Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3951 insertions, 0 deletions

diff --git a/js/src/vm/JSObject.cpp b/js/src/vm/JSObject.cpp
new file mode 100644
index 0000000000..cb78bfff69
--- /dev/null
+++ b/js/src/vm/JSObject.cpp
@@ -0,0 +1,3951 @@
+/* -*- 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/. */
+
+/*
+ * JS object implementation.
+ */
+
+#include "vm/JSObject-inl.h"
+
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/TemplateLib.h"
+
+#include <algorithm>
+#include <string.h>
+
+#include "jsapi.h"
+#include "jsexn.h"
+#include "jsfriendapi.h"
+#include "jsnum.h"
+#include "jstypes.h"
+
+#include "builtin/Array.h"
+#include "builtin/BigInt.h"
+#include "builtin/Eval.h"
+#include "builtin/Object.h"
+#include "builtin/String.h"
+#include "builtin/Symbol.h"
+#include "builtin/WeakSetObject.h"
+#include "frontend/BytecodeCompiler.h"
+#include "gc/Policy.h"
+#include "jit/BaselineJIT.h"
+#include "js/CharacterEncoding.h"
+#include "js/friend/DumpFunctions.h"  // js::DumpObject
+#include "js/friend/ErrorMessages.h"  // JSErrNum, js::GetErrorMessage, JSMSG_*
+#include "js/friend/WindowProxy.h"    // js::IsWindow, js::ToWindowProxyIfWindow
+#include "js/MemoryMetrics.h"
+#include "js/PropertyDescriptor.h"  // JS::FromPropertyDescriptor
+#include "js/PropertySpec.h"        // JSPropertySpec
+#include "js/Proxy.h"
+#include "js/Result.h"
+#include "js/UbiNode.h"
+#include "js/UniquePtr.h"
+#include "js/Wrapper.h"
+#include "util/Memory.h"
+#include "util/Text.h"
+#include "util/Windows.h"
+#include "vm/ArgumentsObject.h"
+#include "vm/BytecodeUtil.h"
+#include "vm/DateObject.h"
+#include "vm/Interpreter.h"
+#include "vm/Iteration.h"
+#include "vm/JSAtom.h"
+#include "vm/JSContext.h"
+#include "vm/JSFunction.h"
+#include "vm/JSScript.h"
+#include "vm/ProxyObject.h"
+#include "vm/RegExpStaticsObject.h"
+#include "vm/Shape.h"
+#include "vm/TypedArrayObject.h"
+
+#include "builtin/Boolean-inl.h"
+#include "gc/Marking-inl.h"
+#include "vm/ArrayObject-inl.h"
+#include "vm/BooleanObject-inl.h"
+#include "vm/Caches-inl.h"
+#include "vm/Compartment-inl.h"
+#include "vm/Interpreter-inl.h"
+#include "vm/JSAtom-inl.h"
+#include "vm/JSContext-inl.h"
+#include "vm/JSFunction-inl.h"
+#include "vm/NativeObject-inl.h"
+#include "vm/NumberObject-inl.h"
+#include "vm/PlainObject-inl.h"  // js::CopyInitializerObject
+#include "vm/Realm-inl.h"
+#include "vm/Shape-inl.h"
+#include "vm/StringObject-inl.h"
+#include "vm/TypedArrayObject-inl.h"
+#include "wasm/TypedObject-inl.h"
+
+using namespace js;
+
+void js::ReportNotObject(JSContext* cx, JSErrNum err, int spindex,
+                         HandleValue v) {
+  MOZ_ASSERT(!v.isObject());
+  ReportValueError(cx, err, spindex, v, nullptr);
+}
+
+void js::ReportNotObject(JSContext* cx, JSErrNum err, HandleValue v) {
+  ReportNotObject(cx, err, JSDVG_SEARCH_STACK, v);
+}
+
+void js::ReportNotObject(JSContext* cx, const Value& v) {
+  RootedValue value(cx, v);
+  ReportNotObject(cx, JSMSG_OBJECT_REQUIRED, value);
+}
+
+void js::ReportNotObjectArg(JSContext* cx, const char* nth, const char* fun,
+                            HandleValue v) {
+  MOZ_ASSERT(!v.isObject());
+
+  UniqueChars bytes;
+  if (const char* chars = ValueToSourceForError(cx, v, bytes)) {
+    JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr,
+                               JSMSG_OBJECT_REQUIRED_ARG, nth, fun, chars);
+  }
+}
+
+JS_PUBLIC_API const char* JS::InformalValueTypeName(const Value& v) {
+  switch (v.type()) {
+    case ValueType::Double:
+    case ValueType::Int32:
+      return "number";
+    case ValueType::Boolean:
+      return "boolean";
+    case ValueType::Undefined:
+      return "undefined";
+    case ValueType::Null:
+      return "null";
+    case ValueType::String:
+      return "string";
+    case ValueType::Symbol:
+      return "symbol";
+    case ValueType::BigInt:
+      return "bigint";
+    case ValueType::Object:
+      return v.toObject().getClass()->name;
+    case ValueType::Magic:
+      return "magic";
+    case ValueType::PrivateGCThing:
+      break;
+  }
+
+  MOZ_CRASH("unexpected type");
+}
+
+// ES6 draft rev37 6.2.4.4 FromPropertyDescriptor
+JS_PUBLIC_API bool JS::FromPropertyDescriptor(JSContext* cx,
+                                              Handle<PropertyDescriptor> desc,
+                                              MutableHandleValue vp) {
+  AssertHeapIsIdle();
+  CHECK_THREAD(cx);
+  cx->check(desc);
+
+  // Step 1.
+  if (!desc.object()) {
+    vp.setUndefined();
+    return true;
+  }
+
+  return FromPropertyDescriptorToObject(cx, desc, vp);
+}
+
+bool js::FromPropertyDescriptorToObject(JSContext* cx,
+                                        Handle<PropertyDescriptor> desc,
+                                        MutableHandleValue vp) {
+  // Step 2-3.
+  RootedObject obj(cx, NewBuiltinClassInstance<PlainObject>(cx));
+  if (!obj) {
+    return false;
+  }
+
+  const JSAtomState& names = cx->names();
+
+  // Step 4.
+  if (desc.hasValue()) {
+    if (!DefineDataProperty(cx, obj, names.value, desc.value())) {
+      return false;
+    }
+  }
+
+  // Step 5.
+  RootedValue v(cx);
+  if (desc.hasWritable()) {
+    v.setBoolean(desc.writable());
+    if (!DefineDataProperty(cx, obj, names.writable, v)) {
+      return false;
+    }
+  }
+
+  // Step 6.
+  if (desc.hasGetterObject()) {
+    if (JSObject* get = desc.getterObject()) {
+      v.setObject(*get);
+    } else {
+      v.setUndefined();
+    }
+    if (!DefineDataProperty(cx, obj, names.get, v)) {
+      return false;
+    }
+  }
+
+  // Step 7.
+  if (desc.hasSetterObject()) {
+    if (JSObject* set = desc.setterObject()) {
+      v.setObject(*set);
+    } else {
+      v.setUndefined();
+    }
+    if (!DefineDataProperty(cx, obj, names.set, v)) {
+      return false;
+    }
+  }
+
+  // Step 8.
+  if (desc.hasEnumerable()) {
+    v.setBoolean(desc.enumerable());
+    if (!DefineDataProperty(cx, obj, names.enumerable, v)) {
+      return false;
+    }
+  }
+
+  // Step 9.
+  if (desc.hasConfigurable()) {
+    v.setBoolean(desc.configurable());
+    if (!DefineDataProperty(cx, obj, names.configurable, v)) {
+      return false;
+    }
+  }
+
+  vp.setObject(*obj);
+  return true;
+}
+
+bool js::GetFirstArgumentAsObject(JSContext* cx, const CallArgs& args,
+                                  const char* method,
+                                  MutableHandleObject objp) {
+  if (!args.requireAtLeast(cx, method, 1)) {
+    return false;
+  }
+
+  HandleValue v = args[0];
+  if (!v.isObject()) {
+    UniqueChars bytes =
+        DecompileValueGenerator(cx, JSDVG_SEARCH_STACK, v, nullptr);
+    if (!bytes) {
+      return false;
+    }
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
+                             JSMSG_UNEXPECTED_TYPE, bytes.get(),
+                             "not an object");
+    return false;
+  }
+
+  objp.set(&v.toObject());
+  return true;
+}
+
+static bool GetPropertyIfPresent(JSContext* cx, HandleObject obj, HandleId id,
+                                 MutableHandleValue vp, bool* foundp) {
+  if (!HasProperty(cx, obj, id, foundp)) {
+    return false;
+  }
+  if (!*foundp) {
+    vp.setUndefined();
+    return true;
+  }
+
+  return GetProperty(cx, obj, obj, id, vp);
+}
+
+bool js::Throw(JSContext* cx, HandleId id, unsigned errorNumber,
+               const char* details) {
+  MOZ_ASSERT(js_ErrorFormatString[errorNumber].argCount == (details ? 2 : 1));
+  MOZ_ASSERT_IF(details, JS::StringIsASCII(details));
+
+  UniqueChars bytes =
+      IdToPrintableUTF8(cx, id, IdToPrintableBehavior::IdIsPropertyKey);
+  if (!bytes) {
+    return false;
+  }
+
+  if (details) {
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr, errorNumber,
+                             bytes.get(), details);
+  } else {
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr, errorNumber,
+                             bytes.get());
+  }
+
+  return false;
+}
+
+/*** PropertyDescriptor operations and DefineProperties *********************/
+
+static const char js_getter_str[] = "getter";
+static const char js_setter_str[] = "setter";
+
+static Result<> CheckCallable(JSContext* cx, JSObject* obj,
+                              const char* fieldName) {
+  if (obj && !obj->isCallable()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_BAD_GET_SET_FIELD, fieldName);
+    return cx->alreadyReportedError();
+  }
+  return Ok();
+}
+
+bool js::ToPropertyDescriptor(JSContext* cx, HandleValue descval,
+                              bool checkAccessors,
+                              MutableHandle<PropertyDescriptor> desc) {
+  // step 2
+  RootedObject obj(cx,
+                   RequireObject(cx, JSMSG_OBJECT_REQUIRED_PROP_DESC, descval));
+  if (!obj) {
+    return false;
+  }
+
+  // step 3
+  desc.clear();
+
+  bool found = false;
+  RootedId id(cx);
+  RootedValue v(cx);
+  unsigned attrs = 0;
+
+  // step 4
+  id = NameToId(cx->names().enumerable);
+  if (!GetPropertyIfPresent(cx, obj, id, &v, &found)) {
+    return false;
+  }
+  if (found) {
+    if (ToBoolean(v)) {
+      attrs |= JSPROP_ENUMERATE;
+    }
+  } else {
+    attrs |= JSPROP_IGNORE_ENUMERATE;
+  }
+
+  // step 5
+  id = NameToId(cx->names().configurable);
+  if (!GetPropertyIfPresent(cx, obj, id, &v, &found)) {
+    return false;
+  }
+  if (found) {
+    if (!ToBoolean(v)) {
+      attrs |= JSPROP_PERMANENT;
+    }
+  } else {
+    attrs |= JSPROP_IGNORE_PERMANENT;
+  }
+
+  // step 6
+  id = NameToId(cx->names().value);
+  if (!GetPropertyIfPresent(cx, obj, id, &v, &found)) {
+    return false;
+  }
+  if (found) {
+    desc.value().set(v);
+  } else {
+    attrs |= JSPROP_IGNORE_VALUE;
+  }
+
+  // step 7
+  id = NameToId(cx->names().writable);
+  if (!GetPropertyIfPresent(cx, obj, id, &v, &found)) {
+    return false;
+  }
+  if (found) {
+    if (!ToBoolean(v)) {
+      attrs |= JSPROP_READONLY;
+    }
+  } else {
+    attrs |= JSPROP_IGNORE_READONLY;
+  }
+
+  // step 8
+  bool hasGetOrSet;
+  id = NameToId(cx->names().get);
+  if (!GetPropertyIfPresent(cx, obj, id, &v, &found)) {
+    return false;
+  }
+  hasGetOrSet = found;
+  if (found) {
+    if (v.isObject()) {
+      if (checkAccessors) {
+        JS_TRY_OR_RETURN_FALSE(cx,
+                               CheckCallable(cx, &v.toObject(), js_getter_str));
+      }
+      desc.setGetterObject(&v.toObject());
+    } else if (!v.isUndefined()) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_BAD_GET_SET_FIELD, js_getter_str);
+      return false;
+    }
+    attrs |= JSPROP_GETTER;
+  }
+
+  // step 9
+  id = NameToId(cx->names().set);
+  if (!GetPropertyIfPresent(cx, obj, id, &v, &found)) {
+    return false;
+  }
+  hasGetOrSet |= found;
+  if (found) {
+    if (v.isObject()) {
+      if (checkAccessors) {
+        JS_TRY_OR_RETURN_FALSE(cx,
+                               CheckCallable(cx, &v.toObject(), js_setter_str));
+      }
+      desc.setSetterObject(&v.toObject());
+    } else if (!v.isUndefined()) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_BAD_GET_SET_FIELD, js_setter_str);
+      return false;
+    }
+    attrs |= JSPROP_SETTER;
+  }
+
+  // step 10
+  if (hasGetOrSet) {
+    if (!(attrs & JSPROP_IGNORE_READONLY) || !(attrs & JSPROP_IGNORE_VALUE)) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_INVALID_DESCRIPTOR);
+      return false;
+    }
+
+    // By convention, these bits are not used on accessor descriptors.
+    attrs &= ~(JSPROP_IGNORE_READONLY | JSPROP_IGNORE_VALUE);
+  }
+
+  desc.setAttributes(attrs);
+  MOZ_ASSERT_IF(attrs & JSPROP_READONLY,
+                !(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
+  return true;
+}
+
+Result<> js::CheckPropertyDescriptorAccessors(JSContext* cx,
+                                              Handle<PropertyDescriptor> desc) {
+  if (desc.hasGetterObject()) {
+    MOZ_TRY(CheckCallable(cx, desc.getterObject(), js_getter_str));
+  }
+
+  if (desc.hasSetterObject()) {
+    MOZ_TRY(CheckCallable(cx, desc.setterObject(), js_setter_str));
+  }
+
+  return Ok();
+}
+
+void js::CompletePropertyDescriptor(MutableHandle<PropertyDescriptor> desc) {
+  desc.assertValid();
+
+  if (desc.isGenericDescriptor() || desc.isDataDescriptor()) {
+    if (!desc.hasWritable()) {
+      desc.attributesRef() |= JSPROP_READONLY;
+    }
+    desc.attributesRef() &= ~(JSPROP_IGNORE_READONLY | JSPROP_IGNORE_VALUE);
+  } else {
+    if (!desc.hasGetterObject()) {
+      desc.setGetterObject(nullptr);
+    }
+    if (!desc.hasSetterObject()) {
+      desc.setSetterObject(nullptr);
+    }
+    desc.attributesRef() |= JSPROP_GETTER | JSPROP_SETTER;
+  }
+  if (!desc.hasConfigurable()) {
+    desc.attributesRef() |= JSPROP_PERMANENT;
+  }
+  desc.attributesRef() &= ~(JSPROP_IGNORE_PERMANENT | JSPROP_IGNORE_ENUMERATE);
+
+  desc.assertComplete();
+}
+
+bool js::ReadPropertyDescriptors(
+    JSContext* cx, HandleObject props, bool checkAccessors,
+    MutableHandleIdVector ids, MutableHandle<PropertyDescriptorVector> descs) {
+  if (!GetPropertyKeys(cx, props, JSITER_OWNONLY | JSITER_SYMBOLS, ids)) {
+    return false;
+  }
+
+  RootedId id(cx);
+  for (size_t i = 0, len = ids.length(); i < len; i++) {
+    id = ids[i];
+    Rooted<PropertyDescriptor> desc(cx);
+    RootedValue v(cx);
+    if (!GetProperty(cx, props, props, id, &v) ||
+        !ToPropertyDescriptor(cx, v, checkAccessors, &desc) ||
+        !descs.append(desc)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/*** Seal and freeze ********************************************************/
+
+static unsigned GetSealedOrFrozenAttributes(unsigned attrs,
+                                            IntegrityLevel level) {
+  // Make all attributes permanent; if freezing, make data attributes
+  // read-only.
+  if (level == IntegrityLevel::Frozen &&
+      !(attrs & (JSPROP_GETTER | JSPROP_SETTER))) {
+    return JSPROP_PERMANENT | JSPROP_READONLY;
+  }
+  return JSPROP_PERMANENT;
+}
+
+/* ES6 draft rev 29 (6 Dec 2014) 7.3.13. */
+bool js::SetIntegrityLevel(JSContext* cx, HandleObject obj,
+                           IntegrityLevel level) {
+  cx->check(obj);
+
+  // Steps 3-5. (Steps 1-2 are redundant assertions.)
+  if (!PreventExtensions(cx, obj)) {
+    return false;
+  }
+
+  // Steps 6-9, loosely interpreted.
+  if (obj->isNative() && !obj->as<NativeObject>().inDictionaryMode() &&
+      !obj->is<TypedArrayObject>() && !obj->is<MappedArgumentsObject>()) {
+    HandleNativeObject nobj = obj.as<NativeObject>();
+
+    // Seal/freeze non-dictionary objects by constructing a new shape
+    // hierarchy mirroring the original one, which can be shared if many
+    // objects with the same structure are sealed/frozen. If we use the
+    // generic path below then any non-empty object will be converted to
+    // dictionary mode.
+    RootedShape last(
+        cx, EmptyShape::getInitialShape(
+                cx, nobj->getClass(), nobj->taggedProto(),
+                nobj->numFixedSlots(), nobj->lastProperty()->getObjectFlags()));
+    if (!last) {
+      return false;
+    }
+
+    // Get an in-order list of the shapes in this object.
+    using ShapeVec = GCVector<Shape*, 8>;
+    Rooted<ShapeVec> shapes(cx, ShapeVec(cx));
+    for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
+      if (!shapes.append(&r.front())) {
+        return false;
+      }
+    }
+    std::reverse(shapes.begin(), shapes.end());
+
+    for (Shape* shape : shapes) {
+      Rooted<StackShape> child(cx, StackShape(shape));
+      bool isPrivate = JSID_IS_SYMBOL(child.get().propid) &&
+                       JSID_TO_SYMBOL(child.get().propid)->isPrivateName();
+      // Private fields are not visible to SetIntegrity.
+      if (!isPrivate) {
+        child.setAttrs(child.attrs() |
+                       GetSealedOrFrozenAttributes(child.attrs(), level));
+      }
+
+      last = cx->zone()->propertyTree().getChild(cx, last, child);
+      if (!last) {
+        return false;
+      }
+    }
+
+    MOZ_ASSERT(nobj->lastProperty()->slotSpan() == last->slotSpan());
+    MOZ_ALWAYS_TRUE(nobj->setLastProperty(cx, last));
+
+    // Ordinarily ArraySetLength handles this, but we're going behind its back
+    // right now, so we must do this manually.
+    if (level == IntegrityLevel::Frozen && obj->is<ArrayObject>()) {
+      obj->as<ArrayObject>().setNonWritableLength(cx);
+    }
+  } else {
+    // Steps 6-7.
+    RootedIdVector keys(cx);
+    if (!GetPropertyKeys(
+            cx, obj, JSITER_HIDDEN | JSITER_OWNONLY | JSITER_SYMBOLS, &keys)) {
+      return false;
+    }
+
+    RootedId id(cx);
+    Rooted<PropertyDescriptor> desc(cx);
+
+    const unsigned AllowConfigure =
+        JSPROP_IGNORE_ENUMERATE | JSPROP_IGNORE_READONLY | JSPROP_IGNORE_VALUE;
+    const unsigned AllowConfigureAndWritable =
+        AllowConfigure & ~JSPROP_IGNORE_READONLY;
+
+    // 8.a/9.a. The two different loops are merged here.
+    for (size_t i = 0; i < keys.length(); i++) {
+      id = keys[i];
+
+      if (level == IntegrityLevel::Sealed) {
+        // 8.a.i.
+        desc.setAttributes(AllowConfigure | JSPROP_PERMANENT);
+      } else {
+        // 9.a.i-ii.
+        Rooted<PropertyDescriptor> currentDesc(cx);
+        if (!GetOwnPropertyDescriptor(cx, obj, id, &currentDesc)) {
+          return false;
+        }
+
+        // 9.a.iii.
+        if (!currentDesc.object()) {
+          continue;
+        }
+
+        // 9.a.iii.1-2
+        if (currentDesc.isAccessorDescriptor()) {
+          desc.setAttributes(AllowConfigure | JSPROP_PERMANENT);
+        } else {
+          desc.setAttributes(AllowConfigureAndWritable | JSPROP_PERMANENT |
+                             JSPROP_READONLY);
+        }
+      }
+
+      // 8.a.i-ii. / 9.a.iii.3-4
+      if (!DefineProperty(cx, obj, id, desc)) {
+        return false;
+      }
+    }
+  }
+
+  // Finally, freeze or seal the dense elements.
+  if (obj->isNative()) {
+    if (!ObjectElements::FreezeOrSeal(cx, obj.as<NativeObject>(), level)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static bool ResolveLazyProperties(JSContext* cx, HandleNativeObject obj) {
+  const JSClass* clasp = obj->getClass();
+  if (JSEnumerateOp enumerate = clasp->getEnumerate()) {
+    if (!enumerate(cx, obj)) {
+      return false;
+    }
+  }
+  if (clasp->getNewEnumerate() && clasp->getResolve()) {
+    RootedIdVector properties(cx);
+    if (!clasp->getNewEnumerate()(cx, obj, &properties,
+                                  /* enumerableOnly = */ false)) {
+      return false;
+    }
+
+    RootedId id(cx);
+    for (size_t i = 0; i < properties.length(); i++) {
+      id = properties[i];
+      bool found;
+      if (!HasOwnProperty(cx, obj, id, &found)) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+// ES6 draft rev33 (12 Feb 2015) 7.3.15
+bool js::TestIntegrityLevel(JSContext* cx, HandleObject obj,
+                            IntegrityLevel level, bool* result) {
+  // Steps 3-6. (Steps 1-2 are redundant assertions.)
+  bool status;
+  if (!IsExtensible(cx, obj, &status)) {
+    return false;
+  }
+  if (status) {
+    *result = false;
+    return true;
+  }
+
+  // Fast path for native objects.
+  if (obj->isNative()) {
+    HandleNativeObject nobj = obj.as<NativeObject>();
+
+    // Force lazy properties to be resolved.
+    if (!ResolveLazyProperties(cx, nobj)) {
+      return false;
+    }
+
+    // Typed array elements are configurable, writable properties, so if any
+    // elements are present, the typed array can neither be sealed nor frozen.
+    if (nobj->is<TypedArrayObject>() &&
+        nobj->as<TypedArrayObject>().length().get() > 0) {
+      *result = false;
+      return true;
+    }
+
+    bool hasDenseElements = false;
+    for (size_t i = 0; i < nobj->getDenseInitializedLength(); i++) {
+      if (nobj->containsDenseElement(i)) {
+        hasDenseElements = true;
+        break;
+      }
+    }
+
+    if (hasDenseElements) {
+      // Unless the sealed flag is set, dense elements are configurable.
+      if (!nobj->denseElementsAreSealed()) {
+        *result = false;
+        return true;
+      }
+
+      // Unless the frozen flag is set, dense elements are writable.
+      if (level == IntegrityLevel::Frozen && !nobj->denseElementsAreFrozen()) {
+        *result = false;
+        return true;
+      }
+    }
+
+    // Steps 7-9.
+    for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
+      Shape* shape = &r.front();
+
+      // Steps 9.c.i-ii.
+      if (shape->configurable() ||
+          (level == IntegrityLevel::Frozen && shape->isDataDescriptor() &&
+           shape->writable())) {
+        *result = false;
+        return true;
+      }
+    }
+  } else {
+    // Steps 7-8.
+    RootedIdVector props(cx);
+    if (!GetPropertyKeys(
+            cx, obj, JSITER_HIDDEN | JSITER_OWNONLY | JSITER_SYMBOLS, &props)) {
+      return false;
+    }
+
+    // Step 9.
+    RootedId id(cx);
+    Rooted<PropertyDescriptor> desc(cx);
+    for (size_t i = 0, len = props.length(); i < len; i++) {
+      id = props[i];
+
+      // Steps 9.a-b.
+      if (!GetOwnPropertyDescriptor(cx, obj, id, &desc)) {
+        return false;
+      }
+
+      // Step 9.c.
+      if (!desc.object()) {
+        continue;
+      }
+
+      // Steps 9.c.i-ii.
+      if (desc.configurable() || (level == IntegrityLevel::Frozen &&
+                                  desc.isDataDescriptor() && desc.writable())) {
+        *result = false;
+        return true;
+      }
+    }
+  }
+
+  // Step 10.
+  *result = true;
+  return true;
+}
+
+/* * */
+
+static inline JSObject* NewObject(JSContext* cx, HandleObjectGroup group,
+                                  gc::AllocKind kind, NewObjectKind newKind,
+                                  uint32_t initialShapeFlags = 0) {
+  const JSClass* clasp = group->clasp();
+
+  MOZ_ASSERT(clasp != &ArrayObject::class_);
+  MOZ_ASSERT_IF(clasp == &JSFunction::class_,
+                kind == gc::AllocKind::FUNCTION ||
+                    kind == gc::AllocKind::FUNCTION_EXTENDED);
+
+  // For objects which can have fixed data following the object, only use
+  // enough fixed slots to cover the number of reserved slots in the object,
+  // regardless of the allocation kind specified.
+  size_t nfixed = ClassCanHaveFixedData(clasp)
+                      ? GetGCKindSlots(gc::GetGCObjectKind(clasp), clasp)
+                      : GetGCKindSlots(kind, clasp);
+
+  RootedShape shape(cx, EmptyShape::getInitialShape(cx, clasp, group->proto(),
+                                                    nfixed, initialShapeFlags));
+  if (!shape) {
+    return nullptr;
+  }
+
+  gc::InitialHeap heap = GetInitialHeap(newKind, group);
+
+  JSObject* obj;
+  if (clasp->isJSFunction()) {
+    JS_TRY_VAR_OR_RETURN_NULL(cx, obj,
+                              JSFunction::create(cx, kind, heap, shape, group));
+  } else if (MOZ_LIKELY(clasp->isNative())) {
+    JS_TRY_VAR_OR_RETURN_NULL(
+        cx, obj, NativeObject::create(cx, kind, heap, shape, group));
+  } else {
+    MOZ_ASSERT(IsTypedObjectClass(clasp));
+    JS_TRY_VAR_OR_RETURN_NULL(
+        cx, obj, TypedObject::create(cx, kind, heap, shape, group));
+  }
+
+  probes::CreateObject(cx, obj);
+  return obj;
+}
+
+void NewObjectCache::fillProto(EntryIndex entry, const JSClass* clasp,
+                               js::TaggedProto proto, gc::AllocKind kind,
+                               NativeObject* obj) {
+  MOZ_ASSERT_IF(proto.isObject(), !proto.toObject()->is<GlobalObject>());
+  MOZ_ASSERT(obj->taggedProto() == proto);
+  return fill(entry, clasp, proto.raw(), kind, obj);
+}
+
+bool js::NewObjectWithTaggedProtoIsCachable(JSContext* cx,
+                                            Handle<TaggedProto> proto,
+                                            NewObjectKind newKind,
+                                            const JSClass* clasp) {
+  return !cx->isHelperThreadContext() && proto.isObject() &&
+         newKind == GenericObject && clasp->isNative() &&
+         !proto.toObject()->is<GlobalObject>();
+}
+
+JSObject* js::NewObjectWithGivenTaggedProto(JSContext* cx, const JSClass* clasp,
+                                            Handle<TaggedProto> proto,
+                                            gc::AllocKind allocKind,
+                                            NewObjectKind newKind,
+                                            uint32_t initialShapeFlags) {
+  if (CanChangeToBackgroundAllocKind(allocKind, clasp)) {
+    allocKind = ForegroundToBackgroundAllocKind(allocKind);
+  }
+
+  bool isCachable =
+      NewObjectWithTaggedProtoIsCachable(cx, proto, newKind, clasp);
+  if (isCachable) {
+    NewObjectCache& cache = cx->caches().newObjectCache;
+    NewObjectCache::EntryIndex entry = -1;
+    if (cache.lookupProto(clasp, proto.toObject(), allocKind, &entry)) {
+      JSObject* obj =
+          cache.newObjectFromHit(cx, entry, GetInitialHeap(newKind, clasp));
+      if (obj) {
+        return obj;
+      }
+    }
+  }
+
+  RootedObjectGroup group(cx, ObjectGroup::defaultNewGroup(cx, clasp, proto));
+  if (!group) {
+    return nullptr;
+  }
+
+  RootedObject obj(cx,
+                   NewObject(cx, group, allocKind, newKind, initialShapeFlags));
+  if (!obj) {
+    return nullptr;
+  }
+
+  if (isCachable && !obj->as<NativeObject>().hasDynamicSlots()) {
+    NewObjectCache& cache = cx->caches().newObjectCache;
+    NewObjectCache::EntryIndex entry = -1;
+    cache.lookupProto(clasp, proto.toObject(), allocKind, &entry);
+    cache.fillProto(entry, clasp, proto, allocKind, &obj->as<NativeObject>());
+  }
+
+  return obj;
+}
+
+static bool NewObjectIsCachable(JSContext* cx, NewObjectKind newKind,
+                                const JSClass* clasp) {
+  return !cx->isHelperThreadContext() && newKind == GenericObject &&
+         clasp->isNative();
+}
+
+JSObject* js::NewObjectWithClassProto(JSContext* cx, const JSClass* clasp,
+                                      HandleObject protoArg,
+                                      gc::AllocKind allocKind,
+                                      NewObjectKind newKind) {
+  if (protoArg) {
+    return NewObjectWithGivenTaggedProto(cx, clasp, AsTaggedProto(protoArg),
+                                         allocKind, newKind);
+  }
+
+  if (CanChangeToBackgroundAllocKind(allocKind, clasp)) {
+    allocKind = ForegroundToBackgroundAllocKind(allocKind);
+  }
+
+  Handle<GlobalObject*> global = cx->global();
+
+  bool isCachable = NewObjectIsCachable(cx, newKind, clasp);
+  if (isCachable) {
+    NewObjectCache& cache = cx->caches().newObjectCache;
+    NewObjectCache::EntryIndex entry = -1;
+    if (cache.lookupGlobal(clasp, global, allocKind, &entry)) {
+      gc::InitialHeap heap = GetInitialHeap(newKind, clasp);
+      JSObject* obj = cache.newObjectFromHit(cx, entry, heap);
+      if (obj) {
+        return obj;
+      }
+    }
+  }
+
+  // Find the appropriate proto for clasp. Built-in classes have a cached
+  // proto on cx->global(); all others get %ObjectPrototype%.
+  JSProtoKey protoKey = JSCLASS_CACHED_PROTO_KEY(clasp);
+  if (protoKey == JSProto_Null) {
+    protoKey = JSProto_Object;
+  }
+
+  JSObject* proto = GlobalObject::getOrCreatePrototype(cx, protoKey);
+  if (!proto) {
+    return nullptr;
+  }
+
+  RootedObjectGroup group(
+      cx, ObjectGroup::defaultNewGroup(cx, clasp, TaggedProto(proto)));
+  if (!group) {
+    return nullptr;
+  }
+
+  JSObject* obj = NewObject(cx, group, allocKind, newKind);
+  if (!obj) {
+    return nullptr;
+  }
+
+  if (isCachable && !obj->as<NativeObject>().hasDynamicSlots()) {
+    NewObjectCache& cache = cx->caches().newObjectCache;
+    NewObjectCache::EntryIndex entry = -1;
+    cache.lookupGlobal(clasp, global, allocKind, &entry);
+    cache.fillGlobal(entry, clasp, global, allocKind, &obj->as<NativeObject>());
+  }
+
+  return obj;
+}
+
+static bool NewObjectWithGroupIsCachable(JSContext* cx, HandleObjectGroup group,
+                                         NewObjectKind newKind) {
+  if (!group->proto().isObject() || newKind != GenericObject ||
+      !group->clasp()->isNative() || cx->isHelperThreadContext()) {
+    return false;
+  }
+
+  return true;
+}
+
+/*
+ * Create a plain object with the specified group. This bypasses getNewGroup to
+ * avoid losing creation site information for objects made by scripted 'new'.
+ */
+JSObject* js::NewObjectWithGroupCommon(JSContext* cx, HandleObjectGroup group,
+                                       gc::AllocKind allocKind,
+                                       NewObjectKind newKind) {
+  MOZ_ASSERT(gc::IsObjectAllocKind(allocKind));
+  if (CanChangeToBackgroundAllocKind(allocKind, group->clasp())) {
+    allocKind = ForegroundToBackgroundAllocKind(allocKind);
+  }
+
+  bool isCachable = NewObjectWithGroupIsCachable(cx, group, newKind);
+  if (isCachable) {
+    NewObjectCache& cache = cx->caches().newObjectCache;
+    NewObjectCache::EntryIndex entry = -1;
+    if (cache.lookupGroup(group, allocKind, &entry)) {
+      JSObject* obj =
+          cache.newObjectFromHit(cx, entry, GetInitialHeap(newKind, group));
+      if (obj) {
+        return obj;
+      }
+    }
+  }
+
+  JSObject* obj = NewObject(cx, group, allocKind, newKind);
+  if (!obj) {
+    return nullptr;
+  }
+
+  if (isCachable && !obj->as<NativeObject>().hasDynamicSlots()) {
+    NewObjectCache& cache = cx->caches().newObjectCache;
+    NewObjectCache::EntryIndex entry = -1;
+    cache.lookupGroup(group, allocKind, &entry);
+    cache.fillGroup(entry, group, allocKind, &obj->as<NativeObject>());
+  }
+
+  return obj;
+}
+
+bool js::NewObjectScriptedCall(JSContext* cx, MutableHandleObject pobj) {
+  gc::AllocKind allocKind = NewObjectGCKind(&PlainObject::class_);
+  NewObjectKind newKind = GenericObject;
+
+  JSObject* obj = NewBuiltinClassInstance<PlainObject>(cx, allocKind, newKind);
+  if (!obj) {
+    return false;
+  }
+
+  pobj.set(obj);
+  return true;
+}
+
+JSObject* js::CreateThis(JSContext* cx, const JSClass* newclasp,
+                         HandleObject callee) {
+  RootedObject proto(cx);
+  if (!GetPrototypeFromConstructor(
+          cx, callee, JSCLASS_CACHED_PROTO_KEY(newclasp), &proto)) {
+    return nullptr;
+  }
+  gc::AllocKind kind = NewObjectGCKind(newclasp);
+  return NewObjectWithClassProto(cx, newclasp, proto, kind);
+}
+
+bool js::GetPrototypeFromConstructor(JSContext* cx, HandleObject newTarget,
+                                     JSProtoKey intrinsicDefaultProto,
+                                     MutableHandleObject proto) {
+  RootedValue protov(cx);
+  if (!GetProperty(cx, newTarget, newTarget, cx->names().prototype, &protov)) {
+    return false;
+  }
+  if (protov.isObject()) {
+    proto.set(&protov.toObject());
+  } else if (newTarget->is<JSFunction>() &&
+             newTarget->as<JSFunction>().realm() == cx->realm()) {
+    // Steps 4.a-b fetch the builtin prototype of the current realm, which we
+    // represent as nullptr.
+    proto.set(nullptr);
+  } else if (intrinsicDefaultProto == JSProto_Null) {
+    // Bug 1317416. The caller did not pass a reasonable JSProtoKey, so let the
+    // caller select a prototype object. Most likely they will choose one from
+    // the wrong realm.
+    proto.set(nullptr);
+  } else {
+    // Step 4.a: Let realm be ? GetFunctionRealm(constructor);
+    Realm* realm = JS::GetFunctionRealm(cx, newTarget);
+    if (!realm) {
+      return false;
+    }
+
+    // Step 4.b: Set proto to realm's intrinsic object named
+    //           intrinsicDefaultProto.
+    {
+      mozilla::Maybe<AutoRealm> ar;
+      if (cx->realm() != realm) {
+        ar.emplace(cx, realm->maybeGlobal());
+      }
+      proto.set(GlobalObject::getOrCreatePrototype(cx, intrinsicDefaultProto));
+    }
+    if (!proto) {
+      return false;
+    }
+    if (!cx->compartment()->wrap(cx, proto)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/* static */
+bool JSObject::nonNativeSetProperty(JSContext* cx, HandleObject obj,
+                                    HandleId id, HandleValue v,
+                                    HandleValue receiver,
+                                    ObjectOpResult& result) {
+  return obj->getOpsSetProperty()(cx, obj, id, v, receiver, result);
+}
+
+/* static */
+bool JSObject::nonNativeSetElement(JSContext* cx, HandleObject obj,
+                                   uint32_t index, HandleValue v,
+                                   HandleValue receiver,
+                                   ObjectOpResult& result) {
+  RootedId id(cx);
+  if (!IndexToId(cx, index, &id)) {
+    return false;
+  }
+  return nonNativeSetProperty(cx, obj, id, v, receiver, result);
+}
+
+static bool CopyPropertyFrom(JSContext* cx, HandleId id, HandleObject target,
+                             HandleObject obj) {
+  // |target| must not be a CCW because we need to enter its realm below and
+  // CCWs are not associated with a single realm.
+  MOZ_ASSERT(!IsCrossCompartmentWrapper(target));
+
+  // |obj| and |cx| are generally not same-compartment with |target| here.
+  cx->check(obj, id);
+  Rooted<PropertyDescriptor> desc(cx);
+
+  if (!GetOwnPropertyDescriptor(cx, obj, id, &desc)) {
+    return false;
+  }
+  MOZ_ASSERT(desc.object());
+
+  // Silently skip JSGetterOp/JSSetterOp-implemented accessors.
+  if (desc.getter() && !desc.hasGetterObject()) {
+    return true;
+  }
+  if (desc.setter() && !desc.hasSetterObject()) {
+    return true;
+  }
+
+  JSAutoRealm ar(cx, target);
+  cx->markId(id);
+  RootedId wrappedId(cx, id);
+  if (!cx->compartment()->wrap(cx, &desc)) {
+    return false;
+  }
+
+  return DefineProperty(cx, target, wrappedId, desc);
+}
+
+JS_FRIEND_API bool JS_CopyOwnPropertiesAndPrivateFields(JSContext* cx,
+                                                        HandleObject target,
+                                                        HandleObject obj) {
+  // Both |obj| and |target| must not be CCWs because we need to enter their
+  // realms below and CCWs are not associated with a single realm.
+  MOZ_ASSERT(!IsCrossCompartmentWrapper(obj));
+  MOZ_ASSERT(!IsCrossCompartmentWrapper(target));
+
+  JSAutoRealm ar(cx, obj);
+
+  RootedIdVector props(cx);
+  if (!GetPropertyKeys(
+          cx, obj,
+          JSITER_PRIVATE | JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS,
+          &props)) {
+    return false;
+  }
+
+  for (size_t i = 0; i < props.length(); ++i) {
+    if (!CopyPropertyFrom(cx, props[i], target, obj)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static bool GetScriptArrayObjectElements(
+    HandleArrayObject arr, MutableHandle<GCVector<Value>> values) {
+  MOZ_ASSERT(!arr->isIndexed());
+
+  size_t length = arr->length();
+  if (!values.appendN(MagicValue(JS_ELEMENTS_HOLE), length)) {
+    return false;
+  }
+
+  size_t initlen = arr->getDenseInitializedLength();
+  for (size_t i = 0; i < initlen; i++) {
+    values[i].set(arr->getDenseElement(i));
+  }
+
+  return true;
+}
+
+static bool GetScriptPlainObjectProperties(
+    HandleObject obj, MutableHandle<IdValueVector> properties) {
+  MOZ_ASSERT(obj->is<PlainObject>());
+  PlainObject* nobj = &obj->as<PlainObject>();
+
+  if (!properties.appendN(IdValuePair(), nobj->slotSpan())) {
+    return false;
+  }
+
+  for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
+    Shape& shape = r.front();
+    MOZ_ASSERT(shape.isDataDescriptor());
+    uint32_t slot = shape.slot();
+    properties[slot].get().id = shape.propid();
+    properties[slot].get().value = nobj->getSlot(slot);
+  }
+
+  for (size_t i = 0; i < nobj->getDenseInitializedLength(); i++) {
+    Value v = nobj->getDenseElement(i);
+    if (!v.isMagic(JS_ELEMENTS_HOLE) &&
+        !properties.emplaceBack(INT_TO_JSID(i), v)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static bool DeepCloneValue(JSContext* cx, Value* vp) {
+  if (vp->isObject()) {
+    RootedObject obj(cx, &vp->toObject());
+    obj = DeepCloneObjectLiteral(cx, obj);
+    if (!obj) {
+      return false;
+    }
+    vp->setObject(*obj);
+  } else {
+    cx->markAtomValue(*vp);
+  }
+  return true;
+}
+
+JSObject* js::DeepCloneObjectLiteral(JSContext* cx, HandleObject obj) {
+  /* NB: Keep this in sync with XDRObjectLiteral. */
+  MOZ_ASSERT(obj->is<PlainObject>() || obj->is<ArrayObject>());
+
+  if (obj->is<ArrayObject>()) {
+    Rooted<GCVector<Value>> values(cx, GCVector<Value>(cx));
+    if (!GetScriptArrayObjectElements(obj.as<ArrayObject>(), &values)) {
+      return nullptr;
+    }
+
+    // Deep clone any elements.
+    for (uint32_t i = 0; i < values.length(); ++i) {
+      if (!DeepCloneValue(cx, values[i].address())) {
+        return nullptr;
+      }
+    }
+
+    return NewDenseCopiedArray(cx, values.length(), values.begin(),
+                               /* proto = */ nullptr, TenuredObject);
+  }
+
+  Rooted<IdValueVector> properties(cx, IdValueVector(cx));
+  if (!GetScriptPlainObjectProperties(obj, &properties)) {
+    return nullptr;
+  }
+
+  for (size_t i = 0; i < properties.length(); i++) {
+    cx->markId(properties[i].get().id);
+    if (!DeepCloneValue(cx, &properties[i].get().value)) {
+      return nullptr;
+    }
+  }
+
+  return NewPlainObjectWithProperties(cx, properties.begin(),
+                                      properties.length(), TenuredObject);
+}
+
+static bool InitializePropertiesFromCompatibleNativeObject(
+    JSContext* cx, HandleNativeObject dst, HandleNativeObject src) {
+  cx->check(src, dst);
+  MOZ_ASSERT(src->getClass() == dst->getClass());
+  MOZ_ASSERT(dst->lastProperty()->getObjectFlags() == 0);
+  MOZ_ASSERT(src->numFixedSlots() == dst->numFixedSlots());
+
+  if (!dst->ensureElements(cx, src->getDenseInitializedLength())) {
+    return false;
+  }
+
+  uint32_t initialized = src->getDenseInitializedLength();
+  for (uint32_t i = 0; i < initialized; ++i) {
+    dst->setDenseInitializedLength(i + 1);
+    dst->initDenseElement(i, src->getDenseElement(i));
+  }
+
+  MOZ_ASSERT(!src->hasPrivate());
+  RootedShape shape(cx);
+  if (src->staticPrototype() == dst->staticPrototype()) {
+    shape = src->lastProperty();
+  } else {
+    // We need to generate a new shape for dst that has dst's proto but all
+    // the property information from src.  Note that we asserted above that
+    // dst's object flags are 0.
+    shape = EmptyShape::getInitialShape(cx, dst->getClass(), dst->taggedProto(),
+                                        dst->numFixedSlots(), 0);
+    if (!shape) {
+      return false;
+    }
+
+    // Get an in-order list of the shapes in the src object.
+    Rooted<ShapeVector> shapes(cx, ShapeVector(cx));
+    for (Shape::Range<NoGC> r(src->lastProperty()); !r.empty(); r.popFront()) {
+      if (!shapes.append(&r.front())) {
+        return false;
+      }
+    }
+    std::reverse(shapes.begin(), shapes.end());
+
+    for (Shape* shapeToClone : shapes) {
+      Rooted<StackShape> child(cx, StackShape(shapeToClone));
+      shape = cx->zone()->propertyTree().getChild(cx, shape, child);
+      if (!shape) {
+        return false;
+      }
+    }
+  }
+  size_t span = shape->slotSpan();
+  if (!dst->setLastProperty(cx, shape)) {
+    return false;
+  }
+  for (size_t i = JSCLASS_RESERVED_SLOTS(src->getClass()); i < span; i++) {
+    dst->setSlot(i, src->getSlot(i));
+  }
+
+  return true;
+}
+
+JS_FRIEND_API bool JS_InitializePropertiesFromCompatibleNativeObject(
+    JSContext* cx, HandleObject dst, HandleObject src) {
+  return InitializePropertiesFromCompatibleNativeObject(
+      cx, dst.as<NativeObject>(), src.as<NativeObject>());
+}
+
+template <XDRMode mode>
+XDRResult js::XDRObjectLiteral(XDRState<mode>* xdr, MutableHandleObject obj) {
+  /* NB: Keep this in sync with DeepCloneObjectLiteral. */
+
+  JSContext* cx = xdr->cx();
+  cx->check(obj);
+
+  // Distinguish between objects and array classes.
+  uint32_t isArray = 0;
+  {
+    if (mode == XDR_ENCODE) {
+      MOZ_ASSERT(obj->is<PlainObject>() || obj->is<ArrayObject>());
+      isArray = obj->is<ArrayObject>() ? 1 : 0;
+    }
+
+    MOZ_TRY(xdr->codeUint32(&isArray));
+  }
+
+  RootedValue tmpValue(cx), tmpIdValue(cx);
+  RootedId tmpId(cx);
+
+  if (isArray) {
+    Rooted<GCVector<Value>> values(cx, GCVector<Value>(cx));
+    if (mode == XDR_ENCODE) {
+      RootedArrayObject arr(cx, &obj->as<ArrayObject>());
+      if (!GetScriptArrayObjectElements(arr, &values)) {
+        return xdr->fail(JS::TranscodeResult_Throw);
+      }
+    }
+
+    uint32_t initialized;
+    if (mode == XDR_ENCODE) {
+      initialized = values.length();
+    }
+    MOZ_TRY(xdr->codeUint32(&initialized));
+    if (mode == XDR_DECODE &&
+        !values.appendN(MagicValue(JS_ELEMENTS_HOLE), initialized)) {
+      return xdr->fail(JS::TranscodeResult_Throw);
+    }
+
+    // Recursively copy dense elements.
+    for (unsigned i = 0; i < initialized; i++) {
+      MOZ_TRY(XDRScriptConst(xdr, values[i]));
+    }
+
+    if (mode == XDR_DECODE) {
+      obj.set(NewDenseCopiedArray(cx, values.length(), values.begin(),
+                                  /* proto = */ nullptr, TenuredObject));
+      if (!obj) {
+        return xdr->fail(JS::TranscodeResult_Throw);
+      }
+    }
+
+    return Ok();
+  }
+
+  // Code the properties in the object.
+  Rooted<IdValueVector> properties(cx, IdValueVector(cx));
+  if (mode == XDR_ENCODE && !GetScriptPlainObjectProperties(obj, &properties)) {
+    return xdr->fail(JS::TranscodeResult_Throw);
+  }
+
+  uint32_t nproperties = properties.length();
+  MOZ_TRY(xdr->codeUint32(&nproperties));
+
+  if (mode == XDR_DECODE && !properties.appendN(IdValuePair(), nproperties)) {
+    return xdr->fail(JS::TranscodeResult_Throw);
+  }
+
+  for (size_t i = 0; i < nproperties; i++) {
+    if (mode == XDR_ENCODE) {
+      tmpIdValue = IdToValue(properties[i].get().id);
+      tmpValue = properties[i].get().value;
+    }
+
+    MOZ_TRY(XDRScriptConst(xdr, &tmpIdValue));
+    MOZ_TRY(XDRScriptConst(xdr, &tmpValue));
+
+    if (mode == XDR_DECODE) {
+      if (!PrimitiveValueToId<CanGC>(cx, tmpIdValue, &tmpId)) {
+        return xdr->fail(JS::TranscodeResult_Throw);
+      }
+      properties[i].get().id = tmpId;
+      properties[i].get().value = tmpValue;
+    }
+  }
+
+  if (mode == XDR_DECODE) {
+    obj.set(NewPlainObjectWithProperties(cx, properties.begin(),
+                                         properties.length(), TenuredObject));
+    if (!obj) {
+      return xdr->fail(JS::TranscodeResult_Throw);
+    }
+  }
+
+  return Ok();
+}
+
+template XDRResult js::XDRObjectLiteral(XDRState<XDR_ENCODE>* xdr,
+                                        MutableHandleObject obj);
+
+template XDRResult js::XDRObjectLiteral(XDRState<XDR_DECODE>* xdr,
+                                        MutableHandleObject obj);
+
+/* static */
+bool NativeObject::fillInAfterSwap(JSContext* cx, HandleNativeObject obj,
+                                   NativeObject* old, HandleValueVector values,
+                                   void* priv) {
+  // This object has just been swapped with some other object, and its shape
+  // no longer reflects its allocated size. Correct this information and
+  // fill the slots in with the specified values.
+  MOZ_ASSERT(obj->slotSpan() == values.length());
+  MOZ_ASSERT(!IsInsideNursery(obj));
+
+  // Make sure the shape's numFixedSlots() is correct.
+  size_t nfixed =
+      gc::GetGCKindSlots(obj->asTenured().getAllocKind(), obj->getClass());
+  if (nfixed != obj->shape()->numFixedSlots()) {
+    if (!NativeObject::generateOwnShape(cx, obj)) {
+      return false;
+    }
+    obj->shape()->setNumFixedSlots(nfixed);
+  }
+
+  if (obj->hasPrivate()) {
+    obj->setPrivate(priv);
+  } else {
+    MOZ_ASSERT(!priv);
+  }
+
+  uint32_t oldDictionarySlotSpan =
+      obj->inDictionaryMode() ? obj->dictionaryModeSlotSpan() : 0;
+
+  Zone* zone = obj->zone();
+  if (obj->hasDynamicSlots()) {
+    ObjectSlots* slotsHeader = obj->getSlotsHeader();
+    size_t size = ObjectSlots::allocSize(slotsHeader->capacity());
+    zone->removeCellMemory(old, size, MemoryUse::ObjectSlots);
+    js_free(slotsHeader);
+    obj->setEmptyDynamicSlots(0);
+  }
+
+  size_t ndynamic =
+      calculateDynamicSlots(nfixed, values.length(), obj->getClass());
+  size_t currentSlots = obj->getSlotsHeader()->capacity();
+  MOZ_ASSERT(ndynamic >= currentSlots);
+  if (ndynamic > currentSlots) {
+    if (!obj->growSlots(cx, currentSlots, ndynamic)) {
+      return false;
+    }
+  }
+
+  if (obj->inDictionaryMode()) {
+    obj->setDictionaryModeSlotSpan(oldDictionarySlotSpan);
+  }
+
+  obj->initSlots(values.begin(), values.length());
+
+  return true;
+}
+
+void JSObject::fixDictionaryShapeAfterSwap() {
+  // Dictionary shapes can point back to their containing objects, so after
+  // swapping the guts of those objects fix the pointers up.
+  if (isNative() && as<NativeObject>().inDictionaryMode()) {
+    shape()->dictNext.setObject(this);
+  }
+}
+
+bool js::ObjectMayBeSwapped(const JSObject* obj) {
+  const JSClass* clasp = obj->getClass();
+
+  // We want to optimize Window/globals and Gecko doesn't require transplanting
+  // them (only the WindowProxy around them). A Window may be a DOMClass, so we
+  // explicitly check if this is a global.
+  if (clasp->isGlobal()) {
+    return false;
+  }
+
+  // WindowProxy, Wrapper, DeadProxyObject, DOMProxy, and DOMClass (non-global)
+  // types may be swapped. It is hard to detect DOMProxy from shell, so target
+  // proxies in general.
+  return clasp->isProxy() || clasp->isDOMClass();
+}
+
+static MOZ_MUST_USE bool CopyProxyValuesBeforeSwap(
+    JSContext* cx, ProxyObject* proxy, MutableHandleValueVector values) {
+  MOZ_ASSERT(values.empty());
+
+  // Remove the GCPtrValues we're about to swap from the store buffer, to
+  // ensure we don't trace bogus values.
+  gc::StoreBuffer& sb = cx->runtime()->gc.storeBuffer();
+
+  // Reserve space for the expando, private slot and the reserved slots.
+  if (!values.reserve(2 + proxy->numReservedSlots())) {
+    return false;
+  }
+
+  js::detail::ProxyValueArray* valArray =
+      js::detail::GetProxyDataLayout(proxy)->values();
+  sb.unputValue(&valArray->expandoSlot);
+  sb.unputValue(&valArray->privateSlot);
+  values.infallibleAppend(valArray->expandoSlot);
+  values.infallibleAppend(valArray->privateSlot);
+
+  for (size_t i = 0; i < proxy->numReservedSlots(); i++) {
+    sb.unputValue(&valArray->reservedSlots.slots[i]);
+    values.infallibleAppend(valArray->reservedSlots.slots[i]);
+  }
+
+  return true;
+}
+
+bool ProxyObject::initExternalValueArrayAfterSwap(
+    JSContext* cx, const HandleValueVector values) {
+  MOZ_ASSERT(getClass()->isProxy());
+
+  size_t nreserved = numReservedSlots();
+
+  // |values| contains the expando slot, private slot and the reserved slots.
+  MOZ_ASSERT(values.length() == 2 + nreserved);
+
+  size_t nbytes = js::detail::ProxyValueArray::sizeOf(nreserved);
+
+  auto* valArray = reinterpret_cast<js::detail::ProxyValueArray*>(
+      cx->zone()->pod_malloc<uint8_t>(nbytes));
+  if (!valArray) {
+    return false;
+  }
+
+  valArray->expandoSlot = values[0];
+  valArray->privateSlot = values[1];
+
+  for (size_t i = 0; i < nreserved; i++) {
+    valArray->reservedSlots.slots[i] = values[i + 2];
+  }
+
+  // Note: we allocate external slots iff the proxy had an inline
+  // ProxyValueArray, so at this point reservedSlots points into the
+  // old object and we don't have to free anything.
+  data.reservedSlots = &valArray->reservedSlots;
+  return true;
+}
+
+/* Use this method with extreme caution. It trades the guts of two objects. */
+void JSObject::swap(JSContext* cx, HandleObject a, HandleObject b,
+                    AutoEnterOOMUnsafeRegion& oomUnsafe) {
+  // Ensure swap doesn't cause a finalizer to not be run.
+  MOZ_ASSERT(IsBackgroundFinalized(a->asTenured().getAllocKind()) ==
+             IsBackgroundFinalized(b->asTenured().getAllocKind()));
+  MOZ_ASSERT(a->compartment() == b->compartment());
+
+  // You must have entered the objects' compartment before calling this.
+  MOZ_ASSERT(cx->compartment() == a->compartment());
+
+  // Only certain types of objects are allowed to be swapped. This allows the
+  // JITs to better optimize objects that can never swap.
+  MOZ_RELEASE_ASSERT(js::ObjectMayBeSwapped(a));
+  MOZ_RELEASE_ASSERT(js::ObjectMayBeSwapped(b));
+
+  /*
+   * Neither object may be in the nursery, but ensure we update any embedded
+   * nursery pointers in either object.
+   */
+  MOZ_ASSERT(!IsInsideNursery(a) && !IsInsideNursery(b));
+  gc::StoreBuffer& storeBuffer = cx->runtime()->gc.storeBuffer();
+  storeBuffer.putWholeCell(a);
+  storeBuffer.putWholeCell(b);
+  if (a->zone()->wasGCStarted() || b->zone()->wasGCStarted()) {
+    storeBuffer.setMayHavePointersToDeadCells();
+  }
+
+  unsigned r = NotifyGCPreSwap(a, b);
+
+  // Do the fundamental swapping of the contents of two objects.
+  MOZ_ASSERT(a->compartment() == b->compartment());
+  MOZ_ASSERT(a->is<JSFunction>() == b->is<JSFunction>());
+
+  // Don't try to swap functions with different sizes.
+  MOZ_ASSERT_IF(a->is<JSFunction>(),
+                a->tenuredSizeOfThis() == b->tenuredSizeOfThis());
+
+  // Watch for oddball objects that have special organizational issues and
+  // can't be swapped.
+  MOZ_ASSERT(!a->is<RegExpObject>() && !b->is<RegExpObject>());
+  MOZ_ASSERT(!a->is<ArrayObject>() && !b->is<ArrayObject>());
+  MOZ_ASSERT(!a->is<ArrayBufferObject>() && !b->is<ArrayBufferObject>());
+  MOZ_ASSERT(!a->is<TypedArrayObject>() && !b->is<TypedArrayObject>());
+  MOZ_ASSERT(!a->is<TypedObject>() && !b->is<TypedObject>());
+
+  // Don't swap objects that may currently be participating in shape
+  // teleporting optimizations.
+  //
+  // See: ReshapeForProtoMutation, ReshapeForShadowedProp
+  MOZ_ASSERT_IF(a->isNative() && a->isDelegate(),
+                a->taggedProto() == TaggedProto());
+  MOZ_ASSERT_IF(b->isNative() && b->isDelegate(),
+                b->taggedProto() == TaggedProto());
+
+  bool aIsProxyWithInlineValues =
+      a->is<ProxyObject>() && a->as<ProxyObject>().usingInlineValueArray();
+  bool bIsProxyWithInlineValues =
+      b->is<ProxyObject>() && b->as<ProxyObject>().usingInlineValueArray();
+
+  // Swap element associations.
+  Zone* zone = a->zone();
+  zone->swapCellMemory(a, b, MemoryUse::ObjectElements);
+
+  if (a->tenuredSizeOfThis() == b->tenuredSizeOfThis()) {
+    // When both objects are the same size, just do a plain swap of their
+    // contents.
+
+    // Swap slot associations.
+    zone->swapCellMemory(a, b, MemoryUse::ObjectSlots);
+
+    size_t size = a->tenuredSizeOfThis();
+
+    char tmp[mozilla::tl::Max<sizeof(JSFunction),
+                              sizeof(JSObject_Slots16)>::value];
+    MOZ_ASSERT(size <= sizeof(tmp));
+
+    js_memcpy(tmp, a, size);
+    js_memcpy(a, b, size);
+    js_memcpy(b, tmp, size);
+
+    a->fixDictionaryShapeAfterSwap();
+    b->fixDictionaryShapeAfterSwap();
+
+    if (aIsProxyWithInlineValues) {
+      b->as<ProxyObject>().setInlineValueArray();
+    }
+    if (bIsProxyWithInlineValues) {
+      a->as<ProxyObject>().setInlineValueArray();
+    }
+  } else {
+    // Avoid GC in here to avoid confusing the tracing code with our
+    // intermediate state.
+    gc::AutoSuppressGC suppress(cx);
+
+    // When the objects have different sizes, they will have different
+    // numbers of fixed slots before and after the swap, so the slots for
+    // native objects will need to be rearranged.
+    NativeObject* na = a->isNative() ? &a->as<NativeObject>() : nullptr;
+    NativeObject* nb = b->isNative() ? &b->as<NativeObject>() : nullptr;
+
+    // Remember the original values from the objects.
+    RootedValueVector avals(cx);
+    void* apriv = nullptr;
+    if (na) {
+      apriv = na->hasPrivate() ? na->getPrivate() : nullptr;
+      for (size_t i = 0; i < na->slotSpan(); i++) {
+        if (!avals.append(na->getSlot(i))) {
+          oomUnsafe.crash("JSObject::swap");
+        }
+      }
+    }
+    RootedValueVector bvals(cx);
+    void* bpriv = nullptr;
+    if (nb) {
+      bpriv = nb->hasPrivate() ? nb->getPrivate() : nullptr;
+      for (size_t i = 0; i < nb->slotSpan(); i++) {
+        if (!bvals.append(nb->getSlot(i))) {
+          oomUnsafe.crash("JSObject::swap");
+        }
+      }
+    }
+
+    // Do the same for proxies storing ProxyValueArray inline.
+    ProxyObject* proxyA =
+        a->is<ProxyObject>() ? &a->as<ProxyObject>() : nullptr;
+    ProxyObject* proxyB =
+        b->is<ProxyObject>() ? &b->as<ProxyObject>() : nullptr;
+
+    if (aIsProxyWithInlineValues) {
+      if (!CopyProxyValuesBeforeSwap(cx, proxyA, &avals)) {
+        oomUnsafe.crash("CopyProxyValuesBeforeSwap");
+      }
+    }
+    if (bIsProxyWithInlineValues) {
+      if (!CopyProxyValuesBeforeSwap(cx, proxyB, &bvals)) {
+        oomUnsafe.crash("CopyProxyValuesBeforeSwap");
+      }
+    }
+
+    // Swap the main fields of the objects, whether they are native objects or
+    // proxies.
+    char tmp[sizeof(JSObject_Slots0)];
+    js_memcpy(&tmp, a, sizeof tmp);
+    js_memcpy(a, b, sizeof tmp);
+    js_memcpy(b, &tmp, sizeof tmp);
+
+    a->fixDictionaryShapeAfterSwap();
+    b->fixDictionaryShapeAfterSwap();
+
+    if (na) {
+      if (!NativeObject::fillInAfterSwap(cx, b.as<NativeObject>(), na, avals,
+                                         apriv)) {
+        oomUnsafe.crash("fillInAfterSwap");
+      }
+    }
+    if (nb) {
+      if (!NativeObject::fillInAfterSwap(cx, a.as<NativeObject>(), nb, bvals,
+                                         bpriv)) {
+        oomUnsafe.crash("fillInAfterSwap");
+      }
+    }
+    if (aIsProxyWithInlineValues) {
+      if (!b->as<ProxyObject>().initExternalValueArrayAfterSwap(cx, avals)) {
+        oomUnsafe.crash("initExternalValueArray");
+      }
+    }
+    if (bIsProxyWithInlineValues) {
+      if (!a->as<ProxyObject>().initExternalValueArrayAfterSwap(cx, bvals)) {
+        oomUnsafe.crash("initExternalValueArray");
+      }
+    }
+  }
+
+  /*
+   * We need a write barrier here. If |a| was marked and |b| was not, then
+   * after the swap, |b|'s guts would never be marked. The write barrier
+   * solves this.
+   *
+   * Normally write barriers happen before the write. However, that's not
+   * necessary here because nothing is being destroyed. We're just swapping.
+   */
+  if (zone->needsIncrementalBarrier()) {
+    a->traceChildren(zone->barrierTracer());
+    b->traceChildren(zone->barrierTracer());
+  }
+
+  NotifyGCPostSwap(a, b, r);
+}
+
+static NativeObject* DefineConstructorAndPrototype(
+    JSContext* cx, HandleObject obj, HandleAtom atom, HandleObject protoProto,
+    const JSClass* clasp, Native constructor, unsigned nargs,
+    const JSPropertySpec* ps, const JSFunctionSpec* fs,
+    const JSPropertySpec* static_ps, const JSFunctionSpec* static_fs,
+    NativeObject** ctorp) {
+  // Create the prototype object.
+  RootedNativeObject proto(
+      cx, GlobalObject::createBlankPrototypeInheriting(cx, clasp, protoProto));
+  if (!proto) {
+    return nullptr;
+  }
+
+  RootedNativeObject ctor(cx);
+  if (!constructor) {
+    ctor = proto;
+  } else {
+    ctor = NewNativeConstructor(cx, constructor, nargs, atom);
+    if (!ctor) {
+      return nullptr;
+    }
+
+    if (!LinkConstructorAndPrototype(cx, ctor, proto)) {
+      return nullptr;
+    }
+  }
+
+  if (!DefinePropertiesAndFunctions(cx, proto, ps, fs) ||
+      (ctor != proto &&
+       !DefinePropertiesAndFunctions(cx, ctor, static_ps, static_fs))) {
+    return nullptr;
+  }
+
+  RootedId id(cx, AtomToId(atom));
+  RootedValue value(cx, ObjectValue(*ctor));
+  if (!DefineDataProperty(cx, obj, id, value, 0)) {
+    return nullptr;
+  }
+
+  if (ctorp) {
+    *ctorp = ctor;
+  }
+  return proto;
+}
+
+NativeObject* js::InitClass(JSContext* cx, HandleObject obj,
+                            HandleObject protoProto_, const JSClass* clasp,
+                            Native constructor, unsigned nargs,
+                            const JSPropertySpec* ps, const JSFunctionSpec* fs,
+                            const JSPropertySpec* static_ps,
+                            const JSFunctionSpec* static_fs,
+                            NativeObject** ctorp) {
+  RootedAtom atom(cx, Atomize(cx, clasp->name, strlen(clasp->name)));
+  if (!atom) {
+    return nullptr;
+  }
+
+  /*
+   * All instances of the class will inherit properties from the prototype
+   * object we are about to create (in DefineConstructorAndPrototype), which
+   * in turn will inherit from protoProto.
+   *
+   * If protoProto is null, default to Object.prototype.
+   */
+  RootedObject protoProto(cx, protoProto_);
+  if (!protoProto) {
+    protoProto = GlobalObject::getOrCreateObjectPrototype(cx, cx->global());
+    if (!protoProto) {
+      return nullptr;
+    }
+  }
+
+  return DefineConstructorAndPrototype(cx, obj, atom, protoProto, clasp,
+                                       constructor, nargs, ps, fs, static_ps,
+                                       static_fs, ctorp);
+}
+
+void JSObject::fixupAfterMovingGC() {
+  if (IsForwarded(group())) {
+    setGroupRaw(Forwarded(group()));
+  }
+}
+
+static bool ReshapeForProtoMutation(JSContext* cx, HandleObject obj) {
+  // To avoid the JIT guarding on each prototype in chain to detect prototype
+  // mutation, we can instead reshape the rest of the proto chain such that a
+  // guard on any of them is sufficient. To avoid excessive reshaping and
+  // invalidation, we apply heuristics to decide when to apply this and when
+  // to require a guard.
+  //
+  // Heuristics:
+  //  - Set UNCACHEABLE_PROTO flag on shape to avoid creating too many private
+  //    shape copies.
+  //  - Only propegate along proto chain if we are mark DELEGATE. This avoids
+  //    reshaping in normal object access cases.
+  //
+  // NOTE: We only handle NativeObjects and don't propegate reshapes through
+  //       any non-native objects on the chain.
+  //
+  // See Also:
+  //  - GeneratePrototypeGuards
+  //  - GeneratePrototypeHoleGuards
+  //  - ObjectGroup::defaultNewGroup
+
+  RootedObject pobj(cx, obj);
+
+  while (pobj && pobj->isNative()) {
+    if (!JSObject::setUncacheableProto(cx, pobj)) {
+      return false;
+    }
+
+    if (!obj->isDelegate()) {
+      break;
+    }
+
+    pobj = pobj->staticPrototype();
+  }
+
+  return true;
+}
+
+static bool SetProto(JSContext* cx, HandleObject obj,
+                     Handle<js::TaggedProto> proto) {
+  // Regenerate object shape (and possibly prototype shape) to invalidate JIT
+  // code that is affected by a prototype mutation.
+  if (!ReshapeForProtoMutation(cx, obj)) {
+    return false;
+  }
+
+  if (proto.isObject()) {
+    RootedObject protoObj(cx, proto.toObject());
+    if (!JSObject::setDelegate(cx, protoObj)) {
+      return false;
+    }
+  }
+
+  RootedObjectGroup oldGroup(cx, obj->group());
+
+  ObjectGroup* newGroup;
+  {
+    AutoRealm ar(cx, oldGroup);
+    newGroup = ObjectGroup::defaultNewGroup(cx, obj->getClass(), proto);
+    if (!newGroup) {
+      return false;
+    }
+  }
+
+  obj->setGroup(newGroup);
+  return true;
+}
+
+/**
+ * Returns the original Object.prototype from the embedding-provided incumbent
+ * global.
+ *
+ * Really, we want the incumbent global itself so we can pass it to other
+ * embedding hooks which need it. Specifically, the enqueue promise hook
+ * takes an incumbent global so it can set that on the PromiseCallbackJob
+ * it creates.
+ *
+ * The reason for not just returning the global itself is that we'd need to
+ * wrap it into the current compartment, and later unwrap it. Unwrapping
+ * globals is tricky, though: we might accidentally unwrap through an inner
+ * to its outer window and end up with the wrong global. Plain objects don't
+ * have this problem, so we use the global's Object.prototype. The code using
+ * it - e.g. EnqueuePromiseReactionJob - can then unwrap the object and get
+ * its global without fear of unwrapping too far.
+ */
+bool js::GetObjectFromIncumbentGlobal(JSContext* cx, MutableHandleObject obj) {
+  Rooted<GlobalObject*> globalObj(cx, cx->runtime()->getIncumbentGlobal(cx));
+  if (!globalObj) {
+    obj.set(nullptr);
+    return true;
+  }
+
+  {
+    AutoRealm ar(cx, globalObj);
+    obj.set(GlobalObject::getOrCreateObjectPrototype(cx, globalObj));
+    if (!obj) {
+      return false;
+    }
+  }
+
+  // The object might be from a different compartment, so wrap it.
+  if (obj && !cx->compartment()->wrap(cx, obj)) {
+    return false;
+  }
+
+  return true;
+}
+
+static bool IsStandardPrototype(JSObject* obj, JSProtoKey key) {
+  Value v = obj->nonCCWGlobal().getPrototype(key);
+  return v.isObject() && obj == &v.toObject();
+}
+
+JSProtoKey JS::IdentifyStandardInstance(JSObject* obj) {
+  // Note: The prototype shares its JSClass with instances.
+  MOZ_ASSERT(!obj->is<CrossCompartmentWrapperObject>());
+  JSProtoKey key = StandardProtoKeyOrNull(obj);
+  if (key != JSProto_Null && !IsStandardPrototype(obj, key)) {
+    return key;
+  }
+  return JSProto_Null;
+}
+
+JSProtoKey JS::IdentifyStandardPrototype(JSObject* obj) {
+  // Note: The prototype shares its JSClass with instances.
+  MOZ_ASSERT(!obj->is<CrossCompartmentWrapperObject>());
+  JSProtoKey key = StandardProtoKeyOrNull(obj);
+  if (key != JSProto_Null && IsStandardPrototype(obj, key)) {
+    return key;
+  }
+  return JSProto_Null;
+}
+
+JSProtoKey JS::IdentifyStandardInstanceOrPrototype(JSObject* obj) {
+  return StandardProtoKeyOrNull(obj);
+}
+
+JSProtoKey JS::IdentifyStandardConstructor(JSObject* obj) {
+  // Note that isNativeConstructor does not imply that we are a standard
+  // constructor, but the converse is true (at least until we start having
+  // self-hosted constructors for standard classes). This lets us avoid a costly
+  // loop for many functions (which, depending on the call site, may be the
+  // common case).
+  if (!obj->is<JSFunction>() ||
+      !(obj->as<JSFunction>().flags().isNativeConstructor())) {
+    return JSProto_Null;
+  }
+
+  GlobalObject& global = obj->as<JSFunction>().global();
+  for (size_t k = 0; k < JSProto_LIMIT; ++k) {
+    JSProtoKey key = static_cast<JSProtoKey>(k);
+    if (global.getConstructor(key) == ObjectValue(*obj)) {
+      return key;
+    }
+  }
+
+  return JSProto_Null;
+}
+
+bool js::LookupProperty(JSContext* cx, HandleObject obj, js::HandleId id,
+                        MutableHandleObject objp,
+                        MutableHandle<PropertyResult> propp) {
+  if (LookupPropertyOp op = obj->getOpsLookupProperty()) {
+    return op(cx, obj, id, objp, propp);
+  }
+  return LookupPropertyInline<CanGC>(cx, obj.as<NativeObject>(), id, objp,
+                                     propp);
+}
+
+bool js::LookupName(JSContext* cx, HandlePropertyName name,
+                    HandleObject envChain, MutableHandleObject objp,
+                    MutableHandleObject pobjp,
+                    MutableHandle<PropertyResult> propp) {
+  RootedId id(cx, NameToId(name));
+
+  for (RootedObject env(cx, envChain); env; env = env->enclosingEnvironment()) {
+    if (!LookupProperty(cx, env, id, pobjp, propp)) {
+      return false;
+    }
+    if (propp) {
+      objp.set(env);
+      return true;
+    }
+  }
+
+  objp.set(nullptr);
+  pobjp.set(nullptr);
+  propp.setNotFound();
+  return true;
+}
+
+bool js::LookupNameNoGC(JSContext* cx, PropertyName* name, JSObject* envChain,
+                        JSObject** objp, JSObject** pobjp,
+                        PropertyResult* propp) {
+  AutoAssertNoPendingException nogc(cx);
+
+  MOZ_ASSERT(!*objp && !*pobjp && !*propp);
+
+  for (JSObject* env = envChain; env; env = env->enclosingEnvironment()) {
+    if (env->getOpsLookupProperty()) {
+      return false;
+    }
+    if (!LookupPropertyInline<NoGC>(cx, &env->as<NativeObject>(),
+                                    NameToId(name), pobjp, propp)) {
+      return false;
+    }
+    if (*propp) {
+      *objp = env;
+      return true;
+    }
+  }
+
+  return true;
+}
+
+bool js::LookupNameWithGlobalDefault(JSContext* cx, HandlePropertyName name,
+                                     HandleObject envChain,
+                                     MutableHandleObject objp) {
+  RootedId id(cx, NameToId(name));
+
+  RootedObject pobj(cx);
+  Rooted<PropertyResult> prop(cx);
+
+  RootedObject env(cx, envChain);
+  for (; !env->is<GlobalObject>(); env = env->enclosingEnvironment()) {
+    if (!LookupProperty(cx, env, id, &pobj, &prop)) {
+      return false;
+    }
+    if (prop) {
+      break;
+    }
+  }
+
+  objp.set(env);
+  return true;
+}
+
+bool js::LookupNameUnqualified(JSContext* cx, HandlePropertyName name,
+                               HandleObject envChain,
+                               MutableHandleObject objp) {
+  RootedId id(cx, NameToId(name));
+
+  RootedObject pobj(cx);
+  Rooted<PropertyResult> prop(cx);
+
+  RootedObject env(cx, envChain);
+  for (; !env->isUnqualifiedVarObj(); env = env->enclosingEnvironment()) {
+    if (!LookupProperty(cx, env, id, &pobj, &prop)) {
+      return false;
+    }
+    if (prop) {
+      break;
+    }
+  }
+
+  // See note above RuntimeLexicalErrorObject.
+  if (pobj == env) {
+    bool isTDZ = false;
+    if (prop && name != cx->names().dotThis) {
+      // Treat Debugger environments specially for TDZ checks, as they
+      // look like non-native environments but in fact wrap native
+      // environments.
+      if (env->is<DebugEnvironmentProxy>()) {
+        RootedValue v(cx);
+        Rooted<DebugEnvironmentProxy*> envProxy(
+            cx, &env->as<DebugEnvironmentProxy>());
+        if (!DebugEnvironmentProxy::getMaybeSentinelValue(cx, envProxy, id,
+                                                          &v)) {
+          return false;
+        }
+        isTDZ = IsUninitializedLexical(v);
+      } else {
+        isTDZ = IsUninitializedLexicalSlot(env, prop);
+      }
+    }
+
+    if (isTDZ) {
+      env = RuntimeLexicalErrorObject::create(cx, env,
+                                              JSMSG_UNINITIALIZED_LEXICAL);
+      if (!env) {
+        return false;
+      }
+    } else if (env->is<LexicalEnvironmentObject>() &&
+               !prop.shape()->writable()) {
+      // Assigning to a named lambda callee name is a no-op in sloppy mode.
+      Rooted<LexicalEnvironmentObject*> lexicalEnv(
+          cx, &env->as<LexicalEnvironmentObject>());
+      if (lexicalEnv->isExtensible() ||
+          lexicalEnv->scope().kind() != ScopeKind::NamedLambda) {
+        MOZ_ASSERT(name != cx->names().dotThis);
+        env =
+            RuntimeLexicalErrorObject::create(cx, env, JSMSG_BAD_CONST_ASSIGN);
+        if (!env) {
+          return false;
+        }
+      }
+    }
+  }
+
+  objp.set(env);
+  return true;
+}
+
+bool js::HasOwnProperty(JSContext* cx, HandleObject obj, HandleId id,
+                        bool* result) {
+  if (obj->is<ProxyObject>()) {
+    return Proxy::hasOwn(cx, obj, id, result);
+  }
+
+  if (GetOwnPropertyOp op = obj->getOpsGetOwnPropertyDescriptor()) {
+    Rooted<PropertyDescriptor> desc(cx);
+    if (!op(cx, obj, id, &desc)) {
+      return false;
+    }
+    *result = !!desc.object();
+    return true;
+  }
+
+  Rooted<PropertyResult> prop(cx);
+  if (!NativeLookupOwnProperty<CanGC>(cx, obj.as<NativeObject>(), id, &prop)) {
+    return false;
+  }
+  *result = prop.isFound();
+  return true;
+}
+
+bool js::LookupPropertyPure(JSContext* cx, JSObject* obj, jsid id,
+                            JSObject** objp, PropertyResult* propp) {
+  bool isTypedArrayOutOfRange = false;
+  do {
+    if (!LookupOwnPropertyPure(cx, obj, id, propp, &isTypedArrayOutOfRange)) {
+      return false;
+    }
+
+    if (*propp) {
+      *objp = obj;
+      return true;
+    }
+
+    if (isTypedArrayOutOfRange) {
+      *objp = nullptr;
+      return true;
+    }
+
+    obj = obj->staticPrototype();
+  } while (obj);
+
+  *objp = nullptr;
+  propp->setNotFound();
+  return true;
+}
+
+bool js::LookupOwnPropertyPure(JSContext* cx, JSObject* obj, jsid id,
+                               PropertyResult* propp,
+                               bool* isTypedArrayOutOfRange /* = nullptr */) {
+  JS::AutoCheckCannotGC nogc;
+  if (isTypedArrayOutOfRange) {
+    *isTypedArrayOutOfRange = false;
+  }
+
+  if (obj->isNative()) {
+    // Search for a native dense element, typed array element, or property.
+
+    if (JSID_IS_INT(id)) {
+      uint32_t index = JSID_TO_INT(id);
+      if (obj->as<NativeObject>().containsDenseElement(index)) {
+        propp->setDenseElement(index);
+        return true;
+      }
+    }
+
+    if (obj->is<TypedArrayObject>()) {
+      JS::Result<mozilla::Maybe<uint64_t>> index = IsTypedArrayIndex(cx, id);
+      if (index.isErr()) {
+        cx->recoverFromOutOfMemory();
+        return false;
+      }
+
+      if (index.inspect()) {
+        if (index.inspect().value() <
+            obj->as<TypedArrayObject>().length().get()) {
+          propp->setTypedArrayElement(index.inspect().value());
+        } else {
+          propp->setNotFound();
+          if (isTypedArrayOutOfRange) {
+            *isTypedArrayOutOfRange = true;
+          }
+        }
+        return true;
+      }
+    }
+
+    if (Shape* shape = obj->as<NativeObject>().lookupPure(id)) {
+      propp->setNativeProperty(shape);
+      return true;
+    }
+
+    // Fail if there's a resolve hook, unless the mayResolve hook tells
+    // us the resolve hook won't define a property with this id.
+    if (ClassMayResolveId(cx->names(), obj->getClass(), id, obj)) {
+      return false;
+    }
+  } else if (obj->is<TypedObject>()) {
+    if (obj->as<TypedObject>().typeDescr().hasProperty(cx, id)) {
+      propp->setNonNativeProperty();
+      return true;
+    }
+  } else {
+    return false;
+  }
+
+  propp->setNotFound();
+  return true;
+}
+
+static inline bool NativeGetPureInline(NativeObject* pobj, jsid id,
+                                       PropertyResult prop, Value* vp,
+                                       JSContext* cx) {
+  if (prop.isDenseElement()) {
+    *vp = pobj->getDenseElement(prop.denseElementIndex());
+    return true;
+  }
+  if (prop.isTypedArrayElement()) {
+    size_t idx = prop.typedArrayElementIndex();
+    return pobj->as<TypedArrayObject>().getElement<NoGC>(cx, idx, vp);
+  }
+
+  // Fail if we have a custom getter.
+  Shape* shape = prop.shape();
+  if (!shape->isDataProperty()) {
+    return false;
+  }
+
+  *vp = pobj->getSlot(shape->slot());
+  MOZ_ASSERT(!vp->isMagic());
+  return true;
+}
+
+bool js::GetPropertyPure(JSContext* cx, JSObject* obj, jsid id, Value* vp) {
+  JSObject* pobj;
+  PropertyResult prop;
+  if (!LookupPropertyPure(cx, obj, id, &pobj, &prop)) {
+    return false;
+  }
+
+  if (!prop) {
+    vp->setUndefined();
+    return true;
+  }
+
+  return pobj->isNative() &&
+         NativeGetPureInline(&pobj->as<NativeObject>(), id, prop, vp, cx);
+}
+
+bool js::GetOwnPropertyPure(JSContext* cx, JSObject* obj, jsid id, Value* vp,
+                            bool* found) {
+  PropertyResult prop;
+  if (!LookupOwnPropertyPure(cx, obj, id, &prop)) {
+    return false;
+  }
+
+  if (!prop) {
+    *found = false;
+    vp->setUndefined();
+    return true;
+  }
+
+  *found = true;
+  return obj->isNative() &&
+         NativeGetPureInline(&obj->as<NativeObject>(), id, prop, vp, cx);
+}
+
+static inline bool NativeGetGetterPureInline(PropertyResult prop,
+                                             JSFunction** fp) {
+  MOZ_ASSERT(prop.isNativeProperty());
+
+  if (prop.shape()->hasGetterObject()) {
+    Shape* shape = prop.shape();
+    if (shape->getterObject()->is<JSFunction>()) {
+      *fp = &shape->getterObject()->as<JSFunction>();
+      return true;
+    }
+  }
+
+  *fp = nullptr;
+  return true;
+}
+
+bool js::GetGetterPure(JSContext* cx, JSObject* obj, jsid id, JSFunction** fp) {
+  /* Just like GetPropertyPure, but get getter function, without invoking
+   * it. */
+  JSObject* pobj;
+  PropertyResult prop;
+  if (!LookupPropertyPure(cx, obj, id, &pobj, &prop)) {
+    return false;
+  }
+
+  if (!prop) {
+    *fp = nullptr;
+    return true;
+  }
+
+  return prop.isNativeProperty() && NativeGetGetterPureInline(prop, fp);
+}
+
+bool js::GetOwnGetterPure(JSContext* cx, JSObject* obj, jsid id,
+                          JSFunction** fp) {
+  JS::AutoCheckCannotGC nogc;
+  PropertyResult prop;
+  if (!LookupOwnPropertyPure(cx, obj, id, &prop)) {
+    return false;
+  }
+
+  if (!prop) {
+    *fp = nullptr;
+    return true;
+  }
+
+  return prop.isNativeProperty() && NativeGetGetterPureInline(prop, fp);
+}
+
+bool js::GetOwnNativeGetterPure(JSContext* cx, JSObject* obj, jsid id,
+                                JSNative* native) {
+  JS::AutoCheckCannotGC nogc;
+  *native = nullptr;
+  PropertyResult prop;
+  if (!LookupOwnPropertyPure(cx, obj, id, &prop)) {
+    return false;
+  }
+
+  if (!prop || !prop.isNativeProperty() || !prop.shape()->hasGetterObject()) {
+    return true;
+  }
+
+  JSObject* getterObj = prop.shape()->getterObject();
+  if (!getterObj->is<JSFunction>()) {
+    return true;
+  }
+
+  JSFunction* getter = &getterObj->as<JSFunction>();
+  if (!getter->isNative()) {
+    return true;
+  }
+
+  *native = getter->native();
+  return true;
+}
+
+bool js::HasOwnDataPropertyPure(JSContext* cx, JSObject* obj, jsid id,
+                                bool* result) {
+  PropertyResult prop;
+  if (!LookupOwnPropertyPure(cx, obj, id, &prop)) {
+    return false;
+  }
+
+  *result = prop && prop.isNativeProperty() && prop.shape()->isDataProperty();
+  return true;
+}
+
+bool js::GetPrototypeIfOrdinary(JSContext* cx, HandleObject obj,
+                                bool* isOrdinary, MutableHandleObject protop) {
+  if (obj->is<js::ProxyObject>()) {
+    return js::Proxy::getPrototypeIfOrdinary(cx, obj, isOrdinary, protop);
+  }
+
+  *isOrdinary = true;
+  protop.set(obj->staticPrototype());
+  return true;
+}
+
+/*** ES6 standard internal methods ******************************************/
+
+bool js::SetPrototype(JSContext* cx, HandleObject obj, HandleObject proto,
+                      JS::ObjectOpResult& result) {
+  // The proxy trap subsystem fully handles prototype-setting for proxies
+  // with dynamic [[Prototype]]s.
+  if (obj->hasDynamicPrototype()) {
+    MOZ_ASSERT(obj->is<ProxyObject>());
+    return Proxy::setPrototype(cx, obj, proto, result);
+  }
+
+  /*
+   * ES6 9.1.2 step 3-4 if |obj.[[Prototype]]| has SameValue as |proto| return
+   * true. Since the values in question are objects, we can just compare
+   * pointers.
+   */
+  if (proto == obj->staticPrototype()) {
+    return result.succeed();
+  }
+
+  /* Disallow mutation of immutable [[Prototype]]s. */
+  if (obj->staticPrototypeIsImmutable()) {
+    return result.fail(JSMSG_CANT_SET_PROTO);
+  }
+
+  /*
+   * Disallow mutating the [[Prototype]] on Typed Objects, per the spec.
+   */
+  if (obj->is<TypedObject>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_CANT_SET_PROTO_OF,
+                              "incompatible TypedObject");
+    return false;
+  }
+
+  /* ES6 9.1.2 step 5 forbids changing [[Prototype]] if not [[Extensible]]. */
+  bool extensible;
+  if (!IsExtensible(cx, obj, &extensible)) {
+    return false;
+  }
+  if (!extensible) {
+    return result.fail(JSMSG_CANT_SET_PROTO);
+  }
+
+  // If this is a global object, resolve the Object class so that its
+  // [[Prototype]] chain is always properly immutable, even in the presence
+  // of lazy standard classes.
+  if (obj->is<GlobalObject>()) {
+    Handle<GlobalObject*> global = obj.as<GlobalObject>();
+    if (!GlobalObject::ensureConstructor(cx, global, JSProto_Object)) {
+      return false;
+    }
+  }
+
+  /*
+   * ES6 9.1.2 step 6 forbids generating cyclical prototype chains. But we
+   * have to do this comparison on the observable WindowProxy, not on the
+   * possibly-Window object we're setting the proto on.
+   */
+  RootedObject objMaybeWindowProxy(cx, ToWindowProxyIfWindow(obj));
+  RootedObject obj2(cx, proto);
+  while (obj2) {
+    MOZ_ASSERT(!IsWindow(obj2));
+    if (obj2 == objMaybeWindowProxy) {
+      return result.fail(JSMSG_CANT_SET_PROTO_CYCLE);
+    }
+
+    bool isOrdinary;
+    if (!GetPrototypeIfOrdinary(cx, obj2, &isOrdinary, &obj2)) {
+      return false;
+    }
+    if (!isOrdinary) {
+      break;
+    }
+  }
+
+  Rooted<TaggedProto> taggedProto(cx, TaggedProto(proto));
+  if (!SetProto(cx, obj, taggedProto)) {
+    return false;
+  }
+
+  return result.succeed();
+}
+
+bool js::SetPrototype(JSContext* cx, HandleObject obj, HandleObject proto) {
+  ObjectOpResult result;
+  return SetPrototype(cx, obj, proto, result) && result.checkStrict(cx, obj);
+}
+
+bool js::PreventExtensions(JSContext* cx, HandleObject obj,
+                           ObjectOpResult& result) {
+  if (obj->is<ProxyObject>()) {
+    return js::Proxy::preventExtensions(cx, obj, result);
+  }
+
+  if (!obj->nonProxyIsExtensible()) {
+    // If the following assertion fails, there's somewhere else a missing
+    // call to shrinkCapacityToInitializedLength() which needs to be found
+    // and fixed.
+    MOZ_ASSERT_IF(obj->is<NativeObject>(),
+                  obj->as<NativeObject>().getDenseInitializedLength() ==
+                      obj->as<NativeObject>().getDenseCapacity());
+
+    return result.succeed();
+  }
+
+  if (obj->is<NativeObject>()) {
+    // Force lazy properties to be resolved.
+    HandleNativeObject nobj = obj.as<NativeObject>();
+    if (!ResolveLazyProperties(cx, nobj)) {
+      return false;
+    }
+
+    // Prepare the elements. We have to do this before we mark the object
+    // non-extensible; that's fine because these changes are not observable.
+    ObjectElements::PrepareForPreventExtensions(cx, nobj);
+  }
+
+  // Finally, set the NOT_EXTENSIBLE flag on the BaseShape and ObjectElements.
+  if (!JSObject::setFlags(cx, obj, BaseShape::NOT_EXTENSIBLE,
+                          JSObject::GENERATE_SHAPE)) {
+    return false;
+  }
+  if (obj->is<NativeObject>()) {
+    ObjectElements::PreventExtensions(&obj->as<NativeObject>());
+  }
+
+  return result.succeed();
+}
+
+bool js::PreventExtensions(JSContext* cx, HandleObject obj) {
+  ObjectOpResult result;
+  return PreventExtensions(cx, obj, result) && result.checkStrict(cx, obj);
+}
+
+bool js::GetOwnPropertyDescriptor(JSContext* cx, HandleObject obj, HandleId id,
+                                  MutableHandle<PropertyDescriptor> desc) {
+  if (GetOwnPropertyOp op = obj->getOpsGetOwnPropertyDescriptor()) {
+    bool ok = op(cx, obj, id, desc);
+    if (ok) {
+      desc.assertCompleteIfFound();
+    }
+    return ok;
+  }
+
+  return NativeGetOwnPropertyDescriptor(cx, obj.as<NativeObject>(), id, desc);
+}
+
+bool js::DefineProperty(JSContext* cx, HandleObject obj, HandleId id,
+                        Handle<PropertyDescriptor> desc) {
+  ObjectOpResult result;
+  return DefineProperty(cx, obj, id, desc, result) &&
+         result.checkStrict(cx, obj, id);
+}
+
+bool js::DefineProperty(JSContext* cx, HandleObject obj, HandleId id,
+                        Handle<PropertyDescriptor> desc,
+                        ObjectOpResult& result) {
+  desc.assertValid();
+  if (DefinePropertyOp op = obj->getOpsDefineProperty()) {
+    return op(cx, obj, id, desc, result);
+  }
+  return NativeDefineProperty(cx, obj.as<NativeObject>(), id, desc, result);
+}
+
+bool js::DefineAccessorProperty(JSContext* cx, HandleObject obj, HandleId id,
+                                HandleObject getter, HandleObject setter,
+                                unsigned attrs, ObjectOpResult& result) {
+  Rooted<PropertyDescriptor> desc(cx);
+
+  {
+    GetterOp getterOp = JS_DATA_TO_FUNC_PTR(GetterOp, getter.get());
+    SetterOp setterOp = JS_DATA_TO_FUNC_PTR(SetterOp, setter.get());
+    desc.initFields(nullptr, UndefinedHandleValue, attrs, getterOp, setterOp);
+  }
+
+  if (DefinePropertyOp op = obj->getOpsDefineProperty()) {
+    MOZ_ASSERT(!cx->isHelperThreadContext());
+    return op(cx, obj, id, desc, result);
+  }
+  return NativeDefineProperty(cx, obj.as<NativeObject>(), id, desc, result);
+}
+
+bool js::DefineDataProperty(JSContext* cx, HandleObject obj, HandleId id,
+                            HandleValue value, unsigned attrs,
+                            ObjectOpResult& result) {
+  Rooted<PropertyDescriptor> desc(cx);
+  desc.initFields(nullptr, value, attrs, nullptr, nullptr);
+  if (DefinePropertyOp op = obj->getOpsDefineProperty()) {
+    MOZ_ASSERT(!cx->isHelperThreadContext());
+    return op(cx, obj, id, desc, result);
+  }
+  return NativeDefineProperty(cx, obj.as<NativeObject>(), id, desc, result);
+}
+
+bool js::DefineAccessorProperty(JSContext* cx, HandleObject obj, HandleId id,
+                                HandleObject getter, HandleObject setter,
+                                unsigned attrs) {
+  ObjectOpResult result;
+  if (!DefineAccessorProperty(cx, obj, id, getter, setter, attrs, result)) {
+    return false;
+  }
+  if (!result) {
+    MOZ_ASSERT(!cx->isHelperThreadContext());
+    result.reportError(cx, obj, id);
+    return false;
+  }
+  return true;
+}
+
+bool js::DefineDataProperty(JSContext* cx, HandleObject obj, HandleId id,
+                            HandleValue value, unsigned attrs) {
+  ObjectOpResult result;
+  if (!DefineDataProperty(cx, obj, id, value, attrs, result)) {
+    return false;
+  }
+  if (!result) {
+    MOZ_ASSERT(!cx->isHelperThreadContext());
+    result.reportError(cx, obj, id);
+    return false;
+  }
+  return true;
+}
+
+bool js::DefineDataProperty(JSContext* cx, HandleObject obj, PropertyName* name,
+                            HandleValue value, unsigned attrs) {
+  RootedId id(cx, NameToId(name));
+  return DefineDataProperty(cx, obj, id, value, attrs);
+}
+
+bool js::DefineDataElement(JSContext* cx, HandleObject obj, uint32_t index,
+                           HandleValue value, unsigned attrs) {
+  RootedId id(cx);
+  if (!IndexToId(cx, index, &id)) {
+    return false;
+  }
+  return DefineDataProperty(cx, obj, id, value, attrs);
+}
+
+/*** SpiderMonkey nonstandard internal methods ******************************/
+
+// Mark an object as having an immutable prototype
+//
+// NOTE: This does not correspond to the SetImmutablePrototype ECMAScript
+//       method.
+bool js::SetImmutablePrototype(JSContext* cx, HandleObject obj,
+                               bool* succeeded) {
+  if (obj->hasDynamicPrototype()) {
+    MOZ_ASSERT(!cx->isHelperThreadContext());
+    return Proxy::setImmutablePrototype(cx, obj, succeeded);
+  }
+
+  if (!JSObject::setFlags(cx, obj, BaseShape::IMMUTABLE_PROTOTYPE)) {
+    return false;
+  }
+  *succeeded = true;
+  return true;
+}
+
+bool js::GetPropertyDescriptor(JSContext* cx, HandleObject obj, HandleId id,
+                               MutableHandle<PropertyDescriptor> desc) {
+  RootedObject pobj(cx);
+
+  for (pobj = obj; pobj;) {
+    if (!GetOwnPropertyDescriptor(cx, pobj, id, desc)) {
+      return false;
+    }
+
+    if (desc.object()) {
+      return true;
+    }
+
+    if (!GetPrototype(cx, pobj, &pobj)) {
+      return false;
+    }
+  }
+
+  MOZ_ASSERT(!desc.object());
+  return true;
+}
+
+/* * */
+
+extern bool PropertySpecNameToId(JSContext* cx, JSPropertySpec::Name name,
+                                 MutableHandleId id,
+                                 js::PinningBehavior pin = js::DoNotPinAtom);
+
+// If a property or method is part of an experimental feature that can be
+// disabled at run-time by a preference, we keep it in the JSFunctionSpec /
+// JSPropertySpec list, but omit the definition if the preference is off.
+JS_FRIEND_API bool js::ShouldIgnorePropertyDefinition(JSContext* cx,
+                                                      JSProtoKey key, jsid id) {
+  if (!cx->realm()->creationOptions().getToSourceEnabled() &&
+      (id == NameToId(cx->names().toSource) ||
+       id == NameToId(cx->names().uneval))) {
+    return true;
+  }
+
+  if (key == JSProto_FinalizationRegistry &&
+      cx->realm()->creationOptions().getWeakRefsEnabled() ==
+          JS::WeakRefSpecifier::EnabledWithoutCleanupSome &&
+      id == NameToId(cx->names().cleanupSome)) {
+    return true;
+  }
+
+  return false;
+}
+
+static bool DefineFunctionFromSpec(JSContext* cx, HandleObject obj,
+                                   const JSFunctionSpec* fs, unsigned flags,
+                                   DefineAsIntrinsic intrinsic) {
+  RootedId id(cx);
+  if (!PropertySpecNameToId(cx, fs->name, &id)) {
+    return false;
+  }
+
+  if (ShouldIgnorePropertyDefinition(cx, StandardProtoKeyOrNull(obj), id)) {
+    return true;
+  }
+
+  JSFunction* fun = NewFunctionFromSpec(cx, fs, id);
+  if (!fun) {
+    return false;
+  }
+
+  if (intrinsic == AsIntrinsic) {
+    fun->setIsIntrinsic();
+  }
+
+  RootedValue funVal(cx, ObjectValue(*fun));
+  return DefineDataProperty(cx, obj, id, funVal, flags & ~JSFUN_FLAGS_MASK);
+}
+
+bool js::DefineFunctions(JSContext* cx, HandleObject obj,
+                         const JSFunctionSpec* fs,
+                         DefineAsIntrinsic intrinsic) {
+  for (; fs->name; fs++) {
+    if (!DefineFunctionFromSpec(cx, obj, fs, fs->flags, intrinsic)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/*** ToPrimitive ************************************************************/
+
+/*
+ * Gets |obj[id]|.  If that value's not callable, returns true and stores an
+ * object value in *vp.  If it's callable, calls it with no arguments and |obj|
+ * as |this|, returning the result in *vp.
+ *
+ * This is a mini-abstraction for ES6 draft rev 36 (2015 Mar 17),
+ * 7.1.1, second algorithm (OrdinaryToPrimitive), steps 5.a-c.
+ */
+static bool MaybeCallMethod(JSContext* cx, HandleObject obj, HandleId id,
+                            MutableHandleValue vp) {
+  if (!GetProperty(cx, obj, obj, id, vp)) {
+    return false;
+  }
+  if (!IsCallable(vp)) {
+    vp.setObject(*obj);
+    return true;
+  }
+
+  return js::Call(cx, vp, obj, vp);
+}
+
+static bool ReportCantConvert(JSContext* cx, unsigned errorNumber,
+                              HandleObject obj, JSType hint) {
+  const JSClass* clasp = obj->getClass();
+
+  // Avoid recursive death when decompiling in ReportValueError.
+  RootedString str(cx);
+  if (hint == JSTYPE_STRING) {
+    str = JS_AtomizeAndPinString(cx, clasp->name);
+    if (!str) {
+      return false;
+    }
+  } else {
+    str = nullptr;
+  }
+
+  RootedValue val(cx, ObjectValue(*obj));
+  ReportValueError(cx, errorNumber, JSDVG_SEARCH_STACK, val, str,
+                   hint == JSTYPE_UNDEFINED ? "primitive type"
+                   : hint == JSTYPE_STRING  ? "string"
+                                            : "number");
+  return false;
+}
+
+bool JS::OrdinaryToPrimitive(JSContext* cx, HandleObject obj, JSType hint,
+                             MutableHandleValue vp) {
+  MOZ_ASSERT(hint == JSTYPE_NUMBER || hint == JSTYPE_STRING ||
+             hint == JSTYPE_UNDEFINED);
+
+  Rooted<jsid> id(cx);
+
+  const JSClass* clasp = obj->getClass();
+  if (hint == JSTYPE_STRING) {
+    id = NameToId(cx->names().toString);
+
+    /* Optimize (new String(...)).toString(). */
+    if (clasp == &StringObject::class_) {
+      StringObject* nobj = &obj->as<StringObject>();
+      if (HasNativeMethodPure(nobj, cx->names().toString, str_toString, cx)) {
+        vp.setString(nobj->unbox());
+        return true;
+      }
+    }
+
+    if (!MaybeCallMethod(cx, obj, id, vp)) {
+      return false;
+    }
+    if (vp.isPrimitive()) {
+      return true;
+    }
+
+    id = NameToId(cx->names().valueOf);
+    if (!MaybeCallMethod(cx, obj, id, vp)) {
+      return false;
+    }
+    if (vp.isPrimitive()) {
+      return true;
+    }
+  } else {
+    id = NameToId(cx->names().valueOf);
+
+    /* Optimize new String(...).valueOf(). */
+    if (clasp == &StringObject::class_) {
+      StringObject* nobj = &obj->as<StringObject>();
+      if (HasNativeMethodPure(nobj, cx->names().valueOf, str_toString, cx)) {
+        vp.setString(nobj->unbox());
+        return true;
+      }
+    }
+
+    /* Optimize new Number(...).valueOf(). */
+    if (clasp == &NumberObject::class_) {
+      NumberObject* nobj = &obj->as<NumberObject>();
+      if (HasNativeMethodPure(nobj, cx->names().valueOf, num_valueOf, cx)) {
+        vp.setNumber(nobj->unbox());
+        return true;
+      }
+    }
+
+    if (!MaybeCallMethod(cx, obj, id, vp)) {
+      return false;
+    }
+    if (vp.isPrimitive()) {
+      return true;
+    }
+
+    id = NameToId(cx->names().toString);
+    if (!MaybeCallMethod(cx, obj, id, vp)) {
+      return false;
+    }
+    if (vp.isPrimitive()) {
+      return true;
+    }
+  }
+
+  return ReportCantConvert(cx, JSMSG_CANT_CONVERT_TO, obj, hint);
+}
+
+bool js::ToPrimitiveSlow(JSContext* cx, JSType preferredType,
+                         MutableHandleValue vp) {
+  // Step numbers refer to the first algorithm listed in ES6 draft rev 36
+  // (2015 Mar 17) 7.1.1 ToPrimitive.
+  MOZ_ASSERT(preferredType == JSTYPE_UNDEFINED ||
+             preferredType == JSTYPE_STRING || preferredType == JSTYPE_NUMBER);
+  RootedObject obj(cx, &vp.toObject());
+
+  // Steps 4-5.
+  RootedValue method(cx);
+  if (!GetInterestingSymbolProperty(cx, obj, cx->wellKnownSymbols().toPrimitive,
+                                    &method)) {
+    return false;
+  }
+
+  // Step 6.
+  if (!method.isNullOrUndefined()) {
+    // Step 6 of GetMethod. js::Call() below would do this check and throw a
+    // TypeError anyway, but this produces a better error message.
+    if (!IsCallable(method)) {
+      return ReportCantConvert(cx, JSMSG_TOPRIMITIVE_NOT_CALLABLE, obj,
+                               preferredType);
+    }
+
+    // Steps 1-3, 6.a-b.
+    RootedValue arg0(
+        cx,
+        StringValue(preferredType == JSTYPE_STRING   ? cx->names().string
+                    : preferredType == JSTYPE_NUMBER ? cx->names().number
+                                                     : cx->names().default_));
+
+    if (!js::Call(cx, method, vp, arg0, vp)) {
+      return false;
+    }
+
+    // Steps 6.c-d.
+    if (vp.isObject()) {
+      return ReportCantConvert(cx, JSMSG_TOPRIMITIVE_RETURNED_OBJECT, obj,
+                               preferredType);
+    }
+    return true;
+  }
+
+  return OrdinaryToPrimitive(cx, obj, preferredType, vp);
+}
+
+/* ES6 draft rev 28 (2014 Oct 14) 7.1.14 */
+bool js::ToPropertyKeySlow(JSContext* cx, HandleValue argument,
+                           MutableHandleId result) {
+  MOZ_ASSERT(argument.isObject());
+
+  // Steps 1-2.
+  RootedValue key(cx, argument);
+  if (!ToPrimitiveSlow(cx, JSTYPE_STRING, &key)) {
+    return false;
+  }
+
+  // Steps 3-4.
+  return PrimitiveValueToId<CanGC>(cx, key, result);
+}
+
+/* * */
+
+bool js::IsPrototypeOf(JSContext* cx, HandleObject protoObj, JSObject* obj,
+                       bool* result) {
+  RootedObject obj2(cx, obj);
+  for (;;) {
+    // The [[Prototype]] chain might be cyclic.
+    if (!CheckForInterrupt(cx)) {
+      return false;
+    }
+    if (!GetPrototype(cx, obj2, &obj2)) {
+      return false;
+    }
+    if (!obj2) {
+      *result = false;
+      return true;
+    }
+    if (obj2 == protoObj) {
+      *result = true;
+      return true;
+    }
+  }
+}
+
+JSObject* js::PrimitiveToObject(JSContext* cx, const Value& v) {
+  MOZ_ASSERT(v.isPrimitive());
+
+  switch (v.type()) {
+    case ValueType::String: {
+      Rooted<JSString*> str(cx, v.toString());
+      return StringObject::create(cx, str);
+    }
+    case ValueType::Double:
+    case ValueType::Int32:
+      return NumberObject::create(cx, v.toNumber());
+    case ValueType::Boolean:
+      return BooleanObject::create(cx, v.toBoolean());
+    case ValueType::Symbol: {
+      RootedSymbol symbol(cx, v.toSymbol());
+      return SymbolObject::create(cx, symbol);
+    }
+    case ValueType::BigInt: {
+      RootedBigInt bigInt(cx, v.toBigInt());
+      return BigIntObject::create(cx, bigInt);
+    }
+    case ValueType::Undefined:
+    case ValueType::Null:
+    case ValueType::Magic:
+    case ValueType::PrivateGCThing:
+    case ValueType::Object:
+      break;
+  }
+
+  MOZ_CRASH("unexpected type");
+}
+
+// Like PrimitiveToObject, but returns the JSProtoKey of the prototype that
+// would be used without actually creating the object.
+JSProtoKey js::PrimitiveToProtoKey(JSContext* cx, const Value& v) {
+  MOZ_ASSERT(v.isPrimitive());
+
+  switch (v.type()) {
+    case ValueType::String:
+      return JSProto_String;
+    case ValueType::Double:
+    case ValueType::Int32:
+      return JSProto_Number;
+    case ValueType::Boolean:
+      return JSProto_Boolean;
+    case ValueType::Symbol:
+      return JSProto_Symbol;
+    case ValueType::BigInt:
+      return JSProto_BigInt;
+    case ValueType::Undefined:
+    case ValueType::Null:
+    case ValueType::Magic:
+    case ValueType::PrivateGCThing:
+    case ValueType::Object:
+      break;
+  }
+
+  MOZ_CRASH("unexpected type");
+}
+
+/*
+ * Invokes the ES5 ToObject algorithm on vp, returning the result. If vp might
+ * already be an object, use ToObject. reportScanStack controls how null and
+ * undefined errors are reported.
+ *
+ * Callers must handle the already-object case.
+ */
+JSObject* js::ToObjectSlow(JSContext* cx, JS::HandleValue val,
+                           bool reportScanStack) {
+  MOZ_ASSERT(!val.isMagic());
+  MOZ_ASSERT(!val.isObject());
+
+  if (val.isNullOrUndefined()) {
+    ReportIsNullOrUndefinedForPropertyAccess(
+        cx, val, reportScanStack ? JSDVG_SEARCH_STACK : JSDVG_IGNORE_STACK);
+    return nullptr;
+  }
+
+  return PrimitiveToObject(cx, val);
+}
+
+JSObject* js::ToObjectSlowForPropertyAccess(JSContext* cx, JS::HandleValue val,
+                                            int valIndex, HandleId key) {
+  MOZ_ASSERT(!val.isMagic());
+  MOZ_ASSERT(!val.isObject());
+
+  if (val.isNullOrUndefined()) {
+    ReportIsNullOrUndefinedForPropertyAccess(cx, val, valIndex, key);
+    return nullptr;
+  }
+
+  return PrimitiveToObject(cx, val);
+}
+
+JSObject* js::ToObjectSlowForPropertyAccess(JSContext* cx, JS::HandleValue val,
+                                            int valIndex,
+                                            HandlePropertyName key) {
+  MOZ_ASSERT(!val.isMagic());
+  MOZ_ASSERT(!val.isObject());
+
+  if (val.isNullOrUndefined()) {
+    RootedId keyId(cx, NameToId(key));
+    ReportIsNullOrUndefinedForPropertyAccess(cx, val, valIndex, keyId);
+    return nullptr;
+  }
+
+  return PrimitiveToObject(cx, val);
+}
+
+JSObject* js::ToObjectSlowForPropertyAccess(JSContext* cx, JS::HandleValue val,
+                                            int valIndex,
+                                            HandleValue keyValue) {
+  MOZ_ASSERT(!val.isMagic());
+  MOZ_ASSERT(!val.isObject());
+
+  if (val.isNullOrUndefined()) {
+    RootedId key(cx);
+    if (keyValue.isPrimitive()) {
+      if (!PrimitiveValueToId<CanGC>(cx, keyValue, &key)) {
+        return nullptr;
+      }
+      ReportIsNullOrUndefinedForPropertyAccess(cx, val, valIndex, key);
+    } else {
+      ReportIsNullOrUndefinedForPropertyAccess(cx, val, valIndex);
+    }
+    return nullptr;
+  }
+
+  return PrimitiveToObject(cx, val);
+}
+
+JSObject* js::GetThisObject(JSObject* obj) {
+  // Use the WindowProxy if the global is a Window, as Window must never be
+  // exposed to script.
+  if (obj->is<GlobalObject>()) {
+    return ToWindowProxyIfWindow(obj);
+  }
+
+  // We should not expose any environments except NSVOs to script. The NSVO is
+  // pretending to be the global object in this case.
+  MOZ_ASSERT(obj->is<NonSyntacticVariablesObject>() ||
+             !obj->is<EnvironmentObject>());
+
+  return obj;
+}
+
+JSObject* js::GetThisObjectOfLexical(JSObject* env) {
+  MOZ_ASSERT(IsExtensibleLexicalEnvironment(env));
+  return env->as<LexicalEnvironmentObject>().thisObject();
+}
+
+JSObject* js::GetThisObjectOfWith(JSObject* env) {
+  MOZ_ASSERT(env->is<WithEnvironmentObject>());
+  return GetThisObject(env->as<WithEnvironmentObject>().withThis());
+}
+
+class GetObjectSlotNameFunctor : public JS::TracingContext::Functor {
+  JSObject* obj;
+
+ public:
+  explicit GetObjectSlotNameFunctor(JSObject* ctx) : obj(ctx) {}
+  virtual void operator()(JS::TracingContext* trc, char* buf,
+                          size_t bufsize) override;
+};
+
+void GetObjectSlotNameFunctor::operator()(JS::TracingContext* tcx, char* buf,
+                                          size_t bufsize) {
+  MOZ_ASSERT(tcx->index() != JS::TracingContext::InvalidIndex);
+
+  uint32_t slot = uint32_t(tcx->index());
+
+  Shape* shape;
+  if (obj->isNative()) {
+    shape = obj->as<NativeObject>().lastProperty();
+    while (shape && (shape->isEmptyShape() || !shape->isDataProperty() ||
+                     shape->slot() != slot)) {
+      shape = shape->previous();
+    }
+  } else {
+    shape = nullptr;
+  }
+
+  if (!shape) {
+    do {
+      const char* slotname = nullptr;
+      const char* pattern = nullptr;
+      if (obj->is<GlobalObject>()) {
+        pattern = "CLASS_OBJECT(%s)";
+        if (false) {
+          ;
+        }
+#define TEST_SLOT_MATCHES_PROTOTYPE(name, clasp) \
+  else if ((JSProto_##name) == slot) {           \
+    slotname = js_##name##_str;                  \
+  }
+        JS_FOR_EACH_PROTOTYPE(TEST_SLOT_MATCHES_PROTOTYPE)
+#undef TEST_SLOT_MATCHES_PROTOTYPE
+      } else {
+        pattern = "%s";
+        if (obj->is<EnvironmentObject>()) {
+          if (slot == EnvironmentObject::enclosingEnvironmentSlot()) {
+            slotname = "enclosing_environment";
+          } else if (obj->is<CallObject>()) {
+            if (slot == CallObject::calleeSlot()) {
+              slotname = "callee_slot";
+            }
+          } else if (obj->is<WithEnvironmentObject>()) {
+            if (slot == WithEnvironmentObject::objectSlot()) {
+              slotname = "with_object";
+            } else if (slot == WithEnvironmentObject::thisSlot()) {
+              slotname = "with_this";
+            }
+          }
+        }
+      }
+
+      if (slotname) {
+        snprintf(buf, bufsize, pattern, slotname);
+      } else {
+        snprintf(buf, bufsize, "**UNKNOWN SLOT %" PRIu32 "**", slot);
+      }
+    } while (false);
+  } else {
+    jsid propid = shape->propid();
+    if (JSID_IS_INT(propid)) {
+      snprintf(buf, bufsize, "%" PRId32, JSID_TO_INT(propid));
+    } else if (JSID_IS_ATOM(propid)) {
+      PutEscapedString(buf, bufsize, JSID_TO_ATOM(propid), 0);
+    } else if (JSID_IS_SYMBOL(propid)) {
+      snprintf(buf, bufsize, "**SYMBOL KEY**");
+    } else {
+      snprintf(buf, bufsize, "**FINALIZED ATOM KEY**");
+    }
+  }
+}
+
+/*** Debugging routines *****************************************************/
+
+#if defined(DEBUG) || defined(JS_JITSPEW)
+
+/*
+ * Routines to print out values during debugging.  These are FRIEND_API to help
+ * the debugger find them and to support temporarily hacking js::Dump* calls
+ * into other code.
+ */
+
+static void dumpValue(const Value& v, js::GenericPrinter& out) {
+  switch (v.type()) {
+    case ValueType::Null:
+      out.put("null");
+      break;
+    case ValueType::Undefined:
+      out.put("undefined");
+      break;
+    case ValueType::Int32:
+      out.printf("%d", v.toInt32());
+      break;
+    case ValueType::Double:
+      out.printf("%g", v.toDouble());
+      break;
+    case ValueType::String:
+      v.toString()->dumpNoNewline(out);
+      break;
+    case ValueType::Symbol:
+      v.toSymbol()->dump(out);
+      break;
+    case ValueType::BigInt:
+      v.toBigInt()->dump(out);
+      break;
+    case ValueType::Object:
+      if (v.toObject().is<JSFunction>()) {
+        JSFunction* fun = &v.toObject().as<JSFunction>();
+        if (fun->displayAtom()) {
+          out.put("<function ");
+          EscapedStringPrinter(out, fun->displayAtom(), 0);
+        } else {
+          out.put("<unnamed function");
+        }
+        if (fun->hasBaseScript()) {
+          BaseScript* script = fun->baseScript();
+          out.printf(" (%s:%u)", script->filename() ? script->filename() : "",
+                     script->lineno());
+        }
+        out.printf(" at %p>", (void*)fun);
+      } else {
+        JSObject* obj = &v.toObject();
+        const JSClass* clasp = obj->getClass();
+        out.printf("<%s%s at %p>", clasp->name,
+                   (clasp == &PlainObject::class_) ? "" : " object",
+                   (void*)obj);
+      }
+      break;
+    case ValueType::Boolean:
+      if (v.toBoolean()) {
+        out.put("true");
+      } else {
+        out.put("false");
+      }
+      break;
+    case ValueType::Magic:
+      out.put("<magic");
+      switch (v.whyMagic()) {
+        case JS_ELEMENTS_HOLE:
+          out.put(" elements hole");
+          break;
+        case JS_NO_ITER_VALUE:
+          out.put(" no iter value");
+          break;
+        case JS_GENERATOR_CLOSING:
+          out.put(" generator closing");
+          break;
+        case JS_OPTIMIZED_OUT:
+          out.put(" optimized out");
+          break;
+        default:
+          out.put(" ?!");
+          break;
+      }
+      out.putChar('>');
+      break;
+    case ValueType::PrivateGCThing:
+      out.printf("<PrivateGCThing %p>", v.toGCThing());
+      break;
+  }
+}
+
+namespace js {
+
+// We don't want jsfriendapi.h to depend on GenericPrinter,
+// so these functions are declared directly in the cpp.
+
+JS_FRIEND_API void DumpValue(const JS::Value& val, js::GenericPrinter& out);
+
+JS_FRIEND_API void DumpId(jsid id, js::GenericPrinter& out);
+
+JS_FRIEND_API void DumpInterpreterFrame(JSContext* cx, js::GenericPrinter& out,
+                                        InterpreterFrame* start = nullptr);
+
+}  // namespace js
+
+JS_FRIEND_API void js::DumpValue(const Value& val, js::GenericPrinter& out) {
+  dumpValue(val, out);
+  out.putChar('\n');
+}
+
+JS_FRIEND_API void js::DumpId(jsid id, js::GenericPrinter& out) {
+  out.printf("jsid %p = ", (void*)JSID_BITS(id));
+  dumpValue(IdToValue(id), out);
+  out.putChar('\n');
+}
+
+static void DumpProperty(const NativeObject* obj, Shape& shape,
+                         js::GenericPrinter& out) {
+  jsid id = shape.propid();
+  if (JSID_IS_ATOM(id)) {
+    JSID_TO_ATOM(id)->dumpCharsNoNewline(out);
+  } else if (JSID_IS_INT(id)) {
+    out.printf("%d", JSID_TO_INT(id));
+  } else if (JSID_IS_SYMBOL(id)) {
+    JSID_TO_SYMBOL(id)->dump(out);
+  } else {
+    out.printf("id %p", reinterpret_cast<void*>(JSID_BITS(id)));
+  }
+
+  if (shape.isDataProperty()) {
+    out.printf(": ");
+    dumpValue(obj->getSlot(shape.maybeSlot()), out);
+  }
+
+  out.printf(" (shape %p", (void*)&shape);
+
+  uint8_t attrs = shape.attributes();
+  if (attrs & JSPROP_ENUMERATE) out.put(" enumerate");
+  if (attrs & JSPROP_READONLY) out.put(" readonly");
+  if (attrs & JSPROP_PERMANENT) out.put(" permanent");
+
+  if (shape.hasGetterValue()) {
+    out.printf(" getterValue %p", shape.getterObject());
+  } else if (!shape.hasDefaultGetter()) {
+    out.printf(" getterOp %p", JS_FUNC_TO_DATA_PTR(void*, shape.getterOp()));
+  }
+
+  if (shape.hasSetterValue()) {
+    out.printf(" setterValue %p", shape.setterObject());
+  } else if (!shape.hasDefaultSetter()) {
+    out.printf(" setterOp %p", JS_FUNC_TO_DATA_PTR(void*, shape.setterOp()));
+  }
+
+  if (shape.isDataProperty()) {
+    out.printf(" slot %u", shape.maybeSlot());
+  }
+
+  out.printf(")\n");
+}
+
+bool JSObject::hasSameRealmAs(JSContext* cx) const {
+  return nonCCWRealm() == cx->realm();
+}
+
+bool JSObject::uninlinedIsProxy() const { return is<ProxyObject>(); }
+
+bool JSObject::uninlinedNonProxyIsExtensible() const {
+  return nonProxyIsExtensible();
+}
+
+void JSObject::dump(js::GenericPrinter& out) const {
+  const JSObject* obj = this;
+  out.printf("object %p\n", obj);
+
+  if (IsCrossCompartmentWrapper(this)) {
+    out.printf("  compartment %p\n", compartment());
+  } else {
+    JSObject* globalObj = &nonCCWGlobal();
+    out.printf("  global %p [%s]\n", globalObj, globalObj->getClass()->name);
+  }
+
+  const JSClass* clasp = obj->getClass();
+  out.printf("  class %p %s\n", clasp, clasp->name);
+
+  const ObjectGroup* group = obj->group();
+  out.printf("  group %p\n", group);
+
+  out.put("  flags:");
+  if (obj->isDelegate()) out.put(" delegate");
+  if (!obj->is<ProxyObject>() && !obj->nonProxyIsExtensible())
+    out.put(" not_extensible");
+  if (obj->maybeHasInterestingSymbolProperty())
+    out.put(" maybe_has_interesting_symbol");
+  if (obj->isBoundFunction()) out.put(" bound_function");
+  if (obj->isQualifiedVarObj()) out.put(" varobj");
+  if (obj->isUnqualifiedVarObj()) out.put(" unqualified_varobj");
+  if (obj->hasUncacheableProto()) out.put(" has_uncacheable_proto");
+  if (obj->hasStaticPrototype() && obj->staticPrototypeIsImmutable()) {
+    out.put(" immutable_prototype");
+  }
+
+  const NativeObject* nobj =
+      obj->isNative() ? &obj->as<NativeObject>() : nullptr;
+  if (nobj) {
+    if (nobj->inDictionaryMode()) {
+      out.put(" inDictionaryMode");
+    }
+    if (nobj->hasShapeTable()) {
+      out.put(" hasShapeTable");
+    }
+    if (nobj->hasShapeIC()) {
+      out.put(" hasShapeCache");
+    }
+    if (nobj->hadElementsAccess()) {
+      out.put(" had_elements_access");
+    }
+    if (nobj->isIndexed()) {
+      out.put(" indexed");
+    }
+    if (!nobj->denseElementsArePacked()) {
+      out.put(" non_packed_elements");
+    }
+    if (nobj->getElementsHeader()->isNotExtensible()) {
+      out.put(" not_extensible");
+    }
+    if (nobj->getElementsHeader()->isSealed()) {
+      out.put(" sealed_elements");
+    }
+    if (nobj->getElementsHeader()->isFrozen()) {
+      out.put(" frozen_elements");
+    }
+    if (nobj->getElementsHeader()->maybeInIteration()) {
+      out.put(" elements_maybe_in_iteration");
+    }
+  } else {
+    out.put(" not_native\n");
+  }
+  out.putChar('\n');
+
+  out.put("  proto ");
+  TaggedProto proto = obj->taggedProto();
+  if (proto.isDynamic()) {
+    out.put("<dynamic>");
+  } else {
+    dumpValue(ObjectOrNullValue(proto.toObjectOrNull()), out);
+  }
+  out.putChar('\n');
+
+  if (nobj) {
+    if (clasp->flags & JSCLASS_HAS_PRIVATE) {
+      out.printf("  private %p\n", nobj->getPrivate());
+    }
+
+    uint32_t reserved = JSCLASS_RESERVED_SLOTS(clasp);
+    if (reserved) {
+      out.printf("  reserved slots:\n");
+      for (uint32_t i = 0; i < reserved; i++) {
+        out.printf("    %3u ", i);
+        out.put(": ");
+        dumpValue(nobj->getSlot(i), out);
+        out.putChar('\n');
+      }
+    }
+
+    out.put("  properties:\n");
+    Vector<Shape*, 8, SystemAllocPolicy> props;
+    for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
+      if (!props.append(&r.front())) {
+        out.printf("(OOM while appending properties)\n");
+        break;
+      }
+    }
+    for (size_t i = props.length(); i-- != 0;) {
+      out.printf("    ");
+      DumpProperty(nobj, *props[i], out);
+    }
+
+    uint32_t slots = nobj->getDenseInitializedLength();
+    if (slots) {
+      out.put("  elements:\n");
+      for (uint32_t i = 0; i < slots; i++) {
+        out.printf("    %3u: ", i);
+        dumpValue(nobj->getDenseElement(i), out);
+        out.putChar('\n');
+      }
+    }
+  }
+}
+
+// For debuggers.
+void JSObject::dump() const {
+  Fprinter out(stderr);
+  dump(out);
+}
+
+static void MaybeDumpScope(Scope* scope, js::GenericPrinter& out) {
+  if (scope) {
+    out.printf("  scope: %s\n", ScopeKindString(scope->kind()));
+    for (BindingIter bi(scope); bi; bi++) {
+      out.put("    ");
+      dumpValue(StringValue(bi.name()), out);
+      out.putChar('\n');
+    }
+  }
+}
+
+static void MaybeDumpValue(const char* name, const Value& v,
+                           js::GenericPrinter& out) {
+  if (!v.isNull()) {
+    out.printf("  %s: ", name);
+    dumpValue(v, out);
+    out.putChar('\n');
+  }
+}
+
+JS_FRIEND_API void js::DumpInterpreterFrame(JSContext* cx,
+                                            js::GenericPrinter& out,
+                                            InterpreterFrame* start) {
+  /* This should only called during live debugging. */
+  ScriptFrameIter i(cx);
+  if (!start) {
+    if (i.done()) {
+      out.printf("no stack for cx = %p\n", (void*)cx);
+      return;
+    }
+  } else {
+    while (!i.done() && !i.isJSJit() && i.interpFrame() != start) {
+      ++i;
+    }
+
+    if (i.done()) {
+      out.printf("fp = %p not found in cx = %p\n", (void*)start, (void*)cx);
+      return;
+    }
+  }
+
+  for (; !i.done(); ++i) {
+    if (i.isJSJit()) {
+      out.put("JIT frame\n");
+    } else {
+      out.printf("InterpreterFrame at %p\n", (void*)i.interpFrame());
+    }
+
+    if (i.isFunctionFrame()) {
+      out.put("callee fun: ");
+      RootedValue v(cx);
+      JSObject* fun = i.callee(cx);
+      v.setObject(*fun);
+      dumpValue(v, out);
+    } else {
+      out.put("global or eval frame, no callee");
+    }
+    out.putChar('\n');
+
+    out.printf("file %s line %u\n", i.script()->filename(),
+               i.script()->lineno());
+
+    if (jsbytecode* pc = i.pc()) {
+      out.printf("  pc = %p\n", pc);
+      out.printf("  current op: %s\n", CodeName(JSOp(*pc)));
+      MaybeDumpScope(i.script()->lookupScope(pc), out);
+    }
+    if (i.isFunctionFrame()) {
+      MaybeDumpValue("this", i.thisArgument(cx), out);
+    }
+    if (!i.isJSJit()) {
+      out.put("  rval: ");
+      dumpValue(i.interpFrame()->returnValue(), out);
+      out.putChar('\n');
+    }
+
+    out.put("  flags:");
+    if (i.isConstructing()) {
+      out.put(" constructing");
+    }
+    if (!i.isJSJit() && i.interpFrame()->isDebuggerEvalFrame()) {
+      out.put(" debugger eval");
+    }
+    if (i.isEvalFrame()) {
+      out.put(" eval");
+    }
+    out.putChar('\n');
+
+    out.printf("  envChain: (JSObject*) %p\n", (void*)i.environmentChain(cx));
+
+    out.putChar('\n');
+  }
+}
+
+#endif /* defined(DEBUG) || defined(JS_JITSPEW) */
+
+namespace js {
+
+// We don't want jsfriendapi.h to depend on GenericPrinter,
+// so these functions are declared directly in the cpp.
+
+JS_FRIEND_API void DumpBacktrace(JSContext* cx, js::GenericPrinter& out);
+
+}  // namespace js
+
+JS_FRIEND_API void js::DumpBacktrace(JSContext* cx, FILE* fp) {
+  Fprinter out(fp);
+  js::DumpBacktrace(cx, out);
+}
+
+JS_FRIEND_API void js::DumpBacktrace(JSContext* cx, js::GenericPrinter& out) {
+  size_t depth = 0;
+  for (AllFramesIter i(cx); !i.done(); ++i, ++depth) {
+    const char* filename;
+    unsigned line;
+    if (i.hasScript()) {
+      filename = JS_GetScriptFilename(i.script());
+      line = PCToLineNumber(i.script(), i.pc());
+    } else {
+      filename = i.filename();
+      line = i.computeLine();
+    }
+    char frameType = i.isInterp()     ? 'i'
+                     : i.isBaseline() ? 'b'
+                     : i.isIon()      ? 'I'
+                     : i.isWasm()     ? 'W'
+                                      : '?';
+
+    out.printf("#%zu %14p %c   %s:%u", depth, i.rawFramePtr(), frameType,
+               filename, line);
+
+    if (i.hasScript()) {
+      out.printf(" (%p @ %zu)\n", i.script(), i.script()->pcToOffset(i.pc()));
+    } else {
+      out.printf(" (%p)\n", i.pc());
+    }
+  }
+}
+
+JS_FRIEND_API void js::DumpBacktrace(JSContext* cx) {
+  DumpBacktrace(cx, stdout);
+}
+
+/* * */
+
+js::gc::AllocKind JSObject::allocKindForTenure(
+    const js::Nursery& nursery) const {
+  using namespace js::gc;
+
+  MOZ_ASSERT(IsInsideNursery(this));
+
+  if (is<ArrayObject>()) {
+    const ArrayObject& aobj = as<ArrayObject>();
+    MOZ_ASSERT(aobj.numFixedSlots() == 0);
+
+    /* Use minimal size object if we are just going to copy the pointer. */
+    if (!nursery.isInside(aobj.getElementsHeader())) {
+      return gc::AllocKind::OBJECT0_BACKGROUND;
+    }
+
+    size_t nelements = aobj.getDenseCapacity();
+    return ForegroundToBackgroundAllocKind(GetGCArrayKind(nelements));
+  }
+
+  if (is<JSFunction>()) {
+    return as<JSFunction>().getAllocKind();
+  }
+
+  /*
+   * Typed arrays in the nursery may have a lazily allocated buffer, make
+   * sure there is room for the array's fixed data when moving the array.
+   */
+  if (is<TypedArrayObject>() && !as<TypedArrayObject>().hasBuffer()) {
+    gc::AllocKind allocKind;
+    if (as<TypedArrayObject>().hasInlineElements()) {
+      size_t nbytes = as<TypedArrayObject>().byteLength().get();
+      allocKind = TypedArrayObject::AllocKindForLazyBuffer(nbytes);
+    } else {
+      allocKind = GetGCObjectKind(getClass());
+    }
+    return ForegroundToBackgroundAllocKind(allocKind);
+  }
+
+  // Proxies that are CrossCompartmentWrappers may be nursery allocated.
+  if (IsProxy(this)) {
+    return as<ProxyObject>().allocKindForTenure();
+  }
+
+  // Inlined typed objects are followed by their data, so make sure we copy
+  // it all over to the new object.
+  if (is<InlineTypedObject>()) {
+    // Figure out the size of this object, from the prototype's TypeDescr.
+    // The objects we are traversing here are all tenured, so we don't need
+    // to check forwarding pointers.
+    TypeDescr& descr = as<InlineTypedObject>().typeDescr();
+    MOZ_ASSERT(!IsInsideNursery(&descr));
+    return InlineTypedObject::allocKindForTypeDescriptor(&descr);
+  }
+
+  // Outline typed objects use the minimum allocation kind.
+  if (is<OutlineTypedObject>()) {
+    return gc::AllocKind::OBJECT0;
+  }
+
+  // All nursery allocatable non-native objects are handled above.
+  return as<NativeObject>().allocKindForTenure();
+}
+
+void JSObject::addSizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf,
+                                      JS::ClassInfo* info) {
+  if (is<NativeObject>() && as<NativeObject>().hasDynamicSlots()) {
+    info->objectsMallocHeapSlots +=
+        mallocSizeOf(as<NativeObject>().getSlotsHeader());
+  }
+
+  if (is<NativeObject>() && as<NativeObject>().hasDynamicElements()) {
+    void* allocatedElements = as<NativeObject>().getUnshiftedElementsHeader();
+    info->objectsMallocHeapElementsNormal += mallocSizeOf(allocatedElements);
+  }
+
+  // Other things may be measured in the future if DMD indicates it is
+  // worthwhile.
+  if (is<JSFunction>() || is<PlainObject>() || is<ArrayObject>() ||
+      is<CallObject>() || is<RegExpObject>() || is<ProxyObject>()) {
+    // Do nothing.  But this function is hot, and we win by getting the
+    // common cases out of the way early.  Some stats on the most common
+    // classes, as measured during a vanilla browser session:
+    // - (53.7%, 53.7%): Function
+    // - (18.0%, 71.7%): Object
+    // - (16.9%, 88.6%): Array
+    // - ( 3.9%, 92.5%): Call
+    // - ( 2.8%, 95.3%): RegExp
+    // - ( 1.0%, 96.4%): Proxy
+
+    // Note that any JSClass that is special cased below likely needs to
+    // specify the JSCLASS_DELAY_METADATA_CALLBACK flag, or else we will
+    // probably crash if the object metadata callback attempts to get the
+    // size of the new object (which Debugger code does) before private
+    // slots are initialized.
+  } else if (is<ArgumentsObject>()) {
+    info->objectsMallocHeapMisc +=
+        as<ArgumentsObject>().sizeOfMisc(mallocSizeOf);
+  } else if (is<RegExpStaticsObject>()) {
+    info->objectsMallocHeapMisc +=
+        as<RegExpStaticsObject>().sizeOfData(mallocSizeOf);
+  } else if (is<PropertyIteratorObject>()) {
+    info->objectsMallocHeapMisc +=
+        as<PropertyIteratorObject>().sizeOfMisc(mallocSizeOf);
+  } else if (is<ArrayBufferObject>()) {
+    ArrayBufferObject::addSizeOfExcludingThis(this, mallocSizeOf, info);
+  } else if (is<SharedArrayBufferObject>()) {
+    SharedArrayBufferObject::addSizeOfExcludingThis(this, mallocSizeOf, info);
+  } else if (is<WeakCollectionObject>()) {
+    info->objectsMallocHeapMisc +=
+        as<WeakCollectionObject>().sizeOfExcludingThis(mallocSizeOf);
+  }
+#ifdef JS_HAS_CTYPES
+  else {
+    // This must be the last case.
+    info->objectsMallocHeapMisc += ctypes::SizeOfDataIfCDataObject(
+        mallocSizeOf, const_cast<JSObject*>(this));
+  }
+#endif
+}
+
+size_t JSObject::sizeOfIncludingThisInNursery() const {
+  // This function doesn't concern itself yet with typed objects (bug 1133593).
+
+  MOZ_ASSERT(!isTenured());
+
+  const Nursery& nursery = runtimeFromMainThread()->gc.nursery();
+  size_t size = gc::Arena::thingSize(allocKindForTenure(nursery));
+
+  if (is<NativeObject>()) {
+    const NativeObject& native = as<NativeObject>();
+
+    size += native.numFixedSlots() * sizeof(Value);
+    size += native.numDynamicSlots() * sizeof(Value);
+
+    if (native.hasDynamicElements()) {
+      js::ObjectElements& elements = *native.getElementsHeader();
+      size += (elements.capacity + elements.numShiftedElements()) *
+              sizeof(HeapSlot);
+    }
+
+    if (is<ArgumentsObject>()) {
+      size += as<ArgumentsObject>().sizeOfData();
+    }
+  }
+
+  return size;
+}
+
+JS::ubi::Node::Size JS::ubi::Concrete<JSObject>::size(
+    mozilla::MallocSizeOf mallocSizeOf) const {
+  JSObject& obj = get();
+
+  if (!obj.isTenured()) {
+    return obj.sizeOfIncludingThisInNursery();
+  }
+
+  JS::ClassInfo info;
+  obj.addSizeOfExcludingThis(mallocSizeOf, &info);
+  return obj.tenuredSizeOfThis() + info.sizeOfAllThings();
+}
+
+const char16_t JS::ubi::Concrete<JSObject>::concreteTypeName[] = u"JSObject";
+
+void JSObject::traceChildren(JSTracer* trc) {
+  TraceCellHeaderEdge(trc, this, "group");
+
+  traceShape(trc);
+
+  const JSClass* clasp = group()->clasp();
+  if (clasp->isNative()) {
+    NativeObject* nobj = &as<NativeObject>();
+
+    {
+      GetObjectSlotNameFunctor func(nobj);
+      JS::AutoTracingDetails ctx(trc, func);
+      JS::AutoTracingIndex index(trc);
+      // Tracing can mutate the target but cannot change the slot count,
+      // but the compiler has no way of knowing this.
+      const uint32_t nslots = nobj->slotSpan();
+      for (uint32_t i = 0; i < nslots; ++i) {
+        TraceEdge(trc, &nobj->getSlotRef(i), "object slot");
+        ++index;
+      }
+      MOZ_ASSERT(nslots == nobj->slotSpan());
+    }
+
+    TraceRange(trc, nobj->getDenseInitializedLength(),
+               static_cast<HeapSlot*>(nobj->getDenseElements()),
+               "objectElements");
+  }
+
+  // Call the trace hook at the end so that during a moving GC the trace hook
+  // will see updated fields and slots.
+  if (clasp->hasTrace()) {
+    clasp->doTrace(trc, this);
+  }
+
+  if (trc->isMarkingTracer()) {
+    GCMarker::fromTracer(trc)->markImplicitEdges(this);
+  }
+}
+
+// ES 2016 7.3.20.
+MOZ_MUST_USE JSObject* js::SpeciesConstructor(
+    JSContext* cx, HandleObject obj, HandleObject defaultCtor,
+    bool (*isDefaultSpecies)(JSContext*, JSFunction*)) {
+  // Step 1 (implicit).
+
+  // Fast-path for steps 2 - 8. Applies if all of the following conditions
+  // are met:
+  // - obj.constructor can be retrieved without side-effects.
+  // - obj.constructor[[@@species]] can be retrieved without side-effects.
+  // - obj.constructor[[@@species]] is the builtin's original @@species
+  //   getter.
+  RootedValue ctor(cx);
+  bool ctorGetSucceeded = GetPropertyPure(
+      cx, obj, NameToId(cx->names().constructor), ctor.address());
+  if (ctorGetSucceeded && ctor.isObject() && &ctor.toObject() == defaultCtor) {
+    jsid speciesId = SYMBOL_TO_JSID(cx->wellKnownSymbols().species);
+    JSFunction* getter;
+    if (GetGetterPure(cx, defaultCtor, speciesId, &getter) && getter &&
+        isDefaultSpecies(cx, getter)) {
+      return defaultCtor;
+    }
+  }
+
+  // Step 2.
+  if (!ctorGetSucceeded &&
+      !GetProperty(cx, obj, obj, cx->names().constructor, &ctor)) {
+    return nullptr;
+  }
+
+  // Step 3.
+  if (ctor.isUndefined()) {
+    return defaultCtor;
+  }
+
+  // Step 4.
+  if (!ctor.isObject()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_OBJECT_REQUIRED,
+                              "object's 'constructor' property");
+    return nullptr;
+  }
+
+  // Step 5.
+  RootedObject ctorObj(cx, &ctor.toObject());
+  RootedValue s(cx);
+  RootedId speciesId(cx, SYMBOL_TO_JSID(cx->wellKnownSymbols().species));
+  if (!GetProperty(cx, ctorObj, ctor, speciesId, &s)) {
+    return nullptr;
+  }
+
+  // Step 6.
+  if (s.isNullOrUndefined()) {
+    return defaultCtor;
+  }
+
+  // Step 7.
+  if (IsConstructor(s)) {
+    return &s.toObject();
+  }
+
+  // Step 8.
+  JS_ReportErrorNumberASCII(
+      cx, GetErrorMessage, nullptr, JSMSG_NOT_CONSTRUCTOR,
+      "[Symbol.species] property of object's constructor");
+  return nullptr;
+}
+
+MOZ_MUST_USE JSObject* js::SpeciesConstructor(
+    JSContext* cx, HandleObject obj, JSProtoKey ctorKey,
+    bool (*isDefaultSpecies)(JSContext*, JSFunction*)) {
+  RootedObject defaultCtor(cx,
+                           GlobalObject::getOrCreateConstructor(cx, ctorKey));
+  if (!defaultCtor) {
+    return nullptr;
+  }
+  return SpeciesConstructor(cx, obj, defaultCtor, isDefaultSpecies);
+}
+
+bool js::Unbox(JSContext* cx, HandleObject obj, MutableHandleValue vp) {
+  if (MOZ_UNLIKELY(obj->is<ProxyObject>())) {
+    return Proxy::boxedValue_unbox(cx, obj, vp);
+  }
+
+  if (obj->is<BooleanObject>()) {
+    vp.setBoolean(obj->as<BooleanObject>().unbox());
+  } else if (obj->is<NumberObject>()) {
+    vp.setNumber(obj->as<NumberObject>().unbox());
+  } else if (obj->is<StringObject>()) {
+    vp.setString(obj->as<StringObject>().unbox());
+  } else if (obj->is<DateObject>()) {
+    vp.set(obj->as<DateObject>().UTCTime());
+  } else if (obj->is<SymbolObject>()) {
+    vp.setSymbol(obj->as<SymbolObject>().unbox());
+  } else if (obj->is<BigIntObject>()) {
+    vp.setBigInt(obj->as<BigIntObject>().unbox());
+  } else {
+    vp.setUndefined();
+  }
+
+  return true;
+}
+
+#ifdef DEBUG
+/* static */
+void JSObject::debugCheckNewObject(ObjectGroup* group, Shape* shape,
+                                   js::gc::AllocKind allocKind,
+                                   js::gc::InitialHeap heap) {
+  const JSClass* clasp = group->clasp();
+  MOZ_ASSERT(clasp != &ArrayObject::class_);
+
+  MOZ_ASSERT_IF(shape, clasp == shape->getObjectClass());
+
+  if (!ClassCanHaveFixedData(clasp)) {
+    MOZ_ASSERT(shape);
+    MOZ_ASSERT(gc::GetGCKindSlots(allocKind, clasp) == shape->numFixedSlots());
+  }
+
+  // Classes with a finalizer must specify whether instances will be finalized
+  // on the main thread or in the background, except proxies whose behaviour
+  // depends on the target object.
+  static const uint32_t FinalizeMask =
+      JSCLASS_FOREGROUND_FINALIZE | JSCLASS_BACKGROUND_FINALIZE;
+  uint32_t flags = clasp->flags;
+  uint32_t finalizeFlags = flags & FinalizeMask;
+  if (clasp->hasFinalize() && !clasp->isProxy()) {
+    MOZ_ASSERT(finalizeFlags == JSCLASS_FOREGROUND_FINALIZE ||
+               finalizeFlags == JSCLASS_BACKGROUND_FINALIZE);
+    MOZ_ASSERT((finalizeFlags == JSCLASS_BACKGROUND_FINALIZE) ==
+               IsBackgroundFinalized(allocKind));
+  } else {
+    MOZ_ASSERT(finalizeFlags == 0);
+  }
+
+  MOZ_ASSERT_IF(clasp->hasFinalize(),
+                heap == gc::TenuredHeap ||
+                    CanNurseryAllocateFinalizedClass(clasp) ||
+                    clasp->isProxy());
+
+  MOZ_ASSERT(!group->realm()->hasObjectPendingMetadata());
+
+  // Non-native classes manage their own data and slots, so numFixedSlots and
+  // slotSpan are always 0. Note that proxy classes can have reserved slots
+  // but they're also not included in numFixedSlots/slotSpan.
+  if (!clasp->isNative()) {
+    MOZ_ASSERT_IF(!clasp->isProxy(), JSCLASS_RESERVED_SLOTS(clasp) == 0);
+    MOZ_ASSERT(!clasp->hasPrivate());
+    MOZ_ASSERT_IF(shape, shape->numFixedSlots() == 0);
+    MOZ_ASSERT_IF(shape, shape->slotSpan() == 0);
+  }
+}
+#endif