src/demangle/ItaniumDemangle.h

//===------------------------- ItaniumDemangle.h ----------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Generic itanium demangler library. This file has two byte-per-byte identical
// copies in the source tree, one in libcxxabi, and the other in llvm.
//
//===----------------------------------------------------------------------===//

#ifndef DEMANGLE_ITANIUMDEMANGLE_H
#define DEMANGLE_ITANIUMDEMANGLE_H

// FIXME: (possibly) incomplete list of features that clang mangles that this
// file does not yet support:
//   - C++ modules TS

#include "DemangleConfig.h"
#include "StringView.h"
#include "Utility.h"
#include <cassert>
#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <utility>

#define FOR_EACH_NODE_KIND(X) \
    X(NodeArrayNode) \
    X(DotSuffix) \
    X(VendorExtQualType) \
    X(QualType) \
    X(ConversionOperatorType) \
    X(PostfixQualifiedType) \
    X(ElaboratedTypeSpefType) \
    X(NameType) \
    X(AbiTagAttr) \
    X(EnableIfAttr) \
    X(ObjCProtoName) \
    X(PointerType) \
    X(ReferenceType) \
    X(PointerToMemberType) \
    X(ArrayType) \
    X(FunctionType) \
    X(NoexceptSpec) \
    X(DynamicExceptionSpec) \
    X(FunctionEncoding) \
    X(LiteralOperator) \
    X(SpecialName) \
    X(CtorVtableSpecialName) \
    X(QualifiedName) \
    X(NestedName) \
    X(LocalName) \
    X(VectorType) \
    X(PixelVectorType) \
    X(SyntheticTemplateParamName) \
    X(TypeTemplateParamDecl) \
    X(NonTypeTemplateParamDecl) \
    X(TemplateTemplateParamDecl) \
    X(TemplateParamPackDecl) \
    X(ParameterPack) \
    X(TemplateArgumentPack) \
    X(ParameterPackExpansion) \
    X(TemplateArgs) \
    X(ForwardTemplateReference) \
    X(NameWithTemplateArgs) \
    X(GlobalQualifiedName) \
    X(StdQualifiedName) \
    X(ExpandedSpecialSubstitution) \
    X(SpecialSubstitution) \
    X(CtorDtorName) \
    X(DtorName) \
    X(UnnamedTypeName) \
    X(ClosureTypeName) \
    X(StructuredBindingName) \
    X(BinaryExpr) \
    X(ArraySubscriptExpr) \
    X(PostfixExpr) \
    X(ConditionalExpr) \
    X(MemberExpr) \
    X(EnclosingExpr) \
    X(CastExpr) \
    X(SizeofParamPackExpr) \
    X(CallExpr) \
    X(NewExpr) \
    X(DeleteExpr) \
    X(PrefixExpr) \
    X(FunctionParam) \
    X(ConversionExpr) \
    X(InitListExpr) \
    X(FoldExpr) \
    X(ThrowExpr) \
    X(UUIDOfExpr) \
    X(BoolExpr) \
    X(StringLiteral) \
    X(LambdaExpr) \
    X(IntegerCastExpr) \
    X(IntegerLiteral) \
    X(FloatLiteral) \
    X(DoubleLiteral) \
    X(LongDoubleLiteral) \
    X(BracedExpr) \
    X(BracedRangeExpr)

DEMANGLE_NAMESPACE_BEGIN

// 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 ENUMERATOR(NodeKind) K ## NodeKind,
    FOR_EACH_NODE_KIND(ENUMERATOR)
#undef ENUMERATOR
  };

  /// 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, };

private:
  Kind K;

  // FIXME: Make these protected.
public:
  /// Tracks if this node has a component on its right side, in which case we
  /// need to call printRight.
  Cache RHSComponentCache;

  /// Track if this node is a (possibly qualified) array type. This can affect
  /// how we format the output string.
  Cache ArrayCache;

  /// Track if this node is a (possibly qualified) function type. This can
  /// affect how we format the output string.
  Cache FunctionCache;

public:
  Node(Kind K_, Cache RHSComponentCache_ = Cache::No,
       Cache ArrayCache_ = Cache::No, Cache FunctionCache_ = Cache::No)
      : K(K_), RHSComponentCache(RHSComponentCache_), ArrayCache(ArrayCache_),
        FunctionCache(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(OutputStream &S) const {
    if (RHSComponentCache != Cache::Unknown)
      return RHSComponentCache == Cache::Yes;
    return hasRHSComponentSlow(S);
  }

  bool hasArray(OutputStream &S) const {
    if (ArrayCache != Cache::Unknown)
      return ArrayCache == Cache::Yes;
    return hasArraySlow(S);
  }

  bool hasFunction(OutputStream &S) const {
    if (FunctionCache != Cache::Unknown)
      return FunctionCache == Cache::Yes;
    return hasFunctionSlow(S);
  }

  Kind getKind() const { return K; }

  virtual bool hasRHSComponentSlow(OutputStream &) const { return false; }
  virtual bool hasArraySlow(OutputStream &) const { return false; }
  virtual bool hasFunctionSlow(OutputStream &) 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(OutputStream &) const {
    return this;
  }

  void print(OutputStream &S) const {
    printLeft(S);
    if (RHSComponentCache != Cache::No)
      printRight(S);
  }

  // Print the "left" side of this Node into OutputStream.
  virtual void printLeft(OutputStream &) 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(OutputStream &) const {}

  virtual StringView getBaseName() const { return StringView(); }

  // 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(OutputStream &S) const {
    bool FirstElement = true;
    for (size_t Idx = 0; Idx != NumElements; ++Idx) {
      size_t BeforeComma = S.getCurrentPosition();
      if (!FirstElement)
        S += ", ";
      size_t AfterComma = S.getCurrentPosition();
      Elements[Idx]->print(S);

      // Elements[Idx] is an empty parameter pack expansion, we should erase the
      // comma we just printed.
      if (AfterComma == S.getCurrentPosition()) {
        S.setCurrentPosition(BeforeComma);
        continue;
      }

      FirstElement = false;
    }
  }
};

struct NodeArrayNode : Node {
  NodeArray Array;
  NodeArrayNode(NodeArray Array_) : Node(KNodeArrayNode), Array(Array_) {}

  template<typename Fn> void match(Fn F) const { F(Array); }

  void printLeft(OutputStream &S) const override {
    Array.printWithComma(S);
  }
};

class DotSuffix final : public Node {
  const Node *Prefix;
  const StringView Suffix;

public:
  DotSuffix(const Node *Prefix_, StringView Suffix_)
      : Node(KDotSuffix), Prefix(Prefix_), Suffix(Suffix_) {}

  template<typename Fn> void match(Fn F) const { F(Prefix, Suffix); }

  void printLeft(OutputStream &s) const override {
    Prefix->print(s);
    s += " (";
    s += Suffix;
    s += ")";
  }
};

class VendorExtQualType final : public Node {
  const Node *Ty;
  StringView Ext;

public:
  VendorExtQualType(const Node *Ty_, StringView Ext_)
      : Node(KVendorExtQualType), Ty(Ty_), Ext(Ext_) {}

  template<typename Fn> void match(Fn F) const { F(Ty, Ext); }

  void printLeft(OutputStream &S) const override {
    Ty->print(S);
    S += " ";
    S += Ext;
  }
};

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(OutputStream &S) const {
    if (Quals & QualConst)
      S += " const";
    if (Quals & QualVolatile)
      S += " volatile";
    if (Quals & QualRestrict)
      S += " restrict";
  }

public:
  QualType(const Node *Child_, Qualifiers Quals_)
      : Node(KQualType, Child_->RHSComponentCache,
             Child_->ArrayCache, Child_->FunctionCache),
        Quals(Quals_), Child(Child_) {}

  template<typename Fn> void match(Fn F) const { F(Child, Quals); }

  bool hasRHSComponentSlow(OutputStream &S) const override {
    return Child->hasRHSComponent(S);
  }
  bool hasArraySlow(OutputStream &S) const override {
    return Child->hasArray(S);
  }
  bool hasFunctionSlow(OutputStream &S) const override {
    return Child->hasFunction(S);
  }

  void printLeft(OutputStream &S) const override {
    Child->printLeft(S);
    printQuals(S);
  }

  void printRight(OutputStream &S) const override { Child->printRight(S); }
};

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(OutputStream &S) const override {
    S += "operator ";
    Ty->print(S);
  }
};

class PostfixQualifiedType final : public Node {
  const Node *Ty;
  const StringView Postfix;

public:
  PostfixQualifiedType(Node *Ty_, StringView Postfix_)
      : Node(KPostfixQualifiedType), Ty(Ty_), Postfix(Postfix_) {}

  template<typename Fn> void match(Fn F) const { F(Ty, Postfix); }

  void printLeft(OutputStream &s) const override {
    Ty->printLeft(s);
    s += Postfix;
  }
};

class NameType final : public Node {
  const StringView Name;

public:
  NameType(StringView Name_) : Node(KNameType), Name(Name_) {}

  template<typename Fn> void match(Fn F) const { F(Name); }

  StringView getName() const { return Name; }
  StringView getBaseName() const override { return Name; }

  void printLeft(OutputStream &s) const override { s += Name; }
};

class ElaboratedTypeSpefType : public Node {
  StringView Kind;
  Node *Child;
public:
  ElaboratedTypeSpefType(StringView Kind_, Node *Child_)
      : Node(KElaboratedTypeSpefType), Kind(Kind_), Child(Child_) {}

  template<typename Fn> void match(Fn F) const { F(Kind, Child); }

  void printLeft(OutputStream &S) const override {
    S += Kind;
    S += ' ';
    Child->print(S);
  }
};

struct AbiTagAttr : Node {
  Node *Base;
  StringView Tag;

  AbiTagAttr(Node* Base_, StringView Tag_)
      : Node(KAbiTagAttr, Base_->RHSComponentCache,
             Base_->ArrayCache, Base_->FunctionCache),
        Base(Base_), Tag(Tag_) {}

  template<typename Fn> void match(Fn F) const { F(Base, Tag); }

  void printLeft(OutputStream &S) const override {
    Base->printLeft(S);
    S += "[abi:";
    S += Tag;
    S += "]";
  }
};

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(OutputStream &S) const override {
    S += " [enable_if:";
    Conditions.printWithComma(S);
    S += ']';
  }
};

class ObjCProtoName : public Node {
  const Node *Ty;
  StringView Protocol;

  friend class PointerType;

public:
  ObjCProtoName(const Node *Ty_, StringView 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(OutputStream &S) const override {
    Ty->print(S);
    S += "<";
    S += Protocol;
    S += ">";
  }
};

class PointerType final : public Node {
  const Node *Pointee;

public:
  PointerType(const Node *Pointee_)
      : Node(KPointerType, Pointee_->RHSComponentCache),
        Pointee(Pointee_) {}

  template<typename Fn> void match(Fn F) const { F(Pointee); }

  bool hasRHSComponentSlow(OutputStream &S) const override {
    return Pointee->hasRHSComponent(S);
  }

  void printLeft(OutputStream &s) const override {
    // We rewrite objc_object<SomeProtocol>* into id<SomeProtocol>.
    if (Pointee->getKind() != KObjCProtoName ||
        !static_cast<const ObjCProtoName *>(Pointee)->isObjCObject()) {
      Pointee->printLeft(s);
      if (Pointee->hasArray(s))
        s += " ";
      if (Pointee->hasArray(s) || Pointee->hasFunction(s))
        s += "(";
      s += "*";
    } else {
      const auto *objcProto = static_cast<const ObjCProtoName *>(Pointee);
      s += "id<";
      s += objcProto->Protocol;
      s += ">";
    }
  }

  void printRight(OutputStream &s) const override {
    if (Pointee->getKind() != KObjCProtoName ||
        !static_cast<const ObjCProtoName *>(Pointee)->isObjCObject()) {
      if (Pointee->hasArray(s) || Pointee->hasFunction(s))
        s += ")";
      Pointee->printRight(s);
    }
  }
};

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.
  std::pair<ReferenceKind, const Node *> collapse(OutputStream &S) const {
    auto SoFar = std::make_pair(RK, Pointee);
    for (;;) {
      const Node *SN = SoFar.second->getSyntaxNode(S);
      if (SN->getKind() != KReferenceType)
        break;
      auto *RT = static_cast<const ReferenceType *>(SN);
      SoFar.second = RT->Pointee;
      SoFar.first = std::min(SoFar.first, RT->RK);
    }
    return SoFar;
  }

public:
  ReferenceType(const Node *Pointee_, ReferenceKind RK_)
      : Node(KReferenceType, Pointee_->RHSComponentCache),
        Pointee(Pointee_), RK(RK_) {}

  template<typename Fn> void match(Fn F) const { F(Pointee, RK); }

  bool hasRHSComponentSlow(OutputStream &S) const override {
    return Pointee->hasRHSComponent(S);
  }

  void printLeft(OutputStream &s) const override {
    if (Printing)
      return;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    std::pair<ReferenceKind, const Node *> Collapsed = collapse(s);
    Collapsed.second->printLeft(s);
    if (Collapsed.second->hasArray(s))
      s += " ";
    if (Collapsed.second->hasArray(s) || Collapsed.second->hasFunction(s))
      s += "(";

    s += (Collapsed.first == ReferenceKind::LValue ? "&" : "&&");
  }
  void printRight(OutputStream &s) const override {
    if (Printing)
      return;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    std::pair<ReferenceKind, const Node *> Collapsed = collapse(s);
    if (Collapsed.second->hasArray(s) || Collapsed.second->hasFunction(s))
      s += ")";
    Collapsed.second->printRight(s);
  }
};

class PointerToMemberType final : public Node {
  const Node *ClassType;
  const Node *MemberType;

public:
  PointerToMemberType(const Node *ClassType_, const Node *MemberType_)
      : Node(KPointerToMemberType, MemberType_->RHSComponentCache),
        ClassType(ClassType_), MemberType(MemberType_) {}

  template<typename Fn> void match(Fn F) const { F(ClassType, MemberType); }

  bool hasRHSComponentSlow(OutputStream &S) const override {
    return MemberType->hasRHSComponent(S);
  }

  void printLeft(OutputStream &s) const override {
    MemberType->printLeft(s);
    if (MemberType->hasArray(s) || MemberType->hasFunction(s))
      s += "(";
    else
      s += " ";
    ClassType->print(s);
    s += "::*";
  }

  void printRight(OutputStream &s) const override {
    if (MemberType->hasArray(s) || MemberType->hasFunction(s))
      s += ")";
    MemberType->printRight(s);
  }
};

class NodeOrString {
  const void *First;
  const void *Second;

public:
  /* implicit */ NodeOrString(StringView Str) {
    const char *FirstChar = Str.begin();
    const char *SecondChar = Str.end();
    if (SecondChar == nullptr) {
      assert(FirstChar == SecondChar);
      ++FirstChar, ++SecondChar;
    }
    First = static_cast<const void *>(FirstChar);
    Second = static_cast<const void *>(SecondChar);
  }

  /* implicit */ NodeOrString(Node *N)
      : First(static_cast<const void *>(N)), Second(nullptr) {}
  NodeOrString() : First(nullptr), Second(nullptr) {}

  bool isString() const { return Second && First; }
  bool isNode() const { return First && !Second; }
  bool isEmpty() const { return !First && !Second; }

  StringView asString() const {
    assert(isString());
    return StringView(static_cast<const char *>(First),
                      static_cast<const char *>(Second));
  }

  const Node *asNode() const {
    assert(isNode());
    return static_cast<const Node *>(First);
  }
};

class ArrayType final : public Node {
  const Node *Base;
  NodeOrString Dimension;

public:
  ArrayType(const Node *Base_, NodeOrString 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(OutputStream &) const override { return true; }
  bool hasArraySlow(OutputStream &) const override { return true; }

  void printLeft(OutputStream &S) const override { Base->printLeft(S); }

  void printRight(OutputStream &S) const override {
    if (S.back() != ']')
      S += " ";
    S += "[";
    if (Dimension.isString())
      S += Dimension.asString();
    else if (Dimension.isNode())
      Dimension.asNode()->print(S);
    S += "]";
    Base->printRight(S);
  }
};

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(OutputStream &) const override { return true; }
  bool hasFunctionSlow(OutputStream &) 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(OutputStream &S) const override {
    Ret->printLeft(S);
    S += " ";
  }

  void printRight(OutputStream &S) const override {
    S += "(";
    Params.printWithComma(S);
    S += ")";
    Ret->printRight(S);

    if (CVQuals & QualConst)
      S += " const";
    if (CVQuals & QualVolatile)
      S += " volatile";
    if (CVQuals & QualRestrict)
      S += " restrict";

    if (RefQual == FrefQualLValue)
      S += " &";
    else if (RefQual == FrefQualRValue)
      S += " &&";

    if (ExceptionSpec != nullptr) {
      S += ' ';
      ExceptionSpec->print(S);
    }
  }
};

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(OutputStream &S) const override {
    S += "noexcept(";
    E->print(S);
    S += ")";
  }
};

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(OutputStream &S) const override {
    S += "throw(";
    Types.printWithComma(S);
    S += ')';
  }
};

class FunctionEncoding final : public Node {
  const Node *Ret;
  const Node *Name;
  NodeArray Params;
  const Node *Attrs;
  Qualifiers CVQuals;
  FunctionRefQual RefQual;

public:
  FunctionEncoding(const Node *Ret_, const Node *Name_, NodeArray Params_,
                   const Node *Attrs_, Qualifiers CVQuals_,
                   FunctionRefQual RefQual_)
      : Node(KFunctionEncoding,
             /*RHSComponentCache=*/Cache::Yes, /*ArrayCache=*/Cache::No,
             /*FunctionCache=*/Cache::Yes),
        Ret(Ret_), Name(Name_), Params(Params_), Attrs(Attrs_),
        CVQuals(CVQuals_), RefQual(RefQual_) {}

  template<typename Fn> void match(Fn F) const {
    F(Ret, Name, Params, Attrs, 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(OutputStream &) const override { return true; }
  bool hasFunctionSlow(OutputStream &) const override { return true; }

  const Node *getName() const { return Name; }

  void printLeft(OutputStream &S) const override {
    if (Ret) {
      Ret->printLeft(S);
      if (!Ret->hasRHSComponent(S))
        S += " ";
    }
    Name->print(S);
  }

  void printRight(OutputStream &S) const override {
    S += "(";
    Params.printWithComma(S);
    S += ")";
    if (Ret)
      Ret->printRight(S);

    if (CVQuals & QualConst)
      S += " const";
    if (CVQuals & QualVolatile)
      S += " volatile";
    if (CVQuals & QualRestrict)
      S += " restrict";

    if (RefQual == FrefQualLValue)
      S += " &";
    else if (RefQual == FrefQualRValue)
      S += " &&";

    if (Attrs != nullptr)
      Attrs->print(S);
  }
};

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(OutputStream &S) const override {
    S += "operator\"\" ";
    OpName->print(S);
  }
};

class SpecialName final : public Node {
  const StringView Special;
  const Node *Child;

public:
  SpecialName(StringView Special_, const Node *Child_)
      : Node(KSpecialName), Special(Special_), Child(Child_) {}

  template<typename Fn> void match(Fn F) const { F(Special, Child); }

  void printLeft(OutputStream &S) const override {
    S += Special;
    Child->print(S);
  }
};

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(OutputStream &S) const override {
    S += "construction vtable for ";
    FirstType->print(S);
    S += "-in-";
    SecondType->print(S);
  }
};

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); }

  StringView getBaseName() const override { return Name->getBaseName(); }

  void printLeft(OutputStream &S) const override {
    Qual->print(S);
    S += "::";
    Name->print(S);
  }
};

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(OutputStream &S) const override {
    Encoding->print(S);
    S += "::";
    Entity->print(S);
  }
};

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); }

  StringView getBaseName() const override { return Name->getBaseName(); }

  void printLeft(OutputStream &S) const override {
    Qualifier->print(S);
    S += "::";
    Name->print(S);
  }
};

class VectorType final : public Node {
  const Node *BaseType;
  const NodeOrString Dimension;

public:
  VectorType(const Node *BaseType_, NodeOrString Dimension_)
      : Node(KVectorType), BaseType(BaseType_),
        Dimension(Dimension_) {}

  template<typename Fn> void match(Fn F) const { F(BaseType, Dimension); }

  void printLeft(OutputStream &S) const override {
    BaseType->print(S);
    S += " vector[";
    if (Dimension.isNode())
      Dimension.asNode()->print(S);
    else if (Dimension.isString())
      S += Dimension.asString();
    S += "]";
  }
};

class PixelVectorType final : public Node {
  const NodeOrString Dimension;

public:
  PixelVectorType(NodeOrString Dimension_)
      : Node(KPixelVectorType), Dimension(Dimension_) {}

  template<typename Fn> void match(Fn F) const { F(Dimension); }

  void printLeft(OutputStream &S) const override {
    // FIXME: This should demangle as "vector pixel".
    S += "pixel vector[";
    S += Dimension.asString();
    S += "]";
  }
};

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(OutputStream &S) const override {
    switch (Kind) {
    case TemplateParamKind::Type:
      S += "$T";
      break;
    case TemplateParamKind::NonType:
      S += "$N";
      break;
    case TemplateParamKind::Template:
      S += "$TT";
      break;
    }
    if (Index > 0)
      S << Index - 1;
  }
};

/// 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(OutputStream &S) const override {
    S += "typename ";
  }

  void printRight(OutputStream &S) const override {
    Name->print(S);
  }
};

/// 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(OutputStream &S) const override {
    Type->printLeft(S);
    if (!Type->hasRHSComponent(S))
      S += " ";
  }

  void printRight(OutputStream &S) const override {
    Name->print(S);
    Type->printRight(S);
  }
};

/// A template template parameter declaration,
/// 'template<typename T> typename N'.
class TemplateTemplateParamDecl final : public Node {
  Node *Name;
  NodeArray Params;

public:
  TemplateTemplateParamDecl(Node *Name_, NodeArray Params_)
      : Node(KTemplateTemplateParamDecl, Cache::Yes), Name(Name_),
        Params(Params_) {}

  template<typename Fn> void match(Fn F) const { F(Name, Params); }

  void printLeft(OutputStream &S) const override {
    S += "template<";
    Params.printWithComma(S);
    S += "> typename ";
  }

  void printRight(OutputStream &S) const override {
    Name->print(S);
  }
};

/// 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(OutputStream &S) const override {
    Param->printLeft(S);
    S += "...";
  }

  void printRight(OutputStream &S) const override {
    Param->printRight(S);
  }
};

/// 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 OutputStream for a pack expansion unless we're already expanding one.
  void initializePackExpansion(OutputStream &S) const {
    if (S.CurrentPackMax == std::numeric_limits<unsigned>::max()) {
      S.CurrentPackMax = static_cast<unsigned>(Data.size());
      S.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->ArrayCache == Cache::No;
        }))
      ArrayCache = Cache::No;
    if (std::all_of(Data.begin(), Data.end(), [](Node* P) {
          return P->FunctionCache == Cache::No;
        }))
      FunctionCache = Cache::No;
    if (std::all_of(Data.begin(), Data.end(), [](Node* P) {
          return P->RHSComponentCache == Cache::No;
        }))
      RHSComponentCache = Cache::No;
  }

  template<typename Fn> void match(Fn F) const { F(Data); }

  bool hasRHSComponentSlow(OutputStream &S) const override {
    initializePackExpansion(S);
    size_t Idx = S.CurrentPackIndex;
    return Idx < Data.size() && Data[Idx]->hasRHSComponent(S);
  }
  bool hasArraySlow(OutputStream &S) const override {
    initializePackExpansion(S);
    size_t Idx = S.CurrentPackIndex;
    return Idx < Data.size() && Data[Idx]->hasArray(S);
  }
  bool hasFunctionSlow(OutputStream &S) const override {
    initializePackExpansion(S);
    size_t Idx = S.CurrentPackIndex;
    return Idx < Data.size() && Data[Idx]->hasFunction(S);
  }
  const Node *getSyntaxNode(OutputStream &S) const override {
    initializePackExpansion(S);
    size_t Idx = S.CurrentPackIndex;
    return Idx < Data.size() ? Data[Idx]->getSyntaxNode(S) : this;
  }

  void printLeft(OutputStream &S) const override {
    initializePackExpansion(S);
    size_t Idx = S.CurrentPackIndex;
    if (Idx < Data.size())
      Data[Idx]->printLeft(S);
  }
  void printRight(OutputStream &S) const override {
    initializePackExpansion(S);
    size_t Idx = S.CurrentPackIndex;
    if (Idx < Data.size())
      Data[Idx]->printRight(S);
  }
};

/// 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 it's 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(OutputStream &S) const override {
    Elements.printWithComma(S);
  }
};

/// 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(OutputStream &S) const override {
    constexpr unsigned Max = std::numeric_limits<unsigned>::max();
    SwapAndRestore<unsigned> SavePackIdx(S.CurrentPackIndex, Max);
    SwapAndRestore<unsigned> SavePackMax(S.CurrentPackMax, Max);
    size_t StreamPos = S.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(S);

    // No ParameterPack was found in Child. This can occur if we've found a pack
    // expansion on a <function-param>.
    if (S.CurrentPackMax == Max) {
      S += "...";
      return;
    }

    // We found a ParameterPack, but it has no elements. Erase whatever we may
    // of printed.
    if (S.CurrentPackMax == 0) {
      S.setCurrentPosition(StreamPos);
      return;
    }

    // Else, iterate through the rest of the elements in the pack.
    for (unsigned I = 1, E = S.CurrentPackMax; I < E; ++I) {
      S += ", ";
      S.CurrentPackIndex = I;
      Child->print(S);
    }
  }
};

class TemplateArgs final : public Node {
  NodeArray Params;

public:
  TemplateArgs(NodeArray Params_) : Node(KTemplateArgs), Params(Params_) {}

  template<typename Fn> void match(Fn F) const { F(Params); }

  NodeArray getParams() { return Params; }

  void printLeft(OutputStream &S) const override {
    S += "<";
    Params.printWithComma(S);
    if (S.back() == '>')
      S += " ";
    S += ">";
  }
};

/// 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(OutputStream &S) const override {
    if (Printing)
      return false;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    return Ref->hasRHSComponent(S);
  }
  bool hasArraySlow(OutputStream &S) const override {
    if (Printing)
      return false;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    return Ref->hasArray(S);
  }
  bool hasFunctionSlow(OutputStream &S) const override {
    if (Printing)
      return false;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    return Ref->hasFunction(S);
  }
  const Node *getSyntaxNode(OutputStream &S) const override {
    if (Printing)
      return this;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    return Ref->getSyntaxNode(S);
  }

  void printLeft(OutputStream &S) const override {
    if (Printing)
      return;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    Ref->printLeft(S);
  }
  void printRight(OutputStream &S) const override {
    if (Printing)
      return;
    SwapAndRestore<bool> SavePrinting(Printing, true);
    Ref->printRight(S);
  }
};

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); }

  StringView getBaseName() const override { return Name->getBaseName(); }

  void printLeft(OutputStream &S) const override {
    Name->print(S);
    TemplateArgs->print(S);
  }
};

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); }

  StringView getBaseName() const override { return Child->getBaseName(); }

  void printLeft(OutputStream &S) const override {
    S += "::";
    Child->print(S);
  }
};

struct StdQualifiedName : Node {
  Node *Child;

  StdQualifiedName(Node *Child_) : Node(KStdQualifiedName), Child(Child_) {}

  template<typename Fn> void match(Fn F) const { F(Child); }

  StringView getBaseName() const override { return Child->getBaseName(); }

  void printLeft(OutputStream &S) const override {
    S += "std::";
    Child->print(S);
  }
};

enum class SpecialSubKind {
  allocator,
  basic_string,
  string,
  istream,
  ostream,
  iostream,
};

class ExpandedSpecialSubstitution final : public Node {
  SpecialSubKind SSK;

public:
  ExpandedSpecialSubstitution(SpecialSubKind SSK_)
      : Node(KExpandedSpecialSubstitution), SSK(SSK_) {}

  template<typename Fn> void match(Fn F) const { F(SSK); }

  StringView getBaseName() const override {
    switch (SSK) {
    case SpecialSubKind::allocator:
      return StringView("allocator");
    case SpecialSubKind::basic_string:
      return StringView("basic_string");
    case SpecialSubKind::string:
      return StringView("basic_string");
    case SpecialSubKind::istream:
      return StringView("basic_istream");
    case SpecialSubKind::ostream:
      return StringView("basic_ostream");
    case SpecialSubKind::iostream:
      return StringView("basic_iostream");
    }
    DEMANGLE_UNREACHABLE;
  }

  void printLeft(OutputStream &S) const override {
    switch (SSK) {
    case SpecialSubKind::allocator:
      S += "std::allocator";
      break;
    case SpecialSubKind::basic_string:
      S += "std::basic_string";
      break;
    case SpecialSubKind::string:
      S += "std::basic_string<char, std::char_traits<char>, "
           "std::allocator<char> >";
      break;
    case SpecialSubKind::istream:
      S += "std::basic_istream<char, std::char_traits<char> >";
      break;
    case SpecialSubKind::ostream:
      S += "std::basic_ostream<char, std::char_traits<char> >";
      break;
    case SpecialSubKind::iostream:
      S += "std::basic_iostream<char, std::char_traits<char> >";
      break;
    }
  }
};

class SpecialSubstitution final : public Node {
public:
  SpecialSubKind SSK;

  SpecialSubstitution(SpecialSubKind SSK_)
      : Node(KSpecialSubstitution), SSK(SSK_) {}

  template<typename Fn> void match(Fn F) const { F(SSK); }

  StringView getBaseName() const override {
    switch (SSK) {
    case SpecialSubKind::allocator:
      return StringView("allocator");
    case SpecialSubKind::basic_string:
      return StringView("basic_string");
    case SpecialSubKind::string:
      return StringView("string");
    case SpecialSubKind::istream:
      return StringView("istream");
    case SpecialSubKind::ostream:
      return StringView("ostream");
    case SpecialSubKind::iostream:
      return StringView("iostream");
    }
    DEMANGLE_UNREACHABLE;
  }

  void printLeft(OutputStream &S) const override {
    switch (SSK) {
    case SpecialSubKind::allocator:
      S += "std::allocator";
      break;
    case SpecialSubKind::basic_string:
      S += "std::basic_string";
      break;
    case SpecialSubKind::string:
      S += "std::string";
      break;
    case SpecialSubKind::istream:
      S += "std::istream";
      break;
    case SpecialSubKind::ostream:
      S += "std::ostream";
      break;
    case SpecialSubKind::iostream:
      S += "std::iostream";
      break;
    }
  }
};

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(OutputStream &S) const override {
    if (IsDtor)
      S += "~";
    S += 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(OutputStream &S) const override {
    S += "~";
    Base->printLeft(S);
  }
};

class UnnamedTypeName : public Node {
  const StringView Count;

public:
  UnnamedTypeName(StringView Count_) : Node(KUnnamedTypeName), Count(Count_) {}

  template<typename Fn> void match(Fn F) const { F(Count); }

  void printLeft(OutputStream &S) const override {
    S += "'unnamed";
    S += Count;
    S += "\'";
  }
};

class ClosureTypeName : public Node {
  NodeArray TemplateParams;
  NodeArray Params;
  StringView Count;

public:
  ClosureTypeName(NodeArray TemplateParams_, NodeArray Params_,
                  StringView Count_)
      : Node(KClosureTypeName), TemplateParams(TemplateParams_),
        Params(Params_), Count(Count_) {}

  template<typename Fn> void match(Fn F) const {
    F(TemplateParams, Params, Count);
  }

  void printDeclarator(OutputStream &S) const {
    if (!TemplateParams.empty()) {
      S += "<";
      TemplateParams.printWithComma(S);
      S += ">";
    }
    S += "(";
    Params.printWithComma(S);
    S += ")";
  }

  void printLeft(OutputStream &S) const override {
    S += "\'lambda";
    S += Count;
    S += "\'";
    printDeclarator(S);
  }
};

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(OutputStream &S) const override {
    S += '[';
    Bindings.printWithComma(S);
    S += ']';
  }
};

// -- Expression Nodes --

class BinaryExpr : public Node {
  const Node *LHS;
  const StringView InfixOperator;
  const Node *RHS;

public:
  BinaryExpr(const Node *LHS_, StringView InfixOperator_, const Node *RHS_)
      : Node(KBinaryExpr), LHS(LHS_), InfixOperator(InfixOperator_), RHS(RHS_) {
  }

  template<typename Fn> void match(Fn F) const { F(LHS, InfixOperator, RHS); }

  void printLeft(OutputStream &S) const override {
    // might be a template argument expression, then we need to disambiguate
    // with parens.
    if (InfixOperator == ">")
      S += "(";

    S += "(";
    LHS->print(S);
    S += ") ";
    S += InfixOperator;
    S += " (";
    RHS->print(S);
    S += ")";

    if (InfixOperator == ">")
      S += ")";
  }
};

class ArraySubscriptExpr : public Node {
  const Node *Op1;
  const Node *Op2;

public:
  ArraySubscriptExpr(const Node *Op1_, const Node *Op2_)
      : Node(KArraySubscriptExpr), Op1(Op1_), Op2(Op2_) {}

  template<typename Fn> void match(Fn F) const { F(Op1, Op2); }

  void printLeft(OutputStream &S) const override {
    S += "(";
    Op1->print(S);
    S += ")[";
    Op2->print(S);
    S += "]";
  }
};

class PostfixExpr : public Node {
  const Node *Child;
  const StringView Operator;

public:
  PostfixExpr(const Node *Child_, StringView Operator_)
      : Node(KPostfixExpr), Child(Child_), Operator(Operator_) {}

  template<typename Fn> void match(Fn F) const { F(Child, Operator); }

  void printLeft(OutputStream &S) const override {
    S += "(";
    Child->print(S);
    S += ")";
    S += 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_)
      : Node(KConditionalExpr), Cond(Cond_), Then(Then_), Else(Else_) {}

  template<typename Fn> void match(Fn F) const { F(Cond, Then, Else); }

  void printLeft(OutputStream &S) const override {
    S += "(";
    Cond->print(S);
    S += ") ? (";
    Then->print(S);
    S += ") : (";
    Else->print(S);
    S += ")";
  }
};

class MemberExpr : public Node {
  const Node *LHS;
  const StringView Kind;
  const Node *RHS;

public:
  MemberExpr(const Node *LHS_, StringView Kind_, const Node *RHS_)
      : Node(KMemberExpr), LHS(LHS_), Kind(Kind_), RHS(RHS_) {}

  template<typename Fn> void match(Fn F) const { F(LHS, Kind, RHS); }

  void printLeft(OutputStream &S) const override {
    LHS->print(S);
    S += Kind;
    RHS->print(S);
  }
};

class EnclosingExpr : public Node {
  const StringView Prefix;
  const Node *Infix;
  const StringView Postfix;

public:
  EnclosingExpr(StringView Prefix_, Node *Infix_, StringView Postfix_)
      : Node(KEnclosingExpr), Prefix(Prefix_), Infix(Infix_),
        Postfix(Postfix_) {}

  template<typename Fn> void match(Fn F) const { F(Prefix, Infix, Postfix); }

  void printLeft(OutputStream &S) const override {
    S += Prefix;
    Infix->print(S);
    S += Postfix;
  }
};

class CastExpr : public Node {
  // cast_kind<to>(from)
  const StringView CastKind;
  const Node *To;
  const Node *From;

public:
  CastExpr(StringView CastKind_, const Node *To_, const Node *From_)
      : Node(KCastExpr), CastKind(CastKind_), To(To_), From(From_) {}

  template<typename Fn> void match(Fn F) const { F(CastKind, To, From); }

  void printLeft(OutputStream &S) const override {
    S += CastKind;
    S += "<";
    To->printLeft(S);
    S += ">(";
    From->printLeft(S);
    S += ")";
  }
};

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(OutputStream &S) const override {
    S += "sizeof...(";
    ParameterPackExpansion PPE(Pack);
    PPE.printLeft(S);
    S += ")";
  }
};

class CallExpr : public Node {
  const Node *Callee;
  NodeArray Args;

public:
  CallExpr(const Node *Callee_, NodeArray Args_)
      : Node(KCallExpr), Callee(Callee_), Args(Args_) {}

  template<typename Fn> void match(Fn F) const { F(Callee, Args); }

  void printLeft(OutputStream &S) const override {
    Callee->print(S);
    S += "(";
    Args.printWithComma(S);
    S += ")";
  }
};

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_)
      : Node(KNewExpr), ExprList(ExprList_), Type(Type_), InitList(InitList_),
        IsGlobal(IsGlobal_), IsArray(IsArray_) {}

  template<typename Fn> void match(Fn F) const {
    F(ExprList, Type, InitList, IsGlobal, IsArray);
  }

  void printLeft(OutputStream &S) const override {
    if (IsGlobal)
      S += "::operator ";
    S += "new";
    if (IsArray)
      S += "[]";
    S += ' ';
    if (!ExprList.empty()) {
      S += "(";
      ExprList.printWithComma(S);
      S += ")";
    }
    Type->print(S);
    if (!InitList.empty()) {
      S += "(";
      InitList.printWithComma(S);
      S += ")";
    }

  }
};

class DeleteExpr : public Node {
  Node *Op;
  bool IsGlobal;
  bool IsArray;

public:
  DeleteExpr(Node *Op_, bool IsGlobal_, bool IsArray_)
      : Node(KDeleteExpr), Op(Op_), IsGlobal(IsGlobal_), IsArray(IsArray_) {}

  template<typename Fn> void match(Fn F) const { F(Op, IsGlobal, IsArray); }

  void printLeft(OutputStream &S) const override {
    if (IsGlobal)
      S += "::";
    S += "delete";
    if (IsArray)
      S += "[] ";
    Op->print(S);
  }
};

class PrefixExpr : public Node {
  StringView Prefix;
  Node *Child;

public:
  PrefixExpr(StringView Prefix_, Node *Child_)
      : Node(KPrefixExpr), Prefix(Prefix_), Child(Child_) {}

  template<typename Fn> void match(Fn F) const { F(Prefix, Child); }

  void printLeft(OutputStream &S) const override {
    S += Prefix;
    S += "(";
    Child->print(S);
    S += ")";
  }
};

class FunctionParam : public Node {
  StringView Number;

public:
  FunctionParam(StringView Number_) : Node(KFunctionParam), Number(Number_) {}

  template<typename Fn> void match(Fn F) const { F(Number); }

  void printLeft(OutputStream &S) const override {
    S += "fp";
    S += Number;
  }
};

class ConversionExpr : public Node {
  const Node *Type;
  NodeArray Expressions;

public:
  ConversionExpr(const Node *Type_, NodeArray Expressions_)
      : Node(KConversionExpr), Type(Type_), Expressions(Expressions_) {}

  template<typename Fn> void match(Fn F) const { F(Type, Expressions); }

  void printLeft(OutputStream &S) const override {
    S += "(";
    Type->print(S);
    S += ")(";
    Expressions.printWithComma(S);
    S += ")";
  }
};

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(OutputStream &S) const override {
    if (Ty)
      Ty->print(S);
    S += '{';
    Inits.printWithComma(S);
    S += '}';
  }
};

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(OutputStream &S) const override {
    if (IsArray) {
      S += '[';
      Elem->print(S);
      S += ']';
    } else {
      S += '.';
      Elem->print(S);
    }
    if (Init->getKind() != KBracedExpr && Init->getKind() != KBracedRangeExpr)
      S += " = ";
    Init->print(S);
  }
};

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(OutputStream &S) const override {
    S += '[';
    First->print(S);
    S += " ... ";
    Last->print(S);
    S += ']';
    if (Init->getKind() != KBracedExpr && Init->getKind() != KBracedRangeExpr)
      S += " = ";
    Init->print(S);
  }
};

class FoldExpr : public Node {
  const Node *Pack, *Init;
  StringView OperatorName;
  bool IsLeftFold;

public:
  FoldExpr(bool IsLeftFold_, StringView 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(OutputStream &S) const override {
    auto PrintPack = [&] {
      S += '(';
      ParameterPackExpansion(Pack).print(S);
      S += ')';
    };

    S += '(';

    if (IsLeftFold) {
      // init op ... op pack
      if (Init != nullptr) {
        Init->print(S);
        S += ' ';
        S += OperatorName;
        S += ' ';
      }
      // ... op pack
      S += "... ";
      S += OperatorName;
      S += ' ';
      PrintPack();
    } else { // !IsLeftFold
      // pack op ...
      PrintPack();
      S += ' ';
      S += OperatorName;
      S += " ...";
      // pack op ... op init
      if (Init != nullptr) {
        S += ' ';
        S += OperatorName;
        S += ' ';
        Init->print(S);
      }
    }
    S += ')';
  }
};

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(OutputStream &S) const override {
    S += "throw ";
    Op->print(S);
  }
};

// MSVC __uuidof extension, generated by clang in -fms-extensions mode.
class UUIDOfExpr : public Node {
  Node *Operand;
public:
  UUIDOfExpr(Node *Operand_) : Node(KUUIDOfExpr), Operand(Operand_) {}

  template<typename Fn> void match(Fn F) const { F(Operand); }

  void printLeft(OutputStream &S) const override {
    S << "__uuidof(";
    Operand->print(S);
    S << ")";
  }
};

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(OutputStream &S) const override {
    S += Value ? StringView("true") : StringView("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(OutputStream &S) const override {
    S += "\"<";
    Type->print(S);
    S += ">\"";
  }
};

class LambdaExpr : public Node {
  const Node *Type;

  void printLambdaDeclarator(OutputStream &S) const;

public:
  LambdaExpr(const Node *Type_) : Node(KLambdaExpr), Type(Type_) {}

  template<typename Fn> void match(Fn F) const { F(Type); }

  void printLeft(OutputStream &S) const override {
    S += "[]";
    printLambdaDeclarator(S);
    S += "{...}";
  }
};

class IntegerCastExpr : public Node {
  // ty(integer)
  const Node *Ty;
  StringView Integer;

public:
  IntegerCastExpr(const Node *Ty_, StringView Integer_)
      : Node(KIntegerCastExpr), Ty(Ty_), Integer(Integer_) {}

  template<typename Fn> void match(Fn F) const { F(Ty, Integer); }

  void printLeft(OutputStream &S) const override {
    S += "(";
    Ty->print(S);
    S += ")";
    S += Integer;
  }
};

class IntegerLiteral : public Node {
  StringView Type;
  StringView Value;

public:
  IntegerLiteral(StringView Type_, StringView Value_)
      : Node(KIntegerLiteral), Type(Type_), Value(Value_) {}

  template<typename Fn> void match(Fn F) const { F(Type, Value); }

  void printLeft(OutputStream &S) const override {
    if (Type.size() > 3) {
      S += "(";
      S += Type;
      S += ")";
    }

    if (Value[0] == 'n') {
      S += "-";
      S += Value.dropFront(1);
    } else
      S += Value;

    if (Type.size() <= 3)
      S += Type;
  }
};

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 StringView Contents;

  static constexpr Kind KindForClass =
      float_literal_impl::getFloatLiteralKind((Float *)nullptr);

public:
  FloatLiteralImpl(StringView Contents_)
      : Node(KindForClass), Contents(Contents_) {}

  template<typename Fn> void match(Fn F) const { F(Contents); }

  void printLeft(OutputStream &s) const override {
    const char *first = Contents.begin();
    const char *last = Contents.end() + 1;

    const size_t N = FloatData<Float>::mangled_size;
    if (static_cast<std::size_t>(last - first) > N) {
      last = first + N;
      union {
        Float value;
        char buf[sizeof(Float)];
      };
      const char *t = first;
      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);
      s += StringView(num, 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 CASE(X) case K ## X: return F(static_cast<const X*>(this));
    FOR_EACH_NODE_KIND(CASE)
#undef CASE
  }
  assert(0 && "unknown mangling node kind");
}

/// Determine the kind of a node from its type.
template<typename NodeT> struct NodeKind;
#define SPECIALIZATION(X) \
  template<> struct NodeKind<X> { \
    static constexpr Node::Kind Kind = Node::K##X; \
    static constexpr const char *name() { return #X; } \
  };
FOR_EACH_NODE_KIND(SPECIALIZATION)
#undef SPECIALIZATION

#undef FOR_EACH_NODE_KIND

inline void LambdaExpr::printLambdaDeclarator(OutputStream &S) const {
  struct LambdaDeclaratorPrinter {
    OutputStream &S;
    void operator()(const ClosureTypeName *LambdaType) {
      LambdaType->printDeclarator(S);
    }

    // Walk through any qualifiers to find the lambda-expression.
    void operator()(const SpecialName *Name) {
      Name->match([&](StringView, const Node *Name) { Name->visit(*this); });
    }
    void operator()(const NestedName *Name) {
      Name->match([&](const Node *, const Node *Name) { Name->visit(*this); });
    }
    void operator()(const LocalName *Name) {
      Name->match([&](const Node *, const Node *Name) { Name->visit(*this); });
    }
    void operator()(const QualifiedName *Name) {
      Name->match([&](const Node *, const Node *Name) { Name->visit(*this); });
    }
    void operator()(const GlobalQualifiedName *Name) {
      Name->match([&](const Node *Child) { Child->visit(*this); });
    }
    void operator()(const StdQualifiedName *Name) {
      Name->match([&](const Node *Child) { Child->visit(*this); });
    }
    void operator()(const Node *) {
      // If we can't find the lambda type, just print '[]{...}'.
    }
  };
  return Type->visit(LambdaDeclaratorPrinter{S});
}

template <class T, size_t N>
class PODSmallVector {
  static_assert(std::is_pod<T>::value,
                "T is required to be a plain old data type");

  T* First;
  T* Last;
  T* Cap;
  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::terminate();
      std::copy(First, Last, Tmp);
      First = Tmp;
    } else {
      First = static_cast<T*>(std::realloc(First, NewCap * sizeof(T)));
      if (First == nullptr)
        std::terminate();
    }
    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;
  }

  void push_back(const T& Elem) {
    if (Last == Cap)
      reserve(size() * 2);
    *Last++ = Elem;
  }

  void pop_back() {
    assert(Last != First && "Popping empty vector!");
    --Last;
  }

  void dropBack(size_t Index) {
    assert(Index <= size() && "dropBack() 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() {
    assert(Last != First && "Calling back() on empty vector!");
    return *(Last - 1);
  }
  T& operator[](size_t Index) {
    assert(Index < size() && "Invalid access!");
    return *(begin() + Index);
  }
  void clear() { Last = First; }

  ~PODSmallVector() {
    if (!isInline())
      std::free(First);
  }
};

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;

  using TemplateParamList = PODSmallVector<Node *, 8>;

  class ScopedTemplateParamList {
    AbstractManglingParser *Parser;
    size_t OldNumTemplateParamLists;
    TemplateParamList Params;

  public:
    ScopedTemplateParamList(AbstractManglingParser *Parser)
        : Parser(Parser),
          OldNumTemplateParamLists(Parser->TemplateParams.size()) {
      Parser->TemplateParams.push_back(&Params);
    }
    ~ScopedTemplateParamList() {
      assert(Parser->TemplateParams.size() >= OldNumTemplateParamLists);
      Parser->TemplateParams.dropBack(OldNumTemplateParamLists);
    }
    void push_back(Node *Param) {
      Params.push_back(Param);
    }
  };

  // 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;

  // 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;
  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) {
    assert(FromPosition <= Names.size());
    NodeArray res =
        makeNodeArray(Names.begin() + (long)FromPosition, Names.end());
    Names.dropBack(FromPosition);
    return res;
  }

  bool consumeIf(StringView S) {
    if (StringView(First, Last).startsWith(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) {
    if (static_cast<size_t>(Last - First) <= Lookahead)
      return '\0';
    return First[Lookahead];
  }

  size_t numLeft() const { return static_cast<size_t>(Last - First); }

  StringView parseNumber(bool AllowNegative = false);
  Qualifiers parseCVQualifiers();
  bool parsePositiveInteger(size_t *Out);
  StringView parseBareSourceName();

  bool parseSeqId(size_t *Out);
  Node *parseSubstitution();
  Node *parseTemplateParam();
  Node *parseTemplateParamDecl();
  Node *parseTemplateArgs(bool TagTemplates = false);
  Node *parseTemplateArg();

  /// Parse the <expr> production.
  Node *parseExpr();
  Node *parsePrefixExpr(StringView Kind);
  Node *parseBinaryExpr(StringView Kind);
  Node *parseIntegerLiteral(StringView Lit);
  Node *parseExprPrimary();
  template <class Float> Node *parseFloatingLiteral();
  Node *parseFunctionParam();
  Node *parseNewExpr();
  Node *parseConversionExpr();
  Node *parseBracedExpr();
  Node *parseFoldExpr();

  /// Parse the <type> production.
  Node *parseType();
  Node *parseFunctionType();
  Node *parseVectorType();
  Node *parseDecltype();
  Node *parseArrayType();
  Node *parsePointerToMemberType();
  Node *parseClassEnumType();
  Node *parseQualifiedType();

  Node *parseEncoding();
  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;

    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.dropBack(State.ForwardTemplateRefsBegin);
    return false;
  }

  /// Parse the <name> production>
  Node *parseName(NameState *State = nullptr);
  Node *parseLocalName(NameState *State);
  Node *parseOperatorName(NameState *State);
  Node *parseUnqualifiedName(NameState *State);
  Node *parseUnnamedTypeName(NameState *State);
  Node *parseSourceName(NameState *State);
  Node *parseUnscopedName(NameState *State);
  Node *parseNestedName(NameState *State);
  Node *parseCtorDtorName(Node *&SoFar, NameState *State);

  Node *parseAbiTags(Node *N);

  /// Parse the <unresolved-name> production.
  Node *parseUnresolvedName();
  Node *parseSimpleId();
  Node *parseBaseUnresolvedName();
  Node *parseUnresolvedType();
  Node *parseDestructorName();

  /// Top-level entry point into the parser.
  Node *parse();
};

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) {
  consumeIf('L'); // extension

  if (look() == 'N')
    return getDerived().parseNestedName(State);
  if (look() == 'Z')
    return getDerived().parseLocalName(State);

  //        ::= <unscoped-template-name> <template-args>
  if (look() == 'S' && look(1) != 't') {
    Node *S = getDerived().parseSubstitution();
    if (S == nullptr)
      return nullptr;
    if (look() != 'I')
      return nullptr;
    Node *TA = getDerived().parseTemplateArgs(State != nullptr);
    if (TA == nullptr)
      return nullptr;
    if (State) State->EndsWithTemplateArgs = true;
    return make<NameWithTemplateArgs>(S, TA);
  }

  Node *N = getDerived().parseUnscopedName(State);
  if (N == nullptr)
    return nullptr;
  //        ::= <unscoped-template-name> <template-args>
  if (look() == 'I') {
    Subs.push_back(N);
    Node *TA = getDerived().parseTemplateArgs(State != nullptr);
    if (TA == nullptr)
      return nullptr;
    if (State) State->EndsWithTemplateArgs = true;
    return make<NameWithTemplateArgs>(N, TA);
  }
  //        ::= <unscoped-name>
  return N;
}

// <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);
  }

  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       ::= StL<unqualified-name>
template <typename Derived, typename Alloc>
Node *
AbstractManglingParser<Derived, Alloc>::parseUnscopedName(NameState *State) {
  if (consumeIf("StL") || consumeIf("St")) {
    Node *R = getDerived().parseUnqualifiedName(State);
    if (R == nullptr)
      return nullptr;
    return make<StdQualifiedName>(R);
  }
  return getDerived().parseUnqualifiedName(State);
}

// <unqualified-name> ::= <operator-name> [abi-tags]
//                    ::= <ctor-dtor-name>
//                    ::= <source-name>
//                    ::= <unnamed-type-name>
//                    ::= DC <source-name>+ E      # structured binding declaration
template <typename Derived, typename Alloc>
Node *
AbstractManglingParser<Derived, Alloc>::parseUnqualifiedName(NameState *State) {
  // <ctor-dtor-name>s are special-cased in parseNestedName().
  Node *Result;
  if (look() == 'U')
    Result = getDerived().parseUnnamedTypeName(State);
  else if (look() >= '1' && look() <= '9')
    Result = getDerived().parseSourceName(State);
  else if (consumeIf("DC")) {
    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
    Result = getDerived().parseOperatorName(State);
  if (Result != nullptr)