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//===--- JSON.h - JSON values, parsing and serialization -------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===---------------------------------------------------------------------===//

///

/// \file

/// This file supports working with JSON data.

///

/// It comprises:

///

/// - classes which hold dynamically-typed parsed JSON structures

///   These are value types that can be composed, inspected, and modified.

///   See json::Value, and the related types json::Object and json::Array.

///

/// - functions to parse JSON text into Values, and to serialize Values to text.

///   See parse(), operator<<, and format_provider.

///

/// - a convention and helpers for mapping between json::Value and user-defined

///   types. See fromJSON(), ObjectMapper, and the class comment on Value.

///

/// - an output API json::OStream which can emit JSON without materializing

///   all structures as json::Value.

///

/// Typically, JSON data would be read from an external source, parsed into

/// a Value, and then converted into some native data structure before doing

/// real work on it. (And vice versa when writing).

///

/// Other serialization mechanisms you may consider:

///

/// - YAML is also text-based, and more human-readable than JSON. It's a more

///   complex format and data model, and YAML parsers aren't ubiquitous.

///   YAMLParser.h is a streaming parser suitable for parsing large documents

///   (including JSON, as YAML is a superset). It can be awkward to use

///   directly. YAML I/O (YAMLTraits.h) provides data mapping that is more

///   declarative than the toJSON/fromJSON conventions here.

///

/// - LLVM bitstream is a space- and CPU- efficient binary format. Typically it

///   encodes LLVM IR ("bitcode"), but it can be a container for other data.

///   Low-level reader/writer libraries are in Bitstream/Bitstream*.h

///

//===---------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_JSON_H

#define LLVM_SUPPORT_JSON_H

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/ADT/STLFunctionalExtras.h"

#include "llvm/Support/Error.h"

#include "llvm/Support/FormatVariadic.h"

#include "llvm/Support/raw_ostream.h"

#include <cmath>

#include <map>

namespace llvm {

namespace json {

// === String encodings ===

//

// JSON strings are character sequences (not byte sequences like std::string).

// We need to know the encoding, and for simplicity only support UTF-8.

//

//   - When parsing, invalid UTF-8 is a syntax error like any other

//

//   - When creating Values from strings, callers must ensure they are UTF-8.

//        with asserts on, invalid UTF-8 will crash the program

//        with asserts off, we'll substitute the replacement character (U+FFFD)

//     Callers can use json::isUTF8() and json::fixUTF8() for validation.

//

//   - When retrieving strings from Values (e.g. asString()), the result will

//     always be valid UTF-8.

/// Returns true if \p S is valid UTF-8, which is required for use as JSON.

/// If it returns false, \p Offset is set to a byte offset near the first error.

bool isUTF8(llvm::StringRef S, size_t *ErrOffset = nullptr);

/// Replaces invalid UTF-8 sequences in \p S with the replacement character

/// (U+FFFD). The returned string is valid UTF-8.

/// This is much slower than isUTF8, so test that first.

std::string fixUTF8(llvm::StringRef S);

class Array;

class ObjectKey;

class Value;

template <typename T> Value toJSON(const std::optional<T> &Opt);

/// An Object is a JSON object, which maps strings to heterogenous JSON values.

/// It simulates DenseMap<ObjectKey, Value>. ObjectKey is a maybe-owned string.

class Object {

  using Storage = DenseMap<ObjectKey, Value, llvm::DenseMapInfo<StringRef>>;

  Storage M;

public:

  using key_type = ObjectKey;

  using mapped_type = Value;

  using value_type = Storage::value_type;

  using iterator = Storage::iterator;

  using const_iterator = Storage::const_iterator;

  Object() = default;

  // KV is a trivial key-value struct for list-initialization.

  // (using std::pair forces extra copies).

  struct KV;

  explicit Object(std::initializer_list<KV> Properties);

  iterator begin() { return M.begin(); }

  const_iterator begin() const { return M.begin(); }

  iterator end() { return M.end(); }

  const_iterator end() const { return M.end(); }

  bool empty() const { return M.empty(); }

  size_t size() const { return M.size(); }

  void clear() { M.clear(); }

  std::pair<iterator, bool> insert(KV E);

  template <typename... Ts>

  std::pair<iterator, bool> try_emplace(const ObjectKey &K, Ts &&... Args) {

    return M.try_emplace(K, std::forward<Ts>(Args)...);

  }

  template <typename... Ts>

  std::pair<iterator, bool> try_emplace(ObjectKey &&K, Ts &&... Args) {

    return M.try_emplace(std::move(K), std::forward<Ts>(Args)...);

  }

  bool erase(StringRef K);

  void erase(iterator I) { M.erase(I); }

  iterator find(StringRef K) { return M.find_as(K); }

  const_iterator find(StringRef K) const { return M.find_as(K); }

  // operator[] acts as if Value was default-constructible as null.

  Value &operator[](const ObjectKey &K);

  Value &operator[](ObjectKey &&K);

  // Look up a property, returning nullptr if it doesn't exist.

  Value *get(StringRef K);

  const Value *get(StringRef K) const;

  // Typed accessors return std::nullopt/nullptr if

  //   - the property doesn't exist

  //   - or it has the wrong type

  std::optional<std::nullptr_t> getNull(StringRef K) const;

  std::optional<bool> getBoolean(StringRef K) const;

  std::optional<double> getNumber(StringRef K) const;

  std::optional<int64_t> getInteger(StringRef K) const;

  std::optional<llvm::StringRef> getString(StringRef K) const;

  const json::Object *getObject(StringRef K) const;

  json::Object *getObject(StringRef K);

  const json::Array *getArray(StringRef K) const;

  json::Array *getArray(StringRef K);

};

bool operator==(const Object &LHS, const Object &RHS);

inline bool operator!=(const Object &LHS, const Object &RHS) {

  return !(LHS == RHS);

}

/// An Array is a JSON array, which contains heterogeneous JSON values.

/// It simulates std::vector<Value>.

class Array {

  std::vector<Value> V;

public:

  using value_type = Value;

  using iterator = std::vector<Value>::iterator;

  using const_iterator = std::vector<Value>::const_iterator;

  Array() = default;

  explicit Array(std::initializer_list<Value> Elements);

  template <typename Collection> explicit Array(const Collection &C) {

    for (const auto &V : C)

      emplace_back(V);

  }

  Value &operator[](size_t I);

  const Value &operator[](size_t I) const;

  Value &front();

  const Value &front() const;

  Value &back();

  const Value &back() const;

  Value *data();

  const Value *data() const;

  iterator begin();

  const_iterator begin() const;

  iterator end();

  const_iterator end() const;

  bool empty() const;

  size_t size() const;

  void reserve(size_t S);

  void clear();

  void push_back(const Value &E);

  void push_back(Value &&E);

  template <typename... Args> void emplace_back(Args &&...A);

  void pop_back();

  iterator insert(const_iterator P, const Value &E);

  iterator insert(const_iterator P, Value &&E);

  template <typename It> iterator insert(const_iterator P, It A, It Z);

  template <typename... Args> iterator emplace(const_iterator P, Args &&...A);

  friend bool operator==(const Array &L, const Array &R);

};

inline bool operator!=(const Array &L, const Array &R) { return !(L == R); }

/// A Value is an JSON value of unknown type.

/// They can be copied, but should generally be moved.

///

/// === Composing values ===

///

/// You can implicitly construct Values from:

///   - strings: std::string, SmallString, formatv, StringRef, char*

///              (char*, and StringRef are references, not copies!)

///   - numbers

///   - booleans

///   - null: nullptr

///   - arrays: {"foo", 42.0, false}

///   - serializable things: types with toJSON(const T&)->Value, found by ADL

///

/// They can also be constructed from object/array helpers:

///   - json::Object is a type like map<ObjectKey, Value>

///   - json::Array is a type like vector<Value>

/// These can be list-initialized, or used to build up collections in a loop.

/// json::ary(Collection) converts all items in a collection to Values.

///

/// === Inspecting values ===

///

/// Each Value is one of the JSON kinds:

///   null    (nullptr_t)

///   boolean (bool)

///   number  (double, int64 or uint64)

///   string  (StringRef)

///   array   (json::Array)

///   object  (json::Object)

///

/// The kind can be queried directly, or implicitly via the typed accessors:

///   if (std::optional<StringRef> S = E.getAsString()

///     assert(E.kind() == Value::String);

///

/// Array and Object also have typed indexing accessors for easy traversal:

///   Expected<Value> E = parse(R"( {"options": {"font": "sans-serif"}} )");

///   if (Object* O = E->getAsObject())

///     if (Object* Opts = O->getObject("options"))

///       if (std::optional<StringRef> Font = Opts->getString("font"))

///         assert(Opts->at("font").kind() == Value::String);

///

/// === Converting JSON values to C++ types ===

///

/// The convention is to have a deserializer function findable via ADL:

///     fromJSON(const json::Value&, T&, Path) -> bool

///

/// The return value indicates overall success, and Path is used for precise

/// error reporting. (The Path::Root passed in at the top level fromJSON call

/// captures any nested error and can render it in context).

/// If conversion fails, fromJSON calls Path::report() and immediately returns.

/// This ensures that the first fatal error survives.

///

/// Deserializers are provided for:

///   - bool

///   - int and int64_t

///   - double

///   - std::string

///   - vector<T>, where T is deserializable

///   - map<string, T>, where T is deserializable

///   - std::optional<T>, where T is deserializable

/// ObjectMapper can help writing fromJSON() functions for object types.

///

/// For conversion in the other direction, the serializer function is:

///    toJSON(const T&) -> json::Value

/// If this exists, then it also allows constructing Value from T, and can

/// be used to serialize vector<T>, map<string, T>, and std::optional<T>.

///

/// === Serialization ===

///

/// Values can be serialized to JSON:

///   1) raw_ostream << Value                    // Basic formatting.

///   2) raw_ostream << formatv("{0}", Value)    // Basic formatting.

///   3) raw_ostream << formatv("{0:2}", Value)  // Pretty-print with indent 2.

///

/// And parsed:

///   Expected<Value> E = json::parse("[1, 2, null]");

///   assert(E && E->kind() == Value::Array);

class Value {

public:

  enum Kind {

    Null,

    Boolean,

    /// Number values can store both int64s and doubles at full precision,

    /// depending on what they were constructed/parsed from.

    Number,

    String,

    Array,

    Object,

  };

  // It would be nice to have Value() be null. But that would make {} null too.

  Value(const Value &M) { copyFrom(M); }

  Value(Value &&M) { moveFrom(std::move(M)); }

  Value(std::initializer_list<Value> Elements);

  Value(json::Array &&Elements) : Type(T_Array) {

    create<json::Array>(std::move(Elements));

  }

  template <typename Elt>

  Value(const std::vector<Elt> &C) : Value(json::Array(C)) {}

  Value(json::Object &&Properties) : Type(T_Object) {

    create<json::Object>(std::move(Properties));

  }

  template <typename Elt>

  Value(const std::map<std::string, Elt> &C) : Value(json::Object(C)) {}

  // Strings: types with value semantics. Must be valid UTF-8.

  Value(std::string V) : Type(T_String) {

    if (LLVM_UNLIKELY(!isUTF8(V))) {

      assert(false && "Invalid UTF-8 in value used as JSON");

      V = fixUTF8(std::move(V));

    }

    create<std::string>(std::move(V));

  }

  Value(const llvm::SmallVectorImpl<char> &V)

      : Value(std::string(V.begin(), V.end())) {}

  Value(const llvm::formatv_object_base &V) : Value(V.str()) {}

  // Strings: types with reference semantics. Must be valid UTF-8.

  Value(StringRef V) : Type(T_StringRef) {

    create<llvm::StringRef>(V);

    if (LLVM_UNLIKELY(!isUTF8(V))) {

      assert(false && "Invalid UTF-8 in value used as JSON");

      *this = Value(fixUTF8(V));

    }

  }

  Value(const char *V) : Value(StringRef(V)) {}

  Value(std::nullptr_t) : Type(T_Null) {}

  // Boolean (disallow implicit conversions).

  // (The last template parameter is a dummy to keep templates distinct.)

  template <typename T,

            typename = std::enable_if_t<std::is_same<T, bool>::value>,

            bool = false>

  Value(T B) : Type(T_Boolean) {

    create<bool>(B);

  }

  // Unsigned 64-bit long integers.

  template <typename T,

            typename = std::enable_if_t<std::is_same<T, uint64_t>::value>,

            bool = false, bool = false>

  Value(T V) : Type(T_UINT64) {

    create<uint64_t>(uint64_t{V});

  }

  // Integers (except boolean and uint64_t).

  // Must be non-narrowing convertible to int64_t.

  template <typename T, typename = std::enable_if_t<std::is_integral<T>::value>,

            typename = std::enable_if_t<!std::is_same<T, bool>::value>,

            typename = std::enable_if_t<!std::is_same<T, uint64_t>::value>>

  Value(T I) : Type(T_Integer) {

    create<int64_t>(int64_t{I});

  }

  // Floating point. Must be non-narrowing convertible to double.

  template <typename T,

            typename = std::enable_if_t<std::is_floating_point<T>::value>,

            double * = nullptr>

  Value(T D) : Type(T_Double) {

    create<double>(double{D});

  }

  // Serializable types: with a toJSON(const T&)->Value function, found by ADL.

  template <typename T,

            typename = std::enable_if_t<std::is_same<

                Value, decltype(toJSON(*(const T *)nullptr))>::value>,

            Value * = nullptr>

  Value(const T &V) : Value(toJSON(V)) {}

  Value &operator=(const Value &M) {

    destroy();

    copyFrom(M);

    return *this;

  }

  Value &operator=(Value &&M) {

    destroy();

    moveFrom(std::move(M));

    return *this;

  }

  ~Value() { destroy(); }

  Kind kind() const {

    switch (Type) {

    case T_Null:

      return Null;

    case T_Boolean:

      return Boolean;

    case T_Double:

    case T_Integer:

    case T_UINT64:

      return Number;

    case T_String:

    case T_StringRef:

      return String;

    case T_Object:

      return Object;

    case T_Array:

      return Array;

    }

    llvm_unreachable("Unknown kind");

  }

  // Typed accessors return std::nullopt/nullptr if the Value is not of this

  // type.

  std::optional<std::nullptr_t> getAsNull() const {

    if (LLVM_LIKELY(Type == T_Null))

      return nullptr;

    return std::nullopt;

  }

  std::optional<bool> getAsBoolean() const {

    if (LLVM_LIKELY(Type == T_Boolean))

      return as<bool>();

    return std::nullopt;

  }

  std::optional<double> getAsNumber() const {

    if (LLVM_LIKELY(Type == T_Double))

      return as<double>();

    if (LLVM_LIKELY(Type == T_Integer))

      return as<int64_t>();

    if (LLVM_LIKELY(Type == T_UINT64))

      return as<uint64_t>();

    return std::nullopt;

  }

  // Succeeds if the Value is a Number, and exactly representable as int64_t.

  std::optional<int64_t> getAsInteger() const {

    if (LLVM_LIKELY(Type == T_Integer))

      return as<int64_t>();

    if (LLVM_LIKELY(Type == T_Double)) {

      double D = as<double>();

      if (LLVM_LIKELY(std::modf(D, &D) == 0.0 &&

                      D >= double(std::numeric_limits<int64_t>::min()) &&

                      D <= double(std::numeric_limits<int64_t>::max())))

        return D;

    }

    return std::nullopt;

  }

  std::optional<uint64_t> getAsUINT64() const {

    if (Type == T_UINT64)

      return as<uint64_t>();

    else if (Type == T_Integer) {

      int64_t N = as<int64_t>();

      if (N >= 0)

        return as<uint64_t>();

    }

    return std::nullopt;

  }

  std::optional<llvm::StringRef> getAsString() const {

    if (Type == T_String)

      return llvm::StringRef(as<std::string>());

    if (LLVM_LIKELY(Type == T_StringRef))

      return as<llvm::StringRef>();

    return std::nullopt;

  }

  const json::Object *getAsObject() const {

    return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;

  }

  json::Object *getAsObject() {

    return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;

  }

  const json::Array *getAsArray() const {

    return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;

  }

  json::Array *getAsArray() {

    return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;

  }

private:

  void destroy();

  void copyFrom(const Value &M);

  // We allow moving from *const* Values, by marking all members as mutable!

  // This hack is needed to support initializer-list syntax efficiently.

  // (std::initializer_list<T> is a container of const T).

  void moveFrom(const Value &&M);

  friend class Array;

  friend class Object;

  template <typename T, typename... U> void create(U &&... V) {

    new (reinterpret_cast<T *>(&Union)) T(std::forward<U>(V)...);

  }

  template <typename T> T &as() const {

    // Using this two-step static_cast via void * instead of reinterpret_cast

    // silences a -Wstrict-aliasing false positive from GCC6 and earlier.

    void *Storage = static_cast<void *>(&Union);

    return *static_cast<T *>(Storage);

  }

  friend class OStream;

  enum ValueType : char16_t {

    T_Null,

    T_Boolean,

    T_Double,

    T_Integer,

    T_UINT64,

    T_StringRef,

    T_String,

    T_Object,

    T_Array,

  };

  // All members mutable, see moveFrom().

  mutable ValueType Type;

  mutable llvm::AlignedCharArrayUnion<bool, double, int64_t, uint64_t,

                                      llvm::StringRef, std::string, json::Array,

                                      json::Object>

      Union;

  friend bool operator==(const Value &, const Value &);

};

bool operator==(const Value &, const Value &);

inline bool operator!=(const Value &L, const Value &R) { return !(L == R); }

// Array Methods

inline Value &Array::operator[](size_t I) { return V[I]; }

inline const Value &Array::operator[](size_t I) const { return V[I]; }

inline Value &Array::front() { return V.front(); }

inline const Value &Array::front() const { return V.front(); }

inline Value &Array::back() { return V.back(); }

inline const Value &Array::back() const { return V.back(); }

inline Value *Array::data() { return V.data(); }

inline const Value *Array::data() const { return V.data(); }

inline typename Array::iterator Array::begin() { return V.begin(); }

inline typename Array::const_iterator Array::begin() const { return V.begin(); }

inline typename Array::iterator Array::end() { return V.end(); }

inline typename Array::const_iterator Array::end() const { return V.end(); }

inline bool Array::empty() const { return V.empty(); }

inline size_t Array::size() const { return V.size(); }

inline void Array::reserve(size_t S) { V.reserve(S); }

inline void Array::clear() { V.clear(); }

inline void Array::push_back(const Value &E) { V.push_back(E); }

inline void Array::push_back(Value &&E) { V.push_back(std::move(E)); }

template <typename... Args> inline void Array::emplace_back(Args &&...A) {

  V.emplace_back(std::forward<Args>(A)...);

}

inline void Array::pop_back() { V.pop_back(); }

inline typename Array::iterator Array::insert(const_iterator P, const Value &E) {

  return V.insert(P, E);

}

inline typename Array::iterator Array::insert(const_iterator P, Value &&E) {

  return V.insert(P, std::move(E));

}

template <typename It>

inline typename Array::iterator Array::insert(const_iterator P, It A, It Z) {

  return V.insert(P, A, Z);

}

template <typename... Args>

inline typename Array::iterator Array::emplace(const_iterator P, Args &&...A) {

  return V.emplace(P, std::forward<Args>(A)...);

}

inline bool operator==(const Array &L, const Array &R) { return L.V == R.V; }

/// ObjectKey is a used to capture keys in Object. Like Value but:

///   - only strings are allowed

///   - it's optimized for the string literal case (Owned == nullptr)

/// Like Value, strings must be UTF-8. See isUTF8 documentation for details.

class ObjectKey {

public:

  ObjectKey(const char *S) : ObjectKey(StringRef(S)) {}

  ObjectKey(std::string S) : Owned(new std::string(std::move(S))) {

    if (LLVM_UNLIKELY(!isUTF8(*Owned))) {

      assert(false && "Invalid UTF-8 in value used as JSON");

      *Owned = fixUTF8(std::move(*Owned));

    }

    Data = *Owned;

  }

  ObjectKey(llvm::StringRef S) : Data(S) {

    if (LLVM_UNLIKELY(!isUTF8(Data))) {

      assert(false && "Invalid UTF-8 in value used as JSON");

      *this = ObjectKey(fixUTF8(S));

    }

  }

  ObjectKey(const llvm::SmallVectorImpl<char> &V)

      : ObjectKey(std::string(V.begin(), V.end())) {}

  ObjectKey(const llvm::formatv_object_base &V) : ObjectKey(V.str()) {}

  ObjectKey(const ObjectKey &C) { *this = C; }

  ObjectKey(ObjectKey &&C) : ObjectKey(static_cast<const ObjectKey &&>(C)) {}

  ObjectKey &operator=(const ObjectKey &C) {

    if (C.Owned) {

      Owned.reset(new std::string(*C.Owned));

      Data = *Owned;

    } else {

      Data = C.Data;

    }

    return *this;

  }

  ObjectKey &operator=(ObjectKey &&) = default;

  operator llvm::StringRef() const { return Data; }

  std::string str() const { return Data.str(); }

private:

  // FIXME: this is unneccesarily large (3 pointers). Pointer + length + owned

  // could be 2 pointers at most.

  std::unique_ptr<std::string> Owned;

  llvm::StringRef Data;

};

inline bool operator==(const ObjectKey &L, const ObjectKey &R) {

  return llvm::StringRef(L) == llvm::StringRef(R);

}

inline bool operator!=(const ObjectKey &L, const ObjectKey &R) {

  return !(L == R);

}

inline bool operator<(const ObjectKey &L, const ObjectKey &R) {

  return StringRef(L) < StringRef(R);

}

struct Object::KV {

  ObjectKey K;

  Value V;

};

inline Object::Object(std::initializer_list<KV> Properties) {

  for (const auto &P : Properties) {

    auto R = try_emplace(P.K, nullptr);

    if (R.second)

      R.first->getSecond().moveFrom(std::move(P.V));

  }

}

inline std::pair<Object::iterator, bool> Object::insert(KV E) {

  return try_emplace(std::move(E.K), std::move(E.V));

}

inline bool Object::erase(StringRef K) {

  return M.erase(ObjectKey(K));

}

/// A "cursor" marking a position within a Value.

/// The Value is a tree, and this is the path from the root to the current node.

/// This is used to associate errors with particular subobjects.

class Path {

public:

  class Root;

  /// Records that the value at the current path is invalid.

  /// Message is e.g. "expected number" and becomes part of the final error.

  /// This overwrites any previously written error message in the root.

  void report(llvm::StringLiteral Message);

  /// The root may be treated as a Path.

  Path(Root &R) : Parent(nullptr), Seg(&R) {}

  /// Derives a path for an array element: this[Index]

  Path index(unsigned Index) const { return Path(this, Segment(Index)); }

  /// Derives a path for an object field: this.Field

  Path field(StringRef Field) const { return Path(this, Segment(Field)); }

private:

  /// One element in a JSON path: an object field (.foo) or array index [27].

  /// Exception: the root Path encodes a pointer to the Path::Root.

  class Segment {

    uintptr_t Pointer;

    unsigned Offset;

  public:

    Segment() = default;

    Segment(Root *R) : Pointer(reinterpret_cast<uintptr_t>(R)) {}

    Segment(llvm::StringRef Field)

        : Pointer(reinterpret_cast<uintptr_t>(Field.data())),

          Offset(static_cast<unsigned>(Field.size())) {}

    Segment(unsigned Index) : Pointer(0), Offset(Index) {}

    bool isField() const { return Pointer != 0; }

    StringRef field() const {

      return StringRef(reinterpret_cast<const char *>(Pointer), Offset);

    }

    unsigned index() const { return Offset; }

    Root *root() const { return reinterpret_cast<Root *>(Pointer); }

  };

  const Path *Parent;

  Segment Seg;

  Path(const Path *Parent, Segment S) : Parent(Parent), Seg(S) {}

};

/// The root is the trivial Path to the root value.

/// It also stores the latest reported error and the path where it occurred.

class Path::Root {

  llvm::StringRef Name;

  llvm::StringLiteral ErrorMessage;

  std::vector<Path::Segment> ErrorPath; // Only valid in error state. Reversed.

  friend void Path::report(llvm::StringLiteral Message);

public:

  Root(llvm::StringRef Name = "") : Name(Name), ErrorMessage("") {}

  // No copy/move allowed as there are incoming pointers.

  Root(Root &&) = delete;

  Root &operator=(Root &&) = delete;

  Root(const Root &) = delete;

  Root &operator=(const Root &) = delete;

  /// Returns the last error reported, or else a generic error.

  Error getError() const;

  /// Print the root value with the error shown inline as a comment.

  /// Unrelated parts of the value are elided for brevity, e.g.

  ///   {

  ///      "id": 42,

  ///      "name": /* expected string */ null,

  ///      "properties": { ... }

  ///   }

  void printErrorContext(const Value &, llvm::raw_ostream &) const;

};