js/src/builtin/Object.cpp
author Bogdan Tara <btara@mozilla.com>
Thu, 23 May 2019 07:44:57 +0300
changeset 475051 490fd8b22deae669be2ee735757b0c8d5e417406
parent 470819 c6941f4b9a41b3a2d8431436eae13db2411d3c75
permissions -rw-r--r--
Merge mozilla-central to mozilla-inbound. a=merge CLOSED TREE

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "builtin/Object.h"

#include "mozilla/MaybeOneOf.h"

#include "builtin/BigInt.h"
#include "builtin/Eval.h"
#include "builtin/SelfHostingDefines.h"
#include "builtin/String.h"
#include "frontend/BytecodeCompiler.h"
#include "jit/InlinableNatives.h"
#include "js/PropertySpec.h"
#include "js/UniquePtr.h"
#include "util/StringBuffer.h"
#include "vm/AsyncFunction.h"
#include "vm/DateObject.h"
#include "vm/EqualityOperations.h"  // js::SameValue
#include "vm/JSContext.h"
#include "vm/RegExpObject.h"

#include "vm/JSObject-inl.h"
#include "vm/NativeObject-inl.h"
#include "vm/Shape-inl.h"

#ifdef FUZZING
#  include "builtin/TestingFunctions.h"
#endif

using namespace js;

using js::frontend::IsIdentifier;

bool js::obj_construct(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  RootedObject obj(cx, nullptr);
  if (args.isConstructing() &&
      (&args.newTarget().toObject() != &args.callee())) {
    RootedObject newTarget(cx, &args.newTarget().toObject());
    obj = CreateThis(cx, &PlainObject::class_, newTarget);
    if (!obj) {
      return false;
    }
  } else if (args.length() > 0 && !args[0].isNullOrUndefined()) {
    obj = ToObject(cx, args[0]);
    if (!obj) {
      return false;
    }
  } else {
    /* Make an object whether this was called with 'new' or not. */
    if (!NewObjectScriptedCall(cx, &obj)) {
      return false;
    }
  }

  args.rval().setObject(*obj);
  return true;
}

/* ES5 15.2.4.7. */
bool js::obj_propertyIsEnumerable(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  HandleValue idValue = args.get(0);

  // As an optimization, provide a fast path when rooting is not necessary and
  // we can safely retrieve the attributes from the object's shape.

  /* Steps 1-2. */
  jsid id;
  if (args.thisv().isObject() && ValueToId<NoGC>(cx, idValue, &id)) {
    JSObject* obj = &args.thisv().toObject();

    /* Step 3. */
    PropertyResult prop;
    if (obj->isNative() && NativeLookupOwnProperty<NoGC>(
                               cx, &obj->as<NativeObject>(), id, &prop)) {
      /* Step 4. */
      if (!prop) {
        args.rval().setBoolean(false);
        return true;
      }

      /* Step 5. */
      unsigned attrs = GetPropertyAttributes(obj, prop);
      args.rval().setBoolean((attrs & JSPROP_ENUMERATE) != 0);
      return true;
    }
  }

  /* Step 1. */
  RootedId idRoot(cx);
  if (!ToPropertyKey(cx, idValue, &idRoot)) {
    return false;
  }

  /* Step 2. */
  RootedObject obj(cx, ToObject(cx, args.thisv()));
  if (!obj) {
    return false;
  }

  /* Step 3. */
  Rooted<PropertyDescriptor> desc(cx);
  if (!GetOwnPropertyDescriptor(cx, obj, idRoot, &desc)) {
    return false;
  }

  /* Steps 4-5. */
  args.rval().setBoolean(desc.object() && desc.enumerable());
  return true;
}

static bool obj_toSource(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  if (!CheckRecursionLimit(cx)) {
    return false;
  }

  RootedObject obj(cx, ToObject(cx, args.thisv()));
  if (!obj) {
    return false;
  }

  JSString* str = ObjectToSource(cx, obj);
  if (!str) {
    return false;
  }

  args.rval().setString(str);
  return true;
}

template <typename CharT>
static bool Consume(const CharT*& s, const CharT* e, const char* chars) {
  size_t len = strlen(chars);
  if (s + len >= e) {
    return false;
  }
  if (!EqualChars(s, chars, len)) {
    return false;
  }
  s += len;
  return true;
}

template <typename CharT>
static void ConsumeSpaces(const CharT*& s, const CharT* e) {
  while (*s == ' ' && s < e) {
    s++;
  }
}

/*
 * Given a function source string, return the offset and length of the part
 * between '(function $name' and ')'.
 */
template <typename CharT>
static bool ArgsAndBodySubstring(mozilla::Range<const CharT> chars,
                                 size_t* outOffset, size_t* outLen) {
  const CharT* const start = chars.begin().get();
  const CharT* s = start;
  const CharT* e = chars.end().get();

  if (s == e) {
    return false;
  }

  // Remove enclosing parentheses.
  if (*s == '(' && *(e - 1) == ')') {
    s++;
    e--;
  }

  // Support the following cases, with spaces between tokens:
  //
  //   -+---------+-+------------+-+-----+-+- [ - <any> - ] - ( -+-
  //    |         | |            | |     | |                     |
  //    +- async -+ +- function -+ +- * -+ +- <any> - ( ---------+
  //                |            |
  //                +- get ------+
  //                |            |
  //                +- set ------+
  //
  // This accepts some invalid syntax, but we don't care, since it's only
  // used by the non-standard toSource, and we're doing a best-effort attempt
  // here.

  (void)Consume(s, e, "async");
  ConsumeSpaces(s, e);
  (void)(Consume(s, e, "function") || Consume(s, e, "get") ||
         Consume(s, e, "set"));
  ConsumeSpaces(s, e);
  (void)Consume(s, e, "*");
  ConsumeSpaces(s, e);

  // Jump over the function's name.
  if (Consume(s, e, "[")) {
    s = js_strchr_limit(s, ']', e);
    if (!s) {
      return false;
    }
    s++;
    ConsumeSpaces(s, e);
    if (*s != '(') {
      return false;
    }
  } else {
    s = js_strchr_limit(s, '(', e);
    if (!s) {
      return false;
    }
  }

  *outOffset = s - start;
  *outLen = e - s;
  MOZ_ASSERT(*outOffset + *outLen <= chars.length());
  return true;
}

enum class PropertyKind { Getter, Setter, Method, Normal };

JSString* js::ObjectToSource(JSContext* cx, HandleObject obj) {
  /* If outermost, we need parentheses to be an expression, not a block. */
  bool outermost = cx->cycleDetectorVector().empty();

  AutoCycleDetector detector(cx, obj);
  if (!detector.init()) {
    return nullptr;
  }
  if (detector.foundCycle()) {
    return NewStringCopyZ<CanGC>(cx, "{}");
  }

  JSStringBuilder buf(cx);
  if (outermost && !buf.append('(')) {
    return nullptr;
  }
  if (!buf.append('{')) {
    return nullptr;
  }

  RootedIdVector idv(cx);
  if (!GetPropertyKeys(cx, obj, JSITER_OWNONLY | JSITER_SYMBOLS, &idv)) {
    return nullptr;
  }

  bool comma = false;

  auto AddProperty = [cx, &comma, &buf](HandleId id, HandleValue val,
                                        PropertyKind kind) -> bool {
    /* Convert id to a string. */
    RootedString idstr(cx);
    if (JSID_IS_SYMBOL(id)) {
      RootedValue v(cx, SymbolValue(JSID_TO_SYMBOL(id)));
      idstr = ValueToSource(cx, v);
      if (!idstr) {
        return false;
      }
    } else {
      RootedValue idv(cx, IdToValue(id));
      idstr = ToString<CanGC>(cx, idv);
      if (!idstr) {
        return false;
      }

      /*
       * If id is a string that's not an identifier, or if it's a
       * negative integer, then it must be quoted.
       */
      if (JSID_IS_ATOM(id) ? !IsIdentifier(JSID_TO_ATOM(id))
                           : JSID_TO_INT(id) < 0) {
        UniqueChars quotedId = QuoteString(cx, idstr, '\'');
        if (!quotedId) {
          return false;
        }
        idstr = NewStringCopyZ<CanGC>(cx, quotedId.get());
        if (!idstr) {
          return false;
        }
      }
    }

    RootedString valsource(cx, ValueToSource(cx, val));
    if (!valsource) {
      return false;
    }

    RootedLinearString valstr(cx, valsource->ensureLinear(cx));
    if (!valstr) {
      return false;
    }

    if (comma && !buf.append(", ")) {
      return false;
    }
    comma = true;

    size_t voffset, vlength;

    // Methods and accessors can return exact syntax of source, that fits
    // into property without adding property name or "get"/"set" prefix.
    // Use the exact syntax when the following conditions are met:
    //
    //   * It's a function object
    //     (exclude proxies)
    //   * Function's kind and property's kind are same
    //     (this can be false for dynamically defined properties)
    //   * Function has explicit name
    //     (this can be false for computed property and dynamically defined
    //      properties)
    //   * Function's name and property's name are same
    //     (this can be false for dynamically defined properties)
    if (kind == PropertyKind::Getter || kind == PropertyKind::Setter ||
        kind == PropertyKind::Method) {
      RootedFunction fun(cx);
      if (val.toObject().is<JSFunction>()) {
        fun = &val.toObject().as<JSFunction>();
        // Method's case should be checked on caller.
        if (((fun->isGetter() && kind == PropertyKind::Getter) ||
             (fun->isSetter() && kind == PropertyKind::Setter) ||
             kind == PropertyKind::Method) &&
            fun->explicitName()) {
          bool result;
          if (!EqualStrings(cx, fun->explicitName(), idstr, &result)) {
            return false;
          }

          if (result) {
            if (!buf.append(valstr)) {
              return false;
            }
            return true;
          }
        }
      }

      {
        // When falling back try to generate a better string
        // representation by skipping the prelude, and also removing
        // the enclosing parentheses.
        bool success;
        JS::AutoCheckCannotGC nogc;
        if (valstr->hasLatin1Chars()) {
          success = ArgsAndBodySubstring(valstr->latin1Range(nogc), &voffset,
                                         &vlength);
        } else {
          success = ArgsAndBodySubstring(valstr->twoByteRange(nogc), &voffset,
                                         &vlength);
        }
        if (!success) {
          kind = PropertyKind::Normal;
        }
      }

      if (kind == PropertyKind::Getter) {
        if (!buf.append("get ")) {
          return false;
        }
      } else if (kind == PropertyKind::Setter) {
        if (!buf.append("set ")) {
          return false;
        }
      } else if (kind == PropertyKind::Method && fun) {
        if (fun->isAsync()) {
          if (!buf.append("async ")) {
            return false;
          }
        }

        if (fun->isGenerator()) {
          if (!buf.append('*')) {
            return false;
          }
        }
      }
    }

    bool needsBracket = JSID_IS_SYMBOL(id);
    if (needsBracket && !buf.append('[')) {
      return false;
    }
    if (!buf.append(idstr)) {
      return false;
    }
    if (needsBracket && !buf.append(']')) {
      return false;
    }

    if (kind == PropertyKind::Getter || kind == PropertyKind::Setter ||
        kind == PropertyKind::Method) {
      if (!buf.appendSubstring(valstr, voffset, vlength)) {
        return false;
      }
    } else {
      if (!buf.append(':')) {
        return false;
      }
      if (!buf.append(valstr)) {
        return false;
      }
    }
    return true;
  };

  RootedId id(cx);
  Rooted<PropertyDescriptor> desc(cx);
  RootedValue val(cx);
  for (size_t i = 0; i < idv.length(); ++i) {
    id = idv[i];
    if (!GetOwnPropertyDescriptor(cx, obj, id, &desc)) {
      return nullptr;
    }

    if (!desc.object()) {
      continue;
    }

    if (desc.isAccessorDescriptor()) {
      if (desc.hasGetterObject() && desc.getterObject()) {
        val.setObject(*desc.getterObject());
        if (!AddProperty(id, val, PropertyKind::Getter)) {
          return nullptr;
        }
      }
      if (desc.hasSetterObject() && desc.setterObject()) {
        val.setObject(*desc.setterObject());
        if (!AddProperty(id, val, PropertyKind::Setter)) {
          return nullptr;
        }
      }
      continue;
    }

    val.set(desc.value());

    JSFunction* fun;
    if (IsFunctionObject(val, &fun) && fun->isMethod()) {
      if (!AddProperty(id, val, PropertyKind::Method)) {
        return nullptr;
      }
      continue;
    }

    if (!AddProperty(id, val, PropertyKind::Normal)) {
      return nullptr;
    }
  }

  if (!buf.append('}')) {
    return nullptr;
  }
  if (outermost && !buf.append(')')) {
    return nullptr;
  }

  return buf.finishString();
}

static bool GetBuiltinTagSlow(JSContext* cx, HandleObject obj,
                              MutableHandleString builtinTag) {
  // Step 4.
  bool isArray;
  if (!IsArray(cx, obj, &isArray)) {
    return false;
  }

  // Step 5.
  if (isArray) {
    builtinTag.set(cx->names().objectArray);
    return true;
  }

  // Steps 6-13.
  ESClass cls;
  if (!GetBuiltinClass(cx, obj, &cls)) {
    return false;
  }

  switch (cls) {
    case ESClass::String:
      builtinTag.set(cx->names().objectString);
      return true;
    case ESClass::Arguments:
      builtinTag.set(cx->names().objectArguments);
      return true;
    case ESClass::Error:
      builtinTag.set(cx->names().objectError);
      return true;
    case ESClass::Boolean:
      builtinTag.set(cx->names().objectBoolean);
      return true;
    case ESClass::Number:
      builtinTag.set(cx->names().objectNumber);
      return true;
    case ESClass::Date:
      builtinTag.set(cx->names().objectDate);
      return true;
    case ESClass::RegExp:
      builtinTag.set(cx->names().objectRegExp);
      return true;
    default:
      if (obj->isCallable()) {
        // Non-standard: Prevent <object> from showing up as Function.
        RootedObject unwrapped(cx, CheckedUnwrapDynamic(obj, cx));
        if (!unwrapped || !unwrapped->getClass()->isDOMClass()) {
          builtinTag.set(cx->names().objectFunction);
          return true;
        }
      }
      builtinTag.set(nullptr);
      return true;
  }
}

static MOZ_ALWAYS_INLINE JSString* GetBuiltinTagFast(JSObject* obj,
                                                     const Class* clasp,
                                                     JSContext* cx) {
  MOZ_ASSERT(clasp == obj->getClass());
  MOZ_ASSERT(!clasp->isProxy());

  // Optimize the non-proxy case to bypass GetBuiltinClass.
  if (clasp == &PlainObject::class_) {
    // This is not handled by GetBuiltinTagSlow, but this case is by far
    // the most common so we optimize it here.
    return cx->names().objectObject;
  }

  if (clasp == &ArrayObject::class_) {
    return cx->names().objectArray;
  }

  if (clasp == &JSFunction::class_) {
    return cx->names().objectFunction;
  }

  if (clasp == &StringObject::class_) {
    return cx->names().objectString;
  }

  if (clasp == &NumberObject::class_) {
    return cx->names().objectNumber;
  }

  if (clasp == &BooleanObject::class_) {
    return cx->names().objectBoolean;
  }

  if (clasp == &DateObject::class_) {
    return cx->names().objectDate;
  }

  if (clasp == &RegExpObject::class_) {
    return cx->names().objectRegExp;
  }

  if (obj->is<ArgumentsObject>()) {
    return cx->names().objectArguments;
  }

  if (obj->is<ErrorObject>()) {
    return cx->names().objectError;
  }

  if (obj->isCallable() && !obj->getClass()->isDOMClass()) {
    // Non-standard: Prevent <object> from showing up as Function.
    return cx->names().objectFunction;
  }

  return nullptr;
}

// ES6 19.1.3.6
bool js::obj_toString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Step 1.
  if (args.thisv().isUndefined()) {
    args.rval().setString(cx->names().objectUndefined);
    return true;
  }

  // Step 2.
  if (args.thisv().isNull()) {
    args.rval().setString(cx->names().objectNull);
    return true;
  }

  // Step 3.
  RootedObject obj(cx, ToObject(cx, args.thisv()));
  if (!obj) {
    return false;
  }

  RootedString builtinTag(cx);
  const Class* clasp = obj->getClass();
  if (MOZ_UNLIKELY(clasp->isProxy())) {
    if (!GetBuiltinTagSlow(cx, obj, &builtinTag)) {
      return false;
    }
  } else {
    builtinTag = GetBuiltinTagFast(obj, clasp, cx);
#ifdef DEBUG
    // Assert this fast path is correct and matches BuiltinTagSlow. The
    // only exception is the PlainObject case: we special-case it here
    // because it's so common, but BuiltinTagSlow doesn't handle this.
    RootedString builtinTagSlow(cx);
    if (!GetBuiltinTagSlow(cx, obj, &builtinTagSlow)) {
      return false;
    }
    if (clasp == &PlainObject::class_) {
      MOZ_ASSERT(!builtinTagSlow);
    } else {
      MOZ_ASSERT(builtinTagSlow == builtinTag);
    }
#endif
  }

  // Step 14.
  // Currently omitted for non-standard fallback.

  // Step 15.
  RootedValue tag(cx);
  if (!GetInterestingSymbolProperty(cx, obj, cx->wellKnownSymbols().toStringTag,
                                    &tag)) {
    return false;
  }

  // Step 16.
  if (!tag.isString()) {
    // Non-standard (bug 1277801): Use ClassName as a fallback in the interim
    if (!builtinTag) {
      const char* className = GetObjectClassName(cx, obj);
      StringBuffer sb(cx);
      if (!sb.append("[object ") || !sb.append(className, strlen(className)) ||
          !sb.append(']')) {
        return false;
      }

      builtinTag = sb.finishAtom();
      if (!builtinTag) {
        return false;
      }
    }

    args.rval().setString(builtinTag);
    return true;
  }

  // Step 17.
  StringBuffer sb(cx);
  if (!sb.append("[object ") || !sb.append(tag.toString()) || !sb.append(']')) {
    return false;
  }

  JSString* str = sb.finishAtom();
  if (!str) {
    return false;
  }

  args.rval().setString(str);
  return true;
}

JSString* js::ObjectClassToString(JSContext* cx, HandleObject obj) {
  const Class* clasp = obj->getClass();

  if (JSString* tag = GetBuiltinTagFast(obj, clasp, cx)) {
    return tag;
  }

  const char* className = clasp->name;
  StringBuffer sb(cx);
  if (!sb.append("[object ") || !sb.append(className, strlen(className)) ||
      !sb.append(']')) {
    return nullptr;
  }

  return sb.finishAtom();
}

static bool obj_setPrototypeOf(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  if (!args.requireAtLeast(cx, "Object.setPrototypeOf", 2)) {
    return false;
  }

  /* Step 1-2. */
  if (args[0].isNullOrUndefined()) {
    JS_ReportErrorNumberASCII(
        cx, GetErrorMessage, nullptr, JSMSG_CANT_CONVERT_TO,
        args[0].isNull() ? "null" : "undefined", "object");
    return false;
  }

  /* Step 3. */
  if (!args[1].isObjectOrNull()) {
    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
                              JSMSG_NOT_EXPECTED_TYPE, "Object.setPrototypeOf",
                              "an object or null",
                              InformalValueTypeName(args[1]));
    return false;
  }

  /* Step 4. */
  if (!args[0].isObject()) {
    args.rval().set(args[0]);
    return true;
  }

  /* Step 5-7. */
  RootedObject obj(cx, &args[0].toObject());
  RootedObject newProto(cx, args[1].toObjectOrNull());
  if (!SetPrototype(cx, obj, newProto)) {
    return false;
  }

  /* Step 8. */
  args.rval().set(args[0]);
  return true;
}

static bool PropertyIsEnumerable(JSContext* cx, HandleObject obj, HandleId id,
                                 bool* enumerable) {
  PropertyResult prop;
  if (obj->isNative() &&
      NativeLookupOwnProperty<NoGC>(cx, &obj->as<NativeObject>(), id, &prop)) {
    if (!prop) {
      *enumerable = false;
      return true;
    }

    unsigned attrs = GetPropertyAttributes(obj, prop);
    *enumerable = (attrs & JSPROP_ENUMERATE) != 0;
    return true;
  }

  Rooted<PropertyDescriptor> desc(cx);
  if (!GetOwnPropertyDescriptor(cx, obj, id, &desc)) {
    return false;
  }

  *enumerable = desc.object() && desc.enumerable();
  return true;
}

static bool TryAssignNative(JSContext* cx, HandleObject to, HandleObject from,
                            bool* optimized) {
  *optimized = false;

  if (!from->isNative() || !to->isNative()) {
    return true;
  }

  // Don't use the fast path if |from| may have extra indexed or lazy
  // properties.
  NativeObject* fromNative = &from->as<NativeObject>();
  if (fromNative->getDenseInitializedLength() > 0 || fromNative->isIndexed() ||
      fromNative->is<TypedArrayObject>() ||
      fromNative->getClass()->getNewEnumerate() ||
      fromNative->getClass()->getEnumerate()) {
    return true;
  }

  // Get a list of |from| shapes. As long as from->lastProperty() == fromShape
  // we can use this to speed up both the enumerability check and the GetProp.

  using ShapeVector = GCVector<Shape*, 8>;
  Rooted<ShapeVector> shapes(cx, ShapeVector(cx));

  RootedShape fromShape(cx, fromNative->lastProperty());
  for (Shape::Range<NoGC> r(fromShape); !r.empty(); r.popFront()) {
    // Symbol properties need to be assigned last. For now fall back to the
    // slow path if we see a symbol property.
    if (MOZ_UNLIKELY(JSID_IS_SYMBOL(r.front().propidRaw()))) {
      return true;
    }
    if (MOZ_UNLIKELY(!shapes.append(&r.front()))) {
      return false;
    }
  }

  *optimized = true;

  RootedShape shape(cx);
  RootedValue propValue(cx);
  RootedId nextKey(cx);
  RootedValue toReceiver(cx, ObjectValue(*to));

  for (size_t i = shapes.length(); i > 0; i--) {
    shape = shapes[i - 1];
    nextKey = shape->propid();

    // Ensure |from| is still native: a getter/setter might have been swapped
    // with a non-native object.
    if (MOZ_LIKELY(from->isNative() &&
                   from->as<NativeObject>().lastProperty() == fromShape &&
                   shape->isDataProperty())) {
      if (!shape->enumerable()) {
        continue;
      }
      propValue = from->as<NativeObject>().getSlot(shape->slot());
    } else {
      // |from| changed shape or the property is not a data property, so
      // we have to do the slower enumerability check and GetProp.
      bool enumerable;
      if (!PropertyIsEnumerable(cx, from, nextKey, &enumerable)) {
        return false;
      }
      if (!enumerable) {
        continue;
      }
      if (!GetProperty(cx, from, from, nextKey, &propValue)) {
        return false;
      }
    }

    ObjectOpResult result;
    if (MOZ_UNLIKELY(
            !SetProperty(cx, to, nextKey, propValue, toReceiver, result))) {
      return false;
    }
    if (MOZ_UNLIKELY(!result.checkStrict(cx, to, nextKey))) {
      return false;
    }
  }

  return true;
}

static bool AssignSlow(JSContext* cx, HandleObject to, HandleObject from) {
  // Step 4.b.ii.
  RootedIdVector keys(cx);
  if (!GetPropertyKeys(
          cx, from, JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS, &keys)) {
    return false;
  }

  // Step 4.c.
  RootedId nextKey(cx);
  RootedValue propValue(cx);
  for (size_t i = 0, len = keys.length(); i < len; i++) {
    nextKey = keys[i];

    // Step 4.c.i.
    bool enumerable;
    if (MOZ_UNLIKELY(!PropertyIsEnumerable(cx, from, nextKey, &enumerable))) {
      return false;
    }
    if (!enumerable) {
      continue;
    }

    // Step 4.c.ii.1.
    if (MOZ_UNLIKELY(!GetProperty(cx, from, from, nextKey, &propValue))) {
      return false;
    }

    // Step 4.c.ii.2.
    if (MOZ_UNLIKELY(!SetProperty(cx, to, nextKey, propValue))) {
      return false;
    }
  }

  return true;
}

JS_PUBLIC_API bool JS_AssignObject(JSContext* cx, JS::HandleObject target,
                                   JS::HandleObject src) {
  bool optimized;
  if (!TryAssignNative(cx, target, src, &optimized)) {
    return false;
  }
  if (optimized) {
    return true;
  }

  return AssignSlow(cx, target, src);
}

// ES2018 draft rev 48ad2688d8f964da3ea8c11163ef20eb126fb8a4
// 19.1.2.1 Object.assign(target, ...sources)
static bool obj_assign(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Step 1.
  RootedObject to(cx, ToObject(cx, args.get(0)));
  if (!to) {
    return false;
  }

  // Note: step 2 is implicit. If there are 0 arguments, ToObject throws. If
  // there's 1 argument, the loop below is a no-op.

  // Step 4.
  RootedObject from(cx);
  for (size_t i = 1; i < args.length(); i++) {
    // Step 4.a.
    if (args[i].isNullOrUndefined()) {
      continue;
    }

    // Step 4.b.i.
    from = ToObject(cx, args[i]);
    if (!from) {
      return false;
    }

    // Steps 4.b.ii, 4.c.
    if (!JS_AssignObject(cx, to, from)) {
      return false;
    }
  }

  // Step 5.
  args.rval().setObject(*to);
  return true;
}

/* ES5 15.2.4.6. */
static bool obj_isPrototypeOf(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  /* Step 1. */
  if (args.length() < 1 || !args[0].isObject()) {
    args.rval().setBoolean(false);
    return true;
  }

  /* Step 2. */
  RootedObject obj(cx, ToObject(cx, args.thisv()));
  if (!obj) {
    return false;
  }

  /* Step 3. */
  bool isPrototype;
  if (!IsPrototypeOf(cx, obj, &args[0].toObject(), &isPrototype)) {
    return false;
  }
  args.rval().setBoolean(isPrototype);
  return true;
}

PlainObject* js::ObjectCreateImpl(JSContext* cx, HandleObject proto,
                                  NewObjectKind newKind,
                                  HandleObjectGroup group) {
  // Give the new object a small number of fixed slots, like we do for empty
  // object literals ({}).
  gc::AllocKind allocKind = GuessObjectGCKind(0);

  if (!proto) {
    // Object.create(null) is common, optimize it by using an allocation
    // site specific ObjectGroup. Because GetCallerInitGroup is pretty
    // slow, the caller can pass in the group if it's known and we use that
    // instead.
    RootedObjectGroup ngroup(cx, group);
    if (!ngroup) {
      ngroup = ObjectGroup::callingAllocationSiteGroup(cx, JSProto_Null);
      if (!ngroup) {
        return nullptr;
      }
    }

    MOZ_ASSERT(!ngroup->proto().toObjectOrNull());

    return NewObjectWithGroup<PlainObject>(cx, ngroup, allocKind, newKind);
  }

  return NewObjectWithGivenProto<PlainObject>(cx, proto, allocKind, newKind);
}

PlainObject* js::ObjectCreateWithTemplate(JSContext* cx,
                                          HandlePlainObject templateObj) {
  RootedObject proto(cx, templateObj->staticPrototype());
  RootedObjectGroup group(cx, templateObj->group());
  return ObjectCreateImpl(cx, proto, GenericObject, group);
}

// ES 2017 draft 19.1.2.3.1
static bool ObjectDefineProperties(JSContext* cx, HandleObject obj,
                                   HandleValue properties,
                                   bool* failedOnWindowProxy) {
  // Step 1. implicit
  // Step 2.
  RootedObject props(cx, ToObject(cx, properties));
  if (!props) {
    return false;
  }

  // Step 3.
  RootedIdVector keys(cx);
  if (!GetPropertyKeys(
          cx, props, JSITER_OWNONLY | JSITER_SYMBOLS | JSITER_HIDDEN, &keys)) {
    return false;
  }

  RootedId nextKey(cx);
  Rooted<PropertyDescriptor> desc(cx);
  RootedValue descObj(cx);

  // Step 4.
  Rooted<PropertyDescriptorVector> descriptors(cx,
                                               PropertyDescriptorVector(cx));
  RootedIdVector descriptorKeys(cx);

  // Step 5.
  for (size_t i = 0, len = keys.length(); i < len; i++) {
    nextKey = keys[i];

    // Step 5.a.
    if (!GetOwnPropertyDescriptor(cx, props, nextKey, &desc)) {
      return false;
    }

    // Step 5.b.
    if (desc.object() && desc.enumerable()) {
      if (!GetProperty(cx, props, props, nextKey, &descObj) ||
          !ToPropertyDescriptor(cx, descObj, true, &desc) ||
          !descriptors.append(desc) || !descriptorKeys.append(nextKey)) {
        return false;
      }
    }
  }

  // Step 6.
  *failedOnWindowProxy = false;
  for (size_t i = 0, len = descriptors.length(); i < len; i++) {
    ObjectOpResult result;
    if (!DefineProperty(cx, obj, descriptorKeys[i], descriptors[i], result)) {
      return false;
    }

    if (!result.ok()) {
      if (result.failureCode() == JSMSG_CANT_DEFINE_WINDOW_NC) {
        *failedOnWindowProxy = true;
      } else if (!result.checkStrict(cx, obj, descriptorKeys[i])) {
        return false;
      }
    }
  }

  return true;
}

// ES6 draft rev34 (2015/02/20) 19.1.2.2 Object.create(O [, Properties])
bool js::obj_create(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Step 1.
  if (!args.requireAtLeast(cx, "Object.create", 1)) {
    return false;
  }

  if (!args[0].isObjectOrNull()) {
    UniqueChars bytes =
        DecompileValueGenerator(cx, JSDVG_SEARCH_STACK, args[0], nullptr);
    if (!bytes) {
      return false;
    }

    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
                             JSMSG_UNEXPECTED_TYPE, bytes.get(),
                             "not an object or null");
    return false;
  }

  // Step 2.
  RootedObject proto(cx, args[0].toObjectOrNull());
  RootedPlainObject obj(cx, ObjectCreateImpl(cx, proto));
  if (!obj) {
    return false;
  }

  // Step 3.
  if (args.hasDefined(1)) {
    // we can't ever end up with failures to define on a WindowProxy
    // here, because "obj" is never a WindowProxy.
    bool failedOnWindowProxy = false;
    if (!ObjectDefineProperties(cx, obj, args[1], &failedOnWindowProxy)) {
      return false;
    }
    MOZ_ASSERT(!failedOnWindowProxy, "How did we get a WindowProxy here?");
  }

  // Step 4.
  args.rval().setObject(*obj);
  return true;
}

// ES2017 draft rev 6859bb9ccaea9c6ede81d71e5320e3833b92cb3e
// 6.2.4.4 FromPropertyDescriptor ( Desc )
static bool FromPropertyDescriptorToArray(JSContext* cx,
                                          Handle<PropertyDescriptor> desc,
                                          MutableHandleValue vp) {
  // Step 1.
  if (!desc.object()) {
    vp.setUndefined();
    return true;
  }

  // Steps 2-11.
  // Retrieve all property descriptor fields and place them into the result
  // array. The actual return object is created in self-hosted code for
  // performance reasons.

  int32_t attrsAndKind = 0;
  if (desc.enumerable()) {
    attrsAndKind |= ATTR_ENUMERABLE;
  }
  if (desc.configurable()) {
    attrsAndKind |= ATTR_CONFIGURABLE;
  }
  if (!desc.isAccessorDescriptor()) {
    if (desc.writable()) {
      attrsAndKind |= ATTR_WRITABLE;
    }
    attrsAndKind |= DATA_DESCRIPTOR_KIND;
  } else {
    attrsAndKind |= ACCESSOR_DESCRIPTOR_KIND;
  }

  RootedArrayObject result(cx);
  if (!desc.isAccessorDescriptor()) {
    result = NewDenseFullyAllocatedArray(cx, 2);
    if (!result) {
      return false;
    }
    result->setDenseInitializedLength(2);

    result->initDenseElement(PROP_DESC_ATTRS_AND_KIND_INDEX,
                             Int32Value(attrsAndKind));
    result->initDenseElement(PROP_DESC_VALUE_INDEX, desc.value());
  } else {
    result = NewDenseFullyAllocatedArray(cx, 3);
    if (!result) {
      return false;
    }
    result->setDenseInitializedLength(3);

    result->initDenseElement(PROP_DESC_ATTRS_AND_KIND_INDEX,
                             Int32Value(attrsAndKind));

    if (JSObject* get = desc.getterObject()) {
      result->initDenseElement(PROP_DESC_GETTER_INDEX, ObjectValue(*get));
    } else {
      result->initDenseElement(PROP_DESC_GETTER_INDEX, UndefinedValue());
    }

    if (JSObject* set = desc.setterObject()) {
      result->initDenseElement(PROP_DESC_SETTER_INDEX, ObjectValue(*set));
    } else {
      result->initDenseElement(PROP_DESC_SETTER_INDEX, UndefinedValue());
    }
  }

  vp.setObject(*result);
  return true;
}

// ES2017 draft rev 6859bb9ccaea9c6ede81d71e5320e3833b92cb3e
// 19.1.2.6 Object.getOwnPropertyDescriptor ( O, P )
bool js::GetOwnPropertyDescriptorToArray(JSContext* cx, unsigned argc,
                                         Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  MOZ_ASSERT(args.length() == 2);

  // Step 1.
  RootedObject obj(cx, ToObject(cx, args[0]));
  if (!obj) {
    return false;
  }

  // Step 2.
  RootedId id(cx);
  if (!ToPropertyKey(cx, args[1], &id)) {
    return false;
  }

  // Step 3.
  Rooted<PropertyDescriptor> desc(cx);
  if (!GetOwnPropertyDescriptor(cx, obj, id, &desc)) {
    return false;
  }

  // [[GetOwnProperty]] is spec'ed to always return a complete property
  // descriptor record (ES2017, 6.1.7.3, invariants of [[GetOwnProperty]]).
  desc.assertCompleteIfFound();

  // Step 4.
  return FromPropertyDescriptorToArray(cx, desc, args.rval());
}

static bool NewValuePair(JSContext* cx, HandleValue val1, HandleValue val2,
                         MutableHandleValue rval) {
  ArrayObject* array = NewDenseFullyAllocatedArray(cx, 2);
  if (!array) {
    return false;
  }

  array->setDenseInitializedLength(2);
  array->initDenseElement(0, val1);
  array->initDenseElement(1, val2);

  rval.setObject(*array);
  return true;
}

enum class EnumerableOwnPropertiesKind { Keys, Values, KeysAndValues, Names };

static bool HasEnumerableStringNonDataProperties(NativeObject* obj) {
  // We also check for enumerability and symbol properties, so uninteresting
  // non-data properties like |array.length| don't let us fall into the slow
  // path.
  for (Shape::Range<NoGC> r(obj->lastProperty()); !r.empty(); r.popFront()) {
    Shape* shape = &r.front();
    if (!shape->isDataProperty() && shape->enumerable() &&
        !JSID_IS_SYMBOL(shape->propid())) {
      return true;
    }
  }
  return false;
}

template <EnumerableOwnPropertiesKind kind>
static bool TryEnumerableOwnPropertiesNative(JSContext* cx, HandleObject obj,
                                             MutableHandleValue rval,
                                             bool* optimized) {
  *optimized = false;

  // Use the fast path if |obj| has neither extra indexed properties nor a
  // newEnumerate hook. String objects need to be special-cased, because
  // they're only marked as indexed after their enumerate hook ran. And
  // because their enumerate hook is slowish, it's more performant to
  // exclude them directly instead of executing the hook first.
  if (!obj->isNative() || obj->as<NativeObject>().isIndexed() ||
      obj->getClass()->getNewEnumerate() || obj->is<StringObject>()) {
    return true;
  }

  HandleNativeObject nobj = obj.as<NativeObject>();

  // Resolve lazy properties on |nobj|.
  if (JSEnumerateOp enumerate = nobj->getClass()->getEnumerate()) {
    if (!enumerate(cx, nobj)) {
      return false;
    }

    // Ensure no extra indexed properties were added through enumerate().
    if (nobj->isIndexed()) {
      return true;
    }
  }

  *optimized = true;

  RootedValueVector properties(cx);
  RootedValue key(cx);
  RootedValue value(cx);

  // We have ensured |nobj| contains no extra indexed properties, so the
  // only indexed properties we need to handle here are dense and typed
  // array elements.

  for (uint32_t i = 0, len = nobj->getDenseInitializedLength(); i < len; i++) {
    value.set(nobj->getDenseElement(i));
    if (value.isMagic(JS_ELEMENTS_HOLE)) {
      continue;
    }

    JSString* str;
    if (kind != EnumerableOwnPropertiesKind::Values) {
      static_assert(NativeObject::MAX_DENSE_ELEMENTS_COUNT <= JSID_INT_MAX,
                    "dense elements don't exceed JSID_INT_MAX");
      str = Int32ToString<CanGC>(cx, i);
      if (!str) {
        return false;
      }
    }

    if (kind == EnumerableOwnPropertiesKind::Keys ||
        kind == EnumerableOwnPropertiesKind::Names) {
      value.setString(str);
    } else if (kind == EnumerableOwnPropertiesKind::KeysAndValues) {
      key.setString(str);
      if (!NewValuePair(cx, key, value, &value)) {
        return false;
      }
    }

    if (!properties.append(value)) {
      return false;
    }
  }

  if (obj->is<TypedArrayObject>()) {
    Handle<TypedArrayObject*> tobj = obj.as<TypedArrayObject>();
    uint32_t len = tobj->length();

    // Fail early if the typed array contains too many elements for a
    // dense array, because we likely OOM anyway when trying to allocate
    // more than 2GB for the properties vector. This also means we don't
    // need to handle indices greater than MAX_INT32 in the loop below.
    if (len > NativeObject::MAX_DENSE_ELEMENTS_COUNT) {
      ReportOutOfMemory(cx);
      return false;
    }

    MOZ_ASSERT(properties.empty(), "typed arrays cannot have dense elements");
    if (!properties.resize(len)) {
      return false;
    }

    for (uint32_t i = 0; i < len; i++) {
      JSString* str;
      if (kind != EnumerableOwnPropertiesKind::Values) {
        static_assert(NativeObject::MAX_DENSE_ELEMENTS_COUNT <= JSID_INT_MAX,
                      "dense elements don't exceed JSID_INT_MAX");
        str = Int32ToString<CanGC>(cx, i);
        if (!str) {
          return false;
        }
      }

      if (kind == EnumerableOwnPropertiesKind::Keys ||
          kind == EnumerableOwnPropertiesKind::Names) {
        value.setString(str);
      } else if (kind == EnumerableOwnPropertiesKind::Values) {
        if (!tobj->getElement<CanGC>(cx, i, &value)) {
          return false;
        }
      } else {
        key.setString(str);
        if (!tobj->getElement<CanGC>(cx, i, &value)) {
          return false;
        }
        if (!NewValuePair(cx, key, value, &value)) {
          return false;
        }
      }

      properties[i].set(value);
    }
  }

  // Up to this point no side-effects through accessor properties are
  // possible which could have replaced |obj| with a non-native object.
  MOZ_ASSERT(obj->isNative());

  if (kind == EnumerableOwnPropertiesKind::Keys ||
      kind == EnumerableOwnPropertiesKind::Names ||
      !HasEnumerableStringNonDataProperties(nobj)) {
    // If |kind == Values| or |kind == KeysAndValues|:
    // All enumerable properties with string property keys are data
    // properties. This allows us to collect the property values while
    // iterating over the shape hierarchy without worrying over accessors
    // modifying any state.

    size_t elements = properties.length();
    constexpr bool onlyEnumerable = kind != EnumerableOwnPropertiesKind::Names;
    constexpr AllowGC allowGC =
        kind != EnumerableOwnPropertiesKind::KeysAndValues ? AllowGC::NoGC
                                                           : AllowGC::CanGC;
    mozilla::MaybeOneOf<Shape::Range<NoGC>, Shape::Range<CanGC>> m;
    if (allowGC == AllowGC::NoGC) {
      m.construct<Shape::Range<NoGC>>(nobj->lastProperty());
    } else {
      m.construct<Shape::Range<CanGC>>(cx, nobj->lastProperty());
    }
    for (Shape::Range<allowGC>& r = m.ref<Shape::Range<allowGC>>(); !r.empty();
         r.popFront()) {
      Shape* shape = &r.front();
      jsid id = shape->propid();
      if ((onlyEnumerable && !shape->enumerable()) || JSID_IS_SYMBOL(id)) {
        continue;
      }
      MOZ_ASSERT(!JSID_IS_INT(id), "Unexpected indexed property");
      MOZ_ASSERT_IF(kind == EnumerableOwnPropertiesKind::Values ||
                        kind == EnumerableOwnPropertiesKind::KeysAndValues,
                    shape->isDataProperty());

      if (kind == EnumerableOwnPropertiesKind::Keys ||
          kind == EnumerableOwnPropertiesKind::Names) {
        value.setString(JSID_TO_STRING(id));
      } else if (kind == EnumerableOwnPropertiesKind::Values) {
        value.set(nobj->getSlot(shape->slot()));
      } else {
        key.setString(JSID_TO_STRING(id));
        value.set(nobj->getSlot(shape->slot()));
        if (!NewValuePair(cx, key, value, &value)) {
          return false;
        }
      }

      if (!properties.append(value)) {
        return false;
      }
    }

    // The (non-indexed) properties were visited in reverse iteration
    // order, call Reverse() to ensure they appear in iteration order.
    Reverse(properties.begin() + elements, properties.end());
  } else {
    MOZ_ASSERT(kind == EnumerableOwnPropertiesKind::Values ||
               kind == EnumerableOwnPropertiesKind::KeysAndValues);

    // Get a list of all |obj| shapes. As long as obj->lastProperty()
    // is equal to |objShape|, we can use this to speed up both the
    // enumerability check and GetProperty.
    using ShapeVector = GCVector<Shape*, 8>;
    Rooted<ShapeVector> shapes(cx, ShapeVector(cx));

    // Collect all non-symbol properties.
    RootedShape objShape(cx, nobj->lastProperty());
    for (Shape::Range<NoGC> r(objShape); !r.empty(); r.popFront()) {
      Shape* shape = &r.front();
      if (JSID_IS_SYMBOL(shape->propid())) {
        continue;
      }
      MOZ_ASSERT(!JSID_IS_INT(shape->propid()), "Unexpected indexed property");

      if (!shapes.append(shape)) {
        return false;
      }
    }

    RootedId id(cx);
    for (size_t i = shapes.length(); i > 0; i--) {
      Shape* shape = shapes[i - 1];
      id = shape->propid();

      // Ensure |obj| is still native: a getter might have been swapped with a
      // non-native object.
      if (obj->isNative() &&
          obj->as<NativeObject>().lastProperty() == objShape &&
          shape->isDataProperty()) {
        if (!shape->enumerable()) {
          continue;
        }
        value = obj->as<NativeObject>().getSlot(shape->slot());
      } else {
        // |obj| changed shape or the property is not a data property,
        // so we have to do the slower enumerability check and
        // GetProperty.
        bool enumerable;
        if (!PropertyIsEnumerable(cx, obj, id, &enumerable)) {
          return false;
        }
        if (!enumerable) {
          continue;
        }
        if (!GetProperty(cx, obj, obj, id, &value)) {
          return false;
        }
      }

      if (kind == EnumerableOwnPropertiesKind::KeysAndValues) {
        key.setString(JSID_TO_STRING(id));
        if (!NewValuePair(cx, key, value, &value)) {
          return false;
        }
      }

      if (!properties.append(value)) {
        return false;
      }
    }
  }

  JSObject* array =
      NewDenseCopiedArray(cx, properties.length(), properties.begin());
  if (!array) {
    return false;
  }

  rval.setObject(*array);
  return true;
}

// ES2018 draft rev c164be80f7ea91de5526b33d54e5c9321ed03d3f
// 7.3.21 EnumerableOwnProperties ( O, kind )
template <EnumerableOwnPropertiesKind kind>
static bool EnumerableOwnProperties(JSContext* cx, const JS::CallArgs& args) {
  static_assert(kind == EnumerableOwnPropertiesKind::Values ||
                    kind == EnumerableOwnPropertiesKind::KeysAndValues,
                "Only implemented for Object.keys and Object.entries");

  // Step 1. (Step 1 of Object.{keys,values,entries}, really.)
  RootedObject obj(cx, ToObject(cx, args.get(0)));
  if (!obj) {
    return false;
  }

  bool optimized;
  if (!TryEnumerableOwnPropertiesNative<kind>(cx, obj, args.rval(),
                                              &optimized)) {
    return false;
  }
  if (optimized) {
    return true;
  }

  // Typed arrays are always handled in the fast path.
  MOZ_ASSERT(!obj->is<TypedArrayObject>());

  // Step 2.
  RootedIdVector ids(cx);
  if (!GetPropertyKeys(cx, obj, JSITER_OWNONLY | JSITER_HIDDEN, &ids)) {
    return false;
  }

  // Step 3.
  RootedValueVector properties(cx);
  size_t len = ids.length();
  if (!properties.resize(len)) {
    return false;
  }

  RootedId id(cx);
  RootedValue key(cx);
  RootedValue value(cx);
  RootedShape shape(cx);
  Rooted<PropertyDescriptor> desc(cx);
  // Step 4.
  size_t out = 0;
  for (size_t i = 0; i < len; i++) {
    id = ids[i];

    // Step 4.a. (Symbols were filtered out in step 2.)
    MOZ_ASSERT(!JSID_IS_SYMBOL(id));

    if (kind != EnumerableOwnPropertiesKind::Values) {
      if (!IdToStringOrSymbol(cx, id, &key)) {
        return false;
      }
    }

    // Step 4.a.i.
    if (obj->is<NativeObject>()) {
      HandleNativeObject nobj = obj.as<NativeObject>();
      if (JSID_IS_INT(id) && nobj->containsDenseElement(JSID_TO_INT(id))) {
        if (!nobj->getDenseOrTypedArrayElement<CanGC>(cx, JSID_TO_INT(id),
                                                      &value)) {
          return false;
        }
      } else {
        shape = nobj->lookup(cx, id);
        if (!shape || !shape->enumerable()) {
          continue;
        }
        if (!shape->isAccessorShape()) {
          if (!NativeGetExistingProperty(cx, nobj, nobj, shape, &value)) {
            return false;
          }
        } else if (!GetProperty(cx, obj, obj, id, &value)) {
          return false;
        }
      }
    } else {
      if (!GetOwnPropertyDescriptor(cx, obj, id, &desc)) {
        return false;
      }

      // Step 4.a.ii. (inverted.)
      if (!desc.object() || !desc.enumerable()) {
        continue;
      }

      // Step 4.a.ii.1.
      // (Omitted because Object.keys doesn't use this implementation.)

      // Step 4.a.ii.2.a.
      if (!GetProperty(cx, obj, obj, id, &value)) {
        return false;
      }
    }

    // Steps 4.a.ii.2.b-c.
    if (kind == EnumerableOwnPropertiesKind::Values) {
      properties[out++].set(value);
    } else if (!NewValuePair(cx, key, value, properties[out++])) {
      return false;
    }
  }

  // Step 5.
  // (Implemented in step 2.)

  // Step 3 of Object.{keys,values,entries}
  JSObject* aobj = NewDenseCopiedArray(cx, out, properties.begin());
  if (!aobj) {
    return false;
  }

  args.rval().setObject(*aobj);
  return true;
}

// ES2018 draft rev c164be80f7ea91de5526b33d54e5c9321ed03d3f
// 19.1.2.16 Object.keys ( O )
static bool obj_keys(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Step 1.
  RootedObject obj(cx, ToObject(cx, args.get(0)));
  if (!obj) {
    return false;
  }

  bool optimized;
  static constexpr EnumerableOwnPropertiesKind kind =
      EnumerableOwnPropertiesKind::Keys;
  if (!TryEnumerableOwnPropertiesNative<kind>(cx, obj, args.rval(),
                                              &optimized)) {
    return false;
  }
  if (optimized) {
    return true;
  }

  // Steps 2-3.
  return GetOwnPropertyKeys(cx, obj, JSITER_OWNONLY, args.rval());
}

// ES2018 draft rev c164be80f7ea91de5526b33d54e5c9321ed03d3f
// 19.1.2.21 Object.values ( O )
static bool obj_values(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Steps 1-3.
  return EnumerableOwnProperties<EnumerableOwnPropertiesKind::Values>(cx, args);
}

// ES2018 draft rev c164be80f7ea91de5526b33d54e5c9321ed03d3f
// 19.1.2.5 Object.entries ( O )
static bool obj_entries(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Steps 1-3.
  return EnumerableOwnProperties<EnumerableOwnPropertiesKind::KeysAndValues>(
      cx, args);
}

/* ES6 draft 15.2.3.16 */
bool js::obj_is(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  bool same;
  if (!SameValue(cx, args.get(0), args.get(1), &same)) {
    return false;
  }

  args.rval().setBoolean(same);
  return true;
}

bool js::IdToStringOrSymbol(JSContext* cx, HandleId id,
                            MutableHandleValue result) {
  if (JSID_IS_INT(id)) {
    JSString* str = Int32ToString<CanGC>(cx, JSID_TO_INT(id));
    if (!str) {
      return false;
    }
    result.setString(str);
  } else if (JSID_IS_ATOM(id)) {
    result.setString(JSID_TO_STRING(id));
  } else {
    result.setSymbol(JSID_TO_SYMBOL(id));
  }
  return true;
}

// ES2018 draft rev c164be80f7ea91de5526b33d54e5c9321ed03d3f
// 19.1.2.10.1 Runtime Semantics: GetOwnPropertyKeys ( O, Type )
bool js::GetOwnPropertyKeys(JSContext* cx, HandleObject obj, unsigned flags,
                            MutableHandleValue rval) {
  // Step 1 (Performed in caller).

  // Steps 2-4.
  RootedIdVector keys(cx);
  if (!GetPropertyKeys(cx, obj, flags, &keys)) {
    return false;
  }

  // Step 5 (Inlined CreateArrayFromList).
  RootedArrayObject array(cx, NewDenseFullyAllocatedArray(cx, keys.length()));
  if (!array) {
    return false;
  }

  array->ensureDenseInitializedLength(cx, 0, keys.length());

  RootedValue val(cx);
  for (size_t i = 0, len = keys.length(); i < len; i++) {
    MOZ_ASSERT_IF(JSID_IS_SYMBOL(keys[i]), flags & JSITER_SYMBOLS);
    MOZ_ASSERT_IF(!JSID_IS_SYMBOL(keys[i]), !(flags & JSITER_SYMBOLSONLY));
    if (!IdToStringOrSymbol(cx, keys[i], &val)) {
      return false;
    }
    array->initDenseElement(i, val);
  }

  rval.setObject(*array);
  return true;
}

// ES2018 draft rev c164be80f7ea91de5526b33d54e5c9321ed03d3f
// 19.1.2.9 Object.getOwnPropertyNames ( O )
bool js::obj_getOwnPropertyNames(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  RootedObject obj(cx, ToObject(cx, args.get(0)));
  if (!obj) {
    return false;
  }

  bool optimized;
  static constexpr EnumerableOwnPropertiesKind kind =
      EnumerableOwnPropertiesKind::Names;
  if (!TryEnumerableOwnPropertiesNative<kind>(cx, obj, args.rval(),
                                              &optimized)) {
    return false;
  }
  if (optimized) {
    return true;
  }

  return GetOwnPropertyKeys(cx, obj, JSITER_OWNONLY | JSITER_HIDDEN,
                            args.rval());
}

// ES2018 draft rev c164be80f7ea91de5526b33d54e5c9321ed03d3f
// 19.1.2.10 Object.getOwnPropertySymbols ( O )
static bool obj_getOwnPropertySymbols(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  RootedObject obj(cx, ToObject(cx, args.get(0)));
  if (!obj) {
    return false;
  }

  return GetOwnPropertyKeys(
      cx, obj,
      JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS | JSITER_SYMBOLSONLY,
      args.rval());
}

/* ES5 15.2.3.7: Object.defineProperties(O, Properties) */
static bool obj_defineProperties(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  /* Step 1. */
  RootedObject obj(cx);
  if (!GetFirstArgumentAsObject(cx, args, "Object.defineProperties", &obj)) {
    return false;
  }

  /* Step 2. */
  if (!args.requireAtLeast(cx, "Object.defineProperties", 2)) {
    return false;
  }

  /* Steps 3-6. */
  bool failedOnWindowProxy = false;
  if (!ObjectDefineProperties(cx, obj, args[1], &failedOnWindowProxy)) {
    return false;
  }

  /* Step 7, but modified to deal with WindowProxy mess */
  if (failedOnWindowProxy) {
    args.rval().setNull();
  } else {
    args.rval().setObject(*obj);
  }
  return true;
}

// ES6 20141014 draft 19.1.2.15 Object.preventExtensions(O)
static bool obj_preventExtensions(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  args.rval().set(args.get(0));

  // Step 1.
  if (!args.get(0).isObject()) {
    return true;
  }

  // Steps 2-5.
  RootedObject obj(cx, &args.get(0).toObject());
  return PreventExtensions(cx, obj);
}

// ES6 draft rev27 (2014/08/24) 19.1.2.5 Object.freeze(O)
static bool obj_freeze(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  args.rval().set(args.get(0));

  // Step 1.
  if (!args.get(0).isObject()) {
    return true;
  }

  // Steps 2-5.
  RootedObject obj(cx, &args.get(0).toObject());
  return SetIntegrityLevel(cx, obj, IntegrityLevel::Frozen);
}

// ES6 draft rev27 (2014/08/24) 19.1.2.12 Object.isFrozen(O)
static bool obj_isFrozen(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Step 1.
  bool frozen = true;

  // Step 2.
  if (args.get(0).isObject()) {
    RootedObject obj(cx, &args.get(0).toObject());
    if (!TestIntegrityLevel(cx, obj, IntegrityLevel::Frozen, &frozen)) {
      return false;
    }
  }
  args.rval().setBoolean(frozen);
  return true;
}

// ES6 draft rev27 (2014/08/24) 19.1.2.17 Object.seal(O)
static bool obj_seal(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  args.rval().set(args.get(0));

  // Step 1.
  if (!args.get(0).isObject()) {
    return true;
  }

  // Steps 2-5.
  RootedObject obj(cx, &args.get(0).toObject());
  return SetIntegrityLevel(cx, obj, IntegrityLevel::Sealed);
}

// ES6 draft rev27 (2014/08/24) 19.1.2.13 Object.isSealed(O)
static bool obj_isSealed(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  // Step 1.
  bool sealed = true;

  // Step 2.
  if (args.get(0).isObject()) {
    RootedObject obj(cx, &args.get(0).toObject());
    if (!TestIntegrityLevel(cx, obj, IntegrityLevel::Sealed, &sealed)) {
      return false;
    }
  }
  args.rval().setBoolean(sealed);
  return true;
}

static bool ProtoGetter(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  RootedValue thisv(cx, args.thisv());
  if (thisv.isPrimitive()) {
    if (thisv.isNullOrUndefined()) {
      ReportIncompatible(cx, args);
      return false;
    }

    if (!BoxNonStrictThis(cx, thisv, &thisv)) {
      return false;
    }
  }

  RootedObject obj(cx, &thisv.toObject());
  RootedObject proto(cx);
  if (!GetPrototype(cx, obj, &proto)) {
    return false;
  }

  args.rval().setObjectOrNull(proto);
  return true;
}

static bool ProtoSetter(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);

  HandleValue thisv = args.thisv();
  if (thisv.isNullOrUndefined()) {
    ReportIncompatible(cx, args);
    return false;
  }
  if (thisv.isPrimitive()) {
    // Mutating a boxed primitive's [[Prototype]] has no side effects.
    args.rval().setUndefined();
    return true;
  }

  Rooted<JSObject*> obj(cx, &args.thisv().toObject());

  /* Do nothing if __proto__ isn't being set to an object or null. */
  if (args.length() == 0 || !args[0].isObjectOrNull()) {
    args.rval().setUndefined();
    return true;
  }

  Rooted<JSObject*> newProto(cx, args[0].toObjectOrNull());
  if (!SetPrototype(cx, obj, newProto)) {
    return false;
  }

  args.rval().setUndefined();
  return true;
}

static const JSFunctionSpec object_methods[] = {
    JS_FN(js_toSource_str, obj_toSource, 0, 0),
    JS_INLINABLE_FN(js_toString_str, obj_toString, 0, 0, ObjectToString),
    JS_SELF_HOSTED_FN(js_toLocaleString_str, "Object_toLocaleString", 0, 0),
    JS_SELF_HOSTED_FN(js_valueOf_str, "Object_valueOf", 0, 0),
    JS_SELF_HOSTED_FN(js_hasOwnProperty_str, "Object_hasOwnProperty", 1, 0),
    JS_FN(js_isPrototypeOf_str, obj_isPrototypeOf, 1, 0),
    JS_FN(js_propertyIsEnumerable_str, obj_propertyIsEnumerable, 1, 0),
    JS_SELF_HOSTED_FN(js_defineGetter_str, "ObjectDefineGetter", 2, 0),
    JS_SELF_HOSTED_FN(js_defineSetter_str, "ObjectDefineSetter", 2, 0),
    JS_SELF_HOSTED_FN(js_lookupGetter_str, "ObjectLookupGetter", 1, 0),
    JS_SELF_HOSTED_FN(js_lookupSetter_str, "ObjectLookupSetter", 1, 0),
    JS_FS_END};

static const JSPropertySpec object_properties[] = {
    JS_PSGS("__proto__", ProtoGetter, ProtoSetter, 0), JS_PS_END};

static const JSFunctionSpec object_static_methods[] = {
    JS_FN("assign", obj_assign, 2, 0),
    JS_SELF_HOSTED_FN("getPrototypeOf", "ObjectGetPrototypeOf", 1, 0),
    JS_FN("setPrototypeOf", obj_setPrototypeOf, 2, 0),
    JS_SELF_HOSTED_FN("getOwnPropertyDescriptor",
                      "ObjectGetOwnPropertyDescriptor", 2, 0),
    JS_SELF_HOSTED_FN("getOwnPropertyDescriptors",
                      "ObjectGetOwnPropertyDescriptors", 1, 0),
    JS_FN("keys", obj_keys, 1, 0),
    JS_FN("values", obj_values, 1, 0),
    JS_FN("entries", obj_entries, 1, 0),
    JS_INLINABLE_FN("is", obj_is, 2, 0, ObjectIs),
    JS_SELF_HOSTED_FN("defineProperty", "ObjectDefineProperty", 3, 0),
    JS_FN("defineProperties", obj_defineProperties, 2, 0),
    JS_INLINABLE_FN("create", obj_create, 2, 0, ObjectCreate),
    JS_FN("getOwnPropertyNames", obj_getOwnPropertyNames, 1, 0),
    JS_FN("getOwnPropertySymbols", obj_getOwnPropertySymbols, 1, 0),
    JS_SELF_HOSTED_FN("isExtensible", "ObjectIsExtensible", 1, 0),
    JS_FN("preventExtensions", obj_preventExtensions, 1, 0),
    JS_FN("freeze", obj_freeze, 1, 0),
    JS_FN("isFrozen", obj_isFrozen, 1, 0),
    JS_FN("seal", obj_seal, 1, 0),
    JS_FN("isSealed", obj_isSealed, 1, 0),
    JS_SELF_HOSTED_FN("fromEntries", "ObjectFromEntries", 1, 0),
    JS_FS_END};

static JSObject* CreateObjectConstructor(JSContext* cx, JSProtoKey key) {
  Rooted<GlobalObject*> self(cx, cx->global());
  if (!GlobalObject::ensureConstructor(cx, self, JSProto_Function)) {
    return nullptr;
  }

  /* Create the Object function now that we have a [[Prototype]] for it. */
  JSFunction* fun = NewNativeConstructor(
      cx, obj_construct, 1, HandlePropertyName(cx->names().Object),
      gc::AllocKind::FUNCTION, SingletonObject);
  if (!fun) {
    return nullptr;
  }

  fun->setJitInfo(&jit::JitInfo_Object);
  return fun;
}

static JSObject* CreateObjectPrototype(JSContext* cx, JSProtoKey key) {
  MOZ_ASSERT(!cx->zone()->isAtomsZone());
  MOZ_ASSERT(cx->global()->isNative());

  /*
   * Create |Object.prototype| first, mirroring CreateBlankProto but for the
   * prototype of the created object.
   */
  RootedPlainObject objectProto(
      cx, NewObjectWithGivenProto<PlainObject>(cx, nullptr, SingletonObject));
  if (!objectProto) {
    return nullptr;
  }

  bool succeeded;
  if (!SetImmutablePrototype(cx, objectProto, &succeeded)) {
    return nullptr;
  }
  MOZ_ASSERT(succeeded,
             "should have been able to make a fresh Object.prototype's "
             "[[Prototype]] immutable");

  /*
   * The default 'new' type of Object.prototype is required by type inference
   * to have unknown properties, to simplify handling of e.g. heterogenous
   * objects in JSON and script literals.
   */
  ObjectGroupRealm& realm = ObjectGroupRealm::getForNewObject(cx);
  if (!JSObject::setNewGroupUnknown(cx, realm, &PlainObject::class_,
                                    objectProto)) {
    return nullptr;
  }

  return objectProto;
}

static bool FinishObjectClassInit(JSContext* cx, JS::HandleObject ctor,
                                  JS::HandleObject proto) {
  Rooted<GlobalObject*> global(cx, cx->global());

  /* ES5 15.1.2.1. */
  RootedId evalId(cx, NameToId(cx->names().eval));
  JSObject* evalobj =
      DefineFunction(cx, global, evalId, IndirectEval, 1, JSPROP_RESOLVING);
  if (!evalobj) {
    return false;
  }
  global->setOriginalEval(evalobj);

#ifdef FUZZING
  if (cx->options().fuzzing()) {
    if (!DefineTestingFunctions(cx, global, /* fuzzingSafe = */ true,
                                /* disableOOMFunctions = */ false)) {
      return false;
    }
  }
#endif

  Rooted<NativeObject*> holder(cx,
                               GlobalObject::getIntrinsicsHolder(cx, global));
  if (!holder) {
    return false;
  }

  /*
   * The global object should have |Object.prototype| as its [[Prototype]].
   * Eventually we'd like to have standard classes be there from the start,
   * and thus we would know we were always setting what had previously been a
   * null [[Prototype]], but right now some code assumes it can set the
   * [[Prototype]] before standard classes have been initialized.  For now,
   * only set the [[Prototype]] if it hasn't already been set.
   */
  Rooted<TaggedProto> tagged(cx, TaggedProto(proto));
  if (global->shouldSplicePrototype()) {
    if (!JSObject::splicePrototype(cx, global, tagged)) {
      return false;
    }
  }
  return true;
}

static const ClassSpec PlainObjectClassSpec = {
    CreateObjectConstructor, CreateObjectPrototype,
    object_static_methods,   nullptr,
    object_methods,          object_properties,
    FinishObjectClassInit};

const Class PlainObject::class_ = {js_Object_str,
                                   JSCLASS_HAS_CACHED_PROTO(JSProto_Object),
                                   JS_NULL_CLASS_OPS, &PlainObjectClassSpec};

const Class* const js::ObjectClassPtr = &PlainObject::class_;