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 //===- llvm/Support/YAMLTraits.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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_YAMLTRAITS_H
 #define LLVM_SUPPORT_YAMLTRAITS_H
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/AlignOf.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/YAMLParser.h"
 #include "llvm/Support/raw_ostream.h"
 #include <array>
 #include <cassert>
 #include <map>
 #include <memory>
 #include <new>
 #include <optional>
 #include <string>
 #include <system_error>
 #include <type_traits>
 #include <vector>
 
 namespace llvm {
 
 class VersionTuple;
 
 namespace yaml {
 
 enum class NodeKind : uint8_t {
   Scalar,
   Map,
   Sequence,
 };
 
 struct EmptyContext {};
 
 /// This class should be specialized by any type that needs to be converted
 /// to/from a YAML mapping.  For example:
 ///
 ///     struct MappingTraits<MyStruct> {
 ///       static void mapping(IO &io, MyStruct &s) {
 ///         io.mapRequired("name", s.name);
 ///         io.mapRequired("size", s.size);
 ///         io.mapOptional("age",  s.age);
 ///       }
 ///     };
 template<class T>
 struct MappingTraits {
   // Must provide:
   // static void mapping(IO &io, T &fields);
   // Optionally may provide:
   // static std::string validate(IO &io, T &fields);
   // static void enumInput(IO &io, T &value);
   //
   // The optional flow flag will cause generated YAML to use a flow mapping
   // (e.g. { a: 0, b: 1 }):
   // static const bool flow = true;
 };
 
 /// This class is similar to MappingTraits<T> but allows you to pass in
 /// additional context for each map operation.  For example:
 ///
 ///     struct MappingContextTraits<MyStruct, MyContext> {
 ///       static void mapping(IO &io, MyStruct &s, MyContext &c) {
 ///         io.mapRequired("name", s.name);
 ///         io.mapRequired("size", s.size);
 ///         io.mapOptional("age",  s.age);
 ///         ++c.TimesMapped;
 ///       }
 ///     };
 template <class T, class Context> struct MappingContextTraits {
   // Must provide:
   // static void mapping(IO &io, T &fields, Context &Ctx);
   // Optionally may provide:
   // static std::string validate(IO &io, T &fields, Context &Ctx);
   //
   // The optional flow flag will cause generated YAML to use a flow mapping
   // (e.g. { a: 0, b: 1 }):
   // static const bool flow = true;
 };
 
 /// This class should be specialized by any integral type that converts
 /// to/from a YAML scalar where there is a one-to-one mapping between
 /// in-memory values and a string in YAML.  For example:
 ///
 ///     struct ScalarEnumerationTraits<Colors> {
 ///         static void enumeration(IO &io, Colors &value) {
 ///           io.enumCase(value, "red",   cRed);
 ///           io.enumCase(value, "blue",  cBlue);
 ///           io.enumCase(value, "green", cGreen);
 ///         }
 ///       };
 template <typename T, typename Enable = void> struct ScalarEnumerationTraits {
   // Must provide:
   // static void enumeration(IO &io, T &value);
 };
 
 /// This class should be specialized by any integer type that is a union
 /// of bit values and the YAML representation is a flow sequence of
 /// strings.  For example:
 ///
 ///      struct ScalarBitSetTraits<MyFlags> {
 ///        static void bitset(IO &io, MyFlags &value) {
 ///          io.bitSetCase(value, "big",   flagBig);
 ///          io.bitSetCase(value, "flat",  flagFlat);
 ///          io.bitSetCase(value, "round", flagRound);
 ///        }
 ///      };
 template <typename T, typename Enable = void> struct ScalarBitSetTraits {
   // Must provide:
   // static void bitset(IO &io, T &value);
 };
 
 /// Describe which type of quotes should be used when quoting is necessary.
 /// Some non-printable characters need to be double-quoted, while some others
 /// are fine with simple-quoting, and some don't need any quoting.
 enum class QuotingType { None, Single, Double };
 
 /// This class should be specialized by type that requires custom conversion
 /// to/from a yaml scalar.  For example:
 ///
 ///    template<>
 ///    struct ScalarTraits<MyType> {
 ///      static void output(const MyType &val, void*, llvm::raw_ostream &out) {
 ///        // stream out custom formatting
 ///        out << llvm::format("%x", val);
 ///      }
 ///      static StringRef input(StringRef scalar, void*, MyType &value) {
 ///        // parse scalar and set `value`
 ///        // return empty string on success, or error string
 ///        return StringRef();
 ///      }
 ///      static QuotingType mustQuote(StringRef) { return QuotingType::Single; }
 ///    };
 template <typename T, typename Enable = void> struct ScalarTraits {
   // Must provide:
   //
   // Function to write the value as a string:
   // static void output(const T &value, void *ctxt, llvm::raw_ostream &out);
   //
   // Function to convert a string to a value.  Returns the empty
   // StringRef on success or an error string if string is malformed:
   // static StringRef input(StringRef scalar, void *ctxt, T &value);
   //
   // Function to determine if the value should be quoted.
   // static QuotingType mustQuote(StringRef);
 };
 
 /// This class should be specialized by type that requires custom conversion
 /// to/from a YAML literal block scalar. For example:
 ///
 ///    template <>
 ///    struct BlockScalarTraits<MyType> {
 ///      static void output(const MyType &Value, void*, llvm::raw_ostream &Out)
 ///      {
 ///        // stream out custom formatting
 ///        Out << Value;
 ///      }
 ///      static StringRef input(StringRef Scalar, void*, MyType &Value) {
 ///        // parse scalar and set `value`
 ///        // return empty string on success, or error string
 ///        return StringRef();
 ///      }
 ///    };
 template <typename T>
 struct BlockScalarTraits {
   // Must provide:
   //
   // Function to write the value as a string:
   // static void output(const T &Value, void *ctx, llvm::raw_ostream &Out);
   //
   // Function to convert a string to a value.  Returns the empty
   // StringRef on success or an error string if string is malformed:
   // static StringRef input(StringRef Scalar, void *ctxt, T &Value);
   //
   // Optional:
   // static StringRef inputTag(T &Val, std::string Tag)
   // static void outputTag(const T &Val, raw_ostream &Out)
 };
 
 /// This class should be specialized by type that requires custom conversion
 /// to/from a YAML scalar with optional tags. For example:
 ///
 ///    template <>
 ///    struct TaggedScalarTraits<MyType> {
 ///      static void output(const MyType &Value, void*, llvm::raw_ostream
 ///      &ScalarOut, llvm::raw_ostream &TagOut)
 ///      {
 ///        // stream out custom formatting including optional Tag
 ///        Out << Value;
 ///      }
 ///      static StringRef input(StringRef Scalar, StringRef Tag, void*, MyType
 ///      &Value) {
 ///        // parse scalar and set `value`
 ///        // return empty string on success, or error string
 ///        return StringRef();
 ///      }
 ///      static QuotingType mustQuote(const MyType &Value, StringRef) {
 ///        return QuotingType::Single;
 ///      }
 ///    };
 template <typename T> struct TaggedScalarTraits {
   // Must provide:
   //
   // Function to write the value and tag as strings:
   // static void output(const T &Value, void *ctx, llvm::raw_ostream &ScalarOut,
   // llvm::raw_ostream &TagOut);
   //
   // Function to convert a string to a value.  Returns the empty
   // StringRef on success or an error string if string is malformed:
   // static StringRef input(StringRef Scalar, StringRef Tag, void *ctxt, T
   // &Value);
   //
   // Function to determine if the value should be quoted.
   // static QuotingType mustQuote(const T &Value, StringRef Scalar);
 };
 
 /// This class should be specialized by any type that needs to be converted
 /// to/from a YAML sequence.  For example:
 ///
 ///    template<>
 ///    struct SequenceTraits<MyContainer> {
 ///      static size_t size(IO &io, MyContainer &seq) {
 ///        return seq.size();
 ///      }
 ///      static MyType& element(IO &, MyContainer &seq, size_t index) {
 ///        if ( index >= seq.size() )
 ///          seq.resize(index+1);
 ///        return seq[index];
 ///      }
 ///    };
 template<typename T, typename EnableIf = void>
 struct SequenceTraits {
   // Must provide:
   // static size_t size(IO &io, T &seq);
   // static T::value_type& element(IO &io, T &seq, size_t index);
   //
   // The following is option and will cause generated YAML to use
   // a flow sequence (e.g. [a,b,c]).
   // static const bool flow = true;
 };
 
 /// This class should be specialized by any type for which vectors of that
 /// type need to be converted to/from a YAML sequence.
 template<typename T, typename EnableIf = void>
 struct SequenceElementTraits {
   // Must provide:
   // static const bool flow;
 };
 
 /// This class should be specialized by any type that needs to be converted
 /// to/from a list of YAML documents.
 template<typename T>
 struct DocumentListTraits {
   // Must provide:
   // static size_t size(IO &io, T &seq);
   // static T::value_type& element(IO &io, T &seq, size_t index);
 };
 
 /// This class should be specialized by any type that needs to be converted
 /// to/from a YAML mapping in the case where the names of the keys are not known
 /// in advance, e.g. a string map.
 template <typename T>
 struct CustomMappingTraits {
   // static void inputOne(IO &io, StringRef key, T &elem);
   // static void output(IO &io, T &elem);
 };
 
 /// This class should be specialized by any type that can be represented as
 /// a scalar, map, or sequence, decided dynamically. For example:
 ///
 ///    typedef std::unique_ptr<MyBase> MyPoly;
 ///
 ///    template<>
 ///    struct PolymorphicTraits<MyPoly> {
 ///      static NodeKind getKind(const MyPoly &poly) {
 ///        return poly->getKind();
 ///      }
 ///      static MyScalar& getAsScalar(MyPoly &poly) {
 ///        if (!poly || !isa<MyScalar>(poly))
 ///          poly.reset(new MyScalar());
 ///        return *cast<MyScalar>(poly.get());
 ///      }
 ///      // ...
 ///    };
 template <typename T> struct PolymorphicTraits {
   // Must provide:
   // static NodeKind getKind(const T &poly);
   // static scalar_type &getAsScalar(T &poly);
   // static map_type &getAsMap(T &poly);
   // static sequence_type &getAsSequence(T &poly);
 };
 
 // Only used for better diagnostics of missing traits
 template <typename T>
 struct MissingTrait;
 
 // Test if ScalarEnumerationTraits<T> is defined on type T.
 template <class T>
 struct has_ScalarEnumerationTraits
 {
   using Signature_enumeration = void (*)(class IO&, T&);
 
   template <typename U>
   static char test(SameType<Signature_enumeration, &U::enumeration>*);
 
   template <typename U>
   static double test(...);
 
   static bool const value =
     (sizeof(test<ScalarEnumerationTraits<T>>(nullptr)) == 1);
 };
 
 // Test if ScalarBitSetTraits<T> is defined on type T.
 template <class T>
 struct has_ScalarBitSetTraits
 {
   using Signature_bitset = void (*)(class IO&, T&);
 
   template <typename U>
   static char test(SameType<Signature_bitset, &U::bitset>*);
 
   template <typename U>
   static double test(...);
 
   static bool const value = (sizeof(test<ScalarBitSetTraits<T>>(nullptr)) == 1);
 };
 
 // Test if ScalarTraits<T> is defined on type T.
 template <class T>
 struct has_ScalarTraits
 {
   using Signature_input = StringRef (*)(StringRef, void*, T&);
   using Signature_output = void (*)(const T&, void*, raw_ostream&);
   using Signature_mustQuote = QuotingType (*)(StringRef);
 
   template <typename U>
   static char test(SameType<Signature_input, &U::input> *,
                    SameType<Signature_output, &U::output> *,
                    SameType<Signature_mustQuote, &U::mustQuote> *);
 
   template <typename U>
   static double test(...);
 
   static bool const value =
       (sizeof(test<ScalarTraits<T>>(nullptr, nullptr, nullptr)) == 1);
 };
 
 // Test if BlockScalarTraits<T> is defined on type T.
 template <class T>
 struct has_BlockScalarTraits
 {
   using Signature_input = StringRef (*)(StringRef, void *, T &);
   using Signature_output = void (*)(const T &, void *, raw_ostream &);
 
   template <typename U>
   static char test(SameType<Signature_input, &U::input> *,
                    SameType<Signature_output, &U::output> *);
 
   template <typename U>
   static double test(...);
 
   static bool const value =
       (sizeof(test<BlockScalarTraits<T>>(nullptr, nullptr)) == 1);
 };
 
 // Test if TaggedScalarTraits<T> is defined on type T.
 template <class T> struct has_TaggedScalarTraits {
   using Signature_input = StringRef (*)(StringRef, StringRef, void *, T &);
   using Signature_output = void (*)(const T &, void *, raw_ostream &,
                                     raw_ostream &);
   using Signature_mustQuote = QuotingType (*)(const T &, StringRef);
 
   template <typename U>
   static char test(SameType<Signature_input, &U::input> *,
                    SameType<Signature_output, &U::output> *,
                    SameType<Signature_mustQuote, &U::mustQuote> *);
 
   template <typename U> static double test(...);
 
   static bool const value =
       (sizeof(test<TaggedScalarTraits<T>>(nullptr, nullptr, nullptr)) == 1);
 };
 
 // Test if MappingContextTraits<T> is defined on type T.
 template <class T, class Context> struct has_MappingTraits {
   using Signature_mapping = void (*)(class IO &, T &, Context &);
 
   template <typename U>
   static char test(SameType<Signature_mapping, &U::mapping>*);
 
   template <typename U>
   static double test(...);
 
   static bool const value =
       (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
 };
 
 // Test if MappingTraits<T> is defined on type T.
 template <class T> struct has_MappingTraits<T, EmptyContext> {
   using Signature_mapping = void (*)(class IO &, T &);
 
   template <typename U>
   static char test(SameType<Signature_mapping, &U::mapping> *);
 
   template <typename U> static double test(...);
 
   static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
 };
 
 // Test if MappingContextTraits<T>::validate() is defined on type T.
 template <class T, class Context> struct has_MappingValidateTraits {
   using Signature_validate = std::string (*)(class IO &, T &, Context &);
 
   template <typename U>
   static char test(SameType<Signature_validate, &U::validate>*);
 
   template <typename U>
   static double test(...);
 
   static bool const value =
       (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
 };
 
 // Test if MappingTraits<T>::validate() is defined on type T.
 template <class T> struct has_MappingValidateTraits<T, EmptyContext> {
   using Signature_validate = std::string (*)(class IO &, T &);
 
   template <typename U>
   static char test(SameType<Signature_validate, &U::validate> *);
 
   template <typename U> static double test(...);
 
   static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
 };
 
 // Test if MappingContextTraits<T>::enumInput() is defined on type T.
 template <class T, class Context> struct has_MappingEnumInputTraits {
   using Signature_validate = void (*)(class IO &, T &);
 
   template <typename U>
   static char test(SameType<Signature_validate, &U::enumInput> *);
 
   template <typename U> static double test(...);
 
   static bool const value =
       (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
 };
 
 // Test if MappingTraits<T>::enumInput() is defined on type T.
 template <class T> struct has_MappingEnumInputTraits<T, EmptyContext> {
   using Signature_validate = void (*)(class IO &, T &);
 
   template <typename U>
   static char test(SameType<Signature_validate, &U::enumInput> *);
 
   template <typename U> static double test(...);
 
   static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
 };
 
 // Test if SequenceTraits<T> is defined on type T.
 template <class T>
 struct has_SequenceMethodTraits
 {
   using Signature_size = size_t (*)(class IO&, T&);
 
   template <typename U>
   static char test(SameType<Signature_size, &U::size>*);
 
   template <typename U>
   static double test(...);
 
   static bool const value =  (sizeof(test<SequenceTraits<T>>(nullptr)) == 1);
 };
 
 // Test if CustomMappingTraits<T> is defined on type T.
 template <class T>
 struct has_CustomMappingTraits
 {
   using Signature_input = void (*)(IO &io, StringRef key, T &v);
 
   template <typename U>
   static char test(SameType<Signature_input, &U::inputOne>*);
 
   template <typename U>
   static double test(...);
 
   static bool const value =
       (sizeof(test<CustomMappingTraits<T>>(nullptr)) == 1);
 };
 
 // has_FlowTraits<int> will cause an error with some compilers because
 // it subclasses int.  Using this wrapper only instantiates the
 // real has_FlowTraits only if the template type is a class.
 template <typename T, bool Enabled = std::is_class_v<T>> class has_FlowTraits {
 public:
    static const bool value = false;
 };
 
 // Some older gcc compilers don't support straight forward tests
 // for members, so test for ambiguity cause by the base and derived
 // classes both defining the member.
 template <class T>
 struct has_FlowTraits<T, true>
 {
   struct Fallback { bool flow; };
   struct Derived : T, Fallback { };
 
   template<typename C>
   static char (&f(SameType<bool Fallback::*, &C::flow>*))[1];
 
   template<typename C>
   static char (&f(...))[2];
 
   static bool const value = sizeof(f<Derived>(nullptr)) == 2;
 };
 
 // Test if SequenceTraits<T> is defined on type T
 template<typename T>
 struct has_SequenceTraits : public std::integral_constant<bool,
                                       has_SequenceMethodTraits<T>::value > { };
 
 // Test if DocumentListTraits<T> is defined on type T
 template <class T>
 struct has_DocumentListTraits
 {
   using Signature_size = size_t (*)(class IO &, T &);
 
   template <typename U>
   static char test(SameType<Signature_size, &U::size>*);
 
   template <typename U>
   static double test(...);
 
   static bool const value = (sizeof(test<DocumentListTraits<T>>(nullptr))==1);
 };
 
 template <class T> struct has_PolymorphicTraits {
   using Signature_getKind = NodeKind (*)(const T &);
 
   template <typename U>
   static char test(SameType<Signature_getKind, &U::getKind> *);
 
   template <typename U> static double test(...);
 
   static bool const value = (sizeof(test<PolymorphicTraits<T>>(nullptr)) == 1);
 };
 
 inline bool isNumeric(StringRef S) {
   const auto skipDigits = [](StringRef Input) {
     return Input.ltrim("0123456789");
   };
 
   // Make S.front() and S.drop_front().front() (if S.front() is [+-]) calls
   // safe.
   if (S.empty() || S == "+" || S == "-")
     return false;
 
   if (S == ".nan" || S == ".NaN" || S == ".NAN")
     return true;
 
   // Infinity and decimal numbers can be prefixed with sign.
   StringRef Tail = (S.front() == '-' || S.front() == '+') ? S.drop_front() : S;
 
   // Check for infinity first, because checking for hex and oct numbers is more
   // expensive.
   if (Tail == ".inf" || Tail == ".Inf" || Tail == ".INF")
     return true;
 
   // Section 10.3.2 Tag Resolution
   // YAML 1.2 Specification prohibits Base 8 and Base 16 numbers prefixed with
   // [-+], so S should be used instead of Tail.
   if (S.starts_with("0o"))
     return S.size() > 2 &&
            S.drop_front(2).find_first_not_of("01234567") == StringRef::npos;
 
   if (S.starts_with("0x"))
     return S.size() > 2 && S.drop_front(2).find_first_not_of(
                                "0123456789abcdefABCDEF") == StringRef::npos;
 
   // Parse float: [-+]? (\. [0-9]+ | [0-9]+ (\. [0-9]* )?) ([eE] [-+]? [0-9]+)?
   S = Tail;
 
   // Handle cases when the number starts with '.' and hence needs at least one
   // digit after dot (as opposed by number which has digits before the dot), but
   // doesn't have one.
   if (S.starts_with(".") &&
       (S == "." ||
        (S.size() > 1 && std::strchr("0123456789", S[1]) == nullptr)))
     return false;
 
   if (S.starts_with("E") || S.starts_with("e"))
     return false;
 
   enum ParseState {
     Default,
     FoundDot,
     FoundExponent,
   };
   ParseState State = Default;
 
   S = skipDigits(S);
 
   // Accept decimal integer.
   if (S.empty())
     return true;
 
   if (S.front() == '.') {
     State = FoundDot;
     S = S.drop_front();
   } else if (S.front() == 'e' || S.front() == 'E') {
     State = FoundExponent;
     S = S.drop_front();
   } else {
     return false;
   }
 
   if (State == FoundDot) {
     S = skipDigits(S);
     if (S.empty())
       return true;
 
     if (S.front() == 'e' || S.front() == 'E') {
       State = FoundExponent;
       S = S.drop_front();
     } else {
       return false;
     }
   }
 
   assert(State == FoundExponent && "Should have found exponent at this point.");
   if (S.empty())
     return false;
 
   if (S.front() == '+' || S.front() == '-') {
     S = S.drop_front();
     if (S.empty())
       return false;
   }
 
   return skipDigits(S).empty();
 }
 
 inline bool isNull(StringRef S) {
   return S == "null" || S == "Null" || S == "NULL" || S == "~";
 }
 
 inline bool isBool(StringRef S) {
   // FIXME: using parseBool is causing multiple tests to fail.
   return S == "true" || S == "True" || S == "TRUE" || S == "false" ||
          S == "False" || S == "FALSE";
 }
 
 // 5.1. Character Set
 // The allowed character range explicitly excludes the C0 control block #x0-#x1F
 // (except for TAB #x9, LF #xA, and CR #xD which are allowed), DEL #x7F, the C1
 // control block #x80-#x9F (except for NEL #x85 which is allowed), the surrogate
 // block #xD800-#xDFFF, #xFFFE, and #xFFFF.
 //
 // Some strings are valid YAML values even unquoted, but without quotes are
 // interpreted as non-string type, for instance null, boolean or numeric values.
 // If ForcePreserveAsString is set, such strings are quoted.
 inline QuotingType needsQuotes(StringRef S, bool ForcePreserveAsString = true) {
   if (S.empty())
     return QuotingType::Single;
 
   QuotingType MaxQuotingNeeded = QuotingType::None;
   if (isSpace(static_cast<unsigned char>(S.front())) ||
       isSpace(static_cast<unsigned char>(S.back())))
     MaxQuotingNeeded = QuotingType::Single;
   if (ForcePreserveAsString) {
     if (isNull(S))
       MaxQuotingNeeded = QuotingType::Single;
     if (isBool(S))
       MaxQuotingNeeded = QuotingType::Single;
     if (isNumeric(S))
       MaxQuotingNeeded = QuotingType::Single;
   }
 
   // 7.3.3 Plain Style
   // Plain scalars must not begin with most indicators, as this would cause
   // ambiguity with other YAML constructs.
   if (std::strchr(R"(-?:\,[]{}#&*!|>'"%@`)", S[0]) != nullptr)
     MaxQuotingNeeded = QuotingType::Single;
 
   for (unsigned char C : S) {
     // Alphanum is safe.
     if (isAlnum(C))
       continue;
 
     switch (C) {
     // Safe scalar characters.
     case '_':
     case '-':
     case '^':
     case '.':
     case ',':
     case ' ':
     // TAB (0x9) is allowed in unquoted strings.
     case 0x9:
       continue;
     // LF(0xA) and CR(0xD) may delimit values and so require at least single
     // quotes. LLVM YAML parser cannot handle single quoted multiline so use
     // double quoting to produce valid YAML.
     case 0xA:
     case 0xD:
       return QuotingType::Double;
     // DEL (0x7F) are excluded from the allowed character range.
     case 0x7F:
       return QuotingType::Double;
     // Forward slash is allowed to be unquoted, but we quote it anyway.  We have
     // many tests that use FileCheck against YAML output, and this output often
     // contains paths.  If we quote backslashes but not forward slashes then
     // paths will come out either quoted or unquoted depending on which platform
     // the test is run on, making FileCheck comparisons difficult.
     case '/':
     default: {
       // C0 control block (0x0 - 0x1F) is excluded from the allowed character
       // range.
       if (C <= 0x1F)
         return QuotingType::Double;
 
       // Always double quote UTF-8.
       if ((C & 0x80) != 0)
         return QuotingType::Double;
 
       // The character is not safe, at least simple quoting needed.
       MaxQuotingNeeded = QuotingType::Single;
     }
     }
   }
 
   return MaxQuotingNeeded;
 }
 
 template <typename T, typename Context>
 struct missingTraits
     : public std::integral_constant<bool,
                                     !has_ScalarEnumerationTraits<T>::value &&
                                         !has_ScalarBitSetTraits<T>::value &&
                                         !has_ScalarTraits<T>::value &&
                                         !has_BlockScalarTraits<T>::value &&
                                         !has_TaggedScalarTraits<T>::value &&
                                         !has_MappingTraits<T, Context>::value &&
                                         !has_SequenceTraits<T>::value &&
                                         !has_CustomMappingTraits<T>::value &&
                                         !has_DocumentListTraits<T>::value &&
                                         !has_PolymorphicTraits<T>::value> {};
 
 template <typename T, typename Context>
 struct validatedMappingTraits
     : public std::integral_constant<
           bool, has_MappingTraits<T, Context>::value &&
                     has_MappingValidateTraits<T, Context>::value> {};
 
 template <typename T, typename Context>
 struct unvalidatedMappingTraits
     : public std::integral_constant<
           bool, has_MappingTraits<T, Context>::value &&
                     !has_MappingValidateTraits<T, Context>::value> {};
 
 // Base class for Input and Output.
 class IO {
 public:
   IO(void *Ctxt = nullptr);
   virtual ~IO();
 
   virtual bool outputting() const = 0;
 
   virtual unsigned beginSequence() = 0;
   virtual bool preflightElement(unsigned, void *&) = 0;
   virtual void postflightElement(void*) = 0;
   virtual void endSequence() = 0;
   virtual bool canElideEmptySequence() = 0;
 
   virtual unsigned beginFlowSequence() = 0;
   virtual bool preflightFlowElement(unsigned, void *&) = 0;
   virtual void postflightFlowElement(void*) = 0;
   virtual void endFlowSequence() = 0;
 
   virtual bool mapTag(StringRef Tag, bool Default=false) = 0;
   virtual void beginMapping() = 0;
   virtual void endMapping() = 0;
   virtual bool preflightKey(const char*, bool, bool, bool &, void *&) = 0;
   virtual void postflightKey(void*) = 0;
   virtual std::vector<StringRef> keys() = 0;
 
   virtual void beginFlowMapping() = 0;
   virtual void endFlowMapping() = 0;
 
   virtual void beginEnumScalar() = 0;
   virtual bool matchEnumScalar(const char*, bool) = 0;
   virtual bool matchEnumFallback() = 0;
   virtual void endEnumScalar() = 0;
 
   virtual bool beginBitSetScalar(bool &) = 0;
   virtual bool bitSetMatch(const char*, bool) = 0;
   virtual void endBitSetScalar() = 0;
 
   virtual void scalarString(StringRef &, QuotingType) = 0;
   virtual void blockScalarString(StringRef &) = 0;
   virtual void scalarTag(std::string &) = 0;
 
   virtual NodeKind getNodeKind() = 0;
 
   virtual void setError(const Twine &) = 0;
   virtual std::error_code error() = 0;
   virtual void setAllowUnknownKeys(bool Allow);
 
   template <typename T>
   void enumCase(T &Val, const char* Str, const T ConstVal) {
     if ( matchEnumScalar(Str, outputting() && Val == ConstVal) ) {
       Val = ConstVal;
     }
   }
 
   // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
   template <typename T>
   void enumCase(T &Val, const char* Str, const uint32_t ConstVal) {
     if ( matchEnumScalar(Str, outputting() && Val == static_cast<T>(ConstVal)) ) {
       Val = ConstVal;
     }
   }
 
   template <typename FBT, typename T>
   void enumFallback(T &Val) {
     if (matchEnumFallback()) {
       EmptyContext Context;
       // FIXME: Force integral conversion to allow strong typedefs to convert.
       FBT Res = static_cast<typename FBT::BaseType>(Val);
       yamlize(*this, Res, true, Context);
       Val = static_cast<T>(static_cast<typename FBT::BaseType>(Res));
     }
   }
 
   template <typename T>
   void bitSetCase(T &Val, const char* Str, const T ConstVal) {
     if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
       Val = static_cast<T>(Val | ConstVal);
     }
   }
 
   // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
   template <typename T>
   void bitSetCase(T &Val, const char* Str, const uint32_t ConstVal) {
     if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
       Val = static_cast<T>(Val | ConstVal);
     }
   }
 
   template <typename T>
   void maskedBitSetCase(T &Val, const char *Str, T ConstVal, T Mask) {
     if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
       Val = Val | ConstVal;
   }
 
   template <typename T>
   void maskedBitSetCase(T &Val, const char *Str, uint32_t ConstVal,
                         uint32_t Mask) {
     if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
       Val = Val | ConstVal;
   }
 
   void *getContext() const;
   void setContext(void *);
 
   template <typename T> void mapRequired(const char *Key, T &Val) {
     EmptyContext Ctx;
     this->processKey(Key, Val, true, Ctx);
   }
 
   template <typename T, typename Context>
   void mapRequired(const char *Key, T &Val, Context &Ctx) {
     this->processKey(Key, Val, true, Ctx);
   }
 
   template <typename T> void mapOptional(const char *Key, T &Val) {
     EmptyContext Ctx;
     mapOptionalWithContext(Key, Val, Ctx);
   }
 
   template <typename T, typename DefaultT>
   void mapOptional(const char *Key, T &Val, const DefaultT &Default) {
     EmptyContext Ctx;
     mapOptionalWithContext(Key, Val, Default, Ctx);
   }
 
   template <typename T, typename Context>
   std::enable_if_t<has_SequenceTraits<T>::value, void>
   mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
     // omit key/value instead of outputting empty sequence
     if (this->canElideEmptySequence() && !(Val.begin() != Val.end()))
       return;
     this->processKey(Key, Val, false, Ctx);
   }
 
   template <typename T, typename Context>
   void mapOptionalWithContext(const char *Key, std::optional<T> &Val,
                               Context &Ctx) {
     this->processKeyWithDefault(Key, Val, std::optional<T>(),
                                 /*Required=*/false, Ctx);
   }
 
   template <typename T, typename Context>
   std::enable_if_t<!has_SequenceTraits<T>::value, void>
   mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
     this->processKey(Key, Val, false, Ctx);
   }
 
   template <typename T, typename Context, typename DefaultT>
   void mapOptionalWithContext(const char *Key, T &Val, const DefaultT &Default,
                               Context &Ctx) {
     static_assert(std::is_convertible<DefaultT, T>::value,
                   "Default type must be implicitly convertible to value type!");
     this->processKeyWithDefault(Key, Val, static_cast<const T &>(Default),
                                 false, Ctx);
   }
 
 private:
   template <typename T, typename Context>
   void processKeyWithDefault(const char *Key, std::optional<T> &Val,
                              const std::optional<T> &DefaultValue,
                              bool Required, Context &Ctx);
 
   template <typename T, typename Context>
   void processKeyWithDefault(const char *Key, T &Val, const T &DefaultValue,
                              bool Required, Context &Ctx) {
     void *SaveInfo;
     bool UseDefault;
     const bool sameAsDefault = outputting() && Val == DefaultValue;
     if ( this->preflightKey(Key, Required, sameAsDefault, UseDefault,
                                                                   SaveInfo) ) {
       yamlize(*this, Val, Required, Ctx);
       this->postflightKey(SaveInfo);
     }
     else {
       if ( UseDefault )
         Val = DefaultValue;
     }
   }
 
   template <typename T, typename Context>
   void processKey(const char *Key, T &Val, bool Required, Context &Ctx) {
     void *SaveInfo;
     bool UseDefault;
     if ( this->preflightKey(Key, Required, false, UseDefault, SaveInfo) ) {
       yamlize(*this, Val, Required, Ctx);
       this->postflightKey(SaveInfo);
     }
   }
 
 private:
   void *Ctxt;
 };
 
 namespace detail {
 
 template <typename T, typename Context>
 void doMapping(IO &io, T &Val, Context &Ctx) {
   MappingContextTraits<T, Context>::mapping(io, Val, Ctx);
 }
 
 template <typename T> void doMapping(IO &io, T &Val, EmptyContext &Ctx) {
   MappingTraits<T>::mapping(io, Val);
 }
 
 } // end namespace detail
 
 template <typename T>
 std::enable_if_t<has_ScalarEnumerationTraits<T>::value, void>
 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
   io.beginEnumScalar();
   ScalarEnumerationTraits<T>::enumeration(io, Val);
   io.endEnumScalar();
 }
 
 template <typename T>
 std::enable_if_t<has_ScalarBitSetTraits<T>::value, void>
 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
   bool DoClear;
   if ( io.beginBitSetScalar(DoClear) ) {
     if ( DoClear )
       Val = T();
     ScalarBitSetTraits<T>::bitset(io, Val);
     io.endBitSetScalar();
   }
 }
 
 template <typename T>
 std::enable_if_t<has_ScalarTraits<T>::value, void> yamlize(IO &io, T &Val, bool,
                                                            EmptyContext &Ctx) {
   if ( io.outputting() ) {
     SmallString<128> Storage;
     raw_svector_ostream Buffer(Storage);
     ScalarTraits<T>::output(Val, io.getContext(), Buffer);
     StringRef Str = Buffer.str();
     io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
   }
   else {
     StringRef Str;
     io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
     StringRef Result = ScalarTraits<T>::input(Str, io.getContext(), Val);
     if ( !Result.empty() ) {
       io.setError(Twine(Result));
     }
   }
 }
 
 template <typename T>
 std::enable_if_t<has_BlockScalarTraits<T>::value, void>
 yamlize(IO &YamlIO, T &Val, bool, EmptyContext &Ctx) {
   if (YamlIO.outputting()) {
     std::string Storage;
     raw_string_ostream Buffer(Storage);
     BlockScalarTraits<T>::output(Val, YamlIO.getContext(), Buffer);
     StringRef Str(Storage);
     YamlIO.blockScalarString(Str);
   } else {
     StringRef Str;
     YamlIO.blockScalarString(Str);
     StringRef Result =
         BlockScalarTraits<T>::input(Str, YamlIO.getContext(), Val);
     if (!Result.empty())
       YamlIO.setError(Twine(Result));
   }
 }
 
 template <typename T>
 std::enable_if_t<has_TaggedScalarTraits<T>::value, void>
 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
   if (io.outputting()) {
     std::string ScalarStorage, TagStorage;
     raw_string_ostream ScalarBuffer(ScalarStorage), TagBuffer(TagStorage);
     TaggedScalarTraits<T>::output(Val, io.getContext(), ScalarBuffer,
                                   TagBuffer);
     io.scalarTag(TagStorage);
     StringRef ScalarStr(ScalarStorage);
     io.scalarString(ScalarStr,
                     TaggedScalarTraits<T>::mustQuote(Val, ScalarStr));
   } else {
     std::string Tag;
     io.scalarTag(Tag);
     StringRef Str;
     io.scalarString(Str, QuotingType::None);
     StringRef Result =
         TaggedScalarTraits<T>::input(Str, Tag, io.getContext(), Val);
     if (!Result.empty()) {
       io.setError(Twine(Result));
     }
   }
 }
 
 namespace detail {
 
 template <typename T, typename Context>
 std::string doValidate(IO &io, T &Val, Context &Ctx) {
   return MappingContextTraits<T, Context>::validate(io, Val, Ctx);
 }
 
 template <typename T> std::string doValidate(IO &io, T &Val, EmptyContext &) {
   return MappingTraits<T>::validate(io, Val);
 }
 
 } // namespace detail
 
 template <typename T, typename Context>
 std::enable_if_t<validatedMappingTraits<T, Context>::value, void>
 yamlize(IO &io, T &Val, bool, Context &Ctx) {
   if (has_FlowTraits<MappingTraits<T>>::value)
     io.beginFlowMapping();
   else
     io.beginMapping();
   if (io.outputting()) {
     std::string Err = detail::doValidate(io, Val, Ctx);
     if (!Err.empty()) {
       errs() << Err << "\n";
       assert(Err.empty() && "invalid struct trying to be written as yaml");
     }
   }
   detail::doMapping(io, Val, Ctx);
   if (!io.outputting()) {
     std::string Err = detail::doValidate(io, Val, Ctx);
     if (!Err.empty())
       io.setError(Err);
   }
   if (has_FlowTraits<MappingTraits<T>>::value)
     io.endFlowMapping();
   else
     io.endMapping();
 }
 
 template <typename T, typename Context>
 std::enable_if_t<!has_MappingEnumInputTraits<T, Context>::value, bool>
 yamlizeMappingEnumInput(IO &io, T &Val) {
   return false;
 }
 
 template <typename T, typename Context>
 std::enable_if_t<has_MappingEnumInputTraits<T, Context>::value, bool>
 yamlizeMappingEnumInput(IO &io, T &Val) {
   if (io.outputting())
     return false;
 
   io.beginEnumScalar();
   MappingTraits<T>::enumInput(io, Val);
   bool Matched = !io.matchEnumFallback();
   io.endEnumScalar();
   return Matched;
 }
 
 template <typename T, typename Context>
 std::enable_if_t<unvalidatedMappingTraits<T, Context>::value, void>
 yamlize(IO &io, T &Val, bool, Context &Ctx) {
   if (yamlizeMappingEnumInput<T, Context>(io, Val))
     return;
   if (has_FlowTraits<MappingTraits<T>>::value) {
     io.beginFlowMapping();
     detail::doMapping(io, Val, Ctx);
     io.endFlowMapping();
   } else {
     io.beginMapping();
     detail::doMapping(io, Val, Ctx);
     io.endMapping();
   }
 }
 
 template <typename T>
 std::enable_if_t<has_CustomMappingTraits<T>::value, void>
 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
   if ( io.outputting() ) {
     io.beginMapping();
     CustomMappingTraits<T>::output(io, Val);
     io.endMapping();
   } else {
     io.beginMapping();
     for (StringRef key : io.keys())
       CustomMappingTraits<T>::inputOne(io, key, Val);
     io.endMapping();
   }
 }
 
 template <typename T>
 std::enable_if_t<has_PolymorphicTraits<T>::value, void>
 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
   switch (io.outputting() ? PolymorphicTraits<T>::getKind(Val)
                           : io.getNodeKind()) {
   case NodeKind::Scalar:
     return yamlize(io, PolymorphicTraits<T>::getAsScalar(Val), true, Ctx);
   case NodeKind::Map:
     return yamlize(io, PolymorphicTraits<T>::getAsMap(Val), true, Ctx);
   case NodeKind::Sequence:
     return yamlize(io, PolymorphicTraits<T>::getAsSequence(Val), true, Ctx);
   }
 }
 
 template <typename T>
 std::enable_if_t<missingTraits<T, EmptyContext>::value, void>
 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
   char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
 }
 
 template <typename T, typename Context>
 std::enable_if_t<has_SequenceTraits<T>::value, void>
 yamlize(IO &io, T &Seq, bool, Context &Ctx) {
   if ( has_FlowTraits< SequenceTraits<T>>::value ) {
     unsigned incnt = io.beginFlowSequence();
     unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
     for(unsigned i=0; i < count; ++i) {
       void *SaveInfo;
       if ( io.preflightFlowElement(i, SaveInfo) ) {
         yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
         io.postflightFlowElement(SaveInfo);
       }
     }
     io.endFlowSequence();
   }
   else {
     unsigned incnt = io.beginSequence();
     unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
     for(unsigned i=0; i < count; ++i) {
       void *SaveInfo;
       if ( io.preflightElement(i, SaveInfo) ) {
         yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
         io.postflightElement(SaveInfo);
       }
     }
     io.endSequence();
   }
 }
 
 template<>
 struct ScalarTraits<bool> {
   static void output(const bool &, void* , raw_ostream &);
   static StringRef input(StringRef, void *, bool &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<StringRef> {
   static void output(const StringRef &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, StringRef &);
   static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
 };
 
 template<>
 struct ScalarTraits<std::string> {
   static void output(const std::string &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, std::string &);
   static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
 };
 
 template<>
 struct ScalarTraits<uint8_t> {
   static void output(const uint8_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, uint8_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<uint16_t> {
   static void output(const uint16_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, uint16_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<uint32_t> {
   static void output(const uint32_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, uint32_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<uint64_t> {
   static void output(const uint64_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, uint64_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<int8_t> {
   static void output(const int8_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, int8_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<int16_t> {
   static void output(const int16_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, int16_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<int32_t> {
   static void output(const int32_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, int32_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<int64_t> {
   static void output(const int64_t &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, int64_t &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<float> {
   static void output(const float &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, float &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<double> {
   static void output(const double &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, double &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 // For endian types, we use existing scalar Traits class for the underlying
 // type.  This way endian aware types are supported whenever the traits are
 // defined for the underlying type.
 template <typename value_type, llvm::endianness endian, size_t alignment>
 struct ScalarTraits<support::detail::packed_endian_specific_integral<
                         value_type, endian, alignment>,
                     std::enable_if_t<has_ScalarTraits<value_type>::value>> {
   using endian_type =
       support::detail::packed_endian_specific_integral<value_type, endian,
                                                        alignment>;
 
   static void output(const endian_type &E, void *Ctx, raw_ostream &Stream) {
     ScalarTraits<value_type>::output(static_cast<value_type>(E), Ctx, Stream);
   }
 
   static StringRef input(StringRef Str, void *Ctx, endian_type &E) {
     value_type V;
     auto R = ScalarTraits<value_type>::input(Str, Ctx, V);
     E = static_cast<endian_type>(V);
     return R;
   }
 
   static QuotingType mustQuote(StringRef Str) {
     return ScalarTraits<value_type>::mustQuote(Str);
   }
 };
 
 template <typename value_type, llvm::endianness endian, size_t alignment>
 struct ScalarEnumerationTraits<
     support::detail::packed_endian_specific_integral<value_type, endian,
                                                      alignment>,
     std::enable_if_t<has_ScalarEnumerationTraits<value_type>::value>> {
   using endian_type =
       support::detail::packed_endian_specific_integral<value_type, endian,
                                                        alignment>;
 
   static void enumeration(IO &io, endian_type &E) {
     value_type V = E;
     ScalarEnumerationTraits<value_type>::enumeration(io, V);
     E = V;
   }
 };
 
 template <typename value_type, llvm::endianness endian, size_t alignment>
 struct ScalarBitSetTraits<
     support::detail::packed_endian_specific_integral<value_type, endian,
                                                      alignment>,
     std::enable_if_t<has_ScalarBitSetTraits<value_type>::value>> {
   using endian_type =
       support::detail::packed_endian_specific_integral<value_type, endian,
                                                        alignment>;
   static void bitset(IO &io, endian_type &E) {
     value_type V = E;
     ScalarBitSetTraits<value_type>::bitset(io, V);
     E = V;
   }
 };
 
 // Utility for use within MappingTraits<>::mapping() method
 // to [de]normalize an object for use with YAML conversion.
 template <typename TNorm, typename TFinal>
 struct MappingNormalization {
   MappingNormalization(IO &i_o, TFinal &Obj)
       : io(i_o), BufPtr(nullptr), Result(Obj) {
     if ( io.outputting() ) {
       BufPtr = new (&Buffer) TNorm(io, Obj);
     }
     else {
       BufPtr = new (&Buffer) TNorm(io);
     }
   }
 
   ~MappingNormalization() {
     if ( ! io.outputting() ) {
       Result = BufPtr->denormalize(io);
     }
     BufPtr->~TNorm();
   }
 
   TNorm* operator->() { return BufPtr; }
 
 private:
   using Storage = AlignedCharArrayUnion<TNorm>;
 
   Storage       Buffer;
   IO           &io;
   TNorm        *BufPtr;
   TFinal       &Result;
 };
 
 // Utility for use within MappingTraits<>::mapping() method
 // to [de]normalize an object for use with YAML conversion.
 template <typename TNorm, typename TFinal>
 struct MappingNormalizationHeap {
   MappingNormalizationHeap(IO &i_o, TFinal &Obj, BumpPtrAllocator *allocator)
     : io(i_o), Result(Obj) {
     if ( io.outputting() ) {
       BufPtr = new (&Buffer) TNorm(io, Obj);
     }
     else if (allocator) {
       BufPtr = allocator->Allocate<TNorm>();
       new (BufPtr) TNorm(io);
     } else {
       BufPtr = new TNorm(io);
     }
   }
 
   ~MappingNormalizationHeap() {
     if ( io.outputting() ) {
       BufPtr->~TNorm();
     }
     else {
       Result = BufPtr->denormalize(io);
     }
   }
 
   TNorm* operator->() { return BufPtr; }
 
 private:
   using Storage = AlignedCharArrayUnion<TNorm>;
 
   Storage       Buffer;
   IO           &io;
   TNorm        *BufPtr = nullptr;
   TFinal       &Result;
 };
 
 ///
 /// The Input class is used to parse a yaml document into in-memory structs
 /// and vectors.
 ///
 /// It works by using YAMLParser to do a syntax parse of the entire yaml
 /// document, then the Input class builds a graph of HNodes which wraps
 /// each yaml Node.  The extra layer is buffering.  The low level yaml
 /// parser only lets you look at each node once.  The buffering layer lets
 /// you search and interate multiple times.  This is necessary because
 /// the mapRequired() method calls may not be in the same order
 /// as the keys in the document.
 ///
 class Input : public IO {
 public:
   // Construct a yaml Input object from a StringRef and optional
   // user-data. The DiagHandler can be specified to provide
   // alternative error reporting.
   Input(StringRef InputContent,
         void *Ctxt = nullptr,
         SourceMgr::DiagHandlerTy DiagHandler = nullptr,
         void *DiagHandlerCtxt = nullptr);
   Input(MemoryBufferRef Input,
         void *Ctxt = nullptr,
         SourceMgr::DiagHandlerTy DiagHandler = nullptr,
         void *DiagHandlerCtxt = nullptr);
   ~Input() override;
 
   // Check if there was an syntax or semantic error during parsing.
   std::error_code error() override;
 
 private:
   bool outputting() const override;
   bool mapTag(StringRef, bool) override;
   void beginMapping() override;
   void endMapping() override;
   bool preflightKey(const char *, bool, bool, bool &, void *&) override;
   void postflightKey(void *) override;
   std::vector<StringRef> keys() override;
   void beginFlowMapping() override;
   void endFlowMapping() override;
   unsigned beginSequence() override;
   void endSequence() override;
   bool preflightElement(unsigned index, void *&) override;
   void postflightElement(void *) override;
   unsigned beginFlowSequence() override;
   bool preflightFlowElement(unsigned , void *&) override;
   void postflightFlowElement(void *) override;
   void endFlowSequence() override;
   void beginEnumScalar() override;
   bool matchEnumScalar(const char*, bool) override;
   bool matchEnumFallback() override;
   void endEnumScalar() override;
   bool beginBitSetScalar(bool &) override;
   bool bitSetMatch(const char *, bool ) override;
   void endBitSetScalar() override;
   void scalarString(StringRef &, QuotingType) override;
   void blockScalarString(StringRef &) override;
   void scalarTag(std::string &) override;
   NodeKind getNodeKind() override;
   void setError(const Twine &message) override;
   bool canElideEmptySequence() override;
 
   class HNode {
   public:
     HNode(Node *n) : _node(n) {}
 
     static bool classof(const HNode *) { return true; }
 
     Node *_node;
   };
 
   class EmptyHNode : public HNode {
   public:
     EmptyHNode(Node *n) : HNode(n) { }
 
     static bool classof(const HNode *n) { return NullNode::classof(n->_node); }
 
     static bool classof(const EmptyHNode *) { return true; }
   };
 
   class ScalarHNode : public HNode {
   public:
     ScalarHNode(Node *n, StringRef s) : HNode(n), _value(s) { }
 
     StringRef value() const { return _value; }
 
     static bool classof(const HNode *n) {
       return ScalarNode::classof(n->_node) ||
              BlockScalarNode::classof(n->_node);
     }
 
     static bool classof(const ScalarHNode *) { return true; }
 
   protected:
     StringRef _value;
   };
 
   class MapHNode : public HNode {
   public:
     MapHNode(Node *n) : HNode(n) { }
 
     static bool classof(const HNode *n) {
       return MappingNode::classof(n->_node);
     }
 
     static bool classof(const MapHNode *) { return true; }
 
     using NameToNodeAndLoc = StringMap<std::pair<HNode *, SMRange>>;
 
     NameToNodeAndLoc Mapping;
     SmallVector<std::string, 6> ValidKeys;
   };
 
   class SequenceHNode : public HNode {
   public:
     SequenceHNode(Node *n) : HNode(n) { }
 
     static bool classof(const HNode *n) {
       return SequenceNode::classof(n->_node);
     }
 
     static bool classof(const SequenceHNode *) { return true; }
 
     std::vector<HNode *> Entries;
   };
 
   Input::HNode *createHNodes(Node *node);
   void setError(HNode *hnode, const Twine &message);
   void setError(Node *node, const Twine &message);
   void setError(const SMRange &Range, const Twine &message);
 
   void reportWarning(HNode *hnode, const Twine &message);
   void reportWarning(Node *hnode, const Twine &message);
   void reportWarning(const SMRange &Range, const Twine &message);
 
   /// Release memory used by HNodes.
   void releaseHNodeBuffers();
 
 public:
   // These are only used by operator>>. They could be private
   // if those templated things could be made friends.
   bool setCurrentDocument();
   bool nextDocument();
 
   /// Returns the current node that's being parsed by the YAML Parser.
   const Node *getCurrentNode() const;
 
   void setAllowUnknownKeys(bool Allow) override;
 
 private:
   SourceMgr                           SrcMgr; // must be before Strm
   std::unique_ptr<llvm::yaml::Stream> Strm;
   HNode *TopNode = nullptr;
   std::error_code                     EC;
   BumpPtrAllocator                    StringAllocator;
   SpecificBumpPtrAllocator<EmptyHNode> EmptyHNodeAllocator;
   SpecificBumpPtrAllocator<ScalarHNode> ScalarHNodeAllocator;
   SpecificBumpPtrAllocator<MapHNode> MapHNodeAllocator;
   SpecificBumpPtrAllocator<SequenceHNode> SequenceHNodeAllocator;
   document_iterator                   DocIterator;
   llvm::BitVector                     BitValuesUsed;
   HNode *CurrentNode = nullptr;
   bool                                ScalarMatchFound = false;
   bool AllowUnknownKeys = false;
 };
 
 ///
 /// The Output class is used to generate a yaml document from in-memory structs
 /// and vectors.
 ///
 class Output : public IO {
 public:
   Output(raw_ostream &, void *Ctxt = nullptr, int WrapColumn = 70);
   ~Output() override;
 
   /// Set whether or not to output optional values which are equal
   /// to the default value.  By default, when outputting if you attempt
   /// to write a value that is equal to the default, the value gets ignored.
   /// Sometimes, it is useful to be able to see these in the resulting YAML
   /// anyway.
   void setWriteDefaultValues(bool Write) { WriteDefaultValues = Write; }
 
   bool outputting() const override;
   bool mapTag(StringRef, bool) override;
   void beginMapping() override;
   void endMapping() override;
   bool preflightKey(const char *key, bool, bool, bool &, void *&) override;
   void postflightKey(void *) override;
   std::vector<StringRef> keys() override;
   void beginFlowMapping() override;
   void endFlowMapping() override;
   unsigned beginSequence() override;
   void endSequence() override;
   bool preflightElement(unsigned, void *&) override;
   void postflightElement(void *) override;
   unsigned beginFlowSequence() override;
   bool preflightFlowElement(unsigned, void *&) override;
   void postflightFlowElement(void *) override;
   void endFlowSequence() override;
   void beginEnumScalar() override;
   bool matchEnumScalar(const char*, bool) override;
   bool matchEnumFallback() override;
   void endEnumScalar() override;
   bool beginBitSetScalar(bool &) override;
   bool bitSetMatch(const char *, bool ) override;
   void endBitSetScalar() override;
   void scalarString(StringRef &, QuotingType) override;
   void blockScalarString(StringRef &) override;
   void scalarTag(std::string &) override;
   NodeKind getNodeKind() override;
   void setError(const Twine &message) override;
   std::error_code error() override;
   bool canElideEmptySequence() override;
 
   // These are only used by operator<<. They could be private
   // if that templated operator could be made a friend.
   void beginDocuments();
   bool preflightDocument(unsigned);
   void postflightDocument();
   void endDocuments();
 
 private:
   void output(StringRef s);
   void output(StringRef, QuotingType);
   void outputUpToEndOfLine(StringRef s);
   void newLineCheck(bool EmptySequence = false);
   void outputNewLine();
   void paddedKey(StringRef key);
   void flowKey(StringRef Key);
 
   enum InState {
     inSeqFirstElement,
     inSeqOtherElement,
     inFlowSeqFirstElement,
     inFlowSeqOtherElement,
     inMapFirstKey,
     inMapOtherKey,
     inFlowMapFirstKey,
     inFlowMapOtherKey
   };
 
   static bool inSeqAnyElement(InState State);
   static bool inFlowSeqAnyElement(InState State);
   static bool inMapAnyKey(InState State);
   static bool inFlowMapAnyKey(InState State);
 
   raw_ostream &Out;
   int WrapColumn;
   SmallVector<InState, 8> StateStack;
   int Column = 0;
   int ColumnAtFlowStart = 0;
   int ColumnAtMapFlowStart = 0;
   bool NeedBitValueComma = false;
   bool NeedFlowSequenceComma = false;
   bool EnumerationMatchFound = false;
   bool WriteDefaultValues = false;
   StringRef Padding;
   StringRef PaddingBeforeContainer;
 };
 
 template <typename T, typename Context>
 void IO::processKeyWithDefault(const char *Key, std::optional<T> &Val,
                                const std::optional<T> &DefaultValue,
                                bool Required, Context &Ctx) {
   assert(!DefaultValue && "std::optional<T> shouldn't have a value!");
   void *SaveInfo;
   bool UseDefault = true;
   const bool sameAsDefault = outputting() && !Val;
   if (!outputting() && !Val)
     Val = T();
   if (Val &&
       this->preflightKey(Key, Required, sameAsDefault, UseDefault, SaveInfo)) {
 
     // When reading an std::optional<X> key from a YAML description, we allow
     // the special "<none>" value, which can be used to specify that no value
     // was requested, i.e. the DefaultValue will be assigned. The DefaultValue
     // is usually None.
     bool IsNone = false;
     if (!outputting())
       if (const auto *Node =
               dyn_cast<ScalarNode>(((Input *)this)->getCurrentNode()))
         // We use rtrim to ignore possible white spaces that might exist when a
         // comment is present on the same line.
         IsNone = Node->getRawValue().rtrim(' ') == "<none>";
 
     if (IsNone)
       Val = DefaultValue;
     else
       yamlize(*this, *Val, Required, Ctx);
     this->postflightKey(SaveInfo);
   } else {
     if (UseDefault)
       Val = DefaultValue;
   }
 }
 
 /// YAML I/O does conversion based on types. But often native data types
 /// are just a typedef of built in intergral types (e.g. int).  But the C++
 /// type matching system sees through the typedef and all the typedefed types
 /// look like a built in type. This will cause the generic YAML I/O conversion
 /// to be used. To provide better control over the YAML conversion, you can
 /// use this macro instead of typedef.  It will create a class with one field
 /// and automatic conversion operators to and from the base type.
 /// Based on BOOST_STRONG_TYPEDEF
 #define LLVM_YAML_STRONG_TYPEDEF(_base, _type)                                 \
     struct _type {                                                             \
         _type() = default;                                                     \
         _type(const _base v) : value(v) {}                                     \
         _type(const _type &v) = default;                                       \
         _type &operator=(const _type &rhs) = default;                          \
         _type &operator=(const _base &rhs) { value = rhs; return *this; }      \
         operator const _base & () const { return value; }                      \
         bool operator==(const _type &rhs) const { return value == rhs.value; } \
         bool operator==(const _base &rhs) const { return value == rhs; }       \
         bool operator<(const _type &rhs) const { return value < rhs.value; }   \
         _base value;                                                           \
         using BaseType = _base;                                                \
     };
 
 ///
 /// Use these types instead of uintXX_t in any mapping to have
 /// its yaml output formatted as hexadecimal.
 ///
 LLVM_YAML_STRONG_TYPEDEF(uint8_t, Hex8)
 LLVM_YAML_STRONG_TYPEDEF(uint16_t, Hex16)
 LLVM_YAML_STRONG_TYPEDEF(uint32_t, Hex32)
 LLVM_YAML_STRONG_TYPEDEF(uint64_t, Hex64)
 
 template<>
 struct ScalarTraits<Hex8> {
   static void output(const Hex8 &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, Hex8 &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<Hex16> {
   static void output(const Hex16 &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, Hex16 &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<Hex32> {
   static void output(const Hex32 &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, Hex32 &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template<>
 struct ScalarTraits<Hex64> {
   static void output(const Hex64 &, void *, raw_ostream &);
   static StringRef input(StringRef, void *, Hex64 &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 template <> struct ScalarTraits<VersionTuple> {
   static void output(const VersionTuple &Value, void *, llvm::raw_ostream &Out);
   static StringRef input(StringRef, void *, VersionTuple &);
   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
 };
 
 // Define non-member operator>> so that Input can stream in a document list.
 template <typename T>
 inline std::enable_if_t<has_DocumentListTraits<T>::value, Input &>
 operator>>(Input &yin, T &docList) {
   int i = 0;
   EmptyContext Ctx;
   while ( yin.setCurrentDocument() ) {
     yamlize(yin, DocumentListTraits<T>::element(yin, docList, i), true, Ctx);
     if ( yin.error() )
       return yin;
     yin.nextDocument();
     ++i;
   }
   return yin;
 }
 
 // Define non-member operator>> so that Input can stream in a map as a document.
 template <typename T>
 inline std::enable_if_t<has_MappingTraits<T, EmptyContext>::value, Input &>
 operator>>(Input &yin, T &docMap) {
   EmptyContext Ctx;
   yin.setCurrentDocument();
   yamlize(yin, docMap, true, Ctx);
   return yin;
 }
 
 // Define non-member operator>> so that Input can stream in a sequence as
 // a document.
 template <typename T>
 inline std::enable_if_t<has_SequenceTraits<T>::value, Input &>
 operator>>(Input &yin, T &docSeq) {
   EmptyContext Ctx;
   if (yin.setCurrentDocument())
     yamlize(yin, docSeq, true, Ctx);
   return yin;
 }
 
 // Define non-member operator>> so that Input can stream in a block scalar.
 template <typename T>
 inline std::enable_if_t<has_BlockScalarTraits<T>::value, Input &>
 operator>>(Input &In, T &Val) {
   EmptyContext Ctx;
   if (In.setCurrentDocument())
     yamlize(In, Val, true, Ctx);
   return In;
 }
 
 // Define non-member operator>> so that Input can stream in a string map.
 template <typename T>
 inline std::enable_if_t<has_CustomMappingTraits<T>::value, Input &>
 operator>>(Input &In, T &Val) {
   EmptyContext Ctx;
   if (In.setCurrentDocument())
     yamlize(In, Val, true, Ctx);
   return In;
 }
 
 // Define non-member operator>> so that Input can stream in a polymorphic type.
 template <typename T>
 inline std::enable_if_t<has_PolymorphicTraits<T>::value, Input &>
 operator>>(Input &In, T &Val) {
   EmptyContext Ctx;
   if (In.setCurrentDocument())
     yamlize(In, Val, true, Ctx);
   return In;
 }
 
 // Provide better error message about types missing a trait specialization
 template <typename T>
 inline std::enable_if_t<missingTraits<T, EmptyContext>::value, Input &>
 operator>>(Input &yin, T &docSeq) {
   char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
   return yin;
 }
 
 // Define non-member operator<< so that Output can stream out document list.
 template <typename T>
 inline std::enable_if_t<has_DocumentListTraits<T>::value, Output &>
 operator<<(Output &yout, T &docList) {
   EmptyContext Ctx;
   yout.beginDocuments();
   const size_t count = DocumentListTraits<T>::size(yout, docList);
   for(size_t i=0; i < count; ++i) {
     if ( yout.preflightDocument(i) ) {
       yamlize(yout, DocumentListTraits<T>::element(yout, docList, i), true,
               Ctx);
       yout.postflightDocument();
     }
   }
   yout.endDocuments();
   return yout;
 }
 
 // Define non-member operator<< so that Output can stream out a map.
 template <typename T>
 inline std::enable_if_t<has_MappingTraits<T, EmptyContext>::value, Output &>
 operator<<(Output &yout, T &map) {
   EmptyContext Ctx;
   yout.beginDocuments();
   if ( yout.preflightDocument(0) ) {
     yamlize(yout, map, true, Ctx);
     yout.postflightDocument();
   }
   yout.endDocuments();
   return yout;
 }
 
 // Define non-member operator<< so that Output can stream out a sequence.
 template <typename T>
 inline std::enable_if_t<has_SequenceTraits<T>::value, Output &>
 operator<<(Output &yout, T &seq) {
   EmptyContext Ctx;
   yout.beginDocuments();
   if ( yout.preflightDocument(0) ) {
     yamlize(yout, seq, true, Ctx);
     yout.postflightDocument();
   }
   yout.endDocuments();
   return yout;
 }
 
 // Define non-member operator<< so that Output can stream out a block scalar.
 template <typename T>
 inline std::enable_if_t<has_BlockScalarTraits<T>::value, Output &>
 operator<<(Output &Out, T &Val) {
   EmptyContext Ctx;
   Out.beginDocuments();
   if (Out.preflightDocument(0)) {
     yamlize(Out, Val, true, Ctx);
     Out.postflightDocument();
   }
   Out.endDocuments();
   return Out;
 }
 
 // Define non-member operator<< so that Output can stream out a string map.
 template <typename T>
 inline std::enable_if_t<has_CustomMappingTraits<T>::value, Output &>
 operator<<(Output &Out, T &Val) {
   EmptyContext Ctx;
   Out.beginDocuments();
   if (Out.preflightDocument(0)) {
     yamlize(Out, Val, true, Ctx);
     Out.postflightDocument();
   }
   Out.endDocuments();
   return Out;
 }
 
 // Define non-member operator<< so that Output can stream out a polymorphic
 // type.
 template <typename T>
 inline std::enable_if_t<has_PolymorphicTraits<T>::value, Output &>
 operator<<(Output &Out, T &Val) {
   EmptyContext Ctx;
   Out.beginDocuments();
   if (Out.preflightDocument(0)) {
     // FIXME: The parser does not support explicit documents terminated with a
     // plain scalar; the end-marker is included as part of the scalar token.
     assert(PolymorphicTraits<T>::getKind(Val) != NodeKind::Scalar && "plain scalar documents are not supported");
     yamlize(Out, Val, true, Ctx);
     Out.postflightDocument();
   }
   Out.endDocuments();
   return Out;
 }
 
 // Provide better error message about types missing a trait specialization
 template <typename T>
 inline std::enable_if_t<missingTraits<T, EmptyContext>::value, Output &>
 operator<<(Output &yout, T &seq) {
   char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
   return yout;
 }
 
 template <bool B> struct IsFlowSequenceBase {};
 template <> struct IsFlowSequenceBase<true> { static const bool flow = true; };
 
 template <typename T, typename U = void>
 struct IsResizable : std::false_type {};
 
 template <typename T>
 struct IsResizable<T, std::void_t<decltype(std::declval<T>().resize(0))>>
     : public std::true_type {};
 
 template <typename T, bool B> struct IsResizableBase {
   using type = typename T::value_type;
 
   static type &element(IO &io, T &seq, size_t index) {
     if (index >= seq.size())
       seq.resize(index + 1);
     return seq[index];
   }
 };
 
 template <typename T> struct IsResizableBase<T, false> {
   using type = typename T::value_type;
 
   static type &element(IO &io, T &seq, size_t index) {
     if (index >= seq.size()) {
       io.setError(Twine("value sequence extends beyond static size (") +
                   Twine(seq.size()) + ")");
       return seq[0];
     }
     return seq[index];
   }
 };
 
 template <typename T, bool Flow>
 struct SequenceTraitsImpl
     : IsFlowSequenceBase<Flow>, IsResizableBase<T, IsResizable<T>::value> {
   static size_t size(IO &io, T &seq) { return seq.size(); }
 };
 
 // Simple helper to check an expression can be used as a bool-valued template
 // argument.
 template <bool> struct CheckIsBool { static const bool value = true; };
 
 // If T has SequenceElementTraits, then vector<T> and SmallVector<T, N> have
 // SequenceTraits that do the obvious thing.
 template <typename T>
 struct SequenceTraits<
     std::vector<T>,
     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
     : SequenceTraitsImpl<std::vector<T>, SequenceElementTraits<T>::flow> {};
 template <typename T, size_t N>
 struct SequenceTraits<
     std::array<T, N>,
     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
     : SequenceTraitsImpl<std::array<T, N>, SequenceElementTraits<T>::flow> {};
 template <typename T, unsigned N>
 struct SequenceTraits<
     SmallVector<T, N>,
     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
     : SequenceTraitsImpl<SmallVector<T, N>, SequenceElementTraits<T>::flow> {};
 template <typename T>
 struct SequenceTraits<
     SmallVectorImpl<T>,
     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
     : SequenceTraitsImpl<SmallVectorImpl<T>, SequenceElementTraits<T>::flow> {};
 template <typename T>
 struct SequenceTraits<
     MutableArrayRef<T>,
     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
     : SequenceTraitsImpl<MutableArrayRef<T>, SequenceElementTraits<T>::flow> {};
 
 // Sequences of fundamental types use flow formatting.
 template <typename T>
 struct SequenceElementTraits<T, std::enable_if_t<std::is_fundamental_v<T>>> {
   static const bool flow = true;
 };
 
 // Sequences of strings use block formatting.
 template<> struct SequenceElementTraits<std::string> {
   static const bool flow = false;
 };
 template<> struct SequenceElementTraits<StringRef> {
   static const bool flow = false;
 };
 template<> struct SequenceElementTraits<std::pair<std::string, std::string>> {
   static const bool flow = false;
 };
 
 /// Implementation of CustomMappingTraits for std::map<std::string, T>.
 template <typename T> struct StdMapStringCustomMappingTraitsImpl {
   using map_type = std::map<std::string, T>;
 
   static void inputOne(IO &io, StringRef key, map_type &v) {
     io.mapRequired(key.str().c_str(), v[std::string(key)]);
   }
 
   static void output(IO &io, map_type &v) {
     for (auto &p : v)
       io.mapRequired(p.first.c_str(), p.second);
   }
 };
 
 } // end namespace yaml
 } // end namespace llvm
 
 #define LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(TYPE, FLOW)                          \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   static_assert(                                                               \
       !std::is_fundamental_v<TYPE> && !std::is_same_v<TYPE, std::string> &&    \
           !std::is_same_v<TYPE, llvm::StringRef>,                              \
       "only use LLVM_YAML_IS_SEQUENCE_VECTOR for types you control");          \
   template <> struct SequenceElementTraits<TYPE> {                             \
     static const bool flow = FLOW;                                             \
   };                                                                           \
   }                                                                            \
   }
 
 /// Utility for declaring that a std::vector of a particular type
 /// should be considered a YAML sequence.
 #define LLVM_YAML_IS_SEQUENCE_VECTOR(type)                                     \
   LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, false)
 
 /// Utility for declaring that a std::vector of a particular type
 /// should be considered a YAML flow sequence.
 #define LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(type)                                \
   LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, true)
 
 #define LLVM_YAML_DECLARE_MAPPING_TRAITS(Type)                                 \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   template <> struct LLVM_ABI MappingTraits<Type> {                            \
     static void mapping(IO &IO, Type &Obj);                                    \
   };                                                                           \
   }                                                                            \
   }
 
 #define LLVM_YAML_DECLARE_MAPPING_TRAITS_PRIVATE(Type)                         \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   template <> struct MappingTraits<Type> {                                     \
     static void mapping(IO &IO, Type &Obj);                                    \
   };                                                                           \
   }                                                                            \
   }
 
 #define LLVM_YAML_DECLARE_ENUM_TRAITS(Type)                                    \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   template <> struct LLVM_ABI ScalarEnumerationTraits<Type> {                  \
     static void enumeration(IO &io, Type &Value);                              \
   };                                                                           \
   }                                                                            \
   }
 
 #define LLVM_YAML_DECLARE_BITSET_TRAITS(Type)                                  \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   template <> struct LLVM_ABI ScalarBitSetTraits<Type> {                       \
     static void bitset(IO &IO, Type &Options);                                 \
   };                                                                           \
   }                                                                            \
   }
 
 #define LLVM_YAML_DECLARE_SCALAR_TRAITS(Type, MustQuote)                       \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   template <> struct LLVM_ABI ScalarTraits<Type> {                             \
     static void output(const Type &Value, void *ctx, raw_ostream &Out);        \
     static StringRef input(StringRef Scalar, void *ctxt, Type &Value);         \
     static QuotingType mustQuote(StringRef) { return MustQuote; }              \
   };                                                                           \
   }                                                                            \
   }
 
 /// Utility for declaring that a std::vector of a particular type
 /// should be considered a YAML document list.
 #define LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(_type)                               \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   template <unsigned N>                                                        \
   struct DocumentListTraits<SmallVector<_type, N>>                             \
       : public SequenceTraitsImpl<SmallVector<_type, N>, false> {};            \
   template <>                                                                  \
   struct DocumentListTraits<std::vector<_type>>                                \
       : public SequenceTraitsImpl<std::vector<_type>, false> {};               \
   }                                                                            \
   }
 
 /// Utility for declaring that std::map<std::string, _type> should be considered
 /// a YAML map.
 #define LLVM_YAML_IS_STRING_MAP(_type)                                         \
   namespace llvm {                                                             \
   namespace yaml {                                                             \
   template <>                                                                  \
   struct CustomMappingTraits<std::map<std::string, _type>>                     \
       : public StdMapStringCustomMappingTraitsImpl<_type> {};                  \
   }                                                                            \
   }
 
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex64)
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex32)
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex16)
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex8)
 
 #endif // LLVM_SUPPORT_YAMLTRAITS_H

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