInfo::Member
             && Op->getName().back() == '*')))
     return nullptr;
 
   Node *Pack = getDerived().parseExpr();
   if (Pack == nullptr)
     return nullptr;
 
   Node *Init = nullptr;
   if (HasInitializer) {
     Init = getDerived().parseExpr();
     if (Init == nullptr)
       return nullptr;
   }
 
   if (IsLeftFold && Init)
     std::swap(Pack, Init);
 
   return make<FoldExpr>(IsLeftFold, Op->getSymbol(), Pack, Init);
 }
 
 // <expression> ::= mc <parameter type> <expr> [<offset number>] E
 //
 // Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/47
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parsePointerToMemberConversionExpr(
     Node::Prec Prec) {
   Node *Ty = getDerived().parseType();
   if (!Ty)
     return nullptr;
   Node *Expr = getDerived().parseExpr();
   if (!Expr)
     return nullptr;
   std::string_view Offset = getDerived().parseNumber(true);
   if (!consumeIf('E'))
     return nullptr;
   return make<PointerToMemberConversionExpr>(Ty, Expr, Offset, Prec);
 }
 
 // <expression> ::= so <referent type> <expr> [<offset number>] <union-selector>* [p] E
 // <union-selector> ::= _ [<number>]
 //
 // Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/47
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseSubobjectExpr() {
   Node *Ty = getDerived().parseType();
   if (!Ty)
     return nullptr;
   Node *Expr = getDerived().parseExpr();
   if (!Expr)
     return nullptr;
   std::string_view Offset = getDerived().parseNumber(true);
   size_t SelectorsBegin = Names.size();
   while (consumeIf('_')) {
     Node *Selector = make<NameType>(parseNumber());
     if (!Selector)
       return nullptr;
     Names.push_back(Selector);
   }
   bool OnePastTheEnd = consumeIf('p');
   if (!consumeIf('E'))
     return nullptr;
   return make<SubobjectExpr>(
       Ty, Expr, Offset, popTrailingNodeArray(SelectorsBegin), OnePastTheEnd);
 }
 
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseConstraintExpr() {
   // Within this expression, all enclosing template parameter lists are in
   // scope.
   ScopedOverride<bool> SaveIncompleteTemplateParameterTracking(
       HasIncompleteTemplateParameterTracking, true);
   return getDerived().parseExpr();
 }
 
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseRequiresExpr() {
   NodeArray Params;
   if (consumeIf("rQ")) {
     // <expression> ::= rQ <bare-function-type> _ <requirement>+ E
     size_t ParamsBegin = Names.size();
     while (!consumeIf('_')) {
       Node *Type = getDerived().parseType();
       if (Type == nullptr)
         return nullptr;
       Names.push_back(Type);
     }
     Params = popTrailingNodeArray(ParamsBegin);
   } else if (!consumeIf("rq")) {
     // <expression> ::= rq <requirement>+ E
     return nullptr;
   }
 
   size_t ReqsBegin = Names.size();
   do {
     Node *Constraint = nullptr;
     if (consumeIf('X')) {
       // <requirement> ::= X <expression> [N] [R <type-constraint>]
       Node *Expr = getDerived().parseExpr();
       if (Expr == nullptr)
         return nullptr;
       bool Noexcept = consumeIf('N');
       Node *TypeReq = nullptr;
       if (consumeIf('R')) {
         TypeReq = getDerived().parseName();
         if (TypeReq == nullptr)
           return nullptr;
       }
       Constraint = make<ExprRequirement>(Expr, Noexcept, TypeReq);
     } else if (consumeIf('T')) {
       // <requirement> ::= T <type>
       Node *Type = getDerived().parseType();
       if (Type == nullptr)
         return nullptr;
       Constraint = make<TypeRequirement>(Type);
     } else if (consumeIf('Q')) {
       // <requirement> ::= Q <constraint-expression>
       //
       // FIXME: We use <expression> instead of <constraint-expression>. Either
       // the requires expression is already inside a constraint expression, in
       // which case it makes no difference, or we're in a requires-expression
       // that might be partially-substituted, where the language behavior is
       // not yet settled and clang mangles after substitution.
       Node *NestedReq = getDerived().parseExpr();
       if (NestedReq == nullptr)
         return nullptr;
       Constraint = make<NestedRequirement>(NestedReq);
     }
     if (Constraint == nullptr)
       return nullptr;
     Names.push_back(Constraint);
   } while (!consumeIf('E'));
 
   return make<RequiresExpr>(Params, popTrailingNodeArray(ReqsBegin));
 }
 
 // <expression> ::= <unary operator-name> <expression>
 //              ::= <binary operator-name> <expression> <expression>
 //              ::= <ternary operator-name> <expression> <expression> <expression>
 //              ::= cl <expression>+ E                                   # call
 //              ::= cp <base-unresolved-name> <expression>* E            # (name) (expr-list), call that would use argument-dependent lookup but for the parentheses
 //              ::= cv <type> <expression>                               # conversion with one argument
 //              ::= cv <type> _ <expression>* E                          # conversion with a different number of arguments
 //              ::= [gs] nw <expression>* _ <type> E                     # new (expr-list) type
 //              ::= [gs] nw <expression>* _ <type> <initializer>         # new (expr-list) type (init)
 //              ::= [gs] na <expression>* _ <type> E                     # new[] (expr-list) type
 //              ::= [gs] na <expression>* _ <type> <initializer>         # new[] (expr-list) type (init)
 //              ::= [gs] dl <expression>                                 # delete expression
 //              ::= [gs] da <expression>                                 # delete[] expression
 //              ::= pp_ <expression>                                     # prefix ++
 //              ::= mm_ <expression>                                     # prefix --
 //              ::= ti <type>                                            # typeid (type)
 //              ::= te <expression>                                      # typeid (expression)
 //              ::= dc <type> <expression>                               # dynamic_cast<type> (expression)
 //              ::= sc <type> <expression>                               # static_cast<type> (expression)
 //              ::= cc <type> <expression>                               # const_cast<type> (expression)
 //              ::= rc <type> <expression>                               # reinterpret_cast<type> (expression)
 //              ::= st <type>                                            # sizeof (a type)
 //              ::= sz <expression>                                      # sizeof (an expression)
 //              ::= at <type>                                            # alignof (a type)
 //              ::= az <expression>                                      # alignof (an expression)
 //              ::= nx <expression>                                      # noexcept (expression)
 //              ::= <template-param>
 //              ::= <function-param>
 //              ::= dt <expression> <unresolved-name>                    # expr.name
 //              ::= pt <expression> <unresolved-name>                    # expr->name
 //              ::= ds <expression> <expression>                         # expr.*expr
 //              ::= sZ <template-param>                                  # size of a parameter pack
 //              ::= sZ <function-param>                                  # size of a function parameter pack
 //              ::= sP <template-arg>* E                                 # sizeof...(T), size of a captured template parameter pack from an alias template
 //              ::= sp <expression>                                      # pack expansion
 //              ::= tw <expression>                                      # throw expression
 //              ::= tr                                                   # throw with no operand (rethrow)
 //              ::= <unresolved-name>                                    # f(p), N::f(p), ::f(p),
 //                                                                       # freestanding dependent name (e.g., T::x),
 //                                                                       # objectless nonstatic member reference
 //              ::= fL <binary-operator-name> <expression> <expression>
 //              ::= fR <binary-operator-name> <expression> <expression>
 //              ::= fl <binary-operator-name> <expression>
 //              ::= fr <binary-operator-name> <expression>
 //              ::= <expr-primary>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseExpr() {
   bool Global = consumeIf("gs");
 
   const auto *Op = parseOperatorEncoding();
   if (Op) {
     auto Sym = Op->getSymbol();
     switch (Op->getKind()) {
     case OperatorInfo::Binary:
       // Binary operator: lhs @ rhs
       return getDerived().parseBinaryExpr(Sym, Op->getPrecedence());
     case OperatorInfo::Prefix:
       // Prefix unary operator: @ expr
       return getDerived().parsePrefixExpr(Sym, Op->getPrecedence());
     case OperatorInfo::Postfix: {
       // Postfix unary operator: expr @
       if (consumeIf('_'))
         return getDerived().parsePrefixExpr(Sym, Op->getPrecedence());
       Node *Ex = getDerived().parseExpr();
       if (Ex == nullptr)
         return nullptr;
       return make<PostfixExpr>(Ex, Sym, Op->getPrecedence());
     }
     case OperatorInfo::Array: {
       // Array Index:  lhs [ rhs ]
       Node *Base = getDerived().parseExpr();
       if (Base == nullptr)
         return nullptr;
       Node *Index = getDerived().parseExpr();
       if (Index == nullptr)
         return nullptr;
       return make<ArraySubscriptExpr>(Base, Index, Op->getPrecedence());
     }
     case OperatorInfo::Member: {
       // Member access lhs @ rhs
       Node *LHS = getDerived().parseExpr();
       if (LHS == nullptr)
         return nullptr;
       Node *RHS = getDerived().parseExpr();
       if (RHS == nullptr)
         return nullptr;
       return make<MemberExpr>(LHS, Sym, RHS, Op->getPrecedence());
     }
     case OperatorInfo::New: {
       // New
       // # new (expr-list) type [(init)]
       // [gs] nw <expression>* _ <type> [pi <expression>*] E
       // # new[] (expr-list) type [(init)]
       // [gs] na <expression>* _ <type> [pi <expression>*] E
       size_t Exprs = Names.size();
       while (!consumeIf('_')) {
         Node *Ex = getDerived().parseExpr();
         if (Ex == nullptr)
           return nullptr;
         Names.push_back(Ex);
       }
       NodeArray ExprList = popTrailingNodeArray(Exprs);
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
       bool HaveInits = consumeIf("pi");
       size_t InitsBegin = Names.size();
       while (!consumeIf('E')) {
         if (!HaveInits)
           return nullptr;
         Node *Init = getDerived().parseExpr();
         if (Init == nullptr)
           return Init;
         Names.push_back(Init);
       }
       NodeArray Inits = popTrailingNodeArray(InitsBegin);
       return make<NewExpr>(ExprList, Ty, Inits, Global,
                            /*IsArray=*/Op->getFlag(), Op->getPrecedence());
     }
     case OperatorInfo::Del: {
       // Delete
       Node *Ex = getDerived().parseExpr();
       if (Ex == nullptr)
         return nullptr;
       return make<DeleteExpr>(Ex, Global, /*IsArray=*/Op->getFlag(),
                               Op->getPrecedence());
     }
     case OperatorInfo::Call: {
       // Function Call
       Node *Callee = getDerived().parseExpr();
       if (Callee == nullptr)
         return nullptr;
       size_t ExprsBegin = Names.size();
       while (!consumeIf('E')) {
         Node *E = getDerived().parseExpr();
         if (E == nullptr)
           return nullptr;
         Names.push_back(E);
       }
       return make<CallExpr>(Callee, popTrailingNodeArray(ExprsBegin),
                             /*IsParen=*/Op->getFlag(), Op->getPrecedence());
     }
     case OperatorInfo::CCast: {
       // C Cast: (type)expr
       Node *Ty;
       {
         ScopedOverride<bool> SaveTemp(TryToParseTemplateArgs, false);
         Ty = getDerived().parseType();
       }
       if (Ty == nullptr)
         return nullptr;
 
       size_t ExprsBegin = Names.size();
       bool IsMany = consumeIf('_');
       while (!consumeIf('E')) {
         Node *E = getDerived().parseExpr();
         if (E == nullptr)
           return E;
         Names.push_back(E);
         if (!IsMany)
           break;
       }
       NodeArray Exprs = popTrailingNodeArray(ExprsBegin);
       if (!IsMany && Exprs.size() != 1)
         return nullptr;
       return make<ConversionExpr>(Ty, Exprs, Op->getPrecedence());
     }
     case OperatorInfo::Conditional: {
       // Conditional operator: expr ? expr : expr
       Node *Cond = getDerived().parseExpr();
       if (Cond == nullptr)
         return nullptr;
       Node *LHS = getDerived().parseExpr();
       if (LHS == nullptr)
         return nullptr;
       Node *RHS = getDerived().parseExpr();
       if (RHS == nullptr)
         return nullptr;
       return make<ConditionalExpr>(Cond, LHS, RHS, Op->getPrecedence());
     }
     case OperatorInfo::NamedCast: {
       // Named cast operation, @<type>(expr)
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
       Node *Ex = getDerived().parseExpr();
       if (Ex == nullptr)
         return nullptr;
       return make<CastExpr>(Sym, Ty, Ex, Op->getPrecedence());
     }
     case OperatorInfo::OfIdOp: {
       // [sizeof/alignof/typeid] ( <type>|<expr> )
       Node *Arg =
           Op->getFlag() ? getDerived().parseType() : getDerived().parseExpr();
       if (!Arg)
         return nullptr;
       return make<EnclosingExpr>(Sym, Arg, Op->getPrecedence());
     }
     case OperatorInfo::NameOnly: {
       // Not valid as an expression operand.
       return nullptr;
     }
     }
     DEMANGLE_UNREACHABLE;
   }
 
   if (numLeft() < 2)
     return nullptr;
 
   if (look() == 'L')
     return getDerived().parseExprPrimary();
   if (look() == 'T')
     return getDerived().parseTemplateParam();
   if (look() == 'f') {
     // Disambiguate a fold expression from a <function-param>.
     if (look(1) == 'p' || (look(1) == 'L' && std::isdigit(look(2))))
       return getDerived().parseFunctionParam();
     return getDerived().parseFoldExpr();
   }
   if (consumeIf("il")) {
     size_t InitsBegin = Names.size();
     while (!consumeIf('E')) {
       Node *E = getDerived().parseBracedExpr();
       if (E == nullptr)
         return nullptr;
       Names.push_back(E);
     }
     return make<InitListExpr>(nullptr, popTrailingNodeArray(InitsBegin));
   }
   if (consumeIf("mc"))
     return parsePointerToMemberConversionExpr(Node::Prec::Unary);
   if (consumeIf("nx")) {
     Node *Ex = getDerived().parseExpr();
     if (Ex == nullptr)
       return Ex;
     return make<EnclosingExpr>("noexcept ", Ex, Node::Prec::Unary);
   }
   if (look() == 'r' && (look(1) == 'q' || look(1) == 'Q'))
     return parseRequiresExpr();
   if (consumeIf("so"))
     return parseSubobjectExpr();
   if (consumeIf("sp")) {
     Node *Child = getDerived().parseExpr();
     if (Child == nullptr)
       return nullptr;
     return make<ParameterPackExpansion>(Child);
   }
   if (consumeIf("sZ")) {
     if (look() == 'T') {
       Node *R = getDerived().parseTemplateParam();
       if (R == nullptr)
         return nullptr;
       return make<SizeofParamPackExpr>(R);
     }
     Node *FP = getDerived().parseFunctionParam();
     if (FP == nullptr)
       return nullptr;
     return make<EnclosingExpr>("sizeof... ", FP);
   }
   if (consumeIf("sP")) {
     size_t ArgsBegin = Names.size();
     while (!consumeIf('E')) {
       Node *Arg = getDerived().parseTemplateArg();
       if (Arg == nullptr)
         return nullptr;
       Names.push_back(Arg);
     }
     auto *Pack = make<NodeArrayNode>(popTrailingNodeArray(ArgsBegin));
     if (!Pack)
       return nullptr;
     return make<EnclosingExpr>("sizeof... ", Pack);
   }
   if (consumeIf("tl")) {
     Node *Ty = getDerived().parseType();
     if (Ty == nullptr)
       return nullptr;
     size_t InitsBegin = Names.size();
     while (!consumeIf('E')) {
       Node *E = getDerived().parseBracedExpr();
       if (E == nullptr)
         return nullptr;
       Names.push_back(E);
     }
     return make<InitListExpr>(Ty, popTrailingNodeArray(InitsBegin));
   }
   if (consumeIf("tr"))
     return make<NameType>("throw");
   if (consumeIf("tw")) {
     Node *Ex = getDerived().parseExpr();
     if (Ex == nullptr)
       return nullptr;
     return make<ThrowExpr>(Ex);
   }
   if (consumeIf('u')) {
     Node *Name = getDerived().parseSourceName(/*NameState=*/nullptr);
     if (!Name)
       return nullptr;
     // Special case legacy __uuidof mangling. The 't' and 'z' appear where the
     // standard encoding expects a <template-arg>, and would be otherwise be
     // interpreted as <type> node 'short' or 'ellipsis'. However, neither
     // __uuidof(short) nor __uuidof(...) can actually appear, so there is no
     // actual conflict here.
     bool IsUUID = false;
     Node *UUID = nullptr;
     if (Name->getBaseName() == "__uuidof") {
       if (consumeIf('t')) {
         UUID = getDerived().parseType();
         IsUUID = true;
       } else if (consumeIf('z')) {
         UUID = getDerived().parseExpr();
         IsUUID = true;
       }
     }
     size_t ExprsBegin = Names.size();
     if (IsUUID) {
       if (UUID == nullptr)
         return nullptr;
       Names.push_back(UUID);
     } else {
       while (!consumeIf('E')) {
         Node *E = getDerived().parseTemplateArg();
         if (E == nullptr)
           return E;
         Names.push_back(E);
       }
     }
     return make<CallExpr>(Name, popTrailingNodeArray(ExprsBegin),
                           /*IsParen=*/false, Node::Prec::Postfix);
   }
 
   // Only unresolved names remain.
   return getDerived().parseUnresolvedName(Global);
 }
 
 // <call-offset> ::= h <nv-offset> _
 //               ::= v <v-offset> _
 //
 // <nv-offset> ::= <offset number>
 //               # non-virtual base override
 //
 // <v-offset>  ::= <offset number> _ <virtual offset number>
 //               # virtual base override, with vcall offset
 template <typename Alloc, typename Derived>
 bool AbstractManglingParser<Alloc, Derived>::parseCallOffset() {
   // Just scan through the call offset, we never add this information into the
   // output.
   if (consumeIf('h'))
     return parseNumber(true).empty() || !consumeIf('_');
   if (consumeIf('v'))
     return parseNumber(true).empty() || !consumeIf('_') ||
            parseNumber(true).empty() || !consumeIf('_');
   return true;
 }
 
 // <special-name> ::= TV <type>    # virtual table
 //                ::= TT <type>    # VTT structure (construction vtable index)
 //                ::= TI <type>    # typeinfo structure
 //                ::= TS <type>    # typeinfo name (null-terminated byte string)
 //                ::= Tc <call-offset> <call-offset> <base encoding>
 //                    # base is the nominal target function of thunk
 //                    # first call-offset is 'this' adjustment
 //                    # second call-offset is result adjustment
 //                ::= T <call-offset> <base encoding>
 //                    # base is the nominal target function of thunk
 //                # Guard variable for one-time initialization
 //                ::= GV <object name>
 //                                     # No <type>
 //                ::= TW <object name> # Thread-local wrapper
 //                ::= TH <object name> # Thread-local initialization
 //                ::= GR <object name> _             # First temporary
 //                ::= GR <object name> <seq-id> _    # Subsequent temporaries
 //                # construction vtable for second-in-first
 //      extension ::= TC <first type> <number> _ <second type>
 //      extension ::= GR <object name> # reference temporary for object
 //      extension ::= GI <module name> # module global initializer
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseSpecialName() {
   switch (look()) {
   case 'T':
     switch (look(1)) {
     // TA <template-arg>    # template parameter object
     //
     // Not yet in the spec: https://github.com/itanium-cxx-abi/cxx-abi/issues/63
     case 'A': {
       First += 2;
       Node *Arg = getDerived().parseTemplateArg();
       if (Arg == nullptr)
         return nullptr;
       return make<SpecialName>("template parameter object for ", Arg);
     }
     // TV <type>    # virtual table
     case 'V': {
       First += 2;
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
       return make<SpecialName>("vtable for ", Ty);
     }
     // TT <type>    # VTT structure (construction vtable index)
     case 'T': {
       First += 2;
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
       return make<SpecialName>("VTT for ", Ty);
     }
     // TI <type>    # typeinfo structure
     case 'I': {
       First += 2;
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
       return make<SpecialName>("typeinfo for ", Ty);
     }
     // TS <type>    # typeinfo name (null-terminated byte string)
     case 'S': {
       First += 2;
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
       return make<SpecialName>("typeinfo name for ", Ty);
     }
     // Tc <call-offset> <call-offset> <base encoding>
     case 'c': {
       First += 2;
       if (parseCallOffset() || parseCallOffset())
         return nullptr;
       Node *Encoding = getDerived().parseEncoding();
       if (Encoding == nullptr)
         return nullptr;
       return make<SpecialName>("covariant return thunk to ", Encoding);
     }
     // extension ::= TC <first type> <number> _ <second type>
     //               # construction vtable for second-in-first
     case 'C': {
       First += 2;
       Node *FirstType = getDerived().parseType();
       if (FirstType == nullptr)
         return nullptr;
       if (parseNumber(true).empty() || !consumeIf('_'))
         return nullptr;
       Node *SecondType = getDerived().parseType();
       if (SecondType == nullptr)
         return nullptr;
       return make<CtorVtableSpecialName>(SecondType, FirstType);
     }
     // TW <object name> # Thread-local wrapper
     case 'W': {
       First += 2;
       Node *Name = getDerived().parseName();
       if (Name == nullptr)
         return nullptr;
       return make<SpecialName>("thread-local wrapper routine for ", Name);
     }
     // TH <object name> # Thread-local initialization
     case 'H': {
       First += 2;
       Node *Name = getDerived().parseName();
       if (Name == nullptr)
         return nullptr;
       return make<SpecialName>("thread-local initialization routine for ", Name);
     }
     // T <call-offset> <base encoding>
     default: {
       ++First;
       bool IsVirt = look() == 'v';
       if (parseCallOffset())
         return nullptr;
       Node *BaseEncoding = getDerived().parseEncoding();
       if (BaseEncoding == nullptr)
         return nullptr;
       if (IsVirt)
         return make<SpecialName>("virtual thunk to ", BaseEncoding);
       else
         return make<SpecialName>("non-virtual thunk to ", BaseEncoding);
     }
     }
   case 'G':
     switch (look(1)) {
     // GV <object name> # Guard variable for one-time initialization
     case 'V': {
       First += 2;
       Node *Name = getDerived().parseName();
       if (Name == nullptr)
         return nullptr;
       return make<SpecialName>("guard variable for ", Name);
     }
     // GR <object name> # reference temporary for object
     // GR <object name> _             # First temporary
     // GR <object name> <seq-id> _    # Subsequent temporaries
     case 'R': {
       First += 2;
       Node *Name = getDerived().parseName();
       if (Name == nullptr)
         return nullptr;
       size_t Count;
       bool ParsedSeqId = !parseSeqId(&Count);
       if (!consumeIf('_') && ParsedSeqId)
         return nullptr;
       return make<SpecialName>("reference temporary for ", Name);
     }
     // GI <module-name> v
     case 'I': {
       First += 2;
       ModuleName *Module = nullptr;
       if (getDerived().parseModuleNameOpt(Module))
         return nullptr;
       if (Module == nullptr)
         return nullptr;
       return make<SpecialName>("initializer for module ", Module);
     }
     }
   }
   return nullptr;
 }
 
 // <encoding> ::= <function name> <bare-function-type>
 //                    [`Q` <requires-clause expr>]
 //            ::= <data name>
 //            ::= <special-name>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseEncoding(bool ParseParams) {
   // The template parameters of an encoding are unrelated to those of the
   // enclosing context.
   SaveTemplateParams SaveTemplateParamsScope(this);
 
   if (look() == 'G' || look() == 'T')
     return getDerived().parseSpecialName();
 
   auto IsEndOfEncoding = [&] {
     // The set of chars that can potentially follow an <encoding> (none of which
     // can start a <type>). Enumerating these allows us to avoid speculative
     // parsing.
     return numLeft() == 0 || look() == 'E' || look() == '.' || look() == '_';
   };
 
   NameState NameInfo(this);
   Node *Name = getDerived().parseName(&NameInfo);
   if (Name == nullptr)
     return nullptr;
 
   if (resolveForwardTemplateRefs(NameInfo))
     return nullptr;
 
   if (IsEndOfEncoding())
     return Name;
 
   // ParseParams may be false at the top level only, when called from parse().
   // For example in the mangled name _Z3fooILZ3BarEET_f, ParseParams may be
   // false when demangling 3fooILZ3BarEET_f but is always true when demangling
   // 3Bar.
   if (!ParseParams) {
     while (consume())
       ;
     return Name;
   }
 
   Node *Attrs = nullptr;
   if (consumeIf("Ua9enable_ifI")) {
     size_t BeforeArgs = Names.size();
     while (!consumeIf('E')) {
       Node *Arg = getDerived().parseTemplateArg();
       if (Arg == nullptr)
         return nullptr;
       Names.push_back(Arg);
     }
     Attrs = make<EnableIfAttr>(popTrailingNodeArray(BeforeArgs));
     if (!Attrs)
       return nullptr;
   }
 
   Node *ReturnType = nullptr;
   if (!NameInfo.CtorDtorConversion && NameInfo.EndsWithTemplateArgs) {
     ReturnType = getDerived().parseType();
     if (ReturnType == nullptr)
       return nullptr;
   }
 
   NodeArray Params;
   if (!consumeIf('v')) {
     size_t ParamsBegin = Names.size();
     do {
       Node *Ty = getDerived().parseType();
       if (Ty == nullptr)
         return nullptr;
 
       const bool IsFirstParam = ParamsBegin == Names.size();
       if (NameInfo.HasExplicitObjectParameter && IsFirstParam)
         Ty = make<ExplicitObjectParameter>(Ty);
 
       if (Ty == nullptr)
         return nullptr;
 
       Names.push_back(Ty);
     } while (!IsEndOfEncoding() && look() != 'Q');
     Params = popTrailingNodeArray(ParamsBegin);
   }
 
   Node *Requires = nullptr;
   if (consumeIf('Q')) {
     Requires = getDerived().parseConstraintExpr();
     if (!Requires)
       return nullptr;
   }
 
   return make<FunctionEncoding>(ReturnType, Name, Params, Attrs, Requires,
                                 NameInfo.CVQualifiers,
                                 NameInfo.ReferenceQualifier);
 }
 
 template <class Float>
 struct FloatData;
 
 template <>
 struct FloatData<float>
 {
     static const size_t mangled_size = 8;
     static const size_t max_demangled_size = 24;
     static constexpr const char* spec = "%af";
 };
 
 template <>
 struct FloatData<double>
 {
     static const size_t mangled_size = 16;
     static const size_t max_demangled_size = 32;
     static constexpr const char* spec = "%a";
 };
 
 template <>
 struct FloatData<long double>
 {
 #if defined(__mips__) && defined(__mips_n64) || defined(__aarch64__) || \
     defined(__wasm__) || defined(__riscv) || defined(__loongarch__) || \
     defined(__ve__)
     static const size_t mangled_size = 32;
 #elif defined(__arm__) || defined(__mips__) || defined(__hexagon__)
     static const size_t mangled_size = 16;
 #else
     static const size_t mangled_size = 20;  // May need to be adjusted to 16 or 24 on other platforms
 #endif
     // `-0x1.ffffffffffffffffffffffffffffp+16383` + 'L' + '\0' == 42 bytes.
     // 28 'f's * 4 bits == 112 bits, which is the number of mantissa bits.
     // Negatives are one character longer than positives.
     // `0x1.` and `p` are constant, and exponents `+16383` and `-16382` are the
     // same length. 1 sign bit, 112 mantissa bits, and 15 exponent bits == 128.
     static const size_t max_demangled_size = 42;
     static constexpr const char *spec = "%LaL";
 };
 
 template <typename Alloc, typename Derived>
 template <class Float>
 Node *AbstractManglingParser<Alloc, Derived>::parseFloatingLiteral() {
   const size_t N = FloatData<Float>::mangled_size;
   if (numLeft() <= N)
     return nullptr;
   std::string_view Data(First, N);
   for (char C : Data)
     if (!(C >= '0' && C <= '9') && !(C >= 'a' && C <= 'f'))
       return nullptr;
   First += N;
   if (!consumeIf('E'))
     return nullptr;
   return make<FloatLiteralImpl<Float>>(Data);
 }
 
 // <seq-id> ::= <0-9A-Z>+
 template <typename Alloc, typename Derived>
 bool AbstractManglingParser<Alloc, Derived>::parseSeqId(size_t *Out) {
   if (!(look() >= '0' && look() <= '9') &&
       !(look() >= 'A' && look() <= 'Z'))
     return true;
 
   size_t Id = 0;
   while (true) {
     if (look() >= '0' && look() <= '9') {
       Id *= 36;
       Id += static_cast<size_t>(look() - '0');
     } else if (look() >= 'A' && look() <= 'Z') {
       Id *= 36;
       Id += static_cast<size_t>(look() - 'A') + 10;
     } else {
       *Out = Id;
       return false;
     }
     ++First;
   }
 }
 
 // <substitution> ::= S <seq-id> _
 //                ::= S_
 // <substitution> ::= Sa # ::std::allocator
 // <substitution> ::= Sb # ::std::basic_string
 // <substitution> ::= Ss # ::std::basic_string < char,
 //                                               ::std::char_traits<char>,
 //                                               ::std::allocator<char> >
 // <substitution> ::= Si # ::std::basic_istream<char,  std::char_traits<char> >
 // <substitution> ::= So # ::std::basic_ostream<char,  std::char_traits<char> >
 // <substitution> ::= Sd # ::std::basic_iostream<char, std::char_traits<char> >
 // The St case is handled specially in parseNestedName.
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseSubstitution() {
   if (!consumeIf('S'))
     return nullptr;
 
   if (look() >= 'a' && look() <= 'z') {
     SpecialSubKind Kind;
     switch (look()) {
     case 'a':
       Kind = SpecialSubKind::allocator;
       break;
     case 'b':
       Kind = SpecialSubKind::basic_string;
       break;
     case 'd':
       Kind = SpecialSubKind::iostream;
       break;
     case 'i':
       Kind = SpecialSubKind::istream;
       break;
     case 'o':
       Kind = SpecialSubKind::ostream;
       break;
     case 's':
       Kind = SpecialSubKind::string;
       break;
     default:
       return nullptr;
     }
     ++First;
     auto *SpecialSub = make<SpecialSubstitution>(Kind);
     if (!SpecialSub)
       return nullptr;
 
     // Itanium C++ ABI 5.1.2: If a name that would use a built-in <substitution>
     // has ABI tags, the tags are appended to the substitution; the result is a
     // substitutable component.
     Node *WithTags = getDerived().parseAbiTags(SpecialSub);
     if (WithTags != SpecialSub) {
       Subs.push_back(WithTags);
       SpecialSub = WithTags;
     }
     return SpecialSub;
   }
 
   //                ::= S_
   if (consumeIf('_')) {
     if (Subs.empty())
       return nullptr;
     return Subs[0];
   }
 
   //                ::= S <seq-id> _
   size_t Index = 0;
   if (parseSeqId(&Index))
     return nullptr;
   ++Index;
   if (!consumeIf('_') || Index >= Subs.size())
     return nullptr;
   return Subs[Index];
 }
 
 // <template-param> ::= T_    # first template parameter
 //                  ::= T <parameter-2 non-negative number> _
 //                  ::= TL <level-1> __
 //                  ::= TL <level-1> _ <parameter-2 non-negative number> _
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseTemplateParam() {
   const char *Begin = First;
   if (!consumeIf('T'))
     return nullptr;
 
   size_t Level = 0;
   if (consumeIf('L')) {
     if (parsePositiveInteger(&Level))
       return nullptr;
     ++Level;
     if (!consumeIf('_'))
       return nullptr;
   }
 
   size_t Index = 0;
   if (!consumeIf('_')) {
     if (parsePositiveInteger(&Index))
       return nullptr;
     ++Index;
     if (!consumeIf('_'))
       return nullptr;
   }
 
   // We don't track enclosing template parameter levels well enough to reliably
   // substitute them all within a <constraint-expression>, so print the
   // parameter numbering instead for now.
   // TODO: Track all enclosing template parameters and substitute them here.
   if (HasIncompleteTemplateParameterTracking) {
     return make<NameType>(std::string_view(Begin, First - 1 - Begin));
   }
 
   // If we're in a context where this <template-param> refers to a
   // <template-arg> further ahead in the mangled name (currently just conversion
   // operator types), then we should only look it up in the right context.
   // This can only happen at the outermost level.
   if (PermitForwardTemplateReferences && Level == 0) {
     Node *ForwardRef = make<ForwardTemplateReference>(Index);
     if (!ForwardRef)
       return nullptr;
     DEMANGLE_ASSERT(ForwardRef->getKind() == Node::KForwardTemplateReference,
                     "");
     ForwardTemplateRefs.push_back(
         static_cast<ForwardTemplateReference *>(ForwardRef));
     return ForwardRef;
   }
 
   if (Level >= TemplateParams.size() || !TemplateParams[Level] ||
       Index >= TemplateParams[Level]->size()) {
     // Itanium ABI 5.1.8: In a generic lambda, uses of auto in the parameter
     // list are mangled as the corresponding artificial template type parameter.
     if (ParsingLambdaParamsAtLevel == Level && Level <= TemplateParams.size()) {
       // This will be popped by the ScopedTemplateParamList in
       // parseUnnamedTypeName.
       if (Level == TemplateParams.size())
         TemplateParams.push_back(nullptr);
       return make<NameType>("auto");
     }
 
     return nullptr;
   }
 
   return (*TemplateParams[Level])[Index];
 }
 
 // <template-param-decl> ::= Ty                          # type parameter
 //                       ::= Tk <concept name> [<template-args>] # constrained type parameter
 //                       ::= Tn <type>                   # non-type parameter
 //                       ::= Tt <template-param-decl>* E # template parameter
 //                       ::= Tp <template-param-decl>    # parameter pack
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseTemplateParamDecl(
     TemplateParamList *Params) {
   auto InventTemplateParamName = [&](TemplateParamKind Kind) {
     unsigned Index = NumSyntheticTemplateParameters[(int)Kind]++;
     Node *N = make<SyntheticTemplateParamName>(Kind, Index);
     if (N && Params)
       Params->push_back(N);
     return N;
   };
 
   if (consumeIf("Ty")) {
     Node *Name = InventTemplateParamName(TemplateParamKind::Type);
     if (!Name)
       return nullptr;
     return make<TypeTemplateParamDecl>(Name);
   }
 
   if (consumeIf("Tk")) {
     // We don't track enclosing template parameter levels well enough to
     // reliably demangle template parameter substitutions, so print an arbitrary
     // string in place of a parameter for now.
     // TODO: Track all enclosing template parameters and demangle substitutions.
     ScopedOverride<bool> SaveIncompleteTemplateParameterTrackingExpr(
         HasIncompleteTemplateParameterTracking, true);
     Node *Constraint = getDerived().parseName();
     if (!Constraint)
       return nullptr;
     Node *Name = InventTemplateParamName(TemplateParamKind::Type);
     if (!Name)
       return nullptr;
     return make<ConstrainedTypeTemplateParamDecl>(Constraint, Name);
   }
 
   if (consumeIf("Tn")) {
     Node *Name = InventTemplateParamName(TemplateParamKind::NonType);
     if (!Name)
       return nullptr;
     Node *Type = parseType();
     if (!Type)
       return nullptr;
     return make<NonTypeTemplateParamDecl>(Name, Type);
   }
 
   if (consumeIf("Tt")) {
     Node *Name = InventTemplateParamName(TemplateParamKind::Template);
     if (!Name)
       return nullptr;
     size_t ParamsBegin = Names.size();
     ScopedTemplateParamList TemplateTemplateParamParams(this);
     Node *Requires = nullptr;
     while (!consumeIf('E')) {
       Node *P = parseTemplateParamDecl(TemplateTemplateParamParams.params());
       if (!P)
         return nullptr;
       Names.push_back(P);
       if (consumeIf('Q')) {
         Requires = getDerived().parseConstraintExpr();
         if (Requires == nullptr || !consumeIf('E'))
           return nullptr;
         break;
       }
     }
     NodeArray InnerParams = popTrailingNodeArray(ParamsBegin);
     return make<TemplateTemplateParamDecl>(Name, InnerParams, Requires);
   }
 
   if (consumeIf("Tp")) {
     Node *P = parseTemplateParamDecl(Params);
     if (!P)
       return nullptr;
     return make<TemplateParamPackDecl>(P);
   }
 
   return nullptr;
 }
 
 // <template-arg> ::= <type>                    # type or template
 //                ::= X <expression> E          # expression
 //                ::= <expr-primary>            # simple expressions
 //                ::= J <template-arg>* E       # argument pack
 //                ::= LZ <encoding> E           # extension
 //                ::= <template-param-decl> <template-arg>
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseTemplateArg() {
   switch (look()) {
   case 'X': {
     ++First;
     Node *Arg = getDerived().parseExpr();
     if (Arg == nullptr || !consumeIf('E'))
       return nullptr;
     return Arg;
   }
   case 'J': {
     ++First;
     size_t ArgsBegin = Names.size();
     while (!consumeIf('E')) {
       Node *Arg = getDerived().parseTemplateArg();
       if (Arg == nullptr)
         return nullptr;
       Names.push_back(Arg);
     }
     NodeArray Args = popTrailingNodeArray(ArgsBegin);
     return make<TemplateArgumentPack>(Args);
   }
   case 'L': {
     //                ::= LZ <encoding> E           # extension
     if (look(1) == 'Z') {
       First += 2;
       Node *Arg = getDerived().parseEncoding();
       if (Arg == nullptr || !consumeIf('E'))
         return nullptr;
       return Arg;
     }
     //                ::= <expr-primary>            # simple expressions
     return getDerived().parseExprPrimary();
   }
   case 'T': {
     // Either <template-param> or a <template-param-decl> <template-arg>.
     if (!getDerived().isTemplateParamDecl())
       return getDerived().parseType();
     Node *Param = getDerived().parseTemplateParamDecl(nullptr);
     if (!Param)
       return nullptr;
     Node *Arg = getDerived().parseTemplateArg();
     if (!Arg)
       return nullptr;
     return make<TemplateParamQualifiedArg>(Param, Arg);
   }
   default:
     return getDerived().parseType();
   }
 }
 
 // <template-args> ::= I <template-arg>* [Q <requires-clause expr>] E
 //     extension, the abi says <template-arg>+
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseTemplateArgs(bool TagTemplates) {
   if (!consumeIf('I'))
     return nullptr;
 
   // <template-params> refer to the innermost <template-args>. Clear out any
   // outer args that we may have inserted into TemplateParams.
   if (TagTemplates) {
     TemplateParams.clear();
     TemplateParams.push_back(&OuterTemplateParams);
     OuterTemplateParams.clear();
   }
 
   size_t ArgsBegin = Names.size();
   Node *Requires = nullptr;
   while (!consumeIf('E')) {
     if (TagTemplates) {
       Node *Arg = getDerived().parseTemplateArg();
       if (Arg == nullptr)
         return nullptr;
       Names.push_back(Arg);
       Node *TableEntry = Arg;
       if (Arg->getKind() == Node::KTemplateParamQualifiedArg) {
         TableEntry =
             static_cast<TemplateParamQualifiedArg *>(TableEntry)->getArg();
       }
       if (Arg->getKind() == Node::KTemplateArgumentPack) {
         TableEntry = make<ParameterPack>(
             static_cast<TemplateArgumentPack*>(TableEntry)->getElements());
         if (!TableEntry)
           return nullptr;
       }
       OuterTemplateParams.push_back(TableEntry);
     } else {
       Node *Arg = getDerived().parseTemplateArg();
       if (Arg == nullptr)
         return nullptr;
       Names.push_back(Arg);
     }
     if (consumeIf('Q')) {
       Requires = getDerived().parseConstraintExpr();
       if (!Requires || !consumeIf('E'))
         return nullptr;
       break;
     }
   }
   return make<TemplateArgs>(popTrailingNodeArray(ArgsBegin), Requires);
 }
 
 // <mangled-name> ::= _Z <encoding>
 //                ::= <type>
 // extension      ::= ___Z <encoding> _block_invoke
 // extension      ::= ___Z <encoding> _block_invoke<decimal-digit>+
 // extension      ::= ___Z <encoding> _block_invoke_<decimal-digit>+
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parse(bool ParseParams) {
   if (consumeIf("_Z") || consumeIf("__Z")) {
     Node *Encoding = getDerived().parseEncoding(ParseParams);
     if (Encoding == nullptr)
       return nullptr;
     if (look() == '.') {
       Encoding =
           make<DotSuffix>(Encoding, std::string_view(First, Last - First));
       First = Last;
     }
     if (numLeft() != 0)
       return nullptr;
     return Encoding;
   }
 
   if (consumeIf("___Z") || consumeIf("____Z")) {
     Node *Encoding = getDerived().parseEncoding(ParseParams);
     if (Encoding == nullptr || !consumeIf("_block_invoke"))
       return nullptr;
     bool RequireNumber = consumeIf('_');
     if (parseNumber().empty() && RequireNumber)
       return nullptr;
     if (look() == '.')
       First = Last;
     if (numLeft() != 0)
       return nullptr;
     return make<SpecialName>("invocation function for block in ", Encoding);
   }
 
   Node *Ty = getDerived().parseType();
   if (numLeft() != 0)
     return nullptr;
   return Ty;
 }
 
 template <typename Alloc>
 struct ManglingParser : AbstractManglingParser<ManglingParser<Alloc>, Alloc> {
   using AbstractManglingParser<ManglingParser<Alloc>,
                                Alloc>::AbstractManglingParser;
 };
 
 DEMANGLE_NAMESPACE_END
 
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #endif
 
 #endif // DEMANGLE_ITANIUMDEMANGLE_H